JP2010217792A - Image forming apparatus, and fixing device control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To raise productivity of an image forming apparatus and to safely control a fixing device even when an abnormal state is caused in the fixing device by quickly supplying power to a fixing heating part after power application. <P>SOLUTION: After the power application, before a CPU 13a which controls the whole starts, power is supplied to the fixing heating part 22a which heats the fixing device by a power supply signal which is generated by a power supply signal generation circuit 12 by hardware configuration. After the fixing heating part 22a becomes predetermined temperature and the CPU 13a starts, the power supply signal is switched to the one from a power supply generation part 13 which performs fixing control by a program to supply power to the fixing heating part 22a. The image forming apparatus is provided with an invalidation circuit 16 which stores, holds, even when the abnormal state is generated in the fixing device while causing the CPU 13a start, the abnormal state in a nonvolatile storage part 21 and an abnormality storage part 17, and invalidates the power supply signal by outputting a fixing abnormal signal and a holding signal. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus including a fixing device for fixing a toner image and a fixing device control method.

  As conventional image forming apparatuses, a copying machine, a printer, a facsimile, and a complex machine (MFP) that combines these functions have been developed. In such an image forming apparatus, the number of functions is increased to be the same as that of a personal computer, the number of objects to be controlled is increasing, and the memory capacity for controlling the number is increasing. For this reason, a plurality of CPUs are provided, and various functions of the image forming apparatus are achieved while the functions are distributed between the CPU that controls the whole and the CPU that controls each unit, and communicates with each other.

  In many image forming apparatuses, a program is downloaded from an SD memory card or the like, and a CPU that controls the entire device performs initial setting of peripheral devices, and based on the downloaded program, peripheral circuits, peripheral device initial settings, and bus settings It is possible to start up the CPU that controls the respective sections after performing the opening process and after the bus is opened. As described above, it takes a lot of time for each unit of the image forming apparatus to be controlled.

  Such an image forming apparatus includes a fixing device that fixes the toner image onto the recording medium by pressurizing and heating the toner image formed on the recording medium by the image forming unit. The fixing device includes a fixing roller for pressing and heating the recording medium. In such an image forming apparatus, first, the CPU for controlling the entire image forming apparatus is started up, and after the bus between the entire CPU and the CPU of the fixing device is opened, the temperature of the fixing heating unit fixing roller is instructed by the CPU of the fixing device. Is controlled, electric power from a commercial power supply (AC power supply) is supplied and heated to a predetermined temperature. As described above, since it takes a very long time until the fixing roller reaches a predetermined temperature after the power is turned on and an image can be formed, this causes a decrease in productivity.

  Therefore, in order to improve the productivity of the image forming apparatus, in Patent Document 1, a circuit for supplying power to the fixing heating unit and a low-temperature detection circuit for the fixing heating unit are provided, and the temperature of the fixing heating unit is higher than a predetermined temperature. In addition, a technique is disclosed in which power is supplied to the fixing heating unit regardless of the CPU of the fixing device, and the power supply is forcibly stopped when the fixing heating unit becomes too hot. ing.

  However, in Patent Document 1, when an image forming apparatus has an abnormality and is turned on after the power is turned off, power is supplied to the fixing heating unit before the CPU can be controlled. Depending on the abnormal contents of the image forming apparatus, there has been a problem that the temperature of the fixing heating unit rises more than necessary and the fixing roller melts, or in the worst case, the fixing apparatus burns out.

  Also, if an abnormality of the fixing device is detected by the CPU during the copying operation, the copying operation is prohibited, and a warning display that the operation unit display cannot be used is displayed, and the main power supply is turned off. When the power is turned on again in this state, power is supplied by a hardware circuit different from the CPU before the CPU starts up. However, if the thermistor that detects the temperature of the fixing heating unit is disconnected or floats, the power supply is continuously performed by the hardware circuit, which may cause the fixing roller to melt, In such a case, there is a problem that the fixing device burns out.

  Furthermore, according to the configuration of Patent Document 1, since the time for supplying the commercial power source to the heater is not fixed, in the worst case, the power may be supplied when the phase is 90 degrees or 270 degrees. . In this case, particularly when the fixing / heating unit is at a low temperature, a large current instantaneously flows to the heater, causing lighting flickering or voltage drop of the commercial power supply, causing other electronic devices to There was a problem of adverse effects.

  The present invention has been made in view of the above, and it is possible to improve the productivity of the image forming apparatus and improve the safety of the fixing apparatus by rapidly supplying power to the fixing heating unit. An object of the present invention is to provide an image forming apparatus and a fixing device control method that can be used.

  In order to solve the above-described problems and achieve the object, the present invention includes a first control unit that controls a fixing device that fixes a toner image by pressurizing and heating a medium on which the toner image is formed. In the image forming apparatus, the fixing heating unit that heats the fixing device, the temperature detection unit that detects the temperature of the fixing heating unit, the power detection unit that detects the generation of power from the power source, and the first control A first power supply signal generating means for generating a power supply signal to the fixing heating means based on a detection signal from the power detection means and a detection signal from the temperature detection means before the unit starts up; After the first control unit starts up, the program detects the detection signal from the power detection unit and the temperature detection unit in place of the power supply signal from the first power supply signal generation unit by a program. Second power supply signal generating means for generating a power supply signal to the fixing heating means based on the detected signal, the first power supply signal generating means and the second power supply signal generating means A power supply means for supplying power to the fixing and heating means in response to a power supply signal from the power supply, an abnormality detection means for detecting an abnormality of the fixing device and outputting an abnormality detection signal, and the first controller In the meantime, when an abnormality detection signal from the abnormality detection means is stored, an abnormality storage means that continues to output an abnormality detection signal until a cancellation instruction is received from the first control unit, and the abnormality storage means or the abnormality detection means At least the first power supply signal generating means among the first power supply signal generating means and the second power supply signal generating means is generated by the abnormality detection signal from And disabling means for disabling the power supply signal that is characterized by having a.

  According to another aspect of the present invention, there is provided a fixing device control method executed by the image forming apparatus. The image forming apparatus includes a first control unit that controls the fixing device, a fixing heating unit, a temperature detecting unit, and a power detecting unit. Means, a first power supply signal generation means, a second power supply signal generation means, a power supply means, an abnormality detection means, an abnormality storage means, and an invalidation means, and the fixing heating means heats the fixing device The step of detecting the temperature of the fixing and heating unit, the step of detecting the power generation by the power detection unit, and the first power supply signal generation unit, Generating a signal for supplying power to the fixing heating unit based on a detection signal from the power detection unit and a detection signal from the temperature detection unit before the first control unit starts up; and Power After the first control unit is started up, the supply signal generation means replaces the power supply signal from the first power supply signal generation means by a program and the detection signal by the power detection means and the temperature detection means Generating a signal for supplying power to the fixing and heating means based on the detection signal from the first and second power supply signal generating means. Supplying power to the fixing and heating means according to the power supply signal, an abnormality detection means detecting an abnormality of the fixing device and outputting an abnormality detection signal, and the abnormality storage means If the abnormality detection signal from the abnormality detection means is stored while the control unit is starting up, the abnormality detection signal continues to be output until a cancel instruction is received from the first control unit. And at least the first power supply signal generating means and the second power supply signal generating means according to an abnormality detection signal from the abnormality storage means or the abnormality detection means. And a step of invalidating the power supply signal generated by the one power supply signal generating means.

  According to the present invention, the fixing heating unit heats the fixing device, the temperature detecting unit detects the temperature of the fixing heating unit, the power detecting unit detects the generation of power from the power source, and the first control unit starts up. Before, the first power supply signal generating means generates a power supply signal to the fixing heating means. After the first control unit is started up, the second power supply signal generating means by the program generates a power supply signal that replaces the first power supply signal generating means, and the power supply means fixes and heats the power supply signal. Since power is supplied to the means, it is possible to quickly supply power to the fixing and heating unit after the power is turned on, and the productivity of the image forming apparatus can be improved. Then, when the abnormality detection unit detects an abnormality of the fixing device and stores the abnormality detection signal in the abnormality storage unit while the first control unit is standing up, until the next instruction from the first control unit is received. Since the abnormality detection signal is continuously output, when the abnormality detection signal from the abnormality storage means or the abnormality detection means is input to the invalidation means, the power supply signals generated by the first and second power supply signal generation means are invalidated. Therefore, the safety of the fixing device can be improved.

