Image forming apparatus

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 the image bearing member onto a recording material;
• an applying portion configured to apply a transfer voltage to the transfer member;
• a fixing unit configured to fix the toner image on the recording material;
• an environmental sensor configured to detect an absolute water content;
• a resistance detection unit configured to detect an index value correlated with an electrical resistance of the transfer portion;
• and
• a controller configured to control the transfer voltage for each recording material and to detect recording material information and information of the toner amount of the toner image, wherein,
• based on the recording material information and the information of the toner amount of the toner image, the controller controls the applying portion so as to subject the transfer voltage:
• i) to constant current control so that a current supplied to the transfer member by the applying portion is substantially constant when the absolute water content indicated by a detection result of the environmental sensor is lower than a predetermined water content value,
• ii) to constant voltage control when the absolute water content indicated by the detection result of the environmental sensor is the predetermined water content value or higher,
• iii) to constant current control so that the current supplied to the transfer member by the applying portion is substantially constant when the electrical resistance of the transfer portion indicated by the index value of the resistance detection unit is lower than a predetermined resistance value, and
• iv) to constant voltage control when the electrical resistance of the transfer portion indicated by the index value of the resistance detection unit is equal to or greater than the predetermined resistance value.