JPH0270406A - Die heating and cooling temperature control device - Google Patents

Abstract

PURPOSE:To stabilize the dimension of a molded product and increase molding yield by controlling a heater installed in a feeding line of heat mediums from a die temperature controller to respective cavities and flow control valves installed in reverse return lines by means of sensors and measuring the temperature of heat mediums installed in an inlet and an outlet of heat medium flow channels of die. CONSTITUTION:The temperature of heat mediums flowing into heat medium channels 16 and 17 of respective cavities 14 and 15 is sensed by temperature sensors 20 and 21 and the temperature medium flowing out is measured by temperature sensors 22 and 23 for the purpose of controlling the flow of heat mediums, and flow control valves 24 and 25 are operated and controlled by the temperature difference of inflow and outflow. In the heating process, the flow control valve 25 of the cavity 15 is microadjusted based on a cavity 14 with small absolute value of heat medium temperature difference as reference as reference in the direction in which the flow gets smaller and the heat medium temperature difference is so controlled as to conform with that of the reference cavity. In the retaining process, the flow control valve 25 of the cavity 15 is micro-adjusted based on the cavity 14 with large absolute value of heat medium temperature difference in the direction in which the flow gets larger and the heat medium temperature difference is so controlled as to conform with that of the reference cavity. Also, control is carried out in the controlling process in a manner same as the heating process.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a heating and cooling temperature control device for gold having a plurality of cavities for plastic molding. The present invention relates to a mold heating/cooling temperature control device suitable for reducing temperature differences between cavities.

[Conventional technology]

In multi-cavity mold molding aimed at improving productivity, uniform mold temperature between cavities is an essential condition for reducing molded product variations.

Furthermore, plastic molded products, such as plastic lenses, have a large thickness ratio between thick and thin parts, and are also required to have high precision and low internal distortion.

Therefore, in the resin filling process, the mold temperature is maintained at a high temperature to reduce the flow resistance of the molten resin.
It is necessary to prevent the occurrence of orientation strain.

Furthermore, in the shaping process, it is necessary to slowly cool the mold temperature to ensure uniform cooling and solidification and to prevent molding distortion.

A conventional mold temperature control device used for heating and cooling includes a high-temperature medium tank and a low-temperature medium tank, as described in, for example, Japanese Unexamined Patent Publication No. 58-215509.

It is composed of each pressure pump and an on-off valve for selecting the heat medium, and by selecting the heat medium,
Controls heating and cooling inside the mold.

In addition, in multi-cavity molding, as a mold structure that equalizes the temperature of each cavity, for example, Japanese Patent Application Laid-Open No. 59-395
As described in Japanese Patent No. 10, there is a device in which the heat medium flow path is connected to form a ladder-like path.

FIG. 7 is an explanatory diagram of a conventional mold heating/cooling temperature control device, in which (α) is a system diagram, 1 is a high temperature tank, 2 is a low temperature tank, and the high temperature tank 1 has a temperature control means. A heater 3, a temperature sensor 4, a pressure pump 5, a supply side on-off valve 6, and a return side on-off valve 7 are provided.
0, a supply side on-off valve 11 and a return side on-off valve 12 are provided.

Inside the mold 13 there are two cavities 14.15,
Heat medium flow paths 16 and 17 are arranged in each case.

Also, 29. ! 10 is an IJ IJ-7 valve for keeping the supply pressure of the heat medium constant; 31, 32, 55, and 34 are reverse valves for controlling the flow direction.

FIG. 6(h) is a conceptual control diagram, in which 26 is a control device, and the heater 3 and cooler 8 are controlled by the outputs of the temperature sensors 4 and 9.
By controlling the heat medium in the high temperature tank 1 and the low temperature tank 2 to a predetermined temperature, the on-off valves 6, 7, 11.12 and the flow rate control valve 24.2 are activated in synchronization with the operation of the molding machine 27.
5 is controlled.

[Problem to be solved by the invention]

The above conventional technology does not take into consideration the temperature difference between cavities during heating and cooling of the mold.
The molded product dimensions varied between cavities, and the yield of molded products decreased significantly.

In order to prevent the temperature difference between the cavities, it is effective to measure and control the flow rate and temperature of the heat medium flowing through the passages provided in each cavity.

However, a device for measuring the flow rate of a heat medium at a high temperature, for example, 200° C. or higher, is very expensive and cannot measure and control the flow rate of many cavities.

SUMMARY OF THE INVENTION An object of the present invention is to provide a mold heating/cooling temperature control device for plastic molding which can be molded with high efficiency and at low cost by molding a large number of plastic lenses with excellent optical performance.

