Power output apparatus and method of controlling the same

Abstract

While a ring gear shaft 126 linked with a drive shaft rotates, a power output apparatus 110 applies a torque to a first motor MG1 attached to a sun gear shaft 125, thereby abruptly increasing a revolving speed of an engine 150, to which a fuel injection is stopped. A torque generated by a frictional force of, for example, a piston in the engine 150 and working as a reaction is applied as a braking torque to the ring gear shaft 126 via a planetary gear 120. The magnitude of the braking torque depends upon the frictional force of, for example, the piston and can be controlled by regulating the revolving speed of the engine 150 by means of the first motor MG1. This control procedure enables the energy consumed by the engine 150 to be output as a braking force to the drive shaft.

Description

This application is a Rule 53(b) Continuation Application No. 09/885,676, filed Jun. 21, 2001, which is a Reissue of U.S. Pat. No. 5,914,575, issued Jun. 22, 1999.

After setting the torque command value Tm1* of the first motor MG1, the control CPU 190 receives the rotational angle θs of the sun gear shaft 125 from the revolver 139 at step S110 and calculates an electrical angle θ1 of the first motor MG1 from the rotational angle θs of the sun gear shaft 125 at step S111. In this embodiment, since a synchronous motor of four-pole pair (that is, four N poles and four S poles) is used as the first motor MG1, the rotational angle θs of the sun gear shaft 125 is quadrupled to yield the electrical angle θ1 (θ1=4θs). The control CPU 190 then detects values of currents 1u1 and 1v1 flowing through the U phase and V phase of three-phase coils 134 in the first motor MG1 with the ammeters 195 and 196 at step S112. Although the currents naturally flow through all the three phases U, V, and W, measurement is required only for the currents passing through the two phases since the sum of the currents is equal to zero. At subsequent step S114, the control CPU 190 executes transformation of coordinates (three-phase to two-phase transformation) using the values of currents flowing through the three phases obtained at step S112. The transformation of coordinates maps the values of currents flowing through the three phases to the values of currents passing through d and q axes of the permanent magnet-type synchronous motor and is executed according to Equation (7) given below. The transformation of coordinates is carried out because the currents flowing through the d and q axes are essential for the torque control in the permanent magnet-type synchronous motor. Alternatively, the torque control may be executed directly with the currents flowing through the three phases. $\begin{array}{cc}\left[\begin{array}{c}\mathrm{Id1}\\ \mathrm{Iq1}\end{array}\right]=\sqrt{2}\left[\begin{array}{cc}-\sin \left(\mathrm{\theta 1}-120\right)& \sin \mathrm{\theta 1}\\ -\cos \left(\mathrm{\theta 1}-120\right)& \cos \mathrm{\theta 1}\end{array}\right]\left[\begin{array}{c}\mathrm{Iu1}\\ \mathrm{Iv1}\end{array}\right]& \left(7\right)\end{array}$

After the transformation to the currents of two axes, the control CPU 190 computes deviations of currents Id1 and Iq1 actually flowing through the d and q axes from current command values Id1* and Iq1* of the respective axes, which are calculated from the torque command value Tm1* of the first motor MG1, and subsequently determines voltage command values Vd1 and Vq1 with respect to the q and a axes at step S116. In accordance with a concrete procedure, the control CPU 190 executes arithmetic operations of Equations (8) and Equations (9) given below. In Equations (9), Kp1, Kp2, Ki1, and Ki2 represent coefficients, which are adjusted to be suited to the characteristics of the motor applied. Each voltage command value Vd1 (Vq1) includes a part in proportion to the deviation ΔI from the current command value I* (the first term on the right side of Equation (9)) and a summation of historical data of the deviations ΔI for ‘i’ times (the second term on the right side).
ΔId1=i1*−Id1
Δiq1=Iq1*−Iq1   (8)
vd1=Kp1·ΔId1+IKi1·ΔId1
Vq1=Kp2·ΔIq1+IKi2·bIq1   (9)

The control CPU 190 then re-transforms the coordinates of the voltage command values thus obtained (two-phase to three-phase transformation) at step S118. This corresponds to an inverse of the transformation executed at step S114. The inverse transformation determines voltages Vu1, Vv1, and Vw1 actually applied to the three-phase coils 134 as expressed by Equations (10) given below: $\begin{array}{cc}\left[\begin{array}{c}\mathrm{Vu1}\\ \mathrm{Vv1}\end{array}\right]=\sqrt{\frac{2}{3}}\left[\begin{array}{cc}\cos \mathrm{\theta 1}& -\sin \mathrm{\theta 1}\\ \cos \left(\mathrm{\theta 1}-120\right)& -\sin \left(\mathrm{\theta 1}-120\right)\end{array}\right]\left[\begin{array}{c}\mathrm{Vd1}\\ \mathrm{Vq1}\end{array}\right]\mathrm{Vw1}=\mathrm{Vu1}-\mathrm{Vv1}& \left(10\right)\end{array}$
driving circuit 191. At step S119, the on- and off-time of the transistors Tr1 through Tr6 in the first driving circuit 191 is PWM (pulse width modulation) controlled, in order to attain the voltage command values Vu1, Vv1, and Vw1 determined by Equations (10) given above.

It is assumed that the torque command values Tm1* of the first motor MG1 is positive when the torque Tm1 is applied in the direction shown in the nomograms of FIGS. 8 and 9. For an identical positive torque command value Tm1*, the first motor MG1 is controlled to carry out the regenerative operation when the torque command value Tm1* acts in reverse of the rotation of the sun gear shaft 125 as in the state of the nomogram of FIG. 8, and controlled to carry out the power operation when the torque command value Tm1* acts in the direction of rotation of the sun gear shaft 125 as in state of the nomogram of FIG. 9. For the positive torque command value Tm1*, both the regenerative operation and the power operation of the first motor MG1 implement the identical switching control. In accordance with a concrete procedure, the transistors Tr1 through Tr6 in the first driving circuit 191 are controlled to enable a positive torque to be applied to the sun gear shaft 125 by the combination of the magnetic field generated by the permanent magnets 135 set on the outer surface of the rotor 132 with the revolving magnetic field generated by the currents flowing through the three-phase coils 134. The identical switching control is executed for both the regenerative operation and the power operation of the first motor MG1 as long as the sign of the torque command value Tm1* is not changed. The braking control routine shown in the flowchart of FIG. 11 is thus applicable to both the regenerative operation and the power operation.

The above control procedure sets the dynamic collinear line either in the state of the nomogram of FIG. 8 or in the state of the nomogram of FIG. 9 and enables the braking force to be applied to the ring gear shaft 126 and eventually to the driving wheels 116 and 118.

As discussed above, the power output apparatus 110 of the embodiment carries out the braking control by the first motor MG1 and the engine 150 and enables the braking force to be applied to the ring gear shaft 126 and eventually to the driving wheels 116 and 118. The procedure of adequately specifying the magnitude of the braking torque Tr* output to the ring gear shaft 126 by taking into account the revolving speed Nr of the ring gear shaft 126 enables the first motor MG1 to carry out the regenerative operation for braking and charge the battery 194 or enables the first motor MG1 to carry out the power operation for braking and discharge the battery 194. Namely the first motor MG1 can implement braking by the regenerative operation or by the power operation according to the remaining charge BRM of the battery 194.

In the braking control routine of the embodiment, the torque command value Tm1* of the first motor MG1 and the target revolving speed Ns* of the sun gear shaft 125 are set to enable the preset braking torque Tr* to be output to the ring gear shaft 126 by means of the first motor MG1 and the engine 150. In accordance with another possible application, the braking torque Tr* may be set based on the remaining charge BRM of the battery 194. This structure keeps the remaining charge BRM of the battery 194 at a desired level.

Although the fuel injection into the engine 150 is stopped in the embodiment, the fuel injection may be carried out to rotate the engine 150 at an idle revolving speed or another adequate revolving speed. The torque Te working as a reaction in the latter case is different from that in the case of the embodiment. The relationship between the amount of fuel injection, the revolving speed Ne, and the torque Te working as a reaction should thus be determined in advance and stored as a map.

