Drive arrangement with collectorless d.c. motor

Abstract

Drive arrangement comprising a collectorless d.c. motor and a rpm-regulating arrangement. The motor comprises a permanent-magnet rotor and a stator winding arrangement. The latter is connected to a current source in dependence upon angular-position signals by means of an electrical commutation arrangement. The rpm-regulating arrangement produces a regulator signal that is a function of the deviation of the rotor's actual rpm from a desired rpm. There is provided an arrangement for modulating the regulator signal in synchronism with the rotation of the rotor. As a result of the action of the modulation arrangement, the current flowing in the stator winding arrangement between each two successive commutation operations initially builds up beginning at a point in time at least approximately coinciding with the point in time at which the commutation occurs, and the drops off again until a point in time at least approximately coinciding with the point in time at which the next-following commutation occurs.

Description

converts the hump-shaped voltage 49 into a modulation signal indicated at 52 which, at least approximately, has the shape of a rectified sinusoidal voltage with its points of inflection coinciding with the points in time 57, 58 at which commutation is to occur. The modulation signal 52 is applied via a coupling capacitor 54, a coupling resistor 55 and a line 56 to the actual-value input of the rpm regulator 40 in order to be superimposed there onto the actual-rpm signal produced by the tachometric generator 42. As a result, the normal regulator signal at the output 38 of the rpm regulator 40--i.e. formed without the feeding back of the modulation signal 52--becomes modulated in synchronism with rotation of the rotor 10 in such a fashion that the current flowing in the stator winding arrangement 11, 12 between each two successive commutation operations initially builds up in a sinusoid-like way beginning at a point in time at least approximately coinciding with the point in time at which there occurs the commutations (i.e. the switch-over from the phase winding 11 to the phase winding 12, or vice versa); reaches a maximum value midway between the two successively occurring commutation operations; and then drops off again in a sinusoid-like way until a point in time at least approximately coinciding with the point in time at which there occurs the next-following commutation operation (i.e. the switch-over from the phase winding 12 to the phase winding 11, or vice versa). The current in the stator winding arrangement 11, 12 reaches a minimum value at the point in time at which commutation occurs. This manner of modulating the current serves during operation the purpose of especially quiet running. Acoustic noise during the commutation is avoided in an effective way. The sinusoidal current in the stator winding arrangement has an especially effective noise-reducing action above all in the case where the motor is of so-called asymmetric construction. Asymmetric construction is herein to be understood to mean that the rotor magnet projects out beyond the stator iron farther at one side than at the other, such as illustrated for example in FIG. 1 of the above mentioned U.S. Pat. No. 4,430,603.

If desired the line 56 can also lead to the desired-value input 43 or to the output 38 of the rpm regulator 40, in the manner indicated in FIG. 1 by broken lines or by dash-dot lines. In the last-mentioned case, an amplifier stage 59 indicated in broken lines in FIG. 1 is possible to be inserted between the resistor 55 and the output 38.

The inventive principle explained herein can also be applied to motors other than those of the two-phase, two-pulse type. FIG. 2 depicts an arrangement is accordance with the invention having a four-phase, four-pulse collectorless d.c. motor comprising four phase windings 11, 12, 11', 12' which are offset by 90°-el. and receive per electrical rotation a cyclical succession of four current pulses via respective semiconductor elements--each of which in the illustrated embodiment is again a combination of end-stage and preceding-stage transistors 13, 14, 15, 16, 13', 15', 16'. To this end there are provided two angular-position transducer arrangements 25, 25' which furnish commutation signals 34, 34', 36, 36', offset one from the next by 90°-el., to four control lines 33, 33', 37, 37'. Two additional diodes 45', 46' are connected between the junction 48 and the junctions of the collectors of transistors 13', 14', with the phase windings 11', 12'. The hump-shaped voltage 49' has a frequency equal to four times the frequency of the commutation signals 34, 34', 36, 36'. In other respects the construction and manner of operation corresponds to that of the arrangement in FIG. 1.

The rpm regulator 40 can be designed in any known manner. Especially suitable are, among others, rpm regulators is accordance with U.S. Pat. No. 4,240,014 of Rolf Mu/ ller, the disclosure of which is incorporated herein by reference.

The angular-position transducer arrangements 25, or 25 and 25', can be in principle be constructed in any other known manner. For example optical angular-position transducers can be provided of the type in which a light beam is interrupted with a frequency dependent upon rotor rpm.

Drive arrangements of the type set forth herein are especially suitable for, among other things, the drives of hard-disk magnetic data storages and the like.

Claims

1. Drive arrangement having a collectorless d.c. motor comprising a permanent-magnet rotor and a stator winding arrangement; an angular-position transducer arrangement which during operation furnishes angular-position signals that are a function of the angular position of the rotor; an electrical commutation arrangement which receives the angular-position signals and selectively connects the stator winding arrangement to a current source; an rpm-measuring arrangement for generating an actual-rpm signal corresponding to the rotor's actual rpm; a desired-value signal generator for furnishing a signal corresponding to the desired rotor rpm; an rpm-regulating arrangement having respective inputs for the actual-rpm signal and desired-rpm signal and an output, for generating a regulator signal that appears at the output of the rpm-regulating arrangement and is a function of the deviation of the actual rpm from the desired rpm of the rotor, and which controls the supply of current to the stator winding arrangement; and an arrangement for modulating the regulator signal by superimposing a modulating signal separate from the actual rpm signal and the desired rpm signal and in synchronism with the rotor's rotation, in such a fashion that the current flowing in the stator winding arrangement between each two successive commutation operations initially builds up beginning at a point in time at least approximately coinciding with the point in time at which the commutation occurs, and then drops off again until a point in time at least approximately coinciding with the point in time at which the next-following commutation occurs.

