JP2012194444A - Fixing device and image forming apparatus including fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of retaining a favorable separability of a recording medium without deteriorating durability of a fixing member, and to provide an image forming apparatus.SOLUTION: The fixing device includes a pressure pad 64 that is disposed in a space surrounded with an internal peripheral surface of a pressure belt 62 that faces a fixing belt 61. The pressure pad 64 includes an escape portion for reducing a pushing pressure towards the fixing roller 63, formed on an exit side of a nip part in which the fixing belt 61 and the pressure belt 62 are separated from each other. A part from a pressing surface to the escape portion of the pressure pad 64 is pressed by an elastic layer 632 of the fixing roller 63 via the fixing belt 61 and the pressure belt 62 such that the fixing belt 61, the pressure belt 62, and the elastic layer 632 of the fixing roller 63 are made to follow the shape of the escape portion of the pressure pad 64, at the exit side of the nip part.

Description

  The present invention relates to a fixing device and an image forming apparatus such as a copying machine, a facsimile, and a printer provided with the fixing device.

  Conventionally, this type of image forming apparatus has been disclosed that includes a fixing device using an endless fixing belt in order to fix an image carried on a recording medium such as paper (see Patent Document 1). ). Since the fixing belt used in this fixing device is as thin as 150 to 750 μm and has a low heat capacity, the rise time (waiting time) from when the power is turned on to when the image can be formed is short. There are advantages such as low power consumption.

  In addition, a fixing device by a direct heating method from the inside of the belt with a halogen heater (see Patent Document 2) and an image heating device by a belt direct heating method by IH (Induction Heating) for further shortening the rise time (see Patent Document 2). A fixing device (see Patent Document 3) is disclosed. Since the halogen heater is much cheaper than the IH coil, the direct heating method using the halogen heater is advantageous in terms of cost.

  In a fixing device that heats a toner image and applies pressure to the recording paper to fix the toner image, the toner that has melted and has a strong adhesive property sticks to a fixing member such as a fixing roller or a fixing belt. The separability is an important issue. For this reason, in order to separate the recording sheet after fixing from a fixing member such as a fixing roller or a fixing belt, a fixing device including a separating plate close to the fixing member with a slight gap is disclosed (patent). Reference 4). The fixing device disclosed in Patent Document 4 is configured such that the gap between the separation plate and the fixing member can be adjusted. However, if the leading end of the recording paper passes through the gap, the fixing device remains wound around the fixing member. There is a risk of becoming.

  There are known fixing devices in which the separation claw is brought into contact with the surface of the fixing member without any gap to improve the separation of the recording paper, but there is a risk of scratching the surface of the fixing member. There is a drawback that the performance is significantly reduced. In particular, if the fixing surface side of the fixing member is scratched, the scar is transferred as it is to the recording paper or the toner is easily offset, leading to a decrease in image quality.

  Accordingly, the pressing member that protrudes in a convex shape with respect to the outer peripheral surface of the fixing roller locally increases the distortion in the elastic layer of the fixing roller in the exit area of the contact portion (nip portion), and the recording material after fixing Discloses a fixing device that can effectively separate a thin recording material without being wound around a fixing roller (see Patent Document 5).

  However, in the fixing device disclosed in Patent Document 5, the nip pressure is locally increased in the exit area of the contact portion (nip portion) so that the distortion in the elastic layer of the fixing roller is locally increased. For this reason, a load is applied to the fixing belt, the fixing roller (pressure belt or pressure roller), and the durability is lowered. In particular, when a sponge is used for the elastic layer of the fixing roller, if the sponge is compressed too much, bubbles are broken and the elastic force is remarkably reduced, so abnormal image generation such as poor fixing of the image, reduction in gloss, offset, etc. I will invite you. Further, even when a thin fixing belt is used, the belt is likely to be broken or damaged due to repeated local distortion of the belt, resulting in a decrease in durability.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a fixing device capable of maintaining good separation of a recording medium without reducing the durability of the fixing member, and the fixing device thereof. An image forming apparatus is provided.

In order to achieve the above object, a first aspect of the present invention is a roller-shaped fixing member having an elastic layer, a heating means for heating the fixing member, and an endless belt-shaped facing member facing the fixing member. A pressing member that is disposed in a space surrounded by the inner peripheral surface of the opposing member and presses the fixing member via the opposing member, and an elastic body layer of the fixing member by the pressing force of the pressing member Is a fixing device that forms a nip portion through which a recording medium passes between the fixing member and the opposing member, wherein the pressing member is a nip portion where the fixing member and the opposing member are separated from each other. An escape portion for reducing the pressing force to the fixing member is formed on the outlet side of the fixing member, and the elastic member layer of the fixing member is pressed from the pressing surface of the pressing member to the escape portion through the opposing member. , The opposing member and the fixing unit In the the elastic layer outlet side of the nip portion and is characterized by being configured so as to follow the shape of the relief portion of the pressing member.
According to a second aspect of the present invention, there is provided an endless belt-shaped fixing member, a heating means for heating the fixing member, a roller having an elastic layer disposed so as to contact an inner peripheral surface of the fixing member, An endless belt-like facing member that faces the fixing member; and a pressing member that is disposed in a space surrounded by the inner peripheral surface of the facing member and presses the roller via the fixing member and the facing member. A fixing device that elastically deforms an elastic layer of the roller by a pressing force of the pressing member to form a nip portion through which a recording medium passes between the fixing member and the opposing member, the pressing member Is formed on the exit side of the nip portion where the fixing member and the opposing member are separated from each other, and an escape portion for reducing the pressing force to the roller is formed, and the fixing member extends from the pressing surface of the pressing member to the escape portion. And the counter member So that the fixing member, the opposing member, and the elastic layer of the roller follow the shape of the relief portion of the pressing member on the outlet side of the nip portion. It is characterized by comprising.
According to a third aspect of the present invention, in the fixing device according to the first or second aspect, the surface pressure of the nip portion is substantially constant from the inlet of the nip portion to the front of the escape portion of the pressing member, It is characterized in that the distance from the nip portion to the outlet of the nip portion is lower than that from the inlet of the nip portion to the front of the escape portion.
According to a fourth aspect of the present invention, in the fixing device according to any one of the first to third aspects, the pressing member is a rigid body, and the escape portion is formed by a step.
According to a fifth aspect of the present invention, in the fixing device according to any one of the first to fourth aspects, the corner portion of the relief portion of the pressing member that is in sliding contact with the inner peripheral surface of the opposing member is subjected to an arc or a chamfering process. It is characterized by that.
According to a sixth aspect of the present invention, there is provided an image forming apparatus comprising: an image forming unit that forms an image on a recording medium; and a fixing device that fixes an image on the recording medium formed by the image forming unit. The fixing device according to any one of claims 1 to 5 is used as the fixing device.

  According to the present invention, the pressing member disposed in the space surrounded by the inner peripheral surface of the facing member facing the roller-shaped or endless belt-shaped fixing member is the roller-shaped or endless belt-shaped fixing member and the endless belt-shaped. An escape portion is formed on the exit side of the nip portion where the opposite member is spaced from the opposite member to reduce the pressing force against the fixing member. In this relief portion, the amount of elastic deformation of the elastic layer of the roller-shaped fixing member or the amount of elastic deformation of the elastic layer of the roller in contact with the inner peripheral surface of the endless belt-shaped fixing member is the other pressing portion by the pressing member. Therefore, on the outlet side corresponding to the relief portion of the nip portion, the internal pressure (pressure acting in the direction perpendicular to the conveyance direction of the recording medium) becomes smaller than other portions of the nip portion. Thereby, the adhesion between the recording medium and the fixing member is weakened on the exit side of the nip portion, and the separation property of the recording medium at the exit of the nip portion is improved. Further, since the curvature of the elastic layer at the exit of the nip portion becomes larger (the radius of curvature becomes smaller) than when no escape portion is provided, the separation between the fixing roller or the endless belt and the recording medium is further improved. Also, unlike conventional technology that increases the separation force by increasing the pressing force (internal pressure) on the outlet side of the nip portion, it has a structure that improves the separation property by reducing the pressing force, such as a fixing roller, endless belt, etc. The durability of the fixing member is not lowered. Therefore, it is possible to maintain good separation of the recording medium without reducing the durability of the fixing member such as the fixing roller and the endless belt.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. The schematic block diagram of an image station. 1 is a schematic configuration diagram of a fixing device. The schematic structure perspective view of a press pad. 6 is a graph showing the relationship between the pressure in the nip portion of the fixing nip portion and the position in the nip width. FIG. 6 is a schematic configuration diagram of a fixing device according to another embodiment. FIG. 10 is a schematic configuration diagram of a fixing device according to another embodiment.

