JP2006243109A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus easily removing a recording medium when jamming or the like is caused. <P>SOLUTION: The image forming apparatus is equipped with: a conveying belt 12 on which recording paper S is placed to be conveyed; image forming parts 13B, 13Y, 13M and 13C constituted to be attached to/detached from the image forming apparatus and including photoreceptor drums 14B, 14Y, 14M and 14C carrying images formed with toner; traveling system sensors 100, 101, 102 and 103 detecting the conveyance state of the recording paper S; and an ascending/descending link lever 106 moving the photoreceptor drums 14B, 14Y, 14M and 14C coming into contact with the conveying belt 12, to a direction where they are separated from the conveying belt 12 by a predetermined distance according to the faulty conveyance of the recording paper S which is judged on the basis of the result of detection by the traveling system sensors 100, 101, 102 and 103. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus that forms an image by fixing toner on a predetermined recording medium.

  2. Description of the Related Art Conventionally, an electrophotographic recording type image forming apparatus that forms an image by fixing toner on a predetermined recording medium is known. Such an image forming apparatus is configured to charge and expose a photosensitive member as an electrostatic latent image carrier, develop the electrostatic latent image formed on the photosensitive member with toner, and transfer the obtained toner image onto a recording medium. Then, an image is formed through a process of fixing the toner image on the recording medium.

  In recent years, in this type of image forming apparatus, a so-called tandem type toner image, in which different color toner images are formed on a plurality of photoconductors and sequentially transferred onto a recording medium conveyed by a belt conveying device. A color image forming apparatus has been developed (see, for example, Patent Document 1).

JP 2000-81802 A

  Specifically, this Patent Document 1 discloses that a transfer material is carried so that an image is formed on each of a plurality of image carriers, and the image is transferred onto a transfer material to form an image. An image forming apparatus is disclosed in which the body has means for separating the image carrier and the image carrier and the transfer material carrier. In particular, in this image forming apparatus, the image carrier and the transfer material carrier are separated from each other, and the cleaning operations of the respective cleaning units are performed in a timed manner, and at least one of the time for starting or stopping the cleaning operation is set. They are controlled differently. As a result, in this image forming apparatus, the wear of the image carrier, the transfer material carrier, and the cleaning means can be reduced, the life can be extended, the consumption of the developer can be reduced, and the cost can be reduced. .

  By the way, in the image forming apparatus described in Patent Document 1 described above, since the recording medium is sandwiched between the plurality of photosensitive members and the belt conveying device, a conveyance failure occurs during image formation and a jam occurs. When this occurs, it has become difficult to remove the recording medium.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of easily removing a recording medium when a jam or the like occurs.

  An image forming apparatus according to the present invention that achieves the above-described object is an image forming apparatus that forms an image by fixing a developer on a predetermined recording medium, and a belt conveying unit that carries the recording medium by placing the recording medium thereon. An image forming unit that is configured to be detachable from the image forming apparatus and includes an image carrier that carries an image formed by the developer, a detection unit that detects a conveyance state of the recording medium, Control means for judging the conveyance failure of the recording medium based on the detection result of the detection means, and the belt that has been in contact with the belt conveyance means according to the judgment of the conveyance failure of the recording medium by the control means And a moving unit that moves the image carrier in a direction away from the belt conveying unit by a predetermined distance.

  In such an image forming apparatus according to the present invention, the image carrier is moved in a direction away from the belt conveying means by a predetermined distance in response to the determination of the conveyance failure of the recording medium. And the belt conveying means do not sandwich the recording medium.

  At this time, when the control unit determines the conveyance failure of the recording medium based on the detection result of the detection unit, the control unit moves the image carrier in a direction away from the belt conveyance unit by a predetermined distance without taking time. It is desirable to control the moving means. As a result, in the image forming apparatus according to the present invention, it is possible to prevent the developer that has been altered by being left for a long time from sticking to the surface of the image carrier.

  Further, in the image forming apparatus according to the present invention, when a plurality of the image forming means including the image carrier are provided, the moving means is a plurality of the image carriers at the first position. A part of the image carrier is selectively moved away from the belt conveying unit by a predetermined distance, and at a second position, all of the plurality of image carriers are separated from the belt conveying unit by a predetermined distance. It is desirable to move in the direction of separating only. Thereby, in the image forming apparatus according to the present invention, a necessary image forming unit can be easily selected from among a plurality of image forming units according to the use such as the print mode.

  Further, the moving means may move the image carrier in a direction away from the belt conveying means by a predetermined distance in response to opening a cover constituting the housing of the image forming apparatus. . Thus, in the image forming apparatus according to the present invention, the recording medium is not sandwiched between the image carrier and the belt conveying unit, and it is not necessary to use an expensive electric component motor, and only an inexpensive gear configuration is used. This can be realized with a low price.

