JP2006112623A - Telescopic shaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a telescopic shaft which is hard to produce a play and excellent in durability even if it is used for a long period. <P>SOLUTION: A ball 15 is located between orbital grooves 16 and 17 of an outer spindle 13 and an inner spindle 14. In normal torque, torque is transmitted through a ball 15 between the inner spindle 14 and the outer spindle 13. At the time of a high torque load, either one of flat parts 21 and 22 of the inner shaft 14 forming a width across flat makes contact with corresponding specification part 31 or 32 of the outer spin 13 to regulate relative rotation amounts of the inner spindle 14 and the outer spindle 13. If it is width across flat, even if size accuracy of the inner spindle 14 and the outer spindle 13 is somewhat scattering, relative rotation amounts of the inner spindle 14 and the outer spindle 13 do not become large. A bent part 33 serving as a deformation promoting part is situated between the specification parts 31 and 32 adjacent to a plane C1 containing a curvature center C1 of each arbitral trench 16 and a central axis A1 of the outer spindle 13. A stress loaded on the outer spindle 13 and a ball 15 is lightened by making the outer spindle 13 easy to bend. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a telescopic shaft formed by connecting an inner shaft and an outer shaft via a rolling element so as to be relatively movable in the axial direction and capable of transmitting torque.

In an automobile steering apparatus, the intermediate shaft is provided between the steering shaft and the steering gear, and transmits a rotational operation force applied to the steering wheel to the steering gear side.
Generally, the intermediate shaft employs a ball spline structure in which a plurality of balls arranged in a row in the axial direction of the intermediate shaft are interposed between corresponding raceway grooves formed on the inner shaft and the cylindrical outer shaft. Yes.

In addition, there has been proposed a telescopic shaft that applies a preload to a rolling element using an elastic restoring force of a cylindrical outer shaft (see, for example, Patent Document 1).
In addition, a telescopic shaft has been proposed in which both the outer shaft and the inner shaft are hollow shafts, and a preload is applied to the rolling elements using the elastic restoring force of the outer shaft and the inner shaft (see, for example, Patent Document 2).
In Patent Document 1, when a high torque is applied, the chevron protrusion formed on the outer peripheral surface of the inner shaft engages with the semicircular recess formed on the inner peripheral surface of the outer shaft. The amount of relative rotation with the outer shaft is regulated.

  However, in the above-described method in which the chevron projection and the semicircular recess are engaged, the relative rotation amount between the inner shaft and the outer shaft may increase due to variations in the dimensional tolerances of each component. In that case, the elasticity of the outer shaft is mainly reduced by long-term use, and as a result, there is a possibility that preload cannot be applied to the rolling elements. When the preload is not applied, play occurs in the rotational direction between the inner shaft and the outer shaft, which causes noise.

On the other hand, when the rolling element interposed between the inner shaft and the outer shaft is urged by an elastic body such as a leaf spring interposed between the inner shaft and the outer shaft, a small torque is transmitted. A telescopic shaft that transmits torque while preventing rattling is proposed (see, for example, Patent Documents 3 and 4).
In addition, a rolling element is interposed between the inner shaft and the outer shaft that are divided into a plurality of divided bodies arranged in the circumferential direction, and the expansion force of the annular leaf spring disposed in the inner shaft is used to An elastic shaft has been proposed that elastically connects an inner shaft and an outer shaft when a small torque is transmitted by elastically urging the shaft in the diameter-expanding direction (see, for example, Patent Document 5).

However, in Patent Documents 3, 4 and 5, the elasticity of an elastic body such as a leaf spring is lowered due to long-term use, so that no preload is applied to the rolling element. There is a risk of generating noise in the direction of rotation.
German Patent Application Publication No. DE37030393A1 German utility model DE20318654U1 specification JP 2003-291824 A JP 2003-291827 A JP 2003-247560 A

  An object of the present invention is to provide a telescopic shaft that is less likely to cause play even when used for a long time and has excellent durability.

  In order to solve the above problems, the present invention provides an elastic structure between an inner shaft and a cylindrical outer shaft that are fitted to each other, a track groove that extends in the longitudinal direction of the inner shaft and the outer shaft, and a track groove that faces each other. Rolling elements arranged in rows in the direction in which the raceway grooves extend, and provided on the outer peripheral surface of the inner shaft at least a pair of opposed flat portions forming a two-sided width therebetween, and the outer shaft The inner peripheral surface is provided with a restricting portion for engaging the corresponding flat portion of the inner shaft to restrict the relative rotation amount of the inner shaft and the outer shaft, the center of curvature of the raceway groove of the outer shaft and the outer shaft. A deformation promoting portion for promoting deformation of the predetermined region is formed in a predetermined region in the circumferential direction of the outer shaft between the flat surface including the central axis and the restricting portion. It is.

