JP2005202219A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus appropriately detecting the abnormality of the temperature of a fixing control system regardless of the variation of power supply voltage and excellent in availability. <P>SOLUTION: In the image forming apparatus 1, a fixing heater control part 6 on/off-controls and applies an AC power supply 10 supplied from the outside to a fixing heater 7 heating a fixing roller, the voltage of the AC power supply 10 is measured by a power supply voltage measuring part 4, and the temperature of the fixing roller is measured by a temperature measuring part 8. A controller 2 monitors the temperature of the fixing roller measured by the measuring part 8 and detects whether abnormality occurs in a fixing heater heating control system according to a prescribed abnormality detecting condition, and changes the abnormality detecting condition in accordance with an AC power supply voltage value measured by the measuring part 4 in the midst of turning on the fixing heater 7. Therefore, overheat in detecting the abnormality is prevented while preventing the erroneous detection of the abnormality of the fixing control system caused by the variation of the AC power supply voltage. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus that appropriately detects an abnormality of a fixing temperature regardless of fluctuations in power supply voltage and has good usability.

  Conventionally, in detecting the abnormality of the fixing heater, as an operation guarantee condition for the image forming apparatus, for example, a detection condition is set such that no abnormality occurs at an AC power supply voltage of a rated minus 10%.

  The conventional image forming apparatus is configured to immediately stop energization of the fixing heater when an abnormality of the fixing heater is detected, and report the abnormal state to the inside and outside of the apparatus. In addition, abnormalities related to the fixing heater are an important problem for ensuring the safety of image forming apparatuses such as copying machines and facsimile machines. In many cases, the user cannot cancel the abnormal state as necessary.

  However, depending on the installation environment of the image forming apparatus, the power supply voltage may not satisfy the operation guarantee condition of the image forming apparatus. If such a state is temporary, it is not abnormal and is constant. There is a demand that the operation should be performed within the conditions to reduce the downtime of the image forming apparatus and the trouble of a service person.

  In recent years, the rise time of the fixing heater has been shortened, the rate of temperature increase per hour has increased, and the fixing temperature when an abnormality is detected rises under the conventional abnormality detection conditions, which is a safety issue. There was a case.

  Conventionally, there has been proposed a temperature control device for a fixing roller that monitors a voltage supplied to the fixing heater and controls a deviation width between a temperature point at which the fixing heater is turned on and a temperature point at which the fixing heater is turned off (patent). Reference 1).

  Conventionally, there has been proposed an image forming apparatus that detects a commercial power supply voltage applied to a thermal fixing unit and determines an application time based on the detected voltage so that the power applied to the thermal fixing unit is constant ( Patent Document 2).

Japanese Patent No. 3148627 JP-A-6-202525

  However, in the above prior art, there is a need for improvement in order to improve usability while appropriately detecting abnormality of the fixing device.

  That is, in the prior art described in Patent Document 1, it is possible to prevent the overshoot and undershoot of the fixing temperature from changing due to fluctuations in the applied voltage. There was a need for improvement in order to improve the usability while performing it appropriately regardless of voltage fluctuations.

  Further, in the prior art described in Patent Document 2, the fixing temperature abnormality detection cannot be controlled by the applied voltage, and the fixing temperature abnormality detection is appropriately performed regardless of the variation in the applied voltage. In order to improve the usability, there was a need for improvement.

  That is, when an abnormality related to the fixing heater is detected, it is necessary to request a service person to analyze the cause of the failure, remove the cause, and cancel the abnormal state.

  However, when the cause of the abnormality detection of the fixing heater is a temporary decrease in the AC power supply voltage, the cause analysis is virtually impossible and there are cases where the abnormal state is merely canceled. In such a case, it is necessary for the user to prevent the occurrence of such a situation because the malfunction of the image forming apparatus causes a downtime that the image forming apparatus cannot be used, resulting in downtime. There is.

  Further, when an abnormal state is detected due to a failure of the temperature measuring means or the like, when the failure is detected, abnormal heating of the fixing unit has already been caused, and the number of parts to be repaired may increase.

  Considering the above two cases, it is necessary to guarantee the operation of the fixing heater, which is expected to operate at the rated AC (alternating current) power supply voltage, at the upper and lower limits of the voltage, which is the operation guarantee condition. It is necessary to set the voltage so that it does not malfunction at the upper and lower limits.

  In this case, by measuring the AC power supply voltage and appropriately changing the abnormality detection condition according to the measurement result, even if the AC power supply voltage changes to an AC power supply voltage that is slightly outside the operation guarantee conditions, the abnormality detection is performed. Can be prevented.

  Further, even if a failure actually occurs in the temperature measuring means, this abnormality can be detected under appropriate conditions to prevent a secondary failure.

  However, the AC power supply voltage varies depending on the status of the AC wiring connected to the image forming apparatus and the power consumption of the image forming apparatus. If the AC power supply line impedance is high, a large amount of power like a fixing heater is consumed. When the power is not consumed, a normal value may be displayed.

  Therefore, the timing of measuring the AC power supply voltage is also important, and when measuring the AC power supply voltage as a characteristic related to the temperature rise of the fixing heater, it is necessary to measure it while the fixing heater is turned on.

