JPH07281490A - Electrophotographic copying machine - Google Patents

Abstract

(57) [Abstract] [Purpose] To prevent the abrasion of the photoconductor and the cleaning blade while reducing the toner waste, and to extend the life of each. A density of a document 35 to be copied is detected by an optical sensor 40, and when the detected density is less than a predetermined value, the charger 21 is charged with a fixed potential over the entire width of the photosensitive drum 20 during the copying process. A toner image is formed on the photosensitive drum 20 over the entire width in the developing tank 22 without being exposed, and the toner image is sent to the cleaner device 24 without being transferred to a sheet, and the toner image of the photosensitive drum 20 and the cleaning blade 25 is transferred. Cleaning is performed by the cleaning blade 25 with a toner image interposed between the toner and the lubricant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic copying machine such as a copying machine or a laser printer equipped with a blade type cleaning device for removing residual toner on a photoconductor,
In particular, it relates to a technique for preventing the photoconductor and the cleaning blade from being worn.

[0002]

2. Description of the Related Art Toner is adhered to an area other than an image forming area on a surface of a photoconductor and the toner is used as a lubricant to intervene between the photoconductor and a cleaning blade to prevent the photoconductor and the cleaning blade from being worn. As a technique to do so, there are those described in Japanese Patent Laid-Open No. 2-116883, Japanese Patent Laid-Open No. 2-148084, Japanese Patent Laid-Open No. 289885, and Japanese Patent Laid-Open No. 4-198974.

According to these contents, a toner image is formed over the entire image width on a non-image area of a photoconductor, and the toner image is cleaned by a cleaning blade to prevent abrasion of the photoconductor and the cleaning blade. I have to.

Further, the above-mentioned operation is set to be carried out for each copy or for every predetermined number of copies during the copy cycle. As a condition for copying a predetermined number of sheets, if the copy original size is smaller than the entire image width,
A method of changing the predetermined number is used.

Although these methods can surely prevent the abrasion of the photoconductor and the cleaning blade, they waste toner much and are not very efficient.

When a document is continuously copied, the toner image on the photoconductor is transferred to a transfer sheet and then cleaned by a cleaning blade as residual toner. It is possible that the toners partially differ in the toner amount and there is no toner image at a small amount. When continuous copying is performed under this condition, the amount of toner to the cleaning blade is partially different, and therefore the edges of the photoconductor and the cleaning blade are worn in the portion where the amount of toner is small, resulting in problems such as defective cleaning.

Therefore, as described above, a toner image is formed on the non-image area of the photoconductor over the entire image width, and the toner is used as a lubricant to prevent abrasion of the photoconductor and the cleaning blade. .

[0008]

The copying cycle in which the abrasion of the photoconductor and the cleaning blade is a practical problem is the case where a plurality of continuous copies are made for a low density original document. When performed: When the copy image density is low or when multiple copies are continuously made in the mode of low charging potential setting.Leave for a long time, turn on the power when the temperature inside the machine is lowered and the rubber hardness of the cleaning blade is increased. This is the case when the photoconductor is rotated by rotating.

Each of these items shows conditions under which the toner adhesion amount of the toner image formed on the photosensitive member in the normal copying process becomes small. In short, if the toner adhesion amount on the photoconductor is small, the residual toner amount on the photoconductor after transfer onto the transfer paper is also small, and therefore, the toner amount to be cleaned is small.
The photoconductor and the cleaning blade are easily worn.

In the conventional method, the toner image described above is always formed over the entire width of the non-image area of the photoconductor in all originals and in all modes, resulting in a great waste of toner and inefficiency.

The present invention was devised in view of such circumstances, and in the above-mentioned copy cycle in which abrasion of the photosensitive member and the cleaning blade is a problem,
The toner image is formed on the photoconductor by detecting the parameters that meet each condition, and the toner is used as a lubricant to reduce the toner waste and prevent the photoconductor and the cleaning blade from being worn. The purpose is to extend the life of the.

[0012]

[Means for Solving the Problems]

(1) The electrophotographic copying apparatus according to claim 1 of the present invention is
In an electrophotographic copying apparatus including a blade-type cleaning device that removes residual toner on a photoconductor, a detection unit that detects the amount of developer removed by the blade-type cleaning device, and a toner image is formed on the photoconductor. A toner image forming means, and the toner image forming means is operated during the copying process based on the detection value by the detecting means, and the toner image is removed by the blade type cleaning device. .

