JP2006113283A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent contamination on a photoreceptor drum or C-stage set deformation of a transfer roller when an image forming apparatus is not used for a long period, as well as to improve user's convenience for a package of an apparatus loaded with a cartridge to prevent paper clogging or image failure caused when a user forgets to remove a sheet material or a spacer between a photoreceptor drum and a transfer roller or forgets to cancel a separated state between them. <P>SOLUTION: In the image forming apparatus having a transfer device to transfer a toner image on a latent image bearing member onto a recording material, the transfer member is moved with respect to the latent image bearing member so as to control the transfer pressure between the latent image bearing member and the transfer member to be lower than the transfer pressure on forming an image. Even when the transfer pressure is controlled to low, the transfer member is automatically moved as linked when the latent image bearing member or the transfer member is driven to rotate by a driving source, and the transfer pressure for image formation is applied between the latent image bearing member and the transfer member. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a laser beam printer, and a facsimile using an electrophotographic process.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a laser beam printer, a developing device that develops a latent image drawn by laser light or the like, a transfer unit that transfers a developed toner image onto a recording material, and a transferred toner image. The mainstream is one provided with a fixing device for fixing on a recording material.

  FIG. 11 shows a conventional laser beam printer as a representative example. Hereinafter, components of the laser beam printer of FIG. 11 will be described. In the printer main body (image forming apparatus main body), a laser scanner 1, a photosensitive drum 2, a printing process unit 5 including a primary charger 3 and a developing roller 4, a transfer roller 6, a fixing device 7, a conveying roller pair 8, a supply roller A paper cassette 9 and a paper feed roller 10 are installed.

  The sheet-like recording material P stacked and stored in the paper feed cassette 9 is fed by a paper feed roller 10 that rotates counterclockwise, is guided to the transport metal plate 11, and is sent to the nip portion of the transport roller pair 8. .

  Next, the recording material P is sent between the photosensitive drum 2 and the transfer roller 6 by the conveying roller pair 8. The photosensitive drum 2 rotates clockwise and is charged to a desired potential by the primary charger 3. Then, an electrostatic latent image is sequentially formed on the outer peripheral surface by the laser light L of the laser scanner 1, and then the electrostatic latent image is developed by the developing roller 4 to form a toner image. The toner images on the photosensitive drum 2 are sequentially transferred from the transfer roller 6 to the recording material P sent between the photosensitive drum 2 and the transfer roller 6. Toner and paper dust remaining on the photosensitive drum 2 at the time of transfer are removed by the cleaning member 12.

  The recording material P onto which the toner image has been transferred in this way is sent to the fixing device 7 where it is heated and pressurized to fix the toner image on the recording material P. Thereafter, the recording material P is sent to the paper discharge roller 14 by the fixing paper discharge conveyance roller pair 13 and then discharged onto the paper discharge tray 15 on the upper surface of the printer main body by the paper discharge roller 14.

  In this conventional laser beam printer, the units such as the process cartridge (printing process unit) 5 and the fixing device 7 are consumable parts and need to be replaced several times during the life of the product. As the above-described fixing device, a heat roller type or a film heating type device is widely used.

  FIG. 12 shows a side view of a transfer portion of a conventional image forming apparatus. Reference numeral 2 shown in FIG. 12 denotes a photosensitive drum in which an organic photoreceptor (OPC) layer is provided on the surface of an aluminum cylinder. The photosensitive drum 2 is uniformly charged by the primary charger 3 and then exposed to an image to form a latent image. The developing roller 4 performs reversal development to form a toner image on the surface thereof. The toner image is transferred onto the paper P that is a recording material conveyed along the transfer guide 16. In the transfer, the photosensitive drum 2 and the transfer roller 6 are applied to a transfer roller 6 having a conductive elastic layer 18 on a metal core 17 by applying a voltage having a polarity opposite to the charging polarity of the toner image from a high voltage power source 19. In the transfer nip N formed in The voltage applied to the transfer roller is changed by the CPU 20 in accordance with the resistance value of the transfer roller, or the magnitude of the voltage is switched and controlled during transfer and non-transfer or when stopped.

  In recent years, it has become mainstream to mount cartridges that are transported and provided to the user while the process cartridge is mounted on the image forming apparatus. In this case, the image forming apparatus is not used for a long time from when the image forming apparatus is shipped until it reaches the end user. When the process cartridge is mounted and the image forming apparatus is not used for a long time, the following problems occur at the nip portion between the photosensitive drum and the transfer roller.

