JPH0419069B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rear two-axle type vehicle in which the rear axle is configured as a self-steering type.

Generally, in a rear dual-axle vehicle with a heavy load, such as a rear dual-axle truck, the last axle that is not driven by the engine is configured as a self-steering type, and cannot reliably support the load of the truck. Naturally, when turning, the turning radius of the truck has been made smaller.

As such, a two-axle truck with its rearmost axle self-steering is typically self-steering.
A self-steering rear wheel axle, which is equipped with a lock cylinder and is swingably connected to both ends of the axle beam, rotatably supports the rear wheel when the truck travels at high speeds and when reversing. It has been equipped to lock in a neutral state, that is, in a state facing straight ahead, to improve the running stability of the truck during high-speed driving, and to ensure safe and reliable reversing of the truck.

However, when the truck is decelerated from high speed to low speed and the steering wheel is operated significantly, the rear wheel axle of the truck will self-lock from the steer lock state during a turn. - Since the vehicle could be switched to a steer state, the turning radius of the truck was suddenly changed at the time of the switch, resulting in a significant change in the steering feel. Conversely, when the truck accelerates from low speed to high speed,
If the steering wheel is operated significantly, the rearmost wheel axle will switch from self-steering to steer lock while the truck is turning, and at the time of the switch, the turning radius of the truck will change rapidly. The steering feel was noticeably changed.

Also, if the truck is braked while driving,
The running of these trucks becomes unstable due to road surface friction and the partial effectiveness of the brakes due to the friction. At times, when a relatively large amount of operation of the steering wheel was performed at the same time, the truck was caught in the direction where the steering angle was further changed, making it difficult to turn in a stable state.

The purpose and problem of this invention is to reduce the turning radius when driving at low speeds, improve driving stability when driving at high speeds, and change from low speed driving to high speed driving.
This suppresses sudden changes in steering feel during relatively large turns when transitioning from high speed driving to low speed driving, enabling more stable driving, and when braking, it maintains a stable posture and enables safe braking. To provide a rear two-axle type vehicle having a self-steering type rear axle that stabilizes steering when reversing.

In relation to the above-mentioned objects and problems, the rear two-axle vehicle of the present invention has a power steering system that steers the front wheels via the front wheel axle in accordance with the operation of the steering wheel, and a rear wheel that rotatably supports the rear wheel. and a steer lock cylinder that locks the rearmost wheel axle that is self-steering according to the turning direction of the vehicle by steering the front wheels, and a fluid that connects a fluid pressure source to the steer lock cylinder. A solenoid valve is placed in the pressure piping, and when the vehicle is running at low speed, the current flowing through the solenoid valve is controlled according to the signal from the vehicle speed sensor, and the solenoid valve is opened and closed to control the steering lock.・The cylinder is made to self-steering, and when the vehicle is running at high speed, the current flowing through the solenoid valve is controlled according to the signal from the vehicle speed sensor, and the solenoid valve is controlled to open and close. The steering lock cylinder is operated to perform a steer lock operation, and when the vehicle is transitioned from low-speed driving to high-speed driving, or from high-speed driving to low-speed driving, the steering
When the wheel is operated relatively significantly, the current flowing through the solenoid valve is controlled according to signals from the vehicle speed sensor and the oil pressure sensor of the power steering hydraulic circuit until the vehicle returns to straight-ahead running. maintaining the solenoid valve in the running state before the vehicle turns and maintaining the steer lock cylinder in the running state before the vehicle turned;
When the vehicle returns to running straight, the current flowing through the solenoid valve is controlled in accordance with the signals from the vehicle speed sensor and oil pressure sensor, and the solenoid valve is controlled to open and close to cause the steer lock cylinder to steer. locking or self-steering operation, and further controlling the current flowing through the solenoid valve in response to a signal from a brake pressure sensor of the hydraulic service brake system when the vehicle is braked; The solenoid valve is controlled to open and close to cause the steer lock cylinder to perform a steer lock operation, and furthermore, when the vehicle is backed up, the current flowing through the solenoid valve is controlled in response to the signal from the back sensor. and a control unit that controls the opening and closing of the solenoid valve to operate the steer lock cylinder, and when the vehicle is running at low speed, the rear wheel axis is self-steering to turn. By reducing the radius, when the vehicle is running at high speed, the last wheel axle is steered and locked to improve running stability, and when the vehicle is making a relatively large turn, the last wheel axle remains in the state it was in before the turn. When the vehicle returns to a straight-ahead state, the rearmost wheel axle is steer-locked or self-steering depending on the vehicle speed, and when the vehicle is braking, the rearmost wheel axle is steered.・The steering wheel is locked to enable safe braking, and when the vehicle is reversing, the rearmost wheel axle is steered and locked to stabilize steering.

