JP2003173071A - Charging device, process cartridge and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent defective charging in a low temperature and low humidity environment and to prolong the service life of a drum in a high temperature and high humidity environment. <P>SOLUTION: An electrophotographic photoreceptor and a charging roll are abutted to each other by using an abutting means which changes its properties according to the temperature and the humidity. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a contact-type charging device for charging a surface of an object to be charged (including static elimination processing) by bringing a charging member into contact with an object to be charged such as a photoreceptor. The present invention relates to an image forming apparatus and a process unit detachable from the image forming apparatus.

[0002]

2. Description of the Related Art For example, in an image forming apparatus such as an electrophotographic apparatus (copier, laser beam printer, etc.) and electrostatic recording apparatus, the surface of an image bearing member such as a photoconductor or a dielectric is charged. A corona discharge device (corona charger) having a wire electrode and a shield electrode has been widely used as a treatment means.

The corona discharge device is effective as a means for uniformly charging the surface of an object to be charged such as an image carrier to a predetermined potential. However, it requires a high-voltage power supply, the charging efficiency is poor,
There are problems that the structure is large and complicated, the cost is high, a relatively large amount of unfavorable ozone is generated by corona discharge, and the discharge wire is contaminated or cut.

In such a corona discharge device, the contact charging means for contacting a charging member to which a voltage has been applied to the body to be charged to charge the surface of the body to be charged can lower the power supply voltage.
Since the structure is simple, there is no cutting of wires, and even if ozone generation is observed, the amount is extremely small, so for example, in an image forming apparatus, an image carrier such as a photoconductor or a dielectric, It is known as a means for charging other surfaces to be charged.

FIG. 1 shows an example of an image forming apparatus having a process cartridge inserted therein. 2 is a side view around the charging roller, and FIG. 3 is a partially cutaway front view around the charging roller.

Reference numeral 1 denotes a member to be charged, which is, for example, a rotating drum type photosensitive member (hereinafter referred to as a photosensitive drum) of an electrophotographic apparatus. The photosensitive drum is rotationally driven in the clockwise direction indicated by the arrow at a predetermined process speed (peripheral speed).

A charging roller 2 has a conductive cored bar 2a as a base material, an elastic layer 2b integrally formed on the outer circumference thereof with a conductive rubber having a low deposition resistance, and an outer circumference of the roller portion. The formed high resistance surface layer (high resistance layer) 2c. That is, the cover layer of the base material has the elastic layer 2b and the surface layer 2c.

The reason why the high resistance layer 2c is provided in the vicinity of the upper layer is as follows.

First, if the resistance of the charging roller 2 is too low, and if a pinhole is generated on the photoconductor even if it is very small, the charging current concentrates there and a voltage drop occurs. Longitudinal direction (contact direction of charging member)
A desired charging potential cannot be obtained over a period of time, resulting in a white band in regular development and a black band in a reversal development system which has become popular in laser beam printers and the like in recent years, resulting in a marked deterioration in image quality.

On the other hand, if the resistance of the charging roller 2 is too high, on the contrary, the current required for charging cannot be sufficiently flowed, resulting in charging failure.

In order to satisfy the above two points, it is of course necessary to provide a certain resistance range, but the resistance range in which these two points are compatible with each other in a single layer is very narrow, and the production is very stable. It's not worth it.

What has been devised there is a contact charging member having at least two layers.

With regard to pinholes, if there is sufficient resistance in the vicinity of the surface layer of the charging member, excessive current will not concentrate there, and therefore sufficient charging ability can be satisfied. Regarding the charging failure, it can be sufficiently prevented by setting the total resistance (product resistance) from the voltage supply source (= core bar) of the charging roller 2 to the surface to a certain level or less, so that the lower layer portion on the core bar (away from the photoreceptor) By providing a low-resistivity layer with sufficient elasticity in the upper part) and a thin layer with relatively high resistance in the upper part (the part close to the photoconductor), the total resistance can be maintained while maintaining relatively high resistance in the vicinity of the surface layer. Is relatively low. As a result, a good image can be stably obtained.

