JP3303567B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using a moving member such as a transfer belt, an intermediate transfer member or a photosensitive member.
In particular, the present invention relates to an image forming apparatus provided with a cleaning device for removing foreign matters such as toner adhered to the surface of a moving body after duplex copying.

[0002]

2. Description of the Related Art In this type of image forming apparatus, a part of a release agent (silicon oil or the like) supplied to a fixing roll or a pressure roll is transferred to a transfer sheet fixed by a fixing device. The transferred oil diffuses into the fibers of the paper in a relatively short time between toner particles or through pinholes. In particular, the oil transferred to the surface of the sheet where no toner image exists is directly diffused into the fibers of the sheet, and has little effect on the operation of the image forming apparatus and the image quality. However, in a color image forming apparatus, particularly a color image forming apparatus that reproduces a large number of colors by superposing three or four color toners, (1) a large number of superposed toners , The toner layer to be fixed becomes thicker. (2) In order to form a color by mixing toners of different colors by fixing, the toner must be sufficiently heated and fluidized. And so on.

For this reason, the fixing device is likely to be offset easily. To prevent the offset, a fixing device having high releasability is required, and a large amount of fixing rolls coated with a rubber-like elastic material such as silicon rubber are required. A fixing device for applying a release agent is used. Since the amount of oil supplied to the transfer paper depends on the image density, when an image having a high image density such as a photograph or a chart is printed, a large amount of oil exists on the toner in the image portion. . When the single-sided printed sheet in such a state is circulated in the image forming apparatus for double-sided printing, the oil adhering to the sheet adheres to a transport roll, a transfer belt, a photoconductor, and the like in a paper transport path. .

Under such conditions, for example, in image formation on the second side in a double-sided printing operation, when the transfer paper after fixing the first side is attracted to the moving body again, it is separated from the moving body. The cleaning agent of the movable body was impaired by the release agent adhered on the movable body due to the release of the mold agent, resulting in poor cleaning. Generally, the toner and the mark for registration correction attached to the transfer belt at the time of a jam are finally removed by a cleaning unit. In this type of image forming apparatus, a blade system is adopted as a cleaning unit in consideration of cleaning efficiency.

However, the coefficient of friction between the cleaning blade and the transfer belt varies depending on the amount of oil adhering to the transfer belt, and the cleaning blade causes a stick-slip phenomenon due to the change in the coefficient of friction. If the cleaning blade vibrates due to the extreme stick-slip phenomenon, the edge of the cleaning blade becomes unstable, and dirt such as toner on the transfer belt passes through the blade, so that a reliable cleaning operation cannot be performed. Was. Japanese Patent Application Laid-Open No. 5-188720 discloses a recording material transporting device having a structure for removing oil on a sheet, and further discloses an image forming apparatus provided with a transfer belt vibration absorbing means. No. 6,086,045.

[0006]

In order to prevent the toner from slipping through by providing a plurality of blades, a cleaning effect is obtained by combining a plurality of blades in a forward direction against the surface to be cleaned. Low. In addition, when the blade is brought into contact with the surface to be cleaned in the opposite direction, the cleaning effect is high. However, when there is little attached matter (lubricant) such as toner on the surface of the moving body, the blade is turned up. In a cleaning device using a plurality of blades, it is not preferable to dispose the cleaning device on the downstream side with less attached matter.

Further, in a cleaning device having a plurality of blades, the holding of the blades is integrated,
The vibration generated in one blade is directly transmitted to another blade. In view of the above, the present invention provides a cleaning mechanism capable of improving the cleaning efficiency with a simple configuration in an image forming apparatus having a cleaning unit using a plurality of blades.

[0008]

According to the present invention, there is provided a cleaning apparatus having a plurality of cleaning blades which are provided in an image forming apparatus according to the present invention and which abut against a moving body which conveys a transfer image, a transfer sheet, etc., for cleaning. The tip of the cleaning blade disposed on the upstream side abuts from the direction opposite to the moving direction of the moving body, and the tip of the cleaning blade disposed on the downstream side abuts in the forward direction on the moving direction of the moving body. It basically has a configuration. In addition, the plurality of cleaning blades are configured to be held by independent holding members, respectively, and the blade disposed on the downstream side is brought into contact with the surface of the moving body depending on the operation state of the blade disposed on the upstream side,
It also has a configuration in which the distance is adjusted.

