Image forming apparatus, and storage method

Abstract

To provide an image forming apparatus capable of suppressing an occurrence of high-temperature offset, and a storage method.SOLUTION: An image forming apparatus 100 includes a first storage processing part 51 for storing width size information corresponding to a size of a sheet in a width direction in contact with a fixation belt in a RAM 13, a determination processing part 53 for using the width size information lastly stored in the RAM 13 to determine whether temperature drop processing for dropping a temperature of the fixation belt is required before starting image formation processing, a second storage processing part 54 for storing the width size information lastly stored in the RAM 13 in a storage part 6 before stopping power supply to the RAM 13, a third storage processing part 55 for storing the width size information lastly stored in the storage part 6 in the RAM 13 after restarting the power supply to the RAM 13, and a fourth storage processing part 56 for storing the width size information corresponding to a predetermined size in the storage part 6 after processing by the third storage processing part 55.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus and a storage method. [Background technology]

[0002] Electrophotographic image forming apparatuses include a fixing unit, such as a fixing belt, that fixes a toner image transferred to a sheet onto the sheet. In this type of image forming apparatus, when an image is formed on a sheet whose width is smaller than a predetermined standard size, the fixing unit may become excessively hot outside the contact area with the sheet. If an image is formed on a sheet with a larger width under these conditions, a problem known as high-temperature offset occurs, in which some of the toner contained in the toner image transferred to the sheet passes through the excessively hot area of ​​the fixing unit and is transferred to the subsequent sheet. In response to this problem, an image forming apparatus is known that, when the width of a sheet on which a next image is to be formed is larger than the width of the sheet on which the previous image was formed, inhibits image formation and performs a temperature reduction process to reduce the temperature of the fixing unit (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-182153 Summary of the Invention [Problem to be solved by the invention]

[0004] In a configuration that determines whether or not the temperature lowering process is necessary based on a comparison between the width direction size of the sheet on which the next image is to be formed and the width direction size of the sheet on which the immediately preceding image was formed, it is necessary to store width direction information corresponding to the width direction size of the sheet on which the last image was formed.In contrast to this, a configuration is conceivable in which the width direction information corresponding to the width direction size of the sheet on which the image was formed in the image forming process is stored in a volatile first storage unit such as a RAM each time an image formation process is executed, and when power supply to the first storage unit is stopped, the width direction information last stored in the first storage unit is saved in a non-volatile second storage unit.

[0005] However, in the above configuration, if power supply to the first storage unit is stopped due to a power outage or the like before the width size information last stored in the first storage unit is saved in the second storage unit, and then power supply to the first storage unit is resumed, the width size information last stored in the second storage unit is treated as the saved width size information, so that it may not be possible to correctly determine whether the temperature reduction process is necessary when the next image formation process is performed, and the occurrence of the high-temperature offset may not be suppressed.

[0006] SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus and a storage method that can suppress the occurrence of high-temperature offset. [Means for solving the problem]

[0007] According to one aspect of the present invention, an image forming apparatus includes a fixing unit, a first storage processing unit, a determination processing unit, a second storage processing unit, a third storage processing unit, and a fourth storage processing unit. The fixing unit fixes a toner image transferred to a sheet to the sheet. The first storage processing unit stores width size information in a volatile first storage unit, the width size information corresponding to the size of the sheet in a width direction perpendicular to a sheet conveyance direction after the sheet has passed a fixing position of the toner image fixed by the fixing unit. When an image forming process for forming an image on the sheet is performed, the determination processing unit determines whether or not a temperature reduction process for reducing the temperature of the fixing unit is required, using the width size information last stored in the first storage unit. When power supply to the first storage unit is stopped, the second storage processing unit stores the width size information last stored in the first storage unit in a non-volatile second storage unit. When power supply to the first storage unit is started, the third storage processing unit stores the width size information last stored in the second storage unit in the first storage unit. After the width size information is stored by the third storage processing unit, the fourth storage processing unit stores the width size information corresponding to the width size of the sheet that has the smallest width size among the sheets on which an image can be formed by the device in the second memory unit.

[0008] A storage method according to another aspect of the present invention is executed in an image forming apparatus including a fixing unit that fixes a toner image transferred to a sheet to the sheet, and includes a first storing step, a determining step, a second storing step, a third storing step, and a fourth storing step. In the first storing step, width size information corresponding to the size of the sheet in a width direction perpendicular to the sheet conveyance direction after the sheet has passed a fixing position of the toner image fixed by the fixing unit is stored in a volatile first storage unit. In the determining step, when an image forming process is performed to form an image on the sheet, the width size information last stored in the first storage unit is used to determine whether a temperature reduction process is required to reduce the temperature of the fixing unit. In the second storing step, when power supply to the first storage unit is stopped, the width size information last stored in the first storage unit is stored in a non-volatile second storage unit. In the third storing step, when power supply to the first storage unit is started, the width size information last stored in the second storage unit is stored in the first storage unit. In the fourth storage step, after storing the width size information in the third storage step, the width size information corresponding to the width size of the sheet having the smallest width size among the sheets on which an image can be formed by the image forming device is stored in the second memory unit. [Effects of the Invention]

