Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1996-04-17
2001-05-22
Fuller, Benjamin R. (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S010000
Reexamination Certificate
active
06234607
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to ink jet printing technology, and is particularly concerned with techniques for suppressing residual ink vibration after ink droplet ejection from the ink jet head.
2. Description of the Related Art
In general, an ink jet head comprises a pressure generating ink ejection chamber for applying pressure to ink to selectively eject it therefrom. One end of the pressure generating chamber is typically connected to an ink tank through an ink supply path, and the other end connects to a nozzle opening from which the ink drops can be ejected. Part of the pressure generating chamber is made to be easily deformed and functions as a diaphragm. This diaphragm is elastically displaced or deformed by an electromechanical converter such as a piezoelectric or electrostatic driver to selectively generate the pressure that ejects ink drops from the nozzle opening.
Recording apparatuses using this type of ink jet head offer outstanding operating characteristics, including low operating noise and low power consumption, and are widely used as hard copy output devices for a variety of information processing devices. As the performance and functionality of information processing devices has improved, demand has also risen for even higher quality and speed printing both text and graphics. This has made urgent the development of technologies enabling even finer ink drops to be ejected consistently at even higher frequencies or print speed.
Because of the structure of the ink jet head as described above, vibration remains in the ink inside the pressure generating chamber (also called the ink chamber because it is filled with ink; hereafter “ink chamber”) after ink ejection, and this residual vibration can easily result in the formation of undesirable ejected ink droplets (also called “satellites”). To avoid this, the conventional approach has been to increase the flow resistance of the ink supply path connecting the ink chamber and ink tank to alternate the residual ink vibration. However, if the flow resistance of the ink supply path is high, the ink refill supply rate of ink to the ink chamber after ink ejecting is reduced, thereby lowering the maximum ink eject frequency, and ultimately the printing speed of the printing device.
Alternatively, as described in JP-A-S56-161172 (1981-161172), residual vibration can be canceled, and satellite emissions thereby prevented, by applying at an appropriate timing after the diaphragm drive signal a complementary signal canceling the residual vibration of the diaphragm. This resolves the problem described above, at least for non-varying droplet applications, and achieves a recording apparatus with a high output speed.
However, with the technology described in JP-A-S56-161172 (1981-161172), the diaphragm must be driven at an appropriate timing determined by the specific vibration period of the ink vibration system in order to cancel the residual vibration of the diaphragm. This is because residual diaphragm vibration may actually be promoted if the cancel signal timing is inappropriate. The technology described in JP-A-S56-161172 (1981-161172) therefore provides a variable resistor for adjusting the signal timing according to the specific vibration period of the ink vibration system. The problem here is that a sufficient vibration damping effect may not be achieved when any of the parameters determining the specific vibration period of the ink vibration system, e.g., the ink viscosity, change as a result of environmental changes, typical of which are ambient temperature fluctuations.
Also, expressing various density gradations by changing the size of the ink droplets formed on the recording medium is a preferred means of improving print quality. The size of the ink droplets output by any recording apparatus (printer) using an ink jet head is determined by various factors, one of which is the size (also called “ink ejection mass”) of the ink drops ejected by the ink jet head.
A technology providing plural electrostrictive means of different sizes in the ink chamber, and separately controlling and driving these electrostrictive means to eject ink droplets of various sizes, is described in JP-A-S55-79171 (1980-79171). But, when the technological concept described in JP-A-S55-79171 (1980-79171) is applied, each of the plural, different size actuators used to deform the diaphragm must be independently driven, increasing the number of wires needed, and thus making it difficult to achieve a high nozzle density. The number of drivers also increases because of the need to separately drive each actuator, and this makes it difficult to reduce the device size.
Objects of the Invention
It is, therefore, an object of the present invention to provide diaphragm vibration dampening in ink jet heads without disturbing conventional ink refill rates to maximize refill speed.
It is a further object of the present invention to provide such vibration dampening in an easily ascertainable and automatically adjustable manner which can eliminate user intervention requirements and user error.
It is yet another objection of the present invention to employ diaphragm vibration dampening in varying-size ink droplet applications while retaining high nozzle densities and relatively low manufacturing and component costs.
SUMMARY OF THE INVENTION
In accordance with these and related objects, an ink jet recording apparatus according to the present invention comprises an ink nozzle for ejecting ink drops; an ink chamber for storing ink; an ink supply path for supplying ink to the ink chamber; a diaphragm formed on an outside wall of the ink chamber, an opposing wall disposed externally to the ink chamber at a position opposing said outside wall and separated a predetermined gap distance from the diaphragm; and a diaphragm driver capable of elastically displacing the diaphragm to where it at least contacts the opposing wall. This ink jet recording apparatus also incorporates an eject signal generator for generating a first drive signal causing ink droplet ejection; a timer for counting a predetermined period from assertion and deassertion of the first drive signal, and then outputting a timing control signal in response thereto; and a complementary signal generator for supplying to the diaphragm driver according to the timing signal a second drive signal forcing the diaphragm to contact the opposing wall.
Because the diaphragm contacts the opposing wall as a result of the second drive signal supplied from the complementary signal generator, the diaphragm is held to the opposing wall with the meniscus of the ink in the ink nozzle drawn toward the inside of the ink chamber. The specific vibration period of the ink vibration system therefore becomes extremely short and the flow rate of the ink flow due to residual vibration increases, thereby causing a rapid decrease in ink system vibration due to viscous loss. Unwanted ink ejecting due to residual vibration in the ink system can thus be prevented, and the ink eject cycle shortened to accomplish high quality printing at high speed.
The timing means in this case preferably outputs the timing signal at the specific timing at which the diaphragm most closely approaches the opposing wall. This makes it possible to attract the diaphragm to the opposing wall by applying a lower voltage. Because the speed of diaphragm displacement at this timing is slow, diaphragm behavior can be consistently controlled irrespective of any variation in the specific vibration period of the ink system (i.e., even if this timing is a constant value.)
The timer may alternatively output the timing signal at a particular time period contained within the interval during which the diaphragm displaces from the position where the volume of the ink chamber is smallest toward the position where the diaphragm is closest to the opposing wall. In this case, the diaphragm begins moving at high speed toward the opposing wall at this timing, having an effect equivalent to that when the specific vibr
Fujii Masahiro
Sakai Shinri
Dickens C.
Fuller Benjamin R.
Seiko Epson Corporation
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