JP2005128243A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that can surely prevent slip scratches of an image carrier (photoreceptor) in an initial state and prevent vibration, such as chatters generated after forming a large number of images in simple and inexpensive constitution, by controlling a proper drive speed based on change of an initial state of the image carrier (photoreceptor) and an intermediate transfer body and a surface state after forming the large number of the images. <P>SOLUTION: The image forming apparatus prevents slip scratch of the image carrier (photoreceptor) in the initial state, by changing a relative speed of the image carrier (photoreceptor) and the intermediate transfer body (belt), in response to the number of forming the images, and prevents vibration, such as chatters generated after forming the large number of the images, in a simple and low-cost constitution. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine using an electrophotographic method, and more particularly, primarily transfers a toner image formed on an image carrier to an intermediate transfer member. Then, the present invention relates to an image forming apparatus in which secondary transfer is performed on a recording medium.

  In an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine using an electrophotographic system, the surface of a photosensitive member (image carrier) is uniformly charged with a predetermined polarity and is based on predetermined document information. A latent image forming process in which exposure is performed with light, a developing process in which the formed latent image is developed into a toner image, and a transfer in which the toner image is transferred to a recording material such as paper and fixed by heating and pressing a fixing roller. -Image formation is performed by sequentially performing the fixing process. In addition, the surface of the photosensitive drum after the toner image transfer is cleaned with a cleaning blade or the like to remove the remaining toner, and if necessary, neutralization by light irradiation or the like is performed to prepare for the next image formation. Is called.

  Further, in such an image forming apparatus, the toner image is not directly transferred to the recording material, but is temporarily transferred to a belt or drum-shaped intermediate transfer member, and then finally transferred from the intermediate transfer member onto the recording material. A technique for transferring is known. In particular, in a full-color image forming apparatus, it is necessary to superimpose toner images of a plurality of colors, but rather than superimposing toner images on a recording material such as paper, the toner images of each color are temporarily formed on the intermediate transfer member. Intermediate transfer (primary transfer) and superimposing and transferring from the intermediate transfer member onto the recording material (secondary transfer) are more reliable without causing inconvenience such as color misregistration due to misregistration of the recording material. In addition, a full color image can be formed.

  The intermediate transfer member used for such applications generally has a structure in which a fluororesin layer is provided on the surface of an elastic substrate (endless belt or drum shape) made of a rubber elastic body. That is, by using an elastic substrate, a nip width necessary for transfer can be secured between the surface of the photosensitive drum on which the toner image to be transferred is formed and the recording material to which the toner image is transferred, and This is because the fluororesin layer can improve releasability and reduce the friction coefficient.

  In an image forming apparatus using such an intermediate transfer member, the toner image formed on the photosensitive drum is transferred to the intermediate transfer member (primary transfer) and transferred to the recording material (secondary transfer). Is performed while moving the intermediate transfer member. In particular, when the intermediate transfer member is an endless belt, the intermediate transfer member is stretched between two or more rollers and a tension of about 1 to 2 N / cm is applied. Therefore, the intermediate transfer member is repeatedly rotated around the roller and linearly moved between the rollers. In addition, the contact portion (primary transfer portion) between the intermediate transfer member and the photosensitive drum is usually driven so that the linear velocity between the two is substantially constant or a constant speed difference (ratio).

  However, when the image forming apparatus is configured in this way, the speed relationship between the photosensitive drum and the intermediate transfer member set at the initial stage is not appropriate after a large number of images are formed due to the degree of wear of the photosensitive drum. That happens. That is, when the surface of the photosensitive drum is in a clean initial state and the linear drum is driven with a constant speed difference between the photosensitive drum and the intermediate transfer body, the photosensitive drum is activated when the photosensitive drum is started due to the speed difference. If there is a large number of scratches in the axial direction of the photosensitive drum appearing in the image and appearing in the image, or if this scratch is generated and the cleaning blade is in contact with the photosensitive drum, the scratch on the photosensitive drum Since the frictional force between the photosensitive drum and the cleaning blade partially changes at a certain portion, rotational jitter occurs in the photosensitive member, which may cause a problem. Therefore, in order to prevent such scratches on the photosensitive drum, it is preferable that the linear speeds of the photosensitive drum and the intermediate transfer member be made to be substantially equal in the initial state.

