JP2653623B2 - Mold clamping control method and device for toggle mold clamping device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for controlling clamping of a toggle type clamping apparatus.

[0002]

2. Description of the Related Art A conventional injection compression molding apparatus is disclosed in Japanese Patent Application Laid-Open No. 61-283520. The injection compression molding apparatus shown here is a so-called direct-acting type, in which a movable plate is directly attached to a piston rod of a mold clamping cylinder, and the movable plate is moved at the same speed (the same amount of movement) as the piston rod. It can be moved. In some injection compression moldings, a molten material is injected into a cavity at a predetermined mold closing stroke position where the mold is not completely closed, and a 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 material is sufficiently compressed. This method is often performed in foam molding and the like.

[0003]

However, the conventional direct-acting injection compression molding apparatus as described above has a problem that it is troublesome to control the position of the movable platen. That is, in the injection compression molding, in the compression step of reducing the cavity volume for the molten material supplied to the mold cavity, it is necessary to apply a compressive force stepwise by advancing the movable platen stepwise. In some cases, a step of slightly increasing the cavity volume during molding (strain removing step) is required during molding to remove distortion of the molded product due to compression molding. In order to control the position of the movable plate, a high-precision sensor for precisely detecting the position of the movable plate and a high-precision flow control device for stopping the movable plate at a predetermined position are required, and the position of the movable plate is controlled. Would be troublesome. In order to solve this problem, it is conceivable to use a toggle type mold clamping device. In the toggle-type mold clamping device, the amount of movement of the toggle mechanism on the movable platen side is smaller than the amount of movement of the toggle mechanism on the side of the crosshead (in proportion to the reciprocal of the force multiplication factor of the toggle mechanism). Even if the moving amount on the side is controlled with normal position accuracy, the position on the movable platen side is controlled with good accuracy (in proportion to the reciprocal of the force multiplication factor of the toggle mechanism). In addition, since the movable platen stops at the position where the links of the toggle mechanism extend straight,
The movable platen side can be decelerated (stopped) without decelerating the crosshead side (mold clamping cylinder side) of the toggle mechanism. However, when injection compression molding is performed using a toggle-type mold clamping device, a final pressing force corresponding to the force increase rate of the toggle mechanism is generated at a position where the links of the toggle mechanism have extended linearly. However, there is a problem that the magnitude of the compressive force at a predetermined stroke position during the mold clamping cannot be easily adjusted by the supply pressure of the mold clamping cylinder as in the case of the direct acting type. That is, in the case of the direct-acting type, the magnitude of the clamping force of the clamping device can be easily adjusted by adjusting the value of the hydraulic pressure supplied to the clamping cylinder. The mold clamping force in the case of
