Valve timing adjustment device

A bearing portion of a planetary rotatable body for providing bearing support in a thrust direction is defined as a planetary thrust bearing portion. A driving-side rotatable body or a driven-side rotatable body, which is configured to contact the planetary thrust bearing portion in the thrust direction, is defined as a specific rotatable body. A bearing portion of the specific rotatable body for providing bearing support in the thrust direction is defined as a specific thrust bearing portion. In a parallel state where the specific thrust bearing portion and the planetary thrust bearing portion are parallel to each other, the specific thrust bearing portion and the planetary thrust bearing portion contact with each other only on one of an eccentric side and a counter-eccentric side of the planetary rotatable body while the counter-eccentric side is opposite to the eccentric side.

TECHNICAL FIELD

The present disclosure relates to a valve timing adjustment device.

BACKGROUND

A previously proposed valve timing adjustment device includes a planetary gear mechanism which has an internal gear section and a planetary gear section. The valve timing adjustment device adjusts a rotational phase of a driven-side rotatable body relative to a driving-side rotatable body. The planetary gear section is urged against the internal gear section by a resilient member to reduce a noise and an impact force generated when the planetary gear section and the internal gear section collide with each other due to, for example, a change in a cam torque.

SUMMARY

According to the present disclosure, there is provided a valve timing adjustment device that includes a driving-side rotatable body, a driven-side rotatable body and a planetary rotatable body. A bearing portion of the planetary rotatable body for providing bearing support in a thrust direction is defined as a planetary thrust bearing portion. The driving-side rotatable body or the driven-side rotatable body, which is configured to contact the planetary thrust bearing portion in the thrust direction, is defined as a specific rotatable body. A bearing portion of the specific rotatable body for providing bearing support in the thrust direction is defined as a specific thrust bearing portion. In a parallel state where the specific thrust bearing portion and the planetary thrust bearing portion are parallel to each other, the specific thrust bearing portion and the planetary thrust bearing portion contact with each other only on one of an eccentric side and a counter-eccentric side of the planetary rotatable body while the counter-eccentric side is opposite to the eccentric side.

DETAILED DESCRIPTION

A previously proposed valve timing adjustment device includes a planetary gear mechanism which has an internal gear section and a planetary gear section. The valve timing adjustment device adjusts a rotational phase of a driven-side rotatable body relative to a driving-side rotatable body. The planetary gear section is urged against the internal gear section by a resilient member to reduce a noise and an impact force generated when the planetary gear section and the internal gear section collide with each other due to, for example, a change in a cam torque.

However, deteriorations in quietness and durability of the valve timing adjustment device are also caused by a collision between the components in the thrust direction in the valve timing adjustment device.

According to the present disclosure, there is provided a valve timing adjustment device configured to be installed to an internal combustion engine and adjust a valve timing of a valve that is opened and closed by a camshaft with a torque transmitted from a crankshaft. The valve timing adjustment device includes a driving-side rotatable body, a driven-side rotatable body, an internal gear section, a planetary rotatable body, an eccentric shaft, and a transmission mechanism. The driving-side rotatable body is configured to be rotated synchronously with the crankshaft about a rotational axis that is coaxial with the camshaft. The driven-side rotatable body is configured to be rotated integrally with the camshaft about the rotational axis. The internal gear section is formed at one of the driven-side rotatable body and the driving-side rotatable body. The planetary rotatable body has a planetary gear section. The planetary gear section is eccentric to the rotational axis and is meshed with the internal gear section. The eccentric shaft supports the planetary rotatable body. The transmission mechanism is configured to transmit rotation between the planetary rotatable body and another one of the driven-side rotatable body and the driving-side rotatable body.

A bearing portion of the planetary rotatable body for providing bearing support in a thrust direction is defined as a planetary thrust bearing portion. The driving-side rotatable body or the driven-side rotatable body, which is configured to contact the planetary thrust bearing portion in the thrust direction, is defined as a specific rotatable body. A bearing portion of the specific rotatable body for providing bearing support in the thrust direction is defined as a specific thrust bearing portion. In a parallel state where the specific thrust bearing portion and the planetary thrust bearing portion are parallel to each other, the specific thrust bearing portion and the planetary thrust bearing portion contact with each other only on one of an eccentric side and a counter-eccentric side of the planetary rotatable body while the counter-eccentric side is opposite to the eccentric side.

