JP5187170B2 - Torque limiter and driving force transmission device - Google Patents

Description

  The present invention relates to a torque limiter and a driving force transmission device.

Conventionally, some driving force transmission devices use a one-way clutch as an intermittent mechanism (see Patent Documents 1 and 2). This driving force transmission device changes torque transmission paths by intermittently interrupting torque from an installed electric motor in an intermittent mechanism according to the driving state of the vehicle.
JP 2007-71382 A JP 2008-32163 A

  However, the conventional driving force transmission device becomes a problem because there is no part for releasing torque when the vehicle is suddenly decelerated or the side brake is pulled. It is conceivable to provide a torque limiter as a part for releasing torque. However, in the conventional torque limiter, the influence of the cam surface inclination angle and the number of cam grooves on the cam radius is large, and the cam rotating member and the rotating member are pressed. The degree of freedom in designing the disc spring is low. For this reason, when the cam radius is changed in accordance with the size of the driving force transmission device and the size of the installation location, it is necessary to redesign the cam surface inclination angle, the number of cam grooves, the load of the disc spring, and the like.

  The present invention has been made paying attention to such a conventional problem, and an object of the present invention is to provide a portion for releasing torque in a driving force transmission device using a suitable torque limiter.

The torque limiter of the driving force transmission device has a first cam surface, has a first rotating member to which torque is input, and a second cam surface, and is coaxial with the first rotating member. And a plurality of balls interposed between the first cam surface of the first rotating member and the second cam surface of the second rotating member. And a spring for pressing the first rotating member or the second rotating member, and at least one of the first cam surface and the second cam surface extends along a plane substantially perpendicular to the axial direction. A plurality of horizontal portions, and a plurality of concave portions located between the plurality of horizontal portions and recessed with respect to the plurality of horizontal portions , wherein the number of the plurality of concave portions is greater than the number of the balls. Features.

  Without increasing the depth of depression of the ball into the recess, the length of the horizontal portion can be adjusted to increase the inclination angle of the recess, and the cam thrust can be reduced. Since the cam thrust can be reduced relative to the input torque to the cam, the spring load can be reduced and the spring can be reduced in size. In addition, the number of balls can be reduced, or the ball diameter can be reduced. Furthermore, by adjusting the length of the horizontal portion, the degree of freedom in designing the cam radius and the ball diameter is increased without being affected by the inclination angle of the recess and the number of recesses.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

<First Embodiment>
A driving force transmission device according to a first embodiment of the present invention will be described. This driving force transmission device is used, for example, in a vehicle as shown in FIG.

  FIG. 1 shows an electric motor type four-wheel drive vehicle equipped with a driving force transmission device 1. In this vehicle, the driving force (torque) from the engine 2 as the main power source is transmitted to the left and right front wheels 5 via the transaxle 3 and the drive shaft 4. The driving force from the electric motor 6 as the auxiliary power source is transmitted to the left and right rear wheels 9 via the driving force transmission device 1 having the speed reducer 7 and the drive shaft 8. The electric motor 6 rotates in the forward direction during forward four-wheel drive travel of the vehicle, rotates in the reverse direction during reverse four-wheel drive travel of the vehicle, and stops during forward two-wheel drive travel of the vehicle.

  Referring to FIG. 2, the driving force transmission device 1 includes a torque limiter 10, a transmission path switching device 30, and a speed reducer 7, which are housed in a casing 70. Torque is input from the electric motor 6 to the cam type torque limiter 10. The torque limiter 10 is provided between the electric motor 6 and the one-way clutches 31 and 32 of the transmission path switching device 30. The output torque from the torque limiter 10 is transmitted to the speed reducer 7 including the differential gear device 50 and the like via the transmission path switching device 30.

  When the input torque from the electric motor 6 is less than the limit value, the torque limiter 10 is inactive, and torque is transmitted to the one-way clutches 31 and 32 of the transmission path switching device 30 via the torque limiter 10. In this case, the first rotating member 11 and the second rotating member 13 of the torque limiter 10 are rotating at the same rotation speed. When the input torque from the electric motor 6 exceeds the limit value, the torque limiter 10 operates to prevent torque from being transmitted to the one-way clutches 31 and 32 of the transmission path switching device 30. In this case, the first rotating member 11 and the second rotating member 13 rotate relative to each other.

