JP5418240B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus including a fixing device that fixes an image formed on a sheet.

  2. Description of the Related Art In recent years, demands for high-quality image output and long-life of electrophotographic process-related parts have increased from the market for electrophotographic image forming apparatuses such as printers and digital multifunction peripherals.

  In response to such market requirements, the width of the fixing member or the paper is limited to either one so that the wear of the fixing member due to the side edge of the paper repeatedly passing through the fixing device does not concentrate on one surface. Techniques for displacement (swing) in the direction have been proposed (Patent Documents 1 and 2, etc.). As a result, image defects (oil stains, gloss unevenness, etc.) due to surface wear of the fixing member and early replacement of the fixing roller are prevented, providing a high-quality image and extending the life of the fixing roller.

  The image forming apparatus described in Patent Document 1 is provided with a position changing unit that can change the position of the transfer paper in the width direction on the upstream side of the transfer of the image forming unit, and matches the position of the transfer paper conveyed to the transfer unit. Thus, the writing start position in the image forming unit is changed. The position of the sheet entering the nip of the fixing roller is displaced in the width direction to prevent local wear of the fixing roller.

  In the image forming apparatus described in Patent Document 2, the transfer fixing body (fixing member) is displaced in the width direction with respect to the paper transported to the transfer fixing apparatus, and the transfer fixing body (fixing member) is formed by the side edge of the paper. This reduces local wear and improves the durability of the transfer fixing member (fixing member).

JP 2003-263090 A JP 2007-148336 A

  However, in the image forming apparatus including the fixing device described in Patent Documents 1 and 2, the lateral position of the fixing member is changed in order to change the relative positional relationship between the fixing member and the paper in the width direction over time. The amount of heat taken from the fixing member to the paper changes with time, and the temperature of the fixing member varies greatly depending on the relative positional relationship between the fixing member and the paper. Therefore, there is a problem that image quality defects such as gloss unevenness and color unevenness occur on the paper on the side end side.

  An object of the present invention is to provide a fixing temperature control that reduces temperature fluctuations that occur at the side edge of the fixing member due to a relative positional change between the fixing member and the paper, and has high quality without gloss unevenness and color unevenness. It is possible to provide an image forming apparatus including a fixing device that can provide an image for a long time and has excellent durability of a fixing member.

  The object is achieved by the invention described below.

1. An image forming unit for forming a toner image on paper;
A fixing member; a heater that heats the fixing member; and a first temperature sensor that detects a temperature of the fixing member, and at least the heat of the fixing member is used to transfer the toner image on the paper to the paper. A fixing device for fixing on top;
A fixing controller that controls the output of the heater based on the detected temperature detected by the first temperature sensor so that the temperature of the fixing member becomes a reference temperature;
An image forming apparatus comprising: a displacement unit configured to displace either the fixing member or the sheet in a width direction orthogonal to a sheet conveyance direction ;
The heater is composed of a central fixing heater that heats a central portion of the fixing member and a both-side fixing heater that heats both side portions of the fixing member,
A second temperature sensor is disposed on one end side in the width direction of the fixing member;
The fixing control unit corrects an end reference temperature according to a displacement amount of the fixing member or the sheet by the displacement unit, and based on a detected temperature detected by the second temperature sensor, An image forming apparatus , wherein the output of the fixing heaters on both sides is controlled so that the temperature on one end side becomes the end reference temperature .

2. The fixing control unit sets the edge reference temperature over time when the sheet is displaced toward the one end side with respect to the fixing member in the relative positional relationship between the fixing member and the sheet. The edge reference temperature is increased with time when the sheet is displaced with time in a position opposite to the one end side with respect to the fixing member in the positional relationship. The image forming apparatus according to 1.

3. 3. The image according to claim 1, wherein a time point at which the edge reference temperature is changed is a time point when a predetermined delay time has elapsed from a time point when the displacement amount of the fixing member or the sheet is set. Forming equipment.

  4). The displacement unit includes a stepping motor, and the fixing control unit calculates the displacement amount based on the number of drive pulses of the stepping motor with respect to a home position. Image forming apparatus.

  5. 5. The image forming apparatus according to claim 1, wherein the displacement unit displaces the fixing device and displaces the fixing member in the width direction with respect to the sheet.

  6). 6. The image forming apparatus according to any one of 1 to 5, wherein the fixing member is an endless belt made of a heat resistant resin.

  7). 6. The image forming apparatus according to any one of 1 to 5, wherein the fixing member is a roller in which a heat-resistant resin layer is formed on a roller-shaped substrate.

The present invention reduces the temperature fluctuation generated at the end portion of the fixing member by correcting the reference temperature for the end portion for maintaining the temperature of the fixing member according to the amount of displacement of the fixing member by the displacing means or the sheet. Therefore, it is possible to provide an image forming apparatus that can stably provide a high-quality image and has excellent durability of the fixing member.

1 is a configuration diagram illustrating an image forming apparatus A including a fixing device according to the present invention. 1 is a cross-sectional view illustrating an embodiment of a heating roller type fixing device 30 according to the present invention. FIG. 6 is a front view showing a displacement means 41 that displaces the fixing device 30 in the width direction. It is sectional drawing which shows the displacement means 41 seen in the AA cross section of FIG. It is a top view which shows the meshing state of A gear and the linear gear of the displacement means 41. FIG. 3 is a block diagram showing a control relationship of the image forming apparatus A. FIG. 3 is a schematic diagram illustrating a relative positional relationship among the fixing belt 311, an upper heating roller 312, and a sheet S. FIG. 6 is a graph showing a correspondence table between a displacement amount L of the fixing device and a correction temperature C (° C.) added to the end set temperature R; 6 is a graph showing a displacement profile of the fixing device according to the first embodiment. It is a graph which shows transition of correction temperature C in a 1st embodiment. 10 is a graph showing a transition of a correction temperature C and a delay correction temperature DC in the fixing control of the second embodiment. 10 is a graph showing a displacement profile of a fixing device according to a third embodiment. It is a graph which shows transition of delay correction temperature DC acquired according to displacement amount L. 1 is a cross-sectional view illustrating an example of a heat roller type fixing device to which a fixing control unit according to the present invention is applicable.

