Image recording apparatus with toner concentration detecting circuit
AssigneeKonica Corporation
InventorsYukio Okamoto, Toshihiko Nakazawa
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Abstract
A toner concentration detecting circuit detects a toner concentration of a two-component developer composed of toner and a carrier by detecting a change of magnetic permeability of the two-component developer. The detecting circuit is used in a developing device of an image recording apparatus. The toner concentration detecting circuit includes a sensor for sensing a change of a magnetic permeability of the two-component developer, a waveform corrector, a counter connected to a control CPU and a gate signal generating circuit connected to the control CPU so that a gate signal is sent to the counter.
Claims7
A toner concentration detecting circuit for a two-component developer including a toner and a carrier in a developing device of an image recording apparatus, said toner concentration detecting circuit comprising:
- (a) a sensor provided in said developing device, for sensing a change of a magnetic permeability of the developer and for outputting an oscillating frequency based on a sensed change of magnetic permeability;
- (b) a waveform corrector for generating a square pulse wave based on said oscillating frequency;
- (c) a gate signal generating circuit for generating a gate signal;
- (d) a counter for counting a number of pulses in said square pulse wave within a first predetermined period of time according to said gate signal, said counter outputting a toner concentration value that is representative of said number of pulses counted by said counter;
- (e) a central processing unit including means for detecting a plurality of said toner concentration values within a second predetermined period of time, and means for comparing one of said toner concentration values with a reference value pre-stored in said central processing unit, said central processing unit generating a toner replenishment command signal, said toner replenishment command signal being representative of the comparison by said central processing unit;
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- (f) toner replenishing means for replenishing a toner in said developing device based on said toner replenishment command signal.
An image forming apparatus for a two-component developer including a toner and a carrier, the image forming apparatus comprising:
- (a) a plurality of developing devices;
- (b) a sensor provided in each of said developing devices, for sensing a change of a magnetic permeability of the developer and for outputting an oscillating frequency based on a sensed change of magnetic permeability;
- (c) a waveform corrector for generating a square pulse wave based on said oscillating frequency;
- (d) a gate signal generating circuit for generating a gate signal;
- (e) a counter for counting a number of pulses in said square pulse wave within a first predetermined period of time according to said gate signal, said counter outputting a toner concentration value that is representative of said number of pulses counted by said counter;
- (f) a central processing unit including means for detecting a plurality of said toner concentration values within a second predetermined period of time, and means in said central processing unit for comparing one of said toner concentration values with a reference value prestored in said central processing unit, said central processing unit generating a toner replenishment command signal, said command signal being representative of the comparison by said central processing unit;
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- (g) toner replenishing means for replenishing a toner in at least one of said developing devices based on said toner replenishment command signal.
Dependencies are inferred from the claim text.