  In addition, since the AC power supply waveform is a sine wave, the AC power supply voltage is often measured by measuring the average value. In order to measure the AC power supply voltage and use it in the program, it is necessary to perform rectification of the AC power supply, averaging, and digitization by the A / D converter.

  The input of the A / D converter is affected by the averaging time constant and becomes a ripple including ripples. If this pulsating current is sampled at an arbitrary timing and the sampled value is handled as a measured value of the AC power supply voltage, it will be a value including fluctuations of the pulsating current and will not be constant, and it will not be an accurate measured value of the power supply voltage. Therefore, it is possible to always obtain an accurate measurement value that is not influenced by the waveform by sampling at the zero cross timing that is in a synchronous relationship with the pulsating waveform.

  In view of this, the invention described in claim 1 is that the fixing heater control means is provided from the outside to the fixing heater of the fixing section for fixing the transfer paper on which the developer image has been transferred, using a fixing roller heated by the fixing heater. The supplied AC power supply is controlled by on / off control, the voltage of the AC power supply supplied from the outside is measured by the power supply voltage measuring means, and the temperature of the fixing roller is measured by the temperature measuring means. When the detecting means monitors the temperature of the fixing roller measured by the temperature measuring means and detects whether there is an abnormality in the fixing heater heating control system based on a predetermined abnormality detecting condition, the abnormality detecting means turns on the fixing heater. By changing the abnormality detection condition according to the AC power supply voltage value measured by the power supply voltage measuring means, the AC power supply voltage changes due to the influence of the impedance of the AC power supply (AC power supply) line. In addition to preventing erroneous detection of an abnormality in the fixing control system due to the occurrence of an abnormality, preventing overheating at the time of detecting an abnormality, appropriately detecting the abnormality to improve safety, and providing an image forming apparatus with good usability The purpose is that.

  The invention according to claim 2 is provided with a zero cross timing detecting means for detecting a zero cross timing of an AC power supply supplied from the outside, and the abnormality detecting means is synchronized with the zero cross timing of the AC power detected by the zero cross timing detecting means. By changing the abnormality detection condition according to the AC power supply voltage value measured by the power supply voltage measurement means, the influence of the output ripple of the power supply voltage measurement means is eliminated, and the abnormality detection condition is set according to the stable power supply voltage measurement result. Change to prevent the detection of abnormalities in the fixing control system due to fluctuations in the AC power supply voltage due to the influence of the impedance of the AC power supply (AC power supply) line, etc., and prevent overheating when an abnormality is detected. An image forming apparatus that performs abnormality detection more appropriately to further improve safety and has good usability It is intended to be subjected.

  In the invention according to claim 3, when the abnormality detection means uses the abnormality determination reference temperature as the abnormality detection condition, and the AC power supply voltage measured by the power supply voltage measurement means is lower than the rated voltage, the abnormality determination reference temperature is lowered. The AC power supply voltage when the fixing heater is turned on is detected by comparing the measured temperature of the fixing roller measured by the temperature measuring means after energizing the fixing heater for a predetermined time and the abnormality determination reference temperature to detect the presence or absence of abnormality. And by setting an appropriate abnormality judgment temperature reference from the temperature rise characteristics, the detection of abnormality due to fluctuations in the AC power supply voltage when the fixing heater is turned on is more appropriately prevented, and overheating at the time of abnormality detection is prevented, It is an object of the present invention to provide an image forming apparatus with good usability while performing abnormality detection more appropriately to further improve safety.

  According to the fourth aspect of the present invention, the abnormality detection means uses the abnormality determination reference temperature as the abnormality detection condition, and the fixing roller measured temperature measured by the temperature measurement means after the fixing heater is energized for a predetermined abnormality determination time, By comparing the abnormality judgment reference temperature and detecting the presence or absence of abnormality, if the AC power supply voltage measured by the power supply voltage measurement means is higher than the rated voltage, the abnormality judgment time is changed to shorten the AC power supply when the fixing heater is lit. Even if the temperature measurement means breaks down by setting an appropriate predetermined time from the voltage and temperature rise characteristics, heating is stopped at an appropriate energization time, and overheating at the time of detecting an abnormality is further prevented more safely. An object of the present invention is to provide an image forming apparatus that can further improve the image quality.

  According to a first aspect of the present invention, there is provided an image forming apparatus for fixing a transfer sheet onto which a developer image has been transferred using a fixing roller heated by a fixing heater, and an alternating current supplied to the fixing heater from the outside. Fixing heater control means for applying on / off control of power, power supply voltage measuring means for measuring the voltage of the AC power supplied from the outside, temperature measuring means for measuring the temperature of the fixing roller, and the temperature An abnormality detecting means for monitoring the temperature of the fixing roller measured by a measuring means and detecting the presence or absence of an abnormality in the fixing heater heating control system based on a predetermined abnormality detecting condition, and an image forming apparatus comprising: The abnormality detection means achieves the above object by changing the abnormality detection condition according to the AC power supply voltage value measured by the power supply voltage measurement means while the fixing heater is lit.