The braking control procedure of the embodiment positively controls the first motor MG1, in order to enable the braking torque Tr* to be applied to the ring gear shaft 126 as a braking force. An alternative braking control procedure electromagnetically fixes the rotor 132 of the first motor MG1, that is, locks up the first motor MG1, in order to enable the braking force to be applied to the ring gear shaft 126. FIG. 12 is a nomogram in this state. While the sun gear shaft 125 is fixed, the planetary gear 120 works as a reduction gear. The rotation of the ring gear shaft 126 multiplied by a reduction ratio is accordingly transmitted as the rotation of the crankshaft 156. This is equivalent to the operation of engine brake. The control operation of the first motor MG1 in this case turns off all the transistors Tr1 through Tr6 in the first driving circuit 191 for driving the first motor MG1.

The following describes the braking control procedure by the first motor MG1, the second motor MG2, and the engine 150. As mentioned previously, the braking control by the first motor MG1, the second motor MG2, and the engine 150 is a combination of the braking control by the first motor MG1 and the engine 150 with the braking control by the second motor MG2. This braking control includes a variety of operations: for example, the operation of applying a braking force corresponding to the step-on amount of the brake pedal 165 to the ring gear shaft 126 and the operation of applying a braking force to the ring gear shaft 126 irrespective of the step-on of the brake pedal 165 while the vehicle runs down a long, continuous slope. In this embodiment, the operation of applying a braking force corresponding to the step-on amount of the brake pedal 165 to the ring gear shaft 126 follows a torque control routine in a braking state shown in the flowcharts of FIGS. 13 and 14. The operation of applying a braking force to the ring gear shaft 126 irrespective of the step-on of the brake pedal 165 while the vehicles runs down a long, continuous slope, follows a continuous braking control routine shown in the flowchart of FIG. 24.

The torque control routine in the braking state shown in the flowcharts of FIGS. 13 and 14 is executed repeatedly at predetermined time intervals (for example, at every 8 msec) while the vehicle runs. When the program enters the routine of FIG. 13, the control CPU 190 of the controller 180 first reads the brake pedal position BP detected by the brake pedal position sensor 165a at step S120. The driver steps on the brake pedal 165 to apply the braking force to the driving wheels 116 and 118. The value of the brake pedal position BP accordingly represents the desired braking torque which the driver requires. The control CPU 190 subsequently determines the braking torque Tr* to be output to the ring gear shaft 126, based on the input brake pedal position BP at step S122. Not the braking torque to be output to the driving wheels 116 and 118 but the braking torque Tr* to be output to the ring gear shaft 126 is determined here according to the brake pedal position BP. This is because the ring gear shaft 126 is mechanically linked with the driving wheels 116 and 118 via the power feed gear 128, the power transmission gear 111, and the differential gear 114 and the determination of the braking torque Tr* to be output to the ring gear shaft 126 thus results in determining the braking torque to be output to the driving wheels 116 and 118. In this embodiment, a map representing the relationship between the braking torque Tr* and the brake pedal position BP is prepared in advance and stored in the ROM 190b. In accordance with a concrete procedure, at step S122, the braking torque Tr* corresponding to the input brake pedal position BP is read from the map stored in the ROM 190b.

The control CPU 190 then reads the remaining charge BRM of the battery 194 measured by the remaining charge meter 199 at step S124, and compares the input remaining charge BRM of the battery 194 with a threshold value Bref at step S126. The threshold value Bref is set as a value close to the fully charged state in which the battery 194 does not require any further charging, and depends upon the type and characteristics of the battery 194. FIG. 15 is a graph showing the relationship between the remaining charge BRM of the battery 194 and the chargeable electric power with the threshold value Bref.

In case that the remaining charge BRM of the battery 194 is less than the threshold value Bref at step S126, the program determines the necessity for charging the battery 194 and sets the torque command value Tm1* of the first motor MG1 equal to zero at step S128 while setting the braking torque Tr* to a torque command value Tm2* of the second motor MG2 at step S130. The control CPU 190 then outputs a signal to stop the fuel injection into the engine 150 from the communication port to the EFIECU 170 at step S132. The program subsequently controls the first motor MG1, the second motor MG2, and the engine 150 based on the preset values at steps S134 through S138. As a matter of convenience of illustration, the control operation of the first motor MG1, the second motor MG2, and the engine 150 are shown as separate steps. In the actual procedure, however, these control operations are carried out in parallel and comprehensively. By way of example, the control CPU 190 simultaneously controls the first motor MG1 and the second motor MG2 by utilizing an interrupting process, while transmitting an instruction to the EFIECU 170 through communication in order to allow the EFIECU 170 to control the engine 150 concurrently.

The control of the first motor MG1 follows a control routine of the first motor MG1 shown in the flowchart of FIG. 16, whereas the control of the second motor MG2 follows a control routine of the second motor MG2 shown in the flowchart of FIG. 17. These control routines are identical with the processing of steps S110 through S119 in the braking control routine of FIG. 11 and are not specifically described here. When the torque command value Tm1* of the first motor MG1 is set equal to zero, the control of the first motor MG1 does not follow the control routine of the first motor MG1 shown in the flowchart of FIG. 16 but turns off all the transistors Tr1 through Tr6 in the first driving circuit 191, as discussed previously. The control of the engine 150 is carried out by the EFIECU 170 which receives the instructions to stop the fuel injection. The EFIECU 170 actually stops the fuel injection as well as the ignition with the ignition plug 162, thereby stopping the operation of the engine 150.

When the remaining charge BRM of the battery 194 is determined to be less than the threshold value Bref at step S126, the operation of setting both the torque Tm1 of the first motor MG1 and the torque Tm2 of the second motor MG2 equal to zero and stopping the operation of the engine 150 (fuel injection) discussed above with the nomogram of FIG. 7 is combined with the operation of enabling the second motor MG2 to apply a torque corresponding to the torque command value Tm2* to the ring gear shaft 126. As shown in the nomogram of FIG. 18, this procedure stops the engine 150 and races the first motor MG1. As discussed previously, this state consumes the least energy, so that a greater portion of the rotational energy (kinetic energy) of the ring gear shaft 126 can be regenerated as electrical energy by the second motor MG2 and stored in the battery 194.

In case that the remaining charge BRM of the battery 194 is not less than the threshold value Bref at step S126, on the other hand, the program determines no necessity for charging the battery 194 and carries out the processing of steps S140 through S152 shown in the flowchart of FIG. 14. This processing sets the torque command value Tm1* of the first motor MG1 and the torque command value Tm2* of the second motor MG2, in order to enable a braking force to be applied to the ring gear shaft 126 while not charging the battery 194. In the routine of FIG. 14, the control CPU 190 of the controller 180 first reads with revolving speed Nr of the ring gear shaft 126 and the revolving speed Ns of the sun gear shaft 125 at step S140, and calculates a braking energy Pr required for braking by Pr=Tr*×Nr at step S142.

The control CPU 190 then sets the target torque Te* and the target revolving speed Ne* of the engine 150 based on the calculated braking energy Pr at step S144. The energy consumed by the engine 150 is identical with the product of the torque Te working as a reaction force and the revolving speed Ne of the engine 150. The braking energy Pr and the target torque Tr* and the target revolving speed Ne* of the engine 150 accordingly satisfy the relationship of Pr=Te*×Ne*. As discussed previously with the graph of FIG. 10, the relationship between the revolving speed Ne of the engine 150 and the torque Te working as a reaction force is determined unequivocally. The required operation accordingly finds a specific point at which the product becomes equal to the braking energy Pr and specifies the torque Te and the revolving speed Ne at the specific point as the target torque Te* and the target revolving speed Ne* of the engine 150. By way of example, the specific point can be obtained as an intersection of a curve A representing the relationship between the revolving speed Ne of the engine 150 and the torque Te working as a reaction force and a constant energy curve Pr as shown in the graph of FIG. 19. In this embodiment, the braking energy Pr and the corresponding revolving speed Ne and torque Te of the engine 150 are stored in the form of a map in the ROM 190b. In accordance with a concrete procedure, at step S144, the revolving speed Ne and the torque Te corresponding to the calculated braking energy Pr are read from the map stored in the ROM 190b and set as the target engine speed Ne* and the target engine torque Te*.

