JP2015022170A - Image heating device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image heating device that accurately detects the failure of the image heating device and the incorrect insertion of a fixing unit.SOLUTION: An engine controller preferentially supplies power to a heating element 3 during the first half of a two full-wave; preferentially supplies power to a heating element 20 during the second half of the two full-wave; and performs abnormality detection on the basis of the duty ratio of the maximum suppliable power Dmax1 calculated on the basis of a result of the detection by a current detection circuit when the power is preferentially supplied to the heating element 3, and the duty ratio of the maximum suppliable power Dmax2 calculated on the basis of a result of the detection by the current detection circuit when the power is preferentially supplied to the heating element 20.

Description

  The present invention relates to an image heating apparatus suitable for use as a fixing device mounted in an image forming apparatus such as an electrophotographic copying machine or an electrophotographic printer.

  As an image heating apparatus mounted on an image forming apparatus such as an electrophotographic copying machine or an electrophotographic printer, there is a configuration having a heating unit including two independently controllable heating elements that generate heat when electric power is supplied (patent) Reference 1). The image heating apparatus of Patent Document 1 calculates the required power corresponding to the temperature of the heating means at every control update timing that is visited every two full wave periods of the commercial AC power supply. In addition, during the control period (two full-wave periods) in which the calculated necessary power is supplied to the heating element, the heating element that supplies power preferentially is switched. Further, when supplying electric power to the heating means, in order not to supply more current than necessary, the current supplied to the heating means is always detected, and the supplied electric power is controlled below the maximum suppliable electric power. That is, when the required power calculated according to the temperature of the heating unit exceeds the maximum supplyable power, the power supplied to the heating element is limited to the maximum supplyable power.

JP 2011-95314 A

  Incidentally, even in the apparatus described in Patent Document 1, when a power supply element to a heating element such as a triac or a peripheral circuit that drives the power supply element fails, a failure of the image heating apparatus is detected quickly. It is hoped that. Further, it is desired to detect erroneous insertion promptly even when a fixing device for another image forming apparatus having a different fixing device configuration constituted by a single heating element is erroneously inserted. However, providing these sensors for detection increases the cost.

  The present invention has been made under such circumstances, and an object thereof is to accurately detect a failure of an image heating apparatus and an erroneous insertion of a fixing device.

  In order to solve the above-described problems, the present invention has the following configuration.

  (1) A heating unit having a first heating element and a second heating element that generate heat by power supplied from an AC power source, a current detection unit that detects a current flowing through the first heating element and the second heating element, Based on the result detected by the current detection means, a calculation means for calculating an upper limit power duty ratio that can be supplied to the heating means, and a power duty ratio equal to or lower than the upper limit power duty ratio calculated by the calculation means An image heating apparatus comprising: control means for controlling power supplied to the first heating element and the second heating element, wherein the control means includes a first half of a predetermined number of cycles of the AC waveform. In the second half of the predetermined number of cycles, power is supplied in preference to the second heating element, and power is supplied in priority to the first heating element. Sometimes said current detection The calculation based on the first upper limit power duty ratio calculated by the calculation means based on the result detected by the stage and the result detected by the current detection means when power is supplied in preference to the second heating element. An image heating apparatus, wherein abnormality detection is performed based on the second upper limit power duty ratio calculated by the means.

  (2) an image carrier, latent image means for forming an electrostatic latent image on the image carrier, developing means for developing the electrostatic latent image formed by the latent image means to form a toner image, The image forming apparatus includes: a transfer unit that transfers the toner image formed by the developing unit onto a recording sheet; and a fixing unit that fixes the recording sheet onto which the toner image is transferred. The fixing unit is described in (1). An image forming apparatus characterized by being an image heating apparatus.

  According to the present invention, it is possible to accurately detect a failure of the image heating apparatus and an erroneous insertion of the fixing device.

1 is a diagram illustrating a configuration of an image forming apparatus according to first and second embodiments. The figure which shows the drive circuit of the fixing control of Example 1,2. Flowchart illustrating fixing control according to the first exemplary embodiment. Table in which the power duty ratio of each heating element corresponding to the supply power duty ratio of Examples 1 and 2 is set The figure explaining the outline of the electric current which flows into the heat generating body by the fixing control of Example 1,2. Flowchart for explaining fixing control according to the second embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail by way of examples with reference to the drawings.

[Configuration of Image Forming Apparatus]
FIG. 1 is a schematic configuration diagram of an image forming apparatus using an electrophotographic process, and shows a case of a laser printer, for example. The laser printer main body 101 (hereinafter referred to as the main body 101) has a cassette 102 for storing the recording paper S, and includes a recording paper presence sensor 103 for detecting the presence or absence of the recording paper S in the cassette 102. The main body 101 includes a recording sheet size sensor 104 that detects the size of the recording sheet S of the cassette 102, a paper feed roller 105 that feeds the recording sheet S from the cassette 102, and the like, which are configured by a plurality of micro switches, for example. Further, the main body 101 includes a registration roller pair 106 that synchronously conveys the recording paper S downstream of the paper supply roller 105 in the conveyance direction of the recording paper S. Further, the main body 101 includes an image forming unit 108 that forms a toner image on the recording paper S based on the laser light from the laser scanner 107 downstream of the registration roller pair 106. Further, the main body 101 includes a fixing device 109 that thermally fixes a toner image formed on the recording paper S downstream of the image forming unit 108. Further, the main body 101 is disposed downstream of the fixing device 109, a paper discharge sensor 110 that detects the conveyance state of the paper discharge unit, a paper discharge roller 111 that discharges the recording paper S, and a stack that stacks the recording paper S that has been recorded. A tray 112 is provided. The conveyance reference of the recording paper S is set so as to be centered with respect to the width of the recording paper S, which is the length in the direction orthogonal to the conveyance direction of the recording paper S. Note that the conveyance reference of the recording paper S may be an edge reference.

