JP2006349104A - Telescopic shaft and telescopic shaft for steering vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a telescopic shaft capable of reducing time and labor required for manufacture and reducing dispersion in slide resistance. <P>SOLUTION: An intermediate shaft 5 is provided with a ball 15 provided between channels 16 and 17 in the axial direction in which an inner shaft 13 and an outer shaft 14 oppose for each other. Pre-load is applied to the ball 15. The balls 15 are arranged adjacent to each other across a protruding bar 22 of the outer shaft 14. A first contact part 31 is formed among each ball 15 and a side part 26 to which the protruding bar 22 corresponds, respectively. A second contact part 32 is formed among each ball 15 and the inner shaft 13, respectively. Distance D1 between the first contact part 31 and a symmetrical face 23 passing through the centers of the channels 17, 17 in the axial direction in two rows is shorter than distance D2 between the second contact part 32 and the symmetrical face 23. Distance D3 between the first contact parts 31 is shorter than outside diameter Db of the ball 15. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

  Some of the above-mentioned telescopic shafts have a ball spline structure (see, for example, Patent Document 1). In Patent Document 1, axial grooves are formed in each of the inner shaft and the outer shaft. A plurality of axial grooves of the inner shaft and the outer shaft are formed at substantially equal intervals in the circumferential direction, and the corresponding axial grooves of the inner shaft and the outer shaft are opposed to each other in the radial direction of the outer shaft, Each is arranged symmetrically with respect to a symmetry plane along the radial direction. Balls are interposed between the axial grooves facing each other.

Each ball has a predetermined size and presses the outer shaft radially outward to increase the distance between the corresponding axial grooves of the inner shaft and the outer shaft. The outer shaft is elastically deformed to generate an elastic restoring force, and applies a preload to the ball.
JP-A-53-24936

Stress is generated on the outer shaft by a load received from the ball. Since the stress generated in the outer shaft is preferably as small as possible, it is required to reduce the stress generated in the outer shaft as much as possible while applying the necessary preload to the ball.
For this purpose, for example, by accurately setting the dimensions of the axial grooves corresponding to each other on the inner shaft and the outer shaft, the amount of pressure on the outer shaft of the ball interposed between the axial grooves is minimized. It is possible to do. However, in this case, it is necessary to increase the dimensional accuracy of the inner shaft, the outer shaft, and the like, which takes time for manufacturing.

  In the case of Patent Document 1, the distance between adjacent balls in the circumferential direction of the outer shaft, that is, the distance (span) between contact points between the outer shaft and each ball in the circumferential direction of the outer shaft is substantially constant. For this reason, the maximum value of the span between contact points between the outer shaft and the corresponding ball is small, and the bending rigidity is high in the radial direction of the outer shaft. As a result, if the amount of pressure applied to the outer shaft by the balls varies due to dimensional errors, etc., even if the variation is small, the variation in the load applied to the outer shaft becomes large. The variation in resistance load) generated when the inner shaft and the outer shaft are moved relative to each other with expansion and contraction increases.

  The present invention has been made under such a background, and an object thereof is to provide a telescopic shaft that requires less labor for manufacturing and that has a small variation in slide resistance.

  In order to achieve the above object, the present invention provides an inner shaft (13) and a cylindrical outer shaft (14) which are fitted together so as to be able to move relative to each other in the axial direction (S) and transmit torque, and an outer periphery of the inner shaft. Formed on the surface (131) and the inner peripheral surface (141) of the outer shaft and interposed between the axial grooves (16, 17) facing each other and the axial grooves of the inner shaft and the outer shaft, A rolling element (15) receiving a preload from the outer shaft, and the axial groove (17) of the outer shaft is provided with an intermediate strip (22) formed to extend in the axial direction on the inner periphery of the outer shaft. It includes two rows of axial grooves (17, 17) adjacent to each other across the circumferential direction (C) of the shaft, and these two rows of axial grooves are symmetrical surfaces (23) along the radial direction (R) of the outer shaft. ), And rolling elements are arranged in a row (19) in each of the two rows of axial grooves, A first contact portion (31) is formed between each of the rolling elements of the two rows of axial grooves and the corresponding side portion (26) of the interposition strip, and the two rows of axial grooves. A second contact portion (32) is formed between each of the rolling elements and the inner shaft, and the distance between the first contact portion and the symmetry plane of each rolling element of the two rows of axial grooves. (D1) is shorter than the distance (D2) between the second contact portion and the plane of symmetry, and the distance (D3) between the first contact portions of the two rows of axial grooves is outside the rolling element. The telescopic shaft (5) is characterized by being shorter than 1.5 times the diameter (Db).

