JP7557201B2 - Joint structure and contraction shaft - Google Patents

Description

The present invention relates to a joint structure for shafts, yokes, etc., which constitute torque transmission members incorporated in steering devices of automobiles, etc. It also relates to a contracting shaft that has a joint structure and is configured so that its entire length can be contracted.

Figure 14 shows a steering device for an automobile described in JP 2017-25964 A (Patent Document 1). The steering device includes a steering wheel 1, a steering shaft 2, a steering column 3, a pair of universal joints 4a, 4b, an intermediate shaft 5, a steering gear unit 6, and a pair of tie rods 7.

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

In the field of steering devices for automobiles, a torque transmission shaft used for torque transmission such as an intermediate shaft may be constructed by connecting multiple shafts. In such cases, a pair of adjacent shafts are joined by welding, enabling torque transmission between the pair of shafts.

In addition, JP 2017-25964 A discloses that an intermediate shaft constituting an automobile steering device is configured as a contracting shaft whose overall length can be contracted only when an automobile crash occurs and a load equal to or greater than a predetermined value is applied to the intermediate shaft in the axial direction.

JP 2017-25964 A

In recent years, there has been an increasing demand for reliability in torque transmission components such as torque transmission shafts. Furthermore, torque transmission components that are constructed by connecting multiple components are required to be able to maintain torque transmission function and not separate from the pair of components even if defects such as cracks or peeling occur in the welds that connect the pair of components.

The present invention has been made to solve the above problems, and aims to provide a connection structure that can ensure torque transmission function even if a defect occurs in the weld and can prevent separation of a pair of components that make up the torque transmission member, and a contraction shaft equipped with this connection structure.

The joint structure of the present invention comprises an insert member, an inserted member, and a weld bead portion.
The insertion member has a first coupling portion at one axial end portion, The first coupling portion may be configured in a hollow cylindrical shape or may be configured in a solid shape.
The inserted member has a cylindrical second connecting portion at the other axial end, into which the first connecting portion is inserted.
The weld bead portion welds and fixes the other axial end of the second joint portion and a portion of the outer circumferential surface of the insertion member that is exposed from the second joint portion.
The first connecting portion has, on its outer circumferential surface, an outer circumferential side uneven portion having an uneven shape in the circumferential direction, and an inner diameter side annular groove.
The second connecting portion has, on its outer peripheral surface, an outer diameter side annular groove arranged at a position radially overlapping with the inner diameter side annular groove, and an embossed recess formed at a bottom of the outer diameter side annular groove, and, on its inner peripheral surface, an inner diameter side uneven portion having an uneven shape in the circumferential direction that engages with the outer diameter side uneven portion to form a torque transmission portion, and an embossed convex portion provided at a position aligned with the embossed recess, arranged inside the inner diameter side annular groove, and forming a slip-out prevention portion.

In one embodiment of the connection structure of the present invention, the dimensions of the outer diameter side annular groove in the axial direction of the inserted member can be one to two times the dimensions of the embossed recess in the axial direction of the inserted member.

In one embodiment of the connection structure of the present invention, the end face on the other axial direction of the inner circumferential convex portion constituting the inner circumferential concave portion is abutted against an abutment surface provided at the end on the other axial direction of the outer circumferential concave portion constituting the outer circumferential concave portion and facing one axial side, thereby enabling the insertion member and the inserted member to be positioned in the axial direction.

In one aspect of the connection structure of the present invention, the outer circumferential side concave-convex portion can be press-fitted (lightly press-fitted) into the inner circumferential side concave-convex portion.
In this case, the outer circumferential concave-convex portion may be provided with a guide portion at one axial end, the guide portion having a circumscribed circle diameter smaller than that of the portion adjacent to the other axial end.

In one aspect of the connection structure of the present invention, each of the embossed convex portion and the embossed concave portion can be disposed at a plurality of positions in the circumferential direction of the second connection portion.
In this case, each of the embossed convex portions and the embossed concave portions can be disposed at two or four locations equidistantly spaced in the circumferential direction of the second joint portion.
Alternatively, each of the embossed convex portion and the embossed concave portion may be disposed at one location in the circumferential direction of the second joint portion.

In one aspect of the connection structure of the present invention, a gap in the radial direction of the first connection portion can be present between a bottom surface of the inner diameter side annular groove and a tip surface of the embossed convex portion.
Furthermore, a gap can be provided in the axial direction of the insertion member between the opposing inner side surfaces of the inner diameter side annular groove and the embossed protrusion.

The contraction shaft of the present invention comprises a large diameter shaft, a small diameter shaft fitted inside the large diameter shaft to enable torque transmission and relative axial displacement with respect to the large diameter shaft, and a joint shaft connected to an axial end of the large diameter shaft.
The large diameter shaft and the joint shaft are connected by the connection structure of the present invention, with the large diameter shaft being the inserted member and the joint shaft being the inserting member.

In one embodiment of the contraction shaft of the present invention, the contraction shaft may constitute an intermediate shaft of a steering device for an automobile.
In this case, the collapsible shaft can be configured so that its entire length can be collapsed only when a vehicle crash occurs and a load of a predetermined value or more is applied to the collapsible shaft in the axial direction.

The connection structure and contraction shaft of the present invention ensures torque transmission function even if a defect occurs in the weld, and prevents separation of the pair of components that make up the torque transmission member.

