JPH03260470A - Closed circuit control device for liquid pressure for car running - Google Patents

Abstract

PURPOSE:To eliminate electric circuit by furnishing the pilot circuit to control the tilt angle of a main pump for running with No.1 and No.2 control valve for by-passing, controlling No.1, No.2 control valve with the liquid pressures on the pump discharge side and suction side, and judging if the car is in forward or reverse motion. CONSTITUTION:A closed circuit is formed from a main pump for running 1, a motor for running 3, and pipings 3, 4. A pilot circuit 23 is composed of a pilot valve 17 to be operated by a lever, a solenoid valve 19, pipings 20, 22, a regulator 21 and an aux. pump 15, and in connection with the pipings 20, 22, a No.1 and No.2 control valve for by-passing 26, 29 are furnished. A forward/reverse judgement selector valve 32 is furnished, which operates the No.1, No.2 control valves upon judgement whether the discharge side liquid pressure of the main pump has exceeded No.1 setting value or whether the suction side liquid pressure has exceeded No.2 setting value which is lower than the No.1, and the pump tilt angle is put in the neutral state by these No.1, No.2 control valves. Thus the control is made without use of any electrical circuit to achieve an enhanced reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a control device for controlling a traveling hydraulic closed circuit for driving a regular traveling hydraulic motor in a vehicle such as a government construction machine. It is something.

(Prior Art) In order to prevent over-speed of the prime mover and hydraulic pump for driving during engine braking, a conventional control device for a hydraulic closed circuit for driving of a vehicle is disclosed in Japanese Patent Application Laid-Open No. 6 (1-125455), for example.
As stated in the publication, the hydraulic pressure on the pump discharge side and the hydraulic pressure on the pump suction side of the main circuit were detected to obtain an electrical signal, which was then processed to control the hydraulic motor. .

(Problems to be Solved by the Invention) In the above conventional configuration, the electrical 1! ! Since it uses a circuit, it has the disadvantage of being unreliable due to severe vibration in vehicles such as industrial construction equipment. Also, the equipment was expensive.

(Means for Solving the Problems) In order to solve the above problems, a control device for a hydraulic closed circuit for running a vehicle according to the present invention controls a pump tilting angle of a main pump for running that is interposed in a main circuit. a pilot circuit that bypasses the pressure fluid of the pilot circuit when the hydraulic pressure on the pump discharge side of the main circuit exceeds a first set pressure, and adjusts the pump tilting angle of the main traveling pump to the hydraulic pressure. a first bypass control valve that gradually returns to a neutral state as the temperature increases;
When the hydraulic pressure on the pump suction side of the main circuit exceeds a second set pressure, the pressure liquid of the pilot circuit is bypassed and the pump tilting angle of the main pump for traveling is changed as the hydraulic pressure increases. a second bypass control valve that gradually returns to a neutral state; and a second bypass control valve that is actuated by the hydraulic pressure of the pilot circuit to supply hydraulic pressure on the pump discharge side of the main circuit to the first bypass control valve as pilot pressure. and a forward/reverse travel discrimination switching valve that supplies hydraulic pressure on the pump suction side of the main circuit to the second bypass control valve as a pilot pressure, and the first set pressure is set to the second set pressure. It is set higher than that.

(Function) The forward/reverse discrimination switching valve is operated by the hydraulic pressure of the pilot circuit, supplies the hydraulic pressure on the pump discharge side of the main circuit to the first bypass control valve as pilot pressure, and also supplies the hydraulic pressure on the pump discharge side of the main circuit to the first bypass control valve. The suction side hydraulic pressure is supplied to the second bypass control valve as pilot pressure.

The first bypass control valve bypasses the pressure fluid in the pilot circuit when the fluid pressure on the pump discharge side of the main circuit exceeds a first set pressure, and adjusts the pump tilting angle of the main traveling pump to the fluid pressure. As the temperature increases, the neutral state is gradually restored. The second bypass control valve bypasses the pressure fluid in the pilot circuit when the fluid pressure on the pump suction side of the main circuit exceeds a second set pressure, which is lower than the first set pressure. The pump tilt angle is gradually returned to the neutral state as the hydraulic pressure increases.

(Major Example) Hereinafter, one example of the present invention will be described based on FIGS. 1 and 2.

