JP2009075513A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of precisely positioning a discharging needle 64 near the exit of a secondary transfer nip formed by the abutment of an intermediate transfer belt 8 and a relatively large transfer counter roller 19 on each other. <P>SOLUTION: The image forming apparatus secondarily transfers a toner image on the belt to recording paper sandwiched between the intermediate transfer belt 8 and the transfer counter roller 19 forming the nip by abutting on each other, and then removes electricity from the recording paper while keeping the discharging needle 64 opposite to the recording paper passed through the secondary transfer nip. In this image forming apparatus, the discharging needle 64 is held by the shaft member 19a of the transfer counter roller 19 via a discharging holder 63. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  In the present invention, a neutralizing member is made to face a recording member to which a visible image on an image carrier is transferred in a transfer nip formed by contact between the image carrier and a nip forming member after passing through the nip. The present invention relates to an image forming apparatus that performs a charge removal process.

  As this type of image forming apparatus, the one described in Patent Document 1 is known. In this image forming apparatus, an electrostatic latent image is formed on a photosensitive member by exposure scanning on a drum-shaped photosensitive member as a latent image carrier, and then the electrostatic latent image is developed by a developing device to obtain a toner image. The toner image on the photoconductor is transferred to the recording paper while the recording paper as the recording member is sandwiched in the transfer nip formed by the contact between the photoconductor and the transfer roller as the nip forming member. A neutralizing needle is fixed to the inner wall of the casing for the transfer roller that exposes a part of the peripheral surface of the transfer roller from its own opening toward the photoreceptor while containing the transfer roller. The recording paper discharged from the transfer nip is subjected to a static elimination process when passing through a position facing the above-described static elimination needle that is grounded or biased. In such a configuration, by removing the charge of the recording paper charged in the transfer nip, the electric field formed on the paper surface due to the charge of the recording paper is extinguished or the strength of the electric field is sufficiently reduced. As a result, it is possible to suppress the occurrence of image disturbance due to scattering of toner particles in the toner image along the electric field on the paper surface.

  In such an image forming apparatus, the earlier the discharge is performed on the recording paper after passing through the transfer nip, the more the image distortion can be suppressed. Therefore, the discharge needle is placed as close as possible to the exit of the transfer nip. It is desirable to arrange with high accuracy.

JP 2002-229348 A

  However, in the image forming apparatus described in Patent Document 1, when a relatively large transfer roller is used, it is necessary to use a large casing corresponding to the roller diameter. In this case, the distance between the exit of the transfer nip and the static elimination needle fixed to the casing is increased simply by leaving the static elimination needle attached to the casing and simply making the casing larger. As a result, it becomes difficult to dispose the charge eliminating needle close to the exit of the transfer nip.

  In the image forming apparatus described in Patent Document 1, an error occurs in the relative position between the transfer roller in the casing and the static elimination needle fixed to the inner wall of the casing due to an assembly error of the transfer roller with respect to the casing. As a result, an error also occurs in the relative position between the transfer nip and the charge eliminating needle, and it is difficult to accurately position the charge eliminating needle with respect to the transfer nip.

  The present invention has been made in view of the above background, and an object thereof is to provide the following image forming apparatus. That is, it is an object of the present invention to provide an image forming apparatus capable of accurately positioning a charge eliminating member in the vicinity of an exit of a transfer nip formed by contact between an image carrier and a relatively large nip forming member.

In order to achieve the above object, an invention according to claim 1 forms an image nip for carrying a visible image and a transfer nip by abutting against the image carrier while being urged toward the image carrier. A nip forming member, a transfer means for transferring a visible image on the image carrier in the transfer nip to a recording member sandwiched in the transfer nip, and a charge eliminating member on the recording member that has passed through the transfer nip. In the image forming apparatus including the neutralizing unit that neutralizes the recording member while facing the recording member, the neutralizing member is held by the nip forming member.
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, a casing for holding the nip forming member is provided, and the neutralizing member is connected to the nip forming member in the casing and an inner wall of the casing. The neutralizing member is held by the nip forming member so as to be positioned in a gap formed between the two.
According to a third aspect of the present invention, in the image forming apparatus of the second aspect, the nip forming member is urged toward the image carrier by an urging means while being held movably held by the casing. It is characterized in that it is brought into contact with the image carrier.
According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the nip forming member is positioned by abutting a part of the nip forming member urged by the urging unit against the positioning portion. It is characterized by this.
According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the latent image carrier that carries a latent image and a developing unit that develops the latent image on the latent image carrier. And the transfer means is configured to transfer the visible image obtained on the latent image carrier by development to the image carrier and then to the recording member. is there.
According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the static eliminator is configured to neutralize the recording member while applying a neutralizing bias to the neutralizing member. It is a feature.
According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the neutralizing member is grounded.
According to an eighth aspect of the present invention, there is provided the image forming apparatus according to any one of the first to seventh aspects, wherein the fixing unit that fixes the visible image transferred to the recording member to the recording member and the neutralizing member are opposed to each other. A guide member that guides the recording member that has passed through the position toward the fixing unit is provided, and the guide member is abutted against the fixing unit and positioned.

