JP2005344747A - Power transmission shaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power transmission shaft for achieving high durability with a smaller size and a lighter weight. <P>SOLUTION: The power transmission shaft comprises an inner shaft 13 and an outer shaft 14 connected to each other in a rotating direction T via a plurality of balls 21 as power transmission elements which are laid between the inner shaft 13 and the cylindrical outer shaft 14 fitted to each other with an intermediate shaft 2, and a gutter-shaped plate member 22 as an energizing member for energizing the balls 21 to a radially outward direction R1 of the inner shaft 13. The plate member 22 with a raceway groove 19 formed includes a receiving portion 27 for rollingly receiving the balls 21, the receiving portion 27 having the most building amount. Thus, stress on the receiving portion 27 is suppressed to achieve high durability. The plate member 22 has a more building amount in part, and so a weight is less increased with the stress being suppressed to achieve a smaller size. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power transmission shaft used for, for example, a steering device of an automobile.

  Some power transmission shafts have, for example, an inner shaft and a cylindrical outer shaft that are fitted to each other, and both shafts are connected by a spline joint. The spline joint includes a groove-like track provided on the outer shaft and the inner shaft and extending in the axial direction, and a plurality of balls interposed between the tracks. Torque is transmitted by providing play to the ball, and the ball is urged by the urging member to suppress the occurrence of rattling in the rotational direction.

The conventional first power transmission shaft has a recess formed on the inner shaft or the outer shaft corresponding to the track, and a track member that fits in the recess and forms the track described above. The urging member uses an elastic body interposed between the recess and the raceway member (see, for example, Patent Documents 1 and 2).
Moreover, the conventional 2nd power transmission shaft has the above-mentioned concave strip and a raceway member, and elastically deforms and uses the above-mentioned raceway member as an urging member. For example, the track member is formed by a plate member having a bowl shape and a constant thickness, and flexing the ball in a flexible manner by bending the central portion in the width direction while supporting both end portions in the width direction. Energize (see, for example, Patent Documents 3, 4, and 5).
JP 2001-50293 A Japanese Utility Model Publication No. 45-19207 JP 2003-291824 A JP 2003-336658 A German Patent No. DE37030393C2

By the way, when trying to apply the above-mentioned power transmission shaft to an intermediate shaft of an automobile steering device, in order to ensure high torsional rigidity, the ball is biased with a high biasing force, and the above-mentioned spline joint There is a demand for miniaturization.
However, in the conventional first power transmission shaft, since the race member and the biasing member are separate, the entire size is increased.

  Further, in the conventional second power transmission shaft, the urging member locally contacts the ball, so that the reaction force from the ball tends to concentrate. In addition to this, the tendency of concentration of reaction force is strengthened for miniaturization, and the amount of elastic deformation tends to be increased in order to obtain a high biasing force. As a result, high stress is generated in the biasing member. Therefore, for example, even if the urging member is a high-strength member, the safety factor tends to be low, and there is a concern that durability under severe use conditions may be reduced.

Further, in the conventional second power transmission shaft, it is conceivable to form the urging member with a thick plate in order to suppress the stress. However, in this case, the weight increases, which is not preferable.
Furthermore, there is a demand for a power transmission shaft that is not limited to the above-described intermediate shaft, and that can achieve a small size and high durability while suppressing an increase in weight.
Accordingly, an object of the present invention is to provide a power transmission shaft that is small in size, can achieve high durability, and can suppress an increase in weight.

  The power transmission shaft of the present invention is the power transmission shaft in which the inner shaft and the outer shaft are connected in the rotational direction via a power transmission element interposed between the inner shaft and the cylindrical outer shaft fitted together. An urging member for urging the transmission element in the radial direction of the inner shaft, the urging member includes a bowl-shaped plate member having a receiving portion for receiving the power transmission element, and the thickness of the receiving portion of the plate member is The amount of the meat other than the receiving portion is larger.

  According to this invention, it is preferable for reducing the size of the power transmission shaft by using the urging member while the plate member forms the receiving portion. In the receiving part of the plate member, the bending moment becomes the largest, but since the thickness of the receiving part is maximized, the stress in the receiving part can be suppressed and high durability can be achieved. Since the thickness of the plate member is partially increased, an increase in weight can be suppressed and a reduction in size can be achieved while suppressing stress.