In addition, the alphanumeric characters in parentheses represent corresponding components in the embodiments described later. The same applies hereinafter.
According to the present invention, two rows of axial grooves adjacent in the circumferential direction of the outer shaft are brought close to each other, and the minimum value of the distance between the axial grooves of the outer shaft with respect to the circumferential direction of the outer shaft is reduced. The maximum distance between the axial grooves on the outer shaft can be increased. That is, the maximum value (maximum span) of the span between the outer shaft and the first contact portion of each rolling element can be increased in the circumferential direction of the outer shaft. Thereby, the outer shaft can be easily bent in the radial direction. Therefore, the stress generated inside the outer shaft can be relaxed by bending the outer shaft in the radial direction. In this way, stress relaxation is achieved by increasing the flexibility in the radial direction of the outer shaft, so that the dimensional accuracy of the specifications of the outer shaft, inner shaft, rolling element, etc. is increased, and There is no need to reduce the load applied to the shaft, and the telescopic shaft can be easily manufactured. Further, since the outer shaft bends (displaces in the radial direction) in accordance with the pressing amount of the rolling element, the force with which the rolling element presses the outer shaft can be prevented from varying. Therefore, it is possible to reduce variations in slide resistance (resistance load generated when the inner shaft and the outer shaft are moved relative to each other as the telescopic shaft expands and contracts).

If the distance between the first contact portions of the two rows of axial grooves is 1.5 times or more the outer diameter of the rolling elements, the outer shaft and the first of the rolling elements in the circumferential direction of the outer shaft. As a result, it becomes difficult to sufficiently secure the flexibility of the outer shaft. Therefore, the upper limit of the distance between the first contact portions of the two rows of axial grooves was set as described above.
In the present invention, the distance between the first contact portions of the two rows of axial grooves may be shorter than the outer diameter of the rolling element. In this case, the maximum span between the first contact portions of the rolling elements in the circumferential direction of the outer shaft can be further increased, and the flexibility in the radial direction of the outer shaft can be further increased.

In the present invention, the rolling elements disposed in each of the two rows of axial grooves may be held by a common cage (33). In this case, each rolling element can be held at a desired position.
In the present invention, two pairs of the axial grooves in the two rows are provided, and these pairs may be arranged at equal intervals in the circumferential direction of the outer shaft. In this case, it is possible to connect the inner shaft and the outer shaft so that torque can be transmitted via the rolling elements without directly contacting the inner shaft and the outer shaft, and the slide resistance can be further reduced.

The present invention also provides a vehicle steering telescopic shaft (5) that transmits the steering torque of the steering member (2) using the telescopic shaft.
According to the present invention, there is an extendable part between the steering member and the steering mechanism (steering mechanism) that operates by receiving the steering torque from the steering member. Thereby, for example, when the telescopic shaft is used as an intermediate shaft disposed between the steering shaft and the steering mechanism, the intermediate shaft is moved when the steering mechanism is displaced with respect to the vehicle body by the input from the steering wheel. Can expand and contract to absorb this displacement and prevent excessive force from being applied to the steering shaft. Further, for example, when the telescopic shaft is used as a steering shaft, it is possible to reduce the impact given to the driver due to the shrinkage of the steering shaft when the vehicle collides.

Preferred embodiments of the present invention will be described with reference to the accompanying drawings.
1 is a schematic diagram of a steering device in which a telescopic shaft according to an embodiment of the present invention is applied to an intermediate shaft, FIG. 2 is a partial cross-sectional view of the intermediate shaft, and FIG. It is sectional drawing which follows an III-III line.
In the following, the case where the telescopic shaft is applied to an intermediate shaft of a vehicle steering (steering) device will be described. However, the present invention may be applied to a telescopic shaft used for other purposes.