1) Drum contamination When low molecular weight components, vulcanizing agents, plasticizers, etc. of the material rubber existing in the roller ooze out on the surface of the transfer roller, and the transfer roller is left in contact with the photosensitive drum for a long time. The material exuded on the surface of the photosensitive drum adheres to disturb the image. In a severe case, the surface of the photosensitive drum is reacted / modified and whitened, and all subsequent images are disturbed. .

2) Transfer roller C set Since the same portion of the elastic roller is pressed against a rigid body called a photosensitive drum for a long time, the elastic member is permanently deformed and C set deformation occurs. This C set deformation causes a paper jam or a transfer failure of the recording material being conveyed. In addition, since the C set deformed flat portion of the transfer roller rotates momentarily during conveyance of the recording material, a horizontal streak occurs in the transfer roller cycle in an image with a high printing rate.

  In addition, the cartridge-packed main body is often placed in a harsh environment such as a high-temperature and high-humidity environment during transportation, and the above-mentioned problems are more likely to occur. Therefore, a shipment form is often adopted in which a sheet material is sandwiched between the photosensitive drum and the transfer roller, or a spacer is inserted to bring the photosensitive drum and the transfer roller into a light pressure or separated state. Alternatively, as shown in Patent Document 1, the present situation is that the above problem is solved by providing a separation mechanism for separating the transfer roller from the photosensitive drum.

JP-A-8-171292

  However, the conventional example has the following drawbacks.

  That is, when a sheet material or a spacer is sandwiched between the photosensitive drum and the transfer roller, it is necessary for the user to perform a complicated operation of removing the sheet material or the spacer before using the image forming apparatus. If the user forgets to remove the sheet material or spacer, that is, if the user starts using the image forming apparatus without bringing the photosensitive drum and the transfer roller into contact with each other with a normal transfer pressure, a paper jam or transfer failure may occur. It causes image defects. Also, when the photosensitive drum and the transfer roller are separated by a separation mechanism that separates the photosensitive drum and the transfer roller, when the user forgets to release the separation and starts using the image forming apparatus, Needless to say, the same problem occurs.

  Accordingly, an object of the present invention is to prevent the photosensitive drum from being contaminated and the transfer roller C set from being generated when the image forming apparatus is not used for a long period of time, and to improve the usability when the cartridge is mounted and packed. This is to prevent the occurrence of a paper jam or an image defect that occurs when the sheet material or spacer between the transfer rollers is forgotten to be removed or when the separation is forgotten.

  In order to achieve the above object, the present invention provides an image forming apparatus including a transfer device that transfers a toner image on a latent image carrier to a recording material, by moving a transfer member relative to the latent image carrier. The transfer pressure between the latent image carrier and the transfer member can be set to a light pressure state smaller than the transfer pressure at the time of image formation, and the drive source can be set even if the transfer pressure is set to a light pressure state. The transfer member automatically moves in conjunction with rotation of the latent image carrier or the transfer member by driving from the transfer member, so that the transfer pressure during image formation is between the latent image carrier and the transfer member. It is characterized by hanging.

  According to the present invention, in the image forming apparatus including a transfer device that transfers the toner image on the latent image carrier to a recording material, the latent image carrier is moved by moving a transfer member relative to the latent image carrier. It is possible to set the body and the transfer member in a separated state, and the transfer member has a drive gear at an end, and when set in the separated state, the drive gear of the transfer member is The distance between the center axes of both gears is set so that the drive gear of the latent image carrier or the drive gear of the main body of the image forming apparatus can be kept in mesh with each other. When the transfer member rotates, the transfer member automatically moves while the drive gear of the transfer member meshes with the drive gear of the latent image carrier or the drive gear of the image forming apparatus main body. Wherein the transfer pressure at the time of image formation is applied between the body and the transfer member.

  Further, the present invention provides an image forming apparatus including a transfer device that transfers a toner image on a latent image carrier to a recording material, and includes a separation member that separates the latent image carrier and a transfer member, The latent image carrier and the transfer member can be set in a separated state by a separation member, and the latent image carrier or the transfer member is rotated by driving from a driving source even in the separated state. The transfer member is automatically moved in conjunction with the transfer member, and a transfer pressure during image formation is applied between the latent image carrier and the transfer member.

