JPH02175472A - Four-wheel steering device of vehicle - Google Patents

Abstract

PURPOSE:To vary the steering angle of rear wheels according to the car velocity by providing a variable throttle valve in a communicating path of an oil path and changing the opening of the valve to adjust the quantity of oil flowing through the communicating path in a four wheel steering device having an oil path communicating an oil chamber of the first hydraulic cylinder and an oil chamber of the second hydraulic cylinder. CONSTITUTION:An oil chamber 21 of the first hydraulic cylinder 11 and an oil chamber 17 of the second hydraulic cylinder 14, and an oil chamber 22 of the hydraulic cylinder 11 and an oil chamber 18 of the second hydraulic cylinder 14 are respectively communicated with each other by oil paths 23, 24, and the oil paths 23, 24 are communicated with each other by oil paths 23, 24, and the oil paths 23, 24 are communicated with each other by a communicating path 25. A variable throttle valve 26, the opening of which is automatically controlled according to the car velocity detected by a car velocity sensor 27, is disposed in the communicating path 25. The quantity of oil flowing through the communicating path 25 is controlled by the variable throttle valve 26 to change to movement of a rack rod 2, that is, the horizontal movement of a rear wheel steering rod 7 to the steering angle of front sheels 1, that is, the steering angle ratio (steering ratio) of rear wheels.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention is a four-wheel steering system for a vehicle, more specifically, it is capable of steering the rear wheels following the steering of the front wheels, and furthermore, it is possible to steer the rear wheels by following the steering of the front wheels. The present invention relates to a steering device that can adjust the ratio to the angle by 211 as appropriate.

Conventional Technology and Problems of the Invention Conventionally, a four-wheel steering system for a vehicle includes a first hydraulic cylinder in which a piston is moved by the left-right movement of a front wheel steering rod, and a rear wheel steering rod is moved in the left-right direction by movement of the piston. a second hydraulic cylinder for driving a rear wheel steering rod;
An oil passage that communicates one oil chamber of the hydraulic cylinder with one oil chamber of the second hydraulic cylinder, and an oil passage that communicates the other oil chamber of the first hydraulic cylinder with the other oil chamber of the second hydraulic cylinder. and fixed throttles provided in both oil passages,
A vehicle in which the rear wheel steering angle is variable in accordance with the front wheel steering speed is known (see Japanese Patent Laid-Open No. 189676/1983).

In this four-wheel steering system, when the steering wheel is suddenly turned, the front wheels are steered accordingly, but due to the presence of a fixed throttle, oil does not suddenly flow into the second hydraulic cylinder, and the rear wheels are steered at a specified speed. There is a time lag before the steering angle is reached. Therefore, even if, for example, the steering wheel must be suddenly turned when the vehicle is running in the ρ1 speed, the steering angle of the rear wheels is small and there is little danger.

However, when it is necessary to turn the steering wheel rapidly at low speeds, such as when entering a garage or changing direction, the advantage of a four-wheel steering device, which is improved turning ability, cannot be fully utilized. There's a problem. Furthermore, if the steering wheel is turned slowly, the steering angle of the rear wheels will increase in accordance with the steering angle of the front wheels, which can be dangerous, for example, when changing lanes while driving at high speed.

An object of the present invention is to solve the above-mentioned problems and to provide a four-wheel steering system for a vehicle that can make the steering angle of the rear wheels variable depending on the vehicle speed.

Means for Solving Three Problems The four-wheel steering system for a vehicle according to the present invention includes a first hydraulic cylinder whose piston is moved by the left-right movement of the front wheel steering rod, and a first hydraulic cylinder whose piston is moved by the left-right movement of the front wheel steering rod; a second hydraulic cylinder for driving a rear wheel steering rod;
An oil passage that communicates one oil chamber of the first hydraulic cylinder with one oil chamber of the second hydraulic cylinder, and communicates the other oil chamber of the first hydraulic cylinder with the other oil chamber of the second hydraulic cylinder. In the four-wheel steering device equipped with an oil passage, the two ura passages are communicated with each other by a communication passage, and the communication passage is provided with an S-shaped valve.

