Image forming apparatus having transfer member rotating faster than image bearing member

• US 5,357,325 A
• Filed: 02/06/1991
• Issued: 10/18/1994
• Est. Priority Date: 01/30/1988
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Kawaguchi, Hideshi
• Primary Examiner(s): Moses, R. L.
• Assistant Examiner(s): BEATTY, ROBERT B
• Application Number:
  US07/652,222
• Time in Patent Office: 1,350 Days
• Field of Search: 355/271, 355/272, 355/274, 355/275, 355/277-281, 355/326, 355/327, 355/282, 355/285
• US Class Current: 399/313
• CPC Class Codes: G03G 15/167 at least one of the recording member or the transfer member being rotatable during the transfer

Abstract

An image forming apparatus having an image bearing member for carrying an image, a transfer member for urging a recording sheet against the image bearing member and transferring an image onto the recording sheet, a driving means for rotationally driving the image bearing member, and a driving force transmission means for transmitting a driving force from the driving means to the transfer member through the image bearing member. The transfer member is then rotated so that the peripheral speed of a portion of the transfer member which urges the sheet against the image bearing member is higher than the peripheral speed of the image bearing member. The image forming apparatus satisfies the following inequality: R_D W_D <R¹ W_T, where R_D is the radius of the image bearing member, R¹ is the minimum radius of the transfer member, W_D is the angular velocity of the image bearing member and W_T is the angular velocity of the transfer member.

Claims

1. An image forming apparatus comprising:

an image bearing member rotatably disposed;

a rotating member for biasing a sheet against said image bearing member, said rotating member transferring, at a nip portion between said image bearing member and said rotating member, an image on said image bearing member onto the sheet;

drive force transmitting means for transmitting a drive force from a drive means to said image bearing member;

a first gear provided on said image bearing member;

a second gear provided on said rotating member, said second gear engaging with said first gear and the drive force being transmitted from said first gear to said second gear;

a pair of rotary feeding members disposed downstream of said rotating member in the sheet moving direction, wherein the distance from a nip portion between said image bearing member and said rotating member to a nip portion between said pair of rotary feeding member is set shorter than the length of the sheet;

wherein upon image transfer, a peripheral speed of a nip portion of said rotating member is set larger than a peripheral speed of a nip portion of said image bearing member such that the image bearing member will receive a first force in a rotating direction thereof from said rotating member, said first gear receiving a second force in a direction opposite to the first force from said second gear when transferring the image;

wherein said image forming apparatus satisfies the following inequality;

R_D ω

_D <

R'"'"'ω

_T, where R_D is the radius of said image bearing member, R'"'"' is the minimum radius of said rotating member, ω

_D is the angular velocity of said image bearing member, and ω

_T is the angular velocity of said rotating member.

2. An image forming apparatus according to claim 1, wherein said image bearing member and rotating member are both rotated with a slipping movement therebetween.

3. An image forming apparatus according to claim 1, wherein said drive force transmitting means has a driving gear and a third gear provided on said image bearing member to engage with said driving gear and the drive force from said driving means is transmitted from said driving gear to said third gear.

4. An image forming apparatus according to claim 1, wherein said drive force transmitting means has a driving gear to engage with said first gear, the drive force from said driving means being transmitted from said driving gear to said first gear.

5. An image forming apparatus according to claim 1, wherein said rotating member has resiliency.

6. An image forming apparatus according to claim 1, wherein said image bearing member is a photosensitive member.

7. An image forming apparatus according to claim 1, wherein said image bearing member has a drum-like shape.

8. An image forming apparatus according to claim 1, wherein said image bearing member has a belt-like shape.

9. An image forming apparatus according to claim 1, wherein said rotating member has a belt-like shape.

10. An image bearing apparatus according to claim 1, wherein said rotating member has a roller-like shape.

11. An image forming apparatus according to claim 1, wherein said paired rotary feeding members fix the image, which is transferred onto the sheet, to the sheet.

