JPH09190143A - Process cartridge and electrophotograic image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a sandy-surface image from being formed extending over the use of a long term and to minimize the chip of a photoreceptor drum. SOLUTION: A process cartridge 10 is provided with an NVRAM 14 storing information related on the using amount of the photoreceptor drum 3. Besides, a device main body is provided with a read-out/write means 16, a judgement means 17 and a high-voltage power source 11 impressing a vibration voltage obtained by superimposing an AC voltage on a DC voltage with respect to an electrostatic charge roller 4. Then, the voltage impressed on the roller 4 is changed according to the using amount of the drum 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process cartridge and an electrophotographic image forming apparatus to which the process cartridge can be attached and detached.

Here, as an electrophotographic image forming apparatus, for example, an electrophotographic copying machine, an electrophotographic printer (for example, L
ED printers, laser beam printers, etc.), electrophotographic facsimile machines, and electrophotographic word processors.

As the process cartridge, a charging means, a developing means or a cleaning means, and an electrophotographic photosensitive member are integrally formed into a cartridge, and the cartridge can be attached to and detached from the main body of the electrophotographic image forming apparatus. Or, the charging means, at least one of the developing means and the cleaning means, and the electrophotographic photosensitive member are integrally made into a cartridge so as to be attachable to and detachable from the main body of the electrophotographic image forming apparatus. The developing means and the electrophotographic photosensitive member are integrally made into a cartridge which can be attached to and detached from the main body of the electrophotographic image forming apparatus.

[0004]

2. Description of the Related Art Conventionally, in an image forming apparatus using an electrophotographic image forming process, an electrophotographic photosensitive member and process means acting on the electrophotographic photosensitive member are integrally formed into a cartridge, and the cartridge is installed in a main body of the apparatus. A process cartridge system that can be attached and detached is used. According to this process cartridge system, the maintenance of the apparatus can be performed by the user himself without relying on a service person, so that the operability can be remarkably improved. Therefore, this process cartridge system is widely used in image forming apparatuses.

An image forming apparatus generally has a photosensitive drum which is an electrophotographic photosensitive member, a charging unit for uniformly charging the photosensitive drum with an electric charge, and an image exposure on the uniformly charged photosensitive drum. Exposure means for forming an electrostatic latent image by developing the toner, developing means for developing the toner as a developer into an electrostatic latent image to make it visible, and means for transferring the toner image on the photosensitive drum onto a recording medium such as paper. It has a barrel transfer roller, a fixing unit that fixes the toner image on the recording medium, and a cleaning unit that scrapes off the residual toner remaining on the photosensitive drum, and repeats the processes of charging, exposure, development, transfer, fixing, and cleaning. ,used.

A corona charger has been used as a conventional electrophotographic charging means, but in recent years, a contact charging device intended for ozone-less and low power consumption has been put into practical use.
Among these, a roller charging method using a conductive roller as a charging member is preferably used from the viewpoint of charging stability. In roller charging, a conductive elastic roller is pressed against the surface of the electrophotographic photosensitive member, and a high voltage is applied to the surface of the electrophotographic photosensitive member to charge the electrophotographic photosensitive member. As the applied voltage, a DC voltage or an oscillating voltage obtained by superimposing an AC voltage on the DC voltage can be used, but the oscillating voltage is preferably used from the viewpoint of uniformity of charging.

[0007]

The present invention is a further development of the above process cartridge.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a process cartridge which does not generate a sand image during long-term use and has a small abrasion of the electrophotographic photosensitive member, and an electrophotographic image forming apparatus provided with the process cartridge. That is.

[0009]

The above object can be achieved by a process cartridge and an electrophotographic image forming apparatus according to the present invention. In summary, the present invention provides a process cartridge detachable from the main body of an electrophotographic image forming apparatus, the electrophotographic photoreceptor including an electrophotographic photosensitive member and a charging unit that contacts and charges at least the electrophotographic photosensitive member. The electrophotographic image forming apparatus main body, the electrophotographic image forming apparatus main body has a power supply means for applying an oscillating voltage obtained by superimposing an AC voltage on a DC voltage with respect to the charging means. The process cartridge is characterized in that the voltage applied to the charging means is changed according to the usage amount.

