JP6897184B2 - Outer tube and its manufacturing method - Google Patents

Description

The present invention relates to an outer tube constituting an intermediate shaft of an automobile steering device and a method for manufacturing the same.

In an automobile steering device, the movement of a steering wheel operated by a driver is transferred to a steering gear unit via a plurality of shafts such as a steering shaft and an intermediate shaft and a universal joint connecting the ends of these shafts. It is configured to communicate. When a car equipped with a steering device that operates in this way causes a collision, the front part of the vehicle body is crushed and the steering gear unit is pushed backward. Therefore, it is considered to prevent the steering wheel from being displaced rearward regardless of such rearward displacement of the steering gear unit, that is, to prevent the steering wheel from being pushed up toward the driver's body. .. For this reason, conventionally, in the event of a primary collision, torque transmission members such as the shaft and yoke that make up the steering device are contracted in the axial direction or plastically deformed to absorb the impact load and rearward the steering wheel. It has been proposed to prevent displacement to.

For example, Japanese Patent Application Publication No. 1344708 and Japanese Patent Application Laid-Open No. 8-72730 describe the structure of a yoke having a bellows portion for preventing the steering wheel from being displaced backward by plastic deformation at the time of a primary collision. Has been done.

Japanese Patent Application Publication No. DE2459246 describes a steering column in which a bellows portion is provided in an axial intermediate portion and the entire length can be contracted by plastically deforming the bellows portion based on an impact load accompanying a secondary collision. Has been done. In such a steering column, the absorption characteristics of the impact load associated with the secondary collision can be adjusted by adjusting the wall thickness of the bellows portion. However, the invention described in Japanese Patent Application Publication No. DE2459246 relates to a steering column, not a shaft or yoke to which a force in the twisting direction is applied with the operation of the steering wheel. Further, the deformation mode when an impact load is applied is not deformed so that the bellows portion is bent, but is deformed so as to contract.

European Patent Application Publication No. 1344708 Japanese Unexamined Patent Publication No. 8-72730 Publication of German patent application DE2459246 Gazette

By the way, a bellows portion that absorbs an impact load by plastically deforming so as to bend at the time of a primary collision can be provided on an outer tube constituting an intermediate shaft. However, if the outer tube is provided with a bellows portion, the following problems may occur.

The outer tube is provided with a female serration portion on the inner peripheral surface of one end in the axial direction, and the female serration portion is engaged with a male serration portion provided on the outer peripheral surface of the inner shaft to form an intermediate shaft. When a bellows portion is formed in the axial middle portion of a hollow metal material and then a female serration portion is formed on the inner peripheral surface of one end portion in the axial direction of this material by broaching, a large axial load is applied to the bellows portion. Therefore, this bellows portion may be crushed in the axial direction. The outer tube whose bellows portion has been crushed must be discarded as a defective product, which causes an increase in cost due to a deterioration in yield.

In view of the above circumstances, an object of the present invention is to realize a structure and a manufacturing method of an outer tube capable of preventing the bellows portion from being crushed in the axial direction when the female serration portion is formed by broaching. There is.

The method for manufacturing an outer tube of the present invention includes a fitting cylinder portion provided on one side in the axial direction and a female serration portion provided on the inner peripheral surface, and a fitting cylinder portion provided on the other side in the axial direction with respect to the fitting cylinder portion. This is a method for manufacturing an outer tube having an inner diameter larger than that of the fitting cylinder portion and having a large diameter cylinder portion having a bellows portion in all or part of the axial direction.

In such a method for manufacturing an outer tube of the present invention, a hollow metal spare material is used, a small-diameter tubular portion provided on one side in the axial direction, the large-diameter tubular portion, and the inner peripheral surface of the small-diameter tubular portion. A material having a stepped surface connecting the above and the inner peripheral surface of the large-diameter tubular portion is obtained. After that, with the stepped surface abutting against the bearing surface of the cylindrical jig, the inner peripheral surface of the small-diameter cylinder portion is broached from one side in the axial direction to the other side in the axial direction. A female serration portion is formed, and the small-diameter tubular portion is used as the fitting tubular portion.