  However, when a certain number of images are formed, wear marks are generated in the entire circumferential direction of the photosensitive drum, and the intermediate transfer member is also composed of components such as minute scratches, roughness, developer, etc. on the surface, or paper components. The adhesion between the two tends to increase the frictional force between them. In such a situation, the drive roller of the intermediate transfer member and the photosensitive drum normally have a rotational vibration of about 50 (μm) or more, so the photosensitive drum and the intermediate transfer member In the contact portion, contact is repeatedly performed at a constant speed or with a speed difference, and the vehicle moves back and forth between the static friction state and the dynamic friction state. As a result, the frictional force between the contact portions is not constant, and vibrations are generated, and chatter noise is generated.

  In order to deal with such a problem, for example, Patent Document 1 discloses that the dynamic friction deviation, which is the standard deviation of the dynamic friction force generated between the photosensitive drum and the intermediate transfer member, is smaller than the average value of the dynamic friction force. It is shown that the contact pressure, the relative speed, the fluctuation range of the dynamic friction force due to the temperature change, the surface roughness of the photosensitive member, and the like are defined. Patent Document 2 discloses an image forming method in which a step of primary transfer of a toner image on an image carrier to an intermediate transfer member is repeated a plurality of times, and then secondary transfer to a recording medium. In order to solve this transfer defect and improve the image quality, the toner aggregation degree, bulk density, volume specific resistance of the intermediate transfer member, linear velocity ratio between the intermediate transfer member and the image carrier, contact pressure, etc. are appropriately determined. It has been shown.

JP 2001-318505 A JP 2001-209255 A

  However, since the image forming apparatus disclosed in Patent Document 1 maintains a constant relative speed between the photosensitive drum and the intermediate transfer member, the fluctuation range of the dynamic frictional force due to the temperature change between the photosensitive drum and the intermediate transfer member is reduced. The surface roughness and the like are defined. In particular, it is necessary to select the material of the surface of the intermediate transfer member and to regulate the state of the surface of the a-Si (amorphous silicon) photoreceptor, which may increase the cost. The method disclosed in Patent Document 2 is not intended to prevent vibration and chatter noise between the photosensitive drum and the intermediate transfer member, but solves transfer defects such as transfer dust and worm-eaten states. In Documents 1 and 2, the linear speed ratio between the photosensitive drum and the intermediate transfer body is specified, but both show that the speed ratio is set, and the image of the photosensitive drum and the intermediate transfer body is only shown. No countermeasures against vibrations and chatter sounds accompanying state changes due to the number of sheets formed are shown.

  For this reason, in the present invention, appropriate driving speed control is performed based on the initial state of the photosensitive drum and the intermediate transfer member and the change in the surface state after forming a large number of images, and the photosensitive member (image carrier) in the initial state. It is an object of the present invention to provide an image forming apparatus that can prevent slip marks (scratches) and reliably prevent vibrations, chatter noises, and the like generated after forming a large number of images with a simple and inexpensive configuration.

In order to solve the above problems, the present invention
In an image forming apparatus comprising: an image carrier that forms a toner image by an electrophotographic method; and an intermediate transfer member that primarily transfers a toner image formed on the image carrier and then secondarily transfers it to a recording medium.
The relative speed between the image carrier and the intermediate transfer member is changed according to the number of images formed.

  Then, the relative speed between the image carrier and the intermediate transfer member is changed in accordance with a predetermined relationship between the number of image formations and the relative speed, and after the number of image formations reaches a predetermined number, the relative speed is made substantially constant. I tried to do it.

The predetermined relative speed is approximately 0.008 to 0.01 when the relative speed is expressed by the following equation.
Relative speed = | 1- (photosensitive linear velocity / intermediate transfer linear velocity) |

  The intermediate transfer member is configured as an endless belt having a resin layer in the lowermost layer, an elastic base layer in the middle, and a fluororesin layer on the contact surface with the image carrier.

  The image forming apparatus of the present invention further includes a counter that counts the number of image formations, and a storage unit that stores a relative speed between the image carrier and the intermediate transfer body corresponding to the number of image formations. Accordingly, the relative speed stored in the storage means is read and the relative speed is changed.

  Furthermore, the image forming apparatus of the present invention is provided with a means for varying the relative speed between the image carrier and the intermediate transfer member.

  In this way, by changing the relative speed between the image carrier and the intermediate transfer body in accordance with the number of image formations, in the initial state, both of them are set to substantially the same speed, and slip marks (scratches) are formed on the image carrier (photosensitive member). After that, for example, when the surfaces of the image carrier (photosensitive member) and the intermediate transfer member deteriorate and the frictional force between them increases, the static friction state and the dynamic friction state occur alternately. In order to prevent vibration and chatter noise, the relative speed of the image bearing member and the intermediate transfer member is changed from a state in which the friction state between the image carrier and the intermediate transfer member repeats a static friction state and a dynamic friction state. It is possible to provide an image forming apparatus in which only the dynamic friction state is generated by changing the relative speed obtained in advance to be only the state.

