JPH0143980Y2 - - Google Patents

Description

[Detailed description of the invention] (Industrial application field) The present invention is a rack and pinion steering force extraction device that transfers the steering force of the rear wheels from a vehicle's four-wheel steering system, particularly a steering system that steers the front wheels. Regarding what to take out through.

(Prior art) In general, when steering a four-wheeled vehicle, it is customary to use the steering wheel to steer only the front wheels. However, when steering only the front wheels, depending on the driving situation, the rear wheels may skid. There are problems in terms of steering and steering performance, such as the turning radius being limited and the turning radius not being effective. Therefore, in recent years, research has been underway into four-wheel steering devices that can steer both the front wheels and the rear wheels.

By the way, when driving at relatively high speeds, if the rear wheels are steered in the same direction as the front wheels, a lateral force will be applied to the front and rear wheels at the same time, and the phase delay from the steering of the steered wheels will be reduced. This makes it possible to maintain the running posture of the vehicle almost on the tangent to the turning circle, and for example, lane changes can be performed smoothly when driving at high speed. Further, when driving at a relatively low speed, steering the rear wheels in the opposite direction to the steering direction of the front wheels allows the direction of the vehicle to be changed significantly, which is advantageous in parallel parking, parking in a garage, etc.

Therefore, the front wheels are not steered significantly when driving at relatively high speeds, and considering that the front wheels are steered significantly when driving at relatively low speeds, the front wheels are not steered significantly when driving at relatively low speeds. A four-wheel steering device has been proposed in which the rear wheels are steered in the same direction, while the rear wheels are steered in the opposite direction in areas where the front wheels are largely steered (see, for example, Japanese Patent Laid-Open No. 55-91458). .

In principle, the four-wheel steering device described above can be realized using various methods, but since the rack and pinion mechanism transmits motion to the sharp, the four-wheel steering device described in Japanese Patent Application Laid-Open No. 122259/1983 is so that you can
There is a device that uses a rack and pinion mechanism to determine the amount of steering of the rear wheels. However, in this device, since the rack for steering the front wheels and the rack for taking out the amount of steering of the rear wheels are integrally provided on the same axis, there is a problem in that it is subject to restrictions in terms of layout.

That is, when a power steering device is provided, a power cylinder,
If a pinion is provided to input the steering operation of the steered wheels, the position of the pinion that takes out the steering force of the rear wheels is fixed, and the layout of the shaft that transmits the amount of steering to the rear wheels is restricted.

Therefore, in order to solve such a problem, the rack of the steering amount take-off device for the rear wheels is installed approximately parallel to the rack gear of the steering device that steers the front wheels, and the rack gear and the rack are connected to a connecting rod. A four-wheel steering system for a vehicle is conceivable, in which the two wheels are connected together.

By doing so, parts can be made common between two-wheel steered vehicles and four-wheel steered vehicles, and the mounting height of the rear wheel steering amount extraction device and the shaft that transmits the steered amount to the rear wheels can be standardized. Since the mounting position can be adjusted, the degree of freedom in layout is increased, the shaft can be positioned approximately in the center of the vehicle body in the left-right direction, and it can be passed through the tunnel section of the floor panel, and the power steering device can be easily installed. There are various advantages such as:

However, in such a device, because the diameter of the end of the rack gear to which the connecting rod is connected becomes larger, the diameter is different from that of the other end of the rack gear. The internal volume of the bellows material that serves as a dust boot covering the left and right sides will also differ. Therefore,
Air intake and exhaust from the bellows member by movement of the rack gear cannot be performed using the conventional method of communicating the left and right bellows members.

Therefore, it is conceivable to provide each bellows member with a breather that opens the inside of the bellows member to the outside, but doing so is disadvantageous because dust, water, etc. are likely to enter through the breather. In particular, since the bellows material is located near the tires, it is prone to mud splashing, which is a problem.

(Purpose of the invention) The present invention reduces the number of breathers for the bellows member serving as a dust boot in a four-wheel steering system for a vehicle as described above, and prevents dust, water, etc. from entering into the bellows member. The purpose is to perform air intake and exhaust inside the bellows member.

