JPH10312143A - Image forming device - Google Patents

Abstract

(57) Abstract: In an image forming apparatus such as a copying machine, filming that occurs when fine powder such as toner or paper powder adheres to an image carrier is reliably prevented without increasing cost. A P sensor (20) is provided at a position upstream of a cleaning device (16) in the rotation direction of a photoconductor (10) to detect background dirt on the surface thereof. Then, the P sensor 20 is operated periodically between the copy operation and the next copy operation (inter-sheet area on the photoconductor), and when the output value becomes equal to or less than a predetermined value, it is determined that filming has occurred. Then, a toner image having a full width of the image formation is formed in the inter-sheet area on the photoconductor 10, and then the toner is scraped off by the cleaning blade 19, and a large amount of toner is sent between the edge of the blade 19 and the photoconductor 10, This removes the fine powder that has been agglomerated to prevent further filming from growing on the photoreceptor 10.

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 such as a copying machine, a printer, a facsimile, or a multifunction machine for forming an image on an image carrier such as a photoreceptor by repeating charging, writing, development, transfer and cleaning. The present invention relates to an image forming apparatus that forms an image by sequentially transferring the image on a sheet.

[0002]

2. Description of the Related Art Conventionally, in this type of image forming apparatus, as shown in FIG. 21, for example, fine particles such as toner and paper dust aggregate between a photosensitive member 1 and an edge 2a of a cleaning blade 2 pressed against the photosensitive member. When the photoreceptor 1 was rotated and cleaned, the surface of the photoreceptor 1 was rubbed with the aggregated fine powder p, and thin film-like filming occurred.

[0003] When such filming occurs, the sensitivity of the surface of the photoreceptor 1 deteriorates due to the filming.
At the time of development, toner also adheres to the background portion of the photoreceptor surface corresponding to the background portion of the recorded paper, causing background stains, thereby deteriorating the image quality on the paper.

Therefore, some conventional image forming apparatuses include:
For example, as shown in FIG. 22, the transfer roller 3 is detachably supported below the photoconductor 1 by a holder member 4, and when filming generated on the photoconductor 1 is removed, the transfer roller 3 is taken out. As shown in FIG. 23, the transfer roller 3
There is something that was replaced. The cleaning member 5 has a sliding contact portion 5b made of foamed rubber provided on, for example, a resin square member 5a.

When filming is removed, the photosensitive member 1 is rotated and the filming is scraped off by a sliding portion 5b which comes into contact with the surface.

Some conventional image forming apparatuses employ a system in which positively charged toner is adhered to the surface of a negatively charged photoreceptor to perform development. However, in such a developing method, when acidic paper or the like using so-called talc as a filler is used as recording paper, the talc has a property of being negatively charged due to friction when it comes into contact with toner or the like. There is a problem that the toner is easily mixed and agglomerated between the edge 2a of the cleaning blade 2 and the surface of the photoconductor 1, and as a result, filming is easily generated.

In view of the above, there is a conventional recording paper which attempts to prevent the occurrence of filming by using a specific paper filled with calcium carbonate which is positively charged when it comes into contact with toner or the like.

[0008]

However, in the above-described conventional apparatus, as shown in FIG. 23, a cleaning member 5 for removing filming is required separately from the original photosensitive member cleaning device 6. Therefore, there has been a problem that the cost increases accordingly.

Further, in the conventional apparatus, it is indispensable to always use the above-mentioned specific sheet as the recording sheet. However, it is practically difficult for all users to always use the specific sheet. However, there is a problem that filming cannot be sufficiently prevented.

[0010]

Therefore, the invention according to the first aspect of the present invention is directed to a photosensitive apparatus by repeating charging, writing, developing, transferring and cleaning as in the following embodiments shown in FIGS. In an image forming apparatus in which an image formed on an image carrier such as the body 10 is sequentially transferred onto a sheet to form an image, P is provided after development and before cleaning to detect background contamination on the image carrier. A background dirt detecting means such as the sensor 20; and periodically operating the background dirt detecting means, and when an output value thereof becomes equal to or less than a predetermined value, a toner image t having a full image forming width on the image carrier. And control means for forming

[0011] Periodically, the background dirt detecting means is operated to detect the background dirt on the image carrier, and when the output value of the background dirt detecting means becomes equal to or less than a predetermined value, the background dirt is detected. A toner image t having the full image forming width is formed.

