Method of supplying developing unit with toner and image forming apparatus using the same

1. A method of supplying toner to a developing unit separate from a toner bottle in an image forming apparatus, the method comprising:

calculating an amount of toner necessary for each sheet of paper;

calculating a time for entering a toner supply mode and an estimated printing delay time based on a remaining amount of toner in the developing unit and the calculated amount of toner for each sheet of paper;

displaying the calculated time for entering the toner supply mode or a number of sheets of paper to be used until the calculated time for entering the toner supply mode, and the estimated printing delay time, on a screen of a user interface unit of the image forming apparatus;

displaying a button for selecting one of a speed mode in which printing is continued without additionally supplying toner and a quality mode in which toner is supplied, on the screen of the user interface unit of the image forming apparatus;

detecting the remaining amount of toner in the developing unit during printing so as to compare the detected remaining amount of toner with a first reference value; and

if the detected remaining amount of toner is greater than the first reference value, continuing printing, and if the detected remaining amount of toner is not greater than the first reference value, determining whether to supply toner to the developing unit based on a selected mode when one of the speed mode and the quality mode is selected by a user,

wherein when the quality mode is selected by the user and toner is being supplied in the quality mode, an estimated time until completion of a supply of toner and a switch-to-speed-mode button are displayed on the user interface screen, and when the switch-to-speed-mode button is clicked by the user, the supply of toner is suspended in a forced manner and printing is continued regardless of the remaining amount of toner, and

when the speed mode is selected by the user and printing is executed without supplying toner, a remaining number of paper sheets necessary for printing and a switch-to-quality mode button are displayed on the user interface screen, and when the switch-to-quality mode button is clicked by the user, printing is suspended in a forced manner and toner is supplied to improve printing quality regardless of the remaining amount of toner.

2. The method of claim 1 , further comprising:

determining whether the remaining amount of toner detected by a sensor is not greater than a second reference value that is smaller than the first reference value; and

if the remaining amount of toner detected by the sensor is not greater than the second reference value, suspending printing and supplying toner.

3. An image forming apparatus comprising:

an image forming unit configured to form images on printing media;

a toner bottle disposed in the image forming unit;

a developing unit separate from the toner bottle and configured to receive toner from the toner bottle for developing images;

a user interface unit which provides a user interface; and

a control unit configured to compare a remaining amount of toner in the developing unit with a first reference value,

wherein if the remaining amount of toner in the developing unit is greater than the first reference value, the control unit signals the image forming unit to continue printing, and if the remaining amount of toner in the developing unit is not greater than the first reference value, the control unit determines whether to supply toner based on a selected mode when one of a speed mode in which printing is continued without additionally supplying toner and a quality mode in which toner is supplied is selected by a user,

wherein the control unit calculates an amount of toner necessary for each sheet of paper, calculates a time for entering a toner supply mode, a number of sheets of paper to be used for printing, and a printing delay time based on the remaining amount of toner in the developing unit and the calculated amount of toner necessary for each sheet of paper, and displays the time for entering the toner supply mode, the number of sheets of paper to be used for printing, and the printing delay time on the user interface unit, and

wherein the user interface unit displays a button to select one of the speed mode in which printing is continued without additionally supplying toner and the quality mode in which toner is supplied,

wherein when the quality mode is selected by the user and toner is being supplied in the quality mode, the control unit displays an estimated time until completion of a supply of toner and a switch-to-speed-mode button on a user interface screen, and when the switch-to-speed-mode button is clicked by the user, the control unit suspends the supply of toner in a forced manner and continues printing regardless of the remaining amount of toner, and

when the speed mode is selected by the user and printing is executed without supplying toner, the control unit displays a remaining number of paper sheets necessary for printing and a switch-to-quality mode button on the user interface screen, and when the switch-to-quality mode button is clicked by the user, the control unit suspends printing in a forced manner and toner is supplied to improve printing quality regardless of the remaining amount of toner.

4. The image forming apparatus of claim 3 , wherein the control unit determines whether the remaining amount of toner in the developing unit is not greater than a second reference value that is smaller than the first reference value, and if the remaining amount of toner of the developing unit is not greater than the second reference value, the control unit signals the image forming unit to suspend printing to supply toner to the developing unit.

5. The image forming apparatus of claim 4 , further comprising a printing mode storage unit storing information about printing mode settings.

6. The image forming apparatus of claim 3 , wherein if a number of sheets of paper used for printing in a speed mode is equal to or greater than a predetermined value, the control unit supplies toner to the developing unit.

7. The image forming apparatus of claim 3 , wherein the control unit calculates an amount of toner used in a speed mode, and if the amount of toner used in the speed mode is equal to or greater than a predetermined value, the control unit supplies toner to the developing unit.

8. The image forming apparatus of claim 3 , wherein if the remaining amount of toner in the developing unit during operation in a speed mode is equal to or smaller than a predetermined value, the control unit supplies toner to the developing unit.