  Then, the relative speed between the image carrier and the intermediate transfer member is changed according to a predetermined relationship between the number of image formations and the relative speed, and after the number of image formations reaches a predetermined number, the relative speed is substantially constant. By doing so, it is possible to change the relative speed without degrading the image formation quality.

The predetermined relative speed is approximately 0008 to 0.01 when the relative speed is expressed by the following equation, whereby an optimum relative speed can be obtained.
Relative speed = | 1- (photosensitive linear velocity / intermediate transfer linear velocity) |

  The intermediate transfer member is an endless belt having a resin layer in the lowermost layer, an elastic base layer in the middle, and a fluororesin layer on the contact surface with the image carrier. However, the elastic base layer can secure a nip with the image carrier (photoreceptor) and the fluororesin layer can reduce the frictional force.

  The image forming apparatus of the present invention further includes a counter that counts the number of image formations, and a storage unit that stores a relative speed between the image carrier and the intermediate transfer body corresponding to the number of image formations. Accordingly, the relative speed stored in the storage means is read and the relative speed is changed, whereby the relative speed between the image carrier and the intermediate transfer body can be changed to a desired speed with a simple and inexpensive configuration.

  Furthermore, the image forming apparatus of the present invention is provided with a means for changing the relative speed between the image carrier and the intermediate transfer member, so that, for example, when a serviceman confirms the chatter sound of the intermediate transfer member during regular service. It is also possible to change the relative speed so that it does not occur.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

  FIG. 1 is a schematic configuration diagram of a tandem type color image forming apparatus to which the present invention is applied, FIG. 2 is a schematic diagram showing a layer configuration of an intermediate transfer member, and FIG. 3 is a relative speed of a photosensitive member (image carrier) and the intermediate transfer member. FIG. 4 is a diagram showing an example of a control block for changing the number of images according to the number of image formations. FIG. 4 is a diagram showing the relationship between the relative speed difference between the photoconductor (image carrier) and the intermediate transfer member, and the number of image formations. This is a graph showing how the vibration of the intermediate transfer member and vibration and chatter sound change.

  In the figure, 1 is a photosensitive member (image carrier) formed in a drum shape, 2 is an intermediate transfer belt as an intermediate transfer member, 3 is a charging device, 4 is exposure by an exposure device (not shown), 5 is a developing device, 6 Is a cleaning device, 7 is a static eliminator, 8 is a primary transfer roller, 10 is a reinforcing resin layer, 11 is an elastic substrate, 12 is a fluororesin-containing surface layer, 21 and 22 are driving rollers and driven rollers of an intermediate transfer belt, 23 is a backup roller, 24 is a cleaning brush for the intermediate transfer belt, 25 is a secondary transfer roller, 26 is a fixing device, 27 is a recording medium (paper), 31 is a motor for driving the photosensitive member, and 32 is a motor for driving the intermediate transfer belt 2. An intermediate transfer member motor for driving the driving roller, 33 is a control circuit for the photosensitive member motor 31 and the intermediate transfer member motor 32, 34 is a control circuit for the image forming apparatus, and 35 is a control circuit 34. A counter that receives an image formation instruction 37 and counts the number of image formations, 36 is a relative speed storage device that stores the relative speed between the photosensitive member 1 and the intermediate transfer belt 2 according to the number of image formations, and 38 is a manual manual operation for relative speed. This is a manual button for changing the relative speed, which is an example of a means for changing the relative speed.

  First, it is examined how the scratches on the photosensitive member, the vibration of the intermediate transfer member, and the chatter noise change depending on the relative speed difference between the photosensitive member 1 and the intermediate transfer member 2 and the number of images formed as shown in FIG. Based on the graph, the concept of the present invention will be briefly described. The measurement conditions of the graph shown in FIG. 4 will be described later.

In FIG. 4, the horizontal axis represents the number of printed sheets (number of images formed) with a unit of 1000 sheets, and the vertical axis represents the relative speed between the photosensitive member 1 and the intermediate transfer belt 2. The relative speed is expressed by the following equation (1). Is done.
| 1- (Photoconductor linear velocity / intermediate transfer belt linear velocity) | (absolute value) (1)
A solid line is a limit line on which a scratch generated on the photosensitive member 1 affects the image. When the relative speed is larger than the solid line, the generated scratch affects the image quality. A dotted line is a limit line in which the vibration and chatter noise of the intermediate transfer belt 2 is generated, and vibration and chatter noise are generated when the relative speed becomes smaller than the dotted line.