In these inventions, the neutralizing member is held by the nip forming member that contacts the image carrier to form the transfer nip, so that the position of the neutralizing member relative to the transfer nip can be freely set regardless of the size of the casing. It becomes possible to do. For this reason, it is possible to dispose the charge eliminating member in the vicinity of the exit of the transfer nip formed by the contact between the image carrier and the relatively large nip forming member.
Further, even if there is an assembly error of the nip forming member with respect to the casing, the relative position between the transfer nip and the charge eliminating member held by the nip forming member is not changed. For this reason, the static eliminator can be positioned with higher accuracy than in the prior art in which the relative position between the nip former and the static eliminator is changed by the assembly error of the nip member.

Hereinafter, an electrophotographic printer (hereinafter simply referred to as a printer) will be described as an example of an embodiment of an image forming apparatus to which the present invention is applied.
First, the basic configuration of the printer will be described. FIG. 1 is a schematic configuration diagram showing the entire printer. In FIG. 1, a printer 100 includes four process units 6Y, 6M, 6C, and 6K for generating toner images of yellow, magenta, cyan, and black (hereinafter referred to as Y, M, C, and K). Yes. These use Y, M, C, and K toners of different colors, but otherwise have the same configuration and are replaced when the lifetime is reached.

  Taking a Y process unit 6Y for generating a Y toner image as an example, this includes a drum-shaped photoreceptor 1Y, a drum cleaning device 2Y, a charge eliminating device (not shown), and a charging device 4Y as shown in FIG. And a developing device 5Y. With these members held in a common unit casing, the unit can be integrally attached to and detached from the printer main body.

  The charging device 4Y uniformly charges the surface of the photoreceptor 1Y that is driven to rotate clockwise in the drawing by a driving unit (not shown). The uniformly charged surface of the photoreceptor 1Y is exposed and scanned by a laser beam L emitted from an optical writing unit 7 serving as a latent image forming unit, and carries an electrostatic latent image for Y. The Y electrostatic latent image is developed into a Y toner image by the developing device 5Y using Y toner. Then, intermediate transfer is performed on the intermediate transfer belt 8.

  The drum cleaning device 2Y removes transfer residual toner attached to the surface of the photoreceptor 1Y after the intermediate transfer process. Further, the static eliminator neutralizes residual charges on the photoreceptor 1Y after cleaning. By this charge removal, the surface of the photoreceptor 1Y is initialized and prepared for the next image formation. Similarly, in the process units 6M, C, and K for other colors, M, C, and K toner images are formed on the photoreceptors 1M, C, and K, and are sequentially superimposed on the Y toner images on the intermediate transfer belt 8. Intermediate transfer. As a result, a four-color superimposed toner image is formed on the intermediate transfer belt 8 as an image carrier.

  The developing device 5Y as developing means includes a developing portion 53Y that accommodates a developing sleeve 51Y, a first accommodating chamber 54Y that accommodates a Y developer containing a magnetic carrier (not shown) and non-magnetic Y toner, and a first accommodating chamber 54Y. 2 housing chamber 55Y and the like. In the developing portion 53Y, a developing sleeve 51Y made of a non-magnetic pipe that is rotationally driven by a driving unit (not shown) exposes a part of its peripheral surface to the outside through an opening provided in the developing casing. As a result, a developing region is formed in which the photoreceptor 1Y and the developing sleeve 51Y face each other with a predetermined gap.

  Inside the developing sleeve 51Y, a magnet roller (not shown) having a plurality of magnetic poles arranged in the circumferential direction is fixed so as not to rotate around the developing sleeve 51Y. The developing sleeve 51Y pumps the Y developer from the second storage chamber 55Y by rotationally driving the Y developer in the second storage chamber 55Y described later while adsorbing the Y developer on the surface by the magnetic force generated by the magnet roller. The Y developer conveyed toward the developing region as the developing sleeve 51Y rotates is rotated by a doctor blade 52Y whose tip is opposed to the surface of the developing sleeve 51Y via a predetermined gap, and the sleeve surface. It enters into the doctor gap formed between the two. At this time, the layer thickness on the sleeve is regulated to substantially the same thickness as the doctor gap. When the developing sleeve 51Y is rotated and transported to the vicinity of the developing region facing the photoreceptor 1Y, the magnetic roller rises on the sleeve under the magnetic force of the developing magnetic pole (not shown) of the magnet roller to form a magnetic brush. .