2. Drive arrangement . .according to claim 1.!. having a collectorless d.c. motor comprising a permanent-magnet rotor and a stator winding arrangement; an angular-position transducer arrangement which during operation furnishes angular-position signals that are a function of the angular position of the rotor; and electrical commutation arrangement which receives the angular-position signals and selectively connects the stator winding arrangement to a current source; and rpm-measuring arrangement for generating an actual-rpm signal corresponding to the rotor's actual rpm; a desired-value signal generator for furnishing a signal corresponding to the desired rotor rpm; and rpm-regulating arrangement having respective inputs for the actual-rpm signal and desired-rpm signal and an output, for generating a regulator signal that appears at the output of the rpm-regulating arrangement and is a function of the deviation of the actual rpm from the desired rpm of the rotor, and which controls to the supply of current to the stator winding arrangement; and an arrangement for modulating the regulator signal in synchronism with the rotor's rotation, in such a fashion that the current flowing in the stator winding arrangement between each two successive commutation operations initially builds up beginning at a point in time at least approximately coinciding with the point in time at which the commutation occurs and then drops off again until a point in time at least approximately coinciding with the point in time at which the next-following commutation occurs, the modulation arrangement being so designed that, superimposed upon the regulator signal that represents a function of the deviation of the actual rpm from the desired rpm, there is a signal corresponding at least approximately to a rectified sinusoid whose points of inflection coincide with the points in time at which commutation occurs.

3. Drive arrangement according to claim 1, the modulation arrangement producing a modulation signal that is superimposed upon the actual-rpm signal.

4. Drive arrangement according to claim 1, the modulation arrangement producing a modulation signal that is superimposed upon the desired-rpm signal.

5. Drive arrangement according to claim 1, the modulation arrangement producing a modulation signal which is superimposed upon the regulator signal that represents a function of the deviation of the actual rpm from the desired rpm of the rotor.

6. Drive arrangement . .according to claim 1.!. having a collectorless d.c. motor comprising a permanent-magnet rotor and a stator winding arrangement; an angular-position transducer arrangement which during operation furnishes angular-position signals that are a function of the angular position of the rotor; an electrical commutation arrangement which receives the angular-position signals and selectively connects the stator winding arrangement to a current source; an rpm-measuring arrangement for generating an actual-rpm signal corresponding to the rotor's actual rpm; a desired-value signal generator for furnishing a signal corresponding to the desired rotor rpm; and rpm-regulating arrangement having respective inputs for the actual-rpm signal and desired-rpm signal and an output, for generating a regulator signal that appears at the output of the rpm-regulating arrangement and is a function of the deviation of the actual rpm from the desired rpm of the rotor, and which controls the supply of current to the stator winding arrangement; and an arrangement for modulating the regulator signal in synchronism with the rotor's rotation, in such a fashion that the current flowing the stator winding arrangement between each two successive commutation operations initially builds up beginning at a point in time at least approximately coinciding with the point in time at which the commutation occurs and then drops off again until a point in time at least approximately coinciding with the point in time at which the next-following commutation occurs, the stator winding arrangement being provided with means for coupling out the voltages that are induced in the windings of the stator winding arrangement and form . .the.!. a modulation signal.

7. Drive arrangement according to claim 6, the modulation arrangement comprising a filter arrangement for shaping the modulation signal into a wave shape approximating to a rectified sinusoid voltage.

8. Drive arrangement having a collectorless d.c. motor comprising

a permanent-magnet rotor and

a stator winding arrangement;

an angular-position transducer arrangement which during operation furnishes angular-position signals that are a function of the angular position of the rotor,

an electrical commutation arrangement which receives the angular-position signals and selectively connects the stator winding arrangement to a current source;

a motor-operation sensing arrangement for generating an actual-value signal having a value corresponding to a predetermined aspect of rotor rotation;

a desired-value signal generator for furnishing a desired-value signal corresponding to the desired value of said predetermined aspect of rotor rotation;

an rpm-regulating arrangement having input means for receipt of signals from which information can be derived concerning the deviation of said desired value from said actual value and having output means, and operative for generating a regulator signal which appears at said output means and which is a function of said deviation, and which controls the supply of current to the stator winding arrangement in a manner maintaining the rpm of said rotor at a predetermined value; and

an arrangement for modulating the regulator signal by superimposing a modulating signal separate from the actual-value signal and the desired-value signal and in synchronism with the rotor's rotation, in such a fashion that the current flowing in the stator winding arrangement between each two successive commutation operations initially builds up beginning at a point in time at least approximately coinciding with the point in time at which the commutation occurs, and then drops off again until a point in time at least approximately coinciding with the point in time at which the next-following commutation occurs.

9. Drive arrangement according to claim 8, the modulation arrangement producing a modulation signal corresponding at least approximately to a rectified sinusoid whose points of inflection coincide with the points in time at which commutation occurs. 10. Drive arrangement according to claim 8, the modulation arrangement producing a modulation signal that is superimposed upon the actual-value signal. 11. Drive arrangement according to claim 8, the modulation arrangement producing a modulation signal that is superimposed upon the desired-value signal. 12. Drive arrangement according to claim 8, the modulation arrangement producing a modulation signal that is superimposed upon the regulator signal which is a function of the deviation of said desired value from said actual value.

Drive arrangement according to claim 8, the stator winding arrangement being provided with means for coupling out voltages that are induced in windings of the stator winding arrangement and form the modulation signal. 14. Drive arrangement according to claim 13, the modulation arrangement comprising a filter arrangement for shaping the modulation signal into a wave shape approximating a rectified sinusoid voltage.