Further, as an apparatus, both ends of 2a are rotatably held by conductive bearings 3 so that the longitudinal direction of the roller is substantially parallel to the generatrix direction of the photosensitive drum 1 and contacted with the surface of the photosensitive drum. The charging roller 2 is brought into contact with the photosensitive drum 1 with a predetermined pressure by urging the bearings 3 at both ends by the conductive pressure springs 4 so as to be movable toward the photosensitive drum.

Reference numeral 5 denotes a power source 10 for applying a bias voltage to the charging roller 2. The power source 10 applies to the charging roller 2 via a conductive pressure spring 4, a conductive bearing 3 and a conductive cored bar 2a. For example, the current voltage V of about 1 to 2 KV
A bias voltage of a superimposed voltage VDC + VAC of a DC or DC voltage and an AC voltage VAC is applied.

As a result, the peripheral surface of the photosensitive drum 1 which is rotationally driven is contact-charged with a predetermined polarity and potential.

[0017]

However, the contact charging device using the charging roller 2 as the charging member as in the above example has the following problems.

Generally, as a method for controlling the amount of current flowing through the charging roller 2, there are control methods generally called constant voltage control and constant current control, but this time, constant current control will be taken as an example.

In the constant current control, the amount of current in the process from the photosensitive drum to the ground (hereinafter referred to as "drum downstream current") is measured, and feedback is applied to keep the value constant. By this control method, a low temperature and low humidity environment (hereinafter referred to as L / L environment) to a high temperature and high humidity environment
A constant drum downstream current is made to flow in all environments up to (hereinafter referred to as H / H environment).

In such a case, in the L / L environment, the resistance of the elastic layer 2b of the charging roller 2 and the high resistance surface layer (high resistance layer) 2c formed on the outer periphery of the roller portion becomes high, The discharge current required for charging cannot be passed sufficiently,
Insufficient charging is caused in the central portion of the charging roller 2 in the longitudinal direction. On the other hand, if an attempt is made to flow a sufficient amount of discharge current in order to prevent charging failure in the L / L environment, H
In the / H environment, the discharge current amount at the longitudinal end portion of the charging roller 2 becomes excessive, and the abrasion of the photosensitive drum becomes large,
It had the drawback of shortening the life of the photosensitive drum (Fig. 6). Needless to say, this problem also applies to the constant voltage control in which the voltage applied to the charging roller 2 is constant.

These problems can be considered by adjusting the drum downstream current according to the environment, that is, reducing the drum downstream current only in the H / H environment. However, according to this method, the discharge current amount in the entire longitudinal direction is reduced. Since the amount is small, the abrasion is good, but in the central portion of the lengthwise direction of the charging roller 2, charging failure is caused due to insufficient discharge amount, and a good image cannot be obtained.

In view of the fact that the point where the life of the photosensitive drum is most cut off is the point corresponding to the end of the charging roller 2, the charging roller 2 contacts the drum in order to reduce the discharge current amount only at this point. If the contact pressure is increased, the discharge current amount at a portion corresponding to the end portion of the charging roller 2 can be made smaller than that at a portion corresponding to the central portion of the charging roller 2 as described later. In the charging roller having an Asker C hardness of 40 ° to 50 °, the spring pressure on one side is around 700 g in the H / H environment, that is, the linear pressure applied to the charging roller. Is preferably around 60 g / cm (Asker C hardness is a hardness measured using a spring-type hardness meter Asker C type (manufactured by Kobunshi Keiki Co., Ltd.) defined in JIS K6050. In the study, the load 500
It was measured as g. It is known from the examination of the applicant of the present invention (Fig. 7).

However, the state before being put in the image forming apparatus,
That is, if the contact pressure of the charging roller 2 with respect to the drum is constantly increased in the process cartridge state, the charging roller 2
Permanent deformation occurs, which is a great adverse effect on image formation.