  In this case, for example, as described in claim 2, the image forming apparatus includes a zero cross timing detection unit that detects a zero cross timing of the AC power supplied from the outside, and the abnormality detection unit includes the zero cross timing. The abnormality detection condition may be changed according to the AC power supply voltage value measured by the power supply voltage measuring means in synchronization with the zero cross timing of the AC power supply detected by the detecting means.

  For example, as described in claim 3, the abnormality detection unit uses an abnormality determination reference temperature as the abnormality detection condition, and the AC power supply voltage measured by the power supply voltage measurement unit is lower than a rated voltage. The abnormality determination reference temperature is changed to a low value, and the temperature of the fixing roller measured by the temperature measuring unit after the fixing heater is energized for a predetermined time is compared with the abnormality determination reference temperature to determine whether the abnormality is present. It may be detected.

  Furthermore, for example, as described in claim 4, the abnormality detection unit uses an abnormality determination reference temperature as the abnormality detection condition, and the temperature measurement unit after the fixing heater is energized for a predetermined abnormality determination time. The measurement temperature of the fixing roller to be measured and the abnormality determination reference temperature are compared to detect the presence / absence of the abnormality, and when the AC power supply voltage measured by the power supply voltage measuring unit is higher than a rated voltage, the abnormality determination time May be changed short.

  According to the image forming apparatus of the first aspect of the present invention, the fixing heater control means is provided with the fixing heater of the fixing unit for fixing the transfer sheet on which the developer image is transferred using the fixing roller heated by the fixing heater. However, the AC power supplied from the outside is controlled by ON / OFF control, the voltage of the AC power supplied from the outside is measured by the power voltage measuring means, and the temperature of the fixing roller is measured by the temperature measuring means. When the abnormality detection unit monitors the temperature of the fixing roller measured by the temperature measurement unit and detects the presence or absence of an abnormality in the fixing heater heating control system based on a predetermined abnormality detection condition, the abnormality detection unit Because the abnormality detection condition is changed according to the AC power supply voltage value measured by the power supply voltage measuring means while the fixing heater is lit, the AC power supply due to the influence of the impedance of the AC power supply (AC power supply) line, etc. In addition to preventing erroneous detection of abnormalities in the fixing control system due to fluctuations, it is possible to prevent overheating at the time of detecting abnormalities, improve the safety by properly detecting abnormalities, Usability can be improved.

  According to the image forming apparatus of the second aspect of the present invention, the zero cross timing detecting means for detecting the zero cross timing of the AC power supplied from the outside is provided, and the abnormality detecting means detects the AC power supply detected by the zero cross timing detecting means. The abnormality detection condition is changed according to the AC power supply voltage value measured by the power supply voltage measurement means in synchronization with the zero-cross timing, so the influence of the output ripple of the power supply voltage measurement means is eliminated and the stable power supply voltage measurement results are met. By changing the abnormality detection conditions, it is possible to more appropriately prevent erroneous detection of abnormality in the fixing control system due to fluctuations in the AC power supply voltage due to the influence of the impedance of the AC power supply (AC power supply) line, Overheating at the time of abnormality detection can be prevented, and safety is further improved by performing abnormality detection more appropriately. Preparative it is, it is possible to improve the usability.

  According to the image forming apparatus of the invention described in claim 3, when the abnormality detection means uses the abnormality determination reference temperature as the abnormality detection condition and the AC power supply voltage measured by the power supply voltage measurement means is lower than the rated voltage, The abnormality determination reference temperature is changed to a low value, and the fixing heater is turned on because the abnormality determination reference temperature is compared with the measurement temperature of the fixing roller measured by the temperature measuring means after the fixing heater is energized for a predetermined time. By setting an appropriate abnormality judgment temperature reference from the AC power supply voltage and temperature rise characteristics at the time, it is possible to more appropriately prevent false detection of abnormality detection due to fluctuations in the AC power supply voltage when the fixing heater is lit. Overheating at the time of detection can be prevented, abnormality detection can be performed more appropriately, safety can be further improved, and usability can be improved. That.

  According to the image forming apparatus of the present invention, the abnormality detection means uses the abnormality determination reference temperature as the abnormality detection condition, and the fixing is measured by the temperature measurement means after the fixing heater is energized for a predetermined abnormality determination time. Since the abnormality temperature is detected by comparing the measured temperature of the roller with the abnormality determination reference temperature, and the AC power supply voltage measured by the power supply voltage measuring means is higher than the rated voltage, the abnormality determination time is changed to a shorter value. Even if the temperature measurement unit fails by setting an appropriate predetermined time from the AC power supply voltage and temperature rise characteristics at the time of lighting, heating can be stopped with an appropriate energization time, further overheating at the time of abnormality detection It can prevent appropriately and can improve safety | security further.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, since the Example described below is a suitable Example of this invention, various technically preferable restrictions are attached | subjected, However, The scope of the present invention limits this invention especially in the following description. As long as there is no description of the effect, it is not restricted to these aspects.

