1. Field of the Invention
The present invention generally relates to image forming apparatuses for forming an image on a recording medium. Particularly, the present invention relates to an inkjet image forming apparatus that forms an image by discharging droplets of a recording fluid onto a recording medium.
2. Description of the Related Art
An inkjet image forming apparatus is known in which droplets of a recording fluid (such as ink) are discharged from a recording head in order to form an image on a recording medium, such as a sheet of paper. Because of the principle of operation of the inkjet image forming apparatus, a part of an ink droplet may be separated as the droplet travels through the space between the recording head and the recording medium, or upon landing on the recording medium. Such separated droplet portions may be scattered in the form of an ink mist, which may remain attached to various surfaces within the image forming apparatus.
The ink mist attached within the image forming apparatus may stain the hand of a user accessing the inside of the apparatus, particularly if the mist accumulates as a layer of dirt or grime. The ink mist may also attach to various sensors within the apparatus, such as optical sensors for detecting a sheet in the image forming apparatus or encoder sensors for detecting a carriage position. As a result, detection accuracy of the sensors may decrease, thereby adversely affecting the recording medium transport function of the image forming apparatus, or resulting in degraded image quality.
In order to prevent the attachment of the ink mist within the image forming apparatus, a technology according to Patent Document 1, for example, collects the mist by causing the mist to be adsorbed on a surface at an appropriate location within the apparatus by using static electricity or corona discharge. At the same time, the technology also makes locations where prevention of mist attachment is desired electrically conductive, and connect these locations to ground. By thus preventing the locations from being charged, the attaching of mist to these locations may be prevented.
In order to collect the mist, a technology according to Patent Document 2 provides a discharge electrode for charging an ink mist and a dust-collecting electrode for collecting the charged ink mist. According to this technology, the discharge electrode and the dust-collecting electrode are supplied with a high voltage from a high-voltage circuit for generating a high voltage used for charging a recording medium transport belt.
However, the technology according to Patent Document 1 is not capable of controlling the amount of charge of the mist, so that the proportion of the charged mist or its intensity may vary. Further, because the charge of the mist also varies greatly depending on the environment, the mist cannot be collected with high efficiency. The technology according to Patent Document 2 requires a separate charging unit for charging the mist, resulting in a cost increase. Further, the efficiency with which the mist can be charged is rather low because of the nature of mist.    Patent Document 1: JP10-264412A    Patent Document 2: JP2005-349799A