[0009] According to the present invention, it is possible to suppress the occurrence of high-temperature offset. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view showing the configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing the system configuration of the image forming apparatus according to the embodiment of the present invention. [Figure 3] FIG. 3 is a cross-sectional view showing the configuration of the image forming unit of the image forming apparatus according to the embodiment of the present invention. [Figure 4] FIG. 4 is a cross-sectional view showing the configuration of the fixing device of the image forming apparatus according to the embodiment of the present invention. [Figure 5] FIG. 5 is a side view showing the configuration of a heater in the image forming apparatus according to the embodiment of the present invention. [Figure 6] FIG. 6 is a flowchart showing an example of an image forming operation control process executed by the image forming apparatus according to the embodiment of the present invention. [Figure 7] FIG. 7 is a flowchart showing an example of width size information storage processing executed by the image forming apparatus according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the following embodiment is an example of a specific embodiment of the present invention and does not limit the technical scope of the present invention.

[0012] [Configuration of image forming apparatus 100] First, the configuration of an image forming apparatus 100 according to an embodiment of the present invention will be described with reference to FIGS.

[0013] For ease of explanation, the vertical direction in the installation state where image forming apparatus 100 is usable (the state shown in FIG. 1) is defined as the up-down direction D1. Also, the front-to-back direction D2 is defined with the left side of image forming apparatus 100 on the paper surface shown in FIG. 1 as the front (front face). Also, the left-to-right direction D3 is defined with the front face of image forming apparatus 100 in the installation state as the reference point.

[0014] Image forming apparatus 100 is a multifunction peripheral that has multiple functions, such as a scanning function for reading an image from an original document, a printing function for forming an image based on image data, a fax function, and a copy function. Note that the present invention may be applied to image forming apparatuses such as printers, fax machines, and copy machines.

[0015] As shown in FIGS. 1 and 2, the image forming apparatus 100 includes an ADF (Auto Document Feeder) 1, an image reading unit 2, an image forming unit 3, a paper feeding unit 4, an operation display unit 5, a storage unit 6, and a control unit 7.

[0016] The ADF 1 transports documents to be scanned by the scanning function, and includes a document setting section, a plurality of transport rollers, a document holder, and a paper ejection section.

[0017] The image reading unit 2 realizes the scanning function and includes a document table, a light source, a plurality of mirrors, an optical lens, and a CCD (Charge Coupled Device).

[0018] The image forming unit 3 realizes the printing function. Specifically, the image forming unit 3 forms a color or monochrome image on a sheet fed from the paper feed unit 4 according to an electrophotographic method.

[0019] The paper feed unit 4 supplies sheets to the image forming unit 3. The paper feed unit 4 includes a paper feed cassette, a manual feed tray, and a plurality of transport rollers.

[0020] The operation display unit 5 is a user interface of the image forming apparatus 100. The operation display unit 5 has a display unit such as a liquid crystal display that displays various information in response to control instructions from the control unit 7, and an operation unit such as operation keys or a touch panel that inputs various information to the control unit 7 in response to user operations.

[0021] The storage unit 6 is a non-volatile storage device. For example, the storage unit 6 is a flash memory. The storage unit 6 is an example of the second storage unit of the present invention.

[0022] The control unit 7 performs overall control of the image forming apparatus 100. As shown in FIG. 2, the control unit 7 includes a CPU 11, a ROM 12, and a RAM 13. The CPU 11 is a processor that executes various types of arithmetic processing. The ROM 12 is a non-volatile storage device that stores in advance information such as control programs for causing the CPU 11 to execute various types of processing. The RAM 13 is a volatile storage device that is used as a temporary storage memory (work area) for the various types of processing executed by the CPU 11. The CPU 11 performs overall control of the image forming apparatus 100 by executing the various control programs that are stored in advance in the ROM 12. The RAM 13 is an example of a first storage unit of the present invention.

[0023] The control unit 7 may be a control unit provided separately from a main control unit that performs overall control of the image forming apparatus 100. The control unit 7 may also be configured with an electronic circuit such as an integrated circuit (ASIC).

[0024] [Configuration of image forming unit 3] Next, the configuration of the image forming section 3 will be described with reference to Figures 1 to 3. Here, Figure 3 is a cross-sectional view showing the configuration of a plurality of image forming units 20, an intermediate transfer belt 26, and a secondary transfer roller 27.

[0025] As shown in FIG. 1, the image forming section 3 includes four image forming units 20, an optical scanning device 25, an intermediate transfer belt 26, a secondary transfer roller 27, a fixing device 28, and a paper discharge tray 29.