Hereinafter, specific examples of the rear two-axle type vehicle of the present invention will be described with reference to the drawings.

FIGS. 1 and 2 show a tenth embodiment of a rear two-axle vehicle according to the invention, which is embodied in a rear two-axle truck.

Thereafter, the two-axle truck 10 includes a front axle 18, in which the front axle 12 is swingably connected to a front axle beam 12a and both ends of the front axle beam 12a, and rotatably supports the front wheels 60, 61. 19, the front wheels 60, 61 are steered by the power steering 15 via the front wheel axles 18, 19 according to the steering input, and the rear front wheels 29, 30 are mounted on the truck 10. The last axle 32, which is driven at 25 and which is then arranged behind the front axles 29, 30, is configured to be self-steering. In this case, the self-steering type rear axle 32 is a rear axle beam 32a and a rear wheel rotatably connected to both ends of the rear axle beam 32a to rotatably support rear wheels 66, 67. The rear wheel axle 33, 34 is assembled from the axles 33, 34, and the rear axle 33, 34 is assembled with the steer lock cylinders 39, 4 depending on the driving conditions of the truck 10.
0 and is selectively placed into self-steer and steer-lock states.

That is, the rear two-axle truck 10 has a power steering wheel 15 that steers its front wheels 60, 61 via its front wheel axles 18, 19 in accordance with the operation of a steering wheel 17, a rearmost wheel 66, A steer lock cylinder 39 rotatably supports the rear wheels 67 and locks the steered rear wheel axles 33, 34 which are self-steering according to the turning direction of the truck 10 by steering the front wheels 60, 61. , 40, and a solenoid valve 50 disposed in the pneumatic piping 49 connecting the air tank 48 to the steer lock cylinders 39, 40, and a current flowing through the solenoid valve 50 according to the running conditions of the truck 10. A control unit 5 controls the opening and closing of the solenoid valve 50 to cause the steer lock cylinders 39 and 40 to perform self-steering and steer lock operations.
4 were provided.

In this truck 10, the control unit 54 controls the current flowing through the solenoid valve 50 in response to a signal from the vehicle speed sensor 56 when the truck 10 is traveling at low speed. The steering lock cylinders 39 and 40 are controlled to open and close to perform a self-steering operation, and when the truck 10 is traveling at high speed, the solenoid valve 50 is controlled in response to a signal from the vehicle speed sensor 56. It controls the flowing current, controls the opening and closing of the solenoid valve 50, causes the steer lock cylinders 39 and 40 to perform a steer lock operation, and further changes the truck 10 from low speed traveling to high speed traveling, or from high speed traveling to low speed. When the steering wheel 17 is operated relatively greatly when the vehicle is shifted to driving, the vehicle speed sensor 56 and the oil pressure sensor 57 of the hydraulic circuit of the power steering 15 are activated until the truck 10 returns to straight-ahead driving. The electric current flowing through the solenoid valve 50 is controlled in response to a signal from the steering wheel, and the solenoid valve 50 is maintained in the running state before the truck 10 turns, and the steer lock cylinders 39 and 40 are moved toward the truck 10. When the truck 10 returns to traveling straight, the current flowing through the solenoid valve 50 is controlled in accordance with the signals from the vehicle speed sensor 56 and the oil pressure sensor 57.
The solenoid valve 50 is controlled to open and close to cause the steer lock cylinders 39 and 40 to perform a steer lock operation or a self steer operation.Furthermore, when the truck 10 is braked, the hydraulic service is activated. The current flowing through the solenoid valve 50 is controlled in accordance with the signal from the brake pressure sensor 68 of the brake system, and the solenoid valve 50 is controlled to open and close to cause the steer lock cylinders 39 and 40 to perform steer lock operation. When the truck 10 is moved backward, the current flowing through the solenoid valve 50 is controlled in accordance with the signal from the back sensor 69, and the solenoid valve 50 is controlled to open and close to open and close the steer lock cylinder 39. , 40 to operate the steering wheel.

