JPH07108572A - Speed control of hydraulic ejector - Google Patents

Abstract

PURPOSE:To ensure stabilitis of an activation and set an initial ejection speed adequately slow by seeking a reference flow control signal for a hydraulic cylinder mechanism in accordance with an ejecting position and correcting the control signal if the ejecting position variation amount is below a set level, when the ejection speed is increased in response to an amount of an ejection. CONSTITUTION:A potentiometer 12 is provided on a piston 1 of a hydraulic cylinder mechanism 10 connected to an ejector and thereby, an increase pattern of the ejection speed proportional to the ejection amount of the ejector is determined. This pattern is divided into an appropriate number of control sections on an ejector shaft, and speed increase data on the ejection speed of each section is calculated. In addition, a reference flow control signal V for controlling the hydraulic cylinder mechanism 10 is calculated based on the speed increase data corresponding to a position signal from the potentiometer 13. On the other, hand, if the variations of the position signal within a unit time is below a minimum set value, the present control signal V is corrected to increase. If the correction signal is below the reference flow level, the flow is controlled thereof the by the reference flow control signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed control method for a hydraulic ejector, which is used in a resin injection molding machine or the like, to project a molded product by being driven to project by a hydraulic cylinder mechanism.

[0002]

2. Description of the Related Art Conventionally, as a mold clamping device used in a resin injection molding machine or the like, a device provided with an ejector driven by a hydraulic cylinder mechanism for releasing and taking out a molded product is known. . By the way, from the viewpoint of improving the molding cycle, it is desirable that the ejecting speed of the ejector is fast, but if it is too fast, a large force acts on the molded product at the time of release, and damage such as whitening phenomenon and cracks may occur. It is easy to occur.

Therefore, in the conventional mold clamping device, for example, by gradually increasing the ejecting speed of the ejector according to the protruding amount or the protruding position, the ejecting speed of the ejector is sufficiently increased when the molded product is released from the mold. In order to prevent damage to the molded product by slowing it down and increasing the protruding speed after releasing from the mold, the molding cycle is improved.

However, in the mold clamping device, in general,
The hydraulic pump that supplies hydraulic oil to the hydraulic cylinder mechanism for driving the ejector is shared with the hydraulic pump that supplies hydraulic oil to the hydraulic cylinder mechanism for opening and closing the mold, and the hydraulic cylinder mechanism for driving the ejector is Since the diameter is very small compared to the hydraulic cylinder mechanism for opening and closing the mold, if the initial ejecting speed of the ejector is set to be sufficiently slow, the required supply flow rate of hydraulic oil to the hydraulic cylinder mechanism for driving the ejector will decrease. However, since the discharge flow rate of the hydraulic pump corresponds to an extremely small discharge quantity in an unstable region, there is a problem that it is extremely difficult to stably control the ejecting speed of the ejector.

Further, conventionally, in general, the protruding position of the ejector is detected by a limit switch or the like, and the discharge flow rate of a hydraulic pump for supplying hydraulic oil to a hydraulic cylinder mechanism for driving the ejector is detected in accordance with the protruding position of the ejector. Since it is controlled, if the initial speed does not come out due to oil leakage or oil temperature rise due to aging etc., the ejector will not move at all and the molding cycle may be interrupted. there were.

[0006]

The present invention has been made in view of the circumstances as described above, and a problem to be solved by the present invention is that the ejecting speed of an ejector is changed from a sufficiently slow protruding speed in the initial stage of projection to a final projecting speed. It is an object of the present invention to provide a speed control method for a hydraulic ejector, which can be controlled advantageously and stably until the speed is reached.

[0007]

In order to solve such a problem, a feature of the present invention is a speed control method for a hydraulic ejector as described above, in which an increase pattern of a projection speed according to a projection amount of the ejector is used. The reference flow rate control signal of the hydraulic cylinder mechanism corresponding to the projecting position of the ejector is determined in advance according to the increase pattern of the projecting speed, while the position change amount of the ejector within the unit time is less than the preset minimum value. If not, the reference flow rate control signal is increased to obtain a corrected flow rate control signal, the hydraulic cylinder mechanism is controlled based on the corrected flow rate control signal, and the value of the corrected flow rate control signal is set to the reference flow rate control signal. After the ejecting position of the ejector that is less than or equal to the signal value,
It is characterized in that the hydraulic cylinder mechanism is controlled based on the reference flow rate control signal.