  According to the invention, the fixing heating means heats the fixing device, the temperature detecting means detects the temperature of the fixing heating means, the power detecting means detects the generation of power from the power source, and the first control unit The first power supply signal generating means generates a power supply signal to the fixing and heating means before the rise of. After the first control unit is started up, the second power supply signal generating means by the program generates a power supply signal that replaces the first power supply signal generating means, and the power supply means fixes and heats the power supply signal. Since the control is performed so that power is supplied to the means, it is possible to quickly supply power to the fixing and heating unit after the power is turned on, and it is possible to improve the productivity of the image forming apparatus. Then, when the abnormality detection unit detects an abnormality of the fixing device and outputs an abnormality detection signal to the invalidation unit, control is performed to invalidate the power supply signals generated by the first and second power supply signal generation units. Therefore, it is possible to improve the safety of the fixing device of the image forming apparatus.

FIG. 1 is a functional block diagram illustrating a fixing device control circuit of the image forming apparatus according to the first embodiment. FIG. 2 is a diagram illustrating a configuration example of a zero-cross signal generation circuit. FIG. 3 is a schematic configuration diagram of a latching relay which is the abnormality storage unit of FIG. FIG. 4 is a block diagram showing a more specific circuit configuration of the fixing device control circuit of FIG. FIG. 5 is a timing chart showing examples of signal waveforms at various parts in FIG. FIG. 6A is a flowchart illustrating the control operation of the fixing device. FIG. 6B is a flowchart for explaining the control operation of the fixing device. FIG. 6C is a flowchart illustrating the control operation of the fixing device. FIG. 6-4 is a flowchart illustrating a control operation of the fixing device. FIG. 7 is a functional block diagram illustrating a fixing device control circuit of the image forming apparatus according to the second embodiment. FIG. 8 is a functional block diagram illustrating a fixing device control circuit of the image forming apparatus according to the third embodiment. FIG. 9 is a functional block diagram illustrating a fixing device control circuit of the image forming apparatus according to the fourth embodiment. FIG. 10 is a timing chart showing an example of signal waveforms in each part of FIG. FIG. 11 is a functional block diagram illustrating a fixing device control circuit of the image forming apparatus according to the fifth embodiment. FIG. 12 is a functional block diagram illustrating a fixing device control circuit of the image forming apparatus according to the sixth embodiment. FIG. 13A is a flowchart for explaining the operation according to the fourth embodiment. FIG. 13-2 is a flowchart for explaining an operation according to the fifth embodiment. FIG. 13C is a flowchart for explaining the operation according to the fourth embodiment. FIG. 13-4 is a flowchart for explaining an operation according to the fifth embodiment. FIG. 13-5 is a flowchart for explaining an operation according to the fourth embodiment. FIG. 13-6 is a flowchart for explaining an operation according to the fifth embodiment. FIG. 13-7 is a flowchart for explaining an operation according to the fourth embodiment.

  Exemplary embodiments of an image forming apparatus and a fixing device control method according to the present invention will be explained below in detail with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a functional block diagram illustrating a fixing device control circuit of the image forming apparatus according to the first embodiment, FIG. 2 is a diagram illustrating a configuration example of a zero-cross signal generation circuit, and FIG. It is a schematic block diagram of the latching relay which is an abnormality memory | storage part of FIG. The fixing device control circuit shown in FIG. 1 includes a zero cross signal generation circuit 11 as power detection means, a power supply signal generation circuit (hardware configuration) 12 as first power supply signal generation means, and a second power supply signal generation. A power supply signal generation unit (software configuration) 13 as a means, a CPU 13a as a first control unit, a switching circuit 14 as a first switching means, an AND circuit 14a, an OR circuit 14b, and a power supply circuit as a power supply means 15, invalidation circuit 16 as invalidation means, transistor 16a, abnormality storage unit 17 as abnormality storage means, fixing heating part temperature detection circuit 18 as temperature detection means, high temperature detection circuit 19 as part of abnormality detection means A thermostat opening / closing circuit 20 as a part of the abnormality detection means, a nonvolatile storage unit 21 as a nonvolatile storage means, Landing device 22, fixing heating unit (heater) 22a as fixing heating means, temperature detection sensor (thermistor) 22b as part of temperature detection means, commercial power supply (AC power supply) 23, buffer circuit 24, inverter circuit 25, and Another CPU circuit 26 is provided as a second control unit.

  The zero-cross signal generation circuit 11 is a circuit that detects whether an AC signal crosses 0V, and is used when the AC signal is turned ON / OFF by an electronic circuit. By turning the switch ON / OFF near zero of the AC voltage, inrush current and transient voltage are suppressed, noise during switching is reduced, and radio interference is suppressed. For example, the zero-cross signal generation circuit 11 shown in FIG. 2 uses a photocoupler 11a composed of a phototransistor 11b and a photodiode 11c. When the AC voltage of the commercial power supply 11d increases, a current flows through the resistor 11e to the photodiode 11c. When the phototransistor 11b is turned on, a current flows through the resistor 11f. In the first embodiment, the zero cross signal generation circuit 11 is used. However, it is not always necessary to use the zero cross signal, and it is possible to detect the presence or absence of power generation from the power source. It may be a circuit.

  Further, when the AC voltage of the commercial power supply 11d decreases, the current of the photodiode 11c decreases, and the current passing through the resistor 11f is cut off by turning off the phototransistor 11b. As described above, the output waveform of the current flowing through the resistor 11f is a waveform surrounded by a two-dot chain line in FIG. 2, and the output waveform inverted by the inverter 11g is a zero cross signal generated by the one-dot chain line in FIG. The output waveform of the circuit 11 is obtained.

  The power supply signal generation circuit 12 is a circuit that generates a power supply signal with a hardware configuration that does not have a program. When the detected temperature of the fixing heating unit 22a is equal to or lower than a set temperature, a signal is output and the set temperature is exceeded. In this case, the signal output is stopped, and the power supply signal is generated based on the temperature detection signal and the signal of the zero cross signal generation circuit 11. For example, when the main power supply is turned on or the energy saving mode is canceled, the DC power supply rises, and when the detected temperature of the fixing heating unit 22a is equal to or lower than the set temperature and a zero cross signal is generated, a power supply signal is generated. As described above, before the fixing control operation by the CPU 13a, which will be described later, becomes possible, it is possible to supply power to the fixing heating unit 22a. This power supply signal is input to the AND circuit 14 a of the switching circuit 14.

  The power supply signal generator 13 that the CPU 13a performs using software includes a CPU 13a, a ROM that stores a program (not shown), a RAM that performs the operation of the program, a timer that serves as timer means described later, the temperature of the fixing heating unit 22a, and the like. It includes an A / D converter to detect, an interrupt control circuit that receives a zero-cross signal, an I / O port that performs input / output control of the image forming apparatus, and the like. The output port of the CPU 13a is in a high impedance state until DC power is supplied when the main power is turned on or the energy saving mode is canceled and the initial setting is performed. Therefore, the input to the AND circuit 14a and the inverter circuit 25 is “ The power supply signal of the power supply signal generation circuit 12 having a hardware configuration is output to the open collector buffer circuit 24 via the OR circuit 14b.

  The switching circuit 14 is a circuit that switches between a power supply signal generated by a power supply signal generation circuit 12 having a hardware configuration and a power supply signal generation unit 13 that the CPU 13a performs using software. The power supply signal from the power supply signal generation circuit 12 having a hardware configuration can inhibit the output of the power supply signal when the CPU 13a outputs “Low” as the input of the AND circuit 14a. In this state, the CPU 13 a can output a “Low” power supply signal to the inverter circuit 25, and can output a power supply signal from the OR circuit 14 b to the open collector buffer circuit 24.

