JP2016008640A - Connecting part between yoke for joint cross universal joint and rotating shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a structure which can prevent the generation of large tensile stress related to a circumferential direction at a periphery of an axial single-side opening of a spline hole.SOLUTION: A spline shaft part 28 is constituted of a small-diameter spline shaft part 30 which is arranged at a half part in an axial direction, and a large-diameter spline shaft part 29 which is arranged at the other half part in the axial direction, and larger than the small-diameter spline shaft part 30. Concretely, an over-pin diameter (OPD), a tooth-tip circle diameter and a tooth-bottom circle diameter of a male spline part which is formed at an external peripheral face of the small-diameter spline shaft part 30 are set smaller than an over-pin diameter, a tooth-tip circle diameter and a tooth-bottom circle diameter of a male spline part which is formed at an external peripheral face of the large-diameter spline shaft part 29, respectively.

Description

  The present invention relates to an improvement in a joint part between a yoke and a rotary shaft constituting a cross shaft universal joint (cardan joint) for connecting, for example, rotational shafts constituting a steering device for an automobile so that torque can be transmitted.

  The automobile steering device is configured as shown in FIG. The movement of the steering wheel 1 operated by the driver is transmitted to the input shaft 6 of the steering gear unit 5 via the steering shaft 2, the universal joint 3a, the intermediate shaft 4, and another universal joint 3b. Then, a pair of left and right tie rods 7 and 7 are pushed and pulled by a rack and pinion mechanism built in the steering gear unit 5, and an appropriate rudder according to the operation amount of the steering wheel 1 is applied to the pair of left and right steering wheels. It is configured to give corners. In the case of the illustrated example, an electric power steering device is incorporated. For this purpose, a housing 10 in which an electric motor 9 is fixed to the front end portion of the steering column 8 at the front end portion of the steering column 8 that supports the steering shaft 2 so as to be rotatable inside is provided as a power source for providing auxiliary force. It is provided by supporting. The output torque (auxiliary force) of the electric motor 9 is applied to the steering shaft 2 through a gear unit or the like provided in the housing 10.

  FIG. 13 shows an example of the structure of the intermediate shaft 4 incorporated in the steering device as described above. In the case of the illustrated example, the intermediate shaft 4 is telescopic in order to prevent the steering wheel 1 from being pushed up to the driver side in the event of a collision. The intermediate shaft 4 has an inner shaft 12 provided with a male spline part 11 on the outer peripheral surface of the tip part (left end part in FIG. 13), and a female spline part 13 into which the male spline part 11 can be inserted on the inner peripheral surface. The outer tube 14 has a circular tubular shape. The male spline portion 11 and the female spline portion 13 are spline-engaged, so that the inner shaft 12 and the outer tube 14 are combined in an extendable manner. Further, the base end portions of the yokes 15 and 15 constituting the universal joints 3a and 3b are welded and fixed to the base end portions of the inner shaft 12 and the outer tube 14, respectively.

