JP2012233981A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately protect a heating part against an abnormal power input while suppressing accuracy in determining protection of the heating part from decreasing.SOLUTION: An image forming apparatus includes: a voltage change rate detection part for detecting abnormality in a voltage change rate where the voltage change rate of an AC power supply at a zero-crossing timing is equal to or more than a permissible value (S125); a determination part for performing an error determination process of determining whether a detected pattern of the abnormality in the voltage change rate detected by the voltage change rate detection part matches a predetermined detecting condition (S152, S155); an energization inhibition part for determining that an error in the AC power supply is detected, if the determination part has determined that the detected pattern matches the predetermined detecting condition, and inhibiting energization from the AC power supply to the heating part (S165); and a detecting-condition change part for changing the predetermined detecting condition for image-forming in which the heating temperature of the heating part is controlled at a first temperature and for stand-by in which the heating temperature is controlled at a second temperature lower than the first temperature (S145, S150).

Description

  The present invention relates to an image forming apparatus, and more particularly to a technique for protecting a heating unit in a power supply abnormality in an image forming apparatus including a heating unit.

  Conventionally, for example, Patent Literature 1 discloses a technique for protecting a heating device (heating unit) when a power supply is abnormal. There, there is disclosed a technique for controlling a heating device that does not depend on the frequency when the zero-cross signal is disturbed by external noise or the like and the frequency detection of the power supply is abnormal.

  However, in the above-described prior art, although the operation of the heating device can be continued even when the zero-cross signal is disturbed and the frequency detection of the power supply is abnormal, the disclosure of dealing with the fluctuation of the power supply waveform as a power supply abnormality is disclosed. Not. For example, when a rectangular wave AC power supply by an uninterruptible power supply is input to the heating device instead of a sinusoidal AC power supply, the rise / fall at the zero cross point of the power supply waveform is steep, that is, the voltage change rate (dv / Dt) increases. Therefore, for example, when TRIAC is used for energization time control of the heater of the heating device, if the voltage change rate (dv / dt) at the zero crossing point exceeds the allowable characteristic value of the device, the TRIAC is set according to the zero crossing of the power source. There was a possibility that could not be turned off. In that case, the heater of the heating device is continuously energized, and there is a possibility that the heating device may malfunction.

  Therefore, the applicant of the present application has already developed an image forming apparatus that suppresses the malfunction of the heating apparatus due to the input of a rectangular wave (Japanese Patent Application No. 2009-269047). Specifically, energization to the heater (heating unit) is prohibited when the voltage change rate is detected a predetermined number of times within a certain period (error determination period) or more than the allowable value.

JP-A-2005-84546

  By the way, if the fixed period is too long, the temperature of the heating device may be increased too much. On the other hand, if the fixed period is too short, for example, it is erroneously detected that the zero cross signal is turned off when the power is turned off. However, there is a possibility that the abnormality is judged even though the power supply is not abnormal. That is, depending on the setting of the error determination period for determining the abnormal power input, there is a risk that abnormal heating may cause a malfunction of the heating unit, and energization of the heating unit may be prohibited even though it is not an abnormal power input. was there.

  The present invention provides a technique for suitably protecting a heating unit against an abnormal power supply input while suppressing deterioration in the accuracy of the protection determination of the heating unit against the abnormal power supply input.

  An image forming apparatus disclosed in this specification is fixed to a recording medium by a heating unit that is heated in response to energization of an AC power source, a temperature detection unit that detects a heating temperature by the heating unit, and the heating unit. An image forming unit that forms an image to be recorded on the recording medium, a zero-cross signal generation circuit that generates a zero-cross signal synchronized with the zero-cross timing of the AC power supply, and a voltage change rate of the AC power supply at the zero-cross timing is an allowable value. The voltage change rate detection unit for detecting the voltage change rate abnormality as described above, a switching unit for switching on / off of energization from the AC power source to the heating unit, and an energization ratio of the AC power source to the heating unit are adjusted. An error determination process is performed to determine whether or not the detection pattern of the voltage change rate abnormality detected by the energization ratio adjusting unit and the voltage change rate detecting unit matches a predetermined detection condition. When the determination unit and the determination unit determine that the detection pattern matches the predetermined detection condition, an energization prohibition for prohibiting energization from the AC power source to the heating unit is detected as an error of the AC power source is detected. And a detection condition changing unit that changes the predetermined detection condition during image formation when the heating temperature is controlled to a first temperature and during standby when the heating temperature is controlled to a second temperature lower than the first temperature; Is provided.

  Further, in the above configuration, the predetermined detection condition is that the voltage change rate abnormality is detected a predetermined number of times or more within an error determination period for performing the error determination process, and the detection condition changing unit includes The error determination period may be set shorter than the standby time during the image formation.

  Further, in the above configuration, the predetermined detection condition is that the voltage change rate abnormality is continuously detected a predetermined number of times within an error determination period for performing the error determination process, and the detection condition changing unit includes: The error determination period may be set shorter during the image formation than during the standby time, and the predetermined number of times may be set smaller than during the image formation during the image formation.

  Further, in the above-described configuration, the error determination period is determined when the heating unit is heated at an energization ratio of 100% by the energization ratio adjusting unit while the heating temperature is controlled during the control of the heating unit with respect to a target temperature. You may make it be less than the safety | security time required after reaching | attaining the target upper limit temperature which temperature can reach | attain until it reaches the heating upper limit temperature higher than the said target upper limit temperature.

  Further, in the above configuration, the energization prohibiting unit turns off the energization by the switching unit after turning off the control of the energization ratio adjusting unit, and the control of the energization ratio adjusting unit is turned off during the error determination period. The time required for the energization prohibition unit to turn off the energization by the switching unit after being added may be less than the security time.

