Shaft connecting structure

Abstract

To provide a shaft connecting structure capable of shortening a swirl radius of a shaft connecting part to save a substantially occupied space of the shaft connecting part.SOLUTION: A shaft connecting structure comprises two shafts, an intermediate pipe 25, and a restraining pipe 40. The intermediate pipe 25 has slits 26a, 26b along an axial direction, and is attached across an outer peripheral surface of each end part of one shaft and the other shaft. The restraining pipe 40 is press-fitted onto the outer peripheral surface of the intermediate pipe 25, to restrain the intermediate pipe 25 from the radial outside.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a shaft connecting structure for a steering device of a vehicle or the like. [Background technology]

[0002] In a vehicle steering device, a steering shaft located inside the passenger compartment and a steering gearbox located in the engine compartment at the front of the passenger compartment are connected to each other via multiple universal joints and a connecting shaft so that rotation can be transmitted. The connecting shaft is located in a narrow space near the dash lower panel in front of the driver's seat. Therefore, to improve assembly workability in the narrow space, the connecting shaft is sometimes divided into a first shaft connected to the steering shaft side and a second shaft connected to the steering gearbox side, and after both shafts are connected to corresponding components on the driver's seat side and the engine compartment side, the ends of the shafts are sometimes connected to each other via a joint member (see, for example, Patent Document 1).

[0003] The shaft connection structure described in Patent Document 1 employs a joint member having the following configuration. That is, the joint member includes a cylindrical portion having a substantially C-shaped cross section into which the tip ends of the first shaft and the second shaft are inserted, and a pair of flange walls extending radially outward from the open end of the C-shape of the cylindrical portion. Female serrations are formed on the inner peripheral surface of the cylindrical portion, and fastening members are provided on the pair of flange walls that can tighten the two together in the approaching direction.

[0004] Male serrations are formed on the outer peripheral surfaces of the first shaft and the second shaft. The tip ends of the first shaft and the second shaft are inserted into the cylindrical portion of the joint member from both axial sides, and the male serrations on the outer peripheral surfaces of each shaft engage with the female serrations on the cylindrical portion. In this state, when the fastening member of the joint member is tightened, the distance between the pair of flange walls narrows, reducing the inner diameter of the cylindrical portion, and the female serrations on the cylindrical portion firmly mesh with the male serrations on each shaft. As a result, the first shaft and the second shaft are connected by the joint member so as to be able to transmit rotation. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 6-107187 Summary of the Invention [Problem to be solved by the invention]

[0006] The joint member used in the shaft connection structure described in Patent Document 1 has a pair of flange walls protruding radially outward from the end of a cylindrical portion with a generally C-shaped cross section. Therefore, when the two connected shafts rotate during use, the flange walls of the joint member rotate in a large radial orbit. This results in an increase in the effective space occupied by the shaft connection portion. Therefore, an improvement in this respect is currently desired.

[0007] SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a shaft connecting structure that can reduce the turning radius of the shaft connecting portion. [Means for solving the problem]

[0008] In order to solve the above problems, the shaft connection structure according to the present invention employs the following configuration. That is, a shaft connecting structure according to one aspect of the present invention is a shaft connecting structure that connects the ends of two shafts, and is characterized by comprising the two shafts, an intermediate pipe that has a slit along the axial direction and is attached across the outer peripheral surfaces of each end of one of the shafts and the other of the shafts, and a restraining pipe that is press-fitted onto the outer peripheral surface of the intermediate pipe and restrains the intermediate pipe from the radial outside.

[0009] When connecting two shafts using the shaft connection structure of this aspect, an intermediate pipe is attached to the outer circumferential surfaces of the two shafts so as to straddle them. Next, in this state, the restraining pipe is moved in the outer circumferential direction of the intermediate pipe, and the restraining pipe is press-fitted onto the outer circumferential surface of the intermediate pipe. When the restraining pipe is press-fitted onto the outer circumferential surface of the intermediate pipe in this manner, the intermediate pipe is pressed radially inward by the restraining pipe, reducing its diameter so as to narrow the width of the slit. As a result, the inner circumferential surface of the intermediate pipe is firmly pressed against the outer circumferential surfaces of the two shafts, and the two shafts are connected so as to be able to transmit rotation.