The control CPU 190 then calculates the target revolving speed Ns* of the sun gear shaft 125 according to Equation (5) given above at step S146, and calculates and sets the torque command value Tm1* of the first motor MG1 according to Equation (11) given below at step S148. Equation (11) is similar to Equation (6), except that the first term on the right side depends upon the target torque Te* of the engine 150. $\begin{array}{cc}{\mathrm{Tm1}}^{*}\leftarrow {\mathrm{Te}}^{*}\times \frac{\rho }{1+\rho }+\mathrm{K1}\left({\mathrm{Ns}}^{*}-\mathrm{Ns}\right)+\mathrm{K2}\int \left({\mathrm{Ns}}^{*}-\mathrm{Ns}\right)dt& \left(11\right)\end{array}$

After setting the torque command value Tm1* of the first motor MG1, the control CPU 190 calculates an electrical energy Pm1 consumed or regenerated by the first motor MG1 according to Equation (12) given below at step S150, and calculates and sets the torque command value Tm2* of the second motor MG2 from the calculated electrical energy Pm1 according to Equation (13) given below at step S152. Km1 and Km2 denote motor efficiencies of the first motor MG1 and the second motor MG2. $\begin{array}{cc}\mathrm{Pm1}\leftarrow \mathrm{Km1}\times {\mathrm{Tm1}}^{*}\times \mathrm{Ns}& \left(12\right)\\ {\mathrm{Tm2}}^{*}\leftarrow \mathrm{Km2}\times \frac{\mathrm{Pm1}}{\mathrm{Nr}}& \left(13\right)\end{array}$

The program then returns to step S132 in the flowchart of FIG. 13 to output a signal for stopping the fuel injection into the engine 150 from the communication port to the EFIECU 170 at step S132, and controls the first motor MG1, the second motor MG2, and the engine 150 based on the preset values at steps S134 through S138.

As an example of such control, the nomogram of FIG. 20 shows the state when the first motor MG1 is controlled to carry out the power operation. Referring to FIG. 20, the ring gear shaft 126 receives the braking torque Tr* as the sum of the divisional torque Ter based on the torque Te working as a reaction and the torque Tm2 corresponding to the torque command value Tm2* output from the second motor MG2. Although not specifically illustrated, the dynamic collinear line falls into the state shown in the nomogram of FIG. 8 when the first motor MG1 is controlled to carry out the regenerative operation. In case that the first motor MG1 carries out the regenerative operation and the second motor MG2 carries out the power operation, the torque output from the second motor MG2 has the direction opposite to the direction of the torque Tm2 shown in FIG. 20.

When the remaining charge BRM of the battery 194 is not less than the threshold value Bref at step S126 in the flowchart of FIG. 13, the electrical energy Pm1 consumed or regenerated by the first motor MG1 is regenerated or consumed by the second motor MG2. The battery 194 is accordingly neither charged nor discharged. This process enables a desired braking force to be output to the ring gear shaft 126 while neither charging nor discharging the battery 194.

In the torque control routine in the braking state of the embodiment, when the remaining charge BRM of the battery 194 is less than the threshold value Bref at step S126, the program sets the torque command value Tm1* of the first motor MG1 equal to zero, thereby stopping the engine 150 and racing the first motor MG1. In accordance with another possible application, however, the engine 150 may be driven at a desired revolving speed. By way of example, in order to drive the engine 150 at a predetermined revolving speed Nst, the processing of steps S128 and S130 in the torque control routine in the braking state shown in the flowcharts of FIGS. 13 and 14 may be replaced with the processing of steps S180 through S188 in a modified torque control routine in the braking state shown in the flowchart of FIG. 21.

In the modified torque control routine in the braking state of FIG. 21, the control CPU 190 of the controller 180 sets the predetermined revolving speed Nst to the target revolving speed Ne* of the engine 150 at step S180, and reads a torque Tst working as a reaction force and corresponding to the predetermined revolving speed Nst from the map (for example, the map of FIG. 10) at step S181. The control CPU 190 then reads the revolving speed Nr of the ring gear shaft 126 at step S182 and calculates the target revolving speed Ns* of the sun gear shaft 125 according to Equation (5) given above at step S184. The control CPU 190 subsequently calculates and sets the torque command value Tm1* of the first motor MG1 according to Equation (14) given below at step S186, and calculates and sets the torque command value Tm2* of the second motor MG2 according to Equation (15) given below at step S188. The program then carries out the processing of steps S132 through S138 in the flowchart of FIG. 13. The nomogram of FIG. 22 shows the state when such control is carried out. The control of the first motor MG1 enables the engine 150 to be driven at the predetermined revolving speed Nst. $\begin{array}{cc}{\mathrm{Tm1}}^{*}\leftarrow \mathrm{Tst}\times \frac{\rho }{1+\rho }+\mathrm{K1}\left({\mathrm{Ns}}^{*}-\mathrm{Ns}\right)+\mathrm{K2}\int \left({\mathrm{Ns}}^{*}-\mathrm{Ns}\right)dt& \left(14\right)\\ {\mathrm{Tm2}}^{*}\leftarrow {\mathrm{Tr}}^{*}-\mathrm{Tst}\times \frac{1}{1+\rho }& \left(15\right)\end{array}$

This modified procedure does not stop the operation of the engine 150 but allows the rotation of the engine 150 at the predetermined revolving speed Nst. When the driver steps on the accelerator pedal 164 in the course of braking control and requires the engine 150 to output the energy Pe corresponding to the step-on amount of the accelerator pedal 164, this modified procedure more quickly realizes the requirement than the procedure of the embodiment. The predetermined revolving speed Nst set to the target revolving speed Ne* of the engine 150 at step S180 may be varied with a variation in revolving speed Nr of the ring gear shaft 126 as shown in the graph of FIG. 23. This further enhances the speed of the procedure of outputting the required energy from the engine 150.

As mentioned above, the operation of applying a braking force to the ring gear shaft 126 irrespective of the step-on of the brake pedal 165 while the vehicle runs down a long, continuous slope, follows a continuous braking control routine shown in the flowchart of FIG. 24. This routine is executed when the driver sets a continuous braking torque Tr2* and steps on neither the accelerator pedal 164 nor the brake pedal 165. The continuous braking torque Tr2* is set through an operation of a switch disposed near the driver's seat. In this embodiment, the continuous braking torque Tr2* can be selected among three different stages.

When the program enters the routine of FIG. 24, the control CPU 190 of the controller 180 first reads the continuous braking torque Tr2* at step S200. The continuous braking torque Tr2* is set through the operation of the switch by the driver and written at a predetermined address in the RAM 190a. In accordance with a concrete procedure, the control CPU 190 reads the data of continuous braking torque Tr2* previously written at the predetermined address at step S200. The control CPU 190 then reads the remaining charge BRM of the battery 194 detected by the remaining charge meter 199 at step S202, and compares the input remaining charge BRM with the threshold value Bref at step S204.

In case that the remaining charge BRM of the battery 194 is not less than the threshold value Bref at step S204, the program determines no necessity for charging the battery 194 and carries out the processing of steps S206 through S218 to set the torque command value Tm1* of the first motor MG1 and the torque command value Tm2* of the second motor MG2, so as to enable the continuous braking torque Tr2* to be output to the ring gear shaft 126 while neither charging nor discharging the battery 194. The processing of steps S206 through S218 is identical with the processing of steps S140 through S152 in the torque control routine in the braking state shown in the flowcharts of FIGS. 13 and 14. The procedure of setting the torque command value Tm1* of the first motor MG1 and the torque command value TM2* of the second motor MG2 in this manner enables the continuous braking torque Tr2* to be output to the ring gear shaft 126 while the battery 194 is kept intact, as discussed previously with the routine of FIGS. 13 and 14.

