JPH0743985A - Electrostatic charging member, process cartridge and image forming device - Google Patents

Abstract

PURPOSE:To decrease the electrostatic charging sounds of a contact electrostatic charging device without generating an electrostatic charging defect. CONSTITUTION:The circumference of an arbor 2a is enclosed by an elastic material 2B consisting of a foamed member 2b and a surface layer member 2c, by which an electrostatic charging roller 2 is constituted. The layer thickness of the surface layer member 2c consisting of a conductive layer 2d and a middle resistance layer 2e is confined to <=300mum. As a result, the hardness of the surface layer member 2c is lowered and the vibrations by the AC component of an applied voltage are decreased when the frequency of the applied voltage by a power source 4 is, for example, <=1500Hz. In addition, the generation of the harmonic components of a vibration frequency is suppressed and the generation of the electrostatic charging sounds unpleasing to ears is effectively suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging which applies an oscillating voltage (a voltage whose voltage value changes periodically with time) and charges the image carrier by coming into contact with or in proximity to the image carrier. The present invention relates to a member, a process cartridge including the charging member, and an image forming apparatus.

[0002]

2. Description of the Related Art A contact type charging device is known as a charging device such as an image forming apparatus. In this contact type charging device, a conductive charging member to which a voltage is applied is brought into contact with an image carrier as a member to be charged, and the charge is directly transferred from the charging member to the photosensitive drum to thereby transfer the surface of the image carrier. Is charged to a predetermined potential. Such a contact charging device can reduce the applied voltage, simplify the power supply, and reduce the amount of ozone generated during the charging process as compared with the non-contact type corona discharge device which has been widely used. It has the advantages that it is a minute amount, therefore the ozone removal filter and the like can be eliminated to simplify the structure of the exhaust system, that it is maintenance-free, and that the structure is simple. For this reason, the contact charging type charging device is used in an image forming apparatus such as an electrophotographic apparatus (copier, laser beam printer), electrostatic recording device, etc., including an image carrier such as a photoconductor and a dielectric, and other photosensitive drums. As a means for charging (hereinafter, simply referred to as "photosensitive drum"), it has attracted attention as a substitute for a corona discharge device and has been put into practical use.

In the above-mentioned contact charging device, in order to uniformly and uniformly charge the surface of the photosensitive drum, an oscillating voltage in which a DC voltage is superimposed on an AC voltage is applied to a conductive contact charging member, and this charging member is charged. A charging method is known in which charging is performed by bringing the photosensitive drum into contact with the photosensitive drum.
149669).

FIG. 15 shows one embodiment thereof. In the figure,
Reference numeral 1 denotes a photosensitive drum (image bearing member), for example, an arrow R1.
It is rotationally driven in a predetermined circumferential speed (process speed).

Reference numeral 2 denotes a conductive charging roller as a contact charging member, which comprises a cored bar (supporting member) 2a and a conductive rubber roller 2r as an elastic body formed on the outer periphery thereof.
The charging roller 2 is pressed against the surface of the photosensitive drum 1 with a predetermined pressing force by pressure springs 3 for urging both ends of the core metal 2a toward the photosensitive drum 1, respectively. Arrow R with rotation in the R1 direction
It rotates in two directions.

Reference numeral 4 is a power supply for applying a voltage to the charging roller 2. A predetermined charging voltage is applied to the charging roller 2 by the power source 4 via the cored bar 2a to uniformly charge the surface of the photosensitive drum 1 which is rotationally driven. The predetermined charging voltage at this time is the oscillation voltage Vac having a peak-to-peak voltage Vpp that is at least twice the charging start voltage of the photosensitive drum 1.
Voltage (Vac + Vd) that is a superposition of the DC voltage Vdc and the DC voltage Vdc.
c).

