JPH07104868A - Temperature adjusting device for injection molding metal die - Google Patents

Abstract

PURPOSE:To perform stable temperature control without any changed, operation of a control parameter even when a metal die is exchanged. CONSTITUTION:This temperature adjusting device is provided with a preprocessing means 10 for preparing the fuzzy input parameters of temperature difference from a set temperature and a temperature change gradient while fetching the detect signal of a temperature sensor 7, processing mode judging means 12 for commanding switching from a fuzzy control mode to a shift processing mode when the temperature difference is within a prescribed value and the temperature change gradient is larger than the prescribed value toward the set temperature, fuzzy inference means 13 for inferring the degree of adjustment to increase/decrease the temperature corresponding to the fuzzy input parameters, and driving control means 14 for turning heater electric power to zero at the time of the shift processing mode, for circulating cold water in the state of closing a direction valve 5, for enlarging the heater electric power corresponding to the degree of adjustment in the state of closing the direction valve 5 when increasing the temperature at the time of the fuzzy control mode on the other hand and for enlarging the aperture of the direction valve 5 corresponding to the degree of adjustment by turning the heater electric power to zero when decreasing the temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a mold with a temperature sensor built in to penetrate a pipe circulating in a cold water tank, and a pump and a heater provided on a mold side pipe of a directional valve in the middle. In response to the temperature detected by the temperature sensor, the cold water may be mixed and circulated from the cold water tank according to the opening degree of the directional valve, or the cold water tank may be bypassed and the cold water may be heated and circulated by the heater when the directional valve is closed. The present invention relates to a temperature adjusting device for an injection molding die that has been developed as described above.

[0002]

2. Description of the Related Art In the temperature control of an injection molding die, when its shape becomes large, the thermal resistance and the heat capacity also become large, and when performing servo control based on a deviation from a set temperature of a temperature sensor incorporated in the die. In order to prevent overshoot or hunting, PID control is performed with parameters peculiar to the normally used mold.

[0003]

However, in such a PID control, when the mold is replaced, especially when the mold is large, the thermal characteristics of the mold largely change, and the shape change causes the mold surface and the temperature sensor to change. Since the thermal characteristics between the built-in positions may be different, there is a problem that overshoot and hunting occur, or conversely, the rising characteristics at the start of molding are poor and offset occurs. Therefore, it is necessary to change the PID parameter when exchanging the mold.

In view of the above, the present invention provides a temperature adjusting device for an injection molding die which can guarantee stable temperature control without changing the control parameters even if the die is replaced. With the goal.

[0005]

In order to achieve this object, the present invention has a temperature sensor built in an injection mold and a water supply pipe circulating in a cold water tank. By connecting a directional valve and installing a pump and heater on the water supply pipe on the injection mold side of this directional valve, in response to the temperature detected by the temperature sensor, the opening degree of the directional valve is controlled to cool water from the cold water tank. The cold water whose mixing ratio is controlled by the pump and the cold water that has been heated by passing through the water supply pipe in the mold, and the cold water can be heated by the heater and circulated by the pump when the directional valve is closed. In the temperature control device for the injection molding die, the detection signal of the temperature sensor is captured at a time interval that is sufficiently smaller than the operating cycle of the injection molding die, and the temperature difference from the set temperature and the temperature change gradient fuzzy When the temperature difference is within a predetermined value and the temperature change gradient is a predetermined value or more toward the set temperature, the temperature adjustment mode is switched from the fuzzy control mode to the shift processing mode. Processing mode determining means for performing, fuzzy inference means for fuzzy inferring the degree of temperature adjustment whether the temperature is raised or lowered with respect to the fuzzy input variable at each of the time intervals, the heater power is set to zero in the shift processing mode, and When chilled water is circulated by the pump with the directional valve closed, and when the temperature is raised in the fuzzy control mode, the heater power is increased by a sufficiently small amount relative to the maximum power with the directional valve closed according to the adjustment degree. However, when lowering the temperature, the heater power is set to zero and the opening degree of the directional valve is increased by a sufficiently small amount relative to the fully open state according to the adjustment degree. Characterized in that a control means.

