JPH0968900A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a transfer paper from being soiled, and to stabilize transportation of the transfer paper. SOLUTION: This image forming device provided with at least, a cleaning blade 33 whose a width is equal to or exceeding the width of the belt 11, on a surface of the belt 11 for transporting the transfer paper to fixing means 7, possible of being elastically bend, and held in press contact therewith, is constituted in such a manner that a scraping property with respect to toner stuck on the belt 11 is raised, soiling of the transfer paper by the residual toner is prevented, slippage of the belt 11 corresponding to a driving roller 9 is restrained, and the transportation of the transfer paper is stabilized, by setting a sum total of a surface roughness of the belt 11 and the surface roughness of the cleaning blade 33, at a value being smaller than the average grain size of toner, or setting the surface roughness of the belt 11 at the value being smaller than a half of the average grain size of the toner.

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 for transferring an image formed by an electrophotographic method onto a transfer paper.

[0002]

2. Description of the Related Art Conventionally, an electrostatic latent image is written on the surface of an image carrier by means of latent image writing means, the electrostatic latent image is developed by means of developing means, and the image on the image carrier is transferred by means of transfer means. A transfer brush is transferred to paper, and the transfer paper after transfer is conveyed to a fixing unit by an endless belt, and the image on the transfer paper is fixed by the fixing unit, and a rotary brush or a fixed brush formed of a pile fabric, or There is an image forming apparatus in which a toner attached to a belt is wiped by a cleaning blade formed of rubber or the like.

[0003]

In an image forming apparatus in which the toner on the belt is wiped with a rotating brush or a fixed brush formed of a pile fabric, the brush has a coarser grain size than the toner particle size. Toner often slips under the brush and belt cleaning is incomplete.

Further, even in an image forming apparatus in which the toner on the belt is wiped off by a rubber cleaning blade, if the surface roughness of the belt is larger than the particle diameter of the toner, some cleaning may come into contact with the belt. If the blade edge is rough, belt cleaning is incomplete.

If the toner is not completely wiped off and remains on the belt in this way, the back surface of the transfer sheet to be conveyed next becomes dirty with the remaining toner. Further, if the toner adheres between the belt and the roller that drives the belt, slippage occurs between the two and the transfer paper becomes unstable. further,
There is a rotary brush or a fixed brush which is used in combination with a rubber cleaning blade, but both have a problem that the transfer paper is soiled due to incomplete cleaning performance, which unnecessarily increases the number of parts and enlarges the apparatus.

[0006]

According to the first aspect of the present invention,
The total of the surface roughness of the belt for conveying the transfer paper to the fixing means and the surface roughness of itself is set to a value smaller than the average particle diameter of the toner of the developing means, and has a width equal to or larger than the width of the belt. In the image forming apparatus, a cleaning blade that flexes elastically is provided in pressure contact with at least the surface of the belt. Therefore, the toner having the average particle size or more is reliably wiped by the cleaning blade. In addition, looking at the volume distribution of all toners, the ratio of toner particles having an average particle size or less is extremely low, and the toner particles are easily bonded to each other by the attraction force due to charging. However, the probability of passing through the cleaning blade is extremely low.

