JPH02207960A - Cylinder position control method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a method for controlling the position of a cylinder piston of a cylinder device, and particularly to an injection molding machine that injects and fills a material into a mold. The present invention relates to a method for controlling the position of a cylinder piston of an extruder cylinder for extruding and molding material through an injection cylinder, a pressure cylinder, and a die of a die-casting machine.

[Prior art] In an injection molding machine or a die-casting machine, when applying pressure while applying vibration when filling a mold with molding material and pressurizing it, the compactness of the molded product increases due to the following effects, for example. It is known that ζ has a reforming effect. In other words, ■) When vibrations are transmitted to the molding material in a molten state, the gas contained in the molding material is easily released, resulting in gas entrainment or inclusion, which is one of the causes of molded product defects. The occurrence of nests due to this decreases.

2) In a molten state. When the molding material comes into contact with the mold cavity, it is rapidly cooled and a solidified film called a chill layer is formed, which deteriorates the fluidity of the molding material. However, when vibrations are transmitted to the molding material, this early solidification can be prevented. Since it suppresses the fluidity and maintains fluidity, the pressure propagation during filling is improved and the crystals of the molding material are made finer. Therefore, the hot water flow is poor, and the water is wrinkled.

This prevents the causes of defects in molded products related to the flow state such as troughs, and the causes of defects such as so-called cavities that occur due to shrinkage when the molding material cools and solidifies under conditions where sufficient pressure is not applied.

In addition, as a device that applies pressure while applying vibration, for example, as described in Japanese Utility Model Application Publication No. 62-56262, high-frequency energy is applied to the hydraulic oil of the cylinder device that fills the molding material into the cavity of the mold. This was done by exciting vibrations using a vibration generator.

[Problems to be Solved by the Invention] In the method of applying pressure vibrations to the hydraulic oil of a cylinder device using the high-frequency vibration generator described above, the high-frequency vibration generator has the ability to generate pressure vibrations higher than the working pressure of the cylinder device itself. Otherwise, effective vibration cannot be imparted to the molding material, which inevitably requires a large-scale high-frequency vibration generator.

In addition, when double-sided pressure vibrations such as those generated by a high-frequency vibration generator are superimposed on the working pressure of the cylinder device,
At the valleys of vibration, the molding material tries to be pushed into the mold cavity, but on the other hand, at the valleys of vibration, the reaction force from the molding material pushes back the cylinder device.

Depending on the molding conditions, it may be undesirable for the cylinder device to be pushed back, but conventional devices cannot deal with such cases.

[Means for solving the problem] The movement stroke amount of the cylinder piston is determined in advance as a target trajectory with respect to time, and the deviation amount between the movement stroke amount of the cylinder piston set as this target trajectory and the actual movement stroke amount is determined in advance. When configured to control the moving stroke amount of the cylinder piston by changing the cylinder chamber pressure that operates the cylinder piston accordingly, the gain value given to the deviation amount can be adjusted to control the movement of the cylinder piston according to the target trajectory. I made it follow while vibrating slightly. In addition, by setting the value of the gain that contributes to the operation in the direction of movement of the cylinder piston, which is the target trajectory, to be relatively larger than the value of the gain that contributes to the operation in the direction opposite to the direction of movement,
The shape of the micro-vibration can also be made to have a roughly step-like shape when viewed as a scale of the movement stroke amount of the cylinder piston with respect to time.

[Function] Among the gain values given to the deviation amount, in particular, the gain value that is multiplied in proportion to the integral value of the deviation amount (a-minute gain) is larger than the gain value that is multiplied in proportion to the deviation amount (proportional gain). Then, the accumulation of deviation amount controls the cylinder chamber pressure that operates the cylinder piston, that is, the cylinder chamber pressure is controlled until a certain amount of deviation accumulation occurs with respect to the target trajectory of the cylinder piston movement stroke amount. Therefore, rather than converging to the target trajectory, it follows the target trajectory while vibrating the amount of deviation.