FIG. 1 is a schematic diagram showing an example of a steering device to which a connecting structure according to an embodiment of the present invention is applied. FIG. 2 is a side view showing an intermediate shaft taken out from the steering device shown in FIG. 1 according to one embodiment of the present invention. FIG. 3 is a cross-sectional view of an intermediate shaft showing one example of an embodiment. FIG. 4 is a side view of one embodiment of the present invention with the intermediate shaft shown in FIG. 2 separated and the contraction shaft removed. FIG. 5 is a perspective view of a contraction shaft showing one example of an embodiment. FIG. 6 is a cross-sectional view of a retraction shaft showing one example of an embodiment. FIG. 7 is a side view showing a combination of a first outer cylinder and a joint shaft which constitute the contraction shaft shown in FIG. 2 according to one embodiment. FIG. 8 is a cross-sectional view of a combination of a first outer cylinder and a joint shaft, showing one example of an embodiment. FIG. 9 is an enlarged view of the right side of FIG. 8 showing an example of an embodiment. FIG. 10 is an enlarged view of part A in FIG. 9, showing an example of the embodiment. FIG. 11 is a partial cross-sectional view showing a step of connecting the first outer cylinder and the joint shaft in accordance with one embodiment. FIG. 12 is an enlarged schematic view of a portion corresponding to part B in FIG. 9, showing one example of the embodiment. FIG. 13 is a diagram showing a joint shaft according to one example of an embodiment, in which (A) is a plan view, (B) is a cross-sectional view taken along line CC of (A), and (C) is a side view. FIG. 14 is a partial cross-sectional side view showing a conventionally known steering device.

[One Example of the Embodiment]
An example of the embodiment will be described with reference to FIGS.

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

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

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

[Intermediate shaft]
The intermediate shaft 5a has a long overall length since it constitutes a steering device for a large automobile, and connects the front end of the steering shaft 2a to the pinion shaft 8a constituting the steering gear unit 6a in a manner enabling torque transmission. The intermediate shaft 5a is constituted by axially connecting a contracting shaft 9 and a telescopic shaft 10. The intermediate shaft 5a has the contracting shaft 9 on one axial side, which is the engine room side, and has the telescopic shaft 10 on the other axial side, which is the driver's seat side.

Contraction shaft
The collapsible shaft 9 is a collapsible shaft having a first inner shaft 11 corresponding to a small diameter shaft, a first outer cylinder 12 corresponding to a large diameter shaft, and a joint shaft 13, and is configured so that its overall length can be collapsed only when an automobile crash occurs and an impact load of a magnitude equal to or greater than a predetermined value is applied in the axial direction. For this purpose, the first inner shaft 11 and the first outer cylinder 12 are coupled to each other so as to be capable of transmitting torque and to be capable of relative displacement in the axial direction during a primary collision. In other words, the first inner shaft 11 and the first outer cylinder 12 are coupled to each other so as to be unable to be relatively displaced in the axial direction in a steady state. In addition, the first outer cylinder 12 and the joint shaft 13 are coupled to each other so as to be capable of transmitting torque and to be unable to be relatively displaced in the axial direction even during a primary collision.

In this example, the first inner shaft 11 is disposed on one axial side of the contraction shaft 9, farther from the telescopic shaft 10, the joint shaft 13 is disposed on the other axial side of the contraction shaft 9, closer to the telescopic shaft 10, and the first outer tube 12 is disposed between the first inner shaft 11 and the joint shaft 13.

First Inner Axis
The first inner shaft 11 has a yoke portion 15 disposed on one axial side, and a shaft portion 16 disposed on the other axial side.

The yoke portion 15 constitutes a universal joint 4d together with another yoke 17 connected to the pinion shaft 8a of the steering gear unit 6a and a cross shaft (not shown). The yoke portion 15 is fixed by welding to one axial end of the shaft portion 16. The yoke portion 15 includes a substantially disk-shaped base portion 18 and a pair of arm portions 19 extending to one axial end from two diametrically opposite positions on the outer peripheral surface of the base portion 18. The base portion 18 has an insertion hole 20 in the radial center thereof through which the one axial end of the shaft portion 16 can be inserted. The pair of arm portions 19 have circular holes 21 formed coaxially with each other in the tip portions thereof. When the universal joint 4d is assembled, bearing cups (not shown) are fitted into the circular holes 21, respectively, to rotatably support the shafts constituting the cross shaft.

The shaft portion 16 is generally cylindrical and solid over almost its entire length. The shaft portion 16 has multiple (two in the illustrated example) male splines 22a, 22b on its outer circumferential surface. The male splines 22a, 22b are spaced apart in the axial direction. Of the male splines 22a, 22b, the male spline 22a located furthest on the other axial side is located at the end of the shaft portion 16 on the other axial side, and the male spline 22b located furthest on one axial side is located in the middle of the shaft portion 16 in the axial direction.

All of the male splines 22a, 22b provided on the shaft portion 16 are in phase with each other in the circumferential direction. Of the male splines 22a, 22b, the male spline 22a located furthest to the other axial side has an axial dimension larger than the remaining male splines 22b, and has an axial dimension that is approximately half the total length of the shaft portion 16.

The shaft portion 16 has a central hole 23 at the end on the other axial side that is open only to the end face on the other axial side. Therefore, the other axial side of the male spline 22a is provided on the outer peripheral surface of the portion of the shaft portion 16 that has been thinned by forming the central hole 23.

The shaft portion 16 has fuse portions 24a, 24b on both axial sides of the male spline 22b. Each of the fuse portions 24a, 24b is formed on the outer peripheral surface of the shaft portion 16, for example, by cutting. Each of the fuse portions 24a, 24b has an outer peripheral surface that is approximately cylindrical, and has a smaller diameter than the bottom circle diameter of the male splines 22a, 22b. The axial dimensions of each of the fuse portions 24a, 24b are the same.

First External Cylinder
The first outer cylinder 12 corresponds to the inserted member, is made of metal, and is configured as a hollow circular tube. The first outer cylinder 12 is welded and fixed to the joint shaft 13 by a weld bead portion 52 described later. For this reason, as shown in FIG. 9, in order to ensure the welding quality of the weld bead portion 52 and to avoid welding defects, the thickness T ₁₂ of the first outer cylinder 12 and the thickness t ₁₃ of the joint shaft 13 (cylindrical portion 33) are set to be approximately the same, or the thickness T ₁₂ (or t ₁₃ ) of the first outer cylinder ₁₂ and the thickness t ₁₃ of the joint shaft 13, whichever is thicker, is restricted to be equal to or less than twice the thickness t ₁₃ (or T ₁₂ ). In the illustrated example, the thickness T ₁₂ of the first outer cylinder 12 and the thickness t ₁₃ of the joint shaft 13 are set to be approximately the same (T ₁₂ ≒ t ₁₃ ).

