JP6909701B2 - Die casting machine and its control method - Google Patents

Description

The present invention relates to a die casting machine having a hydraulic injection mechanism and a method for controlling the die casting machine.

Patent Document 1 discloses a conventional hydraulic injection molding machine. This molding machine supplies hydraulic oil from a hydraulic drive source to the rear oil chamber of the hydraulic cylinder via a servo valve, and moves a movable body coupled to a piston built in the hydraulic cylinder by speed control. In this molding machine, hydraulic oil is supplied to the front oil chamber of the hydraulic cylinder before the speed control is started, and a reverse preload is applied in the direction opposite to the moving direction of the movable body. As a result, when the flood control is applied to the rear oil chamber from the hydraulic drive source, the piston (movable body) is prevented from suddenly popping out forward.

JP-A-2010-208124

When the piston suddenly pops out, for example, when the molding machine is stopped or the operation mode is switched, the oil pressure in the front oil chamber is changed to the oil pressure in the rear oil chamber due to leakage of hydraulic oil when the time elapses in the stopped state. It may occur when it decreases significantly. On the other hand, when the product molding operation is continuously executed, the frequency of occurrence is relatively low. However, since the molding machine executes the operation of applying the reverse pressurization every time in the product molding operation, it may be executed even when the operation is unnecessary. Therefore, there is a problem that the production efficiency of the product is low.

Therefore, an object of the present invention is to provide a die casting machine and a method for controlling the die casting machine, which can suppress a sudden pop-out of an injection piston and effectively improve production efficiency.

In order to achieve the above object, the die casting machine according to one aspect of the present invention supplies the flood control to the injection piston, the injection cylinder that holds the injection piston so as to be movable back and forth, and the rear oil chamber of the injection cylinder. It has a hydraulic supply unit and a servo valve that adjusts the outflow amount of hydraulic oil from the front oil chamber of the injection cylinder. The hydraulic supply unit supplies hydraulic oil to the rear oil chamber, and the servo valve supplies hydraulic oil. A die casting machine for advancing the injection piston by flowing out hydraulic oil from the front oil chamber, the oil pressure detecting unit for detecting the oil pressure in the front oil chamber, and the hydraulic oil supply unit before supplying the hydraulic oil. It is characterized by having an auxiliary oil pressure supply unit that raises the oil pressure of the front oil chamber so that the oil pressure detected by the oil pressure detection unit is lower than the reference value only when the oil pressure is lower than the reference value.

In the present invention, it is preferable that the auxiliary oil supply unit raises the oil pressure in the front oil chamber by supplying hydraulic oil to the front oil chamber.

In the present invention, the auxiliary hydraulic pressure supply unit, Ru increases the hydraulic pressure of the front oil chamber by pressing the injection piston by supplying hydraulic oil to the rear oil chamber forward.

In the present invention, the reference value is preferably 30% to 120% of the oil pressure of the hydraulic oil supplied from the oil pressure supply unit.

In order to achieve the above object, the control method of the die casting machine according to another aspect of the present invention includes an injection piston, an injection cylinder that holds the injection piston so as to be movable back and forth, and an oil chamber behind the injection cylinder. It has a hydraulic supply unit that supplies hydraulic oil and a servo valve that adjusts the outflow amount of hydraulic oil from the front oil chamber of the injection cylinder, and the hydraulic supply unit supplies hydraulic oil to the rear oil chamber. , A method of controlling a die casting machine in which the hydraulic oil is discharged from the front oil chamber by the servo valve to advance the injection piston, and the oil pressure in the front oil chamber is released before the hydraulic oil is supplied by the hydraulic supply unit. Only when it is lower than the reference value , the hydraulic oil is supplied to the rear oil chamber and the injection piston is pressed forward to raise the oil pressure in the front oil chamber so as to be equal to or higher than the reference value. ..

According to the present invention, the front oil chamber is set to be equal to or higher than the reference value only when the oil pressure in the front oil chamber of the injection cylinder is lower than the reference value before the hydraulic oil is supplied to the rear oil chamber of the injection cylinder by the oil supply unit. Increase the oil pressure of. When the oil pressure in the front oil chamber is above the reference value, the oil pressure in the front oil chamber is appropriate, while when it is lower than the reference value, the oil pressure in the front oil chamber is inappropriate and the injection piston suddenly pops out. There is a risk. Further, in the present invention, since the oil pressure is increased only when the oil pressure in the front oil chamber is inappropriate, it is possible to suppress the sudden pop-out of the injection piston and effectively improve the production efficiency.

