CN111065835B

CN111065835B - Torque transmission shaft

Info

Publication number: CN111065835B
Application number: CN201880057293.3A
Authority: CN
Inventors: 森山诚一; 中尾圭佑
Original assignee: NSK Ltd
Current assignee: NSK Ltd
Priority date: 2017-09-07
Filing date: 2018-09-05
Publication date: 2022-04-29
Anticipated expiration: 2038-09-05
Also published as: CN111065835A; WO2019049882A1

Abstract

The invention provides a structure of a torque transmission shaft capable of restraining the whirling of a shaft connected with the torque transmission shaft. The torque transmission shaft (22) is provided with: a shaft body (23) having a yoke (25) integrally formed at one end in the axial direction and female serrations (32) formed on the inner peripheral surface of the other end in the axial direction; and a jig (24) that is separate from the shaft body (23) and that reduces the diameter of the other axial end of the shaft body (23), wherein the shaft body (23) and the jig (24) are welded and fixed.

Description

Torque transmission shaft

Technical Field

The present invention relates to a torque transmission shaft incorporated in a steering device for an automobile or the like.

Background

Fig. 21 shows a known steering device for an automobile described in japanese patent laid-open publication No. 2017-25964. The steering device includes a steering wheel 1, a steering shaft 2, a steering column 3, a pair of universal joints 4a and 4b, an intermediate shaft 5, a steering gear unit 6, and a pair of tie rods 7.

The steering wheel 1 is attached to a rear end portion of a steering shaft 2 rotatably supported inside a steering column 3. The front end portion of the steering shaft 2 is connected to a pinion shaft 8 of the steering gear unit 6 via a pair of universal joints 4a and 4b and an intermediate shaft 5. Then, the rotation of the pinion shaft 8 is converted into linear motion of a rack, not shown, to push and pull the pair of tie rods 7, thereby applying a steering angle corresponding to the operation amount of the steering wheel 1 to the steered wheels. The front-rear direction refers to the front-rear direction of the vehicle body to which the steering device is assembled.

The universal joints 4a and 4b connect the steering shaft 2 and the intermediate shaft 5 and the pinion shaft 8, which are rotation shafts that do not exist on the same straight line with each other, so as to be capable of transmitting torque therebetween. As the universal joints 4a and 4b, a cross-type universal joint including a pair of yokes and a cross shaft described in japanese patent application laid-open publication No. 2011-220398 and the like is used.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2017-25964

Patent document 2: japanese patent laid-open publication No. 2011-

Disclosure of Invention

Problems to be solved by the invention

However, in the steering device mounted on a large automobile, the distance from the steering shaft to the steering unit becomes long. Therefore, it is considered that the steering shaft and the pinion shaft are not directly fixed to the yoke constituting the universal joint, but fixed via a torque transmission shaft called an extension shaft (extension shaft).

Fig. 22(a) to 22(C) show the torque transmission shaft 9 previously considered by the inventors. The torque transmission shaft 9 is disposed between the yoke 10 and a steering shaft, a pinion shaft, or the like 11, and connects the yoke 10 and the shaft 11 to be capable of transmitting torque. The torque transmission shaft 9 has male serrations 12 on an outer peripheral surface of one end portion in the axial direction, and female serrations 13 on an inner peripheral surface of the other end portion in the axial direction. A clamp portion 14 for reducing the diameter of the other end in the axial direction of the torque transmission shaft 9 is integrally provided at the other end in the axial direction of the torque transmission shaft 9. Specifically, a discontinuous portion 15 is formed at one circumferential position of the other end portion in the axial direction of the torque transmission shaft 9, and a pair of flange portions 16 are disposed on both sides of the discontinuous portion 15. The flange portions 16 each have a mounting hole 17 into which a fastening member, not shown, is inserted.

One axial end of the torque transmission shaft 9 is inserted into a base 18 constituting the yoke 10, and the male serrations 12 are engaged with female serrations 19 formed on an inner circumferential surface of the base 18. The torque transmission shaft 9 and the base 18 are welded and fixed over the entire circumference by the weld bead 20.

One axial end of the shaft 11 is inserted into the other axial end of the torque transmission shaft 9, and the female serrations 13 engage with the male serrations 21 formed on the outer peripheral surface of the shaft 11. The outer peripheral surface of the shaft 11 is strongly fastened to the inner peripheral surface of the torque transmission shaft 9 by screwing the tip end portion of the fastening member to the mounting hole 17 or a nut not shown.

The torque transmission shaft 9 is often manufactured by cold forging, and the shape accuracy and the dimensional accuracy are higher than those of the torque transmission shaft manufactured by hot forging, but it is difficult to highly ensure the coaxiality of the male serrations 12 and the female serrations 13 provided at both axial end portions of the torque transmission shaft 9 because the clamping portions 14, in which the flow of the metal material is complicated, are integrally provided. Further, since the torque transmission shaft 9 and the yoke 10 are welded and fixed, the coaxiality between the torque transmission shaft 9 and the yoke 10 is easily lowered by thermal deformation or the like. Therefore, as shown in fig. 22(C), the runout of the shaft connected to the torque transmission shaft 9, that is, the shaft 11a connected via the yoke 10 or the shaft 11 connected to the female serrations 13 may become large. As a result, abnormal noise such as slip noise in the rotational direction and stick-slip vibration noise may be generated in a part of the steering apparatus due to the shaft whirling.

In view of the above circumstances, an object of the present invention is to provide a torque transmission shaft having a structure capable of suppressing the whirling of a shaft connected to the torque transmission shaft.

Means for solving the problems

The torque transmission shaft of the present invention includes a shaft body and a jig.

The shaft body is hollow and has a yoke portion provided at one end portion in the axial direction, a slit provided at the other end portion in the axial direction and extending in the axial direction, and a female serration provided on an inner peripheral surface of the other end portion in the axial direction. The yoke is integrated with the shaft body. On the other hand, the jig is separate from the shaft body.

The jig is a notched cylindrical shape, and has a discontinuous portion disposed at one location in the circumferential direction and a pair of flange portions disposed on both sides in the circumferential direction across the discontinuous portion and each having a mounting hole into which a fastening member is inserted. The jig is externally fitted to the other end portion of the shaft body in the axial direction, and the width of the discontinuous portion is reduced, thereby reducing the diameter of the other end portion of the shaft body in the axial direction.