The process cartridge has a storage means for storing information on the usage amount of the electrophotographic photosensitive member, and the main body of the electrophotographic image forming apparatus makes the electrophotographic image formation the information stored in the storage means. It has a reading / writing means for reading / writing from the main body of the apparatus, and a judging means for judging the usage amount of the electrophotographic photosensitive member based on the information in the storing means, and the charging means according to the judgment result of the judging means. It is preferable to change the voltage applied to.

The electrophotographic image forming apparatus detects a current signal flowing through the electrophotographic photosensitive member when the electrophotographic photosensitive member is charged or discharged, and current detection means for detecting the current signal from the current detecting means. It is preferable to have a film thickness judging means for judging the film thickness of the electrophotographic photosensitive member, and to change the voltage applied to the charging means according to the judgment result of the film thickness judging means.

According to another aspect of the present invention, in a electrophotographic image forming apparatus in which a process cartridge can be attached and detached and which forms an image on a recording medium, (a) an electrophotographic photosensitive member and at least the electrophotographic photosensitive member. A process unit that acts on the electrophotographic photosensitive member, including a charging unit that contacts and charges the body, and the main body of the electrophotographic image forming apparatus,
A process cartridge having a power supply unit for applying an oscillating voltage obtained by superimposing an AC voltage on a DC voltage with respect to the charging unit, and changing the voltage applied to the charging unit according to the usage amount of the electrophotographic photosensitive member. There is provided an electrophotographic image forming apparatus comprising: a mounting unit that is mounted on the apparatus main body; and (b) a conveying unit that conveys the recording medium.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The electrophotographic image forming apparatus and process cartridge according to the present invention will now be described in more detail with reference to the drawings.

First Embodiment A first embodiment of the electrophotographic image forming apparatus and the process cartridge according to the present invention will be described with reference to FIGS.

First, an embodiment of an electrophotographic image forming apparatus to which a process cartridge constructed according to the present invention can be mounted will be described with reference to FIG.

As shown in FIG. 2, the image forming apparatus outputs a laser beam modulated according to an image signal from a scanner unit 1 including a laser, a polygon mirror, and a correction system lens. Then, the laser light is reflected by the folding mirror 2 and is applied to a drum-shaped electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) 3. The photosensitive drum 3 is uniformly charged in advance by a charging roller 4 which is a charging means, and an electrostatic latent image is formed on the surface thereof in response to the irradiation of laser light.

On the other hand, the developer (toner) 24 stored in the developer container 5a, which is the developer accommodating portion of the developing device 5, is
The peripheral surface of the developing roller 5b is conveyed while being charged, and a developable toner layer is formed on the developing roller 5b. The electrostatic latent image is developed by a toner layer and is visualized as a toner image.

On the other hand, the recording material 7, which is a recording medium contained in the cassette 71, is supplied by the paper feed roller 72 at the same time when the latent image is formed on the photosensitive drum 3. The recording material 7 is supplied to the registration roller 73 in synchronization with the formation of the latent image on the photosensitive drum 3. And this recording material 7 is
The registration roller 73 conveys the toner image to the roller-shaped transfer means 6 via the conveying means 30 in synchronization with the front end of the toner image, and the transfer means 6 transfers the toner image onto the recording material 7. The recording material 7 on which the toner image is transferred is fixed to the fixing device 8.
The toner image is fixed there to be a permanent image, and finally discharged to the outside of the apparatus.

The toner remaining on the photosensitive drum 3 is removed by a cleaning device 9 composed of an elastic blade. It should be noted that mounting means 40 for removably mounting the process cartridge 10 are provided at two locations in the apparatus body in the case of the present embodiment.

Next, referring to FIG. 1, a schematic structure of the cartridge 10 will be described. The cartridge 10 collectively includes the photosensitive drum 3, the charging roller 4, the developing device 5, and the cleaning device 9 as a unit. These components are assembled in the cartridge 10 in a predetermined mutual arrangement relationship. The cartridge 10 is inserted and mounted in a predetermined portion in the main body of the image forming apparatus in a predetermined manner, and conversely, is removed from the mounting main body. You can do it.