[Embodiment 1]
FIG. 1 shows an outline of an image forming apparatus to which the present invention is applied. The image forming apparatus 100 is a multifunction peripheral of a copying machine, a printer, and a facsimile machine, and can perform full-color image formation. Other image forming apparatuses, that is, a monochrome machine, a copying machine, a printer, It may be a single facsimile, or another multifunction device such as a multifunction device of a copying machine and a printer. When used as a printer, the image forming apparatus 100 performs an image forming process based on an image signal corresponding to image information received from the outside. This is the same when the image forming apparatus 100 is used as a facsimile.

  The image forming apparatus 100 can form an image on a sheet-like recording medium using not only plain paper generally used for copying, but also OHP sheets, cardboard, cardboard, cardboard, and envelopes. It is. The image forming apparatus 100 is also a double-sided image forming apparatus capable of forming an image on both sides of a transfer sheet as a recording medium as a recording medium.

  The image forming apparatus 100 includes a main body 101 that occupies a central position in the vertical direction and functions as a printer unit, a reading device 21 that is positioned above the main body 101 and that reads a document, and a document on which a document is stacked and loaded. An automatic document feeder 22 which is an automatic document feeder called ADF which is sent out toward 21, and the photosensitive drums 20 </ b> Y, 20 </ b> M, 20 </ b> C, 20 </ b> BK located below the main body 101 and the transfer belt 11. A sheet feeding device 23 serving as a paper feeding device serving as a paper feeding table on which the transfer paper to be conveyed is stacked.

  The image forming apparatus 100 includes a plurality of photosensitive drums 20Y, 20M, 20C, and 20BK that can form images as images corresponding to colors separated into yellow, magenta, cyan, and black, respectively. 1 is a tandem type image forming apparatus that employs a tandem structure in which the two are arranged side by side. The photosensitive drums 20Y, 20M, 20C, and 20BK have the same diameter, and are transfer belts as intermediate transfer belts that are intermediate transfer members that are endless belts disposed almost at the center inside the main body 101 of the image forming apparatus 100. 11 are arranged at equal intervals on the outer peripheral surface side, that is, on the image forming surface side.

  The transfer belt 11 is movable in the arrow A1 direction, which is the clockwise direction in the figure, while facing the respective photosensitive drums 20Y, 20M, 20C, and 20BK. The visible image, that is, the toner image formed on each of the photoconductive drums 20Y, 20M, 20C, and 20BK is superimposed and transferred onto the transfer belt 11 that moves in the direction of the arrow A1, and is then collectively transferred onto the transfer paper. It has become. As described above, the image forming apparatus 100 employs the indirect transfer method. Accordingly, the image forming apparatus 100 is a tandem indirect transfer type electrophotographic apparatus.

  In the superimposing transfer to the transfer belt 11, the toner images formed on the photosensitive drums 20Y, 20M, 20C, and 20BK are transferred to the same position on the transfer belt 11 while the transfer belt 11 moves in the A1 direction. As described above, a primary transfer device as a transfer charger that is disposed at a position facing each of the photosensitive drums 20Y, 20M, 20C, and 20BK across the transfer belt 11 and that is in contact with the inner peripheral surface of the transfer belt 11. As a result of voltage application by the primary transfer rollers 12Y, 12M, 12C, and 12BK, the timing is shifted from the upstream side toward the downstream side in the A1 direction, and the positions immediately below the photosensitive drums 20Y, 20M, 20C, and 20BK, that is, 1 It is performed at the transfer position which is the next transfer position. Since the transfer belt 11 also contributes to this transfer, it can be said that it constitutes a primary transfer device.

  The photosensitive drums 20Y, 20M, 20C, and 20BK are arranged in this order from the upstream side in the A1 direction. The photosensitive drums 20Y, 20M, 20C, and 20BK are provided in image stations 60Y, 60M, 60C, and 60BK, respectively, for forming yellow, magenta, cyan, and black images.

  The image forming apparatus 100 includes an image forming unit 60 which is an image forming unit as an image forming unit configured by four image stations 60Y, 60M, 60C, and 60BK, and below the photosensitive drums 20Y, 20M, 20C, and 20BK. The transfer belt unit 10 is an intermediate transfer unit provided with the transfer belt 11, and faces the transfer belt 11 on the side opposite to the image forming unit 60 with the transfer belt 11 in between. The secondary transfer belt serving as a conveyance belt, which is a paper conveyance belt as a transfer member that is disposed in contact with the transfer belt 11 and rotates in the same direction as the transfer belt 11 and moves endlessly at the contact position with the transfer belt 11. 5 is a secondary transfer unit as a secondary transfer device that transfers the toner image on the transfer belt 11 to transfer paper and conveys the toner image on the transfer belt 11. And a copy unit 76.

  The image forming apparatus 100 also includes an optical scanning device 8 serving as an exposure device serving as an optical writing unit serving as an optical writing device serving as an optical writing device disposed above the image stations 60Y, 60M, 60C, and 60BK, and a sheet. The transfer paper conveyed from the feeding device 23 comes into contact with the transfer paper to temporarily stop the toner image formation timing by the image stations 60Y, 60M, 60C, and 60BK. In other words, the position of the toner image on the transfer belt 11 The registration roller pair 13 that rotates at a predetermined timing in accordance with the transfer belt 11 and feeds out toward the transfer portion between the transfer belt 11 and the secondary transfer belt 5, and that the leading edge of the transfer paper has reached the registration roller pair 13. And a sensor (not shown) for detection.

  The image forming apparatus 100 also serves as a belt-fixing type fixing unit for transferring the toner image on the transfer belt 11 transferred by the secondary transfer unit 76 and fixing the toner image on the transfer paper. A fixing device 6 as a belt fixing device, a paper discharge path for discharging the fixed transfer paper to the outside of the main body 101, and a reverse path for conveying the transfer paper toward the registration roller pair 13 again. The paper discharge unit 79 is disposed below the secondary transfer unit 76 and the fixing device 6 in parallel with the image forming unit 60. The paper discharge unit 79 has one side for recording images on both the front and back sides of the transfer paper. A re-feeding unit that, when the transfer paper on which the image is formed is conveyed to the reversing path, switches the transfer paper to reverse and conveys the transfer paper again toward the registration roller pair 13; A sheet reversing apparatus for Te and a sheet reversing device serving duplex unit 96.

  The image forming apparatus 100 also includes a paper discharge tray 75 as a stack unit that is disposed outside the main body 101 and stacks transfer sheets on which image formation has been performed, and a manual sheet feeding device disposed on the right side surface of the main body 101 in FIG. 33, an operation panel (not shown) that operates the image forming apparatus 100, and a control unit (not shown) as a control unit that controls the operation of the entire image forming apparatus 100.

  In addition to the transfer belt 11, the transfer belt unit 10 includes primary transfer rollers 12Y, 12M, 12C, and 12BK as primary transfer means, and first to third belts wound around the transfer belt 11 and stretched. The transfer belt 11 is interposed between the tension roller 74 and a driving roller 72 as a rotation driving roller that rotationally drives the transfer belt 11 as a support roller, a transfer inlet roller 73 as a driven roller, a tension roller 74 as a driven roller, and the tension roller 74. An intermediate transfer belt cleaning device 14 as a belt cleaning device for cleaning the surface of the sandwiching transfer belt 11, a belt driving motor (not shown) that moves the transfer belt 11 endlessly in the A1 direction by rotationally driving the driving roller 72, and image formation. This is done with multicolor images of two or more colors, or a single color image with black only KazuSatoshi and a transfer belt unit driving means (not shown) for displacing the transfer belt 11 or the like depending on whether carried out in a monochrome image. The rotation driving roller may be constituted by a tension roller 74 or a transfer entrance roller 73. In this case, the other rollers are driven to rotate.

