JP2004332563A - Inverter control system of hydraulic pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable inverter control of a hydraulic pump with a common system regardless of a type and a capacity of the hydraulic pump, and to automatically perform switching between a low speed and a high speed in the hydraulic pump at an optimum timing. <P>SOLUTION: A flow rate switch 6 for detecting a change in a delivery flow rate of the hydraulic pump 2 is arranged to a delivery channel near the pump, and a control panel 7 incorporating an inverter 71 for switching turning of the hydraulic pump to be low speed or high speed based on a signal from the flow rate switch is provided. This flow rate switch has at least one contact in which OFF and ON are switched with a predetermined flow rate (a) being as a boundary, and when increase of the flow rate is detected, the inverter switches the hydraulic pump to the high speed, and when decrease of the flow rate is detected, the inverter switches the hydraulic pump to the low speed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a hydraulic pump inverter control system.
[0002]
[Prior art]
FIG. 4A shows a circuit for supplying pressure to an actuator of a conventional hydraulic pump without an inverter. That is, when the piston 11 of the actuator 1 is advanced, the hydraulic pump 2 is rotated at a high speed, oil is introduced into the left chamber 12 a of the cylinder tube 12 through the electromagnetic control valve 3, and the oil is introduced from the right chamber 12 b of the cylinder tube 12. The oil is returned to the tank 4 through the control valve 3. Then, even when the piston 11 reaches the forward end of the cylinder tube 12, the hydraulic pump 2 operates while maintaining the high-speed rotation in order to maintain the hydraulic pressure. In this case, the oil is substantially returned to the tank 4 from the hydraulic pump 2 without going to the left chamber 12a of the cylinder tube 12. For this reason, there is a problem that the power consumption of the hydraulic pump 2 during the pressure holding is large. This is shown in the graph of FIG. When the piston 11 is moved backward, the same operation may be performed by switching the flow path by the electromagnetic control valve 3.
[0003]
Therefore, an inverter of a hydraulic pump has been conventionally used. There are (1) a sequence control method and (2) a constant pressure control method as an art of converting the conventional hydraulic pump into an inverter.
However, in the (1) sequence control method, a new inverter control circuit that performs inverter control of a motor of a hydraulic pump based on a signal of a control circuit of an existing hydraulic pump system that switches an electromagnetic control valve is newly provided. Need to be added. Therefore, control design and trial operation adjustment are required for each facility individually, which increases costs. In addition, the switching timing between the low speed and the high speed of the hydraulic pump needs to take into account variations in the operation time of the actuators such as cylinders and future delays. Therefore, it is necessary to set the high speed operation time of the hydraulic pump to be longer. In addition, while energy can be saved by using an inverter, there is a problem that a loss of power consumption occurs.
[0004]
On the other hand, in the (2) constant pressure control method, it is necessary to replace with a servo motor type special hydraulic pump unit in order to improve the followability to the pressure fluctuation of the hydraulic pressure in the actuator. There is a problem that the adjustment has to be restarted from the beginning.
As described above, the conventional method of converting the hydraulic pump into an inverter has a problem that the cost is high, the equipment must be adjusted from the beginning, and the risk is large. Especially, the introduction into the existing hydraulic pump system is difficult. It was very difficult.
[0005]
[Problems to be solved by the invention]
The present invention has been made in view of the above problems, and an object thereof is to make it possible to convert a hydraulic pump into an inverter with a common system regardless of the type and capacity of the hydraulic pump, and to use a hydraulic pump of existing equipment. An object of the present invention is to provide a hydraulic pump inverter control system that does not require both a change and a modification of a control circuit, and that can automatically switch between a low speed and a high speed of a hydraulic pump at an optimal timing.
[0006]
[Means for Solving the Problems]
The present invention provides an inverter control system of a hydraulic pump described in each claim as means for solving the above-mentioned problem.
An inverter control system for a hydraulic pump according to a first aspect of the present invention provides a flow rate fluctuation detecting means for detecting a change in the delivery flow rate of the hydraulic pump, and switches the hydraulic pump between low speed and high speed rotation based on a signal from the flow rate fluctuation detecting means. Inverter control means is provided so that the hydraulic pump is rotated at a high speed when an increase in the flow rate is detected, and is rotated at a low speed when the decrease in the flow rate is detected. When the introduction flow rate to the actuator is small, for example, when the delivery flow rate of the hydraulic pump is small, low speed rotation by the inverter can be achieved, and energy saving of the hydraulic pump can be achieved. Further, since the flow fluctuation is used for the inverter control signal, the inverter can be realized by a common system regardless of the type and capacity of the hydraulic pump.
[0007]
The inverter control system according to a second aspect of the present invention includes a control panel having a built-in inverter for switching between high-speed and low-speed rotation of the hydraulic pump based on a signal from the flow switch as the inverter control means. This makes it possible to automatically switch between low speed and high speed rotation of the hydraulic pump at an optimal timing.
