JP5040207B2 - Clamping device - Google Patents

Description

  The present invention relates to a mold clamping device such as a die casting machine or an injection molding machine.

Clamping devices used in die casting machines, injection molding machines, etc., open the mold by the pressure of the molding material in the mold from the start of injection filling of the molding material until the casting or molding is cooled and solidified. It is required to suppress it and tighten it with a force exceeding it. As the mold clamping device, there are structurally known a direct pressure type, a toggle type, a composite type and the like.
The direct pressure type mold clamping device is a device in which a movable plate is directly connected to a ram in a hydraulic cylinder and a mold is directly clamped by a fluid pressure, and is disclosed in Patent Document 1, for example.
In the case of the toggle type, a force generated by a power source such as a hydraulic cylinder is enlarged by a toggle mechanism to obtain a mold clamping force, which is disclosed in Patent Document 2, for example.
A composite type mold clamping device is disclosed in, for example, Patent Document 3 in which a tie bar is directly pulled by a hydraulic cylinder and a mold is clamped.

  Among the conventional mold clamping devices described above, the toggle type mold clamping device generates a clamping force by extending the tie bar, so that the pressure of the molding material injected and filled in the mold cavity exceeds the clamping force. If you try to open the mold, the tie bar stretches so much that the clamping force increases, which automatically acts to prevent burrs. However, if the mold clamping force increases due to thermal deformation accompanying the temperature rise of the mold or mold clamping device, or if the mold cannot be closed, the mold clamping force needs to be corrected, but it changes. There is a problem that it is difficult to immediately control and correct the mold clamping force. The increased mold clamping force described above tends to damage the mold and the mechanical parts of the mold clamping device.

In direct pressure type and compound type mold clamping devices, the mold clamping force is generated by adjusting the hydraulic pressure supplied to the mold clamping cylinder, which is accompanied by thermal deformation accompanying the temperature rise of the mold and mold clamping device. The mold clamping force does not change, and even after the mold is clamped, the mold clamping force can be changed by adjusting the hydraulic pressure within the range of the rated mold clamping force.
However, if the pressure of the molding material injected and filled in the mold cavity exceeds the mold clamping force, the working fluid in the mold clamping cylinder is compressed, so that the mold opens and burrs are generated. Have a problem.

  Therefore, a mold clamping device that solves the above-described conventional problems is disclosed in Patent Document 4. The mold clamping device disclosed in Patent Document 4 can suppress damage to the mold, can stably generate an accurate mold clamping force, and can open the mold even when an injection surge pressure occurs. It is stated that there is no. The mold clamping cylinders provided in the tie bar portion of the mold clamping device are configured so that the cross-sectional area and the supplied hydraulic pressure are the same so that the mold clamping force is uniformly generated. In addition, the mold clamping force of the conventional mold clamping device is generated at the center position of the mold clamping device, for example, in the case of a mold clamping device having four tie bars, at the intersection of the four tie bar center positions.

By the way, in a die casting machine or an injection molding machine, since a high-temperature molding material is injected and filled in a mold and cooled, the mold and the mold clamping device are thermally deformed under the influence of heat. This thermal deformation is due to the fact that the fixed plate for mounting the fixed mold is fixed to the machine base, and the movable plate for mounting the movable mold is also in sliding contact with the machine base. The board has an inverted square shape, that is, an uneven shape in which the upper side of the mold is opened more than the lower side.
For this reason, in the above-described conventional compound mold clamping apparatus in which a mold clamping force is generated at the center of the mold clamping apparatus, the mold mating surface can be completely closed even when the mold is clamped with the rated mold clamping force. However, there was a problem that the molding material entered the mating surface of the mold due to the injection surge pressure at the time of injection filling, and burrs were generated in the molded product. And in order to prevent the burr | flash of a molded product, the big mold clamping force was required, and there existed a problem that a metal mold | die was easy to be damaged by the big mold clamping force.
Japanese Utility Model Publication No. 6-57625 Japanese Patent Laid-Open No. 7-9518 Japanese Patent Laid-Open No. 10-52841 JP 2005-118793 A

  In view of the above-mentioned present situation, the present invention does not generate burrs in a cast product or a molded product even when a die or a mold clamping device is thermally deformed unevenly in molding of a die casting machine or an injection molding machine. It is an object of the present invention to provide a mold clamping device capable of suppressing damage to a mold and adjusting a mold clamping force instantaneously.

