JP2010116955A - Extensible rotation transmission shaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive structure without causing damage such as an impression, even when large torque is transmitted. <P>SOLUTION: In a neutral state of not transmitting rotation between an outer shaft 10b and an inner shaft 11b, rolling surfaces of respective balls 14 and 14 are contacted with bottoms of respective inner side recessed grooves 19a and 19a and outer side recessed grooves 18a and 18a, respectively. In a state of contacting the respective balls 14 and 14 with a part disconnected in the circumferential direction from the bottom part of the respective recessed grooves 19a and 18a by transmitting the rotation between both mutual shafts 10b and 11b, respective inner side butting surfaces 25 and 25 are allowed to abut on respective outer side butting surfaces 26 and 26. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The telescopic rotation transmission shaft according to the present invention is capable of transmitting rotational force (torque), such as a steering shaft and an intermediate shaft (intermediate shaft) constituting an automobile steering device, and can extend and contract in the axial direction. Used as a shaft.

  The steering apparatus for an automobile is configured as shown in FIG. 14, for example, so that the movement of the steering wheel 1 is transmitted to the steering gear unit 2. The movement of the steering wheel 1 is transmitted to the input shaft 6 of the steering gear unit 2 through the steering shaft 3, the universal joint 4a, the intermediate shaft 5, and the universal joint 4b. Then, the steering gear unit 2 pushes and pulls the pair of left and right tie rods 7 and 7 to give a desired steering angle to the steered wheels. In the example shown in FIG. 14, an electric power steering device is incorporated in which an electric motor 8 applies an assisting force corresponding to the force applied by the driver to the steering wheel 1 to the steering shaft 3.

  When the front-rear position of the steering wheel 1 is adjusted according to the physique and driving posture of the driver with the steering device as described above, the steering shaft 3 and the steering column 9 that rotatably supports the steering shaft 3 are used. And extend and contract. For this purpose, the steering shaft 3 is a so-called telescopic steering shaft in which the outer shaft 10 and the inner shaft 11 are freely combined with expansion and contraction and transmission of rotational force by a spline engaging portion. Further, the steering column 9 is a combination of an outer column 12 and an inner column 13 that can be expanded and contracted.

  In order to improve the operational feeling of the steering wheel 1 during normal operation, an excessive backlash in the rotational direction does not occur in the axial sliding portion such as the spline engaging portion of the steering shaft 3. There is a need to. On the other hand, in order to adjust the front / rear position of the steering wheel 1 with a light force, the axial sliding portion needs to be configured to be easily displaced in the axial direction. Conventionally, a structure described in Patent Document 1 is known as a structure that satisfies such conflicting requirements. 15 to 16 show an example of the conventional structure described in Patent Document 1. FIG.

  In the case of the steering shaft 3a having the conventional structure, the outer shaft 10a, the inner shaft 11a, a plurality (three pieces) of balls (steel balls) 14, 14, a retainer 15, and an elastic member (leaf spring) 16 are used. And a plurality (two) of cylindrical members 17 and 17. Of these, the outer shaft 10a is provided with a plurality of (three) outer-side grooves 18 and 18 in the axial direction on the inner peripheral surface so as to be recessed radially outward from the inner peripheral surface. . The inner shaft 11a is provided with a plurality of (three) inner-side grooves 19 and 19 in the axial direction in a state where the inner shaft 11a is recessed radially inward from the outer peripheral surface. Each of the balls 14, 14 includes one outer side groove 18, one of the three outer side grooves 18, 18 (upper side in FIG. 15), and an inner surface facing the outer side groove 18. They are respectively provided between the elastic members 16 engaged with the side concave grooves 19.

  The cage 15 holds the balls 14 and 14 at predetermined intervals in the axial direction of the outer shaft 10a and the inner shaft 11a. The elastic member 16 elastically presses the balls 14 and 14 toward the outer groove 18 (applies a preload). The cylindrical members 17 and 17 are provided between the remaining two outer concave grooves 18 and 18 and the remaining two inner concave grooves 19 and 19, respectively. Yes.

  The balls 14 and 14 and the cylinders are elastically pressed by the elastic member 16 against the inner surface (inner surface) of the (one) outer groove 18. It is possible to prevent rattling from occurring at the engaging portions (contact portions, meshing portions) between the members 17 and 17 and the outer and inner concave grooves 18 and 19. Further, when a large rotational force (torque) is transmitted between the outer shaft 10a and the inner shaft 11a, the elastic member 16 is elastically deformed according to the torque. Based on the elastic deformation of the elastic member 16, the large torque is transmitted through the cylindrical members 17 and 17, and the balls 14 and 14 and the outer side and the inner side are transmitted. It prevents that the surface pressure of the contact part with each concave groove 18 and 19 becomes excessive. When the outer shaft 10a and the inner shaft 11a are relatively displaced in the axial direction, the balls 14 and 14 roll, and the outer peripheral surfaces of the cylindrical members 17 and 17 and the outer side, The inner side grooves (inner side surfaces) of the inner side concave grooves 18 and 19 slide. For this reason, the relative displacement can be performed with a light force.

  However, in the case of the conventional structure described in Patent Document 1 as described above, the number of parts is increased by the provision of the elastic member 16, and the production of parts and the management of parts become troublesome, and the number of assembling steps increases. This may lead to an increase in manufacturing cost of the steering shaft 3a. On the other hand, as a structure in which the relative displacement can be performed with a light force without providing the elastic member 16 as described above, for example, structures described in Patent Documents 2 to 8 have been conventionally known. However, in the case of the structures described in Patent Documents 2 to 8, torque is transmitted only with balls. For this reason, at the time of steering, these balls are not only repeatedly pressed against the same part of the outer and inner concave grooves engaged with the balls, but the surface pressure of the parts may be excessively increased. There is. And when surface pressure becomes large too much like this, an impression (plastic deformation) may arise in the said part. Such an indentation is not preferable because it may cause rattling during steering and may cause the relative displacement in the axial direction between the outer shaft and the inner shaft not to be smoothly performed.

  The indentation is more likely to occur as the torque to be transmitted increases. For example, the steering device shown in FIG. 14 is a so-called column-type electric power steering device in which the electric motor 8 as an auxiliary power source is provided on the steering column side. Such an electric power steering device. In this case, compared to the torque transmitted by the steering shaft 3, the torque transmitted by the intermediate shaft 5 is increased by the amount of auxiliary power. Therefore, when the above-described techniques described in Patent Documents 2 to 8 are adopted for such an intermediate shaft 5 (shaft to which auxiliary power is applied, shaft downstream of the auxiliary power source), Furthermore, it becomes easy to occur. On the other hand, in Patent Document 9, a needle is provided between the inner peripheral surface of the outer shaft and the outer peripheral surface of the inner shaft so as to be able to roll in the axial direction of both shafts. In addition to this ball, a structure is described in which each needle is supported by the needle. In the case of such a structure, it is possible to suppress the formation of indentations due to the balls on the peripheral surfaces of both shafts, but the rolling surface of the needle hits the peripheral surfaces of these shafts. For this reason, it is considered that sufficient durability cannot always be ensured.

International Publication No. 2003/031250 Pamphlet JP 2006-349104 A JP 2007-46769 A JP 2007-16901 A Japanese Patent No. 3694637 Japanese Utility Model Publication No. 3-30621 JP 2004-306919 A JP 2004-168229 A JP 2003-291824 A

  In view of the circumstances as described above, the telescopic rotation transmission shaft according to the present invention should be inexpensive and have a structure that can hardly cause damage such as indentation even when a large rotational force (torque) is transmitted. Invented.