  The laser scanner 107 includes a laser unit 113, a polygon motor 114, an imaging lens 115, a folding mirror 116, and the like. A laser unit 113 serving as a latent image unit emits a laser beam modulated based on an image signal (image signal VDO) transmitted from an external device 131 described later. The polygon motor 114 forms an electrostatic latent image on the photosensitive drum 117 by scanning the laser light emitted from the laser unit 113 on the photosensitive drum 117 which is an image carrier to be described later.

  The image forming unit 108 includes a photosensitive drum 117, a primary charging roller 119, a developing device 120, a transfer charging roller 121, a cleaner 122, and the like necessary for a known electrophotographic process. The fixing device 109 includes a fixing film 132, a pressure roller 133, a ceramic heater 134 provided in the fixing film 132, and a temperature detection element 135 which is a temperature detection means such as a thermistor for detecting the surface temperature of the ceramic heater 134. Prepare. The ceramic heater 134 is controlled to reach a predetermined temperature based on the result detected by the temperature detecting element 135. The main motor 123 applies a driving force to the paper feed roller 105 via a paper feed roller clutch 124 and to the registration roller pair 106 via a registration roller clutch 125. Further, the main motor 123 applies driving force to each unit of the image forming unit 108 including the photosensitive drum 117, the fixing device 109, and the paper discharge roller 111.

  The engine controller 126 controls the electrophotographic process by the laser scanner 107, the image forming unit 108, and the fixing device 109 and controls the conveyance of the recording paper S in the main body 101. The video controller 127 is connected to an external device 131 such as a personal computer via a general-purpose interface 130 (Centronics (registered trademark), RS232C, etc.). The video controller 127 expands the image information transmitted from the general-purpose interface 130 into bit data, and transmits the bit data to the engine controller 126 as the VDO signal 128. The cooling fan 129 releases the heat in the main body 101 to the outside.

[Fixer control circuit]
FIG. 2 shows a fixing control circuit of the fixing device 109 of this embodiment. The electric power of the commercial AC power source 1 (hereinafter referred to as AC power source 1) is a first heating element formed on a ceramic heater 134 which is a heating unit included in the fixing device 109 via the AC filter 2 and the relay 41. It is supplied to the heating element 3 and the heating element 20 as the second heating element. As a result, the heating element 3 and the heating element 20 generate heat. When supplying power to the heating element 3 and the heating element 20, the engine controller 126 connects the relay 41 (hereinafter referred to as “on”). The transistor 43 is a transistor for driving the relay 41, and the base terminal is connected to the RLD terminal of the engine controller 126 via the bias resistor 44. The engine controller 126 outputs a high level signal from the RLD terminal, turns on the transistor 43, and turns on the relay 41. On the other hand, the engine controller 126 outputs a low level signal from the RLD terminal to turn off the transistor 43 and disconnect the relay 41 (hereinafter referred to as “off”). The diode 42 is for suppressing the counter electromotive force generated in the relay 41. The relay 41 is supplied with a voltage VRLY larger than the signal level voltage Vref from a power supply of a system different from Vref.

  Supply of power to the heating element 3 is conducted (on) and shut off (off) in a bidirectional thyristor (hereinafter referred to as triac) 4 in accordance with a signal output from the ON1 terminal of the engine controller 126 (hereinafter referred to as ON1 signal). This is done by controlling Here, the resistors 5 and 6 are bias resistors for the triac 4 that is the first control element. The phototriac coupler 7 is an element for ensuring a creepage distance between the primary and secondary. The resistor 8 is a resistor for limiting the current of the phototriac coupler 7. The engine controller 126 turns on the transistor 9 by outputting a high level signal from the ON1 terminal via the resistor 10. When the transistor 9 is turned on, a current flows through the light emitting diode of the phototriac coupler 7, the phototriac coupler 7 is turned on, and the triac 4 is turned on.

  On the other hand, power is supplied to the heating element 20 by controlling on and off of the triac 13 as the second control element in accordance with a signal output from the ON2 terminal of the engine controller 126 (hereinafter referred to as ON2 signal). . Here, the resistor 14 and the resistor 15 are bias resistors for the triac 13. The phototriac coupler 16 is an element for ensuring a creepage distance between the primary and secondary. The resistor 17 is a resistor for limiting the current of the phototriac coupler 16. The engine controller 126 outputs a high level signal from the ON2 terminal via the resistor 19, thereby turning on the transistor 18. When the transistor 18 is turned on, a current flows through the light emitting diode of the phototriac coupler 16, the phototriac coupler 16 is turned on, and the triac 13 is turned on.

  The AC power supply 1 is input to the zero cross detection circuit 12 via the AC filter 2. The zero cross detection circuit 12 outputs, as a pulse signal, a ZEROX terminal of the engine controller 126 that the AC voltage of the AC power supply 1 is a voltage equal to or lower than a certain threshold value. Hereinafter, the pulse signal output from the zero cross detection circuit 12 is referred to as a zero cross signal (shown as a ZEROX signal). The engine controller 126 detects the edge of the zero cross signal output from the zero cross detection circuit 12 and turns the triac 4 or the triac 13 on or off.

  In the zero cross detection circuit 12, the neutral (hereinafter referred to as “Neutral”) side of the AC voltage is rectified by the rectifier 51. The voltage half-wave rectified by the rectifier 51 is input to the base terminal of the transistor 54 via the resistor 52 and the resistor 53. Accordingly, the transistor 54 is turned on when the neutral side potential is higher than the live (hereinafter referred to as “live”) side potential, and the transistor 54 is turned off when the neutral side potential becomes lower than the live side potential. The photocoupler 57 is an element for securing a creepage distance between the primary and secondary, and the resistor 55 and the resistor 56 are resistors for limiting the current flowing through the photocoupler 57. When the neutral-side potential becomes higher than the live-side potential, the transistor 54 is turned on, so that the light emitting diode in the photocoupler 57 is turned off and the phototransistor in the photocoupler 57 is turned off. Thus, the zero cross detection circuit 12 outputs a high level ZEROX signal. On the other hand, when the neutral side potential becomes lower than the live side potential, the transistor 54 is turned off, so that the light emitting diode in the photocoupler 57 emits light, and the phototransistor in the photocoupler 57 is turned on. As a result, the zero cross detection circuit 12 outputs a low level ZEROX signal. The zero cross signal is a pulse signal whose signal cycle is equal to the frequency cycle of the AC power supply 1, and the signal level changes according to the potential polarity of the AC power supply 1.