  According to the present invention, when the image forming apparatus is not used for a long period of time, it is possible to prevent occurrence of image defects due to drum contamination or transfer roller C set by releasing the pressure applied to the photosensitive drum and the transfer roller. . In addition, since the normal transfer pressure is automatically applied at the first rotation when the power is turned on, it is possible to prevent the occurrence of a paper jam or an image defect due to the user forgetting to remove the transfer pressure release member. Furthermore, it is not necessary for the user to remove the transfer pressure release member before using the image forming apparatus, leading to improved usability.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

<Embodiment 1>
FIG. 1 is a diagram showing the operation of the transfer roller in the present embodiment. The transfer roller 6 of the present embodiment uses a metal core made of aluminum as the core metal 17 and a semiconductive sponge mainly composed of NBR hydrin rubber as the elastic layer 18. The outer diameter is 14.5 mm, the core diameter is 6 mm, and the rubber length in the longitudinal direction is 220 mm. Further, the transfer roller is driven to rotate with the photosensitive drum 2 when the cartridge is mounted.

  FIG. 1A is a view showing the positional relationship between the photosensitive drum and the transfer roller when the image forming apparatus is used (hereinafter referred to as state a). A contact pressure against the photosensitive drum 2 is applied to the transfer roller 6 via a pressure bearing 22 by a transfer spring 21. The transfer spring is fixedly held up and down by the boss 23 of the pressure bearing and the boss 24 protruding from the seat surface. In the state a, as shown in FIG. 1A, the upper and lower bosses 23 and 24 are positioned in the vertical direction with respect to the transfer roller, and the contact pressure of the transfer roller to the photosensitive drum is applied by the transfer spring. It is hanging. The contact pressure in state a becomes the transfer pressure during printing.

  A cored bar holding member 25 is provided at both ends of the transfer roller, and an L-shaped groove 26 is cut out in the cored bar holding member. From the position shown in FIG. 1A, when the cartridge is not mounted, the transfer roller core metal is held at both ends, pushed down, and moved to the upstream side in the recording material conveyance direction (in the direction of the arrow of the metal core). The roller can be set to the position shown in FIG. 1B (hereinafter referred to as state b). When the state b is set, the transfer roller moves to the upstream side in the recording material conveyance direction with respect to the photosensitive drum as compared with the state a. Here, an angle formed by a straight line drawn vertically downward through the center of the photosensitive drum and a straight line connecting the photosensitive drum center and the transfer roller center is defined as a contact angle of the transfer roller with respect to the photosensitive drum.

  In the state a, as shown in FIG. 1A, the transfer roller center is positioned on a straight line drawn vertically downward from the photosensitive drum center, so that the contact angle of the transfer roller with respect to the photosensitive drum is 0 °. On the other hand, in the state b, as shown in FIG. 1B, the contact angle of the transfer roller with respect to the photosensitive drum is θ, and in this embodiment, θ is set to be 30 °. That is, in the state a and the state b, the contact angle of the transfer roller with respect to the photosensitive drum is shifted by 30 °. In the state b, as shown in FIG. 1B, the pressure bearing 22 together with the transfer roller 6 is positioned upstream of the photosensitive drum 2 in the recording material conveyance direction, and the upper and lower bosses 23, Reference numeral 24 denotes a transfer spring 21 fixedly held in an oblique direction with respect to the transfer roller. For this reason, the transfer pressure has escaped, and the distance between the central axes of the photosensitive drum and the transfer roller is set to be larger, so that the transfer pressure is smaller than in the state a.

  A schematic view of the longitudinal end of the transfer roller of the present embodiment is shown in FIG. The metal core holding member 25 is provided outside the pressure bearing 22, and the user can easily hold the metal core end by covering the metal core end with a cap 27. FIG. 2A shows the state a where the transfer pressure during printing is applied, and FIG. 2B shows the state b where the transfer pressure is light. It can be seen that the transfer roller cored bar is held by the groove portion of the cored bar holding member 25, and the transfer roller is located in a lower position (a direction away from the drum) in the state b than in the state a.

  In state b, the photosensitive drum rotates clockwise and the transfer roller receives a driven drive from the photosensitive drum at the time of multiple pre-rotation when the image forming apparatus is powered on or at the time of pre-rotation at the first printing. Here, a rubber member 40 is fitted below the groove portion of the cored bar holding member on the upstream side in the recording material conveyance direction so as to increase the sliding resistance with the transfer roller cored bar. For this reason, when the transfer roller is driven by the photosensitive drum, the transfer roller mandrel cannot rotate, so that the transfer roller is pushed toward the downstream side in the recording material conveyance direction (the arrow direction in FIG. 1B). Pressure is applied, and the metal cores at both ends of the transfer roller move to the position shown in FIG. 1A along the groove of the metal core holding member. At the position shown in FIG. 1A, an upward transfer pressure is applied by the transfer spring, so that the transfer roller does not return to the position shown in FIG. 1B when the image forming apparatus is used thereafter.