The telescopic rotation transmission shaft of the present invention includes an inner shaft, an outer shaft, and a plurality of balls, like the conventionally known telescopic rotation transmission shaft.
Of these, the inner shaft is provided with an inner side groove in the axial direction at a plurality of locations in the circumferential direction of the outer peripheral surface and having an arc shape or a substantially arc shape in cross section and recessed inward in the radial direction. .
Further, the outer shaft is recessed radially outwardly in a circular arc shape or a substantially arc shape in cross section at a position where it is aligned with each inner groove on the inner circumferential surface at a plurality of locations in the circumferential direction. The outer side recessed groove is provided in the axial direction, and the inner shaft can be inserted freely.
Each ball is provided between each inner groove and each outer groove.
And the said outer shaft and the said inner shaft are combined so that transmission of the rotational force between each other and relative displacement of an axial direction are possible.

In particular, in the telescopic rotation transmission shaft of the present invention, the rolling surfaces (surfaces) of the balls are in the neutral state where the rotation transmission is not performed between the outer shaft and the inner shaft. Of the inner groove and at least one of the outer groove (more preferably the inner and outer grooves), the most concave portion in the radial direction. Contact the bottom or near the bottom.
In other words, a contact portion between the rolling surface of each ball and the inner surface of at least one of the inner side groove and the outer side groove (more preferably, the inner side and outer side both grooves). Pressure angle (contact angle), that is, an angle formed by a virtual plane including the center axis of the inner shaft and the outer shaft and the center of the ball and a virtual plane in contact with the contact portion. Specifically, the pressure angle (contact angle) of the contact portion is 45 degrees or more, preferably 60 degrees or more, more preferably 75 degrees or more, and most preferably 90 degrees. In short, when the rolling surface of the ball is brought into contact with the bottom of the groove or near the bottom, the pressure angle (contact angle) is 45 degrees or more (preferably 60 degrees or more, more preferably 75 degrees or more, most preferably Say 90 degrees). When transmitting torque in both directions as in a steering shaft, the pressure angle in the neutral state is set to 90 degrees, excluding assembly errors.

In addition, the inner abutting surfaces are arranged at a plurality of locations on the outer circumferential surface of the inner shaft that are circumferentially separated from the inner side concave grooves, and the inner circumferential surface of the outer shaft is opposed to the inner abutting surface. The outer side abutment surface is provided respectively.
Then, rotation transmission is performed between the outer shaft and the inner shaft so that the balls move in the circumferential direction from the bottom or the vicinity of the bottom of the inner grooves of the inner grooves and the outer grooves. The respective inner side abutting surfaces and the respective outer side abutting surfaces are brought into contact with each other in a state of being in contact with the detached portion.

  When the telescopic rotation transmission shaft of the present invention as described above is implemented, for example, as in the invention described in claim 2, the neutral state and the torque transmitted between the inner shaft and the outer shaft are The respective inner side abutting surfaces and the respective outer side abutting surfaces are not in contact with each other, and the respective balls contact the bottoms of the inner side concave grooves and the outer side concave grooves or the vicinity of the bottoms thereof. In this state, the balls allow relative displacement in the axial direction of the shafts while being in rolling contact with the bottoms of the grooves or the vicinity of the bottoms. Further, the torque transmitted between the two shafts is large, and each ball of the inner surfaces of the concave grooves is in contact with the inner abutting surfaces and the outer abutting surfaces. The distance between each inner side abutting surface and each outer side abutting surface in the neutral state is set so that no indentation is formed in the portion where the rolling surface abuts.

  In the case of carrying out the telescopic rotation transmission shaft of the present invention, preferably, each ball is provided with a tightening margin (including a clearance 0 and a tightening allowance 0) for the inner and outer concave grooves. That is, in the state where the outer shaft and the inner shaft are combined, and in the neutral position where the torque is not applied between the outer shaft and the inner shaft and in the free state (the state where the elastic shaft is not deformed), The outer diameter of the ball in the free state is the same as or slightly smaller than the diameter of the virtual circle (inscribed circle with respect to the cross section) formed by the inner surface of each outer groove on the outer side. (For example, about 1/10 to 1/1000 of the outer diameter of the ball).

  In this way, the tightening allowance given to each of the balls, the relationship between the outer diameter of each of the balls, the cross-sectional shape of each of the concave grooves, and each of the inner side abutting surface and each of the outer side abutting surfaces The interval in the circumferential direction is regulated as follows. First, the tightening allowance of each ball (the difference between the outer diameter of each ball and the diameter of the virtual circle) is related to the radius of curvature of the cross-sectional shape of each concave groove (relationship with the area of the contact ellipse). In the range where each of the balls and the inner and outer grooves are elastically deformed, that is, the inner and outer grooves are not indented (plastically deformed). It is set within a range that does not lead to a decrease and can smoothly expand and contract in the axial direction. Further, within the range where the balls and the inner and outer grooves are elastically deformed, that is, the inner grooves and the outer grooves are not indented due to plastic deformation. The inner side and outer side abutting surfaces are in contact with each other within a range that does not lead to a decrease in durability and can be smoothly expanded and contracted in the axial direction, and the torque is transmitted. .

  Further, when the telescopic rotation transmission shaft of the present invention is implemented, for example, as in the invention described in claim 3, a portion between the outer side concave grooves adjacent in the circumferential direction in the outer shaft. By making the shape bent in a direction indented radially inward, the portion of the outer shaft in which each outer groove is formed is easily elastically deformed in the radial direction. And the surface pressure of the contact part of each inner side ditch | groove and each inner side ditch | groove and each inner side ditch | groove, and the rolling surface of each ball | bowl, and each inner side abutting surface and each outer side abutting surface contact | abut. The amount of torque transmitted between the outer shaft and the inner shaft is regulated in the state (at the moment when both abutting surfaces are connected to each other).

  When the telescopic rotation transmission shaft of the present invention is implemented, for example, as in the invention described in claim 4, the inner abutting surfaces and the outer abutting surfaces are connected to the inner shaft and the outer abutting surface. A flat surface existing on a virtual plane including the central axis of the shaft. And the space | interval of each inner side abutting surface and each outer side abutting surface is enlarged so that it goes to a radial direction outer side from radial inside. With this configuration, when the rotation is transmitted between the shafts, the inner abutting surfaces and the outer abutting surfaces are brought into contact with each other in the direction perpendicular to the abutting surfaces.

  When the telescopic rotation transmission shaft of the present invention is implemented, for example, as in the invention described in claim 5, the outer groove is located at two positions on the outer shaft opposite to the circumferential direction. Each inner groove is provided at two positions on the opposite side of the inner shaft in the circumferential direction. The outer shaft is made by plastic deformation of a metal tube. And regarding the cross-sectional shape perpendicular to the central axis of the outer shaft, there is no undercut part that prevents the movement of the mold in the direction perpendicular to the direction of arrangement of the outer grooves.

Further, when the telescopic rotation transmission shaft of the present invention is implemented, for example, as in the invention described in claim 6, the thickness of the outer shaft is substantially reduced over the entire circumference (for processing such as bending). Except for the difference due to accompanying minor changes).
Alternatively, as in the invention described in claim 7, the outer shaft includes a portion in which each outer side concave groove is formed, and a plurality of protrusions in which the outer peripheral surface side is a partially convex cylindrical surface at a plurality of circumferential positions. Shall be provided. And the top part of each of these protrusion parts is made thinner than another part.

Further, when the telescopic rotation transmission shaft of the present invention is implemented, for example, as in the invention described in claim 8, the center axis of the inner shaft, which exists at the bottom of each inner groove, is the center of curvature. At least one partial cylindrical surface of the convex partial cylindrical surface, and a concave portion cylindrical surface that is present at the bottom of each outer-side concave groove and that has a center axis of curvature of the outer shaft.
Alternatively, when the telescopic rotation transmission shaft of the present invention is implemented, for example, as in the ninth aspect of the invention, at least one of the inner side concave grooves and the outer side concave grooves is provided. The radius of curvature of the cross-sectional shape of the groove is increased at the central portion in the width direction of the concave groove and decreased at the portions near both ends.
Further, when the telescopic rotation transmission shaft of the present invention is implemented, for example, as in the invention described in claim 10, both the inner shaft and the outer shaft are made by plastically deforming a metal tube. Both shafts are elastically deformable in the radial direction.