The photosensitive drum 1 whose surface is uniformly charged is
After that, an electrostatic latent image is formed on the surface by the exposure of the exposure unit 5. Toner (developer) is attached to the electrostatic latent image by the developing device 6 to form a toner image, and the toner image is transferred to the transfer material 7 transported by a transport device (not shown).
The image is transferred by the transfer device 8. The transfer material 7 to which the toner image has been transferred is then fixed with a toner image by a fixing device (not shown), and is ejected to the outside of the apparatus main body as a final copy.

On the other hand, the photosensitive drum 1 after the toner image transfer is
The residual toner remaining on the surface is removed by the cleaning device 9 and is subjected to the next image forming process.

[0009]

However, in the above-mentioned contact type charging member, a vibration noise called "charging sound" is generated due to the AC component of the charging bias, which is a problem.

The mechanism of generating the charging noise will be described below by taking a laser beam printer using the charging roller 2 as an example.
A description will be given with reference to (a) and (b).

In the figure, 1 is a photosensitive drum, 1a is a photosensitive layer, 1b is a grounded aluminum base layer, and the entire photosensitive drum 1 rotates at a speed of 40 mm / s.

At some point in time when the AC voltage applied to the charging member 2 becomes positive, as shown by the thick solid line in FIG. 14 (a), the photosensitive layer 1a is sandwiched between the charging member 2 side and the positive side. Negative charges are induced on the base layer 1b side of the drum 1. As a result of these electric charges attracting each other, an attractive force acts between the charging member 2 and the photosensitive drum 1 to move from the position indicated by the thick solid line to the position indicated by the thin solid line. This is because even if the AC voltage applied to the charging member 2 is reversed, the charges are simply reversed, and a similar attractive force is generated. There is a time when the induced charge disappears between the plus and minus peaks of the AC voltage, and at this time, the attractive force becomes zero. At this time, FIG.
As shown in (b), the charging member 2 returns from the position of the thick solid line in the figure to the position of the thin solid line by its elasticity. Therefore, an attractive force is applied between the charging member 2 and the photosensitive drum 1 at a cycle twice as long as the AC bias, and both the charging member 2 and the photosensitive drum 1 vibrate. As a result, it is considered that "charging noise" is generated. The hollow photosensitive drum 1 is
It may tend to act as a resonator, and it may be considered that the charging member 2 strikes the photosensitive drum 1 to generate “charging sound”. As is clear from the above description, assuming that the frequency of the AC voltage is f and the vibration frequency of the charging member 2 is F, the following relationships exist between them.

2f [Hz] = F [c / s] When the charging member 2 has a resistance layer on the surface thereof, the above-mentioned vibration becomes more complicated, and the generated charging sound has a harmonic component of the above-mentioned vibration frequency. Because of the increase in the sound pressure level, the charging sound may be annoying and unpleasant regardless of the measured sound pressure level.

The following methods have been studied as a solution to the above-mentioned charging noise. The frequency of the applied AC component (charging frequency) is reduced.

If the frequency is set to 300 Hz or less, the charging noise is considerably improved. However, laser beam and LE
In the case of a digital PPC or a laser beam printer that forms an image with D, when the multiple of the pixel density and the charging frequency are close to each other, interference fringes called "moire" occur. To prevent the occurrence of moire, a charging frequency higher than the "interference frequency" determined by the pixel density and the process speed is required. As the pixel density and the process speed increase, the charging frequency required to prevent the generation of moire increases, and the frequency cannot be reduced. For example, when the pixel density is 600 dots / inch and the process speed is 100 mm / s, a charging frequency of about 1000 Hz is required.
Considering further higher pixel density and higher speed, it is expected that it is necessary to support a frequency of at least about 1500 Hz. The peak-to-peak voltage Vpp of the applied AC component is set to twice the charging start voltage or less.

Although it is effective for improving the charging sound, it is not possible to give a sufficiently uniform charge on the photosensitive drum 1, and spot-like uneven charging is likely to occur. A weight or an anti-vibration member such as rubber is inserted inside the photosensitive drum 1.

