JP2006349886A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device being a belt nip fixing device, whose constitution is simple and which can control the tension and the training amount of a belt in accordance with the kind of paper and can be miniaturized, and to provide an image forming apparatus in which the fixing device is mounted. <P>SOLUTION: The fixing device is equipped with: a heating roller; a pressure roller pressed against the heating roller; a belt stretching and laying member arranged on an upstream side in a paper conveying direction with respect to the pressure roller; and the belt wound round the outer circumferences of the pressure roller and the belt stretching and laying member and moving while forming a fixing nip between the heating roller and the belt. Then, the belt stretching and laying member is made turnable, and a pressing member is arranged to abut on the outside of the belt between the pressure roller and the belt stretching and laying member, so that the belt is pressed by the pressing member to turn the belt stretching and laying member, thereby controlling the tension and the training amount of the belt. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a heating roller, a pressure roller that presses against the heating roller, a belt that is attached to the outer periphery of the pressure roller and moves while being sandwiched between the heating roller, and the belt is stretched. The present invention relates to a fixing device that includes a belt stretching member and fixes an unfixed toner image formed on a transfer material, and an image forming apparatus equipped with the fixing device.

  2. Description of the Related Art Conventionally, in image forming apparatuses such as facsimiles, a so-called heating roller type fixing device that heats and fixes an unfixed toner image on a recording paper, in particular, a belt nip type fixing device including a heating roller and a belt pressure contact device has been developed. .

A conventional belt nip type fixing device will be described with reference to FIG. In the heating roller 100, an aluminum hollow roll 103 is coated with HTV silicon rubber as a base layer 102, and a silicon RTV rubber is dip coated as a top coat layer 103 to have a surface close to a mirror surface. A halogen lamp 105 as a heating source is provided inside the heating roller 100. An endless belt 106 made of polyimide resin is stretched at a predetermined tension by three stainless pressure rollers 107, a support roller 108, and a support roller 109. The pressure roller 108 is urged toward the center of the heating roller 100 by a compression coil spring 110 as pressure means, and the endless belt 106 is pressure-bonded to the heating roller 100. The pressure roller 106 is rotationally driven by a motor 111, and the endless belt 106 and the support rollers 108 and 109 are driven to rotate. A pressure auxiliary roller 112 is disposed inside the endless belt 106 between the pressure roller 107 and the support roller 108, and a pressure is applied to the endless belt 106 by the pressure auxiliary roller 112 to control the tension of the endless belt.
Japanese Patent No. 3084690

  In the fixing device disclosed in Patent Document 1, since the pressure assist roller for controlling the tension of the endless belt is disposed inside the endless belt, it is necessary to widen the space inside the endless belt. Further, since the pressure roller and the support roller are fixed in position, the amount of the endless belt wound around the heating roller cannot be changed.

  In order to secure a space for disposing the pressure auxiliary roller, the number of support rollers for stretching the endless belt has to be increased, and as a result, there has been a problem that the peripheral length of the endless belt becomes long. The increase in the number of support rollers and the increase in the circumference of the endless belt lead to an increase in the size of the device. In addition, the increase in the circumference of the endless belt causes the endless belt heated at the nip with the heating roller to move along a predetermined path. In this case, since the circumference is long, the temperature is lowered due to natural heat dissipation, and there is a problem that the warming time from when the power is turned on until reaching a desired temperature and fixing can be increased. Further, it has been found that the amount of the belt wound around the heating roller other than the belt tension is a major factor for the fixing property according to the change of the paper type.

  The present invention solves the above-described conventional problems. In the belt nip fixing device, the configuration is simple, the belt tension and the amount of winding can be controlled according to the paper type, and the size can be reduced. It is an object of the present invention to provide a fixing device and an image forming apparatus equipped with the fixing device.