  According to the telescopic rotation transmission shaft of the present invention configured as described above, it is inexpensive, and even when a large rotational force is transmitted, damage such as indentation can hardly occur ( It is possible to realize a structure that does not lead to a decrease and is able to smoothly extend and contract in the axial direction. For this reason, transmitting a large rotational force (increasing the allowable load torque), performing smooth axial expansion / contraction without rattling, and reducing manufacturing costs can be arranged side by side.

  That is, in the case of the present invention, since it is not necessary to provide an elastic member for applying an elastic force to each ball, it can be configured at a low cost. In addition, since the torque can be transmitted based not only on the balls but also on the abutting surfaces of the inner side and the outer side, the corresponding amount (the contact between the surfaces used for torque transmission) Large torque can be transmitted (allowable load torque can be increased). In addition, the transmission of such a large torque is shared by the abutting surfaces of the inner side and the outer side, so that the surface pressure of the abutting portion between the balls and the inner side and outer side grooves is excessive. It can be prevented from becoming large, and damage such as indentation can be made difficult to occur. In the case of the present invention, the inner side and outer side abutting surfaces can transmit a large torque without using the cylindrical member (cylindrical member) like the conventional structure shown in FIGS. Since it is based on the contact between each other, the number of parts can be reduced, and this aspect can also be constructed at a low cost.

  In addition, in the case of the present invention, the rolling surfaces of the balls are brought into contact with the bottom of at least one of the inner side concave grooves and the outer side concave grooves. As the torque increases, the inner side and outer side abutment surfaces can reliably share the transmission of this torque. That is, at the contact portion between the rolling surface of each ball brought into contact with the bottom of each groove and the groove (the groove where these balls are in contact with each other at the bottom), the pressure angle (contact angle) is Since the torque increases, the component force applied in the direction of receiving the torque is small, and the torque is only slightly increased, and the torque cannot be transmitted only through the balls. For this reason, when the torque is applied at the contact portion between the rolling surface of each ball and the concave groove, relative rotation between the inner shaft and the outer shaft tends to be permitted. Then, with such relative rotation, the abutting surfaces of the inner side and the outer side come into contact with each other, and transmission of this torque is transmitted between the abutting surfaces of the inner side and the outer side as the torque increases. The engaging portion of each is surely shared.

  Further, as the inner shaft and the outer shaft rotate relative to each other, the contact portion between the rolling surface of each ball and the concave groove moves laterally (in the rotational direction) from the contact position in the no-load state where the torque is not applied. ) Tends to be displaced (shifted). For this reason, even if a large torque is applied, even if an indentation is generated on the rolling surface of the concave groove due to contact with the rolling surface of the ball, the position where the indentation is generated is It becomes a position deviated from the contact position with the rolling surface of the ball in a no-load state where it is not applied. For this reason, regardless of the indentation (even if an indentation occurs), the relative displacement in the axial direction of the outer shaft and the inner shaft is performed in a no-load state in which the torque is not applied (the rotation of the telescopic rotation transmission shaft). Expansion and contraction can be performed smoothly.

[First example of embodiment]
1 and 2 show a first example of an embodiment of the present invention corresponding to claims 1 to 6 and 10. In addition, including this example, the feature of the telescopic rotation transmission shaft of the present invention lies in the structure of the portion that combines the inner shaft and the outer shaft so as to be able to expand and contract and to transmit torque. The shape seen from the outside in the radial direction by combining the telescopic rotation transmission shaft is the same as the shape of the steering shaft 3 or the intermediate shaft 5 described in FIG. 14, for example. Therefore, the following description will be made on the basis of a cross-sectional shape related to a virtual plane perpendicular to the central axis in which the structure that characterizes the present invention appears.

The telescopic rotation transmission shaft 20 of the present example includes an inner shaft 11b, an outer shaft 10b, and a plurality of balls 14 and 14.
Of these, the inner shaft 11b and the outer shaft 10b are each formed by pressing a round tube made of metal such as steel or aluminum alloy, and each of the cross-sectional shapes is formed in a generally drum shape. .

  First, with respect to the inner shaft 11b, inner side concave grooves 19a and 19a respectively recessed inward in the radial direction (vertical direction in FIG. 1) at two positions on the outer diameter side opposite to the radial direction are axially arranged. It is formed in a continuous state (in the front and back direction in FIG. 1). In the case of this example, the cross-sectional shape of each of the inner concave grooves 19a, 19a is a single piece having a radius of curvature that is slightly larger than ½ of the outer diameter of each of the balls 14, 14 except for the edges at both ends of the opening. It is an arc. Further, at two positions on the outer circumferential surface of the inner shaft 11b opposite to the diametrical direction, with respect to the circumferential direction of the outer circumferential surface, the portions between the inner concave grooves 19a and 19a protrude toward the outer circumferential surface. The inner side convex portions 21 and 21 each having a V-shaped cross section and the inner side flat portions 22 that connect the inner side convex portions 21 and 21 to each other are formed. The both ends of each of the inner convex portions 21, 21 and the continuous portion of the inner flat portion 22 and the inner concave grooves 19a, 19a are smoothly and continuously formed by curved surfaces having a circular arc cross section. Yes.

  The outer shaft 10b has a larger cross section than the inner shaft 11b so that the inner shaft 11b can be inserted into the outer shaft 10b. With respect to such an outer shaft 10b, outer side grooves 18a and 18a that are recessed inward in the radial direction (vertical direction in FIG. 1) at two positions opposite to the diameter direction on the inner peripheral surface are respectively connected to the shaft. It forms in the state which continues in a direction (front and back direction of FIG. 1). Regarding the cross-sectional shape of each outer side concave groove 18a, 18a, a single circular arc having a radius of curvature slightly larger than ½ of the outer diameter of each of the balls 14, 14, except for the edges at both ends of the opening. Further, at two positions opposite to the diameter direction of the inner peripheral surface of the outer shaft 10b, with respect to the circumferential direction of the inner peripheral surface, a portion between each of the outer side concave grooves 18a, 18a is respectively connected to the inner peripheral surface. The outer side concave portions 23 and 23 each having a V-shaped cross section with a concave side, and an outer side flat portion 24 that connects the outer side concave portions 23 and 23 to each other. Even at both ends of each of the outer side recesses 23, 23 and the continuous portion of the outer side flat portion 24 and each of the outer side recess grooves 18a, 18a, each of the outer side recesses 23, 23 is smoothly continuous by a curved surface having an arcuate cross section. I am letting.

  Both the outer shaft 10b and the inner shaft 11b as described above are formed by pressing a portion (for example, one half of the axial direction) of the metal round tube that is to be stretchably combined. The portion is processed into a cross-sectional shape as shown in FIG. When performing this press working, it has an outer peripheral surface shape that matches the inner peripheral surface shape of the shafts 10b and 11b to be processed (the shape of the contour line of the cross section is the same or smaller by considering the spring back). A core (mandrel) is inserted into a portion to be processed in the round tube. In this state, the round tube is pressed against the outer peripheral surface of the core by a pair of left and right forming dies (pressing dies). The tip surfaces of both molds are shaped to match the outer peripheral shape of the shafts 10b and 11b to be processed. Therefore, along with the pressing operation, the shapes of the outer peripheral surface of the core and the tip surfaces of the two molding dies are transferred to the round tube, and the outer shaft 10b and the inner shaft as shown in FIG. 11b is obtained.

  Therefore, in the case of this example, the thickness of the outer shaft 10b and the inner shaft 11b is substantially the same over the entire circumference. In the case of this example, the outer shaft 10b has an undercut portion that prevents the movement of the mold in the direction perpendicular to the arrangement direction of the outer side concave grooves 18a, 18a (the left-right direction in FIG. 1). do not do. That is, the dimension in the vertical direction in FIG. 1 is the largest at the widthwise central portion where the outer concave grooves 18a, 18a are formed, and gradually decreases toward both ends in the widthwise direction. There is no place where the dimension in the vertical direction increases in the middle from the widthwise center to both ends in the widthwise direction. Therefore, the outer shaft 10b can be pressed by a simple two-part mold. For this reason, it is possible to reduce the cost by simplifying the die device for press working and the cost by shortening the processing time. On the other hand, with respect to the inner shaft 11b, the inner concave grooves 19a, 19a are undercut portions, and therefore, as a molding die for pressing the round tube against the outer peripheral surface of the core, for example, a quadrant type is used. A more complicated mold apparatus is required. In any case, the outer shaft 10b and the inner shaft 11b can be processed with a large processing load using a core. For this reason, both the shafts 10b and 11b can be made of a highly rigid material such as a round tube made of high carbon steel, and it is easy to obtain a telescopic rotation transmission shaft capable of transmitting a large torque.

