JPH05210281A - Contact electrifying member, contact electrifying device and process cartridge - Google Patents

Abstract

PURPOSE:To effectively eliminate the problems on the generation of a charging noise in contact electrification without having the inconvenience of electrification unevenness, the degradation of an image quality and the rising of cost, etc. CONSTITUTION:A contact electrifying member 2 is for a contact electrifying device executing the electrification in such a manner that the electrifying member 2 is abutted on a body 1 to be electrified and composed of at least, a supporting member 2a, an electrifying layer 2c directly coming into contact with the body 1 to be electrified or coming into contact therewith via other layers, and an inside foamed member 2b on the side opposite to the side of the body 1 to be electrified of the electrifying layer 2c, and the thickness (t) of the electrifying layer 2c is 5mum<t<1000mum, as a characteristic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact charging member, a contact charging device, and a process cartridge of an image forming apparatus using them.

[0002]

2. Description of the Related Art For convenience, an image forming apparatus such as an electrophotographic apparatus (copier, printer, etc.), electrostatic recording apparatus, etc. will be described as an example.

In an image forming apparatus such as an electrophotographic apparatus,
Conventionally, a corona discharger which is a non-contact charging system has been mainly used as a means for charging (including discharging) an image carrier such as an electrophotographic photoreceptor or an electrostatic recording dielectric.

Although the corona discharger has an advantage of being uniformly charged, it requires an expensive high-voltage power source, requires a space such as itself and a shield space for the high-voltage power source, and generates corona products such as ozone. However, there is a problem that an additional means / mechanism is required to deal with the problem, which is a factor for increasing the size and cost of the device.

Therefore, recently, instead of the corona discharger, which has many problems, a contact charging type charging means is being adopted. The contact charging is to charge the surface of the body to be charged to a predetermined polarity and potential by bringing a charging member (conductive member) to which a voltage is applied into contact with the body to be charged, which can lower the power supply and generate corona such as ozone. There are advantages such as less material generation, simple structure, and cost reduction.

A roller charging type using a roller body as a contact charging member (JP-A-56-91253) and a blade charging type using a blade body (JP-A-56-194349).
JP-A-56-1), a charging / cleaning combined type (JP-A-56-1).
No. 65166) has been devised.

The applicant of the present invention has previously proposed (Japanese Patent Laid-Open No. 63-1
No. 49669), an oscillating electric field (alternating electric field / AC electric field) having a peak-to-peak voltage (PEAK TO PEAK) which is more than twice the charging start voltage of the charged body when a DC voltage is applied to the contact charging member. That is, a method of forming an electric field or a voltage whose voltage value periodically changes with time between the contact charging member and the body to be charged to charge the surface of the body to be charged (including AC treatment) (hereinafter, AC) The application method) is effective because it allows uniform charging.

The oscillating electric field (voltage) is an oscillating voltage component (hereinafter,
AC component) or a superimposed electric field or voltage of AC component and DC component (voltage corresponding to target charging potential, hereinafter referred to as DC component), and the waveform of AC component is sine wave, rectangular wave, triangular wave, etc. It is appropriate. It may be a rectangular wave voltage formed by periodically turning on and off a DC power supply.

FIG. 8 shows a schematic structure of an example of an image forming apparatus which employs the above-mentioned AC application type contact charging means as the charging means of the image carrier. The image forming apparatus of this example is a laser printer using an electrophotographic process.

Reference numeral 1 denotes a drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) as an image bearing member, which has a predetermined peripheral speed (process speed, for example, 40 m) in a clockwise direction indicated by an arrow A.
(m / sec).

Reference numeral 20 denotes a charging roller as a contact charging member, and a cored bar 21 as a support member, and a conductive solid charging layer 22 (for example, concentrically formed on the outer periphery of the cored bar 21 in a roller shape). It is a so-called integral charging roller composed of a carbon-dispersed conductive rubber layer such as EPDM). The charging roller 20 is arranged substantially parallel to the photosensitive drum 1, and both ends of the cored bar 21 are held by bearing members (not shown).
Further, the pressure spring 23 presses and biases the photosensitive drum 1 toward the photosensitive drum 1 and presses the surface of the photosensitive drum 1 with a predetermined pressing force. In the case of this example, the photosensitive drum 1 is driven and rotated.