  For this purpose, the fixing device according to the first aspect of the present invention includes a heating roller, a pressure roller pressed against the heating roller, a belt stretching member disposed on the upstream side in the paper conveyance direction with respect to the pressure roller, A belt that is attached to the outer periphery of the pressure roller and the belt stretching member and that moves with a fixing nip formed between the pressure roller and the heating roll, the belt stretching member being rotatable, the pressure roller and the belt A pressing member is disposed in contact with the outside of the belt between the stretching members, the belt is pressed by the pressing member, the belt stretching member is rotated, and the belt tension and the amount of winding are controlled.

  According to a second aspect of the present invention, in the fixing device according to the first aspect of the invention, the pressing member is brought into contact with the belt stretching member via a belt.

  The third invention is characterized in that, in the fixing device of the first or second invention, the pressing amount of the pressing member is changed according to the paper type.

  According to a fourth aspect of the present invention, in the fixing device according to any one of the first to third aspects of the present invention, the pressure roller, the belt stretching member, and the frame are fixedly disposed.

  According to a fifth aspect of the present invention, in the fixing device according to any one of the first to fourth aspects of the present invention, an anti-bending material is disposed between the pressure roller and the belt stretching member.

  According to a sixth aspect of the present invention, in the image forming apparatus, the fixing device according to any one of the first to fifth aspects is mounted.

The heating roller of the present invention, a pressure roller pressed against the heating roller, a belt stretching member disposed on the upstream side in the paper conveying direction with respect to the pressure roller, the pressure roller and the belt stretching member And a belt that moves with a fixing nip formed between the belt and the heating roll, the belt stretching member being rotatable, and an outer side of the belt between the pressure roller and the belt stretching member. Since the pressing member can be disposed outside the belt by a configuration in which the pressing member is disposed in contact with the belt, the belt is pressed by the pressing member, the belt stretching member is rotated, and the tension and winding amount of the belt are controlled. Miniaturization can be realized, and the winding amount and tension can be controlled simultaneously, so that appropriate fixing according to the paper type can be achieved.
With the configuration in which the pressing member is in contact with the belt stretching member via the belt, the belt tension and the amount of winding can be easily controlled.
With the configuration in which the pressing amount of the pressing member is changed according to the paper type, appropriate fixing according to the paper type is possible.
With the configuration in which the pressure roller, the belt stretching member and the frame are fixedly disposed, the rotation control around the central axis of the pressure roller of the belt stretching member becomes easy.
The configuration in which the bending prevention material is disposed between the pressure roller and the belt stretching member can reduce the axial deflection of the belt stretching member without using a large-diameter metal roller as the belt stretching member. The belt tension member can be made of a resin having low rigidity, so that the warm-up time can be shortened and the responsiveness of the temperature control can be improved, the apparatus can be miniaturized, and a high-quality image can be obtained. be able to. Furthermore, since the radial load between the pressure roller and the belt stretching member is offset, the configuration of the side frame and the like can be simplified.
By using the image forming apparatus equipped with the fixing device of the present invention, it is possible to reduce the size of the apparatus and obtain an image with high image quality.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a schematic cross-sectional view showing an embodiment of the fixing device of the present invention.
In FIG. 2, the fixing device includes a heating roller 1, a pressure roller 2 pressed against the heating roller 1, and a belt stretching member arranged on the upstream side in the transfer material conveyance direction with respect to the pressure roller. A belt stretching roller 3 and a belt 4 that is attached to the outer periphery of the pressure roller 2 and the belt stretching roller 3 and moves with a fixing nip formed between the heating roller 1 and the belt 4 are provided. The heating roller 1 is covered with an elastic layer 1b on the outer periphery of a cored bar 1a and has a heating source 1c inside, and rotates in the direction A in the figure. The surface layer of the heating roller 1 is in contact with the pressure roller 2 and the belt 4 supported by the belt stretching roller 3. The pressure roll 2 is coated with an elastic layer 2b on the outer periphery of the core metal 2a and rotates in the direction B shown in the figure. A transfer material such as paper enters from the C direction and is discharged in the D direction. A tension force is applied to the belt stretching roller 3 in the direction of arrow G with respect to the pressure roller 2, and tension is applied to the belt 4 so that the pressure roller 2 rotates in the B direction. A pressing force is applied to the roller 1.

