Image forming apparatus

Abstract

This technology provides a way to suppress heater-related failures caused by waveform distortion in the AC power supply, which changes from a sine wave to a square or DC waveform. [Solution] When the relay circuit 133 is turned on, if the zero-cross detection circuit 138 does not generate a zero-cross signal, the control unit 100 controls the image forming unit 4, excluding the heater 93, so that it consumes a second power consumption that is greater than the first power consumption that the image forming unit 4 consumes during normal printing.

Description

Technical Field

[0001] The present application relates to an image forming apparatus provided with a heater for thermally fixing an image formed on a sheet.

Background Art

[0002] Patent Document 1 describes an image forming apparatus configured to prohibit energization from an AC power supply to a heater of a fixing device when a voltage change rate of the AC power supply at a zero-cross timing of the AC power supply is equal to or greater than an allowable amount.

Prior Art Literature

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] One of the reasons why the voltage change rate of the AC power supply at the zero-cross timing of the AC power supply becomes equal to or greater than the allowable amount is that the inrush current flowing from the AC power supply at the start of energization to the heater of the fixing device becomes excessive. To cope with this, in the image forming apparatus described in Patent Document 1, when the voltage change rate of the AC power supply at the zero-cross timing is equal to or greater than the allowable amount, energization from the AC power supply to the heater of the fixing device is prohibited.

[0005] However, the image forming apparatus described in Patent Document 1 does not mention a countermeasure for a case where an inrush current flows from the AC power supply at the start of energization to the heater of the fixing device, and the waveform of the AC power supply collapses from a sine waveform to a rectangular waveform or a DC waveform.

[0006] The present application aims to provide a technique that makes it possible to suppress failures around the heater that occur due to the waveform of the AC power supply collapsing from a sine waveform to a rectangular waveform or a DC waveform. [Means for solving the problem]

[0007] To achieve the above objective, the image forming apparatus described in the embodiment includes a heater, an image forming unit excluding the heater that consumes power to form an image on a sheet, a first power line that connects one power terminal of an AC power supply to one end of the heater and supplies power to the heater, a second power line that connects the other power terminal of an AC power supply to the other end of the heater and supplies power to the heater, a zero-crossing signal generation unit connected to the first power line and the second power line and generating a zero-crossing signal, and a relay circuit provided at least one of the following: between one power terminal and the connection point between the first power line and the zero-crossing signal generation unit, and between the other power terminal and the connection point between the second power line and the zero-crossing signal generation unit, for turning the power supply from the AC power supply on / off. The device comprises: an AC switching circuit provided between the connection point between the first power line and the zero-cross signal generation unit and one end of the heater, or between the connection point between the second power line and the zero-cross signal generation unit and the other end of the heater, which switches the supply / cutoff of power to the heater; an AC / DC conversion circuit connected to the first power line and the second power line, which converts AC power to DC power; a power supply board including the AC / DC conversion circuit that supplies DC power to the image forming unit excluding the heater; and a control unit, wherein the control unit controls the image forming unit excluding the heater so that, in the event of an abnormality where the zero-cross signal generation unit is not generating a zero-cross signal with the relay circuit turned on, the image forming unit excluding the heater consumes a second power consumption that is greater than the first power consumption that the image forming unit excluding the heater consumes during normal printing. [Effects of the Invention]

[0008] In the image forming apparatus described in the embodiment, when the relay circuit is turned on and the zero-crossing signal generation unit is not generating a zero-crossing signal, the image forming unit excluding the heater is controlled to consume a second power consumption that is greater than the first power consumption that the image forming unit excluding the heater consumes during normal printing. This makes it possible to suppress heater-related failures that occur due to waveform distortion of the AC power supply waveform from a sine wave to a square wave or DC wave. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view showing a schematic configuration of a color laser printer according to one embodiment. [Figure 2] Figure 1 is a block diagram showing the control configuration of a color laser printer. [Figure 3] This is a circuit diagram showing the general configuration of the heater control device. [Figure 4] Figure 3 shows a specific circuit diagram of the AC switching circuit included in the circuit diagram. [Figure 5] Figure 3 shows a specific circuit diagram of the zero-crossing detection circuit included in the circuit diagram. [Figure 6] This figure shows the input voltage waveform (a), the voltage waveform after full-wave rectification (b), and the zero-crossing signal waveform (c). [Figure 7] This is a flowchart showing the procedure for the first control process. [Figure 8] Figure 7 is a flowchart showing the detailed procedure for the abnormal power supply detection process included in the first control process. [Figure 9] Figure 8 is a flowchart showing the detailed procedure for the first modified example of the abnormal power supply detection process. [Figure 10] Figure 8 is a flowchart showing the detailed procedure for the second modified example of the abnormal power supply detection process. [Figure 11] Figure 8 is a flowchart showing the detailed procedure for the third modified example of the abnormal power supply detection process. [Figure 12] Figure 8 is a flowchart showing the detailed procedure for the fourth modified example of the abnormal power supply detection process. [Figure 13] Figure 8 is a flowchart showing the detailed procedure for the fifth modified example of the abnormal power supply detection process. [Figure 14] This flowchart shows the procedure for the second control process. [Modes for carrying out the invention]

[0010] The embodiments of this application will be described in detail below with reference to the drawings.

[0011] Figure 1 is a cross-sectional view showing the schematic configuration of a color laser printer 1 according to one embodiment. The color laser printer 1 is an example of an image forming apparatus. Hereinafter, the color laser printer 1 will be abbreviated as printer 1. The printer 1 comprises a housing 2, a transport unit 3, and an image forming unit 4. The housing 2 is the exterior of the printer 1. The transport unit 3 is an example of a sheet transport mechanism. Hereinafter, for the sake of convenience in explanation, the vertical and horizontal directions of the printer 1 will be defined as shown by the arrows in Figure 1. Furthermore, the left-right direction will be defined as the direction from the front of the printer 1, with the left side of the user facing the printer 1 being to the left and the right side being to the right.

[0012] The housing 2 includes a front cover 21, a rear cover 12, a supply tray 31, a discharge tray 22, and first to third transport paths 25 to 27. The front cover 21 is a cover that opens and closes a front opening 2A provided at the front of the housing 2, and is attached to the front of the housing 2 in a manner that allows it to be opened and closed. The rear cover 12 is a cover that opens and closes a rear opening 2B provided at the rear of the housing 2, and is attached to the rear of the housing 2 in a manner that allows it to be opened and closed. The supply tray 31 is attached to the bottom of the housing 2 in a manner that allows it to be detached. A sheet S is placed on the supply tray 31. The sheet S is a standard-sized sheet such as A4 size. The sheet S is a paper medium such as plain paper or cardboard, but is not limited to this, and may also be OHP film. The discharge tray 22 is provided at the top of the housing 2, and a sheet S with an image formed on it is placed on the discharge tray 22.

[0013] The conveyance unit 3 includes a pickup roller 33, a separation roller 34, a registration roller 35, a first conveyance roller 36, a second conveyance roller 37, a first switchback roller 38, a second switchback roller 39, a plurality of third conveyance rollers 40, a flapper 30, and a main motor 106 (see FIG. 2). A part of the second conveyance path 26 is formed by the rear cover 12 in the closed state.

[0014] The pickup roller 33 picks up the sheet S in the supply tray 31 that is pushed upward by the sheet pressing plate 32, and conveys the sheet S toward the first conveyance path 25. The separation roller 34 separates the sheets S picked up by the pickup roller 33 one by one.

[0015] The registration roller 35 is disposed on the upstream side of the image forming unit 4 in the first conveyance path 25. After aligning the direction of the leading end of the sheet S, the registration roller 35 conveys the sheet S toward the image forming unit 4. The conveyance direction in which the registration roller 35 conveys the sheet is a direction from the front toward the rear.