  Although the present invention will be described based on an embodiment, the present invention is not limited to the embodiment. The description in this column does not limit the technical scope of the claims or the meaning of terms.

[Image forming apparatus]
FIG. 1 is a configuration diagram of an image forming apparatus A including a fixing device according to the present invention.

  The image forming apparatus A is called a tandem color image forming apparatus, and includes an image forming unit 10, a paper feeding device 20, a fixing device 30, and the like. The image forming unit 10 includes a plurality of sets of color image forming units 10Y, 10M, 10C, and 10K and a transfer unit.

  On the upper part of the image forming apparatus A, an image reading apparatus B is installed. The document placed on the document table is scanned and exposed by the optical system of the document image scanning exposure apparatus of the image reading apparatus B, and read by the line image sensor. The analog signal photoelectrically converted by the line image sensor is subjected to analog processing, A / D conversion, shading correction, image compression processing and the like in the image processing unit, and then input to the exposure means 3Y, 3M, 3C, 3K. .

  A Y-color image forming unit 10Y that forms a yellow (Y) image includes a charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, and a cleaning unit 5Y disposed around a photosensitive drum 1Y as an image carrier. . The M color image forming unit 10M that forms a magenta (M) color image includes a photosensitive drum 1M as an image carrier, a charging unit 2M, an exposure unit 3M, a developing device 4M, and a cleaning unit 5M. The C color image forming unit 10C that forms a cyan (C) color image includes a photosensitive drum 1C as an image carrier, a charging unit 2C, an exposure unit 3C, a developing device 4C, and a cleaning unit 5C. The K color image forming unit 10K that forms a black (K) image includes a photosensitive drum 1K as an image carrier, a charging unit 2K, an exposure unit 3K, a developing device 4K, and a cleaning unit 5K. The charging unit 2Y and the exposure unit 3Y, the charging unit 2M and the exposure unit 3M, the charging unit 2C and the exposure unit 3C, and the charging unit 2K and the exposure unit 3K constitute a latent image forming unit.

  Reference numerals 4Y, 4M, 4C, and 4K denote developing devices that contain a two-component developer composed of a small particle size toner of yellow (Y), magenta (M), cyan (C), and black (K) and a carrier.

  The transfer unit includes a belt-like intermediate transfer body 6 wound around a plurality of rollers and rotatably supported, a primary transfer unit including primary transfer units 7Y, 7M, 7C, and 7K, and a secondary transfer unit 9 And a secondary transfer portion having

  The toner images of the respective colors formed by the color image forming units 10Y, 10M, 10C, and 10K are sequentially transferred onto the rotating intermediate transfer body 6 by the primary transfer units 7Y, 7M, 7C, and 7K of the primary transfer unit. A synthesized color image is formed.

  A recording medium (hereinafter referred to as “paper”) S stored in a paper storage unit (paper cassette) 21 of the paper supply device 20 is supplied by a paper supply unit (first paper supply unit) 22 and is supplied by a paper supply roller. 23, 24, 25A, 25B, registration rollers (second paper feed unit) 26, etc., are conveyed to the secondary transfer means 9 of the secondary transfer unit, and the color image is transferred onto the paper S. As described above, the image forming unit 10 forms a color image made up of each color toner image on the paper.

  It should be noted that the three-stage paper storage units 21 arranged vertically in the vertical direction below the image forming apparatus A have substantially the same configuration and are given the same reference numerals. Further, the three-stage sheet feeding means 22 has substantially the same configuration and is given the same reference numerals. The paper storage unit 21 and the paper supply means 22 are collectively referred to as a paper supply device 20.

  The size and paper type of the paper S stored in the paper storage unit 21 are displayed on the display screen of the operation unit 11 and are arbitrarily selected and set. It is also possible to automatically set the size of the paper S according to the document size and the copy magnification.

  The sheet S on which the color image is formed by the image forming unit 10 is conveyed to the fixing device 30. Then, heat and pressure are applied, and the color toner image (or toner image) on the paper is fixed on the paper S.

  The fixed sheet S is nipped and conveyed by the conveyance roller pair 37, is discharged out of the apparatus from the discharge roller 27 provided in the discharge conveyance path, and is placed on the discharge tray 28 outside the apparatus. The

  On the other hand, after the color image is transferred to the sheet S by the secondary transfer unit 9, the residual toner is removed by the cleaning unit 8 from the intermediate transfer body 6 that has separated the curvature of the sheet S.

  In the case of reversely discharging the fixed sheet S, the sheet S passes through the conveyance path on the right side of the branch plate 29 arranged at the middle branch point between the fixing device 30 and the sheet discharge roller 27 and is conveyed downward. After being transported to the path r1 (reverse transport path), it is transported in reverse. Then, the paper passes through the conveyance path r <b> 2 on the left side of the branch plate 29 and is discharged out of the apparatus by the paper discharge roller 27.

  In the above description, a color image is formed by the image forming apparatus A, but a case of forming a monochrome image is also included in the present invention.

[Fixing device]
Hereinafter, the fixing device 30 of the image forming apparatus A will be described.

  FIG. 2 is a cross-sectional view showing an embodiment of a heating belt type fixing device 30.

  The fixing device 30 is supported by the device pedestal unit 40 so as to be displaceable in the width direction orthogonal to the paper transport direction.

  The fixing device 30 includes a fixing unit 31 having a fixing belt 311 as a fixing member, a pressure unit 32 having a pressure belt 321 as a fixing member, and a pressure contact mechanism (not shown) that forms a nip N. The toner image t on the sheet S conveyed to the nip N is fixed on the sheet S by the action of heat and pressure.

  The fixing unit 31 includes a fixing belt 311, an upper heating roller 312 that heats the fixing belt 311 with a fixing heater 33 disposed therein as a heat source, an upper pressure roller 313 that presses the fixing belt 311 against the pressure belt 321, and The fixing belt 311 is stretched and rotatably supported.

