Image forming device

Abstract

To reduce capacity of a power supply device connected with an image forming apparatus.SOLUTION: An image forming apparatus comprises: one or more main heaters 34; one or more sub heaters 35; a fixing unit that is heated by the one or more main heaters 34 and the one or more sub heaters 35 to fix a developer image transferred to a medium to the medium; a temperature detection sensor 32 that detects a temperature of the fixing unit; a main heater on / off circuit 140 that turns on or off energization to the one or more main heaters 34; a sub heater on / off circuit 150 that turns on / off the energization to the one or more second heaters; and a control unit 60 that, when receiving a print instruction, if the temperature detected by the temperature detection sensor 32 is lower than a predetermined temperature, controls the main heater on / off circuit 140 and the sub heater on / off circuit 150 to shift timing to turn on the one or more main heaters 34 and timing to turn on the one or more sub heaters 35 from each other.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to an image forming apparatus. [Background technology]

[0002] In a conventional image forming apparatus, the capacity of a smoothing capacitor in an internal power supply is increased in order to supply voltage to each unit of the image forming apparatus in the event of a power outage (see, for example, Patent Document 1).

[0003] In recent years, it has also become common to connect an uninterruptible power supply (UPS) to an AC (Alternating Current) input section of an image forming apparatus to ensure power supply to the image forming apparatus even in the event of a power outage. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-24445 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, when a UPS is connected to an image forming device, the heater inrush current of the image forming device is high, causing the AC voltage of the UPS output to drop, putting the UPS into an overloaded state. This poses the problem that a large-capacity UPS must be used for the image forming device.

[0006] In view of the above, one or more aspects of the present disclosure have an object to make it possible to reduce the capacity of a power supply device connected to an image forming apparatus. [Means for solving the problem]

[0007] An image forming apparatus according to a first aspect of the present disclosure is an image forming apparatus that forms an image on a medium by transferring a developer image to the medium, and includes one or more first heaters, one or more second heaters, a fixing unit that fixes the developer image transferred to the medium to the medium by heating with the one or more first heaters and the one or more second heaters, a temperature detection unit that detects a temperature of the fixing unit, a first heater driving unit that turns on or off the supply of electricity to the one or more first heaters, and a second heater driving unit that turns on or off the supply of electricity to the one or more second heaters, and when an instruction to form the image on the medium is received, if the temperature detected by the temperature detection unit is lower than a predetermined temperature, by causing the first heater driving unit to turn on the one or more first heaters, and causing the second heater driving unit to turn on the one or more second heaters after the temperature detected by the temperature detection unit has reached the predetermined temperature, The heating device further comprises a control unit that shifts a timing at which the one or more first heaters are turned on from a timing at which the one or more second heaters are turned on.

[0008] An image forming apparatus according to a second aspect of the present disclosure is an image forming apparatus that forms an image on a medium by transferring a developer image onto the medium, the image forming apparatus including one or more first heaters that receive power from a commercial power source, store it, and receive power from the commercial power source or the uninterruptible power source via an uninterruptible power source that supplies the stored power in the event of a power outage of the commercial power source, one or more second heaters that receive power from the commercial power source or the uninterruptible power source via the uninterruptible power source, a fixing unit that fixes the developer image transferred to the medium to the medium by being heated by the one or more first heaters and the one or more second heaters, and the one or more second heaters is turned on or off; and if the temperature detected by the temperature detection unit is lower than a predetermined temperature when an instruction to form an image on the medium is received after receiving a notification from the uninterruptible power supply indicating a power outage, a control unit controls the first heater driving unit and the second heater driving unit to shift the timing of turning on the one or more first heaters and the timing of turning on the one or more second heaters.

[0009] An image forming apparatus according to a third aspect of the present disclosure is an image forming apparatus that forms an image on a medium by transferring a developer image onto the medium, the image forming apparatus including one or more first heaters that receive power from a commercial power source, store it, and receive power from the commercial power source or the uninterruptible power source via an uninterruptible power source that supplies the stored power in the event of a power outage of the commercial power source, one or more second heaters that receive power from the commercial power source or the uninterruptible power source via the uninterruptible power source, a fixing unit that fixes the developer image transferred to the medium to the medium by being heated by the one or more first heaters and the one or more second heaters, a temperature detection unit that detects the temperature of the fixing unit, and one or more second heaters that detect the temperature of the fixing unit. the one or more second heaters is turned on or off; and a control unit that, when a temperature detected by the temperature detection unit is lower than a predetermined temperature upon receiving an instruction to form the image on the medium after receiving a notification from the uninterruptible power supply indicating a power outage, controls the first heater driving unit and the second heater driving unit to turn off the one or more first heaters and the one or more second heaters for a predetermined period, and then shifts the timing of turning on the one or more first heaters and the timing of turning on the one or more second heaters. Effect of the Invention

[0010] According to one or more aspects of the present disclosure, it is possible to reduce the capacity of a power supply device connected to an image forming apparatus. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to first to third embodiments. [Diagram 2] 2 is a block diagram illustrating a power supply circuit and a control unit of the image forming apparatus according to the first embodiment. FIG. [Diagram 3] FIG. 2 is a circuit diagram of a power supply circuit. [Figure 4]1A to 1F are time charts illustrating the operation of the image forming apparatus according to the first embodiment. [Diagram 5] 11(A) to 11(F) are time charts for explaining operations assumed for comparison with the first embodiment. [Figure 6] FIG. 11 is a block diagram illustrating a power supply circuit and a control unit of an image forming apparatus according to second and third embodiments. [Figure 7] 13A to 13G are time charts illustrating the operation of the image forming apparatus according to the second embodiment. [Figure 8] 13A to 13G are time charts illustrating the operation of the image forming apparatus according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Embodiment 1 FIG. 1 is a cross-sectional view that illustrates a schematic configuration of an image forming apparatus 100 according to the first embodiment. The image forming apparatus 100 generally includes a paper feed section 1, an image forming section 2, a fixing device 3, and a discharge section 4. The image forming apparatus 100 forms an image on a medium, such as paper, by transferring a toner image, which serves as a developer image, onto the medium.

[0013] The paper feed unit 1 is a medium supply unit for supplying paper as a medium to the image forming unit 2. The paper feed section 1 includes a paper cassette 10, a pickup roller 11, a pair of conveying rollers 12a and 12b, and a pair of registration rollers 13a and 13b.

[0014] The paper cassette 10 is a medium storage unit that stores paper. The pickup roller 11 picks up a sheet of paper from the paper cassette 10 .

[0015] The pair of conveying rollers 12 a and 12 b conveys the sheet of paper picked up by the pickup roller 11 . The pair of registration rollers 13 a and 13 b regulates the skew of the sheet of paper conveyed by the pair of conveying rollers 12 a and 12 b , and sends the sheet of paper to the image forming unit 2 .