  Referring to FIG. 1, a steering device 1 is connected to a steering shaft 3 having a steering member 2 such as a steering wheel (not shown) fixed at one end, and the steering shaft 3 and a universal joint 4 so as to be integrally rotatable. It has an intermediate shaft 5 as a telescopic shaft, 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 meshing with a pinion 7a provided on the pinion shaft 7. And a rack shaft 8 extending in the left-right direction of the vehicle. Tie rods 9 are coupled to both ends of the rack shaft 8, and each tie rod 9 is connected to a corresponding steering wheel 11 via a corresponding knuckle arm 10.

The rack shaft 8 is supported by a housing 12 via a bearing (not shown) so as to be movable in the axial direction. A steering mechanism A (steering mechanism) including a pinion shaft 7, a rack shaft 8, a tie rod 9, a knuckle arm 10 and a steered wheel 11 is configured.
When the steering member 2 is operated to generate a steering torque 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.

  Referring to FIGS. 1 and 2, the intermediate shaft 5 is, for example, a total ball-type ball spline shaft having no cage, and has a rod-shaped inner shaft 13 and a cylindrical outer shaft fitted to the inner shaft 13. The shaft 14 includes a plurality of rolling elements 15 interposed between the inner shaft 13 and the outer shaft 14. The inner shaft 13 and the outer shaft 14 are connected via a plurality of balls 15 so as to be relatively movable in the axial direction S of the inner shaft 13 (outer shaft 14) and capable of transmitting torque.

The inner shaft 13 is formed in an elongated shape in the axial direction S, and one end thereof is connected to the universal joint 4. The inner shaft 13 may be formed by a hollow shaft having a thickness of several mm, for example.
The outer shaft 14 is elongated in the axial direction S, and one end thereof is connected to the universal joint 6. The outer shaft 14 has a substantially circular cross section (annular shape). The thickness of the outer shaft 14 is, for example, several millimeters, and can be elastically deformed when subjected to an external force. The inner shaft 13 and the outer shaft 14 are partially fitted to each other on the other end side.

  2 and 3, outer peripheral surface 131 of inner shaft 13 has a circular cross section. On the outer peripheral surface 131 of the inner shaft 13 and the inner peripheral surface 141 of the outer shaft 14, axial grooves 16 and 17 extending in the axial direction S from the other end toward the one end are formed. The axial grooves 16 of the inner shaft 13 and the axial grooves 17 of the outer shaft 14 are provided in the same number (at least two pairs, four pairs in the present embodiment).

  Each axial groove 16 of the inner shaft 13 and the corresponding axial groove 17 of the outer shaft 14 are opposed to each other, and a track 18 is defined between them. In each track 18, the plurality of balls 15 are arranged in one row 19 arranged in the axial direction S (direction in which the axial grooves 16 and 17 extend). In each row 19, a plurality of (for example, five) balls 15 are provided and aligned in the axial direction S in the corresponding track 18. Grease as a lubricant is injected into each track 18 so that the contact portions between the balls 15 and the corresponding axial grooves 16 and 17 are lubricated.

When the inner shaft 13 and the outer shaft 14 move relative to each other in the axial direction S, the ball 15 rolls with respect to each of the inner shaft 13 and the outer shaft 14. Thereby, the slide resistance (resistance load generated when the inner shaft 13 and the outer shaft 14 are relatively moved in accordance with the expansion and contraction of the intermediate shaft 5) is reduced.
Stoppers 20 and 21 are provided on the other end of the inner shaft 13 and the other end of the outer shaft 14, respectively. The stoppers 20 and 21 are for preventing the balls 15 from being removed from the corresponding track 18 in the axial direction S.

One stopper 20 is formed of a retaining ring fitted in an outer peripheral groove at the other end of the inner shaft 13. The other stopper consists of a retaining ring fitted in the inner peripheral groove at the other end of the outer shaft 14.
One stopper 20 comes into contact with the ball 15 at one end of each row 19 when the intermediate shaft 5 is extended, and further axial movement of the ball 15 is restricted. When the shaft 5 is extended, the ball 15 at the other end of each row 19 comes into contact with the ball 15 to restrict further axial movement of the ball 15.