The charging roller 20 is supplied from the power source 4 via the sliding electrode 24 brought into contact with the mandrel 21 and an AC component having a peak-to-peak voltage which is more than twice the charging start voltage of the photosensitive member and the target charging. An oscillating voltage (V _ac + V _dc ) superposed with the DC component of the voltage corresponding to the potential is applied. As a result, the peripheral surface of the rotary photosensitive drum 1 is uniformly contact-charged by the AC application method.

Next, a laser beam, which is modulated and output from a laser scanner (not shown) corresponding to a time-series electric digital pixel signal of target print (image) information, is output to the charged surface of the rotary photosensitive drum 1. By performing scanning exposure by 5, the print information is written and an electrostatic latent image of the print information is formed.

The latent image is visualized (developed) as a toner image by reversal development by the developing sleeve 6 of the developing device, and the toner image is pressed from the paper feeding portion (not shown) to the pressure nip portion between the photosensitive drum 1 and the transfer roller 8. The images are sequentially transferred onto the transfer material 7 fed to the (transfer site) at a predetermined timing.

The transfer material 7 which has received the toner image transfer is separated from the surface of the photosensitive drum 1 and conveyed to a fixing means (not shown), where it is subjected to the toner image fixing and is output as an image-formed product. After the transfer material is separated, the surface of the rotary photosensitive drum 1 is cleaned by a cleaning blade 9 of a cleaning device (cleaner) to remove residual adhering substances such as transfer residual toner, and is repeatedly used for image formation.

[0016]

By the way, as a problem of the AC charging type contact charging means, generation of vibration noise called "charging sound" due to the AC component of the charging bias applied to the contact charging member can be mentioned.

The mechanism of generation of this charging sound will be described with reference to the model diagram of FIG.

Reference numeral 1 is a photosensitive drum as a member to be charged,
Reference numeral 1b is a grounded conductive base layer (substrate) made of aluminum, and 1a is a photosensitive layer formed on the outer surface of the base layer.
Reference numeral 20 is a charging roller as a contact charging member which is pressed against the surface of the photosensitive drum 1, 21 is a core metal, and 22 is a solid charging layer made of a conductive rubber material such as carbon-dispersed EPDM.

.. Applied vibration voltage (V _ac
The AC component of + V _dc induces a positive charge on the charging layer 22 side and a negative charge on the base layer 1b side across the photosensitive layer 1a as shown by the thick solid line in (a) at a certain moment.

[0020]. Since these positive and negative charges are attracted to each other, the surface of the charging layer 22 is attracted to the photosensitive drum 1 side against the elasticity of the charging layer 22 and is thick from the position of the thick solid line to the position of the thin solid line ((b) is thick). (Solid line position)
Move to.

[0021]. Then, when the AC electric field starts reversing, the positive charges on the side of the charging layer 22 and the negative charges on the side of the base layer 1b start to be canceled by the charges of opposite polarities respectively induced.

When the AC electric field just changes from positive to negative, the positive charge on the charging layer 22 side,
The negative charge on the base layer 1b side disappears. (B) shows the state at the time of disappearance.

.. As a result, the surface of the charging layer 22 is released from the attracting force against the elasticity of the charging layer 22, and the elastic return force causes the elastic returning force to change from the position indicated by the thick solid line in (b) to the position indicated by the thin solid line ((a)). It will return to the position of the solid line).

[0024]. Further, when the AC electric field goes to a negative peak, as shown in (c), negative charges are induced on the charging layer 22 side and positive charges are induced on the base layer 1b side. Therefore, due to the attraction force of both the negative and positive charges, the surface of the charging layer 22 is again attracted to the photosensitive drum 1 side against the elasticity of the charging layer 22 and moves from the position of the thick solid line to the position of the thin solid line. ..

