Patent ID: 12196276

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

This selectable clutch100includes a clutch mechanism101with a selector150, and a selector drive mechanism105, as shown inFIG.1andFIG.2.

The clutch mechanism101includes an inner race110and an outer race120that are coaxial and rotatable relative to each other, a plurality of rollers130disposed between an outer circumferential surface of the inner race110and an inner circumferential surface of the outer race120, a resilient member140radially biasing the rollers130, and the selector150, which is configured to switch the clutch between the free mode that allows relative rotation of the inner race110and outer race120in both forward and reverse directions, and the lock mode that prohibits relative rotation of the inner race110and outer race120in both forward and reverse directions. Reference symbol C inFIG.1andFIG.2denotes the rotation axis.

In this embodiment, the inner race110has a two-step cylindrical shape, and includes a small-diameter cylindrical part111and a large-diameter cylindrical part112continuous with one end of the small-diameter cylindrical part111, as shown also inFIG.3.

The outer race120includes an annular plate-like base part121, a cylindrical support wall part122protruding axially from an inner peripheral edge of the base part121, and a mounting part123provided on an outer circumferential surface of the base part121. A counterbore-like recess is formed at the open end of the support wall part122, for the resilient member140to be set.

The outer circumferential surface of the inner race110and the inner circumferential surface of the outer race120are opposite each other in close proximity. In this embodiment, as shown also inFIG.4, plural support grooves115are formed at predetermined circumferential intervals on the outer circumferential surface of the inner race110, and plural pocket parts125are formed on the inner circumferential surface of the outer race120, each corresponding to each of the rollers130. Note, in this embodiment, while six rollers130are circumferentially arranged at predetermined intervals, there are more support grooves115than the rollers130.

This configuration in which the support grooves115are formed on the outer circumferential surface of the inner race110and the pocket parts125are formed on the inner circumferential surface of the outer race120allows the selector150to be disposed on the outer race120side even though the inner race110is the one that is rotated, providing the selector drive mechanism105with easy access to the selector150. Moreover, since the rollers130are held on the outer race120side, they are less affected by the centrifugal force.

The support grooves115have a roller-holding surface116that is inclined relative to the circumferential direction, and extend in the direction of the rotation axis.

In this embodiment, the support grooves115are formed as recessed grooves with a circular arc cross-sectional shape, for example, to be able to support the rollers130by receiving part of the circumferential surface of the rollers130. The roller-holding surface116is formed by a side face of the groove.

The open edges of the support grooves115are chamfered.

The pocket parts125are configured to be able to accommodate the rollers130, and have a roller-holding surface126that is inclined relative to the circumferential direction.

In this embodiment, the pocket parts125are formed as recessed grooves extending from one end face of the support wall part122in the direction of the rotation axis. The grooves have a cross-sectional shape that is formed by an isosceles trapezoid and a circle that passes through the vertices of the two equal sides, for example. The roller-holding surface126is formed by a side face of the recessed groove.

In this embodiment, the roller-holding surface126of the pocket part125on one side in the forward direction, and the roller-holding surface126on the other side in the reverse direction, are each inclined relative to the radial direction at the same angle. These roller-holding surfaces may instead be formed with a difference in their inclination angles. Such a configuration will allow adjustment of the torque load to be carried both in the forward direction and the reverse direction, which facilitates an attempt to improve performance stability.

The plural rollers130are each shaped to protrude axially outward from one end face of the base part121of the outer race120when accommodated in the pocket parts125. A spring mount groove131extends circumferentially all around on the circumferential surface of the protruded part of the roller.

As shown inFIG.2, the plural rollers130are each restricted from axial movement by an annular plate-like stopper plate180on one axial end and the end walls on the other axial end of the pocket parts125.

The resilient member140, which is a common component shared by the plurality of rollers130, is fitted from inside into the spring mount grooves131of the rollers130, such as to bias the rollers130radially outward toward respective pocket parts125. Namely, the resilient member140is provided such that the rollers130are held on the outer race120side, and biases the rollers130such that the selectable clutch100maintains the free mode.

In this embodiment, the resilient member140is an annular garter spring. A ribbon spring, for example, may be used instead.

