JPH06226416A - Method for controlling pressurizing pin - Google Patents

Abstract

PURPOSE:To control the operation of a pressurizing pin to the optimum condition being suitable to the solidification state of molten metal in a die casting. CONSTITUTION:In each time after starting the operation of the pressurizing pin 4, the stroke quantity of the pressurizing pin 4 is measured and this measured value is compared with the preset master data M. Then, the working pressure of cylinder 5 for operating the pressurizing pin 4 and the flow rate of hydraulic oil are controlled in the direction where the difference between both becomes zero.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a pressure pin in die casting.

[0002]

2. Description of the Related Art Conventionally, as a technique relating to the control of the pressure pin, for example, there is one disclosed in Japanese Patent Application Laid-Open No. 2-75460. According to this technique, the stroke of the pressure pin is measured for each shot. The pressurizing timing of the pressurizing pin in the next shot was controlled based on the measured value.

[0003]

However, this conventional control method only controls the timing of starting the pressurization in the next shot, and the control of the pressurizing pin at the present time is not performed. Therefore, for example, if the stroke of the pressurizing pin is too large due to some trouble, the timing of starting the pressurization in the next shot will be delayed from the optimum timing due to the trouble.

Further, the molten metal in the cavity gradually solidifies with the passage of time. Therefore, in order to maximize the effect of the pressure pin, the pressure pin should be moved at a speed suitable for the solidification state. It needs to be activated,
In the conventional control method described above, the timing of starting the pressurization is controlled, but the pressurizing speed (the moving speed of the pressurizing pin) after starting the pressurization is not controlled at all. Therefore, the pressurizing pin cannot be operated in a state adapted to the solidified state of the molten metal which changes with the passage of time, and thus there is a problem in that the quality varies.

The present invention has been made in order to solve these conventional problems, and by controlling in consideration of the solidification state of the molten metal which changes with time, it is possible to perform die casting with stable quality. It is an object to provide a pin control method.

[0006]

Therefore, according to the present invention, the stroke amount of the pressure pin is measured at each time after the operation of the pressure pin is started, and the measured value is compared with preset master data. The operating pressure of the cylinder that operates the pressurizing pin and the flow rate of the hydraulic oil are controlled so that the difference between the two is zero.

[0007]

According to the above method, the stroke amount of the pressurizing pin is controlled so as to follow preset master data by controlling the pressure and flow rate of the hydraulic oil in the cylinder that operates the pressurizing pin. This master data is set with an optimum stroke amount according to the solidification state of the molten metal which changes with the passage of time. Therefore, the stroke amount of the pressurizing pin is controlled to the optimum state for the solidified state of the molten metal, which changes with time, and real-time control can be performed.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a pressure pin control system for implementing the control method of this example. In the figure, 1 is a movable mold, 2 is a fixed mold, and 3 is a cavity formed by closing both molds 1 and 2.

The pressure pin 4 is incorporated in the fixed mold 2 so as to be able to project into the thick portion of the cavity 3.
The pressurizing pin 4 is coaxially attached to the rod tip of a double-acting hydraulic cylinder 5, and is pushed into the cavity 3 by the operation of the hydraulic cylinder 5 and also retreats from the cavity 3. There is.

The hydraulic cylinder 5 is adapted to operate by switching a 4-port 3-position solenoid valve 7. Pipe line 1 connecting the output port 7a of the solenoid valve 7 and the port 5a on the protruding side of the hydraulic cylinder 5
A pressure control valve 8 is incorporated in the middle of 5. Also,
Between the solenoid valve 7 and the hydraulic pressure source 10, the hydraulic pressure source 10
A flow rate control valve 9 for controlling the amount of oil supplied from is incorporated.

The pressure control valve 8 and the flow control valve 9 are operated by a controller 11, and the controller 11 operates both control valves 8, 9 based on a control value calculated by a CPU 12 of a control device 13. It is supposed to do.

Next, the hydraulic cylinder 5 is provided with a sensor 6 (potentiometer) for measuring the stroke amount and hence the stroke amount of the pressurizing pin 4. This sensor 6 is relay-connected to the CPU 12,
The stroke amount of the pressure pin 4 is read by the CPU 12.

Reference numeral 14 in the drawing is a control board for controlling the entire die casting apparatus, and reference numeral 17 is a plunger tip for injecting the molten metal into the cavity 3.

Next, the operation of the pressurizing pin 4 is controlled as follows by the control system having the above structure. First, the operating state of the pressure pin 4 when die casting is performed under optimum conditions is obtained as master data (target value) by CAE or an actual casting test in advance, and this is stored in the CPU 12. This master data is shown by a solid line in FIG. 2 and is denoted by M. Further, the broken line in the figure shows the actual measurement value of the operating state of the pressure pin in actual casting.

Now, when the time "a" is reached in the actual casting, the control panel 14 issues a command to start the operation of the pressure pin to the controller 11. Then, as shown in FIG. 3, the flow control valve 9 is opened to supply a fixed amount of pressure oil to the circuit, and the solenoid valve 7 is switched to supply this pressure oil to the head side of the hydraulic cylinder 5. This causes the pressure pin 4 to start operating in the protruding direction.

When the pressurizing pin 4 starts to operate, the operation of the pressure control valve 8 and the flow control valve 9 is controlled so that the pressurizing pin 4 operates following the master data M.
That is, the operating speed of the hydraulic cylinder 5, that is, the pressure pin is controlled by controlling both control valves 8 and 9 so that the actual behavior of the pressure pin 4 indicated by the broken line matches the master data M indicated by the solid line in FIG. The pressurizing speed of 4 is controlled.