It is a figure which shows the schematic structure of the die casting machine which concerns on one Embodiment of this invention. It is a flowchart which shows an example of the pressurizing process executed by the control part of the die casting machine of FIG. It is a figure which shows typically the state of the change of the oil pressure of the front oil chamber of an injection cylinder before an injection process. It is a figure which shows the schematic structure of the modification of the die casting machine of FIG.

Hereinafter, the die casting machine according to the embodiment of the present invention will be described with reference to FIGS. 1 to 3.

FIG. 1 is a diagram showing a schematic configuration of a die casting machine according to an embodiment of the present invention. FIG. 2 is a flowchart showing an example of a pressurizing process executed by the control unit of the die casting machine of FIG. FIG. 3 is a diagram schematically showing how the oil pressure in the front oil chamber of the injection cylinder changes before the injection process.

In the die casting machine 1 of the present embodiment, the molten metal is poured into a cavity in a mold in which a fixed mold mounted on a fixed die plate (not shown) and a moving mold mounted on a moving die plate (not shown) are closed. Injection filling.

The die casting machine 1 has an injection piston 11 and an injection cylinder 12 that holds the injection piston 11 so as to be movable in the front-rear direction. The injection cylinder 12 has a rear oil chamber 13 and a front oil chamber 14 partitioned by the injection piston 11. An injection plunger 15 is coupled to the tip of the injection piston 11. The injection plunger 15 is housed in the injection sleeve of the fixed die plate so as to be able to advance and retreat.

Behind the injection piston 11, a piston-type spool 16 that presses the injection piston 11 to advance the injection plunger 15 is arranged. A drive transmission plate 17 is arranged behind the piston type spool 16. The drive transmission plate 17 is moved in the front-rear direction by an electric servomotor 18, a drive transmission mechanism 19 including a drive transmission gear, a ball screw mechanism, and the like. By moving the drive transmission plate 17 forward, the piston type spool 16 is pushed forward.

The piston type spool 16 is not provided integrally with the injection piston 11 and the drive transmission plate 17, but is provided separately from these. A load cell may be provided at the rear end of the piston-type spool 16 to detect the pressure generated when the drive transmission plate 17 presses the piston-type spool 16. The piston type spool 16, the drive transmission plate 17, the electric servomotor 18, and the drive transmission mechanism 19 constitute an electric pressure boosting mechanism.

The die casting machine 1 has an accumulator 21 as a hydraulic supply unit that supplies hydraulic oil to the rear oil chamber 13 of the injection cylinder 12. The accumulator 21 and the rear oil chamber 13 of the injection cylinder 12 are connected by an oil passage a. A first on-off valve 31 (injection forward valve) is arranged on the oil passage a. The first on-off valve 31 communicates with and shuts off the accumulator 21 and the rear oil chamber 13.

The front oil chamber 14 of the injection cylinder 12 and the tank 22 for storing hydraulic oil are connected by an oil passage b. A servo valve 23 is arranged on the oil passage b. The servo valve 23 adjusts the outflow amount of hydraulic oil flowing from the front oil chamber 14 to the tank 22 according to the opening degree.

On the oil passage c arranged in parallel with the oil passage b, a hydraulic pump 24 as an auxiliary oil supply unit and a second on-off valve 32 (injection retreat valve) are arranged in series in order from the tank 22 side. .. The second on-off valve 32 communicates with and shuts off the hydraulic pump 24 and the front oil chamber 14.

The rear oil chamber 13 of the injection cylinder 12 and the portion of the oil passage c between the hydraulic pump 24 and the second on-off valve 32 are connected by an oil passage d. A third on-off valve 33 (injection advance auxiliary valve) is arranged on the oil passage d. The third on-off valve 33 communicates with and shuts off the hydraulic pump 24 and the rear oil chamber 13.