  1 to 9 are diagrams showing an embodiment of the image forming apparatus of the present invention. FIG. 1 is a circuit of a fixing control system of the image forming apparatus 1 to which the embodiment of the image forming apparatus of the present invention is applied. It is a block block diagram.

  In FIG. 1, an image forming apparatus 1 includes a controller 2, a display unit 3, a power supply voltage measurement unit 4, a zero cross timing detection unit 5, a fixing heater control unit 6, a fixing heater 7, a temperature measurement unit 8, and the like. A commercial alternating current (AC) power supply 10 is supplied to the heater controller 6.

  The controller (abnormality detection means) 2 includes a CPU (Central Processing Unit) 21, a ROM (Read Only Memory) 22, a RAM (Random Access Memory) 23, an I / O 24, a timer (TIMER) 25, an A / D converter 26, and the like. The display unit 3, the power supply voltage measurement unit 4, the zero cross timing detection unit 5, the fixing heater control unit 6, and the temperature measurement unit 8 are connected to the controller 2.

  A fixing heater 7 is connected to the fixing heater control section (fixing heater control means) 6 and includes a switching element such as an SSR (Solid State Relay) or a triac, and a controller for an AC power supply 10 supplied from the outside. Based on the control signal from 2, switching processing is performed by the switching element to control the AC power supplied to the fixing heater 7. Examples of the switching method in the fixing heater control unit 6 include a zero cross switching method and a phase control method.

  The power supply voltage measuring unit (power supply voltage measuring means) 4 detects the power supply voltage of the AC power supply 10 and outputs the detected analog voltage detection signal to the A / D converter 26 of the controller 2. As a method for measuring the power supply voltage of the AC power supply 10 in the power supply voltage measuring unit 4, for example, there are an effective value detection method and an average value detection method. However, since the AC power supply waveform is generally a sine wave, A simple average value detection method can be used. Note that the measured value of the power supply voltage measuring unit 4 is output as a DC signal that can be detected by the controller 2, and this output includes ripple.

  The zero-cross timing detection unit (zero-cross timing detection means) 5 includes a full-wave rectifier circuit, a voltage comparison circuit, and the like, detects the zero-cross timing of the AC power supply voltage, and generates a zero-cross timing signal at that timing. This zero cross timing signal is input to the controller 2 and connected to the interrupt signal of the CPU 21 to be used as a reference timing for various AC related controls.

  The temperature measuring unit (temperature measuring means) 8 uses, for example, a thermistor as an element, and is installed in the vicinity of the fixing mechanism unit, mainly in close contact with the surface of the fixing roller. The temperature measurement unit 8 converts the resistance value change due to the temperature of the element into a voltage, extracts the temperature of the fixing roller, and outputs it to the A / D converter 26 of the controller 2.

  The controller 2 uses the RAM 23 as a work memory based on a program stored in the ROM 22, and controls each part of the image forming apparatus 1 to execute processing as the image forming apparatus 1. The energization state of the fixing heater 6 is controlled based on the temperature information from the temperature measurement unit 8, and the fixing system is in an abnormal state based on the voltage detection information from the power supply voltage measurement unit 4 and the temperature information from the temperature measurement unit 8. To monitor.

  Note that the ROM 22, RAM 23, I / O 24, timer 25, A / D converter 26 and the like of the controller 2 may be integrated with the CPU 21.

  The controller 2 converts the temperature information from the temperature measurement unit 8 and the voltage detection information from the power supply voltage measurement unit 4 into digital data by the A / D converter 26 and uses it for control.

  Next, the operation of this embodiment will be described. The image forming apparatus 1 according to the present exemplary embodiment is characterized in that the presence or absence of an abnormality in the fixing system is appropriately detected without being affected by fluctuations in the AC power supply voltage, and the usability is improved while ensuring safety. There is.

  In the image forming apparatus 1, the controller 2 executes the fixing heater main control process shown in FIG. 2, thereby executing the temperature control process and the abnormality detection process for the fixing heater 7.

  That is, when the power of the image forming apparatus 1 is turned on, the controller 2 first performs an initialization process (step S101) as shown in FIG. 2, and when the initialization process is executed, a repeated process is performed. A temperature control process and an abnormality detection process for the fixing heater 7 are executed (steps S102 to S105). In this initialization process, the controller 2 initializes variables necessary at the start of the temperature control process and abnormality detection process of the fixing heater 7, and initializes peripheral functions such as the I / O 24, timer 25, and A / D converter 26. The initialization process including is executed, and this initialization process is executed only once at the start of control.

  When the controller 2 is initialized, the temperature measurement unit 8 acquires the temperature measurement result stored in the RAM 23 as temperature information after the temperature measurement unit 8 detects and digitally converts it with the A / D converter 26 at a zero cross timing described later. Processing is performed (step S102), and then at the zero cross timing described later, the power supply voltage measurement unit 4 detects and digitally converts it with the A / D converter 26, and then acquires the voltage measurement result stored in the RAM 23 as voltage detection information. A power supply voltage measurement process is performed (step S103).

