DEVELOPING DEVICE AND IMAGE FORMING APPARATUS

• US 20180284641A1
• Filed: 03/20/2018
• Published: 10/04/2018
• Est. Priority Date: 03/30/2017
• Status: Active Grant

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Soeta, Yukihiro, Takahashi, Masafumi, Terada, Ryohei, Sadamitsu, Yushi, Shimoi, Yasuhiro, Koga, Yutaka
• Granted Patent: US 10,481,521 B2
• Time in Patent Office: Days
• CPC Class Codes: G03G 15/0808 characterised by the developer supplying means, e.g. structure of developer supply roller
• CPC Class Codes: G03G 15/0812 characterised by the developer regulating means, e.g. structure of doctor blade
• 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 15/0898 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 15/0921 Details concerning the magnetic brush roller structure, e.g. magnet configuration

Abstract

A developing device includes a developer accommodating casing, a developer carrying member, a regulating portion, a magnetic flux generating portion, and a cover portion. A first opposing region between the casing and the developer carrying member is downstream of the developing region and upstream of a second opposing region between the cover portion and the developer carrying member with respect to a rotational direction. The following relationships are satisfied: L1≤L2+L3, and L2≤L3, where L1 is a minimum distance between the developer carrying member and the accommodating casing in the first opposing region, L2 is a minimum distance between the developer carrying member and the cover portion in the second opposing region, and L3 is a minimum distance between the cover portion and the accommodating portion opposing the cover portion.

Claims

1. A developing device comprising:

an accommodating casing configured to accommodate a developer;

a rotatable developer carrying member provided in said accommodating casing and configured to develop, in a developing region, an electrostatic latent image formed on an image bearing member;

a regulating portion provided below said developer carrying member with respect to a vertical direction and configured to regulate an amount of the developer on said developer carrying member;

a magnetic flux generating portion provided inside said developer carrying member and including a first magnetic pole provided downstream of the developing region with respect to a rotational direction of said developer carrying member and a second magnetic pole which is provided adjacently downstream of said first magnetic pole with respect to the rotational direction and which has a polarity identical to a polarity of said first magnetic pole; and

a cover portion provided downstream of the developing region and upstream of a maximum magnetic flux density position of said second magnetic pole with respect to the rotational direction, said cover portion being disposed between said casing and said developer carrying member over a rotational axis direction of said developer carrying member with a gap between itself and said casing and with a gap between itself and said developer carrying member,

wherein a first opposing region between an inner surface of said casing and said developer carrying member is in a side downstream of the developing region and upstream of a second opposing region between said cover portion and said developer carrying member with respect to the rotational direction, and

wherein the following relationships are satisfied;

L1≤

L2+L3, and

L2≤

L3,

where L1 is a minimum distance between said developer carrying member and said accommodating casing in said first opposing region, L2 is a minimum distance between said developer carrying member and said cover portion in said second opposing region, and L3 is a minimum distance between said cover portion and said accommodating portion opposing said cover portion.

2. A developing device according to claim 1, wherein a lower end of said cover portion with respect to the rotational direction is in a side upstream, with respect to the rotational direction, of a minimum magnetic flux density position between said first magnetic pole and said second magnetic pole with respect to the rotational direction.

3. A developing device according to claim 1, wherein a lower end of said cover portion with respect to the longitudinal direction is in a side downstream, with respect to the rotational direction, of a minimum magnetic flux density position between said first magnetic pole and a third magnetic pole provided adjacently upstream of said first magnetic pole with respect to the rotational direction.

4. A developing device according to claim 1, wherein a lower end of said cover portion with respect to the rotational direction is in a side downstream of a maximum magnetic flux density position of said first magnetic pole with respect to the rotational direction.

5. A developing device according to claim 1, wherein a lower end of said cover portion with respect to the rotational direction is in a half-width region of a magnetic flux density of said first magnetic pole with respect to the rotational direction.

6. A developing device according to claim 1, wherein a lower end of said cover portion with respect to the rotational direction is in a side downstream, with respect to the rotational direction, of an upstream end of a half-width region of a magnetic flux density of said first magnetic pole with respect to the rotational direction.

7. A developing device according to claim 1, wherein a lower end of said cover portion with respect to the rotational direction is positioned, with respect to the vertical direction, a horizontal plane passing through a rotation axis of said developer carrying member.

8. An image forming apparatus comprising:

a rotatable image bearing member;

an accommodating casing configured to accommodate a developer;

a rotatable developer carrying member provided in said accommodating casing and configured to develop, in a developing region, an electrostatic latent image formed on said image bearing member, wherein a rotational direction of said image bearing member is opposite to a rotational direction of said developer carrying member;

a regulating portion provided below said developer carrying member with respect to a vertical direction and configured to regulate an amount of the developer on said developer carrying member;

a magnetic flux generating portion provided inside said developer carrying member and including a first magnetic pole provided downstream of the developing region with respect to the rotational direction of said developer carrying member and a second magnetic pole which is provided adjacently downstream of said first magnetic pole with respect to the rotational direction and which has a polarity identical to a polarity of said first magnetic pole; and

a cover portion provided downstream of the developing region and upstream of a maximum magnetic flux density position of said second magnetic pole with respect to the rotational direction, said cover portion being disposed between said casing and said developer carrying member over a rotational axis direction of said developer carrying member with a gap between itself and said casing and with a gap between itself and said developer carrying member,

wherein a first opposing region between an inner surface of said casing and said developer carrying member is in a side downstream of the developing region and upstream of a second opposing region between said cover portion and said developer carrying member with respect to the rotational direction; and

a wall portion projecting from an upstream end portion of said first opposing region with respect to the rotational direction upwardly in a vertical direction and opposing said image bearing member with a gap therebetween over a longitudinal direction of said image bearing member.

9. An image forming apparatus according to claim 8, wherein a projection amount of said wall portion from the upstream end portion is 3 mm or more and 10 mm or less.

10. An image forming apparatus according to claim 8, wherein an interval between said wall portion and said image bearing member in a first region is larger than an interval between said wall portion and said image bearing member in a second region outside said first region with respect to the longitudinal direction of said developer carrying member.

11. An image forming apparatus according to claim 8, wherein a projection amount of said wall portion in a first region is smaller than a projection amount of said wall in a second region outside said first region with respect to the longitudinal direction of said developer carrying member.

12. An image forming apparatus according to claim 10, wherein with respect to the longitudinal direction of said developer carrying member, said first region has a length which is not less than ½

of a developer carrying region so that a center of said first region is a center of said developer carrying region.

13. An image forming apparatus according to claim 11, wherein with respect to the longitudinal direction of said developer carrying member, said first region has a length which is not less than ½

of a developer carrying region so that a center of said first region is a center of said developer carrying region.