In the present invention, the plate thickness of the receiving portion of the plate member may be thicker than the plate thickness of the portion other than the receiving portion. In this case, bending stress can be suppressed, and the power transmission shaft can be reduced in size and weight.
The plate member includes a pair of supported portions provided at a pair of widthwise ends, and the plate thickness of the plate member is gradually increased from each supported portion toward the corresponding receiving portion. There is a case. In this case, a change in bending stress between each supported portion and the corresponding receiving portion can be suppressed, and for example, the bending stress can be made substantially constant. Therefore, the thickness of the portion from each supported portion to the corresponding receiving portion can be set to a value that is not excessive or insufficient while suppressing the stress to be small.

The receiving part includes a pair of receiving parts provided on both sides of the center position between the pair of supported parts, and the plate thickness of the plate member increases from each receiving part toward the center position. It may become thinner gradually. In this case, the plate member can be easily bent, and the urging force can be increased while suppressing an increase in stress.
The plate member may include a through hole provided in a portion excluding the receiving portion. In this case, since the amount of meat can be adjusted by the through hole, for example, a plate member having a constant plate thickness can be used. Moreover, it can be easily bent by the through hole.

  The plate thickness of the plate member may be constant. In this case, the plate member can be formed inexpensively using an inexpensive member having a constant plate thickness.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing a schematic configuration of a vehicle steering apparatus to which a power transmission shaft according to an embodiment of the present invention is applied.
In the present embodiment, the power transmission shaft will be described based on the case where the power transmission shaft is the intermediate shaft 2 of the vehicle steering apparatus 1. However, the present invention is not limited to this, for example, other than the vehicle steering apparatus as described later. It can also be applied to a device.

  Referring to FIG. 1, a vehicle steering apparatus 1 has an intermediate shaft 2 as a power transmission shaft. The intermediate shaft 2 is also called an intermediate shaft, and is provided between a steering shaft 4 connected to the steering wheel 3 and a steering mechanism 5 for steering a wheel (not shown). The intermediate shaft 2 serves to transmit the steering torque applied to the steering wheel 3 to steer the wheels from the steering shaft 4 to the input shaft 6 of the steering mechanism 5.

  The vehicle steering apparatus 1 includes the above-described steering shaft 4 that transmits steering torque, and a steering column 7 that rotatably supports the steering shaft 4 through the inside. The steering wheel 3 is connected to one end of the steering shaft 4, and the input shaft of the steering mechanism 5 is connected to the other end via the first universal joint 8, the intermediate shaft 2, and the second universal joint 9. 6 are connected. When the steering wheel 3 is steered, the steering torque is transmitted to the steering mechanism 5 via the steering shaft 4 or the like, and thereby the wheel can be steered.

  Further, the steering column 7 is provided with an electric motor 10 for assisting steering, and a speed reducer 11 as a transmission mechanism for transmitting the output rotation of the electric motor 10 to the lower shaft 4a of the steering shaft 4. . The electric motor 10 and the speed reducer 11 are supported by the steering column 7. The electric motor 10 can obtain a steering assist force corresponding to the steering torque, the vehicle speed, and the like. Further, in the vehicle steering device 1, the intermediate shaft 2 is configured to be extendable and retractable so as to absorb the change in the position of the steering mechanism 5 that occurs during traveling or assembly.

The intermediate shaft 2 has a shaft shape and is capable of expanding and contracting in the axial direction S1 and capable of transmitting torque, and is provided at one end of the spline joint 12 to form a first universal joint 8. And a connecting portion 9a provided at the other end of the spline joint 12 to form the second universal joint 9.
The spline joint 12 has an inner shaft 13 and a cylindrical outer shaft 14 that are fitted together so as to be able to transmit torque. The inner shaft 13 and the outer shaft 14 are arranged so that the central axes coincide with each other. Parts of the inner shaft 13 and the outer shaft 14 in the axial direction S1 are fitted together with play between each other.

