JPH0446870A - Four-wheel steering device - Google Patents

Abstract

PURPOSE:To permit the speedy turn free from the time delay by connecting a tie rod for front wheel and a tie rod for rear wheel by a connecting member through a double acting type hydraulic cylinder and controlling the supply and cut-off of the pressurized fluid into the cylinder chamber of the double acting type hydraulic cylinder. CONSTITUTION:When a wheel advance-travels at a high speed, an air cylinder selector valve 44 is selected according to the signal supplied from a car speed sensor 6, and the compressed air in an air tank 45 is supplied into a cylinder chamber 34, and two pistons 32 shift up to the contact with a projection part 22a, and the movement of the piston 30 is regulated by nipping the piston 30 from the upper and lower parts, while one connecting member 21 and the other connecting member 29 are fixed, and operated integrally. When a steering wheel 23 is operated in the left turning direction and a front wheel 10 is steered in the direction of arrow D, the movement of a front bell crank 20 is transmitted to a rear bell crank 26 after the integral operation of one connecting member 21, air cylinder 5 and the other connecting member 29, and a rear wheel 13 is steered in the direction of arrow G.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a four-wheel steering device, and in particular, a simple device that can control self-steering in opposite phase steering, in-phase steering, or front two-wheel steering according to the traveling speed of the vehicle. This invention relates to a new four-wheel steering system that can automatically switch and control the vehicle.

BACKGROUND OF THE INVENTION Various conventional four-wheel steering systems have been proposed in which the sideslip angle of the rear wheels that occurs during turning, the amount of steering of the front wheels, or the running speed of the vehicle are used as control elements for rear wheel steering. There is. For example, Japanese Patent Application Laid-Open No. 1983-1980 discloses a system that improves steering stability at high speeds by steering the rear wheels in the same phase as the front wheels when driving at high speeds using the running speed of the vehicle as a control element.
=91457, but in this conventional example, the fulcrum position of the movable arm is changed by controlling the motor according to the running speed, and as another example, as shown in Japanese Patent Application Laid-Open No. 59-81272, There are systems in which a steering device and a rear wheel steering device are connected using a differential gear mechanism, but all of them have problems such as complicated mechanisms, high costs, and difficult maintenance.

Purpose The present invention has been made to eliminate the drawbacks of the prior art described above, and its purpose is to connect a front wheel tie rod and a rear wheel tie rod via a double-acting hydraulic cylinder. By controlling the supply and cutoff of pressure fluid to the cylinder chamber of the double-acting hydraulic cylinder, the front wheels and rear wheels can be steered in the same phase when the vehicle is traveling at high speed. This also enables rapid turning without time delay and improves stability during turning.

Another purpose is to open the cylinder chamber to the atmosphere when the vehicle is running at low speeds, thereby freeing the rear wheels and operating the front and rear wheels in opposite phases as a self-steer system. The goal is to make it smaller and improve its turning performance.

Still another object is to supply pressure fluid to the fluid pressure chamber to fix the rear wheels when reversing, thereby enabling smooth reversing with two-wheel front wheel steering.

Another objective is to simplify the mechanism and reduce costs by adopting a fluid pressure device for the rear wheel steering system.
Another purpose is to facilitate maintenance.

Structure In short, the present invention (claim 1) provides a front wheel arm having a front wheel rotatably supported at one end and a front wheel tie rod pivotally connected to the other end; a link mechanism including a rear wheel arm to which a rear wheel tie rod is pivotally connected, a connecting member that transmits the movement of the front wheel tie rod to the rear wheel tie rod, and a link mechanism that divides the connecting member into two and connects one side to the rear wheel arm; A double-acting hydraulic cylinder in which one member is integrally fixed to the cylinder and the other connecting member is integrally fixed to the piston, a vehicle speed sensor that detects the traveling speed of the vehicle, and the traveling speed of the vehicle detected by the vehicle speed sensor. When the speed is lower than a predetermined speed, the cylinder chamber of the double-acting hydraulic cylinder is opened to the atmosphere, and the front wheels and the rear wheels are operated as a self-steering mechanism in which the front wheels and the rear wheels operate independently and in opposite phases. When the running speed of the is higher than a predetermined speed, pressure fluid is supplied to the cylinder chamber of the double-acting hydraulic cylinder to integrally operate the two connecting members to move the front wheels and the rear wheels in the same phase. The invention is characterized by comprising a control device including a pressure fluid circuit configured to steer the vehicle.