(Structure of the invention) The present invention provides a four-wheel steering system for a vehicle as described above, in which a rack of a rack-pinion steering amount take-out device is installed in parallel with the rack gear of a rack-pinion steering system that steers the front wheels. An end of the rack gear is covered with a first bellows member, an end of the rack is covered with a second bellows member, and the end of the rack gear is covered with a second bellows member.
The second bellows member is in communication with the second bellows member through an air passage, and the steering amount extraction device has a breather that communicates with the second bellows member.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

In FIG. 1 showing the overall configuration of a four-wheel steering system for a vehicle, reference numeral 1 indicates the steering wheels of a rack and pinion type steering system, and the steering shaft 1a of these wheels is a gearbox that houses a motion conversion mechanism such as a well-known rack and pinion mechanism. 2 to a rack gear 4, which is the piston rod of the front power cylinder 3. Both ends of the rack gear 4 are connected to knuckle arms 6, 6 via side rods 5, 5, respectively. is linked to. This results in
By the steering operation of the steering wheel 1, the rack gear 4 moves linearly in the left-right direction of the vehicle body, and the front wheels 8, 8 are steered.

Further, a rack 9 of a rack and pinion type steering force extraction device is integrally connected to the rack gear 4 via a connecting rod 10 substantially parallel to the rack gear 4. A rack pinion 12 fixed to the front end of an input shaft 11 in the longitudinal direction of the vehicle body is meshed with the rack 9, and the rear end of the input shaft 11 is connected to an output shaft 14 in the longitudinal direction of the vehicle body via a rear wheel steering control device 13. The rear end of the output shaft 14 is connected to a rack gear 17, which is a piston rod of a rear power cylinder 16, via a gear box 15, similarly to the front wheel side. This rack gear 17 also has side rods 18, 18 and knuckle arms 19, 1.
It is connected to rear wheels 20, 20 via 9.

21 is a hydraulic pump whose pumping side is connected to the reservoir tank 22 and whose discharge side is connected to the distribution flow valve 23. This distribution flow valve 23 distributes pressure oil from the hydraulic pump 21 to first and second passages 24 and 2.
5. The first passage 24 is a first return passage 2 connected to the reservoir tank 22.
6 and is connected to the front control valve 27. Further, the second passage 25 is also connected to a rear control valve 29 along with a second return passage 28 connected to the reservoir tank 22. Both the control valves 27 and 29 are switched and controlled according to the operation of the steering wheel 1, and one of the left and right chambers of the power cylinders 3 and 16 is connected to the first and second passages 24 and 25, and the other is connected to the first and second passages. They are connected to return passages 26 and 28, respectively. This creates a pressure difference between the left and right chambers of the power cylinders 3, 16, and power assists the steering of the front wheels 8, 8 and the rear wheels 20, 20.

Next, the details of the connection structure between the rack gear 4 and the rack 9 will be explained with reference to FIG.

The end of the rack gear 4 is a ball joint 30.
is connected to the side rod 5 via
It is covered with a first bellows member 31 serving as a dust boot.

A cylindrical support member 32 is fitted on the outside of the ball joint 30, and one end of the connecting rod 10 is fitted onto the support member 32 and connected and fixed with a nut 33 and a lock nut 34. .

The other end of the connecting rod 10 protrudes outward through a bellows member 31, passes through a second bellows member 35 that covers the rack 9, and is connected to the end of the rack 9 via a ball joint 36. There is.

Openings 3 are provided at the inner ends of the bellows members 31 and 35.
1a, 35a are provided, and both openings 31a, 35
a is connected by an air passage 37 made of a pipe. Therefore, the insides of the bellows members 31 and 35 are in communication with each other.

The casing 38 housing the rack 9 is supported by the front power cylinder 3 via a support bracket part 38a, and has an opening 38b at the end opposite to the side from which the rack 9 protrudes.
A breather pipe 39 bent toward the inside of the vehicle body is fitted into the opening. As a result, the second bellows member 35
The inside of the casing 38 is open to the atmosphere through the opening 38b and the breather pipe.