[0026] Of the four image forming units 20, image forming unit 21 (see FIG. 3) forms a Y (yellow) toner image. Of the four image forming units 20, image forming unit 22 (see FIG. 3) forms a C (cyan) toner image. Of the four image forming units 20, image forming unit 23 (see FIG. 3) forms an M (magenta) toner image. Of the four image forming units 20, image forming unit 24 (see FIG. 3) forms a K (black) toner image. In other words, the image forming section 3 forms an image on a sheet using each of the CMYK toners. As shown in FIGS. 1 and 3, the four image forming units 20 are arranged side by side in the order of yellow, cyan, magenta, and black from the front side of the image forming apparatus 100 along the front-rear direction D2.

[0027] 3, each image forming unit 20 includes a photosensitive drum 31, a charging roller 32, a developing device 33, a primary transfer roller 34, and a drum cleaning unit 35. Each image forming unit 20 also includes a toner container 36 shown in FIG.

[0028] An electrostatic latent image is formed on the surface of the photosensitive drum 31. For example, the photosensitive drum 31 has a photosensitive layer formed of amorphous silicon. The photosensitive drum 31 receives a rotational driving force supplied from a motor (not shown) and rotates in a rotation direction D4 shown in FIG. 3. As a result, the photosensitive drum 31 transports the electrostatic latent image formed on its surface.

[0029] A preset charging voltage is applied to the charging roller 32, which charges the surface of the photosensitive drum 31. For example, the charging roller 32 charges the surface of the photosensitive drum 31 to a positive polarity. The surface of the photosensitive drum 31 charged by the charging roller 32 is irradiated with light based on image data emitted from the optical scanning device 25. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 31.

[0030] The developing device 33 develops the electrostatic latent image formed on the surface of the photosensitive drum 31. The developing device 33 includes a pair of stirring members, a magnet roller, and a developing roller. The pair of stirring members stir the developer contained inside the developing device 33. The developer contains toner and carrier. As a result, the toner contained in the developer is positively charged due to friction with the carrier contained in the developer. The magnet roller picks up the developer stirred by the pair of stirring members and supplies the toner contained in the developer to the developing roller. The developing roller transports the toner supplied from the magnet roller to a position facing the photosensitive drum 31. Furthermore, the developing roller receives a preset development bias voltage and supplies the toner transported to the facing position to the photosensitive drum 31. As a result, the electrostatic latent image formed on the surface of the photosensitive drum 31 is visualized (developed). The developing device 33 is supplied with toner from a toner container 36.

[0031] The primary transfer roller 34 receives a supply of a preset primary transfer current and transfers the toner image formed on the surface of the photosensitive drum 31 onto the outer circumferential surface of the intermediate transfer belt 26. As shown in Fig. 3, the primary transfer roller 34 is disposed opposite the photosensitive drum 31 with the intermediate transfer belt 26 sandwiched therebetween.

[0032] The drum cleaning unit 35 removes the toner remaining on the surface of the photosensitive drum 31 after the toner image has been transferred by the primary transfer roller 34 .

[0033] The optical scanning device 25 emits light based on image data toward the surface of the photosensitive drum 31 of each image forming unit 20.

[0034] The intermediate transfer belt 26 is an endless belt member onto which the toner image formed on the surface of the photosensitive drum 31 of each image forming unit 20 is transferred. The intermediate transfer belt 26 is stretched with a predetermined tension by a drive roller 26A (see FIG. 3) and a tension roller 26B (see FIG. 3). The intermediate transfer belt 26 rotates in a rotation direction D5 shown in FIG. 3 when the drive roller 26A rotates due to a rotational driving force supplied from a motor (not shown). As a result, the intermediate transfer belt 26 transports the toner image formed on its outer circumferential surface to a secondary transfer position P1 (see FIG. 3) where the secondary transfer roller 27 transfers the toner image. After the toner image is transferred by the secondary transfer roller 27, the outer circumferential surface of the intermediate transfer belt 26 is cleaned by a belt cleaning device 26C shown in FIG. 3.

[0035] The secondary transfer roller 27 receives a predetermined secondary transfer current and transfers the toner image transferred onto the outer peripheral surface of the intermediate transfer belt 26 onto a sheet supplied from the paper feed unit 4. As shown in FIG. 3, the secondary transfer roller 27 is disposed opposite the drive roller 26A with the intermediate transfer belt 26 sandwiched therebetween. The secondary transfer roller 27 is urged toward the drive roller 26A by a urging member (not shown) so as to contact the intermediate transfer belt 26 with a predetermined nip pressure. The secondary transfer roller 27 transfers the toner image formed on the intermediate transfer belt 26 onto the sheet at a secondary transfer position P1 (see FIG. 3) where the secondary transfer roller 27 contacts the intermediate transfer belt 26. The sheet onto which the toner image has been transferred at the secondary transfer position P1 is transported in a transport direction D6 (see FIG. 1) toward a fixing position P2 (see FIG. 1).