  As a result of intensive studies on means for solving the above problems, the present inventor has found that the mold clamping device has no idea that the clamping force is applied not to the center position of the mold clamping device but to a position corresponding to thermal deformation. The present inventors have found a means for easily and easily generating a clamping force that acts on balance.

The mold clamping device according to claim 1 of the present invention includes a plurality of molds that press a mold in cooperation with a tie bar after the movable mold attached to the movable platen and the fixed die attached to the fixed platen are closed. A hydraulic circuit having a plurality of pressure adjusting valves for supplying pressure oil to the clamping cylinder, adjusting pressure oil to a predetermined pressure, and controlling the hydraulic circuit to inject the injection device; A mold clamping device including a control device configured to have a predetermined mold clamping force in accordance with an injection process in which the plunger moves forward, and position information of an injection plan plunger position sensor provided in the injection apparatus in the injection process. Based on the above, the pressure oil adjusted to at least two different pressures is selectively supplied to each pair of the mold clamping cylinders which are opposed to each other in the upper and lower sides or the left and right sides, and the predetermined surfaces are unbalanced on the mating surfaces of the molds. The mold clamping force of It is characterized in.

The mold clamping apparatus according to claim 2 of the present invention is the invention according to claim 1, wherein the mold clamping force is controlled in three stages of the first step, the second step, and the third step in the injection process . It is characterized by that.
A mold clamping device according to a third aspect of the present invention is characterized in that, in the invention according to the first or second aspect, the hydraulic circuit supplies oil of an accumulator to the mold clamping cylinder.

As described above, according to the mold clamping device of the present invention, at least two different pressures are selectively supplied to the plurality of mold clamping cylinders depending on the mold and the mold clamping device that deform unevenly. Further, the occurrence of a gap between the mold mating surfaces is prevented by the action of the unbalanced mold clamping force, and no burrs are generated in the cast product. And since the minimum mold clamping force can be made to act as needed, damage to a metal mold | die can be suppressed.
In addition, the mold clamping force is changed instantly and in multiple stages according to the injection process, and further, the accumulator oil is supplied, so energy saving and mold clamping force control with a quick response speed can be achieved. Can be realized.

  Below, the die-clamping apparatus of the die-casting machine of the Example of this invention is demonstrated in detail with reference to FIGS. FIG. 1 is an explanatory view showing an embodiment of a mold clamping device of the present invention, and FIG. 2 is an explanatory view showing a section taken along the line AA in FIG. 1 and a hydraulic circuit. FIG. 3 is a graph showing a case where the mold clamping force is controlled to be constant in the injection process, and FIG. 4 is a graph showing a case where the mold clamping force is set in three stages according to the process in the injection process.

  As shown in FIG. 1, a stationary platen 2 that supports a fixed die 3 is fixed to an end of the machine base 1, and a movable platen 4 that supports a movable die 5 is mounted on the machine base 1. It is arranged so as to be able to advance and retract with respect to the stationary platen 2 via the support member 6a. A mold opening / closing device 24 that opens and closes the mold by moving the movable board 4 forward and backward with respect to the fixed board 2 on the movable board support member 6a is attached to the lower end of the movable board 4. FIG. 1 shows the mold clamping apparatus with the mold opened.

Tie bar insertion holes 7 and 8 are formed at the four corners of the fixed platen 2 and the movable platen 4, and the tie bars 10 are inserted through the insertion holes 7 and 8. A tie bar cover 10 a is attached to the tie bar insertion holes 7, 8 of the movable platen 4, and a support 10 b for supporting the tie bar 10 is disposed behind the lower tie bar insertion hole 8.
The upper tie bar 10 engages with the split nut of the split nut device 22 connected to the end of the movable platen side, and the lower tie bar 10 is connected to the intermediate portion of the tie bar insertion holes 7 and 8. Engaging portions 10x and 10y are respectively formed.
The fixed platen side end portion of the tie bar 10 includes an engaging portion 10z in which a spiral groove that engages with the nut of the fixed nut device 23 is formed.