  Furthermore, the image forming apparatus according to the present invention discharges the surface charge of the image carrier included in the image forming unit when the image carrier is moved away from the belt conveying unit by a predetermined distance. When the discharge body for contact is brought into contact with the surface of the image carrier and the image carrier is brought into contact with the belt conveying means, the discharge body is moved in a direction away from the surface of the image carrier. Means may be provided.

  As described above, in the image forming apparatus according to the present invention, when the image carrier in a state where the surface charge is accumulated is moved in the direction away from the belt conveying unit, the surface charge of the image carrier is directly applied to the frame ground. By bringing the discharge body into contact with the surface of the image carrier so that it does not fly to the same level of the conductor, it is possible to eliminate static electricity without causing a discharge shock, and to prevent damage to the image carrier.

  In the present invention, when the recording medium is poorly conveyed, the recording medium is not sandwiched between the image carrier and the belt conveying means, and therefore the recording medium can be easily removed.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

  This embodiment is an electrophotographic recording type image forming apparatus that forms an image by fixing toner as a developer on a predetermined recording medium. In particular, this image forming apparatus forms a toner image of a different color on each of a plurality of photoconductors, and so-called tandem color image formation in which the images are sequentially transferred onto a recording medium conveyed by a belt conveying device. Device.

  First, the image forming apparatus shown as the first embodiment will be described.

  As shown in FIG. 1, the image forming apparatus includes a sheet storage unit 11 that stores a recording sheet S as a recording medium on which no image is recorded. The recording paper S stored in the paper storage unit 11 is fed from the paper storage unit 11 by rotation of a registration roller provided in the front part of the image forming apparatus, and is provided in the medium conveyance path. In response to the rotation of the sheet feeding roller, the sheet is conveyed and placed on the conveyor belt 12 that rotates at a rotation speed corresponding to the printing speed by a motor (not shown).

  The image forming apparatus includes four image forming units 13B, 13Y, 13M, and 13C corresponding to the four colors of black (K), yellow (Y), magenta (M), and cyan (C) in this order. The recording sheets S are juxtaposed from the paper supply side to the paper discharge side. These image forming units 13B, 13Y, 13M, and 13C are configured to be detachable from the image forming apparatus, and image forming using toner of each color is performed on the recording paper S placed on the conveying belt 12. I do. The image forming units 13B, 13Y, 13M, and 13C have the same configuration. Therefore, here, the configuration of the image forming unit 13Y for yellow will be described as a representative.

  The image forming unit 13Y receives a photosensitive drum 14Y as an electrostatic latent image carrier that rotates in a direction indicated by an arrow a in the figure, and a charging roller 15Y that charges the surface of the photosensitive drum 14Y. An LED (Light Emitting Diode) head 16Y that exposes the photosensitive drum 14Y based on the image data, a developing unit that develops the electrostatic latent image formed on the photosensitive drum 14Y with toner, and the obtained toner image And a transfer roller 17Y for transferring the image onto the recording paper S.

  The developing section stores a developing roller 18Y made of a semiconductor rubber material, a developing blade 19Y slidably in contact with the developing roller 18Y, a sponge roller 20Y that conveys an appropriate amount of toner to the developing blade 19Y, and toner. And a toner tank 21Y. Each roller constituting the image forming unit 13Y is rotationally driven by a motor (not shown). In such a developing unit, the toner supplied from the toner tank 21Y reaches the developing blade 19Y via the sponge roller 20Y, and further thinned on the circumference of the developing roller 18Y via the developing blade 19Y. Then, it reaches the contact surface with the photosensitive drum 14Y. At this time, the toner is frictionally charged by being strongly rubbed by the developing roller 18Y and the developing blade 19Y when the thin layer is formed. Here, it is assumed that the toner is negatively charged. In such a developing unit, when the toner is consumed, new toner can be replenished by replacing the toner tank 21Y.

  Further, the image forming unit 13Y includes a cleaning blade 22Y. The cleaning blade 22Y is used to scrape off toner remaining on the surface of the photosensitive drum 14Y, and waste (not shown) provided outside the printing mechanism by the screw shaft 23Y. It is configured to discharge into a toner box.

  Such an image forming unit 13Y forms an electrostatic latent image on the photosensitive drum 14Y, and develops the electrostatic latent image with toner to form a toner image. The toner image on the photosensitive drum 14Y developed by the image forming unit 13Y is transferred onto the recording paper S by the transfer roller 17Y. In the image forming apparatus, the four image forming units 13B, 13Y, 13M, and 13C having such a configuration sequentially form images of each color on the recording paper S to form four color images.

