JPH0382682A - Hydraulic circuit for tractor - Google Patents

Abstract

PURPOSE:To utilize a hydraulic pump with a small displacement and efficiently operate is by providing a main hydraulic circuit and an auxiliary hydraulic circuit, and providing a load sensing valve device feeding the operating oil of a main pump to an auxiliary hydraulic device when the main hydraulic circuit is nonoperational. CONSTITUTION:A main hydraulic circuit 1 feeding the operating oil to a main hydraulic device 7 for lifting a three-point link mechanism 6 from a main pump 4 via a main pipe 5 and an auxiliary hydraulic circuit 2 feeding the operating oil to an auxiliary hydraulic device 10 from an auxiliary pump 8 via an auxilia ry pipe 9 are provided. A load sensing valve device 3 with a spring offset pilot type three-port two-point selector valve 19 is provided, the pressure of a pilot circuit 20 is reduced when the main hydraulic device 7 is nonoperational, thus the selector valve 19 is switched to the right position, and the operating oil of both pumps 4 and 8 is merged at this switching position and fed to the auxil iary hydraulic device 10. The auxiliary pump 8 with a small displacement can be employed.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a hydraulic circuit for a tractor.

(Prior Art) A tractor has a three-point linkage mechanism for attaching a working machine such as a rotary tiller, and is provided with a hydraulic device for raising and lowering the three-point linkage mechanism.

In order to supply hydraulic fluid to the three-point link mechanism lifting hydraulic system, piping is provided from the hydraulic pump to the hydraulic system.

In addition, the tractor can be equipped with other working machines such as a front loader, and in order to supply hydraulic oil to these working machines, the hydraulic oil is branched from the hydraulic piping via an auxiliary control valve (for example, Jitsugan Showa 59-
147539 specification and drawings).

The hydraulic circuit of the conventional tractor is designed on the premise that the hydraulic system for raising and lowering the three-point linkage mechanism and the hydraulic system for the work equipment are never used at the same time, and that only one of them is used. It had been.

(Problem to be Solved by the Invention) By the way, depending on the type of work equipment attached to the three-point linkage mechanism, there are cases in which it is desired to raise and lower the work equipment and at the same time operate a hydraulic system provided on the work equipment. .

However, the conventional hydraulic circuit cannot operate both at the same time.

On the other hand, when two hydraulic devices are operated simultaneously, the conventional one
One hydraulic pump would not have enough capacity. Therefore, it is possible to install two hydraulic pumps and provide dedicated piping for each, but since lifting and lowering of the three-point linkage mechanism is not something that is done all the time, it is not recommended to add one hydraulic pump exclusively for this purpose. will be wasted.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a hydraulic circuit for a tractor that can be used efficiently by adding the minimum required small-capacity hydraulic pump.

(Means for Solving the Problems) In order to achieve the above object, the present invention takes the following measures. That is, the characteristics of the hydraulic circuit of the tractor of the present invention are that the main hydraulic circuit supplies hydraulic oil from the main pump to the main hydraulic system through the main piping, and the hydraulic circuit supplies hydraulic oil from the auxiliary pump to the auxiliary hydraulic system through the auxiliary piping. an auxiliary hydraulic circuit that supplies hydraulic oil; and a load sensing valve device that connects the main piping and the auxiliary piping to supply hydraulic oil from the main pump to the auxiliary hydraulic system when the main hydraulic system is not in operation. The point is that it is equipped.

(Function) According to the present invention, there is a main hydraulic circuit that supplies hydraulic oil from the main pump to the main hydraulic system via the main piping, and an auxiliary hydraulic circuit that supplies hydraulic oil from the auxiliary pump to the auxiliary hydraulic system via the auxiliary piping. Since the hydraulic circuit is provided, the main hydraulic system and the auxiliary hydraulic system can be operated simultaneously.

Furthermore, when the main hydraulic system is not operating, the main hydraulic system is equipped with a load sensing valve device that connects the main pipe and the auxiliary pipe to supply hydraulic oil from the main pump to the auxiliary hydraulic system. When not in use, the main pump's hydraulic fluid is supplied to the auxiliary hydraulic system. Therefore, the auxiliary pump is
A small-capacity device that can supply the minimum hydraulic pressure to the auxiliary hydraulic system required when the main hydraulic system and the auxiliary hydraulic system are used at the same time is sufficient.

(Example) Embodiments of the present invention will be described below based on the drawings.

In the drawing, 1 is the main hydraulic circuit, 2 is the auxiliary hydraulic circuit, and 3 is the main hydraulic circuit.
is a load sensing valve device.

The main hydraulic circuit 1 supplies hydraulic oil from the main pump 4 via the main pipe 5 to the main hydraulic system 7 for lifting and lowering the three-point linkage mechanism 6, and the auxiliary hydraulic circuit 2 supplies hydraulic oil from the auxiliary pump 8 to the main hydraulic system 7 for lifting and lowering the three-point link mechanism 6. The load sensing valve device 3 supplies hydraulic oil to the auxiliary hydraulic system 10 via the piping 9, and the load sensing valve device 3 connects the main piping 5 and the auxiliary piping 9 to the main pump 4 when the main hydraulic system 7 is not operating. The hydraulic oil is supplied to the auxiliary hydraulic system 10.