  Each of the outer shaft 10b and the inner shaft 11b, which are each manufactured as described above, inserts a part of the inner shaft 11b in the axial direction into a part of the outer shaft 10b in the axial direction. The balls 14 and 14 are combined between the outer grooves 18a and 18a and the inner grooves 19a and 19a. That is, the inner-side convex portions 21 and 21 provided at the four positions on the outer peripheral surface of the inner shaft 11b are arranged inside the outer-side concave portions 23 and 23 provided at the four positions on the inner peripheral surface of the outer shaft 10b. And insert it loosely (with a gap in the circumferential direction). At this time, the outer side concave grooves 18a, 18a and the inner side concave grooves 19a, 19a are rotatably held by a cage 15a (see FIG. 2, omitted in FIG. 1). The balls 14 and 14 are assembled (when the shafts 10b and 11b are combined, the balls 14 and 14 are fed together with the cage 15a while being rolled with respect to the grooves 18a and 19a). Along with this feeding, the outer shaft 10b and the inner shaft 11b are slightly elastically deformed, and the rolling surfaces (surfaces) of the balls 14 and 14 and the inner surfaces of the concave grooves 18a and 19a are elastically deformed. Contact each other (a preload is applied to each of the balls 14 and 14). In the case of the structure of this example, the portion between the outer flat portions 24, 24 and the outer concave grooves 18a, 18a in the outer shaft 10b, and the inner shafts in the inner shaft 11b. Since the portion between the side flat portions 22, 22 and the inner side concave grooves 19a, 19a is easily elastically deformed, it is easy to feed the balls 14, 14 and to apply preload to the balls 14, 14. And it can be performed with high accuracy.

  Thus, in a state where the members 10b, 11b, and 14 are combined, torque transmission and axial relative displacement can be performed between the outer shaft 10b and the inner shaft 11b. Further, in a neutral state where no rotation is transmitted between the outer shaft 10b and the inner shaft 11b, the rolling surfaces of the balls 14 and 14 are the inner surfaces of the outer and inner concave grooves 18a and 19a. Of these, they contact the bottom of each of the concave grooves 18a and 19a, which is the most concave portion in the radial direction. That is, in the case of this example, regarding the cross-sectional shape shown in FIG. 1, when a virtual straight line α connecting the centers of the balls 14, 14 is considered, the bottom portions of the grooves 18 a, 19 a in the neutral state Exists on the virtual straight line α. In other words, the cross-sectional shapes of the concave grooves 18a and 19a are symmetric with respect to the virtual straight line α. And in the said neutral state, the center of the contact ellipse which exists in the contact part of each said ditch | groove 18a, 19a and the rolling surface of each said ball | bowl 14,14 also exists on the said virtual straight line (alpha).

  Further, in the case of this example, among the pair of flat surfaces constituting the inner convex portions 21, 21, the flat surfaces facing each other (in the vertical direction in FIG. 1) are defined as inner abutting surfaces. 25 and 25. Of the pair of flat surfaces constituting the outer recesses 23, 23, the flat surfaces facing the inner abutting surfaces 25, 25 are the outer abutting surfaces 26, 26. The inner abutting surfaces 25 and 25 and the outer abutting surfaces 26 and 26 are separated from each other in the neutral state. Further, the distance between each of the inner side abutting surfaces 25, 25 and each of the outer side abutting surfaces 26, 26 is increased from the radially inner side toward the radially outer side. Specifically, the abutting surfaces 25 and 26 are positioned on a virtual plane including the central axes of the outer and inner shafts 10b and 11b in the neutral state. Accordingly, the four inner side abutting surfaces 25, 25 and the outer side abutting surfaces 26, 26 facing each other are inclined with respect to each other by the center angle (stopper angle) θ in the neutral state. In the case of the structure of this example, since such a central angle θ is set, the two shafts 10b and 11b are circumferentially connected with the transmission of torque between the shafts 10b and 11b. When the relative displacement is made with respect to the direction, two sets of the inner side abutting surfaces 25, 25 and the outer side abutting surfaces 26, 26 of the four pairs exist, and two sets of the inner side abutting surfaces 25, 25 and the outer side abutting surface. The contact surfaces 26 and 26 abut on almost the entire surface of the opposed portions. The direction of the force acting on the abutting surface is a direction perpendicular to each of the abutting surfaces 25 and 26.

  The telescopic rotation transmission shaft of the present example configured as described above is in a state where torque is not transmitted between the outer and inner shafts 10b, 11b, or when the torque to be transmitted is small, The rolling surfaces 14 and 14 are in contact with the inner surfaces of the outer and inner concave grooves 18a and 19a at the bottom of the concave grooves 18a and 19a or in the vicinity of the bottom. In this state, the inner abutting surfaces 25, 25 and the outer abutting surfaces 26, 26 are all separated from each other, and the balls 14, 14 are arranged on the outer side, It can roll in the length direction of each inner side concave groove 18a, 19a. For this reason, the outer and inner shafts 10b, 11b can be relatively displaced in the axial direction, and the telescopic rotation transmission shaft can be expanded and contracted with a light force. On the other hand, when a large torque is transmitted between the outer and inner shafts 10b and 11b, the two sets of inner side abutting surfaces 25 and 25 and the outer side abutting surfaces 26 and 26 are provided. It abuts and transmits the part of the torque that the balls 14, 14 cannot transmit.

  According to the telescopic rotation transmission shaft of the present invention constructed and operated as described above, it is inexpensive, and even when a large torque is transmitted, damage such as indentation is unlikely to occur. It is possible to realize a structure that does not lead to a decrease and can smoothly expand and contract in the axial direction. For this reason, transmitting a large torque (increasing the allowable load torque), performing smooth axial expansion / contraction without rattling, and reducing manufacturing costs can be arranged side by side.

  First of all, in order to reduce the cost, there is no need to provide an elastic member (for example, the elastic member 16 in FIGS. 15 to 16) for applying an elastic force to each of the balls 14 and 14, so that any part production, part management, and assembly work can be performed. Can be achieved by simplifying. Further, in the case of this example, transmission of a large torque is applied to each of the inner side and the outer side without using the cylindrical member (cylindrical member) 17 as in the conventional structure shown in FIGS. Since it is based on the contact between the surfaces 25 and 26, the number of parts can be reduced, and the cost can be reduced also from this surface.

  Next, in order to prevent damage such as indentation, the transmission of the torque is performed not only between the balls 14 and 14 but also between the inner abutting surfaces 25 and 25 and the outer abutting surfaces 26 and 26. It can be achieved by performing based on contact. That is, in a state where the abutting surfaces 25 and 26 are in contact with each other, torque transmission between the outer and inner shafts 10b and 11b can be performed over a wide area. As the area of the portion contributing to torque transmission is increased in this way, a large torque can be transmitted (allowable load torque can be increased), and the surface pressure of the portion transmitting torque can be kept low. Further, it is possible to prevent the contact pressure between the balls 14 and 14 and the inner surfaces of the outer side and inner side concave grooves 18a and 19a from being excessively increased, thereby making it difficult to cause damage such as indentations. . That is, in the case of this example, the preload applied to the balls 14, 14 in the neutral state, the inner abutting surfaces 25, 25 and the outer abutting surfaces 26, 26 By adjusting the interval in the circumferential direction, damage such as the indentation is prevented.

