Manufacturing method of steering shaft

Abstract

To provide a method of manufacturing a steering shaft capable of suppressing deformation of a hollow shaft pressed in a pressed-in member.SOLUTION: A method of manufacturing a steering shaft is equipped with a press-in step of pressing a shaft in a pressed-in member by a jig 40. The shaft is equipped with an end surface 235, a first stepped surface 236, and a second stepped surface 237. The jig 40 is equipped with a base 41 facing the end surface 235, a first sleeve 45 facing the first stepped surface 236, a second sleeve 46 facing the second stepped surface 237, a first spring 47 disposed between the first sleeve 45 and the second sleeve 46, and a second spring 48 disposed between the second sleeve 46 and the base 41. In the press-in step, after the first sleeve 45 contacts with the first stepped surface 236, the second sleeve 46 contacts with the second stepped surface 237, and after the second sleeve 46 contacts with the second stepped surface 237, the base 41 contacts with the end surface 235.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present disclosure relates to a method for manufacturing a steering shaft. [Background technology]

[0002] A vehicle is provided with a steering device as a device for transmitting the operation of the steering wheel by the operator (driver) to the wheels. The steering device includes a steering gear for moving the wheels, and a plurality of steering shafts for transmitting the torque applied to the steering wheel to the steering gear. In order to absorb vibrations during driving or to be installed in the vehicle in a shortened state, the steering shafts may have a structure that allows them to expand and contract.

[0003] Patent Document 1 describes an example of a telescopic shaft. The telescopic shaft of Patent Document 1 includes an inner shaft having a male spline portion covered with a coating layer, and an outer tube having a female spline that meshes with the male spline portion. In order to reduce rattling when the male spline portion slides relative to the female spline, the inner shaft and the outer tube are connected in a state with a tightening margin (a state in which the outer tube tightens the inner shaft). On the other hand, it is desirable that the sliding resistance between the inner shaft and the outer tube is constant regardless of the relative positions of the inner shaft and the outer tube. However, if there is variation in the dimensions of the male spline portion or the female spline, the tightening margin between the inner shaft and the outer tube changes depending on the relative positions. If the rigidity of the male spline is high, the rate of change of the sliding resistance between the inner shaft and the outer tube with respect to the change in the tightening margin is likely to be large. In Patent Document 1, the inner shaft is a hollow member, so that the rate of change of the sliding resistance with respect to the change in the tightening margin can be reduced. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-145945 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the manufacturing process of steering shafts, the inner shaft is press-fitted into another member (a press-fit member). However, since the inner shaft is a hollow member, the periphery of the end face of the male spline portion to which the press-fit load is applied may be deformed. As a result, the yield rate of steering shafts decreases.

[0006] The present disclosure has been made in consideration of the above-mentioned problems, and has an object to provide a manufacturing method for a steering shaft that can suppress deformation of the hollow shaft that is press-fitted into a press-fitted member. [Means for solving the problem]

[0007] In order to achieve the above object, a manufacturing method of a steering shaft disclosed herein is a manufacturing method of a steering shaft including a hollow shaft and a press-fitted member into which the shaft is press-fitted, and includes a press-fitting step of press-fitting the shaft into the press-fitted member by a jig, the shaft includes an annular end face on the opposite side to the press-fitted member, an annular first step surface arranged on the press-fitted member side relative to the end face, and an annular second step surface arranged between the end face and the first step surface, and the jig presses a base surface facing the end face in the press-fitting step. the press-fitting step includes a first sleeve facing the first step surface in the press-fitting step, a second sleeve disposed between the base and the first sleeve and facing the second step surface in the press-fitting step, a first spring disposed between the first sleeve and the second sleeve, and a second spring disposed between the second sleeve and the base, wherein, in the press-fitting step, the first sleeve contacts the first step surface, and then the second sleeve contacts the second step surface, and the second sleeve contacts the second step surface, and then the base contacts the end surface.

[0008] As a result, the press-fit force applied to the jig is distributed and transmitted to three locations on the shaft (the first step surface, the second step surface, and the end face). Therefore, deformation of the periphery of the end face is suppressed compared to when the press-fit force is applied only to the end face. Therefore, the manufacturing method of the steering shaft disclosed herein can suppress deformation of the hollow shaft that is press-fitted into the press-fit member.

[0009] As a desirable aspect of the above-mentioned method for manufacturing a steering shaft, the jig has a cylindrical guide portion extending from the base toward the first sleeve, and in the press-fitting process, the shaft is inserted into the guide portion along the inner surface of the guide portion.

[0010] This reduces the possibility that the shaft will tilt relative to the jig during the press-fitting process. Therefore, the manufacturing method of the steering shaft disclosed herein can make the pressure distribution on the first step surface, the second step surface, and the end surface more uniform.

[0011] In a preferred embodiment of the above-mentioned method for manufacturing a steering shaft, the shaft includes a plurality of first teeth extending in an axial direction, and the guide portion includes a plurality of second teeth meshing with the plurality of first teeth.

[0012] This makes it possible to rotate the shaft by rotating the jig, and therefore the manufacturing method of the steering shaft according to the present disclosure makes it easy to adjust the relative angle between the shaft and the pressed-in member in the press-fitting step.

[0013] In a preferred embodiment of the above-mentioned method for manufacturing a steering shaft, the jig includes a shaft fixed to the base and passing through the second spring, the second sleeve, the first spring, and the first sleeve.

[0014] This makes it easy to arrange the second spring, the second sleeve, the first spring, and the first sleeve in a straight line. The manufacturing method of the steering shaft of the present disclosure can make the press-fitting step easier.

