JPH06190884A - Method for controlling position of movable board of injection molding machine - Google Patents

Abstract

(57) [Abstract] [Purpose] A method for controlling the position of the movable plate of an injection molding machine, which has a high accuracy of the movable plate stop position, has little variation in the stop position, and can easily change the stop position of the movable plate. provide. [Structure] In an injection molding machine in which a movable platen 1 is driven by a hydraulic cylinder 3 in a mold clamping direction or a mold opening direction with respect to a fixed platen, the position of the movable platen 1 is detected and its speed is detected. v and acceleration α are calculated, and the distance traveled by the movable platen 1 to a position where the hydraulic cylinder 3 actually stops after a stop command is issued to the hydraulic cylinder 3 is calculated based on the calculated speed v and acceleration α. The movable platen 1 is stopped at a predetermined position by issuing a stop command to the drive device 1 from the predetermined position of the movable platen 1 by the calculated distance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a movable injection molding machine in which a movable platen is driven by a driving device such as a hydraulic cylinder or an electric motor in a mold clamping direction or a mold opening direction with respect to a fixed platen. More specifically, the present invention relates to a movable platen position control method for stopping the movable platen at a predetermined position and a movable platen position control method for switching the movable platen speed at a predetermined position.

[0002]

2. Description of the Related Art An injection molding machine is well known in the art without mentioning a literature name, and generally comprises an injection machine for melting a resin and injecting it into a mold, and a mold device for injecting the molten resin. There is. The mold apparatus is composed of a fixed platen to which the fixed mold is attached, a movable platen to which the movable mold is attached, and a drive device which drives the movable platen in the mold closing direction and the mold opening direction with respect to the fixed platen. The drive device is roughly classified into a direct pressure type and a toggle type, and the direct pressure type is configured such that a movable platen is directly driven by a hydraulic piston / cylinder unit. On the other hand, in the toggle type, the linear motion of the piston of the hydraulic piston / cylinder unit or the rotary motion of the electric motor is converted into the linear motion, and the movable plate is driven via the toggle mechanism. Therefore, it is possible to obtain a molded product by closing the movable plate with respect to the fixed plate by these driving devices, injecting the molten resin from the injection machine into the mold, and waiting for the cooling and solidification to open the mold. it can.

By the way, when performing the above-described injection molding operation, the mold or the movable plate must be opened to a position where the molded product can be taken out, and the injection cycle is shortened during the mold closing operation. Therefore, the mold is closed at a low pressure and a high speed up to a predetermined distance before the mold is completely closed, and at a high pressure and a low speed after that. As described above, the movable platen has a stop position for completion of mold opening during the mold opening operation and a position for changing the mold closing speed during the mold closing operation, and it is desired that these positions are accurate and have no variation. There is. However, a slight time delay of the control device and the drive device is accumulated until an operation command is issued from the control device and the movable plate actually performs the operation, which causes an operation delay. Therefore, conventionally, a mechanical hydraulic damper is installed at the stop position of the movable platen, and the movable platen is collided with the hydraulic damper to stop at a predetermined or designated position. Further, a method is also practiced in which a limit switch is turned on / off depending on the moving position of the movable platen, and the position of the movable platen is controlled by the signal.

[0004]

The mold, that is, the movable platen, can be controlled to a predetermined operating position by the above-mentioned hydraulic damper, limit switch and the like. However,
Since the hydraulic damper is mechanical, the precision of the stop position is difficult to obtain, and the stop position varies. In addition, the injection molding machine changes the mold to change the molded product, but since the thickness of each mold is usually different, it is necessary to change the control position such as the stop position each time, which is troublesome each time. There is also a drawback that requires adjustment. On the other hand, the limit switch has the advantage that the stop position or speed change position can be adjusted relatively easily by adjusting the slider, but the limit switch is also mechanical in nature, and like the hydraulic damper, it does not change the control position. It has a drawback that accuracy is difficult to obtain and that it is necessary to adjust the slider every time the control position is changed. Therefore, the present invention provides a method for controlling the position of a movable plate of an injection molding machine, in which the control position of the movable plate is highly accurate, variation in the control position is small, and the control position of the movable plate can be easily changed. It is an object.

