JP2011133004A - Coupling part for shaft and yoke of universal joint - Google Patents

Abstract

An object of the present invention is to realize a structure capable of improving the torsional rigidity of a joint portion between a shaft 15b and a base end portion 16b of a yoke 11b without increasing the weight and improving the durability of the joint portion. To do.
A shaft 18b is connected to an inner peripheral surface 35 of a connecting portion 18b constituting the base end portion 16b and a portion of the outer peripheral surface of the end portion of the shaft 15b facing the inner peripheral surface 35. A plurality of long protrusions 33 and 36 and concave grooves 34 and 37 in the axial direction are alternately arranged in the width direction perpendicular to the axial direction. Then, the protrusions 33 and 36 and the concave grooves 34 and 37 are engaged with each other.
[Selection] Figure 1

Description

  The present invention relates to an improvement in a coupling portion between a shaft and a universal joint yoke for coupling an end portion of a shaft and a universal joint yoke constituting a steering device. Specifically, by improving the rigidity of the coupling portion in the torsional direction, it is possible to improve the steering feeling of the steering wheel and improve the durability of the coupling portion.

  A steering device for an automobile is configured, for example, as shown in FIG. When the driver rotates the steering shaft 2 based on the operation of the steering wheel 1, this rotation is caused by the steering gear unit via the first universal joint 3, the intermediate shaft 4, and the second universal joint 5. 6 to the input shaft 7. Then, the steering gear unit 6 pushes and pulls the pair of left and right tie rods 8 and 8 along with the rotation of the input shaft 7 to give a steering angle to the steered wheels.

  Conventionally, those having various structures are known as the first and second universal joints 3 and 5 incorporated in the steering device as described above. In consideration of improving the assembly of the steering device, at least one of the first and second universal joints 3 and 5 is made to have a yoke and a shaft (steering shaft 2) constituting the universal joint. The intermediate shaft 4 and the input shaft 7) are also widely used so as to be inserted from the side of the base portion constituting the yoke. FIG. 9 shows one described in Patent Document 1 as an example of a universal joint having such a laterally inserted yoke.

  The universal joint 9 is formed by connecting a pair of yokes 10 and 11 via a cross shaft 12. The four end portions provided on the cross shaft 12 are swingably supported at the tip portions of the yokes 10 and 11 via needle bearings provided in the bearing cups 13 and 13, respectively. . With such a configuration, it is possible to transmit the rotational force between the yokes 10 and 11 whose central axes are not located on the same straight line. When such a universal joint 9 is assembled to a steering device as described above, one yoke 10 (on the right side in FIG. 9) is previously attached to the end of one shaft 14 such as a steering shaft by welding or screwing. The other yoke (left side in FIG. 9) is coupled to the end of the other shaft 15.

  When the steering device is assembled, the one shaft 14 is supported by the vehicle body, and then the one shaft 14 and the other shaft 15 are coupled by the universal joint 9. In this coupling operation, it is often difficult to relatively displace the other shaft 15 and the other yoke 11 constituting the universal joint 9 with respect to the axial direction of the shaft 15. Therefore, in order to enable the coupling work between the other shaft 15 and the universal joint 9, the other yoke 11 constituting the universal joint 9 is connected without moving the one shaft 14 in the axial direction. It is a so-called horizontal insertion type.

  FIGS. 10 to 11 show an example of a connecting portion between such a lateral insertion type yoke 11 and the shaft 15. The base end portion 16 of the yoke 11 has a U-shaped cross section, and a pair of holding plate portions 17a and 17b that are spaced apart from each other across the central axis of the yoke 11, and both the holding plate portions. The connecting part 18 which connects 17a, 17b one end edge (lower end edge of FIGS. 10-11) mutually is provided. The inner side surfaces of the pair of holding plate portions 17a and 17b are set as holding surfaces 19 and 19 that are substantially parallel to each other. Also, through holes 20a and 20b that are substantially concentric with each other are formed near the other ends (the upper ends of FIGS. 10 to 11) of both the holding plate portions 17a and 17b.

  On the other hand, the shaft 15 that joins the tip of the yoke 11 configured as described above has at least a cross-sectional shape of the tip as shown in FIG. That is, a pair of outer flat surfaces 21 and 21 parallel to each other are formed on the outer peripheral surface of the tip portion of the shaft 15, each being a restrained surface. Further, a notch 22 is formed in a portion closer to the tip of one side surface (upper side surface in FIGS. 10 to 11) of the shaft 15 with respect to a direction parallel to both the outer flat surfaces 21 and 21 (up and down direction in FIGS. 10 to 11). is doing.

When the distal end portion of the shaft 15 is coupled to the proximal end portion 16 of the yoke 11, first, the distal end portion of the shaft 15 is arranged on the opening side of the proximal end portion 16 as shown by a solid line in FIG. 9. To do. Then, from this state, for example, the yoke 11 is rotated about the cross shaft 12 from the solid line state to the chain line state in FIG. Is inserted into the base end portion 16 of the yoke 11 with the notch 22 positioned on the rear side in the insertion direction. Incidentally, to the manner performed such a penetration work easily, in a free state of the yokes 11 and the shaft 15, the spacing W ₁₉ of both clamping surfaces 19 and 19 to each other, said both outer planes 21, 21 to each other It is larger than the interval W ₂₁ (W ₁₉ > W ₂₁ ). Therefore, in the state in which the distal end portion of the shaft 15 is inserted into the proximal end portion 16 of the yoke 11 as described above, a positive fit is provided between the both restraining surfaces 19 and 19 and the outer flat surfaces 21 and 21. A gap 23 is formed.