  In the above configuration, the determination unit may execute the error determination process again after the energization prohibition unit turns off the control of the energization ratio adjustment unit and the energization by the switching unit. Good. At that time, the energization ratio adjustment unit adjusts the energization ratio so that the heating temperature when the error determination process is performed again is lower than the first temperature or the second temperature, The detection condition changing unit may make the error determination period when the error determination process is executed again longer than the error determination period during the image formation or during the standby.

  In the above configuration, the energization prohibiting unit controls the energization ratio adjusting unit when the determination unit determines that the detection pattern does not match the predetermined detection condition when the determination unit executes the error determination process again. Then, energization from the AC power source to the heating unit may be resumed in the standby state.

In the above configuration, the error determination period may be longer than the time from when the power is turned off until the power supply voltage becomes equal to or lower than a predetermined voltage.
Further, in the above configuration, the detection condition changing unit may change the error determination period according to the heating temperature when the voltage change rate abnormality is detected.

Further, in the above configuration, the predetermined detection condition is that the voltage change rate abnormality is continuously detected a predetermined number of times, and the detection condition changing unit sets the predetermined number of times to the standby during the image formation. You may make it set less.
At this time, the detection condition changing unit may set the predetermined number of times according to the heating temperature at the first detection of the voltage change rate abnormality during the image formation. The detection condition changing unit may reset the predetermined number of times and the number of detections of the voltage change rate abnormality when the continuous detection of the voltage change rate abnormality is interrupted.

  According to the image forming apparatus of the present invention, the predetermined detection condition for detecting the abnormal power input is the second temperature that is lower than the first temperature and the image forming time when the heating temperature of the heating unit is controlled to the first temperature. It is changed at the time of standby to control. That is, normally, during standby, the load is less than during image formation, and the heating temperature of the heating unit is lower than during image formation. For this reason, during standby, the time for lowering the residual voltage when the power is turned off is longer than when forming an image, and there is a large margin for the upper limit temperature of the heating unit compared with when forming an image. By reflecting such a difference in the predetermined detection condition of the abnormal power input, for example, by making the determination period of the abnormal power input shorter than the standby time at the time of image formation, the heating unit is protected against the abnormal power input. The heating unit can be suitably protected against an abnormal power input while suppressing deterioration in the accuracy of the determination.

1 is a side sectional view showing a schematic configuration of an image forming apparatus according to Embodiment 1 of the present invention. Block diagram schematically showing the configuration related to heating of the fixing device Block diagram showing a schematic configuration of a fixing drive circuit The flowchart which concerns on the electricity supply control process of the halogen heater in Embodiment 1. Time chart of each signal related to energization control processing of Embodiment 1 Time chart of each signal when the power is off The flowchart which concerns on the electricity supply control process of the halogen heater in Embodiment 2. Time chart of each signal related to energization control processing of embodiment 2

<Embodiment 1>
Next, Embodiment 1 of the present invention will be described with reference to FIGS.

1. Configuration of Laser Printer FIG. 1 is a diagram schematically illustrating a longitudinal section of a monochrome laser printer 1 (an example of an “image forming apparatus”) according to the first embodiment. Note that the image forming apparatus is not limited to a monochrome laser printer, and may be, for example, a color laser printer, a color LED printer, or a multifunction peripheral.

  In a monochromatic laser printer (hereinafter simply referred to as “printer”) 1, a toner image is formed by an image forming unit 6 on a tray 3 disposed in a lower part of a main body casing 2 or a sheet 5 supplied from the tray 4. Thereafter, the toner image is heated and fixed by a fixing device (an example of a “heating unit”) 7, and finally, the paper 5 is discharged to a paper discharge tray 8 positioned in the upper part of the main body casing 2. .

  The image forming unit 6 includes a scanner unit 10, a developing cartridge 13, a photosensitive drum 17, a charger 18, a transfer roller 19, and the like.

  The scanner unit 10 is disposed at an upper portion in the main casing 2 and includes a laser light emitting unit (not shown), a polygon mirror 11, a plurality of reflecting mirrors 12, a plurality of lenses (not shown), and the like. In the scanner unit 10, the laser beam emitted from the laser emitting unit is irradiated on the surface of the photosensitive drum 17 by high-speed scanning as indicated by a one-dot chain line through the polygon mirror 11, the reflecting mirror 12, and the lens.

  The developing cartridge 13 is detachably mounted and contains toner therein. Further, a developing roller 14 and a supply roller 15 are provided in the toner supply port of the developing cartridge 13 so as to face each other, and the developing roller 14 is arranged in a state facing the photosensitive drum 17. The toner in the developing cartridge 13 is supplied to the developing roller 14 by the rotation of the supply roller 15 and is carried on the developing roller 14.

  A charger 18 is disposed above the photosensitive drum 17 with a gap therebetween. A transfer roller 19 is disposed below the photosensitive drum 17 so as to face the photosensitive drum 17.

  While the surface of the photosensitive drum 17 is rotated, the surface of the photosensitive drum 17 is first uniformly charged to, for example, positive polarity by the charger 18. Next, an electrostatic latent image is formed on the photosensitive drum 17 by the laser light from the scanner unit 10, and is then carried on the developing roller 14 when the photosensitive drum 17 rotates in contact with the developing roller 14. A toner image is formed by supplying and carrying the toner on the electrostatic latent image on the surface of the photosensitive drum 17. Thereafter, the toner image is transferred to the paper 5 by the transfer bias applied to the transfer roller 19 while the paper 5 passes between the photosensitive drum 17 and the transfer roller 19.