  A developing bias having the same polarity as the toner charging polarity is applied to the developing sleeve 51Y by a developing power source (not shown). Thereby, in the development region, a non-development potential that electrostatically moves Y toner from the background portion side to the sleeve side acts between the surface of the developing sleeve 51Y and the background portion (uniformly charged portion) of the photoreceptor 1Y. . Further, a developing potential for electrostatically moving Y toner from the sleeve side toward the electrostatic latent image acts between the surface of the developing sleeve 51Y and the electrostatic latent image on the photoreceptor 1Y. By the action of this development potential, the Y toner in the Y developer is transferred onto the electrostatic latent image, whereby the electrostatic latent image on the photoreceptor 1Y is developed into a Y toner image.

  The Y developer that has passed through the developing area as the developing sleeve 51Y rotates is separated from the developing sleeve 51Y under the influence of a repulsive magnetic field formed between repelling magnetic poles provided in a magnet roller (not shown). Return to the second storage chamber 55Y.

  A partition wall is interposed between the first storage chamber 54Y in which the first screw member 56Y is disposed and the second storage chamber 55Y in which the second screw member 57Y is disposed. As a result, both storage chambers are partitioned. Each of the partition walls has openings in regions facing both ends in the axial direction of the screw members, and the two storage chambers communicate with each other through the openings.

  Each of the first screw member 56Y and the second screw member 57Y includes a rod-shaped rotary shaft member whose both ends are rotatably supported by a bearing (not shown), and a spiral projecting spirally on the peripheral surface thereof. And have blades. Then, as it is driven to rotate by a driving means (not shown), the Y developer is conveyed in the rotation axis direction by the spiral blade.

  In the first storage chamber 54Y, the Y developer is transported from the front side to the back side in the direction orthogonal to the drawing sheet as the first screw member 56Y is driven to rotate. And if it conveys to the edge part vicinity of the back | inner side of a developing casing, it will approach in the 2nd storage chamber 55Y via the opening which is not shown in the partition wall.

  Above the second storage chamber 55Y, the above-described developing unit 53Y is formed, and the second storage chamber 55Y and the developing unit 53Y communicate with each other in the entire area of the opposing portion. The second screw member 57Y in the second storage chamber 55Y and the developing sleeve 51Y in the developing unit 53Y are opposed to each other while maintaining a parallel relationship.

  In the second storage chamber 55Y, as the second screw member 57Y is driven to rotate, the Y developer is transported from the back side in the direction perpendicular to the drawing surface to the front side. During this transport process, the Y developer around the rotation direction of the second screw member 57Y is appropriately pumped up to the developing sleeve 51Y, and the developed Y developer is appropriately collected from the developing sleeve 51Y. Then, the Y developer transported to the vicinity of the near end of the second storage chamber 55Y in the drawing returns to the first storage chamber 54Y through an opening (not shown) provided in the partition wall.

  A toner concentration detection sensor 58Y comprising a magnetic permeability sensor is fixed to the lower wall of the first storage chamber 54Y, and the toner concentration of the Y developer conveyed by the first screw member 56Y is detected from below and detected. Output voltage according to the result. The controller 20b replenishes an appropriate amount of Y toner into the first storage chamber 54Y by driving a Y toner replenishing device (not shown) as required based on the output voltage value from the toner concentration detection sensor 58Y. As a result, the toner concentration of the Y developer, which has been lowered with the development, is recovered. The developing devices for the other colors have the same configuration as the developing device 5Y for Y.

  In FIG. 1 described above, the optical writing unit 7 is disposed below the process units 6Y, 6M, 6C, and 6K in the drawing. Then, the respective photoconductors in the process units 6Y, 6M, 6C, and KK are individually optically scanned by the four laser beams L emitted from the laser power based on the image information. Thereby, electrostatic latent images for Y, M, C, and K are formed on the photoreceptors 1Y, 1M, 1C, and 1K. The optical writing unit 7 deflects the laser beam L emitted from the light source in the photosensitive body axial direction (main scanning direction) by reflection on the regular polygon reflecting surface of a polygon mirror that is rotationally driven by a motor. Optical scanning in the main scanning direction is performed on the body.

  A paper feed cassette 26 having a paper feed roller 27 is disposed below the optical writing unit 7 in the drawing. This paper feed cassette 26 stores a plurality of recording papers P as recording members in a stacked state, and presses the paper feed roller 27 against the uppermost recording paper P. When the paper feed roller 27 is driven to rotate counterclockwise in the drawing by a driving means (not shown), the uppermost recording paper P is sent out toward the paper feed path.