In the present invention, for example, the shaft body and the jig are welded and fixed, and thus the shaft body and the jig are fixed so as not to be movable in the axial direction. In this case, the female serration may have an incomplete serration portion at one axial end portion, the depth of the groove of the female serration portion being smaller toward one axial side, and the weld-fixing portion between the shaft body and the jig may be located on the outer diameter side of the incomplete serration portion.

Alternatively, the shaft body and the jig can be fixed so as not to be movable in the axial direction by press-fitting (lightly press-fitting) the shaft body into the jig.

The slit may include a stress relaxing portion having a width dimension larger than a portion adjacent to the other side in the axial direction at a depth end portion which is one end portion in the axial direction. The stress relaxation portion may have a shape such as a circular shape, an elliptical shape, or a water droplet shape in plan view, and may have an inner surface formed of a concave curved surface.

Alternatively, the axial one end portion, i.e., the depth end portion of the slit may be positioned on the axial side of the one axial end edge of the female serration. In this case, the shaft body may have a small-diameter cylindrical portion at the other end portion in the axial direction, the female serrations may be provided only on an inner peripheral surface of the small-diameter cylindrical portion, and a depth end portion, which is one end portion in the axial direction of the slit, may be located on one side in the axial direction of the small-diameter cylindrical portion and may be located in a portion having an outer diameter dimension and an inner diameter dimension larger than the small-diameter cylindrical portion. The shaft body may have a tapered cylindrical portion whose outer diameter and inner diameter increase toward the axial direction side at a portion adjacent to the axial direction side of the small-diameter cylindrical portion, and the one axial end portion of the slit may be positioned on the axial direction side of the tapered cylindrical portion.

The shaft body may have a non-toothed portion in which the female serrations are not provided, at a portion of the inner circumferential surface adjacent to both sides of the slit in the circumferential direction.

The shaft body may have an engaging groove that extends in a direction orthogonal to a central axis of the shaft body at a portion of an outer circumferential surface that faces each opening of the mounting hole, and the fastening member may be disposed inside the engaging groove.

The slit and the discontinuous portion may be aligned in circumferential positions, and a width of the slit and a width of the discontinuous portion may be equal to each other in a free state of the shaft body and the jig.

The jig has a hardness higher than that of the shaft body, and has a protrusion which is provided on an inner peripheral surface of an insertion hole in the jig into which the shaft body is inserted, and which is recessed into an outer peripheral surface of the shaft body.

The protrusion may be disposed on a portion of the inner circumferential surface of the insertion hole that is opposite to the discontinuous portion in the diameter direction of the insertion hole.

The outer circumferential surface of the shaft body and the inner circumferential surface of an insertion hole in the jig into which the shaft body is inserted are fitted together in a non-circular manner so as to be incapable of relative rotation.

In this case, the shaft body may have a flat surface portion (linear portion) at least in a circumferential direction of at least a part of an outer circumferential surface and at least in a circumferential direction of at least an inner circumferential surface of the insertion hole.

The shaft body has a stepped surface facing the other axial side on the outer peripheral surface, and the jig can be positioned in the axial direction with respect to the shaft body by abutting the jig against the stepped surface.

Effects of the invention

The torque transmission shaft of the present invention can effectively suppress the whirling of the shaft connected to the torque transmission shaft.

Drawings

Fig. 1 is a perspective view showing a torque transmission shaft according to a first example of the embodiment.

Fig. 2 is an exploded perspective view showing a torque transmission shaft according to a first example of the embodiment.

Fig. 3 is an end view of the torque transmission shaft according to the first example of the embodiment, as viewed from the other axial side.

Fig. 4 is a sectional view a-a of fig. 3.

Fig. 5 is a plan view showing a shaft body of a torque transmission shaft according to a first example of the embodiment.

Fig. 6 is a sectional view showing a jig for a torque transmission shaft according to a first example of the embodiment.

Fig. 7 is an exploded perspective view showing a torque transmission shaft and a shaft connected to the torque transmission shaft according to a first example of the embodiment.

Fig. 8 is a sectional view showing a connection state of a torque transmission shaft and a shaft connected to the torque transmission shaft according to a first example of the embodiment.

Fig. 9 is an end view of a torque transmission shaft clamp according to a second example of the embodiment.

Fig. 10 is a perspective view showing a torque transmission shaft clamp according to a second example of the embodiment.

Fig. 11 is an end view showing a torque transmission shaft of a third example of the embodiment viewed from the other side in the axial direction.

Fig. 12 is a perspective view showing a torque transmission shaft clamp according to a third example of the embodiment.

Fig. 13 is a plan view showing a shaft body of a torque transmission shaft according to a fourth example of the embodiment.

Fig. 14 is a sectional view showing a connection state of a torque transmission shaft and a shaft connected to the torque transmission shaft according to a fifth example of the embodiment.

Fig. 15 is a plan view showing a shaft body of a torque transmission shaft according to a fifth example of the embodiment.

Fig. 16 is a partial cross-sectional view showing a shaft body of a torque transmission shaft according to a fifth example of the embodiment.

Fig. 17 is an end view showing a shaft body of a torque transmission shaft according to a fifth example of the embodiment viewed from the other side in the axial direction.

Fig. 18 is a plan view showing a shaft body of a torque transmission shaft according to a sixth example of the embodiment.

Fig. 19 is a sectional view showing a connection state of a torque transmission shaft and a shaft connected to the torque transmission shaft according to a seventh example of the embodiment.

Fig. 20 is a sectional view showing a connection state of a torque transmission shaft and a shaft connected to the torque transmission shaft according to an eighth example of the embodiment.

Fig. 21 is a partial side sectional view showing a conventional steering device.

In fig. 22, fig. 22(a) is a perspective view showing a structure in which the inventors previously considered that the yoke and the rotary shaft are connected by the torque transmission shaft, fig. 22(B) is an exploded perspective view of the structure shown in fig. 22(a), and fig. 22(C) is a schematic view for explaining a state in which the shaft connected to the torque transmission shaft is oscillated in the structure shown in fig. 22 (a).

Detailed Description

[ first example of embodiment ]

A first example of an embodiment of the present invention will be described with reference to fig. 1 to 8. The torque transmission shaft 22 of the present example is used to connect a steering shaft, which is a steering device incorporated in a large automobile, for example, and does not have rotating shafts on the same straight line, to an intermediate shaft or an intermediate shaft to a pinion shaft so as to transmit torque.

