Temperature control device for injection molding machine with abnormality detection function

Abstract

The present invention provides an injection molding temperature control device that can detect temperature control anomalies more accurately. The injection molding temperature control device involved in one embodiment of the present disclosure controls the output of a heater for heating the target part based on the detection value of a temperature sensor for detecting the temperature of the target part of an injection molding machine, wherein the injection molding machine injects resin into a mold through an injection machine, and the injection molding temperature control device comprises: a temperature control unit that controls the output of the heater so that the detection value of the temperature sensor approaches a predetermined set temperature; a heat supply calculation unit that calculates the heat supply to the target part based on at least one of the driving voltage, duty cycle, and current value of the heater; and an abnormality detection unit that detects the abnormality of the temperature control of the target part based on the detection value of the temperature sensor and the heat supply calculated by the heat supply calculation unit.

Description

Technical Field

[0001] The present invention relates to a temperature control device for an injection molding machine having an abnormality detection function. Background Art

[0002] An injection molding machine that manufactures resin molded products by injecting molten resin into a mold is widely used. In an injection molding machine, a heater and a temperature sensor are provided for each target part of the cylinder of the injection machine and the mold, and the output of the heater is controlled so that the detected value of the temperature sensor approaches a set temperature.

[0003] In an injection molding machine, for example, when the heater deviates from the target part, even if the output of the heater is increased, heat is not transferred to the target part, and thus the detected value of the temperature sensor does not rise. Therefore, when the heater deviates from the target part, the output of the heater may abnormally increase, and the heater may be damaged due to overheating.

[0004] In addition, when the temperature sensor deviates from the target part, although the temperature of the target part rises, the detected value of the temperature sensor remains low. Therefore, the output of the heater may abnormally increase, resulting in a decrease in the quality of the resin molded product, etc.

[0005] As a unit for detecting such an abnormality in a structure related to temperature control of an injection molding machine, Patent Document 1 discloses an injection molding temperature control device (controller) that includes "a control unit that measures the working time of the temperature control unit and detects the temperature of the controlled body when the working time reaches a specified time via the temperature detection unit, and when the detected temperature does not reach the specified temperature, the control unit determines that it is abnormal".

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Laid-Open No. 5-177686 Summary of the Invention

[0009] Problem that the invention aims to solve

[0010] The change in temperature with respect to the working time of the heater is not fixed, for example, due to changes in internal and external conditions such as material temperature and ambient temperature (in Japanese: 雰囲気温度). Therefore, if only relying on the relationship between working time and temperature as described in Patent Document 1, it may not be possible to accurately detect an abnormality in temperature control. Therefore, an injection molding temperature control device that can more accurately detect an abnormality in temperature control is desired.

[0011] Solutions for solving problems

[0012] An injection molding temperature control device involved in one embodiment of the present disclosure controls the output of a heater for heating an object part of an injection molding machine based on a detection value of a temperature sensor for detecting the temperature of the object part of the injection molding machine, wherein the injection molding machine injects resin into a mold through an injection machine, and the injection molding temperature control device comprises: a temperature control unit, which controls the output of the heater so that the detection value of the temperature sensor approaches a prescribed set temperature; a supply heat calculation unit, which calculates the supply heat supplied to the object part based on at least one of a driving voltage, a duty cycle, and a current value of the heater; and an abnormality detection unit, which detects abnormality in the temperature control of the object part based on the detection value of the temperature sensor and the supply heat calculated by the supply heat calculation unit.

[0013] Effects of the Invention

[0014] An injection molding temperature control device according to one embodiment of the present disclosure can detect abnormality in temperature control relatively accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram showing the structure of an injection molding system including an injection molding temperature control device according to an embodiment of the present disclosure.

[0016] Figure 2 Yes means Figure 1 Block diagram of abnormality detection in the injection molding temperature control device.

[0017] Figure 3 This is a graph showing temperature changes during startup of a normal injection molding system.

[0018] Figure 4 This is a graph showing temperature changes at the start-up of the injection molding system with heater deviation.

[0019] Figure 5 This is a graph showing the temperature change of a normal injection molding system during stable operation.