In case that the remaining charge BRM of the battery 194 is less than the threshold value. Bref at step S204, on the other hand, the program determines the necessity for charging the battery 194 and sets the torque command value Tm1* of the first motor equal to zero at step S220 while setting the continuous braking torque Tr2* to the torque command value Tm2* of the second motor MG2 at step S222. The processing of steps S220 and S222 is equivalent to the processing of steps S128 and S130 in the torque control routine in the braking state shown in the flowcharts of FIGS. 13 and 14. The procedure of setting the torque command value Tm1* of the first motor MG1 and the torque command value Tm2* of the second motor MG2 in this manner enables the continuous braking torque Tr2* to be output to the ring gear shaft 126 while the battery 194 is charged, as discussed previously with the routine of FIGS. 13 and 14.

After setting the torque command value Tm1* of the first motor MG1 and the torque command value Tm2* of the second motor MG2, the program outputs a signal for stopping the fuel injection into the engine 150 to the EFIECU 170 at step S224 and controls the first motor MG1, the second motor MG2, and the engine 150 based on the preset values at steps S226 through S230. The processing of steps S226 through S230 is identical with the processing of steps S134 through S138 in the torque control routine in the braking state shown in the flowcharts of FIGS. 13 and 14.

The continuous braking control routine allows the torque corresponding to the preset continuous braking torque Tr2* to be output to the ring gear shaft 126 even when the driver does not step on the brake pedal 165. The vehicle can accordingly run down a long, continuous slope without requiring the driver to continue stepping on the brake pedal 165.

The continuous braking control routine is carried out while the driver steps on neither the accelerator pedal 164 nor the brake pedal 165. This accordingly does not interfere with the torque control in an accelerating state based on the step-on amount of the accelerator pedal 164 or with the torque control in a braking state based on the step-on amount of the brake pedal 165.

This procedure can realize the braking control while the battery 194 is charged or while the battery 194 is kept intact, according to the remaining charge BRM of the battery 194. This keeps the remaining charge BRM of the battery 194 at the level of the threshold value Bref.

Although the magnitude of the continuous braking torque Tr2* is selected among the three different stages in this embodiment, it may be selected among a greater number of stages or fixed to one stage. In this embodiment, the driver sets the magnitude of the continuous braking torque Tr2*. The continuous braking torque Tr2* may, however, be set based on the revolving speed of the driving wheels 116 and 118, that is, the revolving speed Nr of the ring gear shaft 126, or the rate of change of the revolving speed Nr. The latter structure allows a greater braking torque to be output to the ring gear shaft 126 in case of the greater revolving speed Nr of the ring gear shaft 126 (that is, when the vehicle runs at a high speed) or in case of the greater rate of change of the revolving speed Nr of the ring gear shaft 126 (that is, the greater rate of change of the vehicle speed).

In the continuous braking control routine of the embodiment, the braking control with the charge of the battery 194, which is executed when the remaining charge BRM of the battery 194 is less than the threshold value Bref, sets the torque command value Tm1* of the first motor MG1 equal to zero and stops the operation of the engine 150. As discussed with the modified routine of FIG. 21, however, the revolving speed Ne of the engine 150 may be set equal to the predetermined revolving speed Nst. This structure enables the engine 150 to output the required energy quickly in response to the step-on of the accelerator pedal 164.

In the continuous braking control routine of the embodiment, the braking control without the charge of the battery 194, which is executed when the remaining charge BRM of the battery 194 is not less than the threshold value Bref, controls the first motor MG1 and the second motor MG2 to enable the electrical energy Pm1 regenerated or consumed by the first motor MG1 to be consumed or regenerated by the second motor MG2, thereby allowing the continuous braking torque Tr2* to be output to the ring gear shaft 126. In accordance with another possible application, the braking force may be output to the ring gear shaft 126 while the first motor MG1 is kept in the lock-up state as shown in the nomogram of FIG. 12. In this case, although the preset continuous braking torque Tr2* can not be output to the ring gear shaft 126, the braking torque corresponding to the revolving speed Nr of the ring gear shaft 126 can be output to the ring gear shaft 126.

As discussed above, the power output apparatus 110 of the embodiment enables the braking torque Tr* or the continuous braking torque Tr2* to be output to the ring gear shaft 126 by means of the first motor MG1 and the engine 150 or by means of the first motor MG1, the second motor MG2, and the engine 150. Another possible structure outputs part of the braking torque Tr* or the continuous braking torque Tr2* to the ring gear shaft 126 by means of a mechanical friction brake while outputting the residual torque by means of the first motor MG1, the second motor MG2, and the engine 150.

In the power output apparatus 110 of the embodiment, the power output to the ring gear shaft 126 is taken out of the arrangement between the first motor MG1 and the second motor MG2 via the power feed gear 128 linked with the ring gear 122. Like another power output apparatus 110A shown in FIG. 25 as a modified example, however, the power may be taken out of the casing 119, from which the ring gear shaft 126 is extended. FIG. 26 shows still another power output apparatus 110B as another modified example, wherein the engine 150, the planetary gear 120, the second motor MG2, and the first motor MG1 are arranged in this sequence. In this case, a sun gear shaft 125B may not have a hollow structure, whereas a hollow ring gear shaft 126B is required. This modified structure enables the power output to the ring gear shaft 126b to be taken out of the arrangement between the engine 150 and the second motor MG2.

The following describes another power output apparatus 110C as a second embodiment according to the present invention. FIG. 27 schematically illustrates structure of an essential part of the power output apparatus 110C of the second embodiment. Referring to FIG. 27, the power output apparatus 110C of the second embodiment has a similar structure to that of the power output apparatus 110 of the first embodiment, except that the rotor 142 of the second motor MG2 is attached to the crankshaft 156 and that the first motor MG1 and the second motor MG2 have a different configuration. The same constituents as those of the power output apparatus 110 of the first embodiment shown in FIG. 1, as the controller 180, are omitted from the drawing of FIG. 27. The power output apparatus 110C of the second embodiment can also be mounted on the vehicle as shown in the drawing of FIG. 3. The same constituents in the power output apparatus 110C of the second embodiment as those in the power output apparatus 110 of the first embodiment are shown by like numerals and symbols and not specifically described here. The symbols used in the description of the first embodiment have the same meanings in the description of the second embodiment, unless other specified.

In the power output apparatus 110C of the second embodiment, the engine 150, the second motor MG2, the planetary gear 120, and the first motor MG1 are arranged in this sequence as shown in FIG. 27. The rotor 132 of the first motor MG1 is attached to a sun gear shaft 125C, which connects with the sun gear 121 of the planetary gear 120, whereas the planetary carrier 124 is linked with the crankshaft 156 of the engine 150 like the power output apparatus 110 of the first embodiment. The rotor 142 of the second motor MG2 and a resolver 157 for measuring a rotational angle θe of the crankshaft 156 are further attached to the crankshaft 156. A ring gear shaft 126C, which connects with the ring gear 122 of the planetary gear 120, is linked with the power feed gear 128. A resolver 149 for measuring a rotational angle θr of the ring gear shaft 126C is attached to the ring gear shaft 126C.

The power output apparatus 110C of the second embodiment has a different configuration from that of the power output apparatus 110 of the first embodiment. Like the power output apparatus 110 of the first embodiment, however, the three-phase coils 134 of the first motor MG1 is connected to the first driving circuit 191 of the controller 180, and the three-phase coils 144 of the second motor MG2 to the second driving circuit 192. Although not specifically illustrated, the resolver 157 is connected to the input port of the control CPU 190 of the controller 180 through a signal line.

The power output apparatus 110C of the second embodiment works in the following manner. By way of example, it is assumed that the engine 150 is driven at a driving point P1 of the revolving speed Ne and the torque Te and outputs an amount of energy Pe (Pe=Ne×Te) and that the ring gear shaft 126C is driven at another driving point P2 of the revolving speed Nr and the torque Tr and outputs an amount of energy Pr (Pr=Nr×Tr) identical with the energy Pe. This means that the power output from the engine 150 is subjected to the torque conversion and applied to the ring gear shaft 126C. FIGS. 28 and 29 are nomograms in this state.