[0010] It is desirable that rotation restricting portions be provided on the outer circumferential surfaces of the ends of the two shafts and the inner circumferential surface of the intermediate pipe to restrict relative rotation therebetween.

[0011] In this case, the rotation of the two shafts and the intermediate pipe is restricted by the rotation restricting portion, and the intermediate pipe is pressed radially inward by the restraining pipe, so that the two shafts are connected in a state in which the relative rotation between the intermediate pipe and the two shafts is reliably restricted.

[0012] It is more preferable that the rotation restricting portion be configured by male serrations formed on the outer peripheral surface of each of the shafts and female serrations formed on the inner peripheral surface of the intermediate pipe.

[0013] In this case, the male serrations on the outer peripheral surface of each shaft engage with the female serrations on the inner peripheral surface of the intermediate pipe, making it possible to more firmly restrict the relative rotation between each shaft and the intermediate pipe.

[0014] The intermediate pipe may have slits formed in an area near one end in the axial direction where one of the shafts is inserted, and in an area near the other end in the axial direction where the other of the shafts is inserted, and a connecting wall portion without a slit may be provided between the two slits.

[0015] In this case, the circumferential separation portions of the transfer pipe caused by the slits are connected by the connecting wall portion between the two slits. Therefore, before the transfer pipe is assembled to the shafts, the transfer pipe is less likely to bend and deform in the axial, radial, or torsional directions across the slits. Therefore, when this configuration is adopted, the transfer pipe can be assembled to the two shafts easily and in the appropriate position.

[0016] The intermediate pipe may have chamfered portions formed on both circumferential edge portions sandwiching the slit on the outer circumferential surface thereof, the chamfered portions extending along the direction in which the slit extends.

[0017] In this case, by press-fitting the restraint pipe onto the outer peripheral surface of the intermediate pipe, when the intermediate pipe deforms to narrow the slit spacing, the deformation of the intermediate pipe near the slit is less likely to be restrained by contact resistance with the inner peripheral surface of the restraint pipe. In other words, with this configuration, the chamfered portion does not contact the inner peripheral surface of the restraint pipe, so the intermediate pipe does not contact the inner peripheral surface of the restraint pipe near the slit. Therefore, when this configuration is adopted, it is easier to press-fit the restraint pipe into the intermediate pipe, and the shaft connection work is improved.

[0018] The intermediate pipe may be formed so that the outer diameter of a region on one axial end side is larger than the outer diameter of a region on the other axial end side, and the restraint pipe is formed so that the inner diameter of a region on the one axial end side is larger than the inner diameter of a region on the other axial end side.

[0019] In this case, when the restraint pipe is press-fitted onto the outer peripheral surface of the intermediate pipe, if the restraint pipe is moved from the other end toward one end relative to the intermediate pipe, the large-diameter inner diameter portion of the restraint pipe at one end passes through the small-diameter outer diameter portion of the intermediate pipe at the other end in a substantially non-contact state. Then, if the restraint pipe is moved a certain distance, the large-diameter inner diameter portion of the restraint pipe at one end comes into firm contact and engagement with the large-diameter portion of the one end of the intermediate pipe. At the same time, the small-diameter inner diameter portion of the restraint pipe at the other end comes into firm contact and engagement with the small-diameter portion of the intermediate pipe at the other end. Therefore, if this configuration is adopted, the restraint pipe can be easily press-fitted into the intermediate pipe during assembly.

[0020] A restricting flange may be provided at an end portion on the one end side of the intermediate pipe so as to be able to come into contact with an end surface on the one end side of the restraining pipe.

[0021] In this case, when the restraint pipe is moved from the other end toward the one end of the intermediate pipe to press-fit it, the end face of the one end of the restraint pipe abuts against the regulating flange of the intermediate pipe, so that the restraint pipe stops at the appropriate fitting position. Therefore, when this configuration is adopted, it is possible to regulate the fitting position of the restraint pipe and the intermediate pipe to the appropriate position.

[0022] A shaft connection structure according to another aspect of the present invention is a shaft connection structure for connecting the ends of two shafts, characterized in that it comprises the two shafts, an intermediate pipe portion integrally formed on the end of one of the shafts, having a slit along the axial direction and attached to the outer surface of the end of the other shaft, and a restraining pipe press-fitted onto the outer surface of the intermediate pipe portion to restrain the intermediate pipe portion from the radial outside.