[0016] When conveying the sheet S to the outside of the housing 2 and the rear cover 12 is closed, the conveyance unit 3 conveys the sheet S conveyed from the image forming unit 4 by the first conveyance roller 36, and guides the sheet S to the first conveyance path 25 by the flapper 30 (30A). After that, the conveyance unit 3 conveys the sheet S guided to the first conveyance path 25 by the second conveyance roller 37 and the first switchback roller 38, and discharges the sheet S onto the discharge tray 22.

[0017] Furthermore, when the transport unit 3 transports the sheet S outside the housing 2, if the rear cover 12 is open, the transport unit 3 transports the sheet S transported from the image forming unit 4 by the first transport roller 36, guides it towards the rear by the flapper 30 (30B) which swings to the position indicated by the dashed line, and discharges it onto the open rear cover 12 through the rear opening 2B. The printer 1 is capable of forming an image on the sheet S even when the rear cover 12 is open, and the rear cover 12 is a cover that allows the sheet S with the image formed on it to be discharged from the rear opening 2B when it is open.

[0018] Furthermore, when the transport unit 3 transports the sheet S back to the image forming unit 4, it transports the sheet S transported from the image forming unit 4 using the first transport roller 36 and guides it to the first transport path 25 or the second transport path 26 using the flapper 30. If the sheet S is guided to the first transport path 25, the transport unit 3 transports the sheet S in the first transport path 25 to the third transport path 27 using the second transport roller 37 and the first switchback roller 38. If the sheet S is guided to the second transport path 26, the transport unit 3 transports the sheet S in the second transport path 26 to the third transport path 27 using the second switchback roller 39. The third transport path 27 is an example of a transport path for double-sided printing.

[0019] The sheet S, transported along the third transport path 27, is then supplied back to the image forming unit 4 by the third transport roller 40 and the registration roller 35, etc. After an image is formed on the sheet S in the image forming unit 4, it is discharged onto the discharge tray 22 by the transport unit 3.

[0020] The image forming unit 4 has the function of forming an image on the sheet S and transferring the toner image to the sheet S. The image forming unit 4 comprises an exposure unit 5, a drum unit 6, four developing cartridges 7Y, 7M, 7C, and 7K, a transfer unit 8, and a fuser 9. The exposure unit 5 is an example of multiple exposure units. The drum unit 6 and the four developing cartridges 7Y, 7M, 7C, and 7K are an example of multiple developing units. The transfer unit 8 is an example of multiple transfer units.

[0021] The exposure unit 5 is located at the top of the housing 2 and includes a laser light-emitting unit 50 (see Figure 2), a polygon mirror 51 (see Figure 2), a lens (not shown), a reflector (not shown), a polygon motor 52 (see Figure 2), and the like. The exposure unit 5 exposes the surface of the photoreceptor drum 61 by emitting a light beam, indicated by a dashed line, onto the surface of the photoreceptor drum 61.

[0022] The drum unit 6 is positioned within the housing 2 between the supply tray 31 and the exposure unit 5, and comprises four photoreceptor drums 61, four chargers 62, four drum cleaners 63, pinch rollers 64, and a support frame 65 that supports the photoreceptor drums 61 and the like. The drum cleaner 63 is an example of a drum cleaner section. The charger 62 is an example of a charging section. The drum unit 6 can be attached to and detached from the housing 2 through the front opening 2A when the front cover 11 is open. The pinch rollers 64 face the registration rollers 35. The pinch rollers 64 rotate in accordance with the rotation of the registration rollers 35 and transport the sheet S together with the registration rollers 35.

[0023] The developer cartridges 7Y, 7M, 7C, and 7K correspond to four colors, yellow (Y), magenta (M), cyan (C), and black (K), respectively, and are detachably mounted on the drum unit 6 in this order from front to back of the printer 1. Each of the developer cartridges 7Y, 7M, 7C, and 7K is equipped with a developer roller 71, a supply roller 72, and a toner storage section 73. Although the toner colors differ, the other components of each developer cartridge 7Y, 7M, 7C, and 7K are the same, so below, one of them may be referred to simply as "developer cartridge 7."

[0024] The transfer unit 8 is located within the housing 2, between the supply tray 31 and the drum unit 6, and comprises a drive roller 81, a driven roller 82, a conveyor belt 83, and four transfer rollers 84. The conveyor belt 83 is stretched between the drive roller 81 and the driven roller 82, and its upper surface is in contact with the photoreceptor drum 61. The four transfer rollers 84 are located inside the conveyor belt 83, sandwiching the conveyor belt 83 between themselves and the corresponding photoreceptor drum 61.

[0025] The fuser 9 is located behind the image forming unit 4 within the housing 2. More specifically, the fuser 9 is located between the closed rear cover 12 and the image forming unit 4. The fuser 9 has a heating roller 91 for heating the sheet S and a pressurizing unit 92 that holds the sheet S between itself and the heating roller 91. In this embodiment, the heating roller 91 has a heater 93 inside that heats the heating roller 91. The pressurizing unit 92 has an endless belt (indicated by the omission of reference numerals), a pressing pad that holds the endless belt between itself and the heating roller 91, a holder that supports the pressing pad, a belt guide, and the like.

[0026] The image forming unit 4 uniformly charges the surface of the photoreceptor drum 61 with the charger 62 and exposes the surface of the photoreceptor drum 61 with the exposure unit 5, thereby forming an electrostatic latent image on the surface of the photoreceptor drum 61. The image forming unit 4 also supplies toner from the toner storage unit 73 to the supply roller 72, and from the supply roller 72 to the develop roller 71. The toner supplied to the develop roller 71 is carried on the develop roller 71 as the develop roller 71 rotates.

[0027] The image forming unit 4 supplies toner carried on the developing roller 71 to the electrostatic latent image formed on the photoreceptor drum 61, thereby forming a toner image on the surface of the photoreceptor drum 61. Subsequently, the image forming unit 4 transfers the toner image on the photoreceptor drum 61 to the sheet S supplied from the supply tray 31 by the transport unit 3 between the photoreceptor drum 61 and the transport belt 83. After that, the image forming unit 4 transports the sheet S to the fuser 9.

[0028] The fuser unit 9 transports the sheet S between the heating roller 91 and the pressurizing unit 92, thereby fixing the toner image transferred to the sheet S and forming an image on the sheet S.

[0029] The drum cleaner 63 includes a drum cleaning roller 63a and a drum cleaning shaft 63b. A high voltage roller voltage is applied to the drum cleaning roller 63a, which collects toner remaining on the photoreceptor drum 61. The drum cleaning shaft 63b is made of a conductive metal, and a shaft voltage higher than the roller voltage is applied to it, which removes paper dust from the drum cleaning roller 63a. In other words, the drum cleaning shaft 63b uses the shaft voltage to remove paper dust generated inside the housing 2.

[0030] Normally, toner is positively charged and paper dust is negatively charged, so the difference in charge polarity is used to remove toner and paper dust separately from the photoreceptor drum 61. During printing, a negative voltage, for example -400V, is applied to the drum cleaning roller 63a to collect only the toner from the photoreceptor drum 61 onto the drum cleaning roller 63a. Then, during the cleaning operation, a positive voltage, for example 500V, is applied to the drum cleaning roller 63a, and a shaft voltage of 700V DCLNB is applied to the drum cleaning shaft 63b. At this time, the paper dust is collected on the drum cleaning shaft 63b via the drum cleaning roller 63a. The toner is discharged onto the photoreceptor drum 61 and then adheres to the surface of the conveyor belt 83, where it is collected by the belt cleaner 16. The belt cleaner 16 is an example of a belt cleaner unit.

[0031] The belt cleaner 16 comprises a backup roller 16a, a belt cleaning roller 16b, and a belt cleaning shaft 16c. The backup roller 16a faces the belt cleaning roller 16b across the conveyor belt 83, and the belt cleaning roller 16b and the belt cleaning shaft 16c are in contact.