The present invention (claim 2) also provides a front wheel arm having a front wheel rotatably supported at one end and a front wheel tie rod pivotally connected to the other end; A substantially T-shaped rear wheel arm having a rear wheel tie rod pivotally attached to one end and a push rod of a fluid pressure chamber at the other end, and a connecting member for transmitting movement of the front wheel tie rod to the rear wheel tie rod. a link mechanism including the connecting member;
A double-acting fluid pressure cylinder that is divided and integrally fixed with one connecting member to the cylinder and the other connecting member to the piston, and a vehicle speed sensor that detects the traveling speed of the vehicle;
a shift sensor that detects that the transmission of the vehicle is selected to reverse; and a cylinder of the double-acting hydraulic cylinder when the traveling speed of the vehicle detected by the vehicle speed sensor is lower than a predetermined speed. The chamber is opened to the atmosphere and the front wheels and the rear wheels operate independently and in opposite phases to operate as a self-steering mechanism, and when the traveling speed of the vehicle is higher than a predetermined speed, the double-acting type Pressure fluid is supplied to the cylinder chamber of the fluid pressure cylinder to integrally actuate the two connecting members, the front wheels and the rear wheels are steered in the same phase, and the speed change sensor detects that the reverse movement of the speed change device has been selected. If detected, the cylinder chamber of the double-acting fluid pressure cylinder is opened to the atmosphere, and pressure fluid is supplied to the fluid pressure chamber to fix the rear wheel arm and steer only the front wheels. The invention is characterized by comprising a control device including a pressure fluid circuit configured as follows.

The present invention will be explained below with reference to embodiments shown in the drawings. In FIG. 1, a four-wheel steering device 1 according to the present invention includes a front wheel arm 2, a rear wheel arm 3, a link mechanism 4, a double-acting hydraulic cylinder 5, a vehicle speed sensor 6, and a speed change sensor. 8 and a control device 9.

The front wheel arm 2 is for steering the front wheel 10, and has one end 2a rotatably supporting the front wheel 10 and the other end 2a.
b is an L-shaped member to which a front wheel tie rod 11 is pivotally attached, and is arranged as a pair on each of the left and right front wheels 10,
It is configured to rotate by fitting into a pin 12 fixed to a chassis (not shown) to steer the front wheels 10.

The rear wheel arm 3 is for steering the rear wheel 13, and is a substantially T-shaped member.
is rotatably supported, and a rear wheel tie rod 14 is pivotally connected to the other end 3b, and a push rod 16 of an air chamber 15, which is an example of a fluid pressure chamber, is pivotally connected to the other end 3c. They are placed one by one. Then, the rear wheel 1 is rotatably fitted into a pin 18 fixed to the chassis.
It is configured to steer 3.

The link mechanism 4 is for transmitting the movement of the front wheel tie rod 11 to the rear wheel tie rod 14, and one end 20a of the front bell crank 20 is rotatably fitted to a pin 19 fixed to the chassis. The front wheel tie rod 11 is pivotally connected to the substantially central portion 11a, and the other end 20b has one connecting member 2.
One end 21a of 1 is rotatably pivoted.

The other end 21b of one connecting member 21 is fixed to the cylinder 22 of the air cylinder 5, which is an example of a double-acting hydraulic cylinder, so that it operates integrally.

