JP2015231675A - Disconnection/deterioration determination method for heater and injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of determining disconnections and the deterioration status of each heater with good accuracy without adverse effects on temperature control.SOLUTION: A plurality of heaters (2a, 2b and so on) of an injection machine supplied with a current from the R, S and T lines of a three-phase AC power source (5) are divided into an R line connected heater group connected to the R line and an S line connected heater group connected to the S line, and disconnections and deterioration of heaters are determined for individual heater groups. More specifically, for the R line connected heater group, a heater current is detected by an R line current sensor (7r), with a heater alone in the ON state during PWM control as the determination target, and disconnections and deterioration of the heater are determined by comparing the detected results with a predetermined current threshold. Similar procedures are conducted for determination of the S line connected heater group, except that the heater current is detected by an S line current sensor (7s).

Description

  The present invention relates to a heater disconnection / deterioration determination method for determining a disconnection or deterioration state of a heater for heating a heating cylinder of an injection molding machine, and an injection molding machine in which such a method is implemented.

  A plurality of heaters are wound around the heating cylinder of the injection molding machine, and the heating cylinder can be heated by energization. The heating cylinder is also provided with a plurality of temperature sensors. In order to efficiently melt the injection material and adjust the viscosity to be suitable for injection, the heating cylinder is controlled to a desired temperature at each position. The heater is connected to a three-phase AC power source. When the heater is a single-phase heater, the heater is connected as follows. That is, when the three-phase AC power source is Δ-connected, each heater is connected to any two of the three-phase AC electric wires composed of the R line, the S line, and the T line. However, each heater is dispersedly connected so that the number of heaters connected to each of the R line, S line, and T line is substantially equal, so that the load is not concentrated on a specific line. Yes. When Y-connected, the three-phase AC wire consists of R, S, T, and neutral N wires, and each heater is connected to either the R, S, or T wires and the N wire. ing. Also in the case of this Y connection, the heaters are connected so that the number of heaters of the R line, S line, and T line is equal. In this way, each heater energized from the three-phase AC wire is provided with a solid state relay or an electromagnetic contactor, and is turned on / off by a command from the controller. This ON / OFF is performed by PWM control, and the power supply to the heater is adjusted by adjusting the ratio of the energization time for supplying current to the control cycle, that is, the duty ratio. A signal from the temperature sensor is input to the controller, and power supply to the heater is adjusted so that each position of the heating cylinder becomes a predetermined temperature by feedback control. Such a heater deteriorates when used for a long time and eventually breaks. It must be replaced if it is disconnected.

  As a method for detecting the disconnection of the heater, a method in which a current sensor is provided in each heater circuit that supplies power to the heater and the current is constantly monitored is well known. If no current is detected, it can be determined that the heater has been disconnected, and the heater can be reliably determined to be disconnected, but a current sensor is required for each heater.

JP 2000-071306 A JP 2013-202955 A

  Another method for detecting the disconnection of the heater has been proposed by the present applicant in US Pat. According to the method described in Patent Document 1, a current sensor is provided with a common current sensor only in one place, and is not provided in each heater circuit. More specifically, one current sensor is provided for each three-phase AC electric wire that is a power supply line to the heater. When the disconnection is inspected, only one heater is energized, and the current value is measured by a common current sensor. Then, the heaters that are sequentially energized are switched, and the current value of each heater is measured. The controller stores a current value measured when each heater is normal, and compares the measured current value with a normal current value to determine the presence or absence of disconnection.

  Also in Patent Document 2, a method for detecting disconnection of a heater is proposed by the present applicant. Also in the method described in Patent Document 2, as in the method of Patent Document 1, the current sensor is provided with a common current sensor only in one place. In the method described in Patent Document 2, during normal temperature control, the current detected by a common current sensor is compared with the theoretical total current of all heaters that are turned on. If the total theoretical current is below a predetermined amount, it is determined that one of the heaters that are currently ON is disconnected, and then these heaters are turned on one by one to measure the current. Identify the broken heater.

