JP5002697B2 - Temperature control device - Google Patents

Description

  The present invention relates to a temperature control device that controls the temperature of a heating means.

  For example, in a dry electrophotographic apparatus such as a copying machine, a toner image formed on a photosensitive drum is transferred onto a transfer paper by a transfer device, and the toner image on the transfer paper is thermally fixed onto the transfer paper by a heat fixing device. . The fixing roller incorporated in such a heat fixing device incorporates a heater, and the fixing roller is heated by the heater, and the temperature of the fixing roller surface is controlled to be constant.

  As such a temperature controller for a fixing device, for example, a temperature controller as shown in FIGS. 10 to 12 is known.

  First, the temperature control device of FIG. 10 will be described. An AC power supply 103 is connected to the heater 102 of the fixing roller 101 through a switching circuit 104. The surface temperature of the fixing roller 101 is converted into an output signal a having a voltage value corresponding to the temperature by the thermistor 105, input to the input port P 0 of the microcomputer 106, and A / D converted. When the detected temperature is lower than the target temperature, the microcomputer 106 outputs H indicating ON to the switching circuit 104 to the output port P1 (signal b), and when the detected temperature is higher than the target temperature, it means OFF. L to be output is output to the output port P1 (signal b).

  A thermo switch 107 is connected between the AC power source 103 and the heater 102. When the microcomputer 106 continues to turn on the output port P1 that controls on / off of the switching circuit 104 due to a microcomputer runaway or software bug due to electrical noise or the like, the switching circuit 104 is turned on. Subsequently, it works when the temperature of the fixing roller 101 is excessively raised, and the power supply to the fixing roller 101 is cut off.

  Next, the temperature control device of FIG. 11 will be described. An AC power supply 103 is connected to the heater 102 of the fixing roller 101 through a switching circuit 104. The surface temperature of the fixing roller 101 is converted by the thermistor 105 into an output signal a having a voltage value corresponding to the temperature, input to the input port P0 of the microcomputer 116, and A / D converted. Bit 3 of the register 1167 for controlling the output port P1 of the microcomputer 116 is assigned to turn on / off the heater 102. When the detected temperature obtained by converting the signal a input to the input port P0 into the temperature is lower than the target temperature, the microcomputer 116 writes, for example, 1 indicating that the heater is turned on to the bit 3 of the register 1167 to the switching circuit 104. On the other hand, H indicating ON is output to the output port P1 (signal b). On the other hand, when the detected temperature is higher than the target temperature, 0 indicating heater OFF is written in bit 3 of the register 1167 to output the output port. L indicating OFF is output to P1 (signal b).

  Bits other than bit 3 of the register 1167 are assigned to control other input / output ports. A thermo switch 107 is connected between the AC power source 103 and the heater 102 to cut off the power supply to the heater 102 when the fixing roller 101 is overheated.

  Next, the temperature control device of FIG. 12 will be described. This temperature control device differs from the temperature control device of FIG. 11 in that a register 1207 for writing 1 and 0 indicating heater on / off is provided in the IC 120 outside the microcomputer 126, and the register 1207 has an address bus for the microcomputer 126. Data bus, control signal, etc. are connected.

  In the temperature control device of FIG. 10, the thermo switch 107 that should operate when the temperature rises excessively may not operate quickly even if the fixing roller 101 is excessively heated. For example, when the temperature of the fixing roller 101 is excessively raised from room temperature in the morning, it takes time until the temperature of the thermo switch 107 increases. As a result, the fixing roller 101 and the bushing of the fixing roller 101 may be damaged.

  As a method for solving such a problem, for example, a method described in JP-A-4-13681 is known. According to this method, when energization to the heater is forcibly turned off periodically for a certain time, and the heater on-state detected by the heater on / off state detecting means continues for a certain time or longer. The energization to the heater is cut off.

  However, in such a method, when it is determined that there is an abnormality and the power supply to the heater is cut off, it is determined whether a failure has occurred in a switching circuit such as an SSR or an abnormal operation of the microprocessor. I could not.

  Further, even when the temperature of the fixing roller is low, the power supply to the heater is periodically turned off and on, so that there is a problem that the AC power supply voltage fluctuates according to the intermittent current flowing to the heater during energization and interruption. there were.

  On the other hand, in the temperature control device of FIG. 11, the heater 102 is turned on simply by writing 1 to bit 3 of the register 1167, so the heater is turned on due to a simple bug of the microcomputer 116 program or malfunction due to noise or the like. There was a possibility that it was made.