  When the image formation is performed with two or more multi-color images, the transfer belt unit driving means places the transfer belt 11 in a state where the transfer belt 11 is stretched substantially horizontally as shown in FIG. When image formation is performed with a monochrome image by contacting with 20Y, 20M, 20C, and 20BK, the tension roller 74 is displaced and the left side of the drawing is displaced downward, so that the transfer belt 11 is displaced to the photosensitive drums 20Y, 20M. , 20C so that the transfer belt 11 contacts only the photosensitive drums 20BK. When the image formation is performed with a monochrome image, the operations of the image stations 60Y, 60M, and 60C are stopped, including the rotation of the photosensitive drums 20Y, 20M, and 20C. In such a configuration, the four image stations 60Y, 60M, 60C, and 60BK are arranged side by side in the order of the image stations 60C, 60M, 60Y, and 60BK from the upstream in the A1 direction, and development as described below is performed. In any case, the image forming unit 60 is disposed on the linear transfer belt 11 stretched between the tension roller 74 and the driving roller 72. As described above, the order of colors for forming an image varies depending on the aim and characteristics of the image forming apparatus 100 and is not limited.

  In addition to the secondary transfer belt 5, the secondary transfer unit 76 is a tension roller around which the secondary transfer belt 5 is wound. A transfer entrance roller 73 as a backup roller that is provided and pressed against and pressed through the transfer belt 11; and a power supply (not shown) that applies a secondary transfer bias having a polarity opposite to that of the toner to the drive roller 15. ing.

  The driving roller 15 and the transfer entrance roller 73 sandwich the transfer belt 11 and the secondary transfer belt 5 between them, and the secondary transfer belt 11 and the secondary transfer belt 5 come into contact with each other by the sandwiching. A nip is formed. In the secondary transfer nip, by applying a secondary transfer bias, a toner image carried on the transfer belt 11 is electrostatically moved from the transfer belt 11 side toward the drive roller 15 side as described later. A next transfer electric field is formed. Such a toner image is transferred to a transfer sheet conveyed between the transfer belt 11 and the secondary transfer roller 5 by the registration roller 13 by a secondary transfer electric field and a nip pressure as will be described later.

  The secondary transfer unit 76 also has a sheet conveyance function for conveying the transfer paper onto which the toner image has been transferred from the transfer belt 11 to the fixing device 6. The secondary transfer unit 76 includes a transfer roller or a non-contact type. A configuration employing a charger may be used. In this case, another member for transporting the transfer paper toward the fixing device 6 is required.

  The optical scanning device 8 scans and exposes the surfaces to be scanned formed by the surfaces of the photosensitive drums 20Y, 20M, 20C, and 20BK, and forms a laser beam based on an image signal for forming an electrostatic latent image. Scanning with a light source (not shown) that emits the laser light L shown in FIG. 2, a polygon mirror (not shown) that scans the laser light emitted by the light source by its rotation, a polygon motor (not shown) that drives the polygon mirror to rotate, and a polygon mirror The laser beam is imaged on the photosensitive drums 20Y, 20M, 20C, and 20B, and has a large number of optical elements (not shown) such as an f-θ lens (not shown) and a reflection mirror that scan. An LED may be used as the light source.

  The fixing device 6 performs a fixing process for fixing the supported toner image on the surface of the transfer paper by the action of heat and pressure by passing the transfer paper carrying the toner image through the fixing nip. Details of the fixing device 6 will be described later.

  A paper discharge unit 79 transports the fixed transfer paper transported from the fixing device 6 toward the duplex unit 96, a paper discharge roller 98 that discharges the paper to the outside of the main body 101, and a fixed transfer. A switching claw 94 is provided for switching whether the paper is guided to the reversing path with the conveying roller 97 to enter the duplex unit 96 or guided to the paper discharging path with the paper discharging roller 98 to be discharged out of the main body 101.

  The duplex unit 96 is a tray 92 on which transfer paper having an image formed on one side, which has been conveyed from the paper discharge unit 79, is temporarily stacked, a reverse roller 93 that switches back the transfer paper on the tray 92, and a reverse roller. The sheet feeding roller 95 and the like for feeding the transfer sheet switched back by 93 to the registration roller 13 are provided.

  The sheet feeding device 23 includes a paper bank 26 in which a plurality of sheet feeding cassettes 25 that can store a plurality of transfer sheets in a bundle of sheets are arranged in a vertical direction, and a plurality of transfer sheets stacked on the sheet feeding cassette 25. Among them, a feeding roller 24 as a sheet feeding roller that contacts the upper surface of the uppermost transfer sheet, a separation roller 27 that separates the transfer sheets fed by the feeding roller 24 one by one, a sheet feeding roller 24 and a separation roller And a paper feed path 29 through which the transfer paper fed by the roller 27 passes.

  A paper feed path 29 is provided at a downstream end in the transport direction of the transfer paper, and a transport guide plate 37 and a transport roller 28 for transporting the transfer paper fed by the paper feed roller 24 and the separation roller 27 toward the registration roller pair 13. The transfer roller 28 is provided so as to continue from the sheet feeding device 23 into the main body 101, and is also provided in the paper feed path 29 in the main body 101. 28 is disposed.

  In the sheet feeding device 23, the feeding roller 24 is rotated in the counterclockwise direction in the drawing, and the separation roller 27 acts to guide the uppermost transfer paper into the paper feeding path 29, so that the conveying roller 28 The sheet is fed toward the registration roller pair 13 by rotation, and the transferred transfer paper is abutted against the registration roller pair 13 and stopped.

  The manual paper feed device 33 includes a manual feed tray 34 on which transfer paper is stacked, a feed roller 35 as a paper feed roller that contacts the upper surface of the uppermost transfer paper among the transfer papers stacked on the manual feed tray 34, It has a separation roller 36 for separating the transfer paper fed by the feed roller 35 one by one, and a paper sensor for detecting that the transfer paper is placed on the manual feed tray 34.

  In the manual sheet feeding device 33, the feeding roller 35 is driven to rotate in the clockwise direction in the drawing, and the separation roller 36 acts to guide the uppermost transfer sheet into the sheet feeding path 29 on the main body 101 side and to register the sheet. The transfer paper fed to the roller pair 13 is transported against the registration roller pair 13 and stopped.

  The reading device 21 includes a contact glass 21a on which a document is placed, a light source (not shown) that irradiates light on the document placed on the contact glass 21a, and a first light source (not shown) that reflects light reflected from the light source. A first traveling body 21b that has a reflector and travels in the left-right direction in FIG. 1, a pair of second reflectors (not shown) that changes the direction by 180 degrees by reflecting light reflected by the reflector of the first traveling body 21b. A second traveling body 21c provided, an imaging lens 21d for imaging the light from the second traveling body 21c, a reading sensor 21e for receiving the light passing through the imaging lens 21d and reading the contents of the document are provided.

  The automatic document feeder 22 has a document table 22a on which a document is placed. The automatic document feeder 22 is rotatable with respect to the reading device 21, and the contact glass 21a is exposed when the automatic document feeder 22 is rotated upward.

  The operation panel is an operation display unit having a liquid crystal display, a start button that functions as a copy start switch for starting copying, and various key buttons such as a numeric keypad for inputting the number of copies. On the operation panel, it is possible to specify whether image formation is performed with a multicolor image or a monochrome image, and it is possible to set a single-sided print mode, which is a mode for forming an image only on one side of a transfer sheet. Yes. The single-sided print mode includes a direct discharge mode, a reverse discharge mode, and a reverse decal discharge mode, and one of these is selected.

  The control means includes a CPU, a memory as a storage means, and the like.

  Regarding the image stations 60Y, 60M, 60C, and 60BK, the configuration will be described as a representative of the configuration of the image station 60Y including the photosensitive drum 20Y. Since the configuration of other image stations is substantially the same, in the following description, for the sake of convenience, reference numerals corresponding to the reference numerals assigned to the configuration of the image station including the photosensitive drum 20Y are used for other image stations. The detailed description will be omitted as appropriate for the station configuration, and those with Y, M, C, and BK at the end of the reference numerals are used to form yellow, cyan, magenta, and black images, respectively. It is assumed that this is the configuration.

  As shown in FIG. 2, the image station 60Y including the photosensitive drum 20Y has a primary transfer roller 12Y and an image around the photosensitive drum 20Y along the rotation direction B1 that is counterclockwise in the drawing. Density detection means 17Y, cleaning device 70Y as a primary transfer cleaning device as a photosensitive member cleaning device as a cleaning means, charge removal device 90Y as a charge removal means, charging device 30Y as a charging unit as a charging means, and development A developing device 80Y, which is a developing unit as means, and a cartridge case 59Y in which these are integrated are provided.

