JPH05250047A - Metal die temperature adjusting device for injection molding machine - Google Patents

Abstract

PURPOSE:To reduce the effect of disturbance such as a temperature change or the like by sampling the detection temperature of a metal die just before injection synchronously with an injection molding cycle and controlling the sampled detection temperature so as to coincide with a target value. CONSTITUTION:The controller of an injection molding machine 11 outputs an injection timing signal at the timing just before the injection molding machine 11 injects molten resin to a metal die 12. In response to this injection timing signal, deviation between the detection temperature of the metal die 12 and a target temperature is sampled by a controller 15 while using a sampler 30, and PID operation is executed by a PID controller 31. When the deviation is a positive value, a signal is sent from the PID controller 31 to a pulse width modulator 32 for controlling the open/close operation of a magnetoelectric switch 22. When the deviation is a negative value, the PID controller 31 sends a signal to a pulse width modulator 33 for controlling the opening/closing operation of a cooling water control valve 25. Thus, temperature control can be exactly performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold temperature adjusting device for adjusting the temperature of a mold by controlling the temperature of a refrigerant flowing in the mold of an injection molding machine.

[0002]

2. Description of the Related Art As is well known, an injection molding machine has an injection process of injecting (injecting) a molten resin into a mold, a holding pressure cooling process of cooling and fixing the resin in the mold, and The injection molding cycle consisting of a mold opening process for opening the mold to take out the molded product and a mold closing process for closing the mold is repeated. Therefore,
The mold temperature fluctuates periodically in synchronization with the injection molding cycle. It is difficult to directly control the cyclically changing mold temperature with a general temperature controller.

Therefore, the conventional mold temperature adjusting device indirectly controls the temperature of the mold by keeping the temperature of the refrigerant flowing into the mold constant.

[0004]

However, in the conventional mold temperature adjusting device, when the injection molding machine performs the injection molding for a long time, the mold is affected by the disturbance such as the fluctuation of the temperature around the mold. The temperature also fluctuates. Therefore, there is a disadvantage that the weight of the molded product varies as a result.

On the other hand, the applicant of the present application has already proposed a mold temperature adjusting device for adjusting the mold temperature based on the detected temperature of the molten resin and the detected temperature of the mold (Japanese Patent Laid-Open No. 1-14).
1023 gazette). In this proposed mold temperature adjusting device, the fluctuation of the mold temperature is predicted and sequentially compensated for,
It is possible to perform more precise control than a general temperature controller.

However, the proposed mold temperature adjusting device has a drawback that the structure is complicated.

In both of the proposed mold temperature adjusting device and the general temperature adjusting device, the adjusting unit for generating the control signal has the target temperature set by the setting device and the detection detected by the temperature sensor. A continuous deviation from the temperature is supplied, and the control unit generates the control signal based on this continuous deviation.

Therefore, an object of the present invention is to provide a mold temperature adjusting device for an injection molding machine which can reduce the weight variation of molded products.

[0009]

A mold temperature adjusting apparatus for an injection molding machine according to the present invention is an apparatus for adjusting the temperature of a mold by controlling the temperature of a refrigerant flowing in the mold of the injection molding machine. Is based on the temperature sensor that detects the mold temperature, the setter that sets the target temperature of the mold, and the deviation between the target temperature set by this setter and the detected temperature detected by the temperature sensor. It has a control unit that generates a control signal and an operation unit that performs a temperature rising / cooling operation of the refrigerant in response to the control signal.

In the mold temperature adjusting apparatus according to the present invention, the control unit samples the deviation in response to the timing signal immediately before the injection of the resin from the injection molding machine into the mold, and outputs the sampled deviation. Sampling means,
In response to the sampled deviation, the control unit generates a signal as a control signal such that the mold temperature at the sampling point in the injection molding cycle of the next injection molding machine becomes the target temperature. And

In the mold temperature adjusting apparatus, it is preferable that the adjusting section generate a pulse width modulation signal as a control signal.

[0012]

[Function] In order to reduce the variation in the weight of molded products,
It is necessary that the temperature of the mold when the molten resin is injected into the mold be constant for each injection molding cycle.

Therefore, in the present invention, the detected temperature (deviation between the detected temperature and the target temperature) of the mold immediately before injection is sampled in synchronization with the injection molding cycle, and the sampled mold temperature (deviation) is The temperature is controlled to reach the target temperature (zero).

[0014]

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

Referring to FIG. 1, a mold temperature adjusting apparatus 10 according to an embodiment of the present invention includes a mold 12 of an injection molding machine 11.
It is a device that adjusts the temperature of the mold 12 by controlling the temperature of the refrigerant flowing therein.

The mold temperature adjusting device 10 includes a temperature sensor 13
, A digital switch 14, a controller 15, and an operation unit as described later.

The temperature sensor 13 is for detecting the temperature of the mold 12, and is installed in the mold 12 near the resin reservoir. The temperature sensor 13 is, for example, a thermocouple. The mold temperature detected by the temperature sensor (thermocouple) 13 is supplied to the controller 15 as a detected temperature via the amplifier 16.

