KR100517334B1 - Mold Opening/Closing Speed Brake Device using Electro-Rheological Fluid and Control method of the same - Google Patents

Abstract

The present invention relates to a mold opening and closing speed limiting device and a control method capable of precisely controlling the opening and closing position of the mold without the risk of damaging the mold even when the moving die and the mold are opened and closed at a high speed in the molding apparatus of the injection molding machine. The stationary template 18 to which the second mold half 21 is attached, and the first mold half 22 to which the first mold half 22 is attached, move along a plurality of tie bars 20 or other guide devices connected to the stationary template. A moving template 16, a high speed moving cylinder connected to the moving template to move the moving template between an open position and a closed position of the mold, a mold ram 14 and a mold cylinder 12 for boosting the pressure during resin injection; In the injection molding machine, a mold opening and closing speed limiting device (2) using an electrofluidic fluid (4) is provided between the movable die and the tie bar or the mold ram and the mold cylinder, and the limiting device is moved. A housing 3 mounted to the template or mold cylinder 12; An electric rheological fluid (4) filled in a housing and filled with a predetermined width around a predetermined section of the plurality of tie bars or shaped rams (14); An electrode plate installed in the housing and controlling an electric field to an area of the electrofluidic fluid according to a voltage difference; It characterized in that it comprises a controller for limiting the speed of the mold by controlling the magnitude of the voltage difference according to the position of the mold, and controls the position.

Description

Mold Opening / Closing Speed Brake Device using Electro-Rheological Fluid and Control method of the same}

The present invention relates to a mold clamping apparatus of the injection molding machine and a control method thereof, and in particular, even if the moving mold and the mold are opened and closed at high speed, there is no risk of damaging the mold, and the mold opening and closing speed limiting device can accurately control the mold opening and closing position. And a control method thereof.

Injection molding machine can be largely divided into injection device and clamping device. The clamping device fixes and moves the mold, and pushes the mold in the opposite direction to the resin injection direction to prevent the mold sliding during resin injection. Refers to a device that The clamping device can be divided into direct pressure and toggle type.

Conventional direct pressure clamping device generates a clamping force by using the clamping cylinder 12, as shown in Figure 1 and transfer the clamping force directly to the mold 22 through the clamping ram 14, etc. Although this is not necessary, the following problem exists in the above-mentioned switching method from the high speed to the low speed during the mold opening and closing using the booster cylinder 43 or other high speed moving cylinder.

First, since the switching position from the high speed to the low speed during the mold opening and closing is fixed against the change of the speed setting value, when the speed difference between the high speed and the low speed changes, the mold ram 14, the moving template 16 and The inertial force due to the mass of the movable metal including the mold 22 is changed to change the position where the moving template is positioned at a low speed.

For this reason, for example, when the high speed speed setting value is changed to a higher speed, the low speed speed distance becomes shorter, and half of the die 22 of the movable die 16 is fixed to half of the die 21 of the stationary die 18. This can cause a problem of crashing the mold.

On the other hand, when the switching position is set so as to lengthen the low speed speed distance in order to avoid the above problem, it takes a lot of low speed moving time and excessively lengthens the molding cycle, which hinders productivity. In addition, the mold half of the moving die also causes a pause phenomenon in which the movement is temporarily stopped at the position where the flow movement by the inertial force is completed.

In the mold closing stop position, when the moving mold 16 side half mold 22 is in contact with the stationary mold 18 side mold 21 half, if it is not set at a low speed sufficiently, a shock sound is generated and a shock sound is not generated. If the low speed is set so as not to make the operation unstable due to the frictional force between the mold cylinder 12 and the mold ram 14 or the moving plate 16 and the tie bar 20, the operation time is too long and the productivity is impaired. .

On the other hand, in the mold release stop position, when the low speed setting is high, the flow movement amount due to the influence of the inertia force changes from cycle stop position to cycle, and the position where the mold release stop is actually shifted by several mm. Such a phenomenon may cause a grip miss when the molded product is taken out of the mold by an automatic ejector.

On the other hand, if you want to control the speed and position of the mold accurately and quickly without fixing the switching position from the high speed to the low speed, the configuration of the hydraulic circuit requires a high cost, and the maintenance cost of the valve or oil is high. There is this.

