Image forming apparatus and image fixing method

Abstract

The present invention provides an image forming apparatus and an image fixing method capable of performing printing efficiently. The image forming apparatus according to an embodiment includes a fixing device and a control unit. The fixing device includes a first heating source and a second heating source whose heatable range is wider than that of the first heating source and which has a characteristic that the output power decreases as the temperature rises. The control unit controls either the first heating source or the second heating source according to the size of a sheet to be printed to perform printing.

Description

Technical Field

[0001] Embodiments of the present invention relate to an image forming apparatus and an image fixing method. Background Art

[0002] As a countermeasure against the temperature rise at the end of the non-paper-passing area of the fixing device caused by continuous printing in an image forming apparatus, a planar heater with a specific temperature coefficient of resistance is used. The planar heater used here is a planar heater having a characteristic that the output power decreases significantly as the temperature of the heater rises. In such a planar heater, printing may not be performed efficiently due to a decrease in power output in the paper-passing area. This is not limited to planar heaters and may occur in all heating sources having the characteristic that the output power decreases as the temperature rises. Summary of the Invention

[0003] Problems to be Solved by the Invention

[0004] The problem to be solved by the present invention is to provide an image forming apparatus and an image fixing method capable of performing printing efficiently.

[0005] Means for Solving the Problems

[0006] The image forming apparatus according to the embodiment includes a fixing device and a control unit. The fixing device includes a first heating source and a second heating source having a wider heatable range than the first heating source and having a characteristic that the output power decreases as the temperature rises. The control unit controls either the first heating source or the second heating source according to the size of the sheet to be printed to perform printing. Brief Description of the Drawings

[0007] Figure 1 It is a diagram showing an example of the overall configuration of the image forming apparatus according to the embodiment.

[0008] Figure 2 It is a diagram for explaining the internal configuration of the fixing device according to the embodiment.

[0009] Figure 3 It is a diagram showing an example of comparing the sizes of the first heating source and the second heating source in the comparative embodiment.

[0010] Figure 4 It is a diagram for explaining the difference in the temperature coefficient of resistance between the first heating source and the second heating source in the embodiment.

[0011] Figure 5 It is a block diagram showing the hardware configuration of the image forming apparatus according to the embodiment.

[0012] Figure 6 It is a flowchart showing the flow of the image fixing process performed by the image forming apparatus according to the embodiment.

[0013] Symbol Explanation

[0014] 1. Image forming apparatus; 50. Fixer; 51. Fixing belt; 52. Pressure roller; 53. First heating source; 54. Second heating source; 70. Control device; 71. Control unit. Detailed Embodiment

[0015] Hereinafter, an image forming apparatus and an image fixing method according to an embodiment will be described with reference to the accompanying drawings.

[0016] Figure 1 FIG. is a diagram showing an overall configuration example of the image forming apparatus 1 according to the embodiment. The image forming apparatus 1 according to the embodiment is a multifunction peripheral (MFP). The image forming apparatus 1 performs printing based on image forming processing and image fixing processing. The image forming processing is a process of forming an image on a sheet. The image fixing processing is a process of fixing the image formed on the sheet. The sheet is, for example, paper on which characters, images, etc. are formed. The sheet can be any object as long as it is an object on which the image forming apparatus 1 can form an image.

[0017] The image forming apparatus 1 includes an image reading unit 10, a control panel 20, an image forming unit 30, a sheet storage unit 40, a fixer 50, conveying rollers 61a and 61b, paper discharge rollers 62a and 62b, and a control device 70.

[0018] The image reading unit 10 reads the image of the object to be read on the original document as the brightness and darkness of light. For example, the image reading unit 10 reads the image printed on the sheet of the object to be read provided on the original document reading table. The image reading unit 10 records the read image information. The recorded image information can also be transmitted to other information processing devices via a network. The recorded image information can also be used as print data to form an image on a sheet by the image forming unit 30.