  In the present invention, in the normal torque, the torque is transmitted between the inner shaft and the outer shaft via the rolling elements, while the pair of flat portions of the inner shaft forming the two-surface width is formed at the outer shaft at the time of high torque load. Since the relative rotation amount of the inner shaft and the outer shaft is restricted by abutting against the corresponding restricting portions, the rolling elements and the raceway grooves can be prevented from being damaged in advance. If the width is two-sided, even if the dimensional accuracy of the inner shaft and the outer shaft varies somewhat, the relative rotation amount between the inner shaft and the outer shaft is rarely increased. In addition, since a deformation promoting portion is provided in a predetermined region of the outer shaft between the plane including the center of curvature of the raceway groove of the outer shaft and the central axis of the outer shaft and the restricting portion, the outer shaft can be easily bent. The stress applied to the outer shaft and the rolling element can be relieved, and as a result, the preload on the rolling element can be maintained over a long period of time, and a telescopic shaft excellent in durability can be realized.

In the present invention, the deformation promoting part may include at least one of a bent part and a thin part. If it is a bent part or a thin part, a deformation | transformation of an outer shaft can be accelerated | stimulated reliably with a simple structure.
In the present invention, the rolling element may include a ball having a diameter of 10 to 40% of the outer diameter of the outer shaft. For example, when the outer diameter of the outer shaft is 30 mm, if the ball diameter is less than 3 mm, indentation may occur in the ball or the raceway groove, and if the ball diameter exceeds 12 mm, the outer shaft It becomes large and the telescopic shaft becomes larger. If the inner shaft is downsized without changing the outer diameter of the outer shaft so as not to increase the size of the telescopic shaft, the inner shaft becomes insufficient in strength and the contact diameter of the inner ring raceway is reduced, resulting in indentations. Become. Therefore, by setting the ball diameter in the above range, it is possible to reduce the size of the telescopic shaft while preventing the occurrence of indentations such as raceway grooves.

  In the present invention, the thickness of the outer shaft may be 5 to 15% of the outer diameter of the outer shaft. When the thickness of the outer shaft is less than 5% of the outer diameter of the outer shaft, the strength of the outer shaft decreases. Further, when the thickness of the outer shaft exceeds 15% of the outer diameter of the outer shaft, it is necessary to increase the diameter of the outer shaft or to decrease the diameter of the inner shaft. In the former case, the telescopic shaft increases in size. . In the latter case, the inner shaft becomes insufficient in strength, and the contact diameter of the inner ring raceway is reduced. Therefore, by setting the thickness of the outer shaft in the above range, it is possible to reduce the size of the telescopic shaft while preventing the occurrence of indentations such as raceway grooves.

  In the present invention, the contact angle of the ball may be 5 to 40 degrees. When the contact angle of the ball is less than 5 degrees, the play related to the ball becomes large. On the other hand, when the contact angle exceeds 40 degrees, the pair of flat portions of the inner shaft hardly come into contact with the corresponding restricting portions of the outer shaft. Therefore, by setting the contact angle of the ball to 5 to 40 degrees, it is possible to set the relative rotation amount of the inner shaft and the outer shaft to a required size at the time of high torque load while reducing backlash.

  In the present invention, the outer shaft may be formed by a square tube, and a raceway groove for a ball may be formed at each of a pair of opposite corners of the square. In this case, an outer shaft with a raceway groove can be manufactured easily and inexpensively using a square tube as a raw material, and each side of the square tube is formed on a pair of flat portions forming the width of the inner shaft. As a corresponding regulation part, it can be used as it is, and the manufacturing cost can be reduced from this point.

  Further, according to the present invention, the outer shaft includes a pair of facing portions opposed to each other in the radial direction of the outer shaft, and each cross section of the pair of facing portions has an arc shape centering on the central axis of the outer shaft. The outer shaft includes a pair of remaining portions disposed between the pair of opposed portions with respect to the circumferential direction of the outer shaft, and the raceway groove of the outer shaft has an inner peripheral surface of one remaining portion. And the outer groove restricting portion includes a pair of restricting portions formed on the inner peripheral surface of the one remaining portion. And a pair of restricting portions formed on the inner peripheral surface of the other remaining portion.

  In the present invention, since the circumferential region of the outer shaft can be secured as the arcuate facing portion, a large amount of twist in the rotational direction of the outer shaft can be secured. The central angle of the outer shaft corresponding to the arcuate facing portion is preferably in the range of 70 degrees to 110 degrees. By setting the central angle to 70 degrees or more, a sufficient twisting amount of the outer shaft can be ensured. Moreover, by setting it as 110 degrees or less, the space which arrange | positions a track groove and a control part in the remainder part except an opposing part is securable.

Preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic view of a steering device in which a telescopic shaft according to an embodiment of the present invention is applied to an intermediate shaft, and FIGS. 2 and 3 are cross-sectional views of the telescopic shaft.
Referring to FIG. 1, a steering device 1 includes a steering shaft 3 having a steering member 2 such as a steering wheel fixed at one end, and a telescopic shaft connected to the steering shaft 3 via a universal joint 4 so as to be integrally rotatable. As an intermediate shaft 5. Further, the steering device 1 includes a pinion shaft 7 connected to the intermediate shaft 5 via a universal joint 6 so as to be integrally rotatable, and a rack 8a that meshes with a pinion 7a provided on the pinion shaft 7. And a rack shaft 8 extending in the left-right direction.