  The belt stretching member 3 is rotatable about the rotation center axis of the pressure roller 2. A pressing roller 6 is disposed at a position outside the belt 4 between the pressure roller 2 and the belt stretching member 3.

  The tension of the belt 4 affects the pressing force of the belt 4 at the portion where the belt 4 is wound around the heating roller 1. When the pressing force of the belt 4 is strong, the fixing force of the toner to the paper increases. However, if the pressing force of the belt 4 is strong, the stress on the paper and the belt 4 is increased, which tends to cause wrinkles and increase in paper curl. In particular, it greatly affects wrinkles and curls on thin paper.

    As the amount of the belt 4 wound around the heating roller 1 increases, the fixing property increases. However, the curled wrinkles on the paper due to the curvature, or the label paper on which two sheets of paper are bonded together In an envelope, wrinkles are likely to occur due to the speed difference between the upper and lower surfaces.

  3 (a) and 3 (b), when the pressing roller 6 is arranged at a position near the belt stretching member 3 and outside the belt 4, and the belt 4 is pressed by the pressing roller 6, the belt 4 is first deformed. Belt tension increases. Next, the pressing roller 6 comes into contact with the belt stretching member 3 via the belt 4, presses the belt stretching member 3, and the belt stretching member 3 is moved from the dotted line position to the solid line with the rotation center axis of the pressure roller 2 as an axis. The belt 4 is rotated to the position, and the amount of the belt 4 wound around the heating roller 1 is increased.

  In the present invention, the pressing amount of the pressing roller 6 against the belt 4 is changed according to the paper type, and the belt tension and the belt winding amount are controlled. The pressing roller 6 is variable in two stages, a retracted position and a pressing position, and in the case of thin paper or envelope, the pressing roller 6 is positioned in the retracted position to reduce belt tension and winding amount. The belt 4 is pushed by 6 and the belt tension and the amount of winding are increased to improve the fixing property.

  4A and 4B show an embodiment in which the pressing roller 6 is arranged to face the belt stretching member 3 with the belt 4 interposed therebetween. In this embodiment, the belt tension does not change much due to the pressing of the pressing roller 6 against the belt 4, but it is effective when the amount of rotation of the belt stretching member 3 increases and the amount of winding changes greatly.

  By supporting the pressure roller 1, the belt stretching member 3, and the support frame, the rotation control of the belt stretching member 3 is facilitated by the pressing force of the pressing roller 6 to the belt 4.

  FIG. 5 is a diagram showing another embodiment of the present invention. The difference between this embodiment and the embodiment shown in FIG. 2 is that a deflection preventing member 5 is disposed between the pressure roller 2 and the belt stretching member 3. When the belt 4 is attached to the pressure roller 2 and the belt stretching member 3 with a predetermined tension, the belt stretching member 3 may be bent by the tension. For this reason, as the belt stretching member 3, a metal roller having a diameter with little bending in the axial direction is generally used, and tension is applied at both ends of the metal roller. However, when a metal roller having such a diameter is employed, there is a problem in that the heat capacity increases, the warm-up time increases, and the responsiveness of temperature control deteriorates. In addition, there is a problem that it is difficult to save energy because the apparatus becomes larger and the amount of heat radiation increases. If the belt tension roller has a narrow diameter or is made of resin, the belt tension member bends due to the belt tension, and when paper enters from the belt tension member side, image misalignment occurs at the center in the width direction. Has the problem of occurring.

  When the bending prevention member 5 is disposed between the pressure roller 2 and the belt stretching member 3 in the central portion in the axial direction of the belt stretching member 3, the belt stretching member 3 is prevented from being bent due to belt tension, and the belt Since the frame member 3 can be made of a resin having a small diameter and the size of the apparatus is reduced, the central portion thereof is bent. Therefore, the bending prevention member 5 is disposed at the center, and the pressure roller 2 and the belt stretcher are arranged. The warm-up time can be shortened by placing the member in contact with the member.