[0032] When a high-voltage belt cleaning voltage (for example, around 1000V) is applied to the backup roller 16a, the voltage is also applied to the belt cleaning roller 16b and the belt cleaning shaft 16c via the conveyor belt 83, and the toner adhering to the surface of the conveyor belt 83 is recovered via the belt cleaning roller 16b and the belt cleaning shaft 16c.

[0033] The printer 1 further includes a fuser fan 13 and a fuser temperature sensor TH2 within the housing 2. The fuser fan 13 has an impeller (indicated by the omission of the reference numerals) and a fan motor (not shown). The fuser fan 13 expels air from inside the housing 2 to the outside by rotating the impeller with the fan motor. The fuser temperature sensor TH2 is a temperature sensor that outputs a signal corresponding to the temperature of the fuser unit 9, more specifically, the heating roller 91. The fuser temperature sensor TH2 is installed in the fuser unit 9 and is positioned opposite the heating roller 91 in a non-contact manner. For example, a non-contact type thermistor can be used as the fuser temperature sensor TH2.

[0034] Next, the control configuration of printer 1 will be described with reference to Figure 2. As shown in Figure 2, printer 1 further comprises a control unit 100, a display 104, a zero-crossing detection circuit 138, a relay circuit 133, an I / F group 110, a sensor group 111, an AC switching circuit 134, and motor drivers MD1 and MD2. The zero-crossing detection circuit 138 is an example of a zero-crossing signal generation unit.

[0035] The control unit 100 includes a CPU 100A, a ROM 100B, a RAM 100C, and an NVRAM 100D. The ROM 100B stores various control programs and setting values ​​for controlling the printer 1, in particular programs such as the first control process and the second control process described later using Figures 7 and 14, and tables for performing the first control process and the second control process.

[0036] RAM100C and NVRAM100D are used as a work area from which various control programs are read, or as a storage area for temporarily storing data. The CPU100A controls each component of the printer 1 according to the control program read from ROM100B, while storing the processing results in RAM100C or NVRAM100D.

[0037] The I / F group 110 includes, for example, a USB I / F, a wired LAN I / F, a wireless LAN I / F, etc., which are not shown. The sensor group 111 includes, for example, a supply sensor SE1 (see Figure 1), a pre-cash register sensor SE2 (see Figure 1), and a post-cash register sensor SE3 (see Figure 1), etc.

[0038] The supply sensor SE1 is positioned upstream of the pickup roller 33 in the first transport path 25 and is a sensor that detects when the sheet S passes. The supply sensor SE1 can be a sensor with an actuator that swings when the sheet S comes into contact with it, or an optical sensor, etc. The supply sensor SE1 outputs an ON signal when the sheet S is passing and an OFF signal when the sheet S is not passing. The detection signal from the supply sensor SE1 is output to the CPU 101.

[0039] The pre-register sensor SE2 is positioned upstream of the registration roller 35 in the first transport path 25 and is a sensor that detects when the sheet S passes through. The pre-register sensor SE2 has the same configuration as the supply sensor SE1. The detection signal from the pre-register sensor SE2 is output to the CPU 101.

[0040] The post-registration sensor SE3 is positioned upstream of the fuser 9 in the first transport path 25, specifically between the registration roller 35 and the transfer roller 53, and is a sensor that detects when the sheet S passes through. The post-registration sensor SE3 has the same configuration as the supply sensor SE1. The detection signal from the post-registration sensor SE3 is output to the CPU 101.

[0041] The motor driver MD1 is connected to the polygon motor 52 that rotates the polygon mirror 51 of the exposure unit 5, and controls the drive of the polygon motor 52 according to the control signal from the control unit 100.

[0042] The motor driver MD2 controls the drive voltage based on the control signal from the control unit 100 and outputs the drive voltage to the main motor 106 to control the driving of the main motor 106. The main motor 106 drives the four developing rollers 71, the four photoreceptor drums 61, the heating roller 91 of the fuser 9, and the roller group 120. The roller group 120 includes the pickup roller 33, the separation roller 34, the registration roller 35, the first transport roller 36, the second transport roller 37, the first switchback roller 38, the second switchback roller 39, and a number of third transport rollers 40, etc.

[0043] Next, the configuration of the heater control device 130 will be described with reference to Figure 3. The heater control device 130 includes the heater 93 shown in Figure 2, a fixing temperature sensor TH2, a control unit 100, an AC switching circuit 134, a relay circuit 133, and a zero-crossing detection circuit 138. Furthermore, as shown in Figure 3, the heater control device 130 includes a pair of first and second input terminals T1 and T2 for receiving commercial power from a commercial power source, and a current detection circuit 160.

[0044] In this embodiment, the first and second input terminals T1 and T2 are connected to a commercial power supply (not shown) via a UPS 200 located outside the heater control device 130, i.e., outside the printer 1. The UPS 200 is an example of an AC power supply. UPS stands for Uninterruptible Power Supply. The UPS 200 is a device that supplies stable power to equipment in the event of power failures such as blackouts or momentary voltage drops. In this embodiment, the printer 1 is always connected to the UPS 200. That is, one terminal of the UPS 200 is connected to the first input terminal T1, and the other terminal of the UPS 200 is connected to the second input terminal T2. In this way, the printer 1 is supplied with commercial power via the UPS 200, and an AC voltage Vin is supplied inside the heater control device 130.

[0045] Between the first input terminal T1 and the second input terminal T2, a relay circuit 133, a thermostat 141, a heater 93, a current detection circuit 160, an AC switching circuit 134, an AC / DC conversion circuit 140, and a zero-crossing detection circuit 138 are connected. More specifically, the first input terminal T1 and one end H1 of the heater 93 are connected via a first connection path L1. The first connection path L1 is an example of a first power supply line. The relay circuit 133 and the thermostat 141 are located in the first connection path L1. On the other hand, the second input terminal T2 and the other end H2 of the heater 93 are connected via a second connection path L2. The second connection path L2 is an example of a second power supply line. The current detection circuit 160 and the triac 134A (see Figure 4) included in the AC switching circuit 134 are located in the second connection path L2.

[0046] The relay circuit 133 switches on / off the supply of the AC voltage Vin applied to the first and second input terminals T1 and T2 to the heater control device 130, specifically to the heater 93 of the fuser 9, based on a command from the control unit 100. The relay circuit 133 consists of a relay 133A, a transistor 133B, a diode 133C, and various unsigned resistors. Relay 133A is a mechanical relay consisting of, for example, a coil section 133A1 and a contact section 133A2. When the control unit 100 turns on the relay ON signal (for example, to H level), the transistor 133B turns on, current flows to the coil section 133A1, and the contact section 133A2 closes, i.e., connects, due to the action of an electromagnet. As a result, the supply of the AC voltage Vin to the heater control device 130 is turned on. On the other hand, when the control unit 100 turns off the relay ON signal (for example, to L level), the transistor 133B turns off, no current flows to the coil 133A1, the electromagnet stops working, and the contact 133A2 becomes open, i.e., disconnected. As a result, the supply of AC voltage Vin to the heater control device 130 is turned off.

[0047] The thermostat 141 is an element that activates when the heater 93 becomes excessively hot and stops supplying the AC voltage Vin to the heater 93. The thermostat 141 is located near the heater 93 on the first connection path L1. The temperature at which the thermostat 141 activates is, for example, around 400°C.

[0048] The heater 93 performs the function of heating the heating roller 91 that constitutes the fuser unit 9. The heater 93 is housed inside the heating roller 91 in a position that extends in the direction of the central axis of the heating roller 91. An example of a heater 93 is a halogen heater. The AC voltage Vin applied to the heater 93 is switched on and off at predetermined timings by the AC switching circuit 134, as will be described later using Figure 4. This switching operation is sometimes referred to as the switching operation.