  The fixing device 7 is disposed downstream of the image forming unit 6 in the paper conveyance direction, and includes a fixing roller 22, a pressure roller 23 that presses the fixing roller 22, and a halogen heater 33 (“heating”) that heats the fixing roller 22. Part) ”and the like. The halogen heater 33 is connected to the circuit board 25, and energization is controlled by a signal from the circuit board 25. Further, in the vicinity of the halogen heater 33, a temperature sensor 38 configured to detect a heating temperature by the halogen heater 33, for example, a thermistor is provided.

2. Next, with reference to FIG. 2 and FIG. 3, an electrical configuration related to heating of the halogen heater 33 of the fixing device 7 (hereinafter referred to as a heating device) will be described. FIG. 2 is a schematic block diagram of the heating device. FIG. 3 is a block diagram showing a schematic configuration of a fixing driving circuit of the heating device.

  The heating device 30 includes a low-voltage power supply circuit (AC-DC converter) 31, a fixing relay (an example of a “switching unit”) 32, a halogen heater 33, an ASIC (integrated circuit for a specific application) 34, a zero-cross detection circuit (“zero-cross signal generation”). Circuit ”) 40, a fixing drive circuit (an“ energization ratio adjustment unit ”) 50, and the like.

  As shown in FIG. 2, the AC power AC is supplied to the low-voltage power circuit 31 from before the fixing relay 32, and is supplied to the zero cross detection circuit 40 from between the fixing relay 32 and the halogen heater 33. That is, unless the fixing relay 32 is turned on, the AC power supply AC is not supplied to the zero cross detection circuit 40. The AC power supply AC may be supplied to the zero cross detection circuit 40 from the front of the fixing relay 32 without being limited thereto.

  The low-voltage power supply circuit 31 is a well-known AC-DC converter. For example, the low-voltage power circuit 31 converts an AC voltage of 100 V into a DC voltage of 24 V and 3.3 V, and supplies the DC voltage to each unit. The low-voltage power supply circuit 31 generates a reset signal Srs that invalidates the operation of the ASIC 34 when the DC voltage decreases to a predetermined voltage or less when the printer power is off (see FIG. 6). Note that the reset signal Srs is not limited to being generated by the low-voltage power supply circuit 31, and a circuit for generating the reset signal Srs may be provided separately.

  The zero-cross detection circuit 40 is a known zero-cross detection circuit including a full-wave rectification bridge circuit and a comparator, and generates a zero-cross signal Szc synchronized with the zero-cross timing of the AC power supply AC (see FIG. 5).

  The fixing drive circuit 50 adjusts the energization ratio (conduction angle) to the halogen heater 33 of the AC power supply AC. For example, as shown in FIG. 3, the fixing drive circuit 50 includes a triac 52, a phototriac coupler 53, a drive transistor 54, and the like. The phototriac coupler 53 is turned on by the drive transistor 54 in response to a trigger signal Stg that is generated with reference to the falling edge of the zero-cross signal Szc, for example. The triac 52 is turned on in response to the phototriac coupler 53 being turned on, and the AC power source AC is energized to the halogen heater 33 for a predetermined energization time. The predetermined energization time is, for example, from the rising timing of the trigger signal Stg to the zero cross timing of the AC power supply AC. That is, the temperature control of the fixing device 7 by the halogen heater 33 is performed by adjusting the time (energization ratio) from the falling timing of the zero cross signal Szc to the rising timing of the trigger signal Stg with respect to the cycle of the AC power supply AC.

  The fixing relay 32 is provided between the AC power supply AC and the halogen heater 33 and turns on / off the connection between the AC power supply AC and the halogen heater 33. Note that the switching unit is not limited to a relay, and may be configured by a semiconductor element, for example.

  The ASIC (an example of a “determination unit”, “voltage change rate detection unit”, “energization prohibition unit”, and “detection condition change unit”) 34 includes a timer 35, a counter 36, a memory 37, and the like, and energizes the halogen heater 33. Take control. The timer 35 measures the time required for energization control of the fixing device 7 and image formation. The counter 36 is used for counting the number of times related to the energization control of the fixing device 7, for example, the number of times of detecting the voltage change rate abnormality described later. The counter 36 includes a power supply error counter that counts the number of occurrences of power supply errors, which will be described later. The memory 37 includes a ROM and a RAM.

  The ASIC (voltage change rate detection unit) 34 detects whether or not the voltage change rate (hereinafter referred to as “dv / dt”) of the AC power supply AC with respect to the time at the zero cross timing is greater than or equal to an allowable value. The ASIC 34 detects a voltage change rate abnormality when dv / dt is equal to or greater than an allowable value. In the first embodiment, whether or not dv / dt is greater than or equal to an allowable value, that is, whether or not the voltage change rate is abnormal, is not directly detected by dv / dt, but by the pulse width of the zero-cross signal Szc (hereinafter “ This is performed based on whether or not “zero cross width” is equal to or less than a specified value. The specified value of the zero cross width is, for example, 0.1 milliseconds (ms). That is, in the first embodiment, when the zero cross width is 0.1 ms or less, a voltage change rate abnormality in which a waveform abnormality of the AC power supply AC is suspected is detected.

  The detection of whether or not the dv / dt of the AC power supply AC at the zero cross timing is greater than or equal to the allowable value is obtained by sampling the waveform of the AC power supply AC near the zero cross timing, for example. You may make it carry out directly from a waveform.

