Intermediate transfer unit, image forming apparatus, and method of manufacturing an intermediate transfer unit

An intermediate transfer unit comprising:

• an intermediate transfer belt rotatably stretched, the intermediate transfer belt having an outer circumferential surface to which a toner image is transferred from each of a plurality of image carrying members, the intermediate transfer belt rotating while carrying the toner image;
• a plurality of primary transfer members assigned one to each of the plurality of image carrying members, the primary transfer members holding the intermediate transfer belt against the corresponding image carrying members to primarily transfer the toner image to the intermediate transfer belt;
• a plurality of power supply portions assigned one to each of the plurality of primary transfer members, the power supply portions feeding a transfer voltage to the corresponding primary transfer members;
• wherein
• the power supply portions each have
• a power supply line connected to a source of the transfer voltage, and
• a resistor portion arranged between the corresponding primary transfer member and the power supply line,
• the resistor portion includes a plurality of resistive elements having equal or different resistance values, and
• the primary transfer members are each connected to the power supply line via one or more previously selected resistive elements out of the plurality of resistive elements in the corresponding power supply portion,
• the primary transfer members comprise four primary transfer members, and
• if, in order from upstream to downstream along the conveyance direction of the toner image carried and conveyed by the intermediate transfer belt, the resistance value of the resistor portion connected to a first primary transfer members is R1, the resistance value of the resistor portion connected to a second primary transfer members is R2, the resistance value of the resistor portion connected to a third primary transfer members is R3, and the resistance value of the resistor portion connected to a fourth primary transfer members is R4, then R1≥R2≥R3≥R4 is satisfied.