2a and 2b schematically show the movement of the toggle type clamping device. Toggle links are indicated by three thick lines: L ₁ , L ₂ , and L ₃ . The tip of L ₁ is connected to an unillustrated hydraulic cylinder. First, in the mold closing stroke, as shown in FIG. 2A, the link L1 is raised by the hydraulic cylinder, so that the links L ₂ and L ₃ are in a straight line, and the mold 22 is advanced. After mold closing, when the clamping force is generated, the joint points a, c, and b of the links L ₁ , L ₂ , and L ₃ are in a straight line. The elastic restoring force is generated while being stretched to close the molds 21 and 22 firmly. Such a toggle type clamping device naturally has a speed characteristic in which the moving template has a slow speed at the mold closing position and a high speed at the transfer position due to the characteristics of the link mechanism.

However, when the mold is closed due to the mechanical control structure of the link structure, it is difficult to precisely control the fast process such as stopping the mold in order to protect the mold when a molded product or a runner is stuck in the mold or caught in a drop. .

The present invention is to solve the problems of the prior art as described above, high speed during opening and closing of the mold even if a high-cost hydraulic circuit using an electro-fluidic fluid having a quick response in place of conventional hydraulic control or mechanical control The purpose is to limit the speed within a short time at low speed, to protect the mold while reducing the cycle time with accurate and reproducible mold position control, and at the same time to obtain a high quality molded article.

In order to achieve the above object, the present invention provides a fixed template with a second mold half attached, a movable template attached with a first mold half attached and moving along a plurality of tie bars or other guide devices connected to the fixed template. In the injection molding machine including a high speed moving cylinder connected to the moving template to move the moving template between the open position and the closed position of the mold, a mold ram and a mold cylinder for boosting the resin injection,

Between the movable template and the tie bar or the mold ram and the mold cylinder, a mold opening / closing speed limiting device using an electro-fluidic fluid is installed, and the limiting device is filled in a housing mounted on the movable template or the mold cylinder and inside the housing. The magnitude of the voltage difference according to the position of the electro-fluid fluid filled in a predetermined width around the section of the tie bar or the shaped ram and the electrode plate and the mold installed in the housing to control the electric field to the area of the oil-fluid fluid according to the voltage difference. It provides a mold opening and closing speed limiting device using an electro-fluidic fluid, characterized in that it comprises a controller for limiting the speed of the mold by controlling the, and controls the position.

In addition, the present invention comprises the steps of moving the moving template in a state of applying a high pressure to the high speed in the booster cylinder in the high speed moving cylinder or the mold ram and without applying a voltage difference to the electrode plate; When reaching the position where the clamping speed is to be reduced from the high speed to the low speed, the hydraulic pressure is lowered to low pressure, the controller of the speed limiter is turned on and the voltage difference is controlled to lower the speed of the moving template; Advancing the moving template at low pressure while maintaining a constant voltage difference such that the low pressure clamp force is only a small amount greater than the binding force of the polar particles; When the moving template is in the mold closing position, it is achieved by the speed limit and position control method of the mold opening / closing speed limiting device, which comprises turning off the controller and supplying the high pressure oil to the mold cylinder.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Figure 3 is a schematic diagram of a mold clamping apparatus having a mold opening and closing speed limiting device 2 using an electric rheological fluid according to an embodiment of the present invention. Figure 4 is a detailed view of the mold opening and closing speed limiter using the electro-fluidic fluid.

As shown, the clamping device includes a stationary template 18, a moving template 16, a mold cylinder 12, a mold ram 14, a booster cylinder 13 as a high speed moving cylinder, a tie bar 20 and a mold. Opening and closing speed limiter (2).

The mold opening / closing speed limiter 2 includes an electric rheological fluid filled in a space formed between the housing 3 mounted on the movable die 16 and the tie bar 20 and the housing 3, as shown in FIG. 4. (4), an electrode plate 5 in the housing 3 to form an electric field with the electro-fluidic fluid, and an electrode to control the speed and position of the mold by controlling a voltage flowing through the electrode plate 5. It consists of a controller (not shown) electrically connected to the plate 5.

Here, the electrorheological fluid 4 has an isotropic physical phenomenon in which the electrically conductive particles are dispersed and the particles are irregularly dispersed when the electric field does not work. The flow properties change while having a structure of, and have a large yield stress. That is, the yield stress is changed by the chain formation of the electrically conductive particles formed in the fluid, and the strength of the formed chain varies depending on the strength of the electric field, so the yield stress can be easily adjusted by changing the applied electric field.

