JP5228401B2 - Fixing apparatus, fixing method and fixing program - Google Patents

Description

  The present invention relates to a fixing device using induction heating in which an electric coil (induction heating coil) is energized to generate an induction current in the nearest conductor and an image forming apparatus using the fixing device, and more particularly to rectifying alternating current. TECHNICAL FIELD The present invention relates to a fixing device, a fixing method, and a fixing program for controlling induction heating by PWM (Pulse Wide ModulatiON) control that chops the generated direct current with an inverter and supplies power to a resonance circuit including an induction heating coil and a resonance capacitor connected thereto. .

  In an image forming apparatus such as a copying machine or a printer, a method of fixing toner on paper with heat and pressure is often used. As a heating method used for this fixing, there is an induction heating method using heat generated by energizing an electric coil and generating an induced current in the nearest conductor. In the fixing device using the induction heating method, a driving waveform of the switching element is generated by some control means, and the temperature is controlled by the frequency of the driving waveform and the ON / OFF duty. For example, as the time for which the switching element is turned on is longer, the heating energy increases.

  In the induction heating method, when the switching element is turned off, a resonance voltage is generated at both ends thereof. If the switching element is turned on while the resonance voltage is being generated, a great deal of stress is applied to the switching element, which may lead to destruction. For this reason, it is necessary to avoid the resonance voltage generation time zone for the ON timing (ON time width) when generating continuous drive pulses.

  In a conventional induction heating type fixing device, the ON timing (ON time width) of continuous drive pulse generation is variable only within a fixed range, and this fixed range has a sufficient margin based on design calculations and measured values. I decided to have it. For example, when an IGBT (Insulated Gate Bipolar Transistor) is used as the switching element, the ON time width is limited by the rating of the IGBT, the optimum frequency range, the circuit saturation of the coil current waveform, and the like. The fixed range of the ON time width needs to be determined to a value having a sufficient margin in consideration of these.

  In addition, as a fixing device that controls the heating unit by turning on / off the switching element, for example, in Patent Document 1 below, an auxiliary power circuit having a main power circuit that rectifies a current input from a commercial AC power source and an electric double layer capacitor A heating device, a fixing device, and an image forming apparatus that can improve the heating efficiency and shorten the rise time by switching the two power sources are disclosed.

  Also, in Patent Document 2 below, when starting up the fixing device in a cold state, power is supplied from a charged capacitor, the heater element is warmed for a predetermined time, and then switched to a commercial AC power source. A fixing device that prevents voltage fluctuation due to a large current flowing through a power supply is disclosed. In this fixing device, the power supply from the capacitor is turned off, the power supply from the commercial power supply is switched after a predetermined time, and both of them are turned on at the same time. The situation has been resolved.

JP 2004-184963 A JP 2004-286804 A

  However, in the conventional induction heating type fixing device, the ON timing (ON time width) of continuous drive pulse generation is determined by setting a sufficient margin based on the rating of the switching element. For this reason, for example, the ON time is not always optimal for each device, for example, the ON time duration is limited to the lowest frequency of the drive pulse regardless of the circuit limit, and the heat generation efficiency is improved. There was a problem that it was not possible. Further, since the fixing devices described in Patent Document 1 and Patent Document 2 do not assume heating by an induction heating method, the resonance voltage when the switching element is turned off is not taken into consideration.

  The present invention has been made in view of the above, and can set an optimum switching element ON time width for each device, improve the heat generation effect of the device, and promote further energy saving. It is an object to obtain a fixing device, a fixing method, and a fixing program.

In order to solve the above-described problems and achieve the object, the invention according to claim 1 is a fixing in which fixing is performed using a heating coil that is induction-heated, and whether or not current is supplied to the heating coil is switched by a switching element. The apparatus detects a current flowing through the heating coil as a voltage value, and the voltage value reaches a predetermined voltage value corresponding to a maximum limit value of a coil current determined according to a characteristic value of the heating coil. Voltage detecting means for measuring a time interval until and a control means for calculating an allowable range of a time width indicating an interval at which the switching element is closed based on the time interval. .

According to a second aspect of the present invention, in the fixing device according to the first aspect, a default value indicating the range of the time width determined without depending on the maximum limit value of the coil current, and the voltage detecting unit An adjustment value for absorbing tolerances of the measurement circuit included in the storage circuit, and a storage unit for storing the adjustment value, and the control unit further includes the time based on the default value and the adjustment value in addition to the time interval. The allowable range of the width is calculated .