  The temperature detection element 135 is a temperature detection element that detects the temperature on the ceramic heater 134, and a partial pressure value with the resistor 22 is input to the TH terminal of the engine controller 126. The engine controller 126 controls the temperature of the ceramic heater 134 based on a value obtained by converting the voltage value input to the TH terminal into a temperature. The excessive temperature rise prevention element 137 is, for example, a temperature fuse or a thermo switch. If the ceramic heater 134 reaches a thermal runaway due to a failure of the fixing control circuit of the fixing device 109 and the overheat prevention element 137 reaches a predetermined temperature or more, the overheat prevention element 137 is opened and power to the ceramic heater 134 is opened. Supply is cut off.

  The current flowing through the heating element 3 and the heating element 20 is controlled by the triac 4 and the triac 13 and is detected by a current detection unit which is a current detection unit. The current detection unit includes a current transformer 25 (transformer), a bleeder resistor 70, and a current detection circuit 27, and is provided in a power supply path from the AC power supply 1 to the ceramic heater 134. The current flowing through the heating element 3 and the heating element 20 is converted into a voltage by the current transformer 25 and input to the current detection circuit 27 via the bleeder resistor 70. The current detection circuit 27 converts the voltage-converted current waveform into an effective value, and outputs it as an HCRRT signal to the A / D conversion port (HCRRT terminal) of the engine controller 126.

  The CURLIM terminal of the current detection circuit 27 is connected to the base terminal of the transistor 43. While the current detection circuit 27 detects a normal current value, a high level signal is output to turn on the transistor 43. Yes. On the other hand, the current detection circuit 27 outputs a low-level signal from the CURLIM terminal to the base terminal of the transistor 43, for example, when a current value larger than a predetermined threshold value is detected. Thereby, the transistor 43 is turned off, the relay 41 can be turned off directly from the current detection circuit 27, and the power supply to the ceramic heater 134 can be cut off. Thus, the current detection circuit 27 also functions as a safety circuit. Further, the diodes 47, 48, 49 and 50 are full-wave rectification bridge circuits, and the full-wave rectified voltage is input to the low-voltage power supply circuit unit 28.

The amount of heat given to the fixing device 109 is calculated for each zero cross period based on the ZEROX signal detected by the zero cross detection circuit 12 based on the target temperature of the ceramic heater 134 and the detected temperature of the temperature detection element 135. In the present embodiment, description will be given using PI control which is a kind of feedback system control. The calculation of the supplied power duty ratio D using the PI control is determined by the following equation (1).
Supply power duty ratio D = P control value + I control value (1)

In the present embodiment, the supply power duty ratio D is controlled by dividing a zero-cross half-wave corresponding to half of one cycle (also referred to as a half-wave) of the voltage waveform of the AC power supply 1 into 40% and in steps of 2.5%. . Note that the number of divisions of the zero-cross half-wave may be another predetermined number depending on the fixing specification. Further, the P control value of the equation (1) is a control value of proportional control, and is given by the following equation (2) in this embodiment.
P control value = Kp × ΔT (2)
Here, Kp is a proportional gain, and is set to an appropriate value according to the fixing specification in consideration of temperature overshoot and the like and temperature stability. ΔT is a difference between the target temperature and the detected temperature, and is calculated by subtracting the current detected temperature from the target temperature. The I control value in equation (1) is a control value for integral control, and corrects the integral value of ΔT over a certain period, that is, drift from the target value, and is given as an offset to the supply power value in P control. In this embodiment, a counter that integrates the magnitude relationship between the target temperature and the detected temperature is held in the engine controller 126. The engine controller 126 compares the magnitude relationship between the target temperature and the detected temperature every 100 ms, and increments or decrements the counter in each case of positive and negative. When the counter becomes 6 or more or −6 or less, the engine controller 126 increments or decrements the I parameter and resets the counter.

The engine controller 126 serving as calculation means calculates a power duty ratio supplied to the heating element 3 and the heating element 20. At this time, the engine controller 126 calculates the upper limit power duty ratio that can be supplied to the ceramic heater 134 based on the HCRRT signal input from the current detection circuit 27 when power is supplied to the ceramic heater 134. The engine controller 126 as control means controls the ceramic heater 134 to be supplied with power equal to or less than the calculated upper limit power duty ratio (hereinafter referred to as the maximum suppliable power duty ratio Dmax). When calculating the maximum suppliable power duty ratio Dmax, the following equation (3) is used using the current value Irms, the supplied power duty ratio D, and the current limit value Ilimit. The current value Irms is the value of the HCRRT signal output from the current detection circuit 27. The supplied power duty ratio D is the supplied power duty ratio that is currently turned on based on the detection result of the temperature detection element 135.
Dmax = (Ilimit / Irms) ² × (D−a) + b (3)
Here, a and b are certain coefficients corresponding to the resistance value ratio of the heating element 3 and the heating element 20. That is, the heating element 3 has coefficients a and b (referred to as a_3 and b_3) corresponding to the heating element 3, and the heating element 20 has coefficients a and b (referred to as a_20 and b_20) corresponding to the heating element 20. is there. When the resistance value ratios of the heating element 3 and the heating element 20 are the same, a_3 = a_20 and b_3 = b_20, and when the resistance value ratios are different, a_3 ≠ a_20 and b_3 ≠ b_20. It is assumed that the values of the coefficients a and b are stored in association with the heating element, for example, in a memory (not shown).

  The current limit value Ilimit sets an allowable current value that can be supplied to the ceramic heater 134 by subtracting the maximum current value supplied to the low-voltage power supply circuit unit 28 from the rated current of the connected AC power supply 1. As a result, the rated current of the AC power supply 1 can be used as effectively as possible when necessary. Further, when the supply power duty ratio D controlled based on the temperature detected by the temperature detection element 135 such as a thermistor exceeds the maximum supplyable power duty ratio Dmax, the maximum supplyable power duty ratio Dmax is prioritized. . Thus, the engine controller 126 controls the ceramic heater 134 with the maximum suppliable power duty ratio Dmax as an upper limit.

