JPH05200817A - Method and apparatus for controlling mold clamping of injection molder - Google Patents

Abstract

PURPOSE:To obtain the method and apparatus for controlling the mold clamping of an injection molder, with which molding cycle is shortened without the development of noise and vibration in the apparatus. CONSTITUTION:The mold clamping oil chamber 12 of a mold clamping cylinder 10 has an oil pressure sensor 48, which detects the pressure in the oil chamber, and a bypass 40, which relieves the pressure oil in the oil chamber through a pilot operated check type prefill valve 44 to an oil tank 64. The oil pressure sensor 48 is connected through an amplifier 50 to a pressure relief process controlling section 55. On tire other hand, the prefill valve 44 is connected through a directional, control valve 46, which is controlled by a pilot oil path 56 and the controlling section 52, and a pilot oil path 42 to the oil path 32 of an oil hydraulic pump 30. Thus, after tire pressure in the mold clamping oil chamber 12 lowers to the maximum allowable pressure, which gives not shock to the mold clamping oil chamber system detected with the oil pressure sensor, the prefill valve 44 is relieved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold clamping control method and device for clamping and opening a mold of an injection molding machine.

[0002]

2. Description of the Related Art Generally, in an injection molding machine, by alternately supplying pressure oil to a mold clamping oil chamber and a mold opening chamber of a mold clamping cylinder, the mold is clamped and the mold is opened. Between the mold clamping and mold opening processes, a mold clamping force holding process for holding the mold with a predetermined mold clamping force is set, and during this period, the molten material is injected and molded.

However, in the above process, when the mold clamping holding process immediately shifts to the mold opening process, the high pressure oil pressure contained in the mold clamping oil chamber and its hydraulic passage system (mold clamping oil chamber system) is increased. Higher hydraulic pressure (hydraulic fluid) is induced by the force to open the mold, and a shock is generated in the mold clamping oil chamber system, resulting in undesirable noise and vibration in the entire apparatus.

Therefore, in this type of mold clamping control method or device, between the mold clamping force holding step and the mold opening step,
That is, prior to the mold opening process, a depressurizing process is set to release the pressure oil in the mold clamping chamber system to the oil tank, that is, to release the pressure in the mold clamping chamber system. And this depressurization process
Generally, it is configured to be performed via a pilot operated check valve provided on a bypass passage that bypasses the mold clamping oil chamber to the oil tank. According to this, when the mold is opened, no shock is induced in the mold clamping oil chamber system, so that noise or vibration does not occur in the device. The check valve is opened after the pressure in the mold closing oil chamber system has dropped to a predetermined pressure. Because it occurs in.

[0005]

However, in the above-described conventional mold clamping method or apparatus, there are the following drawbacks regarding the depressurizing step.

That is, the opening of the check valve in the depressurization step must be performed after the pressure in the mold clamping chamber system has dropped to the set value as described above. As a substitute means for assuming the pressure drop (predetermined pressure), the valve is provided with a timer for setting the operation time of the check valve, that is, a counter timer for delaying the predetermined time from the depressurization process start signal. ..

However, the predetermined pressure (the pressure in the system for releasing the pressure in the mold clamping oil chamber system) varies depending on the characteristics of the molded product determined by the size, shape, etc. of the molded product, and therefore the delay time is also the same. Changes to. For this reason, conventionally, not only is it difficult to set the delay time, but in reality, in order to reliably avoid a shock that occurs in the mold clamping oil chamber system, there is no choice but to set a too long time. As a result, the molding cycle has been extended.

Therefore, an object of the present invention is to provide a mold clamping control method and apparatus for an injection molding machine, which can achieve the depressurizing step quickly without causing a shock in the mold clamping oil chamber system. To provide.

[0009]

In order to achieve the above object, a method for controlling a mold clamping of an injection molding machine according to the present invention is such that pressure oil is alternately provided in a mold clamping oil chamber and a mold opening oil chamber of a mold clamping cylinder. In the mold clamping control method of the injection molding machine, which supplies the mold and clamps the mold to open the mold, the pressure in the mold clamping oil chamber is reduced to a predetermined pressure preset according to the molded product before the mold opening process. After that, the pressure oil in the mold clamping oil chamber is released into the oil tank to release the pressure in the mold clamping oil chamber.

Then, in order to implement the control method,
A mold clamping control device for an injection molding machine according to the present invention opens a pressure sensor in a mold clamping oil chamber for detecting a pressure in the oil chamber and pressure oil in the oil chamber to an oil tank via a pilot check type prefill valve. A bypass passage is provided to reduce the pressure in the mold clamping oil chamber detected by the hydraulic pressure sensor to a predetermined pressure preset according to the characteristics of the molded product before the mold opening step, and then the prefill valve is closed. It is characterized in that the pressure of the mold clamping oil chamber is released by operating to release the pressure oil in the mold clamping oil chamber into the oil tank.

