JP2010269766A - Power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power steering device capable of determining the steering torque of a steering wheel without fitting a torsion bar and a rotational angle sensor for determining the steering torque of the steering wheel to a steering shaft. <P>SOLUTION: A hollow shaft 51 into which a steering shaft 30 is coaxially inserted includes: a first shaft 51a connected to a steering shaft 20 and rotatable accompanied by the rotation of the steering shaft 20; a second shaft 51b connected to the steering shaft 30 via a ball screw mechanism 52 and connected to an electric motor 53; and an elastic portion 51c elastically torsionally deformable between the first shaft 51a and the second shaft 51b. A first resolver 54 for detecting a rotational angle θ1 of the first shaft 51a is provided at the outer circumference of the first shaft 51a while a second resolver 55 for detecting a rotational angle θ2 of the second shaft 51b is provided at the outer circumference of the second shaft 51b. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a power steering device, and in particular, a steering shaft that supports a steering wheel so as to be integrally rotatable, and extends in the vehicle width direction and can move in the vehicle width direction according to the rotation of the steering shaft to steer wheels. The present invention relates to a power steering apparatus including a steering shaft, a housing that supports the steering shaft in an axial direction (vehicle width direction) and is non-rotatable, and an assist device that applies assist force to the steering shaft.

  In this type of power steering device, for example, it is described in the following Patent Document 1, and in the power steering device described in the following Patent Document 1, it is assembled so that it can rotate with respect to the housing and cannot move in the axial direction. A hollow shaft (motor shaft) in which the steering shaft is coaxially inserted, an electric motor capable of rotating the hollow shaft according to the steering torque of the steering wheel, and a hollow interposed between the hollow shaft and the steering shaft An electric assist device having a screw mechanism (ball screw mechanism) for converting the rotation of the shaft into the axial movement of the steering shaft is provided.

  Further, in the power steering device described in Patent Document 1 below, a pinion shaft (a part of the steering shaft) provided on the lower end side of the steering shaft includes an input shaft on the steering wheel side and a steering shaft side. The input shaft and the output shaft are connected via a torsion bar, and a pinion gear formed on the output shaft and a rack formed on the steering shaft are engaged with each other. In addition, a first resolver that detects the rotation angle of the input shaft relative to the housing is provided on the outer periphery of the input shaft, and a second resolver that detects the rotation angle of the output shaft relative to the housing is provided on the outer periphery of the output shaft. Yes.

JP 2003-75109 A

  For this reason, in the power steering device described in Patent Document 1, when the steering wheel is turned and steered, the steering shaft (pinion shaft) is rotated, and the steering shaft is driven by the engagement of the rack and pinion. Moving in the direction, the wheels are steered. At this time (when the steering wheel is turned), the input shaft and the output shaft of the pinion shaft rotate relative to each other, and the rotation angle of the input shaft detected by the first resolver and the output detected by the second resolver. Based on the rotational angle of the shaft and the torsional rigidity of the torsion bar, the steering torque of the steering wheel is obtained, and the electric motor rotates the hollow shaft in accordance with the steering torque of the steering wheel. Thereby, the rotation of the hollow shaft is converted into the axial movement (movement in the vehicle width direction) of the steering shaft via the screw mechanism, and an electric assist force is applied to the steering shaft.

  By the way, in the power steering apparatus described in the above-mentioned Patent Document 1, the torsion bar, the first resolver, and the second resolver are assembled to the pinion shaft (part of the steering shaft). The mountability of the steering shaft on the vehicle is as much as the axial length of the torsion bar is secured from the upper end (the connection portion of the steering shaft and the steering wheel) to the lower end of the steering shaft (the connection portion of the steering shaft and the steering shaft). There was a risk of getting worse. In other words, the interval for mounting the steering shaft on the vehicle is limited to a predetermined range, and when the torsion bar is assembled to the steering shaft in addition to the intermediate shaft (part of the steering shaft) and the telescopic mechanism, etc. The space connecting the steering shaft on the steering shaft side (pinion shaft with the torsion bar assembled) and the steering shaft on the steering wheel side (steering shaft with the intermediate shaft and telescopic mechanism assembled) There is a possibility that the vehicle mounting property of the steering shaft may deteriorate.

