CN104620005A - Yoke for universal joint and production method therefor - Google Patents

Abstract

A yoke for a universal joint, having provided in a coupling hole (14a): a press-fit hole section (21) for press-fitting an end section of a shaft, provided between a center section and another end section in the axial direction; and a non-press-fit hole section (22) having a larger diameter than the press-fit hole section (21) and not having the shaft end section press-fitted therein, provided at one end section in the axial direction.

Description

Fork for universal joint and manufacturing method thereof

technical field

The present invention relates to improvements in a fork constituting a universal joint (universal coupling) of the cross shaft type for connecting rotating shafts constituting a steering device to each other so as to be able to transmit rotation moment.

Background technique

The steering device of an automobile is configured as shown in FIG. 11 . 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 3 a , the intermediate shaft 4 , and other universal joints 3 b. Furthermore, the pair of left and right tie rods 7, 7 are pushed and pulled by the rack and pinion mechanism built in the steering gear unit 5, and an appropriate steering angle corresponding to the amount of operation of the steering wheel 1 is given to the pair of left and right steering wheels.

As the universal joints 3a, 3b provided in such a steering device, in general, a cross-type universal joint called a universal joint shown as an example in FIG. 12 is widely used. The universal joints 3a, 3b each include a pair of forks 8a, 8b (8c, 8d) and a cross shaft 9 that connects the front ends of the pair of forks 8a, 8b (8c, 8d) to swing. The base of one fork 8a (8c) is coupled and fixed to the rear end of the male shaft 10 as a solid shaft (the front end of the female shaft 11 as a hollow shaft) constituting the intermediate shaft 4 in a torque-transmittable manner. The base of the other fork 8b ( 8d ) is coupled and fixed to the front end of the steering shaft 2 (the rear end of the input shaft 6 ) so that torque can be transmitted. The intermediate shaft 4 is formed by combining a male shaft 10 and a female shaft 11 so that torque can be transmitted and relative displacement in the axial direction is possible.

FIG. 13 shows a first example of a conventional structure of a fork called a plunge type that can be used as one fork 8a, 8c constituting the universal joints 3a, 3b. As described in Patent Document 1 etc. and conventionally known, by performing stamping including punching and bending on metal plate materials such as steel plates, or by performing forging and punching on metal materials such as steel round bars, To integrally manufacture the fork 8e shown in FIG. 13 . Such a fork 8 e includes a base portion 12 and a pair of arm portions 13 , 13 . The base portion 12 is formed in a substantially annular shape, and has a joint hole 14 formed in the axial direction (up and down direction in FIG. 13 ) at the center portion in the radial direction. The coupling hole 14 is a circular hole whose inner peripheral surface is formed as a simple cylindrical surface, or a serrated hole in which concave serrations are formed on the inner peripheral surface of such a circular hole. The arm portions 13 , 13 are provided in a state extending and protruding toward one side in the axial direction (upper side in FIG. 13 ) from two positions on opposite sides in the radial direction of the base portion 12 . Concentric circular holes 15 , 15 are respectively formed at the front ends of the arm portions 13 , 13 . In the state where the cross shaft type universal joint is assembled, cylindrical bearing cups 16 and 16 (refer to FIG. 12 ) are respectively embedded and fixed in the circular holes 15 and 15 . In addition, in the bearing cups 16, 16, the ends of the cross shaft 9 (see FIG. 12 ) are rotatably supported via a plurality of needles 17, 17, respectively. The inner side surfaces of the arm parts 13 and 13 and the single axial side surface of the base part 12 which are opposed to each other are smoothly continuous by concave curved surfaces.

When the base 12 of the above-mentioned fork 8e is coupled to the end of a cylindrical or tubular shaft 18 such as an intermediate shaft, first, the end of the shaft 18 is pressed into the coupling hole 14 of the base 12. (Embedded in an interference fit). In addition, when the coupling hole 14 is a serrated hole, convex serrations are formed on the outer peripheral surface of the end portion of the shaft 18 . And, with pressing, the convex serrations are engaged with the serration holes with an interference. Next, by welding the corner portion between the other axial side surface of the base 12 (lower side surface in FIG. 13 ) and the outer peripheral surface of the shaft 18 , the weld metal 19 is bridged between both surfaces. As a result, the end portion of the shaft 18 is fixed to the base portion 12 of the fork 8e so that torque can be transmitted.

Fig. 14 shows a second example of the conventional structure of the plunge-type fork. In the case of the fork 8f of the second example of the conventional structure, in the base portion 12a, in the peripheral portion of the other end portion in the axial direction of the coupling hole 14, a In comparison, the protruding ring portion 20 has a smaller wall thickness in the radial direction. Then, the protruding ring portion 20 and the shaft 18 are welded in a state where the weld metal 19 is bridged between the outer peripheral surface and the front end surface of the protruding ring portion 20 and the outer peripheral surface of the shaft 18 .

In the case of the second example of such a conventional structure, when the above-mentioned welding is performed, the protruding ring portion 20 can be heated intensively (the heat applied to the protruding ring portion 20 can be made difficult to disperse to the axially intermediate portion side of the base portion 12a ). Therefore, the penetration amount of the outer peripheral surface and the front end surface of the protrusion ring part 20 can be increased, and the strength of a welded part can be easily ensured accordingly.