[0016] The image forming section 2 forms a toner image, as a developer image, on a sheet of paper that has been conveyed thereto. The image forming section 2 includes ID (Image Drum) units 20K, 20Y, 20M and 20C, exposure sections 25K, 25Y, 25M and 25C, a transfer belt 26, a drive roller 27, a driven roller 28, and transfer rollers 29K, 29Y, 29M and 29C.

[0017] The four ID units 20K, 20Y, 20M, and 20C have the same configuration except for the toner colors used, so only the ID unit 20K will be described here. 1, the capital letter K at the end of the reference numerals indicates black, the capital letter Y indicates yellow, the capital letter M indicates magenta, and the capital letter C indicates cyan. In the following description, the capital letters may be omitted as appropriate when there is no need to indicate a particular color.

[0018] The ID unit 20K includes an image carrier 21K as an ID, a charging roller 22K as a charging section, a developing roller 23K as a developing section, and a supply roller 24K as a supply section.

[0019] The image carrier 21K is a photosensitive drum having a photosensitive layer formed on the outer circumferential surface. The charging roller 22K uniformly charges the surface of the image carrier 21K with a high voltage. An electrostatic latent image is formed on the charged surface of the image carrier 21K by the exposure section 25K.

[0020] The developing roller 23K adheres toner as a developer to the electrostatic latent image formed on the surface of the image carrier 21K, thereby forming a toner image as a developer image. The supply roller 24K supplies toner to the developing roller 23K.

[0021] The exposure unit 25 exposes the image carrier 21 to light, thereby forming an electrostatic latent image on the surface of the image carrier 21. Here, an LED head in which LEDs (Light Emitting Diodes) are arranged is used as the exposure unit 25, but the exposure unit 25 is not limited to this example. The transfer belt 26 is formed in an endless shape and transports one sheet of paper.

[0022] The transfer belt 26 is stretched across the drive roller 27 and the driven roller 28, and as the drive roller 27 rotates, the rotational force of the drive roller 27 is supplied to the driven roller 28 via the transfer belt 26, causing the driven roller 28 to rotate in the same direction as the drive roller 27. As the drive roller 27 and the driven roller 28 rotate, a sheet of paper placed on the transfer belt 26 is transported to the position where the ID unit 20 is disposed.

[0023] The transfer roller 29 is a transfer section that transfers the toner image formed on the image carrier 21 onto a sheet of paper conveyed by the transfer belt 26 . Then, the sheet of paper onto which the toner image has been transferred is sent to a fixing device 3.

[0024] The fixing device 3 fixes the toner image transferred onto the sheet of paper onto the sheet of paper. The fixing device 3 includes a fixing roller 30 , a heating section 31 , a temperature detection sensor 32 , and a backup roller 33 .

[0025] The fixing roller 30 is a fixing section that fixes the toner image transferred onto a sheet of paper onto the sheet of paper by being heated by a heating section 31 that is a heat source. The heating unit 31 is a heat source represented by a halogen lamp or a ceramic heater, and in this embodiment, is composed of a plurality of heaters. Here, the heating unit 31 is composed of a main heater and a sub-heater. Details will be described later.

[0026] The temperature detection sensor 32 is a temperature detection unit that detects the temperature of the fixing roller 30. Here, the temperature detection sensor 32 detects the temperature of the surface of the fixing roller 30. For example, a thermistor is used as the temperature detection sensor 32. Based on the temperature detected by the temperature detection sensor 32, the heating unit 31 is controlled so that the fixing roller 30 is at a predetermined temperature. Then, the toner image transferred to a sheet of paper is melted by the heated fixing roller 30.

[0027] The backup roller 33 presses the sheet of paper toward the fixing roller 30, pressing the molten toner image onto the sheet of paper, and fixing the toner image onto the sheet of paper. The sheet of paper is then sent to the discharge section 4.

[0028] The discharge unit 4 discharges the sheet of paper on which the toner image is fixed to the outside of the image forming apparatus 100. For example, the discharge unit 4 includes a pair of discharge rollers 40a and 40b for discharging the sheet of paper to the outside of the image forming apparatus 100.

[0029] FIG. 2 is a block diagram that illustrates the power supply circuit 110 and the control unit 60 of the image forming apparatus 100. As shown in FIG. The power supply circuit 110 functions as a power supply unit for the image forming apparatus 100 . Further, the heating section 31 of the fixing device 3 includes a main heater 34 as a first heater and a sub-heater 35 as a second heater. In FIG. 2, one main heater 34 and one sub-heater 35 are shown, but a plurality of main heaters 34 or a plurality of sub-heaters 35 may be provided. It is also desirable that the power of the main heater 34 is greater than the power of the sub-heater 35 .

[0030] The power supply circuit 110 includes a rectifier smoothing circuit 113, a DC-DC conversion unit 116, a relay circuit 120, an AC zero cross circuit 130, a main heater on / off circuit 140, a sub-heater on / off circuit 150, a main triac short detection circuit 160, a sub-triac short detection circuit 170, and a relay short detection circuit 180.

[0031] The power supply circuit 110 generally operates on an AC voltage output from a commercial power supply 50, but in this embodiment, a case will be described in which the power supply circuit 110 is connected to a UPS 51 that is an uninterruptible power supply as a power supply device. Here, the UPS 51 is a power supply device that receives power from the commercial power source 50, stores the power, and supplies the stored power when a power outage occurs in the commercial power source 50. Therefore, the main heater 34 and the sub-heater 35 receive power from the commercial power source 50 via the UPS 51 when there is no power outage, and from the UPS 51 when there is a power outage.

[0032] The rectifying and smoothing circuit 113 rectifies and smoothes the AC voltage to generate a DC (Direct Current) voltage. The DC-DC conversion unit 116 converts the DC voltage from the rectifying and smoothing circuit 113 into a desired voltage, and supplies the converted DC to the control unit 60. For example, the DC-DC conversion unit 116 supplies DC 24 V to the actuator system and DC 5 V to the logic system.

[0033] Although the power supply circuit 110 converts the voltage to DC 24V or DC 5V here, the control unit 60 may convert the voltage. Furthermore, the type of DC voltage output from the power supply circuit 110 is generally determined by the configuration of the control unit 60. In addition to DC 24V and DC 5V, a DC 3.3V output is also common.

[0034] The relay circuit 120 is connected to the output of the UPS 51 that is connected to the LINE side of the commercial power supply 50, and is a circuit that turns a relay on or off in response to a relay on / off control signal S1 output from the control unit 60.

[0035] The AC zero cross circuit 130 is a circuit connected after the relay circuit 120, and outputs an AC zero cross signal S2 to the control unit 60. The AC zero cross circuit 130 is a circuit used for controlling the on / off of the main heater 34 or the sub-heater 35. For this reason, by connecting the AC zero cross circuit 130 after the relay circuit 120, in the energy saving mode when the main heater 34 and the sub-heater 35 are turned off, the relay circuit 120 is also turned off and the power consumption of the AC zero cross circuit 130 becomes zero, so that low power consumption can be expected. When the AC zero cross circuit 130 is used for another purpose, such as detecting the off state of AC, the AC zero cross circuit 130 may be connected in front of the relay circuit 120.