(2) An electrophotographic copying apparatus according to a second aspect of the present invention is the electrophotographic copying apparatus according to the first aspect, in which the detection density detected by the detection means for detecting the density of the copy original is below a predetermined value. Is to detect the amount of the developer removed by the blade type cleaning device.

(3) An electrophotographic copying apparatus according to a third aspect of the present invention is an electrophotographic copying apparatus equipped with a blade type cleaning device for removing residual toner on a photosensitive member, and an instruction to turn off the power to the apparatus. And a toner image forming unit for forming a toner image on the photoconductor, and when the power-off is instructed by the instructing unit, the toner image forming unit is operated to form the toner image on the photoconductor. The toner image is formed, the toner image is stopped before the blade type cleaning device, and the power is turned off in that state.

[0015]

[Action]

(1) In the electrophotographic copying apparatus of claim 1, when the amount of the detected developer (developing agent removed by the blade type cleaning device) is small, the toner image forming means is operated during the copying process. A toner image is formed on the photoconductor, and the toner image is removed by a blade type cleaning device. When forming a toner image,
An electrostatic latent image is formed over the entire width of the photoconductor and developed without exposure to form a toner image over the entire width on the photoconductor. The toner image on the photoconductor is sent to the blade type cleaning device as it is without being transferred to the paper and is cleaned. As described above, when it is detected that the amount of the developer is small, the toner image is formed over the entire width and the toner of the toner is directly cleaned as the lubricant, so that the photoconductor and the cleaning blade are not worn. It can be prevented.

(2) In the electrophotographic copying apparatus according to the second aspect, the density of the document to be copied is detected, and when the detected density of the document is equal to or lower than a predetermined value, the toner image forming means is provided during the copying process. Is operated to form a toner image on the entire width of the photoconductor, and the toner image is directly cleaned by a blade type cleaning device without being transferred to a sheet. At the time of cleaning, since the toner functions as a lubricant, it is possible to prevent the photoconductor and the cleaning blade from being worn.

(3) Since the temperature inside the copying machine, which has been left for a long time at night, etc., is low and the hardness of the cleaning blade is high, the photoconductor and the cleaning blade are easily stressed when the power is turned on as it is. .

In the electrophotographic copying apparatus of claim 3,
When instructed to turn off the power, immediately turn off the power
Before that, the toner image forming means is operated to form a toner image over the entire width of the photoconductor, and the toner image is stopped immediately before the cleaning blade without being transferred to the sheet. Turn off the power with. Next, when the power is turned on, the toner image on the photoconductor is cleaned by the blade type cleaning device,
Since the toner functions as a lubricant during the cleaning, abrasion of the photoconductor and the cleaning blade can be prevented even if the hardness of the cleaning blade is high.

[0019]

Embodiments of the electrophotographic copying apparatus according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view showing the arrangement of an electrophotographic copying apparatus (copying machine) according to the first embodiment (claim 1).

This copying machine 10 includes a document table 11, a copy lamp 12, a first mirror 13, a second mirror 14,
Third mirror 15, lens 16, fourth mirror 17, fifth mirror 18, sixth mirror 19, photoconductor drum 20 including OPC, charger 21, developing tank 22, transfer charger 23, cleaner device 24 A cleaning blade 25, a conveyor belt 26, a fixing device 27, paper cassettes 28 and 29, a discharge roller 30, a discharge lamp 31, and the like.

When an original is set on the original placing table 11 and the copy start button is pressed, the copy lamp 12,
First mirror 13, second mirror 14, third mirror 1
5 is configured to move in parallel (in the direction of the bidirectional arrow shown in the drawing) along the document table 11.

Light 32 emitted from the copy lamp 12
Are reflected by the document on the document table 11, and the first mirror 13, the second mirror 14, the third mirror 15, the lens 16, the fourth mirror 17, the fifth mirror 18, and the sixth mirror
The surface of the photoconductor drum 20 charged by the charger 21 is irradiated at the exposure point P via the mirror 19. By this irradiation, an electrostatic latent image is formed on the surface of the photoconductor drum 20.

This electrostatic latent image is developed into a toner image by the developing tank 22, and the toner image is transferred by the transfer charger 23 onto the paper supplied from the paper cassette 28 or 29. The sheet on which the toner image is transferred is conveyed to the fixing device 27 by the conveying belt 26, the toner image is fixed on the sheet by the fixing device 27, and then the sheet is discharged to the outside by the discharge roller 30.

