WO2015063583A1

WO2015063583A1 - Parking lock device

Info

Publication number: WO2015063583A1
Application number: PCT/IB2014/002411
Authority: WO
Inventors: Jun HAKAMAGI; Kazutoshi Motoike; Tetsuya Kohno
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2013-11-01
Filing date: 2014-10-30
Publication date: 2015-05-07
Also published as: JP2015085914A

Abstract

A concave surface (20b, 28b) is formed in at least one of a contact area of a parking lock pawl (16) with a cam (30), and a contact area of a sleeve (28) with the cam (30). The concave surface (20b, 28b) comes into contact with the cam (30) from one end portion to the other end portion in an advancing direction when the cam (30) is inserted between the parking lock pawl (16) and the sleeve (28). Therefore, it is possible to maintain contact surface pressure between the parking lock pawl (16) and the cam (30) low, thus restraining wear of the contact area favorably. This means that it is possible to provide a parking lock device for a vehicle (10), which restrains deterioration of durability.

Description

PARKING LOCK DEVICE

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The invention relates to a parking lock device for a vehicle, particularly to an improvement of the parking lock device for a vehicle for restraining deterioration of durability. 2. Description of Related Art

[0002] A parking lock device for a vehicle is known, which includes a parking lock pawl which has a claw portion to be engaged with a tooth space of a parking gear, and is able to move between an engaging position where the claw portion is engaged with the tooth space and a retracting position where the claw portion is not engaged with the engaging tooth space, a sleeve fixed to a casing of a transmission, and a cam which is inserted between the parking lock pawl and the sleeve so that the cam comes into contact with the parking lock pawl and the sleeve, and moves the parking lock pawl to the engaging position. For example, a parking lock device described in Japanese Patent Application Publication No. 2010-202099 (JP 2010-202099 A) is one such example. According to the technology, by providing an inclined surface in the parking lock pawl, the cam is able to advance smoothly when inserted between the parking lock pawl and the sleeve.

SUMMARY OF THE INVENTION

[0003] However, in JP 2010-202099 A, the parking lock pawl and the cam are in point contact with each other, and contact pressure might be high. Therefore, a contact area is worn away, causing a reduction in an engagement amount for the tooth space of the parking gear and the parking lock pawl, and thus possible deterioration of durability of the device. Hence, there has been demands for development of a parking lock device for a vehicle, which restrains deterioration of durability.

[0004] The invention provides a parking lock device for a vehicle, which restrains deterioration of durability.

[0005] An aspect of the invention relates to a parking lock device for a vehicle including a transmission. The parking lock device includes a parking gear, a parking lock pawl, a sleeve, and a cam. The parking lock pawl has a claw portion engaged with a tooth space of the parking gear. The parking lock pawl is configured to move between an engaging position where the claw portion is engaged with the tooth space, and a retracting position where the claw portion is not engaged with the tooth space. The sleeve is fixed to a casing of the transmission. The cam is configured to come into contact with the parking lock pawl and the sleeve by being inserted between the parking lock pawl and the sleeve, and move the parking lock pawl to the engaging position. A concave surface is provided in at least one of a contact area of the parking lock pawl with the cam, and a contact area of the sleeve with the cam. The concave surface is a curved surface that comes into contact with the cam from one end portion to the other end portion in an insertion direction of the cam when the cam is inserted between the parking lock pawl and the sleeve.

[0006] According to the parking lock device, the concave surface is formed in at least one of the contact area of the parking lock pawl with the cam, and the contact area of the sleeve with the cam, and the concave surface is a curved surface that comes into contact with the cam from one end portion to the other end portion in an advancing direction of the cam when the cam is inserted between the parking lock pawl and the sleeve. Therefore, it is possible to maintain contact surface pressure between the parking lock pawl and the cam low, thereby restraining wear of the contact area favorably. In other words, it is possible to provide a parking lock device for a vehicle, which restrains deterioration of durability.