[0020] Figure 6 This is a graph showing temperature changes when the heater deviates during the stable operation of the injection molding system.

[0021] Description of Reference Numerals

[0022] 1: injection molding system; 10: injection molding machine; 11: injection machine; 12: mold; 20: injection molding temperature control device; 21: temperature control unit; 22: supply heat calculation unit; 23: heat release calculation unit; 24: abnormality detection unit; 25: abnormality processing unit; 26: estimation unit; 27: determination unit; 28: correction unit; T: temperature sensor; H: heater. DETAILED DESCRIPTION

[0023] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Figure 1 1 is a schematic diagram showing a configuration of an injection molding system 1 including an injection molding temperature control device according to an embodiment of the present disclosure. The injection molding system 1 includes an injection molding machine 10 and an injection molding temperature control device 20 .

[0024] The injection molding machine 10 includes an injection machine 11 and a mold 12. The injection molding machine 10 performs injection into the mold 12 using the injection machine 11 to manufacture a resin molded product.

[0025] The injection machine 11 includes a cylinder 111, a screw 112 rotatably disposed in the cylinder 111, a nozzle 113 provided at the front end (downstream end) of the cylinder 111, and a supply hopper 114 for supplying resin to the base end (upstreammost end) of the cylinder 111. The injection machine 11 moves the resin from the base end side to the front end side by the rotation of the screw 112, and injects the resin from the nozzle 113.

[0026] The cylinder 111 has a plurality of target parts A1, A2, and A3, each of which is provided with a temperature sensor T and a heater H, and is individually temperature-controlled. In addition, the part closest to the base end of the cylinder 111 is not provided with a heater and is not a target part to be temperature-controlled, but is also provided with a temperature sensor T. In addition, the nozzle 113 is provided with a temperature sensor T and a heater H, and is set as a target part A4 to be temperature-controlled.

[0027] The mold 12 is divided into a fixed mold 121 and a movable mold 122, and a cavity 123 is formed therebetween for injecting resin by the injection machine 11. The fixed mold 121 and the movable mold 122 are respectively provided with a temperature sensor T and a heater H, and are set as target areas A5 and A6 to be individually temperature-controlled.

[0028] The temperature sensor T may be capable of detecting the temperature of the target parts A1 to A6, and may be, for example, a structure having a thermocouple, etc. The heater H may be capable of heating the target parts A1 to A6, and may be, for example, a structure having a heating element Ht and an amplifier Hp, wherein the heating element Ht is mounted on the target part and generates heat by being energized, and the amplifier Hp supplies power to the heating element Ht.

[0029] The injection molding temperature control device 20 controls the output of the heater H for each target area A1 to A6 based on the detection value of the temperature sensor T. The injection molding temperature control device 20 can be implemented by, for example, causing a computer device including a CPU, a memory, and a signal interface for connecting to the temperature sensor T and the heater H to execute an appropriate control program.

[0030] like Figure 2 As shown in more detail, the injection molding temperature control device 20 includes a temperature control unit 21, a heat supply calculation unit 22, a heat release calculation unit 23, an abnormality detection unit 24, and an abnormality processing unit 25. These components are used to distinguish each other in terms of their functions, and may not be clearly distinguished in terms of physical structure and program structure. In addition, the injection molding temperature control device 20 is configured to be able to perform the number of target parts A1 to A6 in parallel by, for example, time-sharing processing. Figure 2 control.

[0031] The temperature control unit 21 controls the output of the heater H so that the detection value of the temperature sensor T approaches a predetermined set temperature. As a control method of the temperature control unit 21, for example, well-known feedback control such as PID control or on-off control can be adopted.

[0032] The heat supply calculation unit 22 calculates the heat supply to be supplied to the target parts A1 to A6, respectively, based on at least one of the driving voltage of the heater H (the output voltage of the amplifier Hp), the duty cycle of the heater H, and the current value of the heater H. That is, the heat supply calculation unit 22 calculates the heat supply to be supplied to the target parts A1 to A6 using the power value input to the heater H as the calorific value of the heater H. Since the temperature change of the target parts A1 to A6 depends on the heat supply, by calculating the heat supply to the target parts A1 to A6, the temperature change of the target parts A1 to A6 is estimated in the abnormality detection unit 24 described later, thereby accurately detecting abnormality in temperature control.

