JP2006224782A - Electric steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric steering device which can prevent a vibration or an uncomfortable noise resulting from a contact between a bushing and a ball nut from being generated even if the bushing moves in a manner to slip out in a direction toward the ball nut. <P>SOLUTION: This electric steering device is equipped with a rod-like steering member 6 which reciprocates in the longitudinal direction in response to the turning of a steering wheel, and the ball nut 21 which is fitted on a ball screw shaft 19 which is formed on the steering member 6 through a ball 20. Then, an auxiliary steering force is transmitted to the steering member 6 by turning the ball nut 21 by the driving of an electric motor. A supporting section 23 which freely slidably supports the ball screw shaft 19 through the bushing 24 is provided at a position being close to the ball nut 21. On the inner periphery of one end section of the ball nut 21 facing the bushing 24, a recess hole section 25 which can accept the bushing 24 is provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electric steering apparatus that applies an auxiliary force by an electric motor to a steering force from a steering wheel.

  2. Description of the Related Art Conventionally, as an electric steering device that applies an assisting force by an electric motor to a steering force from a steering wheel, a rod-like steering member that reciprocates in the longitudinal direction in accordance with the rotation of the steering wheel, and a ball formed on the steering member 2. Description of the Related Art A ball nut that is externally inserted through a plurality of balls on a screw shaft and rotates the ball nut by an electric motor is known (for example, see Patent Document 1).

Further, in this type of electric steering apparatus, a bush is provided that receives a radial load on the ball screw shaft that is generated when traveling on a rough road or the like (see, for example, Patent Document 2). The bush is pressed into a position where the ball screw shaft of the housing that houses the steering member is slidably supported to prevent kickback.
Japanese Patent Laid-Open No. 2003-291830 (FIG. 5) Japanese Patent Laid-Open No. 60-25854 (FIG. 2)

  However, for example, as shown in FIG. 3, when a bush 34 is press-fitted into a support portion 33 that supports a ball screw shaft 32 that is a part of the steering member 31 at a position close to the ball nut 30, the bush 34 However, if the steering member 31 moves in the direction toward the ball nut 30 as the steering member 31 reciprocates, the bush 34 may come into pressure contact with one end edge of the rotating ball nut 30 and vibration or noise may occur. .

  In view of the above disadvantages, the present invention provides an electric steering device that can prevent vibrations and abnormal noise caused by contact between the bush and the ball nut even if the bush moves in a direction toward the ball nut. The purpose is to provide.

  In order to achieve the above object, the present invention provides a rod-like steering member that reciprocates in the longitudinal direction in accordance with the rotation of the steering wheel, and an extrapolation through a plurality of balls on a ball screw shaft formed on the steering member. An electric steering device that transmits an auxiliary steering force to the steering member by rotating the ball nut by driving an electric motor, and is close to the ball nut of the housing that houses the steering member A bushing through which the ball screw shaft is inserted is press-fitted into a portion to be formed, and a support portion for slidably supporting the ball screw shaft is formed through the bush, and one end of the ball nut facing the bush An escape hole having a larger inner diameter than the outer diameter of the bush is formed on the inner periphery of the section.

  According to the present invention, even if the bush is pulled out from the support portion toward one end portion of the ball nut, the bush that has been pulled out from the support portion is received in the escape hole portion at one end portion of the ball nut. As a result, the pressure contact of the bush to the ball nut can be prevented, and the occurrence of vibration and abnormal noise can be prevented.

  Moreover, in this invention, the said escape hole part is set so that the length of the axial direction may become more than the length of the axial direction of the said bush. That is, the axial length of the escape hole is set so that the distance from the ball nut side end surface of the support portion to the innermost end of the escape hole is equal to or greater than the axial length of the bush. ing.

  According to this, even if the bush is pulled out from the support portion over its entire length, the bush is received in the escape hole portion at one end portion of the ball nut over its entire length. At this time, since the press-fitted state of the bush to the support portion is released, even if the bush moves to the back end side of the escape hole portion, it does not come into a press-contact state at the deepest end of the escape hole portion. Generation of sound can be reliably prevented.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a partially broken explanatory view of the electric steering apparatus of the present embodiment, and FIGS. 2A and 2B are enlarged cross-sectional explanatory views showing the main part in FIG.

  As shown in FIG. 1, the electric steering apparatus 1 of the present embodiment includes a steering mechanism 2 and an auxiliary torque mechanism 3 that applies an auxiliary torque to the steering mechanism 2. The steering mechanism 2 inputs a rotation of a steering wheel (not shown) of the vehicle to the input shaft 4 to reciprocate the rod-like steering member 6 in the housing 5 in the longitudinal direction. That is, the rotation of the steering wheel input to the input shaft 4 is converted into the reciprocating motion of the steering member 6 by the conversion mechanism 7 such as a rack and pinion mechanism. The conversion mechanism 7 is provided with a torque sensor 8. The torque sensor 8 detects the steering torque input to the input shaft 4.

  Tie rods 9 are connected to both ends of the steering member 6. Each tie rod 9 is connected to a steerable wheel (not shown) of the vehicle. A steering motion is imparted to the wheels by the steering member 6 moving linearly in the longitudinal direction.

