JPH1192094A - Hydraulic circuit for running - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic circuit for running in which running performance on a road surface having irregularity is excellent, in which inner-outer rotation radius difference is absorbed, and in which compactness can be favorably achieved. SOLUTION: Hydraulic oil is supplied to two lines of oil passages 6, 7 through two spool valves 5a, 5b assembled in a control valve 5 to form similar flow to each other, a selector valve 10 incorporating four circuits is provided to select a parallel connection passage in which hydraulic oil is separately fed to hydraulic motors 3, 4 to respectively drive right and left wheels, and a serial connection passage in which hydraulic oil supplied in similar flow is once merged with each other and then fed through one hydraulic motor 3 to the other hydraulic motor 4, and the passages of the same hydraulic oil flow directions in pump 1 connection side circuits to the selector valve 10 are connected to each other by bypass passages 11, 11 each having a throttle 11a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit for traveling of an industrial vehicle.

[0002]

2. Description of the Related Art Some industrial vehicles use hydraulic pressure to drive running wheels. In models that drive wheels with such hydraulic pressure, hydraulic motors are attached to the left and right wheels, respectively, to adjust the oil amount in the parallel circuit in two stages, and to connect hydraulic circuits that send hydraulic oil to each hydraulic motor in parallel. In some cases, switching between low-speed running and high-speed running is achieved by switching to series. In the former type, as shown in FIG. 6, a hydraulic pressure is replenished via a hydraulic oil passage 19 to a parallel circuit in which a flow collecting valve 18 is provided to evenly distribute hydraulic oil to hydraulic motors 3 and 4 to increase hydraulic pressure. As shown in FIG. 7, in the latter parallel / series switching type, as shown in FIG. 7, a parallel connection (a in FIG. 7) and a series connection (FIG. b) can be selected. In the latter type, for example, as disclosed in Japanese Patent Application Laid-Open No. Hei 6-73092, the operating oil supplied in one system is switched between parallel and series using a switching valve having two circuits. There is also known a technique in which flow paths of hydraulic oil connected to each hydraulic motor and having the same flow direction are connected by a bypass having a throttle.

[0003]

When there is unevenness on the road surface, the vehicle is usually driven in a low speed mode when passing through the road surface. The former type equipped with a diverter valve can escape only by rotation of the grounded wheel, even when the center of gravity is biased to the left or right and one of the wheels rises or the wheel drops into the depression. In the type, hydraulic pressure acts only on one of the wheels, which has been lifted and the load has been reduced, and cannot escape on its own. Because inertia hardly works at low speed,
I get stuck with one wheel spinning. In this case, if the hydraulic pressure is applied to both hydraulic motors by switching in series, the hydraulic oil can be supplied to the ground-side wheel, but the torque is insufficient due to the series connection, and the grounding is essential. You may not be able to get out of the wheel because it cannot be turned. If the vehicle has a turning boom, it is possible to escape by moving the center of gravity by turning the boom, but if the vehicle does not have means for moving the center of gravity largely, the vehicle cannot escape on its own.

Although the former type does not get stuck, a large amount of hydraulic oil must be supplied during high-speed running, so that the size of equipment such as a pump is increased, and assembling space is secured and the assembling work is complicated. In addition, there is a problem of cost increase and the like, since a rotation difference between the inner wheel and the outer wheel cannot be absorbed during turning, there is a disadvantage that a turning radius becomes large and tire wear is accelerated. In this regard, the latter type is advantageous for miniaturization, and the former and the latter have advantages and disadvantages, respectively, such that the difference in rotation between the inner and outer rings can be absorbed. or,
The hydraulic circuit described in Japanese Patent Application Laid-Open No. 6-73092 has a problem that the running performance is reduced in the high-speed mode (series connection) because the bypass circuit is connected in parallel with the motor.

[0005]

SUMMARY OF THE INVENTION The present invention is a hydraulic circuit which is small in size, has a small turning radius, and is excellent in running performance on an uneven road surface. The hydraulic oil is sent out independently for each hydraulic motor to the hydraulic motors that drive the left and right wheels, respectively, and the parallel connection path to be returned is combined with the hydraulic oil supplied at the same flow rate, After sequentially passing one hydraulic motor and the other hydraulic motor, a switching valve incorporating a four-circuit that can select one of a series connection path to be returned in two paths is provided. On the other hand, the flow paths of the hydraulic oil in the circuit on the opposite side to the hydraulic motor connection side are the same, and the independent flow paths are connected by bypass flow paths each having a throttle. The equal flow control is performed by two control valves each including a control valve having two spool valves in one body, and a single control valve having one spool valve in each of which separate dedicated pumps are connected. This can be made possible by a valve or a diverter valve.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A hydraulic circuit according to the present invention will be described with reference to the drawings. In FIG. 1, 1 is a pump that pumps up hydraulic oil in a tank 2 and sends it out to hydraulic motors 3 and 4 for driving left and right wheels, and 5 is a first spool valve 5a.
And a second spool valve 5b which operates the two spool valves 5a and 5b in an interlocked manner to supply the hydraulic oil sent from the oil pump 1 to the two hydraulic circuits 6 and 7. Uniform flow control that distributes by equal amounts is enabled. In the interlocking operation of the spool valves 5a and 5b, both spool valves are moved simultaneously and in the same direction by the same stroke amount by operating one traveling lever (not shown).
The control valve 5 also has a function of sending hydraulic oil returned from the hydraulic circuit of each system to the drain circuit 8 and returning it to the tank 2. In the drawing, reference numerals 9 and 9 denote pressure assurance valves for controlling the flow rate so as not to change even if the operating pressures of the left and right motors and other actuators change.