  FIG. 6 is a schematic cross-sectional view of the overall configuration showing an embodiment of the image forming apparatus according to the present invention. In the figure, 10 is an image forming apparatus, 10a is a housing, 10b is a door, 11 is a paper transport unit, 15 is a cleaning means, 17 is an image carrier, 18 is an image transfer transport means, 20 is a developing means, and 21 is a scanner. Means, 30 is a paper feeding unit, 40 is fixing means, W is an exposure unit, and D is an image forming unit. The fixing unit 40 includes the heating roller 1, the pressure roller 2, and the belt stretching member 3 which are the above-described fixing device of the present invention.

  The image forming apparatus 10 of the present embodiment includes a housing 10a, a paper discharge tray 10c formed on the top of the housing 10a, and a door body 10b that is attached to the front surface of the housing 10a so as to be openable and closable. 1 includes an exposure unit (exposure means) W, an image forming unit D, a transfer belt unit 29 having an image transfer and conveyance means 18, and a paper feed unit 30, and a paper conveyance unit 11 is arranged in the door body 10b. ing. Each unit has a configuration that can be attached to and detached from the main body, and can be removed and repaired or replaced integrally during maintenance or the like.

  The image forming unit D includes image forming stations Y (for yellow), M (for magenta), C (for cyan), and K (for black) that form a plurality (four in this embodiment) of different color images. I have. In each of the image forming stations Y, M, C, and K, an image carrier 17 that is a photosensitive drum, a charging unit 19 that is a corona charging unit and a developing unit that are disposed around the image carrier 17 are provided. Means 20 are included. These image forming stations Y, M, C, and K are arranged in parallel on the lower side of the transfer belt unit 29 so that the image carrier 17 faces upward along an oblique arched line. The order of arrangement of the image forming stations Y, M, C, and K is arbitrary.

  The transfer belt unit 29 is disposed below the housing 10a and is driven to rotate by a drive source (not shown), a driven roll 13 disposed obliquely above the drive roll 12, a tension roll 14, An image transfer conveying means 18 composed of an intermediate transfer belt that is stretched between these three and at least two rolls and driven to circulate in the direction of the arrow in the figure, and a cleaning means 15 that contacts the surface of the image transfer conveying means 18. I have. The driven roll 13, the tension roll 14, and the image transfer / conveying means 18 are arranged in a direction inclined to the left in the drawing with respect to the drive roll 12, and thereby the belt conveying direction when driving the image transfer / conveying means 18 is downward. The belt surface 18a is positioned below, and the belt surface 18b whose transport direction is upward is positioned above.

  Accordingly, the image forming stations Y, M, C, and K are also arranged in a direction inclined to the left in the drawing with respect to the drive roll 12. Then, the image carrier 17 is brought into contact with the belt surface 18a facing downward in the transport direction of the image transfer transport unit 18 along the arched line, and is rotationally driven in the transport direction of the image transfer transport unit 18 as indicated by the arrows in the drawing. The The flexible endless sleeve-shaped image transfer / conveyance means 18 is brought into contact with the image carrier 17 from substantially the same wrapping angle so as to be covered from above, so that the image carrier 17 and the image transfer / conveyance means 18 are in contact with each other. The contact pressure and the nip width between them can be adjusted by controlling the tension applied to the image transfer / conveying means 18 by the tension roll 14, the arrangement interval of the image carrier 17, the winding angle (arch curvature), and the like. .

The drive roll 12 also serves as a backup roll for the secondary transfer roll 39. A rubber layer having a thickness of, for example, about 3 mm and a volume resistivity of 10 ⁵ Ω · cm or less is formed on the peripheral surface of the drive roll 12, and the secondary transfer roll is grounded through a metal shaft. This is a conductive path for the secondary transfer bias supplied via the line 39. Thus, by providing the drive roll 12 with a rubber layer having high friction and shock absorption, it is difficult for the impact when the transfer material enters the secondary transfer portion to be transmitted to the image transfer conveying means 18, and the image quality is deteriorated. Can be prevented. Further, by making the diameter of the drive roll 12 smaller than the diameters of the driven roll 13 and the backup roll 14, the transfer material after the secondary transfer can be easily peeled off by the elastic force of the transfer material itself. Further, the driven roll 13 is also used as a backup roll for the cleaning means 15 described later.

