JP4299718B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering apparatus in which drive torque of an electric motor is applied to a steering wheel via a worm reduction gear.

  Patent Document 1 discloses a power steering device in which an output shaft of an electric motor and an input shaft of a worm speed reducer are connected via a flexible joint. In the flexible joint described in this document, a pair of disk-shaped connecting members (hubs 30 and 31) having a plurality of axial protrusions (drive teeth 31a) projecting on the outer peripheral side are connected to the output shaft and the input shaft. An elastic member (spider) having a plurality of radial protrusions (arms 53) coupled to opposite ends and projecting in the radial direction is sandwiched between the two connecting members (paragraph of Patent Document 1). 0061-0064 and FIGS.

On the other hand, in the worm speed reducer, when the electric motor is rotated, an axial force acts on the worm shaft, and the direction of the axial force is reversed depending on the rotation direction of the electric motor.
Special table 2002-518242

  However, according to the structure described in Patent Document 1, when the axial shakiness occurs on the output shaft or worm shaft of the electric motor, it cannot be absorbed, resulting in deterioration of steering feeling, It is impossible to prevent hitting sound. Such deterioration of steering feeling and occurrence of hitting sound are not preferable because they cause a reduction in quality.

In view of such a problem of the prior art, in order to provide an electric power steering device capable of absorbing axial shakiness generated in the output shaft and worm shaft of the electric motor, claim 1 of the present invention provides an electric motor (9 ) Is applied to the steering wheel (2) via the worm reduction gear (10), and the configuration of the electric power steering device (12) is supported by the first bearing member (19). A plurality of axial directions in which opposed ends of the output shaft (20) of the electric motor and the input shaft (17) of the worm reducer supported by the second bearing member (16) have a plane parallel to the central axis. protrusion pair of connecting members having a (B) (22a · 22b) and said and said connecting member is sandwiched between a pair of connecting members to each other flexure consisting separate one elastic member (23) joint (21) Via are connected to, the axial length of the elastic member (a) has assumed, characterized in that it is the shaft axial length of the direction the convex portion (b) greater than.

According to a second aspect of the present invention, in addition to the above configuration, the predetermined range of at least one of the facing surfaces of the connecting members is on a plane that is not orthogonal to at least one of the output shaft and the input shaft. It was supposed to be a feature. Further, according to a third aspect of the present invention, concave portions (H) for receiving the convex portions are provided on both axial end surfaces of the elastic member.

  According to the present invention, since the elastic member is also interposed in the axial gap between the connecting member and the convex portion, the elastic member can receive the circumferential force and the axial force. That is, since the elastic member absorbs the rattling between the circumferential direction and the axial direction of the worm shaft, it is possible to effectively suppress the deterioration of the steering feeling and the generation of the hitting sound.

  Particularly, since the connecting member and the elastic member are in contact with each other at the inclined surface, the circumferential component force due to the axial force and the axial component force due to the circumferential force are applied to the elastic member. It will interact with each other. Thereby, even when there is a circumferential or axial initial gap between the connecting member and the elastic member, the axial component force and the circumferential component force push each other so that there is no initial gap, It is possible to further enhance the rattling effect in both the axial direction and the circumferential direction.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows a vehicle steering apparatus to which an electric power steering apparatus according to the present invention is applied. This steering apparatus 1 converts a steering shaft 3 connected to a steering wheel 2, a rack shaft 6 connected to a tire 5 via a tie rod 4, and rotational displacement of the steering wheel 2 into axial displacement of the rack shaft 6. For example, a magnetostrictive torque sensor 8 for detecting a steering torque applied to the steering shaft 3, an electric motor 9 for applying an auxiliary steering force to the steering shaft 3, and a rotational torque of the electric motor 9 are boosted. A worm reduction gear 10 and an electric power steering device 12 including a control device 11 for controlling the driving force of the electric motor 9 based on at least the output of the torque sensor 8. The input current to the motor 9 is detected so that a predetermined steering characteristic is obtained according to the detected value. Control apparatus 11 is adapted to PWM control.

  As shown in FIG. 2, the worm speed reducer 10 is built in a speed reducer casing 13 coupled to the casing of the electric motor 9, and a worm wheel 15 integrally coupled to the pinion shaft 14 of the rack and pinion mechanism 7; A worm 18 integrated with an input shaft 17 supported at both ends by a casing 13 having a ball bearing 16 is formed. One end of the input shaft 17 is bent at one end of an output shaft 20 of the electric motor 9 supported by the ball bearing 19. Are connected through.

