JP2008174136A - Vehicular variable steering angle ratio steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicular variable steering angle ratio steering device varying a steering angle ratio more actively. <P>SOLUTION: The variable steering angle ratio steering device 50 is a device for varying the ratio of a steering angle of a steered wheel relative to a steering angle of a steering wheel, and comprises a movable housing 51, an input shaft 61, an output shaft 71, and an eccentric connection part 75, and a coupling 81. The input shaft is supported on the movable housing so as to be made eccentric from the movable housing. The output shaft is made eccentric from the input shaft and the movable housing. The eccentric connection part is provided eccentrically to the output shaft. The coupling connects the eccentric connection part relative to the input shaft relatively movably in an axial perpendicular direction and relatively rotatably. The movable housing, the input shaft, the output shaft and the eccentric connection part are eccentric to each other so that the input shaft and the eccentric connection part are displaced in an approximately same direction relative to a rotation direction of the movable housing when the movable housing is rotated. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a variable steering angle ratio steering device for a vehicle for changing a ratio of a steering angle of a steering wheel to a steering angle of a steering handle, that is, a steering angle ratio.

A variable steering angle ratio steering device for a vehicle arranges an input shaft that rotates by receiving steering torque from a steering handle and an output shaft that transmits steering torque to a steering wheel via a rack and pinion mechanism so as to be eccentric to each other. In addition, the ratio of the turning angle of the steering wheel to the steering angle of the steering wheel is changed by changing the amount of eccentricity of the input shaft with respect to the output shaft (see, for example, Patent Document 1). According to this vehicle variable steering angle ratio steering apparatus, the steering angle ratio can be automatically changed according to the vehicle speed.
Japanese Patent Laid-Open No. 10-250607

  By the way, the behavior of the vehicle (the yawing generated in the vehicle, the slip of the wheel, etc.) can vary greatly depending on the driving situation and the travel location of the vehicle. In order to further improve the maneuverability of the vehicle, it is preferable not only to change the steering angle ratio according to the vehicle speed but also to change the steering angle ratio more actively according to the behavior of the vehicle.

  It is an object of the present invention to provide a technique that can change the steering angle ratio more actively in the variable steering angle ratio steering device for a vehicle.

  According to the first aspect of the present invention, there is provided a variable steering angle ratio steering device for a vehicle that changes a ratio of a steering angle of a steering wheel with respect to a steering angle of a steering handle, and is fixed to the fixed housing and rotatably supported by the fixed housing. The movable housing is disposed at an eccentric position with respect to the movable housing, the input shaft is rotatably supported by the movable housing, and is disposed at an eccentric position with respect to the input shaft and the movable housing. And an output shaft that is rotatably supported by the fixed housing, an eccentric connecting portion that is eccentrically provided on the output shaft, and a relative movement of the eccentric connecting portion in a direction perpendicular to the input shaft. And a coupling for coupling to be impossible so that relative rotation is impossible, and the input shaft receives the steering torque generated by the steering handle. The movable housing, the input shaft, the output shaft, and the eccentric coupling portion are arranged in the rotational direction of the movable housing when the movable housing rotates. On the other hand, the input shaft and the eccentric coupling portion are arranged eccentrically so as to be displaced in substantially the same direction.

  In the invention according to claim 2, when the movable housing is in a neutral position between forward rotation and reverse rotation, the rotation center of the movable housing, the input shaft, the output shaft, and the centers of the eccentric coupling portions are It is configured to be arranged in a line in a direction perpendicular to the axis when viewed from the axial direction of the input shaft.

In the invention according to claim 1, when the movable housing rotates, the movable housing, the input shaft, the output shaft, and the eccentric coupling portion are eccentric from each other so that the input shaft and the eccentric coupling portion are displaced in the rotation direction of the movable housing. Yes.
For this reason, when the movable housing rotates, the input shaft eccentric from the movable housing is displaced (turned) in the rotation direction of the movable housing. The displaced input shaft tends to displace the eccentric coupling portion via the coupling. The eccentric coupling part is displaced (turned) in the displacement direction of the input shaft with the output shaft as the turning center. The output shaft provided with the eccentric coupling part rotates in the displacement direction of the eccentric coupling part.
As described above, even when the steering handle is kept in a neutral state, the output shaft can be substantially connected to the rotation direction of the movable housing by simply rotating the movable housing, via the input shaft, the coupling, and the eccentric coupling portion. It can be displaced (rotated) in the same direction. That is, the output shaft rotates by a compound angle obtained by adding a rotation angle corresponding to the rotation angle of the movable housing to a rotation angle corresponding to the steering angle of the steering handle (steering angle of the input shaft).
Accordingly, the ratio of the steering angle of the steering wheel to the steering angle of the steering wheel (steering angle ratio) can be changed more actively by rotating the movable housing by the rotation angle corresponding to the behavior of the vehicle. Can do. For this reason, since the controllability of the vehicle can be further improved, it is possible to perform the control more easily and more stably.