The inclination angle of the stepped surface with respect to the central axis of the material is preferably 45 degrees or more, preferably 60 degrees or more, more preferably 75 degrees or more, and 90 degrees, that is, the stepped surface. Most preferably, it exists on a virtual plane orthogonal to the central axis.

The stepped surface can be formed by an axially other side surface of a step portion provided between the other end in the axial direction of the small-diameter tubular portion and one end in the axial direction of the large-diameter tubular portion. Alternatively, the stepped surface is oriented toward the other in the axial direction on the inner peripheral surface of the material by cutting the inner peripheral surface of the portion of the material adjacent to the other side in the axial direction of the small-diameter tubular portion. It may be a surface provided in a state of being.

The outer tube of the present invention includes a fitting cylinder portion, a large diameter cylinder portion, and a stepped surface.
Of these, the fitting cylinder portion is provided on one side in the axial direction, and the female serration portion is provided on the inner peripheral surface.
The large-diameter cylinder portion is provided on the other side in the axial direction from the fitting cylinder portion, has an inner diameter larger than that of the fitting cylinder portion, and has a bellows portion in the entire or part of the axial direction.
The stepped surface connects the inner peripheral surface of the fitting cylinder portion and the inner peripheral surface of the large diameter cylinder portion.

Angle of inclination with respect to the central axis of the stepped surface, and 9 0 °, ie, the stepped surface, Ru was present on the imaginary plane perpendicular to the central axis. However, although it is out of the technical scope of the present invention, the inclination angle of the stepped surface with respect to the central axis may be 45 degrees or more, preferably 60 degrees or more, and more preferably 75 degrees or more.

The stepped surface can be formed by an axially other side surface of a step portion provided between the other end in the axial direction of the fitting cylinder and one end in the axial direction of the large diameter cylinder.

In short, in the present invention, a stepped surface is provided on the inner peripheral surface of the intermediate portion in the axial direction, and the stepped surface is pressed against the bearing surface when forming a female serration portion on the inner peripheral surface of one end in the axial direction by broaching, and the stepped surface is pressed against the bellows portion. This is to prevent a force that causes the bellows portion to collapse in the axial direction from being applied.

According to the present invention having the above-described configuration, when the female serration portion is formed by broaching, a large axial load is prevented from being applied to the bellows portion, and the bellows portion is crushed in the axial direction. Can be prevented.

FIG. 1 is a diagram showing an example of an automobile steering device incorporating an intermediate shaft using an outer tube according to an example of the embodiment of the present invention. FIG. 2 is a perspective view showing an outer tube according to an example of the embodiment of the present invention. 3 (A) to 3 (E) are cross-sectional views showing, in order of steps, a method for manufacturing an outer tube according to an example of the embodiment of the present invention. FIG. 4 (A) is a cross-sectional view showing an intermediate shaft using an outer tube according to an example of the embodiment of the present invention in a state before a full-wrap collision occurs, and FIG. 4 (B) is a cross-sectional view of the present invention. FIG. 5 is a cross-sectional view showing an intermediate shaft using an outer tube according to an example of the embodiment of the present invention in a state where a full-wrap collision has occurred. FIG. 5 is a side view showing an intermediate shaft using an outer tube according to an example of the embodiment of the present invention in a state where an offset collision has occurred. FIG. 6 is a cross-sectional view showing how the female serration portion is formed by broaching. FIG. 7 is a cross-sectional view showing a first example of another example of the material with respect to one example of the embodiment of the present invention. FIG. 8 is a cross-sectional view showing a second example of another example of the material with respect to one example of the embodiment of the present invention.

An example of the embodiment of the present invention will be described with reference to FIGS. 1 to 6. In the steering device of an automobile, the rotation of the steering wheel 1 is transmitted to the input shaft 3 of the steering gear unit 2, and the pair of left and right tie rods are pushed and pulled by the rotation of the input shaft 3, and the steering angle is adjusted to the front wheels. Granted. The steering wheel 1 is supported and fixed to the rear end portion of the steering shaft 4, and the steering shaft 4 is rotatably supported by the steering column 5 with the cylindrical steering column 5 inserted in the axial direction. ing. The front end of the steering shaft 4 is connected to the rear end of the intermediate shaft 7 via a universal joint 6.