[0019] The control panel 20 includes a display unit and an operation unit. The display unit is a display device such as a liquid crystal display and an organic EL (ElectroLuminescence) display. The display unit displays various information related to the image forming apparatus 1 under the control of the control device 70. The operation unit includes a plurality of buttons and the like. The operation unit accepts the operation of the user. For example, the operation unit accepts an execution instruction for printing. The operation unit outputs a signal corresponding to the operation performed by the user to the control device 70. In addition, the display unit and the operation unit may be configured as an integrated touch panel.

[0020] The image forming unit 30 performs image forming processing. Specifically, the image forming unit 30 forms an image on a sheet based on the image information generated by the image reading unit 10 or the image information received via a communication line. For example, the image forming unit 30 forms a toner image on a sheet using toner.

[0021] The image forming unit 30 includes a transfer belt 31, an exposure unit 32, a plurality of developing units 33 (developing units 33Y, 33M, 33C, and 33K), a plurality of photosensitive drums 34 (photosensitive drums 34Y, 34M, 34C, and 34K), and a transfer unit 35.

[0022] The transfer belt 31 is an annular intermediate transfer member. The transfer belt 31 rotates in the direction indicated by the arrow (counterclockwise rotation) by the rotation of a roller.

[0023] The exposure unit 32 is disposed at a position facing the photosensitive drums 34 between the developing units 33 and a charger (not shown). The exposure unit 32 irradiates a laser beam based on image information onto the surfaces (photosensitive layers) of the respective photosensitive drums 34Y, 34M, 34C, and 34K. The direction in which the laser beam scans the photosensitive drum is the main scanning direction, and the direction orthogonal to the main scanning direction is the sub-scanning direction. For example, in the present embodiment, the main scanning direction coincides with the axial direction of the photosensitive drum, and the sub-scanning direction coincides with the rotation direction of the transfer belt.

[0024] By the irradiation of the laser beam, the charges on the surfaces (photosensitive layers) of the respective photosensitive drums 34Y, 34M, 34C, and 34K disappear. As a result, an electrostatic pattern is formed at the positions on the surfaces of the photosensitive drums 34Y, 34M, 34C, and 34K irradiated with the laser beam. That is, an electrostatic latent image is formed on the surfaces of the photosensitive drums 34Y, 34M, 34C, and 34K by the irradiation of the laser beam by the exposure unit 32. In addition, the exposure unit 32 may use LED (Light Emitting Diode) light instead of the laser beam.

[0025] The developing units 33Y, 33M, 33C, and 33K supply toner to the photosensitive drums 34Y, 34M, 34C, and 34K. For example, the developing unit 33Y develops the electrostatic latent image on the surface of the photosensitive drum 34Y with yellow (Y). In addition, the developing unit 33M develops the electrostatic latent image on the surface of the photosensitive drum 34M with magenta (M). In addition, the developing unit 33C develops the electrostatic latent image on the surface of the photosensitive drum 34C with cyan (C). In addition, the developing unit 33K develops the electrostatic latent image on the surface of the photosensitive drum 34K with black (K) toner.

[0026] Developers 33Y, 33M, 33C, and 33K form a toner image as a visible image on photoreceptor drums 34Y, 34M, 34C, and 34K. The toner image formed on photoreceptor drums 34Y, 34M, 34C, and 34K is transferred (primary transfer) to transfer belt 31 by a plurality of primary transfer rollers (not shown). A plurality of primary transfer rollers are provided at positions facing photoreceptor drums 34Y, 34M, 34C, and 34K with transfer belt 31 interposed therebetween.

[0027] Transfer unit 35 has a support roller 35a and a secondary transfer roller 35b. Transfer unit 35 transfers the toner image on transfer belt 31 to sheet 41 at secondary transfer position U. Secondary transfer position U is a position where support roller 35a and secondary transfer roller 35b face each other with transfer belt 31 interposed therebetween. Transfer unit 35 applies a transfer bias controlled by a transfer current to transfer belt 31. Transfer unit 35 transfers the toner image on transfer belt 31 to sheet 41 by the transfer bias. The transfer current is controlled by control device 70.