  Next, the controller 2 outputs a lighting control signal to the fixing heater control unit 6 from the temperature information, the control command, and the target temperature information of the fixing heater 7 acquired in step S102, and the fixing heater via the fixing heater control unit 6 7 is controlled (step S104). In the lighting control of the fixing heater 7, the controller 2 uses the past temperature information history of the fixing heater 7 or uses a PID (proportional integral derivative) calculation to turn on the fixing heater 7. -Turn off the light.

  Next, the controller 2 performs an abnormality detection process for detecting whether there is an abnormality in the fixing system based on the temperature information of the fixing heater 7 acquired in step S102 and the voltage detection information acquired in step S103 (step S105). The controller 2 employs a plurality of abnormality detection methods in this abnormality detection process. For example, the controller 2 detects an abnormality in the temperature rise value of the fixing heater 7 per hour, an abnormality that is too high, and the like to measure the temperature. The failure of the unit 8 and the failure of the fixing heater control unit 6 are accurately monitored, and processing for ensuring the safety of the fixing unit, and hence the image forming apparatus 1 is performed.

  When the controller 2 receives the zero-cross timing signal from the zero-cross timing detector 5 during execution of the main process, the controller 2 executes the zero-cross interrupt process shown in FIG. 3 and stores the temperature information in the RAM 23. The voltage measurement result is stored in the RAM 23. That is, the controller 2 activates a zero-cross interrupt every time the AC power source 10 is zero-crossed.

  Then, when the zero cross timing signal is input from the zero cross timing detection unit 5 during execution of the main process, the controller 2 converts the temperature measurement result output from the temperature measurement unit 8 into an A / D converter as shown in FIG. The digitized temperature measurement result is stored in the temperature data area of the RAM 23 as temperature information (step S202), and the voltage measurement result detected by the power supply voltage measurement unit 4 is stored in the A / D converter 26. In step S203, it is checked whether the fixing heater 7 is currently lit (step S204).

  If the fixing heater 7 is turned on in step S204, the controller 2 stores the voltage measurement result digitized by the A / D converter 26 in the power supply voltage data area of the RAM 23 while the heater is turned on, and performs the above main processing. When the fixing heater 7 is turned off in step S205, the voltage measurement result digitized by the A / D converter 26 is stored in the power supply voltage data area of the RAM 23 when the heater is turned off. The process returns to the main process (step S206).

  In this way, the measurement result of the power supply voltage is stored in different memory areas of the RAM 23 while the fixing heater 7 is turned on and off, so that it can be used separately in other program parts.

  Further, the measurement of the power supply voltage is performed at the zero cross timing of the AC power supply 10 because the ripple of the output of the power supply voltage measurement unit 4 fluctuates in synchronization with the zero cross timing as shown in FIG. This is because the power supply voltage is sampled at the timing to prevent the measurement value from fluctuating due to ripple.

  And the controller 2 performs a 1st abnormality detection process, as shown in FIG. In the first abnormality detection process, when the fixing heater 7 is turned on and the fixing roller is raised to a predetermined high fixing temperature, monitoring is performed from the start of control, and the fixing heater control for starting is performed. However, since the temperature of the fixing roller to be detected does not rise, this is a process for detecting a failure such as a failure of the temperature measuring unit 8 or a disconnection of the fixing heater 7.

  First, the controller 2 turns on the fixing heater 7 and starts heater heating control (step S301). When the heater heating starts, the power supply voltage measuring unit 4 measures and the A / D converter 26 converts the digital value into the RAM 23. The stored voltage measurement result is acquired as the AC power supply voltage value at the start of heating, and the abnormality determination reference temperature T1 is selected and determined from this AC power supply voltage value (step S302).

  In the selection / determination of the abnormality determination reference temperature T1, when the acquired AC power supply voltage value is lower than the rated voltage of the AC power supply 10, a lower abnormality determination reference temperature is selected as the abnormality determination reference temperature T1.

  Then, after a predetermined time has elapsed (step S303), the controller 2 digitizes the temperature measurement result output from the temperature measurement unit 8 by the A / D converter 26 and stores the temperature measurement result stored in the RAM 23 as the current temperature of the fixing roller. It is acquired as information, and it is checked whether the current temperature is higher than the abnormality determination reference temperature T1 (step S304). If the current temperature exceeds the abnormality determination reference temperature T1, it is determined as normal and an abnormality is detected. The process ends.

  If it is determined in step S304 that the current temperature does not exceed the abnormality determination reference temperature T1, the controller 2 determines that there is an abnormality, turns off the fixing heater 7, and stops heating the fixing roller (step S305). The necessary abnormality processing is performed and the process ends (step S306).

  That is, as shown in FIG. 6, since the fixing temperature reached in a predetermined time differs according to the AC power supply voltage, when the abnormality determination reference temperature is set to a constant value as in the conventional case, the AC power supply voltage is the abnormality determination reference temperature. Even if the operation guaranteed lower limit is set, a value that is not determined to be abnormal must be selected, and if the AC power supply voltage is high, the fixing temperature at the time of detecting the abnormality becomes high. In this case, if the fixing temperature at the time of detecting an abnormality is not increased, there is a problem that the abnormality is easily detected when the AC power supply voltage is low.