Also, if the value of the gain that contributes to the operation in the direction of movement of the cylinder piston is set relatively large to the value of the gain that contributes to the operation in the direction opposite to the direction of movement, then Although it shows high responsiveness in the opposite direction, the tracking is slow for deviations in the opposite direction. Therefore, when looking at the scale of the movement stroke amount of the cylinder piston with respect to time, the actual movement stroke amount of the cylinder piston rises quickly in the movement direction, but once it exceeds the target trajectory, it moves in the opposite direction. Since the vibration gently moves toward the target trajectory, the shape of the microvibration becomes roughly step-like.

[Example] FIG. 1 is a longitudinal cross-sectional view showing the main parts of a die-casting machine for forming a disc wheel. As shown in the figure, an upper mold 33 that can be opened and closed in the vertical direction. The lower mold 35 and four horizontally movable cores 34 are combined and clamped from above and below in the figure by a mold clamping mechanism (not shown), and the injection sleeve 39 is inserted into the cavity 38 formed thereby. The aluminum alloy (hereinafter referred to as molten metal) 37 in a molten state is filled by the upward movement of the injection plunger 36 and plunger tip 36a by the action of an injection cylinder (not shown).
After a predetermined time (pressurization time lag) has elapsed since the completion of filling the molten metal 37, the solenoid 23a of the direction switching valve 23 is energized to attach it to the cylinder piston 32 of the pressurization cylinder 31. The pressurized plunger 40 is projected into the cavity 38,
The molten metal 37 in the cavity 38 is pressurized to perform a feeder action. 5 is a pump, 4 is a motor that drives pump 5, 6
is an electromagnetic proportional pressure regulating valve, 7 is a tank, and cylinder 3
1 constitutes a pressure source for driving.

In this regard, the present applicant previously filed a patent application filed in Japanese Patent Application No. 63-244.
In No. 552, the following method was proposed in which the pressurizing plunger 40 is controlled so as to follow a target locus of the protrusion stroke amount into the predetermined cavity 38 as time passes from the start of its operation.

First, the movement stroke ist of the pressurizing plunger 40 into the cavity 38 is predetermined in the model section 9 as a target trajectory based on the time t from the start of operation of the pressurizing plunger 40 (t=0). The deviation amount e between the moving stroke amount st set as the target trajectory and the actual moving stroke amount stb of the cylinder piston 32, that is, the pressurizing plunger 40 detected by the position detector 3 (e=st-stb
) is determined by the deviation detection section 10, and upon receiving this deviation fjte, the gain setting section 8 processes it appropriately and outputs a predetermined output signal V to the driver 12 in accordance with the deviation fjte. The driver 12 adjusts the pressure regulating valve 6 according to the magnitude of the output signal V from the gain setting section 8 to control the pressure p of the pressure source. In addition, model part 9. The deviation detection section 10 and the gain setting section 8 constitute a feedback controller 11.

Now, when a controller (not shown) gives an operating command for the pressurizing cylinder 31 to the feedback controller 11, the model section 9, which is also a command signal setting section of the feedback controller 11, has a pressurizing plunger 40 for the one-hour meter, i.e. , a desired trajectory of the movement stroke st of the cylinder piston 32 is programmed in advance, and in response to the above-mentioned operation command, the target movement stroke st is time-divisionally processed every few milliseconds, and the deviation detection unit 10 input. The deviation detection unit IO detects the deviation ie (e=st
-st b) and inputs it to the gain setting section 8. Here, the gain setting section 8.

Based on the result of the deviation amount e, a predetermined P (proportional) IC integral) gain k is multiplied to convert the stroke deviation amount e into a pressure command value V which is a control amount. The driver 12 obtains the pressure command value V, converts it into a signal p that actually drives the pressure regulating valve 6, also called an electromagnetic relief valve, and controls the cylinder head chamber 31a.
The pressure is controlled.

Now, with the above gain, if the integral gain I is made larger than the proportional gain P, as shown in FIG. 2(a), then
Since the pressure command value V is controlled in proportion to the accumulation amount rather than the deviation amount e itself, the cylinder piston 32
Until a certain amount of deviation e accumulates with respect to the target trajectory st of the moving stroke amount, the cylinder chamber pressure v(p)
Rather than converging to the target trajectory, it follows the target trajectory with vibrations due to the accumulated amount of deviation, as shown in FIG. 3(a). In particular, when the proportional gain P is set to approximately zero, no convergence to the target trajectory occurs at all, and the vibration state can be adjusted almost solely by the integral gain. Its characteristics are shown in FIG.