[0028] Sheet storage unit 40 includes one or more paper feed cassettes. The paper feed cassettes store sheets 41 of a predetermined size and a predetermined type. The paper feed cassettes have sheet feed rollers. The sheet feed rollers sequentially take out sheets 41 from the paper feed cassettes. The sheet feed rollers supply the taken-out sheets 41 to conveying unit 80.

[0029] Fuser 50 performs image fixing processing. Specifically, fuser 50 fixes an image (e.g., a toner image) formed on sheet 41 on sheet 41 by heating and pressing sheet 41.

[0030] Conveying rollers 61a and 61b supply sheet 41 fed from the paper feed cassette to image forming unit 30. Conveying rollers 61a and 61b are provided at opposite positions.

[0031] Discharging rollers 62a and 62b discharge sheet 41 having an image formed thereon by fuser 50 to the discharge unit. Discharging rollers 62a and 62b are provided at opposite positions.

[0032] Control device 70 controls each functional unit of image forming apparatus 1.

[0033] Conveying unit 80 conveys sheet 41. Conveying unit 80 includes a conveyance path and a plurality of rollers (not shown). The conveyance path is a path for conveying sheet 41. The rollers rotate according to the control of control device 70 to convey sheet 41.

[0034] Figure 2 It is a diagram for explaining the internal configuration of fuser 50 of the embodiment. Fuser 50 includes a fixing belt 51, a pressure roller 52, a first heating source 53, a second heating source 54, and a temperature sensor 55.

[0035] The fixing belt 51 imparts heat to the sheet 41. The fixing belt 51 is heated by the heat generated when the first heating source 53 or the second heating source 54 provided inside is energized. The first heating source 53 and the second heating source 54 differ in size and resistance temperature coefficient from each other. The fixing belt 51 rotates counterclockwise according to the control of the control device 70. The first heating source 53 and the second heating source 54 are arranged side by side in the fixing device 50.

[0036] The pressure roller 52 is disposed opposite to the fixing belt 51. The pressure roller 52 presses the sheet 41 against the fixing belt 51.

[0037] The first heating source 53 is a planar heater having a heating resistor on its surface. The first heating source 53 is lit or extinguished according to whether there is power supply from the control device 70. The first heating source 53 is a heater having a resistance temperature coefficient (TCR) characteristic in which the change in output power according to the change in temperature is less than the threshold value. That is, the first heating source 53 has a characteristic that even if the temperature of the heater rises, the decrease in output power is less than the threshold value. Therefore, in the first heating source 53, even if the heater itself becomes high temperature, it is difficult for the output power to decrease. The heater width of the first heating source 53 only needs to be a width capable of heating a sheet size with a relatively high printing frequency (hereinafter referred to as the first size). The first size is, for example, A4R or A4, etc.

[0038] The second heating source 54 is a planar heater having a heating resistor on its surface. The second heating source 54 is lit or extinguished according to whether there is power supply from the control device 70. The second heating source 54 is a heater having a resistance temperature coefficient characteristic in which the change in output power according to the change in temperature becomes above the threshold value. That is, the second heating source 54 has a characteristic that if the temperature of the heater rises, the output power decreases significantly. Therefore, in the second heating source 54, if the heater itself becomes high temperature, the output power easily decreases. The heater width of the second heating source 54 only needs to be a width capable of heating a sheet of a size larger than the first size (hereinafter referred to as the second size). The sheet of the second size is, for example, A3, etc.

