JP2005299779A - Flexible shaft used for steering gear of vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent setting a leaf spring so that the generation of an excessive stress is prevented by uniforming stress applied on whole rollers and the leaf spring; and to maintain preloading performance of the leaf spring for a long period. <P>SOLUTION: A flexible shaft is provided with a spline combination between an axial projected ridge 4 formed on an outer periphery of a male shaft 1 and an axial groove 6 formed on an inner periphery of a female shaft 2. A plurality of rollers 7a to 7n are rotatably interposed between an axial groove 3 of the male shaft 1 and an axial groove 5 of the female shaft 2 via the leaf spring 8 used for preloading. The rollers 7a to 7n are comprised of a combination of rollers having different diameters, and the combination of the rollers having different diameters is provided so that the diameter of the rollers 7n and 7n located at a far end is somewhat smaller than that of the rollers 7a and 7a located around the center portion. For example, when the diameter of the rollers located around the center is ϕDa and the diameter of the rollers located at the far end is ϕDn, the ratio is set up to be ϕDa>ϕDn. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a telescopic shaft for vehicle steering that is incorporated in a steering shaft of a vehicle and has a male shaft and a female shaft that are non-rotatable and slidably fitted to each other.

  The telescopic shaft of the steering mechanism portion of the automobile is required to absorb the axial displacement generated when the automobile travels and to transmit the displacement and vibration on the steering wheel. Further, in order to obtain an optimum position for the driver to drive the automobile, a function of moving the position of the steering wheel in the axial direction and adjusting the position is required.

  In any of these cases, the telescopic shaft is required to reduce the rattling noise, to reduce the rattling on the steering wheel, and to reduce the sliding resistance during the sliding operation in the axial direction. The

  For this reason, conventionally, the male shaft of the telescopic shaft is coated with a nylon film, and grease is applied to the sliding portion to absorb or alleviate metal noise, metal hitting sound, etc., and to reduce sliding resistance. The rotation direction play has been reduced.

  However, there is a case where wear of the nylon film progresses with the progress of use and the play in the rotational direction increases. In addition, under conditions where the engine room is exposed to high temperatures, the nylon membrane changes in volume, and the sliding resistance may increase remarkably or wear may be significantly accelerated, resulting in increased rotational play. .

  For this reason, in Patent Documents 1 to 3, a rolling element and an elastic body for preload for applying preload to both shafts are provided between the outer peripheral surface of the male shaft and the inner peripheral surface of the female shaft. It is intervening. Thus, when sliding, the rolling element can be preloaded to the extent that the rolling element is free from rattling with respect to the female shaft, etc., and rattling between both shafts can be prevented. The rolling element can be restrained in the circumferential direction by the body, and the male shaft and the female shaft can be prevented from rattling in the rotational direction.

  By the way, in patent documents 1 thru | or 3, all use the thing of a different material and a shape, respectively for the part of the elastic body for giving a preload to a rolling element, and the part of the race which contacts a rolling element.

The reason is that the portion that contacts the rolling element must withstand a high contact surface pressure. This is because the torque must be transmitted through the rolling elements, and the contact surface of the race portion that contacts the rolling elements must be a hard and strong member, whereas the elastic body that generates a biasing force. This is because it is necessary to form this part from a material that is easily bent, such as a spring.
German Patent Invention DE 3730393C2 JP 2001-50293 A JP 2001-193738 A

  However, as described above, in Patent Documents 1 to 3, it is necessary to use parts of an elastic body that applies a preload to the rolling elements and parts of the race that contact the rolling elements of different materials and shapes. As a result, the manufacturing cost is soaring.

  Moreover, in the Example of patent document 1, the example in which the contact surface of a race and the urging | biasing part are comprised from the leaf | plate spring of a single material is also shown. However, since the leaf springs are connected to each other by the web, the shape becomes complicated, and the assembly cost increases.

  Furthermore, as described above, since torque is transmitted through the rolling elements, the leaf spring must be compatible with withstanding the contact surface pressure of the rolling elements and urging the rolling elements. However, such compatibility is difficult in practice.

  Furthermore, also in the Example of patent document 3, the elastic body and the race surface are comprised integrally. However, since the torque is transmitted through the rolling element as described above, the leaf spring must be able to both endure the contact surface pressure of the rolling element and bias the rolling element. However, such compatibility is difficult in practice.