  As the universal joints 3a and 3b incorporated in the steering device as described above, for example, as described in Patent Documents 1 and 2, a cross shaft type universal joint is used. 14 to 15 show an example of the cross shaft type universal joint described in Patent Document 1 among them. The universal joint 3 includes a pair of yokes 15a and 15b, each of which is formed in a bifurcated shape by a metal material having sufficient rigidity, via a cross shaft 16 made of a hard metal such as an alloy steel such as bearing steel. In this way, the torque is transmitted and coupled. Each of the yokes 15a and 15b includes a base portion 17a and 17b, and a pair of connecting arm portions 18 and 18 for each of the yokes 15a and 15b. Of these, the base portions 17a and 17b are the end portions of the rotating shaft 19 (the base end portion of the inner shaft 12 or the outer tube 14, the front end portion of the steering shaft 2 or the rear end portion of the input shaft 6, see FIG. 12). Torque transmission is supported and fixed freely. Therefore, the base portion 17a of one yoke 15a (the left side in FIGS. 14 to 15) of the yokes 15a and 15b, which is the object of the present invention, is formed in a substantially annular shape as a whole. A spline hole 20 is formed in the central portion of the radial direction 17a so as to penetrate the base portion 17a in the axial direction. Then, the spline shaft portion provided at the end portion of the rotating shaft 19 is press-fitted into the spline hole 20, and the base portion 17 a and the portion of the end portion of the rotating shaft 19 that is separated from the base portion 17 a are all They are connected by so-called all-around welding that is welded over the circumference. On the other hand, of the yokes 15a and 15b, the base portion 17b of the other yoke 15b that is out of the scope of the present invention (on the right side in FIGS. 14 to 15) inserts an end portion of a rotating shaft (not shown). The inner diameter can be enlarged or reduced by forming a circular cylinder with a discontinuous portion in one circumferential direction. The base portion 17b is provided with a pair of flange portions 21a and 21b with the discontinuous portion being sandwiched from both sides in the circumferential direction. And it forms in one flange part 21a in the state which carried out the spline engagement of the female spline part 22 formed in the internal peripheral surface of the said base part 17b, and the spline shaft part provided in the edge part of another rotating shaft which is not shown in figure. The front end of a bolt (not shown) with the flange portion inserted through the through hole 23a is screwed into a nut 24 that is press-fitted into the through hole 23b formed in the other flange portion 21b and tightened. As a result, the distance between the flange portions 21a and 21b is reduced and the diameter of the base portion 17b is reduced, and the end portion of the other rotating shaft is coupled and fixed to the base portion 17b. In the present specification and claims, the term “spline” used for the joint between the base portion of the yoke and the rotating shaft includes what is called “serration” with a fine pitch.

  Further, the connecting arm portions 18 and 18 extend from one axial end of the base portion 17a (17b) to two axially opposite positions on one side in the diametrical direction, and face each other's inner side surfaces. I am letting. In addition, concentric circular holes 25 and 25 are formed in the portions near the tips of the connecting arm portions 18 and 18, respectively.

  The cross shaft 16 has a pair of shaft portions 26a and 26b provided in a state of being orthogonal to each other, and both ends of one shaft portion 26a are connected to the connecting arm portions 18 and 18 of the one yoke 15a. Similarly, both ends of the other shaft portion 26b are formed inside the circular holes 25, 25, and the radial needle bearings are arranged inside the circular holes 25, 25 formed in the coupling arm portions 18, 18 of the other yoke 15b. The two yokes 15a and 15b are oscillated and displaced with a light force with respect to the cross shaft 16 by being pivotally supported via the shafts 27 and 27. Due to such a configuration, the rotational force can be transmitted between the yokes 15a and 15b with the transmission loss suppressed in a state where the central axes of the yokes 15a and 15b do not coincide with each other.

  Of the spline holes 20 formed in the base portion 17a of one yoke 15a, when the rotational force is transmitted between the yokes 15a and 15b constituting the cross shaft type universal joint 3 as described above, the shaft Large hoop stress (circumferential tensile stress) is likely to occur at the peripheral edge of the unidirectional opening. That is, when transmitting the rotational force between the yokes 15a and 15b, as shown exaggeratedly in FIGS. 16 to 17, the coupling arm portions 18 and 18 are twisted (coupled and fixed to the base portion 17a). The direction of rotation around the central axis of the rotating shaft 19 tends to be elastically deformed. As a result, as indicated by a chain line α in FIG. 18, the one-side axial opening of the spline hole 20 is distorted into a non-circular shape (elliptical shape). In particular, in the case of a steering apparatus incorporating a column assist type electric power steering apparatus as shown in FIG. 12 described above, the rotational force transmitted by the universal joint 3 increases, and the distortion of the spline hole 20 as described above becomes significant. . Then, due to such distortion, a part of the inner peripheral edge of the one-side opening in the axial direction of the spline hole 20 whose inner diameter is reduced (a part surrounded by a chain line β in FIG. 18), and an outer peripheral surface of the rotary shaft 19 A large tensile stress in the circumferential direction of the rotary shaft 19 is likely to be concentrated and generated in the portion where the inner diameter dimension is reduced due to an increase in the contact pressure. The generation of such a large tensile stress is disadvantageous in terms of ensuring the durability of the one yoke 15a, and thus the universal joint 3.