  In the invention according to claim 2, when the movable housing is in the neutral position, the centers of the movable housing, the input shaft, the output shaft, and the eccentric coupling portion are arranged in a line in a direction perpendicular to the axis. For this reason, each center can be collected in a small space. Therefore, the variable steering angle ratio steering device for a vehicle can be easily downsized. A small variable steering angle ratio steering device for a vehicle can be easily arranged in a narrow space of the vehicle.

The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.
As an example of a vehicle variable steering angle ratio steering device, an example provided in an electric power steering device will be described. However, the configuration is not limited to that provided in the electric power steering apparatus.

1 to 3 show an electric power steering apparatus 10 including a variable steering angle ratio steering apparatus 50 for a vehicle according to the present invention. As shown in FIG. 1, the electric power steering apparatus 10 includes a steering system 20 that extends from a steering handle 21 of a vehicle to steering wheels 28 and 28, and an auxiliary torque mechanism 30 that applies auxiliary torque to the steering system 20.
Hereinafter, the vehicle variable steering angle ratio steering device 50 is simply referred to as a “variable steering angle ratio steering device 50”. Further, the steering handle 21 is simply referred to as a “handle 21”.

As shown in FIGS. 1 and 2, the steering system 20 has a configuration in which a variable steering angle ratio steering device 50 is incorporated. That is, the handle 21 is connected to the input shaft 61 of the variable steering angle ratio steering device 50 via the steering shaft 22 and the universal joints 23 and 23. The output shaft 71 of the variable steering angle ratio steering device 50 is connected to the rack shaft 25 via the rack and pinion mechanism 24. Both ends of the rack shaft 25 are connected to left and right steering wheels 28, 28 via tie rods 26, 26 and knuckles 27, 27.
The rack and pinion mechanism 24 includes a pinion 24 a attached to the output shaft 71 and a rack 24 b formed on the rack shaft 25.

  As described above, the steering system 20 transmits the steering torque according to the steering of the handle 21 by the driver to the rack shaft 25 via the variable steering angle ratio steering device 50 and the rack and pinion mechanism 24, whereby the rack shaft The steering wheels 28, 28 are steered via 25.

The auxiliary torque mechanism 30 includes a steering torque sensor 31, a control unit 32, an auxiliary motor 33, and a ball screw 34.
The steering torque sensor 31 is incorporated in the variable steering angle ratio steering device 50 and detects the steering torque of the steering system 20 applied to the handle 21. The control unit 32 issues a control signal to the auxiliary motor 33 based on the torque detection signal of the steering torque sensor 31.

  The auxiliary motor 33 is an electric motor for generating an auxiliary torque corresponding to the steering torque based on a control signal of the control unit 32. The motor shaft 33 a of the auxiliary motor 33 is a hollow shaft that surrounds the rack shaft 25.

  The ball screw 34 is a power transmission mechanism for transmitting auxiliary torque to the rack shaft 25, and includes a screw portion 35, nuts 36, and a large number of balls 37. The screw portion 35 is formed on the rack shaft 25. The nut 36 is a rotating member that is assembled to the screw portion 35 via a large number of balls 37, and is also connected to the motor shaft 33a.

  According to the electric power steering apparatus 10, the steering torque transmitted to the input shaft 61 is detected by the steering torque sensor 31, the auxiliary torque corresponding to the steering torque is generated by the auxiliary motor 33, and the auxiliary torque is racked via the ball screw 34. It can be transmitted to the shaft 25. The steering wheels 28 and 28 are steered via the rack shaft 25 by a combined torque obtained by adding the assist torque generated by the assist motor 33 to the steering torque.

  As shown in FIG. 2, the rack shaft 25 extends in the vehicle width direction (left-right direction) and is accommodated in the fixed housing 40. The fixed housing 40 includes a first fixed housing 41 and a second fixed housing 42. The first fixed housing 41 and the second fixed housing 42 are generally tubular members whose one end surfaces are coupled to each other, and are fixed to the vehicle body. The second fixed housing 42 also serves as a motor case for the auxiliary motor 33.

Next, the variable steering angle ratio steering device 50 will be described in detail.
FIG. 3 shows a cross-sectional structure of the variable steering angle ratio steering device 50. FIG. 4 shows a cross-sectional structure of the variable steering angle ratio steering device 50 exposed from the first fixed housing 41, and is shown corresponding to FIG. FIG. 5 shows a disassembled state of the variable steering angle ratio steering device 50 exposed from the first fixed housing 41. 6 is a cross-sectional view taken along line 6-6 of FIG.

  As shown in FIG. 1, the variable steering angle ratio steering device 50 changes the ratio of the steering angles of the steering wheels 28 and 28 to the steering angle of the handle 21. As shown in FIG. 3, the variable steering angle ratio steering device 50 includes a first fixed housing 41 (fixed housing 40), a movable housing 51, an input shaft 61, an output shaft 71, an eccentric connecting portion 75, a coupling 81, and a rudder. It comprises an angle ratio control motor 91 and a transmission mechanism 101.

