JPH0120107B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steering system used in a rear two-axle type vehicle such as a heavy truck or an all-terrain truck.

In general, heavy trucks and rough terrain trucks have been constructed with tandem rear axles, that is, two axles consisting of a rear front axle and a last axle, to reduce the axle load of the truck. Further, since then, two-axle type trucks have adopted either a single-shaft drive or a two-shaft drive, but neither of these two axles is steered and is placed in a fixed state.

In such a rear two-axle type truck, running stability is improved, but when turning, the rear wheels attached to the rear axle of the last axle skid, causing significant wear on the tires of the rear wheels. Further, since then, the minimum turning radius of two-shaft trucks has tended to be relatively larger than that of ordinary trucks.

In addition, in such a rear two-axis type truck,
If the rear wheels attached to the rear wheel axle of the last axle are made steerable, the minimum turning radius of the truck can be reduced, and significant wear on the tires of the rear wheels can be prevented, while driving stability at high speeds can be achieved. Sexuality is damaged. In other words, when the front wheels attached to the front wheel axle of the frontmost axle are steered by front steering, the rear wheels of the last axle will move in a direction that reduces the turning radius in relation to the front steering. steered.

In addition, the steering control method in a 4-axis steering vehicle is
Japanese Patent Laid-Open No. 52-61024 discloses a control device for a rear wheel steering mechanism, and Japanese Patent Laid-Open No. 59-6171 discloses a control device for a rear wheel steering mechanism, but in both of them, the rear power steering oil pump is , as usual,
Since it is located in the engine, in large vehicles, the hydraulic piping becomes long and responsiveness is reduced.

The purpose and problem of this invention is to suppress the decrease in rear steering responsiveness, reduce the turning radius when turning at low speeds, alleviate skidding of tires, and prevent significant wear of the tires. To provide a steering system used in a rear two-axle type vehicle that improves turning performance, improves running stability during high-speed running, and makes turning safe when turning at high-speed running.

Other objects and problems of this invention are to reduce skidding of tires when turning at medium speeds, prevent significant tire wear, enable safe turning, and improve driving safety when driving at medium speeds. The purpose of the present invention is to provide a steering system for use in rear two-axle vehicles.

In order to solve these problems, a steering system used in a rear two-axle vehicle of the present invention is first provided at the front of the two-axle vehicle, and which steers the front wheels rotatably supported by the front wheel axle.・A rear steering wheel that is provided with a steering wheel and a hydraulic actuator and is placed at the rear of the vehicle and is rotatably supported on the rear wheel axle of the last axle, and that steers the rear wheels; and a rear steering wheel that is placed on a transmission and is placed on the transmission. an oil pump driven by engine power taken out from the output shaft of the hydraulic actuator, and a hydraulic circuit connected to the hydraulic actuator, comprising an electromagnetic directional control valve for controlling the direction of pressure oil supplied to and discharged from the hydraulic actuator; It includes a vehicle speed sensor, a steering amount sensor disposed on the front steering wheel, and a predetermined turning pattern for steering the rear wheels in relation to the front steering wheel. The rear wheel is equipped with a control unit that switches the electromagnetic directional control valve to steer the rear wheels either in a steering state according to the turning pattern or in a fixed state according to the signal from the sensor. The steering system used in the rear two-axle vehicle of the present invention is then placed in front of the two-axle vehicle and is rotatably supported by the front wheel axle. a front steering wheel that steers the front wheels located at the rear of the vehicle; a rear steering wheel that is equipped with a hydraulic actuator and is located at the rear of the vehicle and is rotatably supported on the rear wheel axle of the last axle; and a transmission. The hydraulic actuator is equipped with an oil pump located in the transmission and driven by engine power taken out from the output shaft of the transmission, and an electromagnetic directional control valve that controls the direction of pressure oil supplied to and discharged from the hydraulic actuator. a hydraulic circuit connected to the vehicle, a vehicle speed sensor, a steering amount sensor disposed on the front steering wheel, and a predetermined turning pattern for steering the rear wheels in relation to the front steering wheel;
Depending on the signals from the vehicle speed sensor and the steering amount sensor, when driving at low speeds, the steering state is set according to the turning pattern, and when driving at medium speeds, the steering state is fixed based on the predetermined steering amount. and a rear steering controller equipped with a control unit that switches its electromagnetic directional control valves so that the rear wheels are in a fixed state and in a fixed state when driving at high speed. It's there.