The first outer cylinder 12 has, from one axial end, a small diameter cylinder portion 25, a conical cylinder portion 26, and a large diameter cylinder portion 27 that corresponds to the second connecting portion.

The small diameter tube portion 25 is cylindrical and is provided in one half of the axial direction of the first outer tube 12. The small diameter tube portion 25 is formed by ironing the outer circumferential surface of the material, and is configured to have a smaller diameter than the conical tube portion 26 and the large diameter tube portion 27 arranged on the other axial side. As shown in FIG. 8, the small diameter tube portion 25 is provided with a female spline 28 along the entire axial length of its inner circumferential surface. The female spline 28 is formed when the outer circumferential surface of the material is ironed. However, it can also be formed separately by broaching or the like.

As shown in Figures 4 and 6, in the assembled state of the contraction shaft 9, the other axial side of the shaft portion 16 is inserted into the small diameter cylindrical portion 25 located on one axial side of the first outer cylinder 12. Then, only the male spline 22a provided on the end of the outer circumferential surface of the shaft portion 16 on the other axial side is spline-engaged with the female spline 28 provided on the inner circumferential surface of the small diameter cylindrical portion 25 so as to be able to transmit torque. In addition, the male spline 22a is press-fitted into the female spline 28 so that the first inner shaft 11 and the first outer cylinder 12 can be displaced relative to each other in the axial direction during a primary collision. In this example, the male spline 22a is spline-fitted into the female spline 28 in a light press-fit state with a press-fitting force of about 1 kN to 4 kN.

As a result, the first inner shaft 11 and the first outer cylinder 12 cannot move relative to each other in the axial direction in a steady state where no automobile collision has occurred, but when an automobile collision occurs and an impact load of a predetermined value or more is applied in the axial direction, they become capable of moving relative to each other in the axial direction. Therefore, the contracting shaft 9 cannot be contracted in its entire length in a steady state where no automobile collision has occurred, but when an automobile collision occurs and an impact load of a predetermined value or more is applied in the axial direction, its entire length becomes contractible. In addition, when the contracting shaft 9 contracts, it absorbs the energy from the collision.

In this example, in the assembled state of the contraction shaft 9, the entire male spline 22a provided at the other axial end of the outer peripheral surface of the shaft portion 16 is spline-fitted with the female spline 28 provided on the inner peripheral surface of the first outer tube 12. As a result, as shown in FIG. 6, the effective engagement length Lx between the male spline 22a and the female spline 28 in the steady state is set to be longer than the axial dimension La of each of the fuse portions 24a and 24b.

In addition, in the steady state, each of the fuse portions 24a, 24b provided on the shaft portion 16 is exposed from the first outer tube 12.

The conical cylinder portion 26 is configured in a substantially conical cylindrical shape and is disposed on the other axial side of the small diameter cylinder portion 25. The outer diameter dimension and the inner diameter dimension of the conical cylinder portion 26 continuously increase toward the other axial side. The conical cylinder portion 26 is connected to an end portion on one axial side of the large diameter cylinder portion 27.

The large diameter cylindrical portion 27 is cylindrical and is provided in the other axial half of the first outer cylinder 12. The large diameter cylindrical portion 27 is configured to have a larger diameter than the conical cylindrical portion 26 and the small diameter cylindrical portion 25, which are located on one axial side. The large diameter cylindrical portion 27 is provided with female serrations 29, which are uneven in the circumferential direction and correspond to the inner circumferential uneven portion, on the other axial side of the inner circumferential surface.

The large diameter cylindrical portion 27 has an outer diameter side annular groove 30 that is recessed in the radial direction over the entire circumference at the axial middle part of the outer peripheral surface. The outer diameter side annular groove 30 has a trapezoidal cross-sectional shape with an axial dimension that increases toward the radial outside. Therefore, the bottom surface (inner surface) of the outer diameter side annular groove 30 is composed of a flat bottom surface that is flat and located at the axial middle part, and a pair of inclined bottom surfaces that are located on both axial sides of the flat bottom surface. The axial dimension W ₃₀ of the outer diameter side annular groove 30 (the opening and bottom surface) and the depth dimension of the outer diameter side annular groove 30 are each constant over the circumferential direction. The outer diameter side annular groove 30 is formed on the outer peripheral surface of the large diameter cylindrical portion 27 by, for example, performing cutting processing. The cross-sectional shape of the outer diameter side annular groove is not limited to a trapezoidal shape, and a cross-sectional rectangular shape, etc. can be adopted. When the cross-sectional shape of the outer diameter side annular groove is rectangular, the inner surface of the outer diameter side annular groove is composed of a flat bottom surface and a pair of inner side surfaces opposing each other in the axial direction.

As described above, from the viewpoint of ensuring the welding quality of the weld bead portion 52 and avoiding welding defects, it is difficult to make the plate thickness _T12 of the first outer tube 12 sufficiently thin. Therefore, in this state, it is difficult to perform embossing (crimping) as described later on the large diameter tube portion 27 and form the embossed convex portion 32 with high shape accuracy on the inner peripheral surface of the large diameter tube portion 27. Therefore, in this example, the outer diameter side annular groove 30 is formed on the outer peripheral surface of the large diameter tube portion 27, and the plate thickness _T30 at the portion where the outer diameter side annular groove 30 is formed is made smaller than the plate thickness _T12 of the first outer tube 12 ( _T30 < _T12 ). In this example, the plate thickness _T12 of the first outer tube 12 is about 3 mm, and the depth dimension of the outer diameter side annular groove 30 is about 0.5 mm to 1 mm, so that the plate thickness _T30 at the portion where the outer diameter side annular groove 30 is formed is about 2 mm to 2.5 mm. This makes it possible to form the embossed protrusions 32 with high shape accuracy on the inner peripheral surface of the large diameter cylindrical portion 27 while ensuring the welding quality of the weld bead portion 52 and avoiding welding defects.

