JP2010036338A - Method for recovering exhaust heat from mold in molding machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an energy saving technique of a molding machine in which heat energy discharged to a temperature conditioning coolant through a mold is converted into electric energy to be recovered and reused when a molten resin or molten aluminum is cooled after being injected into the mold in an injection molding machine or a die-casting machine. <P>SOLUTION: In a method for recovering exhaust heat from the mold in the molding process, the coolant is circulated in the mold by using a mold temperature conditioning machine in order to keep the temperature of the mold constant, the temperature difference of the coolant between the inlet side and outlet side of the mold is used, and electric energy is obtained by generating power by the use of a thermoelectric conversion module. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  In an injection molding machine or die casting machine that heats plastic and aluminum, etc., melts it, cools and solidifies it after injection filling into the mold and takes out the molded product, it cools the molten resin and aluminum through the mold. The present invention relates to energy-saving technology that converts thermal energy discharged to a cooling medium into electrical energy, recovers it, and reuses it.

  First, the structure and operation of an injection molding machine for molding a plastic product will be described with reference to FIG. The injection molding machine shown in FIG. 5 is an electric type which has become mainstream in recent years.

  The electric injection molding machine 60 is roughly composed of a mold clamping device 61 on the left side of the drawing and an injection device 70 on the right side. The fixed side of the mold 50 is attached to the fixed platen 62, and the movable side is attached to the movable platen 63. The movable platen 63 is connected to the link housing 64 via the link mechanism 65. A servomotor 66 for mold clamping is mounted on the link housing 64, and the crosshead 67 is moved forward and backward by rotating the shaft of the ball screw, and the mold 50 is opened and closed and the mold is moved through the operation of the link mechanism 65. Apply the tightening force.

  The injection device 70 includes a barrel 72 in which a screw 74 is incorporated and a heater 73 is wound around the nozzle 72, a nozzle 75 that is fixed to the tip of the barrel 72 and serves as a flow path for injecting and filling molten resin into the mold 50, A hopper 71 for storing pellet-like (small spherical) resin and feeding it into the barrel 72; a servo motor 76 for rotating the screw 74; an injection servo motor 77 for moving the screw 74 back and forth in the barrel 72; A ball screw 78 for converting the rotational movement of the injection servo motor 77 into a linear movement is provided. The injection device 70 can be moved forward and backward integrally by a drive mechanism (not shown), and the tip of the nozzle 75 can touch the resin inlet of the mold 50 by moving forward.

  The solid pellet-shaped resin stored in the hopper 71 is guided into the barrel 72 along with the rotation of the screw 74 by the rotation of the measuring servo motor 76, and then the helical flight formed on the outer periphery of the screw 74. Is sent forward (leftward in FIG. 5). At that time, the heat of the inner wall surface of the barrel 72 that has risen in temperature due to the heat generated by the heater 73 is received and gradually melted and stored in front of the screw head fixed to the front of the screw 74.

  After the tip of the nozzle 75 is touched to the resin inlet of the mold 50, the mold clamping servomotor 66 is rotated, whereby the movable platen 63 is moved, the mold 50 is closed, and the mold clamping force is loaded. In this state, when the injection servo motor is rotated, the screw 74 moves forward, and the molten resin stored in front of the screw head passes through the nozzle 75 to the cavity of the mold 50 (between the fixed mold and the movable mold). The formed product shape space) is injection-filled.

  The mold 50 has a medium flow path for flowing a cooling medium. In order to cool the molten resin to an appropriate temperature, a cooling medium (water or water) whose temperature is adjusted by a mold temperature controller (not shown). Ethylene glycol, etc.) is distributed and the mold temperature is kept constant. Therefore, the heat held by the injection-filled molten resin is taken away by the cooling medium through the mold 50, and the temperature decreases and solidifies by cooling.

  The structure and operation of a die-casting machine for forming aluminum products is very similar, and the aluminum melted in the melting furnace is heated by the ladle to the injection sleeve and then injected into the mold by the forward movement of the injection plunger. Is done. Similarly, the cooling medium is solidified and cooled while being deprived of heat.

Conventionally, hydraulic devices are used to drive molding machines such as injection molding machines and die casting machines, and hydraulic pumps are rotated by a constant-rotation electric motor, and high-pressure hydraulic oil is discharged and sent to each actuator. Thus, a predetermined operation for molding has been performed.
However, in recent years, an electric molding machine as shown in FIG. 5 which performs this driving by a combination of a servo motor and a ball screw has become mainstream. In the conventional drive system using a hydraulic device, the electric motor and the hydraulic pump always rotate and continue to consume electric power, whereas in the electric system, the servo motor rotates only when each part operates. The amount is very small and energy-saving operation is possible.