Further, the other end 20b of the front hell crank 20 is connected by a connecting rod 25 to a steering device 24 operated by a steering wheel 23.
It is configured to transmit a steering angle of 3 to the front hell crank 20.

The rear bell crank 26 also has a pin 2 fixed to the chassis.
8, one end 26a is pivotally connected to the substantially central portion 14a of the rear wheel tie rod 14, and the other end 14b is rotatably connected to one end 29a of the other connecting member 29. There is. The other end 29b is fixed to the piston 30 of the air cylinder 5, so that they operate integrally.

A damper 31 is attached to the arm portion 14b of the rear wheel tie rod 14, and is configured to stabilize the movement of the rear wheel 13 during self-steering.

The air cylinder 5, which is an example of a double-acting fluid pressure cylinder, has two
This is for operating the two connecting members 21 and 29 integrally or independently of each other, and two pistons 32 slide vertically within the cylinder 22 so as to sandwich a piston 30 therebetween. Air leakage is prevented by gaskets 33 that fit freely and are attached to the respective pistons.

Further, the cylinder 22 is formed with a convex portion 22a, which divides the cylinder chamber 34 into two and limits the amount of movement of the two pistons 32.

The air chamber 15 connected to the rear wheel arm 3 is
A piston 36 is slidably fitted into the cylinder 35, and a compression spring 39 is installed between the piston and 138 to press and bias the piston 36 to the left in the figure. Lid 3
A push rod 16 is slidably fitted to 8.
The push rod is operatively connected to the other end 3c of the rear wheel arm 3 via a turnbuckle 40.

The vehicle speed sensor 6 is for detecting the traveling speed of the vehicle, and is, for example, a tachometer generator connected to an axle (not shown).

The speed change sensor 8 is for detecting that a speed change lever of a speed change device (not shown) is operated to a reverse position, and is, for example, a switch such as a micro-sinch.

The control device 9 is for supplying compressed air to the air cylinder 5 and the air chamber 15 in response to the output signals of the vehicle speed sensor 6 and the speed change sensor 8, and the first controller 41 is for supplying compressed air to the air cylinder 5 and the air chamber 15 in response to the output signals of the vehicle speed sensor 6 and the speed change sensor 8. A switching valve 42;
Further, the second controller 43 is electrically connected to the speed change sensor 8 and the air chamber switching valve 44, and outputs a signal in response to a signal from the vehicle speed sensor 6 or the speed change sensor 8, respectively, and outputs a signal in response to the signal from the vehicle speed sensor 6 or the speed change sensor 8. 42 or 44 solenoid 42
It is configured to switch by exciting either a or 44a.

The input boats 42b and 44b of the air cylinder switching valve 42 and the air chamber switching valve 44 are connected by pipes 46 and 48 to an air tank 45 that stores compressed air. The cylinder chamber 34 of the cylinder 5 and the cylinder chamber 49 of the air chamber 15 are connected to each other by pipes 50 and 51, and the compressed air of the air tank 45 is transferred to each cylinder chamber 3.
4 and 49.

Function The present invention is constructed as described above, and its function will be explained below. In FIGS. 1 and 2, when the vehicle is traveling forward at a low speed, a travel speed signal detected by the vehicle speed sensor 6 is transmitted to the first controller 4. The first controller does not output a signal when the traveling speed is less than a predetermined speed, for example 20-/h, and therefore the air cylinder switching valve 42 cannot be switched.At this time, the cylinder chamber 34 is opened to the atmosphere. Therefore, the air in the cylinder chamber 34 is released in the direction of arrow A and the two pistons 3
2 can move freely within the cylinder 22.

On the other hand, the speed change sensor 8 does not output a signal because the speed change device (not shown) is selected to move forward, and therefore there is no output signal from the second controller 43, so the air chamber switching valve 44 is not switched. , at this time the cylinder chamber 49
The air is released into the atmosphere (in the direction of arrow B) and the piston 3
6 is pressed by the action of the compression spring 39 and is located at the left end in the figure, and the push rod 16 is in a state where it can move freely.