The main pipe 5 includes a first pipe line 11 that connects the main pump 4 and the load sensing valve device R3, and a second pipe line 11 that connects the load sensing valve device 3 and the main control valve device 12 that controls the main hydraulic device 7. The pipe line 13 and the main control valve system [12 and the main hydraulic system 7 are connected to each other]
It is mainly composed of a conduit 14.

The auxiliary pipe 9 includes a fourth pipe IG that connects the auxiliary pop 8 and the auxiliary control valve device 15 that controls the auxiliary hydraulic circuit 0, and a fifth pipe IG that connects the auxiliary control valve device 15 and the auxiliary hydraulic device 10. It consists of a conduit 17.

The load sensing valve assembly W3 and the fourth conduit 16 are connected by a confluence conduit 18.

The load sensing valve device 3 has a spring-off center pilot type three-bottom, two-position switching valve 19, an inlet port of the switching valve 19 is connected to the first pipe line 11, and a first outlet is connected to the first pipe line 11. 2 conduit 13, and the second outlet is connected to confluence conduit I8. And the first pipe line 1
A first pilot circuit 20 is connected between the second pipe line 13 and the switching valve 19 .

The main control valve device 12 connects the pressure reducing valve 21 connected to the second pipe line 13, the control valve 23 connected to the outlet line 22 of the pressure reducing valve 21, and the control valve 23 and the third pipe line 14. A drain circuit 26 is connected to the supply path 24 via a check valve 25.
and a second pilot circuit 28 that connects the control valve 23 and the three-point/two-position switching valve 19. This second pilot circuit 28 is connected to the outlet path 22 and the supply path 2 by the control valve 23.
4 is connected to the supply line 24, and when pressure is built up in the second pilot circuit 28, the first line 11 and the second line 13 are connected. The one-point and two-position switching valve 19 is operated.

Note that 29 is a main relief valve, 30 is a relief valve of the sensing valve device 3, and 31, 32, and 33 are check valves.

According to the hydraulic circuit configured as described above, the hydraulic oil of the auxiliary pump 8 is constantly supplied to the auxiliary hydraulic system 10 via the auxiliary circuit 9.

First, when the main control valve 23 is in the "off" state shown in the figure and the first pipe line 11 and the second pipework 3 are connected, the hydraulic oil from the main pump 4 is supplied to the second pipe line 13. The pressure increases, and the pressure in the first pilot circuit 20 also increases, operating the three-bottom, two-position switching valve 19, and connecting the first conduit 11 and the merging conduit 18.

When the main hydraulic system 7 is not operating, the hydraulic oil from the main pump 4 flows through the confluence pipe 18 to the auxiliary pipe 9, joins with the hydraulic oil from the auxiliary pump 8, and flows to the auxiliary hydraulic system 10. Supplied.

Next, in order to operate the main hydraulic system 7, the main control valve 23 is operated to connect the outlet passage 22 and the supply passage 24.
The pressure of the first viroft circuit 20 decreases.
pressure decreases, the 3-point/2-position switching valve 19 is restored by the spring force, the first pipe line 11 and the second pipe line 13 are brought into communication, and the hydraulic oil of the main pump 4 is transferred to the main hydraulic system 7. Supplied. Thereby, the pressure in the second viroft circuit 28 increases, and the three-point/two-position switching valve 19 maintains the communication state between the first conduit 11 and the second conduit 13.

Next, operate the main control valve 23 to
2 and the supply line 24, the pressure in the second pilot circuit 28 decreases, the pressure in the first pilot circuit 20 increases, and the first conduit 11 and the merging conduit 18 become in communication. .

By moving the main control valve 23 further upward, the lever 34 pushes the pushing piece 35 of the check valve 25, thereby bringing the return path 27 and the drain circuit 26 into communication.

Note that the present invention is not limited to the above embodiments.

(Effects of the Invention) According to the present invention, the main hydraulic system and the auxiliary hydraulic system can be operated simultaneously. Moreover, since the main pump is configured to supply hydraulic oil to the auxiliary hydraulic system when the main hydraulic system is not in operation, the auxiliary pump can be of a minimum capacity, which is economical.

[Brief explanation of drawings]

The drawing is a hydraulic circuit diagram of a tractor showing an embodiment of the present invention. l...Main hydraulic circuit, 2...Auxiliary hydraulic circuit, 3...
Load sensing valve device 1, 4...main pump, 5
...Main piping, 7.. Main hydraulic system, 8.. Auxiliary pump, 9.. Auxiliary piping, 10.. Auxiliary hydraulic system.

Claims (1)

[Claims] (1) A main hydraulic circuit that supplies hydraulic oil from the main pump to the main hydraulic system via the main piping, an auxiliary hydraulic circuit that supplies hydraulic oil from the auxiliary pump to the auxiliary hydraulic system through the auxiliary piping, and the main hydraulic system. A hydraulic circuit for a tractor, comprising a load sensing valve device that connects a main pipe and an auxiliary pipe to supply hydraulic oil from a main pump to an auxiliary hydraulic device when the device is not in operation.