  However, in the image forming apparatus 1 of the present embodiment, the abnormality determination reference temperature T1 corresponding to the AC power supply voltage is selected and determined, so that malfunction of abnormality detection is prevented, and safety is ensured while the image forming apparatus 1 is secured. The operating voltage range of 1 can be expanded.

  FIG. 7 is a flowchart showing the second abnormality detection process. In the second abnormality detection process, when the fixing temperature is raised to a predetermined high temperature, monitoring is performed from the start of the control, and the fixing heater for starting up is detected. Although the temperature of the fixing roller to be detected does not increase in spite of the control, this is a process for detecting a failure of the temperature measuring unit 8 or a failure of the fixing heater 7 or the like.

  First, the controller 2 turns on the fixing heater 7 and starts heater heating control (step S401). When the heater heating starts, the power supply voltage measuring unit 4 measures and the A / D converter 26 converts the digital value to the RAM 23. The stored voltage measurement result is acquired as the AC power supply voltage value at the start of heating, and the abnormality determination time t1 is selected and determined from this AC power supply voltage value (step S402).

  In the selection / determination of the abnormality determination time t1, when the acquired AC power supply voltage value is higher than the rated voltage of the AC power supply 10, a short abnormality determination time is selected and determined as the abnormality determination time t1.

  Then, the controller 2 waits for the selected / determined abnormality determination time t1 to elapse (step S403), digitizes the temperature measurement result output from the temperature measurement unit 8 by the A / D converter 26, and stores it in the RAM 23. The temperature measurement result is acquired as temperature information of the current fixing roller, and it is checked whether the current temperature is higher than the abnormality determination reference temperature (step S404). If the current temperature exceeds the abnormality determination reference temperature T1. Then, it is determined as normal and the abnormality detection process is terminated.

  If the current temperature does not exceed the abnormality determination reference temperature in step S404, the controller 2 determines that there is an abnormality, turns off the fixing heater 7, stops heating of the fixing roller (step S405), and is necessary. An abnormal process is performed and the process ends (step S406).

  Even in this case, as shown in FIG. 6, the time required to reach a predetermined temperature differs depending on the AC power supply voltage. Therefore, if the abnormality determination time is set to a constant value, the AC power supply voltage is guaranteed to operate as the abnormality determination time. A value that does not cause an abnormality even in the case of the lower limit must be selected, and when the AC power supply voltage is high, the fixing temperature at the time of abnormality detection becomes high. In this case, if the fixing temperature at the time of detecting an abnormality is not increased, there is a problem that the abnormality is easily detected when the AC power supply voltage is low.

  However, in the image forming apparatus 1 of this embodiment, the abnormality determination time corresponding to the AC power supply voltage is selected, so that the fixing temperature arrival point at the time of abnormality detection can be kept at a safer temperature, and abnormality determination is performed. While performing appropriately, the operating voltage range of the image forming apparatus 1 can be expanded.

  FIG. 8 is a flowchart showing another example of the third abnormality detection process. This third abnormality detection process detects an abnormality based on a temperature rise value per predetermined lighting time. The process and the second abnormality detection process are used together to detect not only a case where the temperature rises to a predetermined temperature, but also a failure such as a failure of the temperature measuring unit 8 during control for maintaining a constant temperature and a disconnection of the fixing heater 7.

  First, the controller 2 turns on the fixing heater 7 and starts heater heating control (step S501). When the heater heating starts, the power supply voltage measuring unit 4 measures and the A / D converter 26 performs digital conversion to the RAM 23. The stored voltage measurement result is acquired as the AC power supply voltage value KT1 at the start of heating, stored in the RAM 23 (step S502), and the abnormality determination reference temperature T2 is selected and determined from the AC power supply voltage value KT1 at the start of heating. (Step S503).

  In the selection / determination of the abnormality determination reference temperature T2, if the acquired AC power supply voltage value KT1 at the start of heating is lower than the rated voltage of the AC power supply 10, a lower abnormality determination reference temperature is selected as the abnormality determination reference temperature T2. .

  Then, the controller 2 checks whether a certain time has elapsed (step S504), and if not, the controller 2 checks whether the fixing heater 7 has been turned off (step S505).

  If the fixing heater 7 is not turned off in step S505, the controller 2 returns to step S504 to check whether a fixed time has elapsed, and if not, the controller 2 checks whether the fixing heater 7 has been turned off. Repeatedly (steps S504 to S505), and in step S505, if the fixing heater 7 is turned off before a predetermined time elapses, it is determined that it is normal and the abnormality detection process is terminated.

  In step S504, when a fixed time has elapsed without the fixing heater 7 being turned off, the controller 2 digitizes the temperature measurement result output from the temperature measurement unit 8 by the A / D converter 26 and stores the temperature measurement result stored in the RAM 23. Obtained as current fixing roller temperature information, and checks whether the difference between the current temperature and the AC power supply voltage value KT1 at the start of heating is higher than the abnormality determination reference temperature T2 (step S506). If the difference between the AC power supply voltage value KT1 at the start of heating exceeds the abnormality determination reference temperature T2, it is determined as normal and the abnormality detection process is terminated.