  The pressurizing unit 32 includes a pressurizing belt 321, a lower heating roller 322 for heating the pressurizing belt 321 provided with a pressurizing heater 34 as a heat source therein, and a lower press-bonding pressurizing the pressurizing belt 321 to the fixing belt 311. And a roller 323, and a pressure belt 321 is stretched and rotatably supported.

  A pressure contact mechanism (not shown) presses the upper pressure roller 312 and the lower pressure roller 32 together, presses the fixing belt 311 with the fixing roller from inside, and presses the pressure belt 321 with the lower pressure roller 323 to fix. A nip N is formed by pressing the outer surface of the belt 311 and the outer surface of the pressure belt 321.

  Although halogen lamps are used as the fixing heater 33 and the pressure heater 34, induction heating means or the like may be used.

  The fixing heater 33 includes a central fixing heater 331 and a both-side fixing heater 332 described later. The pressure heater 34 is also composed of a center pressure heater 341 and a both-side pressure heater 342 described later.

  Around the upper heating roller 312, a fixing temperature sensor TS1 for detecting the temperature of the fixing belt 311, a cleaning mechanism (not shown) for cleaning residual toner on the fixing belt 311 and a non-heating mechanism for preventing abnormal heating of the upper heating roller 312. The illustrated thermostat and the like are arranged. A pressure temperature sensor TS2, a thermostat for preventing abnormal temperature, and the like are also arranged around the lower heating roller 322.

  The fixing temperature sensor TS1 includes a central fixing temperature sensor TS11 that detects a central portion of the fixing belt 311 in the width direction, and a both-side fixing temperature sensor TS12 that detects one end side of the fixing belt 311 in the width direction.

  The pressure temperature sensor TS2 also detects a fixing temperature sensor TS1 that detects a central portion in the width direction of the pressure belt 321, a center pressure temperature sensor TS21 that detects one end side of the pressure belt 321 in the width direction, and both-side fixing temperature sensors TS22. It consists of and.

  The fixing belt 311 includes an endless belt-like base made of a heat resistant resin, a heat resistant rubber layer formed on the surface of the base, and a heat resistant surface layer formed on the surface of the rubber layer. The substrate is made of a heat resistant resin such as polyimide resin. Its circumference is 80 mm in diameter, its thickness is 70 μm, and its length in the width direction is 367 mm. The rubber layer on the substrate has a thickness of 200 μm, the surface layer is PFA (tetrafluoroethylene / perfluoroalkoxyethylene) having a low surface energy, and the layer thickness is 30 μm.

  The rubber layer on the substrate is formed of, for example, silicone rubber or fluoro rubber. Further, in order to cope with speeding up of image formation, 5-30% by mass of a powder of metal oxide such as silica, alumina, magnesium oxide or the like may be blended in the synthetic rubber as a filler.

  The upper press roller 313 is an elastic roller having an outer diameter of 26 mm having an elastic layer 313B having a thickness of 3 mm on a cored bar 313A made of a metal material such as iron. The elastic layer 313B is a sponge rubber material using a foam material of silicone rubber, fluorine rubber, or silicone rubber, and has a hardness of 30 Hs to 70 Hs (JIS-A rubber hardness).

  The pressure belt 312 uses the same belt as the fixing belt 311 in order to uniformly process the image formed on the back surface of the paper, but is not necessarily limited thereto.

  The lower heating roller 322 is made of a metal material such as aluminum or iron, has an outer diameter of 52 mm, and a length in the width direction of the outer diameter described on the left is 370 mm.

  The lower press roller 323 is an elastic roller having an outer diameter of 26 mm and having a heat-resistant elastic layer 323B having a thickness of 3 mm on a cored bar 323A made of a metal material such as iron. The elastic layer 323B is a sponge rubber material using a foamed material of silicone rubber, fluorine rubber, or silicone rubber, and has a hardness of 30Hs to 70Hs.

  The fixing belt 311 is maintained at a temperature within a predetermined range by turning on the fixing heater 33 in accordance with the output of the fixing temperature sensor TS1 by a fixing controller described later. The pressure belt 312 is also maintained at a temperature within a predetermined range by turning on the pressure heater 34 in accordance with the output of the pressure temperature sensor TS2 by a fixing controller described later.

  The sheet S that has passed through the nip N is separated from the outer peripheral surfaces of the fixing belt 311 and the pressure belt 312 and moves to the conveyance roller pair 37. The separation claw 36 positioned downstream of the nip N smoothly guides the sheet S separated from the fixing belt 311 to the conveyance roller pair 37.

  The roller support unit 38 also serves as the casing 381 of the fixing device 30, and includes the fixing unit 31 including the fixing belt 311, the upper heating roller 312, and the upper pressing roller 313, the pressure belt 311, the lower heating roller 322, and the lower unit. The pressure unit 32 having the pressure roller 323 is supported.

  As shown in the figure, the fixing device 30 has four support shafts 382 that are fixed to the front side and the back side of the bottom of the housing 381, and are rotatably supported by the support shafts 382 4. There are two rollers 383.

  The apparatus pedestal 40 is fixed to the image forming apparatus and supports the mounted fixing device 30 so as to be displaceable in the width direction. The apparatus gantry 40 is fixed to the image forming apparatus, and a gantry member 401 on which a plurality of rotating rollers 383 of the fixing device 30 is placed, and a plurality of regulating portions that regulate the casing 381 of the fixing device 30 so as to be displaceable. 402.

  FIG. 3 is a front view showing a displacing means 41 that is disposed on the front side of the fixing device 30 and on the device mount 40 and displaces the fixing device 30 in the width direction.

  FIG. 4 is a cross-sectional view showing the displacement means 41 as seen in the AA cross section of FIG.

  As shown in FIGS. 3 and 4, the A rotating shaft 412, the B rotating shaft 413, and the C rotating shaft 414 are vertically and rotatably supported by bearings fixed to the gantry member 411.