  The photosensitive drum 20Y, the cleaning device 70Y, the charge eliminating device 90Y, the charging device 30Y, the developing device 80Y, and the image density detecting means 17Y are integrated by a cartridge case 59Y, and an image station 60Y as a process cartridge is integrated. Is configured. The image station 60Y as a process cartridge can draw out the cartridge case 59Y from the main body 101 along a guide rail (not shown) fixed to the main body 101, and can push the cartridge case 59Y into the main body 101. Is detachably installed.

  When pushed into the main body 101, the image station 60Y as a process cartridge is loaded and positioned at a predetermined position suitable for image formation. Making a process cartridge in this way is very preferable because it can be handled as a replacement part, so that the maintainability is remarkably improved. In addition, since the life of each part, which is an element of the process cartridge, is equal, unnecessary replacement is prevented and suppressed, and the structure is further preferable.

  The image station 60Y as a process cartridge includes at least the photosensitive drum 20Y among the photosensitive drum 20Y, the cleaning device 70Y, the charge eliminating device 90Y, the charging device 30Y, the developing device 80Y, and the image density detecting unit 17Y. Another unit is a unit that is configured by being integrated and is detachably installed on the main body 101.

  A primary transfer nip formed by the primary transfer roller 12Y pressing the transfer belt 11 toward the photosensitive drum 20Y is a contact position between the transfer belt 11 and the photosensitive drum 20Y. Constitutes a transfer position NP at which the toner image is transferred to the transfer belt 11. The primary transfer device is not limited to the roller shape as in the present embodiment, and may be configured by a conductive brush shape, a non-contact corona charger, or the like.

  The photosensitive drum 20Y has a linear velocity of 200 mm / s, a diameter of 50 mm, and a thickness of 30 μm.

  The static eliminator 90Y includes a static elimination lamp (not shown) disposed in the vicinity of the surface of the photoconductor drum 20Y, and the surface of the photoconductor drum 20Y is neutralized by making it electrically clean. The static elimination process which initializes the electric potential of this is performed.

  The charging device 30Y includes a charging roller 31Y that rotates in contact with the surface of the photosensitive drum 20Y, and a cleaning roller 32Y as a charging cleaning member that rotates in contact with the charging roller 31Y.

  The charging roller 31Y is connected to a voltage applying means (not shown) for applying a bias of an alternating current component to a direct current, and in the charging region facing the photosensitive drum 20Y, the charging drum 31Y is charged by the discharging device 90Y. A charging step for uniformly charging the surface to a predetermined polarity is performed. The charging potential of the photosensitive drum 20Y by the charging roller 31Y, that is, the pre-exposure potential V0 is −700V.

  The cleaning roller 32Y is driven to rotate by the charging roller 31Y to clean the charging roller 31Y.

  As described above, in this embodiment, a charging system using a contact roller is used. However, the charging system may use a proximity roller or a non-contact scorotron charger. It may be.

  The optical scanning device 8 shown in FIG. 1 applies the laser light L modulated and deflected to a region between a charging region where the charging device 30Y faces the photosensitive drum 20Y and a developing region where the developing device 80Y faces. Image information that is irradiated while scanning and the surface to be scanned on the surface of the photosensitive drum 20Y after being charged by the charging device 30Y is exposed by spot irradiation and visualized as a yellow toner image by the developing device 80Y. An electrostatic latent image forming step of writing an electrostatic latent image according to the above is performed. The beam spot diameter on the surface of the photosensitive drum 20Y by the optical scanning device 8 is 50 × 60 μm, and the light quantity is 0.47 mW. The charged potential of the photosensitive drum 20Y after the exposure by the optical scanning device 8, that is, the post-exposure potential VL is −120V.

  As shown in FIG. 2, the developing device 80Y includes a developing roller 81Y carrying a two-component developer (hereinafter referred to as developer) including a toner and a carrier disposed in close proximity to the photosensitive drum 20Y, and a developing roller 81Y. A doctor blade 82Y that regulates the developer on the roller 81Y to a certain height, and a first conveying screw that is arranged in parallel with each other and agitates the developer and supplies the developer to the developing roller 81Y. 83Y and the second transport screw 84Y, a partition wall 87Y that is a partition plate provided between the first transport screw 83Y and the second transport screw 84Y, and a part of the cartridge case 59Y that houses them. And a developing case 85Y.

  The developing device 80Y also develops a toner concentration sensor 86Y as a toner concentration detecting unit attached to the developing case 85Y below the first conveying screw 83Y, a toner bottle 88Y containing yellow toner, and a developing bias of a DC component. A bias applying unit (not shown) for applying to the roller 81Y and a developing driving unit as a driving unit (not shown) for driving the developing roller 81Y, the first conveying screw 83Y, the second conveying screw 84Y, and the like are included.

  The first conveying screw 83Y, the second conveying screw 84Y, and the partition wall 87Y constitute an agitating unit 38Y that conveys the developer while stirring and supplies the developer to the developing roller 81Y.

  The developing roller 81Y and the doctor blade 82Y occupy a position higher than the agitating unit 38Y, and constitute a developing unit 39Y that transfers the toner of the developer attached to the developing roller 81Y to the photosensitive drum 20Y.

  The developing roller 81Y has a developing sleeve (not shown) that is a developer carrying member that carries the developer on the surface thereof, and a plurality of magnets (not shown) fixed inside the developing sleeve.

  The doctor blade 82Y is disposed so that the tip thereof is close to the developing sleeve.

  The bias applying means applies a developing bias having an appropriate size between the exposed portion and the non-exposed portion of the photosensitive drum 20Y to the developing sleeve.

  In the developing device 80Y, a partition wall 87Y forms a first supply unit that accommodates the developing roller 81Y and the first conveyance screw 83Y and a second supply unit that accommodates the second conveyance screw 84Y. Has been.

  The developer in the developing case 85Y is a two-component developer including a magnetic carrier and a yellow toner that is a negatively charged color toner. The developer is supplied with yellow toner from a toner bottle 88Y. The supplied yellow toner and developer are agitated and mixed while being agitated and conveyed by the first conveying screw 83Y and the second conveying screw 84Y, frictionally charged, supplied to the developing roller 81Y, and pumped up by the magnet roller. Is held by the developing sleeve, and is carried in such a manner that a magnetic brush is formed on the developing sleeve.

  In the developing roller 81Y, the developer carrying amount is regulated by the doctor blade 82Y by the rotation of the developing sleeve, the layer thickness is regulated, the magnetic brush is trimmed to an appropriate amount, and the developer that has been cut off enters the stirring unit 38Y. Returned. The developing roller 81Y also carries an appropriate amount of developer by the doctor blade 82Y to the developing area between the developing roller 81Y and the photosensitive drum 20Y by the rotation and the developing bias by the bias applying means. The yellow toner is electrostatically transferred to an electrostatic latent image formed on the surface of the photoreceptor drum 20Y, and a developing process is performed in which the electrostatic latent image is made visible as a yellow toner image and visualized as an image. It is like that.

  The developer that has consumed the yellow toner by the development leaves the developing sleeve at the position where the magnetic force of the magnet roller has decreased with the rotation of the developing roller 81Y, and returns to the stirring unit 38Y.

  By repeating this, the toner concentration in the agitating unit 38Y becomes low, and when this is detected by the toner concentration sensor 86Y, the toner concentration sensor 86Y detects that the toner concentration has reached a predetermined concentration from the toner bottle 88Y. Toner is replenished and supplied.

  In this embodiment, the developing bias of the DC component is applied by the bias applying means, but the developing bias may be an AC component, or may be an AC component superimposed on the DC component.

  The cleaning device 70Y includes a cleaning case 71Y configured by a part of the cartridge case 59Y that forms a housing thereof, and is housed in the cleaning case 71Y. The tip of the cleaning device 70Y comes into contact with the photosensitive drum 20Y and is on the photosensitive drum 20Y. A cleaning blade 78Y as a cleaning member for performing a cleaning process for scraping off and collecting foreign matters such as transfer residual toner, carrier, paper dust, and the like, which are transfer residues, and a cleaning blade 78Y supported by a cleaning case 71Y The blade support 73Y, a support shaft 77Y that rotatably supports the blade support 73Y on the cleaning case 71Y, and a predetermined elasticity on the photosensitive drum 20Y so that the edge of the cleaning blade 78Y is pressed against the photosensitive drum 20Y. Push with force And a Rubane 79Y.