  If the distal end portion of the shaft 15 is inserted into the proximal end portion 16 of the yoke 11 as described above, then, as shown in FIG. 11, the holding bolts 24 are inserted into the through holes 20a and 20b. At the same time, a nut 26 is screwed into a portion of the male screw portion 25 provided at the tip of the holding bolt 24 and protrudes outside the through hole 20b, and the nut 26 is further tightened with a predetermined torque. Thereby, the space | interval of the said one pair of restraining surfaces 19 and 19 is narrowed, and each these restraining surfaces 19 and 19 are contact | abutted to each said outer plane 21 and 21 (these each restraining surface 19 and 19 makes these each outside The planes 21 and 21 are strongly suppressed). When the nut 26 is tightened, the holding bolt 24 tends to rotate (co-rotate) in the rotation direction of the nut 26 with the friction of the screwed portion between the nut 26 and the male screw portion 25. As a result, the outer peripheral surface of the cam portion 27 provided at the intermediate portion of the holding bolt 24 is pressed against the bottom surface 28 of the notch 22, and the shaft 15 is pressed against the inner side surface 29 of the connecting portion 18. That is, of the outer peripheral surface of the shaft 15, a part of the other side surface (the lower side surface of FIGS. 30 is brought into strong contact with the inner surface 29 of the connecting portion 18. Furthermore, even if the holding bolt 24 and the notch 22 are engaged, and the tightening of the nut 26 is loosened, the shaft 15 can be removed from the inside of the base end portion 16 in the axial direction. To prevent.

  In addition, cylindrical portions 31a and 31b are provided in a base end portion and an intermediate portion, which are portions inserted into the through holes 20a and 20b, of the flange portion of the holding bolt 24, respectively. Then, when the outer peripheral surface of the cam portion 27 is pressed against the bottom surface 28 of the notch 22 at the contact portion between the outer peripheral surface of each cylindrical portion 31a, 31b and the inner peripheral surface of each through hole 20a, 20b. I try to support power.

  In the case of the connecting portion between the shaft 15 and the yoke 11 as described above, the both restraining surfaces 19 and 19 are in relation to the entire surfaces of the both outer flat surfaces 21 and 21 from the viewpoint of sufficiently securing the strength of the connecting portion. It is preferable to abut. However, when the nut 26 is tightened with a predetermined torque as described above in order to complete the coupling portion, the amount by which the space between the restraining surfaces 19, 19 is reduced is a portion close to the restraining bolt 24 and the nut 26 ( It increases in the upper part of FIG. 11 and decreases in the far part (lower part of FIG. 11). For this reason, in a state where the coupling portion is completed, in many cases, as shown in FIG. 11, both the restraining surfaces 19 and 19 and the both outer flat surfaces 21 and 21 are connected to the restraining bolt 24 and the nut. The contact is made only at the portion close to 26, and the fitting gaps 23 and 23 remain in the far portion. As a result, during the operation, there is a possibility that rattling occurs in the coupling portion based on the presence of the respective fitting gaps 23 and 23.

  In order to prevent such rattling, in Patent Document 1, as shown in FIGS. 12 to 13, the inner side surface 29 a of the connecting portion 18 a is a V-shaped concave surface, and the opposing surface 30 a of the shaft 15 a is the inner side surface. 29a describes a structure in which contact is made only at two portions near the center in the width direction. According to such a structure, the shaft 15a is displaced in a direction in which the shaft 15a moves far and away with respect to the pair of holding plate portions 17a and 17b constituting the base end portion 16a of the yoke 11a (the left-right direction in FIGS. This prevents the occurrence of rattling at the joint.

  In the case of the conventional structure described in Patent Document 1 as shown in FIGS. 12 to 13 described above, there is no particular problem when the torque transmitted through the universal joint is not so large. For example, in the case of a steering device incorporating a hydraulic power steering device that has been generally used in the past, all the universal joints have a steering wheel 1 (rather than a power steering device for applying an auxiliary steering force). (See FIG. 8). Therefore, the torque passing through the universal joint remains at a relatively small value before the auxiliary steering force is applied. For this reason, in the conventional structure shown in FIGS. 12 to 13, the surface pressure acting on the contact portion between the facing surface 30a and the inner surface 29a is limited, and the both surfaces 30a and 29a are slack. There is nothing.

  On the other hand, among the electric power steering devices that have been widely used in recent years, particularly in the case of a structure in which an electric motor as an auxiliary power source is installed in the steering column portion, the torque passing through the universal joint is the electric motor. It becomes a large value after the auxiliary steering force is applied by the motor. For this reason, the surface pressure which acts on the contact part of the said opposing surface 30a and the said inner surface 29a becomes large, and these both surfaces 30a and 29a may sag. In the event of a stagnation, rattling occurs at the joint between the yoke 11a and the shaft 15a, causing a driver who operates the steering wheel 1 to feel uncomfortable.

  In Patent Documents 2 and 3, male serrations are formed on the outer peripheral surface of the end of a shaft whose cross-sectional shape is circular or substantially circular (a semicircular shape larger than a semicircular shape), and the yoke whose cross-sectional shape is U-shaped. A structure in which female serrations are formed on the inner surface of the base end portion is described. In the case of the structures described in Patent Documents 2 and 3, the male and female serrations are inserted into the base end portion of the yoke from the opening side of the base end portion. Is going to be engaged. However, in the case of such a structure, among male serrations formed on the outer peripheral surface of the end portion of the shaft, a mountain portion that exists in a direction perpendicular to the insertion direction is a female formed on the inner surface of the base end portion. It is considered that the operation of inserting the end portion into the base end portion is troublesome due to interference with the peak portion of the serration. Further, in the case of the structure described in Patent Document 2, the number of parts increases, resulting in an increase in cost.