  In addition, the ASIC (determination unit) 34 determines whether or not it is detected that dv / dt is equal to or larger than the allowable value, that is, that the zero cross width is equal to or smaller than a specified value (0.1 ms) in accordance with a predetermined detection condition. Judgment processing is performed. That is, the ASIC (determination unit, energization prohibition unit) 34 performs an error determination process as to whether the detection pattern of the voltage change rate abnormality matches a predetermined detection condition. In the error determination process, when it is determined that dv / dt is equal to or greater than an allowable value (an example of a “voltage change rate abnormality detection pattern”) that matches a predetermined detection condition, an ASIC (energization prohibition unit) ) 34 detects that a power supply error that is a waveform abnormality of the AC power supply AC is detected, and controls the fixing relay 32 to prohibit the energization of the halogen heater 33 from the AC power supply AC.

  Here, the ASIC 34 also detects a power supply error when the zero cross signal Szc is not detected within a predetermined time. When the zero-cross signal Szc is not detected, the ASIC 34 recognizes that “a very steep waveform (with a very high voltage change rate) has been input” and determines that a power supply error has occurred.

Also, the ASIC (detection condition changing unit) 34 sets the predetermined detection condition at the time of printing in which the heating temperature Tk is controlled to the first temperature Tk1 (an example at the time of image formation) and the heating temperature Tk is lower than the first temperature. It is changed during standby (corresponding to standby) where the temperature Tk2 is controlled. In the first embodiment, the predetermined detection condition is, for example, that dv / dt is equal to or greater than an allowable value, and that a predetermined number of times (corresponding to a predetermined number of times) Nd within an error determination period Kd for determining a power supply AC AC error. It is continuously detected. At that time, the ASIC 34 sets the error determination period Kd to be shorter than the standby time in which the heating temperature Tk is controlled to the second temperature Tk2 lower than the first temperature Tk1 during printing in which the heating temperature Tk is controlled to the first temperature Tk1. .
Note that the predetermined detection condition is not limited to the above-described condition, and it may be detected that the dv / dt is equal to or greater than a permissible value for a predetermined number of times (corresponding to the predetermined number) within the error determination period Kd. In this case, it may not be continuously detected that dv / dt is equal to or greater than the allowable value.

  The ASIC 34 is connected to the image forming unit 6 and performs various processes related to image formation in addition to energization control of the halogen heater 33.

3. Next, the energization control of the halogen heater 33 according to the first embodiment will be described with reference to FIGS. FIG. 4 is a flowchart schematically showing a procedure of each process related to the energization control of the halogen heater 33, and FIG. 5 is a schematic time chart of signals related to the energization control of the halogen heater. In FIG. 5, a time chart at the time of printing is shown. FIG. 6 is a time chart showing signal waveforms when the printer power is off. In FIG. 6, “heater heating” ON corresponds to a period during which the energization control to the halogen heater 33 is turned on, that is, a period during which the trigger signal Stg is generated. This corresponds to a period in which the energization control to 33 is off, that is, a period in which the trigger signal Stg is not generated. The energization control process of the halogen heater 33 is performed by the ASIC 34 according to a predetermined program at a predetermined cycle when the power supply AC of the printer 1 is turned on, for example.

  When the power supply AC is turned on and the program starts, the ASIC 34 turns on the fixing relay 32 and controls the fixing driving circuit 50 to increase the heating temperature Tk by the halogen heater 33, and the halogen heater at a predetermined energization ratio. 33 is energized (step S110).

  Next, the zero-cross signal Szc from the zero-cross detection circuit 40 is read (step S120), the pulse width of the zero-cross signal Szc, that is, the zero-cross width is counted using the counter 36, and the zero-cross width is equal to or less than a specified value (0.1 ms). Is determined (step S125).

  When it is determined that the zero-cross width is equal to or less than the specified value (step S125: YES), the zero-cross signal detection count Nzc is updated, that is, the voltage change rate abnormality detection count Nzc is counted up (step S130). Next, the ASIC 34 determines whether or not the error determination period Kd and the specified number of times Nd have been set (step S135). When the error determination period Kd and the specified number of times Nd have been set (step S135: YES), the process proceeds to step S152. On the other hand, if the error determination period Kd and the specified number of times Nd have not been set (step S135: NO), it is determined whether or not the current state of the printer 1 is printing (step S140).

  If it is determined that the printer 1 is currently printing (step S140: YES), the error determination period Kd and the specified number of times Nd are set to the error determination period Kdp and the specified number of times Ndp at the time of printing (step S145).

  Here, as shown in FIG. 5, the error determination period Kdp corresponds to a period from time t1 in FIG. 5 to time t3 in FIG. 5 where the voltage change rate abnormality is first detected, and is less than the security time K1. Is done. The error determination period Kdp is not limited to this. For example, as described above, when the predetermined detection condition is to be detected a predetermined number of times or more within the error determination period Kd, the error determination period Kdp is a period from time t1 in FIG. 5 to time t4 in FIG. It may be said.

  Further, the safety time K1 can be reached when the halogen heater 33 is heated by the fixing drive circuit 50 at an energization ratio of 100% during the control of the halogen heater 33 with respect to the target temperature. A period required from reaching the target upper limit temperature Top (corresponding to time t2 in FIG. 5) to reaching the heating upper limit temperature Tkup higher than the target upper limit temperature Top (corresponding to time t5 in FIG. 5) ( (See dotted temperature curve in FIG. 5). That is, there is a relationship of Kdp <K1. Here, the heating upper limit temperature Tkup is the maximum heating temperature Tk that should not be exceeded in the energization control of the halogen heater 33. For example, the fixing roller 22 may be damaged by the heating of the halogen heater 33. Temperature.