Further, in the two-axle type truck 10, the self-steering operation of the steer lock cylinders 39, 40 is such that the steer lock cylinders 39, 40 bring the steer rear wheel axles 33, 34 into a self-steering state. This is the operation of placing the steering lock cylinder 39, 40.
The steer lock operation of the
The cylinders 39, 40 are the steer rear wheel axles 33, 3.
This is the operation of placing the 4 in the steer lock state.

The power steering 15 is swingably attached via king pins to both ends of the front axle beam 12a of the front axle 12 disposed in front of the chassis frame 11 of the truck 10. Its front wheel axle 18,
A pair of knuckles 13, 14 each having a tie rod arm 20, 21 and a tie rod arm 20, 21.
An integral power steering device 1 that rotates a sector shaft (not shown) in accordance with the operation of a rod 22 and a steering wheel 17.
6. A pitman arm (not shown) that transmits the movement of the sector shaft to the tie rod 22, a drag link 23, a knuckle arm 24, and the power steering device 1.
It consists of a hydraulic circuit for 6, etc.

Since the power steering 15 has substantially the same structure as the power steering applied to existing trucks, a detailed explanation of its structure will be omitted.

In addition, the front wheel axle 1 of the nuts 13 and 14
The front wheels 60 and 61 are rotatably supported on the wheels 8 and 19, respectively, as described above.

Therefore, when the steering wheel 17 is rotated, the power steering device 16
causes the knuckles 13, 14 to swing in the same direction, the front wheel axles 18, 19 to swing, and as a result, the steering angles of the front wheels 60, 61 are changed.

Of course, although the power steering device 16 has been described as an integral type, it is also possible to use a semi-integral type or a linkage type.

The front axles 29, 30 then move on their tracks 10.
The vehicle is located at the rear of the chassis frame 11 of the truck and is driven by an engine 25 mounted on the truck.

That is, the front axles 29 and 30 are located at a position closer to the rear of the chassis frame 11, and the axle tube 58 is provided with the final reduction gear 59.
The output shaft of a transmission 26 located behind the engine 25 is connected to a propeller.
It is connected via the shaft 31 to the drive shaft of its final reduction gear 59 .

After that, there are double wheels on both ends of the front axles 29 and 30.
Of course, wheels 62, 63, 64, and 65 as tires are respectively attached.

The self-steering rearmost axle 32 is then positioned behind the front axles 29, 30 to
It is arranged on the frame 11 and is configured to be self-steering depending on the turning direction of the truck 10, as described above. That is, the rearmost axle 32 is constituted by the rear axle beam 32a and the rearmost wheel axles 33, 34;
It is constructed on a steer rear wheel shaft fixed to nuticles 27 and 28. The knuckles 27, 28 are swingably connected to both ends of the rear axle beam via king pins, so that the steer rear wheel axles 33, 34 are pivotably connected at both ends of the rear axle beam 32a. It is possible to steer.

Further, the knuckles 27, 28 are respectively provided with knuckle control arms 35, 36 that project toward the front side of the truck 10, and tie rod arms 37, 38 that project toward the rear side.

The ends of the tie rod arms 37, 38 are connected to each other via a tie rod 47 and a ball joint. Furthermore, at least one of the ends of the tie rod arms 37 and 38 is
A damper filled with gas (not shown), or
Preferably, it is pivotally connected to its rear axle beam 32a via a spring loaded damper (not shown).

Therefore, the pair of knuckles 27, 28 are respectively swung in the same direction around the king pin by the tie rod 47, and as a result, the steer rear wheel axles 33, 34 are self-aligned in the same direction.
Be steered.

The steer lock cylinders 39 and 40 are
The steered rear wheel axles 33, 34 are locked by compressed air from the air tank 48, which will be described later. Rotatably arranged via a universal joint.

The steer lock cylinders 39 and 40 are
A cylinder, a diaphragm disposed within the cylinder, push rods 45, 46 whose one end can be taken in and out of the cylinder, and whose other ends are connected to the diaphragm, and the push rods 45, 46 are pulled. and a return spring disposed within the cylinder so as to allow the cylinder to retract.