  The first fixed housing 41 (fixed housing 40) is a fixed member for housing the movable housing 51, the input shaft 61, the output shaft 71, the eccentric connecting portion 75, the coupling 81, and the transmission mechanism 101, and is opened up and down. Has been.

  The movable housing 51 is a composite housing that includes an upper movable housing 52 and a lower movable housing 54 that is detachably coupled to the lower movable housing 52 via an intermediate board 53. The upper movable housing 52 and the lower movable housing 54 are arranged concentrically with each other.

The upper movable housing 52 is made of a resin cylinder. The lower movable housing 54 is made of a metal cylinder. The center Li of the through hole penetrating vertically in the lower movable housing 54 is eccentric with respect to the rotation center Oh of the lower movable housing 54. The axis of the input shaft 61 is disposed at the center Li of the through hole.
Further, the lower movable housing 54 is supported by the first fixed housing 41 via bearings 55 and 55 such that the lower movable housing 54 is rotatable and restricted in axial movement. An oil seal 56 seals between the inner peripheral surface of the upper opening of the first fixed housing 41 and the outer peripheral surface of the lower movable housing 54. The oil seal 56 is covered with an intermediate board 53.

  As shown in FIGS. 3 and 4, the input shaft 61 transmits the steering torque generated by the handle 21 (see FIG. 1) to the steering wheels 28 and 28 (see FIG. 1) via the coupling 81 and the output shaft 71. It is a member. The input shaft 61 is disposed at a position eccentric with respect to the movable housing 51 and is rotatably supported by the movable housing 51. More specifically, the input shaft 61 includes a first shaft 62, a torsion bar 63, and a second shaft 64 arranged concentrically with each other.

  The first shaft 62 is a tubular shaft that penetrates the upper movable housing 52 in the vertical direction and is rotatably supported by the upper movable housing 52 via a bearing 65. The handle 21 shown in FIG. 1 is connected to the first shaft 62 via the steering shaft 22 and the universal joints 23 and 23.

The torsion bar 63 is a member that literally generates a torsion angle accurately with respect to torque, and generates a relative torsional displacement between the first shaft 62 and the second shaft 64. The torsion bar 63 passes through the first shaft 62. An upper end portion of the torsion bar 63 is coupled to the first shaft 62. The lower end portion of the torsion bar 63 is connected to the upper portion of the second shaft 64 so that relative rotation is restricted.
The second shaft 64 is rotatably supported by the lower movable housing 54 via a bearing 66.

As shown in FIGS. 3 to 5, the output shaft 71 is disposed at a position eccentric with respect to the input shaft 61. An upper end portion of the output shaft 71 is rotatably supported by the first fixed housing 41 via a bearing 72. A lower end portion of the output shaft 71 is rotatably supported by the first fixed housing 41 via a bearing 73 and an axial direction adjustment portion 74. The axial direction adjustment unit 74 adjusts to eliminate an excess gap in the axial direction of the output shaft 71.
The pinion 24a is arranged concentrically with the output shaft 71, and is incorporated in the output shaft 71 so as to be rotatable and restricted in axial movement. The pinion 24a may be integrally formed with the output shaft 71.

  Further, the output shaft 71 has an eccentric connecting portion 75 on the upper end surface. The eccentric connecting portion 75 is a bottomed, perfectly circular hole provided integrally at a position facing the coupling 81 and at a position eccentric from the output shaft 71.

As shown in FIGS. 4 and 5, the coupling 81 couples the eccentric coupling portion 75 to the input shaft 61 so as to be capable of relative movement in a direction perpendicular to the axis and not to be relatively rotated. . The coupling 81 includes an upper flange 82, a lower flange 83, a plurality of balls 84, and a ball holder 85.
The upper flange 82 is connected to the lower end portion of the second shaft 64 so that relative rotation is impossible. The upper flange 82 may be formed integrally with the second shaft 64.
The lower flange 83 is rotatably connected to the eccentric connecting portion 75.
The plurality of balls 84 are engaging members that engage between the upper flange 82 and the lower flange 83. The ball holder 85 is a plate-like member that holds a plurality of balls 84 at a predetermined pitch.

  More specifically, the upper and lower flanges 82 and 83 are elongate rectangular parallelepipeds extending in the direction perpendicular to the second shaft 64, and engaging grooves 82a and 83a are formed on surfaces facing each other. ing. These upper and lower engaging grooves 82a and 83a are grooves having a tapered shape in side view, each of which expands toward the mating surface. The plurality of balls 84 are arranged in a line between the upper and lower engagement grooves 82a and 83a and in the longitudinal direction of the engagement grooves 82a and 83a. The upper and lower flanges 82 and 83 can move relative to each other in a direction perpendicular to the second shaft 64 by contacting the inclined surfaces of the upper and lower engaging grooves 82a and 83a with the plurality of balls 84. In addition, the relative rotation is impossible. That is, the lower flange 83 can be moved relative to the upper flange 82 in the direction perpendicular to the axis.

