JP2005049678A - Color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a transfer belt from having curl and to prevent permanent deformation caused by the creep of a transfer belt cleaning blade when an image forming apparatus is transported or when it is left as it is for a long term. <P>SOLUTION: In order to prevent the curl round rollers of an ITB under a high temperature condition in the case of severe preservation (mainly in the case of transportation) and prevent the permanent deformation caused by the creep of an ITB cleaning blade under the same condition, a pressure releasing member that weakens the tension of the belt and pressing by the blade at the time of shipping from a factory is attached. The pressure releasing member is detached just before using the image forming apparatus. Just by providing the pressure releasing members right and left one by one in an image width direction, the tension of the belt and the pressing by the blade are controlled. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a color image forming apparatus using an electrophotographic method, such as a printer for a computer or a copying machine.

  Some image forming apparatuses perform image formation using an electrophotographic technique in which a developer made of fine powder is electrostatically controlled and adsorbed. For example, an electrostatic latent image is formed on the surface of a photosensitive drum or photosensitive belt as an image carrier, and the electrostatic latent image on the image carrier is developed with a toner or the like as a developer to be visualized. The developed image is transferred onto a transfer material by a transfer device to carry the image, and a toner image on the transfer material is fixed on the transfer material by a fixing device using pressure, heat, or the like. An image is formed by sequentially performing these steps. Further application of this technique to obtain a multi-color image (so-called color image) is possible by using a multi-color developer. In principle, if a yellow, magenta, and cyan developer is used, a full color image can be obtained by mixing colors (in some cases, a black developer is used in addition to the above three types).

  As a configuration of a color image forming apparatus, a developing device for storing the developer is provided for each color, and the plurality of developing devices are arranged on a straight line or a curve to develop an electrostatic latent image corresponding to the developer of each color. There is. There are a direct transfer method and an intermediate transfer method as a method of superimposing a plurality of color images in a color image forming apparatus until a final image is obtained on a transfer material such as paper or a plastic sheet.

  The former direct transfer method is a case where a transfer material is a partner to which a developed image on an image carrier adjacent (or included) with a developing device is transferred in the next step. When the transfer material is brought into contact with the image carrier or passed through a small gap, an electric bias is formed so that the developer on the image carrier is attracted to the transfer material, and the image is directly transferred from the image carrier to the transfer material. Let In a color image forming apparatus having a plurality of developing devices and a plurality of image carriers, a transfer material is moved to an image carrier corresponding to each color, and a developed image corresponding to each color is sequentially transferred to the transfer material.

  On the other hand, in the latter intermediate transfer system, there is a second image carrier that holds all the developed images of the respective colors during the process of transferring the image from the image carrier to the transfer material. From the image carrier corresponding to each color, all the developed images are once held on the second image carrier, and the second image carrier and the transfer material downstream from the transfer position between the first and second image carriers. And an electric bias is formed at the contact point and the image is transferred from the second image carrier to the transfer material. This second image carrier is sometimes called an intermediate transfer member.

  In the intermediate transfer system of the color image forming apparatus, a plurality of first image carriers are arranged arbitrarily, and the second image carrier is arranged so that images are transferred from all the first image carriers. There is what I did.

  A plurality of developing devices (for example, containing yellow, magenta, cyan, and black color toners) having a first image carrier are disposed. The developed images of the respective image carriers are sequentially electrostatically transferred to an intermediate transfer member which is a second image carrier. A full-color image formed of four color toners is collectively electrostatically transferred (sometimes referred to as secondary transfer) from an intermediate transfer member to a transfer material such as paper. The transfer material carrying the image is conveyed to a fixing device using heat or pressure, and the toner on the transfer material is melted and fixed.

  As such an intermediate transfer member, an intermediate transfer belt is used, and a configuration for preventing the intermediate transfer belt from being wrinkled by being left is proposed (for example, see Patent Document 1).

