Development apparatus and image forming apparatus
First Claim
1. A development device comprising:
- a developing container which houses two-component developer including toner and a magnetic carrier;
a developer bearing member which bears the two-component developer; and
a magnetic field generation member which includes a plurality of magnetic poles including first and second magnetic poles having the same polarity and being adjacent to each other in a peripheral direction of the developer bearing member, the magnetic field generation member being arranged inside the developer bearing member,wherein the magnetic field generation member, between the first magnetic pole and the second magnetic pole, includes a low magnetic field area in which a magnetic force measured on a circumferential face approximately coinciding with an outer peripheral face of the developer bearing member is 10 mT or less, and a magnetic force distribution of the developer bearing member in a longitudinal direction at positions at which a magnetic flux density of the low magnetic field area is minimal in the peripheral direction of the developer bearing member is set such that a difference between a maximum magnetic flux density in a range from a maximum position at which an attenuation rate of the magnetic flux density is maximal to a 30 mm distant position toward the center of the developer bearing member and a magnetic flux density on a further center side of the developer bearing member than the range is 3 mT or less, and an absolute value of the magnetic flux density of a further outer side in the longitudinal direction of the developer bearing member than the maximum position is set to 3 mT or less, andwherein, in a space between the developing container and the developer bearing member, an electric field formation member which is arranged in a peripheral area of an end portion of the developer bearing member and can form an electric field repelling normal charged polarity of the toner is included.
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Accused Products
Abstract
A development device wherein a magnetic force distribution of a developer bearing member in a longitudinal direction at positions at which a magnetic flux density of a low magnetic field area is minimal in the peripheral direction of the developer bearing member is set such that a difference between a maximum magnetic flux density in a range from a maximum position at which an attenuation rate of the magnetic flux density is maximal to a 30 mm distant position toward the center of the developer bearing member and a magnetic flux density on a further center side of the developer bearing member than the range is 3 mT or less, and an absolute value of the magnetic flux density of a further outer side in the longitudinal direction of the developer bearing member than the maximum position is set to 3 mT or less.
12 Citations
27 Claims
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1. A development device comprising:
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a developing container which houses two-component developer including toner and a magnetic carrier; a developer bearing member which bears the two-component developer; and a magnetic field generation member which includes a plurality of magnetic poles including first and second magnetic poles having the same polarity and being adjacent to each other in a peripheral direction of the developer bearing member, the magnetic field generation member being arranged inside the developer bearing member, wherein the magnetic field generation member, between the first magnetic pole and the second magnetic pole, includes a low magnetic field area in which a magnetic force measured on a circumferential face approximately coinciding with an outer peripheral face of the developer bearing member is 10 mT or less, and a magnetic force distribution of the developer bearing member in a longitudinal direction at positions at which a magnetic flux density of the low magnetic field area is minimal in the peripheral direction of the developer bearing member is set such that a difference between a maximum magnetic flux density in a range from a maximum position at which an attenuation rate of the magnetic flux density is maximal to a 30 mm distant position toward the center of the developer bearing member and a magnetic flux density on a further center side of the developer bearing member than the range is 3 mT or less, and an absolute value of the magnetic flux density of a further outer side in the longitudinal direction of the developer bearing member than the maximum position is set to 3 mT or less, and wherein, in a space between the developing container and the developer bearing member, an electric field formation member which is arranged in a peripheral area of an end portion of the developer bearing member and can form an electric field repelling normal charged polarity of the toner is included. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A development device comprising:
