JPH065944Y2 - Vehicle steering device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle steering system, and more particularly to a vehicle steering system that uses an air spring to hold a piston in a neutral position.

(Prior art) Recently, as the society matures, high demands are being placed on the driving performance of vehicles. Steering the rear wheels according to the turning of the front wheels, especially when cornering at high speeds A vehicle steering device for improving running stability is mounted on a vehicle.

As a conventional vehicle steering system of this type, for example, Japanese Patent Laid-Open No.
The one described in Japanese Patent Publication No. 1-81869 is known, and is shown as in FIG. In FIG. 1, reference numeral 1 denotes a vehicle steering device, and the vehicle steering device 1 includes a power cylinder 2, a piston 5 that divides the power cylinder 2 into a pair of liquid chambers 3 and 4, and a piston connected to the piston 5. It includes a rod 6, end covers 7 and 8 that pivotally support the piston rod 6, and springs 9 and 10 arranged in the liquid chambers 3 and 4, respectively. When the power assist pressure from the front wheel steering system is low, the springs 9 and 10 press the piston 5 in both directions by the urging force and hold it in the neutral position. On the other hand, when a predetermined hydraulic pressure is applied from the front wheel steering system via the connectors 11 to 14, the piston 5 overcomes the urging force of the springs 9 and 10 and moves from the neutral position to the left and right in the figure together with the piston rod 6, and the piston 5 The rear wheel connected to the rod 6 through the side rods 15 and 16 gives a steering angle according to the steering amount.
When the hydraulic pressure from the front wheel steering system decreases at high speeds, the piston 5 is held in the neutral position by the urging force of the springs 9 and 10, so that the steering angle of the rear wheels becomes zero and the vehicle keeps going straight. Sex is secured.

(Problems to be Solved by the Invention) However, in such a conventional vehicle operation device, the holding means is constituted by the metal springs respectively arranged in the pair of liquid chambers, and the hydraulic pressure from the front wheel steering system is Since the piston is held in the neutral position by the urging force of the holding means when it is low, the holding means (spring) is required to have a larger urging force than the axial force applied from the wheels during high-speed running. In order to obtain a large spring constant, the internal stress of the wire material forming the metal spring increases, the fatigue limit of the wire material decreases, and the springs press against each other, so that the durability of the holding means (spring) decreases. was there.

Also, in order to obtain a large spring constant, the diameter of the wire of the spring must be set to a size comparable to the diameter of the piston rod, for example, so the amount of contraction corresponding to the displacement from the neutral position of the piston Is required for the spring, the free length of the spring is inevitably long,
The axial length of each liquid chamber becomes about three times as long as the displacement amount of the piston, the total length of the power cylinder becomes long, and the power cylinder cannot be mounted on the vehicle unless the tread has a predetermined value or more.

(Object of the Invention) Therefore, the present invention eliminates the fatigue limit in the metal and improves the durability of the holding means by forming the holding means for holding the piston in the cylinder at the neutral position with an air spring instead of the metal spring. It is intended to improve and downsize the power cylinder.

(Means for Solving the Problems) In order to achieve the above object, the vehicle steering system according to the present invention, when a predetermined hydraulic pressure is applied from the hydraulic system in response to the steering of the steering wheel, causes the piston in the cylinder to move in a substantially vehicle width range. A power cylinder for steering the vehicle by displacing the steering wheel according to the displacement amount to the wheels and steering the vehicle. The power cylinder has a piston in the cylinder due to the holding force when the hydraulic pressure is low. In a vehicle steering system provided with a holding means for holding the neutral position, the holding means includes at least a pair of air chambers filled with a gas of a predetermined high pressure, and a pair of air chambers depending on the displacement of the piston. One of them is expanded, the other is compressed, and a volume changing means for generating a holding force according to the pressure in the air chamber is provided.

(Operation) In the present invention, the holding means for holding the piston in the cylinder at the neutral position is constituted by the pair of air chambers and the holding force generating means to form the air spring, and the holding means is urged by the air spring action. And the piston in the cylinder is maintained at the neutral position by the urging force of the holding means.