[0008]

EXAMPLES Examples of the present invention will now be described in detail with reference to the drawings in order to clarify the present invention more specifically.

First, FIG. 2 shows a specific example of a hydraulic circuit for driving an ejector in a mold clamping device for an injection molding machine for carrying out the method of the present invention. In this drawing, reference numeral 10 denotes a hydraulic cylinder mechanism, which is not shown in the drawing, but its piston 12 is connected to an ejector (not shown) so that the piston 12 can reciprocate integrally with the ejector. ing. Also, such a piston 1
2, a potentiometer 13 is attached,
The projecting position of the piston 12 and thus the projecting position of the ejector are detected.

Further, in the hydraulic cylinder mechanism 10, a hydraulic oil supply pipeline 18 and a drain pipeline 2 for a variable discharge pump 16 are provided via a three-position switching type solenoid valve 14.
0 is connected. This allows the solenoid valve 1
In accordance with the switching position of No. 4, the hydraulic oil is supplied to and discharged from the hydraulic cylinder mechanism 10, the piston 12 is driven to reciprocate, and the ejector (not shown) is driven to project and retract. The proportional electromagnetic relief valve 2 is provided between the supply line 18 and the drain line 20.
2 is provided, and the pressure in the supply line 18 can be adjusted.

As shown in FIG. 3, the solenoid valve 14, the variable discharge pump 16 or the proportional electromagnetic relief valve 22 is operated and controlled by the controller 24 so that the ejector operates as intended. It is like this. That is, the drive direction of the ejector is determined by the operation control of the solenoid valve 14, and the hydraulic cylinder mechanism 1 is controlled by the operation control of the variable discharge pump 16 or the proportional electromagnetic relief valve 22.
The driving speed of 0 and the sudden output are determined.

More specifically, the control device 24 is generally composed of a microprocessor, and the CP
A U26, a ROM 28, and a RAM 30 are provided. The potentiometer 13 is connected to the control device 24 via the A / D converter 32, and the position signal of the ejector detected by the potentiometer 13 is input to the control device 24. There is. Further, to the control device 24, via the I / O interface 38,
The solenoid valve 14 is connected and the D / A
The variable discharge pump 16 or the proportional electromagnetic relief valve 22 is connected via the converter 34 and the amplifier 36, and a control signal is sent to the solenoid valve 14, the variable discharge pump 16 or the proportional electromagnetic relief valve 22. It is supposed to be output.

That is, in the ejector drive device having the hydraulic system and the control system configured as described above,
When a mold release / extraction start signal is input, the CPU 26 of the control device 24 uses the storage function of the RAM 30 and according to a program stored in the ROM 28 in advance, the solenoid valve 14, the variable discharge pump 16 or A control signal is output to the proportional electromagnetic relief valve 22, whereby the hydraulic cylinder mechanism 10 is actuated and controlled.

In this case, the solenoid valve 1
The control signal output to 4 is a switching control signal for switching the supply / discharge direction of the hydraulic oil to / from the hydraulic cylinder mechanism 10 in order to control the drive direction of the ejector, and is sent to the variable discharge pump 16 or the proportional electromagnetic relief valve 22. The output control signal is a flow rate control signal for adjusting the supply / discharge flow rate of the hydraulic oil to / from the hydraulic cylinder mechanism 10 in order to control the drive speed of the ejector.

When releasing or taking out the molded product, the solenoid valve 14 is switched so that the piston 12 of the hydraulic cylinder mechanism 10 is driven in the projecting direction, and the ejector initially projects at a sufficiently slow speed. The variable discharge pump 16 or the proportional electromagnetic relief valve 22 is actuated and controlled so as to be started and increased continuously or stepwise.

Here, the variable discharge pump 1
6 or the control of the proportional electromagnetic relief valve 22 by the control device 24 is performed by determining the control signal V, for example, according to the flow chart shown in FIG.