  Further, bits other than bit 3 of the register 1167 are assigned to other input / output ports, and the register 1167 is frequently accessed for purposes other than on / off of the heater 102. Therefore, for purposes other than heater on / off. When the register 1167 is accessed, bit inversion occurs due to electrical noise or the like, and the heater 102 may be turned on unnecessarily.

  In such a case, similar to the temperature control device of FIG. 10, the thermo switch 107 that should operate when the temperature is excessively high may not operate quickly even if the fixing roller is excessively heated. For example, when the temperature of the fixing roller 101 is excessively raised from room temperature in the morning, it takes time until the temperature of the thermo switch 107 increases. As a result, the fixing roller 101 and the bushing of the fixing roller 101 may be damaged.

  Next, in the temperature control device of FIG. 12, the IC 120 is provided outside the microcomputer 126, and the address bus, data bus, control signal, etc. of the microcomputer 126 are connected to the IC 120. Since data is written to 1207, when it is attempted to control the on / off of the heater 102, electrical noise may act on these buses and control signals.

  When the microcomputer 126 tries to perform a write access to another address, a part of the address is inverted due to such electrical noise, and the IC 120 erroneously recognizes that the write to the register 7 is performed. There was a case.

  Due to this misrecognition, the heater 102 is turned on or an access for rewriting a bit allocated to another function arranged in the register 1207 is performed, and the bit 3 for heater on / off is inverted by electrical noise. As a result, the heater 102 may be turned on unnecessarily.

  A first object of the present invention is to solve the above-described problems and provide a temperature control device capable of stopping power supply to a heater before the fixing roller overheats.

  The second object of the present invention is to solve the above-described problems and to detect a failure of the temperature control device without turning off and on the extra heater even when continuous energization of the heater is necessary. An object of the present invention is to provide a temperature control device that can be used.

  The third object of the present invention is to provide a temperature control device that can solve the above-described problems and prevent malfunctions caused by electrical noise.

The present invention provides a temperature detection means for detecting the temperature of the heating means, and when the temperature detected by the temperature detection means is lower than the target temperature, an ON instruction is given, and the detected temperature is higher than the target temperature. , An instruction means for instructing to turn off, the first to nth (≧ 2) registers, and the first register is set to a first predetermined value when the instruction means instructs to turn on, and an instruction to turn off is given. First setting means for setting a second predetermined value when the first setting means, and before the first setting means sets the first predetermined value in the first register, The second setting means for setting a third to n + 1th predetermined value each time ON is instructed by the instruction means, and the contents of the second to nth registers are the third to n + 1th predetermined values, respectively. Same as value In the same case, the first predetermined value is set in the first register in a state where the heating unit ON permission state is determined and the determination unit determines that the heating unit ON permission state is determined. If turned on, the power supply to the heating means is turned on, and when the first setting means sets a second predetermined value in the first register, on / off means to turn off the power supply to the heating means, It is provided with.

  As described above, according to the present invention, since it is configured as described above, the power supply to the heater can be stopped before the fixing roller overheats.

  In addition, according to the present invention, since it is configured as described above, it is possible to detect a failure of the temperature control device without turning off and on the extra heater even when continuous energization of the heater is necessary.

  Furthermore, according to the present invention, since it is configured as described above, it is possible to prevent malfunction caused by electrical noise.

It is a block diagram which shows the 1st Embodiment of this invention. It is a flowchart which shows an example of the program stored in the microcomputer 6. It is a timing chart for explaining temperature control operation. It is a block diagram which shows the example of a circuit which can latch an abnormal signal. It is a block diagram which shows the 2nd Embodiment of this invention. 4 is a flowchart illustrating an example of a program stored in a microcomputer 56. It is a timing chart for explaining temperature control operation. It is a block diagram showing an example of a circuit capable of preventing flicker. It is a block diagram which shows the 3rd Embodiment of this invention. It is a block diagram which shows the 4th Embodiment of this invention. It is a block diagram which shows an example of the conventional temperature control apparatus. It is a block diagram which shows another example of the conventional temperature control apparatus. It is a block diagram which shows the other example of the conventional temperature control apparatus.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
<First Embodiment>
FIG. 1 shows a first embodiment of the present invention. In FIG. 1, reference numeral 2 denotes a heater built in the fixing roller 1, which is connected to an AC power source 3 through a switching circuit 4. Reference numeral 5 denotes a thermistor brought into contact with the fixing roller 1 for detecting the temperature. A voltage signal a corresponding to the temperature from the thermistor 5 is inputted to the input port P0 of the microcomputer 6. A thermoswitch 7 is connected between the AC power supply 3 and the heater 2 and cuts off the power supply to the heater 2 when the fixing roller 1 is overheated. Reference numeral 8 denotes a periodic timer, and a timer input b from the periodic timer 8 is input to the input port P1 of the microcomputer 6. The microcomputer 6 controls the temperature at the timer input period.