[0036] The fixing device 28 fixes the toner image transferred onto the sheet by the secondary transfer roller 27 onto the sheet.

[0037] The sheet on which the toner image has been fixed by the fixing device 28 is discharged onto the paper discharge tray 29.

[0038] [Configuration of fixing device 28] Next, the configuration of the fixing device 28 will be described with reference to FIGS.

[0039] 4, the fixing device 28 includes a fixing belt 41, a heater 42, a heater support portion 43, a pressing member 44, and a pressure roller 45. Also, as shown in FIG. 2, the fixing device 28 includes a temperature sensor 46 and a motor 47.

[0040] The fixing belt 41 fixes the toner image transferred onto the sheet onto the sheet. The fixing belt 41 is an example of the fixing unit of the present invention. Note that the fixing unit of the present invention may be a member having a shape different from a belt, such as a fixing roller.

[0041] As shown in FIG. 4, the fixing belt 41 is an endless belt-shaped member. The fixing belt 41 is flexible. The fixing belt 41 is sandwiched between a heater 42 and a pressure roller 45, and travels in a travel direction D7 (see FIG. 4) following the rotation of the pressure roller 45. The sheet onto which the toner image has been transferred is heated and pressurized as it passes through a fixing position P2 (see FIG. 4) where the toner image is fixed by the fixing belt 41. This causes the toner image transferred to the sheet to be fixed to the sheet. The fixing position P2 is the position where the fixing belt 41 and the pressure roller 45 come into contact with each other.

[0042] The heater 42 heats the fixing belt 41 .

[0043] The heater 42 is formed in a flat plate shape extending in the left-right direction D3 and is provided in contact with the inner circumferential surface 41B of the fixing belt 41 (see FIG. 4).

[0044] As shown in FIG. 5, the heater 42 includes a substrate 42C and a resistance heating element 42D. The substrate 42C is formed in a flat plate shape extending in the left-right direction D3. The resistance heating element 42D is mounted on a first surface 42A (see FIG. 5) of the substrate 42C that contacts the inner circumferential surface 41B of the fixing belt 41. The resistance heating element 42D is connected to a power supply (not shown) via a wiring pattern or the like mounted on the first surface 42A. The resistance heating element 42D generates heat when a current supplied from the power supply flows through it.

[0045] Heater 42 is disposed opposite pressure roller 45 with fixing belt 41 sandwiched therebetween. Heater 42 is pressed against inner circumferential surface 41B of fixing belt 41 by pressure member 44 pressing heater 42 toward pressure roller 45.

[0046] The heater support part 43 supports the heater 42. As shown in Fig. 4, the heater support part 43 has a recess 43A formed therein into which the heater 42 can be fitted. The heater 42 is fitted into the recess 43A of the heater support part 43.

[0047] Furthermore, the heater support part 43 guides the fixing belt 41 so that the fixing belt 41 runs along a predetermined running path. Specifically, the heater support part 43 includes a pair of guide parts 43B (see FIG. 4) that contact the inner circumferential surface 41B of the fixing belt 41 to guide the fixing belt 41.

[0048] The pressing member 44 presses the heater support portion 43 toward the pressure roller 45. The pressing member 44 is provided in contact with the heater support portion 43 and is elongated in the left-right direction D3, which is the width direction of the fixing belt 41. Both ends of the pressing member 44 in the longitudinal direction receive a biasing force from a biasing member (not shown) in a direction toward the pressure roller 45. This causes the pressing member 44 to press the heater support portion 43 toward the pressure roller 45. As the heater support portion 43 is pressed toward the pressure roller 45, the heater 42 supported by the heater support portion 43 is also pressed toward the pressure roller 45.

[0049] Pressure roller 45 is provided in contact with outer peripheral surface 41A of fixing belt 41. Pressure roller 45 includes a metal shaft portion 45A and an elastic layer 45B having elasticity formed on the outer periphery of shaft portion 45A. Shaft portion 45A is rotatably supported by a pair of side plates provided inside the housing of image forming apparatus 100. Pressure roller 45 receives a rotational driving force supplied from motor 47 and rotates in rotation direction D8 (see FIG. 4).

[0050] The temperature sensor 46 detects the temperature of the heater 42 .

[0051] 5, the temperature sensor 46 is provided on the second surface 42B of the heater 42, behind the first surface 42A. For example, the temperature sensor 46 is an electric circuit including a thermistor, and outputs an electric signal corresponding to the temperature at the installation position. The electric signal output from the temperature sensor 46 is input to the control unit 7.

[0052] The motor 47 supplies a rotational driving force to the pressure roller 45 .