JP-A-10-205547 JP 2008-196650 A

  In view of the circumstances as described above, the present invention is a cross shaft type that can prevent the occurrence of a large tensile stress in the circumferential direction at the peripheral edge portion of one axial end portion of the coupling hole formed in the base portion constituting the yoke. The invention was invented to realize the structure of the joint portion between the universal joint yoke and the rotary shaft.

The joint part of the yoke for cross-axis type universal joints of this invention and a rotating shaft is provided with the yoke which comprises a cross-axis type universal joint, and the rotating shaft which rotates at the time of use.
Of these, the yoke has a base portion having a coupling hole formed in the axial direction at the center in the radial direction, and one axial end edge of the base portion, from one position on the opposite side in the diametrical direction with respect to the rotating shaft to one side in the axial direction. And a pair of connecting arm portions provided in a state of extending in the direction.
The rotary shaft is coupled and fixed to the base portion by press-fitting a press-fit portion provided at one end in the axial direction into the inside of the coupling hole from the other axial side of the coupling hole.

  In particular, in the joint portion of the cross shaft type universal joint yoke of the present invention and the rotary shaft, the tightening margin of the portion near the axial end of the press-fitting portion with respect to the inner peripheral surface of the joint hole is also the same as that in the axial direction. The tightening margin of the portion near the end is smaller (the tightening margin of the portion near the one end in the axial direction of the press-fit portion relative to the inner peripheral surface of the coupling hole is negative, that is, the outer peripheral surface of the portion near the one end in the axial direction of the press-fit portion Including a state in which the inner peripheral surface of the coupling hole is closely opposed via a gap).

  In the case where the joint portion between the cross shaft type universal joint yoke and the rotary shaft of the present invention as described above is implemented, it is preferable that at least the axial direction piece of the press-fit portion as in the invention described in claim 2. The interference with respect to the inner peripheral surface of the coupling hole in the half is made smaller toward the one side in the axial direction.

When implementing the present invention as described above, for example, as in the invention described in claims 3 to 4, the coupling hole is a spline hole in which a female spline portion is provided on an inner peripheral surface, and the press-fitting portion Is a spline shaft portion provided with a male spline portion on the outer peripheral surface.
In the case of the invention described in claim 3, at least one of the diameter of the overpin, the tip circle diameter, and the root circle diameter of the male spline portion is set to the axis of the spline shaft portion. The portion closer to one end in the direction is made smaller than the portion closer to the other end in the axial direction.
On the other hand, in the case of the invention described in claim 4, the tooth thickness of the male spline portion is made smaller at the portion near the one end in the axial direction of the spline shaft portion than at the portion near the other end in the axial direction.

  In carrying out the present invention as described above, preferably, as in the invention described in claim 5, the coupling hole is provided so as to penetrate the base portion in the axial direction, and the press-fitting into the coupling hole is performed. Part is press-fitted in a state where one end part in the axial direction of the press-fitting part protrudes from one axial opening of the coupling hole. Then, one or a plurality of circumferential directions of one end portion in the axial direction of the press-fitting portion are plastically deformed radially outward and a caulking portion is provided to prevent the press-fitting portion from coming out of the coupling hole.

According to the joint part of the cross shaft type universal joint yoke and the rotary shaft of the present invention configured as described above, the circumferential direction is formed at the peripheral edge part of one axial end part of the joint hole formed in the base part constituting the yoke. It is possible to prevent a large tensile stress from being generated.
That is, in the case of the present invention, among the press-fit portions provided at one end in the axial direction of the rotating shaft that are press-fitted into the coupling hole, the allowance for the portion near the one end in the axial direction is the same as the allowance for the portion near the other end in the axial direction. Smaller than that. Therefore, even when the pair of coupling arm portions constituting the yoke tend to elastically deform in the torsional direction when the rotational force is transmitted by the cruciform universal joint, the shaft of the coupling hole is used. It can prevent that the contact pressure with the peripheral part of a direction one end part and the outer peripheral surface of the said rotating shaft (press-fit part) becomes large too much. For this reason, it is possible to prevent a large tensile stress in the circumferential direction from being generated in a part of the peripheral portion, and it is possible to improve the durability of the yoke and, consequently, the universal joint.