  The present invention has been made to cope with the above-described problems, and includes a steering shaft that supports a steering wheel so as to be integrally rotatable, and extends in the vehicle width direction and moves in the vehicle width direction according to the rotation of the steering shaft. A steering shaft capable of turning the wheel, a housing that supports the steering shaft in a manner that allows the steering shaft to move in the axial direction, and the steering shaft that can rotate in the axial direction and cannot move in the axial direction. A hollow shaft through which the shaft is coaxially inserted, an electric motor capable of rotating the hollow shaft in accordance with a steering torque of the steering wheel, and the hollow shaft interposed between the hollow shaft and the steering shaft In the power steering device having a screw mechanism that converts the rotation of the steering shaft into the axial movement of the steering shaft, the hollow shaft is connected to the steering shaft and is connected to the steering shaft. A first shaft portion that is rotatable as the ring shaft rotates, and has a second shaft portion that is connected to the steering shaft and connected to the electric motor via the screw mechanism, and the first shaft A first rotation for detecting an angle of rotation of the first shaft portion relative to the housing on an outer periphery of the first shaft portion. An angle sensor is provided, and a second rotation angle sensor for detecting a rotation angle of the second shaft portion relative to the housing is provided on the outer periphery of the second shaft portion.

  In the power steering apparatus according to the present invention, when the steering wheel is turned, the steering shaft rotates, and the first shaft portion of the hollow shaft connected to the steering shaft rotates as the steering shaft rotates. And rotation of the 1st shaft part is transmitted to the 2nd shaft part via an elastic part, and the 2nd shaft part rotates. Thereby, the rotation of the second shaft portion is converted into the axial movement (movement in the vehicle width direction) of the steering shaft via the screw mechanism, and the wheels are steered by the movement of the steering shaft in the vehicle width direction.

  Further, when the steering wheel is turned, the first shaft portion and the second shaft portion are relatively rotated because the first shaft portion and the second shaft portion are connected by an elastic portion that can be elastically deformed. At this time, the steering wheel is steered based on the rotation angle of the first shaft portion detected by the first rotation angle sensor, the rotation angle of the second shaft portion detected by the second rotation angle sensor, and the torsional rigidity of the elastic portion. Torque is determined, and the electric motor rotates the second shaft portion of the hollow shaft in accordance with the steering torque of the steering wheel. Thereby, the rotation of the second shaft portion is converted into the axial movement of the steering shaft via the screw mechanism, and an electric assist force can be applied to the steering shaft.

  By the way, in the power steering apparatus according to the present invention, the hollow shaft through which the steering shaft is coaxially inserted is provided with an elastic portion capable of elastic torsional deformation, and the first rotation is performed on the outer periphery of the first shaft portion of the hollow shaft. Since the angle sensor is provided and the second rotation angle sensor is provided on the outer periphery of the second shaft portion of the hollow shaft, the steering shaft extends from the upper end of the steering shaft (the connecting portion of the steering shaft and the steering wheel). It is not necessary to provide a member corresponding to the torsion bar in the conventional power steering device at the lower end of the wheel (the connecting portion between the steering shaft and the hollow shaft). Therefore, it is not necessary to secure the axial length of the torsion bar in the interval from the upper end of the steering shaft to the lower end of the steering shaft, and the axial length of the steering shaft is shortened as compared with the conventional power steering device. It is possible to improve the vehicle mounting property of the steering shaft.

1 is an overall configuration diagram illustrating a first embodiment of a power steering device according to the present invention. FIG. 2 is an enlarged longitudinal side view along line 2-2 in FIG. 1. FIG. 3 is an enlarged cross-sectional plan view along line 3-3 in FIG. 2. It is the whole block diagram which showed 2nd Embodiment of the power steering apparatus in this invention.