The extension of the tie-bar is limited because the tie-bar elongation is changed by the resistance when the force which resists the compression of the molten material acts as in the case of injection compression molding. The size may be larger than the above. An object of the present invention is to solve such a problem.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems by preventing a mold clamping force exceeding a predetermined value from acting on a movable platen. That is, the mold clamping force setting method of the toggle-type mold clamping device according to the present invention includes the steps of: advancing the crosshead of the toggle mechanism to a predetermined position in the mold closing direction to form a predetermined mold into the molten material in the mold via the toggle mechanism. When the crosshead receives a retreat force greater than a predetermined value based on the force that resists the compression of the molten material by applying a clamping force, the link of the toggle mechanism bends, and the cross mechanism moves to a position where the retraction force balances the mold clamping force. The moving parts such as the head are retracted.
An apparatus for performing the above method is a mold clamping cylinder (10).
The oil is supplied from the main pipe (14) to the mold-clamping-side oil chamber (10b) of the mold-clamping cylinder (10) via the first pipe (16), and the second pipe ( 18)
The piston rod (10a) of the mold clamping cylinder (10) and the cross head (12) of the toggle mechanism (11) integrated therewith are discharged to the main pipe (14) through the
The toggle mechanism (1) is moved by moving
1) to apply a compressive force to the molds (17 and 19) via the first pipe (16).
4) A first switching valve (20), a servo valve (22), and a first pilot check valve (24) provided sequentially from the side.
And a fourth switching valve (40) and a second pilot check valve (42) provided sequentially from the main pipe (14) side in the second pipe (18). (24) has an upstream pilot port (24b) to which the hydraulic pressure downstream of the first pilot check valve (24) is introduced, and the low pressure is set from the high pressure side of the upstream side of the first pilot check valve (24) and the downstream side thereof. The second pilot check valve (4
2) has two pilot ports (42a and 42b)
When the downstream pressure is introduced into the upstream pilot port (42b) and the hydraulic pressure is not introduced into the downstream pilot port (42a), the flow proceeds from the high pressure side to the low pressure side. From the intermediate position between the second pilot check valve (42) and the mold opening side oil chamber (10c) of the mold clamping cylinder (10), which is provided in the second pipe (18). A branch port (42) downstream of the second pilot check valve (42)
a) a second pilot pipe connected to the second pilot pipe, and a fifth switching valve provided in the second pilot pipe.
A pressure head (38) that can detect the oil pressure of the mold-side oil chamber (10b), and a position sensor (56) that can detect the moving position of the crosshead (12). The first pilot check valve (24) is provided in the first pipe (16) and branches from an intermediate position between the first pilot check valve (24) and the mold-clamping-side oil chamber (10b).
A first pilot pipe (32) connected to an intermediate position between the first pilot pipe (32) and the servo valve (22); a shuttle valve (34) provided in the first pilot pipe (32) and having a pressure selection port (34a); A third switching valve (36) provided downstream of the pressure selection port (34a) of the valve (34).
And the first pilot check valve (2
4) has a downstream pilot port (24a), and it is preferable that this is connected to one of the outlet ports of the third switching valve (36). Further, a branch pipe (26) provided in the first pipe (16) and branching from an intermediate position between the servo valve (22) and the first pilot check valve (24), and a branch pipe (26). A second switching valve (28) and a pressure control valve (30) which are sequentially provided.
The downstream side of 0) may be connected to the tank (52). In addition, the code | symbol in a parenthesis shows the corresponding member of an Example.

