JPH0585374A - Motor-driven rear wheel steering gear - Google Patents

Abstract

PURPOSE:To provide a motor-driven rear wheel steering gear heightened in productivity through the comparatively easy manufacture of component members of power transmission mechanism while reducing reverse efficiency of this transmission mechanism to zero, and moreover of low noise. CONSTITUTION:In this motor-driven rear wheel steering gear, transmission mechanism for transmitting the power of an electric motor (m) to a rod 17 is formed of a worm shaft 20 with a worm 21 formed, a ring 24 with an Acme thread part formed therein so as to be meshed with the worm 21, and a lever 29 for interlocking the worm shaft 20 and the ring 24 with each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric rear wheel steering system equipped with a transmission mechanism most suitable for transmitting the rotation of an electric motor to a rod.

[0002]

2. Description of the Related Art FIGS. 3 to 5 show a conventional electric rear wheel steering system. This device is configured as follows. First, the hypoid gear pinion 3 is attached to the motor shaft 2 of the electric motor m fixed to the casing 1. The hypoid gear pinion 3 meshes with the hypoid gear wheel 4. The hypoid gear pinion 3 and the hypoid gear wheel 4 constitute a gear group. Since the gear groups are combined so as to satisfy the condition that the reverse efficiency is 0, the gear groups receive the external force transmitted from the rear wheel (not shown) during traveling. Therefore, the electric motor m is not rotated by the external force from the rear wheels.

Further, the hypoid gear wheel 4 is
It is rotatably supported by the casing 1 by bearings 5 and 6. A support shaft 7 is fitted and fixed to the hypod gear wheel 4. A plate body 9 having a cutout portion 8 is attached to the upper portion of the support shaft 7. The plate body 9 is connected to a potentiometer 11 provided on the cover 10. The support shaft 7 and the potentiometer 11 are connected as follows. That is, the potentiometer 11 has the lever portion 12. The lever portion 12 is fitted in the cutout portion 8 of the plate body 9. As a result, the rotation of the support shaft 7 is transmitted to the potentiometer 11. Further, since the potentiometer 11 is connected to a controller (not shown), the potentiometer 11 can detect the rotation angle of the support shaft 7 and send the information to the controller.

A concave portion 13 is formed in the vicinity of the lower central portion of the hypoid gear wheel 4. A spherical bearing 14 provided in the recess 13 rotatably supports one end of the stud shaft 15. This stud shaft 15
The support shaft 7 of the hypoid gear wheel 4 is eccentric by an eccentric amount e. (See Figure 5)

A taper portion 16 is formed on the other end of the stud shaft 15, that is, on the side opposite to the spherical bearing 14. The tapered portion 16 is adapted to coincide with the tapered hole portion 18 formed in the rod 17. The taper portion 16 is fitted and fixed in the taper hole portion 18. Further, another potentiometer 19 shown in FIG. 4 is attached to the rod 17. The potentiometer 19 detects the moving distance of the rod 17 and sends the information to the controller. This rod 17 is a bush 3
It is slidably supported by the casing 1 by 9 and moves along its axial direction. The movement is transmitted to the side rods (not shown) attached to both ends of the rod 17 and the rear wheels attached via the side rods to steer the rear wheels. That is, since the moving distance of the rod 17 corresponds to the steering angle of the rear wheel, the steering angle of the rear wheel can be known by measuring the moving distance of the rod 17. Thereby, the moving distance of the rod 17 is read by the potentiometer 19 and the information is sent to the controller.

The operation of the electric rear wheel steering system configured as described above will be described below. First, when the electric motor m whose rotation is controlled by a signal from a controller (not shown) is rotated, the hypoid gear pinion 3 attached to the motor shaft 2 is also rotated. As a result, the hypoid gear wheel 4 meshing with the hypoid gear pinion 3 also rotates. When the hypoid gear wheel 4 rotates, the stud shaft 15 rotates around the axis of the hypoid gear wheel 4. (Stud shaft 15
Is eccentric with respect to the support shaft 7 of the hypoid gear wheel 4 by an eccentric amount e. ) Such movement of the stud shaft 15 is allowed only in the linear direction along the axis of the rod 17. And for other movements, spherical bearing 1
Absorbed by 4. Therefore, the rotation of the electric motor m is converted into the linear motion of the rod 17 as described above, and the rear wheels (not shown) at both ends of the rod 17 are steered. Further, even if the external force from the rear wheel is transmitted to the gear group, the reverse efficiency of the gear group is 0, so that the electric motor m is not rotated by the force from the rear wheel side.