In each of the conventional structures described above, the entire joint hole 14 is used as a press-fit hole portion for press-fitting the end portion of the shaft 18 . In the surface portion of such coupling hole 14 , as the end portion of shaft 18 is press-fitted, a large circumferential stress (tensile stress in the circumferential direction) is generated. On the other hand, at one end opening peripheral portion (part P of FIGS. 13 and 14 ) of the joint hole 14 as the continuation of the axial single side surface of the base 12 ( 12 a ) and the inner peripheral surface of the joint hole 14 , when assembled Torque transmission is performed with the cross-type universal joint, and stress concentration due to torsion occurs. That is to say, in the case of each of the above-mentioned conventional structures, the one-end opening peripheral portion (P portion) of the joint hole 14 overlaps with each other to generate a large circumferential stress caused by press-fitting and a stress concentration caused by torsion, Thus, the maximum value of the stress becomes larger. Therefore, the design for ensuring the strength of the base 12 (12a) becomes difficult.

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2013-24369

Contents of the invention

The problem to be solved by the invention

The present invention is an invention for realizing the structure and its manufacturing method in view of the above-mentioned circumstances, that is, as the end of the shaft is press-fitted into the coupling hole, a large surface layer portion of the press-fit hole portion of the coupling hole will be generated. The hoop stress and the yoke for a universal joint in which stress concentration due to torsion occurs at the peripheral edge of the one-end opening of the coupling hole during torque transmission can be easily designed to ensure strength.

Solution to the problem

The above objects of the present invention are achieved by the following structures.

(1) A fork for a universal joint, comprising:

a base portion formed in a ring shape and having a coupling hole formed in the axial direction at a radial center portion; and

a pair of arm portions protruding from two positions on radially opposite sides of the base portion to one side in the axial direction,

In the above-mentioned fork for the universal joint,

The coupling hole is configured such that at least the axially intermediate portion from the axially intermediate portion to the other end portion serves as a press-fit hole portion for press-fitting the end portion of the shaft, and the portion adjacent to the press-fit hole portion in the axial direction is One axial end portion is a non-press-fit hole portion having a diameter larger than that of the press-fit hole portion and an end portion of the shaft that is not press-fitted.

(2) According to the yoke for a universal joint described in (1), the base portion and the shaft are welded.

(3) The yoke for a universal joint according to (1) or (2), wherein a chamfer is provided on a continuous portion between the inner peripheral surface of the non-press-fitting hole portion and one axial side surface of the base portion.

(4) The yoke for a universal joint according to any one of (1) to (3), wherein in the base portion, a protruding ring portion is provided around the other end portion in the axial direction of the coupling hole, The protruding ring portion has a smaller radial thickness than a surrounding portion near the other end portion in the axial direction of the coupling hole.

(5) According to the yoke for a universal joint described in (4), the wall thickness in the radial direction of the protruding ring portion becomes smaller toward the axial tip side.

(6) The yoke for a universal joint according to any one of (1) to (5), wherein the non-press-fit hole portion is formed in a direction perpendicular to the direction in which the inner surfaces of the pair of arm portions face each other. The two positions on the opposite sides in the radial direction are each provided with a rigidity-reducing concave portion that is recessed in the radial direction and opened on one axial side surface of the base portion.

(7) A method of manufacturing the yoke for a universal joint described in (4),

Prepare a metal mold for punching with a non-press-fit hole processing surface corresponding to the above-mentioned non-press-fit hole portion on the outer peripheral surface of the front end portion, and after obtaining a substantially disc-shaped or After the intermediate material of the substantially cylindrical base part thickness part is formed, the front end part of the above-mentioned punching metal mold is pressed into the inside of the above-mentioned base part thickness part from the central part of the axial single side surface of the above-mentioned base part thickness part. The portion of the press-fitted portion that is integrated with the processed surface for the non-press-in hole portion is set as the above-mentioned non-press-in hole portion, and the central portion of the other axial side of the thickness portion for the base portion is bulged in the axial direction, And this protruding part is used as the thickness part for protruding ring parts for forming the said protruding ring part.

(8) The method of manufacturing the yoke for a universal joint according to (7),

The press-fit hole portion is formed in the central portion of the thickness portion for the base,

The protruding ring portion is formed by removing the central portion of the protruding ring portion thickness portion along with the formation of the press-fit hole portion,

Press-fit the end of the shaft into the press-fit hole,

And the said protruding ring part and the said shaft are welded so that the said protruding ring part may be covered.

(9) The method of manufacturing the yoke for a universal joint according to (7),

The object of manufacture is the yoke for a universal joint described in (4), which is provided with an inverted yoke on the continuous portion of the inner peripheral surface of the non-press-fit hole portion and the one axial side surface of the above-mentioned base portion. corners, and forming the above-mentioned chamfers by press working,

On the outer peripheral surface of the front end portion of the above-mentioned punching die, in addition to the above-mentioned non-press-fit hole portion processing surface, there is also provided a chamfering portion processing surface corresponding to the above-mentioned chamfering portion as a processing surface,

By press-fitting the front end portion of the press die from the central portion of one axial side surface of the thickness portion for the base constituting the intermediate material into the thickness portion for the base, the portion of the pressed-in portion that is not the same as the above-mentioned The part where the processed surface for the press-in hole part is integrated is the above-mentioned non-press-fit hole part, and the part which is integrated with the processed surface for the chamfer part is the said chamfer part.

