JP4458291B2 - Injection device and injection control method - Google Patents

Description

  The present invention relates to a plunger type injection device for filling a mold cavity with a molten metal and an injection control method using the same.

  A conventional plunger type injection device used in a die-casting method in which a molten metal such as an aluminum alloy is injected into a mold cavity at a high speed, and is cast, is generally a hydraulic cylinder that operates an injection plunger, hydraulic pressure It has a structure equipped with a pump, accumulator, hydraulic control valve and the like. Then, the hydraulic pressure accumulated in the accumulator by the hydraulic pump is supplied to the hydraulic cylinder by the hydraulic control valve, and the injection plunger is operated to inject the molten metal. At this time, the injection speed and pressure can be controlled by adjusting the pressure and flow rate of the hydraulic oil supplied to the hydraulic cylinder by the hydraulic control valve. Also, in the die casting method, an accumulator that accumulates two different pressures for high-speed injection, pressure increase, and holding is provided in order to increase and hold the molten metal pressure after filling the mold cavity at high speed. There is also an injection device.

  However, in the die casting method, in order to improve the molding quality, it is important to stabilize the injection speed. However, in the conventional injection device using the hydraulic cylinder, the flow rate of hydraulic oil supplied to the hydraulic cylinder by the hydraulic control valve Since the plunger speed is controlled by adjusting the pressure, the responsiveness is low, it is difficult to detect the load of the plunger, and it is difficult to perform feedback control, so it is difficult to obtain a stable injection speed. In addition, since an expensive hydraulic control valve or the like is required, equipment costs are increased.

Therefore, conventionally, for example, as described in Patent Document 1, a ball screw mechanism driven by an electric servo motor and a hydraulic cylinder operated by hydraulic pressure of a hydraulic pump and an accumulator are connected in series to an injection plunger, An injection device has been proposed in which a plunger is operated by electric and hydraulic pressure. This makes it possible to improve the controllability of the injection speed by using an electric servo motor during high-speed injection, and easily obtain a large holding force by using a hydraulic cylinder during pressure increase and holding. It becomes possible.
JP 2000-84654 A

  However, the injection device described in Patent Document 1 has the following problems. Since the ball screw mechanism and the hydraulic cylinder are connected in series, the thrust of the hydraulic cylinder is transmitted to the plunger via the ball screw shaft. For this reason, the ball screw shaft needs to have a certain diameter to ensure the required strength, but if the ball screw shaft has a large diameter, it is difficult to move the plunger at high speed. In addition, the structure is complicated and equipment costs are high.

Therefore, as described in Patent Document 2, the present applicant has proposed an injection device in which a ball screw mechanism for driving a plunger and a hydraulic cylinder are arranged in parallel. As a result, the load acting on the ball screw mechanism at the time of pressure increase and holding can be reduced, so that the diameter of the ball screw shaft can be reduced, high speed operation is possible, and miniaturization and long life are achieved. Can be achieved.
JP 2006-887 A

  In the injection device that performs injection control by switching from injection and filling by the electric motor described above to pressure increase and holding by a hydraulic cylinder, the timing of switching greatly affects the molding quality. Since the filling state varies due to air or gas entrainment, the switching timing is not constant. For this reason, the timing of the filling of the molten metal by the electric motor and the start of pressure increase by the hydraulic cylinder do not match, the plunger thrust temporarily decreases, or the plunger speed rises excessively to generate surge pressure, There is a possibility that the filling state becomes unstable and the molding quality is lowered. In addition, the accumulated pressure of the accumulator due to the outside air temperature and the change in viscosity of hydraulic oil in the hydraulic cylinder, or variations in the amount of hot water supply, molten air, gas entrainment, etc. cause the holding pressure of the hydraulic cylinder to fluctuate and the molding quality deteriorates. Sometimes.

  The present invention has been made in view of the above points, and an object thereof is to provide an injection device and an injection control method capable of improving the quality of a molded product by optimizing the control of an electric motor and a hydraulic cylinder. To do.