[0005]

The molten material is injected into the mold cavity, and the crosshead of the toggle mechanism is advanced to a predetermined position, thereby positioning the movable platen at the corresponding position to compress the molten material in the mold cavity. With the toggle mechanism fully extended, the maximum compression force acts on the molten material, and compression molding is performed. If a strain relief step is required after compression molding, the movable platen is retracted by a predetermined amount by retracting the crosshead to a predetermined position. The moving amount of the movable plate is multiplied by the force magnification (usually 50 to 6).
(Approximately 0). Therefore, even if a high-precision position sensor and a high-precision flow control device are not used, the mold can be accurately positioned at a desired position by controlling the position of the crosshead using a normal-precision position sensor. Can be.

FIG. 1 shows an embodiment of the present invention. The mold clamping cylinder 10 is mounted on the mold clamping housing 21. The piston rod 10 a of the mold clamping cylinder 10 is connected to the crosshead 12 of the toggle mechanism 11. The left end (not shown) of the link of the toggle mechanism 11 is connected to the mold clamping housing 21. A movable platen 13 is attached to the right end of the link of the toggle mechanism 11 in the drawing. A fixed board 15 is fixed at a position facing the movable board 13.
The mold clamping housing 21 and the fixed platen 15 are made of four tie bars 2.
3 (only one tie bar is shown in FIG. 1). Tie bar 23 is movable plate 13
Penetrates. A movable die 17 is attached to the movable plate 13, and a fixed die 19 is attached to the fixed plate 15. A molten material can be injected from an injection device (not shown) into a mold cavity during or after mold closing. The tie bar 23 of the mold clamping device can be extended by a predetermined length by the piston rod 10a of the mold clamping cylinder 10 advancing from the left retracted position in the drawing to the illustrated position. A first switching valve 20, a servo valve 22, and a first pilot check valve 24 are sequentially provided from the main pipe 14 side to a first pipe 16 that connects the mold clamping side oil chamber 10 b of the mold clamping cylinder 10 to the main pipe 14. Is provided. The first pilot check valve 24 has two pilot ports 24
a and 24b, and are arranged so as not to obstruct the flow from the main pipe 14 to the mold-clamping-side oil chamber 10b in a state where the hydraulic pressure is not supplied to the downstream pilot port 24a. The first pipe 16 is provided with a branch pipe 26 that branches from an intermediate position between the servo valve 22 and the first pilot check valve 24.
8 and a pressure control valve 30 are provided. The downstream side of the pressure control valve 30 is connected to the tank 52. The pressure control valve 30 is operated by a signal from a controller (not shown).
The value of the control pressure can be changed. Also the first
The pipe 16 has a first branch connected from an intermediate position between the first pilot check valve 24 and the mold clamping side oil chamber 10 b of the mold clamping cylinder 10 and connected to an intermediate position between the first pilot check valve 24 and the servo valve 22. A pilot pipe 32 is provided, and a shuttle valve 34 is provided on the pilot pipe 32. The pressure selection port 34a of the shuttle valve 34 is connected to the downstream pilot port 24a of the first pilot check valve 24 via a third switching valve 36 provided downstream of the shuttle valve 34. The branch portion of the first pilot pipe 32 is also connected to the upstream pilot port 24b. 1st piping 16
Is also connected to a pressure head 38. A fourth switching valve 40 and a second pilot check valve 42 are sequentially provided from the main pipe 14 side in the second pipe 18 connecting the mold opening side oil chamber 10 c of the mold clamping cylinder 10 and the main pipe 14. I have. The second pilot check valve 42 has two pilot ports 42a and 42b. When the hydraulic pressure is not supplied to the downstream pilot port 42a, the flow from the main pipe 14 to the mold opening side oil chamber 10c is controlled. It is arranged in the direction that does not hinder. The second pipe 18 has the second
A second pilot pipe 44 is provided which branches from an intermediate position between the pilot check valve 42 and the mold opening side oil chamber 10c of the mold clamping cylinder 10 and is connected to a downstream pilot port 42a of the second pilot check valve 42. A fifth switching valve 46 is provided for this. Second pilot pipe 4
The branch portion 4 is also connected to the upstream pilot port 42b. A third pilot pipe 48 branching from the main pipe 14 of the second pipe 18 and communicating with the pilot port 22a of the servo valve 22 is provided, and a pressure reducing valve 50 and a filter 58 are sequentially provided from the main pipe 14 side. Is provided. The pressure reducing valve 50 reduces the pressure of the main pipe 14 to a predetermined value, and introduces oil filtered to a predetermined cleanliness level through the filter 58 into the pilot port 22 a of the servo valve 22. Thus, the servo valve 22 is switched at a predetermined switching speed. The filter 58 has a pressure switch 54 that outputs a signal when the pressure difference between the inlet side and the outlet side becomes larger than a predetermined value. A position sensor 56 that can detect the moving position of the crosshead 12 is provided on a fixed portion (not shown).

