JPS6092990A - Two rear-shaft type car - Google Patents

Abstract

PURPOSE:To prevent troubles and improve the steering stability by protecting an electrical contact from the excessive pushing-in by restricting the pushing-in position by forming a stopper stage onto the poppet bore of a pressure sensor arranged in a hydraulic circuit for power steering. CONSTITUTION:When a power steering is steered, the pressure in a feeding pipe 75 increases, and since the pressure in a return pipe 76 is close to the atmospheric pressure, a high pressure is applied onto the high-pressure connecting port 84 of a pressure sensor 57. Though a poppet 85 is pushed-in against the pressure of a poppet chamber 86 and a setting spring 91, the pushing-in position of the poppet 85 is such that the total pressure applied onto a stopper stage 85 formed in a bore 82 is not applied onto a push rod 93 and an electrical contact 92, and these articles can be protected from high pressure. Therefore, the breakage of the rod 93 and the contact defect of the contact point 92, etc. are prevented, and the operation trouble of the pressure sensor is prevented beforehand, and the steering stability is assured.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rear two-axle type vehicle in which the rear wheel axle is of a caster type.

Generally, in a rear dual-axle vehicle with a heavy load, such as a rear dual-axle truck, the last wheel axle that is not driven by an engine is configured as a caster type rear wheel axle, which not only reliably supports the load of the truck, but also When the truck turns, it self-steering to reduce the turning radius.

Such a rear two-axle type truck with a caster type rear wheel axle is usually equipped with a steer lock cylinder, and when the truck is traveling at high speed and when reversing, the caster type steer rear wheel axle is used. in a neutral state, i.e.
It has been designed to be locked in the straight-ahead direction, thereby increasing the running stability of the truck when traveling at high speeds, and also ensuring safe and reliable reversing of the truck.

However, when the truck decelerates from high speed driving to low speed driving, the steer lock cylinder operates and the steer rear wheel axle changes from the steer lock state to the self steer state. When turning in such a self-steering state, the operating force required on the steering wheel is of course lighter than that in the steer-locked state, and the amount of force required to operate the steering wheel is As the turning radius of the truck becomes smaller, the operating feel tends to change between the steer/lock state and the self-steering state.

The purpose of this invention is to make a caster-type steer rear wheel axle self-operating.
Either the steer state or the steer lock state,
It reduces the turning radius depending on the driving conditions and improves driving stability at high speeds, and when the steered rear wheel axle transitions from self-steering to steer-locked state, and steer-locked. When returning from a self-steering state to a self-steering state, it reduces the change in operating feeling and enables safer driving. To provide a rear two-axle vehicle that improves the pressure resistance of the pressure sensor used in the vehicle, prevents operational troubles of the pressure sensor, guarantees steering stability, and enables proper and reliable steering at all times. It is in.

In order to solve these problems, the rear two-axle vehicle of the present invention has a control valve that slides the control valve, oil pump color flow, and oil pump by steering input.
y, l-roll valve and hiso controls.
A power steering system that uses pressure oil passed through a valve to operate a power cylinder to steer the front wheel axle, and a caster-type steer rear wheel axle that self-steering according to the turning direction of the vehicle by steering the front wheel axle. A steer lock cylinder that locks the steer rear wheel axle, a fluid pressure source that supplies pressurized fluid to the steer lock cylinder, and fluid pressure piping that connects the steer lock cylinder and the fluid pressure source. a casing comprising a solenoid valve provided in the casing, a high pressure connection port and a poppet bore in communication with the high pressure connection port, so as to form a poppet chamber isolated from the high pressure connection port in the poppet bore; a poppet fitted in the poppet bore so as to be able to reciprocate; a stopper stage formed in the poppet bore so as to regulate the pushing position of the poppet;
A low pressure connection port formed in the casing so as to communicate with the poppet chamber presses the pot against the high pressure connection port side of the poppet chamber.
A setting ring located in the chamber, and an electrical contact located in its casing to be deenergized and energized in response to the reciprocating sliding of its poppet, connects its high pressure connection port to its control valve. A pressure sensor is connected to the pressure port side, and its low pressure connection port is connected to the discharge port side of the control valve, and electrically connected to the solenoid valve, and responsive to the output signal from the vehicle speed sensor and the pressure sensor. The configuration includes a control unit that controls the opening and closing of the solenoid valve.
Furthermore, the control unit receives output signals from the pack position sensor in addition to the output signals from the vehicle speed sensor and pressure sensor, and enables opening/closing control of the solenoid valve. .

