Image forming apparatus, operation control method

Abstract

To provide an image forming apparatus and an operation control method capable of suppressing the generation of abnormal images. [Solution] The image forming apparatus 10 includes a fixing belt and pressure rollers that form a fixing nip section, a movable unit that moves along a width direction perpendicular to the sheet transport direction, a detection processing unit 94 that detects humidity at the installation location of the image forming apparatus 10, an accumulation processing unit 95 that accumulates a specific value based on the length in the transport direction of the sheet obtained for each sheet passing through the fixing nip section and the detection result by the detection processing unit 94, and a movement processing unit 96 that moves the movable unit when the accumulated value of the specific value exceeds a threshold.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus and an operation control method.

Background Art

[0002] An electrophotographic image forming apparatus includes a fixing member such as a fixing belt and a pressing member such as a pressing roller (see, for example, Patent Document 1). The fixing member and the pressing member form a fixing nip portion that fixes the toner image transferred to the sheet onto the sheet.

Prior Art Documents

Patent Documents

[0003] [[ID=:22]]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the image forming apparatus, as the sheet repeatedly passes through the fixing nip portion, wear of the contact portion of the fixing member with the side end portion of the sheet progresses more than other portions. When the wear of the contact portion of the fixing member with the side end portion of the sheet progresses, streak-like scratches are formed on the fixing member along the conveyance direction of the sheet, and streak-like abnormal images are generated in the output image due to the scratches.

[0005] On the other hand, the length in the conveyance direction of the sheet obtained for each sheet passing through the fixing nip portion is integrated, and when the integrated value of the length exceeds a predetermined threshold value, a configuration is conceivable in which a movable unit including the fixing member and the pressing member is moved in the width direction of the sheet.

[0006] However, wear at the contact portion of the fixing member with the sheet progresses more easily when the water content of the sheet is low. Therefore, in the above configuration, which controls the movement of the movable unit without considering the water content of the sheet, it may not be possible to move the movable unit at the appropriate timing, and the occurrence of the abnormal image may not be suppressed.

[0007] The object of the present invention is to provide an image forming apparatus and an operation control method that can suppress the generation of abnormal images. [Means for solving the problem]

[0008] An image forming apparatus according to one aspect of the present invention comprises a movable unit, a detection processing unit, an integration processing unit, and a movement processing unit. The movable unit includes a fixing member and a pressing member that form a fixing nip portion for fixing a toner image transferred to a sheet onto the sheet, and is moved along a width direction perpendicular to the conveying direction of the sheet. The detection processing unit detects the humidity at the installation location of the apparatus. The integration processing unit integrates the length in the conveying direction of the sheet, acquired for each sheet passing through the fixing nip portion, and a specific value based on the detection result by the detection processing unit. The movement processing unit moves the movable unit when the integrated value of the specific value exceeds a predetermined threshold.

[0009] Another aspect of the present invention relates to an operation control method that is performed in an image forming apparatus comprising a fixing member and a pressing member that form a fixing nip portion for fixing a toner image transferred to a sheet onto the sheet, and a movable unit that moves along a width direction perpendicular to the conveying direction of the sheet, and includes a detection step, an accumulation step, and a movement step. In the detection step, the humidity at the installation location of the image forming apparatus is detected. In the accumulation step, a specific value based on the length in the conveying direction of the sheet obtained for each sheet passing through the fixing nip portion and the detection result from the detection step is accumulated. In the movement step, the movable unit is moved if the accumulated value of the specific value exceeds a predetermined threshold. [Effects of the Invention]

[0010] According to the present invention, the occurrence of abnormal images can be suppressed. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a configuration diagram of an image forming apparatus according to an embodiment. [Figure 2] Figure 2 shows the configuration of the main part of the fixing device in the image forming apparatus according to the embodiment. [Figure 3] Figure 3 is a front view of the fixing device in the image forming apparatus according to the embodiment. [Figure 4] Figure 4 is a perspective view of the fixing unit in the image forming apparatus according to this embodiment. [Figure 5] Figure 5 is a perspective view of the support unit and the movable unit in the image forming apparatus according to the embodiment. [Figure 6] Figure 6 is a plan view of the drive mechanism and reciprocating mechanism in an image forming apparatus according to an embodiment. [Figure 7] Figure 7 is a block diagram showing the system configuration of an image forming apparatus according to an embodiment. [Figure 8] Figure 8 is a flowchart showing an example of the operation control process performed in the image forming apparatus according to this embodiment. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described below with reference to the drawings. Note that the following embodiments are merely examples of the present invention and do not limit the technical scope of the present invention.