[0009]

The cleaning blade disposed on the upstream side of the moving body abuts on the surface of the moving body in a direction opposite to the moving direction of the moving body to perform cleaning, and foreign substances that pass through the blade and remain on the belt are removed upstream. It is wiped off by a cleaning blade disposed on the downstream side, the pressure contact force of which is adjusted according to the movement state such as vibration of the blade disposed on the downstream side.

[0010]

An embodiment of the present invention will be described with reference to the drawings. Embodiment 1 FIG. 3 shows a full-color image forming apparatus embodying the present invention. The full-color image forming apparatus includes image carriers (photosensitive drums) 2Y, 2M, 2C, 2 rotatably supported on a rotating shaft.
K, and an image forming unit is arranged on the outer peripheral portion of each image carrier (photosensitive drum). The image forming means may be any means, but the image forming means shown in this embodiment is separated into primary chargers 3Y, 3M, 3C, and 3K which uniformly charge the surface of the photosensitive drum to, for example, -500 to 800V. Irradiates the light image or the light image corresponding thereto
Exposure means for forming an electrostatic latent image on Y, 2M, 2C, 2K, for example, an exposure means (not shown) comprising a laser beam exposure device or the like, and an electrostatic latent image on photosensitive drums 2Y, 2M, 2C, 2K. Developing devices 5Y, 5M, 5C for visualizing images
5K.

The developing devices 5Y, 5M, 5C and 5K contain developers such as toners of four colors of yellow, cyan, magenta and black, and form a uniformly charged electrostatic latent image on the photosensitive drum. Developing conditions such as a developing bias are selected so that the respective toners adhere to the portion where the laser beam is applied. The visible image (toner image) developed on the photosensitive drum is transferred to a transfer sheet 70 conveyed by a transfer belt conveying device that moves in the direction of arrow A by a drive shaft 9 and shafts 10 to 12 that follow the drive shaft 9. . The transfer paper 70 supplied from the paper feeding devices 300, 305, and 310 is attracted to the transfer belt 7 by the attracting corona discharger 14, and is sequentially conveyed to transfer positions provided to face the respective photosensitive drums. . On the opposite side of the transfer belt 7 are a paper suction roll 13 and a suction corona discharger 14.
Is provided, and charges are injected into the transfer paper 70 to adsorb the transfer material (paper) to the transfer belt. Different voltages (for example, voltages of +4.2 KV to 12.0 KV) are applied to the transfer corona dischargers 8Y, 8M, 8C, and 8K in the transfer device, and the transfer current is +50 μA to +2000 μA.

After the transfer is completed, the transfer paper 70 is peeled off from a corona discharger 29 to which a DC bias of AC oscillation can be applied to weaken the electrostatic attraction to the transfer belt 7 and an insulating member such as resin. It is separated from the transfer belt 7 by the claw 21 and guided to the fixing device 100. The sheet 70 separated from the transfer belt 7 by the separation claw 21 is
As a result, the toner image is heated and fixed. At this time, a large amount of a release agent such as silicone oil is applied to the surface of the paper in order to prevent the toner image from being offset to the fixing roll 105 or the pressure roll 110.

In the case of single-sided printing, the paper 70 is discharged through the discharge side transport path 240. For double-sided printing,
The sheet 70 is sent to the sheet reversing conveyance path 230, and the paper passing through the conveyance path is turned upside down.
0, is advanced to the upstream side of the image forming apparatus, is again sent to the transfer belt 7, and the toner image is transferred to the back surface (second surface) of the sheet.