When the image forming apparatus is used for a long time, various elements such as the photosensitive drum, the charging device, the developing device, and the cleaning device are consumed and the print quality is deteriorated. It is sufficient to replace the process cartridge, and user-free maintenance can be realized.

The photosensitive drum 3 used in this embodiment is a drum cylinder 3a made of a conductive material such as aluminum and having a negatively charging photosensitive layer 3b formed on the outer peripheral surface thereof and having a diameter of 30 mm. It is rotationally driven in a predetermined direction at a predetermined process speed (peripheral speed). In the OPC photosensitive layer 3b, the charge transport layer 3d is formed on the charge generation layer 3c.

The charge generating layer 3c is formed by vacuum depositing a charge generating material such as an azo pigment such as Sudan Red or Diane Blue, or a phthalocyanine pigment such as perylene resin, copper phthalocyanine or titanyl phthalocyanine, or by using the charge generating material as polystyrene or acrylic. It is formed by dispersing in a binder resin such as a resin and applying the dispersion liquid. The charge generation layer 3c has a thickness of 5 μm or less, preferably 0.05 to 3 μm.

The charge transport layer 3d is formed by using a coating liquid prepared by dissolving a charge transport substance such as a hydrazone compound or a styryl compound in a resin having film-forming property such as polyester, polycarbonate or polystyrene. The thickness of the charge transport layer 3d is 5 to 40 μm, preferably 10 to 30 μm.

In this embodiment, the charge generation layer 3c has a thickness of 0.1 μm.
The thickness of the charge transport layer 3d is 20 μm, the initial thickness of the photosensitive layer 3b is about 20 μm, and a good image can be obtained when the thickness of 10 μm or more remains. did.

The charging roller 4 used in this embodiment is a core metal 4a.
A conductive elastic body 4b is formed on the surface of the core, and both ends of the cored bar are rotatably held and pressed against the outer peripheral surface of the photosensitive drum 3 with a predetermined pressing force, and driven by the rotation of the photosensitive drum 3. Rotate. The conductive elastic body 4b is made of urethane resin or EPD.
It is possible to use a known one in which carbon, a metal oxide such as tin oxide or titanium oxide is dispersed in a solid state or sponge state such as M and NBR.

A predetermined bias is applied to the charging roller 4 from a high voltage power source 11 provided in the main body of the image forming apparatus through a core metal 4a, and the surface of the photosensitive layer 3b of the photosensitive drum 3 is set to a predetermined potential. To be charged. As the applied bias, an oscillating voltage obtained by superimposing a DC voltage and an AC voltage was used.

As shown in the graph of FIG. 3, the relationship between the number of prints X and the film thickness d of the photoconductor measured by the above-described structure is as follows: The peak-to-peak voltage V of the vibration voltage applied to the charging roller 4.
There was a linear relationship in which the slope varied depending on pp. This inclination is the abrasion amount Δd (μm) of the photoconductor layer per print.
/ Sheet), and the above-mentioned relationship is based on this abrasion amount Δd (μ
(m / sheet) and the peak-to-peak voltage Vpp, it was found to be as shown in the graph of FIG. That is, under a certain peak-to-peak voltage Vpp, the number of prints X is proportional to the film thickness d of the photoconductor, so that the film thickness d of the photoconductor can be calculated from the information on the number of prints.
The photoconductor film thickness d in FIG. 3 is an actual film thickness measured using a film thickness measuring device (Fischer Permascope E-111).

The relationship between the photoconductor film thickness d (μm) and the so-called peak-to-peak voltage Vpp at which a so-called sand image is not generated is shown in the graph of FIG. 5, and is expressed by the following relational expression (1). You can

Vpp ≧ 40d + 1200 (1) Here, in the output image developed by the reversal developing system, the amount of discharge of the charging roller is small, and therefore the photoconductor drum is sufficiently charged. It is a black-spotted image that appears in the missing part. It is known that such a sandy image is remarkably generated when the peak-to-peak voltage of the vibration voltage applied to the charging roller is small.

