Intermediate Shaft

Abstract

To provide an intermediate shaft of which the whirling can be suppressed.SOLUTION: An intermediate shaft 5b is configured by axially connecting a contraction shaft 9a and a telescopic shaft 10a, each of which has a double pipe structure. The contraction shaft 9a is comprised of a first inner shaft 11a and a first outer cylinder 12a, the first outer cylinder 12a is comprised of a hollow shaft body 31 and a clamp 32 in the shape of a partial cylinder for reducing the diameter of the shaft body 31. The shaft body 31 has, on an inner periphery from an end on axial one side to an axial intermediate portion, a female spline 36 engaging with a male spline 28 provided on an outer periphery of the first inner shaft 11a and has, on an inner periphery of an end on the axial other side, a female serration 40 engaging with a male serration 54 provided on an outer periphery of an axial end on one side in an axial direction of a second outer cylinder 15a comprising the telescopic shaft 10a.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an intermediate shaft that constitutes a steering device for an automobile. [Background technology]

[0002] 41 shows a conventional steering device for an automobile, which is described in JP 2017-25964 A. The steering device includes a steering wheel 1, a steering shaft 2, a steering column 3, a pair of universal joints 4a, 4b, an intermediate shaft 5, a steering gear unit 6, and a pair of tie rods 7.

[0003] The steering wheel 1 is attached to the rear end of a steering shaft 2 that is rotatably supported inside a steering column 3. The front end of the steering shaft 2 is connected to a pinion shaft 8 of a steering gear unit 6 via a pair of universal joints 4a, 4b and an intermediate shaft 5. The rotation of the pinion shaft 8 is converted into linear motion of a rack shaft (not shown) to push and pull a pair of tie rods 7, thereby applying a steering angle to the steered wheels according to the amount of operation of the steering wheel 1. Note that the fore-aft direction refers to the fore-aft direction of the vehicle body to which the steering device is assembled.

[0004] The universal joints 4a, 4b connect the steering shaft 2 and the intermediate shaft 5, and the intermediate shaft 5 and the pinion shaft 8, which are rotational axes that are not coaxial with each other, in a manner enabling torque transmission between them.

[0005] In steering devices mounted on large automobiles, the distance from the steering shaft to the steering gear unit is long, so an intermediate shaft with a long overall length is often used to connect the steering shaft and the steering gear unit.

[0006] Additionally, intermediate shafts are required to protect the driver in the event of a car collision by contracting their overall length, and to prevent vibrations input to the tires while driving from being transmitted to the steering wheel.

[0007] In view of these circumstances, the present inventors, prior to the present invention, have considered a structure in which two types of shafts are connected in the axial direction. FIG. 42 shows an intermediate shaft 5a described in International Publication No. 2018 / 139577, which the present inventors have previously completed. The intermediate shaft 5a is formed by connecting a contraction shaft 9 arranged on one axial side and a telescopic shaft 10 arranged on the other axial side in the axial direction. Each of the contraction shaft 9 and the telescopic shaft 10 has a double tube structure.

[0008] The contractible shaft 9 is a collapsible shaft having a first inner shaft 11 and a first outer cylinder 12, and is configured so that its overall length can be contracted only when an automobile crash occurs and an impact load of a predetermined magnitude or greater is applied in the axial direction. For this purpose, a male spline 13 provided on the other axial end of the outer circumferential surface of the first inner shaft 11 is engaged with a female spline 14 provided on one axial end of the inner circumferential surface of the first outer cylinder 12 so as to be capable of transmitting torque, and the fitting portion between the first inner shaft 11 and the first outer cylinder 12 is a so-called elliptical fit.

[0009] The telescopic shaft 10 has a second outer tube 15 and a second inner shaft 16, and is configured so that its entire length can be extended or retracted in a steady state in which no automobile collision has occurred. For this purpose, one axial side of the second inner shaft 16 is inserted inside the other axial side of the second outer tube 15, and multiple balls 19, rollers 20, etc. are disposed between a female groove 17 provided on the inner peripheral surface of the second outer tube 15 and a male groove 18 provided on the outer peripheral surface of the second inner shaft 16.

[0010] In addition, the first outer tube 12 constituting the contraction shaft 9 and the second outer tube 15 constituting the telescopic shaft 10 are connected in a manner enabling torque transmission. For this purpose, the male serrations 22 provided at one axial end of the outer peripheral surface of the second outer tube 15 are engaged in a manner enabling torque transmission with the female serrations 21 provided at the other axial end of the inner peripheral surface of the first outer tube 12. In addition, the other axial end of the first outer tube 12 is reduced in diameter, and the inner peripheral surface of the first outer tube 12 fastens the outer peripheral surface of the one axial end of the second outer tube 15.

[0011] The intermediate shaft 5a as described above can be used as a steering device for large automobiles in which the distance from the steering shaft to the steering gear unit is long because the overall length can be secured. In addition, in the event of a collision, the collapsible shaft 9 and the telescopic shaft 10 can be both collapsed, thereby protecting the driver. Furthermore, the vibration input to the tires during driving can be absorbed by expanding and contracting the telescopic shaft 10, thereby preventing the vibration from being transmitted to the steering wheel. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] JP 2017-25964 A [Patent Document 2] International Publication No. 2018 / 139577 Summary of the Invention [Problem to be solved by the invention]

[0013] The intermediate shaft 5a described in WO 2018 / 139577 still has room for improvement in terms of suppressing swing.

[0014] That is, in the intermediate shaft 5a, the first outer cylinder 12 of the contraction shaft 9, which is connected to the telescopic shaft 10, is formed by welding a tube 23 having a female spline 14 on its inner circumferential surface and a clamp 24 having a female serration 21 on its inner circumferential surface. For this reason, it is difficult to ensure a high degree of concentricity between the female spline 14 and the female serration 21, and whirling is likely to occur between the first inner shaft 11 of the contraction shaft 9 connected via the female spline 14 and the second outer cylinder 15 of the telescopic shaft 10 connected via the female serration 21. In particular, the intermediate shaft 5a is prone to large whirling due to its long overall length.

[0015] In addition to the structure described in WO 2018 / 139577, it is also possible to integrally form the tube and the clamp that constitute the first external cylinder, for example, by forging. However, even in such a case, the flow of the metal material becomes complicated, making it difficult to ensure a high degree of concentricity between the female spline and the female serration.

[0016] The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide an intermediate shaft capable of suppressing whirling. [Means for solving the problem]

[0017] The intermediate shaft of the present invention constitutes a steering device for an automobile, and is configured by axially connecting a first torque transmission shaft and a second torque transmission shaft, each of which has a yoke at an axially opposite end. The first torque transmission member has a first connecting shaft. The second torque transmission member has a second connection side shaft that is connected to the first connection side shaft so as to be able to transmit torque. Either the first connecting side shaft or the second connecting side shaft has a hollow shaft body and a notched cylindrical clamp, and an inner shaft which constitutes either the first torque transmission shaft or the second torque transmission shaft together with the one shaft is an outer tube into which torque can be transmitted and relative displacement in the axial direction is possible. The first torque transmission shaft or the second torque transmission shaft including the one shaft has a double tube structure. The shaft body has a first female side engagement portion provided on its inner surface in a range from the end on one axial side to the middle axial portion, which engages with a first male side engagement portion provided on the outer surface of the inner shaft, a second female side engagement portion provided on its inner surface at the end on the other axial side, which engages with a second male side engagement portion provided on the outer surface of the end of the other of the first connecting side shaft and the second connecting side shaft, and a slit provided at the end on the other axial side, extending in the axial direction, and having an opening end on the other axial side. The axial dimension of the first female engagement portion is larger than the axial dimension of the first male engagement portion, and the first female engagement portion and the first male engagement portion have a dimensional relationship that allows them to remain engaged even when one of the shafts is contracted. The shaft body has a small diameter cylindrical portion in which the first female side engagement portion is formed along the entire axial length of its inner surface, a fitting cylindrical portion in which the second female side engagement portion is formed along the entire axial length of its inner surface, and a large diameter cylindrical portion disposed between the small diameter cylindrical portion and the fitting cylindrical portion and having a larger diameter than the small diameter cylindrical portion. The large diameter cylindrical portion has a small diameter side conical cylindrical portion, an intermediate cylindrical portion, and a fitting side inclined portion, and is a relief portion having an inner diameter larger than the tooth bottom circle diameter of the first female side engaging portion. The large diameter cylindrical portion is formed with only the slit as a hole penetrating in the radial direction, and one axial end of the slit is located in the intermediate cylindrical portion. The axial dimension of the large diameter cylindrical portion is shorter than the axial dimension of the small diameter cylindrical portion, and the axial dimension of the intermediate cylindrical portion of the large diameter cylindrical portion is shorter than the axial dimension of the fitting cylindrical portion. The clamp is Fitting cylinder and the other axial end of the shaft body is capable of being reduced in diameter. 。 before The first torque transmission shaft or the second torque transmission shaft including the other shaft may or may not have a double tube structure.

[0018] In the intermediate shaft according to one aspect of the present invention, the first torque transmission shaft may be a contractible shaft having a double tube structure and configured so that its entire length can be contracted only when an automobile crash occurs and an impact load of a predetermined value or more is applied in the axial direction, and the second torque transmission shaft may be a telescopic shaft having a double tube structure and configured so that its entire length can be expanded and contracted in a steady state when no automobile crash occurs.

[0019] In the intermediate shaft according to one aspect of the present invention, the one shaft can be the connecting side first shaft constituting the first torque transmission shaft, and the first male side engagement portion can be press-fitted into the first female side engagement portion. Alternatively, in an intermediate shaft according to one aspect of the present invention, the one shaft is the second connecting shaft constituting the second torque transmission shaft, and the first male side engaging portion has a surface covered with a synthetic resin coating layer and can be slidably engaged with the first female side engaging portion.

[0023] In one aspect of the intermediate shaft of the present invention, the inner shaft, which constitutes either the first torque transmission shaft or the second torque transmission shaft together with the one of the shafts, can be provided with a fuse portion in a part in the axial direction, the fuse portion having a smaller diameter than the parts adjacent to the inner shaft on both axial sides.

[0024] In an intermediate shaft according to one aspect of the present invention, the first male side engagement portion can be a male spline, the first female side engagement portion can be a female spline, the second male side engagement portion can be a male serration, and the second female side engagement portion can be a female serration. Alternatively, the cross-sectional shape of at least one of the first male engagement portion and the first female engagement portion, and the second male engagement portion and the second female engagement portion may be polygonal or petal-shaped.

[0025] In the intermediate shaft according to one aspect of the present invention, the shaft body and the clamp can be fixed by welding.

[0026] In the intermediate shaft according to one aspect of the present invention, the shaft body and the clamp can be fixed together by a plastic deformation portion formed in at least one of the shaft body and the clamp.

[0027] In the intermediate shaft according to one aspect of the present invention, the outer circumferential surface of the other axial end of the shaft body and the inner circumferential surface of the clamp can be fitted in a non-circular manner so as to be non-rotatable relative to each other.

