Claims
- 1. An image forming apparatus, comprising:
- a movable image bearing member;
- image forming means for forming an image on said image bearing member;
- a charging member contactable with a transfer material at a transfer position to transfer the image from said image bearing member to the transfer material;
- voltage applying means for applying a voltage to said charging member, said voltage applying means applying a constant voltage between said charging member and said image bearing member when the transfer material is present at the transfer position, wherein said voltage applying means applies a constant current to said charging member during a time period in which the transfer material is absent from the transfer position;
- wherein the constant voltage is a sum of a voltage provided during application of the constant current and a predetermined voltage.
- 2. An apparatus according to claim 1, wherein said charging member and the transfer material have resistances which vary depending on ambient conditions.
- 3. An apparatus according to claim 2, wherein the ambient conditions include ambient humidity and ambient temperature.
- 4. An apparatus according to claim 1, wherein said image forming means includes charging means for charging said image bearing member, exposure means for exposing said image bearing member to light in accordance with image information, and means for forming a toner image by depositing toner to a latent image provided by said exposure means.
- 5. An apparatus according to claim 4, wherein the voltage provided during application of the constant current corresponds to a sum of a voltage across said charging member during application of the constant current and a voltage across said image bearing member not charged by said charging means during application of the constant current.
- 6. An apparatus according to claim 4, wherein the voltage provided during application of the constant current corresponds to a sum of a voltage across said charging member during application of the constant current, and a voltage across said image bearing member during application of the constant current.
- 7. An apparatus according to claim 4, wherein the application of the constant current is carried out before said image bearing member is charged by said charging means.
- 8. An apparatus according to claim 4 or 5, wherein the predetermined voltage corresponds to a sum of a potential difference between a potential of a toner image portion of said image bearing member and a potential of a toner image portion of said image bearing member relative to the charging member as the image bearing member approaches the transfer position during the constant current application, and a voltage across the transfer material in the case the constant current flowed through a transfer material having a maximum resistance.
- 9. An apparatus according to claim 8, wherein the transfer material having the maximum resistance is a transfer material left in a low temperature and low humidity condition.
- 10. An apparatus according to claim 7, wherein the voltage provided during the application of the constant current corresponds to a sum of a voltage across said charging member and a voltage across said image bearing member during application of the constant current.
- 11. An apparatus according to claim 8, wherein the maximum resistance transfer material is an OHP transparent sheet kept under 15.degree. C. and 10% of relative humidity.
- 12. An apparatus according to claim 8, wherein the maximum resistance transfer material is plain paper kept under 15.degree. C. and 10% of relative humidity.
- 13. An apparatus according to claim 8, wherein the potential of said image bearing member relative to the charging member as said image bearing member approaches the transfer position during the constant current application is substantially 0.
- 14. An apparatus according to claim 1, wherein said charging member is contacted to said image bearing member.
- 15. An apparatus according to claim 1, wherein said transfer position is a position where said image bearing member and said charging member are faced to each other.
- 16. An apparatus according to claim 1, wherein the application of the constant current is carried out before image transfer.
- 17. An apparatus according to claim 1, wherein said charging member is in the form of a roller.
- 18. An apparatus according to claim 1, wherein said charging member includes EPDM layer.
- 19. An apparatus according to claim 1, wherein the voltage provided during the constant current application corresponds to a sum of a voltage applied to said charging member during the constant current application and a voltage applied to said image bearing member during the constant current application.
- 20. An apparatus according to claim 1, wherein said predetermined voltage is constant independently of the voltage provided during application of the constant current.
- 21. An image forming apparatus comprising,
- a movable image bearing member;
- image forming means for forming an image on said image bearing member, said image forming means including charging means for charging said image bearing member, exposure means for exposing said image bearing member to light in accordance with an image signal, and means for forming a toner image by depositing toner to a latent image provided by said exposure means;
- a charging member contactable with a transfer material at a transfer position to transfer the image from said image bearing member to the transfer material;
- voltage applying means for applying a voltage to said charging member, said voltage applying means applying a constant voltage between said charging member and said image bearing member when the transfer material is present at the transfer position, wherein said voltage applying means applies a constant current to said charging member during a time period in which the transfer material is absent from the transfer position;
- wherein the constant voltage is a sum of a voltage provided during the application of the constant current and a predetermined voltage, wherein the predetermined voltage corresponds to a sum of a potential difference between a potential of the toner image portion of said image bearing member and a potential of said image bearing member relative to the charging member as the image bearing member approaches the transfer position during the constant current application, and a voltage across the transfer material in the case where constant current flows through a transfer material having a maximum resistance.