[0036] The main heater on / off circuit 140 is a first heater driving unit that turns on or off the power supply to the main heater . For example, the main heater on / off circuit 140 is a circuit that is connected to the rear stage of the AC zero-cross circuit 130 and turns the main heater 34 on or off by a main heater on / off control signal S3 output from the control unit 60. In this embodiment, the main heater on / off circuit 140 is connected to the neutral side of the commercial power supply 50, but the main heater on / off circuit 140 may be connected to either the LINE side or the neutral side. When the main heater on / off circuit 140 is connected to the LINE side, the relay circuit 120 is connected to the neutral side, and when the main heater on / off circuit 140 is connected to the neutral side, the relay circuit 120 is connected to the LINE side.

[0037] The sub-heater on / off circuit 150 is a second heater driving unit that turns on or off the power supply to the sub-heater . For example, the sub-heater on / off circuit 150 is a circuit that is connected to the rear stage of the AC zero-cross circuit 130 and turns the sub-heater 35 on or off by a sub-heater on / off control signal S4 output from the control unit 60. In the present embodiment, the sub-heater on / off circuit 150 is connected to the neutral side of the commercial power supply 50, but the sub-heater on / off circuit 150 may be connected to either the LINE side or the neutral side. When the sub-heater on / off circuit 150 is connected to the LINE side, the relay circuit 120 is connected to the neutral side, and when the sub-heater on / off circuit 150 is connected to the neutral side, the relay circuit 120 is connected to the LINE side.

[0038] The main triac short detection circuit 160 is connected to the rear stage of the main heater on / off circuit 140, and outputs a main triac short detection signal S5 to the control unit 60. The sub-triac short detection circuit 170 is connected to the rear stage of the sub-heater on / off circuit 150, and outputs a sub-triac short detection signal S6 to the control unit 60. The relay short detection circuit 180 is connected to the rear stage of the relay circuit 120, and outputs a relay short detection signal S7 to the control unit 60.

[0039] The control unit 60 controls the processing in the image forming apparatus 100 . For example, when the control unit 60 receives a print instruction, which is an instruction to form an image on a medium, if the temperature detected by the temperature detection sensor 32 is lower than a predetermined temperature, the control unit 60 controls the main heater on / off circuit 140 and the sub-heater on / off circuit 150 to shift the timing at which the main heater 34 is turned on and the timing at which the sub-heater 35 is turned on.

[0040] As described above, the main heater 34 and the sub-heater 35 are halogen heaters, ceramic heaters, or the like, and have the characteristic that their resistance value is low at low temperatures. For this reason, when these heaters are turned on after being off for a long time, the inrush current becomes high. Since the resistance value of a halogen heater is particularly low at low temperatures, the inrush current is particularly high, and when the main heater 34 and the sub-heater 35 are turned on at the same time, the inrush current becomes even higher. Therefore, when the temperature detected by the temperature detection sensor 32 is lower than a predetermined temperature, the control unit 60 shifts the timing for turning on the main heater 34 and the timing for turning on the sub-heater 35 so that they are not turned on at the same time, thereby suppressing the effects of inrush current.

[0041] For example, the control unit 60 can suppress the effects of inrush current by turning on the sub-heater 35 after the current flowing through the main heater 34 has reached a steady state, in other words, after the current has reached a steady state where a stable current flows rather than an inrush current state. For this reason, in the first embodiment, when the temperature detected by the temperature detection sensor 32 reaches a predetermined temperature, it is determined that the current flowing through the main heater 34 has reached a steady state, and the sub-heater 35 is turned on. It is preferable that the predetermined temperature here is a temperature below which an inrush current flows through the main heater 34 and the sub-heater 35. Such a temperature may be determined in advance by experiment or the like. Note that the first embodiment is not limited to this example, and for example, the sub-heater 35 may be turned on when a predetermined period of time has elapsed since the main heater 34 was turned on. The predetermined period here may be a period of time that is sufficient for the current flowing through the main heater 34 to reach a steady state through experiments or the like.

[0042] In addition, when the temperature detected by the temperature detection sensor 32 is equal to or higher than a predetermined temperature, the control unit 60 can quickly bring the temperature of the fixing roller 30 to the set temperature by simultaneously turning on the main heater 34 and the sub-heater 35.

[0043] The control unit 60 includes a CPU 61 , a ROM 62 , a RAM 63 , a temperature acquisition unit 64 , a sensor on / off circuit 65 , a high-voltage power supply 66 , a head control unit 67 , and an actuator driving unit 68 .

[0044] The CPU 61 is a device that performs various processes by executing programs stored in a ROM 62, which is a non-volatile memory that stores programs and data such as setting data, etc. The CPU 61 has a built-in counter for measuring time, etc.

[0045] The RAM 63 is a volatile memory for storing and retrieving data. The temperature acquisition unit 64 divides the output of the temperature detection sensor 32 of the fixing device 3 by resistors, and outputs the divided voltage to the CPU 61 as a temperature detection signal.

[0046] The sensor on / off circuit 65 is composed of transistors, and in the power saving mode, a sensor off signal is output from the CPU 61 to turn off the power supplied to the various sensors 70. The high-voltage power supply 66 is a power supply that applies a high voltage to the image carrier 21 and various rollers of the image forming unit 2 shown in FIG.

[0047] The head control unit 67 is an exposure control unit that controls the on / off of the LED head used as the exposure unit 25 shown in FIG. The actuator driving unit 68 is a dedicated driver that outputs a driving signal to the actuator 71 based on a logic signal output from the CPU 61 .

[0048] The various sensors 70 include paper path sensors (not shown) for detecting paper position arranged in the paper feed section 1, the image forming section 2, the fixing device 3 and the discharge section 4, as well as sensors for correcting image density and color shift.

[0049] The actuator 71 includes motors, clutches, solenoids, cooling fans, etc. (not shown) that are driven by the actuator drive unit 68 and are arranged in the paper feed unit 1, the image forming unit 2, the fixing device 3 and the discharge unit 4.

[0050] FIG. 3 is a circuit diagram of the power supply circuit 110 according to the first embodiment. The power supply circuit 110 includes a protection element 111, a filter 112, a rectifying and smoothing circuit 113, a DC-DC conversion unit 116, a relay circuit 120, an AC zero cross circuit 130, a main heater on / off circuit 140, a sub-heater on / off circuit 150, a main triac short detection circuit 160, a sub-triac short detection circuit 170, and a relay short detection circuit 180.

[0051] The protective element 111 is composed of a fuse for overcurrent protection, a varistor for lightning surge protection, or the like. The filter 112 is generally composed of a common coil or a choke coil, and a capacitor.

[0052] The rectifying and smoothing circuit 113 is composed of a rectifying diode 114 and an electrolytic capacitor 115 . The rectifier diode 114 is made up of four diodes, and generally, an element called a bridge diode containing four elements is often used.

[0053] In order to suppress the inrush current of the electrolytic capacitor 115 when the power is turned on, an inrush suppression circuit (not shown) is provided at the input portion of the power supply circuit 110. As the inrush suppression circuit, a circuit combining a thermistor, a resistor, and a triac which is a switching element, or a relay is used.