JP 7-295395 A

  The intermediate transfer member of the image forming apparatus includes a belt / film-like one and a roller-like one. All of these perform the transfer process (from the first image carrier to the second image carrier or from the second image carrier to the transfer material) while rotating. These two shapes have different points in the arrangement inside the image forming apparatus.

  When the intermediate transfer member has a cylindrical roller shape, the first image carrier and the secondary transfer device must be arranged on the outer periphery of the intermediate transfer member. For example, if the one arranged on the outer periphery becomes larger, the intermediate transfer member must be enlarged while remaining cylindrical. The occupied volume of the intermediate transfer member is exponentially increased, which leads to enlarging the image forming apparatus.

  On the other hand, in the belt-like intermediate transfer member, the belt cross-sectional shape can be set by the arrangement of the tension roller. Therefore, there is an advantage that the degree of freedom in arrangement in the image forming apparatus is increased. The above-mentioned image carrier and transfer device can also be arranged on a straight line. Further, for example, if two tension rollers are used, the thickness equivalent to the roller diameter becomes the belt occupation, and the belt occupation volume can be reduced. As a result, the space efficiency of the image forming apparatus can be increased and the apparatus can be downsized.

  However, in order to rotate the belt-shaped intermediate transfer member, there must be a certain belt tension. If the tension is low, the belt will slip and cannot rotate stably. When transferring from the photosensitive drum to the belt, or when performing secondary transfer from the belt to a transfer material such as paper, an unstable rotation causes the image to expand and contract in the belt rotation direction. As a result, the image is defective.

  Similarly, in the case of the direct transfer system, the belt has a paper transport function. For this reason, if the belt rotates in an unstable manner, a defect occurs during image transfer onto paper.

  From the above, a certain level of belt tension is required for stable belt rotation.

  On the other hand, the belt is made of a plastic or rubber-based thin film that is less stretched and formed into a seamless shape. In particular, a belt made of a material having high rigidity such as polyimide has a relatively low expansion and contraction and can set a high tension. It is suitable for stable rotation.

  However, if the belt is placed under high tension (for example, 60 ° C or higher) with high tension applied to the belt, and then placed at room temperature, the belt is caught on the roller arc by the rollers that stretch the belt. It will harden as it is (it ’s also called “rolling candy”). For example, when a device is being transported and stored using a ship, there is a high possibility that the temperature will be high. If the belt is kept under tension under this condition, the belt is not rotated, and the belt is hardened in the form of being applied to the stretching roller. When this apparatus prints an image over the user's hand, a transfer failure occurs at a hardened place.

  The same can be said for not only the belt using the intermediate transfer system but also the direct transfer system to paper.

  Next, a case where a rubber blade is used for cleaning the transfer belt will be described.

  In the intermediate transfer system, a cleaning mechanism is provided immediately before the position where the image on the photosensitive drum is transferred to the belt so that residual toner that has not been transferred from the belt to the paper does not adhere to the new image. If residual toner passes through the cleaning mechanism, there is a risk that a new image will be superimposed on the previous image. Naturally, the image is defective.

  The cleaning mechanism has a configuration in which a rubber blade is applied to the belt surface to scrape the remaining toner. This method has a relatively simple structure and can provide good cleaning efficiency. For example, urethane rubber or the like is used as the material. Apply pressure to the blade so that the edge of the rubber blade hits the belt. When this pressing force is low, residual toner may slip through the blade edge. In order to maintain the pressing force, the rubber blade is pressed so as not to exceed the creep deformation limit of the rubber blade, and the repulsive force of the rubber blade is ensured. The rubber blade is pressed in a bent state.

  However, as described in the above “belt curl”, if the rubber blade is pressed and bent and left under high temperature conditions, the rubber blade undergoes creep deformation. As a result, the residual toner slips through and image defects occur.

  According to the present invention, creep deformation of a belt or a rubber blade can be prevented under high temperature conditions such as during transportation and storage.