  Further, the image forming apparatus includes a fixing unit 26 having heated rollers 24 and 25 downstream of the image forming units 13B, 13Y, 13M, and 13C. The fixing device 26 fixes the toner image on the recording paper S by heat and pressure. In the image forming apparatus, when the image is fixed on the recording paper S by such a fixing device 26, the recording paper S is transported and discharged to the outside in accordance with the rotation of a roller (not shown), and is placed on the stacker. Load it.

  Furthermore, the image forming apparatus includes four traveling system sensors 100, 101, 102, and 103 that detect the conveyance state of the recording sheet S from the upstream side to the downstream side in the conveyance direction of the recording sheet S. The traveling system sensor 100 is provided in the vicinity of the registration roller, and detects whether or not the recording paper S fed from the paper storage unit 11 has reached the registration position. The traveling system sensor 101 is provided in the vicinity of the paper feed roller and detects whether or not the recording paper S has reached the paper feed roller. Further, the traveling system sensor 102 is provided on the upstream side of the transport belt 12 and detects whether the recording paper S has reached the upstream side of the transport belt 12. Furthermore, the traveling system sensor 103 is provided on the downstream side of the fixing device 26 and detects whether or not the leading edge of the recording paper S has passed through the fixing device 26.

  In the image forming apparatus, as shown in FIG. 2, the outputs of these four travel system sensors 100, 101, 102, 103 are monitored by a control unit 104 including a CPU (Central Processing Unit) or the like. In the image forming apparatus, different output signals are output from the control unit 104 in accordance with the detection results of the four travel system sensors 100, 101, 102, and 103.

  Further, the image forming apparatus drives the motor 105 under the control of the control unit 104, and raises the image forming units 13B, 13Y, 13M, and 13C shown in FIG. , 14Y, 14M, and 14C are configured to drive an elevating link lever 106 that moves in a direction away from the conveying belt 12 by a predetermined distance. That is, in the image forming apparatus, as shown in FIG. 3A, in the normal time, the rotary shafts 106 of the photosensitive drums 14B, 14Y, 14M, and 14C have the rotary link lever 106 having an uneven sectional shape. Are positioned in the recesses of the photosensitive drums 14B, 14Y, 14M, and 14C, and the transfer rollers 17B, 17Y, 17M, and 17C provided to face the photosensitive drums 14B, 14Y, 14M, and 14C, respectively. Image forming portions 13B, 13Y, 13M, and 13C are disposed so as to contact the belt 12. On the other hand, the image forming apparatus drives the idle gear 107 through the motor 105 under the control of the control unit 104, and further forms integrally with the lift link lever 106 through the idle gear 107. By driving the gear portion 108, the lifting link lever 106 is moved in the horizontal direction as shown in FIG. 3B, and the respective rotation shafts of the photosensitive drums 14B, 14Y, 14M, and 14C are moved. By being positioned on the convex portion of the lift link lever 106, it is possible to select an operation for moving the photosensitive drums 14B, 14Y, 14M, and 14C in a direction away from the conveying belt 12 by a predetermined distance.

  In such an image forming apparatus, when continuous operation is performed in a normal state where no jamming of the recording paper S occurs, charging and exposure of the photosensitive drums 14B, 14Y, 14M, and 14C, and the photosensitive member Development of electrostatic latent images formed on the drums 14B, 14Y, 14M, and 14C with toner, toner image recording paper S by the photosensitive drums 14B, 14Y, 14M, and 14C and the transfer rollers 17B, 17Y, 17M, and 17C An image forming operation is performed by repeatedly performing processes such as upward transfer and fixing of the toner image on the recording paper S by the fixing device 26 for each color. On the other hand, in the image forming apparatus, when the jam of the recording sheet S occurs during the image forming operation due to the state of the recording sheet S, the state of the medium conveyance path, and various other factors, The operation of removing the recording paper S is assisted by performing the following operation.

  FIG. 4 shows output waveforms of the traveling system sensors 100, 101, 102, and 103 when a normal continuous image forming operation is performed. That is, each of the travel system sensors 100, 101, 102, and 103 outputs a high-level signal only for a predetermined time t2 when the presence of the recording paper S is detected and the paper is present. Binary data corresponding to the presence or absence of the recording paper S is output according to the printing speed, such as outputting a low level signal when the presence of the recording paper S is not detected and there is no paper. Are output at a predetermined time interval t1. In the image forming apparatus, the control unit 104 monitors binary data output from such traveling system sensors 100, 101, 102, and 103.