Significant advantages and benefits obtained by the steering system for use in a dual-axle vehicle of the present invention so constructed are that the hydraulic piping connecting the oil pump to the hydraulic actuator is short; The resistance of the hydraulic piping is reduced, and as a result, the decrease in the responsiveness of the rear steering is suppressed, and the rear steering can be operated quickly, allowing the rear two-axle vehicle to turn at low speeds. When the vehicle is turning, the rear wheels of the last axle are steered according to the signals from the vehicle speed sensor and the steering amount sensor according to a predetermined turning pattern, so the turning radius of the vehicle can be reduced and the tire There is less skidding, especially at the rear wheels, which prevents significant wear on the tires, improves turning performance, and when the vehicle is running at high speed, the rear wheels are fixed. This improves running stability and makes turning safer.Furthermore, when the vehicle turns at medium speed, if the steering angle of the front wheels is within a predetermined angle, If the rear wheel is stationary and the steering angle of its front wheel exceeds a predetermined angle, the rear wheel will be steered in relation to the front wheel, reducing tire skidding and preventing significant wear on that tire. This makes it possible to turn safely, improving turning performance and driving stability, and extremely reducing rear wheel skidding when turning, allowing for a longer distance between the rear and front axles and the last axle. Even when driving on rough roads, the wheels are prevented from slipping, the load is applied evenly to both axles, the design conditions for always equalizing the ground load are eased, and vehicle design becomes easier.

Therefore, the present invention is certainly useful and suitable as a steering device for rear two-axle type vehicles, such as heavy trucks and rough terrain trucks.

Hereinafter, preferred specific examples of the steering system used in the rear two-axle vehicle according to the present invention will be explained.
This will be explained with reference to the drawings.

The figure shows a frontmost axle 52 to which front wheel axles 14, 15 are swingably connected to both ends, rear front axles 59, 60, and a rearmost axle 53 to which rear wheel axles 29, 30 are swingably connected to both ends. 10 schematically shows a specific example 10 of the steering system of the present invention applied to a rear two-axle type truck 50.

This steering system 10 is equipped with an integral power steering device 21 and is then placed in front of a two-axle truck 50, and when a steering wheel 19 is operated, the front wheel axle 1
Front wheels 61, 62 rotatably supported by 4, 15
A front steering wheel 11 for steering the truck, and a hydraulic actuator 36 are arranged at the rear of the truck 50, and the rear wheel axle 2 of the rear axle 53 is arranged at the rear of the truck 50.
Rear wheels 67, 68 rotatably supported by 9, 30
a rear steering wheel 26 that steers the
5, an oil pump 44 is driven by the power of the engine 54 and is taken out from the output shaft of the transmission 55, and an electromagnetic directional control valve 45 that controls the direction of the pressure oil supplied to and discharged from the hydraulic actuator 36. The hydraulic actuator 36
a hydraulic circuit 43 connected to the vehicle speed sensor 41 , a steering amount sensor 42 disposed on the front steering wheel 11 , and a predetermined sensor for steering the rear wheels 67 , 68 in relation to the front steering wheel 11 . Built-in turning pattern,
The vehicle speed sensor 41 and the steering amount sensor 42
When driving at low speeds, the vehicle will be steered according to the turning pattern, and when driving at medium speeds,
The electromagnetic directional control valve 45 is operated so that the rear wheels 67 and 68 are fixed or steered based on a predetermined amount of steering, and the rear wheels 67 and 68 are fixed when traveling at high speed. The rear steering controller 40 is provided with a control unit 48 for switching operation.

That is, the rear two-axle type truck 50 to which the steering system 10 is applied has a rear front axle 5 to which wheels 63, 64, 65, and 66 are attached.
9, 60 are driven by the engine 54 mounted on the truck 50, and the front wheel axles 14, 15 rotatably supporting the front wheels 61, 62 are connected to the steering wheel 19.
According to the operation of the power steering device 2
1, and when the truck 50 travels at low speed, the rear wheel axles 29, 30, which rotatably support the rear wheels 67, 68, rotate the front wheels 61, 6 according to a predetermined turning pattern.
2, and its track 50
However, when driving at medium speed, the rear wheels 67 and 68
is steered or held in a fixed or steered state based on a predetermined steering amount, and furthermore, when the truck 50 travels at high speed, the rear wheels 67 and 68 are in the fixed state. Of course, it is manufactured in such a way that it is held in a straight forward state.