This is a very effective method of suppressing the vibration of the photosensitive drum 1 to reduce the charging noise, but there are problems such as an increase in manufacturing cost and an increase in the weight of the process cartridge. Foam the charging member to reduce the specific gravity.

The purpose is to foam the charging member 2 to reduce the energy for converting the vibration into vibration by striking the photosensitive drum 1 and hitting the photosensitive drum 1, and to absorb the vibration by the elasticity of the foamed charging member 2. I am trying. This measure is very effective in reducing the sound pressure level of charging noise. The foaming member used is polystyrene, polyolefin, polyester, polyurethane, polyamide or the like. In addition, conductive powder such as carbon or tin oxide may be dispersed and blended with these to impart conductivity. However, the charging member 2 requires a surface layer (for example, a resistance layer) that covers the foamed member in order to prevent uneven charging locally. Due to the presence of this surface layer, a high frequency is likely to be generated, and an offensive charging sound may be generated regardless of the measured sound pressure level.

According to the present applicants, when the sound pressure level of the charging sound is about the same, when the ratio of the 2nd to 3rd overtone components (= 4f, 6f) to the vibration frequency F (= 2f) is large in the sense of hearing. A panel test (about 40 subjects) showed a strong tendency to feel uncomfortable.

In the above panel test, the "unpleasantness" of the charging sound was digitized and judged as follows. A laser beam printer with a process cartridge that can be replaced is installed in the anechoic chamber, and the contact charging member A becomes a "standard sound source"
Two process cartridges having the same configuration, which are respectively equipped with the contact charging member B to be measured and the contact charging member B, are prepared.
Five to seven test subjects (panelists) are seated in front of the above laser beam printer, and the process cartridges equipped with the above-mentioned contact charging members A and B are alternately mounted to generate a charging sound. The test subject evaluated the level of "pleasantness to discomfort" of the contact charging member B with respect to the contact charging member A on the auditory sensation in the following five grades, and the average value of the evaluations was regarded as "discomfort".

1 quiet (against A), barely audible 2 somewhat quiet (against A), audible with caution 3 almost equivalent (against A) No. 4 Slightly noisy (against A), (sounding) annoying 5 Noisy, (sounding) uncomfortable AC component is 2 kVpp, 1500 Hz The result of applying a charging bias is shown in FIG. The sound pressure level in the figure is obtained by measuring the charging sound according to item 6 of ISO 7779. The intensity of the 2f sound, which is the vibration frequency, is
A microphone is placed on the front surface of the printer described above, and the displayed values are those obtained by FFT analysis of the waveform, which is shown for relative comparison of each sample (each contact charging member). The degree of occurrence of high-frequency components (4f sound and 6f sound) is indicated by the ratio to the intensity of the 2f sound described above. The “standard sound source” contact charging member 2 used here was subjectively selected in advance by the majority of the subjects (about 40 people) as “not practically concerned about sound”, and was tested in the above panel test. It is set so that the subject's evaluation criteria do not change. Samples A to G in FIG. 13 are made by imitating various elastic materials similar to the contact charging member in order to investigate the “discomfort”, and the charging member includes those that are not practical.

From the result of FIG. 13, when the sound pressure levels are considered to be equivalent, 4f which is a high frequency component in the charging sound.
A sound, a 6f sound, or both of them, which are obviously stronger than the 2f sound, are evaluated as “noisy and uncomfortable”. Similarly, when the intensity of either the 4f sound or the 6f sound has the same intensity as that of the 2f sound, the level is set to be "anxious about the sound". In SampleG, although the 2f sound is louder than others, the level of discomfort is relatively low.

Therefore, as a countermeasure against the charging noise, it is necessary to reduce the sound pressure level and suppress the high frequency component.

Therefore, in the present invention, by setting the layer thickness of the surface layer member covering the foamed member to 300 μm or less, the charging noise is reduced without causing uneven charging, deterioration of image quality, high cost and the like. An object is to provide a member, a process cartridge, and an image forming apparatus.

