JPH06258991A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the generation of a defect in an image by preventing the generation of an electrostatic history on a photosensitive body caused by an electrifying material coming into contact with the photosensitive body, while an image forming device is stopped for nonworking. CONSTITUTION:In the image forming device forming an electrostatic latent image on the surface of an endless photosensitive body capable of moving, making electrified toner stick to the electrostatic latent image, to develop it and transfer the obtained toner image onto a recording paper and then, removing the untransferred toner of a part remaining on the photosensitive body by a cleaning blade coming into contact with the surface of the photosensitive body and composed of an elastic body, the photosensitive body is driven so as to consecutively move intermittently or at 1/5-1/1000 speed of a normal speed, during a nonimage forming period from the completion of an image forming cycle to the start of the next image forming cycle, as well, as a characteristic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention forms an electrostatic latent image on the surface of a moving endless photoconductor, develops it by attaching charged toner to the electrostatic latent image, and transfers the toner image to recording paper. After that, the present invention relates to an image forming apparatus that removes untransferred toner partially remaining on the photoconductor with a cleaning blade made of an elastic body that contacts the surface of the photoconductor. The present invention relates to an image forming apparatus in which the occurrence of image defects is prevented by preventing the occurrence of electrostatic covering on the photoconductor.

[0002]

2. Description of the Related Art In recent years, the image quality of copying machines / printers has been remarkably improved, and many products have been able to faithfully reproduce subtle halftone images. Most of these products are of the type that forms a toner image on a photoconductor and transfers it to recording paper, and most of these products employ a small-sized, low-cost blade cleaning device.

[0003]

These copying machines / printers have the following problems. That is, when the copying machine is operated again 15 to 30 minutes or more after the completion of the operation of the copying machine (for example, after lunch break), it corresponds to the vicinity of the position where the cleaning blade of the photoconductor was in contact while the copying machine was stopped. A streak density increasing portion appears in the low density halftone portion of the copy image at the position. This image quality defect is gradually faded if the copying machine is continuously operated, and finally disappears, but 30 to 50 after the copying is started.
Striped image defects remain on the sheet, which is a problem.

The above image quality defect is caused by the following mechanism / process. (1) During operation of the copying machine, a toner dam is formed in front of the blade edge, and the toner dam is negatively charged by friction with the surface of the photoconductor. (2) While the copying machine is stopped, the negatively charged toner dam 7 is held in front of the edge of the blade 6, and a positive image charge is induced on the surface of the photoconductor 1 facing the area.
(See FIG. 1) (3) An electric field is generated between the mirror image charge and the substrate, and the density of trap sites in the charge generation layer (CGL) 3 increases as the stop period elapses due to the action of this electric field. (4) When the copier is operated in the above state and the action of the toner dam is cut off, the image charge moves to the substrate side, and a part of the CG
It is captured by the trap site in L3. (5) Although some electrons of the hole / electron pair generated in CGL3 in the exposure step are trapped by the trap sites, many electrons are already filled in the above-mentioned region, so the electrons are CTL (charge). The rate of reaching the transport layer) 2 increases.

As a result, the potential of this portion becomes lower than normal and appears as black streaks on the copy (see FIG. 2). A halftone electrostatic latent image is formed on the photoconductor in the area corresponding to the toner dam as shown in FIG. When the image is formed, the surface potential of the photoconductor becomes as shown by the area D in FIG. 2, and the potential drops by ΔV (about 10 V) from the adjacent portion which should have the same potential.

The applicant's earlier application (FE92-007
In 16), the residual charge on the surface of the photoconductor is eliminated by the AC corona in the latter half of the image forming cycle, thereby reducing the occurrence of electrostatic covering history that gradually occurs after the end of the image forming cycle. It cannot be a countermeasure. SUMMARY OF THE INVENTION It is an object of the present invention to prevent the occurrence of image defects by preventing a charged substance in contact with a photoconductor from causing an electrostatic history on the photoconductor while the image forming apparatus is not operating. .

[0007]

SUMMARY OF THE INVENTION According to the present invention, an electrostatic latent image is formed on the surface of a moving endless photosensitive member, charged toner is attached to the electrostatic latent image for development, and the toner image is recorded on a recording paper. In an image forming apparatus for removing untransferred toner partially remaining on the photoconductor after being transferred to a photoconductor by a cleaning blade made of an elastic body contacting the surface of the photoconductor, the photoconductor is
1/5 of the normal or intermittent speed during the non-image forming period after the end of the image forming cycle and before the start of the next image forming cycle
It is characterized by being driven so as to move continuously at a speed of 1/1000.

The photosensitive member is driven at a time interval of one hour or less during the non-image forming period, and the amount of movement may be several mm or more per one driving. Further, by using the signal of the image forming condition setting or the preliminary work before the image forming cycle start signal is output, the driving of the photosensitive member in the non-image forming period is stopped, and at the same time, the photosensitive member is suitable for starting the image forming cycle. The drive may be returned to the fixed position.