  Both the conventional method of providing a current sensor for each heater circuit, the method described in Patent Document 1, and the method described in Patent Document 2 are excellent because they can reliably detect the disconnection of the heater. . However, there are also problems to be solved. Specifically, the conventional method has a problem that the cost of the injection molding machine increases because current sensors are required for all the heater circuits. In particular, in a large injection molding machine, the number of heaters is large, resulting in an increase in cost. If the number of current sensors is large, there is a problem that the wiring becomes complicated, and the frequency of failure of the current sensors increases accordingly. In the method described in Patent Document 1, detection of disconnection of the heater is performed during operation, that is, during temperature control, but ON / OFF of the solid state relay and the electromagnetic contactor is performed regardless of temperature control. As a result, there is a problem that the temperature control is adversely affected by disturbance of the control. If the detection frequency of the heater disconnection is reduced, the influence on the temperature control can be reduced. However, this will delay the discovery of the heater disconnection. The method described in Patent Document 2 has a problem when heaters having greatly different theoretical currents are mixed. For example, if the current measured when a heater with a large current and a heater with a small current are turned on at the same time is smaller than the theoretical total current, this is due to an error of the heater with a large current, or a heater with a small current It may not be possible to judge whether this is due to disconnection. In addition, both the conventional method and the method described in Patent Document 1 have a problem in that only the disconnection of the heater can be detected. That is, since it is impossible to predict disconnection in advance by determining the deterioration of the heater, it is not possible to prepare an alternative heater. Then, when the heater is disconnected, the injection molding machine cannot be stopped for a long time.

  An object of the present invention is to provide a heater disconnection / deterioration determination method and an injection molding machine that solve the above-described problems, and specifically, it is possible to control temperature in spite of low cost. It is an object of the present invention to provide a heater disconnection / deterioration determination method and an injection molding machine that can accurately determine the disconnection and deterioration state of each heater without adversely affecting the heater.

  In order to achieve the above object, the present invention provides a plurality of heaters connected to the R line, the S line, and the T line of the three-phase AC wire so that the number of connections is equal. This is configured as a heater disconnection / deterioration determination method for determining disconnection / deterioration of the heater in an injection molding machine that is independently PWM controlled by the control unit. The heater disconnection / deterioration method is such that a heater group connected to the R line among a plurality of heaters is an R line connection heater group, and a heater group connected to the S line is an S line connection heater group, and PWM While performing the control, each heater group is determined independently. For example, in the R-line connected heater group, the current measured by the R-line current sensor provided on the R line is the current set for the one heater when only one of the heaters is ON. When it is smaller than the threshold value, it is determined that the heater is deteriorated or disconnected. In the S-line connected heater group, the current measured by the S-line current sensor provided on the S-line is the current set for the one heater when only one of the heaters is ON. When the value is smaller than the threshold value, it is determined that the heater is deteriorated or disconnected.

