JPH0516401Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control circuit for a plurality of variable displacement pumps.

Generally, in construction machinery equipped with 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, multiple hydraulic pumps are coaxially driven by an engine, etc., and pressure oil is supplied to various work actuators. are supplied by hydraulic pumps connected to each. However, depending on the work, it may be necessary to combine the pressure oil of one pump with the pressure oil of the other pump to fully operate only a specific actuator.

Conventionally, devices that combine the discharge amounts of multiple pumps are disclosed in Japanese Patent Publication No. 53-9346 and Utility Model Application Publication No. 1983-
As seen in Japanese Patent No. 173502, there is a system in which the directional control valve is switched and merged using a hydraulic pilot, but it is not possible to control the amount of oil discharged from the pump itself. In addition, in Japanese Patent Application Laid-open No. 50-66908,
The inching function (throttling) of the directional control valves corresponding to the two pumps is used to make small movements of the hydraulic cylinders that are actuators, and by creating a difference in the pilot pressure that operates both control valves, the amount of oil supplied from the pumps is reduced. There are also things that can be controlled. However, in either method, the pump that supplies the amount of oil is of a fixed displacement type. However, in recent years, variable displacement hydraulic pumps have come into use in order to improve machine performance and save energy, and it has become necessary to control not only the operation of the switching valve but also the pump discharge amount itself.

For this reason, the switching operation of the switching valve is performed using pilot pressure, and the pilot pressure also controls the swash plate of the variable displacement hydraulic pump to control the discharge amount, and moreover, multiple variable displacement hydraulic pumps can be controlled independently. At the same time, there is a need for something that can control a plurality of pumps at the same time even if one of these pumps is operated, and also allows the pressure oil of one pump to merge with the pressure oil of the other pump.

In order to satisfy this requirement, the present invention uses a hydraulic system that is equipped with multiple variable displacement hydraulic pumps, each with an actuator such as a motor. It is possible to control the drive of each actuator by controlling the discharge amount of multiple variable displacement hydraulic pumps with one operation depending on the work type, and at the same time, operate the merging valve to merge and control the drive of a specific actuator. The object of the present invention is to provide a control circuit for a plurality of variable displacement pumps that makes it possible to do this.

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

The drawing is a hydraulic circuit diagram according to the present invention, and in the drawing, 1a and 1b are variable displacement hydraulic pumps. Reference numerals 5a and 5b are control cylinders for tilting the angle of the swash plate to vary the discharge amount of the variable displacement hydraulic pump, and are driven by pressure oil sent from ports 21a and 21b. Pilot signal pressure P _S is sent to the ports 20a and 20b, and the control valve 6
a, 6b to control the stroke of the control cylinder, and pumps 1a, 1 in response to the pilot signal pressure P _S.
The discharge amount Q of b is proportionally controlled. Reference numeral 2 denotes a fixed displacement pump as a fixed pump for the pilot, and control cylinder 5 of the variable displacement hydraulic pumps 1a and 1b.
The driving pressure and pilot signal pressure of the switching valves 4a and 5b, and the pilot pressure of the switching valves 4a and 4b and the merging valve 14 are supplied. 19 is a relief valve.
3a and 3b are hydraulic motors for the work machine as actuators, and switching valves 4a and 4b are respectively provided.
The amount of oil is supplied and discharged. These switching valves 4a, 4b
The merging valve 14 and the merging valve 14 are switched by pilot oil pressure. 15a and 15b are relief valves. Reference numerals 7a, 8a and 7b, 8b are manual variable pressure reducing valves, each of which is arranged in a pair as shown in the figure, one of which is operated by a single manual lever. To explain the operation using pump 7a as an example, pump 2
When the manual lever is tilted from the neutral position to the left side in the figure, the pressure oil supplied from the valve is reduced in proportion to the tilting angle of the lever and is supplied as pilot signal pressure to the port on the right side in the figure of the shuttle valve 9a and the directional control valve 4a. be done. Note that the relationship between the tilting angle α of the manual lever and the pilot signal pressure P _S is proportional. 9a,
9b is a shuttle valve which selects the higher pressure oil supplied from the left and right ports in the figure and supplies it from the lower port in the figure. Numerals 11a and 13 are normally open type electromagnetic two-way valves which close the oil passage when energized. Reference numerals 11b and 12 are normally closed electromagnetic two-way valves which close the oil passage when energized.

