JPH027104Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to an improvement of a steering device for a special vehicle such as a crane truck.

(Background technology) This type of steering device has a power cylinder attached to the rear wheels in addition to the front wheels, so that in addition to front two-wheel steering, four-wheel steering and so-called crab-leg steering can be performed. (For example, Tokuko Sho 57-
No. 41391, Publication No. 48-2584).

In addition, the direction of the driver's seat may be changed with the crane or other high-quality objects.
Japanese Utility Model Application Publication No. 197365/1983 has proposed a system in which the operation of the power cylinder is reversed when the vehicle turns 180 degrees so that the steering wheel can be operated with the same feeling as during normal driving.

By the way, in such devices, the hydraulic source (hydraulic pump) that supplies hydraulic pressure to the power cylinder in response to handle operation is driven in synchronization with the engine, so if a problem occurs with the engine, the operation will be interrupted. In addition, the driving force for the switching valve for four-wheel steering and crab-leg steering is also taken from the above-mentioned hydraulic power source. If the engine stops, you will not be able to steer the car, you will not be able to change the valves, and you will not be able to tow it with another vehicle.

(Purpose and structure of the invention) The present invention was developed by focusing on these problems, and in addition to the above-mentioned hydraulic pump, an emergency pump that is driven in synchronization with the axle is provided, which can be used to control steering in the event of engine trouble. The necessary power assist power and four wheels,
The purpose of the present invention is to provide a steering device for a vehicle that secures driving force (pipe pressure) for returning a switching valve for crab-leg steering to a neutral position, that is, to steering two front wheels.

(Example) FIG. 1 is a side view of a crane truck. In this case, in addition to a driver's cab 1a for steering the vehicle body, a cockpit 1b that rotates integrally with the crane 3 relative to the vehicle body 2 is provided. The cockpit 1b is equipped with a steering handle 4b like the driver's cab 1a.

In Fig. 2, 5 and 6 indicate hydraulic cylinders (power cylinders) attached to the left and right front wheels 7 and 8. The steering knuckles 10 and 11 of 8 are each rotatably connected to one end of the steering knuckles 10 and 11 by a pin.

The hydraulic cylinders 7 and 8 are connected to the steering handle 4a of the operator's cab 1a as well as to the operator's cabin 1b of the crane 3.
The front wheels 7 and 8 are moved in conjunction with the steering handle 4b and expanded and contracted by the pressure oil supplied by the hydraulic pumps 12 and 13 (main pumps), thereby changing the direction of the front wheels 7 and 8 integrally.

Reference numeral 14 indicates a control valve that switches the flow of pressure oil from the hydraulic pumps 12 and 13 according to the direction of rotation of the steering handle 4a in the driver's cab 1a, and 15 similarly controls the flow of pressure oil in the direction of rotation of the steering handle 4b in the operator's cabin 1b. The control valve that switches depending on the situation is shown.

When the steering handle 4a of the control valve 14 is rotated clockwise, pressure oil flows as indicated by the solid line arrow in the figure, causing the right hydraulic cylinder 6 to expand and simultaneously the left hydraulic cylinder 5 to contract. In other words, the front wheels 7 and 8 face toward the right side of the vehicle body.

On the other hand, when the steering handle 4a is rotated to the left, the flow of pressure oil changes as indicated by the dotted line arrow in the figure, causing the hydraulic cylinders 5 and 6 to operate in the opposite direction, causing the front wheels 7 and 8 to turn toward the left side of the vehicle body. change.

Note that the oil returned during the operation of the hydraulic cylinders 5 and 6 is returned to the reservoir tank 16 via the control valve 14.

On the other hand, the control valve 15 is similar to the control valve 14, and when the steering handle 4b is rotated clockwise, pressure oil flows from the reservoir tank 16 as shown by the solid line arrow, and the hydraulic cylinder 5 is turned so as to direct the front wheels 7 and 8 toward the right side of the vehicle body. and 6 are operated, and when the steering handle 4b is rotated to the left, the hydraulic cylinders 5 and 6 are reversely operated so as to change the direction of the front wheels 7 and 8 to the left side of the vehicle body.

Also in this case, the return oil from the hydraulic cylinders 5 and 6 is returned to the reservoir tank 16 via the control valve 15.

17 to 19 are the hydraulic cylinders 5 and 6 in the driver's cab 1a
and the steering handles 4a and 4bb of the cockpit 1b.
~19 adopts an electromagnetic pilot operation type that is linked with one switch and switches at the same time, and the driver's cab 1a
During steering, the route to the control valve 15 for pressure oil from the hydraulic pumps 12 and 13 and the return oil from the hydraulic cylinders 5 and 6 is cut off, and the route to the control valve 14 is opened. Control valve 1 is switched when steering with
The route to control valve 15 is opened by cutting off the route to control valve 15.

Hydraulic pumps 12 and 13 are driven in synchronization with the engine, and their hydraulic lines are joined via a switching valve 20.

