Image forming apparatus with constant voltage and constant current control

An image forming apparatus, comprising:

• a movable image bearing member;
• image forming means for forming a toner image on said image bearing member;
• a charging member opposed to said image bearing member to transfer the image from said image bearing member onto an image recording material at a transfer station, said charging member having a resistance which changes in accordance with at least one of ambient temperature and humidity;
• voltage applying means for applying a voltage to said charging member, wherein said voltage applying means applies a voltage to said charging member to control at a constant voltage said charging member when an image region of said image bearing member is in the transfer station and to control at a constant current said charging member during at least part of a period when said image region is not in the transfer station, wherein during the constant current control, a voltage V1 corresponding to the voltage applied to the charging member is stored, and a voltage V2 during the constant voltage control is equal to the voltage V1 multiplied by a coefficient R, wherein the coefficient R is larger than 1.

An image forming apparatus, comprising:

• a movable image bearing member;
• charging means for charging said image bearing member;
• image forming means for forming a toner image on said image bearing member using electric charging;
• transfer means for transferring the toner image from said image bearing member to an image recording material at a transfer station, wherein said transfer means includes a charging member contactable to a back side of the image recording material and means for applying a voltage to said charging member, wherein said voltage applying means controls at a constant voltage said charging member when an image region of said image bearing member is in the transfer station, and during at least a part of a period when the image region is not in the transfer station, said voltage applying means applies a voltage having a polarity which is the same as the charging polarity of said charging means to said charging member, and wherein a level of said constant voltage to be applied during the constant voltage control is determined when said voltage applying means applies the voltage which is the same as the charging polarity of said charging means to said charging member.

An image forming apparatus, comprising:

• image forming means for forming an image on a recording material, said image forming means including an image bearing member, a charging member for opposing the image bearing member and power supply means for supplying electric power to the charging member;
• constant current control means for supplying a constant current to the charging member;
• and
• voltage control means for supplying a constant voltage to the charging member, wherein the constant voltage V.sub.2 is determined on the basis of a voltage V.sub.1 which is provided when said constant current control means is operated, and wherein the voltage V.sub.2 is larger than the voltage V.sub.1.

An image forming apparatus, comprising:

• image forming means for forming an image on a recording material, said image forming means including an image bearing member, a charging member opposing the image bearing member and power supply means for supplying electric power to the charging member;
• constant current control means for supplying a constant current to the charging member so as to maintain a constant level of current flow from said charging member to said image bearing member;
• and
• image formation control means for controlling an image formation parameter of said image forming means on the basis of plural sampled voltage values provided when said constant current control means is operated.

An image forming apparatus, comprising:

• image forming means for forming an image on a recording material, said image forming means including an image bearing member, a charging member for opposing the image bearing member and power supply means for supplying electric power to the charging member;
• voltage control means for supplying a constant voltage V.sub.1 to the charging member;
• and
• image formation control means for controlling a parameter of image forming operation of said image forming means on the basis of a current provided when said voltage control means is operated.

An image forming apparatus, comprising:

• image forming means for forming an image on a recording material, said image forming means including an image bearing member, charging means for charging the image bearing member, a charging member contactable to image bearing member, and power supply means for supplying electric power to the charging member;
• constant current control means for supplying a constant current to the charging member in a polarity the same as a charging polarity of said charging means;
• and
• image formation control means for controlling a parameter of image forming operation by said image forming means on the basis of a voltage provided when said current control means is operated.