JPS6033865A - Method for controlling injection speed - Google Patents

Abstract

PURPOSE:To link driving of a pulse motor and to perform surely entire injection by starting driving of the pulse motor in the rear stage when the difference in frequency of the control pulse trains corresponding to the change points of adjacent injection speeds attains a prescribed value or below. CONSTITUTION:The control pulse train corresponding to the target injection speed from a speed setter 9a is generated at every change point of the injection speed in the position of a piston rod 2 of an injection cylinder 1 detected by means of a striker 5 connected to the rod 2, limit switches 6a-6e and a signal detector 7 and the injection speed by the cylinder 1 is controlled via a pulse motor 20 and a flow rate control valve 21. The driving of said motor 20 by the control pulse train generated in accordance with the speed change point of the adjacent rear stage in the above-mentioned control method is started on condition that the difference in frequency from the control pulse train corresponding to the speed change point of the fore stage attains the prescribed value or below. The driving of the motor 20 is thus surely linked and the entire stage is completed surely as intended.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an injection speed control method in a die casting machine, an injection molding machine, etc.

[Prior art]

FIG. 1 is a diagram schematically showing an injection cylinder and an injection speed control mechanism of a die-casting machine that is considered to be standard. In the figure, molten metal is supplied to the piston rod 2 of the injection cylinder 1 through the coupling 3 into the mold (
An injection pusher 4 for casting (not shown) is connected. Further, a striker 5 is connected to the piston rod 2 or the coupling 3, and a limit switch 5si is provided at the retraction limit position of the piston rod 2 by the striker 5. The limit switches 6b to 6d provided therein and the limit switch 6e provided at the forward limit position of the piston rod 2 are turned on and off. On the other hand, the output signals of the limit switches 6a to 6e are input to the signal detector 7. Above striker 5. The limit switches 6a to 6e and the signal detector 7 constitute a position detector for the injection plunger 4.

The output signal of the signal detector 7 is input to the control signal generator 8, and the control signal generator 8 detects whether or not the injection stroke of the injection plunger 4 has reached the injection speed change point based on this input signal. Ru.

When the injection stroke reaches the injection speed change point, the control signal generator 8 generates an analog control signal corresponding to the target injection speed preset in the speed setting device 9, and this control signal is used to control the servo control. By supplying the pulp to the pulp 10, its opening degree is controlled. The servo pulp 10 is connected to the injection cylinder 1 by a hydraulic circuit 11,
The amount of liquid introduced into the injection cylinder 1 is adjusted according to the opening degree. As a result, the injection plunger 4 connected to the piston quartet 2 in the injection cylinder 1 is able to release the servo pulp 1.
The moving speed is controlled according to the opening degree of 0. That is, the injection speed is controlled to the target speed by a control signal generated at each change point.

Fig. 2 is a graph showing a pattern of changes in the injection speed that changes due to such control.The horizontal axis shows the injection stroke st, and the vertical axis shows the injection speed V. In the injection stroke a where injection starts at
In the injection strokes c and d where c and 5d are turned on, an example is shown in which the speed is changed toward the target speed V8°v4. Usually, the section from vo to v2 is the sleeve filling area, the section v2 is the gate passing area, and the section from v2 to v4
The section after reaching vo until returning to vo is called the cavity filling region.

By the way, in such an injection speed control mechanism, from the time when the control signal corresponding to the target speed starts to be generated until the injection speed actually starts to change, there are many factors such as the inertia of the mechanical parts and the hydraulic circuit 11, the compressibility of the hydraulic fluid, etc. There is a certain delay time due to Therefore, considering this delay time, the control signal generation start timing, that is, the limit switch 6
It is necessary to adjust the installation positions of a to 6e. Therefore, if the installation position is not adjusted, the injection speed change pattern in the cavity filling area will be as shown in Fig. 3, and the injection process will end before reaching the final speed v4. There is.

In order to solve such problems, a control pulse train is used as a control signal, and this control pulse train drives a pulse motor to control the opening degree of the flow rate control pulp, thereby increasing the accuracy of the control operation. A method has been proposed in which the installation positions of the limit switches 6a to 6e are adjusted with due consideration to the delay time.

In such a method, in sections where the velocity gradient is relatively large, for example in the cavity filling region, two limit switches must be placed in close proximity to change the speed from v2 to v8 and from v8 to v4, respectively. Situations may occur.

However, if the two limit switches are placed too close together, the speeds will change from v2 to v8 and from v8 to V.

As shown in FIG. 4, the control pulse trains pVg and pV4 for respectively changing Δ may overlap by a time period. Therefore, normally in such a case, priority is given to the control pulse train pV4, but conventionally, the control pulse train pv8 is given priority and the servo pulp is controlled without considering the frequency difference between the control pulse train pVB and pv4. Therefore, if the frequency difference between both pulse trains pvB and pv4 is large, the pulse motor will step out, resulting in an uncontrollable state.