[0025]

The present invention has been made in view of the above circumstances, and an elastic body held by a supporting member is brought into contact with an image carrier to apply a charging voltage to the supporting member. In the charging member for charging the image carrier through the elastic body, the elastic body surrounds the foamed member supported by the supporting member and directly contacts the image carrier. Alternatively, a plurality of surface layer members are provided, and the layer thickness of the surface layer member is 300 μm or less.

In this case, an oscillating voltage obtained by superimposing a DC voltage on an AC voltage having a frequency of 1500 Hz or less may be applied to the elastic body via the supporting member.

Further, the process cartridge includes at least the image carrier, the above-mentioned charging member, and a cartridge container for accommodating the image carrier and the charging member in an integrated manner, with respect to the main body of the image forming apparatus. The feature is that it is detachably attached.

Further, the image forming apparatus includes the image carrier, the above-mentioned charging member, exposing means for exposing the image carrier to form an electrostatic latent image, and toner attached to the electrostatic latent image. It is characterized in that it is provided with a developing device for forming a toner image by means of this and a transfer device for transferring the toner image onto a transfer material.

Further, the image forming apparatus may have a mounting means for detachably mounting the above process cartridge.

[0030]

According to the above structure, the hardness of the surface layer member is reduced by setting the layer thickness of the surface layer member covering the foamed member to 300 μm or less. For example, when the frequency of the applied voltage is 1500 Hz or less, the AC component of the applied voltage is reduced. This suppresses the vibration caused by the noise and also suppresses the overtone component of the vibration frequency to suppress the generation of annoying charging sound.

In addition, by thinning the surface layer member, the charging member is easily pressed against the image carrier, and even if the axial length of the charging member is increased, the charging member floats away from the image carrier due to irregular deformation. Since it adheres without forming a part, no defective charging is observed. Further, since the contact charging member weakens the force of hitting the image bearing member, it is possible to suppress the "toner fusion" phenomenon that occurs when the residual toner that has passed through the cleaning device is pressed against the image bearing member by the contact charging member. .

[0032]

Embodiments of the present invention will be described below with reference to the drawings. <Embodiment 1> FIG. 1 is a schematic view showing a vertical section of a charging roller 2 as a charging member according to the present invention, and FIG. 2 is a schematic view showing a section of one end side in a direction along a cored bar 2a. is there.

In these figures, 1 is a member to be charged (image carrier)
Is a rotary type photosensitive drum having a negative or positive charging polarity. Reference numeral 2 is a charging roller as a contact charging member. The charging roller 2 is composed of a cored bar 2a made of a metal such as stainless steel as a support member and an elastic body 2B surrounding the cored bar 2a. The elastic body 2B is configured such that a foamed member (foamed layer) 2b which is concentrically and integrally formed on the outer periphery of the core metal 2a in the shape of a roller is covered with a conductive layer 2d and a medium resistance layer 2e as a surface layer member 2c. belongs to.

The foam member 2b is formed by dispersing conductive powder such as carbon or tin oxide in a foam member made of polystyrene, polyolefin, polyester, polyurethane, polyamide or the like, or a flexible member made of EPDM or urethane foam. It is a member having a low volume resistivity and a specific weight of 0.1 g / cm ³ or more and 0.6 g / cm ³ or less. In this embodiment, carbon is dispersed in foamed polyurethane. Two
Reference numeral b'denotes a bubble portion (filled bubble of air, nitrogen, argon gas, etc.) of the foam member 2b. Foamed member 2 of this embodiment
As b, a specific foam having a specific weight of 0.5 g / cm ³ is used.

The conductive layer 2d is the bubble portion 2 in the foam member 2b.
It is provided to prevent local uneven charging due to b '.