According to a second aspect of the present invention, for example, as shown in the following embodiments shown in FIGS.
In an image forming apparatus in which an image formed on an image carrier such as the photoconductor 10 by repeating writing, development, transfer, and cleaning is sequentially transferred onto a sheet to form an image, the image forming apparatus is provided before development and before cleaning. A background dirt detecting means such as a P sensor 20 for detecting background dirt on the image carrier; and periodically operating the background dirt detecting means to detect the background dirt when the output value becomes equal to or less than a predetermined value. Control means for changing the contact angle of the cleaning blade 19.

Periodically, the background dirt detecting means is operated to detect the background dirt on the image carrier, and when the output value of the background dirt detecting means becomes a predetermined value or less, cleaning of the image carrier is performed. The contact angle of the blade 19 is changed.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, for example, the following FIG.
As in the embodiment shown in FIG. 3, when the output value of the background dirt detecting means becomes equal to or less than a predetermined value, a display means for displaying the fact is provided.

According to a fourth aspect of the present invention, for example, as shown in the following embodiments shown in FIGS.
In an image forming apparatus in which an image formed on an image carrier such as the photoreceptor 10 by repeating writing, development, transfer, and cleaning is sequentially transferred onto a sheet to form an image, the cleaning device 16 controls the image carrier. A recycling conveyance path 3 for returning the collected toner collected from above to the inside of the developing device 13.
4, a waste path 41 for discharging the collected toner to the waste container 40, a background dirt detecting means such as a P sensor 20 provided after development and before cleaning to detect the background dirt on the image carrier, and the background When the output value of the dirt detecting means becomes equal to or less than a predetermined value, the collected toner is transferred to the waste path 41.
And a switching means such as a shutter 45 for guiding the shutter to the outside.

When the toner collected by the cleaning device 16 is returned to the developing device 13, when the output value of the background contamination detecting device becomes equal to or less than a predetermined value, the conveying route of the collected toner is switched by the switching device and the collected toner is discarded. It is guided to 41 and discharged to the waste container 40 through the waste path 41.

According to a fifth aspect of the present invention, in the image forming apparatus of the fourth aspect, for example, as in the embodiment shown in FIG. And a toner consumption mode for consuming the toner in the developing device 13 when the time comes.

When the toner collected by the cleaning device 16 is returned to the developing device 13, when the output value of the background contamination detecting means becomes a predetermined value or less, the switching means discharges the collected toner to the waste container 40 through the waste path 41. With
The toner in the developing device 13 is consumed by setting the toner consumption mode.

The invention according to claim 6 is the invention according to claims 1, 2,
In the image forming apparatus described in 3, 4, or 5, for example, as shown in the following embodiments shown in FIGS. 17 to 20, the background dirt detecting means is provided on the image carrier which is likely to generate filming f. It is provided at a position corresponding to the position in the width direction.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of an image forming unit of a laser copying machine according to an embodiment of the present invention.

In the figure, reference numeral 10 denotes a drum-shaped photosensitive member as an image bearing member. Around the photoreceptor 10, an eraser 12, a developing device 13, and a transfer device 1 are arranged in the order of rotation of the photoreceptor 10 (clockwise in the drawing) from a charging device 11 provided above the photoreceptor 10.
4, a paper separating device 15, a cleaning device 16, and a charge removing device 17 are provided.

When making a copy, although not shown, the pressure plate is opened, a document is set on the contact glass, the pressure plate is closed and the document is pressed, and then the copy start key is pressed. Thus, at the same time that the image of the document is read by the document reading optical mechanism (not shown), the photosensitive member 10 is rotated,
The sheet is conveyed below the photoconductor 10.