The torque transmission shaft 22 includes a hollow cylindrical shaft body 23 and a notched cylindrical (substantially U-shaped) clamp 24, which are formed separately from each other. In the following description, the axial direction refers to the axial direction of the torque transmission shaft 22 unless otherwise specified. In addition, the one end side in the axial direction is a side where the yoke portion 25 is present, and is a left end side in fig. 1, 2, 4, 5, 7, and 8. The other end side in the axial direction is a side on which the jig 24 is disposed, and is a right end side in fig. 1, 2, 4, 5, 7, and 8.

The shaft body 23 is integrally manufactured by performing forging (cold forging or hot forging) and cutting on a raw material such as a carbon steel cast steel (SC material). The shaft body 23 includes a two-fork yoke 25 at one axial end portion and a cylindrical portion 26 at the other axial end portion and an intermediate portion.

The yoke 25 constitutes a cross-type universal joint and includes a pair of

arm portions

27a and 27 b. The

arm portions

27a, 27b extend from two positions on one axial end edge of the tube portion 26, which are diametrically opposite sides, to one axial side. The

wrist portions

27a, 27b have circular holes 28 coaxial with each other. The circular hole 28 is provided with a bearing cup and a needle roller, not shown, for rotatably supporting a shaft portion constituting the cross shaft, respectively, inside.

The cylindrical portion 26 constituting the shaft body 23 is hollow cylindrical as a whole, and includes a large-diameter cylindrical portion 29, a tapered cylindrical portion 30, and a small-diameter cylindrical portion 31 in this order from the axial side.

The large diameter cylindrical portion 29 is a stepped cylindrical shape, and the other axial end edge of the large diameter cylindrical portion 29 is connected to one axial end edge of the tapered cylindrical portion 30. The large diameter cylinder 29 has an outer diameter and an inner diameter larger than those of the small diameter cylinder 31.

The tapered tube portion 30 has a partial tapered tube shape, and the outer diameter and the inner diameter of the tapered tube portion 30 decrease toward the other axial side. The other axial end edge of the tapered tube portion 30 is connected to one axial end edge of the small-diameter tube portion 31.

The small-diameter cylindrical portion 31 is cylindrical and is disposed in a range from an axial intermediate portion to an axial other end portion of the shaft body 23. The outer peripheral surface of the small-diameter cylindrical portion 31 is cylindrical surface-shaped with an outer diameter dimension that is constant throughout the axial direction, and the inner peripheral surface of the small-diameter cylindrical portion 31 has female serrations 32 throughout the entire length. As shown in fig. 7 and 8, an end portion of a steering shaft, a pinion shaft, or the like 47 is inserted into the inside of the small diameter cylinder portion 31, and male serrations 48 formed on an outer peripheral surface of the shaft 47 are engaged with the female serrations 32.

The small-diameter cylindrical portion 31 includes a slit 33 extending in the axial direction at a portion corresponding to the circumferential position (phase) of one of the arm portions 27a constituting the yoke portion 25. The slit 33 communicates the inner peripheral surface and the outer peripheral surface of the small-diameter cylinder portion 31. One axial end portion, i.e., the deep end portion X of the slit 33 is located at an axial intermediate portion of the small-diameter cylindrical portion 31, and the other axial end edge portion of the slit 33 is open at the other axial end edge of the small-diameter cylindrical portion 31 (the shaft body 23). The slit 33 includes a stress relaxing portion 34 at a deep end portion X thereof, and the stress relaxing portion 34 has a width larger than a portion adjacent to the other side in the axial direction and has a substantially circular opening shape in a plan view (see fig. 5). By providing the slit 33 at the other end portion in the axial direction of the shaft body 23 in this way, the other end portion in the axial direction of the shaft body 23 (the other half portion in the axial direction of the small-diameter cylinder portion 31) can be reduced in diameter. Further, by providing the stress relaxing portion 34 at the deep end portion X of the slit 33, it is possible to prevent damage such as cracking from occurring at the deep end portion X of the slit 33 where stress is likely to concentrate when the shaft body 23 is reduced in diameter.

The shaft body 23 further includes an engagement groove 35 extending in a direction orthogonal to the central axis of the shaft body 23 at a portion of the outer peripheral surface of the other axial end portion of the small-diameter cylinder portion 31 that coincides with the circumferential position of one of the arm portions 27a constituting the yoke portion 25. That is, the engagement groove 35 is formed to intersect the slit 33. The intersection of the engaging groove 35 and the slit 33 is a wide portion having a width dimension larger than the portions of the slit 33 adjacent to both sides in the axial direction of the intersection. The engagement recess 35 is formed in a partial cylindrical surface shape, and has a radius of curvature substantially equal to that of the mounting hole 40a (40b) formed in the jig 24.

The jig 24 is fitted to the other axial end of the shaft body 23, and has a function of reducing the diameter of the other axial end of the shaft body 23. Specifically, the jig 24 is fitted to the other axial end of the small-diameter cylindrical portion 31 of the shaft body 23, and the other axial half of the small-diameter cylindrical portion 31 is reduced in diameter. The jig 24 is manufactured by subjecting a raw material such as S35C, which is a carbon steel for machine structural use, having a higher hardness than the material constituting the shaft body 23 to hot forging, cutting, or the like, or subjecting a raw material such as S10C, S15C, which is a carbon steel for machine structural use, to cold forging, which causes work hardening.

The jig 24 is a cylindrical shape (substantially U-shaped) with a notch as a whole, and includes: a semi-cylindrical base 36; a pair of flange portions 37 arranged at both circumferential ends of the base portion 36 and having a substantially rectangular plate shape; and a discontinuous portion 38 provided at a circumferential one-point position between the pair of flange portions 37. In other words, a pair of flange portions 37 are disposed on both sides across the discontinuous portion 38. In a state where the jig 24 is fixed to the other end portion in the axial direction of the shaft body 23, the discontinuous portion 38 and the slit 33 of the shaft body 23 are aligned in the circumferential direction. In this example, the width of the discontinuous portion 38 in the free state of the jig 24 and the width of the slit 33 in the free state of the shaft body 23 (small-diameter cylindrical portion 31) are the same. The thickness dimensions of the pair of flange portions 37 are the same.