  The forward one-way clutch 31 includes an inner ring 31a, an outer ring 31b, and a sprag 31c interposed between the inner and outer rings. The reverse one-way clutch 32 includes an inner ring 32a, an outer ring 32b, and a sprag 32c interposed between the inner and outer rings. The outer ring 31b of the forward one-way clutch 31 and the outer ring 32b of the reverse one-way clutch 32 are integrally formed. The forward one-way clutch 31 is locked (engaged) when the torque input from the torque limiter 10 to the outer rings 31b and 32b is in the forward direction (forward direction), and the forward one-way clutch 31 is in the forward direction (forward direction). Torque is transmitted to the inner ring 31a. The reverse one-way clutch 32 is locked when the torque input from the torque limiter 10 to the outer wheels 31b and 32b is in the reverse direction (reverse direction), and the driving force in the reverse direction (reverse direction) is obtained. Is transmitted to the inner ring 32a.

  The forward one-way clutch 31 is engaged during forward four-wheel drive of the vehicle. At this time, the torque from the electric motor 6 rotates the left and right rear wheels 9 in the forward direction via the forward one-way clutch 31, the output shaft 35 of the transmission path switching device 30, and the differential gear device 50. When the vehicle is driving forward two wheels, the electric motor 6 is stopped and the forward one-way clutch 31 is not engaged, so that the left and right rear wheels 9 rotate in the forward direction via the output shaft 35 and the differential gear device 50. Although transmitted to the inner ring 31a, the inner ring 31a idles with respect to the outer ring 31b. Further, when the vehicle is driving forward two wheels, the torque cam mechanism 33 is not engaged, and the rotation of the left and right rear wheels 9 in the forward direction is not transmitted to the inner wheel 32 a of the reverse one-way clutch 32. The reverse one-way clutch 32 is engaged when the vehicle is driven with four reverse wheels. At this time, the torque from the electric motor 6 rotates the left and right rear wheels 9 in the reverse direction via the reverse one-way clutch 32, the engaged torque cam mechanism 33, the output shaft 35, and the differential gear device 50.

  When torque is transmitted from the torque limiter 10 to the transmission path switching device 30 and when torque is transmitted from the transmission path switching device 30 to the differential gear device 50, the torque is amplified. Torque is amplified according to the gear ratio between the output gear provided on the output shaft 19 of the torque limiter 10 and the outer ring gears of the forward / reverse one-way clutches 31 and 32. Torque is transmitted from the output gear 37 provided on the output shaft 35 of the transmission path switching device 30 to the ring gear 39 of the differential gear device 50. The reducer 7 also includes a ring gear 39 of the differential gear device 50 and an output gear 37 of the transmission path switching device 30, and the torque is amplified according to the gear ratio. Since the torque limiter 10 is provided at a position in the previous stage where the torque is amplified and increased, that is, between the forward / reverse one-way clutches 31 and 32 and the electric motor 6, the input torque limit value of the torque limiter 10 is reduced. The cam radius of the torque limiter 10 and the load of the disc spring 17 can be reduced. That is, the torque limiter 10 can be reduced in size.

  Note that details of the transmission path switching device 30 and the differential gear device 50 are described in Patent Document 2, and thus description thereof is omitted.

  The torque limiter 10 will be described in detail with reference to FIG. FIG. 3 is a partially enlarged view of the torque limiter 10.

  The torque limiter 10 includes a first rotating member (input-side rotating member) 11, a second rotating member (output-side rotating member) 13, a plurality of balls 15, a disc spring 17, and an output shaft 19. The first rotating member 11 functions as an input shaft that is coupled to the electric motor 6 and receives torque. The first rotating member 11 and the output shaft 19 are rotatably supported on the casing 70 by bearings. The second rotating member 13 is provided coaxially facing the first rotating member 11, and the first rotating member 11 and the second rotating member 13 rotate around substantially the same rotation axis. To do. Usually, this axis of rotation also coincides with the axis 16 of the rotating member. A first cam groove (input-side cam groove) 12 is provided on the end face 28 of the first rotating member 11, and a second cam groove (output-side cam groove) is provided on the end face 29 of the second rotating member 11. ) 14 is provided.

  A plurality of spherical balls 15 are inserted between the first cam groove 12 of the first rotating member 11 and the second cam groove 14 of the second rotating member 13. Here, the surface of the first rotating member 11 through which the ball 15 passes is referred to as a first cam surface, and the surface of the second rotating member 13 through which the ball 15 passes is referred to as a second cam surface. The first and second cam grooves 12, 14 and the plurality of balls 15 constitute a cam mechanism. If necessary, the retainers for holding the plurality of balls 15 in the holes so as to prevent the balls 15 from dropping from the cam mechanism are end surfaces 28 of the first rotating member 11 and end surfaces of the second rotating member 11. 29 may be provided. The cage has a ring shape, is arranged coaxially with the first rotating member 11 and the second rotating member 11, and holds the ball 15 so as to keep the distance between the balls 15 constant. .