Further, the image forming apparatus is a copying machine,
The image forming condition setting or preparatory work signal is a signal from the copy condition setting button such as the copy number setting button or the copy size setting button on the control panel of the image forming apparatus (copying machine), which is pressed before the copy start button is pressed. It may be. Further, the image forming apparatus is a copying machine, and the signal of the image forming condition setting or the preliminary work is such that the opening / closing of the original pressing cover, the original size detecting sensor under the original table, the original insertion detecting sensor of the automatic original feeding device, etc. It may be a signal from a sensor / switch that is activated before pressing the copy start button.

Further, the image forming apparatus may be a printer, and the image forming condition setting or preliminary work signal may be a reception initial signal of the printer.

[0011]

According to the present invention, the photosensitive member is intermittently or 1/5 to 1/1000 of the normal speed during the non-image forming period of the image processing apparatus.
It is driven to move continuously at the speed of. By this rotation, the toner dam in front of the edge of the cleaning blade does not continuously stay at the same position on the photoconductor, and the generation of streaks is completely prevented. Moreover, since the photosensitive member and the cleaning blade are driven so as to move at a speed much lower than the speed during operation, the life of the photosensitive member and the cleaning blade is not shortened remarkably.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The features of the present invention will be specifically described below based on embodiments with reference to the drawings. FIG. 3 is a partial schematic sectional view showing an essential part of an electrophotographic copying machine to which the present invention can be applied.

Around the drum-shaped photosensitive member 11 using an organic optical semiconductor, a charging corotron 12, an exposure device 13 provided with a laser light source (not shown) such as a semiconductor laser,
The developing roll 14 has a dielectric film 16a on the outer peripheral surface, and the dielectric film 16 is provided at a position facing the photoconductor 11.
a transfer drum 16 in which a transfer corotron 15 is arranged on the inner peripheral side of a, a charge eliminating corotron 17, a cleaning device 18,
The static elimination lamps 19 and the like are sequentially arranged. The cleaning device 18 includes a cleaning blade 18a, a cleaning auxiliary brush 18b, a toner transport auger 18c, and the like.

The surface of the photoconductor 11 rotating in the direction of the arrow is
First, it is uniformly negatively charged by the charging corotron 12. Subsequently, the surface of the photoconductor 11 is irradiated with the light beam from the exposure device 3 to form an electrostatic latent image. In this example,
The image portion of the document is irradiated with the beam, and the background portion is not irradiated. The electrostatic latent image on the photoconductor 11 is visualized by the negatively charged toner on the developing roll 14 to form a toner image. Subsequently, this toner image is transferred onto a recording paper attracted to a transfer drum 16 having a dielectric film 16a stretched on the surface thereof by the action of a transfer corotron 15 which causes a positive corona discharge, and is fixed by a fixing device (not shown). The copy is complete.

On the other hand, the residual toner on the photoconductor 11 that has not been transferred is caused by the action of the static elimination corotron 17 in which a negative DC voltage of 0.5 kV is superimposed on an alternating current of 3.8 kV, and flocking that mechanically disturbs the residual toner. After being acted on by the cleaning auxiliary brush 18b composed of a brush, it is removed by the elastic cleaning blade 18a composed of polyurethane rubber, drops on the brush 18b again, and is then wiped off by the flicker 20 from the brush 18b to convey the toner. It drops on the auger 18c and is collected in a waste toner bottle (not shown). The photoconductor 11 that has been cleaned by the cleaning blade 18a is further subjected to the action of the static elimination lamp 19 and thus the photoconductor 1
The negative charge remaining in 1 is erased and the next image forming cycle is started.

The cleaning blade 18a has a thickness of 2 m.
The residual toner is removed by pressing the surface of the photoconductor 11 with polyurethane rubber having m and hardness of 70 °. A part of the removed residual toner is as shown in FIG.
A toner dam with a width of about 1 to 1.5 mm is formed at the tip. While the photoconductor 11 is rotating, this toner dam
The photoconductor 11 is always frictionally charged by rubbing and is strongly negatively charged. As a result, if no measures are taken, the streak generation process described above causes the copying machine to reach 0.5-4.
If it is used after being rested for about an hour, an image quality defect occurs in a 20 to 50% halftone image area.

