JP2001356565A - Electrifying device and cylindrical photoreceptor therein for electrophotography - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrifying device where unevenness in an image is not generated by restraining noise corresponding not only to the number of oscillation that is twice the oscillating voltage but also to the number of oscillation that is four times that and an electrophotographic photoreceptor utilized for it. SOLUTION: In the electrifying device provided with the cylindrical photoreceptor for electrophotography with a restraining member for resonance installed in contact with inside of the cylindrical photoreceptor and a contact electrifying member with a hardness of >=55 deg. that is in contact with an outer surface of the photoreceptor to electrify the photoreceptor, the ratio between the length of contact 'a' of the restraining member for the resonance with the inside of the photoreceptor and the length of contact 'b' with the outer surface of the photoreceptor of the contact electrifying member is made to be a/b>=0.5.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member using contact charging as a surface charging method, and a charging device including the photosensitive member.

2. Description of the Related Art An electrophotographic photosensitive member used in an electrophotographic apparatus such as a copying machine or a laser beam printer is required to uniformly charge the surface of the photosensitive member to a predetermined potential in order to execute an electrophotographic process. It is necessary, and as a charging method, a charging method by a corona discharge method has been generally performed. Recently, the generation of ozone due to corona discharge has become a problem, and in order to suppress the generation of ozone, a contact charging method capable of lowering the applied voltage, such as roller charging, has been used in many cases. The contact charging method is a method in which a charging member is brought into direct contact with the surface of an electrophotographic photosensitive member to charge the surface of the photosensitive member. Examples of such a method include a brush charging method in which charging is performed by contact with a brush, in addition to the roller charging method described above. The advantage of this contact charging method is that the applied voltage is lower than that of the corona discharge type charging device, so that the amount of generated ozone is greatly reduced as described above, and the structure of the charging device is relatively simple and compact. In the contact charging method, the surface of the photoconductor is directly charged by a superimposed voltage of a DC voltage and an AC voltage applied to a contact charging member such as a charging roller. In the electrophotographic process, the surface of a photoreceptor that rotates about a cylindrical axis in a charging device is first uniformly charged in a dark place by the above-described contact charging method, and the charged surface is exposed to images such as images and characters. To form an electrostatic latent image, develop with toner, transfer and fix the toner image on a support such as paper to obtain an image or print, and remove and clean the photosensitive layer surface after transfer of the toner image. By sequentially performing these electrophotographic processes while the photoconductor rotates, images or prints can be obtained continuously. One of the problems associated with the contact charging method in such an electrophotographic process is that the AC voltage to be applied must be set so that uniform charging can be obtained even when the rotation speed of the photoconductor is increased in order to increase the process speed. As the frequency is increased, there is a problem of charging noise generated by inducing resonance at a certain frequency or higher between the photosensitive member and the charging roller (see Japanese Patent Application Laid-Open No. 4-68682). Such charging noise,
An attractive force acts between the charging roller and the surface of the photoreceptor in an oscillating electric field. Vibrating with each other. The noise is generated by a mechanism in which these hit each other. It is known that this noise is mainly composed of sounds having frequencies corresponding to twice and four times the frequency of the applied vibration voltage. In a normal office, sounds in this frequency range are very uncomfortable, and it is required to suppress the charging noise to a level at which the uncomfortable feeling is eliminated. In order to suppress such charging noise, it is known that, for example, when a cylindrical member 11 having a predetermined weight as shown in the cross-sectional view of the photoconductor of FIG. (Japanese Patent Laid-Open No. 5-3)
5166, JP-A-5-35167 and JP-A-5-35048). Further, when the cylindrical member is inserted into the inside of the electrophotographic photosensitive member, the cylindrical member adheres to the inner surface of the photosensitive member with a predetermined frictional force using the cut slit despite its outer diameter larger than the inner diameter of the photosensitive member. Japanese Patent Application Laid-Open No. 8-54804 describes that when pressed and held as described above, an effect of suppressing noise can be obtained regardless of the weight of the cylindrical member. On the other hand, in Japanese Patent Application Laid-Open No. 8-328357, it is necessary to lower the hardness of the entire resin layer of the charging member such as a charging roller to 55 degrees or less so as to have flexibility so as to suppress noise. It is stated that there is.