Equations (16) through (19) given below are obtained from the equilibrium on the dynamic collinear line in the nomogram of FIG. 28. Equation (16) is obtained from the equilibrium of the energy Pe output from the engine 150 with the energy Pr output to the ring gear shaft 126C, and Equation (17) as the total energy input to the planetary carrier 124 via the crankshaft 156. Equations (18) and (19) are led by dividing a torque Tc acting on the planetary carrier 124 into divisional torques Tcs and Tcr acting on the coordinate axes S and R. $\begin{array}{cc}\mathrm{Te}\times \mathrm{Ne}=\mathrm{Tr}\times \mathrm{Nr}& \left(16\right)\\ \mathrm{Tc}=\mathrm{Te}+\mathrm{Tm2}& \left(17\right)\\ \mathrm{Tcs}=\mathrm{Tc}\times \frac{\rho }{1+\rho }& \left(18\right)\\ \mathrm{Tcr}=\mathrm{Tc}\times \frac{\rho }{1+\rho }& \left(19\right)\end{array}$

The equilibrium of forces on the dynamic collinear line is essential for the stable state of the dynamic collinear line. It is accordingly required to set the torque Tm1 equal to the divisional torque Tcs and the torque Tr equal to the divisional torque Tcr. The torques Tm1 and Tm2 are thus expressed by Equations (20) and (21) given below:
Tm1=Tmρ  (20)
Tm2=Tr×(1+ρ)−Te   (21)

The power output from the engine 150 and defined by the torque Te and the revolving speed Ne is converted to the power defined by the torque Tr and the revolving speed Nr and output to the ring gear shaft 126C by allowing the first motor MG1 to apply the torque Tm1 expressed by Equation (20) to the sun gear shaft 125C and allowing the second motor MG2 to apply the torque Tm2 expressed by Equation (21) to the crankshaft 156. In the state of the nomogram of FIG. 28, the direction of the torque output from the first motor MG1 is opposite to the direction of the rotation of the rotor 132. The first motor MG1 accordingly functions as a generator and regenerates the electrical energy Pm1 expressed at the product of the torque Tm1 and the revolving speed Ns. The direction of the torque output from the second motor MG2 is, on the other hand identical with the direction of the rotation of the rotor 142. The second motor MG2 accordingly functions as a motor and consumes the electrical energy Pm2 expressed as the product of the torque Tm2 and the revolving speed Nr.

Although the revolving speed Ns of the sun gear shaft 125C is positive in the nomogram of FIG. 28, it may be negative according to the revolving speed Ne of the engine 150 and the revolving speed Nr of the ring gear shaft 126C as shown in the nomogram of FIG. 29. In the latter case, the first motor MG1 applies the torque in the direction of rotation of the rotor 132 and thereby works as a motor to consume the electrical energy Pm1 given as the product the torque Tm1 and the revolving speed Ns. The second motor MG2, on the other hand, applies the torque in reverse of the rotation of the rotor 142 and thereby works as a generator to regenerate the electrical energy Pm2, which is given as the product of the torque Tm2 and the revolving speed Nr, from the ring gear shaft 126.

Like the operation principle of the power output apparatus 110 of the first embodiment, the operation principle of the second embodiment is on the assumption that the efficiency of power conversion by the planetary gear 120, the motors MG1 and MG2, and the transistors Tr1 through Tr16 is equal to the value ‘1’, which represents 100%. In the actual state, however, the conversion efficiency is less than the value ‘1’, and it is required to make the energy Pe output from the engine 150 a little greater than the energy Pr output to the ring gear shaft 126C or alternatively to make the energy Pr output to the ring gear shaft 126C a little smaller than the energy Pe output from the engine 150. As discussed previously, the energy loss due to the mechanical friction in the planetary gear 120 is significantly small and the synchronous motors used as the motors MG1 and MG2 have the efficiency very close to the value ‘1’, so that the efficiency of power conversion is practically equal to the value ‘1’. For the matter of convenience, in the following discussion of the second embodiment, the efficiency is thus considered equal to the value ‘1’ (=100%), unless other specified.

The braking control by the first motor MG1 and the engine 150 carried out in the power output apparatus 110 of the first embodiment is applicable to the power output apparatus 110C of the second embodiment, provided that the second motor MG2 is not driven. The first motor MG1 is accordingly controlled to carry out the regenerative operation or the power operation and enables a braking force to be output to the ring gear shaft 126C. The braking control by the first motor MG1 and the engine 150 has been discussed in detail with the drawings of FIGS. 7 through 12, and is not specifically described here. The following describes the braking control by the first motor MG1, the second motor MG2, and the engine 150 carried out in the power output apparatus 110C of the second embodiment. Since the second motor MG2 is not attached to the ring gear shaft 126C, the power output apparatus 110C of the second embodiment can not carry out the braking control by the second motor MG2.

In the braking control by the first motor MG1 and the engine 150 carried out in the power output apparatus 110 of the first embodiment, the torque Te acting as a reaction force is determined corresponding to the preset revolving speed Ne of the engine 150 in the graph of FIG. 10. The braking torque that can be output to the ring gear shaft 126 thus depends upon the revolving speed Ne of the engine 150. Namely the structure of the first embodiment can not increase or decrease the braking force output to the ring gear shaft 126 while keeping the revolving speed Ne of the engine 150 unchanged. In the power output apparatus 110C of the second embodiment, on the other hand, the second motor MG2 is attached to the crankshaft 156 of the engine 150 and can output the torque to the crankshaft 156, thereby enabling the braking force output to the ring gear shaft 126C to increase or decrease while keeping the revolving speed Ne of the engine 150 unchanged. The revolving speed Ne of the engine 150 in the braking state can be set to a desired level through the control of the second motor MG2. In the second embodiment, the braking control by the first motor MG1, the second motor MG2, and the engine 150 follows a torque control routine in a braking state shown in the flowcharts of FIGS. 30 and 31 and a continuous braking control routine shown in the flowchart of FIG. 34.

The torque control routine in the braking state shown in the flowcharts of FIGS. 30 and 31 is executed repeatedly at predetermined time intervals (for example, at every 8 msec) while the vehicle runs. When the programs enters the routine of FIG. 30, the control CPU 190 of the controller 180 first reads the revolving speed Ne of the engine 150 at step S300. The revolving speed Ne of the engine 150 may be calculated from the rotational angle θe of the crankshaft 156 measured by the resolver 157. Alternatively the revolving speed Ne of the engine 150 may be measured directly with the speed sensor 176 attached to the distributor 160. In the latter case, the control CPU 190 receives data of the revolving speed Ne from the EFIECU 170 connected to the speed sensor 176 through communication.

The control CPU 190 then reads the brake pedal position BP detected by the brake pedal position sensor 165a at step S302, and determines the braking torque Tr* to be output to the ring gear shaft 126C, based on the input brake pedal position BP at step S304. The procedure of determining the braking torque Tr* is identical with that explained in the first embodiment. The control CPU 190 subsequently reads the remaining charge BRM of the battery 194 measured by the remaining charge meter 199 at step S306, and compares the input remaining charge BRM of the battery 194 with the threshold value Bref at step S308.

In case that the remaining charge BRM of the battery 194 is less than the threshold value Bref at step S308, the program determines the necessity for charging the battery 194 and sets a calculated value according to the equation of Tm1*=Tr*×ρ to be torque command value Tm1* of the first motor MG1 at step S310 while setting a calculated value according to Equation (22) given below to the torque command value Tm2* of the second motor MG2 at step S312. The first term on the right side of Equation (22) is obtained from the equilibrium on the dynamic collinear line shown in the nomograms of FIGS. 28 and 29. The second term on the right side is a proportional term to cancel the deviation of the revolving speed Ne of the engine 150 from the value ‘0’, and the third term on the right side is an integral term to cancel the stationary deviation. In the stationary state (that is, when the revolving speed Ne of the engine 150 is equal to zero), the torque command value TM2* of the second motor MG2 is set equal to the first term on the right side Tr*×(1+ρ) obtained from the equilibrium on the dynamic collinear line. K3 and K4 in Equation (22) denote proportional constants.
Tm2*←Tr*×(1+ρ)−K3=Ne−K4∫Nedt   (22)

The control CPU 190 then outputs a signal for stopping the fuel injection into the engine 150 from the communication port to the EFIECU 170 at step S314 and controls the first motor MG1, the second motor MG2, and the engine 150 based on the preset values at steps S316 through S320. Like the first embodiment, although the control operations of the first motor MG1, the second motor MG2, and the engine 150 are shown as separate steps for convenience in the second embodiment, these control operations in the actual state are carried out in parallel and comprehensively. The control procedures of the first motor MG1, the second motor MG2, and the engine 150 at steps S316 through S320 in the routine of FIG. 30 of the second embodiment are identical with those at steps S134 through S318 in the torque control routine in the braking state of the first embodiment shown in the flowcharts of FIGS. 13 and 14, and thus not specifically described here.

