JPS6237236B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic pump control device for a drive hydraulic circuit for a movable object having a large moment of inertia, such as an upper revolving body of a hydraulic excavator.

The required flow rate of a hydraulic motor for driving such a rotating structure gradually increases as the rotating structure accelerates. Conventionally, at the start of a turn when the required flow rate is low, a surplus flow rate discharged from the pump more than necessary is discharged from the relief valve, which wastes energy and is uneconomical. The present invention provides a device that controls the discharge flow rate of a variable displacement pump according to the required flow rate and minimizes energy waste.

Therefore, as shown in FIGS. 1 and 2, the present invention includes a control cylinder 2 having a piston 1 that is displaced by manual operation, and a control cylinder 2 that is linked to the displacement of the piston 1 and directly connected to a variable displacement pump 3. A control rod 4 controls the discharge amount of the pump 3 independently of the relief pressure, and a conduit equipped with a restriction for allowing pressure oil to flow into the control cylinder 2 by the manual operation is used to control the discharge amount of the pump 3 above a certain level. It has a switching valve 5 which is shut off by pressure.

Each embodiment of the present invention will be explained in detail below with reference to the drawings.As shown in FIG. It is driven by a prime mover. The discharge flow rate of the hydraulic pump 3 is controlled by a control rod 4 which is directly connected to the variable displacement hydraulic pump 3 and linked to the displacement of the piston 1 of the control cylinder 2.
The hydraulic chambers 7a and 7b of the control cylinder 2 communicate with a manual operating device via the switching valve 5, and the manual operating device operates according to the operating lever 8 and the displacement of the lever 8. It consists of operating valves 9a, 9b that generate hydraulic pressure, and a constant displacement hydraulic pump 10 that communicates with the valves 9a, 9b.

The operation of this device will be explained in detail below.

(1) For driving the swing hydraulic motor 6 that swings the swing structure (not shown), the operating lever 8 is connected to the operating valve 9, for example.
When the lever 8 is rotated toward the b side, a pressure corresponding to the rotation angle of the lever 8 is generated in the conduit 11b, and the piston 1 of the control cylinder 2 is moved to the right against the springs 12a and 12b. Then, the discharge flow rate of the variable displacement pump 3 increases in proportion to the displacement of the piston 1 via the control rod 4 which is directly connected to the variable displacement pump 3 and interlocks with the piston 1.

(2) However, at the time when the rotating body (not shown) starts to swing, the load on the swing motor 6 is large due to the large moment of inertia of the rotating body, and the amount of hydraulic oil flowing into the motor 6 is small. Therefore, the hydraulic oil discharged from the pump 3 as the control rod 4 is displaced becomes high pressure in the pipe line 13b, and is partially flowed into the pipe line 13a through the relief pressure 14b. Continuation of such diversion significantly increases energy waste.

(3) Therefore, the present invention operates the switching valve 5 via the shuttle valve 15 and the pilot pipe 16 with the high pressure of the discharge side pipe 13b of the variable hydraulic pump 3, and the pipe 11b allows pressure oil to flow into the control cylinder 2. At the same time, the conduit 11a through which pressure oil flows out from the control cylinder 2 is also shut off. As a result, the control piston 1 is locked, the movement of the control rod 4 is stopped, and the increase in the discharge flow rate of the variable hydraulic pump 3 is stopped.

(4) After a while, when the load on the swing hydraulic motor 6 is reduced due to the acceleration of the swing body (not shown), the pipe 13b
The pressure decreases, the switching valve 5 of the control cylinder 2 is returned to the normal position, the locking condition of the control piston 1 is released, the piston 1 is allowed to move rightward, and the discharge amount of the variable displacement pump 3 is increased.

(5) Then, when the increase in the discharge amount of the pump 3 becomes larger due to the required flow rate of the hydraulic motor 6, the above
(1) to (4) are repeated, and finally the piston 1 moves to a position where the pressure in the hydraulic chamber 7b and the sum of the reaction forces of the springs 12a and 12b are balanced, and the discharge of the variable displacement pump 3 The flow rate is set to a value depending on the position of the piston 1.

Through the above operation, the discharge flow rate of the variable displacement hydraulic pump 3 increases by approximately the same amount as the increase in the required flow rate of the swing hydraulic motor 6, and as a result, the surplus flow rate passing through the relief pressure 14, which would otherwise be wasted energy, is suppressed to a minimum. obtain. However, while the required flow rate of the swing hydraulic motor 6 increases continuously with its acceleration,
The discharge flow rate of the variable displacement pump increases stepwise. Therefore, it is necessary to suppress this step-like step to a small level by appropriately selecting the throttles 17a and 17b disposed in the middle of the pipes 11a and 11b, and to approximately approximate the continuous increase described above.

The embodiment shown in FIG. 1 described above is a closed circuit using a variable displacement pump 3 with bidirectional discharge.
The present invention can be realized by the hydraulic circuit shown in FIG. 2 even if the variable displacement pump 3 is a unidirectional discharge type and the drive circuit of the swing hydraulic motor 6 is an open circuit.

That is, in FIG. 2, the discharge amount of the variable displacement hydraulic pump 3 becomes larger than the required flow rate of the swing hydraulic motor,
When the discharge pressure of the pump 3 becomes higher than a certain level, the switching valve 5 is actuated via the pilot line 16, communication with the line 11 is cut off, the piston rod side hydraulic chamber 7b of the control cylinder 2 is sealed, and the piston 1 is closed.
This is to lock the movement of the variable displacement pump 3 and stop the discharge amount of the variable displacement pump 3 from increasing. The subsequent control operations are also carried out in the same manner as in the closed circuit shown in FIG.

As described above, the present invention uses a simple hydraulic circuit to adjust the hydraulic pressure in time according to the required flow rate of the swing hydraulic motor, regardless of the operation of the relief valve, regardless of whether the variable displacement hydraulic pump has bidirectional discharge or one-way discharge. It is possible to control the discharge amount of the pump and minimize energy waste.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic circuit diagram showing a first embodiment of the present invention, and FIG. 2 is a circuit diagram showing a second embodiment of the invention. DESCRIPTION OF SYMBOLS 1...Piston, 2...Control cylinder, 3...Variable displacement pump, 4...Control rod, 5...Switching valve, 6...Swivel hydraulic motor, 7...Hydraulic chamber, 8...Operation lever, 9...Operating rod, 10...Constant displacement Hydraulic pump, 11...pipe line, 1
2...Spring, 13...Pipeline, 14...Relief valve, 15
... Shuttle valve, 16... Pilot pipe, 17... Throttle, 18... Swing hydraulic motor and its control circuit.

Claims (1)

[Claims] 1 A control cylinder having a piston that is displaced by manual operation, and a control cylinder that is linked to the displacement of the piston,
a control rod that is directly connected to the variable displacement hydraulic pump and controls the discharge amount of the variable displacement hydraulic pump regardless of the relief pressure; and a conduit that is equipped with a restriction that allows pressure oil to flow into the control cylinder by the manual operation. A discharge flow rate control device for a variable displacement pump, comprising a switching valve that shuts off at a discharge pressure of the pump above a certain level.