  As described above, when the error determination period Kdp is less than the safety time K1, the energization prohibiting process for the halogen heater 33 is performed after the voltage change rate is detected a predetermined number of times or more. However, it can suppress suitably that heating temperature Tk reaches | attains heating upper limit temperature Tkup. That is, even if a power supply error occurs when the rectangular wave AC power supply AC is input, inconvenience occurs in the control of the energization ratio by the triac 52 of the fixing drive circuit 50, and the state of heating at the energization ratio of 100% is continued. Even when the heating temperature Tk reaches the heating upper limit temperature Tkup, the power supply error is detected and the energization prohibition process for the halogen heater 33 is performed, so the heating temperature Tk reaches the heating upper limit temperature Tkup. Can be suitably suppressed.

  Further, as shown in FIG. 6, the error determination period Kdp is from when the power is turned off (corresponding to time toff in FIG. 6) to when the power supply voltage 3.3V becomes equal to or lower than a predetermined voltage (corresponding to time trs in FIG. 6). This period is longer than the voltage holding period K2. In FIG. 6, the printer 1 is turned off at time toff, and the zero cross signal Szc is not detected. Further, at time trs, the power supply voltage 3.3V becomes equal to or lower than the predetermined voltage, the reset signal Srs becomes 0V, and the operation of the ASIC 34 is stopped. Here, the low voltage power supply circuit 31 generates a reset signal Srs of 0 V by detecting a predetermined voltage.

  In this way, by making the error determination period Kdp longer than the voltage holding period K2, when a power error is detected even when the zero-cross signal Szc is not detected by the error determination period Kdp, the error determination period Kdp is caused by a charging element or the like when the power is off. It is possible to prevent erroneous detection of a power supply error due to a residual power supply voltage. Specifically, the predetermined voltage is, for example, 2.8V. Further, the voltage holding period K2 is set to 0.5 seconds, for example, depending on the load capacity at the time of printing (K2p), and is set to 2 seconds, for example, based on the starting load (K2s) (steps S220 and 225 in FIG. 7). reference).

That is, in the first embodiment, the error determination period Kdp is
K2 <Kdp <K1
Is set to the value of Specifically, the error determination period Kdp corresponds to the period from time t1 to time t4 in FIG. 5, for example, 1 second, and the specified number Ndp is, for example, 120 times (power supply) as the number of times detected in the error determination period Kdp. (When the frequency is 60 Hz). When the predetermined detection condition is that the predetermined number of times is detected within the error determination period Kd, the predetermined number Ndp is set to, for example, 100 times as the number of times detected within the error determination period Kdp. Is done.

  On the other hand, if it is determined in step S140 that the printer 1 is not currently printing, that is, if it is determined that the printer 1 is currently in standby (standby) (step S140: NO), the error determination period Kd and The specified number of times Nd is set to the error determination period Kds during standby and the specified number of times Nds (step S150). Here, the error determination period Kds is set to, for example, 2.5 seconds, and the specified number of times Nds is set to, for example, 300 times (when the power supply frequency is 60 Hz). When the predetermined detection condition is that the predetermined number of times is detected within the error determination period Kd, the predetermined number Nds is set to, for example, 250 times as the number of detections within the error determination period Kdp. Is done.

  As described above, the error determination period Kds during standby is longer than the error determination period Kdp during printing, and the specified number Nds during standby is greater than the specified number Ndp during printing. That is, normally, during printing in which the heating temperature Tk is higher than that during standby, the error determination period Kd is shorter than that during standby. In this way, by making the error determination period Kd at the time of printing shorter than at the standby time, even if the control of the triac 52 becomes ineffective during the error determination period Kd due to the rectangular wave input, to the halogen heater 33. The amount of power supplied can be reduced. Therefore, it is possible to suitably secure the halogen heater 33. In addition, by making the error determination period Kds during standby longer than the error determination period Kdp during printing, it is possible to suppress degradation in the accuracy of the protection determination of the halogen heater 33 against rectangular wave input. In other words, the halogen heater 33 can be secured safely while suppressing the deterioration of the accuracy of the halogen heater 33 protection judgment with respect to the rectangular wave input.

  Next, in step S152, the ASIC 34 determines whether or not the error determination period Kd (Kdp or Kds) has elapsed from time t1. When it is determined that the error determination period Kd has elapsed (step S152: YES), the ASIC 34 detects the number of detections Nzc of the zero-cross signal Szc whose zero-cross width is equal to or less than the specified value, that is, the number of detections Nzc of the voltage change rate abnormality is the specified number of times. It is determined whether or not Nd (Ndp or Nds) has been reached (step S155).

  When the detection frequency Nzc of the voltage change rate abnormality has not reached the specified number Ndp or the specified number Nds (step S155: NO), the error determination period Kd and the specified number Ndp are set in order to newly start the power supply error detection. Reset (step S157) and return to step S120. That is, the number of detections Nzc does not reach the specified number of times Ndp or the specified number of times Nds despite the end of the error determination period Kd because the voltage change rate abnormality has not occurred continuously. Reset the data.

  On the other hand, if the detected number Nzc of the voltage change rate abnormality reaches the prescribed number Ndp or the prescribed number Nds (step S155: YES), the ASIC 34 determines that the fixing drive circuit 50 supplies the halogen heater 33 to the power supply error. The energization control is stopped (step S160). Specifically, the ASIC 34 stops the conduction angle control of the triac 52. In parallel with stopping the energization control to the halogen heater 33 by the fixing drive circuit 50, the fixing relay 32 is turned off to turn off the energization to the halogen heater 33 (corresponding to time t3 in FIG. 5: Step S165). ). Next, in order to newly detect a power supply error, the error determination period Kd and the specified number of times Ndp are reset (step S167).