Peak-to-peak voltage Vpp at which sand image is not generated
The fact that the value of changes with the film thickness d of the photoconductor can be considered as follows. That is, as the printing operation is repeated, the surface of the photosensitive drum is gradually scraped, and the film thickness of the photosensitive layer on the surface of the photosensitive drum becomes thin. When the photoconductor film becomes thinner, the impedance of the photoconductor drum decreases, and the voltage applied to the photoconductor drum during charging increases, so that discharge easily occurs, and the sand image as described above is less likely to occur. Become. That is, when the surface of the photosensitive drum is thinned by repeating printing, a good image can be obtained even if the AC component Vpp of the vibration voltage applied to the charging roller is reduced.

Therefore, in this embodiment, the process cartridge is provided with a storage medium, and the number of prints is stored in the storage medium.
By changing the peak-to-peak voltage Vpp of the vibration voltage applied to the charging roller stepwise according to the number of prints,
It is possible to charge with a minimum required peak-to-peak voltage Vpp without generating a sandy image, and to extend the life of the photosensitive drum.

The storage means used in the present invention is not particularly limited as long as it rewritably stores and holds the signal information, but for example, an electric storage such as a RAM or a rewritable ROM. Means, magnetic recording medium, magnetic bubble memory, magneto-optical memory, or other magnetic storage means can be used. In this embodiment, the NV storage device is a non-volatile storage device in terms of ease of handling and cost.
(Non Volatile) RAM was used.

The block cartridge of the process cartridge of FIG. 1 and the sequence flowchart of FIG. 6 will be specifically described below.

The non-volatile memory means 14 incorporated in the process cartridge 10 is connected via a connector 15 to a read / write means 16 provided in the main body of the apparatus. When the printing operation is started, first, the reading / writing means 16 in the apparatus main body reads the number of prints X from the nonvolatile storage means 14 in the cartridge (S1).
The read number X of prints is compared and judged by the judgment means 17 with a preset number of drum life X0 (for example, 7750) (S2), and if the number of prints X exceeds the drum life number X0, the CPU 13 The user is informed of the warning by the warning notifying means 18 via (S3).

On the other hand, when the number of printed sheets X has not reached the end of life, it is compared with the set number of sheets X1 (for example, 5000 sheets) (S4), and when the number of printed sheets X exceeds the set number of sheets X1, the peak-to-peak voltage is reached. Vpp to V1 (eg 1700
V) (S5).

Similarly, the set number of sheets X2 (for example, 3000)
Number of sheets), and compare with the set number of sheets X3 (for example, 1500 sheets) (S
6 and S8), the peak-to-peak voltage Vpp is V2 (for example, 1800 V), V3 when the set number is exceeded.
(For example, 1900V) (S7, S9). When the number of printed sheets X is equal to or smaller than the set number of sheets X3 (for example, 1500 sheets), the peak-to-peak voltage Vpp becomes V4 (for example, 2000V) (S10). The set peak-to-peak voltage is high voltage power supply 1
1 is applied to the charging roller 4 to form an image (S1
1).

When a series of printing operations is completed, the reading / writing means 16 adds the number of prints in the non-volatile storage means 14 in the process cartridge by one to perform update writing (S12), and the printing operation is completed. .

7 and FIG. 7 are graphs showing the transition of the photosensitive member film thickness when the printing operation is actually repeated with the configuration of this embodiment and the transition of the peak-to-peak voltage actually applied to the charging roller at the time of image formation. Each is shown in the graph of 8. For comparison with this example, the results when the peak-to-peak voltage applied to the charging roller was fixed at 2000 V regardless of the photoconductor film thickness are also shown as a comparative example. In the case of the comparative example, the photoconductor film thickness was 10 μm after printing 5,000 sheets, and the life was reached.
With the configuration of this embodiment, up to 7750 sheets can be printed, and the life of the photosensitive drum can be extended.

As described above, the process cartridge is provided with the storage medium, and the number of prints is stored in the storage medium.
By changing the peak-to-peak voltage Vpp of the oscillating voltage applied to the charging roller according to the number of prints, it is possible to charge with the minimum necessary peak-to-peak voltage Vpp without generating a sandy image during long-term use. Therefore, it has become possible to extend the life of the photosensitive drum.