In this example, the rolling surfaces of the balls 14 and 14 are brought into contact with the inner surfaces of the outer and inner concave grooves 18a and 19a at the groove bottoms of the concave grooves 18a and 19a. Therefore, as the torque transmitted between the outer and inner shafts 10b, 11b increases, the transmission of this torque is transmitted to the inner abutting surfaces 25, 25 and the outer abutting surfaces 26. , 26 can be surely assigned to the abutting portion. That is, at the contact portions between the rolling surfaces of the balls 14 and 14 and the inner surfaces of the outer and inner concave grooves 18a and 19a, the pressure angles (contact angles) θ ₁ and θ ₂ become large. The component force applied to the direction which receives the said torque is small, and the efficiency which these each balls 14 and 14 transmit this torque is bad. In other words, a large torque is difficult to be transmitted through these balls 14 and 14. For this reason, when the torque is applied at the contact portion between the rolling surfaces of the balls 14 and 14 and the inner surfaces of the outer and inner concave grooves 18a and 19a, the outer and inner shafts 10b and 11b Relative rotation tends to be allowed. As a result of such relative rotation, the inner abutting surfaces 25, 25 and the outer abutting surfaces 26, 26 are easily brought into contact with each other. These abutment surfaces 25 and 26 can be surely shared. In addition, in the case of this example, the pressure angle θ ₃ (not shown) between the abutting surfaces 25 and 26 is made small (approximately 0 degrees), so Torque can be reliably supported at the contact part (large torque can be transmitted reliably).

It is ideal that the pressure angle θ ₃ between the abutting surfaces 25 and 26 is 0 degree as in this example. If the pressure angle θ _{3 is set} to 0 degree and the abutting surfaces 25 and 26 contact each other at a right angle, the abutting surfaces 25 and 26 are rubbed in the surface direction even when a large torque is transmitted. Therefore, the wear of each of the abutting surfaces 25 and 26 can be suppressed. However, both the shafts 10b, 11b are determined by the magnitude of the torque to be transmitted (the maximum value of the torque to be transmitted is not so large) and the wall thickness of the round tubes constituting the outer and inner shafts 10b, 11b. Depending on the rigidity, etc. (when this rigidity is large), it can be increased to about 30 degrees.

As is clear from the above description, out of the pressure angles θ ₁ , θ ₂ , θ ₃ , the pressure angles θ ₁ , θ ₂ related to the balls 14, 14 (the center of the balls 14, 14 and the outer, The angle between the virtual plane including the central axes of the inner shafts 10b and 11b and the virtual plane in contact with the contact portion between the rolling surface of each of the balls 14 and 14 and the mating surface is large. , 26 is made smaller in pressure angle θ ₃ . In particular, in the case of the structure of this example in which the characteristics related to torque transmission are symmetric with respect to the rotation direction, the pressure angles θ ₁ and θ ₂ related to the balls 14 and 14 are set to 90 degrees. Therefore, the contact position between the rolling surfaces of the balls 14 and 14 and the inner surfaces of the outer and inner concave grooves 18a and 19a is displaced from the bottom of the concave grooves 18a and 19a to the side with a small torque. Easy to do. For this reason, for example, when the cross-sectional shape of the outer side and inner side concave grooves 18a and 19a is a single circular arc, its radius of curvature is made slightly larger than the radius of the balls 14 and 14, The contact position in the neutral state is defined as the groove bottom. In contrast, the pressure angle θ ₃ between the abutting surfaces 25 and 26, that is, the abutting surfaces 25 and 26 are in contact with each other, the abutting surfaces 25 and 26 and the outer shaft. The angle formed between the central axis of 10b and the inner shaft 11b and the virtual plane including the centers of the abutting portions of the respective abutting surfaces 25 and 26 is made as small as possible as described above.

  Further, in the case of this example, the clearance angle (the stopper angle θ) between the abutting surfaces 25 and 26 in the circumferential direction is set to the outer and inner concave grooves 18a and 19a in the circumferential direction. And a clearance angle between the balls 14 and 14 (the angles at which the outer shafts 10b and 11b rotate relative to each other while the balls 14 and 14 transmit little or no torque). ing. For this reason, this torque can be transmitted at an appropriate location as the transmission torque increases.

  That is, in a state where the torque to be transmitted is small, only the balls 14, 14 are based on the engagement (engagement) between the outer side and inner side concave grooves 18 a, 19 a and the balls 14, 14. When the torque is transmitted and the torque is large, the abutting surfaces 25 and 26 are also engaged (abutted) to transmit the torque. Thus, the clearance angle of the engaging part between the rolling surfaces of the balls 14 and 14 and the outer and inner concave grooves 18a and 19a, and the inner and outer abutting surfaces 25 and 26, respectively. In this simple structure that only regulates the clearance angle (stopper angle θ) of these, the transmission of torque can be surely shared by each of the abutting surfaces 25, 26, and this surface can also be constructed at low cost ( Manufacturing costs can be reduced). Further, as described above, by restricting the clearance angles, the relative displacement in the axial direction between the outer and inner shafts 10b and 11b (expansion and contraction of the telescopic rotation transmission shaft) can be reduced. (The sliding contact between the inner and outer abutment surfaces 25, 26 can be reduced), and the relative displacement (extension / contraction operation) can be smoothly performed also from this surface.

  Further, in the case of this example, the balls 14, 14 are provided with tightening allowances for the outer and inner grooves 18a, 19a (the balls 14, 14 and the grooves 18a, Since the contact portion 19a has a negative gap and a preload is applied to each of the balls 14 and 14, the outer shaft 10b can be provided without providing the elastic member (for example, the elastic member 16 in FIGS. 15 to 16). And the inner shaft 11b can be prevented from rattling in the rotational direction. In particular, in the case of the structure of this example, the balls 14 and 14 are applied to the balls 14 and 14 without particularly increasing the shape accuracy and dimensional accuracy of the constituent members based on the shapes and structures of the shafts 10b and 11b. Preload can be regulated to an appropriate value. That is, since the outer shaft 10b has bent portions having a V-shaped cross section for forming the outer concave portions 23, 23 on both sides of the portion where the outer concave groove 18a is formed, The portion where the outer side concave groove 18a is formed is easily elastically displaced in the radial direction of the outer shaft 10b. Similarly, the portion of the inner shaft 11b where the inner groove 19a is formed is also easily elastically deformed in the radial direction of the inner shaft 11b. In short, the portions where the outer side and inner side concave grooves 18a and 19a are formed so as to sandwich the balls 14 and 14 are easily deformed, and the balls 14 and 14 are irrelevant to some dimensional errors. The amount of change in the preload applied to the can be reduced. For this reason, it is possible to effectively prevent rattling in the rotational direction based on this preload application while suppressing an increase in cost.

  If rattling as described above can be tolerated (for example, if there is no problem during running even if some rattling occurs), there is a margin for tightening within a range in which this rattling can be tolerated. (For example, the outer diameter of each of the balls 14, 14 is set to the outer and inner grooves 18a, 19a). It is also possible to make it smaller than the diameter of a virtual circle formed by the inner surface of the If the tightening allowance is not provided in this way, the contact point position between the inner surface of each of the outer and inner concave grooves 18a and 19a and the rolling surface of each of the balls 14 and 14 depends on the torque. Therefore, even when an indentation is generated, the relative displacement in the axial direction of the outer shaft 10b and the inner shaft 11b (extension and contraction of the telescopic rotation transmission shaft) is smoothly performed regardless of the presence of the indentation. Can be done.

FIG. 3 shows the change in the contact point position between the rolling surface of each ball 14 and the inner surface of each of the outer side and inner side concave grooves 18a and 19a in the case of a structure in which each ball 14 has a tightening allowance. Is shown. 3A and 3B, each of the outer side and inner side concave grooves 18a and 19a has a single circular arc. 3A shows a state when no load is applied (state where no torque is applied), and FIG. 3B shows a state where torque is applied. Further, the points α shown in FIGS. 3A and 3B are the inner surfaces (inner surfaces) of the outer side and inner side concave grooves 18a and 19a in an unloaded and neutral state. The contact point position with the rolling surface of each said ball | bowl 14 is shown. When torque is applied between the shafts 10b and 11b from the neutral state shown in FIG. 3A, as shown in FIG. 3B, each ball 14 and each outer side Based on the elastic deformation of the inner side concave grooves 18a, 19a, the contact point position changes from the point α to the point β, the radius of curvature R of the inner surface of each of the outer side and inner side concave grooves 18a, 19a and the ball 14 It is displaced in proportion to the distance {δ ₁ , δ _{2 in} FIG. 3B} according to the radius (= D / 2).