In order to solve the above-mentioned problems, the invention according to claim 1 is directed to a plunger for filling a mold cavity with a molten metal, a hydraulic cylinder for applying thrust to the plunger, and an electric motor for driving the plunger. A rotation motor, and a rotation-linear motion conversion mechanism interposed between the plunger and the electric rotation motor and arranged in parallel with the hydraulic cylinder, and the plunger is driven by the electric rotation motor to melt the molten metal Injecting and filling the cavity in the mold, the pressure of the molten metal filled in the cavity is increased and held by the hydraulic cylinder,
After the speed of the electric rotary motor is controlled according to a predetermined target speed, torque control is performed so as to generate a predetermined torque. After the electric rotary motor is switched from speed control to torque control, the hydraulic cylinder is operated to The pressure of the molten metal filled in the cavity is increased and maintained .
According to a second aspect of the present invention, there is provided the injection apparatus according to the first aspect, wherein the pressure of the molten metal filled in the cavity is detected, and the torque of the electric rotary motor is adjusted based on the detected pressure. And controlling the pressure of the molten metal filled in the cavity.
According to a third aspect of the present invention, there is provided an injection apparatus according to the first or second aspect, wherein after the control of the electric rotary motor is switched from speed control to torque control, the speed of the plunger is monitored and the speed of the plunger is monitored. When the motor reaches a predetermined speed limit, the torque of the electric rotary motor is controlled to brake the movement of the plunger.
According to a fourth aspect of the present invention, there is provided a plunger for filling a mold cavity with a molten metal, a hydraulic cylinder for applying a thrust to the plunger, an electric rotary motor for driving the plunger, the plunger and the electric motor. The plunger is driven by the electric rotary motor using an injection device having a rotation-linear motion conversion mechanism that is interposed between the rotary motor and arranged in parallel with the hydraulic cylinder. In the injection control method in which the cavity of the mold is injected and filled, and the pressure of the molten metal filled in the cavity is increased and held by the hydraulic cylinder,
After the speed of the electric rotary motor is controlled according to a predetermined target speed, torque control is performed so as to generate a predetermined torque. After the electric rotary motor is switched from speed control to torque control, the hydraulic cylinder is operated to The pressure of the molten metal filled in the cavity is increased and maintained .
According to a fifth aspect of the present invention, in the injection control method according to the fourth aspect, the pressure of the molten metal filled in the cavity is detected, and the torque of the electric rotary motor is adjusted based on the detected pressure. Thus, the pressure of the molten metal filled in the cavity is controlled.
According to a sixth aspect of the present invention, there is provided an injection control method according to the fourth or fifth aspect, wherein after the control of the electric rotary motor is switched from speed control to torque control, the speed of the plunger is monitored, When the speed reaches a predetermined speed limit, the torque of the electric rotary motor is controlled to brake the movement of the plunger.

  According to the injection device and the injection control method of the present invention, the plunger is driven by the electric rotary motor to fill the mold with the molten metal, and the pressure of the filled molten metal is increased and held by the hydraulic cylinder. Therefore, it is possible to efficiently perform filling, pressure-increasing and holding of the molten metal. At this time, by controlling the speed of the electric rotary motor and then switching to torque control, the charging by the electric rotary motor is increased by the hydraulic cylinder. The transition to pressure and holding can be performed smoothly, and the molding quality can be improved.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
The injection apparatus according to the present embodiment is a plunger type injection apparatus for filling a die casting mold with a molten metal such as an aluminum alloy. As shown in FIG. 1, the injection device 1 includes an injection sleeve 3 coupled to a mold 2 that forms a cavity C, a plunger 4 that is slidably fitted to the injection sleeve 3, and a rod 5 of the plunger 4. Are connected to the rod 5 of the plunger 4, and are connected to the rod 5 of the plunger 4. A rotation-linear motion conversion mechanism), an injection electric servo motor 9 (hereinafter referred to as injection motor 9) (electric rotation motor) for driving the ball screw mechanism 8, a controller 10 for controlling the hydraulic device 7 and the injection motor 9. It has.

  The injection sleeve 3 communicates with the cavity C of the mold 2 and is provided with an injection port 11 for injecting molten metal into the upper portion of the side wall on the base end side. The operating rod 13 of the hydraulic cylinder 6 is connected to the rod 5 of the plunger 4 fitted to the injection sleeve 3 by a coupling 12.

