JP2006232048A - Electric steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric steering device capable of preventing positional slippage of a belt against a pulley, facilitating processing and assembling work of teeth of a driven pulley and furnished with the compact driven pulley. <P>SOLUTION: A ball nut 21 is externally inserted into a ball screw stem 19 furnished on a steering member 6 to reciprocate by turning of a steering wheel through a ball 20. A driving pulley 12 having angle teeth is provided on a drive shaft of an electric motor 10, and the driven pulley 13 having angle teeth is provided on a ball nut 21. The belt 14 has angle teeth and connects the driving pulley 12 and the driven pulley 13 to each other. Additionally, the driven pulley 13 is not furnished with a flange and has width in the axial direction roughly the same as width (a) in the axial direction of the belt 14. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

  Conventionally, as this type of electric steering device, a steering member that reciprocates in the longitudinal direction according to the rotation of a steering wheel, and a ball that is extrapolated via a plurality of balls to a ball screw shaft formed on the steering member There are known ones including a nut, a drive pulley provided on a drive shaft of an electric motor, and a driven pulley connected to the drive pulley via a belt and rotating integrally with the ball nut (for example, Patent Document 1). According to this, since the belt is interposed in the power transmission path between the electric motor and the steering member, vibration from the steering member is not transmitted to the electric motor, and the rotation accuracy of the electric motor is maintained. Can do.

  Further, in this type of electric steering apparatus, both pulleys and belts are formed by adopting toothed pulleys for both pulleys of the drive pulley and the driven pulley, and making the belts spanned between the pulleys be toothed belts. It has been done to prevent slipping. Furthermore, in order to reduce vibration and noise due to meshing between the teeth of the belt and the teeth of each pulley, a belt with a helical tooth is adopted, and a pulley with a helical tooth corresponding to the helical tooth of the belt is used as a driving pulley. And a driven pulley are known (see, for example, Patent Document 2).

By the way, when the helical belt is wound around the helical driving pulley and the helical driven pulley and is rotated, it receives an axial thrust force due to the meshing of the helical teeth. As a result, the belt passing position with respect to the pulley is likely to be shifted in the axial direction (width direction), and the meshing state at the time of rotation may not be maintained. For this reason, each pulley is provided with flanges projecting in the outer circumferential direction at both ends in the axial direction. With this flange, the position of the belt is regulated within a predetermined axial width, and the belt from the pulley is Prevents disconnection.
JP 2003-291830 A JP 2004-314770 A

  However, even when the flange is provided to prevent the belt from coming off the pulley, the belt receives an axial thrust force due to the meshing of the helical teeth, so that a biased tension is applied to the belt and the belt is Life may be reduced.

  In addition, since each pulley must form teeth between both flanges, the flange becomes an obstacle when forming the teeth, which makes it difficult to process the teeth. Moreover, even in the assembly work when the belt is passed, there is an inconvenience that the flange becomes an obstacle and the work efficiency is lowered.

  In order to facilitate the tooth processing on the pulley and the belt passing work, it may be possible to attach the flange detachably from the pulley body, but the number of parts increases and the assembly man-hour increases. There is a disadvantage that the production efficiency is lowered.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an electric steering apparatus that can prevent a positional deviation of a belt with respect to a pulley and that is easy to process and assemble a tooth of a driven pulley and includes a compact driven pulley. It is in.

  In order to achieve such an object, the present invention is an electric steering apparatus that applies an auxiliary torque by an electric motor to a steering torque from a steering wheel, and is a rod-shaped reciprocating member in the longitudinal direction according to the rotation of the steering wheel. A steering member, a ball nut formed on the ball screw shaft formed on the steering member via a plurality of balls, a toothed driving pulley provided on the driving shaft of the electric motor, and a tooth on the driving pulley. Comprising a toothed driven pulley connected via a belt and rotating integrally with the ball nut, wherein the tooth of the belt extends from one side edge in the belt width direction to the other side from the belt width center. The teeth of the drive pulley and the driven pulley are formed in a mountain shape corresponding to the teeth of the belt. Characterized in that it is.

  According to the present invention, the belt, the driving pulley, and the driven pulley mesh with each other with the chevron-shaped teeth, so that it is possible to reliably prevent the positional deviation of the belt with respect to each pulley during rotation, and there is no bias in the belt. Since it is not applied, it is possible to prevent a reduction in belt life.

  Furthermore, in the present invention, the driven pulley does not include flanges at both ends in the axial direction, and has an axial width substantially the same as the width of the belt.

  As described above, since the belt is not displaced from each pulley due to the engagement of the chevron-shaped teeth, the driven pulley does not require a flange for regulating the belt from both ends of the belt in the axial direction. It becomes. Thereby, when processing and forming teeth on the outer peripheral surface of the driven pulley, the flange does not become an obstacle, and the processing of the teeth on the driven pulley can be easily performed. Moreover, even in the assembly work when the belt is wound around the driven pulley, the work is facilitated by not providing the flange. Furthermore, the axial width of the driven pulley can be made substantially the same as the axial width of the belt (specifically, the same as the axial width of the belt or slightly larger than the axial width of the belt). The driven pulley can be formed relatively compact. As a result, the space for mounting the driven pulley in the electric steering apparatus can be reduced, and the electric steering apparatus can be downsized.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view showing an electric steering apparatus of the present embodiment, FIG. 2 is a cross-sectional explanatory view of a main part, and FIG. 3 is an explanatory perspective view of a driven pulley.