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

Core metal 2a; diameter 6 mm, length 256 m
m stainless round bar Foaming member 2b; Carbon dispersed foaming polyurethane Specific weight 0.5 g / cm ³ Volume resistance value 10 ³ Ω · cm Layer thickness 2.8 mm, Length 230 mm Surface layer member 2c; Layer thickness 300 μm Conductive layer 2d; A large amount of carbon in EPDM and urethane,
Conductive powder such as tin oxide dispersed Volume resistance value 10 ⁵ Ω · cm Layer thickness 80 μm Medium resistance layer 2e; epichlorohydrin rubber Volume resistance value 10 ⁹ Ω · cm Layer thickness 220 μm Charging roller weight; 68 g Charging Roller hardness: 41 ° (Asker C) In the charging roller 2 as well, similar to the conventional one shown in FIG. 15, both ends of the cored bar 2a are held by bearing members (not shown), and the pressure spring 3 is used. A predetermined pressing force is applied to the surface of the photosensitive drum 1 by pressing and urging it toward the photosensitive drum 1, in this embodiment,
They are pressed against each other with a total pressure of 1000 g and are driven to rotate as the photosensitive drum 1 rotates. An AC voltage is applied to the charging roller 2 from a power source 4 via a sliding electrode (not shown) in contact with the core metal 2a of the charging roller 2. In this embodiment, 2.0 kVpp, 1500H.
z DC voltage; superimposed oscillation voltage (Va) obtained by superimposing an AC voltage of a DC voltage corresponding to the target charging potential and a DC voltage.
c + Vdc) is applied. As a result, the photosensitive drum 1
The surface is contact-charged uniformly to the target charging potential by the AC application method.

For comparison, the sound pressure level of the charging sound was measured by changing the layer thickness of the medium resistance layer 2e of this embodiment. The measurement was carried out in accordance with ISO 7779, item 6.
Further, the generation of unpleasant sound was evaluated by the above panel test. The applied voltage is the oscillating voltage described above.

The results are shown in FIG. When the evaluation value of the discomfort that is considered to be practically no problem is set to "3.0" or less, the layer thickness of the surface layer member 2c capable of handling the charging frequency of 1500 Hz needs to be 300 µm or less from the above results. I know there is.

For such an effect of reducing the charging noise,
It goes without saying that the foaming state of the foaming member 2b is the same whether it is a single cell or an open cell. <Embodiment 2> As shown in FIGS. 3 and 4, the charging roller 2 according to the present embodiment includes a foaming member 2b supported by a core metal 2a.
Surface layer member 2c composed of layers, that is, tube 2 of medium resistance
f, the conductive layer 2g provided on the inner peripheral surface of the tube 2f, and the high resistance layer 2h provided on the outer peripheral surface of the tube 2f. Note that FIG. 3 and FIG.
3A and 3B are diagrams corresponding to FIGS. 1 and 2 of the first embodiment, respectively.

As shown in FIG. 5, the charging roller 2 having such a structure is prepared by first forming the foaming member 2b in which the raw material is foamed, and inserting the core metal 2a and the surface member 2c into the foaming member 2b. As shown in FIG. 6, the tube 2f and the high resistance layer 2h
There is a method in which a cored bar 2a is erected inside a surface layer member 2c made of, for example, and the foaming member 2b is inserted into the cored bar 2a and foamed in a fixed state. This is advantageous in terms of surface property, accuracy, and cost, as compared with the method in which the formed foam member 2b is sequentially covered with the respective layers constituting the surface layer member 2c as in the first embodiment. The tube 2f covering the conductive foam member 2b is substantially separated from the foam member 2b.
The same applies to the core metal 2a and the foam member 2b.
Furthermore, in order to prevent axial displacement, the tube 2f and the foam member 2b, and the core metal 2a and the foam member 2b may be partially fixed.

The high resistance layer 2h is the photosensitive layer 1 of the photosensitive drum 1.
It was provided in order to perform stable charging without leaking the applied bias even if a pinhole was generated in a.

The specific specifications of this embodiment are as follows.