[0013] [Configuration of the image forming apparatus 10] The image forming apparatus 10 according to this embodiment performs printing using an electrophotographic method. The printing process is the process of forming an image on a sheet SH.

[0014] As shown in FIG. 1, the image forming apparatus 10 includes a sheet storage unit 2, a sheet conveyance device 3, and a printing device 4. Further, as shown in FIG. 7, the image forming apparatus 10 includes a humidity sensor 7, an operation display unit 8, and a control unit 9. The sheet conveyance device 3, the printing device 4, the humidity sensor 7, and the control unit 9 are housed in a main body unit 1 (see FIG. 1) which is a housing.

[0015] The sheet storage unit 2 can store a plurality of sheets SH.

[0016] The sheet conveyance device 3 includes a sheet feeding device 30 and a plurality of pairs of conveyance rollers 31.

[0017] The sheet feeding device 30 feeds the sheets SH in the sheet storage unit 2 one by one to the conveyance path 300. The conveyance path 300 is a passage for the sheet SH.

[0018] The plurality of pairs of conveyance rollers 31 convey the sheet SH along the conveyance path 300. One of the plurality of pairs of conveyance rollers 31 discharges the sheet SH with an image formed thereon from the conveyance path 300 onto the discharge tray 1a (see FIG. 1).

[0019] The printing device 4 performs the printing process on the sheet SH conveyed along the conveyance path 300. The image formed on the sheet SH is a toner image.

[0020] The printing device 4 includes an optical scanning unit 40, one or more image forming units 4x, a transfer device 45, and a fixing device 5.

[0021] The image forming unit 4x includes a photoreceptor 41, a charging device 42, a developing device 43, and a drum cleaning device 44.

[0022] The charging device 42 charges the surface of the photoreceptor 41. The optical scanning unit 40 scans the charged surface of the photoreceptor 41 with a beam of light. Thereby, the optical scanning unit 40 forms an electrostatic latent image on the surface of the photoreceptor 41.

[0023] The developing device 43 develops the electrostatic latent image into a toner image by supplying toner to the surface of the photoreceptor 41. The transfer device 45 transfers the toner image formed on the surface of the photoreceptor 41 to the sheet SH.

[0024] The transfer device 45 transfers the toner image to the sheet SH at the transfer position P1 (see Figure 1) in the transport path 300.

[0025] In this embodiment, the printing apparatus 4 is a tandem-type color printing apparatus equipped with a plurality of image forming units 4x. The transfer apparatus 45 includes an intermediate transfer belt 450, a plurality of primary transfer devices 451, a secondary transfer device 452, and a belt cleaning device 453.

[0026] In the example shown in Figure 1, the printing device 4 comprises four image forming units 4x corresponding to four toner colors: yellow, magenta, cyan, and black. The transfer device 45 comprises four primary transfer units 451 corresponding to the four image forming units 4x.

[0027] The intermediate transfer belt 450 is rotatably supported by a plurality of support rollers 454. One of the support rollers 454 is rotated by a belt drive device (not shown), thereby causing the intermediate transfer belt 450 to rotate.

[0028] Each primary transfer device 451 transfers the toner image formed on the surface of the photoreceptor 41 in each image forming unit 4x to the surface of the intermediate transfer belt 450. As a result, a composite toner image, formed by combining the four toner images, is created on the surface of the intermediate transfer belt 450.

[0029] The intermediate transfer belt 450 rotates while carrying the synthetic toner image. The secondary transfer device 452 transfers the synthetic toner image formed on the surface of the intermediate transfer belt 450 to the sheet SH at the transfer position P1.

[0030] The drum cleaning device 44 removes primary waste toner from the surface of the photoreceptor 41. The primary waste toner is the toner remaining on the surface of the photoreceptor 41 that has passed through the primary transfer device 451.

[0031] The belt cleaning device 453 removes secondary waste toner from the surface of the intermediate transfer belt 450. The secondary waste toner is the toner remaining on the surface of the intermediate transfer belt 450 that has passed through the secondary transfer device 452.

