JP3462951B2 - Temperature control device for injection molding machine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved temperature control device for an injection molding machine.

[0002]

Cylinders and nozzles of injection molding machines, injection screws, and injection molding in which the temperature of each part such as a fixed side mold, a movable side mold and a hot sprue attached to the injection molding machine is controlled by a heater. Machines are already known. Generally, a temperature detecting means such as a thermocouple is used as a means for detecting the actual temperature of the controlled object, and the controller turns on / off the heater based on the difference between the detected temperature and the set temperature.
By controlling the time, the actual temperature of the controlled object is made to match the set temperature.

However, if the injection molding machine is used for a long period of time, the temperature detecting means may fail and the temperature control of the controlled object may become impossible. In particular, when a thermocouple is used as the temperature detecting means, if a break occurs in this thermocouple, the temperature of the controlled object is zero regardless of the actual temperature (the electromotive force of the thermocouple is zero).
Therefore, the control device constantly performs ON / OF control in which the ON time of the heater is maximized,
The heater temperature rises abnormally. As a result, carbonization of the resin in the cylinder and nozzle, disconnection of the heater, and
There is also a risk of causing problems such as distortion in each part of the mold.

Conventionally, with respect to such a problem, when the disconnection of the thermocouple is detected, the electric power supply to the heater is completely stopped, and further, the operation of the injection molding machine is forcibly stopped to interrupt the molding work. Was dealt with by.

Of course, from the standpoint of ensuring the safety of the injection molding machine and preventing the entry of defective products, such processing is unavoidable, but once the power of the heater is completely turned off. If the cylinders, nozzles, etc. are cooled, it takes a lot of time to raise the temperature of the cylinders, nozzles, etc. to the moldable temperature again, and the efficiency of the molding operation is significantly reduced.

In particular, when the operator is out of the seat or operates the injection molding machine in an unmanned operation, a considerable amount of time is required before the operation of the injection molding machine or the supply of the heater power supply is actually confirmed. Since time has passed, the cylinders, nozzles, etc. have completely cooled down, and even if the operator discovers an abnormality, it is often the case that not only the restarting of the molding work but also the purging work of the residual resin cannot be started immediately. .

[0007]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to cause an abnormality in the temperature detecting means when operating the injection molding machine in an unmanned state to cause injection molding. Even when the operation of the machine is stopped,
It is an object of the present invention to provide a temperature control device for an injection molding machine, which can restart the operation of the injection molding machine immediately after detecting an abnormality.

[0008]

SUMMARY OF THE INVENTION The present invention is an injection molding method in which the temperature of each member of the injection molding machine is controlled by controlling the heater ON / OFF so that the temperature detected by the temperature detecting means matches the set temperature. in the temperature control device of the machine, the temperature detection
Abnormality detecting means for detecting an abnormality in the output means, and the abnormality detecting means
If no abnormality in the temperature detecting means is detected by the step,
The ON time and OFF time of ON / OFF control are updated sequentially.
The new memory means and the abnormality detection means can be used to detect the temperature.
When a step abnormality is detected, the stored O
ON / OFF control of the heater in N hours and OFF time
The above-mentioned object is achieved by the constitution characterized in that a means for controlling is provided .

[0009]

[0010]

In this configuration, a preset ON
Not the time and the OFF time, but the ON time and the OFF time of the heater at the last moment when the temperature detecting means is normally operating in the closed loop control at the last moment.
Since the ON / OFF control is performed, the temperature of the temperature control target can be maintained in a state close to the set temperature with relatively high accuracy even when there is a disturbance element such as a difference in environmental temperature or humidity. Therefore, similar to the above, even if it is necessary to forcibly stop the operation of the injection molding machine itself due to an abnormality in the temperature detecting means, such as during unmanned operation, at least,
Since there is no concern that the temperature of the heater will rise abnormally, it is not necessary to turn off the power to the heater. In other words, even if the injection molding machine is forcibly stopped due to an abnormality in the temperature detection means during unattended operation, the operator immediately performs the residual resin purging work and the temperature detection means repair after the abnormality detection to perform the injection molding work. Can be restarted.

Further , instead of the means for sequentially updating and storing the ON time and the OFF time, means for sequentially updating and storing the ON time or the OFF time in the set ON / OFF control cycle may be provided . Since the set ON / OFF control cycle is constant, if one of the ON time and the OFF time is known, the other is self-evident and the ON / OFF control can be performed without any trouble.

