Image forming apparatus

• US 20020006289A1
• Filed: 04/27/2001
• Published: 01/17/2002
• Est. Priority Date: 04/28/2000
• Status: Active Grant

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Saito, Seiji, Shimura, Masaru, Nakamori, Tomohiro, Takami, Hiroshi
• Granted Patent: US 6,564,023 B2
• Time in Patent Office: Days
• US Class Current: 399/50
• CPC Class Codes: G03G 15/0266 Arrangements for controlling the amount of charge
• CPC Class Codes: G03G 2215/021 by contact, friction or induction

Abstract

An image forming apparatus includes an image bearing member; a charge member for electrically charging the image bearing member while contacting to the image bearing member: voltage applying means for applying an oscillating voltage including a component of AC voltage to the charge member; first detecting means for detecting an average of the AC current applied to the charge member from the voltage applying means; second detecting means for detection a value of the AC current corresponding to a peak of the AC voltage; and control means for effecting control such that when a detected current value of the detecting means is smaller than a first predetermined value, the detected current value of the first detecting means is at the first predetermined value, and when the detected current value of the first detecting means is larger than the first predetermined value, a current value of the second detecting means is at a second predetermined value.

Claims

1. An image forming apparatus comprising:

an image bearing member;

a charge member for electrically charging said image bearing member while contacting to said image bearing member;

voltage applying means for applying an oscillating voltage including a component of AC voltage to said charge member;

first detecting means for detecting an average of the AC current applied to said charge member from said voltage applying means;

second detecting means for detection a value of the AC current corresponding to a peak of the AC voltage; and

control means for effecting control such that when a detected current value of said detecting means is smaller than a first predetermined value, the detected current value of said first detecting means is at the first predetermined value, and when the detected current value of said first detecting means is larger than the first predetermined value, a current value of said second detecting means is at a second predetermined value.

2. An apparatus according to claim 1, wherein said first detecting means detects an average of a half wave current of the AC current.

3. An apparatus according to claim 1, further comprising phase detecting means for detecting a phase of the AC voltage.

4. An apparatus according to claim 3, wherein said first detecting means detects an average of the AC current in a predetermined phase range on the basis of an output of said phase detecting means.

5. An apparatus according to claim 3, wherein said second detecting means detects a value of the AC current based on an output of said phase detecting means.

6. An apparatus according to claim 1, wherein the AC voltage is a sine wave AC voltage.

7. Apparatus according to claim 1, wherein said first detecting means and said second detecting means detects currents having different polarities, respectively.

8. An apparatus according to claim 1, wherein said voltage applying means applies to said charge member a DC voltage superimposed with said AC voltage.

9. Apparatus according to claim 1, further comprising a process cartridge detachably mountable to the main assembly of said apparatus, said process cartridge containing said image bearing member and said charge member as a unit.

10. An image forming apparatus comprising:

an image bearing member;

a charge member for electrically charging said image bearing member while contacting to said image bearing member;

voltage applying means for applying an oscillating voltage including a component of AC voltage to said charge member;

detecting means for detecting an average of an AC current supplied to charge member from said voltage applying means in a voltage range wherein an absolute value of the AC voltage is not less than a predetermined value; and

control means for effecting control such that average detected current value of said detecting means is at a predetermined value.

11. An apparatus according to claim 10, wherein said voltage range includes a peak of the AC voltage and a neighborhood thereof.

12. An apparatus according to claim 10, further comprising resistance current detecting means for detecting a resistance load current component of an average detected current of said detecting means, wherein said control means switches the predetermined value in accordance with a detected value of said resistance current detecting means.

13. Apparatus according to claim 10, wherein the AC voltage is a sine wave AC voltage.

14. An apparatus according to claim 10, wherein said voltage applying means applies to said charge member a DC voltage superimposed with said AC voltage.

15. An apparatus according to claim 10, further comprising a process cartridge detachably mountable to the main assembly of said apparatus, said process cartridge containing said image bearing member and said charge member as a unit.