[0006]

The preprocessing means fetches the detection signal of the temperature sensor at predetermined time intervals and sequentially outputs the fuzzy input variables of the temperature difference from the set temperature and the temperature change gradient. The processing mode determination means takes in a fuzzy input variable and determines whether to operate in the shift processing mode of only water circulation in which the cold water tank is bypassed to the drive control means or in the fuzzy control mode. In the fuzzy control mode, the fuzzy inference means infers the adjustment degree of the temperature rise and fall according to the fuzzy input variable, and when the temperature is raised with respect to the drive control means, the heater power is supplied according to the adjustment degree with the directional valve closed. When the temperature is lowered, the heater power is set to zero and the heater power is set to zero, and the opening degree of the directional valve is increased slightly to the fully open state according to the adjustment degree.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the construction of a temperature adjusting device for an injection mold according to an embodiment of the present invention. In the figure, 1, 1
a is a pair of molds of several tens of tons into which an injection molding material of, for example, about 200 ° C. is injected, and is opened and closed in a cycle of about 100 seconds to perform injection molding. In these molds, water supply pipes 9 and 9a are respectively arranged for raising and lowering the temperature thereof, and the same temperature adjusting device is attached thereto, respectively, and only the mold 1 side will be described below.

The water supply pipe 9 is connected to an inlet / outlet port of the cold water tank 2 whose temperature is controlled at, for example, about 15 ° C. to form a circulation path for circulating cold water. Along the way, a branch pipe 9b is connected, and the cold water from the cold water tank 2 and the cold water from the branch pipe 9b absorbing the heat generated in the mold 1 are passed through a directional valve 5 whose opening degree is controlled by a motor. The bypass passage is configured so that the waste heat of the mold 1 can be used for mixing and heating the cold water. A heater 3 whose drive power for heating cold water is variably controlled and a pump 4 which circulates the cold water are mounted in the bypass passage. A temperature sensor 7 is built in the mold 1 20 mm deep from the surface. Then, with the configuration described below, this temperature sensor is controlled so as to detect a set temperature of 42 ° C., for example.

Reference numeral 10 captures a detection signal of the temperature sensor 7 through the interface section 11 at intervals of 2 seconds to set a temperature of 4
It is a preprocessing means for generating a fuzzy input variable by detecting a temperature difference from 2 ° C. and a temperature change gradient. Reference numeral 12 is a processing mode determination means for determining whether to operate in the shift processing mode (only the circulation without cooling and heating) or the fuzzy control mode according to the temperature difference / temperature change gradient and the current control amount. 13 is the membership function of the antecedent part and the consequent part and if / then for the fuzzy input variable.
Based on the fuzzy rule of the type, the opening degree of the directional valve 5 is widened by what percentage of the fully open state with the electric power of the heater 3 being zero, or the heater electric power of the maximum electric power when the directional valve 5 is closed. It is a fuzzy inference means that fuzzy infers the degree of adjustment of temperature rise and fall relative to the current state, depending on whether it is increased.
Reference numeral 14 denotes a drive control means, which is supplied with the shift processing mode signal and the adjustment degree data through the interface portion 11 to set the drive power of the heater 3 to zero in the shift processing mode, and close the directional valve 5 fully to only the pump 4. In the fuzzy control mode, the electric power of the heater 3 when the directional valve 5 is fully closed or the opening degree of the directional valve 5 when the heater power is zero is adjusted based on the adjustment degree data.

2, the processing mode judging means 12 has a temperature difference region 12a of ± 0.2 ° C. and + 3 ° C. and −3 ° C.
Within the temperature deviation within 2 ° C, the detected temperature change gradient corresponds to the temperature control direction with a predetermined magnitude -1 ° C / s and +
The areas 12b and 12c (shown by hatching) of 0.6 ° C./s or more are determined as the shift processing mode, and the remaining areas are determined as the fuzzy control area. In the area 12a, considering the control processing time and the equipment operation time, the control is not intentionally performed within the adjustment error range. In the regions 12b and 12c, when the measured value is moving in the direction of the set temperature near the set temperature, if the control amount further heading in the same direction remains, the thermal characteristics of the mold 1 cause a time delay and the target Since there is a possibility of penetrating the value, the control amount is advanced to the state of only water circulation so as to naturally go to the target value, and the control amount in the opposite direction is output from there. In the area 12c, the device is primarily intended for cooling, and the heater 3 has an auxiliary function of performing temperature control with high accuracy, and the temperature range is narrowed corresponding to the increase in cooling capacity.