The effects of the invention are as follows.

In the case of the yoke for a universal joint described in (1), the surface layer portion of the press-fit hole portion of the joint hole is a portion where a large hoop stress is generated as the end of the shaft is press-fitted into the joint hole. , the continuous portion between the inner peripheral surface of the non-press-in hole portion of the coupling hole and the axial side of the base (the peripheral portion of the opening at one end of the coupling hole) is transmitted when the cross shaft universal joint is assembled. In a portion where stress concentration due to torsion occurs during torque, the above-mentioned surface layer portion and the above-mentioned continuous portion exist at positions separated from each other. Therefore, in the case of the present invention, compared with each of the above-mentioned conventional structures, the portion where a large hoop stress is generated due to press-fitting and the portion where stress concentration due to torsion occurs overlaps each other, and the structure generated on the base is reduced. The maximum value of the stress is suppressed to be low. As a result, the design for securing the strength of the base can be easily performed.

According to the yoke for a universal joint described in (2), since the base and the shaft are welded, the base of the yoke and the end of the shaft are more firmly connected and fixed.

According to the yoke for a universal joint described in (3), since the chamfer is provided at the continuous portion between the inner peripheral surface of the non-pressing hole portion of the coupling hole and the axial side surface of the base portion, it is possible to relax the tension. Stress concentration caused by torsion in this continuous portion. Therefore, the maximum value of the stress generated on the base is suppressed to be lower. As a result, the design for ensuring the strength and rigidity of the base can be performed more easily.

In the case of the yoke for a universal joint described in (4), when the base is coupled to the end of the shaft, if the end of the shaft is pressed into the coupling hole, and the outer peripheral surface of the shaft and the protruding ring If these shafts and the protruding ring are welded in a state where the weld metal is bridged between the outer peripheral surface and the front end face of the part, then when the welding is performed, the protruding ring can be heated intensively (the heat applied to the protruding ring can be made difficult to Scatter toward the axial middle part side of the base). Therefore, the amount of penetration of the outer peripheral surface and the front end surface of the protruding ring portion can be increased, and accordingly, it becomes easy to secure the strength of the welded portion.

According to the yoke for a universal joint described in (5), since the radial thickness of the protruding ring portion becomes smaller toward the axial front end side, the end portion of the shaft is press-fitted into the press-fit hole. In this state, it is possible to prevent the surface pressure acting on the fitting portion between the press-fit hole portion and the end portion of the shaft from becoming concentrated at a portion corresponding to the axial front end portion of the protruding ring portion.

According to the yoke for a universal joint described in (6), based on the existence of the pair of recesses for reducing rigidity, in the continuous portion between the inner peripheral surface of the non-press-fit hole portion and the axial side surface of the base portion, The rigidity in the circumferential direction of the parts other than the two rigidity reduction recesses is reduced. Therefore, accordingly, when torque is transmitted in a state where the cross-type universal joint is assembled, the amount of elastic deformation in the circumferential direction of the portion can be increased. As a result, it is possible to respectively relax the portions (four portions where the stress concentration due to torsion becomes particularly large) that are in phase with both ends in the width direction of the proximal end portions of the pair of arm portions in the circumferential direction, which are part of the portion. stress concentration.

According to the method of manufacturing a yoke for a universal joint described in (7), the press-fitting metal mold is pressed into the inside of the thickness portion for a base from the center portion of one side in the axial direction of the thickness portion for a base of the intermediate material. The front end portion can simultaneously form a non-press-fit hole portion and a protruding ring portion thickness portion for forming a protruding ring portion. Therefore, the manufacturing cost of the yoke for universal joints is suppressed.

According to the method of manufacturing a yoke for a universal joint described in (8), when performing welding, the protruding ring portion can be heated intensively, thereby increasing the penetration amount of the outer peripheral surface and the front end surface of the protruding ring portion, and correspondingly, It becomes easy to ensure the strength of the welded part.

According to the method of manufacturing a yoke for a universal joint described in (9), the press-fitting metal mold is pressed into the inside of the thickness portion for a base from the central portion of one side in the axial direction of the thickness portion for a base of the intermediate material. The front end portion can simultaneously form a non-press-fit hole portion, a chamfer portion, and a protruding ring portion thickness portion for forming a protruding ring portion. Therefore, the manufacturing cost of the yoke for universal joints is suppressed.

Description of drawings

FIG. 1 is a perspective view showing a fork of a first example of an embodiment of the present invention.

Fig. 2(A) is an end view of the fork seen from above (B). (B) is a sectional view of the fork. (C) is an end view of the fork seen from below (B).

Fig. 3 is an enlarged view of part a of Fig. 2(B).

4(A) to (C) are cross-sectional views illustrating an example of a method of manufacturing a fork in the order of steps.

Fig. 5 is a cross-sectional view for explaining the process of obtaining the intermediate material shown in Fig. 4(B) from the intermediate material shown in Fig. 4(A).

Fig. 6 is a partial sectional view showing a state in which the end of the shaft is coupled and fixed to the base of the fork.

FIG. 7(A) is an enlarged view of part b of FIG. 6 , with weld metal omitted. (B) is the same figure as (A) concerning a comparative example.

Fig. 8(A) is an end view showing a second example of the embodiment of the present invention, viewed from the front end side of the fork. (B) is a c-c cross-sectional view showing (A) with the arm portion omitted.

