JPH07213108A - Hydraulic pressure controlling apparatus for power vehicle - Google Patents

Abstract

PURPOSE:To obtain a compact-sized low-cost apparatus for the control of hydraulic pressure of a power vehicle such as tractor. CONSTITUTION:This hydraulic oil pressure controlling apparatus is provided with a hydraulic oil supplying channel 28 between a single action hydraulic cylinder 6 and a hydraulic pump 25 inserted in a working machine lifting system, an oil-discharging channel 48 between the hydraulic cylinder 6 and a hydraulic oil tank 26, a lifting electromagnetic proportional control valve 29 inserted in the hydraulic oil supplying channel 28 and a lowering electromagnetic proportional control valve 30 inserted in the oil discharging channel 48. Both of the electromagnetic proportional control valves 29, 30 are composed of shut-off valves 33, 36 and pilot-operation type pressure control valves 32, 37.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control system for a power vehicle such as a tractor.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 3, a hydraulic control device of this type is used for raising a hydraulic oil supply oil passage 28f connecting a hydraulic cylinder 6f for lifting a working machine and a hydraulic pump 25f. An electromagnetic proportional control valve 29f, a descending electromagnetic proportional control valve 30f, and a rapid descending valve 24f are provided so as to intervene, and when a descending command is input to a control unit (not shown), the descending electromagnetic proportional control valve 30f And the solenoid of the rapid lowering valve 24f are both excited, and only when the pressure in the hydraulic cylinder 6f falls below a predetermined pressure, the rapid lowering valve 24f switches to the side communicating with the tank 26f and flows into the hydraulic cylinder 6f. The working oil is discharged to the hydraulic tank 26f and the lift arm is rotated downward.

The rapid lowering valve 24f is used when a working machine is not connected to a lift arm such as a tractor.
This is provided in order to enable the lift arm to rotate downward when the pressure in the hydraulic cylinder 6f is reduced.

[0004]

By the way, in the case of such a conventional device, the descending electromagnetic proportional control valve 30 is usually used.
While controlling the solenoid 51f of f, the hydraulic oil in the back chamber of the holding check valve 50f is discharged to adjust the opening of the holding check valve 50f to change the descending speed of the working machine. In such a configuration,
Since special valves such as the rudding check valve 50f and the rapid lowering valve 24f are required, the number of parts is increased, the manufacturing cost is increased, and the valve structure itself is complicated.

[0005]

The present invention has been proposed in view of the above-mentioned problems, and therefore, the following technical means have been taken. That is, the hydraulic oil supply oil passage 28 is formed between the hydraulic cylinder 6 for moving up and down the working machine connected to the machine body and the hydraulic pump 25.
6 and a hydraulic tank 26, an oil discharge passage 48 is formed, an ascending electromagnetic proportional control valve 29 is provided in the pressure oil supply oil passage 28, and a descending oil flow passage 48 is provided in the oil discharge passage 48. In a hydraulic control device for a power vehicle in which an electromagnetic proportional control valve 30 is installed,
The rising electromagnetic proportional control valve 29 is a first opening / closing valve 33 for rising.
And a pilot-operated first pressure control valve 32, and the descending electromagnetic proportional control valve 30 is composed of a second descending on-off valve 36 and a pilot-operated second pressure control valve 37. A hydraulic control device for a power vehicle is configured as described above.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. First, the structure will be described. 1 is a tractor,
Front and rear wheels 2 and 3 are provided at the front and rear portions of the body, respectively, and are configured to transmit the rotational power of the engine 4 to the propulsion shaft of the rear wheels 3 via a transmission device (not shown) in the mission case 5. ing.

A hydraulic cylinder case 7 having a single-acting hydraulic cylinder 6 for raising and lowering the working machine is provided above the mission case 5. The hydraulic cylinder case 7 is provided on both left and right sides of the hydraulic cylinder case 7. Lift arms 8, 8 are rotatably attached to the section. Lower links 9, 9 are pivotally attached to the lower rear part of the body of the tractor-1, and lift rods 11, 11 are interposed between the lower links 9, 9 and the lift arms 8, 8. There is. Further, a rotary tiller 14 is movably connected to a rear portion of a three-point link device 13 including a top link 12 connected to the upper rear part of the machine body and a pair of left and right lower links 9, 9.

Next, the hydraulic circuit shown in FIG. 2 will be described. The hydraulic pump 25 driven by the rotational power of the engine 4 and the hydraulic cylinder 6 are connected by a pressure oil supply oil passage 28, and an ascending electromagnetic proportional control valve 29 and a descending electromagnetic proportional control valve 30 are provided therebetween. Is installed. The rising electromagnetic proportional control valve 29 is composed of a first opening / closing valve 33, which is a rising / closing valve, and a pilot pressure-operated first pressure control valve 32. Three
Reference numeral 4 is a pressure compensation valve. The first opening / closing valve 33 is a chamber 33 that shuts off the connection between the hydraulic cylinder 6 and the hydraulic pump 25.
a and a chamber 33b in which the hydraulic cylinder 6 and the hydraulic pump 25 communicate with each other, and normally, the pressure oil supply oil passage 28 is shut off by the pressing force of the spring 33c. When a current is applied to the solenoid 32a of the first pressure control valve 32, a back pressure is applied to the first opening / closing valve 33, and the opening of the first opening / closing valve 33 changes in response to a change in pilot pressure. The amount of working pressure oil sent to the cylinder 6 is adjusted to change the rising speed.

