1. Field of the Invention
The present invention relates to a printing apparatus and driving force transfer control method. Particularly, the present invention relates to a printing apparatus having a switching mechanism which, if necessary, utilizes movement of a carriage to switch the transfer destination of the driving force of a driving source for conveying a printing medium, in order to drive another mechanism, and a driving force transfer control method for the apparatus.
2. Description of the Related Art
An inkjet printing apparatus prints by discharging ink from a printhead onto a printing medium. The inkjet printing apparatus has the following advantages. For example, the printhead can be easily downsized and can print a high-resolution image quickly. The printing apparatus can print on plain paper without any special processing. The apparatus requires low running cost, and hardly generates noise because of non-impact printing. The apparatus can easily print a color image with inks of multiple colors.
The printhead of the printing apparatus is generally formed by arraying small orifices. In some cases, ink becomes non-dischargeable or unprintable due to bubbles or dust entering the orifices, or high ink viscosity upon evaporation of ink solvent. In this case, the ink is refreshed to eliminate the cause of the discharge failure.
Most general-purpose serial printing apparatuses employ a DC motor as a driving source for scanning a carriage supporting a printhead. Such a printing apparatus often uses a DC motor even as a driving source for conveying a printing medium in a direction perpendicular to the moving direction of the carriage.
Printing apparatuses capable of driving a plurality of mechanisms using a single driving source have been developed to decrease the number of motors serving as driving sources for the sake of cost reduction of the apparatuses, space-saving, and the like.
A printing apparatus of this type includes a switching mechanism for switching a mechanism to be driven, as needed.
An example of conventional driving switching mechanisms proposed for a serial printing apparatus utilizes driving of a carriage.
The driving switching mechanism can convey a printing medium and drive a recovery mechanism using a single conveyance motor. A clutch gear is arranged as a mechanism for switching the driving. When the carriage moves to a switching position, the clutch gear is pushed by the carriage to engage with an LF gear. At the switching position, a home position sensor cannot detect the light shielding plate of the carriage and thus determines that the carriage has reached the switching position. The driving switching operation can be reliably executed using movement of the carriage. Conventional techniques pertaining to this mechanism include one disclosed in Japanese Patent Laid-Open No. 9-141966.
In this prior art, the cap of a printhead is interposed between a clutch gear and a switching position (home position).
This arrangement suffers the following problem when the switching position is set between the clutch gear and the cap or at the same position as the clutch gear and the home position sensor has not correctly detected the carriage position. That is, it cannot be determined whether the carriage is appropriately pushing the clutch gear or the printhead is capped. This problem prevents reliable execution of the driving switching operation using movement of the carriage.