JP2007255533A - Connection structure of yoke and shaft of universal joint and power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent play of a connection structure of a yoke and a shaft of a universal joint. <P>SOLUTION: This connection structure 22 has a fitting part 26 of the yoke 18 of the universal joint 10, an end part 3b of the shaft 3, and a bolt 24 as a shaft member for tightening and fixing the end part 3b. The bolt 24 passes through shaft insertion holes 30, 31, 32 of the yoke 18 and the shaft 3 and is screwed into a nut 25 to tighten and fix the shaft 3 between a pair of flat plates 27 and 28 of the yoke 18. Since the shaft insertion hole 32 of the shaft 3 crosses an axial line 3c of the center of rotation as a shaft axis of the shaft 3, the bolt 24 can tighten and fix the shaft axis 3c of the shaft 3 and a part in its vicinity securely. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a coupling structure between a universal joint yoke and a shaft, and a power steering apparatus using the same.

FIG. 6 is a cross-sectional view of a connecting structure between a yoke and a shaft of a conventional universal joint. Referring to FIG. 6, as a first prior art for the connecting structure between universal joint yoke 50 and shaft 51 corresponding thereto, a fitting groove having a U-shaped cross section is formed at the end of universal joint yoke 50. 52 is formed, and the end of the shaft 51 having an oval cross section is fitted into the fitting groove 52. A bolt 53 for tightening the shaft 51 is disposed in a U-shaped open side portion of the fitting groove 52 with respect to the shaft 51 and is fitted in an engaging groove 54 formed on the top of the peripheral surface of the shaft 51. The shaft 51 is prevented from coming off from the yoke 50 in the axial direction (see, for example, FIG. 4 of Patent Document 1).
JP 2004-360814 A

  However, in the first prior art, since the bolt 53 passes through a position off the axis 55 of the shaft 51, the shaft 51 is tightened with only a portion close to the bolt 53 in a one-sided state. A gap 56 is opened between the portion of the shaft 51 on the far side from the inner surface of the fitting groove 52. As a result, for example, when a large torque acts on the shaft 51, the shaft 51 may swing around the portion 57 on the side close to the bolt 53 (see arrow M), and rattling may occur.

Therefore, in order to suppress rattling, in the second prior art, referring to the cross-sectional view of FIG. 7, a concave groove 58 is formed in the bottom of the fitting groove 52 of the yoke 50 of the first prior art. In this groove 58, the ridge 59 of the shaft 51 is fitted (see, for example, FIG. 3 of Patent Document 1).
However, since a gap 60 for assembly is required between the groove 58 and the ridge 59, rattling may occur as in the first prior art.

  Accordingly, an object of the present invention is to provide a coupling structure between a universal joint yoke and a shaft that can reliably prevent the occurrence of rattling between the universal joint yoke and the shaft, and a power steering device using the same. is there.

  The connection structure between the yoke and the shaft of the universal joint of the present invention includes a pair of parallel flat plates having shaft insertion holes, and a connecting portion that connects the first ends of these flat plates in a U shape. A universal joint yoke, a pair of flat side surfaces facing each of the pair of flat plates of the yoke and forming a two-sided width therebetween, and a shaft including a shaft insertion hole penetrating the side surfaces, the yoke and the shaft A shaft member for fastening and fixing the shaft between the pair of flat plates, the shaft insertion hole of the shaft intersects the shaft center of the shaft, the shaft of the yoke The second end portions of the pair of flat plates extend from the pair of flat side surfaces of the shaft toward the open side of the U shape.

  According to the present invention, the shaft member can securely tighten the shaft center and the vicinity thereof, so that the side surface of the shaft and the flat plate of the yoke are prevented from coming into contact with each other. Further, since the flat plate extends to the U-shaped open side from the side surface, the shaft member can tighten the shaft even at the end of the side surface on the open side. Accordingly, it is possible to reliably prevent the rattling between the yoke and the shaft.