  The A gear G1 and the B gear G2 are mounted on the A rotating shaft 412, and the C gear G3 and the D gear G4 are mounted on the B rotating shaft 393. The C rotation shaft 414 is a drive shaft of a displacement motor M1 fixed to the gantry member 411, and an E gear G5 is attached to the C rotation shaft 414.

  The B gear G2 meshes with the C gear G3, the D gear G4 meshes with the E gear G5, and as a result, the A gear G1 is rotated by the drive of the displacement motor M1 to constitute a drive connection.

  The linear gear G6 has a configuration in which spur teeth are expanded in the width direction, and is fixed to the bottom notch 38C of the housing 381 (see FIG. 5), and meshes with the A gear G1 of the displacement means 41. Yes.

  FIG. 5 is a schematic diagram (plan view) showing the meshing state of the A gear G1 and the linear gear G6 of the displacement means.

  The broken line in the figure shows the state of the casing 381 and the linear gear G6 displaced to the farthest side, and the solid line shows the state displaced to the foremost side. L1 indicates a displacement range (a distance from the foremost side to the farthest side) in which the casing 381 of the fixing device 30, that is, the fixing belt 311 and the pressure belt 321 are displaced.

  The casing 381 as the roller support portion 38 can be displaced within the displacement range of L1 in the width direction as shown by the arrow a or the arrow b in FIG. 4 by driving the displacement motor M1. In other words, the fixing belt 311 and the pressure belt 321 as a pair of fixing members integrally supported by the housing 381 can be displaced in the width direction within the displacement range L1 by driving the displacement motor M1. On the other hand, the sheet S is conveyed at a predetermined position in the width direction of the image forming apparatus A.

  Therefore, since the position of the sheet S repeatedly carried in is swung within the displacement range L1, the wear of the fixing roller due to the end of the sheet side is not concentrated in one place but dispersed, and a fixing belt as a pair of fixing members, etc. Allows long life.

  The illustrated first position sensor PS1 is a means for detecting whether or not the casing 381 has moved to the foremost position, and the second position sensor PS2 has determined whether or not the casing 381 has moved to the innermost position. It is a means to detect. The first position sensor PS1 and the second position sensor PS2 are configured to switch the detection signal from ON to OFF when the detection hole 381W at the bottom of the housing 381 reaches each detection position. L2 is substantially equal to the displacement range L1, and indicates the distance between the detection position of the first position sensor PS1 and the detection position of the second position sensor PS2.

  The displacement motor M1 is a stepping motor, and can rotate the C rotation shaft 414 by a predetermined step angle by applying a pulse for passing a current sequentially to each excitation coil. Further, the C rotation shaft 414 is rotated in the reverse direction by reversing the excitation order.

  The position (displacement amount) of the fixing device 30 displaced in the width direction can be arbitrarily changed by appropriately controlling the change of the pulse interval applied to the exciting coil and the switching of the excitation order in order.

  If the intermediate position between the first position sensor PS1 and the second position sensor PS2 is a reference position, the fixing device 30 can be displaced within a range from -L1 / 2 to + L1 / 2 with an arbitrary speed profile around the reference position. is there.

  When the displacement amount (displacement position) with respect to the reference position is unknown (undefined), the first position sensor PS1 or the second position sensor PS2 is used as a home position, and the fixing device 30 is moved to a desired displacement position. it can.

  As described above, the fixing control unit 101F generates a driving pulse for driving the displacement motor M1 based on a predetermined temporal pattern, thereby displacing (swinging) the fixing device 30 in the width direction at a desired speed pre-fill. Is possible. Further, the displacement amount L of the fixing device 30 can be calculated (set) from the number of drive pulses of the displacement motor M1 generated after the home position has passed.

[Control configuration]
FIG. 6 is a block diagram illustrating a control relationship of the image forming apparatus A.

  The image forming apparatus A includes a control unit 101, a printer unit 102, an image processing unit 103, an operation display unit 105, a storage unit 104, a transmission / reception unit 106, a print controller unit 107, and the like. Each unit is connected by a bus 110. In addition, the image forming apparatus A communicates with the image reading apparatus B installed on the upper part of the image forming apparatus A via the bus 110.

  The control unit 101 includes a CPU, a ROM, a RAM, and the like, reads a system program and various processing programs stored in the ROM, expands them in the RAM, and centrally controls each unit of the image forming apparatus A according to the expanded programs. .

  The control unit 101 controls the operation of the printer unit 102, and includes a fixing control unit 101F that controls the fixing device 30 according to the present invention.

  The operation display unit 105 is configured by an LCD (Liquid Crystal Display), and displays various operation buttons, device status display, operation status of each function, and the like on the display screen according to instructions of a display signal input from the control unit 101. Do. Various operation buttons such as a numeric button and a start button are provided, and an operation signal generated by the button operation is output to the control unit 101.

  The image reading apparatus B reads an original as R, G, B analog signals, converts the analog signals into digital signals by an A / D converter, and generates R, G, B image data. Thereafter, the image data is output to the image processing unit 103 of the image forming apparatus A via the bus.

  The image processing unit 103 converts R, G, and B image data input from the image reading apparatus B into Y, M, C, and K color image data that can be processed by the control unit 101. Further, γ correction processing is performed in accordance with the output characteristics of the printer unit 102, or binarization processing such as an error diffusion method is performed to generate print data of Y, M, C, and K colors. The print data is output to the control unit 101.

  When the transmission / reception unit 106 receives a print job from a personal computer on the network, the transmission / reception unit 106 transfers the received print job to the print controller unit 107. The print job is composed of processing information related to print processing and print data (file).

  The print controller unit 107 generates print data that is image data of Y, M, C, and K colors based on the contents of the print job, and outputs the print data to the control unit 101 corresponding to the processing information.

  The printer unit 102 operates each of the image forming units 10Y, 10M, 10C, 10K, the fixing device 30 and the like based on the image data input from the image processing unit 103 and the printer controller unit 107, and a sheet on which a color image is formed. Is output from the image forming apparatus A.