[Means to solve the problem]

The above purpose is to control the flow rate control valve provided in the supply path of the heat medium from the mold temperature controller to each cavity or the return path from each cavity to the mold temperature controller, and the heater provided in the supply path.
This is achieved by controlling the temperature of the heat medium provided at the inlet and outlet of the heat medium flow path of the mold using sensors that measure the temperature of the heat medium.

[Effect]

The present invention focuses on the temperature and flow rate of the heat medium flowing into each cavity of a mold, and particularly the flow rate of the heat medium flowing through each cavity and the temperature difference between the inlet and outlet sides of each cavity. This is what I focused on.

The fine adjustment heater on the inlet side of the heat medium flow path of each cavity is controlled by the output of the temperature sensor on the inlet side and is driven to match the temperature of the heat medium flowing into the cavity.

In addition, the flow rate control valve provided for each cavity is controlled by the output of the temperature sensor on the outlet side of the heat medium flow path of each cavity, and is controlled by the output of the temperature sensor on the outlet side of the inlet side and the outlet side. Driven to match outputs.

As a result of the above, it is possible to match the temperature and flow rate of the heat medium flowing into the heat medium flow path of each cavity.

Thereby, the temperature of each cavity becomes the same, it is possible to prevent variations in the dimensions of the molded product between the cavities, and to improve the yield of the molded product.

〔Example〕

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

FIG. 1 is an explanatory diagram of an embodiment of the mold heating/cooling temperature control device according to the present invention, and the same reference numerals as in FIG. 7 indicate the same parts.

Figure (α) is a system diagram, in which each heat medium flow path 16°1
7 is provided with fine adjustment heaters 1B, 19 and temperature sensors 20, 21 on the inlet side, and temperature sensors 22, 23 on the outlet side.

FIG. 2(b) is a conceptual control diagram, in which 26 is a control device, and the heater 3 and cooler 8 are controlled by the outputs of the temperature sensors 4 and 9.
The heat medium in the high temperature tank 1 and the low temperature tank 2 is controlled to a predetermined temperature by controlling the temperature sensors 20 and 21.
The heaters 18 and 19 are controlled by the output of the temperature sensor 22.
, 23 controls the flow rate control valves 24, 25,
In synchronization with the operation of the molding machine 27, the on-off valves 6, 7°11.12
and controls the flow rate control valves 24 and 25.

Here, the operation shown in FIG. 1 to obtain the mold temperature pattern as shown in FIG. 2 will be described below.

FIG. 2 is an explanatory diagram of the mold temperature change pattern with respect to time and the operation of each on-off valve and flow rate control valve, and 28 is, for example, the temperature of the cavity 14.

The mold temperature pattern is during the time interval α, from temperature T to rt
t, and during a time interval, the temperature T! It is then set to be cooled from temperature T to T during a time interval C, and then held at temperature T during a time interval d.

Therefore, the temperature of the heat medium in the high temperature tank 1 is set to T! The temperature of the heat medium in the low temperature tank 2 is set and controlled by the control device 26 to a temperature that is sufficiently high compared to T, and the temperature of the heat medium in the low temperature tank 2 is set to a temperature that is sufficiently low compared to T.

Here, for the time interval α, the on-off valve 6.7 is opened, the on-off valve 11.12 is closed, the flow rate control valve 24.25 is set to a large flow rate,
A large amount of the heat medium in the high temperature tank is flowed into the heat medium flow paths 16 and 17 to heat the cavities 14 and 15.

Next, during the time interval, the on-off valves 6, 7, 11.12 are the same as in the time interval α, and the flow rate control valve 24.25 is set to a small flow rate, so that the temperature of the cavity 14.15 is maintained at T.

to hold. Next, during the time interval C, the on-off valves 6. 1
6g 17 and cool the cavity 14.15.

Next, the fine adjustment heaters 18, 19 and the flow control valve 24 are used to reduce temperature variations between cavities, which is an object of the present invention.
, 25, the operation of the temperature sensor 20.21.22.25 will be explained.

Here, when the temperature is controlled by a conventional mold thermal cooling temperature control device as shown in FIG. A difference δ in mold temperature occurs. Here, 28°28' is, for example, the temperature of the cavity 14.15. The cause of these differences is the heating medium flow path 1 (S, 17
It is the difference between the temperature and flow rate of the heat medium flowing into the

Here, in order to control the temperature of the heat medium flowing in, the temperature of the heat medium flowing into the heat medium flow path 1 (S, 17) of each cavity 14, 15 is measured by the temperature sensors 20, 21, and the fine adjustment heaters 18, 19 The structure was designed to drive and control the

In this embodiment, in each of the heating, holding, and cooling steps, the lower inflow heat medium temperature, for example, the output of the temperature sensor 20, is determined as the reference temperature, and the cavity on the reference temperature side,
For example, the output of the fine adjustment heater 18 on the 14th side is zero, and the output of other cavities, such as the fine adjustment heater 19 on the 15th side, is controlled in proportion to the difference in inflow heat medium temperature from the reference temperature, such as the output of the temperature sensor 21.