The invention according to claim 3 is the fixing device according to claim 2, further comprising adjustment value changing means for changing the adjustment value stored in the storage means in accordance with an operation of an operator. .

According to a fourth aspect of the present invention, there is provided a fixing method in a fixing device in which the presence or absence of current supply to the heating coil to be induction-heated is switched by a switching element, the current flowing through the heating coil is detected as a voltage value, Based on the voltage recognition step for measuring the time until the voltage value reaches a predetermined voltage value corresponding to the maximum limit value of the coil current determined according to the characteristic value of the heating coil, based on the time interval, And a control step of calculating an allowable range of a time width indicating an interval at which the switching element is closed.

According to a fifth aspect of the present invention, in the fixing method according to the fourth aspect, the fixing device includes a default value indicating the range of the time width determined without depending on the maximum limit value of the coil current. And an adjustment value for absorbing tolerances of the measurement circuit used in the voltage recognition step, and in the control step, based on the default value and the adjustment value in addition to the time interval. Then, the allowable range of the time width is calculated .

According to a sixth aspect of the present invention, in the fixing method according to the fifth aspect, the method further includes an adjustment value changing step of changing the adjustment value stored in the storage unit according to an operation of an operator. .

  According to a seventh aspect of the present invention, a computer is caused to execute the fixing method according to any one of the fourth to sixth aspects.

According to the present invention, the current flowing through the heating coil is detected as a voltage value, and the voltage value reaches a predetermined voltage value corresponding to the maximum limit value of the coil current determined according to the characteristic value of the heating coil. Time interval is measured, and based on the measured time interval, the allowable range of the time width indicating the interval at which the switching element is closed is calculated. An optimum range can be set, and the heat generation effect of the apparatus can be improved and further energy saving can be promoted.

  Exemplary embodiments of a fixing device according to the present invention will be explained below in detail with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a block diagram showing the configuration of the fixing device according to the first embodiment of the present invention. The fixing device of the present embodiment is, for example, a part of the constituent elements of the image forming apparatus, and is a device for fixing toner using induction heating. The fixing device according to the present embodiment includes a drive side (primary side) device 100, a control side (secondary side) device 200, a pulse transformer 204, and a photocoupler 205.

  The driving apparatus 100 includes an AC power source 101, a current detection unit 108 that detects an AC current output from the AC power source 101, a rectification unit 102 that rectifies the AC current into a DC current, and filters the rectified DC current. A filter unit 103, a switching element 104, a resonance capacitor 105, a heating coil 106 that generates a magnetic field when a current flows, a power supply voltage blocking unit 107 that blocks a power supply voltage based on an instruction from the control device 200, A rectifying unit 109 that rectifies an alternating current into a direct current and a fixing unit 300 that is heated by a magnetic field generated by the heating coil 106 are provided.

  The control-side device 200 includes a control unit 201 that generates drive pulses for controlling the drive-side device 100, an AND circuit 202, a safety unit 203 that determines whether there is an abnormality, and a current rectified by the rectification unit 109. And a voltage recognizing unit (voltage detecting means) 206 for measuring the saturation value of the coil current. The AND circuit 202 performs an AND operation on the drive pulse generated by the control unit 201 and the output of the safety unit 203. The output of the AND circuit 202 is transmitted to the driving device 100 in an insulated state by the pulse transformer 204. The switching element 104 opens and closes based on this drive pulse. The switching element 104 is closed while the drive pulse is ON, and the switching element 104 is open while the drive pulse is OFF. Further, the output of the rectifying unit 109 is input to the voltage recognizing unit 206 via the photocoupler 205. In this embodiment, the pulse transformer 204 and the photocoupler 205 do not belong to either the drive side device 100 or the control side device 200. However, the present invention is not limited to this, and the drive side device 100 and the control side device 200 are not limited thereto. It is good also as a structure contained in either.

  In addition, the control unit 201 includes an optimal time width determination unit 400. The optimal time width determination unit 400 further includes a CPU (Central Processing Unit) 401, a ROM (Read Only Memory) 402, and a RAM (Random Access). Memory) 403 and nonvolatile memory 404.

  In the fixing device of the present embodiment, an AC voltage is supplied to the heating coil 106 by the opening and closing of the switching element 104, and is also shut off. When the switching element 104 is closed, the AC voltage supplied from the AC power supply 101 is supplied to the heating coil 106 via the rectifying unit 102 and the filter unit 103. When an AC voltage is supplied to the heating coil 106, an AC magnetic field is generated in the heating coil 106. An eddy current is generated in the fixing unit 300 by the generated AC magnetic field, and the fixing unit 300 is heated.