In each row 19, a contact angle is applied to the balls 15, and a preload is applied to the balls 15, whereby a clearance between the balls 15 and the corresponding inner shaft 13 and outer shaft 14 is obtained. And the play in the rotational direction between the inner shaft 13 and the outer shaft 14 via the ball 15 is restricted, and the torsional rigidity of the intermediate shaft 5 is increased.
Specifically, by interposing the ball 15 between the axial grooves 16 and 17, the outer shaft 14 is elastically deformed radially outward (elastically expanded), and an elastic restoring force is applied to the outer shaft 14. The contraction force by is generated. Thereby, the ball 15 is elastically held between the axial grooves 16 and 17 of the inner shaft 13 and the outer shaft 14 facing each other. That is, the ball 15 is elastically sandwiched between the axial grooves 16 and 17 facing each other by using the outer shaft 14 as an elastic body for preloading.

  The feature of the present embodiment is that the two rows of axial grooves 17, 17 provided on the outer shaft 14 are arranged close to each other so that the outer shaft 14 and each ball are in the circumferential direction C of the outer shaft 14. 15, the minimum value Dmin of the distance between the contact portions (the distance between the first contact portions 31 to be described later, hereinafter simply referred to as the span) is reduced, and the maximum value Dmax of the span is increased accordingly. In the radial direction R of the outer shaft 14, the flexibility is improved.

Specifically, the outer shaft 14 is formed with convex strips 22 as intervening strips extending in the axial direction S, and the two rows of the outer shaft 14 are sandwiched between the convex strips 22 in the circumferential direction C of the outer shaft 14. Axial grooves 17, 17 are adjacent to each other.
Two pairs of the axial grooves 17 and 17 of the two rows of the outer shaft 14 are provided, and these pairs are arranged at equal intervals (180 degrees apart) in the circumferential direction C of the outer shaft 14. Since the two rows of axial grooves 17 and 17 of the outer shaft 14 and the other two rows of axial grooves 17 and 17 have the same configuration, the following description will be given. The axial grooves 17 and 17 in the row will be mainly described.

The ridge 22 protrudes inward in the radial direction R from the inner peripheral surface 141 of the outer shaft 14, and the thickness of the portion including the ridge 22 in the outer shaft 14 does not include the ridge 22. It is thicker than the thickness of the part. The cross-sectional shape of the ridges 22 is a smooth curve having a mountain shape, and stress concentration is unlikely to occur.
The ridges 22 are formed so that the balls 15 arranged in the corresponding two rows of axial grooves 17 and 17 do not contact each other. The amount of protrusion of the ridges 22 in the radial direction R (the amount of protrusion from the inner peripheral surface 141 of the outer shaft 14) is, for example, approximately half of the outer diameter Db of the ball 15.

The two rows of axial grooves 17 and 17 (projections 22) of the outer shaft 14 are formed symmetrically with respect to a virtual symmetry plane 23 along the radial direction R of the outer shaft 14. The symmetry plane 23 includes the central axis 24 of the outer shaft 14 and includes the top 25 (tip portion) of the ridge 22.
The ridge 22 is formed with a pair of side portions 26 facing each other with the top portion 25 (symmetric surface 23) interposed therebetween, and these side portions 26 are continuous with the inner peripheral surface 141. The cross-sectional shape in the vicinity of the connecting portion between the side portion 26 of the ridge 22 and the inner peripheral surface 141 is a curve having a radius of curvature slightly larger than the radius Db / 2 of the ball 15, and is a shape corresponding to the ball 15. Yes. The two rows of axial grooves 17 and 17 of the outer shaft 14 include the side portions 26 of the ridge 22 and the inner peripheral surface 141 in the vicinity thereof.

The inner shaft 13 is formed with a groove 27 extending in the axial direction S and facing the protrusion 22 of the outer shaft 14 in the radial direction R. Two rows of axial grooves 16, 16 adjacent to each other of the inner shaft 13 are formed in the recess 27.
The concave stripe 27 is radially inward of the outer peripheral surface 131 of the inner shaft 13 and is formed in a symmetrical shape with the symmetry plane 23 as the center. With respect to the circumferential direction C, the concave stripes 27 have a longer circumferential length than the convex stripes 22. The bottom portion 28 of the concave stripe 27 has a shape in which the central portion in the circumferential direction C protrudes outward in the radial direction R from both side portions thereof.