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

FIGS. 1 to 4 schematically show a rear two-axle vehicle IO of the invention, embodied as a rear two-axle truck.

Thereafter, the two-axle truck 10 has its front wheel axles 18 and 19 steered by the power steering 15 in response to the steering input, and the rear and front wheel axles 29 and 30 are driven by the ennons 25 mounted on the truck 10, and , then front wheel axle 2
The rearmost wheel axle 33.34 arranged at the rear of 9.30 is configured as a caster-type steer rear wheel axle, and depending on the driving conditions of the truck 10, a steer lock cylinder 89.40 is used to control the rear wheel axle after the steer. Wheel sets 33, 34
is configured to be placed in either a self-steering state or a steer-locked state.

That is, after that, the two-axle truck IO is operated by a steering wheel 15 that steers the front wheel axle 18, 19 according to the operation of the steering wheel 17, and a rear wheel axle 29, 30 driven by the engine 25. , a caster-type steer rear wheel axle 33.34 that self-steers according to the turning direction of the truck 10 by steering the front wheel axle 18, 19, and a steer lock cylinder that locks the steered rear wheel axle 33.34. 39.40, an air tank 48 that supplies compressed air to the steer lock cylinder 39.40, and a pneumatic piping 49 connecting the steer lock/cylinder 39.40 and the air tank 48. The provided solenoid valve 50 and the solenoid valve 50
electrically connected to the vehicle speed sensor 56. and the
A pressure sensor 57 provided in the hydraulic system 55 of the 9-power steering wheel 15. Further, in response to an input signal from a pack motion sensor (not shown), the solenoid valve 50
The structure includes a control unit 54 for controlling opening and closing.

The power steering 15 is rotatably attached via a king bin to both ends of the front axle beam 12 located in front of the chassis frame 11 of the truck IO, and is connected to the front wheel axle 18,19. and a pair of knuckles 13°14 with tie rod arms 20.21, the tie rod arms 20.2
Tie rods 22 connecting one ends to each other. A/tegral-type lateral steering device 16 that rotates a sector shaft (not shown) in response to the operation of the steering wheel 17. 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. The hydraulic system 5 of the e-war steering device 16
It consists of 5 etc.

Of course, the steering device 16 has a control function as a directional control valve, as shown in FIG.
Valve flow 9 Cylinder 71 as a booster
1) The oil pump 68 sucks up the pressure oil stored in the zanos 72, and further, the pressure oil is passed through the flow control pulp 69 to adjust the flow rate of the pressure oil. The pressure at which the flow rate adjustment was made like that? The reason is that the pressure of the control knob 70 is 4-
) 7: NC send, sono control noklua''
By sliding the control/repulse solenoid (not shown) at 70, the cut-off cylinder 71
75; Motion i / ``It is configured to be done.

Since the power steering 15 is configured substantially the same as the power steering link applied to existing trucks, a detailed explanation of its configuration will be omitted.

one! i, the front wheel axle of the knuckle 13.14 18°1
Front wheels 60 and 61 are respectively attached to 9.

Therefore, if the steering wheel 17 is rotated, the nine-wheel steering device 16 rotates the knuckles 13,14 in the same direction and the front wheel axle 18,19 is steered, As a result, its front wheel 6
The steering angle of 0.61 can be changed.

Of course, although the 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 rear front wheel axle 29.30 is connected to the chassis of the truck 1o.
It is disposed at the rear of the frame 11 and is driven by an engine 25 mounted on the truck.

That is, the front wheel axle 29.30 then
A transmission 26 is arranged at a rearward position in the frame 11 and is rotatably housed in an axle tube 58 provided with a final reduction gear 59, and is arranged behind the engine 25.
The output shaft of the drive shaft is connected to the drive shaft of the final reduction gear 59 via the roller chassis (31).