[0011]

According to the present invention, the pressure oil in the mold clamping oil chamber system is released in the depressurizing step after the pressure in the system is lowered to a predetermined pressure preset according to the characteristics of the molded product ( This predetermined pressure is detected by the oil pressure sensor provided in the mold clamping oil chamber and opened to the oil tank), and it is achieved by operating the pilot check type prefill valve on the bypass path that bypasses the mold clamping oil chamber to the oil tank. It

Therefore, according to the present invention, the depressurizing step can be performed quickly and without shock, regardless of the type of the molded product, and the molding cycle can be shortened.

[0013]

Next, a method for controlling a mold clamping of an injection molding machine according to the present invention will be described with reference to an embodiment of a mold clamping control device for carrying out the method.
The following is a detailed description with reference to the accompanying drawings.

Referring to FIG. 1, first, a general structure of an injection molding machine and its mold clamping control will be briefly described.
The injection molding machine uses a mold clamping oil chamber 12 inside the mold clamping cylinder 10.
The mold clamping ram 16 with a piston 16a is divided into the mold opening chamber 14 and the mold opening chamber 14. A movable plate 20 slidably supported by a fixed plate 18 via a tie bar 22 is movably attached to the mold clamping ram 16, and both the plates 18 and 2 are attached.
The fixed mold 24 and the movable mold 26 are held at 0, respectively. Then, in such a configuration, by supplying pressure oil to the mold clamping oil chamber 12 via a hydraulic circuit described in detail below, the mold clamping ram 16 moves rightward in the drawing,
The movable mold 26 on the movable platen 20 is clamped to the fixed mold 24 on the fixed platen 18, and the mold clamping ram 16 moves leftward by supplying pressure oil to the mold opening chamber 14, so that both molds are moved. 24 and 26 are opened.

However, in the present invention, the hydraulic circuit, particularly the hydraulic circuit for the mold clamping oil chamber 12, is on the hydraulic passage 32 from the hydraulic pump 30 and the branch hydraulic passage 34 connecting the mold clamping oil chamber 12. , A pilot check valve 38, a hydraulic passage 32, and a branch hydraulic passage 34.
By-pass oil passage 40 and pilot oil passage 4 connecting to
2 is provided with a pilot check type prefill valve 44 and a direction switching valve 46, and a pressure release process control section 52 connected to a hydraulic pressure sensor 48 connected to the branch hydraulic path 34 via an amplifier 50. It The directional switching valve 36 and the pilot check valve 38, and the pilot check type prefill valve 44 and the directional switching valve 46 are connected via pilot oil passages 54 and 56, respectively. It is integrated with the entire process control unit 58. On the other hand, the hydraulic circuit related to the mold opening chamber 14 is composed of a direction switching valve 62 provided on a branch hydraulic passage 60 connecting the hydraulic passage 32 and the mold opening chamber 14. Reference numerals 64, 64 ... In the drawings all indicate oil tanks.

The mold clamping control device of the present invention having such a structure operates as follows. Therefore, referring also to FIG. 2, first, when the direction switching valve 62 is operated to the a position and the one-way switching valve 36 is operated to the b position via the all process control device section 58, the pressure oil in the mold oil opening chamber 14 is compressed. Is discharged to the oil tank, while pressure oil is supplied into the mold clamping oil chamber 12, whereby the mold clamping ram 16 moves to the right in the drawing to move both molds 26, 2
4 is clamped. That is, the mold clamping step T1 is completed.

Then, the pressure (pressure of the pressure oil) P in the mold clamping oil chamber 12 rises, but this pressure is automatically set to a predetermined pressure P1 via the depressurization process control section 52, and the mold clamping is performed. The force holding step T2 is started. In this mold clamping force holding step, the prefill valve 44 is closed and the direction switching valve 36 is
Is operating in the neutral position c (the position shown in the figure), and therefore the pressure in the mold clamping oil chamber 12 system is sealed. Further, in this case, the rising process and the holding state of the pressure P can be constantly monitored via the hydraulic pressure sensor 48. Next, when the mold clamping force holding step T2 is completed, the direction switching valve 36 first moves to the a position via the depressurization step control section 52,
As a result, the pilot check valve 38 is opened, the pressure oil in the mold clamping oil chamber 12 is appropriately leaked into the oil tank 64, and when the pressure P decreases to a predetermined pressure P2, the directional control valve 46 a When the pilot check type prefill valve 44 is opened, the pressure oil in the mold clamping oil chamber 12 is quickly discharged (opened) into the oil tank 64. That is, the depressurization step T3 is completed promptly. In this case, the decreasing process of the pressure P can be constantly monitored through the hydraulic pressure sensor 48. And finally, the whole process control unit 58
When the direction switching valve 62 is operated to the b position (the position shown in the drawing) via the, the pressure oil is supplied into the mold opening chamber 14 and the mold clamping ram 16
Goes to the left in the figure, and both molds 26 and 24 are opened. That is, the mold opening step T4 is completed. Note that, here, the mold clamping oil chamber pressures P1 (corresponding to the mold clamping force) and P2 in the mold clamping force holding step T2 and the depressurizing step T3 are the optimum mold clamping force (determined according to the characteristics of the molded product). The optimum pressure) and the highest possible pressure (maximum allowable pressure) that can avoid a shock when discharging the pressure oil are preset.

