IMAGE FORMING APPARATUS

• US 20170277068A1
• Filed: 03/17/2017
• Published: 09/28/2017
• Est. Priority Date: 03/22/2016
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Naito, Norihito, Shindo, Go, Mochizuki, Masataka
• Granted Patent: US 10,599,063 B2
• Time in Patent Office: Days
• CPC Class Codes: G03G 15/0266 Arrangements for controlling the amount of charge
• CPC Class Codes: G03G 15/065 Arrangements for controlling the potential of the developing electrode
• CPC Class Codes: G03G 15/0815 characterised by the developer handling means after the developing zone and before the supply, e.g. developer recovering roller
• CPC Class Codes: G03G 15/0856 Detection or control means for the developer level
• CPC Class Codes: G03G 15/0898 for preventing toner scattering during operation, e.g. seals sealing the donor member G03G15/0817; sealing the magnetic brush G03G15/0942
• CPC Class Codes: G03G 15/5008 Driving control for rotary photosensitive medium, e.g. speed control, stop position control
• CPC Class Codes: G03G 15/5037 the characteristics being an electrical parameter, e.g. voltage

Abstract

When, in a state where a developer borne by a developer bearing member is sandwiched by an opposing portion of an image bearing member and the developer bearing member, C denotes capacitance between the image bearing member and the developer bearing member, ΔV denotes a development contrast, Q/S denotes a charge amount per unit area of the developer borne by the developer bearing member, and Δv denotes a peripheral velocity ratio which is a ratio of a peripheral velocity of the developer bearing member to a peripheral velocity of the image bearing member, a first peripheral velocity ratio is set so that |Q/S×Δv|≦|C×ΔV| is satisfied, and a second peripheral velocity ratio which is larger than the first peripheral velocity ratio is set so that |Q/S×Δv|>|C×ΔV| is satisfied.

Claims

1. An image forming apparatus, comprising:

an image bearing member;

a developer bearing member configured to perform a development operation in which an electrostatic image formed on the image bearing member is developed with a developer;

driving means configured to rotationally drive the image bearing member and the developer bearing member respectively so that the peripheral velocities of each is variable individually;

latent image forming means configured to form an electrostatic image on the image bearing member by forming a light-part potential and a dark-part potential on the image bearing member; and

applying means configured to apply a developing bias to the developer bearing member, wherein

when a peripheral velocity ratio is defined as a ratio of the peripheral velocity of the developer bearing member to the peripheral velocity of the image bearing member, the driving means is configured to be capable of driving the image bearing member and the developer bearing member at a first peripheral velocity ratio and a second peripheral velocity ratio which is larger than the first peripheral velocity ratio, and when

C denotes capacitance between the image bearing member and the developer bearing member in a state that the developer is sandwiched between the image bearing member and the developer bearing member while the developer is supplied to the image bearing member from the developer bearing member,

Δ

V denotes a development contrast which is a potential difference between the light-part potential and the developing bias,

Q/S denotes a charge amount per unit area of the developer borne by the developer bearing member, and

Δ

v denotes the peripheral velocity ratio,

the first peripheral velocity ratio is set so that a relationship expressed by |Q/S×

Δ

v|≦

|C×

Δ

V| is satisfied, and

the second peripheral velocity ratio is set so that a relationship expressed by |Q/S×

Δ

v|>

|C×

Δ

V| is satisfied.

2. The image forming apparatus according to claim 1, wherein the first peripheral velocity ratio and the second peripheral velocity ratio are set so that an amount of the developer remaining on the developer bearing member after the development operation in a case where the development operation is performed at the second peripheral velocity ratio is larger than that in a case where the development operation is performed at the first peripheral velocity ratio.

3. The image forming apparatus according to claim 1, further comprising

detecting means configured to detect temperature and humidity, wherein

when a temperature detected by the detecting means is equal to or lower than a prescribed temperature and a humidity detected by the detecting means is equal to or lower than a prescribed humidity, the latent image forming means changes the light-part potential or the applying means changes a magnitude of the developing bias to be applied so that a second development contrast which is smaller than a first development contrast is formed.

