JP3220789B2 - Depressurizing method of mold clamping cylinder - 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 for depressurizing a mold clamping cylinder for depressurizing a mold clamping cylinder after applying a predetermined mold clamping pressure to a mold.

[0002]

2. Description of the Related Art Generally, in an injection molding machine, a mold is clamped by a mold clamping device, a resin is injected and filled into the mold by the injection device, and then the mold is opened to take out a molded product. By the way, usually, the clamping pressure by the clamping device becomes considerably high. Therefore, when a clamping cylinder which constitutes a direct pressure type mold opening / closing mechanism is used for the clamping device, after the clamping pressure is applied. When depressurizing, the high-pressure oil discharged from the mold clamping cylinder suddenly flows into the return piping and valves of the hydraulic circuit, and the impact at this time causes vibration and noise in the mold clamping device. Invite.

[0003] For this reason, conventionally, Japanese Patent Application Laid-Open No. 5-20081
As disclosed in Japanese Patent Publication No. 7, a pilot check valve and a pilot check type prefill valve are connected in parallel to the mold clamping cylinder, and at the time of depressurization, the pilot check valve is first opened to reduce the pressure of the mold clamping cylinder once. The pressure and the pressure are reduced, and then the pilot check type prefill valve is opened to avoid the vibration and noise at the time of depressurization by a method of performing the full depressurization to the mold clamping cylinder.

[0004]

However, the above-described conventional depressurizing method has two check valves having different characteristics, namely,
The need for a pilot check valve and a pilot check type prefill valve and a directional control valve to control each check valve are required. There was a problem that increased the cost.

The present invention has been made to solve the problems existing in the prior art, and eliminates the generation of vibration and noise at the time of depressurization, while reducing the number of components in the hydraulic circuit and simplifying the configuration. An object of the present invention is to provide a method for depressurizing a mold clamping cylinder which can reduce the size and cost of the entire apparatus.

[0006]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method for depressurizing a mold clamping cylinder, comprising the steps of: holding a hydraulic pressure of a mold clamping cylinder by a pilot check valve; After applying the pressure Pcm, when the pilot check valve 2 is opened to depressurize the mold clamping cylinder 1, the pilot check valve 2 is depressurized by intermittently controlling the opening from the start of depressurization. It is characterized by the following. The pilot check valve 2 can be controlled to open and close based on preset opening and closing patterns Xa and Xb.
b can be set by the opening time ta ..., the closing time tb ... and the number of times of opening and closing.

Accordingly, the mold clamping pressure Pc is applied to the mold 3.
m, the pilot check valve 2 is intermittently opened from the start of depressurization when the press-release cylinder 1 is depressurized. It is avoided, and the impact when flowing into the return pipe, valve or the like of the hydraulic circuit is reduced.

[0008]

Next, preferred embodiments according to the present invention will be described in detail with reference to the drawings.

First, the configuration of a mold clamping device that can carry out the depressurizing method according to the present embodiment will be described with reference to FIG.

In FIG. 4, Mc is a mold clamping device, 11 is a fixed plate supporting the fixed die 3c, and 12 is a movable plate supporting the movable die 3m. This fixed type 3c and movable type 3m
Constitutes the mold 3. On the other hand, reference numeral 1 denotes a low-speed high-pressure type mold clamping cylinder, and a piston rod 1 r of the mold clamping cylinder 1 is connected to a movable plate 12. Reference numerals 13 and 14 denote a pair of high-speed and low-pressure mold opening / closing cylinders arranged on both sides of the mold clamping cylinder 1, and the piston rods 13 r and 14 r of the mold opening / closing cylinders 13 and 14 are respectively coupled to the movable platen 12.

