A valve lifter with a variable lift mechanism is required to be deployed at a predetermined angle with respect to a cam unit, and the present invention is intended to achieve this requirement with a simple configuration without too much processing such as a fitting of the conventional longitudinal groove and a pin.
A cam sliding contact surface of a valve lifter on which a high lift cam and a low lift cam slides is formed to be a smooth inclined surface and a cam slide starting point is lower than a cam slide terminating point, thereby establishing an elevation difference between the cam slide starting point and the cam slide terminating point. As a result, since the high lift cam and the low lift cam always move uphill on the cam sliding contact surface, namely, from the low cam slide starting point toward the high cam terminating point along the slope of the cam sliding contact surface, the valve lifter is not subjected to a force around the reciprocating axis from the cam and therefore, the direction of the valve lifter is maintained constant.
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2. A cylindrical direct-acting valve lifter of an internal combustion engine with a variable lift mechanism which can switch between a high lifter comprising a high lift cam sliding surface with which a high lift cam comes into slidable contact and low lifter comprising a low lift cam sliding surface with which a low lift cam comes into slidable contact, wherein;
the high lift cam sliding surface and the low lift cam sliding surface are integrally formed with an upper surface of the valve lifter and are formed as inclined surfaces whose surface roughness is smooth;
each of the inclined surfaces of the cam sliding contact surfaces is formed by a crowned surface and a cam slide starting point on the cam sliding contact surface is positioned to be lower than a cam slide terminating point thereon; and
the high lift cam and the low lift cam come into point contact with a the cam slide starting point on the cam sliding contact surface that is higher than a center of the cam sliding contact surface, the high lifter and the low lifter rotate due to friction resistance generated by a rotation of the high lift cam and the low lift cam, the cam slide starting point is arrived to a lower position on the cam sliding contact surface and the rotation of the high lift cam lifter and the low lift cam lifter stops, and the high lift cam and the low lift cam moves along the inclined surface of the cam sliding contact surface to the cam slide terminating point that is higher than the cam slide starting point.
3. A cylindrical direct-acting valve lifter of an internal combustion engine with a variable lift mechanism which can switch between a high lifter comprising a high lift cam sliding surface with which a high lift cam comes into slidable contact and low lifter comprising a low lift cam sliding surface with which a low lift cam comes into slidable contact, wherein;
the high lift cam sliding surface and the low lift cam sliding surface are integrally formed with an upper surface of the valve lifter and are formed as inclined surfaces whose surface roughness is smooth;
each of the inclined surfaces of the cam sliding contact surfaces is formed by a reverse-crowned surface and a cam slide starting point on the cam sliding contact surface is positioned to be lower than a cam slide terminating point thereon; and
the high lift cam and the low lift cam come into point contact with a the cam slide starting point on the cam sliding contact surface that is higher than a center of the cam sliding contact surface, the high lifter and the low lifter rotate due to friction resistance generated by a rotation of the high lift cam and the low lift cam, the cam slide starting point is arrived to a lower position on the cam sliding contact surface and the rotation of the high lift cam lifter and the low lift cam lifter stops, and the high lift cam and the low lift cam moves along the inclined surface of the cam sliding contact surface to the cam slide terminating point that is higher than the cam slide starting point.
1. A cylindrical direct-acting valve lifter of an internal combustion engine with a variable lift mechanism which can switch between a high lifter comprising a high lift cam sliding surface with which a high lift cam comes into slidable contact and low lifter comprising a low lift cam sliding surface with which a low lift cam comes into slidable contact, wherein;
the high lift cam sliding surface and the low lift cam sliding surface are integrally formed with an upper surface of the valve lifter and are formed as inclined surfaces whose surface roughness is smooth;
each of the inclined surfaces of the cam sliding contact surfaces is formed by a flat surface inclined with respect to a plane perpendicular to a reciprocating direction of the valve lifter and a cam slide starting point on the cam sliding contact surface that is the inclined surface is positioned to be lower than a cam slide terminating point thereon; and
the high lift cam and the low lift cam come into point contact with a the cam slide starting point on the cam sliding contact surface that is higher than a center of the cam sliding contact surface, the high lifter and the low lifter rotate due to friction resistance generated by a rotation of the high lift cam and the low lift cam, the cam slide starting point is arrived to a lower position on the cam sliding contact surface and the rotation of the high lift cam lifter and the low lift cam lifter stops, and the high lift cam and the low lift cam moves along the inclined surface of the cam sliding contact surface to the cam slide terminating point that is higher than the cam slide starting point.