  The cleaning device 70Y is also rotatably supported by the cleaning case 71Y, and the cleaning blade 78Y scrapes off the transfer residual toner and the like from the photosensitive drum 20Y, and also removes unnecessary items such as waste toner generated by the removal. The photosensitive drum is provided with a discharge screw 18Y that is a recovery screw as a waste toner conveying screw that is discharged toward one side of the paper in FIG. 2 and a protective agent 42Y as a lubricant that is a lubricant protecting the photosensitive drum 20Y. And a protective film forming device 40Y as a lubricant coating device which is a lubricant coating device which is a protective film forming means to be applied to 20Y.

  The protective film forming apparatus 40Y includes an image carrier protecting agent which is a solid lubricant formed in a bar shape, a protective agent 42Y as an image carrier protecting agent, and a direction opposite to the rotation direction B1 of the photosensitive drum 20Y, that is, Lubricant application member as a scraping member that rotates in the counter direction D1 and scrapes off the protective agent 42Y to supply the photosensitive drum 20Y and apply it to protect the photosensitive drum 20Y. A brush roller 47Y as a lubricant application brush roller, which is a fur brush application brush as a lubricant application brush.

  The protective film forming apparatus 40Y also holds the protective agent 42Y and supports it with respect to the cleaning case 71Y, and supports 49Y as a lubricant holding member that supports the protective agent 42Y in the direction of contacting and separating from the brush roller 47Y. It has a spring 48Y as a spring member as a lubricant pressurizing spring, which is a pressurizing spring as an elastic member as a pressing means for pressing the protective agent 42Y against the brush roller 47Y via the support 49Y.

  The protective film forming apparatus 40Y also includes a cleaning blade 78Y, a voltage applying unit, and a lubricant application driving unit as a driving unit configured to rotate and drive the brush roller 47Y.

  The brush roller 47Y contacts the photosensitive drum 20Y at a position TP downstream of the transfer position NP and upstream of a later-described cleaning position CP in the B1 direction, and at this position TP, the protective agent 42Y contacts the photosensitive drum 20Y. It can be applied. This position TP is a lubricant application position.

  The brush roller 47Y rotates in the direction D1 by the transmission of the rotational driving force from the lubricant application driving means. By this rotation, after the protective agent 42Y is scraped and adhered to the fiber portion of the brush roller 47Y, the surface of the photosensitive drum 20Y at the lubricant application position TP when the brush roller 47Y is in contact with the photosensitive drum 20Y. To be applied.

  The cleaning blade 78Y is made of polyurethane rubber, and is in contact with the photosensitive drum 20Y at an angle similar to a so-called counter type, that is, a reading type. The cleaning position CP is a position where the cleaning blade 78Y contacts the photosensitive drum 20Y and unnecessary materials such as transfer residual toner on the photosensitive drum 20Y are cleaned.

  At the cleaning position CP, the cleaning blade 78Y applies a protective agent 42Y applied or supplied to the photosensitive drum 20Y at the lubricant application position TP by the brush roller 47Y on the photosensitive drum 20Y, and forms a film on the surface of the photosensitive drum 20Y. It functions as a coating blade for forming a protective film as a protective layer. The cleaning blade 78Y leveles the protective agent 42Y on the photosensitive drum 20Y so as to eliminate even a slight distribution unevenness in the protective agent 42Y on the photosensitive drum 20Y.

  Thus, when the brush roller 47Y is rotationally driven, the cleaning device 70Y is driven as the protective film forming device 40Y. The rotation direction of the brush roller 47Y may be the forward direction instead of the reverse direction to the B1 direction.

  The film formed on the surface of the photoconductive drum 20Y by the protective agent 42Y has a function of preventing the surface of the photoconductive drum 20Y from being deteriorated due to proximity discharge, and the protective film forming apparatus 40Y functions as a discharge deterioration preventing means. It is. The deterioration here refers to both wear of the photosensitive drum 20Y due to discharge, acceleration of the wear, and activation of the surface of the photosensitive drum 20Y.

  In addition, the coating prevents deterioration such as wear caused by friction between the photosensitive drum 20Y and the cleaning blade 78Y, and the protective film forming apparatus 40Y functions as a friction deterioration preventing unit.

  As described above, the protective film forming apparatus 40Y suppresses the deterioration by applying the protective agent 42Y to the surface of the photosensitive drum 20Y.

  Further, the protective film forming apparatus 40Y is a contact brush in which the brush roller 47Y is in contact with the photosensitive drum 20Y, and cleans unnecessary materials such as transfer residual toner on the photosensitive drum 20Y, like the cleaning blade 78. It functions as a cleaning brush as a cleaning member.

  In the image forming apparatus 100 having such a configuration, when copying is performed, a document is set on the document table 22a of the automatic document feeder 22 or the automatic document feeder 22 is rotated upward to be on the contact glass 21a. After the document is placed on the automatic document feeder 22, the automatic document feeder 22 is rotated downward to close the document and press the document, and then the start button on the operation panel is pressed. The document set on the automatic document feeder 22 is, for example, a bundle-shaped sheet document, and the document set on the contact glass 21a is, for example, a single-bound document that is bound in a main shape. When the image forming apparatus 100 is used as a printer, an image forming start operation is performed after image data to be formed is selected and input by an external input device such as a PC connected to the image forming apparatus 100.

  When copying is performed and the document is set on the document table 22a, the document is read by the reading device 21 after the set document is sent onto the contact glass 21a. When the document is placed on 21a, the reading device 21 reads the document when the start button is pressed, and image data is generated.

  Based on the generated image data or the input image data, the image stations 60Y, 60M, 60C, and 60BK having the above-described configuration operate. In addition, when the start button is pressed, in parallel with the document reading operation, each device in the image stations 60Y, 60M, 60C, and 60BK, which are each process cartridge, the transfer belt unit 10, the secondary transfer unit 76, and the fixing device. 6 etc. start driving each. For example, the rotation of the photosensitive drums 20Y, 20M, 20C, 20BK, the transfer belt 11, and the fixing belt 64 is started.

  In the image station 60Y, as described above, the surface of the photosensitive drum 20Y is uniformly charged by the charging device 30Y along with the rotation in the B1 direction, and an electrostatic latent image is formed by the optical scanning device 8, The electrostatic latent image is developed with yellow toner by the developing device 80Y, and the yellow toner image is primarily transferred to the transfer belt 11 by the primary transfer roller 12Y to perform a first transfer process, and after the transfer. Unnecessary substances including the remaining toner are removed by the cleaning device 70Y and used for the next charge removal and charging by the charge removal device 90Y and the charging device 30Y. At this time, the lubricant 42Y is applied to the photosensitive drum 20Y with a suitable particle diameter while suppressing or preventing the unevenness of the surface thereof, and the state of the photosensitive drum 20Y is kept good. A toner image is satisfactorily formed.

  In the other photoconductor drums 20M, 20C, and 20BK, the toner images of the respective colors are similarly formed while maintaining the good state, and the formed toner images of the respective colors, that is, single-color images, are transferred to the primary transfer roller 12M. , 12C, and 12BK, primary transfer is sequentially performed sequentially at the same position on the transfer belt 11 that moves in the A1 direction. A four-color superimposed toner image composed of toner images superimposed on the transfer belt 11, that is, a full-color composite color image that is a four-color toner image, is transferred to the secondary transfer belt 5 as the transfer belt 11 rotates in the A1 direction. To the secondary transfer nip, which is a position opposite to the second transfer nip, is secondarily transferred onto the transfer paper, and a second transfer process is performed, and a full-color image is carried on the transfer paper.

  As for the transfer paper conveyed between the transfer belt 11 and the secondary transfer belt 5, one feed roller 24 of the sheet feeding device 23 is selected by pressing the start button, and the corresponding paper feed cassette is rotated by this rotation. 25, fed from the manual feed tray 33 by the rotation of the feed roller 35 of the manual paper feed device 33, or fed from the duplex unit 96. The toner image on the transfer belt 11 is transferred to the secondary transfer belt by the registration roller pair 13 based on the detection signal from the sensor. 5 is sent out at a timing facing 5. Such a feed operation is started substantially simultaneously with the document reading operation described above.