[Object and structure of the invention]

The present invention was made to solve these drawbacks, and its purpose is to reliably chain the pulse motor drives even when the control pulse trains generated at adjacent speed change points are shipped automatically, so that all injection It is an object of the present invention to provide an injection speed control method that can reliably complete a process as scheduled.

For this purpose, the present invention is designed such that the drive of the pulse motor by the control pulse train generated corresponding to the speed change point in the subsequent stage is such that the frequency difference with the control pulse train corresponding to the speed change point in the previous stage is less than a predetermined value. It is designed to start on the condition that something has happened.

〔Example〕

5 to 10 are graphs showing changes in the frequency of the control pulse train applied to the pulse motor in the present invention, with the horizontal axis representing time and the vertical axis representing pulse frequency (pps). First, in FIG. 5, when the control pulse train PF generated at the speed change point in the previous stage and the control pulse train pB generated at the speed change point in the latter stage overlap after time tl, both pulse trains P
At time t2 when the pulse frequencies of F+PB match, this pulse train PB is interrupted by the subsequent control pulse train PB.
This shows an example in which the pulse motor is started to be driven by K. By starting the drive using the control pulse train PB in the latter stage in this way, it is possible to completely prevent the pulse motor from stepping out when shifting from the pulse train PF to the drive to pa, and furthermore, the injection speed can be made smoother. can be shifted to a new speed.

Next, similarly in FIGS. 6 and 7, the control pulse train PF in the former stage and the control pulse train PB in the latter stage are at time t1.
If they overlap later, both pulse trains PF and PB
At time t2 when the pulse frequencies of
An example in which driving by B is started is shown. In this case as well, the same advantages as in the example of FIG. 5 can be obtained.

On the other hand, in FIG. 8, after driving at a constant frequency for a certain period of time Δt from time t2 when the pulse frequency of the previous-stage control pulse train pF and the pulse frequency of the subsequent-stage control pulse train PB coincide, the driving is performed by the subsequent-stage control pulse train PB. An example of starting the . As a result, it is possible to prevent the pulse motor from stepping out of synchronization, and also to alleviate drastic changes in the injection speed that occur when the injection speed changes from a decelerated state to an accelerated state.

Next, in FIG. 9, when the subsequent control pulse train pB occurs at time t1 while the pulse motor is being driven by the previous control pulse train PF, the drive by the previous stage control pulse train pF is interrupted at time t2. After driving at a constant frequency for a time Δti, deceleration driving is performed using a pulse train Pc corresponding to a predetermined deceleration characteristic, and at time t2 when the pulse frequency of this deceleration drive final pulse train pc and the subsequent control pulse train pB match, the constant frequency is reached. An example is shown in which the drive is switched to the drive by the control pulse train pB of the subsequent stage after Δt2 time has elapsed.

This prevents the pulse motor from stepping out, and
It is possible to quickly reach the target injection speed corresponding to the control pulse PB in the latter stage.

In FIG. 10, the control pulse train PB in FIG.
An example is shown in which Δ occurs after shifting to constant speed driving by the previous stage control pulse pF, and in this case as well, after being decelerated by the deceleration pulse train Pc as in the case of FIG.
It is driven at a constant speed for t2 time. After this constant speed driving, a shift is made to driving using the control pulse train PH in the subsequent stage.

In addition, in the above explanation, when driving from one control pulse train pF to the other control pulse train PB,
Although the condition is that the pulse frequencies of both pulse trains match, the condition may be changed to a condition that the frequency difference is within a range where the pulse motor does not step out.

FIG. 11 is a block diagram showing an embodiment of an injection speed control mechanism to which the present invention is applied. In the figure, the same parts as in FIG. 1 are given the same reference numerals.

The control pulse generator 8a detects whether the injection stroke has reached the injection speed change point based on the input signal from the signal detector 7, and if it has reached the point, the control pulse generator 8a detects whether or not the injection stroke has reached the injection speed change point, and if it has reached the injection speed change point, the control pulse generator 8a detects whether or not the injection stroke has reached the injection speed change point. Outputs a control pulse train with time intervals corresponding to the injection speed. As a result, the pulse motor 20 rotates by an amount proportional to the number of pulses, and the opening degree of the flow control pulp 21 is controlled. Thereby, the moving speed of the injection plunger 4 is controlled according to the opening degree of the flow rate control pulp 21. The control pulse generator 8a performs control as shown in FIGS. 5 to 10.

Next, the structure of the double-pulse motor 20 and the flow rate control pulp 21 will be explained using FIG. 12.

