JP2005180587A - Variable gear ratio mechanism and steering control device for vehicle equipped with the variable gear ratio mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a whole device radially compact by uniquely disposing and configuring ball bearings that journal an eccentric cam. <P>SOLUTION: A gear ratio variable mechanism is provided between a steering shaft 2 and an output shaft 4 and configured as follows. A gear ratio variable mechanism 6, for changing and controlling the rotational force transmitted from the steering shaft to the output shaft to a predetermined gear ratio, comprises a first external gear 21 and a first internal gear 22 on the steering shaft side, and a second internal gear 23 and a second external gear 24 on the output shaft side, and also comprises a virtually cylindrical eccentric cam 17 relatively rotatably supporting the connecting part 25 between the internal gears at an eccentric hole 28. The ball bearings 26, 27 rotatably supporting the eccentric cam are disposed between each inner peripheral surface of both end parts 17c, 17d of the eccentric cam and each outer peripheral surface of the steering shaft 2 and the output shaft 4 of smaller diameters respectively. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a gear ratio variable mechanism that transmits a rotation ratio (gear ratio) of an input shaft to an output shaft with a variable gear ratio, and a vehicle steering control device that uses the gear ratio variable mechanism.

  For example, as a conventional gear ratio variable mechanism used in a vehicle steering control device, for example, one described in Patent Document 1 below is known.

  In brief, this vehicle steering control device is provided with a gear ratio variable mechanism that varies the gear ratio by an electric motor between an input shaft on the steering wheel side and an output shaft on the turning angle side. Yes.

  In this gear ratio variable mechanism, first and second internal gears having different outer diameters are provided at opposite ends of the input shaft and the output shaft on the same axis, and the outer gears have different outer diameters. The first and second external gears are meshed, and the external gears are fixed to the rotation shaft.

An eccentric cam that controls the revolution of the rotary shaft is supported on the rotary shaft so as to be relatively rotatable. The eccentric cam is controlled to rotate by an electric motor through a worm mechanism, whereby the input shaft and the output shaft are output. The relative rotation amount generated between the shaft and the shaft is controlled.
German Patent No. 10160313

  In the conventional gear ratio variable mechanism, the bearing that rotatably supports the eccentric cam is interposed between the eccentric cam and the housing and is supported by the housing. There is a problem that the entire apparatus becomes larger in the radial direction by the size of the bearing in the radial direction.

  The present invention has been devised in view of the technical problem of the conventional gear ratio variable mechanism, and the invention according to claim 1 is characterized in that, in particular, a bearing for rotatably supporting an eccentric cam is provided as a first external tooth. Between the outer periphery of the input shaft and the output shaft and the inner periphery of the eccentric cam that are axially spaced from the meshing part of the gear and the first internal gear and the meshing part of the second external gear and the second internal gear It is characterized by being provided in.

  According to the present invention, the bearing is not disposed between the housing as in the prior art, but is provided at a position avoiding the meshing portion of each gear, so that the radial expansion by the bearing is prevented, The entire apparatus can be reduced in size.

  According to a second aspect of the present invention, the gear ratio variable mechanism according to the first aspect is provided between the input shaft and the output shaft, and a rotational force transmitted from the input shaft to the output shaft is applied to a predetermined gear. It is characterized by conversion control to a ratio.

  According to the present invention, the eccentric cam bearing of the gear ratio variable mechanism applied to the vehicle steering control device is located at the position described in claim 1, that is, the position avoiding the meshing portion of each gear, and the eccentric cam. Therefore, the same effect as that of the invention of claim 1 can be obtained.

  Hereinafter, an embodiment in which a gear ratio variable mechanism according to the present invention is applied to a steering control device for a vehicle will be described in detail with reference to the drawings.