Specifically, first, a target speed increase pattern of the ejector speed is set according to the shape and material of the molded product. In addition, this acceleration pattern is generally determined by a relational expression between the ejector position and the ejector speed, and for example, as shown in FIG. 4, a plurality of types (NO. 10 types of acceleration patterns) can be created and can be determined by selecting from them.

Further, the acceleration pattern is divided into an appropriate number of control sections on the ejector position axis (for example, 10 equal parts), and the acceleration data of the ejector for each control section (ejector protrusion speed in the section). Ratio to the final speed setting value) and stores the calculation result in the speed-up data table. Note that this speed-up data table is obtained, for example, by collecting the speed at the intersection of the curve of each speed-up pattern and the dividing line of the plurality of control sections as speed-up data for each speed-up pattern in FIG. Can be created.

Then, in step S1 in FIG.
The ejector drive control of the ejector is started, and the subsequent step S2
In, the potentiometer 13 to the A / D converter 32
The signal input via the is input to A as the current position of the ejector.

Subsequently, in step S3, it is confirmed from the value of the above A which control section in the predetermined speed-up pattern is currently in, and then step S4.
At, it is determined whether the confirmed result is the final control section. If it is not the final control section, in step S5, the speed increase data in the current control section is selected from the preset speed increasing data table. On the other hand, if it is the final control section, immediately step S1
4, the final speed set value is set to the control signal: V, and in step S15, the control signal: V is set in the D / A converter 34 and output, and the process ends.

Further, if it is not the final control section, in step S6 following step S5, the output calculation value v is obtained according to the following equation based on the selected speed-up data. That is, the calculated value v obtained in this way is a reference control signal (reference flow rate control signal) theoretically obtained based on the target speed increase pattern of the ejector speed.

Output calculation value = K (acceleration data × final speed setting value × GAIN + NULL) + initial speed setting value K: constant for changing acceleration pattern GAIN: flow rate setting value NULL for producing ejector specified speed NULL : Constant considering the idling of the pump at low speed

Then, in step S7, it is determined whether or not the fixed cycle timer has timed out. If the time has expired, the process proceeds to step S8. If the time has not expired, the process immediately proceeds to step S11. It should be noted that this fixed-cycle timer is reset immediately after a time-up, restarts, and repeats the time-up for each unit time. It is desirable that the unit time be adjustable, for example, to about 20 ms. Is set.

Then, in step S8, the signal input from the potentiometer 13 via the A / D converter 32 is input to B as the current position of the ejector. Then, in step S9, the amount of change in the ejector position within the time period from step S2 to step S8:
By obtaining B-A, it is determined whether or not the change amount is larger than the minimum value: d of the position change amount within a preset unit time. The value of d is desirably adjustable and is set to, for example, about 0.1 mm.

Then, the amount of change in the ejector position: BA
Is smaller than the minimum value: d, in step S10, a value obtained by adding a preset signal increase amount: α to the currently set control signal: v is set as a control signal: V, and then in step S11. followed by. The value of the signal increment: α is preferably adjustable, and is set to 2.5 mV, for example. On the other hand, if the amount of change in ejector position: BA is larger than the minimum value: d, the process immediately proceeds to step S11.

Then, in step S11, it is determined whether or not the control signal: V is smaller than the calculated value calculated in step S6. If V is smaller than the calculated value, the calculated value is set to the control signal V in step S12, and then the process proceeds to step S13. On the other hand, V
If is not smaller than the calculated value, the process immediately proceeds to step S13.

Further, in step S13, it is determined whether or not the control signal: V is smaller than the final speed set value. If V is not smaller than the final speed set value, the final speed set value is set to the control signal: V in step S14, and then the process proceeds to step S15. On the other hand, if V is smaller than the final speed set value, the process immediately proceeds to step S15.

Then, in step S15, the control signal: V is set in the D / A converter 34 and output, and the process ends.

Further, the steps S1 to S15 as described above are repeated, and the control signal: V is sequentially rewritten, whereby the ejection drive of the ejector according to the target speed-up pattern is realized. Become.

That is, in such a control method, in steps S7 to S10, the movement of the ejector is confirmed, and when the movement amount of the ejector is equal to or smaller than the minimum value, the control signal theoretically obtained by calculation ( The correction correction signal (correction flow rate control signal) is output by increasing correction to the reference flow rate control signal).