Here, when the steering wheel 23 is operated in the direction of turning left, for example, the steering operation moves the connecting rod 25 in the direction of arrow C via the steering device 24, and the front bell crank 25 is moved in the direction of arrow C.
Rotate 0 counterclockwise. The movement is transmitted to the left and right front wheel arms 2 by the front wheel tie rod 11, causing the front wheel arms to rotate counterclockwise and bending the front wheel 1o in the direction indicated by the arrow.

As the front bell crank 20 rotates, one connecting member 21
Also moves in the direction of arrow C, but since the cylinder chamber 34 is open to the atmosphere, this movement is not transmitted to the other connecting member 29.

Cornering force is generated in the rear wheels 13 as the front wheels 10 are steered to the left, and the rear wheels 1 are in a state where they can move freely.
3 rotates in the direction of arrow E and acts in the opposite phase as so-called self-steering, allowing the vehicle to turn in an extremely small radius.

Next, with reference to FIG. 3, a case where the vehicle travels forward at high speed will be described. The air cylinder switching valve 42 is switched in response to a signal from the vehicle speed sensor 6, and compressed air in the air tank 45 is supplied to the cylinder chamber 34 (as indicated by the arrow F).
direction), the two pistons 32 move until they come into contact with the convex portions 22a, sandwiching the pistons 30 from above and below to restrict the movement of the pistons, and fixing the one connecting member 21 and the other connecting member 29. Let it work together.

Here, when the steering wheel 23 is operated in the left turning direction and the front wheels 10 are steered in the direction of the arrow, the movement of the front bell crank 20 is caused by the one connecting member 21, the air cylinder 5, and the other connecting member 29 acting integrally. The signal is transmitted to the rear bell crank 26, and the rear wheels 13 are steered in the direction of arrow G. That is, by steering the front wheels 10 and the rear wheels 13 in the same phase, it is possible to stably turn at high speed.

When reversing, referring to FIG. 4, the air chamber switching valve 44 is switched by a signal from the speed change sensor 8 to supply compressed air in the air tank 45 to the cylinder chamber 49 (in the direction of arrow H), and the piston 36 is moved in the direction shown in the figure. Compression spring 39 to the right
The push rod 16 is pushed out against the force of [38]. Since the bushing loft of the left rear wheel (not shown) is also pushed out in the same way, the rear wheel 13 connected by the rear wheel tie rod 14 is fixed in a state facing forward. Here, by steering the front wheels 10 in the direction of the arrow in the same manner as described above, the vehicle can smoothly retreat.

In addition, although the description has been made with reference to the case of turning to the left, it goes without saying that the same effect also occurs when turning to the right.

Effects As described above, the present invention connects the front wheel tie rod and the rear wheel tie rod with a connecting member via a double-acting hydraulic cylinder, and supplies pressure fluid to the cylinder chamber of the double-acting hydraulic cylinder. By controlling the front and rear wheels when the vehicle is traveling at high speed, the front wheels and rear wheels can be steered in the same phase, and as a result, it is possible to make quick turns without time delay and to improve stability when turning. It has the effect of

Furthermore, when the vehicle is running at low speeds, by opening the cylinder chamber to the atmosphere, the front and rear wheels can be operated in opposite phases as a self-steering system that frees up the rear wheels, reducing the turning radius and improving turning performance. There is an effect that can be done. Furthermore, when reversing, pressure fluid can be supplied to the fluid pressure chamber to fix the rear wheels, so the rear wheels can be smoothly retreated using two-wheel front wheel steering, and the disadvantage of unstable rear wheel direction does not arise at all. . In addition, we have adopted a fluid pressure device for the rear wheel steering system, which simplifies the mechanism.
This has the effect of reducing costs and making maintenance easier.