4. The cylindrical direct-acting valve lifter of an internal combustion engine of
a hydraulic pressure pin laterally penetrating the high lifter is provided so that the high lifter and the low lifter can be switched by moving the hydraulic pressure pin so as to insert a leading end portion into the low lifter, thereby integrating the high lifter and the low lifter, or moving the hydraulic pressure pin away from the low lifter, thereby disconnecting the high lifter and the low lifter.
5. The cylindrical direct-acting valve lifter of an internal combustion engine of
a hydraulic pressure pin laterally penetrating the high lifter is provided so that the high lifter and the low lifter can be switched by moving the hydraulic pressure pin so as to insert a leading end portion into the low lifter, thereby integrating the high lifter and the low lifter, or moving the hydraulic pressure pin away from the low lifter, thereby disconnecting the high lifter and the low lifter.
6. The cylindrical direct-acting valve lifter of an internal combustion engine of
a hydraulic pressure pin laterally penetrating the high lifter is provided so that the high lifter and the low lifter can be switched by moving the hydraulic pressure pin so as to insert a leading end portion into the low lifter, thereby integrating the high lifter and the low lifter, or moving the hydraulic pressure pin away from the low lifter, thereby disconnecting the high lifter and the low lifter.
7. The cylindrical direct-acting valve lifter of an internal combustion engine of
one half of the crowned surface with respect to a center thereof is formed as a horizontal plane and another half of the crowned surface is formed as a declivitous plane, and a border between the horizontal plane and the declivitous plane is continuously connected by a smooth curved plane.
8. The cylindrical direct-acting valve lifter of an internal combustion engine of
one half of the reverse-crowned surface with respect to a center thereof is formed as a declivitous plane and another half of the reverse-crowned surface is formed as a horizontal plane, and a border between the declivitous plane and the horizontal plane is continuously connected by a smooth curved plane.
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This application claims priority to International Patent Application No. PCT/JP2012/072158 filed on Aug. 31, 2012, the entire contents of which are hereby incorporated by reference. U.S. Pat. No. 9,657,606 is a continuation of PCT/JP2012/072158 the entirety of which is incorporated herein by reference.
The present invention relates to a cylindrical direct-action valve lifter of an internal combustion engine incorporated in a valve train of the internal combustion engine. Among such valve lifters, the present invention particularly relates to a valve lifter with a variable lift mechanism.
This type of the valve lifter is configured to enable an amount of lift to be altered between a high valve lift and a low valve lift by switching operation of a cam unit integrating a high lift cam and a low lift cam between its high lifter with a high lift cam sliding contact surface and its low lifter with a low lift cam sliding contact surface. Generally, in the case where the lift is high, a high efficiency can be achieved at a high revolution while the efficiency is lowered at a low revolution. To the contrary, in the case where the lift is low, a high efficiency can be achieved at a low revolution while the efficiency is lowered at a high revolution. Therefore, the lift of the valve is switched between a high lift suitable for a high revolution and a low lift suitable for a low revolution.
The valve lifter with a variable lift mechanism having the above configuration has to be deployed at a predetermined angle with respect to the cam unit.
One reason is to prevent the cam and the valve lifter from colliding with each other. If the valve lifter rotates around the reciprocating axis and changes the direction thereof, the high lifter deviates from its fixed position and in the case where the internal combustion engine is driven using the low lift cam, the high lift cam comes off the high lifter and crashes into the low lifter to be destroyed.
A second reason is to prevent an oil feeding passage from deviating in position. In the valve lifter with a variable lift mechanism having the above configuration, a cam switching mechanism of the valve lifter is operated by feeding hydraulic pressure from the side of the engine and if the valve lifter rotates and the direction thereof changes, the position of the oil feeding opening on the engine side and that of the oil receiving port on the valve lifter side deviate from each other, whereby the feeding of oil is hindered and the cam switching mechanism acts up.
For these reasons, the valve lifter needs to be deployed at a predetermined angle with respect to the cam unit, in other words, the valve lifter is required to have directionality relative to the cam unit. Conventionally, these needs are satisfied by providing a detent means in the valve lifter.
