JP3234645B2 - Mold heating method and injection molding apparatus in injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for heating a mold in an injection molding machine and an injection molding apparatus.

[0002]

2. Description of the Related Art Injection molding machines are well known, not to mention the name of the literature, and there are a horizontal type, a vertical type and the like. In any case, an injection cylinder and a rotary drive in the cylinder are used. And a screw driven also in the direction. A heating device is provided on the outer periphery of the injection cylinder to melt the resin inside. Therefore,
When the screw is driven, for example, the resin material supplied from the hopper is melted by heat applied from an external heating device and heat generated by the shearing action, frictional action, etc. due to the screw rotation in the process of being sent by the screw rotating action. The screw can then be driven into the mold in a known manner via a nozzle by axial driving of the screw. on the other hand,
A mold for molding the molten resin is provided in front of the injection cylinder, and the temperature of the mold is controlled by a temperature controller. The temperature controller generally includes a tank for storing a heat medium, a heater for heating the heat medium in the tank, and a pump for circulating the heat medium between the mold and the tank. Therefore, when the heater is energized to heat the heat medium in the tank to a predetermined temperature and drive the pump, the heat medium circulates between the mold and the tank,
The mold is heated to a predetermined temperature. In this way, the dimensional accuracy and characteristics of the injection molded product can be stabilized.

[0003]

As described above, even with a conventional injection molding machine, an injection molded product having high dimensional accuracy can be obtained by heating a mold. However, there is a drawback that energy loss is large. That is, the heating device of the injection cylinder is heated to around 200 ° C. However, since this heating device is provided on the outer peripheral portion of the cylinder, it is needless to say that the heating device is used for melting the resin inside the cylinder. Also, the amount of heat escaping to the outside is large, and the energy loss is large. In addition, when heat escapes to the outside in this way, energy is lost, and the temperature of the environmental atmosphere is increased, thereby deteriorating the working environment. For this reason, a separate air conditioner is provided to improve the working environment, so that more energy is required. The heat medium for heating the mold is considerably lower than the temperature of the heating device of the injection cylinder, for example, about 70 to 80 ° C., and is heated in the tank, so that energy loss is relatively small. . However, it is necessary to heat with a heater, and the electric power is still used. As described above, the temperature of the injection cylinder heating device is relatively high, and the amount of heat that escapes is large. On the other hand, the heating temperature of the mold is considerably lower than the temperature of the heating device of the injection cylinder. Thus, the temperature of the injection cylinder heating device,
Although there is a temperature difference between the heating temperature of the mold and the temperature, there is a characteristic in terms of temperature, but this characteristic has not been utilized conventionally. Accordingly, it is an object of the present invention to provide a method of heating a mold and an injection molding apparatus in an injection molding machine with low energy loss, utilizing the above-described features.

[0004]

According to the present invention, in order to achieve the above object, a heating device provided on an outer peripheral portion of an injection cylinder heats a resin inside the injection cylinder and kneads and melts the resin with a screw. When the mold is injected into the mold, heat is exchanged between the heat escaping from the heating device to the outside and a heat medium, and the mold is heated by the heat exchanged heat medium. The invention according to claim 2 is configured to heat the mold by adjusting the temperature of the heat exchanged heat medium. According to a third aspect of the present invention, there is provided an injection cylinder unit having a heating device provided on an outer peripheral portion of an injection cylinder, a mold for molding a molten resin injected from the injection cylinder unit into a predetermined product, and the injection cylinder unit. A heat exchanger provided near the outer peripheral portion of the heat exchanger, and a pipe device connecting the heat exchanger and the mold. The invention according to claim 4, wherein the pipe device or the heat exchanger is And a heat medium temperature adjusting means.

[0005]

According to the present invention, the injection cylinder unit is driven to inject the molten resin into the mold. At this time, the resin inside is heated by a heating device on the outer peripheral portion of the injection cylinder. When heating, heat escapes to the outside, and the escaped heat and the heat medium are exchanged in a heat exchanger. Then, the heat medium subjected to the heat exchange flows into the mold by the pipeline device, and heats or heats the mold. According to the fourth aspect of the present invention, the temperature of the heat medium is controlled, and the heat medium flows into the mold to heat or heat the mold.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention can be implemented in various forms. Although the injection molding machine can be carried out by a horizontal type or a vertical type, only an example in which the injection molding machine is implemented by a horizontal type injection molding machine is shown. Although the heat medium can be implemented with heat-resistant ethylene glycol, an example is shown in which the heat medium is implemented with water. When the operation is performed with water, when the temperature is higher than a predetermined value, there is an advantage that the temperature can be reduced only by directly adding water. When working with ethylene glycol, it is desirable to control the heat exchanger so that it does not overheat. This is because the use of ethylene glycol results in indirect cooling, which increases the size of the apparatus. An example in which the temperature of the heat medium is controlled by the inclination angle of the heat exchanger and an example in which the temperature is controlled by a separate heating device and cooling water are shown, but when accuracy is not required for the temperature control of the mold, It can be controlled only by the inclination angle of the heat exchanger. Furthermore, the inclination of the heat exchanger is
It is also possible to make it constant and to radiate heat in a pipeline. However, these examples are not shown.