Thus, in order to achieve the above object, the invention according to claim 1 is composed of a single-phase heater, and the number of connections for each of the R-line, S-line, and T-line of the three-phase AC wire is substantially uniform. In the injection molding machine in which a plurality of heaters connected to the three-phase AC electric wire are PWM-controlled independently by individually provided switches, the disconnection / deterioration of the heater is determined. A heater disconnection / deterioration determination method, wherein the heater disconnection / deterioration determination method includes a heater group connected to the R line among the plurality of heaters as an R line connection heater group, and the S line. The heater group connected to the S-line connected heater group is set as an S-line connected heater group, and each of the heater groups is determined independently while performing the PWM control. The heater deteriorates or breaks when the current measured by the R-line current sensor provided on the R-line is smaller than the current threshold value set for the single heater at the timing when only the heater is ON. The S-line connected heater group determines that the current measured by the S-line current sensor provided on the S-line is at the timing when only one of the heaters is ON. It is configured as a heater disconnection / deterioration determination method for an injection molding machine, wherein it is determined that the heater has deteriorated or disconnected when the current threshold value set for the heater is smaller.
The invention according to claim 2 is the heater disconnection / deterioration determination method according to claim 1, wherein among the plurality of heaters, a heater group connected to the T-line is a T-line connection heater group, In the T-line connected heater group, the current measured by the T-line current sensor provided on the T-line is the current set for the one heater when only one of the heaters is ON. It is configured as a heater disconnection / degradation determination method for an injection molding machine, wherein it is determined that the heater is deteriorated / disconnected when the value is smaller than the threshold value.
According to a third aspect of the present invention, in the method according to the first or second aspect, the PWM control includes two types of first half ON type control and second half ON type control, and the first half ON type control is performed at the start of a control cycle. The second half ON type control is turned off at the start of the control cycle, and turned on at a predetermined timing and corresponds to the duty ratio at the end of the control cycle. When one arbitrary heater is determined in each heater group, one of the first half ON type control and the second half ON type control is determined for the one heater. Control, and the other heaters in the heater group perform the other control, thereby providing a timing when only one of the arbitrary heaters is turned on. Configured as a disconnection or degradation determination method of the heater of the injection molding machine, characterized by determining a disconnection or degradation of one heater.
A fourth aspect of the present invention is the method according to any one of the first to third aspects, wherein the total power of the plurality of heaters is also calculated. It is configured as a determination method.
According to a fifth aspect of the present invention, there is provided an injection molding machine in which the heater disconnection / deterioration determination method according to any one of the first to fourth aspects is implemented.

  As described above, according to the present invention, it is composed of a single-phase heater, and is connected to the three-phase AC wire so that the number of connections to the R-wire, S-wire, and T-wire of the three-phase AC wire is substantially equal. Multiple heaters are configured as a heater disconnection / deterioration determination method for determining heater disconnection / degradation in an injection molding machine that is independently PWM controlled by individually provided switches. Has been. That is, it is intended for an injection molding machine in which general PWM control is performed. According to the present invention, in the heater disconnection / deterioration determination method, a heater group connected to the R line among a plurality of heaters is defined as an R line connected heater group, and a heater group connected to the S line is defined as S. A line-connected heater group is used, and each heater group is determined independently while performing PWM control. In the R-line connected heater group, the current measured by the R-line current sensor provided in the R line is the current set in the one heater when only one of the heaters is ON. When it is smaller than the threshold value, it is determined that the heater is deteriorated or disconnected, and the S-line connected heater group is an S-line current sensor provided on the S-line when only one of these heaters is ON. When the current measured at is smaller than the current threshold value set for the one heater, it is determined that the heater is deteriorated or disconnected. Then, at least four effects can be obtained. The first effect is that the current can be measured with an R-line or S-line current sensor of a three-phase AC electric wire, so that the number of current sensors can be minimized and the cost can be reduced. Since the 2nd effect should just be judged for every heater group, it can judge efficiently. If all the heaters provided in the injection molding machine are targeted, it is difficult to find the timing when only the heater to be judged is ON and the other heaters are OFF. Each heater group is divided and determined for each heater group. Since the number of heaters belonging to the heater group is small, the timing when only the heater to be determined is ON frequently occurs. That is, it can be determined frequently and the efficiency of the determination is high. The third effect is that the current is measured with only one heater ON, so that the heater current is measured, and since this is only compared with the current threshold, the criterion is simple. Is a point. That is, only a single heater can be evaluated, and when it is smaller than the current threshold value, it can be determined that it is disconnected or deteriorated. The fourth effect is that the determination can be made without interfering with the PWM control. That is, the timing of only one heater is found in the control cycle of the PWM control and the determination is made for this heater, so there is no disturbance in the PWM control. This does not affect the temperature control. By the way, in this method, since only one heater is ON in the control cycle is a target of determination, depending on the heater, it may not be a target of determination. However, in a heater that has deteriorated, the resistance value gradually increases and the heater current decreases, so that the duty ratio inevitably increases to obtain a desired amount of heat generation. As a result, in the control cycle, it is easy to generate a timing at which only the heater having deteriorated is turned on. That is, as the heater deteriorates, it is likely to become a determination target heater, and there is no particular problem.

