JPS5823026Y2 - Concrete pump drive control device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a drive control device for a concrete pump driven by an electric motor.

Conventionally, this type of pump is equipped with a cylinder for pumping concrete, and the cylinder is driven by supplying fluid from a variable displacement pump driven by an electric motor, and the flow rate of the fluid is controlled by a displacement control device of the pump according to its pressure. Generally, the cylinder is controlled and driven at a constant force, but this type of pump is moved when the construction site is relocated, and in this case, if the power frequency changes, the motor rotation speed will fluctuate, for example. 60 concrete pumps equipped with 50Hz electric motors
If used in a 50Hz region, the motor speed will increase, resulting in an increase in flow rate and overload.On the other hand, if the motor is equipped with a 60Hz motor, the required power will decrease in a 50Hz region due to a decrease in the motor speed. However, there is a disadvantage that electric motor power cannot be effectively provided.

The purpose of the present invention is to eliminate such inconveniences, and the present invention supplies fluid from a variable displacement pump 2 driven by an electric motor 1 to a cylinder 3 of a concrete pump to drive the concrete pump. 2, a pump displacement control device 6 having a control cylinder 4 actuated by the discharge pressure and a control valve 5 opposite to the control cylinder 4 actuated by pilot pressure to control the action of the discharge pressure on the control cylinder 4; In the case where the pump flow rate to the cylinder 3 of the concrete pump is controlled, the control valve 5 is connected to the control valve 5 through a pilot circuit 8 provided with a first throttle 7 to operate the control valve 5 in the direction of the control cylinder 4. At the same time, the pilot circuit 8 between the control valve 5 and the first throttle 7 is connected to the tank 1 via the second throttle 9 and the on-off valve 10.
Connect to 1 and admonish.

In the illustrated example, one electric motor 1 drives two variable displacement pumps 2a, 2b and is connected via a gear box 14 so as to drive two pilot pumps 12, 13. 2b each discharge circuit 15
a, 15b are joined together and connected via a valve unit 16 to a cylinder 17 of a concrete pump.

The discharge circuit 18 of one pilot pump 12 is connected to the pressure reducing valve 1
The discharge circuit 20 of the other pilot pump 13 is connected to the concrete pump agitator hydraulic motor 22 and cleaning hydraulic motor 23 via a multiple control valve 21. be done.

The two variable displacement pumps 2a and 2b are configured to discharge fluid under the control of one pump displacement control device 6, and the pump displacement control device 6 is configured such that its control cylinder 4 or control valve 5 Actuates the rod 24 of the control cylinder 4
Pump 2a connected to said rod 24 when it is moved, for example upwards in the drawing.

The pump discharge amount is decreased by tilting the swash plate 2b, etc., and when the rod 24 is moved downward in the drawing, the pump discharge amount is increased.

25 is a spring interposed between the spool of the control valve 5 and the rod 24.

Reference numeral 26 indicates a pressure circuit in which the rond side chamber 4a and the head side chamber 4b of the control cylinder 4 are connected via the control valve 5, and the pressure circuit 26 is connected via check valves 27, 28, and 29, respectively. variable displacement pump 2a.

2b or the highest discharge pressure of the pilot pump 12 is introduced, and this pressure constantly acts on the chamber 4a on the Rondo side of the control cylinder 4, and the control valve 5 is kept in the closed position by the pressure of the discharge circuit 18 of the pilot pump 12. When actuated from 5a to open position 5b, it acts on the head side chamber 4b.

The pilot circuit 8 is provided by branching off the discharge circuit 15a of one variable displacement pump 2a, and is connected to the piston 30 that presses the spool of the control valve 5.

Reference numeral 31 denotes a branch path that branches off from the rear of the first throttle 7 of the pilot circuit 8 and continues to the tank 11, and is provided with the second throttle 9 and the on-off valve 10.

A case will be described in which the pump control device is set to match the operation of the electric motor 1 for 60 Hz, and is used at 50 Hz.