[0032] The fixing device 5 heats and pressurizes the synthesized toner image on the sheet SH at the fixing position P2 (see Figure 1) in the transport path 300. This fixes the synthesized toner image to the sheet SH. The fixing position P2 is located downstream of the transfer position P1 in the transport direction D4 (see Figure 1) of the sheet SH.

[0033] As shown in Figure 2, the fixing device 5 includes a heater 51, a fixing belt 52, a fixing roller 520, a pressure roller 53, and a sheet separating member 5200.

[0034] The fixing belt 52 is a flexible cylindrical member that encloses the fixing roller 520. The fixing belt 52 is heated by the heater 51.

[0035] The fixing roller 520 is a cylindrical member that supports the fixing belt 52 from the inside of the fixing belt 52. The fixing roller 520 has a cylindrical core metal portion 521 and an elastic portion 522 formed on the outer circumference of the core metal portion 521.

[0036] The fixing roller 520 is rotatably supported. The fixing belt 52 is rotatable together with the fixing roller 520.

[0037] The fixing belt 52 comprises a conductive base material, an elastic layer formed on the outer periphery of the base material, and a release layer formed on the outer periphery of the elastic layer. The base material is made of nickel. The elastic layer is made of silicone rubber. The release layer is made of PFA tubing.

[0038] The heater 51 is positioned opposite the outer circumferential surface of the fixing belt 52. In this embodiment, the heater 51 is an electromagnetic induction heating device. The heater 51 primarily heats the base material of the fixing belt 52 by electromagnetic induction.

[0039] The pressure roller 53 is rotatably supported. Like the fixing roller 520, the pressure roller 53 also has a cylindrical core portion 531 and an elastic portion 532 formed on the outer circumference of the core portion 531.

[0040] The pressure roller 53 is driven and rotated by a drive device (not shown). The fixing belt 52 and the fixing roller 520 rotate in conjunction with the pressure roller 53.

[0041] The fixing belt 52 heats the toner image formed on the sheet SH. The pressure roller 53 applies pressure to the toner image toward the sheet SH.

[0042] The fixing belt 52 and the pressure roller 53 transport the sheet SH onto which the toner image has been transferred, and form a fixing nip section that fixes the toner image to the sheet SH. Fixing position P2 is the position where the fixing nip section is formed. The fixing belt 52 and the pressure roller 53 are arranged side by side along a horizontal plane (see Figure 1). The heater 51 heats the fixing belt 52 on the side opposite to the pressure roller 53. The fixing belt 52 is an example of a fixing member of the present invention. The pressure roller 53 is an example of a pressure member of the present invention.

[0043] The sheet separation member 5200 separates the sheet SH from the fixing belt 52 when the sheet SH adheres to the fixing belt 52.

[0044] The humidity sensor 7 detects the humidity at the location where it is installed. The humidity sensor 7 is located inside the main body 1. In other words, the humidity sensor 7 detects the humidity inside the image forming apparatus 10. For example, the humidity sensor 7 detects the absolute humidity inside the image forming apparatus 10. The humidity sensor 7 may also be located outside the main body 1.

[0045] The operation display unit 8 is the user interface of the image forming apparatus 10. The operation display unit 8 has a display unit and an operation unit. The display unit displays various information in response to control instructions from the control unit 9. Specifically, the display unit is a display device such as a liquid crystal display. The operation unit inputs various information to the control unit 9 in response to user operations. Specifically, the operation unit is an operating device including operation keys and a touch panel.

[0046] The control unit 9 comprehensively controls the image forming apparatus 10. As shown in Figure 7, the control unit 9 comprises a CPU 90, ROM 91, RAM 92, and a storage unit 93. The CPU 90 is a processor that performs various arithmetic operations. The ROM 91 is a non-volatile memory device in which information such as control programs for causing the CPU 90 to perform various operations is pre-stored. The RAM 92 is a volatile or non-volatile memory device used as a temporary memory (work area) for the various operations performed by the CPU 90. The storage unit 93 is a non-volatile memory device such as flash memory. The CPU 90 comprehensively controls the image forming apparatus 10 by executing various control programs pre-stored in the ROM 91. Note that the control unit 9 may be a separate control unit from the main control unit that comprehensively controls the image forming apparatus 10. Also, the control unit 9 may be composed of electronic circuits such as an integrated circuit (ASIC).

[0047] In this embodiment, the fixing device 5 is divided into a heating unit 5a and a fixing unit 5b (see Figure 3). The heating unit 5a has a heater 51. The fixing unit 5b has a fixing belt 52, a fixing roller 520, and a pressure roller 53.

