Electrophotography – Image formation – Photoconductive member
Reexamination Certificate
2001-12-06
2003-10-28
Lee, Susan S. Y. (Department: 2852)
Electrophotography
Image formation
Photoconductive member
C399S050000, C399S149000, C399S175000
Reexamination Certificate
active
06640072
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus that has a charging member for contacting an image bearing member to charge it, in which a peripheral velocity difference is formed between the image bearing member and the charging member.
2. Related Background Art
a) Transfer-type Image Forming Apparatus
A transfer-type image forming apparatus is an apparatus with a system and configuration for causing a first image bearing member such as an electrophotographic photosensitive member and an electrostatic recording dielectric to form and bear a transferable image in an appropriate image forming process such as an electrophotographic process and an electrostatic recording process and to transfer the transferable image to a second image bearing member and repeatedly using the first image bearing member for image formation.
For example, an image forming apparatus such as a copying machine/laser beam printer utilizing a transfer electrophotographic process basically has an electrophotographic photosensitive member as a first image bearing member, which is generally a rotary drum type, charging means for uniformly charging the surface of the rotary photosensitive member in predetermined polarity and potential, image exposing means for forming an electrostatic latent image (electronic latent image) on a charging processing surface of the rotary photosensitive member, developing means for developing the electrostatic latent image as a toner image, transferring means for transferring the toner image from the surface of the photosensitive member to transfer paper as a second image bearing member, fixing means for fixing the toner image transferred to the transfer paper side as a permanently fixed image and photosensitive member cleaning means (cleaner) for removing transfer residual toner from the surface of the rotary photosensitive member, from which the toner image has been transferred to the transfer paper side, to clean the surface of the photosensitive member.
The transfer paper that was subjected to an image fixing processing by the fixing means is discharged as a product on which an image is formed (copy, print). The surface of the photosensitive member cleaned by the cleaning means serves image formation repeatedly.
b) Contact Charging Means
As charging means for uniformly charging a surface of a photosensitive member in predetermined polarity and potential, a corona charger has been conventionally used.
The corona charger is disposed non-contactingly opposing a charged member and exposes the surface of the charged member to a corona shower discharged from the corona charger, to which a high pressure is applied, to charge the surface in predetermined polarity and potential.
Instead, a contact electrifying apparatus has been put to practical use in recent years. This causes a conductive charging member of a roller type (charging roller), a fur brush type, a magnetic brush type, a blade type and the like to contact a photosensitive member as a charged member and applies a predetermined charging bias to it to charge the surface of the photosensitive member in predetermined polarity and potential. The contact electrifying apparatus has advantages in terms of low ozone, low electric power and the like compared with the corona charger.
As a method of applying a charging bias to a contact charging member, there are a DC bias method for applying only a direct current bias and an AC bias method for superimposing a direct current bias on an alternating current bias to apply the superimposed bias.
Two types of charging systems, namely a corona charging system and a contact injection charging system (direct charging system) are mixed in a charging mechanism (mechanism of charging, charging principle) of contact charging. Respective properties emerge depending on which one is more predominant.
The corona charging system is a system for using a discharge phenomenon such as the corona discharge that occurs in a microscopic gap between a contact charging member and a charged member to charge the charged member with a product of discharge. This corona charging system produces a small amount of ozone although it is significantly less than that in the case of the corona charger.
The contact injection charging system is a system in which a charge is directly injected in a charged member from a contact charging member, whereby the surface of the charged member is charged. This is also called direct charging or injection charging.
In U.S. Pat. No. 5,809,379 and the like, there is proposed a method of injecting a charge via a charging roller, a charging brush, a magnetic brush formed of conductive magnetic particles, or a contact charging member or the like of conductive particulates or the like carried on a roller to perform the contact injection charging.
Since the contact injection charging does not use the discharge phenomenon, a voltage required for charging is equivalent to only a desired surface potential of a photosensitive member and does not produce ozone. Thus, it is an ozoneless and low power charging method.
Since the contact injection charging does not use the discharge phenomenon in a microscopic gap, its charging capability and charging uniformity largely depend on a probability of contact between a surface of a photosensitive member and a charging member. It is a general practice to give a velocity difference between the surface of the photosensitive member and the contact charging member in order to increase this probability of contact.
c) Cleanerless (Cleanerless Process, Toner Recycle Process)
For the transfer-type image forming apparatus, there is proposed a method of causing an electrifying apparatus or a developing apparatus to perform cleaning (removal) of residual toner after transfer (transfer residual toner) on a photosensitive member without specifically providing a special purpose cleaner for compactness of the apparatus, reduction of costs, ecology and the like (cleaning simultaneous with charging or cleaning simultaneous with development).
That is, in a general transfer-type image forming apparatus, transfer residual toner remaining on a photosensitive member after transfer is removed from the surface of the photosensitive member by a special purpose cleaner to be waste toner. However, it is preferable from the viewpoint of maintenance or ecology that the waste toner is not produced.
Thus, there has been developed a cleanerless image forming apparatus with a configuration in which a cleaner is eliminated and a transfer residual toner on a photosensitive member after transfer is removed from the surface of the photosensitive member through the cleaning simultaneous with development by a developing apparatus and collected in the developing apparatus for reusing. That is, the developing apparatus also works as a cleaner for collecting transfer residual toner remaining on the photosensitive member after a toner image is transferred to a transferring material.
The cleaning simultaneous with development is a method of collecting toner remaining on a photosensitive member after transfer by a fog removing bias (a fog removing potential difference V
back
that is a potential difference between a direct current voltage to be applied to a developing apparatus and a surface potential of the photosensitive member) at the time of development in the next and subsequent processes. According to this method, since the transfer residual toner is collected in the developing apparatus and reused in the next and subsequent processes, waste toner is not discharged. In addition, since it is cleanerless, there is a significant advantage in terms of space and compactness, reduction of costs and the like of an image forming apparatus can be realized.
d) Contact Charging, Transfer and Cleanerless Image Forming Apparatus
In a transfer and cleanerless image forming apparatus, if a contact electrifying apparatus is adopted as charging means of a photosensitive member as an image bearing member, a positive ghost due to poor collection of
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Lee Susan S. Y.
LandOfFree
Image forming apparatus including an image bearing member... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Image forming apparatus including an image bearing member..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Image forming apparatus including an image bearing member... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3122291