JPH0788621A - Detection of galling of pressurizing plunger in pressurized casting machine - Google Patents

Abstract

PURPOSE:To obtain a high quality pressurized cast product without cast defect by automatically and easily executing the detection of galling of a pressurizing plunger in a pressurized casting machine. CONSTITUTION:Feedback control is executed to an advancing stroke of the pressurizing plunger 17 so as to follow to the aimed locus To showing the preset stroke rate ST with time of the pressurizing plunger 17 into a die cavity 18. The preset average MA of a metal pressure in the pressurizing plunger 17 in the deciding section and the preset upper limit value MH of the metal pressure are compared and the galling of the pressurizing plunger 17 is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die casting machine for injecting 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 to obtain a cast product. For example, when feedback control of pressurizing work by the pressurizing plunger of the pressurizing device is performed by computer control, the galling of the pressurizing plunger is automatically detected to improve the machine body or The present invention relates to a method for detecting galling of a pressure plunger in a pressure casting machine capable of giving an alarm for an abnormal state of the pressure plunger.

[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. While applying pressure, cooling water flows into and passes through the pressure plunger to exert a cooling effect on the molten metal from the center side, which realizes a pressure casting method that 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 movement stroke of the pressurizing plunger of the pressurizing device is set to the operation of the plunger. A target locus is set over time using a computer based on the time from the start point, and control is performed so as to follow the target locus, thereby optimizing the movement stroke of the pressure plunger and improving casting accuracy. A pressure casting machine designed to achieve the above and a control method thereof have already been filed by the present applicant in Japanese Patent Application No. 63-2
Proposed as No. 44552. In the above casting machines, for example, as shown in FIG. 6, the maximum stroke value T _P of the target locus T _O, i.e., the pressure plunger protrudes most with respect to the molten metal in the cavity of the mold apparatus a position, the value T _P a sandwiched upper limit a, may be set a lower limit value B in advance, as shown by the dotted line, detects a maximum stroke value C of the trajectory Ta actual stroke volume, it The quality of the pressure cast product was judged by comparing it with the upper and lower limits A and B. That is, if the lower limit value B is exceeded, the amount of pressurization stroke of the pressurizing plunger cannot give the required riser effect to the molten metal in the cavity, or the cooling liquid is introduced into the plunger to make the die. Even if an attempt is made to give the required cooling effect to the molten metal part away from the surface via the pressure plunger, if the sufficient cooling effect cannot be given due to the insufficient plunge amount of the plunger, the denseness may be lost or It is judged that a cast product in which When the upper limit A is exceeded, the amount of protrusion of the pressurizing plunger with respect to the molten metal in the cavity of the mold device becomes large, and the biscuit part generated in the lower mold of the mold device is cut and separated from the casting part. It is judged that the process of taking out products will be hindered. On the other hand, in the die casting machine, in the process of injecting the molten metal into the cavity of the mold device from the injection sleeve of the injection device to which the molten metal is supplied, the molten metal injection is performed by detecting the gall of the tip of the injection plunger. A method for preventing gas entrainment and lowering of the molten metal temperature due to the waving operation of the injection plunger tip in the process is disclosed, for example, in Japanese Patent Publication No. 60-26626 by the present applicant. In this known plunger chip galling detection method, the pressure change of the injection plunger is constantly detected by the pressure detector, the differential value of the detected pressure change is obtained by the differentiator, and the differential value is compared with the set value by the comparison circuit to determine the plunger. A detection method is disclosed in which the degree of chipping of a chip is detected and an alarm is issued if necessary.

