JPS5934005A - Hydraulic circuit of variable-capacity pump - Google Patents

Abstract

PURPOSE:To select an automatic operation or a manual operation by producing pilot pressure in two systems, a manually-operated reducing valve and a solenoid valve in a circuit for controlling the discharge quantity of a variable-capacity hydraulic pump by pilot pressure. CONSTITUTION:An apparatus for supplying and discharging pressurized oil from a variable-capacity pump 1 to and from an actuator through a direction changing valve 4 includes manually-operated variable reducing valves 7, 8. Respective inlet ports of the valves are connected to a pilot fixed pump 2 and the outlet ports thereof are respectively connected to solenoid on-off valves 9, 10. The outlets of these valves 9, 10 are branched in three directions, and one branch oil path is connected to right and left pilot ports of the direction changing valve 4. Another branch oil path is connected to each other through a shuttle valve 11, so that pilot pressure P2 from the valve 11 is conducted to a slant plate control cylinder 5 and a control valve 6. The remaining branch oil path is connected to output ports of solenoid on-off valves 12, 13 connected to a supply pipeline of the pump 2.

Description

[Detailed description of the invention] The present invention relates to a hydraulic circuit that controls the discharge amount of a pump.

In general, construction machinery uses manual operation to operate the hydraulic mechanism that is its driving source. In recent years, there has been a demand for automation in construction machinery, and it has become necessary to have a mechanism that can be operated manually or automatically depending on the construction site.

Therefore, it is an object of the present invention to provide a hydraulic circuit that meets this need.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a hydraulic circuit diagram according to the present invention.

In Fig. 1, 1 is a variable displacement hydraulic pump.

2 is a fixed pump for the pilot, 3 is a hydraulic motor which is an actuator, and 4 is a hydraulic pilot operation direction switching valve. When the #I+pressure pilot operation direction switching valve 4 is switched, the pressure oil from the hydraulic pump 1 is transferred to the actuator. Supply and discharge to the hydraulic motor 3. 5 is a control cylinder for controlling the swash plate angle of the variable displacement hydraulic pump 1, and 6 is a control valve.

7 and 8 are manual variable pressure reducing valves, and the inlet side boat is connected to the pilot fixed pump 2. The exit side boat is a solenoid on/off valve 9. Connect with 10-1.

The outlet sides of the electromagnetic on/off valves 9 and 10 are branched into three directions.

One branch oil passage of each electromagnetic on-off valve 9, 10 is connected to the left and right pilot boat of the directional control valve 4, and the other branch oil passage is connected to each other via the shuttle valve 11, and the pilot boat is connected to the pilot boat from the shuttle valve 11. Control cylinder 5. as pressure Ps. The pilot pressure Alt is connected to the control valve 6, and the discharge amount of the variable displacement hydraulic pump 1 is controlled by the pilot pressure Ps. Solenoid on-off valve 12.1
Connect to the outlet side boat of 3, solenoid on-off valve 12.13
The inlet side boats are each connected to the supply oil line of the fixed pilot pump 2. Further, this supply r'+It path is connected so that pilot pressure oil is supplied to the spring chamber of the control cylinder 5 as pilot pressure PT.

In addition, 14 is the safety relief valve of the system side circuit, 15
is the safety relief valve of the pilot circuit. The pump characteristics of the hydraulic pump 1 are as shown in FIG. 2, and the electromagnetic on/off valves 9.1.0, 12, and 13 are connected to an electric circuit 1 (not shown) and are operated in response to an electric signal from the electric circuit 1.

In the hydraulic circuit constructed in this manner, the solenoid on/off valves 9 and 10 are opened during manual operation, and the solenoid on/off valves 12 and 13 are closed (as shown in FIG. 1). Hydraulic pump 1
, 2 are both driven by a drive means shown in the figure, and pressure oil is discharged from the hydraulic pumps 1 and 2. When one of the manual pressure reducing valves 7 and 8 is operated, for example, when the manual pressure reducing valve 7 is operated, the pressure oil of the fixed pilot pump 2 is sent to the electromagnetic on-off valve 9 in accordance with the operation of the manual pressure reducing valve 7. , one pressure oil flows into the right boat of the directional switching valve and switches the directional switching valve 4. The other side, which has passed through the electromagnetic on-off valve 9, is pyromagnetic from the shuttle valve 11.

As the pressure Ps, the control cylinder 5. The control valve 6 is operated to control the discharge amount of the /11] pressure pump as shown in FIG. The pressure oil sent from the hydraulic pump 1 in this way reaches the hydraulic motor 31 via the directional control valve 4, and then the hydraulic motor 3
Rotate forward (or reverse).

Similarly, when manual pressure reducing valve 8 is activated, solenoid on-off valve 1
0, the pressure 411 flows into the pilot pressure oil passage (Ps ura passage) via the left boat of the directional control valve 4 and the twist valve 11, and performs the operation opposite to the above.

Next, to explain the automatic mode, solenoid on/off valves 9 and 13 (
Alternatively, 12) is closed, and solenoid on/off valves 10 and 12 (or 13) are opened. Hydraulic pumps 1 and 2 are both driven by a drive means shown in the figure, and I? Pressure oil is discharged from the I+ pressure pumps 1 and 2.

The pressure oil of the fixed pilot pump 2 is sent to the electromagnetic on-off valve (because the manual pressure reducing valves 7 and 8 are not operated, the pressure oil is cut before the pressure reducing valve 7.8).One pressure oil is directional. The right boat ζ of the valve 4 flows in and switches the direction switching valve 4. The other side that has passed through the electromagnetic on-off valve 12 is applied to the control cylinder 5. as a pilot pressure Ps by the shuttle valve 11. control valve 6
is operated to control the discharge amount of the hydraulic pump 1 as shown in FIG. Note that point A in FIG. 2 is the switching pressure of the directional switching valve 4. The subsequent operations are the same as in the manual operation, so their explanation will be omitted.

In this way, according to this embodiment, there are 1 manual pressure reducing valve 7.8, an electromagnetic on/off valve 9, 10.12.13. Tsuyatle valve 1
To provide a simple hydraulic circuit combining 1.

It is possible to select between two systems: manual and automatic.

In short, according to the present invention, in a hydraulic circuit that supplies and discharges pressure oil from a variable displacement hydraulic pump to an actuator by switching operation of a switching valve, and controls the discharge amount of the hydraulic pump using pilot pressure, the pilot pressure is manually controlled. The pressure is generated in two systems, a pressure reducing valve and a solenoid valve, and by incorporating a means for selecting between the two systems, manual or automatic selection can be easily performed, which is useful in practice.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram of the present invention, and FIG. 2 is a pump characteristic diagram thereof. 1 ・Variable displacement hydraulic pump, 2 ・Fixed pilot pump, 3 ・Hydraulic motor, 4...ni 1 pressure pi o y
) Operation direction switching valve, 5... Control cylinder. 6...Control valve, 7,8...Manual variable pressure reducing valve. 9, 10.12.13 Solenoid on/off valve, 1]...
Tsuyatle valve

Claims (1)

[Claims] In a hydraulic circuit that supplies and discharges pressure oil from a variable displacement hydraulic pump to an actuator by switching a switching valve, and controls the discharge H1 of the hydraulic pump using a pilot pressure, the pilot pressure is controlled by a manual pressure reducing valve and a solenoid valve. A hydraulic circuit for a variable displacement pump, characterized in that it incorporates means for generating electricity in two systems and making it possible to select between the two systems.