Engaging device

An engaging device includes: inner and outer rings as two rotating elements; and an engaging piece, between the rings, projecting in a radial direction. Further, the engaging piece is attached to one of the rotating elements and another rotating element serves as an engaged member and movable in an axial direction, the engaging piece includes a first inclined portion in a tip end of a surface facing the another rotating element, the another rotating element includes a tapered portion, in a portion coming into contact with the first inclined portion, and in accordance with a position of the another rotating element, a state is switched between a one-way clutch state and a free state.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application claims priority to and incorporates by reference the entire contents of Japanese Patent Application No. 2018-001384 filed in Japan on Jan. 9, 2018.

BACKGROUND

The present disclosure relates to an engaging device.

U.S. Pat. No. 9,151,345 discloses an engaging device including an engaging piece which projects radially so as to switch between a state in which the engaging piece can mesh with an engaged member and a state in which the engaging piece cannot mesh with the engaged member. In the engaging device, a state is switched between the state in which the engaging piece can mesh and the state in which the engaging piece cannot mesh in accordance with a rotation of a selector member, coupled with an actuator, in a circumferential direction.

However, in the configuration disclosed in U.S. Pat. No. 9,151,345, since one of the engaged members is a fixed member, the engaging device can serve as a brake but cannot serve as a clutch. In the clutch, two members to be engaged with each other are rotating elements. Therefore, it is difficult to make a structure in which a main body of the actuator is fixed a clutch.

SUMMARY

There is a need for providing an engaging device including an engaging piece which projects radially and capable of serving as a clutch.

An engaging device includes: an inner ring and an outer ring serving as two rotating elements rotating around a same rotational central axis; and an engaging piece, provided between the inner ring and the outer ring, projecting in a radial direction. Further, the engaging piece is attached to one of the rotating elements out of the inner ring and the outer ring so as to rotate integrally and another rotating element serves as an engaged member with which the engaging piece is engaged and as a moving member movable in an axial direction, the engaging piece includes a first inclined portion, inclined with respect to the axial direction, in a tip end of a surface facing the another rotating element in the radial direction, the another rotating element includes a tapered portion, inclined with respect to the axial direction, in a portion coming into contact with the first inclined portion, and in accordance with a position in the axial direction of the another rotating element, a state is switched between a one-way clutch state, in which a rotational direction is limited to one direction in which the inner ring and the outer ring are relatively rotatable, and a free state, in which the inner ring and the outer ring are freely rotatable.

DETAILED DESCRIPTION

An engaging device according to an embodiment of the present disclosure is hereinafter described in more detail with reference to the accompanying drawings.

FIG. 1is an illustrative view schematically illustrating an engaging device1according to an embodiment. The engaging device1is provided with an inner ring2as a first rotating element, an outer ring3as a second rotating element, an engaging piece4, and a snap ring5. In the engaging device1, the inner ring2and the outer ring3rotating around the same rotational central axis O can be engaged with each other by means of the engaging piece4so as to rotate integrally. Note that a direction along the rotational central axis O is herein referred to as an axial direction.

The inner ring2is an annular rotating member integrally rotating with the engaging piece4. An accommodating unit21which accommodates the engaging piece4is formed on an outer periphery of the inner ring2. A plurality of accommodating units21is provided at predetermined intervals in a circumferential direction. A spring6which biases the engaging piece4is provided within the accommodating unit21in addition to the engaging piece4. The engaging piece4in the accommodating unit21is provided in a manner such that a tip end41thereof is pushed radially outward by the spring6to stand, and the movement of the engaging piece4in the axial direction is limited by the snap ring5so as not to drop off in the axial direction. The snap ring5is attached to the inner ring2. Spline teeth are provided on an inner periphery of the inner ring2.

The outer ring3is an annular rotating member located outside the inner ring2in a radial direction and is a moving member movable in the axial direction by a linear actuator7(illustrated inFIG. 7) to be described below. The outer ring3and the inner ring2are arranged in positions overlapping in the axial direction, and an inner periphery3aof the outer ring3and the outer periphery of the inner ring2are opposed to each other in the radial direction. The inner periphery3aof the outer ring3is divided into two areas having different functions on one side and the other side in the axial direction. The inner periphery3ais such that the one side in the axial direction is formed of a first inner peripheral surface31which is an engageable area (One-Way Clutch (OWC) area) and the other side in the axial direction is formed of a second inner peripheral surface32which is an area not engageable (free area).