As the photoreceptor 10 rotates, first, its surface is uniformly charged (-900 V) by a charging device 11, and a laser writing device (not shown) applies a laser to the surface in accordance with the above-described read contents. The writing is performed by irradiating light L,
An electrostatic latent image is formed on 0. Next, an unnecessary charge in an image non-formation area on the surface of the photoconductor 10 is removed by the erase 12. Then, when passing through the position of the developing device 13, a developing bias (-200v) is applied to the developing sleeve 13a to attach the toner, and the latent image on the photoconductor 10 is visualized. Then, the visible image is transferred to a sheet conveyed below the photoconductor 10 by the transfer device 14.

After the transfer, the sheet is separated from the photoreceptor 10 by a sheet separating device 15 and is conveyed to a fixing device (not shown). The sheet is discharged to the discharge stack shown in the figure.

On the other hand, the surface of the photoreceptor 10 after image transfer is cleaned by a cleaning blade 19 of a cleaning device 16.
To scrape and collect residual toner. Further, the photoconductor 1
The surface 0 is neutralized by the neutralization device 17 to be initialized.

In the above-described laser copying machine, the background contamination of the photoconductor 10 is located downstream of the transfer device 14 between the developing device 13 and the cleaning device 16 downstream of the photoconductor 10 in the rotation direction. Is provided.

As the background contamination detecting means 20, a so-called P sensor, which is a light reflection type photo sensor and outputs a voltage in accordance with the intensity of light reflected from the surface of the photoreceptor 10, is used.

FIG. 2 shows the output characteristics of the P sensor 20. FIG. 2 shows the output ratio (Vsp / Vsg) of the P sensor 20 on the upper side of the vertical axis, the toner adhesion amount (m / a) on the photoreceptor 10 on the horizontal axis, and the copied value on the lower side of the vertical axis. 4 is a graph showing the relationship between the image density (ID) on a sheet, the image density and the toner adhesion amount, and the output ratio of the P sensor 20. Vsp is an output of the P sensor 20 in a state where toner is attached, and Vsg is an output in a state where toner is not attached.

As can be seen from FIG. 2, the ID on the copy paper
The output ratio (Vsp / Vsg) of the P sensor 20 decreases as the amount of toner adhered to the photoconductor 20 increases substantially in proportion to In this embodiment, the output Vsg of the P sensor 20 is 4 when the toner is not attached on the photoconductor 20.
V is adjusted.

In the above-described laser copying machine, as shown in FIG. 3, the growth of filming occurring on the photoreceptor 10 is controlled by, for example, a CPU (control means).

First, after the end of the previous copy operation and before the next copy operation is performed, it is determined in step S1 whether or not the number of copies has exceeded 500 since the previous background dirt detection operation. If the number of sheets has not been reached, the background copy detection operation is not performed, and the next copy operation is started. 50
If the number exceeds zero, the process proceeds to step S2.

In step S2, the charging device 11
While the transfer device 14 is turned off, the erase 12 and the static eliminator 17 are turned on, the developing clutch of the developing device 13 is turned on to rotate the developing sleeve 13a, and a developing bias of -70V is applied to the developing sleeve 13a. , P sensor 20 is turned on. Then, in the next step S3,
The P sensor 20 detects background contamination on the photoconductor 20.

FIG. 4 shows the relationship between the development potential and the image density by plotting the image density (ID) on the copied paper on the vertical axis and the development potential (V) on the horizontal axis. Then, when background contamination is detected by the P sensor 20 as described above, the development start voltage is almost 0 V as shown by the solid line in FIG. When the developing bias is about -70 V, the toner hardly adheres to the photoreceptor 10, so that Vsg output from the P sensor 20 remains at 4 V.

However, if filming occurs on the photoreceptor 10, the development start voltage becomes small (negative) as shown by the dotted line in FIG. Toner adheres. Then, at this time, the output value Vsg of the P sensor 20 changes in accordance with the toner adhesion amount, and the P sensor 20 shows a smaller value than when no filming has occurred.