  The heating energy increases as the ON time width of the drive pulse (the time during which the drive pulse is turned on) is longer. In the prior art, when generating a continuous drive pulse, an allowable range of the ON time width is set as a fixed range in advance, and the ON time width is determined by temperature control within the set fixed range. The range of the fixed value of the ON time is determined in advance from the element characteristics and the like, and is not necessarily the optimum value for each fixing device. In the present embodiment, the ON time width is determined based on the measured value of the saturation value of the coil current flowing through the heating coil 106, whereby the ON time width is fixed to each fixing device. Set to be optimal. In the fixing device of the present embodiment, the temperature of the fixing unit 300 is monitored by a temperature monitor unit (not shown), and the control unit 201 is within the range determined by the optimum time determination process based on the temperature. Similarly, the ON time width is controlled.

  Next, the ON time width optimization process according to the present embodiment will be described. In the present embodiment, the current detector 108 detects the commercial current output from the AC power supply 101 and rectifies the commercial current detected by the rectifier 109. Prior to actual operation of the fixing device, the second voltage recognition unit 206 of the control-side device 200 sends a dummy pulse, and the coil current is based on the current rectified by the rectifier 109 via the photocoupler 205. The ON time width corresponding to the maximum limit value is measured. Then, the optimum time width determination unit 400 determines the optimum upper limit value of the ON time width for generating the most efficient driving pulse for the fixing device based on the measurement result.

  The method for determining the lower limit value of the ON time width is not particularly limited. For example, the rated value of the IGBT, the optimum frequency range (the lowest frequency to the highest frequency), and the like are determined as in the conventional case. In the present embodiment, the upper limit value is determined in consideration of not only the coil current but also these parameters. A value obtained by adding a minimum margin to an ON time width range that takes into account parameters such as the rated value of the IGBT and the optimum frequency range (lowest frequency to maximum frequency) is stored in the ROM 402 in advance as a default value of the ON time width range. Store it.

  FIGS. 2-1 to 2-3 are flowcharts showing an example of the optimum time width determining process executed by the CPU 401 constituting the optimum time width determining unit 400. FIGS. The control program for performing these optimum time width determination processes is stored in the ROM 402, and the CPU 401 reads this program from the ROM 402 and loads it into the RAM 403, so that the CPU 401 can execute this program.

  FIG. 2A is a flowchart of an optimum time width determination process performed when the fixing device (image processing apparatus) is turned on or returned from the energy saving mode in the ON time width optimization process. First, when the power of the fixing device is turned on (including the return from the energy saving mode), the optimum time width determination process is started. Then, the CPU 401 reads and checks the operation mode selection flag stored in the nonvolatile memory 404, and determines which mode is set (step S11). This selection flag is a flag for determining the timing for performing the optimum time width determination process of the switching element. In the present embodiment, the following two modes are provided as the execution timing.

  The first mode is a mode (hereinafter referred to as an automatic execution mode) in which the optimum time width determination process is automatically executed every time the apparatus is turned on (including when returning from the energy saving mode). The second mode is: This is a mode in which the operation is performed when instructed by the operator (hereinafter referred to as operator instruction mode).

  In the automatic execution mode, the optimum time width determination process is performed every time the power is turned on. Therefore, the frequency of the process execution is high, and it is possible to always set the ON time width range suitable for the apparatus with high accuracy. However, in the automatic execution mode, the time required for startup at power-on is longer than in the operator instruction mode. In the operator instruction mode, the process is executed when instructed by the operator. Therefore, the time required for startup at power-on is not as long as the automatic execution mode, but the accuracy of the optimum time width determination process for the apparatus is the automatic execution mode. Than fall. This selection flag can be set by an operation process by an operator described later.

  If it is determined in step S11 that the automatic execution mode is set (step S11 automatic execution mode), the CPU 401 obtains a measured value of the ON time width corresponding to the maximum limit value of the coil current from the voltage recognition unit 206. Obtain (step S12). Next, the CPU 401 stores the measurement value in the RAM 403 (step S13). Then, the CPU 401 calculates the range of the optimum ON time width based on the measured value, the default value stored in the ROM 402, and the adjustment value stored in the nonvolatile memory 404 (step S14). The adjustment value is a variable for absorbing the tolerance of the measurement circuit itself with respect to the measurement value (either a positive value or a negative value can be set). It is determined for each apparatus, and the determined numerical value is stored in the ROM 402. This adjustment value can also be set by an operation process by an operator described later. Here, the calculation method of step S14 is a method of adding the measurement value, the default value, and the adjustment value, but is not limited to this, and any method may be used as long as it is an appropriate calculation method.