[0023] When connecting two shafts using this shaft connection structure, the intermediate pipe portion provided on one shaft is attached to the outer peripheral surface of the end of the other shaft. Next, in this state, the restraining pipe is moved in the outer circumferential direction of the intermediate pipe portion to press-fit the restraining pipe onto the outer circumferential surface of the intermediate pipe portion. When the restraining pipe is press-fitted onto the outer circumferential surface of the intermediate pipe portion in this manner, the intermediate pipe portion is pressed radially inward by the restraining pipe, reducing its diameter so as to narrow the width of the slit. As a result, the inner circumferential surface of the intermediate pipe portion is firmly pressed against the outer circumferential surface of the other shaft, and the two shafts are connected so as to be able to transmit rotation. [Effects of the Invention]

[0024] According to the present invention, the restraining pipe is press-fitted onto the outer circumferential surface of the intermediate pipe or intermediate pipe portion, thereby firmly connecting the two shafts via the intermediate pipe or intermediate pipe portion. Therefore, when the shaft connecting structure according to the present invention is adopted, the turning radius of the shaft connecting portion can be reduced, and the actual space occupied by the shaft connecting portion can be saved. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a side view of a steering device employing the shaft connecting structure of a first embodiment. [Figure 2] FIG. 2 is a perspective view showing a shaft connecting portion of the first embodiment. [Figure 3] FIG. 2 is an exploded perspective view of a shaft coupling portion according to the first embodiment. [Figure 4] FIG. 2 is a perspective view of an intermediate pipe according to the first embodiment. [Figure 5] 5 is an end view of an intermediate pipe according to the first embodiment, viewed from the direction of arrow V in FIG. 4. FIG. [Figure 6] FIG. 10 is an exploded side view of the shaft coupling portion of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, each embodiment of the present invention will be described with reference to the drawings. Note that the same reference numerals are used to designate parts with common functions in each embodiment, and duplicated descriptions will be omitted.

[0027] First Embodiment FIG. 1 is a side view of a steering device 1 for a vehicle that employs the shaft connecting structure of this embodiment. The steering device 1 includes a steering shaft 2 connected to a steering wheel (not shown) inside the vehicle interior 7, a relay shaft unit 4 connected to the steering shaft 2 via a universal joint 3, a steering gearbox 6 connected to the relay shaft unit 4 via another universal joint 5, and tie rods (not shown) that transmit the output of the steering gearbox 6 to the left and right front wheels.

[0028] The steering device 1 of this embodiment is a so-called steer-by-wire type electric steering device. The steering device 1 is equipped with a fail-safe mechanism in case of an emergency such as a failure in the electrical system. The fail-safe mechanism is constituted by a relay shaft unit 4. An electromagnetic clutch 15 is provided in the middle of the relay shaft unit 4, and during normal driving, the electromagnetic clutch 15 blocks direct power transmission from the steering shaft 2 to the steering gear box 6. Then, in an emergency, the electromagnetic clutch 15 is switched to a power-transmitting state, enabling mechanical power transmission from the steering shaft 2 to the steering gear box 6.

[0029] The steering shaft 2 is rotatably supported by a steering column 8 inside the passenger compartment 7. The steering gear box 6 is disposed in a front compartment 9 in front of the passenger compartment 7. In addition to the steering gear box 6, the front compartment 9 also houses the vehicle's drive devices, such as the motor and engine, and suspension devices. The passenger compartment 7 and the front compartment 9 are separated by a dash lower panel 10.

[0030] The relay shaft unit 4 includes an upper shaft assembly 11 and a lower shaft assembly 13. One end of the upper shaft assembly 11 is connected to the steering shaft 2 via a universal joint 3. One end of the lower shaft assembly 13 is connected to the upper shaft assembly 11, and the other end is connected to an input shaft 12 of the steering gearbox 6 via a universal joint 5. The upper shaft assembly 11 and the lower shaft assembly 13 are connected to each other so as to be rotatable together by serration fitting and fastening with a fastening member, for example.