  In order to set the transfer roller to the state b, as described above, when the cartridge is not mounted, the both ends of the transfer roller cored bar are held and pushed down to move upstream in the recording material conveyance direction. In the image forming apparatus of the present embodiment, it is recommended to set the state b when the user does not use the image forming apparatus for a long period of time or when the user transports the cartridge with the cartridge mounted. This can reduce drum contamination and C-set deformation of the transfer roller when the image forming apparatus is not used for a long period of time. Also, when the image forming apparatus is left for a long period of time and then used again, the transfer pressure is automatically applied during printing at the first rotation, so the paper when the user prints without releasing the transfer pressure release mechanism. Occurrence of image defects such as clogging and transfer defects can be prevented.

  Further, in the present embodiment, the cartridge mounting and transport is performed, and the image forming apparatus is shipped in the state b. With the transfer pressure release mechanism of the present embodiment, the transfer pressure can be easily released at the time of shipment, and drum contamination and C-set deformation of the transfer roller during cartridge mounting and transportation can be reduced. In addition, since the transfer pressure at the time of printing is automatically applied by the user, it is possible to prevent the occurrence of image defects such as paper jams and transfer defects when the user performs printing without releasing the transfer pressure release mechanism. it can. Furthermore, there is no need for a separation member such as a sheet material or a spacer, which is not only cost-effective, but also it is not necessary for the user to perform a complicated operation of removing the transfer pressure release member before using the image forming apparatus. Improvement of usability can be realized.

  In the present embodiment, the core metal holding member is provided with the L-shaped groove, but the two grooves may not intersect at a right angle. In addition, the groove portion in which the transfer roller cored bar is fitted and slid and rotated when the image forming apparatus is used at the position shown in FIG. 1A is cut out in a semicircular shape to reduce sliding resistance. As the material of the core metal holding member, it is desirable to use a mold member such as POM (polyacetal) resin or PPS (polyphenylene sulfide) resin which is excellent in durability, wear resistance and workability. In this embodiment, the distance between the central axes of the photosensitive drum and the transfer roller is set to be larger than that in the state a in order to reduce the transfer pressure applied in the state b. Since the transfer pressure escapes only by moving the roller, it is not always necessary to change the distance between the central axes of the photosensitive drum and the transfer roller in the states a and b.

  As described above, when the image forming apparatus is not used for a long period of time, it is possible to prevent the occurrence of image defects due to drum contamination or the transfer roller C set by releasing the pressure applied to the photosensitive drum and the transfer roller. Further, since the transfer pressure at the time of printing is automatically applied at the first rotation when the power is turned on, it is possible to prevent the occurrence of a paper jam or an image defect due to the user forgetting to release the transfer pressure release mechanism. Further, since a sheet material, a spacer, and the like are unnecessary, and it is not necessary for the user to release the transfer pressure releasing mechanism before using the image forming apparatus, the usability is improved.

<Embodiment 2>
Next, a second embodiment of the present invention will be described. Note that a description of the same parts as those in the first embodiment will be omitted.

  In the first embodiment, an example in which the transfer roller is driven to rotate with the photosensitive drum has been described. However, in such a configuration, since the photosensitive drum and the transfer roller rotate at the same speed, the character is omitted. May occur.

  FIG. 3 shows an enlarged view of the toner image after being transferred to the recording material. The left end of FIG. 3 is a normal toner image, and on the right side, only the outline portion 28 of the toner image is transferred, and the central portion 29 is missing due to transfer failure. This phenomenon is called hollowing out and is known to occur easily with vertical thin lines. In order to prevent this hollowing out, one means is to improve the transferability of the character center by rotating the transfer roller quickly against the drum and rubbing it. As a configuration for rotationally driving the transfer roller with a peripheral speed difference from the drum, the drum driving gear is a stepped gear as shown in FIG. 4A, or the opposite side of the drum driving gear as shown in FIG. It is conceivable to provide a transfer driving gear on the surface.