The large diameter cylindrical portion 27 has a plurality of concave embossed recesses 31 at the bottom of the outer diameter side annular groove 30 on the outer peripheral surface. The embossed recesses 31 have a substantially cylindrical shape and a circular cross-sectional shape. The embossed recesses 31 open only to the bottom surface of the outer diameter side annular groove 30. In the illustrated example, the embossed recesses 31 open to the flat bottom surface of the bottom surface of the outer diameter side annular groove 30. The axial dimension (diameter dimension) W ₃₁ of the embossed recesses 31 is 1/2 to 1 times the axial dimension W ₃₀ of the opening of the outer diameter side annular groove 30. Therefore, the axial dimension W ₃₀ of the opening of the outer diameter side annular groove 30 is 1 to 2 times the axial dimension W ₃₁ of the embossed recesses 31. In the illustrated example, the axial dimension W ₃₀ of the outer diameter side annular groove 30 is twice the axial dimension W ₃₁ of the embossed recesses 31. The axial dimension _W31 of the embossed recess 31 is the same as the axial dimension of the flat bottom surface constituting the bottom surface of the outer diameter side annular groove 30. However, the axial dimension _W31 of the embossed recess 31 may be made larger than the axial dimension of the flat bottom surface of the outer diameter side annular groove 30, and the embossed recess 31 may be opened to both the flat bottom surface and the inclined bottom surface. Alternatively, the axial dimension _W31 of the embossed recess 31 may be made smaller than the axial dimension of the flat bottom surface of the outer diameter side annular groove 30.

The large-diameter cylindrical portion 27 has a plurality of convex embossed protrusions 32 on its inner peripheral surface. The embossed protrusions 32 are provided at positions that align with the embossed recesses 31, i.e., on the opposite side of the embossed recesses 31 in the radial direction of the large-diameter cylindrical portion 27. The embossed protrusions 32 have a generally cylindrical shape. As described below, the embossed recesses 31 and the embossed protrusions 32 are each formed after the cylindrical portion 33 of the joint shaft 13 is inserted inside the large-diameter cylindrical portion 27.

The embossed recesses 31 and the embossed protrusions 32 are arranged at equal intervals in the circumferential direction of the large-diameter cylindrical portion 27. The embossed recesses 31 and the embossed protrusions 32 may be provided at four locations, each with a phase shift of 90 degrees in the circumferential direction, or may be provided at only two locations on the radially opposite sides of the large-diameter cylindrical portion 27, with a phase shift of 180 degrees in the circumferential direction.

In this example, the embossed convex portion 32 is formed on the inner peripheral surface of the large diameter cylindrical portion 27 as follows. That is, the tip of a cylindrical tool (pin) is used to press multiple circumferential points on the outer peripheral surface of the large diameter cylindrical portion 27 radially inward, and the corresponding portions are semi-sheared (half-punched). As a result, a substantially cylindrical embossed recess 31 is formed at the bottom of the outer diameter side annular groove 30 on the outer peripheral surface of the large diameter cylindrical portion 27, and multiple circumferential points on the inner peripheral surface of the large diameter cylindrical portion 27 are protruded radially inward to form a substantially cylindrical embossed convex portion 32. In short, by embossing the large diameter cylindrical portion 27, the embossed recess 31 is formed on the outer peripheral surface of the large diameter cylindrical portion 27, and the material extruded by the formation of the embossed recess 31 is protruded radially inward from the inner peripheral surface of the large diameter cylindrical portion 27 to form the embossed convex portion 32. When forming the embossed convex portion 32, a pair of tools can be placed on the radially opposite side of the large diameter cylindrical portion 27, and the tips of the pair of tools can be moved closer to each other to simultaneously form two embossed convex portions 32 (embossed concave portions 31). The embossed concave portions 31 have a depth dimension smaller than the plate thickness of the large diameter cylindrical portion 27, and an inner surface shape that matches the outer surface shape of the tip portion of the tool. The embossed convex portion 32 has a height dimension that is approximately the same as the depth dimension of the embossed concave portions 31. In this example, the depth dimension of the embossed concave portions 31 (the height dimension of the embossed convex portion 32) is 0.5 mm to 3 mm, and the diameter dimension of the embossed concave portions 31 (the diameter dimension of the embossed convex portion 32) is approximately 2 mm to 2.5 mm.

<Joint shaft>
The joint shaft 13 corresponds to an insertion member, is made of metal, and is configured to be substantially cylindrical as a whole. The joint shaft 13 has a cylindrical portion 33 corresponding to a first coupling portion on one axial side.

The outer peripheral surface of the cylindrical portion 33 has male serrations 34 with a circumferentially uneven shape that corresponds to the outer peripheral uneven portion, and an inner diameter side annular groove 35 arranged to cross the axial middle portion of the male serrations 34 in the circumferential direction. In other words, the outer peripheral surface of the cylindrical portion 33 has male serrations 34 on both axial sides of the inner diameter side annular groove 35.

The inner diameter side annular groove 35 is formed on the outer peripheral surface of the cylindrical portion 33, for example, by cutting. The outer diameter of the bottom surface 36 of the inner diameter side annular groove 35 is smaller than the bottom circle diameter of the male serration 34. The inner diameter side annular groove 35 has a trapezoidal cross-sectional shape. In the illustrated example, the axial dimension of the opening of the inner diameter side annular groove 35 is larger than the axial dimension _W30 of the opening of the outer diameter side annular groove 30 provided in the first outer tube 12. However, it is sufficient that the axial dimension of the opening of the inner diameter side annular groove is larger than the diameter dimension (axial dimension) of the embossed convex portion, and it can also be smaller than the axial dimension of the opening of the outer diameter side annular groove.

The male serration 34 has a guide section 37 at one axial end, located forward of the cylindrical section 33 in the insertion direction, which has a smaller circumscribed circle diameter (tooth tip circle diameter) than the adjacent section on the other axial end.

The joint shaft 13 has a medium diameter hole 38 with a cylindrical inner peripheral surface at the axial middle of the inner peripheral surface, and a large diameter hole 39 with a cylindrical inner peripheral surface at one axial end of the inner peripheral surface. Therefore, of the pair of male serrations 34 arranged on both axial sides of the inner diameter side annular groove 35, the male serration 34 arranged on one axial side is formed in a thinner part than the male serration 34 arranged on the other axial side. The inner diameter of the medium diameter hole 38 is slightly larger than the circumscribed circle diameter of the male spline 22a that constitutes the first inner shaft 11. This makes it possible to insert the male spline 22a into the inside of the medium diameter hole 38 when the contraction shaft 9 is contracted.