Further , instead of the means for sequentially updating and storing the ON time and OFF time, the detected temperature is sequentially updated and stored.
And an abnormality in the temperature detecting means is detected ,
With the stored ON time and OFF time, the
Instead of the means for ON / OFF control of the data,
Hand to perform the ON / OFF control 憶temperatures as detected temperature
A step is provided.

Further, while the temperature detecting means is operating normally, the ON time and OFF of the heater in one molding cycle
Means for obtaining an average value of time (or average value of detected temperature) and updating and storing the average value for each molding cycle are provided , and when the abnormality of the temperature detecting means is detected by the abnormality detecting means, the storage is performed. ON / OF of the heater by the average value of the ON time and the OFF time (or the average value of the stored detected temperatures as the detected temperature).
The same purpose as described above can be achieved by providing means for performing F control.

In this configuration, the preset ON
Time and OFF time, or ON time and OFF time (or detected temperature) obtained by closed loop control at the last moment when the temperature detecting means is normally operating, not heater ON time and OFF in one molding cycle Average value of time (or average value of detected temperature)
Then, the ON / OFF control of the heater is performed thereafter. Therefore, in addition to disturbance factors such as differences in environmental temperature and humidity, the heater is turned on / off in a manner that also absorbs temperature changes due to changes in the mode of the injection molding machine itself such as injection / holding pressure, metering, cooling, and mold opening. The control is performed, and the temperature of the temperature control target can be maintained at a temperature close to the set temperature with considerably high accuracy. Therefore, similarly to the above, there is no fear that the temperature of the heater will abnormally rise even if the temperature detecting means has an abnormality during unmanned operation. In other words, even if the injection molding machine is forcibly stopped due to an abnormality in the temperature detection means during unattended operation, the operator immediately performs the residual resin purging work and the temperature detection means repair after the abnormality detection to perform the injection molding work. Can be restarted. Furthermore, since the temperature of the temperature controlled object can be maintained at a temperature close to the set temperature with considerably high accuracy, the injection molding work can be continued without stopping the operation of the injection molding machine depending on the product to be molded. However, there are cases where defective products do not occur.

Further, there may be provided a means for sequentially updated and stored the average of the ON time or OFF time in the setting ON / OFF control period, instead of means for updating stores an average value of the ON time and OFF time . Furthermore
In addition, the abnormality detection means detects an abnormality in the temperature detection means.
If stored, the stored ON time and OF are stored.
Of means for controlling ON / OFF of the heater in F time
Instead, the average value of the stored temperatures is used as the detected temperature.
Means for performing ON / OFF control may be provided.

Since the set ON / OFF control cycle is constant, if one of the average value of the ON time and the average value of the OFF time is known, the other is trivial and the ON / OFF is turned on without any trouble.
Control can be implemented. Of course, each of the above ON / O
PID control can be applied to the FF control.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an outline of a cylinder of an injection molding machine to which the present invention is applied and a control device for driving and controlling the injection molding machine.

Reference numeral 1 is an injection screw, 2 is a cylinder, 3 is a cylinder head attached to the tip of the cylinder 2, 4 is a nozzle fixed to the cylinder head 3, and the outer circumference of the nozzle 4, the cylinder head 3 and the cylinder 2. Band heaters B1 to B6 ... Are mounted. In particular, the cylinder 2 including the cylinder head 3 is divided into a plurality of heating zones, and band heaters B2 to B6 ... Thermocouples TH1 to TH6 for detecting the temperature of each heating zone by the band heaters B1 to B6 ...
.. is attached, and the temperature is controlled for each heating zone. In FIG. 1, a band heater B1 for the nozzle 4, a band heater B2 for the cylinder 2 including the thermocouple TH1 and the cylinder head 3 are provided.
-B6, thermocouples TH2-TH6 as temperature detecting means are shown.

Reference numeral 5 denotes a heater power supply circuit for heating the band heaters B1 to B6 ...
˜B6 ... Includes a switch for passing current. 6,7
Is an A / D converter for converting an analog signal into a digital signal, and the A / D converter 6 includes a cylinder head 3 and a cylinder 2
Thermocouples TH2 to TH6 for detecting the temperature of each heating zone
The output signals of are sequentially input in sequence, the input signals are converted into digital signals, and a channel signal (a signal indicating which thermocouple) is input to the input circuit 21 of the control device 100.
The data (temperature information) converted into the digital signal of the channel is output.