[0015] In a preferred embodiment of the above-mentioned method for manufacturing a steering shaft, the axle has a flange portion at a tip end, the flange portion having an outer diameter larger than an inner diameter of the first sleeve.

[0016] This prevents the second spring, the second sleeve, the first spring, and the first sleeve from coming off the base in the jig.The manufacturing method of the steering shaft of the present disclosure can make the press-fitting step easier.

[0017] As a desirable aspect of the above-mentioned steering shaft manufacturing method, the axle has a large diameter portion that penetrates the first sleeve and a small diameter portion that penetrates the second sleeve, and the outer diameter of the large diameter portion is larger than the inner diameter of the second sleeve.

[0018] This allows the second sleeve to be positioned by the step surface between the small diameter portion and the large diameter portion. Therefore, there are fewer restrictions on the length and spring constant of the first and second springs compared to when the second sleeve is positioned by balancing the elastic forces of the first and second springs. Therefore, the manufacturing method of the steering shaft disclosed herein makes it easier to adjust the load distribution among the three points of the shaft (the first step surface, the second step surface, and the end face).

[0019] As a desirable aspect of the above-mentioned manufacturing method of a steering shaft, the axial length of the large diameter portion is greater than the sum of the displacement of the first spring and the displacement of the second spring that occurs between the time when the first sleeve contacts the first step surface and the time when the base contacts the end surface.

[0020] As a result, when the base comes into contact with the end surface, the first sleeve overlaps the large diameter portion. Therefore, the first sleeve does not come off the large diameter portion. The manufacturing method of the steering shaft disclosed herein can reduce the possibility of the first sleeve rattling during the press-fitting process. Effect of the Invention

[0021] The method for manufacturing a steering shaft according to the present disclosure can suppress deformation of the hollow shaft that is press-fitted into the press-fit member. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic diagram of a steering device according to an embodiment. [Diagram 2] FIG. 2 is a perspective view of the steering device according to the embodiment. [Diagram 3] FIG. 3 is a cross-sectional view of an intermediate shaft according to an embodiment. [Figure 4] FIG. 4 is a cross-sectional view of a jig used in manufacturing the steering shaft of this embodiment. [Diagram 5] FIG. 5 is an exploded perspective view of the jig of the present embodiment. [Figure 6] FIG. 6 is an exploded perspective view of the jig and the inner shaft of the present embodiment. [Figure 7] FIG. 7 is a cross-sectional view of the jig and the inner shaft in the press-fitting step of the present embodiment. [Figure 8] FIG. 8 is a cross-sectional view of the jig and the inner shaft in the press-fitting step of the present embodiment. [Figure 9] FIG. 9 is a cross-sectional view of the jig and the inner shaft in the press-fitting step of the present embodiment. [Figure 10] FIG. 10 is a cross-sectional view of the jig and the inner shaft in the press-fitting step of the present embodiment. [Figure 11] FIG. 11 is a cross-sectional view of a jig used in manufacturing the steering shaft of the modified example. [Figure 12] FIG. 12 is an exploded perspective view of a jig according to a modified example. [Figure 13] FIG. 13 is an exploded perspective view of a jig and an inner shaft of a modified example. [Figure 14] FIG. 14 is a cross-sectional view of the jig and the inner shaft in a press-fitting step of the modified example. [Figure 15]FIG. 15 is a cross-sectional view of the jig and the inner shaft in a press-fitting step of the modified example. [Figure 16] FIG. 16 is a cross-sectional view of the jig and the inner shaft in a press-fitting step of the modified example. [Figure 17] FIG. 17 is a cross-sectional view of the jig and the inner shaft in a press-fitting step of the modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The present invention will be described in detail below with reference to the drawings. Note that the present invention is not limited to the following modes for carrying out the invention (hereinafter, referred to as embodiments). Furthermore, the components in the following embodiments include those that a person skilled in the art can easily imagine, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the components disclosed in the following embodiments can be appropriately combined.

[0024] (Embodiment) Fig. 1 is a schematic diagram of a steering device of an embodiment. Fig. 2 is a perspective view of the steering device of the embodiment. As shown in Fig. 1, a steering device 80 includes a steering wheel 81, a steering shaft 100, and a steering force assist mechanism 83.

[0025] 1, the steering shaft 100 includes a first shaft 82, a first universal joint 84, a second shaft 85, and a second universal joint 86. The first shaft 82 includes an input shaft 82a and an output shaft 82b. One end of the input shaft 82a is connected to the steering wheel 81. The other end of the input shaft 82a is connected to the output shaft 82b. One end of the output shaft 82b is connected to the input shaft 82a. The other end of the output shaft 82b is connected to the first universal joint 84.

[0026] As shown in FIG. 1 , one end of the second shaft 85 is connected to the first universal joint 84. The other end of the second shaft 85 is connected to the second universal joint 86. The second shaft 85 is also called an intermediate shaft. One end of the pinion shaft 87 is connected to the second universal joint 86. The other end of the pinion shaft 87 is connected to a steering gear 88. The first universal joint 84 and the second universal joint 86 are, for example, Cardan joints. The rotation of the first shaft 82 is transmitted to the pinion shaft 87 via the second shaft 85. The second universal joint 86 is connected to the pinion shaft 87.

[0027] As shown in Fig. 1, the steering gear 88 includes a pinion 88a and a rack 88b. The pinion 88a is connected to a pinion shaft 87. The rack 88b meshes with the pinion 88a. The steering gear 88 converts the rotational motion transmitted to the pinion 88a into linear motion by the rack 88b. The rack 88b is connected to a tie rod 89. The angle of the wheels changes as the rack 88b moves.