  Embodiments of the present invention will be described below with reference to FIGS. 1 to 3 show a first embodiment of an electric power steering apparatus according to the present invention. The electric power steering apparatus includes a steering wheel 10 that can be turned and a steering wheel 10. A steering shaft 20 to be supported, a steering shaft 30 extending in the vehicle width direction (left-right direction of the vehicle), a housing 40 for supporting the steering shaft 30 so as to be movable in the axial direction (vehicle width direction), and a steering shaft An electric assist device 50 for applying an electric assist force to 30 is provided.

  As shown in FIG. 1, the steering wheel 10 is supported on the upper end of the steering shaft 20 so as to be integrally rotatable. The steering shaft 20 is rotatably assembled to the housing 40 via a bearing Br1 and a bearing Br2. Further, as shown in FIGS. 2 and 3, the worm wheel 21 is assembled to the lower end portion of the steering shaft 20 so as to be integrally rotatable.

  As shown in FIG. 1, the steering shaft 30 is integrated with a screw shaft 52 a of a ball screw mechanism 52 in the electric assist device 50 at an intermediate portion, and is attached to an end stopper 41 assembled to the housing 40 at the left portion. It is supported so as to be movable in the axial direction, and is supported so as to be movable in the axial direction by an end stopper 42 assembled to the housing 40 at the right side. The steering shaft 30 is spline-fitted to an inner spline 41a provided on the end stopper 41 by an outer spline 30a provided on the outer periphery of the left portion. Thereby, the steering shaft 30 is supported so as to be movable in the axial direction and non-rotatable with respect to the housing 40. The steering shaft 30 is connected to the left and right front wheels FW1 and FW2 via ball joints (not shown), tie rods (not shown), knuckle arms (not shown), and the like at both left and right ends. Thereby, when the steering shaft 30 moves in the vehicle width direction, the left and right front wheels FW1, FW2 are steered.

  As shown in FIGS. 1 to 3, the housing 40 extends in the same direction (vehicle width direction) as the steering shaft 30 and is fixed to a vehicle body side member (not shown). As shown in FIGS. 2 and 3, the housing 40 has a bulging portion 40a that protrudes in the left direction (front direction of the vehicle) in FIG. 2 in order to accommodate the worm wheel 21 assembled to the steering shaft 20. have.

  As shown in FIG. 1, the electric assist device 50 includes a hollow shaft 51 in which the steering shaft 30 is coaxially inserted, and a ball screw mechanism 52 interposed between the hollow shaft 51 and the steering shaft 30. An electric motor 53 capable of rotating the hollow shaft 51, a first resolver 54 (first rotation angle sensor) and a second resolver 55 (second rotation angle sensor) provided on the outer periphery of the hollow shaft 51, and an electric motor An electric control device 56 for controlling the operation of 53 is provided.

  As shown in FIG. 1, the hollow shaft 51 has a first shaft portion 51a connected to the steering shaft 20 via a worm gear mechanism GM on the left side, and a ball screw mechanism 52 on the right side. It has the 2nd shaft part 51b connected with the steering shaft 30, and has the elastic part 51c which connects the 1st shaft part 51a and the 2nd shaft part 51b, and can be elastically torsionally deformed. A slight gap is formed between the hollow shaft 51 and the steering shaft 30.

  As shown in FIGS. 2 and 3, a worm 51 a 1 is formed in the first shaft portion 51 a, and the worm wheel 21 assembled to the worm 51 a 1 and the steering shaft 20 meshes. The worm 51a1 and the worm wheel 21 constitute the worm gear mechanism GM described above, and the rotation of the steering shaft 20 is accelerated and transmitted to the rotation of the first shaft portion 51a. In this embodiment, when the steering shaft 20 (worm wheel 21) rotates once, the first shaft portion 51a (worm 51a1) rotates 20 times (the speed increase ratio becomes 20). The speed increase ratio described above can be changed as appropriate.