On the other hand, the surface of the photosensitive drum 20 after the transfer of the toner image is cleaned by the cleaner device 24 and the cleaning blade 25. This cleaning method is a blade cleaning method in which toner is scraped off at the edge of a cleaning blade 25 made of urethane rubber. The electrostatic latent image on the photosensitive drum 20 after cleaning is discharged by the discharging lamp 31.

FIG. 2 shows a state in which the photosensitive drum 20 is being cleaned by the cleaning blade 25. The cleaning blade 25 is constantly in pressure contact with the surface of the photosensitive drum 20 during the process of forming an image. The residual toner 33 is present between the edge of the cleaning blade 25 and the photoconductor drum 20, and serves as a lubricant between them to reduce the friction coefficient to some extent.

Next, a second embodiment (claim 2) will be described.

FIG. 3 is a front view showing a means for detecting the original density, and FIG. 4 is a plan view thereof. Reference numeral 35 is a document, 36 is a table glass, 37 is a reflector, 38 is a light control plate, and 40 is an optical sensor. Front (F) on the reflector 37,
Three slit-shaped openings 37a of a center (C) and a rear (R) are formed, and three optical sensors 40 are arranged below each of them.

When the copy start switch is pressed, the copy lamp 12 is turned on and the optical system scans. At this time, the light reflected from the document 35 is detected by the three optical sensors 40 of F, C, and R. Each optical sensor 40
The output waveform of the above is shown in FIG. The lower the original density (the whiter the original), the larger the amount of reflected light and the larger the sensor output.

These three optical sensors 40 of F, C and R
Output waveforms are averaged individually over the entire area of the original scan, and the lowest position is selected. If the output of the optical sensor 40 at that position is equal to or higher than a predetermined value, in other words, the original density is equal to or lower than the predetermined value. For example, in the middle of the copying process, after the copying of a predetermined number of sheets is completed, the copying process is temporarily stopped and the mode is changed to the idling mode.

In the idling mode, the rotating photoconductor drum 20 is charged at a fixed potential by the charger 21 over the entire width, and a uniform electrostatic latent image is formed on the photoconductor drum 20 without exposure. . This electrostatic latent image is developed into a toner image by the developing tank 22. In the idling mode, feeding and transfer are suspended. The toner image is sent to the cleaner device 24 and the cleaning blade 25 as it is without being transferred to the paper, and is cleaned as a lubricant for the photoconductor drum 20 and the cleaning blade 25. Therefore, when a plurality of low-density originals are continuously copied, abrasion of the photoconductor drum 20 and the cleaning blade 25 is prevented,
It is possible to extend their life.

The idling mode is completed as described above, and the normal copying process which was temporarily stopped on the way is restarted.

The above operation is shown in the flowchart of FIG. When the copy start switch is pressed, the document density is detected before the copy process starts. At this point, it is set whether or not to execute the idling mode during the copying process. The idling mode is set when the document density is below a predetermined value. After that, the copying process is started, and if the idling mode is set, the copying process is interrupted after a predetermined number of copies and the idling mode is executed. When the idling mode is finished, the copying process is continued again, and when the set number of actual copies is finished, the copying process is finished.

Next, a third embodiment will be described.

FIG. 7 is a sectional view showing the structure of the developing tank.
41 is a toner, 42 is a toner replenishing roller, 43 is a stirring roller, 44 is a magnet roller, 45 is a spike-up adjusting plate, and 46 is a toner controller which detects the mixture ratio (toner concentration) of the carrier of the developer and the toner. .

When the copy start switch is pressed, the normal copying process starts.

The output of the toner control sensor 46 at this time is monitored. The output waveform is shown in FIG.

When the transition of the toner density when a plurality of copies are made using an original having a high original density or an original having a low original density, if the original density is high, the control width of the toner control sensor 46 ( Between the upper and lower limits, the toner concentration changes with a small waveform ripple (solid line). If the document density is low, the toner density changes with the control width of the toner control sensor 46 in a state where the waveform ripple is large (dotted line). This occurs because the balance between the amount of replenished toner and the amount of toner used for development is out of balance.