[0053] In the image forming apparatus 100, when an image is formed on a sheet whose width size is smaller than a predetermined reference size, the temperature of the fixing belt 41 may become excessively high outside the contact area with the sheet. If an image is formed on a sheet whose width size is larger in this state, a problem called high-temperature offset occurs, in which part of the toner contained in the toner image transferred to the sheet is transferred to the subsequent sheet via the excessively high-temperature area of ​​the fixing belt 41. In response to this, there is known an image forming apparatus that prohibits image formation and executes a temperature reduction process to reduce the temperature of the fixing belt 41 when the width size of the sheet on which the next image is to be formed is larger than the width size of the sheet on which the previous image was formed.

[0054] In this embodiment, the width direction is the same direction as the left-right direction D3. In this embodiment, the reference size is the width direction size of the largest sheet in the width direction among sheets on which an image can be formed in the image forming apparatus 100. The reference size may be a size smaller than the width direction size of the largest sheet in the width direction among sheets on which an image can be formed in the image forming apparatus 100.

[0055] In a configuration that determines whether the temperature lowering process is necessary based on a comparison between the width direction of the sheet on which the next image will be formed and the width direction of the sheet on which the immediately preceding image was formed, it is necessary to store width size information corresponding to the width direction of the sheet on which the last image was formed. The width size information indicates the width direction of the sheet. Alternatively, a configuration is conceivable in which the width size information corresponding to the width direction of the sheet on which the image was formed in the image forming process is stored in RAM 13 each time an image forming process is executed, and the width size information last stored in RAM 13 is saved in storage unit 6 when power supply to RAM 13 is stopped.

[0056] However, in the above-described configuration, if power supply to the RAM 13 is stopped due to a power outage or the like before the width size information last stored in the RAM 13 is saved in the storage unit 6, and then power supply to the RAM 13 is resumed, the width size information last stored in the storage unit 6 is treated as the saved width size information. Therefore, when the next image forming process is executed, it may not be possible to correctly determine whether the temperature reduction process is necessary, and the occurrence of the high-temperature offset may not be suppressed.

[0057] In contrast to this, the image forming apparatus 100 according to the embodiment of the present invention can suppress the occurrence of the high-temperature offset, as will be described below.

[0058] [Configuration of control unit 7] Next, the configuration of the control unit 7 will be described with reference to FIG.

[0059] As shown in FIG. 2, the control unit 7 includes a first storage processing unit 51, a detection processing unit 52, a determination processing unit 53, a second storage processing unit 54, a third storage processing unit 55, and a fourth storage processing unit 56.

[0060] Specifically, an operation control program for causing the CPU 11 to function as each of the above-mentioned processing units is stored in advance in the ROM 12 of the control unit 7. The CPU 11 executes the operation control program stored in the ROM 12 to function as each of the above-mentioned processing units.

[0061] The operation control program may be recorded on a computer-readable recording medium such as a CD, DVD, or flash memory, and may be read from the recording medium and stored in a storage device such as the memory unit 6. Some or all of the processing units included in the control unit 7 may be configured with electronic circuits. The operation control program may also be a program for causing multiple processors to function as the processing units included in the control unit 7.

[0062] The first storage processing unit 51 stores in RAM 13 width size information corresponding to the width size of the sheet that has passed through the fixing position P2 (see Figure 4) of the toner image by the fixing belt 41.

[0063] For example, every time a sheet passes through the fixing position P2, the first storage processing unit 51 stores the width size information corresponding to the sheet in the RAM 13. Note that, when the image forming process is completed, the first storage processing unit 51 may store the width size information corresponding to the sheet that last passed through the fixing position P2 in the RAM 13.

[0064] For example, each time a sheet passes through the fixing position P2, the first storage processing unit 51 overwrites and stores the width size information corresponding to the sheet in a predetermined first storage area in the RAM 13. The first storage area is a storage area that can store only one piece of width size information. Note that the first storage area may be a storage area that can store multiple pieces of width size information.

[0065] The detection processing unit 52 detects the temperature of the fixing belt 41 .

[0066] For example, the detection processing unit 52 detects the temperature of the fixing belt 41 using the temperature sensor 46. Note that the detection processing unit 52 may detect the temperature of the fixing belt 41 using a sensor capable of detecting the temperature of the fixing belt 41.

[0067] When the image forming process for forming an image on a sheet is executed, the judgment processing unit 53 uses the width size information last stored in RAM 13 to determine whether or not a temperature reduction process for reducing the temperature of the fixing belt 41 is necessary.

[0068] For example, the determination processing unit 53 determines that the temperature lowering process is necessary when both the size condition and the temperature condition are satisfied, and determines that the temperature lowering process is unnecessary when either or both of the size condition and the temperature condition are not satisfied.

[0069] Here, the size condition is that the size in the width direction of the sheet on which an image is next formed is larger than the size in the width direction of the sheet on which an image is formed immediately before.

[0070] The temperature condition is that the temperature of the fixing belt 41 detected by the detection processing unit 52 exceeds a predetermined threshold value. In other words, when the temperature of the fixing belt 41 detected by the detection processing unit 52 is equal to or lower than the threshold value, the determination processing unit 53 determines that the temperature lowering process is unnecessary.