  The hydraulic cylinder 6 is a single-acting cylinder, and a hydraulic device 7 is connected to an oil chamber 15 defined by a piston 14, and is operated by supplying and discharging hydraulic oil to and from the oil chamber 15 by the hydraulic device 7. The rod 13 can be expanded and contracted.

  The hydraulic device 7 includes a tank 16 that stores hydraulic oil, a hydraulic pump 17 that is a hydraulic source, a pump motor 18 that drives the hydraulic pump 17, an accumulator 19 that accumulates the hydraulic pressure generated by the hydraulic pump 17, and an accumulator 19. A pressure increase switching valve 20 that supplies and discharges hydraulic oil to and from the hydraulic cylinder 6, a prefill valve 21 (pilot check valve) that transfers hydraulic oil between the tank 16 and the hydraulic cylinder 6, and a hydraulic pump 17. And a check valve 22 that allows only the flow of hydraulic oil from the side to the accumulator 19 side. By controlling the pump motor 18, the pressure increase switching valve 20, and the prefill valve 21 with a control signal from the controller 10, hydraulic oil at a predetermined pressure can be supplied to and discharged from the hydraulic cylinder 6.

  In the ball screw mechanism 8, a plurality of steel balls are loaded between the screw grooves formed on the screw shaft 23 and the nut 24, and the rotation of the screw shaft 23 is caused by rolling of the steel balls between the screw grooves. It is designed to convert to linear motion. The screw shaft 23 is disposed in parallel with the rod 5 of the plunger 4 and the operation rod 13 of the hydraulic cylinder 6, and is fixed in the axial direction and rotatably supported. The screw shaft 23 is connected to the shaft 26 of the injection motor 9 by a coupling 25. The nut 24 is connected to the rod 5 of the plunger 4 and the operating rod 13 of the hydraulic cylinder 6, and rotates the screw shaft 23 by the injection motor 9, thereby moving the plunger 4 by linear movement along the screw shaft 23. A position sensor 27 such as a resolver for detecting the rotational position of the shaft 26 is attached to the injection motor 9. A load sensor 28 such as a load cell that detects an axial load acting on the plunger 4 is attached to the rod 5 of the plunger 4.

  The controller 10 monitors pressure signals (not shown) for detecting the pressure in the accumulator 19 and the oil chamber 15 of the hydraulic cylinder 6, and detection signals from the position sensor 27, and the injection motor 9, pump motor 18, pressure increase switching valve 20. The operation of the prefill valve 21 is controlled to execute the following injection operation.

  The pressure increase switching valve 20 is closed to cut off the communication between the accumulator 19 and the hydraulic cylinder 6, the hydraulic pump 17 is driven by the pump motor 18, the hydraulic oil is supplied to the accumulator 19, and the hydraulic oil at a predetermined pressure is supplied to the accumulator 19. Accumulate pressure.

  After injecting the molten metal M into the injection sleeve 3 from the injection port 11, the injection motor 9 is operated and the plunger 4 is advanced by the ball screw mechanism 8 to fill the cavity C of the mold 2 with the molten metal M. At this time, the prefill valve 21 is opened and hydraulic oil is introduced from the tank 16 into the oil chamber 15, so that the operation rod 13 of the hydraulic cylinder 6 follows the movement of the plunger 4 by the injection motor 9 and the ball screw mechanism 8. Can be made. Then, the controller 10 controls the rotation speed (plunger speed) of the injection motor 9 to perform injection according to a predetermined plunger speed pattern (for example, see FIG. 2A) (speed control).

  When the position sensor 27 detects that the plunger 4 has reached the predetermined control mode switching position indicated by the point P1 in FIG. 2E, the controller 10 changes the control of the injection motor 9 from the above speed control to the torque control. Switch. This torque control is performed such that the injection motor 9 generates a predetermined torque in the injection direction (the forward direction of the plunger 4), and can be executed by adjusting the power supplied to the injection motor by an inverter or the like. At this time, the speed of the plunger 4 is monitored by the position sensor 27 so that the plunger speed does not exceed a predetermined maximum speed.

