Image forming apparatus

• US 20050196201A1
• Filed: 12/15/2004
• Published: 09/08/2005
• Est. Priority Date: 12/15/2003
• Status: Active Grant

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Moriya, Shuji, Hagiwara, Kazunari, Shimizu, Yasushi, Chigono, Yasunori, Osada, Hikaru, Okuda, Kouichi
• Granted Patent: US 7,239,831 B2
• Time in Patent Office: Days
• US Class Current: 399/270
• CPC Class Codes: G03G 15/065 Arrangements for controlling the potential of the developing electrode
• CPC Class Codes: G03G 2215/0617 contact development (i.e. the developer layer on the donor member contacts the latent image carrier)

Abstract

An image forming apparatus includes an image bearing member; charging means for electrically charging the image bearing member; a rotatable developer carrying member for carrying a developer to develop an electrostatic image formed on the image bearing member with the developer, the developer carrying member being supplied with a developing bias voltage comprising an AC voltage; non-rotatable magnetic field generating means, disposed inside the developer carrying member, for magnetically attracting the developer on the developer carrying member, wherein the developer carrying member has a surface elastic layer, and the developer carrying member is press-contacted to the image bearing member, and the developer is one component magnetic toner, and a maximum value of an absolute value of the developing bias voltage |V| max (V) and a surface potential of the image bearing member charge by the charging means is Vd global purposes V), satisfy,
|V|max≦|Vd|.

Claims

1. An image forming apparatus comprising:

an image bearing member;

charging means for electrically charging. said image bearing member;

a rotatable developer carrying member for carrying a developer to develop an electrostatic image formed on said image bearing member with the developer, said developer carrying member being supplied with a developing bias voltage comprising an AC voltage;

non-rotatable magnetic field generating means, disposed inside said developer carrying member, for magnetically attracting the developer on said developer carrying member,

wherein said developer carrying member has a surface elastic layer, and said developer carrying member is press-contacted to said image bearing member, and the developer is one component magnetic toner, and

a maximum value of an absolute value of the developing bias voltage |V| max (V) and a surface potential of the image bearing member charge by said charging means is Vd global purposes V), satisfy,

|V|max≦

|Vd|.

2. An apparatus according to claim 1, wherein |V|max≦

0.9≦

|Vd| is satisfied.

3. An apparatus according to claim 1, further comprising electrostatic image forming means for forming the electrostatic image on said image bearing member charged by said charging means, where in a potential of a low potential portion of the electrostatic image Vl (V), and a maximum value of the developing bias voltage Vmax (V), and a minimum value of the developing bias voltage Vmin (V) satisfy,

when Vl≦

0, Vmax≦

Vl; and

when Vl>

0, Vmin>

Vl.

4. An apparatus according to claim 1, further comprising transferring means for transferring the image of the developer formed on the image bearing member onto a transfer material.

5. An apparatus according to claim 1, wherein said developer carrying member develops the electrostatic image by a reverse development.

6. An apparatus according to claim 1, wherein said elastic layer has a microhardness of 40-98°

.

7. An apparatus according to claim 1, further comprising supplying means for supplying the developer onto said developer carrying member, and a developer amount regulating member for regulating an amount of the developer carried on said developer carrying member.

8. An apparatus according to claim 1, wherein said elastic layer has a hardness which is lower than that of a surface of said image bearing member.

9. An apparatus according to claim 1, wherein said developing bias voltage comprises an AC voltage component and a DC voltage opponent.

10. An apparatus according to claim 1, wherein said image bearing member, said developer carrying member and said magnetic field generating means are contained in a process cartridge detachably mountable to a main assembly of said image forming apparatus.

11. An apparatus according to any one of the preceding claims, wherein said developer carrying member effects a developing operation and simultaneously effects a developer collecting operation for collecting the developer remaining on said image bearing member.