  A registration roller pair 28 is disposed near the end of the paper feed path, and the recording paper P fed to the paper feed path is sandwiched between the rollers of the registration roller pair 28. As soon as the recording paper P is sandwiched between the rollers, the registration roller pair 28 temporarily stops the rotation of the roller pair. Then, the rotational driving of the roller pair is resumed at a timing at which the recording paper P can be superimposed on the four-color superimposed toner image on the intermediate transfer belt 8, and the recording paper P is sent out to a secondary transfer nip described later.

  Above the process units 6Y, 6M, 6C, and 6K, there is disposed a transfer unit 15 that moves the intermediate transfer belt 8 serving as an image carrier endlessly in the counterclockwise direction in the figure. The transfer unit 15 as transfer means includes four primary transfer rollers 9Y, 9M, 9C, 9K, a secondary transfer roller 12, a cleaning backup roller 13, a tension roller 14 and the like in a loop of the intermediate transfer belt 8. Yes. The intermediate transfer belt 8 is endlessly moved counterclockwise in the figure by the rotational drive of the secondary transfer roller 12 while being stretched by these rollers.

  The primary transfer rollers 9Y, 9M, 9C, and 9K sandwich the intermediate transfer belt 8 that is moved endlessly in this manner between the photoreceptors 1Y, 1M, 1C, and 1K. Thus, primary transfer nips for Y, M, C, and K are formed by contact between the photoreceptors 1Y, 1M, 1C, and 1K and the front surface of the intermediate transfer belt 8. The primary transfer rollers 9Y, 9M, 9C, and 9K are each applied with a primary transfer bias having a polarity (for example, plus) opposite to the charging polarity of the toner by a transfer power source (not shown). On the other hand, the secondary transfer roller 12, the cleaning backup roller 13, and the tension roller 14 are all grounded.

  The intermediate transfer belt 8 sequentially passes through the primary transfer nips for Y, M, C, and K along with the endless movement thereof, and Y, M, and C on the photoreceptors 1Y, M, C, and K are sequentially transferred. , K toner images are sequentially superimposed and transferred intermediately.

  In addition to the members described so far, the transfer unit 15 has a transfer counter roller 19 and a belt cleaning device 10 outside the loop of the intermediate transfer belt 8. The transfer counter roller 19 is in contact with the front surface of the belt at a position facing the secondary transfer roller 12 in the belt loop via the belt to form a secondary transfer nip. The recording paper P is sent out from the registration roller pair 28 toward the secondary transfer nip at the timing when the four-color superimposed toner image formed on the intermediate transfer belt 8 enters the secondary transfer nip.

  A secondary transfer bias having the same polarity (for example, minus) as the charging polarity of the toner is applied to the secondary transfer roller 12 in the belt loop by a transfer power source (not shown). The transfer counter roller 19 outside the belt loop is grounded. As a result, a secondary transfer electric field for electrostatically moving the toner on the intermediate transfer belt 8 from the belt side toward the transfer counter roller 19 side is formed in the secondary transfer nip. The four-color superimposed toner image is collectively transferred to the recording paper P in close contact with the four-color superimposed toner image on the intermediate transfer belt 8 in the secondary transfer nip by the action of the secondary transfer electric field or nip pressure. Thus, a full color image is formed in combination with the white color of the recording paper P.

  Transfer residual toner that has not been secondarily transferred to the recording paper P adheres to the intermediate transfer belt 8 after passing through the secondary transfer nip. This is removed from the belt surface by the belt cleaning device 10.

  A fixing device 20 is disposed above the secondary transfer nip in the drawing. The recording paper P discharged from the secondary transfer nip while being peeled off from the intermediate transfer belt 8 and the transfer counter roller 19 is fed into the fixing device 20. Then, the full color image is fixed on the surface by heating or pressurizing when passing through a fixing nip by contact between a fixing roller containing a heat source such as a halogen lamp and a pressure roller pressed against the fixing roller. The

  Thereafter, the recording paper P is discharged out of the apparatus through a pair of paper discharge rollers 29. A stack unit 30 is formed on the upper surface of the printer main body, and the recording paper P discharged to the outside by the discharge roller pair 29 is sequentially stacked on the stack unit 30.

  Between the transfer unit 15 and the stack part 30 above the bottle unit 31, a bottle housing part 31 is disposed. The bottle storage unit 31 stores toner bottles 32Y, 32M, 32C, and 32K that store Y, M, C, and K toners for supply. The toner bottles 32Y, 32M, 32C, and 32K are placed on the bottle container 31 from the top for each toner color. The Y, M, C, and K toners in the toner bottles 32Y, 32M, 32C, and 32K are respectively developed by developing units for the process units 6Y, 6M, 6C, and 6K by Y, M, C, and K toner replenishers that are not shown. Is replenished as needed. These toner bottles 32Y, 32M, 32C, and 32K are detached from the printer 100 main body independently of the process units 6Y, 6M, 6C, and 6K.