Therefore, the present invention focuses on the fact that the output value Vsg of the P sensor 20 changes in accordance with the occurrence of filming as described above, and as shown by an arrow a in FIG.
P at which the image density (ID) on copy paper is equivalent to 0.1
The Vsg of 3.3 V (Vsp / Vsg slightly exceeds 0.8) of the sensor 20 is used as a guide for the occurrence of filming, and when Vsg ≦ 3.3, it is determined that filming has occurred on the photoconductor 10.

Therefore, as shown in FIG. 3, in step S3, background contamination of the photoreceptor 10 is detected from the change in Vsg of the P sensor 20, and in the next step S4, Vsg ≦ 3.3.
Determine whether or not.

If Vsg ≦ 3.3, it is determined that filming has not occurred on the photoreceptor 10, and the next copy operation is started. On the other hand, if Vsg ≦ 3.3, it is determined that filming has occurred, and step S5
To automatically switch to the inter-sheet toner input mode, for example.

Then, the photosensitive member 10 is rotated and charged / developed, and on the photosensitive member 10, for example, as shown in FIG. A halftone toner image t is formed.

FIG. 6 shows the timing of the above-described normal image formation, and FIG. 7 shows the timing of forming the toner image t. As can be seen from the comparison between the two figures, when forming the toner image t, the inter-sheet area on the photoreceptor 10 is charged (charge potential -500 V), and after the charge, the charge is removed by the erase 12 to form the toner image t. I do.

Then, after the formation of the toner image t, the toner of the toner image t is scraped off the photosensitive member 10 by the cleaning blade 19 of the cleaning device 16 as shown in FIG. Then, the large amount of toner is sent between the edge 19a of the cleaning blade 19 and the photoreceptor 10, and the aggregated state of the aggregated fine powder p is broken and removed together with the toner. Thus, the filming is prevented from growing further due to the aggregated fine powder p.

Thus, the filming prevention operation is completed. After that, every time the number of copies exceeds 500,
The output value Vsg is repeatedly detected by the P sensor 20 and Vsg ≦
In the case of 3.3, it is determined that filming has occurred.
A toner image t is formed to prevent filming growth.

By the way, in the illustrated embodiment described above,
As shown in FIG. 3, when detecting the Vsg of the P sensor 20, the charging device 11 is turned off in step S2. For example, as shown in FIG. After the voltage is applied once to the upper sheet interval area, the charge is removed by the erase 12 and the Vs of the P sensor 20 is removed at the position where the charge is removed.
g should be detected.

When the Vsg of the P sensor 20 is detected as described above, the development start voltage is lower as indicated by a chain line in the case of once charging than in the case of no charging as indicated by a dotted line in FIG. Therefore, the occurrence of filming can be detected earlier.

Further, in the above-mentioned laser copying machine, as shown in FIG. 10, for example, the growth of filming generated on the photoreceptor 10 can be prevented by controlling the CPU.

First, in step S1, the copy start key is depressed. Then, as shown in step S2, the main motor is started, and the P sensor 20 and the static eliminator 1 are started.
7. When the erase 12 is turned on and the developing bias is applied to the developing sleeve 13a, while the charging bias / developing clutch is still off, as shown in step S3, the output of the P sensor 20 before the start of the developing operation, as shown in step S3. Detect value Vsg1 and store it.

Thereafter, in the next step 4, normal image formation is started, and when the image formation is completed in step S5, in step 6, the number of copies is reduced by 500 from the previous background dirt detection operation. It is determined whether or not the number has been exceeded. Then, when the number exceeds 500, the process proceeds to step 7, and similarly to step S2a in the case of FIG.
The developing clutches of the erase 12, the neutralizing device 17, the charging device 11, and the developing device 13 are turned on, and the P sensor 20 is turned on again, while the transfer bias is turned off and a developing bias (-70v) is applied to the developing sleeve 13a. . Then, in the next step S8, the output value Vsg2 of the P sensor 20 is detected again.

Then, in step S9, the ratio between the output value Vsg1 of the P sensor 20 before the start of the developing operation and Vsg2 at the time of the developing bias of -70 V is calculated, and the ratio is Vsg2.
/Vsg1≦0.82 is determined.

