JP2704470B2 - Pressure stroke control method in pressure casting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for injecting molten metal into a cavity of a mold by an injection device and pressing the molten metal in the mold by a pressure device having a pressure plunger to obtain a cast product. Pressing stroke control in pressure casting, in which when the pressurizing operation of the pressurizing device is controlled by computer control, the quality judgment of the cast product and the abnormality judgment of the casting process are performed by the computer. It is about the method.

[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 molten metal injected into a mold by a pressure device having a pressure plunger is pressurized by pressurization. Injection and flow of cooling water into the pressurized plunger while applying pressure, to provide a cooling effect from the center side of the molten metal, thereby realizing a pressurized casting method that prevents the occurrence of nests due to runoff inside the workpiece. Casters are already well known. In a pressure casting machine, the movement stroke of the pressure plunger of the pressure device is set as a target trajectory using a computer over time based on the time from the start of operation of the plunger, and the target trajectory is set as the target trajectory. As such, feedback control is performed.

[0003] In the above casting machines, for example, as shown in FIG. 4, the maximum stroke value T _P of the target locus T _O, i.e., with respect to the molten metal pressurizing plunger cavity of the mold apparatus It is the most protruding position, and its value T _P
Is set in advance, and the maximum stroke value C of the trajectory Ta of the actual stroke amount is detected as shown by the dotted line, and is compared with the upper and lower limit values A and B. Thus, the quality of the pressure cast product is determined. That is, if the lower limit value B is not reached, the pressurizing stroke of the pressurizing plunger cannot provide a required feeder effect to the molten metal in the cavity, or a coolant is introduced into the plunger to mold the mold. Even if an attempt is made to provide the required cooling effect to the molten metal part away from the surface via a pressure plunger,
In the case where a sufficient cooling effect cannot be given due to the insufficient plunger plunging amount, it is judged that a cast product lacking in density or having burrs is generated. In addition, the upper limit A
When the pressure exceeds the value, the projecting amount of the pressurized plunger against 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 cast part, which hinders the product removal process. Is determined to occur.

[0004]

However, in the above-described conventional pressure stroke control method, the quality judgment of the pressure casting is determined by an upper limit value and a lower limit value sandwiching the maximum stroke value of the target trajectory of the pressure plunger. No consideration is given to the stroke trajectory from the start of the operation of the pressure plunger to the reaching of the maximum stroke value. Recently, it has been found that the stroke trajectory of the pressurizing plunger within several seconds after the start of the operation of the pressurizing plunger affects the quality. The present invention focuses on the above-mentioned conventional problems, and an object of the present invention is to provide an accurate method for determining the quality of a pressure-cast product.

[0005]

According to the present invention, in a pressure casting method using a pressure casting machine, when controlling the stroke amount of a pressure plunger, a horizontal axis is set as a time axis and a stroke amount is set as a vertical axis. When controlling along the set target trajectory, attention is paid to the deviation between the target trajectory and the actual stroke amount trajectory. , When the deviation is positive, and when the deviation is negative, the sum of the squares of the deviation is obtained, and whether the actual stroke operation of the pressurizing plunger is appropriate in accordance with the sum and the magnitude with respect to a preset control value, respectively. Whether the product is good or bad in the pressure casting, or whether the operation of the pressure casting machine should be continued or stopped, is determined.

[0006]

In controlling the stroke amount of the pressurizing plunger as described above, the horizontal axis is used as the time axis and the stroke amount is set along the vertical axis. Focusing on the deviation in the trajectory of the quantity, in the time-division processing for each set time within a preset time from the start of the operation of the pressurizing plunger,
When the sum of the squares of the deviations when the deviation is positive is larger than the control value, and when the sum of the squares of the deviations when the deviation is negative is smaller than the control value, it is determined that the stroke operation of the pressurizing plunger is defective. And issue an alarm.

[0007]

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 performing a pressure stroke control method of a pressure casting method according to the present invention. The mold 10 includes an upper mold 12 and a lower mold 14 that can be opened and closed relatively vertically, and a core 16 that opens and closes from the side with respect to the vertical opening and closing axis of the upper mold 12 and the lower mold 14.
Are provided. 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, a cavity 18 as a casting space is formed.
The injection plunger 1 of the injection device 13 is
As the plunger tip 1 and the plunger tip 11 a rise, the molten metal 20 previously supplied into the injection sleeve 15 is injected to fill the cavity 18. The supply of the molten metal to the injection device 13 is generally provided such that, when the injection device 13 is at the position retracted downward, the injection device 13 is further inclined to the side at the retracted position, and is supplied into the injection sleeve 15 by the molten metal supply machine. Have been.