  FIG. 1 shows an outline of a vehicle steering control apparatus according to a first embodiment. A rack and pinion mechanism for steering a steering shaft 2 as an input shaft connected to a steering wheel 1 and front and left steered wheels FL and FR. 3, a steering mechanism 5 that drives the rack and pinion mechanism 3 via the output shaft 4 according to the steering angle of the steering shaft 2, and a steering mechanism 2 that is provided separately from the steering mechanism 5. And a gear ratio variable mechanism 6 for driving the rack and pinion mechanism 3 according to the steering angle.

  Further, the steering angle sensor 7 which is a steering angle detecting means for detecting the steering angle and steering torque of the steering shaft 2 and the turning wheels FL and FR of the both steered wheels FL and FR according to the sliding position of the rack bar of the rack and pinion mechanism 3. An actual turning angle sensor 8 which is an actual turning angle detection means for detecting an actual turning angle, and the steering means 5 and a gear ratio variable mechanism based on information signals from the steering angle sensor 7 and the actual turning angle sensor 8. And an electronic controller 9 for controlling 6.

  The rack and pinion mechanism 3 includes a rack bar 3a fixed to the tie rod 10 and a pinion gear 3b meshing with the rack bar 3a. The rack bar 3a is a knuckle connected to both ends of the tie rod 10. It is linked to both steered wheels FL, FR via arms 10a, 10a.

  As shown in FIG. 1, the output shaft 4 includes an upper shaft 4 a linked to the steering shaft 2 via a gear ratio variable mechanism 6, and the rack 4 to the upper shaft 4 a via a torsion bar 11. A lower shaft 4 b connected to the pinion gear 3 b of the pinion mechanism 3. A torque sensor 11 a that detects a steering torque, which is a torque difference between the upper shaft 4 a and the lower shaft 4 b, by twisting the torsion bar 11 is provided on the outer periphery of the torsion bar 11.

  The steering mechanism 5 includes a reduction gear mechanism 12 linked to a pinion gear through the lower shaft 4b, and an electric drive motor 13 capable of rotating forward and reverse through the gear mechanism 12 to rotate the pinion gear. The gear mechanism 12 is provided with the actual turning angle sensor 8 for detecting the current actual turning angle by detecting the sliding position on the rack bar 3a.

  As shown in FIGS. 2 to 5, the gear ratio variable mechanism 6 includes a first gear gear 15 on the steering shaft 2 side and a second gear gear 16 on the output shaft 4 side that are arranged in series in the housing 14. And an eccentric cam 17 which is arranged on the outer peripheral side of the first and second gear gears 15 and 16 and applies a revolving force to the gear gears 15 and 16 by eccentric rotation, and the electronic controller 9 And an actuator 18 that controls the rotation of the eccentric cam 17.

  The steering shaft 2 and the output shaft 4 are configured such that a front end portion 2a and an upper shaft 4a facing each other are coaxially arranged in the housing 14, and a support hole 4c formed in an end portion of the upper shaft 4a along the axial direction. A tip portion 2b of the tip portion 2a is supported in a relatively rotatable manner through a cylindrical bush 19, and is slightly movable in the axial direction.

  As shown in FIG. 2, the housing 14 is fixed to the vehicle body, is formed in a stepped cylindrical shape, and is provided with ball bearings 20 and 20 provided in the front and rear end portions, and the front end portion 2a of the steering shaft 2 and the output. The end portion of the upper shaft 4a of the shaft 4 is rotatably supported.

  As shown in FIGS. 2 and 4, the first gear gear 15 includes a first external gear 21 coaxially provided on the outer peripheral surface of the tip end portion 2 a of the steering shaft, and the first external gear 21. And a cylindrical first internal gear 22 meshing in an eccentric state from the outside.

  On the other hand, as shown in FIGS. 2 and 5, the second gear gear 16 includes a cylindrical second internal gear 23 integrally coupled to the first internal gear 22 from the axial direction, and the output shaft 4. And a second external gear 24 that is coaxially provided on the outer peripheral surface of the end of the upper shaft 4a and meshes with the second internal gear 23 in an eccentric state.