[0028] As shown in Fig. 1, the steering force assist mechanism 83 includes a reduction gear 92 and an electric motor 93. The reduction gear 92 is, for example, a worm reduction gear. Torque generated by the electric motor 93 is transmitted to a worm wheel via a worm inside the reduction gear 92, causing the worm wheel to rotate. The reduction gear 92 increases the torque generated by the electric motor 93 by means of the worm and the worm wheel. The reduction gear 92 applies an auxiliary steering torque to the output shaft 82b. That is, the steering device 80 is of a column assist type.

[0029] As shown in Fig. 1, the steering device 80 includes an ECU (Electronic Control Unit) 90, a torque sensor 94, and a vehicle speed sensor 95. The electric motor 93, the torque sensor 94, and the vehicle speed sensor 95 are electrically connected to the ECU 90. The torque sensor 94 outputs the steering torque transmitted to the input shaft 82a to the ECU 90 through CAN (Controller Area Network) communication. The vehicle speed sensor 95 detects the traveling speed (vehicle speed) of a vehicle body on which the steering device 80 is mounted. The vehicle speed sensor 95 is provided on the vehicle body, and outputs the vehicle speed to the ECU 90 through CAN communication.

[0030] The ECU 90 controls the operation of the electric motor 93. The ECU 90 acquires signals from a torque sensor 94 and a vehicle speed sensor 95. When an ignition switch 98 is on, the ECU 90 is supplied with power from a power supply device 99 (e.g., an on-board battery). The ECU 90 calculates an auxiliary steering command value based on the steering torque and the vehicle speed. The ECU 90 adjusts the value of power supplied to the electric motor 93 based on the auxiliary steering command value. The ECU 90 acquires information on an induced voltage from the electric motor 93 or information output from a resolver or the like provided in the electric motor 93. The force required to operate the steering wheel 81 is reduced by the ECU 90 controlling the electric motor 93.

[0031] FIG. 3 is a cross-sectional view of an intermediate shaft of an embodiment. As shown in FIG. 3, the second shaft 85 includes an outer tube 10 and an inner shaft 20. The outer tube 10 is a hollow member made of metal. The outer tube 10 is substantially cylindrical. The outer tube 10 is connected to a second universal joint 86. The inner shaft 20 is a hollow member made of metal. The inner shaft 20 is substantially cylindrical. The inner shaft 20 is connected to a first universal joint 84. The outer tube 10 and the inner shaft 20 are relatively movable in the axial direction. This absorbs vibrations during vehicle travel. In addition, the second shaft 85 can be assembled into the vehicle in a contracted state.

[0032] In the following description, the direction along the rotation axis Z of the second shaft 85 is simply described as the axial direction. The direction along the line that passes through the center of the rotation axis Z and is perpendicular to the axial direction is simply described as the radial direction. The radial direction is also called the radial direction. The direction along the circumference centered on the rotation axis Z is simply described as the circumferential direction. The circumferential direction can also be said to be the tangent direction of the circle centered on the rotation axis Z. In addition, the direction from the first universal joint 84 to the second universal joint 86 is simply described as the forward direction. The forward direction is the left direction in FIG. 3. The direction from the second universal joint 86 to the first universal joint 84 is simply described as the rearward direction. The rearward direction is the rightward direction in FIG. 3.

[0033] As shown in FIG. 3, the outer tube 10 includes a main body portion 11 and a female spline portion 13. The main body portion 11 is connected to the second universal joint 86. The outer diameter of the main body portion 11 decreases toward the rear. The female spline portion 13 is disposed rearward of the main body portion 11. The outer diameter of the female spline portion 13 is approximately constant. The female spline portion 13 includes a plurality of teeth 131 on its inner circumferential surface. The teeth 131 extend in the axial direction. The plurality of teeth 131 are disposed at equal intervals in the circumferential direction.

[0034] As shown in FIG. 3, the inner shaft 20 includes a main body 21 and a male spline portion 23. The main body 21 is connected to a first universal joint 84. The main body 21 is press-fitted into a yoke 841 of the first universal joint 84. The outer diameter of the main body 21 is substantially constant. The male spline portion 23 is disposed in front of the main body 21. The outer diameter of the male spline portion 23 is larger than the outer diameter of the main body 21 and is substantially constant. The outer peripheral surface of the male spline portion 23 is resin-coated. The male spline portion 23 is inserted into the female spline portion 13 and fitted into the female spline portion 13. The male spline portion 23 is connected to the female spline portion 13 with a tightening margin. The state with a tightening margin means a state in which the outer diameter of the male spline portion 23 before connection is larger than the inner diameter of the female spline portion 13. In other words, the male spline portion 23 is press-fitted into the female spline portion 13. This reduces rattling when the male spline portion 23 slides relative to the female spline portion 13. A lubricant is disposed between the male spline portion 23 and the female spline portion 13. The lubricant is, for example, grease.

[0035] As shown in FIG. 3, the male spline portion 23 includes a thin portion 232, a thick portion 231, a plurality of teeth 230, an end surface 235, a first step surface 236, and a second step surface 237. The thin portion 232 is disposed at the front end of the female spline portion 13. The outer diameter and inner diameter of the thin portion 232 are substantially constant. The thick portion 231 is disposed rearward of the thin portion 232. The outer diameter and inner diameter of the thick portion 231 are substantially constant. The outer diameter of the thick portion 231 is the same as the outer diameter of the thin portion 232. The inner diameter of the thick portion 231 is smaller than the inner diameter of the thin portion 232. The plurality of teeth 230 are provided on the outer peripheral surfaces of the thin portion 232 and the thick portion 231. The teeth 230 extend in the axial direction. The plurality of teeth 230 are disposed at equal intervals in the circumferential direction. The teeth 230 mesh with the teeth 131 of the outer tube 10. The teeth 230 are, for example, serrations.