The control device 100 includes a CNC CPU 115 which is a numerical control microprocessor and a PM which is a programmable machine controller microprocessor.
CPU 108 for C, servo CPU 110 which is a microprocessor for servo control, and A / D converter 10
6 has a CPU 107 for pressure monitoring for detecting the injection holding pressure and the back pressure at the time of measurement from the pressure detector on the main body of the injection molding machine through 6 to perform sampling processing, and the mutual input via the bus 112. Information can be transmitted between the microprocessors by selecting the output.

The PMC CPU 108 is connected with the ROM 103 storing a sequence program for controlling the sequence operation of the injection molding machine and the RAM 104 used for temporary storage of operation data, and the CNC CPU 115.
A ROM 117 storing a control program for driving and controlling each axis of the electric injection molding machine and a RAM 118 used for temporary storage of calculation data are connected to the.

Further, each of the servo CPU 110 and the pressure monitoring CPU 107 has a ROM 111 storing a control program dedicated to servo control, a RAM 109 used for temporary storage of data, and a sampling process of injection holding pressure and back pressure. ROM 101 storing a control program for the RAM and RAM used for temporary storage of data
102 is connected.

Further, the servo CPU 110 includes the CPU
Based on the command from 110, the servo amplifier that drives the servo motor of each axis for mold clamping, ejector, injection, screw rotation, etc. is connected, and from the position / speed detector attached to the servo motor of each axis Output is servo CPU1
It is supposed to be returned to 10. The current position of each axis is calculated by the servo CPU 110 based on the feedback pulse from the position / speed detector, and updated and stored in the current position storage register of each axis.

In FIG. 1, the servo amplifier 10 for one axis is shown.
5, only the injection servo motor M1 and the position / speed detector P1 corresponding thereto are shown, but the configuration of each axis for mold clamping, ejector, sprue break, etc. is the same as this. However, for the screw rotation type, it is not necessary to detect the current position, and only the speed may be detected.

Manual data input device 119 with display
Is connected to the bus 112 via a CRT display circuit 116 so that a graph display screen, a function menu can be selected, various data input operations can be performed, and a numeric keypad for inputting numerical data and various function keys can be used. It is provided. The non-volatile memory 114 is a memory for storing molding data that stores molding conditions and various set values, parameters, macro variables, and the like related to injection molding work.

With the above configuration, the PMC CPU 108
Controls the sequence operation of the entire electric injection molding machine, and C
The NC CPU 115 distributes pulses to the servo motors of the respective axes based on the operation program of the ROM 117 for each axis, the molding conditions of the non-volatile memory 114, etc.
The PU 110 performs position loop control, speed loop control, current loop control, etc. in the same manner as in the conventional case based on the movement commands pulse-distributed to each axis and the position and speed feedback signals detected by the position / speed detector. Servo control is performed and so-called digital servo processing is executed to perform injection molding work.

Further, the PMC CPU 108 repeatedly executes a temperature control process for feedback controlling the temperature of each heating zone set in the non-volatile memory 114 as a background process after the power is turned on at predetermined intervals. There is. The temperature control process in this embodiment is based on the set temperature Ts of each heating zone and the detected temperature Tn of each heating zone for each set ON / OFF control cycle T of each band heater. Hereinafter referred to as PID calculation),
The heater power supply circuit 5 is closed via the output circuit 22 only for the calculation result calculated by this PID calculation, that is, for the heating time Tp, and the corresponding band heater is heated (see FIG. 5A). ). Naturally, the lower the detected temperature Tn is with respect to the set temperature Ts, the larger the ratio of the heating time Tp to the set ON / OFF control cycle T becomes.

Needless to say, such temperature control processing is performed for each band heater B1 to B6 ... With different set temperatures of the heating zones.
The contents of the process control are the same except that the OFF control cycle T, the setting state of the temperature Ts, and the detected temperature Tn are different. Therefore, only one heater will be described here as an example. The ON / OFF control cycle T of the band heater attached to the heating zone having a small heat capacity is set shorter than the ON / OFF control cycle T of the band heater attached to the heating zone having a large heat capacity.

However, in such a control method, temperature control cannot be executed unless temperature information Tn from the thermocouple is obtained, and when the thermocouple is disconnected, the temperature control is completely abandoned. There is a problem that you have to do it.