That is, if the integral gain I is made small, the result shown in FIG. 4 (a
), the frequency f is small (the period T is large)
Therefore, the amplitude a becomes large. Conversely, when the integral gain I is increased, the frequency f becomes larger (the period T becomes smaller) and the amplitude a becomes smaller, as shown in FIG. 4(b).

Furthermore, as shown in Fig. 2(b), the value of the gain that contributes to the operation in the direction of movement of the cylinder piston is set to be relatively large compared to the value of the gain that contributes to the operation in the opposite direction to the direction of movement. , that is, the deviation e is the same as the above definition e=st−s
tb, if the slope tp of the gain in the region where the deviation e takes a positive value is made relatively larger than the slope Lm of the gain in the region where the deviation e takes a negative value, the moving direction (in the example fwd Although it shows high responsiveness to deviations occurring in the opposite direction (bwd direction), it follows slowly to deviations occurring in the opposite direction (bwd direction). Therefore, as shown in FIG. 3(b), when looking at the scale of the moving stroke amount of the cylinder piston 32 with respect to time, the actual moving stroke amount of the cylinder piston 32 quickly rises in the moving direction, but - If it exceeds the trajectory, it will operate in the opposite direction.

Since the vibration gradually moves toward the target trajectory, the shape of the microvibration becomes approximately step-like. Note that the stepwise vibration in this case also basically exhibits the same characteristics as shown in Fig. 4,
When the gain is decreased, the frequency f is decreased and the amplitude is increased, and conversely, when the gain is increased, the frequency f is increased and the amplitude is decreased.

As mentioned above, in this embodiment, the cylinder piston 3
Figure 3 (jL) with respect to the original target trajectory by simply adjusting the gain of the feedback controller 11 that controls the operation of step 2.
, (b) As shown in Figure 4, vibrations can be arbitrarily superimposed.

Although this example was applied to the operation of a pressurizing plunger, it can also be applied to an injection plunger, and also to a cylinder device similarly intended for filling and pressurizing. Needless to say, the present invention can be similarly applied to cylinder devices and other cylinder devices.

[Effects of the Invention] In the present invention, since the structure described in the claims is adopted, the molding material can be easily applied to the mold while applying vibration without requiring a large-scale device unlike the conventional method. As a result, the quality of the molded product can be improved.

Furthermore, the applied vibration state can be adjusted as desired, and in particular, it has become possible to cope with step-like vibrations of the movement stroke of the cylinder piston over time, which was not possible in the past.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a vertical cross-sectional view and a control circuit diagram showing the main parts of a vertical die-casting machine.
Figures 2 (a) and (b) are explanatory diagrams showing the states of the integral gain and proportional gain P, and Figures 3 (a) and (b) are lines showing the tracking state of the cylinder piston movement stroke amount with respect to the target trajectory. 4(a) and 4(b) are diagrams showing differences in tracking characteristics due to differences in gain. 3...Position detector, 6...Pressure regulating valve, 8...Gain setting section, 9...
・, Model section, ・10... Deviation detection section. 11... Feedback controller. 12... Driver, 31... Pressure cylinder, 32... Cylinder piston, 33... Upper mold, 34... Core, 35...Lower mold, 36.Old injection plunger, 36a■.Plunger tip- 38...Cavity, 39...Injection sleeve, 40... Pressurized plunger. Figure 2 Figure 3 (a) (b) Patent applicant Ube Industries, Ltd.

Claims (1)

[Claims] A cylinder chamber in which the moving stroke amount of the cylinder piston is predetermined as a target trajectory with respect to time, and the cylinder piston is operated according to the deviation amount between the moving stroke amount of the cylinder piston set as the target trajectory and the actual moving stroke amount. When the movement stroke amount of the cylinder piston is controlled to follow by changing the pressure, the gain value given to the deviation amount is adjusted to follow the target trajectory while vibrating. A method for controlling the position of a cylinder.