  The switching circuit control unit 9 includes an output port 10, a monitoring timer 11, and an AND gate 12. The bus and control signals from the microcomputer 6 are input to the output port 10 of the switching circuit control unit 9, and the microcomputer 6 accesses the output port 10 to control on / off of the heater 2. The output port 10 can control the signal c for controlling the switching circuit 4 to be on (H) or off (L) by performing write access for the microcomputer 6 to turn on / off the port P2. The monitoring timer 11 monitors the access from the microcomputer 6 to the output port 10 and outputs an abnormality signal d that becomes L when an abnormality is detected. Then, the output signal c of the output port 10 and the monitoring timer abnormality signal d are ANDed by the AND gate 12, and as a result, when an abnormality is detected by the monitoring timer, the control signal e connected to the switching circuit 4 becomes L. .

  A microcomputer 6, a periodic timer 8, and a switching circuit control unit 9 are arranged on the engine board, and an AC power supply 3 and a switching circuit 4 are arranged on the power supply board.

  Next, the temperature control operation will be described. When the timer output b from the period timer 8 is input to the input port P0, the microcomputer 6 A / D converts the voltage signal a output from the thermistor 5 into a temperature, and compares this detected temperature with the target temperature. When the detected temperature is higher than the target temperature, a write access is performed to turn off the port P2 for the output port 10. On the other hand, when the detected temperature is lower than the target temperature, the port P2 is turned on for the output port 10. Perform write access.

  The microcomputer 6 is programmed to perform a write access for turning on the port P2 to the output port 10 every time the timer output b of the cycle timer 8 is received even when the heater is continuously turned on.

  The monitoring timer 11 measures time while the output port 10 is turned on, and when there is a write access to turn on the port P2 again or a write access to turn off the port P2 to the output port 10, Reset the time. When the output port is turned on, the monitoring timer 11 outputs an abnormal signal when there is no write access for turning on the port P2 again or write access for turning off the port P2 for a preset time. This set time is set longer than the cycle time of the cycle timer 8.

  The abnormality signal d output from the monitoring timer 11 becomes L when an abnormality is detected, and is input to the AND gate 10, and when the abnormality is detected, the output e of the AND gate 10 is set to L, so that the switching circuit 4 is turned off.

  FIG. 2 is a flowchart showing an example of a program stored in the microcomputer 6. When temperature control is required, the timer output (P1: signal b) from the periodic timer 8 is waited at S0, and when the timer output is present, the voltage signal a from the thermistor 5 is converted to temperature at S1. Compare the detected temperature with the target temperature. If the detected temperature is higher than the target temperature, in S5, write access is performed to turn off the port P2 to the output port 10, and then the process returns to S0 and waits for the next timer output. On the other hand, if the detected temperature is lower than the target temperature in S1, the write access for turning on the port P2 is performed to the output port 10, and then the process returns to S0.

  Even when the output port P2 is already H and the detected temperature is lower than the target temperature, since the write access for turning on the port P2 is performed for the output port 10 in the process of S2, the microcomputer 6 If there is no abnormality in operation, write access to the port P2 is always performed periodically, and the monitoring timer 11 does not detect abnormality.

  Therefore, it is possible to detect that the operation of the microcomputer 6 is abnormal by detecting the abnormality of the monitoring timer 11.

  Next, the temperature control operation will be described with reference to the timing chart of FIG. The timer output b of the period timer 8 outputs a timer pulse at a constant period. When the timer output b of the periodic timer is input, the microcomputer 6 compares the detected temperature detected by the thermistor 5 with the target temperature. When the detected temperature is higher than the target temperature, a write access for setting the port P2 (signal c) to L to the switching circuit 4 is performed, and the heater 2 is not energized.

  On the other hand, when the detected temperature is lower than the target temperature when the timer output b from the periodic timer 8 is input, the microcomputer 6 performs a write access for setting the output port P2 (signal c) to the switching circuit 4 to H. I do.

  If the detected temperature does not reach the target temperature even when the timer output of the next periodic timer 8 is input, the microcomputer 6 returns to H again even if the control signal c to the switching circuit 4 has already been H. Write access is performed.

  When the microcomputer 6 and the periodic timer 8 are operating normally, even when the heater is continuously turned on, the write access to the output port P2 is performed every period of the periodic timer 8 as shown in FIG. become. That is, the existence of such a write access indicates that the periodic temperature control is normally performed.