The digital switch 14 is a setting device for setting the target temperature of the mold 12. The target temperature set by the digital switch 14 is supplied to the controller 15.

The controller 15 generates a control signal based on the deviation between the target temperature and the detected temperature. Here, the control signal includes a first control signal and a second control signal. The operation unit performs the temperature rising / cooling operation of the refrigerant in response to the control signal as described later.

The operating portion is a coolant tank 17 for storing a coolant, and a pipe 1 for allowing the coolant to flow through the die 12 along the arrow in FIG.
8 and a pump 19 for constantly sending the refrigerant from the refrigerant tank 17 into the pipe 18. Therefore, the refrigerant in the refrigerant tank 17 is guided to the mold 12 through the pipe 18, undergoes heat exchange there, and then circulates so as to return to the refrigerant tank 17 again. The operation unit further includes a heating unit (described later) for heating the refrigerant and a cooling unit (described later) for cooling the refrigerant.

The heating section includes a heater 20 provided in the refrigerant tank 17, an AC power supply 21 for supplying electric power to the heater 20, and an electromagnetic switch 22 for turning on / off the electric power supply to the heater 20. , With. The opening / closing of the electromagnetic switch 22 is controlled by a first control signal from the controller 15.

On the other hand, the cooling unit is a heat exchanger 23 provided in a pipe 18 for returning the refrigerant from the mold 12 into the refrigerant tank 17.
A water faucet 24 which is a cooling water supply source for supplying cooling water such as tap water to the heat exchanger 23;
And a cooling water opening / closing valve 25 for adjusting the amount of cooling water to be flowed to. The opening / closing of the cooling water opening / closing valve 25 is controlled by a second control signal from the controller 15.

An injection timing signal, which will be described later, is supplied to the controller 15 from a control device (not shown) of the injection molding machine 11. The injection timing signal is output immediately before the injection molding machine 11 injects the molten resin into the mold 12. As will be described in detail later, the controller 1
In response to this injection timing signal, 5 samples the detected temperature of the mold (deviation between the detected temperature and the target temperature), and the sampled mold temperature (deviation) becomes the target temperature (zero). By sending such a control signal to the electromagnetic switch 22 or the cooling water opening / closing valve 25, the temperature of the refrigerant is raised / cooled.

The configuration of the controller 15 will be described with reference to FIG. FIG. 2 shows a portion surrounded by a broken line in FIG. 1, that is, the digital switch 14 and the controller 1.
5 and the amplifier 16 are shown. The portion surrounded by the solid line in FIG. 2 may be configured by a microcomputer or the like.

The controller 15 includes an analog / digital converter (A / D) 26, first and second data input sections (D / I) 27 and 28, a subtractor 29, a sampler 30, and a later-described sampler 30. And an adjusting unit.

The analog / digital converter 26 converts the mold detection temperature amplified by the amplifier 16 into a digital detection temperature signal. The first data input unit 27 outputs a sampling signal in response to the injection timing signal supplied from the injection molding machine 11 (FIG. 1). The second data input unit 28 takes in the mold target temperature set by the digital switch 14 as a digital target temperature signal. The subtractor 29 is
The digital detected temperature signal is subtracted from the digital target temperature signal, and the result of this subtraction is output as a temperature deviation signal indicating a temperature deviation. The sampler 30 samples the temperature deviation signal in response to the sampling signal and supplies the sampled temperature deviation signal to the adjusting unit.

The adjusting section includes a PID controller (PID) 31 and
First and second pulse width modulators (PWM) 32 and 33, and first and second data output section (D / O) 34
And 35.

The PID controller 31 performs PID calculation on the sampled temperature deviation signal and outputs the calculation result. Here, when the sampled temperature deviation signal shows a positive value, the PID controller 31 outputs the first calculation result signal as the calculation result. On the other hand, when the sampled temperature deviation signal shows a negative value, the PID controller 31 outputs the second calculation result signal as the calculation result. The first and second operation result signals are respectively the first and second pulse width modulators 32 and 33.
Is supplied to. The first and second pulse width modulators 32 and 33 perform PWM conversion of the first and second operation result signals, respectively, and perform first and second pulse width modulation (PW).
M) Output the signal. The first data output unit 34 has a first
Of the electromagnetic switch 22 using the PWM signal of
(FIG. 1). The second data output unit 35 has a second
Is sent to the cooling water opening / closing valve 25 (FIG. 1) as a second control signal.

Therefore, in response to the sampled temperature deviation signal, the adjusting section outputs a signal such that the temperature of the mold 12 at the sampling point in the next injection molding cycle of the injection molding machine 11 becomes the target temperature. It is generated as a control signal.

Hereinafter, referring to FIG. 1, FIG. 2 and FIG.
The operation of the mold temperature adjusting apparatus according to the present invention will be described.