  A boss portion 82 b of the upper flange 82 is rotatably supported by the lower movable housing 54 via a bearing 86. The lower flange 83 has a connecting shaft 83b extending downward from the lower end surface. The connecting shaft 83b is rotatably fitted to an eccentric connecting portion 75 made of a hole via a bearing 87.

  The upper and lower flanges 82 and 83 are interposed between the lower surface of the lower movable housing 54 and the upper surface of the output shaft 71 with upper and lower thrust bearings 88 and 89 being restricted in axial movement.

  As shown in FIG. 6, the steering angle ratio control motor 91 has a motor shaft 91 a extending in a direction perpendicular to the rotation center line Oh of the lower movable housing 54 (movable housing 51), and is attached to the first fixed housing 41. Electric motor, that is, a drive unit. The motor shaft 91 a extends into the first fixed housing 41.

  The transmission mechanism 101 is a worm gear mechanism including a worm shaft 102 connected to the motor shaft 91a, a worm 103 formed on the worm shaft 102, and a worm wheel 104 formed on the outer peripheral surface of the lower movable housing 54. is there. The worm 103 meshes with the worm wheel 104.

The worm shaft 102 is rotatably supported by the first fixed housing 41 via a hollow eccentric sleeve 105 and a bearing 106.
More specifically, the hollow eccentric sleeve 105 is a tubular member that is rotatably inserted into the hole of the first fixed housing 41. The worm shaft 102 is arranged eccentrically with respect to the rotation center of the hollow eccentric sleeve 105 and is rotatably supported by the hollow eccentric sleeve 105 via a bearing 106.

  By rotating the hollow eccentric sleeve 105 with a tool, the distance from the rotation center Oh of the worm wheel 104 (lower movable housing 54) to the center of the worm shaft 102 changes. In this way, the backlash of the worm 103 with respect to the worm wheel 104 can be easily adjusted. After the adjustment is completed, the hollow eccentric sleeve 105 may be fixed to the first fixed housing 41 by bolting or the like.

  As is clear from the above description, since the transmission mechanism 101 is constituted by a worm gear mechanism, the steering caused by tooth backlash compared with the case where other gear transmission systems (for example, planetary gear mechanisms) are employed. The backlash removal work of the system 20 (see FIG. 1) (work to remove a minute play space generated between parts) is extremely simple.

As shown in FIG. 6, the lower movable housing 54 has a cam groove 54a and a rotation range restricting groove 54b on the outer peripheral surface.
The cam groove 54 a is formed so that the groove depth changes in the circumferential direction of the lower movable housing 54. By detecting the amount of change in the depth of the cam groove 54a by the displacement sensor 111 attached to the first fixed housing 41, the rotational angle of the lower movable housing 54 and the amount of displacement of the axis Li of the input shaft 61 are indirectly detected. can do.

  The rotation range restricting groove 54b is elongated in the circumferential direction so as to restrict the rotation range of the lower movable housing 54. The lower movable housing 54 can be rotated until the stopper pin 112 attached to the first fixed housing 41 hits the end of the rotation range regulating groove 54b.

Next, the arrangement relationship among the movable housing 51, the input shaft 61, the output shaft 71, and the eccentric connecting portion 75 will be described in detail.
As shown in FIGS. 5 and 6, the rotation center line Oh of the movable housing 51, the axis line Li of the input shaft 61, the axis line Lo of the output shaft 71, and the center line Lc of the eccentric connecting portion 75 are eccentric to each other. Are arranged in parallel with each other.

  Here, the direction in which the axis line Li of the input shaft 61 is eccentric with respect to the rotation center line Oh of the movable housing 51 is referred to as a rotation neutral direction A0, that is, a rotation neutral position A0. The angle of the rotational neutral position A0 is set to 0 °. Further, a straight line that passes through the rotation center line Oh and points to the rotation neutral position A0 is referred to as a reference straight line Ls. As shown in FIG. 6, the reference straight line Ls is set parallel to the worm shaft 102, for example.

  When the lower movable housing 54 (movable housing 51) faces the rotation neutral position A0, the rotation center line Oh (rotation center Oh) of the movable housing 51, the axis line Li (center Li) of the input shaft 61, and the output shaft 71 The axial line Lo (center Lo) and the center line Lc (center Lc) of the eccentric connecting portion 75 are arranged in a line in a direction perpendicular to the input shaft 61 when the input shaft 61 is viewed from the axial direction. Has been. That is, the axis line Li, the axis line Lo, and the center line Lc are arranged on the reference straight line Ls passing through the rotation center line Oh.