A case will be described in which the variable displacement hydraulic pumps 1a and 1b are constantly controlled independently to drive the hydraulic motors 3a and 3b of the working machine.

To drive the hydraulic motor 3a, tilt the manual lever of the manual variable pressure reducing valve consisting of a pair of pressure reducing valves 7a and 8a to the left in the figure. The oil generates a pilot signal pressure P _S according to the tilting angle α of the manual lever, and one side is connected to the port 20a of the variable displacement hydraulic pump 1a via a shuttle valve 9a and an electromagnetic two-way valve 11a through branched piping. supplied to
In order to operate the control valve 6a according to the value of P _S , an amount of oil is discharged according to the inclination of the swash plate operated by the control cylinder 5a. The other is the switching valve 4
The spool is switched to the right block, and the amount of oil discharged from the variable displacement hydraulic pump 1a is supplied to the hydraulic motor 3a. At this time, the spool of the switching valve 4a is switched when the manual lever tilting angle α is a certain value, and the variable displacement hydraulic pump is set to discharge oil at a slightly larger tilting angle α. It is preferable to be able to finely control the amount from 0 to the maximum by adjusting the tilting angle of a manual lever. The operation is the same except that when the manual lever is tilted to the right in the figure, the pressure reducing valve 8a is activated, the switching direction of the switching valve 4a is reversed, and the rotational direction of the hydraulic motor 3a is reversed.

The same goes for driving the hydraulic motor 3b, but since the two-way electromagnetic valves 11b and 12 in the piping are closed, the pilot hydraulic pressure supplied from the shuttle valve 9b is directly applied to the port 20 of the variable displacement hydraulic pump.
b and is supplied as a pilot signal pressure.
Next, a case will be described in which the discharge amounts of the variable displacement hydraulic pumps 1a and 1b are combined to drive the hydraulic motor 3b.

First, the electromagnetic 2 is turned on by a button switch (not shown).
The valves 11a, 11b, 12, and 13 are energized.
Buttons 11a and 13 close the oil passages, and buttons 11b and 12 open them. For ease of use, these buttons are provided on the manual levers of the manual variable pressure reducing valves 7b and 8b. When the manual levers of the manual variable pressure reducing valves 7b and 8b are tilted to the left in the figure, the pressurized oil supplied from the fixed displacement pump 2 generates pilot oil pressure according to the tilt angle of the manual lever, and one of the two branches is supplied as the spool switching pressure of the switching valve 4b through branched piping, switching the spool. The other branch is supplied to the piping 1 through the shuttle valve 9b.
Pilot pressure is supplied to the port 20a of the variable displacement hydraulic pump 1a via the electromagnetic two-way valve 11b, which is energized and has its oil passage open, and the amount of oil corresponding to the pilot pressure is discharged. At this time, the electromagnetic two-way valve 11a is energized and its oil passage is closed, so no oil flows to the piping 10a. The pilot pressure is supplied to the port 20a of the variable displacement hydraulic pump 1a via the electromagnetic two-way valve 12, which is also energized and has its oil passage open, and is supplied as a spool switching pressure to the junction valve 14, which is provided to join the discharge amounts of the variable displacement hydraulic pumps 1a and 1b. At this time, the electromagnetic two-way valve 13 is energized and its oil passage is closed, so the pilot pressure is not drained. The piping 10b finally connects to the port 20b of the variable displacement hydraulic pump 1b.
It is connected to a valve that discharges an amount of oil according to the pilot pressure.