  According to another invention, the PWM control consists of two types, the first half ON type control and the second half ON type control. The first half ON type control is turned on at the start of the control cycle and turned off after the ON time corresponding to the duty ratio. The second half ON-type control is turned off at the start of the control cycle, and is turned on at a predetermined timing so that an ON time corresponding to the duty ratio is obtained at the end of the control cycle. When one of the heaters is determined, one control of the first half ON type control and the second half ON type control is performed for the one heater, and the other heater of the heater group performs the other control, Thereby, only one arbitrary heater is turned on, and the disconnection / deterioration of the arbitrary one heater is determined. Then, for any heater in the heater group, it is possible to create a timing for turning on only that heater. If it does so, a disconnection and deterioration determination can be reliably implemented about a desired heater. Note that neither the first half ON-type control nor the second half ON-type control affects the duty ratio, so there is no concern that temperature control will be affected even if the control is switched.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows typically the injection molding machine which concerns on the 1st Embodiment of this invention, The (a) is a control block diagram of an injection molding machine, The (a) is each provided in the injection molding machine The table | surface which shows the connection state to the three-phase alternating current electric wire of a heater, and the (c) are graphs which show the ON / OFF state of each heater by which PWM control is carried out. It is a figure which shows typically the injection molding machine which concerns on the 2nd Embodiment of this invention, The (a) is a control block diagram of an injection molding machine, The (a) is each provided in the injection molding machine The table | surface which shows the connection state to the three-phase alternating current electric wire of a heater, and the (c) are graphs which show the ON / OFF state of each heater by which PWM control is carried out. It is a graph which shows the ON / OFF state of the heater by which PWM control is carried out. In this Embodiment, it is a graph which shows the ON / OFF state of the heater controlled by PWM, The (a) (b) shows the ON / OFF state of one heater controlled by the different method of PWM control. It is a graph, The (c) is a graph which shows the ON / OFF state of a some heater.

  Hereinafter, this embodiment will be described. The heater disconnection / deterioration determination method according to the present embodiment is a method for determining disconnection / deterioration of a plurality of heaters provided in a heating cylinder of an injection device constituting an injection molding machine. The heater is supplied with power from a three-phase AC power source. The heater targeted by the present invention is a so-called single-phase heater, which is a heater generally used in an injection molding machine. Such a single-phase heater is selectively connected to any one of the electric wires that supply the three-phase AC power, but the connection method differs depending on the connection method of the three-phase AC power. First, as a first embodiment, an explanation will be given of an injection molding machine in which a three-phase AC power supply for supplying a current to each heater is a three-phase AC electric wire in which an R line, an S line, and a T line are Δ-connected.

  The injection molding machine according to the first embodiment of the present invention is also an injection apparatus for melting and injecting an injection material, a mold clamping apparatus for clamping a mold, and the like, as in a conventional general injection molding machine. FIG. 1A schematically shows the heating cylinder 1 of the injection apparatus according to the first embodiment. A plurality of heaters 2a, 2b,... Are wound around the heating cylinder 1 and heated. In the present embodiment, the three-phase AC power supply for supplying current to these heaters 2a, 2b,... Is connected in a Δ connection in 5R phase, S phase, and T phase. Accordingly, in the present embodiment, each of the heaters 2a, 2b,... Is connected to two predetermined wires among the three-phase AC wires composed of R lines, S lines, and T lines. However, the heaters 2a, 2b,... Are connected in a distributed manner so that the load is not concentrated on a specific electric wire. More specifically, in the present embodiment, as shown in the table of FIGS. 1A and 1A, the first heater 2a is connected to the R and S lines with the second heater. 2b is for the S and T lines, the third heater 2c is for the T and R lines, the fourth heater 2d is for the R and S lines, the fifth heater 2e is for the S and T lines, and 6 heaters 2f are connected to the T line and the R line, respectively. Each of these heaters 2a, 2b,... Is provided with a switch 4a, 4b,. The switches 4a, 4b,... Are composed of solid-state relays, that is, SSRs, electromagnetic contactors, etc., and can be turned on / off at high speed.