[0039] As described above, the first heating source 53 is a heater having a lower resistance temperature coefficient than the second heating source 54. A low resistance temperature coefficient means that printing can be performed while maintaining the output power even during continuous printing. Therefore, the image forming apparatus 1 uses the first heating source 53 having a low resistance temperature coefficient when printing the first size. On the other hand, in the case of the second size where it is difficult to heat the entire sheet by the first heating source 53, the image forming apparatus 1 uses the second heating source 54.

[0040] The temperature sensor 55 measures the temperature of the fixing belt 51. The temperature sensor 55 sends the measured temperature of the fixing belt 51 to the control device 70.

[0041] Figure 3 FIG. is an example showing the sizes of the first heating source 53 and the second heating source 54 in the comparative embodiment.

[0042] As Figure 3 shown, the first heating source 53 has a first width capable of heating the entire paper width of the first size. The second heating source 54 has a second width capable of heating the entire paper width of the second size.

[0043] Figure 4 FIG. is a diagram for explaining the difference in the resistance temperature coefficient between the first heating source 53 and the second heating source 54 in the embodiment.

[0044] Figure 4 The horizontal axis of represents the temperature of the heating source, and the vertical axis represents the output power of the heating source. In Figure 4 two lines 61 and 62 are shown. The line 61 has a resistance temperature coefficient characteristic in which the change in output power according to the change in temperature is less than the threshold value, that is, it is a line showing the relationship between the temperature and the output power in the first heating source 53. The line 62 has a resistance temperature coefficient characteristic in which the change in output power according to the change in temperature becomes above the threshold value, that is, it is a line showing the relationship between the temperature and the output power in the second heating source 54. As is apparent from Figure 4 , in the second heating source 54, the change in output power according to the change in temperature is large. In such a case, it is difficult to achieve high productivity. On the other hand, in the first heating source 53, even if the temperature rises, the output power hardly changes. Therefore, even if the temperature of the first heating source 53 rises due to continuous printing, printing can be continued. As a result, high productivity can be achieved.

[0045] Figure 5 FIG. is a block diagram showing the hardware configuration of the image forming apparatus 1 according to the embodiment. In addition, in Figure 5 only the characteristic hardware configuration of the image forming apparatus 1 in the present embodiment is shown.

[0046] The image forming apparatus 1 includes an image reading unit 10, a control panel 20, an image forming unit 30, a sheet storage unit 40, a fixing unit 50, an engine controller 60, a control device 70, an auxiliary storage device 120, and a network interface 130. Each functional unit is connected via a system bus 11 so as to be able to perform data communication.

[0047] Description of the image reading unit 10, the control panel 20, the image forming unit 30, the sheet storage unit 40, and the fixing unit 50 is omitted. Hereinafter, the control device 70, the auxiliary storage device 120, and the network interface 130 will be described.

[0048] The control device 70 includes a control unit 71, a ROM (Read Only Memory) 72, and a RAM (Random Access Memory) 73. The control unit 71 is, for example, a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). The control unit 71 controls the operations of the respective functional units of the image forming apparatus 1. The control unit 71 executes various processes by expanding and executing the programs stored in the ROM 72 in the RAM 73. In addition, appropriate functions implemented by the control unit 71 may be performed by an ASIC (Application Specific Integrated Circuit). An ASIC is a dedicated circuit for implementing specific functions.

[0049] For example, the control unit 71 controls either the first heating source 53 or the second heating source 54 according to the size of the sheet to be printed to perform printing. For example, the control unit 71 controls the first heating source 53 to perform printing when printing a sheet of the first size. For example, the control unit 71 controls the second heating source 54 to perform printing when printing a sheet of the second size. For example, when either the first heating source 53 or the second heating source 54 malfunctions, the control unit 71 controls the display of the control panel 20.

[0050] The ROM 72 stores programs for operating the control unit 71. The RAM 73 is a memory that temporarily stores data used by the respective functional units included in the image forming apparatus 1. In addition, the RAM 73 may store the digital data generated by the image reading unit 10. The RAM 73 may also temporarily store jobs and job logs.