  Next, the CPU 401 reads and checks the operation mode selection flag stored in the nonvolatile memory 404, and determines which mode is set (step S15). If it is determined that the automatic execution mode is set (step S15 automatic execution mode), the range of the optimum ON time width calculated in step S14 is stored in the RAM 403 (step S16), and the process is terminated.

  If it is determined in step S11 that the operator instruction mode is set (step S11 operator instruction mode), the process is terminated. If it is determined in step S15 that the operator instruction mode is set (step S15 operator instruction mode), the range of the optimum ON time width calculated in step S14 is stored in the nonvolatile memory 404 (step S17). The process is terminated.

  FIG. 2-2 is a flowchart illustrating an example of processing during normal operation of the ON time width optimization processing. The optimum time width determination process during the normal operation is started after the optimum time width determination process described with reference to FIG. In the normal operation, the control unit 201 generates a drive pulse based on the temperature monitor. First, the CPU 401 counts the time (operation time) after the start of the normal operation and stores it in the nonvolatile memory 404 (step S21). Then, the CPU 401 determines whether or not there is an interrupt request from an operation unit (not shown) by an operator's operation (step S22). If it is determined that there is no interrupt request due to the operator's operation (No in step S22), it is determined whether or not the value counted in step S21 has reached the set time stored in the ROM 402 (step S23). The set time is a waiting time for receiving an interrupt request, and an appropriate time for receiving an interrupt request is stored in the ROM 402 in advance.

  When it is determined that the value counted in step S21 has reached the set time stored in the ROM 402 (Yes in step S23), the CPU 401 clears the count value (step S24) and has been described with reference to FIG. The process proceeds to step S12 of the optimum time width determination process. As a result, the optimum ON time width is calculated. If it is determined that the value counted in step S21 has not reached the set time stored in the ROM 402 (No in step S23), the process returns to step S21.

  If it is determined in step S22 that there is an interrupt request due to the operator's operation (Yes in step S22), the operation processing by the operator described later is performed (step S25).

  FIG. 2-3 is a flowchart illustrating an example of an operation process performed by an operator of the ON time width optimization process. This process is started when there is an interrupt request by an operator's operation in step S22 of the process during the normal operation described with reference to FIG. First, the CPU 401 determines whether or not the instruction by the operator's operation on the operation unit is an instruction to change the operation mode (step S31). If it is determined that the instruction is to change the operation mode (Yes in step S31), the CPU 401 changes the selection flag stored in the nonvolatile memory 404 to the content instructed from the operation unit (step S32). Then, the process proceeds to step S21 in FIG. 2-2, and the process returns to the process during the normal operation.

  If it is determined that the instruction is not an instruction to change the operation mode (No at Step S31), it is determined whether or not the instruction from the operation unit is a change of the adjustment value (Step S33). If it is determined that the adjustment value is changed (Yes in step S33), the CPU 401 changes the adjustment value stored in the nonvolatile memory 404 to the content instructed from the operation unit (step S34). The process proceeds to step S21 in 2-2, and the process returns to the process during the normal operation.

  If it is determined that the adjustment value is not changed (No in step S33), it is determined whether or not the instruction from the operation unit is an instruction to perform the ON time width optimization process (step S35). If it is determined that the instruction is to execute the ON time width optimization process (Yes in step S35), the CPU 401 proceeds to step S12 of the optimal time width determination process described in FIG. Perform processing operations. If it is determined that the instruction is not an instruction to perform the optimum time width determination process (No in step S35), the process ends.

  Next, processing of the safety unit 203 according to the present embodiment will be described. In the present embodiment, the optimum value of the ON time width is stored in the RAM 403 or the nonvolatile memory 404 by the above-described ON time width optimization processing, but the ON time width of the actual drive pulse generated by the control unit 201 is this. When the optimum value is exceeded, the safety unit 203 detects it as an abnormality and performs an abnormality detection process.

  FIG. 3A is a flowchart illustrating an example of the abnormality detection process according to the present embodiment. First, the safety unit 203 monitors the drive pulse generated by the control unit 201 and sent to the drive side device 100, and whether or not the ON time width of the drive pulse exceeds the above-described optimum value (ON time width allowable range). Is determined (step S41). It is assumed that the control unit 201 transmits the optimal value to the safety unit 203 every time the value is updated by the optimal time width determination process.

