Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1998-08-17
2001-09-11
Fuller, Benjamin R. (Department: 2855)
Incremental printing of symbolic information
Ink jet
Controller
C310S316010
Reexamination Certificate
active
06286922
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an inkjet recording apparatus which is capable of ejecting ink droplets by making use of a piezoelectric element, and more particularly to a control system and method which controls a driving pulse applied to the piezoelectric element.
2. Description of the Related Art
There has recently been a growing interest in non-impact recording methods, because noise while recording is extremely small to such a degree that it can be neglected. Particularly, inkjet recording methods are extremely effective in that they are structurally simple and in that they can perform high-speed recording directly onto ordinary medium. There has been proposed an inkjet recording method making use of a piezoelectric element.
In the inkjet recording method making use of a piezoelectric element, a driving pulse is applied to a selected piezoelectric element and thereby the piezoelectric element is deformed to eject an ink droplet. The waveform of the driving pulse is very important to stabilize the ink ejection and improve the quality of printing because the stable and proper waveform of the driving pulse produces the stable amount of ejected ink droplet and the optimal ejection velocity. However, a variation in waveform of the the driving pulse is cause by variations in capacitance of the piezoelectric element and characteristics of each circuit element, resulting in variations in amount and ejection velocity of ink droplet.
To stabilize the ink droplet ejection to improve the quality of printing, there has been proposed an inkjet head driver in Japanese Patent Unexamined Publication No. 6-182993. The inkjet head driver sets a driving pulse to a desired voltage by adjusting the time constant and the rising time of the driving pulse.
However, the rising time is adjusted by changing the variable resistor or replacing a resistor with another resistor. Therefore, it is necessary to do the resistor adjustment prior to shipments and such adjustment is a time-consuming step. Further, after shipments, it is very difficult to adjust the rising time to cancel out a variation in pulse waveform due to a change of ambient temperature, resulting in reduced stability of the quality of printing.
Another inkjet head driver has been proposed in Japanese Patent Unexamined Publication No. 8-112894. The inkjet head driver measures the slope of leading or trailing edge of a trapezoidal driving pulse and controls the output current of a variable current source depending on an error obtained by comparing the measured slope with a preset slope.
However, the conventional inkjet head driver needs the steps of slope measurement which is not simple, resulting in increased burden upon a control processor.
SUMMARY OF THE INVENTION
It is an objective of the present invention to provide control system and method for use in an inkjet recording apparatus which can achieve the reliable and stable ink droplet ejection with simplified control.
According to the present invention, a control system for controlling a driving pulse applied to a piezoelectric element of an inkjet head is comprised of a variable-voltage source for producing a control voltage depending on a control signal; a pulse generator for generating a driving pulse having a voltage waveform with a slope determine depending on the control voltage; a monitor for monitoring a peak voltage of the driving pulse; and a controller for adjusting the control signal so that the peak voltage reaches a predetermined voltage.
As described above, the control signal is adjusted so that the peak voltage reaches the predetermined voltage and the waveform of the driving pulse is automatically set to a desired trapezoidal waveform with a slope determined depending on the control voltage. Therefore, the piezoelectric element properly deforms with stability even in the case of a change in temperature, resulting in the stable quality of printing.
Further, only the control voltage causes the slope and the height of the voltage waveform to be determined. Therefore, the waveform control is simplified with improved stability.
The pulse generator may be comprised of a constant-current source for producing first and second constant currents determined by the first and second control voltages, respectively; a waveform forming circuit for producing a voltage pulse having the voltage waveform by charging a capacitor with the first constant current for a first predetermined time period and then discharging the capacitor with the second constant current for a second predetermined time period; and an amplifier for amplifying the voltage pulse to produce the driving pulse.
The waveform forming circuit may be comprised of a timing generator for generating a first timing pulse having a pulse width of the first predetermined time period and a second timing pulse having a pulse width of the second predetermined time period wherein there is a predetermined time interval between a trailing edge of the first timing pulse and a leading edge of the second timing pulse; and a waveform controller for producing the voltage pulse having a trapezoidal waveform where a leading-edge slope and a height of the trapezoidal waveform is determined by the first constant current, a trailing-edge slope is determined by the second constant current.
REFERENCES:
patent: 5212497 (1993-05-01), Stanley et al.
patent: 5631675 (1997-05-01), Futagawa
patent: 5757392 (1998-05-01), Zhang
patent: 5-116350 (1993-05-01), None
patent: 6-182997 (1994-07-01), None
patent: 6-182993 (1994-07-01), None
patent: 7-148920 (1995-06-01), None
patent: 8-112894 (1996-05-01), None
patent: 9-201963 (1997-08-01), None
Patent Abstracts of Japan vol. 17, No. 24. Apr. 9, 1992 JP 4-249721.*
Derwent Publications Ltd., XP002117621 (English language abstract of JP 08 112894A, published May 7, 1996).
Patent Abstracts of Japan, vol. 199, No. 712, Dec. 25, 1997 (English language abstract of JP 09 201963, published Aug. 5, 1997).
Patent Abstracts of Japan, vol. 199, No. 711, Nov. 28, 1997 (English language abstract of JP 09 187949, published Jul. 22, 1997).
Patent Abstracts of Japan, vol. 18, No. 526, Oct. 5, 1994 (English language abstract of JP 06 182993, published Jul. 5, 1994).
Dickens C.
Foley & Lardner
Fuller Benjamin R.
NEC Corporation
LandOfFree
Inkjet head control system and method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Inkjet head control system and method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Inkjet head control system and method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2481695