JP2007145273A - Steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact steering device capable of varying a transmission ratio. <P>SOLUTION: Since the steering device adopts a constitution having no sun gear at a center different from a general planetary gear mechanism, meshing of gears is only meshing of an internal gear with an external gear (planetary gear). Since the meshing of the external gear with the internal gear is the contact of recession surfaces and projection surfaces, an meshing ratio becomes high and bending stress of a tooth base and a contact surface pressure become advantageous as compared with meshing of the external gears each other. Accordingly, outstanding miniaturization can be accomplished as compared with a conventional mechanism using a sun gear. Further, since stress generated on the gear is small, a resin material can be used as a gear material and not only light weight but also suppression of noise of the gear can be accomplished. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a steering device, and more particularly to a steering device capable of superimposing a steering angle.

In a vehicle, a steering device in which a so-called steering gear ratio is fixed, in which the relationship between the rotation angle of the steering wheel and the turning angle of the tire has a one-to-one correspondence, is generally used. However, in the case of a steering device in which the steering gear ratio is fixed, the steering gear ratio is set to ensure high-speed stability of the vehicle. In other words, the steering gear ratio is often set large so that the vehicle does not respond sensitively during high-speed traveling. However, in the case of such a steering gear ratio, it is necessary to rotate the steering wheel a lot during low speed traveling such as in a garage, and the operation becomes complicated. With respect to such a problem, Patent Document 1 discloses that a steering angle superimposing mechanism (a mechanism that can change the relationship between an input angle and an output angle using a differential mechanism) is provided in the steering apparatus to superimpose the steering angle. Has been.
Japanese Patent Laid-Open No. 2002-87312

  According to the rudder angle superimposing mechanism described in Patent Document 1, the transmission ratio (here, the rotational speed of the output shaft of the rudder angle superimposing mechanism / the rotational speed of the input shaft) is made variable according to the vehicle speed or the like. For example, when traveling on the high side, the transmission ratio is increased to suppress the turning angle of the wheel against the rotation of the steering wheel to ensure straight running stability, and at low speed traveling, the transmission ratio is decreased to reduce the steering wheel The steering operation can be prevented from becoming complicated when entering a garage or the like by increasing the turning angle of the wheel with respect to the rotation of the vehicle.

  However, Patent Document 1 discloses a rudder angle superimposing mechanism that uses a planetary gear type differential mechanism and that can be arranged in the column part. However, since this uses a gear mechanism, the meshing teeth Since the number is basically small, it is difficult to reduce the size of a vehicle having a large vehicle weight that must transmit a large torque. In addition, when a planetary differential mechanism with a fixed motor is used as described above, the steering ratio is not 1 when the motor is locked at an arbitrary angle as a fail-safe when the motor fails. is there. In order to set the transmission ratio to 1, a separate speed change mechanism is required, which causes problems such as high cost, increased inertia and friction, and deteriorated operability due to increased backlash.

  The present invention has been made in view of the problems of the related art, and an object of the present invention is to provide a steering device that is compact and has a variable transmission ratio.

The steering device according to the first aspect of the present invention comprises:
An input shaft to which steering force is transmitted from the steering wheel;
A first internal gear coupled to the input shaft;
A first planetary gear meshing with the first internal gear;
An output shaft for transmitting steering force to the steering mechanism;
A second internal gear coupled to the output shaft;
A second planetary gear meshing with the second internal gear;
A carrier that rotatably supports the first internal gear and the second internal gear with their phases fixed;
And an actuator for displacing the carrier with respect to the input shaft.

The steering device of the second invention is
An input shaft to which steering force is transmitted from the steering wheel;
An output shaft for transmitting steering force to the steering mechanism;
A first transmission means having an internal gear and a planetary gear meshing with the internal gear, and transmitting a steering force from the input shaft to the output shaft;
An electric motor that outputs an auxiliary torque to the output shaft according to a steering force transmitted from the input shaft to the output shaft;
Second transmission means for transmitting auxiliary torque of the electric motor to the output shaft;
The second transmission means includes a worm coupled to a rotating shaft of the electric motor and a worm wheel coupled to the output shaft and meshing with the worm.
The internal gear is formed on the inner periphery of the worm wheel.