[0007] According to the parking lock device, by maintaining contact surface pressure between the parking lock pawl and the cam low, it is possible to reduce sliding friction in a contact area between the parking lock pawl and the cam. Therefore, an increase in operation load for releasing parking lock is prevented favorably. Further, because of the parking lock state, only small force needs to be applied to the parking lock pawl. Therefore, there is an advantage that the sizes of the parking lock pawl and the parking gear are reduced. Size reduction of the device causes an increase in load. However, according to the parking lock device stated above, contact surface pressure between the parking lock pawl and the cam is maintained low, and the device is able to endure large load. As a result, downsizing of the device is made possible.

[0008] In the parking lock device, the parking lock pawl may have an introduction curved surface. In the contact area of the parking lock pawl with the cam, the concave surface may be continuous from the introduction curved surface in the insertion direction when the cam is inserted between the parking lock pawl and the sleeve. This way, it is possible to favorably reduce contact surface pressure between the parking lock pawl and the cam in a practical form. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a perspective view explaining a main part of a structure of a parking lock device for a vehicle as a preferred example of the invention, and shows a parking lock released state;

FIG. 2 is a perspective view showing a parking lock state of the parking lock device for a vehicle shown in FIG. 1 ;

FIG. 3 is a sectional view showing a part of the structure of the parking lock device for a vehicle shown in FIG. 1 ;

FIG. 4 is a perspective view showing an example of a structure of a concave surface formed in a parking lock pawl of the parking lock device for a vehicle shown in FIG. 1;

FIG. 5 is a perspective view showing an example of a structure of a concave surface formed in a sleeve of the parking lock device for a vehicle shown in FIG. 1 ; FIG. 6 is a partial sectional view explaining details of a contact area between the parking lock pawl and a cam of the parking lock device for a vehicle shown in FIG. 1 ; and

FIG. 7 is partial sectional view explaining details of a contact area between the sleeve and the cam of the parking lock device for a vehicle shown in FIG. 1.

DETAILED DESCRIPTION OF EMBODIMENTS

[0010] The invention is favorably applied to a manual parking lock device for a vehicle, in which the cam is driven mechanically in accordance with an operation position of a shift operation device. Alternatively, the invention is favorably applied to a parking lock device for a vehicle of a shift-by-wire mechanism, in which the cam is driven by an actuator in accordance with an operation position of a shift operation device.

[0011] In the invention, it is preferred that the concave surface is formed between a flat surface portion facing a cam surface of the cam, and an introduction curved surface as described hereinafter, in a contact area of the parking lock pawl with the cam.

[0012] In the invention, it is preferred that the sleeve includes the introduction curved surface, the concave surface is formed in a contact area of the sleeve with the cam continuously from the introduction curved surface in an advancing direction when the cam is inserted between the parking lock pawl and the sleeve, and a curvature radius of the concave surface is equal to or larger than a curvature radius of the cam surface of the cam and smaller than a curvature radius of the introduction curved surface.

[0013] In the invention, it is preferred that the concave surface is formed between an inner periphery surface of the sleeve and the introduction curved surface in the contact area of the sleeve with the cam.

[0014] A preferred example of the invention is explained in detail below based on the drawings. In the drawings used for the explanation below, each portion is not necessarily depicted with accurate dimensional ratios.

[Example]

[0015] FIG. 1 and FIG. 2 are perspective views showing a main part of a structure of a parking lock device 10 for a vehicle as a preferred example of the invention. In FIG. 1 and FIG. 2, structures of a later-described preload spring 36 and so on are not shown. The parking lock device 10 is a mechanism that stops (locks) rotation of a wheel shaft (not shown) when a vehicle is stopped, and is provided inside a casing 12 for a transmission (an automatic transmission, a transaxle) (not shown). The parking lock device 10 includes a parking gear 14 connected directly or indirectly to the wheel shaft (not shown). For example, a counter shaft (not shown), which structures a part of a power transmission path between an output shaft of the transmission and a differential gear mechanism, is provided inside the casing 12, and the parking gear 14 is provided and fixed to a shaft end of the counter shaft. The parking gear 14 is structured into a gear shape with a plurality of teeth i4a on an outer peripheral side. A tooth space 14b is formed between the teeth 14a located next to each other. In short, the parking gear 14 has the plurality of tooth spaces 14b.