A tie bar insertion hole 7 of the fixed platen 2 has a piston 27 built therein, a mold clamping cylinder 25 (pressing means) having oil chambers 28 and 29 is disposed, and a fixing nut device 23 is attached to the end of the piston 27. It becomes the composition. Further, the mold clamping cylinder 25 is provided with a port 25 a for supplying and discharging pressure oil into the oil chamber 28.
After the mold opening / closing device is driven and the mold is closed, the hydraulic unit 35 is operated to supply the pressure oil to the oil chamber 28, the pressure oil is discharged from the oil chamber 29, and the piston 27 is driven. The fixed nut device 23 that is tightly connected to the end portion of the piston 27 and engaged with the engaging portion 10z of the tie bar 10 by the driving of the piston 27 is the anti-mold mounting surface side ( Since the driving force is received in the direction (right direction in FIG. 1), the movable platen 4 after the mold closing is further pressed by the fixed platen 4, and the mold clamping operation is performed following the mold closing operation.

  As described above, in the embodiment shown in FIG. 1, the mold clamping cylinder 25 is disposed in the tie bar insertion holes 7 and 8 of the fixed platen 2 and the tie bar 10 is driven in the mold clamping direction to clamp the mold. For example, the tie bar insertion holes 7 and 8 part of the fixed platen 2 are fixed to the side opposite to the die mounting surface, and the tie bar insertion holes 7 and 8 part of the movable platen 4 are antimetallized. A mold clamping cylinder 25 may be disposed between the mold mounting surface side and the split nut device 22 to drive the tie bar 10 in the mold opening direction and apply a mold clamping force.

  Reference numeral 30 denotes an injection apparatus that injects and fills molten metal, which is a molding material, into the mold while the mold is clamped. The injection plunger 31 is driven by an injection cylinder together with a plunger tip (not shown) attached to the tip of the plunger 31 to advance and inject molten metal into the mold. The injection plunger position sensor 32 detects the position of the injection plunger 31 that moves forward.

As shown in FIG. 2, the die clamping machine of the die casting machine has a hydraulic circuit 40 and a control device 50. And the hydraulic circuit 40 and the control apparatus 50 which are shown in FIG. 2 are one Embodiment of this invention.
Hydraulic circuit diagram 40 for generating mold clamping force includes a hydraulic pressure source 41, an accumulator 42, direction switching valves 43a and 43b, proportional electromagnetic pressure reducing valves 44a and 44b, proportional electromagnetic relief valves 45a and 45b, a check valve 46, and And pressure detectors 47a and 47b.
The hydraulic circuit 40 supplies pressure oil from the hydraulic source 41 or the accumulator 42 to the oil chambers 28 and 29 of the mold clamping cylinder 25 and discharges the pressure oil from the oil chambers 28 and 29 of the mold clamping cylinder 25.

The proportional electromagnetic pressure reducing valves 44a and 44b receive a control signal from the control unit 52 based on the set value of the mold clamping force setting unit 51 of the control device 50 and the position information of the injection plunger position sensor 32, etc. The pressure oil supplied from the accumulator 42 is reduced and adjusted, and supplied to the direction switching valves 43a and 43b.
The A port of the direction switching valve 43a is connected to the oil chamber 28 of the clamping cylinder 25 above the mold and the port 25a, and the B port of the direction switching valve 43a is the oil chamber of the clamping cylinder 25 above the mold. 29 and a port (not shown), respectively. The A port of the direction switching valve 43b is connected to the oil chamber 28 of the clamping cylinder 25 below the mold and the port 25a, and the B port of the direction switching valve 43a is the oil chamber of the clamping cylinder 25 below the mold. 29 and a port (not shown), respectively. When the sol-a of each of the direction switching valves 43a and 43b is excited in response to a command from the control unit 52 of the control device 50, the pressure oil adjusted by the proportional electromagnetic pressure reducing valves 44a and 44b is transferred from the P port. The oil is supplied to the oil chamber 28 of the clamping cylinder 25 through the A port.