  2 and 3, in this embodiment, the spline joint 12 can rigidly connect the inner shaft 13 and the outer shaft 14 in the rotational direction T1 (also referred to as a circumferential direction) so that torque can be transmitted. A rigid connecting element 15 and an elastic connecting element 16 that elastically connects the inner shaft 13 and the outer shaft 14 in the rotational direction T1 are provided. Both the rigid connecting element 15 and the elastic connecting element 16 allow relative movement in the axial direction S1 of the inner shaft 13 and the outer shaft 14.

The rigid connecting element 15 has a plurality of pairs of concave stripes 17 and convex stripes 18 as spline teeth that can be engaged with each other. The recess 17 is formed on the inner shaft 13 and extends in the axial direction S1. The ridges 18 are formed on the outer shaft 14 so as to face the ridges 17 and extend in the axial direction S1. A predetermined amount of play is provided between the pair of concave stripes 17 and convex stripes 18 in the circumferential direction.
The elastic connecting element 16 is provided at a position where the inner shaft 13 and the outer shaft 14 face each other, and a plurality of pairs (for example, three pairs) of track grooves 19 and 20 as tracks extending in the axial direction S1, and each pair of track grooves. A plurality of power transmission elements and rolling balls 21 (only part of which are shown) respectively interposed between 19 and 20 and a plurality of corresponding balls 21 held between the pair of raceway grooves 19 and 20 are provided on the inner shaft. And a plate member 22 as an urging member for urging the diametrically outward R1.

The plate member 22 has a bowl shape (inverted Ω shape). The inner shaft 13 is formed with a holding groove 23 extending in the axial direction S1 for holding each plate member 22. The inner shaft 13 and the outer shaft 14 are elastically connected in the rotational direction T1 through a plurality of balls 21.
The holding groove 23 of the inner shaft 13 is formed by a pair of edge portions 24 serving as support portions extending in parallel with the axial direction S1, and corresponding portions 25a of the plate member 22 or portions 25a in the vicinity of the edge portion 25 are supported. (See FIG. 4). The edge 25 is supported when a large transmission torque is applied, and the portion 25a in the vicinity of the edge 25 is supported when the transmission torque is not applied or small. Further, a predetermined amount of gap is provided between the inner surface of the holding groove 23 and the plate member 22.

  In the intermediate shaft 2, when no transmission torque is applied between the inner shaft 13 and the outer shaft 14, or when a transmission torque of a predetermined value or less is applied, the plate member 22 of the elastic coupling element 16 causes the intermediate shaft 2 to radially outward. The inner shaft 13 and the outer shaft 14 are elastically connected to each other in the circumferential direction via a ball 21 elastically biased toward R1. By connecting only through the elastic connecting element 16, the relative movement resistance of the inner shaft 13 and the outer shaft 14 in the axial direction S1 is reduced. When a transmission torque of a predetermined value or less is applied, the torque is transmitted between the inner shaft 13 and the outer shaft 14 only through the elastic connecting element 16. When a large transmission torque is applied exceeding a predetermined value, the plate member 22 is bent and the shafts 13 and 14 are rotated relative to each other by a minute amount so that the shafts 13 and 14 are rigidly connected via the rigid connecting element 15. Connected. At this time, the elastic connecting element 16 also contributes to torque transmission between the shafts 13 and 14.

The plurality of balls 21 are made of steel balls having the same diameter. For each pair of raceway grooves 19 and 20, a plurality of balls 21 are held by a cage 26 and lined up in the axial direction S1.
Referring to FIG. 4, the raceway groove 20 is formed of a concave line formed integrally with the inner peripheral surface of the outer shaft 14. The concave stripe extends in the axial direction S1 by a predetermined length and has a pair of inclined surfaces inclined with respect to the radial direction. Each of the pair of inclined surfaces has a pair of guide portions 20 a that guide the rolling of the ball 21. The pair of guide portions 20a are spaced apart from each other in the circumferential direction in the cross section and are disposed to face each other, and both extend parallel to the axial direction S1. The pair of guide portions 20a restricts the relative movement of the ball 21 to the radially outer side R1 and both sides in the circumferential direction.

