Image forming apparatus and image forming method

An image forming method comprising:

• alternately outputting a first voltage and a second voltage from a power supply to transfer a toner image on an image carrier onto a recording medium nipped in a transfer nip when the toner image on the image carrier is transferred onto the recording medium, the transfer nip being formed by a transfer member configured to abut against the image carrier for carrying the toner image, wherein
• the first voltage is for transferring the toner image from the image carrier onto the recording medium in a transfer direction,
• the second voltage has an opposite polarity of the first voltage, and
• a time-averaged value of voltages that include the first voltage and the second voltage is set to a polarity in the transfer direction and is set in a transfer direction side with respect to a median between a maximum and a minimum of the voltages.

An image forming apparatus comprising:

• a transfer member configured to abut against an image carrier for carrying a toner image to form a transfer nip;
• and
• a power supply configured to output any one of a direct current bias voltage and a superimposed bias voltage for transferring the toner image on the image carrier onto a recording medium nipped in the transfer nip, wherein
• the superimposed bias voltage includes a first voltage for transferring the toner image from the image carrier onto the recording medium in a transfer direction and a second voltage having an opposite polarity of the first voltage, the first voltage and the second voltage being alternately output when the toner image on the image carrier is transferred onto the recording medium, and a time-averaged value of the bias voltage is set to a polarity in the transfer direction and is set in a transfer direction side with respect to a median between a maximum and a minimum of the bias voltage, and
• a voltage output from the power supply is switched between the direct current bias voltage and the superimposed bias voltage based on a type of the recording medium.

An image forming apparatus comprising:

• an image configured to carry a toner image;
• a transfer member configured to form a transfer nip between the image carrier and the transfer member;
• and
• a power supply configured to output any one of a direct current bias voltage and a superimposed bias voltage for transferring the toner image on the image carrier onto a recording medium nipped in the transfer nip, wherein
• the superimposed bias voltage includes a first peak voltage having a polarity to move the toner image from the image carrier onto the recording medium in the transfer nip and a second peak voltage having an opposite polarity of the first peak voltage, the first peak voltage and the second peak voltage being alternately output when the toner image on the image carrier is transferred onto the recording medium, and
• the superimposed bias voltage is set to satisfy A>B, where A is a time period in which the power supply outputs a voltage on a first peak voltage side with respect to a median between the first peak voltage and the second peak voltage in one cycle, and B is a time period in which the power supply outputs a voltage on a second peak voltage side with respect to the median in one cycle.