JPH05138325A - Method for controlling pressurizing stroke in pressurized casting - Google Patents

Abstract

PURPOSE:To reduce delay of the response just after starting of the control and to improve the followup ability by applying an interpolation of quadratic curve in the time base from a proportional gain constant at the time of starting the control and a proportional gain constant after passing the time and making the proportional gain constant within the passing time variable. CONSTITUTION:The proportional gain constant P is calculated with the interpolation of quadratic curve from the time (t) of starting working of a pressurizing plunger 17 through a PID control arithmetic setting part 5 and an arithmetic processing is executed based on the result of deviation (e) together with an integral I and a differential D gain constants and converted into a pressure command value Pc. At the time of inputting the pressure command value Pc in a driver 4, this value is converted into a signal Prf for driving a solenoid relief valve 5 to control the pressure in a hudraulic source 6, and the hydraulic force to a pressurizing cylinder 8 is controlled through a directional changing valve 7. By this method, the feedback control is executed to the actual stroke quantity of the pressurizing plunger 17 and the stable feeder head effect of the necessary level is always given to molten metal. 20, and a casting product having close structure without shrinkage cavity, etc., can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is to obtain a cast product by injecting a molten metal into a cavity of a mold by an injection device and pressurizing the molten metal in the mold by a pressure device having a pressure plunger. The present invention relates to a pressure stroke control method in pressure casting.

[0002]

2. Description of the Related Art A molten metal is injected into a cavity of a mold device by an injection plunger of an injection device, while a pressurizing device having a pressure plunger presses the molten metal injected into the mold by pressing. The pressure casting method realizes a pressure casting method in which cooling water flows in and passes through the pressure plunger to give a cooling effect to the molten metal from the center side and prevents the formation of cavities due to the sink in the workpiece. Casting machines are already known. Further, in a casting machine having an injection device for injecting the molten metal into the mold and a pressurizing device for pressurizing the molten metal injected into the mold,
The moving stroke of the pressurizing plunger of the pressurizer is set as a target trajectory using a computer over time based on the time from the start of operation of the plunger, and feedback control is performed along the target trajectory. There is. As the control calculation formula of this feedback control, the PID control calculation formula is used, and the pressure plunger stroke control is
For example, as shown by the proportional gain P _A being constant in FIG. 3, one PID constant is used.

[0003]

However, in the above-described conventional pressurizing stroke control method, one PID constant is used for feedback control.
If the D constant is set in the steady state where the plunger is moving, a response delay of, for example, about 1 second occurs immediately after the control is started. Immediately after the control is started, the deviation between the target value of the plunger stroke and the actual stroke value is small, so the hydraulic pressure, that is, the control output value is small, and the plunger cannot be operated. The present invention focuses on the above-mentioned conventional problems, and an object thereof is to improve followability in feedback control of a pressure plunger stroke.

[0004]

[Means for solving the problem] In the pressure casting method using a pressure casting machine, when controlling the stroke amount of the pressure plunger, the horizontal axis is set as the time axis and the stroke amount is set as the vertical axis. When performing feedback control to obtain the same stroke amount, time-based quadratic curve interpolation is performed using the preset proportional gain constant at the start of control and the preset proportional gain constant after the elapse of time.
The proportional gain constant within a preset elapsed time can be changed.

[0005]

As described above, in the present invention, since the proportional gain constant within the preset elapsed time can be changed, the proportional gain constant at the start of control is made considerably larger than the proportional gain constant after the elapsed time, Even if the deviation between the target value of the plunger stroke immediately after the start of control and the actual stroke value is small, the control output value can be increased, the response delay immediately after the start of control is reduced, and the followability is improved.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a mechanism diagram of a mold apparatus and a pressure casting system for carrying out the pressure stroke control method of the pressure casting method according to the present invention. The mold 10 includes an upper mold 12 and a lower mold 14 which can be relatively opened and closed relative to each other, and a core 16 which is opened and closed laterally with respect to the vertical opening and closing axis of the upper mold 12 and the lower mold 14.
And is configured. Of course, FIG. 1 shows a state where the mold apparatus 10 is clamped by a mold clamping mechanism (not shown). These upper mold 12, lower mold 14, core 1
6, the cavity 18 which is a casting space is formed,
In the cavity 18, the injection plunger 1 of the injection device 13
The molten metal 20 previously supplied into the injection sleeve 15 is injected by the ascent of 1 and the plunger tip 11a to fill the cavity 18. For supplying the molten metal to the injection device 13, when the injection device 13 is in a position retracted downward, the molten metal is supplied to the injection sleeve 15 by a molten metal feeder, and the structure is generally provided. Has been.