[0003]

However, in the above-mentioned method for detecting galling of the pressure plunger, the pressure change of the injection plunger is constantly measured and detected by the pressure detector, and the differential value of the detected pressure change is detected by the differentiator. Although the galling degree of the plunger tip is detected in the comparison circuit through the comparison circuit via the setting circuit, it is necessary to newly install individual hard circuit means such as a differentiator and a comparator in the pressure casting machine. However, there are problems that the equipment becomes complicated and the cost increases. Further, since the injection plunger and the pressure plunger have different behaviors when galling occurs, the galling of the pressure plunger may not be accurately detected by the above galling detection method. Although not known, a method of feedback controlling the operation of the pressurizing plunger using a computer has recently been adopted, and the computer means in the pressurizing plunger performing the feedback control is effectively used. There is a demand for development of a method for detecting galling in a pressure plunger of a pressure device.

[0004]

In order to solve the above problems, in the present invention, the action of the injection device is used to fill the mold with molten metal and to provide a pressurizing device provided in the injection device. In the method for detecting the galling of the pressurizing plunger in the pressurizing casting machine that pressurizes the molten metal in the mold by pushing the pressurizing plunger, the preset stroke amount of the pressurizing plunger into the mold cavity is shown. Feedback control of the forward movement stroke of the pressure plunger is performed to follow the target trajectory, and
The average value of the metal pressure of the pressurizing plunger in the preset judgment section is compared with the preset upper limit value of the metal pressure, and the galling of the pressurizing plunger is checked according to the frequency of exceeding the upper limit value. The presence / absence is detected. Also, in the second invention, instead of the metal pressure of the first invention,
The pressure difference between the head pressure of the pressure plunger and the rod pressure is adopted.

[0005]

In the present invention, the stroke amount in the pressurizing and feeder operations of the pressurizing plunger is set in advance as a target trajectory with the horizontal axis as the time axis and the vertical axis as the position (stroke amount), and then the actual operation is performed. The stroke of the pressurizing plunger in the inside is feedback-controlled by computer means so as to follow this target locus, and the average value of the metal pressure in the judgment section having a preset time interval is taken out from the metal pressure measured by the pressure detector. In comparison with the preset metal pressure setting value for galling detection, when the actual metal pressure average value is larger than the set metal pressure, an alarm is issued according to the degree. Therefore, the galling detection is automatically processed, and the arithmetic processing is performed inside the computer means, and the galling detection recognized as an abnormality is notified by an alarm. Further, in the second invention, the metal pressure is estimated by using the head pressure and rod pressure of the pressure cylinder that operates the pressure plunger without measuring the actual metal pressure. Can be omitted.

[0006]

Embodiments of the present invention will now be described in detail with reference to the drawings. 1 to 5 relate to an embodiment of the present invention,
FIG. 1 is a block diagram showing the configuration of the main part of the pressure casting machine, FIG. 2 is a time-metal pressure curve diagram in a normal state, and FIG. 3 is a time-metal pressure curve diagram in an abnormal state (when galling occurs). FIG. 4 is a time-metal pressure curve diagram for explaining the galling detection method of the present invention, and FIG. 5 is a flow chart showing an operating procedure for detecting galling of the pressure plunger.

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 a 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 in which 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
By the ascent of 1 and the plunger tip 11a, the molten metal 20 previously supplied into the injection sleeve 15 is injected and the cavity 18 is filled. 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 is tilted further to the side. Has been.

The upper mold 12 is opposed to the injection plunger 11.
A pressurizing plunger 17 of a pressurizing device is slidably arranged in the upper part of the above, and can be projected into the cavity 18. The pressurizing plunger 17 is connected to a piston 8c of a pressurizing cylinder 8 attached to the mold device 10 by a movable plate (not shown). The tip portion 25 of the pressure plunger 17 is at the gate seal position of the mold cavity 18,
That is, the lower mold 14 is provided so as to be able to project to a position where it starts entering the central hole opening 18a. The operation of the pressurizing cylinder 8 is started by supplying the pressure oil supplied from the hydraulic pressure source 6 to the cylinder chamber 8a or 8b via the direction switching valve 7. At this time, the return oil returns to the tank 19. That is, the solenoid SOL-a of the direction switching valve 7 is excited to guide the pressure oil of the hydraulic source 6 to the one head chamber 8a of the pressurizing cylinder 8 through the oil passage 21a, and at the same time, the rod chamber 8a.
When the hydraulic oil b is released to the tank 19 through the oil passage 21b, the piston 8c moves forward, and the tip 25 of the pressure plunger 17 is moved to the cavity 18 of the die assembly 10 as shown in the figure.
Project inside. On the contrary, the solenoid S of the directional control valve 7
When OL-b is excited, the piston 8c of the pressurizing cylinder 8 rises contrary to the above, and the tip portion 2 of the pressurizing plunger 17 is moved.
5 returns from the inside of the cavity 18 so as to be housed in the upper mold 12 and operates. The lower mold 14 is provided with a pressure detector 70 facing the cavity 18, and a pressure signal is transmitted momentarily to a pressure plunger control means described later via a terminal 70a.