In the injection molding machine 11, as shown in the first line of FIG. 3, an injection step of injecting (injecting) the molten resin into the die 12 and a holding pressure for cooling and fixing the resin in the die 12 are carried out. The injection cycle consisting of a cooling step, a mold opening step of opening the mold to take out the molded product from the mold 12, and a mold closing step of closing the mold 12 is repeated.

Therefore, the temperature of the mold 12 periodically changes in synchronization with the injection molding cycle, as shown in the second line of FIG.

The control device of the injection molding machine 11 outputs an injection timing signal at a timing immediately before the injection molding machine 11 injects the molten resin into the mold 12, as shown in the third line of FIG.

In response to this injection timing signal, the controller 15 samples the deviation between the detected temperature of the mold 12 and the target temperature with the sampler 30, and the PID controller 31 performs PID calculation (control) on the sampled deviation. Calculation) (4th line in FIG. 3).

More specifically, if the sampled deviation is a positive value, the PID controller 31 first calculates a signal representing the time ratio of turning on in one injection molding cycle in the opening / closing operation of the electromagnetic switch 22. The result signal is supplied to the first pulse width modulator 32. In response to the first operation result signal, the first pulse width modulator 32 operates as shown in FIG.
The first PWM signal as shown in the line is sent to the electromagnetic switch 22 as the first control signal via the first data output unit 34. Thereby, the temperature of the refrigerant in the refrigerant tank 17 is increased by the heater 20 so that the temperature of the mold 12 at the sampling point in the next injection molding cycle of the injection molding machine 11 becomes the target temperature.

On the other hand, if the sampled deviation is a negative value, the PID controller 31 uses, as the second operation result signal, a signal indicating the time ratio of turning on in one injection molding cycle in the opening / closing operation of the cooling water opening / closing valve 25. It is supplied to the second pulse width modulator 33. In response to the second operation result signal, the second pulse width modulator 33 outputs the second PWM signal as shown in the fifth line of FIG. 3 to the second data output unit 3.
As a second control signal via the cooling water opening / closing valve 25
Send to. Thus, the refrigerant in the refrigerant tank 17 is cooled by the heat exchanger 23 so that the temperature of the mold 12 at the sampling point in the next injection molding cycle of the injection molding machine 11 becomes the target temperature.

As described above, by adjusting the timing of starting the control operation immediately after the PID calculation in both the control operation of the temperature raising operation and the cooling operation of the refrigerant,
The timing of the control operation of the injection molding cycle can be the same every time.

In the above embodiment, the deviation between the detected temperature of the mold immediately before the injection and the target temperature is sampled in synchronization with the injection molding cycle, and the sampled deviation is controlled to be zero. Of course, the detected temperature of the mold immediately before the injection may be sampled in synchronization with the injection molding cycle, and the sampled mold temperature may be controlled to be the target temperature.

[0039]

As described above, according to the present invention, the detected temperature of the mold immediately before the injection (deviation between the detected temperature and the target temperature).
Is sampled in synchronism with the injection molding cycle, and the sampled mold temperature (deviation) is controlled to be the target temperature (zero). Therefore, the following effects are achieved.

The mold temperature immediately before injection can be kept constant.

When a large number of molded products are molded over a long period of time, the influence of disturbance such as temperature change on the mold is reduced as compared with the conventional method of keeping the refrigerant temperature constant. Can be done.

As compared with the asynchronous mold temperature control system, the weight variation of the molded product can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a mold temperature adjusting apparatus according to an embodiment of the present invention together with an injection molding machine and a mold.

FIG. 2 is a block diagram showing details of a controller in FIG.

FIG. 3 is a time chart for explaining the operation of the mold temperature adjusting device of FIG.

[Explanation of symbols]

 10 Mold Temperature Control Device 11 Injection Molding Machine 12 Mold 13 Temperature Sensor 14 Digital Switch (Setting Device) 15 Controller 29 Subtractor 30 Sampler 31 PID Controller (PID) 32, 33 Pulse Width Modulator (PWM)

Claims (2)

[Claims] 1. A device for adjusting the temperature of the mold by controlling the temperature of a refrigerant flowing in the mold of an injection molding machine, the temperature sensor detecting the temperature of the mold, and the metal mold. A setter that sets a target temperature of the mold, a control unit that generates a control signal based on a deviation between the target temperature set by the setter and the detected temperature detected by the temperature sensor, and a controller that responds to the control signal. In the mold temperature adjusting device having an operation unit for performing temperature rising / cooling operation of the refrigerant by means of the above, the control unit controls the timing signal immediately before injecting the resin from the injection molding machine into the mold. In response, sampling means is provided for sampling the deviation and outputting the sampled deviation; and, in response to the sampled deviation, the sampling means at the sampling point in the next injection molding cycle of the injection molding machine. Mold temperature adjusting apparatus of an injection molding machine, characterized in that it comprises an adjustment unit for the temperature of the mold to generate a signal such that the target temperature of said control signal. 2. The mold temperature adjusting device for an injection molding machine according to claim 1, wherein the adjusting section generates a pulse width modulation signal as the control signal.