For example, in
The reference numeral 105 in
In the thus constituted valve lifter with a variable lift mechanism, the same technical advantages can be obtained as those in
The conventional detent means requires too much processing such as the forming of the longitudinal groove, the attachment of the pin and the like, and the detent means is not only troublesome to manufacture the detent means but also complicating in configuration. Therefore, the detent means is inevitably abraded away and degraded in durability. Thus, the conventional detent means gives arise troubles such as the occurrence of a strange sound.
The problem to be solved by the present invention is to achieve the desirable directionality of the valve lifter with a variable lift mechanism without complicating the structure of the valve lifter.
According to the present invention, the cam sliding contact surface with which a high lift cam and a low lift cam come into slidable contact is formed to be a smooth inclined surface and a position of the sliding contact surface at which the cam initially comes into contact is disposed lower than a position of the sliding contact surface at which the cam ceases to be in contact, thereby establishing an elevation difference between these points.
In the present invention, both a high lift cam and a low lift cam slide uphill on an inclined cam sliding contact surface, namely, from a lower region of the sliding contact surface with which the cam initially comes into contact toward a higher region of the sliding contact surface at which the cam ceases to be in contact. As a result, since the sliding locus of the cam on the cam sliding contact surface is along the slope of the inclined surface of the cam sliding contact surface, the valve lifter is not subjected to a force around the reciprocating axis from the cam and therefore, the direction of the valve lifter is maintained constant.
Thus, according to the present invention, unlike the conventional detent means, since the detent can be realized by simply machining the cam sliding contact surface into an inclined surface, thereby reducing the number of components and the weight of the valve lifter. Further, since it is unnecessary to form a longitudinal groove for preventing rotation on the side of the cylinder bore, processing cost can be reduced. Excellent technical advantages such as simplicity of assembling components, ease of fabricating the valve lifter, and enhanced reliability of the valve lifter thanks to elimination of the risk of abrasion and occurrence of a strange sound.
In
The reference numeral 18 designates a cylinder bore and the intake port 12 is closed by pressing the intake valve 13 against the intake port 12 using a coil spring 19 provided in the cylinder bore 18. The cam 16 (16a or 16b) is constituted so as to press the valve lifter 15 downward in
The cam sliding contact surface 20 of the valve lifter 15 is provided with a high lifter 15a having a high lift cam sliding contact surface 20a and low lifters 15b, 15b having low lift cam sliding contact surfaces 20b, 20b (See
As apparent from the above, in the state shown in
In
Here, the cam sliding contact surface 20 (the high lift cam sliding contact surface 20a and/or the low lift cam sliding contact surface 20b) according to the present invention is configured as a smooth inclined surface.
As a result, as shown in
The same applies to a case where the cam 16 rotates in the reverse direction.
In the case where the cam 16 rotates in the reverse direction, the cam slide starting point corresponds to point B in
As apparent from the above, according to the present invention, since the cam sliding contact surface 20 is configured as an inclined surface, the cam slide starting point arrives at the low position L of the cam sliding contact surface 20 and the rotation of the valve lifter 15 stops, irrespective of the rotational direction of the cam 16.
The inclined surface of the cam sliding contact surface 20 is not limited to a flat surface (See
As shown in
In the example in which the cam sliding contact surface 20 has the reverse crowned shape, similarly to in the case of the cam sliding contact surface 20 having the crowned shape, the cam slide starting point becomes lower than the cam slide terminating point B.
In the case where the outer diameter of the valve lifter 15 is equal to 30 mm, it is necessary for the elevation difference to exceed 15 μm and it is preferable for the elevation difference to be equal to or larger than 30 μm. By calculations, the mean gradient is equal to or larger than 0.05% (=0.015/30×100).
Moreover, there are valve lifters with a variable lift mechanism which are different in arrangement relationship between the high lifter having the high cam sliding contact surface and the low lifter having the low cam sliding contact surface.
The present invention can be widely applied to a valve lifter with a variable lift mechanism built in an internal combustion engine of, for example, an automobile, industrial vehicle or the like.
The reference numeral 11 designates a cylinder head, the reference numeral 12 designates an intake port, the reference numeral 13 designates an intake valve, the reference numeral 14 designates a valve stem, the reference numeral 15 designates a valve lifter, the reference numeral 16 designates a cam, the reference numeral 18 designates a cylinder bore, the reference numeral 19 designates a coil spring, the reference numeral 20 designates a cam sliding contact surface, the reference symbol A designates a cam slide starting point on the cam sliding contact surface, and the reference symbol B designates a cam slide terminating point on the cam sliding contact surface, respectively.
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