  The image transfer / conveying means 18 is arranged in a direction inclined to the right in the drawing with respect to the drive roll 12, and correspondingly, each of the image forming stations Y, M, C, K is also illustrated with respect to the drive roll 12. Then, it may be arranged along the oblique arch shape in the direction inclined to the right side, that is, on the left and right objects in FIG.

  Suitable materials for the image transfer / conveyance means include PC resin, PET resin, polyimide resin, urethane resin, silicon resin, polyether resin, polyester resin, etc. Of course, conductivity, rigidity, etc. For the purpose of setting the degree, friction coefficient and the like to desired characteristics, a corresponding additive or the like may be added, and the rigidity can be set to a desired rigidity by setting the thickness.

  In this embodiment, the image transfer / conveying means is formed of urethane resin and polyether resin which are relatively small in rigidity and have permanent distortion and no creep, and the tension is 40 N by the urging force of the roll, and the winding angle of the image carrier is 4 °. The contact pressure acting on the nip portion was set to about 2.8 N (= 40 N × sin 4 °), and stable transfer conditions were set. However, in consideration of the above-mentioned materials, the desired transfer conditions can be set by setting a combination of a tension of 10N to 100N and a winding angle of the image carrier of 0.5 ° to 15 ° by the urging force of the roll. It was confirmed that it was possible.

  The primary transfer member 16 is disposed at a position in contact with the inner side of the image transfer conveying means as a transfer bias applying means for forming an image by sequentially superimposing and transferring the toner images, but applying the contact pressure as described above. Therefore, it is not necessary to apply a pressing force for forming the transfer nip. Simply contact with the image transfer / conveying means as a means capable of ensuring energization, for example, a conductive roll or rigid contactor rotating in contact with the image transfer / conveying means, or a conductive elastic member such as a leaf spring, resin A conductive brush formed by a group of fibers such as can also be configured. Accordingly, the sliding resistance with the image transfer / conveying means is small, and not only can the lifetime of each other be improved, but also it can be constructed at low cost.

  As described above, in the image forming apparatus according to the present embodiment, a plurality of image carriers 17 are arranged in parallel, and the endless sleeve-like shape is flexible with a posture having substantially the same winding angle with respect to each image carrier 17. The image transfer / conveying means 18 is placed in contact and stretched around at least two rolls 12 and 13 and rotated. The image transfer / conveying means 18 is applied with tension by any of the rolls 12 and 13 to carry an image. The toner image on the body 17 is configured to be transferred in a superimposed manner. In this way, substantially the same nip is easily formed at the contact portion between the image carrier 17 and the image transfer conveying means 18 according to substantially the same winding angle, and the contact pressure at the contact portion is also substantially the same. Composed.

  On the other hand, in the image transfer member 17 and the image transfer / conveying means 18 driven in contact therewith, it is preferable that the moving peripheral speeds of the contact portions coincide with each other. It is not realistic to set the speed completely at a constant speed due to variations in the outer diameter of 17 or eccentricity or the eccentricity of the driving means, the diameter of the driving roll 12 of the image transfer / conveying means 18, or variations in the driving means.

  Therefore, when these variations are taken into consideration, the moving speed of the image transfer / conveying means 18 becomes relatively fast or slow with respect to the moving speed of the image carrier 17, and the transfer conditions are set. This is not preferable. Rather, it is preferable to provide a relative speed difference that is shifted to one of the image carrier 17 and the relative speed. However, if an extreme speed difference is provided, the toner image transported by the image carrier 17 is transferred to the image transfer transport means 18, and the position of the toner image is shifted to cause image disturbance. It is preferable to provide a speed difference.