Hereinafter, an embodiment of the present invention will be described. The injection machine includes a cylinder 2 as is well known in the art. A screw is provided in the cylinder 2 so as to be rotatable and axially drivable, and a nozzle 3 is attached to a tip of the cylinder 2. Although not shown in the figure, a mold device is arranged in front of the nozzle 3. Further, heating devices 4, 4, which are, for example, band heaters, are provided on the outer periphery of the cylinder 2. A drive box 5 is provided behind the cylinder 2, and the screw is appropriately driven in a rotational direction and an axial direction by drive means in the box.

[0008] Around the cylinder 2, that is, a heating device 4,
At the outer peripheral portion of each of the heating devices 4, 4, a gutter-shaped heat insulating cover 10 is provided at a predetermined distance from the outer surface of the heating device 4, 4,. The heat retaining cover 10 covers substantially the entire length of the cylinder 2, and a heat exchanger 12 having substantially the same length is provided on one upper edge 11.
In addition, a heat retaining lid 14 is provided on the other upper edge 13. The heat exchanger 12 includes a hinge 15 on the heat insulating cover 10,
It is attached at 15. Therefore, the heat exchanger 12
The opening of the heat retaining cover 10 can be substantially closed, or can be opened as shown in the drawing. In order to drive the heat exchanger 12 in this manner, the heat exchanger 12
A piston / cylinder unit 17 is provided between the heat insulation cover 10 and the bracket 16. Insulation lid 1
Like the heat exchanger 12, the hinge 4 is attached to the heat retaining cover 10 by a hinge so as to be openable and closable, and is driven to be opened and closed by a piston / cylinder unit.

The heat exchanger 12 is formed in a box shape from, for example, an aluminum panel, and a flow path through which water serving as a heat medium flows is formed inside. The heat exchanger 12 has a plurality of fins inside to improve a heat exchange rate. Are provided as appropriate. Heat exchanger 1
2 are flexible water inlet hose 18 and tap water hose 1
9 are attached respectively.

The mold 1 is schematically shown at the lower right of the figure, and the mold 1 and the heat exchanger 12 are connected via a pipeline device 30. The pipe device 30 includes a first water tank 31,
It is composed of a temperature control water tank 32, a pipe connecting these water tanks 31 and 32 with the heat exchanger 12 and the mold 1, a pump and a valve interposed in the pipe.

The temperature control water tank 32 has a hot water pipe 3 below it.
7 and a tapping pipe 38 and an overflow pipe 34 above.
And are connected respectively. A cooling water supply pipe 39 is attached to an upper lid of the temperature control water tank 32. A thermometer 36 composed of, for example, a thermocouple and a sheath heater 40 are provided inside. A pump 42 is interposed in the tapping pipe 38, and a discharge pipe 41 of the pump 42 can be connected to the mold 1. A return pipe 43 detachably connected to the mold 1 is provided with first and second three-way solenoid valves 44 and 45, and is connected to the water inlet hose 18 provided in the heat exchanger 12. .

An outgoing pipe 46 is connected to the tapping hose 19 of the heat exchanger 12, and the outgoing pipe 46 is connected below the first water tank 31. On the upper part of the first water tank 31, the other of the hot water pipe 37 connected to the temperature control water tank 32 is attached. The first water tank 31 is also provided with a thermometer 50, and the upper lid is provided with a discharge pipe 52 in which a solenoid valve 51 is interposed. Between the discharge pipe 41 coming out of the pump 42 and the port of the second three-way solenoid valve 45,
A purge pipe 53 is connected. The purge pipe 53 is provided with a relief valve 54 and a check valve 55, and a branch pipe 59.
Is connected to the drain 56. Discharge pipe 4 of pump 42
A bypass pipe 60 for short-circuiting the mold 1 is provided between the mold 1 and the return pipe 43 of the mold 1.
An electromagnetic valve 61 is interposed. An air supply pipe 70 is also connected to the discharge pipe 41. In the figure, reference numeral 57 denotes a communication pipe, and reference numerals 58, 58, denote check valves.

Next, the operation of the above embodiment will be described.
As is well known in the art, the cylinders 2 are heated by the heating devices 4 and 4 to melt the resin therein. The screw is appropriately driven in the rotation direction and the axial direction by the driving means in the driving box 5 to inject the molten resin into the mold 1. Before injection as described above, the discharge pipe 41 and the return pipe 4
3 is connected. On the other hand, the first water tank 31 and the temperature control water tank 3
Fill with water. The solenoid valve 61 of the bypass pipe 60 for short-circuiting the mold 1 is opened, and the first and second three-way solenoid valves 44,
45 is switched so that water flows in the direction indicated by the arrow in the figure. Then, the pump 42 is started. Then, water is discharged from the pump 42 to the discharge pipe 41 and the bypass pipe 6.
0, return pipe 43 and first and second three-way solenoid valves 44 and 45
Through the heat exchanger 12. Then, heat is exchanged in the heat exchanger 12, flows into the first water tank 31 from the outgoing pipe 46, flows from the hot water pipe 37 to the temperature control water tank 32, and is sucked by the pump 42.

