Detachable developing device for providing first and second voltages for an image forming apparatus

• US 5,761,589 A
• Filed: 03/06/1996
• Issued: 06/02/1998
• Est. Priority Date: 03/06/1995
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Ota, Toshihiro, Awata, Tokio, Murakami, Satoshi, Kido, Eiichi, Wakada, Shigeyuki, Yui, Yuhi
• Primary Examiner(s): Lee, Shuk
• Application Number:
  US08/610,549
• Time in Patent Office: 818 Days
• Field of Search: 399/222, 399/260, 399/258, 399/265, 399/273, 399/274, 399/279, 399/283, 399/284, 399/252, 399/285
• US Class Current: 399/284
• CPC Class Codes: G03G 15/0812 characterised by the developer regulating means, e.g. structure of doctor blade
• CPC Class Codes: G03G 2215/0866 Metering member

Abstract

A developing device attachable to and detachable from a printer using a non-magnetic monocomponent developer. Two different voltages are applied respectively to a developing roller and a toner layer thickness regulating device from a power source of the apparatus main body side through a terminal and a contacting spring. A voltage is applied directly to the developing roller from the contacting spring whereas a Zener diode is provided in a path connecting the contacting spring and toner layer thickness regulating device to apply another voltage to the toner layer thickness regulating device. The voltage applied to the toner layer thickness regulating device is dropped below the power supply voltage by the Zener voltage when a low-printing-ratio image is produced. Thus, the number of the terminals connecting the apparatus main body and developing device is reduced to one. Accordingly, defective connections at the contacting portions of the terminal can be prevented and the manufacturing costs can be reduced while a satisfactory image is produced.

Claims

1. A developing device, employed in an image forming apparatus, for developing a static latent image formed on a photosensitive body, the developing device comprising:

a developer carrying body for holding a developer layer on a surface thereof and for transporting a developer by physical contact with said photosensitive body, a first voltage which is constant being supplied to said developer carrying body from a power source of an image forming apparatus main body;

a conductive developer layer thickness regulating member, connected to said power source, for regulating said developer layer to a constant thickness by physical contact with said developer carrying body; and

a constant voltage element, provided in a path connecting said power source and said conductive developer layer thickness regulating member, for applying a second voltage which is constant to said conductive developer layer thickness regulating member, said constant voltage element generating a third voltage which is constant using a current generated in response to a balance between a surface potential of said photosensitive body and a potential of said power source, said second voltage being different from said first voltage.

2. The developing device as defined in claim 1, wherein said constant voltage element is a Zener diode.

3. The developing device as defined in claim 1, wherein the third voltage generated by said constant voltage element has an upper limit to keep a potential of a surface of said developer layer on said developer carrying body lower than a surface potential which said photosensitive body had when a developing process started.

4. The developing device as defined in claim 1, wherein a transporting speed of said developer carrying body is not high enough to fuse the developer onto said conductive developer layer thickness regulating member, but is greater higher than a speed at which a surface of said photosensitive body moves when developing the static latent image.

5. The developing device as defined in claim 1, wherein an absolute value of the surface potential of said photosensitive body is set greater than an absolute value of a potential of said developer carrying body by 100V-500V.

6. The developing device as defined in claim 1, wherein said photosensitive body is charged to a polarity reversed with respect to a polarity of said developer as a result of triboelectric charging.

7. The developing device as defined in claim 1, wherein said developer is a non-magnetic monocomponent developer.

8. The developing device as defined in claim 1, wherein the developing device is a reversal development type device for attracting a negatively charged developer to an exposed portion of a surface of said photosensitive body,

said constant voltage element generating the third voltage using a current flowing from the surface of said photosensitive body to said power source.

9. The developing device as defined in claim 1, wherein the developing device is a normal development type device for attracting positively charged developer to a non-exposed portion of a surface of said photosensitive body,

said constant voltage element generating the third voltage using a current flowing from the surface of said photosensitive body to said power source.

10. The developing device as defined in claim 1, wherein said constant voltage element generates a voltage ranging from 10V to 500V.

11. The developing device as defined in claim 7, wherein a primary resin of said non-magnetic monocomponent developer is one of a styrene-acrylic copolymer and a polyester resin.

12. The developing device as defined in claim 1, wherein said developer carrying body is a developing roller, a peripheral speed of said developing roller being increased by a factor of 1.1 to 2.0 with respect to a speed at which a surface of said photosensitive body moves when developing the static latent image.

13. The developing device as defined in claim 1, wherein said developer carrying body is made of a conductive, resilient rubber material.

14. The developing device as defined in claim 13, wherein said developer carrying body has a resistance value in a range between 10⁶ Ω

and 10⁸ Ω

.

15. The developing device as defined in claim 13, wherein said developer carrying body has a hardness in a range between 50°

and 90°

in ASKER C.

16. The developing device as defined in claim 1, wherein said conductive developer layer thickness regulating member is made of one of aluminium or iron.

17. The developing device as defined in claim 1, wherein said conductive developer layer thickness regulating member is made of a conductive resin.

18. The developing device as defined in claim 1, further comprising a spring for pressing said conductive developer layer thickness regulating member against said developer carrying body at a predetermined pressure.

19. The developing device as defined in claim 18, wherein said predetermined pressure is in a range between 500 gf and 2000 gf.