After the transfer belt 7 has been peeled off from the transfer sheet 70, the corona discharger 23 for discharging the inner belt, which is provided so as to sandwich the transfer belt, is provided while the transfer belt advances from the most downstream transfer step to the most upstream transfer step. The charge is removed by the outer belt charge removing corona discharger 24. The corona discharger for belt neutralization is an AC corona discharger to which a DC bias of AC oscillation can be applied similarly to the peeling means 29. The surface of the transfer belt 7 from which the charge has been removed is used as a transfer belt cleaning unit (apparatus).
It is cleaned by 50 and enters a new round.

Next, a cleaning device mounted on the image forming apparatus of the present invention will be described. Embodiment 1 (see FIGS. 1 and 2) The transfer belt cleaning device 50 is disposed downstream of the corona dischargers 23 and 24 for static elimination. The transfer belt 7
Highly insulating materials such as polyethylene terephthalate (PET) film, polyvinylidene fluoride resin film, polyester film, polycarbonate film, and polyetheretherketone film are used. After cutting this material to a predetermined size, it is an endless belt body connected at both ends by, for example, ultrasonic welding,
The transfer paper is placed and transported.

The cleaning device 50 removes a registration mark for registration correction, a toner image patch for density control, untransferred toner at the time of paper jam, and the like from the surface of the transfer belt from which the charge has been removed. The transfer belt cleaning device 50 mainly includes a cleaning brush 51 and a first cleaning blade 5 as auxiliary means for cleaning.
3, a second cleaning blade 55, and a cleaning unit 57 for accommodating a collected toner box for storing the cleaned toner. The cleaning brush 51 comes into contact with the belt 7 that has passed through the static eliminators 23 and 24 and sweeps off dust adhering to the surface of the belt 7.

The first cleaning blade 53 is provided downstream of the cleaning brush 51, and the blade edge 533 is brought into contact with the belt 7 from which dust has been removed by the brush 51. Etc. The first cleaning blade 53 has the blade edge 533 positioned on the drive roll 9 via the belt 7 and is disposed so as to come into contact with the belt in the direction opposite to the traveling direction (this contact method is called a doctor method). . The first cleaning blade 53 is attached to the cleaning unit 57 so that the edge of the cleaning blade always contacts the surface of the transfer belt 7.

The second cleaning blade 55 is located on the downstream side of the first cleaning blade 53, and the blade edge 555 contacts the driving roll 9 via the belt 7. The blade edge 555 of the second cleaning blade 55 contacts in the forward direction along the traveling direction of the belt 7 (this contact method is called a wiper method). The second cleaning blade 55 slides on the belt 7 to remove dust such as toner remaining on the transfer belt 7 after passing through the first cleaning blade 53.

Looking at the characteristics of the cleaning blades of the doctor type and the wiper type, the cleaning blades of the doctor type have higher cleaning performance than the blades of the wiper type, but require high contact position accuracy in operation. Due to this fact, the first cleaning blade 53, which mainly performs the cleaning operation on the belt, adopts a doctor type arrangement having a high cleaning performance, and cleans the toner that has passed through the first cleaning blade 53. Cleaning blade 55 whose position accuracy may be relatively low
Are arranged in a wiper system.

As described above, by arranging the doctor blade having a high cleaning effect on the upstream side and the wiper blade which does not turn up on the downstream side, the blade can be turned up in both a normal use state and a blade vibration state. A good cleaning effect that does not occur can be obtained. Also, the cleaning blade does not depend on the contact method,
Fluctuation of the friction coefficient between the contact portion edge and the member to be cleaned constantly causes vibration. However, in a full-color image forming apparatus having a double-sided function, the fluctuation of the friction coefficient is further accelerated due to oil adhesion to the transfer belt. Is done. If the rigidity of the mounting portion is low, the vibration of the blade is transmitted from the blade itself to the holding member and the cleaner housing, and is amplified to resonate. In particular, in an apparatus provided with a plurality of cleaning blades, these interfere with each other and the vibration is amplified. Therefore, each of the cleaning blades 53 and 55 having a different mounting method shown in this embodiment is held by an independent holding member, so that even if vibration occurs in one blade, it may affect other blades. In addition, the inconvenience of the related art can be solved. Next, characteristics of the materials of the cleaning blades 53 and 55 will be examined. The cleaning blade is a plate-like body formed from a thermosetting polyurethane rubber material. The rubber material has both elastic properties and viscous properties, and requires a certain degree of elasticity for the cleaning action. This characteristic can be determined by its rebound resilience.