If Vsg ≦ 0.82, it is determined that filming has occurred, and the next step S10
Then, in the same manner as described above, the mode is switched to the inter-sheet toner input mode, and a toner image t is formed on the photoreceptor 10 to prevent filming growth.

Therefore, in the embodiment shown in FIG. 10, the output value Vsg1 of the P sensor 20 before the start of the developing operation is
Since the occurrence of filming is detected from the ratio to Vsg2 when the developing bias is -70 V, it is possible to prevent the occurrence of filming from being erroneously detected due to contamination of the detection surface of the P sensor 20.

Next, according to the second aspect of the present invention, for example, a laser copying machine similar to that described above is provided with a cleaning device 16 as shown in FIG.

The cleaning device 16 includes a base plate 25 which is long in the longitudinal direction of the photosensitive member 10 described above. The base plate 25 has one side bent downward in FIG. 11 and provided with shaft portions 25a and 25b at both end edges on the other side, and an arm portion 25c extending substantially perpendicularly to one shaft portion 25a and to the left in the drawing. Is provided. And it is mounted so as to be rotatable around both shaft portions 25a and 25b in a cleaning case (not shown).

Further, the base plate 25 has L
A plate-shaped blade holder plate 26 is overlapped and screwed, and a cleaning blade 19 made of rubber or the like is attached to the lower end of the blade holder plate 26 in a downward direction. Then, the edge 19a of the tip is placed on the surface of the photoconductor 10 not shown in FIG.
Abut at an angle of degrees.

The cleaning device 16 includes a solenoid (not shown). By operating the solenoid, the cleaning device 16 rotates the base plate 25 via the arm 25c, and adjusts the contact angle of the cleaning blade 19 with the photosensitive member 10. ,
It is configured so that it can be changed from 17.5 degrees to 10 degrees.

Then, as shown in FIG. 12, as in the case shown in FIG.
If the output value Vsg of 0 is 3.3 or less, it is determined that filming has occurred, and in the next step 5a, the mode is automatically switched to the blade contact angle changing mode. Then, the solenoid is operated to rotate the cleaning blade 19,
The contact angle with respect to the photoconductor 10 is changed from 17.5 degrees to 10 degrees. Then, the fine powder p aggregated between the edge 19a of the cleaning blade 19 and the surface of the photoconductor 10 collapses, and filming is prevented from further growing on the photoconductor 10 due to the aggregated fine powder p.

According to the third aspect of the invention, for example, in a laser copying machine similar to the above,
When the output value Vsg of the sensor 20 becomes equal to or less than a predetermined value of 3.3, a display means is provided for indicating the fact.

Although not shown, a liquid crystal display (LCD) on an operation unit provided in the copying machine body is used as the display means. When the output value Vsg of the P sensor 20 is 3.3 or less, for example, as shown in FIG. 13, it is determined that filming has occurred, and in step S5b, for example, "service" is displayed on the LCD on the operation unit. Please contact the man. "

In this case, the serviceman looks at the display on the LCD and operates, for example, a mode switch to select the above-described inter-sheet toner input mode or the blade contact angle changing mode according to the filming state. Photoreceptor 10
It is desirable to be able to cope with the occurrence of the above filming.

Further, the laser copying machine may be connected to a service company or the like via a public line so as to automatically contact the service company or the like when the occurrence of filming is detected.

Next, FIG. 14 shows a schematic configuration of a toner recycling type laser copying machine according to an embodiment of the present invention. This laser copying machine has an image forming section provided with a P sensor 20 and the like similar to the laser copying machine shown in FIG. 1, and a toner conveying device indicated by reference numeral 30 in front of the image forming section in FIG. Prepare.

The toner conveying device 30 includes a bottom of the cleaning case 31 of the cleaning device 16 and the developing device 13.
The upper toner hopper section 32 is connected to a transport pipe 33 with a recycle transport path 34 formed in the transport pipe 33. Further, the transport pipe 33 is provided with a toner disposal port 35 that is opened downward in the middle thereof.