If the variable operation throttle valve is kept fully open, when the front wheels are steered, the piston of the first hydraulic cylinder moves together with the front wheel steering rod, and most of the oil chambers on the side where the piston moves are It flows into the oil chamber on the opposite side of the first hydraulic cylinder through the communication passage. Further, since the two /ltl chambers of the second hydraulic cylinder are connected to each other via the communication passage, the pressure inside the inner oil chamber is equal. Therefore, the piston of the second hydraulic cylinder does not move, and as a result the rear wheel steering rod does not move and the rear wheels are not steered.

If the i+J variable throttle valve is fully open, when the front wheels are steered, the piston of the first hydraulic cylinder moves together with the front wheel steering rod, and the oil in the oil chamber on the side where the piston moves flows through the oil passage. and flows into one of the oil chambers of the second hydraulic cylinder. The inflowing oil causes the piston to move, which in turn moves the rear wheel steering rod to steer the rear wheels.

In addition, by changing the opening degree of the variable throttle valve and adjusting the amount of water flowing through the communication path, it is possible to change the amount of left-right movement of the rear wheel steering rod and the rear wheel steering angle when the front wheel steering angle is constant. can.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to the drawings. Are the same objects and parts the same throughout all drawings? No. 1 will be given and the explanation will be omitted.

FIG. 1 shows the configuration of a vehicle equipped with a four-wheel steering system according to the present invention.

The front wheel steering device that steers the front wheels (1) of the vehicle is of the rack and pinion type, and both ends of the rack rod (front wheel steering rod) (2) are attached to the tie rods (4) on the knuckle arms (3) of the front wheels (1).
) are connected via. By rotating the steering wheel (5), the rack rod (2) moves in the left-right direction, and the front wheels (1,') are steered.

Rear wheel steering rod (7) of the rear wheel steering device that steers the rear wheels (6)
Both ends are connected to the knuckle arm (8) of the rear wheel (6) via a tie rod (9). And the rear wheel (・
By moving the rudder rod (7) in the left-right direction, the rear wheels (6) are steered.

A first hydraulic cylinder (II) is provided in the rack t1 (2). The first hydraulic cylinder (11) has a rack rod (2
) and a piston (13) fixed to the rack rod (2) so as to move together with the rack rod (2). The cylinder tube (12) is fixed to the vehicle body, and the rack rod (2)
When the piston (13) moves relative to the cylinder tube (12), the volumes of the left and right oil chambers (21) and (22) change. The rear wheel steering rod (7) is provided with a second hydraulic cylinder (14) for driving the rear wheel steering rod. The second hydraulic cylinder (14) is fixed to a cylinder tube (+5) arranged around the rear wheel steering rod (7) and to the rear wheel steering rod (7) so as to move together with the rear wheel steering rod (7). It consists of a piston (1G). The cylinder tube (15) is identified on the vehicle body, and when the rack rod (2) moves, the piston (1G) moves relative to the cylinder tube (15), and the volume of the left and right oil chambers (+7) (1g) increases. change.

Inside the second hydraulic cylinder (14) are left and right oil chambers (17).
A spring (19) is arranged which holds the piston (1B) in a neutral position when the pressure difference within (18) is small.

Further, the inner diameter of the second hydraulic cylinder (14) is larger than the inner diameter of the first hydraulic cylinder (11).

In this four-wheel steering device, the front wheel (1) and the rear wheel <a> are steered in opposite phases, and the first hydraulic cylinder (11)
The left oil chamber (21) and the left oil chamber (17) of the second hydraulic cylinder (14), and the right oil chamber (22) of the first hydraulic cylinder (II) and the second hydraulic cylinder (14). The oil chambers (18) on the right side are communicated with each other by oil passages (23) and (24), respectively. Both oil passages (23) and (24) are communicated through a communication passage (25). Communication path (25)
In accordance with the vehicle speed detected by the vehicle speed sensor (27),
A variable throttle valve (26) whose opening degree is automatically controlled by a controller (28) is provided, and the amount of oil flowing through the communication passage (25) is controlled by this variable throttle valve (26). . And inner hydraulic cylinders (11) (14)
, both oil passages (23), (24), a communication passage (25), and a variable throttle valve (2B) constitute a four-wheel steering hydraulic circuit. In addition, in order to compensate for oil leakage from the four-wheel steering hydraulic circuit, a supply line (3I) extending from the oil tank (29) is connected to Ryoura Road (23024), and a pump (32 ) allows oil to be supplied to the four-wheel steering hydraulic circuit. There is a check valve (33) in the supply path (31).
is provided. Moreover, a return path (35) provided with a relief valve (30) is provided in the supply path (31).