According to a second aspect of the present invention, a cleaning blade which has a width equal to or greater than the width of the belt and elastically bends is provided on at least the surface of the belt that conveys the transfer paper to the fixing means. In addition, the image forming apparatus is such that the surface roughness of the belt is set to a value of ½ or less of the average particle diameter of the toner of the developing unit. Therefore, since the accuracy of the surface roughness of the cleaning blade is significantly higher than that of a brush or the like, even if the surface roughness of the cleaning blade is not regulated, the surface roughness of the belt against which the cleaning blade is brought into contact with the toner average particle By setting the diameter smaller than the diameter to ½, the gap at the contact portion between the belt and the cleaning blade can be maintained at about the average particle diameter of the toner. As a result, the toner having an average particle size or more is reliably wiped by the cleaning blade. In addition, looking at the volume distribution of all toners, the ratio of toner particles having an average particle size or less is extremely low, and the toner particles are easily bonded to each other by the attraction force due to charging. However, the probability of passing through the cleaning blade is extremely low.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 is an image forming apparatus main body. A plurality of paper feed cassettes 2 are provided at the bottom of the image forming apparatus main body 1, and paper feed rollers 3 for drawing out transfer paper are rotatably provided at the end portions of these paper feed cassettes 2. A conveyance roller 6 is provided in a paper feed path 5 that guides the transfer paper pulled out by the paper feed roller 3 to the registration roller 4. Conveyor belt 8 that conveys the transfer paper supplied by the registration rollers 4 to the fixing device 7, which is a fixing unit.
Is an endless belt 11 wound around a driving roller 9 and a driven roller 10 driven by a motor (not shown), and a tension roller 12 rotatable on the inner surface of the belt 11.
It is a structure in which is pressed. Further, a paper discharge tray 13 is formed on the top of the image forming apparatus main body 1, and a paper discharge tray 14 is provided on the side. In the paper discharge path 15 that guides the transfer paper that has passed through the fixing device 7 to the upper paper discharge tray 13, a paper discharge roller 16 that discharges the transfer paper and a discharge tray for the transfer paper are selectively discharged. A rotatable switching claw 17 for switching to the 14 side is provided.

In addition, on the upper part of the conveyor belt 8, from the upstream side to the downstream side in the conveying direction of the transfer sheet, yellow,
Developing units 18Y, 18M, 18C, and 18BK for forming magenta, cyan, and black images are sequentially arranged. These developing units 18Y, 18M, 18
C and 18BK are a photoconductor 20 which is an image carrier rotatably provided on both side plates 19 of the image forming apparatus main body 1, and a photoconductor 2.
A charger 21 for uniformly charging the surface of the photosensitive drum 20 and the photoconductor 20.
It comprises a developing device 22 for forming an image of the electrostatic latent image on the top, a cleaner 23 for cleaning the surface of the photoconductor 20, and a discharge lamp 24 for removing charges on the surface of the photoconductor 20. Further, below the photoconductor 20, a transfer roller 25 that is a transfer unit that comes into contact with the inner surface of the conveyor belt 8 is rotatably provided.

Further, on the side plate 19 of the image forming apparatus main body 1, deflection scanning type exposure devices 26Y, 26M, 26C and 26BK which are latent image writing means corresponding to the developing units 18Y, 18M, 18C and 18BK, respectively. Is provided with a support member 27. That is, the side plate 19 is provided with a plurality of shafts 28, 29, 30 and the shafts 28, 30 are provided with locking means (pins) 31 for locking the support member 27.

In the present embodiment, the exposure device 26
Y, 26B, 26M, and 26BK not only write an image on the photoconductor 20, but also write a correction pattern including information on the optical density of the image on the photoconductor 20. Only this correction pattern is transferred to the belt 11. Then, a CCD image sensor 32 that reads the correction pattern on the belt 11 and feeds the read data back to an image control unit (not shown) as data for correcting the developing conditions and the like faces the outer periphery of the drive roller 9. It is arranged.

Further, a cleaning means 34 having a cleaning blade 33 which comes into elastic contact with the belt 11 on the outer circumference of the driven roller 10 is provided.
As shown in FIGS. 2 to 4, the cleaning means 34
Has a plate holder 35 to which the cleaning blade 33 is fixed, and a holder 37 for fixing the plate holder 35 with a screw 36. By biasing the holder 37 with a spring 38, the cleaning blade 33 is moved to the belt 11. Are pressed against each other with a contact angle of about 20 °. The contact angle referred to here is a tangent line in the rotation direction on the belt 11 with which the edge of the cleaning blade 33 comes into contact with the cleaning blade 33 in order to effectively wipe off the toner on the belt 11 by the edge of the cleaning blade 33, and the cleaning angle. This is the angle formed by the blade 33. The belt 11 is made of thermosetting polyimide resin,
It has a thickness of 100 μm and an electric resistance of 10 ¹² Ω · cm. The cleaning blade 33 is made of silicon rubber.

