1. Field of the Invention
The present invention relates to an image forming apparatus such as a copier, a laser-beam printer, or a facsimile machine.
2. Description of Related Art
A typical laser-beam printer including a controller that performs image processing and an engine that performs image formation performs image formation by following, for example, a timing chart of FIG. 18A. Specifically, when the controller receives image information and a print instruction from a host computer, the controller transmits a print reservation command to the engine on the basis of the received print instruction. Furthermore, at a point of time when analysis of the image information received from the host computer and conversion of the image information into bitmap data have been completed and it has become possible to transmit a video signal, the controller transmits a print start command to the engine. When the engine receives the print start command, the engine starts a pre-process (hereinafter, also referred to as a pre-rotation sequence) that is a preparation operation for performing a print operation, and performs a print sequence that is the print operation. After that, the engine performs a post-process (hereinafter, also referred to as a post-rotation sequence) that is a finish operation for finishing the print operation, so that the print operation is completed.
In the above-mentioned print operation, a method for reducing a time period (hereinafter, also referred to as a FPOT (First Print Out Time)) taken until an image for a first sheet is formed is disclosed in Japanese Patent Laid-Open No. 2004-234551. Specifically, as illustrated in FIG. 18B, first, a controller receives image information and a print instruction from a host computer. It is proposed that, after that, the image information is analyzed, and a command (hereinafter, also referred to as a print-start notification command) for notifying the engine of a predicted time period taken until a print start command can be transmitted is provided. The engine compares the predicted time period (Tprint) of which the engine has been notified from the controller with a time period (Tpre) taken to perform a pre-rotation sequence. Then, in the case where the predicted time period (Tprint) of which the engine has been notified from the controller is shorter than the time period (Tpre) taken to perform the pre-rotation sequence, the engine starts the pre-rotation sequence at a point in time when the print-start notification command is received. In contrast, in the case where the predicted time period (Tprint) of which the engine has been notified from the controller is longer than the time period (Tpre) taken to perform the pre-rotation sequence, the engine starts the pre-rotation sequence later so that the pre-rotation sequence will finish while the time period over which the pre-rotation sequence is performed is coinciding with the predicted time period (Tprint). Accordingly, an appropriate FPOT is realized in accordance with the size of the image information transmitted from the host computer to the controller, and deterioration of consumable items such as photosensitive drums can be reduced.
However, also in the method of the related art, in the case where the predicted time period (Tprint) is longer than the time period (Tpre) taken to perform the pre-rotation sequence, even when image expansion performed by the controller has finished, the pre-rotation sequence has not finished yet, so that an appropriate FPOT is not realized. For this reason, for example, a method is considered, in which the FPOT is reduced by starting the pre-rotation sequence, using a start point, a time at which a print reservation command is transmitted to the engine. However, when the pre-rotation sequence is immediately started at a point in time when a print reservation is confirmed, in the case in which a long time is taken to expand image information because the size of the image information is large and in which a long time is taken until a print start command can be received, the pre-rotation sequence finishes too early. When the pre-rotation sequence has finished too early, there is a probability that this will lead to deterioration of consumable items such as photosensitive drums.
The present invention according to the present application has been made in view of circumstances described above, and it is an object of the present invention to make the FPOT appropriate in accordance with the time taken to expand image information and to reduce deterioration of consumable items such as photosensitive drums.