Further, the toner conveying device 30 is provided with a waste container 40 below the conveying pipe 33. Waste container 40
Is provided with a pipe portion 40a extending upward on the left side in FIG. 14, and a waste path 41 is formed in the pipe portion 40. The upper end opening of the pipe portion 40a is connected to the toner waste port 35, and an electric shutter 45 for opening and closing the toner waste port 35 is provided therebetween.

Then, in the toner recycling type laser copying machine, at the time of copying, the residual toner is scraped off from the surface of the photoconductor 10 by the cleaning blade 19 of the cleaning device 16 and collected in the cleaning case 31. Thus, the collected toner is conveyed to the near side in the drawing in the cleaning case 31 by a collection coil (not shown), further conveyed through a recycle conveyance path 34 by a conveyance coil (not shown), and is transferred into the toner hopper 32 of the developing device 13. Return and use again for development.

On the other hand, between the copying operation and the next copying operation, as in the case shown in FIG. 10 is detected. And
As shown in FIG. 15, the output value Vsg of the P sensor 20 is 3.3.
If it is less than the above, in step 5c, it is determined that filming has occurred, and the shutter 45 is opened. The collected toner passing through the recycling conveyance path 34 is transferred to the toner disposal port 3.
5 to the waste path 41 to interrupt the toner recycling. Then, the collected toner is discharged to the waste container 40 through the waste path 41.

When such filming occurs,
By interrupting the toner recycling, the talc in the fine powder together with the toner is prevented from entering the developing device 13 any more. This prevents filming on the photoconductor 10 from proceeding due to talc as in the related art.

According to the fifth aspect of the present invention, for example, in the above-mentioned toner recycling type laser copying machine,
For example, when the output value Vsg of the P sensor 20 is a predetermined 3.3 V
, The collected toner is disposed in the waste container 40 as described above.
A shutter 45 for discharging the toner to the developing device 1
3, a toner consumption mode for consuming the remaining toner is provided.

Then, for example, as shown in FIG.
When the output value Vsg of the sensor 20 becomes 3.3 or less, it is determined in step 5d that filming has occurred, the shutter 45 is opened, and then the mode is switched to the toner consumption mode in step S6a. Then, the photosensitive member 10 is rotated and charged and developed, and a black solid image of toner is formed on the photosensitive member 10. In this way, the toner remaining in the developing device 13 is forcibly consumed until it is exhausted. Thereafter, in step S7a, the shutter 45 is closed, and toner recycling can be restarted.

Therefore, when such filming occurs, by suspending toner recycling,
The talc in the fine powder is prevented from being mixed into the developing device 13 any more, and the talc already mixed in the developing device 13 is consumed together with the toner.
The filming on 0 is prevented more reliably.

By the way, at the time of copying, a large amount of paper dust is particularly generated from the widthwise end of the copy paper passing under the photoreceptor 10, and
For this reason, the photoconductor 1 is located at a position corresponding to the end in the width direction.
Paper powder is more likely to adhere to the surface of No. 0, and as a result, filming f as shown in FIGS.

If, for example, A4 copy paper is often passed in the horizontal direction, filming f occurs as shown in FIG. 17A, and if the paper is often passed in the vertical direction, (b) As shown in FIG.
Thus, in the case of FIG. 17B, if a copy is rarely made using a large-size sheet such as A3, image unevenness occurs on the copy sheet S as shown in FIG.

Therefore, according to the present invention, in the above-described laser copying machine, for example, the P sensor 20 corresponds to the position in the width direction on the photosensitive member 10 where filming is likely to occur. It is configured to be provided at a position, that is, a position corresponding to the width direction end of the copy sheet.

In the above laser copying machine, for example, A4
In many cases, the P sensor 20 is installed at a position in the width direction of the photoconductor 10 corresponding to one end in the width direction of the A4 sheet S, for example, as shown in FIG.

Further, in the invention according to claim 6, it is preferable that, for example, the P sensor 20 is provided so as to be movable in the width direction on the photoreceptor 10.

