CN114096758B

CN114096758B - Switchable ratchet clutch

Info

Publication number: CN114096758B
Application number: CN201980098445.9A
Authority: CN
Inventors: P·布尔克
Original assignee: Schaeffler Technologies AG and Co KG
Current assignee: Schaeffler Technologies AG and Co KG
Priority date: 2019-08-07
Filing date: 2019-08-07
Publication date: 2024-09-03
Anticipated expiration: 2039-08-07
Also published as: WO2021025692A1; DE112019007605T5; CN114096758A

Abstract

A switchable ratchet clutch that enables four different modes of operation based on the relative rotational positions of the cam ring and the inner ring. In the relative position of the centers, the outer ring is free to rotate in either direction relative to the inner ring. In either extreme relative position, the outer ring is prevented from rotating in either direction relative to the inner ring. In the intermediate position either side of the central position, the outer ring is allowed to rotate in one direction but not in the other. A plurality of pawls are supported on the inner ring and urged radially out of engagement with the outer ring by springs on a spring carrier. The spring carriage moves with the cam ring between unidirectional positions, but when moved into the extreme position, the cam ring rotates relative to the spring carriage.

Description

Switchable ratchet clutch

Technical Field

The present disclosure relates generally to the field of clutches. More particularly, the present disclosure relates to a ratchet clutch that is switchable among five modes including a free-free mode, two one-way modes, and two lock-lock modes.

Background

Automotive transmissions establish a variety of selectable speed ratios between the engine and driven wheels. For a discrete ratio transmission, the speed ratio is typically selected by engaging a particular clutch. The clutch limits relative rotation between the components, one or both of which may otherwise rotate relative to the transmission housing. Some clutches rely on friction to limit relative movement. On the other hand, ratchet clutches have pawls or other components that engage to resist relative movement in one direction, and ratchet teeth to permit relative movement in the opposite direction.

Some ratchet clutches are fully passive devices. Other ratchet clutches can be switched between modes. For example, the switchable ratchet clutch may include a first mode that allows relative rotation in two directions and a second mode that allows relative rotation in only one direction. Previously known selectable four-mode ratchet clutches are formed by combining multiple dual-mode ratchet clutches.

Disclosure of Invention

The switchable ratchet clutch includes an inner ring, an outer ring, a cam ring, a plurality of pawls, and a plurality of ratchet springs. The outer ring has an internal tooth profile and is supported for rotation relative to the inner ring. The cam ring is supported for rotation relative to the inner ring within a first range. The plurality of pawls are supported by the inner ring. Each of the plurality of ratchet springs urges a respective pawl radially toward the cam ring and positions the respective pawl relative to the outer ring based on a relative rotational position of the cam ring relative to the inner ring. In the first relative rotational position, the respective pawl does not engage the outer ring. In the second relative rotational position, the respective pawl engages the tooth profile to prevent rotation of the outer ring relative to the inner ring in the first direction while allowing relative rotation in the second direction. In the third relative rotational position, the respective pawls engage the tooth profile to prevent rotation of the outer ring relative to the inner ring in the second direction while allowing relative rotation in the first direction. In the fourth and fifth relative rotational positions, the respective pawls engage the profile to prevent rotation of the outer ring relative to the inner ring in the first and second directions. The first relative rotational position may be between the second relative rotational position and the third relative rotational position. The second relative rotational position may be between the first relative rotational position and the fourth relative rotational position. The third relative rotational position may be between the first relative rotational position and the fifth relative rotational position. The spring carrier may be supported for rotation relative to the inner ring within a second range that is less than the first range. The ratchet spring may be fixed to the spring frame. A plurality of return springs may act between the cam ring and the spring mount. Rotation of the spring holder relative to the inner ring may change the center of force of the ratchet spring on the pawl, thereby urging the pawl to tilt into engagement with the tooth profile. Each pawl may include a first arm and a second arm. The first arm may be configured to engage the tooth profile to prevent relative rotation in the first direction. The second arm may be configured to engage the tooth profile to prevent relative rotation in the second direction.

