JPH06297528A - Flow rate-controlling method for clamping cylinder in toggle type injection molding machine - Google Patents

Abstract

PURPOSE:To enable compression force as it is set for each set position to act respectively on metal molds 38, 40 by using a toggle type clamping device. CONSTITUTION:A flow rate per each transfer section supplied to a clamping cylinder 10 is automatically set on the basis of a distance per each transfer section of a movable part on a movable platen 30 side predetermined, a set transfer time per each transfer section, and dimensional items of a toggle mechanism 12. Further, a transfer distance per each stroke section of the movable part on the clamping cylinder side such as a cross head 12a or the like predetermined, and a time while the movable part moves for a stroke section are set and stored. A transfer time of the movable part is measured per each stroke section in a molding cycle. Those are compared with corresponding set time to obtain each time difference. Then, a flow rate supplied to the clamping cylinder can be also regulated so that a time difference per each stroke section can become respectively zero in the next molding cycle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a mold clamping cylinder flow rate in a toggle type injection molding machine.

[0002]

2. Description of the Related Art As a conventional injection compression molding apparatus, there is one disclosed in Japanese Patent Application Laid-Open No. 61-283520. The injection compression molding device shown in this is a so-called direct-acting type, in which the movable platen is directly attached to the piston rod of the mold clamping cylinder, and the movable platen is at the same speed (same movement amount) as the piston rod. It can be moved. Among injection compression molding, there is a method in which a molten resin is injected into a cavity at a predetermined mold closing stroke position where the mold is not closed, and the compression process is started in the middle of the mold closing. That is, there is a molding method in which the compression stroke is relatively long and the molten resin is sufficiently compressed. This method is often used in foam molding and the like.

[0003]

However, the conventional direct-acting type injection compression molding apparatus as described above has a problem that it is troublesome to control the speed of the movable plate, and in particular, as described above. In the case of molding with a long compression stroke, it is necessary to control the speed of the movable plate over a long stroke. That is, in injection compression molding, a compressive force is applied to the molten resin supplied to the mold cavity by decreasing the cavity volume (moving the movable platen forward), but controlling the speed of the movable platen from the start of compression. There is a need to. Also, in the case of a direct-acting type mold clamping device, the final compression process is performed with the movable side mold abutting against the fixed side mold (mold touch state), so the impact at the time of abutting will cause In order to avoid damaging the mold, it is necessary to decelerate the movable platen from a position before the abutting position, which makes it difficult to control the speed of the movable platen. As a solution to this problem, it is possible to use a toggle type mold clamping device. Even if the toggle type mold clamping device drives the crosshead part of the toggle mechanism at a constant speed, the moving speed on the link end side (movable plate side) increases as the link is bent in a linear shape and shortened. It has the characteristic that the moving speed on the movable platen side becomes slower as the extended state where the two extend straight to each other, and the movable platen stops at the position where the links of the toggle mechanism have completely extended linearly. . That is, it is possible to decelerate (stop) the movable platen side without decelerating the crosshead side (mold clamping cylinder side) of the toggle mechanism. However, when performing injection compression molding using a toggle type mold clamping device, there is a problem that controlling so that a predetermined compression force acts at a predetermined position is not so easy as in the case of the direct acting type. . The present invention aims to solve such problems.

[0004]

According to the present invention, a stroke section determined in advance, a time during which a movable portion of a mold clamping device moves in this section, and dimensional specifications of a toggle mechanism are set for each stroke section. The above problem is solved by setting the flow rate to be supplied to the mold clamping cylinder. That is, the method of controlling the flow rate of the mold clamping cylinder in the toggle type injection molding machine of the present invention is the distance for each predetermined moving section of the movable part of the movable plate side of the toggle type mold clamping apparatus, and the set moving time for each moving section. The flow rate for each moving section supplied to the mold clamping cylinder is automatically set based on the dimensions of the toggle mechanism. It should be noted that a predetermined moving distance for each stroke section of the movable portion of the mold clamping cylinder side such as the crosshead and the time during which the movable section moves in the stroke section are set and stored, and the stroke section is set in the molding cycle. The moving time of the movable part is measured for each time, and these are compared with the corresponding set time to obtain the respective time differences, and in the next molding cycle, the time differences for each of the stroke sections are set to 0 respectively. The flow rate supplied to the tightening cylinder can be adjusted. Further, the flow rate can be adjusted for each predetermined molding cycle.