  When it is determined that the ON time width of the drive pulse has exceeded the optimum value (step S41 Yes), the safety unit 203 transmits an abnormality detection signal to the control unit 201, and the control unit 201 operates the power supply voltage cutoff unit 107. An instruction for stopping is transmitted, and the power supply voltage shut-off unit 107 stops the fixing device by shutting off the current supply from the AC power supply 101 (step S42), and ends the process. If it is determined that the ON time width of the drive pulse does not exceed the optimum value (No in step S41), the determination in step S41 is repeated.

  The abnormality detection process is not limited to the process described with reference to FIG. 3A. It is determined whether or not the image forming apparatus is executing a job (job: copy, print, etc.). In this case, the fixing device may be stopped after the job is completed. FIG. 3B is a flowchart illustrating an example of an abnormality detection process including a determination during job execution. First, the safety unit 203 performs the same process as step S41 in FIG. When it is determined that the ON time width of the drive pulse does not exceed the optimum value (No in step S51), the determination in step S51 is repeated as in the case of FIG.

  When it is determined that the ON time width of the drive pulse has exceeded the optimum value (Yes in step S51), the safety unit 203 transmits an abnormality detection signal to the control unit 201, and whether or not the control unit 201 is executing a job. Is determined (step S52). Whether or not the job is being executed is notified to the control unit 201 by a control signal or the like from the control unit of the entire image forming apparatus (not shown). When it is determined that the job is being executed (Yes in step S52), the job being executed is continuously executed, and the control unit 201 continues the operation necessary for executing the job (step S53).

  Then, the control unit 201 determines whether or not the job being executed is completed (step S54). If it is determined that the job being executed has been completed (Yes at Step S54), the fixing device is stopped (Step S55) similarly to Step S42 of FIG. 3A, and the process is terminated.

  If it is determined in step S52 that the job is not being executed (No in step S52), the process proceeds to step S55, and the fixing device is stopped (step S55). If it is determined in step 54 that the job has not been completed (No in step S54), the determination in step S54 is repeated.

  By performing the processing shown in FIG. 3-2, even if several jobs are continuously reserved, only one job being executed is completed, and then the fixing device is stopped. Since the next job is not executed, the danger of operating the fixing device for a long time after detecting an abnormality can be prevented.

  Further, as the abnormality detection process, the fixing device may not be stopped immediately after the abnormality is detected, but may be stopped when an abnormality is detected a predetermined number of times. FIG. 3C is a flowchart illustrating an example of an abnormality detection process for stopping the fixing device when an abnormality is detected a predetermined number of times. First, the safety unit 203 performs the same process as step S41 of FIG. When it is determined that the ON time width of the drive pulse does not exceed the optimum value (No in step S61), the determination in step S61 is repeated as in the case of FIG.

  If it is determined that the ON time width of the drive pulse has exceeded the optimum value (step S61 Yes), the safety unit 203 transmits an abnormality detection signal to the control unit 201, and the CPU 401 of the control unit 201 holds the counter 1 is added to the value K (step S62). Note that the initial value of the counter value held by the CPU 401 is 0. Then, the CPU 401 determines whether or not the counter value K is equal to the predetermined allowable value S (step S63). The predetermined allowable value S is an allowable value for the number of times of abnormality detection until the fixing device is stopped, and is stored in the nonvolatile memory 404 in advance.

  When it is determined that the counter value K is equal to the predetermined allowable value S (Yes in Step S63), the control unit 201 stops the fixing device similarly to Step S42 in FIG. 3A (Step S55). After the counter value K is cleared to 0, the process is terminated. When it is determined that the counter value K is not equal to the predetermined allowable value S (No in step S63), the process returns to step S61.

  By performing the processing as shown in FIG. 3C, even when the actual ON time width exceeds the optimum value and an abnormality detection signal is sent, the abnormality detection is permitted up to (S-1) times. To work. Therefore, even if the image processing apparatus is executing a job when an abnormality is detected, it is possible to execute a continuous job to some extent before stopping the fixing apparatus.