A method of operating a switchable ratchet clutch includes rotating a cam ring relative to a first ring to switch between modes of operation. The cam ring rotates clockwise relative to the first ring to transition from the free-free mode to the first unidirectional mode. In the free-free mode, the second ring is allowed to rotate in either direction relative to the first ring. In the first unidirectional mode, the second ring is allowed to rotate in a first direction relative to the first ring but is prevented from rotating in a second direction relative to the first ring. The cam ring is further rotated clockwise relative to the first ring to transition from the first unidirectional mode to the first lock-lock mode. In the first lock-and-lock mode, the second ring is prevented from rotating in either direction relative to the first ring. The cam ring rotates counterclockwise relative to the first ring to transition from the free-free mode to the second unidirectional mode. In the second unidirectional mode, the second ring is allowed to rotate in a second direction relative to the first ring but is prevented from rotating in the first direction relative to the first ring. The cam ring may be further rotated counter-clockwise relative to the first ring to transition from the second unidirectional mode to the second lock-and-lock mode. In the second lock-and-lock mode, the second ring is prevented from rotating in either direction relative to the first ring. The first direction may be a counterclockwise direction and the second direction may be a clockwise direction. In the free-free mode, the ratchet spring may be fixed to the spring holder and may urge the pawl radially out of engagement with the second ring. The transition from the free-free mode to the first unidirectional mode may include rotating the spring holder clockwise via a link between the cam ring and the spring holder, thereby changing a center of the ratchet spring against the force of the pawl to urge the pawl to rotate into engagement with the profile of the second ring. The transition from the first unidirectional mode to the first lock-and-lock mode may include limiting further rotation of the spring holder and forcing the pawl into engagement with two teeth of the profile of the second ring via the ramped surface of the cam ring.

Drawings

Fig. 1 is an end view of a switchable ratchet clutch in a free-free mode.

Fig. 2 is a cross-sectional view of the switchable ratchet clutch of fig. 1 in a free-free mode.

Fig. 3 is a first schematic view of the switchable ratchet clutch of fig. 1 in a free-free mode.

Fig. 4 is a second schematic view of the switchable ratchet clutch of fig. 1 in a free-free mode.

FIG. 5 is a partial cross-sectional view of the switchable ratchet clutch of FIG. 1 in a first unidirectional mode.

FIG. 6 is a partial cross-sectional view of the switchable ratchet clutch of FIG. 1 in a first lock-and-lock mode.

FIG. 7 is a partial cross-sectional view of the switchable ratchet clutch of FIG. 1 in a second unidirectional mode.

FIG. 8 is a partial cross-sectional view of the switchable ratchet clutch of FIG. 1 in a second lock-and-lock mode.

Detailed Description

Various embodiments of the present disclosure are described herein. It should be appreciated that like reference numbers appearing in different drawing views identify identical or functionally similar structural elements. It is also to be understood that the disclosed embodiments are merely examples and that other embodiments may take various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the embodiments. As will be appreciated by one of ordinary skill in the art, the various features illustrated and described with reference to any of the figures may be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combination of features illustrated provides representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of the present disclosure may be desired for particular applications or implementations.

The terminology used herein is for the purpose of describing particular aspects only and is not intended to limit the scope of the present disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods, devices, or materials similar or equivalent to those described herein can be used in the practice or testing of the present disclosure, the following example methods, devices, and materials are now described.

Fig. 1-4 illustrate a selectable clutch in a free-free mode. In the free-free mode, the outer ring 10 is free to rotate in either direction relative to the inner ring 12. The actuating mechanism is simplest if the inner ring 12 is stationary relative to the gearbox housing. Any description of the movement of the various components should be interpreted as movement relative to the inner ring 12 throughout this document. The cam ring 14 is supported for rotation over a limited range of angles. The desired mode of the selectable clutch is enabled by rotating the cam ring 14 to a corresponding position within the range of motion. In addition to the free-free modes illustrated in fig. 1-4, two unidirectional modes and two lock-lock modes are available. In the unidirectional mode, the outer ring 10 is free to rotate in one direction but is prevented from rotating in the other direction. In the lock-and-lock mode, the outer ring 10 is prevented from rotating in either direction.

A plurality of pairs of lugs 16A and 16B axially project from the inner ring 12. A plurality of pawls 18 are circumferentially supported between the lugs. The shape of the lugs and the engagement surface of the pawl are selected to allow a range of radial movement and a range of rotational or tilting movement of the pawl. The spring holder 20 is supported for rotation over a limited range of angles. The range of motion of the spring mount 20 is substantially less than the range of motion of the cam ring 14. As best seen in fig. 2, the return spring 22 urges the spring mount 20 into rotational alignment with the cam ring 14. A ratchet spring 24 is fixed to the spring holder 20 and pushes against the pawl 18. As best seen in fig. 3 and 4, the ratchet spring 24 is secured to a boss extending axially from the spring holder 20 between the outer ring 10 and the dogs 18. The ratchet spring 24 may be a leaf spring that pushes against the pawl in two different positions. In the free-free mode illustrated in fig. 1-4, the spring force is concentrated on the pawls and acts to urge the pawls radially inward toward the cam ring 14. In this position, the entire pawl 18 remains away from the inner tooth profile 26 of the outer ring. Since the dogs do not contact the outer ring 10, the dogs do not limit the rotation of the outer ring 10.