  The present invention has been made in view of the circumstances as described above, and is easy to assemble, while significantly reducing the manufacturing cost, and uniformizing the stress applied to all the rolling elements and the leaf springs. An object of the present invention is to provide a telescopic shaft for vehicle steering that prevents the occurrence of stress and prevents the leaf spring from sag and maintains the preload performance required over a long period of time.

In order to achieve the above object, a telescopic shaft for vehicle steering according to claim 1 of the present invention is incorporated in a steering shaft of a vehicle, and is used for vehicle steering in which a male shaft and a female shaft are fitted non-rotatably and slidably. In the telescopic axis,
A torque transmitting portion provided on each of the outer peripheral portion of the male shaft and the inner peripheral portion of the female shaft, and in contact with each other at the time of rotation;
An axial relative movement between the male shaft and the female shaft is provided between an axial groove in the outer peripheral portion of the male shaft and an axial groove in the inner peripheral portion of the female shaft at a position different from the torque transmitting portion. A rolling element that rolls, and a preload portion that is arranged radially adjacent to the rolling element and that provides an elastic body that preloads the male shaft and the female shaft via the rolling element. , And
The rolling elements in the same axial groove are characterized by a combination of different diameters.

  The telescopic shaft for vehicle steering according to claim 2 of the present invention is characterized in that the combination of the different diameters is such that the rolling element at the end of the array is smaller in diameter than the other rolling elements.

  The telescopic shaft for vehicle steering according to claim 3 of the present invention is characterized in that the diameter of the combination of the different diameters decreases from the center to the end of the array.

  The telescopic shaft for vehicle steering according to claim 4 of the present invention is characterized in that a difference in diameter between the adjacent rolling elements is in a range of 1 to 20 μm.

  As described above, according to the present invention, since the rolling elements that are the first torque transmission members in the same axial groove are a combination of different diameters, the stress applied to all the rolling elements and the leaf springs. By preventing the occurrence of excessive stress by preventing the occurrence of excessive stress, it is possible to prevent sag of the leaf spring, maintain the preload performance required over a long period of time, and extend the life.

  In addition, it is not necessary to tighten the dimensional accuracy, and since the preload component and the race surface of the rolling element can be made of a single material (integral molded product), assembly is easy and manufacturing costs are significantly reduced. You can also.

  Hereinafter, a telescopic shaft for vehicle steering according to an embodiment of the present invention will be described with reference to the drawings.

(Overall configuration of vehicle steering shaft)
FIG. 1 is a side view of a steering mechanism portion of an automobile to which a vehicle steering telescopic shaft according to an embodiment of the present invention is applied.

  In FIG. 1, an upper steering shaft portion 120 (a steering column 103 and a swinging shaft 104 rotatably supported by the steering column 103 are attached to a member 100 on the vehicle body side via an upper bracket 101 and a lower bracket 102. A steering wheel 105 attached to the upper end of the steering shaft 104, a lower steering shaft portion 107 connected to the lower end of the steering shaft 104 via a universal joint 106, and a steering shaft joint 108 to the lower steering shaft portion 107. A pinion shaft 109 connected via a pin, a steering rack shaft 112 connected to the pinion shaft 109, and the steering rack shaft 112 is supported to elastically move to another frame 110 of the vehicle body. Steering mechanism from a fixed steering rack support member 113 via 111 is formed.

  Here, the upper steering shaft portion 120 and the lower steering shaft portion 107 use the vehicle steering telescopic shaft (hereinafter referred to as the telescopic shaft) according to the embodiment of the present invention. The lower steering shaft portion 107 is formed by fitting a male shaft and a female shaft. The lower steering shaft portion 107 absorbs axial displacement generated when the automobile travels, and the steering wheel. The performance which does not transmit the displacement and vibration on 105 is required. In such performance, the vehicle body has a sub-frame structure, and the member 100 for fixing the upper part of the steering mechanism and the frame 110 to which the steering rack supporting member 113 is fixed are separated, and the steering rack supporting member 113 is This is required in the case of a structure that is fastened and fixed to the frame 110 via an elastic body 111 such as rubber. In other cases, when the steering shaft joint 108 is fastened to the pinion shaft 109, an operator may need to have a telescopic function so that the telescopic shaft is once contracted and then fitted to the pinion shaft 109 and fastened. . Further, the upper steering shaft portion 120 at the upper part of the steering mechanism also has a male shaft and a female shaft fitted to each other. The upper steering shaft portion 120 is used for a driver to drive a car. In order to obtain an optimal position, the function of moving the position of the steering wheel 105 in the axial direction and adjusting the position is required, and thus a function of expanding and contracting in the axial direction is required. In all the cases described above, it is possible to reduce the rattling noise of the fitting portion on the telescopic shaft, to reduce the backlash feeling on the steering wheel 105, and to reduce the sliding resistance when sliding in the axial direction. Required.