Therefore, the present invention has been made in view of the above problems, and an object thereof is to secure a discharge current amount that does not cause charging failure in an L / L environment and does not cause an adverse effect on an image. At the same time, it is an object of the present invention to provide a charging device, a process unit, and an image forming apparatus, which prevent deterioration of scraping without causing charging failure even in an H / H environment, and extend the life of the photosensitive drum.

Another object of the present invention is to provide a charging device, a process unit and an image forming apparatus which can prevent the harmful effect of the C set of the charging roller while having the above structure.

[0026]

The above object can be achieved by a charging device, a process cartridge and an image forming apparatus according to the present invention.

According to the first aspect of the present invention, the charging roller is disposed in contact with the electrophotographic photosensitive member and charges the electrophotographic photosensitive member by applying a voltage, and the charging roller is applied to the electrophotographic photosensitive member. In a charging device having a contacting means for contacting, the shape or position of the contacting means changes depending on both the temperature and / or humidity conditions, and thus the electrophotographic photosensitive member and the charging roller. There is provided a charging device characterized in that the contact pressure between the contact pressures changes continuously or stepwise to determine a plurality of contact pressures.

According to the second aspect of the present invention, the contact means is operated by the operating means provided in the image forming apparatus in which the charging device can be attached and detached, so that the shape or position of the contact means can be controlled by temperature and humidity. A charging device according to a first aspect of the present invention is provided, which changes according to both conditions or one of the conditions.

According to the third aspect of the present invention, at least a part of the abutting means is made of a polymer material whose volume changes according to both or one of temperature and humidity conditions. A charging device according to the first aspect of the present invention is provided.

According to a fourth aspect of the present invention, an electrophotographic photosensitive member,
And a charging roller disposed in contact with the electrophotographic photosensitive member and charging the electrophotographic photosensitive member by applying a voltage,
In a process cartridge having contact means for contacting the charging roller with the electrophotographic photosensitive member, the shape or position of the contact means changes depending on both the temperature and / or humidity conditions. Provided is a process cartridge characterized in that the contact pressure between the electrophotographic photosensitive member and the charging roller is continuously or stepwise changed to determine a plurality of contact pressures.

According to the fifth aspect of the present invention, the contact means is operated by the operation means provided in the image forming apparatus in which the process cartridge can be attached and detached, so that the shape or position of the contact means can be controlled by temperature and humidity. 5. It changes according to both conditions or any one of the conditions.
The process cartridge described in 1. is provided.

According to a sixth aspect of the present invention, at least a part of the abutting means is made of a polymer material whose volume changes in accordance with the temperature and / or humidity conditions. A process cartridge according to the fourth aspect of the present invention is provided.

According to the seventh invention, an electrophotographic photosensitive member,
And a charging roller disposed in contact with the electrophotographic photosensitive member and charging the electrophotographic photosensitive member by applying a voltage,
In an image forming apparatus in which a process cartridge having a contacting means for contacting the charging roller with the electrophotographic photosensitive member is detachable, and which has an operating means for acting on the contacting means, the position or shape of the operating means is The contact pressure changes between the electrophotographic photosensitive member and the charging roller by changing the temperature and / or humidity and / or acting on the contacting means. There is provided an image forming apparatus characterized by continuously or stepwise changing and determining a plurality of contact pressures.

According to an eighth aspect of the present invention, at least a part of the operating means is composed of a polymer material whose volume changes according to the conditions of both and / or temperature and humidity. An image forming apparatus according to a seventh aspect of the present invention is provided.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 shows an image forming apparatus in which the contact type charging device according to the present invention is used as a primary charging means for an electrophotographic photosensitive drum (hereinafter referred to as a photosensitive drum) as an image bearing member which is a member to be charged. The schematic block diagram of an example is shown.
The image forming apparatus of this example is a laser beam printer using a transfer type electrophotographic process.