The intermediate shaft 7 includes an inner shaft 8 arranged on the front side and an outer tube 9 arranged on the rear side, and is configured so that the entire length can be contracted only when a large impact load is applied in the axial direction. ..

A male serration portion 10 is provided along the axial direction on the outer peripheral surface of the latter half of the inner shaft 8. In this example, the inner shaft 8 of the intermediate shaft 7 and the input shaft 3 of the steering gear unit 2 are integrated. That is, a pinion gear 11 is provided at the front end of the inner shaft 8, and the pinion gear 11 is meshed with the rack teeth of the rack shaft 12 of the steering gear unit 2. However, the front end portion of the inner shaft 8 may be configured to be connected to the rear end portion of the input shaft 3 via a universal joint so as to be able to transmit torque.

As shown in FIGS. 2 and 3 (E), the outer tube 9 has a hollow circular tubular shape, and is fitted with a fitting tube portion 13 provided at one end in the axial direction (left end in FIGS. 2 to 6). The large-diameter cylinder portion 14 provided on the other side in the axial direction (right side in FIGS. 2 to 6) from the combined cylinder portion 13, the inner peripheral surface of the fitting cylinder portion 13 and the inner peripheral surface of the large-diameter cylinder portion 14. It is provided with a stepped surface 23 for connecting the above. In this example, the stepped surface 23 is composed of the axially other side surface of the stepped portion 15 provided between the other end in the axial direction of the fitting cylinder portion 13 and the one end portion in the axial direction of the large diameter tubular portion 14. There is. That is, the stepped surface 23 is composed of a portion between the inner peripheral edge of the other end portion in the axial direction of the fitting cylinder portion 13 and the inner peripheral edge of the one end portion in the axial direction of the large diameter tubular portion 14. In the illustrated example, one side of the outer tube 9 in the axial direction is arranged on the front side of the vehicle, and the other side of the outer tube 9 in the axial direction is arranged on the rear side of the vehicle.

A female serration portion 16 is provided on the inner peripheral surface of the fitting cylinder portion 13. Such a female serration portion 16 and the other half portion in the axial direction (the right half portion in FIG. 4A) of the male serration portion 10 of the inner shaft 8 are serrated and fitted.

Further, in this example, the fitting portion between the outer tube 9 and the inner shaft 8 is a so-called elliptical fitting. That is, plastically deformed portions 17a and 17b having an elliptical cross section are provided at one end in the axial direction of the fitting cylinder portion 13 constituting the outer tube 9 and the other end in the axial direction of the inner shaft 8, respectively. .. In FIG. 4A, wavy lines are provided in the formation ranges of the plastic deformation portions 17a and 17b, respectively. The plastically deformed portions 17a and 17b serve as resistance when the outer tube 9 and the inner shaft 8 are displaced relative to each other in the axial direction. By providing such plastically deformed portions 17a and 17b, torque can be transmitted between the fitting cylinder portion 13 constituting the outer tube 9 and the other end portion in the axial direction of the inner shaft 8 and is large in the axial direction. It is coupled so that relative displacement in the axial direction is possible only when an impact load is applied. Further, in this example, in order to enhance the shock absorbing capacity when the intermediate shaft 7 contracts in the axial direction, the axial length of the fitting cylinder portion 13 is set to the coupling provided at the other end in the axial direction of the outer tube 9. It is sufficiently longer than the axial length of the tubular portion 18, specifically, twice or more, preferably three times or more. In the illustrated example, the axial length of the fitting cylinder portion 13 is about three times the axial length of the coupling cylinder portion 18.

The plastic deformation portions 17a and 17b as described above are formed as follows.

First, the other end in the axial direction of the inner shaft 8 is slightly inserted into one end in the axial direction of the fitting cylinder portion 13 constituting the outer tube 9. In other words, one end in the axial direction of the female serration portion 16 and the other end in the axial direction of the male serration portion 10 are serrated and fitted. Next, one end of the fitting cylinder 13 in the axial direction is crushed from the outside in the radial direction by a tool, and the inner peripheral surface of the one end in the axial direction of the fitting cylinder 13 and the outer peripheral surface of the other end in the axial direction of the inner shaft 8 are crushed. It is plastically deformed into an elliptical cross section. As a result, the plastic deformation portion 17a is provided at one end in the axial direction of the fitting cylinder portion 13, and the plastic deformation portion 17b is provided at the other end in the axial direction of the inner shaft 8. After that, the outer tube 9 and the inner shaft 8 are displaced relative to each other in the axial direction so as to reduce the total length of the intermediate shaft 7, and the total length of the intermediate shaft 7 is set to a predetermined axial length in a normal use state. As a result, the plastically deformed portion 17a of the outer tube 9 and the plastically deformed portion 17b of the inner shaft 8 are arranged apart from each other in the axial direction.