The front steering 11 is connected to the front wheel axles 14, 15 and the tie rod arm 1.
A pair of knuckles 12 are rotatably attached to both ends of a front axle beam 52 disposed in front of the chassis frame 51 of the truck 50 via king pins 24 and 25, respectively. , 13, an integral power steering device that rotates a sector shaft (not shown) in accordance with the rotation of a tie rod 18 that connects the ends of the tie rod arms 16 and 17, and a steering wheel 19. 21, a pitman arm (not shown) that transmits the movement of its sector shaft to its tie rod 18, a drag link 22, a nut
Arm 23, its power steering device 21
It consists of a hydraulic system (not shown) for the

Since the front steering wheel 11 has substantially the same structure as the steering wheel applied to existing trucks, a description of the components of the front steering wheel 11 will be omitted.

Of course, the front wheels 61 and 62 are attached to the front wheel axles 14 and 15, respectively.

Therefore, by operating the steering wheel 19, the power steering device 21 rotates the knuckles 12, 13 in the same direction, the front wheel axles 14, 15 are steered, and the front wheels 61, 62 are steered. The angle can be changed.

Of course, although the power steering device 21 has been described as being of an integral type, it is also possible to use a semi-integral type or a linkage type.

Furthermore, the front steering 11 has been described as being equipped with a power steering device 21 in consideration of reducing the operating force on the steering wheel 19. It is also possible to configure it as a manual steering system.

The front axles 59, 60 then move on their tracks 50.
The vehicle is disposed at a position near the rear of the chassis frame 51 of the vehicle, and is configured to be driven by an engine 54 mounted on the truck 50.

That is, the front axles 59 and 60 are located at a position closer to the rear of the chassis frame 51, and the axle tube 57 is provided with the final reduction gear 58.
The output shaft of a transmission 55 located at the rear of the engine 54 is connected to a propeller.
It is connected via a shaft 56 to the drive shaft of its final reduction gear 58 .

Of course, after that, on both ends of the front axles 59, 60,
Wheels 63, 64, 65 as double tires,
66 are attached to each.

The rear steering wheel 26 is connected to the rear wheel axle 29,3.
0 and tie rod arms 31 and 32, respectively, and a rear axle beam 53 disposed at the rear of the chassis frame 51 of the truck 50, that is, rearwardly of the rear and front axles 59 and 60 described above. King pins 34,3 at both ends of
A pair of knuckles 27 and 28 are rotatably attached to each other via a tie rod 33 that connects the ends of the tie rod arms 31 and 32 to each other, and a hydraulic actuator 36 that drives the tie rod 33. It is composed of.

The knuckles 27, 28 and the tie rod 33 are constructed in the same manner as those in the front steering wheel 11 described above, so a description of their construction will be omitted.

The actuator 36 is a hydraulic cylinder,
A cylinder 37, a connecting rod 38 fixed to one end of the cylinder 37, a piston (not shown) fitted into the cylinder bore of the cylinder 37 so as to be able to reciprocate and slide, and a connecting rod 38 fixed to one end of the cylinder 37;
The operating rod 39 can be inserted and removed from the other end of the operating rod 39, and the other end is connected to the piston.

Of course, the cylinder 37 is provided with a pair of ports on one side and the other end respectively communicating with the cylinder bores on either side of the piston.

The hydraulic cylinder 36 so configured
The connecting rod 38 is rotatably connected to the rear axle beam 53 at a substantially central position, and the operating rod 39 is connected to the connecting portion between the tie rod 33 and the tie rod arm 32. It is rotatably connected to.

Of course, in that rear steering wheel 26,
Thereafter, rear wheels 67 and 68 are attached to the wheel axles 29 and 30, respectively.

Therefore, when the hydraulic cylinder 36 is driven, the knuckles 27, 28 rotate in the same direction, and then the wheel axles 29, 30 are steered, and the steering angles of the rear wheels 67, 68 are changed.