  That is, as described above, in the initial state where the surface of the photoconductor 1 with a small number of images formed in FIG. 4 is clean, the photoconductor 1 and the intermediate transfer belt 2 increase when the relative speed exceeds ± 0.002. Scratches are generated in the axial direction of 1 and appear in the image, resulting in a defect. Further, when the number of printed sheets (number of images formed) exceeds about 50K (50,000), uniform scratches and wear marks that are not problematic in actual use occur on the entire circumferential direction of the photoreceptor 1, but the number of printed sheets Even if the relative speed is increased with an increase in the number of images formed, scratches due to rubbing with the intermediate transfer belt 2 do not appear as image defects.

  On the other hand, regarding the intermediate transfer belt 2, if the number of printed sheets (number of formed images) exceeds about 40K sheets (40,000 sheets), surface scratches, roughness, components such as developer, or adhesion of paper components may occur. The frictional force between the photosensitive member 1 and the photosensitive member 1 tends to increase, and the repetition of the static friction region and the dynamic friction region caused by the rotational shake of the photosensitive member 1 and the intermediate transfer member driving roller becomes remarkable, and the relative speed remains low. In this case, vibration and chatter noise are generated at the contact portion between the photosensitive member 1 and the intermediate transfer belt 2.

  For this reason, when the number of printed sheets (the number of images formed) increases, the vibration and chatter noise between the photoreceptor 1 and the intermediate transfer belt 2 are reduced by reducing the static friction area where the frictional force is large and shifting it to the dynamic friction area side. Can be prevented. Further, the relative speed for preventing the vibration and chatter noise of the intermediate transfer belt 2 is increased when the number of printed sheets (number of formed images) exceeds a predetermined number, that is, about 160K sheets (160,000 sheets). It becomes substantially constant, and can be prevented by setting the relative speed represented by the above equation (1) to ± 0.008 or more. When using an intermediate transfer member having a fluororesin coat layer on its surface, if this value exceeds ± 0.010, the intermediate transfer member has a higher releasability, which may cause transfer failure. The upper limit is ± 0.010.

  Accordingly, in the present invention, the relative speed between the photosensitive member 1 and the intermediate transfer belt 2 is changed according to the number of printed sheets (number of formed images) so as to be not less than the dotted line and not more than the solid line in FIG. (The number of image formations) is a predetermined number (in the example of FIG. 4, about 160K sheets, that is, the friction state between the photosensitive member 1 and the intermediate transfer belt 2 changes from a state of repeating a static friction state and a dynamic friction state to a dynamic friction state only. When the relative speed between the photosensitive member 1 and the intermediate transfer belt 2 reaches an image forming number that can be maintained substantially constant even if image formation is further performed), the line between the photosensitive member 1 and the intermediate transfer belt 2 The speed ratio is between about 0.990 and 0.992, or between about 1.010 and 1.008.

  By changing the relative speed between the photosensitive member 1 and the intermediate transfer belt 2 in this manner, scratches on the photosensitive member 1 appear in the image, resulting in a defective image, or the intermediate transfer belt 2 generates vibration or chatter noise. It is possible to provide an image forming apparatus that does not cause the above problem.

  FIG. 1 is an example of an image forming apparatus of the present invention constructed according to such a concept. FIG. 2 is a diagram showing a schematic layer configuration of the intermediate transfer belt 2. FIG. It is the figure which showed an example of the control block for changing a speed according to the number of printed sheets (the number of image formation).

  First, an image forming apparatus to which the present invention is applied will be briefly described with reference to FIG. In the tandem type color image forming apparatus shown in FIG. 1, an intermediate transfer belt 2 as an intermediate transfer member is stretched between a pair of driving and driven rollers 21 and 22 and a backup roller 23. On the upper side, the photoreceptors 1 as image carriers are arranged side by side so as to be in contact with the intermediate transfer belt 2, for example, for each color of black, cyan, magenta, and yellow. Around each photoconductor 1, a charging device 3 such as a scorotron, an exposure device (not shown) for performing exposure 4, a developing device 5, a cleaning device 6, and a static eliminator 7 are disposed. A primary transfer roller 8 is disposed so as to face the photoreceptor 1 with the transfer belt 2 interposed therebetween.

