JP6217209B2 - Universal joint yoke - Google Patents

Description

  The present invention relates to an improvement in a yoke constituting a cross shaft universal joint (cardan joint) for connecting rotational shafts constituting a steering device so as to transmit torque.

  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 also incorporated, which uses the electric motor 25 as a power source to reduce the force required to operate the steering wheel 1.

  The intermediate shaft 4 incorporated in such a steering device uses a telescopic type in order to prevent the steering wheel 1 from being pushed up to the driver side in the event of a collision. FIG. 5 shows an example of the structure of a telescopic intermediate shaft 4 that has been generally used conventionally. The intermediate shaft 4 is formed with an inner shaft 9 provided with a male spline portion 8 on the outer peripheral surface of the tip portion (left end portion in FIG. 5) and a female spline portion 10 into which the male spline portion 8 can be inserted on the inner peripheral surface. The outer tube 11 has a circular tubular shape. The male spline portion 8 and the female spline portion 10 are spline-engaged, so that the inner shaft 9 and the outer tube 11 are combined in an extendable manner. Further, the base end portions of the yokes 12a and 12b constituting the universal joints 3a and 3b are welded and fixed to the base end portions of the inner shaft 9 and the outer tube 11, respectively.

  FIG. 6 shows one described in Patent Document 1 as an example of a conventionally known universal joint that can be used as the universal joints 3a and 3b. The universal joint 3 shown in FIG. 6 is formed by connecting a pair of yokes 12 a and 12 b via a single cross shaft 13 so as to transmit torque. Each of the yokes 12a and 12b includes a base portion 14a and 14b, and a pair of connecting arm portions 15a and 15b for each of the yokes 12a and 12b. These base parts 14a and 14b are coupled and fixed to freely transmit torque to the base end part of the inner shaft 9 or the outer tube 11 (or the front end part of the steering shaft 2 or the rear end part of the input shaft 6), which is a rotating shaft. For this purpose, coupling holes 16 and 16 are provided. That is, the male serration portion provided on the outer peripheral surface of the proximal end portion of the inner shaft 9 or the outer tube 11 (or the front end portion of the steering shaft 2 or the rear end portion of the input shaft 6) is connected to the coupling holes 16 and 16. The inner shaft 9 or the outer tube 11 (or the steering shaft 2 or the input shaft 6) and the yokes 12a and 12b transmit torque by engaging with a female serration portion provided on the inner peripheral surface of the inner shaft. It is freely coupled and fixed. In addition, circular holes 17a and 17b are formed concentrically with respect to the yokes 12a and 12b, respectively, at the ends of the coupling arm portions 15a and 15b. The cross shaft 13 is formed by providing four shaft portions 18 and 18 in a state where the central axes of the adjacent shaft portions 18 and 18 are orthogonal to each other. The shafts 18 and 18 are rotatably supported inside the circular holes 17a and 17b via cup-shell radial needle bearings 19 and 19, respectively, to form the universal joint 3.

  As a yoke constituting the cross shaft type universal joint as described above, Patent Document 2 discloses a yoke structure formed by subjecting a metal plate having sufficient rigidity, such as a steel plate, to press working such as punching or bending. Have been described. Patent Document 3 describes a yoke structure formed by subjecting a metal material to forging which is plastic working.