In the present invention, the pair of flat side surfaces of the shaft preferably include a forged surface. In this case, since the side surface can be made strong, it is possible to prevent the occurrence of rattling over a long period. Further, the side surface can be formed at low cost.
The power steering device of the present invention is interposed between a steering shaft connected to a steering member and a steering mechanism, and connects an intermediate shaft for transmitting an assist force by an electric motor and a pair of ends of the intermediate shaft to corresponding shafts. A pair of universal joints, and at least one of the pair of universal joints is connected to a corresponding shaft by a connecting structure between a yoke and a shaft of the universal joint according to claim 1 or 2. To do. According to the present invention, when the assist force of the electric motor is large, it is possible to prevent the intermediate shaft from being vibrated. Therefore, it is possible to prevent the generation of abnormal noise due to the vibration.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
In the present embodiment, the connection structure between the yoke and the shaft of the universal joint will be described in the case where the connection structure is applied to a power steering device. However, the connection structure described above may be applied to, for example, a steering device for manual steering, It can also be applied to a device.
FIG. 1 is a schematic diagram of a schematic configuration of a power steering apparatus according to an embodiment of the present invention. Referring to FIG. 1, a power steering device 1 includes a steering shaft 3 that rotatably supports a steering wheel 2 as a steering member and transmits steering torque, and wheels (not shown) by steering torque from the steering shaft 3. For example, a rack and pinion mechanism, and an intermediate shaft 5 provided between the steering shaft 3 and the steering mechanism 4 as a telescopic shaft for transmitting rotation therebetween. is doing.

As will be described later, universal joints 10 and 11 are provided at both ends of the intermediate shaft 5. The universal joints 10 and 11 are connected to the steering shaft 3 as a corresponding shaft and the input shaft 9 of the steering mechanism 4 by the connecting structures 22 and 23.
The steering shaft 3 is inserted into the steering column 6 and is rotatably supported by the steering column 6. The steering shaft 3 includes an upper shaft 7 and a lower shaft 8 that are fitted in the axial direction so as to be movable relative to each other and transmit torque. The steering wheel 2 is connected to the end of the upper shaft 7 that is one end 3 a of the steering shaft 3, and the above-described steering mechanism is connected to the end of the lower shaft 8 that is the other end 3 b via the intermediate shaft 5. Four input shafts 9 (for example, pinion shafts) are connected. When the steering wheel 2 is steered, the steering torque is transmitted to the input shaft 9 of the steering mechanism 4 via the steering shaft 3, the universal joint 10, the intermediate shaft 5, and the universal joint 11, thereby steering the wheel. Can do.

  Further, the power steering device 1 can obtain a steering assist force according to the steering torque by the electric motor 12 supported by the steering column 6. That is, the power steering apparatus 1 is provided in association with the steering shaft 3 and generates a steering assist force based on a torque sensor 13 for detecting a steering torque and an output signal, a vehicle speed signal, etc. from the torque sensor 13. An electric motor 12 to be driven, a speed reducer 14 for decelerating the rotation of the output shaft of the electric motor 12, a speed reducer 14 and a torque sensor 13 are housed and supported, and the electric motor 12 is supported and one of the steering columns 6 is supported. And a housing 15 forming a portion.

  When the steering wheel 2 is operated, the steering torque is detected by the torque sensor 13, and the electric motor 12 generates a steering assist force (also referred to as assist force) in accordance with the torque detection result and the vehicle speed detection result. The steering assist force is transmitted to the steering shaft 3 via the speed reducer 14, and is transmitted from the steering shaft 3 to the steering mechanism 4 via the intermediate shaft 5 together with the movement of the steering wheel 2 to steer the wheels.

The intermediate shaft 5 is also called an intermediate shaft. A universal joint 10 and a universal joint 11 are connected to a pair of ends of the intermediate shaft 5. The intermediate shaft 5 serves to transmit the steering torque applied to the steering wheel 2 to steer the wheels and the assist force by the electric motor 12 from the steering shaft 3 to the input shaft 9 of the steering mechanism 4.
The intermediate shaft 5 has an inner shaft 16 and a cylindrical outer shaft 17. The inner shaft 16 and the outer shaft 17 are arranged concentrically with each other, and the one end 17a of the outer shaft 17 and the one end 16a of the inner shaft 16 are fitted to each other so as to be relatively movable in the axial direction S1 of the inner shaft 16 and capable of transmitting torque. Are combined. One end of the universal joint 10 is connected to the other end 17 b of the outer shaft 17. Further, one end of the universal joint 11 is connected to the other end 16 b of the inner shaft 16.