  Regardless of whether or not a preload is applied to each ball 14, by applying a large torque, the inner surfaces of the outer and inner concave grooves 18a and 19a and the rolling surfaces of the balls 14 are temporarily assumed. Even if an indentation is generated at the contact portion, the position of the contact point is displaced as described above, and thus the indentation is generated at the position of the point β. Since the position β where the indentation is generated is shifted from the contact point position α when there is no load, the relative displacement in the axial direction between the outer shaft 10b and the inner shaft 11b that is performed when there is no load (extension and contraction of the telescopic rotation transmission shaft). ) Can be performed smoothly regardless of the presence of the indentation. Regardless of whether or not a preload is applied to each ball 14, in the actual case, as described above, when a large torque is applied, each of the inner side and outer side abutting surfaces 25 is provided. , Because the abutting portions between 26 transmit a large part of this torque, the indentation is unlikely to occur. In addition, the contact area of the contact part of each of these contact surfaces 25 and 26 is large, and the surface pressure which acts on these each contact part is restrained low. For this reason, even if the shafts 10b and 11b are made by plastically deforming a low carbon steel round tube, it is sufficient that the shafts 10b and 11b are damaged by deformation or wear due to large torque transmission. Can be suppressed.

  In contrast to the structure of this example as described above, FIG. 4 shows a structure in which the outer side and inner side concave grooves 18b and 19b have a Gothic arch cross-sectional shape. In the case of such a Gothic arch-shaped structure, as shown in FIG. 4A, the contact point position α is the center portion of each of the outer side and inner side concave grooves 18b and 19b (even when no load is applied). Deviation from the portion with the largest groove depth). In such a structure, the torsional rigidity can be increased, but the displacement amount (displacement amount) of the contact point position is difficult to increase (the displacement amount is small) when a large torque is applied. It's not a structure. However, as will be described later, if the cross-sectional shape of one of the grooves is a Gothic arch, and the cross-sectional shape of the other groove is a non-Gothic arch, The displacement amount of the contact point position can be secured. Furthermore, by providing a thin portion on a part of the outer shaft 10b and the inner shaft 11b, the outer shaft 10b and the inner shaft 11b are provided with elastic portions of the outer side and inner side grooves 18b and 19b. If it is easy to deform, even if the cross-sectional shape of each of the concave grooves 18b and 19b is a Gothic arch shape, the contact point position can be easily shifted from α to β. Further, by making the elastic deformation easy, the torque can be transmitted between the abutting surfaces 25 and 26 from a state where a small torque is applied. .

  In any case, in the case of this example, the rolling surface of each of the balls 14 and 14 in the neutral state is the groove bottom portion of the inner surfaces of the outer side and inner side concave grooves 18a and 19a (18b and 19b). Therefore, when torque is applied to the contact portion, relative rotation between the inner shaft 11b and the outer shaft 10b tends to be permitted. For this reason, if excessive torque is applied, a part of the inner surface of each of the outer and inner concave grooves 18a and 19a (18b and 19b) is contacted with the rolling surface of each of the balls 14 and 14. Even if the impression based on the contact is generated, the position where the impression is generated is a position deviated from the contact position with the rolling surface of the balls 14 and 14 in the no-load state where the torque is not applied. For this reason, even if indentation occurs, the axial relative displacement between the outer shaft 10b and the inner shaft 11b (expansion / contraction of the telescopic rotation transmission shaft), which is performed in an unloaded state where the torque is not applied, is smoothly performed. Yes.

Further, in the case of this example, the outer side and inner side concave grooves 18a and 19a (18b and 19b) are arranged at a plurality of positions at equal intervals in the circumferential direction of the inner shaft 11b and the outer shaft 10b (positions at two positions of 180 degrees). Therefore, the outer and inner concave grooves 18a and 19a are easily elastically deformed uniformly, and the concave grooves 18a and 19a can be less likely to be damaged such as indentations.
In the case of this example, as shown in FIG. 2, the balls 14, 14 are held by a cage 15 a to position the balls 14, 14. Shaking in the axial direction of each of the outer side and inner side concave grooves 18a, 19a (18b, 19b) is prevented. Therefore, the inner shaft 11b that constitutes the telescopic rotation transmission shaft while properly maintaining the distance between the balls 14 and 14 (the axial length of the portion where the balls 14 and 14 are installed). And securing the bending rigidity of the fitting portion between the outer shaft 10b and the outer shaft 10b. Further, by providing the cage 15a, the balls 14 and 14 can be easily assembled between the outer side and inner side concave grooves 18a and 19a (18b and 19b).

  In the illustrated example, the rolling surfaces of the balls 14 and 14 are brought into contact with the groove bottoms of the outer side concave grooves 18a and 18a and the groove bottoms of the inner side concave grooves 19a and 19a. (It is in contact with the groove bottoms of both concave grooves 18a, 19a). On the other hand, it is made to contact only the groove bottom part of any one of the outer side concave grooves 18a, 18a and the inner side concave grooves 19a, 19a. You can also. That is, the cross-sectional shape of any one of the outer-side concave grooves 18a, 18a and the inner-side concave grooves 19a, 19a is a single arc, and the other cross-sectional shape is a Gothic arch shape. Of these, the rolling surface of each of the balls 14 and 14 can be brought into contact with the bottom of the groove only in one concave groove whose cross-sectional shape is a single arc.

[Second Example of Embodiment]
FIG. 5 shows a second example of an embodiment of the present invention corresponding to claims 1 to 6. In the case of this example, the inner shaft 11c is a solid metal body. That is, in the case of this example, the inner shaft 11c is made by subjecting a raw material such as a metal bar to plastic working such as forging or by subjecting it to a cutting process. In the case of this example, inner side concave grooves 19b, 19b, inner side convex portions 21a, 21a, and an inner side flat portion 22a are formed on the outer peripheral surface of the inner shaft 11c which is a solid body. Yes. For this reason, in the case of this example, the rigidity can be improved instead of increasing the material cost, processing cost, and weight of the inner shaft 11c as compared with the case of the first example of the embodiment described above. In the illustrated example, the distance between the inner-side butting surfaces 25 and 25 and the outer-side butting surfaces 26 and 26 in the neutral state is constant, but as in the first example of the embodiment described above. The distance can be increased from the radially inner side toward the radially outer side. Since the structure and operation of the other parts are the same as in the case of the first example of the embodiment described above, overlapping illustrations and descriptions are omitted.

[Third example of embodiment]
FIG. 6 also shows a third example of the embodiment of the present invention corresponding to claims 1 to 6. In the case of this example, the shape of the portion between the pair of outer side concave grooves 18b, 18b in the outer shaft 10c, and the pair of inner side concave grooves 19b, 19b in the inner shaft 11d. The shape of the intermediate portion is different from that of the second example of the embodiment described above. That is, in this example, the inner side flat portions 22a (see FIG. 5) between the inner side convex portions 21a and 21a are omitted, and the inner side convex portions 21a and 21a adjacent to each other in the circumferential direction are omitted. Directly continuous. Since the structure and operation of other parts are the same as in the case of the second example of the above-described embodiment, overlapping illustrations and descriptions are omitted.