[0005]

[Operation] Based on a predetermined distance for each moving section of the movable platen-side movable section, a set moving time for each moving section, and dimensional specifications of the toggle mechanism, for each moving section supplied to the mold clamping cylinder. Automatically set the flow rate. Accordingly, during the mold clamping process, the movable part on the movable platen side is controlled so as to move in a predetermined movement section for a predetermined time. In the case of claim 2,
The moving time of the movable part on the mold clamping cylinder side in a predetermined stroke section is measured. The measurement time is compared with the set time, and the time difference is calculated. The flow rate corresponding to the time difference is calculated, and the corrected flow rate is supplied to the mold clamping cylinder in the next cycle. As a result, it is possible to finally move the movable unit on the movable plate side for each moving section according to the set time via the toggle mechanism.

[0006]

【Example】

(First Embodiment) FIG. 1 shows a first embodiment of the present invention. A mold clamping housing 34 is arranged at a position facing the fixed platen 32. The movable platen 30 is arranged between the fixed platen 32 and the mold clamping housing 34. The mold clamping housing 34 and the movable platen 30 are connected by the toggle mechanism 12.
That is, one end of each of the plurality of links of the toggle mechanism 12 is connected to the mold clamping housing 34,
The other end side is connected to the movable platen 30, respectively. The fixed plate 32 and the mold clamping housing 34 include four tie bars 3
6 (however, only two are visible in the figure). The tie bars 36 penetrate the movable plate 30, respectively. That is, the movable plate 30 has the tie bar 36.
Is guided by the axial movement. A movable mold 38 is fixed to the movable plate 30, and a fixed mold 40 is fixed to the fixed plate 32. Mold clamping housing 3
A mold clamping cylinder 10 is attached to 4. The piston rod 10 a of the mold clamping cylinder 10 penetrates the center of the mold clamping housing 34 and is connected to the crosshead portion 12 a of the toggle mechanism 12. A position sensor 24 is provided at a position facing the cross head 12a on the mold clamping housing 34 side. The position sensor 24 can detect the moving position of the crosshead 12a. A controller 26 is provided for inputting a measurement position signal from the position sensor 24. The controller 26 has a timekeeping function,
It is possible to measure the time required to move a predetermined stroke section based on the signal of the measurement position from the position sensor 24, and to control the switching positions of the switching valves 18 and 22 described later. A hydraulic pressure source 14 for supplying hydraulic pressure to the mold clamping cylinder 10 is provided. Main piping 2 of hydraulic source 14
1, a flow rate adjusting valve 16 and a main switching valve 18 are sequentially connected toward the downstream side. The flow rate adjusting valve 16 can adjust the flow rate supplied to the mold clamping cylinder 10 by adjusting the throttle opening degree of the flow rate adjusting valve 16. A branch pipe 25 is provided in the main pipe 21 at a position upstream of the position where the flow rate adjusting valve 16 is provided, and a relief valve 28 is provided therein. The return side of the relief valve 28 communicates with the tank 29. The relief valve 28 is the hydraulic power source 14.
The upper limit pressure of can be set. The main switching valve 18 is a three-position switching valve, and one port (the port on the upper left side in the drawing) of the main switching valve 18 is connected to the mold clamping side oil chamber 10b of the mold clamping cylinder 10 via the first pipe 23. . Pilot check valve 20 having pilot port 20a in first pipe 23
Is provided. One end of a pilot pipe 33 is connected to the pilot port 20a of the pilot check valve 20. The other end of the pilot pipe 33 is connected to the first pipe 2
It is connected with 3. The pilot switching valve 22 is provided in the pilot pipe 33. That is, the pilot check valve 20 is provided with the pilot switching valve 22 at a symbol position (solenoid excitation position) opposite to the symbol position shown in the drawing.
The hydraulic pressure from the mold clamping side oil chamber 10b of the mold clamping cylinder 10 is introduced into a to prevent the flow from the mold clamping cylinder 10 side to the main switching valve 18 side. In the state in which the pilot port 20a is in the non-excitation position, the pilot port 20a communicates with the tank 29, and the flow from the high pressure side to the low pressure side (usually from the main switching valve 18 side to the mold clamping cylinder 10 side). Flow). As a result, as shown in FIG. 2, the piston rod 10a of the mold clamping cylinder 10 moves the stroke s.
At the time of moving by 1, the compressive force f1 of a predetermined magnitude acts on the movable platen 30, and similarly the strokes s2, s3, and sn.
The corresponding compressive forces f2, f3, and fn act on the movable platen 30 when they are moved. The phantom line in FIG. 2 shows the relationship of the compression force with respect to the stroke position of the direct acting type mold clamping device. The other port of the main switching valve 18 (the port on the upper right side in the drawing) is connected to the mold opening side oil chamber 10 of the mold clamping cylinder 10 via the second pipe 27.
connected to c.