  The developing devices 5 arranged around the photoreceptors 1 are filled with black toner, cyan toner, magenta toner, or yellow toner, respectively, and each color toner is obtained by a known electrophotographic method. An image is formed. That is, each photoconductor 1 is uniformly charged to a predetermined polarity by the charging device 3, and further, when exposure 4 is performed with light based on predetermined image information, the potential of the light irradiating portion is lowered, thereby causing an electrostatic latent image. Is formed. The toner of each color supplied by the developing device 5 under a predetermined developing bias adheres to the formed electrostatic latent image portion (potential drop portion), and a toner image is formed.

  Each color toner image formed on each photoconductor 1 in this way is driven in the direction of the arrow in FIG. 1 by a primary transfer roller 8 to which a primary transfer bias potential (a polarity opposite to the charging polarity of the toner) is applied. Then, the toner images are sequentially transferred onto the intermediate transfer belt 2 that is the intermediate transfer member, and the colors are superimposed to form a full-color toner image. The toner image is further transferred to a recording medium (paper) 27 conveyed between the secondary transfer roller 25 and the backup roller 23 with a secondary transfer bias having a reverse polarity to the toner image applied to the secondary transfer roller 25. The transferred recording medium (paper) 27 is further sent to the fixing device 26 to fix the toner image.

  Then, the toner remaining without being primarily transferred from the photoreceptor 1 to the intermediate transfer belt 2 is removed by the cleaning device 6, and the remaining charge is discharged by the charge remover 7. The toner remaining on the intermediate transfer belt 2 after the secondary transfer is cleaned by the cleaning brush 24 and prepared for the next image formation.

  Among these, the intermediate transfer belt 2 as an intermediate transfer member has a belt-like elastic base 11 and a fluororesin-containing surface layer 12 provided on the surface, as shown in FIG. On the opposite side of the belt-shaped elastic substrate 11 from the fluororesin-containing surface layer 12, a reinforcing resin layer 10 is provided.

The elastic substrate 11 in the form of a belt is made of various rubbers or resins such as polyolefin resin, polyester resin, polyamide resin, polystyrene resin, acrylic resin, styrene-acrylic copolymer resin, polycarbonate resin, vinyl chloride resin, silicon resin, It is formed from chloroprene rubber, polybutadiene rubber, isoprene rubber, urethane rubber, EPDM, acrylic rubber, etc., and its volume resistance value is usually 10 ^8.5 to 10 by blending conductive agent particles such as carbon black and various metal powders. It is adjusted to ^11.5 Ω · cm, particularly preferably in the range of 10 ⁹ to 10 ¹¹ Ω · cm. If the volume resistance value is too large, the primary transfer or the secondary transfer property by applying a predetermined transfer bias voltage may be impaired. If the volume resistance value is too small, the surface resistance value of the intermediate transfer belt 2 varies. This is because transfer irregularities or the like occur and image defects are likely to occur. Further, the thickness of the belt-like elastic substrate 11 is preferably in the range of 300 to 600 μm. The thicker the thickness, the greater the bending stress generated on the surface layer 12 by the rollers 21 and 22 that drive the intermediate transfer belt 2 and the more likely the cracks occur. This is because variations in surface resistance are likely to occur.

  The elastic base 11 in the form of a belt preferably has a hardness (JIS A hardness) of 75 degrees or less. If the hardness is too high, it will be difficult to ensure a sufficient nip width between the photosensitive member 1 and the primary transfer roller 8 and the secondary transfer roller 25, and transfer efficiency may be reduced, or the roller 21, There is a possibility that the driving of the intermediate transfer belt 2 by 22 may be difficult.

  Examples of the fluororesin forming the surface layer 12 include polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), polychloro Use trifluoroethylene (PCTFE), ethylene / tetrafluoroethylene copolymer (ETFE), ethylene / chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), etc. However, polytetrafluoroethylene (PTFE) is most preferable in terms of releasability and low friction coefficient. By forming such a surface layer 12, durability can be improved, and toner adhesion to the surface of the intermediate transfer belt 2 can be suppressed to improve cleaning properties.

Further, the surface layer 12 has a volume resistance in the range of 10 ¹² to 10 ¹³ Ω · cm, thereby suppressing variations in surface resistance, and the primary transfer roller 8 and the secondary transfer roller 25 are used. It is suitable for performing all the transfer effectively. Furthermore, the thickness of the surface layer 12 is preferably in the range of 3 to 8 μm. If the thickness exceeds 8 μm, the bending stress may increase and cracks may be easily generated. If the thickness is less than 3 μm, the durability of the surface layer 12 itself is impaired.