The problem is that the lower the original density is, the less toner is consumed in the transition of toner concentration, so that toner is not replenished and the toner concentration changes at the lower limit of the control width of the toner control sensor 46 for a long time. It means that The toner control width has a maximum width of about 1% in toner concentration, and if the toner is not replenished for a long time, the toner agitation time becomes long and the toner charge amount also becomes high. Therefore, when a plurality of low-density originals are copied, the density of the toner image formed on the photoconductor drum 20 tends to decrease. Therefore, the abrasion of the photoconductor drum 20 and the cleaning blade 25 may increase.

Therefore, when the output of the toner control sensor 46 is monitored and the toner is not supplied for a predetermined time after the copying process starts, it is considered that the density of the copied document is low, and in the first embodiment. Transition to the idling mode shown. As a result, a toner image is formed on the photosensitive drum 20 over the entire width, and the toner image is directly transferred to the cleaner device 24 for cleaning without being transferred to the paper. At that time, since the toner functions as a lubricant, it is possible to prevent the photoconductor drum 20 and the cleaning blade 25 from being worn and to extend their life.
After that, the normal copying process is restarted.

The above operation is shown in the flowchart of FIG. When the copy start switch is pressed, the copying process starts. After that, the output of the toner control sensor 46 is monitored every number of actual copies, and if it is detected that toner is not replenished for a predetermined time or more and the sensor output does not rise, the copying process is interrupted and the idling mode is executed. It When the idling mode is finished, the copying process is continued again, and when the set number of actual copies is finished, the copying process is finished.

Next, a fourth embodiment will be described.

As shown in FIG. 1, a reflection type infrared density sensor 47 for detecting the density of the toner image on the photosensitive drum 20 is arranged immediately before the cleaner device 24 around the photosensitive drum 20.

Immediately before the copying process is started by pressing the copy start switch, a toner patch is formed on the photosensitive drum 20 under a fixed process condition, and the density of the toner patch is detected by the infrared density sensor 47. . When the detected value is equal to or lower than the predetermined density, it is determined that the density is lowered due to the deterioration of the characteristics of the developer or the characteristics of the photosensitive drum. After that, the copying process is started, and when the output of the infrared density sensor 47 is low, the copying process is interrupted every predetermined number of sheets, and the mode is changed to the idling mode. As a result, a toner image is formed on the photosensitive drum 20 over the entire width, and the toner image is directly transferred to the cleaner device 24 for cleaning without being transferred to the paper.

At this time, since the toner functions as a lubricant, it is possible to prevent the photoconductor drum 20 and the cleaning blade 25 from being worn and to extend their life.
After that, the normal copying process is restarted.

FIG. 10 shows the characteristics of the infrared density sensor 47 used in this embodiment. Since the infrared density sensor 47 is a reflective sensor, the sensor output has a lower value as the detected density is higher, but in calculation, the decrease amount from the base value is used as the sensor output.

The above operation is shown in the flowchart of FIG. When the copy start switch is pressed, the copying process starts. Toner patches are formed on the photoconductor drum 20 under fixed process conditions at the time of pre-rotation before the start, and thereafter, the output of the infrared density sensor 47 is monitored every number of actual copies, and when the density is below a predetermined density. The copying process is interrupted and the idling mode is executed. When the idling mode is finished, the copying process is continued again, and when the set number of actual copies is finished, the copying process is finished.

Next, a fifth embodiment will be described.

In this embodiment, a copy mode changeover switch (not shown in FIG. 1) is used to set the mode in which the charge potential of the photoconductor drum is lower than that in the normal copy mode, that is, the mode in which the image density is low, eg, photo mode ) Is selected and a plurality of sheets are copied, the copying process is started, and after the copying of a predetermined number of sheets is completed, the copying process is interrupted and the mode is changed to the idling mode. As a result, a toner image is formed on the photosensitive drum 20 over the entire width, and the toner image is directly transferred to the cleaner device 24 for cleaning without being transferred to the paper. At that time, since the toner functions as a lubricant, it is possible to prevent the photoconductor drum 20 and the cleaning blade 25 from being worn and to extend their life. After that, the normal copying process is restarted.

Here, the normal mode and the photo mode will be briefly described.

During each process operation in the normal mode (high potential / high density) and the photographic mode (low potential / low density), there is no significant difference and only the process conditions change. The process condition is two, that is, the charging potential of the photoconductor drum 20 charged by the charger 21 and the developing bias potential applied between the photoconductor drum 20 and the ground when developing with the developer filled in the developing tank 22. There is one.