  When the toner images of all colors are transferred and carried on the transfer paper, the transfer paper enters the fixing device 6 and passes through the fixing portion between the fixing belt 61 and the pressure belt 62 as an endless belt-like fixing member. The carried toner image is fixed by the action of heat and pressure, and a good color image is formed on the transfer paper by this fixing process. The fixed transfer paper that has passed through the fixing device 6 is stacked on the paper discharge tray 75 via the paper discharge roller 98 according to the position of the switching claw 94, or when the duplex copying mode is selected. Then, the sheet enters the duplex unit 96 through the transport roller 97 and prepares for duplex image formation. On the other hand, the transfer belt 11 that has finished the secondary transfer is cleaned by removing residual toner and the like remaining on the intermediate transfer belt cleaning device 14 to prepare for the next image formation.

  When such an image formation is performed, the fixing belt 61 is driven to rotate and receives pressure from the pressure belt 62 as a facing member. However, in order to perform good fixing and form a high-quality image, the fixing belt 61 is used. It is important to suppress or prevent deterioration with time of the fixing member such as the pressure belt 62 and the like. Therefore, in the fixing device 6, measures against deterioration with time of the fixing belt 61 and the pressure belt 62 are taken. Details of the fixing device 6 including this point will be described.

  FIG. 3 is a schematic configuration diagram of the fixing device 6. As shown in FIG. 3, the fixing device 6 includes a fixing belt 61, a fixing roller 63, a pressure belt 62, a pressure pad 64 as a pressing member, and an induction heating unit 65 as a heating unit that heats the fixing belt 61. Consists mainly of. The fixing belt 61 is wound so that there is no gap around the fixing roller 63, and a pressure pad 64 provided inside the pressure belt 62 presses the fixing roller 63 through the fixing belt 61 and fixes the fixing belt 63. A nip portion N is formed. The induction heating unit 65 is provided outside the upper portion of the fixing belt 61 and heats the fixing belt 61.

  Although not shown in part, the fixing device 6 supports a driving unit that rotationally drives the fixing roller 63, a pressure unit that pressurizes the pressure pad 64 toward the fixing roller 63, and the pressure pad 64. A temperature sensor 611 serving as a temperature detection means that detects the temperature of the outer peripheral surface of the fixing belt 61 that is disposed at a position facing the fixing roller 63 with the fixing belt 61 interposed therebetween, and a detection signal of the temperature sensor 611 are input. In response to this detection signal, a temperature control device as temperature control means for controlling energization of the induction heating coil 651 so that the temperature of the outer peripheral surface of the fixing belt 61 becomes a predetermined temperature, and a downstream side of the fixing nip portion N, that is, The transfer paper provided on the surface side of the fixing belt 61 and the pressure belt 62 which are disposed on the left side in FIG. And a separation plate 66 for releasing, respectively.

  The pressurizing means of the pressurizing pad 64 pressurizes the pressurizing pad 64 toward the fixing roller 63 by pressurization with a spring and a lever, and a fixing nip is provided between the fixing belt 61 and the pressing belt 62. Part N is formed.

  The fixing roller 63 is provided with an elastic body 632 as an elastic body layer around a metal core 631. The elastic body 632 is made of a material selected from sponges such as rubber sponge, soft rubber, and the like. When the elastic body 632 is made of sponge, it is advantageous in that the temperature rises well due to high heat insulation, a large amount of deformation can be obtained, and a large nip width is secured along the rotation direction of the fixing roller 63. . However, the problem is a decrease in elastic force over time.

  The fixing belt 61 has a support as an endless base material and a surface layer provided on the surface of the support. The support is composed of a layer made of a ferromagnetic material such as nickel that generates heat by induction heating, a magnetic flux shielding layer as an adjusting means made of a material with low permeability such as copper. Further, in order to supplement the strength of the belt, it can be used in combination with a heat resistant resin such as polyimide. The thickness of the support is desirably 100 μm or less from the viewpoint of suppressing the heat capacity, and is 20 to 60 μm in this embodiment. Since the surface layer is in pressure contact with transfer paper and toner, the surface layer is formed of an elastic layer having a thickness of 100 to 300 μm made of a highly releasable silicone rubber and the like, and a highly releasable resin covering the surface of the elastic layer. And an outermost layer having a thickness of 5 to 40 μm. Examples of such resins include silicone resins, fluororesins, specifically, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer ( FEP) is used, and in this embodiment, the elastic layer is formed by coating PFA on the elastic layer. The length of the fixing belt 61 in the rotation direction is about 30 mm in the fixing belt 61 shown in FIG. The length of the pressure belt 62 in the rotation direction is about 25 mm.

  As for the temperature sensor 611, a thermopile is used as a non-contact sensor in FIG. However, a contact type thermocouple, thermistor, or the like may be used if it does not obstruct paper feeding.

  The driving means (not shown) has a gear or the like driven by a driving unit provided on the main body side, drives the fixing roller 63 to rotate, and presses the fixing belt 61 and pressurizes by friction at the fixing nip N. The belt 62 is driven at a constant speed by a driven rotation at a linear speed of 100 to 300 mm / sec.

  The width of the fixing nip portion N, that is, the nip width along the rotation direction of the fixing roller 63 is determined by adjusting the diameter of the fixing roller 63, the width of the contact surface of the pressure pad 64, and the thickness and hardness of the elastic layer 632. Set to a value. The temperature and the surface pressure of the fixing nip N are determined based on the temperature control device and the pressure pad 64 so that image defects such as so-called cocoon skin with minute unevenness as unevenness in image, lack of gloss, and poor graininess occur. It is set on the condition that a predetermined amount of heat and pressure are applied by the pressurizing means.

  The induction heating unit 65 generates magnetic flux and heats the fixing belt 61. The induction heating unit 65 includes an induction heating coil 651, a coil guide 652, and a core unit 655 having a center core 653 and a side core 654. The coil guide 652 is made of a resin material having high heat resistance and holds the induction heating coil 651 and the core portion 655. The core portion 655 is made of a material having high magnetic permeability such as ferrite. The center core 653 is installed at the center of the induction heating coil 651, and the side core 654 is installed at the end of the induction heating coil 651. The induction heating unit 65 configured in this manner functions as a heating unit that heats the fixing belt 61 at a heating position that is a position facing the fixing belt 61.

  A temperature sensor 611 is installed on the outer peripheral surface of the fixing belt 61 at the center in the width direction as temperature detecting means for detecting the temperature in the center in the width direction of the fixing belt 61. A temperature detection / comparison circuit (not shown) controls the induction heating unit (induction heating coil 651) 65 based on the detection result detected by the temperature sensor 611. As a temperature detection element of the temperature sensor 611, a thermistor, a thermopile, or the like can be used. Although not shown, a thermostat is in contact with a part of the outer peripheral surface of the fixing belt 61 (the central portion in the width direction). When the temperature of the fixing belt 61 detected by the thermostat exceeds a predetermined temperature, the energization to the induction heating unit 65 is cut off by the thermostat.

The fixing device 6 configured as described above operates as follows.
The fixing roller 63 rotates in the arrow E1 direction, and the fixing belt 61 and the pressure belt 62 also rotate in the arrow F1 direction. The fixing belt 61 is heated at a position facing the induction heating unit 65 (heating position). Specifically, a high-frequency alternating current is passed through the induction heating coil 651 with a power supply circuit (not shown) so that the lines of magnetic force are alternately switched between the inner core and the core portion 655 in both directions. At this time, the fixing belt 61 itself is directly heated by electromagnetic induction by the induction heating unit 65.

  FIG. 4 is a perspective view of the pressure pad 64. The pressure pad 64 is made of a resin material that has high heat insulation and good sliding properties with the inner peripheral surface of the pressure belt 62. Moreover, as shown in FIG. 4, the part corresponded to a nip exit part becomes a shape which has the escape part A in the one side edge part. In the illustrated example, the escape portion A is formed with a step. From the side corresponding to the nip entrance (upper right side in the figure) to the front of the escape portion A is a flat surface. Further, the three corners 642 of the pressure pad 64 that slides with the inner peripheral surface of the pressure belt 62 are chamfered or rounded. For example, the corner portion 642 of the pressure pad 64 is chamfered with c = 0.5 to 1.0 mm or R-processed with r = 0.5 to 1.0 mm. The durability is prevented from being lowered by keeping the bending radius below.

  FIG. 5 shows the relationship between the pressure in the nip portion of the fixing nip portion N formed by pressing the pressure pad 64 shown in FIG. 4 against the fixing roller 63 via the fixing belt 61 and the pressure belt 62 and the position in the nip width. It is a graph which shows a relationship. The internal pressure of the fixing nip portion N shown in FIG. 5 shows a pressure distribution in a direction perpendicular to the sheet conveyance direction of the recording paper in the range from the inlet of the fixing nip portion N to the outlet of the fixing nip portion N. .