Second Embodiment Next, a second embodiment according to the present invention will be described with reference to FIGS.

This embodiment is a modification of the first embodiment, and its purpose is to deal with the case where the same cartridge is used at a plurality of process speeds. A plurality of process speeds are required when switching resolutions in the same main body, or when cartridge compatibility is provided between a plurality of models having different process speeds. In order to achieve the above-mentioned object, in the present embodiment, the process cartridge is provided with a non-volatile storage medium, and the amount of abrasion of the photosensitive member film thickness of the photosensitive drum is accumulated and stored therein, and applied to the charging roller according to the accumulated amount of abrasion. The peak-to-peak voltage Vpp of the oscillating voltage is determined.

The process cartridge used in this embodiment is basically the same as that used in the first embodiment. Process the cartridge with process speed Vp = 50 mm / se
c and Vp = 100 mm / sec, the peak-to-peak voltage Vpp actually measured when printed by an image forming apparatus and 1
FIG. 9 shows the relationship with the abrasion amount Δd of the photoconductor layer per sheet print.
Are shown in the graph, and can be approximated by the following relational expressions.

When Vp = 50 mm / sec: Δd = 0.000004Vpp-0.006 (2) When Vp = 100 mm / sec: Δd = 0.000005Vpp-0.0075 (3) In this embodiment, the process cartridge is provided with a non-volatile storage medium, and the abrasion amount of the photoconductor layer obtained from the process speed and the peak-to-peak voltage Vpp is integrated and stored, and the charging roller is charged according to the accumulated abrasion amount. A plurality of process speeds were dealt with by determining the peak-to-peak voltage Vpp of the oscillating voltage applied to.

The process cartridge will be specifically described below with reference to the block diagram of the process cartridge shown in FIG. 10 and the sequence flowchart shown in FIG.

The non-volatile memory means 14 incorporated in the process cartridge 10 is connected to the read / write means 16 provided in the main body of the apparatus via the connector 15. When the printing operation is started, first, the reading / writing means 16 in the main body of the apparatus reads the accumulated abrasion amount Y from the nonvolatile storage means 14 in the cartridge (S2).
1). The read accumulated wear amount Y is the drum life wear amount Y0 (for example, 10 μm) preset by the determination means 17.
When the integrated abrasion amount Y exceeds the drum life abrasion amount Y0, the warning is informed to the user by the alarm informing means 18 via the CPU 13 (S2).
3).

On the other hand, when the accumulated abrasion amount Y has not reached the end of the life, it is compared with the set abrasion amount Y1 (for example, 7.8 μm) (S24), and when the accumulated abrasion amount Y exceeds the set abrasion amount Y1. The peak-to-peak voltage Vpp is V1 (for example, 170
It is set to 0V (S25).

Similarly, the set abrasion amount Y2 (for example, 5.4)
.mu.m), and compared with the set abrasion amount Y3 (for example, 3 .mu.m) (S
26, S28), when the set abrasion amount is exceeded, the peak-to-peak voltage Vpp is V2 (for example, 1800 V),
It becomes V3 (for example, 1900V) (S27, S29).
When the integrated abrasion amount Y is equal to or less than the set abrasion amount Y3 (for example, 3 μm), the peak-to-peak voltage Vpp is V4 (for example, 2000).
V) (S30). Set peak-to-peak voltage Vpp
Is applied to the charging roller 4 from the high voltage power source 11 to form an image (S31).

When a series of printing operations is completed, the CPU
13 determines the process speed Vp (S32), and calculates the scraping amount Δd for one sheet according to the process speed Vp from the above-described formula (2) or formula (3) (S33, S3).
4).

When Vp = 50 mm / sec: Δd = 0.000004Vpp-0.006 (2) When Vp = 100 mm / sec: Δd = 0.000005Vpp-0.0075 (3) Calculation The scraped amount Δd is the read / write means 16
The non-volatile storage means 1 in the process cartridge
4 is added to the accumulated wear amount Y of 4 and updated and written (S
35), the print operation is ended.