[0048] By moving the heating unit 5a to a position away from the fixing unit 5b, the fixing unit 5b can be pulled out from the main body 1 in a removal direction D11 (see Figure 6) along the first direction D1. The first direction D1 is the direction along the centerlines of rotation of the fixing belt 52 and the pressure roller 53. In this embodiment, the first direction D1 is the depth direction of the image forming apparatus 10.

[0049] [Configuration of heating unit 5a and fixing unit 5b] The heating unit 5a includes a heater 51 and a support 54 (see Figure 3). The support 54 is a member that supports the heater 51.

[0050] The fixing unit 5b includes a support unit 55 and a movable unit 56 (see Figures 3 and 4). The movable unit 56 includes a fixing belt 52, a fixing roller 520, and a pressure roller 53.

[0051] The support unit 55 supports the movable unit 56 from below.

[0052] As shown in Figures 4 and 5, the support unit 55 comprises a support surface portion 551, an opening 552, a protruding portion 553, and a side wall portion 554.

[0053] The support surface 551 forms a support surface that supports the movable unit 56. The support surface 551 is formed in a flat plate shape perpendicular to the vertical direction D3. The vertical direction D3 is the up and down direction. The first direction D1 is also a direction perpendicular to the vertical direction D3. The support surface 551 is formed in an elongated shape in the first direction D1. Figure 5 shows the movable unit 56 lifted from the support surface 551.

[0054] The opening 552 is provided in the support surface 551. The sheet SH being transported to the anchoring position P2 passes through the inside of the opening 552.

[0055] The protruding portion 553 is provided so as to protrude from the support surface of the support surface portion 551 toward the movable unit 56. Specifically, the protruding portion 553 protrudes upward from the support surface portion 551. The protruding portion 553 is formed in a cylindrical shape. However, the protruding portion 553 may be formed in a rectangular prism shape. As shown in Figure 5, the support unit 55 includes two protruding portions 553 arranged at an interval in the first direction D1.

[0056] The side wall portion 554 is erected along one end of the support surface portion 551 in the first direction D1. Specifically, the side wall portion 554 is erected along the upstream end of the support surface portion 551 in the removal direction D11.

[0057] The movable unit 56 rotatably supports the fixing roller 520 and the pressure roller 53. The fixing roller 520 supports the fixing belt 52. That is, the fixing belt 52 is supported by the movable unit 56 via the fixing roller 520.

[0058] As shown in Figures 4 and 5, the movable unit 56 includes a bottom portion 561 and a guide portion 562.

[0059] The bottom surface 561 forms the bottom surface of the movable unit 56. The bottom surface 561 is formed in a flat plate shape perpendicular to the vertical direction D3. The bottom surface 561 is formed in an elongated shape in the first direction D1. The bottom surface 561 is placed on the support surface 551 of the support unit 55. The bottom surface 561 has an opening (not shown) for passing the sheet SH to the fixing position P2. A fixing belt 52, fixing roller 520, and pressure roller 53 are provided on the upper side of the bottom surface 561.

[0060] The guide portion 562 is provided on the bottom portion 561. The guide portion 562 is formed so that the protrusions 553 of the support unit 55 can be inserted into it. Specifically, the guide portion 562 is a hole formed in the bottom portion 561. The guide portion 562 is formed to be elongated in the first direction D1. The guide portion 562 is provided in correspondence with the two protrusions 553 provided on the support unit 55. In other words, the movable unit 56 has two guide portions 562 that are spaced apart in the first direction D1. When the movable unit 56 is attached to the support unit 55, the two protrusions 553 are inserted into the two guide portions 562.

[0061] The support unit 55 and the movable unit 56 are provided so as to be able to be integrally inserted into and removed from the main body 1, which is the housing of the image forming apparatus 10, along the first direction D1.

[0062] Incidentally, in the image forming apparatus 10, as the sheet SH repeatedly passes through the fixing nip section, wear progresses more rapidly at the contact points between the fixing belt 52 and the side edges of the sheet SH than at other points. As wear progresses at the contact points between the fixing belt 52 and the side edges of the sheet SH, streaky scratches are formed on the fixing belt 52 along the transport direction D4, and these scratches cause streaky abnormal images to appear in the output image.

[0063] In contrast, in the image forming apparatus 10, the movable unit 56 is moved along the width direction of the sheet SH. The width direction is the same direction as the first direction D1.