[0031] The upper shaft assembly 11 includes the above-mentioned electromagnetic clutch 15, a clutch input shaft 14 connected to the input side of a disengagement mechanism in the electromagnetic clutch 15, and a clutch output shaft 16 connected to the output side of the disengagement mechanism in the electromagnetic clutch 15. A universal joint 3 is provided on the end of the clutch input shaft 14 that protrudes from the electromagnetic clutch 15. The clutch output shaft 16 includes a first shaft 17 and a second shaft 18 that are coaxially arranged, and a joint member 19 that connects the two shafts 17, 18. The output side of the disengagement mechanism in the electromagnetic clutch 15 is connected to the first shaft 17 so as to be rotatable together with it.

[0032] The lower shaft assembly 13 includes an outer tube 20, one end of which is connected to an end of the second shaft 18 of the upper shuttle assembly 11 so as to be rotatable together with the outer tube 20, and an output shaft 21 connected in a fitted state to the other end of the outer tube 20. The outer tube 20 and the output shaft 21 are connected so as to be rotatable together with each other, and when an impact load is input in the axial direction, the output shaft 21 sinks into the outer tube 20. The lower shaft assembly 13 absorbs the energy of the input impact load by frictional resistance and the like. A universal joint 5 is provided at the end of the output shaft 21 opposite the outer tube 20.

[0033] The dash lower panel 10 is provided with a through-hole 22 through which the clutch output shaft 16 of the upper shaft assembly 11 is inserted. In this embodiment, a main portion of the electromagnetic clutch 15 of the upper shaft assembly 11 is disposed inside the passenger compartment 7, and a portion of the electromagnetic clutch 15 and the clutch output shaft 16 protrude toward the front compartment 9 through the through-hole 22. As shown in FIG. 1, the relay shaft unit 4 is installed in the vehicle so as to be inclined downward toward the front side of the vehicle (the left side in FIG. 1).

[0034] FIG. 2 is a perspective view showing the connecting portion (shaft connecting portion) between the first shaft 17 and the second shaft 18, and FIG. 3 is an exploded perspective view of this connecting portion (shaft connecting portion). As shown in Fig. 3, male serrations 23 are formed on the outer peripheral surface of the end of the first shaft 17. The male serrations 23 are formed in areas spaced apart in the axial direction of the first shaft 17, with an annular groove 24 between them. Similarly, male serrations 30 are formed on the outer peripheral surface of one end of the second shaft 18 (the end connected to the first shaft 17). The male serrations 30 are formed in areas spaced apart in the axial direction of the second shaft 18, with an annular groove 31 between them. Similar male serrations 32 are also formed on the outer peripheral surface of the other end of the second shaft 18. These male serrations 32 are intended to be coupled to the outer tube 20 (lower shaft assembly 13) shown in Fig. 1 so as to be rotatable together. Female serrations (not shown) are formed on the inner peripheral surface of the outer tube 20, and the male serrations 32 on the other end of the second shaft 18 mesh with these female serrations.

[0035] As shown in Fig. 3, the joint member 19 includes an intermediate pipe 25 that straddles and covers the outer peripheral surfaces of the ends of the first shaft 17 and the second shaft 18, and a restraining pipe 40 that is press-fitted onto the outer peripheral surface of the intermediate pipe 25. The intermediate pipe 25 is made of a metal such as an aluminum alloy. The restraining pipe 40 is made of a metal such as iron or an aluminum alloy. The materials that make up the intermediate pipe 25 and the restraining pipe 40 are not limited to these.

[0036] Fig. 4 is a perspective view of the intermediate pipe 25, and Fig. 5 is an end view of the intermediate pipe 25 corresponding to the view of the arrow V in Fig. 4. For ease of explanation, the side of the intermediate pipe 25 that is connected to the second shaft 18 may be referred to as the "front" and the side that is connected to the first shaft 17 may be referred to as the "rear." The intermediate pipe 25 is formed in a generally cylindrical shape as a whole, and has a pair of slits 26a, 26b formed in the axial direction in its peripheral wall. The pair of slits 26a, 26b extend inward in the axial direction from the same circumferential position in the peripheral wall of the intermediate pipe 25. A connecting wall portion 27 without a slit is provided between the pair of slits 26a, 26b in the peripheral wall of the intermediate pipe 25. The connecting wall portion 27 is provided in a generally central position in the axial direction of the intermediate pipe 25.