The partial cutting side view which shows the 1st example of embodiment of this invention. The principal part enlarged side view which similarly takes out and shows a rotating shaft. The figure similar to FIG. 2 shown in the state before providing a male spline part. The figure similar to FIG. 2 which shows the 2nd example of embodiment of this invention. The figure similar to FIG. 2 which shows the 3rd example. The figure similar to FIG. 2 which shows the 4th example. The figure similar to FIG. 1 which shows the same 5th example. The figure similar to FIG. 2 which shows the said 6th example. The same figure (A) as FIG. 1 which shows the 7th example, and the X section enlarged view (B) of (A). The figure similar to FIG. 1 which shows the 8th example. The end view which shows the state which looked at the yoke for demonstrating the structure which can be implemented in combination with this invention from the axial direction one side. The partially cut side view which shows an example of the steering apparatus known conventionally. The partial cutting side view which takes out and shows an intermediate shaft. The side view which shows an example of the cross-shaft type universal joint known conventionally. The figure seen from the lower part of FIG. 14 shown in the state which cut | disconnected a part. The perspective view which exaggerates and shows the state which the yoke elastically deformed with transmission of rotational force. The end view seen from the upper part of FIG. The figure similar to FIG. 17 shown in the state which does not transmit rotational force.

[First example of embodiment]
1 to 3 show a first example of an embodiment of the present invention corresponding to claims 1 and 3. It should be noted that a feature of the present invention including this example is that a large tensile stress in the circumferential direction is applied to the peripheral edge portion of the opening on one axial side (the right side in FIG. 1) of the spline hole 20 of the base portion 17a constituting the yoke 15a. It is in a structure to prevent it from occurring. Since the structure and operation of the other parts are the same as those conventionally known, including the conventional structure shown in FIGS. 14 to 15 described above, overlapping illustrations and descriptions are omitted or simplified. The description will focus on the features of this example.

  Also in the case of this example, the base portion 17a of the yoke 15a is formed in a substantially annular shape as a whole in the same manner as the conventional structure shown in FIGS. 14 to 15 described above, and at the central portion in the radial direction of the base portion 17a, The spline hole 20 is formed so as to penetrate the base portion 17a in the axial direction. The diameters of the spline holes 20 (overpin diameter, tip diameter, and root diameter) are the same in the axial direction. Then, a spline shaft portion 28 having an outer peripheral surface as a male spline portion provided at one axial end portion of the solid or hollow rotating shaft 19a is press-fitted into the spline hole 20 from the other axial opening, and the base portion The yoke 15a is welded by welding the other end surface in the axial direction of 17a (the left end surface in FIG. 1) and the outer peripheral surface of the intermediate portion of the rotating shaft 19a (the portion adjacent to the spline shaft portion 28) over the entire circumference. The rotary shaft 19a is coupled and fixed. In the case of this example, one end portion in the axial direction of the spline shaft portion 28 is protruded from one side opening in the axial direction of the spline hole 20.

  In particular, in the case of this example, the spline shaft portion 28 includes a small-diameter spline shaft portion 30 provided in a front half portion (a half portion in the axial direction and the right half portion in FIGS. 1 and 2), and a base half portion (axial direction). The other half portion is a large-diameter spline shaft portion 29 having a larger diameter than the small-diameter spline shaft portion 30 provided in the left half portion of FIGS. Specifically, an overpin diameter (OPD), a tip circle diameter, and a root circle diameter of the male spline portion formed on the outer peripheral surface of the small-diameter spline shaft portion 30 are set on the outer peripheral surface of the large-diameter spline shaft portion 29. The formed male spline part has an overpin diameter, a tip circle diameter, and a root circle diameter smaller than each other. Thereby, the interference with respect to the radial direction of the small-diameter spline shaft portion 30 with respect to the inner peripheral surface of the spline hole 20 is also made smaller than the interference with respect to the radial direction of the large-diameter spline shaft portion 29. Of the spline shaft portion 28, a range of 50 to 80% of the total length of the spline shaft portion 28 is the large-diameter spline shaft portion 29, and a range of 20 to 50% is the small-diameter spline shaft portion 30. As a result, of the fitting portion (spline engaging portion) between the spline hole 20 and the spline shaft portion 28, a range of 50 to 80% of the total length of the spline hole 20 is fitted with the large-diameter spline shaft portion 29. The range of 20 to 50% is fitted with the small-diameter spline shaft portion 30. The operation of forming such a spline shaft portion 28 is performed as follows, for example. First, as shown in FIG. 3, the metal bar 31 used as the material of the rotary shaft 19a is cut, and the end of the bar 31 has an axial diameter of one half in the axial direction. The stepped shaft portion 32 is smaller than the outer diameter of the other half portion. The spline shaft portion 28 is formed by rolling each of the stepped shaft portion 32 on the outer peripheral surface of the half piece in the axial direction and the outer peripheral surface of the other half portion in the axial direction. Alternatively, the end portion of the single cylindrical surface bar has a shape corresponding to the outer surface shape of the spline shaft portion 28 {the inner diameter of the back half (overpin diameter, tooth tip diameter and root diameter). The spline shaft portion 28 can be formed by pressing into a die smaller than the inner diameter of the opening half.