Tie rods 9 are coupled to the pair of ends of the rack shaft 8, respectively. Each tie rod 9 is connected to a corresponding steered wheel 11 via a corresponding knuckle arm 10.
The rack shaft 8 is supported by the housing 12 via an unillustrated bearing so as to be movable in the axial direction. A steering mechanism 100 is configured including the pinion shaft 7, the rack shaft 8, the tie rod 9, the knuckle arm 10, and the steering wheel 11.

When the steering member 2 is operated and the steering shaft 3 is rotated, this rotation is converted into a linear motion of the rack shaft 8 along the left-right direction of the vehicle by the pinion 7a and the rack 8a. Thereby, steering of the steered wheel 11 is achieved.
The intermediate shaft 5 as a telescopic shaft includes a cylindrical outer shaft 13 and an inner shaft 14 fitted to the outer shaft 13. The outer shaft 13 and the inner shaft 14 are connected so as to be able to move relative to each other in the axial direction X and transmit torque via balls 15 as a plurality of rows of rolling elements.

  2 and 3, track grooves 16 and 17 extending in the axial direction are formed on the inner peripheral surface 131 of the outer shaft 13 and the outer peripheral surface 141 of the inner shaft 14, respectively. The track grooves 16 of the outer shaft 13 and the track grooves 17 of the inner shaft 14 are arranged in the same number (one pair in the present embodiment) at equal intervals in the circumferential direction and face each other. A track path 18 is defined between the track grooves 16 and 17 of the outer shaft 13 and the inner shaft 14 facing each other. In each track 18, the balls 15 described above are interposed in one row in the axial direction X (direction in which the track grooves 16 and 17 extend). The cross section of each raceway groove 16, 17 forms an arc having a radius slightly larger than the radius of the ball 15. As shown in FIG. 2, the contact angle B1 of the ball 15 is set in the range of 5 to 40 degrees.

The balls 15 in each row are collectively held in the corresponding track 18 by a common holder 19. As shown in FIG. 3, the retainer 19 is made of, for example, a synthetic resin, and includes a long plate member that extends along the axial direction X with an arcuate cross section. The holder 19 forms a holding hole 20 for the ball 15 that is arranged at predetermined intervals along the longitudinal direction.
Referring to FIG. 2 again, the inner shaft 13 is formed by a hollow shaft, that is, a tube. On the outer peripheral surface 141 of the inner shaft 14, two opposing pairs of flat portions 21 and 22 that form a two-surface width are formed between each other, and on the inner peripheral surface 131 of the outer shaft 13, Restricting portions 31 and 32 for restricting the relative rotation amount of the outer shaft 13 and the inner shaft 14 by engaging with the corresponding flat portions 21 and 22 are formed.

  On the outer peripheral surface 141 of the inner shaft 14, a pair of projecting portions 25 and 26 having a rectangular cross-section projecting radially outward in opposition to each other are formed. The direction in which the pair of balls 15 face each other and the direction in which the pair of protrusions 25 and 26 face each other are orthogonal to each other. One projecting portion 25 includes a pair of opposed flat portions 21 and 21 on its outer surface, and the other projecting portion 26 includes a pair of opposed flat portions 22 and 22 on its outer surface.

The outer shaft 13 is similar to the inner shaft 14. The outer shaft 13 forms a pair of projecting portions 27 and 28 projecting radially outward at positions corresponding to the projecting portions 25 and 26 of the inner shaft 14, respectively. As a result, the outer shaft 13 defines recesses 29 and 30 for accommodating the corresponding protrusions 25 and 26 of the inner shaft inside the protrusions 27 and 28, respectively.
On the inner surface of the concave portion 29, restricting portions 31, 31 composed of a pair of flat portions parallel to each other are formed. Each restricting portion 31 faces the corresponding flat portion 21. In addition, on the inner surface of the recess 30, restricting portions 32, 32 made of a pair of flat portions parallel to each other are formed. Each restricting portion 32 faces the corresponding flat portion 22.

  Further, the outer shaft 13 is a bent portion 33 as a deformation promoting portion between the base end portions of the projecting portions 27 and 28 and the remaining arc-shaped portion of the outer shaft 13. That is, in the region between the center axis A1 of the outer shaft 13 and the plane C1 including the center of curvature A2 of each track groove 16 of the outer shaft 13 and the restricting portions 31 and 32 adjacent to each track groove 16, the outer shaft A bending portion 33 is formed as a deformation promoting portion for promoting the deformation of 13. The bent portion 33 is provided at the base end portion of the protruding portions 27 and 28 of the outer shaft 13.

  According to the present embodiment, when normal torque is applied, torque is transmitted between the inner shaft 14 and the outer shaft 13 via the ball 15. On the other hand, when a high torque is applied, either one of the pair of flat portions 21 and 22 of the inner shaft 14 abuts on the corresponding restricting portions 31 and 32 of the outer shaft 13, respectively. The relative rotation amount of 14 and the outer shaft 13 is regulated. Therefore, damage to the ball 15 and the raceway grooves 16 and 17 can be prevented in advance.