As described above, the specific thrust bearing portion and the planetary thrust bearing portion contact with each other on the one of the eccentric side and the counter-eccentric side and are spaced from each other on the other one of the eccentric side and the counter-eccentric side. In this way, a higher degree of freedom of tilting and a higher degree of positioning precision of the planetary rotatable body can be achieved. When the planetary rotatable body is tilted, a projected size of the planetary rotor in the axial direction is increased, and a clearance in the thrust direction between the planetary rotatable body and the specific rotatable body sides is reduced. In addition, the planetary rotatable body and the driving-side rotatable body contact with each other while changing the tilt angle of the planetary rotatable body relative to the driving-side rotatable body, so that the impact force is reduced. Therefore, the noise and the impact force, which are caused by the collision between the planetary rotatable body and the specific rotatable body, can be reduced, and thereby it is possible to achieve the improved quietness and the improved durability.

Hereinafter, embodiments of a valve timing adjustment device will be described with reference to the drawings. The same reference sign is used for substantially identical constituent elements among the embodiments, and description of the same will be omitted for the sake of simplicity. In addition, not only the combination of the configurations explicitly mentioned in the description of each embodiment, but also partial combinations of the constituent elements of respective embodiments can be made even if such a combination is not explicitly mentioned as long as there is no particular obstacle to the combination.

First Embodiment

As shown inFIG. 1, a valve timing adjustment device10according to a first embodiment is installed to a torque transmission path that extends from a crankshaft5to a camshaft6at an internal combustion engine of a vehicle. The camshaft6opens and closes intake valves or exhaust valves (not shown) which serve as valves. The valve timing adjustment device10adjusts the valve timing of these valves.

The valve timing adjustment device10includes an actuator11, a control unit12and a phase shift unit13.

The actuator11is an electric motor such as a brushless motor. The actuator11includes a housing21and a control shaft22. The housing21rotatably supports the control shaft22. The control unit12includes, for example, a motor driver, a microcomputer, and the like, and rotationally drives the control shaft22by controlling energization of the actuator11.

As shown inFIGS. 1 to 4, the phase shift unit13includes a driving-side rotatable body23, a driven-side rotatable body24, an eccentric shaft25, a planetary rotatable body26, and a transmission mechanism27.

The driving-side rotatable body23is coaxial with the camshaft6and includes a sprocket member31, which is shaped in a bottomed tubular form, and a cover member32, which is shaped in a stepped tubular form and is joined to the sprocket member31. The driving-side rotatable body23receives the other constituent members24,25,26,27. The sprocket member31is coupled to the crankshaft5through a transmission member7such as a chain. Therefore, the driving-side rotatable body23is rotated about a rotational axis O, which is coaxial with the camshaft6, synchronously with the crankshaft5.

The driven-side rotatable body24is shaped in a bottomed tubular form and is fixed to an end part of the camshaft6through a bottom of the driven-side rotatable body24. The driven-side rotatable body24is coaxial with the camshaft6and rotatably supports the sprocket member31from a radially inner side of the sprocket member31. Therefore, the driven-side rotatable body24is rotated integrally with the camshaft6about the rotational axis O and is rotatable relative to the driving-side rotatable body23.

The internal gear section28is integrally formed in one piece with the driven-side rotatable body24at an inner periphery of a tubular portion of the driven-side rotatable body24. The internal gear section28is a gear section which is configured such that an addendum circle of the gear section is located on a radially inner side of a dedendum circle of the gear section.

The eccentric shaft25is shaped in a tubular form and is coaxial with the camshaft6. The eccentric shaft25is supported by a radial bearing33, which is installed at an inside of the cover member32such that the eccentric shaft25is rotatable about the rotational axis O. An eccentric portion34, which is eccentric to the rotational axis O, is formed at a portion of the eccentric shaft25an extent of which overlaps with an extent the internal gear section28in the axial direction.