The large-diameter tubular portion 14 includes a cylindrical intermediate tubular portion 19 provided at one end in the axial direction and whose inner and outer diameters do not change with respect to the axial direction, a bellows portion 20 provided in the intermediate portion in the axial direction, and an axial direction. It is provided with a coupling cylinder portion 18 provided at the other end portion. The intermediate tubular portion 19 may have a conical tubular shape or may be omitted, and additionally or alternatively, a cylindrical or conical tubular shape may be formed between the bellows portion 20 and the coupling tubular portion 18. It is also possible to provide a cylindrical portion of.

As will be described later, the bellows portion 20 is a portion that absorbs the impact load due to the collision by plastically deforming so as to bend at the time of an offset collision. Therefore, the bellows portion 20 has a torsional strength that is not deformed by a load applied in the torsional direction based on the driver operating the steering wheel 1 or the like in a normal time before a collision accident occurs. The bellows portion 20 is configured by arranging a plurality of mountain portions having a large diameter portion and valley portions having a small diameter portion alternately in the axial direction. In this example, the inner diameter of the valley portion of the bellows portion 20 is larger than the inner diameter of the coupling cylinder portion 18 and is the same as the inner diameter of the intermediate cylinder portion 19. However, the inner diameter of the valley portion of the bellows portion 20 can be made larger than the inner diameter of the intermediate cylinder portion 19.

A second female serration portion 21 is provided on the inner peripheral surface of the coupling cylinder portion 18. A male serration portion provided on the outer peripheral surface of one end (front end) in the axial direction of the transmission shaft 22 which is coupled and fixed to the yoke constituting the universal joint 6 is serrated and fitted to the second female serration portion 21 to be coupled. The transmission shaft 22 is coupled and fixed to the tubular portion 18 so that torque can be transmitted. However, as a method of coupling the coupling cylinder portion 18 constituting the outer tube 9 and the other end portion of the transmission shaft 22 in the axial direction so as to be able to transmit torque, instead of the serration fitting as described above, or serration fitting. At the same time, a method such as welding can also be used. In any case, in this example, the coupling cylinder portion 18 and the transmission shaft 22 are coupled so that the coupling cylinder portion 18 and the transmission shaft 22 are not displaced relative to each other in the axial direction.

The step portion 15 is provided in a state of being bent at a right angle from the other end in the axial direction of the fitting cylinder portion 13 toward the outward in the radial direction. Therefore, the stepped surface 23 formed by the other side surfaces in the axial direction of the stepped portion 15 has a circular ring shape and exists on a virtual plane orthogonal to _{the central axis O 9 of the outer tube 9.} The width dimension of the stepped surface 23 in the radial direction depends on the magnitude of the load applied to the material 24 in the axial direction during broaching, which will be described later, but is 0.5 times or more the wall thickness of the outer tube 9. It is 2 times or less, preferably 1 time or more and 1.5 times or less.

In the outer tube 9 of this example, the inner diameter of the coupling cylinder portion 18 (groove bottom diameter of the second female serration portion 21) d ₁₈ is set to the bellows portion 20 which is the smallest inner diameter portion of the large diameter cylinder portion 14. valleys and smaller than the inner diameter _{d 14} of the intermediate tubular portion 19 is made larger than the _{d 13} (groove bottom diameter of the female serration portion ₁₆₎ the inner diameter of the fitting cylinder _{13 (d 13 <d 18 <} d 14) .. _{When the second female serration portion 21 is formed by swaging, the inner diameter d 18} of the coupling cylinder portion 18 after the formation of the second female serration portion 21 is the inner diameter d of the fitting cylinder portion 13. It may be the same as ₁₃ or smaller than _{this inner diameter d 13.} However, even in this case, the inner diameter d ₁₃ of the fitting tube portion 13 is smaller than the inner diameter d ₁₄ of the smallest part of the large-diameter cylindrical portion 14.