  In any case, the yoke constituting the cross shaft type universal joint as described above ensures rigidity with respect to the moment applied to the connecting portion between the rotating shaft and the yoke as the torque is transmitted between the rotating shafts. Becomes important. The reason for this will be described with reference to FIG. That is, stress is applied to the continuous portions 20, 20 between the one end surface of the base portion 14 and the inner side surfaces of the coupling arm portions 15, 15 that constitute the yoke 12 based on the moment generated with the transmission of torque. In particular, in the case of the steering apparatus incorporating the electric power steering apparatus shown in FIG. 4 described above, the torque to be transmitted increases, and the stress applied to the continuous parts 20, 20 also increases. Such a stress is generated by the virtual straight lines α and α connecting the circumferential edges of the inner side surfaces of the connecting arm portions 15 and 15 and the central axis O of the rotating shaft. The yoke 12 is likely to be concentrated at the intersections X and X with the opening edge of the coupling hole 16, and damage such as cracks may occur in the yoke 12 starting from the intersections X and X as a long-term use. . In order to prevent the concentration of stress causing such damage, as shown by a two-dot chain line β in FIG. 7B, the curvature radius of the cross-sectional shape of the continuous portion 20 is increased, and the thickness of the portion is increased. It is possible to increase the size. However, when the radius of curvature of the cross-sectional shape of the continuous portion 20 is increased, when the universal joint 3 (see FIG. 6) is configured, it becomes easy to interfere with the counterpart yoke, and the joint angle (a pair of the universal joints). There arises a problem that the inclination angle between the central axes of the yokes cannot be increased or the weight increases. On the other hand, it is conceivable to increase the swing displacement width of this rotating shaft relative to another rotating shaft by increasing the axial length of the rotating shaft, but it is difficult to ensure the collapse stroke at the time of the secondary collision. There is a possibility that the entire steering device becomes large. Further, there is a possibility that the moment applied from the rotating shaft to the connecting portion between the rotating shaft and the yoke becomes large.

JP-A-8-270669 JP 2011-220398 A JP 2008-298267 A

  In view of the circumstances as described above, the present invention was invented to realize a universal joint yoke structure that can sufficiently ensure the strength and rigidity against the moment around the rotation axis while ensuring the joint angle of the universal joint. is there.

The yoke for a universal joint according to the present invention includes a base portion and a pair of coupling arm portions.
Of these, the base has a coupling hole for coupling and fixing the end of the rotating shaft.
Further, both the connecting arm portions are provided so as to extend to one axial direction from two positions on the diametrically opposite side of the base portion.
In particular, in the case of the universal joint yoke according to the present invention, a continuous portion between the inner side surface of both the connecting arm portions and the one axial end surface of the base portion is smoothly continuous with a plurality of curved surfaces or planes having different curvature radii in cross-sectional shape. This is a composite curved surface. Of the continuous portion, a portion including an intersection of an imaginary straight line connecting both circumferential edges of the inner side surfaces of the coupling arm portions and the central axis of the rotating shaft and an opening edge portion of the coupling hole. The radius of curvature of the cross-sectional shape is made larger than the radius of curvature of the cross-sectional shape of the portion not including this intersection (the curvature is reduced).

  According to the universal joint yoke of the present invention configured as described above, the joint angle of the universal joint incorporating the universal joint yoke is ensured, and the strength and rigidity against the moment around the rotation axis are sufficiently ensured. Can do. That is, the continuous portion of the inner surface of the pair of connecting arm portions constituting the universal joint yoke and the one end surface of the base portion is formed as a composite curved surface. The radius of curvature of the cross-sectional shape of the portion including the intersection of the imaginary straight line connecting the circumferential edge of the side surface and the central axis of the rotating shaft and the opening edge of the coupling hole for coupling and fixing the end of the rotating shaft Is larger than the radius of curvature of the cross-sectional shape of the portion not including this intersection. For this reason, a stress based on the moment applied to the joint between the rotary shaft and the universal joint yoke is transmitted to the portion including the intersection between the two continuous portions as torque is transmitted between the rotary shafts. Concentration can be prevented, and sufficient strength and rigidity can be secured. Further, it is possible to prevent the wall thickness of both the continuous portions from becoming excessively thick, to secure a joint angle of the universal joint incorporating the universal joint yoke, and to suppress an increase in weight.

The end view (A) of the yoke which shows the 1st example of embodiment of this invention, and aa sectional drawing (B) of (A). The figure similar to (B) of Drawing 1 showing the 2nd example. The figure similar to (B) of Drawing 1 showing the 3rd example. 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 disassembled perspective view which shows an example of the conventional structure of a cross-shaft type universal joint. The end view (A) which takes out and shows a yoke, and BB sectional drawing (B) of (A).