  On the other hand, when there is an abnormality in the operation of the microcomputer 6 or the like, periodic write access is not performed while the output port 10 outputs H as in the signal c ′, and the abnormality signal d ′ is output from the monitoring timer 11. It is output and it is detected that some abnormality has occurred in the operation of the microcomputer 6.

  When an abnormality is detected and an abnormality detection signal is output, the signal can be latched by the latch 13 as shown in FIG. 4 so that the heater is not turned on again.

  If the operation of the microcomputer 6 of the temperature control system becomes abnormal, all devices controlled by the microcomputer 6 may be abnormally controlled, and the microcomputer 6 continues to operate as it is. It is not preferable to make it. Therefore, it is desirable to reset the microcomputer 6 when a temperature control abnormality is detected. In such a case, after the microcomputer 6 is reset and restarted, an abnormal operation is performed again, and the heater 2 is turned on even though the temperature of the temperature control target is high. Although the microcomputer 6 is reset so that the latched abnormality detection signal is not reset, the microcomputer 6 can be maintained without being reset.

  As described above, the method of masking the control signal to the switching circuit 4 has been described as a method of shutting off the power supply to the heater. However, a shutoff relay is provided between the power supply and the relay, and power supply to the heater is shut off by the abnormality detection signal. May be.

  In the present embodiment, the description has been given separately for each functional block. However, for example, the cycle timer 8 may be built in the microcomputer 6 or the monitoring timer 11 may be built in the microcomputer 6.

  An IC including the periodic timer 8, the monitoring timer 11, the output port P2, and the like can also be configured.

  The heater 2 may be a heater having an induction coil and an electromagnetic induction heating member.

  Moreover, although the example using the thermistor 5 which is a contact-type temperature sensor was demonstrated as a temperature detection means, it may replace with this and may use the non-contact-type temperature sensor which incorporated the thermistor 5. FIG.

<Second Embodiment>
FIG. 5 shows a second embodiment of the present invention. This embodiment is different from the first embodiment in the abnormality detection method. That is, in the first embodiment, when the output port 10 is turned on, the monitoring timer 11 has no write access to turn on the port P2 again or no write access to turn off the port P2 for a preset time, An abnormal signal was output.

  On the other hand, in the present embodiment, when the timer output b from the periodic timer 8 enters the input port P1, the microcomputer 56 performs A / D conversion on the voltage signal a output from the thermistor 5 and converts it into a temperature. After that, the control signal f for turning on / off the switching circuit 4 is output from the output port P2 in comparison with the target temperature. The monitoring timer 511 measures time while the control signal f is H indicating that the switching circuit 4 is on, and is reset while the control signal f is L indicating that the switching circuit 4 is off. The monitoring timer 511 outputs an abnormal signal d when the control signal f remains in the H state for a preset time. This set time is set longer than the cycle time of the cycle timer 8. The abnormality signal d output from the monitoring timer 511 is L when an abnormality is detected, and is input to the AND gate 10. When the abnormality is detected, the heater-on signal is masked, so that the heater is turned off.

  In the second embodiment, the microcomputer 56, the cycle timer 8, and the monitoring timer 511 are arranged on the engine board, and the AC power supply 3, the switching circuit 4, and the AND gate 10 are arranged on the power supply board.

  FIG. 6 is a flowchart showing an example of a program stored in the microcomputer 56. When temperature control is required, in S60, the timer output b from the periodic timer 8 to the port P1 is waited. When there is a timer input, in S61, the detected temperature obtained by converting the voltage signal a from the thermistor 5 into temperature is When the target temperature is compared and the detected temperature is higher than the target temperature, L (control signal f) indicating heater off is output to the output port P2 in S65, and the process returns to S60 to wait for the next timer input. On the other hand, if the detected temperature is lower than the target temperature in S61, a signal L (control signal f) indicating heater off is once sent to the output port P2 in S62, and a predetermined minute time (in S63). For example, after waiting for 100 ns), in S64, a signal H (control signal f) indicating heater ON is sent to the output port P2, and the process returns to S60.

  Therefore, even when the output port P2 is already H and the detected temperature is lower than the target temperature, the output port P2 is once set to L and then set to H in the processing of S62 to S64. If there is no abnormality in the operation, the output port P2, etc., the control signal f will always be L periodically, and the monitoring timer 511 will not detect abnormality.

  Therefore, by detecting the abnormality of the monitoring timer 511, the abnormality of the microcomputer 56 and the abnormality of the control signal f driven by the output port P2 or the output port P2 can be detected.