When a so-called full-lap collision occurs in which the entire front surface of the vehicle body collides with another vehicle while the vehicle equipped with the steering device provided with the intermediate shaft 7 as described above occurs, the entire steering gear unit 2 is strongly pushed backward. Is done. As a result, an impact load directed to the other side (rearward) in the axial direction is applied to the inner shaft 8 (input shaft 3). When an impact load in the axial direction is applied to the inner shaft 8, the inner shaft 8 is displaced rearward with respect to the outer tube 9 as shown in FIG. 4 (B) from the state shown in FIG. 4 (A), and is intermediate. The shaft 7 shortens the total length while absorbing the impact load. This makes it possible to prevent the steering wheel 1 from being displaced rearward and pushed up toward the driver's body. When such a full-wrap collision occurs, the rigidity of the bellows portion 20 and the rigidity of the bellows portion 20 are increased so that the inner shaft 8 and the outer tube 9 can start relative displacement before the bellows portion 20 collapses in the axial direction. The magnitude of the coupling strength between the inner shaft 8 and the fitting cylinder portion 13 is adjusted.

On the other hand, when a so-called offset collision occurs in which a part of the front surface of the vehicle body is biased in the width direction and collides with another automobile or the like, the engine room may be deformed and the intermediate shaft 7 may not be able to contract in the axial direction. .. In this case, the outer tube 9 is bent at the bellows portion 20 as shown in FIG. 5 based on the impact load due to the collision. As a result, the impact load is absorbed, and the bent intermediate shaft 7 is housed in the gap existing between the peripheral parts to prevent the intermediate shaft 7 from being displaced rearward. Therefore, even in the case of an offset collision, it is possible to prevent the steering wheel 1 from being displaced rearward and pushed up toward the driver's body. When such an offset collision occurs, whether the inner shaft 8 and the outer tube 9 are displaced relative to each other in the axial direction and the overall length of the intermediate shaft 7 contracts depends on how the impact load is applied and the deformation of the engine room. It depends on the mode and so on.

A method of manufacturing the outer tube 9 constituting the intermediate shaft 7 as described above will be described with reference to FIG.

First, a metal pipe material such as an iron-based alloy such as carbon steel for machine structure (STKM) or a light alloy such as an aluminum alloy is cut to a predetermined length to form a circle as shown in FIG. 3 (A). Obtain a tubular first reserve material 25. Next, one half of the first spare material 25 in the axial direction is drawn to obtain a stepped cylindrical second spare material 26 as shown in FIG. 3 (B). The second spare material 26 includes a small diameter cylinder portion 27 on one side in the axial direction, a large diameter cylinder portion 14 on the other side in the axial direction, the other end portion in the axial direction of the small diameter cylinder portion 27, and one end in the axial direction of the large diameter cylinder portion 14. It is composed of a step portion 15 provided so as to connect the portions. The step portion 15 is provided in a state of being bent outward in the radial direction from the other end in the axial direction of the small diameter tubular portion 27. Therefore, the stepped surface 23, which is the other side surface in the axial direction of the step portion 15, exists on a virtual plane orthogonal to _{the central axis O 26 of the second spare material 26.}

Next, the second preliminary material 26 is subjected to plastic working such as hydroforming (bulge forming) or roll forming to obtain the material 24 as shown in FIG. 3 (C). That is, the bellows portion 20 is formed by plastically deforming the axially intermediate portion of the large-diameter tubular portion 14. At the same time, one side of the large-diameter tubular portion 14 in the axial direction of the bellows portion 20 is the intermediate tubular portion 19, and the other side of the large-diameter tubular portion 14 in the axial direction of the bellows portion 20 is the opening-side tubular portion 32. And. The axial length of the material 24 is smaller than the axial length of the second spare material 26.

Next, of the material 24, a female serration portion 16 is formed on the inner peripheral surface of the small-diameter tubular portion 27 by broaching from one side in the axial direction toward the other side in the axial direction, and is shown in FIG. 3 (D). To obtain an intermediate material 28 such as.