Therefore, the operation of the manual lever that drives the hydraulic motor 3b and the electromagnetic two-way valves 11a, 11b, 12,
By energizing 13, variable displacement pumps 1a and 1b
The discharge amount of the switching valves 4b and 4b can be simultaneously controlled.
Since the merging valve 14 is also switched, the amount of oil discharged from the variable displacement hydraulic pump 1a passes through the center bypass of the switching valve 4a and the merging valve, merges with the amount of oil discharged from the variable displacement pump 1b, and is supplied to the hydraulic motor 3b. be done.

According to the present invention described above, it is possible to control the discharge amount by independently operating a plurality of variable displacement pumps, and also to control the discharge amount at the same time even in one operation, and to perform merging control by disposing a merging valve. Note that the manual lever tilting angle α and the oil amount Q in the case of merging can be finely controlled from the discharge amount 0 to the maximum oil amount.

In short, according to the present invention, pressure oil from a variable displacement hydraulic pump is supplied to and discharged from an actuator provided corresponding to the variable displacement hydraulic pump by the switching operation of a switching valve, and the switching operation of the switching valve is controlled by the variable displacement hydraulic pump. This is done by hydraulic pressure supplied from a fixed pilot pump installed separately from the displacement hydraulic pump to a manual variable pressure reducing valve installed corresponding to the actuator, and a corresponding variable pressure reducing valve is supplied by hydraulic pressure from a manually adjustable pressure reducing valve. In a hydraulic circuit configured to control the discharge amount of a displacement hydraulic pump, a merging valve is provided in the supply/discharge circuit to one actuator, and the supply/discharge path is connected to the other supply/discharge path via the merging valve so as to be merging, A switching valve is interposed between the hydraulic circuits from the manual variable pressure reducing valves that control the discharge amount of each variable displacement hydraulic pump,
By making it possible to control the discharge amount and combine the discharge amounts of multiple variable displacement hydraulic pumps with a single manual variable pressure reducing valve, each hydraulic pressure can be adjusted even when operated alone or simultaneously when the discharge amounts of one hydraulic pump are combined. The discharge amount of the pump can be controlled by the secondary pressure of the manual variable pressure reducing valve, which is useful for work.

[Brief explanation of the drawing]

The drawing shows a control circuit for a plurality of variable displacement pumps according to the present invention. 1a, 1b...variable displacement hydraulic pump, 2...
Fixed pump for pilot, 3a, 3b...Hydraulic motor, 4a, 4b...Hydraulic pilot operation direction switching valve, 5a, 5b...Control cylinder, 6a, 6b
... Control valve, 7a, 7b, 8a, 8b ... Manual variable pressure reducing valve, 9a, 9b ... Shuttle valve, 11
a, 11b, 12, 13...Solenoid on/off valve, 1
4... Merging valve.

Claims (1)

[Scope of utility model registration request] Pressure oil from a plurality of variable displacement hydraulic pumps is supplied to and discharged from an actuator provided corresponding to the variable displacement hydraulic pump by switching operation of a switching valve, and the switching operation of the switching valve is controlled by the switching operation of the variable displacement hydraulic pump. This is performed by hydraulic pressure supplied from a separately provided fixed pump for the pilot to a manual variable pressure reducing valve provided corresponding to the actuator, and further by hydraulic pressure from the manual variable pressure reducing valve. In a hydraulic circuit configured to control the discharge amount of a hydraulic pump, a merging valve is provided in the supply/discharge circuit to one actuator, and the supply/discharge route is connected to the other supply/discharge route via the merging valve so as to be able to merge with each other. A switching valve is interposed between the hydraulic circuits from the manual variable pressure reducing valve that controls the discharge volume of variable displacement hydraulic pumps, allowing the discharge volume control and merging of multiple variable displacement hydraulic pumps with one manual variable pressure reducing valve. A control circuit for a variable displacement pump characterized by the following.