The planetary rotatable body26includes a planetary gear section35which is eccentric to the rotational axis O and is meshed with the internal gear section28. The planetary gear section35is a gear section that is configured such that an addendum circle of the gear section is located on a radially outer side of a dedendum circle of the gear section. The planetary rotatable body26is supported by a radial bearing36installed at an outside of the eccentric portion34such that the planetary rotatable body26is rotatable about a spin axis C. The planetary gear section35integrally makes a planetary motion while changing a meshing location, at which the planetary gear section35and the internal gear section28are meshed with each other, in response to the rotation of the eccentric shaft25relative to the driving-side rotatable body23. At this time, the planetary rotatable body26revolves around the rotational axis O while rotating around the spin axis C under the state where the planetary rotatable body26is meshed with the driven-side rotatable body24on an eccentric side.

A plurality of resilient members37are placed between the radial bearing36and the eccentric side part of the eccentric portion34. The resilient members37urge the planetary rotatable body26toward the eccentric side in the radial direction through the radial bearing36. Therefore, the planetary gear section35maintains a meshed state where the planetary gear section35and the internal gear section28are meshed with each other.

The transmission mechanism27transmits rotation between the driving-side rotatable body23and the planetary rotatable body26while absorbing the eccentricity between the driving-side rotatable body23and the planetary rotatable body26. Specifically, the transmission mechanism27is an Oldham mechanism that includes: a plurality of primary engaging grooves41formed at the sprocket member31; a plurality of secondary engaging projections42formed at the planetary rotatable body26; and a slider43that transmits rotation between the primary engaging grooves41and the secondary engaging projections42while swinging in the radial direction relative to the primary engaging grooves41and the secondary engaging projections42. The slider43includes: a ring44; a plurality of primary engaging projections45which radially outwardly project from the ring44and respectively fitted to the primary engaging grooves41; and a plurality of secondary engaging grooves46which are formed at an inner periphery of the ring44and are respectively fitted to the secondary engaging projections42.

The valve timing adjustment device10, which has the above-described configuration, adjusts a rotational phase (hereinafter simply referred to as “rotational phase”) of the driven-side rotatable body24relative to the driving-side rotatable body23within a predetermined phase adjustment range according to a rotational state of the control shaft22. As a result, the valve timing adjustment, which is suitable for the operational state of the internal combustion engine, can be realized.

Specifically, in a state where the control shaft22is rotated at the same speed as that of the driving-side rotatable body23, and thereby the eccentric shaft25does not rotate relative to the driving-side rotatable body23, the planetary rotatable body26does not have a planetary motion. As a result, the rotatable bodies23,24rotate integrally with the planetary rotatable body26so that the rotational phase does not substantially change, and thereby the current valve timing is maintained.

In contrast, when the control shaft22is rotated at a lower speed relative to the rotational speed of the driving-side rotatable body23or is rotated in the opposite direction relative to the rotational direction of the driving-side rotatable body23, the eccentric shaft25is rotated relative to the driving-side rotatable body23in a retarding direction. At this time, the planetary rotatable body26makes the planetary motion. Thus, the driven-side rotatable body24is rotated in the retarding direction relative to the driving-side rotatable body23to retard the rotational phase so that the valve timing is retarded.

In contrast, when the control shaft22is rotated at a higher speed relative to the rotational speed of the driving-side rotatable body23, the eccentric shaft25is rotated relative to the driving-side rotatable body23in an advancing direction. At this time, the planetary rotatable body26makes the planetary motion. Thus, the driven-side rotatable body24is rotated in the advancing direction relative to the driving-side rotatable body23to advance the rotational phase so that the valve timing is advanced.

The phase adjustment range, within which the rotational phase is adjusted, is limited when stoppers47of the driven-side rotatable body24are engaged to and are stopped by the driving-side rotatable body23at one side or the other side in the rotational direction.

Next, a bearing structure of the planetary rotatable body26for providing bearing support in a thrust direction will be described.

As in the case of the valve timing adjustment device10, when the direction of the torque inputted to the planetary gear mechanism is periodically switched, the impact noise and collision wear caused by a collision between components become an issue. This type of collision occurs not only on the torque-transmitting surfaces of gears and the Oldham mechanism, but also on the thrust bearing sites (i.e., the axial limiting sites). The valve timing adjustment device10has a configuration for limiting the collision in the thrust direction of the planetary rotatable body26.