  For this reason, each center Oh, Li, Lo, and Lc can be collected in a small space. Therefore, the vehicle variable steering angle ratio steering device 50 can be easily downsized. The small variable steering angle ratio steering device 50 for a vehicle can be easily arranged in a narrow space of the vehicle.

  Further, as shown in FIG. 5, the output shaft 71, the input shaft 61, and the eccentric coupling portion 75 are arranged at positions far from the rotation center line Oh of the movable housing 51 in this order on the reference straight line Ls. Yes.

  On the reference straight line Ls, the eccentric amounts (offset amounts) S1 to S5 are set as follows. The eccentric amount (first eccentric amount) of the axis line Lo of the output shaft 71 with respect to the rotation center line Oh of the movable housing 51 is S1. The eccentric amount (second eccentric amount) of the axis Li of the input shaft 61 with respect to the axis Lo of the output shaft 71 is S2. The eccentric amount (third eccentric amount) of the center line Lc of the eccentric connecting portion 75 with respect to the axis line Li of the input shaft 61 is S3. The eccentric amount (fourth eccentric amount) of the axis Li of the input shaft 61 with respect to the rotation center line Oh of the movable housing 51 is S4. The fourth eccentricity S4 has a relationship of S4 = S1 + S2. The eccentric amount (fifth eccentric amount) of the center line Lc of the eccentric connecting portion 75 with respect to the axis line Lo of the output shaft 71 is S5. The fifth eccentricity S5 has a relationship of S5 = S2 + S3. The values of these eccentric amounts S1 to S5 are set so as to be optimum conditions.

The above description is summarized as follows.
The input shaft 61 can turn in the rotation direction of the movable housing 51 with the rotation center line Oh of the movable housing 51 as the turning center. The eccentric connecting portion 75 can turn in the turning direction of the input shaft 61 with the axis Lo of the output shaft 71 as the turning center.

  As described above, the movable housing 51, the input shaft 61, the output shaft 71, and the eccentric connecting portion 75 are arranged so that the input shaft 61 and the eccentric shaft 75 are substantially in the same direction as the rotational direction of the movable housing 51 when the movable housing 51 rotates. The connecting portions 75 are arranged eccentrically so as to be displaced.

  The amount of eccentricity S3 from the axis Li to the center line Lc (that is, the amount of eccentricity S3 of the eccentric connecting portion 75 with respect to the input shaft 61) changes according to the displacement of the input shaft 61. The coupling 81 is configured to allow rotation of the movable housing 51 by allowing a change in the eccentric amount S3.

  Incidentally, as shown in FIGS. 3 and 4, the steering torque sensor 31 detects a relative “torsional displacement” between the first shaft 62 and the second shaft 64 connected by the torsion bar 63. Thus, the steering torque of the steering system 20 (see FIG. 1) is detected.

  Specifically, the steering torque sensor 31 is a non-contact torque sensor (variable inductance sensor) that includes a slider 122 with a core 121 and a coil 123. The slider 122 is spanned between the first shaft 62 and the second shaft 64, and can be displaced in the axial direction in accordance with the relative “torsional displacement” of the first and second shafts 62, 64. is there. The coil 123 is attached to the upper movable housing 52 so as to surround the outer periphery of the core 121, and converts the displacement amount of the slider 122 (displacement amount of the core 121) into an electric signal. This electric signal becomes a torque detection signal.

Next, the operation of the variable steering angle ratio steering apparatus 50 having the above configuration will be described.
As shown in FIG. 3, the rotation angle of the output shaft 71 (the rotation angle of the pinion 24 a) in the variable steering angle ratio steering device 50 is detected by the rotation angle sensor 113.
As shown in FIG. 1, the control unit 32 also serves as a control unit of the variable steering angle ratio steering device 50. That is, the control unit 32 controls the steering angle ratio control motor 91 based on the determination signal of the vehicle behavior determination unit 114, the displacement amount detection signal of the displacement sensor 111, and the rotation angle detection signal of the rotation angle sensor 113. To emit.

The vehicle behavior determination unit 114 detects and determines “vehicle behavior” such as a steering angle, a steering speed, a vehicle speed, a yaw rate, and a wheel slip rate, and issues a determination signal to the control unit 32.
The steering angle ratio control motor 91 performs forward / reverse control of the movable housing 51 (see FIG. 5) according to the behavior of the vehicle based on the control signal of the control unit 32.

  For this reason, as shown in FIG. 5, the movable housing 51 rotates forward and backward in the range of the rotation angle θi from the right displacement angle Ai1 to the left displacement angle Ai2 with the rotation neutral position A0 as a reference. The rotation neutral position A0 is at an intermediate position between the right displacement angle Ai1 and the left displacement angle Ai2.