As described above, the process cartridge is provided with the storage medium, the accumulated abrasion amount of the photoconductor layer is stored therein, and the peak-to-peak voltage Vpp of the vibration voltage applied to the charging roller is stored according to the accumulated abrasion amount. As a result of the change, it becomes possible to charge with the minimum required peak-to-peak voltage Vpp without generating a sandy image during long-term use, and it is possible to achieve a long life of the photosensitive drum.

Further, the abrasion amount of the photoconductor layer is obtained from the applied peak-to-peak voltage Vpp and the process speed Vp.
Even when the same cartridge is used at multiple process speeds, it is possible to detect the exact thickness of the photoconductor layer.

Third Embodiment Next, a third embodiment according to the present invention will be described with reference to FIGS. The feature of this embodiment is that the peak-to-peak voltage Vpp of the vibration voltage applied to the charging roller by detecting the photoconductor film thickness.
Is to be changed according to the film thickness.

The basic technique for detecting the thickness of the photoconductor used in this embodiment is to measure the DC current Idc flowing through the photoconductor when the surface potential of the photoconductor is decreased from Vd to 0, and measure the photoconductor layer 3
The film thickness d of b is derived. DC current Idc is
Photoconductor film thickness is d, relative permittivity is ε, permittivity in vacuum is ε
0, the effective charging width of the primary charger is L, and the process speed is Vp, it is expressed by the following relational expression (4).

| Idc | = εε0LVpVd / d (4) In equation (4), ε, ε0, L, Vp, and Vd can be regarded as constants, and therefore DC current It can be seen that Idc is inversely proportional to the photoconductor film thickness d. In this embodiment, the AC component of the vibration voltage applied to the charging roller 4 at the time of detecting the film thickness is set to the frequency 10
00 Hz, peak-to-peak voltage Vpp = 2000V, and DC component Vd = -700V.

DC current Id actually measured in this configuration
The relationship between c and the photoconductor film thickness d is shown in the graph of FIG. 12, and the photoconductor film thickness d is calculated by the following relational expression (5).
Can be derived. The photoconductor film thickness d in FIG. 12 is an actual film thickness measured using a film thickness measuring device (Fischer Permascope E-111).

D = 300 / Idc (5) Further, the relation between the photoconductor film thickness d and the lower limit value of the peak-to-peak voltage Vpp at which the sand image does not occur can be expressed by the relational expression (6). As already known in Example 1.

Vpp = 40d + 1200 (6) By applying the peak-to-peak voltage pp thus obtained to the charging roller, a sand image is not generated and abrasion of the photoconductor layer is minimized. It becomes possible.

A specific method for detecting the photosensitive member film thickness and deriving the peak-to-peak conductive thickness applied to the charging roller will be described below with reference to the configuration diagram of FIG. 13 and the flowchart of FIG.

First, a discharging bias (frequency 1000 Hz, AC voltage of Vpp = 2000 V) is applied to the charging roller 4 from the high voltage power source 11 to apply the photosensitive layer 3 b of the photosensitive drum 3.
The surface potential of is set to 0 V (S41).

Thereafter, the charging roller 4 is charged with a charging bias (frequency 1000 Hz, AC voltage of Vpp = 2000 V).
Oscillation voltage that superimposes DC voltage of 700V)
The photosensitive drum 3 is rotated twice or more while being applied from 1 to uniformly charge the surface potential of the photosensitive member to Vd = -700V (S42).

Next, with the photosensitive drum 3 still rotating,
Static elimination bias for the charging roller 4 (frequency 1000 Hz, V
The surface of the photoconductor is neutralized by applying pp = 2000V AC voltage) (S43). DC current Idc flowing at this time
Is detected by the detection circuit 12. The detected current value Idc is sent to the judging means 17, and the current value Idc is calculated by the above equation (5).
The photoconductor film thickness d is derived from dc (S45) and compared with a preset life film thickness d0 of the photoconductor drum (S45).
46) If the film thickness is less than the life film thickness, the life warning device 18 notifies the user of the warning through the CPU 13 (S).
47) On the other hand, when it is judged that the film thickness is equal to or longer than the life film thickness, the peak-to-peak voltage V applied to the charging roller is further calculated by the equation (6).
pp is derived (S48), and the photoconductor film thickness detection and peak-to-peak voltage derivation sequence ends.