  The raceway groove 19 is formed of a concave line defined by the inner surface of the bowl-shaped plate member 22. The concave stripe extends in the axial direction S1 by a predetermined length and has a pair of inclined surfaces inclined with respect to the radial direction. The pair of inclined surfaces have a pair of guide portions 19 a that guide the rolling of the ball 21. The pair of guide portions 19a are spaced apart from each other in the circumferential direction in the cross section and are disposed to face each other, and both extend parallel to the axial direction S1. The pair of guide portions 19a restricts the relative movement of the ball 21 toward the radially inner side R2 and both sides in the circumferential direction.

The pair of guide portions 19 a of the raceway groove 19 and the pair of guide portions 20 a of the raceway groove 20 face each other with a plurality of balls 21 interposed therebetween. As the plurality of balls 21 rolls between the pair of guide portions 19a of the raceway groove 19 and the pair of guide portions 20a of the raceway groove 20, the balls 21 move along the axial direction S1, and the inner shaft 13 and the outer The shaft 14 moves relative to the axial direction S1.
The plate member 22 is formed by a plate spring having a bowl shape. The plate member 22 includes a pair of receiving portions 27 that receive the balls 21 between the pair of edge portions 25, 25 described above. Further, the plate member 22 has an engaging portion (not shown) that engages with the inner shaft 13, and by the action of this engaging portion, the relative movement of the plate member 22 with respect to the inner shaft 13 in the axial direction S <b> 1 is performed. It is regulated.

The surface of each receiving portion 27 includes the above-described guide portion 19 a that guides the rolling of the ball 21. The pair of receiving portions 27 are arranged to be separated from each other on both sides of the center position 28 between the pair of edge portions 25 in the width direction W1 of the plate member 22. More specifically, the pair of receiving portions 27 are arranged at positions that divide the bowl-shaped portion of the plate member 22 into approximately three equal parts.
In the present embodiment, the thickness of the receiving portion 27 of the plate member 22 is the largest, and the remaining portions other than the receiving portion 27, for example, the width direction end portion 22a and the meat portions of the vicinity portion 22b of the central position 28, respectively. Has been more than the amount. The thickness of each part is compared with the thickness per unit length in the direction in which the plate member 22 extends in the cross section. In the present embodiment, the thickness of each part is set to a desired amount by adjusting the thickness of the plate member 22.

  FIG. 5 is a graph showing the relationship between the plate thickness L of the plate member 22 and the distance P from the edge 25 in the width direction. In this graph, the plate thickness L at a predetermined position is shown on the vertical axis, and the distance P from one edge to the predetermined position in the width direction is shown on the horizontal axis. The value P1 of the distance P is the distance to one receiving portion 27 corresponding to one edge 25, the value P2 is the distance to the central position 28, the distance P3 is the distance to the other receiving portion 27, and the distance P4 is the other The distance to the edge 25 is shown.

  4 and 5, the plate thickness L of the plate member 22 is gradually increased from each edge portion 25 toward the corresponding receiving portion 27 (P0 to P1, P3 to P4). The portion 27 is thickest. Specifically, the relationship between the distance P from one edge 25 to a predetermined position along the width direction W1 and the plate thickness L at the predetermined position includes a portion that satisfies the parabolic function relationship. For example, the relationship between the parabolic functions is satisfied between the portion adjacent to the edge portion 25 and the corresponding receiving portion 27. In this relationship, the bending stress generated in the plate member 22 can be made constant.

Further, the plate thickness L of the plate member 22 is gradually reduced from each receiving portion 27 toward the central position 28 (P1 to P2, P2 to P3).
The plate thickness value L1 of the receiving portion 27 of the plate member 22 is thicker than the plate thickness value L2 of the edge portion 25 of the width direction end portion 22a (L1> L2), and the plate thickness of the portion 22b passing through the central position 28. It is thicker than the value L3 (L1> L3). This value L3 is larger than the value L2 (L3> L2).