[0028] In an intermediate shaft according to one embodiment of the present invention, the clamp further includes a discontinuous portion located at one circumferential location, a pair of flange portions located on either side of the discontinuous portion in the circumferential direction, each flange portion having a mounting hole into which a fastening member is inserted, and a partially cylindrical connecting portion circumferentially connecting the pair of flange portions, wherein the connecting portion can be provided with a notch in the other axial side portion that is recessed toward one axial side further than the end face of the other axial side of the flange portions. Effect of the Invention

[0031] According to the present invention, an intermediate shaft capable of suppressing whirling can be realized. [Brief description of the drawings]

[0032] [Figure 1] FIG. 1 is a partial cutaway side view showing an example of a steering device equipped with an intermediate shaft according to a first example of an embodiment. [Diagram 2] FIG. 2 is a side view showing an intermediate shaft according to the first example of the embodiment. [Diagram 3] FIG. 3 is a side view showing the intermediate shaft according to the first example of the embodiment, separated into a contraction shaft and an extension shaft. [Figure 4] FIG. 4 is a cross-sectional view showing an intermediate shaft according to a first example of the embodiment. [Diagram 5] FIG. 5 is a side view showing a contraction shaft constituting an intermediate shaft according to a first example of an embodiment in a steady state before contraction. [Figure 6] FIG. 6 is a partial cross-sectional view showing a contraction shaft constituting an intermediate shaft according to a first example of an embodiment in a steady state before contraction. [Figure 7] FIG. 7 is a partial cross-sectional view showing a contractible shaft constituting an intermediate shaft according to a first example of the embodiment in a contracted state. [Figure 8]FIG. 8 is a diagram showing a first outer cylinder constituting a contraction shaft of an intermediate shaft according to a first example of an embodiment, (A) being a plan view, and (B) being a side view. [Figure 9] FIG. 9 is a cross-sectional view showing a first outer cylinder constituting a contraction shaft of an intermediate shaft according to a first example of the embodiment. [Figure 10] FIG. 10A is a cross-sectional view taken along line AA in FIG. 8B, and FIG. 10B is a cross-sectional view taken along line BB in FIG. 8B. [Figure 11] FIG. 11 is a plan view showing a shaft body constituting a first outer cylinder of a contraction shaft according to the first embodiment. [Figure 12] FIG. 12 is a side view showing a shaft body constituting a first outer cylinder of a contraction shaft according to the first embodiment. [Figure 13] FIG. 13 is a perspective view showing a clamp constituting a first outer cylinder of a contraction shaft according to the first embodiment. [Figure 14] FIG. 14(A) is a plan view showing a clamp constituting the first outer tube of the retractable shaft in the first embodiment, and FIG. 14(B) is a side view showing a clamp constituting the first outer tube of the retractable shaft in the first embodiment. [Figure 15] FIG. 15 is a diagram showing a second example of the embodiment, and corresponds to FIG. [Figure 16] FIG. 16 is a diagram showing a second example of the embodiment, and corresponds to FIG. [Figure 17] FIG. 17 is a side view showing a second inner shaft constituting the telescopic shaft of the intermediate shaft according to the second example of the embodiment. [Figure 18] FIG. 18 is an enlarged partial cross-sectional view showing a portion corresponding to the right part of FIG. 9, showing a third example of the embodiment. [Figure 19] FIG. 19 is an enlarged view of a portion corresponding to the right part of FIG. 9, showing a fourth example of the embodiment. [Figure 20] FIG. 20 is a diagram showing a fifth example of the embodiment, and corresponds to FIG. 10(A). [Figure 21]FIG. 21 is a view corresponding to FIG. 13, showing a clamp constituting a first outer cylinder of a retractable shaft, in accordance with a fifth embodiment. [Figure 22] FIG. 22 is an enlarged view of a portion corresponding to the right part of FIG. 8(B) showing a sixth example of the embodiment. [Figure 23] FIG. 23 is a view taken along the arrow C in FIG. 22, showing a sixth example of the embodiment. [Figure 24] FIG. 24 is a cross-sectional view taken along line DD in FIG. 22, showing a sixth example of the embodiment. [Diagram 25] FIG. 25 is an enlarged view of a portion corresponding to the right part of FIG. 11, showing a seventh example of the embodiment. [Figure 26] FIG. 26 is an end view showing a first outer cylinder constituting a contraction shaft according to the seventh embodiment. [Figure 27] FIG. 27 is an enlarged view of a portion corresponding to the right part of FIG. 11, showing an eighth example of the embodiment. [Figure 28] FIG. 28 is an enlarged view of a portion corresponding to the right part of FIG. 8(B) showing an eighth example of the embodiment. [Figure 29] FIG. 29 is a diagram showing a ninth example of the embodiment, and corresponds to FIG. 14(B). [Diagram 30] FIG. 30 is a partial cutaway side view showing a clamp constituting a first outer tube of a contraction shaft according to a tenth embodiment. [Diagram 31] FIG. 31 is a partial cross-sectional view showing a state before the diameter of a shaft body constituting a first outer cylinder is reduced, according to a tenth example of the embodiment. [Diagram 32] FIG. 32 is a partial cross-sectional view showing a shaft body constituting a first outer cylinder in a diameter-reduced state according to a tenth example of the embodiment. [Diagram 33] FIG. 33 is an enlarged view of a portion corresponding to the right part of FIG. 8(B) showing an eleventh example of the embodiment. [Diagram 34] FIG. 34 is an enlarged view of a portion corresponding to the right part of FIG. 11, showing an eleventh example of the embodiment. [Diagram 35]FIG. 35 is a perspective view showing a first outer cylinder constituting a contraction shaft according to a twelfth example of the embodiment. [Diagram 36] FIG. 36 is a half cross-sectional view showing a first outer cylinder constituting a contraction shaft according to a twelfth example of the embodiment. [Figure 37] FIG. 37 is a diagram showing a twelfth example of the embodiment, which corresponds to FIG. 8(A). [Figure 38] FIG. 38 is an end view showing a first outer cylinder constituting a contraction shaft according to a twelfth example of the embodiment. [Figure 39] FIG. 39 is a partial cross-sectional view showing a first outer cylinder constituting a contraction shaft according to a thirteenth embodiment. [Diagram 40] FIG. 40 is an end view showing a first outer cylinder constituting a contraction shaft according to a thirteenth embodiment. [Diagram 41] FIG. 41 is a partially cutaway side view showing a steering device of a conventional structure. [Diagram 42] FIG. 42 is a cross-sectional view showing an example of an intermediate shaft constituting a steering device mounted on a large automobile. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] [First Example of Implementation] The first embodiment will be described with reference to FIGS. 1 to 14. FIG.

[0034] The steering device of this example is installed in a large automobile and includes a steering wheel 1a, a steering shaft 2a, a steering column 3a, a pair of universal joints 4c, 4d, an intermediate shaft 5b, a steering gear unit 6a, and a pair of tie rods 7a.

[0035] The steering shaft 2a is rotatably supported inside a steering column 3a supported on the vehicle body. A steering wheel 1a operated by a driver is attached to the rear end of the steering shaft 2a, and the front end of the steering shaft 2a is connected to a pinion shaft 8a of a steering gear unit 6a via a universal joint 4c, an intermediate shaft 5b, and another universal joint 4d.

[0036] Therefore, when the driver turns the steering wheel 1a, the rotation of the steering wheel 1a is transmitted to the pinion shaft 8a of the steering gear unit 6a. The rotation of the pinion shaft 8a is converted into linear motion of the rack shaft meshed with the pinion shaft 8a, which pushes and pulls the pair of tie rods 7a. As a result, a steering angle according to the amount of operation of the steering wheel 1a is applied to the steered wheels. The fore-aft direction refers to the fore-aft direction of the vehicle body to which the steering device is attached. In the following description, the axial direction refers to the axial direction of the intermediate shaft 5b unless otherwise specified. In this example, one axial side corresponds to the front side of the vehicle body, and the other axial side corresponds to the rear side of the vehicle body.

[0037] [Intermediate shaft] The intermediate shaft 5b has a long overall length because it constitutes a steering device for a large automobile, and connects the front end of the steering shaft 2a to the pinion shaft 8a constituting the steering gear unit 6a so as to be able to transmit torque. The intermediate shaft 5b is constituted by axially connecting a contracting shaft 9a having a double tube structure corresponding to the first torque transmission shaft and a telescopic shaft 10a having a double tube structure corresponding to the second torque transmission shaft. The intermediate shaft 5b has the contracting shaft 9a on one axial side, which is the engine room side, and the telescopic shaft 10a on the other axial side, which is the driver's seat side. The contracting shaft 9a and the telescopic shaft 10a are respectively provided with yokes 25 and 61 at the ends on the opposite sides in the axial direction. That is, the contracting shaft 9a has the yoke 25 constituting the universal joint 4d at one axial end, and the telescopic shaft 10a has the yoke 61 constituting the universal joint 4c at the other axial end.

[0038] Contraction shaft The collapsible shaft 9a corresponds to the first torque transmission shaft, and is a collapsible shaft having a first inner shaft 11a and a first outer cylinder 12a, and is configured so that its overall length can be collapsed only when an automobile crash occurs and an impact load of a predetermined value or more is applied in the axial direction. For this reason, the first inner shaft 11a and the first outer cylinder 12a are connected so as to be capable of transmitting torque and to be capable of relative displacement in the axial direction during a primary collision. In other words, the first inner shaft 11a and the first outer cylinder 12a are connected so that relative displacement in the axial direction is not possible in a steady state.

[0039] In the intermediate shaft 5b of this example, the first inner shaft 11a is disposed on one axial side of the contraction shaft 9a, far from the telescopic shaft 10a, and the first outer tube 12a is disposed on the other axial side of the contraction shaft 9a, closer to the telescopic shaft 10a. Therefore, in this example, the first outer tube 12a corresponds to the first connecting shaft described in the claims. Also, the first outer tube 12a corresponds to one of the shafts described in the claims.

[0040] 《First inner shaft》 The first inner shaft 11a has a yoke 25 disposed on one axial side, and a rod-shaped portion 26 disposed on the other axial side.

[0041] The yoke 25, together with another yoke 27 connected to the pinion shaft 8a of the steering gear unit 6a and a cross shaft (not shown), constitutes a universal joint 4d.

[0042] The rod-shaped portion 26 is generally cylindrical and solid over almost the entire length. The rod-shaped portion 26 has a male spline 28, which corresponds to the first male engaging portion described in the claims, on the outer circumferential surface of the other axial side portion. Of the outer circumferential surface of the rod-shaped portion 26, the portion adjacent to the one axial side of the male spline 28 is a cylindrical surface whose outer diameter does not change and is smaller than the tooth bottom circle diameter of the male spline 28. The rod-shaped portion 26 has a center hole 29 at the end on the other axial side that opens only on the end face on the other axial side. Therefore, the other axial side portion of the male spline 28 is provided on the outer circumferential surface of the portion of the rod-shaped portion 26 that is thinned by forming the center hole 29.

[0043] Rod-shaped portion 26 has a fuse portion 30 on one axial side, the fuse portion 30 having a smaller diameter than adjacent portions on both axial sides. Fuse portion 30 is formed on the outer circumferential surface of rod-shaped portion 26, for example, by cutting. Fuse portion 30 has an outer circumferential surface that is substantially cylindrical, and has the smallest outer diameter of all portions of rod-shaped portion 26. In the illustrated example, rod-shaped portion 26 has only one fuse portion 30, but it may have multiple fuse portions spaced apart in the axial direction.

[0044] First External Cylinder The first outer cylinder 12a has a shaft body 31 and a clamp 32 disposed around the other axial side of the shaft body 31.

[0045] The shaft body 31 is made as a whole by performing forging (cold forging or hot forging) and cutting on a cylindrical material. The shaft body 31 is configured as a hollow cylindrical tube as a whole, with an axially intermediate portion having a larger diameter than both axially opposite portions. The shaft body 31 has, from one axial end in this order, a small diameter cylindrical portion 33, a large diameter cylindrical portion 34, and a fitting cylindrical portion 35.

[0046] The small diameter cylindrical portion 33 is cylindrical and is provided in a range from one axial end of the shaft body 31 to the axial middle portion. The small diameter cylindrical portion 33 is formed by ironing the outer circumferential surface of a material, and is configured to have a smaller diameter than the large diameter cylindrical portion 34 adjacently disposed on the other axial side. The small diameter cylindrical portion 33 is provided with a female spline 36, which corresponds to the first female side engagement portion described in the claims, over the entire axial length of its inner circumferential surface. The female spline 36 is formed when the outer circumferential surface of the material is ironed. However, it may also be formed separately by broaching or the like.

[0047] The female spline 36 has a larger axial dimension than the male spline 28 provided on the first inner shaft 11a. Specifically, the female spline 36 has an axial dimension that is about two to three times that of the male spline 28. In a steady state in which no automobile collision has occurred, only one axial side portion of the female spline 36 is spline-engaged with the male spline 28. The other axial side portion of the female spline 36 is spline-engaged with the male spline 28 when an automobile collision occurs and an impact load of a predetermined value or greater is applied to the contraction shaft 9a in the axial direction.