FIG. 5A shows an arrangement of particles of an electrorheological fluid when an electric field is not applied, and FIG. 5B shows an arrangement of particles of an electrorheological fluid by forming a chain when an electric field is applied.

In the mold opening / closing speed limiter using the electrofluidic fluid, polar particles are aligned between the tie bar 20 and the speed limiter 2 according to the presence or absence of an electric field existing between the electrode plates 5.

In order for the moving template 16 to move, the binding force of the aligned polar particles must be broken and moved. Therefore, the speed of the moving template 16 can be easily restricted by controlling the magnitude of the voltage difference input to the electrode plate 5. . In addition, after being controlled below a certain level, the speed of the mold 22 is applied by applying a voltage to the electrode plate 5 so that the binding force of the polar particles is greater than the hydraulic force of the booster cylinder 13 which moves the mold including the inertia force. By setting 0 to 0, the position can be controlled so that the mold stops at a constant position.

Fig. 6 is a flow chart illustrating a mold opening and closing speed limit according to the position at the time of mold closing, and Fig. 7 shows the magnitude of the hydraulic pressure applied to the mold ram at that time, the control voltage difference applied to the electrode plate 5, and the mold 22 to be controlled. ) Shows the speed according to the position.

Also, in the graphs of FIGS. 7A, 7B, and 7C, x ₁ , x ₂ , and x ₃ are positions at which the speed of the mold starts to decrease from high speed to low speed, positions at which the speed is reduced to low speed, and low pressure dies are started. Represents a closed position, respectively.

The opening and closing speed limiting method of the mold and the position control method will be described according to the control flowchart.

First, when the mold 22 is being transferred for mold opening and closing, high pressure is applied to the booster cylinder 13 in the high speed moving cylinder or the mold ram to increase the speed, and no voltage difference is applied to the electrode plate 5.

When the moving template 16 reaches the position where the clamping speed is to be reduced from high speed to low speed, that is, at the x1 position, the hydraulic pressure drops to low pressure because there is no need to move the mold anymore, the controller of the speed limiter is turned on and the voltage difference Control the speed down the template. The voltage difference may be set as follows as an example.

Here, x ₁ , x ₂ is set by the user through a controller, it can be easily measured using a position sensor (not shown) that can sense the position of the movable plate 16 can be used for voltage difference control.

m is the mass of the molds 21 and 22 to be changed for each molded article, and the last term P ₂ m of the voltage difference changes the voltage difference applied to the electrode plate 5 according to the mold mass, that is, compensates the inertial force of the mold This solves the above problem that the flow rate of the mold changes according to the amount of change of inertia according to its mass.

When the mold is P _1, P ₂ are each controlled constant value came to x ₂ position (When they come to a low-pressure mold clamping position) so that there is no risk of mold damage, and the value to be set by the user to give by limiting low the velocity, v ₀ Is a reference value of the speed for controlling so that breakage does not occur. P ₁ and P ₂ are set according to the values of x ₁ and x ₂ .

In FIG. 7, the speed of the mold can be controlled from high speed to low speed in a short time according to the control of the voltage difference, and the template starts to slow down from high speed to low speed. Since the low pressure is continuously applied from the position of x ₁ to the mold closing position (x ₃ ), there is no pause of the mold. When the moving template 16 and the mold 22 come to the x ₂ position according to the setting of the P ₁ and P ₂ values, the user may obtain a desired low speed v ₀ .

Now when the mold 22 is at the x ₂ position to make the low pressure mold, the hydraulic pressure pushes the mold ram 14 to a low pressure state. At this time, if the voltage difference is kept constant at P ₃ so that the low-pressure clamping force is only a little larger than the binding force of the polar particles, between the clamping cylinder 12 and the clamping ram 14 at the low speed state described above, or the moving template 16 and It is possible to advance low pressure to a position of x ₃ at a stable low speed without the problem of unstable operation caused by the friction force between the tie bars 20. You can easily control the forward speed by adjusting the P ₃ value.

When the template is in the x ₃ position, the controller is turned off as shown in FIG. 7, and the high pressure oil is supplied to the mold cylinder 12 to increase the pressure.

After the resin injection and cooling is completed, the mold opening process of opening the mold and retracting the moving template 16 at high speed for taking out the product takes the steps opposite to the advance mold closing process described above.