12 to 14 show the relationship between charging and development of the copying machine. FIG. 12 shows the transition of the charging potential when the photosensitive drum 20 is charged and exposed. Photoconductor drum 2
If 0 is charged and then exposed, the potential of the photosensitive drum 20 is canceled by the exposure. Here, it is assumed that the original has a white portion and a black portion. If the white part is scanned by the optical system, a large amount of the reflected light will be incident on the photoconductor drum 20, and the black part will have a small reflected light. Therefore, the charging potential of the photoconductor drum 20 changes depending on the document density. In other words, the higher the document density, the higher the charging potential,
The lower the document density, the lower the charging potential.

FIG. 13 shows the distribution of the charging potential when the character "A" is formed on the photosensitive drum 20 as an electrostatic latent image. In the figure, (a) is the original, and (b) is the charged potential on the virtual line in the original.

The portion of the charging potential peak higher than the developing bias potential (hatched portion) attracts the toner in the developer due to the electrical relationship, and forms a toner image on the photosensitive drum 20.

The difference between the process conditions of the normal mode and the photographic mode is set so that the difference between the charging potential and the developing bias potential, that is, the area of the shaded portion which is the developing potential changes. In the normal mode, the development potential is large, and in the photographic mode, the development potential is small.

The difference between the images in the normal mode and the photographic mode is
Description will be made with reference to the gamma characteristics of copy (relationship diagram between document density and copy density) as shown in FIG.

If the developing potential is high, the saturation density of the developer has a gamma characteristic and the reproduction range of the original density is narrowed. However, since high density reproduction can be maintained, it is suitable for a normal mode for copying a character original or the like. ing. On the other hand, if the developing potential is small, the gamma characteristic changes at a saturation density of the developer or lower, so that the reproduction range of the original density becomes wide, but the copy density becomes low. Therefore, it is suitable for a photo mode for copying a photo or the like.

The process conditions set in the normal mode and the photographic mode of this embodiment are set as shown in Table 1.

[0059]

[Table 1]

The above operation is shown in the flowchart of FIG. When the copy start switch is pressed, it is judged whether the copy mode is low density (photo mode),
If it is the photo mode, set the idling mode and start the copying process. When it is determined that the idling mode has been set and the predetermined number has been reached after the copying of the predetermined number of sheets is completed, the copying process is interrupted and the idling mode is executed. Is formed, and is directly transferred to the cleaner device 24 for cleaning without being transferred to a sheet. At this time, since the toner functions as a lubricant, the photoconductor drum 20 and the cleaning blade 25 are prevented from being worn, and the life is extended. When the idling mode is finished, the copying process is continued again, and when the set number of actual copies is finished, the copying process is finished.

As described above, it is possible to prevent the photoconductor drum 20 and the cleaning blade 25 from being worn when a plurality of sheets are continuously copied in the low charge potential setting mode in which the copy image density is low.

Next, a sixth embodiment (claim 3) will be described.

In this embodiment, the rubber hardness of the cleaning blade 25 changes depending on the temperature inside the machine. The material used for the cleaning blade 25 is rubber or plastic, but generally urethane rubber is often used. In this embodiment, it is assumed that it is made of urethane rubber.

As shown in FIG. 16, urethane rubber has the characteristic that its rubber hardness changes with temperature. The lower the temperature, the higher the rubber hardness, and the cleaning blade 2
5 and the photoconductor drum 20 are susceptible to stress. In many cases, the temperature inside the machine drops from when the main power supply of the copying machine is turned off, and is stable at a low temperature level immediately before the next power supply is turned on. In particular, the copying machine installed in an office or the like has a very low temperature inside the machine in the early morning.

Therefore, in this embodiment, the main power is turned off.
When the instruction is given, the main power source is not immediately turned off, but the photoconductor drum 20 is rotated, and the electrostatic latent image is formed by uniformly charging the photoconductor drum 20 with a fixed potential over the entire width of the photoconductor drum 20. .

The power source itself delays the time when it is actually turned off by a timer. The electrostatic latent image is developed in the developing tank 22 to form a uniform toner image on the photoconductor drum 20. This toner image is not transferred to the paper, and is stopped immediately before the cleaner device 24 so that the photosensitive drum 20 stops.
To stop the rotation of.