  If the difference between the current temperature and the AC power supply voltage value KT1 at the start of heating does not exceed the abnormality determination reference temperature T2 in step S506, the controller 2 determines that there is an abnormality and turns off the fixing heater 7 Heating of the fixing roller is stopped (step S507), necessary abnormality processing is performed, and the process is terminated (step S508).

  FIG. 9 is a flowchart showing another example of the fourth abnormality detection process. This fourth abnormality detection process monitors the fixing heater lighting time and detects an abnormality based on a temperature rise value per predetermined lighting time. Therefore, not only when the first abnormality detection process and the second abnormality detection process are used together to raise the temperature to a predetermined temperature, but also the failure of the temperature measuring unit 8 during the control for maintaining a constant temperature or the fixing heater 7 Detects failures such as disconnection.

  First, the controller 2 turns on the fixing heater 7 and starts heater heating control (step S601). When the heater heating starts, the power supply voltage measuring unit 4 measures and the A / D converter 26 performs digital conversion to the RAM 23. The stored voltage measurement result is acquired as the AC power supply voltage value KT1 at the start of heating and stored in the RAM 23 (step S602), and the abnormality determination time t2 is selected and determined from the AC power supply voltage value KT1 at the start of heating (step S602). Step S603).

  In the selection / determination of the abnormality determination time t2, if the acquired AC power supply voltage value KT1 at the start of heating is higher than the rated voltage of the AC power supply 10, a short abnormality determination time is selected as the abnormality determination time t2.

  Then, the controller 2 checks whether the selected / determined abnormality determination time t2 has elapsed (step S604), and if the abnormality determination time t2 has not elapsed, it checks whether the fixing heater 7 has been turned off (step S605).

  If the fixing heater 7 is not turned off in step S605, the controller 2 returns to step S604 to check whether the abnormality determination time t2 has elapsed. If the abnormality determination time t2 has not elapsed, the fixing heater 7 is turned off. In step S605, if the fixing heater 7 is turned off before the abnormality determination time t2 elapses, it is determined that the operation is normal, and the abnormality detection process is terminated. .

  In step S604, when the abnormality determination time t2 has elapsed without the fixing heater 7 being turned off, the controller 2 digitizes the temperature measurement result output from the temperature measurement unit 8 by the A / D converter 26 and stores the temperature in the RAM 23. The measurement result is acquired as current fixing roller temperature information, and it is checked whether the difference between the current temperature and the heating start AC power supply voltage value KT1 is higher than the abnormality determination reference temperature (step S606). If the difference between the temperature and the AC power supply voltage value KT1 at the start of heating exceeds the abnormality determination reference temperature, it is determined as normal and the abnormality detection process is terminated.

  In step S606, if the difference between the current temperature and the AC power supply voltage value KT1 at the start of heating does not exceed the abnormality determination reference temperature, the controller 2 determines that there is an abnormality and turns off the fixing heater 7 for fixing. The heating of the roller is stopped (step S607), necessary abnormality processing is performed, and the process is terminated (step S608).

  As described above, the image forming apparatus 1 of the present embodiment controls the fixing heater to the fixing heater 7 of the fixing unit that fixes the transfer sheet on which the toner image is transferred using the fixing roller heated by the fixing heater 7. The unit 6 applies the AC (alternating current) power supply 10 supplied from the outside by turning it on / off, measures the voltage of the AC power supply 10 supplied from the outside by the power supply voltage measuring unit 4, and the fixing roller The temperature is measured by the temperature measuring unit 8, and the controller 2 monitors the temperature of the fixing roller measured by the temperature measuring unit 8 and detects whether there is an abnormality in the fixing heater heating control system based on a predetermined abnormality detection condition. In doing so, the controller 2 changes the abnormality detection condition in accordance with the AC power supply voltage value measured by the power supply voltage measurement unit 4 while the fixing heater 7 is lit.

  Therefore, it is possible to prevent erroneous detection of an abnormality in the fixing control system due to fluctuations in the AC power supply voltage due to the influence of the impedance of the AC power supply (AC power supply) line, and it is possible to prevent overheating when an abnormality is detected. In addition, it is possible to improve safety by appropriately performing abnormality detection and improve usability.

  The image forming apparatus 1 of the present embodiment also includes a zero cross timing detection unit 5 that detects the zero cross timing of the AC power supply 10, and the controller 2 is synchronized with the zero cross timing of the AC power supply detected by the zero cross timing detection unit 5. The abnormality detection condition is changed according to the AC power supply voltage value measured by the power supply voltage measuring unit 4.

  Therefore, the influence of the output ripple of the power supply voltage measuring unit 4 is eliminated, the abnormality detection condition is changed according to the stable power supply voltage measurement result, and the fluctuation of the AC power supply voltage due to the influence of the impedance of the AC power supply (AC power supply) line, etc. In addition to preventing erroneous detection of abnormalities in the fixing control system due to the occurrence of abnormalities, it is possible to prevent overheating when an abnormality is detected, further improving safety by performing abnormality detection more appropriately. In addition, the usability can be improved.