In the case of carrying out this example, if the tightening allowance of the small-diameter spline shaft portion 30 with respect to the inner peripheral surface of the spline hole 20 can be made smaller than the tightening allowance of the large-diameter spline shaft portion 29, the male spline portion overshoots. Any one or any two of the pin diameter, the tip circle diameter, and the root circle diameter may be configured to be smaller in the small diameter spline shaft portion 30 than in the large diameter spline shaft portion 29. You can also.
Further, the allowance of the small-diameter spline shaft portion 30 with respect to the inner peripheral surface of the spline hole 20 is made negative (the outer peripheral surface of the small-diameter spline shaft portion 30 and the inner peripheral surface of the spline hole 20 are closely opposed to each other through a gap. You can also.
However, in any case, the large-diameter spline shaft portion 29 of the spline shaft portions 28 is fitted and fixed in a state of having a sufficient tightening margin inside the spline hole 20 (press-fit state by interference fit). (Spline engagement).

According to the joint portion between the universal joint yoke and the rotating shaft of this example as described above, a large tensile stress in the circumferential direction is generated in the peripheral edge portion of the one-side axial opening of the spline hole 20. Can be prevented.
That is, in the case of the present example, the small-diameter spline shaft portion provided in one half of the axial direction of the spline shaft portion 28 in the fitting portion (spline engagement portion) between the spline hole 20 and the spline shaft portion 28. The tightening allowance of 30 on the inner peripheral surface of the spline hole 20 is made smaller than the allowance on the inner peripheral surface of the spline hole 20 of the large-diameter spline shaft portion 29 provided in the other half portion in the axial direction. Accordingly, as the rotational force is transmitted by the universal joint, the pair of coupling arm portions 18 and 18 constituting the yoke 15a tend to be elastically deformed in the twisting direction (direction rotating around the central axis of the rotating shaft 19a). Thus, even when the axial one-side opening of the spline hole 20 is distorted into a non-circular shape, the portion of the peripheral edge of the axial one-side opening has a reduced inner diameter, and the spline shaft portion 28 ( The contact pressure with the outer peripheral surface of the small-diameter spline shaft portion 30) can be prevented from becoming excessively large. As a result, it is possible to prevent a large tensile stress in the circumferential direction from occurring in a portion of the peripheral edge where the inner diameter is reduced, and to improve the durability of the yoke 15a and the universal joint. You can plan.

In the case of this example, the work of press-fitting the spline shaft portion 28 into the spline hole 20 can be facilitated. That is, among the spline shaft portions 28, the diameter of the small-diameter spline shaft portion 30 provided in one half of the axial direction is made smaller than the diameter of the large-diameter spline shaft portion 29 provided in the other half of the axial direction. By inserting the small-diameter spline shaft portion 30 into the spline hole 20 at the initial stage of press-fitting the spline shaft portion 28 into the spline hole 20, the spline shaft portion 28 and the spline hole 20 You can align. Therefore, it is possible to facilitate the work of press-fitting the spline shaft portion 28 in the correct posture from the other side in the axial direction of the spline hole 20 to the inside of the spline hole 20. Note that the coupling portion between the yoke 15a and the rotary shaft 19a restricts the large-diameter spline shaft portion 29 to the length range, so that a sufficient coupling strength in use can be secured.
When the present invention is carried out, the coupling hole formed in the central portion in the radial direction of the base portion constituting the yoke is a simple circular hole, and the spline shaft portion 28 of the rotary shaft 19a is press-fitted into this circular hole. You can also do it. In this case, each tooth constituting the male spline portion provided on the outer peripheral surface of the spline shaft portion 28 is fitted in a state having a tightening margin on the inner peripheral surface of the circular hole.