Since a pair of flat surfaces 21 and 22 forming a two-plane width between each other are used, even if the dimensional accuracy of the inner shaft 14 and the outer shaft 13 varies somewhat, the relative rotational amount of the inner shaft 14 and the outer shaft 13 is large. There is little to be.
Moreover, as a deformation | transformation promotion part between the plane C1 containing the center axis line A1 of the outer shaft 13, and the curvature center A2 of each track groove 16 of the outer shaft 13, and the control parts 31 and 32 adjacent to each track groove 16, respectively. Therefore, the outer shaft 13 can be easily bent. Therefore, the stress applied to the outer shaft 13 and the ball 15 can be relaxed. As a result, the pre-pressure on the ball 15 can be maintained over a long period of time, and the intermediate shaft 5 as a telescopic shaft having excellent durability can be realized.

Moreover, the deformation | transformation of the outer shaft 13 can be reliably accelerated | stimulated with the simple structure which uses the bending part 33 as a deformation | transformation promotion part.
The diameter of the ball 15 is preferably in the range of 10 to 40% of the outer diameter of the outer shaft 13. That is, if the diameter of the ball 15 is less than 10% of the outer diameter of the outer shaft 13, indentations may occur in the ball 15 and the raceway grooves 16 and 17. Further, when the diameter of the ball 15 exceeds 40% of the outer diameter of the outer shaft 13, the outer shaft 13 becomes larger, and the intermediate shaft 5 as a telescopic shaft becomes larger. If the inner shaft 14 is downsized without changing the outer diameter of the outer shaft 13 so as not to increase the size, the inner shaft 14 becomes insufficient in strength and the contact diameter of the inner ring raceway is reduced, so that indentations are likely to be formed. .

Therefore, by setting the ball diameter in the range of 10 to 40% of the outer diameter of the outer shaft 13, it is possible to reduce the size of the intermediate shaft 5 while preventing indentation of the raceway grooves 16, 17 and the like. For example, when the outer diameter of the outer shaft 13 is 30 mm, the diameter of the ball 15 is preferably set in the range of 3 to 12 mm.
The contact angle of the ball 15 is preferably 5 to 40 degrees. When the contact angle of the ball is less than 5 degrees, the play related to the ball 15 becomes large. On the other hand, when the contact angle exceeds 40 degrees, the two pairs of flat portions 21 and 22 of the inner shaft 14 are less likely to contact the corresponding restricting portions 31 and 32 of the outer shaft. Therefore, by setting the contact angle B1 of the ball 15 to 5 to 40 degrees, the relative rotation amount of the inner shaft 14 and the outer shaft 13 at the time of high torque load can be set to a required size while reducing backlash. it can.

  Further, when the gaps S1 formed between the flat portions 21 and 22 and the corresponding restricting portions 31 and 32 are equal, the amount of the gap S1 is preferably 0.01 to 0.5 mm. . If the clearance S1 is less than 0.01 mm, the restricting portions 31 and 32 may work during transmission of normal torque. On the other hand, when the gap S1 exceeds 0.5 mm, the relative rotation amount between the outer shaft 13 and the inner shaft 14 becomes excessive. Therefore, the relative rotation amount is set within the required range by setting the gap S1 in the range of 0.01 to 0.5 mm.

  Further, the thickness of the outer shaft 13 is preferably set in a range of 5 to 15% of the outer diameter of the outer shaft 13. If the wall thickness is less than 5% of the outer diameter of the outer shaft 13, there is a concern about insufficient strength. Further, when the thickness exceeds 15% of the outer diameter of the outer shaft 13, it is difficult to ensure the bending of the outer shaft 13. Therefore, by setting the thickness of the outer shaft 13 in a range of 5 to 15% of the outer diameter of the outer shaft 13, the outer shaft 13 is easily bent while ensuring the strength of the outer shaft 13. For example, when the outer diameter of the outer shaft 13 is 30 mm, the thickness of the outer shaft 13 is preferably set in the range of 1.5 to 4.5 mm.

Center angle of the outer shaft 13 corresponding to a region between the plane C1 including the center axis A1 of the outer shaft 13 and the center of curvature A2 of each track groove 16 and the restricting portions 31 and 32 adjacent to each track groove 16 respectively. P1 is preferably in the range of 30 to 60 degrees. The central angle P1 corresponds to a phase difference between the plane C1 and the corresponding restricting portions 31 and 32.
When the central angle P1 is less than 30 degrees, in addition to the stress acting on the restriction portion, the stress acting on the vicinity of the raceway groove 16 is increased, and plastic deformation is likely to occur. Further, when the central angle P1 exceeds 60 degrees, in addition to the stress acting on the restricting portion, the stress acting on the protruding portions 27 and 28 becomes large, and there is a problem that plastic deformation is likely to occur. Therefore, the center angle P1 is set in a range of 30 to 60 degrees. A more preferable range of the central angle P1 is 40 to 50 degrees.