  As shown in FIG. 5, the internal pressure of the fixing nip portion N is slightly different from the entrance of the fixing nip portion N to the point B before the portion corresponding to the escape portion A (the central portion is slightly higher because of the fixing roller). Although it is slightly lower as it goes to the end, it is generally constant. On the other hand, in the portion corresponding to the relief portion A, that is, in the range from the point B to the point C (exit of the fixing nip portion), the internal pressure rapidly decreases after passing the point B, and the point C (fixing nip). After a slight increase at the exit of the section, it becomes zero.

Since the internal pressure is reduced on the exit side of the fixing nip portion N, the contact between the fixing belt 61 and the recording paper is weakened on the exit side of the fixing nip portion N and the separability is improved as compared with the case where the internal pressure is not reduced. To do.
Further, by forming the relief portion A in the pressure pad 64, as shown in FIG. 3, the curvature of the elastic layer 632 of the fixing belt 61 and the fixing roller 63 at the exit (point C) of the fixing nip portion N is escaped. Since it becomes larger than the case where the portion A is not formed, the separation between the fixing belt 61 and the recording paper is further improved.
Furthermore, the discharge angle of the recording paper at the exit of the fixing nip portion N can be made downward from the horizontal direction, and the separability is significantly improved as compared with the case where the discharge angle is horizontal.
In addition, unlike the conventional technique in which the internal pressure (surface pressure) on the outlet side of the fixing nip N is increased to improve the separation, the internal pressure is reduced to improve the separation. The durability of the fixing members such as the fixing belt 61 and the pressure belt 62 does not deteriorate. Therefore, it is possible to maintain good separation of the recording paper without deteriorating the durability of the fixing members such as the fixing roller 63, the fixing belt 61, and the pressure belt 62.

[Embodiment 2]
FIG. 6 is a schematic configuration diagram of a fixing device according to another embodiment.
As shown in FIG. 6, the fixing device 700 according to the embodiment heats the fixing belt 701, the fixing roller 63, the pressure belt 62, the pressure pad 64, and the fixing belt 61. It is mainly comprised from the heater 703 as a heating means to perform.

  As shown in FIG. 6, the fixing device 700 has a fixing belt 701 stretched by a fixing roller 63 and a stretching roller 702, and a pressure pad 64 provided inside the pressure belt 62 passes through the fixing belt 701. The fixing roller 63 is pressed to form a fixing nip portion N. A heater 703, which is a halogen heater as a heating unit for heating the fixing belt 701, is provided inside the fixing belt 701, and further, a first reflection that prevents direct light from the heater 703 from being applied to the stretching roller 702. A plate 704 and a second reflecting plate 705 that prevents direct light from the heater 703 from being applied to the fixing roller 63 are provided.

  The driving unit for the fixing roller 63, the pressing unit for the pressure pad 64, the temperature sensor 611 for detecting the temperature of the outer peripheral surface of the fixing belt 701, and the separation plate 66 are the same as those described with reference to FIG. Omitted.

  In addition, a temperature control device is provided as a temperature control unit that receives a detection signal of the temperature sensor 611 and controls the operation of the heater 703 so that the temperature of the outer peripheral surface of the fixing belt 701 becomes a predetermined temperature in accordance with the detection signal. .

  The elastic layer 632 of the fixing roller 63 has the same configuration as that described with reference to FIG.

  The tension roller 702 includes a metal core 721, an elastic layer 722 provided so as to be wound around the outer periphery of the core 721, and a core 721 so as to protrude from an end surface in the width direction of the core 721. It has a rotating shaft which is provided integrally and is rotatably supported by a bearing (not shown) as a center of rotation of the stretching roller 702. The elastic layer 722 is made of rubber as an elastic body, and ensures friction with the inner surface of the fixing belt 701. Thereby, wear of the fixing belt 701 due to sliding between the stretching roller 702 and the fixing belt 701 is reduced.

  The fixing belt 701 has a support as an endless base material and a surface layer provided on the surface of the support. The support is made of a highly heat-resistant material such as metal that can withstand direct light from the halogen heater 703, but a heat-resistant resin or the like may be used in some cases. Examples of the metal material forming the support include nickel, aluminum, stainless steel, and copper. Examples of the material of the heat resistant resin include polyimide, polyamideimide, polyether ether ketone, and the like. In this embodiment, stainless steel is used. The support may be formed as a multilayer of resin and metal, such as a belt in which nickel is electroformed on polyimide resin. The thickness of the support is desirably 100 μm or less from the viewpoint of suppressing the heat capacity, and is 20 to 60 μm in this embodiment. Since the surface layer is in pressure contact with transfer paper and toner, the surface layer is formed of an elastic layer having a thickness of 100 to 300 μm made of a highly releasable silicone rubber and the like, and a highly releasable resin covering the surface of the elastic layer. And an outermost layer having a thickness of 5 to 40 μm. Examples of such resins include silicone resins, fluororesins, specifically, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer ( FEP) is used, and in this embodiment, the elastic layer is formed by coating PFA on the elastic layer. The length of the fixing belt 701 in the rotation direction is 30 to 40 mm in diameter before being stretched over the fixing roller 63 and the stretching roller 702 shown in FIG.

  The heater 703, the first reflecting plate 704, and the second reflecting plate 705 are provided on the inner side of the fixing belt 701, in other words, on the inner peripheral surface side, and the stretching roller 702 and the fixing roller 63 are directly connected to the inner side of the fixing belt 701. Since heating is not performed, there is little space for heat to escape except for the fixing belt 701, and the temperature raising efficiency of the fixing belt 701 is improved.

  The pressurizing means of the pressurizing pad 64 pressurizes the pressurizing pad 64 toward the fixing roller 63 by pressurization with a spring and a lever, and a fixing nip portion is provided between the fixing belt 701 and the pressing belt 62. N is formed.

  The driving means (not shown) has a gear or the like driven by a driving unit provided on the main body side, drives the fixing roller 63 to rotate, and at the same time, fixes the fixing belt 701 and the tension belt by friction at the fixing nip N. The roller 702 and the pressure belt 62 are driven by a driven rotation at a linear speed of 100 to 300 mm / sec. That is, the fixing belt 701 and the pressure belt 62 are driven at a constant speed by the accompanying rotation.

  The fixing nip width and the internal pressure of the fixing nip N are the same as those of the fixing device 6 of the first embodiment.

  In the fixing device 700 of the present embodiment, the halogen heater 703 used as a heating unit is less expensive than the induction heating unit 65 used in the fixing device 6 of the first embodiment. Thus, it is possible to provide a low-cost fixing device capable of maintaining good separation of recording paper without deteriorating the durability of fixing members such as the fixing roller 63, the fixing belt 701, and the pressure belt 62. Can do.

[Embodiment 3]
FIG. 7 is a schematic configuration diagram of a fixing device according to still another embodiment.
In the fixing device 800 according to the present embodiment, compared to the fixing device 6 of the first embodiment, the heating means is a halogen heater 801, and the halogen heater 801 is disposed inside the cored bar 631 of the fixing roller 63. The difference is that the fixing belt is not provided, and the surface of the fixing roller 63 has a release layer made of, for example, the above-mentioned PFA. Other configurations are the same as those of the fixing device 6 of the first embodiment, and detailed description thereof is omitted. Further, the fixing nip width and the internal pressure of the fixing nip portion N are the same as those of the fixing device 6 of the first embodiment.

  In the fixing device 800 of the present embodiment, the halogen heater 801 used as a heating unit is cheaper than the induction heating unit 65 used in the fixing device 6 of the first embodiment and the fixing belt is not provided. The fixing device is lower in cost than the fixing device 700 of the second embodiment.