In such a configuration, the variable throttle valve (2
By changing the opening degree of B) and adjusting the amount of oil flowing through the communication passage (25), the amount of movement of the rack rod (2), that is, the rear wheel steering rod (7) relative to the steering angle of the front wheel 1) is adjusted. )
The amount of movement in the left-right direction of the rear wheels (6), that is, the ratio of the steering angles (steering ratio) of the rear wheels (6) can be changed. If the variable throttle valve (26) is fully open, for example, the steering wheel (5)
) to the right and move the rack rod (2) to the left.
The front wheels (1) are steered to the right. In this case, by moving the piston (13) of the first hydraulic cylinder (11) to the left together with the rack rod (2), the left oil chamber (21)
Most of the oil in ) flows into the oil chamber (22) on the right side of the first hydraulic cylinder (11) through the communication passage (25). In addition, two oil chambers (1) of the second hydraulic cylinder (I4)
7) (ill) are connected to each other via the communication passage (25), so the pressure inside the inner oil chambers (17) and (18) is approximately equal.

Therefore, the left oil chamber (
No oil flows into the piston (17), and the piston (10) is
+9> is held in the neutral position. As a result, the rear wheel steering rod (7) does not move and the rear wheels (6) are not steered. If the variable throttle valve (26) is fully closed, for example, turn the steering wheel (5) to the right to close the rack rod (2).
When the front wheel (1) is steered to the right by moving the rack rod (2) to the left, the piston of the first hydraulic cylinder (11) moves to the left together with the rack rod (2), thereby
The oil in the left oil chamber (2I) flows into the left oil chamber (17) of the second hydraulic cylinder (14) through the oil passage (23). The inflowing oil causes the piston (16) to move to the right, and as a result, the rear wheel steering rod (7) moves to the right, and the rear wheels (6) are steered in the opposite phase to the front wheels (1). . Since the inner diameter of the second hydraulic cylinder (14) is larger than the inner diameter of the first hydraulic cylinder (11), the rear wheel steering angle is smaller than the front wheel steering angle. In this way, when the variable throttle valve (2B) is in the fully closed state, the above-mentioned steering ratio becomes maximum. As the opening degree of the variable throttle valve (2B) increases, the steering ratio decreases (becomes).

During high-speed running, the variable throttle valve (2B) is fully open. Then, the piston (16) is held at the neutral position by the spring (19). As a result, the rear wheel steering rod (7) does not move and the rear wheels (8) are not steered.

When driving at low speeds, such as when parking in a garage, the variable throttle valve (2B) is fully open. Then, the rear wheels (B) are steered in the opposite phase to the front wheels (1) so that the above-mentioned steering ratio becomes maximum.

Therefore, the maneuverability is improved.

FIG. 2 shows another embodiment of the invention. In FIG. 2, the four-wheel steering system is such that the front wheels and rear wheels are steered in the same phase, and the oil chamber (21) on the left side of the first hydraulic cylinder (11) and the second hydraulic cylinder (14) oil chamber on the right side (1
8), and the right oil chamber (
22) and the left oil chamber (17) of the second hydraulic cylinder (14).
) are communicated with each other by an oil passage (3B>(37)).

In such a configuration, the variable throttle valve (2G) is fully opened during high-speed running. Then, when the steering wheel (5) is turned to the right and the rack rod (2) is moved to the left, the front wheels (1) are steered to the right. in this case,
As the piston (13) of the first hydraulic cylinder (11) moves to the left together with the rack rod (2), the oil in the left oil chamber (21) passes through the oil passage (30) to the second hydraulic cylinder. It flows into the oil chamber (18) on the right side of the hydraulic cylinder (14). The inflow of water causes the piston (16) to move to the left, and as a result, the rear wheel steering rod (7) moves to the left, so that the rear wheel (6) moves to the front wheel ( It is steered in the same phase as 1). Therefore, running stability during high-speed running is improved. Then, as the variable throttle valve (2G) is gradually opened, the above-mentioned steering ratio becomes smaller.