The pressure of the hydraulic power 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 electric signal input 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, is configured to be detectable 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 or a personal computer is provided, and the pressure plunger control means 22 projects the pressure plunger 17 into the mold cavity 18 with respect to time. compared over time the command input signal from the target locus T _O set as can command signal setting unit 1, the position detector command signal setting unit 1 and the input signal is a detection signal of 9 changes in stroke volume due to operation, 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, and 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 unit 22. Input means 23 consisting of scan, for example, a ROM and a RAM memory, a display unit 24 composed of CRT, are formed by computing means such as a microprocessor MPU or CPU. Then, the command signal setting unit 1, the deviation calculation unit 2, the PID control calculation setting unit 3
Constitutes a feedback controller for the pressure cylinder 8 which activates the pressure plunger 17. Therefore,
The output of the PID control calculation setting unit 3 is sent to an electromagnetic relief valve 5 forming a pressure adjusting valve via a driver 4 and an I / O means (not shown). Thus, the pressure cylinder 8 is feedback controller and an electromagnetic relief valve 5, is feedback-controlled by a directional control valve 7, the stroke amount S _t of the pressure plunger 17 is controlled so as to follow the target locus T _O.

In the pressure plunger stroke control,
The metal pressure M _P at the tip of the pressurizing plunger 17 is measured by the pressure detector 70 described above.
In order to reduce the complexity of providing the pressure detector 70 in the above, the following measured value can be used instead. The pressure P on the head side 8a of the piston 8c of the pressurizing cylinder 8 of FIG.
_H and the pressure P _R on the rod side 8b are detected by pressure detectors 26a, 26
The metal pressure M _P is obtained by subtracting the reverse propulsive force due to the rod-side back pressure from the propulsive force due to the head-side pressure and dividing it by the cross-sectional area of the pressure plunger 17.