FIG. 15 shows the charging roller 4 when detecting the photoconductor film thickness.
Applied voltage and DC current Idc flowing through the photosensitive drum 3
FIG. In the figure, currents are flowing at the time of charging 0 to Vd and at the time of static elimination of Vd to 0, and the current values of both should be the same in principle. If a defect such as a pinhole occurs, an excessive leak current that does not actually contribute to charging flows into this portion, causing erroneous measurement. Therefore, the DC current Idc was measured at the time of static elimination (P part in the figure).

The above-described detection of the photoconductor film thickness is carried out when the image forming apparatus is powered on and every time a predetermined number of sheets are printed. Further, the peak-to-peak voltage Vpp of the vibration voltage applied to the charging roller during image formation is controlled to a value derived by the CPU, while the peak-to-peak voltage Vpp of the vibration voltage applied to the charging roller at the time of detecting the film thickness of the photoconductor is always 2000V. It was fixed to and controlled.

FIG. 16 shows the transition of the photosensitive member film thickness when the printing operation is repeatedly performed with the above-described configuration and the transition of the peak-to-peak voltage actually applied to the charging roller during image formation.
17 and the graph of FIG. 17, respectively. In order to compare with this example, the results of Example 1 and the comparative example used in Example 1 are also shown. In the case of the comparative example, the life of the photosensitive member reached 10 μm after printing 5,000 sheets and in the case of printing 7,750 sheets in the example 1, but with the configuration of this example, 8
It was possible to print up to 000 sheets, and it was possible to extend the life of the photosensitive drum.

As described above, the peak-to-peak voltage Vp of the vibration voltage applied to the charging roller is detected by detecting the photoconductor film thickness.
By changing p according to the film thickness, it becomes possible to charge with a minimum required peak-to-peak voltage Vpp without generating a sand image during long-term use, and to achieve a long life of the photoconductor drum. Became possible.

[0067]

As is clear from the above description, according to the present invention, a sand image is not generated during long-term use, and the electrophotographic photosensitive member is less likely to scrape, so that a high quality image can be obtained. It is possible to provide a process cartridge capable of achieving a long life of the electrophotographic photosensitive member, and an electrophotographic image forming apparatus including the process cartridge.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a process cartridge according to a first exemplary embodiment.

FIG. 2 is a configuration diagram showing an image forming apparatus according to the present invention.

FIG. 3 is a graph showing the relationship between the number of printed sheets and the film thickness of the photoconductor according to Example 1.

FIG. 4 is a graph showing the relationship between the peak-to-peak voltage and the photoconductor scraping amount according to the first embodiment.

FIG. 5 is a graph showing the relationship between the photoconductor film thickness and the charging bias in which a sand image is not generated according to the first embodiment.

FIG. 6 is a flowchart of control according to the first embodiment.

FIG. 7 is a graph showing the relationship between the number of prints and the film thickness of the photoconductor for showing the effect of Example 1.

FIG. 8 is a graph showing the relationship between the number of prints and the peak-to-peak voltage for showing the effect of the first embodiment.

FIG. 9 is a graph showing the relationship between the peak-to-peak voltage and the amount of abrasion of the photoconductor layer according to the second embodiment.

FIG. 10 is a block diagram showing a process cartridge according to a second embodiment.

FIG. 11 is a flowchart of control according to the second embodiment.

FIG. 12 is a graph showing the relationship between the photoconductor film thickness d and the DC current according to Example 3.

FIG. 13 is a block diagram showing a process cartridge according to a third embodiment.

FIG. 14 is a flowchart showing control of film thickness detection / Vpp derivation according to the third embodiment.

FIG. 15 is a timing chart showing film thickness detection control according to the third embodiment.

FIG. 16 is a graph showing the relationship between the number of prints and the photoconductor film thickness for showing the effect of Example 3.