When the remaining charge BRM of the battery 194 is determined to be less than the threshold value Bref at step S308, the control procedure enables the dynamic collinear line to fall into the state in which the engine 150 is at a stop, as shown in the nomogram of FIG. 32. In this state, while the second motor MG2 outputs the torque Tm2, the revolving speed Ne of the engine 150 is equal to zero. The energy consumed by the second motor MG2 accordingly gives a minimum value. Most of the energy generated by the braking operation can thus be regenerated by the first motor MG1 as the electrical energy, with which the battery 194 is charged. As clearly understood from the nomogram of FIG. 32, the process of locking up the second motor MG2 may substitute for the process of setting the torque command value Tm2* of the second motor MG2 at step S312.

In case that the remaining charge BRM of the battery 194 is not less than the threshold value Bref at step S308, on the other hand, the program determines no necessity for charging the battery 194 and carries out the processing of steps S330 through S338 shown in the flowchart of FIG. 31. This processing sets the torque command value Tm1* of the first motor MG1 and the torque command value Tm2* of the second motor MG2, in order to enable a braking force to be applied to the ring gear shaft 126C while not charging the battery 194. In the routine of FIG. 31, the control CPU 190 of the controller 180 first reads the revolving speed Nr of the ring gear shaft 126C at step S330, and calculates a braking energy Pr required for braking by Pr=Tr*×Nr at step S332.

The control CPU 190 then sets the target torque Te* and the target revolving speed Ne* of the engine 150 based on the calculated braking energy Pr at step S334. The relationship between the calculated braking energy Pr and the revolving speed Ne and the torque Te of the engine 150 and the technique of determining the target engine speed Ne* and the target engine torque Te* are discussed previously at step S144 in the torque control routine in the braking state of the first embodiment shown in the flowcharts of FIGS. 13 and 14.

The control CPU 190 subsequently sets a calculated value according to the equation of Tm1*=Tr*×ρ to the torque command value Tm1* of the first motor MG1 at step S336 while setting a calculated value according to Equation (23) given below to the torque command value Tm2* of the second motor MG2 at step S338. The first and the second terms on the right side of Equation (23) are obtained from the equilibrium on the dynamic collinear line shown in the nomogram of FIG. 33. The third term on the right side is a proportional term to cancel the deviation of the revolving speed Ne of the engine 150 from the target engine speed Ne*, and the fourth term on the right side is an integral term to cancel the stationary deviation. The nomogram of FIG. 33 shows the target driving state when the first motor MG1, the second motor MG2, and the engine 150 are controlled after the processing of steps S330 through S338.
Tm2*=←Tr*×(1+ρ)−Te*+K3(Ne*−Ne(Ne*−Ne)dt   (23)

The control CPU 190 then outputs a signal for stopping the fuel injection into the engine 150 from the communication port to the EFIECU 170 at step S314 and controls the first motor MG1, the second motor MG2, and the engine 150 based on the preset values at steps S316 through S320.

The control procedure enables a divisional torque Tcr (braking torque Tr*) based on the torque Tc, which is the sum of the torque Te working as a reaction and the torque Tm2 corresponding to the torque command value Tm2* output from the second motor MG2, to be applied to the ring gear shaft 126C, as shown in the nomogram of FIG. 33. In the state of the nomogram of FIG. 33, the revolving speed Ns of the sun gear shaft 125C is positive. The first motor MG1 is accordingly controlled to carry out the power operation, whereas the second motor MG2 is controlled to regenerate the electrical energy Pm1 that is consumed by the first motor MG1. When the revolving speed Ns of the sun gear shaft 125C is negative, on the contrary, the first motor MG1 carries out the regenerative operation and the second motor MG2 carries out the power operation to consume the electrical energy Pm1 that is regenerated by the first motor MG1.

When the remaining charge BRM of the battery 194 is determined to be not less than the threshold value Bref at step S308, the second motor MG2 regenerates or consumes the electrical energy Pm1 that is consumed or regenerated by the first motor MG1. The battery 194 is thus neither charged nor discharged. This procedure enables a desired braking force to be output to the ring gear shaft 126C while neither charging nor discharging the battery 194.

In the torque control routine in the braking state of the second embodiment, when the remaining charge BRM of the battery 194 is less than the threshold value Bref at step S308, the first motor MG1 and the second motor MG2 are controlled to make the revolving speed Ne of the engine 150 equal to zero. Another possible procedure may, however, control the first motor MG1 and the second motor MG2 to allow the engine 150 to be driven at a desired revolving speed. In this case, the revolving speed Ne of the engine 150 is controlled to a predetermined value by regulating the revolving speed Ns of the sun gear shaft 125C. For that purpose, the processing of steps S180 through S188 in the modified torque control routine in the braking state shown in the flowchart of FIG. 21 is applied to the structure of the second embodiment, in which the second motor MG2 is attached to the crankshaft 156. The modified procedure does not stop the operation of the engine 150 but allows the rotation of the engine 150 at the determined revolving speed. When the driver steps on the accelerator pedal 164 in the course of the braking control, this modified structure enables the required energy to be output from the engine 150 without delay.

The operation of applying a braking force to the ring gear shaft 126C irrespective of the step-on of the brake pedal 165 while the vehicle runs down a long, continuous slope, follows a continuous braking control routine shown in the flowchart of FIG. 34. Like the continuous braking control routine of the first embodiment shown in the flowchart of FIG. 24, this routine is executed when the driver sets a continuous braking torque Tr2* and steps on neither the accelerator pedal 164 nor the brake pedal 165. The continuous braking torque Tr2* is set through an operation of a switch disposed near the driver's seat. In the second embodiment, the continuous braking torque Tr2* can be selected among three different stages.

When the program enters the routine of FIG. 34, the control CPU 190 of the controller 180 first reads the continuous braking torque T42* at step S400, and receives the data of revolving speed Ne of the engine 150 at step S402. The continuous braking torque Tr2* is input in the same manner as the first embodiment. The control CPU 190 then reads the remaining charge BRM of the battery 194 detected by the remaining charge meter 199 at step S404, and compares the input remaining charge BRM with the threshold value Bref at step S406.

In case that the remaining charge BRM of the battery 194 is not less than the threshold value Bref at step S406, the program determines no necessity for charging the battery 194 and carries out the processing of steps S408 through S416 to set the torque command value Tm1* of the first motor MG1 and the torque command value Tm2* of the second motor MG2, so as to enable the continuous braking torque Tr2* to be output to the ring gear shaft 126C while neither charging nor discharging the battery 194. The processing of steps S408 through S416 is identical with the processing of steps S330 through S338 in the torque control routine in the braking state shown in the flowcharts of FIGS. 30 and 31. The procedure of setting the torque command value Tm1* of the first motor MG1 and the torque command value Tm2* of the second motor MG2 in this manner enables the continuous braking torque Tr2* to be output to the ring gear shaft 126C while the battery 194 is kept intact, as discussed previously.

In case that the remaining charge BRM of the battery 194 is less than the threshold value Bref at step S406, on the other hand, the program determines the necessity for charging the battery 194 and sets a calculated value according to the equation of Tm1*=Tr2*×ρ to the torque command value Tm1* of the first motor MG1 at step S418 while setting a calculated value according to Equation (22) to the torque command value Tm2* of the second motor MG2 at step S420. The processing of steps S418 and S420 is equivalent to the processing of steps S310 and S312 in the torque control routine in the braking state shown in the flowcharts of FIGS. 30 and 31. As discussed previously, the procedure of setting the torque command value Tm1* of the first motor MG1 and the torque command value Tm2* of the second motor MG2 in this manner enables the continuous braking torque Tr2* to be output to the ring gear shaft 126C while the battery 194 is charged.