[0005]

In order to achieve the above object, the present invention drives a movable platen in a mold clamping direction or a mold opening direction with respect to a fixed platen by a driving device such as a hydraulic cylinder or an electric motor. In such an injection molding machine, the position of the movable platen is detected, the speed and acceleration of the movable platen are calculated, and an operation command to be performed next is issued to the drive device, and then the operation is actually performed. The distance that the movable plate travels to the position to be calculated is calculated based on the calculated speed and acceleration, and the next operation to be performed on the drive device by the calculated distance from the predetermined position of the movable plate 1. It is configured to control the movable platen to a predetermined position by issuing a command. In the invention described in claim 2, the operation command to be executed next in claim 1 is a stop command at the time of mold opening operation, and the invention in claim 3 is the operation command to be executed next in claim 1. Is composed of a speed switching command at the time of mold closing operation.

[0006]

The present invention can be implemented in various forms. For example, it is possible to control the changing position for changing the mold closing speed of the movable platen from high speed to low speed. At this time, the position of the movable platen is detected, the speed and acceleration thereof are calculated, and the distance that the movable platen moves to the position where the movable plate is actually operated after the high-voltage low-speed closing speed command is issued to the drive device, Further, based on the calculated speed and acceleration, the mold closing speed of the movable platen is calculated by issuing a high-voltage low-speed mold closing operation command to the drive device at a predetermined distance from the predetermined position of the movable platen. It is possible to change to a high-pressure low-speed closing speed at a predetermined position. As described above, the drive device that drives the movable plate in the mold closing direction and the mold opening direction is the hydraulic piston
There are a direct pressure type in which the movable plate is directly driven by the cylinder unit, and a toggle type in which the rotary motion of the hydraulic piston / cylinder unit or the electric motor is converted into a linear motion and the movable plate is driven via a toggle mechanism. In the following embodiments, only a case where the movable platen is applied to a direct pressure type mold clamping machine and the movable platen is stopped at a designated position or a predetermined position during the mold opening operation will be described. The movable platen is driven by a hydraulic piston / cylinder unit, an electric motor, or the like directly or via a toggle mechanism. Therefore, the speed and acceleration of the movable plate can be calculated from the speed and acceleration of the piston of the hydraulic piston / cylinder unit, or the rotational speed and acceleration of the electric motor. Or hydraulic piston
It can also be calculated from the speed of supply and discharge of the pressure oil supplied to and discharged from the cylinder unit, and the amount of change in the current value flowing through the electric motor. However, since these arithmetic methods are obvious to those skilled in the art, they are not specifically shown.

An embodiment of the present invention will be described below. Figure 1
As shown in, the movable platen 1 according to the present embodiment is
It is adapted to be directly driven by the rod 31 of the hydraulic piston / cylinder unit 3. The position of the movable platen 1,
The velocity and the acceleration are detected by the position sensor 2. The position sensor 2 and the control device 8 are connected by a line 9. A well-known sensor is applied to the position sensor 2, and, for example, the movable platen 1 is determined from the capacitance of the capacitor or the magnetic flux of the coil.
Is detected, and the speed and acceleration of the movable platen 1 are detected from the changing speed of the capacitance of the capacitor or the changing speed of the magnetic flux of the coil. The control device 8 is composed of, for example, a microcomputer.

A pipe line 41 is connected to the cylinder head 32 side of the hydraulic piston / cylinder unit 3, and a pipe line 42 is connected to the rod side thereof. Further, the proportional solenoid valve 4 is interposed in these conduits 41 and 42. The proportional solenoid valve 4 is connected to the control device 8 by a line 10 and can be switched to the A, B and C positions. A relief valve 5 is interposed in a discharge line 43 of the pump 6 that connects the proportional solenoid valve 4 and the pump 6, and the relief valve 5 is connected to a control device 8 by a line 11 and receives a signal from the control device 8. It is supposed to be unloaded at.

Next, the operation of this embodiment will be described. In the state shown in FIG. 1, that is, when the proportional solenoid valve 4 is in the C position, the relief valve 5 is unloaded by a signal from the control device 8, and the pressure oil discharged from the pump 6 is discharged from the relief valve 5. The load of the pump 6 is reduced by returning directly to the tank 7. Proportional solenoid valve 4 based on a signal from controller 8
Is switched to the A position, the pressure oil discharged from the pump 6 becomes a pressure controlled by the relief valve 5, and the discharge pipeline 43 moves to the A position of the proportional solenoid valve 4 and the pipeline 41.
And is supplied to the cylinder head 32 side of the hydraulic piston / cylinder unit 3. Since the piston rod 33 side is opened by the conduit 42, the proportional solenoid valve 4, and the return conduit 44, the piston 34 is driven leftward in the figure, and drives the movable platen 1 in the mold clamping direction, for example.