  As shown in FIG. 1, the second shaft portion 51b is assembled to the housing 40 through the bearing Br3 on the outer periphery of the right end portion and is immovable in the axial direction (vehicle width direction). The nut 52b in the ball screw mechanism 52 is supported so as to be integrally rotatable. The second shaft portion 51b is connected to the left end of the rotor 53b in the electric motor 53 so as to be integrally rotatable at the right end. The elastic portion 51c has a torsional rigidity K, and can be elastically deformed when the steering wheel 10 and the steering shaft 20 rotate. Due to the elastic torsional deformation of the elastic portion 51c, the first shaft portion 51a and the second shaft portion 51b are relatively rotatable.

  As shown in FIG. 1, the ball screw mechanism 52 is for decelerating the rotation of the second shaft portion 51 b of the hollow shaft 51 and converting it into axial movement of the steering shaft 30. It is provided coaxially. Further, the ball screw mechanism 52 includes the screw shaft 52a and the nut 52b described above, and between a male screw groove (not shown) formed in the screw shaft 52a and a female screw groove (not shown) formed in the nut 52b. A plurality of interposed balls 52c and a deflector (not shown) that is assembled to the nut 52b and infinitely circulates each ball 52c are provided.

  As shown in FIG. 1, the electric motor 53 is disposed coaxially with the housing 40, and includes a stator 53 a fixed to the housing 40 and a rotor 53 b that can rotate with respect to the housing 40. . The stator 53 a is formed in a hollow shape and is connected to the electric control device 56. The stator 53a can rotate the rotor 53b by the assist current A output from the electric control device 56, and the second shaft portion 51b and the nut 52b can be rotated by the rotation of the rotor 53b. The rotor 53b is formed in a hollow shape, and is assembled to the housing 40 via the bearing Br4 at the right end so as to be rotatable and immovable in the axial direction.

  The first resolver 54 is an electromagnetic rotation angle sensor. As shown in FIG. 1, the first resolver 54 is provided on the outer periphery of the right end portion of the first shaft portion 51a, and is a resolver stator (not shown) fixed to the housing 40. And a resolver rotor (not shown) fixed to the first shaft portion 51a. The first resolver 54 is connected to the electric control device 56, detects the rotation angle θ1 of the first shaft portion 51a with respect to the housing 40, and outputs the rotation angle θ1 to the electric control device 56. ing.

  The second resolver 55 is an electromagnetic rotation angle sensor. As shown in FIG. 1, the second resolver 55 is provided on the outer periphery of the left end portion of the second shaft portion 51b and is fixed to the housing 40 (not shown). ) And a resolver rotor (not shown) fixed to the second shaft portion 51b. The second resolver 55 is connected to the electric control device 56, detects the rotation angle θ2 of the second shaft portion 51b with respect to the housing 40, and outputs the rotation angle θ2 to the electric control device 56. ing. In addition, since the detailed structure of the resolver stator and resolver rotor mentioned above is well-known, the description is abbreviate | omitted.

  The electric control device 56 includes a CPU, a ROM, a RAM, an I / O, and the like, and includes a difference θ1-θ2 between the rotation angle θ1 detected by the first resolver 54 and the rotation angle θ2 detected by the second resolver 55, and elasticity. Based on the torsional rigidity K of the portion 51c, the steering torque T of the steering wheel 10 is obtained by calculation. In addition, the electric control device 56, the steering torque T, the vehicle speed V detected by a vehicle speed sensor (not shown), the engine speed rpm, and the rotation angle θ2 of the second shaft portion 51b with respect to the housing 40 (that is, Based on the rotation angle of the rotor 53 b with respect to the housing 40, the motor assist current A is obtained by calculation, and this motor assist current A is output to the stator 53 a of the electric motor 53.

  In the first embodiment configured as described above, when the steering wheel 10 is rotated and steered, the steering shaft 20 rotates, and the first of the hollow shaft 51 connected to the steering shaft 20 via the worm gear mechanism GM. The shaft portion 51a rotates as the steering shaft 20 rotates. Then, the rotation of the first shaft portion 51a is transmitted to the second shaft portion 51b via the elastic portion 51c, and the rotation of the second shaft portion 51b moves in the axial direction of the steering shaft 30 (vehicle) via the ball screw mechanism 52. The left and right front wheels FW1, FW2 are steered by the movement of the steering shaft 30 in the vehicle width direction.