The rear steering controller 40
is arranged in the transmission 55 and the transmission 55
An oil pump 44 driven by the power of the engine 54 taken out from the output shaft of the hydraulic cylinder 36, and an electromagnetic directional control valve 45 for controlling the direction of pressure oil supplied to and discharged from the hydraulic cylinder 36. A hydraulic circuit 43 connected by hydraulic pipes 46 and 47, a vehicle speed sensor 41 located behind the transmission 55, and a front steering wheel 1.
1, a steering amount sensor 42 disposed around the steering shaft 20, a predetermined turning pattern for steering the rear wheels 67, 68 in relation to the front steering wheel 11, and a vehicle speed sensor 42 disposed around the steering shaft 20; 41 and a signal from the steering amount sensor 42, when traveling at low speed, the steering state is set according to the turning pattern, and when traveling at medium speed, the steering state is fixed or steered based on a predetermined steering amount. A rear steering controller 40 includes a control unit 48 that switches the electromagnetic directional control valve 45 so that the rear wheels 67 and 68 are in a fixed state and in a fixed state when driving at high speed. It was composed of

As described above, the hydraulic circuit 43 includes the oil pump 44, the electromagnetic directional control valve 45 that controls the direction of the flow of pressure oil generated by the oil pump 44, and the electromagnetic directional control valve 45. It is comprised of a pair of hydraulic piping 46, 47 which connects the cylinder port to the oil port of the hydraulic cylinder 36.

The oil pump 44 is attached to the rear of the transmission 55, is driven by the power of the engine 54 taken out from the output shaft of the transmission 55, and generates a predetermined hydraulic pressure.

In this way, since the oil pump 44 is arranged close to the hydraulic cylinder 36, in this hydraulic circuit 43, the hydraulic piping 46,
The length of 47 is the length of the engine 54.
The length is shorter than that in the case where the pump 44 is disposed, and accordingly, the line resistance of the hydraulic pipes 46 and 47 is reduced, and a decrease in the responsiveness of the rear steering 26 is suppressed.

The electromagnetic directional control valve 45 is a solenoid valve, and is a tandem center type equipped with a spool, and has a pump port, a tank port, and
It has a pair of cylinder ports, and when the solenoid coil is energized, pressure can be applied from the pump port to either cylinder port, and simultaneously from the other cylinder port to the tank port. It has a structure that switches the flow of oil.

Therefore, the solenoid valve 45 has its pump port connected to the outlet of the oil pump 44 and its tank port connected to the oil pump 44.
4, and is attached to the oil pump 44 with a gasket interposed therebetween, and connects the cylinder port to the oil port of the hydraulic cylinder 36 through the hydraulic piping 46, 4.
7 is connected.

Of course, the solenoid valve 45 is
The solenoid coil of the solenoid valve 45 is connected to the output circuit of the control unit 48 so as to be controlled by the unit 48.

The vehicle speed sensor 41 detects the rotational speed of the output shaft of the transmission 55, is arranged behind the transmission 55, and is connected to an input circuit of a control unit 48, which will be described later.

Of course, it is preferable to use a non-contact type vehicle speed sensor 41 in consideration of the limitation of the usable rotational speed of the converter bearing and the load on the output shaft of the transmission 55.

The steering amount sensor 42 detects the rotation speed, rotation direction, and rotation angle of the steering shaft 20 in the above-mentioned front steering 11.
0 at a predetermined position, and is connected to the input circuit of the control unit 48.

Of course, it is desirable that the steering amount sensor 42 has a high resolution as a rotation sensor, has low power consumption, and can generate a reliable and large signal as an output. Semiconductor types are used.

The control unit 48 incorporates a predetermined turning pattern for steering the rear wheels 67 and 68 in relation to the above-mentioned front steering 11, and receives signals from the vehicle speed sensor 41 and the steering amount sensor 42. When driving at low speeds, the steering state is set according to the turning pattern, when driving at medium speeds, the steering state is fixed or steered based on a predetermined steering amount, and when driving at high speeds, the steering state is set to be fixed or steered based on the predetermined steering amount. In the fixed state, the solenoid valve 45 is operated to switch the rear wheels 67 and 68, respectively, and is mainly composed of an input and output circuit, an arithmetic circuit, a memory circuit, and a control circuit. .

That is, the control unit 48
always inputs the signal from the vehicle speed sensor 41, and when the truck 50 is traveling at low speed, inputs the signal from the steering amount sensor 42, and turns the rear wheels 67, 68 according to a predetermined turning pattern. front wheel 6
The solenoid valve 45 is controlled so that the rear wheels 67, 68 are steered following the rear wheels 67, 62, and when the truck 50 is traveling at a medium speed, the rear wheels 67, 68 are to a fixed state, or
controlling the solenoid valve 45 so that the rear wheels 67, 68 are steered to follow the front wheels 61, 62;
Further, when the truck 50 is traveling at high speed, the electromagnetic mechanism is designed to hold the rear wheels 67, 68 in a fixed state, in other words, to lock the piston of the hydraulic cylinder 36 at a substantially neutral position. Control valve 45.