[0037] Female serrations 33 are formed on the inner peripheral surface of the transfer pipe 25. The female serrations 33 are formed continuously from one axial end to the other axial end of the inner peripheral surface of the transfer pipe 25. However, the female serrations 33 may be formed separately in one axial end region and the other axial end region of the inner peripheral surface of the transfer pipe 25. The tip ends of the first shaft 17 and the second shaft 18 are inserted into the inner peripheral surface of the transfer pipe 25 from both axial sides. At this time, the male serrations 23, 30 on the outer peripheral surfaces of the first shaft 17 and the second shaft engage with the female serrations 33 on the inner peripheral surface of the transfer pipe 25. The slits 26a, 26b of the transfer pipe 25 are formed in at least the regions of the peripheral wall of the transfer pipe 25 into which the first shaft 17 and the second shaft are inserted. In this embodiment, the male serrations 23, 30 of the first shaft 17 and the second shaft 18 and the female serrations 33 of the intermediate pipe 25 that engage with these male serrations 23, 30 constitute a rotation restricting portion that restricts relative rotation between the two.

[0038] The outer diameter of the peripheral wall of the intermediate pipe 25 at one axial end (rear end) is larger than the outer diameter of the other axial end (front end). Hereinafter, the larger outer diameter region at one end of the intermediate pipe 25 will be referred to as the "large diameter section 25a," and the relatively smaller outer diameter region at the other end will be referred to as the "small diameter section 25b." Between the large diameter section 25a and the small diameter section 25b of the intermediate pipe 25 is a medium diameter section 25c, whose outer diameter is slightly larger than that of the small diameter section 25b (its outer diameter is smaller than that of the large diameter section 25a). A tapered section 25d connects the rear end of the medium diameter section 25c to the large diameter section 25a. The outer diameter of the tapered section 25d gradually increases from the medium diameter section 25c side toward the large diameter section 25a side.

[0039] A restricting flange 28 that projects radially outward is formed at the axial end (rear end) of the large diameter portion 25a of the intermediate pipe 25. This restricting flange 28 restricts the press-fit position of a restraining pipe 40, which will be described later, to a fixed position.

[0040] Furthermore, flat chamfered portions 34a, 34b are provided on both circumferential edges of the outer peripheral surface of the intermediary pipe 25 that sandwich the slits 26a, 26b. Each of the chamfered portions 34a, 34b is formed to fit along each of the slits 26a, 26b of the intermediary pipe 25. The chamfered portions 34a formed on both circumferential edges of one slit 26a and the chamfered portions 34b formed on both circumferential edges of the other slit 26b are each shaped by cutting a portion of the outer surface of the intermediary pipe 25 into a D-shape, as shown in FIG. 5 . Therefore, when the restraining pipe 40 (described later) is press-fitted into the outer peripheral surface of the intermediary pipe 25, these chamfered portions 34a, 34b do not come into contact with the inner peripheral surface of the restraining pipe 40.

[0041] The restraint pipe 40 is formed in a substantially cylindrical shape as a whole. The axial length of the restraint pipe 40 is set to be substantially the same as the axial length of the intermediate pipe 25. The inner diameter of the restraint pipe 40 in a region on one axial end side (rear end side) is larger than the inner diameter of the region on the other axial end side (front end side). The inner diameter of the restraint pipe 40 in a region on one axial end side (rear end side) is slightly smaller than the outer diameter of the large diameter portion 25a of the intermediate pipe 25. Similarly, the inner diameter of the restraint pipe 40 in a region on the other axial end side (front end side) is slightly smaller than the outer diameter of the small diameter portion 25b of the intermediate pipe 25. The portion of the restraint pipe 40 between the large inner diameter portion on one end side and the small inner diameter portion on the other end side is formed to be smaller than the inner diameter of the large inner diameter portion on the one end side.

[0042] Next, a method for connecting the first shaft 17 and the second shaft 18 will be described. The first shaft 17 is assembled to the main body of the electromagnetic clutch 15 in advance. In this state, the tip ends of the first shaft 17 and the second shaft 18 are arranged to face each other in preparation for connection.

[0043] Thereafter, the ends of the first shaft 17 and the second shaft 18 are inserted from both axial sides into the inner circumferential surface of the intermediate pipe 25. As a result, the intermediate pipe 25 is attached to the first shaft 17 and the second shaft 18 so as to straddle the ends of these shafts, and the female serrations 33 on the inner circumferential surface side are engaged with the male serrations 23, 30 of the first shaft 17 and the second shaft 18.