  Further, in Patent Document 4, a concave groove having a rectangular cross section is formed on the inner surface of the central portion in the width direction of the connecting portion of the base end portion of the yoke having a U-shaped cross section, and the convex formed on the end portion of the shaft. A structure for engaging the groove with the concave groove is described. In the case of such a structure, instead of facilitating the operation of inserting the end portion of the shaft into the base end portion of the yoke, excessive stress is easily applied to the engaging portion between the concave groove and the convex strip, Damage, such as cracks, easily occurs from the corners of the concave grooves. In order to prevent the occurrence of such damage, it is necessary to ensure a sufficient thickness at the base end of the yoke, and it is considered difficult to achieve both lightweight and durable durability of the universal joint. . In addition, since the clearance in the rotation direction of the engaging portion between the concave groove and the convex strip cannot be made zero, the rattling of the engaging portion cannot be completely eliminated, and the driver feels uncomfortable enough. It is difficult to eliminate.

  In view of the circumstances as described above, the present invention can improve the rigidity in the torsional direction of the joint between the shaft and the yoke of the universal joint without particularly increasing the weight. The present invention has been invented to realize a coupling portion between the shaft and the yoke of the universal joint that can improve the durability of the coupling portion and improve the durability of the coupling portion.

The joint portion between the shaft of the present invention and the universal joint yoke is similar to the conventional joint portion between the shaft and the universal joint yoke described above, and includes a shaft, a pair of restrained surfaces, a yoke, A pair of holding plate portions, a connecting portion, a through hole, a holding bolt, and a nut are provided.
Of these, the shaft rotates during use.
Further, the both restrained surfaces are provided on both side surfaces of the tip portion of the shaft.
The yoke constitutes a universal joint and has a base end portion opened on one side.
The holding plate portions constitute the base end portion and are provided apart from each other with the central axis of the yoke interposed therebetween, and the inner side surfaces facing each other are opposed to the both held surfaces. It has a restraining surface.
Moreover, the said connection part comprises the said base end part, and connects the anti-opening side edge of both the said control board parts mutually.
The through holes are formed substantially concentrically with each other at the opening side portions of the both holding plate portions. In the present specification and claims, substantially concentric does not have to be completely concentric, but the state where the misalignment between the central axes is small enough not to interfere with the insertion of the holding bolt. Say.
Moreover, the said holding | suppressing volt | bolt is spanned between the said both suppressing board parts by inserting in the said through-hole.
Further, the nut is screwed into a portion projecting to the outside of the through hole at the tip of the holding bolt.
Further, the holding bolt is a cam bolt in which a portion facing the end portion of the shaft is a cam portion having a non-circular cross-sectional shape, and when the nut is tightened, the end portion of the shaft is clamped by the cam portion. It pushes into the back of the base end of the yoke.
Further, the surface on the opening side of the base end portion among the both surfaces of the connecting portion is an inner peripheral surface facing surface, and the outer peripheral surface of the shaft is opposed to the inner peripheral surface facing surface. The outer peripheral surface is the opposite surface.

  In particular, in the joint portion between the shaft of the present invention and the yoke of the universal joint, a long ridge and a recess that are long in the axial direction of the shaft are respectively formed on the outer peripheral surface facing surface and the inner peripheral surface facing surface. A plurality of grooves are alternately arranged in the width direction perpendicular to the axial direction. And each said protrusion and each said concave groove formed in the said outer peripheral surface side opposing surface, and each said concave groove and each said protrusion formed in the said inner peripheral surface side opposing surface are meshed | engaged mutually.

In the case of implementing such a coupling portion between the shaft of the present invention and the yoke of the universal joint, preferably, the width dimension of each of the protrusions is changed from the proximal end portion to the distal end portion as in the invention described in claim 2. The width dimension of each groove is gradually decreased as it goes from the opening to the bottom.
Or, as in the invention described in claim 3, the end of the shaft is inserted between the holding plate portions, and the holding bolt is tightened to reduce the interval between the holding plate portions. In the state, the sum of the thicknesses of the gaps existing between the both holding surfaces and the both holding surfaces, the protrusions and the concave grooves present on the outer peripheral surface side and the inner peripheral surface side opposite surfaces Less than ½ of the pitch.
Preferably, as in the invention described in claim 4, the inner circumferential surface side facing surface is a partially cylindrical concave surface, and the outer circumferential surface side facing surface is a partially cylindrical convex surface.

  According to the present invention configured as described above, the rigidity in the torsional direction of the joint portion between the shaft and the universal joint yoke can be improved without particularly increasing the weight, thereby improving the steering feeling of the steering wheel. In addition, it is possible to realize a joint portion between the shaft and the universal joint yoke that can improve the durability of the joint portion.

  First, the torsional rigidity can be improved by meshing each protrusion formed on both the outer peripheral surface side and the inner peripheral surface side and each concave groove. That is, by engaging the protrusions and the concave grooves, the opposing surfaces are not displaced in the rotational direction around the central axis of the shaft. Therefore, the end portion of the shaft has a diametrically opposite position, i.e., a portion close to the opening of the pair of restraining plate portions that are strongly restrained by tightening the restraining bolts, the protrusions, and the concave grooves. Displacement in the rotational direction is prevented by a sufficiently large force at the portion closer to the back end of the base end portion that is disengaged from the opening. For this reason, displacement of the shaft and the yoke including the base end portion in the twisting direction is prevented by a sufficiently large force, and the torsional rigidity of the coupling portion is improved, thereby improving the steering feeling.