After that, it goes without saying that wheels 62, 63, 64, 65 as double tires are respectively attached to both ends of the front wheel axle 29, 30.

The caster-type steer rear wheel axle 33,34 is then configured to be self-steerable behind the front wheel axle 29,30 depending on the turning direction of the truck 10. That is, the steer rear wheel axle 33.34 is fixed to a knuckle 27.28, and the knuckle 27.28 is rotatably attached to each end of the rear axle beam 32 via a king bin.

Furthermore, the knuckle 27.28 is the track 10
It has a knuckle control arm 35, 36 that projects forwardly and a tie rod arm 37, 38 that projects rearwardly.

The ends of the tie rod arms 37, 38 are connected to each other via a tie rod 47.

Therefore, the pair of knuckles 27.28 is
The rods 47 rotate about the king pins in the same direction, so that their caster steer rear axles 33,34 are self-steered in the same direction.

The steer lock cylinders 39 and 40 lock the steer rear wheel axles 33 and 34 using compressed air from an air tank 48, which will be described later.
．． 34, it is rotatably arranged on the rear axle beam 32 via a universal joint.

The steer lock cylinder 39.40 comprises a cylinder, a diaphragm disposed within the cylinder, and a bushing rod 45.46 which can be moved in and out of the cylinder at one end and connected to the diaphragm at the other end. , and a return spring disposed within the cylinder to retract the bushing rod 45,46.

A steer lock cylinder 39 so configured.
40 is rotatably attached to the ends of brackets 41 and 42 fixed at a predetermined distance to the rear axle beam 32 via universal joints, and the bushing rods 45 + 46 end are connected to the knuckles. ·Control·
Arms 35 and 36 are directed toward the ends.

Of course, the universal joint includes a cross guide, and the steer lock cylinder 39.
9.40 is connected to its bracket 41.42.

Furthermore, the lock rod 45.46 end of the steer lock cylinder 39.40 is connected to the knuckle control arm 35.36 via the sleeve 43.44.
connected at the end.

The sleeve 43,44
One end is open to form a rod guide bore for reciprocatingly receiving the 5.46 end, and the other end is galle jointed to the knuckle control arm 35.36 end.

Therefore, if the bushing rod 45.46 of the steer lock cylinder 39.40 is pushed out by air pressure, the tip of the bushing rod 45.46 will be the tip of the bushing rod 45.46 of the steer lock cylinder 39.440. The knuckle control arm 35.
36 as well as the rotation of the knuckles 27, 28 about the king pin is restricted, in other words, the caster type steer rear wheel axle 33, 34 is placed in a steer lock state.

Of course, when the steer lock cylinder 39.40 bushing rod 45.46 is retracted, the tip of the bushing rod 45.46 is separated from the bottom wall of the rod guide bore and the bushing is retracted.・Rod 4
5.46 is allowed for reciprocating movement of its sleeve 43.44 with respect to its caster-type steer rear axle 33.46.
34 is placed in self-steering.

The air tank 48 is connected to the steer lock cylinders 9 and 40 via pneumatic piping 49, respectively. The compressed air in the air tank 48 is driven by the engine 25 of the truck 10. Of course, the air is supplied from an air conditioner (not shown).

The solenoid valve 50 has a pneumatic line 49 connecting its air tank 48 and its steer lock cylinder 39,40.
It is set in.

The solenoid valve 50 is tank port) 51.71J da.
Port 52. and a three-way control valve each having an exhaust port 53, the exhaust port 53 is
Connecting the tank port 51 to the cylinder port 52 at the same time the tank port 51 is closed, or connecting the cylinder port 52 to the exhaust port 53 at the same time the tank port 51 is closed. It is configured to be selective.

A control unit 54 is electrically connected to the solenoid coil of the solenoid valve 50 and controls the vehicle speed control 56 .
and the hydraulic system 5 of the A-war steering 15 mentioned above.
The pressure sensor 67 provided in the back position sensor
It controls the opening and closing of the circuit, and is composed of input and output circuits, an arithmetic circuit, a memory circuit, a control circuit, and a power supply circuit.