The fuzzy inference means 13 uses if shown in FIG.
Memory 13 for storing fuzzy rules in / then format
a, a memory 13b for storing the membership function shown in FIG. 4 as its antecedent, a memory 13c for storing the membership function shown in FIG. 5 as its antecedent, and an arithmetic unit 13d. .

This arithmetic unit detects the degree of membership of the membership function for the temperature difference and the membership function for the temperature change gradient shown in FIGS. 4A and 4B. In FIG. 4A,
SA means low temperature, SM means a little low, MM means a set temperature, ML means a little high, LA means high. Figure 4B
In the SA, the temperature change gradient decreases corresponding to SA, SM
Means a slight decrease, MM means no change, ML means a slight increase, and LA means an increase. Then, the degree of membership of the membership function of the consequent part is detected according to the fuzzy rules shown in FIG. 3 for the fuzzy input variables of the temperature difference and the temperature change gradient. Here, PB greatly raises the water flow temperature, PM raises,
PS means a little increase, ZE does not change, NB greatly decreases, NM lowers, NS means a little lower. Finally, the center of gravity of the output composition function derived in accordance with the membership degree of the membership function shown in FIG. 5 is calculated, and the percentage of the maximum power of the heater 3 to be increased or the maximum opening degree of the directional valve 5 is widened. The velocity type control data, which is the percentage of the opening degree to be output, is output as the adjustment degree data. The% value is 10% at maximum for the heater power and 8% for the opening degree, which is relatively slightly smaller in view of the large cooling capacity. The fuzzy inference means 13 is provided with a pre-processing means 10 and a processing mode judging means 12 and a C such as a memory.
It is configured using PU. The operation of the temperature adjusting device for the injection molding die thus configured is as follows.

As a fuzzy input variable, a temperature difference of, for example, + 0.3 ° C. as shown by a dotted line A in FIG. 4A and a temperature change gradient of + 0.17 ° C./sec as shown by a dotted line B in FIG. 4B are detected. Then, the fuzzy inference means 13 determines that the degree of belonging to ML is 0.5 for the temperature difference,
It is determined that the degree of belonging to MM is 0.2, the degree of belonging to ML is 0.3, and the degree of belonging to LA is 0.7 for the temperature change gradient. Next, the internal inference shown by a black frame in FIG. 3 is performed, and the degree of belonging is determined according to the well-known and / or rule.

Next, with respect to the membership functions of FIG. 5, for the membership degrees 0.2 and 0.3 with respect to the common NM, the larger membership degree 0.3 is adopted according to the and / or rule, and the bold line is used. The combined center of gravity of the triangles truncated by the corresponding three belonging degrees is calculated to obtain the adjustment degree data of the opening degree of 4.5% indicated by the dotted line C. As a result, the drive control means 14 sets the electric power of the heater 3 to zero and opens the directional valve 5 wider than the present condition by an opening degree of 4.5% of the fully opened state, thereby increasing the mixing degree of cold water. After 2 seconds, when the adjustment degree data of the opening degree of 4.5% is obtained again, it is widened by 4.5% of the fully open state.

FIG. 6 illustrates the case where different temperature control states are reached. In FIG. 6A, the temperature deviation of the circle D is ≧ −2 when the heater 3 is heating by fuzzy control.
When reaching the shift processing region where the temperature gradient of ° C is ≥ +1 ° C / sec, both cooling and heating are interrupted (shown in the control state of 50% in the figure). This avoids the possibility of causing a delay due to the thermal time constant of the mold 1 and causing overshoot (indicated by the dotted line in the figure) due to the immediately preceding heating. And
As shown by the solid line in the figure, the shift processing in the circle D region moves toward the set temperature without performing extra heating.
When the temperature approaches the set temperature, the temperature is slightly cooled, and the temperature gradually approaches the set temperature. The dotted line in the figure is based on the assumption that the shift process is not performed.

In FIG. 6B, the temperature deviation of the circle E is ≤ + 3 ° C.,
When the temperature gradient reaches the shift treatment area of ≤-0.8 ° C / sec, only water circulation is performed in the same manner, and in the + temperature area close to the set temperature, fuzzy control reversely slightly heats to suppress overshoot. To approach the set temperature.