[0036] The end face 235 is an end face facing forward at the front end of the thin-walled portion 232. The end face 235 can also be said to be an end face of the inner shaft 20 on the opposite side to the yoke 841. The end face 235 is annular about the rotation axis Z. The first step surface 236 is a part of the inner circumferential surface of the male spline portion 23. The first step surface 236 is disposed rearward (on the yoke 841 side) with respect to the end face 235. The first step surface 236 is annular about the rotation axis Z. In a cross section including the rotation axis Z, the first step surface 236 is inclined with respect to the rotation axis Z. The diameter of the first step surface 236 becomes smaller toward the rear (on the yoke 841 side). The second step surface 237 is a part of the inner circumferential surface of the male spline portion 23. The second step surface 237 is disposed between the end face 235 and the first step surface 236. The second step surface 237 is annular about the rotation axis Z. In a cross section including the rotation axis Z, the second step surface 237 is inclined with respect to the rotation axis Z. The diameter of the second step surface 237 decreases toward the rear (first step surface 236 side). The maximum diameter of the second step surface 237 is larger than the maximum diameter of the first step surface 236 and smaller than the maximum diameter of the end surface 235.

[0037] When the dimensions of the male spline portion 23 or the female spline 13 vary, the interference between the inner shaft 20 and the outer tube 10 may change depending on the relative position. When the male spline 23 is, for example, a solid member with high rigidity, the rate of change in the sliding resistance between the inner shaft 20 and the outer tube 10 with respect to the change in the interference is likely to be large. In contrast, the inner shaft 20 of this embodiment is a hollow member, and therefore the rigidity is easily reduced. As a result, the steering shaft 100 of this embodiment can reduce the rate of change in the sliding resistance with respect to the change in the interference. On the other hand, when the inner shaft 20 is press-fitted into the yoke 841 of the first universal joint 84, the inner shaft 20, which is a hollow member, may be deformed. For example, the thin-walled portion 232 may be deformed. For this reason, a method for manufacturing a steering shaft that can simultaneously reduce the rigidity of the inner shaft 20 and suppress the deformation when the inner shaft 20 is press-fitted into the yoke 841 is required.

[0038] Fig. 4 is a cross-sectional view of a jig used in manufacturing the steering shaft of this embodiment, Fig. 5 is an exploded perspective view of the jig of this embodiment, and Fig. 6 is an exploded perspective view of the jig and inner shaft of this embodiment.

[0039] As described above, when manufacturing the steering shaft 100, the inner shaft 20 is press-fitted into the yoke 841 of the first universal joint 84. The manufacturing method of the steering shaft 100 of this embodiment includes a press-fitting step of press-fitting the second shaft 85 into the yoke 841. In the press-fitting step, a jig 40 shown in FIG. 4 is used. As shown in FIG. 4, the jig 40 includes a base 41, a guide portion 42, a shaft 43, a first sleeve 45, a second sleeve 46, a first spring 47, and a second spring 48.

[0040] 4, the base 41 is a cylindrical member. The base 41 has a screw thread on its inner circumferential surface. That is, the hole in the base 41 is an internal thread. The base 41 has a third pressing surface 411 that faces the end surface 235 of the inner shaft 20 in the press-fitting process.

[0041] The guide portion 42 is a cylindrical member extending from the base 41. The guide portion 42 is formed integrally with the base 41. The guide portion 42 has an opening at the end opposite the base 41, into which the inner shaft 20 is inserted. The guide portion 42 has a plurality of teeth 420 on its inner circumferential surface. The plurality of teeth 420 are, for example, serrations. When the inner shaft 20 is inserted into the guide portion 42 in the press-fitting process, the plurality of teeth 420 mesh with the plurality of teeth 230 of the male spline portion 23.

[0042] The axle 43 is a rod fixed to the base 41. The axle 43 passes through the second spring 48, the second sleeve 46, the first spring 47, and the first sleeve 45. The axle 43 includes a large diameter portion 431, a small diameter portion 433, a fixing portion 435, and a flange portion 437. The large diameter portion 431 is cylindrical and passes through the first spring 47 and the first sleeve 45. The small diameter portion 433 is disposed on the base 41 side of the large diameter portion 431. The small diameter portion 433 is cylindrical and has an outer diameter smaller than the outer diameter of the large diameter portion 431. There is a step between the small diameter portion 433 and the large diameter portion 431. The small diameter portion 433 passes through the second spring 48 and the second sleeve 46. The fixing portion 435 is disposed on the base 41 side of the small diameter portion 433. The fixing portion 435 includes a screw thread on its outer circumferential surface. That is, the fixing portion 435 is a male screw. The fixing portion 435 is attached to a hole (female screw) in the base 41. The flange portion 437 is disposed at the end opposite the base 41. The outer diameter of the flange portion 437 is larger than the outer diameter of the large diameter portion 431. The outer diameter of the flange portion 437 is equal to or smaller than the inner diameter of the main body portion 21 of the inner shaft 20.

[0043] The first sleeve 45 is a cylindrical member. The inner diameter of the first sleeve 45 is equal to or larger than the outer diameter of the large diameter portion 431 and smaller than the outer diameter of the flange portion 437. The first sleeve 45 contacts the flange portion 437. The first sleeve 45 has a first pressing surface 451 that faces the first step surface 236 of the inner shaft 20 in the press-fitting process. The first pressing surface 451 is annular about the central axis C of the base 41. In a cross section including the central axis C, the first pressing surface 451 is inclined with respect to the central axis C. Specifically, it is desirable that the angle that the first pressing surface 451 makes with the central axis C in the cross section including the central axis C is 15° or more and 30° or less. The diameter of the first pressing surface 451 becomes smaller as it moves away from the base 41. In a state in which the inner shaft 20 is inserted into the guide portion 42 in the press-fitting process, the central axis C substantially coincides with the rotation axis Z. In a state in which the central axis C coincides with the rotation axis Z, the first pressing surface 451 becomes parallel to the first step surface 236 .