In such an image forming apparatus, when a signal for forming an image is input from a host computer (not shown) or the like, the transfer paper in the paper feed cassette 2 is fed and the nip of the registration roller 4 is fed. Stand by in contact with the section. On the other hand, images are sequentially formed from the photoconductor 20 on the right side. That is, in the yellow developing unit 18Y,
During the process of rotating the photoconductor 20, the charger 21 causes the photoconductor 20 to move.
The surface of is charged, the exposure device 26Y scans the charged light with the beam light to form an electrostatic latent image, and the developing device 22 develops the electrostatic latent image. Similarly, images are selectively formed on the photoconductors 20 of the magenta developing unit 18M, the cyan developing unit 18C, and the black developing unit 18BK. Then, since the registration rollers 4 rotate in synchronization with these image forming timings, the image on the photoconductor 20 is transferred by the transfer roller 25 while the transfer paper is being transferred by the transfer belt 8. Transfer belt 8
The transfer paper that has reached the end portion of is separated from the belt 11 that is bent on the driving roller 9 having a small curvature and goes straight to the fixing device 7, which fixes the transferred image. The transfer paper after fixing is discharged to the discharge receiver 13 or the discharge tray 14.

In the process of forming an image, toner may drop from the photoconductor 20 or the transfer paper on the surface of the belt 11, but since the cleaning blade 33 is pressed against the belt 11 rotating counterclockwise. Then, the toner adhering to the belt 11 is wiped off by the cleaning blade 33 and stored in a toner receiver (not shown).

Here, the total of the surface roughness of the belt 11 and the surface roughness of the cleaning blade 33 is set to a value smaller than the average particle diameter of the toner. Specifically, the average particle size of the non-magnetic one-component toner is 10 μm, and the belt 11
Has a surface roughness Rz of 3.0 μm or less, and the cleaning blade 33 has a surface roughness Rz of 5 μm or less and an edge (ridge line).
The accuracy is 6 μm or less. Therefore, even if the cleaning blade 33 is brought into contact with the belt 11 at the surface or the edge, a gap for passing the toner having an average particle size or more is not formed between the two. Therefore, the toner having a particle size equal to or larger than the average particle size does not pass under the cleaning blade 33 and is reliably wiped by the cleaning blade 33.

Further, the toner is made into fine particles by a pulverization method, and as a result of the measurement, particles of the toner having a volume of 3 μm or less are not found. Further, looking at the distribution (volume distribution) of toner particles by size, the distributions of toner particles having a volume of 4 μm and 5 μm, which are considered to be the minimum of toner particles, are extremely low at 0.2% and 0.3%, respectively. . Moreover, since the toner particles are easily bonded to each other by the attraction force due to frictional electrification, even if a gap of up to 8 μm is formed between the belt 11 and the cleaning blade 33, the fine toner particles having a particle diameter of 4 μm or 5 μm can be used. It was confirmed by experiments that the probability of passing is extremely low. A slight gap formed between the belt 11 and the cleaning blade 33 can be further reduced by elastically contacting and bending the both, so that the cleaning performance is further improved. As a result, the transfer paper is not contaminated by the toner remaining on the belt 11, and the belt 11 is not slipped on the drive roller 9 by the toner remaining on the belt 11, thus stabilizing the transfer paper. It can be transported at a speed. The above is the effect corresponding to the invention of claim 1.

Further, since the accuracy of the surface roughness of the cleaning blade 33 is remarkably higher than that of a conventional pile brush or the like, the cleaning blade 33 is pressed against the surface even if the surface roughness of the cleaning blade 33 is not regulated. By setting the surface roughness of the belt 11 to be ½ (5 μm or less), which is smaller than the toner average particle diameter, the gap in the contact portion between the belt 11 and the cleaning blade 33 is set to be the average particle diameter of the toner. Can be maintained to a degree. As a result, the cleaning blade 33 can reliably wipe off toner having an average particle size or more. Further, as described above, the ratio of the toner having the average particle size or less is extremely low, and the toner particles are easily bonded to each other by the attraction force due to charging, so that the particle size is 4 μm or 5 μm, which is the average particle size or less. Even with toner having a minute particle diameter, the probability that the toner will pass through the cleaning blade 33 becomes extremely low, and the cleaning performance of the toner on the belt 11 can be improved. The above is the effect corresponding to the second aspect of the invention.