  In the present embodiment, the example in which the monitoring timer 511 is arranged on the engine board has been described. However, the monitoring timer 511 may be arranged on the power supply board instead of the engine board.

  Next, the operation will be described with reference to FIG. The period timer 8 outputs a timer output b at a constant period (for example, 200 ms) (FIG. 7B). When the microcomputer 56 receives the timer output b of the period timer 8, the microcomputer 56 compares the temperature detected by the thermistor 5 (FIG. 7A) with the target temperature, and if the detected temperature is higher than the target temperature, the switching circuit 4 is set to L, and the heater 2 is not energized.

  When the detected temperature is lower than the target temperature when the timer output b from the periodic timer 8 is input, the microcomputer 56 once sets the control signal f to the switching circuit 4 to L and then to H (FIG. 7). (C)). If the detected temperature does not reach the target temperature even when the timer output b of the next periodic timer 8 is input, the microcomputer 56 again sets the control signal f to the switching circuit 4 to -H and then sets it to H. (FIG. 7 (c)).

  Therefore, when the microcomputer 56, the output port P2, the timer, the control signal, etc. are normal, the control signal f is a small pulse width L pulse as shown in FIG. Will have. That is, the presence of such an L pulse indicates that periodic temperature control is normally performed.

  On the other hand, when there is an abnormality, H continues for a certain time or more like the control signal f (FIG. 7 (e)), and an abnormal signal is output from the monitoring timer 9 (FIG. 7 (f)). The monitoring timer 511 detects that some abnormality has occurred.

  In the present embodiment, even when the control signal f of the switching circuit 4 is continuously set to H, an abnormality such as the microcomputer 56 is detected by periodically sandwiching L. However, if the switching circuit 4 is periodically turned off and on by L periodically sandwiched, adverse effects such as flicker may occur.

  Therefore, as shown in FIG. 8, the abnormality detection signal output from the monitoring timer 511 when an abnormality is detected is latched by the latch 813, the signal latched by the latch 813 by the AND gate 812, and the control signal from the microcomputer 56. f is ANDed, and the output of the AND gate 812 is output to the switching circuit 4 via the filter 814.

  As described above, the heater is not turned on again by latching the abnormal signal d, and the output of the AND gate 812 is output to the switching circuit 4 via the filter 814. Will not respond to the L pulse.

  Further, if the temperature control system becomes abnormal, there is a possibility that the microcomputer 56 that performs the control has become abnormal, and it is not preferable to continue the operation of the microcomputer 56 as it is.

  In that case, it is desirable to reset the microcomputer 56 when a temperature control abnormality is detected. After the microcomputer 56 is reset and restarted, the microcomputer 56 is reset so that the abnormal operation is performed again and the heater is not turned on even though the temperature of the temperature control target is high. However, the energization to the heater can be continuously cut off by keeping the latched abnormality detection signal without resetting.

  Although the control signal to the switching circuit 4 is masked to cut off the energization to the heater, a cut-off relay is provided between the power source and the relay so that the power supply to the heater is cut off by the abnormality detection signal. Good.

  In this embodiment, an example in which each functional block is divided has been described. However, for example, the microcomputer 56 may include the periodic timer 8 or may further include the monitoring timer 9. Good. Further, an IC including the periodic timer 8, the monitoring timer 9, the output port P2, and the like can be configured.

<Third Embodiment>
FIG. 9 shows a third embodiment of the present invention. This embodiment is different from the first embodiment in the temperature control method. That is, in the first embodiment, when the output port 10 is turned on, the monitoring timer 11 has no write access to turn on the port P2 again or no write access to turn off the port P2 for a preset time, An abnormal signal was output.

  On the other hand, in the present embodiment, the microcomputer 96 has a heater protect register 961 and a heater ON / OFF register 962. When 1 is written in the least significant bit (LSB) of the heater protect register 961 by the microcomputer 96, the heater ON permission state is entered. When 1 is written to the LSB of the heater ON / OFF register 962 by the microcomputer 96 in the heater ON permission state, the output port P2 (signal g) of the microcomputer 96 becomes H indicating the heater ON, and as a result, the switching circuit 4 The heater 2 is turned on and power is supplied to the heater 2.

  When the microcomputer 96 needs to control the temperature of the heater 2, it periodically converts the voltage signal a input to the input port P0 into a temperature. When the detected temperature is lower than the target temperature, the heater 2 is turned on, and the detected temperature Is higher than the target temperature, the heater 2 is turned off.