[0044] The second sleeve 46 is a cylindrical member. The inner diameter of the second sleeve 46 is equal to or larger than the outer diameter of the small diameter portion 433 and smaller than the outer diameter of the large diameter portion 431. The second sleeve 46 contacts the step surface between the small diameter portion 433 and the large diameter portion 431. The second sleeve 46 has a second pressing surface 461 that faces the second step surface 237 of the inner shaft 20 in the press-fitting process. The second pressing surface 461 is annular about the central axis C. In a cross section including the central axis C, the second pressing surface 461 is inclined with respect to the central axis C. Specifically, the angle that the second pressing surface 461 makes with the central axis C in a cross section including the central axis C is preferably 15° or more and 30° or less. The diameter of the second pressing surface 461 becomes smaller as it moves away from the base 41. When the central axis C coincides with the rotation axis Z, the second pressing surface 461 is parallel to the second step surface 237 .

[0045] The first spring 47 is disposed between the first sleeve 45 and the second sleeve 46. One end of the first spring 47 contacts the first sleeve 45. The other end of the first spring 47 contacts the second sleeve 46.

[0046] The second spring 48 is disposed between the second sleeve 46 and the base 41. One end of the second spring 48 contacts the second sleeve 46. More specifically, one end of the second spring 48 fits into a recess provided in the surface of the second sleeve 46 on the base 41 side. The other end of the second spring 48 contacts the base 41. More specifically, the other end of the second spring 48 fits into a recess provided in the surface of the base 41 on the second sleeve 46 side.

[0047] 7 to 10 are cross-sectional views of the jig and the inner shaft in the press-fitting process of this embodiment. As shown in FIG. 7, in the press-fitting process, the male spline portion 23 of the inner shaft 20 is inserted into the guide portion 42 of the jig 40. The male spline portion 23 enters the inside of the guide portion 42 while being guided by the inner circumferential surface of the guide portion 42. The teeth 230 of the male spline portion 23 mesh with the teeth 420 of the guide portion 42. The first sleeve 45 passes through the thin portion 232 and enters the inside of the thick portion 231. The second sleeve 46 enters the inside of the thin portion 232.

[0048] When the male spline portion 23 is further inserted into the guide portion 42 from the state shown in FIG. 7, the first pressing surface 451 of the first sleeve 45 comes into contact with the first step surface 236 as shown in FIG. 8. This causes the press-fitting force applied to the jig 40 to be transmitted to the inner shaft 20 via the first pressing surface 451. In addition, the first pressing surface 451 comes into contact with the first step surface 236, making it difficult for the central axis C of the jig 40 to deviate from the rotation axis Z of the inner shaft 20. Thereafter, the flange portion 437 and the large diameter portion 431 enter the inside of the main body portion 21 of the inner shaft 20. The first spring 47 sandwiched between the first sleeve 45 and the second sleeve 46 begins to contract.

[0049] When the male spline portion 23 is further inserted into the guide portion 42 from the state shown in FIG. 8, the second pressing surface 461 of the second sleeve 46 comes into contact with the second step surface 237 as shown in FIG. 9. This causes the pressurizing force applied to the jig 40 to be transmitted to the inner shaft 20 via the second pressing surface 461. In addition, the second pressing surface 461 comes into contact with the second step surface 237, making it more difficult for the central axis C of the jig 40 to deviate from the rotation axis Z of the inner shaft 20. The first pressing surface 451 comes into contact with the first step surface 236 and the second pressing surface 461 comes into contact with the second step surface 237, making it more difficult for the central axis C to tilt with respect to the rotation axis Z. Thereafter, the second spring 48 sandwiched between the second sleeve 46 and the base 41 begins to contract.

[0050] When the male spline portion 23 is further inserted into the guide portion 42 from the state shown in Fig. 9, the third pressing surface 411 of the base 41 comes into contact with the end surface 235, as shown in Fig. 10. As a result, the press-fitting force applied to the jig 40 is transmitted to the inner shaft 20 via the first pressing surface 451, the second pressing surface 461, and the third pressing surface 411.

[0051] Specifically, the elastic force generated in the first spring 47 in the state of Fig. 9 (the maximum elastic force of the first spring 47) is smaller than the elastic force generated in the second spring 48 in the state of Fig. 10 (the maximum elastic force of the second spring 48). In addition, the press-fitting force applied to the jig 40 is larger than the sum of the maximum elastic force of the first spring 47 and the maximum elastic force of the second spring 48. As a result, the press-fitting force applied to the jig 40 is distributed and transmitted to three locations (the first step surface 236, the second step surface 237, and the end surface 235) of the inner shaft 20.

[0052] 10, the axial length of the large diameter portion 431 is greater than the sum of the displacements of the first spring 47 and the second spring 48 that occur from when the first pressing surface 451 comes into contact with the first step surface 236 until when the third pressing surface 411 comes into contact with the end surface 235. Therefore, as shown in FIG. 10, the first sleeve 45 overlaps the large diameter portion 431 at the point in time when the third pressing surface 411 comes into contact with the end surface 235. The first sleeve 45 does not come off the large diameter portion 431.

