Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1995-07-31
2001-12-18
Fuller, Benjamin R. (Department: 2855)
Incremental printing of symbolic information
Ink jet
Controller
C347S014000, C347S013000, C347S057000, C347S060000
Reexamination Certificate
active
06331039
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to ink jet recording apparatus and method in which a driving pulse width is modulatable.
Recently, various types of printers have been developed as output devices for personal computers, word processors, facsimile machines or the like in offices. Among such printers, an ink jet type printer, in which ink is ejected to a recording material, is advantageous in that the recording noise level is low, that high quality recording is possible, that downsizing is easy, or the like.
Among ink jet recording type printers, a cartridge type is widely used in which an ink container for containing ink and a recording head for converting an electric signal to thermal energy by a electrothermal transducer element to produce film boiling of the ink so that the ink is ejected by a pressure of a bubble created by the boiling are provided.
The ink jet cartridge is advantageous in that the cost can be reduced because the passages between the recording head and the ink container are shortened, and in addition, the ink consumption for ink ejection recovery operation is minimized. If the quantity of the ink in the ink container corresponds to the service life of the recording head, the exchange of the cartridge by a user, in effect, performs the maintenance operation for the recording head and for the ink replenishment. Corresponding to the intention of the user, color recording and monochromatic recording cartridges are exchangeable in some machines already on sale.
In the recording apparatus using such a recording head, a driving pulse applied to the electrothermal transducer is determined in consideration of a quantity of the heat per unit area of an ink contact surface of the electrothermal transducer element and durability against stress caused by the heat.
On the other hand, as one of conditions for accomplishing high quality of the image in an Ink jet recording apparatus, there is information of ink ejection quantity to avoid non-uniformity In the image. In one example to achieve this, a temperature (ambient temperature) under which the recording-head cartridge is placed, and the temperature of the recording head per se, are taken into account for the control of the driving pulse. This is because the viscosity and the surface tension or the like of the ink changes in accordance with the ambient temperature with the result of change of the flow resistance in the ink supply system including ink container and ink supply path or the like and because the change of the temperature of the recording head namely the temperature of the ink in the ejecting portion results in the change in the ink ejection amount as the case may be. In such a case, if the driving pulses are constant, the ejection amount changes, and therefore, the uniformity is not achieved.
FIG. 2
is a diagram representing ambient temperature dependency of the ejection amount when the driving pulse condition is fixed, in which Tenv is the ambient temperature and Vd is the ejection amount.
As shown in the Figure, the ejection amount linearly increases with increase of the ambient temperature. The inclination of the line is defined as ambient temperature dependence coefficient, which is expressed as follows:
Kenv=&dgr;Vd/&dgr;Tenv[p1/°C.drop]
The coefficient Kenv is determined by the structure of the recording head cartridge, ink property and the like.
FIG. 3
is a diagram of a dependency of the ejection amount on the head temperature (the head temperature is equal to the ink temperature in the ejecting portion because the temperature property is static) when the driving pulse is fixed.
As shown in this Figure, the ejection amount Vd substantially linearly increases in the temperature range shown therein with increase of the head temperature TH. The inclination is defined as a head temperature dependence coefficient KH, which is expressed:
Ki=&dgr;Vd/&dgr;TH[p1/°C./drop]
The coefficient KR is also determined by the ink property or the like.
It has been proposed in an application having been assigned to the assignee of this application that the change of the ejection amount due to the ink temperature variation is removed by PWM (pulse width modulation) driving for the electrothermal transducer elements (ejection heaters) to accomplish a constant ejection amount.
FIG. 4
illustrates divided pulses relating to the PWM drive.
In this Figure, the ordinate represents a driving voltage applied (v), and the abscissa represents the time period of the application of the pulse. In the Figure, P1 is a pulse width of the first one (pre-pulse) of the divided heat pulses; P3 is a pulse width of the second pulse (main pulse); P2 is an interval time (rest period) between the pulses P1 and P2; and T0, T1, T2, T3 are time periods for determining P1, P2 and P3.
The PWM ejection amount controls are classified into two types. One of them is as disclosed In Japanese Laid-Open Patent Application No. 92565/1993. This method is shown in
FIG. 5
, wherein the time periods T2 and T3 are constant, and the period T1 is modulated. In other words, the width P1 of the prepulse is modulated. This will be called prepulse width modulation driving method. With this driving method shown in
FIG. 5
, the interval time P2 is also modulated in accordance with the modulation of the prepulse. Another method is as disclosed in Japanese Laid-Open Patent Application No. 169659/1993, for example. This is shown in
FIG. 6
of this application, the time intervals (T1−T0) and (T3−T2) are constant, and the time interval (T2−T1) is modulated. In other words, the pulse width interval time) P2 between the prepulse P1 and the main pulse P3 is modulated without changing the pulse widths of the prepulse P1 and the main pulse P3. This is called V interval time modulation driving method.
Referring to
FIG. 7
, the change of the ejection amount in the prepulse width modulating method will be described. In
FIG. 7
, the ordinate represents ejection amount Vd, and the abscissa represents a width of the prepulse P1, wherein arN designates non-ejection area wherein the ink is not ejected, and arB is a bubble formation area wherein the ink is ejected by the prepulse P1.
FIG. 7
shows the change of the ejection amount when the main pulse P1 is constant.
With the increase of T1 namely P1, the ejection amount increases. When a predetermined peak is exceeded, it is decreased, and falls in the region of bubble formation by the width P1. With this driving method, the setting of T1 may be optimized, so that the linearity in the change of the ejection amount relative to the modulation of T1 can be provided, in which case, the control is easy.
Referring to
FIG. 8
, the description will be made as to the interval time modulation method. In
FIG. 8
, the ordinate represents the ejection amount Vd, the abscissa represents the interval time t.
With the increase of the interval time P2, the ejection amount increases, and falls in an area arN incapable of bubble formation. With this driving method, it is preferable that the prepulse width is maximum under the condition that the bubble is not formed. In this case, it is equal to the maximum of P1 in the prepulse width modulation driving method. In this driving method, the temperature increase of the recording head is a problem. When the temperature rise is suppressed by not using the divided pulses in the high temperature area and decreasing the pulse width (single pulse), (T2−T1) is decreased with increase of the temperature, and (T1−T0) is reduced from the point of time at which (T2−T1) is zero. By doing so, the above-described control can be effected, and therefore, the modulation is possible with maintenance of the continuity of the pulse width.
FIG. 9
shows a pulse profile upon P2=(T2−T1)=0.
In either of the prepulse width modulating driving method and an interval time modulation driving method, the maximum width of the overall pulses (T3−T0) is limited by driving frequency or the like from the s
Iwasaki Osamu
Kanematsu Daigoro
Otsuka Naoji
Takahashi Kiichiro
Yano Kentaro
Canon Kabushiki Kaisha
Dickens C.
Fitzpatrick ,Cella, Harper & Scinto
Fuller Benjamin R.
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