According to a third aspect of the present invention, the inverter control system has at least one contact that switches between ON and OFF at a predetermined flow rate.
[0008]
In the inverter control system according to the fourth aspect, the predetermined flow rate is set to a flow rate smaller than the maximum discharge amount of the hydraulic pump during the low-speed rotation operation, whereby the hydraulic pump is switched from the low-speed rotation to the high-speed rotation. Is performed reliably.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an inverter control system for a hydraulic pump according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an example of a hydraulic circuit diagram employing an inverter control system for a hydraulic pump according to the present invention. This hydraulic circuit has two actuators 1 each consisting of a large cylinder 1A and a small cylinder 1B. The large cylinder 1A is connected to a hydraulic pump 2 via an electromagnetic three-position switching control valve 3A, and the small cylinder 1B Is connected to the hydraulic pump 2 via an electromagnetic two-position switching control valve 3B. This hydraulic pump 2 is directly connected to the motor 5. Reference numeral 4 denotes a tank. The hydraulic pump 2 does not need to be a pressure-compensated variable displacement hydraulic pump as shown in FIG. 1, but may be any type of hydraulic pump.
[0010]
In the inverter control system according to the present invention, a flow switch 6 serving as a flow fluctuation detecting means is provided in a discharge flow path near the hydraulic pump 2 and an inverter control means for controlling the hydraulic pump 2 in response to a signal from the flow switch 6. The control panel 7 is provided. An inverter 71 is built in the control panel 7, and a power line for a hydraulic pump from outside was directly connected to the motor 5 as shown by a two-dot chain line in FIG. The power cable after the inverter is connected to the motor 5 from outside through the inverter 71 as shown by a solid line. In this case, the existing hydraulic pump and control circuit are not changed.
[0011]
As shown in FIG. 2, the flow rate switch 6 is turned off when a flow rate equal to or more than the predetermined flow rate a flows, and turned on when the flow rate is less than the predetermined flow rate a (including flow rate = 0). At least one flow switch contact. The predetermined flow rate a is set to a flow rate smaller than the maximum discharge flow rate of the hydraulic pump during the low-speed operation of the inverter as shown in FIG. The flow switch 6 may be turned on when a flow rate equal to or more than the predetermined flow rate a flows, and turned off when the flow rate is less than the predetermined flow rate a. In FIG. 2, arrows indicate a discharge flow rate range of the hydraulic pump during high-speed rotation and a discharge flow rate range of the hydraulic pump during low-speed rotation.
[0012]
The inverter 71 of the control panel 7 switches the motor 5, that is, the hydraulic pump 2, to high-speed rotation based on a switch OFF signal from the flow switch 6. Similarly, the inverter 71 switches the hydraulic pump 2 to low-speed rotation based on a switch ON signal from the flow switch 6. In this way, the inverter 71 switches between high-speed and low-speed rotation of the hydraulic pump 2 based on the switch OFF or ON signal from the flow switch 6.
[0013]
The operation of the inverter control system for a hydraulic pump according to the present invention configured as described above will be described. Now, when the three-position switching control valve 3A is switched from the neutral position in FIG. 1 to an offset position, for example, an offset position on the left side, the large cylinder 1A starts the forward operation. When the two-position switching control valve 3B is at the position shown in FIG. 1, the small cylinder 1B also moves forward. Then, the flow rate of the oil flowing through the flow rate switch 6 rapidly increases, and the flow rate switch 6 transmits a switch OFF signal. The inverter 71 of the control panel 7 receives this signal and switches the hydraulic pump 2 to the high-speed rotation operation, and the discharge amount of the hydraulic pump 2 increases.
[0014]
When the large cylinder 1A reaches the forward end and the actuator stops and enters the fluid pressure holding operation, and then the small cylinder 1B also reaches the forward end and the actuator stops and enters the fluid pressure keeping operation, the flow rate switch is activated. The flow rate of the oil flowing through 6 decreases rapidly (including the flow rate = 0), and the flow rate switch 6 transmits a switch ON signal. That is, when the actuator is stopped and the pressure holding operation is started, only the oil for maintaining the pressure flows into the large cylinder 1A and the small cylinder 1B, and the remaining oil flows from the hydraulic pump 2 as shown by the broken line in FIG. Return to the tank 4 as it is. Therefore, the flow rate of the oil flowing through the flow rate switch 6 decreases rapidly. When the inverter 71 receives the switch ON signal from the flow rate switch 6, the inverter 71 switches the hydraulic pump 2 to the low-speed rotation operation, and the discharge amount of the hydraulic pump 2 further decreases.