  The fixing control unit 101F controls the motor driving unit 108 and the heater driving unit 109 to swing the fixing device 30 in the width direction with respect to the sheet and to maintain the temperature in the entire region of the fixing belt 311 within a predetermined range. I have control.

  The motor driving unit 108 drives the displacement motor according to the driving pulse output from the fixing control unit 101F, and displaces the fixing device 30 in the width direction.

  The heater driving unit 109 drives the lighting of the fixing heaters 33 (331, 332) and the pressure heaters 34 (341, 342) independently based on the signal output from the fixing control unit 101F to set the temperature of the fixing belt to a predetermined value. Maintained in range.

  Next, the temperature stabilization control of the fixing belt 311 executed by the fixing control unit 101F according to the present invention will be described in detail.

  FIG. 7 is a schematic diagram showing a relative positional relationship among the fixing belt 311, the upper heating roller 312, and the paper S.

  Actually, the fixing belt 311 and the upper heating roller 312 are displaced in the width direction, but FIG. 7 shows the relative positional relationship between the sheet S and the fixing belt 311 in a simple manner. 312 is stationary and the paper is expressed as being displaced in the width direction.

  As illustrated, the fixing heater 33 includes a central fixing heater 331 and both-side fixing heaters 332. The central fixing heater 331 heats the central portion of the upper heating roller, and the heat generating portion corresponds to the normal paper width size. The both-side fixing heater 332 heats both sides of the upper heating roller, and the heat generating portions are on both sides of the heat generating portion of the central fixing heater 331.

  As shown in the figure, the fixing temperature sensor TS1 is disposed on the one end side (rear side) of the fixing belt in the width direction and the central fixing temperature sensor TS11 that detects the temperature of the center portion of the fixing belt 311. And an end fixing temperature sensor TS12 for detecting the temperature of the fixing belt 311 corresponding to the rear end.

Sr in the figure indicates a state in which the sheet is displaced to the rearmost side (right side in the figure) in the width direction with respect to the fixing belt 311 (upper heating roller 312). A broken line Sf indicates a state in which the sheet is displaced to the foremost side (left side in the drawing) in the width direction. L1 is a displacement range of the fixing device shown in FIG. 5 in which the sheet is displaced relative to the fixing belt 311 (upper heating roller 312). X ₁ and X ₂ indicated by alternate long and short dash lines are reference positions corresponding to the center position of the displacement range L1.

The fixing control unit 101F in FIG. 6 compares the detected value of the central fixing temperature sensor TS11 with the central reference temperature, and if the detected value is lower than the central reference temperature, an ON signal for lighting the central fixing heater 331 is sent to the heater driving unit 109. Output to. On the other hand, when the temperature becomes equal to or higher than the central reference temperature, an OFF signal for turning off the central fixing heater 331 is output to the heater driving unit 109. Similarly, the detected value of the end fixing temperature sensor TS12 is compared with the end reference temperature, and if the detected value is lower than the end reference temperature, an ON signal for turning on the both-side fixing heater 332 is output to the heater driving unit 109. To do. When the temperature becomes equal to or higher than the end reference temperature, an OFF signal for turning off the both-side fixing heater 332 is output to the heater driving unit 109.

  However, when the sheet is displaced with respect to the fixing device, that is, the fixing belt 311 to the Sr state or the Sf state shown in the figure, the amount of heat flowing from the fixing belt 311 to the sheet on the rear end side or front end side of the fixing belt 311 is large. Differences occur. As a result, when the sheet is in the state of Sr that is located at the rearmost position with respect to the fixing member, the rear end side where the end fixing temperature sensor TS12 is arranged is controlled based on the end reference temperature, so that the desired temperature is reached. On the other hand, on the front end side where the end fixing temperature sensor TS12 is not disposed, the temperature is controlled to be higher than the desired temperature.

  On the other hand, when the sheet is in the Sf state, the temperature is similarly controlled near the desired temperature on the rear end side where the end fixing temperature sensor TS12 is disposed, but desired on the front end side where the end fixing sensor TS12 is not disposed. The temperature is controlled to be lower than the temperature.

  Thus, on the front end side of the fixing belt 311 not provided with the end fixing temperature sensor TS12, a difference with respect to the original control temperature is generated according to the relative displacement of the sheet. It is low when the paper is displaced to the near side with respect to the reference position, and conversely becomes high when the paper is displaced to the back side with respect to the reference position. As a result, the amount of heat applied from the fixing belt 311 fluctuates in the toner image on the paper passing through the front end side where the end fixing temperature sensor TS12 is not disposed, due to the displacement of the fixing belt 311 (fixing device 30), and uneven glossiness. (Deterioration), image quality problems such as color unevenness occur.

The fixing control unit 101F according to the present invention outputs a driving pulse to the motor driving unit so as to displace the fixing device with a predetermined profile in the width direction, and next to the end set temperature R according to the displacement amount L of the fixing device. The correction calculation process shown in the equation is performed, the end reference temperature CR is acquired, and the ON / OFF signal of the both-side fixing heater 332 is output to the heater drive unit 109 based on the end reference temperature CR. By such control, the fluctuation amount of the fixing belt temperature is suppressed on the front end side of the fixing belt without the fixing temperature sensor.

Edge reference temperature CR = edge setting value R + correction temperature C
FIG. 8 is a graph showing a correspondence table between the displacement amount L of the fixing device and the correction temperature C (° C.) added to the end set value R. The horizontal axis represents the displacement L (mm) of the fixing device when the reference position is L = 0. Positive indicates a state where the fixing device is displaced rearward with respect to the reference position, and negative indicates a state where the fixing device is displaced forward. The vertical axis represents the correction temperature C, and is indicated by a value (° C.) converted into the temperature of the fixing belt. Here, the displacement range L1 is 20 mm.

  That is, the fixing control unit 101F increases the end reference temperature CR with time when the fixing device is displaced with time relative to the paper, and the fixing device is relatively forward with respect to the paper. Control is performed so that the end reference temperature CR is lowered when it is displaced to the side with time.