FIG. 4 shows the temperature difference from this reference temperature and the fine adjustment heater output. As another control method, as shown in the figures in parentheses in Figure 4, the cavity serving as the reference temperature is kept constant, the output of the fine adjustment heater of this cavity is set to 50% of the rated output, and the fine adjustment of other cavities is set to 50% of the rated output. There is a method of making the output of the heater proportional to the difference from this reference temperature.

Next, each cavity 14 is used to control the flow rate of the heating medium.
．． The temperature of the heat medium flowing into the heat medium flow paths 16 and 15 of No. 15 is measured by temperature sensors 20 and 21, and the temperature of the heat medium flowing out is measured by temperature sensors 22 and 23, and the flow rate is controlled based on the temperature difference between the inflow and outflow. The structure is such that the valves 24 and 25 are driven and controlled.

Here, FIG. 5 shows the relationship between the temperature difference of the heat medium between the inlet and the outlet and the flow rate of the heat medium. The temperature difference is based on the inlet side heat medium, 57 is the cooler, and 38 is during heating and holding.

Therefore, in the heating process, the flow rate control valve 25 of other cavities, such as 15, is finely adjusted in the direction of decreasing the flow rate, using the cavity with a small absolute value of the heat medium temperature difference, for example, 14, as a reference, and Control to match the cavity.

In the holding step, the cavity with a large absolute value of the heat medium temperature difference, for example 14, is used as a reference, and the flow rate control valve 25 of other cavities, for example 15, is finely adjusted in the direction of increasing the flow rate, so that the heat medium temperature is set to the reference cavity. Control to match.

In addition, in the cooling process, the cavity with a small absolute value of the heat medium temperature difference, for example 14, is used as a reference, and the flow rate control valve 25 of the other cavities, for example 15, is finely adjusted in the direction of decreasing the flow rate to reduce the heat medium temperature difference. Control to match the reference cavity.

In the above example, the heating and cooling processes are performed on the high flow rate side, and the holding process is performed on the low flow rate side, at both ends of the control range of the flow rate control valve.

However, if there is sufficient margin in the control range of the flow control valve, the absolute value of the heat medium temperature difference in a certain cavity is used as the standard, and if the absolute value of the heat medium temperature difference in other cavities is larger than the standard, the flow rate is If it is small, the flow rate may be increased and the heat medium temperature difference may be controlled to match that of the reference cavity.

In addition, if the temperature of the heat medium flowing into each cavity 14, 15 is the same by controlling the fine adjustment heaters 18, 19, in order to finely adjust the flow rate control valves 24, 25, the temperature difference of the heat medium at the inlet and outlet is adjusted. The outlet side heat medium temperature may be used instead of .

In this example, the temperature of the high-temperature tank and the low-temperature tank was set to 195°C and 50°C, respectively.1 The maximum flow rate in each cavity was 2.
j/min, maximum residual dust temperature 170°C, minimum temperature 80°C, conventional heating rate δ1#2°C/min, mold temperature δ
By using the mold heating/cooling temperature control device according to the present invention, the temperature that had been generated at β1.5°C was changed to δ, #0.5°C.
, δ! #CL The temperature could be set at 5°C. the result,
The conventional molded product size variation between cavities of 10μm has been reduced to 3μm.
It was possible to reduce the thickness to less than the corner, thereby improving the molding yield.

FIG. 6 is an explanatory diagram of another embodiment of the mold heating/cooling temperature control device according to the present invention, (α) is a system diagram, (h) is a control conceptual diagram, and the same symbols as in FIG. 1 are have the same functionality,
Reference numeral 35 in the same figure ( ) is a storage unit, which stores the outputs of a certain specific cavity, for example, the 14 temperature sensors 20 and 22, or the average value of the outputs among the cavities for one cycle;
And it has a structure that can output this in synchronization with the cycle.

In the same figure (α), in the initial stage, the fine adjustment heaters 18, 19 and the flow rate control valves 24, 25 are controlled by the temperature sensors 20, 21, 22, 23 between each cavity, as in the first embodiment. Control is performed to reduce the difference in inflow temperature and the difference in outflow temperature.