  Furthermore, in the present embodiment, based on the determination in step S41 (or step S51, step S61), the safety unit 203 determines whether the AND circuit 202 is normal or abnormal (the case where the actual ON time width exceeds the optimum value is abnormal). And a determination signal are sent out. The AND circuit 202 performs an AND operation on the output of the safety unit 203 and the drive pulse generated by the control unit 201, and sends an ON signal to the switching element 104 only when the output of the safety unit 203 is a value indicating normality. To do. For this reason, transmission of a signal having an ON time width exceeding the optimum value can be surely prevented, and safety measures can be strengthened. In this embodiment, both the ON signal transmission control by the AND circuit 202 and the stop process by the power supply voltage cutoff unit 107 are performed. However, only one of them may be performed. Moreover, as the power supply voltage interruption | blocking part 107, you may make it use a relay etc., for example.

  In the present embodiment, the fixing device is stopped using the power supply voltage shut-off unit 107, but instead of being stopped by the power supply voltage shut-off unit 107, the control unit 201 sends an OFF signal to the switching element 104. Thus, the fixing device may be stopped.

  Further, when the abnormality detection signal is received from the safety unit 203, the control unit 201 notifies the operator or the service person by, for example, displaying a serviceman call (SC) display or an abnormal lamp lighting on the LCD or the like. You may make it notify that the fixing device stopped abnormally. When displaying the SC, an SC number is assigned in advance for each cause of the abnormal stop, and the abnormal stop according to the present invention (in the present invention, the actual switching element ON time width exceeds the optimum value is abnormal). By making it possible to determine (stop), it is possible to quickly take action after the fixing device stops.

  Next, the voltage recognition unit 206 of the present embodiment will be described. FIG. 4 is a block diagram illustrating a configuration of the voltage recognition unit 206. The voltage recognition unit 206 according to this embodiment includes a comparator 501 and a timer counter 502. A signal A input to + of the comparator 501 is an output of the photocoupler 205. The threshold voltage corresponding to the maximum limit value of the coil current of the heating coil 106 (threshold voltage obtained by converting the maximum limit value of the coil current into a voltage value) is set to − of the comparator 501. That is, when the output A of the photocoupler 205 (converted value of coil current voltage) A input to + of the comparator 501 exceeds the threshold voltage set to − of the comparator, the output of the comparator 501 becomes High, and when it falls below, it becomes Low. Become. The maximum limit value of the coil current of the heating coil 106 is set in advance from the characteristic value of the heating coil. The output of the comparator 501 is output to the STOP input of the timer counter 502 and also output to the CPU 401 of the control unit 201 as a STOP signal.

  Further, the CPU 401 of the control unit 201 outputs a high drive pulse for one pulse to the AND circuit 202 and outputs a clock pulse to CLK-IN of the timer counter 502. The timer counter 502 starts counting when a clock pulse is received, and stops counting when a signal indicating High is input from the STOP input. Further, the DATA input / output of the timer counter 502 is connected to the CPU 401 of the control unit 201 via the data bus B, and the CPU 401 can recognize the count value of the timer counter 502 via the data bus B. Further, the CPU 401 can clear the count value via the data bus B. As described above, the CPU 401 may start supplying clock pulses to the timer counter 502 at the start of measurement. The timer counter 502 counts at a predetermined time interval set in advance, and the CPU 401 starts counting. Only a signal indicating that (START signal) may be supplied.

  FIG. 5 is a flowchart showing an example of an ON time width measurement process corresponding to the coil current limit value of the present embodiment. The program for this process is stored in the ROM 402 of the optimum time width determination unit 400, and the CPU 401 reads the program from the ROM 402 and executes it. This process is executed, for example, when the measurement value is acquired in step S12 of the above-described optimum time width determination process. For example, the measurement process may be performed periodically.

  First, the CPU 401 outputs only one drive pulse to the AND circuit 202 (step S71). FIG. 6A is a diagram illustrating an example of pulses output at this time. As shown in FIG. 6A, a pulse that is High for a certain time is output. The switching element 104 is driven by this pulse, and a current flows through the heating coil 106. The voltage recognizing unit 206 compares the output of the photocoupler 205 (the converted voltage value of the coil current) with the threshold voltage corresponding to the maximum limit value of the coil current as described above, and the output of the photocoupler 205 is the threshold value. When the voltage is exceeded, a STOP signal is sent to the CPU 401.

  The CPU 401 determines whether or not a STOP signal has been detected (step S72), and if detected (step S72 Yes), reads the count value of the timer counter 502 via the data bus and acquires it as a measurement value (step S72). S74), the process is terminated. If it is determined in step S72 that the STOP signal has not been detected (No in step S72), the CPU 401 determines whether or not a predetermined set time has elapsed (step S73). If it is determined that the predetermined set time has not elapsed (No at step S73), the process returns to step S72.