  On the other hand, the pressure oil in the oil chamber 29 of the mold clamping cylinder 25 is returned to the tank by connecting the B ports of the direction switching valves 43a and 43b to the T port. In this way, the mold clamping force is generated by supplying the pressure oil adjusted to the pressure by the two proportional electromagnetic pressure reducing valves 44a and 44b to the oil chamber 28 of the mold clamping cylinder 25.

  When the sol-b of the direction switching valves 43a and 43b is excited, the oil chamber 28 of the mold clamping cylinder 25 is returned to the T port via the A port. The proportional electromagnetic relief valves 45a and 45b are used for pressure control when the pressure oil in the oil chamber 28 of the mold clamping cylinder 25 is lowered from high pressure to low pressure. For example, when the pressure is released at the end of mold clamping, Controlled based on The pressure detectors 47a and 47b detect the pressure in the oil chamber 28 of the mold clamping cylinder 25, convert the detected signal, and display it as a mold clamping force. The check valve 46 is intended to prevent the pressure oil in the accumulator 42 and the oil chamber 28 of the mold clamping cylinder 25 from flowing back toward the hydraulic power source 41.

  As shown in FIG. 2, in this embodiment, different pressures are obtained by using a pair of clamping cylinders provided on two tie bars above the mold (top side) and two below the mold (ground side). The circuit configuration is adjustable. The configuration for generating the clamping force by selectively supplying pressure oil adjusted to at least two different pressures to the clamping cylinder according to the present invention is not limited to the present embodiment, and the upper right and lower sides shown in FIG. The circuit configuration includes a pair of clamping cylinders provided on each of the two tie bars and the left tie bar, and the circuit configuration includes a pair of clamping cylinders provided on the upper right and lower left and upper left and lower right tie bars.

  Further, a circuit configuration in which a pressure adjusting valve is provided for each of the four mold clamping cylinders to supply and discharge the pressure oil to the mold clamping cylinders may be employed. As described above, selectively supplying the pressure oil of the present invention to the mold clamping cylinder indicates selection of a combination of a plurality of mold clamping cylinders and a plurality of pressure regulating valves, and is a port of an electromagnetic switching valve. It is not intended to be a choice.

3 and 4 are graphs showing an example of the relationship between the injection process and the mold clamping force. The injection process includes injection low speed, injection high speed, pressure increase and cooling processes.
In the injection process, first, the injection plunger 31 moves forward at an injection low speed, and the injection plunger position sensor 32 detects a predetermined position S1 set in advance and is switched to an injection high speed. Next, the molten metal, which is a molding material, moves forward at an injection speed and is filled in the mold cavity, and is switched to a pressure increasing process at a predetermined timing S2 to press the molten metal. In the injection process, the maximum mold clamping force is required at the timing of switching from the injection high speed at which the molten metal is fully filled into the mold cavity to the pressure increasing process.
The cooling is a process in which the cast product is cooled and solidified, and is switched in response to the pressure increase completion signal P1, and after the cast product is cooled, the mold is opened and the cast product is taken out from the mold.

FIG. 3 is a graph showing an example of controlling the mold clamping force to be set constant in the injection process. The vertical axis represents the magnitude of the mold clamping force, and the horizontal axis represents the process time.
In FIG. 3, the lower part of the graph shows the set value of the clamping force generated by the lower pair of clamping cylinders, and the upper part of the graph shows the setting value of the clamping force generated by the upper pair of clamping cylinders. The lower pair of mold clamping cylinders is set to 4508 KN and the upper pair of mold clamping cylinders are set to different values of 6762 KN, and the entire mold clamping apparatus shows a setting state in which 11270 KN acts on the mold in an unbalanced manner.
As shown in FIG. 3, the mold clamping force is a constant mold clamping force from the completion of the mold clamping until the cooling process of the injection process is completed.