For example, as shown in FIG. 20, an elongate feed screw 50 having an external thread formed on the outer periphery is rotatably supported by a suitable support member in the width direction of the photoreceptor 10, and a P sensor 20 is mounted on the feed screw 50. Is attached. P sensor 20
Has a sensor part 20a and a mounting part 20a, and is provided on the mounting part 20b through a female screw part (not shown). Then, the feed screw 50 is inserted into the female screw portion to engage the male screw portion, and the mounting portion 20a is arranged on a guide (not shown) in the engaged state. In addition, feed screw 5
The gear 52 is provided at one end with a gear 52 that meshes with a motor gear 51a of the motor 51.

Further, although not shown in this copying machine,
A counting means is provided for counting the number of sheets passed for each size of copy sheet.

Then, based on the counting result for each paper size by the counting means, a copy paper having a large number of passed paper sheets is determined. Then, based on the determination result, the motor 5
By driving the feed screw 1 to rotate the feed screw 50, the P sensor 20 is moved to a position corresponding to one end in the width direction of the copy sheet where filming is likely to occur.

Therefore, in this embodiment, the occurrence of filming can be detected by the P sensor 20 faster and more reliably in accordance with the use condition of the copy paper which differs for each user.

[0077]

Therefore, according to the first aspect of the present invention, the background dirt is periodically detected by the background dirt detecting means.
When the output value becomes equal to or less than a predetermined value, a toner image is formed on the image carrier, and at the time of cleaning, a fine powder aggregated on the image carrier together with the toner of the toner image can be removed. Without incurring high costs,
Filming on the image carrier can be reliably prevented from occurring. In addition, if filming does not occur, unnecessary consumption of toner is not required, which is economical.

According to the second aspect of the present invention, the background dirt is periodically detected by the background dirt detecting means, and when the output value becomes equal to or less than a predetermined value, the contact angle of the cleaning blade with respect to the image carrier. In this manner, the fine powder agglomerated between the edge of the blade and the surface of the image carrier is collapsed. Can be prevented from occurring.

According to the third aspect of the present invention,
When the output value of the background dirt detecting means is equal to or less than a predetermined value,
The fact is displayed on the display means and, for example, a service person or the like is notified so that the filming prevention means of the contents described in claim 1 or 2 can be properly adopted.
Filming on the image bearing member can be reliably prevented from occurring without increasing the cost as in the conventional case. In addition, since the problem can be dealt with before a problem occurs on the image by a service person or the like, it is possible to prevent the image forming apparatus from becoming unusable.

According to the fourth aspect of the present invention, the background stain is periodically detected by the background stain detecting means, and when the output value becomes equal to or less than a predetermined value, the toner collected by the cleaning device is switched to the switching means. And discharge it to a waste container,
Conventionally, in order to suspend toner recycling,
This prevents talc in the paper dust that caused the filming from being returned to the developing device together with the toner, thereby causing filming to occur at a high cost even in an image forming apparatus employing a toner recycling method. Can be reliably prevented.

According to the fifth aspect of the present invention,
When the output value of the background dirt detecting means is equal to or less than a predetermined value,
Since the toner recycling is interrupted and the toner remaining in the developing device is forcibly consumed together with the talc, the occurrence of filming on the image carrier is more reliably prevented. be able to.

According to the invention of claim 6, in addition to the above,
Since the background dirt detection means is provided at a position corresponding to the width direction position on the image carrier where filming is likely to occur,
The occurrence of filming can be detected at a relatively early stage to prevent its progress.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an image forming unit of a laser copying machine according to an embodiment of the present invention.

FIG. 2 is a graph showing output characteristics of a P sensor provided in the laser copying machine.

FIG. 3 is a flowchart showing a method of preventing filming occurring on a photoconductor of the laser copying machine.

FIG. 4 is a graph showing the relationship between the development potential of the laser copying machine and the image density (ID) on copy paper.

FIG. 5 is an explanatory perspective view showing a photoconductor on which a toner image is formed when filming is detected.

FIG. 6 is a timing chart showing normal image forming timing of the laser copying machine.

FIG. 7 is a timing chart showing image forming timing when forming a toner image when filming is detected by the laser copying machine.