[0048] As shown in Fig. 5 and Fig. 6, in the assembled state of the contraction shaft 9a, the other axial side of the first inner shaft 11a is inserted into one axial side of the small diameter cylindrical portion 33 constituting the first outer cylinder 12a. Then, the male spline 28 provided on the other axial side of the outer circumferential surface of the rod-shaped portion 26 is spline-engaged with the female spline 36 provided on the inner circumferential surface of the small diameter cylindrical portion 33 so as to be capable of transmitting torque. Also, the male spline 28 is press-fitted into the female spline 36 so that the first inner shaft 11a and the first outer cylinder 12a can be displaced relative to each other in the axial direction during a primary collision. In this example, the male spline 28 is spline-fitted into the female spline 36 in a light press-fit state where the press-fitting force is about 1 to 4 kN.

[0049] As a result, the first inner shaft 11a and the first outer cylinder 12a cannot move relative to each other in the axial direction in a steady state where no automobile collision has occurred, but when an automobile collision occurs and an impact load of a predetermined value or more is applied in the axial direction, the first inner shaft 11a and the first outer cylinder 12a can move relative to each other in the axial direction. Therefore, the entire length of the collapsible shaft 9a cannot be contracted in a steady state where no automobile collision has occurred, but when an automobile collision occurs and an impact load of a predetermined value or more is applied in the axial direction, the entire length can be contracted. In addition, when the collapsible shaft 9a contracts, it absorbs energy due to the collision.

[0050] In addition, in the steady state, the fuse portion 30 provided on the rod-shaped portion 26 is exposed from the first outer cylinder 12a.

[0051] The large diameter cylindrical portion 34 is disposed in the axial middle portion of the shaft body 31. As shown in Fig. 9, the large diameter cylindrical portion 34 has a small diameter side conical cylindrical portion 37, an intermediate cylindrical portion 38, and a fitting side inclined portion 39. The large diameter cylindrical portion 34 is disposed adjacent to the other axial side of the female spline 36 provided on the inner peripheral surface of the small diameter cylindrical portion 33, and forms a relief portion 80 having an inner diameter larger than the bottom circle diameter of the female spline 36.

[0052] The small diameter side conical cylinder portion 37 is configured in a substantially conical cylindrical shape and is disposed on one axial side of the large diameter cylinder portion 34. The small diameter side conical cylinder portion 37 has an outer diameter dimension and an inner diameter dimension that continuously increase toward the other axial side. The small diameter side conical cylinder portion 37 is connected to the end portion of the small diameter cylinder portion 33 on the other axial side.

[0053] The intermediate cylindrical portion 38 is configured in a substantially cylindrical shape, and is disposed in the axial middle portion of the large diameter cylindrical portion 34. The inner circumferential surface and the outer circumferential surface of the intermediate cylindrical portion 38 are each cylindrical surfaces whose diameter dimension does not change along the axial direction.

[0054] The fitting-side inclined portion 39 has a generally conical outer surface shape, and is disposed on the other axial side of the large-diameter cylindrical portion 34. The outer diameter of the outer peripheral surface of the fitting-side inclined portion 39 continuously decreases toward the other axial side. The inner peripheral surface of the fitting-side inclined portion 39 is provided with a portion of the female serrations 40, which will be described later. The fitting-side inclined portion 39 is connected to an end portion on one axial side of the fitting cylindrical portion 35.

[0055] The fitting tubular portion 35 is cylindrical and disposed at the other axial end of the shaft body 31. The fitting tubular portion 35 has an outer diameter substantially equal to the outer diameter of the small diameter tubular portion 33. The fitting tubular portion 35 is provided with female serrations 40, which correspond to the second female side engagement portion described in the claims, over the entire axial length of the inner peripheral surface. The female serrations 40 are formed by broaching, pressing, or the like. The axial dimension of the fitting tubular portion 35 is slightly larger than the axial dimension of the clamp 32. The axial dimension of the female serrations 40 is sufficiently shorter than the axial dimension of the female spline 36. In the illustrated example, the axial dimension of the female serrations 40 is approximately 1 / 5 of the axial dimension of the female spline 36. The female serrations 40 and the female spline 36 can be machined separately or simultaneously. When the female serrations 40 and the female splines 36 are machined simultaneously, the tooth shapes and phases are the same, but when the female serrations 40 and the female splines 36 are machined separately, the tooth shapes and phases can be made different from each other.

[0056] 11 and 12, the fitting cylindrical portion 35 has an engagement groove 41 on the outer circumferential surface of the axially intermediate portion thereof, the engagement groove 41 extending in a direction perpendicular to the central axis of the shaft body 31. The radius of curvature of the engagement groove 41 is substantially the same as the radius of curvature of a mounting hole 48a (48b) provided in the clamp 32, which will be described later.

[0057] The outer circumferential surface of the fitting tubular portion 35 is a cylindrical surface whose outer diameter dimension does not change along the axial direction. The contour shape of the fitting tubular portion 35 is a circular shape (a perfect circle) except for the portion where the engagement groove 41 is formed.

[0058] The shaft body 31 has a slit 42 extending in the axial direction in a range from the intermediate cylindrical portion 38 of the large diameter cylindrical portion 34 located from the axial middle portion to the end portion on the other axial side to the fitting cylindrical portion 35. The slit 42 communicates with the inner peripheral surface and the outer peripheral surface of the shaft body 31, and is formed at one location in the circumferential direction of the shaft body 31. Specifically, the slit 42 is formed in the axial direction so as to cross the engagement groove 41. The intersection of the slit 42 and the engagement groove 41 forms a wide portion 43 whose width is larger than that of the portion of the slit 42 that is not adjacent to the intersection.

[0059] One axial side of the slit 42 is a closed end, and is located in the axial middle of the intermediate cylindrical portion 38 that is on one axial side of the fitting cylindrical portion 35. The other axial side of the slit 42 is an open end, and opens to the edge of the other axial side of the fitting cylindrical portion 35 (shaft main body 31). As such, since the end of the slit 42 on one axial side is a closed end and the end on the other axial side is an open end, the rigidity of the fitting cylindrical portion 35 onto which the clamp 32 is fitted is higher in the portion on one axial side near the closed end of the slit 42 than in the portion on the other axial side near the open end of the slit 42.

[0060] In this example, the width of the slit 42 is constant over the entire length. Such a slit 42 is formed by cutting using a rotary cutting tool such as a cutter. Therefore, the cross-sectional shape of the end (rear end) on one axial side of the slit 42 is partially arc-shaped. Although not shown, a stress relaxation part having a width larger than that of the part adjacent to the other axial side and having a substantially circular opening shape in a plan view can be provided at the rear end of the slit 42. If such a stress relaxation part is provided, it is possible to effectively prevent damage such as cracks from occurring at the rear end of the slit 42 where stress is likely to concentrate when the shaft body 31 is reduced in diameter.

[0061] The clamp 32 is fitted onto the other axial end of the shaft body 31 and is used to reduce the diameter of the other axial end of the shaft body 31. Specifically, the clamp 32 is fitted onto the fitting tubular portion 35 of the shaft body 31 and is used to reduce the diameter of the range extending from the other axial end of the large diameter tubular portion 34 in which the slit 42 is formed to the fitting tubular portion 35. Such a clamp 32 can be made by subjecting a material having a higher hardness than the material constituting the shaft body 31, such as S35C, which is carbon steel for mechanical construction, to hot forging or cutting. Alternatively, the clamp 32 can be made by subjecting a material such as S10C or S15C, which is carbon steel for mechanical construction, to cold forging, which causes work hardening.

[0062] As shown in FIG. 13, the clamp 32 is configured in an overall notched cylindrical shape (approximately U-shaped) and includes a discontinuous portion 44, a pair of flange portions 45 each having an approximately rectangular plate shape, a semi-cylindrical connecting portion 46, and an insertion hole 47.

[0063] The discontinuous portion 44 is provided at one location in the circumferential direction of the clamp 32, located between the pair of flange portions 45. The pair of flange portions 45 are arranged on both sides of the discontinuous portion 44. The connecting portion 46 is located on the opposite side of the discontinuous portion 44 in the diametric direction of the clamp 32, and connects the pair of flange portions 45 to each other in the circumferential direction. The insertion hole 47 is for inserting the fitting tubular portion 35 of the shaft main body 31, and is formed by the inner peripheral surface of the connecting portion 46 and the radially inner surfaces of the pair of flange portions 45. The insertion hole 47 has a partially cylindrical surface shape, and the inner diameter dimension thereof is the same as or slightly larger than the outer diameter dimension of the fitting tubular portion 35 in the free state of the clamp 32.

[0064] 10, when the clamp 32 is fixed to the fitting tubular portion 35 of the shaft body 31, the circumferential positions of the discontinuous portion 44 and the slit 42 coincide with each other. In this example, the width dimension of the discontinuous portion 44 in the free state of the clamp 32 and the width dimension of the slit 42 in the free state of the shaft body 31 (fitting tubular portion 35) are approximately the same.

[0065] The pair of flanges 45 are provided with mounting holes 48a, 48b coaxially penetrating in the plate thickness direction at the portions where the flanges 45 are aligned with each other. 47 The mounting holes 48a, 48b are disposed at a twisted position with respect to the fitting cylinder portion 35 of the shaft body 31, and open into the insertion hole 47. Of the pair of mounting holes 48a, 48b, one mounting hole 48a is a through hole, and the other mounting hole 48b is a screw hole. With the clamp 32 fixed to the fitting cylinder portion 35 of the shaft body 31, the engagement grooves 41 are located at positions facing the openings of the pair of mounting holes 48a, 48b, respectively. In other words, the axial positions of the pair of mounting holes 48a, 48b and the engagement groove 41 are aligned. The plate thicknesses (thickness dimensions) of the pair of flange portions 45 are approximately the same as each other.

[0066] The connecting portion 46 is configured in a semi-cylindrical shape. The connecting portion 46 has a notch 49 on the other axial side portion, which is recessed toward one axial side from the end face on the other axial side of the flange portion 45. The notch 49 extends in the circumferential direction of the connecting portion 46 and is aligned with the central axis O of the shaft body 31. 31 (=Center axis O of insertion hole 47 47 ) and the central axis O of the mounting holes 48a, 48b 48 The notch 49 has a substantially triangular shape when viewed from the axial direction of the mounting holes 48a, 48b, as shown in FIG. 14B. Therefore, the axial width L 49 increases in the circumferential direction of the connecting portion 46 away from the flange portion 45 (toward the upper side in FIG. 14B), and is the largest at the portion located on the opposite side of the discontinuous portion 44 in the diametric direction of the clamp 32 (the upper end portion in FIG. 14B). In other words, the axial width L of the notch 49 49 is smallest at both circumferential end portions of the connecting portion 46 and is largest at the circumferential center portion of the connecting portion 46.

[0067] The edge of the notch 49 on one axial side is aligned with the central axis O of the mounting holes 48a, 48b. 48 The other axial end edge of the notch 49 is located on the other axial side of the center axis O of the mounting holes 48a, 48b. 48 and the central axis O of the shaft body 31 31 14B) respectively perpendicular to the central axis O of the shaft body 31. 31 14B)。 On the other hand, the mounting holes 48a and 48b are located slightly closer to the mounting holes 48a and 48b (on the lower side in FIG. 14B).

[0068] The connecting portion 46 has the same axial width as the flange portions 45 at both circumferential end portions connected to the pair of flange portions 45, but the axial width becomes smaller the further away from the flange portions 45 in the circumferential direction. The axial width of the connecting portion 46 is about 3 / 5 of the axial width of the flange portions 45 at the circumferential center portion located opposite the discontinuous portion 44 in the diameter direction of the clamp 32.