However, as described in the above-mentioned publication, when the hardness of the resin material of the contact charging member is reduced, permanent deformation occurs in the surface material during repeated contact with the photosensitive member. Another problem that charging unevenness on the surface of the photoreceptor leads to image unevenness is likely to occur. Therefore, if possible, the hardness of the resin material of the contact charging member should be 55 degrees or more. In order to solve the problem of image unevenness due to permanent deformation as described above, the present inventor suppressed the noise level even if the hardness of the resin material of the contact charging member was increased to 55 degrees or more and the flexibility of the resin was reduced. In various investigations as to whether or not it was possible, the relationship between the weight of the resonance sound suppressing member inserted into the photoconductor and the suppressing effect was analyzed. As a result, as described above, regarding the relationship between the insertion of the predetermined weight member into the photoreceptor and the noise suppression effect, the suppression of the sound having a frequency corresponding to twice the frequency of the applied vibration voltage requires weight. Although a correlation is observed, the oscillation voltage of 4
Since the sound corresponding to the double frequency has no correlation with the weight, the effect of suppressing the sound is not always sufficiently exhibited. In addition, it is considered that an invention in which the hardness of the charging member is reduced to 55 degrees or less has occurred. Therefore, if a countermeasure for a sound having a frequency four times as high as the vibration voltage is separately found, it is considered that the resonance sound may be suppressed even when the hardness of the charging member is 55 degrees or more. The present invention provides a charging device that suppresses noise corresponding to not only a frequency twice as high as a vibration voltage but also a frequency four times as high and does not cause image unevenness, and an electrophotographic photosensitive member used in the charging device. The purpose is to:

SUMMARY OF THE INVENTION It is an object of the present invention to provide a cylindrical electrophotographic photosensitive member having a resonance noise suppressing member provided inside a cylindrical photosensitive member and a contact with the outer surface of the photosensitive member. A contact charging member having a hardness of 55 degrees or more provided for charging the photoreceptor, and a contact length a of the resonance sound suppressing member to the inner surface of the photoreceptor and an outer surface of the photoreceptor of the contact charging member. The ratio of the contact length b to a / b ≥ 0.5
With the charging device described above (the invention of claim 1),
Achieved. The following is preferred as the cylindrical electrophotographic photosensitive member used in the first aspect of the present invention. That is, the resonance sound suppressing member inscribed in the cylindrical electrophotographic photoreceptor is made of a cylindrical resin having a diameter larger than the inner diameter of the photoreceptor, and the photoreceptor is formed using a slit-shaped notch formed in the cylindrical axis direction. It is inserted inside and fixed to the inner surface of the photosensitive body by the elastic force of the resin (the invention of claim 2). Further, as an embodiment of the invention of the second aspect, the following is preferable. That is, it is assumed that a metal elastic material is attached to the inside of the cylindrical resin resonance sound suppressing member to reinforce the elastic force (the invention of claim 3).