[0053] The manufacturing method of the steering shaft of this embodiment does not necessarily have to be applied to the assembly of the inner shaft 20 and the yoke 841. The manufacturing method of the steering shaft of this embodiment can be widely applied to the manufacture of a steering shaft including a hollow shaft and a press-fitted member into which the shaft is press-fitted. The inner shaft 20 is merely one example of a shaft, and the yoke 841 is merely one example of a press-fitted member. For example, the press-fitted member may be a torsion bar or the like.

[0054] The mandrel 43 of the jig 40 does not necessarily have to include the large diameter portion 431 and the small diameter portion 433. For example, in the mandrel 43, the diameter of the portion that holds the second sleeve 46 may be the same as the diameter of the portion that holds the first sleeve 45. Furthermore, the jig 40 does not necessarily have to include the mandrel 43. For example, the first sleeve 45, the first spring 47, the second sleeve 46, and the second spring 48 may be housed in the guide portion 42.

[0055] As described above, the manufacturing method of the steering shaft of this embodiment is a manufacturing method of the steering shaft 100 including a hollow shaft (inner shaft 20) and a press-fitted member (yoke 841) into which the shaft is press-fitted. The manufacturing method of the steering shaft of this embodiment includes a press-fitting step of press-fitting the shaft into the press-fitted member by a jig 40. The shaft includes an annular end face 235 on the opposite side to the press-fitted member, an annular first step surface 236 disposed on the press-fitted member side relative to the end face 235, and an annular second step surface 237 disposed between the end face 235 and the first step surface 236. The jig 40 includes a base 41, a first sleeve 45, a second sleeve 46, a first spring 47, and a second spring 48. The base 41 faces the end face 235 in the press-fitting step. The first sleeve 45 faces the first step surface 236 in the press-fitting step. The second sleeve 46 is disposed between the base 41 and the first sleeve 45, and faces the second step surface 237 in the press-fitting process. The first spring 47 is disposed between the first sleeve 45 and the second sleeve 46. The second spring 48 is disposed between the second sleeve 46 and the base 41. In the press-fitting process, the first sleeve 45 contacts the first step surface 236, and then the second sleeve 46 contacts the second step surface 237, and then the second sleeve 46 contacts the second step surface 237, and then the base 41 contacts the end surface 235.

[0056] As a result, the press-in force applied to the jig 40 is distributed and transmitted to three locations (the first step surface 236, the second step surface 237, and the end surface 235) of the shaft (inner shaft 20). Therefore, compared with the case where the press-in force is applied only to the end surface 235, deformation of the periphery of the end surface 235 is suppressed. Therefore, the manufacturing method of the steering shaft of this embodiment can suppress deformation of the hollow shaft pressed into the press-in member. Note that if the natural length of the first spring 47 is shorter than the length from the first step surface 236 to the second step surface 237, the second sleeve 46 can contact the second step surface 237 first in the press-in process. However, since the natural length of the first spring 47 is shorter than the length from the first step surface 236 to the second step surface 237, the first sleeve 45 cannot contact the first step surface 236 after the second sleeve 46 contacts the second step surface 237. If the second sleeve 46 comes into contact with the second step surface 237 and then the first sleeve 45 comes into contact with the first step surface 236, deformation of the peripheral portion of the end surface 235 is difficult to suppress.

[0057] In the manufacturing method of the steering shaft of this embodiment, a jig 40 includes a cylindrical guide portion 42 extending from a base 41 toward a first sleeve 45. In a press-fitting step, the shaft (inner shaft 20) is inserted into the guide portion 42 along the inner circumferential surface of the guide portion 42.

[0058] This reduces the possibility that the shaft (inner shaft 20) will be tilted relative to the jig 40 during the press-fitting process. Therefore, the manufacturing method for a steering shaft of the present embodiment can make the pressure distribution on each of the first step surface 236, the second step surface 237, and the end surface 235 more uniform.

[0059] In the method for manufacturing a steering shaft of this embodiment, the shaft (inner shaft 20) has a plurality of first teeth (teeth 230) extending in the axial direction. The guide portion 42 has a plurality of second teeth (teeth 420) that mesh with the plurality of first teeth (teeth 230).

[0060] This makes it possible to rotate the shaft (the inner shaft 20) by rotating the jig 40. Therefore, the manufacturing method for a steering shaft of this embodiment makes it possible to easily adjust the relative angle between the shaft (the inner shaft 20) and the pressed-in member (the yoke 841) in the press-in process.

[0061] In the manufacturing method of the steering shaft of this embodiment, a jig 40 is fixed to a base 41 and includes a shaft 43 that passes through a second spring 48 , a second sleeve 46 , a first spring 47 and a first sleeve 45 .

[0062] This makes it easy to arrange the second spring 48, the second sleeve 46, the first spring 47, and the first sleeve 45 in a straight line. The manufacturing method of the steering shaft of the present embodiment can make the press-fitting process easier.

[0063] In the manufacturing method of the steering shaft of this embodiment, the axle 43 is provided with a flange portion 437 having an outer diameter larger than the inner diameter of the first sleeve 45 at the tip end.

[0064] This prevents the second spring 48, the second sleeve 46, the first spring 47, and the first sleeve 45 from coming off the base 41 in the jig 40. The manufacturing method of the steering shaft of the present embodiment can make the press-fitting process easier.

[0065] In the manufacturing method of the steering shaft of this embodiment, the axle 43 has a large diameter portion 431 that penetrates the first sleeve 45 and a small diameter portion 433 that penetrates the second sleeve 46. The outer diameter of the large diameter portion 431 is larger than the inner diameter of the second sleeve 46.