[0033] The heat supply calculation unit 22 can calculate the heat supply to the target parts A1 to A6 by taking into account the flow rate of the resin flowing in from the upstream side. That is, the heat supply calculation unit 22 can calculate the heat supply to the target parts A1 to A6 by deducting the heat taken away by the resin flowing in from the upstream side due to the low temperature resin flowing in from the calorific value of the heater H. In addition, when a higher temperature resin is supplied to the target parts A1 to A6 from the upstream side, the heat supply calculation unit 22 can calculate the heat supply to the target parts A1 to A6 by adding the calorific value of the heater H to the heat supplied by the resin.

[0034] Specifically, the amount of heat taken away by the resin or the amount of heat supplied by the resin can be calculated by multiplying the difference between the detection value of the temperature sensor T of the target area A1 to A6 and the detection value of the temperature sensor T of the area adjacent to the upstream side, the flow rate of the resin, and the specific heat of the resin. By considering the flow rate of the resin in this way, the abnormality of the temperature control can be more accurately determined in the abnormality detection unit 24. In addition, when the amount of heat taken away by the inflowing resin or the amount of heat supplied by the inflowing resin is sufficiently small compared to the calorific value of the heater H, even if the amount of heat is ignored, the error is sufficiently small.

[0035] The heat release calculation unit 23 calculates the heat release amount from the target parts A1 to A6 to the outside based on the detection value of the temperature sensor T for each target part A1 to A6. By using the calculated heat release amount, the abnormality detection unit 24 can more accurately detect abnormality in temperature control.

[0036] The heat release calculation unit 23 can calculate the heat release by further considering the flow rate of the resin, that is, the flow rate of the resin injected from the injection machine 11 to the mold 12 (for example, the volume flow rate that can be calculated from the rotation speed of the screw 112). As a result, the abnormality detection unit 24 can more accurately estimate the temperature change of the target parts A1 to A6, and thus accurately detect abnormalities in temperature control.

[0037] The abnormality detection unit 24 detects abnormality of components related to temperature control of the target parts A1 to A6 based on the detection value of the temperature sensor T, the supplied heat amount calculated by the supplied heat amount calculation unit 22, and the heat amount calculated by the heat amount calculation unit 23. The abnormality detection unit 24 includes an estimation unit 26 for estimating the temperature of the target parts A1 to A6, a determination unit 27 for determining abnormality of temperature control based on the detection value of the temperature sensor T and the estimated value of the estimation unit 26, and a correction unit 28 for correcting the heat amount used by the estimation unit 26 in the calculation.

[0038] The estimation unit 26 estimates the temperature of the target parts A1 to A6 based on the amount of heat obtained by subtracting the heat release calculated by the heat release calculation unit 23 from the amount of heat supplied calculated by the heat supply calculation unit 22, that is, the amount of heat change inside the target parts A1 to A6. More specifically, the estimation unit 26 can calculate the temperature change of the target parts A1 to A6 as a value obtained by dividing the integral value of the difference between the amount of heat supplied to the target parts A1 to A6 and the heat release of the target parts A1 to A6 by the heat capacity C of the target parts A1 to A6. If the amount of heat supplied is Wh and the heat release is Wr, the relationship with the temperature change ΔT is expressed as C·ΔT=∫(Wh-Wr)dt.

[0039] In order to obtain the estimated value of the current temperature of the target parts A1 to A6, it is necessary to add the temperature change amount to the initial temperature. The detection value of the temperature sensor T at the start of control or the measured value of the ambient temperature can be used as the initial temperature, or a fixed value within a normal initial temperature range can be used as the initial temperature. When the estimation unit 26 uses Celsius temperature, the initial temperature can be considered to be 0°C, thereby omitting the addition of the initial temperature.