  Furthermore, in the technique disclosed in Patent Document 1, during deceleration control of a heavy object such as a mold opening / closing operation, a current generated by the servo motor is supplied to the charging device and stored as electric energy, and the subsequent operation of the molding machine is necessary. I try to reuse it at any time. In the ordinary technology, the generated current flows through the regenerative resistor and is released to the atmosphere as heat, so the energy saving effect is further increased.

Japanese Patent No. 3451480

In plastic injection molding, the electrical energy supplied to the heater to heat the barrel changes to the thermal energy of the molten resin. Further, the electric energy given to the metering servomotor for rotating the screw also changes to the thermal energy of the molten resin when kneading the high-viscosity molten resin. Furthermore, the electrical energy given to the servo motor for injection in order to advance the screw with a large force is also converted into the thermal energy of the molten resin by the shearing heat generation action that occurs when the molten resin flows.
In this way, the electrical energy given to the heater, the servo motor for weighing, and the servo motor for injection is all converted to the heat energy of the molten resin, and the heat energy of the cooling medium through the mold during solidification cooling in the mold. As absorbed. And when it cools with the chiller with which the inside of a metal mold temperature controller is equipped, it changes into high temperature air and is discharge | released in air | atmosphere.

  Similarly, in die casting of aluminum, the electric energy given to the melting furnace for melting aluminum is also taken away by the cooling medium when solidified and cooled in the mold, and is radiated to the atmosphere in the temperature controller. Abandoned.

In the invention disclosed in Patent Document 1, only the electric energy given to the mold opening / closing servomotor is collected by the charging device and reused.
The present invention aims to contribute to energy-saving operation of a molding machine by recovering and reusing electric energy given to a heater, a metering servomotor, and an injection servomotor.

In order to solve the above problems, in the present invention,
A product formed by injecting and filling molten resin or aluminum into a cavity, which is a space formed between a fixed mold and a movable mold, and then opening the fixed mold and the movable mold after cooling and solidification. In the molding process of removing the mold, in order to keep the temperature of the mold constant, the cooling medium is circulated in the mold using a mold temperature controller, and the cooling medium on the entry side to the mold and the exit side from the mold A method for recovering exhaust heat from a mold that obtains electric energy by generating electric power using a thermoelectric conversion module using the temperature difference of the cooling medium is used.
Further, the obtained electrical energy is stored in a charger and used as electrical energy necessary for the molding operation.
Further, the obtained electric energy is used as electric energy for driving a cooling fan of a control device for controlling the molding machine.
Power generation using the temperature difference between the cooling medium entering the mold and the cooling medium exiting from the mold after the temperature is adjusted by the molding machine, mold, mold temperature controller, and mold temperature controller The exhaust heat recovery device of the molding machine is composed of a thermoelectric conversion device provided with a thermoelectric conversion module capable of obtaining electrical energy.
The molding machine is an electric system.

By converting the heat energy that was previously discarded as waste heat from the mold into electrical energy and recovering it, it can be reused as energy to operate the molding machine, saving energy and reducing the cost of electricity. Can be achieved.
In particular, when used in an electric molding machine with a regenerative function that has a high energy saving function, almost no energy is released and discarded, so that the energy consumed in the molding operation can be brought close to zero.

  Embodiments according to the present invention will be described below with reference to the drawings.

  In the present invention, the temperature difference between the cooling medium entering the mold from the mold temperature controller and the cooling medium emerging from the mold is used to generate power by giving the thermoelectric conversion module a temperature difference, and exhaust heat is discharged. Collect and reuse as electrical energy.

First, the principle and state of generating electricity using heat by the thermoelectric conversion module will be described with reference to FIG.
Physical phenomena such as the Seebeck effect and the Peltier effect in which heat flow and current influence each other are collectively referred to as “thermoelectric effect”. The thermoelectric effect is generated in a circuit in which metals or semiconductors having different thermoelectric powers are joined. When there is a temperature difference at the junction, the phenomenon in which current is generated in this circuit is called the Seebeck effect. The thermoelectric conversion module having the Seebeck effect is used as a power generation device.
On the other hand, when a current is passed through the above-described circuit, a phenomenon occurs in which one of the joints generates heat and the other absorbs heat, and this phenomenon is called the Peltier effect. A thermoelectric conversion module having the Peltier effect is also called a Peltier element, and this Peltier element is used to cool the temperature of an electrical component or the like.