The joint shaft 13 has a female serration 40 on the other axial half of the inner surface located on the other axial side of the medium diameter hole portion 38. The bottom circle diameter of the female serration 40 is smaller than the inner diameter of the medium diameter hole portion 38.

The joint shaft 13 has an axially extending slit 41 in the other axial half, and a pair of flanges 42 that protrude radially outward on both circumferential sides of the slit 41. One of the pair of flanges 42 has a screw hole 43, and the other has a through hole. The screw hole 43 and the through hole are arranged coaxially. In the illustrated example, a cap 44 is fitted into the medium diameter hole 38 to prevent foreign matter such as moisture from passing through the inside of the joint shaft 13.

<<Connection structure between outer cylinder and joint shaft>>
11 , the cylindrical portion 33 of the joint shaft 13 is inserted into the large diameter cylindrical portion 27 of the first outer cylinder 12, whereby the male serrations 34 are press-fitted (lightly press-fitted) into the female serrations 29, and the male serrations 34 and the female serrations 29 are engaged with each other (convex-concave engagement). The male serrations 34 and the female serrations 29 form a torque transmission portion 45.

In this example, the cylindrical portion 33 of the joint shaft 13 is inserted into the large-diameter cylindrical portion 27 until the other axial end of the large-diameter cylindrical portion 27 abuts against the other axial end of the male serration 34. Specifically, as shown in FIG. 12, the cylindrical portion 33 is inserted into the large-diameter cylindrical portion 27 until the other axial end of the serration teeth 46 constituting the female serration 29 provided on the inner peripheral surface of the large-diameter cylindrical portion 27 abuts against the abutment surface 48 facing one axial side, which is located at the other axial end of the serration groove 47 constituting the male serration 34. This allows the joint shaft 13 to be positioned in the axial direction relative to the first outer tube 12. The serration teeth 46 correspond to the inner peripheral convex portion, and the serration groove 47 corresponds to the outer peripheral concave portion. In this example, the guide portion 37 is provided at the one axial end of the male serration 34, which is located forward in the insertion direction of the cylindrical portion 33, and therefore the workability of the insertion operation of the cylindrical portion 33 can be improved.

In addition, when the cylindrical portion 33 of the joint shaft 13 is inserted inside the large diameter cylindrical portion 27 of the first outer tube 12 and the axial positioning of the joint shaft 13 relative to the first outer tube 12 is performed, the inner diameter side annular groove 35 provided on the outer peripheral surface of the cylindrical portion 33 and the outer diameter side annular groove 30 provided on the outer peripheral surface of the large diameter cylindrical portion 27 are arranged in a radially overlapping (overlapping) position. More specifically, the outer diameter side annular groove 30 is arranged inside the inner diameter side annular groove 35 in the axial direction. Then, in this state, the large diameter cylindrical portion 27 is embossed. When performing the embossing, the axial positioning of the tool used for the embossing is performed, for example, based on the end face on the other axial side of the joint shaft 13. Note that the axial positioning of the tool is not limited to the end face on the other axial side of the joint shaft 13, but other parts such as the end face on one axial side of the first outer tube 12 can also be used.

By embossing, a plurality of embossed recesses 31 are formed on the bottom surface of the outer diameter side annular groove 30 on the outer peripheral surface of the large diameter cylindrical portion 27, and a plurality of embossed protrusions 32 are formed on the inner peripheral surface of the large diameter cylindrical portion 27. The embossed protrusions 32 are then positioned inside the inner diameter side annular groove 35. As a result, the embossed protrusions 32 and the inner diameter side annular groove 35 form the retaining portion 49.

When the embossed protrusion 32 is disposed inside the inner annular groove 35, a radial gap exists between the tip surface 50 of the embossed protrusion 32 and the bottom surface 36 of the inner annular groove 35. In addition, an axial gap exists between the embossed protrusion 32 and the opposing inner surfaces 51 of the inner annular groove 35.

In this example, as described above, the workpiece is pressed with a small diameter tool (pin) and the embossing process is performed to semi-shear the part, forming a substantially cylindrical embossed protrusion 32 on the inner peripheral surface of the large diameter cylindrical portion 27. This makes it difficult for plastic deformation to occur in parts of the large diameter cylindrical portion 27 other than the part pressed by the tool, and prevents the roundness of the outer peripheral surface of the large diameter cylindrical portion 27 from decreasing. Furthermore, in this example, the outer diameter side annular groove 30 is formed on the outer peripheral surface of the large diameter cylindrical portion 27 to reduce the plate thickness of the part where the outer diameter side annular groove 30 is formed, and the bottom (flat bottom surface) of the outer diameter side annular groove 30 is pressed radially inward with the tool to form the embossed protrusion 32, so that the press load required to form the embossed protrusion 32 can be kept low. In addition, when the embossing process is performed, the weld bead portion 52 described later has not yet been formed between the first outer tube 12 and the joint shaft 13, but since the male serration 34 is press-fitted into the female serration 29, the coaxiality between the first outer tube 12 and the joint shaft 13 can be ensured, and the first outer tube 12 and the joint shaft 13 can be prevented from rattling. Furthermore, since a radial gap exists between the bottom surface 36 of the inner diameter side annular groove 35 and the tip surface 50 of the embossed protrusion 32, and an axial gap exists between the mutually opposing inner side surfaces 51 of the inner diameter side annular groove 35 and the embossed protrusion 32, it is possible to prevent the roundness of the outer circumferential surface of the large diameter tube portion 27 from decreasing due to the formation of the embossed protrusion 32.

Furthermore, in this example, the portion of the outer circumferential surface of the joint shaft 13 exposed from the large diameter cylindrical portion 27 and the end face on the other axial side of the large diameter cylindrical portion 27 are welded and fixed over the entire circumference by a weld bead portion 52. The weld bead portion 52 has a cross-sectional shape, such as an approximately quarter circle shape, an approximately triangular shape, or an approximately rectangular shape, and has an outer diameter that is the same as or smaller than the outer diameter of the large diameter cylindrical portion 27.