[Fixing control of this embodiment]
The fixing control by the engine controller 126 of this embodiment is shown in the flowchart of FIG. In the present embodiment, the resistance value ratio between the heat generating element 3 and the heat generating element 20 will be described as 1, but the resistance value ratio between the heat generating element 3 and the heat generating element 20 may be a different value. When the power is turned on, the engine controller 126 causes the apparatus to transition to the standby state in S1. In S2, the engine controller 126 determines whether or not a print command from the user has been received. Here, the print command from the user may be transmitted from the external device 131 or may be transmitted from an operation panel (not shown) included in the main body 101. If the engine controller 126 determines in S2 that it does not receive a print command, it repeats the process in S2. If the engine controller 126 determines in S2 that a print command has been received, it starts a printing operation in S3 and performs print control. In S4, the engine controller 126 outputs a high level signal from the RLD terminal, turns on the relay 41, and starts temperature control of the ceramic heater 134.

  In S5, the engine controller 126 starts PI control based on the temperature detected by the temperature detecting element 135. First, the engine controller 126 determines a target temperature for fixing processing from conditions such as the environment in which the main body 101 is placed, the history of previous printing, and the size of the recording paper S to be passed. Based on the detection result (TH signal) of the temperature detection element 135 so that the ceramic heater 134 reaches the predetermined target temperature, the engine controller 126 performs PI as described in Expression (1) and Expression (2). The supply power duty ratio D is calculated by a calculation formula. Then, the engine controller 126 controls the temperature of the ceramic heater 134 with the calculated supply power duty ratio D. The engine controller 126 has a control table shown in FIG. 4, for example, showing the calculated supply power duty ratio D and the current phase angle supplied to the heating element 3 and the heating element 20. The engine controller 126 controls the temperature of the ceramic heater 134 based on the control table of FIG.

  Here, FIG. 4 shows the phase angle α (°) of the heating element (simply referred to as priority heating element) at the time of the supply power duty ratio D and the phase of the auxiliary heating element (simply referred to as auxiliary heating element). Angle β (°) is shown. Furthermore, the power duty ratio (%) when the heating element 3 is a priority heating element, the power duty ratio (%) when the heating element 20 is a priority heating element, and the average power when power is supplied at the power duty ratio Is shown. When the phase angle is 0 °, power is supplied over the full wave (one cycle of the AC waveform) (shown as full wave supply), and when the phase angle is 180 °, no power is supplied. (Indicated as supply off). FIG. 4 will be described later. In the present embodiment, the update timing of the supplied power duty ratio D (also the PI value) is every two full waves of the AC waveform of the AC power supply 1 (that is, two cycles of the AC waveform). Note that the update timing (also the control update timing) of the supplied power duty ratio D may be every 2n full waves (n is a positive integer).

  In the present embodiment, the supply power duty ratio D alternates heating elements that supply power with priority in the first half full wave and the second half full wave. Specifically, power is supplied in preference to the heating element 3 in the first half of a predetermined number of cycles of the AC waveform, and power is supplied in priority to the heating element 20 in the second half of the predetermined number of cycles. As described above, in this embodiment, the predetermined number of cycles is two. That is, the first half 1 full wave (also the first half 1 cycle) uses the heating element 3 as a priority heating element, the heating body 20 serves as an auxiliary heating element, and the second half 1 full wave (also the second half 1 cycle) gives priority to the heating element 20. The heating element and the heating element 3 are used as auxiliary heating elements. In S6, the engine controller 126 preferentially supplies power to the heating element 3 in the first half of the full wave. The heating element 20 may be a priority heating element for the first half full wave, and the heating element 3 may be a priority heating element for the second half full wave. In S7, the engine controller 126 determines whether the supplied power duty ratio D calculated in S5 is from 0 to 20 or from 21 to 40. As described above, in this embodiment, the control method of the heating element 3 and the heating element 20 is changed depending on whether the supply power duty ratio D is 0 to 20 or 21 to 40.

  If the engine controller 126 determines in S7 that the calculated supply power duty ratio D is from 0 to 20, the process proceeds to S9. In S9, the engine controller 126 supplies the phase angle α (°) for supplying power to the heating element 3 and the power to the heating element 20 based on the calculated supply power duty ratio D and the control table of FIG. To obtain a phase angle β (°). Here, in this embodiment, when the supply power duty ratio D is 0 to 20, as shown in FIG. 4, the phase angle β (° for supplying power to the heating element 20 as the auxiliary heating element is shown. ) Is 180 °, and the power supply to the heating element 20 is stopped (shown as OFF). The engine controller 126 controls the triac 4 by outputting the ON1 signal, and controls the triac 13 not to be driven by setting the ON2 signal to a low level, for example. That is, only the heating element 3 is set to the phase control state (described as phase angle energization in FIG. 3). The phase angle α of the heating element 3 is set to a value shown in FIG. For example, when the supply power duty ratio D calculated by the engine controller 126 in S5 is 16, the heating element 3 as the priority heating element is controlled with a phase angle of 60.5 °. When the supplied power duty ratio D calculated by the engine controller 126 is 0, the phase angle α and the phase angle β are both OFF from FIG. 4, and the engine controller 126 turns off the triacs 4 and 13. That is, when the calculated supply power duty ratio D = 0, the heating elements 3 and 20 are not supplied with power. The engine controller 126 stores the current value detected when the heating element 3 is a priority heating element by the current detection circuit 27 in, for example, a memory (not shown).