[0069] For this reason, the shape of the connecting portion 46 when viewed from the axial direction of the mounting holes 48a, 48b is trapezoidal as if the shoulder (corner) on the other axial side has been cut off at an angle. As a result, the end face on the other axial side of the connecting portion 46 (the boundary position in the axial direction between the connecting portion 46 and the notch 49) is linearly inclined in a direction toward one axial side as it moves away from the flange portion 45 in the circumferential direction of the connecting portion 46. In other words, the end face on the other axial side of the connecting portion 46 is inclined relative to the central axis O of the insertion hole 47, like the end face on one axial side of the connecting portion 46. 47 , and does not exist on a virtual plane perpendicular to the central axis O of the insertion hole 47. 47 In this embodiment, the portion of the other axial side of the fitting cylindrical portion 35 that is located on the opposite side of the slit 42 in the diametric direction is not covered by the connecting portion 46 of the clamp 32 and is exposed to the outside through the cutout 49.

[0070] In this example, the shaft body 31 and the clamp 32 are fixed together. The structure for fixing the shaft body 31 and the clamp 32 together is not particularly limited, but for example, a structure for fixing the shaft body 31 and the clamp 32 by welding can be adopted. In this case, a configuration for spot welding can be adopted between the opening edge on one axial side of the insertion hole 47 of the clamp 32 and the outer circumferential surface of the shaft body 31. Alternatively, a structure for plastically deforming (crimping) the shaft side engaging portion or the clamp side engaging portion can be adopted, in which a convex (or concave) shaft side engaging portion (not shown) formed on the outer circumferential surface of the shaft body 31 and a concave (or convex) clamp side engaging portion (not shown) formed on the inner circumferential surface of the clamp 32 are engaged with each other. In any case, in a state in which the shaft body 31 and the clamp 32 are fixed together, the relative rotation between the shaft body 31 and the clamp 32 is prevented, and the relative displacement in the axial direction is prevented.

[0071] To couple and fix the shaft body 31 and the clamp 32, first, the other axial end of the shaft body 31 is inserted into the inside of the insertion hole 47 of the clamp 32 from one axial side of the clamp 32. Then, the circumferential positions of the discontinuous portion 44 of the clamp 32 and the slit 42 of the shaft body 31 are aligned, and the axial positions of the pair of mounting holes 48a, 48b and the engagement groove 41 are aligned.

[0072] Next, a fastening bolt 50 (see FIG. 9), which corresponds to a fastening member, is placed inside the pair of mounting holes 48a, 48b and the engaging groove 41. Specifically, the portion of the fastening bolt 50 near the base end is inserted inside one mounting hole 48a, which is a through hole, and the middle portion of the fastening bolt 50 is placed inside the engaging groove 41. In this state, the tip end of the fastening bolt 50 is slightly screwed into the other mounting hole 48b, which is a screw hole, that is, to the extent that the diameter of the fitting cylinder portion 35 is not reduced. Then, the engaging groove 41 and the fastening bolt 50, both ends of which are supported by the clamp 32, are key-engaged. This prevents the clamp 32 from slipping out of the shaft body 31 to the other axial direction, and prevents the shaft body 31 and the clamp 32 from rotating relative to each other. Finally, the shaft body 31 and the clamp 32 are joined and fixed by a fixing means such as welding.

[0073] Telescopic shaft The telescopic shaft 10a corresponds to the second torque transmission shaft, and has a configuration in which the entire length can be extended and retracted even in a steady state in which the automobile is not in a collision accident. The telescopic shaft 10a includes a second outer cylinder 15a, a second inner shaft 16a, a plurality of balls 19a, a plurality of rollers 20a, and a plurality of leaf springs 51.

[0074] In the intermediate shaft 5b of this example, the second outer cylinder 15a is disposed on one axial side of the telescopic shaft 10a, closer to the contraction shaft 9a, and the second inner shaft 16a is disposed on the other axial side of the telescopic shaft 10a, farther from the contraction shaft 9a. Therefore, in this example, the second outer cylinder 15a corresponds to the second connecting shaft described in the claims.

[0075] Second External Cylinder The second outer tube 15a is, for example, a cold forged product, and as shown in Fig. 4, is integrally provided with a solid (approximately cylindrical) male shaft portion 52 disposed at one end in the axial direction, and a bottomed cylindrical female tube portion 53 disposed adjacent to the other axial side of the male shaft portion 52. The male shaft portion 52 and the female tube portion 53 are disposed coaxially. The outer diameter of the male shaft portion 52 is smaller than the outer diameter of the female tube portion 53, and the axial length of the male shaft portion 52 is sufficiently shorter than the axial length of the female tube portion 53.

[0076] The male shaft portion 52 is a portion that connects to the first outer tube 12a that constitutes the contraction shaft 9a, and has male serrations 54, which correspond to the second male engaging portion described in the claims, at the axially middle portion of the outer circumferential surface. A circumferential groove 55 is provided at one location on the outer circumferential surface of the male shaft portion 52, which is formed to cross the male serrations 54 in the circumferential direction.

[0077] The female cylindrical portion 53 is a portion into which the second inner shaft 16a is slidably inserted. The female cylindrical portion 53 has, on its inner peripheral surface, first female grooves 56 and second female grooves 57, each of which extends in the axial direction, alternately arranged in the circumferential direction. Each of the first female grooves 56 and the second female grooves 57 has a cross-sectional shape that is a concave arc shape.

[0078] 《Second inner shaft》 The second inner shaft 16a is solid over its entire length. The second inner shaft 16a has first male grooves 58 and second male grooves 59, each of which extends in the axial direction, alternately arranged in the circumferential direction on the outer circumferential surface of one axial side portion. The first male groove 58 has a substantially isosceles trapezoidal cross section, and the circumferential width of the opening is wider than the circumferential width of the bottom portion. In contrast, the second male groove 59 has a concave arc cross section. A circular stopper 60 is engaged on the outer circumferential surface of the end portion on one axial side of the second inner shaft 16a. This prevents the balls 19a arranged inside the first male groove 58 and the rollers 20a arranged inside the second male groove 59 from slipping out of the first male groove 58 and the second male groove 59 to one axial side. A yoke 61 separate from the second inner shaft 16a is fixed by welding to the end portion on the other axial side of the second inner shaft 16a. The yoke 61, together with another yoke 62 connected to the front end of the steering shaft 2a and a cross shaft (not shown), constitutes a universal joint 4c.

[0079] When the second inner shaft 16a is inserted into the second outer cylinder 15a, the circumferential phases of the first male groove 58 and the first female groove 56 are aligned, and the circumferential phases of the second male groove 59 and the second female groove 57 are aligned. Then, a plurality of balls 19a are disposed between the first male groove 58 and the first female groove 56. Furthermore, a leaf spring 51 is disposed between the first male groove 58 and the plurality of balls 19a, and a preload is applied to the plurality of balls 19a. Furthermore, one roller 20a is disposed between each of the second male groove 59 and the second female groove 57.

[0080] In the telescopic shaft 10a as described above, the second inner shaft 16a and the second outer cylinder 15a are combined so as to be able to transmit torque and to be able to extend and retract the entire length in a steady state. In addition, in the telescopic shaft 10a, when transmitting low torque, the plurality of balls 19a and the leaf spring 51 transmit the torque between the second inner shaft 16a and the second outer cylinder 15a, and when the transmitted torque increases, the plurality of rollers 20a transmit the increased torque. In addition, when the second inner shaft 16a and the second outer cylinder 15a are relatively displaced in the axial direction, the plurality of balls 19a roll between the first male groove 58 and the first female groove 56, and the plurality of rollers 20a slide between the second male groove 59 and the second female groove 57. In addition, the plurality of balls 19a are pressed against the inner surface of the first female groove 56 by the elasticity of the leaf spring 51, so that rattling between the second inner shaft 16a and the second outer cylinder 15a is prevented.

[0081] As shown in FIG. 3, when the contraction shaft 9a and the telescopic shaft 10a are axially connected, the male shaft portion 52 of the second outer tube 15a constituting the telescopic shaft 10a is inserted into the inside of the fitting tubular portion 35 of the first outer tube 12a constituting the contraction shaft 9a. Then, the male serrations 54 on the outer peripheral surface of the male shaft portion 52 are serrated-engaged with the female serrations 40 on the inner peripheral surface of the fitting tubular portion 35 so as to be torque-transmittable. This prevents relative rotation between the first outer tube 12a and the second outer tube 15a. In addition, the middle portion of the tightening bolt 50 is inserted into the inside of the circumferential groove 55 on the outer peripheral surface of the male shaft portion 52 through the wide portion 43 which is the intersection of the engagement groove 41 and the slit 42, and the circumferential groove 55 and the tightening bolt 50 are key-engaged. This prevents the first outer tube 12a and the second outer tube 15a from moving relative to each other in the axial direction. Furthermore, by increasing the amount of engagement of the tightening bolt 50 with the other mounting hole 48b of the clamp 32, the width dimension of the discontinuous portion 44 is reduced, and the diameter of the fitting tubular portion 35 of the shaft body 31 is reduced. Then, the inner peripheral surface of the fitting tubular portion 35 tightly fastens the outer peripheral surface of the male shaft portion 52. This connects the contracting shaft 9a and the telescopic shaft 10a in a manner that allows torque transmission.

[0082] In the steering device of this embodiment, in a steady state, the second outer cylinder 15a and the second inner shaft 16a constituting the telescopic shaft 10a are displaced relative to each other in the axial direction, so that the intermediate shaft 5b is telescopic. This absorbs vibrations input to the tires during driving. In addition, in the event of a so-called full-wrap collision in which the entire front of the vehicle body collides with another vehicle, the telescopic shaft 9a and the telescopic shaft 10a are both telescopic. This absorbs the impact of the collision and prevents the steering wheel 1a from being pushed up toward the driver.

[0083] According to the intermediate shaft 5b of this embodiment as described above, whirling can be suppressed. That is, in this example, the first outer cylinder 12a constituting the contraction shaft 9a is composed of a shaft body 31 and a clamp 32 separate from the shaft body 31. Only the shaft body 31 is provided with a female spline 36 for torque-transmitting engagement with the first inner shaft 11a and a female serration 40 for torque-transmitting engagement with the second outer cylinder 15a constituting the telescopic shaft 10a. This ensures high concentricity between the female spline 36 and the female serration 40 provided on the inner circumferential surface of the shaft body 31. This makes it possible to suppress whirling between the first inner shaft 11a connected via the female spline 36 and the second outer cylinder 15a connected via the female serration 40. As a result, even in the intermediate shaft 5b of this example, which has a long overall length, whirling can be sufficiently suppressed.

[0084] In addition, the axial dimension of the female spline 36 provided on the inner peripheral surface of the shaft body 31 constituting the first external cylinder 12a is made sufficiently larger than the axial dimension of the male spline 28 provided on the outer peripheral surface of the rod-shaped portion 26 constituting the first inner shaft 11a. In a steady state, only one axial side portion of the female spline 36 is spline-engaged with the male spline 28. Therefore, in the event of a collision accident, the male spline 28 can be spline-engaged with the other axial side portion of the female spline 36 to contract the contractible shaft 9a. In addition, when the contractible shaft 9a is in a contracted state, it is possible to prevent a situation in which torque transmission between the first inner shaft 11a and the first external cylinder 12a becomes impossible and the operation of the steering wheel 1a becomes unable to be transmitted to the steered wheels. In a completely contracted state of the contractible shaft 9a, the male spline 28 The other axial end of the large-diameter cylindrical portion 34 (relief portion 80) is disposed inside the large-diameter cylindrical portion 34.

[0085] In addition, the other axial side portion of the male spline 28 is provided on the outer peripheral surface of a portion of the rod-shaped portion 26 that is thinned by forming the center hole 29. This makes it possible to reduce the radial rigidity of the portion where the other axial side portion of the male spline 28 is provided, compared to a structure that does not have the center hole 29. This makes it possible to make the spline fitting portion between the male spline 28 and the female spline 36 less sensitive to fluctuations in sliding resistance relative to interference. As a result, the relative displacement in the axial direction between the first inner shaft 11a and the first external cylinder 12a can be stably and smoothly performed.

[0086] In addition, the fuse portion 30 provided on the rod-shaped portion 26 is exposed from the first outer tube 12a in a steady state, and is configured to have a smaller diameter than the adjacent portions of the rod-shaped portion 26 on both axial sides. Therefore, when a so-called offset collision occurs in which a part of the front of the vehicle body collides with another vehicle, the fuse portion 30 can be bent or twisted based on the impact load associated with the collision. Therefore, the impact of the collision can be effectively absorbed. In addition, the deformation of the fuse portion 30 causes a shift in the steering position, and the driver can be notified that the intermediate shaft 5b has been damaged.