  Further, as shown in FIG. 6, the outer diameter d of the first external gear 21 is smaller than the outer diameter d1 of the second external gear 24.

  Further, as shown in FIG. 7, the first internal gear 22 and the second internal gear 23 are integrally connected by a thin cylindrical coupling portion 25 at the center, and the first internal gear Each inner diameter d3 of 22 is formed smaller than the inner diameter d4 of the second internal gear 23. Therefore, in the connecting portion 25, the boundary between the internal gears 22 and 23 is a step portion 25a.

  Further, as shown in FIGS. 6 and 7, the tooth portions formed inside and outside each of the gears 21 to 24 are formed on helical teeth 21a to 24a, and the torsional directions thereof are set to the same direction. ing. Further, the torsional angles θ1 and θ2 of the helical teeth 21a to 24a are set substantially the same.

  As shown in FIGS. 2, 3, 8, and 9, the eccentric cam 17 is formed in a substantially cylindrical shape, and two ball bearings 26, 27 whose front and rear end portions 17c, 17d are first bearings. The steering shaft 2 and the output shaft 4 are supported so as to be rotatable relative to each other.

  That is, both ends 17c and 17d in the axial direction of the eccentric cam 17 are meshed with the helical teeth 21a and 22a of the first external gear 21 and the first internal gear 22 and the second internal gear 23 and the second internal gear 23. 2 It extends in the axial direction spaced apart from the meshing portion of the helical teeth 23a, 24a of the external gear 24, and between each inner peripheral surface of each end portion 17c, 17d and each outer peripheral surface of the steering shaft 2 and the output shaft 4. The two ball bearings 26 and 27 are arranged on the surface.

  The center P of the eccentric cam 17 is arranged concentrically with the axes of both the shafts 2 and 4, and the center P1 is eccentric from the center P by a predetermined amount inside the main body 17a on the steering shaft 2 side. An eccentric hole 28 is formed.

  Further, a coupling portion 25 between the internal gears 22 and 23 is rotatably supported through one ball bearing 29 which is a second bearing fixed to the inner peripheral surface of the eccentric hole 28.

  That is, the ball bearing 29 is held while the outer race 29a is held in the step groove 28a formed in the inner peripheral surface of the eccentric hole 28 while being restricted from moving in the axial direction on the steering shaft 2 side, while the inner race 29b is The step 25a of the coupling portion 25 is held while being restricted from moving in the axial direction on the output shaft 4 side.

  The internal gears 22 and 23 are connected to the external gears 21 via the ball bearings 29 by spring members 30 of holding holes 17b provided in the radial direction in the maximum thickness portion of the eccentric cam body 17a. , 24 direction.

  The actuator 18 includes a reversible electric motor 31 held on the inner peripheral side of the housing 14 and a reduction gear provided between the electric motor 31 and the eccentric cam 17.

  As shown in FIG. 2, the reduction gear is fixed to the outer peripheral surface of the step diameter portion of the main body 17a of the eccentric cam 17 and the worm shaft 32a coupled to the rotating shaft of the electric motor 31, and the worm shaft 32a. It is comprised from the worm wheel 32b which meshes with.

  Then, the rotational force transmitted from the electric motor 31 is transmitted to the eccentric cam 17 by the reduction gear, and the internal gears 22 and 23 are revolved by forward and reverse rotation of the eccentric cam 17 so that the steering shaft 2 and the output shaft 4 are rotated. The gear ratio (deceleration, speed increase ratio) is variably controlled.

  The electronic controller 9 has a built-in microcomputer and, as shown in FIG. 1, is detected by the steering angle θ, the actual steering angle θ ′, and the torque sensor 11a from the steering angle sensor 7 and the actual steering angle sensor 8, respectively. The steering motor T and the drive motor 13 are electrically operated by inputting information signals such as a steering torque T, a current vehicle speed V detected by a vehicle speed sensor (not shown), a target actual steering angle obtained by a control circuit, and a target assist torque command signal. A control current is output to the motor 31.