Therefore, even when the initial speed of the ejector is set to be sufficiently slow, the defective starting of the ejector can be completely prevented.
The projecting operation can be stably performed at a sufficiently slow speed. Therefore, therefore, the flow rate of the hydraulic oil supplied to the hydraulic cylinder mechanism 10 is extremely small, and the variable discharge pump 1
Slow speed while effectively preventing ejector malfunction due to the unstable region of No. 6 and ejector malfunction due to oil leakage or oil temperature rise due to secular change of equipment, etc. Drive the ejector with
It is possible to prevent damage when the molded product is released or taken out.

Further, in this control method, after the ejector is activated and reaches a predetermined protrusion speed, the correction is not performed in steps S7 to S10, and based on the control signal theoretically obtained by calculation. Since the ejecting speed of the ejector is controlled by the ejector, the ejector is driven at a higher speed in accordance with a desired increasing pattern of the ejecting speed, and the molding cycle can be advantageously improved.

The embodiments of the present invention have been described in detail above, but these are literal examples and the present invention should not be construed as being limited to such specific examples.

For example, the unit time for repeating the position detection of the ejector, the minimum value (d) of the amount of change in the ejector position within the unit time, or the control signal when the amount of change in the ejector position is less than the minimum value The value of the added signal increment (α) is not limited in any way and can be determined appropriately.

Further, in the above embodiment, the acceleration pattern of the target ejector speed is divided into an appropriate number of control sections,
Although the data table is created by calculating the speed-up data of the ejector for each control section, it is also possible to directly calculate the output calculation value from the relational expression of the target speed-up pattern.

Further, it is of course possible to use a detector other than the potentiometer as illustrated in order to detect the protruding position of the ejector.

Although not listed one by one, the present invention is
Based on the knowledge of those skilled in the art, it can be implemented in various modified, modified, and improved modes, and
It goes without saying that all such embodiments are included in the scope of the present invention without departing from the spirit of the present invention.

[0038]

As is apparent from the above description, according to the method of the present invention, the control signal is corrected when the ejector does not have the minimum ejecting speed. Even if it is set to be slow, it is possible to effectively prevent defective operation of the ejector due to unstable operation of the hydraulic pump, secular change of equipment, and the like, and to realize stable ejector speed control.

Therefore, it is possible to set the ejecting initial speed of the ejector to be sufficiently slow while sufficiently ensuring the stability of operation, thereby improving and stabilizing the molding cycle, and molding. Both release of the product and prevention of damage at the time of removal can be advantageously achieved.

[Brief description of drawings]

FIG. 1 is a flowchart showing an example of a speed control method for an ejector according to the present invention.

FIG. 2 is an explanatory view schematically showing one specific example of a hydraulic circuit for driving an ejector controlled according to the flow chart shown in FIG.

3 is a block diagram showing an example of a control system applied to the hydraulic circuit shown in FIG.

FIG. 4 is a graph showing a specific example of preset acceleration patterns of a plurality of types of ejector speeds.

[Explanation of symbols]

 10 Hydraulic Cylinder Mechanism 12 Piston 13 Potentiometer 14 Solenoid Valve 16 Variable Discharge Pump 22 Proportional Electromagnetic Relief Valve 24 Controller

Claims (1)

[Claims] 1. A speed control method for an ejector, which is provided in a mold clamping device and is driven to protrude by a hydraulic cylinder mechanism to eject a molded product, wherein an increase pattern of the protrusion speed is preset according to the protrusion amount of the ejector. When the reference flow rate control signal of the hydraulic cylinder mechanism corresponding to the ejecting position of the ejector is obtained according to the increase pattern of the ejecting speed, and the position change amount of the ejector within a unit time is less than a preset minimum value. In addition, the reference flow rate control signal is increased to obtain a corrected flow rate control signal, the hydraulic cylinder mechanism is controlled based on the corrected flow rate control signal, and the value of the corrected flow rate control signal is equal to the reference flow rate control signal. Controlling the hydraulic cylinder mechanism based on the reference flow rate control signal after the ejecting position of the ejector that has become equal to or less than a value Speed control method for a hydraulic ejector, characterized.