The fixing control unit 101F compares the detected temperature of the end fixing temperature sensor TS12 (FIG. 7) with the end reference temperature CR output from the fixing control unit 101F, and the detected temperature is lower than the end reference temperature CR. In addition, an ON signal for turning on the both-side fixing heater 332 (FIG. 7) is output to the heater driving unit 109. On the other hand, when the temperature becomes equal to or higher than the end reference temperature CR, an OFF signal for turning off the both-side fixing heater 332 is output to the heater driving unit 109.

As described above, the fixing control unit according to the present invention controls the output of the both-side fixing heater 332 based on the end reference temperature CR corrected with respect to the end set temperature R in accordance with the displacement amount L of the fixing device. Compared to the conventional method of controlling the output of the both-side fixing heater 332 based on the end reference temperature CR which is always fixed to the end set temperature R, the fixing belt on the front end side where the end fixing temperature sensor TS12 is not disposed is provided. Allows the temperature to be kept within a small fluctuation range.

  An embodiment according to the fixing control unit of the present invention will be described below.

[First Embodiment]
FIG. 9 is a graph showing a displacement profile of the fixing device according to the first embodiment. The horizontal axis represents time (sec) corresponding to the progress of the image forming process. The vertical axis represents the displacement L of the fixing device (fixing belt) with respect to the reference position. As shown in the figure, the fixing device (fixing belt) is periodically displaced in a range from −10 mm to +10 mm based on a sine function (amplitude = 10 mm).

  FIG. 9 shows such a state in which the fixing device 30 is positioned at the reference position of the displacement range at the start of the image forming operation and is in the process of displacing the fixing device backward.

  FIG. 10 is a graph showing the transition of the correction temperature C (° C.) added to the end set temperature R in the first embodiment. The horizontal axis is the time synchronized with FIG. 9, and the vertical axis is the correction temperature (° C.) acquired by the fixing control unit.

  The fixing control unit obtains the correction temperature C shown in FIG. 10 according to the displacement L in FIG. 9 with reference to the correspondence table in FIG. It changes periodically with a sine function (amplitude = 5 ° C.) as shown.

  Table 1 shows the temperature distribution (axial direction) of the fixing belt measured when the image forming process is actually executed by the fixing control method of the comparative example. The fixing control method of the comparative example controls lighting of the end heater based on the end reference temperature CR that is always fixed to the end set temperature R.

  The columns in Table 1 show three typical temperatures in the width direction of the fixing belt. It is divided into a front end portion, a central portion, and a rear end portion. Each row in Table 1 is a temperature distribution of the fixing belt measured in two typical displacement states of the fixing device (fixing roller). The upper row shows the temperature distribution of the fixing belt when the displacement amount L of the fixing device is −10 mm, that is, the fixing device is displaced most forward. The lower row shows the temperature distribution in a state where L = + 10 mm and the most rearward displacement.

  As shown in Table 1, the rear end portion where the end fixing temperature sensor is arranged is stable similarly to the central portion, but the temperature of the front end portion where no end fixing temperature sensor is arranged fluctuates up and down, and is the highest. The temperature fluctuation range that is the difference between the temperature and the minimum temperature is 14 ° C. Also in the evaluation of the image on the processed paper, excessive gloss, insufficient gloss, gloss unevenness, color unevenness, and density unevenness occurred on the near side without the end fixing temperature sensor TS12.

  Table 2 shows the temperature distribution (axial direction) of the fixing roller measured when the image forming process is actually executed by the image forming apparatus A including the fixing control unit of the first embodiment.

  As shown in Table 2, the fixing controller of the present invention that controls lighting of the end heater based on the end reference temperature CR obtained by adding the correction temperature C to the end set temperature R includes an end fixing temperature sensor. The temperature fluctuation range difference at the rear end increases from 1 ° C. to 4 ° C., the temperature fluctuation range at the front end without the end fixing temperature sensor decreases from 14 ° C. to 11 ° C., and the deviation of the entire fixing roller is It improved from 14 degreeC to 11 degreeC.

  As a result, improvement was also confirmed in image quality evaluation such as gloss unevenness and density unevenness. However, improvement matters such as gloss unevenness being pointed out in an area close to the outermost edge in the width direction remain, and further temperature stabilization measures are desired.

[Second Embodiment]
For further improvement, the inventors investigated the behavior of the fixing belt temperature distribution when the fixing device was displaced, and found the following phenomenon.

  The above phenomenon is that a change in the temperature distribution of the fixing belt appears after a predetermined time with respect to the displacement of the fixing device. The predetermined time, that is, the predetermined delay time Td, is a constant that varies depending on the fixing device specifications such as the heat capacity of the upper heating roller and the fixing method.

The fixing control unit according to the second embodiment of the present invention performs both-side fixing based on the end reference temperature CR similarly obtained in the first embodiment in consideration of the delay time Td determined by the fixing device specifications. The output of the heater 332 is controlled and will be described below.

Similar to the first embodiment, the displacement amount L is obtained during the operation time T1. Then, the correction temperature C is acquired based on the displacement amount L. Next, the correction temperature C is stored in the nonvolatile memory in association with T1. On the other hand, the correction temperature C stored in the nonvolatile memory when the delay time Td has elapsed with respect to T1 is read from the nonvolatile memory and acquired as the delay correction temperature DC. Next, the delay correction temperature DC is added to the edge setting temperature R to obtain the edge reference temperature CR, and the output of the both-side fixing heater 332 is controlled based on the edge reference temperature CR.

  FIG. 11 is a graph showing the transition of the correction temperature C and the delay correction temperature DC in the fixing control of the second embodiment. The horizontal axis is the time indicating the progress of the image forming process. The vertical axis represents the correction temperature C and the delay correction temperature DC. The broken line in the figure is the transition of the correction temperature C used by the fixing control unit of the first embodiment. A solid line is a transition of the delay correction temperature DC used by the fixing control unit of the second embodiment.

  As shown in the figure, the delay correction temperature DC that actually changes the end reference temperature changes with respect to the correction temperature C acquired from the displacement L by a delay time Td.