In this way, the maximum adjustment degree is made sufficiently small with respect to the maximum opening degree of the directional valve and the maximum electric power of the heater, and the fuzzy control and shift in small steps at a time interval sufficiently smaller than the operation cycle of the mold. In combination with processing, and in the range close to the set temperature, fuzzy reasoning adjusts the temperature in the opposite direction depending on the temperature change gradient, thereby performing highly accurate temperature adjustment for injection molds with different thermal characteristics. .

[0018]

As described above, according to the present invention, the fuzzy control type, which is a small step with respect to the current state, is added in consideration of human experience based on the information on the temperature difference of the mold and the temperature change gradient with respect to the set value. By performing the temperature adjustment and the interruption thereof, it becomes possible to realize the temperature adjusting device for the injection molding die which does not require the adjustment of the control parameters for various dies having different thermal characteristics.
The device can be constructed inexpensively as compared with the PID control type.

The maximum adjustment degree is smaller than about 10% with respect to the maximum opening degree of the directional valve and the maximum electric power of the heater,
By performing temperature adjustment at a time interval of several% of the operating cycle of the mold, small-step fuzzy control is performed, and the response delay to a large change is complemented by a shift process in advance so that injection molding with different thermal characteristics can be performed. Highly accurate temperature adjustment is possible for the mold.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a temperature adjusting device for an injection molding die according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an operation mode of the device.

FIG. 3 is a diagram showing a fuzzy rule.

FIG. 4 shows a membership function of an antecedent part of fuzzy inference, where A in FIG. 4 is for a temperature difference and B in FIG. 4 is for a temperature change gradient.

FIG. 5 is a diagram showing a membership function of a consequent part of fuzzy inference.

FIG. 6 is a diagram illustrating the operation of the same device.

[Explanation of symbols]

 1 Mold 2 Cold Water Tank 3 Heater 4 Pump 5 Directional Valve 7 Temperature Sensor 9 Water Supply Pipe

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Yoruna Suzuki, Nobunta, Tauraminato-cho, Yokosuka City, Kanagawa Kanto Automobile Industry Co., Ltd. (72) Inventor, Tetsuichi Mineo 1-6-14-406, Shiki City, Saitama (72) Inventor Seiichi Shibuya 2-15-20 Gotenyama, Musashino City, Tokyo

Claims (2)

[Claims] 1. A water supply pipe circulating a cold water tank with a temperature sensor built into an injection mold, and a directional valve connected in the middle of the water supply pipe to supply water to the injection mold side of the directional valve. By installing a pump and heater in the pipe, in response to the temperature detected by the temperature sensor, the opening degree of the directional valve is controlled to cool the cold water from the cold water tank and the cold water heated through the water supply pipe in the mold. In the temperature control device of the injection mold, which allows circulating cold water whose mixing ratio is controlled by a pump, and which allows the cold water to be heated by a heater and circulated by the pump when the directional valve is closed. The signal is taken in at a time interval sufficiently smaller than the operation cycle of the injection mold, and pre-processing means for creating a fuzzy input variable of the temperature difference from the set temperature and the temperature change gradient, and the temperature difference is a predetermined value or more. When the temperature change gradient is equal to or higher than a predetermined value toward the set temperature, the processing mode determination means for issuing a command to switch the temperature adjustment mode from the fuzzy control mode to the shift processing mode, and the temperature for the fuzzy input variable are set. Fuzzy inference means for fuzzy inferring the degree of temperature adjustment to increase or decrease for each of the time intervals;
In the shift processing mode, the heater power is set to zero and the chilled water is circulated by the pump with the directional valve closed. On the other hand, when the temperature is increased in the fuzzy control mode, the directional valve is closed according to the adjustment degree. The heater power is increased by a sufficiently small amount with respect to the maximum power, and when the temperature is lowered, the heater power is set to zero and the opening degree of the directional valve is set to a sufficiently small amount with respect to the fully opened state according to the adjustment degree. And a drive control unit for increasing the size of the injection molding die. 2. The degree of adjustment is inferred as a% value smaller than about 10% with respect to the maximum opening degree of the directional valve and the maximum electric power of the heater, and the preprocessing means outputs the detection signal of the temperature sensor to the number of operating cycles of the mold. % Is taken in every time interval.
Temperature control device for injection molding dies.