Image forming apparatus and control method thereof

A method of controlling an image forming apparatus having a developing roller mounted to be spaced with a photo-sensitive body and supplying a developing agent to the photo-sensitive body, and a bias-applying part applying a predetermined bias to the developing roller through a current-conducting path to the photo-sensitive body from the developing roller, the method comprising:

• supplying a first test AC voltage having a set first frequency to the developing roller;
• detecting a first developing current flowing through the developing roller corresponding to the first test AC voltage having the first frequency;
• applying a second test AC voltage having a set second frequency to the developing roller;
• detecting a second developing current flowing through the developing roller corresponding to the second test AC voltage having the second frequency;
• calculating a resistance of the developing roller and a developing gap between the developing roller and the photo-sensitive body using data of the first and second test AC voltages and data of the first and second developing currents detected in response to the respective first and second test AC voltages;
• and
• supplying the developing roller with a bias voltage of a driving condition corresponding to the calculated resistance of the developing roller and the calculated developing gap.

A method of controlling an image forming apparatus having a developing roller mounted to be spaced with a photo-sensitive body and supplying a developing agent to the photo-sensitive body, a bias-applying part applying a predetermined bias to the developing roller through a current-conducting path to the photo-sensitive body from the developing roller, the method comprising:

• applying a set test AC voltage to the developing roller;
• detecting a developing current flowing through the developing roller in response to the test AC voltage;
• calculating a resistance of the developing roller and a developing gap between the developing roller and the photo-sensitive body using information on a phase difference between the test AC voltage and the developing current;
• and
• supplying the developing roller with a bias of a driving condition corresponding to the calculated resistance of the developing roller and the calculated developing gap.

A method of controlling an image forming apparatus having a developing roller mounted to be spaced with a photo-sensitive body and supplying a developing agent to the photo-sensitive body, and a bias-applying part supplying a predetermined bias to the developing roller through a current-conducting path to the photo-sensitive body from the developing roller, the method comprising:

• supplying a set test AC voltage to the developing roller using the bias-applying part;
• storing time data of a developing current flowing through the developing roller in response to the set test AC voltage;
• detecting first and second developing current values corresponding to respective first and second time periods after a reference time at which a peak value of the current occurs in response to the test AC voltage;
• calculating a resistance of the developing roller and a developing gap between the developing roller and the photo-sensitive body according to the first and second developing current values and time data;
• and
• supplying the developing roller with a bias of a driving condition corresponding to the calculated resistance of the developing roller and the calculated developing gap.