FIG. 7 schematically shows the operation of the variable steering angle ratio steering device 50, and is shown corresponding to FIGS. Hereinafter, a description will be given with reference to FIG.
In FIG. 7, (a) to (c) show the following contents. FIG. 7A shows a turning locus of the axis Li of the input shaft 61 with the rotation center Oh of the movable housing 51 as the turning center, and is shown corresponding to FIG. FIG. 7C shows a turning trajectory of the center line Lc of the eccentric connecting portion 75 with the axis line Lo of the output shaft 71 as the turning center. FIG. 7B shows a complex turning trajectory obtained by superimposing FIG. 7A and FIG. 7B.

Here, the operation of the variable steering angle ratio steering device 50 in the case where the handle 21 (see FIG. 1) is maintained in the neutral state, that is, in the straight traveling steering state will be described.
As a matter of course, the driver continues to hold the handle 21 while the vehicle is traveling. When the handle 21 is kept in a neutral state by the driver, the input shaft 61 does not rotate (spin) around the axis line Li regardless of whether the movable housing 51 is rotated. Since the input shaft 61 does not rotate, the coupling 81 does not rotate around the axis line Li. That is, when the movable housing 51 is rotated, the input shaft 61 and the coupling 81 only turn (revolve) around the rotation center Oh of the movable housing 51.

In FIG. 7A, when the movable housing 51 faces the rotation neutral position A0, the axis Li of the input shaft 61 is at the neutral point Pin on the reference straight line Ls.
When the movable housing 51 is rotated rightward (in the direction of the arrow R1) by the rotation angle “θi / 2”, the axis line Li is displaced to the right displacement angle Ai1. That is, the axis line Li is displaced (turns) from the neutral point Pin to the right displacement point Pi1.
On the other hand, when the movable housing 51 is rotated leftward (in the direction of the arrow R2) by the rotation angle “θi / 2”, the axis line Li is displaced to the left displacement angle Ai2. That is, the axis line Li is displaced from the neutral point Pin to the left displacement point Pi2.

  When the movable housing 51 faces the rotation neutral position A0, the engagement grooves 82a and 83a of the coupling 81 extend along the reference straight line Ls as shown in FIG. 7B. The coupling 81 is connected to the input shaft 61 such that relative rotation is impossible. For this reason, when the axis line Li of the input shaft 61 is displaced, it moves parallel to the right or left with respect to the reference straight line Ls. That is, the straight line Lcp (coupling line Lcp) passing through the axis line Li of the input shaft 61 and the center line Lc of the eccentric coupling portion 75 moves in parallel to the reference straight line Ls.

When the axis Li is displaced from the neutral point Pin to the right displacement point Pi1, the center line Lc of the eccentric connecting portion 75 is displaced from the neutral point Pon to the right displacement point Po1. On the other hand, when the axis Li is displaced from the neutral point Pin to the left displacement point Pi2, the center line Lc of the eccentric connecting portion 75 is displaced from the neutral point Pon to the left displacement point Po2.
That is, as shown in FIG. 7C, the eccentric connecting portion 75 turns in the range of the rotation angle θo from the right displacement angle Ao1 to the left displacement angle Ao2 with the axis line Lo of the output shaft 71 as the turning center. Do (displace). As a result, the output shaft 71 is driven by the eccentric connecting portion 75 and rotates within the range of the rotation angle θo.

  The above description is summarized as follows. As shown in FIG. 5, when the movable housing 51 rotates, the input shaft 61 eccentric from the movable housing 51 is displaced (turned) in the rotation direction of the movable housing 51. The displaced input shaft 61 tends to displace the eccentric connecting portion 75 via the coupling 81. The eccentric connecting part 75 is displaced (turned) in the displacement direction of the input shaft 61 with the output shaft 71 as a turning center. That is, the input shaft 61 and the eccentric coupling portion 75 are displaced in substantially the same direction with respect to the rotation direction of the movable housing 51. The output shaft 71 provided with the eccentric connecting portion 75 rotates in the displacement direction of the eccentric connecting portion 75.

  Accordingly, the input shaft 61, the coupling 81, and the eccentric connecting portion 75 can be swung only by rotating the movable housing 51 without rotating the input shaft 61 while keeping the handle 21 (see FIG. 1) in a neutral state. Can be made. As a result, the output shaft 71 can be displaced (rotated) in the rotational direction of the movable housing 51 via the input shaft 61, the coupling 81, and the eccentric coupling portion 75.

  That is, the output shaft 71 rotates by a compound angle obtained by adding a rotation angle corresponding to the rotation angle of the movable housing 51 to a rotation angle corresponding to the steering angle of the handle 21 (steering angle of the input shaft 61). By rotating the output shaft 71, the steering wheels 28, 28 can be steered via the rack and pinion mechanism 24 and the rack shaft 25 as shown in FIGS.

  Therefore, the ratio of the steering angle of the steering wheels 28 and 28 to the steering angle of the steering wheel 21 (steering angle ratio) is made more active by rotating the movable housing 51 by a rotation angle corresponding to the behavior of the vehicle. Can be changed.