  If it is determined that the predetermined set time has elapsed (step S73 Yes), error processing is performed (step S75). As error processing, for example, processing such as notifying an operator by performing error display or the like is performed.

  FIG. 6B is a diagram illustrating an example of a waveform of a current flowing in the heating coil 106 when driven by the drive pulse illustrated in FIG. 6A. FIG. 6B illustrates an example in which the voltage recognizing unit 206 sends a STOP signal exceeding the maximum limit value of the coil current during the driving by the driving pulse. FIG. 6C is a diagram illustrating an example of the output of the comparator 501 of the voltage recognition unit 206 when the current illustrated in FIG. 6B flows through the heating coil 106.

  As described above, in the present embodiment, the saturation value of the coil current flowing through the heating coil 106 is measured, and the allowable range (optimum value) of the ON time width of the switching element is determined based on the measurement value. For this reason, an appropriate ON time width reflecting the characteristics of the individual fixing devices can be set, and efficient heating control can be performed.

(Second Embodiment)
FIG. 7 is a block diagram showing the configuration of the voltage recognition unit of the fixing device according to the second embodiment of the present invention. The configuration of the fixing device other than the voltage recognition unit of the present embodiment is the same as that of FIG. 1 described in the first embodiment.

  The voltage recognition unit according to the present embodiment includes an A / D (analog-digital) converter 503 and a timer counter 502a. A signal A input to Analog-IN of the A / D converter 503 is an output of the photocoupler 205. A clock pulse for sampling the signal A is supplied from the control unit 401 to Sample-CLK of the A / D converter 503. The DATA output of the A / D converter 503 is connected to the data bus B, and the data bus B is connected to the CPU 401 of the control unit 201. The CPU 401 can acquire the signal A via the data bus B.

  The timer counter 502a has the same function as that of the timer counter 502 of the first embodiment, but the START / STOP signal from the CPU 401 is input to the START input of the timer counter 502a, and the START and STOP control of the timer counter 502a is performed. Is performed by the CPU 401.

  The DATA input / output of the timer counter 502a is connected to the CPU 401 of the control unit 201 via the data bus B, and the CPU 401 can read the count value of the timer counter via the data bus B. Further, the CPU 401 can clear the count value via the data bus B. Here, as in the first embodiment, the CPU 401 supplies clock pulses to the timer counter 502. However, the timer counter 502a counts at a preset time interval, and the CPU 401 counts the count. Only a signal indicating the start (START signal) may be supplied.

  The CPU 401 of the control unit 201 outputs the drive pulse High for one pulse to the AND circuit 202, and transmits the START / STOP signal to High (indicating a START instruction) to the timer counter 502a. The timer counter 502a starts counting based on the clock pulse supplied from the control unit 401 when the transmitted START / STOP signal becomes High. Then, the CPU 401 refers to the signal A of the A / D (analog-digital) converter 503, and when the signal A exceeds a threshold voltage obtained by converting the preset maximum limit value of the coil current, the START / STOP signal Set to Low and transmit. It is assumed that the threshold voltage value is stored in advance in the ROM 401, for example. The timer counter 502a stops counting when the transmitted START / STOP signal becomes Low.

  FIG. 8 is a flowchart showing an example of an ON time width measurement process corresponding to the coil current limit value of the present embodiment. The program for this process is stored in the ROM 402 of the optimum time width determination unit 400, and the CPU 401 reads the program from the ROM 402 and executes it. This process is executed, for example, when measurement values are acquired in step S12 of the optimum time width determination process described in the first embodiment. For example, the measurement process may be performed periodically.

  First, the CPU 401 outputs only one drive pulse to the AND circuit 202 and sets the START / STOP signal to High and transmits it to the timer counter 502a (step S81). The switching element 104 is driven by this pulse, and a current flows through the heating coil 106. Further, the timer counter 502a starts counting when the START / STOP signal becomes High.

  The CPU 401 reads the signal A (voltage conversion value of coil current) from the voltage recognition unit via the data bus B (step S82). Then, the CPU 401 determines whether or not the signal A is below a threshold voltage corresponding to the maximum limit value of the coil current (step S83). When it is determined that the signal A is equal to or higher than the threshold voltage corresponding to the maximum limit value of the coil current (No in step S83), the START / STOP signal is set to Low and transmitted to the timer counter 502a, and the timer counter 502a counts. Stop (step S84). Then, the CPU 401 reads the count value of the timer counter 502a via the data bus B, acquires it as a measurement value (step S85), and ends the process.