  That is, the electronic controller 9 rotates the steering wheel 1 left and right to rotate the drive motor 13 forward and backward based on information signals such as the steering angle θ, the actual steering angle θ ′, the vehicle speed V, etc. Normal steering control for the steered wheels FL and FR is performed via the pinion mechanism 3.

  On the other hand, when the steering wheel 1 is rotated while the electric motor 31 is not energized, the first external gear 21 rotates in the same direction as the steering shaft 2 rotates, and the first internal gear 25 meshed therewith. Rotates due to rotation. At the same time, the second internal gear 23 rotates (spins) in the same direction, and the second external gear 24 meshed with the second internal gear rotates to transmit the rotational torque to the output shaft 4.

  Further, when the steering wheel 1 is rotated in a predetermined driving state of the vehicle, the electric motor 31 is energized accordingly and the eccentric cam 17 is moved in one direction (for example, right direction) via the worm gears 32a and 32b. The first internal gear 21 revolves around the first external gear 21 while revolving in one direction. At the same time, the second internal gear 23 revolves around the second external gear 24. While spinning.

  For this reason, the output shaft 4 is transmitted with, for example, increased rotational torque by changing the gear ratio.

  On the other hand, when the steering wheel 1 is rotated, when the eccentric motor 17 is rotated in the opposite direction (for example, the left direction) by the electric motor 31, the first internal gear 21 rotates around the first external gear 21. The second internal gear 23 also rotates around the second external gear 24 while revolving in the same direction.

  For this reason, the output shaft 4 is transmitted with, for example, a reduced rotational torque due to a change in gear ratio.

  At this time, as shown in FIG. 6, when the first external gear 21a is rotated to the right (in the direction of the white arrow), for example, it is applied to the tooth side surface of the helical tooth 22a of the first internal gear 22. The forces are forces in the tangential directions f1 and f2 that are substantially perpendicular to the tooth side surface 22b direction (torsion direction) of the helical tooth 22a and the axial direction on the second internal gear 23 direction side along the torsion direction of the helical tooth 22a. It is distributed to the force to f3.

  On the other hand, the second internal gear 23 rotates synchronously with the rotation of the first internal gear 22 to transmit the rotational torque to the second external gear 24. 2 The reaction force acts on the internal gear 23, and this component force is tangential to the tooth side surface 23b of the helical tooth 23a of the second internal gear 23 (opposite to the first internal gear 22). (Tangential direction) forces f4 and f5 and an axial force f6 on the first internal gear 22 direction side along the twist angle of the helical teeth 23a.

  As described above, the component force directions generated in the internal gears 22 and 23, particularly the axial component forces f3 and f6, are directed in opposite directions (compression directions). The gears 22 and 23 cancel each other's component forces, so that free movement in the same axial direction is suppressed.

  Therefore, the occurrence of backlash at the bearing 29 that supports the internal gears 22 and 23 is sufficiently suppressed, and deterioration of the rotational torque transmission efficiency and steering feeling of the gears 21 to 24 can be prevented.

  In addition, when the internal gears 22 and 23 rotate in the opposite direction, the component forces applied to the internal gears 22 and 23 act in directions away from each other, so that free movement of the internal gears 22 and 23 in the axial direction is suppressed.

  Further, since the steering shaft 2 and the output shaft 4 are slightly movable relative to each other in the axial direction via the bush 19, it is possible to always mesh the helical teeth 21a to 24a in close contact. . For this reason, the rotational torque transmission efficiency of each gear 21-24 becomes favorable.

  Further, since the ball bearing 29 is provided on the outer peripheral surface of the coupling portion 25 of the first internal gear 22 and the second internal gear 23, the rigidity of the coupling portion 25 is increased. For this reason, it becomes possible to fully counter each component force in the compression and tension directions applied to the internal gears 22 and 23.

