Electrophotography – Diagnostics – Consumable
Reexamination Certificate
2002-01-22
2004-03-30
Brase, Sandra (Department: 2852)
Electrophotography
Diagnostics
Consumable
C399S050000, C399S167000
Reexamination Certificate
active
06714746
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus such as an electrophotographic image forming apparatus to which a contact electrifying means is applied, and a process cartridge which is detachably attachable onto the image forming apparatus.
In this specification, the electrophotographic image forming apparatus is so adapted as to form an image on a recording medium by using an electrophotographic image forming system. The electrophotographic image forming apparatus is exemplified by an electrophotographic copying machine, an electrophotographic printer (for example, a laser beam printer and an LED printer), a facsimile machine, a word processor and so on.
Also, the process cartridge is so adapted as to integrate an electrifying means with a developing means and an electrophotographic photosensitive member drum into a cartridge, and to make the cartridge detachably attachable to an electrophotographic image forming apparatus main body. Also, the process cartridge is so adapted as to integrate the electrifying means with the electrophotographic photosensitive member drum into a cartridge so as to be detachably attachable on the electrophotographic image forming apparatus main body.
2. Related Background Art
Up to now, in an image forming apparatus using an electrophotographic image forming process, there is applied a process cartridge system in which the electrophotographic photosensitive member and the process means that affects the electrophotographic photosensitive member are integrated into a cartridge, and the cartridge is detachably attached to the image forming apparatus.
The process cartridge system can remarkably improve the operability since the maintenance of the device can be conducted by a user per se without relying on a service man. For that reason, the process cartridge system has been widely employed in the image forming apparatus.
In the above-mentioned image forming apparatus and process cartridge, an electrifying process for electrifying an image bearing member to a uniform potential is required in formation of an electrostatic latent image on the image bearing member, and a corona electrifying apparatus (non-contact with the image bearing member) has been frequently employed as the electrifying apparatus. However, the corona electrifying apparatus has suffered from such problems in that a large amount of ozone is generated, and that a high voltage of about 10 kV must be applied between the electrifying apparatus and the image bearing member, and so on.
As the electrifying means that solves the above problems, in recent years, a so-called contact electrifying apparatus, in which a voltage is applied to an electrifying member that is in direct contact with the image bearing member to uniformly electrify the image bearing member, has been proposed and put in practical use.
A representative one of the above-mentioned contact electrifying apparatus is a roller electrifying apparatus in which a middle-resistant layer is disposed on a front layer of a conductive base roller, and the roller is rotated in accordance with the rotation of the image bearing member. A predetermined voltage is applied between the roller and the image bearing member by a power supply, to thereby electrify the image bearing member to a uniform potential.
There are two voltage applying methods stated below:
1) a method of applying only a d.c. voltage; and
2) a method of applying a voltage resulting from superimposing an a.c. voltage on a d.c. voltage.
In case of the above method 1), for example, in order to set the potential of the image bearing member to −600 V, it is necessary to apply a voltage of about −1300 V to the electrifying member. In case of the above method 2), the potential of the image bearing member can be similarly set to −600 V by applying a d.c. voltage of −600 V and a superimposed a.c. voltage of 1500 Vpp or higher.
In this case, the electrifying mechanism complies with the Paschen's law in any case, in which a discharge phenomenon occurs in a region that satisfies Paschen's law to electrify the image bearing member when the roller and the image bearing member are located at a specific distance.
However, the contact electrifying apparatus of this type conducts the same operation as that of the corona discharging device that has been initially described, and generates ozone, although the amount of ozone is remarkably suppressed as compared with the corona electrifying apparatus, as is apparent from the above-mentioned electrifying mechanism. Ozone generates nitrogen oxide and leads to a phenomenon that, in the case where nitrogen oxide sticks onto the image bearing member, an image defect occurs due to electrifying failure because the resistance of nitrogen oxide is low.
Under the circumstances, Japanese Patent Application Laid-open No. 6-3921 has proposed an electrifying process that eliminates the above-mentioned problem of ozone occurrence and can further lower a voltage applied to the electrifying apparatus with the elimination of the above-mentioned problem.
In this electrifying process the surface potential of the image bearing member can be set to substantially the same potential as the voltage applied to the electrifying apparatus. This is enabled by performing charge injection to the image bearing member by directly transferring the charges with respect to the image bearing member surface that is in contact with the electrifying member without using the discharge phenomenon.
As the electrifying apparatus for realizing the above-mentioned injection electrifying process, a sponge roller electrifying apparatus will be described. In this type, relatively low resistant particles (conductive particles), which are called charge accelerating particles, are stuck on a blank shell portion in the surface of the electrifying sponge roller that is in contact with the image bearing member. The contact electrifying system (direct injection electrifying) using the charge accelerating particles has been disclosed in Japanese Patent Application Laid-open No. 10-307454, Japanese Patent Application Laid-open No. 10-307455, Japanese Patent Application Laid-open No. 10-307456, Japanese Patent Application Laid-open No. 10-307457, Japanese Patent Application Laid-open No. 10-307458, Japanese Patent Application Laid-open No. 10-307459, and so on. In this system, a d.c. voltage of −600 V is applied to the electrifying sponge roller by a power supply. For that reason, a portion of the image bearing member which is in contact with the electrifying sponge roller is going to have the same potential as the d.c. voltage. In this situation, if charges are injected from the electrifying sponge roller to the image bearing member over the energy barrier of the image bearing member surface, the image bearing member is electrified. On the other hand, in the case where the charges are again moved to the electrifying sponge roller from the image bearing member when the charges cannot go over the energy barrier or the electrifying sponge roller and the image bearing member are spaced apart from each other, the image bearing member is not electrified. This phenomenon largely depends on the energy barrier or the charge retaining capacity of the surface of the image bearing member, whereas if the phenomenon is considered as a competing reaction, the frequency of opportunities that the electrifying sponge roller comes in contact with the image bearing member becomes important.
In order to increase the frequency, it is effective to stick the charge accelerating particles onto the surface of the electrifying sponge roller to enhance the adhesion of the electrifying sponge roller with the image bearing member, and to reverse the rotating direction of the electrifying sponge roller with respect to the forward direction of the image bearing member (the contact surfaces of the image bearing member and the electrifying sponge roller move in opposite directions while being abrasively slid on each other) to incr
Akutsu Takashi
Batori Yoshiyuki
Morioka Masanari
Sasago Yoshikazu
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