Image forming apparatus

• US 20020159782A1
• Filed: 01/30/2002
• Published: 10/31/2002
• Est. Priority Date: 02/01/2001
• Status: Active Grant

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Suzuki, Jun, Sakaizawa, Katsuhiro, Shimura, Masaru, Tsuruya, Satoshi
• Granted Patent: US 6,603,935 B2
• Time in Patent Office: Days
• US Class Current: 399/50
• CPC Class Codes: G03G 15/0216 by bringing a charging member into contact with the member to be charged, e.g. roller, brush chargers
• CPC Class Codes: G03G 2221/0005 Cleaning of residual toner

Abstract

An object of the present invention is to provide an image forming apparatus in which when a first area to be an image forming area of the image bearing member exists in said nip portion, a superimposed voltage resulting from a direct current voltage and an alternating voltage having a peak to peak voltage smaller than an alternating voltage applied when a charging potential of the image bearing member is converged is applied to the charging member, and wherein when a part of a second area to be a non-image area of the image bearing member exists in said nip portion, a direct current voltage without an alternating voltage is applied to the charging member.

Claims

1. An image forming apparatus comprising:

an image bearing member;

a flexible charging member for forming a nip portion with said image bearing member and for charging said image bearing member, said nip portion being provided with a conductive particle; and

developing means for developing an electrostatic image formed on said image bearing member with a developer, said developing means being capable of conducting collection operation for collecting a remaining developer on said image bearing member;

wherein when a first area to be an image forming area of said image bearing member exists in said nip portion, a superimposed voltage resulting from a direct current voltage and an alternating voltage having a peak to peak voltage smaller than an alternating voltage applied when a charging potential of said image bearing member is converged is applied to said charging member, and

wherein when a part of a second area to be a non-image area of said image bearing member exists in said nip portion, a direct current voltage without an alternating voltage is applied to said charging member.

2. An image forming apparatus according to claim 1, wherein said charging member scrapes the developer on said image bearing member and expels the scraped developer to a downstream side in a moving direction of said image bearing member of said nip portion.

3. An image forming apparatus according to claim 1, wherein said charging member is provided with a foaming layer on a surface thereof.

4. An image forming apparatus according to claim 3, wherein said foaming layer carries said conductive particle.

5. An image forming apparatus according to claim 1, wherein said conductive particle has friction charging polarity that charges the developer with normal charging polarity.

6. An image forming apparatus according to claim 1, wherein said conductive particle has charging polarity opposite to charging polarity of said charging member.

7. An image forming apparatus according to claim 1 or 2, wherein said charging member can rotate in an opposite direction to a rotational direction of said image bearing member in said nip portion.

8. An image forming apparatus according to claim 1, wherein said charging member has a peripheral velocity different from that of said image bearing member.

9. An image forming apparatus according to claim 1, wherein the peak to peak voltage is 500 V or higher.

10. An image forming apparatus according to claim 1 or 2, wherein the peak to peak voltage is less than 1,200 V.

11. An image forming apparatus according to claim 1, wherein a particle diameter of said conductive particle is 0.1 to 3 μ

m.

12. An image forming apparatus according to claim 1, wherein said conductive particle is 10¹² Ω

·

cm or lower.

13. An image forming apparatus according to claim 1, wherein said developing means can conduct the collection operation for collecting the remaining developer on said image bearing member simultaneously with developing operation.

14. An image forming apparatus according to claim 1 or 13, wherein said apparatus comprises transferring means for transferring an image formed on said image bearing member to a transferring member, and the developer remaining on said image bearing member after transfer by said transferring means reaches said nip portion.

15. An image forming apparatus according to claim 1, wherein said image bearing member has electrostatic image forming means for forming the electrostatic image on said image bearing member charged by said charging member.

16. An image forming apparatus according to claim 15, wherein said image bearing member is a photosensitive body, and said electrostatic image forming means is exposing means for exposing said photosensitive body.

17. An image forming apparatus according to claim 1, wherein said developing means is provided with a developer carrying member for carrying the developer, and said developer carrying member is provided so as to contact said image bearing member.

18. An image forming apparatus according to claim 1, wherein the developer is externally added with said conductive particle, and when said second area where the direct current voltage without the alternating voltage is applied to said charging member passes through a developing area, an electric field is formed in a direction that said conductive particle is transferred to said image bearing member from said developing means.

19. An image forming apparatus according to claim 1, wherein the developer used by said developing means has a shape factor SF-1 of 100 to 150 and a shape factor SF-2 of 100 to 140.

20. An image forming apparatus according to claim 1, wherein said image bearing member and said charging member are provided in a process cartridge that is detachably attachable to a main body of said apparatus.

21. An image forming apparatus according to claim 1, wherein said charging member has a roller shape.