[0051] The auxiliary storage device 120 is, for example, a hardware device or an SSD (solid state drive) and stores various data. The various data are, for example, digital data, jobs, and job logs, etc.

[0052] The network interface 130 transmits and receives data to and from other devices. Here, the other devices refer to information processing devices such as personal computers, for example. The network interface 130 operates as an input interface and receives print data or instructions sent from other devices. As an instruction sent from other devices, there is an execution instruction for printing, etc. In addition, the network interface 130 operates as an output interface and sends data to other devices.

[0053] Figure 6 It is a flowchart showing the flow of the image fixing process performed by the image forming apparatus 1 in the embodiment. Figure 6The processing shown is executed when an execution instruction for printing is given to the image forming apparatus 1.

[0054] The control unit 71 determines the print size specified by the execution instruction for printing (ACT101). Specifically, the control unit 71 determines whether the print size specified by the execution instruction for printing is equal to or less than the first size or the second size. When the print size specified by the execution instruction for printing is equal to or less than the first size (ACT101: equal to or less than the first size), the control unit 71 executes ACT102.

[0055] On the other hand, when the print size specified by the execution instruction for printing is the second size (ACT101: second size), the control unit 71 executes ACT108.

[0056] The control unit 71 performs temperature control of the first heating source 53 (ACT102). Specifically, the control unit 71 supplies power to the first heating source 53 to raise the temperature of the first heating source 53. The control unit 71 stands by for a predetermined period until the temperature of the first heating source 53 rises. Preferably, the predetermined period is longer than the time it takes for the temperature of the heating source to reach the ready temperature when performing temperature control of the heating source. The control unit 71 determines whether the temperature of the fixing belt 51 has reached the ready temperature based on the temperature information obtained by the temperature sensor 55 after the predetermined period has elapsed (ACT103).

[0057] When the ready temperature is reached (ACT103: yes), the fixing unit 50 performs fixing processing based on the first heating source 53 (ACT104). Specifically, when the temperature of the fixing belt 51 reaches the ready temperature, the control unit 71 controls various rollers to convey the sheet to the fixing unit 50. The sheet passes through the fixing unit 50, and the image formed on the sheet is fixed on the sheet. At this time, since the heating source being heated is the first heating source 53, fixing processing based on the first heating source 53 is executed. After that, a fixed sheet is formed and Figure 6 the processing ends.

[0058] In the processing of ACT103, when the ready temperature is not reached (ACT103: no), the control unit 71 determines that the first heating source 53 has failed (ACT105). After that, the control unit 71 controls the display of the control panel 20 (ACT106). Specifically, the control unit 71 causes information indicating that printing can be performed even if the printing speed is decreased due to the failure of the first heating source 53 to be displayed on the screen of the control panel 20. After that, the control unit 71 determines whether an execution instruction for printing has been given (ACT107).

[0059] When an execution instruction for printing has been given (ACT107: yes), the control unit 71 executes ACT108.

[0060] On the other hand, in the case where there is no execution instruction for printing (ACT107: No), Figure 6 the process ends. Here, the case where there is no execution instruction for printing means the case where an instruction to end printing is given, or the case where no operation is performed within a predetermined period.

[0061] As the process of ACT108, the control unit 71 performs temperature control of the second heating source 54 (ACT108). Specifically, the control unit 71 supplies power to the second heating source 54 to raise the temperature of the second heating source 54. The control unit 71 stands by for a predetermined period until the temperature of the second heating source 54 rises. The control unit 71 determines whether the temperature of the fixing belt 51 has reached the ready temperature based on the temperature information obtained by the temperature sensor 55 after a predetermined period (ACT109).