  Here, the power supply circuit 15 is configured by a phototriac, and the power supply to the fixing heating unit 22a by the commercial power supply (AC power supply) 23 is ON / OFF controlled by the output of the open collector buffer circuit 24.

  The invalidation circuit 16 includes a transistor 16a. When an abnormal signal is input through any of the resistors R1 to R4, the transistor 16a is turned on, and the output of the open collector buffer circuit 24 is “Low”. Thus, the power supply is prohibited by invalidating the power supply signal.

  The abnormality storage unit 17 is a storage unit that is different from the nonvolatile storage unit 21. In the first embodiment, a latching relay as shown in FIG. 3 is adopted. As shown in FIG. 3, when the CPU 13a of the power supply signal generation unit 13 passes a current through the first coil 17a, the iron core 17c of the electromagnet is magnetized and the iron piece 17d is attracted to the iron core 17c (moves to the position of the broken line). The movable contact 17e is closed. In this state, even if the energization of the first coil 17a is stopped, the iron piece 17d is kept adsorbed on the iron core 17c by the residual magnetic flux due to the semi-hard magnetic material.

  Subsequently, when the CPU 13a of the power supply signal generator 13 passes a current through the second coil 17b wound in the opposite direction to the first coil 17a, the residual magnetic flux of the semi-hard magnetic material is reduced and the attractive force is reduced. As a result, the force for attracting the iron piece 17d is weakened, and the force of the return spring 17f is overcome, whereby the iron piece 17d is returned to the position of the solid line, and the movable contact 17e is opened to be in a resting state. For example, when the CPU 13a detects an abnormality in the fixing device 22, the movable contact 17e is closed by energizing the first coil 17a, and the state is maintained even when the main power is turned off in this state. Since this state is maintained even when the main power supply is turned on again, the power supply signal from the power supply signal generation circuit 12 and the power supply signal generation unit 13 is invalidated by the invalidation circuit 16 that receives this retention signal. can do.

  Further, when a release signal is input by a special operation from an operation unit (not shown), the CPU 13a can release the abnormality of the fixing device 22 by energizing the second coil 17b.

  The fixing heating unit temperature detection circuit 18 is a circuit that detects the temperature of the fixing heating unit 22a by a temperature detection sensor 22b provided at a predetermined location of the fixing heating unit 22a.

  The high temperature detection circuit 19 is a circuit that outputs a signal when the temperature of the fixing heating unit 22a exceeds a preset temperature. This detected temperature is naturally set to a temperature higher than the temperature at which power supply is stopped. When the high temperature detection signal is input to the power supply signal generation unit 13 controlled by the CPU 13a, the CPU 13a stores the high temperature detection signal in the nonvolatile storage unit 21 and also stores it in the abnormality storage unit 17. The holding signal is continuously output to the invalidation circuit 16.

  The thermostat opening / closing circuit 20 is a circuit that is provided in the fixing heating unit 22a and is constituted by a thermostat using a bimetal system. When the fixing roller in the fixing device 22 reaches a melting temperature, the thermostat opening / closing circuit 20 is provided in the thermostat opening / closing circuit 20. The switch part is opened. The thermostat opening / closing circuit 20 employs a thermostat of a type that, once opened, maintains an open state even if the temperature drops. The output of the thermostat opening / closing circuit 10 is input to a power supply signal generation unit 13 including an invalidation circuit 16 and a CPU 13a. When the switch section in the thermostat switching circuit 20 is opened, the transistor 16a of the invalidation circuit 16 is turned on to invalidate the power supply signal. Then, the CPU 13 a stores the thermostat release information in the nonvolatile storage unit 21 and holds the abnormal state in the abnormal storage unit 17.

  The nonvolatile storage unit 21 is a storage unit that backs up a RAM with a battery, an EEPROM, or the like, and can be directly read and written by the CPU 13a. The nonvolatile storage unit 21 stores abnormality information of the fixing device, adjustment information of the fixing device, program control information, and the like.

  The fixing device 22 fixes the toner image on the recording paper by heating and pressurizing the toner image formed on the recording paper with a fixing roller. The fixing roller in the fixing device 22 is provided with a heater that constitutes the fixing heating unit 22a, and a thermistor 22b whose resistance value decreases as the temperature rises is provided in the vicinity thereof so that the temperature can be measured. Yes.

  The other CPU circuit 26 includes a plurality of CPUs, and here, the occurrence of an abnormality in the fixing device 22 can be double monitored together with the CPU 13a.

  FIG. 4 is a more specific configuration diagram of the circuit configuration of the fixing device control circuit of FIG. 1, and FIG. 5 is a timing chart showing signal waveform examples of each part of FIG. 4, the same functional blocks as those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted.

  The fixing heating unit temperature detection circuit 18 includes an open collector comparator 18a, a thermistor 22b connected in series to the resistor R5, and a divided voltage input to the negative terminal side of the comparator 18a, and to the positive terminal side of the comparator 18a. Is supplied with a divided voltage of the resistors R6 and R7. Further, when the temperature of the fixing heating unit 22a is lower than the set temperature, the comparator 18a outputs a temperature detection signal to the latch circuit 12a of the power supply signal generation circuit 12, but the temperature of the fixing heating unit 22a increases, When the temperature reaches a preset temperature, the temperature detection signal output is stopped. The values of the resistor R5, the resistor R6, the resistor R7, and the thermistor 22b are selected so that this operation is possible. The temperature at which the temperature detection signal output is stopped is controlled by the CPU 13a, and the resistor R5, the resistor R6, the resistor R7, and the thermistor 22b are selected so that the temperature is lower than the temperature at which the power supply is stopped.

  The divided voltage of the fixing heating unit temperature detection circuit 18 is input to an A / D converter that detects the temperature of the fixing heating unit 22a in the CPU 13a of the power supply signal generation unit 13. The CPU 13a detects the input voltage of the A / D converter and generates a power supply signal.

  The power supply signal generation circuit 12 includes a latch circuit 12a, a reset circuit 12b, and an AND circuit 12c. The latch circuit 12 a inputs the output from the comparator 18 a of the fixing heating part temperature detection circuit 18 to the clock terminal, and latches at the rising edge of the zero cross signal input from the zero cross signal generation circuit 11. Therefore, the output of the latch circuit 12a is output in synchronization with the zero cross signal. The reset circuit 12b is a circuit that initializes the CPU 13a in hardware when the power is turned on, and is configured to be input to the reset terminal of the latch circuit 12a via the AND circuit 12c.

  Furthermore, the high temperature detection circuit 19 includes a comparator 19a, a resistor R8, and a resistor R9. The divided voltage of the thermistor 22b connected in series to the resistor R5 of the fixing heating unit temperature detection circuit 18 is input to the + terminal side of the comparator 19a, and the resistor R8 and the resistor R9 are connected to the − terminal side of the comparator 19a. The divided voltage is input. For this reason, when the temperature of the fixing heating unit 22a exceeds a preset temperature, the high temperature detection circuit 19 outputs a detection signal notifying that the temperature is abnormal to the invalidation circuit 16 and the power supply signal generation unit 13 by the CPU 13a. To do. The temperature detection resistors R8 and R9 of the high temperature detection circuit 19 are selected in advance as resistance values that are equal to or higher than the temperature at which the comparator 19a stops outputting the power supply signal and the CPU 13a detects the temperature at which the power supply is stopped. Other configurations are the same as those in FIG.

  Moreover, as shown in FIG. 5, the waveform diagram of each part of FIG. 4 is an alternating current waveform generated by the commercial power supply 23 using a sine wave. The zero cross signal output from the zero cross signal generation circuit 11 is a signal for detecting that the AC signal of the commercial power supply 23 crosses 0V. The output from the comparator 18 a of the fixing heating part temperature detection circuit 18 is input to the clock terminal of the latch circuit 12 a of the power supply signal generation circuit 12 and is latched at the rising edge of the zero cross signal from the zero cross signal generation circuit 11. Yes.