Embodiments of the present invention provide means for overcoming the above deficiencies, which will be described below. As shown in FIG. 4, in the state where no countermeasure is taken, a problematic line appears from the copy after the copying machine is paused for about 15 minutes or more.
Therefore, if the toner dam does not stay in the same portion of the photosensitive member for 15 minutes or more, the electrostatic covering history at the level of generating streaks does not occur on the photosensitive member. Therefore, there is no problem if the photoconductor is constantly rotating during the rest period of the copying machine. However, when rotating at the same speed as during operation, the photoconductor, the cleaning blade, and the like are worn out and their life is shortened remarkably. In order to achieve the purpose, it is sufficient that the photoconductor rotates even a little at a time.
It rotates at a peripheral speed of 0.8 mm / sec, which is 1/200 of the normal speed, while the copier is idle. By this rotation, the toner dam in front of the edge of the cleaning blade does not continuously stay at the same position on the photoconductor, and the generation of streaks is completely prevented.

The condition in which streaks tend to occur, which is a problem in the present invention, is low temperature, low humidity, and continuous use before operation stop. FIG. 4 shows the relationship between the operation stop time after continuous copying of 200 sheets at a temperature of 10 ° C. and a humidity of 30% and the streak generation grade of the first copy after the stop in a state in which no countermeasure is taken and the prior art. A comparison is made between the state in which the countermeasure according to (FE92-007116) is taken and the state in which the countermeasure according to the present invention is taken, and the effect according to the embodiment of the present invention is perfect and no copy streaks occur.

Incidentally, the uncounted measures and the lines in the prior art are gradually alleviated about 3 hours after the copying machine is stopped. The reason for this is that the charge of the toner dam is gradually released, and accordingly, the image charge is also released, and the electrostatic history on the photoconductor side is gradually recovered. In FIG. 3, the peripheral speed of the transfer drum 16 and the ON / OFF of the drive are completely synchronized with the photosensitive drum 11. Further, a film 16a made of a dielectric material is stretched around the peripheral surface of the transfer drum 16, and a leading end and a rear end of the film 16a are fixed at a 16c portion by a film mounting bar 16b. Further, at the position where the portion 16b faces the photoconductor 11, the film 16a is not affected by the transfer corotron 15, and the toner image cannot be transferred even if the recording paper is at the transfer position. Therefore, the circumference of the transfer drum 16 is set to be larger than the maximum size of recording paper that can be used.

The recording paper is supplied at a timing approximately 5 mm rearward from the rear end of the film mounting bar 16b of the transfer drum 16 at a timing such that the front end thereof always coincides with each other. The toner image of the first color is transferred to the transfer area 16a.
The recording paper on which the image of the first color is transferred rotates while being attracted to the transfer drum, and the transfer of the second, third, and fourth colors is performed again. At this time, it goes without saying that the peeling roller 23 is in the OFF state, and the peeling finger 24, the transfer drum cleaner 27, and the recording paper suction roll 22 are in the separated state.

After the transfer of the four color toner images is completed, the recording paper is subjected to the static elimination action of the peeling corotron 23 to reduce the attracting force with the transfer drum, and then the peeling finger 24 brought into contact with the transfer drum. It is peeled off from the transfer drum and fixed by a fixing device (not shown). On the other hand, the transfer drum, which has completed the transfer, has a charge-removing corotron 25, in order to remove the electrostatic charge remaining on the film toward the next copying cycle.
26, and further, after receiving the action of the transfer drum cleaner 27 in order to remove the toner slightly attached to the area on the film that was not in contact with the recording paper,
The film mounting bar 16b stops at a position facing the photosensitive drum.

Next, when the copying machine starts to operate again, when the copying start button is pressed, the motor for driving the photoconductor drum starts to rotate, and the photoconductor drum and the transfer drum connected thereto rotate at the same time. Start. Then, the transfer drum and a pair of transfer drum position detection sensors provided in the transfer drum detect the position of the transfer drum, and based on the detected time, the exposure start position on the photosensitive drum and the recording paper suction onto the transfer drum. It controls the important timing required for copying, such as the start position.

However, according to the above embodiment, the photosensitive member,
And because the transfer drum moves during the rest period of the copier,
The photosensitive drum and the transfer drum are not in the fixed positions when the copy start button is pressed. For this reason, the time required for the position detection sensor to output a signal is delayed by one rotation of the transfer drum (about 3.3 seconds) at the maximum, compared with the case where the film mounting bar is at the position facing the photosensitive drum. I will end up. This delay is equal to the time from when the copy start button is pressed until the first sheet of recording paper finishes copying and is ejected from the copying machine, resulting in a great loss in productivity of the copying machine.

In order to prevent this, in this embodiment, the driving of the photoconductor in the non-image forming period is stopped by utilizing the signal of the image forming condition setting or the preliminary work before the image forming cycle start signal is output, At the same time, the photosensitive member is driven and returned to a fixed position suitable for starting the image forming cycle. The image forming condition setting or preparatory work signal is a) from a copy condition setting button such as a copy number setting button or a copy size setting button on the control panel of the image forming apparatus (copier), which is pressed before the copy start button is pressed. Signal, b) Opening / closing of document holding cover, document size detection sensor at the bottom of the document table, document insertion detection sensor of automatic document feeder, etc. Signal from sensor / switch that operates before pressing copy start button or initial reception of printer Is one of the signals. Regardless of which of the methods a) to c) is adopted, it is possible to return the recording paper mounting bar of the transfer drum to a position facing the photoconductor drum within approximately 3 seconds, which leads to the above productivity. You can avoid the problems involved.