Next, the operation of the first embodiment will be described.
First, as a preparatory work, the controller 26 is instructed to move time t1 for each predetermined stroke position s1, s2, s3, and sn.
t2, t3, and tn (these total times are T) are stored as set times, respectively. Further, based on these data, the initial valve opening degree of the flow rate adjusting valve 16 for each stroke section is calculated by the controller 26 and automatically stored as each set valve opening degree. The relief valve 28 is set to a predetermined set relief pressure. This completes the preparation for injection compression molding.

Next, one molding cycle is started. That is, with the pilot switching valve 22 in the non-excited position (symbol position shown in FIG. 1), the main switching valve 18 is switched to the symbol position on the right side of the drawing, and the valve opening is set from the hydraulic power source 14 to the initial setting. The oil whose flow rate is adjusted by the flow rate adjusting valve 16 is supplied to the main pipe 21, the main switching valve 18, the first pipe 23,
Through the pilot check valve 20 and the mold clamping cylinder 1
0 to the mold clamping side oil chamber 10b, and the piston rod 10a
And the crosshead 12a integral with this is advanced. During mold closing, a molten resin is injected into the mold cavity from an injection device (not shown) at a predetermined timing, and a compression process is performed. During the compression process, the position of the crosshead 12a is detected by the position sensor 24, and the predetermined position s1, s
The time required to move to 2, s3, and sn is measured and input to the controller 26. The controller 26 is
These measurement times are compared with the set time, and the difference between the two times is calculated. No correction signal is output while the time difference is smaller than the predetermined value, but when the time difference is larger than the predetermined value, the stored value of the throttle opening amount corresponding to the valve opening correction amount corresponding to the time difference is stored. To fix. As a result, in the next cycle, the flow rate corresponding to the correction valve opening is supplied to the mold clamping side oil chamber 10b of the mold clamping cylinder 10, and the crosshead 1
The time required for the 2a to move to the predetermined stroke position will be matched with the set time. That is, the compression force as set acts on the movable platen 30 at the predetermined stroke position.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention. In the second embodiment, instead of the hydraulic circuit shown in FIG. 1, a main circuit 48 including a hydraulic source and a mold clamping cylinder 1 are provided.
A switching valve 42 and a servo valve 44 are provided between the zero oil chambers 10b and 10c, and a pressure head 46 that can detect the pressure in the mold clamping side oil chamber 10b is provided. The signal from the pressure head 46 is input to the servo valve 44. A tie bar extension detecting device 50 capable of measuring the amount of extension of the tie bar 36 is provided at the fixed portion on the mold clamping housing 34 side.
Is provided. The signal from the tie bar extension detection device 50 is input to a control device (not shown).