[0016] The parking lock device 10 includes a parking lock pawl 16 having a claw portion 16a that is engaged with the tooth space 14b of the parking gear 14. The parking lock pawl 16 is able to move between an engaging position (a parking lock position) where the claw portion 16a is engaged with (fitted to) the tooth space 14b, and a retracting position (a non-parking lock position) where the claw portion 16a is not engaged with the tooth space 14b. FIG. 1 shows a state where the parking lock pawl 16 is in the retracting position, and FIG. 2 shows a state where the parking lock pawl 16 is in the engaging position. As shown in FIG. 1 and FIG. 2, the parking lock pawl 16 is formed into a longitudinal shape (a lever shape), and the claw portion 16a is provided in a center part in the longitudinal direction of the parking lock pawl 16. A distal end portion 16b is supported on the casing 12 by a pin 18 so that the distal end portion 16b is able to turn. A contact portion 20 to be brought into contact with a later-described cam 30 is provided in an end potion on the opposite side of the distal end portion 16b. In this structure, the parking lock pawl 16 turns about the pin 18 between the retracting position shown in FIG. 1 and the engaging position shown in FIG. 2. Preferably, the parking lock pawl 16 is always biased by a return spring (not shown) towards the retracting position, in other words, a position where the claw portion 16a is not engaged with the tooth space 14b. [0017] The parking lock device 10 includes a shaft member 22 that is driven to rotate in accordance with a shift operation position of a shift operation device such as a shift lever (not shown), a detent member 24 that is fixed to a given position of the shaft member 22 so that the detent member 24 is not able to rotate relative to the shaft member 22, and provided about an axis of the shaft member 22 to be able to turn, and a parking rod 26, a distal end portion of which is connected to the detent member 24 to be able to turn. The shaft member 22 may be an element of a manual device that is mechanically driven to rotate in accordance with a shift operation position of a shift operation device, or an element of so-called a shift-by-wire mechanism that is driven to rotate by an actuator in accordance with a shift operation position of a shift operation device. A cam surface 24a is provided in an outer peripheral edge portion of the detent member 24. The cam surface 24a has recessed valley portions in order to position the detent member 24 at the parking lock position and the non-parking lock position. The parking rod 26 is connected to an end portion of the detent member 24 on the opposite side of the side where the cam surface 24a is provided, so that the parking rod 26 is able to turn. The detent member 24 is also referred to as a detent plate, a parking lever, a detent lever, a click stop plate, and so on.

[0018] The cam (a parking lock cam) 30 is fitted to a distal end portion of the parking rod 26, in other words, an end portion on the opposite side of the side connected to the detent member 24 so that the parking rod 26 is able to turn. The cam 30 is able to move in a longitudinal direction. A sleeve 28 is fixed to the casing 12. The cam 30 is able to move between an insertion position, where the cam 30 is inserted between the contact portion 20 of the parking lock pawl 16 and the sleeve 28, and a separation position, where the cam 30 is not inserted between the contact portion 20 and the sleeve 28.

[0019] FIG. 3 is a view explaining details of structures of the contact portion 20, the sleeve 28, the cam 30, and so on in the parking lock device 10, and shows a part of the structures in cross section. FIG. 3 shows a state where the cam 30 is inserted between the contact portion 20 and the sleeve 28 and brought into contact with the contact portion 20 and the sleeve 28, and the parking lock pawl 16 is in the engaging position. As shown in FIG. 3, a cam surface 32 is provided on a side peripheral portion (a side peripheral surface) of the cam 30. Preferably, the cam surface 32 is formed into a tapered shape, in which a diameter dimension is gradually reduced in the advancing direction (shown by an arrow B in FIG. 3) of the cam 30 when inserted between the parking lock pawl 16 and the sleeve 28. Further, a tapered surface 34, in which a diameter dimension is gradually reduced in the advancing direction, is formed in a distal end portion of the cam 30 in the advancing direction as an introduction portion for the cam 30 to be inserted between the parking lock pawl 16 and the sleeve 28. In the distal end portion of the parking rod 26, the coil_^shaped preload spring 36, which biases the cam 30 by using previously-set preload towards a distal end stopper (not shown), is inserted between a spring seat (not shown) fixed to a given position of the parking rod 26, and the cam 30. The cam 30 structured as stated above is supported so as to be able to move in the longitudinal direction (in an axis direction near the cam 30) of the parking rod 26, and the cam 30 is able to move in a sliding manner relative to the contact portion 20 of the parking lock pawl 16 and the sleeve 28.