As shown in FIG. 4, the thermoelectric conversion module includes a thermoelectric conversion element including a P-type semiconductor 1 and an N-type semiconductor 2 connected in a π-type. Thermoelectric conversion elements are typically materials such as bismuth-tellurium compounds, antimony-tellurium compounds, bismuth-tellurium-antimony compounds, bismuth-tellurium-selenium compounds, lead-germanium compounds, silicon-germanium compounds, etc. Is used.
The P-type semiconductor 1 and the N-type semiconductor 2 have substantially the same height, and are connected to the π-type via the electrode 3. The electrode 3 is a flat conductive metal plate and desirably has low electrical resistance. A cold-side electrically insulating substrate 6 and a warm-side electrically insulating substrate 7 are in contact with the electrode 3. The cold-side electrical insulating substrate 6 and the hot-side electrical insulating substrate 7, is suitably a material having a property and an insulating property and good thermal conductivity, such as aluminum nitride (AlN) or aluminum oxide (Al 2 _{O 3)} such as Ceramic is used.

  In the thermoelectric conversion module having such a configuration, a + side electrode 5 and a − side electrode 4 are connected to a light bulb using a wiring to create a closed circuit. And the temperature difference is given to a thermoelectric conversion element by cooling the cold side electrical insulation board | substrate 6 and making it low temperature, and warming the warm side electrical insulation board | substrate 7 and making it high temperature. Then, an electromotive force is generated between the plus side electrode 5 and the minus side electrode 4, a current flows through the circuit, and the light bulb is turned on. It can be seen that such a phenomenon is the Seebeck effect, electric power can be extracted from heat, and heat energy can be converted into electric energy.

FIG. 3 is an exploded perspective view showing the configuration of the thermoelectric conversion module 10 according to the embodiment of the present invention.
The 32 P-type semiconductors 1 and 32 N-type semiconductors 2 formed in a columnar shape have substantially the same height, are alternately arranged, are joined to a plurality of electrodes 3, and are connected in series in a π-type. ing.
An externally connected negative side electrode 4 is joined to the lower end surface of the P-type semiconductor 1 arranged in the start row of the start column, and the lower end surface of the N-type semiconductor 2 arranged in the end row of the start column is The positive electrode 5 connected externally is joined.
The number and size of the P-type semiconductor 1 and the N-type semiconductor 2 are appropriately selected so that an electric device connected to the outside and using generated power can generate electricity at a desired current value or voltage value.

In the P-type semiconductor 1, the N-type semiconductor 2 and the electrodes 3 to 5 connected in this way, the upper-side electrode 3 is the cold-side electrically insulating substrate 6, and the lower-side electrodes 3 to 5 are the warm-side electrically-insulating substrate. 7 are respectively joined.
When the cold-side electrically insulating substrate 6 is cooled and the warm-side electrically insulating substrate 7 is heated, a temperature difference is generated, and an electromotive force is generated between the − side electrode 4 and the + side electrode 5.

In FIG. 2, a thermoelectric conversion device 40 according to an embodiment of the present invention will be described. As shown in the diagram on the left side of FIG. 2, the thermoelectric conversion device 40 is roughly divided into a thermoelectric conversion module 10, a cold side block 20, and a warm side block 30. The cold block 20 is joined to the cold electrical insulating substrate 6 of the thermoelectric conversion module 10, and the warm block 30 is joined to the warm electrical insulating substrate 7. The cold block 20 and the warm block 30 are preferably made of a material that can easily transmit the temperature to the thermoelectric conversion module 10, and copper (Cu) or aluminum (Al) having a high temperature diffusivity is suitable.

The right side of FIG. 2 is a cross-sectional view of the thermoelectric conversion device 40. Inside the cold side block 20 and the warm side block 30, the cold side medium flow path 21 and the temperature through which the cooling medium from the mold temperature controller flows. The side medium flow path 31 penetrates. The cold-side medium flow path 21 and the warm-side medium flow path 31 are connected to the cold-side medium pipe 22 and the warm-side medium pipe 32, respectively, and flow the cooling medium between the temperature controller and the mold.
Moreover, it is preferable that the outer side is covered with the heat insulating cover 41, and the temperature of the cooling medium is easily transmitted to the thermoelectric conversion module 10 efficiently.

In FIG. 1, the structure of a metal mold | die, a thermoelectric conversion apparatus, a metal mold temperature controller, a molding machine control apparatus, piping, and wiring concerning the Example of this invention is demonstrated.
The fixed mold 51 is connected to the thermoelectric conversion device 40 and the fixed temperature controller via the cold medium pipe 22 and the warm medium pipe 32. Further, the negative electrode 4 and the positive electrode 5 of the thermoelectric conversion device 40 are electrically connected to the molding machine control device by an electric wiring 80, and the generated electric power is guided into the control device.