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a developer bearing member which bears and conveys two-component developer including toner and a carrier and supplies the developer to a developing area; a magnetic field generation member which is fixedly arranged inside the developer bearing member; a layer-thickness regulation member which is arranged to face the developer bearing member and regulates a developer layer thickness of the developer bearing member; a first chamber which includes a first opening portion disposed to face a peripheral face of the developer bearing member and supplies the developer to the developer bearing member through the first opening portion; a first stirring member which is arranged inside the first chamber; a second chamber which includes a second opening portion disposed to face the peripheral face of the developer bearing member, collects the developer from the developer bearing member through the second opening portion, and circulates the developer between the first chamber and the second chamber; and a second stirring member which is arranged inside the second chamber; wherein the magnetic field generation member includes magnetic poles of the same polarity adjacent to each other in a peripheral direction of the developer bearing member, and between the magnetic poles is a low magnetic field area in which a magnetic force measured on a circumferential face approximately coinciding with an outer peripheral face of the developer bearing member is 10 mT or less, and a magnetic force distribution of the developer bearing member in a longitudinal direction at positions at which a magnetic flux density of the low magnetic field area is minimal in the peripheral direction of the developer bearing member is set such that a difference between a maximum magnetic flux density in a range from a maximum position at which an attenuation rate of the magnetic flux density is maximal to a 30 mm distant position toward the center of the developer bearing member and a magnetic flux density on a further center side of the developer bearing member than the range is 3 mT or less, and an absolute value of the magnetic flux density of a further outer side in the longitudinal direction of the developer bearing member than the maximum position is set to 3 mT or less. - View Dependent Claims (10, 11, 12, 13, 14)
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15. A development device comprising:
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a developing container which houses two-component developer including toner and a carrier; a developer bearing member which bears the two-component developer; and a magnetic field generation member which forms a low magnetic field area of a magnetic force by using magnetic poles having the same polarity adjacent to each other among a plurality of magnetic poles arranged inside the developer bearing member; a layer-thickness regulation member which is arranged to face the developer bearing member and regulates a thickness of the developer of the developer bearing member; and a developer seal which is arranged in an end portion of the developer bearing member, wherein the magnetic field generation member includes magnetic poles of the same polarity adjacent to each other in a peripheral direction of the developer bearing member, and between the magnetic poles is a low magnetic field area in which a magnetic force measured on a circumferential face approximately coinciding with an outer peripheral face of the developer bearing member is 10 mT or less, and a magnetic force distribution of the developer bearing member in a longitudinal direction at positions at which a magnetic flux density of the low magnetic field area is minimal in the peripheral direction of the developer bearing member is set such that a difference between a maximum magnetic flux density in a range from a maximum position at which an attenuation rate of the magnetic flux density is maximal to a 30 mm distant position toward the center of the developer bearing member and a magnetic flux density on a further center side of the developer bearing member than the range is 3 mT or less, and an absolute value of the magnetic flux density of a further outer side in the longitudinal direction of the developer bearing member than the maximum position is set to 3 mT or less, and wherein the developer seal is arranged to enclose the developer bearing member on a further downstream side than the low magnetic field area on a further upstream side than the layer-thickness regulation member in a rotation direction of the developer bearing member. - View Dependent Claims (16, 17, 18, 19, 20)
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21. A development device comprising:
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a developing container which houses developer; a developer bearing member which bears the developer; a magnetic field generation member which is fixedly arranged inside the developer bearing member; and a pair of repulsive magnetic poles having the same polarity adjacent to each other among a plurality of magnetic poles generated by the magnetic field generation member, wherein the magnetic field generation member, between the magnetic poles having the same polarity adjacent to each other, includes a low magnetic field area in which a magnetic force measured on a circumferential face approximately coinciding with an outer peripheral face of the developer bearing member is 10 mT or less, and a magnetic force distribution of the developer bearing member in a longitudinal direction at positions at which a magnetic flux density of the low magnetic field area is minimal in the peripheral direction of the developer bearing member is set such that a difference between a maximum magnetic flux density in a range from a maximum position at which an attenuation rate of the magnetic flux density is maximal to a 30 mm distant position toward the center of the developer bearing member and a magnetic flux density on a further center side of the developer bearing member than the range is 3 mT or less, and an absolute value of the magnetic flux density of a further outer side in the longitudinal direction of the developer bearing member than the maximum position is 3 mT or less, and wherein the development device includes an end-portion sealing member which is arranged to be detachably attachable so as to fill in a gap between the developing container and the developer bearing member in an end portion of the developer bearing member. - View Dependent Claims (22, 23, 24, 25, 26, 27)
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Specification