[0064] The fixing unit 5b further includes a reciprocating mechanism 57 that moves the movable unit 56 back and forth along the first direction D1 (see Figure 6).

[0065] The image forming apparatus 10 further includes a drive mechanism 6 located within the main body 1 (see Figure 6). The drive mechanism 6 is fixed to the main body frame of the main body 1.

[0066] The drive mechanism 6 comprises a reduction gear mechanism 61 including an output gear 611 and an output engagement part 62. The output engagement part 62 is formed integrally with the output gear 611. The output engagement part 62 rotates at the same speed as the output gear 611.

[0067] The reduction gear mechanism 61 transmits the rotational force of a motor (not shown) to the output gear 611 while reducing its speed. The output engagement part 62 is a rotating body that transmits rotational force to the movable unit 56 of the fixing unit 5b.

[0068] The reciprocating mechanism 57 comprises an input engagement portion 571 and a cylindrical cam 572. The input engagement portion 571 is provided projecting from the side wall portion 554 of the support unit 55 in the mounting direction D12. The mounting direction D12 is the opposite direction to the removal direction D11. The input engagement portion 571 engages with the output engagement portion 62. The input engagement portion 571 transmits the rotational force of the output engagement portion 62 to the cylindrical cam 572. The input engagement portion 571 and the cylindrical cam 572 are provided at both ends of a shaft member extending in the first direction D1. The shaft member is rotatably supported by the side wall portion 554.

[0069] The movable unit 56 of the fixing unit 5b has a cam engaging portion 563 that engages with the cylindrical cam 572. As the cylindrical cam 572 rotates, the cam engaging portion 563 reciprocates along the first direction D1.

[0070] As the cam engagement portion 563 reciprocates along the first direction D1, the entire movable unit 56 reciprocates along the first direction D1. In other words, the reciprocating mechanism 57 converts the rotational motion of the output engagement portion 62 into the reciprocating motion of the movable unit 56.

[0071] The guide portion 562 of the movable unit 56 guides the protruding portion 553 of the support unit 55, which swings relative to the movable unit 56, along the first direction D1. The guide portion 562, which is oscillated by the reciprocating mechanism 57, is restricted from moving in the second direction D2, which is perpendicular to the first direction D1, by the protruding portion 553. In other words, the movement of the movable unit 56, which is oscillated by the reciprocating mechanism 57, in the second direction D2 is restricted by the protruding portion 553. The second direction D2 is the lateral direction of the image forming apparatus 10. Also, the second direction D2 is perpendicular to the vertical direction D3.

[0072] Incidentally, one possible configuration is to accumulate the length D4 in the transport direction of each sheet SH that passes through the fixing nip section, and move the movable unit 56 in the width direction when the accumulated length exceeds a predetermined threshold.

[0073] However, wear at the contact point between the fixing belt 52 and the sheet SH progresses more easily the lower the water content of the sheet SH. This is because the lower the water content of the sheet SH, the lower the adhesion between the sheet SH and the fixing belt 52, and the lower the adhesion between the sheet SH and the fixing belt 52, the more likely minute slippage will occur between the sheet SH and the fixing belt 52. Therefore, in the above configuration, which controls the movement of the movable unit 56 without considering the water content of the sheet SH, it may not be possible to move the movable unit 56 at the appropriate timing, and the occurrence of the abnormal image may not be suppressed.

[0074] In contrast, the image forming apparatus 10 according to the embodiment of the present invention can suppress the occurrence of the abnormal image, as will be explained below.

[0075] [Functional configuration of the control unit 9] As shown in Figure 7, the control unit 9 comprises a detection processing unit 94, an integration processing unit 95, and a movement processing unit 96.

[0076] Specifically, the ROM 91 of the control unit 9 contains in advance an operation control program that causes the CPU 90 to function as each of the above-mentioned processing units. The CPU 90 then functions as each of the above-mentioned processing units by executing the operation control program stored in the ROM 91. Some or all of the processing units included in the control unit 9 may be composed of electronic circuits. Furthermore, the operation control program may be a program that causes multiple processors to function as each of the processing units included in the control unit 9.

[0077] The detection processing unit 94 detects the humidity at the installation location of the image forming apparatus 10.