  It should be noted that when the voltage change rate abnormality detection count Nzc reaches the specified count Ndp or the specified count Nds, it is not possible to simultaneously stop the energization control of the halogen heater 33 and turn off the fixing relay 32. I can't. As shown by the dotted line in FIG. 5, when the heating temperature Tk reaches the target upper limit temperature Topup, the energization control to the halogen heater 33 is stopped (see time t2 in FIG. 5), and the voltage change rate abnormality detection count Nzc is The fixing relay 32 may be turned off when the specified number of times Ndp or the specified number of times Nds is reached.

  Next, the ASIC 34 stops energization control to the halogen heater 33 and turns off the fixing relay 32, thereby determining whether or not an error (print error), for example, paper jam has occurred. (Step S170). This determination is usually made based on error detection information generated when an error occurs during the image forming process.

  When it is determined that an error accompanying the printer operation error has not occurred (step S170: NO), the fixing relay 32 is turned on and the energization control to the halogen heater 33 is resumed in order to re-determine the power supply error. (Step S175: corresponding to time t6 in FIG. 5), the halogen heater 33 is heated and the heating temperature Tk is detected (Step S180).

  When the ASIC 34 performs the error determination process again, that is, when the power error is redetermined, the energization ratio is set so that the heating temperature Tk is lower than the first temperature Tk1 or the second temperature Tk2. It is preferable that the error determination periods Kdp and Kds are longer than the initially set error determination periods Kdp and Kds, respectively. In this case, since the error determination condition (predetermined detection condition) is relaxed, the reliability of the error redetermination process can be improved.

  Next, the ASIC 34 determines whether or not the heating temperature Tk is within a specified temperature increase range (step S185). Here, the specified temperature rise range is, for example, from the target lower limit value at the time of printing shown in FIG. 5 to the target upper limit temperature Topup. If it is determined that the heating temperature Tk is within the specified temperature rise range (step S185: YES), the power supply error has been resolved or the power supply error has been erroneously determined due to noise or the like. Return. On the other hand, if it is determined that the heating temperature Tk is not within the specified temperature rise range (step S185: NO), the power supply error has not been eliminated, and the power supply error counter has been counted. The process is counted up and the process is temporarily terminated (step S190).

  Note that the processing relating to error redetermination in steps S170 to S185 may be omitted. That is, assuming that a power supply error has occurred, after the fixing relay 32 is turned off in step S165, the process may proceed to step S190.

  In addition, when the ASIC 34 does not determine that the voltage change rate abnormality is detected in accordance with the predetermined detection condition when the power supply error determination process is executed again (step S155: NO), the process from step S120 is performed via step S157. When the operation is resumed, the fixing drive circuit 50 is controlled so that energization from the AC power supply AC to the halogen heater 33 is performed under temperature control during standby, that is, under conduction angle control of the triac 52 during standby. You may be allowed to resume. In this case, when energization is resumed by re-determination, it is performed in a standby state, so that security at the time of resumption can be achieved.

  In addition, when the frequency of the AC power supply AC is constant and the specified number of times Nd is the number of consecutive occurrences of voltage change rate abnormality, the error determination period Kd and the specified number of times Nd are in a proportional relationship. For this reason, in steps S145 and S150, only the prescribed times Ndp and Nds may be set, and the processing in steps S152 and S157 may be omitted.

4). Effect of Embodiment 1 Heating in a predetermined period is performed during printing in which the heating temperature Tk of the halogen heater 33 is controlled to the first temperature Tk1 and in standby mode in which the heating temperature Tk is controlled to the second temperature Tk2 lower than the first temperature Tk1. The total amount of heat is greater during printing. Therefore, in the first embodiment, the zero-cross signal Szc whose error determination period Kd and zero-cross width are equal to or less than the specified values, which are detection conditions when detecting an abnormality (rectangular wave input) in the power supply waveform based on the pulse width of the zero-cross detection signal Szc. The predetermined number of times Nd that is the number of times of detection is changed between printing and standby. As a result, even if the triac 52 of the fixing drive circuit 50 becomes uncontrollable by the rectangular wave input, the error determination period Kd and the specified number of times Nd are appropriately changed according to the use state of the printer 1 to The heater 33 is suitably protected.

  Specifically, by making the error determination period Kdp during printing shorter than during standby (Kds), even if the control of the triac 52 becomes ineffective during the error determination period Kdp due to rectangular wave input, The amount of power supplied to the halogen heater 33 can be reduced. Therefore, it is possible to suitably secure the halogen heater 33. In addition, by making the error determination period Kds during standby longer than the error determination period Kdp during printing, it is possible to suppress degradation in the accuracy of the protection determination of the halogen heater 33 against rectangular wave input. In other words, the halogen heater 33 can be secured safely while suppressing the deterioration of the accuracy of the halogen heater 33 protection judgment with respect to the rectangular wave input.

  The error determination period Kd is a period longer than the time K2 from when the power is turned off until the power supply voltage becomes equal to or lower than a predetermined voltage. Therefore, it is possible to prevent erroneous detection of a power supply error due to a residual voltage of the power supply voltage caused by a charging element or the like when the power is off.

  In addition, since error redetermination is performed, it is possible to suppress erroneous determination of a power supply error due to noise on the AC power supply AC.

<Embodiment 2>
Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 7 is a flowchart schematically showing a procedure of each process related to energization control of the halogen heater in the second embodiment. FIG. 8 is a schematic time chart of signals relating to energization control of the halogen heater in the second embodiment. In FIG. 7, the same steps as those shown in FIG. 5 of the first embodiment are denoted by the same step numbers, and description thereof is omitted. FIG. 8 shows a time chart during printing.