  Further, in FIG. 5, the travel system sensor 100 in the case where the second recording sheet S of the printed matter composed of three recording sheets is not fed from the sheet storage unit 11 due to poor feeding. , 101, 102, 103 are shown. The output waveforms of the traveling system sensors 100, 101, 102, and 103 in the normal state are set to the interval time t1 as shown in FIG. 4, but in the image forming apparatus, the output waveform is shown in FIG. As described above, when the output of the traveling system sensor 100 does not become high level even after the time obtained by adding the predetermined margin Δt3 to the time t1, the paper storage unit 11 is controlled under the control of the control unit 104. It is determined that a jam has occurred between the position and the registration position. In the image forming apparatus, when it is determined that the jam has occurred, the drive system is immediately stopped under the control of the control unit 104 as shown in FIG. As described above, the elevating link lever 106 is driven via the motor 105 to move the photosensitive drums 14B, 14Y, 14M, and 14C away from the transport belt 12 by a predetermined distance.

  Then, in the image forming apparatus, as shown in FIG. 7, the top cover 30 constituting the casing of the image forming apparatus is opened so that the inside can be visually recognized, and the user's hand reaches the place where the jam has occurred. Is removed from the image forming units 13B, 13Y, 13M, and 13C configured to be detachable from the image forming apparatus as described above until the image can be easily reached. The recording sheet S can be removed in the direction indicated by the arrow b.

  Here, in the image forming apparatus, the image forming units 13B, 13Y, 13M, and 13C are opposed to the photosensitive drum 14 in the image forming unit 13 that is not removed as the image forming units 13B, 13Y, 13M, and 13C are separated from the conveying belt 12 by a predetermined distance. The transfer roller 17 provided in this manner is placed at a position separated by a predetermined distance. Therefore, in the image forming apparatus, the recording paper S is not sandwiched between the photosensitive drum 14 and the transfer roller 17, and the load when removing the recording paper S can be almost eliminated.

  As described above, in the image forming apparatus, when it is determined that a jam has occurred under the control of the control unit 104, the drive system is stopped immediately, and the elevating link lever 106 is driven via the motor 105, whereby the photosensitive member is detected. The drums 14B, 14Y, 14M, and 14C are moved in a direction away from the conveyor belt 12 by a predetermined distance. As described above, when it is determined that a jam has occurred, the photosensitive drum 14 and the transfer roller 17 are controlled so as to be immediately separated without taking a long time. If the sheet is left in contact with the recording medium 12 through the pressure sensor 12, the pressure remains applied to the jammed recording sheet S and the photosensitive drum 14, and as a result, the toner changes in quality and the photosensitive element is changed. This is to prevent sticking to the surface of the drum 14.

  In the image forming apparatus, similarly to the travel system sensor 100, the control unit 104 controls the output of the travel system sensors 101 and 102 that detect whether or not the recording sheet S has reached a predetermined position. When determining whether or not a jam has occurred, it is determined that the outputs of the travel system sensors 101 and 102 do not become a high level even when a predetermined margin Δt3 is added to the paper-free interval time t1. It may be a material.

  On the other hand, in the image forming apparatus, the control unit 104 controls based on the output of the traveling system sensor 103 that detects whether or not the leading edge of the recording paper S has passed a predetermined position (fixing device 26). When judging the occurrence of a jam, the following operation is performed.

  FIG. 8 shows that the first recording sheet S of the printed matter composed of a plurality of recording sheets continuously causes jam on the bellows after the fixing process by the fixing unit 26 as shown in FIG. The output waveforms of the travel system sensors 100, 101, 102, and 103 when the paper is not fed are shown. In this case, the output waveform of the traveling system sensor 103 is at a high level indicating the presence of paper in response to the recording paper S reaching the traveling system sensor 103 after the fixing process is completed. Due to the inability to pass the traveling system sensor 103, the low level is not changed. Here, the output waveforms of the traveling system sensors 100, 101, 102, and 103 in the normal state are set to t2 when the paper is detected as shown in FIG. As shown in FIG. 8, if the output of the traveling system sensor 103 does not become low level even after the time obtained by adding the predetermined margin Δt 4 to the time t 2, the fixing is performed under the control of the control unit 104. It is determined that a jam has occurred after passing through the container 26. Also in this case, if the image forming apparatus determines that a jam has occurred, as described above, the drive system is immediately stopped under the control of the control unit 104, as shown in FIG. As described above, the elevating link lever 106 is driven via the motor 105 to move the photosensitive drums 14B, 14Y, 14M, and 14C away from the transport belt 12 by a predetermined distance. Thereby, in the image forming apparatus, the recording sheet S can be easily removed.