The steer lock cylinders 39, 40 thus configured are rotatably attached via universal joints to the ends of brackets 41, 42 fixed to the rear axle beam 32a at a predetermined distance. , the push rod 45, 46
The end is the nutkul control arm 35,
It is directed toward the 36 end side.

Of course, the universal joint includes a cross spider, and the steer lock cylinders 39, 40 are configured to move in three dimensions.
Lock cylinders 39, 40 to their brackets 4
It is connected to 1,42.

Furthermore, the steer lock cylinder 39,
The ends of the push rods 45 and 46 of the push rod 40 are connected to the ends of the knuckle control arms 35 and 36 through sleeves 43 and 44.

The sleeves 43, 44 are open at one end to form a rod guide bore to receive the ends of the push rods 45, 46 in a reciprocating manner, and the other end is opened to form a rod guide bore to receive the ends of the push rods 45, 46 in a reciprocating manner. A ball joint is connected at the end.

Therefore, the steer lock cylinder 39,
If the push rods 45, 46 of 40 are pushed out by air pressure, the tips of the push rods 45, 46 will hit the bottom wall of the rod guide bore of the sleeves 43, 44, and the knuckle control Not only the arms 35 and 36, but also the nut 2 centered on the king pin.
In other words, the steer rear wheel shafts 33, 34 are placed in a steer-locked state.

Of course, that steer lock cylinder 39,4
When the push rods 45, 46 of 0 are retracted, the tips of the push rods 45, 46 are separated from the bottom wall of the rod guide bore, and the sleeves relative to the push rods 45, 46 are moved away from the bottom wall of the rod guide bore. 43, 44 is allowed to reciprocate, and as a result, the steered rear wheel axles 33, 34 are placed in a self-steering condition.

The air tank 48 is connected to the steer lock cylinders 39, 40 via pneumatic piping 49.
are connected to each. that air tank 4
The compressed air in 8 is supplied to the engine 2 of the truck 10.
Air compressor driven by 5 (not shown)
Of course, it will be supplied from.

The solenoid valve 50 is provided in a pneumatic line 49 connecting the air tank 48 and the steer lock cylinders 39,40.

The solenoid valve 50 is connected to the tank port 5.
1, a three-way control valve having a cylinder port 52 and an exhaust port 53, which closes its exhaust port 53 by an electric signal and at the same time connects its tank port 51 to its cylinder port 5.
The cylinder port 52 is connected to the exhaust port 53 at the same time as the tank port 51 is closed and the cylinder port 52 is connected to the exhaust port 53.

The control unit 54 is electrically connected to the solenoid coil of the electromagnetic valve 50, the vehicle speed sensor 56, and the oil pressure sensor 5 provided in the hydraulic system of the power steering 15 described above.
7. Afterwards, hydraulic service for the two-shaft truck 10.
Brake pressure sensor 6 installed in the brake system
8, and controls the opening and closing of the solenoid valve 50 according to the input signal from the back sensor 69 provided in the transmission 26 of the truck 10, and includes an input and output circuit, an arithmetic circuit, a memory circuit, and a control circuit. , and a power supply circuit.

The vehicle speed sensor 56, like existing vehicle speed sensors, is placed in the transmission 26 of the truck 10, detects the rotational speed of the output shaft of the transmission 26, converts the rotational speed into an electrical signal, It is configured to send the signal to the control unit 54. Therefore, the vehicle speed sensor 56
is electrically connected to the input circuit of the control unit 54.

The oil pressure sensor 57 is arranged in the hydraulic system of the power steering 15, that is, on the discharge side of the oil pump 55, and
5 to the power steering device 16, converts the pressure into an electrical signal, and sends the signal to its control unit 54. The oil pressure sensor 57 is therefore electrically connected to the input circuit of the control unit 54.

The brake pressure sensor 68 is a hydraulic service sensor for braking the last wheels 66, 67 attached to the caster type steer rear wheel axles 33, 34.
It is installed in the brake system to detect the pressure of the brake oil in the brake system, convert that pressure into an electrical signal, and use that signal to control the brake system.
The data is configured to be sent to unit 54. Of course, the brake pressure sensor 68 is electrically connected to the input circuit of the control unit 54.

