JPH0236786Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a rear wheel steering device for a front and rear wheel steered vehicle that can steer the rear wheels of the vehicle in conjunction with the steering operation of the front wheels.

[Prior art]

As a conventional rear wheel steering device, a front wheel steering link mechanism and a rear wheel steering link mechanism are connected via a link or a rotating shaft, and the front wheel steering angle is transmitted to the rear wheels by these links, rotating shafts, etc. There is something. Among these, the ones that use links are, for example,
Although proposed in Japanese Patent Application No. 114768, since the links in such a device must be increased in size due to the need to increase rigidity, a type using a rotating shaft is advantageous.

[Problem that the invention attempts to solve]

By the way, when changing the front and rear wheel steering angle ratio according to the vehicle speed in a rear wheel steering system using a rotating shaft, a steering angle ratio variable mechanism (coupling mechanism) is installed between the rotating shaft and the rear wheel side steering link mechanism. ) to convert the rotation of the rotary shaft into linear motion and input it to the variable steering angle mechanism. In this case, if the rotation of the rotary shaft is converted into linear motion by the rack and pinion mechanism, there is a disadvantage that the variable steering angle ratio mechanism becomes large because the movement range of the rack is large.

In addition, in a type of rear wheel steering device that uses links, when changing the front and rear wheel steering angle ratio according to vehicle driving conditions such as vehicle speed by lever ratio conversion, it is connected to both steering link mechanisms and moves in the front and rear direction. Each link is connected to each swinging end of the swinging lever, but these connections are difficult to control because they draw an arcuate trajectory when the swinging lever swings.

Furthermore, when adopting a power assist mechanism for rear wheel steering in a vehicle that employs these variable steering angle ratio mechanisms, the linear motion output from the variable steering angle ratio mechanism must be further converted into rotational motion. No.

[Means for solving problems]

The present invention has been developed to address these problems, and its gist is to include a first rotary shaft whose front end is connected to the front wheel side steering link mechanism, extends rearward, and rotates in response to the steering operation of the front wheels. ,
A second rotary shaft whose rear end is connected to the rear wheel side steering link mechanism, extends forward and steers the rear wheels by rotation of the second rotary shaft, and a connecting mechanism that connects both of these rotary shafts. An arm-shaped connecting member is attached to the rear end of the first rotary shaft and moves only in the axial direction as the rotary shaft rotates; a spherical connecting member that is rotatable along a plane; an engaging member that protrudes from the rear end of the arm-like connecting member and engages with an arcuate long hole provided on the outer periphery of the spherical connecting member;
and a drive means for rotating the spherical connecting member to change the inclination angle of the arc-shaped elongated hole with respect to the second rotating shaft according to the driving condition of the vehicle. It's in the device.

[Effect of invention]

As a result, in the present invention, the rotation of the first rotary shaft is converted into an axial movement by the arm-shaped connecting member of the connecting mechanism, and the same movement is further converted into a rotational movement by the spherical connecting member. It can be transmitted to two rotating shafts.
Therefore, the rear wheels are steered in response to the steering operation of the front wheels.

Further, in the present invention, the angle of inclination of the arcuate slot provided in the spherical connecting member with respect to the second rotating shaft is related to the conversion rate from axial motion to rotational motion, and the inclination direction of the arcuate slot is related to the conversion rate from axial motion to rotational motion. It relates to the direction of rotation of the second rotating shaft. Therefore, by controlling the rotation of the spherical connecting member by the driving means, the front and rear wheel steering angle ratio can be changed appropriately according to the vehicle speed, and the steering direction of the rear wheels with respect to the front wheels can be changed in the same phase or in the same phase.
It can be of either reverse phase.

[Effect of idea]

Therefore, according to the present invention, it is possible to configure a rear wheel steering device that can change the front and rear wheel steering angle ratio without increasing the size of the coupling mechanism (steering angle variable variable mechanism), and when power assisting rear wheel steering. has the advantage of being able to adopt a power assist mechanism that has been commonly used in the past.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings. FIG. 1 schematically shows a vehicle equipped with a rear wheel steering device according to the present invention.

In this vehicle, a rack bar 11 constituting a front wheel side steering link mechanism 10 is displaced in the left and right direction by operation of a steering wheel WS, and is connected via a tie rod 13 to a knuckle arm 12 that provides a steering angle to each front wheel WF. There is. Furthermore, the rack bar 21 constituting the rear wheel side steering link mechanism 20 is displaced in the left-right direction by a second rotating shaft 30b, which will be described later, and is connected via a tie rod 23 to a knuckle arm 22 that provides a steering angle to each rear wheel WR. has been done. Both rack bars 11, 21 of these steering link mechanisms 10, 20 are connected to a pair of front and rear rotating shafts 30a, 3.
0b and a connecting mechanism 30c.

The first rotating shaft 30a is the main shaft 3
1. Intermediate shaft 32 and pinion shaft 3
The main shaft 31 is connected to the rack bar 11 via an intermediate shaft 32 and a pinion shaft 33. This main shaft 31 is rotatably supported by the vehicle body and extends a predetermined length toward the rear of the vehicle body. The second rotating shaft 30b is formed as a pinion shaft, is rotatably supported by the vehicle body, and is connected to the rack bar 21 by meshing with it. These two rotating shafts 30a, 30b are connected to a connecting mechanism 30.
They are interconnected by c.

Therefore, the connecting mechanism 30c is shown in FIGS. 2 and 3.
As shown in the figure, a first connecting member 34, which is an arm-shaped connecting member of the present invention, is assembled to the rear end of the main shaft 31 of the first rotating shaft 30a, and a first connecting member 34 is assembled to the front end of the second rotating shaft 30b. The second connecting member 35 is a spherical connecting member of the present invention, the engaging pin 36 is an engaging member of the present invention protruding from the rear end of the arm portion 34a of the first connecting member 34, and the second connecting member The main component is an electric motor 37 that rotates the motor 35.