  In addition, when the steering wheel 10 is turned, the first shaft portion 51a and the second shaft portion 51b are connected by the elastic portion 51c that can be elastically deformed, so that the first shaft portion 51a and the second shaft portion 51b are connected. Relative rotation. At this time, the electric control device 56 determines the difference θ1−θ2 between the rotation angle θ1 of the first shaft portion 51a detected by the first resolver 54 and the rotation angle θ2 of the second shaft portion 51b detected by the second resolver 55, and Based on the torsional rigidity K of the elastic portion 51c, the steering torque T of the steering wheel 10 is obtained by calculation. The steering torque T, the vehicle speed V, the engine speed rpm, and the rotation angle of the rotor 53b with respect to the housing 40 (by the second resolver 55). Based on the detected rotation angle θ 2), a motor assist current A is obtained by calculation, and this motor assist current A is output to the stator 53 a of the electric motor 53. Thereby, the stator 53a of the electric motor 53 rotates the rotor 53b and the second shaft portion 51b, and the rotation of the second shaft portion 51b is converted into the axial movement of the steering shaft 30 via the ball screw mechanism 52, and the steering is performed. It is possible to apply an electric assist force to the shaft 30.

  By the way, in the power steering apparatus according to the present invention, the elastic portion 51c is provided in the hollow shaft 51 through which the steering shaft 30 is coaxially inserted, and the first resolver is provided on the outer periphery of the first shaft portion 51a of the hollow shaft 51. 54, and the second resolver 55 is provided on the outer periphery of the second shaft portion 51b of the hollow shaft 51, so that the upper end of the steering shaft 20 (the connecting portion of the steering shaft 20 and the steering wheel 10). Therefore, it is not necessary to provide a member corresponding to the torsion bar in the conventional power steering device at the lower end of the steering shaft 20 (the connecting portion of the steering shaft 20 and the first shaft portion 51a of the hollow shaft 51). Therefore, it is not necessary to secure the axial length of the torsion bar in the interval from the upper end of the steering shaft 20 to the lower end of the steering shaft 20, and the axial length of the steering shaft 20 is larger than that of the conventional power steering device. It can be shortened, and the vehicle mountability of the steering shaft 20 can be improved.

  In the first embodiment, the rotation angle θ2 of the second shaft portion 51b detected by the second resolver 55 with respect to the housing 40 is used to calculate the steering torque T, and the rotor 53b relative to the housing 40 is used. It is used to calculate the motor assist current A as the rotation angle. For this reason, in order to detect the rotation angle of the rotor 53b with respect to the housing 40, it is not necessary to provide a separate rotation angle sensor, and it can be implemented at low cost.

  In the first embodiment configured as described above, the present invention is implemented in the electric power steering apparatus. However, in the present invention, as in the second embodiment shown in FIG. The present invention can be similarly applied to a hybrid type power steering device provided in the same type of power steering device.

  In the second embodiment shown in FIG. 4, the hydraulic assist unit 160 is provided on the right side of the housing 40 and applies a hydraulic assist force to the steering shaft 30, the hollow shaft 51, and the housing 40. Is connected to the control valve 162 for controlling the hydraulic oil supplied to the hydraulic cylinder 161, the hydraulic pump 163 for supplying the hydraulic oil to the control valve 162, and the hydraulic pump 163 and the control valve 162. A reservoir 164. In the second embodiment, the second shaft portion 51b of the hollow shaft 51 and the nut 52b of the ball screw mechanism 52 are integrally configured.

  Since the configuration other than the configuration of the second embodiment described above is substantially the same as the configuration of the first embodiment described above, the same reference numerals are given to corresponding portions, and the description thereof is omitted. The operational effects of the second embodiment described above are substantially the same as the operational effects of the first embodiment described above, except that a hydraulic assist force is applied to the steering shaft 30 in addition to the electric assist force. Therefore, the description is omitted.