  Thereafter, when the position sensor 27 detects that the plunger 4 has reached a predetermined pressure increase switching position indicated by a point P2 in FIG. 2 (E), the pressure increase switching valve 20 is opened and the operation accumulated in the accumulator 19 is performed. Oil is supplied to the oil chamber 15 of the hydraulic cylinder 6. As a result, as shown in FIG. 2D, the pressure in the oil chamber 15 of the hydraulic cylinder 6 (head-side pressure) increases, and the power L2 of the hydraulic cylinder 6 is added to the plunger in addition to the power L1 of the injection motor 9. 4, the injection pressure is increased and held at a predetermined injection pressure, as shown in FIG.

  At this time, the pressure increase switching position P2 is set before the filling completion position P3 where the filling is actually completed by an amount corresponding to the response time T of the pressure increasing switching valve 20. In addition, the control mode switching position P1 is set sufficiently close to the filling completion position P3 in consideration of fluctuations in the filling completion position P3 due to errors in the amount of hot water supply, air and gas entrainment, and the plunger 4 is The plunger speed control pattern is set so that the plunger speed reaches the final filling speed before reaching the control mode switching position P1.

  Then, the molten metal is filled into the cavity C of the mold 2 and cooled and solidified, and then the mold is opened to remove the molded product.

  Thus, by performing the injection operation (dynamic control region) with the injection motor 9, the injection speed can be controlled easily and accurately, and the molding quality can be improved. On the other hand, by increasing and maintaining the injection pressure by the hydraulic cylinder 6 (static control region), a large output can be easily generated, so that stable pressure increase and holding force can be obtained efficiently. it can. Further, by assisting the hydraulic cylinder 6 with the injection motor 9 in increasing and holding the injection pressure, the hydraulic device 7 can be reduced in pressure and size. In this way, by optimally using electric and hydraulic pressures, it is possible to improve the molding quality and to achieve downsizing, energy saving and cost reduction of the apparatus.

  Since the ball screw mechanism 8 for converting the rotational motion of the injection motor 9 into a linear motion and the hydraulic cylinder 6 for pressure increase and holding are arranged in parallel, a large load due to the reaction force of pressure increase and holding is applied to the ball screw mechanism. Therefore, the ball screw mechanism 8 can be reduced in diameter and can be operated at high speed. Further, the ball screw mechanism 8 can be downsized, and the service life is improved.

  In addition, after the injection motor 9 is switched from speed control to torque control, the hydraulic cylinder 6 is operated to proceed to the pressure increasing and holding process, so that the filling completion position due to variations in the amount of hot water supply, air and gas entrainment, etc. Even when P3 fluctuates, the injection motor 9 can reliably apply a constant thrust to the plunger 4, so that it is possible to prevent the injection pressure from decreasing when switching from electric to hydraulic pressure, and stable molding. Quality can be obtained.

  Next, a second embodiment of the present invention will be described mainly with reference to FIG. Since the present embodiment is generally similar in configuration to the first embodiment except that the control content by the controller 10 is different, the same parts are the same as those in the first embodiment. Only different parts will be described in detail with reference numerals.

  In the injection device 1 according to the present embodiment, the controller 10 switches the control of the injection motor 9 from speed control to torque control, and then feeds back the axial load acting on the plunger 4 detected by the load sensor 28 to give a predetermined target. Compared with the pattern, the torque of the injection motor 9 is controlled so that the axial load acting on the plunger 4 matches the target pattern (see FIG. 3C). Thus, the power L2 of the hydraulic cylinder 6 is assisted by the power L1 of the injection motor 9 to obtain a desired pressure increase and holding pressure (see FIG. 3B). Instead of the load sensor 28, a pressure sensor for detecting the pressure in the cavity C may be provided in the mold 2 and the detected pressure of this pressure sensor may be fed back.

  Thereby, pressure increase and holding pressure of the hydraulic cylinder 6 due to changes in the accumulated pressure of the accumulator 19 and the hydraulic oil viscosity of the hydraulic cylinder 6 due to the outside air temperature, variation in the amount of hot water supply, air and gas entrainment during filling, etc. Even when there is a fluctuation, the fluctuation can be adjusted by the injection motor 9 and the pressure can be increased and held according to the target pattern, and a stable molding quality can be obtained.

  Next, a third embodiment of the present invention will be described mainly with reference to FIG. Since the present embodiment is generally similar in configuration to the first embodiment except that the control content by the controller 10 is different, the same parts are the same as those in the first embodiment. Only different parts will be described in detail with reference numerals.