The switching valve 20 switches in response to the differential pressure (generated by an orifice) before and after the switching valve 20.
While the pressure oil from the hydraulic pumps 12 and 13 is combined at the position shown in the figure at low engine speeds with a small differential pressure,
When the engine speed increases and the differential pressure increases, the switch is made to release the pressure oil from one of the hydraulic pumps 12 to the reservoir tank 16, thereby preventing excessive supply of pressure oil at high engine speeds.

By the way, similar to the front wheels 7 and 8, the rear wheels 21 and 22
Hydraulic cylinders 23 and 24 are also attached to the vehicle, allowing four-wheel steering and crab-leg steering.

Here, 25 indicates a switching valve for four-wheel rotation and crab-leg steering, and the switching valve 25 is in the neutral position and cuts off the supply of pressure oil to the hydraulic cylinders 23 and 24, that is, normal two-wheel steering is performed. When switching to crab-foot steering, the hydraulic lines are connected in parallel and the hydraulic cylinders 23 and 24 are operated so that the rear wheels 21 and 22 are directed in the same direction as the front wheels 7 and 8 move.

On the other hand, when the switching valve 25 switches to four-wheel steering, the hydraulic lines are connected in a cross state, and the hydraulic cylinders 23 and 24 are connected so that the rear wheels 21 and 22 are turned in the opposite direction simultaneously with the movement of the front wheels 7 and 8. Activate.

In this case, the switching valve 25 is switched via an actuator (not shown), and the actuator is supplied with a check valve 2 with a high valve opening pressure as a driving force.
6 and the check valve 27, which is located closer to the hydraulic pumps 12 and 13 and has a lower opening pressure, and when a changeover switch (not shown) is operated, the stroke position of the actuator is displaced and the changeover is performed. The valve 25 is adapted to be switched to a desired valve position.

28 is an emergency pump provided in parallel with the hydraulic pumps 12 and 13, and the emergency pump 28 is driven in synchronization with the axle.

The hydraulic line of the emergency pump 28 joins the hydraulic line of the hydraulic pumps 12 and 13 between the check valves 26 and 27 via the switching valve 29.

The switching valve 29 is a differential pressure responsive type like the switching valve 20, and has check valves 2 with different opening pressures.
When the hydraulic pressure upstream of the check valve 27 from the hydraulic pressure between 6 and 27, that is, the supply amount from the hydraulic pumps 12 and 13, falls below a predetermined value, the pressure oil from the emergency pump 28 is also stopped at the valve position as shown in the figure. While supplying the control valve 14 or 15,
When the above-mentioned differential pressure is above a predetermined value, the switch is made to cut off the supply of pressure oil from the emergency pump 28 and return a portion of the pressure oil from the hydraulic pumps 12 and 13 to the reservoir tank 16. It's summery.

Note that check valves 30a to 30d are provided so that pressure oil can be supplied even if the axle rotates in the opposite direction and the suction port and discharge port of the emergency pump 28 are reversed.

31 is a control valve 15 that connects hydraulic cylinders 5 and 6 (four wheels, rear wheels 21 and 2 during crab-leg steering).
The switching valve 31 is a switching valve that switches the flow of pressure oil sent to the hydraulic cylinders 23 and 24 (also added to the hydraulic cylinders 23 and 24) according to the orientation of the cockpit 1b.
When the cockpit is facing the front of the vehicle body, the hydraulic lines connecting the control valve 15 and hydraulic cylinders 5 and 6 are connected in parallel, while when the cockpit 1b is rotated 180 degrees and facing the rear of the vehicle body, the hydraulic lines are connected in a cross state. do.

32 is a valve that adjusts the flow rate and pressure of pressure oil sent to the control valve 14 or 15. This valve 32 releases excess oil that exceeds the adjusted flow rate to the reservoir tank 16, and increases the differential pressure before and after the throttle to increase pump efficiency. keep constant.

33 is the oil filter, 34 is the oil filter for the high pressure line, 35 is the tie rod for front wheels 7 and 8, 36 is the tie rod for rear wheels 21 and 22, 37 is the rear axle 38 and 39 is the steering knuckle for the rear wheels 21 and 22. be.

Next, the operation based on such a configuration will be explained.

During steering in the driver's cab 1a (during normal driving), the switching valves 17 to 19 are switched to cut off the passage of pressure oil through the control valve 15 and open the passage through the control valve 14.

In this state, the steering wheel 4a of the driver's cab 1a
For example, when the vehicle is rotated clockwise, the front wheels 7 and 8 are turned to the right side of the vehicle body via the hydraulic cylinders 5 and 6 according to the rotation angle, and the vehicle body moving forward turns to the right, and the vehicle body retreating to the left turns to the left.

Also, when switching from normal operation to crab-leg steering by switching the switching valve 25, the hydraulic lines are connected in parallel through the switching valve 25, and the rear wheels 21
Pressure oil also flows into the hydraulic cylinders 23 and 24 of the front wheels 7 and 8, and the rear wheels 2 move in the same direction at the same time as the front wheels 7 and 8 move.
1 and 22 and turn the steering wheel 4a to the right, for example, the vehicle moving forward will move diagonally to the right, and the vehicle moving backward will diagonally move to the left.