(First embodiment)
FIG. 2 is a transverse sectional view of the telescopic shaft for vehicle steering according to the first embodiment of the present invention. FIG. 3 is a sectional view taken along line III-III in FIG. FIG. 4 is a perspective view of the leaf spring and the rolling element according to the first embodiment. FIG. 5 is a partially enlarged perspective view of the end portion of the shaft according to the first embodiment of the present invention.

  As shown in FIGS. 2 and 3, the telescopic shaft for vehicle steering (hereinafter referred to as the telescopic shaft) includes a male shaft 1 and a female shaft 2 that are non-rotatable and slidably fitted to each other.

  In the present embodiment, a plurality of axial ridges 4 are formed to extend on the outer peripheral surface of the male shaft 1. These axial ridges 4 are male parts for spline fitting, but may be male parts for serration fitting or simply for convex / concave fitting.

  A plurality of axial grooves 6 are formed on the inner peripheral surface of the female shaft 2 so as to extend at positions facing the axial ridges 4 of the male shaft 1. These axial grooves 6 are female parts for spline fitting, but may be female parts for serration fitting or simply for uneven fitting.

  In addition, the axial ridge 4 and the axial groove 6 described above constitute a torque transmission portion which is a constituent element of the present invention described in claim 1 of the claims.

  On the outer peripheral surface of the male shaft 1, three axial grooves 3 that are equally arranged at intervals of 120 degrees (phase) in the circumferential direction are formed to extend. Correspondingly, three axial grooves 5 that are equally arranged at intervals of 120 degrees (phase) in the circumferential direction are formed to extend on the inner peripheral surface of the female shaft 2.

  Between the axial groove 3 of the male shaft 1 and the axial groove 5 of the female shaft 2, a plurality of rigid spherical bodies 7a, 7n (rolling) are rolled during the relative axial movement of the two shafts 1 and 2. (Moving body, ball) is interposed so that it can roll freely. The axial groove 5 of the female shaft 2 has a substantially arc-shaped cross section or a Gothic arch shape.

  The axial groove 3 of the male shaft 1 is composed of a pair of inclined planar side surfaces 3a and a bottom surface 3b formed flat between the pair of planar side surfaces 3a.

  Between the axial groove 3 of the male shaft 1 and the spherical bodies 7a and 7n, an elastic body 8 for contacting and preloading the spherical bodies 7a and 7n is interposed.

  The elastic body 8 is in contact with the spherical bodies 7a and 7n in a substantially arc shape at two points, and is separated from the spherical body side contact section 8a at a predetermined interval in the circumferential direction. The groove surface side contact portion 8b that contacts the planar side surface 3a of the axial groove 3 of the male shaft 1, and the spherical body side contact portion 8a and the groove surface side contact portion 8b are elastically biased in a direction away from each other. And a bottom portion 8d facing the bottom surface 3b of the axial groove 3.

  The urging portion 8c has a substantially U shape and is bent in a substantially arc shape, and the spherical body side contact portion 8a and the groove surface side contact portion 8b are mutually connected by the bent urging portion 8c. Can be elastically biased so as to be separated from each other.

  As shown in FIGS. 3 and 4, in the present embodiment, the elastic body side contact portion 8a that contacts the spherical bodies 7a and 7n is formed in a substantially arc shape. Thereby, the contact surface pressure with the spherical bodies 7a and 7n can be lowered rather than the planar shape. The surface hardness may be uniform throughout or may be partially changed.

  A stopper plate 9 that locks the elastic body 8 in the axial direction with a slight clearance so that the elastic body 8 does not fall off is provided at the end on the side where the male shaft 1 is inserted into the female shaft 2. 10 is fastened to the male shaft 1. The stopper plate 9 also serves to prevent the rolling elements 7a and 7n from coming off the axial groove 3 of the male shaft 1. Thus, the telescopic shaft for vehicle steering according to the present embodiment is configured.

  In the telescopic shaft as described above, when the shaft rotates (at the time of high torque transmission), the axial ridge 4 and the axial groove 6 come into contact with each other to constitute a torque transmission portion.