Fig. 9(A) is an end view showing a third example of the embodiment of the present invention, viewed from the front end side of the fork. (B) is a d-d sectional view of (A).

FIG. 10 is a diagram similar to FIG. 3 , showing another example of the shape of the chamfered portion that can be employed when implementing the present invention.

Fig. 11 is a partially cutaway side view showing an example of a conventionally known steering device.

Fig. 12 is a partially cutaway side view of an intermediate shaft of a conventional cross-type universal joint to which yokes of the vertical insertion type are coupled at both ends thereof.

13 is a partial cross-sectional view showing a state in which the end of the shaft is coupled and fixed to the base of the fork of the first example of the conventional structure.

Fig. 14 is the same view as Fig. 13, related to the fork of the second example of the conventional structure.

15 is an enlarged sectional view of main parts showing a fourth example of the embodiment of the present invention.

16 is an enlarged sectional view of main parts showing a fifth example of the embodiment of the present invention.

Detailed ways

(first example of embodiment)

1 to 7 show a first example of an embodiment of the present invention. The features of this example are mainly the structure of the joint hole 14a provided in the radial center portion of the base portion 12b, and the method of manufacturing the fork 8g provided with such a joint hole 14a. Including the fact that the protruding ring portion 20 that can improve the welding strength is provided at the central portion of the other side in the axial direction of the base portion 12b, the structure and function of other parts are the same as those of the second example of the conventional structure shown in FIG. 14 above. Since they are the same, overlapping descriptions will be omitted or will be briefly described, and the following description will focus on the characteristic parts of this example. In the following description, in the axial direction of the fork 8g (and its intermediate material), one side refers to the upper side in each of Fig. 1, Fig. 2B, Fig. 4 to Fig. 6, and the other side refers to these the lower side of each figure.

In the case of the fork 8g of this example, the joint hole 14a is used as the press-fit hole part 21 for press-fitting the end part of the shaft 18 from the axial middle part to the other end part. Also, one axial end adjacent to the press-fit hole 21 in the axial direction is a non-press-fit hole 22 whose diameter is larger than that of the press-fit hole 21 and which cannot press-fit the end of the shaft 18 . The press-fit hole portion 21 and the non-press-fit hole portion 22 are arranged concentrically with each other, and an annular (circular in the illustrated example) is provided between the axial end edges of the press-fit hole portion 21 and the non-press-fit hole portion 22. wheel-shaped) stepped surface 23. The press-fit hole portion 21 is a circular hole or a zigzag hole similar to the coupling hole 14 constituting the fork 8f in the second example of the conventional structure shown in FIG. 14 described above. On the other hand, the non-pressing hole portion 22 is a circular hole whose inner peripheral surface is a simple cylindrical surface. In the continuation of the inner peripheral surface of the non-press-fit hole portion 22 and the axial single side surface of the base portion 12b (including a concave curved surface that smoothly continues the axial single side surface and the inner surfaces of the pair of arm portions 13, 13.), throughout The entire circumference is provided with an R-chamfered portion 24 whose cross-sectional shape is partially arc-shaped as shown in FIG. 3 . In the case of this example, the R-chamfered portion 24 is formed by press working.

Next, the manufacturing method of the fork 8g of this example which has the above-mentioned structure is demonstrated. In the case of manufacturing the fork 8g, first, by carrying out stamping work including punching and bending work on metal plate materials such as steel plates, or by carrying out forging work on metal materials such as steel round bars, obtain Fig. 4 ( A) First intermediate material 25 shown. The first intermediate material 25 includes: a substantially disc-shaped or substantially cylindrical base thickness portion 26 for forming the base portion 12b; A pair of arm portion thickness portions 27 , 27 each formed in a substantially rectangular plate shape for forming the pair of arm portions 13 , 13 are provided in a protruding state.

After such a first intermediate material 25 is obtained, next, in the state where the first intermediate material 25 is disposed in the cavity of a not-shown die, it is drawn from the central portion of one side in the axial direction of the thickness portion 26 for the base to The inside of the base thickness portion 26 is press-fitted into the front end portion of a pressing die (pressing punch) 28 shown in FIG. 5 . The front end surface of the press die 28 is a circular plane perpendicular to the axial direction. The radially outer portion of the front end surface of the press die 28 is a processed surface 29 for a stepped surface that is a processed surface that coincides with the stepped surface 23 . The outer peripheral surface of the front end portion of the punching die 28 is the processed surface 30 for the non-press-fit hole which is the same as the inner peripheral surface of the non-press-fit hole 22, and the processed surface 30 which is the same as the R-chamfered part 24. The R-chamfered part of the surface is processed surface 31. In addition, the processed surface 29 for a stepped surface and the processed surface 30 for a non-press-fit hole part are smoothly continuous by the convex curved surface whose cross-sectional shape is partially arc-shaped. And, as mentioned above, by pressing the front end portion of the metal die 28 for punching from the central portion of one axial side surface of the thickness portion 26 for the base into the inside of the thickness portion 26 for the base, the axis of the thickness portion 26 for the base is pressed. Concave toward the center of one side. And, in this recessed part (the part that is pressed into the front end portion of the metal mold 28 for pressing), the part that is integrated with the processed surface 29 for the stepped surface is set as the stepped surface 23, and the processed surface for the non-press-in hole part is used as the stepped surface. 30 is defined as the non-press-fit hole portion 22 , and the portion integrated with the processed surface 31 for the R-chamfered portion is referred to as the R-chamfered portion 24 . In addition, the central portion of the other axial side surface of the base thickness portion 26 is bulged in the axial direction, and the bulged portion is used as the protruding ring portion thickness portion 32 for forming the protruding ring portion 20, and is provided. It is the second intermediate material 33 shown in FIG. 4(B).