The photosensitive drum 1 comprises a photosensitive drum layer 1b (thickness, for example, 20) formed of an organic photoconductive layer (OPC) on the outer peripheral surface of a drum base 1a made of a grounded conductive material such as aluminum.
diameter of 30 mm, which has a predetermined process speed (peripheral speed) of, for example, 5
It is driven to rotate at 0 mm / sec. Selenium, amorphous silicon, ZnO, or the like can be used as the photoreceptor layer.

Reference numeral 2 denotes a charging roller as a contact charging member. For example, a conductive core metal 2a made of iron or the like as a base material (core material) is an elastic layer EPDM (which is integrally formed on the outer periphery of the conductive core metal 2a. A terpolymer of ethylene propylene diene) conductive rubber roller portion 2b, and a resistance layer 2c which is a coating layer mainly composed of epichlorohydrin rubber formed on the outer periphery thereof. That is, the charging member includes a base material, an elastic layer, and a resistance layer as the charging member approaches the photosensitive drum.

A power source 10 is connected to the core metal 2a of the charging roller 2.
Thus, an oscillating voltage, which is a superimposed voltage of the negative DC voltage and the AC voltage, is applied. At this time, on the surface of the rotary photosensitive drum 1 that has been negatively charged by the charging roller 2, at a constant print density Ddpi corresponding to the time series electric digital pixel signal of the target image information output from the laser scanner 12. By scanning exposure with the image-modulated laser beam 5, the potential of the exposed portion is attenuated and an electrostatic latent image is formed on the surface of the photosensitive drum 1. To the latent image surface, the negatively charged toner is supplied from the developing sleeve 4 of the developing device 6 to reversely develop the latent image.

On the other hand, the transfer material P is fed from a paper feeding section (not shown) through the guide 7 to the contact nip portion (transfer section) between the photosensitive drum 1 and the transfer roller 8 as a transfer member.
The toner image on the surface of the photosensitive drum 1 is transferred to the transfer material P side by the transfer bias having a polarity opposite to the charging polarity of the toner applied from the power source 10 to the transfer roller 8 while being fed in time with the toner image on the surface. Are sequentially transferred (transcribed) to.

The transfer material P that has passed through the transfer portion is the photosensitive drum 1
It is separated from the surface and introduced into a fixing unit (not shown) to undergo image fixing, and is output as an image formed product (print).

After the transfer material is separated, the surface of the photosensitive drum 1 is cleaned by a cleaning device 9 to remove adhering contaminants such as untransferred toner, and is repeatedly used for image formation.

Reference numeral 11 denotes a control unit (CPU) for automatically setting the bias applying power source 10 for the charging roller 2 and the transfer roller 8 to a predetermined application timing and a predetermined potential. Reference numeral 20 denotes a temperature / humidity sensor 20 that measures temperature / humidity outside or inside the image forming apparatus main body.

The charging roller 2, the developing device 6, the cleaning device 9, and the photosensitive drum 1 as an image carrier are supported by the process unit 13. The process unit 13 is attachable to and detachable from a laser beam printer which is an image forming apparatus.
Is slid along the guide 14, that is, moved in the direction perpendicular to the paper surface of FIG. However, the process unit 13 may include at least the charging roller 2 and the photosensitive drum 1.

As shown in FIG. 2, the charging roller 2 is rotatably supported by the conductive bearings 3 at both ends of the core metal 1a so that the longitudinal direction of the roller is substantially parallel to the generatrix direction of the photosensitive drum 1. Contacting the surface of the photoconductor drum, and the bearings 3 on both ends of the roller are biased by the conductive pressure springs 4 so as to be movable in the direction of the photoconductor drum. Abutted. In this example, the spring constant of the pressure spring 4 is 0.08 Kg / mm on one side. Further, the applied pressure is 1 Kg in total pressure, with the spring on one side being 500 g. If the total pressure exceeds 2 kg, the friction of the roller 2 and the drum 1 becomes severe, so the pressure is preferably 2 kg or less. The charging roller 2 is the photosensitive drum 1 in this example.
Driven by the rotation of.