  Furthermore, since the backlash can be eliminated by pressing the internal gears 22 and 23 against the external gears 21 and 24 by the spring member 30, the occurrence of hitting sound between the helical teeth 21a to 24a is prevented. it can.

  Moreover, according to this embodiment, the ball bearings 26 and 27 that rotatably support the eccentric cam 17 are not the housing, but the steering shaft 2 and the output shaft 4 that avoid the meshing portions of the gears 21 to 24. , The enlargement in the radial direction by the ball bearings 26 and 27 is prevented, and the overall size of the apparatus can be reduced.

  Further, since each of the ball bearings 26 and 27 is provided on the outer periphery of the steering shaft 2 and the output shaft 4 having a relatively small diameter, each ball bearing is compared with the case where it is disposed between the outer periphery of the eccentric cam 17 and the housing. The outer diameters of 26 and 27 can be further reduced.

  For this reason, in addition to the downsizing of the apparatus, the apparatus can be reduced and the manufacturing cost can be reduced.

  Further, since both end portions 17c and 17d of the eccentric cam 17 are supported by the ball bearings 26 and 27, respectively, the eccentric cam 17 can be stably supported.

  Also, the eccentric bearing 17 and the internal gears 22 and 23 can always be rotated relatively smoothly by the ball bearing 29 as the second bearing, and the outer diameter of the ball bearing 29 can be made sufficiently small. it can. In addition, since the ball bearing 29 is disposed at the coupling portion 25 that is substantially the center position of each internal gear 22, 23, the first and second internal gears 22, 23 can be supported in a balanced manner. .

  Further, since the rotational torque of the electric motor 31 is transmitted to the eccentric cam 17 by the worm shaft 32a and the worm wheel 32b which are reduction gears, the torque transmission efficiency is improved.

The technical ideas other than the inventions described in the respective claims ascertained from the embodiments will be described below together with the effects thereof.
(1) The gear ratio variable mechanism according to claim 1, wherein the bearing is provided between the eccentric cam and at least one of the input shaft and the output shaft.

Since the bearing is provided on the outer periphery of the input shaft or output shaft having a relatively small diameter, the outer diameter of the bearing can be further reduced as compared with the case where the bearing is disposed between the outer periphery of the eccentric cam and the housing. For this reason, the apparatus can be reduced and the manufacturing cost can be reduced.
(2) The gear according to claim 1, wherein a second bearing is provided between the eccentric cam and each internal gear to rotatably support each internal gear with respect to the eccentric cam. Variable ratio mechanism.

According to the present invention, the eccentric cam and the internal gears can always be smoothly and relatively rotated by the second bearing, and the outer diameter of the second bearing can be made sufficiently small.
(3) The gear ratio variable mechanism according to claim 1, wherein the second bearing is disposed at a coupling portion between the first internal gear and the second internal gear.

According to the present invention, since the second bearing is disposed at the coupling portion located substantially at the center of both internal gears, the first and second internal gears can be supported in a balanced manner.
(4) The eccentric cam is formed in a substantially cylindrical shape along the axial direction of each of the internal gears, and the bearing is provided between one end portion of the eccentric cam in the axial direction and the input shaft, and the other end portion and the output shaft. The gear ratio variable mechanism according to any one of Claims 1 and (1) to (3), wherein the gear ratio variable mechanism is interposed between the gears.

According to the present invention, since both ends of the eccentric cam in the axial direction are supported by the two bearings, the eccentric cam can be stably supported.
(5) The actuator includes a reversible electric motor held on the inner peripheral side of the housing, and a reduction gear provided between the electric motor and the eccentric cam.
The reduction gear is composed of a third gear portion coupled to the rotating shaft of the electric motor, and a fourth gear portion fixed to the outer peripheral surface of the eccentric cam and meshing with the third gear portion,
The gear ratio variable mechanism according to claim 1, wherein the fourth gear portion is disposed in the vicinity of the bearing.

