Image forming apparatus
AssigneeCanon Kabushiki Kaisha
InventorKosuke Takeuchi
Life of this patent
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Abstract
A carrier collecting device includes a rotatable sleeve and a magnet non-rotatably disposed inside the sleeve, and collects the carrier on the image bearing member. A first bias is applied to the sleeve during the image forming operation. A second bias is applied to the sleeve in a predetermined mode during non-image forming. When, a duration of a voltage of a reverse polarity to a charging polarity of the toner is t1, a duration of a voltage of a same polarity as the charging polarity of the toner is t2, and a ratio of t1 with respect to one period (t1+t2) of the AC voltage of the bias applied to the sleeve is a duty ratio, a duty ratio of the AC voltage of the second bias is lower than a duty ratio of the AC voltage of the first bias.
Claims19
An image forming apparatus configured to execute an image forming operation, the image forming apparatus comprising:
- a rotatable image bearing member on which an electrostatic latent image is formed;
- a developing unit including a developer container that accommodates a developer including a toner and a carrier, and a developer bearing member that bears the developer to develop the electrostatic latent image formed on the image bearing member into a toner image;
- a transfer member to which the toner image borne on the image bearing member is transferred;
- a carrier collecting device that includes a rotatable sleeve disposed to face the image bearing member and a magnet non-rotatably disposed inside the sleeve, and collects the carrier on the image bearing member,
- a bias application unit that applies a bias including an AC voltage to the sleeve;
- and
- a controller that controls the bias application unit, wherein
- the sleeve is disposed downstream of a development position at which the electrostatic latent image formed on the image bearing member is developed and upstream of a transfer position at which the toner image borne on the image bearing member is transferred to the transfer member, in a rotation direction of the image bearing member,
- the controller controls the bias application unit to apply a first bias to the sleeve during the image forming operation, and controls the bias application unit to apply a second bias to the sleeve in a predetermined mode during non-image forming, and
- when, in one period of the AC voltage of the bias applied to the sleeve by the bias application unit, a duration of a voltage of a reverse polarity to a charging polarity of the toner with respect to a DC potential of the sleeve is t1, a duration of a voltage of a same polarity as the charging polarity of the toner with respect to the DC potential of the sleeve is t2, and a ratio of t1 with respect to one period (t1+t2) of the AC voltage of the bias applied to the sleeve by the bias application unit is a duty ratio, a duty ratio of the AC voltage of the second bias is lower than a duty ratio of the AC voltage of the first bias.
An image forming apparatus configured to execute an image forming operation, the image forming apparatus comprising:
- a rotatable image bearing member on which an electrostatic latent image is formed;
- a developing unit including a developer container that accommodates a developer including a toner and a carrier, and a developer bearing member that bears the developer to develop the electrostatic latent image formed on the image bearing member into a toner image;
- a transfer member to which the toner image borne on the image bearing member is transferred;
- a carrier collecting device that includes a rotatable sleeve disposed to face the image bearing member and a magnet non-rotatably disposed inside the sleeve, and collects the carrier on the image bearing member,
- a bias application unit that applies a bias including an AC voltage to the sleeve;
- and
- a controller that controls the bias application unit, wherein
- the sleeve is disposed downstream of a development position at which the electrostatic latent image formed on the image bearing member is developed and upstream of a transfer position at which the toner image borne on the image bearing member is transferred to the transfer member, in a rotation direction of the image bearing member,
- the controller controls the bias application unit to apply a first bias to the sleeve during the image forming operation, and controls the bias application unit to apply a second bias to the sleeve in a predetermined mode during non-image forming, and
- when, in one period of the AC voltage of the bias applied to the sleeve by the bias application unit, a duration of a voltage of a reverse polarity to a charging polarity of the toner with respect to a DC potential of the sleeve is t1, a duration of a voltage of a same polarity as the charging polarity of the toner with respect to the DC potential of the sleeve is t2, and a ratio of t1 with respect to one period (t1+t2) of an AC voltage of the bias applied to the sleeve by the bias application unit is a duty ratio, a duty ratio of the AC voltage of the second bias is lower than 50%.
Dependencies are inferred from the claim text.