  If the engine controller 126 determines in S7 that the calculated supply power duty ratio D is 21 to 40, the process proceeds to S8. In S8, the engine controller 126 supplies the phase angle α (°) for supplying power to the heating element 3 and the power to the heating element 20 based on the calculated supply power duty ratio D and the control table of FIG. To obtain a phase angle β (°). Here, in this embodiment, when the supply power duty ratio D is 21 to 40, as shown in FIG. 4, the phase angle α (° for supplying power to the heating element 3 as the priority heating element is shown. ) Is 0 °, and power is supplied to the heating element 3 over the entire wave (hereinafter referred to as full-wave power supply). That is, when the power supplied only to the heating element 3 cannot supply the power required for the fixing device 109, the engine controller 126 sets the heating element 3 to the full-wave power supply state (in FIG. The heating element 20 is also phase-controlled by the ON2 signal. The phase angle β of the heating element 20 is set to the value shown in FIG. For example, when the supply power duty ratio D calculated by the engine controller 126 in S5 is 32, the heating element 3 as the priority heating element has a phase angle of 0 °, and the heating element 20 as the auxiliary heating element has a phase angle of Control as 80.9 °. When the supply power duty ratio D is 20, the engine controller 126 supplies the heating element 3 to full-wave power and turns off the heating element 20, and when the supply power duty ratio D is 40, the engine controller 126 and the heating element 20. Is controlled as a full-wave power supply state. The engine controller 126 stores the current value detected when the heating element 3 is a priority heating element by the current detection circuit 27 in, for example, a memory (not shown).

  In S10, the engine controller 126 calculates a maximum suppliable power duty ratio Dmax. The engine controller 126 supplies a maximum suppliable power duty ratio Dmax, which is an upper limit power duty ratio, based on the HCRRT signal input from the current detection circuit 27 when supplying power to the heating element 3 and the heating element 20. Is calculated. Then, the engine controller 126 performs control so that electric power that is equal to or less than the calculated maximum suppliable power duty ratio Dmax is supplied to the ceramic heater 134. Engine controller 126 calculates maximum suppliable power duty ratio Dmax from the above-described equation (3). That is, it is calculated based on the detection result Irms by the current detection circuit 27 and the supplied power duty ratio D and the current limit value Ilimit based on the detection result of the temperature detection element 135. Here, the maximum suppliable power duty ratio which is the first upper limit power duty ratio calculated by the engine controller 126 during the first half of the full wave (heating element 3 priority) is Dmax1.

  In S11, the engine controller 126 preferentially supplies power to the heating element 20 for the second half of the full wave. In S12, the engine controller 126 determines whether the supplied power duty ratio D calculated in S5 is from 0 to 20 or from 21 to 40. As described above, in the present embodiment, the control method of the heating element 3 and the heating element 20 differs depending on whether the calculated supply power duty ratio D is 0 to 20 or 21 to 40. The engine controller 126 performs control by exchanging the priority heat generators in the first half of the full wave.

  If the engine controller 126 determines in S12 that the calculated supply power duty ratio D is from 0 to 20, the process proceeds to S14. In S14, the engine controller 126 supplies the power to the heating element 3 and the phase angle α (°) for supplying power to the heating element 20 based on the calculated supply power duty ratio D and the control table of FIG. To obtain a phase angle β (°). Here, in this embodiment, when the supply power duty ratio D is 0 to 20, as shown in FIG. 4, the phase angle β (° for supplying power to the heating element 3 as an auxiliary heating element is shown. ) Is 180 °, and power supply to the heating element 3 is stopped (shown as OFF). The engine controller 126 controls the triac 13 by outputting the ON2 signal, and controls the triac 4 not to be driven by turning the ON1 signal to a low level, for example. That is, only the heating element 20 is in the phase control state. The phase angle α of the heating element 20 is set to a value shown in FIG. When the supply power duty ratio D calculated by the engine controller 126 is 0, the triac 4 and the triac 13 are turned off. That is, when the supplied power duty ratio D = 0 is calculated, no power is supplied to the heating element 3 and the heating element 20. The engine controller 126 stores the current value detected when the heating element 20 is a priority heating element by the current detection circuit 27 in, for example, a memory (not shown).

  If the engine controller 126 determines in S12 that the calculated supply power duty ratio D is 21 to 40, the process proceeds to S13. In S13, the engine controller 126 supplies a phase angle α (°) for supplying power to the heating element 20 and the heating element 3 based on the calculated supply power duty ratio D and the control table of FIG. To obtain a phase angle β (°). Here, in this embodiment, when the supply power duty ratio D is 21 to 40, as shown in FIG. 4, the phase angle α (° for supplying power to the heating element 20 as the priority heating element is shown. ) Is 0 ° and full-wave power is supplied to the heating element 20. That is, when the power supplied to only the heating element 20 cannot supply the power required for the fixing device 109, the engine controller 126 keeps the heating element 20 in the full-wave power supply state and the heating element 3 by the ON1 signal. Phase control. The phase angle β (°) of the heating element 3 is set to a value shown in FIG. When the supplied power duty ratio D is 20, the engine controller 126 supplies the heating element 20 with full-wave power and turns off the heating element 3, and when the supplied power duty ratio D is 40, the engine controller 126 and the heating element 3 20 is controlled to be in a full-wave power supply state. In S15, the engine controller 126 calculates the maximum suppliable power duty ratio Dmax using Expression (3) during the period of the latter half 1 full wave (the heating element 20 has priority). It is assumed that the maximum suppliable power duty ratio, which is the second upper limit power duty ratio calculated by the engine controller in S15, is Dmax2. The engine controller 126 stores the current value detected when the heating element 20 is a priority heating element by the current detection circuit 27 in, for example, a memory (not shown).

(Current waveform flowing through each heating element)
In FIG. 5, the waveform of the current flowing through the heating element 3 and the heating element 20 in the control described so far will be described. Here, in both FIG. 5A and FIG. 5B, the current waveform of the heating element 3 is shown on the upper side, and the current waveform of the heating element 20 is shown on the lower side. Is shown. FIG. 5A shows a current waveform when the supply power duty ratio D calculated by the engine controller 126 is 0 to 20. FIG. First, in period A (heating element 3 priority period), heating element 3 is a priority heating element. When the supply power duty ratio D is 0 to 20, the heating element 20 is in the off state in the period A, and no power is supplied to the heating element 20. On the other hand, the heating element 3 is controlled by the phase angle α, and the phase angle α is a value corresponding to the supply power duty ratio D of FIG. In period A, engine controller 126 calculates maximum suppliable power duty ratio Dmax1 (S10 in FIG. 3).

