Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-04-30
2001-12-25
Noori, Max (Department: 2855)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06332672
ABSTRACT:
BACKGROUND OF INVENTION
The present invention relates to an ink jet recording head for expanding or contracting a part of a pressure generating chamber communicating with a nozzle aperture by an actuator for flexural oscillation so as to jet an ink droplet from the nozzle aperture.
An ink jet recording head has two types of a piezoelectric vibration type for mechanically deforming a pressure generating chamber and pressurizing ink and a bubble jet type provided with a heater element in a pressure generating chamber for pressurizing ink by the pressure of bubbles generated because of the heat of the heater element. The piezoelectric vibration type of recording head is further classified into two types of a first recording bead using a piezoelectric vibrator displaced in an axial direction and a second recording head using a piezoelectric vibrator displaced by flexure. As for the first recording head, although high-speed driving is enabled and recording in high density, there is a problem that the number of manufacturing steps in large because cutting is required for machining a piezoelectric vibrator and three-dimensional assembly is required when a piezoelectric vibrator is fixed to a pressure generating chamber.
In the meantime, as for the second recording head, as a silicon monocrystalline substrate is used for base material, a pressure generating chamber and a passage such as a reservoir are formed by anisotropic etching, an elastic film can be extremely thin and the pressure generating chamber and a piezoelectric vibrator can be formed very precisely by forming the piezoelectric vibrator using a film forming technique such as sputtering piezoelectric material. Also, the opening area of the pressure generating chamber can be reduced as much as possible and recording density can be enhanced.
However, as a metallic plate is still used for a nozzle plate to maintain the working precision of a nozzle aperture, there is a problem that the whole recording head is distorted due to differential thermal expansion when the piezoelectric vibrator is fixed by burning. Such a problem can be solved by using a thermal expansion characteristic adjusting member disclosed in Japanese Patent Application Unexamined Publication No. Hei. 6-122197. However, there is a problem that if a piezoelectric vibrator is constituted by sputtering piezoelectric material, the piezoelectric vibrator is thin and a higher electric field is applied in the case of driving at the same voltage, compared with a piezoelectric vibrator constituted by burning a green sheet. Therefore, if humidity in the atmosphere is absorbed, leak current between driving electrodes is readily increased and finally, dielectric breakdown is caused.
SUMMARY OF THE INVENTION
The present invention is made to solve such problems and the object is to provide an ink jet recording head in which the failure of the operation caused by the change of a piezoelectric vibrator formed using film forming technique due to external environment such as humidity is solved by forming a sealed atmosphere and a problem caused by the change of pressure in the sealed atmosphere is solved.
According to the first aspect to the invention, there is provided an ink jet recording head comprising: a nozzle;
a passage formed substrate having partitions forming at least a row of pressure generating chambers, which is communicated with said nozzle;
an elastic film forming a part of the pressure generating chambers;
a piezoelectric vibrator formed on a diaphragm opposite to said pressure generating chamber; and
a cap member joined to the side of the piezoelectric vibrator of the passage formed substrate for sealing space in a state in which space to extent that a movement is not prevented is secured; and
pressure change absorbing means for absorbing the change of pressure in the space of the cap member.
In the first aspect of the invention, the piezoelectric active part is insulated from outside by the cap member and pressure inside the cap is kept fixed by the pressure change absorbing means.
According to the second aspect of the invention, there is provided the ink jet recording head according to the first aspect, wherein the pressure change absorbing means is an elastic porous member provided in the cap member.
In the second aspect, the variation of pressure inside the cap member is absorbed by the elastic porous member provided in the cap member.
According to the third aspect of the invention, there is provided the ink jet recording head according to the first aspect, wherein: the pressure change absorbing member is a flexible part provided in the cap member; and the space in the cap member is opposite to the outside via the flexible part.
In the third embodiment, the change of pressure in the cap member is absorbed by the flexible part.
According to the fourth aspect of the invention, there is provided the ink jet recording head according to the first aspect, wherein: a dummy pressure generating chamber to which ink is not supplied is provided next to the pressure generating chamber; and the pressure change absorbing means is a flexible plate forming a boundary between the dummy pressure generating chamber and the space in the cap member.
In the fourth aspect, the change of pressure in the cap member is absorbed by the flexible plate forming the boundary between the dummy pressure generating chamber and the space in the cap member.
According to the fifth aspect of the invention, there is provided the ink jet recording head according to the fourth aspect, wherein the flexible plate is defined by at least elastic film of the dummy pressure generating chamber.
In the fifth aspect, the change of pressure in the cap member is absorbed by the diaphragm.
According to the sixth aspect of the invention, there is provided the ink jet recording head according to the first aspect, wherein the whole cap member is made of flexible material.
In the sixth aspect, the change of pressure in the cap member is absorbed by the whole cap member.
According to the seventh aspect of the invention, there is provided the ink jet recording head according to the sixth aspect, wherein the flexible material is paper the inner surface of which is coated or aluminum.
In the seventh embodiment, the change of pressure in the cap member is effectively absorbed.
According to the eighth aspect of the invention, there is provided the ink jet recording head according to either six or seventh aspect, wherein the flexible material is joined to the passage formed substrate by welding aluminum.
In the eighth aspect, the cap member is readily and securely joined to the passage formed substrate.
According to the ninth aspect of the invention, there is provided the ink jet recording head according to any one of the preceding aspects, wherein: the pressure generating chamber is formed by applying anisotropic etching to a silicon monocrystalline substrate; and each layer of the piezoelectric vibrator is formed by forming a film and lithography.
In the ninth aspect, a large number of ink jet recording heads provided with high density nozzle apertures can be relatively easily manufactured.
According to the tenth aspect of the invention, there is provided the ink jet recording head according to any one of the preceding aspects, wherein: a reservoir connected to the pressure generating chamber is formed in the passage formed substrate; and a nozzle plate provided with the nozzle apertures is joined.
In the tenth aspect, an ink jet recording head for jetting ink from a nozzle aperture can be readily realized.
According to the eleventh aspect of the invention, there is provided the ink jet recording head according to any one of the first to ninth aspects, wherein a passage unit for forming a common ink chamber for supplying ink to the pressure generating chamber and a passage for connecting the pressure generating chamber and the nozzle aperture is joined to the passage formed substrate.
In the eleventh aspect, ink is jetted from a nozzle aperture via the passage unit.
REFERENCES:
patent: 5499042 (1996-03-01), Yanaga
Nishiwaki Tsutomu
Sakai Shinri
Yazaki Shiro
Dickens C.
Noori Max
Seiko Epson Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
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