The characteristics of the high rebound resilience material and low rebound resilience material are shown in Table 1.

[Table 1] Although the rebound resilience of the rubber material is also shown in the graph shown in FIG. 4, it is highly dependent on the environment. For example, when the temperature of both the high rebound resilience material and the low rebound resilience material is low, the rebound resilience is low, and the resilience increases as the temperature increases. But,
The high rebound resilience material has good cleaning performance and low permanent deformation at low temperature and low humidity, but has poor vibration absorption. The low rebound resilience material has poor cleaning performance at low temperature and low humidity and large permanent deformation, but has good vibration absorption performance. From these facts, it is preferable to use a high resilience material for the first cleaning blade 53 which requires high cleaning performance.

Further, when the coefficient of friction between the cleaning blade and the belt to be cleaned increases, a stick-slip phenomenon occurs. When the blade repeats vibration, the high resilience material cannot absorb the vibration. . And this vibration becomes sound energy and may generate abnormal noise. The second cleaning blade, which cleans only the toner passing through the first cleaning blade 53, has a considerably small amount of toner reaching the blade edge, and thus easily causes the stick-slip phenomenon as described above. Therefore, it is preferable to use a low rebound resilience material having a high vibration absorbing effect for the second cleaning blade 55. This cleaning device can be disposed with high positional accuracy by using a high repulsion elastic material for the first cleaning blade 53, and the cleaning efficiency is good. Further, by using a low rebound resilient material for the second cleaning blade 55, it is possible to prevent generation of abnormal noise called so-called blade squeal.

Second Embodiment (See FIG. 6) In this embodiment, the arrangement position of the first cleaning blade is changed. The second cleaning blade 550 has its edge 557 pressed against the drive roll 9 by a wiper method to obtain a high pressing force. The first cleaning blade 530 is disposed in a doctor system, but the edge 537 of the blade
Is in contact with Abutting position s ₁ is the belt 7 is made to position the dimension S upstream of the position S ₂ in contact with the drive roll 9. The dimension S can be selected from 0 mm to 8 mm, but a distance of about 4 mm is particularly preferable. When the film thickness of the belt 7 is, for example, 75 μm, the thickness of the seam portion fused by ultrasonic welding is about 100 to 120 μm. FIG. 6 shows the vibration of the tip of the blade in contact with the drive roll 9 in this case. That is, when the blade vibrates at the seam portion, the amplitudes of T ₁ , T ₂ , T ₃ , and T ₄ are (P ₁
−P ₂ ).

However, when the contact portion of the blade 530 is detached from the drive roll 9, the vibration of the blade edge 537 when the seam portion passes, as shown in FIG.
₃ -P ₂ ) is much smaller than the amplitude (P ₁ -P ₂ ).
This is because there is nothing to support the belt, so that when the seam passes, the belt 7 can slightly escape in the direction pressed by the blade, and as a result, the vibration of the blade 530 is suppressed. In the cleaning device according to this embodiment, the vibration of the first cleaning blade 530 is suppressed, the amplitude is small, and a reliable cleaning effect can be obtained on the upstream side of the belt 7.

Third Embodiment In this embodiment, the pressing force of the downstream wiper blade is relatively higher than that of the upstream doctor blade. FIG. 8 shows the characteristics of the cleaning property with respect to the change in the cleaning pressure. Generally, when examining the doctor system, although there are other factors such as the contact angle, the cleaning performance with respect to the cleaning pressure is as shown in the graph, and the wiper system indicated by the line a is the cleaning method with the doctor system pressurized indicated by the line b. Poor. That is, the wiper method requires a relatively strong cleaning pressure as compared with the doctor method. In this embodiment, the thickness is 2.0 mm and the free length is 10.5 m.
As a result of a test using a cleaning blade having the same cross-sectional shape of m and a rubber hardness (JIS A scale) of 70 °, a doctor method was used to completely remove the toner remaining on the surface of the transfer belt by about 1.0 gf / mm (unit). Width) In the wiper method, a cleaning pressure of 2.2 gf / mm or more was required. Therefore, the contact force of the second cleaning blade 55 on the surface of the belt 7 is
It is set to be about twice as high as the contact force of the first cleaning blade 53 on the surface of the belt 7.