Next, an example of the steering angle ratio characteristic in the variable steering angle ratio steering apparatus 50 having the above configuration will be described based on FIG. 8 with reference to FIGS. 1 and 5.
FIG. 8 is a steering angle ratio characteristic diagram of the variable steering angle ratio steering device 50. The horizontal axis is the steering angle α of the steering wheel, the vertical axis is the steering angle β of the steering wheel, and the steering angle α of the steering wheel 21 is shown. The ratio (steering angle ratio) of the steering angle β of the steering wheels 28, 28 is shown.

A curve indicated by a thin solid line is a steering angle ratio characteristic line St (reference steering angle ratio characteristic line St) when the movable housing 51 faces the rotation neutral position A0.
According to the reference steering angle ratio characteristic line St, the following can be understood. When the steering wheel 21 is steered to the right (steering in the + direction), the steering angle β of the steering wheels 28 and 28 increases (increases in the + direction) as the steering angle α increases. On the other hand, when the steering wheel 21 is steered left (steered in the − direction), the steering angle β of the steering wheels 28 and 28 increases (increases in the − direction) as the steering angle α increases.

A curve indicated by a thin broken line is a steering angle ratio characteristic line Co1 (steering angle ratio characteristic line Co1 at the time of right correction) when the movable housing 51 is rotated to the right displacement angle Ai1.
The steering angle ratio characteristic line Co1 at the time of right correction has a characteristic in which the steering angle β of the steering wheels 28 and 28 is shifted in the right steering direction with respect to the reference steering angle ratio characteristic line St. For example, when the steering wheel 21 is not steered (α = 0 °), the steering angle β of the steering wheels 28 and 28 is shifted by + βa in the right steering direction.

A curve indicated by a thin two-dot chain line is a steering angle ratio characteristic line Co2 (steering angle ratio characteristic line Co2 at the time of left correction) when the movable housing 51 is rotated to the left displacement angle Ai2.
The steering angle ratio characteristic line Co2 at the time of left correction has a characteristic in which the steering angle β of the steering wheels 28 and 28 is shifted in the left steering direction with respect to the reference steering angle ratio characteristic line St. For example, when the steering wheel 21 is kept in a neutral state (α = 0 °), the steering angle β of the steering wheels 28 and 28 is shifted by −βa in the left steering direction.

The amount by which the steering angle ratio characteristic line Co1 during right correction and the steering angle ratio characteristic line Co2 during left correction shift with respect to the reference steering angle ratio characteristic line St changes in accordance with the rotation angle of the movable housing 51. To do.
Thus, the steering angle ratio characteristic can be changed in the range of the steering angle ratio characteristic line Co1 at the time of right correction and the steering angle ratio characteristic line Co2 at the time of left correction.

When the movable housing 51 is rotated in the same direction as the steering direction of the handle 21, the steering angle ratio characteristic in which the steering angle .beta. State). As a result, the steering wheels 28 and 28 can be quickly steered.
For example, the handle 21 is rotated rightward, that is, the movable housing 51 is rotated rightward (arrow R1 direction) to the maximum angle while rotating the input shaft 61 (arrow Hr direction) in FIG. At this time, the steering angle ratio characteristic shown in FIG. 8 shifts from the reference steering angle ratio characteristic line St to the steering angle ratio characteristic line Co1 at the time of right correction.

  On the other hand, when the movable housing 51 is rotated in the direction opposite to the steering direction of the handle 21, the steering angle ratio characteristic is obtained in which the steering angle β of the steering wheels 28 and 28 is reduced as compared with the case where the movable housing 51 is not rotated (so-called). , Switch back to the state). As a result, the steering wheels 28 can be gently steered.

By the way, when the axis line Lo of the output shaft 71 is made to coincide with the rotation center Oh of the movable housing 54, the respective steering angle ratio characteristic lines St, Co1, and Co2 become straight lines, that is, a linear steering angle ratio. It becomes a characteristic.
On the other hand, in this embodiment, the axis line Lo of the output shaft 71 is eccentric with respect to the rotation center Oh of the movable housing 54. As a result, the steering angle ratio characteristic lines St, Co1, and Co2 can be curved, that is, a curved steering angle ratio characteristic can be obtained. For this reason, more fine steering angle ratio control can be performed.

  As is clear from the above description, the input shaft 61, the coupling 81, and the eccentric connecting portion 75 can be simply rotated by rotating the movable housing 51 without rotating the input shaft 61 while keeping the handle 21 in a neutral state. The output shaft 71 can be displaced (rotated) in the rotational direction of the movable housing 51 via the. That is, the output shaft 71 is obtained by adding (adding) a rotation angle corresponding to the rotation angle of the movable housing 51 to a rotation angle corresponding to the steering angle α of the handle 21 (steering angle of the input shaft 61). Rotate.