In this way, the surface of the charging layer 22 corresponds to the positive and negative reversal of the AC electric field, and the surface of the charging layer 22 is changed to the charging layer 2.
The charging member 20 vibrates with the application of the oscillating voltage due to the repeated phenomenon of the movement of pulling the photosensitive drum 1 toward the photosensitive drum 1 side against the elasticity of 2 and the returning movement by releasing the pulling force. It is considered that the photosensitive drum 1 is hit for the first time, and as a result, "charging noise" is generated.

Assuming that the frequency of the AC electric field (voltage) is f and the vibration frequency of the charging member 20 is F, the charging member 20 vibrates twice during one cycle of the AC voltage, as is clear from the above description. Therefore, there is the following relationship between both f and F.

2f (H _Z ) = F (c / s) The charging sound is not limited to the case where the contact charging member is the charging roller, but is generated by the charging blade, the charging pad or the like by the same mechanism.

As a charging noise reducing measure, an oscillating voltage (V _ac + V _dc ) which is a charging bias applied to the contact charging member 20.
If the peak-to-peak voltage V _PP of the AC component is less than twice the charging start voltage of the body to be charged, the charging noise can be improved to a considerably low level.

However, in the AC charging type contact charging,
Lowering the peak-to-peak voltage V _PP of the AC component means A
A so-called "leveling effect" that allows uniform charging by applying C component
As a result, the uniform charging cannot be obtained on the body to be charged, and spot-like uneven charging occurs. This is because the contact surface between the charging member 20 and the member to be charged 1 is microscopically uneven, and an ideal contact surface cannot be obtained.

In the electrophotographic image forming process, the spot-like uneven charging state of the photosensitive drum 1 as the member to be charged causes spot-like black spot image unevenness corresponding to the spot-like uneven charging in the output image, which is high. I can't get a quality image.

As another method for reducing the charging noise,
It has been proposed to insert a vibration isolating member made of rubber or the like inside the photosensitive drum 1, which is a member to be charged, but there are drawbacks in terms of deformation, weight increase, and manufacturing cost of the photosensitive drum 1,
It has not been put to practical use.

Further, it has been proposed that the charging roller 20 be made hollow so that the charging mass (striking force, striking energy) with which the charging roller 20 strikes the photosensitive drum 1 is reduced to reduce the charging noise. 10 and 11 show this embodiment, FIG. 10 is a cross-sectional model view of the hollow charging roller 20, and FIG. 11 is a vertical cross-sectional model view.

That is, the conductive rubber roller portion which is the charging layer 22 is a hollow body. 25 shows the hollow part. In such a configuration, by setting the wall thickness t of the hollow conductive rubber roller portion, which is the charging layer 22, to about 1 mm, an oscillating voltage as a charging bias is applied and the charging roller 20 vibrates by the mechanism described above. Also, since the mass of hitting the photosensitive drum 1 is small, the charging sound can be suppressed to a level at which there is no problem.

However, when the charging roller 20 is pressed by the pressure spring 23 on both ends of the cored bar 21 and pressed against the photosensitive drum 1, a part of the hollow charging layer 22 is indicated by a chain double-dashed line 22 'in FIG. As it floats from the surface of the photosensitive drum 1, the charging roller 20 as shown in FIG.
The charging failure portion a corresponding to the rotation cycle of No. 1 occurred. This phenomenon was not a problem in the A4 size machine in which the axial length of the charging roller 2 is short, but it becomes remarkable in the A3 size machine in which the axial length of the charging roller 2 is long.

Therefore, an object of the present invention is to effectively solve the problem of the generation of charging noise in contact charging without causing other inconveniences such as uneven charging, deterioration of image quality and high cost.

[0036]

SUMMARY OF THE INVENTION The present invention is a contact charging member, a contact charging device, and a process cartridge having the following features.

(1) A contact charging member of a contact charging device for charging a charging member by bringing it into contact with a member to be charged, and the contact charging member includes at least a support member and a direct or other layer on the member to be charged. A contact charging member characterized by comprising a charging layer in contact with the charging layer and an inside foaming member on the side opposite to the charged body side of the charging layer, and having a thickness t of 5 μm <t <10000 μm. ..