  According to the first aspect of the present invention, the first planetary gear meshing with the first internal gear, the second planetary gear meshing with the second internal gear, the first internal gear and the second internal gear. Since the steering force is transmitted from the input shaft to the output shaft using a carrier that rotatably supports the toothed gear in a state where the phase is fixed, a sun gear is not required as in the prior art. Yes, the configuration can be made compact accordingly. Furthermore, steering angle superimposition can be realized by displacing the carrier with respect to the input shaft by the actuator.

  According to the second aspect of the present invention, the electric assist of the steering force can be realized by outputting the auxiliary torque of the electric motor to the output shaft according to the steering force transmitted from the input shaft to the output shaft. . Furthermore, a more compact configuration can be realized by forming the internal gear on the inner periphery of the worm wheel that constitutes the second transmission means for transmitting the auxiliary torque of the electric motor to the output shaft.

  The first transmission means is provided in the column portion, and when the steering force is transmitted so that the rotation angle of the output shaft relative to the rotation angle of the input shaft can be changed, steering angle superposition can be realized.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a conceptual diagram showing a steering apparatus according to the present embodiment. In FIG. 1, a steering wheel 1 is connected to an input shaft 2 constituting a part of a steering shaft. The lower end of the input shaft 2 inserted into the column tube 4 is connected to the output shaft 3 via a drive unit 100 attached to the lower end of the column tube 4. The output shaft 3 that receives the auxiliary steering force from the drive unit 100 is connected to the intermediate shaft 5 via a cardan joint CJ. The intermediate shaft 5 is connected to the pinion shaft 6 via a cardan joint CJ. The pinion 6a formed at the lower end of the pinion shaft 6 meshes with the rack teeth 7a of the rack shaft 7 extending in the direction intersecting with the pinion 6a. Both ends of the rack shaft 7 are connected to steering mechanisms 9 and 9 for steering the pair of tires 10 and 10 via tie rods 8 and 8.

  Signals such as vehicle speed, yaw, lateral G wheel side, lateral load, and engine output are input from the vehicle control device VCU to the steering control device SCU. Transmits a control signal from the steering angle ratio controller CT1 to the steering angle motor 113 of the drive unit 100, and outputs a control signal from the EPS controller CT2 to the auxiliary steering motor 119 of the drive unit 100.

  FIG. 2 is a cross-sectional view of the drive unit 100. FIG. 3 is a partial cross-sectional perspective view of the drive unit 100, but the housing is omitted. A column tube 4 is attached to the top of the housing 101. The input shaft 2 is inserted into the column tube 4 and is rotatably supported by a bearing (not shown). Between the column tube 4 and the input shaft 2, an input shaft sensor 102 that detects a rotation angle of the input shaft 2 with respect to the column tube 4 is provided. The lower end of the input shaft 2 is hollow, and the upper end of the torsion bar 103 inserted therein is pin-coupled to the input shaft 2. On the other hand, the lower end of the torsion bar 103 is pin-coupled to the upper portion of the gear case 104. Reference numeral 104 is an input shaft of the rudder angle superimposing mechanism.

  A hollow case-shaped gear case (first internal gear) 104 has first internal teeth 104 a formed on the inner periphery thereof, and is rotatably supported by a bearing 105 with respect to the housing 101. Between the housing 101 and the gear case 104, a gear case sensor 106 that detects a rotation angle of the gear case 104 with respect to the housing 101 is provided.

  A plurality of first planetary gears 107 are arranged at equal intervals in the circumferential direction so as to mesh with the first inner teeth 104 a of the gear case 104. The shaft 108 having one end (upper end) press-fitted into the central hole of each first planetary gear 107 is formed by press-fitting the other end (lower end) into the central hole of the second planetary gear 109. The first planetary gear 107, the shaft 108, and the second planetary gear 109 need not be press-fitted and may be configured to move integrally such as key connection. Each shaft 108 passes through a disk-shaped carrier 110 provided between the first planetary gear 107 and the second planetary gear 109, and is rotatably supported by a needle bearing 111. That is, the first planetary gear 107 and the second planetary gear 109 are supported by the carrier 110 in a state where the phases are fixed with respect to each other when viewed in the axial direction of the output shaft 2.

