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US 5,860,049 AGranted
Developing apparatus and picture image forming apparatus
AssigneeHitachi, Ltd.
InventorsTakao Kumasaka, Tatsuo Igawa, Shigetaka Fujiwara, Nobuyoshi Hoshi
Life of this patent
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Abstract
By employing a developer using ferrite system carriers, a developing process can be carried out using a low brushing force by a magnetic portion having the same polarity in a developing unit in a developing roller. A relationship between a circumferential speed Up (mm/sec) of a photoconductor, a ratio K of a circumferential speed of a developing sleeve of the developing roller to the circumferential speed of the photoconductor, and a developing potential difference .DELTA.V (V) is set to 1.5.ltoreq.(K.times..DELTA.V/Up).ltoreq.2.1.
Claims7
A developing apparatus comprising:
- a photoconductor on which an electrostatic latent image is formed;
- a rotating developing sleeve arranged in opposing relationship to said photoconductor with a developing gap being provided therebetween;
- a magnet body fixedly arranged in said developing sleeve;
- a first magnetic pole element and a second magnetic pole element adjacently arranged in spaced relationship on said magnet body so as to face said developing gap and having same polarity for forming a first magnetic force peak and a second magnetic force peak in said developing gap;
- a developer of mixed carriers and toners, responsive to a developing bias applied to said developing sleeve, so as to form a magnetic brush of developer on an outer peripheral surface of said developing sleeve for brushing developer against said photoconductor, whereby said electrostatic latent image on said photoconductor is developed, wherein
- said carriers are ferrite system carriers;
- an angle .theta.s formed between said first magnetic force peak and said second magnetic force peak produced by said first and second magnetic pole elements having same polarity is 20.degree.-40.degree., and
- a magnetic force of a trough portion formed between said first magnetic force peak and said second magnetic force peak is set to less than 400 gausses;
- wherein said developing gap is 0.7-1.2 mm.
6 more elements
A developing apparatus comprising:
- a photoconductor on which an electrostatic latent image is formed;
- a rotating developing sleeve arranged in opposing relationship to said photoconductor with a developing gap being provided therebetween;
- a magnet body fixedly arranged in said developing sleeve;
- a first magnetic pole element and a second magnetic pole element adjacently arranged in spaced relationship on said magnet body so as to face said developing gap and having same polarity for forming a first magnetic force peak and a second magnetic force peak in said developing gap;
- a developer of mixed carriers and toners, responsive to a developing bias applied to said developing sleeve, so as to form a magnetic brush of developer on an outer peripheral surface of said developing sleeve for brushing developer against said photoconductor, whereby said electrostatic latent image on said photoconductor is developed, wherein
- said carriers are ferrite system carriers;
- an angle .theta.s formed between said first magnetic force peak and said second magnetic force peak produced by said first and second magnetic pole elements having same polarity is 20.degree.-40.degree., and
- a magnetic force of a trough portion formed between said first magnetic force peak and said second magnetic force peak is set to less than 400 gausses;
- wherein a relationship between a circumferential speed Up (mm/sec) of said photoconductor, a ratio K of a circumferential speed of said developing sleeve to the circumferential speed of said photoconductor, and a potential difference .DELTA.V (V) between a potential of said electrostatic latent image and a potential of a developing bias is set to 1.5.ltoreq.(K.times..DELTA.V/Up).ltoreq.2.1.
6 more elements
A developing apparatus comprising:
- a photoconductor on which an electrostatic latent image is formed;
- a rotating developing sleeve arranged in opposing relationship to said photoconductor with a developing gap being provided therebetween;
- a magnet body fixedly arranged in said developing sleeve;
- a first magnetic pole element and a second magnetic pole element adjacently arranged in spaced relationship on said magnet body so as to face said developing gap and having same polarity for forming a first magnetic force peak and a second magnetic force peak in said developing gap;
- a developer of mixed carriers and toners, responsive to a developing bias applied to said developing sleeve, so as to form a magnetic brush of developer on an outer peripheral surface of said developing sleeve for brushing developer against said photoconductor, whereby said electrostatic latent image on said photoconductor is developed, wherein
- said carriers are ferrite system carriers;
- an angle .theta.s formed between said first magnetic force peak and said second magnetic force peak produced by said first and second magnetic pole elements having same polarity is 20.degree.-40.degree., and
- a magnetic force of a trough portion formed between said first magnetic force peak and said second magnetic force peak is set to less than 400 gausses;
- wherein a relationship between a circumferential speed Up (mm/sec) of said photoconductor and a ratio K of a circumferential speed of said developing sleeve to the circumferential speed of said photoconductor is set to 1.0.ltoreq.K.ltoreq.1.0+(110/Up).
6 more elements
Dependencies are inferred from the claim text.