  The output shaft 19 of the torque limiter 10 is provided coaxially with the first and second rotating members 11 and 13, and transmits torque transmitted through the first and second rotating members 11 and 13. Output to the switching device 30 side. The inner peripheral surface of the ring-shaped second rotating member 13 is toothed and is splined to the output shaft 19. Therefore, the second rotating member 13 can slide in the axial direction with respect to the output shaft 19. The tip of the output shaft 19 passes through the ring-shaped disc spring 17. The disc spring 17 is inserted between the second rotating member 13 and the flange portion 20 of the output shaft 19 and presses the second rotating member 13 against the ball 15 side. Torque from the output shaft 19 is input to the forward one-way clutch 31 or the reverse one-way clutch 32 of the transmission path switching device 30 and transmitted from the transmission path switching device 30 to the differential gear device 50.

  Next, the shape of the cam groove or the cam surface will be described with reference to FIGS. FIG. 4 shows a schematic end view of the first or second rotating member 11, 13. FIG. 5 shows a cross-sectional view in the circumferential direction of the cam mechanism at a cross-section passing through the bottom portion in the radial direction of the cam groove (a chain line in FIG. 4). Here, the first cam groove 12 of the first rotating member 11 and the second cam groove 14 of the second rotating member 13 have the same shape.

  Normally, the first and second cam grooves 12 and 14 have the shape shown in FIG. 6, but in the present embodiment, the shape is shown in FIG. 5 with the horizontal portion 21. The first and second cam grooves 12, 14 (or the first and second cam surfaces) each have a plurality of horizontal portions 21 extending along a plane substantially perpendicular to the direction of the shaft 16, and a plurality of Are provided with a plurality of recesses 22 positioned between the horizontal portions 21. In the present embodiment, the plurality of horizontal portions 21 extend along the substantially circumferential direction with respect to the shaft 16. The recess 22 has a groove depth d deeper than the horizontal portion 21 and is recessed with respect to the horizontal portion 21. The cross sections in the radial direction of the first and second cam grooves 12 and 14 are described as rectangular for the sake of simplicity, but other shapes such as a U shape and an arc shape may be used. In the present embodiment, the concave portion 22 is composed of two inclined portions 23 facing each other. The inclined portion 23 has a non-zero angle θ as an inclination angle (cam angle) with respect to the circumferential direction. For this reason, the groove depth d increases toward the deepest portion of the recess 22.

  When the input torque input from the electric motor 6 to the torque limiter 10 is less than the limit value, the torque limiter 10 is in an inoperative state. At this time, each ball 15 is fixed at the lowest position in the axial direction in the recess 22 by the load of the disc spring 17, and the first rotating member 11 and the second rotating member 13 rotate at the same rotational speed. Torque is transmitted from the first rotating member 11 to the second rotating member 13. When the input torque from the electric motor 6 exceeds the limit value, the torque limiter 10 is activated. At this time, each ball 15 moves by rolling on the inclined portion 23 from the lowermost position toward the outside of the concave portion 22 in the concave portion 22. For this reason, the first rotating member 11 and the second rotating member 13 rotate relative to each other, and torque is not transmitted from the first rotating member 11 to the second rotating member 13.

  With reference to FIG. 7, the conditions under which the torque limiter 10 operates will be described. FIG. 7 shows the balance of the cam mechanism. Assuming that the input torque at the start of operation of the torque limiter 10 is T1, the cam radius is Lc, the cam angle of the cam groove is θ, and the disc spring initial load is Fs, the following equation (1) It is necessary to satisfy the conditions.

  T1 / (Lc × tanθ)> Fs (1)

  The cam radius is a distance from the shaft 16 to the center of the ball 15 (or the center in the radial direction of the cam groove) in the first rotating member 11 or the second rotating member 13. Moreover, the left side of Formula (1) represents the thrust (thrust load) of a cam mechanism.