  As a result, the rotational force of the electric motor 9 is boosted by the reduction ratio between the worm wheel 15 and the worm 18 and transmitted to the pinion shaft 14 integrated with the worm wheel 15 and input to the rack shaft 6 as an axial force. .

  Since the basic control procedure of the electric power steering device 12 is the same as that of the known technology, further explanation is omitted here.

  A flexible joint 21 that connects the output shaft 20 of the electric motor 9 and the input shaft 17 of the worm speed reducer 10 is formed between the output shaft 20 of the electric motor 9 and the input shaft 17 of the worm speed reducer 10 as shown in FIG. It consists of a pair of connecting members 22a and 22b fixed to opposite ends, and one elastic member 23 sandwiched between two connecting members.

  The pair of connecting members 22a and 22b have the same shape in this embodiment, and a plurality of (in this embodiment) a disk-shaped portion D and a plurality of (in the present embodiment) projecting at positions where the circumference is equally divided. 3) and the axial convex portion B. The elastic member 23 has a cylindrical shape, and concave portions H for receiving the axial convex portions of the respective connecting members are formed on both axial end surfaces thereof. Here, the axial dimension “a” of the elastic member 23 is larger than the length dimension “b” of the axial convex part B of each of the connecting members 22a and 22b, and the protruding end of the axial convex part B of each of the connecting members 22a and 22b. The concave portion H has a bottom so that the two come into contact with each other.

  In this way, by making the axial dimension a of the elastic member 23 larger than the length dimension b of the axial projection B, the meshing pressure angle between the worm wheel 15 and the worm 18 accompanying the rotation of the electric motor 9 is changed. 4, the axial force P and the circumferential force Q act, and the circumferential force Q is a portion between the adjacent recesses H of the elastic member 23. The axial force P is received at the bottom of the concave portion H of the elastic member 23 interposed between the axial convex portion B and the disc portion D. Therefore, according to the structure of the present invention, the input shaft 17 can be prevented from rattling between the axial direction and the circumferential direction, so that the torque fluctuation is absorbed by the elastic member 23 interposed in the circumferential gap between both convex portions B. In combination with this, it is possible to suppress the deterioration of the steering feeling and the generation of a hitting sound.

As shown in FIGS. 5 and 6, the opposing surfaces of the disk portion D of at least one (for example, the connecting member 22 a on the output shaft 20 side) and the axial end surface of the elastic member 23 are connected to the output shaft 20 and Since the connecting member 22a and the elastic member 23 are brought into contact with each other on the inclined surface by being placed on a plane that is not orthogonal to the axis of the input shaft 17, the axial component due to the axial force and the axial direction due to the circumferential force Will interact with each other with respect to the elastic member 23. As a result, even when there are circumferential and axial initial gaps between the connecting members 22a and 22b and the elastic member 23, they are pressed against each other so that the initial gap is eliminated by the circumferential force and the axial component force. It will be. Therefore, it is possible to further enhance the effect of suppressing the axial and circumferential play, and to make the effect of suppressing the deterioration of steering feeling and the generation of hitting sound even more remarkable.

It is a schematic block diagram of the steering device for motor vehicles to which this invention was applied. FIG. 2 is a side view showing a partially cut away worm reduction gear with an electric motor according to the present invention. It is a disassembled perspective view of the flexible joint by this invention. It is explanatory drawing of an effect | action of the flexible joint by this invention. It is a principal part side view of a modification. It is a principal part side view of another modification.

Explanation of symbols

2 Steering wheel 9 Electric motor 10 Worm speed reducer 12 Electric power steering device 17 Input shaft 20 of the worm speed reducer Output shaft 21 of the electric motor Flexible joints 22a and 22b Connecting member 23 Elastic member B Axial convex part H Concave part

Claims (3)

An electric power steering device configured to add a driving torque of an electric motor to a steering wheel via a worm reducer,
A plurality of shafts in which opposing ends of the output shaft of the electric motor supported by the first bearing member and the input shaft of the worm speed reducer supported by the second bearing member have surfaces parallel to the central axis. A pair of connecting members having directional protrusions and the connecting member sandwiched between the pair of connecting members are connected via a flexible joint made of a single elastic member separate from each other;
The electric power steering device according to claim 1, wherein an axial length of the elastic member is larger than an axial length of the axial convex portion. 2. The electric power steering apparatus according to claim 1, wherein a predetermined range of at least one of the facing surfaces of the connecting members is on a plane that is not orthogonal to at least one of the output shaft and the input shaft. 3. The electric power steering apparatus according to claim 1, wherein the elastic member includes concave portions that receive the convex portions on both axial end surfaces thereof.

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