Foaming member 2b: Carbon-dispersed foamed epichlorohydrin rubber Specific weight 0.4 g / cm ³ Volume resistance value 10 ³ Ω · cm Layer thickness 2.6 mm, length 230 mm Surface layer member 2c; Layer thickness 300 μm Tube 2f; Polyurethane heat Plastic elastomer Volume resistance value 10 ⁷ Ω · cm Layer thickness 150 μm Conductive layer 2 g; Large amount of carbon in EPDM and urethane,
Conductive powder such as tin oxide dispersed Volume resistance value 10 ⁵ Ω · cm Layer thickness 10 μm High resistance layer 2h; epichlorohydrin rubber Volume resistance value 10 ¹⁰ Ω · cm Layer thickness 140 μm Charging roller weight; 69 g Charging Roller hardness: 42 ° (Asker C) Pressing force on the photosensitive drum 1: Total pressure 1000 g Applied vibration voltage AC voltage Vac; 2.0 kVpp, 1
500 Hz DC voltage Vdc; DC voltage corresponding to target charging potential For comparison, the sound pressure level of the charging sound was measured by changing the layer thickness of the medium resistance layer of this example. The measurement is IS
O 7779, item 6. Further, the generation of unpleasant sound was evaluated by the above panel test. The applied voltage is the oscillating voltage described above.

The results are shown in FIG. In the tube type charging roller 2 as in this embodiment, the thickness of the tube 2f cannot be reduced so much that the hardness of the tube 2f is slightly higher than that of the first embodiment, and the tube 2f is separated from the foaming member 2b. Therefore, the vibration of the tube 2f is relatively free, so that high frequency components are likely to be generated. If the evaluation value of discomfort that is considered to be practically no problem is set to "3.0" or less,
From the above-mentioned results, it is understood that the layer thickness of the surface layer member 2c capable of handling the charging frequency of 1500 Hz needs to be 300 μm or less. <Embodiment 3> As shown in FIGS. 7 and 8, the charging roller 2 of the present embodiment includes a non-conductive foam member 2b supported by a core metal 2a, a surface layer member 2c composed of four layers, that is, Medium resistance tube 2i, conductive layer 2j provided on the inner peripheral surface of tube 2i, and medium resistance layer 2 covering the outer peripheral surface of tube 2i
k, and a protective layer 2l that covers the intermediate resistance layer 2k. 7 and 8 are diagrams corresponding to FIGS. 1 and 2 of the first embodiment, respectively. This tube type surface layer member 2c has a core metal 2 at the longitudinal end.
It is bonded to a and maintains electrical continuity. Protective layer 2l
Is provided in order to prevent the surface layers of the photosensitive drum 1 and the charging roller 2 from being contaminated, and a material that is chemically compatible with the surface layer of the photosensitive layer 1a is selected. However, as in this embodiment,
By layering the surface layer member 2c, the surface layer member 2c
Hardness tends to increase.

The specific specifications of this embodiment are as follows.

Foamed member 2b; Foamed epichlorohydrin rubber Specific weight 0.35 g / cm ³ Volume resistance value 10 ¹⁰ Ω · cm Layer thickness 2.6 mm, length 230 mm Surface layer member 2c; Layer thickness 285 μm Tube 2i; Polyurethane thermoplastic elastomer volume Resistance value 10 ⁷ Ω · cm Layer thickness 150 μm Conductive layer 2j; Large amount of carbon in EPDM and urethane,
Conductive powder such as tin oxide dispersed Volume resistance value 10 ⁵ Ω · cm Layer thickness 10 μm Medium resistance layer 2k; epichlorohydrin rubber Volume resistance value 10 ¹⁰ Ω · cm Layer thickness 120 μm Protective layer 2l; N- Methoxymethylated nylon Volume resistance value 10 ⁹ Ω · cm Layer thickness 5 μm Charging roller weight; 70 g Charging roller hardness; 44 ° (Asker C) Pressing force on photosensitive drum 1; Total pressure 1000 g Applied vibration voltage AC voltage Vac; 2.0 kVpp , 6
00 Hz DC voltage Vdc; DC voltage corresponding to target charging potential For comparison, the sound pressure level of the charging sound was measured by changing the layer thickness of the medium resistance layer of this example. The measurement is IS
O 7779, item 6. Further, the generation of unpleasant sound was evaluated by the above panel test. The applied voltage is the oscillating voltage described above.