On the other hand, reference numeral 20 denotes a hydraulic circuit connected to the mold clamping cylinder 1. The hydraulic circuit 20 includes a pilot check valve 2, a directional control valve 21, an electromagnetic control valve 22, an oil tank 23, an accumulator (accumulator). ) 24, a check valve 25, and hydraulic pumps 26a and 26b. In this case, the rear oil chamber of the mold clamping cylinder 1 is connected to the direction switching valve 21 via the pilot check valve 2, and the direction switching valve 21 is connected to the hydraulic pump 26a and the oil tank 23. The front oil chamber of the mold clamping cylinder 1 is connected to an oil tank 23. On the other hand, the pilot port of the pilot check valve 2 is connected to the electromagnetic control valve 22, and the electromagnetic control valve 22 is connected to the control port of the direction switching valve 21. Furthermore, the hydraulic pump 2
6b is connected to an accumulator 24 via a check valve 25, and the accumulator 24 is connected to an electromagnetic control valve 22.
Connect to In addition, 27 is a pump motor, and 28 is an oil filter. Reference numeral 30 denotes a control unit, which has a function of giving the electromagnetic control valve 22 a switching command signal Dc including information on an opening / closing pattern Xa (Xb) described later.

Next, the operation of the mold clamping step including the method of depressing the mold clamping cylinder 1 according to the present embodiment will be described with reference to FIGS.

First, an opening / closing pattern X for controlling opening / closing of the pilot check valve 2 at the time of depressurization is previously stored in the control unit 30.
Set a. Thereby, the control unit 30 outputs the switching command signal Dc that matches the opening / closing pattern Xa at the time of depressurization.
That is, as shown in FIG. 1, the switching command signal Dc includes a valve opening signal for opening the pilot check valve 2 for the opening time ta, tc, te from the start of depressurization, and a pilot check valve for the closing time tb, td. The control unit 30 alternately sequentially outputs the valve open signal and the valve close signal. in this way,
The opening / closing pattern Xa is set by the opening time ta ..., the closing time tb ... and the number of times of opening / closing. FIG. 1 shows the open times ta, tc, t
e is 0.08 [second], 0.07 [second], 0.3
3 seconds, and the closing times tb and td are set to 0.0
An example is shown in which 1 [sec] and 0.01 [sec] are set.
In addition, such opening time ta ..., closing time tb ... and the number of times of opening / closing can be appropriately set according to molding conditions, the type of molded product, and the like. For example, in FIG. 2, the opening times ta, tc, and te are respectively set. 0.1 [sec], 0.07 [sec], 0.25 [sec]
And the closing times tb and td are each 0.05
Other opening / closing patterns X set to [sec] and 0.03 [sec]
b is exemplified.

On the other hand, at the time of mold clamping, the mold opening / closing cylinder 13,
By controlling the drive of the movable plate 14, the movable platen 12 is advanced to perform the mold closing process, and thereafter, the electromagnetic control valve 22 is switched to the right symbol. As a result, the direction switching valve 21 is switched to the right symbol, so that the pressure oil discharged from the hydraulic pump 26a is supplied to the rear oil chamber of the mold clamping cylinder 1 through the direction switching valve 21 and the pilot check valve 2, The mold 3 is clamped by a predetermined clamping pressure Pcm. In this case, even after the supply of the pressurized oil from the hydraulic pump 26a is stopped after the mold clamping pressure Pcm is applied, the hydraulic pressure of the mold clamping cylinder 1, that is, the mold clamping pressure Pcm remains unchanged by the pilot check valve 2. Is held at the size of Thereafter, a resin is injected and filled into the mold 3 by an injection device (not shown), and after a cooling time has elapsed, the process shifts to a depressurizing step.

Next, the depressurizing step (depressurizing method) will be described with reference to the flowchart shown in FIG.

First, a switching command signal Dc is supplied from the control unit 30 to the electromagnetic control valve 22. Since the switching command signal Dc matches the opening / closing pattern Xa, a valve opening signal is output first according to the opening / closing pattern Xa, and the opening control of the pilot check valve 2 is performed (step S1). That is, when the electromagnetic control valve 22 is switched to the left symbol, the hydraulic pressure of the accumulator 24 is applied to the pilot port of the pilot check valve 2, and the pilot check valve 2 is opened (step S2). When the opening time ta has elapsed, a valve closing signal is output according to the opening / closing pattern Xa, and the closing control of the pilot check valve 2 is performed (steps S3 and S3).
4). That is, the electromagnetic control valve 22 is switched to the intermediate symbol (neutral position), and the pilot check valve 2 is closed (step S5). In this case, since the opening time ta is as short as about 0.08 [sec] as described above, high-pressure and rapid discharge of pressure oil from the mold clamping cylinder 1 is prevented, and the return pipe of the hydraulic circuit 20 is The impact when flowing into the pilot check valve 2 or the like is reduced.