Therefore, the axial lengths of the liquid chamber and the air chamber in the cylinder are determined according to the amount of displacement of the piston, the axial length of the power cylinder is reduced, and there is a problem when the holding means is constituted by a metal spring. The fatigue limit of the metal is eliminated and the durability of the holding means is improved.

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

FIG. 1 is a diagram showing an embodiment of a vehicle steering system according to the present invention.

First, the configuration will be described. In the figure, 21 is a vehicle steering device. The vehicle steering system 21 includes a power cylinder 22, a piston 23 that freely slides in the power cylinder 22, a pair of liquid chambers 24 and 25 partitioned by the piston 23 in the power cylinder 22, and liquid chambers 24 and 25. Housings 26 and 27 for respectively sealing the open ends of the power cylinder 22, a housing 28 for sealing the open ends of the power cylinder 22, a piston rod 29 fixed to the piston 23 and displaced integrally, and a piston rod 29 The bearings 31 to 33 that stop are included. Connectors 34 to 37 are attached to the outside of the power cylinder 22, and the connectors 34 to 37 are connected to a hydraulic device (not shown) and a front wheel steering device via a pipe, and the working fluid flows into the liquid chambers 24, 25. Drain. When a predetermined hydraulic pressure is applied from the hydraulic device according to the steering of the steering wheel, the piston 23 is displaced from the neutral position in the left-right direction in the drawing according to the supply amount of the hydraulic fluid. The piston rod 29 is displaced together with the piston 23,
A steering angle corresponding to the displacement amount of the piston 23 is given to a rear wheel (not shown) connected via the side rods 38, 39. Also,
The power cylinder 22 is provided with holding means 41 for holding the piston 23 in the power cylinder 22 at the neutral position by the holding force when the hydraulic pressure from the hydraulic device is low. The holding means 41 is a pair of air chambers 42, 43 provided in the vehicle width direction,
A volume changing means 44 fixed to the piston rod 29 and moving together with the piston 23, and gas inlets 45, 46 for filling a pair of air chambers 42, 43 with gas of a predetermined high pressure are provided. The volume changing means 44 generates a holding force corresponding to the effective pressure receiving area and the gas pressure in the pair of air chambers 42, 43, and the holding force biases the piston rod 29 in both directions to move the piston 23 to the neutral position. Hold. Further, the volume changing means 44 expands one of the pair of air chambers 42 and 43 and compresses the other in accordance with the displacement of the piston 23, and attaches it according to the internal pressure on the compression side of the pair of air chambers 42 and 43. A force is generated and the piston rod 29 is biased by the biasing force to return the piston 23 to the neutral position. The side rods 38 and 39 are covered with dust covers 47 and 48, and the dust covers 47 and 48 prevent intrusion of muddy water or the like from the outside. Further, 50 to 53 are packings, 54 to 58 are seal rings, and the packings 50 to 53 and the seal rings 54 to 58 maintain liquid tightness in the liquid chambers 24 and 25 and air tightness in the pair of air chambers 42 and 43. is doing. The sealing 57 is a combination ring of an O ring and a Teflon ring.

Next, the operation will be described.

When the steering wheel is steered by the driver,
A predetermined hydraulic pressure is applied to the front wheel steering device from a hydraulic device (not shown) in response to the steering of the steering wheel, and the front wheels (not shown) are also steered. At the same time, the hydraulic pressure from the hydraulic device is applied to the vehicle steering system 1 via the piping (not shown) and the connectors 34 to 37, and the hydraulic chamber 2 is driven by the hydraulic pressure from the hydraulic device.
There is a pressure difference between 4,25 and the piston
The axial force generated by 23 exceeds the urging force of the holding means 41, the piston 23 is moved in the lateral direction in the figure by the displacement amount according to the supply amount of hydraulic fluid, and the steering angle according to the displacement amount is changed to the rear wheel. Given to.

On the other hand, when the power assist pressure from the front wheel steering device is low, the axial force generated by the piston 23 is smaller than the holding force generated by the holding means 41, and the piston force is generated by the holding force.
23 is biased in both directions to maintain the neutral position. The holding means 41 generates a holding force as follows. That is, the volume changing means 44 is bidirectionally pressed by the high pressure gas inside the air chambers 42 and 43, the volume changing means 44 generates a holding force corresponding to the product of the pressure receiving area and the gas pressure, and the holding force changes the volume. Means 44 press the piston rod 29 in both directions to hold it in the neutral position.