Using the resilient member140that is a common component shared by the plurality of rollers130enables a reduction in the number of components as well as in the size. The use of one resilient member also facilitates the setting of the biasing force required to ensure that the inner race110and outer race120do not engage during the rotation of the inner race110at a certain speed or more.

The selector150, which is composed of a cylindrical member, is axially adjacent the outer race120that is formed with the pocket parts125, and disposed coaxially with the inner race110and outer race120.

The selector150is provided such as to be rotatable independently of the inner race110and outer race120. The selector is configured to move the rollers130radially when rotated, to switch the selectable clutch100between the free mode and the lock mode. In this embodiment, when the selectable clutch100is in the free mode, rotating the selector150in the locking direction (counterclockwise inFIG.1) can cause the rollers130accommodated in the pocket parts125to move radially inward toward the support grooves115. When the selectable clutch100is in the lock mode, rotating the selector150in the unlocking direction (clockwise inFIG.1) can cause the rollers130supported by the support grooves115to move radially outward toward the pocket parts125.

An inner circumferential surface of the selector150forms a roller-holding surface151that makes contact with the rollers130when the rollers130are supported by the support grooves115(seeFIG.5).

As shown inFIG.4, on the inner circumferential surface of the selector150are formed roller-receiving recesses152that are configured to be able to receive the rollers130when the selectable clutch100is in the free mode in which the rollers130are accommodated in the pocket parts125.

The roller-receiving recess152includes a tapered guide surface153configured to radially move the roller130toward the support groove115as the selector150is rotated in the locking direction.

This selectable clutch100includes a rotation restriction mechanism for restricting the movable range of the selector150.

In this embodiment, the rotation restriction mechanism is made up of pin members127and rotation restriction grooves156. The pin members127extend axially from one side of the base part121of the outer race120that is formed with the pocket parts125. The rotation restriction grooves156extend circumferentially on the inner circumferential surface of the selector150such as to allow the pin members127to slide therein.

The selector drive mechanism105includes, as shown inFIG.1, a linear actuator160with a drive shaft161that is driven to reciprocate in one direction (left and right direction inFIG.1); a drive rod165coupled at one end to the drive shaft161and connected at the other end to a bearing part155on an outer circumferential surface of the selector150such as to be movable back and forth in the one direction between a free position to switch the selectable clutch100to the free mode and a lock position to switch the selectable clutch100to the lock mode; and a delay spring170disposed to be resiliently deformed in a compressed manner when the drive rod165is moved toward the lock position to rotate the selector150in the locking direction.

In this embodiment, the delay spring170is a coil spring, with the drive rod165passing therethrough.

The actuator160has a lock position retention function for keeping the selector150in position by retaining the drive rod165at the lock position when the selectable clutch100is switched to the lock mode. This function reliably prevents unintended rotation of the selector150that may occur by vibration, for example, so that the lock mode can be maintained.

This selectable clutch100also includes a rod position restriction mechanism for restricting the movable range of the drive rod165.

In this embodiment, as shown inFIG.1, the rod position restriction mechanism is formed by a position restriction part124on the mounting part123of the outer race120that is positioned beyond the lock position in the one direction.

In the selectable clutch100described above, the roller-holding surface116of the support groove115and the roller-holding surface126of the pocket part125are formed with inclination angles such that when the roller130is held therebetween, a force acts on the roller130in a direction to move the roller130toward the pocket part125. In the lock mode, the roller130is held by the roller-holding surface116of the support groove115, the roller-holding surface126of the pocket part125, and the roller-holding surface151of the selector150.

More specifically, as shown inFIG.5, when the inner race110and outer race120engage, the roller130receives a normal force Tb [N] expressed as (Tr·sin θ1) from the roller-holding surface116of the support groove115, where Tr [N] is the load acting on the roller130. Angle θ1represents the angle [°] expressed as (90°−θn), where θn is the angle [°] of the load acting surface of the roller-holding surface116relative to the radial direction.