  Next, when the period B (the heating element 20 priority period) is reached, the heating element that preferentially supplies power is switched, and the heating element 20 becomes the priority heating element. When the supply power duty ratio D is 0 to 20, the heating element 3 is in the OFF state in the period B, and no power is supplied to the heating element 3. On the other hand, the heating element 20 is controlled by the phase angle α, and the phase angle α becomes a value corresponding to the supply power duty ratio D of FIG. In period B, engine controller 126 calculates maximum suppliable power duty ratio Dmax2 (S15 in FIG. 3). When the second full wave ends, the supply power duty ratio D is newly calculated, and the third full wave and the fourth full wave are similarly controlled. That is, the control update timing comes every two full waves. In this way, the heating element to which power is preferentially supplied is switched between the heating element 3 and the heating element 20 for every full wave.

  FIG. 5B shows a current waveform when the supply power duty ratio D calculated by the engine controller 126 is 21 to 40. First, in period C (heating element 3 priority period), heating element 3 is a priority heating element. When the supply power duty ratio D is 21 to 40, the heating element 3 that is the priority heating element in the period C is in a full-wave power supply state (shown as FULL ON in the figure). On the other hand, the heating element 20 is controlled by the phase angle β, and the phase angle β has a value corresponding to the supply power duty ratio D of FIG. In period C, engine controller 126 calculates maximum suppliable power duty ratio Dmax1 (S10 in FIG. 3).

  Next, when the period D (the heating element 20 priority period) is reached, the heating element that preferentially supplies power is switched, and the heating element 20 becomes the priority heating element. When the supply power duty ratio D is 21 to 40, the heating element 20 that is the priority heating element in the period D is in the full-wave power supply state. On the other hand, the heating element 3 is controlled by the phase angle β, which is a value corresponding to the supply power duty ratio D of FIG. In period D, engine controller 126 calculates maximum suppliable power duty ratio Dmax2 (S15 in FIG. 3).

  Next, in S16, the engine controller 126 calculates the difference between the maximum suppliable power duty ratio Dmax1 calculated in S10 during the first half full-wave period and the maximum suppliable power duty ratio Dmax2 calculated in S15 during the second half full-wave period. It is determined whether or not a predetermined value or more. Here, the difference | Dmax1-Dmax2 | between the maximum suppliable power duty ratio Dmax1 and the maximum suppliable power duty ratio Dmax2 is referred to as a divergence. For example, in this embodiment, it is determined whether or not the deviation is 10 or more. Here, in the normal state, even if the variation factors such as the resistance value variations of the heating element 3 and the heating element 20, the variation of the current detection circuit 27, and the quantization error are accumulated, the deviation does not become 10 or more. It is set as follows. As a case where the divergence is 10 or more, one of the failures of the triac 4 and the triac 13 can be considered. In addition, when the divergence is 10 or more, there may be a failure in the peripheral circuits (phototriac couplers 7 and 16, transistors 9 and 18, etc.) that drive the triac 4 and the triac 13. Further, when the deviation is 10 or more, disconnection of the electric wire supplying power to the heating element 3 and the heating element 20, disconnection of the connector, or the like can be considered. Further, even when a fixing device having only one heating element is erroneously inserted, power is not supplied to either the heating element 3 or the heating element 20. When a fixing device composed of a single heating element is erroneously inserted, and the lamp is turned on with priority given to the one not connected to the heating element, the maximum supplyable power duty ratio Dmax always calculates the upper limit. For this reason, the divergence from the maximum suppliable power duty ratio Dmax in which the heating element is connected to the drive circuit becomes large. For this reason, even when a fixing device including one heating element is erroneously inserted, abnormality detection can be performed because the deviation of the present embodiment is 10 or more.

  If the engine controller 126 determines in S16 that the difference between the maximum suppliable power duty ratio Dmax1 and the maximum suppliable power duty ratio Dmax2 is less than 10 (less than a predetermined value), the process proceeds to S17. In S17, the engine controller 126 determines that there is no failure factor as described above, and compares the maximum supplyable power duty ratio Dmax1 and the maximum supplyable power duty ratio Dmax2. If the engine controller 126 determines in S17 that Dmax1 ≧ Dmax2, the process proceeds to S18. In S18, in the next two full-wave cycles, the engine controller 126 sets the maximum suppliable power duty ratio to Dmax2, and the supplied power duty ratio D is equal to or less than the maximum suppliable power duty ratio Dmax2 (Dmax2 ≧ D). To control. On the other hand, when the engine controller 126 determines in S17 that Dmax1 <Dmax2, the process proceeds to S19. In S19, in the next two full-wave cycles, the engine controller 126 sets the maximum suppliable power duty ratio to Dmax1, and the supplied power duty ratio D is equal to or less than the maximum suppliable power duty ratio Dmax1 (Dmax1 ≧ D). To control. As described above, the engine controller 126 supplies power to the heating element 3 and the heating element 20 so as to be equal to or less than the power duty ratio that is smaller of the maximum supplyable power duty ratio Dmax1 and the maximum supplyable power duty ratio Dmax2. To control.

  Here, the processing of S18 and S19 will be described. As described above, a value obtained by subtracting the maximum current value supplied to the low-voltage power supply circuit unit 28 from the rated current of the connected AC power supply 1 is set as an allowable current value that can be supplied to the ceramic heater 134, and the allowable It is necessary to control below the current value. For this reason, the allowable current value is obtained by adopting the smaller value of the maximum suppliable power duty ratio Dmax1 and the maximum suppliable power duty ratio Dmax2 as in S18 and S19. Is not exceeded.