4. The image forming apparatus according to claim 3, wherein when a temperature detected by the detecting means is equal to or higher than a prescribed temperature and a humidity detected by the detecting means is equal to or higher than a prescribed humidity, the latent image forming means changes the light-part potential so that a third development contrast which is larger than the first development contrast is formed.

5. The image forming apparatus according to claim 1, wherein the latent image forming means includes:

charging means configured to charge the image bearing member to form the dark-part potential on the image bearing member, and

exposing means configured to expose the charged image bearing member to form the light-part potential on the image bearing member,

wherein the light-part potential is changed by changing an amount of light for exposure by the exposing means.

6. The image forming apparatus according to claim 1, wherein the driving means is configured to rotate the image bearing member and the developer bearing member so that the image bearing member and the developer bearing member move in a same direction at an opposing portion where the image bearing member and the developer bearing member oppose each other.

7. The image forming apparatus according to claim 1, wherein

the driving means is configured to:

set the peripheral velocity of the image bearing member in the case of the first peripheral velocity ratio same as that in the case of the second peripheral velocity ratio; and

set the peripheral velocity of the developer bearing member higher in the case of the second peripheral velocity ratio than that in the case of the first peripheral velocity ratio.

8. The image forming apparatus according to claim 1, wherein

the driving means is configured to:

set the peripheral velocity of the developer bearing member in the case of the first peripheral velocity ratio same as that in the case of the second peripheral velocity ratio; and

set the peripheral velocity of the image bearing member lower in the case of the second peripheral velocity ratio than that in the case of the first peripheral velocity ratio.

9. The image forming apparatus according to claim 1, wherein

the driving means is configured to make the second peripheral velocity ratio larger than the first peripheral velocity ratio by:

setting the peripheral velocity of the developer bearing member lower in the case of the second peripheral velocity ratio than that in the case of the first peripheral velocity ratio;

setting the peripheral velocity of the image bearing member lower in the case of the second peripheral velocity ratio than that in the case of the first peripheral velocity ratio;

wherein an amount of reduction of the peripheral velocity of the developer bearing member is different from an amount of reduction of the peripheral velocity of the image bearing member.

10. The image forming apparatus according to claim 1, wherein the first peripheral velocity ratio and the second peripheral velocity ratio are set so that an image can be formed at the second peripheral velocity ratio on a recording material longer than the one on which an image is formed at the first peripheral velocity ratio.

11. The image forming apparatus according to claim 1, wherein the first peripheral velocity ratio and the second peripheral velocity ratio are set so that a laid-on level of the developer per unit area of an image formed on a recording material in a case of the second peripheral velocity ratio is higher than that in a case of the first peripheral velocity ratio.

12. The image forming apparatus according to claim 1, further comprising:

a supplying member configured to supply a developer to the developer bearing member;

a developing chamber in which the supplying member is arranged;

a housing chamber configured to communicate with the developing chamber and house the developer; and

a conveying member arranged in the housing chamber and configured to convey the developer toward the developing chamber, wherein

a communication port through which the developing chamber and the housing chamber communicate is positioned above the conveying member in the housing chamber.

13. An image forming apparatus, comprising:

an image bearing member;

a developer bearing member configured to perform a development operation in which an electrostatic image formed on the image bearing member is developed with a developer; and

driving means configured to rotationally drive the image bearing member and the developer bearing member respectively so that the peripheral velocities of each is variable individually, wherein

when a peripheral velocity ratio is defined as a ratio of the peripheral velocity of the developer bearing member to the peripheral velocity of the image bearing member, the driving means is configured to be capable of driving the image bearing member and the developer bearing member at a first peripheral velocity ratio and a second peripheral velocity ratio which is larger than the first peripheral velocity ratio, and wherein

the first peripheral velocity ratio and the second peripheral velocity ratio are set so that an amount of the developer remaining on the developer bearing member after the development operation in a case where the development operation is performed at the second peripheral velocity ratio is larger than that in a case where the development operation is performed at the first peripheral velocity ratio.