[0078] For example, the detection processing unit 94 detects the absolute humidity at the location where the image forming apparatus 10 is installed. For example, the detection processing unit 94 uses the humidity sensor 7 to detect the absolute humidity inside the image forming apparatus 10.

[0079] The integration processing unit 95 integrates specific values ​​obtained for each sheet SH passing through the fixing nip section. These specific values ​​are based on the length D4 in the transport direction of the sheet SH and the detection results from the detection processing unit 94.

[0080] For example, the specific value is calculated by multiplying the length D4 in the transport direction of the sheet SH by a coefficient corresponding to the humidity detected by the detection processing unit 94.

[0081] For example, in the image forming apparatus 10, table data showing the correspondence between the absolute humidity at the installation location of the image forming apparatus 10 and the coefficient is pre-stored in the storage unit 93. In the table data, the correspondence between the absolute humidity at the installation location of the image forming apparatus 10 and the coefficient is defined such that the coefficient increases as the absolute humidity at the installation location of the image forming apparatus 10 decreases. The higher the absolute humidity at the installation location of the image forming apparatus 10, the greater the moisture content of the sheets SH stored in the sheet storage unit 2. In other words, the absolute humidity at the installation location of the image forming apparatus 10 can be said to be a value corresponding to the moisture content of the sheets SH stored in the sheet storage unit 2. The table data can be determined based on the results of experiments investigating the relationship between the absolute humidity at the installation location of the image forming apparatus 10 and the amount of wear on the fixing belt 52 when a predetermined number of sheets SH are transported using the sheet transport device 3.

[0082] For example, the integration processing unit 95 uses the table data to obtain the coefficient corresponding to the humidity detected by the detection processing unit 94. Then, the integration processing unit 95 calculates the specific value by multiplying the length of the conveying direction D4 in the sheet SH by the obtained coefficient.

[0083] For example, the integration processing unit 95 integrates the specific value for each group of sheets SH that share the same length in the width direction.

[0084] For example, in the image forming apparatus 10, the sheets SH used for printing are classified into one of the following groups: Group 1, Group 2, Group 3, Group 4, Group 5, and Group 6.

[0085] Specifically, a sheet SH of A4 portrait size with a width of 210 mm (millimeters) is classified into the first group.

[0086] Furthermore, A4 landscape-sized sheet SH and A3 portrait-sized sheet SH, which have a width of 297 mm (millimeters), are classified into the second group.

[0087] Furthermore, the B5 portrait-sized sheet SH, which has a width of 182 mm, is classified into the third group.

[0088] Furthermore, B5 landscape-sized sheet SH and B4 portrait-sized sheet SH, which have a width of 257 mm, are classified into the fourth group.

[0089] Furthermore, a Letter-sized sheet SH with a width of 8.5 inches is classified into the fifth group.

[0090] Furthermore, Letter-sized sheets SH with a width of 11 inches and Ledger-sized sheets SH are classified into the sixth group.

[0091] For example, in the image forming apparatus 10, six integrated value storage units corresponding to the six aforementioned groups are pre-installed in the storage unit 93. Each of these integrated value storage units stores the integrated value of the specific value. Note that the values ​​stored in each of these integrated value storage units are zero when the image forming apparatus 10 is shipped from the factory.

[0092] For example, the accumulation processing unit 95 accumulates the specific values ​​obtained each time the print process is executed by performing a process to calculate the specific value corresponding to the sheet SH transported in the print process, and a process to add the calculated specific value to the value stored in the accumulation value storage unit corresponding to the group to which the sheet SH belongs.

[0093] The movement processing unit 96 moves the movable unit 56 when the cumulative value of the specified value exceeds the threshold.

[0094] For example, the movement processing unit 96 moves the movable unit 56 when the cumulative value of the specific values ​​corresponding to any of the groups exceeds the threshold.

[0095] Here, the accumulation processing unit 95 accumulates the specified value for each accumulation period until the movable unit 56 is moved by the movement processing unit 96.

[0096] Specifically, the integration processing unit 95 resets the values ​​stored in each of the integration value storage units to zero when the movable unit 56 is moved by the movement processing unit 96. The integration period is the period from the initial start of the image forming apparatus 10, or from the time when the values ​​stored in each of the integration value storage units are reset to zero, until the movable unit 56 is moved by the movement processing unit 96.

[0097] Furthermore, the movement processing unit 96 moves the movable unit 56 to a position within the movement range of the movable unit 56 that has never been previously positioned when the cumulative value of the specific value exceeds the threshold.