[0020] As shown in FIG. 3, the contact portion 20 of the parking lock pawl 16 includes a cam introduction curved surface (an introduction curved surface) 20a. The cam introduction curved surface 20a is, for example, a partially cylindrical concave surface which is formed to be inclined in a contact area of the contact portion 20 with the cam 30 at a position where the tapered surface 34 of the cam 30 is brought into contact (abutted) when the cam 30 is inserted between the parking lock pawl 16 and the sleeve 28. Preferably, a curvature radius of the cam introduction curved surface 20a is equal to or larger than a curvature radius of the tapered surface 34 of the cam 30. The sleeve 28 includes a cam introduction curved surface 28a. The cam introduction curved surface 28a is, for example, a partially conical concave surface which is formed to be inclined in a contact area of the sleeve 28 with the cam 30 at a position where the tapered surface 34 of the cam 30 is brought into contact (abutted) when the cam 30 is inserted between the parking lock pawl 16 and the sleeve 28. Preferably, a curvature radius of the cam introduction curved surface 28a is equal to or larger than a curvature radius of the tapered surface 34 of the cam 30. [0021] When the shaft member 22 is rotated in a direction shown by an arrow A in accordance with a shift operation position of the shift operation device (not shown) from the state of the parking lock device 10 shown in FIG. 1, in other words, in the state of the retracting position where the claw portion 16a is not engaged with the tooth space 14b, the detent member 24 integrally provided in the shaft member 22 is turned in the same direction, and the parking rod 26 is drawn out in the direction shown by the arrow B. Thus, the cam 30 is pushed out in the direction shown by the arrow B due to biasing force of the preload spring 36, and brought to the insertion position where the cam 30 is inserted between the contact portion 20 of the parking lock pawl 16 and the sleeve 28 and brought into contact with the contact portion 20 and the sleeve 28. Since the cam 30 is brought to the insertion position, the contact portion 20 of the parking lock pawl 16 is moved in a direction away from the sleeve 28, and the parking lock pawl 16 is moved (turned) to the engaging position shown in FIG. 2. In the state where the parking lock pawl 16 is in the engaging position, in other words, in the parking lock state, rotation of the wheel shaft connected with the parking gear 14 is restrained.

[0022] When the shaft member 22 is rotated in a direction shown by an arrow A' in accordance with a shift operation position of the shift operation device (not shown) from the state of the parking lock device 10 shown in FIG. 2, in other words, the engaging position where the claw portion 16a is engaged with the tooth space 14b, the detent member 24 integrally provided with the shaft member 22 is turned in the same direction, and the parking rod 26 is drawn out in a direction shown by an arrow B'. Thus, the cam 30 is drawn out in the direction shown by the arrow B', pulled out from between the contact portion 20 of the parking lock pawl 16 and the sleeve 28, and brought to the separation position. As the cam 30 is brought to the separation position, the parking lock pawl 16 is biased by biasing force of a return spring (not shown) towards a position where the claw portion 16a is not engaged with the tooth space 14b, and the parking lock pawl 16 is moved (turned) to the retracting position shown in FIG. 1. In the state where the parking lock pawl 16 is in the retracting position, in other words, in a parking lock released state, rotation of the wheel shaft connected with the parking gear 14 is allowed (the wheel shaft rotates freely).