As described above, since the mold opening and closing speed limiting device directly brakes the moving mold 16 or the mold ram 14, the hydraulic control for controlling the mold or the mold ram by controlling the flow rate that is input / discharged in the existing direct pressure mold apparatus. It is possible to reduce the influence of the inertia force than the method, and to limit the speed and position of the mold in a more accurate and faster time due to the control characteristics of the electro-fluidic fluid.

In addition, in the case of the hydraulic control method, an expensive hydraulic circuit configuration is required in order to accurately and precisely control the speed and position of the mold, and a maintenance cost of the valve or oil is required more than that of a general hydraulic circuit. Economical as it replaces precision hydraulic circuits for speed limiting and position control

As described above, according to the present invention, the electrically conductive particles of the electrofluidic fluid may be aligned or unaligned within a short time depending on the presence or absence of an electric field, and the binding force between particles is proportional to the size of the electric field. It is possible to limit the speed within a short time from high speed to low speed during opening and closing. By using this, accurate and reproducible position control can shorten the cycle time and protect the mold, and at the same time obtain a good molded part. In addition, there is no need for costly precision hydraulic circuits, which results in an inexpensive maintenance cost of the valve or oil.

1 is an exemplary view showing a conventional direct pressure mold clamping device.

Figure 2a, 2b is an exemplary view showing a model of the movement of the conventional toggle type clamping device.

3 is a block diagram of a mold clamping device according to the present invention;

Figure 4 is a detailed view of the mold opening and closing speed limiter according to the present invention

Figure 5a, 5b is a particle arrangement according to whether the electric field of the electro-fluidic fluid applied.

6 is a flow chart of the mold opening and closing speed limit according to an embodiment of the present invention.

7A to 7C are graphs of hydraulic pressure, voltage difference, and speed according to positions at the time of mold opening and closing speed limitation.

<Explanation of symbols for the main parts of the drawings>

2: mold opening and closing speed limiting device

3: housing

4: Rheological fluid

5: electrode plate

14: shape ram

16: moving template

20: tie bar

Claims (3)

A stationary template 18 to which the second mold half 21 is attached, a movable template 16 to which the first mold half 22 is attached and moving along the tie bar 20, and an open position of the mold; A high speed moving cylinder 13 for operating the movable die 16 between the closed positions, a clamping cylinder 12 as a boosting device for closing the mold to withstand the injection pressure during injection in the closed position of the mold, and a mold ram ( In the injection molding machine including 14), Between the moving template 16 and the tie bar 20 is installed a mold opening and closing speed limiting device 2 for limiting the opening and closing speed of the mold by using an electric magnetic field, The mold opening and closing speed limiting device (2) A housing (3) mounted to the movable template (16); An electric rheological fluid (4) filled in a space formed between the tie bar (20) and the housing (3); An electrode plate (5) embedded in the housing (3) for controlling the electric field in the region of the electrofluidic fluid (4) according to the voltage difference; Mold opening and closing speed limiting device using an electric rheological fluid, characterized in that it comprises a controller for controlling the position of the mold 22 by controlling the magnitude of the voltage difference according to the position of the mold (22), and controls the position. In the speed limit and position control method of the mold opening and closing speed limiter of claim 1, Applying a high pressure to a high speed moving cylinder or a booster cylinder in the mold ram to increase the speed and moving the moving template without applying a voltage difference to the electrode plate (S10); When reaching the position where the clamping speed is to be reduced from the high speed to the low speed, dropping the hydraulic pressure to low pressure, turning on the controller of the speed limiter and controlling the voltage difference to lower the speed of the moving template (S20); Advancing the moving template at low pressure while maintaining a constant voltage difference such that the low pressure clamp force is only a small amount greater than the binding force of the polar particles (S30); Speed limit and position control method of the mold opening and closing speed limiting device comprising the step (S40) of turning off the controller and supplying the high pressure oil to the mold cylinder when the moving die is in the mold closing position. 3. The method of controlling speed and position of a mold opening and closing speed limiting device according to claim 2, wherein the method for controlling the voltage difference uses a voltage difference ΔV obtained by the following equation. (Where x ₁ and x ₂ represent positions at which the speed of the mold starts to decrease from high speed to low speed, positions at which the speed is reduced to low speed and start low pressure mold, respectively, m denotes the mass of the mold to be changed for each molded part, P ₂ is a value so that there is no risk of mold damage (when they come to a low-pressure mold clamping position) when the mold is came to x ₂ where the control constant value the user sets to give, limit lower the speed, P ₂ x _1, x ₂ is set according to the value.)