Also, the back sensor 69 is a back up sensor.
The sensor 69 is provided in the transmission 26 of the truck 10, detects movement when the change lever is operated in reverse, and sends an electric signal indicating whether the change lever is operated to the reverse side to the control. - configured to send to unit 54; The back up sensor 69
Of course, like the vehicle speed sensor 56, oil pressure sensor 57, and brake pressure sensor 68 described above, it is electrically connected to the input circuit of the control unit 54.

The rear two-axle type vehicle 10 of the present invention has the same structure as the existing rear two-axle type truck except for the above-mentioned parts, so a description of these structures will be omitted.

Next, to describe the running of the above-mentioned rear two-axle type truck 10, when the truck 10 is running at a low speed, the solenoid valve 50 is activated by the signal from the vehicle speed sensor 56 under the control of the control unit 54. - Port 51 is closed and its cylinder port 52 is connected to its exhaust port 53.

That is, the steer lock cylinder 3
The compressed air in the cylinder chambers 9 and 40 escapes to the atmosphere from its exhaust port 53, and is discharged from its push rods 45 and 46 by return springs.
are each retracted inside.

As a result, the sleeves 43, 44 are allowed to reciprocate with respect to the push rods 45, 46, the steer rear wheel axles 33, 34 are placed in a self-steer state, and the turning radius when the truck 10 travels at low speed is adjusted. became smaller.

At that time, the steer lock cylinder 39,
40 is rotatably supported on the rear axle beam 32a of its rearmost axle 32 via a universal joint, so that in response to self-steering of its steer rear axles 33, 34, its steer lock cylinder 39 , 40 can be freely changed, and as a result, the steer lock cylinders 39, 40 are self-steering of the steer rear wheel axles 33, 34.
Self-steering was extremely smooth, with virtually no interference.

Also, when the truck 10 runs at high speed,
Under the control of the control unit 54 and by a signal from the vehicle speed sensor 56, the solenoid valve 5
0's exhaust port 53 is closed and its tank port 51 communicates with its cylinder port 52.

That is, compressed air from the air tank 48 is sent into the cylinder chambers of the steer lock cylinders 39, 40, the diaphragm is moved against its return spring, and the push rods 45, 46 are moved outward. are pushed out respectively.

As a result, the ends of the push rods 45, 46 are connected to the rods in the sleeves 43, 44.
It hits the bottom wall of the guide bore, restricts the reciprocating movement of the sleeves 43, 44 with respect to the push rods 45, 46, and the steer rear wheel shafts 33, 34.
is placed in steer lock condition and its track 1
Driving stability when the 0 is running at high speeds has been improved.

Of course, when the truck 10 moves backward,
When the change lever of the transmission 26 is operated in reverse, the signal from the back up sensor 69 is transferred to the control unit 5.
4 is input, the solenoid valve 50 is opened and closed by the output signal from the control unit 54, and the steer rear wheel axles 33 and 34 are placed in the steer lock state, as in the case of high-speed running described above. , maneuverability when reversing has been stabilized.

Furthermore, when the truck 10 decelerates from high-speed running and transitions to low-speed running, when the steering wheel 17 is rotated through a relatively large operating angle, the oil pressure in the hydraulic circuit of the power steering 15 decreases. The oil pressure sensor 57 sends an output signal to the control unit 54.

In that way, the control unit 54 controls the vehicle speed sensor 56 and the oil pressure sensor 57.
When the control unit 54 receives the respective signal from the vehicle, the control unit 54 sends an output signal to the solenoid valve 50, as in the case of high speed driving, so that the exhaust port 53 of the solenoid valve 50 is closed. , its tank port 51 is connected to its cylinder port 51.
Port 52 is contacted.

Therefore, when the truck 10 decelerates from high-speed running and transitions to low-speed running, if the steering wheel 17 is operated relatively largely, the steered rear wheel axles 33, 34 become self-steering. The steering wheel was kept in the locked state without being locked, and the operating feeling was prevented from changing suddenly. That is, in this case,
Since the hydraulic pressure of the hydraulic piping of the power steering 15 is increased until the operation of the steering wheel 17 is completed, the steering rear wheel axle 3
3 and 34 are temporarily suspended from being returned to the self-steering state and held in the steer-locked state.