[0071] For example, the temperature reduction process is a process in which the execution of the image forming process is restricted and the driving of the heater 42 is stopped, and the motor 47 is driven to rotate the fixing belt 41 and the pressure roller 45. Note that the temperature reduction process may also be a process in which a cooling device such as a blower fan capable of cooling the fixing belt 41 is driven together with the motor 47, and the execution of the image forming process is restricted and the driving of the heater 42 is stopped.

[0072] The determination processing unit 53 may determine that the temperature lowering process is necessary when the size condition is satisfied.

[0073] The second storage processing unit 54 stores the width size information last stored in the RAM 13 in the storage unit 6 when power supply to the RAM 13 is stopped.

[0074] For example, when the power supply stop condition is satisfied, the second storage processing unit 54 overwrites the width size information stored in the first storage area of ​​the RAM 13 and stores it in a predetermined second storage area in the storage unit 6. The second storage area is a storage area that can store only one piece of width size information. Note that the second storage area may be a storage area that can store multiple pieces of width size information.

[0075] For example, the power supply stopping condition includes that the power switch of the image forming apparatus 100 is operated while the power of the image forming apparatus 100 is on. When the power switch of the image forming apparatus 100 is operated while the power of the image forming apparatus 100 is on, the power supply to the control unit 7 including the RAM 13 is stopped.

[0076] The power supply stop condition also includes a condition that the operation mode of image forming apparatus 100 is transitioned from a normal mode to a power saving mode in which power consumption is reduced compared to the normal mode. In the power saving mode, power supply to control unit 7 including RAM 13 is stopped. For example, the transition condition includes a condition that, when the operation mode of image forming apparatus 100 is the normal mode, a no-operation state in which image forming apparatus 100 is not operated continues for a predetermined period of time. The transition condition also includes a condition that a predetermined operation is performed on operation / display unit 5.

[0077] When power supply to the RAM 13 is started, the third storage processing unit 55 stores the width size information last stored in the storage unit 6 in the RAM 13.

[0078] For example, when power supply to the RAM 13 is started, the third storage processing unit 55 overwrites the width size information stored in the second storage area of ​​the storage unit 6 into the first storage area of ​​the RAM 13.

[0079] In the image forming apparatus 100, when the power switch of the image forming apparatus 100 is operated while the power of the image forming apparatus 100 is off, power supply to the control unit 7 including the RAM 13 is started. In the image forming apparatus 100, when the operation mode of the image forming apparatus 100 transitions from the power saving mode to the normal mode, power supply to the control unit 7 including the RAM 13 is started. For example, in the image forming apparatus 100, when the operation mode of the image forming apparatus 100 is the power saving mode, if a predetermined return condition is satisfied, the operation mode returns from the power saving mode to the normal mode. For example, the return condition includes acceptance of a user operation on the operation / display unit 5. In addition, the return condition includes input of an instruction to execute the image formation process from an external information processing apparatus.

[0080] After the third storage processing unit 55 stores the width size information, the fourth storage processing unit 56 stores in the memory unit 6 the width size information corresponding to the width size of a specific sheet that has the smallest width size among the sheets on which an image can be formed by the image forming device 100.

[0081] For example, after the third storage processing unit 55 stores the width size information, the fourth storage processing unit 56 overwrites and stores the width size information corresponding to the width direction size of the specific sheet in the second storage area of ​​the storage unit 6.

[0082] Below, an example of the procedure of each process executed by the control unit 7 and the storage method of the present invention will be described.

[0083] [Image formation operation control processing] 6, an example of the procedure of the image forming operation control process executed by the control unit 7 in the image forming apparatus 100 will be described. Here, steps S11, S12, etc. represent the numbers of the processing procedures (steps) executed by the control unit 7. Note that the control unit 7 executes the image forming operation control process when an instruction to execute the image forming process is input.

[0084] <Step S11> First, in step S11, the control unit 7 determines whether the size condition is met.

[0085] Specifically, the control unit 7 determines that the size condition is met when the widthwise size of the sheet on which the next image will be formed is larger than the size (the width size information) stored in the first memory area of ​​RAM 13.

[0086] Here, if the control unit 7 determines that the size condition is met (Yes in S11), it shifts the process to step S12. On the other hand, if the size condition is not met (No in S11), it shifts the process to step S14.

[0087] <Step S12> In step S12, the control unit 7 determines whether the temperature condition is satisfied. The processes of steps S11 and S12 are an example of a determination step of the present invention, and are executed by the determination processing unit 53 of the control unit 7.

[0088] Specifically, the control unit 7 detects the temperature of the fixing belt 41 using the temperature sensor 46. This process is executed by the detection processing unit 52 of the control unit 7.

[0089] Then, when the detected temperature of the fixing belt 41 exceeds the threshold value, the control unit 7 determines that the temperature condition is satisfied.