  The auxiliary torque mechanism 3 includes an electric motor 10 disposed along the outer surface of the housing 5 in which the steering member 6 is accommodated, and a torque transmission mechanism 11 that transmits the auxiliary torque generated by the electric motor 10 to the steering member 6. It has. The electric motor 10 is controlled by a control means (not shown) according to the steering torque detected by the torque sensor 8, and generates an auxiliary torque corresponding to the steering torque.

  As shown in FIG. 1, the torque transmission mechanism 11 includes a drive pulley 12 connected to the electric motor 10, a driven pulley 13 connected to the steering member 6, and a belt 14 stretched between the pulleys 12 and 13. It is comprised by. The drive pulley 12 is rotatably supported via a rotating shaft 18 between a pair of ball bearings 16 and 17 that are fitted and held inside a support case 15 of the electric motor 10. The rotary shaft 18 of the drive pulley 12 is driven by the electric motor 10 by being connected coaxially with the output shaft of the electric motor 10. The rotation of the drive pulley 12 is transmitted to the driven pulley 13 via the belt 14, and the rotation of the driven pulley 13 is applied to the reciprocating motion of the steering member 6 as an auxiliary steering force.

  That is, a ball screw shaft 19 is formed in the steering member 6 near the electric motor 10, and a ball nut 21 is coupled to the ball screw shaft 19 via a plurality of balls 20. As shown in FIG. 2A, the ball nut 21 is attached to the housing 5 of the steering member 6 by an angular ball bearing 22 so as to be rotatable and immovable in the axial direction. The driven pulley 13 is fastened and fixed to a ball nut 21 and rotates integrally with the ball nut 21.

  Further, in the vicinity of the ball nut 21 at the end of the housing 5, as shown in FIG. 2A, a support portion 23 that slidably inserts and supports the ball screw shaft 19 is formed. A bush 24 is press-fitted into the support portion 23, and kickback is prevented by the bush 24. In other words, the support portion 23 slidably supports the ball screw shaft 19 of the steering member 6 via the bush 24, and prevents the steering member 6 from bending with respect to the kickback received from the road surface. Smooth rotation of the nut 21 is ensured.

  Further, as shown in FIG. 2A, an escape hole 25 is formed in the inner periphery of one end of the ball nut 21 that faces the bush 24 in the vicinity of the support 23. The escape hole portion 25 has an inner diameter larger than the outer diameter of the bush 24, and has an axial length that is greater than or equal to the axial length of the bush 24. As a result, a gap 26 is formed between the outer peripheral wall of the ball screw shaft 19 and the bush 24 can be accommodated.

  Next, the operation of this embodiment will be described. When the vehicle is in a straight traveling state and the steering force of the steering wheel is not input to the input shaft 4, the torque sensor 8 does not generate an output signal, and the electric motor 10 connected to the shaft of the drive pulley 12 generates auxiliary torque. do not do. At this time, the steering member 6 also does not move, and the steering force does not act on the wheels (not shown).

  On the other hand, when the vehicle is about to turn a curve, the driver turns the steering wheel. At this time, the steering force applied to the input shaft 4 is transmitted to the steering member 6 via the conversion mechanism 7 and is transmitted to the wheels via the tie rod 9. At the same time, torque corresponding to the steering force applied to the input shaft 4 is detected by the torque sensor 8, and the rotation of the electric motor 10 driven based on the detection signal causes the drive pulley 12, the driven pulley 13, and the ball nut 21. The auxiliary force is applied to the steering member 6 through the ball screw shaft 19.

  At this time, in the support portion 23, the ball screw shaft 19 is slidably guided through the bush 24, and the steering member 6 is reciprocated with high accuracy. Here, when the sliding contact between the ball screw shaft 19 and the bush 24 is repeated, as shown in FIG. 2 (c), the bush 24 is moved as the ball screw shaft 19 slides. It is conceivable that the protrusion extends from the support portion 23 toward the ball nut 21. At this time, the gap 26 formed inside the escape hole portion 25 provided in the ball nut 21 prevents interference between the bush 24 and the ball nut 21, and the bush 24 is pressed against the ball nut 21. Since it does not occur, it is possible to reliably prevent the occurrence of vibration and abnormal noise.

Explanatory drawing which partially fractures and shows the electric steering apparatus of one Embodiment of this invention. Cross-sectional explanatory drawing which expands and shows the principal part in FIG. Cross-sectional explanatory drawing which shows a part of conventional electric steering device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electric steering device, 6 ... Steering member, 10 ... Electric motor, 19 ... Ball screw shaft, 20 ... Ball, 21 ... Ball nut, 23 ... Support part, 24 ... Bush, 25 ... Escape hole part.

Claims (2)

A rod-like steering member that reciprocates in the longitudinal direction in accordance with the rotation of the steering wheel, and a ball nut that is externally inserted through a plurality of balls on a ball screw shaft formed on the steering member, and drives an electric motor An electric steering device that rotates the ball nut to transmit an auxiliary steering force to the steering member,
A bush that inserts the ball screw shaft is press-fitted into a portion close to the ball nut of the housing that houses the steering member, and a support portion that slidably supports the ball screw shaft through the bush is formed. ,
An electric steering device, wherein an escape hole portion having an inner diameter larger than an outer diameter of the bush is formed on an inner periphery of one end portion of the ball nut facing the bush.   2. The electric steering apparatus according to claim 1, wherein the escape hole portion is set such that an axial length thereof is equal to or greater than an axial length of the bush. 3.

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