20. The developing device as defined in claim 1, wherein said path connecting said power source and said conductive developer layer thickness regulating member is a voltage applying line for said conductive developer layer thickness regulating member, said voltage applying line being embedded in a frame of the developing device.

21. The developing device as defined in claim 1, wherein said photosensitive body includes an organic photoconductive film having a primary resin which is polycarbonate.

22. The developing device as defined in claim 1, wherein said photosensitive body is a cylindrical photosensitive drum.

23. The developing device as defined in claim 1, further comprising a developer supplying member for transporting and supplying the developer to said developer carrying body.

24. The developing device as defined in claim 23, wherein said developer supplying member is a developer supplying roller, said developer supplying roller being provided around said developer carrying body to rotate without having any physical contact with said developer carrying body.

25. The developing device as defined in claim 24, wherein said developer supplying roller is a regular polyprism, a polygonal face of said regular polyprism having five to eight sides.

26. The developing device as defined in claim 23 further including a developer stirring roller for stirring the developer to transport the developer to said developer supplying member.

27. The developing device as defined in claim 24, wherein said developer carrying body is a developing roller, a rotational axis of said developing roller and a rotational axis of said developer supplying roller being parallel to each other.

28. The developing device as defined in claim 27, further comprising a developer applying member, provided around a side surface of said developing roller, for pressing the developer transported from said developer supplying roller against said developing roller, said developer applying member having a circular arc convex surface opposing said side surface, said developer applying member having an end portion touching a side surface of said developer supplying roller for scraping off the developer adhering to said developer supplying roller.

29. The developing device as defined in claim 28, further comprising a developer stirring roller for stirring the developer to transport the developer to said developer supplying roller, wherein said developing applying member is provided with a through hole, extra developer scraped off by said conductive developer layer thickness regulating member being returned to said developer stirring roller through said through hole.

30. A developing device, employed in an image forming apparatus, for developing a static latent image formed on a photosensitive body, the developing device comprising:

a developer carrying body for holding a developer layer on a surface thereof and for transporting a developer by physical contact with said photosensitive body, a first voltage which is constant being supplied to said developer carrying body from a power source of an image forming apparatus main body;

a conductive developer layer thickness regulating member, connected to said power source, for regulating said developer layer to a constant thickness by physical contact with said developer carrying body; and

a potential difference generating element, provided in a path connecting said power source and said conductive developer layer thickness regulating member, for applying a second voltage which is constant to said conductive developer layer thickness regulating member by generating a potential difference between said power source and said conductive developer layer thickness regulating member using a current generated in response to a difference between a surface potential of said photosensitive body and a potential of said power source, said second voltage being different from said first voltage.

31. The developing device as defined in claim 30, wherein said potential difference generating element is a resistor.

32. The developing device as defined in claim 30, wherein said potential difference generating element is a varistor.

33. A developing device, employed in an image forming apparatus, for developing a static latent image formed on a photosensitive body, the developing device comprising:

a developer carrying body for holding a developer layer on a surface thereof and for transporting a developer by physical contact with said photosensitive body, a first voltage which is constant being supplied to said developer carrying body from a power source of an image forming apparatus main body;

a conductive developer layer thickness regulating member, connected to said power source, for regulating said developer layer to a constant thickness by physical contact with said developer carrying body; and

a constant voltage element, provided in a path connecting said power source and said conductive developer layer thickness regulating member, for applying a second voltage which is constant to said conductive developer layer thickness regulating member, said constant voltage element generating a third voltage which is constant using a current running between said power source and said conductive developer layer thickness regulating member, said second voltage being different from said first voltage,

the developing device being attachable to and detachable from said image forming apparatus main body,

the developing device being electrically connected to said power source of said image forming apparatus main body through a single junction terminal when attached to said image forming apparatus main body,

said single junction terminal being composed of one terminal portion formed in a frame of the developing device and another terminal portion formed on said image forming apparatus main body, said one terminal portion and said another terminal portion being separable.

34. A method of developing a static latent image on a photosensitive body of a developing device in an image forming apparatus comprising the steps of:

applying a developer layer on a surface of a developer carrying body;

applying a first voltage which is constant from a power source of the image forming apparatus to the developer carrying body;

regulating a thickness of the developer layer on the surface of the developer carrying body with a regulating member;

applying a second voltage which is constant to the regulating member, the second voltage being provided by a constant voltage element provided in a path between the regulating member and the power source,

the constant voltage element generating a third voltage which is constant using a current generated in response to a balance between a surface potential of the photosensitive body and a potential of the power source, the second voltage being different than the first voltage; and

contacting the developer carrying body with the photosensitive body to transport the developer from the developer carrying body to the photosensitive body.

35. A method of developing a static latent image on a photosensitive body of a developing device in an image forming apparatus comprising the steps of:

applying a developer layer on a surface of a developer carrying body;

applying a first voltage which is constant from a power source of the image forming apparatus to the developer carrying body;

regulating a thickness of the developer layer on the surface of the developer carrying body with a regulating member;

applying a second voltage which is constant to the regulating member, the second voltage being provided by a potential difference generating element provided in a path between the regulating member and the power source,

the potential difference generating element generating a potential difference between the power source and the regulating member using a current generated in response to a difference between a surface potential of the photosensitive body and a potential of the power source, the second voltage being different than the first voltage; and

contacting the developer carrying body with the photosensitive body to transport the developer from the developer carrying body to the photosensitive body.