  Torque limiter maximum operation when input torque to the torque limiter 10 is T2, maximum drop depth of the ball is h, maximum disc spring allowable deflection is t, and disc spring load at maximum disc spring deflection is Fs_max At the time (when the ball 15 exceeds the recess 22), it is necessary to satisfy the conditions of the following formulas (2) and (3).

  t ≧ 2 × h (2)

  T2 / (Lc × tanθ) ≦ Fs_max (3)

  Here, the drop depth h of the ball is the distance between the axially lowermost surface of the ball 15 and the bottom of the horizontal portion 21 of the cam groove when the ball 15 is at the lowest position in the recess. is there.

  By providing the horizontal portion 21 with the cam groove shape as shown in FIG. 5, the cam angle θ can be increased without maintaining and increasing the ball drop depth h. Accordingly, since the cam thrust can be reduced with respect to the input torque to the cam mechanism, the disc spring load can be reduced, and the disc spring can be reduced in size. In addition, the number of recesses and balls can be reduced, or the ball diameter can be reduced. Furthermore, since the number of recesses or the number of balls is reduced, the number of balls that cross the cam mountain (horizontal portion) at the maximum operation of the torque limiter is reduced, so that vibration and noise can be reduced. In addition, since the cam groove has a horizontal portion, the degree of freedom in designing the cam radius and the ball diameter increases without being affected by the cam angle and the number of recesses.

  In the above description, the first cam groove 12 and the second cam groove 14 have the same shape, but the present invention is not limited to this, and the first cam groove 12 and the second cam groove 14 have different shapes. It can also be. That is, the horizontal portion may be provided only in one of the cam groove or the cam surface.

At least one of the advantageous effects the first cam groove (cam surface) and a second cam groove (cam surface), a plurality of horizontal portions extending along the plane substantially perpendicular to the axial direction, the plurality of horizontal portions And a plurality of recesses that are located in between and are recessed with respect to the plurality of horizontal portions (the groove depth is deeper than the horizontal portions). Accordingly, the cam angle (inclination angle) θ of the recess can be increased without increasing the depth of the ball dropping into the recess, and the cam thrust can be reduced. Since the cam thrust can be reduced relative to the input torque to the cam mechanism, the disc spring load can be reduced, and the disc spring can be reduced in size. In addition, the number of balls can be reduced, or the ball diameter can be reduced. Furthermore, the degree of freedom in designing the cam radius and the ball diameter is increased by adjusting the length of the horizontal portion without being affected by the cam angle θ of the cam surface and the number of recesses.

  By providing a torque limiter having a cam mechanism that can be reduced in size between the forward / reverse one-way clutch and the electric motor, the torque limit value of the torque limiter can be reduced, so that the torque limiter can be further reduced in size. Can proceed.

<Modification of First Embodiment>
FIG. 8 shows a modification of the first embodiment. In FIG. 3, the disc spring 17 is interposed between the second rotating member 13 and the flange portion 20 of the output shaft 19 and presses the second rotating member 13 against the ball 15 side. However, the torque limiter may have another arrangement of members. For example, as shown in FIG. 8, the first rotating member 11 is provided separately from the input shaft 25, and the disc spring 17 is interposed between the first rotating member 11 and the flange portion 26 of the input shaft 25. In addition, the first rotating member 11 may be pressed against the ball 15 side. Even in this modification, the operational effects of the first embodiment can be obtained.

Second Embodiment
The second embodiment will be described with reference to FIG. In the following description, parts having the same functions as those described above are denoted by the same reference numerals, and redundant description is omitted as appropriate.

  In the second embodiment, the number of cam grooves or cam surface recesses 22 is greater than the number of balls 15. Compared to the first embodiment, the length of the horizontal portion 21 is shortened, and a cam groove is provided between the horizontal portions 21. By adopting this cam groove shape, the number of recesses 22 can be increased with respect to the number of balls. Other configurations are the same as those of the first embodiment.

  In the second embodiment, the frequency of use of a single recess is reduced, so that the durability of the cam groove is improved. As a result, materials having low strength and durability (low cost) can be used for the first and second rotating members 11 and 13. Further, as in the first embodiment, by having a horizontal portion in the cam groove, the degree of freedom in designing the cam circumferential diameter and ball diameter is increased without being affected by the cam angle and the number of recesses.

<Third Embodiment>
The third embodiment will be described with reference to FIG. In the following description, parts having the same functions as those described above are denoted by the same reference numerals, and redundant description is omitted as appropriate.

