JPH06226417A - 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:Timing of starting the working of the pressurizing pin 4 is set to the time to the time when die temp. drops at a prescribed value, and in each time after starting the operation, the stroke quantity of the pressurizing pin 4 is measured and compared with the preset master data M. Then, the working pressure of a 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, and the cooling of the pressurizing pin 4 is started at the time after the lapse of prescribed time from the timing of starting the operation of the pressurizing pin 4.

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, there is one disclosed in, for example, Japanese Patent Application Laid-Open No. 58-9758. According to this, the timing of starting the pressurization of the pressurizing pin was controlled based on the mold temperature or the molten metal temperature.

[0003]

Here, the molten metal in the cavity is gradually solidified with the passage of time, and in order to maximize the effect of the pressurizing pin, it is suitable for the solidification speed of this molten metal. It is necessary to operate the pressure pin at a speed.

However, according to the above conventional control method, although the timing of starting the pressurization of the pressurizing pin is controlled, the pressurizing speed (the moving speed of the pressurizing pin) after starting the pressurizing is controlled at all. Didn't. 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.

Generally, this type of pressurizing pin is cooled by circulating cooling water inside the pressurizing pin to prevent its deformation or melting damage due to heat load. The cooling state of this pressure pin was not controlled at all, and since it was cooled from the start of the operation of the pressure pin, the molten metal around it began to solidify early, and therefore the operation of the pressure pin was restricted. In this respect as well, there is a problem in that the solidified state of the molten metal varies, and therefore the quality is not stable.

The present invention has been made in view of these conventional problems, and an object of the present invention is to provide a control method of a pressure pin which can perform stable die casting.

[0007]

For this reason, the present invention sets the timing for starting the operation of the pressurizing pin at the time when the mold temperature falls to a predetermined value, and at each time after the operation is started, the above-mentioned addition is performed. The stroke amount of the pressure pin is measured, and this measured value is compared with preset master data, and the operating pressure of the cylinder that operates the pressure pin and the flow rate of hydraulic oil are controlled in the direction to make the difference between them zero. In addition, cooling of the pressure pin is started when a predetermined time has elapsed from the timing of starting operation of the pressure pin.

[0008]

According to the above method, the timing of starting the operation of the pressurizing pin is set at the time when the mold temperature reaches the predetermined value, so that when the molten metal is solidified to an appropriate state, the pressurizing pin is applied. The pressure is started.

The stroke amount of the pressurizing pin after the pressurization is started follows the preset master data by controlling the pressure and flow rate of the hydraulic oil in the cylinder that operates the pressurizing pin. Controlled. Here, this master data is set with an optimum stroke amount at each time 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 an optimum state that matches the solidified state of the molten metal that changes with time.

Further, since the cooling of the pressurizing pin is started after a lapse of a predetermined time after the start of pressurization, the operation of the pressurizing pin is not hindered by the cooling of the pressurizing pin, and the operation is controlled to the above-mentioned optimum state. You can

[0011]

Embodiments of the present invention will be described below 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 end 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 operates by switching the solenoid valve 7. Both solenoids of the solenoid valve 7 are relay-connected to the controller 11 of the control device 13, so that the solenoid valve 7 operates according to a command from the controller 11, and thus the hydraulic cylinder 5 and the pressurizing pin 4 operate. This controller 11
Is controlled by.

A pressure control valve 8 is incorporated in the middle of a conduit 20 connecting the output port 7a of the solenoid valve 7 and the projecting port 5a of the hydraulic cylinder 5. A flow control valve 9 for controlling the amount of oil supplied from the hydraulic source 10 is provided between the solenoid valve 7 and the hydraulic source 10.
Is built in.

The operations of the pressure control valve 8 and the flow rate control valve 9 are controlled by a controller 11. The controller 11 controls the CPU 1 of the controller 13.
Both control valves 8, 9 based on the control value calculated by 2
To operate.

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 so that the stroke amount of the pressure pin 4 is
12 is read.

The pressurizing pin 4 has a water cooling function. That is, inside the hydraulic cylinder 5, a water supply pipe 18 and a drain pipe 19 are pierced through the wall surface on the head side, and the water supply pipe 18 and the drain pipe 19 are further provided.
Although not shown in the figure, each of them reaches the inside of the pressurizing pin 4 through the inside of the rod of the hydraulic cylinder 5 and is connected to each other at the tips. The water supply pipe 18 is connected to a water supply source (not shown) via a solenoid valve 15, and switching of the solenoid valve 15 is controlled by the controller 11. As a result, the solenoid valve 15 is switched to the open side to circulate the cooling water from the water supply pipe 18 to the drain pipe 19 to cool the pressurizing pin 4 and thus to positively cool the molten metal around the pressurizing pin 4. Therefore, the timing for starting the cooling of the pressurizing pin 4 and the cooling time are appropriately controlled by the controller 11.

Next, a thermocouple 16 as a temperature sensor is embedded in the fixed mold 2 in the vicinity of the pressure pin 4. The thermocouple 16 is relay-connected to the control device 13, so that the mold temperature near the pressurizing pin 4 is controlled by the CPU.
12 is read. Although the thermocouple 16 is used in this example, the invention is not limited to this.
The point is that the temperature sensor is capable of measuring the temperature around the pressurizing pin 4, converting it into an electric signal and inputting it to 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 chip for injecting the molten metal into the cavity 3.

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

In actual casting, the mold temperature in the vicinity of the pressing pin 4 is measured by the thermocouple 16. When the temperature drops to a predetermined value at time a as shown in FIG. Is entered. When the CPU 12 reads that the mold temperature has dropped to a predetermined temperature, the controller 11 issues a signal to start the operation of the pressure pin at this point.