The pocket part125receives a component of force Tc [N] expressed as (Tb·cos θ2) parallel to the roller-holding surface126from roller130in the direction along the roller-holding surface126of the pocket part125from, as well as a normal force Td [N] expressed as (Tb·sin θ2) perpendicular to the roller-holding surface126. Angle θ2represents the angle [°] expressed as (90°−(θn−θg)), where θgis the angle [°] of the roller-holding surface126relative to the radial direction. Furthermore, a frictional force Tf [N] expressed as μ·Td acts on the roller-holding surface126, where μ represents the friction coefficient of the roller-holding surface126.

Therefore, the roller130receives a push-out force Nc [N] expressed as (Tc−μTd) along the roller-holding surface126of the pocket part125toward the pocket part125, as well as a component of force N [N] expressed as (Nc·cos θ2) radially outward. The component N of the push-out force Nc and the biasing force of the resilient member140are received by the roller-holding surface151of the selector150, which enables the inner race110and outer race120to engage each other. Rotating the selector150in the unlocking direction can separate the selector150from the rollers130, and allows the lock to be released.

When the selectable clutch100according to this embodiment is in the free mode in which the drive rod165is located at the free position, the rollers130, being biased by the resilient member140, are positioned inside the pocket parts125of the outer race120and in the roller-receiving recesses152of the selector150, as shown inFIG.6A. The rollers130are separated from the inner race110during its rotation, which facilitates reduction of friction loss and noise.

When the selectable clutch100is switched from the free mode to the lock mode, as the drive rod165is driven toward the lock position, the selector150rotates in the locking direction so that the respective guide surfaces153of the roller-receiving recesses152of the selector150make contact with the rollers130, as shown inFIG.6B.

When the support grooves115of the inner race110and the pocket parts125of the outer race120are out of alignment at this time, the delay spring170provided to the selector drive mechanism105, by being compressed, allows the drive rod165to move further toward the lock position, while the selector150is stopped from rotating, as shown inFIG.6C. Accordingly, the selectable clutch100maintains a lock wait state.

During the rotation of the inner race110at a certain speed or more, the rollers130attempting to move toward the support grooves115, by an erroneous operation or malfunction of the selector150, are thrust back toward the pocket parts125by the chamfered open edges of the support grooves115. This reliably prevents chipping or damage caused by the impact of sudden engagement between the inner race110and outer race120, which facilitates extension of the service life, as well as ensures high safety.

When the support grooves115and the pocket parts125come into alignment, the biasing force of the delay spring170is released as shown inFIG.6D, allowing the selector150to rotate in the locking direction. The rollers130then move radially toward the support grooves115by the action of the guide surfaces153of the roller-receiving recesses152.

At this time, the pin members127and rotation restriction grooves156restricting the movable range of the selector150can prevent the selector150from overrunning, ensuring the reliable switching between the free mode and the lock mode.

When the selectable clutch100is held in the lock wait state, the position restriction part124that restricts the movable range of the drive rod165prevents the delay spring170from being excessively compressed. This saves the delay spring170itself from being damaged, as well as prevents an excessive action of the selector150when the biasing force of the delay spring170is released, so that overrunning of the selector150can be prevented even more reliably.

When the rollers130move into the support grooves115, the roller-holding surface116of the support grooves115and the roller-holding surface126of the pocket parts125hold the rollers130in the circumferential direction, as well as the roller-holding surface151of the selector150makes contact with the rollers130, and thus the inner race110and outer race120engage with each other.

No windup or torsional deflection occurs in the races engaged this way as would in frictional clutches when torque is transmitted, which allows the selectable clutch100to be designed as a high-rigidity clutch, and helps design a simple structure that can achieve stable engagement. Moreover, the surface pressure that acts on the rollers130and the roller-holding surfaces116,126, and151during engagement can be reduced. This allows the clutch to be designed with inexpensive materials that are more resistant to chipping, which may be caused by impact, or wear. The rollers130rotating themselves and substantially not engaging at the same point allow the durability of the clutch to be improved and the service life to be extended. Furthermore, the large number of rollers130accommodated in a small space, each roller130contributing to the locking in both forward and reverse directions, enable size reduction, and allow the clutch to transmit high torque despite the small size.