The plate member 22 forms, for example, a plate material (not shown) as an intermediate for production in which the plate thickness is changed to a desired value in the width direction by rolling as plastic processing, and this plate material is bent. Thus, it can be obtained by forming it into a bowl shape. The plate member 22 can be obtained with high strength by plastic working, which is preferable.
As described above, in the present embodiment, the plate member 22 is also preferable to reduce the size of the intermediate shaft 2 by forming the receiving portion 27 as the track member and also serving as the urging member. In addition, the bending moment is the largest in the receiving portion 27 of the plate member 22, but since the thickness of the receiving portion 27 is maximized, the stress in the receiving portion 27 can be suppressed and high durability can be achieved. it can. Since the thickness of the plate member 22 is partially increased, an increase in weight can be suppressed and a reduction in size can be achieved while suppressing stress. Further, since the stress can be suppressed, the selection range of materials that can be used for the plate member 22 can be widened.

Further, the plate thickness L1 of the receiving portion 27 of the plate member 22 is the thickest, that is, thicker than the plate thickness of the portion other than the receiving portion 27. In this case, bending stress can be suppressed, and the intermediate shaft 2 can be reduced in size and weight.
The plate thickness L of the plate member 22 is gradually increased from each edge portion 25 toward the corresponding receiving portion 27. Thereby, the change of the bending stress in the part 22c between each edge part 25 and the receiving part 27 corresponding can be suppressed, for example, a bending stress can be made substantially constant. Therefore, the plate thickness of the portion 22c from each edge 25 to the corresponding receiving portion 27 can be set to a value that is not excessive or insufficient while suppressing the stress to be small.

The plate thickness L of the plate member 22 is gradually reduced from each receiving portion 27 toward the central position 28. In this case, the plate member 22 can be easily bent, and the urging force can be increased while suppressing an increase in stress.
When the rigid coupling element 15 and the elastic coupling element 16 are used in combination, the transmission torque carried by the elastic coupling element 16 can be made smaller than the transmission torque carried by the entire intermediate shaft 2. Can be miniaturized.

The plate member 22 is accommodated in the holding groove 23 of the inner shaft 13 without being provided on the outer shaft 14. In this case, it is preferable because the intermediate shaft 2 can be reduced in size in the radial direction.
In the intermediate shaft 2 described above, the torsional rigidity can be increased, so that the driver does not feel rattling or the torsional rigidity is insufficient in the vehicle steering apparatus 1, and the steering stability can be improved. . Further, in the electric power steering apparatus in which the steering assisting electric motor 10 is provided in the steering column 7, the transmission torque of the intermediate shaft 2 and thus the stress tends to increase, but the stress that tends to increase is intermediate in the present embodiment. It can be suppressed by the shaft 2, which is preferable.

Moreover, the following modifications can be considered about this embodiment. In the following description, differences from the above-described embodiment will be mainly described, description of similar configurations will be omitted, and in the case of illustration, corresponding parts are denoted by the same reference numerals.
A modification of the plate member 22 will be described with reference to FIG. In the graph of FIG. 6, the values P1, P2,... Of the distance P on the vertical axis, the horizontal axis, and the horizontal axis are shown as in FIG. In the plate member 22 shown in FIG. 6, in the part between a pair of receiving parts 27 (P1-P3), the plate | board thickness L of the plate member 22 is made constant (for example, L1), and the amount of meat is made constant. In this case, the stress generated between the pair of receiving portions 27 can be made constant.

  In addition, the plate thickness L of the plate member 22 between each edge portion 25 and the corresponding receiving portion 27 is, for example, the distance from the edge portion 25 to the predetermined position in the width direction W1 and the plate thickness at the predetermined position. It is also conceivable that the relationship satisfies a relationship other than a parabolic function, for example, a linear function. It is also conceivable that the plate thickness L of the portion from each edge 25 to the corresponding receiving portion 27 is set to a constant value L1, and the plate thickness of the tip side portion from the edge 25 is made thin.

  Referring to FIG. 7, the plate member 22 </ b> A includes a through hole 29 provided in a portion excluding the receiving portion 27 (illustrated by a one-dot chain line), for example, an end portion 22 a and a vicinity portion 22 b of the central position 28. You may make it. In this case, the thickness of the receiving portion 27 of the plate member 22A is maximized, and is equal to the thickness of the receiving portion 27 of the plate member 22 described above. Since the thickness can be adjusted by the through hole 29, a plate member having a constant plate thickness can be used. For example, the plate thickness of the plate member 22A is a constant value L1 regardless of the position, whereby the plate member 22A can be formed inexpensively using an inexpensive member with a constant plate thickness. Further, the plate member 22 </ b> A can be easily bent by the through hole 29. As the through-hole 29, the periphery of the through-hole 29 may be closed, or a part of the periphery of the through-hole may be open to the outside to form a notch shape.