  Similarly, the central angle of the outer shaft corresponding to the region between the plane C1 and the bent portion 33 is preferably in the range of 30 to 60 degrees. When the central angle is less than 30 degrees, in addition to the stress acting on the restricting portion, the stress acting on the vicinity of the raceway groove 16 becomes large, and there is a problem that plastic deformation tends to occur. In addition, when the central angle exceeds 60 degrees, in addition to the stress acting on the restricting portion, the stress acting on the protrusions 17 and 18 becomes large, and there is a problem that plastic deformation is likely to occur. Therefore, the center angle is set in the range of 30 to 60 degrees. A more preferable range of the central angle is 40 to 50 degrees.

In the present embodiment, the ball 15, the flat portions 21, 22 and the restricting portions 31, 32 are arranged on the same cross section, but the same effect can be obtained even if they are not arranged on the same cross section. Needless to say.
Next, FIG. 4 shows another embodiment of the present invention. Referring to FIG. 4, in the present embodiment, a pair of flat portions 210, 210 that form a two-sided width between each other are formed on outer peripheral surface 141 of solid inner shaft 14 </ b> A. Flat portions 310 and 310 facing the flat portions 210 and 210 are formed on the inner peripheral surface 131 of the cylindrical outer shaft 13A. A restricting portion 311 is formed at one end in the longitudinal direction of each flat portion 310, and a restricting portion 312 is formed at the other end.

In addition, a pair of bent portions 33A and 33B that bend in opposite directions are formed in a region between the plane C1 including the central axis A1 of the outer shaft 13A and the center of curvature A2 of each track groove 16 and the adjacent restricting portions 311 and 312. The outer shaft 13A is spaced apart in the circumferential direction. That is, the pair of bent portions 33A and 33B has a wave shape.
Also in the present embodiment, the same operational effects as in the embodiment of FIG. 2 can be obtained. That is, even if the dimensional accuracy of the inner shaft 14A and the outer shaft 13A varies somewhat, the relative rotation amount of the inner shaft 14A and the outer shaft 13A is rarely increased.

  A wave shape as a deformation promoting portion is formed in a region between the plane C1 including the center axis A1 of the outer shaft 13A and the center of curvature A2 of each track groove 16 and the restricting portions 311 and 312 adjacent to each track groove 16 respectively. Since the pair of bending portions 33A and 33B to be presented are provided, the outer shaft 13A can be more easily bent, and the stress applied to the outer shaft 13A and the ball 15 can be reduced. As a result, the pre-pressure on the ball 15 can be maintained over a long period of time, and the intermediate shaft 5 as a telescopic shaft having excellent durability can be realized. Further, the deformation of the outer shaft 13A can be surely promoted with a simple configuration using the bent portions 33A and 33B as the deformation promoting portions.

Further, at the time of assembly, as shown in FIG. 5, the pair of flat portions 310, 310 of the outer shaft 13A are clamped by applying a force F from the outer side, whereby the raceway groove 16 of the outer shaft 13A is moved outward (arrow G). See). Thereby, the ball 15 can be easily incorporated between the raceway grooves 16 and 17 at the time of assembly.
Further, the outer shaft 13A of the outer shaft 13A corresponding to the region between the plane C1 including the center axis A1 of the outer shaft 13A and the center of curvature A2 of each track groove 16 and the restricting portions 311 and 312 adjacent to each track groove 16 respectively. The central angle P2 is preferably in the range of 30 to 60 degrees. If the central angle P2 is less than 30 degrees, in addition to the stress acting on the restricting portion, the stress acting on the vicinity of the raceway groove 16 becomes large, which tends to cause plastic deformation. Further, when the central angle P2 exceeds 60 degrees, in addition to the stress acting on the restricting portion, the stress acting on the projecting portions 27 and 28 becomes large, and there is a problem that plastic deformation is likely to occur. Therefore, the center angle P2 is set in the range of 30 to 60 degrees. A more preferable range of the central angle P2 is 40 to 50 degrees.

  The central angle of the outer shaft 13A corresponding to the area between each plane C1 and the bent portion 33B on the side far from the plane C1 is preferably in the range of 30 to 60 degrees. When the central angle is less than 30 degrees, in addition to the stress acting on the restricting portion, the stress acting on the vicinity of the raceway groove 16 becomes large, and there is a problem that plastic deformation tends to occur. In addition, when the central angle exceeds 60 degrees, in addition to the stress acting on the restricting portion, the stress acting on the protruding portions 27 and 28 becomes large, and there is a problem that plastic deformation is likely to occur. Therefore, the center angle is set in the range of 30 to 60 degrees. A more preferable range of the central angle is 40 to 50 degrees.

In the embodiment of FIG. 4, the inner shaft 14A may be formed using a hollow shaft, that is, a tube.
Next, FIG. 6 shows still another embodiment of the present invention. Referring to FIG. 6, in the present embodiment, an inner shaft 14B having a star shape similar to a cylindrical outer shaft 13B having a star shape is used. In the present embodiment, the bent portions 33C to 33F that are distributed over the entire circumference of the outer shaft 13B and alternately bent in the opposite direction are arranged, so that the outer shaft 13B can be more easily bent. In the present embodiment, the inner shaft 14B may be a hollow shaft.