The results are shown in FIG. When the evaluation value of the discomfort that is considered to be practically no problem is set to "3.0" or less, the layer thickness of the surface layer member 2c capable of handling the charging frequency of 1500 Hz needs to be 300 µm or less from the above results. I know there is.

As in this embodiment, if the surface layer member 2c of the charging roller 2 can be electrically connected, the foam member 2b does not need to have conductivity, and of course the material, specific gravity, hardness, etc., for suppressing charging noise. You can choose freely. <Fourth Embodiment> A fourth embodiment will be described with reference to FIG.

The present embodiment is a process cartridge of an image forming apparatus using the contact type charging member or the charging device described in any of the first to third embodiments as a charging means of the image carrier.

The process cartridge of this embodiment is a drum-shaped electrophotographic photosensitive member (photosensitive drum) as an image bearing member.
1, a charging roller 2 as a contact charging member, a developing device 6,
The four process devices of the cleaning device 9 are integrally incorporated in the cartridge container C. Also,
The apparatus main body of the image forming apparatus to which the process cartridge is mounted is provided with mounting means for mounting the process cartridge in a detachable manner (not shown).

The charging roller 2 is the same as that described in Embodiments 1 to 3, and is pressed against the photosensitive drum 1 by a pressure spring (not shown) and driven to rotate as the photosensitive drum 1 rotates. To do.

In the developing device 6, 60 is a developing sleeve, 61 is a container for storing toner (developer) T, and 62 is a toner stirring rod in the storing container 61. The toner T is stirred and directed toward the developing sleeve 60. Send out. Reference numeral 63 is a developing blade for coating the developing sleeve 60 with the toner T to a uniform thickness.

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

Reference numeral 11 denotes a drum shutter of the process cartridge, which can be opened and closed freely from the closed state shown by the solid line to the open state shown by the dotted line. Drum shutter 11
Is in the closed state shown by the solid line when the process cartridge is taken out from the apparatus main body (not shown) of the image forming apparatus, and the surface of the photosensitive drum 1 that is exposed to the outside is concealed to protect the surface of the photosensitive drum 1. .

When the process cartridge is adhered to the main body of the apparatus, the drum shutter 11 is opened as indicated by the dotted line, or the drum shutter 11 is automatically opened during the process of mounting the process cartridge so that the process cartridge is properly opened. When mounted, the externally exposed portion surface of the photosensitive drum 1 is in pressure contact with the transfer roller (transfer device, see FIG. 15) 8 on the image forming apparatus main body side.

Further, the process cartridge and the apparatus main body are mechanically and electrically coupled to each other, and the driving mechanism on the apparatus main body side can drive the photosensitive drum 1, the developing sleeve 60, the stirring rod 62 and the like on the process cartridge side. The application of a charging bias to the charging roller 2 on the process cartridge side by the electric circuit on the apparatus main body side, the developing sleeve 60
A developing bias can be applied to the image forming apparatus, and the image forming operation can be executed.

Reference numeral 12 is an exposure window provided between the cleaning device 9 of the process cartridge and the developing device 6,
Output laser light (exposure means) 5 from a laser scanner (not shown) on the apparatus main body side passes through the exposure window 12 and enters the process cartridge, and the surface of the photosensitive drum 1 is scanned and exposed.

In the present embodiment, as described above, the charging roller 2 produces almost no charging sound even when the oscillating voltage in which the DC voltage is superposed on the AC voltage is applied, so that the charging sound is substantially inaudible. It is possible to construct a very compact process cartridge.