When driving at low speeds, such as when parking in a garage, the variable throttle valve (28) is fully open. Then, similarly to the embodiment shown in FIG. 1, the piston (16) of the second hydraulic cylinder (14)
is held in a neutral position, and the rear wheels (G) are not steered.

FIG. 3 shows yet another embodiment of the invention.

In FIG. 3, a four-bottom, two-position switching valve (40) is arranged across both oil passages (23) and (24).

This switching valve (40) is automatically or manually switched between an opposite phase position and an in-phase position. At the opposite phase position, four-wheel steering or front wheel steering is performed in the same manner as in the embodiment shown in FIG. 1, and in the same phase position, four-wheel steering or front wheel steering is performed in the same manner as in the embodiment shown in FIG. . Switching valve (40
) is automatically switched, it is controlled to switch to the opposite phase position until the vehicle speed reaches a preset vehicle speed, and to switch to the same phase position when the set vehicle speed is exceeded. At this time, the variable throttle valve (26) opens and the switching valve (4
0) and is automatically controlled according to the vehicle speed. In other words, it is fully open at low speeds, gradually opened as the vehicle speed increases, becomes fully open when the set vehicle speed is reached, gradually closes when the set vehicle speed is exceeded, and is controlled to be fully closed at high speeds. be done. Therefore, at low speeds, the rear wheels (8) are steered in the opposite phase to the front wheels (1) so that the above-mentioned steering ratio is maximized, and the n1 variable throttle valve (26)
As the opening degree increases, the steering ratio gradually decreases, and at the set vehicle speed, only the front wheels (1) are steered. When the set vehicle speed is exceeded, the rear wheels (8) will shift to the front wheels (
1,), and the variable throttle valve (
As the opening degree of 26) increases, the above-mentioned steering ratio gradually increases, and the above-mentioned steering ratio becomes maximum at high speed.

In the above embodiment, the variable throttle valve is controlled by the controller (
28), but
Manually switch only to fully open state and fully open state,
Adjustment of the opening degree between both states may be automatically controlled.

Effects of the Invention According to the four-wheel steering device of the present invention, as described above,
By controlling the amount of oil flowing through the communication path using the variable throttle valve, it is possible to maintain the rear wheels in a neutral position or to control the steering angle of the rear wheels. Therefore, by controlling the opening degree of the variable throttle valve according to the vehicle speed, it is possible to perform two-wheel steering or adjust the steering angle of the rear wheels according to the vehicle speed.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a vehicle equipped with a four-wheel steering device showing an embodiment of the present invention, FIG. 2 is a schematic configuration diagram of a vehicle equipped with a four-wheel steering device showing another embodiment of the invention, FIG. 3 is a schematic diagram of a vehicle equipped with a four-wheel steering system showing still another embodiment of the present invention. (2) Rack rod, (7) Rear wheel steering rod, (1
1)...First hydraulic cylinder, ([3)...Piston, (14)...Second hydraulic cylinder for driving rear wheel steering rod,
(17) (lit)...Oil chamber of the second hydraulic cylinder, (
21) (22)... Oil chamber of the first hydraulic cylinder, (23
) (24) (30) (37)...oil passage, (25)
...Communication furnace, (26)...Variable throttle valve. Above, 'Applicant: Koyo Seiko Co., Ltd.

Claims (1)

[Scope of Claims] A first hydraulic cylinder whose piston is moved by the left-right movement of the front wheel steering rod, and a second hydraulic cylinder for driving the rear wheel steering rod which moves the rear wheel steering rod left and right by the movement of the piston.
A hydraulic cylinder, one oil chamber of the first hydraulic cylinder, and a second hydraulic cylinder.
an oil passage that communicates with one oil chamber of the hydraulic cylinder;
In a four-wheel steering device equipped with an oil passage that communicates the other oil chamber of a hydraulic cylinder with the other oil chamber of a second hydraulic cylinder, both oil passages are communicated by a communication passage, and a variable throttle valve is provided in the communication passage. A four-wheel steering system for vehicles equipped with.