FIG. 1 is a circuit diagram of a hydraulic closed circuit for running a vehicle equipped with a control device according to an embodiment of the present invention. There is a pipe 2 at the -h° discharge port of the main pump 1 for advancement.
The other end of the pipe 2 is connected to one inlet of a traveling motor 3 consisting of a hydraulic motor. One end of a pipe 4 is connected to the other inlet of the travel motor 3, and the other end of the pipe 4 is connected to the other discharge port of the main travel pump 1. In other words, the main pump for running
A closed circuit is constituted by the piping 2, the traveling motor 3, and the piping 4, and this closed circuit constitutes the main circuit 5. One end of a pipe 6 is connected to the middle part of the pipe 2,
The other end of the pipe 6 is connected to the intermediate portion of the pipe 4. Check valves 7 and 8 are interposed in the pipe 6. The check valve 7 is located between the pipe 2 and the check valve 8, and allows pressure oil to pass only from the pipe 2 side to the check valve 8 side. Check valve 8 is connected to piping 4
Pressure liquid is allowed to pass only from the side to the reverse 112 valve 7 side. One end of the pipe 9 is connected to the middle part of the pipe 2, and the other end of the pipe 9 is connected to the middle 1fuJ section of the pipe 4. A reverse 11 valve 1 (1, 11) is installed in the pipe 9. The check valve 10 is located between the pipe 2 and the reverse 11/valve 11, and the check valve 10 is located between the pipe 2 and the reverse 11/valve 11. Passage of pressure oil only to: γ.Check valve 1
Allows the passage of pressure fluid only to the side. One end of piping 12 is connected to the portion of piping 6 between check valve 7 and check valve 8, and the other end of piping 12 is connected to check valve 10 of piping 9 and check valve 1.
It is connected to the part between 1 and 1. A relief valve 13 is installed in the pipe 12. One end of a pipe 16 is connected to the discharge port of an auxiliary pump 15 that is driven by a prime mover (not shown) in the same way as the main pump 1 for traveling, and the other end of the pipe 16 is connected to a first port of a pilot valve 17. has been done.

One end of a pipe 18 is connected to the second port of the pilot valve 17, and the other end of the pipe 18 is a solenoid valve that is operated based on the operation of a forward/reverse switching control lever (not shown)]9
is connected to the first port of the. One end of the piping 20 is connected to the second port of the solenoid valve 19, and the piping 20
The other end is connected to one hydraulic oil inlet/outlet of a regulator 21 that controls the pump tilt angle of the main pump 1 for traveling. A pipe 22 is connected to the other hydraulic oil inlet and outlet of the regulator 21.
One end of the pipe 22 is connected to the solenoid valve 19, and the other end of the pipe 22 is connected to the solenoid valve 19.
is connected to the third port of the The pilot valve 17 switches between a state in which the pipes 16 and the pipes 18 communicate with each other and a state in which they are cut off by operating a travel control lever (not shown), and continuously controls the pressure supplied from the pipe 16 to the pipe 18. Control. That is, the auxiliary pump 15, the piping 16, the pilot valve 17, the piping 18, the solenoid valve 19, the piping 20, the regulator 21, and the piping 22 constitute a pilot circuit 23 that controls the pump tilt angle of the main pump 1 for traveling. . One end of a pipe 25 is connected to the middle part of the pipe 20, and the other end of the pipe 25 is connected to a first bypass control valve 26.
It is connected to the port of No. 1. One end of a pipe 27 is connected to the second port of the first bypass control valve 26, and the other end of the pipe 27 is connected to an intermediate portion of the pipe 22. One end of a pipe 28 is connected to the intermediate portion of the pipe 25, and the other end of the pipe 28 is connected to the first ports of two second high-bus control wells. One end of a piping 30 is connected to the second port of the second bypass control valve 29, and the other end of the piping 30 is connected to an intermediate portion of the piping 27. One end of a pipe 31 is connected to the intermediate part of the pipe 28, and the other end of the pipe 31 is connected to a switching valve 3 for determining forward/reverse movement.
It is connected to one pilot pressure supply port of 2. One end of a pipe 33 is connected to the intermediate portion of the pipe 27, and the other end of the pipe 33 is connected to the other pilot pressure supply port of the forward/reverse motion determination switching valve 32. Forward/forward discrimination switching valve 3
One end of the piping 35 is connected to the first port of the piping 2, and the other end of the piping 35 is connected to the intermediate portion of the piping 2.

A throttle 36 is interposed in the pipe 35.

One end of a pipe 37 is connected to the second port of the switching valve 32 for forward/reverse motion determination, and the other end of the pipe 37 is connected to an intermediate portion of the pipe 4. A throttle 38 is interposed in the pipe 37. One end of a pipe 39 is connected to the third port of the switching valve 32 for forward/reverse motion discrimination, and the other end of the three pipes is connected to a second port.
It is connected to the pilot pressure supply port of the bypass control valve 29.