[0060]

As described above, according to the present invention,
By setting the layer thickness of the surface layer member that covers the foamed member to 300 μm or less, the hardness of the surface layer member is reduced, and when the frequency of the applied voltage is, for example, 1500 Hz or less, the applied voltage A
It is possible to reduce the vibration due to the C component and suppress the generation of the overtone component of the vibration frequency to effectively suppress the generation of annoying charging sound.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating a vertical cross section of a charging member according to a first exemplary embodiment.

FIG. 2 is a schematic view showing a cross section in the core bar direction in the vicinity of the end of the charging member.

FIG. 3 is a schematic view showing a vertical cross section of a charging member of Example 2.

FIG. 4 is a schematic view showing a cross section in the core bar direction near the end of the charging member.

FIG. 5 is a diagram illustrating a method of manufacturing a charging roller.

FIG. 6 is a diagram illustrating another method of manufacturing the charging roller.

FIG. 7 is a schematic view showing a vertical cross section of a charging member of Example 3.

FIG. 8 is a schematic diagram showing a cross section in the core bar direction in the vicinity of the end of the charging member.

FIG. 9 is a vertical cross-sectional view showing the configuration of a process cartridge of Example 4.

FIG. 10 is a diagram showing the relationship among the surface layer member thickness, sound pressure level, and panel evaluation of Example 1.

FIG. 11 is a diagram showing the relationship between the surface layer member thickness, sound pressure level, and panel evaluation in Example 2.

FIG. 12 is a diagram showing the relationship among the surface layer member thickness, sound pressure level, and panel evaluation of Example 3.

FIG. 13 is a diagram showing a relationship between a contact charging member, sound pressure level, and panel evaluation.

14 (a) and 14 (b) are views showing a generation mechanism of a charging sound.

FIG. 15 is a schematic diagram showing the vicinity of a photosensitive drum of a conventional image forming apparatus.

[Explanation of sign]

 DESCRIPTION OF SYMBOLS 1 Image bearing member (charged member, photosensitive drum) 2 Charging member (charging roller) 2B Elastic body 2a Support member (core metal) 2b Foaming member (elastic body) 2b 'Bubble part 2c Surface layer member 2d, 2g, 2j Conductive layer 2e, 2k Medium resistance layer 2f, 2i tube 2h High resistance layer 2l Protective layer 3 Pressure spring 4 Power supply 5 Exposure means (output laser light) 6 Developing device 7 Transfer material 8 Transfer device 9 Cleaning device C Cartridge container

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location G03G 21/18 (72) Inventor Koichi Suwa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Hiroshi Sato 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Satoshi Inami 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Tetsuya Sano 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (5)

[Claims] 1. A charging member for bringing an elastic body held by a supporting member into contact with an image carrier and applying a charging voltage to the supporting member to charge the image carrier through the elastic body, wherein the elastic body is used. Is provided with a foam member supported by the support member and a single-layer or multiple-layer surface layer member that surrounds the foam member and directly contacts the image carrier, and has a layer thickness of 300 μm or less. A charging member characterized by: 2. The charging member according to claim 1, wherein an oscillating voltage in which a DC voltage is superimposed on an AC voltage having a frequency of 1500 Hz or less is applied to the elastic body via the supporting member. 3. An image forming apparatus, comprising at least the image carrier, the charging member according to claim 1 or 2, and a cartridge container that integrally houses the image carrier and the charging member. A process cartridge that is detachably attached to the main body. 4. The image carrier, the charging member according to claim 1 or 2, exposure means for exposing the image carrier to form an electrostatic latent image, and toner on the electrostatic latent image. An image forming apparatus comprising: a developing device that adheres toner to form a toner image; and a transfer device that transfers the toner image onto a transfer material. 5. An image forming apparatus, comprising: mounting means for detachably mounting the process cartridge according to claim 3.