  In the injection device 1 of the present embodiment, the controller 10 switches the control of the injection motor 9 from speed control to torque control, and then continuously monitors the speed of the plunger 4 based on the detection of the position sensor 27, and the plunger 4 is predetermined. Is reached, the torque command value to the injection motor 9 is reduced to brake the movement of the plunger 4. Here, when the inertial mass such as the rod 5 moving with the plunger 4, the piston 14 of the hydraulic cylinder 6 and the operating rod 13 collides with the molten metal when filling is completed, a surge pressure is generated by the impact and the molded product It is determined as a speed at which no adverse effect such as occurrence of burrs occurs.

  Thereby, for example, when the amount of hot water supply is less than the reference and the hydraulic cylinder 6 is actuated and the plunger 4 is accelerated and reaches the speed limit before the molten metal is filled (see the broken line portion in FIG. 4A), the injection motor 9 (See the broken line portion in FIG. 4C) and braking the movement of the plunger 4 can alleviate the impact at the completion of filling and suppress the generation of surge pressure due to collision. (Refer to the broken line portion in FIG. 4B), stable molding quality can be obtained.

It is a figure which shows schematic structure of the injection device which concerns on one Embodiment of this invention. It is a graph which shows the operating state of the injection device which concerns on 1st Embodiment of this invention. It is a graph which shows the operating state of the injection device which concerns on 2nd Embodiment of this invention. It is a graph which shows the operating state of the injection device which concerns on 3rd Embodiment of this invention.

Explanation of symbols

  1 injection device, 2 molds, 4 plunger, 6 hydraulic cylinder, 8 ball screw mechanism (rotation-linear motion conversion mechanism), 9 electric servo motor for injection (electric rotation motor), C cavity

Claims (6)

A plunger for filling the mold cavity with a molten metal, a hydraulic cylinder for applying a thrust to the plunger, an electric rotary motor for driving the plunger, and an interposition between the plunger and the electric rotary motor And a rotary-linear motion conversion mechanism arranged in parallel with the hydraulic cylinder, and the plunger is driven by the electric rotary motor to inject and fill the molten metal into the cavity of the mold. In the injection device configured to increase and hold the pressure of the filled molten metal by the hydraulic cylinder,
After the speed of the electric rotary motor is controlled according to a predetermined target speed, torque control is performed so as to generate a predetermined torque. After the electric rotary motor is switched from speed control to torque control, the hydraulic cylinder is operated to An injection apparatus characterized by increasing and maintaining the pressure of a molten metal filled in a cavity . The pressure of the molten metal filled in the cavity is detected, and the pressure of the molten metal filled in the cavity is controlled by adjusting the torque of the electric rotary motor based on the detected pressure. The injection device according to claim 1. After switching the control of the electric rotary motor from speed control to torque control, the speed of the plunger is monitored, and when the speed of the plunger reaches a predetermined speed limit, the torque of the electric rotary motor is controlled to The injection device according to claim 1 or 2, wherein the movement of the plunger is braked. A plunger for filling the mold cavity with a molten metal, a hydraulic cylinder for applying a thrust to the plunger, an electric rotary motor for driving the plunger, and an interposition between the plunger and the electric rotary motor The plunger is driven by the electric rotary motor to inject and fill the molten metal into the mold cavity using an injection device having a rotation-linear motion conversion mechanism arranged in parallel with the hydraulic cylinder. In the injection control method, the pressure of the molten metal filled in the cavity is increased and held by the hydraulic cylinder.
After the speed of the electric rotary motor is controlled according to a predetermined target speed, torque control is performed so as to generate a predetermined torque. After the electric rotary motor is switched from speed control to torque control, the hydraulic cylinder is operated to An injection control method characterized by increasing and maintaining the pressure of a molten metal filled in a cavity . The pressure of the molten metal filled in the cavity is detected, and the pressure of the molten metal filled in the cavity is controlled by adjusting the torque of the electric rotary motor based on the detected pressure. The injection control method according to claim 4. After switching the control of the electric rotary motor from speed control to torque control, the speed of the plunger is monitored, and when the speed of the plunger reaches a predetermined speed limit, the torque of the electric rotary motor is controlled to 6. The injection control method according to claim 4, wherein the movement of the plunger is braked.

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