  In the first embodiment, among the three-phase AC wires, an R-line current sensor 7r is provided on the R line, and an S-line current sensor 7s is provided on the S line. A heater disconnection / degradation method, which will be described later, is implemented by the line current detected by these. In the present embodiment, the line voltage between the R line and the T line with respect to the T line and the line voltage between the S line and the T line are respectively measured by the voltmeters 10rt and 10st. Yes. From the line voltage and the two-phase line currents of the R phase and the S phase, the heater power is also calculated by a well-known two-watt meter method. These current sensors 7r and 7s are originally power calculation current sensors, and the present invention may use the current sensors 7r and 7s to determine whether the heater is disconnected or deteriorated. it can.

  In the heating cylinder 1 according to the present embodiment, a plurality of temperature sensors are embedded as in the conventional heating cylinder. The temperatures detected by these temperature sensors are input to the controller 8 of the injection molding machine. Specifically, the temperature is input to the temperature controller 9 of the controller 8. However, neither the temperature sensor nor the input signal from the temperature sensor to the temperature controller 9 is shown in FIG. Also in the injection molding machine according to the present embodiment, the temperature of the heating cylinder 1 is controlled by PWM control as in other general injection molding machines. That is, in the controller 8, the temperature controller 9 obtains a deviation between the preset target temperature and the detected temperature, and determines the ratio of current supply to the heaters 2a, 2b,... So that the deviation is reduced. To do. That is, the ratio of the ON time in the control cycle of PWM control, that is, the duty ratio is determined. The PWM controller 11 turns on / off the switches 4a, 4b,... According to the determined duty ratio.

  The controller 8 is provided with a functional block for determining the disconnection / deterioration of the heater, which is shown as the heater determination 13 in FIG. Further, the heater determination 13 can acquire the current threshold value of each heater 2a, 2b,... From the heater information 14 provided in the internal memory of the controller 8. This current threshold is a reference for determining the disconnection or deterioration state of the heaters 2a, 2b,..., And is the lowest value of the normal range of the heater current flowing through the heaters 2a, 2b,. Such a current threshold value is stored in the heater information 14 in advance. These current threshold values are determined with reference to the rated current values of the heaters 2a, 2b,. Alternatively, it is determined with reference to the heater current measured in the initial stage of use of each heater 2, 2b,.

  Hereinafter, a heater disconnection / deterioration determination method according to the present embodiment will be described. This method is performed while controlling the temperature of the heating cylinder 1 by PWM control. That is, the temperature controller 9 obtains a deviation between the target temperature and the temperature measured by the temperature sensor, and adjusts the duty ratio in each heater 2a, 2b,. Based on the adjusted duty ratio, the PWM controller 11 turns on / off the switches 4a, 4b,... To supply current to the heaters 2a, 2b,. While performing such conventional PWM control, the disconnection / deterioration of the heater is determined. FIG. 1C shows the ON / OFF state of the current of the first, second,... 6 heaters 2a, 2b,... In a predetermined two control cycles when the PWM control is performed. . All of the heaters 2a, 2b,... Are turned on at the start of the control cycle, and are turned off in the middle of the control cycle based on the respective duty ratios. Of these heaters 2a, 2b,..., Heaters 2a, 2c, 2d, and 2f connected to the R line are R-line connected heater groups, and heaters 2a, 2b, 2e, and 2d connected to the S line are S. A group of wire connection heaters. Some of the heaters 2a, 2b,... Belong to both the R-line connection heater group and the S-line connection heater group, but none belong to either. The heater disconnection / deterioration determination method according to the present embodiment is performed independently for each of these heater groups.