Further, since the central angle P2 of the outer shaft 13B corresponding to the region between each plane C1 and the restricting portions 31 and 32 is in the range of 30 to 60 degrees, the restricting portions 311 and 312 function as a stopper. It is easy to fulfill. It is preferable to positively regulate the relative rotation between the outer shaft 13B and the inner shaft 14B at this position.
Next, FIG. 7 shows still another embodiment of the present invention. Referring to FIG. 7, the feature of the present embodiment is that the outer shaft 13C is formed by a square tube, and the inner shaft 14C is also formed by a similar solid rectangular shaft. Track grooves 16 for the balls 15 are formed in a pair of opposite corners 132, 132 of the outer shaft 13C which are opposite to each other. The corners 132 and 132 are formed with bulged protrusions 51 and 52 projecting radially outward using the original R-shaped portions of the corners 132 and 132, respectively. Bent portions 33G and 33H as deformation promoting portions are formed at the base end portion of 52.

  According to the present embodiment, the outer shaft 13C with the raceway groove 16 can be easily and inexpensively manufactured using a square tube as a raw material. Moreover, each side of the square tube can be used as it is as the restricting portions 31 and 32 corresponding to the pair of flat portions 21 and 22 forming the two-surface width of the inner shaft 14C, and the manufacturing cost is also reduced from this point. be able to. The restricting portions 31 and 32 are disposed in the vicinity of the corner portions 133 and 133 where the ball 15 is not disposed.

  As shown in FIG. 8, a square cylindrical cage surrounding the inner shaft 14C can be used as the cage 19A. In this case, the retainer 19 </ b> A forms an opening 191 corresponding to a region including the corner 133 where the restricting portions 31 and 32 are disposed. In this case, the balls 15 in each row can be assembled together using the cylindrical retainer 19A, and assemblability can be improved.

FIG. 9 shows still another embodiment of the present invention. Referring to FIG. 9, the features of the present embodiment are as follows. That is, the outer shaft 13D is formed by a tube having a substantially uniform thickness over the entire circumference. The basic shape of the outer shaft 13D is circular in cross section. The basic shape of the inner shaft 14D is a rectangular cross section.
The outer peripheral surface 141 of the inner shaft 14D has a first pair of flat portions 41 and 42 facing each other, a second pair of flat portions 43 and 44 facing each other, and a third pair of flat portions 45 facing each other. , 46. A pair of raceway grooves 17 are formed on the outer peripheral surface 141 of the inner shaft 14D so as to face each other across the center of the cross section of the inner shaft 14D. The flat portion 41 and the flat portion 43 are disposed on the same plane, and one track groove 17 is disposed between the flat portion 41 and the flat portion 43. Further, the flat part 42 and the flat part 44 are arranged on the same plane, and the other track groove 17 is arranged between the flat part 42 and the flat part 44.

  On the inner peripheral surface 131 of the outer shaft 13D, a pair of raceway grooves 16 that oppose the raceway groove 17 of the inner shaft 14D, and regulation portions 71, 42 that face the flat portions 41, 42, 43, and 44, respectively, with a gap therebetween. 72, 73, 74 are formed. The outer shaft 13D has a pair of mountain-shaped protrusions 53 and 54 protruding outward in the radial direction, and corresponding track grooves 16 are formed by recesses formed inside the protrusions 53 and 54, respectively. ing.

  The outer shaft 13D has a pair of facing portions 75 and 76 that face each other. The pair of opposed portions 75 and 76 are opposed to the flat portions 45 and 46 of the inner shaft 14D, respectively. The cross section of a pair of opposing part 75 and 76 has comprised the circular arc shape centering on central-axis line A1 of 13 A of outer shafts. Between the center axis A1 of the outer shaft 13D and the plane C1 including the center of curvature A2 of each track groove 16 of the outer shaft 13D, and the restricting portions 71, 72, 73, 74 adjacent to each track groove 16, respectively. A bent portion 330 is formed as a deformation promoting portion. The bent portion 330 is formed by a protruding portion that protrudes inward in the radial direction so that a part of the outer peripheral surface of the outer shaft 13D is depressed.

  The outer shaft 13D includes a pair of remaining portions 77 and 78 disposed between the pair of facing portions 75 and 76 in the circumferential direction of the outer shaft 13D. One raceway groove 17 and a pair of restricting portions 71 and 73 are formed on the inner peripheral surface of one remaining portion 77. One raceway groove 16 is disposed between the pair of restricting portions 71 and 73. The other track groove 16 and a pair of restricting portions 72 and 74 are formed on the inner peripheral surface of the other remaining portion 78. The other raceway groove 16 is disposed between the pair of restricting portions 72 and 74.