  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 is configured to reciprocate the steering member 6 in the housing 5 in the longitudinal direction by inputting rotation of a steering wheel (not shown) of the vehicle to the input shaft 4. 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. And a steering motion is given to a wheel by the steering member 6 moving linearly in the longitudinal direction.

  The auxiliary torque mechanism 3 includes an electric motor 10 attached to the housing 5 and a torque transmission mechanism 11 that transmits auxiliary torque generated by the electric motor 10 to the steering member 6. The electric motor 10 is controlled by a control means (not shown) that inputs a detection signal of the torque sensor 8, and generates an auxiliary torque corresponding to the steering torque detected by the torque sensor 8.

  As shown in FIG. 2, 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 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 rotating shaft 18 of the drive pulley 12 is connected to the output shaft of the electric motor 10 and is driven by 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 force.

  That is, a ball screw shaft 19 is formed on the steering member 6 corresponding to the position of the electric motor 10, and a ball nut 21 is coupled to the ball screw shaft 19 via a plurality of balls 20. 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, as shown in part in FIG. 3, a toothed belt is adopted as the belt 14. That is, a plurality of teeth 14a are formed on the belt 14 at predetermined intervals in the circumferential direction on the inner peripheral side which is a contact surface with the pulleys 12 and 13. The teeth 14a of the belt 14 are formed in a mountain shape extending from the central portion in the width direction of the belt 14 inclining in the same circumferential direction toward the one side edge and the other side edge of the belt 14 in the width direction. As shown in FIGS. 2 and 3, the driving pulley 12 and the driven pulley 13 are also toothed pulleys. The teeth 23 of the driving pulley 12 and the driven pulley 13 are teeth 14 a formed on the belt 14. It is formed in a mountain shape corresponding to.

  As shown in FIG. 2, the drive pulley 12 has the teeth 23 in a pulley body 24 formed integrally with the rotary shaft 18, and has a pair of flanges 25 on both sides in the axial direction of the pulley body 24. The pulley main body 24 and the flanges 25 are separated from each other, so that the teeth 23 can be processed on the pulley main body 24 before the flange 25 is attached.

  2 and 3, the driven pulley 13 does not include a flange or the like that restricts the movement of the belt 14 in the axial direction (width direction), and the axial width of the driven pulley 13 is the axial direction of the belt 14. It is formed substantially the same as the width a.

  As shown in FIG. 2, the electric motor 10 is attached to a motor attachment portion 26 formed in the housing 5 via the support case 15. The support case 15 is fixed to the electric motor 10, and the support case 15 and the motor mounting portion 26 are not shown, but the distance between the axis of the drive pulley 12 and the axis of the driven pulley 13 is omitted. Are connected to each other so that they can be separated or approached. As a result, the distance between the shaft centers of the pulleys 12 and 13 is adjusted to a predetermined distance, and an appropriate tension is applied to the belt 14 spanned between the pulleys 12 and 13.

  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.

  In the present embodiment, the belt 14 has mountain-shaped teeth 14 a and the driving pulley 12 and the driven pulley 13 have mountain-shaped teeth 23, so that the rotational force of the driving pulley 12 is efficiently applied to the belt 14. In addition to being transmitted, the meshing of the teeth 14a and 23 does not cause any deviation in the position where the belt 14 is stretched with respect to the pulleys 12 and 13. In addition, since the driven pulley 13 does not include a flange or the like, the workability of the teeth 23 with respect to the driven pulley 13 is good. Further, since the driven pulley 13 is not provided with a flange or the like, there is nothing obstructing the assembly of the driven pulley 13 of the belt 14 and the assemblability is good. Further, since the driven pulley 13 has substantially the same width as the width a of the belt 14, the space for mounting the driven pulley 13 in the housing 5 can be reduced, and the size of the apparatus can be prevented from being increased. .

Explanatory drawing which shows the electric steering device of one Embodiment of this invention. Cross-sectional explanatory drawing of the principal part in the electric steering device of this embodiment. The explanatory perspective view of the driven pulley in this embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electric steering device, 6 ... Steering member, 10 ... Electric motor, 12 ... Drive pulley (toothed pulley), 13 ... Driven pulley (toothed pulley), 14 ... Belt (toothed belt), 14a, 23 ... Teeth, 19: Ball screw shaft, 20: Ball, 21: Ball nut, a: Axial width of belt.

Claims (2)

An electric steering device that applies auxiliary torque by an electric motor to steering torque from a steering wheel,
A rod-like steering member that reciprocates in the longitudinal direction in accordance with the rotation of the steering wheel, a ball nut externally inserted through a plurality of balls on a ball screw shaft formed on the steering member, and a drive shaft of the electric motor A toothed drive pulley provided on the toothed belt, and a toothed driven pulley connected to the drive pulley via a toothed belt and rotated integrally with the ball nut,
The teeth of the belt are formed in a mountain shape extending incline in the same circumferential direction from the central portion in the width direction of the belt toward one side edge and the other side edge in the width direction of the belt,
The teeth of the drive pulley and the driven pulley are formed in a mountain shape corresponding to the teeth of the belt.   2. The electric steering apparatus according to claim 1, wherein the driven pulley does not include flanges at both ends in the axial direction, and has an axial width substantially the same as the width of the belt.

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