As described above, according to the present embodiment, the fixing device 800 includes the fixing roller 63 as a roller-shaped fixing member having the elastic body 632 as an elastic layer, the heater 801 as a heating unit that heats the fixing roller 63, and A pressure belt 62 as an endless belt-like facing member facing the fixing roller 63 and a space surrounded by the inner peripheral surface of the pressure belt 62 are arranged to press the fixing roller 63 via the pressure belt 62. A pressure pad 64 as a pressing member. The elastic body 632 of the fixing roller 63 is elastically deformed by the pressing force of the pressure pad 64 so that the recording medium is interposed between the fixing roller 63 and the pressure belt 62. A fixing nip portion N is formed as a passing nip portion. The pressure pad 64 is formed with an escape portion A for reducing the pressing force to the fixing roller 63 on the exit side of the fixing nip portion N where the fixing roller 63 and the pressure belt 62 are separated from each other. From the pressing surface to the relief portion A, the elastic body 632 of the fixing roller 63 is pressed through the pressure belt 62, and the pressure belt 62 and the elastic body 632 of the fixing roller 63 are moved to the exit side of the fixing nip portion N. The pressure pad 64 is configured to follow the shape of the relief portion A. In the escape portion A, the elastic deformation amount of the elastic body 632 of the fixing roller 63 is smaller than that of the other pressing portions by the pressure pad 64. The pressure acting in the direction perpendicular to the conveyance direction of the medium is smaller than that in other portions of the fixing nip N. As a result, the adhesion between the recording medium and the fixing roller 63 is weakened on the exit side of the fixing nip portion N, and the separation property from the recording medium is improved at the exit of the fixing nip portion N. Further, since the curvature of the elastic body 632 at the exit of the fixing nip portion N becomes larger (the radius of curvature becomes smaller) than when the escape portion A is not provided, the separation between the fixing roller 63 and the recording medium is further improved. . Also, unlike the prior art in which the pressing force (internal pressure) on the outlet side of the fixing nip portion N is increased to improve the separability, the pressing roller is reduced to improve the separability. The durability of the fixing member such as the pressure belt 62 does not deteriorate. Therefore, it is possible to maintain good separation of the recording medium without reducing the durability of the fixing member such as the fixing roller 63 and the pressure belt 62.
Further, according to the present embodiment, the fixing device 6 includes the fixing belt 61 as an endless belt-shaped fixing member, the induction heating unit 65 as a heating unit that heats the fixing belt 61, and the inner peripheral surface of the fixing belt 61. A fixing roller 63 having an elastic body 632 as an elastic layer disposed so as to be in contact with the pressure belt, a pressure belt 62 as an endless belt-like facing member facing the fixing belt 61, and an inner peripheral surface of the pressure belt 62 And a pressure pad 64 as a pressing member that presses the fixing roller 63 via the fixing belt 61 and the pressure belt 62, and the fixing roller is pressed by the pressing force of the pressure pad 64. The elastic body 632 of 63 is elastically deformed to form a fixing nip portion N as a nip portion through which the recording medium passes between the fixing belt 61 and the pressure belt 62. The pressure pad 64 is formed with an escape portion A for reducing the pressing force to the fixing roller 63 on the exit side of the fixing nip portion N where the fixing belt 61 and the pressure belt 62 are separated from each other. From the pressing surface to the relief portion A, the elastic body 632 of the fixing roller 63 is pressed through the fixing belt 61 and the pressure belt 62, and the fixing belt 61, the pressure belt 62, and the elastic body 632 of the fixing roller 63 are connected. On the outlet side of the fixing nip portion N, the shape of the relief portion A of the pressure pad 64 is configured. In the escape portion A, the amount of elastic deformation of the elastic body 632 of the fixing roller 63 is smaller than that of other pressing portions by the pressure pad 64, so that the internal pressure (on the outlet side of the fixing nip portion N corresponding to the escape portion A ( The pressure acting in the direction perpendicular to the conveyance direction of the recording medium is smaller than that of the other fixing nips N. As a result, the adhesion between the recording medium and the fixing belt 61 is weakened on the exit side of the fixing nip portion N, and the separation property from the recording medium is improved at the exit of the fixing nip portion N. Further, since the curvatures of the elastic body 632 and the fixing belt 61 at the exit of the fixing nip N are larger (the radius of curvature is smaller) than when the escape portion A is not provided, the separation property between the fixing belt 61 and the recording medium is increased. Is further improved. Also, unlike the prior art in which the pressing force (internal pressure) on the outlet side of the fixing nip portion N is increased to improve the separability, the pressing roller is reduced to improve the separability. The durability of the fixing member such as the fixing belt 61 does not deteriorate. Therefore, it is possible to maintain good separation of the recording medium without deteriorating the durability of the fixing member of the fixing roller 63 and the fixing belt 61. Further, according to the present embodiment, the surface of the fixing nip N The pressure is substantially constant from the entrance of the fixing nip portion N to the front side of the pressure pad 64 escaping portion A. It was configured so as to be significantly reduced. As a result, the adhesion between the recording medium and the fixing belt 61 is weakened on the exit side of the fixing nip portion N, and the separation property from the recording medium is improved at the exit of the fixing nip portion N.
According to the present embodiment, the pressure pad 64 is a rigid body, and the relief portion A is formed with a step. It is easy to form a step in the pressure pad 64, and the manufacturing cost of the pressure pad 64 can be reduced.
In addition, according to the present embodiment, the corner portion 642 of the relief portion A of the pressure pad 64 that is in sliding contact with the inner peripheral surface of the pressure belt 62 as the opposing member is subjected to arcuate (R processing) or chamfering processing. ing. As a result, when the inner peripheral surface of the pressure belt 62 and the corner portion 642 of the pressure pad 64 are in sliding contact, the pressure belt 62 does not fall below a predetermined bending radius, thereby reducing durability. Can be prevented.

6,700,800 Fixing device 8 Optical scanning device 10 Transfer belt unit 60 Image station 61 Fixing belt 62 Pressure belt 63 Fixing roller 64 Pressure pad 65 Induction heating unit 100 Image forming device 631 Core metal 632 Elastic body 703, 801 Halogen Heater A Escape part N (of pressure pad) Fixing nip

JP 2004-246240 A Japanese Patent Laying-Open No. 2005-092080 JP 2007-156171 A JP 2009-288692 A JP 2008-020907 A

Claims (6)

A roller-shaped fixing member having an elastic layer;
Heating means for heating the fixing member;
An endless belt-like facing member facing the fixing member;
A pressing member that is disposed in a space surrounded by an inner peripheral surface of the opposing member, and that presses the fixing member via the opposing member;
A fixing device that elastically deforms an elastic body layer of the fixing member by a pressing force of the pressing member to form a nip portion through which a recording medium passes between the fixing member and the opposing member;
The pressing member is provided with an escape portion on the exit side of the nip portion where the fixing member and the opposing member are separated from each other, and reduces a pressing force to the fixing member.
The elastic member layer of the fixing member is pressed from the pressing surface of the pressing member to the relief portion via the counter member, and the counter member and the elastic layer of the fixing member are pressed at the outlet side of the nip portion. A fixing device configured to follow the shape of the relief portion of the pressing member. An endless belt-shaped fixing member;
Heating means for heating the fixing member;
A roller having an elastic layer disposed so as to be in contact with the inner peripheral surface of the fixing member;
An endless belt-like facing member facing the fixing member;
A pressing member disposed in a space surrounded by an inner peripheral surface of the facing member, and pressing the roller via the fixing member and the facing member;
A fixing device that elastically deforms an elastic layer of the roller by a pressing force of the pressing member to form a nip portion through which a recording medium passes between the fixing member and the opposing member;
The pressing member is formed with a relief portion for reducing the pressing force to the roller on the exit side of the nip portion where the fixing member and the facing member are separated from each other.
The elastic member layer of the roller is pressed from the pressing surface of the pressing member to the relief portion via the fixing member and the opposing member, and the fixing member, the opposing member, and the elastic body layer of the roller are A fixing device configured to follow the shape of the relief portion of the pressing member on the outlet side of the nip portion. The fixing device according to claim 1 or 2,
The surface pressure of the nip is
Is substantially constant from the entrance of the nip portion to the front of the relief portion of the pressing member;
A fixing device characterized in that the distance from the escape portion to the exit of the nip portion is lower than that from the entrance of the nip portion to the front of the relief portion. The fixing device according to any one of claims 1 to 3,
The fixing device according to claim 1, wherein the pressing member is a rigid body, and the escape portion is formed with a step. The fixing device according to any one of claims 1 to 4,
The fixing device according to claim 1, wherein a corner portion of the relief portion of the pressing member that is in sliding contact with the inner peripheral surface of the opposing member is arced or chamfered. An image forming unit that forms an image on a recording medium;
A fixing device for fixing an image on the recording medium formed by the image forming unit,
An image forming apparatus using the fixing device according to claim 1 as the fixing device.

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