  Furthermore, in the image forming apparatus 1 according to the present embodiment, when the controller 2 uses the abnormality determination reference temperature as the abnormality detection condition and the AC power supply voltage measured by the power supply voltage measurement unit 4 is lower than the rated voltage, the abnormality determination is performed. The reference temperature is changed to a low value, and the presence / absence of an abnormality is detected by comparing the measurement temperature of the fixing roller measured by the temperature measurement unit 8 after energizing the fixing heater for a predetermined time with the abnormality determination reference temperature.

  Accordingly, an appropriate abnormality determination temperature reference is set based on the AC power supply voltage and temperature rise characteristics when the fixing heater 7 is turned on, so that erroneous detection of abnormality detection due to fluctuations in the AC power supply voltage when the fixing heater 7 is turned on is made more appropriate. In addition, it is possible to prevent overheating at the time of detecting an abnormality, and more appropriately detect an abnormality to further improve safety and improve usability.

  Further, in the image forming apparatus 1 of the present embodiment, the controller 2 uses the abnormality determination reference temperature as the abnormality detection condition, and the fixing roller measured by the temperature measuring unit 8 after energizing the fixing heater 7 for a predetermined abnormality determination time. When the AC power supply voltage measured by the power supply voltage measuring unit 4 is higher than the rated voltage, the abnormality determination time is changed to be shorter.

  Therefore, even if the temperature measurement unit 8 fails by setting an appropriate predetermined time from the AC power supply voltage and temperature rise characteristics when the fixing heater 7 is turned on, the heating can be stopped in an appropriate energization time, It is possible to more appropriately prevent overheating at the time of detection and further improve safety.

  The invention made by the present inventor has been specifically described based on the preferred embodiments. However, the present invention is not limited to the above, and various modifications can be made without departing from the scope of the invention. Needless to say.

  Regardless of fluctuations in the power supply voltage, it is possible to appropriately detect an abnormality in the fixing temperature and to apply to an image forming apparatus such as a facsimile apparatus, a copying apparatus, a composite apparatus, or a printer with good usability.

1 is a circuit block diagram of a fixing control system of an image forming apparatus to which an embodiment of the image forming apparatus of the present invention is applied. 3 is a flowchart showing fixing heater main control processing by the image forming apparatus of FIG. 1. 3 is a flowchart showing zero-cross interrupt processing by the image forming apparatus in FIG. 1. Explanatory drawing of the output and zero cross timing of the power supply voltage measurement part of FIG. The flowchart which shows the 1st abnormality detection process by the controller of FIG. FIG. 2 is a diagram illustrating a difference in a temperature increase change of a fixing roller depending on an AC power supply voltage in FIG. 1. The flowchart which shows the 2nd abnormality detection process by the controller of FIG. The flowchart which shows the 3rd abnormality detection process by the controller of FIG. The flowchart which shows the 4th abnormality detection process by the controller of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Controller 3 Display part 4 Power supply voltage measurement part 5 Zero cross timing detection part 6 Fixing heater control part 7 Fixing heater 8 Temperature measurement part 10 AC power supply 21 CPU
22 ROM
23 RAM
24 I / O
25 Timer 26 A / D Converter

Claims (4)

  A fixing unit that fixes a transfer sheet on which a developer image has been transferred using a fixing roller heated by a fixing heater, and a fixing heater that applies on / off control to an AC power source supplied from the outside to the fixing heater. Control means; power supply voltage measuring means for measuring the voltage of the AC power supplied from the outside; temperature measuring means for measuring the temperature of the fixing roller; and monitoring the temperature of the fixing roller measured by the temperature measuring means And an abnormality detecting means for detecting the presence or absence of an abnormality in the fixing heater heating control system based on a predetermined abnormality detecting condition, wherein the abnormality detecting means is configured to turn on the fixing heater. The image forming apparatus, wherein the abnormality detection condition is changed according to the AC power supply voltage value measured by the power supply voltage measuring means.   The image forming apparatus includes a zero-cross timing detection unit that detects a zero-cross timing of the AC power supplied from the outside, and the abnormality detection unit synchronizes with the zero-cross timing of the AC power detected by the zero-cross timing detection unit. The image forming apparatus according to claim 1, wherein the abnormality detection condition is changed according to the AC power supply voltage value measured by the power supply voltage measuring unit.   The abnormality detection means uses an abnormality determination reference temperature as the abnormality detection condition, and when the AC power supply voltage measured by the power supply voltage measurement means is lower than a rated voltage, the abnormality determination reference temperature is changed to a low value, 2. The presence or absence of the abnormality is detected by comparing a temperature measured by the fixing roller measured by the temperature measuring means after energizing the fixing heater for a predetermined time with the abnormality determination reference temperature. 2. The image forming apparatus according to 2. The abnormality detection unit uses an abnormality determination reference temperature as the abnormality detection condition, and the temperature measurement unit measures the temperature measured by the temperature measurement unit after energizing the fixing heater for a predetermined abnormality determination time and the abnormality determination standard. The abnormality determination time is changed to be shorter when the AC power supply voltage measured by the power supply voltage measuring means is higher than a rated voltage while detecting the presence or absence of the abnormality by comparing temperatures. The image forming apparatus according to claim 2.

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