The two circuits 6, 7 are connected to hydraulic motors 3, 4 via a switching valve 10 containing four circuits, and the flow of hydraulic oil on the pump connection side of the switching valve 10 is the same. Independent channels (6
a and 7a, and 6b and 7b) are connected to each other by bypass channels 11, 11 having a throttle 11a. The switching valve 10 includes a parallel circuit in which the supply oil passages 6a and 7a and the return oil passages 6b and 7b in the two circuits 6 and 7 are separately connected to the hydraulic motors 3 and 4 by a switching operation, The supply oil passages 6a and 7a in the two circuits 6 and 7 are integrated into one system, sent to the other hydraulic motor 4 via one hydraulic motor 3, and then sent to the transport oil passage 6
b and 7b can be selected.

When the parallel circuit side (low-speed operation mode) is selected by the switching valve 10 and the control valve 5 is operated, for example, to the forward side, as shown in FIG.
a, 5b is supplied to each supply passage 6
The hydraulic oil sent to the hydraulic motors 3 and 4 via the motors 3 and 4 and returned through the individual motors 3 and 4 is supplied to each return path 6
b, 7b and returned to the oil tank 2 via the spool valves 5a, 5b, and the rotation of the hydraulic motors 3, 4 advances the vehicle at a low speed. Circuits 6 and 7 for supplying hydraulic oil to each motor
Are constituted by independent circuits, and are connected by bypass passages 11 and 11 having throttles, so that when one wheel floats up, some hydraulic oil also flows to the oil passage on one side. Since the pressure set by the control valve 5 increases according to the throttle amount, a torque required for escape from the hydraulic motor on the ground side can be obtained. or,
The movement of the hydraulic oil between the two circuits 6, 7 is allowed by the bypass passages 11, 11 having the throttle, so that the rotational difference between the inner ring and the outer ring is absorbed, so that the turning radius can be increased and the tire can be enlarged. A wear reduction effect is exhibited.

When the series circuit side (high-speed operation mode) is selected, the supply paths 6a and 7a of each system are integrated into one system by a switching valve 10 as shown in FIG. When the hydraulic oil sent to the hydraulic motor 4 and sent out from the hydraulic motor 4 passes through the switching valve 10 again, it is separated into return paths 6b and 7b of the respective systems, and the oil is passed through the spool valves 5a and 5b. Returned to tank 2. As a result, the vehicle travels at a high speed, and in this case, since the two pumps are in a series circuit, both pumps are efficiently driven with a small amount of oil, so that a large-capacity pump or a huge control valve is not required. If the flow of the hydraulic oil is reversed by switching the spool valve (not shown), the hydraulic motor rotates in the reverse direction and travels backward.

In the above-described embodiment, a control valve in which two spool valves are integrally incorporated is used for equal flow control. However, as shown in FIG. Hydraulic oil may be supplied to two control valves 12, 13 having spool valves 12a, 13a by dedicated pumps 14, 15, respectively. By separating the control valves 12 and 13 for each of the spool valves 12a and 13a, the individual equivalent pumps 14 and 15 and the control valves 12 and 13 can be reduced in size, and they can be dispersed in an empty space in the vehicle. Space saving and cost saving can be achieved by arranging, and workability at the time of assembly is also improved.

As shown in FIG. 5, one system oil path is once divided into two system oil passages, and the two system oil passages are equally controlled by the diversion / collection valve 16 and sent to the hydraulic motor 1. If the system is integrated and returned, the control valve 17 only needs to be provided with one spool valve 17a, and the bypass flow path 11 need only be mounted on the circuit side where the flow collecting valve 16 is mounted. Therefore, the piping can be greatly simplified.

According to the present invention, a low-speed mode and a high-speed mode can be selected by switching a switching valve of a motor between parallel and series by using two hydraulic circuits of equal flow control. The switching valve structure is a circuit that connects two flow paths in the hydraulic system in the same hydraulic fluid flow direction in the circuit on the pump connection side to the valve with each other in a bypass flow path having a throttle. For example, although the hydraulic pilot type is adopted in the embodiment, the hydraulic pilot type can be changed to a solenoid type, and the means for controlling the uniform flow, the connection position of the bypass flow path, and the like can be changed appropriately.

