Ink jet recording head

Details Ink jet recording head Ink jet recording head

2003-04-22

2004-06-29

Gordon, Raquel Yvette (Department: 2853)

Incremental printing of symbolic information

Ink jet

Ejector mechanism

C347S054000

Reexamination Certificate

active

06755510

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet recording apparatus for forming ink liquid droplets by discharging ink for the performance of recording. The invention also relates to an ink jet recording head used for such recording apparatus.
2. Related Background Art
It is generally practiced to provide a printer, a copying machine, a printing device for facsimile equipment or the like with the structure that prints images formed by dot patterns on a printing medium, such as paper, thin plastic sheet, or cloths, among some others, in accordance with image information. The printing apparatuses of the kind are classified into those using ink jet method, wire-dot method, thermal method, and laser beam method depending on the printing method adopted by each of them.
Of those ones, the ink jet method is such as to perform printing by discharging ink from a recording head to a printing medium. The ink jet method makes it possible to print images in high precision at high speed. Further, being of non-impact type, noises are smaller with such advantage that it is easier to print color images by use of multiple color ink.
Of the ink jet methods currently available, the bubble jet printing method invented by the applicant hereof makes it possible to discharge ink by the utilization of pressure exerted when liquid is heated to bubble. For the bubble jet printing method, heaters that heat liquid can be arranged in high density easily. Thus, as an advantage, among many, that this method provides, an apparatus can be structured with ease for the performance of high-resolution printing at high speed.
For the ink jet recording apparatus of bubble jet printing method, ink is usually used as printing liquid. Therefore, with the evaporation of ink, its viscosity may change or with possible mixture of bubbles in ink, the performance of ink discharge is affected by such causes to produce unfavorable effect on prints in some cases.
More specifically, at the early stage of the installation of an ink jet recording head on an ink jet recording apparatus or at the time of exchanging ink tanks, the mixture of bubbles occurs in ink when ink is filled in the ink jet recording head. Also, as time elapses, even in a state where ink is filled in the ink jet recording head, the air may be allowed to enter the discharge ports that discharge ink or fitting portions of ink supply passages. Then, in some cases, bubbles may be created in ink. If such bubbles exist in a large amount in the vicinity of ink discharge portion, discharges are disabled (causing non-discharge) to change the ink discharge amounts and discharge speeds, hence impeding the normal recording in some cases.
Here, therefore, it is necessary to adopt the technology and technique specially made available for reliably maintaining the ink discharge function of the recording head for an ink jet recording apparatus. Among such technologies and techniques, there is known a method in which suction recovery process is executed to suck ink, which resides in the vicinity of the discharge portion, from the recording head for appropriately removing mixed bubbles and overly viscous ink together with ink thus sucked out. The head recovery device that executes the suction recovery process is generally structured with a cap for capping, which closely covers the discharge port surface where discharge ports of the recording head are open, and a suction pump that performs suction inside the cap. The suction recovery process executed by the head recovery device is such that the recording head moves to the position facing the cap, and after capping, the inside of the cap is sucked by use of the suction pump, and then, bubbles and overly viscous ink in the recording head are sucked and removed together with ink sucked out at that time. The suction recovery process of the kind is now an important art among the technologies and techniques for reliably maintaining an ink jet recording apparatus.
In recent years, it has been required that the ink jet recording apparatus should record images in the so-called high quality having precisely adjusted gradation therefor. As one of the methods that make the formation of such images possible, it is devised to provide the discharge units for one recording head in order to discharge liquid droplets in different discharge amounts. In such a case, the balance required for desirable performance of discharges may differ on various aspects per discharge unit, which makes it impossible to execute any stabilized operation of recording sometimes.
For example, usually, for the discharge portion where liquid droplet is discharged in a comparatively large amount (hereinafter referred to as a large discharge portion), the discharge port area and the sectional area of the flow path communicated with the discharge port are made larger than the discharge portion where liquid droplet is discharged in a comparatively small amount (hereinafter referred to as a small discharge portion). As a result, the flow resistances in the large discharge portion and the small discharge portion are made different greatly. Therefore, the characteristics of bubble removal become different when these portions are covered by one cap, and the suction recovery process is made under the same condition.
Also, as compared with the large discharge portion, the small discharge portion is easier to be affected by the higher viscosity of ink resulting from evaporation, because the area of the discharge port is smaller to make the flow resistance higher. Consequently, when a recording operation is executed after a specific time elapses without any recording operation, there is a fear that non-discharge takes place in the small discharge portion at the time of the first shot of ink or there is encountered a phenomenon (called viscous plug phenomenon) that a desired amount of discharge cannot be obtained.
Also, the characteristics of refilling, that is, the refilling of liquid subsequent to the liquid discharge, are made different in the large discharge portion and the small discharge portion, thus resulting in a fear that stabilized liquid discharges cannot be performed.
Also, if a structure is arranged so that liquid is supplied from one liquid supply port to the large discharge portion and the small discharge portion, the vibration of liquid exerts influence on the small discharge portion nearby, which is propagated from the large discharge portion when liquid is discharged from that portion, and there is a fear that stabilized liquid discharges cannot be performed.
SUMMARY OF THE INVENTION
Now, therefore, with attention given to the technical problems discussed above with respect to the conventional art, the present invention is designed. It is an object of the invention to provide an ink jet recording head with intermixed large discharge portion and small discharge portion, which is capable of performing stabilized recording with various balances well kept for the large and small discharge portions, and also, to provide an ink jet recording apparatus having such ink jet recording head mounted thereon.
It is another object of the invention to provide an ink jet recording head with intermixed large discharge portion and small discharge portion, for which it is attempted to reduce the influence of liquid vibrations propagated when liquid is discharged from discharge ports nearby in the small discharge portion, while enhancing the refilling characteristics in the small discharge portion to make stabilized recording possible, and also, to provide an ink jet recording apparatus having such ink jet recording head mounted thereon.
In order to achieve the aforesaid objects, the ink jet recording head of the present invention comprises a first discharge portion for discharging liquid from a first discharge port as liquid droplet in a specific amount, a second discharge portion for discharging liquid from a second discharge port as liquid droplet in a larger amount than that of the first discharge portion, and an opening provided on

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