  Here, the image forming apparatus has a structure in which the image forming units 13B, 13Y, 13M, and 13C are moved instead of the conveyor belt 12. This is because the jam occurs and the inside of the image forming apparatus is undetermined. This is because the recording paper S on which the adhered toner is placed is adsorbed on the conveyance belt 12 and the toner may be scattered by vibrations caused by the movement of the conveyance belt 12 and vibrations of the drive motor in this state. is there. Accordingly, in the image forming apparatus, the image forming units 13B, 13Y, 13M, and 13C are moved so that the inside of the image forming apparatus is contaminated with the scattered toner, and the recording paper S is removed to remove the recording paper S. It is possible to reduce the possibility of toner adhering to a user who tries to contact the toner.

  Further, in the image forming apparatus, the elevating link lever 106 can selectively separate the photosensitive drums 14B, 14Y, 14M, and 14C in the plurality of image forming units 13B, 13Y, 13M, and 13C from the conveyance belt 12. Composed. That is, the image forming apparatus is configured to be able to select the image forming unit 13 of a necessary color according to the print mode.

  FIGS. 10A to 10C show how the plurality of image forming units 13B, 13Y, 13M, and 13C are selectively separated from the conveying belt 12. FIG. In the image forming apparatus, when operating in the color printing mode, as shown in FIG. 10A, the photosensitive drums 14B, 14Y, 14M, and 14C in all the image forming units 13B, 13Y, 13M, and 13C. The respective photosensitive drums 14B, 14Y, 14M, and 14C are brought into contact with the conveyor belt 12 by positioning the respective rotation shafts in the recesses in the lift link lever 106 having an uneven cross-sectional shape. In the image forming apparatus, when operating in the monochrome printing mode, as shown in FIG. 10B, the lifting link lever 106 is moved to the first position in the horizontal direction, and the image forming units 13Y and 13M are moved. , 13C, the rotation shafts of the photosensitive drums 14Y, 14M, and 14C are positioned on the convex portions of the lifting link lever 106, and the rotation shafts of the photosensitive drums 14B in the image forming unit 13B are moved to the lifting link lever 106. By positioning it in the recess, only the photosensitive drum 14B is brought into contact with the conveying belt 12, and the other photosensitive drums 14Y, 14M, and 14C are separated from the conveying belt 12. Further, in the image forming apparatus, when a jam occurs, as shown in FIG. 10C, the lifting link lever 106 is moved horizontally to the second position, and all the image forming units 13B and 13Y are moved. , 13M, and 13C, the rotation shafts of the photosensitive drums 14B, 14Y, 14M, and 14C are positioned on the convex portions of the lift link lever 106, so that the photosensitive drums 14B, 14Y, 14M, and 14C are transported. The state is separated from 12.

  As described above, in the image forming apparatus, the photosensitive drums 14B, 14Y, 14M, and 14C in the plurality of image forming units 13B, 13Y, 13M, and 13C can be selectively separated from the transport belt 12 according to the application. .

  As described above, in the image forming apparatus shown as the first embodiment of the present invention, if it is determined that a jam has occurred during the image forming operation, the image forming unit 13B, The photosensitive drums 14B, 14Y, 14M, and 14C in 13Y, 13M, and 13C are stopped in a state where they are separated from the transfer rollers 17B, 17Y, 17M, and 17C and the conveying belt 12, so that the photosensitive drums 14B, 14Y, 14M, and 14C are stopped. The recording paper S jammed between 14C and the transfer rollers 17B, 17Y, 17M, and 17C can be easily removed, and the toner is left on the surfaces of the photosensitive drums 14B, 14Y, 14M, and 14C when left for a long time. It can prevent sticking.

  Next, an image forming apparatus shown as the second embodiment will be described.

  In the image forming apparatus shown as the second embodiment, the power for driving the elevating link lever is not due to the use of a motor but utilizes the force generated when the top cover is opened. Therefore, in the description of the second embodiment, the same components as those in the description of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 11, the image forming apparatus shown as the second embodiment includes a fulcrum gear 121 provided in the vicinity of the rotation fulcrum of the top cover 30 and a gear formed integrally with the lifting link lever 106. Part 122.

  In such an image forming apparatus, when it is determined that a jam has occurred under the control of the control unit 104, the drive system is immediately stopped. In this state, in the image forming apparatus, as shown in FIG. 12, the fulcrum gear 121 is integrally formed with the lifting link lever 106 in accordance with the opening of the top cover 30 in the direction indicated by the arrow c. And the fulcrum gear 121 rotates in the direction indicated by the arrow d. Accordingly, in the image forming apparatus, the lifting link lever 106 moves in the horizontal direction, and the respective rotation shafts of the photosensitive drums 14B, 14Y, 14M, and 14C are positioned on the convex portions of the lifting link lever 106. Then, the photosensitive drums 14B, 14Y, 14M, and 14C are moved away from the transport belt 12 by a predetermined distance.