As described above, a predetermined bias voltage is applied to the charging roller 2 from the bias power source 10 through the conductive pressure spring 4 and the conductive cored bar 2a to rotate the photosensitive drum. The peripheral surface of No. 1 is charged with a predetermined polarity and potential. Here, the charging is performed by the discharge generated in the minute gap between the photosensitive drum and the charging roller 2. In the case of this example, it is negatively charged. The charging roller 2 has a DC voltage of -600 V and a peak-to-peak voltage of 1 from the bias power source 10.
An oscillating voltage, which is a superimposed voltage of a sinusoidal AC voltage of 400 VPP to 2000 VPP, is applied. Here, if the peak-to-peak voltage of the oscillating voltage is less than twice the charging start voltage value of the photoconductor drum 1 that is the member to be charged, spot-like charging unevenness occurs on the photoconductor drum 1, so that uniform charging is performed. It is desirable that the charging start voltage value is twice or more. This charging start voltage is defined as follows.

That is, when only a direct current voltage is applied to the contact charging member with respect to an object to be charged having a potential of 0 and gradually increased, the photosensitive drum, which is the object to be charged, responds to the applied current voltage. Try to write a graph of surface potential. At this time,
DC voltage is taken every 100V, but 100V is the first point when the surface potential appears when the surface potential is 0.
Take 10 points for each. From these 10 points, the minimum 2 in statistics
A straight line is drawn by the multiplication method, and when the surface potential is 0 on this straight line, the value of the applied DC voltage is the charging start voltage.

When the photosensitive drum 1 having the organic photoconductive layer of this embodiment was used as the member to be charged, the charging start voltage value was 560V.

Next, the structure, method, and sequence of actually changing the contact pressure of the charging roller 2 to the photosensitive drum 1 depending on the environment will be described with reference to FIGS.
12. FIG. 12 is a block diagram of a command system for changing the contact pressure of the charging roller 2 with respect to the photosensitive drum 1.

A structure for changing the contact pressure of the charging roller 2 with respect to the photosensitive drum 1 will be described with reference to FIGS.

The pressing means 21 are installed at two locations on the end of the charging roller 2. In FIG. 5 or FIG. 8, members above the pressing means 21 (pressing means 21, vertical gear 2
4, gear 25, motor 26) are installed in the main body of the image forming apparatus, and those shown below are those previously installed in the process cartridge. Further, as a mechanism for moving the pressing member 21 of the charging roller 2 up and down, as shown in FIG.
Is inseparably attached to the vertical gear 24,
The vertical gear 24 and the gear 25 are in mesh with each other, and the gear 25 is coaxially connected to the motor 26.
A command is issued from U11 to the power supply 10 to instruct the motor 26 to be biased.
1 is a mechanism for moving up and down.

The method of increasing the spring pressure of the charging roller 2 against the photosensitive drum is as follows.

First, the initial state of the charging roller 2 is shown in FIG.
In the state of (A), the motor 26 instructed by the CPU 11 rotates from this state, so that the gear 25
Rotates counterclockwise, and the vertical gear 2
4. The pressing member 21 is driven downward. Further pressing member 2
The moving member 22, which is in contact with the end of 1, drives downward along the groove provided in the process unit 13. As a result, the pressure spring attached to the moving member 22 is compressed, and the state shown in FIG.

Next, a sequence for changing the contact pressure of the charging roller 2 to the photosensitive drum 1 by using the temperature and humidity sensor 20 when the power is turned on will be described with reference to FIG.

The power source 10 is turned on (STEP 101), and the temperature / humidity sensor 20 measures the temperature / humidity in which the image forming apparatus is installed (STEP 102). Then, it is judged whether or not the temperature is 30 degrees or more and the humidity is 50% or more (STEP 103), the temperature is 30 degrees or more and the humidity is 50%.
When it is above, the position of the charging roller 2 is pushed down by the pressing member 21 from FIG. 8 (A) to FIG. 8 (B) (STEP).
104), turn off the power supply 10 of the temperature and humidity sensor 20 (ST
EP105), and ends (STEP106). Temperature is 3
If the temperature is less than 0 degrees or the humidity is less than 50%, the condition shown in FIG.
Power supply for temperature and humidity sensor 20
Turn off 0 (STEP105) and end (STEP10).
6).