[0040] When the difference between the detection value of the temperature sensor T and the estimated value of the estimation unit 26 exceeds a predetermined abnormal threshold, the determination unit 27 determines that the temperature control is abnormal. That is, when the current temperature of the target parts A1 to A6 estimated based on the heat supplied to the target parts A1 to A6 is excessively higher than the current detection value of the temperature sensor T, it can be determined that the temperature sensor T cannot correctly measure the temperature of the target parts A1 to A6, or the heater H cannot properly heat the target parts A1 to A6.

[0041] The correction unit 28 corrects the amount of heat (the value obtained by subtracting the amount of heat released from the amount of heat supplied) used by the estimation unit 26 in the calculation so as to reduce the difference between the detection value of the temperature sensor T and the estimated value of the estimation unit 26. Specifically, the correction unit 28 adds the amount of heat input to the estimation unit 26 to a value obtained by multiplying the difference between the detection value of the temperature sensor T and the estimated value of the estimation unit 26 by a predetermined correction coefficient Kp. In this way, the difference between the initial temperature used by the estimation unit 26 and the actual temperature of the target parts A1 to A6 at the start of control can be compensated, and the difference between the estimated value and the detected value can be prevented from increasing due to the accumulation of errors included in the calculated values ​​of the amount of heat supplied and the amount of heat released even though there is no abnormality in the structure related to the temperature control. In addition, if the correction coefficient Kp is set too large, it may also offset the deviation between the estimated value and the detected value when an abnormality occurs in the structure related to the temperature control, so it is preferably set to the minimum value.

[0042] When the abnormality detection unit detects an abnormality in the temperature control, the abnormality processing unit 25 performs at least one of reporting the abnormality and stopping the output of the heater H. Thus, the heater H or the target parts A1 to A6 can be prevented from being damaged by heat, thereby suppressing the production of low-quality injection molded products due to the operation of the injection molding system under inappropriate temperature conditions.

[0043] Next, temporal changes in the temperature of the heater H (heat generating element Ht) of the injection molding system 1 , the temperature of the target site A1 (the detection value of the temperature sensor T), and the amount of heat generated by the heater H will be specifically described.

[0044] Figure 3The example shows the changes of various values ​​when the injection molding system 1 with all normal structures related to temperature control is started, that is, when the temperature of each target part A1 to A6 is raised from room temperature to the set temperature that can be manufactured. In this example, the detection value of the temperature sensor T is consistent with the temperature of the target part A1. As shown in the figure, the output of the heater H becomes the maximum output at startup, and when the detection value of the temperature sensor T increases to a certain extent, the output of the heater H decreases, and then increases and decreases within a small range so that the detection value of the temperature sensor T is maintained at the set temperature.

[0045] Figure 4 The following example shows the changes in various values ​​when the injection molding system 1 is started without the heater H installed at the target part A1. In this example, since heat is not transferred from the heater H to the target part A1, only the heater H is heated up, and the target part A1 is only slightly heated up due to heat conduction from the adjacent target part A2. In this case, the temperature of the heater H becomes very high, and if no treatment is taken, the heater H and surrounding components may be damaged.

[0046] However, in the injection molding system 1, the injection molding temperature control device 20 checks the difference between the heating value of the heater H and the temperature rise of the target part A1 to detect abnormality in temperature control, so the heater H is stopped from generating heat or the operator takes measures before the heater H is damaged.

[0047] Figure 5 The example shows changes in various values ​​of the injection molding system 1 in stable operation with all the temperature control-related structures being normal. In this example, the output of the heater H increases and decreases within a small range, and the temperature of the target part A1 and the detection value of the temperature sensor T corresponding thereto are maintained substantially at the set temperature.

[0048] Figure 6 The following example shows the changes in the values ​​when the heater H is separated from the target area A1 during the stable operation. When the heater H is separated from the target area A1, the temperature of the heater H that cannot release heat to the target area A1 rises, while the temperature of the target area A1 that is not supplied with heat by the heater H gradually decreases.

[0049] In this case as well, the temperature of the heater H becomes very high. If left untreated, the heater H and surrounding components may be damaged. However, the injection molding temperature control device 20 detects abnormalities in temperature control, thereby stopping the heater H from generating heat or allowing the operator to take countermeasures before the heater H is damaged.