When the female serration portion 16 is formed by broaching, as shown in FIG. 6, a cylindrical jig 29 is inserted into the inner diameter side of the material 24 from the opening on the other side in the axial direction of the material 24, and the material 24 is formed. The stepped surface 23 of the above is abutted against the annular bearing surface 30 which is one end surface in the axial direction of the jig 29 over the entire circumference. The jig 29 is fixed to a support base of a broach tool or the like, and is regulated so as not to be displaced in the axial direction with respect to the material 24 during broaching. With the stepped surface 23 of the material 24 abutting against the bearing surface 30 of the jig 29, the brooch 31 is inserted into the inner diameter side of the small diameter tubular portion 27 constituting the material 24 from the axial one-side opening of the material 24. Then, the brooch 31 is displaced toward the other side in the axial direction, the inner peripheral surface of the small diameter tubular portion 27 is cut from one side in the axial direction toward the other side in the axial direction, and the small diameter tubular portion 27 is female serrated on the inner peripheral surface. It is a fitting cylinder portion 13 provided with the portion 16. The inner diameter d _{29 of the} jig 29 is made larger than the outer diameter D _{31 of the} brooch 31 so that the inner peripheral surface of the jig 29 is not cut by the broach 31. On the other hand, the outer diameter of the jig 29 is matched with the inner diameter of the inner diameter of the intermediate cylinder portion 19 and the inner diameter of the opening side cylinder portion 32, whichever is smaller, or is slightly smaller than that of the jig 29. The coaxiality with the material 24 is secured. After forming the female serration portion 16 on the inner peripheral surface of the small diameter tubular portion 27, the brooch 31 is pulled out from the inner diameter side of the material 24.

In the illustrated example, the inner peripheral surface of the small-diameter tubular portion 27 of the material 24 is broached in a state where the axial directions of the material 24 are aligned with each other in the horizontal direction. However, the broaching process shall be performed with the axial directions of the material 24 aligned in the vertical direction, that is, with one end in the axial direction of the material 24 on the upper side and the other end in the axial direction on the lower side. You can also.

Then, a second female serration portion 21 is formed on the inner peripheral surface of the opening-side tubular portion 32 provided at the other end in the axial direction of the large-diameter tubular portion 14 constituting the intermediate material 28 by swaging or the like. That is, the outer tube 9 is obtained by providing the coupling cylinder portion 18 having the second female serration portion 21 on the inner peripheral surface at the other end in the axial direction of the large diameter cylinder portion 14. When the second female serration portion 21 is formed by swaging, the inner diameter of the coupling cylinder portion 18 after processing is smaller than the inner diameter of the opening side cylinder portion 32 before processing. However, the second female serration portion 21 may be formed by broaching. In this case, when cutting the inner peripheral surface of the opening side tubular portion 32 with the brooch, a second female serration is applied so that a large force that causes the bellows portion 20 to be crushed is not applied to the bellows portion 20. The module of unit 21 is set small.

As described above, in this example, when the inner peripheral surface of the small-diameter tubular portion 27 constituting the material 24 is broached to form the female serration portion 16, the stepped surface 23 of the material 24 is broached. It abuts against the support surface 30 of the jig 29 fixed to the support base of the above. Therefore, when the inner peripheral surface of the small diameter tubular portion 27 is cut by the brooch 31, when a load directed to the other side in the axial direction is applied to the material 24, the stepped surface 23 is pressed against the bearing surface 30, and the bearing surface 30 presses the material 24 against the bearing surface 30. , The load is bearing. In short, when the female serration portion 16 is formed on the material 24 by broaching, it is possible to prevent a large axial load from being applied to the bellows portion 20, and it is possible to prevent the bellows portion 20 from being crushed in the axial direction. As a result, the occurrence of defective products can be prevented and the yield can be improved.

Further, the outer tube 9 of this example is integrally formed as a whole by subjecting the first spare material 25, which is made of metal and has a circular tubular shape, to plastic working or cutting. On the other hand, as in the structure described in European Patent Application Publication No. 1344708 and Japanese Patent Application Laid-Open No. 8-72730, when the bellows portion and the portion for connecting to other members are manufactured as separate parts, It takes time and effort to join these parts by welding or the like. In this example, since the labor of joining such parts by management and welding can be omitted, the manufacturing cost of the outer tube 9 can be reduced accordingly.