  The drum drive gear 32 is driven from the main motor of the main body, and the transfer drive gear 31 attached to one side of the transfer roller is driven from the drum gear 30. Here, since the drum driving gear 32 and the transfer driving gears 30 and 31 have different gear pitches, a circumferential speed difference is generated between the drum and the transfer roller. That is, the gear pitch of the transfer drive gear 31 is slightly larger than the gear pitch of the drum drive gear 32, and the transfer roller rotates one or more times with respect to one rotation of the drum. In order to improve the hollowing out, it is known that the rotation speed of the transfer roller should be about 102 to 105% faster than that of the drum. 4 (b), which is configured to rotate with a peripheral speed difference of 105% with respect to the drum.

  FIG. 5A is a diagram showing the positional relationship between the photosensitive drum and the transfer roller when the image forming apparatus according to the present embodiment is used (hereinafter referred to as state a). A contact pressure against the photosensitive drum 2 is applied to the transfer roller 6 via a pressure bearing 22 by a transfer spring 21. The transfer spring is fixedly held up and down by the boss 23 of the pressure bearing and the boss 24 protruding from the seat surface. In the state a, as shown in FIG. 5A, the upper and lower bosses 23 and 24 are positioned in the vertical direction with respect to the transfer roller, and the contact pressure of the transfer roller to the photosensitive drum is applied by the transfer spring. It is hanging. The contact pressure in state a becomes the transfer pressure during printing.

  Reference numeral 30 denotes a drum gear attached to the end of the photosensitive drum, and reference numeral 31 denotes a transfer driving gear attached to the transfer roller core, which mesh with each other. A cored bar holding member 25 is provided at both ends of the transfer roller, and an L-shaped groove 26 is cut out in the cored bar holding member. From the position shown in FIG. 5A, when the cartridge is not mounted, both ends of the transfer roller cored bar are held down and moved to the upstream side in the recording material conveyance direction (in the direction of the arrow of the cored bar in the figure), thereby transferring The roller can be set to the position shown in FIG. 5B (hereinafter referred to as state b).

  When the state b is set, the transfer roller moves to the upstream side in the recording material conveyance direction with respect to the photosensitive drum as compared with the state a. In the state b, as shown in FIG. 5B, the pressure bearing 22 is located on the upstream side in the recording material conveyance direction with respect to the photosensitive drum 2 together with the transfer roller 6, and the upper and lower bosses 23, 24 are A transfer spring 21 is fixedly held in an oblique direction with respect to the transfer roller. Further, the distance between the central axes of the photosensitive drum and the transfer roller is set to be larger than the sum of the radii of the two, and in the state b, the transfer roller is separated from the surface of the photosensitive drum. Further, even when the photosensitive drum and the transfer roller are in the separated state, the distance between the center axes of both gears is set so that the drum gear 30 and the transfer drive gear 31 can maintain the meshed state.

  A schematic diagram of the longitudinal end portion of the transfer roller of the present embodiment is shown in FIG.

  The metal core holding member 25 is provided outside the pressure bearing 22, and the user can easily hold the metal core end by covering the metal core end with a cap 27. FIG. 6A shows a state a in which a transfer pressure is applied during printing, and FIG. 6B shows a state b in which the photosensitive drum and the transfer roller are separated from each other. As described above, the transmission means is configured so that the rotation is transmitted from the photosensitive drum to the transfer roller even when the transfer roller is in the state b separated from the surface of the photosensitive drum.

  When the photosensitive drum rotates clockwise and the transfer drive gear receives a driving force from the drum gear at the time of the pre-multi-rotation when the image forming apparatus is turned on from the state b or the pre-rotation at the time of first printing. At the same time, the cored bar at both ends of the transfer roller is moved along the groove portion of the cored bar holding member in response to the pressing force downstream in the recording material conveyance direction (the arrow direction in FIG. 5B). ) Position. At the position shown in FIG. 5A, an upward transfer pressure is applied by the transfer spring, so that the transfer roller does not return to the position shown in FIG. 5B when the image forming apparatus is used thereafter.

  In the image forming apparatus of the present embodiment, it is recommended to set the state b when the user does not use the image forming apparatus for a long period of time or when the user transports the cartridge with the cartridge mounted. Accordingly, it is possible to prevent drum contamination and C-set deformation of the transfer roller when the image forming apparatus is not used for a long period of time. In the first embodiment, the transfer pressure is light. However, in this embodiment, the photosensitive drum and the transfer roller are separated from each other, so that drum contamination and C-set deformation of the transfer roller are completely prevented. Is possible. Also, when the image forming apparatus is left for a long period of time and then used again, the transfer pressure is automatically applied during printing at the first rotation, so the paper when the user prints without releasing the transfer pressure release mechanism. Occurrence of image defects such as clogging and transfer defects can be prevented.