Fig. 5 illustrates the mode of the clutch in a first unidirectional mode in which the outer ring 10 is free to rotate counter-clockwise relative to the inner ring 12 but is restricted from rotating clockwise relative to the inner ring 12. This mode is enabled by rotating the cam ring 14 clockwise. In response, the return spring 22 forces the spring frame 20 to also rotate clockwise. Pawl 18 includes two arms 28A and 28B. As the spring holder 20 rotates relative to the inner ring 12, the force of the ratchet spring 24 deflects on the pawl 18 such that the pawl tilts into a position in which the first arm 28A engages one of the teeth of the tooth profile 26. This engagement prevents clockwise rotation of the outer ring 10. Any clockwise torque on the outer ring 12 is transferred to the inner ring 12 by the dogs 18 via lugs 16B. When the outer ring 10 rotates in a counter-clockwise direction, the teeth of the tooth profile 26 push the first arm 28A apart against the force of the ratchet spring 24. At most a small amount of parasitic drag torque is transferred from the outer ring 10 to the inner ring 12 in a counter-clockwise direction. In order to avoid the large forces associated with abrupt stopping of the outer ring 10, a transition from the free-free mode to this first unidirectional mode preferably occurs when the outer ring rotates counter-clockwise or at least below a threshold clockwise speed.

Fig. 6 illustrates a mode of the clutch in a first lock-up mode in which relative rotation in both directions is prevented. The first lock-lock mode is enabled from the first unidirectional mode by further rotating the cam ring 14 clockwise. The boss 30A of the spring carrier 20 contacts the ledge 16A of the inner ring 12, thereby preventing further clockwise rotation of the spring carrier 20. Thus, further rotation of the cam ring 14 causes the return spring 22 to become compressed. As the cam ring 14 rotates clockwise, the cam profile 32A of the cam ring 14 forces the pawls 18 radially outward, compressing the ratchet spring 24. In the radially extended position, both the first arm 28A and the second arm 28B engage respective teeth of the tooth profile 26. As in the first unidirectional mode described above, any clockwise torque on the outer ring 12 is transferred to the inner ring 12 by the dogs 18 via lugs 16B. In addition, any counterclockwise torque on the outer ring 12 is transferred to the inner ring 12 by the dogs 18 via lugs 16A. In order to avoid the large forces associated with abrupt stopping of the outer ring 10, a transition from the first unidirectional mode to this first lock-and-lock mode preferably occurs when the outer ring is stationary or at least below a threshold counter-clockwise speed.

Fig. 7 illustrates the mode of the clutch in a second unidirectional mode in which the outer ring 10 is free to rotate clockwise relative to the inner ring 12 but is restricted from rotating counter-clockwise relative to the inner ring 12. This mode is enabled from the free-free mode by rotating cam ring 14 counterclockwise. In response, the return spring 22 forces the spring carrier 20 to also rotate counterclockwise. As the spring holder 20 rotates relative to the inner ring 12, the force of the ratchet spring 24 deflects on the pawl 18 such that the pawl tilts into a position in which the second arm 28B engages one of the teeth of the tooth profile 26. This engagement prevents counterclockwise rotation of the outer ring 10. Any counterclockwise torque on the outer ring 12 is transferred to the inner ring 12 by the dogs 18 via lugs 16A. When the outer ring 10 rotates in a clockwise direction, the teeth of the tooth profile 26 push the second arm 28B apart against the force of the ratchet spring 24. At most a small amount of parasitic drag torque is transferred in a clockwise direction from the outer ring 10 to the inner ring 12. In order to avoid the large forces associated with abrupt stopping of the outer ring 10, a transition from the free-free mode to the second unidirectional mode preferably occurs when the outer ring rotates clockwise or at least below a threshold counter-clockwise speed.

Fig. 8 illustrates a mode of the clutch in a second lock-up mode in which relative rotation in both directions is prevented. The second lock-lock mode is enabled from the second unidirectional mode by further rotating the cam ring 14 counterclockwise. The boss 30B of the spring carrier 20 contacts the ledge 16B of the inner ring 12, thereby preventing further counterclockwise rotation of the spring carrier 20. Thus, further rotation of the cam ring 14 causes the return spring 22 to become compressed. As the cam ring 14 rotates counterclockwise, the cam profile 32B of the cam ring 14 forces the pawls 18 radially outward, compressing the ratchet spring 24. In the radially extended position, both the first arm 28A and the second arm 28B engage respective teeth of the tooth profile 26. As in the second unidirectional mode described above, any counterclockwise torque on the outer ring 12 is transferred to the inner ring 12 by the dogs 18 via lugs 16A. In addition, any clockwise torque on the outer ring 12 is transferred to the inner ring 12 by the dogs 18 via lugs 16B. In order to avoid the large forces associated with abrupt stopping of the outer ring 10, a transition from the second unidirectional mode to this second lock-and-lock mode preferably occurs when the outer ring is stationary or at least below a threshold clockwise speed.