  In the image forming apparatus, as shown in FIG. 7, the image forming unit configured to be detachable from the image forming apparatus until the user can easily reach the place where the jam has occurred. Of the 13B, 13Y, 13M, and 13C, the minimum required number of image forming units can be removed and the recording paper S can be removed.

  As described above, in the image forming apparatus shown as the second embodiment of the present invention, the photoconductive drums 14B, 14Y, and 14C in the image forming units 13B, 13Y, 13M, and 13C according to the opening of the top cover 30. 14M and 14C can be separated from the transfer rollers 17B, 17Y, 17M, and 17C and the conveyor belt 12, and are clogged between the photosensitive drums 14B, 14Y, 14M, and 14C and the transfer rollers 17B, 17Y, 17M, and 17C. The recording paper S can be easily removed. In particular, in this image forming apparatus, since the elevating link lever 106 is driven by a mechanical configuration, it is not necessary to use a motor which is an expensive electrical component, and can be realized only by an inexpensive gear configuration. Price can be achieved.

  Next, an image forming apparatus shown as a third embodiment will be described.

  The image forming apparatus shown as the third embodiment takes measures against problems that occur when realizing the image forming apparatus shown as the first embodiment and the second embodiment. By implementing in combination with the first embodiment or the second embodiment, the effect is enhanced. Accordingly, in the description of the third embodiment, the same reference numerals are given to the same configurations as those in the first embodiment and the second embodiment, and the detailed description thereof is omitted. To do.

  First, problems that occur when realizing the image forming apparatus shown as the first embodiment and the second embodiment will be described.

  Usually, the image forming apparatus is used in a state where the surface of the photosensitive drum 14 is charged to several hundred volts or more. Accordingly, in the image forming apparatus, when the operation is temporarily stopped from that state and the image forming unit 13 is attached or detached, or when the photosensitive drum 14 in which surface charges are accumulated is separated from the conveying belt 12, the photosensitive member. It is conceivable that a discharge with respect to a conductor provided in the vicinity is generated by the surface charge of the drum 14. In addition, since a current flows on the surface of the photosensitive drum 14 during discharge, the characteristics of the photosensitive drum 14 may be damaged.

  The image forming apparatus shown as the third embodiment takes measures to prevent such a discharge shock.

  13 and 14 are side sectional views of the image forming unit 13 in the image forming apparatus shown as the third embodiment. The image forming unit 13 includes a discharge body 201 for forcibly discharging the surface charge of the photosensitive drum 14. The discharge body 201 is formed integrally with two shafts 203 and 204 that rotate about a rotation fulcrum 202. The discharge body 201 is urged in the direction of arrow e in FIG. As shown in FIG. 13, the discharge body 201 contacts the surface of the photosensitive drum 14 by rotating the shafts 203 and 204 around the rotation fulcrum 202 in the direction of the arrow f in FIG. On the other hand, when the shafts 203 and 204 are rotated in the reverse direction, the shafts are moved away from the surface of the photosensitive drum 14. More specifically, the discharge body 201 is formed in various shapes according to the shape of the image forming unit 13, the shape of the image forming apparatus, and the like. For example, as shown in FIG. 16 is a shape that can be brought into contact with or separated from a part of the surface in the direction, or a shape that can be brought into contact with or separated from substantially the entire surface in the longitudinal direction of the photosensitive drum 14 as shown in FIG. The surface charge is discharged by contact.

  Such an image forming apparatus performs the following operation when the photosensitive drum 14 is in contact with the conveyance belt 12 or when the photosensitive drum 14 is separated from the conveyance belt 12.

  FIG. 17A shows the image forming apparatus in a state where the photosensitive drum 14 is in contact with the transport belt 12, and FIG. 17B shows an enlarged view of the image forming unit 13 in the same state.

  In the image forming apparatus, when the removed image forming section 13 is set, as shown in FIG. 17B, the shaft 203 comes into contact with the abutting section 206 provided inside the image forming apparatus. The force in the direction indicated by the arrow g in FIG. As a result, the discharge body 201 formed integrally with the shafts 203 and 204 that rotate about the rotation fulcrum 202 is fixed at one end to the housing of the image forming unit 13, and the arrow in FIG. It moves to a position away from the photosensitive drum 14 against the biasing force of the spring 205 biased in the direction indicated by e. In the image forming apparatus, when the discharge body 201 exists at this position, the image forming process is not adversely affected by the discharge. That is, in the image forming apparatus, in this state, the surface charge of the photosensitive drum 14 does not fly to the discharge body 201.