As a result, the contact pressure of the charging roller 2 is increased only in the H / H environment according to the environment in which the main body of the image forming apparatus is installed before printing, thereby extending the life of the drum in the H / H. At the same time, it is possible to provide a process cartridge and an image forming apparatus that do not cause charging failure in the L / L environment.

Next, a sequence for changing the contact pressure of the charging roller 2 to the photosensitive drum 1 by using the temperature / humidity sensor 20 during printing will be described with reference to FIG. When the cumulative number of printed sheets after the power is turned on reaches 500n (n = 1, 2, 3, ...) (STEP20
Power on the temperature and humidity sensor 20 to 1) (STEP2
02), it is determined whether the temperature is 30 degrees or more and the humidity is 50% or more (STEP 203). When the temperature is less than 30 degrees or the humidity is less than 50%, the position of the pressing member 21 of the charging roller 2 is determined. Is in the initial position (STE
If the position of the pressing member 21 of the charging roller 2 is at the initial position, the power of the temperature / humidity sensor 20 is turned off (STEP 208) and the process is ended (STEP 20).
9). When the position of the pressing member 21 of the charging roller 2 is not at the initial position, the position of the charging roller 2 is returned from FIG. 8 (B) to FIG. 8 (A) by the pressing member 21 (STEP 20.
5) Turn off the power of the temperature and humidity sensor 20 (STEP20
8) and end the process (STEP209).

When the temperature is 30 degrees or more and the humidity is 50% or more, it is judged whether or not the position of the pressing member 21 of the charging roller 2 is in the initial position (STEP 206), and the pressing member 21 of the charging roller 2 is moved. If the position is the initial position, the position of the charging roller 2 is pushed down by the pressing member 21 from FIG. 8 (A) to FIG. 8 (B) (STEP 207), the power of the temperature / humidity sensor 20 is turned off (STEP 208), and the process is terminated (STEP 208). (STEP209). When the position of the pressing member 21 of the charging roller 2 is not at the initial position, the temperature / humidity sensor 20 is used as it is.
Power off (STEP208) and finish (STEP208)
209).

As a result, even during printing, the contact pressure of the charging roller 2 is increased only in the H / H environment according to the environment in which the main body of the image forming apparatus is installed, and the life of the drum in the H / H is extended. In addition, it is possible to provide a process cartridge and an image forming apparatus that do not cause a charging failure in the L / L environment.

Immediately after the power source 10 is turned off, the temperature / humidity sensor 20 is used to detect the photosensitive drum 1 of the charging roller 2.
A sequence for returning the contact pressure to the original will be described with reference to FIG.

Immediately after the main body is turned off (STEP30
1) It is determined whether or not the pressing member 21 of the charging roller 2 is in the initial position (STEP 302), and if it is in the initial position, the process is ended as it is (STEP 304), but the pressing member 21 of the charging roller 2 is in the initial position. If not, the member is returned to the initial position (STEP 303) and the process ends (STEP).
304).

As a result, after printing is completed,
The contact pressure of the charging roller 2 is lowered, and C is set in the main body of the image forming apparatus.
It is possible to provide a process cartridge and an image forming apparatus that do not cause a set.

Note that the temperature and humidity in the temperature and humidity sensor 20 is judged, whether the pressing member 21 of the charging roller 2 is at the initial position is judged, and the command to apply a predetermined voltage to the voltage 10 is issued. Unit (CPU).

(Embodiment 2) In this embodiment, the schematic structure of the image forming apparatus is almost the same as that in Embodiment 1, and therefore its explanation is omitted.