[Second Example of Embodiment]
FIG. 4 shows a second example of an embodiment of the present invention corresponding to claims 1 to 3. In the case of this example, of the spline shaft portion 28a provided at the end portion of the rotating shaft 19b, the overpin diameter of the male spline portion formed on the outer peripheral surface of the tip half portion (the right half portion in FIG. 4), the tooth tip circle The diameter and the root circle diameter are made smaller toward the one axial side (the right side in FIG. 4). Accordingly, the tightening margin in the radial direction of the front half portion 33 of the spline shaft portion 28a with respect to the inner peripheral surface of the spline hole 20 (see FIG. 1) of the yoke 15a is reduced toward the one side in the axial direction.
The configuration and operation of the other parts are the same as in the first example of the embodiment described above.

[Third example of embodiment]
FIG. 5 also shows a third example of the embodiment of the present invention corresponding to claims 1 to 3. In the case of this example, the diameter of the entire spline shaft portion 28b provided at the end of the rotating shaft 19c is reduced toward the one side in the axial direction (right side in FIG. 5) (formed on the outer peripheral surface of the spline shaft portion 28b). The diameter of the tip circle and the root circle of the male spline portion is reduced toward the one side in the axial direction, thereby reducing the overpin diameter toward the one side in the axial direction). The cross-sectional shape (bus shape) extending in the axial direction of the tooth tip surface and the tooth bottom surface of the male spline portion formed on the outer peripheral surface of the spline shaft 28b is a partial arc shape. Thus, the tightening margin in the radial direction of the spline shaft portion 28b with respect to the inner peripheral surface of the spline hole 20 (see FIG. 1) of the yoke 15a is reduced toward the one side in the axial direction.
The configuration and operation of the other parts are the same as in the first example of the embodiment described above.

[Fourth Example of Embodiment]
FIG. 6 also shows a fourth example of the embodiment of the present invention corresponding to claims 1 to 3. In the case of this example, by reducing the root diameter of the male spline portion formed on the outer peripheral surface of the spline shaft portion 28c of the rotating shaft 19d so as to decrease toward one side in the axial direction, the diameter of the overpin increases toward one side in the axial direction. The tip diameter is constant over the axial direction. According to this example, it is possible to facilitate the work of press-fitting the spline shaft portion 28c into the spline hole 20 (see FIG. 1) of the yoke 15a.
The configuration and operation of the other parts are the same as in the third example of the embodiment described above.

[Fifth Example of Embodiment]
FIG. 7 shows a fifth example of an embodiment of the present invention corresponding to claims 1 and 3. In the case of this example, a bottomed cylindrical spline hole 20a is formed in the base portion 17c constituting the yoke 15c so as to open only at the base end surface (the other end surface in the axial direction, the left end surface in FIG. 7) of the base portion 17c. The spline shaft portion 28 of the rotary shaft 19a is press-fitted into the spline hole 20a. According to this example, it is possible to suppress the occurrence of tensile stress in the circumferential direction generated at the peripheral edge of the back end portion of the spline hole 20a based on the presence of the bottom portion of the spline hole 20a.
The configuration and operation of the other parts are the same as in the first example of the embodiment described above.