  On the other hand, in the image forming apparatus, when the operation is temporarily stopped due to the occurrence of a jam or the like and the image forming unit 13 is separated from or removed from the transport belt 12, the operation is performed as follows. FIG. 18A shows the image forming apparatus in a state where the photosensitive drum 14 is separated from the conveyance belt 12, and FIG. 18B shows the image forming unit 13 in the same state in an enlarged manner.

  In this case, in the image forming apparatus, the force indicated by the arrow g in FIG. 17B does not act on the shaft 203, so that the force is applied in the direction indicated by the arrow e as shown in FIG. The biased shaft 204 moves together with the discharge body 201 in a direction in contact with the surface of the photosensitive drum 14. Thereby, in the image forming apparatus, the surface charge of the photosensitive drum 14 can be discharged via the discharge body 201. In the image forming apparatus, when the discharge body 201 is in direct contact with the photosensitive drum 14 and discharged directly to the frame ground, a discharge shock is caused and the photosensitive drum 14 is damaged. Therefore, an element 207 having a predetermined resistance characteristic is interposed between the discharge body 201 and the frame ground.

  As described above, in the image forming apparatus shown as the third embodiment of the present invention, when the photosensitive drum 14 in a state where surface charges are accumulated is moved in the direction away from the conveying belt 12, the photosensitive drum 14 is moved. The discharge body 201 via the element 207 is brought into contact with the surface of the photosensitive drum 14 so that the surface charge of the body drum 14 does not fly directly to a conductor having the same level as the frame ground, thereby eliminating static electricity without causing a discharge shock. It is possible to prevent the photosensitive drum 14 from being damaged. In this image forming apparatus, not only when a jam occurs, but also when the image forming unit 13 is removed from the image forming apparatus at an arbitrary timing such as when consumables are replaced, the discharge body 201 is exposed to light. The effect of protecting the photosensitive drum 14 by contacting the surface of the photosensitive drum 14 is also achieved.

  The present invention is not limited to the embodiment described above. For example, in the above-described embodiment, the case where the present invention is applied to a tandem color image forming apparatus has been described. However, the present invention can be applied to any apparatus that performs image formation. The present invention is suitable for application to various printers including monochrome printers, facsimile machines, copying machines, and apparatuses having these functions in combination.

  Thus, it goes without saying that the present invention can be modified as appropriate without departing from the spirit of the present invention.

1 is a cross-sectional view showing a schematic configuration of an image forming apparatus shown as a first embodiment of the present invention. FIG. 2 is a block diagram showing a configuration of a control system in the image forming apparatus shown as the first embodiment of the present invention. FIG. 2 is a cross-sectional view of a main part illustrating a schematic configuration of the image forming apparatus illustrated as the first embodiment of the present invention, and illustrates a state in which the image forming unit is in contact with a conveyance belt. FIG. 2 is a cross-sectional view of a main part showing a schematic configuration of the image forming apparatus shown as the first embodiment of the present invention, and shows a state in which the image forming part is separated from the conveying belt. It is a figure which shows the output waveform of the traveling system sensor in the case of performing normal continuous image forming operation. It is a figure which shows the output waveform of a traveling system sensor when a recording paper is not fed from a paper storage part. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus illustrated as a first embodiment of the present invention, and is a diagram illustrating a state immediately after a jam occurs. 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus shown as a first embodiment of the present invention, and shows a state in which a top cover is opened and an image forming unit is removed. FIG. 6 is a diagram illustrating an output waveform of a traveling system sensor when a recording sheet causes a jam on the bellows after the fixing process is completed and is not normally discharged. 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus shown as a first embodiment of the present invention, and shows a state immediately after a recording sheet causes a jam on a bellows after completion of fixing processing. 1 is a cross-sectional view of a main part illustrating a schematic configuration of an image forming apparatus illustrated as a first embodiment of the present invention, and illustrates a state when operating in a color printing mode. 1 is a cross-sectional view of a main part illustrating a schematic configuration of an image forming apparatus illustrated as a first embodiment of the present invention, and illustrates a state when operating in a monochrome printing mode. 1 is a cross-sectional view of a main part illustrating a schematic configuration of an image forming apparatus illustrated as a first embodiment of the present invention, and is a diagram illustrating a state when a jam occurs. FIG. 4 is a cross-sectional view of a main part illustrating a schematic configuration of an image forming apparatus illustrated as a second embodiment, and illustrates a state in which the image forming unit is in contact with a conveyance belt. FIG. 4 is a cross-sectional view of a main part illustrating a schematic configuration of an image forming apparatus illustrated as a second embodiment of the present invention, and a state in which the image forming unit is separated from a conveyance belt. FIG. 6 is a side sectional view showing a schematic configuration of an image forming unit in an image forming apparatus shown as a third embodiment of the present invention, and showing a state where a discharge body is in contact with the surface of a photosensitive drum. FIG. 6 is a side sectional view showing a schematic configuration of an image forming unit in an image forming apparatus shown as a third embodiment of the present invention, and is a diagram showing a state where a discharge body is separated from the surface of a photosensitive drum. It is a figure which shows schematic structure of the discharge body made into the shape which can be contacted / separated with respect to the one part surface in the longitudinal direction of a photoconductor drum. It is a figure which shows schematic structure of the discharge body made into the shape which can contact / separate with respect to the substantially whole surface in the longitudinal direction of a photoconductor drum. FIG. 10 is a cross-sectional view of a main part showing a schematic configuration of an image forming apparatus shown as a third embodiment of the present invention, and shows a state where the image forming part is in contact with a conveyance belt. FIG. 3 is a side cross-sectional view illustrating a schematic configuration of an image forming unit, and illustrates a state where a photosensitive drum is in contact with a conveyance belt. FIG. 10 is a cross-sectional view of a main part illustrating a schematic configuration of an image forming apparatus illustrated as a third embodiment of the present invention, and a state in which the image forming unit is separated from a conveyance belt. FIG. 3 is a side cross-sectional view illustrating a schematic configuration of an image forming unit, and is a diagram illustrating a state in which a photosensitive drum is separated from a conveyance belt.