To switch the selectable clutch100from the lock mode to the free mode, the drive rod165is driven from the lock position toward the free position to rotate the selector150in the unlocking direction. At this time, the resilient member140biases the rollers130toward the pocket parts125. Further, the roller-holding surfaces126of the pocket parts125and the roller-holding surfaces116of the support grooves115are formed with inclination angles such that, when the rollers130are held therebetween, a force acts on the rollers130in a direction to move the rollers toward the pocket parts125. Therefore, the selector150can be rotated easily with a small force even when some torque still remains. As the roller-holding surface151of the selector150is moved away from the rollers130, the rollers130can separate from the support grooves115, so that the lock can readily be released.

While the configuration described in the embodiment above as the selector drive mechanism105is equipped with a linear actuator as the drive source, the selector drive mechanism105may have a rotary actuator as the drive source as shown inFIG.7, or a configuration that uses a worm gear mechanism as shown inFIG.8.

The clutch mechanism101of the selectable clutch100shown inFIG.7has the same configuration as that of the selectable clutch100shown inFIG.1. Like reference numerals are given to the same components and description thereof will be omitted.

The selector drive mechanism105of the selectable clutch100shown inFIG.7includes a rotary actuator160with a drive shaft161that is driven and rotated in both forward and reverse directions; a rotary arm162provided to the drive shaft161; a drive rod165coupled at one end to the rotary arm162and connected at the other end to the bearing part155on the outer circumferential surface of the selector150such as to move back and forth in the one direction between a free position to switch the selectable clutch100to the free mode and a lock position to hold the selectable clutch100in the lock mode; and a delay spring170disposed to be resiliently deformed in a compressed manner when the drive rod165is moved toward the lock position.

In this embodiment, the delay spring170is a coil spring, with the drive rod165passing therethrough.

The actuator160has a lock position retention function for keeping the selector150in position by retaining the drive rod165at the lock position when the selectable clutch100is switched to the lock mode. This function reliably prevents unintended rotation of the selector150that may occur by vibration, for example, so that the lock mode can be maintained.

In this selectable clutch100, when switching the selectable clutch100from the free mode to the lock mode, the drive shaft161is driven and rotated in the forward direction to rotate the rotary arm162, to move the drive rod165toward the lock position. When the support grooves115of the inner race110and the pocket parts125of the outer race120are out of alignment at this time, the delay spring170is compressed, allowing the drive rod165to move further toward the lock position, while the selector150is stopped from rotating. Accordingly, the selectable clutch100maintains a lock wait state.

When the support grooves115and the pocket parts125come into alignment, the biasing force of the delay spring170is released, allowing the selector150to rotate in the locking direction. The rollers130then move radially toward the support grooves115by the action of the guide surfaces153of the roller-receiving recesses152. When the rollers130move into the support grooves115, the roller-holding surface116of the support grooves115and the roller-holding surface126of the pocket parts125hold the rollers130in the circumferential direction, as well as the roller-holding surface151of the selector150makes contact with the rollers130, and thus the inner race110and outer race120engage with each other.

To switch the selectable clutch100from the lock mode to the free mode, the drive shaft161is driven and rotated in the reverse direction to rotate the rotary arm162, to move the drive rod165toward the free position. This rotates the selector150in the unlocking direction, moving the roller-holding surface151of the selector150away from the rollers130, and allowing the rollers130to separate from the support grooves115, so that the lock is released.

The clutch mechanism101of the selectable clutch shown inFIG.8is configured the same as the selectable clutch100shown inFIG.1except for the selector150configuration. Like reference numerals are given to the same components and description thereof will be omitted.

The selector150is formed with worm gear teeth157on its outer circumferential surface to function as a worm wheel.

The selector drive mechanism105of the selectable clutch shown inFIG.8includes, as shown also inFIG.9, an actuator160; a drive rod165driven by the actuator160to rotate in forward and reverse directions; a worm163slidable relative to the drive rod165and meshing with the worm gear teeth157of the selector150; a spring receptacle166provided to the drive rod165at one end of the worm163; and a delay spring170, with the drive rod165passing therethrough, disposed at one end of the spring receptacle166.