The upper die 12 is opposed to the injection plunger 11.
A pressure plunger 17 of the pressure device is slidably disposed above the upper part of the cavity and is projectable into the cavity 18. The pressure plunger 17 is connected to a piston 8c of a pressure cylinder 8 attached to a movable plate (not shown). The tip of the pressurizing plunger 17 is provided so as to be able to project to a gate seal position of the mold cavity 18, that is, a position where it starts to enter the central hole opening 18a of the lower mold 14. The operation of the pressurizing cylinder 8 is performed by applying pressure oil supplied from the hydraulic pressure source 6 to the cylinder chamber 21 via the direction switching valve 7.
It is activated by supplying a or 21b. At this time, the return oil returns to the tank 19. That is, by energizing the solenoid SOL-a of the direction switching valve 7, the hydraulic power source 6
If the hydraulic oil in the rod chamber 8b is released to the tank 19 via the oil passage 21b at the same time as the hydraulic oil in the rod chamber 8b is guided to the head chamber 8a of the pressurizing cylinder 8 via the oil passage 21a, the piston 8
c advances, and the tip of the pressure plunger 17 projects into the cavity 18 of the mold apparatus 10 as shown in the figure. On the contrary, when the solenoid SOL-b of the direction switching valve 7 is excited, the piston 8c of the pressurizing cylinder 8 rises in the opposite manner, and the tip of the pressurizing plunger 17 is housed in the upper mold 12 from the cavity 18. It works as it is done.

The pressure of the hydraulic pressure source 6 can be controlled by the electromagnetic relief valve 5 which is an electromagnetic proportional automatic pressure valve. That is, the pressure relief from the hydraulic pressure source 6 can be controlled according to the magnitude of the input electric signal to the electromagnetic relief valve 5, and thus the protrusion pressure of the pressurizing plunger 17 can be controlled. The stroke position or stroke amount when the piston 8c of the pressurizing cylinder 8, that is, the pressurizing plunger 17 projects or retracts with respect to the cavity 18, can be detected by the position detector 9 including, for example, a potentiometer, An electric signal can be output according to the position.

On the other hand, a pressure plunger control means 22 comprising computer means such as a microcomputer and a personal computer is provided, and this pressure plunger control means 22 projects the pressure plunger 17 into the mold cavity 18 with respect to time. The command signal setting unit 1, which can set the change in the stroke amount by the time as the target locus T ₀ , compares the input signal which is the detection signal of the position detector 9 with the command input signal from the command signal setting unit 1 and calculates, The deviation output signals of the deviation calculation unit 2 and the deviation calculation unit 2 which output the deviation output signals corresponding to the deviation values of both of these input signals are received, appropriate gain calculation processing is performed, and a predetermined value corresponding to the deviation output signal is received. And a PID control calculation setting unit 3 for outputting an output signal of the pressure plunger control means 22. The input means 23 is a computer, memory such as ROM and RAM, display means 24 is a CRT, and arithmetic means such as a microprocessor MPU or CPU. The command signal setting unit 1, the deviation calculation unit 2, and the PID control calculation setting unit 3 constitute a feedback controller for the pressurizing cylinder 8 that activates the pressurizing plunger 17. Therefore, P
The output of the ID control calculation setting section 3 is sent to an electromagnetic relief valve 5 which constitutes a pressure adjusting valve via a driver 4 and an I / O means (not shown). Therefore, the pressurizing cylinder 8 is feedback-controlled by the feedback controller, the electromagnetic relief valve 5, and the direction switching valve 7, and the stroke amount of the pressurizing plunger 17 is controlled so as to follow the target locus T ₀ .

FIG. 2 is a time t-proportional gain constant P curve according to the present invention. In FIG. 2, the proportional gain constant P at the start of control is P _S , and the proportional gain constant after the elapsed time t _A is P
_A. Note that P _S , t _A , and P _A are set in advance. The linear gain constant is expressed as follows when linearly interpolated on a time basis.