In addition to providing the plate members 22, 22 </ b> A on the inner shaft 13, it is conceivable to provide the plate members 22, 22 </ b> A on the outer shaft 14, and it may be provided on at least one of the inner shaft 13 and the outer shaft 14.
Further, the power transmission element is not limited to the ball 21, and is, for example, a roller as a rolling element, an abacus ball-shaped rolling element, that is, a rotating body-shaped rolling element whose cross-sectional shape including an axis is a rhombus, It is also conceivable to use one in which each piece is formed by a convex curve line.

  Further, the power transmission shaft of the present embodiment may be applied to a power transmission shaft including an inner shaft and an outer shaft that are connected to each other without being relatively moved in the axial direction S1. For example, in the above-described spline joint, this corresponds to a case where the elastic coupling element includes a power transmission element having a columnar shape extending in the axial direction S1 instead of the ball 21. Also in this case, the effect of reducing the stress can be obtained by increasing the thickness of the receiving portion of the plate member.

  In addition to the intermediate shaft 2 of the vehicle steering apparatus 1, the power transmission shaft of the present embodiment may be applied to various industrial machines and devices. In addition, various design changes can be made within the scope of matters described in the claims.

It is a mimetic diagram showing a schematic structure of a steering device for vehicles to which a power transmission shaft of one embodiment of the present invention is applied. It is a partial longitudinal cross-sectional view of the principal part of the intermediate shaft shown in FIG. It is III-III sectional drawing of the intermediate shaft shown in FIG. FIG. 4 is an enlarged cross-sectional view of a main part of the intermediate shaft shown in FIG. 3. It is a graph which shows the relationship between plate | board thickness L in the predetermined position of the board member shown in FIG. 3, and the distance P to the predetermined position from the edge part about the width direction. It is a graph which shows the relationship between plate | board thickness L in the predetermined position, and the distance P to the predetermined position from the edge part about the width direction about the modification of the plate member of this invention. It is a partial cross section perspective view which shows the other modification of the board member of this invention.

Explanation of symbols

2 Intermediate shaft (power transmission shaft)
13 Inner shaft 14 Outer shaft 21 Ball (power transmission element)
22 Plate member (biasing member)
22A Plate member (biasing member)
22a End (part excluding receiving part, part other than receiving part)
22b part (parts other than the receiving part, parts other than the receiving part)
25 Edge (supported part)
27 Receiving portion 28 Center position 29 Through hole L Plate member thickness L1 Receiving portion plate thickness R1 Radially outward R2 Radially inward T1 Rotating direction W1 Width direction

Claims (6)

In the power transmission shaft in which the inner shaft and the outer shaft are connected in the rotational direction via a power transmission element interposed between the inner shaft and the cylindrical outer shaft fitted together.
An urging member for urging the power transmission element in the radial direction of the inner shaft;
The biasing member includes a bowl-shaped plate member having a receiving portion for receiving a power transmission element,
A power transmission shaft, wherein a thickness of a receiving portion of the plate member is larger than a thickness of a portion other than the receiving portion.   The power transmission shaft according to claim 1, wherein the plate thickness of the receiving portion of the plate member is thicker than the plate thickness of a portion other than the receiving portion.   3. The power transmission shaft according to claim 2, wherein the plate member includes a pair of supported portions respectively provided at a pair of end portions in the width direction, and a plate thickness of the plate member is received from each supported portion. A power transmission shaft characterized by being gradually thickened toward the part.   The power transmission shaft according to claim 3, wherein the receiving portion includes a pair of receiving portions provided on both sides sandwiching a central position between the pair of supported portions, and the plate thickness of the plate member is A power transmission shaft that is gradually made thinner from each receiving portion toward the center position.   The power transmission shaft according to claim 1, wherein the plate member includes a through hole provided in a portion excluding the receiving portion. 6. The power transmission shaft according to claim 5, wherein the plate member has a constant plate thickness.

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