FIG. 2 is a front view of a main part of the power steering apparatus 1 of FIG. Referring to FIG. 2, the universal joint 10 includes a yoke 18 provided at the other end 3 b of the steering shaft 3, a yoke 19 provided at the other end 17 b of the outer shaft 17 as one end of the intermediate shaft 5, And a cross shaft 20 connecting the yokes 18 and 19.
The universal joint 11 is configured in the same manner as the universal joint 10. The universal joint 11 connects the yoke 18 provided at the end of the input shaft 9, the yoke 19 provided at the other end 16 b of the inner shaft 16 as the other end of the intermediate shaft 5, and the yokes 18, 19. And a cross shaft 20.

Although not shown, the cross shaft 20 has a trunk portion disposed at the center of the cross shape and four trunnions as four shaft portions protruding in a cross shape from the trunk portion. Each trunnion is provided with a bearing.
Each yoke 18 and 19 is U-shaped and has a pair of arm portions 21. In FIG. 2, only one arm portion 21 of the yoke 18 of the universal joint 10 is illustrated, and only one arm portion 21 of the yoke 18 of the universal joint 11 is illustrated. The pair of arm portions 21 are parallel to each other. Each arm portion 21 is formed with a fitting hole (not shown) for a corresponding trunnion of the cross shaft 20. A corresponding trunnion of the cross shaft 20 is rotatably supported through a bearing fitted and held in the fitting hole.

  In the present embodiment, an end 3b of the steering shaft 3 as a corresponding shaft is connected to one yoke 18 of one universal joint 10 by a first connection structure 22 described later. The other yoke 19 of the universal joint 10 is connected to one yoke 19 of the other universal joint 11 via the intermediate shaft 5. The other yoke 18 of the universal joint 11 is connected to the input shaft 9 of the steering mechanism 4 as a corresponding shaft by a second connecting structure 23 described later.

The first and second connection structures 22 and 23 have the same configuration. Hereinafter, the first connection structure 22 will be described.
FIG. 3 is an enlarged view of a main part of FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. FIG. 5 is an exploded perspective view of the main part of FIG. First, referring to FIG. 3 and FIG.
The first connection structure 22 includes a yoke 18 of the universal joint 10, an end portion 3 b of a steering shaft 3 (hereinafter also referred to as the shaft 3) as a connection target shaft, and a shaft member for fixing the shaft 3. And a nut 25 for fixing the shaft 3 in cooperation with the bolt 24.

In the present embodiment, the bolt 24 intersects the rotation center axis 3 c as the shaft center of the shaft 3, penetrates the yoke 18 and the shaft 3, and is screwed into the nut 25. The bolt 24 and the nut 25 function as fixing means, and the shaft 3 is fastened and fixed.
Referring to FIGS. 4 and 5, bolt 24 has a head 24a and a screw shaft 24b. A male screw is formed on the screw shaft 24b.

The nut 25 includes a nut main body 25a having a hexagonal column shape and a cylindrical portion 25b having a cylindrical shape extending from the nut main body 25a. The nut main body 25a and the cylinder part 25b are integrally formed. The nut 25 has a screw hole 25c. The screw hole 25c has an internal thread and is formed at a predetermined depth from the end surface of the cylindrical portion 25b.
The nut 25 has a self-locking function. As a structure for the self-locking function, a structure having a synthetic resin plate having an inner diameter smaller than the bolt diameter at one end of the screw hole 25a of the nut 25 can be exemplified. Other known self-locking structures can be employed.

The yoke 18 has the above-described pair of arm portions 21 to be connected to the cross shaft 20 (see FIG. 3) and a fitting portion 26 to be fitted to the end portion 3 b of the shaft 3. The fitting part 26 connects the pair of arm parts 21 to each other. The pair of arm portions 21 and the fitting portion 26 are integrally formed by press molding.
The fitting part 26 has a U-shaped cross section. The shaft 3 is fitted and fixed inside the U-shape of the fitting portion 26. The fitting portion 26 includes a pair of flat plates 27 and 28 that are parallel to each other and a connecting portion 29 that is a curved plate that connects the first end portions 27a and 28a of the flat plates 27 and 28 in a U shape. is doing.