  According to the present invention, since the third gear portion and the fourth gear portion are used as the reduction gears and the bearing is provided in the vicinity of the reduction gears, the rotational torque of the electric motor can be efficiently transmitted to the eccentric cam. it can.

  The present invention is not limited to the configuration of the above-described embodiment. For example, the two ball bearings 26 and 27 that support the eccentric cam 17 can be configured by plain bearings, and one of them is a ball. A bearing may be used and the other may be a plain bearing. Further, the reduction gear may be constituted by a spur gear instead of the worm gear. The bearing may be provided between the outer periphery of the eccentric cam and the housing.

1 is an overall schematic diagram of a vehicle steering control device according to a first embodiment of the present invention. It is a longitudinal section of the gear ratio variable mechanism provided for this embodiment. It is the sectional view on the AA line of FIG. FIG. 3 is a sectional view taken along line B-B in FIG. 2. It is CC sectional view taken on the line of FIG. It is a front view which shows the 1st, 2nd external gear provided to this embodiment. It is a longitudinal cross-sectional view which shows the 1st, 2nd internal gear provided to this embodiment. It is upper half sectional drawing which shows the eccentric cam with which this embodiment is provided. It is a side view of the eccentric cam.

Explanation of symbols

1 ... Steering wheel 2 ... Steering shaft (input shaft)
DESCRIPTION OF SYMBOLS 3 ... Rack and pinion mechanism 4 ... Output shaft 5 ... Steering mechanism 6 ... Gear ratio variable mechanism 7 ... Steering angle sensor (steering angle detection means)
8 ... Actual turning angle sensor (actual turning angle detection means)
9 ... Electronic controller (control means)
DESCRIPTION OF SYMBOLS 13 ... Drive motor 17 ... Eccentric cam 17c, 17d ... Extension both ends 18 ... Actuator 21 ... 1st external gear 22 ... 1st internal gear 23 ... 2nd internal gear 24 ... 2nd external gear 26, 27 ... Ball bearing (first bearing)
28 ... Eccentric hole 29 ... Ball bearing (second bearing)
FL / FR: Steering wheel

Claims (2)

A first external gear provided coaxially with the input shaft;
A first internal gear meshing with the first external gear in an eccentric state;
A second internal gear integrally provided from the axial direction to the first internal gear;
A second external gear meshing with the second internal gear in an eccentric state;
An output shaft that is disposed substantially coaxially with the input shaft and on which the second external gear is provided coaxially;
An eccentric cam that rotatably supports an outer peripheral surface between the internal gears on an inner peripheral surface of an eccentric hole formed therein, and rotates coaxially with the input shaft;
A bearing that rotatably supports the eccentric cam;
A gear ratio variable mechanism including an actuator that revolves the internal gears by rotationally controlling the eccentric cam to variably control the gear ratio between the input shaft and the output shaft;
The gear is characterized in that the bearing is provided at a position axially separated from a meshing portion between the first external gear and the first internal gear and a meshing portion between the second external gear and the second internal gear. Variable ratio mechanism. An input shaft coupled to the steering wheel;
Steering angle detection means for detecting the steering angle of the input shaft;
An output shaft arranged substantially coaxially with the input shaft and linked to the steered wheels;
An actual turning angle detecting means for detecting a turning angle of the steered wheel;
A steering mechanism for applying a steering force to the steered wheels via the output shaft;
Control means for controlling the steering mechanism based on angle information signals from the steering angle detection means and the actual turning angle detection means;
A vehicle steering control device comprising:
The gear ratio variable mechanism according to claim 1 is provided between the input shaft and the output shaft, and the rotational force transmitted from the input shaft to the output shaft is controlled to be converted to a predetermined gear ratio. A steering control device for a vehicle provided with a variable gear ratio mechanism.

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