JP2001234869A - Pump system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform stable speed control regardless of load. SOLUTION: A pump 1 connected to an electric motor 2 is provided with a rotating speed detector 3. The encoder value ec from the rotating speed detector 3, the rotating speed command value from a controller 4, and three-phase alternating current values R, S, T are inputted to a driver 5, and the rotating speed of the electric motor 2 is controlled by a closed loop on the basis of the output value from the driver 5. An actuator can thereby be stably controlled without being influenced by the heat generation of the electric motor 2 and the magnitude of load.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pump system for controlling the speed and pressure of an actuator such as a hydraulic cylinder by controlling the rotation speed of a pump that drives the actuator.

[0002]

2. Description of the Related Art Conventionally, as a pump system for controlling the speed and pressure of an actuator of this type, a pump system for controlling the rotation speed of a pump using a servomotor and a system for controlling the rotation speed of a pump by inverter control are known. Etc. are known.

FIG. 4 is a block diagram of a pump system for controlling the number of rotations of a pump using a servomotor. A rotation speed detector 33 for detecting the rotation speed of a servomotor 32 connected to a pump 31 is shown in FIG. The output value ec from the encoder and the output value from the controller 34 that receives the rotation speed command of the servo motor 32 are input to the servo motor 3
And a driver 35 for controlling the number of rotations. In addition,
In the figure, R, S, and T denote current values from the R, S, and T phases of the three-phase AC power supply, and E denotes ground.

FIG. 5 is a block diagram of a pump system for controlling the number of revolutions of an electric motor by inverter control. A command current from a controller 44 receiving a flow command of a pump 41 is frequency-converted by an inverter 46. Then, the rotation speed of the electric motor 42 is changed and the rotation speed of the pump 41 is controlled by inputting the electric power to the electric motor 42.

[0005]

However, in such a conventional pump system, a system using closed-loop control by a servomotor having a rotation speed detector requires either the servomotor itself or its auxiliary equipment. Therefore, it is extremely expensive as a whole, and application to general systems other than limited systems is not desirable.

Further, the encoder normally used for detecting the rotation speed of the servomotor uses the maximum allowable capacity of the servomotor because the allowable insulation temperature of the circuit board is lower than the allowable limit temperature of the motor itself. There is also a problem that can not be.

On the other hand, an open-loop control system using an inverter can be constructed relatively inexpensively. However, when a high-efficiency and inexpensive three-phase induction motor having a simple structure is used for an electric motor, slipping occurs. Due to the characteristics, the rotation speed changes depending on the load of the actuator. Therefore, it cannot be applied to a system that requires stable speed control irrespective of the magnitude of the load, such as a molding machine. The present invention has been made in view of the above points, and has as its object to provide an inexpensive pump system capable of obtaining stable speed control.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a pump system comprising an electric motor, a pump connected to the electric motor, and a controller for instructing the electric motor to rotate. In the above, a rotational speed detector is provided in the pump, and a flow rate of the pump is controlled by a rotational speed control of the pump based on an output value of the rotational speed detector and a command value from the controller to the electric motor. The present invention is to provide a pump system which has been described.

[0009] In the above pump system,
The electric motor is preferably a three-phase induction motor, and the pump is preferably a variable displacement pump. Further, in the pump system having the above-described variable displacement pump, the variable displacement pump is provided with a detector capable of detecting a specific tilt angle, and the variable displacement pump is provided in accordance with a change in an output signal of the detector. It is more preferable that the rotation speed of the pump be automatically reduced to switch to the pressure control mode.

The pump system according to the present invention is constructed as described above, so that an expensive servo motor system is not used, and there is no need to provide a rotation speed detector in the electric motor, and the pump speed can be kept low and stable. Control can be performed, and it is possible to configure an energy-saving and low-noise pump system.

[0011]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a configuration diagram showing an embodiment of a pump system according to the present invention, and FIG. 2 is a longitudinal sectional view showing an example of a variable displacement pump with a rotation speed detector.