As illustrated inFIGS. 2 and 3, the first inner peripheral surface31which is the OWC area is the inner periphery3aformed to have a relatively small diameter and is provided with an engaging unit33to be engaged with the engaging piece4. A plurality of engaging units33each having a shape in which a part of the first inner peripheral surface31is recessed radially outward is provided at predetermined intervals in the circumferential direction. A second inner peripheral surface32which is the free area is the inner periphery3aformed to have a relatively large diameter and is formed into a cylindrical shape over an entire area in the circumferential direction. A tapered portion34inclined with respect to the axial direction is provided at a boundary between the first inner peripheral surface31and the second inner peripheral surface32. The first inner peripheral surface31of the small diameter and the second inner peripheral surface32of the large diameter are connected to each other via the tapered portion34having an inclined surface. The tapered portion34having the inclined surface in which a corner of a stepped portion is chamfered is provided with a predetermined length in the circumferential direction. For example, a position in a circumferential direction of the tapered portion34is different from a position in the circumferential direction of the engaging unit33. The tapered portion34is the inclined surface which comes into contact with a first inclined portion43(illustrated inFIG. 4and the like) of the engaging piece4.

The engaging piece4is a plate-shaped movable member which engages with the outer ring3. The engaging piece4is such that the tip end41projects radially outward while being attached to the accommodating unit21of the inner ring2. A plurality of engaging pieces4is arranged such that the tip ends41are oriented in the same direction in the circumferential direction. Since the tip end41projects radially outward from the accommodating unit21by means of the spring6, the engaging piece4serves as a claw member which meshes in the circumferential direction.

As illustrated inFIGS. 4 and 5, the engaging piece4includes the tip end41, a fulcrum shaft portion42, a first inclined portion43, and a second inclined portion44. The tip end41includes an engaging surface engaging with the engaging unit33of the outer ring3. The fulcrum shaft portion42being a portion serving as a fulcrum when the tip end41swings is held within the accommodating unit21. Each of the first inclined portion43and the second inclined portion44includes an inclined surface obtained by chamfering a corner on a side of the tip end41of the engaging piece4. The first inclined portion43is an inclined portion obtained by chamfering a corner on the side of the tip end41and one side in the axial direction of the surface opposed to the outer ring3in the radial direction (radially outer surface). The second inclined portion44is an inclined portion obtained by chamfering a corner on the side of the tip end41and the one side in the axial direction of the surface opposed to the inner ring2in the radial direction (radially inner surface).

As illustrated inFIG. 6, the engaging device1is provided in a manner such that the outer ring3is movable in the axial direction in a state where the inner ring2and the outer ring3are arranged in positions opposed to each other in the radial direction. The engaging device1can be switched between a one-way clutch state (hereinafter referred to as an “OWC state”) with the rotational direction limited to one direction in which the inner ring2and the outer ring3are relatively rotatable, and a bidirectional free state (hereinafter, referred to as a “free state”) in which the inner ring2and the outer ring3can freely rotate without any limitation in the rotational directions of the inner ring2and the outer ring3. In the OWC state, the engaging piece4is engageable with the engaging unit33. On the other hand, in the free state, the engaging piece4cannot be engaged with the engaging unit33.

Herein, the linear actuator7is described with reference toFIG. 7. As illustrated inFIG. 7, the outer ring3is mechanically coupled with the linear actuator7via a shift fork8. A return spring9is connected to the shift fork8. The return spring9generates a force (biasing force) to bias the shift fork8toward the linear actuator7. The linear actuator7is provided with a main body71fixed to a fixing member such as a case and a movable piece72which moves in the axial direction. The movable piece72projects in the axial direction from the main body71and is mechanically coupled with the shift fork8via a waiting spring10. When the position in the axial direction of the outer ring3changes, the engaging device1switches between the free state (refer toFIG. 8) and the OWC state (refer toFIG. 9). In both the free state and the OWC state, the outer ring3is disposed in the position in the axial direction facing the inner ring2in the radial direction. Note that the linear actuator7may be any of a hydraulic type, an electric motor, an electromagnetic type or the like. In the engaging device1according to this embodiment, only the outer ring3is movable in the axial direction. A movement of the outer ring3from one side to the other side in the axial direction as illustrated inFIG. 7is herein refers to as a stroke. At the time of the stroke of the outer ring3, the outer ring3is moved to the other side in the axial direction against the biasing force of the return spring9.

As illustrated inFIG. 8, in the free state, the position in the axial direction of the outer ring3is such that the second inner peripheral surface32faces the inner ring2but the first inner peripheral surface31does not face the inner ring2. In this case, since the engaging piece4cannot be engaged with the second inner peripheral surface32, it becomes the free state in which the inner ring2and the outer ring3can be freely rotate with respect to each other.

