Paper feeding device and image forming apparatus

摘要

A remaining amount detector measures beforehand a distance H where there is one sheet. A motor displaces a lifting plate to a paper-feeding position upon storing paper in the feeding unit. The remaining amount detector measures a distance y1 to the lower face of a paper stack. Thereafter, upon transport of paper from the stack, a control unit causes the remaining amount detector to measure a distance y2 for every predetermined number n of fed sheets. A remaining sheet calculation unit calculates a displacement y1−y2=Δy to the bottom of the paper stack S, and calculates the thickness of one sheet on the basis of the displacement Δy and the number n of fed sheets (t=Δy/n). The remaining sheet calculation unit divides the thickness (H−y2) of the paper stack by the thickness t of one paper sheet, and calculates the number of remaining sheets m as (m=((H−y2)/t)+1).

主权项

1. A paper feeding device, comprising:
a storing section which is removably fitted to a device main body, and in which a recording medium is stored; a transport section which feeds out and transports, sheet by sheet, the recording medium stored in the storing section; a lifting section which is provided in the storing section and on which the recording medium is placed, and which is raised and lowered between a retreat position closest to the bottom face of the storing section and a paper-feeding position at which the topmost face of the placed recording medium abuts the transport section; a driving section which raises and lowers the lifting section; a measurement unit which is disposed above the lifting section and which measures a distance down to the topmost face of the recording medium placed on the lifting section when the lifting section is at the retreat position; a sheet number calculation unit which calculates the number of sheets of the recording medium that is placed on the lifting section, on the basis of the distance to the topmost face of the recording medium as measured by the measurement unit; a power control unit which has an ordinary mode in which power is supplied to the transport section, the driving section, the measurement unit and the sheet number calculation unit, and a power saving mode in which power is supplied to the measurement unit and the sheet number calculation unit, and which controls a supply of power to the sections and units, power consumption in the power saving mode being lower than in the ordinary mode; an angle detection unit which detects an inclination angle of the lifting section; and an angle/initial sheet number storage unit which stores beforehand the number of sheets of the recording medium placed on the lifting section, in association with the inclination angle of the lifting section; wherein in the ordinary mode, the driving section displaces the lifting section in such a manner that the lifting section is at the paper-feeding position at all times, and in the power saving mode, the driving section displaces the lifting section to the retreat position and does not displace the lifting section from the retreat position to the paper-feeding position, and after the driving section has displaced the lifting section to the paper-feeding position, the sheet number calculation unit determines the number of sheets of the recording medium placed on the lifting section by reading the corresponding number of sheets of the recording medium from the angle/initial sheet number storage unit, on the basis of the inclination angle of the lifting section detected by the angle detection unit.