  The R-line connection heater group is as follows. In the R-line connected heater group, when only one heater is ON while the other heaters are OFF during the control cycle, this heater is determined as a determination target heater. In the example of FIG. 1C, in the R-line connected heater group, only the third heater 2c is turned on at the timing indicated by reference numeral 16. The third heater 2c is set as a determination target, and current is detected by the R-line current sensor 7r at this timing. The detected current is a heater current flowing through the determination target heater 2c. This heater current is compared with the current threshold value of the third heater 2c defined in the heater information 14, and when it is equal to or larger than the current threshold value, it is determined as normal. However, when it is smaller than the current threshold, it is determined that the heater 2c to be determined is deteriorated or disconnected, and the controller 8 issues an alarm. The same determination is made for the S-line connected heater group. That is, in the S-line connected heater group, the heater that is turned on independently at a predetermined timing in the control cycle is the first heater 2 a, and this timing is indicated by reference numeral 17. With this as the determination target heater, the current is detected by the S-line current sensor 7s at this timing. The detected heater current is compared with a current threshold value defined for the first heater 2a, and if it is smaller than the current threshold value, it is determined that the heater is disconnected or deteriorated.

  If the PWM control is continued, the duty ratios of the heaters 2a, 2b,. Then, for each heater group, the heaters that are independently ON in the control cycle also change. If it does so, disconnection and deterioration of a heater will be determined by making the determination object into the heater turned on independently in each heater group at that time. In other words, in the R-line connected heater group, if there is a timing at which heaters other than the third heater 3c are turned on independently within the control cycle, the heater is determined to be disconnected / deteriorated as a determination target, The same applies to the S-line connected heater group.

  The injection molding machine according to the second embodiment of the present invention will be described with reference to FIG. Since the injection molding machine according to the second embodiment of the present invention is similar to the injection molding machine 1 according to the first embodiment, members and function blocks having the same functions are the same as those in the first embodiment. The same code | symbol as the injection molding machine 1 which concerns on a form is attached | subjected, and description is abbreviate | omitted. In the second embodiment, a three-phase AC power supply 5 'that supplies current to the heaters 2a, 2b,... Is different from the first embodiment. In other words, in the second embodiment, the three-phase AC power supply 5 ′ is Y-connected, and R, S, and T lines, which are current lines for R, S, and T phases, and neutral or neutral. A current is supplied to the heaters 2a, 2b,... In this embodiment, each heater 2a, 2b,... Is connected to a predetermined one of the R line, S line, and T line, and the N line. However, as in the first embodiment, the heaters 2a, 2b,... Are dispersedly connected so that the load does not concentrate on a specific electric wire. Specifically, in the present embodiment, as shown in the table of FIGS. 2A and 2A, the first heater 2a is connected to the R line and the N line with the second heater. 2b for S and N lines, 3rd heater 2c for T and N lines, 4th heater 2d for R and N lines, 5th heater 2e for S and N lines, 6 heaters 2f are connected to the T line and the N line, respectively. By the way, it is likely that a heater can be connected to two of the three electric wires R, S, and T excluding the N wire in the Y-connected three-phase AC electric wires. For example, the heater is connected to the R and S lines, the S and T lines, or the T and R lines. In such a case, the heater connected to the R and S lines is connected to the R or S line, and the heater connected to the S and T lines is connected to the S or T line. The heater connected to the T line and the R line may be considered as a heater connected to the T line or the S line, and the heater current can be measured by a current sensor provided on each line. In other words, even in such a case, as is easily understood by those skilled in the art, the heater breaks in the same manner as the injection molding machine according to the first embodiment in which the three-phase AC power source is Δ-connected. Deterioration can be determined. Therefore, in the following, except for such a special connection method, one of the heaters 2a, 2b,... Is connected to the N line, and the other terminal is any of the R line, the S line, and the T line. The description will be limited to a general connection state where the connection is established.

In the second embodiment, a current sensor is provided on each line of the three-phase AC electric wire. That is, an R line current sensor 7r is provided for the R line, an S line current sensor 7s is provided for the S line, and a T line current sensor 7t is provided for the T line. Further, voltmeters 10t, 10s, and 10r are provided on each line, and the phase voltage is measured by these. Also in the second embodiment, the total power is calculated from the phase current and phase voltage of each line.