In this embodiment, the actuator160has a lock position retention function that retains torque and keeps the selector150in position when the selectable clutch100is in the lock mode. This function reliably prevents unintended rotation of the selector150that may occur by vibration, for example, so that the lock mode can be maintained. The lock position retention function may be realized by a design that utilizes the self-locking nature of the worm gear mechanism.

In this embodiment, the worm163at its other end is in contact with a position restriction part124on one side in the free mode. The movable range of the worm163, when moving in the direction in which the delay spring170is resiliently deformed in a compressed manner, is restricted by one end of the spring receptacle166making contact with another position restriction part124on the other side.

In this selectable clutch, when switching the selectable clutch from the free mode to the lock mode, the drive rod165is driven and rotated in the forward direction to rotate the worm163, to rotate the selector150in the locking direction. When the support grooves115of the inner race110and the pocket parts125of the outer race120are out of alignment at this time, the selector150is stopped from rotating, while the worm163and the spring receptacle166are moved relative to the drive rod165, as shown inFIG.10A. Accordingly, the delay spring170is compressed, and the selectable clutch maintains a lock wait state.

When the support grooves115and the pocket parts125come into alignment, the biasing force of the delay spring170is released, allowing the worm163and the spring receptacle166to move toward the free position as well as the selector150to rotate in the locking direction, as shown inFIG.10B. The rollers130then move radially toward the support grooves115by the action of the guide surfaces153of the roller-receiving recesses152. When the rollers130move into the support grooves115, the roller-holding surface116of the support grooves115and the roller-holding surface126of the pocket parts125hold the rollers130in the circumferential direction, as well as the roller-holding surface151of the selector150makes contact with the rollers130, and thus the inner race110and outer race120engage with each other.

To switch the selectable clutch from the lock mode to the free mode, the drive rod165is driven and rotated in the reverse direction to rotate the worm163, to rotate the selector150in the unlocking direction. This moves the roller-holding surface151of the selector150away from the rollers130. As a result, the rollers130receive both of the load toward the pocket parts125, from the roller-holding surface126of the pocket parts125and the roller-holding surface116of the support grooves115, and the biasing force of the resilient member140. The rollers130thus separate from the support grooves115, allowing the lock to be released.

While the delay spring is provided in the selector drive mechanism in the embodiments described above, the clutch mechanism may include the delay spring.

The clutch mechanism101in the embodiment shown inFIG.11toFIG.13is configured with the outer race120, selector150, and a rotary plate185that forms a selector drive mechanism, aligned in this order adjacent each other in the axial direction. The clutch mechanism101basically has the same configuration as that of the embodiments described above. The same components as those of the embodiments described above are given the same reference numerals, and description thereof will be omitted.

The selector150has a plurality of circumferentially extending delay spring seat grooves154on one side, formed along a circle concentric to the rotation axis C. The delay spring seat grooves154are circumferentially arranged at predetermined intervals, at positions radially more outside than the roller-receiving recesses152.

In each delay spring seat groove154are set a coiled delay spring170, and a pin member171at one circumferential end (clockwise leading end inFIG.11andFIG.12). The pin members171are fixed to the rotary plate185.

The selector150has a plurality of circumferentially extending guide grooves158on one side. In each guide groove158is inserted a coupling pin member187that connects the rotary plate185and the outer race120, such as to be slidable in the groove.

The rotary plate185is formed with circumferentially extending pin member slots186for the coupling pin members187to pass through and slide inside, corresponding to the guide grooves158of the selector150. This clutch mechanism101is provided with a lock position retention mechanism190for keeping the selector150in the lock position when the selectable clutch is in the lock mode.

The lock position retention mechanism190includes a plunger191with a plunger bore that opens radially outward, a biasing means193accommodated in the plunger bore and biasing the plunger191radially inward, and a spring receptacle194fixed to an axial outer end of the biasing means193.