When the switching valve 25 is switched to four-wheel steering, for example, by rotating the steering handle 4a to the right, the front wheels 7 and 8
The rear wheels 21 and 22 point to the left at the same angle as the front wheels 7 and 8, and the vehicle moving forward turns to the right with a much smaller turning radius than during normal driving, and the vehicle moving backward makes a similar left turn. Do the following.

On the other hand, when steering while operating the crane 3 in the cockpit 1b, the switching valves 17 to 19 are switched to cut off the path of the control valve 14 and open the path of the control valve 15.

In this state, when the steering handle 4b in the cockpit 1b is rotated, the hydraulic cylinders 5 and 6 are actuated by the pressure oil from the control valve 15, and the directions of the front wheels 7 and 8 are changed.

In this case, by switching the switching valve 25 for four-wheel and crab-leg steering, crab-leg and four-wheel steering of the vehicle body can be performed in the same manner as in the driver's cab 1a.

Also, when the cockpit 1b rotates together with the crane 3 and faces toward the rear, the switching valve 31 switches to cross and connect the hydraulic lines, connecting the hydraulic cylinders 5 and 6 so that the cockpit 1b faces toward the front of the vehicle. If there is, it will have the opposite effect.

In this state, if the steering wheel 4b is rotated clockwise, for example, the front wheels 7 and 8 will turn to the left with respect to the front of the vehicle, and the vehicle moving forward will turn left, and the vehicle moving backward will turn right, but the cockpit 1b is facing the rear of the vehicle body, so the front and rear of the vehicle body are reversed for the driver, so the vehicle body moving forward of the cockpit 1b turns to the right, and the vehicle body moving backward turns left.

In other words, the driver can operate the steering wheel with the same feeling as when the cockpit 1b faces the front of the vehicle.

However, when the switching valve 25 is switched to crab-leg steering, the steering wheel can be operated with a normal steering feel regardless of the orientation of the cockpit 1b. Therefore, the switching valve 31 is returned to the parallel connection state.

By the way, the present invention provides an emergency pump 28 that is driven in synchronization with the axle in addition to the hydraulic pumps 12 and 13 that are driven in synchronization with the engine, and connects the hydraulic line of the emergency pump 28 to a differential pressure responsive type. Check valves 2 with different opening pressures are connected via a switching valve 29.
6 and 27 merges with the hydraulic line of the hydraulic pumps 12 and 13, and the pilot pressure for the switching valve 25 for four-wheel and crab-leg steering is taken from between the check valves 26 and 27. For example, even if the engine stops, that is, the hydraulic pumps 12 and 13 stop in a state of crab-leg steering at a construction site, if the vehicle is towed by another vehicle, the emergency pump 28 will be driven and the hydraulic pressure will be supplied as power assist force. In addition to supplying the switching valve 25 and enabling steering, the pilot pressure as a driving force for the switching valve 25 is secured, and the switching valve 25 can be returned to the front two-wheel steering mode.

Therefore, there is no problem in towing the vehicle on public roads.

Also, if the discharge amount of the hydraulic pumps 12 and 13 decreases below a predetermined value for some reason, the switching valve 29
Since the pressure oil is also supplied from the emergency pump 28, the steering wheel operation does not suddenly become heavy, especially when driving at low speeds.

(Effects of the invention) In summary, according to the invention, even in the event of engine trouble, the power assist force necessary for steering and the hydraulic pressure as the driving force for switching the switching valve for four-wheel and crab-leg steering can be secured. This not only improves driving safety but also allows other vehicles to tow it on public roads.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a side view of a crane truck, and FIG. 2 is a schematic configuration diagram of a steering device. 1a...driver's cab, 4a...steering handle, 5,
6...Hydraulic cylinder, 7,8...Front wheel, 12,1
3... Hydraulic pump, 14... Control valve, 21, 22... Rear wheel, 23, 24... Hydraulic cylinder, 25... Four wheels, crab foot steering switching valve, 26, 27... Check valve, 28...Emergency pump, 29...Switching valve.

Claims (1)

[Scope of Claim for Utility Model Registration] In a steering system for a vehicle in which a power cylinder is attached to the rear wheels in addition to the front wheels, and in addition to front two-wheel steering, four-wheel steering and crab-leg steering can be performed, In addition to the hydraulic pumps that are driven synchronously, there is also an emergency pump that is driven synchronously with the axle, and the emergency pump's hydraulic line joins the hydraulic pump's hydraulic line via a differential pressure-sensitive switching valve. A check valve with a high opening pressure is installed downstream of the merging point, and a check valve with a low opening pressure is installed in the hydraulic line of the hydraulic pump upstream of the merging point. A steering device for a vehicle, characterized in that pilot pressure is guided to a switching valve for crab-leg steering.