[0007]

The conventional electric rear wheel steering system as described above has the following problems. That is, the hypoid gear pinion and the hypoid gear wheel, which are used in the gear group with the reverse efficiency set to 0, need to be assembled after the tooth contact of the meshing is adjusted at the time of assembly. Therefore, there is a problem that the number of assembling steps increases. Further, the processing of these gears requires a dedicated gear cutting machine, and the processing becomes complicated. Therefore, there is a problem that the production cost becomes high. Further, there is a problem that noise is generated due to meshing of gears.

The object of the present invention is to make the constituent members of the power transmission mechanism relatively easy to improve the productivity, and to reduce the reverse efficiency of the transmission mechanism to zero, and also to drive the rear wheel with low noise. To provide a steering device.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention uses a power unit controlled to have a reverse efficiency of 0, which is controlled by a controller in accordance with a steering angle of front wheels.
In a rear wheel steering device that steers rear wheels, an electric motor whose rotation is controlled by a controller is mounted in a casing, and a worm shaft mounted on a motor shaft of the electric motor and a worm formed on the worm shaft are mounted in the casing. And a ring having an acme screw part formed therein for meshing with the worm, and a lever for connecting the acme screw part and a rod for steering the rear wheel to thereby interlock them.

[0010]

The rotation of the electric motor controlled by the controller rotates the worm shaft connected to the motor shaft. When the worm shaft rotates, the worm formed on the worm shaft also rotates. When the worm rotates, the acme thread that meshes with the worm moves the ring linearly. At this time, a lever that interlocks the ring and the rod receives the linear motion of the ring and swings to transmit the motion to the rod. The rod that receives the swing of the lever moves linearly. Then, the rear wheel is steered by the rod making a linear movement along the axis. In this way, the worm, the acme screw portion, and the lever transmit the rotation of the electric motor to the rod. Compared with, for example, hypoid gears, these components do not require special machining techniques or machines and can be manufactured at low cost.

[0011]

1 and 2 show an embodiment of the present invention. The same reference numerals are used for the same components as those of the conventional example described above,
Detailed description thereof will be omitted.

An electric motor m whose rotation is controlled by a controller (not shown) is attached to the casing 1. A worm shaft 20 is attached to the motor shaft 2 of the electric motor m. A worm 21 is formed on the worm shaft 20, and the worm shaft 20 itself is rotatably supported by the casing 1 at both ends by a bearing 22 and a bearing holder 23. Further, one end of the worm shaft 20, that is, the side opposite to the motor shaft 2 side is connected to the potentiometer 11. The potentiometer 11 is connected to the controller, detects the rotation angle of the electric motor m via the worm shaft 20, and feeds back the information to the controller.

As described above, both ends of the worm shaft 20 are supported by the bearings 22, and the worm shaft 20 penetrates the ring 24 located between the bearings 22. This ring 24 has an acme threaded portion 2 on the inside.
5 is formed and meshes with the worm 21. Further, a concave portion 27 is formed inside the step portion 26 below the ring 24. A spherical bearing 28 is attached to the recess 27. One end of a lever 29 is attached to this spherical bearing 28. A through hole 30 is provided substantially in the middle of the lever 29 in the longitudinal direction. A bearing 31 is fitted in the hole 30, and a stud bolt 32 is passed through the fitted bearing 31 and screwed to the casing 1. When this screwing is performed, plain bushes 33 are interposed at both ends of the bearing 31. Thus lever 2
When the 9 is screwed to the casing 1 with the stud bolt 32, the bearing 31 and the plain bush 33 are used, so that the lever 29 can freely rotate about the stud bolt 32. Also, the other end of the lever 29,
In other words, on the side opposite to the one attached to the ring 24,
It is attached to the rod 17. The mounting method is as follows. That is, there is a hole 34 at the position where the rod 17 is attached to the lever 17. A spherical bearing 35 is attached to this hole 34, and a lever 29 is attached thereto.