  On the outer periphery of the carrier 110, worm wheel teeth 110a are formed. A steering angle worm 112 meshes with the worm wheel teeth 110a. The rudder angle worm 112 is connected to a rotating shaft 113a of a rudder angle motor 113 which is an actuator. An arbitrary preload is applied between the rudder angle worm 112 and the worm wheel teeth 110a by being attached to the housing 101 at the tip of the rotation shaft 113a and biasing the rotation shaft 113a in the direction of the carrier 110. A preloading device PS1 (FIG. 3) is provided. Such a preload device PS1 is described in, for example, Japanese Patent Application Laid-Open No. 2004-306898.

  The output shaft 3 has a thin shaft portion 3a having a thin upper diameter, a thick shaft portion 3b having a large lower diameter, and a hollow disk portion (second internal gear) 3c formed therebetween. The hollow disk portion 3c is arranged to face the gear case 104 with the carrier 110 interposed therebetween. The thin shaft portion 3 a extends through the central hole of the carrier 110 to the gear case 104, and the tip thereof is supported by the bearing 120 so as to be relatively rotatable with respect to the gear case 104. The thick shaft portion 3b is rotatably supported by bearings 114 and 115 with respect to the housing 101. The carrier 110 is rotatably supported by bearings 121 and 122 with respect to the thin shaft portion 3a.

  Further, the output shaft 3 has second internal teeth 3d formed on the inner periphery of the hollow disk portion 3c, and the second planetary gear 109 meshes with the second inner teeth 3d. Between the housing 101 and the output shaft 3, an output shaft sensor 116 that detects a rotation angle of the output shaft 3 with respect to the housing 101 is provided. Here, the gear case 104, the first planetary gear 107, the carrier 110, the second planetary gear 109, and the hollow disk portion 3c of the output shaft 3 constitute a first transmission means (steering angle superposition mechanism).

  A resin worm wheel annular portion (also referred to as a worm wheel) 117 is bonded to the outer periphery of the hollow disk portion 3 c of the output shaft 3, and worm wheel teeth 117 a formed on the outer periphery mesh with the auxiliary steering worm 118. is doing. The trapping steering worm 118 and the worm wheel annular portion 117 constitute second transmission means (power steering mechanism). The auxiliary steering worm 118 is connected to the rotation shaft 119a of the auxiliary steering motor 119. At the tip of the rotating shaft 119a, it is attached to the housing 101, and the rotating shaft 113a is urged toward the worm wheel annular portion 117, so that it is optional between the auxiliary steering worm 118 and the worm wheel teeth 117a. A preloading device PS2 (FIG. 3) that provides a preload is arranged. Such a preload device PS2 is described in, for example, Japanese Patent Application Laid-Open No. 2004-306898.

  Next, the operation of the present embodiment will be described. First, the numbers of teeth of the first planetary gear 107, the second planetary gear 109, the first internal teeth 104a, and the second internal teeth 3d are Za, Zb, Zia, and Zib, respectively. However, if Za / Zia ≠ Zb / Zib (when the planetary gears 107 and 109 are the same module), the relationship between the angle of the gear case 104, the angle of the output shaft 3, and the angle of the carrier 110 is uniquely determined. These can be used as a differential mechanism. That is, when the angle of the carrier 110 is controlled, the rotational phase between the gear case 104 (= input shaft 2) and the output shaft 3 can be controlled. More specifically, when the rotation speed of the carrier 110 per one rotation of the input shaft 2 is Nw, the output shaft 3 is ((Zia × Zb) + (Zia−Za) · (Za−Zb) · Nw). ÷ Rotate by (Zib × Za). However, the planetary gears 107 and 109 are the same module and are standard gears (dislocation coefficient 0).

  When signals such as vehicle speed, yaw, lateral G wheel side, lateral load, and engine output are input from the vehicle control unit VCU, the steering angle ratio controller CT1 of the steering control unit SCU determines the optimum transmission ratio, and the steering The angle motor 113 is driven and controlled. More specifically, in the drive unit 100, when it is desired to set the transmission ratio to 1, when the input shaft 2 rotates counterclockwise by the angle θ by the operation of the steering wheel 1, the rudder angle motor 113 is driven and the worm 112 is driven. Then, the carrier 110 is rotated by an angle λ0 represented by the following equation (1).