After setting the torque command value Tm1* of the first motor MG1 and the torque command value Tm2* of the second motor MG2, the program outputs a signal for stopping the fuel injection into the engine 150 to the EFIECU 170 at step S422 and controls the first motor MG1, the second motor MG2, and the engine 150 based on the preset values at steps S424 through S428. The processing of steps S424 through S428 is identical with the processing of steps S134 through S138 in the torque control routine in the braking state of the first embodiment shown in the flowcharts of FIGS. 13 and 14.

The continuous braking control routine of the second embodiment allows the torque corresponding to the preset continuous braking torque Tr2* to be output to the ring gear shaft 126C even when the driver does not step on the brake pedal 165. The vehicle can accordingly run down a long, continuous slope without requiring the driver to continue stepping on the brake pedal 165. The continuous braking control routine is carried out while the driver steps on neither the accelerator pedal 164 nor the brake pedal 165. This accordingly does not interfere with the torque control in an accelerating state based on the step-on amount of the accelerator pedal 164 or with the torque control in a braking state based on the step-on amount of the brake pedal 165.

This procedure can realize the braking control while the battery 194 is charged or while the battery 194 is kept intact, according to the remaining charge BRM of the battery 194. This keeps the remaining charge BRM of the battery 194 at the level of the threshold value Bref.

List the first embodiment, although the magnitude of the continuous braking torque Tr2* is selected among the three different stages in the second embodiment, it may be selected among a greater number of stages or fixed to one stage. The continuous braking torque Tr2* may be set based on the revolving speed of the driving wheels 116 and 118, that is, the revolving speed Nr of the ring gear shaft 126C, or the rate of change of the revolving speed Nr. When the remaining charge BRM of the battery 194 is less than the threshold value Bref, the continuous braking control routine of the second embodiment stops the operation of the engine 150. As discussed previously, however, the revolving speed Ne of the engine 150 may be set equal to a predetermined value. This structure enables the engine 150 to output the required energy quickly in response to the step-on of the accelerator pedal 164.

As discussed above, the power output apparatus 110C of the second embodiment enables the braking torque Tr* or the continuous braking torque Tr2* to be output to the ring gear shaft 126C by means of the first motor MG1 and the engine 150 or by means of the first motor MG1, the second motor MG2, and the engine 150. Another possible structure outputs part of the braking torque Tr* or the continuous braking torque Tr2* to the ring gear shaft 126C by means of a mechanical friction brake while outputting the residual torque by means of the first motor MG1, the second motor MG2, and the engine 150.

In the power output apparatus 110C of the second embodiment, the second motor MG2 is interposed between the engine 150 and the first motor MG1. Like another power output apparatus 110D given as a modified example in FIG. 35, however, the engine 150 may be interposed between the first motor MG1 and the second motor MG2. In the power output apparatus 110C of the second embodiment, the power output to the ring gear shaft 126C is taken out of the arrangement between the first motor MG1 and the second motor MG2 via the power feed gear 128 linked with the ring gear 122. Like still another power output apparatus 110E shown in FIG. 36 as another modified example, however, the power may be taken out of the casing 119, from which a ring gear shaft 126E is extended.

In the power output apparatus 110 of the first embodiment, the power output apparatus 110C of the second embodiment, and their modified examples, the crankshaft 156 is linked with the planetary carrier 124 of the planetary gear 120, whereas the sun gear shaft 125 is linked with the first motor MG1 and the ring gear shaft 126 is linked with the power transmission gear 111, which connects with the drive shaft 112, via the power feed gear 128. The crankshaft 156, the first motor MG1, and the power transmission gear 111 may, however, be linked with the three shafts of the planetary gear 120 in any desired combination. In any case, the input and output powers, that is, the respective torque command values in each torque control procedure, can be readily obtained from the nomograms.

The present invention is not restricted to the above embodiments or its modified examples, but there may be many modifications, changes, and alterations without departing from the scope or spirit of the main characteristics of the present invention.

The power output apparatus 110 of the first embodiment and its modified examples discussed above are applied to the FR-type or FF-type two-wheel-drive vehicle. In another modified example of FIG. 37, however, a power output apparatus 110F is applied to a four-wheel-drive vehicle. In this structure, the second motor MG2 is separated from the ring gear shaft 126 and independently arranged in the rear-wheel portion of the vehicle, so as to drive the rear driving wheels 117 and 119. The ring gear shaft 126 is, on the other hand, connected to the differential gear 114 via the power feed gear 128 and the power transmission gear 111, in order to drive the front driving wheels 116 and 118. The torque control procedures of the first embodiment are also applicable to this structure.

Although the gasoline engine is used as the engine 150 in the power output apparatus 110 of the first embodiment and the power output apparatus 110C of the second embodiment, the principle of the invention is also applicable to other internal combustion engines and external combustion engines, such as Diesel engines, turbine engines, and jet engines.

In the power output apparatus 110 of the first embodiment and the power output apparatus 110 of the second embodiment, the planetary gear 120 is used as the three shaft-type power input/output means. Another available example is a double-pinion planetary gear having plural sets of planetary pinion gears. One planetary gear in each pair is linked with the sun gear while the other is linked with the ring gear, and the pair of planetary pinion gears are linked with each other to revolve around the sun gear while rotating on its axis. Another other devices or gear unit, such as a differential gear, is also applicable for the three shaft-type power input/output means, as long as it can determine powers input to and output from the residual one shaft based on predetermined powers input to and output from any two shafts among the three shafts.

Permanent magnet (PM)-type synchronous motors are used as the first motor MG1 and the second motor MG2 in the first and the second embodiments discussed above. Any other motors which can implement both the regenerative operation and the power operation, such as variable reluctance (VR)-type synchronous motors, vernier motors, d.c. motors, induction motors, superconducting motors, and stepping motors, may, however, be used according to the requirements.

Transistor inverters are used as the first and the second driving circuits 191 and 192 in the power output apparatus 110 of the first embodiment and the power output apparatus 110C of the second embodiment. Other available examples include IGBT (insulated gas bipolar mode transistor) inverters, thyristor inverters, voltage PWM (pulse width modulation) inverters, square-wave inverters (voltage inverters and current inverters), and resonance inverters.

The battery 194 in the above embodiments may include Pb cells, NiMH cells, Li cells, or the like cells. A capacitor may be used in place of the battery 194.

Although the power output apparatus is mounted on the vehicle in all the above embodiments, it may be mounted on other transportation means like ships and airplanes as well as a variety of industrial machines.

It should be clearly understood that the above embodiments are only illustrative and not restrictive in any sense. The scope and spirit of the present invention are limited only by the terms of the appended claims.

Claims

1. A power output apparatus for outputting power to a drive shaft, said power output apparatus comprising:

an engine having an output shaft;

a motor having a rotating shaft and inputting and outputting power to and from said rotating shaft;

three shaft-type power input/output means having three shafts, including the output shaft and the rotating shaft, respectively linking said engine and said drive shaft, said three shaft-type power input/output means inputting and outputting power to and from a residual one shaft, based on predetermined powers input to and output from any two shafts among said three shafts;

storage battery means for supplying and receiving an electrical energy required for inputting and outputting power to and from said motor; and

braking control means for controlling said engine and said motor, based on a charging state of said storage battery means, in order to enable a braking force to be applied to said drive shaft.

2. A power output apparatus in accordance with claim 1, wherein said braking control means comprises means for enabling said motor to carry out a regenerative operation, thereby applying a braking force to said drive shaft.