As described above, when the water as the heat medium circulates, the temperature of the water is measured by the thermometer 50 of the first water tank 31. When the water temperature matches the set temperature of the mold 1 or is within an allowable range, it is not necessary to adjust the inclination angle of the heat exchanger 12 and it is necessary to adjust the water temperature in the temperature control water tank 32. Nor. Therefore, the solenoid valve 61 of the bypass pipe 60
Is closed and water flows into the mold 1. When the mold 1 reaches a predetermined temperature, the molten resin is injected from the nozzle 3 of the cylinder 2 into the mold 1 as described above.

When the water temperature measured by the thermometer 50 in the first water tank 31 is lower than the set temperature of the mold 1, although not shown in the drawing, the control device controls the piston / cylinder unit 17
To tilt the heat exchanger 12. That is, cylinder 2
Of the heating devices 4, 4,. Therefore, the amount of heat exchange increases and the temperature of water rises. When the temperature is higher than the set temperature, the heat exchanger 12 is driven in the opposite direction. In this way, the inclination angle of the heat exchanger 12 is controlled so that the water temperature becomes the set temperature of the mold 1. Heat exchanger 1
If the set temperature cannot be controlled at the inclination angle of 2, the water temperature is adjusted in the temperature adjusting water tank 32. For example, when the temperature is lower than the set temperature, the heater 40 is energized. The water temperature at this time is measured by the thermometer 36 and the heater 40 is controlled. When the temperature is higher than the set temperature, for example, tap water is supplied from the cooling water supply pipe 39. Excess water is discharged from the overflow pipe 34. As described above, when the set temperature is reached, the molten resin is injected into the mold 1 from the nozzle 3 of the cylinder 2 as described above.

When the mold 1 is replaced, the water in the mold 1 is drained as follows. That is, the second three-way solenoid valve 4
5 is switched, and air is blown from the air supply pipe 70. Then, the air flows to the purge pipe 53 through the discharge pipe 41, the mold 1, the return pipe 43, and the first and second three-way solenoid valves 44 and 45. Therefore, the water in the mold 1 is similarly drained from the branch pipe 59 to the drain 56.

According to this embodiment, various functions can be obtained. For example, the heat exchanger 12 can be tilted away from the heating devices 4, 4, and so that the heat exchanger 12 can also be used as a radiator. That is, when the temperature of the mold 1 is set low, since the atmospheric temperature is lower than the temperature of water as the refrigerant, the heat exchanger 1
2 can also be used as a radiator. When the heat exchanger 12 does not need to be used, the heating device 4 is
4. It is possible to prevent heat radiation. Heat exchanger 1
When 2 is not used, the first solenoid valve 44 is switched to short-circuit the return pipe 43 to the hot water pipe 37. At this time,
The water temperature can be adjusted in the temperature adjusting water tank 32 as in the conventional case.

[0018]

As described above, according to the present invention, the resin inside the injection cylinder is heated by the heating device provided on the outer periphery of the injection cylinder, and the resin is kneaded and melted by the screw and injected into the mold. At this time, heat exchanged between the heat escaping from the heating device to the outside and the heat medium is performed, and the mold is heated by the heat exchanged heat medium, so that the heat can be effectively used. Therefore, unlike the conventional case, heat does not escape from the heating device of the injection cylinder without deteriorating the working environment,
Also, energy for improving the working environment is not particularly required.
According to another aspect of the present invention, since the mold is heated by adjusting the temperature of the heat exchanged heat medium, a high-quality injection-molded product can be obtained in addition to the above-described effects.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Die 2 Cylinder 4, 4 Heating device 12 Heat exchanger 30 Pipe line device 31 First water tank 32 Temperature control water tank 42 Pump 36, 50 Thermometer

Claims (4)

(57) [Claims] A heating device provided in an outer peripheral portion of an injection cylinder heats a resin inside the injection cylinder, kneads and melts the resin with a screw, and injects the resin into a mold. A method for heating a mold in an injection molding machine, comprising exchanging heat between the devices 4 and 4 to the outside and a heat medium, and heating the mold 1 with the heat exchanged heat medium. 2. A method for heating a mold in an injection molding machine, wherein the mold is heated by adjusting the temperature of the heat exchanged heat medium according to claim 1. A heating device (4) is provided on an outer peripheral portion of the injection cylinder (2).
An injection cylinder unit provided with an injection cylinder 4, a mold 1 for molding a molten resin injected from the injection cylinder unit into a predetermined product, and a heat exchanger 12 provided near an outer peripheral portion of the injection cylinder unit. An injection molding apparatus comprising a heat exchanger 12 and a pipeline device 30 connecting the mold 1 to each other. 4. An injection molding apparatus according to claim 3, wherein the pipe device 30 or the heat exchanger 12 is provided with a heat medium temperature adjusting means.