The vehicle speed sensor 5G is arranged in the transmission 26 of the truck 1O, like the existing vehicle speed sensor, and
It is configured to detect the rotational speed of the output shaft of No. 6, convert the rotational speed into an electrical signal, and send the signal to its control unit 54. Therefore, the vehicle speed sensor 56 is electrically connected to the input circuit of the control unit 54.

The pressure sensor 57 is configured to convert a predetermined pressure difference into an electrical signal, and as understood from FIG. 4, the high pressure connection port 84 and the high pressure connection port 8
The poppet bore 82 is connected to the poppet bore 82, and the poppet bore 85, which will be described later, is provided in the poppet bore 82.
A casing 81 is provided with a stopper step 89 for regulating the pushing position of the casing 81, and a poppet chamber 86 isolated from its high pressure connection port 84 is connected to its poppet chamber 81.
2 and a low pressure connection port 90 formed in the casing 81 to communicate with the poppet chamber 86; In response to the reciprocating sliding movement of the setting spring 91 disposed in the t't chamber 8G and the two ends 85 so as to press the poppet 85 toward the high pressure connection port 84 side,
electrical contacts 92 arranged on its casing 81 to be deenergized and energized.

The casing 81 has a poppet bore 82 that is open at one end, and a stone P ring 83 is screwed into the open end of the poppet via 82 so that the stone
By screwing in F ring 83, the poppet ? A high pressure connection port 84 is formed at the open end of the opening 82 .

Of course, that stone! - The ring 83 facilitates the work of fitting a poppet 85, which will be described later, into the poppet door 82 so as to be able to reciprocate and slide. A ring 83 is screwed into the open end of the poppet bore 82 to restrict the sliding position of the poppet 85 onto the upper blade.

The poppet bore 82 also has an inner diameter in its lower portion that is smaller than the inner diameter in its upper portion so that there is no stone between the upper and lower portions of the poppet bore 82. A step 89 is formed. The first stage 89 regulates the downward sliding position, that is, the amount of movement, of the poppet 85 within the poppet pore 82, and in addition, the J? Poppet 5 is electrical contact 9
To prevent pushing 2 excessively, that issue? This prevents the electrical contact 92 from being deformed or damaged due to excessive pushing of the corrugated wave 85, thereby preventing the occurrence of poor contact.

The poppet 85 is the t? Inside the Otbore 82, the stone groove ring 83 and the A stage 89 are fitted so as to be able to reciprocate and slide.

That's how poppet 85 becomes its poppet boa sz
If fitted within the poppet bore 82
A poppet chamber 86 isolated from the high pressure connection boat 84 is formed in the inboard portion of the.

Further, the poppet 85 is provided with a ring groove 87 on its outer periphery in order to improve the sealing performance with the poppet bore 82, and an O-ring 88 is fitted into the ring groove 87.

The low pressure connection port 90 connects the poppet chamber 8
6 is formed in the casing 81 thereof.

Setting spring 91 is a coil spring disposed in poppet chamber 86 and presses poppet 85 upwardly, ie, toward stopper ring 83 .

Of course, the spring constant of the setting spring 91 is determined depending on the pressure of the pressure oil to be detected in the hydraulic circuit of the ie war steering 15 in which the pressure sensor 57 is used.

Therefore, the poppet 85 is connected to the high voltage connection I-to 84.
slides within its poppet bore 82 depending on the pressure of the hydraulic oil applied to its low pressure connection port 90 and the spring constant of its setting spring 91.

The electrical contact 9z is the 7y! Takutsuto L? It is arranged in an insulating chamber 9G formed in the casing 81 below the bore 2 and isolated from the poppet 82, and in response to the movement of the poppet 85, the extinguisher is inserted through the bushing rod 93. energized and configured to be energized.

That is, the bushing rod 93 is integrally provided with a pressure grate 94 at the lower end, and the bushing rod 93 is passed through a partition wall 95 that partitions the poppet door 82 and the insulating chamber 96, and Is that the end of Gutshu Rod 93? The pressure grate 94 is reciprocatably housed in the insulating chamber 9G so as to be in contact with the lower surface of the bed 85.