Next, when the closing time tb has elapsed, the opening control of the pilot check valve 2 is performed (step S).
6). Thereafter, similar processing is sequentially repeated according to the opening / closing pattern Xa. As a result, in the depressurization step, the pilot check valve 2 is depressurized while being intermittently opened from the start of depressurization. As described above, the pilot check valve 2 is connected to the return pipe of the hydraulic circuit 20, the pilot check valve 2, and the like. On the other hand, the impact of the high pressure oil suddenly flowing is reduced, and the generation of vibration and noise is eliminated. In particular, when the opening / closing is controlled by the opening / closing pattern Xa in FIG. 1, an improvement effect of reducing noise by about 3 to 6 [dB] is obtained. Pc in FIG. 1 is the hydraulic pressure of the mold clamping cylinder 1,
That is, it shows a state where the mold clamping pressure Pcm decreases. Further, since only one pilot check valve 2 is required, the number of components in the hydraulic circuit 20 can be reduced and the configuration can be simplified as compared with the conventional device, so that the size and cost of the entire device can be reduced.

On the other hand, when the opening / closing control of the pilot check valve 2 based on the opening / closing pattern Xa is completed, that is, when the depressurizing process is completed, the process proceeds to the mold opening process (step S7). In the mold opening process, the movable platen 12 is retracted by performing drive control of the mold opening / closing cylinders 13 and 14 to perform the mold opening process (step S8). In the mold opening process, the pilot check valve 2 is controlled to open. Note that Po in FIG.
3 and 14 show mold opening pressures.

The embodiment has been described in detail above.
The present invention is not limited to such an embodiment,
The detailed configuration, method, numerical values, and the like can be arbitrarily changed, added, or deleted without departing from the gist of the present invention.

[0020]

As described above, according to the method for depressurizing the mold clamping cylinder according to the present invention, the hydraulic pressure of the mold clamping cylinder is held by the pilot check valve to apply a predetermined mold clamping pressure to the mold, and then the pilot When the mold check cylinder is depressurized by opening the check valve, the pilot check valve is intermittently opened from the start of depressurization to depressurize, so that the following remarkable effects are obtained.

[0021] Since the impact when the pressure oil from the mold clamping cylinder flows into the return pipe or valve of the hydraulic circuit is reduced,
Generation of vibration and noise based on this can be eliminated.

At the same time, since only one pilot check valve is sufficient, it is possible to reduce the size and cost of the entire apparatus by reducing the number of components in the hydraulic circuit and simplifying the configuration.

[Brief description of the drawings]

FIG. 1 is a timing chart showing a relationship between an opening / closing pattern of a pilot check valve and a corresponding mold clamping pressure in a depressurizing method according to an embodiment of the present invention;

FIG. 2 is a timing chart showing another opening / closing pattern of the pilot check valve in the same pressure release method;

FIG. 3 is a flowchart for explaining the depressurizing method;

FIG. 4 is a hydraulic circuit diagram of a mold clamping device capable of performing the depressurizing method.

[Explanation of symbols]

 Reference Signs List 1 mold clamping cylinder 2 pilot check valve 3 mold Pcm mold clamping pressure Xa opening / closing pattern Xb opening / closing pattern ta ... opening time tb ... closing time

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B29C 45/64-45/84

Claims (3)

(57) [Claims] 1. A mold for holding a hydraulic pressure of a mold clamping cylinder by a pilot check valve and applying a predetermined mold clamping pressure to a mold, and then opening the pilot check valve to release the pressure of the mold clamping cylinder. A method for depressurizing a mold clamping cylinder, comprising depressurizing the pilot check valve by intermittently controlling the opening of the pilot check valve from the start of depressurization. 2. The method according to claim 1, wherein said pilot check valve is controlled to open and close based on a preset opening and closing pattern. 3. The method according to claim 2, wherein the opening / closing pattern is set based on an opening time, a closing time, and the number of times of opening / closing.