As shown inFIGS. 2 to 5, the planetary rotatable body26includes a planetary thrust bearing portion51which serves as a bearing portion for providing thrust support in the thrust direction. The driving-side rotatable body23, which serves as a specific rotatable body that contacts the planetary thrust bearing portion51in the thrust direction, includes a specific thrust bearing portion52that is a bearing portion for providing bearing support in the thrust direction. The planetary thrust bearing portion51and the specific thrust bearing portion52form a thrust bearing between the planetary rotatable body26and the driving-side rotatable body23.

The planetary thrust bearing portion51is formed by distal end portions of a plurality of projections53which project toward the driving-side rotatable body23in the axial direction. In the first embodiment, the number of the projections53is six, and these projections53are arranged at equal intervals along a circle that is concentric with the spin axis C. Two of the six projections53serve as the primary engaging projections45.

As shown inFIGS. 4, 6 and 7, the specific thrust bearing portion52is an inner periphery of an end portion of the driving-side rotatable body23located on the planetary rotatable body26side and is formed by a circular ring portion that is coaxial with the rotational axis O. The specific thrust bearing portion52includes a specific receiving surface54that is in a form of a circular ring and is configured to contact the planetary thrust bearing portion51. InFIGS. 4 and 7, each which shows a cross section that extends along the rotational axis O and is parallel with an eccentric direction, the specific receiving surface54is spaced from the planetary thrust bearing portion51toward the radially outer side. Specifically, a relief space exists on the radially inner side of the specific receiving surface54to relieve a counter-eccentric side part of the planetary thrust bearing portion51into the relief space when the planetary rotatable body26is tilted such that the eccentric side of the planetary thrust bearing portion51contacts the specific receiving surface54while the counter-eccentric side part of the planetary thrust bearing portion51, which is opposite to the eccentric side part of the planetary thrust bearing portion51in the radial direction, approaches the driving-side rotatable body23. Therefore, in a parallel state where the specific thrust bearing portion52and the planetary thrust bearing portion51are parallel to each other, the specific thrust bearing portion52and the planetary thrust bearing portion51contact with each other only on the eccentric side of the planetary rotatable body26.

Advantages

As described above, according to the first embodiment, in the parallel state where the specific thrust bearing portion52and the planetary thrust bearing portion51are parallel to each other, the specific thrust bearing portion52and the planetary thrust bearing portion51contact with each other only on the eccentric side of the planetary rotatable body26. As described above, the specific thrust bearing portion52and the planetary thrust bearing portion51contact with each other on the eccentric side and are spaced from each other on the counter-eccentric side, so that a higher degree of freedom of tilting and a higher degree of positioning precision of the planetary rotatable body26can be achieved. When the planetary rotatable body26is tilted, a projected size of the planetary rotatable body26in the axial direction is increased, and a clearance in the thrust direction between the planetary rotatable body26and the driving-side rotatable body23is reduced. In addition, at the time of collision, the planetary rotatable body26and the driving-side rotatable body23contact with each other while changing the tilt angle of the planetary rotatable body26relative to the driving-side rotatable body23so that the collision impact is reduced. Therefore, the noise and impact force, which are caused by the collision between the planetary rotatable body26and the driving-side rotatable body23in the thrust direction, can be reduced, and thereby it is possible to achieve the improved quietness and the improved durability.

In addition, at least a portion of the planetary rotatable body26can maintain a small clearance in the thrust direction between the portion of the planetary rotatable body26and the driving-side rotatable body23, so that it is possible to limit vigorous movement (e.g., rattling) of the planetary rotatable body26in the axial direction.

In the most of cases, the force, which tilts the planetary rotatable body26, is a radial component force generated by the torque transmitted at the meshed part between the planetary gear section35and the internal gear section28. Therefore, the tilting direction of the planetary rotatable body26becomes a direction perpendicular to the eccentric direction. In the first embodiment, the specific thrust bearing portion52and the planetary thrust bearing portion51are configured to contact with each other on the eccentric side and are spaced from each other on the counter-eccentric side, so that a tiltable range of the planetary rotatable body26is increased, and the valve timing adjustment device implements the improved quietness.