As described above, according to the present invention, the depressurizing step T
Since the pressure oil in the mold clamping oil chamber system in 3 can be released (discharged) accurately at the maximum allowable pressure determined by the characteristics of the molded product, a shock in the mold clamping oil chamber system can be reliably prevented. At the same time, the depressurizing process time can be significantly shortened. Further, according to the present invention, the pressure decrease from the optimum pressure P1 to the maximum allowable pressure P2 is performed by appropriately and forcibly leaking the pressure oil via the pilot check valve 38 provided in the mold clamping oil chamber system. Therefore, the process time required for the pressure decrease can be shortened as compared with the conventional device in which the pressure is generally decreased by the mold clamping and the natural leakage of the pressure oil between the oil chambers of the mold. Here, the graph shown by the dotted line in FIG. 2 shows the depressurizing process time T3 ′ and the total process time T ′ in the conventional apparatus for comparison. Furthermore, according to the present invention, since the mold clamping force during the mold clamping holding step T2 can be maintained at the optimum pressure, the quality of the molded product can be improved.

As described above, according to the present invention, the molding cycle can be greatly shortened without generating noise or vibration in the apparatus. Furthermore, the quality of the molded product can be improved.

The present invention has been described above with reference to a preferred embodiment, but the present invention is not limited to the above embodiment.
Many design changes are possible without departing from the spirit.

[0021]

As described above, the method and apparatus for controlling the mold clamping of the injection molding machine according to the present invention include the hydraulic pressure sensor for detecting the pressure in the mold clamping oil chamber of the mold clamping cylinder.
A bypass oil passage is provided to open the pressure oil in this oil chamber to the oil tank via the pilot check type prefill valve, which allows the pressure in the mold clamping oil chamber detected by the hydraulic pressure sensor to be formed prior to the mold opening process. Since the pre-fill valve is actuated to release the pressure in the mold clamping chamber to a predetermined pressure preset according to the characteristics of the product, that is, after the pressure has dropped to the maximum allowable pressure, It is possible to reliably prevent a shock generated in the mold clamping oil chamber and to significantly reduce the depressurizing process time. Further, according to the present invention, since the mold clamping force during the mold clamping force maintaining step can be maintained at the optimum pressure via the hydraulic pressure sensor,
The quality of the molded product can be improved.

Therefore, according to the present invention, the molding cycle can be shortened and the quality of the molded product can be further improved without generating noise or vibration in the apparatus.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of an apparatus for carrying out a mold clamping control method for an injection molding machine according to the present invention.

FIG. 2 is a graph showing a variation in mold clamping oil chamber pressure corresponding to each process time according to a mold clamping control method in the apparatus shown in FIG.

[Explanation of symbols]

10 Clamping Cylinder 12 Clamping Oil Chamber 14 Cylinder Opening Chamber 16 Clamping Ram 16a Piston 18 Fixed Plate 20 Moving Plate 22 Tie Bar 24 Fixed Mold 26 Moving Mold 30 Hydraulic Pump 32 Hydraulic Path 34 Branch Hydraulic Path 36 Directional Switching Valve 38 Pilot check valve 40 Bypass oil passage 42 Pilot oil passage 44 Pilot check type prefill valve 46 Direction switching valve 48 Oil pressure sensor 50 Amplifier 52 Depressurization process control unit 54, 56 Pilot oil passage 58 All process control unit 60 Branch hydraulic passage 62 direction Switching valve 64 oil tank

Claims (2)

[Claims] 1. A mold opening control method for an injection molding machine, wherein pressure oil is alternately supplied into a mold closing oil chamber and a mold opening chamber of a mold clamping cylinder to perform mold clamping and mold opening, in a mold opening step. Prior to the release, the pressure in the mold clamping oil chamber is reduced to a predetermined pressure that is preset according to the molded product, and then the pressure oil in the mold clamping oil chamber is released into the oil tank to release the pressure in the mold clamping oil chamber. A mold clamping control method for an injection molding machine, comprising: 2. A mold clamping control device for an injection molding machine, wherein pressure oil is alternately supplied to a mold clamping oil chamber and a mold opening oil chamber of a mold clamping cylinder to clamp and open a mold. The chamber is provided with a hydraulic pressure sensor for detecting the pressure in the oil chamber and a bypass passage for opening the pressure oil in the oil chamber to the oil tank via a pilot check type prefill valve. After reducing the detected pressure in the mold clamping oil chamber to a predetermined pressure preset according to the characteristics of the molded product, the prefill valve is operated to release the pressure oil in the mold clamping oil chamber into the oil tank. A mold clamping control device for an injection molding machine, wherein the mold clamping oil chamber is depressurized.