  The member is held so as to weaken the belt tension and the blade pressing force during transportation and storage in a high temperature condition. The member is attached at the time of shipment, and the member is removed immediately before the apparatus is operated over the user's hand. If the pressure applied to each of them is small, it is possible to fall below the creep limit, and it is possible to ensure the set pressure on the belt and blade by simply removing the release member.

  Further, if this member can be removed with at least one left and right action, usability can be maintained.

  In this way, it is possible to stabilize the running of the intermediate transfer type or direct transfer type belt of the image forming apparatus and to improve the transfer image.

  As described above, the following effects can be obtained in the color image forming apparatus.

  Even when an intermediate transfer belt or electrostatic belt is used in an intermediate transfer method or a direct transfer method, and a blade such as rubber is used as a belt cleaning member, the tension applied to the belt and the pressing force applied to the blade are It must be loosened in a high temperature environment. For example, after assembling the device, a member for releasing two forces is attached and shipped. Keep the device unaffected by pressure in a high temperature environment such as when shipping a ship. If the pressure release member is removed when the device reaches the user's hand, the belt tension and blade pressing force necessary for the operation of the device are secured.

  Therefore, it is possible to prevent image transfer failure.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  A first embodiment according to the present invention will be described.

  A schematic configuration of a color image forming apparatus utilizing an electrophotographic system is shown in FIG. The color image forming apparatus A as an example is a laser beam printer that can form a four-color full-color image.

  A color image forming apparatus A that performs image formation through a process of fixing an image visualized with a developer (for example, toner) onto a transfer material by heat or the like is a drum-type electrophotographic image serving as a first image carrier. Photosensitive drums 1Y, 1M, 1C, and 1BK are provided as photosensitive members. The photosensitive drum 1 (when these symbols are common to Y, M, C, and BK, these symbols are omitted) is driven to rotate, for example, counterclockwise by driving means (not shown).

  A charging device 2 that uniformly charges the surface of the photosensitive drum 1, an exposure device 3 that flashes a light source (for example, laser light or LED light) based on image information, and forms an electrostatic latent image on the photosensitive drum 1, a photosensitive device A developing device 4 that develops toner by attaching toner to the electrostatic latent image on the drum 1, and an intermediate transfer unit 5 are installed as a second image carrier to which the toner image on the photosensitive drum 1 is transferred. The intermediate transfer member 5b in this case has a belt shape and rotates clockwise.

  The developing device 4 including the photosensitive drum 1 is fixedly disposed in parallel to the intermediate transfer unit 5. The developing device 4 that develops the electrostatic latent image on the photosensitive drum 1 has four developer accommodating portions that accommodate four color toners. Each developer accommodating portion is provided with a developer carrying roller 4a that bears toner as a developer on the surface and faces the photosensitive drum 1 when the developer accommodating portion faces the photosensitive drum 1. The electrostatic latent image on the photosensitive drum 1 can be developed by the developer carrying roller 4a.

  By sequentially transferring and superimposing the developed image on the photosensitive drum 1 to one opposing intermediate transfer body unit 5 for each color, one full-color developed image electrostatically adsorbed on the intermediate transfer body 5b is formed. In order to transfer the toner from the photosensitive drum 1 to the intermediate transfer belt 5b, transfer means 5d for generating an electric bias with respect to the photosensitive drum is provided on the opposite side of the photosensitive drum.

  After one developed image is formed on the intermediate transfer member 5b, the intermediate transfer member 5b further rotates to a location E where the developed image is transferred to the transfer material. The transfer material in the transfer material storage box 6 is supplied to the transfer location E by the feeding / conveying device 7 at a predetermined timing. At this transfer location E, transfer means 5e for generating an electric bias with respect to the transfer belt 5b is provided on the opposite side of the transfer belt 5b with the transfer material interposed therebetween.

  In this way, the toner image is transferred to the transfer material by using the electrostatic attraction force. Further, in order to fix the toner image to the transfer material, the transfer material is conveyed to a fixing device. In the fixing device, heat and pressure are used to melt and fix the toner on the transfer material.