  Each of the pair of side portions 29 of the recess 27 is smoothly connected to the bottom portion 28 and the outer peripheral surface 131 of the inner shaft 13. The cross-sectional shape in the vicinity of the connecting portion between the bottom portion 28 of the concave stripe 27 and each side portion 29 is a curve having a radius of curvature slightly larger than the radius Db / 2 of the ball 15 and is a shape corresponding to the ball 15. . The two rows of axial grooves 16, 16 of the inner shaft 13 include the side portions 29 of the recess 27 and the bottom portion 28 in the vicinity thereof.

  With the above configuration, the first contact portions 31 are formed between the balls 15 of the two axial grooves 17, 17 in the two rows of the outer shaft 14 and the corresponding side portions 26 of the ridges 22. A second contact portion 32 is formed between each of the balls 15 of the two axial rows 17 and 17 of the outer shaft 14 and the corresponding side portion 29 of the recess 27 of the inner shaft 13. Yes. In this way, each ball 15 is in a two-point angular contact that makes contact with the corresponding axial grooves 16 and 17 of the inner shaft 13 and the outer shaft 14, respectively.

  The distance (straight line distance) between the first contact portion 31 of each ball 15 of the two axial grooves 17 and 17 of the outer shaft 14 and the symmetry plane 23 is a predetermined distance D1. . Similarly, the distance (linear distance) between the second contact portion 32 of each ball 15 and the symmetry plane 23 is a predetermined distance D2. The distance D1 is shorter than the distance D2 (D1 <D2). Thereby, the inclination with respect to the symmetry plane 23 of the straight line passing through the first and second contact portions 31 and 32 of each ball 15 is opposite to each other on one side and the other side of the two rows of axial grooves 17 and 17. It has become.

Further, the distance D3 (linear distance) between the first contact portions 31 of the two axial grooves 17 and 17 of the outer shaft 14 is shorter than 1.5 times the outer diameter Db of the ball 15 (D3 <1). .5Db).
When the distance D3 is 1.5 times or more the outer diameter Db of the ball 15 (D3 ≧ 1.5 Db), the outer shaft 14 and the first contact portion 31 of each ball 15 between the outer shaft 14 and the circumferential direction C of the outer shaft 14. The minimum value Dmin of the span is increased, and as a result, it is difficult to sufficiently secure the flexibility of the outer shaft 14. Therefore, the upper limit of the distance D3 is set in this way.

The distance D3 between the first contact portions 31 is equal to or less than the outer diameter Db of the ball 15 (including a length shorter than Db), and each of the two rows of the axial grooves 17 and 17 of the outer shaft 14. It is preferable that the values are such that the balls 15 do not contact each other.
As described above, according to the present embodiment, the two rows of the axial grooves 17 and 17 adjacent to the circumferential direction C of the outer shaft 14 are brought close to each other, and the axial groove 17 of the outer shaft 14 with respect to the circumferential direction C. , 17 can be made smaller to increase the maximum value of the distance between the axial grooves 17 of the outer shaft 14.

That is, the maximum value Dmax (maximum span) of the span between the outer shaft 14 and the first contact portion 31 of each ball 15 in the circumferential direction C of the outer shaft 14 can be increased. Thereby, the outer shaft 14 can be easily bent in the radial direction R.
Therefore, the prestress is applied to the ball 15 by the elastic restoring force of the outer shaft 14 (contraction force in the radial direction R), and the stress generated in the outer shaft 14 can be relaxed by bending the outer shaft 14 in the radial direction R. In this way, stress relaxation is achieved by increasing flexibility in the radial direction R of the outer shaft 14, so that the dimensional accuracy of the specifications of the outer shaft 14, the inner shaft 13, the ball 15, etc. is increased, and the ball It is not necessary to reduce the load applied from 15 to the outer shaft 14, and the intermediate shaft 5 can be easily manufactured.