In the fixing control of the second embodiment, when the delay time Td elapses from the time when the displacement amount L is acquired, the end reference temperature CR corrected with respect to the end set temperature R according to the displacement amount L is set. Based on this, the output of the both-side fixing heater 332 is controlled.

  Here, Td = 40 sec is set. As described above, the delay time Td is a constant that varies depending on various fixing specifications such as the heat capacity of the upper heating roller.

  In FIG. 11, during the delay time Td from the start of the image forming process, the non-correction state is forcibly set (the delay correction temperature DC is set to zero). Thus, the initial correction profile to be applied at the start of processing differs depending on the fixing device idling operation when the image forming process is stopped, and is determined based on various experimental data obtained by actually operating the image forming apparatus. In addition, the initial correction profile to be actually applied is determined as appropriate in consideration of the degree of influence on the image quality over the control load.

  Table 3 shows the temperature distribution (axial direction) of the fixing roller measured when the image forming process is actually executed by the image forming apparatus A including the fixing control unit according to the second embodiment.

  As shown in Table 3, in the fixing control unit according to the second embodiment of the present invention in consideration of the delay time, the temperature fluctuation range of the rear end portion where the end fixing temperature sensor is arranged is increased from 4 ° C. to 7 ° C. However, the temperature fluctuation range at the front end without the end fixing temperature sensor was reduced from 11 ° C. to 7 ° C., and the deviation of the entire fixing roller was improved to 7 ° C. As a result, in the image quality evaluation such as gloss unevenness and density unevenness, image defects were eliminated and a significant improvement was confirmed.

[Third Embodiment]
The third embodiment according to the fixing control unit of the present invention is different from the second embodiment in the displacement profile for swinging the fixing device in the width direction. The fixing device is displaced at a constant speed between the first position sensor PS1 and the second position sensor PS2 shown in FIGS.

  FIG. 12 is a graph showing a displacement profile of the fixing device according to the third embodiment. The horizontal axis represents time (sec), and the vertical axis represents the displacement amount L of the fixing device (fixing belt) with respect to the reference position. The fixing device (fixing belt) repeats a reciprocating movement at a constant speed in a range from −10 mm to +10 mm as shown in the figure.

  FIG. 13 is a graph showing the transition of the delay correction temperature DC acquired in accordance with the displacement amount L of the displacement profile of FIG. Forty seconds is set as the delay time Td.

  It is confirmed that the image forming apparatus including the fixing control unit according to the third embodiment of the present invention can achieve the same level of improvement as the second embodiment in the deviation of the entire fixing roller and the image quality evaluation. Therefore, the fixing control unit according to the present invention can be applied to various displacement profiles that swing the fixing device in the width direction.

  Although the above embodiment mainly describes the temperature control of the fixing belt 311, it can be similarly applied to the temperature control of the pressure belt 321, and an equivalent effect has been confirmed.

  As described above, the image forming apparatus A including the fixing control unit of the present invention displaces the fixing belt 311 and the pressure belt 321 as fixing members with respect to the sheet S in the width direction, and localizes the fixing member by the end of the sheet. Long wear of the fixing member can be realized by preventing repeated repeated wear. Further, by correcting the end reference temperature for maintaining the temperature of the fixing member in accordance with the amount of displacement of the fixing member, it is a problem according to the present invention and is caused by temperature unevenness occurring on the end side of the fixing member. In addition, it is possible to improve and eliminate image quality defects such as gloss unevenness and color unevenness.

  In the above-described embodiment according to the present invention, the fixing belt 311 and the pressure belt 321 are used as the fixing member, but the present invention is not limited to this. The fixing control unit according to the present invention is also applicable to a heat roller type fixing device in which a fixing belt as a fixing member is replaced with a fixing roller, or a pressure belt as a fixing member is replaced with a pressure roller.

  FIG. 14 is a cross-sectional view showing an example of a heat roller type fixing device 30 to which the fixing control unit according to the present invention can be applied.

  The fixing device 30 includes a fixing roller F1 and a pressure roller F2 as a pair of fixing members, a fixing heater 33 as a heat source for heating the fixing roller F1, a pressure heater 34 as a heat source for heating the pressure roller F2, and the like. Have

  The fixing roller F <b> 1 and the pressure roller F <b> 2 are rotatably supported by the casing of the fixing device 30 and form a nip N by being pressed against each other.

As the fixing heater 33 and the pressure heater 34, a halogen lamp, induction heating means, or the like is used. The fixing heater 33 includes a central fixing heater 331 and a both-side fixing heater 332 (not shown), and the pressure heater 34 includes a central pressure heater 341 and an end pressure heater 342 (not illustrated).

  A central fixing temperature sensor TS11, an end fixing temperature sensor TS12, and the like are disposed around the fixing roller F1. A central pressure temperature sensor TS21, an end pressure temperature sensor TS22, and the like are also disposed around the pressure roller F2.

  The fixing roller F1 is composed of a core metal F11 as a thermally conductive base, an elastic layer F12, a coating layer F13 and the like.

  The fixing roller F1 is a cylindrical member having an outer diameter of 20 to 70 mm. As the cylindrical metal core F11, an aluminum material having good thermal conductivity is mainly used, and a nonmagnetic stainless steel material, heat resistant glass, or the like is also used. The core metal F11 has a required mechanical strength and has a thickness (wall thickness) of 0.8 to 10 mm.

  The elastic layer F12 is formed of a heat resistant rubber such as silicone rubber. Furthermore, in order to cope with speeding up of image formation, 5-30% by mass of a powder of metal oxide such as silica, alumina, magnesium oxide or the like is added as a filler. The elastic layer F12 has a thickness (wall thickness) of 0.3 to 3 mm, preferably 1 to 3 mm, and a rubber hardness of 5Hs to 30Hs as a JIS-A rubber hardness.

  The coating layer F13 is a heat-resistant resin layer such as silicone rubber or PFA that is coated on the outer side (outer peripheral surface) of the elastic layer F12 and has high releasability. The pressure roller F2 has an outer diameter of about 30 to 70 mm.