[0054] The DC-DC converter 116 converts the direct current voltage. The relay circuit 120 is constituted by a relay 121 and a diode 122 for preventing a back electromotive force of the relay coil, and is turned on or off by a relay on / off control signal S 1 output from the CPU 61 .

[0055] A relay on / off control signal S1 is input to one side of the relay coil, and the other side is connected to GND. Note that the relay 121 may be controlled by two control signals, with the GND connection being the control signal.

[0056] The AC zero cross circuit 130 is a circuit that includes a rectifier diode 131 and a photocoupler 132, and outputs a High level at a zero cross point of the AC voltage to the CPU 61. The above-described configuration of the AC zero cross circuit 130 is an example, and the configuration is not particularly limited.

[0057] The main heater on / off circuit 140 is composed of a main phototriac 141 that is turned on or off by a main heater on / off control signal S3 output from the CPU 61, and a main triac 142 that is a switch unit that is turned on or off when the main phototriac 141 is turned on or off. Here, one side of the photodiode of the main phototriac 141 is connected to GND, but the main phototriac 141 may be controlled by two control signals, with the GND connection being used as a control signal.

[0058] The sub-heater on / off circuit 150 is composed of a sub-phototriac 151 that is turned on or off by a sub-heater on / off control signal S4 output from the CPU 61, and a sub-triac 152 that is a switch unit that is turned on or off when the sub-phototriac 151 is turned on or off.

[0059] One side of the photodiode of the sub-phototriac 151 is connected to GND, but the sub-phototriac 151 may be controlled by two control signals, with the GND connection serving as a control signal.

[0060] The main triac short detection circuit 160 is disposed after the main triac 142 of the main heater on / off circuit 140, and is composed of rectifier diodes 161 and 162 and a photocoupler 163. The main triac short detection circuit 160 outputs a high level to the CPU 61 at the timing of a half wave of the AC voltage.

[0061] The circuit configuration of the main triac short detection circuit 160 may be the same as that of the AC zero cross circuit 130, but in the case of the AC zero cross circuit 130, when a square wave AC voltage is input, the width of the AC zero cross signal S2 becomes narrow, which may make it impossible to detect by the control unit 60. For this reason, detecting the AC half-wave voltage using the main triac short detection circuit 160 makes it possible to more reliably detect the AC wave and square wave AC voltage.

[0062] 3, the anode of rectifier diode 161 is connected to the neutral side of commercial power supply 50, and the cathode of rectifier diode 162 is connected to the LINE side, so that the main triac short detection signal S5 output to control unit 60 is a pulse signal with an AC voltage on the positive side. However, it is also possible to connect the anode of rectifier diode 161 to the LINE side and the cathode of rectifier diode 162 to the neutral side, so that a pulse signal is output with an AC voltage on the negative side.

[0063] The sub-triac short detection circuit 170 is disposed after the sub-triac 152, and is composed of rectifier diodes 171 and 172 and a photocoupler 173. The sub-triac short detection circuit 170 outputs a high level to the CPU 61 at the timing of a half wave of the AC voltage.

[0064] The circuit configuration of the sub-triac short detection circuit 170 may be the same as that of the AC zero-cross circuit 130, but in the case of the AC zero-cross circuit 130, when a square-wave AC voltage is input, the width of the AC zero-cross signal S2 becomes narrow, which may make it impossible to detect by the control unit 60. For this reason, detecting the AC half-wave voltage using the sub-triac short detection circuit 170 makes it possible to more reliably detect the AC wave and square-wave AC voltage.

[0065] 3, the anode of rectifier diode 171 is connected to the neutral side of commercial power supply 50, and the cathode of rectifier diode 172 is connected to the LINE side, so that the triac short detection signal output to control unit 60 is a pulse signal with AC voltage on the positive side. However, it is also possible to connect the anode of rectifier diode 171 to the LINE side and the cathode of rectifier diode 172 to the neutral side, so that a pulse signal is output with AC voltage on the negative side.

[0066] The relay short detection circuit 180 is disposed after the relay 121 of the relay circuit 120, and is composed of rectifier diodes 181 and 182 and a photocoupler 183. The relay short detection circuit 180 outputs a high level to the CPU 61 at the timing of a half wave of the AC voltage.

[0067] In the relay short detection circuit 180 shown in FIG. 3, two rectifier diodes 181 and 182 are mounted in one circuit, but only one rectifier diode may be mounted. Furthermore, the circuit configuration of the relay short detection circuit 180 may be the same as that of the AC zero cross circuit 130, but in the case of the AC zero cross circuit 130, when a square wave AC voltage is input, the width of the AC zero cross signal S2 becomes narrow, and it may become impossible to detect it in the control unit 60. For this reason, detecting the AC half-wave voltage with the relay short detection circuit 180 makes it possible to more reliably detect the AC wave and square wave AC voltage.

[0068] 3, the anode of rectifier diode 181 is connected to the LINE side of commercial power supply 50, and the cathode of rectifier diode 182 is connected to the Neutral side, so that the relay short detection signal S7 output to control unit 60 is a pulse signal with the AC voltage on the negative side. However, the anode of rectifier diode 181 may be connected to the Neutral side, and the cathode of rectifier diode 182 may be connected to the LINE side, so that a pulse signal is output with the AC voltage on the positive side.

[0069] The fixing device 3 includes a main heater 34, typically a halogen heater or a ceramic heater, a sub-heater 35, a temperature detection sensor 32 functioning as a temperature detection unit, typically a thermistor or a thermopile, and a thermostat 36 for protection. When the aforementioned relay 121 and main triac 142 are turned on, voltage is supplied to the main heater 34.

[0070] 4(A) to 4(F) are time charts for explaining the operation of image forming apparatus 100 according to the first embodiment.

[0071] FIG. 4A shows the AC voltage output from commercial power supply 50, that is, the AC voltage input to UPS 51.

[0072] Fig. 4(B) shows the thermistor temperature, which is the temperature detected by temperature detection sensor 32 of fixing device 3. Specifically, Fig. 4(B) shows the temperature obtained by converting the thermistor signal output from temperature detection sensor 32 by control unit 60.

[0073] 4(C) shows the main heater on / off control signal S3 output from the control unit 60 to the main heater on / off circuit 140. The main heater on / off control signal S3 indicates that the main heater 34 is turned on when it is High, and indicates that the main heater 34 is turned off when it is Low.

[0074] 4(D) shows the sub-heater on / off control signal S4 output from the control unit 60 to the sub-heater on / off circuit 150. The sub-heater on / off control signal S4 indicates that the sub-heater 35 is turned on when it is High, and indicates that the sub-heater 35 is turned off when it is Low.

[0075] FIG. 4E shows the heater current, which is the current flowing through the main heater 34 and the sub-heater 35. FIG. 4(F) shows the UPS output voltage, which is the voltage output from the UPS 51.