[0015]
Next, the retreating operation of the large cylinder 1A in which the three-position switching control valve 3A switches to the right offset position and the retreating operation of the small cylinder 1B in which the two-position switching control valve 3B switches to the right position are also described above. The same operation as the forward operation of the cylinders 1A and 1B is performed.
As described above, only when the actuator 1 is operating (both cylinders are moving forward or backward), the hydraulic pump 2 is in the high-speed rotation operation. When the actuator 1 is stopped (both cylinders are holding pressure), the hydraulic pump 2 is turned on. It becomes low-speed rotation operation, and can switch between high-speed and low-speed automatically at the optimal timing.
[0016]
FIGS. 3A and 3B show a graph (a) and a table (b) comparing the energy saving effects of the case without the inverter and the case of employing the inverter of the present invention. In this case, a large cylinder 1A having a diameter of 40 mm and a stroke length of 75 mm, and a small cylinder 1B having a diameter of 20 mm and a stroke length of 30 mm are used. FIG. 3 (a) shows the pressure and power consumption in one cycle from the start of the hydraulic pump to the forward movement of the large cylinder → holding pressure → the advancement of the small cylinder → holding pressure of both cylinders → backward movement of both cylinders → holding pressure of both cylinders. 5 is a graph showing a change in the graph. The thin solid line indicates the case without the conventional inverter, and the thick solid line indicates the case with the inverter of the present invention. The cycle time per cycle is 10 seconds. From this graph, during the operation of the actuator, the present invention consumes more power than the case without the conventional inverter, but during the stop of the actuator (during the pressure holding), the present invention shows the case without the conventional inverter. It can be seen that the power consumption is smaller than in the case and the power consumption is improved as a whole.
FIG. 3B is a table comparing the power consumption (KW) between the case without the conventional inverter and the case with the inverter of the present invention during the pressure holding and in one cycle. The numbers in parentheses indicate%. According to this, in one cycle, the power can be reduced to about 60% in the case of the inverter of the present invention with the inverter, without the inverter. That is, an energy saving effect of about 40% can be achieved.
[0017]
FIG. 4 is a diagram for briefly comparing and explaining the difference between the configuration and the operation effect of (a) the conventional inverter-less system and (b) the inverter system of the present invention. That is, as described above, in the present invention, the flow rate switch 6 is provided in the hydraulic circuit, and the inverter 7 switches the high-speed operation and the low-speed rotation operation of the hydraulic pump 2 in response to the signal of the flow rate switch 6. For this reason, the power consumption of the hydraulic pump 2 during pressure holding (when the actuator is stopped at the forward end or the backward end) can be reduced by almost half. In FIG. 4, the upper part is a schematic system diagram, the lower part is a graph explaining the operation of the cylinder, and the lower part is a graph showing the flow rate and the power consumption corresponding to the operation of the cylinder.
[Brief description of the drawings]
FIG. 1 is a diagram showing a hydraulic circuit employing an inverter control system for a hydraulic pump according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating the operation of a flow switch and a hydraulic pump.
FIGS. 3A and 3B show a graph (a) and a table (b) comparing the energy saving effect of the conventional inverter without the inverter and the inverter of the present invention with the inverter.
4A and 4B are diagrams for briefly comparing and explaining differences in the configuration and operation effects between the conventional inverter-less system and the inverter system of the present invention.
[Explanation of symbols]
1: Actuator (cylinder)
1A large cylinder 1B small cylinder 2 hydraulic pump 3 (electromagnetic) control valve 3A (electromagnetic) 3 position switching control valve 3B (electromagnetic) 2 position switching control valve 4 tank 5 motor 6 Flow switch (flow fluctuation detecting means)
7. Control panel (inverter control means)
71… Inverter

Claims (4)

The inverter control system of the hydraulic pump used for the hydraulic circuit of various actuators
Flow rate fluctuation detection means for detecting a change in the delivery flow rate of the hydraulic pump,
Inverter control means for switching the hydraulic pump to low-speed rotation or high-speed rotation based on a signal from the flow rate fluctuation detection means,
With
Inverter control of the hydraulic pump, wherein the hydraulic pump switches to high-speed rotation when the flow rate fluctuation detecting means detects an increase in flow rate, and the hydraulic pump switches to low-speed rotation when detecting a decrease in flow rate. system. The flow rate fluctuation detecting means is a flow rate switch provided in a discharge flow path near the hydraulic pump, and the inverter control means includes an inverter for switching the hydraulic pump between low speed and high speed based on a signal from the flow switch. The inverter control system for a hydraulic pump according to claim 1, wherein the control panel is a control panel. The inverter control system for a hydraulic pump according to claim 2, wherein the flow switch has at least one contact that switches between a switch ON and a switch OFF at a predetermined flow rate. The hydraulic pump inverter control system according to claim 3, wherein the predetermined flow rate is set to a flow rate smaller than a maximum discharge flow rate of the hydraulic pump during low-speed rotation operation.

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