[Brief explanation of drawings]

The drawings relate to an embodiment of the present invention, and FIG. 1 is a plan view showing the entire four-wheel steering system, FIG. 2 is a plan view of the main part showing the steering state during low-speed forward movement, and FIG. 3 is also a high-speed forward view. FIG. 4 is a plan view of the main part showing the steering state when the vehicle is moving backward at a low speed. 1 is a four-wheel steering device, 2 is a front wheel arm, 2a is one end, 2
b is the other end, 3 is a rear wheel arm, 3a is one end, 3b is the other end, 3c is the other end, 4 is a link mechanism, 5 is an air cylinder which is an example of a double-acting hydraulic cylinder, 6 is a vehicle speed sensor , 8
is a gear shift sensor, 9 is a control device, 10 is a front wheel, 11 is a front wheel tie rod, 13 is a rear wheel, 14 is a rear wheel tie rod,
15 is an air chamber which is an example of a fluid pressure chamber, 16 is a push rod, 21 is one connecting member, 22 is a cylinder, 29 is the other linking member, 30 is a piston, and 4 is a cylinder chamber.

Claims (1)

[Claims] 1. A front wheel arm with a front wheel rotatably supported at one end and a front wheel tie rod pivotally connected at the other end, and a rear wheel arm rotatably supported at one end and a rear wheel arm at the other end. a link mechanism including a rear wheel arm to which a tie rod is pivotally connected, and a connecting member that transmits movement of the front wheel tie rod to the rear wheel tie rod;
A double-acting hydraulic cylinder in which the connecting member is divided into two parts and one connecting member is integrally fixed to the cylinder and the other connecting member is integrally fixed to the piston, a vehicle speed sensor that detects the traveling speed of the vehicle, and the vehicle speed. When the traveling speed of the vehicle detected by the sensor is lower than a predetermined speed, the cylinder chamber of the double-acting hydraulic cylinder is opened to the atmosphere, and the front wheels and the rear wheels are independently moved to opposite phases. When the traveling speed of the vehicle is higher than a predetermined speed, pressurized fluid is supplied to the cylinder chamber of the double-acting hydraulic cylinder to integrally connect the two connecting members. A four-wheel steering device comprising: a control device including a pressure fluid circuit configured to operate and steer the front wheels and the rear wheels in the same phase. 2. A front wheel arm with a front wheel rotatably supported at one end and a front wheel tie rod pivotally connected to the other end, and a rear wheel arm rotatably supported at one end and a rear wheel tie rod pivotally connected to the other end. a link mechanism including a substantially T-shaped rear wheel arm connected to the push rod of a fluid pressure chamber at the other end, a connecting member that transmits movement of the front wheel tie rod to the rear wheel tie rod, and the connecting member a double-acting hydraulic cylinder that is divided into two parts and integrally fixed with one connecting member to the cylinder and the other connecting member to the piston; a vehicle speed sensor that detects the traveling speed of the vehicle; and a transmission device of the vehicle. a speed change sensor that detects that the vehicle is selected to move backward; and a cylinder chamber of the double-acting hydraulic cylinder that is opened to the atmosphere when the traveling speed of the vehicle detected by the vehicle speed sensor is lower than a predetermined speed. to operate the front wheels and the rear wheels as a self-steering mechanism in which they operate independently and in opposite phases, and when the traveling speed of the vehicle is higher than a predetermined speed, the cylinder of the double-acting hydraulic cylinder When the speed change sensor detects that the front wheels and the rear wheels are steered in the same phase by supplying pressure fluid to the chamber to integrally operate the two connecting members, and the reverse movement of the speed change device is selected. is a pressurized fluid configured to open the cylinder chamber of the double-acting hydraulic cylinder to the atmosphere, supply pressure fluid to the fluid pressure chamber, fix the rear wheel arm, and steer only the front wheels; A four-wheel steering device comprising a control device including a circuit.