In this example, the cylindrical portion 33 of the joint shaft 13 is inserted into the large-diameter cylindrical portion 27 of the first outer tube 12, and embossed protrusions 32 are formed at multiple locations on the inner peripheral surface of the large-diameter cylindrical portion 27 in the circumferential direction. Then, the weld bead portion 52 is formed between the outer peripheral surface of the joint shaft 13 and the end face of the other axial side of the large-diameter cylindrical portion 27, axially separated from the embossed protrusions 32. This prevents the influence of the welding heat when forming the weld bead portion 52 from being transmitted to the embossed protrusions 32. Furthermore, since the male serrations 34 are pressed into the female serrations 29, the coaxiality of the first outer tube 12 and the joint shaft 13 can be ensured when forming the weld bead portion 52, and the first outer tube 12 and the joint shaft 13 can also be prevented from rattling.

Telescopic shaft
The telescopic shaft 10 is configured so that its entire length can be extended and retracted even in a steady state where the automobile is not in a collision accident. The telescopic shaft 10 includes a second outer cylinder 53, a second inner shaft 54, a plurality of balls 55, a plurality of rollers 56, and a plurality of leaf springs 57.

In the intermediate shaft 5a of this example, the second outer tube 53 is disposed on one axial side of the telescopic shaft 10, closer to the contraction shaft 9, and the second inner shaft 54 is disposed on the other axial side of the telescopic shaft 10, farther from the contraction shaft 9.

Second External Cylinder
The second outer tube 53 is, for example, a cold forged product, and as shown in Fig. 3, integrally comprises a solid (approximately cylindrical) male shaft portion 58 disposed at one end in the axial direction, and a bottomed cylindrical female tube portion 59 disposed adjacent to the other axial side of the male shaft portion 58. The male shaft portion 58 and the female tube portion 59 are disposed coaxially. The outer diameter of the male shaft portion 58 is smaller than the outer diameter of the female tube portion 59, and the axial length of the male shaft portion 58 is sufficiently shorter than the axial length of the female tube portion 59.

The male shaft portion 58 is a portion that connects to the joint shaft 13 that constitutes the contraction shaft 9, and has male serrations 60 in the axially middle portion of the outer circumferential surface. A circumferential groove 61 is provided at one location on the outer circumferential surface of the male shaft portion 58, which is formed to cross the male serrations 60 in the circumferential direction.

The female tube portion 59 is a portion into which the second inner shaft 54 is slidably inserted. The female tube portion 59 has first female grooves 62 and second female grooves 63, each of which extends in the axial direction, arranged alternately in the circumferential direction on its inner circumferential surface. Each of the first female grooves 62 and second female grooves 63 has a cross-sectional shape that is a concave arc shape.

"Second Inner Axis"
The second inner shaft 54 is solid over its entire length. The second inner shaft 54 has first male grooves 64 and second male grooves 65, each of which extends in the axial direction, alternately arranged in the circumferential direction on the outer circumferential surface of one axial side portion. The first male groove 64 has a substantially isosceles trapezoidal cross section, and the circumferential width of the opening is wider than the circumferential width of the bottom portion. In contrast, the second male groove 65 has a concave arc cross section. A circular stopper 66 is engaged on the outer circumferential surface of the end portion on one axial side of the second inner shaft 54. This prevents the balls 55 arranged inside the first male groove 64 and the rollers 56 arranged inside the second male groove 65 from slipping out of the first male groove 64 and the second male groove 65 to the one axial side. A yoke 67 separate from the second inner shaft 54 is fixed by welding to the end portion on the other axial side of the second inner shaft 54. The yoke 67, together with another yoke 68 connected to the front end of the steering shaft 2a and a cross shaft (not shown), constitutes a universal joint 4c.

When the second inner shaft 54 is inserted inside the second outer cylinder 53, the circumferential phases of the first male groove 64 and the first female groove 62 are aligned, and the circumferential phases of the second male groove 65 and the second female groove 63 are aligned. Then, a plurality of balls 55 are placed between the first male groove 64 and the first female groove 62. Furthermore, a leaf spring 57 is placed between the first male groove 64 and the plurality of balls 55, and a preload is applied to the plurality of balls 55. Also, one roller 56 is placed between each of the second male groove 65 and the second female groove 63.

In the telescopic shaft 10 described above, the second inner shaft 54 and the second outer tube 53 are combined so that they can transmit torque and can expand and contract over their entire length in a steady state. In addition, in the telescopic shaft 10, when transmitting low torque, the multiple balls 55 and the leaf spring 57 transmit torque between the second inner shaft 54 and the second outer tube 53, and when the transmitted torque increases, the multiple rollers 56 transmit the increased torque. In addition, when the second inner shaft 54 and the second outer tube 53 are displaced relative to each other in the axial direction, the multiple balls 55 roll between the first male groove 64 and the first female groove 62, and the multiple rollers 56 slide between the second male groove 65 and the second female groove 63. In addition, the multiple balls 55 are pressed against the inner surface of the first female groove 62 by the elasticity of the leaf spring 57, so that rattling between the second inner shaft 54 and the second outer tube 53 is prevented.

When the contraction shaft 9 and the telescopic shaft 10 are axially connected, the male shaft portion 58 of the second outer tube 53 constituting the telescopic shaft 10 is inserted into the inside of the joint shaft 13 constituting the contraction shaft 9. Then, the male serrations 60 on the outer peripheral surface of the male shaft portion 58 are engaged with the female serrations 40 on the inner peripheral surface of the joint shaft 13 in a torque-transmitting manner. This prevents relative rotation between the joint shaft 13 and the second outer tube 53. In addition, the middle portion of the tightening bolt 69 screwed into the screw hole 43 of the joint shaft 13 is inserted into the inside of the circumferential groove 61 on the outer peripheral surface of the male shaft portion 58, and the circumferential groove 61 and the tightening bolt 69 are key-engaged. This prevents relative movement between the joint shaft 13 and the second outer tube 53 in the axial direction. In addition, by increasing the amount of engagement of the tightening bolt 69, the width dimension of the slit 41 of the joint shaft 13 is reduced, and the diameter of the joint shaft 13 is reduced. Then, the inner surface of the joint shaft 13 tightly clamps the outer surface of the male shaft portion 58. This connects the contraction shaft 9 and the telescopic shaft 10 in a manner that allows torque transmission.