FIG. 8 is a state explanatory view showing a state in which the aggregated fine powder is scraped off from the photosensitive member by the toner of the toner image when the toner image is cleaned after the toner image is formed.

FIG. 9 is a flowchart showing another filming prevention method in the laser copying machine according to the first embodiment.

FIG. 10 is a flowchart showing still another filming prevention method.

FIG. 11 is a perspective view showing a cleaning device of a laser copying machine according to an embodiment of the present invention.

FIG. 12 is a flowchart showing a filming prevention method by the laser copying machine.

FIG. 13 is a flow chart showing a method for preventing filming of the laser copying machine according to the embodiment of the present invention.

FIG. 14 is a schematic configuration diagram showing an image forming unit and a toner conveying device in a toner recycling type laser copying machine according to an embodiment of the present invention.

FIG. 15 is a flowchart showing a filming prevention method of the laser copying machine.

FIG. 16 is a flow chart showing a method for preventing filming of the laser recycling machine of the toner recycling type according to the embodiment of the present invention.

FIGS. 17A and 17B are explanatory perspective views showing states of the photoconductor in which filming has occurred on the surface when A4 paper has been passed in a large amount in the horizontal direction in FIG. .

FIG. 18 is a partial plan view showing a copy sheet in which image unevenness has occurred due to the filming.

FIG. 19 is an explanatory view showing the installation position of a P sensor in the laser copying machine according to one embodiment of the present invention.

FIG. 20 is a perspective view showing the P sensor and its moving mechanism.

FIG. 21 is a state explanatory view showing a state in which filming occurs on a photoconductor in a conventional image forming apparatus.

FIG. 22 is a schematic configuration diagram of a conventional image forming apparatus including the filming preventing unit.

FIG. 23 is a schematic configuration diagram showing a state in which the transfer roller is replaced with a cleaning member of a filming preventing unit in the image forming apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 photoconductor (image carrier) 13 developing device 16 cleaning device 19 cleaning blade 20 P sensor (background dirt detecting means) 34 recycling transport path 40 waste container 41 waste path 45 shutter (switching means) f filming t toner image

Claims (6)

[Claims] 1. An image forming apparatus for transferring an image formed on an image carrier by repeating charging, writing, development, transfer, and cleaning to a sheet in order to form an image, wherein the image forming apparatus is provided before cleaning after development. A background dirt detecting means for detecting background dirt on the image carrier; and periodically operating the background dirt detecting means to form an image on the image carrier when an output value thereof is equal to or less than a predetermined value. An image forming apparatus comprising: a control unit that forms a full width toner image. 2. An image forming apparatus in which an image formed on an image carrier by repeating charging, writing, development, transfer, and cleaning is sequentially transferred onto a sheet to form an image. A background dirt detection means for detecting background dirt on the image carrier; and a cleaning blade contacting the image carrier when the output value of the background dirt detection means is periodically reduced to a predetermined value or less. An image forming apparatus, comprising: control means for changing an angle. 3. The image forming apparatus according to claim 1, further comprising a display unit for displaying, when an output value of the background stain detection unit becomes equal to or less than a predetermined value, that fact. 4. An image forming apparatus in which an image formed on an image carrier by repeating charging, writing, development, transfer and cleaning is sequentially transferred onto a sheet to form an image, wherein the image carrier is cleaned by a cleaning device. A recycling path for returning the collected toner from above to the developing device, a waste path for discharging the collected toner to a waste container, and a background stain provided after development and before the cleaning to detect the background stain on the image carrier. An image forming apparatus comprising: a detection unit; and a switching unit that guides the collected toner to the waste path when an output value of the background contamination detection unit is equal to or less than a predetermined value. 5. The image forming apparatus according to claim 4, further comprising a toner consumption mode for consuming toner in the developing device when an output value of the background stain detecting unit becomes equal to or less than a predetermined value. 6. The image forming apparatus according to claim 1, wherein the background dirt detecting means is provided at a position corresponding to a width direction position on the image carrier where filming is likely to occur. Image forming device.