  In each of the above-described embodiments, the first resolver 54 is used as the first rotation angle sensor that detects the rotation angle θ1 of the first shaft portion 51a with respect to the housing 40, and the rotation angle θ2 of the second shaft portion 51b with respect to the housing 40. Although the second resolver 55 is used as the second rotation angle sensor for detecting the first rotation angle, the first rotation angle sensor and the second rotation angle sensor are not limited to the resolver that is an electromagnetic rotation angle sensor. For example, a rotary encoder that is an optical rotation angle sensor may be used.

  Further, in each of the above-described embodiments, the mechanism for rotating the first shaft portion 51a with the rotation of the steering shaft 20 is formed in the worm wheel 21 assembled to the steering shaft 20 and the first shaft portion 51a. Although the worm gear mechanism GM including the worm 51a1 is configured and implemented, the above-described mechanism is not limited to the worm gear mechanism GM. For example, the bevel gear assembled to the steering shaft 20 and the first shaft It can also be configured and implemented as a bevel gear mechanism comprising a bevel gear assembled to the portion 51a.

  Further, in each of the above-described embodiments, the rotation angle of the rotor 53b with respect to the housing 40 and the rotation angle θ2 of the second shaft portion 51b with respect to the housing 40 detected by the second resolver 55 are the same. Although the motor rotation angle sensor that can detect the rotation angle 53b is not provided, the above-described motor rotation angle sensor may be provided separately.

  In each embodiment described above, the ball screw mechanism 52 is used as the screw mechanism. However, the screw mechanism is not limited to the ball screw mechanism 52. For example, a trapezoidal screw mechanism may be used. Is possible.

DESCRIPTION OF SYMBOLS 10 ... Steering wheel, 20 ... Steering shaft, 21 ... Worm wheel, 30 ... Steering shaft, 40 ... Housing, 41, 42 ... End stopper, 50 ... Electric assist device, 51 ... Hollow shaft, 51a ... First shaft part, 51a1 ... Worm, 51b ... Second shaft portion, 51c ... Elastic portion, 52 ... Ball screw mechanism, 52a ... Screw shaft, 52b ... Nut, 52c ... Ball, 53 ... Electric motor, 53a ... Stator, 53b ... Rotor, 54 ... First Resolver, 55 ... second resolver, 56 ... electric control device, θ1, θ2 ... rotation angle, K ... torsional rigidity, T ... steering torque, V ... vehicle speed, rpm ... engine speed, A ... motor assist current, Br1, Br2 , Br3, Br4 ... bearings, GM ... worm gear mechanism, FW1, FW2 ... left and right front wheels, 160 ... hydraulic assist Device 161 ... Hydraulic cylinder 162 ... Control valve 163 ... Hydraulic pump 164 ... Reservoir

Claims (1)

A steering shaft that supports the steering wheel so as to rotate integrally, a steering shaft that extends in the vehicle width direction and can move in the vehicle width direction according to the rotation of the steering shaft and steer the wheel, and the steering shaft A housing that is axially movable and non-rotatable, a hollow shaft that is rotatably and axially non-movable with respect to the housing, and the steering shaft is coaxially inserted; An electric motor capable of rotating the hollow shaft in accordance with a steering torque; and a screw mechanism interposed between the hollow shaft and the steering shaft to convert rotation of the hollow shaft into axial movement of the steering shaft. In the power steering device
The hollow shaft has a first shaft portion that is connected to the steering shaft and is rotatable with the rotation of the steering shaft, and is connected to the steering shaft and the electric motor via the screw mechanism. A second shaft portion, and an elastic portion capable of elastic torsional deformation between the first shaft portion and the second shaft portion;
A first rotation angle sensor that detects a rotation angle of the first shaft portion with respect to the housing is provided on an outer periphery of the first shaft portion, and an outer periphery of the second shaft portion includes the first shaft angle sensor. A power steering device, wherein a second rotation angle sensor for detecting a rotation angle with respect to the housing is provided.

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