  As described above, in this embodiment, when the heater 2 is turned on, a predetermined value is written in the heater protect register 961, and after the heater ON permission state is set, the predetermined value is written in the heater ON / OFF register 962. Therefore, compared to the conventional example in which the heater is turned on / off with a single register, the possibility of erroneously turning on the heater 2 when the microcomputer 96 malfunctions is reduced, and the malfunction can be reduced. it can.

  Note that when the heater 2 is turned off, unlike the case of the heater ON in which a predetermined value is written in the LSBs of the heater protect register 961 and the heater ON / OFF register 962, the least significant bit LSB of the heater ON / OFF register 962 is set to 0. By writing, the heater 2 can be turned off, and the heater protect register 961 can be completely cleared so that heater on is not permitted.

  Alternatively, when the heater is turned on, when a predetermined value is written to the LSB of the heater on / off register 962 in the heater on permission state, the heater 2 is turned on and all the heater protect registers are cleared. You can also.

  The registers related to the heater ON operation are separated from other functions such as a motor ON / OFF function and a solenoid ON / OFF function in consideration of safety when the microcomputer 96 malfunctions. Is desirable.

  Further, when a heater is turned on, if a specific value is not written in specific bits of the heater protect register 961 and heater ON / OFF register 962 but a keyword composed of a plurality of bits is written in each register, noise or the like may occur. The risk of erroneous writing due to bit moss can be reduced.

  As described above, in the case of having a register configuration, since a predetermined value is not written in the heater protect register 961, the heater is turned on in the LSB of the heater ON / OFF register 962 even though the heater on is not permitted. When 1 is written, it means that an operation that cannot be performed in the normal operation of the microcomputer 96 has been performed, and it can be determined that the microcomputer 96 is not operating normally.

  If the operation of the microcomputer 96 becomes abnormal with respect to temperature control, there is a possibility that the microcomputer 96 itself performing the control has become abnormal, and it is not preferable that the microcomputer 96 continue to operate as it is. It is desirable to reset the microcomputer 96 when the error is detected.

  In such a case, after the microcomputer 96 is reset and restarted, the abnormal operation is performed again, and the heater 2 is turned on even though the temperature of the temperature control target is high. Although the microcomputer 96 is reset so that the abnormal signal is latched, the heater-on signal can be masked with the abnormal signal so that the heater-on signal is not output.

  Although an example in which each of the above registers is built in the microcomputer 96 has been described, an IC including these registers may be configured.

<Fourth embodiment>
FIG. 13 shows a fourth embodiment of the present invention. This embodiment is different from the third embodiment in the configuration of the register. That is, in the third embodiment, the heater protect register 961 and the heater ON / OFF register 962 are used.

  On the other hand, in this embodiment, the microcomputer 106 includes a heater protect register 1011, a heater ON register 1012, and a heater OFF register 1013.

  When the keyword “19” is written in the heater protect register 1011 by the microcomputer 106, the heater ON permission state is set. When “C8” is written to the heater ON register 1012 by the microcomputer 106 in the heater ON permission state, an H pulse is output to the signal s, the SR-FF 1014 that receives the signal is set, and the output port h of the microcomputer 106 is set. As a result, the switching circuit 104 is turned on and electric power is supplied to the heater 102. Both the heater protect register 1011 and the heater ON register 1012 are cleared to “00” by the H pulse of the signal s.

  On the other hand, when the heater 102 is turned off, if the microcomputer 106 sets “1” to the LSB of the heater OFF register 1013, an H pulse is output to the signal r, and the SR-FF 1014 that receives it is reset. The output port h of the computer 106 becomes L indicating heater OFF, and as a result, the switching circuit 104 is turned off and the power of the heater 102 is cut off. The heater OFF register 1013 is cleared to 0 by the H pulse of the signal r.

  When the temperature control of the heater 102 is necessary, the microcomputer 106 waits for the timer output output from the timer 108 to be input to the input port P1, and when the timer output is input, the voltage input to the input port P0. The signal a is converted into a temperature. When the detected temperature is lower than the target temperature, the heater 102 is turned on by the above-described procedure, and when the detected temperature is higher than the target temperature, the heater 102 is turned off.

  Even if it is necessary to turn on the heater continuously, the microcomputer 106 is programmed to turn on the heater 2 in accordance with the above-described procedure every time there is a timer output of the periodic timer 108.

  The monitoring timer 115 measures time while the output port P2 is turned on, and resets the time when an H pulse is generated in the signal s or signal r. When the output port is turned on, the monitoring timer 115 outputs an abnormal signal when there is no H pulse in the signal s or the signal r for a preset time or longer. This set time is set longer than the cycle time of the cycle timer 108.