The jig 24 has an insertion hole 39 into which the small-diameter cylindrical portion 31 of the shaft body 23 is inserted. The insertion hole 39 has a notched cylindrical surface formed by the inner peripheral surface of the base portion 36 and the radially inner surfaces of the pair of flange portions 37. The insertion hole 39 has an inner diameter that is the same as or slightly larger than an outer diameter of the small-diameter cylinder 31 in a free state of the jig 24.

The pair of flange portions 37 have coaxial mounting

holes

40a and 40b at their respective portions that are integrated with each other. The mounting

holes

40a and 40b are formed at positions twisted with respect to the central axis of the insertion hole 39, respectively, and open to the insertion hole 39. One mounting hole 40a of the pair of mounting

holes

40a and 40b is a through hole, and the other mounting hole 40b is a screw hole. The catching grooves 35 are located at the following positions: the jig 24 is fixed to the other end portion of the shaft body 23 in the axial direction, and faces the portion of the pair of mounting

holes

40a and 40b that opens into the insertion hole 39.

In this example, in a state before the jig 24 is welded and fixed to the other end portion in the axial direction of the shaft body 23, the fastening bolt 49 as a fastening member is inserted into the pair of mounting

holes

40a and 40b and is disposed inside the engagement recess 35. Specifically, a portion of the fastening bolt 49 near the base end is inserted into one of the mounting holes 40a as a through hole, and the intermediate portion of the fastening bolt 49 is disposed inside the engagement groove 35. In this state, the tip end portion of the fastening bolt 49 is screwed into the other mounting hole 40b, which is a threaded hole, to a slight extent that the small-diameter cylindrical portion 31 is not reduced in diameter. With such a configuration, since the engaging recess 35 is engaged with the fastening bolt 49 whose both end portions are supported by the jig 24, the shaft body 23 and the jig 24 can be positioned in the axial direction. In addition, the shaft body 23 and the jig 24 can be prevented from rotating relative to each other.

In this example, the shaft body 23 and the jig 24 are welded and fixed. Specifically, a weld 41 is formed by spot welding at one circumferential location on the opposite side of the slit 33 in the diameter direction of the shaft body 23 in a portion between the opening edge of the insertion hole 39 of the jig 24 on one axial side and the outer circumferential surface of the shaft body 23, whereby the shaft body 23 and the jig 24 are weld-fixed. In this example, since the welded portion 41 is formed in the portion of the shaft body 23 on the opposite side to the slit 33 in the diameter direction, the amount of deflection (balance of the amount of deflection) of the pair of flange portions 37 at the time of clamping can be prevented from being deteriorated by the provision of the welded portion 41.

To manufacture the torque transmission shaft 22 having the above-described structure, first, the other end portion in the axial direction of the shaft body 23 is inserted from one axial side into the insertion hole 39 of the jig 24. At this time, in order to position (phase align) the shaft body 23 and the jig 24 in the circumferential direction, the discontinuous portion 38 of the jig 24 and the slit 33 of the shaft body 23 are aligned in the circumferential direction, and a plate-shaped phase aligning member, for example, is inserted into the discontinuous portion 38 and the slit 33. Next, the shaft body 23 and the jig 24 are relatively moved in the axial direction until the axial positions of the pair of mounting

holes

40a and 40b and the engagement recess 35 match. Next, the fastening bolts 49 are disposed inside the pair of mounting

holes

40a and 40b and the engaging grooves 35, whereby the shaft body 23 and the jig 24 are positioned in the axial direction and the relative rotation between the shaft body 23 and the jig 24 is prevented. Finally, the shaft body 23 and the jig 24 are welded and fixed.

In the use state of the torque transmission shaft 22, the yoke 25 disposed at one end in the axial direction of the torque transmission shaft 22 is combined with other yokes and cross shafts, not shown. Thereby, the torque transmission shaft 22 is connected to an intermediate shaft having another yoke such as an intermediate shaft so as to be capable of transmitting torque. On the other hand, a steering shaft, a pinion shaft, and the like 47 are inserted inside the small-diameter tube portion 31, and male serrations 48 formed on the outer peripheral surface of the shaft 47 engage with female serrations 32 formed on the inner peripheral surface of the small-diameter tube portion 31. Thereby, relative rotation of the torque transmission shaft 22 and the shaft 47 is prevented. Further, the intermediate portion of the fastening bolt 49 is inserted through the large width portion that is the intersection of the engaging groove 35 and the slit 33 into the inside of the annular groove 50 that is disposed on the outer peripheral surface of the distal end portion of the shaft 47 so as to cross the male serrations 48 in the circumferential direction, and the annular groove 50 and the fastening bolt 49 are key-engaged. This prevents the shaft 47 and the torque transmission shaft 22 from moving relative to each other in the axial direction. Further, by increasing the amount of screwing of the fastening bolt 49 to the other mounting hole 40b, the width of the discontinuous portion 38 is reduced and the small-diameter cylindrical portion 31 is reduced in diameter, so that the outer peripheral surface of the shaft 47 is strongly fastened by the inner peripheral surface of the small-diameter cylindrical portion 31. The torque transmission shaft 22 and the steering shaft and pinion shaft 47 are thereby coupled to each other so as to transmit torque.

According to the torque transmission shaft 22 of the present example, the whirling of the shaft connected to the torque transmission shaft 22 can be suppressed. That is, in the torque transmission shaft 22 of this example, the jig 24 is not integrated with the shaft body 23, but welded and fixed to the shaft body 23. Therefore, the yoke 25 and the female serrations 32 disposed at both axial end portions of the shaft body 23 are highly coaxial. The shaft body 23 and the yoke 25 are not welded and fixed as a single body, but are integrally formed. Therefore, the welding can be completed without being affected by thermal deformation during welding, and the coaxiality of the yoke 25 with respect to the shaft body 23 (tube portion 26) can be highly ensured. Therefore, the whirling of the shaft connected to the yoke 25 and the shaft 47 connected to the female serrations 32 can be suppressed. As a result, abnormal noise (such as sliding abnormal noise in the rotational direction and stick-slip vibration abnormal noise) caused by the whirling of the shaft is prevented from occurring in a part of the steering apparatus. Further, since the shaft body 23 is hollow, the weight of the entire torque transmission shaft 22 is also reduced.