  Since the telescopic shaft of the present embodiment has such a structure, the male shaft 1 and the female shaft 2 are slidably in contact with each other at each torque transmitting portion due to the presence of the preload portion. During relative movement in the axial direction with respect to the female shaft 2, the rollers 7a and 7n can slide with each other and can roll.

  Even if the axial ridge 4 formed on the male shaft is formed on the female shaft side and the axial groove 6 formed on the female shaft is formed on the male shaft side, An effect is obtained. Further, the curvature of the axial groove 5 may be different from the curvature of the rolling elements 7a and 7n, and both may be formed so as to be in an oval point contact. Further, the rolling elements 7a and 7n may be spherical bodies. Further, the elastic body 8 may be a leaf spring. Further, a lower sliding load can be obtained by applying grease to the sliding surface and the rolling surface.

  The telescopic shaft of the present embodiment configured as described above is superior to the prior art in the following points.

  If the sliding surface is purely sliding as in the prior art, the preload load for preventing rattling could only be kept at a certain level. That is, the sliding load is the friction coefficient multiplied by the preload, and if the preload is increased to prevent rattling and improve the rigidity of the telescopic shaft, the sliding load will increase. This is because it falls into a vicious circle.

  In this respect, in the present embodiment, the preload portion employs a rolling mechanism of the rolling elements 7a and 7n in the relative movement in the axial direction, so that the preload load is not increased without causing a significant increase in the sliding load. Can be raised. As a result, it is possible to achieve the prevention of rattling and the improvement of rigidity that could not be achieved conventionally without increasing the sliding load.

  At the time of high torque transmission, the axial ridge 4 of the torque transmission portion plays a role of torque transmission by contacting the axial groove 6, and the elastic body 8 is elastically deformed in the preloading portion so that the spherical bodies 7 a and 7 n The male shaft 1 and the female shaft 2 are restrained in the circumferential direction to prevent rattling and transmit low torque.

  For example, when torque is input from the male shaft 1, rattling is prevented since the preload of the elastic body 8 is applied in the initial stage.

  As the torque further increases, the axial ridges 4 of the torque transmitting portion and the side surfaces of the axial grooves 6 come into strong contact, and the axial ridges 4 receive a stronger reaction force than the spherical bodies 7a and 7n. The torque transmission unit mainly transmits torque. Therefore, in this embodiment, it is possible to reliably prevent backlash in the rotational direction of the male shaft 1 and the female shaft 2, and to transmit torque in a highly rigid state.

Further, since the axial ridge 4 and the axial groove 6 are continuously contacted in the axial direction and receive the load during torque transmission, the contact pressure is higher than that of the rolling elements 7a and 7n receiving the load by point contact. There are various effects such as being able to keep it low. Therefore, the following items are superior to the conventional example in which the entire row has a ball rolling structure.
・ The damping effect at the sliding part is larger than that of the ball rolling structure. Therefore, vibration absorption performance is high.
-If the same torque is transmitted, since the axial ridge 4 can keep the contact pressure lower, the axial length of the torque transmitting portion can be shortened and the space can be used effectively.
-If the same torque is transmitted, since the axial ridge 4 can keep the contact pressure lower, an additional step for curing the axial groove surface of the female shaft by heat treatment or the like is unnecessary.
・ The number of parts can be reduced.
・ Assembly can be improved.
・ Assembly costs can be reduced.
-Since the torque transmission is mainly performed by the torque transmission unit, the number of rolling elements 7a and 7n can be reduced, and the collapse stroke can be increased.

In addition, the following items are superior to the conventional example in which all the rows are spline-fitted and all the rows slide in that the rolling elements 7a and 7n are partially employed.
・ Since rolling is used, sliding load can be kept low.
・ Preload can be increased, and long-term rattling and high rigidity can be achieved at the same time.

  Conventionally, the spherical bodies (rolling bodies) are all formed with the same diameter. On the other hand, in the present embodiment, as shown in FIGS. 3 and 4, the spherical bodies 7a, 7a, 7n are composed of combinations of different diameters, and the combination of different diameters is the most in the array. The diameters of the spherical bodies 7n, 7n at the ends are set to be slightly smaller than the diameters of the spherical bodies 7a, 7a, 7a near the other center.

That is, if the diameter of the spherical body 7a near the center is φDa and the diameter of the outermost spherical body 7n is φDn,
φDa> φDn
It is set to be. In addition, it is preferable that the difference of the diameter of the adjacent spherical body 7a and the spherical body 7n exists in the range of 1-20 micrometers.