  Further, in the present embodiment, the cartridge mounting and transport is performed, and the image forming apparatus is shipped in the state b. With the transfer pressure release mechanism according to the present embodiment, the transfer pressure can be easily released at the time of shipment, and drum contamination and C-set deformation of the transfer roller during cartridge mounting and transportation can be completely prevented. . In addition, since the transfer pressure at the time of printing is automatically applied by the user, it is possible to prevent the occurrence of image defects such as paper jams and transfer defects when the user performs printing without releasing the transfer pressure release mechanism. it can. Furthermore, there is no need for a separation member such as a sheet material or a spacer, which is not only cost-effective, but also it is not necessary for the user to perform a complicated operation of removing the transfer pressure release member before using the image forming apparatus. Improvement of usability can be realized.

  In the present embodiment, the core metal holding member is provided with the L-shaped groove, but the two grooves may not intersect at a right angle. Further, in the groove portion in which the transfer roller cored bar is fitted and slid and rotated at the position of FIG. 5A when the image forming apparatus is used, the groove is cut out in a semicircular shape to reduce sliding resistance. As the material of the core metal holding member, it is desirable to use a mold member such as POM (polyacetal) resin or PPS (polyphenylene sulfide) resin which is excellent in durability, wear resistance and workability. Although an example in which the transfer roller is driven from the photosensitive drum has been described, the present invention can be applied even when the transfer roller is driven from the main motor of the main body. In this case, the distance between the central axes of both gears is set so that the main motor gear and the transfer drive gear of the main body can be kept engaged with each other in the state b.

  As described above, when the image forming apparatus is not used for a long time, the photosensitive drum and the transfer roller are separated from each other, so that the occurrence of image defects due to drum contamination or the transfer roller C set can be completely prevented. Further, since the transfer pressure at the time of printing is automatically applied at the first rotation when the power is turned on, it is possible to prevent the occurrence of a paper jam or an image defect due to the user forgetting to release the transfer pressure release mechanism. Further, since a sheet material, a spacer, and the like are unnecessary, and it is not necessary for the user to release the transfer pressure releasing mechanism before using the image forming apparatus, the usability is improved.

<Embodiment 3>
Next, a third embodiment of the present invention will be described. In addition, description is abbreviate | omitted about the location similar to Embodiment 1,2.

  In this embodiment, a movable spacer is provided in a transfer nip portion formed by a photosensitive drum and a transfer roller. FIG. 7 is a diagram showing the operation of the spacer in the present embodiment. FIG. 7A is a diagram showing the positional relationship among the photosensitive drum, the transfer roller, and the movable spacer when the image forming apparatus is used (hereinafter referred to as state a).

  The movable spacer 33 is provided at both ends of the transfer roller core 17 and has a left-right symmetrical L-shaped groove 34 and a lever 35. The user holds the movable spacer lever 35 from the position shown in FIG. 7A and rotates it 180 ° in either the upstream or downstream direction of the recording material conveying direction when the cartridge is not mounted. The movable spacer can be fixed at the position shown in FIG. 7B by fitting 17 to the position shown in FIG. At this time, the spacer portion 36 of the movable spacer projects inward from the end of the transfer roller rubber to a position of 7 mm in the longitudinal direction. If the cartridge is mounted in this state, a gap is formed between the photosensitive drum and the transfer roller as shown in FIG. 7B, and it is possible to set the separated state (hereinafter referred to as state b). ).

  In the state b, the photosensitive drum rotates clockwise and the transfer roller rotates counterclockwise at the time of multiple rotations before the image forming apparatus is powered on or at the time of the first printing, and the movable spacer is the photosensitive drum. Alternatively, as shown in FIG. 7C, the movable spacer receives the driven force from the transfer roller and receives a pressing force downstream in the recording material conveyance direction (arrow direction in FIG. 7B). Simultaneously with the transfer nip portion, the transfer pressure during printing is applied to the photosensitive drum and the transfer roller. Thereafter, the movable spacer rotates in the direction of the arrow in FIG. 7C due to its own weight, and returns to the state in FIG. Note that the transfer roller core is fitted at different positions in the state a and the state b in the groove portion of the movable spacer.

  FIG. 8 shows a method of pressing the photosensitive drum and the transfer roller in the state a and the state b of the present embodiment.