In addition, the outer surface shape of the protruding ring portion thickness portion 32 is identical to the outer surface shape of the protruding ring portion 20 except for the opening of the press-fit hole portion 21 . In the case of this example, in order to obtain the outer surface shape of the thickness portion 32 for the protruding ring portion, in the portion of the inner surface of the die that faces the cavity, the center portion of the other side in the axial direction of the thickness portion 26 for the base is The opposing portion is provided with a receiving recess having an inner surface matching the outer surface of the protruding ring portion thickness portion 32 . Furthermore, as described above, the outer surface of the protruding ring portion thickness portion 32 as described above is obtained by filling the receiving concave portion with the thickness bulged from the central portion of the other axial side surface of the base portion thickness portion 26 in the axial direction. surface shape.

After the second intermediate material 33 as described above is obtained, next, punching and cutting are performed on the central portion of the base thickness portion 26 constituting the second intermediate material 33 (when the press-fit hole portion 21 is set as a serrated hole). In the case of , broaching for forming concave serrations is also performed to form the press-fit hole portion 21 . The protruding ring portion 20 is formed by removing the central portion of the protruding ring portion thickness portion 32 along with the formation of the press-fit hole portion 21 . Then, the circular holes 15 and 15 are formed by performing punching and cutting on the front end parts of the arm part thickness parts 27 and 27 . In addition, by performing other post-processing as needed, the fork 8g as shown in FIG.4(C) is completed.

When connecting the end of the shaft 18 to the base 12b of the fork 8g as described above, as shown in FIG. When the press-fit hole portion 21 is a serrated hole, convex serrations are formed on the outer peripheral surface of the end portion of the shaft 18 , and the convex serrations are engaged with the serrated hole with an interference amount as the press-fitting is performed. In addition, when the press-fit hole 21 is a circular hole whose inner peripheral surface is a simple cylindrical surface, the outer peripheral surface of the end portion of the shaft 18 is formed as a cylindrical surface, and the cylindrical surface has an interference with the The press-fit hole portion 21 constituted by a circular hole engages. Alternatively, the press-fit hole 21 may be a circular hole, the outer peripheral surface of the end portion of the shaft 18 may be convex serrations, and the convex serrations may be press-fitted into the press-fit hole 21 . Alternatively, the press-fit hole 21 may be a serrated hole, the end peripheral surface of the shaft 18 may be a cylindrical surface, and the cylindrical surface may be press-fit into the press-fit hole 21 . Next, the protruding ring portion 20 and the shaft are welded in a state where the weld metal 19 is bridged between the outer peripheral surface and the front end surface of the protruding ring portion 20 and the outer peripheral surface of the shaft 18, that is, in a state where the entire protruding ring portion 20 is covered. 18. In particular, when the shaft 18 is a hollow shaft, the protruding ring portion 20 and the shaft 18 have substantially the same thickness, and both the shaft 18 and the fork 8g are equally melted during welding, thereby improving the welding strength.

In the case of this example, in the coupling hole 14 a, the axially intermediate portion including the portion corresponding to the protruding ring portion 20 to the other end portion serves as the press-fit hole portion 21 . In addition, the outer peripheral surface of the protruding ring portion 20 is a partially conical surface inclined in a direction in which the diameter becomes smaller toward the axial front end side of the protruding ring portion 20 . Therefore, the radial thickness (rigidity) of the protruding ring portion 20 becomes smaller toward the axial front end side. Therefore, in the state where the end of the shaft 18 is press-fitted into the press-fit hole 21, it is possible to prevent the surface pressure σ _P acting on the fitting portion between the press-fit hole 21 and the end of the shaft 18 from being in contact with the protruding ring. The portion corresponding to the axial front end of the portion 20 becomes concentrated and high.

That is, as shown in FIG. 7(B), since the outer peripheral surface of the protruding ring portion 20a is made into a cylindrical shape, when the radial wall thickness (rigidity) of the protruding ring portion 20a is constant in the axial direction, the effect The surface pressure σ _P at the fitting portion tends to increase concentratedly at the portion corresponding to the axial front end portion of the protruding ring portion 20a (the above-mentioned press-fit inlet side end portion, ie, the lower end portion in the figure). In contrast, in this example, as shown in FIG. 7(A), since the radial thickness (rigidity) of the protruding ring portion 20a becomes smaller toward the axial front end side, it is possible to prevent the The surface pressure σ _P of the joint becomes concentrated and high at the portion corresponding to the axial front end portion of the protruding ring portion 20 (the lower end portion in the figure). Therefore, in the case of this example, at the end portion near the shaft 18, the shear stress applied at the boundary portion between the region where the surface pressure _σP acts and the region where the surface pressure _σP does not act is effectively suppressed. As a result, the design for securing the durability of the boundary portion can be easily performed. Such an effect is particularly advantageous when the shaft 18 is a hollow shaft. In order to sufficiently obtain the effect of suppressing surface pressure as described above, it is preferable to set the inclination angle of the outer peripheral surface (partial conical surface) of the protruding ring portion 20 with respect to the central axis of the protruding ring portion 20 within a range of 20 to 70 degrees.