Between each of the raceway groove 16, the bent portion 330, the restricting portions 71 to 74, and the facing portions 75 and 76, a curved line having a radius of curvature larger than the thickness of the outer shaft 13D is smoothly continuous. Moreover, it is preferable that the tops of the protrusions 53 and 54 of the outer shaft 13 </ b> D are disposed on a circumference C <b> 2 including the outer peripheries of the facing portions 75 and 76.
According to the present embodiment, the restricting portions 71 to 74 are arranged close to the raceway groove 16 on the outer shaft 13D. The remaining portions excluding the raceway groove 16 and the restricting portions 71 to 74 adjacent to both sides thereof are a pair of opposing portions 75 and 76 having an arc shape centering on the central axis A1 of the outer shaft 13D. The area is wide in the circumferential direction. Therefore, a large amount of twist in the rotation direction of the outer shaft 13D can be ensured.

  Specifically, the central angle P3 of the outer shaft 13D corresponding to each of the facing portions 75 and 76 is set in a range of 70 degrees to 110 degrees. By setting the central angle P3 to 70 degrees or more, sufficient torsional strength of the outer shaft 13D can be ensured. The reason why the central angle P3 is set to 110 degrees or less is to secure a space for arranging the raceway grooves 16 and the restricting portions 71 to 74 in the remaining portions 77 and 78.

In the outer shaft 13D, between the plane C1 including the central axis A1 of the outer shaft 13D and the center of curvature A2 of each track groove 16, and the restricting portions 71, 72, 73, 74 adjacent to the track grooves 16, respectively. A central angle P4 of the outer shaft 13D corresponding to the region is in a range of 15 degrees to 25 degrees.
In addition, as described above, the arc-shaped facing portions 75 and 76 that can ensure a large amount of twist are smoothly connected to the restricting portions 71 to 74, so that stress concentration in the raceway groove 16 and the restricting portions 71 to 74 is reduced. Can be relaxed. As a result, the strength and durability of the outer shaft 13D are improved.

Even if all the balls 15 fall off the raceway grooves 16 and 17, torque is transmitted between the shafts 13D and 14D by the engagement between the flat portions 41 to 44 and the restricting portions 71 to 74. As a result, the steering function can be ensured.
Also, in the inner shaft 14D, since the flat portions 41 to 44 for restricting the rotation of both the shafts 13D and 14D are arranged close to the raceway grooves 17, the inner shaft 14D can be thinned. . As a result, the weight reduction of the inner shaft 14D can be achieved.

Next, FIG. 10 shows still another embodiment of the present invention. Referring to FIG. 10, the present embodiment differs from the embodiment of FIG. 9 in that undulating portions 47 and 48 for reducing the thickness are used instead of the third pair of flat portions 45 and 46. It is in the point provided. In FIG. 10, lines L1 and L2 indicated by alternate long and short dash lines correspond to the positions of the flat portions 45 and 46 in the embodiment of FIG.
Each undulation 47, 48 is formed with a ridge 49 and a pair of ridges 50 extending in the axial direction of the inner shaft 14E. The contour of the ridge 49 is a round shape along the circumference centered on the central axis A1 of the outer shaft 13D, thereby ensuring the torsional strength of the inner shaft 14E. The recess 50 has a smooth curved cross section.

According to the present embodiment, it is possible to reduce the weight while ensuring the torsional strength of the inner shaft 14E. As a result, it is possible to reduce the weight of the intermediate shaft 5 as a telescopic shaft.
Next, FIG. 11 shows still another embodiment of the present invention. Referring to FIG. 11, the present embodiment is different from the embodiment of FIG. 9 in that a tube is used as the inner shaft 14F and a hollow shape is used to reduce the weight. Further, instead of the third flat portions 45 and 46, a bulging portion 55 that protrudes radially outward in a gentle mountain shape is formed. This is to make the torsional strength of the inner shaft 14F made of a tube equivalent to the strength of the solid inner shaft 14D of the embodiment of FIG.

According to the present embodiment, it is possible to reduce the weight while ensuring the torsional strength of the inner shaft 14F. As a result, it is possible to reduce the weight of the intermediate shaft 5 as a telescopic shaft.
The present invention is not limited to the above-described embodiments. In each of the above-described embodiments, as shown in FIG. 12, the cage is eliminated to form a total ball, and before and after the balls 15 forming a row. For example, the ball 15 may be biased from both sides using a biasing member 61 such as a compression coil spring. In that case, the outer shaft 13 and the inner shaft 14 may be provided with plastic deformation portions 62 and 63 as ball withdrawal preventing portions, respectively, so that the ball 15 is prevented from falling off.

Moreover, in each said embodiment, as shown in FIG. 13, you may use the thin part 65 as a deformation | transformation promotion part. You may comprise a bending part by a thin part.
In each of the above embodiments, it is preferable that the surface hardness of at least one of the outer shaft and the inner shaft is in the range of 400 to 550 Hv in terms of Vickers hardness. When the surface hardness is less than 400 Hv, the surface hardness of the ball 15 is generally about 700 Hv, and the hardness difference is large, so that indentations are easily formed. If the surface hardness of at least one of the outer shaft and the inner shaft exceeds 550 Hv, the shaft may bend due to thermal deformation during the curing process. Therefore, it is preferable to set the above range. However, it is preferable to perform nitriding on at least one of the outer shaft and the inner shaft because the surface hardness can be cured to about 700 Hv while suppressing thermal deformation.