[0066] This makes it possible to position the second sleeve 46 by the step surface between the small diameter portion 433 and the large diameter portion 431. Therefore, there are fewer restrictions on the length and spring constant of the first spring 47 and the second spring 48, compared to the case where the second sleeve 46 is positioned by balancing the elastic forces of the first spring 47 and the second spring 48. Therefore, the manufacturing method of the steering shaft of this embodiment makes it easier to adjust the load distribution at three points (first step surface 236, second step surface 237, and end surface 235) of the shaft (inner shaft 20).

[0067] In the manufacturing method of the steering shaft of this embodiment, the axial length of the large diameter portion 431 is greater than the sum of the displacement of the first spring 47 and the displacement of the second spring 48 that occurs between the time when the first sleeve 45 contacts the first step surface 236 and the time when the base 41 contacts the end face 235.

[0068] As a result, when the base 41 comes into contact with the end face 235, the first sleeve 45 overlaps the large diameter portion 431. Therefore, the first sleeve 45 does not come off the large diameter portion 431. The manufacturing method of the steering shaft of this embodiment can reduce the possibility that the first sleeve 45 will rattle in the press-fitting process.

[0069] (Modification) Fig. 11 is a cross-sectional view of a jig used in manufacturing a steering shaft of a modified example. Fig. 12 is an exploded perspective view of the jig of the modified example. Fig. 13 is an exploded perspective view of the jig and inner shaft of the modified example. Note that the same components as those described in the above-mentioned embodiment are given the same reference numerals and duplicated descriptions will be omitted.

[0070] As shown in FIG. 12, the inner shaft 30 is hollow and includes a main body portion 31, a male spline portion 33, and a protrusion portion 35. The main body portion 31 is connected to the first universal joint 84. The main body portion 31 is press-fitted into a yoke 841 of the first universal joint 84. The outer diameter of the main body portion 31 is approximately constant. The male spline portion 33 is disposed in front of the main body portion 31. The outer diameter of the male spline portion 33 is larger than the outer diameter of the main body portion 31 and is approximately constant. The outer peripheral surface of the male spline portion 33 is resin-coated. The male spline portion 33 is inserted into the female spline portion 13 (see FIG. 3) and fitted into the female spline portion 13. The male spline portion 33 is connected to the female spline portion 13 with a tightening margin. A lubricant is disposed between the male spline portion 33 and the female spline portion 13. The lubricant is, for example, grease.

[0071] 12, the protruding portion 35 protrudes forward from the male spline portion 33. The protruding portion 35 includes an end face 355, a first step surface 356, and a second step surface 357.

[0072] The end surface 355 is an end surface facing forward at the front end of the protruding portion 35. The end surface 355 can also be said to be an end surface of the inner shaft 30 on the opposite side to the yoke 841. The end surface 355 is annular about the rotation axis Z. The first step surface 356 is a part of the outer circumferential surface of the protruding portion 35. The first step surface 356 is disposed rearward (on the yoke 841 side) with respect to the end surface 355. The first step surface 356 is annular about the rotation axis Z. In a cross section including the rotation axis Z, the first step surface 356 is perpendicular to the rotation axis Z. The second step surface 357 is a part of the outer circumferential surface of the protruding portion 35. The second step surface 357 is disposed between the end surface 355 and the first step surface 356. The second step surface 357 is annular about the rotation axis Z. In a cross section including the rotation axis Z, the second step surface 357 is perpendicular to the rotation axis Z. The maximum diameter of the second step surface 357 is smaller than the maximum diameter of the first step surface 356 and is larger than the maximum diameter of the end surface 355 .

[0073] As shown in FIG. 11, the jig 60 includes a base 61, a guide portion 62, a first sleeve 65, a second sleeve 66, a first spring 67, and a second spring 68.

[0074] 11, the base 61 is a cylindrical member. The base 61 has a screw thread on its inner circumferential surface. That is, the hole in the base 61 is an internal thread. The base 61 has a third pressing surface 611 that faces the end surface 355 of the inner shaft 20 in the press-fitting process.

[0075] The guide portion 62 is a cylindrical member extending from the base 61. The guide portion 62 is formed integrally with the base 61. The guide portion 62 has an opening at the end opposite the base 61, into which the inner shaft 30 is inserted.

[0076] The first sleeve 65 is a cylindrical member. The first sleeve 65 has a first pressing surface 651 that faces the first step surface 356 of the inner shaft 30 in the press-fitting process. The first pressing surface 651 is annular about the central axis C of the base 61. In a cross section including the central axis C, the first pressing surface 651 is perpendicular to the central axis C.

[0077] The second sleeve 66 is a cylindrical member. The second sleeve 66 has a second pressing surface 661 that faces the second step surface 357 of the inner shaft 30 in the press-fitting process. The second pressing surface 661 is annular about the central axis C. In a cross section including the central axis C, the second pressing surface 661 is perpendicular to the central axis C.

[0078] The first spring 67 is disposed between the first sleeve 65 and the second sleeve 66. One end of the first spring 67 contacts the first sleeve 65. The other end of the first spring 67 contacts the second sleeve 66.

[0079] The second spring 68 is disposed between the second sleeve 66 and the base 61. One end of the second spring 68 contacts the second sleeve 66. More specifically, one end of the second spring 68 fits into a recess provided in the surface of the second sleeve 66 on the base 61 side. The other end of the second spring 68 contacts the base 61. More specifically, the other end of the second spring 68 fits into a recess provided in the surface of the base 61 on the second sleeve 66 side.

[0080] 14 to 17 are cross-sectional views of the jig and the inner shaft in the press-fitting step of the modified example. As shown in Fig. 14, in the press-fitting step, the inner shaft 30 is inserted into the guide portion 62 of the jig 60. The inner shaft 30 enters the inside of the guide portion 62 while being guided by the inner circumferential surface of the guide portion 62.