[0011]

[Formula 1]

[0012]

[Formula 2]

Therefore, in the PID control calculation setting unit 3 of FIG.
Performs PID operation processing using the proportional gain constant P that between _S and P _A is calculated by a quadratic curve interpolation.

The operation of the mold apparatus and the pressure casting system configured as above will be described. As shown in FIG. 1, when the injection plunger 11 completes the filling of the molten metal, a host controller (not shown) issues an operation command of the pressure plunger 17 at predetermined time intervals to the pressure plunger control means 22.
The solenoid SOL-a of the directional control valve 7
To excite. In the command signal setting unit 1 of the pressurizing plunger control means 22, a desired locus of the stroke amount St of the pressurizing plunger 17 with respect to time t from the start of the plunger operation is programmed in advance as the above-mentioned target locus T _0. Therefore, when the above-mentioned operation command is received, the target trajectory T ₀
The stroke amount St is subjected to time-division processing every few milliseconds, for example, and is input to the deviation calculator 2. The deviation calculation unit 2 calculates a deviation e (= St−St ′) from the actual stroke position St ′ of the pressure plunger 17 detected by the position detector 9, and the calculated deviation e (= St−St ′) is sent to the PID control calculation setting unit 3. input.

The PID control calculation setting unit 3 calculates the proportional gain constant P by the quadratic curve interpolation as described above from the time t from the start of the operation of the pressurizing plunger 17,
The PID calculation process is performed based on the result of the deviation e together with the integral I and the differential D gain constant, and the pressure command value P that is the control amount is obtained.
Convert to c. When the pressure command value Pc is input, the driver 4 converts it into a signal Prf that actually drives the electromagnetic relief valve 5, controls the pressure of the hydraulic pressure source 6, and controls the pressure of the hydraulic pressure source 6 through the directional switching valve 7 to the oil pressure cylinder 8. The pressure is controlled. In this way, by controlling the pressure for operating the pressurizing cylinder 8 on the basis of the deviation between the target trajectory T ₀ in the stroke amount of the pressurizing plunger 17 and the actual stroke amount Ta, the actual pressure of the pressurizing plunger 17 is controlled. The stroke amount is feedback-controlled, and as a result, the pressurizing plunger 17 always gives the molten metal 20 a stable feeder effect of a required level, and a dense and good-quality cast product having no shrinkage cavities inside can be obtained. Like

[0016]

As described above, according to the present invention,
When performing feedback control of the pressure plunger stroke, the preset proportional gain constant at the start of control and the preset proportional gain constant after the elapse of time
Time-based quadratic curve interpolation is performed to make the proportional gain within a preset elapsed time relatively fast at the beginning, and then relatively slowly, and finally to a desired constant gain that is constant. By slowing down, the proportional gain constant at the start of control is increased, the response delay immediately after the start of control is eliminated, and the actual stroke can be controlled quickly and smoothly along the target trajectory. It is possible to manufacture a high-quality cast processed product that does not have cavities or cracks that occur in the product.

[Brief description of drawings]

FIG. 1 is a mechanism diagram showing one embodiment of a mold apparatus and a pressure casting system for carrying out the method of the present invention.

FIG. 2 is a time-proportional gain diagram for explaining the pressure stroke control method according to the present invention.

FIG. 3 is a time-proportional gain diagram showing an example of a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Command signal setting part 2 Deviation calculation part 3 PID control calculation setting part 8 Pressurizing device 9 Position detector 10 Mold device 11 Injection plunger 13 Injection device 17 Pressurizing plunger 18 Cavity 20 Molten metal 22 Pressurizing plunger control means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location G05B 13/02 A 9131-3H

Claims (1)

[Claims] 1. In pressure casting in which the molten metal is filled in the mold by the action of the injection device and the pressure plunger facing the injection device is moved forward to press the molten metal in the mold,
When performing feedback control of the pressure plunger stroke, the preset proportional gain constant at the start of control and the preset proportional gain constant after the elapse of time
A pressurizing stroke control method in press casting, characterized in that time-based quadratic curve interpolation is performed to make a proportional gain constant variable within a preset elapsed time.