[0090] Here, if the control unit 7 determines that the temperature condition is satisfied (Yes in S12), the control unit 7 shifts the process to step S13. On the other hand, if the temperature condition is not satisfied (No in S12), the control unit 7 shifts the process to step S14.

[0091] <Step S13> In step S13, the control unit 7 executes the temperature lowering process.

[0092] <Step S14> In step S14, the control unit 7 executes the image forming process.

[0093] [Width size information storage process] 7, an example of the procedure for width size information storage processing executed by the control unit 7 in the image forming apparatus 100 will be described. Note that the control unit 7 executes the width size information storage processing when the image forming apparatus 100 is powered on or when the operation mode of the image forming apparatus 100 returns from the power saving mode to the normal mode.

[0094] <Step S21> First, in step S21, the control unit 7 stores the width size information last stored in the memory unit 6 in the RAM 13. The process of step S21 is an example of a third storage step of the present invention, and is executed by the third storage processing unit 55 of the control unit 7.

[0095] Specifically, the control unit 7 overwrites the width size information stored in the second storage area of ​​the storage unit 6 into the first storage area of ​​the RAM 13.

[0096] <Step S22> In step S22, the control unit 7 stores the width size information corresponding to the width direction size of the specific sheet in the memory unit 6. The process of step S22 is an example of a fourth storage step of the present invention, and is executed by the fourth storage processing unit 56 of the control unit 7.

[0097] Specifically, the control unit 7 overwrites and stores the width size information corresponding to the width size of the specific sheet in the second storage area of ​​the storage unit 6. As a result, even if power supply to RAM 13 is stopped due to a power outage or the like before the width size information last stored in RAM 13 is saved to the storage unit 6, and then power supply to RAM 13 is resumed, the width size information corresponding to the width size of the specific sheet is treated as the saved width size information. This makes it possible to avoid determining that the temperature reduction process is unnecessary when the next image formation process is performed, even though it is necessary. This makes it possible to suppress the occurrence of high-temperature offset.

[0098] <Step S23> In step S23, the control unit 7 determines whether or not the power supply stop condition is met.

[0099] Specifically, the control unit 7 determines that the power supply stop condition is satisfied when the power switch of the image forming apparatus 100 is operated. Also, the control unit 7 determines that the power supply stop condition is satisfied when the transition condition is satisfied.

[0100] Here, if the control unit 7 determines that the power supply stop condition is satisfied (Yes in S23), the control unit 7 shifts the process to step S26. On the other hand, if the power supply stop condition is not satisfied (No in S23), the control unit 7 shifts the process to step S24.

[0101] <Step S24> In step S24, the control section 7 determines whether the sheet has passed the fixing position P2 (see FIG. 4).

[0102] Here, when the control unit 7 determines that the sheet has passed the fixing position P2 (Yes in S24), the control unit 7 shifts the process to step S25. On the other hand, when the sheet has not passed the fixing position P2 (No in S24), the control unit 7 shifts the process to step S23.

[0103] <Step S25> In step S25, the control unit 7 stores the width size information corresponding to the sheet that has passed the fixing position P2 in the RAM 13. The process of step S25 is an example of a first storing step of the present invention, and is executed by the first storage processing unit 51 of the control unit 7.

[0104] Specifically, the control unit 7 overwrites and stores the width size information corresponding to the sheet that has passed the fixing position P2 in the first storage area of ​​the RAM 13.

[0105] <Step S26> In step S26, the control unit 7 stores the width size information last stored in the RAM 13 in the memory unit 6. The process of step S26 is an example of a second storage step of the present invention, and is executed by the second storage processing unit 54 of the control unit 7.

[0106] Specifically, the control unit 7 overwrites the width size information stored in the first storage area of ​​the RAM 13 into the second storage area of ​​the storage unit 6.

[0107] In this way, in the image forming apparatus 100, after power supply to the RAM 13 is started and the width size information last stored in the storage unit 6 is stored in the RAM 13, the width size information corresponding to the width size of the specific sheet is stored in the storage unit 6. As a result, even if power supply to the RAM 13 is stopped due to a power outage or the like before the width size information last stored in the RAM 13 is saved to the storage unit 6, and then power supply to the RAM 13 is resumed, the width size information corresponding to the width size of the specific sheet is treated as the saved width size information. This makes it possible to avoid determining that the temperature reduction process is unnecessary when the next image forming process is performed, even though it is necessary. This makes it possible to suppress the occurrence of high-temperature offset.

