The present invention generally relates to an image recording apparatus with a scanner unit, and more particularly to an image recording apparatus with a scanner unit which selectively performs a printer mode in which an image is printed on a copy sheet, and a scanner mode in which an image is read from a document. This apparatus is applicable to laser printers, copying machines, facsimile machines and others.
Conventionally, a printing apparatus with a scanner unit can perform a scanner mode and a printer mode. When the scanner mode is performed by this printing apparatus, an original document is passed through a scanner unit and an image is read from the document by illuminating the document with light emitted by a light source of the scanner unit so that a signal indicating the original image is produced from the light reflected from the document.
In the meantime, when the printer mode is performed by the printing apparatus mentioned above, a copy sheet is fed from a paper cassette in the printing apparatus, and the copy sheet is transported to a photosensitive drum via a pair of registration rollers. The photosensitive drum is electrostatically charged by a charging unit, and the surface of the photosensitive drum is exposed to light emitted by a light source of an optical recorder unit, so that an electrostatic latent image in accordance with an image signal is formed on the photosensitive drum. By means of the pair of registration rollers, the time of forming the electrostatic latent image on the photosensitive drum is harmonized with the time of transporting the copy sheet to the photosensitive drum.
FIG. 1 shows the construction of the optical recorder unit provided within the above mentioned printing apparatus. As described above, at this optical recorder unit, an electrostatic latent image is formed on a photosensitive medium. A light beam emitted by a laser diode 1 of the optical recorder unit in accordance with an image signal modulated by a driver 7 is passed through a collimator lens 2 and a cylindrical lens 3, and it is deflected by a polygonal mirror 4 which is rotated by a driving motor (not shown) around a rotating axis of the polygonal mirror 4. The deflected light beam is passed through a focusing lens 5 and a troidal lens 6 to convert the light beam into a converging light beam. This converging light beam is cast on a photosensitive drum 8 to form a beam spot on the photosensitive drum 8. Because the polygonal mirror 4 is rotated by the driving motor around the rotating axis of the polygonal mirror 4, the photosensitive drum 8 is scanned by the converging light beam from the polygonal mirror 4 in a main scanning direction indicated by an arrow A in FIG. 1. The photosensitive drum 8 is also rotated around its rotating axis, and it is scanned by the converging light beam in a sub scanning direction perpendicular to the main scanning direction. Thus, an electrostatic latent image is formed on the photosensitive drum 8 by the optical recorder unit in accordance with the image signal.
In the printing apparatus described above, a developing unit including a toner cartridge is provided. When the electrostatic latent image on the photosensitive drum is passed through the developing unit, the electrostatic latent image is developed on the photosensitive drum with toner, so that the electrostatic latent image is made visible. This toner image is transferred by a transfer charging unit from the photosensitive drum to a copy sheet. This copy sheet has been transported to the photosensitive drum 8 via the registration rollers in a synchronized manner. Then, the copy sheet with the toner image is transported from the photosensitive drum to a fixing unit including a fixing heater, so that the toner image is fixed to the copy sheet by the heat and pressure of the fixing unit. The copy sheet is then transported from the fixing unit to a copy sheet ejection outlet part of the printing apparatus. Each copy sheet transported from the fixing unit is stacked at the copy sheet ejection outlet part.
However, in the above described printing apparatus, during the scanner mode operation in which the scanner unit is operated, some print processing units including the optical recorder unit, the fixing unit and the transfer charging unit, which should be used in the printer mode only, are unnecessarily driven. Thus, in the above described printing apparatus, there is a problem in that the driving of such printing processing units for a long period of time during the scanner mode operation will shorten an operational life of each of the units in the printing apparatus, and also the electric energy consumed by the printing apparatus is higher than a reasonable energy consumption level. Also, the construction of the conventional printing apparatus is bulky because both the driving mechanism of the built-in scanner and the driving mechanism of the print processing units are necessary.
Moreover, at the time of an original document sheet being passed through the transfer charging unit or the fixing unit when the scanner mode is performed in the printing apparatus described above, there is a problem in that an original document to be scanned may be damaged due to the pressure of the transfer charging unit or the heat and pressure of the fixing unit, and that a residual toner on the photosensitive medium is transferred to the original document sheet.