  The pressure roller F2 is a lower cylindrical member that forms a pair with the fixing roller F1, and includes a heat conductive base F21, an elastic layer F22, and a coating layer F23. The constituent members of the pressure roller F2 are formed with substantially the same material, characteristics, and dimensions as the constituent members of the fixing roller F1.

  For example, the elastic layer F22 is a silicone rubber layer, a fluorine rubber layer, or a sponge-like silicone rubber layer. And the layer thickness (thickness) of an elastic layer is 0.3-5 mm, and rubber hardness is 30Hs-70Hs (JIS-A rubber hardness).

  The pressure roller F2 is rotatably supported at a fixed position, and is pressed against the upper fixing roller F1 by a biasing force of a spring to form a flat nip N with the fixing roller F1.

  The sheet S that has passed through the nip N is separated from the outer peripheral surfaces of the fixing roller F1 and the pressure roller F2, and moves to the conveyance roller pair 37. The separation claw 36 positioned downstream of the nip N smoothly guides the paper S separated from the fixing roller F1 to the conveyance roller pair 37.

  The roller support unit 38 integrally supports the fixing roller F 1 and the pressure roller F 2 that presses against the fixing roller to form the nip N, and also serves as a casing 381 of the fixing device 30.

  As described above, the image forming apparatus A including the fixing control unit according to the present invention displaces the fixing roller F1 and the pressure roller F2 as the fixing members with respect to the sheet S in the width direction, and localizes the fixing member by the end of the sheet. Long wear of the fixing member can be realized by preventing repeated repeated wear. Furthermore, the end reference temperature for maintaining the temperature of the fixing member is corrected according to the displacement amount of the fixing member, which is a problem according to the present invention, which is caused by temperature unevenness occurring on the end side of the fixing member. Improve and eliminate gloss unevenness and color unevenness.

  In the above-described embodiment, the fixing device is continuously displaced with a predetermined displacement profile with respect to the progress of the image forming process. Anyway.

  In the above embodiment, the displacement amount L of the fixing device 30 is set according to the operation time of the fixing device 30 or the image forming apparatus A. However, the number of sheets S to be processed or the length of the sheet S to be processed is set. The displacement positions of the fixing roller F1 and the pressure roller F2 may be displaced accordingly.

  The embodiment according to the present invention may be configured such that the apparatus mount unit 40 having the displacement unit 41 is attached to the image forming apparatus A integrally with the fixing device 30.

  In the above-described embodiment of the present invention, the roller support portion 38 that rotatably supports the fixing roller F1 and the pressure roller F2 is the casing 381 of the fixing device 30, and the casing 381 can be displaced in the width direction. ing. The roller support portion 38 may be separated from the casing 381 of the fixing device so that the roller support portion 38 can be displaced in the width direction with respect to the casing 381. This embodiment is also within the scope of the present invention. It is.

  In the embodiment according to the present invention described above, the fixing device is displaced in the width direction. However, the fixing control unit according to the present invention displaces (oscillates) the paper entering the fixing device by fixing the fixing device in the width direction. This is applicable to an image forming apparatus having a paper displacement mechanism, and is within the scope of a right object.

DESCRIPTION OF SYMBOLS 10 Image formation part 30 Fixing apparatus 311 Fixing belt (fixing member)
321 Pressure belt (fixing member)
33 Fixing heater 34 Pressurizing heater 41 Displacement means 101 Control unit 101F Fixing control unit 108 Motor driving unit 109 Heater driving unit A Image forming apparatus C Correction temperature F1 Fixing roller (fixing member)
F2 pressure roller (fixing member)
L Displacement N Nip M1 Displacement motor R End set temperature CR End reference temperature (reference temperature)
S paper Td delay time TS1 fixing temperature sensor (temperature sensor)
TS2 Pressure temperature sensor (temperature sensor)

Claims (7)

An image forming unit for forming a toner image on paper;
A fixing member; a heater that heats the fixing member; and a first temperature sensor that detects a temperature of the fixing member, and at least the heat of the fixing member is used to transfer the toner image on the paper to the paper. A fixing device for fixing on top;
A fixing controller that controls the output of the heater based on the detected temperature detected by the first temperature sensor so that the temperature of the fixing member becomes a reference temperature;
An image forming apparatus comprising: a displacement unit configured to displace either the fixing member or the sheet in a width direction orthogonal to a sheet conveyance direction ;
The heater is composed of a central fixing heater that heats a central portion of the fixing member and a both-side fixing heater that heats both side portions of the fixing member,
A second temperature sensor is disposed on one end side in the width direction of the fixing member;
The fixing control unit corrects an end reference temperature according to a displacement amount of the fixing member or the sheet by the displacement unit, and based on a detected temperature detected by the second temperature sensor, An image forming apparatus , wherein the output of the fixing heaters on both sides is controlled so that the temperature on one end side becomes the end reference temperature . The fixing control unit sets the edge reference temperature over time when the sheet is displaced toward the one end side with respect to the fixing member in the relative positional relationship between the fixing member and the sheet. The edge reference temperature is increased with time when the sheet is displaced with time in a position opposite to the one end side with respect to the fixing member in the positional relationship. The image forming apparatus according to 1. 3. The image according to claim 1, wherein a time point at which the edge reference temperature is changed is a time point when a predetermined delay time has elapsed from a time point when the displacement amount of the fixing member or the sheet is set. Forming equipment.   4. The apparatus according to claim 1, wherein the displacement unit includes a stepping motor, and the fixing control unit calculates the amount of displacement based on the number of drive pulses of the stepping motor with respect to a home position. The image forming apparatus described.   The image forming apparatus according to claim 1, wherein the displacing unit displaces the fixing device and displaces the fixing member in the width direction with respect to the sheet.   The image forming apparatus according to claim 1, wherein the fixing member is an endless belt made of a heat resistant resin.   6. The image forming apparatus according to claim 1, wherein the fixing member is a roller in which a heat-resistant resin layer is formed on a roller-shaped substrate.

Images