  When the speed difference caused by the above contents is set to a relative speed difference shifted to one of the plurality of image carriers 17, the speed difference is calculated in consideration of the ability from mass production and the limit of image disturbance. The speed of the image transfer / conveying means 18 with respect to the moving speed of the image carrier 17 is preferably about ± (direction) 3 ± (variation) 2%.

  Further, when the moving speed of the image carrier 17 and the moving speed of the image transfer / conveying means 18 are constant, the toner image is transferred by the electric energy action of the transfer bias, but when the above speed difference is provided. Since the mechanical scraping action is added in addition to the electric energy action to improve the transfer efficiency, the process of cleaning the transfer residual toner on the image carrier 17 can be eliminated or simplified.

  Further, if a relative speed difference is provided between the moving speed of the image carrier 17 and the moving speed of the image transfer / conveyance means 18, the flexible image transfer / conveyance means 18 is placed between the drive rollers 12 or to the image carrier 17. It is not preferable because slack occurs between the contact nips. Therefore, when the speed of the image transfer / conveyance means 18 is shifted in the fast direction with respect to the image carrier 17, the drive roll 12 of the image transfer / conveyance means 18 is disposed on the downstream side, and the image carrier 17 has an image. When shifting the speed of the transfer / conveyance means 18 in the slow direction, if the drive roll 12 of the image transfer / conveyance means 18 is arranged on the upstream side, the occurrence of the slack can be prevented, and a preferable transfer condition can be set.

  The cleaning unit 15 is provided on the side of the belt surface 18a facing downward in the transport direction, and a cleaning blade 15a that removes toner remaining on the surface of the image transfer transport unit 18 after the secondary transfer, and a toner transport that transports the collected toner A member 15b is provided. The cleaning blade 15 a is in contact with the image transfer / conveyance means 18 at a portion where the image transfer / conveyance means 18 is wound around the driven roll 13. Further, a primary transfer member 16 is brought into contact with the back surface of the image transfer conveying unit 18 so as to face an image carrier 17 of each of the image forming stations Y, M, C, and K described later. A transfer bias is applied.

  The exposure means W is disposed in a space formed obliquely below the image forming unit D disposed in the oblique direction. A paper feeding unit 30 is disposed below the exposure unit W and at the bottom of the housing 10a. The exposure means W is entirely housed in a case, and the case is disposed in a space formed obliquely below the belt surface facing downward in the transport direction. A single scanner means 21 comprising a polygon mirror motor 21a and a polygon mirror (rotating polygon mirror) 21b is horizontally disposed at the bottom of the case, and a plurality of laser light sources 23 modulated by image signals of respective colors. In the optical system B that reflects and scans the laser beam by the polygon mirror 21b and deflects and scans the image carrier, the single f-θ lens 22 and the scanning light path of each color are not parallel to the image carrier 17 respectively. A plurality of reflecting mirrors 24 are arranged so as to be folded.

  In the exposure means W configured as described above, an image signal corresponding to each color is emitted from the polygon mirror 21b with a laser beam modulated and formed based on a common data clock frequency, and the f-θ lens 22 and the reflection mirror 24 are passed through. After that, the image carrier 17 of each image forming station Y, M, C, K is irradiated to form a latent image. By providing the reflecting mirror 24, the scanning optical path can be bent, the height of the case can be lowered, and the optical system can be made compact. In addition, the reflection mirror 24 is arranged so that the scanning optical path lengths to the image carrier 17 of the image forming stations Y, M, C, and K are the same. In this way, the length of the optical path from the polygon mirror 21b of the exposure means W to the image carrier 17 to the image carrier 17 (optical path length) for each image forming unit D is configured to be substantially the same, thereby scanning in each optical path. The scanning widths of the emitted light beams are also substantially the same, and no special configuration is required for image signal formation. Therefore, the laser light source can be modulated and formed based on a common data clock frequency even though it is modulated corresponding to images of different colors by different image signals, and uses a common reflecting surface. Color misregistration caused by a relative difference in the sub-scanning direction can be prevented, and a simple and inexpensive color image forming apparatus can be configured.