First, when driving the electric motor 1 at 60 Hz, the on-off valve 10 is closed in advance, and the pressure in the discharge circuit 15a of the variable displacement pump 2a rotated by the electric motor 1 is applied to the control valve 5 via the pilot circuit 8. Acts on piston 30.

This causes the control valve 5 to move downward from the illustrated position against the spring 25 and the control cylinder 4.

Along with this downward movement, the rod 24 also moves to reduce the pump discharge amount, but when the control valve 5 moves to the open position 5b that communicates the pressure circuit 26 to the control cylinder 4, the pumps 2a and 2b are closed. The highest pressure of the discharge pressure or the pilot pump 12 is in the chamber 4 on the head side of the control cylinder 4.
As a result, the pump displacement control device 6 controls the discharge amount of the variable displacement pumps 2a and 2b to decrease when the pump discharge pressure increases, and controls the discharge amount to increase when the discharge pressure decreases. The pump 2a is adjusted so that the product of the discharge pressure P and the discharge amount Q as shown by the solid line in FIG. 2 is constant.

2b.

If this electric motor 1 is driven with a 50Hz power source, the rotational speed will be reduced by about 20%, and the pump 2a will remain unchanged.

The output of motor 2b draws an output curve as shown by the dotted line in FIG. 8 is connected to the tank 11 via the first throttle 7 and the second throttle 9 of the branch passage 31, and the pressure in the pilot circuit 8 becomes the pressure reduced by the pressure in the discharge circuit 15a by both the throttles 7 and 9. Therefore, the pushing force acting on the control valve 5 via the piston 30 also decreases, and the pump displacement control device 6 increases the discharge amount even though the pump discharge pressure is lower than when the frequency is 60Hz, as shown in FIG. Even if the actual pump discharge pressure is Pl' or P2', the discharge pressure is controlled as if it were Pol or Po2, and the pump discharge amount is Pl' or P2'.
Or, it becomes the amount of 22 points, and even if the electric motor 1 is driven at 50H2, the same output as when driving at 60Hz can be obtained.

In this case, by setting the first diaphragm I and the second diaphragm 9 as variable diaphragms and appropriately determining their area ratios, control suitable for the motor rotation speed of 50 Hz can be performed.

If the electric motor 1 is for 50 Hz and the pump control device is set accordingly, overloading of the electric motor can be prevented by opening and closing the on-off valve 10 in the same way when driving it at 60 Hz.

In this way, according to the present invention, even if the concrete pump is moved to an area with a different power supply frequency, it is possible to cope with changes in the rotational speed of the motor simply by operating the on-off valve 10, making effective use of the motor output and preventing overload. , its structure is relatively simple and can be manufactured at low cost.

[Brief explanation of the drawing]

FIG. 1 is a diagram of an embodiment of the device of the present invention, and FIG. 2 is an output curve diagram thereof. 1... Electric motor, 2... Variable displacement pump, 3... Concrete pump cylinder, 4...
...Control cylinder, 5...Control valve, 6.
...Pump capacity control device, 7...First throttle, 8...Pilot circuit, 9...Second throttle, 10...Opening/closing Valve, 11...Tank.

Claims (1)

[Scope of utility model registration request] Fluid from a variable displacement pump 2 driven by an electric motor 1 is supplied to a cylinder 3 of a concrete pump to drive it, and the variable displacement pump 2 is connected to a control cylinder 4 operated by its discharge pressure in the opposite direction. a pump displacement control device 6 having a control valve 5 actuated by pilot pressure to control the action of the discharge pressure on the control cylinder 4;
is provided to control the pump flow rate to the cylinder 3 of the concrete pump, and a pilot circuit 8 is provided in which the control valve 5 is provided with a first throttle 7 to operate the control valve 5 in the direction of the control cylinder 4. A pilot circuit 8 which introduces the discharge pressure through the control valve 5 and the first throttle 7
is connected to a tank 11 via a second throttle 9 and an on-off valve 10.