1. Field of the Invention
The present invention relates to an ink storage apparatus for storing ink supplied to an ink ejecting section for ejecting liquid to a print medium and a print head including the ink storage apparatus.
2. Description of the Related Art
An inkjet print apparatus has been known in which ink is ejected through a print head to a print medium to perform printing. Such an inkjet print apparatus (hereinafter also simply referred to as a print apparatus) generally performs a high-definition printing by a small print head in which a plurality of nozzles for ejecting ink are formed with a high density.
By arranging the small print heads and supplying inks of different colors to the respective print heads, a color printing of a print medium can be performed with a relatively low cost and small configuration. Thus, the inkjet print apparatus has been used for various print apparatuses for business and family uses such as a printer, a facsimile, and a copier.
In the inkjet print apparatus as described above, an ink supply system for supplying ink to a recording head generally includes therein a negative pressure generating means. Ink subjected to the negative pressure by the negative pressure generating means is supplied to a print head and an ink ejecting element performs an ink ejecting operation. In order to stabilize the ink ejecting operation in the print head as described above, what is important is how to process air bubbles mixed in or generated in the print head.
Japanese Patent Laid-Open No. H10-250079 (1998) discloses a configuration in which an ink ejecting section includes therein at least one chambers for air bubbles generated from the ink ejecting element so that the generated air bubbles are accumulated in the chamber. In the case of this configuration, when the capacity of the chamber reaches its limit, an ink supply flow path is blocked by air bubbles to prevent ink supply, causing an inoperable status. Thus, this configuration requires an ink tank as a consumable good to include an ink ejecting section and the ink tank must be exchanged with the new one before the limit of the chamber capacity is reached.
Another print head configuration in which an ink tank and an ink ejecting section are separately provided is disclosed in Japanese Patent Laid-Open No. 2007-168421. This print head includes a main high-capacity liquid chamber and a plurality of low-capacity liquid chambers that are formed via a filter and that communicate with one another. All of the liquid chambers are filled with ink. By using the configuration as described above to feed ink into the print head, air bubbles flowing into and generated in the print head can be caused to remain in the filter section and can be emitted without causing an increased flow path resistance.
In the case of this configuration however, ink is desirably supplied through a circulating system because emitted ink is unused as waste liquid. This may cause a possibility where ink is deteriorated due to the heat from the ink ejecting section. This also limits applicable negative pressure generating means. Therefore, this configuration cannot be used to a configuration as disclosed in Japanese Patent Laid-Open No. 2006-326855 in which a fan is directly connected to a print head to actively control a negative pressure.
Another configuration is disclosed in Japanese Patent Laid-Open No. 2008-03025. In this configuration, one space in a print head liquid chamber includes both of an ink layer and an air layer and a liquid chamber includes an exhaust opening that is connected to the air layer separately from an ink supply opening and an ink eject opening and that is opened to the outside. By the configuration as described above, air bubbles flowing into and generated in the print head are caused to move upward to reach the air layer and air in air bubbles is emitted via the exhaust opening to the outside.
However, the ink layer and the air layer have an unclear interface therebetween because a conventional print head has a difficulty in securely eliminating the air bubbles from the ink layer through the air layer (hereinafter vapor-liquid separation). This has caused a possibility where the air layer is filled with air bubbles. This has caused a possibility where air bubbles may enter an unexpected part to thereby cause a failure. One example is a disadvantage that the unclear interface between the ink layer and the air layer prevents an appropriate control of the amount of ink in the print head.
Therefore, it is required to eliminate the air bubbles flowed into or generated in the ink storage apparatus of the print head and to effectively realize the vapor-liquid separation.