[ second example of embodiment ]

A second example of the embodiment of the present invention will be described with reference to fig. 9 and 10. In this example, the jig 24a has a projection 42 projecting radially inward at a portion of the inner peripheral surface of the insertion hole 39. The protrusion 42 has a function of preventing the jig 24a from rotating relative to the shaft body 23 until the jig 24a is welded and fixed to the other end portion in the axial direction of the shaft body 23 (see fig. 1).

The protrusion 42 has a substantially triangular cross-sectional shape and is disposed on a portion of the inner peripheral surface of the insertion hole 39 that is opposite to the discontinuous portion 38 in the diameter direction of the insertion hole 39. The protrusion 42 extends over the entire axial direction of the insertion hole 39.

In this example, the shaft body 23 and the jig 24a are positioned in the circumferential direction before the other end portion in the axial direction of the shaft body 23 is inserted (press-fitted) into the insertion hole 39 of the jig 24 a. When the other end portion in the axial direction of the shaft body 23 is inserted into the insertion hole 39, at least the tip end portion of the protrusion 42 is recessed into the outer peripheral surface of the shaft body 23. This prevents the shaft body 23 and the jig 24a from rotating relative to each other in a state before the shaft body and the jig are welded and fixed. In this example, since the protrusion 42 is disposed on the opposite side of the discontinuous portion 38, the jig 24a is prevented from being expanded in diameter due to the presence of the protrusion 42 when the other end portion in the axial direction of the shaft body 23 is inserted into the insertion hole 39. Therefore, the protrusion 42 can be effectively recessed into the outer peripheral surface of the shaft body 23. Including the point where the shaft body 23 and the jig 24a are welded and fixed, the other configurations and operational effects are the same as those of the first example of the embodiment.

[ third example of embodiment ]

A third example of the embodiment of the present invention will be described with reference to fig. 11 and 12. In this example, in order to prevent the jig 24b from rotating relative to the shaft body 23a until the jig 24b is welded and fixed to the other end portion in the axial direction of the shaft body 23a, the outer circumferential surface of the shaft body 23a and the inner circumferential surface of the insertion hole 39a of the jig 24b are fitted in a non-circular shape.

The shaft body 23a has a flat shaft body side plane portion 43 on a portion of the outer peripheral surface of the other end portion in the axial direction opposite to the slit 33 in the diameter direction of the shaft body 23. Therefore, the contour of the outer peripheral surface of the other end portion in the axial direction of the shaft body 23a is substantially D-shaped, which is formed by an arc portion and a straight portion. The jig 24b has a flat-surface-shaped jig-side flat surface portion 44 at a portion of the inner peripheral surface of the insertion hole 39a opposite to the discontinuous portion 38 in the diameter direction of the insertion hole 39 a. Therefore, the contour shape of the inner peripheral surface of the insertion hole 39a of the jig 24b is also substantially D-shaped, which is formed by the circular arc portion and the linear portion.

In this example, when the other end portion in the axial direction of the shaft body 23a is inserted into the insertion hole 39a of the jig 24b, the flat shaft-body-side flat surface portion 43 and the flat jig-side flat surface portion 44 are in surface contact with each other. This makes it possible to fit the outer peripheral surface of the shaft body 23a and the inner peripheral surface of the insertion hole 39a of the jig 24b in a non-circular manner, thereby preventing the shaft body 23a and the jig 24b from rotating relative to each other. Including the point where the shaft body 23a and the jig 24b are welded and fixed, the other configurations and operational effects are the same as those of the first example of the embodiment.

[ fourth example of embodiment ]

A fourth example of the embodiment of the present invention will be described with reference to fig. 13. In this example, the shaft body 23b has a substantially annular (C-shaped) stepped surface 45 facing the other axial end of the outer circumferential surface (the axial intermediate portion of the outer circumferential surface of the small-diameter cylindrical portion 31) at the other axial end. Specifically, the other end in the axial direction of the small-diameter cylinder portion 31 is provided with a fitting cylinder portion 46 having an outer diameter smaller than that of a portion adjacent to one side in the axial direction, and the stepped surface 45 is disposed at one end in the axial direction of the fitting cylinder portion 46. In this example, the fitting cylindrical portion 46 is formed by cutting the outer peripheral surface of the other end portion in the axial direction of the small-diameter cylindrical portion 31. When the jig 24 (see fig. 1) is fitted to the fitting cylinder portion 46, the jig 24 can be positioned in the axial direction with respect to the shaft body 23b by abutting the axial end surface of the jig 24 against the stepped surface 45. Including the point where the shaft body 23b and the jig 24 are welded and fixed, the other configurations and operational effects are the same as those of the first example of the embodiment.

[ fifth example of embodiment ]

A fifth example of the embodiment will be described with reference to fig. 14 to 17. In this example, the cylindrical portion 26a of the shaft body 23c includes, in order from the axial side, a large diameter cylindrical portion 29a, a large diameter side tapered cylindrical portion 51, an intermediate diameter cylindrical portion 52, a small diameter side tapered cylindrical portion 53, and a small diameter cylindrical portion 31 a.

The large-diameter cylindrical portion 29a is disposed at one axial end of the cylindrical portion 26 a. The other axial end edge of the large-diameter cylindrical portion 29a is connected to one axial end edge of the large-diameter side conical cylindrical portion 51. The outer diameter and the inner diameter of the large diameter cylinder 29a are larger than those of the other portion that is present on the other axial side of the large diameter cylinder 29a and that constitutes the cylinder 26 a. That is, the large diameter tube portion 29a has the largest outer diameter and inner diameter among the tube portions 26 a.

The large diameter side cylindrical portion 51 has a partial cylindrical shape in which the outer diameter and the inner diameter decrease toward the other axial side. The other axial end edge of the large diameter side cylindrical portion 51 is connected to one axial end edge of the intermediate diameter cylindrical portion 52.

The intermediate diameter cylinder portion 52 is disposed at an axially intermediate portion of the cylinder portion 26 a. The outer diameter and the inner diameter of the intermediate diameter cylinder 52 are constant in the axial direction. Further, the other axial end edge of the intermediate diameter cylinder portion 52 is connected to one axial end edge of the small diameter side tapered cylinder portion 53.