Next, the operation of this embodiment will be described. The piston 10d of the mold clamping cylinder 10 is located at a retracted position on the left side of the illustrated position, and
a, the movable mold 17 is located at the mold opening position via the toggle mechanism 11 and the movable platen 13. 1st switching valve 20, 3rd
By switching the switching valve 36 and the servo valve 22 from the illustrated position (non-excited position) to the symbol position on the left side in the figure, the first pilot check valve 24 is allowed to flow from the high pressure side to the low pressure side. A predetermined hydraulic pressure is applied from the main pipe 14 to the mold clamping side oil chamber 10b of the mold clamping cylinder 10 via the first pipe 16, the first switching valve 20, the servo valve 22, and the first pilot check valve 24. Supplied. Further, the fourth switching valve 40 and the fifth switching valve 46 on the second pipe 18 side are switched from the illustrated position (non-excited position) to the symbol position on the right side in the figure. That is, the downstream pilot port 42 a of the second pilot check valve 42 communicates with the tank 52, but the pressure of the mold opening side oil chamber 10 c of the mold closing cylinder 10 is reduced by the second pilot check valve 4.
Since the second pilot check valve 42 is introduced into the upstream side pilot port 42b, the second pilot check valve 42 is in a check-open state, allowing the flow from the mold-opening oil chamber 10c to the fourth switching valve 40 side, and 16 and the second pipe 18 are in communication. The cross-sectional area of the mold-side oil chamber 10b is the mold-open-side oil chamber 1
Since the cross-sectional area of the piston rod 10a is larger than the cross-sectional area of 0c, the piston 10d of the mold clamping cylinder 10, the piston rod 10a, and the crosshead 1 integrated therewith.
2 starts to move to the right in the figure. This makes the toggle mechanism 1
1 changes from the bent state to the extended state, and the movable mold 17 starts to be closed. During mold closing, a molten material is injected into the mold cavity from an injection device (not shown) at a predetermined timing. The magnitude of the oil pressure in the mold-clamping-side oil chamber 10b is measured by the pressure head 38 and output to a controller (not shown). The moving position of the crosshead 12 is the position sensor 5
6 and output to the controller. When the position sensor 56 detects that the crosshead 12 has reached a predetermined position (detects that the tie bar 23 has been extended by a predetermined amount), the servo valve 22 is switched to the neutral position shown in FIG. The 2 switching valve 28 is switched to the symbol position on the opposite side from the illustrated position (non-excitation position). As a result, the hydraulic pressure of the mold-clamping-side oil chamber 10b increases with the first pipe 16, the first pilot check valve
The pressure is introduced into the pressure control valve 30 through the switching valve 28, and the pressure of the pressure control valve 30 is adjusted such that the force based on the pressure of the mold clamping side oil chamber 10b becomes a value corresponding to a predetermined mold clamping force. (Based on the signal of the pressure head 38, the pressure control valve 3
0 is adjusted). Therefore, when the movable mold 17 is pushed leftward in the drawing by the reaction force due to the compression of the molten material injected into the mold cavity, the toggle mechanism 11 is maintained so that the predetermined compression force is maintained. While bending
The entire movable part moves to the left in the drawing, and the movable part stops at a position where the compression force is balanced with the retreating force. Thereby, the tie bar 23 can be prevented from being stretched more than necessary.

[0008] In the injection compression molding, in the compression step, a compressive force is applied stepwise by moving the movable platen 13 stepwise. In the case of performing such multi-stage compression, When the position sensor 56 detects that the crosshead 12 has moved to the predetermined first-stage compression position, the third switching valve 36 is moved from the excitation position (blocking position) on the opposite side to the illustrated position from the non-excitation position (illustrated). The downstream pilot port 24a is switched to the communication state. As a result, the higher one of the upstream pressure and the downstream pressure is introduced into the downstream pilot port 24a through the shuttle valve 34 to the downstream pilot port 24a of the first pilot check valve 24. The pilot check valve 24 is locked. That is,
The crosshead 12 stops at that position (the movable platen 13 stops at that position). Movable board 13
Is stopped at the first stage compression position for a predetermined time,
It is moved by a predetermined stroke, stopped again as described above, and such an operation is repeated, and it is sequentially executed until the final stage compression.

In the above embodiment, the position sensor 56 for detecting the moving position of the crosshead 12 is provided. However, the position of the piston rod 10a may be measured. Further, instead of the position sensor 56, a tie bar extension amount sensor for detecting the extension of the tie bar 23 may be provided. in this case,
Instead of controlling the switching of the switching valve or the like based on the moving position of the crosshead 12, the switching of the switching valve or the like may be controlled based on the amount of extension of the tie bar 23. In the description of the above embodiment, the first pipe 16
And a branch pipe 26 branching from an intermediate position between the servo valve 22 and the first pilot check valve 24,
Although the switching valve 28 and the pressure control valve 30 are sequentially provided, and the downstream side of the pressure control valve 30 is connected to the tank 52,
Such a branch circuit may not be provided, and the servo valve 22 may be used to control the retreat pressure of the piston of the mold-clamping-side oil chamber 10 of the mold-clamping cylinder 10.

[0010]

As described above, according to the present invention, even when the toggle-type mold clamping device is used, the injection compression molding can be performed without excessively stretching the tie bar. Also, a molding method such as multi-stage compression molding can be performed.