The cooling medium adjusted to a desired temperature by the temperature controller is led to the cold side block 20 of the thermoelectric conversion device 40 through the cold side pipe 22, and further leaves the cold side block 20 and passes through the cold side pipe 22. Enter the mold. While flowing through the medium flow path 53 provided in the mold, the temperature of the cooling medium rises due to heat from the mold. And it passes through the warm side medium flow path 31 of the warm side block 30 of the thermoelectric conversion device 40 through the warm side medium pipe 32, and returns to the mold temperature controller through the warm side medium pipe 32.
The same applies to the movable mold.

A method of recovering waste heat from the mold and reusing it as electric energy using the mold and the thermoelectric converter configured as described above will be described.
During the continuous molding operation of the molding machine, the thermal energy of the high-temperature molten resin injected and filled in the mold cavity is transferred to the mold through the cavity surface, so that the mold temperature rises. Therefore, in order to keep the mold temperature constant, the cooling medium is constantly circulated from the mold temperature controller to the mold.

Meanwhile, a cooling medium adjusted to a desired temperature by the mold temperature controller is circulated through the cold side block 20 of the thermoelectric conversion device 40, and the heat of the molten resin is passed through the mold within the mold. The cooling medium with increased temperature is distributed. Therefore, a temperature difference arises in the thermoelectric conversion module 40, and the thermoelectric conversion module 40 always continues electric power generation.
The generated electric power is sent to the molding machine control device via the electric wiring 80. Then, it is stored in an electrically connected charger (not shown) and reused as a power source for operating the molding machine, or used as a power source for rotating a fan for adjusting the air temperature in the control device.

  As described above, the electric energy given to the heater, measuring servo motor or injection servo motor is recovered as heat from the mold and converted into electric energy, which can be reused. It becomes.

  The above-described embodiment is an example of the present invention, and the present invention is not limited by the embodiment, but is defined only by matters described in the claims, and other embodiments than the above are also possible. It can be implemented.

It is a figure which shows the metal mold | die, temperature controller, thermoelectric conversion apparatus, and control apparatus by the Example of this invention. It is a figure which shows the thermoelectric conversion apparatus by the Example of this invention. It is a disassembled perspective view of the thermoelectric conversion module by the Example of this invention. It is a figure which shows the state of the electric power generation by a thermoelectric conversion module. It is a figure which shows a general electric injection molding machine and a mold apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 P-type semiconductor 2 N-type semiconductor 3 Electrode 4-side electrode 5 + side electrode 6 Cold side electric insulation board 7 Warm side electric insulation board 10 Thermoelectric conversion module 11 Electric wiring 20 Cold side block 21 Cold side medium flow path 22 Cold side Medium pipe 30 Warm side block 31 Warm side medium flow path 32 Warm side medium pipe 40 Thermoelectric conversion device 41 Thermal insulation cover 50 Mold device 51 Fixed side mold 52 Movable side mold 53 Medium flow path 60 Electric injection molding machine 61 type Clamping device 62 Fixed platen 63 Movable platen 64 Link housing 65 Link mechanism 66 Servo motor for mold clamping 67 Cross head 70 Injection device 71 Hopper 72 Barrel 73 Heater 74 Screw 75 Nozzle 76 Weighing servo motor 77 Injection servo motor 78 Injection ball Screw 80 Electrical wiring

Claims (5)

A product formed by injecting and filling molten resin or aluminum into the cavity, which is the space formed between the fixed mold and the movable mold, and then opening the fixed mold and the movable mold after cooling and solidification. In the molding process of taking out
In order to keep the temperature of the mold constant, a cooling medium is circulated in the mold using a mold temperature controller, and the temperature difference between the cooling medium entering the mold and the cooling medium exiting from the mold A method for recovering exhaust heat from a mold, wherein electric energy is obtained by generating electricity using a thermoelectric conversion module.
A method of operating a molding machine, characterized in that the electrical energy obtained by the method of claim 1 is stored in a charger and used as electrical energy when necessary for a molding operation.
A method for operating a molding machine, wherein the electrical energy obtained by the method of claim 1 is used as electrical energy for driving a cooling fan of a control device for controlling the molding machine.
Power generation using the temperature difference between the cooling medium entering the mold and the cooling medium exiting from the mold after the temperature is adjusted by the molding machine, mold, mold temperature controller, and mold temperature controller An exhaust heat recovery device for a molding machine, comprising a thermoelectric conversion device including a thermoelectric conversion module capable of obtaining electrical energy.
  The exhaust heat recovery apparatus for a molding machine according to claim 4, wherein the molding machine is of an electric type.

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