The small-diameter side tapered tube portion 53 has a partial tapered tube shape in which the outer diameter and the inner diameter decrease toward the other side in the axial direction. The other axial end edge of the small-diameter side tapered tube portion 53 is connected to one axial end edge of the small-diameter tube portion 31 a.

The small-diameter cylindrical portion 31a is disposed at the other end portion in the axial direction of the cylindrical portion 26a, and is substantially cylindrical. The small-diameter cylindrical portion 31a is formed by reducing the diameter of the other end portion in the axial direction of the cylindrical portion 26 a. The small-diameter cylindrical portion 31a has an outer diameter and an inner diameter smaller than those of the other portions of the cylindrical portion 26a existing on one axial side of the small-diameter cylindrical portion 31 a. That is, the small-diameter cylindrical portion 31a has the smallest outer diameter and inner diameter among the cylindrical portions 26 a.

An axially intermediate portion of the outer peripheral surface of the small-diameter cylinder portion 31a is provided with a substantially annular (C-shaped) stepped surface 45 facing the other axial side. Therefore, in this example, the jig 24 is abutted against the stepped surface 45, whereby the jig 24 can be positioned in the axial direction with respect to the shaft body 23 c. Therefore, when the shaft body 23c and the jig 24 are welded and fixed, it is not necessary to dispose the fastening bolt 49 inside the engagement recess 35. In this example, as in the structure of the first example of the embodiment, the shaft body 23c and the jig 24 are welded and fixed by forming the welding portion 41 by spot welding at one circumferential position on the opposite side of the slit 33 in the diameter direction of the shaft body 23c in the portion between the opening edge of the insertion hole 39 on one axial side of the jig 24 and the outer circumferential surface of the shaft body 23 c.

The inner peripheral surface of the small-diameter tube portion 31a is provided with female serrations 32a extending over the entire length of the small-diameter tube portion 31 a. In this example, the female serrations 32a are provided only on the inner peripheral surface of the small-diameter tube portion 31a out of the inner peripheral surface of the tube portion 26 a. The female serrations 32a have incomplete serration portions 55 at one axial end portion, and the depth (inner diameter) of the grooves of the female serrations constituting the female serrations 32a decreases toward one axial side of the incomplete serration portions 55. As shown in fig. 14, an end portion of a steering shaft, a pinion shaft, or the like 47 is inserted inside the small diameter cylinder portion 31a, and male serrations 48 formed on an outer peripheral surface of the shaft 47 are engaged with the female serrations 32 a. However, the incomplete serration part 55 of the female serration 32a has a structure that cannot smoothly engage with the male serration 48. In this example, since the stepped surface 45 is disposed at the axially intermediate portion of the outer peripheral surface of the small-diameter cylinder portion 31a, the incomplete serration portion 55 is positioned on the one axial side of the one axial end surface of the jig 24 in a state where the jig 24 is positioned in the axial direction with respect to the shaft body 23c by abutting the jig 24 against the stepped surface 45. The welded portion 41 is present between the partial serration 55 and the one axial end surface of the shaft 47 in the axial direction. Therefore, the portion of the female serrations 32a that engages with the male serrations 48 of the shaft 47 is prevented from being thermally deformed by welding, and the jig 24 and the shaft 47 can be smoothly coupled.

In this example, the slit 33a is provided so as to extend in the axial direction from the intermediate axial portion to the other axial end portion of the cylindrical portion 26a and to extend in the axial direction from the inner diameter cylindrical portion 52 to the small diameter cylindrical portion 31 a. The axial one end portion, i.e., the deep end portion X of the slit 33a is positioned at the axial other end portion of the intermediate diameter cylinder portion 52 existing on the axial side of the small diameter cylinder portion 31a, and the axial other end edge portion of the slit 33a is open at the axial other end edge of the small diameter cylinder portion 31a (the shaft body 23 c). The portion of the slit 33a adjacent to the other axial side of the deep end portion X, that is, the axial side portion, is located on the small-diameter side tapered tubular portion 53. Therefore, the female serrations 32a are not provided on the inner peripheral surface of the portion of the cylindrical portion 26a where the depth end X of the slit 33a is located. Therefore, the depth end X of the slit 33a is positioned on the axial side of one axial end edge of the female serration 32 a.

In this example, the stress relaxing portion 34 (see fig. 1 and the like) is not provided at the depth end portion X of the slit 33a, and the width dimension of the slit 33a in the circumferential direction is constant over the entire length. Such a slit 33a is formed by cutting using a rotary cutting tool such as a cutter. Therefore, as shown in fig. 16, the cross-sectional shape of the depth end portion X (one axial end edge) of the slit 33a is partially circular-arc-shaped. However, the stress relaxing portion 34 may be provided at the depth end X of the slit 33a, and the stress relaxing portion 34 may have a width larger than a portion adjacent to the other side in the axial direction. The slits 33a are disposed at positions shifted in phase by 90 degrees from the pair of

arm portions

27a and 27b constituting the yoke portion 25.

In this example, the non-toothed portion 54 in which the female serrations 32a are not formed is provided at a portion of the inner peripheral surface of the small-diameter cylinder portion 31a adjacent to both sides of the slit 33a in the circumferential direction. That is, the toothless portion 54 has a partial cylindrical surface having an inner diameter dimension substantially equal to the inscribed diameter of the valley portion of the female serration 32 a.

In this example, since the depth end portion X of the slit 33a is positioned in the intermediate diameter cylindrical portion 52 having a larger outer diameter and inner diameter than the small diameter cylindrical portion 31a, the stress generated at the depth end portion X of the slit 33a when the other end portion in the axial direction of the shaft body 23c is reduced in diameter can be made smaller than when the depth end portion is positioned in the small diameter cylindrical portion 31 a. Further, since the female serrations 32a are not present on the axial direction side of the depth end portions X of the slits 33a, the depth end portions X of the slits 33a and the trough portions of the female serrations 32a are prevented from being axially continuous (the intersection points of the depth end portions X with the trough portions of the female serrations 32a are thin). Therefore, the stress concentration at the deep end portion X of the slit 33a can be alleviated. In this example, since the processing for forming the stress relaxing portion at the deep end portion X of the slit 33a can be omitted, the processing cost of the slit 33a can be suppressed. Further, since it is not necessary to perform deburring on the depth end portion of the slit 33a, the processing cost can be suppressed from this point of view.