  FIG. 15 is a schematic diagram for explaining an aspect of a static elimination needle in a conventional printer. In this figure, a transfer roller 202 as a nip forming member is brought into contact with a photosensitive member 201 as an image carrier to form a transfer nip. The transfer roller 202 is rotatably held by a roller casing 203. The upper portion of the roller casing 203 is supported by the rotating shaft 205 so as to be able to swing. However, the lower portion is urged by the urging coil spring 206 so that a rotational force in the clockwise direction in FIG. The As a result, the transfer roller 202 held by the roller casing 203 abuts against the photoconductor 201. A static elimination needle 204 is fixed to the upper end portion of the roller casing 203 and swings around the rotation shaft 205 together with the roller casing 203.

  When a recording sheet (not shown) discharged from the transfer nip passes through a position facing the charge eliminating needle 204, the charge generated in the transfer nip is discharged.

  In such a configuration, an error occurs in the relative position between the transfer roller 202 in the roller casing 203 and the static elimination needle 204 fixed to the casing due to an assembly error of the transfer roller 202 with respect to the roller casing 203. As a result, an error also occurs in the relative position between the transfer nip and the static elimination needle 204, and it is difficult to accurately position the static elimination needle 204 with respect to the transfer nip.

  When a relatively large diameter transfer roller 202 is used, the roller casing 203 containing the transfer roller 202 also has a wide width (dimension in the vertical direction on the paper surface) corresponding to the roller diameter. The distance between the outlet and the static elimination needle 204 fixed to one end side in the width direction of the casing is increased. This makes it difficult to dispose the static elimination needle 204 close to the exit of the transfer nip.

Next, a characteristic configuration of the printer will be described.
FIG. 3 is an enlarged configuration diagram illustrating an enlarged configuration around the secondary transfer nip in the printer. In the drawing, an opening / closing unit 60 is disposed on the right side of the transfer unit 15. The opening / closing unit 60 is supported so as to be swingable in the direction of the arrow in the figure around a rotation shaft provided in a region (not shown), and a roller casing 60a as a holding body that covers the transfer counter roller 19, and 2 A guide portion 60b for guiding the recording paper after passing through the next transfer nip toward the paper receiving port 20a of the fixing device 20; When the opening / closing unit 60 is rotated by a predetermined angle in the clockwise direction in the drawing from the state shown in the drawing, the opening / closing unit 60 is largely separated from the transfer unit 15. Thereby, the transfer unit 15 is largely exposed to the outside through a housing door (not shown) on the right side of the opening / closing unit 60 in the drawing. This makes it possible to easily remove jammed paper generated at the secondary transfer nip and its surroundings.

  The roller casing 60a of the opening / closing unit 60 includes a bearing 61 that rotatably receives shaft portions 19a protruding from both ends in the axial direction of the roller portion of the transfer counter roller 19 serving as a nip forming member. This bearing is held so as to be movable in a longitudinal direction of a long hole provided in a side plate (not shown) of the roller casing 60a, and moves toward and away from the intermediate transfer belt 6 by this movement. The bearing 61 is urged toward the intermediate transfer belt 6 by the urging coil spring 62 as urging means, so that the transfer counter roller 19 is simultaneously urged and brought into contact with the intermediate transfer belt 8. .

  A static elimination holder 63 is engaged with the bearing 61, and a static elimination needle 64 as a static elimination member is fixed to the static elimination holder 63. As a result, the static elimination needle 64 is held on the shaft portion 19 a of the transfer counter roller 19 via the static elimination holder 63 and the bearing 61.

  FIG. 4 is a perspective view showing the static elimination holder 63 and the static elimination needle 64 fixed to the static elimination holder 63. The static elimination needle 64 has a plurality of needle portions 64a protruding in a comb shape from the upper surface thereof. These needle portions 64a are formed by punching and bending a stainless steel plate having a thickness of 0.3 [mm]. As for the static elimination needle 64, the base board part used as the base of the needle part 64a is being fixed to the static elimination holder 63 with the fixing screw 65. FIG.

  FIG. 5 is an enlarged schematic view showing the needle portion 64 a of the static elimination needle 64. In the static elimination needle 64 of this printer, the arrangement pitch P of the needle portions 64a is set to 3 [mm], the base thickness W is set to 1 [mm], and the protruding height h from the base portion 64b is set to 4 [mm]. is doing. In this printer, the static elimination needle 64 is formed by processing a stainless steel plate, but may be made of a metal different from stainless steel or a conductive plastic. Moreover, you may employ | adopt the static elimination member of other shapes, such as a static elimination brush, instead of the static elimination needle which has a needle part.