  As a result, the output shaft 3 rotates counterclockwise at the same angle θ. At this time, feedback control can be performed by inputting output signals of the input shaft sensor 102, the gear case sensor 106, and the output shaft sensor 116 to the steering angle ratio controller CT1 of the steering control unit SCU.

  On the other hand, when the transmission ratio is desired to be greater than 1, when the input shaft 2 rotates counterclockwise by the angle θ, the steering angle motor 113 is driven to rotate the carrier 110 through the worm 112 by the angle λa (> λ0). Then, the output shaft 3 rotates by an angle (θ + a) (when Za> Zb). As a result, the large steering angle of the tire 10 can be output in response to the input of the small steering angle of the steering wheel 1, so that when the vehicle speed is low, the transmission ratio is increased, and turning with a small radius such as garage entry with a small steering angle. Can be made possible.

  On the other hand, when the transmission ratio is desired to be smaller than 1, when the input shaft 2 rotates counterclockwise by the angle θ, the steering angle motor 113 is driven and the carrier 110 is moved to the angle λd (<λ0, Za via the worm 112). When rotated by> Zb), the output shaft 3 rotates by an angle (θ−d). Accordingly, since the small steering angle of the tire 10 can be output in response to the input of the large steering angle of the steering wheel 1, stable high-speed traveling can be performed by preventing the steering characteristics from becoming too sensitive.

  Furthermore, if the vehicle is in a straight traveling state and no steering force is input from the steering wheel 1 to the input shaft 2, the torsion bar 103 does not twist, so the output signal of the input shaft sensor 102 and the output of the gear case sensor 106 Since there is no phase delay with respect to the signal, the EPS controller CT2 of the steering control unit SCU does not drive the auxiliary steering motor 119, and no auxiliary steering force is generated.

  On the other hand, when the driver operates the steering wheel 1 when the vehicle is about to turn a curve, the torsion bar 103 is twisted according to the force, and relative rotation occurs between the input shaft 2 and the gear case 104. To do. Then, a phase lag occurs between the output signal of the input shaft sensor 102 and the output signal of the gear case sensor 106. Based on this, the EPS controller CT2 of the steering control unit SCU responds to the direction and amount of this relative rotation. Since the drive signal is transmitted to the auxiliary steering motor 119, the auxiliary steering motor 119 generates a desired auxiliary steering force. The torque generated by the auxiliary steering motor 119 is decelerated by the power transmission unit composed of the worm 118 and the worm wheel annular portion 117 and transmitted to the output shaft 3, whereby steering assist can be performed.

  Furthermore, in order to prevent vehicle spin and the like, if a slip or slip angle of a wheel is detected from vehicle information (yaw rate, vehicle speed, wheel speed, steering angle, etc.), the steering angle ratio controller CT1 and EPS controller of the steering control unit SCU are detected. CT2 can automatically give a corrected steering angle by performing the driving control of the steering angle motor 113 and the driving control of the auxiliary steering motor 119 in a coordinated manner.

  Unlike the general planetary gear mechanism, the drive unit 100 of the present embodiment employs a configuration that does not have a sun gear at the center, and therefore the meshing of the gears is performed between an internal gear and an external gear (planetary gear). It is only meshing with. Since the meshing of the external teeth and the internal teeth is a contact between the concave surface and the convex surface, the meshing rate is increased, and the bending stress and the contact surface pressure of the tooth root are advantageous as compared with the meshing between the external gears. Therefore, it is possible to significantly reduce the size as compared with the conventional mechanism using the sun gear. Furthermore, since the stress generated in the gear is small, it is possible to use a resin as a gear material, and it is possible not only to reduce the weight but also to suppress the noise of the gear. Therefore, in this embodiment, 66 nylon (glass fiber reinforced) is used as the resin. As other materials, high-strength engineering plastics such as Duracon can be used.

  Furthermore, it is possible to reduce the size by combining steel and resin, such as using resin for the internal gear and making the planetary gear made of steel. In addition, in the present embodiment, the second internal teeth 3d of the output shaft 3 are provided on the radially inner side of the worm wheel annular portion 117 that transmits the steering assist torque. Thereby, the installation space can be effectively used, and the drive unit 100 as a whole can be made a smaller system. The column portion actuator is particularly required to be light and small in order to protect the occupant in the event of a vehicle collision. However, with the above-described configuration, such a requirement can be met.