As illustrated inFIG. 9, in the OWC state, the outer ring3in the axial direction is disposed at a position in which the first inner peripheral surface31faces the inner ring2. In this case, since the first inner peripheral surface31is an engaging surface including the engaging unit33with which the engaging piece4can engage, it becomes the OWC state in which the inner ring2and the outer ring3may engage with each other.

FIG. 10is an enlarged schematic diagram illustrating the engaging device1in the free state.FIG. 11is a cross-sectional view illustrating a case of stroking the outer ring3in the axial direction in the free state. In the free state, the engaging piece4is in a standing state projecting radially outward and the outer ring3is rotatable in both directions. Note thatFIG. 10illustrates a case where the engaging device1is seen from the one side to the other side in the axial direction.

As illustrated inFIG. 10, in a case where the outer ring3rotates in the direction from the fulcrum shaft portion42toward the tip end41side of the engaging piece4, the engaging device1can be in an overrun state. The overrun state herein refers to a state in which the outer ring3to be engaged can rotate over the engaging piece4. In this case, for example, when the inner ring2stops rotating, a state in which the outer ring3rotates from the fulcrum shaft portion42side toward the tip end41side of the engaging piece4is the overrun state. When the inner ring2and the outer ring3rotate, the overrun state can be defined by a relationship between the rotational direction and a rotational speed (rotational rate). Specifically, when the tip end41side of the engaging piece4is forward in the rotational direction of the inner ring2and the outer ring3, the overrun state occurs when the rotational rate of the outer ring3is higher than the rotational rate of the inner ring2. When the rotational direction is opposite to this, that is, that is, when the fulcrum shaft portion42side of the engaging piece4is forward in the rotational direction of the inner ring2and the outer ring3, the overrun state occurs when the rotational rate of the inner ring2is higher than the rotational rate of the outer ring3. Then, in the overrun state, switching control by the linear actuator7is performed, and switching operation from the free state to the OWC state is performed.

As illustrated inFIG. 11, at the time of the switching operation from the free state to the OWC state, thrust (ACT thrust) which is an axial direction load acts on the outer ring3from the linear actuator7and the outer ring3moves toward the other side in the axial direction so as to approach the engaging piece4side. In this case, the tapered portion34of the outer ring3comes into contact with the first inclined portion43of the engaging piece4. As illustrated inFIG. 12, when the tapered portion34comes into contact with the first inclined portion43, a force directed inward in the radial direction acts on the engaging piece4. Since both a contact surface of the tapered portion34and a contact surface of the first inclined portion43are inclined with respect to the axial direction, the ACT thrust of the outer ring3is decomposed (changed) into components including a radial component (depressing component force) and acts on the engaging piece4. As illustrated inFIG. 13, the radial component refers to a force pushing down the tip end41of the engaging piece4radially inward. By operating the linear actuator7in the overrun state to switch from the free state to the OWC state, it is possible to push down the tip end41side of the engaging piece4by the ACT thrust, so that it becomes possible to stroke the outer ring3in the axial direction without requiring a phase synchronization. As illustrated inFIG. 14, when the outer ring3rotates in the overrun direction, a force to lay the tip end41of the engaging piece4on the accommodating unit21side can act on the engaging piece4from the outer ring3.

FIG. 15is a schematic diagram illustrating a ratchet state. Note thatFIG. 15illustrates a case where the engaging device1is seen from the other side in the axial direction.

As illustrated inFIG. 15, in the free state, there may be a case where the outer ring3rotates in the direction toward the tip end41side of the engaging piece4(a ratchet direction). In the free state, when the outer ring3rotates in the ratchet direction, the engaging piece4comes into contact with the second inner peripheral surface32. In the ratchet direction, it is possible to suppress the stroke of the outer ring3at a predetermined rotational rate or higher. For example, when the inner ring2stops rotating, a state in which the outer ring3rotates from the tip end41side to the fulcrum shaft portion42side of the engaging piece4is the ratchet state. When the fulcrum shaft portion42side of the engaging piece4is forward in the rotational direction of the inner ring2and the outer ring3, it becomes the ratchet state if the rotational rate of the outer ring3is higher than the rotational rate of the inner ring2. When the rotational direction is opposite to this direction, that is, when the tip end41side of the engaging piece4is forward in the rotational direction of the inner ring2and the outer ring3, it becomes the ratchet state if the rotational rate of the inner ring2is higher than the rotational rate of the outer ring3. In the free state, when the outer ring3rotates in the ratchet direction, there may be a case where the outer ring3is bounced off the engaging piece4in the axial direction.