Further, since the outer shaft 14 bends (displaces in the radial direction R) according to the pressing amount of the ball 15, it is possible to prevent the force with which the ball 15 presses the outer shaft 14 from varying. Therefore, variation in slide resistance can be reduced.
Furthermore, by making the distance D3 between the first contact portions 31 and 31 of the outer shaft 14 shorter than the outer diameter Db of the ball 15, the first contact portion 31 of the ball 15 with respect to the circumferential direction C of the outer shaft 14. The maximum value Dmax of the span between them can be made longer, and the flexibility in the radial direction R of the outer shaft 14 can be further increased.

Two pairs of axial grooves 17 and 17 in two rows of the outer shaft 14 are provided, and these pairs are arranged at equal intervals in the circumferential direction C of the outer shaft 14. Thereby, it is possible to connect the inner shaft 13 and the outer shaft 14 so that torque can be transmitted via the ball 15 without directly contacting the inner shaft 13 and the outer shaft 14, and the slide resistance can be further reduced.
Furthermore, by providing the intermediate shaft 5, an extendable part exists between the steering member 2 and the steering mechanism A that operates by receiving the steering torque from the steering member 2. Thereby, when the steering mechanism A is displaced with respect to the vehicle body by the input from the steering wheel 11, the intermediate shaft 5 can be expanded and contracted to absorb this displacement, and an excessive force can be prevented from being applied to the steering shaft 3. .

Moreover, the protruding item | line 22 protrudes from the internal peripheral surface 141 of the outer shaft 14, is easy to make the protruding item | line 22 oppose heating means, such as a high frequency coil, and is easy to heat the protruding item | line 22 locally. Therefore, it is easy to locally quench (inductively quench) only the axial groove 17 in the outer shaft 14.
Furthermore, since the cross section of the outer shaft 14 has a circular shape, the outer shaft 14 can be formed into a shape in which stress concentration hardly occurs. Further, the outer shaft 14 can be easily formed with a simple shape. Further, typically, a vehicle is provided with a through hole through which the intermediate shaft 5 passes through the bulkhead of the vehicle body, and a floor seal (seal member) is attached between the through hole and the outer shaft 14 of the intermediate shaft 5. ing.

The floor seal is usually formed in an annular shape and is disposed between the peripheral edge of the through hole and the outer peripheral surface of the outer shaft 14, but the outer periphery of the outer shaft 14 can be matched to the inner peripheral shape of the floor seal. it can. That is, a commonly used annular floor seal can be used as it is, and the cost can be reduced.
FIG. 4 is a cross-sectional view of a main part of another embodiment of the present invention, and FIG. 5 is a cross-sectional view taken along the line VV of FIG. In the following description, differences from the embodiment shown in FIGS. 1 to 3 will be mainly described, and the same components are denoted by the same reference numerals and description thereof will be omitted.

Referring to FIGS. 4 and 5, the feature of the present embodiment is that the balls 15 disposed in the two axial grooves 17, 17 of the outer shaft 14 are each a cage 33 that is common to each other. It is in a held point.
The retainer 33 is made of, for example, a synthetic resin and includes a plate-shaped main body 34. The main body 34 is formed long in the axial direction S and straddles between the two axial grooves 17 and 17 provided in the outer shaft 14. A plurality of notches 35 are formed in the main body 34 corresponding to the balls 15.

Corresponding balls 15 are respectively held in these notches 35. Each notch 35 is opened to a corresponding edge of the main body 34 in the circumferential direction C. Each notch 35 is provided with a pair of clamping parts 36 that clamp the corresponding balls 15 in the axial direction S (only one clamping part 36 in the axial direction S is shown in FIG. 4).
The inclination of the straight line L passing between the first and second contact portions 31 and 32 of each ball 15 with respect to the symmetry plane 23 is opposite to each other on one side and the other side of the two rows of axial grooves 17 and 17. Yes.

Therefore, when the intermediate shaft 5 receives one torque in the rotational direction, the balls 15 in either one of the two axial grooves 17 and 17 of the outer shaft 14 out of the balls 15 are A clamping force is received from the outer shaft 14.
Similarly, when the intermediate shaft 5 receives the other torque in the rotational direction, of the balls 15, the balls 15 in the other of the two rows of axial grooves 17, 17 of the outer shaft 14 are connected to the inner shaft 13 and the outer shaft 15. A clamping force is received from the shaft 14.