(2) A contact charging member of a contact charging device for charging by charging a charging member to which an oscillating voltage is applied to a member to be charged, the contact charging member being at least a supporting member,
The charging layer is in contact with the body to be charged directly or through another layer, and the foaming member on the inner side opposite to the side of the body to be charged has a thickness t of 5 μm <t <10000 μm. A contact charging member characterized by being present.

(3) In the contact charging device for charging by charging the charging member to the member to be charged, the contact charging member includes at least the support member and the charging layer which is in contact with the member to be charged directly or through another layer. The contact charging device is characterized in that the charging layer has an inner foamed member opposite to the side to be charged, and the charging layer has a thickness t of 5 μm <t <10000 μm.

(4) In the contact charging device for charging by charging the charging member to which the oscillating voltage is applied to the member to be charged, the contact charging member is at least directly connected to the support member and the member to be charged or through another layer. A contact charging device comprising a charging layer in contact with the charging layer and a foaming member on the inner side of the charging layer, which is opposite to the side to be charged. The charging layer has a thickness t of 5 μm <t <10000 μm.

(5) In a process cartridge including at least an image carrier and a charging unit for the image carrier, which is attached to and detached from an image forming apparatus, the charging unit brings the charging member into contact with the image carrier. Is a contact charging device that performs charging by means of at least a supporting member, a charging layer that is in contact with a member to be charged directly or through another layer, and an inner side of the charging layer opposite to the member to be charged. The process cartridge, wherein the charging layer has a thickness t of 5 μm <t <10000 μm.

[0042]

[Operation] The foam material is, for example, polystyrene / polyolefin /
It may be a foaming member such as polyester / polyurethane / polyamide type, etc., in which conductive powder such as carbon / tin oxide is dispersed and blended to impart conductivity, and the above charging member is a foaming member. Mainly composed of a member and a thin charging layer (conductive layer), it is much lighter than a conventional solid charging member and has a low hardness.

In the case of such a light charging member having low hardness, as in the hollow charging roller 20 shown in FIGS. 10 and 11, even if the AC component of the applied vibration voltage causes the vibration phenomenon by the mechanism described above, it is not covered. Since the mass that hits the charged body is small,
The generated charging sound is at a level that does not cause a problem
For example, it is reduced to 50 dB or less). This is similar to the fact that tapping a drum with a light, soft Styrofoam or rolled newspaper, rather than hitting a drum with a heavy, hard oak tree, is similar to the sound.

.. Further, since the charging layer has a foamed member inside thereof, it can be backed up well even if it is thin, so that even if the charging member is pressed against the surface of the member to be charged, it is asymmetrically deformed and becomes a space between the member and the surface to be charged. Since it does not come into contact with the surface of the charged body over the entire length without causing a floating portion,
Even if the axial length of the charging member is lengthened, no defective charging occurs.

According to the experiment, if the thickness t of the charging layer is too thin (5 μm or less), the rigidity of the charging layer disappears and the charging layer easily vibrates when an oscillating voltage is applied. As a result, the charging layer floats from the surface of the body to be charged according to the oscillating voltage, and charging failure occurs. If the thickness t is too thick (10000 μm or more), the charging layer vibrates when an oscillating voltage is applied and the force to hit the body to be charged becomes large. As a result, the charging noise becomes loud and exceeds the allowable level of 50 dB.

Therefore, in the present invention, the thickness t of the charging layer is 5 μm.
The setting was made larger and smaller than 10000 μm.

.. To be able to reduce the generated charging noise means to be able to increase the frequency of the AC component of the vibration voltage applied to the contact charging member, which is a problem with the scanning laser light called "moiré" which was a problem at low frequencies. It has become possible to eliminate the occurrence of moire interference fringes on an image due to interference with uneven charging due to the AC component frequency.

.. In the image forming apparatus, since the contact charging member weakens the force of hitting the image bearing member as the charged member, it is possible to suppress the "toner fusion" phenomenon that occurs when the toner remaining after cleaning is pressed against the image bearing member surface. Became possible.