  In this way, in order to improve the torsional rigidity of the coupling portion, a plurality of ridges and concave grooves provided on each of both surfaces are engaged between the opposing surfaces, so that the torsional rigidity is increased. The total sum of the areas of the engaging surfaces that contributes to the improvement of the width is increased. For this reason, the surface pressure acting on each of the engagement surfaces can be kept low, and the engagement surfaces can be prevented from sagging (plastically deformed in the direction of being crushed). As a result, even when a large torque is transmitted over a long period of time, it is possible to suppress the occurrence of rattling in the coupling portion and improve durability. In addition, there are a plurality of engaging portions between the respective protrusions and the respective concave grooves, and these engaging portions share and transmit the torque, so that excessive stress is applied to any of the engaging portions. There is no. For this reason, the durability can be improved without particularly increasing the weight.

Sectional drawing similar to FIG. 11 which shows an example of embodiment of this invention. The fragmentary sectional view for demonstrating the shape of the coupling | bond part of the base end part of a yoke, and the edge part of a shaft. The end view of a shaft for demonstrating the direction of the force which acts on the edge part of a shaft. FIG. 5 is a partial cross-sectional view for explaining the behavior of the engaging portion between each protrusion and each groove when torque is transmitted between the shaft and the yoke in the structure of an example of the embodiment. The fragmentary sectional view for demonstrating the behavior at the time of the torque transmission between a shaft and a yoke by the conventional structure. FIG. 6A is a diagram showing the relationship between the magnitude of this torque and the twist angle, which is the relative displacement between the shaft and the yoke, when torque is applied to the connecting portion between the shaft and the yoke. FIG. 4 shows a case of the embodiment of the present invention shown in FIG. 4, and FIG. 5B shows a case of the conventional structure shown in FIG. The partial end elevation of a shaft which shows another example of the shape of each protrusion and each ditch | groove formed in the edge part outer peripheral surface of a shaft. The perspective view which shows an example of the steering device provided with the coupling | bond part of the shaft used as the object of this invention, and the yoke of a universal joint. The side view which shows the state which couple | bonds the edge part of a shaft, and the base end part of a yoke with the structure used as the object of this invention. XX sectional drawing of FIG. 9 which shows the 1st example of a conventional structure. Sectional drawing similar to FIG. 10 which shows the state which screwed the nut to the front-end | tip part of the holding | suppressing bolt formed in each through-hole, and also tightened. Sectional drawing similar to FIG. 11 which shows the 2nd example of a conventional structure. The Y section enlarged view of FIG.

  1 to 4 show an example of an embodiment of the present invention. The feature of this example is that the end of the shaft 15b and the base end of the yoke 11b are improved in order to improve the rigidity of the joint between the end of the shaft 15b and the base end 16b of the yoke 11b constituting the universal joint. The structure of the engaging portion with the portion 16b is devised. Since the structure and operation of other parts of the universal joint such as the shape and structure other than the base end part 16b of the yoke 11b and the end part of the shaft 15b are the same as those of the conventional structure described above, The illustration and description will be omitted or simplified, and the following description will focus on the features of this example.

A pair of outer flat surfaces 21 and 21, each of which is a restrained surface, are provided in parallel to each other on the outer peripheral surface of the end portion of the shaft 15 b. Both the outer flat surfaces 21 and 21 are formed by flatly scraping two positions on the opposite side in the diametrical direction of the end portion of the shaft 15b, which originally had a round bar shape with a circular cross section. Accordingly, the shaft 15b between the portion 32a at the end portion outer peripheral surface of the both outer plane 21, 21 deviated circumferentially, 32b of the original shape, part-cylindrical about the central axis O ₁₅ of the shaft 15b Surface (see FIG. 2). Among these two portions 32a and 32b, the portion 32a facing the inner peripheral surface of the connecting portion 18b of the base end portion 16b in the assembled state corresponds to the outer surface facing surface described in the claims.

  Further, in the case of the structure of this example, both the portions 32a and 32b are formed by connecting the long protrusions 33 and 33 and the grooves 34 and 34 that are long in the axial direction (front and back directions in FIGS. 1 to 4). By arranging alternately with respect to the direction, a partial gear shape (partial spline shape) is obtained. It should be noted that, of the inter-space portions 32a and 32b, a portion facing the cam portion 27 of the restraint bolt 24 in a state where the end portion of the shaft 15b and the proximal end portion 16b of the yoke 11b are coupled to each other. And a notch 22 that is pressed by the cam portion 27 as the nut 26 is tightened. As will be described later, the protrusions 33 and 33 and the concave grooves 34 and 34 are protrusions 36 and 36 and concave grooves 37 and 37 formed on the inner peripheral surface 35 of the connecting portion 18b of the base end portion 16b. Is engaged. Therefore, functionally, the protrusions 33 and 33 and the concave grooves 34 and 34 are formed in the portion 32b between the portions 32a and 32b on the side where the notch 22 is formed. There is no need. However, due to a problem in processing the protrusions 33 and 33 and the concave grooves 34 and 34, the protrusions 33 and 33 and the concave grooves 34 and 34 are formed in both the portions 32 a and 32 b. You can do it. Even when the protrusions 33 and 33 and the concave grooves 34 and 34 are formed in the intermediate portion 32b on the side where the cutout 22 is formed, the protrusions 33 are formed at least after the cutout 22 is formed. , 33 and the concave grooves 34, 34 are present only in a portion axially deviated from the notch 22 (the protrusions 33, 33 and the concave grooves 34, 34 do not exist in the notch 22 portion). .