In the case of the yoke for universal joints of this example constituted as described above, the surface portion of the press-fit hole portion 21 of the joint hole 14a is relatively formed as the end of the shaft 18 is press-fitted into the joint hole 14a. The portion with large circumferential stress, the continuous portion between the inner peripheral surface of the non-press-fit hole portion 22 of the joint hole 14a and the axial single side surface of the base portion 12b (the portion where the R chamfered portion 24 is provided) is when assembled In the part where stress concentration due to torsion occurs when torque is transmitted in the state where the cross shaft universal joint is present, the surface part of the press-fit hole part 21 of the joint hole 14a and the non-press-fit hole part 22 of the joint hole 14a The continuous part (the part where the R-chamfered part 24 is provided) between the inner peripheral surface and the one axial side surface of the base part 12b exists in the position separated from each other. Therefore, in the case of this example, compared with the structure in which the portion where a large hoop stress due to press fitting occurs and the portion where stress concentration due to torsion occurs overlap each other like the above-mentioned conventional structures, the The maximum value of the stress generated on the base portion 12b is suppressed to be low. As a result, design for securing the strength of the base portion 12b can be easily performed.

In addition, in the case of this example, since the R-chamfered portion 24 is provided at the continuous portion between the inner peripheral surface of the non-press-fit hole portion 22 and one axial side surface of the base portion 12b, it is possible to alleviate the stress generated in the continuous portion. Stress concentration due to torsion. In addition, in the case of this example, the R-chamfered portion 24 is formed by press working. Therefore, compressive residual stress can be imparted to the surface layer portion of the continuous portion. Since the compressive residual stress has the effect of suppressing the occurrence of damage such as cracks due to the stress applied during use, the allowable stress of the continuous portion can be increased. As a result, the design for securing the strength of the base portion 12b can be performed more easily.

In addition, in the case of this example, by pressing the front end portion of the punching die 28 into the inside of the base thickness portion 26 from the central portion of one axial side surface of the base thickness portion 26 of the first intermediate material 25, it is possible to Simultaneously, the stepped surface 23 , the non-press-fit hole portion 22 , the R-chamfered portion 24 , and the protruding ring portion thickness portion 32 are formed. Therefore, the manufacturing cost of the yoke for universal joints is suppressed.

(second example of embodiment)

FIG. 8 shows a second example of the embodiment of the present invention. In the case of the fork 8h of this example, in the non-press-fit hole portion 22a constituting the joint hole 14b, it is positively aligned with the inner side surfaces of the pair of arm portions 13, 13 in the opposite direction (the vertical direction in FIG. 8A ). Two positions on the opposite side of the radial direction (the left and right directions in FIG. 8A and FIG. 8B ) of the intersection (the phases related to the rotation direction are shifted every 90 degrees) are respectively provided as part of the non-press-fit hole portion 22a along the radial direction. Rigidity-reducing recesses 35 , 35 are recessed and open to one side surface in the axial direction of the base 12 c. Moreover, also in the case of this example, the fork 8h is manufactured by the method similar to the case of the 1st example of embodiment mentioned above. For this reason, on the processing surface 30 for the non-pressing hole part and the processing surface 31 (refer to FIG. consistent shape. Moreover, when carrying out this invention, the R chamfer part 24 can also be formed only in the part deviated from the recessed parts 35 and 35 for rigidity reductions in the circumferential direction. In this case, what is necessary is just to provide the processed surface 31 for R chamfers only in the part corresponding to this shifted part.

According to the yoke for a universal joint of this example having the above-mentioned structure, due to the existence of the recesses 35 and 35 for reducing rigidity, a gap between the inner peripheral surface of the non-press-fit hole portion 22a and one axial side surface of the base portion 12c is formed. In the continuation portion (the portion where the R-chamfered portion 24 is provided), the rigidity in the circumferential direction of the portion other than the rigidity-reducing recessed portions 35 and 35 can be reduced. Accordingly, when torque is transmitted in a state where the cross shaft type universal joint is assembled, the amount of elastic deformation in the circumferential direction of the portion can be increased. As a result, it is possible to respectively relax the portions in phase with both ends in the width direction of the base end portions of the arm portions 13, 13 in the circumferential direction, that is, the stress concentration due to torsion, which is particularly large in FIG. The stress concentration of the four parts (α part) indicated by the oblique lattice. The structure and function of other parts are the same as those of the first example of the above-mentioned embodiment.

(third example of embodiment)

FIG. 9 shows a third example of the embodiment of the present invention. In the case of the fork 8i of this example, guide recesses 36, 36 are respectively provided at the widthwise intermediate portions of the front ends of the inner surfaces of the pair of arm portions 13a, 13a. In addition, a part of the circular holes 15 , 15 provided at the front ends of the arms 13 a , 13 a (ends on the front end side of the arms 13 a , 13 a ) are opened to the guide recesses 36 , 36 . This makes it easy to insert each shaft portion of the cross shaft 9 (see FIG. 12 ) into the round holes 15 , 15 through the guide recesses 36 , 36 .