Of course, the control unit 48 stores a predetermined turning pattern based on the Ackerman system in a memory circuit, and adjusts the running speed of the truck 50 based on the turning pattern.
Depending on the rotation speed, rotation direction, and rotation angle of the steering shaft 20 in the front steering 11, the rear steering 26
The steering direction and steering angle of the rear wheels 67, 68 are determined by the steering wheel.

Next, to describe the running of the rear two-axle truck 50 to which the above-mentioned steering system 10 is applied, when the truck 50 is running, the signal from the vehicle speed sensor 41 is transmitted to the control unit 4.
8 is always input.

When the truck 50 is traveling at a low speed and the front wheels 61, 62 are steered by operating the steering wheel 19, the steering amount sensor 42 detects the rotation speed, rotation direction, and direction of the steering shaft 20. , detect the rotation angle,
The output signal is sent to its control unit 48.

The control unit 48 controls the solenoid valve 45 in accordance with the output signal based on a turning pattern stored in advance, and the hydraulic cylinder 36 is driven, so that the rear wheels 67 and 68 are controlled by the rear steering 26. Be steered.

For example, if the front steering wheel 11 is steered to the left in order to turn the truck 50 to the left, the rear steering wheel 26
is steered to the right at a predetermined steering angle to reduce the turning radius.

Therefore, the turning radius of the truck 50 when running at low speed is reduced, significant wear of the rear wheels 67, 68 is prevented, and turning performance is improved.

Further, when the truck 50 is traveling at high speed, the control unit 48 controls the solenoid valve 45 in accordance with the output signal from the vehicle speed sensor 41, and moves the piston in the hydraulic cylinder 36 to a substantially neutral position. Lock.

That is, the rear wheels 67 and 68 are held fixed by the rear steering wheel 26.

Therefore, the running stability of the truck 50 at high speeds is improved, and safe turning is possible by steering the front steering wheel 11.

Furthermore, when the truck 50 is traveling at a medium speed, if the steering angle of the front wheels 61, 62 is within a predetermined angle, the rear wheels 67, 68 are placed in a fixed state; When the steering angle exceeds the predetermined angle, the rear wheels 67, 6
8 is steered in relation to its front wheels 61, 62.

That is, when the truck 50 is running at a medium speed, when the front wheels 61 and 62 are steered at a relatively small steering angle, that is, within a predetermined steering angle, the rear wheels 67 and 68 are kept in a fixed state, and the running is stabilized. gender is ensured.

Further, when the truck 50 is running at medium speed, the front wheels 61 and 62 have a relatively large steering angle, that is,
When the vehicle is steered beyond a predetermined steering angle, the rear wheels 67, 68 are steered in relation to the front wheels 61, 62, resulting in less tire wear, a smaller turning radius, and improved turning performance. be done.

From the above, when compared with the steering systems that have already been proposed and used, the steering system used in the rear two-axle vehicle of the present invention is as follows:
A front steering wheel and a rear steering wheel are provided. - A hydraulic circuit equipped with an electromagnetic directional control valve that controls the direction of pressure oil supplied to and discharged from the hydraulic actuator of the steering wheel, and connected to the hydraulic actuator, a vehicle speed sensor, and a steering amount sensor placed on the front steering wheel. , incorporating a predetermined turning pattern for steering the rear wheels in relation to its front steering, its vehicle speed sensor, and
A control unit that switches the electromagnetic directional control valve to steer the rear wheels to either a steering state according to the turning pattern or a fixed state in response to a signal from the steering amount sensor. The control unit is configured to incorporate a predetermined turning pattern for steering the rear wheels in relation to the front steering, and responsive to signals from the vehicle speed sensor and the steering amount sensor. When driving at low speeds, the steering condition follows the turning pattern.
The electromagnetic directional control valve is set so that when driving at medium speeds, the rear wheels are fixed or steered based on a predetermined amount of steering, and when driving at high speeds, the rear wheels are placed in a fixed state. Since the steering system used in the dual-axle vehicle according to the present invention is constructed where valve switching is performed, the hydraulic piping connecting the oil pump to the hydraulic actuator in the hydraulic circuit becomes shorter. Along with this, the pipe resistance of the hydraulic piping is reduced, and as a result, a decrease in the responsiveness of the rear steering is suppressed.In other words, the rear steering is operated quickly.
Furthermore, when a rear two-axle vehicle turns at low speed, the rear wheels are steered according to signals from the vehicle speed sensor and the steering amount sensor according to a predetermined turning pattern, and the turning radius of the vehicle is can be made smaller, the skidding of the vehicle's tires is reduced, and in particular the skidding of the rear wheels is extremely reduced, significant wear of the tires is prevented, turning performance is improved, and the vehicle can run at high speeds. When the vehicle is running at high speed, the rear wheels are kept stationary, improving driving stability, and when the vehicle is turning at high speed, turning is safer, and when the vehicle is turning at medium speed, When the steering angle of the front wheels is within a predetermined angle, the rear wheels are placed in a fixed state, and if the steering angle of the front wheels exceeds the predetermined angle, the rear wheels are steered in relation to the front wheels. This reduces the possibility of skidding of the tires, prevents significant wear on the tires, and enables safe turning.Moreover, this improves turning performance and running stability, and greatly reduces the possibility of skidding of the rear wheels when turning. This reduces the distance between the rear and front axles and the last axle, which prevents the wheels from slipping even when driving on rough roads, distributes the load evenly on both axles, and ensures that the ground load is always equalized. Design conditions are relaxed,
Vehicle design becomes easier.