  In any case, the protrusions 33 and 33 and the concave grooves 34 and 34 are formed by an appropriate processing method such as rolling, die forming, or press forming. In the case of the rolling process, the shaft 15b is rotated while pressing the rolling die against the outer peripheral surface of the end of the shaft 15b, and the shape of the pressing die is changed to the outer peripheral surface of the end of the shaft 15b. Transfer is performed (the portion near the outer diameter of the end of the shaft 15b is plastically deformed). Further, in the case of die forming, the end portion of the shaft 15b is pressed into the die in the axial direction, and the portions to be the concave grooves 34 and 34 are cut off. Further, in the case of press molding, a pressing die is pressed against the outer peripheral surface of the end portion of the shaft 15b, and the shape of the pressing die is transferred to the outer peripheral surface of the end portion of the shaft 15b (the portion closer to the outer diameter of the end portion of the shaft 15b). Is plastically deformed).

  In addition, in the forming operation of the protrusions 33 and 33 and the concave grooves 34 and 34 by the rolling process, the die forming, and the press forming as described above, the outer flat surfaces 21 and 21 and the notch 22 are formed. You can do it later. However, in order to ensure the accuracy of the shape and dimensions (including the pitch) of the protrusions 33, 33 and the concave grooves 34, 34, the outer flat surfaces 21, 21, and the notches 22, After forming the ridges 33, 33 and the respective concave grooves 34, 34, it is preferable to form both the outer flat surfaces 21, 21 and the notch 22 (particularly, each ridge 33, by rolling and pressing). 33 and the respective concave grooves 34, 34).

  Further, regarding the shape of each of the protrusions 33 and 33 and the concave grooves 34 and 34, in addition to the trapezoid as shown in the figure, a triangle, an involute shape, and a round tooth shape (U-shape) as shown in FIG. You can also do it. Whichever shape is adopted, the processing mold is detached after the projections 33 and 33 and the concave grooves 34 and 34 are processed, and further, the projections 33 and 33 and the concaves are formed. The grooves 34 and 34 have a shape that can reliably engage and disengage the protrusions 36 and 36 and the concave grooves 37 and 37 formed on the inner peripheral surface 35 of the connecting portion 18b. Specifically, the undercut portion does not exist with respect to the displacement direction of the mold and the protrusions 36 and 36 and the grooves 37 and 37. More specifically, with respect to the width direction (the vertical direction in FIGS. 1 to 4) of the both outer planes 21, 21, any circumferential side surface of each of the ridges 33, 33 is not limited to the ridges 33, 33 The portion closer to the tip of the base plate is formed so as not to protrude (overhang) from the portion closer to the base end. Therefore, as in this example, the shape of each of the protrusions 33 and 36 is gradually reduced in width from the proximal end to the distal end, and each of the concave grooves 34 and 37 has a respective width. , Gradually decrease from the opening toward the bottom.

  As shown in FIGS. 1, 2, and 4, the yoke 11b constituting the universal joint for coupling and fixing the end portion of the shaft 15b as described above has a base end portion 16b opened on one side. The base end portion 16b has a U-shaped cross section, and a pair of holding plate portions 17a and 17b that are spaced apart from each other across the central axis of the yoke 11b, and both the holding plate portions 17a. , 17b (the lower end edges in FIGS. 1, 2, and 4) are connected to each other. Among these, the shape and structure of the pair of holding plate portions 17a and 17b are the same as those of the conventional structure described above.

  In the case of the structure of this example, the inner peripheral surface 35 which is the surface on the opening side of the base end portion 16b among the both surfaces of the connecting portion 18b is a partially cylindrical concave surface described in the claims. It corresponds to the inner peripheral surface side facing surface. In the case of this example, the protrusions 33 and 33 and the concave grooves 34 and 34 formed on the inner peripheral surface 35 of the end portion outer peripheral surface 32a of the end portion of the shaft 15b. Plural ridges 36 and 36 and concave grooves 37 and 37 to be engaged are formed respectively. The shapes of the protrusions 36, 36 and the concave grooves 37, 37 are substantially the same as the shapes of the protrusions 33, 33 and the concave grooves 34, 34 formed in the intermediate portion 32a. The strips 33, 33 and the concave grooves 37, 37 are configured such that the concave grooves 34, 34 and the projections 36, 36 are engaged with each other without rattling.

  Regarding the method of forming the protrusions 36 and 36 and the concave grooves 37 and 37 in the inner peripheral surface 35 portion, the protrusions 33 and 33 and the concave grooves 34 and 34 are formed in the intermediate portion 32a. Of the methods, die molding and press molding can be employed. In order to secure the shape accuracy and dimensional accuracy of the protrusions 36 and 36 and the concave grooves 37 and 37, the processing of the protrusions 36 and 36 and the concave grooves 37 and 37 requires the base end 16b. It is preferable to carry out after processing into a U-shaped cross section. For this reason, it is difficult to form the protrusions 36 and 36 and the concave grooves 37 and 37 by rolling.

  Whichever method is used to form the protrusions 36 and 36 and the concave grooves 37 and 37, the circumferential side surfaces of the protrusions 36 and 36 and the concave grooves 37 and 37, and the protrusions 33. , 33 and the circumferential side surface of each of the concave grooves 34, 34 is a state where the end of the shaft 15 b is pushed into the recess of the base end portion 16 b by the cam portion 27 of the holding bolt 24 without any gap. Each shape accuracy and dimensional accuracy are ensured so as to touch. The engagement state between the circumferential side surfaces is not particularly limited. Preferably, the end portion of the shaft 15b is pushed out from the base end portion 16b by the engagement portion between the circumferential side surfaces during torque transmission. If the direction force is not generated, or if it is generated, it should be kept small. This point will be described with reference to FIGS.