  The abnormality signal d outputted from the monitoring timer 115 becomes L when abnormality is detected, is latched by the latch 116 and inputted to the AND gate 1017, and when abnormality is detected, the output e of the AND gate 1017 is made L, so that the switching circuit 104 is turned off. Is done.

  As described above, in this embodiment, when the heater 102 is turned on, a predetermined value is written in the heater protect register 1014, and after the heater is turned on, the predetermined value is written in the heater ON register 1012. Compared to the conventional example in which the heater is turned on / off with a single register, the possibility of erroneously turning on the heater 102 when the microcomputer 106 malfunctions is reduced, and the malfunction can be reduced.

  Similarly to the first embodiment, when it is necessary to continuously turn on the heater 102, “19” is periodically written in the heater protect register 1011 and then “C8” is written in the heater ON register 1012. If the operation of writing "" has to be performed and this is not performed, it can be determined that an abnormality has occurred in the operation of the microcomputer 106.

Further, regarding the heater protect register 1011 and the heater ON register 1012, if the following accesses are made, it can be determined that the operation of the microcomputer 106 is abnormal. That is,
• When the contents of the heater protect register 1011 are other than “19” and “00”.
• When the heater ON register 1012 content is other than “C8” and “00”.
The heater ON register 1012 becomes “C8” even though the heater protect register 1011 is “00”.
It is three. Therefore, in these cases, the heater 102 is turned off.

  Registers related to heater-on operation may be separate from other functions such as a motor on / off function and a solenoid on / off function, considering the safety during microcomputer malfunction. desirable.

  If the operation of the microcomputer becomes abnormal with regard to temperature control, the microcomputer that performs the control itself may have become abnormal, and it is not desirable to continue the operation of the microcomputer as it is. It is desirable to reset the microcomputer when it does.

  In such a case, after the microcomputer is reset and restarted, the abnormal operation is performed again, and the heater 102 is not turned on even though the temperature of the temperature control target is high. As described above, although the microcomputer is reset, after the abnormal signal is latched, the heater on signal is masked with the abnormal signal so that the heater on signal is not output.

  Although an example in which each of the above registers is built in a microcomputer has been described, an IC including these registers can also be configured.

DESCRIPTION OF SYMBOLS 1,101 Fixing roller 2,102 Heater 3,103 AC power supply 4,104 Switching circuit 5,105 Thermistor 6,56,96,106 Microcomputer 7,107 Thermo switch 8,108 Period timer 9 Switching circuit control part 10 Output port 11, 115, 511 Monitoring timer 12, 1017 AND gate 13, 116, 813 Latch 814 Filter 961, 1011 Heater protection register 962 Heater ON / OFF register 1012 Heater ON register 1013 Heater OFF register 1014 SR-FF

Claims (28)