Further, when external force is applied from the wheels and the piston 23 is moved in the left-right direction, one of the pair of air chambers 42, 43 expands, the other compresses, and the gas pressure on the compression side rises. Also, an urging force similar to that of a metal spring is generated according to the amount of displacement of the piston 23, and the urging force urges the volume changing means 44 in the direction opposite to the moving direction.
23 is returned to its original neutral position (hereinafter referred to as the air spring action). Here, the holding force generated by the holding means 41 is determined by the effective pressure receiving area of the volume changing means 44 and the gas pressure in the pair of air chambers 42, 43, and the air spring action is the pair of air chambers 42, 4
Determined by 3 volumes and gas pressure. Therefore, in this embodiment, by properly setting the gas pressure, the axial length of the pair of air chambers 42, 43 can be set to be the same as the displacement amount of the piston 23. Similarly, since the force generated by the liquid chambers 24, 25 and the axial length of the liquid chambers 24, 25 are irrelevant,
The axial length of the liquid chambers 24, 25 can be set according to the displacement amount of the piston 23, and the axial length of the power cylinder 22 can be shortened.

As described above, in this embodiment, unlike the conventional example in which the spring is arranged in the pair of liquid chambers, the holding means 41 is provided outside the liquid chambers 24 and 25, and the axial length of the liquid chambers 24 and 25 is set to the piston 23. Since the power cylinder 22 is set according to the displacement amount, the axial length of the power cylinder 22 can be shortened, and the vehicle steering device 21 can be applied to a vehicle model with a narrow tread that cannot be conventionally mounted. Also,
In the present embodiment, unlike the conventional example in which the holding means is composed of a metal spring, the air spring action of gas is used, so the fatigue limit due to metal fatigue can be eliminated, and the durability of the holding means 41 can be improved. .

Further, in this embodiment, since the holding force can be set in the pair of air chambers 42, 43 by the gas pressure,
One type of vehicle steering device 21 having different holding forces can be freely manufactured, and the application range of the vehicle steering device 21 can be expanded.

In the present embodiment, the pair of air chambers 42, 43 is provided inside the power cylinder 22, but not limited to this, the pair of air chambers is provided outside the power cylinder 22, and the inner air chambers 42, 43 are provided.
The vehicle steering device 21 can be further expanded in this case.

Further, similarly, an accumulator is provided outside the power cylinder, the pair of air chambers 42, 43 is filled with a liquid instead of gas and communicates with the accumulator, and the holding means is configured by utilizing the air spring action of the accumulator. Of course, you can do that.

(Effect) According to the present invention, since the holding force is generated by the air spring action and the holding force holds the piston in the cylinder at the neutral position, the liquid chamber and air in the cylinder The axial length of the chamber can be determined according to the amount of displacement of the piston, the power cylinder can be downsized, and the fatigue limit of metal, which is a problem with metal springs, can be eliminated and the durability of the holding means can be improved. it can.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a vehicle steering apparatus according to the present invention, and FIG. 2 is a sectional view showing a conventional vehicle steering apparatus. 21 …… Vehicle steering device, 22 …… Power cylinder, 23 …… Piston, 41 …… Holding means, 42,43 …… A pair of air chambers, 44 …… Volume changing means.

Claims (1)

[Scope of utility model registration request] 1. When a predetermined hydraulic pressure is applied from a hydraulic device in response to steering of a steering wheel, a piston in a cylinder is displaced in a substantially vehicle width direction, and a steering angle corresponding to the displacement amount is applied to the wheel. A vehicle steering apparatus comprising a power cylinder for steering a vehicle, wherein the power cylinder is provided with a holding means for holding a piston in the cylinder at a neutral position by a holding force when the hydraulic pressure is low, The holding means expands at least one of the pair of air chambers filled with a gas of a predetermined high pressure and one of the pair of air chambers according to the displacement of the piston, compresses the other, and responds to the pressure inside the air chamber. A vehicle steering system comprising: a volume changing unit that generates a holding force.