The first connecting member 34 is assembled at its base 34b to the rear end of the main shaft 31 via a ball nut mechanism, and is attached to a rail 38 provided on the vehicle body side.
It is designed to be able to slide only in the front-back direction on the top a. The second connecting member 35 has a hemispherical shape and has an arcuate elongated hole 35a of a predetermined length at the top thereof. It is assembled so as to be rotatable along parallel planes (in the direction of the arrow in FIG. 2).
In the second connecting member 35, the engaging pins 36 are inserted into the arcuate elongated holes 35a and engage with each other, and mesh with the drive gear 37a of the electric motor 37 disposed on the connecting portion 38b to rotate. It is becoming possible to move. Note that reference numerals 38c and 38c in FIG.
Reference numerals 38d and 38e indicate a drive circuit, a controller for controlling the drive circuit, and a vehicle speed sensor.
7, its drive is appropriately controlled according to the vehicle speed.

As a result, the second connecting member 35 rotates in the direction of the arrow shown in FIG.
The angle of inclination of the rotating shaft 30b relative to the second rotating shaft 30b is changed.

In the vehicle configured in this manner, when the steering wheel WS is operated, the rack bar 11 is displaced in the left-right direction to steer the front wheels WF. During this steering, the first rotating shaft 30a rotates and slides the first connecting member 34 in the front-rear direction depending on the amount of rotation.

Therefore, the arcuate elongated hole 35 of the second connecting member 35
If a is parallel to the second rotating shaft 30b as shown in FIGS. 4a and 4b, even if the first connecting member 34 slides in the direction of the arrow or in the opposite direction, the engagement pin 36 moves inside the arcuate elongated hole 35a without engaging with it. As a result, the second
The rotating shaft 30b is not rotated, and even if the front wheel WF is steered, the rear wheel WR is maintained in a neutral state.

Further, when the arc-shaped elongated hole 35a is inclined at a predetermined angle θ with respect to the second rotating shaft 30b as shown in FIGS. 5a and 5b, the engagement pin 36 engages with the arc-shaped elongated hole 35a While doing so, the second rotary shaft 30b is rotated in the direction of the arrow in the figure by moving as shown in FIGS. 6a and 6b. As a result, the rear wheel WR is steered according to the amount of rotation of the second rotary shaft 30b.
Note that when the first connecting member 34 slides in the direction opposite to the direction of the arrow, the second rotating shaft 30b also rotates in the opposite direction and steers the rear wheel WR in the opposite direction.

By the way, the second sliding movement of the first connecting member 34
The conversion rate of the rotary shaft 30b into rotational motion increases in accordance with the inclination angle θ when the inclination angle θ of the circular arc-shaped elongated hole 35a is within a predetermined range. Also, the second rotating shaft 3 with respect to the sliding direction of the first connecting member 34
The rotation direction of 0b is determined as either forward or reverse depending on the inclination direction (the inclination angle is θ or −θ) of the circular arc-shaped elongated hole 35a. Therefore, if the second connecting member 35 is rotated by the electric motor 37 and the inclination angle θ and the inclination direction of the arc-shaped elongated hole 35a are appropriately controlled according to the vehicle speed, the rear wheel WR can be brought into phase with the front wheel WF. The vehicle can be steered in any of the directions of , reverse phase, and the front and rear wheel steering angle ratio can be changed as appropriate depending on the vehicle speed.

Furthermore, in this embodiment, each of the structural members 34 and 35 constituting the coupling mechanism 30c is small and the amount of displacement thereof is small, so the coupling mechanism 30c is lightweight and small. Further, since the rear wheel WR is steered by the rotation of the second rotary shaft 30b, there is an advantage that a commonly used power assist mechanism can be used as is when power assisting the steering of the rear wheel WR.

[Brief explanation of the drawing]

FIG. 1 is a plan view schematically showing an example of a vehicle equipped with a rear wheel steering device according to the present invention, FIG. 2 is an enlarged perspective view of a coupling mechanism in the steering device, and FIG. 3 is an enlarged longitudinal section of the same mechanism. The side view, FIGS. 4a and 4b, 5a and 5b, and 6a and 6b are explanatory diagrams of the operation of the mechanism. Explanation of symbols, 10, 20... Steering link mechanism, 11, 21... Rack bar, 30a, 3
0b... Rotating shaft, 30c... Connection mechanism, 3
4, 35...Connection member, 35a...Circular long hole,
36... Engagement pin, 37... Electric motor.

Claims (1)

[Scope of utility model registration request] a first rotary shaft whose front end is connected to the front wheel steering link mechanism, extends rearward and rotates in response to steering operation of the front wheels; and a first rotary shaft whose rear end is connected to the rear wheel steering link mechanism and extends forward. A second rotary shaft that steers the rear wheels by rotation, and a coupling mechanism that connects these two rotary shafts, and the coupling mechanism is assembled to the rear end of the first rotary shaft and rotates the first rotary shaft. an arm-shaped connecting member that moves only in the axial direction, a spherical connecting member that is assembled to the front end of the second rotating shaft and is rotatable along a plane parallel to the second rotating shaft, and the arm-shaped connecting member an engaging member that protrudes from the rear end and engages with an arcuate elongated hole provided on the outer periphery of the spherical connecting member; and a second rotation of the arcuate elongated hole by rotating the spherical connecting member. A rear wheel steering device for a front and rear wheel steered vehicle, comprising a drive means that changes an inclination angle with respect to the shaft according to the driving condition of the vehicle.