The plunger191is slidably accommodated in a plunger housing hole that extends radially from one of the guide grooves158of the rotary plate185and opens in an outer circumferential surface of the rotary plate185. With the spring receptacle194fixed to the rotary plate185, the tip of the plunger is in contact with the circumferential surface on the radially inner side of the pin member slot186. The tip of the plunger191exposed inside the pin member slot186is formed in a conical shape. When the selector150is rotated in the locking direction, the plunger191, as it presses the coupling pin member187, moves in the direction to compress the biasing means193by the action of the tapered surface.

When the selectable clutch is held in the free mode, the plunger191is positioned on one side in the unlocking direction (clockwise inFIG.13) of the coupling pin member187, as shown inFIG.13. When the support grooves115of the inner race110and the pocket parts125of the outer race120are in alignment and the selector150rotates in the locking direction, the plunger191moves radially outward such as to ride over the coupling pin member187as shown inFIG.14A. After that, when the selectable clutch is switched to the lock mode, the plunger191, having ridden over the coupling pin member187, is moved over to the side in the locking direction (counterclockwise) of the coupling pin member187, as shown inFIG.14B. Thus, unintended rotation of the selector150in the unlocking direction, which may occur by vibration, for example, can be reliably prevented, so that the lock mode can be mechanically retained.

In this clutch mechanism101, when the selector150is rotated in the locking direction in switching the selectable clutch from the free mode to the lock mode, the selector150is stopped from rotating when the support grooves115of the inner race110and the pocket parts125of the outer race120are out of alignment. Meanwhile, the pin members171press and compress the delay springs170as the rotary plate rotates, so that the selectable clutch keeps the lock wait state. As soon as the support grooves115of the inner race110and the pocket parts125of the outer race120come into alignment, the biasing force of the delay springs170is released, allowing the selector150to rotate in the locking direction. Thus the inner race110and the outer race120engage each other, with the rollers130held by the support grooves115, pocket parts125, and selector150.

The selector drive mechanism may be of any type, i.e., any of the configurations with a linear or rotary actuator, or a worm gear, as those used as the selector drive mechanism in the selectable clutches according to the embodiments described above. Alternatively, any suitable gear mechanism may be used to directly drive or rotate the selector.

The selectable clutch may be provided with the lock position retention function by employing an actuator that has a position retention function in itself. In this case, the clutch mechanism need not be configured to include a lock position retention mechanism.

While embodiments of the present invention have been described above in detail, the present invention is not limited to the embodiments described above. Various design changes may be made without departing from the scope of the present invention set forth in the claims.

For example, while the outer race is fixed and the inner race is rotated in the configurations described in respective embodiments, other configurations are also possible, such as an outer race being rotated relative to a fixed inner race, or the inner race and outer race being both rotatable.

In the embodiments described above, the support grooves are formed in the outer circumferential surface of the inner race, while the pocket parts are formed in the inner circumferential surface of the outer race. The resilient member is set such as to bias the rollers radially outward. Instead, the support grooves may be formed in the inner circumferential surface of the outer race, the pocket parts may be formed in the outer circumferential surface of the inner race, and the resilient member may be set such as to bias the rollers radially inward.

In the embodiments described above, the resilient member is a common component shared by the plurality of rollers. Instead, a plurality of resilient members may be provided corresponding to respective rollers.

The selectable clutches in the embodiments described above are designed to be switchable between two operating modes, two-way free mode and two-way lock mode. The selectable clutch can also be designed switchable between three or four operating modes including one-way lock mode, by disposing pairs of rollers such as to be supported by respective pairs of adjacent support grooves, with first pocket parts and second pocket parts provided corresponding to each of the pairs of rollers. The selector in this case may be configured to be able to move one or both of the pairs of rollers in the radial direction.

The selectable clutch according to the present invention is significantly useful for building a vehicle parking lock system, for example. Namely, the selectable clutch according to the present invention, when locked, does not unlock unless the selector is operated to release the rollers from the hold. Even when torque is input due to the condition of the road on which the vehicle is parked or for some other reason, the clutch will not unlock so that the vehicle can be maintained at rest. On the other hand, the clutch allows itself to be unlocked when the selector is separated from the rollers. Therefore, the clutch can readily be unlocked even under a torque load, i.e., even with some torque being applied to the inner race or outer race, such as when the vehicle is parked on a slope.