In this example, the non-toothed portion 54 is provided in the inner peripheral surface of the small-diameter cylindrical portion 31a at portions located on both sides of the slit 33a in the circumferential direction, and therefore, when the axial other end portion of the shaft body 23c is reduced in diameter, the male serrations 48 formed on the outer peripheral surface of the shaft 47 can be prevented from being partially abutted. Therefore, it is possible to prevent the tooth breakage and the occurrence of chipping of the serrations due to excessive stress concentration, which may be a problem in the case where the female serrations are formed on both sides in the circumferential direction of the slit 33 a.

In the shaft body 23c of this example, the cylinder 26a has a three-stage structure including a small-diameter cylinder 31a, an intermediate-diameter cylinder 52, and a large-diameter cylinder 29 a. Therefore, the operation of forging the metal material to manufacture the shaft body 23c can be facilitated as compared with the case of manufacturing the shaft body 23 having the cylindrical portion 26 of the two-stage structure including the small-diameter cylindrical portion 31 and the large-diameter cylindrical portion 29 by forging as in the first example of the embodiment.

In the shaft body 23c of this example, the cylindrical portion 26 has a three-stage structure, and the female serrations 32a are provided only on the inner peripheral surface of the small-diameter cylindrical portion 31 a. Therefore, compared to the cylindrical portion 26 of the first example of the embodiment in which the cylindrical portion 26 has a two-stage structure and the shaft body 23 in which the female serrations 32 are provided in the axial direction on the inner peripheral surface of the small-diameter cylindrical portion 31 of the cylindrical portion 26, the shaft body 23c of this example can be shortened in the axial length of the female serrations 32 a. Therefore, in the shaft body 23c of this embodiment, the machining cost for forming the female serrations 32a by broaching, pressing, or the like is suppressed to be lower than that of the shaft body 23 of the first embodiment. Other structures and operational effects are the same as those of the first example of the embodiment.

[ sixth example of embodiment ]

A sixth example of the embodiment of the present invention will be described with reference to fig. 18. In this example, the cylindrical portion 26b of the shaft body 23d has a two-stage structure in which a small-diameter cylindrical portion 31b and a large-diameter cylindrical portion 29b are connected by a tapered cylindrical portion 30 a. However, in the shaft body 23d of this example, the axial length of the small diameter cylindrical portion 31b is made smaller than the axial length of the small diameter cylindrical portion 31 of the shaft body 23 of the first example of the embodiment. In other words, the axial position of the tapered tube portion 30a of the shaft body 23d is set to the other axial side than the axial position of the tapered tube portion 30 of the shaft body 23 according to the first example of the embodiment. Thus, the axial length of the female serrations 32b formed on the inner peripheral surface of the small-diameter cylinder portion 31b is made smaller than the axial length of the female serrations 32 in the first example of the embodiment, and the machining cost for forming the female serrations 32b is suppressed.

In the shaft body 23d of this example, the axial one end portion, i.e., the deep end portion X of the slit 33a is positioned at the axial other end portion of the large-diameter cylindrical portion 29 b. In other words, the portion of the slit 33a adjacent to the other axial side of the depth end portion X, that is, the one axial side portion, is located on the tapered tube portion 30 a. Further, a substantially annular stepped surface 45 facing the other axial side is present in an axially intermediate portion of the outer peripheral surface of the small-diameter cylinder portion 31 b. Other structures and operational effects are the same as those of the first and fifth examples of the embodiment.

[ seventh example of embodiment ]

A seventh example of the embodiment of the present invention will be described with reference to fig. 19. In this example, the axial position of the stepped surface 45a is located on the axial side of the structure of the fifth example of the embodiment. Therefore, the axial length of the fitting cylinder portion 46a is longer than the axial length of the fitting cylinder portion 46 of the fifth example of the embodiment. In this example, the axial position of the stepped surface 45a coincides with the axial position of the incomplete serration part 55 disposed at one axial end of the female serration 32 a. That is, the stepped surface 45a is located radially outward of the partial serration 55.

When the jig 24c is fitted to the fitting cylindrical portion 46a, the jig 24c can be positioned in the axial direction with respect to the shaft body 23e by abutting the axial end surface of the jig 24c against the stepped surface 45 a. In this example, the axial length of the jig 24c is also made longer than the axial length of the jig 24 in the fifth example of the embodiment by setting the axial length of the fitting cylindrical portion 46a to be longer than the axial length of the fitting cylindrical portion 46 in the fifth example of the embodiment.

In this example, as in the structure of the first example of the embodiment, the shaft body 23e and the jig 24c are welded and fixed by forming the weld 41 at one circumferential location on the opposite side of the slit 33 in the diameter direction of the shaft body 23e in the portion between the opening edge of the insertion hole 39 of the jig 24a on one axial side and the outer circumferential surface of the shaft body 23e by spot welding. In this example, since the stepped surface 45 is located radially outward of the incomplete serration part 55, the axial position of the welded part 41 coincides with the axial position of the incomplete serration part 55. That is, the welded portion 41 is located radially outward of the partial serration 55.

In this example, since the welded portion 41 is located radially outward of the incomplete serration portion 55 which does not perform serration engagement with the male serration 48 of the shaft 47, the portion of the female serration 32a which engages with the serration 48 of the shaft 47 can be prevented from being thermally deformed by welding, and the jig 24c and the shaft 47 can be smoothly coupled. Further, since the axial length of the fitting cylinder portion 46a is larger than the axial length of the fitting cylinder portion 46 of the fifth example of the embodiment, the fitting length of the shaft body 23e and the jig 24c can be sufficiently secured, and the fitting strength can be stabilized. Other structures and operational effects are the same as those of the first and fifth examples of the embodiment.

[ eighth example of embodiment ]

An eighth example of the embodiment of the present invention will be described with reference to fig. 20. The shaft body 23f of this example has a stress relaxing section 34 at the depth end X of the slit 33, as in the case of the shaft body 23 of the first example of the embodiment. The shaft body 23f includes the non-toothed portion 54 in the inner peripheral surface of the small-diameter cylinder portion 31 at portions located on both sides of the slit 33 in the circumferential direction, as in the case of the shaft body 23c of the fifth example of the embodiment. This prevents the male serrations 48 formed on the outer peripheral surface of the shaft 47 from partially abutting when the other end portion in the axial direction of the shaft body 23f is reduced in diameter. Including the point where the shaft body 23e and the jig 24 are welded and fixed, the other configurations and operational effects are the same as those of the first and fifth embodiments.