  Further, the surface layer 12 may be formed of the above-described fluororesin alone, but since the fluororesin is inferior in film formability, it is usually a polyurethane resin, polyolefin resin, polyester resin, polyamide resin, polystyrene resin, acrylic resin. Surface layer 12 is obtained by dispersing thermoplastic resin such as styrene-acrylic copolymer resin, polycarbonate resin, polyurethane resin such as vinyl chloride resin, or thermosetting resin as binder and dispersing fluororesin in such binder. Is preferably formed. In this case, in order to ensure a desired low friction coefficient and releasability, the content of the fluororesin is preferably 5% by weight or more. Such a surface layer 12 is formed, for example, by dissolving or dispersing a binder resin and a fluororesin in an appropriate solvent, applying the resin, and baking it.

Further, it is preferable to form a reinforcing resin layer 10 on the back surface of the elastic base 11 having a belt shape. By providing such a reinforcing resin layer 10, it is possible to effectively prevent transfer misalignment due to expansion and contraction of the elastic base 11 having a belt shape. This reinforcing resin layer 10 also has a volume of 10 ^8.5 to 10 ^11.5 Ω · cm, particularly 10 ⁹ to 10 ¹¹ Ω · cm, similarly to the elastic substrate 11 in the form of a belt, for effective transfer. It should have resistance, and its thickness should be in the range of 80 to 100 μm.

  Further, the primary transfer roller 8 and the secondary transfer roller 25 are formed of conductive rubber such as foamed EPDM, for example, and a cleaning blade or a cleaning roller can be used instead of the cleaning brush 24.

  In the above description, the present invention has been described with an example in which the intermediate transfer belt 2 is used as an intermediate transfer member. However, the intermediate transfer member used in the present invention is not limited to a transfer belt, but is a drum-like one. It goes without saying that is also applicable. In the drum-shaped intermediate transfer member, an elastic substrate corresponding to the belt-shaped elastic substrate 11 is provided on the surface of an aluminum drum or the like, and a surface layer containing a fluororesin is formed. The image forming apparatus may also be a color image forming apparatus of a type in which a plurality of developing devices filled with toner of each color are arranged around one photoconductor, and an intermediate transfer member is used. Any monochrome image forming apparatus may be used.

  In the image forming apparatus of the present invention configured as described above, the relative speed storage device 36 shown in the block diagram of FIG. 3 stores the relative speed of the photosensitive member 1 and the intermediate transfer belt 2 with respect to the number of printed sheets (number of formed images). As described with reference to FIG. 4, the values are stored so that the photosensitive member 1 is not damaged and the intermediate transfer belt 2 does not vibrate or generate chatter noise. That is, as described above, the relative speed between the photosensitive member 1 and the intermediate transfer belt 2 is set to be not less than the dotted line in FIG. 4 and not more than the solid line, and the number of printed sheets (the number of images formed) is a predetermined number (in FIG. 4). In this example, the ratio of the linear velocity between the photosensitive member 1 and the intermediate transfer belt 2 is a value between approximately 0.990 and 0.992, or approximately between 1.010 and 1.008. Remember as.

  Then, the control circuit 34 reads the value stored in the relative speed storage device 36 in accordance with the value of the counter 35, and in the initial state of the image forming apparatus (when the number of images formed immediately after shipment is small), FIG. As clearly shown in the graph, the motor control circuit 33 controls the photosensitive member motor 31 and the intermediate transfer belt so that the relative speed between the photosensitive member 1 and the intermediate transfer belt 2 is substantially constant, that is, the absolute value of the relative speed is 0.002 or less. An instruction is given to control the speed of the body motor 32. When the image formation instruction 37 is received, the control circuit 34 forms an image of each color on the photoreceptor 1 for each color of black, cyan, magenta, and yellow as described above, and each color is formed on the intermediate transfer belt 2. The toner image is transferred to the recording medium 27, and the counter 35 counts the number of images formed.

  Based on the count value of the counter 35, the control circuit 34 reads the relative speed stored in the relative speed storage device 36, and as described above, the photosensitive member 1 is not damaged and the intermediate transfer belt 2 vibrates. The motor control circuit 33 is instructed to provide a relative speed at which no chatter noise is generated.