The pressure compensating valve 34 discharges the hydraulic oil from the hydraulic pump 25 to the hydraulic tank 26 when the first opening / closing valve 33 is not operating, and pumps when the first opening / closing valve 33 is switched to the rising side. The side pressure acts as a back pressure on the pressure compensating valve 34 and confines the pressure in the pressure oil supply oil passage 28. On the other hand, the descending electromagnetic proportional control valve 30 has a second opening / closing valve 36 as a descending side opening / closing valve and a pilot operated second pressure control valve 37, and the second opening / closing valve 36 is a hydraulic cylinder-6. 36a for cutting off the communication between the hydraulic tank 26 and the hydraulic tank 26
And a chamber 36b for maintaining the communication state, and in the normal state, the spring 38 is switched to a side for preventing discharge of the hydraulic oil in the hydraulic cylinder-6.

The second pilot-operated pressure control valve 37 is provided with oil passages 40 and 41 so that the hydraulic cylinder 6 is a cylinder on the side thereof.
Both the pressure and the pump pressure on the hydraulic pump 25 side are applied. That is, the oil discharge passage 48 of the hydraulic cylinder-6.
The oil passage 40 branched from and the oil passage 41 branched from the pressure oil supply oil passage 28 are configured to be hooked on the second pressure control valve 37. Further, in the middle of the oil passages 40 and 41, the check valve 42,
43 is interposed.

When a current is applied to the solenoid 37a of the second pressure control valve 37, the back pressure acts on the second opening / closing valve 36, and the second opening / closing valve 36 is switched to the chamber 36b side so that the inside of the hydraulic cylinder-6 is closed. The hydraulic oil of the above is discharged into the tank 26, and the lift arms 8 and 8 are lowered. The opening of the second opening / closing valve 36 can be adjusted by changing the value of the current flowing through the solenoid 37a of the second pressure opening / closing valve 37, and the amount of hydraulic oil discharged from the hydraulic cylinder 6 to the tank 26 can be adjusted. To change the descent speed.

Next, the operation of the above example will be described. Tractor-1
When the engine 4 is rotated to drive the hydraulic pump 25, the working pressure oil passes through the pressure oil supply oil passage 28 and reaches the rising electromagnetic proportional control valve 29 first. Hydraulic operation lever not shown,
When a signal on the work machine rising side is input to the control unit by the lifting switch or the like, the solenoid 32a of the first pressure control valve 32 is excited and the pilot pressure is supplied to the first opening / closing valve 3 via the oil passage 46.
As a result, the first opening / closing valve 33 is switched to the chamber 33b side, pressure oil is supplied to the hydraulic cylinder-6, and the lift arms 8 and 8 are raised. On the other hand, when a hydraulic operating lever (not shown), an elevating switch, etc. are operated to output a signal on the lower side to the lowering electromagnetic proportional control valve 30, the solenoid 37a of the pilot operated second pressure control valve 37 is excited, The oil passage 45 communicates with the oil passages 40 and 41, whereby
The internal pressure on the hydraulic cylinder 6 side or the pressure on the hydraulic pump 25 side is applied to the second opening / closing valve 36, and is switched to the chamber 36b side, and the hydraulic oil in the hydraulic cylinder 6 is collected in the hydraulic tank 26.

[0013]

As described above, according to the present invention, the hydraulic cylinder 6 for lifting and lowering the working machine connected to the machine body and the hydraulic pump 25.
And a hydraulic oil supply oil passage 28 is formed between the hydraulic cylinder 6 and the hydraulic tank 26, and an oil discharge passage 48 is formed between the hydraulic cylinder 6 and the hydraulic tank 26. Valve 2
In the hydraulic control device for a power vehicle in which 9 is installed, and an electromagnetic proportional control valve 30 for descending is installed in the oil discharge passage 48, the electromagnetic proportional control valve 29 for ascending is the first electromagnetic proportional control valve for ascending. It is composed of an on-off valve 33 and a pilot operated first pressure control valve 32, and the descending electromagnetic proportional control valve 30 is composed of a second descending on-off valve 36 and a pilot operated second pressure control valve 37. Therefore, at the time of supplying and discharging the operating pressure oil to the hydraulic cylinder 6, by simply energizing the pressure control valves 32 and 37 of both upward and downward pilot operation type, the on-off valve 33 corresponding thereto is supplied. , 36 can be controlled accurately, and as a result, a special valve such as a rapid lowering valve required in the past can be dispensed with, which can be constructed at a low cost, and the structure of the valve can be simplified to make the entire apparatus compact.

[Brief description of drawings]

FIG. 1 is an overall side view of a tractor.

FIG. 2 is a hydraulic circuit diagram.

FIG. 3 is a hydraulic circuit diagram of a conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 tractor 6 hydraulic cylinder 8,8 lift arm 13 3 point link device 14 rotary tiller 25 hydraulic pump 28 pressure oil supply oil passage 29 rising electromagnetic proportional control valve 30 falling electromagnetic proportional control valve 32 First pressure control valve 33 First opening / closing valve 34 Pressure compensation valve 36 Second opening / closing valve 37 Second pressure control valve

Claims (1)

[Claims] 1. A pressure oil supply oil passage 28 between a hydraulic cylinder 6 for raising and lowering a working machine connected to a machine body and a hydraulic pump 25.
Is formed, an oil discharge passage 48 is formed between the hydraulic cylinder 6 and the hydraulic tank 26, and an ascending electromagnetic proportional control valve 29 is provided in the pressure oil supply oil passage 28. In the hydraulic control system for a power vehicle in which the descending electromagnetic proportional control valve 30 is provided in the oil passage 48, the ascending electromagnetic proportional control valve 29 includes the ascending first opening / closing valve 33 and the pilot operated type. 1 power control valve 32, and the lowering electromagnetic proportional control valve 30 is configured by a second lowering opening / closing valve 36 and a pilot operated second pressure control valve 37. Vehicle hydraulic control device.