  A transfer roller bearing 37 is attached to the end of the core metal 17 of the transfer roller 6, and a contact pressure against the photosensitive drum 2 is applied by the transfer spring 21 via the transfer roller bearing. The transfer spring is fixedly held up and down by a boss 23 of the transfer roller bearing and a boss 24 protruding from the seat surface. A bearing holder 38 is installed at both ends of the transfer roller and accommodates the transfer roller bearing and presses it with a patch to apply contact pressure to the photosensitive drum. FIG. 8A shows the state a where the transfer pressure during printing is applied, and FIG. 8B shows the state b where the photosensitive drum and the transfer roller are separated from each other. In the state b, as described above, the transfer roller is pushed downward by the spacer portion 36 of the movable spacer 33 so that the photosensitive drum and the transfer roller are separated from each other, and the transfer spring 21 is contracted in the up and down directions. The bosses 23 and 24 are fixed and held.

  A schematic diagram of the longitudinal end of the transfer roller of the present embodiment is shown in FIG.

  FIG. 9 shows an example in which the transfer roller rotates following the photosensitive drum. The movable spacer 33 is installed inside the transfer roller bearing 37. FIG. 9A shows the state a where the transfer pressure during printing is applied, and FIG. 9B shows the state b where the photosensitive drum and the transfer roller are separated from each other. FIG. 10 shows an example in which the transfer roller has a drive gear and is driven from the drum gear. The transfer drive gear 31 is provided inside the transfer roller bearing 37, and the movable spacer 33 is installed inside the transfer drive gear 31. FIG. 10A shows the state a in which the transfer pressure during printing is applied, and FIG. 10B shows the state b in which the photosensitive drum and the transfer roller are separated from each other. In the state b, the figure shows a case where the drum gear and the transfer drive gear are separated from each other. However, even when the photosensitive drum and the transfer roller are separated from each other as in the second embodiment, the drum gear and the transfer drive gear are It may be possible to maintain a meshed state.

  The material of the movable spacer is preferably ABS (acrylonitrile-butadiene-styrene) resin, which is lightweight, inexpensive and excellent in workability. In the present embodiment, the transfer nip portion that sandwiches the spacer is a non-image forming region at both ends, and even if the C roller set deformation of the transfer roller occurs at the spacer contact portion, an image defect is caused. There is nothing. Further, the spacer contact portion of the photosensitive drum is a raw tube, and the CT layer is an uncoated region.

  In the image forming apparatus of the present embodiment, it is recommended to set the state b when the user does not use the image forming apparatus for a long period of time or when the user transports the cartridge with the cartridge mounted. Accordingly, it is possible to prevent drum contamination and C-set deformation of the transfer roller when the image forming apparatus is not used for a long period of time.

  In Embodiment 2, if the transfer roller does not have a drive gear, the photosensitive drum and the transfer roller could not be separated from each other. However, in this embodiment, the transfer roller can be separated by using a separation member. Even when the photosensitive drum is driven to rotate, the photosensitive drum and the transfer roller can be separated from each other, and drum contamination and C-set deformation of the transfer roller can be completely prevented. In addition, when the image forming apparatus is left for a long period of time and then used again, the spacer is automatically removed during the first rotation, and the transfer pressure is applied during printing, so the user can print without releasing the transfer pressure release mechanism. The occurrence of image defects such as paper jams and transfer defects can be prevented.

  Further, in the present embodiment, the cartridge mounting and transport is performed, and the image forming apparatus is shipped in the state b. With the transfer pressure release mechanism according to the present embodiment, the transfer pressure can be easily released at the time of shipment, and drum contamination and C-set deformation of the transfer roller during cartridge mounting and transportation can be completely prevented. . In addition, since the transfer pressure at the time of printing is automatically applied by the user, it is possible to prevent the occurrence of image defects such as paper jams and transfer defects when the user performs printing without releasing the transfer pressure release mechanism. it can. Furthermore, since it is not necessary for the user to perform a complicated operation of removing the transfer pressure release member before using the image forming apparatus, usability can be improved.

  As described above, when the image forming apparatus is not used for a long time, the photosensitive drum and the transfer roller are separated from each other, so that the occurrence of image defects due to drum contamination or the transfer roller C set can be completely prevented. Further, since the transfer pressure at the time of printing is automatically applied at the first rotation when the power is turned on, it is possible to prevent the occurrence of a paper jam or an image defect due to the user forgetting to release the transfer pressure release mechanism. Furthermore, it is not necessary for the user to release the transfer pressure release mechanism before using the image forming apparatus, leading to improved usability.