In the present embodiment, the first on-off valve 31, the second on-off valve 32, and the third on-off valve 33 are composed of solenoid valves that drive the valve body by a solenoid. Of course, the present invention is not limited to this, and as each valve, for example, another type of valve in which the valve body is driven by a motor may be adopted.

The die casting machine 1 has an oil pressure sensor 25 as an oil pressure detection unit that detects the oil pressure of the front oil chamber 14 of the injection cylinder 12.

The die casting machine 1 has a control unit 40 that controls the overall operation. The control unit 40 includes, for example, a microcomputer for an embedded device having a CPU, ROM, RAM, EEPROM, various I / O interfaces, and the like. The control unit 40 controls the operations of the servo valve 23, the hydraulic pump 24, the first on-off valve 31, the second on-off valve 32, and the third on-off valve 33. Further, the control unit 40 acquires the oil pressure of the front oil chamber 14 detected by the oil pressure sensor 25. The control unit 40 controls the operation of various drive units in various processes such as a mold closing process, a pouring process, an injection process, a pressure increasing process, a mold opening process, and a product extrusion process.

The die casting machine 1 repeatedly executes each process in an automatic mode in which a series of operations in product molding are automatically performed. First, a movable die plate (not shown) is driven to mold the fixed mold and the movable mold (mold closing step). Next, the molten metal is injected into the injection sleeve of a fixed die plate (not shown) (pouring step). Then, the oil pressure of the hydraulic oil in the accumulator 21 is increased, the first open / close valve 31 is opened and supplied to the rear oil chamber 13 of the injection cylinder 12, and in synchronization with this, the hydraulic oil is supplied from the front oil chamber 14 by the servo valve 23. To move the injection piston 11 forward. At this time, the outflow amount of hydraulic oil is adjusted by the opening degree of the servo valve 23, the injection piston 11 is advanced at a low speed and then advanced at a high speed, and the molten metal in the injection sleeve is injected and filled into the cavity of the mold by the injection plunger 15. (Injection process). Further, the electric servomotor 18 is operated to advance the piston type spool 16 together with the drive transmission plate 17 to press the injection piston 11 (pressure increasing step). After that, the mold is opened (mold opening process) and the product is extruded from the cavity (product extrusion process).

Next, an example of the pressurizing process according to the present invention in the control unit 40 of the die casting machine 1 of the present embodiment described above will be described with reference to the flowchart of FIG. This pressurizing process (pressurizing step) is started near the end of the mold closing step and is executed in parallel with the pouring step, and if necessary, continues after the pouring step.

At the start of the mold closing process, the servo valve 23, the first on-off valve 31, the second on-off valve 32, and the third on-off valve 33 are all in the closed state, and the hydraulic pump 24 is in the stopped state.

The control unit 40 acquires the oil pressure of the front oil chamber 14 detected by the oil pressure sensor 25 at the end of the mold closing process and the end of the pouring process and compares it with the reference value (S110, S120). In the present embodiment, the reference value is 5 MPa, which is set to a value of 50% with respect to 10 MPa, which is the oil pressure of the hydraulic oil supplied by the accumulator 21. The reference value is set based on the oil pressure of the hydraulic oil of the accumulator 21 so that the injection piston 11 does not suddenly pop out when the hydraulic oil is supplied to the rear oil chamber 13 by the accumulator 21. The reference value can be appropriately set according to the configuration of the die casting machine 1, the product shape, etc., and is preferably set in the range of 30% to 120% of the oil pressure of the hydraulic oil supplied by the accumulator 21, and is preferably 50% to 120%. A range of 100% is more preferable.

When the oil pressure in the front oil chamber 14 is equal to or higher than the reference value (N in S120), the control unit 40 ends the process of this flowchart.

On the other hand, when the oil pressure in the front oil chamber 14 is lower than the reference value (Y in S120), the control unit 40 opens the second open / close valve 32 and operates the hydraulic pump 24 (S130). As a result, hydraulic oil is supplied to the front oil chamber 14, and the oil pressure in the front oil chamber 14 rises. In step S130, the third on-off valve 33 may be opened instead of the second on-off valve 32 so that the hydraulic oil is supplied to the rear oil chamber 13. As a result, the oil pressure in the rear oil chamber 13 rises, the injection piston 11 is pressed forward, and the oil pressure in the front oil chamber 14 rises. Alternatively, both the second on-off valve 32 and the third on-off valve 33 may be opened, and even if this is done, the oil pressure in the front oil chamber 14 rises as a result.