FIG. 17 is a graph showing the relationship between the number of prints and the peak-to-peak voltage for showing the effect of the third embodiment.

[Explanation of symbols]

 3 Photoreceptor Drum (Electrophotographic Photoreceptor) 4 Charging Roller (Charging Means) 10 Process Cartridge 11 High Voltage Power Supply 12 Detection Circuit (Current Detection Means) 13 CPU 14 NVRAM (Storage Means) 16 Read / Write Means 17 Judgment Means

Claims (10)

[Claims] 1. A process cartridge attachable to and detachable from a main body of an electrophotographic image forming apparatus, comprising: an electrophotographic photosensitive member; and a charging means for charging at least the electrophotographic photosensitive member by contacting the electrophotographic photosensitive member. Process means, the electrophotographic image forming apparatus main body has a power supply means for applying an oscillating voltage obtained by superimposing an AC voltage on a DC voltage with respect to the charging means, the amount of use of the electrophotographic photoreceptor A process cartridge characterized in that the voltage applied to the charging means is changed in response to the change. 2. The electrophotographic image forming apparatus main body further comprises storage means for storing information on the usage amount of the electrophotographic photoconductor, and the electrophotographic image forming apparatus main body stores the information stored in the storage means from the electrophotographic image forming apparatus main body. It has a reading / writing means for reading / writing, and a judging means for judging the usage amount of the electrophotographic photosensitive member based on the information in the storage means, and applies it to the charging means according to the judgment result of the judging means. The process cartridge according to claim 1, wherein the voltage is changed. 3. A current detection unit for detecting a current signal flowing through the electrophotographic photosensitive member when the electrophotographic image forming apparatus main body charges or discharges the electrophotographic photosensitive member, and a detection current of the current detection unit. A film thickness judging means for judging the film thickness of the electrophotographic photosensitive member from a signal, and changing the voltage applied to the charging means according to the judgment result of the film thickness judging means. 1 process cartridge. 4. The process cartridge further comprises:
The process cartridge according to claim 1, 2 or 3, further comprising a developing means for developing the latent image formed on the electrophotographic photosensitive member. 5. The process cartridge further comprises:
4. The process cartridge according to claim 1, further comprising a cleaning unit for removing toner remaining on the electrophotographic photosensitive member. 6. An electrophotographic image forming apparatus, wherein a process cartridge is attachable / detachable and forms an image on a recording medium, wherein (a) an electrophotographic photosensitive member and at least the electrophotographic photosensitive member are charged to be charged. And a process unit that acts on the electrophotographic photosensitive member, including a unit, and the electrophotographic image forming apparatus main body has a power supply unit that applies an oscillating voltage obtained by superimposing an AC voltage on a DC voltage to the charging unit. A process cartridge that changes the voltage applied to the charging unit according to the amount of the electrophotographic photosensitive member used,
An electrophotographic image forming apparatus, comprising: mounting means for mounting the apparatus body, and (b) a conveying means for conveying the recording medium. 7. The process cartridge has storage means for storing information on the amount of use of the electrophotographic photosensitive member, and the electrophotographic image forming apparatus main body reads / writes information stored in the storage means. Read / write means for determining the amount of electrophotographic photosensitive member to be used based on the information stored in the storage means, and changes the voltage applied to the charging means in accordance with the determination result of the determination means. The electrophotographic image forming apparatus according to claim 6, wherein the electrophotographic image forming apparatus comprises: 8. A film of the electrophotographic photosensitive member based on a current detection means for detecting a current signal flowing through the electrophotographic photosensitive member when the electrophotographic photosensitive member is charged or discharged. 7. An electrophotographic image forming apparatus according to claim 6, further comprising: a film thickness judging unit for judging a thickness, and changing a voltage applied to the charging unit according to a judgment result of the film thickness judging unit. 9. The process cartridge further comprises:
9. The electrophotographic image forming apparatus according to claim 6, further comprising a developing unit for developing the latent image formed on the electrophotographic photosensitive member. 10. The process cartridge according to claim 6, further comprising a cleaning unit for removing toner remaining on the electrophotographic photosensitive member.
Alternatively, the electrophotographic image forming apparatus of 8.