[0076] Next, FIGS. 4(A) to (F) will be explained according to the time shown on the horizontal axis. First, at time t01, an AC voltage normally output from the commercial power supply 50 is input to the UPS 51 and input to the power supply circuit 110 as a UPS output voltage.

[0077] Power supply circuit 110 rectifies and smoothes the AC voltage in rectifying and smoothing circuit 113, converts it to DC 24V and DC 5V in DC-DC conversion unit 116, and outputs these voltages to control unit 60. This makes image forming apparatus 100 operable. Here, the AC input voltage during normal output is set to voltage V1.

[0078] At time t01, the control unit 60 has not received a print instruction from the host 72, so the main heater on / off control signal S3 is low, the main heater 34 is off, and the sub-heater on / off control signal S4 is low, so the sub-heater 35 is off. If there is no print instruction for a long period of time, the thermistor temperature will be the same as the ambient temperature of the image forming apparatus 100, resulting in a low temperature state. This shows a low temperature state when there is no print instruction for a long period of time. Therefore, the heater current is 0A, and the UPS output voltage is V1, which is the normal output voltage.

[0079] It is assumed that the control unit 60 receives a print instruction from the host 72 at time t02. In this case, when the thermistor temperature is lower than a certain predetermined temperature, the main heater on / off control signal S3 goes high, the main phototriac 141 turns on, and the main triac 142 turns on, supplying an AC voltage to the main heater 34.

[0080] On the other hand, in the first embodiment, at time t02, the sub-heater on / off control signal S4 continues to be low, and the sub phototriac 151 continues to be off. As a result, no AC voltage is supplied to the sub-heater 35, but the thermistor temperature increases due to the main heater 34, and the heater current also increases.

[0081] As described above, the resistance values ​​of the main heater 34 and the sub-heater 35 are low at low temperatures, so that if they are turned on after being off for a long period of time, the inrush current becomes large. For this reason, in the first embodiment, when the thermistor temperature is lower than a certain predetermined temperature, for example, temperature T3, the main heater 34 is turned on and the sub-heater 35 is turned off, thereby suppressing the heater inrush current. For this reason, the relationship is: inrush current of the main heater 34≦heater current I1 of the main heater 34 and the sub-heater 35 during normal operation<inrush current I2 of the main heater 34 and the sub-heater 35. Here, temperature T3 is the temperature below which an inrush current flows through the main heater 34 and the sub-heater 35. At this time, the UPS output voltage is within the rated current of the UPS 51, so that the voltage V1 during normal output can continue.

[0082] At time t03, the thermistor temperature reaches a predetermined temperature T3, the main heater on / off control signal S3 continues to output a high level, and the sub-heater on / off control signal S4 is switched from a low level to a high level by the control unit 60. This turns on the sub-heater 35, and the thermistor temperature continues to rise.

[0083] At time t04, the control unit 60 keeps the main heater on / off control signal S3 at a high output and the sub-heater on / off control signal S4 at a high output, causing the thermistor temperature to continue to rise and reach temperature T2, which is the set temperature. As a result, the main heater on / off control signal S3 goes to a low output, and the sub-heater on / off control signal S4 goes to a low output, causing the heater current to become 0 A. At this time, the UPS output voltage is voltage V1 during normal output. Although not shown, thereafter, the control unit 60 controls the main heater 34 and the sub-heater 35 to turn on and off in order to keep temperature T2, which is the set temperature of the thermistor, constant.

[0084] Next, for comparison with the operation of the power supply circuit 110 shown in FIG. 4, an example will be described in which it is assumed that the control unit 60 turns on the main heater 34 and the sub-heater 35 simultaneously.

[0085] 5(A) to (F) are time charts for explaining operations assumed for comparison with the first embodiment.

[0086] 5(A) to (F) respectively represent the AC voltage, thermistor temperature, main heater on / off control signal S3, sub-heater on / off control signal S4, heater current, and UPS output voltage, similar to FIGS. 4(A) to (F).

[0087] FIGS. 5(A) to (F) will be explained according to the time shown on the horizontal axis. First, at time t11, the AC voltage normally output from the commercial power supply 50 is input to the UPS 51 and input as a UPS output voltage to the power supply circuit 110. The operation at time t11 is similar to the operation at time t01 in FIGS. 4(A) to 4(F).

[0088] It is assumed that the control unit 60 receives a print instruction from the host 72 at time t12. In this case, the control unit 60 turns on both the main heater 34 and the sub-heater 35. Specifically, the main heater on / off control signal S3 goes High, the main phototriac 141 goes on, and the main triac 142 goes on, so that an AC voltage is supplied to the main heater 34. Also, the sub-heater on / off control signal S4 goes High, the sub phototriac 151 goes on, and the sub-triac 152 goes on, so that an AC voltage is supplied to the sub-heater 35. This causes the thermistor temperature to rise. Also, the heater current increases.

[0089] Here, an inrush current flows to both the main heater 34 and the sub heater 35, so that a larger current flows than in the case of Fig. 4(E). Therefore, the heater current I1 during normal operation is smaller than the inrush current I2, exceeding the rated current of the UPS 51, causing the UPS output voltage to drop or become distorted. The UPS output voltage V1 during normal output is set to be larger than the UPS output voltage V2 during an abnormality.

[0090] At time t13, the control unit 60 keeps the main heater on / off control signal S3 at a high level and keeps the sub heater on / off control signal S4 at a high level, causing the thermistor temperature to rise and reach a predetermined temperature T1. At temperature T1, the heater inrush current becomes saturated, the heater current becomes the normal current I1, and the UPS output voltage becomes the normal output voltage V1.

[0091] The operation at time t14 is similar to the operation at time t04 in FIGS.

[0092] As described above, according to the first embodiment, when the AC output of the commercial power source 50 is normal or during a power outage, if the heater temperature of the image forming apparatus 100 is lower than a predetermined temperature, the heater inrush current can be suppressed by controlling to prohibit multiple heaters from being turned on simultaneously. This makes it possible to use the UPS 51 within its rated current, eliminating the need to use a large-capacity UPS and enabling the system to be made more compact.

[0093] Embodiment 2 1, image forming apparatus 200 according to the second embodiment generally includes a paper feed section 1, an image forming section 2, a fixing device 3, and a discharge section 4. In the configuration shown in FIG. 1, image forming apparatus 200 according to the second embodiment is similar to image forming apparatus 100 according to the first embodiment.

[0094] FIG. 6 is a block diagram that illustrates a power supply circuit 110 and a control unit 80 of an image forming apparatus 200 according to the second embodiment. The power supply circuit 110 of the image forming apparatus 200 according to the second embodiment is configured similarly to the power supply circuit 110 of the image forming apparatus 100 according to the first embodiment.

[0095] The control unit 80 controls the processing in the image forming apparatus 200 . For example, when the control unit 80 receives a print instruction after receiving a notice from the USP 51 indicating a power outage, if the temperature detected by the temperature detection sensor 32 is lower than a predetermined temperature, the control unit 80 controls the main heater on / off circuit 140 and the sub-heater on / off circuit 150 to shift the timing for turning on the main heater 34 and the timing for turning on the sub-heater 35. The method for shifting the timing is the same as in the first embodiment.