At this time, the photosensitive drum 20 remains charged, but the charging is naturally canceled with the passage of time. Further, in consideration of the case where the cancellation is insufficient, when the photoconductor drum 20 rotates when the power is turned on, at the same time, the charge removal lamp 31 is turned on and the photoconductor drum 20 is turned on.
May be neutralized.

The toner image on the photoconductor drum 20 is immediately sent to the cleaning blade 25 when the photoconductor drum 20 rotates when the main power source is turned on next time, and the toner functions as a lubricant.
Even when the rubber hardness of No. 5 is high, the photoconductor drum 20
Therefore, it is possible to prevent the cleaning blade 25 from being worn and to extend the service life thereof. After that, the normal copying process starts.

The above operation is shown in the flowchart of FIG.

As will be described from the steps in the middle, when the copying process ends, the process is stopped and the main switch is turned off. At this time, only the operation is performed, and the main switch itself is turned off with a time lag after the following flow is performed. When the main switch is turned off, the process starts rotating, the idling mode is executed, a toner image is formed over the entire width of the photosensitive drum 20, the process is stopped, and the main switch is turned off with a time lag. .

Next, when the main switch is turned on, warm-up cleaning is executed and the photosensitive drum 20
The upper toner image is immediately sent to the cleaning blade 25 for cleaning. Then, when the copy start switch is pressed, the process rotates and the copy process starts.

Next, a seventh embodiment will be described.

In this embodiment, in contrast to the same phenomenon as in the sixth embodiment, the electrostatic latent image is uniformly charged at a fixed potential over the entire width of the photosensitive drum 20 by the charger 21 immediately before the end of the copying operation. To form. The electrostatic latent image is developed in the developing tank 22, and a toner image is uniformly formed on the photoconductor drum 20.

Immediately before this toner image enters the cleaner device 24, the rotation of the photosensitive drum 20 is stopped. Even if the main power source is turned off as it is after the photoconductor drum 20 is stopped, the photoconductor drum 20 remains charged, but the charging is naturally canceled with the passage of time. Further, in consideration of the case where the cancellation is insufficient, when the photoconductor drum 20 rotates when the power is turned on, the charge removal lamp 31 may be turned on and the photoconductor drum 20 may be removed at the same time.

The toner image on the photoconductor drum 20 is immediately sent to the cleaning blade 25 when the photoconductor drum 20 rotates when the main power source is turned on next time, and the toner functions as a lubricant.
Even when the rubber hardness of No. 5 is high, the photoconductor drum 20
Therefore, it is possible to prevent the cleaning blade 25 from being worn and to extend the service life thereof. After that, the normal copying process starts.

The above operation is shown in the flowchart of FIG.

When the main switch is turned on, warm-up is started, and the photosensitive drum 20 is destaticized and residual toner is cleaned to enable copying. After that, when the copy start switch is pressed,
The process spins and the copying process starts.

When the copying process for the set number of copies is completed, the idling mode is immediately executed, a toner image is formed over the entire width of the photosensitive drum 20, the process is stopped, and the main switch is turned off. Next, when the main switch is turned on, the toner image on the photoconductor drum 20 is immediately sent to the cleaning blade 25 for cleaning.

Compared to the sixth embodiment, the cleaning process is simplified because the toner image is used as a lubricant during the copying operation.

[0080]

【The invention's effect】

(1) According to the electrophotographic copying apparatus of claim 1, when it is detected that the amount of the developer is small, a toner image is formed over the entire width of the photoconductor during the copying process, and the toner image is transferred to a sheet. Without sending to the cleaning section,
Since the toner is used as a lubricant for cleaning, it is possible to prevent abrasion of the photoconductor and the cleaning blade, and it is possible to extend the life of the photoconductor and the cleaning blade while reducing toner waste.

(2) According to the electrophotographic copying apparatus of the second aspect, the density of the document to be copied is detected, and when the detected density of the document is below a predetermined value, the photoconductor A toner image is formed over the entire width, and the toner image is sent to the cleaning section without being transferred to paper, and the toner is used as a lubricant for cleaning, so it is possible to prevent abrasion of the photoconductor and the cleaning blade. It is possible to extend the service life of the photoconductor and the cleaning blade while reducing the waste of.

(3) Since the temperature inside the copying machine left for a long time at night or the like is low and the hardness of the cleaning blade is high, the photoconductor and the cleaning blade are susceptible to stress when the power is turned on as it is. .