In addition, unlike a case where the clearance in the thrust direction is reduced by urging the planetary rotatable body in the axial direction with a resilient member or the like, the noise and the impact force can be reduced without requiring an additional component in the first embodiment.

Second Embodiment

In a second embodiment, as shown inFIG. 8, the planetary thrust bearing portion512is formed by an end portion of the planetary rotatable body26which is located on the driven-side rotatable body24side of the planetary rotatable body26. The specific thrust bearing portion522is formed by a circular ring portion of the driven-side rotatable body24which is placed to oppose the planetary thrust bearing portion512in the axial direction and is coaxial with the rotational axis O. Therefore, in a parallel state where the specific thrust bearing portion522and the planetary thrust bearing portion512are parallel to each other, the specific thrust bearing portion522and the planetary thrust bearing portion512contact with each other only on the eccentric side of the planetary rotatable body26.

The thrust bearing may be provided between the planetary rotatable body26and the driven-side rotatable body24in the above-described manner. Even with this configuration, the specific thrust bearing portion522and the planetary thrust bearing portion512contact with each other on the eccentric side and are spaced from each other on the counter-eccentric side, so that the advantages, which are similar to those of the first embodiment, can be achieved.

Third Embodiment

In a third embodiment, as shown inFIG. 9, the radial bearing33is placed on the inner side of the tubular portion of the driven-side rotatable body24. When the radial bearing33is placed on the opposite side of the planetary rotatable body26, which is opposite to the specific thrust bearing portion52, the eccentric shaft25is more likely to tilt. Thereby, when the planetary rotatable body26is tilted, the clearance in the thrust direction is reduced. Thus, the noise and the impact force can be effectively reduced.

Fourth Embodiment

In a fourth embodiment, as shown inFIGS. 10 and 11, the outer diameter of the planetary thrust bearing portion514is reduced in comparison to the outer diameter of the planetary thrust bearing portion51of the first embodiment. Specifically, a recess61is formed at each of the projections53at a location which is on the radially outer side of the planetary thrust bearing portion514, and the recess61is recessed in a direction opposite to the specific thrust bearing portion52. The outer diameter B of the planetary thrust bearing portion514is smaller than the inner diameter A of the specific thrust bearing portion52. Therefore, as shown inFIG. 12, the counter-eccentric side of the specific receiving surface54is spaced away from the planetary thrust bearing portion514in the radial direction, so that the counter-eccentric side half of the specific receiving surface54will not contact the planetary thrust bearing portion514.

With the above configuration, the specific thrust bearing portion52and the planetary thrust bearing portion51can be reliably spaced from each other on the counter-eccentric side, so that the planetary rotatable body26is more likely to be tilted, and thereby the noise and the impact force can be effectively reduced.

Fifth Embodiment

In a fifth embodiment, as shown inFIG. 13, the specific thrust bearing portion52has a specific receiving surface545that is a tapered surface formed at an inner periphery of the specific thrust bearing portion52such that the specific receiving surface545is progressively spaced away from the planetary thrust bearing portion51in an inner radial direction. With the above configuration, the specific thrust bearing portion52and the planetary thrust bearing portion51can be reliably spaced from each other on the counter-eccentric side, so that the planetary rotatable body26is more likely to be tilted, and thereby the noise and the impact force can be effectively reduced.

Sixth Embodiment

In a sixth embodiment, as shown inFIG. 14, the specific thrust bearing portion52has a specific receiving surface546that is a curved surface formed at an inner periphery of the specific thrust bearing portion52such that the specific receiving surface546is progressively spaced away from the planetary thrust bearing portion51in the inner radial direction. With the above configuration, the specific thrust bearing portion52and the planetary thrust bearing portion51can be reliably spaced from each other on the counter-eccentric side, so that the planetary rotatable body26is more likely to be tilted, and thereby the noise and the impact force can be effectively reduced.

Seventh Embodiment

In a seventh embodiment, as shown inFIG. 15, the planetary thrust bearing portion51has a tapered surface63that is formed at an outer periphery of the planetary thrust bearing portion51such that the tapered surface63is progressively spaced away from the specific thrust bearing portion52in an outer radial direction. With the above configuration, the specific thrust bearing portion52and the planetary thrust bearing portion51can be reliably spaced from each other on the counter-eccentric side, so that the planetary rotatable body26is more likely to be tilted, and thereby the noise and the impact force can be effectively reduced.