[First example of embodiment]
FIG. 1 shows a first example of an embodiment of the present invention. The feature of this example is a structure for sufficiently ensuring the strength and rigidity against the moment around the rotation axis while securing the joint angle of the universal joint incorporating the yoke 12c. Since the structure and operation of the other parts are the same as in the case of the conventional structure shown in FIG. 6, the overlapping description and illustration will be omitted or simplified, and the following description will focus on the features of this example.

  In the case of this example, the continuous portions 20a, 20a between the inner side surfaces of the pair of coupling arm portions 15, 15 constituting the yoke 12c and one end surface of the base portion 14 are at portions where the radii of curvature related to the cross-sectional shape are at least adjacent to each other. A plurality of different curved surfaces (three in the example shown in the figure) and a plane are combined to form a complex curved surface. That is, each of the continuous portions 20a and 20a has an inner diameter side curved surface portion 21 that is partially arc-shaped in cross section and continuous with one end surface of the base portion 14, and an inner surface of the coupling arm portion 15 that is partially arc-shaped in cross section. The outer diameter side curved surface portion 22 that is continuous with the inner surface and the outer diameter side curved surface portions 21 and 22 are smoothly continuous with the flat surface portion 23 having an infinite curvature radius. And by appropriately regulating the curvature radii of both the inner diameter side and outer diameter side curved surface portions 21, 22, the inclination angle of the flat surface portion 23 with respect to one end surface of the base portion 14 is set to about 0 to 20 degrees, Of the continuous portion 20a, virtual straight lines α and α connecting the circumferential edges of the inner side surfaces of the coupling arm portions 15 and 15 and the central axis O of the rotation shaft coupled and fixed to the coupling hole 16, and this coupling A portion including the intersections X and X with the opening edge of the hole 16 is positioned on the flat surface portion 23.

  The yoke 12c as described above is manufactured by subjecting a metal plate having sufficient rigidity, such as a steel plate, to press processing such as punching or bending, or by subjecting a metal material to forging which is plastic processing. . When the yoke 12c is made by press working, when the metal plate is punched by press working, the portions that should be the two continuous portions 20a and 20a in the completed state are smoothly continuous with a plurality of curves and straight lines having different curvature radii. Punched into a complex curve. The yoke 12c is made by bending the base plate thus obtained. On the other hand, when the yoke 12c is manufactured by forging, the shape of the portion of the inner surface of the metal material that matches the continuous portions 20a and 20a is the shape of the continuous portions 20a and 20a. It is made by plastically deforming it in a mold that is a composite curved surface that meets the requirements.

  According to the yoke 12c of the present example configured as described above, while securing the joint angle of the universal joint in which the yoke 12c is incorporated, the periphery of the rotation shaft whose end is coupled and fixed to the coupling hole 16 of the yoke 12c is secured. The strength and rigidity against the moment can be sufficiently secured. In other words, in the case of this example, the continuous portions 20a and 20a between the inner surface of the pair of connecting arm portions 15 and 15 and the one end surface of the base portion 14 to which stress based on this moment is applied are curved surfaces having different curvature radii related to the cross-sectional shape. And a complex curved surface consisting of a straight line and a smooth line. In particular, in the case of this example, of the continuous parts 20a and 20a, stresses based on the moment are likely to concentrate on both circumferential edges of the inner side surfaces of the connecting arm parts 15 and 15 and the rotation shaft. The cross-sectional shape of the portion including the intersections X and X of the virtual straight lines α and α connecting the central axis O and the opening edge of the coupling hole 16 are flat surface portions 23 and 23 having infinite curvature radii. . Therefore, the stress based on the moment can be prevented from concentrating on the portion including the intersections X and X, and the strength and rigidity of the yoke 12c can be ensured. Even if the strength and rigidity of the yoke 12c are secured, it is possible to prevent the continuous portions 20a and 20a from becoming thicker and to secure the joint angle of the universal joint incorporating the yoke 12c. At the same time, an increase in the weight of the yoke 12c can be suppressed.