It is a figure explaining operation | movement of the transfer roller of Embodiment 1 of this invention. It is a schematic diagram of the transfer roller longitudinal end part of Embodiment 1 of the present invention. It is a schematic diagram explaining a transfer omission. It is a figure explaining the position of the transfer drive gear with which the drum was equipped. It is a figure explaining operation | movement of the transfer roller of Embodiment 2 of this invention. It is a schematic diagram of the transfer roller longitudinal end part of Embodiment 2 of the present invention. It is a figure explaining operation | movement of the spacer of Embodiment 3 of this invention. It is a figure explaining operation | movement of the transfer roller bearing of Embodiment 3 of this invention. It is a schematic diagram of the longitudinal end in the case of the transfer roller drum driven drive of Embodiment 3 of the present invention. It is a schematic diagram of the longitudinal end part in the case of the transfer roller drive of Embodiment 3 of this invention. It is sectional drawing of the conventional image forming apparatus. It is a sectional view of a transfer part of a conventional image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser scanner 2 Photosensitive drum 3 Primary charger 4 Developing roller 5 Process cartridge 6 Transfer roller 7 Fixing device 8 Conveyance roller pair 9 Paper feed cassette 10 Paper feed roller 11 Conveyance sheet metal 12 Cleaning member 13 Fixing discharge conveyance roller pair 14 Discharge Roller 15 Discharge tray 16 Transfer guide 17 Transfer roller core 18 Transfer roller elastic layer 19 High voltage power supply 20 CPU
DESCRIPTION OF SYMBOLS 21 Transfer spring 22 Pressure bearing 25 Core metal holding member 30 Drum gear 31 Transfer drive gear 32 Drum drive gear 33 Movable spacer 37 Transfer roller bearing 38 Transfer roller bearing holder 40 Core metal rotation prevention member L Laser beam P Recording material N Transfer nip

Claims (6)

In an image forming apparatus comprising a transfer device for transferring a toner image on a latent image carrier to a recording material,
By moving the transfer member relative to the latent image carrier, the transfer pressure between the latent image carrier and the transfer member can be set to a light pressure state smaller than the transfer pressure at the time of image formation. Even if the transfer pressure is set to a light pressure state, the latent image carrier is automatically moved in conjunction with rotation of the latent image carrier or the transfer member by driving from a driving source, whereby the latent image is moved. An image forming apparatus, wherein a transfer pressure during image formation is applied between a carrier and the transfer member.   When the transfer pressure of the latent image carrier and the transfer member is set to a light pressure state, and when the transfer pressure during image formation is applied between the latent image carrier and the transfer member, 2. The image forming apparatus according to claim 1, wherein the contact angle between the latent image carrier and the transfer member is different. In an image forming apparatus comprising a transfer device for transferring a toner image on a latent image carrier to a recording material,
By moving the transfer member relative to the latent image carrier, the latent image carrier and the transfer member can be set in a separated state, and the transfer member has a drive gear at an end portion. And when set in the separated state, the drive shaft of the transfer member can maintain the state in which the drive gear of the latent image carrier or the drive gear of the image forming apparatus main body is engaged with each other. A distance is set, and when the latent image carrier or the transfer member is rotated by driving from a drive source, the drive gear of the transfer member drives the drive gear of the latent image carrier or the image forming apparatus main body. An image forming apparatus, wherein a transfer pressure during image formation is applied between the latent image carrier and the transfer member by automatically moving the transfer member while meshing with a gear.   The member for holding the transfer member on both sides is provided with an L-shaped groove, and the transfer member can be held at two positions on both ends of the groove. When the transfer member is held, the latent image carrier and the transfer member are in a light pressure or separated state, and when the transfer member is held at the second position, the latent image carrier. The image forming apparatus according to claim 1, wherein a transfer pressure at the time of image formation is applied between the transfer member and the transfer member. In an image forming apparatus comprising a transfer device for transferring a toner image on a latent image carrier to a recording material,
A separation member that separates the latent image carrier from the transfer member, and the separation member can set the latent image carrier and the transfer member to a separation state; the separation member is set to a separation state; However, when the latent image carrier or the transfer member is rotated by driving from the driving source, the separation member automatically moves in conjunction with the rotation of the latent image carrier and the transfer member. An image forming apparatus in which a transfer pressure is applied.   The spacing member is provided with an L-shaped groove, and when the latent image carrier and the transfer member are in a separated state, transfer between the latent image carrier and the transfer member during image formation is performed. 6. The image forming apparatus according to claim 5, wherein the position of the groove in which the transfer member is fitted to the separation member is different from that when the pressure is applied.

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