Explanation of symbols

11 Paper storage unit 12 Conveyor belt 13, 13B, 13Y, 13M, 13C Image forming unit 14, 14B, 14Y, 14M, 14C Photosensitive drum 15B, 15Y, 15M, 15C Charge roller 16B, 16Y, 16M, 16C LED head 17 , 17B, 17Y, 17M, 17C Transfer roller 18B, 18Y, 18M, 18C Developing roller 19B, 19Y, 19M, 19C Developing blade 20B, 20Y, 20M, 20C Sponge roller 21B, 21Y, 21M, 21C Toner tank 22B, 22Y, 22M, 22C Cleaning blade 23B, 23Y, 23M, 23C Screw shaft 24, 25 Roller 26 Fixing device 30 Top cover 100, 101, 102, 103 Traveling system sensor 104 Control unit 105 Motor 106 Lifting phosphorus Lever 107 idle gear 108,122 gear portion 121 supporting point gear 201 discharger 202 pivot point 203, 204, shaft 205 spring 206 abutting section 207 element S recording sheet

Claims (5)

An image forming apparatus that forms an image by fixing a developer on a predetermined recording medium,
Belt conveying means for placing and conveying the recording medium;
An image forming unit configured to be detachable from the image forming apparatus and including an image carrier that carries an image formed by the developer;
Detecting means for detecting a conveyance state of the recording medium;
Control means for determining a conveyance failure of the recording medium based on a detection result of the detection means;
Moving means for moving the image carrier, which has been in contact with the belt conveying means, in a direction away from the belt conveying means by a predetermined distance in response to the conveyance failure of the recording medium being determined by the control means. An image forming apparatus comprising: When the control unit determines the conveyance failure of the recording medium based on the detection result of the detection unit, the control unit moves the image carrier in a direction away from the belt conveyance unit by a predetermined distance without taking time. The image forming apparatus according to claim 1, wherein the moving unit is controlled. A plurality of the image forming means including the image carrier are provided,
The moving means selectively moves a part of the plurality of image carriers in a direction away from the belt conveying means by a predetermined distance at the first position, and moves to the second position. The image forming apparatus according to claim 1, wherein all of the plurality of image carriers are moved in a direction away from the belt conveying unit by a predetermined distance. The moving means moves the image carrier in a direction away from the belt conveying means by a predetermined distance in response to opening a cover constituting the housing of the image forming apparatus. The image forming apparatus according to any one of claims 1 to 3. The image forming means has a discharge body for discharging the surface charge of the image carrier,
In the image forming apparatus, when the image carrier is moved away from the belt conveyance means by a predetermined distance, the image carrier is brought into contact with the surface of the image carrier, and the image carrier is conveyed to the belt. 5. The discharge body moving means for moving the discharge body in a direction away from the surface of the image carrier when contacting the means. 5. Image forming apparatus.