[0049] The fixing temperature sensor TH2 is located near the heater 93. The fixing temperature sensor TH2 detects the temperature of the heater 93 and outputs the detected temperature information to the control unit 100. The current detection circuit 160 is located on the second connection path L2, between the other end H2 of the heater 93 and the AC switching circuit 134. The current detection circuit 160 detects the current value flowing through the heater 93 and outputs it to the control unit 100.

[0050] The AC / DC conversion circuit 140 is connected to a third connection path L3 and a second connection path L2. The third connection path L3 is a path that branches off from the first connection path L1 at a position between the relay circuit 133 and the thermostat 141. The third connection path L3 is also an example of a first power line. The AC / DC conversion circuit 140 converts the AC voltage Vin supplied via the third connection path L3 and the second connection path L2, for example, AC 100V, into DC 24V and DC 3.3V. The AC / DC conversion circuit 140 supplies this DC 24V and DC 3.3V to each element in the printer 1. Since a known circuit can be used as the AC / DC conversion circuit 140, the illustration and explanation of its specific circuit configuration are omitted.

[0051] The zero-cross detection circuit 138 is also connected to the third connection path L3 and the second connection path L2. Figure 5 shows an example of the specific circuit configuration of the zero-cross detection circuit 138. As shown in Figure 6, the zero-cross detection circuit 138 switches the zero-cross signal Vout from a high level to a low level and outputs it when the absolute value of the voltage falls below the voltage threshold Vth. As shown in Figure 5, the zero-cross detection circuit 138 is composed of a diode bridge circuit 150 and a signal output circuit 151.

[0052] The diode bridge circuit 150 has four diodes, the first to fourth diodes D1 to D4. The diode bridge circuit 150 is constructed by connecting in parallel a first series-connected diode, which is formed by connecting the cathode of the first diode D1 to the anode of the second diode D2, and a second series-connected diode, which is formed by connecting the cathode of the third diode D3 to the anode of the fourth diode D4. The connection point J1 between the cathode of the first diode D1 and the anode of the second diode D2 is connected to the first connection path L1 via the third connection path L3. The connection point J4 between the cathode of the third diode D3 and the anode of the fourth diode D4 is connected to the second connection path L2 via an unsigned resistor.

[0053] The signal output circuit 151 includes a photocoupler 151A, a transistor 151B, and various unsigned resistors. The input side of the signal output circuit 151 is connected between the connection point J2 between the anode of the second diode D2 and the anode of the fourth diode D4, and the connection point J3 between the cathode of the first diode D1 and the cathode of the third diode D3.

[0054] The AC voltage Vin is full-wave rectified by the diode bridge circuit 150 to obtain the rectified signal Vs. The rectified signal Vs is the signal output by the diode bridge circuit 150 from the AC voltage Vin. The rectified signal Vs is converted into an optical signal by the light-emitting diode of the photocoupler 151A. If the rectified signal Vs is greater than or equal to the voltage threshold Vth, the photodetector of the photocoupler 151A reacts to the optical signal from the light-emitting diode of the photocoupler 151A, and current flows through the photodetector. As current flows through the photocoupler 151A, current no longer flows between the emitter and collector of the transistor 151B, and the zero-crossing signal Vout becomes a high-level voltage. On the other hand, if the rectified signal Vs is less than the voltage threshold Vth, the photodetector of the photocoupler 151A does not react to the optical signal from the light-emitting diode of the photocoupler 151A, and no current flows through the photodetector. As a result, base current flows through transistor 151B, causing current to flow between the emitter and collector of transistor 151B, and the zero-crossing signal Vout becomes a low-level voltage. Since the zero-crossing signal Vout is a pulse signal, it may also be referred to as the zero-crossing pulse signal Vout below.

[0055] The AC switching circuit 134 switches the AC voltage applied to the heater 93 based on commands from the control unit 100. Figure 4 shows an example of a specific circuit configuration of the AC switching circuit 134. As shown in Figure 4, the AC switching circuit 134 consists of a triac 134A, a phototriac coupler 134B, a transistor 134C, and various unsigned resistors. The triac 134A is located in the second connection path L2 and performs the switching operation of the AC voltage Vin applied to the heater 93.

[0056] When the control unit 100 turns on the heat-on signal Sb to the AC switching circuit 134, for example to a high level, the transistor 134C turns on, igniting the triac 134A via the phototriac coupler 134B and performing the required switching operation. On the other hand, when the control unit 100 turns off the heat-on signal Sb to the AC switching circuit 134, for example to a low level, the transistor 134C turns off, stopping the operation of the phototriac coupler 134B. As a result, the ignition of the triac 134A via the phototriac coupler 134B stops, and the required switching operation stops. In this case, the control unit 100 performs this control based on the temperature information of the heater 93 detected by the fixing temperature sensor TH2 and the output signal voltage Vout of the zero-cross detection circuit 138. Note that a known circuit is used as the AC switching circuit 134, so a detailed explanation of its operation is omitted.

[0057] Figure 6 shows the waveforms of the rectified signal Vs from the diode bridge circuit 150 ((b)) and the zero-crossing signal Vout from the zero-crossing detection circuit 138 ((c)) when the relay circuit 133 is ON, with the input voltage Vin being a sine wave ((a)). The horizontal dotted line in the waveform diagram of the rectified signal Vs indicates the threshold voltage Vth at which the photocoupler 151A operates. When the rectified signal Vs is below the threshold voltage Vth from the rising edge of the sine wave, no current flows through the photocoupler 151A, but when the voltage exceeds the threshold voltage Vth, current flows through the photocoupler 151A. As a result, the zero-crossing detection circuit 138 outputs the zero-crossing signal Vout shown in Figure 6(c).

[0058] The power supply board 125 is equipped with first and second input terminals T1 and T2, a relay circuit 133, an AC switching circuit 134, an AC / DC conversion circuit 140, and a zero-crossing detection circuit 138. Furthermore, as shown in Figure 2, the battery 126 is connected to the power supply board 125 via a relay 127. The relay 127 switches the connection between the power supply board 125 and the battery 126 on / off based on a command from the control unit 100. When the connection between the power supply board 125 and the battery 126 is turned on, the battery 126 is charged.

[0059] The control processes performed by printer 1, configured as described above, will be explained in detail below with reference to Figures 7 to 14.

[0060] Figure 7 shows the procedure of the first control process executed by the control unit 100, in particular by the CPU 100A. This first control process is started, for example, when printer 1 starts printing. This first control process describes the control processes to be performed on printer 1 before printing starts, but does not describe the control processes to be performed on printer 1 after printing has started. Hereafter, in the description of each process, steps will be denoted as "S".

[0061] In Figure 7, first the CPU 100A turns on the relay ON signal and the heat ON signal Sb (S10). Then, the CPU 100A determines whether or not it has detected the zero-crossing signal Vout from the zero-crossing detection circuit 138 (S11). Whether or not the zero-crossing signal Vout has been detected can be determined, for example, based on whether or not a high-level voltage and a low-level voltage switch within one cycle. In other words, the CPU 100A determines that it has detected the zero-crossing signal Vout if the high-level voltage and low-level voltage switch within one cycle, and determines that it has not detected the zero-crossing signal Vout if the high-level voltage does not switch to a low-level voltage. If the zero-crossing signal Vout is detected in the determination in S11 (S11: YES), the CPU 100A starts printing (S20) and then terminates the first control process.

[0062] On the other hand, if the zero-crossing signal Vout is not detected in the judgment of S11 (S11:NO), the CPU100A determines that the voltage waveform of the AC voltage Vin has distorted from a sine wave to a square wave or DC wave, that is, that the UPS200 is an abnormal power supply, and executes the abnormal power supply detection process (S12).