  Only differences from the first embodiment will be described below. The second embodiment is different from the first embodiment in that the specified number of times Nd is calculated based on the heating temperature Tk when a power supply error is detected. The specified number Nd is a continuous number in which the voltage change rate abnormality is continuously detected a predetermined number of times, and the error determination period Kd is not used as an error determination condition.

That is, in step S135A of FIG. 7, it is determined whether or not the prescribed number Nd (Ndp or Nds) has been set. When the specified number of times Nd is not set (step S135A: NO), the ASIC 34 detects the current state when the zero-cross signal Szc whose zero-cross width is equal to or less than the specified value is first detected (corresponding to the time t1 in FIG. 8). The heating temperature Tk is read, and the specified number of times Ndp or Nds is calculated based on the heating temperature Tk (step S215).
The prescribed number of times Ndp is calculated, for example, as (Tkup−Tk) /0.5> Ndp. The specified number of times Nds is calculated as (Tkup−Tk) /0.3> Nds, for example.

  Next, when it is determined that the current state of the printer 1 is printing (step S140: YES), the voltage holding period K2p at the time of printing is defined by, for example, a load capacity (step S220). On the other hand, when it is determined that the current printer 1 is in the standby state (step S140: No), the standby voltage holding period K2s is defined by, for example, the startup load (step S225).

  Next, the ASIC 34 sets the specified times Ndp and Nds so as to satisfy the relationship of K2 <Kd based on the calculated specified times Ndp and Nds and the specified K2p and K2s (step S230). Next, when it is determined that the number of consecutive detections Nzc of the zero-cross signal Szc whose zero-cross width is equal to or less than the predetermined value, that is, the number of consecutive detections Nzc of abnormal voltage change rate has reached the specified number Nd (step S155: YES, FIG. 8). ), The energization control to the halogen heater 33 is stopped (step S160: corresponding to time t3 in FIG. 8).

  Next, the ASIC 34 determines whether or not the heating temperature Tk is within a specified temperature increase range (step S235). Here, the specified temperature rise range is, for example, from the target lower limit value during printing shown in FIG. 8 to the upper limit threshold value Tth. The upper limit threshold Tth, for example, a temperature lower than the heating upper limit temperature Tkup by a predetermined temperature (see FIG. 8). When it is determined that the heating temperature Tk is within the specified temperature rise range, that is, when it is determined that the heating temperature Tk is equal to or lower than the upper limit threshold Tth (step S235: YES), the processing returns to step S120. That is, the number of continuous detections of the voltage change rate abnormality reaches the specified number Nd (Ndp or Nds), but the heating temperature Tk is within the specified temperature rise range, so that the halogen heater is not turned off. The process related to the energization control is continued.

  For example, it is assumed that the power supply error is resolved at time t7 in FIG. 8 and a zero cross signal Szc having a normal zero cross width is detected. Then, the energization control to the halogen heater 33 is resumed in response to the detection of the normal zero cross signal Szc (corresponding to time t8 in FIG. 8). In this case, the energization to the halogen heater 33 is continued without turning off the fixing relay 32.

  On the other hand, when it is determined that the heating temperature Tk is not within the specified temperature increase range, that is, when the heating temperature Tk has increased to the upper limit threshold Tth (step S235: NO, see the dotted temperature curve in FIG. 8), the fixing relay 32 (Step S240: corresponding to time t5 in FIG. 8; see broken line). As a result, the heating temperature Tk decreases after time t5 as indicated by the broken line. Then, assuming that a power supply error has occurred, the count value of the power supply error counter is incremented, and the process is temporarily terminated (step S190).

  When the continuous detection of the voltage change rate abnormality is interrupted (step S125: NO), the ASIC 34 resets the predetermined continuous number Nd and the voltage change rate abnormality detection number Nzc (step S205). As a result, it is possible to remove the influence due to noise or the like generated during the continuous detection of the voltage change rate abnormality and accurately detect the voltage change rate abnormality continuously.

  In the case where the energization of the fixing relay 32 is turned off after the energization control to the halogen heater 33 is turned off as in the second embodiment, the error determination period Kdp is set as shown in FIG. The time (Kdp + Koff) obtained by adding the time (Koff) from time t3 when the energization control to the halogen heater 33 is stopped to time t5 when the energization of the fixing relay 32 is turned off is less than the safety time K1 (time t2 to t6). It is preferable to do. That is, it is preferable that Kdp + Koff <K1. In this case, although the energization control to the halogen heater 33 is turned off, that is, the energization to the halogen heater 33 by the triac 52 is controlled to be turned off, the triac 52 is turned off due to a power supply error. Even if this is not possible, the fixing device 7 can be suitably protected. As described above, when the predetermined detection condition is to be detected a predetermined number of times or more within the error determination period Kd, the error determination period Kdp is a period from time t1 to time t4 in FIG. Also good.

  Further, as described above, when the specified number of times Nd is a continuous number, the specified number of times Nd and the error determination period Kd are in a proportional relationship. Therefore, in the second embodiment, the error determination period Kd may be used instead of the specified number of times Nd. Good.

4). Effect of Embodiment 2 During printing, a specified number Ndp (predetermined number of consecutive times) is set according to the heating temperature Tk when the voltage change rate abnormality is first detected. Therefore, the power supply error detection can be suitably performed within the allowable range of the heating temperature Tk by reducing the specified number of times Ndp as the heating temperature Tk is higher, that is, by shortening the error determination period.