The upper die 12 faces the injection plunger 11.
A pressurizing plunger 17 of a pressurizing device is slidably disposed at an upper portion of the pressurizing device and can protrude into the cavity 18. The pressure plunger 17 is connected to a piston 8c of a pressure cylinder 8 mounted on a movable plate (not shown). The tip of the pressurizing plunger 17 is provided so as to be able to protrude to the gate seal position of the mold cavity 18, that is, the position where it starts to enter the central hole 18 a of the lower mold 14. The operation of the pressurizing cylinder 8 is performed by supplying the pressure oil supplied from the hydraulic pressure source 6 to the cylinder chamber 21 through the direction switching valve 7.
It is activated by supplying it to a or 21b. At this time, the return oil returns to the inside of the tank 19. That is, the solenoid SOL-a of the direction switching valve 7 is excited to
Is guided to one head chamber 8a of the pressurizing cylinder 8 via the oil passage 21a, and at the same time, the hydraulic oil in the rod chamber 8b is released to the tank 19 via the oil passage 21b.
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. Conversely, when the solenoid SOL-b of the directional control valve 7 is excited, the piston 8c of the pressurizing cylinder 8 rises, and the tip of the pressurizing plunger 17 is housed in the upper die 12 from inside the cavity 18, contrary to the above. Return to work.

The pressure of the hydraulic pressure source 6 is controlled by an electromagnetic relief valve 5 comprising an electromagnetic proportional automatic pressure valve. That is, the pressure relief from the hydraulic pressure source 6 is controlled in accordance with the magnitude of the electric signal input to the electromagnetic relief valve 5, so that the protrusion pressure of the pressurizing plunger 17 can be controlled. The stroke position or the stroke amount when the piston 8c of the pressurizing cylinder 8, ie, the pressurizing plunger 17 projects or retreats with respect to the cavity 18, is configured to be detectable by a position detector 9 composed of, 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 this 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, Receiving the deviation output signals of the deviation operation unit 2 and the deviation operation unit 2 for transmitting the deviation output signals corresponding to the deviation values of these two input signals, an appropriate gain operation process is performed, and a predetermined gain operation corresponding to the deviation output signal is performed. And a PID control operation setting unit 3 for outputting an output signal of the computer. The input means 23 comprises a mouse, for example, a memory such as a ROM and a RAM, the display means 24 comprises a CRT, and arithmetic means such as a microprocessor MPU and a CPU. The command signal setting section 1, the deviation calculation section 2, and the PID control calculation setting section 3 constitute a feedback controller for the pressurizing cylinder 8 that starts the pressurizing plunger 17. Therefore, P
The output of the ID control calculation setting unit 3 is sent to an electromagnetic relief valve 5 serving as a pressure regulating valve via a driver 4 and 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 of the pressure plunger 17 is controlled so as to follow the target locus T _O.

The operation of the mold apparatus and the pressure casting system configured as described above will be described. As shown in FIG. 1, when filling of the molten metal by the injection plunger 11 is completed, a host controller (not shown) issues an operation command of the pressurizing plunger 17 at a predetermined time interval to the pressurizing plunger control means 22.
And the solenoid SOL-a of the direction switching valve 7
To excite. The command signal setting unit 1 of the pressure plunger control means 22, in advance, the desired trajectory of the stroke amount St of the plunger operation starting pressurization plunger with respect to time t from the time point 17 is programmed set as the target trajectory T _O above When the above operation command is received, the target trajectory T _O
Is subjected to time-sharing processing, for example, every several milliseconds, and is input to the deviation calculation unit 2. The deviation calculating unit 2 calculates a deviation e (= St−St ′) from the actual stroke position St ′ of the pressurizing plunger 17 detected by the position detector 9, and stores this in the PID control calculation setting unit 3. input.

The PID control calculation setting section 3 has an integral I and a differential D
Based on the result of the deviation e together with the gain constant, a PID calculation process is performed to convert to a pressure command value Pc which is a control amount.
When the pressure command value Pc is input, the driver 4 converts the pressure command value Pc into a signal Prf for actually driving the electromagnetic relief valve 5, controls the pressure of the hydraulic pressure source 6, and controls the oil pressure to the pressurizing cylinder 8 via the direction switching valve 7. Controlling pressure. Thus, based on the deviation of the actual stroke amount Ta target trajectory T _O at the stroke amount of the pressure plunger 17, by controlling the pressure for actuating the pressure cylinder 8, the actual pressurizing plunger 17 The stroke amount is feedback-controlled, and as a result, the pressurizing plunger 17 always gives a required level of a stable feeder effect to the molten metal 20, and a dense cast product having good quality without any shrinkage cavities can be obtained. Become like

[0013] Now, by setting the target locus T _O, as described above, also control the stroke of the pressure plunger 17 by the feedback control method, as described above, the temperature of the mold apparatus 10 in the casting process by variation of the various processing conditions such as conditions, never stroke trajectory Ta actual pressure plunger 17 is executed is always coincides with the target locus T _O. However, from the viewpoint of the quality of the cast product, there is a case where even if there is a discrepancy between the two trajectories, the product can be sufficiently used as a product. In the present invention, the operation of the pressurizing plunger 17 is feedback-controlled, and the quality of the pressurized cast product is determined using the deviation between the target stroke amount and the actual stroke amount of the pressurizing plunger.