As mentioned above, from the specific examples of the present invention explained with reference to the drawings, those who have ordinary knowledge in the technical field to which this invention pertains will understand the following:
Various design modifications and changes can be easily made, and furthermore, the content of this invention is essential to the realization of the invention that accomplishes the task of the invention,
It is derived from the technical essence of the invention, which is the nature of the invention, and can be easily replaced by a mode that is objectively recognized as incorporating it.

[Brief explanation of drawings]

The figure is a schematic diagram showing a specific example of a steering system used in a rear two-axle type vehicle according to the present invention, which is applied to a rear two-axle type truck. 11...Front steering, 12, 13
...Natsukuru, 14,15...Front wheel axle, 26...
... Rear steering, 27, 28 ... Knuckle, 29, 30 ... Rear wheel axle, 36 ... Hydraulic actuator, 40 ... Rear steering controller, 41 ... Vehicle speed sensor, 42 ... Steering amount sensor, 43 ... Hydraulic circuit, 45 ... Solenoid valve, 4
8... Control unit, 50... Rear two-axle type truck.

Claims (1)

[Claims] 1. A front steering wheel disposed at the front of a rear two-axle type vehicle for steering the front wheels rotatably supported by the front wheel axle; and a hydraulic actuator disposed at the rear of the vehicle. , a rear steering wheel that steers the rear wheels rotatably supported by the rear wheel axle of the last axle, and an oil steering wheel that is arranged in the transmission and driven by the power of the engine taken out from the output shaft of the transmission.
A pump, a hydraulic circuit connected to the hydraulic actuator and equipped with an electromagnetic directional control valve that controls the direction of pressure oil supplied to and discharged from the hydraulic actuator, a vehicle speed sensor, a steering amount sensor disposed on the front steering wheel, It has a built-in predetermined turning pattern for steering the rear wheels in relation to the front steering, and performs steering according to the turning pattern according to signals from the vehicle speed sensor and the steering amount sensor. situation,
and a rear steering controller comprising a control unit that switches the electromagnetic directional control valve so as to steer the rear wheels in one of the fixed states. . 2. A front steering wheel located at the front of a rear two-axle type vehicle, which steers the front wheels rotatably supported by the front wheel axle, and a front steering wheel equipped with a hydraulic actuator, which is located at the rear of the vehicle and steers the front wheels rotatably supported by the front wheel axle. The rear steering wheel is rotatably supported on the shaft and steers the rear wheels, and the oil steering wheel is placed in the transmission and driven by the engine's power, which is taken out from the output shaft of the transmission.
A pump, a hydraulic circuit connected to the hydraulic actuator and equipped with an electromagnetic directional control valve that controls the direction of pressure oil supplied to and discharged from the hydraulic actuator, a vehicle speed sensor, a steering amount sensor disposed on the front steering wheel, It has a built-in predetermined turning pattern for steering the rear wheels in relation to the front steering, and when driving at low speed, the turning pattern is determined according to signals from the vehicle speed sensor and the steering amount sensor. When driving at medium speeds, the rear wheels are fixed or steered based on a predetermined amount of steering, and when driving at high speeds, the rear wheels are set to a fixed state. , the control that switches the electromagnetic directional control valve.
A steering system used in a rear two-axle vehicle, including a rear steering controller with a unit.