Further, when the truck 10 accelerates from a low-speed running state and shifts to high-speed running, if the steering wheel 17 is operated relatively greatly, the control unit 54
controls its solenoid valve 50 in response to signals from its vehicle speed sensor 56 and oil pressure sensor 57, and in its solenoid valve 50, its tank port 51 is closed and its cylinder port 52 is connected to its exhaust port 53. You will be contacted.

Therefore, the steered rear wheel shafts 33, 34 are not steer-locked and are maintained in a self-steering state, thereby preventing the steering feeling from changing suddenly.

Again, the steering wheel 17
The power steering 15 until the operation is completed.
Since the hydraulic pressure of the hydraulic piping has been increased, the return of the steered rear wheel shafts 33, 34 to the steer lock state is temporarily suspended and the self steer state is maintained.

In this way, in this truck 10, when the steering wheel 17 is operated relatively greatly when transitioning from low-speed driving to high-speed driving or from high-speed driving to low-speed driving, the truck 10 is operated until the steering wheel 17 returns to straight-ahead driving. During this period, the control unit 54 controls the vehicle speed sensor 56 and the oil pressure sensor 57.
The current flowing through the solenoid valve 50 is controlled according to the signal from the vehicle, and the solenoid valve 50 is maintained in the running state before the turn, and the steer lock cylinders 39 and 40 are maintained in the running state before the turn. hold and
That is, the steer rear wheel shafts 33 and 34 are maintained in a self-steering state or a steer-locked state, thereby preventing sudden changes in steering sensation.
Then, when you return to straight-ahead driving, the control
The unit 54 controls the current flowing through the solenoid valve 50 in response to signals from the vehicle speed sensor 56 and the oil pressure sensor 57, and controls the opening and closing of the solenoid valve 50 to cause the steer lock cylinders 39 and 40 to steer. A locking operation or a self-steering operation is performed, and the steered rear wheel axles 33, 34 are placed in a steer-locked state or a self-steering state.

Also, when the truck 10 is running, the brake
When the brake is applied by depressing the pedal and the hydraulic pressure in the hydraulic service brake system increases, the control unit 54 inputs the signal from the brake pressure sensor 68, and the control unit 54 inputs the signal from the brake pressure sensor 68.
The solenoid valve 50 is opened and closed by the output signal from the unit 54, and the steer rear wheel axles 33, 34 are placed in a steer lock state, and the truck 10 is in a stable state, as in the case of high-speed running described above. Safe braking is achieved.

As understood from the above, the rear two-axle vehicle of the present invention includes power steering for steering the front wheels via the front wheel axle in response to steering wheel operation, rotatably supporting the rear wheel, A steer lock cylinder locks the rear wheel axle, which is self-steering according to the turning direction of the vehicle by steering the front wheels, and fluid pressure piping connects a fluid pressure source to the steer lock cylinder. When the vehicle is running at low speed, the current flowing through the solenoid valve is controlled according to the signal from the vehicle speed sensor, and the solenoid valve is opened and closed to control the steering lock cylinder. When the vehicle is running at high speed, the current flowing through the solenoid valve is controlled according to the signal from the vehicle speed sensor, and the solenoid valve is controlled to open and close to perform the self-steering operation. The steering lock cylinder is operated to perform a steering lock operation, and the steering control is also controlled when the vehicle is transitioned from low speed driving to high speed driving, or from high speed driving to low speed driving.
When the wheel is operated relatively significantly, the current flowing through the solenoid valve is controlled according to signals from the vehicle speed sensor and the oil pressure sensor of the power steering hydraulic circuit until the vehicle returns to straight-ahead running. maintaining the solenoid valve in the running state before the vehicle turns and maintaining the steer lock cylinder in the running state before the vehicle turned;
When the vehicle returns to running straight, the current flowing through the solenoid valve is controlled according to the signals from the vehicle sensor and the oil pressure sensor, and the solenoid valve is opened and closed to control the steering lock cylinder. locking or self-steering operation, and further controlling the current flowing through the solenoid valve in response to a signal from a brake pressure sensor of the hydraulic service brake system when the vehicle is braked; The solenoid valve is controlled to open and close to cause the steer lock cylinder to perform a steer lock operation, and furthermore, when the vehicle is backed up, the current flowing through the solenoid valve is controlled in response to the signal from the back sensor. Since the present invention is equipped with a control unit that controls the opening and closing of the solenoid valve and operates the steer lock cylinder, the self-steering type vehicle can be operated at low speeds. The rearmost wheel axle is placed in a self-steering condition with its steer-lock cylinder to reduce the turning radius, and when driving at high speed, the self-steering last wheel axle is placed in a steer-lock condition with its steer-lock cylinder. The driving stability is improved by placing the vehicle in the vehicle, and it changes from low-speed driving to high-speed driving.
Alternatively, if the steering wheel is operated relatively significantly when transitioning from high-speed to low-speed driving, the self-steering rear wheel axle may shift from its steering lock until returning to straight-ahead driving. The cylinder maintains the vehicle in its pre-turning state, in a so-called self-steering or steer-locked state, preventing sudden changes in steering sensation, and thereby enabling stable cornering. , when braking the vehicle, the self-steering rear wheel axle is placed in a steer-lock condition by the steer-lock cylinder to maintain the vehicle in a stable position and enable safe braking; , when the vehicle is reversing, the self-steering rear wheel axle is placed in a steer-lock condition with its steer-lock cylinder to stabilize the steering, thus improving the steering stability and improving the steering stability of large vehicles. It is extremely useful and practical for people.