As illustrated inFIG. 16, in the free state, when the outer ring3rotates in the ratchet direction, an inclined portion35of the outer ring3faces the second inclined portion44of the engaging piece4. Then, as illustrated inFIG. 17, in the ratchet state, when the outer ring3moves toward the other side in the axial direction by the ACT thrust, the inclined portion35comes into contact with the second inclined portion44. In this case, by a circumferential direction load (torque) acting on the engaging piece4from the outer ring3, a reaction force (component force against stroke), acting in the direction opposite to the direction of the ACT thrust, acts on the outer ring3. Due to the reaction force in the axial direction, the outer ring3is bounced off to the side opposite to a stroke direction. When the rotational rate of the outer ring3is high, the outer ring3is bounced off to the side opposite to the stroke direction by the second inclined portion44which is the chamfered end face of the engaging piece4. Therefore, it is possible to prevent the stroke (prevent quick engagement) in the ratchet state. Furthermore, as illustrated inFIGS. 18 and 19, in the ratchet state, a force is generated that raises the tip end41of the engaging piece4radially outward due to the circumferential direction load acting on the second inclined portion44from the inclined portion35. That is, even when the inclined portion35comes into contact with the engaging piece4, it is possible to maintain the standing state of the engaging piece4, so that the ratchet state can be maintained. Note that, in the ratchet state, when the outer ring3is bounced off the engaging piece4, the outer ring3can be bounced off (displaced in the axial direction) to the direction opposite to the stroke direction as the waiting spring10contracts.

As described above, according to the embodiment, the engaging device1including the engaging piece4projecting in the radial direction can act as a clutch. Also, in the structure in which the outer ring3is moved in the axial direction by the linear actuator7, it is possible to selectively switch between the OWC state and the free state. When switching from the free state to the OWC state, by stroking the outer ring3in the overrun state, the tapered portion34can come into contact with the first inclined portion43to push down the engaging piece4radially inward. This eliminates the necessity of phase synchronization, so that a responsiveness in switching between the free state and the OWC state is improved.

Also, by attaching the engaging piece4to the inner ring2, the engaging piece4can stand by a centrifugal force, so that meshing with the outer ring3is more surely performed.

Note that, as a modified embodiment, the accommodating unit21and the engaging piece4of the inner ring2may have a structure of limiting a standing angle of the engaging piece4. In this case, the engaging piece4and the second inner peripheral surface32may not necessarily be in contact with each other in the free state. As an example, a rear end of the engaging piece4comes into contact with a wall surface of the accommodating unit21to be formed to have a structure of limiting the standing of the engaging piece4. As a result, in the free state, since the engaging piece4and a cylindrical surface on an inner peripheral side of the outer ring3are not in contact with each other, an occurrence of drag loss due to sliding of the outer ring3with the engaging piece4can be suppressed, and power loss can be reduced accordingly.

According to an embodiment, when switching from the free state to the one-way clutch state, the tapered portion pushes down the inclined portion radially inward, so that switching operation can be performed without requiring a phase synchronization. Therefore, switching responsiveness is improved.

According to an embodiment, when switching from the free state to the one-way clutch state, the tapered portion provided between the first inner peripheral surface and the second inner peripheral surface can come into contact with the first inclined portion of the engaging piece to push down the tip end of the engaging piece radially inward, so that the phase synchronization is no longer necessary. This improves the responsiveness of the switching operation.

According to an embodiment, it is possible to stroke the outer ring in the axial direction in an overrun state. As a result, since the tapered portion comes into contact with the inclined portion, it is possible to switch without requiring the phase synchronization and the responsiveness of the switching operation is improved.

According to an embodiment, since the outer ring is bounced off to the direction opposite to a stroke direction by the second inclined portion of the engaging piece, it is possible to suppress a rapid engagement of the engaging piece with the outer ring when a rotational rate of the outer ring is high.

According to an embodiment, an occurrence of drag loss due to sliding of the outer ring with the engaging piece in the free state can be suppressed, and a power loss can be reduced accordingly.

In the present disclosure, since the engaging piece and the engaging surface include the tapered portion, the engaging piece is automatically pushed down in an overrun direction. Therefore, when the state transits from an opened state to an engaged state, it is not necessary to synchronously rotate the engaging piece and the engaging surface of the rotating element. Therefore, deterioration in responsiveness from the opened state to the engaged state may be suppressed.