  In FIG. 3 described above, the static elimination needle 64 is held by the shaft portion 19a of the transfer counter roller 19 in such a posture that the tip of the needle portion 64a faces the recording paper after passing through the secondary transfer nip. A static elimination bias (for example, -2 kV) having the same polarity as the toner charging polarity is applied to the static elimination needle 64 by a power source (not shown), or a ground wire is connected. The recording sheet immediately after passing through the secondary transfer nip is conveyed toward the fixing device 20 while maintaining a minute gap with respect to the tips of the plurality of needle portions 64a of the static elimination needle 64. At this time, a discharge is generated between the recording paper and the tip of the needle portion 64a in accordance with the amount of charging of the recording paper charged by the secondary transfer current generated in the secondary transfer nip. The paper is neutralized.

  In such a configuration, it is possible to dispose the static elimination needle 64 closer to the outlet of the secondary transfer nip than when the static elimination needle 64 is fixed to the roller casing 60a. Further, as the roller portion of the transfer counter roller 19 is brought into contact with the intermediate transfer belt 8 by the urging force of the urging coil spring, the static elimination needle 64 held by the shaft portion 19a of the transfer counter roller 19 is moved to the secondary transfer nip. Can also be positioned. Furthermore, even if there is an assembly error of the transfer facing roller 19 with respect to the roller casing 60a, the relative position between the secondary transfer nip and the static elimination needle 64 held by the shaft portion 19a of the transfer facing roller 19 is not changed. The static elimination needle 64 can also be accurately positioned with respect to the secondary transfer nip.

  FIG. 6 is an enlarged configuration diagram showing the static elimination holder 63 in a state where the holding posture is not regulated, together with the surrounding configuration. In the figure, the outer edge shape of the bearing 61 that rotatably receives the shaft portion 19a of the transfer counter roller 19 is an oval shape. On the other hand, the engaging part 63b of the static elimination holder 63 with the bearing 61 has a shape in which a partial notch is provided in a part of a perfect circular ring.

  When engaging the engaging portion 63b of the static elimination holder 63 with the bearing 61, as shown in FIG. 7, the engaging portion 63b is engaged with the notch of the engaging portion 63b facing the longitudinal side of the oval bearing 61. The bearing 61 is passed through the notch of the portion 63b. When the bearing 61 is completely inserted into the ring of the engaging portion 63b in this way, the static eliminating holder 63 is rotated around the bearing 61 as shown in FIG. Then, since the wide part of the bearing 61 comes to face the notch of the engaging part 63b in the ring of the engaging part 63b, the bearing 61 cannot pass through the notch. This prevents the engagement portion 63b from coming off from the bearing 61. Thereafter, as shown in FIG. 9, the static elimination holder 63 is further rotated, and the pin 63 a of the static elimination holder 63 shown in FIG. 6 is fitted into a long hole 60 c provided in the side plate of the opening / closing unit 60. As a result, as shown in FIG. 3, the static elimination needle 64 is placed on the shaft portion 19a of the transfer facing roller 19 in a posture in which the tip of the static elimination needle 64 fixed to the static elimination holder 63 faces the recording paper being conveyed. Hold.

  In this state, when the transfer counter roller 19 slightly moves away from or approaches the intermediate transfer belt 8 as the thick paper enters or passes through the secondary transfer nip, the static elimination holder 63 is moved. It swings slightly around the pin 63a fitted in the long hole 60c. As a result, the static elimination needle 64 approaches or moves away from the belt following the movement of the transfer counter roller 19, so that the distance between the static elimination needle 64 and the secondary transfer nip is kept constant.

  When removing the static elimination holder 63 from the bearing 61, the static elimination holder 63 should just be operated in the reverse procedure to the procedure of FIGS. 7-9 shown previously. Although there are many opportunities for foreign matters such as paper dust and toner to adhere to the static elimination needle 64, in this printer, the static elimination holder 63 can be easily removed from the bearing 61 and cleaned or replaced.

  In FIG. 3, the opening / closing unit 60 has an abutting protrusion 60d at the upper end thereof. When the opening / closing unit 60 is closed with respect to the printer main body, as shown in FIG. It is locked in a state of being abutted against the 20 abutted portions 20b. As a result, the guide portion 60 b of the opening / closing unit 60 is positioned with respect to the fixing device 20. In such a configuration, even if the transfer counter roller 19 slightly moves as the thick paper enters or passes through the secondary transfer nip, the guide portion 60b is firmly positioned in the vicinity of the fixing device 20. Yes. For this reason, it is possible to avoid the occurrence of a jam due to the movement of the guide portion 60b.