  The spherical bodies 7n, 7n at the extreme ends have a higher contact stress with the leaf spring 9 than the spherical bodies 7a, 7a,. This is because the spherical bodies are not arranged in the A and B regions of FIG. 3 of the leaf spring 9, so that the most spherical bodies 7 n and 7 n are separated from the A and B regions where the leaf spring 9 is in a free state. It is because you must receive the reaction force of.

  Therefore, in the present embodiment, the diameters of the spherical bodies 7n, 7n at the end are set to be slightly smaller than the diameters of the spherical bodies 7a, 7a,. The reaction force is reduced, the stress applied to all the spherical bodies 7a,... 7n and the leaf spring 9 is made uniform, and the occurrence of excessive stress is prevented. Thus, the preload performance required over a long period can be maintained, and the life can be extended.

  In addition, since it is not necessary to tighten the dimensional accuracy and the preload component (leaf spring 9) and the race surface of the spherical bodies 7a,. It is easy and the manufacturing cost can be significantly reduced.

  In addition to the above description, the components of the telescopic shaft according to the present embodiment are preferably configured as shown in Table 1 and Table 2 below.

また、本実施の形態では、図２、図３、および図５に示すように、雄軸１の軸方向凸条４は、その両端部に、テーパー形状部Ｔを有している。また、軸方向凸条４の両端部及び中間部では、その角部に、曲面形状部Ｒを有している。

Moreover, in this Embodiment, as shown in FIG.2, FIG.3 and FIG.5, the axial direction protruding item | line 4 of the male shaft 1 has the taper-shaped part T in the both ends. Moreover, in the both ends and intermediate part of the axial ridge 4, it has the curved-surface-shaped part R in the corner | angular part.

  As shown in FIG. 2, the female shaft 2 is also formed at the corners of the ridge 6 a formed between the two axial grooves 6 and the standing wall 6 b on the end side of the axial groove 6. And has a curved surface portion R.

(Second Embodiment)
FIG. 6 is a longitudinal sectional view of a telescopic shaft for vehicle steering according to the second embodiment of the present invention.

  As is apparent from the drawings, the basic structure of the second embodiment is the same as that of the first embodiment described above, and only differences will be described.

  In the present embodiment, the diameters of the most spherical bodies 7n, 7n are set to be slightly smaller than the diameters of the spherical bodies 7a, 7a,. A cage (retainer) 20 for holding the bodies 7a, ... 7n is provided.

  Thereby, the cage (retainer) 20 can prevent all the spherical bodies 7a,... 7n having different diameters from falling apart and obtain a more uniform stress distribution.

(Third embodiment)
FIG. 7 is a longitudinal sectional view of a telescopic shaft for vehicle steering according to a third embodiment of the present invention.

  As is apparent from the drawings, the third embodiment has the same basic structure as the above-described first embodiment, and only differences will be described.

  In the present embodiment, combinations of different diameters of the spherical bodies 7a, 7b, and 7n are set so that the diameters of the spherical bodies 7a, 7b, and 7n gradually decrease from the center toward the end.

That is, if the diameter of the spherical body 7a near the center is φDa, the diameter of the adjacent spherical body 7b is φDb, and the diameter of the outermost spherical body 7n is φDn,
φDa>φDb> φDn
It is set to be. In addition, it is preferable that the difference of the diameter of the spherical body 7a, the spherical body 7b, and the spherical body 7n is in the range of 1 to 20 μm, respectively.

  In this case, the stress applied to all the spherical bodies 7a, 7b... 7n and the leaf spring 9 can be made even more uniform to prevent the generation of excessive stress.

(Fourth embodiment)
FIG. 8 is a cross-sectional view of the telescopic shaft for vehicle steering according to the fourth embodiment of the present invention.

  As is apparent from the drawings, the fourth embodiment has the same basic structure as that of the first embodiment described above, and only differences will be described.

  This embodiment is characterized in that the solid lubricating film 11 is formed on the outer peripheral surface of the male shaft 1. In this way, by forming the solid lubricating film 11 on the outer peripheral surface of the male shaft 1, the contact resistance between the axial ridge 4 and the axial groove 6 of the torque transmitting portion can be lowered, so that the total sliding The load (referred to as a sliding load generated during normal use in the structure of the present invention in which both rolling and sliding are applied) can be made lower than in the case of the first embodiment. Solid lubricant coatings can be obtained by dispersing and mixing molybdenum disulfide powder in a resin and then spraying or dipping it to form a coating, or by dispersing and mixing PTFE (tetrafluoroethylene) in a resin. A film or the like formed by baking or dipping is used. Further, a resin may be coated instead of the solid lubricating film. Other configurations, operations, and effects are the same as those in the first embodiment described above.