  The above is the outline of the image forming apparatus according to the present invention. In the above description, the relative speed has been described to be automatically changed based on the count value of the counter 35. When the relative speed fine adjustment manual button 38 provided in the image forming apparatus is manually operated, the relative speed is manually changed when the user recognizes the chatter noise or the service person recognizes the chatter noise during the periodic inspection. The relative speed at which chatter noise and vibration do not occur may be used. In this case, the relative speed may be changed while listening to vibration and chatter generated by the image forming apparatus, and the operation of the manual button 38 for changing relative speed may be stopped when the chatter or vibration disappears. In addition, as a means for changing the relative speed, a variable relative speed mode (displaying the relative speed as a numerical value on the display unit of the image forming apparatus) is provided in a mode that can be operated only by a serviceman or an administrator of the apparatus, and a numerical value is input. Thus, the relative speed may be changed.

Hereinafter, embodiments in an actual image forming apparatus will be described. First, a chloroprene rubber belt (thickness: 500 μm, JIS A hardness: 70 degrees, volume resistance 10 ^10.5 Ω · cm) is used as the elastic substrate 11 of the intermediate transfer body 2, and a reinforcing resin layer 10 is formed on the back surface thereof as a polyfluoride rubber layer 10. A vinylidene chloride resin layer (thickness: 100 μm, volume resistance 10 ¹⁰ Ω · cm) was provided. In addition, the fluororesin-containing surface layer 12 (thickness: 5 μm, volume resistance 10 ^12.4 Ω · cm) is a coating solution obtained by dispersing a PTFE-containing polyurethane resin composition containing an appropriate amount of carbon black in a solvent. It was prepared, applied on a rubber belt, and formed by baking at 140 to 160 ° C. for 30 minutes. The volume resistivity can be measured in accordance with JIS K6991 using a circular electrode (for example, HR probe of Hirester IP manufactured by Mitsubishi Yuka Co., Ltd.).

  The intermediate transfer belt 2 formed as described above is a full color image forming apparatus (color printer: product number LSC-5016N, manufactured by Kyocera Mita) having a structure as shown in FIG. 100 mm / s), and a printing test of about 200K sheets (200,000 sheets) was performed. The result is the graph shown in FIG.

  In FIG. 4, the horizontal axis represents the number of printed sheets (the number of images formed) with 1000 units as described above, and the vertical axis represents the relative speed between the photosensitive member 1 and the intermediate transfer belt 2, and the relative speed is (1 ) Expression. A solid line is a limit line in which a scratch generated on the photosensitive member 1 affects the image. When the relative speed is larger than the solid line, the image quality is deteriorated. A dotted line is a limit line where the vibration and chatter noise of the intermediate transfer belt 2 is generated, and the vibration and chatter noise are generated when the relative speed becomes smaller than the dotted line.

  That is, in the initial state where the surface of the photoconductor 1 with a small number of images formed is clean, if the relative speed between the photoconductor 1 and the intermediate transfer belt 2 exceeds ± 0.002, the photoconductor 1 is scratched in the axial direction. When the number of printed sheets (number of formed images) exceeds about 50K (50,000), it is uniform on the entire circumferential direction of the photoreceptor 1 and there is no problem in practical use. However, even if the relative speed is increased as the number of printed sheets (number of formed images) increases, scratches due to rubbing with the intermediate transfer belt 2 do not appear as image defects.

  Further, when the number of printed sheets (number of formed images) exceeds about 40K sheets (40,000 sheets), the intermediate transfer belt 2 increases the frictional force between the photosensitive element 1 and the intermediate transfer belt drive roller. Vibration and chatter noise are generated by the repetition of the static friction region and the dynamic friction region caused by the rotational vibration. For this reason, when the number of printed sheets (number of formed images) increases, this vibration and chatter noise can be prevented by increasing the relative speed, but the number of printed sheets (number of formed images) is about 160K (160,000). If it exceeds the relative speed, the relative speed for preventing the vibration and chatter noise is substantially constant and may be ± 0.008 or more (± 0.010 or less). In addition, after the number of printed sheets reaches about 160k or more, the relative speed may be kept constant, or the relative speed may be appropriately changed in order to obtain a central value in a suitable range.

  As described above, by changing the relative speed between the photosensitive member 1 and the intermediate transfer belt 2 in accordance with the number of image forming sheets, in the initial state, both of them are made substantially constant speed and slip marks ( After that, for example, when the surfaces of the image bearing member (photosensitive member) and the intermediate transfer member deteriorate and the frictional force between them increases, the static friction state and the dynamic friction state occur alternately. In order to prevent the occurrence of vibration and chatter noise, the relative speed is changed according to the number of formed images from the state where the friction state between the photoreceptor 1 and the intermediate transfer belt 2 repeats the static friction state and the dynamic friction state. It is possible to obtain an image forming apparatus in which only the dynamic friction state is generated by changing the relative speed obtained in advance to be only the dynamic friction state.