[Sixth Example of Embodiment]
FIG. 8 shows a sixth example of an embodiment of the present invention corresponding to claims 1 and 2. In the case of this example, from the base half 34 whose outer peripheral surface is a single cylindrical surface at the end of the rotating shaft 19e, and the first half 35 of a partial truncated cone shape whose outer diameter decreases toward the tip side. A press-fitting portion 36 is provided. That is, in this example, no male spline part is formed on the outer peripheral surface of the press-fitting part 36. Then, such a press-fitting portion 36 is press-fitted into a coupling hole formed in the base of the yoke and having a single cylindrical surface on the inner peripheral surface (no irregularities in the circumferential direction). As a result, the tightening margin in the radial direction of the press-fit portion 36 with respect to the inner peripheral surface of the coupling hole is made smaller than the base half portion 34 in the front half portion 35, and the tightening margin in the radial direction of the front half portion 35. Can be reduced toward the tip side.
The configuration and operation of the other parts are the same as in the first example of the embodiment described above.

[Seventh example of embodiment]
FIG. 9 shows a seventh example of the embodiment of the present invention corresponding to the first, third, and fifth aspects. In the case of this example, the tightening margin with respect to the inner peripheral surface of the spline hole 20 of the small-diameter spline shaft portion 30a provided in the tip half portion (half axial portion) of the spline shaft portion 28d of the rotating shaft 19f is negative ( The outer peripheral surface of the small-diameter spline shaft portion 30a and the inner peripheral surface of the spline hole 20 are made to face each other through a gap). And, the spline shaft portion 28d is plastically deformed radially outward at two positions in the circumferential direction of the tip portion protruding from one axial opening of the spline hole 20, and is provided with caulking portions 37, 37. . This prevents the spline shaft portion 28d from coming out of the spline hole 20.

According to this example configured as described above, as the caulking portions 37, 37 are formed, the other side surface in the axial direction of both the caulking portions 37, 37 and the outer peripheral surface of the small-diameter spline shaft portion 30a. Even when the sag 38 occurs in the continuous portion, it is possible to prevent stress from concentrating on the peripheral edge portion of the one-side axial opening of the spline hole 20. That is, unlike the case of this example, the spline shaft portion provided at the end portion of the rotary shaft has a large tightening margin over the entire spline hole in the spline hole provided in the base portion of the yoke. When the inner fitting is fixed in the state, the sag generated when the caulking portion is formed is pressed against the inner peripheral edge of the opening of the spline hole, and there is a possibility that stress is generated in the portion. On the other hand, in the case of this example, the tightening margin with respect to the inner peripheral surface of the spline hole 20 of the small-diameter spline shaft portion 30a is negative, and the press-fit portion (large-diameter spline shaft portion 29) and the caulking portion 37, 37 can be separated from each other in the axial direction, so that even when the sag 38 is generated, the sag 38 can be prevented from being pressed against the inner peripheral edge of the one-side axial opening of the spline hole 20 (can escape). . Further, since the tensile stress can hardly be concentrated on the peripheral edge portion of the one-side axial opening of the spline hole 20, it is possible to increase the caulking strength when the two caulking portions 27, 27 are pressed against the one axial end surface of the base portion 17a.
The configuration and operation of the other parts are the same as in the first example of the embodiment described above.

[Eighth Example of Embodiment]
FIG. 10 shows an eighth example of an embodiment of the present invention corresponding to claims 1 and 4. Among the examples of the embodiment described above, the first to fifth and seventh examples are at least one of the overpin diameter, tip circle diameter, and root circle diameter of the male spline portion formed on the outer peripheral surface of the spline shaft portion. By making one diameter smaller in the axial direction near one end of the spline shaft than in the axial other end, the tightening margin in the radial direction of the spline shaft with respect to the inner peripheral surface of the spline hole is reduced in the axial direction. The portion near one end is smaller than the portion near the other end in the axial direction. On the other hand, in the case of this example, the tooth thickness of the male spline portion formed on the outer peripheral surface of the spline shaft portion 28e is the tip half portion (a half portion in the axial direction, the right half portion in FIG. 10) 39. The base half (the other half in the axial direction and the left half in FIG. 10) 40 is smaller. As a result, the fastening margin in the circumferential direction of the spline shaft portion 28e with respect to the inner peripheral surface of the spline hole 20 is configured to be smaller than the base half portion 40 in the front half portion 39.
The configuration and operation of the other parts are the same as in the first example of the embodiment described above. Note that, as in this example, the structure in which the interference in the circumferential direction of the spline shaft portion with respect to the inner peripheral surface of the spline hole is reduced by reducing the tooth thickness of the male spline portion is the same as in the first embodiment. It can also be implemented in combination with 1 to 5 or 7 examples.