  FIG. 11 is a side view showing the side plate 11 of the transfer unit 15 together with the opening / closing unit 60. FIG. 12 is an enlarged schematic view showing the positioning cutout portion 11a of the side plate 11 and the surrounding configuration in an enlarged manner. In these drawings, a bearing 61 movably held by a roller casing 60a while rotatably receiving the transfer counter roller 19 is provided on the side plate 11 of the transfer unit 15 at a protruding portion from the side surface of the roller casing 60a. The positioning notches 11a are moved. The transfer counter roller 19 is positioned with respect to the transfer unit 15 by the bearing 61 abutting against the bottom of the positioning notch 11a. By positioning the transfer counter roller 19 in this way, the size and position of the secondary transfer nip can be stabilized, and the occurrence of transfer defects due to variations in size and position can be suppressed.

  FIG. 13 is an enlarged configuration diagram showing a secondary transfer nip and its surrounding configuration in a printer according to a first modification in which a part of the configuration of the printer according to the embodiment is changed to another mode. In the drawing, the pin 63 a of the static elimination holder 63 is engaged with a long hole of the side plate of the opening / closing unit 60, and this long hole extends in the same direction as the biasing direction of the transfer counter roller by the biasing coil spring 62. ing. This direction is also the moving direction of the transfer counter roller 19. In the printer according to the first modified example, when the transfer counter roller 19 moves slightly as the thick paper enters or passes through the secondary transfer nip, the static elimination needle 64 follows the movement. Moves in the same direction as the direction of movement.

  The example of the printer in which the image carrier is the intermediate transfer belt 8 has been described so far. However, in the transfer nip due to the contact between the image carrier different from the intermediate transfer belt 8 and a nip forming member such as a transfer counter roller. The present invention can also be applied to an image forming apparatus that transfers a toner image to a recording member. The example of the printer having the transfer counter roller 19 as the nip forming member has been described. However, the present invention can also be applied to an image forming apparatus using a nip forming member having a different form from the roller shape, such as a transfer brush. is there.

  FIG. 14 shows a transfer nip formed by contact between a photosensitive member 1 which is a latent image carrier and an image carrier and a transfer roller 70 to which a transfer bias having a polarity opposite to the charging polarity of the toner is applied. FIG. 5 is an enlarged configuration diagram showing a configuration around a secondary transfer nip in a printer according to a second modification to which the present invention is applied in a configuration for transferring a toner image on a sensitive body to a recording paper. Also in such a printer, the same effect as the printer according to the embodiment can be obtained with respect to the static elimination needle 64.

  As described above, in the printer according to the embodiment, the roller casing 60a that holds the transfer counter roller 19 that is the nip forming member is provided, and the charge eliminating needle 64 that is the charge eliminating member is connected to the transfer counter roller 19 in the roller casing 60a and the roller casing 60a. The neutralizing needle 64 is held by the transfer counter roller 19 so as to be positioned in a gap formed between the inner wall and the inner wall. In such a configuration, by preventing the recording paper P from entering the gap by the static elimination needle 64, it is possible to avoid the occurrence of a jam due to the leading edge of the recording paper P entering the gap.

  Further, the transfer counter roller 19 is urged toward the intermediate transfer belt 8 by an urging coil spring 62 as an urging means while being movably held in the roller casing 60a, and is brought into contact with the intermediate transfer belt 8. Yes. In this configuration, the biasing direction is more stable by reducing the distance between the transfer counter roller 19 and the biasing coil spring 62 than in the configuration in which the roller casing is biased to bring the transfer counter roller into contact with the intermediate transfer belt. It can be made.

  Further, the transfer counter roller 19 is positioned by abutting the shaft portion 19a, which is a part of the transfer counter roller 19 biased by the bias coil spring 62, with the positioning notch portion 11a as the positioning portion. . With such a configuration, as described above, the size and position of the secondary transfer nip can be stabilized, and the occurrence of transfer defects due to variations in the size and position can be suppressed.

  Also provided is a photosensitive member as a latent image carrier for carrying a latent image and a developing device as a developing means for developing the latent image on the photosensitive member, and the toner image obtained on the photosensitive member by the development is transferred to the intermediate transfer belt. The transfer unit 15 serving as transfer means is configured so that the image is transferred to the recording paper P after being transferred to the recording paper P. With such a configuration, the static elimination needle 64 can be satisfactorily brought close to the exit of the transfer nip (secondary transfer nip) formed at a position relatively distant from the photoreceptor, and can be accurately positioned.

  In the case where the static elimination means including the static elimination needle 64 and a power source is configured so as to neutralize the recording paper while applying the static elimination bias to the static elimination needle 64, compared with a configuration in which the static elimination needle 64 is simply grounded. The discharge of the recording paper P and the charge eliminating needle 64 is generated with a smaller charge amount of the recording paper P. Thereby, more reliable static elimination can be performed.