A method for detecting galling of the pressure plunger 17 in the pressure casting machine configured as described above will be described. As described above, when the head pressure P _H of the pressurizing cylinder 8 is controlled to change so that the stroke of the pressurizing plunger 17 follows the target locus using the computer means,
When no galling occurred, a change in metal pressure M as shown in FIG. 2 was measured. Pressurization plunger 1 shown in FIG.
A temporary sudden rise in the metal pressure M (peak pressure) that occurs immediately after the start of the forward movement of No. 7 causes a process in which the outer peripheral portion of the molten metal in the mold cavity 18 cools and pushes through the state of solidification into a thin film or the pressure plunger 17. This is normal because the friction between the contact part in the mold and static friction changes from static friction to dynamic friction. After the initial peak pressure, the necessary and sufficient metal pressure for controlling to follow the target trajectory is measured. On the other hand, when the pressurizing plunger 17 has a galling phenomenon, as shown in FIG. 3, a metal pressure M substantially the same as the peak pressure immediately after the forward start is applied to the pressurizing plunger 17 thereafter. If the head pressure P _H is not applied to the head side of the pressurizing cylinder 8 so as to be generated, it is difficult to move forward, and therefore the metal pressure inevitably becomes a constant high value. Moreover, the deviation between the target trajectory and the actual stroke also becomes large. Thus, it was confirmed experimentally that there was a clear difference in the measured waveform of the metal pressure between when galling occurred and when it was not controlled by computer feedback control. Therefore, in the present invention, as shown in FIG. 4, at any two times t _1, t ₂ at which the peak pressure after the start is considered to disappear.
The average metal pressure M _{A in} the judgment section ΔT between the two is compared with a preset high metal pressure M _{H of} approximately the peak pressure, and the stroke amount of the pressurizing plunger 17 is determined according to the flowchart shown in FIG. After performing feedback control and measurement of the metal pressure, the average value M _A of the metal pressures between the judgment sections t _{1 and} t ₂ described above is calculated, and the magnitude relationship with the set metal pressure (metal pressure upper limit setting value) M _H is calculated. When the state in which the metal pressure average value M _A is larger than the set metal pressure M _H is connected up to a predetermined number of counts, it is considered that a galling phenomenon has occurred and an abnormal alarm signal is transmitted. I decided to do it. As described above, the metal pressure M may be a measured value by the pressure detector 70 or the head pressure P of the pressurizing cylinder 8.
A converted value based on _H and rod pressure P _R may be adopted. Especially in the latter case, the drilling for attaching the pressure detector 70 to the lower mold 14 and the maintenance of the pressure detector 70 are omitted, and the manufacturing cost is also reduced. As described above, according to the present invention, the stroke amount in the pressurizing and feeder operations of the pressurizing plunger is set in advance as the target locus, and the feedback stroke is controlled so that the actual stroke of the pressurizing plunger follows the target locus. At the same time, the metal pressure is measured or estimated to obtain the average value of the metal pressure in the preset judgment section during the stroke, and the abnormal state is compared with the assumed metal pressure set value. When the former exceeds the latter, Or, I decided to send an alarm when that condition persists,
The galling detection is carried out automatically and by a calculation process inside the computer means, and there is no internal defect in the cast product due to defective feeding or insufficient cooling in the pressing process of the pressure casting machine based on the galling. A quality product is obtained.

[0013]

As described above, since the casting defect of the pressure cast product can be controlled by the method for detecting the galling of the pressure plunger in the pressure casting machine of the present invention, a high quality pressure cast product can be obtained. .

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a main part of a pressure casting machine according to an embodiment of the present invention.

FIG. 2 is a time-metal pressure curve diagram in a normal state of the pressure casting machine according to the present invention.

FIG. 3 is a time-metal pressure curve diagram at the time of abnormality of the pressure casting machine according to the present invention.

FIG. 4 is a time-metal pressure curve diagram for explaining the galling detection method of the present invention.

FIG. 5 is a flowchart showing a detection processing procedure of the galling detection method of the present invention.

FIG. 6 is an explanatory diagram showing a conventional stroke amount control method for a pressure plunger.

[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 26a, 26b Pressure detector 70 Pressure detector 70a Terminal M Metal pressure M _H Set metal pressure (upper limit) M _A Average metal pressure P _H Head pressure P _R Rod pressure T _a Track of actual stroke amount T _O Target track S _t Stroke amount t time

Claims (2)

[Claims] 1. Pressure casting in which a molten metal is filled in a mold by the action of an injection device and a pressing plunger of a pressurizing device provided in the injection device is caused to make a projecting stroke to press the molten metal in the mold. In a method for detecting galling of a pressure plunger in a machine, feedback control of a forward movement stroke of the pressure plunger is performed so as to follow a preset target trajectory indicating a stroke amount of the pressure plunger into the mold cavity over time. At the same time, the average value of the metal pressure of the pressurizing plunger within a preset judgment section is compared with the preset upper limit value of the metal pressure, and the pressurizing plunger's frequency is exceeded according to the frequency of exceeding the upper limit value. A method for detecting the galling of a pressure plunger in a pressure casting machine that detects the presence or absence of galling. 2. The method for detecting galling of a pressure plunger in a pressure casting machine according to claim 1, wherein the metal pressure of the pressure plunger is a pressure difference between the head pressure of the pressure cylinder and the rod pressure.