While exemplary embodiments are described above, the exemplary embodiments are not intended to describe all possible forms covered by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure. As previously described, features of the various embodiments may be combined to form further embodiments of the disclosure that may not be explicitly described or illustrated. While various embodiments may be described as providing advantages or being superior to other embodiments or implementations of the prior art in terms of one or more desired features, those of ordinary skill in the art will recognize that one or more features or characteristics may be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. As such, to the extent that any embodiment is described as being less desirable in one or more features than other embodiments or prior art implementations, such embodiments are not beyond the scope of the present disclosure and may be desirable for a particular application.

Claims

1. A switchable clutch comprising:

a first ring;

a second ring having a tooth profile and supported for rotation relative to the first ring;

A cam ring supported for rotation relative to the first ring within a first range;

A plurality of pawls supported by the first ring; and

A plurality of ratchet springs, each ratchet spring urging a respective pawl toward the cam ring and positioning the respective pawl relative to the second ring based on a relative rotational position of the cam ring relative to the first ring such that

In the first relative rotational position, the respective pawl does not engage the second ring,

In a second relative rotational position, the respective pawl engages the tooth profile to prevent rotation of the second ring relative to the first ring in a first direction while allowing relative rotation in a second direction,

In a third relative rotational position, the respective pawl engages the tooth profile to prevent rotation of the second ring relative to the first ring in the second direction while allowing relative rotation in the first direction,

In a fourth relative rotational position, the respective pawl engages the tooth profile to prevent rotation of the second ring relative to the first ring in the first and second directions,

Wherein each of the plurality of pawls includes:

a first arm configured to engage the tooth profile to prevent relative rotation in the first direction; and

A second arm configured to engage the tooth profile to prevent relative rotation in the second direction.

2. The switchable clutch of claim 1, wherein the first relative rotational position is between the second relative rotational position and the third relative rotational position.

3. The switchable clutch of claim 2, wherein the second relative rotational position is between the first relative rotational position and the fourth relative rotational position.

4. A switchable clutch according to claim 3, wherein:

In a fifth relative rotational position of the cam ring with respect to the first ring, each ratchet spring positions the respective pawl with respect to the second ring such that the respective pawl engages the tooth profile to prevent rotation of the second ring with respect to the first ring in the first and second directions,

The third relative rotational position is between the first relative rotational position and the fifth relative rotational position.

5. The switchable clutch according to one of claims 1 to 4, further comprising:

A spring mount supported for rotation relative to the first ring within a second range that is less than the first range, wherein the ratchet spring is fixed to the spring mount; and

A plurality of return springs acting between the cam ring and the spring carrier, wherein rotation of the spring carrier relative to the first ring changes a center of force of the ratchet spring on the pawl, thereby urging the pawl to tilt into engagement with the tooth profile.

6. A method of operating a switchable clutch according to one of claims 1 to 5, the method comprising:

Rotating the cam ring clockwise relative to the first ring to transition from a free-free mode to a first unidirectional mode, wherein in the free-free mode the second ring is allowed to rotate in either direction relative to the first ring, and wherein in the first unidirectional mode the second ring is allowed to rotate in a first direction relative to the first ring but prevented from rotating in a second direction relative to the first ring;

further rotating the cam ring clockwise relative to the first ring to transition from the first unidirectional mode to a first lock-lock mode, wherein in the first lock-lock mode, the second ring is prevented from rotating in either direction relative to the first ring; and

The cam ring is rotated counter-clockwise relative to the first ring to transition from the free-free mode to a second unidirectional mode, wherein in the second unidirectional mode the second ring is allowed to rotate in the second direction relative to the first ring but the second ring is prevented from rotating in the first direction relative to the first ring.

7. The method of claim 6, further comprising:

The cam ring is further rotated counter-clockwise relative to the first ring to transition from the second unidirectional mode to a second lock-lock mode, wherein in the second lock-lock mode, the second ring is prevented from rotating in either direction relative to the first ring.

8. A method of operating the switchable clutch of claim 5, the method comprising:

Rotating the cam ring counter-clockwise relative to the first ring to transition from the free-free mode to a second unidirectional mode, wherein in the second unidirectional mode the second ring is allowed to rotate relative to the first ring in the second direction but prevented from rotating relative to the first ring in the first direction, wherein:

In the free-free mode, a ratchet spring secured to the spring holder urges a pawl radially out of engagement with the second ring; and

The transition from the free-free mode to the first unidirectional mode includes rotating the spring holder clockwise via a link between the cam ring and the spring holder, thereby changing a center of force of the ratchet spring against the pawl to urge the pawl to rotate into engagement with a tooth profile of the second ring.

9. The method of claim 8, wherein the transition from the first unidirectional mode to the first lock-and-lock mode comprises:

limiting further rotation of the spring holder; and

The pawl is forced into engagement with two teeth of the profile of the second ring via a ramp of the cam ring.