Eighth Embodiment

In an eighth embodiment, as shown inFIG. 16, the specific thrust bearing portion528is formed by a ring portion that is coaxial with the rotational axis O, and the specific thrust bearing portion528has a recess65that is formed such that an outer periphery of the specific thrust bearing portion528is recessed in a direction opposite to the planetary rotatable body26relative to an inner periphery of the specific thrust bearing portion528. In the parallel state where the specific thrust bearing portion528and the planetary thrust bearing portion51are parallel to each other, the specific thrust bearing portion528contacts the planetary thrust bearing portion51only on the counter-eccentric side.

As described above, the specific thrust bearing portion528and the planetary thrust bearing portion51may contact with each other on the counter-eccentric side and may be spaced from each other on the eccentric side. Even with this configuration, when the planetary rotatable body26is tilted, the clearance in the thrust direction is reduced. Thus, the advantages, which are similar to those of the first embodiment, can be achieved.

Ninth Embodiment

In a ninth embodiment, as shown inFIGS. 17 and 18, the planetary thrust bearing portion519is formed by distal end portions of the projections53which are placed on the eccentric side when the rotational phase is a specific phase. A plurality of projections67, which are placed on the counter-eccentric side when the rotational phase is the specific phase, have an axial length that is shorter than that of the projections53, which are placed on the eccentric side. Specifically, an axial step (axial gap) is formed between the projections67and the projections53. With the above configuration, the specific thrust bearing portion52and the planetary thrust bearing portion519contact with each other only on the eccentric side when the rotational phase is the specific phase.

The specific phase is a rotational phase during the idling rotation of the engine in which the noise is particularly prominent. Thus, when the planetary rotatable body26is tilted to reduce the clearance in the thrust direction during the idling rotation of the engine in which the noise is particularly prominent, the noise and the impact force can be reduced.

Furthermore, in the ninth embodiment, the control unit12controls the operation of the valve timing adjustment device such that the rotational phase is not kept at the specific phase when the engine rotational speed is a high rotational speed range which is equal to or higher than 3000 rpm. As a result, it is possible to limit the planetary gear section35from being excessively tilted at the high rotational speed of the engine and promoting wear.

Tenth Embodiment

In a tenth embodiment, as shown inFIG. 19, there is provided an urging portion69that urges the planetary rotatable body26toward the specific thrust bearing portion52. In the tenth embodiment, the urging portion69is a disc spring. However, the urging portion69may be formed by an elastic body or an oil pressure generating means. When the pressure is pre-applied in the thrust direction in this way, the clearance is further reduced. Thus, the noise and the impact force can be further effectively reduced.

Eleventh Embodiment

In an eleventh embodiment, as shown inFIG. 20, a radial bearing71placed between the eccentric portion34and the planetary rotatable body26is an angular contact ball bearing. An axial component of a force, which is exerted at the radial bearing71by the resilient members (serving as urging portions)37, urges the planetary rotatable body26toward the specific thrust bearing portion52. When the pressure is pre-applied in the thrust direction in this way, the clearance is further reduced. Thus, the noise and the impact force can be further effectively reduced.

Other Embodiments

In the ninth embodiment, the planetary thrust bearing portion519is provided at the part of the planetary rotatable body26partially located in the rotational direction, so that the specific thrust bearing portion52and the planetary thrust bearing portion519contact with each other only at the eccentric side only at the specific phase. Alternatively, in another embodiment, a recess may be provided at a part of the specific thrust bearing portion partially located in the rotational direction, so that the specific thrust bearing portion and the planetary thrust bearing portion contact with each other only at the eccentric side at the specific phase.

In another embodiment, the internal gear section may be formed at the driving-side rotatable body. Furthermore, the transmission mechanism may be configured to transmit the rotation between the driven-side rotatable body and the planetary rotatable body.

The present disclosure has been described with reference to the embodiments. However, the present disclosure should not be limited to the embodiments and the configurations described therein. The present disclosure also includes various variations and variations within an equivalent range. Furthermore, other combinations and other forms including various combinations and various forms of only one element, or more, or less, are also within the scope and spirit of the present disclosure.