The operation of the second embodiment is such that the switching valve 42 supplies the hydraulic pressure from the main circuit 48 to either one of the mold clamping side oil chamber 10b and the mold opening side oil chamber 10c of the mold clamping cylinder 10. Switch to the pressure head 4
The flow rate is controlled by the servo valve 44 in accordance with the signal from 6, and it is determined whether or not a predetermined compression force is applied at a predetermined stroke position.
A controller (not shown) makes a determination based on the signal of (1), outputs a control signal to the servo valve 44, and feedback control is performed so that a predetermined compression force acts. This is similar to the case of the embodiment.

In the description of the first embodiment described above,
After automatically setting the valve opening of the flow rate adjusting valve 16, the time for each stroke section is measured, and the valve opening of the flow rate adjusting valve 16 is corrected based on the time difference between the measurement time and the set time. When it is determined that conditions such as oil temperature are stable and the valve opening degree is only automatically set and correction work is not necessary, it is possible not to perform subsequent adjustment work. On the contrary, when the oil temperature and other conditions are likely to change, the valve opening of the flow rate adjusting valve 16 may be adjusted every predetermined molding cycle. Further, in the above description of the respective embodiments, the position sensor 24 detects the moving position of the cross head 12a of the toggle mechanism 12, but the movement of another movable portion such as the piston rod 10a of the mold clamping cylinder 10 is detected. It is also possible to detect the position.

[0012]

As described above, according to the present invention, even when the toggle type mold clamping device is used, the set compression force can be applied to the mold at each set position. Therefore, it is possible to perform injection compression molding as set.

[Brief description of drawings]

FIG. 1 is a diagram showing a toggle type mold clamping device for carrying out the present invention.

FIG. 2 is a diagram illustrating a relationship between a stroke of a mold clamping cylinder and a compression force.

FIG. 3 is a diagram showing another device for carrying out the present invention.

[Explanation of symbols]

 10 mold clamping cylinder 10a piston rod 10b mold clamping side oil chamber 10c mold opening side oil chamber 12 toggle mechanism 12a crosshead 14 hydraulic power source 16 flow rate adjusting valve 18 main switching valve 20 pilot check valve 20a pilot port 21 main line 22 pilot switching valve 23 First Pipe 24 Position Sensor 25 Branch Pipe 26 Controller 27 Second Pipe 28 Relief Valve 29 Tank 30 Movable Plate 32 Fixed Plate 34 Mold Clamping Housing 36 Tie Bar 38 Movable Side Mold 40 Fixed Side Mold

Claims (3)

[Claims] 1. Clamping based on a predetermined distance for each moving section of a movable part on the movable plate side of a toggle type mold clamping device, a set moving time for each moving section, and dimensional specifications of a toggle mechanism. A method for controlling the flow rate of a mold clamping cylinder in a toggle type injection molding machine that automatically sets the flow rate for each moving section supplied to the cylinder. 2. A predetermined moving distance for each stroke section of a movable portion on the mold clamping cylinder side such as a crosshead, and a time during which the movable section moves in the stroke section,
Is set and stored, the moving time of the movable part is measured for each stroke section in the molding cycle, and the time difference is calculated by comparing these with the corresponding set time. A method of controlling a flow rate of a mold clamping cylinder in a toggle-type injection molding machine, characterized in that a flow rate supplied to the mold clamping cylinder is adjusted so that a time difference for each section becomes zero. 3. The method for controlling the flow rate of a mold clamping cylinder in a toggle type injection molding machine according to claim 2, wherein the flow rate is adjusted every predetermined molding cycle.