Temperature detecting means for detecting the temperature of the heating means;
Indicating means for instructing on when the temperature detected by the temperature detecting means is lower than the target temperature, and instructing to turn off when the detected temperature is higher than the target temperature;
First to nth (≧ 2) registers;
A first setting means for setting a first predetermined value to the first register when instructed by the instructing means, and a second predetermined value when instructing to turn off;
Prior to the first setting means setting the first predetermined value in the first register, the second to n-th registers are changed to the third to n + 1-th time each time the instruction means instructs to turn on. A second setting means for setting a predetermined value;
Determining means for determining whether the contents of the second to n-th registers are the same as the predetermined values of the third to n + 1, respectively, and determining the heating means ON permission state in the same case;
When the first predetermined value is set in the first register in a state where the determination unit determines that the heating unit is on, the power supply to the heating unit is turned on, and the first register is turned on. An on / off means for turning off the power supply to the heating means when the first setting means sets the second predetermined value.   2. The temperature control device according to claim 1, wherein the second to n-th registers have addresses different from the addresses of the first registers.   3. The clear means for clearing the second to n-th registers when the determination means determines that the heating means is in an on-permitted state and the first predetermined value is set in the first register. A temperature control device comprising:   4. The clearing means for clearing the first register when the determination means determines that the heating means is in an on-permitted state and the first predetermined value is set in the first register. A temperature control device comprising:   5. The clearing means according to claim 1, wherein the on / off means turns off the heating means and clears the second to nth registers when the second predetermined value is set in the first register. A temperature control device comprising:   6. The on / off device according to claim 1, wherein the on / off means determines that an abnormality has occurred when the contents of the second to n-th registers are in a clear state or different from the third to n + 1 predetermined values, respectively. A temperature control device characterized in that the power supply to the heating means is turned off.   7. The heating means according to claim 1, wherein the on / off means determines that an abnormality has occurred when the contents of the first register are in a clear state or different from the first predetermined value or the second predetermined value. The temperature control apparatus characterized by turning off the power supply to.   8. The apparatus according to claim 1, wherein the on / off means has an abnormality when the first predetermined value is written in the first register even though the heating means is not permitted to be turned on. A temperature control device characterized in that the power supply to the heating means is judged to be turned off.   9. The temperature control apparatus according to claim 1, further comprising a notification unit that notifies the occurrence of an abnormality when it is determined by the on / off unit that an abnormality has occurred.   10. The temperature control apparatus according to claim 1, further comprising an initialization unit that initializes the temperature control apparatus when it is determined that an abnormality has occurred. In Claim 10, when it is determined that an abnormality has occurred by the on-off means, holding means for holding an abnormal state;
And a prohibiting unit for prohibiting power supply to the heating unit by the on / off unit after being initialized by the initializing unit when an abnormal state is held by the holding unit. Control device. Temperature detecting means for detecting the temperature of the heating means;
Indicating means for instructing on when the temperature detected by the temperature detecting means is lower than the target temperature, and instructing to turn off when the detected temperature is higher than the target temperature;
First to mth (≧ 3) registers;
First setting means for setting a first predetermined value when ON is instructed to the first register by the instructing means;
Second setting means for setting a second predetermined value to the second register when OFF is instructed by the instruction means;
Prior to the first setting means writing a predetermined value in the first register, third setting means for setting the third to m-th predetermined values in the third to m-th registers, respectively;
Determining means for determining whether or not all the contents of the third to m-th registers are the same as the third to m-th predetermined values, and determining the heating means ON permission state in the same case;
When the first predetermined value is set in the first register in a state where the determination unit determines that the heating unit is permitted, the power supply to the heating unit is turned on, and the second register is turned on. An on / off means for turning off the power supply to the heating means when a predetermined value of 2 is written.   13. The temperature control device according to claim 12, wherein the first to m-th registers have addresses different from the addresses of registers other than the first to m-th registers.   14. The temperature control apparatus according to claim 12, wherein the first to m-th registers have different addresses.   15. The heating device ON permission state according to any one of claims 12 to 14, wherein the first register and the third to m-th items are determined when the first predetermined value is set in the first register. A temperature control device comprising clear means for clearing a register.   16. The on / off means according to any one of claims 12 to 15, wherein when the second predetermined value is set in the second register, the heating means is turned off and the second register is cleared. Temperature control device.   17. The on / off means according to claim 12, wherein the on / off means determines that an abnormality has occurred when the contents of the third to m-th registers are different from the clear state or the third to m-th predetermined values. A temperature control device characterized in that the power supply to the heating means is turned off.   18. The on / off means according to claim 12, wherein when the contents of the first register are in a clear state or different from a first predetermined value, it is determined that an abnormality has occurred and the power supply to the heating means is turned off. And a temperature control device.   19. The abnormality according to claim 12, wherein the on / off unit has an abnormality when the first predetermined value is written in the first register even though the heating unit is not permitted to be turned on. A temperature control device characterized in that the power supply to the heating means is judged to be turned off.   20. The temperature control apparatus according to claim 12, wherein the on / off means includes a notifying means for notifying occurrence of an abnormality when it is determined that an abnormality has occurred.   21. The temperature control apparatus according to claim 12, further comprising an initialization unit that initializes the temperature control apparatus when it is determined that an abnormality has occurred. In claim 21,
When it is determined that an abnormality has occurred, holding means for holding an abnormal state;
And a prohibiting unit for prohibiting power supply to the heating unit by the on / off unit after being initialized by the initializing unit when an abnormal state is held by the holding unit. Control device.   23. The temperature control device according to claim 1, wherein the heating unit is a fixing roller having a heater.   23. The temperature control device according to claim 1, wherein the heating unit includes an induction coil and an electromagnetic induction heating member.   25. The temperature control device according to claim 1, wherein the temperature detection unit includes a contact-type temperature sensor that detects a temperature in contact with an object.   26. The temperature control device according to claim 25, wherein the contact temperature sensor is a contact thermistor.   25. The temperature control device according to claim 1, wherein the temperature detection unit includes a non-contact temperature sensor that performs temperature detection without contact with an object.   28. The temperature control device according to claim 27, wherein the non-contact temperature sensor includes a thermistor.

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