Therefore, in the present embodiment, further, in order to maintain the temperature of the heating zone at the set temperature with a certain degree of accuracy even when the thermocouple is broken, a temperature control process as shown in FIG. For example, the setting ON / OFF control cycle T
It is designed to be executed repeatedly at a cycle sufficiently shorter than that.

CPU 1 for PMC which has started the temperature control processing
08 first determines whether or not the initial setting completion flag F1 is set (step a1). At this stage, the value of the flag F1 remains the initial value, so the PMC CPU 108 sets the flag F1. (Step a1
1) Further, it is determined whether or not the disconnection detection flag F2 is set (step a5). Normally, immediately after the temperature control is started, the thermocouple is not broken, and the flag F2 remains at the initial value.
The PU 108 reads the current temperature Tn of the heating zone detected by the thermocouple via the input circuit 21 (step a).
6), the value corresponding to the output when the thermocouple is broken (0
It does not mean ° C), that is, whether or not the thermocouple is broken (step a7).
As mentioned earlier, there should be no disconnection at this stage.

Next, the PMC CPU 108 performs PID calculation based on the detected temperature Tn and the set temperature Ts of the heating zone set in the non-volatile memory 114 to match the temperature of the heating zone with the set temperature. The heating time Tp of the band heater is calculated, and this value is stored in the register R (step a8). Then, the elapsed time measurement timer Tx is restarted (step a9), the heater power supply circuit 5 is closed via the output circuit 22, the heating of the corresponding band heater is started (step a10), and the temperature control process of this cycle is performed. To finish.

Since the initial setting completion flag F1 has already been set in the next processing cycle, the PMC CPU 108 determines that the elapsed time Tx after the start of energization is the current value of the register R, that is, the heating after the determination processing of step a1. It is determined whether or not the time Tp has been reached (step a2), and if not reached, the temperature control process of this cycle is ended.

Thereafter, the PMC CPU 108 performs steps a1 and a in the same manner as above at every predetermined cycle until the elapsed time Tx after the start of energization reaches the heating time Tp.
Only the determination process 2 is repeatedly executed.

When it is confirmed that the elapsed time Tx has reached the heating time Tp in the determination processing of step a2, P
The MC CPU 108 opens the heater power supply circuit 5 via the output circuit 22, stops heating of the corresponding band heater (step a3), and sets the elapsed time Tx after the start of energization O
It is determined whether or not the N / OFF control cycle T has been reached (step a4).

If the elapsed time Tx has not reached the ON / OFF control cycle T, the PMC CPU 108 keeps heating the corresponding band heater until the elapsed time Tx reaches the ON / OFF control cycle T. In the same manner as described above, only the processes of steps a1 to a4 are repeatedly executed. As a result, the corresponding band heater is ON /
In the OFF control period T, heating is performed only during the first Tp and cooling is performed during the remaining T-Tp (see FIG. 5A).

When it is confirmed by the determination processing in step a4 that the elapsed time Tx has reached the ON / OFF control cycle T, the PMC CPU 108 causes the disconnection detection flag F2.
Is set (step a)
5). If the disconnection detection flag F2 is not set,
The PMC CPU 108 re-establishes the current temperature T of the heating zone.
n is read (step a6), and it is determined whether or not the value corresponds to the output when the thermocouple is disconnected, that is, whether or not the thermocouple is disconnected (step a7),
If no disconnection has occurred, perform step a as described above.
The process from 8 to step a10 is executed, and the next ON / O
The energization time Tp corresponding to the FF control cycle T is obtained, updated and set in the register R, the elapsed time measurement timer Tx is restarted to start energization to the corresponding band heater, and the temperature control process of this cycle is ended. .

Therefore, as long as the thermocouple is not broken, O
For each N / OFF control cycle T, the energization time Tp for eliminating the difference between the current temperature Tn of the heating zone and the set temperature Ts at that time is calculated, and only during the first Tp of the ON / OFF control cycle T. The process of heating the corresponding band heater and cooling this band heater only during the remaining T-Tp is repeatedly executed.

Of course, since the difference between the set temperature Ts and the detected temperature Tn is large at the startup stage when the power is turned on, the setting ON /
The heating time Tp occupies a large proportion of the OFF control cycle T, but as time elapses and the heating zone approaches the state of thermal equilibrium and the deviation is eliminated, the proportion of the heating time Tp occupies becomes smaller, and the heating time Tp is almost in equilibrium. When the state is reached, that is, when the state in which only the heat newly taken up by the resin and the outside air supplied to the heating zone needs to be compensated by the heating from the band heater, the heating time Tp is set to ON /
The proportion occupied in the OFF control cycle T stabilizes at a substantially constant value, for example, as shown in FIG. 5A, regardless of the elapsed time.