In the steering device of this example, in a steady state, the second outer cylinder 53 and the second inner shaft 54 that constitute the telescopic shaft 10 are displaced relative to each other in the axial direction, causing the intermediate shaft 5a to telescope. This absorbs vibrations input to the tires while driving. In addition, in the event of a so-called full-wrap collision, in which the entire front of the vehicle body collides with another vehicle, the telescopic shaft 9 and the telescopic shaft 10 each contract. This absorbs the impact of the collision and prevents the steering wheel 1a from being thrust upward toward the driver.

In this example having the above configuration, even if a defect occurs in the weld bead portion 52 connecting the first outer tube 12 and the joint shaft 13, which are a pair of shafts constituting the intermediate shaft 5a, which is a torque transmission shaft, the torque transmission function can be ensured and separation of the first outer tube 12 and the joint shaft 13 can be prevented.

That is, even if a defect occurs in the weld bead portion 52, torque can be transmitted between the joint shaft 13 and the first outer tube 12 by the torque transmission portion 45, which is formed by engaging the male serrations 34 of the joint shaft 13 with the female serrations 29 of the first outer tube 12 in a concave-convex engagement (serration engagement). Furthermore, the embossed convex portion 32 formed on the inner peripheral surface of the large diameter tube portion 27 of the first outer tube 12 is disposed inside the inner diameter side annular groove 35 provided on the joint shaft 13, forming a retaining portion 49, which can prevent the joint shaft 13 from coming out of the first outer tube 12 in the axial direction.

In addition, the thickness _T12 of the large diameter cylindrical portion 27 of the first outer tube 12 and the thickness _t13 of the cylindrical portion 33 of the joint shaft 13 are set to be approximately the same, or the thickness _T12 (or _t13 ) of the larger of the thicknesses _T12 of the first outer tube ₁₂ and t13 of the joint shaft 13 is restricted to be equal to or less than twice the thickness _t13 (or _T12 ) of the smaller of the thicknesses T12 of the first outer tube 12 and t13 of the joint shaft 13. This ensures the welding quality of the weld bead portion 52 and prevents welding defects. Furthermore, in this example, instead of directly embossing the large diameter cylindrical portion 27 having the larger thickness _t13 , the outer diameter side annular groove 30 is formed on the outer peripheral surface of the large diameter cylindrical portion 27, and the bottom surface of the outer diameter side annular groove 30 is embossed to form the embossed protrusion 32 on the inner peripheral surface of the large diameter cylindrical portion 27. Therefore, it is possible to ensure the welding quality of the weld bead portion 52 and avoid welding defects while ensuring the shape accuracy of the embossed protrusions 32 .

In addition, in this example, when performing the embossing process, the axial positioning of the tool used for embossing is performed based on the end face on the other axial side of the joint shaft 13. Therefore, by checking whether the embossed recess 31 is formed inside (at the bottom) of the outer diameter side annular groove 30, it is possible to check whether the axial positioning of the joint shaft 13 relative to the first outer tube 12 has been performed correctly, and it is also possible to check whether the embossed protrusion 32 is positioned inside the inner diameter side annular groove 35. Therefore, the quality control of the joint between the first outer tube 12 and the joint shaft 13 can be performed visually. It is also possible to perform automatic quality inspection using a camera or the like.

The retaining portion 49 is also positioned axially away from the weld bead portion 52. This effectively prevents the welding heat generated when forming the weld bead portion 52 from being transmitted to the retaining portion 49. This effectively prevents the retaining function from being impaired by forming the weld bead portion 52.

In addition, the embossed protrusions 32 that form the retaining portion 49 are formed on the inner peripheral surface of the large-diameter cylindrical portion 27 by embossing using a small-diameter tool, which prevents the roundness of the outer peripheral surface of the large-diameter cylindrical portion 27 from decreasing. Furthermore, in this example, a radial gap and an axial gap are provided between the embossed protrusions 32 and the inner-diameter annular groove 35, which also prevents the roundness of the outer peripheral surface of the large-diameter cylindrical portion 27 from decreasing.

The outer peripheral surface of the shaft portion 16 constituting the first inner shaft 11 is provided with intermittent male splines 22a, 22b whose phases in the circumferential direction are in agreement with each other. Furthermore, the effective engagement length Lx between the male spline 22a and the female spline 28 in the steady state is set to be longer than the axial dimension La of each of the fuse portions 24a, 24b. Therefore, even if a collision accident occurs and the contraction shaft 9 contracts, at least one of the male splines 22a, 22b can be spline-engaged with the female spline 28. Therefore, when the contraction shaft 9 is in a contracted state, it is possible to prevent torque transmission between the first inner shaft 11 and the first outer cylinder 12 from becoming impossible, and the operation of the steering wheel 1a from being unable to be transmitted to the steering wheel. When the contraction shaft 9 is completely contracted, the male spline 22a is disposed inside the large diameter cylinder portion 27 and the joint shaft 13.

Furthermore, in a steady state, each of the fuse portions 24a, 24b is exposed from the first outer cylinder 12 and is configured to have a smaller diameter than the bottom circle diameter of the male splines 22a, 22b. Therefore, in the event of a so-called offset collision in which part of the front of the vehicle body collides with another vehicle, at least one of the fuse portions 24a, 24b can bend or twist based on the impact load associated with the collision. This makes it possible to effectively absorb the impact of the collision.

The above describes an embodiment of the present invention, but the present invention is not limited to this and can be modified as appropriate without departing from the technical concept of the invention.