The flow chart of FIG. 2 will be mainly described below. When molten resin is injected from a not-shown injection machine into the mold and cooled and solidified, a signal is applied from the control device 8 to the proportional solenoid valve 4 via the line 10 to switch to the B position. Then, the movable platen 1 is driven in the mold opening direction, but the current position (L) signal at the time of driving is detected by the position sensor 2 and input to the control device 8 through the line 9 (step S1). The control device 8 calculates the speed v and the acceleration α of the movable plate 1 (step 2). Then, when moving in the mold opening direction at a predetermined speed v and acceleration α, the expected distance (Lmv) to advance from when the mold opening stop signal is output to when the mold is actually stopped is defined as the speed calculated in step 2. The calculation is performed based on the acceleration α (step S3). The control device 8 further controls the stop position (L
end) is compared with the sum (L + Lmv) of the current position (L) of the movable platen 1 and the expected distance (Lmv) (step S4). The stop position (Lend) of the movable platen 1 is the sum (L
If it is larger than + Lmv), the process returns to step S1. When it becomes equal or smaller on the contrary, a stop signal of the movable platen 1 is issued and the movable platen 1 is stopped.
Is stopped (step S5). That is, the control device 8
Outputs a stop signal of the movable plate 1 to the proportional solenoid valve 4 via the line 10. Then, the proportional solenoid valve 4 switches to the C position, the movable platen 1 advances by the expected distance (Lmv), and the movable platen 1 stops at a predetermined position or a designated position.
Further, the control device 8 outputs an unload signal to the relief valve 5 through the line 11, and the oil discharged from the pump 6 is stored in the tank 7
Shorted to. Further, when the control position is changed by exchanging the mold, the setting can be easily changed by changing the set value of the control device 8.

[0011]

As described above, according to the present invention, the movable platen is driven in the mold clamping direction or the mold opening direction with respect to the fixed platen by the driving device such as the hydraulic cylinder and the electric motor. In the molding machine, while detecting the position of the movable plate, calculating the speed and acceleration of the movable plate, the movable plate is moved to a position where it actually operates after issuing an operation command to be performed next to the drive device. The moving distance is calculated based on the calculated speed and acceleration, and the movable device is moved by issuing an operation command to be performed next to the drive device before the predetermined position of the movable plate 1 by the calculated distance. Since the board is controlled to a predetermined position, the control position is accurate and there is little variation in the control position. Further, the control position can be changed, for example, only by inputting an operation command to the control device, and there is an advantage that it does not require a troublesome adjustment such as a conventional hydraulic damper or slider. According to the invention described in claim 2, since the operation command to be executed next is the stop command at the time of the mold opening operation, the movable platen can be stopped at a predetermined position accurately and without variation. There is also an advantage that the troublesome adjustment is not required for changing the stop position, for example, only by inputting a command to the control device. According to the third aspect of the present invention, since the operation command to be executed next is the speed switching command during the mold closing operation, the speed switching position during the mold closing operation can be accurately controlled. Further, as described above, it is easy to change the speed switching position.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of the present invention.

FIG. 2 is a flow chart showing the operation of the embodiment of the present invention.

[Explanation of symbols]

1 movable plate 2 position sensor 3 hydraulic piston / cylinder unit (driving device) 8 control device

Claims (3)

[Claims] 1. An injection molding machine in which a movable platen 1 is driven in a mold clamping direction or a mold opening direction with respect to a fixed platen by a drive device 3 such as a hydraulic cylinder or an electric motor. While detecting the position (step S1),
The speed v and the acceleration α are calculated (step S2), and the distance traveled by the movable plate 1 to the position where the movable device 1 actually operates after issuing the operation command to be performed next is calculated. Calculated based on the speed v and the acceleration α (step S3), and by issuing an operation command to be performed next to the drive device 1 before the predetermined position of the movable plate 1 by the calculated distance, A method of controlling the position of a movable plate of an injection molding machine, which controls the movable plate 1 to a predetermined position. 2. A position control method for a movable platen 1 of an injection molding machine, wherein the operation command to be executed next according to claim 1 is a stop command at the time of mold opening operation. 3. A position control method for a movable platen 1 of an injection molding machine, wherein the operation command to be executed next according to claim 1 is a speed switching command during mold closing operation.