[0098] For example, when the image forming apparatus 10 is shipped from the factory, the movable unit 56 is positioned at one end of the first direction D1 within the range of motion of the movable unit 56. Then, each time the timing for the movement of the movable unit 56 arrives, the movement processing unit 96 moves the movable unit 56 to the other side of the first direction D1 by a predetermined distance. For example, the movement processing unit 96 moves the movable unit 56 to the other side of the first direction D1 by 0.02 mm (millimeters) at a time.

[0099] [Motion control processing] The operation control method of the present invention will be described below with reference to Figure 8, along with an example of the procedure for operation control processing performed by the control unit 9 in the image forming apparatus 10. Here, steps S11, S12, etc. represent the numbers of the processing procedures (steps) performed by the control unit 9. The operation control processing is performed when an execution instruction for a print job to perform the print processing on one or more sheets SH is input.

[0100] <Step S11> First, in step S11, the control unit 9 detects the humidity at the installation location of the image forming apparatus 10. The process in step S11 is an example of the detection steps of the present invention and is performed by the detection processing unit 94 of the control unit 9.

[0101] Specifically, the control unit 9 uses the humidity sensor 7 to detect the absolute humidity inside the image forming apparatus 10.

[0102] <Step S12> In step S12, the control unit 9 uses the table data to obtain the coefficient corresponding to the humidity detected by the processing in step S11.

[0103] <Step S13> In step S13, the control unit 9 performs the printing process on one sheet SH that is transported by the sheet transport device 3.

[0104] <Step S14> In step S14, the control unit 9 calculates the specific value corresponding to the sheet SH on which the print process was performed by the processing in step S13.

[0105] Specifically, the control unit 9 calculates the specific value corresponding to the sheet SH by multiplying the length of the transport direction D4 in the sheet SH on which the printing process was performed by the process in step S13 by the coefficient obtained by the process in step S12.

[0106] <Step S15> In step S15, the control unit 9 updates the value stored in the cumulative value storage unit corresponding to the group to which the sheet SH, which has been printed by the process in step S13, belongs, based on the specific value obtained by the process in step S14. The processes in steps S12, S14, and S15 are examples of the cumulative steps of the present invention and are performed by the cumulative processing unit 95 of the control unit 9.

[0107] Specifically, the control unit 9 adds the specific value obtained by the process in step S14 to the value stored in the cumulative value storage unit corresponding to the group to which the sheet SH to which the print process was performed belongs, by the process in step S13.

[0108] <Step S16> In step S16, the control unit 9 determines whether the print job has been completed.

[0109] If the control unit 9 determines that the print job has finished (Yes in S16), it proceeds to step S17. If the print job has not finished (No in S16), the control unit 9 proceeds to step S13.

[0110] <Step S17> In step S17, the control unit 9 determines whether the cumulative value of the specific value after updating by the processing in step S15, which was the last step executed, exceeds the threshold.

[0111] Here, if the control unit 9 determines that the cumulative value of the specific value after the update performed by the last executed step S15 exceeds the threshold (Yes side of S17), it moves the process to step S18. If the cumulative value of the specific value after the update performed by the last executed step S15 does not exceed the threshold (No side of S17), the control unit 9 terminates the operation control process.

[0112] <Step S18> In step S18, the control unit 9 moves the movable unit 56. The process in step S18 is an example of a movement step of the present invention and is performed by the movement processing unit 96 of the control unit 9.

[0113] Specifically, the control unit 9 moves the movable unit 56 by a predetermined distance to the other side of the first direction D1 (the direction away from the initial placement position).

[0114] <Step S19> In step S19, the control unit 9 resets the values ​​stored in each of the integrated value storage units to zero.

[0115] Thus, in the image forming apparatus 10, the moisture content of the sheet SH is taken into consideration when controlling the movement of the movable unit 56. Compared to a configuration in which the movement of the movable unit 56 is controlled without considering the moisture content of the sheet SH, this allows the movable unit 56 to be moved at a more appropriate timing, thereby suppressing the occurrence of abnormal images.

[0116] [Notes on the invention] The following is an overview of the invention extracted from the above-described embodiments. Note that each configuration and processing function described below can be selected and combined as desired.