  The transfer material that has passed through the fixing device 8 is discharged to the paper discharge tray 10 by the transport unit 9. A curve 20 indicates a transfer material conveyance path.

  FIG. 2 shows a configuration of a belt tension generating unit and a belt cleaning unit of the image forming apparatus.

  The yellow toner image on the photosensitive drum 1Y is transferred to the intermediate transfer belt 5b by the potential difference between the photosensitive drum 1Y and the primary transfer roller 5dY. In the full-color image forming apparatus, images of yellow, magenta, cyan, and black toner are sequentially transferred onto the intermediate transfer belt 5b (corresponding portions are not shown, and the color order is not determined). The toner image superimposed on the intermediate transfer belt 5b is rotated and conveyed in the direction of the arrow to the secondary transfer portion E while being electrostatically adsorbed on the belt.

  At the same time as the toner image is transported to the secondary transfer portion E, a transfer material 73 such as paper is transported to the secondary transfer portion E, and on the belt due to the potential difference and pressing between the intermediate transfer belt 5b and the secondary transfer roller 5e. The toner image is transferred to the transfer material 73. Then, the transfer material 73 on which the toner image is carried is conveyed to the fixing unit 8.

  In order to stably rotate and convey the belt, there must be a certain amount of tension with the belt stretched. The value depends on the size, material, and tension shape of the belt. For example, a certain set value is determined in the range of 1 to 10 kg on one side in the axial width direction. In FIG. 2, a belt tension is generated by applying a compression spring 53 to the tension roller 51. The tension roller 51 is movable in the direction in which the compression spring 53 acts. A fixing block 57 is provided at the other end of the compression spring 53 and supports the spring 53. Usually, in order to keep the roller pressure balance constant, pressure members 53 are arranged at both ends of the roller.

  Here, it is assumed that the belt is not rotating under a high temperature condition and a high tension is applied to the belt. For example, when shipping using a ship or a car after shipment from the factory, the atmosphere of the apparatus may become abnormally high. Thereafter, when the apparatus is cooled to room temperature such as a state where the apparatus is used, a portion of the belt that is hung on the stretching roller becomes hard due to its curvature shape. For example, this may occur when the belt material is polyimide.

  In order to prevent this creep phenomenon, it is necessary to lower the belt tension. As a method, the influence of a member (for example, a compression spring) that generates belt tension may be reduced in a high temperature environment.

  Next, the belt cleaning unit will be described.

  When the toner image on the intermediate transfer belt 5 b passes through the secondary transfer portion E, most of the toner image is transferred to the transfer material 73. The remaining portion is not transferred to the transfer material 73 but is conveyed while adsorbed on the belt. When the remaining toner is conveyed to the primary transfer portion, it overlaps with a new image to be formed next. Then, it becomes an image defect.

  In order to maintain a good image, a belt cleaning member is arranged on the way from the secondary transfer portion to the primary transfer portion. In FIG. 2, a blade 55 such as a rubber material is pressed against the belt 5b. By applying the edge of the blade 55 to the belt 5b, the remaining toner is scraped off and collected from the belt 5b (a collecting mechanism is not shown).

  By positioning the blade 55 on the side plate that supports the belt stretching roller, the blade 55 can be placed with high accuracy with respect to the roller 54 facing the blade 55. In FIG. 3, the tension spring 59 is used to generate the blade pressure, and the blade support 56 is pressed by the pressing member 58 to press the blade 55.

  The problem here is a defect in the next image due to residual toner. If the pressure of the blade 55 against the belt 5b is weak, the remaining toner slips through the gap between the belt 5b and the blade 55. The blade must provide uniform pressure over the image width. The blade pressure must be ensured while the image forming apparatus is in operation.