[0062] In the case where the ready temperature is reached (ACT109: Yes), the fixing device 50 performs a fixing process based on the second heating source 54 (ACT110). Specifically, when the temperature of the fixing belt 51 reaches the ready temperature, the control unit 71 controls various rollers to convey the sheet to the fixing device 50. The sheet passes through the fixing device 50, so that the image formed on the sheet is fixed on the sheet. At this time, since the heating source being heated is the second heating source 54, a fixing process based on the second heating source 54 is performed. After that, a fixed sheet is formed and Figure 6 the process ends.

[0063] In the process of ACT109, in the case where the ready temperature is not reached (ACT109: No), the control unit 71 determines that the second heating source 54 has failed (ACT111). After that, the control unit 71 determines whether the first heating source 53 has failed (ACT112). Specifically, similarly to the second heating source 54, the control unit 71 determines whether the first heating source 53 has failed based on whether the ready temperature is reached by performing temperature control of the first heating source 53. For example, when the ready temperature is reached after a predetermined period, the control unit 71 determines that the first heating source 53 has not failed. On the other hand, when the ready temperature is not reached after a predetermined period, the control unit 71 determines that the first heating source 53 has failed.

[0064] In the case where the first heating source 53 has failed (ACT112: Yes), the control unit 71 calls a maintenance person for the failure of the heating source (ACT113). Specifically, when both the first heating source 53 and the second heating source 54 have failed, the control unit 71 outputs the failure information to the outside. For example, the control unit 71 causes the error lamp provided in the image forming apparatus 1 to blink. For example, the control unit 71 displays an error on the screen of the control panel 20.

[0065] On the other hand, when the first heating source 53 does not malfunction (ACT112: No), the control unit 71 controls the display of the control panel 20 (ACT113). Specifically, the control unit 71 causes information indicating that printing can be performed if the size is equal to or smaller than the first size due to the malfunction of the second heating source 54 to be displayed on the screen of the control panel 20. After that, the control unit 71 determines whether an execution instruction for printing has been given (ACT115).

[0066] When an execution instruction for printing has been given (ACT115: Yes), the control unit 71 performs the processing after ACT102.

[0067] On the other hand, when an execution instruction for printing has not been given (ACT115: No), Figure 6 the processing ends.

[0068] According to the image forming apparatus 1 configured as described above, printing can be performed efficiently. Specifically, the image forming apparatus 1 controls either the first heating source 53 or the second heating source 54 according to the size of the sheet to be printed, and performs printing. The first heating source 53 has a width capable of heating, for example, the first size, and has a characteristic that even if the temperature of the heater rises, the reduction rate of the output power is less than the threshold value. The second heating source 54 has a width capable of heating, for example, a second size larger than the first size, and has a characteristic that if the temperature of the heater rises, the output power decreases significantly. Further, the image forming apparatus 1 switches the heating source used according to the size of the sheet to be printed. Thereby, not all sizes of sheets are printed by the second heating source 54. Therefore, it is possible to suppress a decrease in the number of printed sheets due to a decrease in the power output in the paper passing area. In addition, since the first heating source 53 has a characteristic that even if the temperature of the heater rises, the reduction rate of the output power is less than the threshold value, the output power does not decrease significantly even during continuous printing. That is, as long as it is equal to or smaller than the first size, high productivity can be achieved. Therefore, printing can be performed efficiently.

[0069] When the image forming apparatus 1 performs printing of a size equal to or smaller than the first size, it heats the range of the first size. Thereby, energy saving can be achieved as compared with the case where the range of the second size is always heated.

[0070] The image forming apparatus 1 has a plurality of heating sources. Therefore, the image forming apparatus 1 can continue printing by using the second heating source 54 even when the first heating source 53 malfunctions. Further, since the heating source is switched and printing is continued, it is possible to reduce the inconvenience to the user until the malfunctioning heating source is repaired.

[0071] The image forming apparatus 1 determines whether the heat source has failed based on the temperature information from the temperature sensor 55. Thus, the heat source failure can be determined without requiring an additional circuit.

[0072] Hereinafter, modifications of the image forming apparatus 1 will be described.