  6A to 6D are flowcharts for explaining the control operation of the fixing device. First, in FIG. 6A, when the main power is turned on or the power saving mode is canceled and the DC power is started, the CPU 13a performs the following operation.

  That is, the CPU 13a performs initial settings when the power is turned on, such as CPU, peripheral device initial settings, memory clear, memory initial settings, OS activation, communication confirmation with peripheral CPUs, and peripheral device initial settings (step S100). .

  Next, the CPU 13a checks whether or not there is a service man call (hereinafter, also referred to as SC) code that detects an abnormality related to the fixing device in the nonvolatile storage unit 21 (step S101). In addition to the SC code in which the abnormality is detected, the non-volatile storage unit 21 also stores information such as thermistor disconnection, fixing reload, and continuous heater lighting.

  If the CPU 13a confirms that any SC code is stored (YES in step S101), the CPU 13a moves to FIG. 6-2 and sends a signal for setting the abnormality storage unit 17 (latching relay in FIG. 3) to the port. And the abnormality storage unit 17 stores the fixing device abnormality (step S102).

  Subsequently, the CPU 13a outputs a signal for invalidating the power supply signal from the power supply signal generation circuit 12 to the AND circuit 14a of the switching circuit 14 (step S103).

  Further, the CPU 13a also outputs a signal for invalidating the power supply signal to the invalidation circuit 16 (step S104).

  And CPU13a outputs the signal which opens the power supply relay (not shown) which opens and closes the power supply circuit 15 (step S105), and the flowchart of FIG. 6-2 is complete | finished. With this operation, when the SC code is not released, power supply to the fixing heating unit 22a is prohibited even when the power is turned on again.

  If the CPU 13a confirms that no SC code is stored in the nonvolatile storage unit 21 in step S101 in FIG. 6A (NO in step S101), a plurality of CPUs are installed in the image forming apparatus. Whether or not there is an SC code output from another CPU circuit 26 that double monitors the occurrence of an abnormality in the fixing device 22 is checked (step S106).

  When the CPU 13a confirms that there is an SC code output from another CPU circuit 26 (YES in step S106), the CPU 13a stores the SC code in the nonvolatile storage unit 21 (step S107), and then the above FIG. Steps S102 to S105 are performed.

  In step S106, when the CPU 13a confirms that there is no SC code output from the other CPU circuit 26, the CPU 13a confirms whether there is an open signal from the thermostat switching circuit 20 through the input port (step S108). When there is an open signal from the thermostat opening / closing circuit 20, after the SC code for opening the thermostat is stored in the non-volatile storage unit 21 (step S109), the processing from step S102 to step S105 in FIG. Is called.

  In step S108, when the CPU 13a confirms that there is no open signal from the thermostat switching circuit 20, the CPU 13a confirms whether there is an output of a high temperature detection signal from the high temperature detection circuit 19 (step S110). When there is an output of the high temperature detection signal, the high temperature SC code is stored in the nonvolatile storage unit 21 (step S111), and then the processing of steps S102 to S105 in FIG. 6-2 described above is performed.

  Further, in step S110, when the CPU 13a confirms that there is no output of the high temperature detection signal from the high temperature detection circuit 19, in order to confirm whether or not the thermistor 22b is disconnected, the resistance value of the thermistor 22b is supplied with power supplied. The port voltage of the A / D converter of the CPU 13a is confirmed for a certain period as to whether or not changes (step S112). When there is no change in the port voltage of the A / D converter, it is assumed that the thermistor 22b is disconnected, and after the thermistor disconnection SC code is stored in the nonvolatile storage unit 21 (step S113), the above-described FIG. Steps S102 to S105 are performed.

  In step S112, if the thermistor 22b is not disconnected (NO in step S112), the process proceeds to step S120 in FIG. 6-3. That is, the CPU 13a outputs a switching signal for invalidating the power supply signal from the power supply signal generation circuit 12 to the AND circuit 14a of the switching circuit 14 in order to perform power control of the fixing device 22 itself (step S120). Thereby, the power control of the stationary device 22 is switched from the power supply signal generation circuit 12 to the power supply signal generation unit 13 by the CPU 13a.

  Subsequently, the CPU 13a checks the port voltage of the A / D converter and checks whether or not the temperature of the fixing heating unit 22a is equal to or lower than a set value (step S121). When the temperature of the fixing heating unit 22a is equal to or lower than the set value, the CPU 13a outputs a power supply signal from the port to the inverter circuit 25 (step S122).

  Subsequently, the CPU 13a checks whether or not the temperature of the fixing heating unit 22a is equal to or higher than a set value (step S123). When the temperature of the fixing heating unit 22a is equal to or higher than the set value, the CPU 13a outputs a power supply OFF signal for stopping power supply from the port to the inverter circuit 25 (step S124).

  Thereafter, the operation returns to (C) of FIG. 6A, and the operations after step S106 for confirming whether there is an SC code output from another CPU circuit 26 are repeated.

  By performing the operation described above, the temperature of the fixing heating unit 22a of the fixing device 22 can be controlled within a certain temperature range.

  The operation of outputting the power supply signal from the port of the CPU 13a to the inverter circuit 25 (step S122) is performed in the zero cross signal interrupt routine from the zero cross signal generation circuit 11.

  Next, in the flowchart of FIG. 6-4, the power supply signal generation circuit 12 supplies power until the temperature of the fixing heating unit 22a of the fixing device 22 rises to a preset temperature, and the temperature of the fixing heating unit 22a. When the temperature rises to a preset temperature, the operation of switching the power supply to the power supply signal generator 13 by the CPU 13a will be described.

  That is, when the thermistor 22b is not disconnected in step S112 of the flowchart of FIG. 6A, the process proceeds to step S130 of FIG. 6-4. Here, the CPU 13a determines whether or not the temperature of the fixing heating unit 22a of the fixing device 22 has reached or exceeded a set value. When the temperature of the fixing heating unit 22a becomes equal to or higher than the set value, the CPU 13a switches a switching signal for invalidating the power supply signal of the power supply signal generation circuit 12 in order to perform power control of the fixing device 22 itself. To the AND circuit 14a (step S131). Thereby, the power control of the stationary device 22 is switched from the power supply signal generation circuit 12 to the power supply signal generation unit 13 by the CPU 13a.

  Subsequently, the CPU 13a confirms the port voltage of the A / D converter, and confirms whether or not the temperature of the fixing heating unit 22a is equal to or lower than a set value (step S132). When the temperature of the fixing heating unit 22a is equal to or lower than the set value, the CPU 13a outputs a power supply signal from the port to the inverter circuit 25 (step S133).

  Subsequently, the CPU 13a checks whether or not the temperature of the fixing heating unit 22a is equal to or higher than a set value (step S134). When the temperature of the fixing heating unit 22a is equal to or higher than the set value, the CPU 13a outputs a power supply OFF signal for stopping power supply from the port to the inverter circuit 25 (step S135).

  The subsequent operation returns to (C) of FIG. 6-1 as in FIG. 6-3, and the operations after step S106 for confirming whether there is an SC code output from another CPU circuit 26 are repeated. It is. In step S130 of FIG. 6-4, if the temperature of the fixing heating unit 22a is not equal to or higher than the set value, the process returns to (C) of FIG. .

  As described above, according to the first embodiment, before the CPU 13a starts up, the power supply signal generation circuit 12 having a hardware configuration keeps the fixing heating unit 22a of the fixing device 22 up to a preset temperature. A power supply signal is supplied to the power supply circuit 15 to raise the fixing heating unit 22a to a preset temperature. After the CPU 13a starts up, the switching circuit 14 is used to switch from the power supply signal generation circuit 12 to the power supply signal generation unit 13 by a program, so that it is possible to quickly supply power to the fixing heating unit 22a. The productivity of the forming apparatus can be improved.