[0096] The control unit 80 includes a CPU 81 , a ROM 82 , a RAM 63 , a temperature acquisition unit 64 , a sensor on / off circuit 65 , a high-voltage power supply 66 , a head control unit 67 , and an actuator driving unit 68 . The RAM 63, temperature acquisition unit 64, sensor on / off circuit 65, high-voltage power supply 66, head control unit 67 and actuator drive unit 68 of the control unit 80 in embodiment 2 are similar to the RAM 63, temperature acquisition unit 64, sensor on / off circuit 65, high-voltage power supply 66, head control unit 67 and actuator drive unit 68 of the control unit 60 in embodiment 1.

[0097] Here, the UPS 52 in the second embodiment outputs a power outage detection signal S8 indicating whether or not a power outage has occurred to the control unit 80. This allows the control unit 80 to receive a notification indicating that a power outage has occurred.

[0098] The ROM 82 in the second embodiment differs from the ROM 62 in the first embodiment in the programs stored therein. Therefore, the CPU 81 in the second embodiment differs from the CPU 61 in the first embodiment in the processes it executes.

[0099] In the second embodiment, the CPU 81 executes almost the same process as in the first embodiment. However, in the second embodiment, when the power failure detection signal S8 indicating a power failure is input from the UPS 52 and the CPU 81 receives a print instruction from the host 72 while the CPU 81 is receiving power from the UPS 52, the CPU 81 turns on the sub-heater 35 after a predetermined period has elapsed, as in the first embodiment.

[0100] 7A to 7G are time charts for explaining the operation of image forming apparatus 200 according to the second embodiment.

[0101] FIG. 7A shows the AC voltage output from commercial power supply 50, similar to FIG.

[0102] 7B shows a power outage detection signal output from the UPS 52 having a function of detecting a power outage. When the power outage detection signal is High, it indicates that the system is normal, in other words, that there is no power outage, and when the power outage detection signal is Low, it indicates that there is a power outage.

[0103] 7(C) to (G) respectively show the thermistor temperature, the main heater on / off control signal S3, the sub-heater on / off control signal S4, the heater current, and the UPS output voltage, similar to FIGS. 4(B) to (F).

[0104] Next, FIGS. 7(A) to (G) will be explained according to the time shown on the horizontal axis. First, at time t21, the AC voltage normally output from the commercial power supply 50 is input to the UPS 52 and input to the power supply circuit 110 as a UPS output voltage.

[0105] Power supply circuit 110 rectifies and smoothes the AC voltage in rectifying and smoothing circuit 113, converts it to DC 24V and DC 5V in DC-DC conversion unit 116, and outputs these voltages to control unit 80. This makes image forming apparatus 200 operable. Here, the AC input voltage during normal output is set to voltage V1.

[0106] At time t21, the control unit 80 has not received a print instruction from the host 72, so the main heater on / off control signal S3 is low, the main heater 34 is off, and the sub-heater on / off control signal S4 is low, so the sub-heater 35 is off. If there is no print instruction for a long period of time, the thermistor temperature will be the same as the ambient temperature of the image forming apparatus 200, resulting in a low temperature state. This shows a low temperature state when there is no print instruction for a long period of time. Therefore, the heater current is 0A, and the UPS output voltage is V1, which is the normal output voltage.

[0107] At time t22, a power outage occurs in the commercial power supply 50, and the UPS 52 outputs a power outage detection signal indicating that a power outage has occurred to the control unit 80. Here, the power outage detection signal may be a command. Furthermore, such a signal or command may be output to a PC (Personal Computer) serving as the host 72, rather than to the control unit 80, and may be provided from the PC to the control unit 80. In this case, the control unit 80 receives a notification indicating that a power outage has occurred via the PC serving as the host 72.

[0108] At time t23, the control unit 80 receives a print instruction from the host 72. In this case, when the thermistor temperature is lower than a predetermined temperature, the control unit 80 causes the main heater on / off control signal S3 to go High, the main phototriac 141 to turn on, and the main triac 142 to turn on, thereby supplying an AC voltage to the main heater 34.

[0109] Meanwhile, also in the second embodiment, at time t23, the sub-heater on / off control signal S4 remains low, and the sub phototriac 151 remains off. As a result, no AC voltage is supplied to the sub-heater 35, but the thermistor temperature rises due to the main heater 34, and the heater current also rises. However, by turning on the main heater 34 and turning off the sub-heater 35, the heater inrush current can be suppressed, and so the relationship is: inrush current of the main heater 34≦heater current I1 of the main heater 34 and the sub-heater 35 during normal operation<inrush current I2 of the main heater 34 and the sub-heater 35. At this time, the UPS output voltage is within the rated current of the UPS 52, so that the voltage V1 during normal output can be continued.

[0110] At time t24, the thermistor temperature reaches a predetermined temperature T3, the main heater on / off control signal S3 continues to output a high level, and the sub-heater on / off control signal S4 is switched from a low level to a high level by the control unit 80. This turns on the sub-heater 35, and the thermistor temperature continues to rise.

[0111] At time t25, the control unit 80 keeps the main heater on / off control signal S3 at a high output and the sub-heater on / off control signal S4 at a high output, causing the thermistor temperature to continue to rise and reach temperature T2, which is the set temperature. As a result, the main heater on / off control signal S3 goes to a low output, and the sub-heater on / off control signal S4 goes to a low output, causing the heater current to become 0 A. At this time, the UPS output voltage is voltage V1 during normal output. Although not shown, thereafter, the control unit 80 performs on / off control of the main heater 34 and the sub-heater 35 to maintain temperature T2, which is the set temperature of the thermistor, constant.

[0112] As described above, according to the second embodiment, when the heater temperature of the image forming apparatus 200 is lower than a predetermined temperature during a power outage of the AC output of the commercial power source 50, the heater inrush current can be suppressed by controlling the heaters to be prohibited from being turned on simultaneously. This makes it possible to use the UPS 52 within its rated current. This eliminates the need to use a large-capacity UPS, making it possible to miniaturize the system.

[0113] Embodiment 3 1, image forming apparatus 300 according to the third embodiment generally includes a paper feed section 1, an image forming section 2, a fixing device 3, and a discharge section 4. In the configuration shown in FIG. 1, image forming apparatus 300 according to the third embodiment is similar to image forming apparatus 100 according to the first embodiment.

[0114] As shown in FIG. 6, the image forming apparatus 300 according to the third embodiment includes a power supply circuit 110 and a control unit 90. The power supply circuit 110 and the control unit 90 are electrically connected to the power supply circuit 110. The power supply circuit 110 of the image forming apparatus 300 according to the third embodiment is configured similarly to the power supply circuit 110 of the image forming apparatus 100 according to the first embodiment.