Therefore, when a torque is applied to the intermediate shaft 5, the ball 15 in one of the two axial grooves 17 and 17 receives the clamping force from the inner shaft 13 and the outer shaft 14 and holds its position. The other ball 15 is also held in its position via the holder 33. Therefore, each ball 15 can be reliably held at a desired position.
The present invention is not limited to the above embodiments. For example, two pairs of the axial grooves 17 and 17 of the outer shaft 14 may be provided in only one pair, or may be provided in three or more pairs. Alternatively, an annular spring member (ring spring) may be attached to the outer periphery of the outer shaft 14 so that the spring 15 applies a preload to the ball 15 with a force that binds the outer shaft 14.

  Furthermore, the telescopic shaft of the present invention may be applied to a steering shaft. In this case, the steering member is fixed to one of the inner shaft and the outer shaft of the steering shaft, and the other is connected to the intermediate shaft via the universal joint so as to be integrally rotatable. Thus, if the vehicle collides, the driver collides with the steering member (secondary collision), and an impact load is applied to the steering shaft, the steering shaft contracts to reduce the impact given to the driver. Can do.

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. It is a partial cross section figure of an intermediate shaft. It is sectional drawing which follows the III-III line of FIG. It is sectional drawing of the principal part of another embodiment of this invention. It is sectional drawing which follows the VV line of FIG.

Explanation of symbols

2 ... steering member, 5 ... intermediate shaft (expandable shaft), 13 ... inner shaft, 14 ... outer shaft, 15 ... ball (rolling element), 16, 17 ... axial groove, 19 ... row, 22 ... projection ( Intervening strip), 23 ... symmetrical surface, 26 ... (protruding strip) side portion, 31 ... first contact portion, 32 ... second contact portion, 33 ... cage, 131 ... outer peripheral surface (inner shaft), 141 ... inner peripheral surface (outer shaft), C ... circumferential direction, D1 ... distance between first contact portion and symmetry surface, D2 ... distance between second contact portion and symmetry surface, D3 ... Distance (between first contact portions), Db ... outer diameter of ball, R ... radial direction, S ... axial direction.

Claims (5)

An inner shaft and a cylindrical outer shaft fitted together so as to be relatively movable in the axial direction and capable of transmitting torque to each other;
An axial groove formed on each of the outer peripheral surface of the inner shaft and the inner peripheral surface of the outer shaft and facing each other;
A rolling element interposed between the axial grooves of the inner shaft and the outer shaft and receiving preload from the inner shaft and the outer shaft,
The axial groove of the outer shaft includes two rows of axial grooves adjacent to each other with an interposed strip formed so as to extend in the axial direction on the inner periphery of the outer shaft in the circumferential direction of the outer shaft,
These two rows of axial grooves are symmetrical with respect to each other about a plane of symmetry along the radial direction of the outer shaft,
The rolling elements are arranged in rows in each of the two rows of axial grooves,
A first contact portion is formed between each of the rolling elements of the two rows of axial grooves and a corresponding side portion of the interposition strip,
A second contact portion is formed between each of the rolling elements of the two rows of axial grooves and the inner shaft,
The distance between the first contact portion and the symmetry plane of each rolling element of the two rows of axial grooves is shorter than the distance between the second contact portion and the symmetry plane,
The telescopic shaft, wherein a distance between the first contact portions of the two rows of axial grooves is shorter than 1.5 times the outer diameter of the rolling element.   2. The telescopic shaft according to claim 1, wherein a distance between the first contact portions of the two rows of axial grooves is shorter than an outer diameter of the rolling element.   3. The telescopic shaft according to claim 1, wherein the rolling elements disposed in each of the two rows of axial grooves are held by a common cage.   The telescopic shaft according to any one of claims 1 to 3, wherein two pairs of the axial grooves in the two rows are provided, and these pairs are arranged at equal intervals in the circumferential direction of the outer shaft. . A telescopic shaft for steering a vehicle that transmits a steering torque of a steering member using the telescopic shaft according to any one of claims 1 to 4.

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