The connecting portion 29 has an inner surface 29 a as a receiving portion inside the fitting portion 26. The inner surface 29a has a concave curved shape in cross section, for example, a circular arc shape in cross section.
The pair of flat plates 27 and 28 has inner side surfaces 27 c and 28 c as clamping portions inside the fitting portion 26. Inner side surfaces 27c and 28c of the pair of flat plates 27 and 28 are respectively flat surfaces, extend in parallel with each other, and are arranged to face each other at a predetermined interval. The predetermined interval is equal to the interval between the side surfaces 3d and 3e of the shaft 3 or slightly wider than this interval.

A housing groove for incorporating the shaft 3 from the U-shaped open side is defined by the inner side surfaces 27c, 28c of the pair of flat plates 27, 28 and the inner surface 29a of the connecting portion 29.
One flat plate 27 has a shaft insertion hole 30 for insertion of the bolt 24. The other flat plate 28 has a shaft insertion hole 31 for inserting the bolt 24 and holding the nut 25. The central axes of the shaft insertion holes 30 and 31 of the pair of flat plates 27 and 28 coincide with each other.

The shaft 3 has an end portion 3b and an adjacent portion 3f as an axially intermediate portion adjacent to the end portion 3b. The rotation center axis 3c of the shaft 3 passes through the shape center in the cross section of the adjacent portion 3f.
The cross-sectional shape of the end portion 3 b is an oval shape that is long along one radial direction of the shaft 3. In the longitudinal direction X, the end portion 3b is larger than the adjacent portion 3f. With respect to the width direction Y, which is a direction orthogonal to the longitudinal direction X, the end 3b is smaller than the adjacent portion 3f.

The peripheral surface of the end 3b is convexly curved to connect the side surfaces 3d and 3e as a pair of flat sandwiched portions that form a two-surface width therebetween and one edge of the pair of side surfaces 3d and 3e. It has a bottom surface 3g and a convexly curved top surface 3h connecting the other edges of the pair of side surfaces 3d and 3e.
The bottom surface 3g has a circular arc shape in cross section, and the radius of this arc is equal to the radius of the arc of the inner surface 29a of the connecting portion 29 of the yoke 18.

The side surfaces 3d and 3e extend in the transverse direction along the longitudinal direction X of the transverse cross section. In the longitudinal direction X, the side surfaces 3d and 3e extend longer to the top surface 3h side as the other side than to the bottom surface 3g side as the one side. That is, the distance between the edges of the side surfaces 3d, 3e on the top surface 3h side and the axis 3c is longer than the distance between the edges of the side surfaces 3d, 3e on the bottom surface 3g side and the axis.
Moreover, the edge part 3b has the shaft insertion hole 32 which penetrates the center part of a pair of side surface 3d, 3e. The shaft insertion hole 32 intersects the longitudinal direction X of the transverse cross section at a right angle and extends at a right angle to the rotation center axis 3c as the axis of the shaft 3.

  The end 3b is formed by forging the schematic shape, and then the bottom surface 3g and the shaft insertion hole 32 are formed by cutting. The entire side surfaces 3d and 3e are formed by a forged surface formed by forging. The bottom surface 3g is formed by a cut surface obtained by cutting, but may be formed by a forged surface, or may be formed by a cut surface and a forged surface. The top surface 3h is formed by swelling of the surplus generated as the side surfaces 3d and 3e are formed by forging, and is left in the forged state, and is not subjected to post-processing.

  With reference to FIGS. 3 and 4, the end 3 b of the shaft 3 is fitted into the fitting portion 26 of the yoke 18. In this state, the second end portions 27b and 28b of the pair of flat plates 27 and 28 of the yoke 18 are directed toward the open side of the U shape from the edges of the side surfaces 3d and 3e of the shaft 3 on the top surface 3h side. It extends at a predetermined distance. Inner side surfaces 27 c and 28 c of the pair of flat plates 27 and 28 face the side surfaces 3 d and 3 e of the shaft 3. The inner surface 29a of the connecting portion 29 is in contact with the bottom surface 3g of the shaft 3 and receives the bottom surface 3g. Thereby, the rotation center axis 3c of the shaft 3 passes through the center position 20a of the cross shaft 20 (corresponding to the intersection of the center axes of the four trunnions). The shaft insertion holes 30, 31, and 32 are arranged concentrically with each other.