In each of the above embodiments, it is preferable that at least one of the outer shaft and the inner shaft is made of chrome steel or chrome molybdenum steel because the allowable stress can be increased and the safety factor can be set high.
In each of the above embodiments, if at least one of the outer shaft and the inner shaft is formed of a tempered material (material subjected to quenching and tempering), the allowable stress can be increased and the safety factor can be set high. This is preferable.

FIG. 1 is a schematic view of a steering apparatus in which a telescopic shaft according to an embodiment of the present invention is applied to an intermediate shaft. FIG. 2 is a cross-sectional view of an intermediate shaft as a telescopic shaft. FIG. 3 is a cross-sectional view of an intermediate shaft as a telescopic shaft. FIG. 4 is a cross-sectional view of a telescopic shaft according to another embodiment of the present invention. FIG. 5 is an explanatory diagram when the ball is incorporated into the telescopic shaft. FIG. 6 is a cross-sectional view of a telescopic shaft according to still another embodiment of the present invention. FIG. 7 is a cross-sectional view of a telescopic shaft according to still another embodiment of the present invention. FIG. 8 is a cross-sectional view of a telescopic shaft according to still another embodiment of the present invention. FIG. 9 is a cross-sectional view of a telescopic shaft according to still another embodiment of the present invention. FIG. 10 is a schematic cross-sectional view of a main part of a telescopic shaft according to still another embodiment of the present invention. FIG. 11 is a cross-sectional view of a telescopic shaft according to still another embodiment of the present invention. FIG. 12 is a cross-sectional view of a telescopic shaft according to still another embodiment of the present invention. FIG. 13 is a cross-sectional view of a telescopic shaft according to still another embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Steering device, 2 ... Steering member, 3 ... Steering shaft, 5 ... Intermediate shaft (expandable shaft), 7 ... Pinion shaft, 8 ... Rack shaft, 13, 13A-13D ... Outer shaft, 14, 14A-14F ... Inner shaft, 15 ... ball (rolling element), 16, 17 ... raceway groove, 18 ... raceway, 19, 19A ... cage, 20 ... holding hole, 21, 22, 41 to 46 ... flat part, 31, 32, 71-74 ... restricting part, 33, 33A-33H, 330 ... bent part (deformation promoting part), 65 ... thin part, 75, 76 ... opposing part, 77, 78 ... remaining part, 132 ... corner part, A1 ... Center axis (outer shaft), A2 ... center of curvature (outer shaft raceway groove), B1 ... contact angle, C1 ... plane, X ... axial direction (direction in which raceway groove extends)

Claims (7)

An inner shaft and a cylindrical outer shaft fitted together,
Track grooves extending in the longitudinal direction of the inner shaft and the outer shaft and facing each other;
Rolling elements that are elastically sandwiched between mutually opposing raceway grooves and form a row in the direction in which the raceway grooves extend,
The outer peripheral surface of the inner shaft is provided with at least a pair of flat portions facing each other and forming a two-surface width therebetween,
The inner peripheral surface of the outer shaft is provided with a restricting portion for engaging the corresponding flat portion of the inner shaft to restrict the relative rotation amount of the inner shaft and the outer shaft,
A deformation promoting portion for accelerating the deformation of the predetermined region in a predetermined region in the circumferential direction of the outer shaft between the plane including the curvature center of the raceway groove of the outer shaft and the central axis of the outer shaft and the restricting portion. A telescopic shaft characterized in that is formed.   2. The telescopic shaft according to claim 1, wherein the deformation promoting portion includes at least one of a bent portion and a thin portion.   3. The telescopic shaft according to claim 1, wherein the rolling element includes a ball having a diameter of 10 to 40% of the outer diameter of the outer shaft.   4. The telescopic shaft according to claim 3, wherein the thickness of the outer shaft is 5 to 15% of the outer diameter of the outer shaft.   5. The telescopic shaft according to claim 3, wherein the contact angle of the ball is 5 to 40 degrees.   6. The telescopic structure according to claim 3, wherein the outer shaft is formed by a square tube, and a raceway groove for a ball is formed at each of a pair of opposite corners of the square. shaft. In any one of Claim 1 to 5,
The outer shaft includes a pair of facing portions facing each other in the radial direction of the outer shaft,
Each of the cross-sections of the pair of opposed portions has an arc shape centered on the central axis of the outer shaft,
The outer shaft includes a pair of remaining portions disposed between the pair of opposed portions in the circumferential direction of the outer shaft,
The raceway groove of the outer shaft includes a raceway groove formed on the inner peripheral surface of one remaining portion, and a raceway groove formed on the inner peripheral surface of the other remaining portion,
The outer shaft restricting portion includes a pair of restricting portions formed on an inner peripheral surface of one remaining portion and a pair of restricting portions formed on an inner peripheral surface of the other remaining portion.

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