[0115] The control unit 90 controls the processing in the image forming apparatus 300 . For example, when the control unit 90 receives a print instruction after receiving a notice from the UPS 52 that a power outage has occurred, if the temperature detected by the temperature detection sensor 32 is lower than a predetermined temperature, the control unit 90 controls the main heater on / off circuit and the sub-heater on / off circuit 150 to turn off the main heater 34 and the sub-heater 35 for a predetermined period, and then shifts the timing for turning on the main heater 34 and the timing for turning on the sub-heater 35. The method for shifting the timing is the same as in the first embodiment.

[0116] The control unit 90 includes a CPU 91 , a ROM 92 , a RAM 63 , a temperature acquisition unit 64 , a sensor on / off circuit 65 , a high-voltage power supply 66 , a head control unit 67 , and an actuator driving unit 68 . The RAM 63, temperature acquisition unit 64, sensor on / off circuit 65, high-voltage power supply 66, head control unit 67 and actuator drive unit 68 of the control unit 90 in embodiment 3 are similar to the RAM 63, temperature acquisition unit 64, sensor on / off circuit 65, high-voltage power supply 66, head control unit 67 and actuator drive unit 68 of the control unit 60 in embodiment 1.

[0117] Here, the UPS 52 in the third embodiment outputs to the control unit 90 a power failure detection signal S8 indicating whether or not a power failure has occurred.

[0118] The ROM 92 in the third embodiment differs from the ROM 62 in the first embodiment in the programs stored therein. Therefore, the CPU 91 in the third embodiment differs from the CPU 61 in the first embodiment in the processes it executes.

[0119] In the third embodiment, the CPU 91 executes substantially the same process as in the first embodiment. However, if the CPU 91 receives a print instruction from the host 72 while a power outage detection signal S8 indicating a power outage is being input from the UPS 52, the CPU 91 turns on the main heater 34 after a predetermined period of time has elapsed.

[0120] In addition, when the power outage detection signal S8 from the UPS 52 indicates that there is no power outage, the CPU 91 may shift the timing for turning on the main heater 34 and the timing for turning on the sub-heater 35 before a predetermined period has elapsed, as in embodiment 1.

[0121] 8(A) to 8(G) are time charts for explaining the operation of image forming apparatus 300 according to the third embodiment.

[0122] FIG. 8(A) shows the AC voltage output from commercial power supply 50, similar to FIG. 4(A).

[0123] 8B shows a power outage detection signal output from the UPS 52 having a function of detecting a power outage. When the power outage detection signal is High, it indicates that the system is normal, in other words, that there is no power outage, and when the power outage detection signal is Low, it indicates that there is a power outage.

[0124] 8(C) to (G) respectively represent the thermistor temperature, the main heater on / off control signal S3, the sub-heater on / off control signal S4, the heater current, and the UPS output voltage, similar to FIGS. 4(B) to (F).

[0125] Next, FIGS. 8(A) to (G) will be explained according to the time shown on the horizontal axis. First, at time t31, the AC voltage normally output from the commercial power supply 50 is input to the UPS 52 and input to the power supply circuit 110 as a UPS output voltage.

[0126] Power supply circuit 110 rectifies and smoothes the AC voltage in rectifying and smoothing circuit 113, converts it to DC 24V and DC 5V in DC-DC conversion unit 116, and outputs these voltages to control unit 90. This puts image forming apparatus 300 into an operable state. Here, the AC input voltage during normal output is set to voltage V1.

[0127] At time t31, the control unit 90 has not received a print instruction from the host 72, so the main heater on / off control signal S3 is low, the main heater 34 is off, and the sub-heater on / off control signal S4 is low, and the sub-heater 35 is off. If there is no print instruction for a long period of time, the thermistor temperature will be the same as the ambient temperature of the image forming apparatus 300, resulting in a low temperature state. This shows a low temperature state when there is no print instruction for a long period of time. Therefore, the heater current is 0A, and the UPS output voltage is V1, which is the normal output voltage.

[0128] At time t32, a power outage occurs in the commercial power supply 50, and the UPS 52 outputs a power outage detection signal indicating the power outage to the control unit 90. Here, the power outage detection signal may be a command. Furthermore, such a signal or command may be output to a PC serving as the host 72, rather than to the control unit 90, and may be provided from the PC to the control unit 90.

[0129] At time t33, the control unit 90 receives a print instruction from the host 72. In this case, if the thermistor temperature is lower than a predetermined temperature, the control unit 90 keeps the main heater 34 and the sub-heater 35 off during the predetermined period from time t33 to time t34. Specifically, the main heater on / off control signal S3 continues to output low, and the sub-heater on / off control signal S4 also continues to output low. By performing such an operation, abnormalities in the UPS output voltage are suppressed, and if the power outage is restored in a short time, it becomes possible to return to normal operation. The predetermined period here is also called a standby period. This standby period is a time period corresponding to a short-term power outage, and here is set to, for example, 20 ms with a margin added to the short-term power outage (instantaneous blackout) of 10 ms, but is not limited to this example.

[0130] At time t34, when the standby period has elapsed, the main heater on / off control signal S3 goes High, the main phototriac 141 turns on, and the main triac 142 turns on, so that an AC voltage is supplied to the main heater 34.

[0131] Meanwhile, also in the third embodiment, at time t34, the sub-heater on / off control signal S4 remains low, and the sub phototriac 151 remains off. As a result, no AC voltage is supplied to the sub-heater 35, but the thermistor temperature rises due to the main heater 34, and the heater current also rises. However, by turning on the main heater 34 and turning off the sub-heater 35, the heater inrush current can be suppressed, and so the relationship is: inrush current of the main heater 34≦heater current I1 of the main heater 34 and the sub-heater 35 during normal operation<inrush current I2 of the main heater 34 and the sub-heater 35. At this time, the UPS output voltage is within the rated current of the UPS 52, so that the voltage V1 during normal output can be continued.

[0132] At time t35, the thermistor temperature reaches a predetermined temperature T3, the main heater on / off control signal S3 continues to output a high level, and the sub-heater on / off control signal S4 is switched from a low level to a high level by the control unit 90. This turns on the sub-heater 35, and the thermistor temperature continues to rise.

[0133] At time t36, the control unit 90 keeps the main heater on / off control signal S3 at a high output and the sub-heater on / off control signal S4 at a high output, so that the thermistor temperature continues to rise and reaches temperature T2, which is the set temperature. As a result, the main heater on / off control signal S3 goes to a low output, and the sub-heater on / off control signal S4 goes to a low output, and the heater current becomes 0 A. At this time, the UPS output voltage is voltage V1 during normal output. Although not shown, thereafter, the control unit 90 controls the main heater 34 and the sub-heater 35 to turn on and off in order to keep temperature T2, which is the set temperature of the thermistor, constant.

[0134] As described above, according to the third embodiment, when a print instruction is received during a power outage of the AC output of the commercial power source 50, the heater is turned off for a predetermined period of time, so that if the power outage subsides in a short time, printing can be started in normal operation.