  Therefore, the steering angle ratio characteristic of the steering angle β of the steering wheels 28 and 28 with respect to the steering angle α of the steering wheel 21 is more actively optimized by automatically rotating the movable housing 51 forward and backward according to the behavior of the vehicle. Can be changed to conditions. For this reason, since the controllability of the vehicle can be further improved, it is possible to perform the control more easily and more stably.

  For example, optimal steering can be performed in accordance with the behavior of the vehicle, such as an actual steering angle ratio characteristic line Re indicated by a thick solid line. It is also possible to steer the steering wheel 21 back to the neutral position (counter-steering).

In the embodiment of the present invention, the fixed housing 40 may be formed by integrally forming the first and second fixed housings 41 and 42.
Further, the movable housing 51 may be one in which an upper movable housing 52, an intermediate board 53, and a lower movable housing 54 are integrally formed.

Further, the input shaft 61 may be one in which the torsion bar 63 is eliminated and the first shaft 62 and the second shaft 64 are integrally formed (even if constituted by a single shaft). Good.)
In that case, the steering torque sensor 31 may be constituted by a magnetostrictive torque sensor. The magnetostrictive torque sensor has a configuration in which a magnetostrictive film is formed on the outer peripheral surface of the input shaft 61. According to the magnetostrictive torque sensor, the steering torque can be detected by detecting the change in magnetostriction generated in the magnetostrictive film in accordance with the steering torque applied to the input shaft 61 by the electric coil and the magnetostriction detection circuit.

  The coupling 81 is engaged with the input shaft 61 so as to be relatively movable in the direction perpendicular to the axis and not rotatable relative to the input shaft 61, and the eccentric portion of the output shaft 71 can be rotated at an eccentric position of the coupling 81. Anything that engages may be used.

  Further, the eccentric connecting portion 75 may have a shaft configuration extending from the output shaft 71 toward the lower flange 83. In that case, the lower flange 83 has a connecting hole for fitting the eccentric connecting portion 75 formed of a shaft.

  The variable steering angle ratio steering device 50 of the present invention is suitable for being mounted on a passenger car.

1 is a schematic diagram of an electric power steering apparatus including a vehicle variable steering angle ratio steering apparatus according to the present invention. FIG. 2 is a detailed view of an auxiliary motor, a ball screw, a vehicle variable steering angle ratio steering device, and a rack shaft shown in FIG. 1. FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. 2. FIG. 4 is a cross-sectional view of the vehicle variable steering angle ratio steering apparatus shown in FIG. 3. FIG. 5 is an exploded view of the vehicle variable steering angle ratio steering apparatus shown in FIG. 4. FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. FIG. 5 is an operation diagram of the vehicle variable steering angle ratio steering device shown in FIG. 4. It is a steering angle ratio characteristic diagram of the variable steering angle ratio steering device according to the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Electric power steering device, 21 ... Steering handle, 28 ... Steering wheel, 40 ... Fixed housing, 50 ... Variable steering angle ratio steering device for vehicles, 51 ... Movable housing, 61 ... Input shaft, 71 ... Output shaft, 75 ... Eccentric coupling part 81... Coupling, A0... Neutral rotation position, Lc... Center of eccentric coupling part, Li ... Center of input shaft, Lo ... Center of output shaft, Oh ... Rotation center of movable housing, S3 ... Eccentric amount of the eccentric connecting portion (third eccentric amount), α: steering angle of the steering wheel, β: steering angle of the steering wheel.

Claims (2)

A variable steering angle ratio steering device for a vehicle that changes a ratio of a steering angle of a steering wheel to a steering angle of a steering wheel,
A fixed housing;
A movable housing rotatably supported by the fixed housing;
An input shaft that is arranged in an eccentric position with respect to the movable housing and is rotatably supported by the movable housing;
An output shaft disposed at a position eccentric to the input shaft and the movable housing, and rotatably supported by the fixed housing;
An eccentric coupling provided eccentric to the output shaft;
The eccentric connecting portion comprises a coupling that allows relative movement in a direction perpendicular to the axis with respect to the input shaft and that cannot be relatively rotated.
The input shaft is a member that transmits a steering torque generated by the steering handle to the steering wheel via the coupling and the output shaft,
The movable housing, the input shaft, the output shaft, and the eccentric coupling portion displace the input shaft and the eccentric coupling portion in substantially the same direction with respect to the rotation direction of the movable housing when the movable housing rotates. Are arranged eccentrically with each other,
A variable steering angle ratio steering device for vehicles.   When the movable housing is in a neutral position between forward rotation and reverse rotation, the rotation center of the movable housing, the input shaft, the output shaft, and the centers of the eccentric coupling portions are viewed from the axial direction of the input shaft. The variable steering angle ratio steering device for a vehicle according to claim 1, wherein the steering angle ratio steering device is arranged in a line in a direction perpendicular to the axis.

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