The surface roughness of the belt 11 and the cleaning blade 33 is better if it is lower than the above value. However, considering the manufacturing surface, the above set value can obtain practical effects. Furthermore, not only the surface of the belt 11 but also the cleaning blade 33 is pressed against the inner surface,
As a result, the toner attached to the inner surface of the belt 11 may be wiped off.

[0019]

According to the invention of claim 1, the total of the surface roughness of the belt for conveying the transfer paper to the fixing means and the surface roughness of itself is set to a value smaller than the average particle diameter of the toner of the developing means. Since a cleaning blade having a width equal to or greater than the width of the belt and elastically bent is provided in pressure contact with at least the surface of the belt, it is possible to reliably wipe the toner having an average particle size or more with the cleaning blade. You can In addition, looking at the volume distribution of all toners, the proportion of toners having an average particle size or less is extremely low, and since the toners are easily bonded to each other by the attraction force due to charging, even a toner having a minute particle size can pass through the cleaning blade. The probability of exiting is extremely low. Therefore, the cleaning performance of the toner adhering to the belt can be improved, the transfer paper can be prevented from being contaminated by the residual toner, and the belt can be prevented from slipping on the drive roller by the residual toner, so that the transfer paper can be stably conveyed.

According to a second aspect of the present invention, a cleaning blade having a width equal to or larger than the width of the belt and elastically bent is provided on at least the surface of the belt for conveying the transfer paper to the fixing means. At the same time, since the surface roughness of the belt is set to a value equal to or less than ½ of the average particle diameter of the toner of the developing means, the accuracy of the surface roughness of the cleaning blade is remarkably higher than that of a brush or the like. Even if the surface roughness of the cleaning blade is not regulated, the surface roughness of the belt against which the cleaning blade is brought into pressure contact is set to ½ which is smaller than the toner average particle diameter, so that The gap in the contact portion can be maintained at about the average particle size of the toner. As a result, the toner having an average particle size or more is reliably wiped by the cleaning blade.
In addition, looking at the volume distribution of all toners, the proportion of toners having an average particle size or less is extremely low, and since the toners are easily bonded to each other by the attraction force due to charging, even a toner having a minute particle size can pass through the cleaning blade. The probability of exiting is extremely low. Therefore, the cleaning performance of the toner adhering to the belt can be improved, the transfer paper can be prevented from being contaminated by the residual toner, and the belt can be prevented from slipping on the drive roller by the residual toner, so that the transfer paper can be stably conveyed.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view showing an internal structure of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a partial front view showing a relationship between a belt and a cleaning unit.

FIG. 3 is an exploded perspective view of a cleaning unit.

FIG. 4 is a side view showing a supporting structure of a cleaning blade.

[Explanation of symbols]

7 fixing means 11 belt 20 image carrier 22 developing means 25 transfer means 26Y, 26M, 26C, 26BK latent image writing means 33 cleaning blade

Claims (2)

[Claims] 1. An electrostatic latent image is written on the surface of an image bearing member by a latent image writing unit, the electrostatic latent image is developed by a developing unit, and an image on the image bearing member is transferred onto a transfer sheet by a transfer unit. In an image forming apparatus configured to transfer and transfer the transfer paper after transfer to a fixing unit by an endless belt and fix the image on the transfer paper by the fixing unit, the surface roughness of the belt and the surface roughness of itself. Is set to a value smaller than the average particle diameter of the toner of the developing means, and a cleaning blade having a width equal to or greater than the width of the belt and elastically bent is pressed against at least the surface of the belt. An image forming apparatus characterized by being provided. 2. An electrostatic latent image is written on the surface of the image bearing member by a latent image writing unit, the electrostatic latent image is developed by a developing unit, and the image on the image bearing member is transferred onto a transfer paper by a transfer unit. An image forming apparatus configured to transfer and transfer the transfer paper after transfer to a fixing unit by an endless belt and fix the image on the transfer paper by the fixing unit, and a width of the belt on at least the surface of the belt. A cleaning blade having an equal width or more and elastically bent is provided in pressure contact, and the surface roughness of the belt is set to a value of half or less of the average particle diameter of the toner of the developing means. An image forming apparatus characterized by the above.