[0081] When the inner shaft 30 is further inserted into the guide portion 62 from the state shown in Fig. 14, the first pressing surface 651 of the first sleeve 65 comes into contact with the first step surface 356, as shown in Fig. 15. This causes the press-fitting force applied to the jig 60 to be transmitted to the inner shaft 30 via the first pressing surface 651. After that, the first spring 67 sandwiched between the first sleeve 65 and the second sleeve 66 begins to compress.

[0082] When the inner shaft 30 is further inserted into the guide portion 62 from the state shown in Fig. 15, the second pressing surface 661 of the second sleeve 66 comes into contact with the second step surface 357, as shown in Fig. 16. This causes the press-fitting force applied to the jig 60 to be transmitted to the inner shaft 30 via the second pressing surface 661. After that, the second spring 68 sandwiched between the second sleeve 66 and the base 61 begins to compress.

[0083] 16, the third pressing surface 611 of the base 61 comes into contact with the end surface 355, as shown in Fig. 17. This causes the pressurizing force applied to the jig 60 to be transmitted to the inner shaft 30 via the first pressing surface 651, the second pressing surface 661, and the third pressing surface 611.

[0084] Specifically, the elastic force (maximum elastic force of the first spring 67) generated in the state of FIG. 16 is smaller than the elastic force (maximum elastic force of the second spring 68) generated in the state of FIG. 17. Also, the press-fitting force applied to the jig 60 is larger than the sum of the maximum elastic force of the first spring 67 and the maximum elastic force of the second spring 68. As a result, the press-fitting force applied to the jig 60 is distributed and transmitted to three locations (the first step surface 356, the second step surface 357, and the end surface 355) of the inner shaft 30. As a result, deformation of the periphery of the end surface 355 is suppressed compared to the case where the press-fitting force is applied only to the end surface 355. [Explanation of symbols]

[0085] 10 Outer tube 11 Main body 13 Female spline part 20 Inner shaft 21 Main body 23 Male spline part 30 Inner shaft 31 Main body 33 Male spline part 35 Protrusion 40 Jig 41 Base 42 Guide section 43 Mandrel 45 1st Sleeve 46 Second Sleeve 47 First Spring 48 2nd Spring 60 Jig 61 Base 62 Guide part 65 First Sleeve 66 Second Sleeve 67 First Spring 68 2nd Spring 80 Steering device 81 Steering Wheel 82 1st Shaft 82a Input shaft 82b Output shaft 83 Steering force assist mechanism 85 Second Shaft (Shaft) 87 Pinion shaft 88 Steering gear 88a Pinion 88b Rack 89 Tie rod 90 ECU 92 Reducer 93 Electric Motor 94 Torque Sensor 95 Vehicle speed sensor 98 Ignition Switch 99 Power supply 100 Steering shaft 131 teeth 230 teeth 231 Thick wall part 232 Thin section 235 End face 236 1st step surface 237 2nd step surface 355 End face 356 1st step surface 357 2nd step surface 411 Third pressing surface 420 teeth 431 Large diameter section 433 Small diameter section 435 Fixed part 437 Flange 451 First pressing surface 461 Second pressing surface 611 Third pressing surface 651 First pressing surface 661 Second pressing surface 841 Yoke (Pressed-in component) C center axis Z Rotation Axis

Claims

1. A method for manufacturing a steering shaft including a hollow shaft and a press-fit member into which the shaft is press-fitted, comprising the steps of: a press-fitting step of press-fitting the shaft into the press-fit member using a jig; The shaft is an annular end surface on the opposite side to the press-fit member; a first annular step surface disposed on the side of the press-fit member relative to the end surface; an annular second step surface disposed between the end surface and the first step surface; Equipped with The jig is a base facing the end surface in the press-fitting step; a first sleeve facing the first step surface in the press-fitting step; a second sleeve disposed between the base and the first sleeve and facing the second step surface in the press-fitting step; a first spring disposed between the first sleeve and the second sleeve; a second spring disposed between the second sleeve and the base; Equipped with In the press-fitting step, the first sleeve comes into contact with the first step surface, and then the second sleeve comes into contact with the second step surface, and the second sleeve comes into contact with the second step surface, and then the base comes into contact with the end surface. A method for manufacturing a steering shaft.

2. The jig includes a cylindrical guide portion extending from the base toward the first sleeve, In the press-fitting step, the shaft is inserted into the guide portion along an inner peripheral surface of the guide portion. A method for manufacturing a steering shaft according to claim 1.

3. The shaft includes a first plurality of teeth extending axially therefrom; The guide portion includes a plurality of second teeth that mesh with the plurality of first teeth. The method for manufacturing a steering shaft according to claim 2 .

4. The jig is fixed to the base and includes a mandrel passing through the second spring, the second sleeve, the first spring, and the first sleeve. A method for manufacturing a steering shaft according to any one of claims 1 to 3.

5. The mandrel has a flange portion at its tip, the flange portion having an outer diameter larger than the inner diameter of the first sleeve. The method for manufacturing a steering shaft according to claim 4.

6. The mandrel includes a large diameter portion that passes through the first sleeve and a small diameter portion that passes through the second sleeve, The outer diameter of the large diameter portion is larger than the inner diameter of the second sleeve. The method for manufacturing a steering shaft according to claim 4 or 5.

7. The axial length of the large diameter portion is greater than the sum of the displacement of the first spring and the displacement of the second spring that occurs from when the first sleeve comes into contact with the first step surface until when the base comes into contact with the end surface. The method for manufacturing a steering shaft according to claim 6.

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