(Fifth embodiment)
FIG. 9 is a cross-sectional view of a telescopic shaft for vehicle steering according to a fifth embodiment of the present invention.

  As is clear from the drawings, the fifth embodiment has the same basic structure as that of the first embodiment described above, and only differences will be described.

  In the present embodiment, three axial ridges 4 each having a substantially arc-shaped cross-sectional shape that are equally spaced at 120 degree intervals in the circumferential direction on the outer peripheral surface of the male shaft 1 are formed to extend. Correspondingly, three axial grooves 6 having a substantially arc-shaped cross section are formed on the inner peripheral surface of the female shaft 2 so as to be opposed to the three axial ridges 4 of the male shaft 1. ing. When sliding, the axial ridge 4 and the axial groove 6 are in principle non-contact with each other, but when high torque is transmitted, they are in contact with each other to form a torque transmission portion. The axial ridges 4 and the axial grooves 6 are substantially arc-shaped in cross section or Gothic arch shape, but may have other shapes. Other configurations, operations, and effects are the same as those in the first embodiment described above.

  In addition, this invention is not limited to embodiment mentioned above, A various deformation | transformation is possible.

1 is a side view of a steering mechanism portion of an automobile to which a telescopic shaft for vehicle steering according to an embodiment of the present invention is applied. It is a cross-sectional view of the telescopic shaft for vehicle steering according to the first embodiment of the present invention. It is sectional drawing along the III-III line of FIG. It is a perspective view of the leaf | plate spring and rolling element which concern on 1st Embodiment. It is a partial expanded perspective view of the edge part of the axis | shaft which concerns on 1st Embodiment of this invention. It is a longitudinal cross-sectional view of the telescopic shaft for vehicle steering which concerns on 2nd Embodiment of this invention. It is a longitudinal cross-sectional view of the telescopic shaft for vehicle steering which concerns on 3rd Embodiment of this invention. It is a cross-sectional view of a telescopic shaft for vehicle steering according to a fourth embodiment of the present invention. It is a cross-sectional view of a telescopic shaft for vehicle steering according to a fifth embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Male shaft 2 Female shaft 3 Axial groove 3a Planar side surface 3b Bottom surface 4 Axial ridge 5 Axial groove 6 Axial groove 7a, 7b, 7n Spherical body (ball, rolling element)
8 Elastic body 8a Spherical body side contact part (transmission member side contact part)
8b Groove surface side contact portion 8c Energizing portion 8d Bottom portion 9 Stopper plate 10 Caulking portion 11 Solid lubricating film 20 Cage
DESCRIPTION OF SYMBOLS 100 Member 101 Upper bracket 102 Lower bracket 103 Steering column 104 Steering shaft 105 Steering wheel 106 Universal joint 107 Lower steering shaft part 108 Steering shaft joint 109 Pinion shaft 110 Frame 111 Elastic body 112 Steering rack 120 Upper steering shaft part

Claims (4)

In the telescopic shaft for vehicle steering, which is incorporated in the steering shaft of the vehicle and the male shaft and the female shaft are slidably fitted to each other,
A torque transmitting portion provided on each of the outer peripheral portion of the male shaft and the inner peripheral portion of the female shaft, and in contact with each other at the time of rotation;
An axial relative movement between the male shaft and the female shaft is provided between an axial groove in the outer peripheral portion of the male shaft and an axial groove in the inner peripheral portion of the female shaft at a position different from the torque transmitting portion. A rolling element that rolls, and a preload portion that is arranged radially adjacent to the rolling element and that provides an elastic body that preloads the male shaft and the female shaft via the rolling element. , And
A telescopic shaft for vehicle steering, wherein the rolling elements in the same axial groove are a combination of different diameters.   The telescopic shaft for vehicle steering according to claim 1, wherein the combination of different diameters is such that the rolling element at the end of the array is smaller in diameter than the other rolling elements.   The telescopic shaft for vehicle steering according to claim 1 or 2, wherein the combination of different diameters decreases in diameter from the center to the end of the array.   4. The telescopic shaft for vehicle steering according to claim 1, wherein a difference in diameter between the adjacent rolling elements is in a range of 1 to 20 μm. 5.

Images