[0044] Next, the restraint pipe 40 is moved from the outer periphery side of the second shaft 18 toward the outer periphery of the intermediary pipe 25. At this time, because the inner diameter of one axial end of the restraint pipe 40 is set smaller than the outer diameter of the other axial end of the intermediary pipe 25, the restraint pipe 40 can be inserted with almost no resistance up to a position where it overlaps with the intermediary pipe 25 to a certain extent in the axial direction. Then, when the restraint pipe 40 moves axially to a certain position, the large inner diameter region of the one axial end of the restraint pipe 40 is fitted into the large diameter portion 25a of the intermediary pipe 25, and the small inner diameter region of the other axial end is fitted into the small diameter portion 25b of the intermediary pipe 25.

[0045] If the restraint pipe 40 continues to be press-fitted into the intermediate pipe 25, the intermediate pipe 25 is pressed radially inward by the restraint pipe 40, and the diameter of the intermediate pipe 25 decreases so as to narrow the width of each of the slits 26a, 26b. As a result, the female serrations 33 of the intermediate pipe 25 become firmly engaged with the male serrations 23, 30 of the first shaft 17 and the second shaft 18.

[0046] Furthermore, when the restraint pipe 40 is press-fitted into the intermediate pipe 25 to a certain position, the end face on one axial end of the restraint pipe 40 abuts against the restricting flange 28 at the end of the intermediate pipe 25. At this point, the press-fitting of the restraint pipe 40 into the intermediate pipe 25 is completed.

[0047] As described above, the shaft connection structure of this embodiment can firmly connect the first shaft 17 and the second shaft 18 via the intermediate pipe 25 by press-fitting the restraint pipe 40 onto the outer circumferential surface of the intermediate pipe 25. As a result, the shaft connection portion does not protrude significantly radially outward. Therefore, when the shaft connection structure of this embodiment is adopted, the turning radius of the shaft connection portion can be reduced, and the actual space occupied by the shaft connection portion can be saved.

[0048] Furthermore, in the shaft coupling structure of this embodiment, rotation restricting portions (male serrations 23, 30 and female serrations 33) that restrict relative rotation between the first shaft 17 and the second shaft 18 are provided on the outer peripheral surfaces of the first shaft 17 and the second shaft 18 and on the inner peripheral surface of the intermediate pipe 25. Therefore, when this configuration is adopted, it becomes possible to couple the first shaft 17 and the second shaft 18 in a state in which the relative rotation between the intermediate pipe 25 and the two shafts is more reliably restricted.

[0049] In particular, in the shaft coupling structure of this embodiment, the rotation restricting portion is made up of the male serrations 23, 30 formed on the outer peripheral surfaces of both shafts and the female serrations 33 formed on the inner peripheral surface of the transfer pipe 25. When this configuration is adopted, the engagement of the male serrations 23, 30 on the outer peripheral surfaces of both shafts with the female serrations 33 on the inner peripheral surface of the transfer pipe 25 makes it possible to more firmly restrict the relative rotation between both shafts and the transfer pipe 25.

[0050] Furthermore, in the shaft coupling structure of this embodiment, slits 26a, 26b are formed in a region on one axial end side of the intermediary pipe 25 into which the first shaft 17 is fitted, and in a region on the other axial end side into which the second shaft 18 is fitted, respectively, and a coupling wall portion 27 without a slit is provided between the two slits 26a, 26b. Therefore, before the intermediary pipe 25 is assembled to both shafts, the coupling wall portion 27 can suppress bending deformation of the intermediary pipe 25 in the axial, radial, or torsional directions across the slits 26a, 26b. Therefore, when this configuration is adopted, the intermediary pipe 25 can be assembled to the two shafts easily and in the appropriate position.

[0051] Furthermore, in the shaft coupling structure of this embodiment, chamfered portions 34a, 34b are provided on both circumferential edge portions of the outer circumferential surface of the intermediary pipe 25 that sandwich the slits 26a, 26b, so as to extend along the direction in which the slits 26a, 26b extend. Therefore, when the restraint pipe 40 is press-fitted onto the outer circumferential surface of the intermediary pipe 25, the portions of the intermediary pipe 25 near the slits 26a, 26b (chamfered portions 34a, 34b) do not come into contact with the inner circumferential surface of the restraint pipe 40. Therefore, when the intermediary pipe 25 is deformed by reducing its diameter due to the press-fitting of the restraint pipe 40, this deformation is less likely to be hindered by frictional resistance between the intermediary pipe 25 and the inner circumferential surface of the restraint pipe 40. Therefore, when this configuration is adopted, the restraint pipe 40 can be easily press-fitted into the intermediary pipe 25, improving the workability of coupling the two shafts.