  In the injection molding according to the second embodiment, the heaters 2a, 2b,... Are controlled by PWM control. While performing this PWM control, the disconnection / deterioration of the heater according to the present embodiment is determined. To do. Of these heaters 2a, 2b,..., The heaters 2a and 2d connected to the R line are R-line connected heater groups, the heaters 2b and 2e connected to the S-line are S-line connected heater groups, and the T-line Let the heaters 2c and 2f connected to the T-line connected heater group. In the second embodiment, each heater 2a, 2b,... Belongs to one of the heater groups, but does not belong to a plurality of heater groups. For each heater group, the disconnection / degradation of the heater is determined independently. Specifically: FIG. 2C shows the ON / OFF state of the currents of the first, second,... 6 heaters 2a, 2b,... In a predetermined two control cycles when PWM control is performed. ing. For the R-line connected heater group, the first heater 2a is turned on independently at the timing indicated by reference numeral 18 in the control cycle. At this timing, the heater current is measured by the R-line current sensor 7r and compared with the current threshold value set for the heater 2a. When the heater current is smaller than the current threshold, it is determined that the heater is disconnected or deteriorated and an alarm is generated. Similarly, for the T-line connected heater group, the third heater 2 c is turned on alone at the timing indicated by reference numeral 19. At this timing, the heater current is measured by the T-line current sensor 7t and compared with the current threshold value set for the heater 2c. When the heater current is smaller than the current threshold, it is determined that the heater is disconnected or deteriorated and an alarm is generated. The same is applied to the S-line connected heater group, and the heater current detected by the S-line current sensor is compared with the current threshold value.

  In the heater disconnection / deterioration determination method according to the present embodiment, since the heater disconnection / deterioration is determined independently for each heater group, the determination can be performed efficiently. However, when an arbitrary heater group is considered, only heaters that are controlled with a higher duty ratio than the others among the heaters belonging to the heater group can be determined. Then, there is a possibility that the determination target heater is biased toward a specific heater. However, it is possible to almost certainly determine deterioration of a deteriorated heater by this method. In general, the heater H has a large heater current If in the state where the heater H is not deteriorated at the initial stage of use, as indicated by a graph 20 in FIG. Since the heater current If is large, the heat generation amount is large, and the ON time in the control cycle can be short. That is, the duty ratio is small. However, when the battery deteriorates after being used for a long time, the heater current I 'of the heater H decreases as shown by the graph of reference numeral 21. That is, it approaches the current threshold Is. If it does so, in order to ensure the required calorific value, ON time in a control cycle will become long. That is, the duty ratio increases. Thereby, it becomes easy to become a heater to be determined. That is, if the heaters 2a, 2b,... Deteriorate, the duty ratio inevitably increases and becomes a determination target heater, so that the deteriorated heater can be almost surely disconnected / degraded.

  Next, a heater disconnection / deterioration determination method according to another embodiment will be described. Similarly to the method described above, this method is used to determine disconnection / deterioration with the heater as a determination target at the timing when only one heater is turned on in the control cycle in each heater group. In this case, the timing for turning on only one sheet is generated for a desired heater. As a result, the disconnection / degradation determination method can always be performed for any of the heaters 2a, 2b,. In implementing this method, two types of control methods are prepared as PWM control, namely, the first half ON type control and the second half ON type control. The first half ON type control is a control method that is turned on at the start of the control cycle and turned off in accordance with the duty ratio as shown in FIG. In this first half ON type control, it is turned off immediately before the end of the control cycle. On the other hand, as shown in FIG. 4A, the latter half ON type control is turned off at the start of the control cycle, is turned on at a predetermined timing, and the ON time is just set to the duty ratio at the end of the control cycle. Control to respond. That is, in the latter half ON type control, it is turned on immediately before the end of the control cycle.