  Then, the relative speed between the photosensitive member 1 and the intermediate transfer belt 2 is changed in accordance with a predetermined relationship between the number of image formations and the relative speed, and after the number of image formations reaches a predetermined number, the relative speed is substantially reduced. By making it constant, the relative speed can be changed without degrading the image forming quality.

  The predetermined relative speed is approximately 0008 to 0.01 when the relative speed is expressed by the equation (1), whereby an optimum relative speed can be obtained.

  The intermediate transfer belt 2 is an endless belt having a reinforcing resin layer 10 in the lowermost layer, an elastic base layer 11 in the middle, and a fluororesin-containing surface layer 12 in the contact surface with the photoreceptor 1. Thus, the intermediate transfer belt 2 can be prevented from extending more than necessary by the reinforcing resin layer 10, and the elastic base layer 11 can secure a nip with the photoreceptor 1 and the frictional force can be reduced by the fluororesin-containing surface layer 12. Can do.

  The image forming apparatus of the present invention further includes a counter 35 that counts the number of image formations, and a storage device 36 that stores the relative speeds of the image carrier and the intermediate transfer member corresponding to the number of image formations. The relative speed stored in the storage device 36 is read out in accordance with the count result and the relative speed is changed to change the relative speed between the photoreceptor 1 and the intermediate transfer belt 2 to a desired speed with a simple and inexpensive configuration. Can do.

  Furthermore, the image forming apparatus of the present invention is provided with the variable means 38 for changing the relative speed between the photosensitive member 1 and the intermediate transfer belt 2, so that, for example, during a regular service, a serviceman confirmed the chatter noise of the intermediate transfer belt. Sometimes it is possible to change the relative speed so that it does not occur.

  By changing the relative speed of the image carrier (photoreceptor) and the intermediate transfer member (belt) according to the number of images formed, slip marks (scratches) of the image carrier (photoreceptor) in the initial state are prevented. Thus, it is possible to provide an image forming apparatus that can reliably prevent vibration, chatter noise, and the like generated after forming a large number of images with a simple and inexpensive configuration.

1 is a schematic configuration diagram of a tandem color image forming apparatus to which the present invention is applied. FIG. 3 is a diagram showing an outline of a layer structure of an intermediate transfer member. FIG. 4 is a diagram illustrating an example of a control block for changing a relative speed between an image carrier (photosensitive member) and an intermediate transfer member according to the number of image formations. We investigated how the scratches on the image carrier (photosensitive member), the vibration of the intermediate transfer member, and the chatter sound change depending on the relative speed difference between the image carrier (photosensitive member) and the intermediate transfer member and the number of images formed. It is a graph.

Explanation of symbols

31 Photoconductor motor 32 Intermediate transfer body motor 33 Motor control circuit 34 Control circuit 35 Counter 36 Relative speed storage device 37 Image formation instruction 38 Relative speed change manual button

Claims (6)

An image forming apparatus comprising: an image carrier that forms a toner image by an electrophotographic method; and an intermediate transfer member that primarily transfers a toner image formed on the image carrier and then secondarily transfers it to a recording medium.
An image forming apparatus, wherein a relative speed between the image carrier and the intermediate transfer member is changed according to the number of image forming sheets.   The relative speed between the image carrier and the intermediate transfer member is changed in accordance with a predetermined relationship between the number of image formations and the relative speed, and the relative speed is made substantially constant after the number of image formations reaches a predetermined number. The image forming apparatus according to claim 1. The image forming apparatus according to claim 2, wherein the predetermined relative speed is approximately 0.008 to 0.01 when the relative speed is expressed by the following equation.
Relative speed = | 1- (photosensitive linear velocity / intermediate transfer linear velocity) |   2. The endless belt according to claim 1, wherein the intermediate transfer member is an endless belt having a resin layer in the lowermost layer, an elastic base layer in the middle, and a fluororesin layer on the contact surface with the image carrier. Image forming apparatus.   The image forming apparatus according to claim 1, further comprising: a counter that counts the number of image formations; and a storage unit that stores a relative speed between the image carrier and the intermediate transfer body corresponding to the number of image formations. An image forming apparatus comprising: reading out a relative speed stored in the storage unit according to a result, and changing the relative speed.   The image forming apparatus according to claim 1, wherein the image forming apparatus includes a variable means for changing a relative speed between the image carrier and the intermediate transfer member.

Images