Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2001-04-17
2003-01-07
Hallacher, Craig (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
Reexamination Certificate
active
06502914
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink-jet recording apparatus for jetting ink drops from a nozzle opening by vibration of a piezoelectric-vibrator and printing on a recording paper or others, and a method for driving an ink-jet recording head thereof.
2. Description of the Related Art
Generally, an ink-jet recording apparatus has a recording head with many nozzle openings in the sub-scanning direction (the recording paper feeding direction). The recording head is moved in the main scanning direction (the direction of the recording paper width) by a carriage mechanism. Predetermined paper feeding is executed, and a desired printing result is obtained. On the basis of dot pattern data obtained by expanding print data input from a host computer, ink drops are jetted from each nozzle opening of the recording head respectively in predetermined timing. Each of the ink drops is jetted and adhered to a print recording medium of a recording paper or others, thereby dots are formed and printing is carried out.
The recording head mentioned above generally transfers deformation of a piezoelectric-vibrator to a vibration plate so as to contract a pressure generating chamber, increase the inner pressure, and jet ink drops from the nozzle openings. The aforementioned deformation of the piezoelectric-vibrator is obtained by changing a drive voltage input to the piezoelectric-vibrator. Therefore, ink drops are jetted by expanding and contracting the pressure generating chamber.
Each piezoelectric-vibrator used for the recording head of the ink-jet recording apparatus is assumed as an ideal capacitor from the viewpoint of design. Namely, the voltage (segment voltage) of the piezoelectric-vibrator is considered to continuously hold the voltage during the time of non-supply of the drive signal mentioned above. On the basis of this consideration, the drive signal is preset so as to keep the initial voltage and terminal voltage on the same level.
However, an actual piezoelectric-vibrator has an insulation resistance. Therefore, when it is left as it is with no drive signal supplied, it is found that the vibrator voltage gradually drops by natural discharge. The drop of the vibrator voltage, for example, is caused by non-uniformity of the piezo-electric body of the piezo-electric layer. Moreover, when the electrodes of the piezoelectric vibrator are short-circuited by a foreign substance existing between the electrodes, the drop of the vibrator voltage is caused.
Accordingly, a means for applying a voltage to the piezoelectric vibrator in the standby state with no drive signal applied (hereinafter referred to as a voltage recovery means) is proposed so as to recover the vibrator voltage dropped by discharge up to the intermediate voltage which is the standby voltage of the piezoelectric vibrator. For example, in Japanese Patent No. 3097155 (Japanese Patent Laid-Open Publication No. 4-310748, Japanese Patent Application No. 3-77718), a piezoelectric element charging means for compensating for a reduction in the charge due to discharge of the piezo-electric element by applying the charging voltage to the piezo-electric element in different timing from the print timing of the piezo-electric element is described.
Meanwhile, the drop amount of the vibrator voltage increases as the time from supply end of an earlier drive signal to supply start of a later drive signal, that is, the non-supply period of the drive signal becomes longer. Further, when the film thickness of the piezoelectric vibrator becomes thinner (as the electric field intensity becomes higher), the vibrator voltage drops remarkably. As a result, in a piezoelectric vibrator of a small volume (thin film thickness) requested recently, even if the non-supply period of the drive signal is very short, the difference between the vibrator voltage dropped due to discharge and the initial voltage of the later waveform element increases.
Furthermore, recently, to increase the height difference of the vibration damping waveform to be applied to the piezoelectric vibrator after ink drops are jetted, there is a tendency to set the intermediate voltage, which is the standby voltage, high. The drop amount of the vibrator voltage increases as the vibrator voltage increases. Therefore, as the intermediate voltage is set higher, the drop amount of the vibrator voltage increases.
As mentioned above, recently, the drop amount of the vibration voltage tends to increase. When the vibrator voltage is recovered by the voltage recovery means in a state that the vibrator voltage drops greatly, a problem arises that ink drops are accidentally jetted from the nozzle opening at the same time.
In the conventional ink-jet recording apparatus mentioned above, it is very difficult to include both the drive waveform for medium dots and the drive waveform of minute dots in the drive signal (COM) in one print cycle (one drive cycle). The reason is that the standby voltage suited to the drive waveform for medium dots and the standby voltage suited to the drive waveform for minute dots do not coincide with each other generally. When the standby voltage suited to the drive waveform for medium dots is fit to the standby voltage suited to the drive waveform for minute dots, the height difference of the drive waveform for medium dots itself becomes too large. As a result, a problem arises that at the time of jet of medium dots, air bubbles are apt to be taken into the nozzle opening. When air bubbles are taken into the nozzle opening like this, the inner pressure of the pressure generating chamber is not increased normally. As result, ink drops are not jetted normally, causing defective jet.
In the conventional ink-jet recording apparatus mentioned above, even if the ink viscosity is changed due to changing of the environmental temperature around the recording apparatus, ink drops are jetted by the same drive signal regardless of changing of the environment. Therefore, for example, when the ink viscosity is lowered due to a high-temperature environment or others, the meniscus is apt to become unstable and air bubbles are easily taken into the nozzle opening as mentioned above. Furthermore, when the operation environment of the recording apparatus is changed and the ink viscosity is changed, the jet characteristics are also changed and a problem arises that a fixed print quality cannot be easily obtained.
SUMMARY OF THE INVENTION
The present invention was developed with the foregoing in view and is intended to provide an ink-jet recording apparatus and a method for driving an ink-jet recording head thereof for surely preventing accidental ink drops at the time of recovery of the vibrator voltage by the voltage recovery means.
Another object of the present invention is to provide an ink-jet recording apparatus and a method for driving an inkjet recording head thereof for jetting ink drops without taking air bubbles into the nozzle opening.
Still another object of the present invention is to provide an ink-jet recording apparatus and a method for driving an ink-jet recording head thereof for preventing air bubbles from taking into the nozzle opening even if the environmental conditions around the recorder are changed.
According to the present invention, an ink-jet recording apparatus includes: a recording head having a piezoelectric vibrator for expanding and contracting a pressure generating chamber connected to a nozzle opening; and drive signal generator for generating a drive signal to be applied to said piezoelectric vibrator so as to drive said piezoelectric vibrator; wherein said drive signal includes an expansion waveform element for changing a voltage so as to expand said pressure generating chamber, a contraction waveform element for changing a voltage so as to contract said pressure generating chamber expanded by said expansion waveform element and jet an ink drop from said nozzle opening, and a vibration damping waveform element which changes from a terminal voltage of said contraction waveform element to a vibratio
Hosono Satoru
Otokita Kenji
LandOfFree
Ink-jet recording apparatus and method for driving ink-jet... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ink-jet recording apparatus and method for driving ink-jet..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ink-jet recording apparatus and method for driving ink-jet... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3055197