In the case of carrying out the present invention, the circumferential position of the slit provided in the shaft body is not limited to the position shown in each of the embodiments. The number of slits is not limited to one, and a plurality of slits may be provided. The shape of the stress relaxation portion formed at the depth end portion of the slit is not limited to the shape shown in each example of the embodiment, and any shape such as an elliptical shape or a water droplet shape may be used. The pair of mounting holes provided in the jig may be through holes, respectively, and may be used in combination with a nut. In the fixing structure of the shaft body and the jig, the shaft body and the jig can be fixed so as not to move in the axial direction by pressing (lightly pressing) the shaft body into the jig instead of welding. In addition, when the present invention is implemented, the structures of the respective examples of the embodiment can be implemented by appropriately combining them. For example, the structure of the second example or the third example of the embodiment capable of preventing the relative rotation of the shaft body and the jig and the structure of the fourth example of the embodiment capable of positioning the jig with respect to the shaft body in the axial direction can be simultaneously implemented.

Description of the symbols

1-a steering wheel, 2-a steering shaft, 3-a steering column, 4a, 4 b-a universal joint, 5-an intermediate shaft, 6-a steering gear unit, 7-a tie rod, 8-a pinion shaft, 9-a torque transmission shaft, 10-a yoke, 11 a-a shaft, 12-a pin, 13-a box, 14-a clamping portion, 15-a discontinuous portion, 16-a flange portion, 17-a mounting hole, 18-a base, 19-a box, 20-a weld bead portion, 21-a pin, 22-a torque transmission shaft, 23a, 23b, 23c, 23d, 23e, 23 f-a shaft body, 24a, 24b, 24 c-a clamp, 25-a yoke portion, 26a, 26 b-a cylindrical portion, 27a, 27 b-a, a wrist portion, 28-a circular hole, 29a, 29 b-a large-diameter cylindrical portion, 30 a-a, 31a, 31 b-a, 32 b-a cylindrical portion, 32 b-a, 32-a cylindrical portion, 33. 33 a-slit, 34-stress relaxation portion, 35-engagement groove, 36-base portion, 37-flange portion, 38-discontinuous portion, 39 a-insertion hole, 40a, 40 b-mounting hole, 41-welding portion, 42-projection portion, 43-shaft body side flat portion, 44-jig side flat portion, 45-step surface, 46-fitting cylinder portion, 47-shaft, 48-male tooth, 49-fastening bolt, 50-annular groove, 51-large diameter side conical cylinder portion, 52-intermediate diameter cylinder portion, 53-small diameter side conical cylinder portion, 54-toothless portion, 55-incomplete-serration portion, X-depth end portion.

Claims

1. A torque transmission shaft is provided with:

a hollow shaft body having a yoke portion provided at one axial end portion, a slit provided at the other axial end portion and extending in the axial direction, and a female serration provided on an inner circumferential surface of the other axial end portion; and

a notched cylindrical jig having a discontinuous portion disposed at one position in a circumferential direction and a pair of flange portions disposed on both sides in the circumferential direction with the discontinuous portion interposed therebetween and each having a mounting hole into which a fastening member is inserted,

the jig is fitted to the other axial end of the shaft body to reduce the width of the discontinuous portion, thereby reducing the diameter of the other axial end of the shaft body,

the above-mentioned torque transmission shaft is characterized in that,

the shaft body has a small-diameter cylindrical portion at the other axial end, the female serrations are provided only on the inner peripheral surface of the small-diameter cylindrical portion,

the axial end of the slit is located closer to the axial direction than the small-diameter tube, and is located closer to the axial direction than the axial end of the female serration, and has a larger outer diameter and a larger inner diameter than the small-diameter tube.

2. The torque transmitting shaft of claim 1,

the shaft body and the jig are fixed so as not to be movable in the axial direction.

3. The torque transmitting shaft of claim 2,

the shaft body and the jig are welded and fixed.

4. The torque transmitting shaft of claim 3,

the end portion of the female serration on the one axial side has an incomplete serration portion in which a groove depth of the female serration groove becomes smaller toward the one axial side, and a weld-fixing portion of the shaft body and the jig is located on an outer diameter side of the incomplete serration portion.

5. The torque transmission shaft according to any one of claims 1 to 4,

the slit includes a stress relaxing portion having a width dimension larger than a width dimension of a portion adjacent to the other side in the axial direction at an end portion on the one side in the axial direction.

6. The torque transmitting shaft of claim 1,

the shaft body has a tapered cylindrical portion whose outer diameter and inner diameter increase toward one axial side in a portion adjacent to one axial side of the small-diameter cylindrical portion, and the end portion of the slit on the one axial side is located on one axial side of the tapered cylindrical portion.

7. The torque transmission shaft according to any one of claims 1 to 4 and 6,

the shaft body has a non-toothed portion in which the female serrations are not provided, at a portion of an inner circumferential surface adjacent to both sides of the slit in a circumferential direction.

8. The torque transmission shaft according to any one of claims 1 to 4 and 6,

the shaft body has an engaging recess extending in a direction orthogonal to a central axis of the shaft body at a portion of an outer peripheral surface thereof facing the opening of the mounting hole, and the fastening member is disposed inside the engaging recess.

9. The torque transmission shaft according to any one of claims 1 to 4 and 6,

the slit and the discontinuous portion are aligned in circumferential positions, and a width dimension of the slit and a width dimension of the discontinuous portion in a free state of the shaft body and the jig are identical to each other.

10. The torque transmission shaft according to any one of claims 1 to 4 and 6,

11. The torque transmission shaft according to any one of claims 1 to 4 and 6,

the outer peripheral surface of the shaft body and the inner peripheral surface of an insertion hole in the jig into which the shaft body is inserted are fitted together in a non-circular manner so as not to be able to rotate relative to each other.

12. The torque transmission shaft according to any one of claims 1 to 4 and 6,

the shaft body has a stepped surface facing the other side in the axial direction on an outer peripheral surface thereof, and the jig is brought into contact with the stepped surface, whereby the jig is positioned in the axial direction with respect to the shaft body.