[Fourth Example of Embodiment]
FIG. 7 shows a fourth example of the embodiment of the invention corresponding to claims 1 to 5 and 7. In the case of this example, of the outer peripheral surface of the inner shaft 11d, the flat surfaces 27 and 27 are formed on the tops of the portions corresponding to the protruding portions described in claim 7 in the claims, The thickness of each of these tops is made smaller (thinner) than the other parts. That is, the flat surfaces 27 and 27 are formed at the tops of the bulged portions of the outer side concave grooves 18b and 18b and the outer side concave portions 23 and 23, each of which corresponds to the protruding portion. is doing. These flat surfaces 27 and 27 may be machined or may be plastic working by pressing.

  In any case, the thickness of each of the tops is reduced by the amount corresponding to the formation of the flat surfaces 27 and 27 so that the tops are easily elastically deformed. For this reason, in the case of this example, it is possible to easily elastically deform the portions where the outer side concave grooves 18b, 18b are formed. As the torque transmitted between the outer shaft 10d and the inner shaft 11d increases, the abutting surfaces 25 and 26 of the inner side and the outer side are easily brought into contact with each other, and the outer side concave grooves 18b, 18b and each inner side recessed groove 19b, 19b can be made hard to form an indentation. Since the structure and operation of other parts are the same as in the case of the second example of the embodiment described above, overlapping illustrations and descriptions are omitted.

[Fifth Example of Embodiment]
FIG. 8 also shows a fifth example of the embodiment of the invention corresponding to claims 1 to 5 and 7. In the case of this example, as in the case of the third example of the embodiment shown in FIG. 6 described above, the shape of the portion between the pair of outer side concave grooves 18b, 18b in the outer shaft 10e, In addition, the shape of the portion between the pair of inner side concave grooves 19b, 19b in the inner shaft 11e is different from that of the fourth example of the above-described embodiment. Since the structure and operation of other parts are the same as in the case of the fourth example, overlapping illustrations and descriptions are omitted.

[Sixth Example of Embodiment]
FIG. 9 shows a sixth example of an embodiment of the present invention corresponding to claims 1 and 8. In the case of this example, a convex part cylindrical surface 28 having the center axis of the inner shaft 11f as the center of curvature is formed at the bottom of each inner side concave groove 19c. On the other hand, each outer side ditch | groove 18b is making the cross-sectional shape into single arc shape similarly to each embodiment described previously. According to such a structure of this example, a dead zone in which torque transmission is hardly performed between the inner shaft 11f and the outer shaft 10b can be set in a predetermined angle range centered on the neutral position. In other words, as long as the rolling surface of each ball 14 installed between each inner groove 19c and each outer groove 18b is in rolling contact with the convex cylindrical surface 28, the inner shaft. Torque transmission between 11f and the outer shaft 10b is not substantially performed as shown in the central portion of the solid line A in FIG.

  In FIG. 10, the horizontal axis indicates the relative displacement (angle) between the inner shaft 11f and the outer shaft 10b, and the vertical axis indicates the magnitude of torque transmitted between the shafts 11f and 10b. Show. Further, in the solid line A in FIG. 10, the central horizontal portion (region a portion) indicates a portion where the rolling surface of each ball 14 rolls into contact with the convex cylindrical surface 28 and torque transmission is not performed. ing. Further, the portions present on both sides of the horizontal portion and having a relatively gentle inclination angle are portions where the rolling surfaces of the balls 14 are out of the convex cylindrical surface 28 in the inner concave grooves 19c. The outer side abutting grooves 18b are in contact with each other, but the inner side and outer side abutting surfaces 25 and 26 (see, for example, FIG. 1) are separated from each other, and a portion where torque is transmitted is shown. ing. Furthermore, the part where the inclination angle of both ends is steep indicates a part where torque transmission is performed in a state where the abutting surfaces 25 and 26 of the inner side and the outer side are in contact with each other. Further, δ in FIG. 10 is a hysteresis based on the preload applied to each ball 14. A broken line B in FIG. 10 indicates the relationship between the relative displacement and the transmission torque in the structure having no convex cylindrical surface 28 as shown in FIG.

As is clear from FIG. 10 as described above, according to the structure of this example, the dead zone can be set around the neutral position that coincides with the vertical axis. For this reason, when used as a steering shaft or an intermediate shaft, kickback from the wheel can be hardly transmitted to the steering wheel. However, a certain amount of torque is transmitted based on the presence of the hysteresis δ, and the hysteresis δ can be adjusted by changing the preload applied to the balls 14. Therefore, based on the adjustment of the preload, the transmission characteristic at the neutral position can be tuned, and for example, the straight running stability can be improved by operating the steering wheel. On the other hand, according to the characteristics of the respective embodiments described above shown by the broken line b in FIG. 10, a somewhat large torsional rigidity can be obtained even in the vicinity of the neutral position. When used, it is possible to improve the response related to giving the steering angle to the steered wheel based on the operation of the steering wheel.
In order to provide the dead zone, in place of the convex portion cylindrical surface 28 or together with the convex portion cylindrical surface 28, a concave portion cylinder having the center axis of the outer shaft as the center of curvature is provided at the bottom of each outer side concave groove. A surface can also be provided.
Since the structure and operation of other parts are the same as those of the above-described embodiments, overlapping illustrations and descriptions are omitted.

[Seventh example of embodiment]
FIG. 11 shows a seventh example of the embodiment of the invention corresponding to claims 1 and 9. In the case of this example, the curvature radii R ₁ and R ₂ of the cross-sectional shape of each outer-side groove 18c are made different at the width direction center and both ends of each outer-side groove 18c. Yes. That is, the radius of curvature R ₁ in the range of ± θa with respect to the center in the width direction of each outer side concave groove 18c, that is, the center line, is larger than the radius of curvature R _{2 in} the range of θb at both ends (R ₁ > and R ₂₎ and. However, the radius of curvature R _{2 at} both ends is also set to 1/2 or more of the outer diameter of each ball 14 (R ₂ ≧ D / 2).

According to such a structure of this example, the characteristics relating to torque transmission of the telescopic rotation transmission shaft formed by combining the outer shaft 10f and the inner shaft (not shown) can be changed in multiple stages as shown in FIG. . That is, in the neutral position near the rolling surface of the balls 14, in the state where the radius of curvature of the cross-sectional shape at the center of each outer side groove 18c is in contact with the portion of R _1, said telescopic rotation The torsional rigidity of the transmission shaft is relatively low. On the other hand, the rolling surface of each ball 14 is in contact with a portion having a radius of curvature R ₂ at both ends in the width direction of each outer groove 18c. When the abutting surfaces 25 and 26 (see, for example, FIG. 1) are separated from each other, the torsional rigidity of the telescopic rotation transmission shaft is slightly increased. In this state, a contact ellipse existing at the contact portion between the rolling surface of each ball 14 and each outer groove 18c becomes large, and an indentation hardly occurs in each outer groove 18c. Furthermore, when the inner and outer abutment surfaces 25 and 26 are in contact with each other, as shown by the steep portions of the inclination angles at both ends in FIG. 12, the torsional rigidity of the telescopic rotation transmission shaft is shown. Becomes higher.
In order to change the characteristics in multiple stages as described above, the cross-sectional shape of each inner-side groove is changed to the center portion and both end portions instead of the outer-side groove 18c or together with the outer-side groove 18c. You can also change it.
Since the structure and operation of other parts are the same as those of the first to fifth examples of the respective embodiments described above, overlapping illustrations and descriptions are omitted.

[Eighth Example of Embodiment]
FIG. 13 shows an eighth example of the embodiment of the present invention corresponding to the first, second, fifth, and sixth aspects. In the case of this example, the outer shaft 10g is formed in a square pipe shape except for the portions where the outer side concave grooves 18b and 18b are formed, and the inner shaft 11g is excluded except for the portions where the inner side concave grooves 19b and 19b are formed. It has a prismatic shape. In the case of such a structure of this example, since the shapes of the shafts 10g and 11g are simple, it is easy to process and cost reduction is facilitated. However, in the outer shaft 10g, the portions where the outer concave grooves 18b and 18b are formed are not easily elastically deformed, so that it is difficult to adjust the preload applied to the balls 14 and 14. Further, it becomes difficult to match the timing at which the rigidity of the telescopic rotation transmission shaft changes depending on the rotation direction.
Since the structure and operation of other parts are the same as those of the above-described embodiments, overlapping illustrations and descriptions are omitted.