In the embodiment, the actual hydraulic circuit is
The traveling hydraulic motor incorporates a counterbalance valve, a hydraulic release parking brake, and a drain circuit, but these are not directly related to the present invention, and therefore, illustration and description thereof are omitted.

[0014]

According to the first aspect of the present invention, even if the load balance between the left and right wheels is greatly disturbed, a constant pressure is ensured even on the side of the hydraulic motor having a large load by means of a pressure-compensating control valve or a diverter valve. When running at low speeds, only the lifted one wheel does not run idle and cannot run, and the bypass flow path with the throttle efficiently absorbs the difference between the inside and outside of the turning radius and reduces tire wear. It is planned. Also, at the time of high-speed running, since both hydraulic motors are connected in series, it is not necessary to increase the oil amount just because of high-speed running, and the pumps and valves can be small. Further, according to the second aspect of the present invention, the control valves are arranged in a distributed manner, and the control valves can be efficiently assembled by utilizing a narrow empty space in the vehicle.
Further, according to the third aspect of the present invention, the number of parts is reduced and the piping is simplified.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a traveling hydraulic circuit according to the present invention.

FIG. 2 is an explanatory diagram showing a flow of hydraulic oil when a low-speed traveling mode is selected.

FIG. 3 is an explanatory diagram showing a flow of hydraulic oil when a high-speed traveling mode is selected.

FIG. 4 is an explanatory diagram of a modification in which motors are independently provided in two circuits.

FIG. 5 is an explanatory diagram of a modified example in which uniform flow control is enabled by a flow collecting valve.

FIG. 6 is an explanatory diagram of a conventional example.

FIG. 7 is an explanatory diagram of a conventional example.

[Explanation of symbols]

1. Pump, 2. Tank, 3, 4. Hydraulic motor,
5 ・ Control valve, 5a, 5b ・ ・ Spool valve, 6,7 ・ ・ Hydraulic circuit, 8 ・ ・ Drain circuit, 9 ・ ・ Pressure assurance valve, 10 ・ ・ Switching valve with 4 built-in circuits, 11 ・.Bypass circuit, 11a..Throttle, 12, 1
3 ・ ・ Control valve 、 12a 、 13a ・ ・ Spool valve 、 15 ・ 15 ・ ・ Pump 、 16 ・ ・ Diversion collecting valve 、 17
..Control valve, 17a..Spool valve, 18
··· Separating / collecting valve, 19 ··· Increase oil passage, switching valve (incorporating two circuits)

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[Procedure amendment]

[Submission date] September 22, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A hydraulic circuit according to the present invention will be described with reference to the drawings. In FIG. 1, 1 is a pump that pumps up hydraulic oil in a tank 2 and sends it out to hydraulic motors 3 and 4 for driving left and right wheels, and 5 is a first spool valve 5a.
And a second spool valve 5b which operates the two spool valves 5a and 5b in an interlocked manner to supply the hydraulic oil sent from the oil pump 1 to the two hydraulic circuits 6 and 7. Uniform flow control that distributes by equal amounts is enabled. In the interlocking operation of the spool valves 5a and 5b, both spool valves are moved simultaneously and in the same direction by the same stroke amount by operating one traveling lever (not shown).
The control valve 5 also has a function of sending hydraulic oil returned from the hydraulic circuit of each system to the drain circuit 8 and returning it to the tank 2. In the drawing, reference numerals 9 and 9 denote pressure compensating valves for controlling the flow rate so as not to change even if the operating pressures of the left and right motors and other actuators change.

Claims (4)

[Claims] 1. A parallel connection path for independently sending and returning hydraulic oil supplied in two systems by uniform flow control to hydraulic motors for driving left and right wheels for each hydraulic motor independently. The hydraulic fluid supplied at the same flow rate is merged, and after passing one hydraulic motor and the other hydraulic motor in order, it is possible to select any one of a series connection path to be returned in two paths. A switching valve having a built-in four circuit is provided, and the flow paths of the hydraulic oil in the circuits connected to the hydraulic motor connection side and the opposite side with respect to the switching valve are the same, and the flow paths independent of each other are throttled. Traveling hydraulic circuit connected by a bypass flow path having a. 2. The traveling hydraulic circuit according to claim 1, wherein the equal flow control is enabled by a control valve having two spool valves in one body. 3. The control system according to claim 1, wherein said equal flow control is enabled by using a dedicated equal pump for each of two control valves having one spool valve in separate bodies. Traveling hydraulic circuit. 4. The traveling hydraulic circuit according to claim 1, wherein the equal flow control is enabled by a branching valve.