FIG. 4 is a graph showing an example of controlling the mold clamping force in multiple stages according to each process of the injection process, where the vertical axis represents the magnitude of the mold clamping force and the horizontal axis represents the process time. .
In FIG. 4, the lower part of the graph shows the set value of the clamping force generated by the lower pair of clamping cylinders, and the upper part of the graph shows the setting value of the clamping force generated by the upper pair of clamping cylinders. Yes. The mold clamping force is set and controlled in three stages of a first step and a second step in the injection process and a third step in the cooling process. The first step is from the completion of mold clamping to the predetermined switching position S0 set ahead of the switching position S1 to the high injection speed, and the second step is that the timer t1 keeps a predetermined time after the pressure increasing completion P1 from the switching position S0. The third step is from the start of the timer t1 to the completion of the cooling process until the timer t1 completes.

As shown in FIG. 4, the lower pair of mold clamping cylinders are set to different values of 5635 KN for the first step, 5145 KN for the second step, and 2940 KN for the third step. The upper pair of mold clamping cylinders are set to different values of 5635KN for the first step, 6125KN for the second step, and 2940KN for the third step. In the entire mold clamping apparatus, 11270 KN is applied to the mold in the first and second steps, and 5880 KN is applied to the mold in an unbalanced manner in the third step.

3 and 4 described above are not limited to the present invention, and needless to say, are numerical values for explaining the gist of the invention. It is of course possible to set the values to be the same.
In FIG. 4, the transition to the second step at the S0 position ahead of the injection high-speed switching position S1 prevents the control response delay because the maximum mold clamping force is required in the injection high-speed process and the pressure increasing process. The purpose is that.

  If the present invention is applied, even when the mold clamping device or the mold is deformed unevenly due to the influence of heat or the like and the parallelism is distorted, the mold clamping force of the entire mold clamping device is not increased. The parallelism can be corrected by pressing partially and imbalanced. In addition, the center position of the projected area of the mold or molded product does not match the center position of the mold clamping force, and an unbalanced load is generated in the mold clamping device after mold clamping and at the time of injection filling with molten metal. Even when casting burrs are ejected from the mating surfaces, the casting burrs can be prevented from being ejected by partial pressing without increasing the clamping force of the entire clamping device.

In the mold clamping apparatus according to the present invention, the mold clamping force is generated by providing a hydraulic circuit that selectively supplies at least two different pressures to the plurality of mold clamping cylinders. Even if heat is uniformly deformed, burrs are not generated in the cast product or the molded product, and damage to the mold can be suppressed and the mold clamping force can be adjusted instantaneously.

It is explanatory drawing which shows one Embodiment of the mold clamping apparatus of this invention. It is explanatory drawing which shows the cross section and the hydraulic circuit of the AA arrow in FIG. It is a graph which shows the case where the mold clamping force is controlled uniformly in the injection process. It is a graph which shows the case where the mold clamping force is set in three steps according to a process in an injection process.

Explanation of symbols

2 fixed plate 3 fixed die 4 movable plate 5 movable die 10 tie bar 25 clamping cylinder 30 injection device 40 hydraulic circuit 42 accumulator 44a, 44b pressure regulating valve 50 control device S0 switching position S2 to second step S1 injection high-speed start position S2 Pressure increase start position P1 Pressure increase completion signal t1 Timer

Claims (3)

A plurality of clamping cylinders that press the mold in cooperation with the tie bar after the movable mold attached to the movable plate and the fixed die attached to the fixed plate are closed;
A hydraulic circuit having a plurality of pressure adjusting valves for supplying pressure oil to the mold clamping cylinder and adjusting the pressure oil to a predetermined pressure;
A mold clamping device comprising: a control device that controls the hydraulic circuit so as to obtain a predetermined mold clamping force in accordance with an injection process in which an injection plunger of the injection device moves forward;
In the injection step, based on position information of an injection plan plunger position sensor provided in the injection device, pressure oil adjusted to at least two different pressures is provided for each pair of the mold clamping cylinders facing each other vertically or horizontally. A mold clamping apparatus, wherein the mold clamping device is selectively supplied to cause the predetermined mold clamping force to act unbalanced on the mating surfaces of the molds .   The mold clamping device according to claim 1, wherein the mold clamping force is controlled in three stages of a first step, a second step, and a third step in the injection process.   3. The mold clamping apparatus according to claim 1, wherein the hydraulic circuit supplies accumulator oil to the mold clamping cylinder.

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