[Second Example of Embodiment]
FIG. 2 shows a second example of the embodiment of the present invention. In the case of the yoke 12d of this example, the continuous portion 20b includes an inner diameter side curved surface portion 21a having a partial arc shape in cross section and continuing to one end surface of the base portion 14, and an inner surface of the coupling arm portion 15 having a partial arc shape in cross section. The continuous outer diameter side curved surface portion 22a is made to continue smoothly. In this example, it is significantly _{(R 21a>} R _22a) than the radius of curvature _{R 22a} in the radius of curvature _{R 21a} in the inner diameter side curved portion 21a the outer diameter side curved surface portion 22a. Then, both radii of curvature R _21a and R _22a are appropriately adjusted, and a virtual straight line α connecting the circumferential end edges of the inner side surface of the coupling arm 15 and the central axis O of the rotating shaft coupled and fixed to the yoke 12d. The portion including the intersection X between {see FIG. 1A} and the opening edge of the coupling hole 16 is positioned on the inner diameter curved surface portion 21a.
Since the configuration and operation of the other parts are the same as those in the first example of the above-described embodiment, redundant description is omitted.

[Third example of embodiment]
FIG. 3 shows a third example of the embodiment of the present invention. In the case of the yoke 12e of this example, each of the continuous portions 20c has a partial arc shape in cross section, an inner diameter side curved surface portion 21b continuous with one end surface of the base portion 14, and an outer diameter side curved surface continuous with the inner surface of the coupling arm portion 15. It is assumed that the portion 22b and the curved surface portion 24 between the both inner diameter side and outer diameter side curved surface portions 21b and 22b are smoothly continuous. The radius of curvature _{R 24} of the curved surface portion 24 is larger than the radius of curvature _{R 21b} of the inner diameter side curved portion _{21b (R 24> R 21b)} , and greater than the radius of curvature _{R 22b} of the outer diameter side curved portion 22b ( R ₂₄ > R _22b ). An imaginary straight line α {see FIG. 1 (A)} that connects both circumferential edges of the inner side surface of the connecting arm portion 15 and the central axis O of the rotating shaft connected and fixed to the yoke 12e, and the connecting hole 16 A portion including the intersection point X with the opening edge portion is positioned on the curved surface portion 24.
Since the configuration and operation of the other parts are the same as those in the first example of the above-described embodiment, redundant description is omitted.

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 Male spline part 9 Inner shaft 10 Female spline part 11 Outer tube 12, 12a-12e Yoke 13 Cross shaft 14, 14a, 14b Base portion 15, 15a, 15b Coupling arm portion 16 Coupling hole 17a, 17b Circular hole 18 Shaft portion 19 Radial needle bearing 20, 20a, 20b Continuous portion 21, 21a, 21b Inner diameter side curved surface portion 22, 22a, 22b Outer diameter Side curved surface portion 23 Flat surface portion 24 Curved surface portion 25 Electric motor

Claims (1)

A base having a coupling hole for coupling and fixing the end of the rotating shaft;
In a universal joint yoke provided with a pair of coupling arm portions provided in a state of extending from one radial position to two axial positions opposite to the base in the radial direction,
A continuous portion between the inner side surface of both the connecting arm portions and the one axial end surface of the base portion is a curved surface or a composite curved surface formed by smoothly continuing a plurality of curved surfaces or planes having different curvature radii of the cross-sectional shape. Then, the radius of curvature of the cross-sectional shape of the portion including the intersection of the virtual straight line connecting the circumferential end edges of the inner side surfaces of the both connecting arm portions and the central axis of the rotating shaft and the opening edge portion of the connecting hole, A universal joint yoke characterized by being larger than the radius of curvature of the cross-sectional shape of the portion not including the intersection.

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