  In the first embodiment, the groove-shaped horizontal portion is provided as a part of the cam groove. However, in the third embodiment, the horizontal portion 41 is provided as a mere horizontal plane instead of the groove-shaped horizontal portion. Part of the horizontal end surface 28 of the first rotating member or the horizontal end surface 29 of the second rotating member is the horizontal portion 41 of the cam surface as it is. Thus, the first cam surface through which the ball 15 passes on the first rotating member 11 and the second cam surface through which the ball 15 passes on the second rotating member 13 are horizontal portions (horizontal planes). 41 and a plurality of recesses 42 are provided. The horizontal portion (horizontal plane) 41 extends along a plane substantially perpendicular to the axial direction. The plurality of recesses 42 are positioned between the plurality of horizontal portions 41 and take a shape that is recessed with respect to the plurality of horizontal portions 41.

  In order to prevent the ball from dropping off when the ball moves on the horizontal surface 41, a ring-shaped cage 43 for holding a plurality of balls 15 is appropriately attached to the cam mechanism of the torque limiter 10 as shown in FIG. It is preferable to provide it.

  In the third embodiment, the same effects as in the first embodiment can be obtained. In addition, since the horizontal end surface 28 of the first rotating member or a part of the horizontal end surface 29 of the second rotating member is used as it is as the horizontal portion 41 of the cam surface, the cam surface can be easily formed.

  Without being limited to the embodiments described above, various modifications and changes are possible within the scope of the technical idea, and it is obvious that these are also included in the technical scope of the present invention.

  For example, although the disc spring 17 is given as an example of a component that applies a load to the cam mechanism, a component (elastic body) that can be stroked in the axial direction by applying a load, such as a coil spring, may be used instead. In the embodiment, the driving force transmission device has a one-way clutch as a clutch mechanism, but may have another clutch such as a two-way clutch.

It is a schematic block diagram of the vehicle carrying a driving force transmission device. It is a section side view of the driving force transmission device concerning a 1st embodiment. It is the elements on larger scale of the torque limiter concerning a 1st embodiment. It is a schematic end view of the rotating member according to the first embodiment. It is a circumferential direction sectional view of the cam mechanism concerning a 1st embodiment. It is a circumferential direction sectional view of a conventional cam mechanism. It is a figure explaining the operating condition of a torque limiter. It is the elements on larger scale of the torque limiter which concerns on the modification of 1st Embodiment. It is a circumferential direction sectional view of a cam mechanism concerning a 2nd embodiment. It is a schematic end view of the rotating member according to the third embodiment. It is a circumferential direction sectional view of a cam mechanism concerning a 3rd embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Driving force transmission apparatus 10 Torque limiter 11 1st rotation member 12 1st cam groove (1st cam surface)
13 Second rotating member 14 Second cam groove (second cam surface)
15 ball 17 spring (disc spring)
21 Horizontal portion 22 Recessed portion 31 Forward one-way clutch 32 Reverse one-way clutch 41 Horizontal portion (horizontal plane)
42 recess

Claims (3)

A first rotating member having a first cam surface and receiving torque;
A second rotating member having a second cam surface and provided coaxially facing the first rotating member;
A plurality of balls interposed between the first cam surface of the first rotating member and the second cam surface of the second rotating member;
A spring for pressing the first rotating member or the second rotating member, and
At least one of the first cam surface and the second cam surface has a plurality of horizontal portions extending along a plane substantially perpendicular to the axial direction, and is positioned between the plurality of horizontal portions and arranged on the plurality of horizontal portions. A plurality of concave portions recessed with respect to the
A torque limiter for a driving force transmission device , wherein the number of the plurality of recesses is greater than the number of the balls . A first rotating member having a first cam groove and receiving torque;
A second rotating member having a second cam groove and provided coaxially facing the first rotating member;
A plurality of balls interposed between the first cam groove of the first rotating member and the second cam groove of the second rotating member;
A spring for pressing the first rotating member or the second rotating member, and
At least one of the first cam groove and the second cam groove includes a plurality of horizontal portions extending along a plane substantially perpendicular to the axial direction, and the plurality of horizontal portions positioned between the plurality of horizontal portions. With a plurality of recesses having a deep groove depth ,
A torque limiter for a driving force transmission device , wherein the number of the plurality of recesses is greater than the number of the balls .   A driving force transmission device in which torque is input from a motor,
  The torque limiter according to claim 1 or 2,
  A clutch to which torque is transmitted from the motor via the torque limiter;
  A speed reducer that amplifies the torque transmitted from the clutch,
  The driving force transmission device, wherein the torque limiter is provided between the clutch and the motor.

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