Piezoelectric ink jet recording head formed by press working

An ink jet recording head comprising:

• an ink passage unit formed by superposing a nozzle plate, an ink passage plate and a cover plate, the nozzle plate having a plurality of nozzles, the ink passage plate having a first surface and a second surface which are opposite to each other and having a plurality of pressure producing chambers connected to the nozzles respectively and having an ink reservoir communicating with the pressure producing chambers via a plurality of ink inlet ports, the cover plate being joined to the first surface of the ink passage plate;
• and
• a pressure generator for applying pressure to an ink in the pressure producing chambers;
• the ink passage plate comprising a first sheet having the first surface and a second sheet having the second surface, the first sheet and the second sheet being superposed, the second sheet being made of a metal sheet having the second surface and a third surface opposite to each other,
• the first sheet having a plurality of through holes corresponding to the pressure producing chambers, a through hole corresponding to the reservoir, and a plurality of through holes for forming the ink inlet ports, the ink inlet ports being shaped and arranged to allow the through holes corresponding to the pressure producing chambers to communicate with the through hole corresponding to the reservoir,
• the second sheet having a plurality of recesses forming the pressure producing chambers and a through hole forming the reservoir, the through hole forming the reservoir being formed from the second surface to the third surface in the metal sheet, the recesses forming the pressure producing chambers being formed in the third surface of the metal sheet by press working, the recesses forming the pressure producing chambers being connected to the through holes corresponding to the pressure producing chamber, the through hole forming the reservoir being connected to the through hole corresponding to the reservoir, and
• a protuberance-forming recess being formed in the second surface of the metal sheet by the press working so that portions surrounding the recesses forming the pressure producing chambers protrude when the recesses forming the pressure producing chambers are formed in the third surface of the metal sheet by the press working.