[0108] [Notes on the Invention] The following is a summary of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0109] <Appendix 1> an image forming apparatus comprising: a fixing unit that fixes a toner image transferred to a sheet to the sheet; a first storage processing unit that stores width size information corresponding to the width size of the sheet that has passed a fixing position of the toner image by the fixing unit in a volatile first memory unit, the width size information corresponding to the width size of the sheet that is perpendicular to the sheet conveying direction when the sheet has passed a fixing position of the toner image by the fixing unit; a judgment processing unit that determines whether or not a temperature reduction process is required to reduce the temperature of the fixing unit using the width size information last stored in the first memory unit when an image forming process is performed to form an image on the sheet; a second storage processing unit that stores the width size information last stored in the first memory unit in a non-volatile second memory unit when power supply to the first memory unit is stopped; a third storage processing unit that stores the width size information last stored in the second memory unit in the first memory unit when power supply to the first memory unit is started; and a fourth storage processing unit that stores the width size information corresponding to the width size of the sheet that has the smallest width size among the sheets on which the image can be formed by the image forming apparatus in the second memory unit after the third storage processing unit has stored the width size information.

[0110] <Appendix 2> 2. The image forming apparatus according to claim 1, wherein the first storage processing unit stores the width size information in the first memory unit every time the sheet passes through the fixing position.

[0111] <Appendix 3> An image forming apparatus as described in Appendix 1 or 2, further comprising a detection processing unit that detects the temperature of the fixing unit, and the judgment processing unit determines that the temperature reduction processing is unnecessary when the temperature of the fixing unit detected by the detection processing unit is equal to or lower than a predetermined threshold.

[0112] <Appendix 4> a determination step, when an image forming process for forming an image on the sheet is performed, of determining whether or not a temperature reduction process for reducing the temperature of the fixing unit is necessary, using the width size information last stored in the first storage unit; a second storage step, when power supply to the first storage unit is stopped, of storing the width size information last stored in the first storage unit in a non-volatile second storage unit; a third storage step, when power supply to the first storage unit is started, of storing the width size information last stored in the second storage unit in the first storage unit; and a fourth storage step, after storing the width size information in the third storage step, of storing the width size information last stored in the second storage unit in the second storage unit, corresponding to the width size of the sheet having the smallest width size among the sheets on which an image can be formed by the image forming device. [Explanation of symbols]

[0113] 1 ADF 2 Image reading unit 3 Image forming unit 4 Paper feed section 5 Operation display section 6 Memory section 7 Control Unit 20 Image forming unit 25 Optical scanning device 26 Intermediate transfer belt 27 Secondary transfer roller 28 Fixing device 29 Paper output tray 41 Fixing belt 42 Heater 43 Heater support 44 Pressing member 45 Pressure Roller 46 Temperature Sensor 47 Motor 51 First storage processing unit 52 Detection processing section 53 Judgment processing unit 54 Second storage processing unit 55 Third storage processing unit 56 Fourth storage processing unit 100 Image forming device

Claims

1. a fixing unit that fixes the toner image transferred onto the sheet; a first storage processing unit that stores width size information corresponding to a size of the sheet in a width direction perpendicular to a conveyance direction of the sheet, the size having passed a fixing position of the toner image by the fixing unit, in a volatile first storage unit; a determination processing unit that determines, when an image forming process for forming an image on the sheet is executed, whether or not a temperature reduction process for reducing the temperature of the fixing unit is necessary, using the width size information last stored in the first storage unit; a second storage processing unit that stores the width size information last stored in the first storage unit in a non-volatile second storage unit when power supply to the first storage unit is stopped; a third storage processing unit that stores the width size information last stored in the second storage unit in the first storage unit when power supply to the first storage unit is started; a fourth storage processing unit that stores, in the second storage unit, the width size information corresponding to the width direction size of the sheet having the smallest width direction size among the sheets on which an image can be formed by the image forming device, after the width size information is stored by the third storage processing unit; An image forming apparatus comprising:

2. the first storage processing unit stores the width size information in the first storage unit every time the sheet passes through the fixing position; The image forming apparatus according to claim 1 .

3. a detection processing unit that detects the temperature of the fixing unit, the determination processing unit determines that the temperature lowering process is unnecessary when the temperature of the fixing unit detected by the detection processing unit is equal to or lower than a predetermined threshold value; 3. The image forming apparatus according to claim 1.

4. 1. A storage method executed in an image forming apparatus having a fixing unit that fixes a toner image transferred onto a sheet, the method comprising: a first storing step of storing width size information corresponding to a size in a width direction perpendicular to a conveyance direction of the sheet of the sheet that has passed a fixing position of the toner image by the fixing unit in a volatile first storage unit; a determination step of determining, when an image forming process for forming an image on the sheet is executed, whether or not a temperature reduction process for reducing the temperature of the fixing unit is necessary, using the width size information last stored in the first storage unit; a second storage step of storing the width size information last stored in the first storage unit in a non-volatile second storage unit when power supply to the first storage unit is stopped; a third storing step of storing the width size information last stored in the second storage unit in the first storage unit when power supply to the first storage unit is started; a fourth storage step of storing, in the second storage unit, the width size information corresponding to the width direction size of the sheet having the smallest width direction size among the sheets on which an image can be formed by the image forming apparatus, after the width size information is stored in the third storage step; Storage method including.

Images