Electrical contacts 92 are deenergized and energized via the bushing rod 93 in response to movement of the poppet 85.
A lead ring grate 97 disposed on the bottom wall of the insulation chamber 96 and a lead ring plate 9
A fixed contact 98 is arranged on the bottom wall of the pressure plate 94 and is insulated from the lead plate 99.
The ring plate 97 is electrically connected to the lead plate 99 and is restrained between the lead ring plate 97 and the lead plate 99 so as to push the pressure plate 94 upwardly. It is composed of a return spring 100.

Of course, in the pressure sensor 57 configured as described above, lead wires (not shown) are connected to the lead ring plate 97 and the fixed contact 98, respectively, and these lead wires are connected to the outside of the casing 81. Each of them has been expanded. Still that lead ring great 9
7 and fixed contact 98 to its casing 8.
It is also possible to ground it to 1.

The pressure sensor 57 configured as described above has its high pressure connection, t? -) 84 is the control knob 7
0 pressure port door 3 side, and its low pressure connection port 9
0 are respectively connected to the discharge port 74 side of the control valve 70, and the lead wires connected to the electrical contacts 92 of the pressure sensor 57 are electrically connected to the input circuit of the control unit 54 of the control valve 70. .

Of course, if the high pressure and low pressure connection ports 84.90 are connected to the pressure and discharge ports) 73.74, respectively, as shown in FIG. Preferably, the connected supply and return lines 75,76 are each provided with a connector 77,78, with its high pressure connection port 84 connected to its connector 77, and its low pressure connection port 90 connected to its connector 78, respectively.

Next, to describe the running of the above-mentioned rear twin-axle truck 10, when the truck IO is running at a low speed, the tank port 51 of the solenoid valve 50 is controlled by a signal from the vehicle speed sensor 56 under the control of the control unit 54. is closed and the cylinder port 52 is exhausted from the exhaust 71? -) 53 will be contacted.

That is, the compressed air within the steer lock cylinder 39, 40 cylinder chamber is vented to the atmosphere through its exhaust port 53, and the bushing rods 45, 46 are retracted inwardly by the return springs.

As a result, reciprocating movement of the sleeve 43.44 relative to the push rod 45.46 is allowed, and the caster-type steer rear wheel axle 33.34 is placed in a self-steering condition, which facilitates turning when the truck 1o is traveling at low speed. radius becomes smaller.

At this time, the steer lock cylinders 39, 40 are rotatably supported on the rear axle beam 32 via a universal joint, so that the steer lock cylinders 39, 40 are rotatably supported by the rear axle beam 32 in accordance with the self-steering of the steer rear wheel axles 33, 34. The orientation of the steer lock cylinders 39, 40 can be changed freely.

Therefore, the steer lock cylinders 39, 40 do not substantially interfere with the self-steering of the steered rear wheel axles 33, 34, and the self-steering is performed extremely smoothly.

Further, when the truck 1o travels at high speed, the exhaust port 53 of the solenoid valve 5o is closed in response to a signal from the vehicle speed sensor 56 under the control of the control unit 54, and the tank port 51 is closed to the cylinder port. 52 will be contacted.

That is, compressed air from the air tank 48 is directed into the cylinder chamber of its steer lock cylinder 39.40, the diaphragm is moved against the return valve, and the gutshu rod 45.46 is moved. Each is pushed outward.

As a result, the bushing rods 45, 46 (D tips of the rod guides in the sleeves 43, 44) touch the bottom wall of the bushing rods 45, 46 (D), and the reciprocating movement of the sleeves 43, 44 with respect to the bushing rods 45, 46 is restricted. The caster-type steer rear wheel axles 33, 34 are placed in a steer-locked state, and running stability when the truck 1o runs at high speed is improved.

Of course, when the truck 1o backs up, the transmission 2
The back up switch is automatically energized by the reverse operation of step 6, and the electromagnetic coil of the solenoid valve 50 is energized by the energization of the pack up switch. The caster-type steer rear wheel shafts 33 and 34 are placed in a steer lock state, thereby stabilizing maneuverability when reversing.