  The heater disconnection / deterioration judgment method according to this embodiment can also be implemented in any of the injection molding machines according to the first and second embodiments described above, and any heater group can have any heater. Can be determined. In order to simplify the description, it is assumed that all of the heaters 2a, 2b, 2c, 2d, and 2e belong to the same heater group. When the heater 2c is selected as a determination target in such a heater group, the heater 2c is temperature controlled by the latter half ON type control, and the other heaters 2a, 2b,. Then, as shown in FIG. 4C, at the time t1 immediately before the end of the control cycle, only the determination target heater 2c is turned on. In this state, since the heater current of the heater 2c can be measured by the current sensor provided in the three-phase AC power supply, the heater current is compared with the current threshold value as in the heater disconnection / deterioration method according to the previous embodiment. Disconnection and deterioration can be determined. When other heaters 2a, 2b,... Are to be determined, only the heater to be determined is controlled by the latter half ON type control, and the other heaters are controlled by the first half ON type control. In the same manner, heater disconnection / deterioration determination is performed.

  In such a heater disconnection / degradation determination method, the heater to be determined is controlled by the latter half ON-type control and the other heaters are controlled by the first half ON-type control. That is, the determination target heater is controlled by the first half ON type control, and the other heaters are controlled by the second half ON type control. If it does in this way, it will be in the state where only the heater for judgment is turned on immediately after the start of a control cycle. Thereby, the heater current can be measured, and the disconnection / deterioration determination of the heater can be performed.

DESCRIPTION OF SYMBOLS 1 Heating cylinder 2 Heater 4 Switch 5 Three-phase alternating current power supply 7r, 7s, 7t R line, S line, T line current sensor 8 Controller 9 Temperature controller 13 Heater determination 14 Heater information

Claims (5)

A plurality of heaters connected to the three-phase AC wires are individually configured so that the number of connections to the R-wire, S-wire, and T-wire of the three-phase AC wires is substantially equal. A heater disconnection / deterioration determination method for determining disconnection / deterioration of a heater in an injection molding machine that is independently PWM controlled by a switch provided in the heater,
In the heater disconnection / deterioration determination method, a heater group connected to the R line among the plurality of heaters is an R line connected heater group, and a heater group connected to the S line is connected to an S line. While performing the PWM control as a heater group, each of the heater groups is determined independently,
In the R-line connected heater group, the current measured by the R-line current sensor provided on the R line is set to the one heater at the timing when only one of the heaters is ON. When the current is smaller than the current threshold, it is determined that the heater has deteriorated or disconnected,
In the S-line connected heater group, the current measured by the S-line current sensor provided on the S-line is set to the one heater at the timing when only one of the heaters is ON. A heater disconnection / deterioration determination method for an injection molding machine, wherein the heater is determined to be deteriorated / disconnected when smaller than a current threshold value.   The heater disconnection / deterioration determination method according to claim 1, wherein among the plurality of heaters, a heater group connected to the T line is a T line connection heater group, and the T line connection heater group includes these When the current measured by the T-line current sensor provided on the T-line is smaller than the current threshold value set for the one heater when only one of the heaters is ON, A method for determining disconnection / deterioration of a heater of an injection molding machine, wherein the determination is that the deterioration / disconnection is present. The method according to claim 1 or 2, wherein the PWM control includes two types of first half ON type control and second half ON type control,
The first half ON type control is turned on at the start of the control cycle and turned off after the ON time corresponding to the duty ratio,
The second half ON-type control is turned off at the start of the control cycle, and is turned on at a predetermined timing so that an ON time corresponding to the duty ratio is obtained at the end of the control cycle,
When determining any one heater in each of the heater groups, one of the first half ON type control and the second half ON type control is performed on the one heater, and the other heater group is controlled. In the injection molding machine, the heater performs the other control so that only one of the heaters is turned on, and the disconnection / deterioration of the one heater is determined. Heater disconnection / degradation method.   The method according to any one of claims 1 to 3, wherein a total power of the plurality of heaters is also calculated.   An injection molding machine, wherein the heater disconnection / deterioration determination method according to any one of claims 1 to 4 is performed.

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