First, referring to FIG. 2, a swash plate type piston pump with pressure compensation (hereinafter referred to as "pump") used in this embodiment will be described.
) Will be described. On a center line C of a pump main body 10 constituting an outer casing of the pump 1, a rotation transmission shaft 11 for transmitting a rotational force from a three-phase induction motor (hereinafter referred to as “electric motor”) 2 shown in FIG. A concentric cylinder block 12 is provided outside the rotation transmission shaft 11.
And are slidably mounted in the axial direction.

A plurality of cylinder pits 12a are provided on the same pitch circle from the center of the cylinder block 12 in parallel with the central axis C and at equal intervals in the circumferential direction. 13 are slidably inserted, and these pistons 13 reciprocate to perform a pumping action of sucking and discharging hydraulic oil.

A swash plate 14 which can be tilted within a predetermined range with respect to a direction orthogonal to the center line C is provided inside the pump body 10.
The spherical portion 13a formed at one end of each piston 13 is swingably mounted on a piston shoe 16 connected by an annular shoe plate 15, and the piston shoe 16 comes into sliding contact with the swash plate 14. I have. Swash plate 14
Is integrally slidably contacted with a bearing (not shown) formed integrally with the pump body 10 and swings around a rotation center line X orthogonal to the center line C.

The lower part of the pump body 10 has a control piston 2
0 is a control piston rod 2 fixed to the pump body 10
1, one end of the control piston 20 is pressed against the lower end of the yoke 17. Pump body 1
A spring 24 is engaged between a bias piston 22 and a fixed bias piston rod 23 at an upper portion of the bias piston 22, and a spherical portion 2 integrally formed on the right end side of the bias piston 22 in the drawing.
2 a is pressed against the upper end of the yoke 17.

A valve plate 25 fixed to the left end face of the pump body 10 in the drawing is in sliding contact with the left end face of the cylinder block 12 to form a bearing for the cylinder block 12 and supply the cylinder block 12a with its cylinder pit 12a. Forming a fluid seal portion. The valve plate 25 is provided with a suction-side kidney port as a fluid supply hole and a discharge-side kidney port (both not shown) as a fluid discharge hole on a pitch circle facing the cylinder pit 12a.
Further, a well-known rotation speed detector 3 for detecting the rotation speed of the rotation transmission shaft 11 and a pressure compensation valve 7 are provided outside the pump body 10.

Next, the operation of the swash plate type piston pump constructed as described above will be briefly described. Pressure oil having a pressure controlled by a control device (not shown) is supplied to an oil passage 21 a formed in the control piston rod 21, and presses the control piston 20 to a lower portion of the yoke 17. Further, the bias piston 22 is pressed against the upper part of the yoke 17 by the spring 24. In this way, the guide oil 20 is guided to the control piston 20 so that the yoke 17 swings and the bias piston 2
The stroke of each piston 13 is changed by the tilt angle θ of the yoke 17 determined by the balance with the moment of 2, and the discharge flow rate of the pump is determined, so that the pump displacement can be changed. Then, the rotation speed of the pump at that time can be detected by the rotation speed detector 3.

FIG. 1 is a block diagram of a pump system using such a pump 1 with a rotation speed detector. The pump speed is determined by changing the rotation speed of the pump 1 from the output value ec from the encoder of the rotation speed detector 3 and the controller. 4 and the command value of the number of revolutions of the electric motor 2 together with the R, S, and T currents are input to the driver 5. This makes it possible to configure a pump rotation speed control system that performs closed loop control of the rotation speed. Although not shown, the pump 1 is connected to an actuator such as a hydraulic cylinder to control the speed and pressure of the actuator.

According to such a pump system, the rotation speed detector 3 is attached to the pump 1.
The rotational speed detector 3 having a low allowable temperature limit is not affected by the heat generated by the electric motor 2, and the electric motor 2 can exhibit its ability up to the temperature rise limit, and is stable regardless of the load. The speed of the actuator can be controlled, and there is no need to use an expensive servomotor. Further, since the energy loss is small, the temperature rise of the working oil can be suppressed low, and the amount of the tank oil can be reduced.