[0050] As described above, the injection molding temperature control device 20 can relatively accurately detect abnormalities in the structure related to temperature control of the injection molding machine 10 , and thus it is possible to prevent the injection molding temperature control device 20 from being damaged.

[0051] The embodiments of the present disclosure are described above, but the present invention is not limited to the aforementioned embodiments. In addition, the effects described in the embodiments are only the best effects produced by the present invention, and the effects of the present invention are not limited to the effects described in the embodiments.

[0052] The injection molding temperature control device according to the present disclosure can control the temperature of a single control object.

[0053] In the injection molding temperature control device involved in the present disclosure, the heat release calculation unit can also calculate the heat release from the target part to the outside based on the supplied heat calculated by the supplied heat calculation unit, and can also calculate the heat release from the target part to the outside based on both the detection value of the temperature sensor and the heat release calculated by the supplied heat calculation unit.

[0054] In the injection molding temperature control device of the present disclosure, the heat release calculation unit can be omitted. Generally, the heat release is sufficiently small compared to the heat generated by the heater, so even if the heat release is ignored, the error is small. In addition, when the abnormality detection unit has a correction unit, the correction unit can generate an offset corresponding to the heat release.

[0055] In the injection molding temperature control device according to the present disclosure, the abnormality detection unit may be configured to detect abnormality in temperature control based on a detection value of a temperature sensor and a behavior of heat supply without estimating the temperature of the target site.

[0056] In the injection molding temperature control device according to the present disclosure, the correction unit can be omitted.

Claims

1. An injection molding temperature control device, which controls the output of a heater for heating a target portion based on a detection value of a temperature sensor for detecting a temperature of a target portion of an injection molding machine, wherein the injection molding machine injects a resin into a mold by an injection machine, the injection molding temperature control device comprising: a temperature control unit configured to control the output of the heater so that the detection value of the temperature sensor approaches a predetermined set temperature; a heat supply calculation unit that calculates a heat supply to be supplied to the target site based on at least one of a driving voltage, a duty ratio, and a current value of the heater; as well as An abnormality detection unit detects abnormality in temperature control of the target site due to the temperature sensor being deviated from the target site or the heater being deviated from the target site based on the detection value of the temperature sensor and the supplied heat amount calculated by the supplied heat calculation unit.

2. The injection molding temperature control device according to claim 1, characterized in that: The abnormality detection unit has: an estimating unit that estimates a temperature of the target part based on the supplied heat amount calculated by the supplied heat calculating unit; The determination unit determines that the temperature control is abnormal when a difference between a detection value of the temperature sensor and an estimated value of the estimation unit exceeds a predetermined abnormality threshold.

3. The injection molding temperature control device according to claim 2, characterized in that: The abnormality detection unit further includes a correction unit that corrects the amount of heat used in the calculation by the estimation unit so as to reduce the difference between the detection value of the temperature sensor and the estimation value of the estimation unit.

4. The injection molding temperature control device according to any one of claims 1 to 3, characterized in that: further comprising a heat release calculation unit for calculating the amount of heat released from the target part to the outside based on at least one of the detection value of the temperature sensor and the supplied heat calculated by the supplied heat calculation unit, The abnormality detection unit detects abnormality in temperature control based on the detection value of the temperature sensor, the supply heat amount calculated by the supply heat amount calculation unit, and the heat release amount calculated by the heat release calculation unit.

5. The injection molding temperature control device according to claim 4, characterized in that: The heat release amount calculation unit calculates the heat release amount further taking into account the flow rate of the resin.

6. The injection molding temperature control device according to any one of claims 1 to 3, characterized in that: The heat supply calculation unit calculates a heat supply amount to be supplied to the target site in consideration of a flow rate of the resin flowing in from an upstream side.

7. The injection molding temperature control device according to any one of claims 1 to 3, characterized in that: The device further includes an abnormality processing unit configured to perform at least one of reporting the abnormality and stopping output of the heater when the abnormality detection unit detects an abnormality in the temperature control.

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