In this example, the step portion 15 is provided in a state of being bent at a right angle outward in the radial direction from the other end in the axial direction of the fitting cylinder portion 13, and the stepped surface 23 which is the other side surface in the axial direction of the step portion 15 is provided as an outer. It exists on a virtual plane orthogonal to the central axis O _{9 of the tube 9.} However, the stepped surface 23 is pressed against the bearing surface 30 of the jig 29 based on the load applied to the material 24 in the axial direction when the inner peripheral surface of the small diameter tubular portion 27 of the material 24 is broached. As long as the load can be supported by the surface 30, as shown in FIG. 7, a partial conical surface inclined with respect _{to the central axis O 24 may be used.} When the stepped surface 23 is _{a partial conical surface inclined with respect to the central axis O 24} , the bearing surface 30 is also a partial conical surface inclined by the same angle in the same direction as the stepped surface 23. That is, the stepped surface 23 and the bearing surface 30 are made parallel to each other. The inclination angle θ of the stepped surface 23 with respect to the central axis O ₂₄ is 45 degrees or more, although it depends on the width dimension of the stepped surface 23 in the radial direction and the magnitude of the load applied to the material 24 in the axial direction during broaching. , 60 degrees or more, more preferably 75 degrees or more. However, from the surface that efficiently supports the load applied to the material 24 in the axial direction by the bearing surface 30 during broaching, the inclination angle θ is set to 90 degrees, that is, the stepped surface 23 is the material 24. Most preferably, it exists on a virtual plane orthogonal to the central axis O _24.

In this example, a stepped portion 15 provided so as to connect the other end in the axial direction of the small diameter tubular portion 27 and one end in the axial direction of the large diameter tubular portion 14 is provided, and the axial direction of the stepped portion 15 and the like. The side surface is a stepped surface 23 for abutting against the bearing surface 30 during broaching, but the structure of the stepped surface is not limited to the structure of this example. For example, as shown in FIG. 8, the inner peripheral surface of the hollow material 24a, which is adjacent to the other side in the axial direction of the small-diameter tubular portion 27, is cut to form an axis on the inner peripheral surface of the material 24a. A stepped surface 23a facing the other side may be formed. In the illustrated example, the outer diameter of the small diameter cylinder portion 27 and the outer diameter of the intermediate cylinder portion 19a provided at one end of the large diameter cylinder portion 14a in the axial direction are the same.

In this example, the inner shaft 8 is arranged on the front side and the outer tube 9 is arranged on the rear side, but the outer tube 9 can be arranged on the front side and the inner shaft 8 can be arranged on the rear side. In this case, at the time of use, one side in the axial direction of the outer tube 9 is arranged on the rear side of the vehicle, and the other side in the axial direction of the outer tube 9 is arranged on the front side of the vehicle. However, it is preferable to arrange the outer tube 9 on the rear side from the viewpoint of increasing the moment applied to the bellows portion 20 of the outer tube 9 at the time of an offset collision to facilitate the deformation of the bellows portion 20.

In this example, the fitting portion between the outer tube 9 and the inner shaft 8 is a so-called elliptical fitting, and the outer tube 9 and the inner shaft 8 are relative to each other in the axial direction only when a large impact load is applied in the axial direction. It is fitted so that it can be displaced. On the other hand, the outer tube and the inner shaft can be fitted to each other with a light force so as to be relatively displaced in the axial direction. Specifically, for example, the outer peripheral surface of the inner shaft can be coated with a synthetic resin, and further grease can be applied to fit the axial end portion of the inner shaft into the fitting cylinder portion of the outer tube. .. Alternatively, the axial end of the inner shaft and the fitting cylinder of the outer tube may be fitted via a rolling element such as a ball or a roller.

In the step of forming the outer tube 9 from the circular tubular first preliminary material 25, the female serration portion 16 is formed by broaching after forming the bellows portion 20 and the stepped surface 23, and the female serration portion 16 is formed by broaching, unless there is a contradiction. The order can be changed or they can be carried out at the same time. Specifically, for example, after forming the second female serration portion 21 (see FIG. 3 (E)) on the inner peripheral surface of the other end portion in the axial direction of the large diameter tubular portion 14, the inner peripheral surface of the small diameter tubular portion 27 The female serration portion 16 may be formed by broaching (see FIG. 3D). Further, after forming the bellows portion 20 in the axial intermediate portion of the first spare material 25, the axial half portion of the first spare material 25 is drawn to form the step portion 15 to form the stepped surface 23. It can also be formed.