Moreover, also in the case of this example, the fork 8i is manufactured by the same method as the case of the 1st example of embodiment mentioned above. Further, the guide recesses 36 , 36 are formed simultaneously with the formation of the non-press-fit hole portion 22 , the protruding ring portion thickness portion 32 , and the R-chamfered portion 24 (see FIG. 4B ). For this reason, on the outer peripheral surface near the base end portion of the metal mold 28 (refer to FIG. 5 ) for pressing in advance, a process for guiding recesses 36 , 36 (for forming the guiding recesses 36 , 36 ) consistent with the guiding recesses 36 , 36 is provided. noodle. The structure and function of other parts are the same as those of the first example of the above-mentioned embodiment.

Moreover, when implementing this invention, it is also possible to provide the recessed part 36 for a guide, 36 with respect to the fork of the 2nd example of embodiment mentioned above. Also in this case, the guide recesses 36 , 36 can be formed in the same manner as in the third example of the above-mentioned embodiment.

(Fourth example of embodiment)

Fig. 15 shows a fourth example of the embodiment of the present invention. In this example, the non-press-fit hole portion 22 is not provided in the fork 8e, but a shaft small-diameter cylindrical portion 40 as a non-press-fit portion is provided at the end of the shaft 18 on the fork 8e side. The shaft small-diameter cylindrical portion 40 also suppresses the maximum value of the stress generated in the base portion 12 of the yoke 8e to be low similarly to the non-press-fit hole portion 22 . In addition, in this example, an example in which the present invention is applied to a universal joint yoke using a fork 8e without a protruding ring portion 20 is shown, but when a fork with a protruding ring portion 20 is used The present invention can also be applied to the universal joint forks of 8g, 8h, 8i. In addition, the coupling hole 14 may not be a round hole, but a zigzag hole. In this case, convex serrations are formed on the outer peripheral surface of the end portion of the shaft 18 .

(fifth example of embodiment)

Fig. 16 shows a fifth example of the embodiment of the present invention. In this example, the non-press-fit hole portion 22 is not provided in the fork 8e, but the large chamfered portion 41 is provided in the fork 8e. The chamfered portion 41 also suppresses the maximum value of the stress generated in the base portion 12 of the yoke 8e to be low, similarly to the non-press-fit hole portion 22 . In addition, in this example, an example in which the present invention is applied to a universal joint yoke using a fork 8e without a protruding ring portion 20 is shown, but when a fork with a protruding ring portion 20 is used The present invention can also be applied to the universal joint forks of 8g, 8h, 8i. In addition, the coupling hole 14 may not be a round hole, but a zigzag hole. In this case, convex serrations are formed on the outer peripheral surface of the end portion of the shaft 18 .

Industrial availability

When implementing the present invention, chamfering does not necessarily have to be provided at the continuation portion between the inner peripheral surface of the non-press-fit hole portion of the coupling hole and the one axial side surface of the base. Moreover, when providing a chamfered part, the chamfered part may be the C chamfered part 34 whose cross-sectional shape shown in FIG. 10 is linear.

In addition, when implementing the method for manufacturing a yoke for a universal joint according to the present invention, for example, it may be configured to use a shape in which the processed surface 31 (see FIG. In the same way as in the above-mentioned embodiment, the non-press-fit hole portion 22 and the thickness portion 32 for the protruding ring portion are simultaneously formed, and thereafter, press processing using another stamping die or cutting The chamfer 24 is formed in the continuous part by processing in another process (see FIG. 4 ).

And, in the case of manufacturing the fork of the present invention, when the fork is equipped with a chamfer 24 and a pair of rigidity reduction recesses 35, 35 (refer to FIG. The stamping process of the metal mold for stamping is to simultaneously form the non-pressing hole portion 22 and the protruding ring portion thickness portion 32 (see FIG. 4 ), and thereafter, the chamfered portion 24 and the rigidity-reducing concave portions 35, 35 are simultaneously formed by press working using a second press die.

And, in the case of manufacturing the fork of the present invention, when the fork is provided with a chamfer 24 and a pair of guide recesses 36, 36 (see FIG. Using the press working of a metal mold, and in the same way as the above-mentioned embodiment, the non-press-fit hole portion 22 (see FIG. 4 ) {or 22a (see FIG. 8 )} and the thickness portion 32 for the protruding ring portion ( Referring to FIG. 4 ), thereafter, the chamfered portion 24 and the guide recesses 36 , 36 are simultaneously formed by press working using a second press die.

In addition, in the case of manufacturing the fork of the present invention, when the fork has a chamfer 24, a pair of rigidity reduction recesses 35, 35, and a pair of guide recesses 36, 36 (see FIGS. 8 and 9 ) In this case, the non-press-fit hole portion 22 without the rigidity-reducing recesses 35 and 35 may be simultaneously formed by press working using the first press die in the same manner as in the above-mentioned embodiment. and the thickness portion 32 (refer to FIG. 4 ) for the protruding ring portion, and then, the chamfered portion 24, the recessed portions 35, 35 for reducing rigidity, and the recessed portion 36 for guiding are simultaneously formed by press working using a second press die. 36.

In addition, when implementing the present invention, the protruding ring portion does not necessarily have to be used as a portion that bridges the weld metal with the shaft, and may be used only as a portion for securing the axial length of the coupling hole.

Furthermore, when implementing the present invention, the other end portion in the axial direction of the coupling hole may not be a press-fit hole portion but may be a non-press-fit hole portion.