[0063] Figure 8 shows the detailed procedure for processing when an abnormal power supply is detected. In Figure 8, the CPU 100A instructs the motor driver MD2 to increase the rotation speed of the main motor 106 compared to normal printing (S30). Next, the CPU 100A increases the rotation speed of the fan motor for the fuser fan 13 compared to normal printing (S31). Furthermore, the CPU 100A instructs the motor driver MD1 to increase the rotation speed of the polygon motor 52 compared to normal printing (S32).

[0064] Then, the CPU 100A notifies the display 104 to open the rear cover 12 (S33) and increases the brightness of the display 104 compared to normal printing (S34). Furthermore, the CPU 100A turns on the relay 127 to charge the battery 126 (S35) and then terminates the abnormal power supply detection process.

[0065] The processes from S30 to S35, with the exception of the process in S33, all correspond to processes that control the image forming unit 4, excluding the heater 93 of the fuser 9, so that it consumes a second power consumption that is greater than the first power consumption that it normally consumes during printing. The process in S33 is to prompt the user to release the excess air inside the housing 2, as the temperature of the air inside the housing 2 rises due to the consumption of the second power consumption by the image forming unit 4, excluding the heater 93.

[0066] Returning to Figure 7, the CPU 100A determines whether the detected current value detected by the current detection circuit 160 is less than or equal to the threshold current (S13). The CPU 100A waits as long as the detected current value > threshold current (S13: NO), and when the detected current value ≤ threshold current (S13: YES), the CPU 100A proceeds to S14. As described above, the current detection circuit 160 detects the current value flowing through the heater 93. On the other hand, in the abnormal power supply detection process, the image forming unit 4, excluding the heater 93, is controlled so that it consumes a second power consumption that is greater than the first power consumption consumed by the image forming unit 4 during normal printing. Therefore, when the abnormal power supply detection process is executed, the current value flowing through the heater 93 should decrease. In the determination in S13, it is determined whether the current value flowing through the heater 93 has reached or below a predetermined threshold current.

[0067] In S14, CPU100A turns off the relay ON signal and the heat ON signal Sb. If the current flowing through heater 93 exceeds the threshold current, turning off the relay ON signal may cause arc discharge at the contact portion 133A2 of relay 133A, potentially leading to welding of the contact portion 133A2. Therefore, by setting the threshold current to a current value where arc discharge is not expected to occur at the contact portion 133A2, the occurrence of arc discharge can be suppressed, thereby preventing welding of the contact portion 133A2. This makes it possible to suppress failures around heater 93 that occur due to waveform distortion in the UPS200, such as a change from a sine wave to a square wave or DC wave.

[0068] Next, CPU 100A displays an error message on display 104 (S15) and puts printer 1 into an error stop state. An example of the error message is a notification that UPS 200 is experiencing a power supply malfunction and prompts the user to disconnect UPS 200 from printer 1 and connect printer 1 directly to the commercial power supply.

[0069] In the abnormal power supply detection process shown in Figure 8, all processes from S30 to S35 are executed to cause the image forming unit 4, excluding the heater 93, to consume a second power consumption. However, it is also possible to extract and execute only some of these processes. In short, it is sufficient that the current flowing to the heater 93 reaches a predetermined threshold current or less after the abnormal power supply detection process has been executed. However, it is not preferable to extract only the process from S33 to constitute the abnormal power supply detection process. This is because the process from S33 does not correspond to the process of controlling the image forming unit 4, excluding the heater 93, so that it consumes a second power consumption that is greater than the first power consumption that the image forming unit 4 of the fuser 9 consumes during normal printing.

[0070] Figure 9 shows a detailed procedure for the first modified version of the abnormal power supply detection process shown in Figure 8. The abnormal power supply detection process in Figure 9 differs from the abnormal power supply detection process in Figure 8 only in the process at S33. Therefore, in Figure 9, processes that are the same as those in Figure 8 are given the same step numbers, and their explanations are omitted as appropriate. The processes in Figures 10 to 14, which will be described later, may also include processes similar to those in the previously described figures. For such processes, the same step numbers are given, and their explanations are omitted as appropriate.

[0071] In Figure 9, the CPU 100A instructs the drive unit to open the rear cover 12 (S33'). The drive unit is not shown, but for example, in Figure 1, it is located near the rear opening 2B of the rear cover 12. Any mechanism can be used for the drive unit, as long as it performs the operation of opening the rear cover 12 in response to an instruction from the printer 1. When the instruction S33' is given, the drive unit opens the rear cover 12. Therefore, compared to notification prompting the opening of the rear cover 12, as in S33 in Figure 8, it is possible to eliminate the possibility of the user forgetting to open the rear cover 12 and to save the user the trouble of opening the rear cover 12.

[0072] Figure 10 shows a detailed procedure for a second modified version of the abnormal power supply detection process shown in Figure 8. In the abnormal power supply detection process in Figure 8, the rotation speed of the main motor 106 is increased compared to normal printing without transporting the sheet S. In contrast, the abnormal power supply detection process in Figure 10 differs in that the sheet S is transported while the rotation speed of the main motor 106 is increased compared to normal printing.

[0073] In Figure 10, the CPU 100A increases the rotational speed of the main motor 106 compared to normal printing (S30), and then executes a pickup command (S40). As a result, the CPU 100A turns on an electromagnetic clutch (not shown) that transmits the driving force of the main motor 106 to the pickup roller 33. Consequently, the sheet S in the supply tray 31, which has been pushed upward by the sheet pressing plate 32, is picked up by the pickup roller 33 and begins to be transported toward the first transport path 25.

[0074] Next, the CPU 100A determines whether the sheet S has been discharged from the first transport path 25 onto the discharge tray 22 (S41). If it is determined that the sheet S has not been discharged onto the discharge tray 22 (S41: NO), the CPU 100A waits until it is discharged. On the other hand, if it is determined that the sheet S has been discharged onto the discharge tray 22 (S41: YES), the CPU 100A terminates the abnormal power supply detection process. The determination in S41 can be made, for example, based on whether a predetermined time has elapsed since the post-register sensor SE3 detected the rear end of the sheet S, that is, the time obtained by dividing the distance on the first transport path 25 from when the rear end of the sheet S passes the post-register sensor SE3 until it passes the downstream end of the first transport path 25 by the transport speed, plus a predetermined buffer time. Alternatively, if a sensor such as a discharge sensor is provided on the first transport path 25 downstream of the post-register sensor SE3, the determination can be made based on the output of that sensor.

[0075] Thus, in the abnormal power supply detection process shown in Figure 10, the process in S30 causes the image forming unit 4, excluding the heater 93, to consume the second power, and the processes in S40 and S41 cause the temperature rise of the air inside the housing 2 to escape to the outside of the housing 2 via the sheet S.

[0076] If the abnormal power supply detection process shown in Figure 10 is not executed once and the detected current value does not become ≤ threshold current, then the process should be repeated multiple times.

[0077] Figure 11 shows a detailed procedure for a third modified example of the abnormal power supply detection process shown in Figure 8. In the abnormal power supply detection process in Figure 10, one sheet S is picked up from the supply tray 31, transported along the first transport path 25, and discharged onto the discharge tray 22. In contrast, the abnormal power supply detection process in Figure 11 differs in that the one sheet S picked up from the supply tray 31 is transported along the first transport path 25, then transported along the third transport path 27 for double-sided printing from a switchback position along the way, and then transported again along the first transport path 25 and discharged onto the supply tray 31.