  According to the first embodiment, when the power supply signal is supplied to the power supply circuit 15 by the power supply signal generation circuit 12 before the CPU 13a starts up, the abnormality storage unit 17 stores the abnormal state of the fixing device 22. If the high temperature detection circuit 19 or the thermostat opening / closing circuit 20 detects a temperature abnormality of the fixing device, the invalidation circuit 16 invalidates the power supply signal of the power supply signal generation circuit 12, and thus the fixing device 22. Can be prevented from being heated, and the safety of the fixing device can be improved.

  In particular, according to the first embodiment, after the CPU 13a is started up, the power supply signal generator 13 can be switched to a program, and the fixing device 22 can be monitored by the CPU 13a or another CPU circuit 26. When an abnormality occurs in the fixing device, the abnormality occurrence is stored and held in the nonvolatile storage unit 21 and the abnormality storage unit 17. Therefore, after the main power is turned off and the power is turned on again, the power supply signal generated by the power supply signal generation circuit 12 can be immediately invalidated by the abnormality storage unit 17 even before the CPU 13a starts up. I can do it. Thereby, unnecessary power supply to the fixing device 22 can be reliably prevented.

(Second Embodiment)
FIG. 7 is a functional block diagram illustrating a fixing device control circuit of the image forming apparatus according to the second embodiment. The feature of the second embodiment is that the disabling circuit 16 in FIG. 1 of the first embodiment is arranged between the power supply signal generation circuit 12 and the switching circuit 14, thereby providing a power supply signal. Only the power supply signal generated by the generation circuit 12 is invalidated, and the power supply signal generated by the power supply signal generation unit 13 is input to the power supply circuit 15 via the switching circuit 14. Since the configuration other than that is the same as that in FIG.

  As described above, according to the second embodiment, before the CPU 13a starts up, the power supply signal generation circuit 12 having a hardware configuration supplies power until the fixing heating unit 22a of the fixing device 22 rises to a preset temperature. The supply signal is supplied to the power supply circuit 15, and the fixing heating unit 22a is raised to a preset temperature. After the CPU 13a is started, the switching circuit 14 is used to switch from the power supply signal generation circuit 12 to the power supply signal generation unit 13 by a program, so that the power supply to the fixing heating unit 22a is quickly performed, so that image formation is performed. The productivity of the apparatus can be improved.

  Further, according to the second embodiment, when the power supply signal generation circuit 12 supplies a power supply signal to the power supply circuit 15 before the CPU 13a starts up, the abnormality storage unit 17 stores the abnormal state of the fixing device 22. If the high temperature detection circuit 19 or the thermostat opening / closing circuit 20 detects a temperature abnormality of the fixing device, the invalidation circuit 16 invalidates the power supply signal of the power supply signal generation circuit 12, and thus the fixing device 22. Can be prevented from being heated more than necessary, and the safety of the fixing device can be improved.

  Further, according to the second embodiment, after the CPU 13a is started, the fixing device 22 can be safely controlled without using the invalidation circuit 16 by switching to the power supply signal generator 13 by the program. . If an abnormality occurs in the fixing device during that time, the CPU 13a stores the abnormality occurrence in the nonvolatile storage unit 21 and the abnormality storage unit 17 and holds it. Therefore, after the main power is turned off and the power is turned on again, the power supply signal generated by the power supply signal generation circuit 12 can be immediately invalidated by the abnormality storage unit 17 even before the CPU 13a starts up. I can do it. Thereby, unnecessary power supply to the fixing device 22 can be reliably prevented.

(Third embodiment)
FIG. 8 is a functional block diagram illustrating a fixing device control circuit of the image forming apparatus according to the third embodiment. As shown in FIG. 8, the third embodiment is characterized by a system controller 27 as a second control unit that controls the entire image forming apparatus, which is a control unit different from the CPU 13a, and the operation of the system controller 27. In addition to the temperature detection sensor (thermistor) 22b for detecting the temperature of the fixing heating unit 22a of the fixing device 22, a thermistor 29 for detecting the temperature of the fixing heating unit 22a is provided. There is in point. The rest of the configuration is the same as that in FIG.

  As described above, according to the third embodiment, the system controller 27 that monitors the fixing device 22 in parallel with the CPU 13 a double monitors the occurrence of an abnormality in the fixing device 22 based on the temperature detected by the unique thermistor 29. As a result, even if one monitoring system goes down, the other system can detect an abnormality in the fixing device 22 and prevent the occurrence of an abnormal state. In addition to the effect of the embodiment, the fixing device can be controlled more safely.

(Fourth embodiment)
FIG. 9 is a functional block diagram showing a fixing device control circuit of the image forming apparatus according to the fourth embodiment, and FIG. 10 is a timing chart showing examples of signal waveforms of respective parts in FIG. FIGS. 13-3, 13-5, and 13-7 are flowcharts for explaining the operation according to the fourth embodiment. A feature of the fourth embodiment is that a phase control signal is generated by a hardware configuration in place of the power supply signal generation circuit 12 of the fixing device control circuit of FIG. 1 or FIG. 4 according to the first embodiment. The phase control signal generation circuit 30 is provided.

  In the phase control signal generation circuit 30, when the transistor 30a is turned on by a signal from the zero cross signal generation circuit 11, the power stored in the capacitor C1 is discharged through the resistor R11 and the transistor 30a. When the signal from the zero cross signal generation circuit 11 is turned OFF, the capacitor C1 is charged by the resistor R10 and discharged again by the next zero cross signal.

  The charge / discharge voltage from the phase control signal generation circuit 30 is input to the negative terminal side of the open collector comparator 2 a constituting the fixing heating unit temperature detection circuit 18. Further, a voltage divided by a resistor R5 connected in series with a thermistor 22b that detects the temperature of the fixing heating unit 22a is input to the + terminal side of the comparator 18a. As described above, the fixing heating portion temperature detection circuit 18 includes the resistor R5 and the comparator 18a connected in series with the thermistor 22b. The resistance value of the thermistor 22b increases when the temperature of the fixing heating unit 22a is low (the voltage level of the + terminal of the comparator input in FIG. 10 also increases). Therefore, the phase control signal width output by the comparator 18a is Narrow (see comparator output in FIG. 10). However, as the temperature of the fixing heating unit 22a rises, the resistance value of the thermistor 22b decreases (the voltage level of the + terminal of the comparator input in FIG. 10 also decreases), so the phase control signal width output from the comparator 18a gradually increases. (Refer to the comparator output in FIG. 10).

  The power supply signal output from the phase control signal generation circuit 30 through the fixing heating unit temperature detection circuit 18 is input to the AND circuit 14 a of the switching circuit 14. Therefore, when the DC power source is turned on by turning on the main power source or canceling the energy saving mode, when the detected temperature of the fixing heating unit 22a is equal to or lower than the set value and the zero cross signal is generated, the phase-controlled power supply signal may be generated. it can. For this reason, the fixing device control circuit according to the fourth embodiment can quickly supply power to the fixing heating unit 22a before the fixing control operation by the CPU 13a becomes possible, thereby improving the productivity of the image forming apparatus. be able to.

  The waveform diagram of each part of FIG. 9 shown in FIG. 10 shows the AC waveform of the commercial power supply 23 as a sine wave, the zero cross signal for detecting that the AC signal of the commercial power supply 23 crosses 0 V, and the fixing heating unit temperature detection circuit 18. A voltage input to the-terminal of the comparator 18a, a voltage input to the + terminal, an output (phase control period signal) of the comparator 18a as a comparison result, and a power supply signal waveform supplied to the heater are shown. Has been. As shown in FIG. 10, the phase control period signal, which is a comparator output, has an ON time (On-duty) according to the difference between the voltage input to the negative terminal of the comparator 18a and the voltage input to the positive terminal. Change. In other words, since a large current easily flows to the heater instantaneously when the temperature of the fixing heating unit 22a is low, the phase control period signal as a comparator output is narrowed when the temperature of the fixing heating unit 22a is low, and the fixing is performed. When the temperature of the heating unit 22a rises, the width is automatically adjusted to gradually increase. As shown in FIG. 10, this power supply signal is output by cutting off the AC waveform of the commercial power supply during the ON time of the comparator output (phase control period signal).