[0023] In the parking lock device described above, in a case of a conventional technology, the parking lock pawl and the cam can be in point contact with each other when the cam is at the insertion position where the cam is inserted between the parking lock pawl and the sleeve and brought into contact with the parking lock pawl and the sleeve. This causes a problem of deterioration of durability of the device. For example, in a case where operations are carried out to park a vehicle only by braking force of a parking lock device on a slope, or to stop a vehicle from a running state by braking force of a parking lock device, the parking lock pawl and the parking gear mesh with each other, and load is applied on a mating surface between the parking lock pawl and the cam. With repeated application of load, the contact surface of the cam with the parking lock pawl becomes rough (damaged). Also, a contact surface of the parking lock pawl with the cam is worn away. Because of the rough contact surface of the cam with the parking lock pawl, load for pulling out the cam from between the parking lock pawl and the sleeve in the direction shown by the arrow B' in FIG. 2 is increased. Therefore, operation load for releasing a lock state (an operation to shift from P range) by the parking lock device is increased. Due to wear of the contact surface of the parking lock pawl with the cam, the position of the parking lock pawl is lowered when locked by the parking lock device (and, as a result, the contact portion comes closer to the sleeve in the state where the cam is inserted). This can reduce an engagement amount between the claw portion of the parking lock pawl and the tooth space of the parking gear.

[0024] Therefore, in the parking lock device 10 according to this example, a concave surface, which follows the side peripheral surface of the cam 30, in other words, the cam surface 32, is formed in at least one of the contact area of the parking lock pawl 16 with the cam 30 and the contact area of the sleeve 28 with the cam 30. FIG. 4 is a view showing an example of a structure of, for example, a partially cylindrical concave surface 20b that is formed to be inclined more than the cam introduction curved surface 20a in the contact portion 20 of the parking lock pawl 16. As shown in FIG. 4, it is preferred that the concave surface 20b is formed continuously from the cam introduction curved surface 20a in the advancing direction shown by the arrow B in FIG. 3 in the contact area of the parking lock pawl 16 with the cam 30. It is more preferred that the concave surface 20b is formed between a generally flat-shaped flat surface portion 20c and the cam introduction curved surface 20a in the contact area of the parking lock pawl 16 with the cam 30. The flat surface portion 20c corresponds to a surface facing the cam surface 32 of the cam 30 in the contact area of the parking lock pawl 16 with the cam 30. Preferably, the concave surface 20b is a partial cylindrical surface corresponding to a given curvature radius. It is preferred that the curvature radius of the concave surface 20b is generally equal to a curvature radius of the cam surface 32 of the cam 30. In other words, curvature of the concave surface 20b is generally the same as curvature of the cam surface 32.

[0025] FIG. 5 is a view showing an example of a structure of a concave surface 28b formed in the contact area of the sleeve 28 with the cam 30. As shown in FIG. 5, it is preferred that the concave surface 28b is formed continuously from the partially conical cam introduction curved surface 28a in the advancing direction shown by the arrow B in FIG 3, in the contact area of the sleeve 28 with the cam 30. It is further preferred that the concave surface 28b is formed to be inclined between an inner peripheral surface 28c having a cylindrical surface and the cam introduction curved surface 28a, in the contact area of the sleeve 28 with the cam 30. Preferably, the concave surface 28b is a partial cylindrical surface corresponding to a given curvature radius. It is preferred that a curvature radius of the concave surface 28b is generally equal to the curvature radius of the cam surface 32 of the cam 30. In other words, the curvature of the concave surface 28b is generally equal to the curvature of the cam surface 32.

[0026] FIG. 6 is a partial sectional view for explaining details of the contact area between the contact portion 20 and the cam 30 when the cam 30 is inserted between the parking lock pawl 16 and the sleeve 28, and a range corresponding to the concave surface 20b in the advancing direction is shown as "a". FIG. 7 is a partial sectional view for explaining details of the contact area between the sleeve 28 and the cam 30 when the cam 30 is inserted between the parking lock pawl 16 and the sleeve 28, and a range corresponding to the concave surface 28b in the advancing direction is shown as "b". As shown in FIG. 6 and FIG. 7, it is preferred that the concave surfaces 20b, 28b come into contact with the cam 30 from an end portion through the other end portion in the advancing direction when the cam 30 is inserted between the contact portion 20 of the parking lock pawl 16 and the sleeve 28. In short, in the contact area between the contact portion 20 and the cam 30, the concave surface 20b of the contact portion 20 is brought into line contact, and therefore surface contact with the cam surface 32 of the cam 30 in the range shown as "a" in FIG. 6. In the contact area between the sleeve 28 and the cam 30, the concave surface 28b of the sleeve 28 is brought into line contact, and therefore surface contact with the cam surface 32 of the cam 30 in the range shown by "b" in FIG. 7. In the parking lock device 10, either one of the concave surfaces 20b, 28b may be formed. Preferably, the concave surface 20b is formed in the contact portion 20 of the parking lock pawl 16. This means that the concave surface 28b does not necessarily have to be formed in the sleeve 28.