  The telescopic rotation transmission shaft of the present invention can be applied to the intermediate shaft 5 among the structural members of the automotive steering apparatus including the electric power steering apparatus shown in FIG. . However, the present invention is not limited to the intermediate shaft 5 and can be implemented as the steering shaft 3 disposed inside the steering column 9. Furthermore, the present invention is not limited to the shaft constituting the automobile steering device, but can be implemented as a rotation transmission shaft constituting various rotary machine devices such as machine tools and playground equipment.

Sectional drawing regarding the virtual plane orthogonal to the central axis which shows the 1st example of embodiment of this invention. XX sectional drawing of FIG. FIGS. 2A and 2B are views corresponding to a Y portion in FIG. 1 in which the cross-sectional shape of the groove is a single circular arc, in which FIG. 1A shows a state where no rotational force (torque) is applied (no load), and FIG. The state where (torque) is applied is shown. FIG. 2 is a view corresponding to a Y portion in FIG. 1 in which the cross-sectional shape of the groove is a Gothic arch, where (A) shows a state where no rotational force (torque) is applied (no load), and (B) shows a rotational force ( The state where torque is applied is shown. Sectional drawing similar to FIG. 1 which shows the 2nd example of embodiment of this invention. Sectional drawing similar to FIG. 1 showing the third example. Sectional drawing similar to FIG. 1 showing the fourth example. Sectional drawing similar to FIG. 1 showing the fifth example. The partial expanded sectional view equivalent to the Y section of Drawing 1 showing the 6th example. The diagram which shows the relationship between the relative displacement amount of both inner and outer shafts, and the magnitude | size of the torque transmitted between these both shafts for demonstrating the characteristic of this 6th example. The fragmentary expanded sectional view equivalent to the Y section of FIG. 1 which shows the 7th example of embodiment of this invention. The diagram similar to FIG. 10 for demonstrating the characteristic of this 7th example. Sectional drawing similar to FIG. 1 which shows the 8th example of embodiment of this invention. The partial vertical side view which shows an example of the steering device for motor vehicles. Sectional drawing which shows an example of the expansion-contraction type rotational transmission shaft known conventionally. The exploded perspective view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering gear unit 3, 3a Steering shaft 4a, 4b Universal joint 5 Intermediate shaft 6 Input shaft 7 Tie rod 8 Electric motor 9 Steering column 10, 10a, 10b, 10c, 10d, 10e, 10f, 10g Outer shaft 11, 11a, 11b, 11c, 11d, 11e, 11f, 11g Inner shaft 12 Outer column 13 Inner column 14 Ball 15, 15a Cage 16 Elastic member 17 Cylindrical member 18, 18a, 18b, 18c Outer side concave groove 19, 19a, 19b , 19c, 19d Inner side concave groove 20 Telescopic rotation transmission shaft 21, 21a Inner side convex portion 22, 22a Inner side flat portion 23 Outer side concave portion 24 Outer side flat portion 25 Inner side abutting surface 26 Outer side abutting surface 27 flat Surface 28 convex partial cylindrical surface

Claims (10)

  An inner shaft having an inner groove formed in an axial direction at a plurality of locations in the circumferential direction of the outer circumferential surface and having an arc-shaped or substantially arc-shaped cross section and recessed radially inward, and a circle on the inner circumferential surface The outer side groove is provided in the axial direction at a position where it is aligned with each of the inner grooves at a plurality of positions in the circumferential direction, and the outer side groove is provided with an arc shape or a substantially arc shape and is recessed radially outward. An outer shaft into which an inner shaft can be inserted, and a plurality of balls respectively provided between each inner groove and each outer groove, and the outer shaft and the inner shaft are connected to each other. In a telescopic rotation transmission shaft that combines torque transmission and axial relative displacement possible, in the neutral state where rotation transmission is not performed between the outer shaft and the inner shaft, The rolling surface of the ball is Of the inner grooves of at least one of the outer-side grooves, the inner surface is in contact with the bottom or the vicinity of the bottom, which is the most recessed portion in the radial direction. Inner side abutting surfaces are provided at a plurality of locations that deviate in the circumferential direction from the concave groove, and outer side abutting surfaces are provided on the inner circumferential surface of the outer shaft at portions facing the inner side abutting surface, respectively. Rotational transmission is performed between the outer shaft and the inner shaft, and the balls are in contact with the inner groove and the outer circumferential groove from the bottom of the outer groove. A telescopic rotation transmission shaft, wherein each inner side abutting surface and each outer side abutting surface are brought into contact with each other.   In the neutral state, the torque transmitted between the inner shaft and the outer shaft is small, and each inner side abutting surface and each outer side abutting surface do not come into contact with each other. Each ball is in contact with the bottom of each outer side groove or the vicinity of the bottom of each groove, and the balls are in rolling contact with the bottom of each groove or near the bottom of each groove. In the state where the relative displacement in the axial direction of both shafts is allowed, the torque transmitted between the two shafts is large, and each inner side abutting surface and each outer side abutting surface are in contact with each other, Each inner side abutting surface and each outer side abutting surface in the neutral state so that no indentation is formed in a portion of the inner surface of the concave groove where the rolling surface of each ball abuts. The interval is set as described in claim 1 Reduced rotation transmitting shaft.   By forming the portion between the outer side concave grooves adjacent to each other in the circumferential direction in the outer shaft into a shape bent in a radially inward concave direction, each outer side concave groove in the outer shaft is formed. The formed portion is easily elastically deformed in the radial direction, and the contact pressure between the inner groove of each outer side groove and each inner side groove and the rolling surface of each ball, and each inner side abutment The magnitude | size of the torque transmitted between the said outer shaft and inner shaft in the state which the surface and each outer side abutting surface contact | abutted was described in any one of Claims 1-2. Telescopic rotation transmission shaft.   Each inner side abutting surface and each outer side abutting surface are flat surfaces existing on a virtual plane including the center axis of the inner shaft and the outer shaft, and each of these inner side abutting surfaces and each outer side abutting surface And increasing the distance from the inside in the radial direction toward the outside in the radial direction, when transmitting the rotation between the two shafts, the inner abutment surfaces and the outer abutment surfaces, The telescopic rotation transmission shaft according to any one of claims 1 to 3, which is brought into contact with each abutment surface in a direction perpendicular to each other.   Each outer side groove is provided at two positions on the outer shaft on the opposite side in the circumferential direction, and each inner side groove is provided at two positions on the inner shaft on the opposite side in the circumferential direction. It is made by plastically deforming a metal tube. With respect to the cross-sectional shape perpendicular to the central axis of the outer shaft, the mold is moved in the direction perpendicular to the arrangement direction of the outer side grooves. The telescopic rotation transmission shaft according to any one of claims 1 to 4, wherein there is no undercut portion to be obstructed.   The telescopic rotation transmission shaft according to any one of claims 1 to 5, wherein the thickness of the outer shaft is substantially the same over the entire circumference.   The outer shaft is provided with a plurality of protrusions in which the outer peripheral surface side is a partially convex cylindrical surface at a plurality of locations in the circumferential direction including the portion where each outer groove is formed. The telescopic rotation transmission shaft according to any one of claims 1 to 5, which is thinner than the portion.   A convex cylindrical surface with the center axis of the inner shaft existing at the bottom of each inner groove and a concave portion with the center axis of the outer shaft existing at the bottom of each outer groove. The telescopic rotation transmission shaft according to any one of claims 1 to 7, wherein at least one partial cylindrical surface of the cylindrical surface is provided.   The radius of curvature of the cross-sectional shape of at least one of the inner-side concave grooves and the outer-side concave grooves is large at the center in the width direction of the concave groove and small at both ends. The telescopic rotation transmission shaft according to any one of 7.   The inner shaft and the outer shaft are both made by plastically deforming a metal tube, and both the shafts can be elastically deformed in the radial direction. The telescopic rotation transmission shaft described in the item.

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