  In S20, the engine controller 126 determines whether or not the print job has ended. If it is determined that the print job has not ended, the process returns to S5. On the other hand, if the engine controller 126 determines in S20 that the print job has ended, the power supply to the heating element 3 and the heating element 20 is ended in S21, and the printing operation is ended.

  If the engine controller 126 determines in S16 that the difference between the maximum suppliable power duty ratio Dmax1 and the maximum suppliable power duty ratio Dmax2 is 10 or more, the process proceeds to S22. If the deviation is 10 or more, the engine controller 126 determines that there is an abnormality in the heating element 3 and the heating element 20 due to the above-described causes, and supplies power to the heating element 3 and the heating element 20 in S22. Kill. In S23, the engine controller 126 warns the user via a display panel (not shown) mounted on the main body 101. Thereby, usability can be improved. Note that the process of S23 may not be performed.

  As described above, in this embodiment, in the fixing device 109 having two heating elements, the priority heating elements are alternately replaced for every full wave of the AC power supply 1, and the maximum suppliable power duty ratio Dmax1 calculated by each is changed. And the maximum suppliable power duty ratio Dmax2. As a result, it is possible to quickly detect that there is an abnormality in an element that contributes to supplying power to one of the heating elements, or that the fixing device is mistakenly inserted. And the power supply to a heat generating body can be interrupted | blocked safely. Furthermore, it is possible to reliably warn the user of an abnormality. As described above, according to this embodiment, it is possible to accurately detect a failure of the image heating apparatus and an erroneous insertion of the fixing device.

  The second embodiment is different from the first embodiment in control when the difference between the maximum suppliable power duty ratio Dmax1 and the maximum suppliable power duty ratio Dmax2 is 10 or more. In the present embodiment, when the deviation is 10 or more, the power supply to the heating element 3 and the heating element 20 is not finished, and the current detection result when the heating element 3 is given priority and the heating element 20 is given priority. Replace the current detection result. Then, in a state where the current detection result when the heating element 3 is prioritized and the current detection result when the heating element 20 is prioritized, the maximum supplyable power duty ratio Dmax1 and the maximum supplyable power duty ratio Dmax2 are respectively set. calculate. If the difference between the maximum suppliable power duty ratio Dmax1 and the maximum suppliable power duty ratio Dmax2 is smaller than 10 as a result of replacing the current detection result, incorrect wiring in which the heating element 3 and the heating element 20 are replaced and wired Judge. And the state which replaced the electric current detection result of the heat generating body 3 and the electric current detection result of the heat generating body 20 is continued, and the electric power supply to the heat generating body 3 and the heat generating body 20 is continued. The configuration of the control circuit of the image forming apparatus and the ceramic heater 134 is the same as that of the first embodiment, and the same reference numerals are given and description thereof is omitted.

[Fixing control of this embodiment]
The fixing control by the engine controller 126 of this embodiment is shown in the flowchart of FIG. In addition, the same step number is attached | subjected to the same process as the flowchart of FIG. 3 demonstrated in Example 1, and description is abbreviate | omitted. In the present embodiment, the description will be made assuming that the resistance value ratio between the heating element 3 and the heating element 20 is 1.5 (resistance value of the heating element 3: resistance value of the heating element 20 = 1.5: 1). This embodiment can be applied if the resistance value ratio is a numerical value other than 1. When the resistance value ratio is 1: 1, even if the heating element 3 and the heating element 20 are replaced and wired, it does not mean that the wiring is incorrect.

  In S16, the engine controller 126 calculates the divergence between the maximum suppliable power duty ratio Dmax1 and the maximum suppliable power duty ratio Dmax2, and determines whether the divergence is smaller than 10. If the engine controller 126 determines in S16 that the deviation is smaller than 10, it determines that there is no failure factor as described in the first embodiment, and proceeds to the process in S17. If the engine controller 126 determines in S16 that the difference between the maximum suppliable power duty ratio Dmax1 and the maximum suppliable power duty ratio Dmax2 is 10 or more, the process proceeds to S47. In this case, the engine controller 126 determines that there is some abnormality in the power supply system to the heating element 3 and the heating element 20, or there is an incorrect wiring of the fixing device 109 described later.

  In S47, the engine controller 126 replaces (or replaces) the current detection result when the heating element 3 is the priority heating element with the current detection circuit 27 and the current detection result when the heating element 20 is the priority heating element. The maximum supplyable power duty ratio Dmax2 is calculated. Here, the current detection result when the heating element 3 is set as the priority heating element by the current detection circuit 27 is a value stored in the memory or the like (not shown) by the engine controller 126 in S8 or S9. Further, the current detection result when the heating element 20 is set as the priority heating element by the current detection circuit 27 is a value stored by the engine controller 126 in a memory (not shown) or the like in S13 or S14. The engine controller 126 calculates Dmax2 using the current detection result when the heating element 3 is the priority heating element and the coefficients a and b (a_20, b_20) of the heating element 20. In S48, the engine controller 126 calculates the maximum suppliable power duty ratio Dmax1 by replacing the current detection result of the heating element 20 with the current detection result from the heating element 3. That is, the engine controller 126 calculates Dmax1 using the current detection result when the heating element 20 is the priority heating element and the coefficients a and b (a_3, b_3) of the heating element 3. Here, the current detection results of the heating element 3 and the heating element 20 are interchanged by driving the heating element 20 with the ON1 signal that is the driving signal of the heating element 3 and the ON2 signal that is the driving signal of the heating element 20. This is to confirm whether the heating element 3 is not driven. That is, it is for confirming whether an incorrect wiring of the fixing device 109 has occurred.