[0052] Furthermore, in the shaft coupling structure of this embodiment, the outer diameter of one axial end (rear end) region of the intermediary pipe 25 is larger than the outer diameter of the other axial end (front end) region, and the inner diameter of one axial end (rear end) region of the restraint pipe 40 is larger than the inner diameter of the other axial end (front end) region. Therefore, when the restraint pipe 40 is press-fitted onto the outer peripheral surface of the intermediary pipe 25, if the restraint pipe 40 is moved from the other end toward one end relative to the intermediary pipe 25, the large-diameter inner diameter portion at one end of the restraint pipe 40 passes through the small-diameter outer diameter portion at the other end of the intermediary pipe 25 in a substantially non-contact state. When the restraint pipe 40 is moved in this manner to a certain extent, the large-diameter inner diameter portion at one end of the restraint pipe 40 comes into firm contact and engagement with the large-diameter portion at one end of the intermediary pipe 25, and the small-diameter inner diameter portion at the other end of the restraint pipe 40 comes into firm contact and engagement with the small-diameter portion at the other end of the intermediary pipe 25. Therefore, when this configuration is adopted, the restraining pipe 40 can be easily press-fitted into the intermediate pipe 25 during assembly.

[0053] Furthermore, in the shaft coupling structure of this embodiment, a restricting flange 28 that can abut against an end face of one end of the restraint pipe 40 is provided at an end portion on one end side of the intermediary pipe 25. Therefore, when the restraint pipe 40 is press-fitted, the end face on one end side of the restraint pipe 40 abuts against the restricting flange 28 of the intermediary pipe 25, thereby stopping the restraint pipe 40 at an appropriate fitting position. Therefore, when this configuration is adopted, it is possible to restrict the fitting position of the restraint pipe 40 and the intermediary pipe 25 to an appropriate position.

[0054] Second Embodiment 6 is an exploded side view of the shaft connector of this embodiment. In this embodiment, the shaft connector is applied to the intermediate shaft unit 4 of the steering device (see FIG. 1) in the same manner as in the first embodiment. In the shaft connecting portion of this embodiment, an intermediate pipe portion 125 is formed integrally with the end of the first shaft 117. The intermediate pipe portion 125 is formed in a cylindrical shape with a bottom that is open on the side facing the end of the second shaft 18. A slit 26b is formed in the peripheral wall of the intermediate pipe portion 125 along the axial direction. Female serrations 33 are formed on the inner peripheral surface of the intermediate pipe portion 125. The end of the second shaft 18 is inserted into the peripheral wall of the intermediate pipe portion 125, and male serrations 30 formed on the outer peripheral surface of the second shaft engage with the female serrations 33 on the inner peripheral surface of the intermediate pipe portion 125.

[0055] In this state, the restraint pipe 40 is press-fitted onto the outer peripheral surface of the intermediate pipe portion 125. When the restraint pipe 40 is press-fitted onto the outer peripheral surface of the intermediate pipe portion 125 in this manner, the width of the slits 26b in the intermediate pipe portion 125 narrows, and the diameter of the intermediate pipe portion 125 decreases. As a result, the female serrations 33 on the inner peripheral surface of the intermediate pipe portion 125 come firmly into mesh with the male serrations 30 of the second shaft.

[0056] In the shaft coupling portion of this embodiment, the restraint pipe 40 is press-fitted onto the outer circumferential surface of the intermediate pipe portion 125, thereby enabling the first shaft 117 and the second shaft 18 to be firmly coupled via the intermediate pipe portion 125. Therefore, also in the case of this embodiment, the shaft coupling portion does not protrude significantly radially outward. Therefore, when the shaft connecting structure of this embodiment is adopted, the turning radius of the shaft connecting portion can be reduced, and the actual space occupied by the shaft connecting portion can be saved.