One end of a piping 40 is connected to the fourth port of the forward/reverse switching valve 32, and the other end of the piping 40 is connected to a pilot pressure supply port of the first bypass control valve 26. That is, when the hydraulic pressure supplied to the pilot pressure supply port of the bypass control valve 26 of l; 1181 via the pipe 40 exceeds the first set pressure determined by the spring force of the spring 26a, the first bypass The control valve 26 is actuated to communicate the first port and the second port, and the flow passage cross-sectional area of the communication passage corresponds to the difference between the oil pressure supplied to the pilot pressure supply port and the first set pressure. It gradually becomes larger. Further, when the hydraulic pressure supplied to the pilot pressure supply ports of the two second bypass control valves via the piping 39 exceeds the second set pressure determined by the spring force of the spring 29a, the second bypass control valve 29 is actuated to communicate the first port and the second port, and the flow path disconnection IIj product of the communication path corresponds to the star of the oil pressure supplied to the pilot pressure supply port and the second set pressure. It gradually becomes larger. One end of a pipe 41 is connected to the intermediate portion of the pipe 16, and the other end of the pipe 41 is connected to a tank flow path. A support valve 42 is interposed in the pipe 41. One end of a fitting 43 is connected to the intermediate portion of the pipe 16, and the other end of the pipe 43 is connected to a portion of the pipe 9 between the check valve 10 and the check valve 11.

Next, I will explain the operation. Now, the main driving pump 1 and the auxiliary pump 15 are driven by the engine, and the piping 16 and the piping 18 are connected through the pilot valve 17. ! It is assumed that the pipe 18 and the pipe 20 communicate with each other, and the pipe 22 communicates with the tank flow path. In this state, the main pursuit pump 1 discharges pressure from one outlet, and the traveling motor 3 rotates in the normal direction, so that the vehicle moves forward. For example, assume that in the main circuit 5, the pipe 2 is on the high pressure side and the pipe 4 is on the low pressure side. In addition, the hydraulic pressure on the pressure surface of the distribution F 20 is supplied to one pilot pressure supply port of the switching valve 32 for forward/reverse determination through the pipes 25, 28, and 31. The pipe 35 and the pipe 40 communicate with each other, and the pipe 37 and the three pipes communicate with each other. Therefore, the hydraulic pressure of the pressure oil in pipe 2 is the same as that in pipe 35 and pipe 40.
The hydraulic pressure of the pressure oil in the pipe 4 is supplied to the pilot pressure supply port of the first bypass control valve 26 via the pipe 37 and the pipe 39, and the pilot pressure is supplied to the second bypass control valve 29 via the pipe 37 and the pipe 39. fed into the mouth. Here, the load on the travel motor 3 increases, the oil pressure of the pressure oil in the pipe 2 increases, and the oil pressure supplied to the pilot pressure supply port of the first bypass control valve 26 exceeds the first set pressure. Then, the first bypass control valve 26 is activated, the pipe 25 and the pipe 27 are brought into communication, and a part of the pressure oil in the pipe 20 is bypassed to the pipe 22.

The flow path cross-sectional area of the communication path between the piping 25 and the piping 27 corresponds to the difference between the oil pressure supplied to the pilot pressure supply port of the first bypass control valve 26 and the first set pressure. As the oil pressure increases, the flow rate of the pressure oil bypassed from the pipe 20 to the pipe 22 increases, the pump tilt angle of the main pump 1 for traveling decreases, and the discharge amount gradually decreases.

-X, downhill, etc., the running motor 3 is forcibly adapted to act as a pump, and the main running pump 1 acts as a motor. In this state, the pipe 4 is on the high pressure side and the pipe 2 is on the low pressure side. When the oil pressure of the pressure oil in the pipe 4 increases and the oil pressure supplied to the pilot pressure supply port of the second bypass control valve 29 exceeds the second set pressure,
The second bypass control valve 29 is actuated to communicate the pipe 28 and the pipe 30, and a portion of the pressure oil in the pipe 20 is bypassed to the pipe 22. The cross-sectional area of the communication path between the pipe 28 and the pipe 30 corresponds to the difference between the oil pressure supplied to the pilot pressure supply port of the second bypass control valve 29 and the second set pressure. As the oil pressure of the pressure oil increases, the flow rate of the pressure oil bypassed from the pipe 20 to the pipe 22 increases, and the pump tilt angle of the main pump 1 for traveling decreases, causing the pump 1
absorption torque decreases. Here, the second set pressure is
The relationship between the hydraulic pressure P of the pressure oil in the pipe 4 during engine braking or the pressure oil P in the pipe 2 during non-engine braking and the pump tilt angle α of the main pump 1 for following is lower than the set pressure of It will look like Figure 2. In Fig. 2, the horizontal axis is the oil pressure P1, the vertical axis is the pump tilt angle α, the thick line A is the pump absorption torque diagram during non-engine braking, and the broken line B is the pump absorption torque diagram during engine braking. C is the output torque diagram of the prime mover when the engine is not braking,
The broken lines each indicate the absorption torque diagram that the prime mover can withstand during engine braking. These are pilot valve 1
This is the characteristic when the output by No. 7 is maximized and the pressure in the 18 parts of the piping is adjusted to the maximum.

