JP3529584B2 - Variable pump controller - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable pump controller, and more particularly to a variable pump controller for driving an injection cylinder of an injection molding machine.

[0002]

2. Description of the Related Art Generally, in an injection molding machine, an injection cylinder is used to fill a molten resin into a mold to mold a desired molded product. When driving the injection cylinder, a variable pump supplies hydraulic pressure to the injection cylinder to control the injection speed.

Now, with reference to FIG. 3, a control device for controlling the drive of the injection cylinder will be outlined.

A variable pump 13 is connected to the injection cylinder 11 via a hose and a pipe (hereinafter simply referred to as a pipe) 12, and a tank (oil source) 14 is connected to the variable pump 13. . The variable pump 13 is driven by an electric motor 15 and supplies hydraulic pressure from a tank 14 to the injection cylinder 11.

The variable pump 13 is, for example, a swash plate type variable pump, and the capacity of the variable pump 13 is controlled by adjusting the position of the swash plate. That is, the variable pump 13
The capacity of is controlled by the swash plate drive cylinder section 16.

A piston 16a is arranged in the swash plate drive cylinder portion 16, whereby the swash plate drive cylinder portion 16 is located on the right side chamber (right side chamber) and the left side chamber (left side chamber) in the figure. ) And is divided into. And
The shaft body of the piston 16a is connected to the variable pump 13. Further, as shown in the figure, a swash plate position detector 17 is attached to the shaft of the piston 16a, and the swash plate position detector 1
Reference numeral 7 detects a swash plate position and supplies a flow rate (hydraulic flow rate) corresponding to the detected swash plate position to the pump control section 18 as a flow rate detection signal.

As shown, the swash plate drive cylinder portion 16
An electromagnetic proportional valve 19 is connected to the electromagnetic proportional valve 19, and hydraulic pressure is selectively supplied to the right side chamber and the left side chamber by the electromagnetic proportional valve 19. The solenoid proportional valve 19 is controlled by the pump controller 18 as described later.

When injecting the molten resin from the injection cylinder 11 into a mold (not shown), the electric motor 15 is driven and hydraulic oil (hydraulic pressure) is supplied from the variable pump 13 to the injection cylinder 11.
Is supplied to. Then, a flow rate command (hydraulic flow rate command) according to the melt injection speed is given to the pump control unit 18. The pump control unit 18 includes a subtractor 18a and a driver 18b. The subtractor 18a calculates the difference between the flow rate command and the flow rate detection signal and outputs the flow rate deviation. This flow rate deviation is given to the solenoid proportional valve 19 via the driver 18b, and the solenoid proportional valve 19 adjusts the hydraulic pressure amount to be supplied to the swash plate drive cylinder portion 16 according to the flow rate deviation. As a result, the piston 16a is driven rightward or leftward in the figure, and the swash plate position of the variable pump 13 is changed according to the movement amount of the piston 16a.
That is, the capacity is controlled. As described above, the swash plate position detector 17 detects the swash plate position according to the position of the piston 16a, and gives the flow rate (hydraulic flow rate) corresponding to the detected swash plate position to the pump control unit 18 as a flow rate detection signal.

In this way, the capacity of the variable pump 13 is controlled so that the flow rate deviation becomes zero, and the injection cylinder 11 injects the molten resin into the mold at the speed specified by the flow rate command.

[0010]

By the way, when the molten resin is filled in the mold by the injection cylinder 11, when the amount of the resin in the mold reaches a predetermined amount, the pressure in the mold rapidly rises. At this time, a sudden load pressure is applied to the injection cylinder 11, which compresses the hydraulic system, particularly the hydraulic oil in the pipe 2. That is, the volume of hydraulic oil is reduced.

When such hydraulic fluid compression occurs, an error occurs between the calculated hydraulic fluid flow rate and the actual hydraulic fluid flow rate. In other words, the actual hydraulic oil flow rate is insufficient, and as a result,
The injection speed will decrease. That is, there is a problem that the molten resin cannot be injected into the mold at a speed specified by the flow rate command. In other words, there is a problem that the conventional variable pump control device cannot control the variable pump to a flow rate according to the flow rate command.

An object of the present invention is to provide a variable pump control device capable of accurately controlling a variable pump to a flow rate according to a flow rate command.

[0013]

According to the present invention, there is provided a control device for controlling a variable pump for supplying hydraulic oil to an injection cylinder to drive the injection cylinder, the pressure detecting device detecting the pressure of the hydraulic oil. A pressure sensor for outputting a pressure detection value, and a compensation flow rate command value by compensating the flow rate command value with a flow rate command value of the variable pump according to the injection speed and a compensation value calculated from the pressure detection value. and compensating means for, controlling the flow rate of the variable pump in accordance with the compensation flow rate command value
And a control means for controlling the speed of the injection cylinder .

[0014]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below with reference to the drawings.

Referring to FIG. 1, in the illustrated variable pump controller, the same components as those of the variable pump controller shown in FIG. 3 are designated by the same reference numerals.

The illustrated variable pump control device is provided with a pump control unit having a configuration different from that of the pump control unit 18 shown in FIG. 3, and is shown by a reference numeral 20 in the illustrated example. The pump control unit 20 further includes a differentiating unit 20a, a gain unit 20b, and an adder 20c in addition to the subtractor 18a and the driver 18b. A pressure sensor 21 is provided in the pipe 12.
Is attached, and the pressure (hydraulic pressure) of the hydraulic circuit is detected by the pressure sensor 21. That is, the pressure sensor 21 detects the pressure of the hydraulic circuit and outputs the pressure detection value.