  Returning to FIG. 9 again, the output port of the CPU 13a becomes high impedance until the DC power supply rises and is initially set by turning on the main power supply or canceling the energy saving mode. Therefore, the AND circuit 14a of the switching circuit 14 Then, the input to the inverter circuit 25 becomes high, and the power supply signal from the phase control signal generation circuit 30 by the hardware configuration is output to the open collector buffer circuit 24 via the OR circuit 14b.

  The switching circuit 14 is a circuit that switches between power supply signals generated by the phase control signal generation circuit 30 having a hardware configuration and the power supply signal generation unit 13 by the CPU 13a, and the power supply generated by the phase control signal generation circuit 30. As for the signal, the output of the power supply signal generated by the phase control signal generation circuit 30 can be prohibited by setting the input of the AND circuit 14a to (Low) the output from the CPU 13a. In this state, when the CPU 13a outputs the power supply signal (Low) generated by the power supply signal generator 13 to the inverter circuit 25, the power supply signal is output from the OR circuit 14b to the buffer circuit 24 of the open collector.

  The power supply signal generation unit 13 includes a CPU 13a, a ROM that stores a program (not shown), a RAM that operates the program, a timer, an A / D converter that detects the temperature of the fixing heating unit 22a, and an interrupt that receives a zero-cross signal. A control circuit, an I / O port for performing input / output control of the image forming apparatus and the like are provided. Other configurations are the same as those in FIGS. 1, 4, 7, and 8, and the description of the configurations is omitted.

  Next, operations according to the fourth embodiment will be described with reference to FIGS. 13-1, 13-3, 13-5, and 13-7. First, in step S101 of FIG. 6A, when the SC code is stored in the nonvolatile storage unit 21 (YES in step S101), or an abnormal state in which the SC code is stored in the nonvolatile storage unit 21 occurs. In the case (steps S107, 109, 111, 113), the CPU 13a sends a signal to the storage unit 17 (refer to the latching relay in FIG. 3) to store a fixing device abnormality from the port as shown in FIG. Output (step S140).

  Subsequently, a signal for invalidating the power supply signal of the phase control signal generation circuit 30 is output to the AND circuit 14a of the switching circuit 14 (step S141), and a signal for invalidating the power supply signal is supplied to the invalidation circuit 16. In step S142, a signal for opening a power supply relay (not shown) for opening and closing the power supply circuit is output (step S143), and the process ends.

  Even when the SC code is not canceled by the special input from the operation unit, the power supply to the fixing heating unit 22a can be prohibited by performing this operation even if the power of the image forming apparatus is turned on again. it can.

  Further, in step S101 in FIG. 6A, no SC code is stored in the nonvolatile storage unit 21, no SC code is output from another CPU (step S106), and there is no open signal from the thermostat switching circuit. When there is no output of a high temperature detection signal (step S110) and the thermistor is not disconnected (step S112), that is, when there is no abnormality in the fixing device, as shown in FIG. In addition, since the CPU 13a performs fixing control itself, the switching circuit 14 is switched from the phase control signal generation circuit 30 to the power supply signal generation unit 13 by the CPU 13a (step S160).

  Then, the CPU 13a confirms the port voltage of the A / D converter, and confirms whether or not the temperature of the fixing heating unit 22a is equal to or lower than the set value (step S161). When the temperature of the fixing heating unit 22a is equal to or lower than the set value, the CPU 13a outputs a power supply signal to the inverter circuit 25 through the port (step S162).

  Further, the CPU 13a checks whether or not the temperature of the fixing heating unit 22a is equal to or higher than a set value (step S163). When the temperature of the fixing heating unit 22a is equal to or higher than the set value, the CPU 13a outputs a signal for stopping power supply from the port to the inverter circuit 25 (step S164). By this operation, the temperature of the fixing heating unit 22a can be controlled so as to be within a certain temperature range. The subsequent processing returns to FIG. 16A and the processing in step S106 and subsequent steps is performed.

  The operation in which the CPU 13a outputs the power supply signal to the inverter circuit 25 through the port is performed in the zero cross signal interrupt routine from the zero cross signal generation circuit 11.

  Further, in the operation according to the fourth embodiment, when NO is obtained in step S112 in FIG. 6A, that is, when there is no abnormality in the fixing device, as shown in FIG. 13-5. Using the timer of the CPU 13a, for example, the time (N) during which the inrush current to the heater is reduced is counted (step S180). When a certain time (N) elapses, the inrush current to the heater is reduced and it is not necessary to perform phase control. Therefore, the CPU 13a sends a signal for invalidating the power supply signal from the phase control signal generation circuit 30 to the switching circuit 14. Output (step S181).

  Subsequent steps S182 to 185 are the same as steps S161 to 164 described above, and control is performed so that the temperature of the fixing heating unit 22a falls within a certain temperature range, and the process returns to FIG. Processing is performed.

  Furthermore, in the operation according to the fourth embodiment, when NO is obtained in step S112 in FIG. 6A, that is, when no abnormality occurs in the fixing device, as shown in FIG. 13-7. Then, it is determined whether or not the temperature of the fixing heating unit 22a is equal to or higher than the set value (step S200). If the temperature is equal to or higher than the set value, the inrush current to the heater is reduced and phase control need not be performed. The CPU 13a outputs a signal for invalidating the power supply signal from the phase control signal generation circuit 30 to the switching circuit 14 (step S201).

  Subsequent steps S202 to 205 are the same as steps S161 to 164 described above, and control is performed so that the temperature of the fixing heating unit 22a falls within a certain temperature range, and the process returns to FIG. Processing is performed.

  As described above, according to the fourth embodiment, after the power is turned on and before the CPU 13a starts up, the phase control signal generation circuit 30 is used to quickly supply power to the fixing heating unit 22a, thereby enabling the image forming apparatus. Productivity can be improved. In addition, the fixing heating unit 22a before supplying power has a risk of inrush current to the heater due to low temperature, but by generating a power supply signal whose phase is controlled by the phase control signal generation circuit 30, Safety can be improved. Further, after the time (N) during which the inrush current to the heater is reduced or the fixing heating unit 22a reaches the set temperature, the phase control signal generation circuit 30 supplies the power supply signal generation unit 13 of the CPU 13a. Since the power supply signal is switched, an inrush current to the heater is prevented, and it is possible to prevent the occurrence of flickering of lighting, compliance with harmonic regulations, or adverse effects on other electronic devices due to the voltage drop of the commercial power supply.

(Fifth embodiment)
FIG. 11 is a functional block diagram showing a fixing device control circuit of an image forming apparatus according to the fifth embodiment. FIGS. 13-2, 3-4, and 13-6 are the same as those in the fifth embodiment. It is a flowchart explaining this operation. The feature of the fifth embodiment is that before the CPU 13a starts up, the power supply signal generated by the phase control signal generation circuit 30 as the first power supply signal generation means is used to supply power to the fixing heating unit 22a. When the temperature of the fixing heating unit 22a rises to some extent, the power supply signal is generated by the power supply signal generation circuit 32 serving as the third power supply signal generation means. After the CPU 13a has started up, the second power supply means is provided. The power supply signal is generated by the power supply signal generation unit 13 and the fixing device is controlled. Other configurations are the same as those in FIG. 9, and the same functional blocks are denoted by the same reference numerals, and the description of the configurations is omitted.

  As shown in FIG. 11, in the fifth embodiment, a switching circuit 31 that switches between power supply signals generated by the phase control signal generation circuit 30 and the power supply signal generation circuit 32 is newly provided. A voltage divided by a resistor R5 connected in series with a thermistor 22b for detecting the temperature of the fixing heating unit 22a is input to the + terminal side of the comparator 18a of the fixing heating unit temperature detection circuit 18, and a phase is input to the − terminal side. An output signal from the control signal generation circuit 30 is input.