Generally speaking, until the temperature of each heating zone reaches a set value, fully automatic operation or unmanned operation is not started. After that, that is, the heating time Tp is set to ON
It can be considered that the ratio occupying the / OFF control period T becomes substantially constant.

Therefore, when a break occurs in the thermocouple under such a circumstance, the PMC CPU 108 causes this abnormality at least from the occurrence of the break to the elapse of the set ON / OFF control cycle T. It is detected in the discrimination processing in step a7. The determination processing in step a7 is ON / OFF
This is because it is repeatedly executed every control cycle T.

The PMC CPU 108 which has detected the disconnection of the thermocouple in the determination processing of step a7, the disconnection detection flag F2.
Is set (step a12), a warning message relating to the occurrence of disconnection is displayed on the screen of the manual data input device with a display 119 (step a13), and then steps a9 and step are performed in the same manner as when no disconnection occurs. The process of a10 is executed, the elapsed time measurement timer Tx is restarted, the energization of the corresponding band heater is started, and the temperature control process of this cycle is ended.

However, when the occurrence of disconnection is detected, the process of step a8 is not executed, so the energization time Tp
Is not rewritten, and the value of the energization time Tp obtained in the process of step a8 before the occurrence of disconnection is directly stored in the register R.
Will be held in.

As a result of the disconnection flag F2 being set by the detection of the disconnection, even if the value of the elapsed time measurement timer Tx reaches the set ON / OFF control cycle T in the subsequent processing cycles, the processing of steps a6 to a8 is performed. The processes of steps a12 and a13 are not executed.

Therefore, after the occurrence of disconnection of the thermocouple, regardless of the actual temperature of the heating zone, ON / O of the band heater is turned on by the value of the energization time Tp calculated immediately before the disconnection.
The FF control will be repeated. Naturally, this control does not require detection of the actual temperature with a thermocouple.

As described above, after the temperature of the heating zone is raised to the set temperature Ts and becomes stable, the heating time Tp is set to O.
Since the ratio to the N / OFF control cycle T becomes a substantially constant value regardless of the elapsed time, the temperature of the heating zone can be set to the set temperature with a certain degree of accuracy even if the feedback control by the thermocouple is not necessarily performed. It is possible to maintain.

Of course, such temperature control cannot be generally said to be suitable for the molding operation of a precise product, but at least it is detected by the breakage of the thermocouple as in the case where the feedback control is continued as it is. When the output becomes zero, the apparent temperature deviation does not increase, the temperature of the heating zone becomes abnormally high, and the band heater does not burn out. Further, since there is no problem that the resin in the cylinder 2 is carbonized, the band heater can be directly energized.

Therefore, in the case where a rough product is being molded, the injection molding machine can be continuously operated while the band heater is energized to continue the molding operation, and the operator has a manual data input device 119 with a display. After confirming the disconnection message, the thermocouple replacement work and the like may be performed at a later time.

Further, in the case where a precision product is being molded, it is not possible to continue the molding operation as it is, so step a with the band heater still energized.
In step 13, the driving of the injection molding machine body is stopped. In this case, the molding operation cannot be continued, but even if the operator has left his / her seat or the thermocouple has been disconnected and the injection molding machine has been left unattended during molding operation during unattended operation. Since the temperature does not drop, there is an advantage that the operator can restart the injection molding work by immediately purging the residual resin and repairing the thermocouple after confirming the abnormality of the thermocouple.

If it is necessary to continue the injection molding operation for a product having a certain degree of precision even after the thermocouple is broken, the temperature control process as shown in FIGS. 3 and 4 is performed. It is desirable to apply it to obtain the average value of the ON time of the band heater in one molding cycle, and perform ON / OFF control of the band heater after the thermocouple is disconnected.

According to the temperature control process as shown in FIGS. 3 and 4, the band heater absorbs the temperature change due to the mode change of the injection molding machine itself such as injection / holding pressure, metering, cooling and mold opening. ON / OFF control of
The temperature of the heating zone can be maintained at a temperature close to the set temperature with considerably high accuracy, and even for products with a certain degree of precision,
It becomes possible to continue the injection molding work as it is after the thermocouple is broken.