[0049]

【Example】

<Embodiment 1> (FIGS. 1 to 3) FIG. 1 is a cross-sectional model view of one embodiment of the contact charging member or contact charging device of the present invention, and FIG. 2 is a vertical cross-sectional model view of one end side.

Reference numeral 1 denotes a rotary photosensitive drum having a negative or positive charging polarity as a member to be charged.

Reference numeral 2 is a charging roller as a contact charging member. The charging roller 2 includes a metal cored bar 2a made of stainless steel or the like as a supporting member, and a foaming member (foaming layer) 2b formed concentrically and integrally on the outer periphery of the cored bar 2a.
The charging member 2c has a triple-layer structure in which the outer peripheral surface and both end surfaces of the foam member 2b are covered.

The foaming member 2b is a foaming member of polystyrene / polyolefin / polyester or the like, and is a flexible / low specific gravity member obtained by dispersing and foaming conductive powder such as carbon / tin oxide in EPDM or urethane. 2b 'is a bubble portion (enclosed bubble of air, nitrogen, argon gas, etc.) of this foam member.

The charging layer 2c is a conductive rubber material layer such as carbon-dispersed EPDM. t indicates the thickness of the charging layer 2c, and is set in the range of 5 μm <t <10000 μm. This will be described later.

If the conductive charging layer 2c on the outer periphery of the foam member 2b extends to the end face of the foam member 2b and is electrically connected to the conductive core metal 2a as shown in FIG. 2, the foam member 2b is strongly conductive. It doesn't have to be sex.

The specifications of the charging roller 2 in this embodiment are as follows.

Core metal 2a Diameter 9 mm, length 332
mm stainless round bar Foaming member 2b EPDM foamed body in which conductive powder is dispersed, specific gravity 0.4 layer thickness 2.3 mm, length 310 mm Charging layer 2c Carbon dispersed EPDM conductive rubber material layer Volume resistance value 10 ⁵ Ωcm layer thickness t 80 μm charging roller 2 weight 177 g, hardness 35 degrees (ASKER-C) This charging roller 2 is also the conventional charging roller 20 of FIG.
Similarly, both ends of the cored bar 2a are held by bearing members (not shown), and the pressure spring 23 presses and urges the photosensitive drum 1 toward the photosensitive drum 1 so that a predetermined pressing force is applied to the photosensitive drum 1 surface. The photosensitive drum 1 is brought into pressure contact with a total pressure of 1000 g and is driven to rotate with the rotation of the photosensitive drum 1 (it may be positively or reversely driven). The charging roller 2 is supplied with an AC voltage V _ac from a power source 4 through a sliding electrode 24 brought into contact with the charging roller core 2a, and in the present embodiment, 2.0 KV _PP , 600 H.
A superposed vibration voltage (V _ac + V _dc ) of _Z , the DC voltage V _dc , and the DC voltage corresponding to the target charging potential is applied. As a result, the peripheral surface of the rotary photosensitive drum 1 is uniformly contact-charged to the target charging potential by the AC application method.

(1) In the charging roller 2, the outer member of the cored bar 2a is composed of the foaming member 2b and the thin charging layer 2b, and the charging roller as a whole is much lighter than the conventional solid charging roller 20 of FIG. Also, the hardness is low.

For example, as a conventional solid integral charging roller 20, a cored bar 21 is a stainless steel rod having a diameter of 9 mm and a length of 332 mm. A charging layer 22 is a carbon-dispersed solid EPDM conductive rubber having a specific gravity of 1.0 and a volume resistance value of 10. The charging roller 20 having a thickness of ⁵ Ωcm, a thickness of 2.5 mm, and a length of 310 mm has a weight of 185 g and a hardness of 60 degrees (ASK).
ER-C).

Therefore, like the hollow charging roller 20 of FIGS. 10 and 11, the charging roller 2 of this embodiment strikes the photosensitive drum 1 even when the AC phenomenon of the applied vibration voltage causes the vibration phenomenon by the mechanism described above. Since the mass is small, the generated charging noise can be reduced to a level at which there is no problem.