  Further, in this embodiment, by arranging the scanning optical system below the apparatus, the vibration of the scanning optical system due to the vibration that the drive system of the image forming means gives to the frame that supports the apparatus can be minimized. Degradation of image quality can be prevented. In particular, by arranging the scanner means 21 at the bottom of the case, the vibration that the polygon motor 21a itself gives to the entire case can be minimized, and deterioration of the image quality can be prevented. Further, by making the number of polygon motors 21a, which are vibration sources, one, vibration applied to the entire case can be minimized.

  The paper feed unit 30 includes a paper feed cassette 35 in which transfer materials are stacked and held, and a pickup roll 36 that feeds the transfer materials from the paper feed cassette 35 one by one. The paper transport unit 11 includes a pair of gate rolls 37 (one roll is provided on the housing 10a side) that defines the timing of feeding the transfer material to the secondary transfer unit, the drive roll 12 and the image transfer transport means 18. A secondary transfer roll 39 serving as a secondary transfer unit pressed against the main recording medium, a main recording medium conveyance path 38, a fixing unit 40, a discharge roll pair 41, and a duplex printing conveyance path 42.

  The secondary image (unfixed toner image) secondarily transferred to the transfer material is fixed at a predetermined temperature at the nip portion formed by the fixing unit 40. In the present embodiment, the fixing unit 40 is disposed in a space formed obliquely above the belt surface 18b facing upward in the transfer belt conveyance direction, in other words, in a space opposite to the image forming station with respect to the transfer belt. Therefore, heat transfer to the exposure unit W, the image transfer conveyance unit 18, and the image formation unit can be reduced, and the frequency of performing the color misregistration correction operation for each color can be reduced. In particular, the exposure means W is located farthest from the fixing means 40, and the displacement of the scanning optical system components due to heat can be minimized, thereby preventing color misregistration.

  In the present embodiment, the image transfer / conveyance means 18 is arranged in a direction inclined with respect to the drive roll 12, so that a wide space is created in the right side space in the drawing, and the fixing means 40 can be arranged in that space. In addition, downsizing can be realized, and heat generated by the fixing unit 40 is transmitted to the exposure unit W, the image transfer conveyance unit 18 and the image forming stations Y, M, C, and K located on the left side. Can be prevented. Further, since the exposure unit W can be arranged in the space on the lower left side of the image forming unit D, the vibration of the scanning optical system of the exposure unit W due to the vibration applied to the housing 10a by the drive system of the image forming means is minimized. The image quality can be suppressed and deterioration of the image quality can be prevented.

  In this embodiment, the use of the spherical toner increases the primary transfer efficiency (approximately 100%), and each image carrier 17 is provided with a cleaning means for collecting the primary transfer residual toner. Not done. Thereby, it becomes possible to arrange each image carrier 17 composed of a photosensitive drum having a diameter of 30 mm or less close to each other, and the apparatus can be miniaturized.

  Further, the corona charging means 19 is adopted as the charging means in accordance with the absence of the cleaning means. When the charging unit is a roll, a small amount of primary transfer residual toner that is present on the image carrier 17 accumulates on the roll to cause a charging failure, but the corona charging unit 19 that is a non-contact charging unit. Can prevent toner from adhering and can prevent charging failure.

  In the above-described embodiment, the intermediate transfer belt is configured to contact the image carrier 17 as the image transfer conveyance unit 18. However, the transfer material is adsorbed on the surface to be conveyed and moved, and a toner image is formed on the surface of the transfer material. A transfer material conveyance belt that forms and conveys an image by sequentially superimposing and transferring the image may be configured to contact the image carrier 17 as the image transfer conveyance means 18. In this case, the difference from the above embodiments is that the belt conveyance direction of the transfer material conveyance belt which is the image transfer conveyance means 18 is upward in the opposite direction on the lower surface in contact with the image carrier 17.

