1. (Field of the Invention)
This invention relates to an ink jet head, and a cleaning device and a cleaning method employed in the manufacture of the ink jet head.
2. (Description of the Related Art)
In recording data on a recording sheet with an ink jet head, ink is jetted from the minute orifices of the ink jet head so as to stick on the recording sheet. The orifices are extremely small in diameter, several tens of micro-meters (.mu.m). This is a main cause for the trouble that dust or foreign matters are caught in the orifices, thus obstructing an ink jetting operation. If that trouble occurs, the manufacture of the ink jet head is lowered in yield.
In order to eliminate this difficulty, for instance Japanese Patent Application (OPI) No. Sho 63-5947 (the term "OPI" as used herein means an "unexamined published application") has disclosed a method in which a cleaning passageway is formed in the wall of an ink passageway near the orifices in such a manner that it is communicated with the outside of the ink jet head body, and a cleaning solution is allowed to flow in the cleaning passageway to remove dust and foreign matters from the orifices.
On the other hand, in order to increase the repetitive response frequency of the ink jet head or to decrease the drive voltage, an on-demand type ink jet head is popularly employed which has a flow path structure as shown in FIG. 16. That is, as shown in FIG. 16, ink supply passageways 8 and ink supply passageway throttles 7 smaller in diameter than the former 8 are provided on the side of a common ink chamber 15 communicated with pressure chambers 10, to suppress the flow of ink to the ink chamber 15. It is true that this structure has improved the response characteristic and the drive voltage of the ink jet head; however, the latter is still disadvantageous in the following point: The ink supply passageway throttles 7 of the ink supply passageways 8 are several tens of micro-meters in diameter similarly as in the case of the orifices. Therefore, dust or foreign matters coming in the ink chamber 15 during manufacture, being moved by the ink, block the ink supply passageway throttles 7, so that the ink is not smoothly jetted from the orifices 11. The present inventors have conducted research on the ink jet head, and found that it is possible to remove foreign matters from the pressure chambers 10, but it is not possible to remove foreign matters from the ink supply passageway throttles 7. In addition, the inventors have investigated where the foreign matters are caught in the ink jet head, and found that 99% of the foreign matters are caught at the ink supply passageway throttles 7, and the remaining at the orifices 11. This means that it is essential to prevent foreign matters from being caught at the ink supply passageway throttles 7.
On the other hand, a method of washing away foreign matters from the pressure chamber has been proposed in the art; however, it is not concrete. That is, the foreign matters cannot be completely removed merely by running a cleaning solution, and it is necessary to improve the cleaning solution running method.
If a cleaning solution for cleaning mechanical parts is employed for removal of the foreign matters, the remaining solution may clog up the ink jet head when dried, or it reacts with the ink, to form depositions which may damage the components of the ink jet head.