  The blade 55 is made of a soft material such as rubber and is pressed without damaging the belt by using rubber elastic force. The fact that rubber is used means that, as in the case of the intermediate transfer belt described above, if a strong pressure is continuously applied in a high temperature environment, the rubber blade may creep and cause permanent deformation. There is. In FIG. 2 and the like, only the edge of the blade 55 is in contact with the belt 5b, but the blade may be bent and used within elastic deformation in order to improve cleaning properties. When the permanent deformation occurs, the rubber elastic force becomes weak, and the pressing force necessary for the original belt cleaning is reduced. For this reason, the residual toner easily slips through.

  In order to prevent this blade creep phenomenon, it is necessary to reduce the blade pressing force. As a method for this, the influence of a member (for example, a tension spring) that generates a blade pressing force may be reduced in a high temperature environment.

  It is necessary to loosen the tension applied to the intermediate transfer belt 5b and the pressing force applied to the blade 55 described above in a high temperature environment. For example, after assembling the device, a member for releasing two forces is attached and shipped. Keep the device unaffected by pressure in a high temperature environment such as when shipping a ship. If the pressure release member is removed when the device reaches the user's hand, the belt tension and blade pressing force necessary for the operation of the device are secured.

  In FIG. 4, a pressure release member 61 is attached, and a part 62 of the pressure release member 61 acts on the bearing 52 of the tension roller 51 to forcibly compress the spring 53. Therefore, the force of the spring 53 acting on the belt 5b is reduced, and the belt tension can be reduced. Further, a part 63 of the pressure releasing member 61 supports the pressing member 58 so that the blade pressure by the spring 59 via the pressing member 58 is weakened. FIG. 4 illustrates the blade 55 being separated from the belt 5b. However, if the blade pressure is reduced, the tip of the blade 55 does not necessarily have to be separated from the belt 5b.

  The pressure release member 61 acts on both the belt tension side and the blade pressing side. Therefore, it is possible to prevent permanent deformation of the belt 5b and the blade 55 in a high temperature environment such as during transportation of the device, and a good image can be obtained by removing the pressure release member 61 once attached just before using the device. It is done.

  FIG. 6 shows a second embodiment of the present invention.

  Similar to the image forming apparatus using the intermediate transfer method in the first embodiment, the belt / blade deformation can be prevented even in the direct transfer type image forming apparatus having no intermediate transfer member.

  In the direct transfer system, a configuration is adopted in which transfer is performed directly from an image carrier such as the photosensitive drum 1 to a transfer material such as paper conveyed by the electrostatic belt 50. The transfer material carrying the toner image is conveyed to the fixing device 8 and fixed on the transfer material.

  First, as for the electrostatic belt, as in the first embodiment, when the tension roller trace on the electrostatic belt is attached, the image transfer portion from the photosensitive drum to the paper overlaps with the “roller trace”. There is a possibility that the behavior of the paper at the time of transfer is remarkably deteriorated. As a result, the image transfer onto the paper becomes poor. Therefore, it is necessary to prevent the electrostatic belt from being permanently deformed by creep in a high temperature environment.

  In addition, the electrostatic belt cleaning member is necessary even in the direct transfer method. The reason is described below. Basically, the toner image on the photosensitive drum is attracted to the paper, so that the toner does not adhere to the electrostatic belt. However, there is a case where the image forming apparatus itself performs image correction so that a good image can always be provided. For example, density correction is performed for each color, and writing / transfer timing is corrected for each color. At that time, the image on the photosensitive drum may be transferred to the electrostatic belt. If the toner image on the electrostatic belt is not removed after the correction, “back stain” on the paper will occur during the next image formation. Therefore, the electrostatic belt must be cleaned immediately before image transfer. If a rubber blade system is employed for this cleaning member, blade deformation occurs and the set pressure cannot be ensured, as in the first embodiment.

  Therefore, it is necessary to loosen the tension applied to the electrostatic belt and the pressing force applied to the blade described above in a high temperature environment. For example, after assembling the device, a member for releasing two forces is attached and shipped. Keep the device unaffected by pressure in a high temperature environment such as when shipping a ship. If the pressure release member is removed when the device reaches the user's hand, the belt tension and blade pressing force necessary for the operation of the device are secured.