- 22. An image forming apparatus, comprising:
- a movable image bearing member;
- image forming means for forming an image on said image bearing member, said image forming means including charging means for charging said image bearing member, exposure means for exposing said image bearing member to light in accordance with an image signal, and means for forming a toner image by depositing toner to a latent image provided by said exposure means;
- a charging member contactable with a transfer material at a transfer position to transfer the image from said image bearing member to the transfer material;
- voltage applying means for applying a voltage to said charging member, said voltage applying means applying a constant voltage between said charging member and said image bearing member when the transfer material is present at the transfer position, wherein said voltage applying means applies a constant current to said charging member during a time period in which the transfer material is absent from the transfer position;
- wherein the constant voltage is a sum of a voltage provided during the application of the constant current and a predetermined voltage, wherein the predetermined voltage corresponds to a sum of a potential difference between a potential for the toner image portion of said image bearing member and a potential of said image bearing member relative to the charging member as the image bearing member approaches the transfer position during the constant current application, and a voltage across the transfer material in the case the constant current flows through the transfer material which is in the form of an OHP transparent sheet and which is left under 15.degree. C. and 10% relative humidity.
- 23. An image forming apparatus, comprising:
- a movable image bearing member;
- image forming means for forming an image on said image bearing member, said image forming means including charging means for charging said image bearing member, exposure means for exposing said image bearing member to light in accordance with an image signal, and means for forming a toner image by depositing toner to a latent image provided by said exposure means;
- a charging member contactable with a transfer material at a transfer position to transfer the image from said image bearing member to the transfer material;
- voltage applying means for applying a voltage to said charging member, said voltage applying means applying a constant voltage between said charging member and said image bearing member when the transfer material is present at the transfer position, wherein said voltage applying means applies a constant current to said charging member during a time period in which the transfer material is absent from the transfer position;
- wherein the constant voltage is a sum of a voltage provided during application of the constant current and a predetermined voltage, wherein the predetermined voltage corresponds to a sum of a potential difference between a potential of the toner image portion of said image bearing member and a potential of said image bearing member relative to the charging member as the image bearing member approaches the transfer position during the constant current application, and a voltage across the transfer material in the case the constant current flows through the transfer material which is in the form of plain paper and which is left under 15.degree. C. and 10% relative humidity.
- 24. An apparatus according to claim 21, 22 or 23, wherein the potential of said image bearing member relative to the charging member as said image bearing member approaches the transfer position during the constant current application is substantially 0.
- 25. An image forming apparatus, comprising:
- a movable image bearing member;
- image forming means for forming a toner image on said image bearing member;
- a charging member contactable with a transfer material at a transfer position to transfer the image from said image bearing member to the transfer material;
- power supply means for supplying a voltage to said charging member while the transfer material is present at the transfer position;
- determining means for determining the voltage to be applied to said charging member as a function of a voltage which is produced when a voltage is applied to said charging member without the transfer material at the transfer position, wherein said function includes adding a variable value based on a change of electric resistance of said charging member and a constant value which is constant regardless of change of the resistance of the transfer material.
- 26. An apparatus according to claim 25, wherein the voltage produced is a voltage produced between said charging member and said image bearing member when the constant current is supplied to said charging member.
- 27. An apparatus according to claim 25, wherein the voltage applied between said charging member and said image bearing member during the transfer operation corresponds to a sum of the produced voltage and the constant value.
- 28. An apparatus according to claim 27, wherein the voltage produced is a voltage produced between said charging member and said image bearing member when the constant current is supplied to said charging member.
- 29. An apparatus according to claim 28, wherein the constant value corresponds to a sum of a potential difference between a potential of a toner image portion of said image bearing member and a potential of a toner image portion of said image bearing member relative to the charging member as said image bearing member approaches the transfer position during the constant current application, and a voltage across the transfer material in the case the constant current flowed through a transfer material having a maximum resistance.
- 30. An apparatus according to claim 28, wherein the potential of the toner image portion of said image bearing member relative to the charging member as the image bearing member approaches the transfer position during the constant current application is substantially 0.
- 31. An apparatus according to claim 29, wherein the maximum resistance transfer material is plain paper kept under 15.degree. C. and 10% of relative humidity.
- 32. An apparatus according to claim 29, wherein the maximum resistance material is an OHP transparent sheet kept under 15.degree. C. and 10% of relative humidity.
- 33. An apparatus according to claim 18, wherein the constant value is constant independently of the voltage produced.
- 34. An apparatus according to claim 18, wherein said charging member is contacted to said image bearing member.
Priority Claims (1)
Number |
Date |
Country |
Kind |
1-296289 |
Nov 1989 |
JPX |
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Parent Case Info
This application is a continuation of application Ser. No. 07/613,006 filed Nov. 15, 1990, now abandoned.
US Referenced Citations (9)
Foreign Referenced Citations (6)
Number |
Date |
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0323226 |
Jul 1989 |
EPX |
0338546 |
Oct 1989 |
EPX |
0367245 |
May 1990 |
EPX |
59-012469 |
Jan 1984 |
JPX |
61-014671 |
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0123385 |
May 1990 |
JPX |
Continuations (1)
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Number |
Date |
Country |
Parent |
613006 |
Nov 1990 |
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