Fourth Embodiment In this embodiment, the pressing force of the second cleaning blade 55 is adjusted according to the cleaning state of the first cleaning blade 53, the image forming mode, image information, and the like. The second cleaning blade 55 includes a support plate 52 rotatably attached to the cleaning unit 57.
It is stuck to. The support plate 52 is connected to the apparatus main body via a spring 62 disposed at one end of an inverted L-shaped support frame 61 fixed to the apparatus main body, and is urged toward the apparatus main body (see FIG. 2). A pressing piece 63 is rotatably attached to the other end of the support frame 61. When the pressing piece 63 is rotated counterclockwise, the supporting plate 52 is pressed. The support plate 52 rotates in the direction of the drive roll 9 against the urging force of the spring 62, and the second cleaning blade 55 attached to the support plate 52 advances in the direction of the belt 7 and contacts the transfer belt 7. (The state shown by the solid line in FIG. 1). The contact and separation of the second cleaning blade 55 from and to the surface of the belt 7 are controlled by a controller based on the amount of dust such as toner remaining on the belt.

(A) The pressing force of the second cleaning blade is adjusted according to the condition of the first cleaning blade. A-1 A strain caused by vibration of the first cleaning blade is detected by a strain gauge. When the fluctuation of the measured value of the strain becomes large, the pressing force of the second cleaning blade is made stronger than the normal pressing force. A-2 The drive load of the drive roll is detected by a change in the current value of the drive motor or the like. When the fluctuation of the driving load of the driving roll becomes large, the pressing force of the second cleaning blade is made stronger than the normal pressing force. According to this method, when the fluctuation of the friction coefficient of the first cleaning blade with the belt becomes large, the vibration of the cleaning blade is generated, and at the same time, the load fluctuation of the driving roll is generated. When the numerical value of the driving load of the driving roll increases, that is, when the friction coefficient increases, the vibration of the cleaning blade is generated, and the first cleaning blade , The amount of toner remaining on the belt after passing through increases. Along with this, the pressure contact force of the second cleaning blade is increased, and the cleaning performance is enhanced.

(B) The pressing force of the second cleaning blade is controlled in accordance with the operation selection mode of the image forming apparatus (duplex copy mode selection, set number, number of documents, paper size, etc.) and image density information. In the case of a double-sided copy mode, a large number of set sheets, a large number of documents, a high image density, or the like, where a large amount of release agent adheres to the transfer belt, the pressing force of the second cleaning blade is increased.
As shown in FIG. 9, the amount of the release agent (oil) adhering to the transfer paper increases as the image density increases, and the amount of the toner increases, and the amount of oil adhering increases. When the amount of oil increases, the cleaning performance of the first cleaning blade of the doctor system decreases, and as a result, foreign matters such as toner remaining on the belt increase. Therefore, the pressing force of the second cleaning blade is increased to improve the cleaning efficiency. To improve.

In the above embodiment, for simplicity of explanation, one cleaning blade is provided upstream and one cleaning blade is provided downstream.
Although the cleaning devices are individually provided, a plurality of blades may be provided upstream and a plurality of blades may be provided downstream. Further, in the above-described embodiment, the cleaning target is the insulative endless belt that adsorbs and holds the transfer paper, and is a tandem type color copying machine capable of recording on both sides with a release agent supply type toner fixing unit. The moving body includes a drum-shaped photosensitive body, a belt-shaped photosensitive body, and a belt-shaped intermediate transfer body that holds and conveys a transferred image.

[0030]

The image forming apparatus of the present invention performs cleaning by changing the contact method at two locations, upstream and downstream, of the belt that conveys a transferred image or a transfer sheet, thereby performing a reliable cleaning operation. Further, the cleaning means disposed on the upstream side is brought into contact with the belt in the opposite direction to the traveling direction to improve the cleaning efficiency, and when it is predicted that there is residual dust, the cleaning means on the downstream side is operated. be able to.