In the second embodiment of the present invention, the surface of the photoreceptor is about 30 mm at intervals of 10 minutes during the rest period of the copying machine.
Rotate in the forward direction. If the photoconductor is stopped within 10 minutes, no streaks are generated as shown in FIG. 4 and there is no problem. The speed of the photoreceptor during intermittent rotation may be the same as that during normal rotation, but in the second embodiment it is set to 10 mm / sec. When the moving distance of the photoconductor during intermittent rotation becomes an integral multiple of the circumferential length of the photoconductor, the relative position of the toner dam to the photoconductor is always the same, and the effect of preventing streak generation is completely lost.

In the above embodiment, the color copying machine having the transfer drum is described. However, it is necessary that the image forming area on the photosensitive member such as a belt-shaped photosensitive member having no transfer drum and a photosensitive member having a seam is always constant. Color /
The present invention can be applied to both black and white.

[0027]

According to the present invention, the photoconductor is driven so as to move intermittently during the non-image forming period of the image processing apparatus or continuously at a speed much lower than the normal speed. By this rotation, the toner dam in front of the edge of the cleaning blade does not continuously stay at the same position on the photoconductor, and the generation of streaks is completely prevented. Moreover, since the photosensitive member and the cleaning blade are driven so as to move at a speed much lower than the speed during operation, the life of the photosensitive member and the cleaning blade is not shortened remarkably.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing retention of a toner dam on a photoconductor that causes image quality defects in a conventional technique.

FIG. 2 is a graph showing a decrease in potential on the surface of a photoconductor due to retention of toner dams in the related art.

FIG. 3 is a partial schematic sectional view showing a main part of an electrophotographic copying machine to which the present invention can be applied.

FIG. 4 is a graph comparing the effects of the present invention and the prior art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charge transport layer (CTL) 3 Charge generation layer (CGL) 4 Blocking layer (UCL) 5 Aluminum substrate 6 Blade 7 Toner dam 11 Photoconductor 12 Charging corotron 13 Exposure device 14 Developing roll 15 Transfer corotron 16 Transfer drum 16a Dielectric Body film 6a 17 Static eliminator Corotron 18 Cleaning device 18a Cleaning blade 18b Cleaning auxiliary brush 18c Toner transport auger 19 Static eliminator 20 Flicker 21 Recording paper adsorption corotron 22 Adsorption roll 23 Peeling coton 24 Peeling finger 25 Peeling corotron 26 Peeling corotron 27 Transfer drum cleaner

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B41J 2/455 G03G 15/00 102 303

Claims (6)

[Claims] 1. An electrostatic latent image is formed on the surface of a moving endless photoconductor, and charged toner is attached to the electrostatic latent image for development.
In the image forming apparatus, after the toner image is transferred onto a recording paper, the untransferred toner partially remaining on the photoconductor is removed by a cleaning blade made of an elastic body that contacts the surface of the photoconductor. It is characterized in that it is driven so as to move intermittently or at a speed of 1/5 to 1/1000 of the normal speed even during the non-image forming period after the end of the image forming cycle until the start of the next image forming cycle. Image forming apparatus. 2. The photosensitive member is set to 1 during a non-image forming period.
The image forming apparatus according to claim 1, wherein the image forming apparatus is driven at a time interval of time or less, and the amount of movement thereof is less than one revolution per one drive. 3. A signal of image forming condition setting or preliminary work before the image forming cycle start signal is output,
3. The image forming apparatus according to claim 1, wherein the driving of the photoconductor during the non-image forming period is stopped, and at the same time, the photoconductor is driven and returned to a fixed position suitable for starting an image forming cycle. 4. The image forming apparatus is a copying machine, and the image forming condition setting or preliminary work signal is copied by a copy number setting button, a copy size setting button or the like on a control panel of the image forming apparatus (copying machine). 4. The image forming apparatus according to claim 3, wherein the signal is from a copy condition setting button that is pressed before the start button is pressed. 5. The image forming apparatus is a copying machine, and the image forming condition setting or preparatory work signals are used to open / close a document pressing cover, a document size detection sensor under a document table, and a document insertion detection of an automatic document feeder. The image forming apparatus according to claim 3, wherein the signal is a signal from a sensor / switch, such as a sensor, which is activated before the copy start button is pressed. 6. The image forming apparatus is a printer,
The image forming apparatus according to claim 3, wherein the image forming condition setting or preliminary work signal is a reception initial signal of the printer.