Further, when the truck 10 decelerates from high-speed running and transitions to low-speed running, the solenoid valve 50 is opened and closed by a signal from the vehicle speed sensor 56 under the control of the control unit 540, and after the caster type steer. wheel set 33
, 34 The case 7 is returned to the steered state, but when the steering wheel 17 is rotated through a relatively large operating angle in such a state, the hydraulic pressure of the hydraulic system 55 of the ρ-war steering 15 increases, As a result, the pressure at the pressure port 3 in the control valve 70 becomes higher than the pressure at the discharge port 74.

That is, in the) 9-war steering 15,
When the steering is performed, the pressure in the supply pipe 75 rises to -, and the pressure in the return pipe 76 is still close to atmospheric pressure, so the high pressure connection port 84 of the pressure sensor 57 Extremely high pressure is applied and the poppet 85 is driven by the pressure in the poppet chamber 86 and the setting spring 9.
It is pushed in against 1.

When the poppet 85 is thus pushed in, the bushing rod 93 and brake grate 94 are pushed in and the reed plate 99 contacts the fixed contact 98 so that the output signal from its pressure sensor 57 is - Sent to unit 54.

As described above, when the control unit 54 inputs the respective signals from the vehicle speed sensor 56 and the pressure sensor 57, the control unit 5
4 is the solenoid valve 5, which is the same as when driving at high speed.
0, which closes the exhaust port 53 of its solenoid valve 50 and connects its tank port 51 to its cylinder port 52.

Therefore, when the truck 10 decelerates from high-speed travel and transitions to low-speed travel, the steering
While the wheel 17 is being operated relatively largely, its caster-type steer rear wheel axle 33° 34 is not self-steering and is maintained in a steer-locked state, resulting in a sudden change in the operating feel. thwarted.

Also, when the truck 10 increases its speed from low speed running to high speed running, the solenoid valve 50 is controlled by the vehicle speed sensor 56 under the control of the control unit 54.
The caster-type steering rear wheel axle 33, 34 is returned to the self-steering state by a signal from・
The oil pressure in the hydraulic system 55 of the steering wheel 15 increases, so that the pressure in the pressure port door 3 at its control valve 70 becomes higher than the pressure in the exhaust port 74;
The above-mentioned truck 10 is operated in the same manner as when the truck 10 is transitioned from high-speed traveling to low-speed traveling, and in this way, even when the truck 10 is transitioned from low-speed traveling to high-speed traveling, the steering wheel 17 is operated to a large extent. While the caster type steer rear wheel shaft is 33°34
does not switch from self-steering to steer lock,
The steering wheel 17 is switched after the operation of the steering wheel 17 is completed, and a sudden change in the operation feeling is prevented.

Of course, extremely high pressure is applied to the high-pressure connection port 84 of the pressure sensor 57, but the pushing position of the poppet 85 is regulated by a stopper step 89 formed within the poppet bore 82. All of the pressure applied to the poppet 85 is not applied to the bushing rod 93 or electrical contacts 92, thereby protecting the bushing rod 93 and electrical contacts 92 from high pressure, thereby preventing damage to the bushing rod 93. Poor contact at the electrical contact 92 is prevented.