The temperature control process shown in FIGS. 3 and 4 will be briefly described below. First, the processes of steps b1 to b8 are the same as those of steps a1 to
The same as the processing of step a8, and the processing of steps b11 and b12 are the same as the processing of steps a9 and a10 in the above-described embodiment,
The processing of step b13, step b17, and step b19 is the same as the processing of step a11, step a12, and step a13 in the above-described embodiment.

The difference between this embodiment and the above-described embodiment is that the processing of step b8 corresponding to the processing of step a8 in the above-described embodiment and the processing of step a9 in the above-described embodiment are exclusively performed. Step b
Between the processing of 11 and the processing of 11, the processing for obtaining the average time Tb of one molding cycle occupied by the heating time Tp with respect to the set ON / OFF control cycle T is inserted.

That is, the PMC CPU 108, similar to the above-described embodiment, in the state where the thermocouple is not broken, the heating time of the band heater for making the temperature of the heating zone equal to the set temperature for each processing cycle. After calculating Tp and storing it in the register R (step b8), it is judged whether or not this processing cycle coincides with the mold closing start timing of the injection molding machine (start of one molding cycle) (step b8).
9) If it is not the mold closing start timing, the heating time Tp calculated in this processing cycle is set to the heating total time storage register Ti.
Is accumulated and stored (step b10).

If this processing cycle coincides with the mold closing start timing, the PMC CPU 108 divides the value of the heating total time storage register Ti by the value of the molding cycle timer Ty to obtain one molding cycle time Ty. On the other hand, the ratio [Ti / Ty] occupied by the total heating time Ti of the band heater is calculated (see FIG. 5B), and the ratio is set to ON / OF.
An average time Tb for heating the band heater during the one-set ON / OFF control period T by multiplying the F control period T (see FIG. 5).
(See (c)) (step b14). Then, the heating time Tp obtained in the processing of step b8 in this processing cycle is updated and stored in the total heating time storage register Ti (step b15), and the molding cycle timer Ty is restarted (step b16).

As a result, the molding cycle timer Ty stores the time required from one mold closing start timing to the next mold closing start timing, that is, the time required for one molding cycle (see FIG. 5A). , Heating total time memory register T
Since i stores the integrated value of the time during which the band heater is energized during the one molding cycle (see FIG. 5).
(Refer to (b)), the setting ON / OFF control cycle T becomes [Ti /
Ty], one setting ON / OFF control cycle T
That is, the average value of the time Tb (see FIG. 5C) during which the band heater should be energized is calculated during the period. In the determination process of step b9 in this embodiment, the mold closing start timing is used as the determination reference. In short, the required time for one molding cycle is stored in the molding cycle timer Ty, and one molding cycle is stored in the heating total time storage register Ti. Since it is sufficient to store the total energization time between them, there is no problem in setting the timing such as the start of injection, the start of weighing, the start of mold opening, etc., as the determination criterion.

After the wire breakage occurs in the thermocouple, the wire breakage detection flag F2 is set in the same manner as in the above-described embodiment (step b17), and the energization time of the band heater in each heating zone is broken. It is fixed to the value of the energization time Tb obtained in the process of step b8 at the time of completion of the molding cycle before the occurrence (step b1).
8).

Of course, while the thermocouple is alive, feedback control is performed based on the current temperature Tn of the heating zone and the set temperature Ts, so injection molding such as injection / holding pressure, metering, cooling, mold opening, etc. It is possible that the environment around the heating zone changes due to a change in the mode of the machine itself, and the value of the energization time Tp calculated in each ON / OFF control cycle may fluctuate. For example, since the total mass of the metal that contacts the tip of the nozzle 4 is reduced in the mold open state, the heat radiation amount of the nozzle 4 is reduced and the time required for energizing the band heater B1 is shortened, but when the die is closed, For example, the total mass of metal that contacts the tip of the nozzle 4 increases, the amount of heat released by the nozzle 4 increases, and the time required for energizing the band heater B1 increases.