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a charging device according to the present invention and an electrophotographic photoreceptor used therein. (Example 1) Length 350mm, outer diameter 30mmφ, inner diameter 28.
Inside a photoreceptor 1 in which a photosensitive layer is formed on the outer surface of a 5 mm cylindrical aluminum substrate, a cylindrical resonance sound suppressing member 12 (5 mm thick, 64 to 320 mm long, The outer diameter of 28.9 mm) is reduced in diameter using a notched slit (not shown) and inserted. The resonance noise suppressing member 12 has a diameter larger than the inner diameter of the photoconductor 1 so as to be held by the frictional force on the inner surface of the photoconductor using the elastic force of the resin. This resonance sound suppressing member 1
In order to further increase the pressing force on the photoconductor 1, a spring material 13 (length 50) made of stainless steel is provided inside the photoconductor 1.
Or 160 mm, thickness 0.5 mm). The shape of the elastic force reinforcing member is also a cylindrical shape in which a slit is formed similarly to the resonance sound suppressing member 12. Its length and thickness can be varied freely to adjust the required reinforcing elasticity. The contact charging member 100 is formed of a hard urethane rubber provided with conductivity by carbon powder or the like, and a resistance surface layer such as an acrylic resin or a nylon resin, and is formed as a metal mandrel.
The thickness of the contact charging member is about 5 to 10 mm, and the length is A3
It is 320 mm corresponding to standard paper, and the diameter of the metal mandrel is 4 to 6 mm. The length of the contact charging member corresponds to the contact length b. The hardness (Asker hardness) of the contact charging member was adjusted to 60 degrees by adjusting the material and thickness. On the other hand, the length of the resonance sound suppressing member 12, that is, the above-mentioned contact length a is set to 0.
2, 0.4, 0.5, 0.6, 0.8, 1.0 times, ie 64 mm, 128 mm, 160 mm, 192 mm, 256 m
m, 320 mm, and a charging device including a cylindrical electrophotographic photosensitive member having such a resonance sound suppressing member and the contact charging member is incorporated in a contact charging type process cartridge having a vibration voltage of 650 Hz. The noise generated when operating in the printer was measured. In order to clarify the effect of the present invention on noise suppression, the measured sound frequency was set to 2600 Hz, which is a vibration voltage four times the applied vibration voltage. (Embodiment 2) The contact length b is set to 2 corresponding to B4 standard paper.
The length of the contact charging member (contact length a) was set to 0.2, 0.4, 0.5, 0.6, 0 of the contact charging member having a hardness of 58 mm and a hardness of 58 degrees, respectively. .8, 1.0
Double, i.e. 54mm, 108mm, 134mm, 162mm,
A charging device made of a photoreceptor under the same conditions as in Example 1 except that the length was changed to 216 mm and 268 mm and the length was set to 310 mm was changed to 68.
The noise generated when the device was incorporated into a contact charging type process cartridge having a vibration voltage of 7.5 Hz and operated in a printer was measured. The frequency of the measured sound was 2750 Hz, which is a vibration voltage four times the applied vibration voltage. (Embodiment 3) The contact length b is set to 2 corresponding to A4 standard paper.
The length of the contact charging member (contact length a) was set to 0.2, 0.4, 0.5, 0.6, and 0 of the contact charging member having a contact length of 24 mm and a hardness of 55 degrees, respectively. .8, 1.0
Double, ie 45mm, 90mm, 112mm, 135mm, 1
712. A charging device comprising a photosensitive member under the same conditions as in Example 1 except that the length was changed to 80 mm and 224 mm and the length was changed to 275 mm.
The noise generated when incorporated in a contact charging type process cartridge having an oscillating voltage of 5 Hz and operated in a printer was measured. The measured sound frequency was 2850 Hz, which is a vibration voltage four times the applied vibration voltage. FIG. 3 shows the results of noise measurement in Examples 1 to 3, wherein the vertical axis represents sound energy (relative magnification), and the horizontal axis represents a / b according to the present invention.
(Ratio of contact length) is plotted. The value of the sound energy on the vertical axis is a relative value that differs depending on the measuring instrument and the measuring method. Generally, when this value is 15 or more, people feel discomfort in the office. Based on this numerical value (15), a / b ≧ 0 regardless of the frequency of the voltage applied to the contact charging member and the contact length b.
At 5 the sound energy is 15 or less, and the noise suppressing effect is remarkable, while at a / b <0.5, it is found that noise is generated to the extent that a person feels uncomfortable. Example 1
When the image of the process cartridge was evaluated in a printer having a resolution of 1200 dpi, the results shown in Table 1 were obtained. From this table, it can be seen that no image unevenness occurs when a / b is 0.5 or more. It is considered that the image unevenness that occurs when a / b ≦ 0.4 is not due to the deformation of the contact charging member, but is caused by the vibration of the charging member being transmitted to the photoconductor.

[Table 1] From the above, it can be seen that when a / b ≧ 0.5, noise corresponding to a frequency four times the vibration voltage is suppressed, and image unevenness does not occur.

According to the present invention, a cylindrical electrophotographic photosensitive member having a resonance sound suppressing member provided inside a cylindrical photosensitive member, and a photosensitive member in contact with the outer surface of the photosensitive member And a contact length a of the resonance sound suppressing member with respect to the inner surface of the photoconductor and a contact length of the contact charging member with the outer surface of the photoreceptor. By setting the ratio of b to a / b ≧ 0.5, the charging device can obtain not only a frequency twice as high as the vibration voltage but also a frequency of 4 times.
It is possible to provide a charging device that suppresses noise corresponding to double frequency and does not cause image unevenness, and a photoconductor for electrophotography used in the charging device.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment of a charging device and a photoreceptor of the present invention.

FIG. 2 is a cross-sectional view of a conventional photoconductor.

FIG. 3 is a diagram showing the relationship between a / b and sound energy according to the present invention.

[Explanation of symbols]

1: photoreceptor, 12: resonance sound suppressing member, 10
0: Contact charging member.

Claims (3)

[Claims] 1. A cylindrical electrophotographic photosensitive member having a resonance sound suppressing member inscribed inside a cylindrical photosensitive member, and a photosensitive member for charging the photosensitive member by contacting the outer surface of the photosensitive member. A contact charging member having a hardness of 55 degrees or more, the contact length of the resonance sound suppressing member with respect to the inner surface of the photosensitive body a
A ratio of a contact length b of the contact charging member to the outer surface of the photoreceptor is set to a / b ≧ 0.5. 2. The resonance sound suppressing member inscribed in a cylindrical electrophotographic photosensitive member is made of a cylindrical resin having a diameter larger than the inner diameter of the photosensitive member, and utilizes a slit-shaped notch formed in a cylindrical axis direction. 2. The photoconductor is inserted into the photoconductor and held inside the photoconductor by the elastic force of the resin.
A cylindrical electrophotographic photosensitive member used in the charging device described in the above. 3. The cylindrical electrophotographic photosensitive member according to claim 2, wherein a metal elastic material is attached inside the cylindrical resin resonance sound suppressing member to reinforce the elastic force.