[0087] In addition, the first outer tube 12a can suppress precession of the male shaft portion 52 of the second outer tube 15a connected to the other axial end of the shaft body 31, thereby suppressing fretting wear at the serration engagement portion between the female serrations 40 of the shaft body 31 and the male serrations 54 of the male shaft portion 52. That is, the slit 42 provided in the shaft body 31 has a closed end at one axial end and an open end at the other axial end, so that the rigidity of the fitting tubular portion 35 into which the clamp 32 is fitted is higher at the one axial end portion near the closed end of the slit 42 than at the other axial end portion near the open end of the slit 42. For this reason, unlike the structure of this example, when the fitting tubular portion 35 is reduced in diameter using a clamp that does not have a notch at the connecting portion, the fitting tubular portion 35 tends to deform more at the other axial end portion than at the one axial end portion. Therefore, the surface pressure between the inner peripheral surface of the fitting tubular portion 35 and the outer peripheral surface of the male shaft portion 52 is higher at the other axial end portion than at the one axial end portion. In other words, the male shaft portion 52 is tightly clamped at the other axial end portion of the fitting tubular portion 35, and is relatively loosely clamped at the portion located on the one axial side of the fitting tubular portion 35. For this reason, the male shaft portion 52 is more likely to precess around the portion tightly clamped by the other axial end portion of the fitting tubular portion 35. When such precession occurs, fretting wear occurs at the serration engagement portion between the female serrations 40 and the male serrations 54, and the amount of wear tends to become excessive.

[0088] In contrast, in this example, the notch 49 is provided in the other axial side portion of the connecting portion 46 constituting the clamp 32, and the other axial side portion of the fitting tubular portion 35, which has low rigidity, is not covered by the connecting portion 46. Therefore, when the fitting tubular portion 35 is reduced in diameter by the clamp 32, a larger tightening force can be applied to the one axial side portion of the fitting tubular portion 35, which has high rigidity, compared to the other axial side portion, which has low rigidity. Therefore, the deformation amount generated in the fitting tubular portion 35 can be made closer to each other in the one axial side portion and the other axial side portion. Therefore, the surface pressure between the inner peripheral surface of the fitting tubular portion 35 and the outer peripheral surface of the male shaft portion 52 can also be made closer to each other in the one axial side portion and the other axial side portion. As a result, the precession of the male shaft portion 52 connected to the end portion on the other axial side of the shaft body 31 can be suppressed. Therefore, the fretting wear can be suppressed from occurring in the serration engagement portion between the female serrations 40 and the male serrations 54. This can prevent rattling from occurring between the first outer cylinder 12a and the second outer cylinder 15a, and can also prevent abnormal noise caused by the rattling from occurring.

[0089] Also, because the notch 49 is positioned on the other axial side of the central axis of the mounting holes 48a, 48b, when the fitting tubular portion 35 is reduced in diameter by the clamp 32, a large tightening force can be applied by the connecting portion 46 to the one axial side portion of the fitting tubular portion 35, which has high rigidity. This makes it possible to effectively increase the surface pressure between the inner peripheral surface of the one axial side portion of the fitting tubular portion 35 and the outer peripheral surface of the male shaft portion 52. Furthermore, the edge portion on the other axial side of the notch 49 is positioned on the central axis O of the mounting holes 48a, 48b. 48 and the central axis O of the shaft body 31 31 14B) respectively perpendicular to the central axis O of the shaft body 31. 31The slits 42 are positioned slightly closer to the mounting holes 48a and 48b than the slits 42 (the lower side in FIG. 14B). Therefore, the semicircular arc-shaped portion of the other axial end edge of the shaft body 31, which is located on the opposite side of the slits 42 in the diametric direction, is exposed to the outside and is not covered by the connecting portion 46. Therefore, when the fitting tube portion 35 is reduced in diameter by the clamp 32, the tightening force applied to the other axial end edge of the shaft body 31 can be sufficiently reduced. Therefore, the precession of the male shaft portion 52 connected to the end portion of the other axial end of the shaft body 31 can be more effectively prevented. In addition, the notch 49 is formed only in the connecting portion 46 and not in the flange portion 45, so that the fitting length of the clamp 32 relative to the shaft body 31 in the axial direction can be secured. Therefore, the attitude of the clamp 32 relative to the shaft body 31 can be stabilized.

[0090] [Second Example of the Implementation Form] The second embodiment will be described with reference to Figures 15 to 17. In this embodiment, components similar to those in the first embodiment are given the same reference numerals as in the first embodiment, and detailed descriptions thereof will be omitted.

[0091] This example is a modified example of the first embodiment, in which the contraction shaft 9a used as a collapsible shaft in the first embodiment is partially modified in structure to be used as an extension shaft 10b that is capable of sliding at all times.

[0092] The intermediate shaft 5c in this example is configured by connecting in the axial direction a contractible shaft 9b having a double tube structure corresponding to the first torque transmission shaft and a telescopic shaft 10b having a double tube structure corresponding to the second torque transmission shaft. In this example, one axial side corresponds to the rear side of the vehicle body, and the other axial side corresponds to the front side of the vehicle body. Therefore, the intermediate shaft 5c has the contractible shaft 9b on the other axial side, which is the engine room side, and has the telescopic shaft 10b on one axial side, which is the driver's seat side.

[0093] Contraction shaft The collapsible shaft 9b corresponds to the first torque transmission shaft, and is a collapsible shaft having a first inner shaft 11b and a first outer cylinder 12b, and is configured so that its entire length can be collapsed only when an automobile crash occurs and an impact load of a predetermined value or more is applied in the axial direction. For this purpose, the first inner shaft 11b and the first outer cylinder 12b are coupled to each other so as to be capable of transmitting torque and to be capable of relative displacement in the axial direction during a primary collision. As a specific coupling structure between the first inner shaft 11b and the first outer cylinder 12b, a structure similar to that of the first embodiment, such as a combination of spline engagement and press-fitting, or various conventionally known structures can be adopted, and therefore detailed explanations will be omitted.

[0094] In the intermediate shaft 5c of this example, similar to the structure of the first example of the embodiment, the first inner shaft 11b is disposed on the other axial side of the contraction shaft 9b, farther from the telescopic shaft 10b, and the first outer tube 12b is disposed on one axial side of the contraction shaft 9b, closer to the telescopic shaft 10b. Therefore, in this example, the first outer tube 12b corresponds to the first connecting shaft described in the claims. The first outer tube 12b has a male shaft portion 52a with male serrations 54a on the outer circumferential surface at one end in the axial direction.

[0095] Telescopic shaft The telescopic shaft 10b corresponds to the second torque transmission shaft, and has a configuration in which its entire length can be extended and retracted even in a steady state in which the automobile is not in a collision accident. The telescopic shaft 10b is a partially modified version of the contractible shaft 9a used as the collapsible shaft in the first embodiment, and includes a second outer cylinder 15b and a second inner shaft 16b.

[0096] In the intermediate shaft 5c of this example, the second outer tube 15b is disposed on the other axial side of the telescopic shaft 10b, closer to the contraction shaft 9b, and the second inner shaft 16b is disposed on one axial side of the telescopic shaft 10b, farther from the contraction shaft 9b. Therefore, in this example, the second outer tube 15b corresponds to the second connecting shaft described in the claims. Also, the second outer tube 15b corresponds to one of the shafts described in the claims.

[0097] The second inner shaft 16b has a similar structure to the first inner shaft 11a constituting the contraction shaft 9a according to the first embodiment, except that a synthetic resin coating layer 63 is provided on the surface of the male spline 28a and that the arrangement direction in the axial direction is opposite. The second outer cylinder 15b has a similar structure to the first outer cylinder 12a constituting the contraction shaft 9a according to the first embodiment, except that the arrangement direction in the axial direction is opposite. The coating layer 63 can be made of, for example, polyamide resin.

[0098] In the assembled state of the telescopic shaft 10b, the male splines 28a constituting the second inner shaft 16b are spline-engaged with the female splines 36 (see FIG. 6, etc.) provided on the inner peripheral surface of the second outer cylinder 15b via the coating layer 63 so as to be torque-transmittable and axially slidable. With this configuration, the telescopic shaft 10b is configured so that its entire length can be telescopically extended or retracted in a steady state.

[0099] In this example, the male serrations 54a on the male shaft portion 52a of the first outer tube 12b are engaged with the female serrations 40 (see FIG. 9, etc.) on the inner peripheral surface of the other axial end of the shaft body 31 constituting the second outer tube 15b in a torque-transmitting manner. In addition, the clamp 32 constituting the second outer tube 15b reduces the diameter of the fitting tube portion 35 on the other axial end of the shaft body 31. As a result, the inner peripheral surface of the fitting tube portion 35 tightens the outer peripheral surface of the male shaft portion 52a. With this configuration, the contracting shaft 9b and the telescopic shaft 10b are axially connected.

[0100] In this example having the above configuration, the male spline 28a constituting the second inner shaft 16b is caused to slide in the axial direction relative to the female spline 36 provided on the inner peripheral surface of the second outer cylinder 15b, thereby enabling the telescopic shaft 10b to extend and retract. In addition, since the surface of the male spline 28a is covered with a synthetic resin coating layer 63, the sliding resistance when the telescopic shaft 10b extends and retracts can be kept low. The other configurations and effects are the same as those of the first embodiment.

[0101] When implementing the present invention, the connection structure between the shaft body and the clamp can be modified as appropriate, for example as described below.

[0102] [Third Example of the Implementation Form] The third example of the embodiment will be described with reference to Fig. 18. In this example, components similar to those in the first example of the embodiment are given the same reference numerals as those in the first example of the embodiment, and detailed descriptions thereof will be omitted.

[0103] In this example, the end portion on the other axial direction side of the outer circumferential surface of the shaft body 31 is cut to form a substantially annular (C-shaped) step surface 64 facing the other axial direction side on a portion of the outer circumferential surface of the shaft body 31 adjacent to one axial direction side of the fitting cylindrical portion 35a. Also, no notch is formed in the connecting portion 46a of the clamp 32a, and the axial width of the connecting portion 46a is constant in the circumferential direction.

[0104] In the above example, when the clamp 32a is fitted onto the fitting cylindrical portion 35a, the end face on one axial side of the clamp 32a is abutted against the step surface 64, thereby enabling the clamp 32a to be positioned axially relative to the shaft body 31. The other configurations and effects are the same as those of the first embodiment.

[0105] [Fourth Example of the Implementation Form] A fourth example of the embodiment will be described with reference to Fig. 19. In this example, components similar to those in the first example of the embodiment are given the same reference numerals as those in the first example of the embodiment, and detailed descriptions thereof will be omitted.

[0106] In this example, a weld 65 is formed by spot welding at one circumferential location on the opposite side of the slit 42 in the diameter direction of the shaft body 31 in the portion between the opening edge on one axial side of the insertion hole 47 of the clamp 32a (the radially inner edge of the end face on one axial side of the connecting portion 46a) and the outer circumferential surface of the shaft body 31, and the shaft body 31 and the clamp 32a are welded and fixed together.

[0107] In the above-described example, the welded portion 65 is formed on the diametrically opposite side of the shaft body 31 from the slit 42, thereby preventing the provision of the welded portion 65 from affecting the amount of deflection of the pair of flange portions 45 during clamping (causing the amount of deflection to become unbalanced). The other configurations and effects are the same as those of the first embodiment.

[0108] [Fifth Example of the Implementation Form] A fifth example of the embodiment will be described with reference to Figures 20 and 21. In this example, components similar to those in the first example of the embodiment are given the same reference numerals as those in the first example of the embodiment, and detailed descriptions thereof will be omitted.

[0109] In this example, in order to prevent the clamp 32b from rotating relative to the shaft body 31a before the clamp 32b is fixed to the other axial end of the shaft body 31a, the outer peripheral surface of the shaft body 31a and the inner peripheral surface of the insertion hole 47a of the clamp 32b are fitted together in a non-circular manner to prevent relative rotation.