[0135] In the above-described first to third embodiments, the sub-heater 35 is turned on when the thermistor temperature reaches a predetermined temperature T3, but the first to third embodiments are not limited to such examples. If the influence of the inrush current can be suppressed, the sub-heater 35 may be turned on when the thermistor temperature reaches a reference temperature that is lower than the temperature T3 or higher than the temperature T3. The reference temperature may be determined in advance by an experiment or the like.

[0136] In the above-described first to third embodiments, a printer device, particularly a tandem type four-color printer device, has been used for explanation, but the first to third embodiments are not limited to the above examples. For example, the present invention can be implemented in other image forming devices such as a printer device with five or more colors, a printer device with less than four colors, a monochrome printer device, or a copying machine. In addition, the uninterruptible power supply connected to the part where AC is input has been explained using a UPS, but the first to third embodiments are not limited to such examples. For example, a portable power supply may be used instead of the UPS. [Explanation of symbols]

[0137] 100,200,300 image forming apparatus, 50 commercial power supply, 51,52 UPS, 60,80,90 control unit, 110 power supply circuit, 113 rectification smoothing circuit, 116 DC-DC conversion unit, 120 relay circuit, 130 AC zero cross circuit, 140 main heater on / off circuit, 150 sub heater on / off circuit, 160 main triac short detection circuit, 170 sub triac short detection circuit, 180 relay short detection circuit.

Claims

1. An image forming apparatus that forms an image on a medium by transferring a developer image onto the medium, comprising: one or more first heaters; one or more second heaters; a fixing section that fixes the developer image transferred to the medium to the medium by being heated by the one or more first heaters and the one or more second heaters; a temperature detection unit that detects the temperature of the fixing unit; a first heater driving unit that turns on or off the power supply to the one or more first heaters; a second heater driving unit that turns on or off the power supply to the one or more second heaters; a control unit which, when receiving an instruction to form the image on the medium, causes the first heater driving unit to turn on the one or more first heaters if the temperature detected by the temperature detection unit is lower than a predetermined temperature, and causes the second heater driving unit to turn on the one or more second heaters after the temperature detected by the temperature detection unit reaches the predetermined temperature, thereby shifting the timing at which the one or more first heaters are turned on and the timing at which the one or more second heaters are turned on. An image forming apparatus comprising:

2. An image forming apparatus that forms an image on a medium by transferring a developer image onto the medium, comprising: one or more first heaters; one or more second heaters; a fixing section that fixes the developer image transferred to the medium to the medium by being heated by the one or more first heaters and the one or more second heaters; a temperature detection unit that detects the temperature of the fixing unit; a first heater driving unit that turns on or off the power supply to the one or more first heaters; a second heater driving unit that turns on or off the power supply to the one or more second heaters; a control unit which, when receiving an instruction to form the image on the medium, causes the first heater driving unit to turn on the one or more first heaters if the temperature detected by the temperature detection unit is lower than a predetermined temperature, and causes the second heater driving unit to turn on the one or more second heaters after the temperature detected by the temperature detection unit reaches a predetermined reference temperature, thereby shifting the timing at which the one or more first heaters are turned on and the timing at which the one or more second heaters are turned on. An image forming apparatus comprising:

3. An image forming apparatus that forms an image on a medium by transferring a developer image onto the medium, comprising: one or more first heaters that receive power from a commercial power source, store the power, and receive power from the commercial power source or the uninterruptible power source via an uninterruptible power source that supplies the stored power when the commercial power source is interrupted; one or more second heaters that receive power from the commercial power source or the uninterruptible power source via the uninterruptible power source; a fixing section that fixes the developer image transferred to the medium to the medium by being heated by the one or more first heaters and the one or more second heaters; a temperature detection unit that detects the temperature of the fixing unit; a first heater driving unit that turns on or off the power supply to the one or more first heaters; a second heater driving unit that turns on or off the power supply to the one or more second heaters; and a control unit which, when the temperature detected by the temperature detection unit is lower than a predetermined temperature when an instruction to form the image on the medium is received after a notification indicating a power outage is received from the uninterruptible power supply, controls the first heater driving unit and the second heater driving unit to shift a timing for turning on the one or more first heaters and a timing for turning on the one or more second heaters. An image forming apparatus comprising:

4. An image forming apparatus that forms an image on a medium by transferring a developer image onto the medium, comprising: one or more first heaters that receive power from a commercial power source, store the power, and receive power from the commercial power source or the uninterruptible power source via an uninterruptible power source that supplies the stored power when the commercial power source is interrupted; one or more second heaters that receive power from the commercial power source or the uninterruptible power source via the uninterruptible power source; a fixing section that fixes the developer image transferred to the medium to the medium by being heated by the one or more first heaters and the one or more second heaters; a temperature detection unit that detects the temperature of the fixing unit; a first heater driving unit that turns on or off the power supply to the one or more first heaters; a second heater driving unit that turns on or off the power supply to the one or more second heaters; a control unit which, when the temperature detected by the temperature detection unit is lower than a predetermined temperature when an instruction to form the image on the medium is received after a notification indicating a power outage is received from the uninterruptible power supply, controls the first heater driving unit and the second heater driving unit to turn off the one or more first heaters and the one or more second heaters for a predetermined period, and then shifts a timing for turning on the one or more first heaters from a timing for turning on the one or more second heaters. An image forming apparatus comprising:

5. The notification is sent to the control unit using a power outage detection signal indicating whether or not a power outage has occurred.

5. The image forming apparatus according to claim 3, wherein

6. The notification is sent to the control unit as a command indicating that a power outage has occurred.

5. The image forming apparatus according to claim 3, wherein

7. The control unit receives the notification via a host that instructs the formation of the image.

5. The image forming apparatus according to claim 3, wherein

8. The control unit causes the first heater driving unit to turn on the one or more first heaters, and after a current flowing through the one or more first heaters reaches a steady state, causes the second heater driving unit to turn on the one or more second heaters, thereby shifting a timing for turning on the one or more first heaters from a timing for turning on the one or more second heaters.

7. The image forming apparatus according to claim 3, wherein:

9. The control unit causes the first heater driving unit to turn on the one or more first heaters, and after the temperature detected by the temperature detection unit reaches the predetermined temperature, causes the second heater driving unit to turn on the one or more second heaters, thereby shifting a timing for turning on the one or more first heaters from a timing for turning on the one or more second heaters.

7. The image forming apparatus according to claim 3, wherein:

10. The control unit causes the first heater driving unit to turn on the one or more first heaters, and after the temperature detected by the temperature detection unit reaches a predetermined reference temperature, causes the second heater driving unit to turn on the one or more second heaters, thereby shifting a timing for turning on the one or more first heaters from a timing for turning on the one or more second heaters.

7. The image forming apparatus according to claim 3, wherein:

11. The control unit causes the second heater driving unit to turn on the one or more second heaters after a predetermined period has elapsed since the control unit caused the first heater driving unit to turn on the one or more first heaters, thereby shifting a timing for turning on the one or more first heaters from a timing for turning on the one or more second heaters.

7. The image forming apparatus according to claim 3, wherein:

Images