Therefore, when the desired residual dust temperature pattern is obtained and the temperature difference between the cavities is sufficiently small, an external signal is input and a specific cavity for one cycle, for example, 14 temperature sensors 20, 22 , or the average value of the outputs between the cavities, that is, the average of the outputs of temperature sensors 20 and 21 and the average of the outputs of temperature sensors 22 and 23.
) is stored in the storage device 35.

In the next cycle, the output of the temperature sensor stored in the storage device 35 is outputted again in synchronization with the cycle, and this is used as the reference value of the temperature sensors 20, 21, 22, and 23.
Drive control of fine adjustment heaters 18, 19 and flow rate control valves 24,25. As a result, it is possible to reduce variations in temperature between cavities and between cavities, reduce variations in temperature between cavities, reduce variations in molded product dimensions, and improve molding yield.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to reduce the difference in heating/cooling rate and gold grave temperature between a large number of cavities without the need for equipment such as an expensive flow meter, and the molded product in each cavity can be reduced. Dimensional stability is increased, molding yield is improved, and it is possible to provide a mold heating/cooling temperature control device with excellent functions while eliminating the drawbacks of the above-mentioned prior art.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of an embodiment of the mold heating/cooling temperature control device according to the present invention, Fig. 2 is an explanatory diagram of the mold temperature change pattern with respect to time and the operation of each on-off valve and flow rate control valve, and Fig. 5 is an explanatory diagram of the mold temperature pattern, Fig. 4 is an explanatory diagram of the relationship between the temperature difference from the reference temperature and the fine adjustment heater output, and Fig. 5 is an explanatory diagram of the relationship between the heat medium temperature difference between the inlet and outlet and the heat medium flow rate. , FIG. 6 is an explanatory diagram of another embodiment of the mold heating/cooling temperature control device according to the present invention, and FIG. 7 is an explanatory diagram of a conventional mold heating/cooling temperature control device. 1・・・・・・・・・・・・・・・・・・・・・・・・
・・・High temperature tank 2・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・Cold tank 6.7.11.12
・・・・・・Opening/closing valve 13・・・・・・・・・・・・・・・
・・・・・・・・・Mold 14.15 ・・・・・・・・・
・・・・・・Cavity 16.17・・・・・・
...Heat medium flow path 18.19 ......
......Fine adjustment heater 20.21.22.23
・・・Temperature sensor 24.25・・・・・・・・・・・・
・・・Flow rate control valve 35・・・・・・・・・・・・・・・
・・・・・・・・・Memory part 1 Takaj Utashiku 1415
Goyagoti 2021 Temperature difference in temperature 1613 Mold 1613 Heater 2425 Flow rate measurement J#p valve 1 Figure 2 Figure 5 Figure 4 (O) Consideration I7 Temperature difference A' C) (+1) Punishment 5 figure 8th and exit? Temperature difference between 4 Kunu (C) 1,600 figures Cb)

Claims (1)

[Claims] 1. A plurality of heat medium tanks for selectively supplying heat medium set at a plurality of temperatures to a molding die, a heat medium temperature adjustment means, a pressure pump, and a heat medium. In a mold heating/cooling temperature control device consisting of a selective supply on/off valve, independent heat medium flow paths are arranged in multiple cavities, and a fine adjustment heater and a temperature sensor are installed on the inlet side of the heat medium flow path, and on the outlet side of the heat medium flow path. A temperature sensor is installed on the side, and a flow control valve is installed on the inlet side or the outlet side, and the difference between the output of the inlet side sensor and the output of the outlet side sensor, or the difference between the output of the outlet side and the inlet side sensor is the same between each cavity. A mold heating/cooling temperature control device comprising a control device for driving the fine adjustment heater and the flow rate control valve. 2. In claim 1, the fine adjustment heater and the flow rate control valve are driven so that the difference between the output of the inlet side sensor and the output of the outlet side sensor, or the output of the outlet side and inlet side sensor, matches a set value. A mold heating/cooling temperature control device comprising a control device. 3. In claim 1, the output of the inlet side sensor and the outlet side sensor during one cycle is stored, and this output value is used as a set value, and in subsequent cycles, the output of the inlet side sensor and the output of the outlet side sensor, Or a mold heating and cooling temperature control device, comprising a control device that drives the fine adjustment heater and the flow rate control valve so that the difference between the outputs of the sensors on the outlet side and the inlet side matches the set value. . 4. The mold heating/cooling temperature control device according to claim 1, 2 or 3, further comprising a control device for synchronizing the operation of the on-off valve and the operation of the molding machine.