A bolt 24 is inserted into the shaft insertion holes 30, 31, 32 and screwed into a nut 25 held in the shaft insertion hole 31 of the flat plate 28. The end 3b is fastened between the head 24a of the bolt 24 and the nut body 25a of the nut 25 via a pair of flat plates 27 and 28.
In a state in which the shaft 3 is tightened, the side surface 3d of the shaft 3 abuts against the inner side surface 27c of the flat plate 27 in a surface contact state in a region surrounding the bolt 24. At the same time, the side surface 3e of the shaft 3 is in contact with the inner side surface 28c of the flat plate 28 in a surface contact state in a region surrounding the bolt 24.

  As described above, in this embodiment, the connecting structure 22 between the yoke 18 and the shaft 3 of the universal joint 10 includes a pair of parallel flat plates 27 and 28 having shaft insertion holes 30 and 31, and the flat plates 27 and 28. The yoke 18 of the universal joint 10 including a connecting portion 29 that connects the first ends 27a and 28a in a U shape is provided. Further, the connecting structure 22 has a pair of flat side surfaces 3d and 3e that face the pair of flat plates 27 and 28 of the yoke 18 and form a two-surface width therebetween, and shafts that penetrate these side surfaces 3d and 3e. A shaft 3 including an insertion hole 32 is provided. The connection structure 22 includes a bolt 24 as a shaft member that passes through the yoke 18 and the shaft insertion holes 30, 31, 32 of the shaft 3 and is fastened and fixed between the pair of flat plates 27, 28. Yes. The shaft insertion hole 32 of the shaft 3 intersects the rotation center axis 3 c as the shaft center of the shaft 3, and the second ends 27 b and 28 b of the pair of flat plates 27 and 28 of the yoke 18 are a pair of the shaft 3. The flat side surfaces 3d and 3e extend toward the U-shaped open side.

  According to the present embodiment, the bolt 24 can securely tighten the shaft center of the shaft 3 and its vicinity, so that the side surfaces 3d and 3e of the shaft 3 and the flat plates 27 and 28 of the yoke 18 come into contact with each other. Is prevented. Further, since the flat plates 27 and 28 extend to the open side of the U shape from the side surfaces 3d and 3e, the bolt 24 can tighten the shaft 3 also at the end portions of the side surfaces 3d and 3e on the open side. Accordingly, it is possible to reliably prevent the rattling between the yoke 18 and the shaft 3.

  In the present embodiment, the pair of flat side surfaces 3d and 3e of the shaft 3 are forged surfaces. In this case, since the strength of the side surfaces 3d and 3e can be increased, the occurrence of rattling can be prevented over a long period of time. Further, the side surfaces 3d and 3e can be formed at low cost. In order to obtain this effect, the forged surface may be only a part of the side surfaces 3d and 3e. The side surfaces 3d and 3e may include a forged surface formed by forging.

By the way, in the conventional electric power steering apparatus of an automobile, vibration is generated when the steering wheel is fully turned, and an abnormal noise may be generated along with the vibration. As a cause of this vibration, if a large torque is applied to the intermediate shaft, it is considered that rattling occurs between the yoke of the universal joint of the intermediate shaft and the shaft, and vibration is generated.
On the other hand, in the power steering device 1 of the present embodiment, an intermediate shaft 5 that is interposed between the steering shaft 3 connected to the steering wheel 2 and the steering mechanism 4 and transmits the assist force by the electric motor 12, and the intermediate shaft 5. A pair of universal joints 10 and 11 for connecting a pair of end portions of the shaft 5 to a shaft 3 and an input shaft 9 as corresponding shafts are provided. The universal joint 10 is connected to the shaft 3 as a corresponding shaft by the connecting structure 22 described above. At the same time, the universal joint 11 is connected to the input shaft 9 as a corresponding shaft by the connecting structure 23 described above.