The engaging portions between the circumferential side surfaces are inclined with respect to the direction in which the end portion of the shaft 15b is inserted into and extracted from the base end portion 16b, which is indicated by a chain line α in FIG. Further, when torque transmission between the shaft 15b and the yoke 11b, to the each engaging portion is basically, as shown by arrows in FIG. 3, the center of the center O ₁₅ of the shaft 15b A force in the normal direction of the arc β is applied (in fact, the center is slightly shifted as will be described later). And the force which raises the surface pressure of a contact part is added to each said circumferential direction side surface which comprises each said engagement part based on the force of each said arrow direction in the orthogonal | vertical direction with respect to these each side surface. Of the reaction force against this force, the component force directed toward the opening side (upper side in FIG. 2) of the base end portion 16b becomes the force in the direction of pushing the end portion of the shaft 15b from the base end portion 16b. However, as long as the magnitude of this component force does not become larger than the frictional force acting on each engaging portion, a force in the direction of pushing out from the base end portion 16b is actually applied to the end portion of the shaft 15b. There is nothing. Further, the magnitude of the component force is different for each engaging portion.

  For example, in FIG. 2 to FIG. 3, consider a case where clockwise torque is transmitted from the shaft 15b side to the yoke 11b. In this case, the rotation direction front side surface of the projections 33, 33 on the shaft 15b side and the rotation direction rear side surface of the projections 36, 36 on the yoke 11b side contact each other to transmit the torque. In this case, the inclination angle of each pair of side surfaces constituting each of the engaging portions with respect to the insertion / removal direction indicated by the chain line α is different for each of the engaging portions. As the inclination angle increases, the component force toward the opening side increases, and this component force tends to exceed the friction force. Conversely, the smaller the tilt angle, the smaller this component force, and the friction force tends to greatly exceed this component force. In the above case, even if the shaft 15b tends to be pushed out from the base end portion 16b in the right half portion of FIG. 2, the left half portion has a force to stop the shaft 15b in the base end portion 16. Become big enough. In order not to generate a force in a direction in which the end portion of the shaft 15b is pushed out from the base end portion 16b, the entire engaging portion is more than a force in a direction to push out the shaft 15b from the base end portion 16b. What is necessary is just to exceed the force of stopping in the base end part 16b.

  In the case of this example, the engaging portions are arranged symmetrically with respect to the chain line α passing through the center of the shaft 15b. Therefore, in the engaging portion between the circumferential side surfaces of the (center) protrusion 36 and the concave groove 34 existing on the chain line α, the force for stopping is higher than the force in the pushing direction. The inclination angle (pressure angle) θ of the pair of circumferential side surfaces constituting the engaging portion with respect to the chain line α is set in relation to the friction coefficient between these two side surfaces. For this reason, in the case of this example, when torque is transmitted between the shaft 15b and the yoke 11b, a force in the direction of pushing the end portion of the shaft 15b from the base end portion 16b is hardly generated. Even if temporarily, due to the presence of the holding bolt 24, the end portion of the shaft 15b is not pushed out of the base end portion 16b.

  When assembling the structure of this example, the end portion of the shaft 15b is inserted between the notch 22 between the restraining plate portions 17a and 17b constituting the base end portion 16b with the restraining bolt 24 not attached. From the side of the portion 32a on the opposite side, insertion is performed as shown in FIG. And while engaging each said protrusion 33, 33 formed in the part 32a between this, and the concave groove 37, 37 formed in the internal peripheral surface 35 of the connection part 18b which comprises the said base end part 16b, this, The protrusions 36, 36 formed on the inner peripheral surface 35 are engaged with the concave grooves 34, 34 formed on the intermediate portion 32a. In the case of this example, the state immediately after inserting the end portion of the shaft 15b between the two holding plate portions 17a and 17b, that is, the interval between the two holding plate portions 17a and 17b by tightening the holding bolt 24. In a state prior to shrinking, the distance between the two restraining plate portions 17a and 17b is made slightly larger than the width of the end portion of the shaft 15b. Specifically, the total thickness of the gaps 38 and 38 existing between the pair of holding surfaces 19 and 19 that are the inner surfaces of the both holding plate portions 17a and 17b and the both outer planes 21 and 21. Is made smaller than ½ of the pitch between the protrusions 33 and 36 and the concave grooves 34 and 37. Accordingly, the protrusions 33 and 36 and the concave grooves 34 and 37 are uniquely engaged (there is no possibility that the engaged state becomes an irregular state). Furthermore, the end surfaces of the protrusions 33 and 36 are not easily brought into contact with each other, and the operation of engaging the protrusions 33 and 36 with the concave grooves 34 and 37 can be easily performed.

  As described above, after inserting the end portion of the shaft 15b into the base end portion 16b and engaging the protrusions 33 and 36 with the concave grooves 34 and 37, the holding plate portions 17a The holding bolt 24 is inserted into the through holes 20a and 20b of the holding bolt 17b, and a nut 26 is screwed into the male screw portion 25 at the tip of the holding bolt 24. Then, the nut 26 is tightened. At the initial stage of the tightening operation of the nut 26, the cam portion 27 formed at the intermediate portion of the holding bolt 24 contacts the bottom surface 28 of the notch 22 formed at the end portion of the shaft 15b. In this state, since the holding bolt 24 does not rotate any more, the nut 26 can be tightened while preventing the holding bolt 24 from rotating together. Further, since the holding bolt 24 tends to rotate with the rotation of the nut 26 during the tightening operation, the cam portion 27 faces the end portion of the shaft 15b toward the back portion of the base end portion 16b. Press strongly. As a result, the end of the shaft 15b is pushed into the back of the base end 16b, and the protrusions 33 and 36 and the concave grooves 34 and 37 are engaged (engaged) with no gap.