[0110] The shaft body 31a has a flat shaft-side flat portion 66 on the outer circumferential surface of the other axial end portion, on the portion opposite the slit 42 in the diametric direction of the shaft body 31a. Therefore, the contour shape of the outer circumferential surface of the fitting cylindrical portion 35a is substantially D-shaped and made up of an arc portion and a straight portion. The clamp 32b has a flat clamp-side flat portion 67 on the inner circumferential surface of the insertion hole 47a, on the portion opposite the discontinuous portion 44 in the diametric direction of the insertion hole 47a. Therefore, the contour shape of the inner circumferential surface of the insertion hole 47a of the clamp 32b is also substantially D-shaped and made up of an arc portion and a straight portion.

[0111] In this example, when the other axial end of the shaft body 31a is inserted into the inside of the insertion hole 47a of the clamp 32b, the flat shaft-side flat portion 66 comes into surface contact with the flat clamp-side flat portion 67. This allows a non-circular fit between the outer circumferential surface of the shaft body 31a and the inner circumferential surface of the insertion hole 47a of the clamp 32b, preventing relative rotation between the shaft body 31a and the clamp 32b. The other configurations and effects are the same as those of the first embodiment.

[0112] [Sixth Example of the Embodiment] The sixth example of the embodiment will be described with reference to Figures 22 to 24. In this example, components similar to those in the first example of the embodiment are given the same reference numerals as in the first example of the embodiment, and detailed descriptions thereof will be omitted.

[0113] In this example, a shaft-side engaging portion 68, which is a convex strip extending in the axial direction, is provided on the outer peripheral surface of the shaft body 31b in a range from the axial middle portion to the other end portion. The shaft-side engaging portion 68 is provided on the outer peripheral surface of the shaft body 31b on the opposite side to the slit 42 in the diametric direction of the shaft body 31b. The shaft-side engaging portion 68 has a semicircular cross section, and the height and width from the central axis of the shaft body 31b to the top are constant over the entire length.

[0114] In contrast, the inner peripheral surface of the insertion hole 47b of the clamp 32c is provided with a clamp-side engagement portion 69, which is a concave groove extending in the axial direction and can be engaged with the shaft-side engagement portion 68. The clamp-side engagement portion 69 is provided on the inner peripheral surface of the insertion hole 47b on the opposite side to the discontinuous portion 44 in the diametric direction of the insertion hole 47b. The clamp-side engagement portion 69 is provided across the entire axial width of the insertion hole 47b and opens on each of the end faces on both axial sides of the clamp 32c. The clamp-side engagement portion 69 has a semicircular cross section and has a constant depth and width over its entire length.

[0115] In this example, the shaft body 31b is inserted into the insertion hole 47b of the clamp 32c from the other axial side, so that the shaft side engaging portion 68 enters into the clamp side engaging portion 69. The shaft side engaging portion 68 and the clamp side engaging portion 69 are engaged with each other in a concave-convex manner to prevent the shaft body 31b and the clamp 32c from rotating relative to each other. Furthermore, the shaft side engaging portion 68 is deformed by crimping (for example, plastically deformed so as to rise toward the axial end face side of the clamp 32c) to form a crimped deformation portion 70 in the portion. This prevents the shaft body 31b and the clamp 32c from displacing relative to each other in the axial direction. In this example, the shaft side engaging portion 68 and the clamp side engaging portion 69 are used to fix the clamp 32c to the fitting tube portion 35 of the shaft body 31b. Therefore, the work of welding and fixing the shaft body 31b and the clamp 32c can be omitted. Although not shown in the drawings, the shaft side engaging portion may be a concave groove extending in the axial direction, and the clamp side engaging portion may be a convex ridge extending in the axial direction. The other configurations and effects are the same as those of the first embodiment.

[0116] [Seventh Example of the Implementation Form] The seventh example of the embodiment will be described with reference to Figures 25 and 26. In this example, components similar to those in the first example of the embodiment are given the same reference numerals as those in the first example of the embodiment, and detailed descriptions thereof will be omitted.

[0117] In this example, a wide portion 71 having a width dimension larger (for example, about three to six times larger) than a portion adjacent to one axial side is provided in the other axial half of the slit 42a, which is aligned with the fitting cylinder portion 35b in the axial direction. Therefore, the fitting cylinder portion 35b has a substantially C-shaped shape when viewed from the axial direction, and flat shaft side engagement surface portions 72 are provided on both circumferential end faces on both sides of the wide portion 71. In this example, the pair of shaft side engagement surface portions 72 are located on the same imaginary plane parallel to the central axis of the shaft main body 31c. Such a pair of shaft side engagement surface portions 72 are simultaneously formed by cutting.

[0118] Meanwhile, the contour shape of the inner peripheral surface of insertion hole 47c of clamp 32d is substantially D-shaped with an arc portion and a pair of straight portions. Of the inner peripheral surface of insertion hole 47c, portions (straight portions) formed by the radially inner surfaces of the pair of flange portions 45 are each formed as clamp-side engagement surface portions 73 having a flat surface shape.

[0119] In this example, the end of the shaft body 31c on the other axial side is inserted into the insertion hole 47c of the clamp 32d, and the clamp 32d is fitted to the fitting cylinder 35b. The pair of shaft side engagement surface portions 72 and the pair of clamp side engagement surface portions 73 are engaged (contacted) in the circumferential direction, thereby preventing the shaft body 31c and the clamp 32d from rotating relative to each other. In addition, the end face on the other axial side of the shaft body 31c is deformed by crimping at a plurality of locations (three locations in the illustrated example) in the circumferential direction to form crimped deformation portions 70a as plastic deformation portions in the corresponding portions. These crimped deformation portions 70a are then pressed against the end face on the other axial side of the clamp 32d. This prevents the shaft body 31c and the clamp 32d from displacing relative to each other in the axial direction. Therefore, in this example as well, the work of welding and fixing the shaft body 31c and the clamp 32d can be omitted. The other configurations and effects are the same as those of the first embodiment.

[0120] [Eighth Example of the Implementation Form] An eighth example of the embodiment will be described with reference to Figures 27 and 28. In this example, components similar to those in the first example of the embodiment are given the same reference numerals as those in the first example of the embodiment, and detailed descriptions thereof will be omitted.

[0121] This example is a modification of the seventh example of the embodiment, and a locking groove 74 is formed around the entire outer circumferential surface of the shaft body 31c on one axial side of the fitting cylindrical portion 35b. The locking groove 74 has a rectangular cross section and a constant depth over its entire length.

[0122] On the other hand, the clamp 32e has a locking slit 75 on one axial side thereof facing the locking groove 74 formed in the shaft body 31c. The locking slit 75 is formed by moving a cutting tool (not shown) in a direction perpendicular to the central axis of the clamp 32e over a range from the top of the connecting portion 46a (lower end portion in FIG. 28) constituting the clamp 32e to the radial middle portion of the pair of flange portions 45 (up-down middle portion in FIG. 28), and communicates the inner and outer surfaces of the clamp 32e (the inner and outer peripheral surfaces of the connecting portion 46a and the inner and outer side surfaces in the width direction of the flange portions 45). The width of the locking slit 75 is the same as the width of the locking groove 74, and is slightly larger than the thickness of a retaining ring 76 described later.

[0123] In this example, the other axial end of the shaft body 31c is inserted into the insertion hole 47c (see FIG. 26) of the clamp 32e, and the clamp 32e is fitted to the fitting cylinder 35b. The pair of shaft side engagement surface portions 72 and the pair of clamp side engagement surface portions 73 (see FIG. 26) are engaged (contacted) in the circumferential direction to prevent the shaft body 31c and the clamp 32e from rotating relative to each other. That is, the pair of shaft side engagement surface portions 72 and the pair of clamp side engagement surface portions 73 are engaged in the circumferential direction to form a rotation prevention portion that prevents the shaft body 31c and the clamp 32e from rotating relative to each other. Furthermore, a stop ring 76, which is an engagement member, is provided so as to span the engagement groove 74 and the engagement slit 75.

[0124] The retaining ring 76 is an E-ring in the illustrated example, and is formed into a segmented annular shape having an opening at one location in the circumferential direction by performing a press punching process on a metal plate made of an elastic material such as spring steel or stainless spring steel. The thickness dimension of the retaining ring 76 is slightly smaller than the width dimensions of the locking groove 74 and the locking slit 75. Such a retaining ring 76 is elastically attached (fitted) to the locking groove 74 by locking the inner diameter side portion to the locking groove 74. The portion of the retaining ring 76 that protrudes radially outward from the locking groove 74 (the radial intermediate portion) is disposed inside the locking slit 75 and engaged with the clamp 32e in the axial direction. This prevents the shaft body 31c and the clamp 32e from being displaced relative to each other in the axial direction. Therefore, in this example, the crimped deformation portion as shown in the seventh example of the embodiment can be omitted. The other configurations and effects are the same as those of the first and seventh embodiments.

[0125] [Ninth Example of the Implementation Form] A ninth example of an embodiment will be described with reference to Fig. 29. In this example, components similar to those in the first example of an embodiment are given the same reference numerals as those in the first example of an embodiment, and detailed descriptions thereof will be omitted.

[0126] In this example, only the shape of the clamp 32f that fits onto the fitting tubular portion 35 (see FIG. 11, etc.) of the shaft body 31 is different from the structure of the first example of the embodiment. That is, a notch 49a that is substantially rectangular in shape as viewed from the axial direction of the mounting hole 48a (48b) is formed in the other axial side portion (half portion) of the connecting portion 46b that constitutes the clamp 32f. The axial width L of the notch 49a is constant in the circumferential direction of the connecting portion 46b. Therefore, the connecting portion 46b in which the notch 49a is formed has a substantially rectangular shape as viewed from the axial direction of the mounting hole 48a (48b) with the other axial side half portion cut off. The end face on the other axial side of the connecting portion 46b (the boundary position in the axial direction between the connecting portion 46b and the notch 49a) is parallel to the end face on one axial side of the connecting portion 46b and is aligned with the central axis O of the insertion hole 47. 47 It exists on a virtual plane perpendicular to the

[0127] The notch 49a is aligned with the central axis O of the mounting hole 48a (48b). 48 29. Specifically, the edge of the notch 49a on one axial side is at approximately the same axial position as the edges of the mounting holes 48a, 48b on the other axial side. Also, the end of the notch 49a in the circumferential direction of the connecting portion 46b is disposed parallel to the central axis of the shaft body 31 (see FIG. 12, etc.) and is aligned with the central axis O of the mounting hole 48a (48b). 48 and the central axis O of the shaft body 31 31 29 ) respectively perpendicular to the central axis O of the shaft body 31. 31 29. Upper In this example, the portion of the other axial side portion of the fitting cylindrical portion 35 (see FIG. 12, etc.) that is located on the opposite side of the slit 42 (see FIG. 11, etc.) in the diameter direction is exposed to the outside through the notch 49a over a wider range than in the first example of the embodiment.

[0128] In the present example as described above, the formation range of the cutout 49a is made larger than in the first example of the embodiment, so that the fastening force acting from the clamp 32f on the other axial side portion of the fitting tubular portion 35, which has lower rigidity, can be made smaller. The other configurations and effects are the same as those of the first embodiment.

[0129] [Tenth Example of the Implementation Form] A tenth example of the embodiment will be described with reference to Figures 30 to 32. In this example, components similar to those in the first example of the embodiment are given the same reference numerals as in the first example of the embodiment, and detailed descriptions thereof will be omitted.

[0130] In this example, the inner peripheral surface of the end of the insertion hole 47d of the clamp 32g on the other axial side has an annular groove 77 that is larger in inner diameter than the portion adjacent to the one axial side, that is, recessed radially outward. Therefore, the inner peripheral surface of the insertion hole 47d has a stepped cylindrical surface. The annular groove 77 opens to the end edge of the other axial side of the clamp 32g and the discontinuous portion 44 (see FIG. 10, etc.). The annular groove 77 is formed over the entire circumference of the insertion hole 47d. The depth of the annular groove 77 is constant in the circumferential and axial directions. The axial dimension of the annular groove 77 is also constant in the circumferential direction, and is about 1 / 6 to 1 / 3 of the axial dimension of the clamp 32g (about 1 / 5 in the illustrated example). In addition, since the inner surface of the insertion hole 47d is formed by the inner surface of the connecting portion 46a and the radial inner surfaces of the pair of flange portions 45, a portion of the annular groove 77 is formed on the inner surfaces of the connecting portion 46a and the radial inner surfaces of the pair of flange portions 45.