When the solenoid valve 19 is switched to the reverse state, the hydraulic pressure of the pressure oil in the pipe 22 is supplied to the other pilot pressure supply port of the forward/reverse determination switching valve 32 via the pipe 27 and the pipe 33. The advance determination switching valve 32 is switched, the hydraulic pressure of the pressure oil in the pipe 4 is supplied to the pilot pressure supply port of the first bypass control valve 26, and the hydraulic pressure of the pressure oil in the pipe 2 is supplied to the second bypass control valve. 29 is supplied to the pilot pressure supply port. Therefore, as is clear from the symmetry of the main circuit 5, the same control operation is performed when the vehicle is moving backward as when it is moving forward.

In this way, when the prime mover acts as a pump, the absorption torque of the prime mover is smaller than during normal operation, so if the absorption torque diagram of the main pump 1 for driving is set to be smaller during engine braking than when non-engine braking, Since the prime mover can always be used in its optimum state without overloading the prime mover, its power can be utilized to the fullest, and over-synchronization of the prime mover, main pump 1 for traveling, and motor 3 can be effectively prevented, resulting in a long life. It is possible to aim for Furthermore, since no electrical circuit is used, there is no reduction in reliability due to vibration, and furthermore, the manufacturing cost is low.

(Effects of the Invention) As explained above, according to the present invention, the pilot circuit that controls the pump tilting angle of the main pump for travel installed in the main circuit and the hydraulic pressure on the pump discharge side of the main circuit The first control for Ibus bypasses the pressure fluid in the pilot circuit and gradually returns the pump tilting angle of the main pump for travel to a neutral state as the fluid pressure increases when the pressure exceeds the set pressure. When the hydraulic pressure on the pump suction side of the main circuit exceeds the second set pressure, the pressure wave of the pilot circuit is bypassed and the pump rotation angle of the running soil pump is gradually neutralized as the hydraulic pressure increases. a second bypass control valve that is operated by the hydraulic pressure of the pilot circuit to supply hydraulic pressure on the discharge side of the main circuit pump to the first bypass control valve as pilot pressure; A switching valve for determining forward/reverse movement is provided to supply fluid pressure on the suction side to a second bypass control valve as a pilot pressure, and the first set pressure is set higher than the second set pressure, so that when the engine is braked, Since the absorption torque diagram of the main drive pump is set to be smaller than when the engine is not braking, the prime mover can always be used in the optimum condition, making the most of its power, and also reducing overload of the prime mover, main drive pump, and motor. It is possible to effectively prevent rotation and extend the service life. Also, since no electrical circuit is used,
There is no reduction in reliability due to vibration, and the manufacturing cost is low.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a hydraulic closed circuit for running in a vehicle equipped with a control device according to a major embodiment of the present invention, and Fig. 2 shows the hydraulic pressure of the main circuit in the same circuit and the pump inclination of the main pump for running. FIG. 3 is an explanatory diagram of the relationship with rotation angle. DESCRIPTION OF SYMBOLS 1... Main pump for running, 5... Main circuit, 23... Pilot circuit, 26... First bypass control valve, 2
32... Second bypass control valve, 32... Forward/forward determination switching valve

Claims (1)

[Claims] 1. A pilot circuit that controls the pump tilting angle of the main pump for traveling installed in the main circuit, and a pilot circuit that controls the pump tilt angle of the main pump for traveling when the hydraulic pressure on the pump discharge side of the main circuit exceeds a first set pressure. a first bypass control valve that bypasses pressure fluid to gradually return the pump tilting angle of the main traveling pump to a neutral state as the fluid pressure increases; and a fluid on the pump suction side of the main circuit. A second system that bypasses the pressure fluid in the pilot circuit when the pressure exceeds a second set pressure, and gradually returns the pump tilting angle of the main traveling pump to a neutral state as the fluid pressure increases. a bypass control valve operated by the hydraulic pressure of the pilot circuit to supply hydraulic pressure on the pump discharge side of the main circuit to the first bypass control valve as pilot pressure, and a pump suction side of the main circuit; a switching valve for determining forward/reverse movement that supplies the hydraulic pressure to the second bypass control valve as a pilot pressure, and the first set pressure is set higher than the second set pressure. A control device for the hydraulic closed circuit for vehicle running.