FIG. 3 shows a pressure control valve 8 and a flow control valve 9.
Shows the change over time in the control values of both control valves 8 and 9. According to this, when the signal for starting the pressurizing pin operation is input from the control panel 14 to the controller 11 at the time a, the flow rate control value (shown by the solid line in the figure) is raised to a constant value as described above. The flow rate control valve 9 is opened by a predetermined amount, whereby a fixed amount of pressure oil flows into the pipe line 15 via the electromagnetic valve 7.

At the same time, the pressure control value (indicated by the broken line in the figure) is gradually increased from time a, the pressure of the pressure oil flowing into the pipe line 15 is increased, and the thrust of the hydraulic cylinder 5 is gradually increased. Will be raised to.

Here, as shown in FIG. 2, the actual stroke amount of the pressurizing pin 4 is deviated to a smaller amount than the master data M between the time points a and b, which is the pressurizing pin 4. It is shown that the pressurization speed of is slower than the optimum speed. The measured value of the stroke amount is measured by the sensor 6, converted into an electric signal, and then the CPU 12
Entered in.

Therefore, in this case, the controller 11 controls the pressure control valve 8 so as to increase the pressure control value as described above, whereby the stroke amount of the pressurizing pin 4 is increased per unit time (pressurizing). Increase the speed). That is, the difference between the measured value and the master data M is X, the elapsed time from the start of pressurization (time a) is T, and the gain coefficient is R.
In this case, the CPU 1 calculates the control value = X × T × R.
2 and the pressure control valve 8 is operated based on this to increase the pressure in the conduit 15. As a result, the thrust of the hydraulic cylinder 5 increases, and therefore the change over time in the stroke amount thereof gradually increases, and coincides with the master data M at time b. As shown in FIG. 3, the control value of the flow rate control valve 9 is kept constant during the time period a-b, and the flow rate of the pressure oil in the circuit is controlled so as not to change.

Next, during the time period bc, the stroke amount of the pressurizing pin 4 deviates to the larger side than the master data M. Therefore, in this case, the flow rate control value is controlled by the controller 11 so as to reduce the opening degree of the flow rate control valve 9 in order to reduce the increase amount of the stroke amount per unit time (see FIG. 3). This control is also performed based on the calculation by the CPU 12 in the same manner as described above, and the pipeline 15
The flow rate of pressure oil inside is gradually reduced. As a result, the temporal change in the stroke amount of the pressurizing pin 4 (pressurizing speed) gradually decreases, and coincides with the master data M at time c. In this case, the pressure control value is held constant as shown in the figure.

As described above, according to the control method of this embodiment, the pressure control valve is controlled so that the stroke amount of the pressurizing pin 4 in actual casting follows the master data M, that is, the difference between the two becomes zero. 8 and the flow control valve 9 are controlled to control the pressure and flow rate of the hydraulic cylinder 5 that moves the pressurizing pin 4.

Therefore, the stroke amount of the pressurizing pin 4 is controlled in real time with the passage of time, and is controlled to the optimum stroke amount suitable for the solidified state of the molten metal which changes every moment. A product in a good solidified state can be stably obtained regardless of variations.

Further, according to the control method of this embodiment, since the pressurizing speed of the pressurizing pin 4 is controlled over a certain fixed time of, for example, several seconds, the timing of starting the operation of the pressurizing pin 4 is strict. It is not necessary to set to, and the operation may be started within the range of a certain time period. From this, the variation in the timing of starting the operation of the pressure pin 4 is absorbed,
Also in this respect, it becomes possible to perform die casting with stable quality.

Furthermore, by detecting an actual value of the stroke amount of the pressurizing pin 4 or an abnormal value of the control value issued from the controller 11, troubles such as molds can be found at an early stage. It can also have a function of detecting.

In this example, the configuration using the potentiometer as the sensor 6 is illustrated, but the sensor 6 is not limited to this, and other means such as an encoder may be used. In short, the stroke amount of the hydraulic cylinder 5 is measured. Anything that can be converted into an electric signal and output to the CPU 12 may be used. Further, other configurations can be implemented by making various modifications without departing from the scope of the claims.

[0027]

According to the present invention, since the stroke amount of the pressure pin is controlled in real time according to the elapsed time,
The pressurizing pin can be operated in an optimum state suitable for the solidification state of the molten metal, and thus die casting can be performed with stable quality.

[Brief description of drawings]

FIG. 1 is a control circuit diagram of a pressure pin showing an embodiment of the present invention.

FIG. 2 is a graph showing a temporal change in the stroke amount of a pressurizing pin, comparing master data with measured values.

FIG. 3 is a graph showing temporal changes in pressure control value and flow rate control value.

[Explanation of symbols]

 1 ... Movable mold 2 ... Fixed mold 3 ... Cavity 4 ... Pressurizing pin 5 ... Hydraulic cylinder 6 ... Sensor 7 ... Solenoid valve 8 ... Pressure control valve 9 ... Flow control valve 11 ... Controller 12 ... CPU 14 ... Die casting control panel

Claims (1)

[Claims] 1. At each time after starting the operation of the pressure pin, the stroke amount of the pressure pin is measured, the measured value is compared with preset master data, and the difference between the two is set to zero. A method for controlling a pressurizing pin, characterized in that the operating pressure of a cylinder for operating the pressurizing pin and the flow rate of hydraulic oil are controlled.