This application is based on Japanese patent application 2013-147233 filed on July 16, 2013, Japanese patent application 2013-228672 filed on November 1, 2013, Japanese patent application 2014-108684 filed on May 27, 2014, and 2014 Japanese Patent Application No. 2014-116393 filed on June 5, the contents of which are incorporated herein by reference.

Explanation of symbols

1—steering wheel, 2—steering shaft, 3a, 3b—universal joint, 4—intermediate shaft, 5—steering gear unit, 6—input shaft, 7—tie rod, 8a～8i—fork, 9—cross shaft , 10—male shaft, 11—female shaft, 12, 12a~12c—base, 13, 13a—arm, 14, 14a, 14b—combining hole, 15—round hole, 16—bearing cup, 17—needle , 18—shaft, 19—welding metal, 20, 20a—protruding ring, 21—pressed hole, 22, 22a—non-pressed hole, 23—step surface, 24—R chamfer, 25—the first 1. Intermediate material, 26—thickness portion for base portion, 27—thickness portion for arm portion, 28—metal mold for stamping, 29—processed surface for step surface, 30—processed surface for non-pressing hole portion, 31—R chamfer Part processing surface, 32—thickness portion for protruding ring portion, 33—second intermediate material, 34—C chamfer, 35—recess for rigidity reduction, 36—recess for guiding, 40—small diameter cylindrical portion of shaft (non- Press-fit part), 41—chamfering part (non-press-fit part).

Claims (9)

1. A fork for a universal joint, comprising: a base portion formed in a ring shape and having a coupling hole formed in the axial direction at a radial center portion; and a pair of arm portions protruding from two positions on radially opposite sides of the base portion to one side in the axial direction, The above-mentioned fork for universal joint is characterized in that, The coupling hole is configured such that at least the axially intermediate portion from the axially intermediate portion to the other end portion serves as a press-fit hole portion for press-fitting the end portion of the shaft, and the portion adjacent to the press-fit hole portion in the axial direction is One axial end portion is a non-press-fit hole portion having a diameter larger than that of the press-fit hole portion and an end portion of the shaft that is not press-fitted. 2. The fork for a universal joint according to claim 1, wherein: The above-mentioned base and the above-mentioned shaft are welded. 3. The fork for a universal joint according to claim 1 or 2, wherein: A chamfer is provided at a continuous portion between the inner peripheral surface of the non-press-fit hole portion and the one axial side surface of the base portion. 4. The yoke for a universal joint according to any one of claims 1 to 3, wherein: In the above-mentioned base part, a protruding ring part having a wall thickness in the radial direction compared with the surrounding part near the other axial end part of the above-mentioned coupling hole is provided on the surrounding part of the other axial end part of the above-mentioned coupling hole. get smaller. 5. The yoke for a universal joint according to claim 4, wherein: The radial thickness of the protruding ring portion becomes smaller toward the axial front end side. 6. The yoke for a universal joint according to any one of claims 1 to 5, wherein: The non-press-fit hole portion is provided at two positions on radially opposite sides perpendicular to a direction in which the inner surfaces of the pair of arm portions oppose each other, and is provided with a radially recessed opening on one axial side surface of the base portion. Rigidity reduction with recessed part. 7. A method for manufacturing a yoke for a universal joint, which is the method for manufacturing a yoke for a universal joint according to claim 4, wherein: Prepare a metal mold for punching with a non-press-fit hole processing surface corresponding to the above-mentioned non-press-fit hole portion on the outer peripheral surface of the front end portion, and after obtaining a substantially disc-shaped or After the intermediate material of the substantially cylindrical base part thickness part is formed, the front end part of the above-mentioned punching metal mold is pressed into the inside of the above-mentioned base part thickness part from the central part of the axial single side surface of the above-mentioned base part thickness part. The portion of the press-fitted portion that is integrated with the processed surface for the non-press-in hole portion is set as the above-mentioned non-press-in hole portion, and the central portion of the other axial side of the thickness portion for the base portion is bulged in the axial direction, And this protruding part is used as the thickness part for protruding ring parts for forming the said protruding ring part. 8. The method of manufacturing a yoke for a universal joint according to claim 7, wherein: The press-fit hole portion is formed in the central portion of the thickness portion for the base, The protruding ring portion is formed by removing the central portion of the protruding ring portion thickness portion along with the formation of the press-fit hole portion, Press-fit the end of the shaft into the press-fit hole, And the said protruding ring part and the said shaft are welded so that the said protruding ring part may be covered. 9. The method of manufacturing a yoke for a universal joint according to claim 7, wherein: The object of manufacture is the yoke for universal joint according to claim 4, which is provided with an inverted groove on the continuous portion between the inner peripheral surface of the non-press-fit hole portion and the one axial side surface of the base portion. corners, and forming the above-mentioned chamfers by press working, On the outer peripheral surface of the front end portion of the above-mentioned punching die, in addition to the above-mentioned non-press-fit hole portion processing surface, there is also provided a chamfering portion processing surface corresponding to the above-mentioned chamfering portion as a processing surface, By press-fitting the front end portion of the press die from the central portion of one axial side surface of the thickness portion for the base constituting the intermediate material into the thickness portion for the base, the portion of the pressed-in portion that is not the same as the above-mentioned The part where the processed surface for the press-in hole part is integrated is the above-mentioned non-press-fit hole part, and the part which is integrated with the processed surface for the chamfer part is the said chamfer part.