In FIG. 12, 22 is a pulp body having a hydraulic oil inlet 23 from the axial direction and a hydraulic oil outlet 24 perpendicular to the axis, 25 is a spool that moves in the axial direction in the pulp body 22, and 26 is A nut shaft 27 is integrally provided at the rear of the spool 25. A screw shaft 29 is screwed into the inner shaft center of the nut shaft 26 by a ball screw 28.
30 is a joint that connects the screw shaft 27 with the shaft of the shaft motor 20, and 30 is a key that prevents the nut shaft 26 from rotating and guides its movement in the axial direction.

The spool 25 moves back and forth in the axial direction in response to the rotation of the pulse motor 20, instantaneously opening and closing the pulp and adjusting the opening degree to control the flow rate. As described above, this flow rate control pulp 21 is produced by moving a spool 25 to a pulse motor 20 within a cylindrical pulp body 22 having a hydraulic oil inlet 23 at the end face in the axial direction and a hydraulic oil outlet 24 at the side surface. The system controls the flow rate by driving in the 114II linear direction by the action of The driving force required for switching is reduced, and the flow rate control pulp 21 can further improve the performance of high-speed flow rate switching and reduce the driving force.

In this flow rate control pulp 21, the amount of opening of the spool 25 is determined by the rotation amount, that is, the rotation angle, of the pulse motor 20 according to the control pulse train from the control pulse generator 8a, and the flow rate to the injection cylinder 1 is controlled. Furthermore, the rate of change of the flow rate, that is, the rise state of the speed, is determined by the magnitude of the rotational speed of the pulse motor 20 during the rotation.

In addition, in the flow rate control pulp 21 that has brought about such a structure and action, the spool 2 actually changes in response to a command to change the speed.
It is possible to suppress the time t1 until the valve starts to open to less than 1 millisecond at maximum, and the response is extremely good compared to conventional ordinary flow control pulp. Accuracy has also improved significantly.

A permanent magnet 31 is fixed to a part of the surface of the nut shaft 26, and a magnetic position detector 33 called a zero cross sensor is attached to the permanent magnet 31 and a part of the opposing casing 32, for example. The position detector 33 is constituted by a proximity switch that is sensitive to the movement of the permanent magnet 31, and can accurately detect the moving distance of the nut shaft 26 and the spool 25 in the axial direction and feed it back to the control device. Further, the zero position of the spool 25 can be electrically detected by the action of the permanent magnet 31 and the position detector 33, and the pulse motor 20 can be accurately stopped at that position via the control pulse generator 8a. You can also do it like this.

Note that the position detector 33 has an accuracy of 0.01'5'l.
1O can be used.

In this embodiment, since the flow control pulp 21 driven by the front pulse motor 20 is used, the inertia is small, the response is good, and the control can be performed reliably and easily.

〔Effect of the invention〕

As explained above, in the present invention, the pulse motor is driven by the control pulse train generated in response to the speed change point in the subsequent stage, so that the frequency difference with the control pulse train corresponding to the speed change point in the previous stage becomes less than a predetermined value. The system is designed to start on the condition that this is the case.

Therefore, even if the control pulse trains generated at adjacent speed change points overlap, the pulse motor can reliably transition from the first injection speed to the second injection speed without stepping out, and the entire injection process can be scheduled. The process can be completed without fail.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an example of the injection speed control mechanism of a die-casting machine, Figs. 2 and 3 are graphs showing an example of the relationship between the stroke of the injection cylinder and the injection speed, and Fig. 4 (,) - (,) are diagrams showing the relationship between injection speed characteristics and control pulse trains, Figures 5 to 10 are pulse train frequency characteristic diagrams showing embodiments of the present invention, and Figure 11 is injection speed control to which the present invention is applied. Block diagram showing one embodiment of the mechanism, No. 12
The figure is a sectional view showing the structure of flow control pulp. 1...Injection cylinder, 2...Piston rod, 4...Injection plunger, 5a-6e...Limit switch, 7...Signal detector, 8a...
Control pulse generator, 9 & Speed setter, 20
...Pulse motor, 21...Flow rate control pulp. Figure 5 PPS PPS Figure 9 Figure 6 PPS Figure 8 PS Procedural Amendment Form) 1. Display of the case 1982 Patent Application No. 141436 2, Name of the invention Injection speed control method 3, Person making the amendment Relationship to the case Patent Applicant

Claims (1)

[Claims] In an injection speed control method, a control pulse train corresponding to a target injection speed is generated for each change point in the injection speed, and the pulse motor is driven by this control pulse train to control the injection speed of the injection cylinder to the target speed. The pulse motor is driven by a control pulse train generated corresponding to a subsequent speed change point among the control pulse trains generated at the change point, such that the frequency difference between the control pulse train and the control pulse train corresponding to the previous speed change point is equal to or less than a predetermined value. An injection speed control method characterized in that the injection speed is started on the condition that the injection speed has changed.