[0078] In Figure 11, the CPU 100A waits until the sheet S reaches the switchback position (S42: NO). When the sheet S reaches the switchback position (S42: YES), the CPU 100A reverses the drive of the main motor 106 (S43). At this time, the CPU 100A also increases the rotational speed of the main motor 106 compared to normal printing. The decision in S42 can be made in the same way as the decision in S41 in Figure 10, for example, based on whether a predetermined time has elapsed since the post-register sensor SE3 detected the rear end of the sheet S, that is, the time obtained by dividing the distance on the first transport path 25 from when the rear end of the sheet S passes the post-register sensor SE3 until it reaches the switchback position of the first transport path 25 by the transport speed, plus a predetermined buffer time. It goes without saying that the predetermined time used in the decision in S42 is different from the predetermined time used in the decision in S41.

[0079] Then, the CPU 100A waits until sheet S is ejected (S41: NO), and once sheet S is ejected (S41: YES), the CPU 100A terminates the abnormal power supply detection process.

[0080] As described above, in the abnormal power supply detection process shown in Figure 11, the process in S30 causes the image forming unit 4, excluding the heater 93, to consume the second power, and the processes in S40 to S43 allow the temperature rise of the air inside the housing 2 to escape to the outside of the housing 2 via the sheet S. Furthermore, in the abnormal power supply detection process shown in Figure 11, the distance that a single sheet S is transported from the time it is picked up until it is discharged to the discharge tray 22 is longer compared to the abnormal power supply detection process shown in Figure 10. As a result, if the detected current value ≤ threshold current is not met after executing the abnormal power supply detection process only once, the number of times the abnormal power supply detection process shown in Figure 11 is repeated can be reduced compared to the number of times the abnormal power supply detection process shown in Figure 10 is repeated, and the transport of unnecessary sheets S can be reduced.

[0081] In the abnormal power supply detection process shown in Figure 11, the sheet S is placed with its front and back surfaces facing upwards and transported along the first transport path 25 once at a time. However, it is also possible to transport the sheet along the first transport path 25 multiple times or more.

[0082] Figure 12 shows a detailed procedure for the fourth modified version of the abnormal power supply detection process shown in Figure 8. In the abnormal power supply detection process in Figure 10, the sheet S is transported along the first transport path 25, but no image is formed on the sheet S. In contrast, the abnormal power supply detection process in Figure 12 differs in that, in addition to transporting the sheet S, an image is formed on the sheet S using solid black.

[0083] In Figure 12, the CPU 100A picks up the sheet S in S40 and starts forming a solid black image on the sheet S being transported along the first transport path 25 (S45). Alternatively, instead of forming a solid black image, a solid color of another color may be used. Furthermore, similar to the abnormal power supply detection process in Figure 11, the sheet S may be transported along the third transport path 27 for double-sided printing, and a solid image may be formed on both sides of the sheet S.

[0084] Thus, in the abnormal power supply detection process shown in Figure 12, the process in S30 causes the image forming unit 4, excluding the heater 93, to consume a second power, and the processes in S40 and S41 allow the temperature rise of the air inside the housing 2 to escape to the outside of the housing 2. Furthermore, since the process in S45 uses the charger 62, exposure unit 5, transfer unit 8, and developing unit, the second power consumption consumed by the image forming unit 4, excluding the heater 93, when the abnormal power supply detection process shown in Figure 10 is executed is greater than the second power consumption consumed by the image forming unit 4, excluding the heater 93, when the abnormal power supply detection process shown in Figure 12 is executed.

[0085] Figure 13 shows a detailed procedure for the fifth modified example of the abnormal power supply detection process shown in Figure 8. The abnormal power supply detection process in Figure 13 uses a different method from the abnormal power supply detection process in Figure 8, but similar to the abnormal power supply detection process in Figure 8, it does not transport the sheet S and causes the image forming unit 4, excluding the heater 93, to consume the second power.

[0086] In Figure 13, the CPU 100A starts the operation of the charger 62, exposure unit 5, transfer unit 8, and developing unit (S50-S53). Each operation may be the same as the operation during normal printing.

[0087] Next, CPU 100A starts the operation of drum cleaner 63 (S54) and belt cleaner 16 (S55), and then terminates the abnormal power supply detection process.

[0088] In this abnormal power supply detection process, all of the processes from S50 to S55 are executed to cause the image forming unit 4, excluding the heater 93, to consume the second power. However, it is also possible to select and execute only some of these processes. In short, it is sufficient that the current flowing to the heater 93 reaches below a predetermined threshold current after the abnormal power supply detection process is executed.

[0089] Figure 14 shows the procedure of the second control process executed by the control unit 100, in particular by the CPU 100A. This second control process is a modified version of the first control process. Therefore, the CPU 100A only needs to execute either the first or the second control process.

[0090] In the first control process, after executing the abnormal power supply detection process in S12, in S13, the system waits until the detected current value becomes ≤ threshold current, and then the relay ON signal is turned off to turn off the relay circuit 133. In contrast, the second control process differs in that it uses a timer to measure the elapsed time after the abnormal power supply detection process is executed, and when a predetermined time has elapsed or more, the relay ON signal is turned off to turn off the relay circuit 133.

[0091] In Figure 14, the CPU 100A starts the timer (S17) if it does not detect a zero-crossing signal Vout from the zero-crossing detection circuit 138 (S11: NO). The timer can be a so-called software timer, for example, which increments an unshown timer area allocated on RAM 100C at predetermined time intervals. Of course, the timer can also be configured using hardware.

[0092] Next, CPU 100A executes the abnormal power supply detection process (S12). This abnormal power supply detection process can be any one of the abnormal power supply detection processes shown in Figures 8 to 13 above.

[0093] Then, CPU 100A waits until the timer has measured a predetermined time (S18:NO), and once the predetermined time has been measured (S18:YES), it proceeds to process S14. Processes S14 and the subsequent S15 have been described above, so they will not be explained again here.

[0094] When the CPU 100A executes the abnormal power supply detection process in S12, the image forming unit 4, excluding the heater 93, consumes a second power consumption that is greater than the first power consumption consumed during normal printing. Therefore, after a predetermined time has elapsed, the current flowing to the heater 93 should be below a predetermined threshold current. Consequently, even if the current flowing to the heater 93 is not actually detected by the current detection circuit 160, there is little risk of the contact portion 133A2 welding together after a predetermined time has elapsed following the execution of the abnormal power supply detection process, even if the relay circuit 133 is turned off. Thus, since the current detection circuit 160 is not used in the second control process, the current detection circuit 160 can be omitted.

[0095] As described above, the printer 1 of this embodiment includes a heater 93, an image forming unit 4 excluding the heater 93 that consumes power to form an image on the sheet S, a first connection path L1 that connects one power terminal of the UPS 200 to one end H1 of the heater 93 and supplies power to the heater 93, a second connection path L2 that connects the other power terminal of the UPS 200 to the other end H2 of the heater 93 and supplies power to the heater 93, a zero-cross detection circuit 138 connected to the third connection path L3 and the second connection path L2 and generating a zero-cross signal, and one power terminal and the first connection path L1 and zero-cross The system includes a relay circuit 133 provided between the connection point with the loss detection circuit 138 to turn the power supply from the UPS 200 on / off, an AC switching circuit 134 provided between the connection point between the second connection path L2 and the zero-cross detection circuit 138 and the other end H2 of the heater 93 to switch the supply / cutoff of power to the heater 93, an AC / DC conversion circuit 140 connected to the third connection path L1 and the second connection path L2 to convert the UPS 200 into a DC power supply, a power supply board 125 including the AC / DC conversion circuit 140 that supplies DC power to the image forming unit 4 excluding the heater 93, and a control unit 100.

[0096] Furthermore, the control unit 100 controls the image forming unit 4, excluding the heater 93, to consume a second power consumption greater than the first power consumption consumed by the image forming unit 4 during normal printing, in the event of an abnormality where the zero-crossing detection circuit 138 does not generate a zero-crossing signal while the relay circuit 133 is turned on.