[Brief explanation of drawings]

FIG. 1 is a schematic view showing a specific example of the rear two-axle type vehicle of the present invention, which is embodied in a rear two-axle type truck, and FIG. FIG. 2 is an enlarged partial schematic view showing the structure around the steering rear wheel shaft. 11... Chassis frame, 13, 14... Natsukuru, 15... Power steering, 17...
...Steering wheel, 18,19...Front wheel axle, 27,28...Natsukuru, 33,34...
Steer rear wheel axle, 39, 40...Steer lock
Cylinder, 48... Air tank, 49... Pneumatic piping, 50... Solenoid valve, 54... Control unit, 55... Oil pump, 56...
... Vehicle speed sensor, 57 ... Oil pressure sensor, 68 ... Brake pressure sensor, 69 ... Back sensor.

Claims (1)

[Claims] 1. Power steering that steers the front wheels via the front wheel axle in response to the operation of the steering wheel, and power steering that rotatably supports the rearmost wheel and steers the front wheels of the vehicle. A steer lock cylinder that locks the rearmost wheel axle that self-steers depending on the direction of turning; a solenoid valve disposed in a fluid pressure piping that connects a fluid pressure source to the steer lock cylinder; When driving at low speeds, the current flowing through the solenoid valve is controlled according to the signal from the vehicle speed sensor, and the solenoid valve is controlled to open and close to cause the steer lock cylinder to perform self-steering operation.
When the vehicle is running at high speed, the current flowing through the solenoid valve is controlled according to the signal from the vehicle speed sensor, and the solenoid valve is opened and closed to control its steering.
The lock cylinder is operated to steer lock, and when the vehicle is transitioned from low speed driving to high speed driving, or from high speed driving to low speed driving,
When the steering wheel is operated relatively significantly, until the vehicle returns to straight-line driving,
The current flowing through the solenoid valve is controlled in response to signals from the vehicle speed sensor and the oil pressure sensor of the power steering hydraulic circuit, and the solenoid valve is maintained in the running state before the vehicle turns, thereby steering the vehicle. The lock cylinder is held in the running state before the vehicle turned, and when the vehicle returns to straight running, the current flowing to the solenoid valve is controlled according to the signals from the vehicle speed sensor and oil pressure sensor. , controls the opening and closing of the solenoid valve to cause the steer lock cylinder to perform a steer lock operation or a self steer operation, and furthermore, when the vehicle is braked, the brakes of the hydraulic service brake system are activated. The current flowing through the solenoid valve is controlled in accordance with the signal from the pressure sensor, and the solenoid valve is controlled to open and close to cause the steer lock cylinder to perform a steer lock operation. The controller controls the current flowing through the solenoid valve according to the signal from the back sensor, controls the opening and closing of the solenoid valve, and causes the steer lock cylinder to operate the steer lock.
A rear two-axle vehicle equipped with a unit.