[0131] As shown in FIG. 31, before the clamp 32g is fitted around the fitting tubular portion 35 and the fitting tubular portion 35 is reduced in diameter by the clamp 32g, the outer peripheral surface of the end portion to the middle portion of the fitting tubular portion 35 on one axial side and the inner peripheral surface of the end portion to the middle portion of the insertion hole 47d on one axial side are in contact over the entire circumference. In contrast, an annular gap 78 having a substantially rectangular cross section exists between the outer peripheral surface of the end portion on the other axial side of the fitting tubular portion 35 and the inner peripheral surface of the end portion on the other axial side of the insertion hole 47d (the bottom portion of the annular groove 77). Note that the depth of the annular groove 77 is exaggerated in FIG. 31. The actual depth of the annular groove 77 is set so that the radial dimension of the annular gap 78 is about several tens of μm to 500 μm before the clamp 32g is fitted around the fitting tubular portion 35 and the fitting tubular portion 35 is reduced in diameter.

[0132] In the above-described embodiment, when the fitting tubular portion 35 is reduced in diameter by the clamp 32g, the bottom of the annular groove 77 gradually comes into contact with the outer circumferential surface of the fitting tubular portion 35 from one axial side to the other axial side as the reduction progresses. Therefore, in the process of reducing the diameter of the fitting tubular portion 35 by the clamp 32g, the outer circumferential surface of the end portion or middle portion of the fitting tubular portion 35 on one axial side comes into contact with the inner circumferential surface of the end portion or middle portion of the insertion hole 47d on one axial side, and an annular gap 78 exists between the outer circumferential surface of the end portion on the other axial side of the fitting tubular portion 35 and the inner circumferential surface of the end portion on the other axial side of the insertion hole 47d. Finally, as shown in FIG. 32, (a part of) the annular gap 78 remains between the other axial side portion of the bottom of the annular groove 77 and the outer circumferential surface of the fitting tubular portion 35, or the entire bottom of the annular groove 77 comes into contact with the outer circumferential surface of the fitting tubular portion 35 (the annular gap 78 has completely disappeared).

[0133] In either case, the clamp 32g can apply a large clamping force to the one axial side portion of the fitting tubular portion 35, which has a high rigidity. The clamping force applied from the clamp 32g to the other axial side portion of the fitting tubular portion 35, which has a low rigidity, can be made smaller than that in the case where the annular groove 77 is not provided. Therefore, when the fitting tubular portion 35 is reduced in diameter by the clamp 32g, the amount of deformation occurring in the fitting tubular portion 35 can be made closer to each other in the one axial side portion and the other axial side portion. Therefore, the surface pressure between the inner peripheral surface of the fitting tubular portion 35 and the outer peripheral surface of the male shaft portion 52 can also be made closer to each other in the one axial side portion and the other axial side portion. As a result, the precession of the male shaft portion 52 connected to the end portion on the other axial side of the shaft main body 31 can be suppressed. Therefore, the fretting wear can be suppressed from occurring in the serration engagement portion between the female serration 40 and the male serration 54. This can prevent rattling from occurring between the shaft main body 31 and the male shaft portion 52, and can also prevent abnormal noise caused by rattling from occurring. The other configurations and effects are the same as those of the first embodiment.

[0134] [Eleventh Example of the Embodiment] An eleventh example of an embodiment will be described with reference to Fig. 33 and Fig. 34. In this example, components similar to those in the first example of an embodiment are given the same reference numerals as those in the first example of an embodiment, and detailed descriptions thereof will be omitted.

[0135] In this example, an auxiliary groove 79 is provided in a circumferential part of the outer circumferential surface of the fitting side inclined portion 39 of the large diameter cylindrical portion 34, which is offset from the fitting cylindrical portion 35 to one side in the axial direction, in the outer circumferential surface of the shaft main body 31d. The auxiliary groove 79 is arranged in parallel to the engagement groove 41, and the phase of the auxiliary groove 79 in the circumferential direction coincides with that of the engagement groove 41. Such an auxiliary groove 79 is formed so as to intersect with the axial middle portion (or the axial other side portion) of the slit 42. The intersection of the auxiliary groove 79 and the slit 42 also forms a wide portion 43a whose opening width is larger than that of the portions of the slit 42 adjacent to both axial sides of the intersection. Therefore, the slit 42 has wide portions 43, 43a whose openings are expanded in the circumferential direction at two positions, the axial other side portion intersecting with the engagement groove 41 and the axial middle portion intersecting with the auxiliary groove 79.

[0136] The auxiliary groove 79 is a broach groove formed by broaching, and is machined at the same time as the engagement groove 41. 31Two broaching tools (not shown) arranged in parallel to each other in a direction perpendicular to the shaft body 31d are simultaneously moved in the axial direction of the broaching tools (front-back direction in FIG. 33, up-down direction in FIG. 34) to form an engagement groove 41 on the outer circumferential surface of the fitting cylindrical portion 35 of the outer circumferential surface of the shaft body 31d, and an auxiliary groove 79 on the outer circumferential surface of the fitting-side inclined portion 39. The auxiliary groove 79 is configured in a partially cylindrical shape, and its radius of curvature is determined in relation to the rigidity of the other axial side portion of the shaft body 31d, but in the illustrated example, it is the same as the radius of curvature of the engagement groove 41. Note that in this example, the engagement groove 41 and the auxiliary groove 79 are machined simultaneously, but the engagement groove 41 and the auxiliary groove 79 may be machined in order. Even when the engagement groove 41 and the auxiliary groove 79 are machined in sequence, the engagement groove 41 and the auxiliary groove 79 are arranged in parallel, so that the engagement groove 41 and the auxiliary groove 79 can be machined in sequence without redoing the chuck of the workpiece on the broaching machine, thereby reducing processing costs.

[0137] In the above-described embodiment, the auxiliary groove 79 is formed in the outer peripheral surface of the shaft body 31d at a portion that is offset from the fitting tubular portion 35 toward one axial side so as to intersect with the slit 42, thereby thinning (removing) the wall thickness of the portion and forming a wide portion 43a with an opening that is circumferentially expanded at the intersection with the slit 42. This reduces the rigidity of the fitting tubular portion 35 at the one axial side portion near the closed end of the slit 42. This allows the rigidity of the fitting tubular portion 35 to be closer to each other at the one axial side portion and the other axial side portion, so that the amount of deformation occurring in the fitting tubular portion 35 when the fitting tubular portion 35 is reduced in diameter can be closer to each other at the one axial side portion and the other axial side portion. This allows the surface pressure between the inner peripheral surface of the fitting tubular portion 35 and the outer peripheral surface of the male shaft portion 52 (see FIG. 3, etc.) to be closer to each other at the one axial side portion and the other axial side portion. As a result, precession can be suppressed in the male shaft portion 52 connected to the other axial end of the shaft body 31d. This can suppress fretting wear in the serration engagement portion between the female serrations 40 and the male serrations 54 (see FIG. 3, etc.). This can prevent rattling from occurring between the shaft body 31d and the male shaft portion 52, and can also prevent abnormal noise caused by rattling.

[0138] In this example, the engagement groove 41 and the auxiliary groove 79 are broached grooves formed by broaching, and the engagement groove 41 and the auxiliary groove 79 are simultaneously processed. This makes it possible to minimize an increase in the number of processing steps (number of processes) that occurs due to the formation of the auxiliary groove 79. This makes it possible to suppress an increase in processing costs. The other configurations and effects are the same as those of the first embodiment.

[0139] [Twelfth Example of the Embodiment] A twelfth example of an embodiment will be described with reference to Figures 35 to 38. In this example, components similar to those in the first example of an embodiment are given the same reference numerals as in the first example of an embodiment, and detailed descriptions thereof will be omitted.

[0140] The first outer cylinder 12c of this example includes a shaft body 31e and a clamp 32.

[0141] The shaft body 31e has, in order from one axial end, a small diameter cylindrical portion 33a, a large diameter cylindrical portion 34a, and a fitting cylindrical portion 35a. The inner peripheral surface of the small diameter cylindrical portion 33a is provided with a female spline 36, which corresponds to the first female side engagement portion described in the claims. The axial dimension of the small diameter cylindrical portion 33a (female spline 36) is shorter than that of the structure of the first example of the embodiment.

[0142] The inner peripheral surface of the fitting tubular portion 35a is provided with female serrations 40, which correspond to the second female engaging portion described in the claims. The clamp 32 is fitted onto the outer peripheral surface of the fitting tubular portion 35a. A step surface 64 facing the other axial side is formed on a portion of the outer peripheral surface of the shaft main body 31e adjacent to one axial side of the fitting tubular portion 35a. The end face of the clamp 32 on one axial side abuts against the step surface 64. This allows the clamp 32 to be positioned in the axial direction relative to the shaft main body 31e.

[0143] The large diameter cylindrical portion 34a is disposed at a position adjacent to the other axial side of the female spline 36, and is a relief portion 80a having an inner diameter larger than the bottom circle diameter of the female spline 36. The large diameter cylindrical portion 34a has a small diameter side conical cylindrical portion 37, a bellows portion 81, and a fitting side inclined portion 39.

[0144] The bellows portion 81 has a torsional strength that does not deform even when subjected to a torsional load applied by the driver operating the steering wheel 1a (see FIG. 1) during a normal state before a collision occurs, but when a collision occurs and an impact load of a predetermined value or more is applied in the axial direction, the bellows portion 81 can be crushed or bent in the axial direction. The bellows portion 81 is configured by arranging a plurality of large-diameter crests 81a and small-diameter troughs 81b alternately in the axial direction. In this example, the top of the crests 81a and the bottom of the troughs 81b each have a circular arc shape in cross section. The inner diameter of the troughs 81b constituting the bellows portion 81 is also larger than the tooth bottom circle diameter of the female spline 36.

[0145] In the present embodiment as described above, even if the female spline 36 and the male spline 28 (see FIG. 4) are not displaced relative to each other in the axial direction during a collision accident, or the amount of relative displacement between the female spline 36 and the male spline 28 is small, the bellows portion 81 is crushed in the axial direction, so that the amount of contraction of the contraction shaft 9a (see FIG. 4, etc.) can be sufficiently ensured. In addition, in the event of a so-called offset collision, the first outer cylinder 12c can be plastically deformed so as to be bent by the bellows portion 81. In addition, since the clamp 32 is provided with the discontinuous portion 44, it is possible to prevent a large axial load from being applied to the bellows portion 81 when the fitting cylinder portion 35a is inserted into the insertion hole 47 of the clamp 32. This makes it possible to prevent the bellows portion 81 from being crushed in the axial direction. The other configurations and effects are the same as those of the first embodiment.

[0146] [Thirteenth Example of the Embodiment] A thirteenth embodiment will be described with reference to Figures 39 and 40. In this embodiment, components similar to those in the first and twelfth embodiments are given the same reference numerals as those in the first and twelfth embodiments, and detailed descriptions thereof will be omitted.

[0147] The first outer cylinder 12d of this example includes a shaft body 31f and a clamp 32.

[0148] The shaft body 31f has, in order from one axial end, a small diameter cylindrical portion 33a, a large diameter cylindrical portion 34b, and a fitting cylindrical portion 35a. The inner peripheral surface of the small diameter cylindrical portion 33a is provided with a female spline 36, which corresponds to the first female side engagement portion described in the claims. The inner peripheral surface of the fitting cylindrical portion 35a is provided with a female serration 40, which corresponds to the second female side engagement portion described in the claims. The clamp 32 is fitted onto the fitting cylindrical portion 35a.