Then, the control unit 40 acquires the oil pressure of the front oil chamber 14 detected by the oil pressure sensor 25 and compares it with the target value (S140, S150). In the present embodiment, the target value is 8 MPa, which is higher than the reference value, and is set to a value of 80% with respect to 10 MPa, which is the oil pressure of the hydraulic oil supplied by the accumulator 21. The target value can also be appropriately set according to the configuration of the die casting machine 1, the product shape, and the like. The target value may be set to the same value as the reference value.

If the oil pressure in the front oil chamber 14 is lower than the target value, the control unit 40 continues to supply hydraulic oil (Y in S150). Then, when the oil pressure in the front oil chamber 14 exceeds the target value (N in S150), the hydraulic pump 24 is stopped and the second on-off valve 32 and the third on-off valve 33 are closed (S160), and the processing of this flowchart is performed. To finish. At the end time, if the pouring process is completed, the injection process proceeds, and if the pouring process is not completed, the process of this flowchart is executed again.

The above-mentioned pressurizing process has been described in the automatic mode, but is not limited to this. In addition to the automatic mode, for example, a pressurizing operation may be executed when switching modes (switching between manual mode and automatic mode) or when manually executing an injection process (advancing the injection piston 11) in the manual mode. ..

Examples of changes in the oil pressure in the front oil chamber 14 of the injection cylinder 12 before the injection process are shown in FIGS. 3 (a) to 3 (c). In FIG. 3A, line A shows a state in which the oil pressure of the front oil chamber 14 is maintained above the reference value in the mold closing step and the pouring step. In this case, the operation of increasing the oil pressure of the front oil chamber 14 is not performed. Line B shows the state of change when the oil pressure in the front oil chamber 14 gradually decreases and falls below the reference value near the end of the mold closing process. In FIG. 3B, the C line shows the reference value near the end of the pouring process, although the oil pressure in the front oil chamber 14 gradually decreased and exceeded the reference value at the end of the mold closing process. The state of change when it falls below is shown. In FIG. 3C, line D shows the change when the oil pressure of the front oil chamber 14 is 0 when the injection process is manually executed. As shown in each figure, when it is detected that the oil pressure in the front oil chamber 14 is lower than the reference value in the pressurizing process (pressurizing step), the oil pressure is increased to the target value (line B, line C, line D).

From the above, according to the present embodiment, the reference value or more is obtained only when the oil pressure in the front oil chamber 14 of the injection cylinder 12 is lower than the reference value before the hydraulic oil is supplied to the rear oil chamber 13 of the injection cylinder 12 by the accumulator 21. The oil pressure of the front oil chamber 14 is increased so as to be. When the oil pressure of the front oil chamber 14 is equal to or higher than the reference value, the oil pressure of the front oil chamber 14 is appropriate, while when the oil pressure of the front oil chamber 14 is lower than the reference value, the oil pressure of the front oil chamber 14 is inappropriate and the injection piston 11 is suddenly moved. There is a risk of popping out. In this embodiment, since the oil pressure in the front oil chamber 14 is increased only when the oil pressure is improper, it is possible to suppress the sudden pop-out of the injection piston 11 and effectively improve the production efficiency.

The die casting machine 1 of the above-described embodiment has an electric pressure boosting mechanism, but is not limited thereto. For example, as shown in FIG. 4, the present invention can be applied to a die casting machine 1A having a hydraulic pressure boosting mechanism instead of the electric pressure boosting mechanism. In FIG. 4, the same components as those in the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted.

