Patent ID: 9740146
Date: 2017-08-22
CPC Classifications: G03G

Claim:
1. An image forming apparatus comprising: an image bearing member configured to bear a toner image; a transfer member configured to form a transfer portion where the toner image is transferred from said image bearing member onto an intermediary transfer member; a voltage source configured to apply a voltage to said transfer member; a speed setting portion configured to set a speed of said image bearing member at either one of speeds including a first speed and a second speed different from the first speed; a test mode executing portion configured to execute an operation in a test mode in which the speed of said image bearing member is set at a predetermined speed and a target voltage at which a predetermined target current corresponding to the predetermined speed is obtained from a relationship between a voltage and a current when the voltage is applied to said transfer member in a period in which the toner image does not exist at the transfer portion; a renewing mode executing portion configured to execute an operation in a voltage renewing mode in which a first target voltage is obtained by executing the operation in the test mode at the first speed and then is renewed and further configured to execute an operation in a conversion coefficient renewing mode in which a second target voltage is obtained by executing the operation in the test mode at the second speed and a conversion coefficient is obtained from the first target voltage renewed in an immediately preceding voltage renewing mode and the second target voltage and then is renewed, wherein said renewing mode executing portion executes the operation in the voltage renewing mode at a frequency higher than a frequency of the operation in the conversion coefficient renewing mode; and a setting portion configured to set a voltage applied to said transfer member, in a period in which the toner image exists at the transfer portion when image formation is executed at the first speed, at the first target voltage renewed in an immediately preceding voltage renewing mode and further configured to set the voltage applied to said transfer member, in a period in which the toner image exists at the transfer portion when the image formation is executed at the second speed, at a voltage on the basis of the first target voltage renewed in an immediately preceding voltage renewing mode and the conversion coefficient renewed in an immediately preceding conversion coefficient renewing mode.