12. An image forming apparatus according to claim 1, further including biasing means for biasing said rotating member against said image bearing member in a direction orthogonal to a linear line offset by a pressure angle between said first and second gears from a tangential line passing through the point where said image bearing member and rotating member are brought into contact each other.

13. An image forming apparatus according to claim 5, wherein said rotating member has a sponge layer.

14. An image forming apparatus according to claim 1, wherein the second force maintains said drive means and said drive force transmitting means in an engaged state.

15. An image forming apparatus according to claim 1, wherein voltage is biased between said image bearing member and rotating member for transferring.

16. An apparatus according to claim 12, wherein said biasing means is a spring.

17. An apparatus according to claim 3 or 4, wherein said first gear receives the second force from said second gear so as to maintain the engagement between said third gear and said drive gear.

18. An apparatus according to claim 1, wherein said second force is a force in a direction opposite to a rotational direction of said image bearing member.

19. An image forming apparatus according to claim 1, wherein said pair of rotary feeding members fix the image transferred onto the sheet.

20. An image forming apparatus according to claim 1, wherein said first gear comprises a plurality of first gear teeth and said second gear comprises a plurality of second gear teeth, and wherein a second force received by said first gear causes at least one of said plurality of first gear teeth to continuously engage at least one of said plurality of second gear teeth.

21. An image forming apparatus comprising:

an image bearing member rotatably disposed;

a rotating member for biasing a sheet against said image bearing member, said rotating member transferring, at a nip portion between said image bearing member and said rotating member, an image on said image bearing member onto the sheet;

drive force transmitting means for transmitting a drive force from a drive means to said image bearing member;

a first gear provided on said image bearing member;

a second gear provided on said rotating member, said second gear engaging with said first gear;

a pair of rotary feeding members disposed downstream of said rotating member in the sheet moving direction, wherein the distance from a nip portion between said image bearing member and said rotating member to a nip portion between said pair of rotary feeding members is shorter than the length of the sheet; and

biasing means for biasing said rotating member against said image bearing member in a direction orthogonal to a linear line offset by a pressure angle between said first and second gears from a tangential line passing through the point where said image bearing member and said rotating member are brought in to contact with each other;

wherein said image forming apparatus satisfies the following inequality;

R_D ω

_D <

R'"'"'ω

_T, where R_D is the radius of said image bearing member, R'"'"' is the minimum radius of said rotating member, ω

_D is the angular velocity of said image bearing member, and ω

_T is the angular velocity of said rotating member.

22. An apparatus according to claim 21, wherein a peripheral speed of said rotating member is larger than that of said image bearing member at said nip portion when transferring the image.

23. An apparatus according to claim 21, wherein said apparatus has a drive force transmitting means for transmitting the drive force from said driving means to said image bearing member.

24. An apparatus according to claim 23, wherein said drive force transmitting means has a driving gear and a third gear provided on said image bearing member to engage with said driving gear and the drive force from said driving means is transmitted from said driving gear to said third gear.

25. An apparatus according to claim 23, wherein said drive force transmitting means has a driving gear to engage with said first gear, the drive force from said driving means being transmitted from said driving gear to said first gear.

26. An apparatus according to claim 21, wherein said rotating member has resiliency.

27. An apparatus according to claim 21, wherein said image bearing member is a photosensitive member.

28. An apparatus according to claim 26, wherein said rotating member has resiliency.

29. An apparatus according to claim 21, wherein voltage is biased between said image bearing member and said rotating member for transferring said image.

30. An image forming apparatus according to claim 21, wherein said pair of rotary feeding members fix the image transferred onto the sheet.

31. An image forming apparatus according to claim 21, wherein said first gear comprises a plurality of first gear teeth, wherein said second gear comprises a plurality of second gear teeth, and wherein a second force received by said first gear causes at least one of said plurality of first gear teeth to continuously engage at least one of said plurality of second gear teeth.