  After the mutual current detection results of the heating element 3 and the heating element 20 are exchanged in S47 and S48, the engine controller 126 again determines in S49 that the difference between the maximum supplyable power duty ratio Dmax1 and the maximum supplyable power duty ratio Dmax2 It is determined whether the number is 10 or more. If the engine controller 126 determines in S49 that the deviation is 10 or more, the process proceeds to S22. In this case, as in the first embodiment, it is determined that a triac failure, a peripheral circuit failure, or a heating element is an erroneous insertion of one fixing device. On the other hand, if the engine controller 126 determines that the deviation is smaller than 10 in S49, it determines that the wiring is incorrect and proceeds to the process of S17. If the engine controller 126 determines that the fixing device 109 is miswired, the current detection result when the heating element 3 is the priority heating element and the current detection result when the heating element 20 is the priority heating element are displayed. It is assumed that Dmax1 and Dmax2 are calculated by replacing them. In this embodiment, the control after S17 can be continued by performing such control. As described above, the engine controller 126 determines whether there is an abnormality in the power supply means to one of the heating elements, or an incorrect insertion of a fixing device including one heating element, or an incorrect wiring of the fixing device 109. Can be determined.

  As described above, in this embodiment, the fixing unit 109 having two heating elements is alternately replaced with the priority heating element for every full wave of the AC power source 1. And it is the cheap structure of comparing the maximum suppliable electric power duty ratio Dmax1 calculated by each and the maximum suppliable electric power duty ratio Dmax2. As a result, in this embodiment, an abnormality in the power supply means to one heating element or an erroneous insertion of a fixing device composed of one heating element is quickly detected, and the power supply to the heating element is safely cut off. be able to. Further, it is possible to reliably warn the user of an abnormality, and it is possible to perform normal fixing control even when the heating element and the control circuit output are miswired. As described above, according to this embodiment, it is possible to accurately detect a failure of the image heating apparatus and an erroneous insertion of the fixing device.

DESCRIPTION OF SYMBOLS 1 AC power supply 3, 20 Heating element 27 Current detection circuit 126 Engine controller 134 Ceramic heater

Claims (11)

Heating means having a first heating element and a second heating element that generate heat by electric power supplied from an AC power source;
Current detection means for detecting a current flowing through the first heating element and the second heating element;
Calculation means for calculating an upper limit power duty ratio that can be supplied to the heating means based on a result detected by the current detection means;
Control means for controlling the power supplied to the first heating element and the second heating element so that the power duty ratio is equal to or lower than the upper limit power duty ratio calculated by the calculating means;
An image heating apparatus comprising:
The control means preferentially supplies power to the first heating element in the first half of the predetermined number of cycles of the AC waveform, and supplies power to the second heating element in the second half of the predetermined number of cycles. ,
The power duty ratio of the first upper limit calculated by the calculation means based on the result detected by the current detection means when power is supplied with priority over the first heating element, and priority over the second heating element. An image heating apparatus, wherein abnormality detection is performed based on a second upper limit power duty ratio calculated by the calculation means based on a result detected by the current detection means when power is supplied.   The calculating means calculates the first upper limit power duty ratio and the second upper limit power duty ratio according to a resistance value ratio between the first heating element and the second heating element. The image heating apparatus according to claim 1. A first control element for turning on or off the power supplied to the first heating element;
A second control element for turning on or off the power supplied to the second heating element;
With
When the difference between the first upper limit power duty ratio and the second upper limit power duty ratio is greater than or equal to a predetermined value, the control means includes the heating means, the first control element, and the second The image heating apparatus according to claim 1, wherein at least one of the control elements is abnormal or it is determined that the image heating apparatus having only one heating element is erroneously inserted. The resistance value ratio between the first heating element and the second heating element is different, and a difference between the first upper limit power duty ratio and the second upper limit power duty ratio is not less than the predetermined value. If there is
The calculating means includes
Calculating the second upper limit power duty ratio using the result detected by the current detection means when power is supplied in preference to the first heating element;
Calculate the first upper limit power duty ratio using the result detected by the current detection means when power is supplied in preference to the second heating element,
Thereafter, the control means
If the difference between the first upper limit power duty ratio and the second upper limit power duty ratio is less than the predetermined value, the first heating element and the second heating element may be miswired. The image heating apparatus according to claim 3, wherein the image heating apparatus is determined to be present. The resistance value ratio between the first heating element and the second heating element is different, and a difference between the first upper limit power duty ratio and the second upper limit power duty ratio is not less than the predetermined value. If there is
The calculating means includes
Calculating the second upper limit power duty ratio using the result detected by the current detection means when power is supplied in preference to the first heating element;
Calculate the first upper limit power duty ratio using the result detected by the current detection means when power is supplied in preference to the second heating element,
Thereafter, the control means
When the difference between the first upper limit power duty ratio and the second upper limit power duty ratio is greater than or equal to the predetermined value, the heating means, the first control element, and the second control element 4. The image heating apparatus according to claim 3, wherein at least one of the image heating apparatus is abnormal or an image heating apparatus having only one heating element is erroneously inserted.   The control means, when the difference between the first upper limit power duty ratio and the second upper limit power duty ratio is less than the predetermined value, the first upper limit power duty ratio and 4. The power supplied to the first heating element and the second heating element is controlled so as to be equal to or less than the smaller one of the second upper limit power duty ratios. Or the image heating apparatus of 4. Temperature detecting means for detecting the temperature of the heating means,
The said control means controls said 1st control element and said 2nd control element so that the said heating means may become predetermined temperature based on the result detected by the said temperature detection means. 7. The image heating apparatus according to any one of items 1 to 6.   The image heating apparatus according to claim 1, wherein the predetermined number of periods of the AC waveform is a 2n period (n is a positive integer) of the AC waveform.   The current detection unit includes a transformer and a current detection circuit that detects a current via the transformer, and is provided in a power supply path from the AC power source to the heating unit. The image heating apparatus according to claim 1, wherein a flowing current is detected.   When the control means determines that at least one of the heating means, the first control element, and the second control element is abnormal or that the image heating apparatus having only one heating element is erroneously inserted. The image heating apparatus according to claim 3, wherein power supply to the heating unit is stopped. An image carrier;
Latent image means for forming an electrostatic latent image on the image carrier;
Developing means for developing the electrostatic latent image formed by the latent image means to form a toner image;
A transfer means for transferring the toner image formed by the developing means to a recording paper;
Fixing means for fixing the recording paper onto which the toner image has been transferred;
With
The image forming apparatus according to claim 1, wherein the fixing unit is the image heating apparatus according to claim 1.

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