[0073] The first heat source 53 may be a heater that does not have a resistance temperature coefficient characteristic.

[0074] The first heat source 53 may be a heater lamp including a halogen lamp or an induction heating system as long as it has a resistance temperature coefficient characteristic in which a change in output power due to a change in temperature is smaller than a threshold value.

[0075] The second heat source 54 may be a heater lamp including a halogen lamp or an induction heating system as long as it has a resistance temperature coefficient characteristic in which a change in output power due to a change in temperature becomes equal to or greater than a threshold value.

[0076] A part of the functions of the image forming device 1 in the above-mentioned embodiment can also be realized by a computer. In this case, the program for realizing the function is recorded in a computer-readable recording medium. In addition, it can also be realized by making the computer system read the program recorded in the recording medium recording the above-mentioned program and executing it. In addition, the "computer system" mentioned here refers to a computer system including hardware such as an operating system and peripheral devices. In addition, "computer-readable recording medium" refers to a removable medium, a storage device, etc. The removable medium is a floppy disk, a magneto-optical disk, a ROM, a CD-ROM, etc. In addition, the storage device is a hardware device built into the computer system, etc. Further, "computer-readable recording medium" refers to a computer-readable recording medium that dynamically maintains the program in a short time, such as a communication line when sending a program via a communication line. The communication line is a network such as the Internet, a telephone line, etc. In addition, the "computer-readable recording medium" can also be a volatile memory inside the computer system of a server or client. The volatile memory maintains the program for a certain period of time. In addition, the above-mentioned program is a program for realizing a part of the aforementioned functions. In addition, the above-mentioned program may be further combined with a program already recorded in the computer system to realize the above-mentioned functions.

[0077] Although several embodiments are described, these embodiments are only presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the scope of the purpose of the invention. These embodiments and their variations are included in the scope and purpose of the invention, and are also included in the invention described in the claims and their equivalents.

Claims

1. An image forming apparatus, characterized in that, Comprising: A fixing device having a first heating source and a second heating source, the first heating source having a characteristic that the decreasing amplitude of the output power as the temperature rises becomes less than a threshold value, and the second heating source having a wider heatable range than the first heating source and having a characteristic that the decreasing amplitude of the output power becomes above the threshold value as the temperature rises; and A control unit that controls either the first heating source or the second heating source according to the size of the sheet to be printed to perform printing, When a failure occurs in either the first heating source or the second heating source among the first heating source and the second heating source, the control unit controls the non-failed heating source to perform the printing instead of according to the size of the sheet to be printed.

2. The image forming apparatus according to claim 1, characterized in that, The first heating source has a width capable of heating a first size, The second heating source has a width capable of heating a second size larger than the first size, The control unit controls the first heating source to perform printing when printing a sheet of the first size or less, and controls the second heating source to perform printing when printing a sheet of the second size.

3. The image forming apparatus according to claim 1 or 2, characterized in that, The fixing device is provided with a temperature sensor for acquiring temperature information, The control unit determines a failure based on the temperature information obtained by the temperature sensor.

4. The image forming apparatus according to claim 3, characterized in that, After temperature control is performed on the first heating source or the second heating source as the control object, if the temperature information acquired by the temperature sensor is below a predetermined temperature, the control unit determines that a failure has occurred in the first heating source or the second heating source as the control object.

5. An image fixing method, characterized in that, According to the size of the sheet to be printed, either the first heating source or the second heating source is controlled to perform printing. The first heating source has a characteristic that the decreasing amplitude of the output power as the temperature rises becomes less than a threshold value, and the second heating source has a wider heatable range than the first heating source and has a characteristic that the decreasing amplitude of the output power becomes above the threshold value as the temperature rises. When a failure occurs in either the first heating source or the second heating source, the image fixing method controls the non-failed heating source to perform the printing instead of according to the size of the sheet to be printed.

Images