  According to the structure of the connecting portion between the shaft of this example and the yoke of the universal joint, the torsional rigidity of the connecting portion can be improved. That is, since the protrusions 33 and 36 and the concave grooves 34 and 37 are engaged with each other without a gap, the intermediate portion 32a of the outer peripheral surface of the shaft 15b and the connecting portion 18b of the base end portion 16b. The inner peripheral surface 35 is not displaced in the rotational direction around the central axis of the shaft 15b. On the other hand, of the end portion of the shaft 15b, the portion closer to the other intermediate portion 32b, that is, the portion closer to the opening of the holding plate portions 17a and 17b, is sufficiently secured by tightening the holding bolt 24 and the nut 26. It is in a state of being restrained by a large force (given a large preload). Therefore, the end portion of the shaft 15b is positioned opposite to the diametrical direction, that is, the portion near the opening of the holding plate portions 17a, 17b, which is strongly held down by tightening the holding bolt 24, and the protrusions 33, The displacement in the rotational direction is prevented by a sufficiently large force at the portion closer to the back end of the base end portion 16b that is disengaged from the opening, which is engaged with the groove 36 and the concave grooves 34, 37. Therefore, displacement of the shaft 15b and the yoke 11b including the base end portion 16b in the twisting direction is prevented by a sufficiently large force, and the torsional rigidity of the coupling portion is improved and the steering feeling is improved. Can be planned.

  Further, this improvement in steering feeling is due to the fact that the angle of inclination of the engaging portion (meshing portion) between the protrusions 33 and 36 and the concave grooves 34 and 37 is slightly different for each of the plurality of engaging portions. Can also be obtained. This point will be described with reference to FIGS. In FIG. 4, when the shaft 15b rotates in the clockwise direction, the shaft 15b is pointed with respect to the base end portion 16b of the yoke 11b, i.e., at the front end edge in the rotational direction of the portion 32b near the opening. There is a tendency to twist clockwise with respect to the base end portion 16b around the contact portion of the holding plate portion 17b with the holding surface 19. As a result, the rotation direction front side surfaces of the protrusions 33, 33 on the shaft 15b side are pressed against the rotation direction rear side surfaces of the protrusions 36, 36 on the yoke 11b side, and torque transmission is performed.

There is essentially no gap in the engaging portion between the side surfaces of each of the protrusions 33 and 36, but the shaft 15b is long in the front and back direction in FIG. A slight gap (micro gap) is formed in the engaging portion between the side surfaces of each of the protrusions 33 and 36 by being displaced so as to be twisted in the direction of entering and exiting the base end portion 16b (vertical direction in FIG. 4). Tend to occur. At the time of torque transmission, the size of the minute gap (the value of the thickness with respect to the twisting direction) related to the twisting direction of the shaft 15b centered on the point A is not uniform. Specifically, an angle θ formed between the straight lines L _{1 to} L _{7 in} FIG. 4 connecting the point A and the engaging portions and the side surfaces of the protrusions 33 and 36 constituting the engaging portions. about ₁ through? ₇ is large, the value of the minute gap is increased. Then, as is clear from FIG. 4, each of these angles θ _{1 to} θ ₇ is larger as the engaging portion on the side of the holding plate portion 17b where the swing center point A is present (θ ₁ <θ ₂ </. <Θ ₆ <θ ₇ ). Accordingly, the value of each minute gap is the largest at the engaging portion on the side of the pressing plate portion 17b, and decreases as the distance from the pressing plate portion 17b increases.

  At the time of torque transmission between the shaft 15b and the yoke 11b, when the torque is small, the holding plate portions 17a and 17b that are coupled to each other by tightening the holding bolt 24 and the nut 26, Of the end portion of the shaft 15b, the torque is transmitted at a contact portion with the opening portion of the base end portion 16b. In this state, even if a minute gap exists in each of the engaging portions, the minute gap remains. When the torque to be transmitted gradually increases and this torque cannot be transmitted only at the portion near the opening, a part of this torque begins to be transmitted even at the engaging portion between the protrusions 33 and 36. Prior to starting to transmit torque at each of the engaging portions, the minute gaps existing in the engaging portions are eliminated, and the circumferential side surfaces of the protrusions 33 and 36 are brought into contact with each other. However, since the values of the minute gaps existing in the engagement portions are not uniform, the engagement portions do not start torque transmission at the same time (begin to contribute to torque transmission). Specifically, torque transmission is started from the engaging portion on the side far from the holding plate portion 17b where the value of each minute gap is small. As for the other engaging portions, torque transmission is started sequentially as the value of torque to be transmitted increases. In a state where the torque to be transmitted is sufficiently large, all the engaging portions contribute to the transmission of the torque based on the elastic deformation of the protrusions 33 and 36 (a part of the torque is applied respectively). State).

  In the process in which the value of the torque to be transmitted rises and each of the engaging portions starts to contribute to torque transmission sequentially, the rigidity (transmission torque) of the coupling portion between the base end portion 16b of the yoke 11b and the end portion of the shaft 15b. (Twisting angle) gradually increases. Since the rigidity of the coupling portion increases stepwise as the plurality of engaging portions sequentially start torque transmission, the magnitude of the torque transmitted by the coupling portion and the twist angle of the coupling portion As shown in FIG. 6A, the relationship becomes relatively smooth even in a process in which each of the engaging portions starts to contribute to torque transmission sequentially. For this reason, it is difficult to deteriorate the steering feeling of the steering wheel. On the other hand, in the case of the conventional structure as shown in FIG. 5, in the process of increasing the torque to be transmitted, one of the outer flat surfaces 21 at the end of the shaft 15a and one of the restraining surfaces 19 of the yoke 11a Since the rigidity suddenly increases at the moment of contact, the steering feeling of the steering wheel tends to deteriorate.