In this embodiment, the energizing time of the band heater is not adjusted by coping with such a change in the cooling characteristic of the heating zone during one molding cycle (a change in the mode of the injection molding machine itself). As already mentioned, the amount of heat for one molding cycle given to each heating zone when the thermocouple is in a healthy condition and the feedback control of the temperature and the open loop control after the thermocouple is broken Since the amount of heat for one forming cycle given to each heating zone is equal, the fluctuation of the disturbance can be leveled as a whole to make the amount of heat supplied for one forming cycle uniform, and the thermocouple remains disconnected. Even when the injection molding work is continued, the temperature of the heating zone does not rise or fall more than necessary, and the temperature of the heating zone is set to a more appropriate value as compared with the above embodiment. It can be held.

Therefore, similarly to the above-mentioned embodiment, it is not necessary to turn off the power source of the band heater when the thermocouple is disconnected, and further, even for a product having a certain degree of precision, the injection molding work is continued after the thermocouple is disconnected. It becomes possible to do it.

In the above embodiment, after the disconnection occurs, O
ON / OFF of band heater with constant N / OFF control cycle T
Although the one for adjusting the value of the time Tp (or Tb) has been described, it goes without saying that the ON / OFF control cycle T is kept constant and O
The same processing as described above can be performed by adjusting the FF time T-Tp (or T-Tb).

Furthermore, the ON time and the OFF time itself in the final ON / OFF control cycle when the thermocouple is alive, or the final ON time for one molding cycle when the thermocouple is alive. It is also possible to obtain and store the average of the OFF time and the OFF time, and execute the ON / OFF control after the wire break according to these values.

Further, if it is not necessary to continue the molding work after the thermocouple is disconnected and simply to prevent the resin from sticking due to the temperature decrease of the cylinder 2, the ON time of the band heater in the immediately preceding processing cycle is stored. It is not always necessary to obtain the average value of the ON time of the band heater before one molding cycle, and the value set in the register R when the disconnection is detected may be a preset setting value.

As a matter of course, each of the embodiments described in detail above is not limited to the cylinder of the injection molding machine, but also various other members that require temperature control, such as a fixed-side mold or a movable mold attached to the injection molding machine. It can be easily applied to peripheral devices such as side molds and hot sprue.

In one embodiment of the present invention, the heater O
Although the N time and the OFF time are stored, the detected temperature may be sequentially updated and stored instead of storing these times. In this case, the processes of steps a5 and a12 in FIG.
Between step 7 and step a8 (when Tn is not 0), a process of updating and storing the temperature read in step a6 in the register R'is added, and in step a8, PID control is performed by the detected temperature Tn stored in this register R '. Perform the energizing time. Then, when Tn = 0 is detected in step a7 and a break in the thermocouple is detected, step a1
The disconnection display corresponding to No. 3 is performed, and the processing of step a is performed without performing the processing of updating and storing the added read temperature in the register R '. As a result, the temperature control after the disconnection is performed by the temperature detected immediately before the disconnection occurs, and the energization time Tp obtained in step a8 is fixed to the energization time immediately before the disconnection.

Further, as a method corresponding to the method of obtaining the average value shown in FIGS. 3 and 4, instead of obtaining the average value of the energization time, the average value of the detected temperature is obtained, and when a disconnection occurs, this PID control may be performed according to the average value of the detected temperatures.

In the above-described one embodiment of the present invention, the temperature control process is performed by the control device 100 for controlling the injection molding machine. However, a temperature controller is provided to set the target temperature set by the temperature controller. The present invention can also be applied to the case where the PID control is performed by the temperature detected by the thermocouple as the temperature detecting means and the feedback control is performed so that the detected temperature matches the set target temperature. In such a case, the ON time or OFF time output from the temperature controller is output to the control device 100, the control device 100 updates and stores the ON time or OFF time, and the thermocouple is disconnected. When ON is detected, the stored ON time or OFF time may be output to the temperature controller, and the temperature controller may control the ON time or OFF time.

Furthermore, the control device 100 detects and updates and stores the temperature at every predetermined cycle through the temperature controller or directly from the thermocouple, and when the disconnection of the thermocouple is detected, the signal from the thermocouple is detected. Instead, the stored detected temperature is configured to be output to the temperature controller, and after the thermocouple is disconnected, the temperature controller outputs PID control or the like using the temperature output from the control device 100 as the detected temperature, and turns it on / off.
It should be controlled.

[0070]

According to the present invention, even if an abnormality occurs in the temperature detecting means of the injection molding machine, the temperature of the temperature control target can be maintained at a temperature close to the set temperature with a certain degree of accuracy thereafter. It is not necessary to stop the power supply to the heater even when an abnormality occurs in the temperature detecting means during the unmanned operation of the injection molding machine.