According to the electrophotographic copying apparatus of the third aspect, when the power-off instruction is issued, the power is not immediately turned off, but before that, a toner image is formed over the entire width of the photosensitive member and the paper is printed. The power is turned off in a state where the toner image is stopped immediately before the cleaning blade without being transferred. Next, when the power is turned on, the toner image on the photoconductor is cleaned, and the toner functions as a lubricant during the cleaning, so even if the hardness of the cleaning blade is high, the wear of the photoconductor and the cleaning blade is prevented. Therefore, it is possible to extend the life of the photoconductor and the cleaning blade while reducing the waste of toner.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of an electrophotographic copying apparatus (copying machine) according to a first embodiment of the present invention.

FIG. 2 is a front view showing a state where the photosensitive drum is cleaned by a cleaning blade in the first embodiment.

FIG. 3 is a front view showing a means for detecting a document density in the first embodiment.

FIG. 4 is a plan view showing a means for detecting a document density in the first embodiment.

FIG. 5 is an output waveform diagram of three optical sensors in the first embodiment.

FIG. 6 is a flowchart for explaining the operation according to the second embodiment.

FIG. 7 is a sectional view showing the structure of a developing tank in the second embodiment.

FIG. 8 is an output waveform diagram of the Tonacon sensor in the second embodiment.

FIG. 9 is a flowchart for explaining the operation according to the third embodiment.

FIG. 10 is a characteristic diagram of a reflective infrared density sensor in the third embodiment.

FIG. 11 is a flowchart for explaining the operation according to the fourth embodiment.

FIG. 12 is a diagram showing changes in charging potential when the photosensitive drum is charged and exposed in the fourth embodiment.

FIG. 13 is a diagram showing a distribution of charging potential when a character is formed into an electrostatic latent image on a photosensitive drum in a fourth embodiment.

FIG. 14 is a characteristic diagram showing the relationship between the document density and the copy density in the fourth embodiment.

FIG. 15 is a flowchart for explaining the operation according to the fifth embodiment.

FIG. 16 is a characteristic diagram showing the relationship between the rubber hardness and the temperature of the urethane rubber that constitutes the cleaning blade.

FIG. 17 is a flowchart for explaining the operation according to the sixth embodiment.

FIG. 18 is a flowchart for explaining the operation according to the seventh embodiment.

[Explanation of symbols]

 11 ... Original placing table 12 ... Copy lamp 16 ... Lens 20 ... Photosensitive drum 21 ... Charger 22 ... Development tank 23 ... Transfer charger 24 ... Cleaner device 25 ... Cleaning blade 27 ... Fixing Device 28 ... Paper cassette 31 ... Static electricity removal lamp 33 ... Residual toner 34 ... Original 40 ... Optical sensor 41 ... Toner 42 ... Toner supply roller 43 ... Stirring roller 44 ... Magnet roller 46 ... Tonacon Sensor 47 ... Reflective infrared density sensor

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Koichi Takenouchi 22-22 Nagaike-cho, Abeno-ku, Osaka, Osaka Prefecture Sharp Corporation (72) Inventor Keizo Kitamura 22-22 Nagaike-cho, Abeno-ku, Osaka, Osaka Within the corporation

Claims (3)

[Claims] 1. An electrophotographic copying apparatus comprising a blade-type cleaning device for removing residual toner on a photoconductor, and a detection means for detecting the amount of developer removed by the blade-type cleaning device, and a photoconductor on the photoconductor. A toner image forming means for forming a toner image, and the toner image forming means is operated during the copying process based on the detection value by the detecting means, and the toner image is removed by the blade type cleaning device. And an electrophotographic copying machine. 2. The amount of the developer removed by the blade type cleaning device is detected by detecting the density detected by the detection means for detecting the density of the copy original to be a predetermined value or less. The electrophotographic copying machine described in 1. 3. An electrophotographic copying apparatus comprising a blade type cleaning device for removing residual toner on a photoconductor, an instruction means for instructing power-off of the device, and a toner image formation for forming a toner image on the photoconductor. And means,
When the power off is instructed by the instructing means,
An electrophotographic copying machine characterized in that the toner image forming means is operated to form a toner image on a photoconductor, the toner image is stopped before the blade type cleaning device, and the power is turned off in this state. .