When the bellows portion 20 is formed by hydrofoam molding, a thin portion having a smaller radial thickness than the other portions may be provided in the axial intermediate portion of the second spare material 26. This thin portion is formed by cutting the inner peripheral surface or the outer peripheral surface of the axial intermediate portion of the second spare material 26, or the inner peripheral surface or the outer peripheral surface of the axial intermediate portion of the second spare material 26. It can be formed by performing a rolling process that pushes and plastically deforms in the radial direction. If the second spare material 26 is provided with a thin-walled portion, the hydraulic pressure during hydrofoam molding can be prevented from becoming excessively large while sufficiently ensuring the radial thickness of the fitting cylinder portion 13 and the coupling cylinder portion 18. it can. The wall thickness of the bellows portion 20 after molding is smaller than the wall thickness of the other portions. As described above, in the structure in which the wall thickness of the bellows portion 20 is smaller than the wall thickness of the other portions, the effect of the present invention of preventing the bellows portion 20 from being crushed when the female serration portion 16 is formed can be obtained. It can be obtained more prominently.

1 Steering wheel 2 Steering gear unit 3 Input shaft 4 Steering shaft 5 Steering column 6 Universal joint 7 Intermediate shaft 8 Inner shaft 9 Outer tube 10 Male serration part 11 Pinion gear 12 Rack shaft 13 Fitting cylinder part 14, 14a Large diameter cylinder part 15 Step 16 Female serration part 17a, 17b Plastic deformation part 18 Coupling cylinder part 19, 19a Intermediate cylinder part 20 Bellows part 21 Second female serration part 22 Transmission shaft 23, 23a Step surface 24, 24a Material 25 First spare material 26 2nd spare material 27 Small diameter cylinder 28 Intermediate material 29 Jig 30 Support surface 31 Brooch 32 Open side cylinder

Claims (5)

A fitting cylinder portion provided on one side in the axial direction and having a female serration portion on the inner peripheral surface, and a fitting cylinder portion provided on the other side in the axial direction with respect to the fitting cylinder portion and having an inner diameter larger than that of the fitting cylinder portion. It is a method of manufacturing an outer tube including a large-diameter tubular portion having a bellows portion.
From a hollow metal spare material, a small-diameter cylinder provided on one side in the axial direction, the large-diameter cylinder, the inner peripheral surface of the small-diameter cylinder, and the inner peripheral surface of the large-diameter cylinder are connected. After obtaining a material having a stepped surface to be formed, the stepped surface is abutted against a bearing surface of a cylindrical jig, and then on the inner peripheral surface of the small diameter cylinder portion from one side in the axial direction to the other side in the axial direction. A method for manufacturing an outer tube in which the female serration portion is formed by performing a broaching process so that the small diameter cylinder portion is used as the fitting cylinder portion. The method for manufacturing an outer tube according to claim 1, wherein the stepped surface exists on a virtual plane orthogonal to the central axis of the material. The first or second aspect of claim 1 or 2, wherein the stepped surface is an axially other side surface of a step portion provided between the axially other end of the small diameter cylinder and one axial end of the large diameter cylinder. How to manufacture the outer tube. A fitting cylinder part provided on one side in the axial direction and a female serration part provided on the inner peripheral surface, and a fitting cylinder part.
A large-diameter cylinder portion provided on the other side in the axial direction from the fitting cylinder portion, having an inner diameter larger than that of the fitting cylinder portion, and having a bellows portion.
It is provided with a stepped surface for connecting the inner peripheral surface of the fitting cylinder portion and the inner peripheral surface of the large diameter cylinder portion .
An outer tube in which the stepped surface exists on a virtual plane orthogonal to the central axis. The stepped surface is composed of the other axial side of the step portion provided between the axial direction one end portion of said the other axial end portion of the fitting tubular portion larger cylindrical portion, in claim 4 The described outer tube.

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