Therefore, even if the injection molding machine is forcibly stopped due to an abnormality in the temperature detecting means during unmanned operation and the injection molding machine is left as it is, the cylinder or the like does not cool down, and the operator who returns is returned. Immediately after confirming the abnormality of the temperature detecting means, the residual resin purging operation or repairing operation can be performed to restart the injection molding operation.

Further, in the case of molding a rough product, it is possible to continue the injection molding work without stopping the operation of the injection molding machine in order to prevent the generation of defective products. There is.

[Brief description of drawings]

FIG. 1 is a block diagram showing the outline of a cylinder of an injection molding machine according to an embodiment to which the present invention is applied and a control device for driving and controlling the injection molding machine.

FIG. 2 is a flowchart showing an outline of temperature control processing by a control device of the injection molding machine of the embodiment.

FIG. 3 is a flowchart showing an outline of temperature control processing in another embodiment.

FIG. 4 is a continuation of the flowchart showing the outline of the temperature control processing.

FIG. 5: O of the heater with a constant ON / OFF control cycle
It is an operation principle figure at the time of implementing temperature control of a heating zone by adjusting N time or OFF time.

[Explanation of symbols]

1 screw 2 cylinders 3 cylinder head 4 nozzles 5 Heater power supply circuit 6,7 A / D converter B1-B7 band heater TH1 to TH7 thermocouple 100 control device 108 PMC CPU 114 non-volatile memory

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-4-164622 (JP, A) JP-A-4-276417 (JP, A) JP-A-62-121120 (JP, A) JP-A-62- 35824 (JP, A) JP-A-60-242029 (JP, A) JP-A-4-148912 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B29C 45/78 B29C 45 / 74 B29C 45/84

Claims (6)

(57) [Claims] 1. A temperature control device for an injection molding machine, wherein the heater is ON / OFF-controlled so that the temperature detected by the temperature detecting means matches a set temperature, thereby controlling the temperature of each member of the injection molding machine. Abnormality detecting means for detecting an abnormality of the temperature detecting means, and means for successively updating and storing the ON time and OFF time of the ON / OFF control if the abnormality detecting means does not detect the abnormality of the temperature detecting means, When the detection means detects an abnormality in the temperature detection means, the stored ON time and OFF are stored.
A temperature control device for an injection molding machine, comprising a means for performing ON / OFF control of the heater depending on time. Instead of claim 2 wherein the means for sequentially updating and storing the ON time and OFF time, for an injection molding machine according to claim 1 further comprising means for sequentially updating and storing the ON time or OFF time in the setting ON / OFF control period Temperature control device. 3. A means for sequentially updating and storing the detected temperature instead of sequentially updating and storing the ON time and the OFF time, and when an abnormality of the temperature detecting means is detected by the abnormality detecting means, it is stored in the memory. ON time and O
Instead of the means for performing ON / OFF control of the heater in the FF time, the stored temperature is used as the detected temperature for ON / O.
Temperature control apparatus for an injection molding machine according to claim 1, further comprising a means for performing FF control. 4. A temperature control device for an injection molding machine, wherein the temperature of each member of the injection molding machine is controlled by ON / OFF controlling the heater so that the temperature detected by the temperature detecting means matches the set temperature. An abnormality detecting means for detecting an abnormality of the temperature detecting means, and if the abnormality detecting means does not detect an abnormality of the temperature detecting means, an average value of the ON time and the OFF time of the heater in one molding cycle is obtained, and the average value is calculated. For updating and storing each of the molding cycles, and when the abnormality detecting means detects an abnormality in the temperature detecting means, the stored ON time and OFF
A temperature control device for an injection molding machine, comprising a means for performing ON / OFF control of the heater depending on time. 5. Instead of means for updating stores an average value of the ON time and OFF time, according to claim 4 further comprising means for sequentially updated and stored the average of the ON time or OFF time in the setting ON / OFF control period Temperature controller for injection molding machine. 6. A means for obtaining and updating an average value of detected temperatures instead of the means for updating and storing the average value of the ON time and the OFF time, and the abnormality of the temperature detecting means is detected by the abnormality detecting means. In the case, the ON / OF of the heater is turned on / off by the stored ON time and OFF time.
5. The temperature control device for an injection molding machine according to claim 4, further comprising means for performing ON / OFF control by using an average value of the stored temperatures as a detection temperature, instead of means for performing F control.