Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-11-15
2004-01-06
Hsieh, Shih-Wen (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S023000
Reexamination Certificate
active
06672704
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a liquid ejecting apparatus having an ejection head capable of ejecting a liquid from a nozzle opening, and a method of cleaning the ejection head.
As liquid ejecting apparatuses for ejecting a liquid from a nozzle opening, there are an ink-jet type recording apparatus capable of ejecting an ink solution onto a printing recording medium, a filter manufacturing apparatus for manufacturing a color filter by ejecting color materials of red, green, and blue onto the surface of a glass substrate, and a liquid-crystal injecting apparatus for injecting a liquid crystal of a predetermined amount into grids making up picture elements.
Hereafter, a description will be given of the related art with reference to an example of the ink-jet type recording apparatus which is a kind of liquid ejecting apparatus.
In this ink-jet type recording apparatus, an ink solution is ejected from nozzle openings by the actuation of pressure generating elements. These nozzle openings are very small through holes. For this reason, when the thickening of the liquid occurs in the vicinities of the nozzle openings, there occur such problems that the jet speed of the liquid changes and that the jet direction becomes curved.
To prevent such trouble, various recovering operation is performed in the ink-jet type recording apparatus. For example, the so-called flushing operation is carried out in which ink droplets are ejected immediately before the recording operation so as to eliminate thickened ink. In addition, the so-called fine vibration operation for allowing the ink in the vicinities of the nozzle openings to slightly flow to disperse the thickened ink in the ink cartridge and the suction cleaning for sucking the ink solution in a recording head through the nozzle openings are also carried out. Further, JP-A-9-295411 discloses an apparatus in which the aforementioned flushing operation is effected at a frequency higher than a frequency at which drive pulses are generated at the time of recording.
The aforementioned operations exhibit advantages in cases where the thickened liquid located in close proximity to a nozzle surface is eliminated. However, in cases where the viscosity of the liquid increases in deep recesses of the nozzle openings or the degree of thickening is high, it is difficult to eliminate the thickened liquid by these operations.
SUMMARY OF THE INVENTION
The invention has been devised to overcome the above-described problems, and its object is to provide a liquid ejecting apparatus capable of eliminating a thickened liquid in the vicinities of the nozzle openings, as well as a method of cleaning an ejection head.
In order to solve the aforesaid object, the invention is characterized by having the following arrangement.
(1) A liquid ejecting apparatus comprising:
an ejection head including a nozzle opening capable of ejecting a liquid, a pressure generating chamber communicating to the nozzle opening, and a pressure generating element for changing a pressure in the liquid inside the pressure generating chamber;
a drive signal generator for generating a drive signal including a drive pulse to be applied to the pressure generating element;
an application controller for controlling an application of the drive signal to the pressure generating element; and
a suction unit for sucking the liquid in the ejection head through the nozzle opening,
wherein the drive signal generator is capable of generating a first drive signal which is used when the liquid is ejected toward an object of ejection and a second drive signal which is used at the time of the cleaning operation of the ejection head and whose frequency at which a drive pulse is generated is higher than that of the first drive signal, and
wherein the suction unit is actuated in association with the application of the second drive signal to the pressure generating element.
(2) The liquid ejecting apparatus according to (1), wherein
the suction unit includes a cap member having a sealed hollow portion which is open to a nozzle surface side of the ejection head, a negatively pressurizing unit communicating to the cap member to negatively pressurize the sealed hollow portion, and a negative-pressurization controller for controlling the actuation of the negatively pressurizing unit, and
the nozzle surface is sealed with the nozzle opening opposed to an interior of the sealed hollow portion, and the negatively pressurizing unit is actuated in the sealed state to suck the liquid inside the ejection head.
(3) The liquid ejecting apparatus according to (1), wherein the suction unit is actuated after the application of the second drive signal to the pressure generating element.
(4) The liquid ejecting apparatus according to (1), wherein the suction unit is actuated during the second drive signal is applied to the pressure generating element.
(5) The liquid ejecting apparatus according to (2), wherein the cap member is capable of being disposed at a position spaced apart from the nozzle surface in a state that the sealed hollow portion is opposed to the nozzle surface, and
the application controller applies the second drive signal to the pressure generating element in the spaced-apart state.
(6) The liquid ejecting apparatus according to (2), wherein the application controller applies the second drive signal to the pressure generating element in a state that the nozzle surface is sealed by the cap member.
(7) The liquid ejecting apparatus according to (6), wherein the application controller applies the second drive signal to the pressure generating element in a state that the liquid is accumulated in the sealed hollow portion.
(8) The liquid ejecting apparatus according to (7), wherein the liquid is accumulated in the sealed hollow portion by actuating the negatively pressurizing unit in a state that the nozzle surface is sealed by the cap member.
(9) The liquid ejecting apparatus according to (8), wherein the liquid accumulated in the sealed hollow portion and the nozzle surface are brought into contact with each other in the state that the nozzle surface is sealed by the cap member.
(10) The liquid ejecting apparatus according to (6), wherein
an opening-closing valve whose opening and closing are controlled by the negative-pressurization controller is provided midway in an open-to-atmosphere passage having one end communicating to the sealed hollow portion of the cap member and another end open to the atmosphere, and
the negative-pressurization controller closes the opening-closing valve in the state that the nozzle surface is sealed by the cap member, and the negative-pressurization controller opens the opening-closing valve and actuates the negatively pressurizing unit when the sealing of the nozzle surface is released.
(11) The liquid ejecting apparatus according to (1), wherein the application controller intermittently applies the second drive signal to the pressure generating element a plurality of times.
(12) The liquid ejecting apparatus according to (1), wherein the application controller is capable of selecting pressure generating elements to which the second drive signal is applied.
(13) The liquid ejecting apparatus according to (12), wherein the ejection head has a plurality of nozzle blocks each having a common liquid supply source, and
the application controller applies the second drive signal to each unit of the pressure generating elements belonging to the nozzle block.
(14) The liquid ejecting apparatus according to (13), wherein the suction unit is capable of sucking the liquid for each nozzle block.
(15) The liquid ejecting apparatus according to (12), wherein
the ejection head has a plurality of nozzle rows each having nozzle openings formed in a row, and
the application controller applies the second drive signal alternately to odd-numbered nozzle openings and even-numbered nozzle openings which belong to one nozzle row.
(16) The liquid ejecting apparatus according to (1), wherein the application controller periodically effects application of the second drive signal and
Katakura Takahiro
Momose Kaoru
Morikoshi Koji
Sano Tsuyoshi
Takemoto Kiyohiko
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