(2) Further, since the charging layer 2c has the foaming member 2b on the inner side thereof, it can be backed up even if it is thin (5 μm or more) and the shape can be maintained well, so that the charging roller 2 is pressed against the surface of the photosensitive drum 1. Even when the charging roller 2 is contacted with the surface of the photosensitive drum 1, the surface of the photosensitive drum 1 is pressed against and in close contact with the surface of the photosensitive drum 1 without forming a floating portion. The charging failure portion a (FIG. 12) corresponding to the rotation cycle of the charging roller such as the charging roller 20 is not observed.

(3) The contact charging device shown in FIGS. 1 and 2 was set in an anechoic chamber, and the generated charging noise was measured when the thickness t of the charging layer 2c of the charging roller 2 was variously changed.

The measurement was carried out in accordance with ISO 7779, item 6. The result is shown in FIG.

In FIG. 3, the vertical line on the right side shows the degree of charging failure, 1 indicates a level at which no charging failure is observed on the output image sample, and 2 indicates a level at which a charging failure is slightly recognized. 3 shows a level at which a poor charging is clearly recognized.

As can be seen from this result, when the thickness t of the charging layer 2c is too thin (5 μm or less), the charging layer 2c loses its rigidity and the charging layer 2c easily vibrates when an oscillating voltage is applied. Will end up. As a result, the charging layer 2c floats from the surface of the photosensitive drum 1 according to the oscillating voltage, and charging failure occurs.

In FIG. 3, the left vertical line indicates the sound pressure level,
As is clear from the figure, the thickness t is too thick (10
000 μm or more), the charging layer 2c vibrates when an oscillating voltage is applied, and the force for hitting the photosensitive drum 1 becomes large like the conventional solid charging roller. as a result,
The charging sound becomes loud and exceeds the allowable level of 50 dB.

From the above results, the thickness t of the charging layer 2c is 5
It can be seen that it must be larger than μm and smaller than 10,000 μm.

The ratio of the thickness of the foam member 2b to the thickness of the charging layer 2c is
Generally, it is set in the range of 10: 1 to 100: 1.

(4) The fact that the generated charging noise can be reduced means that the frequency of the AC component of the vibration voltage applied to the contact charging member can be increased, which causes "moire" which is a problem at low frequencies. It has become possible to eliminate the occurrence of moire interference fringes on an image due to interference of so-called scanning laser light and uneven charging caused by the AC component frequency.

(5) Charging roller 2 as a contact charging member
Since the force of hitting the photosensitive drum 1 is weakened, it is possible to suppress the "toner fusion" phenomenon that occurs when the toner remaining after cleaning is pressed against the surface of the photosensitive drum 1.

<Embodiment 2> (FIGS. 4 and 5) In this embodiment, in the charging roller 2 of Embodiment 1 described above, a high resistance layer 2d such as epichlorohydrin rubber or paper is provided on the outer peripheral surface of the charging layer 2c. It is a thing. Reference numeral 2e (FIG. 5) is a conductive flange made of metal or conductive resin provided on both end surfaces of the charging roller 2, and electrically connects the core metal 2a and the charging layer 2c.

The high resistance layer 2d is formed when the charging roller faces a low withstand voltage defect portion such as a pinhole portion on the photosensitive drum 1.
It works to prevent the electric current from leaking intensively to the pinholes and the like and causing the abnormal discharge.

The thickness t of the charging layer 2c includes the high resistance layer 2d. In this embodiment, the high resistance layer 2d is 20
μm and the thickness of the charging layer 2c is 80 μm, t = 100 μm
When m was set, the charging sound was 41 dB (the applied oscillating voltage was the same as in Example 1), which was at a level where there was no practical problem.

By further providing the high resistance layer 2d on the outer side of the charging layer 2c as described above, not only the charging noise is reduced, but also if the photosensitive drum 1 has a defect such as a pinhole, no abnormal discharge occurs. There is a merit that it can be charged.

Further, a bleeding prevention layer for preventing bleeding of a plasticizer or the like from the inside of the charging roller can be provided outside the high resistance layer 2d. In this case, the thickness t of the charging layer 2c is also equal to The thicknesses of the layer 2c, the high resistance layer 2d, and the exudation preventing layer such as nylon are all added.