  This will be described in detail with reference to FIG. The tension on the belt 50b is generated by the force from the spring 503 applied to the bearing 502 of the tension roller 501. The blade 505 is pressed against the belt 50b supported by the roller 504, and the pressing force is generated by a spring 509. The generated force is transmitted to the pressing member 508, and the pressing member 508 rotates around the fulcrum 603 to press the blade 506.

  The bearing 502 is supported by a part 602 of the pressure releasing member 601, and the belt tension is weakened. On the other hand, the pressing member 508 is supported by the pressure releasing member 601 part 603 to weaken the blade pressing force. By these actions, permanent deformation of the belt 50b and the blade 505 can be prevented. This pressure release member 601 is arranged immediately before the shipment of the apparatus, and the belt tension and the blade pressing force can be lowered during the transportation of the apparatus (in a high temperature environment). If the apparatus is released to the user and the pressure release member 601 is removed immediately before use, problems for image formation will not occur. Even if the pressure release member 601 is attached, it can be taken by one action on the left and right, so that the usability is not significantly impaired.

1 is a schematic sectional view of a color image forming apparatus according to a first embodiment of the present invention. In the first embodiment of the present invention, a partial schematic diagram is shown. In the first embodiment of the present invention, a partial schematic diagram is shown. In the first embodiment of the present invention, a partial schematic diagram is shown. In the first embodiment of the present invention, a partial schematic diagram is shown. FIG. 2 is a schematic sectional view of a color image forming apparatus according to a second embodiment of the present invention. In the second embodiment of the present invention, a partial schematic diagram is shown.

Explanation of symbols

1Y, 1M, 1C, 1BK ... photosensitive drum (image carrier)
5 ... Intermediate transfer unit 5b ... Intermediate transfer belt
55 ... Blade
61 ... Pressure release member
50 ・ ・ ・ ・ Electrostatic adsorption unit
50b ... Electrostatic adsorption belt
505 ・ ・ ・ ・ Blade
601 ... Pressure release member

Claims (4)

There are an image carrier that carries an electrostatic latent image, an exposure device for forming an electrostatic latent image on the image carrier, and a plurality of developing devices that develop the electrostatic latent image of the image carrier, There is also a belt-like intermediate transfer member for simultaneously carrying a plurality of images in the process of transferring the toner image on the image carrier to the transfer material, and transferring the images to the transfer material at once. In a color image forming apparatus having a rubber blade-shaped cleaning member for cleaning the body,
There is a tension generating member for the belt-shaped intermediate transfer member, and there is a pressing force generating member for pressing the cleaning member against the belt, and a member capable of simultaneously releasing the force generated by the tension generating member and the pressing force generating member. A color image forming apparatus. There are an image carrier that carries an electrostatic latent image, an exposure device for forming an electrostatic latent image on the image carrier, and a plurality of developing devices that develop the electrostatic latent image of the image carrier, In addition, there is an electrostatic transfer belt that conveys a transfer material facing a plurality of the image carriers and electrically transfers a toner image on the image carrier to the transfer material. In a color image forming apparatus having a rubber blade-shaped cleaning member for cleaning,
There is a tension generating member for the electrostatic transfer belt, and there is a pressing force generating member for pressing the cleaning member against the electrostatic transfer belt, and the generated force by the tension generating member and the pressing force generating member is released simultaneously. A color image forming apparatus comprising a possible member. 3. A color image forming apparatus according to claim 1, wherein the generated force simultaneous releasing members are arranged one by one in both directions perpendicular to the conveyance of the transfer material. 3. The color generating force simultaneous releasing member according to claim 1 or 2, wherein the releasing force simultaneous releasing member is arranged in both directions perpendicular to the conveyance of the transfer material, and the releasing member can be removed by one operation each time. Image forming apparatus.