Although not shown, the insides of the left and right first bellows members 31 communicate with each other.

With the above configuration, when the steering wheel 1 is rotated clockwise from the neutral position, the mechanism in the gear box 2 operates to move the rack gear 4 to the left, and the front wheels 8, 8
is steered to the right. In that case, the front control valve 27 is controlled in accordance with the amount of steering, and the front power cylinder 3 provides power assistance.

Along with this, the rack 9 also moves to the left, so that the input shaft 11 rotates clockwise due to the engagement between the rack 9 and the pinion 12.

Therefore, in a range where the steering angle of the front wheels 8, 8 is small and the rotation angle of the input shaft 11 is small, the output shaft 14 is rotated clockwise under the control of the rear wheel steering control device 13.
The rear wheels 20, 20 are steered to the right by power assist from the rear power cylinder 16.

Furthermore, when the rightward steering angle of the front wheels 8, 8 becomes equal to or greater than the set angle θ ₁ and the rotation angle of the input shaft 11 increases, the rear wheel steering control device 13 controls the output shaft 14 to rotate to the left. (rear control valve 29
control is also reversed), so the rear wheels 20, 20, which had been steered to the right, begin to be steered to the left.
As the front wheels 8, 8 are further steered to the right, the rear wheels 20, 20 pass the neutral position and are steered to the left.

During the above-mentioned operation, as the rack gear 4 moves, the first bellows member 31 covering the end of the rack gear 4 and the second bellows member 35 covering the end of the rack 9 expand and contract, and their internal volumes change. However, since the insides of both bellows members 31 and 35 are open to the atmosphere via the breather pipe 39, the intake and exhaust of them is performed smoothly. In addition, only one breather pipe 39 is required to be opened to the atmosphere, and since it is located inside the vehicle body, mud splashed by tires, dust, water, etc. can be effectively prevented from entering through the breather pipe 39. be done.

Incidentally, when the steered wheel 1 is rotated counterclockwise from the neutral position and the front wheels 8, 8 are steered to the left, the operation is the same as described above except that the operation is reversed.

In the above embodiment, the air passage 37 was constructed with a pipe, but as shown in FIG.
It may also be configured with an air passage 41 passing through the bellows portion members 35 and 37 and communicating with each other. In this way, the pipes and the openings 31a, 3 for attaching the pipes
Since 5a is not required, there is no leakage or tearing, and the sealing performance is improved.

(Effects of the invention) Since the present invention is constructed as described above, the number of breathers that communicate the inside of the bellows part material with the atmosphere can be reduced, and the ingress of dust, water, etc. can be prevented, and the air intake and exhaust inside the bellows part material It can be performed.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is an overall configuration diagram of a four-wheel steering system for a vehicle, and FIG. 2 is a detailed diagram showing the connection structure between the rack gear of the front power cylinder and the rack of the steering amount take-off device. , FIG. 3 is a diagram similar to FIG. 2 of a modified example. 1... Steering wheel, 3... Front power cylinder,
4, 17... Rack gear, 8... Front wheel, 9... Rack, 10... Connection rod, 13... Rear wheel steering control device, 16... Rear power cylinder, 20...
Rear wheel, 31...first bellows member, 35...second bellows member, 37...air passage, 39...breather pipe, 40...connecting rod, 41...air passage.

Claims (1)

[Scope of utility model registration request] A four-wheel steering device having a rack-pinion type steering device that steers the front wheels of a vehicle, and which also steers the rear wheels in accordance with the steering of the front wheels, wherein a rack-pinion type steering amount extraction device is provided in a rack gear of the steering device. racks are arranged in parallel, an end of the rack gear is covered with a first bellows member, an end of the rack is covered with a second bellows member, and the first and second bellows members communicate with each other via an air passage. . A four-wheel steering system for a vehicle, wherein the steering amount extraction device has a breather communicating with a second bellows member.