[0097] Thus, in the printer 1 of this embodiment, when the relay circuit 133 is turned on and the zero-crossing detection circuit 138 does not generate a zero-crossing signal, the image forming unit 4, excluding the heater 93, is controlled to consume a second power consumption that is greater than the first power consumption consumed by the image forming unit 4 during normal printing. This makes it possible to suppress failures around the heater 93 that occur due to waveform distortion of the UPS 200 waveform from a sine wave to a square wave or DC waveform.

[0098] Furthermore, the printer 1 is equipped with a current detection circuit 160 that detects the current value flowing through the heater 93, and the control unit 100 is characterized in that, when the current detection circuit 160 detects that the current value flowing through the heater 93 has fallen below a predetermined current value (S13: YES), it turns off the relay circuit 133 (S14). As a result, the relay circuit 133 is turned off when the current value flowing through the heater 93 has decreased sufficiently, so that welding of the contact portion 133A2 of the relay 133A of the relay circuit 133 can be suppressed.

[0099] Furthermore, the printer 1 is equipped with a timer, and the control unit 100 starts timing using the timer when the image forming unit 4, excluding the heater 93, starts control to consume the second power, and turns off the relay circuit 133 when the timer timing reaches a predetermined time. As a result, the relay circuit 133 is turned off when the current flowing to the heater 93 has decreased sufficiently, so that the contact portion 133A2 of the relay 133A of the relay circuit 133 is prevented from welding.

[0100] Furthermore, the image forming unit 4, excluding the heater 93, includes at least one of the following: a main motor for driving the sheet transport mechanism, a fan motor for exhausting air from inside the printer 1 to the outside of the printer 1, and a polygon mirror motor for rotating the polygon mirror included in the exposure unit. The control unit 100 controls the image forming unit 4, excluding the heater 93, to consume a second power consumption by increasing the rotation speed of the motors 52 and 106 included in the image forming unit 4, excluding the heater 93, compared to normal printing. This ensures that even if the UPS 200 becomes an abnormal power supply, the current flowing to the heater 93 can be sufficiently reduced. This makes it possible to suppress failures around the heater 93 that occur when the waveform of the UPS 200 changes from a sine wave to a square wave or DC waveform.

[0101] Furthermore, the printer 1 further comprises a housing 2 that forms the exterior of the printer 1 and houses the heater 93 and the image forming unit 4, the housing having an opening formed near the heater 93 and a cover provided to open and close the opening, and a display 104. The image forming unit 4, excluding the heater 93, has a fan motor for expelling air from inside the housing 2 to the outside of the housing 2. The control unit 100, in the event of an abnormality, increases the rotation speed of the fan motor compared to normal printing so that the image forming unit 4, excluding the heater 93, consumes a second power, and also provides a notification on the display 104 prompting the opening of the rear cover 12. This ensures that even if the UPS 200 becomes an abnormal power source, the current flowing to the heater 93 can be sufficiently reduced. In addition, since the display 104 provides a notification prompting the opening of the rear cover 12, if the user opens the rear cover 12 in accordance with this notification, the temperature rise of the air inside the housing 2 can be suppressed.

[0102] Furthermore, the power for the display 104 is supplied from the power supply board 125, and the control unit 100 increases the brightness of the display 104 in the event of an abnormality, compared to normal printing. This further reduces the current flowing to the heater 93 when the UPS 200 becomes an abnormal power source.

[0103] Furthermore, the printer 1 further comprises a housing that forms the exterior of the printer 1 and houses the heater 93 and the image forming unit 4, the housing having an opening 2B formed near the heater 93 and a rear cover 12 provided to open and close the opening 2B, and a drive unit that drives the rear cover 12 to open and close, the image forming unit 4 excluding the heater 93 has a fan motor for expelling air from inside the housing 2 to the outside of the housing 2, and the control unit 100, in the event of an abnormality, increases the rotation speed of the fan motor compared to normal printing so that the image forming unit 4 excluding the heater 93 consumes a second power, and opens the rear cover 12 with the drive unit. This makes it possible to sufficiently reduce the current flowing to the heater 93 even if the UPS 200 becomes an abnormal power supply. Furthermore, it is possible to eliminate the possibility of the user forgetting to open the rear cover 12 and to save the user the trouble of opening the rear cover 12.

[0104] Furthermore, the image forming unit 4, excluding the heater 93, has a main motor 106 for driving the transport unit 3, and the control unit 100, in the event of an abnormality, increases the rotational speed of the main motor 106 compared to normal printing, and transports the sheet S by the transport unit 3. This allows the current flowing to the heater 93 to be sufficiently reduced even if the UPS 200 becomes a faulty power source. In addition, the temperature rise of the air inside the housing 2 can be released to the outside of the housing 2 via the sheet S.

[0105] Furthermore, the image forming unit 4, excluding the heater 93, includes a charging unit, an exposure unit, a developing unit, and a transfer unit, and the control unit 100 is characterized in that, in the event of an abnormality, the transport unit 3 and the image forming unit 4 perform solid black printing on the sheet S. This allows the current flowing to the heater 93 to be sufficiently reduced even if the UPS 200 becomes a faulty power supply, and the temperature rise of the air inside the housing 2 can be released to the outside of the housing 2 via the sheet S. Moreover, by performing solid black printing on the sheet S, the current flowing to the heater 93 can be further reduced because the charger 62, exposure unit 5, transfer unit 8, and developing unit are used.

[0106] Furthermore, the transport unit 3 is capable of transporting the sheet S along the third transport path 27, and the control unit 100 is characterized in that, in the event of an abnormality, the transport unit 3 repeatedly transports the sheet S along the third transport path 27. This allows the current flowing to the heater 93 to be sufficiently reduced even if the UPS 200 becomes a faulty power source. In addition, the temperature rise of the air inside the housing 2 can be released to the outside of the housing 2 via the sheet S.

[0107] Furthermore, the image forming unit 4, excluding the heater 93, includes a plurality of chargers 62, an exposure unit 5, a drum unit 6, four developing cartridges 7Y, 7M, 7C, and 7K, a transfer unit 8, a plurality of drum cleaners 63, and a belt cleaner 16. The control unit 100 is characterized in that, in the event of an abnormality, it simultaneously operates each part included in the image forming unit 4, excluding the heater 93. This ensures that even if the UPS 200 becomes a faulty power source, the current flowing to the heater 93 can be sufficiently reduced.

[0108] Furthermore, the printer 1 is equipped with a battery 126 connected to the power supply board 125, and the control unit 100 is characterized in that it charges the battery 126 in the event of an abnormality. This makes it possible to sufficiently reduce the current flowing to the heater 93 even if the UPS 200 becomes a faulty power supply.

[0109] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention.

[0110] (1) In the above embodiment, a halogen heater that utilizes radiant heat was exemplified as the heater 93, but it is not limited to this, and for example, a ceramic heater or carbon heater that utilizes the heat generated by a resistor may also be used. Furthermore, the heater may be placed outside the heating element rather than inside it.

[0111] (2) In the above embodiment, a printer that forms a color image on a sheet was given as an example of an image forming apparatus, but it is not limited to this, and for example, a printer configured to form a monochrome image on a sheet may also be used. Furthermore, the image forming apparatus is not limited to a printer, and for example, a copier equipped with a document reading device such as a flatbed scanner may also be used.

[0112] (3) In the above embodiment, the printer 1 is connected to the UPS 200, and commercial power is supplied to the printer 1 via the UPS 200. However, the printer 1 is not limited to this, and the printer 1 may be connected to the commercial power supply and the commercial power is supplied directly to the printer 1. In this case as well, if the inrush current that flows when power is first supplied to the heater 93 of the fuser 9 becomes excessive, and the sinusoidal waveform of the commercial power supply becomes distorted and outputs a square waveform or a DC waveform, the method of this embodiment can be applied in the same way.