[0057] The present invention is not limited to the above-described embodiment, and various design modifications are possible without departing from the spirit of the present invention. For example, in the first embodiment, the first shaft 17 and the second shaft 18 of the relay shaft unit 4 are connected inside the front compartment 9 of the vehicle, but the connecting portion of the first shaft 17 and the second shaft 18 may be located inside the passenger compartment 7.

[0058] In addition, in each of the above embodiments, a meshing structure of male serrations and female serrations is used as the rotation restricting portion that restricts the relative rotation between the shaft and the intermediate pipe, but the rotation restricting portion is not limited to this. For example, the rotation restricting portion may be a rotation restricting portion using a key and key groove, or may be one in which flat surfaces such as a two-sided width or a D-cut portion are provided on the outer peripheral surface of the shaft and flat convex portions that abut on these flat surfaces are provided on the inner peripheral surface of the intermediate pipe. It is also possible to restrict rotation only by frictional resistance between the outer circumferential surface of each shaft and the inner circumferential surface of the intermediate pipe, without providing a special rotation restricting portion for restricting relative rotation between each shaft and the intermediate pipe.

[0059] Furthermore, in the above embodiment, the shaft connecting structure according to the present invention is employed in the relay shaft unit for fail-safe measures in a steer-by-wire steering device, but the application of the shaft connecting structure according to the present invention is not limited to this. For example, the shaft connecting structure according to the present invention may be applied to a steering device in which a steering shaft is connected to a steering gearbox so as to be able to transmit power at all times.

[0060] Furthermore, in the above embodiment, the shaft connection structure of the present invention is applied to a steering device of a vehicle, but the shaft connection structure of the present invention can also be applied to shaft connection portions of equipment other than steering devices. [Explanation of symbols]

[0061] 17,117...1st shaft (shaft) 18...Second shaft (shaft) 23...Male serration (rotation control part) 25...Intermediate pipe 26a, 26b...Slit 27...Connecting wall section 28...Regulation flange 30...Male serration (rotation control part) 33...Female serration (rotation control part) 34a, 34b… Chamfered part 40...Restraint pipe 125...Intermediate pipe section

Claims

1. A shaft connection structure that connects the ends of two shafts, Two of the shafts; an intermediate pipe having a slit along the axial direction and attached across the outer peripheral surfaces of the ends of one of the shafts and the other of the shafts; a restraining pipe that is press-fitted onto an outer peripheral surface of the intermediate pipe and restrains the intermediate pipe from the radially outer side; A shaft connecting structure comprising:

2. 2. The shaft connecting structure according to claim 1, wherein rotation restricting portions are provided on the outer peripheral surfaces of the ends of the two shafts and the inner peripheral surface of the intermediate pipe to restrict relative rotation therebetween.

3. The shaft connecting structure according to claim 2, characterized in that the rotation restricting portion is composed of male serrations formed on the outer peripheral surface of each of the shafts and female serrations formed on the inner peripheral surface of the intermediate pipe.

4. The shaft connection structure according to claim 1 or 2, characterized in that the slits are formed in the intermediate pipe in an area near one end in the axial direction where one of the shafts is inserted, and in an area near the other end in the axial direction where the other of the shafts is inserted, and a connecting wall portion without a slit is provided between the two slits.

5. The shaft connecting structure according to claim 1 or 2, characterized in that chamfered portions are provided on both circumferential edges of the outer surface of the intermediate pipe that sandwich the slit, along the extension direction of the slit.

6. the intermediate pipe is formed so that an outer diameter of a region on one end side in the axial direction is larger than an outer diameter of a region on the other end side in the axial direction, 3. The shaft connecting structure according to claim 1, wherein the restraining pipe has an inner diameter in a region on the one end side in the axial direction that is larger than an inner diameter in a region on the other end side in the axial direction.

7. 7. The shaft connecting structure according to claim 6, wherein a restricting flange is provided at an end portion on the one end side of the intermediate pipe so as to be able to abut against an end surface on the one end side of the restraining pipe.

8. A shaft connection structure that connects the ends of two shafts, Two of the shafts; an intermediate pipe portion that is integrally formed on one end of the shaft, has a slit along the axial direction, and is attached to an outer circumferential surface of the other end of the shaft; a restraining pipe that is press-fitted onto an outer peripheral surface of the intermediate pipe portion and restrains the intermediate pipe portion from the radially outer side; A shaft connecting structure comprising:

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