  If it is determined that the signal A is below the threshold voltage corresponding to the maximum limit value of the coil current (Yes in step S83), the CPU 401 determines whether or not a predetermined set time has elapsed (step S86). If it is determined that the predetermined set time has not elapsed (No at step S86), the process returns to step S83.

  If it is determined that the predetermined set time has elapsed (step S86 Yes), error processing is performed (step S87). As error processing, for example, processing such as notifying an operator by performing error display or the like is performed.

  Thus, in this embodiment, the voltage recognition unit is configured by the A / D converter 503 and the timer counter 502a. As a result, the same effect as in the first embodiment can be obtained.

  As described above, the fixing device, the fixing method, and the fixing program of the present invention are useful for an image forming apparatus using a fixing device using induction heating.

1 is a block diagram illustrating a configuration of a fixing device according to a first embodiment. It is a flowchart of an optimal time width determination process. It is a flowchart which shows an example of the process in normal operation operation | movement of ON time width optimization process. It is a flowchart which shows an example of the operation processing by the operator of ON time width optimization processing. It is a flowchart which shows an example of the abnormality detection process of this Embodiment. It is a flowchart which shows an example of the abnormality detection process including judgment during job execution. 6 is a flowchart illustrating an example of an abnormality detection process for stopping the fixing device when an abnormality is detected a predetermined number of times. It is a block diagram which shows the structure of a voltage recognition part. It is a flowchart which shows an example of the measurement process of ON time width corresponded to a coil current limit value. It is a figure which shows an example of a drive pulse. It is a figure which shows an example of the waveform of the electric current which flows into a heating coil, when it drives by a drive pulse. It is a figure which shows an example of the output of the comparator of a voltage recognition part. FIG. 6 is a block diagram illustrating a configuration of a voltage recognition unit of a fixing device according to a second embodiment. It is a flowchart which shows an example of the measurement process of ON time width corresponded to the coil current limit value of 2nd this Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Drive side apparatus 101 AC power supply 102,109 Rectification part 103 Filter part 104 Switching element 105 Resonance capacitor 106 Heating coil 107 Power supply voltage cutoff part 108 Current detection part 200 Control side apparatus 201 Control part 202 AND circuit 203 Safety part 204 Pulse transformer 205 Photocoupler 400 Optimal time width determination unit 401 CPU
402 ROM
403 RAM
404 Nonvolatile memory 300 Fixing unit 501 Comparator 502, 502a Timer counter 503 A / D converter

Claims (7)

A fixing device that performs fixing using a heating coil that is induction-heated, and switches the presence or absence of current supply to the heating coil by a switching element,
Detecting the current flowing through the heating coil as a voltage value, and the voltage value is determined in accordance with the characteristic value of the heating coil from the time when a driving pulse for closing the switching element is sent. Voltage detection means for measuring a time interval until a predetermined voltage value corresponding to the value is reached;
Control means for calculating an allowable range of a time width indicating an interval at which the switching element is closed based on the time interval;
A fixing device comprising: Storage means for storing a default value indicating the range of the time width determined without depending on the maximum limit value of the coil current, and an adjustment value for absorbing tolerance of a measurement circuit included in the voltage detection means Further comprising
The fixing device according to claim 1, wherein the control unit calculates an allowable range of the time width based on the default value and the adjustment value in addition to the time interval . The fixing device according to claim 2 , further comprising an adjustment value changing unit that changes the adjustment value stored in the storage unit according to an operation of an operator . A fixing method in a fixing device that performs fixing using a heating coil that is induction-heated and switches the presence or absence of current supply to the heating coil by a switching element,
Detecting the current flowing through the heating coil as a voltage value, and the voltage value is determined in accordance with the characteristic value of the heating coil from the time when a driving pulse for closing the switching element is sent. A voltage recognition step for measuring a time interval until a predetermined voltage value corresponding to the value is reached;
Based on the time interval, a control step for calculating an allowable range of a time width indicating an interval at which the switching element is closed;
A fixing method comprising the steps of: The fixing device includes a default value indicating a range of the time width determined without depending on a maximum limit value of the coil current, an adjustment value for absorbing tolerance of a measurement circuit used in the voltage recognition step, Storage means for storing
The fixing method according to claim 4, wherein in the control step, an allowable range of the time width is calculated based on the default value and the adjustment value in addition to the time interval . The fixing method according to claim 5 , further comprising an adjustment value changing step of changing the adjustment value stored in the storage unit according to an operation of an operator .   A fixing program for causing a computer to execute the fixing method according to claim 4.

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