When implementing the present invention, the outer circumferential uneven portion provided on the outer circumferential surface of the inserting member is not limited to the male serrations described in the embodiment, but may be a male spline, or may be configured with a concave groove (key groove) or ridge at one or more circumferential locations on the outer circumferential surface. The cross-sectional shape of the outer circumferential uneven portion may also be polygonal or petal-shaped. Similarly, the inner circumferential uneven portion provided on the inner circumferential surface of the inserted member is not limited to the female serrations described in the embodiment, but may be a female spline, or may be configured with a concave groove (key groove) or ridge at one or more circumferential locations on the inner circumferential surface. The cross-sectional shape of the inner circumferential uneven portion may also be polygonal or petal-shaped.

When implementing the present invention, the inserting member and the inserted member are not limited to the shaft described in the embodiment, but a yoke or other members can be used. Therefore, the connection structure of the present invention can also be used, for example, in the connection between the yoke and the shaft. Furthermore, when implementing the present invention, the axial positioning of the inserting member relative to the inserted member is not limited to a configuration in which the end face of the inner circumferential convex portion constituting the inner circumferential convex portion abuts against an abutment surface provided in the outer circumferential convex portion, but other configurations can also be used.

In addition, when implementing the present invention, the number and shape of the embossed convex portions and embossed concave portions, as well as the shapes of the inner diameter side annular groove and the outer diameter side annular groove are not limited to the structures described in the embodiments, and may be changed as long as the function of preventing the inserting member from coming off the inserted member is achieved.

LIST OF SYMBOLS 1, 1a Steering wheel 2, 2a Steering shaft 3, 3a Steering column 4a, 4b, 4c, 4d Universal joint 5, 5a Intermediate shaft 6, 6a Steering gear unit 7, 7a Tie rod 8, 8a Pinion shaft 9 Contraction shaft 10 Telescopic shaft 11 First inner shaft 12 First outer cylinder 13 Joint shaft 15 Yoke portion 16 Shaft portion 17 Yoke 18 Base portion 19 Arm portion 20 Insertion hole 21 Circular hole 22a, 22b Male spline 23 Center hole 24a, 24b Fuse portion 25 Small diameter cylinder portion 26 Conical cylinder portion 27 Large diameter cylinder portion 28 Female spline 29 Female serration 30 Outer diameter side annular groove 31 Embossed recess 32 Embossed protrusion 33 Cylindrical portion 34 Male serration 35 Inner diameter side annular groove 36 Bottom surface 37 Guide portion 38 Medium diameter hole portion 39 Large diameter hole portion 40 Female serration 41 Slit 42 Flange portion 43 Screw hole 44 Cap 45 Torque transmission portion 46 Serration teeth 47 Serration groove 48 Abutment surface 49 Anti-slip portion 50 Tip surface 51 Inner surface 52 Weld bead portion 53 Second outer cylinder 54 Second inner shaft 55 Ball 56 Roller 57 Leaf spring 58 Male shaft portion 59 Female cylinder portion 60 Male serration 61 Circumferential groove 62 First female groove 63 Second female groove 64 First male groove 65 Second male groove 66 Stopper 67 Yoke 68 Yoke 69 Fastening bolt

Claims (10)

An insertion member having a first coupling portion at one end portion in an axial direction;
an inserted member having a cylindrical second connecting portion at an end portion on the other axial side into which the first connecting portion is inserted;
a weld bead portion formed by welding an end portion on the other axial side of the second joint portion and a portion of an outer circumferential surface of the insertion member that is exposed from the second joint portion,
The first connecting portion has an outer peripheral surface including an outer peripheral side uneven portion having an uneven shape in the circumferential direction and an inner diameter side annular groove,
The second coupling portion has, on its outer peripheral surface, an outer diameter side annular groove arranged at a position radially overlapping with the inner diameter side annular groove, and an embossed recess formed at a bottom of the outer diameter side annular groove, and also has, on its inner peripheral surface, an inner peripheral side uneven portion having an uneven shape in the circumferential direction that constitutes a torque transmission portion by uneven engagement with the outer peripheral side uneven portion, and an embossed protrusion provided at a position aligned with the embossed recess, disposed inside the inner diameter side annular groove, and constituting a slip-out prevention portion.
Bonding structure. The connection structure according to claim 1, wherein the dimension of the outer diameter side annular groove in the axial direction of the inserted member is 1 to 2 times the dimension of the embossed recess in the axial direction of the inserted member. The connection structure according to any one of claims 1 to 2, in which the end face on the other axial direction of the inner circumferential convex portion constituting the inner circumferential concave portion is abutted against an abutment surface provided at the end on the other axial direction of the outer circumferential concave portion constituting the outer circumferential concave portion, facing one axial side, thereby positioning the inserting member and the inserted member in the axial direction. The connection structure according to any one of claims 1 to 3, wherein the outer circumferential uneven portion is press-fitted into the inner circumferential uneven portion. The connection structure according to claim 4, wherein the outer circumferential uneven portion has a guide portion at one end in the axial direction, the guide portion having a smaller circumscribed circle diameter than the portion adjacent to the other axial side. The connection structure according to any one of claims 1 to 5, wherein each of the embossed convex portions and the embossed concave portions is disposed at a plurality of locations in the circumferential direction of the second connection portion. The connection structure according to any one of claims 1 to 6, wherein a gap exists in the radial direction of the first connection portion between the bottom surface of the inner diameter side annular groove and the tip surface of the embossed protrusion. The connection structure according to any one of claims 1 to 7, wherein a gap exists between the opposing inner surfaces of the inner diameter side annular groove and the embossed protrusion in the axial direction of the insertion member. A contraction shaft including a large diameter shaft, a small diameter shaft fitted inside the large diameter shaft to enable torque transmission and relative axial displacement with respect to the large diameter shaft, and a joint shaft connected to an axial end of the large diameter shaft,
A contraction shaft, wherein the large diameter shaft and the joint shaft are connected by the connection structure described in any one of claims 1 to 8, the large diameter shaft being the inserted member and the joint shaft being the inserting member. The collapsible shaft according to claim 9, wherein the collapsible shaft constitutes an intermediate shaft of a steering device for an automobile, and is configured to be capable of collapsing its entire length only when a collision accident occurs in an automobile and a load of a predetermined value or more is applied to the collapsible shaft in an axial direction.

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