[0117] <Note 1> An image forming apparatus comprising: a fixing member and a pressing member that form a fixing nip portion for fixing a toner image transferred to a sheet onto the sheet, a movable unit that moves along a width direction perpendicular to the conveying direction of the sheet, a detection processing unit that detects humidity at the installation location of the apparatus, an integration processing unit that accumulates a specific value based on the length in the conveying direction of the sheet acquired for each sheet passing through the fixing nip portion and the detection result by the detection processing unit, and a movement processing unit that moves the movable unit when the accumulated value of the specific value exceeds a predetermined threshold.

[0118] <Note 2> The image forming apparatus according to Appendix 1, wherein the accumulation processing unit accumulates the specified value for each group of sheets having a common length in the width direction, and the movement processing unit moves the movable unit when the accumulated value of the specified value corresponding to any of the groups exceeds the threshold.

[0119] <Note 3> The image forming apparatus according to Appendix 1 or 2, wherein the accumulation processing unit accumulates the specific value for each accumulation period until the movable unit is moved by the movement processing unit, and the movement processing unit moves the movable unit to a position within the movement range of the movable unit that has never been previously positioned.

[0120] <Note 4> The image forming apparatus according to any one of the appendices 1 to 3, wherein the detection processing unit detects the absolute humidity at the installation location of the apparatus.

[0121] <Note 5> An operation control method performed in an image forming apparatus comprising a fixing member and a pressurizing member that form a fixing nip portion for fixing a toner image transferred to a sheet onto the sheet, and a movable unit that moves along a width direction perpendicular to the conveying direction of the sheet, the operation control method comprising: a detection step for detecting the humidity at the installation location of the image forming apparatus; an accumulation step for accumulating a specific value obtained for each sheet passing through the fixing nip portion, based on the length in the conveying direction of the sheet and the detection result from the detection step; and a movement step for moving the movable unit when the accumulated value of the specific value exceeds a predetermined threshold. [Explanation of Symbols]

[0122] 1: Main body 2: Seat storage section 3: Sheet conveying device 4: Printing device 4x: Image forming section 5: Fixing device 5a: Heating unit 5b: Fixing unit 6: Drive mechanism 7: Humidity sensor 8: Operation display section 9: Control Unit 10: Image forming apparatus 51: Heater 52: Fixing belt 53: Pressure roller 55: Support Unit 56: Movable Unit 57: Reciprocating mechanism 91: CPU 92 :ROM 93: RAM 94: Storage section 94: Detection Processing Unit 95: Summarization Processing Unit 96: Mobile Processing Unit

Claims

1. A movable unit that includes a fixing member and a pressing member that form a fixing nip portion for fixing the toner image transferred to the sheet onto the sheet, and moves along the width direction perpendicular to the conveying direction of the sheet, A detection processing unit that detects the humidity at the installation location of the device, An integration processing unit that accumulates the length in the transport direction of each sheet obtained for each sheet passing through the fixing nip section and a specific value based on the detection result by the detection processing unit, A movement processing unit moves the movable unit when the cumulative value of the specified value exceeds a predetermined threshold, An image forming apparatus equipped with the following features.

2. The summing processing unit sums the specific values ​​for each group of sheets that share the same length in the width direction. The movement processing unit moves the movable unit when the cumulative value of the specific values ​​corresponding to any of the groups exceeds the threshold. The image forming apparatus according to claim 1.

3. The accumulation processing unit accumulates the specified value for each accumulation period until the movable unit is moved by the movement processing unit. The movement processing unit moves the movable unit to a position within the movable unit's range of motion that has never been previously positioned when the cumulative value of the specific value exceeds the threshold. The image forming apparatus according to claim 1 or 2.

4. The detection processing unit detects the absolute humidity at the installation location of the device. The image forming apparatus according to claim 1 or 2.

5. An operation control method performed in an image forming apparatus comprising a fixing member and a pressing member that form a fixing nip portion for fixing a toner image transferred to a sheet onto the sheet, and a movable unit that moves along a width direction perpendicular to the conveying direction of the sheet, wherein the movable unit includes a fixing member and a pressing member that form a fixing nip portion for fixing a toner image transferred to the sheet onto the sheet, A detection step for detecting the humidity at the installation location of the image forming apparatus, A summation step which involves summing the length in the transport direction of each sheet obtained for each sheet passing through the fixing nip section and a specific value based on the detection result of the detection step, A movement step in which the movable unit is moved when the cumulative value of the specified value exceeds a predetermined threshold, A method for controlling operation that includes this.

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