  Then, the divided voltage by the resistor R5 connected in series with the thermistor 22b of the fixing heating part temperature detection circuit 18 is more than the divided voltage of the resistor R13 connected in series with the resistor R12 of the power supply signal generating circuit 32. Becomes low (when a high temperature is detected), the comparator 32d outputs a power supply signal to the AND circuit 32f. The output of the AND circuit 32f is input to the latch circuit 32a. This signal is latched at the rising edge of the zero cross signal, and the output (power supply signal) of the latch circuit 32 a is input to the OR circuit 31 a of the switching circuit 31.

  The output of the comparator 32d is input to an open collector inverter circuit 31b, and the power supply signal from the phase control signal generation circuit 30 is invalidated by the output of the inverter circuit 31b. As described above, when the fixing heating unit 22 a rises to a preset temperature, the power supply signal from the phase control signal generation circuit 30 is automatically switched to the power supply signal of the power supply signal generation circuit 32. The switching circuit 31 is a circuit that switches the power supply signal of the phase control signal generation circuit 30 to the power supply signal of the power supply signal generation circuit 32.

  Further, the temperature of the fixing heating unit 22a is increased, the resistance value of the thermistor 22b is decreased, and the divided voltage of the resistor 15 connected in series with the resistor R14 input to the + terminal of the comparator 32e becomes the fixing heating. When it becomes higher than the divided voltage of the part temperature detection circuit 10, the output of the comparator 32e is inverted. The inverted power supply stop signal is input to the AND circuit 32f. The output of the AND circuit 32f is input to the latch circuit 32a. The power supply stop signal is latched at the rising edge of the zero cross signal, and the output of the latch circuit 32a is input to the OR circuit 31a of the switching circuit 31. As a result, when the temperature of the fixing heating unit 22a further rises, the power supply of the power supply signal generation circuit 32 is stopped.

  The power supply is stopped, the temperature of the fixing heating unit decreases, the resistance value of the thermistor increases, and the divided voltage of the resistor 15 connected in series with the resistor R14 is the divided voltage of the fixing heating unit temperature detection circuit 10. When it becomes lower, the output of the comparator 32e is inverted again and input to the AND circuit 32f, and input from the AND circuit 32f to the latch circuit 32a. This power supply signal is latched at the rising edge of the zero-cross signal, and the latch circuit 32a The output is input to the OR circuit 31a of the switching circuit 31. By such an operation, the temperature of the fixing heating unit 22a is controlled within a certain range.

  The divided voltage of the fixing heating unit temperature detection circuit 18 is also connected to the A / D converter input of the CPU 13a, and the CPU 13a detects the A / D converter input voltage and generates a power supply signal. Yes.

  When the CPU 13a detects a preset temperature by the input terminal of the A / D converter, the reset circuit 32c outputs a reset signal for resetting the latch circuit 32a to the AND circuit 32b, and the power supply signal generation circuit 32 supplies power. Stop.

  Further, after the CPU 13a is started up, a signal for prohibiting the power supply signal from the switching circuit 31 is output to the AND circuit 14a of the switching circuit 14, and the signal is switched to the power supply signal from the power supply signal generating unit 13. The temperature of the fixing heating unit 22a is detected by the input terminal of the A / D converter, and a power supply signal is output to the inverter circuit 25. Other configurations and operations are the same as those in FIGS. 1, 4, 7, 8, and 9, and therefore, a duplicate description is omitted.

  Next, operations according to the fifth embodiment will be described with reference to FIGS. 13-2, 3-4, and 13-6. First, in step S101 of FIG. 6A, when the SC code is stored in the nonvolatile storage unit 21 (YES in step S101), or an abnormal state in which the SC code is stored in the nonvolatile storage unit 21 occurs. If it is (steps S107, 109, 111, 113), as shown in FIG. 13-2, the CPU 13a sends a signal for storing an abnormality in the fixing device to the abnormality storage unit 17 (see the latching relay in FIG. 3) from the port. Output (step S150).

  Subsequently, a signal for invalidating the power supply signal of the phase control signal generation circuit 30 is output to the AND circuit 14a of the switching circuit 14 (step S151), and a signal for invalidating the power supply signal of the power supply signal generation circuit 32. Is output to the power supply signal generation circuit 32 (step S152), a signal for invalidating the power supply signal is output to the invalidation circuit 16 (step S153), and power (not shown) for opening and closing the power supply circuit is output. A signal for opening the supply relay is output (step S154), and the process ends.

  If NO in step S112 of FIG. 6A, that is, if no abnormality has occurred in the fixing device, as shown in FIG. 13-4, the temperature of the fixing heating unit 22a is equal to or higher than a set value. If the temperature is equal to or higher than the set value, the inrush current to the heater is reduced and there is no need to perform phase control. Therefore, the CPU 13a switches from the phase control signal generation circuit 30 or the power supply signal generation circuit 32 to the power supply signal generation unit 13 side by the switching circuit 14 (step S171).

  Subsequent steps S172 to 175 are the same as steps S161 to 164 described above. After controlling the temperature of the fixing heating unit 22a to be within a certain temperature range, the process returns to FIG. Is performed.

  Furthermore, in the operation according to the fifth embodiment, if NO is obtained in step S112 in FIG. 6A, that is, if no abnormality has occurred in the fixing device, as shown in FIG. 13-6. Using the timer of the CPU 13a, for example, the time (N) during which the inrush current to the heater is reduced is counted (step S190). When a certain time (N) elapses, the inrush current to the heater is reduced and it is not necessary to perform phase control. Therefore, the CPU 13a sends a signal for invalidating the power supply signal from the phase control signal generation circuit 30 to the switching circuit 14. Output (step S191). In addition, a signal for invalidating the power supply signal of the power supply signal generation circuit 32 is output to the power supply signal generation circuit 32 (step S192).

  Subsequent steps S193 to 196 are the same as steps S161 to 164 described above, and control is performed so that the temperature of the fixing heating unit 22a falls within a certain temperature range, and the process returns to FIG. Processing is performed.

  As described above, according to the fifth embodiment, after the power is turned on and before the CPU 13a starts up, first, power is supplied to the fixing heating unit 22a using the phase-controlled power supply signal of the phase control signal generation circuit 30. When the temperature of the fixing / heating unit becomes equal to or higher than a predetermined temperature, the power supply signal generation circuit 32 is switched. Further, when the temperature of the fixing / heating unit 22a becomes equal to or higher than a set value or when a predetermined time has elapsed, Then, the power supply control to the fixing heating unit 22a is performed. Thereby, the productivity of the image forming apparatus can be improved. In addition, the fixing heating unit 22a before supplying power may be inrush current to the heater because of its low temperature. However, by generating a power supply signal whose phase is controlled by the phase control signal generation circuit 30, safety can be obtained. Can be improved. Further, after the time (N) during which the inrush current to the heater is reduced or the fixing heating unit 22a reaches the set temperature, the CPU 13a receives the signal from the phase control signal generation circuit 30 or the power supply signal generation circuit 32. Since the power supply signal is switched to the power supply signal generator 13, the inrush current to the heater is surely prevented, the flickering of the lighting is prevented, the harmonic regulation is dealt with, or the voltage of the commercial power supply is reduced to other electronic devices. Adverse effects can be prevented.

(Sixth embodiment)
FIG. 12 is a functional block diagram illustrating a fixing device control circuit of the image forming apparatus according to the sixth embodiment. The feature of the sixth embodiment is that a circuit for invalidating the power supply signal generated by the phase control signal generation circuit 30 and the power supply signal generation circuit 32 by the CPU 13a, and for detecting the temperature of the fixing heating unit 22a. The thermistor 29 is provided separately from the thermistor 22b of the fixing heating unit temperature detection circuit 18, and the system controller 27 and the operation unit control circuit 28 are used to monitor the fixing measure abnormality separately from the CPU 13a.