[Brief description of the drawings]

FIG. 1 is a structural explanatory view of a cleaning device.

FIG. 2 is an explanatory diagram of a non-operation state of the cleaning device.

FIG. 3 is a schematic diagram of an image forming apparatus.

FIG. 4 is a graph showing the characteristics of each material of a cleaning blade.

FIG. 5 is a structural explanatory view of another embodiment of the cleaning device.

FIG. 6 is an explanatory diagram of a vibration state of the transfer belt.

FIG. 7 is an explanatory diagram of a vibration state of the transfer belt.

FIG. 8 is a graph showing a relationship between cleaning pressure and cleaning performance.

FIG. 9 is a graph showing the relationship between the image density and the amount of attached silicone oil.

[Explanation of symbols]

Reference Signs List 7 transfer belt, 9 drive roll, 50 cleaning device, 51 cleaning brush, 52 support plate, 53 first cleaning blade, 55 second
Cleaning blade, 61 support frame, 63 pressing pieces.

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-5-341696 (JP, A) JP-A-6-208262 (JP, A) JP-A-6-175457 (JP, A) JP-A-4- 328785 (JP, A) JP-A-6-27860 (JP, A) JP-A-2-148168 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 21/10-21 / 12 G03G 15/16-15/16 103

Claims (8)

(57) [Claims] 1. An image forming apparatus comprising: a cleaning device that removes deposits on a surface of a moving body, wherein the cleaning device has a plurality of cleaning blades whose tips are pressed against the surface of the moving body, and a moving direction of the surface of the moving body. The tip of the cleaning blade disposed on the upstream side of the cleaning blade abuts on the surface of the moving body from the opposite direction to the surface of the moving body, and the distal end of the cleaning blade disposed on the downstream side of the cleaning blade faces the moving direction of the surface of the moving body. come in contact with the forward direction, to a mobile surface of the cleaning blade to be disposed downstream
Pressure of the cleaning blade installed on the upstream side
An image forming apparatus configured to be adjusted according to the working condition . 2. An image forming apparatus comprising: a cleaning device for removing deposits on a surface of a moving body, wherein the cleaning device has a plurality of cleaning blades each having a tip pressed against the surface of the moving body, and a moving direction of the surface of the moving body. The tip of the cleaning blade arranged on the upstream side of the cleaning blade contacts the surface of the moving body from the opposite direction to the surface of the moving body, and the tip of the cleaning blade arranged on the downstream side of come in contact with the forward, impact resilience of the cleaning blade to be disposed upstream below
Higher than the rebound resilience of the cleaning blade installed on the flow side
Image forming apparatus . 3. A cleaning blade, independent become held by the holding member according to claim 1 or 2 image forming apparatus according. 4. A cleaning blade disposed on the downstream side of the tip of the blade is pressed against the moving surface position, the image forming apparatus movably constructed comprising according to claim 1 or 2, wherein at a position spaced apart. 5. An image forming apparatus according to claim 1 or 2, wherein the
An image forming apparatus comprising: a release agent supply type toner fixing unit; a double-sided recording unit for a transfer sheet; and a cleaning device that removes deposits on a surface of a moving body. 6. The image forming apparatus according to claim 5 , wherein the pressure of the cleaning blade disposed on the downstream side against the surface of the moving body is adjusted according to an operation selection mode of the image forming apparatus. 7. The image forming apparatus according to claim 5 , wherein the pressure of the cleaning blade disposed on the downstream side to the surface of the moving body is adjusted according to the image density information. 8. A moving body is an endless belt that holds and conveys an image or a transfer sheet. The endless belt is stretched and conveyed by a plurality of rolls including a driving roll, and a cleaning blade disposed downstream is a roll. pressed against the endless belt located above the cleaning blade image forming apparatus according to claim 1 or 2, wherein become configured to press the endless belt at an upstream position of the roll to be disposed upstream.