  Further, when the static elimination needle 64 is grounded, the recording paper P can be neutralized without using a static elimination power source, thereby reducing the cost.

  In the printer according to the embodiment, the fixing device 20 that fixes the toner image transferred to the recording paper P on the recording paper P and the fixing device 20 that fixes the recording paper P that has passed through the position opposite to the static elimination needle 64 is fixed to the fixing device. And a guide portion 60b serving as a guide member for guiding toward the position 20, and the guide portion 60b is abutted against the abutted portion 20b of the fixing device 20 and positioned. In such a configuration, as described above, in this configuration, even if the transfer counter roller 19 slightly moves as the thick paper enters or passes through the secondary transfer nip, the guide portion 60b is not fixed to the fixing device. It is firmly positioned around 20. For this reason, it is possible to avoid the occurrence of a jam due to the movement of the guide portion 60b.

1 is a schematic configuration diagram illustrating a printer according to an embodiment. FIG. 3 is an enlarged configuration diagram showing a process unit for Y of the printer and its surroundings. FIG. 3 is an enlarged configuration diagram illustrating an enlarged configuration around a secondary transfer nip in the printer. FIG. 3 is a perspective view showing a static elimination holder of the printer and a static elimination needle fixed to the static elimination holder. The schematic diagram which expands and shows the needle part of the static elimination needle. The expansion block diagram which shows the static elimination holder of the state which is not regulating the holding attitude with the surrounding structure. The schematic diagram for demonstrating the 1st process in the attachment procedure of the static elimination holder. The schematic diagram for demonstrating the 2nd process in the attachment procedure. The schematic diagram for demonstrating the 3rd process in the attachment procedure. FIG. 3 is an enlarged schematic diagram showing an abutted portion of the fixing device of the printer and a surrounding configuration in an enlarged manner. FIG. 3 is a side view showing a side plate of a transfer unit of the printer together with an opening / closing unit. The expansion schematic diagram which expands and shows the positioning notch part of the same side board, and its surrounding structure. FIG. 9 is an enlarged configuration diagram illustrating a secondary transfer nip and surrounding configuration in a printer according to a first modification. FIG. 9 is an enlarged configuration diagram illustrating a secondary transfer nip and a surrounding configuration in a printer according to a second modification. The schematic diagram for demonstrating the aspect of the static elimination needle in the conventional printer.

Explanation of symbols

1Y, M, C, K: photoconductor (latent image carrier)
5Y: Developing device (developing means)
8: Intermediate transfer belt (image carrier)
15: Transfer unit (transfer means)
19: Transfer facing roller (nip forming member)
20: Fixing device (fixing means)
60a: Roller casing 60b: Guide part (guide member)
62: Energizing coil spring (urging means)
64: Static elimination needle (static elimination member)
P: Recording paper (recording member)

Claims (8)

An image carrier that carries a visible image; a nip forming member that forms a transfer nip by being abutted against the image carrier while being biased toward the image carrier; and a recording member that is sandwiched between the transfer nips. On the other hand, a transfer means for transferring a visible image on the image carrier in the transfer nip, and a charge eliminating means for discharging the recording member while making the charge removing member face the recording member that has passed through the transfer nip. In the image forming apparatus,
An image forming apparatus, wherein the charge eliminating member is held by the nip forming member. The image forming apparatus according to claim 1.
A casing for holding the nip forming member is provided, and the charge eliminating member is disposed in a gap formed between the nip forming member in the casing and the inner wall of the casing. An image forming apparatus, wherein the image forming apparatus is held by the nip forming member. The image forming apparatus according to claim 2.
An image forming apparatus, wherein the nip forming member is urged toward the image carrier by an urging means while being held movably in the casing, and is brought into contact with the image carrier. . The image forming apparatus according to claim 3, wherein
An image forming apparatus, wherein a part of the nip forming member urged by the urging means is abutted against a positioning portion to position the nip forming member. The image forming apparatus according to any one of claims 1 to 4,
A latent image carrier for carrying a latent image and a developing means for developing the latent image on the latent image carrier are provided, and the visible image obtained on the latent image carrier by development is displayed on the image carrier. An image forming apparatus, wherein the transfer unit is configured to transfer to the recording member after transfer to the recording member. The image forming apparatus according to claim 1,
An image forming apparatus, wherein the charge removing unit is configured to discharge the recording member while applying a discharge bias to the discharge member. The image forming apparatus according to claim 1,
An image forming apparatus, wherein the charge eliminating member is grounded. The image forming apparatus according to claim 1,
A fixing unit that fixes the visible image transferred to the recording member to the recording member; and a guide member that guides the recording member that has passed through a position facing the neutralizing member toward the fixing unit. An image forming apparatus characterized in that a member is positioned by abutting against the fixing means.

Images