A method for determining the quality of a pressure-cast product according to the present invention will be described with reference to FIGS. FIG. 2 is a time t-stroke amount St curve for explaining the pressurizing stroke control method according to the present invention. FIG. 3 is a flowchart of the pressurizing stroke control method according to the present invention. As shown in FIG. 3, before the start of the pressurizing plunger stroke control, the pressurizing plunger control means 22 instructs the pressurizing plunger stroke control to pass / fail the first reference value Y _U , the second reference value Y _D , control time t _c for _determining, setting the division processing intervals t _e time. The above setting is performed by the pressurizing plunger control means 2
2 is set in advance from the input unit 23 in the command signal setting unit 1 provided with the second memory unit, for example, the RAM unit which can be rewritten.

When the operation command of the pressure plunger 17 is given to the pressure plunger control means 22, the time division processing interval t
The feedback control of the pressurizing plunger stroke is performed by the time-division processing for each _e . In time division processing during the control time _{t c} for determining the pressure plunger stroke control start _{(t l ~t n = t b} ), the deviation _e n measured value St _'n and the target value St _n of the stroke volume ( = St _n -
A price function operation is performed from St ′ _n ).

[0016]

(Equation 1)

[0017]

(Equation 2)

That is, when the deviation is positive and when the deviation is negative, the sum of the squares of the deviations is used as each price function (X _D , X _U ). The reason why the sum of the squares of the deviation is used instead of the sum of the deviations is that the larger the deviation, the worse the evaluation.

[0019] It to determine the acceptability of the pressure plunger stroke control the magnitude of the target value function X _D and Shirubeka second reference value Y _D, target value function X _U and Shirubeka first reference value Y _U. This determination can be executed in the pressurizing plunger control unit 22 by the deviation calculation unit 2 including a calculation unit such as a CPU or an MPU. When target value function X _D is smaller than the target value the second reference value Y _D, or Shirubeka function X when _U is greater than the target value first reference value Y _U is pressurized plunger 17
As the stroke control failure, for example, an alarm is displayed on the display means 24 of the pressurizing plunger control means 22, an alarm lamp (not shown) is turned on, or an alarm buzzer is issued. Further, when the target value function X _D is target value larger than the second reference value Y _D, and target value function X
When _U is less than the target value first reference value Y _U is a normal stroke control of the pressure plunger, casting processing steps to emit good display signal determines that obtained by processing the normal casting I do. In this embodiment, the pass / fail judgment is made for each shot. However, the judgment is not made for each shot. For example, when the standard value is exceeded two or three times in succession, an alarm command or a correction command is issued for the first time. You may make it emit.

[0020]

As described above, according to the present invention, in the pressure casting method, in the time-sharing process for each predetermined time within a predetermined time from the start of the operation of the pressure plunger, If the deviation between the set stroke amount of the target trajectory of the pressurizing plunger and the actual stroke position of the pressurizing plunger is positive or negative, the sum of the squares of the deviations is calculated, and the sum is set in advance. By judging the quality of the pressure-cast product according to the magnitude of the control value, the quality of the pressure-cast product is controlled from the aspect of the feeder effect and cooling effect by the pressure plunger, and the occurrence of biscuit separation is controlled. This has the effect of producing a cast product that meets certain acceptable quality standards at a high yield. In addition, there is an effect that the performance of the pressure casting machine can be maintained by preventing damage to structural elements of the pressure casting machine such as a mold device and prompting a corrective action or the like as soon as possible.

[Brief description of the drawings]

FIG. 1 is a mechanical diagram showing one embodiment of a mold apparatus and a pressurizing apparatus system for implementing a method of the present invention.

FIG. 2 is a time-stroke amount curve for explaining a pressing stroke control method according to the present invention.

FIG. 3 is a flowchart of a pressing stroke control method according to the present invention.

FIG. 4 is a 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 Melt 22 Pressurizing plunger control means

Claims (1)

(57) [Claims] In a pressure casting in which a molten metal is filled into a mold by the action of an injection device and a molten metal in the mold is pressed by advancing a pressure plunger, a predetermined value is set from the start of operation of the pressure plunger. When performing time-division processing for each predetermined time within the time, if the deviation between the preset stroke amount of the target trajectory of the pressurizing plunger and the actual stroke position of the pressurizing plunger is positive, In the case of (1), the pressure stroke control in the pressure casting is characterized in that the sum of the squares of the deviations is obtained, and the quality of the pressure casting is determined in accordance with the sum of the deviations and the magnitude of the predetermined control value. Method.