The die casting machine 1A has a pressure boosting piston 51 whose tip is arranged in the rear oil chamber 13 of the injection cylinder 12, and a pressure boosting cylinder 52 that holds the pressure boosting piston 51 so as to be movable in the front-rear direction. Further, the die casting machine 1A has a pressure increasing accumulator 54 that supplies hydraulic oil to the rear oil chamber 53 of the pressure increasing cylinder 52. The pressure boosting accumulator 54 and the rear oil chamber 53 of the pressure booster cylinder 52 are connected by an oil passage e. A fourth on-off valve 55 (pressure boosting valve) is arranged on the oil passage e. The fourth on-off valve 55 communicates and shuts off the pressure increasing accumulator 54 and the rear oil chamber 53. In the pressure boosting step, the die casting machine 1A increases the oil pressure of the hydraulic oil in the pressure boosting accumulator 54, opens the fourth opening / closing valve 55, and supplies the hydraulic oil to the rear oil chamber 53 of the pressure boosting cylinder 52. As a result, the pressure boosting piston 51 advances and presses (pressure boosts) the injection piston 11. In the die casting machine 1A, the pressurizing process (pressurizing step) executed before the injection step is the same as that of the above-described embodiment.

Although embodiments of the present invention have been described above, the present invention is not limited to these examples. As long as the gist of the present invention is provided, a person skilled in the art appropriately adding, deleting, or changing the design of the above-described embodiment, or combining the features of the embodiment as appropriate is also present. Included in the scope of the invention.

1, 1A ... Die casting machine, 11 ... Injection piston, 12 ... Injection cylinder, 13 ... Rear oil chamber, 14 ... Front oil chamber, 15 ... Injection plunger, 16 ... Piston type spool, 17 ... Drive transmission plate, 18 ... Electric servo Motor, 19 ... Drive transmission mechanism, 21 ... Accumulator, 22 ... Tank, 23 ... Servo valve, 24 ... Hydraulic pump, 25 ... Hydraulic sensor, 31 ... 1st open / close valve, 32 ... 2nd open / close valve, 33 ... 3rd open / close Valve, 40 ... Control unit, 51 ... Pressure boosting piston, 52 ... Pressure boosting cylinder, 53 ... Rear oil chamber, 54 ... Pressure boosting accumulator, 55 ... Fourth opening / closing valve, a to e ... Oil passage

Claims (4)

The injection piston, the injection cylinder that holds the injection piston so that it can move back and forth, the hydraulic supply unit that supplies hydraulic oil to the rear oil chamber of the injection cylinder, and the amount of hydraulic oil that flows out from the front oil chamber of the injection cylinder. A die-casting machine that has a servo valve that adjusts the amount of hydraulic oil, supplies hydraulic oil to the rear oil chamber by the hydraulic supply unit, and causes the hydraulic oil to flow out from the front oil chamber by the servo valve to advance the injection piston. And
The oil pressure detection unit that detects the oil pressure in the front oil chamber and
Auxiliary oil supply unit that raises the oil pressure in the front oil chamber so that it becomes equal to or higher than the reference value only when the oil pressure detected by the oil pressure detection unit is lower than the reference value before the hydraulic oil is supplied by the oil pressure supply unit. and, the possess,
The auxiliary hydraulic pressure supply unit, the die casting machine, characterized in Rukoto increase the hydraulic pressure of the front oil chamber by pressing the injection piston forward to supply the hydraulic oil to the rear oil chamber. The die casting machine according to claim 1, wherein the auxiliary oil supply unit raises the oil pressure in the front oil chamber by supplying hydraulic oil to the front oil chamber. The die casting machine according to claim 1 or 2 , wherein the reference value is 30% to 120% of the oil pressure of the hydraulic oil supplied from the hydraulic pressure supply unit. The injection piston, the injection cylinder that holds the injection piston so that it can move back and forth, the hydraulic supply unit that supplies hydraulic oil to the rear oil chamber of the injection cylinder, and the amount of hydraulic oil that flows out from the front oil chamber of the injection cylinder. A die-casting machine that has a servo valve that adjusts the amount of hydraulic oil, supplies hydraulic oil to the rear oil chamber by the hydraulic supply unit, and causes the hydraulic oil to flow out from the front oil chamber by the servo valve to advance the injection piston. It is a control method of
Only when the oil pressure in the front oil chamber is lower than the reference value before the hydraulic oil is supplied by the hydraulic supply unit, the hydraulic oil is supplied to the rear oil chamber and the injection piston is pressed forward to obtain the reference value. A method for controlling a die casting machine, characterized in that the oil pressure in the front oil chamber is increased so as described above.

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