[Brief description of the drawings]

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

[Explanation of symbols]

 Reference Signs List 10 mold clamping cylinder 10a piston rod 10b mold clamping side oil chamber 10c mold opening side oil chamber 11 toggle mechanism 12 crosshead 14 main pipe 16 first pipe 17 movable mold 18 second pipe 19 fixed mold 20 first switching Valve 22 Servo valve 23 Tie bar 24 First pilot check valve 26 Branch piping 28 Second switching valve 30 Pressure control valve 32 First pilot piping 34 Shuttle valve 36 Third switching valve 38 Pressure head 40 Fourth switching valve 42 Second pilot check Valve 44 Second pilot pipe 46 Fifth switching valve 48 Third pilot pipe 50 Filter 52 Tank 54 Pressure switch 56 Position sensor

Claims (4)

(57) [Claims] A cross-head of a toggle mechanism is advanced to a predetermined position in a mold closing direction to apply a predetermined mold clamping force to a molten material in a mold through the toggle mechanism, thereby resisting compression of the molten material. When the crosshead is subjected to a predetermined retreat force based on the force to be applied, the movable mechanism such as the crosshead is retracted to a position where the retraction force is balanced with the mold clamping force while the link of the toggle mechanism is bent. Clamping control method of a toggle-type clamping device for injection compression molding. 2. A mold clamping side oil chamber (1) of a mold clamping cylinder (10).
0b) is supplied with oil from the main pipe (14) via the first pipe (16) and from the oil chamber (10c) on the mold opening side of the mold clamping cylinder (10) via the second pipe (18). (1
Drain the oil in 4) and close the mold cylinder (10).
By moving the piston rod (10a) and the crosshead (12) of the toggle mechanism (11) integral therewith in the mold clamping direction, the mold (1) is moved through the toggle mechanism (11).
A clamping control device for a toggle-type mold clamping device for applying a compressive force to the first and second switching valves (7, 19), the first switching valve (16) being provided in the first piping (16) sequentially from the main piping (14). 20), a servo valve (22), a first pilot check valve (24), a fourth switching valve (40) sequentially provided from a main pipe (14) side to a second pipe (18), and a second pilot check valve. A check valve (42), and the first pilot check valve (24) has an upstream pilot port (24b) through which hydraulic pressure downstream of the first pilot check valve (24) is introduced.
The second pilot check valve (42) is arranged so as not to obstruct the flow from the high pressure side to the low pressure side of the upstream side and the downstream side of the first pilot check valve (24). Has two pilot ports (42a and 42b), a downstream pressure is introduced into the upstream pilot port (42b), and no hydraulic pressure is introduced into the downstream pilot port (42a). In this state, it is arranged so as not to obstruct the flow from the high pressure side to the low pressure side, is provided in the second pipe (18), and opens the second pilot check valve (42) and the mold clamping cylinder (10). A pilot port (42a) that branches off from an intermediate position with the side oil chamber (10c) and is downstream of the second pilot check valve (42).
A second pilot pipe (44) connected to the second pilot pipe (44), a fifth switching valve (46) provided in the second pilot pipe (44), and a pressure head (38) capable of detecting the oil pressure of the mold clamping side oil chamber (10b). ), And a position sensor (56) capable of detecting a moving position of the crosshead (12). 3. A first pilot check valve (24) provided in the first pipe (16) and a mold clamping side oil chamber (10).
b) a first pilot pipe (32) that branches off from an intermediate position between the first pilot check valve (24) and the servo valve (22) and is connected to the first pilot pipe (32). A shuttle valve (34) having a pressure selection port (34a) and a third switching valve (36) provided downstream of the pressure selection port (34a) of the shuttle valve (34). The first pilot check valve (24) has a downstream pilot port (24a), and is connected to one of the outlet ports of the third switching valve (36). 3. A mold clamping control device of the toggle-type mold clamping device according to 2. 4. A branch pipe (26) provided in the first pipe (16) and branching from an intermediate position between the servo valve (22) and the first pilot check valve (24).
And a second switching valve (2) sequentially provided in the branch pipe (26).
8) and a pressure control valve (30), wherein the downstream side of the pressure control valve (30) is connected to the tank (52). Tightening control device.