3. A power output apparatus in accordance with claim 1, for outputting power to a drive shaft, said power output apparatus comprising:

an engine having an output shaft;

a motor having a rotating shaft and inputting and outputting power to and from said rotating shaft;

three shaft-type power input/output means having three shafts, including the output shaft and the rotating shaft, respectively linking said engine and said drive shaft, said three shaft-type power input/output means inputting and outputting power to and from a residual one shaft, based on predetermined powers input to and output from any two shafts among said three shafts;

storage battery means for supplying and receiving an electrical energy required for inputting and outputting power to and from said motor; and

braking control means for controlling said engine and said motor, based on charging state of said storage battery means, in order to enable a braking force to be applied to said drive shaft, wherein said braking control means comprises means for enabling said motor to carry out a power operation, thereby applying a braking force to said drive shaft.

4. A power output apparatus in accordance with claim 1, wherein said braking control means comprises means for controlling said motor, in order to enable said motor to motor said engine.

5. A power output apparatus in accordance with claim 1, for outputting power to a drive shaft, said power output apparatus comprising:

an engine having an output shaft;

a motor having a rotating shaft and inputting and outputting power to and from said rotating shaft;

three shaft-type power input/output means having three shafts, including the output shaft and the rotating shaft, respectively linking said engine and said drive shaft, said three shaft-type power input/output means inputting and outputting power to and from a residual one shaft, based on predetermined powers input to and output from any two shafts among said three shafts;

storage battery means for supplying and receiving an electrical energy required for inputting and outputting power to and from said motor; and

braking control means for controlling said engine and said motor, based on a charging state of said storage battery means, in order to enable a braking force to be applied to said drive shaft, wherein said braking control means comprises means for locking up said motor.

6. A power output apparatus in accordance with claim 1, said power output apparatus further comprising:

a second motor for inputting and outputting power to and from said drive shaft, in addition to said motor working as a first motor,

wherein said storage battery comprises means for supplying and receiving an electrical energy required for inputting and outputting power to and from said second motor,

said braking control means comprising means for controlling said engine, said first motor, and said second motor, in order to enable a braking force to be applied to said drive shaft.

7. A power output apparatus in accordance with claim 6, said power output apparatus further comprising:

charging state detection means for detecting the charging state of said storage battery means,

wherein said braking control means comprises means for controlling said engine, said first motor, and said second motor based on the charging state of said storage battery means detected by said detection means, thereby applying a braking force to said drive shaft.

8. A power output apparatus in accordance with claim 7, wherein said braking control means comprises means for regulating the charging state of said storage battery means detected by said charging state detection means to be within a predetermined range.

9. A power output apparatus in accordance with claim 6, wherein said braking control means comprises means for controlling said second motor in order to enable said second motor to apply a braking force to said drive shaft, while controlling said first motor in order to make power input to and output from said motor equal to zero.

10. A power output apparatus in accordance with claim 6, wherein said braking control means comprises means for controlling said second motor in order to enable said second motor to apply a braking force to said drive shaft, while controlling said engine and said first motor in order to set a driving state of said engine to a predetermined operating condition.

11. A power output apparatus in accordance with claim 10, said power output apparatus further comprising:

driving state detection means for detecting a driving state of said drive shaft; and

braking-time driving state setting means for setting the redetermined predetermined operating condition based on the driving state of said drive shaft detected by said driving state detection means.

12. A power output apparatus in accordance with claim 10, wherein the driving state of said engine represents a revolving speed of said output shaft of said engine.

13. A power output apparatus in accordance with claim 6, wherein said braking control means comprises means for controlling said first motor, in order to enable said first motor to motor said engine.

14. A power output apparatus in accordance with claim 6, wherein said braking control means comprises means for controlling said first motor and said second motor, in order to enable an electrical energy represented by said second motor to be identical with an electrical energy consumed by said first motor.

15. A power output apparatus in accordance with claim 1, said power output apparatus further comprising:

a second motor for inputting and outputting power to and from said output shaft of said engine, in addition to said motor working as a first motor,

wherein said storage battery means comprises means for supplying and receiving an electrical energy required for inputting and outputting power to and from said second motor,

said braking control means comprising means for controlling said engine, said first motor, and said second motor, in order to enable a braking force to be applied to said drive shaft.

16. A power output apparatus in accordance with claim 15, said power output apparatus further comprising:

charging state detection means for detecting the charging state of said storage battery means,

wherein said braking control means comprises means for controlling said engine, said first motor, and said second motor based on the charging state of said storage battery means detected by said charging state detection means.

17. A power output apparatus in accordance with claim 16, wherein said braking control means comprises means for regulating the charging state of said storage battery means detected by said charging state detection means to be within a predetermined range.

18. A power output apparatus in accordance with claim 15, wherein said braking control means comprises means for controlling said first motor in order to enable said first motor to motor said engine, while controlling said second motor in order to enable said second motor to apply a braking force to said output shaft of said engine.

19. A power output apparatus in accordance with claim 15, wherein said braking control means comprises means for controlling said first motor and said second motor, in order to enable an electrical energy regenerated by said second motor to be identical with an electrical energy consumed by said first motor.

20. A method of controlling a power output apparatus for outputting power to a drive shaft, said method comprising the steps of:

(a) providing (1) engine having an output shaft; (2) a first motor having a rotating shaft and inputting and outputting power to and from said rotating shaft; (3) a second motor for inputting and outputting power to and from said drive shaft; and (4) three shaft-type power input/output means having three shafts, including the output shaft and the rotating shaft, respectively linking said engine and said drive shaft, said three shaft-type power input/output means inputting and outputting power to and from a residual one shaft, based on predetermined powers input to and output from any two shafts among said three shafts;

(b) controlling said second motor, in order to enable said second motor to apply a braking force to said drive shaft; and

(c) controlling said engine and said first motor, in order to set a driving state of said engine to a predetermined operating condition.

21. A method of controlling a power apparatus for outputting power to a drive shaft, said method comprising the steps of:

(a) providing (1) an engine having an output shaft; (2) a first motor having a rotating shaft and inputting and outputting power to and from said rotating shaft; (3) a second motor for inputting and outputting power to and from said drive shaft; (4) three shaft-type power input/output means having three shafts respectively linking said engine and said drive shaft, said three shaft-type power input/output means inputting and outputting power to and from a residual one shaft, based on predetermined powers input to and output from any two shafts among said three shafts; and (5) storage battery means for supplying and receiving an electrical energy required for inputting and outputting power to and from said first motor, and supplying and receiving an electrical energy required for inputting and outputting power to and from said second motor; and

(b) controlling said engine, said first motor, and said second motor, in order to apply a braking force to said drive shaft while keeping a charging state of said storage battery means within a predetermined range.

22. A power output apparatus for outputting power to a drive shaft, said power output apparatus comprising:

an engine having an output shaft;

a motor having a rotating shaft and inputting and outputting power to and from said rotating shaft;

three shaft-type power input/output means having three shafts, including the output shaft and the rotating shaft, respectively linking said engine and said drive shaft, said three shaft-type power input/output means inputting and outputting power to and from a residual one shaft, based on predetermined powers input to and output from any two shafts among said three shafts;

storage battery means for supplying and receiving an electrical energy required for inputting and outputting power to and from said motor; and

braking control means for controlling said engine and said motor, based on a charging state of said storage battery, in order to enable a braking force to be applied to said drive shaft;

a remaining charge detection means that detects the remaining charge of the storage battery means; and

an engine driving means that drives said engine in a predetermined operating condition, which enables said motor to regenerate electric power, when the remaining charge of the battery is less than a predetermined threshold value.

23. A method of controlling a power output apparatus, for outputting power to a drive shaft, having an engine with an output shaft, a motor with a rotating shaft, and a three shaft-type power input/output means having three shafts, including the output shaft and the rotating shaft, respectively linking said engine and said drive shaft, the method comprising:

inputting and outputting power to and from said rotating shaft;

inputting and outputting power, via the three shaft-type power input/output means, to and from a residual one shaft, based on predetermined powers input to and output from any two shafts among said three shafts;

supplying and receiving an electrical energy, from a storage battery means, required for inputting and outputting power to and from said motor;

controlling, using a braking controlling means, said engine and said motor based on a charging state of said storage battery means, in order to enable a braking force to be applied to said drive shaft; and

enabling said motor to carry out a power operation, thereby applying a braking force to said drive shaft by means of said braking control means.