  In the case of the sixth embodiment, the SC code output from the CPU (not shown) of the system controller 27 is stored in the non-volatile storage unit 21 and the abnormality storage unit 17, so that the fixing device 22 is installed in addition to the CPU 13 a. It can be monitored closely.

  In the following, a description will be given of the parts characteristic of the sixth embodiment. First, when the CPU 13a of the power supply signal generation unit 13 outputs a signal for resetting the latch circuit 32a from the reset circuit 32c to the AND circuit 32b of the power supply signal generation circuit 32, the output of the power supply signal from the latch circuit 32a is prohibited. Is done.

  When the CPU 13a outputs a signal for invalidating the signal from the phase control signal generation circuit 30 to the buffer circuit 31c of the open collector of the switching circuit 31, the power supply signal from the phase control signal generation circuit 30 is invalidated.

  On the other hand, the fixing heating unit 22a is provided with a thermistor 29 separately from the thermistor 22b. When the CPU of the system controller 27 detects an abnormality of the fixing device by the thermistor 29, the fixing heating unit 22a is connected to the power supply signal generator 13 via the bus. The detected abnormal SC code is output. Upon receiving the abnormal SC code from the system controller 27, the CPU 13a stores the abnormal SC code in the nonvolatile storage unit 21 and the abnormal storage unit 17.

  As described above, according to the sixth embodiment, in addition to the effects of the fifth embodiment, the system controller 27 different from the CPU 13a double monitors the fixing device using the specific thermistor 29. Therefore, even if one of the systems goes down, the fixing device can be properly controlled without being affected by this, and safety is improved.

11 Zero Cross Signal Generation Circuit 12 Power Supply Signal Generation Circuit 13 Power Supply Signal Generation Unit 13a CPU
DESCRIPTION OF SYMBOLS 14 Switching circuit 15 Power supply circuit 16 Invalidation circuit 17 Abnormal memory | storage part 18 Fixing heating temperature detection circuit 19 High temperature detection circuit 20 Thermostat opening / closing circuit 21 Non-volatile memory | storage part 22 Fixing apparatus 22a Fixing heating part 22b Thermistor (temperature detection sensor)
23 Commercial power supply 24 Buffer circuit 25 Inverter 26 Other CPU circuit 27 System controller 28 Operation control circuit 29 Thermistor (temperature detection sensor)
30 phase control signal generation circuit 31 switching circuit 32 power supply signal generation circuit

JP 2006-58824 A

Claims (10)

An image forming apparatus including a first control unit that controls a fixing device that fixes a toner image by pressurizing and heating a medium on which a toner image is formed.
Fixing heating means for heating the fixing device;
Temperature detecting means for detecting the temperature of the fixing heating means;
Power detection means for detecting power generation from the power source;
A first power supply signal that generates a signal for supplying power to the fixing heating unit based on a detection signal from the power detection unit and a detection signal from the temperature detection unit before the first control unit starts up. Generating means;
After the first control unit starts up, instead of the power supply signal from the first power supply signal generating means by a program, based on the detection signal by the power detection means and the detection signal by the temperature detection means. Second power supply signal generating means for generating a signal for supplying power to the fixing heating means,
Power supply means for supplying power to the fixing heating means by power supply signals from the first power supply signal generating means and the second power supply signal generating means;
An abnormality detection means for detecting an abnormality of the fixing device and outputting an abnormality detection signal;
An abnormality storage means for continuously outputting an abnormality detection signal until a release instruction is received from the first control section when an abnormality detection signal from the abnormality detection means is stored while the first control section is standing up; ,
Generated by at least the first power supply signal generating means out of the first power supply signal generating means and the second power supply signal generating means by the abnormality detection signal from the abnormality storage means or the abnormality detection means. Disabling means for disabling the power supply signal
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the abnormality storage unit is capable of storing an abnormality detection signal from the abnormality detection unit even when power is not supplied. When the first control unit detects an abnormality of the fixing device while the first control unit is standing up, the apparatus further includes a nonvolatile storage unit that stores an abnormality detection signal of the fixing device.
The image forming apparatus according to claim 1, wherein the first control unit stores the detected abnormality detection signal in the nonvolatile storage unit and also in the abnormality storage unit. A second control unit that monitors the occurrence of an abnormality of the fixing device in parallel with the first control unit;
The second control unit stores the detected abnormality detection signal in the non-volatile storage unit, and combines the one or more abnormality detection signals stored in the non-volatile storage unit into one to The image forming apparatus according to claim 3, wherein the image forming apparatus is stored in a storage unit.   The first switching means for switching the power supply signal output to the power supply means from the first power supply signal generation means to the second power supply signal generation means. 5. The image forming apparatus according to any one of 4 above.   The first control unit outputs a power supply signal to be output to the power supply unit from the first power supply signal generation unit to the first switching unit based on a detection result by the temperature detection unit. The image forming apparatus according to claim 5, wherein the image forming apparatus is switched to a second power supply signal generating unit. In addition to detecting power generation from the power source, the power detection means can detect the phase of the voltage change of the AC power source,
The first power supply signal generating means supplies power to the fixing heating means based on a detection signal from the power detection means and a detection signal from the temperature detection means before the first control unit starts up. Generate a signal to
The second power supply signal generation means is configured to replace the power supply signal from the first power supply signal generation means by a program after the first control unit has started up and the detection result by the power detection means. The image forming apparatus according to claim 1, wherein a signal for supplying power to the fixing heating unit is generated based on a detection signal from the temperature detection unit. A third power supply signal that generates a signal for supplying power to the fixing heating unit based on the detection signal from the power detection unit and the detection signal from the temperature detection unit before the first control unit starts up. Generating means;
A power supply signal generated by the first power supply signal generation means and a power supply signal generated by the third power supply signal generation means are switched and output based on a detection signal from the temperature detection means. Two switching means;
The first switching means switches between the power supply signal output from the second switching means and the power supply signal generated by the second power supply signal generating means, and supplies the power supply. The image forming apparatus according to claim 7, wherein the image forming apparatus outputs the image to a unit. The control unit includes timer means for measuring time,
When the controller measures the time preset by the timer means, the first switching means causes the first power supply signal generating means or the power supply signal of the third power supply signal generating means to The image forming apparatus according to claim 7, wherein the image forming apparatus is switched to a power supply signal of the second power supply signal generating unit. A fixing device control method executed by the image forming apparatus,
The image forming apparatus includes a first control unit that controls the fixing device, a fixing heating unit, a temperature detection unit, a power detection unit, a first power supply signal generation unit, a second power supply signal generation unit, and a power supply. Means, abnormality detection means, abnormality storage means, and invalidation means,
The fixing heating means heating the fixing device;
The temperature detecting means detecting the temperature of the fixing heating means;
The power detection means detecting power generation from a power source; and
The first power supply signal generating means supplies power to the fixing heating means based on the detection signal from the power detection means and the detection signal from the temperature detection means before the first control unit starts up. Generating a signal to be
The second power supply signal generation means is configured to detect a signal detected by the power detection means instead of the power supply signal from the first power supply signal generation means by a program after the first control unit is started. Generating a signal for supplying power to the fixing heating unit based on a detection signal from the temperature detection unit;
The power supply means supplies power to the fixing heating means by power supply signals from the first power supply signal generation means and the second power supply signal generation means;
The abnormality detecting means detecting an abnormality of the fixing device and outputting an abnormality detection signal;
When the abnormality storage means stores the abnormality detection signal from the abnormality detection means while the first control unit is starting up, the abnormality detection signal is output until a cancellation instruction is received from the first control unit next time. The process of continuing to take out,
The invalidating means uses at least the first power among the first power supply signal generating means and the second power supply signal generating means in accordance with an abnormality detection signal from the abnormality storage means or the abnormality detection means. Invalidating the power supply signal generated by the supply signal generating means;
Including a fixing device control method.

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