In this embodiment, the pressing means 21 is made of ultra-high density high density polyethylene having a length of 125 mm, and one end in the length direction is fixed to the main body of the image forming apparatus, so that the temperature rises. Then, since the length is increased, the same effect as that of the first embodiment can be obtained, and unlike the first embodiment, the drive system such as the motor is not necessary, and thus the cost can be reduced. Specifically, in an environment of 10 ° C., it becomes as shown in FIG. 13 (A), and in an environment of 32.5 ° C., it becomes 2.5 mm long and becomes as shown in FIG. 13 (B). Since the spring pressure of the charging roller 2 increases as the temperature becomes higher, the life of the drum in a high temperature environment can be extended.

(Embodiment 3) In this embodiment, the schematic structure of the image forming apparatus and the pressing means of the charging roller 2 are substantially the same as those in Embodiment 1 and therefore will be omitted.

In the first embodiment, the pressing means 21 are installed at two locations on the end of the charging roller 2. However, in the present embodiment, the image forming apparatus and the process cartridge are placed under the high temperature and high humidity environment. The mechanical strain of
In the case where the contact of the charging roller 2 on the driving side only is small and the abrasion of the photosensitive drum corresponding to the outer portion is large, the pressing means 21 is installed only on the driving side.
It is possible to further reduce the cost while obtaining the same effect as. That is, it is possible to extend the life of the drum in a high temperature environment while preventing the cost from rising sharply.

(Embodiment 4) In this embodiment, the schematic structure of the image forming apparatus and the pressing means for the charging roller 2 are substantially the same as those in Embodiment 2 and therefore will be omitted.

In the second embodiment, the pressing means 21 are installed at two locations on the end of the charging roller 2. However, in the present embodiment, the image forming apparatus and the process cartridge are placed under the high temperature and high humidity environment. The mechanical strain of
When the contact of the charging roller 2 only on the non-driving side is small and the abrasion of the photosensitive drum corresponding to the outer portion is large, the pressing means 21 is installed only on the non-driving side, so that the same as in the second embodiment. The cost can be further reduced while the effect is obtained. In other words, while preventing the cost increase,
The life of the drum can be extended in a high temperature environment.

[0070]

As described above, according to the charging device, the process cartridge or the image forming apparatus of the present invention, it is possible to secure the discharge current amount which does not cause the charging failure in the L / L environment while maintaining the H / H. Even in the environment, it is possible to prevent deterioration of shaving without causing charging failure and to extend the life of the photosensitive drum.

Another object of the present invention is to provide a charging device, a process unit and an image forming apparatus which can prevent the harmful effect of the C set of the charging roller 2 while having the above-mentioned structure.

[Brief description of drawings]

FIG. 1 is a cross-sectional view in which a process cartridge is attached to an image forming apparatus.

FIG. 2 is a side view of a charging device.

FIG. 3 is a partially cutaway front view of the charging device.

FIG. 4 is a cross-sectional view of the process cartridge according to the first exemplary embodiment of the present invention mounted on an image forming apparatus.

FIG. 5 is a partially cutaway front view of the charging device according to the first exemplary embodiment of the present invention.

FIG. 6 is a graph of discharge current amount vs. drum downstream current in an H / H environment or an L / L environment.

FIG. 7 is a list of the amount of scraping, the life of the drum, and the evaluation of the image when the spring pressure for contacting the charging roller with the photosensitive drum is shaken.

FIG. 8 is a cross-sectional view of the first embodiment of the present invention.

FIG. 9 is a sequence chart at power-on of the main body according to the first embodiment of the present invention.

FIG. 10 is a sequence chart during printing according to the first embodiment of the present invention.

FIG. 11 is a sequence chart when the power of the main body is turned off according to the first embodiment of the present invention.

FIG. 12 is a block diagram of Embodiment 1 of the present invention.

FIG. 13 is a sectional view of Embodiment 2 of the present invention.