FIG. 3 is a longitudinal sectional view showing the structure of a swash plate type piston pump used in another embodiment of the present invention. The structure of the pump itself is the same as that shown in FIG. The same reference numerals are given to the same parts, and the description of those parts is omitted.

In this embodiment, a position sensor 8 composed of a limit switch is provided below the pump body 10 as a detector for detecting a specific tilt angle of the swash plate 14.
When the tilt angle θ becomes a predetermined angle (for example, near 0 °), the yoke 17 integral with the swash plate 14 comes into contact with the movable portion 8a of the position sensor 8, thereby turning the position sensor 8 on or off or An output for switching between high and low is generated. When this output is input to the controller 4 shown in FIG. 1, the controller 4 issues a signal for automatically reducing the pump rotation speed to a predetermined speed and shifting to the pressure control mode.

According to this embodiment, in addition to the effects of the previous embodiment, it is possible to automatically switch between speed control and pressure control without mounting a sensor on the actuator system side. Further, by reducing the rotation speed of the electric motor 2 during pressure control, it is possible to improve the energy saving and low noise effects.

[0023]

As described above, according to the present invention,
By providing a rotation speed detector in the pump, the rotation speed detector is not affected by the heat generated by the electric motor,
It is possible to make full use of the capability of the electric motor, and to configure a pump system that performs stable speed control of the actuator regardless of the magnitude of the load.

In the above pump system,
A system using a three-phase induction motor as the electric motor can efficiently and inexpensively configure the system, and if a variable displacement pump is used as the pump, it has a relatively simple configuration and high efficiency over a wide range. Gear shifting becomes possible.

Further, in the pump system using the above-mentioned variable displacement pump, a detector provided with a detector capable of detecting a specific tilt angle, and the rotation speed of the pump is reduced by the output thereof is applied. It is possible to automatically switch between the speed control mode and the pressure control mode without providing a sensor on the actuator system side, and realize an energy-saving and low-noise pump system by reducing the rotation speed in the pressure control mode. be able to. At the same time, since the energy loss is small, the temperature rise of the working oil can be suppressed low, and the tank oil amount can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing an example of the swash plate type piston pump.

FIG. 3 is a longitudinal sectional view showing a swash plate type piston pump according to another embodiment of the present invention.

FIG. 4 is a configuration diagram showing an example of a conventional pump system.

FIG. 5 is a configuration diagram showing another example of a conventional pump system.

[Explanation of symbols]

 1: Swash plate type piston pump (pump) 2: Three-phase induction motor (electric motor) 3: Rotation speed detector 4: Controller 5: Driver 8: Position sensor (detector) 10: Pump body

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroyuki Ishikawa 2-16-46 Minamikamata, Ota-ku, Tokyo Inside Tokimec Co., Ltd. (72) Inventor Tetsuji Machida 2-16-46 Minamikamata, Ota-ku, Tokyo Stock F-term in the company Tokimec (reference) 3H045 AA04 AA09 AA12 AA24 AA33 AA35 BA19 BA20 BA32 BA38 CA09 CA13 DA05 EA17 EA26 EA34 3H070 AA01 BB04 BB06 BB11 CC02 CC11 CC19 CC37 DD56 DD60

Claims (4)

[Claims] 1. A pump system comprising: an electric motor, a pump connected to the electric motor, and a controller for instructing the electric motor to control the number of rotations. A pump system, wherein a flow rate of the pump is controlled by a rotation speed control of the pump based on an output value of a detector and a command value from the controller to the electric motor. 2. The pump system according to claim 1, wherein the electric motor is a three-phase induction motor. 3. The pump system according to claim 1, wherein the pump is a variable displacement pump. 4. The pump system according to claim 3, wherein the variable displacement pump is provided with a detector capable of detecting a specific tilt angle, and the variable displacement pump is provided in response to a change in an output signal of the detector. A pump system wherein the rotation speed of a pump is automatically reduced to switch to a pressure control mode.