[0113] (4) In the above embodiment, as explained with reference to Figure 3, only one relay circuit 133 is placed on the first connection path L1. However, it is not limited to this, and it may also be placed on the second connection path L2. In addition to the relay circuit 133, another relay circuit 330 having the same circuit configuration may be placed on the second connection path L2. In this case, the other relay circuit 330 should be placed on the second connection path L2 between the connection point of the second input terminal T2 and the zero-cross detection circuit 138 (in the heater control device 130 of Figure 5, the connection point J4 of the diode bridge circuit 150 is connected via a resistor on the second connection path L2).

[0114] (5) In the above embodiment, as described with reference to Figure 3, the AC switching circuit 134 is positioned between the connection point between the second connection path L2 and the zero-crossing detection circuit 138 and the other end H2 of the heater 93. However, it is not limited to this, and may also be positioned between the connection point between the first connection path L1 and the zero-crossing detection circuit 138 and one end H1 of the heater 93.

[0115] (6) In the above embodiment, as described with reference to Figure 3, the AC / DC conversion circuit 140 is connected to the third connection path L3 and the second connection path L2. That is, one terminal of the AC / DC conversion circuit 140 is connected to the first input terminal T1 with the relay circuit 133 in between. However, the embodiment is not limited to this, and one terminal of the AC / DC conversion circuit 140 may also be connected directly to the first input terminal T1 without the relay circuit 133 in between, similar to the other terminal. [Explanation of Symbols]

[0116] 1...Color laser printer, 2...Housing, 2B...Rear opening, 3...Transport unit, 4...Image forming unit, 5...Exposure unit, 8...Transfer unit, 9...Fuser, 12...Rear cover, 13...Fuser fan, 16...Belt cleaner, 22...Discharge tray, 25...First transport path, 26...Second transport path, 27...Third transport path, 31...Supply tray, 33...Pickup roller, 52...Polygon motor, 62...Charger, 61...Photoconductor drum, 63...Drum cleaner, 63a...Drum cleaning roller, 71...Developing roller, 83...Transport belt, 91...Heating roller, 93...Heater, 100...Control unit, 100A...CPU, 100B...ROM, 100C...RAM 100D...NVRAM, 104...Display, 106...Main motor, 110...I / F group, 111...Sensor group, 120...Roller group, 125...Power supply board, 126...Battery, 127...Relay, 130...Heater control device, 133,330...Relay circuit, 133A...Relay, 133A2...Contact part, 134...AC switching circuit, 138...Zero crossing detection circuit, 140...AC / DC conversion circuit, 160...Current detection circuit, 200...UPS, H1...One end, H2...Other end, L1...First connection path, L2...Second connection path, L3...Third connection path, MD1,MD2...Motor driver, S...Sheet, SE3...Post-register sensor, TH2...Fusing temperature sensor.

Claims

1. Heater and, An image forming unit, excluding the heater, which consumes power to form an image on a sheet, A first power line for supplying power to the heater by connecting one power terminal of the AC power supply to one end of the heater, A second power line connects the other power terminal of the aforementioned AC power supply to the other end of the heater and supplies power to the heater, A zero-cross signal generation unit connected to the first power line and the second power line, which generates a zero-cross signal, A relay circuit is provided in at least one of the following locations: between one of the power terminals and the connection point between the first power line and the zero-cross signal generation unit, and between the other power terminal and the connection point between the second power line and the zero-cross signal generation unit, to turn the power supply from the AC power source on / off. An AC switching circuit is provided between the connection point between the first power line and the zero-cross signal generation unit and one end of the heater, or between the connection point between the second power line and the zero-cross signal generation unit and the other end of the heater, for switching the supply / cutoff of power to the heater. An AC / DC conversion circuit connected to the first power line and the second power line, which converts the AC power to a DC power, A power supply board that includes the AC / DC conversion circuit and supplies the DC power to the image forming section excluding the heater, Control unit and Equipped with, The control unit, When the relay circuit is turned on, if the zero-crossing signal generation unit is not generating the zero-crossing signal, the image forming unit, excluding the heater, is controlled to consume a second power consumption greater than the first power consumption consumed by the image forming unit during normal printing. An image forming apparatus characterized by the following features.

2. The image forming apparatus further, A current detection circuit for detecting the current value flowing through the heater, Equipped with, The control unit, If the current detection circuit detects that the current flowing to the heater has fallen below a predetermined value, the relay circuit is turned off. The image forming apparatus according to feature 1.

3. The image forming apparatus further, Timer, Equipped with, The control unit, The timer starts timing when the image forming unit, excluding the heater, begins the control that consumes the second power consumption. The relay circuit is turned off when the timer reaches a predetermined time. The image forming apparatus according to feature 1.

4. The image forming unit, excluding the heater, includes at least one of the following: a main motor for driving the sheet transport mechanism, a fan motor for discharging air from inside the image forming apparatus to the outside of the image forming apparatus, and a polygon mirror motor for rotating the polygon mirror included in the exposure unit. The control unit, In the event of the aforementioned abnormality, the rotational speed of the motor included in the image forming unit, excluding the heater, is increased compared to that during normal printing, thereby controlling the image forming unit, excluding the heater, to consume the second power consumption. The image forming apparatus according to feature 1.

5. The image forming apparatus further, A housing that forms the exterior of the image forming apparatus and houses the heater and the image forming unit, the housing having an opening formed near the heater and a cover provided to open and close the opening, The display and Equipped with, The image forming unit, excluding the heater, has a fan motor for discharging air from inside the housing to the outside of the housing. The control unit, In the event of the aforementioned abnormality, the rotation speed of the fan motor is increased compared to that during normal printing, thereby controlling the image forming unit (excluding the heater) to consume the second power, and a notification prompting the opening of the cover is displayed on the display. The image forming apparatus according to feature 1.

6. The power for the display is supplied from the power supply board. The control unit, In the event of the aforementioned abnormality, the brightness of the display is increased compared to that during normal printing. The image forming apparatus according to feature 5.

7. The image forming apparatus further, A housing that forms the exterior of the image forming apparatus and houses the heater and the image forming unit, the housing having an opening formed near the heater and a cover provided to open and close the opening, A drive unit for opening and closing the cover, Equipped with, The image forming unit, excluding the heater, has a fan motor for discharging air from inside the housing to the outside of the housing. The control unit, In the event of the aforementioned abnormality, the rotation speed of the fan motor is increased compared to that during normal printing, thereby controlling the image forming unit, excluding the heater, to consume the second power, and the cover is opened by the drive unit. The image forming apparatus according to feature 1.

8. The image forming unit, excluding the heater, has a main motor for driving the sheet transport mechanism. The control unit, In the event of the aforementioned abnormality, the sheet transport mechanism transports the sheet while increasing the rotational speed of the main motor compared to that during normal printing. The image forming apparatus according to feature 1.

9. The image forming unit, excluding the heater, includes a charging unit, an exposure unit, a developing unit, and a transfer unit. The control unit, In the event of the aforementioned abnormality, the sheet transport mechanism and the image forming unit perform solid black printing on the sheet. The image forming apparatus according to feature 8.

10. The sheet transport mechanism is capable of transporting the sheet along a transport path for double-sided printing. The control unit, In the event of the aforementioned abnormality, the sheet transport mechanism repeatedly transports the sheet along the transport path for double-sided printing. The image forming apparatus according to feature 8.

11. The image forming unit, excluding the heater, includes a plurality of charging units, a plurality of exposure units, a plurality of developing units, a plurality of transfer units, a plurality of drum cleaning units, and a belt cleaning unit. The control unit, In the event of the aforementioned abnormality, the parts included in the image forming unit, excluding the heater, are operated simultaneously. The image forming apparatus according to feature 1.

12. The image forming apparatus further, The battery connected to the aforementioned power supply board, Equipped with, The control unit, In the event of the aforementioned abnormality, the battery is charged. The image forming apparatus according to feature 1.

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