When injecting the molten resin from the injection cylinder 11 into a mold (not shown), the electric motor 15 is driven and hydraulic oil (hydraulic pressure) is supplied from the variable pump 13 to the injection cylinder 11.
Is supplied to. Then, a flow rate command (hydraulic flow rate command) according to the melt injection speed is given to the pump control unit 20 .

A pressure detection value is given from the pressure sensor 21 to the pump control section 20. Since the compression amount of the hydraulic oil is proportional to the pressure change, the pump control unit 20 calculates the pressure change amount per unit time by differentiating the pressure detection value by the differentiating unit 20a, and the pressure change amount is gained. Give to part 20b.

Further, the compression amount of the hydraulic oil is determined by the injection cylinder 11
Also, since it is proportional to the volume of the hydraulic oil in the pipe 12, the gain section 20b adjusts the gain according to the volume of the hydraulic oil and outputs it as a compensation value. Then, this compensation value is given to the adder 20c.

The adder 20c compensates the flow rate command with a compensation value and outputs it as a compensated flow rate. The subtractor 18a calculates the difference between the compensation flow rate and the flow rate detection signal provided from the swash plate position detector 17, and outputs the flow rate deviation. This flow rate deviation is given to the solenoid proportional valve 19 via the driver 18b, and the solenoid proportional valve 19 adjusts the hydraulic pressure amount to be supplied to the swash plate drive cylinder portion 16 according to the flow rate deviation. As a result, the piston 16a is driven rightward or leftward in the figure, and the swash plate position of the variable pump 13 is changed according to the movement amount of the piston 16a.
That is, the capacity is controlled. As described above, the swash plate position detector 17 detects the swash plate position according to the position of the piston 16a, and gives the flow rate (hydraulic flow rate) corresponding to the detected swash plate position to the pump control unit 18 as a flow rate detection signal.

Referring also to FIG. 2, the variable pump control device described in FIG. 3 (conventional variable pump control device) and the variable pump control device described in FIG. 1 (variable pump control device according to the present invention) are used. The control result when the speed of the injection cylinder is controlled will be described.

When the filling of the molten resin from the injection cylinder into the mold is started, the injection speed control according to the flow rate command is performed as described above. When the amount of resin in the mold reaches a predetermined amount (when it is almost filled), the pressure in the mold rapidly increases. At this time, a sudden load pressure is applied to the injection cylinder 11, which compresses the hydraulic system, particularly the hydraulic oil in the pipe 2. That is, the volume of hydraulic oil is reduced.

When such hydraulic oil compression occurs, the actual hydraulic oil flow rate becomes insufficient, and in the conventional variable pump control device, the injection speed decreases as shown by the solid line in FIG. That is, the injection speed cannot be controlled to be constant according to the flow rate command.

On the other hand, in the variable pump control device according to the present invention, even if a sudden load pressure is applied to the injection cylinder 11 to reduce the volume of the hydraulic oil, the flow rate command is issued according to the change in the hydraulic oil pressure as described above. Because of the compensation, the injection speed can be kept constant until the filling is completed, as shown by the broken line in FIG.

[0025]

As described in the foregoing, the present invention detects the pressure of the hydraulic oil, so as to compensate for the flow rate command corresponding to the injection speed in accordance with the detected value, depending on the compensation flow rate command value
Control the flow rate of the variable pump to control the speed of the injection cylinder.
Since the control is performed , there is an effect that the injection can always be performed at a constant speed even when the hydraulic oil is compressed.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an example of a variable pump control device according to the present invention.

2 is a diagram showing flow rate control in the variable pump control device shown in FIG. 1 in comparison with a conventional example.

FIG. 3 is a diagram for explaining a conventional variable pump control device.

[Explanation of symbols]

11 injection cylinder 12 piping 13 Variable pump 14 tanks 15 electric motor 16 Swash plate drive cylinder 17 Swash plate position detector 18, 20 Pump control unit 19 Solenoid proportional valve 21 Pressure sensor

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Claims (3)

(57) [Claims] 1. A control device for supplying a hydraulic oil to an injection cylinder to control a variable pump for driving the injection cylinder, the pressure sensor detecting a pressure of the hydraulic oil and outputting a pressure detection value. A compensation means for compensating the flow rate command value with a flow rate command value of the variable pump according to the injection speed and a compensation value calculated from the pressure detection value to obtain a compensated flow rate command value; According to the flow rate of the variable pump to control the speed of the injection cylinder.
Variable pump control apparatus characterized by a control means for performing. 2. The variable pump control device according to claim 1, wherein the compensation means differentiates the pressure detection value to obtain a pressure change amount per unit time, and the pressure change amount is predetermined. 2. A variable pump control device, comprising: a gain adjusting unit that adjusts a gain by the gain of 1 to obtain a compensation value; and an adding unit that compensates the flow rate command with the compensation value to obtain the compensated flow rate command value. 3. The variable pump control device according to claim 2, wherein the control means detects a flow rate of the variable pump and outputs a detected flow rate value, the compensation flow rate command value and the detection value. A variable pump control device comprising: a deviation calculating means for calculating a deviation from a flow rate value; and an adjusting means for adjusting a flow rate of the variable pump according to the deviation.