  Thereby, the occurrence of rattling between the yoke 18 of the universal joint 10 and the shaft 3 can be prevented, and at the same time, the occurrence of rattling between the yoke 18 of the universal joint 11 and the input shaft 9 can be prevented. Therefore, it is possible to prevent the intermediate shaft 5 from vibrating even when the assist force of the electric motor 12 is large when the steering wheel 2 is fully turned. As a result, it is possible to prevent abnormal noise from being generated with this vibration.

  In addition, when any one of a pair of universal joints 10 and 11 is connected with the corresponding axis | shaft by the above-mentioned connection structure 22 and 23, the above-mentioned vibration can be suppressed. Moreover, it is preferable that the connection structures 22 and 23 are applied to both the universal joints 10 and 11. It suffices that at least one of the pair of universal joints 10 and 11 is connected to the corresponding shaft by the connecting structures 22 and 23 described above.

  Moreover, the following modifications can be considered about this embodiment. In the following description, differences from the above-described embodiment will be mainly described, and the same components are denoted by the same reference numerals and description thereof is omitted. For example, it is conceivable that the side surfaces 3d and 3e of the shaft 3 are formed by cutting surfaces that have been cut. The axis of the shaft 3 is the rotation center axis 3c of the shaft 3, but is a line (not shown) that passes through the center of gravity of the cross section of the end 3b of the shaft 3 and is parallel to the rotation center axis 3c. Also good. Further, with respect to the longitudinal direction X, the central axis of the shaft insertion hole 32 may be disposed at a position different from the axis of the shaft 3 and intersect each other. In addition, various design changes can be made within the scope of matters described in the claims.

It is a mimetic diagram of a schematic structure of a power steering device of an embodiment of the present invention. It is a front view of the principal part of the power steering apparatus shown in FIG. It is an enlarged view of the principal part shown in FIG. It is sectional drawing which shows the IV-IV cross section of FIG. It is a disassembled perspective view of the principal part of FIG. It is sectional drawing of the connection structure of the yoke of a universal joint as a 1st prior art, and a shaft. It is sectional drawing of the connection structure of the yoke of a universal joint as a 2nd prior art, and a shaft.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Power steering apparatus, 2 ... Steering wheel (steering member), 3 ... Steering shaft (shaft), 3c ... Center axis of rotation (shaft axis), 3d, 3e ... Side surface (forged surface), 4 ... Steering mechanism, 5 ... Intermediate shaft 10, 11 ... Universal joint, 12 ... Electric motor, 18, 19 ... Yoke, 22, 23 ... Connection structure, 24 ... Bolt (shaft member), 27, 28 ... Flat plate, 27a, 28a ... (Flat plate) First end, 27b, 28b ... (second plate) second end, 29 ... connecting portion, 30, 31 ... shaft insertion hole (yoke shaft insertion hole), 32 ... shaft insertion hole (shaft of the shaft) Shaft insertion hole)

Claims (3)

A universal joint yoke including a pair of parallel flat plates each having a shaft insertion hole, and a connecting portion connecting the first ends of the flat plates in a U-shape;
A shaft including a pair of flat side surfaces respectively facing the pair of flat plates of the yoke and forming a two-plane width therebetween, and a shaft insertion hole penetrating these side surfaces;
A shaft member for penetrating the shaft insertion hole of the yoke and the shaft and fastening the shaft between the pair of flat plates and fixing the shaft;
The shaft insertion hole of the shaft intersects the shaft center,
The second end portion of the pair of flat plates of the yoke extends from the pair of flat side surfaces of the shaft toward the open side of the U-shape. Construction. In claim 1,
The pair of flat side surfaces of the shaft includes a forged surface, and the universal joint yoke and shaft connection structure. An intermediate shaft that is interposed between a steering shaft that is connected to the steering member and the steering mechanism, transmits an assist force by the electric motor, and a pair of universal joints that connect a pair of end portions of the intermediate shaft to the corresponding shafts, respectively. With
3. A power steering apparatus, wherein at least one of a pair of universal joints is connected to a corresponding shaft by a connecting structure between a universal joint yoke and a shaft according to claim 1 or 2.

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