<Embodiment 3> (FIG. 6) In this embodiment, the contact charging member is a blade type (charging blade).
FIG. 6 is a schematic cross-sectional view of the charging blade 2A or the contact charging device. Charging blade 2A
The contact charging device using can have a simpler configuration than that using a charging roller.

The charging blade 2A is a foam member made of polystyrene, polyolefin, polyester, etc., EPDM,
A blade-shaped foam member 2b in which conductive powder such as carbon and tin oxide is dispersed in urethane, a charging layer 2c covering the outer peripheral surface of the foam member, and this is attached via a conductive adhesive 2f. It is composed of an electrode plate 2g as a supported supporting member.

The tip of the charging blade 2A is appropriately pressed against the surface of the photosensitive drum 1 against the waist of the blade, and the electrode plate 2g as a supporting member is attached and fixed to the immovable member 30. Is provided.

An oscillating voltage (V _ac + V _dc ) is applied to the charging blade 2A from the power source 4 through the supporting member 2g as an electrode plate, and the surface of the rotating photosensitive drum 1 is uniformly contact-charged by the AC application method. It

In this example, the charging noise generated when the charging blade 2A having the following specifications was used was 40 dB (the applied oscillating voltage was the same as in Example 1).

Foaming member 2b E in which conductive powder is dispersed
PDM foam, specific gravity 0.3 length 10 mm, length 310 mm, thickness 3 mm Charging layer 2c Carbon dispersed EPDM conductive rubber material layer Volume resistance value 10 ¹⁰ Ωcm Layer thickness t 500 μm Charging blade 2A hardness 40 degrees (ASKER- C) Free length L 5 mm of charging blade 2A Total pressure of pressing on photosensitive drum 1 700g Therefore, charging noise of charging blade 2A can be reduced, and pressing pressure of charging blade 2A on photosensitive drum 1 is There is an advantage that it can be controlled by using the waist.

<Embodiment 4> (FIG. 7) This embodiment is a process cartridge of an image forming apparatus using a contact charging member or a contact charging device according to the present invention as charging means for an image carrier.

The process cartridge according to the present embodiment includes four process devices including a rotary drum type electrophotographic photosensitive member 1 as an image carrier, a charging roller 2 as a contact charging member, a developing device 60 and a cleaning device 90. It will be.

The charging roller 2 has the same structure as that of the first or second embodiment.

In the developing device 60, 6 is a developing sleeve,
61 is a container for accommodating the developer (toner) T, and 62 is the container 6
The toner stirring bar in 1 serves to stir the toner T and to send it out toward the developing sleeve. Reference numeral 63 denotes a developing blade for coating the developing sleeve 6 with the toner T in a uniform thickness.

In the cleaning device 90, 9 is a cleaning blade, and 91 is a toner reservoir for accumulating the toner collected by the cleaning blade 9.

Reference numeral 11 denotes a drum shutter of the process cartridge, which can be freely opened and closed from a closed state shown by a solid line to an opened state as shown by a chain double-dashed line. When the process cartridge is taken out from the image forming apparatus main body (not shown), it is in the closed state shown by the solid line, and the externally exposed part surface of the photosensitive drum 1 is hidden to protect the photosensitive drum surface.

When the process cartridge is attached to the main body of the image forming apparatus, the shutter 11 is opened as shown by the chain double-dashed line, or the shutter 11 automatically opens during the process of attaching the process cartridge, When properly mounted, the externally exposed portion surface of the photosensitive drum 1 is in a state of being in pressure contact with the transfer roller 8 on the image forming apparatus main body side.

Further, the process cartridge and the image forming apparatus main body are mechanically and electrically coupled to each other, and the drive mechanism on the image forming apparatus main body side includes the photosensitive drum 1 on the process cartridge side, the developing sleeve 6, the stirring rod 62 and the like. It becomes possible to drive, and it becomes possible to apply a charging bias to the charging roller 2 on the process cartridge side, a developing bias to the developing sleeve 6 and the like by an electric circuit on the image forming apparatus main body side, so that an image forming operation can be executed. become.