  In the case of the structure of this example, as described above, in order to improve the torsional rigidity of the coupling portion, the inner peripheral surface 35 of the connecting portion 18b of the base end portion 16b of the yoke 11b and the shaft 15b Since the protrusions 33, 36 and the concave grooves 34, 37, each having a plurality of intermediate portions 32a on each of both surfaces, are engaged with each other, the area of the engaging surface that contributes to the improvement of the torsional rigidity is increased. The sum is widened. For this reason, the surface pressure acting on each of the engagement surfaces can be kept low, and the engagement surfaces can be prevented from sagging (plastically deformed in the direction of being crushed). As a result, even when a large torque is transmitted over a long period of time, it is possible to improve durability by suppressing the occurrence of rattling in the coupling portion. In addition, since excessive stress is not partially applied, the required strength can be ensured without increasing the size of each component, miniaturization is possible, and both weight reduction and improved durability are achieved. Easy to plan. Such a structure of this example is built into a so-called column type electric power steering device in which an electric motor as an auxiliary power source is installed in a steering column portion, and is rattled even when a large torque is inputted. It can be suitably used as a structure that does not easily generate.

  The above description relates to a case where the present invention is implemented at a joint portion between a shaft and a universal joint yoke for coupling an end portion of a shaft and a universal joint yoke constituting a steering apparatus for an automobile. explained. However, the present invention can also be implemented by a joint portion between a shaft incorporated in various mechanical devices other than the steering device and a yoke of a universal joint. Also, the basic shape of the inner peripheral surface facing surface provided on the yoke side and the outer peripheral surface facing surface provided on the shaft side (the shape before forming the ridge and the concave groove) is as in the example shown in the figure. It is not limited to a partially cylindrical concave surface or convex surface, and may be a flat surface.

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3 First universal joint 4 Intermediate shaft 5 Second universal joint 6 Steering gear unit 7 Input shaft 8 Tie rod 9 Universal joint 10 Yoke 11, 11a, 11b Yoke 12 Cross shaft 13 Bearing cup 14 Shaft 15 , 15a, 15b Shaft 16, 16a, 16b Base end portion 17a, 17b Holding plate portion 18, 18a, 18b Connecting portion 19 Holding surface 20a, 20b Through hole 21 Outer plane 22 Notch 23 Fitting gap 24 Holding bolt 25 Male screw portion 26 Nut 27 Cam portion 28 Bottom surface 29, 29a Inner side surface 30, 30a Opposing surface 31a, 31b Column portion 32a, 32b Part 33 Projection 34 Concave groove 35 Inner circumferential surface 36 Projection 37 Concave groove 38 Clearance

Japanese Patent Laid-Open No. 2006-97884 JP-A-9-133150 Japanese Patent Laid-Open No. 9-210074 JP 2004-360814 A

Claims (4)

  A shaft that rotates during use, a pair of restrained surfaces provided on both side surfaces of the distal end portion of the shaft, a base end portion that is open on one side, and constituting a universal joint, and a central axis of the yoke A pair of restraining plate portions constituting the base end portion, and the both restraining plates, with inner surfaces facing each other as the restraining surfaces opposed to the both restrained surfaces. The opposite edges of the openings are connected to each other to form the base end portion, the concentric through holes formed in the opening side portions of the holding plate portions, and the both through holes. The holding bolt includes a holding bolt that is spanned between the holding plate portions by being inserted, and a nut that is screwed to a portion protruding to the outside of the through hole at the tip of the holding bolt. The portion facing the end of the shaft has a non-circular cross-sectional shape. The cam bolt is a cam bolt that pushes the end of the shaft into the back of the base end of the yoke as the nut is tightened. The shaft on the opening side of the base end portion is an inner peripheral surface facing surface, and the outer peripheral surface of the shaft is the outer surface facing the inner peripheral surface facing surface. In the joint portion with the yoke of the universal joint, each of the outer peripheral surface facing surface and the inner peripheral surface facing surface has a plurality of long ridges and concave grooves each in the axial direction of the shaft, Alternatingly arranged in the width direction perpendicular to the axial direction, the protrusions and concave grooves formed on the outer peripheral surface facing surface, and the inner peripheral surface facing surface Each groove and each protrusion are meshed with each other. Binding portion of the yoke of the shift and universal joint.   2. The shaft and the universal joint according to claim 1, wherein the width dimension of each protrusion gradually decreases from the proximal end portion toward the distal end portion, and the width dimension of each concave groove gradually decreases from the opening portion toward the bottom portion. Joint with the yoke.   Insert the end of the shaft between a pair of holding plates and tighten the holding bolts to reduce the distance between these holding plates, between the holding surfaces and the holding surfaces. The total thickness of the existing gaps is smaller than 1/2 of the pitch between the ridges and the concave grooves existing on both the outer peripheral surface side and the inner peripheral surface side opposing surfaces. The joint part of the shaft described in 1 and the yoke of a universal joint.   The shaft and universal joint yoke according to any one of claims 1 to 3, wherein the inner peripheral surface-side facing surface is a partially cylindrical concave surface, and the outer peripheral surface-side facing surface is a partially cylindrical convex surface. And joints.

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