[0149] The large diameter cylindrical portion 34b is disposed at a position adjacent to the other axial side of the female spline 36, and is a relief portion 80b having an inner diameter larger than the bottom circle diameter of the female spline 36. The large diameter cylindrical portion 34b has a small diameter side conical cylindrical portion 37, an intermediate cylindrical portion 38a, and a fitting side inclined portion 39.

[0150] The intermediate cylindrical portion 38a is configured to be substantially cylindrical, and is disposed in the axial middle portion of the large diameter cylindrical portion 34b. The inner and outer circumferential surfaces of the intermediate cylindrical portion 38a are each cylindrical surfaces whose diameter dimension does not change along the axial direction.

[0151] The intermediate cylindrical portion 38a has a plurality of through holes 82 penetrating in the radial direction. In the illustrated example, each of the through holes 82 is a slit-shaped long hole (elliptical hole) whose circumferential dimension is longer than its axial dimension. The through holes 82 are arranged in the circumferential direction at each of a plurality of locations of the intermediate cylindrical portion 38a that are equally spaced in the axial direction. The phases (circumferential positions) of a pair of through holes 82 adjacent to each other in the axial direction are different from each other. For this reason, in this example, the through holes 82 are arranged distributed around the entire circumference of the intermediate cylindrical portion 38a, rather than being arranged biased to a portion of the circumferential direction of the intermediate cylindrical portion 38a.

[0152] When implementing the present invention, the through holes may be in a shape other than an elongated hole, such as a circular hole or a rectangular hole, or may be elongated holes whose axial dimension is longer than their circumferential dimension. A combination of multiple through holes of different shapes may also be used. Furthermore, the phases of all or some of the through holes in the circumferential direction may be aligned, or the through holes may be disposed at multiple locations in the circumferential direction.

[0153] In the case of this example having the above configuration, since the through holes 82 are formed in the intermediate cylindrical portion 38a, the axial rigidity and bending rigidity of the intermediate cylindrical portion 38a can be kept low. Therefore, when a collision accident occurs, the intermediate cylindrical portion 38a is crushed in the axial direction, so that the amount of contraction of the contracted shaft 9a (see FIG. 4, etc.) can be sufficiently secured. Furthermore, during an offset collision, the first outer tube 12d can be plastically deformed so as to be bent at the intermediate cylindrical portion 38a. Furthermore, since the through holes 82 are distributed and arranged on the entire circumference of the intermediate cylindrical portion 38a in this example, the bending direction of the first outer tube 12d is not limited. Furthermore, since the through holes 82 can be easily formed by performing a boring process on the intermediate cylindrical portion 38a using a press, a drill, or the like, the processing cost of the shaft main body 31f can be kept low. Furthermore, by changing the shape, number, and formation position of the through holes 82, the rigidity of the intermediate cylindrical portion 38a can be easily adjusted to an appropriate size. The other configurations and effects are the same as those of the first and twelfth embodiments.

[0154] Although the embodiment of the present invention has been described above, the present invention is not limited to this, and can be modified as appropriate without departing from the technical concept of the invention. Furthermore, the structures of the examples of the embodiment can be combined as appropriate as long as no contradiction occurs.

[0155] For example, when carrying out the present invention, the first torque transmission shaft and the second torque transmission shaft are not limited to a double-tube structure, as in the structures of the examples of the embodiments. Of the first torque transmission shaft and the second torque transmission shaft, it is sufficient that one of the torque transmission shafts, which includes one shaft having a shaft body and a clamp, has a double-tube structure, and the other torque transmission shaft may or may not have a double-tube structure. In addition, the cross-sectional shape of at least one of the first female engagement portion provided on the inner peripheral surface of the shaft body from the end on one axial side to the axial middle portion and the second female engagement portion provided on the inner peripheral surface of the end on the other axial side of the shaft body may be polygonal or petal-shaped. In addition, a protrusion protruding radially inward is provided at one or more points on the inner peripheral surface of the insertion hole of the clamp, and the tip of the protrusion is caused to bite into the outer peripheral surface of the shaft, thereby preventing relative rotation between the shaft body and the clamp. In addition, a toothless portion (cylindrical surface portion) where no female serrations are formed may be provided on the inner peripheral surface of the fitting cylindrical portion, in a portion adjacent to both sides of the slit in the circumferential direction. In this case, when the fitting tubular portion is reduced in diameter, the female serrations can be prevented from locally abutting on the male serrations formed on the outer peripheral surface of the shaft. In addition, when carrying out the present invention, the circumferential position of the slits provided in the shaft body is not limited to the positions shown in the examples of the embodiment. The number of slits is not limited to one, and multiple slits can be provided. When a stress relief portion is formed at the inner end of the slit, the shape of the stress relief portion can be any shape, such as an elliptical shape or a teardrop shape. In addition, the pair of mounting holes provided in the clamp can be made into through holes and used in combination with a nut. Furthermore, the fitting tubular portion of the shaft body can be pressed (lightly pressed) into the insertion hole of the clamp to fix the shaft body and the clamp. [Explanation of symbols]

[0156] 1, 1a Steering wheel 2, 2a Steering shaft 3, 3a Steering column 4a~4d Universal joint 5, 5a, 5b, 5c Intermediate shaft 6, 6a Steering gear unit 7, 7a Tie rod 8, 8a Pinion shaft 9, 9a, 9b Contraction shaft 10, 10a, 10b Telescopic shaft 11, 11a, 11b First inner shaft 12, 12a, 12b, 12c, 12d First outer cylinder 13 Male spline 14 Female Spline 15, 15a, 15b Second outer cylinder 16, 16a, 16b Second inner shaft 17 Female Gutter 18 Male Gutter 19, 19a Ball 20, 20a Roller 21 Female Serration 22 Male Serration 23 Tube 24 Clamp 25 York 26, 26a Rod-shaped part 27 York 28, 28a male spline 29 Center hole 30 Fuse section 31, 31a, 31b, 31c, 31d, 31e, 31f Shaft body 32, 32a, 32b, 32c, 32d, 32e, 32f, 32g clamps 33, 33a Small diameter cylinder part 34, 34a, 34b Large diameter cylindrical portion 35, 35a, 35b Fitting cylinder part 36 Female Spline 37 Small diameter cone tube 38, 38a Intermediate cylindrical section 39 Mating side inclined portion 40 Female Serration 41 Engagement groove 42, 42a Slit 43, 43a wide section 44 Discontinuities 45 Flange part 46, 46a, 46b connection part 47, 47a, 47b, 47c, 47d Insertion holes 48a, 48b Mounting holes 49, 49a Notch 50 Fastening bolt 51 Leaf spring 52, 52a Male shaft part 53 Female cylinder part 54, 54a Male serration 55 Circumferential groove 56 First Female Gutter 57 Second Female Gutter 58 First Male Gutter 59 Second Male Gutter 60 Stopper 61 York 62 York 63 Coating Layer 64 Step surface 65 Welding 66 Shaft side flat surface 67 Clamp side flat surface 68 Shaft side engagement part 69 Clamp side engagement part 70, 70a Crimping deformation part 71 Wide section 72 Shaft side engagement surface 73 Clamp side engagement surface 74 Locking groove 75 Retaining slit 76 Retaining ring 77 Circular groove 78 Annular gap 79 Auxiliary groove 80, 80a, 80b Recess 81 Bellows section 81a Yamabe 81b Valley 82 Through hole

Claims

1. An intermediate shaft constituting an automobile steering device, the intermediate shaft being configured by axially connecting a first torque transmission shaft and a second torque transmission shaft, each of which has a yoke at an axially opposite end, The first torque transmission shaft has a connecting side first shaft, the second torque transmission shaft has a second connection shaft connected to the first connection shaft so as to be able to transmit torque, one of the first connecting shaft and the second connecting shaft has a hollow shaft body and a notched cylindrical clamp, and an inner shaft constituting either the first torque transmission shaft or the second torque transmission shaft together with the one shaft is an outer cylinder into which an inner shaft is inserted so as to be capable of transmitting torque and to be displaced relatively in an axial direction; the first torque transmission shaft or the second torque transmission shaft including the one shaft has a double tube structure, the shaft body has a first female side engagement portion provided on its inner peripheral surface in a range from the end on one axial side to an axial middle portion, the first female side engagement portion engaging with a first male side engagement portion provided on the outer peripheral surface of the inner shaft, a second female side engagement portion provided on its inner peripheral surface at the end on the other axial side, the second female side engagement portion engaging with a second male side engagement portion provided on the outer peripheral surface at the end of the other of the first connecting shaft and the second connecting shaft, and a slit provided at the end on the other axial side, extending in the axial direction and having an open end on the other axial side; an axial dimension of the first female engagement portion is larger than an axial dimension of the first male engagement portion, and the first female engagement portion and the first male engagement portion have a dimensional relationship such that they remain engaged with each other even when one of the shafts is contracted; the shaft body has a small diameter cylindrical portion having the first female side engagement portion formed along the entire axial length of its inner circumferential surface, a fitting cylindrical portion having the second female side engagement portion formed along the entire axial length of its inner circumferential surface, and a large diameter cylindrical portion disposed between the small diameter cylindrical portion and the fitting cylindrical portion and having a diameter larger than that of the small diameter cylindrical portion, the large diameter cylindrical portion has a small diameter side conical cylindrical portion, an intermediate cylindrical portion, and a fitting side inclined portion, and is a relief portion having an inner diameter larger than a bottom circle diameter of the first female side engagement portion, The large-diameter cylindrical portion is formed with only the slit as a hole penetrating in a radial direction, and one axial end of the slit is located in the intermediate cylindrical portion, an axial dimension of the large diameter cylindrical portion is shorter than an axial dimension of the small diameter cylindrical portion, and an axial dimension of the intermediate cylindrical portion of the large diameter cylindrical portion is shorter than an axial dimension of the fitting cylindrical portion, The clamp is fitted onto the fitting cylindrical portion and is capable of reducing the diameter of the other axial end of the shaft body. Intermediate shaft.

2. the first torque transmission shaft has a double-tube structure and is a contractible shaft configured to be contractible in its entirety only when an automobile crash occurs and an impact load of a predetermined value or more is applied in the axial direction, The second torque transmission shaft has a double tube structure and is an extendable shaft configured to be extendable and retractable in its entire length in a steady state in which no collision accident has occurred.

2. The intermediate shaft according to claim 1.

3. the one shaft is the first connecting shaft constituting the first torque transmission shaft, The first male engagement portion is press-fitted into the first female engagement portion.

3. The intermediate shaft according to claim 2.

4. the one shaft is the second connecting shaft constituting the second torque transmission shaft, The first male engaging portion has a surface covered with a coating layer made of synthetic resin and is slidably engaged with the first female engaging portion.

3. The intermediate shaft according to claim 2.

5. The intermediate shaft according to any one of claims 1 to 4, wherein the inner shaft, which constitutes either the first torque transmission shaft or the second torque transmission shaft together with the one shaft, is provided with a fuse portion in a part of the axial direction, the fuse portion having a smaller diameter than parts of adjacent parts on both axial sides.

6. 6. The intermediate shaft according to claim 1, wherein the first male side engagement portion is a male spline, the first female side engagement portion is a female spline, the second male side engagement portion is a male serration, and the second female side engagement portion is a female serration.

7. The intermediate shaft according to any one of claims 1 to 6, wherein the shaft body and the clamp are fixed by welding.

8. The intermediate shaft according to any one of claims 1 to 6, wherein the shaft body and the clamp are fixed together by a plastically deformed portion formed in at least one of the shaft body and the clamp.

9. 9. The intermediate shaft according to claim 1, wherein an outer circumferential surface of the other axial end of the shaft body and an inner circumferential surface of the clamp are non-circularly fitted together to prevent relative rotation.

10. the clamp further includes a discontinuous portion disposed at one location in the circumferential direction, a pair of flange portions disposed on either side of the discontinuous portion in the circumferential direction, each flange portion having an attachment hole into which a fastening member is inserted, and a partially cylindrical connecting portion connecting the pair of flange portions together in the circumferential direction, The connecting portion has a notch at the other axial side portion, the notch being recessed toward the one axial side from the end face at the other axial side of the flange portion. An intermediate shaft according to any one of claims 1 to 9.

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