The outline of the operation of the entire image forming apparatus as described above is as follows.
(1) When a print command signal (image forming signal) from a host computer or the like (not shown) is input to the control unit of the image forming apparatus 10, the image of each image forming station Y, M, C, K is displayed. The carrier 17, each roll of the developing unit 20, and the image transfer / conveying unit 18 are driven to rotate.
(2) The outer peripheral surface of the image carrier 17 is uniformly charged by the charging means 19.
(3) The exposure unit W selectively exposes the outer peripheral surface of the image carrier 17 that is uniformly charged in each image forming station Y, M, C, K according to the image information of each color. An electrostatic latent image is formed.
(4) The toner image is developed by the developing means 20 from the electrostatic latent image formed on each image carrier 17.
(5) The primary transfer member 16 of the image transfer conveying means 18 is applied with a primary transfer voltage having a polarity opposite to the charged polarity of the toner, so that the toner image formed on the image carrier 17 is transferred to the primary transfer portion. As the conveying means 18 moves, the images are sequentially transferred onto the image transfer conveying means 18.
(6) In synchronization with the movement of the image transfer conveying means 18 that has primarily transferred the primary image, the transfer material stored in the paper feed cassette 35 is fed to the secondary transfer roll 39 via the resist roll pair 37. Is done.
(7) The primary transfer image is a secondary transfer roll 39 that is joined to the transfer material at the secondary transfer portion in synchronization and pressed toward the drive roll 12 of the image transfer conveying means 18 by a pressing mechanism (not shown). A bias having a polarity opposite to that of the next transfer image is applied, and the primary transfer image formed on the image transfer conveying means 18 is secondarily transferred to the synchronously fed transfer material.
(8) The transfer residual toner in the secondary transfer is conveyed in the direction of the driven roll 13 and scraped off by the cleaning means 15 disposed opposite to the roll 13, and the image transfer conveyance means 18 is It is refreshed and the cycle can be repeated again.
(9) When the transfer material passes through the fixing unit 40, the toner image on the transfer material is fixed, and then the transfer material is directed to a predetermined position (if the double-sided printing is not performed, the double-sided printing is performed toward the discharge tray 10c. In this case, the paper is conveyed toward the conveyance path 42 for double-sided printing.

  Although the embodiment of the present invention has been described above, the present invention is not limited to this, and a conventionally known or well-known technique can be replaced or added as necessary.

1 is a cross-sectional view of a fixing device to which the present invention is applied. It is a figure for demonstrating one Embodiment of this invention. It is a figure for demonstrating one Embodiment of this invention. It is a figure for demonstrating one Embodiment of this invention. It is a figure for demonstrating one Embodiment of this invention. It is a figure for demonstrating one Embodiment of this invention.

Explanation of symbols

  1: heating roller, 2: pressure roller, 3: belt stretching member, 4: belt, 5: deflection preventing member, 6: pressing roller, 10: image forming apparatus, 11: paper transport unit, 15: cleaning means, 17: Image carrier, 18: Image transfer / conveying means, 20: Developing means, 21: Scanner means, 30: Paper feeding unit, 40: Fixing means, W: Exposure unit, D: Image forming unit

Claims (6)

A heating roller, a pressure roller pressed against the heating roller, a belt stretching member disposed upstream of the pressure roller in the paper conveying direction, and an outer periphery of the pressure roller and the belt stretching member. And a belt that moves with a fixing nip formed between the belt and the heating roll. The belt stretching member is rotatable, and a pressing member is disposed outside the belt between the pressure roller and the belt stretching member. , And a belt is pressed by a pressing member to control the belt tension and the amount of winding. The fixing device according to claim 1, wherein the pressing member is brought into contact with the belt stretching member via a belt. The fixing device according to claim 1, wherein the pressing amount of the pressing member is changed according to a paper type. The fixing device according to claim 1, wherein the fixing device is fixedly disposed on the pressure roller, a belt stretching member, and a frame. The fixing device according to claim 1, wherein an anti-bending material is disposed between the pressure roller and the belt stretching member. An image forming apparatus comprising the fixing device according to claim 1.

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