This invention includes a power steering system for steering a front wheel axle, a caster type steer rear wheel axle, a steer lock cylinder for the steer rear wheel axle, and a fluid pressure source for the cylinder. The control unit includes a solenoid valve provided in a fluid pressure pipe connecting the cylinder and the fluid pressure source, and a control unit that controls opening and closing of the solenoid valve, and the control unit includes a vehicle speed sensor, and
Since the solenoid valve is controlled according to the input signal from the pressure sensor installed in the power steering hydraulic system, the caster-type steer rear wheel axle can be operated in either the self-steer state or the steer-lock state. The turning radius is reduced depending on the driving conditions, and the driving stability at high speeds is improved.Moreover, when the steered rear wheel axle changes from the self-steer state to the steer-lock state, When returning from the steer-locked state to the self-steering state, the operating sensation is less likely to change suddenly, and the pressure sensor
High voltage connection? - a casing with a poppet bore communicating with the high pressure connection port and a poppet chamber isolated from the high pressure connection port;
The poppet fitted into the bore, and the stone or step formed in the poppet bore, and the month? a low pressure connection port in communication with a rigid chamber, a setting spring disposed in the poppet chamber, and an electrical contact that is deenergized and energized in response to reciprocal sliding of the poppet;
The strafe e-stage regulates the push-in position of the poppet and prevents the poppet from being pushed too far, so that the entire pressure applied to the poppet is not applied to the electrical contact and the electrical contact It protects the poppet from excessive pushing, prevents the electrical contact from deforming or breaking, prevents contact failure from occurring, and greatly improves the pressure resistance of the contact under high pressure. Pressure is reliably converted into an electric signal, operational troubles of the pressure sensor are prevented, steering stability is guaranteed, and proper and reliable steering is always possible, making it extremely practical.

As mentioned above, from the specific examples of this invention described with reference to the drawings, various design modifications and changes can be easily made by those who have ordinary knowledge in the technical field to which this invention pertains. Furthermore, the structure of this invention can be easily replaced with an embodiment essentially the same as this invention that satisfies essentially the same problems as that invention and achieves the same effects as this invention. I guess it will happen.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing a rear two-axle type vehicle of the present invention, which is embodied as a rear two-axle type truck, and Fig. 2 is a schematic diagram showing the caster type steer rear wheel shaft of the rear two-axle type truck shown in Fig. 1. Figure 3 is an enlarged schematic diagram showing the structure of the /F qua-steering in the rear two-axle truck shown in Figure 1, and Figure 4 is the diagram shown in Figure 3. . It is a longitudinal cross-sectional view which shows the pressure sensor in P power steering. 10... Rear two-axle truck, 11... Shirt frame, 13.14... Knuckle, 15... Power
Steering, 17...Steering wheel, 1
8.19...Front wheel axle, 27.28...Nakno to 33.34...Caster type steer rear wheel axle, 39.40
... Steering lock cylinder, 48 ... Air tank, 49 ... Pneumatic piping, 50 ... Solenoid valve, 54
...Control unit, 55...Hydraulic system,
56... Vehicle speed sensor, 57... Pressure sensor, 81...
...Casing, 82...Poppet Hζa, 84.
...High pressure connection port, 85...Poppet, 86...
, 4Q/t chamber, 89...st/e stage,
9o...Low pressure connection port, 91...Setting spring, 92...Electric contact. 2L/3 figures of concave cakes! ! , 2UjJ 8 tail j4 mouth nail

Claims (1)

[Claims] The control valve spool of the control pulp is slid by the steering type crab, and the flow control valve spool from the oil pump is operated by the pressure oil that passes through the control pulp to operate the four cylinder. power steering that steers the front wheel axle, a caster-type steer rear wheel axle that self-steers according to the turning direction of the vehicle by steering the front wheel axle, and a steer lock that locks the steered rear wheel axle. A cylinder, a fluid pressure source that supplies pressurized fluid to the steer lock cylinder, a solenoid valve provided in the fluid pressure piping connecting the steer lock cylinder and the fluid pressure source, and a high pressure connection port. and a casing having a poppet bore in communication with the high pressure connection port, the poppet bore reciprocally sliding to form a poppet chamber isolated from the high pressure connection port within the 4' cut bore. a stopper stage formed in the poppet bore to regulate the depressed position of the poppet, a low pressure connection port formed in the casing to communicate with the poppet chamber; a setting spring disposed in the poppet chamber to urge the poppet against the high pressure connection port side and disposed in the casing to be deenergized and energized in response to reciprocal sliding of the poppet; electrically connected to the solenoid valve and a pressure sensor whose high pressure connection port is connected to the pressure port side of the control pulp and whose low pressure connection port is connected to the discharge port side of the control pulp. , vehicle speed sensor, and
A rear two-axle vehicle equipped with a control unit that controls opening and closing of the solenoid valve according to an output signal from the pressure sensor.