  In this embodiment, the worms 112 and 118 are moved in the direction of the carrier 110 and the worm wheel annular portion 117 by the preload devices PS1 and PS2 (which may be simple springs). Each of them is configured to be energized. Thus, the backlash of the worm tooth surface is removed and the carrier 110 is displaced in the radial direction, whereby the first planetary gear 107 and the second planetary gear 109 and the first internal teeth 104a and the second internal teeth 3d meshing with the first planetary gear 107 and the second planetary gear 109 are obtained. The backlash between the two can be removed, and the operational feeling can be improved.

  In addition, the steering angle worm 112 cannot be reversely operated (the steering angle motor 113 is rotated by the force transmitted from the carrier 110) so that the steering angle worm 112 can be steered in the event of a failure. It has a worm lead angle. Accordingly, the carrier 110 does not rotate even when the rudder angle motor 113 becomes free, so that the rotational force of the input shaft 2 can be transmitted to the output shaft 3. However, at this time, the transmission ratio does not become 1, and Zia × Zb ÷ Zib ÷ Za. However, when Zb and Za are close to each other, the transmission ratio is about 0.7 to 0.9 and close to 1. The transmission ratio can be set so that normal steering is sufficient.

  Since the efficiency of the worm that makes reverse operation impossible is low, the steering angle motor 113 may need to be enlarged in order to compensate for the torque loss. Therefore, when a highly efficient worm (or a transmission mechanism such as a gear) is used, the rudder angle motor 113 is a type in which the rotating shaft 113a is provided with an electromagnetic brake, and when the rudder angle motor 113 fails, the rotating shaft It is good also as a structure which locks 113a.

  The present invention has been described above with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be modified or improved as appropriate.

It is a key map showing the steering device concerning this embodiment. It is sectional drawing of the drive unit 100 concerning this Embodiment. 3 is a partial cross-sectional perspective view of the drive unit 100. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Input shaft 3 Output shaft 3a Thin shaft part 3b Thick shaft part 3c Hollow disk part 3d 2nd internal tooth 4 Column tube 5 Intermediate shaft 6 Pinion shaft 6a Pinion 7 Rack shaft 7a Rack tooth 8,8 Tie rod 9,9 Steering mechanism 10, 10 Tire 100 Drive unit 101 Housing 102 Input shaft sensor 103 Torsion bar 104 Gear case 104a First internal gear 105 Bearing 106 Gear case sensor 107 First planetary gear 108 Shaft 109 Second planetary gear 110 Carrier 110a Worm wheel tooth 111 Needle Bearing 112 Steering angle worm 113 Steering angle motor 113a Rotating shaft 114, 115 Bearing 116 Output shaft sensor 117 Worm wheel annular portion 117a Worm wheel tooth 118 Auxiliary steering worm 119 Auxiliary steering motor 119 CT1 steering ratio rotary shaft 120 bearing 121 bearing CJ Cardan joint controller CT2 controller PS1, PS2 pressure unit SCU steering control apparatus VCU vehicle controller

Claims (3)

An input shaft to which steering force is transmitted from the steering wheel;
A first internal gear coupled to the input shaft;
A first planetary gear meshing with the first internal gear;
An output shaft for transmitting steering force to the steering mechanism;
A second internal gear coupled to the output shaft;
A second planetary gear meshing with the second internal gear;
A carrier that rotatably supports the first internal gear and the second internal gear with their phases fixed;
And an actuator for displacing the carrier with respect to the input shaft. An input shaft to which steering force is transmitted from the steering wheel;
An output shaft for transmitting steering force to the steering mechanism;
A first transmission means having an internal gear and a planetary gear meshing with the internal gear, and transmitting a steering force from the input shaft to the output shaft;
An electric motor that outputs an auxiliary torque to the output shaft according to a steering force transmitted from the input shaft to the output shaft;
Second transmission means for transmitting auxiliary torque of the electric motor to the output shaft;
The second transmission means includes a worm coupled to a rotating shaft of the electric motor and a worm wheel coupled to the output shaft and meshing with the worm.
A steering apparatus, wherein the internal gear is formed on an inner periphery of the worm wheel. 3. The steering apparatus according to claim 2, wherein the first transmission unit is provided in a column portion and transmits a steering force such that a rotation angle of the output shaft with respect to a rotation angle of the input shaft can be changed.

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