The rod 17 is slidably supported by a bush 36 attached to the casing 1. Further, rear wheels (not shown) are attached to both ends of the rod 17 through side rods (not shown) as in the conventional example. Further, as in the conventional example, the groove 17 is provided in the rod 17, and the potentiometer 19 is provided on the casing 1 at a position corresponding to the groove 37.
Is attached. In this groove 37, the potentiometer 19
The lever portion 38 is inserted to detect the moving distance of the rod 17, and the information is sent to the controller connected to the potentiometer 19. Also, potentiometer 1
9 may be attached at a position where the swing of the lever 2 is detected.

The operation of the rear wheel steering system having the above-described structure will be described. When the electric motor m is rotated by the control signal of the controller, the worm shaft 20 attached to the motor shaft 2 is rotated. When the worm shaft 20 rotates, the worm 21 formed on the worm shaft 20 also rotates. When the worm 21 rotates, the ring 24 is moved along the axis of the worm shaft 20 by the acme screw portion 25 formed in the ring 24 that meshes with the worm 21. The linear movement distance of the ring 24 is determined by the rotation angle of the electric motor m. When the ring 24 linearly moves along the axis of the worm shaft 20, the ring 24
A lever 29 connecting the rod 17 and the rod 17 swings around the stud bolt 32. The swinging of the lever 29 causes the rod 17 to move along the axis thereof to steer the rear wheels.

The lever 29 can swing about the stud bolt 32 because the spherical bearings 28 and 35 on the ring 24 side and the rod 17 side absorb movements other than linear movements. Further, in order to reduce the rotation speed of the electric motor m to a value suitable for moving the rod 17 to steer the rear wheels, the ratio of the pitch of the acme screw portion 25 and the length of the lever 29 (lever 29 The length from the center of the stud bolt 32 to the center of the spherical bearing 28 on the ring 24 side is set to l _1, and similarly, the length from the center of the stud bolt 32 to the center of the spherical bearing 35 on the rod 17 side is set to l ₂ . Can be performed by determining the ratio of l ₁ and l ₂ ). Further, the acme screw portion 25 and the worm 21
Is the same as the relationship between bolts and nuts, as can be seen from its shape. That is, the nut on the bolt cannot be rotated by the force in the direction along the axis of the bolt.
From this, even if an external force acts on the rear wheel and a force that moves the rod 17 in the direction along the axis thereof acts,
The worm shaft 21 is not rotated by the worm 21 and the acme screw portion 25. Therefore, even if an external force acts on the rear wheel when the electric motor m is stopped while the rear wheel is steered, the rear wheel is not affected by the external force and remains steered. Since the position of is maintained, stable driving is possible.

[0017]

[Effect] In order to transmit the rotation of the electric motor as a linear motion of the rod, a ring having an acme screw portion formed inside, a worm shaft having a worm formed therein, and a ring connecting them are used. For this reason, for example, problems such as when using hypoid gear, that is, when using a special gear cutting machine, when combining,
It is easy to manufacture and inexpensive because there is no reduction in productivity due to adjustment of the tooth contact between gears.

[Brief description of drawings]

FIG. 1 is a front sectional view.

FIG. 2 is a side sectional view.

FIG. 3 is a front sectional view of a conventional example.

FIG. 4 is an enlarged cross-sectional view taken along the line IV of FIG.

5 is a sectional view taken along line VV of FIG.

[Explanation of symbols]

 1 Casing 17 Rod 20 Worm shaft 21 Worm 24 Ring 25 Acme screw part 29 Lever m Electric motor

Claims (1)

[Claims] 1. A rear wheel steering system that steers the rear wheels by a power unit having a reverse efficiency of 0 driven by being controlled by the controller according to the steering angle of the front wheels, and an electric motor whose rotation is controlled by the controller. A worm shaft mounted on the motor shaft of the electric motor, a worm formed on the worm shaft, and a ring having an acme screw portion for meshing with the worm formed therein. An electric rear wheel steering device having a structure in which an acme screw portion and a rod for steering the rear wheels are connected to each other and a lever for interlocking the both is provided.