[Explanation of symbols]

1 photoconductor drum 2 charging roller 2a core metal 2b conductive elastic layer 2c resistance layer 3 Charging roller bearing 4 Conductive pressure spring 5 laser light 6 developing roller 7 Paper transport guide 8 Transfer roller 9 cleaner container 10 power supplies 11 CPU (control unit) 12 laser scanner 13 process units 14 Guide 20 temperature and humidity sensor 21 Pressing Member of First Embodiment 22 Moving member 24 Vertical gear 25 gears 26 motor

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H027 DA13 DA14 EA01 EC06 EC20                 2H071 BA05 BA13 BA27 BA29 DA06                       DA15                 2H200 FA01 FA16 GB41 HA02 HA29                       HB12 HB31 LA01 LA17 LA38                       PA14 PA23 PB27 PB28

Claims (9)

[Claims] 1. A charging roller, which is disposed in contact with the electrophotographic photosensitive member and charges the electrophotographic photosensitive member when a voltage is applied, and a contact means for contacting the charging roller with the electrophotographic photosensitive member. In the charging device, the contact pressure between the electrophotographic photosensitive member and the charging roller is continuous by changing the shape or the position of the contact means depending on the condition of temperature and / or humidity. A charging device characterized in that it changes a plurality of abutting pressures by changing in a stepwise or stepwise manner. 2. The contacting means is operated by an operating means provided in an image forming apparatus in which a charging device can be attached and detached, so that the contacting means has a shape and / or position corresponding to both the temperature and the humidity. The charging device according to claim 1, wherein the charging device changes according to the condition. 3. The charging device according to claim 1, wherein at least a part of the contact means is made of a polymer material whose volume changes in accordance with the temperature and / or humidity conditions. . 4. An electrophotographic photosensitive member, and a charging roller which is disposed in contact with the electrophotographic photosensitive member and charges the electrophotographic photosensitive member by applying a voltage, and the charging roller contacts the electrophotographic photosensitive member. In a process cartridge having contact means for contacting, the shape or position of the contact means changes depending on the condition of temperature and / or humidity, so that the electrophotographic photosensitive member and the charging roller are changed. The contact pressure between is continuous,
Alternatively, the process cartridge is characterized in that it is changed in stages and a plurality of contact pressures are determined. 5. The contact means is acted by an operating means provided in an image forming apparatus in which a process cartridge can be attached and detached, so that the shape or position of the contact means corresponds to both or one of temperature and humidity. The process cartridge according to claim 4, wherein the process cartridge changes according to the condition. 6. The process cartridge according to claim 4, wherein at least a part of the abutting means is made of a polymer material whose volume changes in accordance with temperature and / or humidity conditions. . 7. An electrophotographic photosensitive member, and a charging roller that is disposed in contact with the electrophotographic photosensitive member and that charges the electrophotographic photosensitive member by applying a voltage, and the charging roller contacts the electrophotographic photosensitive member. In an image forming apparatus in which a process cartridge having an abutting means for making contact is detachable and which has an operating means that acts on the corresponding contacting means, the position or shape of the operating means is both temperature and / or humidity. By changing with one condition and acting on the corresponding contact means,
An image forming apparatus characterized in that the contact means is changed, and the contact pressure between the electrophotographic photosensitive member and the charging roller is continuously or stepwise changed to determine a plurality of contact pressures. 8. The image forming apparatus according to claim 7, wherein at least a part of the operating means is made of a polymer material whose volume changes in accordance with the temperature and / or humidity conditions. . 9. An electrophotographic photosensitive member, and a charging roller which is disposed in contact with the electrophotographic photosensitive member and charges the electrophotographic photosensitive member by applying a voltage, and the charging roller contacts the electrophotographic photosensitive member. A process cartridge having a contacting means for contacting with the contacting means is attachable and detachable, and an operating means that acts on the contacting means and a detecting means that detects both or both of temperature and humidity inside or outside the main body of the image forming apparatus, In an image forming apparatus having a signal processing means for instructing the acting means to change based on the result of the detecting means, the signal processing means is changed to the acting means based on the result of the detecting means. Command, the shape or position of the operating means is changed, and the operating means acts on the corresponding contact means in the process cartridge, whereby the shape or position of the contact means is changed, and the electrophotographic Continuous contact pressure between the optical member and the charging roller, or stepwise changed, the image forming apparatus characterized by determining a plurality of contact pressure.