[0027] As explained so far, in the parking lock device 10 according to the example, the contact area is brought into line contact and thus surface contact with the cam 30 when the cam 30 is inserted between the parking lock pawl 16 and the sleeve 28, and contact surface pressure is reduced due to Hertzian contact stress. In particular, since the contact area of the contact portion 20 with the cam surface 32 of the cam 30 is formed as the concave surface 20b, the contact area with the cam 30 may be in surface contact with the cam 30 in a practical form, and contact surface pressure is dramatically reduced. Thus, it is possible to keep contact surface pressure between the parking lock pawl 16 and the cam 30 low, thereby reducing defects such as a rough surface of the cam 30 and wear of the contact area of the parking lock pawl 16 with the cam 30, in severe use environments. The same effect is obtained when contact surface pressure between the sleeve 28 the cam 30 is reduced by forming the concave surface 28b in the sleeve 28. Thus, it is possible to restrain an increase in sliding friction between the parking lock pawl 16 and the cam 30, and restrain an increase in operation load for releasing parking lock. Moreover, by restraining wear of the parking lock pawl 16, it is possible to reduce an amount of change of the location of the parking lock pawl 16 (a push-up stroke when switching from the retracting position to the engaging position), there is an advantage that sizes of the parking gear 14 and the parking lock pawl 16 are reduced.

[0028] As stated so far, according to this example, the concave surface 20b, 28b is formed at least one of the contact area of the parking lock pawl 16 with the cam 30, and the contact area of the sleeve 28 with the cam 30, and the concave surfaces 20b, 28b are in contact with the cam 30 from one end portion through the other end portion in the advancing direction when the cam 30 is inserted between the parking lock pawl 16 and the sleeve 28. Therefore, it is possible to restrain contact surface pressure between the parking lock pawl 16 and the cam 30, thereby restraining wear of the contact area favorably. In short, it is possible to provide the parking lock device for a vehicle 10, which restrains a deterioration of durability.

[0029] The parking lock pawl 16 includes the cam introduction curved surface 20a, and the concave surface 20b is formed continuously from the cam introduction curved surface 20a in the advancing direction when the cam 30 is inserted between the parking lock pawl 16 and the sleeve 28, in the contact area of the parking lock pawl 16 with the cam 30. Therefore, it is possible to favorably reduce contact surface pressure between the parking lock pawl 16 and the cam 30 in a practical form.

[0030] The preferred example of the invention has been explained in detail based on the drawings. However, the invention is not limited to the example, and is carried out with various changes added without departing from the gist of the invention.

Claims

CLAIMS:

1. A parking lock device for a vehicle including a transmission, the parking lock device comprising:

a parking gear;

a parking lock pawl having a claw portion engaged with a tooth space of the parking gear, the parking lock pawl configured to move between an engaging position where the claw portion is engaged with the tooth space, and a retracting position where the claw portion is not engaged with the tooth space;

a sleeve fixed to a casing of the transmission; and

a cam configured to come into contact with the parking lock pawl and the sleeve by being inserted between the parking lock pawl and the sleeve, and move the parking lock pawl to the engaging position, a concave surface provided in at least one of a contact area of the parking lock pawl with the cam, and a contact area of the sleeve with the cam, and the concave surface being a curved surface that comes into contact with the cam from one end portion of the concave surface to the other end portion of the concave surface in an insertion direction of the cam when the cam is inserted between the parking lock pawl and the sleeve.

2. The parking lock device according to claim 1 , wherein

the parking lock pawl has an introduction curved surface, and,

in the contact area of the parking lock pawl with the cam, the concave surface is continuous from the introduction curved surface in the insertion direction when the cam is inserted between the parking lock pawl and the sleeve.