  Among the examples of the embodiment of the present invention described above, the structures according to the first to fifth, seventh, and eighth examples can be implemented in combination with the structure described in Patent Document 2. That is, as shown in FIG. 11, when the rotational force is transmitted by the universal joint, when the pair of connecting arm portions 18 and 18 tend to elastically deform in the twist direction, The virtual straight line connecting the central axis of the spline hole 20b and the circumferential edge of the connecting arm portion 18 in the circumferential direction of the inner peripheral surface of the spline hole 20b, and the opening edge of the spline hole 20b. It is also possible not to provide the female spline part in the part including the intersection (the part surrounded by the chain line γ in FIG. 11).

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3, 3a, 3b Universal joint 4 Intermediate shaft 5 Steering gear unit 6 Input shaft 7 Tie rod 8 Steering column 9 Electric motor 10 Housing 11 Male spline part 12 Inner shaft 13 Female spline part 14 Outer tube 15 Yoke 16 Cross shafts 17a, 17b Base 18 Coupling arm 19, 19a-19f Rotating shaft 20, 20a Spline hole 21a, 21b Flange 22 Female serration 23a, 23b Through hole 24 Nut 25 Circular hole 26a, 26b Shaft 27 Radial needle bearing 28, 28a to 28e Spline shaft portion 29 Small-diameter spline shaft portion 30, 30a Large-diameter spline shaft portion 31 Bar 32 Stepped shaft portion 33 Tip half portion 34 Base half portion 35 Tip half portion 36 Press-fit portion 37 Crimper 38 Dare 39 First half 40 Base half

Claims (5)

A yoke that forms a cross shaft universal joint, and a rotating shaft that rotates during use,
Of these, the yoke has a base portion having a coupling hole formed in the axial direction in the central portion in the radial direction and one axial end edge of the base portion, and extends from one position on the diametrically opposite side to one axial direction. A pair of coupling arms provided in a state,
The rotary shaft is a cross shaft type that is fixedly coupled to the base by press-fitting a press-fit portion provided at one end in the axial direction into the inside of the coupling hole from the other axial side of the coupling hole. At the joint between the universal joint yoke and the rotary shaft,
A cross shaft type universal joint yoke, characterized in that a tightening margin at one end portion in the axial direction of the press-fitting portion with respect to an inner peripheral surface of the coupling hole is smaller than a tightening margin at a portion near the other end in the axial direction. And the connecting part of the rotating shaft.   The yoke for a cross-shaft type universal joint according to claim 1, wherein a tightening margin of at least one axial half of the press-fitting portion with respect to the inner peripheral surface of the coupling hole is reduced toward the one axial side. Joint with the rotating shaft.   The coupling hole is a spline hole in which a female spline portion is provided on an inner peripheral surface, and the press-fit portion is a spline shaft portion in which a male spline portion is provided on an outer peripheral surface, and an overpin diameter of the male spline portion; The diameter of at least one of a tip circle diameter and a root circle diameter is made smaller in the axial direction one end portion of the spline shaft portion than in the axial other end portion. The joint part of the yoke for cross-axis-type universal joints described in any one of these, and a rotating shaft.   The coupling hole is a spline hole in which a female spline portion is provided on an inner peripheral surface, and the press-fit portion is a spline shaft portion in which a male spline portion is provided on an outer peripheral surface. The yoke for the cross shaft type universal joint according to any one of claims 1 to 3, wherein the portion of the spline shaft portion is closer to one end in the axial direction than the other end portion in the axial direction. Coupling part.   The coupling hole is provided in a state of passing through the base portion in the axial direction, the press-fitting portion is inserted into the coupling hole, and an axial end portion of the press-fitting portion projects from an axial one-side opening of the coupling hole. It is possible to cause the press-fitting part to come out from the coupling hole by plastically deforming one or more circumferential directions at one end in the axial direction of the press-fitting part radially outwardly and providing a caulking part. The joint part of the yoke for cross-axis-type universal joints and the rotating shaft described in any one of Claims 1-4 which is preventing.

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