  Even when the number of detected voltage change rate abnormalities reaches the specified number Ndp and the energization control to the halogen heater 33 is stopped, if the heating temperature Tk is within the specified temperature rise range, the fixing relay 32 is turned on. Until the heating temperature Tk exceeds the specified temperature rise range without being turned off, the detection of the voltage change rate abnormality is continued. Therefore, even when the energization control to the halogen heater 33 is stopped, if the heating temperature Tk does not exceed the specified temperature rise range, the fixing relay 32 is not turned off, and the number of times the fixing relay 32 is turned off is reduced. can do. As a result, it is possible to reliably suppress the heating temperature Tk from reaching the heating upper limit temperature Tkup while suppressing the deterioration of the fixing relay 32.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.

  (1) Also in the first embodiment, the ASIC 34 (detection condition changing unit) calculates the error determination period Kd according to the heating temperature Tk when the voltage change rate abnormality is detected, and changes the setting of the error determination period Kd. You may do it. In this case, since the error determination period Kd is changed in real time in accordance with the heating temperature Tk when the voltage change rate abnormality is detected, the power source error determination process is performed accurately corresponding to the heating temperature Tk at that time. In addition, the halogen heater 33 can be accurately protected when a power supply error occurs.

DESCRIPTION OF SYMBOLS 1 ... Monochrome laser printer, 3 ... Paper, 6 ... Image formation part, 7 ... Fixing device, 32 ... Fixing relay, 33 ... Halogen heater, 34 ... ASIC, 38 ... Temperature sensor, 40 ... Zero cross detection circuit, 50 ... Fixing drive Circuit, 52 ... Triac

Claims (13)

A heating section that is heated in response to energization of an AC power source;
A temperature detection unit for detecting a heating temperature by the heating unit;
An image forming unit for forming an image fixed on the recording medium by the heating unit on the recording medium;
A zero-cross signal generation circuit that generates a zero-cross signal synchronized with the zero-cross timing of the AC power supply;
A voltage change rate detection unit for detecting a voltage change rate abnormality in which the voltage change rate of the AC power supply at the zero cross timing is equal to or greater than an allowable value;
A switching unit that switches on / off of energization from the AC power source to the heating unit;
An energization ratio adjusting unit for adjusting an energization ratio to the heating unit of the AC power source;
A determination unit that performs an error determination process as to whether a detection pattern of the voltage change rate abnormality by the voltage change rate detection unit matches a predetermined detection condition;
When the determination unit determines that the detection pattern matches the predetermined detection condition, an energization prohibiting unit that prohibits energization from the AC power source to the heating unit, as an error of the AC power source is detected,
A detection condition changing unit that changes the predetermined detection condition during image formation in which the heating temperature is controlled to a first temperature and standby time in which the heating temperature is controlled to a second temperature lower than the first temperature;
An image forming apparatus comprising: The image forming apparatus according to claim 1.
The predetermined detection condition is that the voltage change rate abnormality is detected a predetermined number of times or more within an error determination period for performing the error determination process,
The detection condition changing unit is an image forming apparatus in which the error determination period is set shorter during the image formation than during the standby. The image forming apparatus according to claim 1.
The predetermined detection condition is that the voltage change rate abnormality is continuously detected a predetermined number of times within an error determination period for performing the error determination process,
The detection condition changing unit
The image forming apparatus, wherein the error determination period is set shorter during the image formation than during the standby, and the predetermined number of times is set smaller than during the image formation during the image formation. The image forming apparatus according to claim 2 or 3,
In the error determination period, when the heating unit is heated by the energization ratio adjusting unit at an energization ratio of 100%, the heating temperature can be reached by the heating temperature during the control of the heating unit with respect to the target temperature. An image forming apparatus that is less than a security time required to reach a heating upper limit temperature higher than the target upper limit temperature after reaching the upper limit temperature. The image forming apparatus according to claim 4.
The energization prohibition unit is configured to turn off the energization by the switching unit after turning off the control of the energization ratio adjustment unit,
In the error determination period, the time required for the energization prohibition unit to turn off the energization by the switching unit after the control of the energization ratio adjustment unit is turned off is less than the security time. apparatus. The image forming apparatus according to claim 4.
The determination unit is an image forming apparatus that executes the error determination process again after the energization prohibition unit turns off the control of the energization ratio adjustment unit and the energization by the switching unit. The image forming apparatus according to claim 6.
The energization ratio adjustment unit adjusts the energization ratio so that the heating temperature when the error determination process is executed again is lower than the first temperature or the second temperature,
The detection condition changing unit is an image forming apparatus in which the error determination period when the error determination process is executed again is longer than the error determination period during the image formation or during the standby. The image forming apparatus according to claim 6 or 7, wherein:
The energization prohibiting unit controls the energization ratio adjusting unit when the determination unit determines that the detection pattern does not match the predetermined detection condition when the determination unit performs the error determination process again, and controls the AC power source. An image forming apparatus that resumes energization to the heating unit from the standby state. The image forming apparatus according to any one of claims 2 to 8,
The image forming apparatus, wherein the error determination period is longer than a time from when the power is turned off until the power supply voltage becomes a predetermined voltage or less. The image forming apparatus according to any one of claims 2 to 9,
The detection condition changing unit is an image forming apparatus that changes the error determination period according to the heating temperature when the voltage change rate abnormality is detected. The image forming apparatus according to claim 1.
The predetermined detection condition is that the voltage change rate abnormality is continuously detected a predetermined number of times,
The detection condition changing unit is configured to set the predetermined number of times less during the image formation than during the standby. The image forming apparatus according to claim 11.
The detection condition changing unit is configured to set the predetermined number of times according to the heating temperature at the first detection of the voltage change rate abnormality at the time of image formation. The image forming apparatus according to claim 11 or 12,
The detection condition changing unit is configured to reset the predetermined number of times and the number of detected voltage change rate anomalies when continuous detection of the voltage change rate anomaly is interrupted.

Images