Reference numeral 12 denotes an exposure passage provided between the cleaning device 90 and the developing device 60 of the process cartridge, which is a laser scanner (not shown) on the image forming apparatus main body side.
The output laser beam 5 from the laser beam enters the process cartridge through the exposure passage 12 to scan and expose the surface of the rotary photosensitive drum 1.

As described above, the charging roller 2 hardly generates a charging sound even when an oscillating voltage is applied, so that a very compact process cartridge having substantially no charging sound can be constructed.

[0091]

As described above, according to the present invention, the problem of the generation of charging noise in contact charging is effectively prevented without causing other inconvenient situations such as uneven charging, deterioration of image quality, and high cost. Can be resolved.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a contact charging member (charging roller) or a contact charging device according to the first embodiment.

FIG. 2 is a vertical sectional model view of one end side of the device.

FIG. 3 is a graph showing the relationship between the thickness of the charging layer, the level of charging failure, and the generated charging noise.

FIG. 4 is a schematic cross-sectional view of a contact charging member (charging roller) or a contact charging device according to the second embodiment.

FIG. 5 is a vertical sectional model view of one end side of the device.

FIG. 6 is a schematic cross-sectional view of a contact charging member (charging blade) or a contact charging device according to a third embodiment.

FIG. 7 is a schematic cross-sectional view of a process cartridge according to a third embodiment.

FIG. 8 is a schematic configuration diagram of an example of an image forming apparatus using a contact charging device.

9 (a), (b), and (c) are explanatory views of a mechanism of generating a charging sound.

FIG. 10 is a schematic cross-sectional view of a hollow charging roller

[Fig. 11] Similarly, a vertical cross-section model diagram

[FIG. 12] Due to the irregular deformation of the hollow charging roller,
Diagram showing the charging failure part that occurs corresponding to the rotation cycle of the charging roller

[Explanation of symbols]

1 Photosensitive Drum as Charged Member 2.2A / 20 Charging Roller or Charging Blade as Contact Charging Member 2a / 2g Core Metal or Electrode Plate as Supporting Member 2b Foaming Member 2c Charging Layer 4 Charging Bias Applied Power Supply

Claims (5)

[Claims] 1. A contact charging member of a contact charging device for charging by charging a charging member to a body to be charged, the contact charging member being at least a support member and directly or through another layer to the body to be charged. The contact charging member is characterized in that the charging layer is in contact with the charging layer, and the foaming member on the inner side of the charging layer opposite to the side to be charged. The charging layer has a thickness t of 5 μm <t <10000 μm. 2. A contact charging member of a contact charging device for charging by charging a charging member to which an oscillating voltage is applied to a member to be charged, wherein the contact charging member is at least directly on the support member and the member to be charged. Alternatively, the charging layer is composed of a charging layer in contact with the other layer and an inside foaming member on the opposite side of the charging side of the charging layer, and the charging layer has a thickness t of 5 μm <t <10000 μm. Contact charging member. 3. A contact charging device for charging a charging member by bringing it into contact with a member to be charged, the contact charging member being at least a support member, and a charging layer in contact with the member to be charged directly or through another layer. A contact charging device comprising an inner foaming member on the side opposite to the charged body side of the charging layer, wherein the charging layer has a thickness t of 5 μm <t <10000 μm. 4. A contact charging device for charging by charging a charging member to which an oscillating voltage is applied to an object to be charged, wherein the contact charging member is at least supported by the support member and directly or through another layer. A contact charging device comprising a charging layer in contact with the charging layer and a foaming member on the inner side of the charging layer which is opposite to the side to be charged. The charging layer has a thickness t of 5 μm <t <10000 μm. 5. In a process cartridge including at least an image carrier and a charging unit for the image carrier, which is attached to and detached from an image forming apparatus, the charging unit brings a charging member into contact with the image carrier. It is a contact charging device that performs charging, and the contact charging member includes at least a supporting member, a charging layer that is in direct contact with a body to be charged or through another layer, and an inner side of the charging layer opposite to the side of the body to be charged. A process cartridge comprising a foamed member and a charging layer having a thickness t of 5 μm <t <10000 μm.