When a signal for starting the operation of the pressurizing pin is issued at time a, first, the flow control valve 9 is opened to supply a predetermined amount of pressure oil as shown in FIG. Pressure oil is supplied to the head side of the hydraulic cylinder 5. As a result, the pressure pin 4 starts to operate 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 pressure control valve 8 and the flow rate control valve 9 are controlled so that the actual operating state of the pressurizing pin 4 shown by the broken line in FIG. The pressurizing speed of the pin 4 is controlled.

FIG. 4 shows the operating state of the pressure control valve 8 and the flow rate control valve 9, that is, the change over time in the control value that governs the operation of both control valves 8 and 9. According to this, time a
When a signal for starting the operation of the pressurizing pin is issued from the controller 11 at, the flow rate control value (shown by the solid line in the figure) is raised to a constant value as described above, and the flow rate control valve 9 is opened by a predetermined amount. As described above, a certain amount of pressure oil flows into the conduit 20 via the solenoid 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 20 is increased, and the thrust of the hydraulic cylinder 5 is gradually increased. Will be raised to.

Here, as shown in FIG. 3, the actual stroke amount of the pressurizing pin 4 is deviated to a smaller amount than the master data M between the times a and b. 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 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, the pressure control valve 8 is operated based on this to increase the pressure in the conduit 20. As a result, the thrust of the hydraulic cylinder 5 increases, and therefore the change over time of the stroke amount thereof gradually increases, and coincides with the master data M at time b. As shown in FIG. 4, 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. 4). Similarly to the above, this control is also performed based on the calculation by the CPU 12, and the pipeline 2
The flow rate of pressure oil within 0 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.

Further, in parallel with the control of both control valves 8 and 9, the timing of starting cooling of the pressurizing pin 4 is controlled. That is, as shown in FIG. 5, when only time t1 elapses from time a, a signal is issued from the controller 11 to switch the electromagnetic valve 15, the cooling water is supplied to the water supply pipe 18, and the cooling of the pressurizing pin 4 is started. To be done. When a time t2 has elapsed from the start of cooling, the solenoid valve 15 is switched to stop the circulation of the cooling water, so that the cooling of the pressurizing pin 4 is completed.

As described above, according to the control method of this embodiment, the pressure is adjusted 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. The operation of the control valve 8 and the flow rate control valve 9 is 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 be the optimum stroke amount which is adapted to the solidified state of the molten metal, which varies from moment to moment. Regardless of this, a product in a good solidified state can be stably obtained.

Further, since the timing of starting the pressurizing pin is set based on the mold temperature, it is unlikely to be affected by fluctuations in the hot water temperature, etc., and the same timing can be stabilized.

Further, since the cooling of the pressure pin 4 is started after a lapse of time t1 from the time a, the molten metal around the pressure pin is rapidly cooled and solidified immediately after the pressure pin is actuated. The problem that the operation of the pin 4 is obstructed is eliminated, and therefore the operation of the pressure pin 4 can be controlled as described above without any obstacle.

Further, by appropriately setting the time t1 and the time t2 with respect to the cooling of the pressurizing pin 4, it becomes possible to cool the periphery of the pressurizing pin in an optimum state, and also in this respect, the quality is stabilized. In addition to the above, it is possible to cool the pressurizing pin 4 by circulating the cooling water for a necessary time, so that the useless cooling of the pressurizing pin 4 when not operating can be eliminated, thus saving the cooling water. You will be able to plan.

In the embodiment described above, the sensor 6
Although the configuration using the potentiometer has been illustrated as an example, the sensor 6 is not limited to this, and may be another means such as an encoder. In short, the stroke amount of the hydraulic cylinder 5 is measured and converted into an electric signal. It is only necessary that the data can be output to the CPU 12 as a result. Further, the temperature sensor for measuring the mold temperature is not limited to the thermocouple 16, and various modifications can be made without departing from the scope of the claims.

[0036]

According to the present invention, the stroke amount of the pressurizing pin is controlled in real time according to the elapsed time, and the cooling of the pressurizing pin is started after a predetermined time has elapsed from the start of operation of the pressurizing pin. Therefore, the pressurizing pin can be operated in an optimum state adapted to the solidified 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 changes over time in mold temperature.

FIG. 3 is a graph showing a temporal change in the stroke amount of a pressure pin by comparing master data with an actually measured value.

FIG. 4 is a graph showing temporal changes in pressure control value and flow rate control value.

FIG. 5 is a timing diagram showing an operating state of a solenoid valve for switching cooling water.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Movable mold 2 ... Fixed mold 3 ... Cavity 4 ... Pressurizing pin 5 ... Hydraulic cylinder 6 ... Sensor 7 ... Electromagnetic valve (for pressurizing pin operation) 8 ... Pressure control valve 9 ... Flow control valve 10 ... Hydraulic source 11 ... Controller 12 ... CPU 13 ... Control device 14 ... Die-casting control panel 15 ... Electromagnetic valve (for cooling pressurizing pin) 16 ... Thermocouple 18 ... Water supply pipe 19 ... Drain pipe

Claims (1)

[Claims] 1. The timing for starting the operation of the pressure pin is set at the time when the mold temperature drops to a predetermined value, and the stroke amount of the pressure pin is measured at each time after the operation is started. The measured value is compared with preset master data, and the operating pressure of the cylinder that operates the pressurizing pin and the flow rate of hydraulic oil are controlled in the direction to reduce the difference between them, and the operation of the pressurizing pin is started. The method for controlling a pressurizing pin is characterized in that cooling of the pressurizing pin is started at a time point when a predetermined time has passed after the timing.