JPH08244238A - Ink jet recording apparatus - Google Patents

Abstract

PURPOSE: To enable high-resolution recording of recording dots without requiring a highly advanced machining technology or a complicated drive method, by providing means for specifying the flying direction of ink droplets so that the interval between ink droplet-landing points on a recording medium is shorter than the interval between ink ejecting points. CONSTITUTION: A recording head 21 comprises a plurality of piezoelectric oscillators 8 provided on a concave substrate 9, and a piano-concave acoustic lens 20 provided thereon for converging ultrasonic waves generated thereby. Provided over the acoustic lens 20 are an ink chamber 3 and a slit-like nozzle unit 10. It is designed that the geometric centers of the slit-like nozzle unit 10 and the concave substrate 9 coincide with the center axis of a cylindrical recording paper support roller 5. Thereby the ink droplets ejected from the nozzles 10 fly toward the center of the concave face where the nozzles 10 are arranged. Since the interval between flying ink droplets decreases as they fly farther, the ink droplet interval is shorter than the interval between the ink ejecting points when the ink droplets reach and stick to recording paper 7 supported on the peripheral face of the roller 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printer which prints an image on a recording paper by ejecting liquid ink as small droplets, and more particularly to the structure of an ink ejection portion of a recording head.

[0002]

2. Description of the Related Art Conventionally, liquid ink is used as recording paper (medium).
2. Description of the Related Art Ink jet printers are known that fly upward to form recording dots. This ink jet printer has the advantages that it is less noisy than other recording methods and does not require processing such as development and fixing, and is attracting attention as a plain paper recording technology.

Many ink jet printer systems have been devised up to now, but in particular, a system in which ink droplets are ejected by the pressure of vapor generated by the heat of a heating element, for example, Japanese Patent Publication Nos. 56-9429 and 61-61. 59911, and a method of ejecting ink droplets by a pressure pulse due to displacement of a piezoelectric body, for example, Japanese Patent Publication No. 53-12138, is typical. However, these methods require individual nozzles for each recording dot, and local ink concentration is likely to occur, and the nozzles tend to be clogged. Therefore, the recording heads based on these methods are mainly
It has been put to practical use as a serial scanning type head that is mounted on a carriage and repeats scanning in a direction orthogonal to the recording paper conveyance direction.

On the other hand, in order to overcome the drawbacks of these methods, a method using ultrasonic waves (IBM TDB, in which droplets are ejected from the ink liquid surface by using the pressure of an ultrasonic beam generated from a piezoelectric body). vol.16, no.
4, pp. 1168 (1973-10), USP-43
08547 (1981), USP-4697195 (1)
987), USP-4751529 (1988), US
P-4751530 (1988), USP-50418.
49 (1991), JP-A-62-66943, JP-A-6.
3-162253, JP-A-63-166545, JP-A-63-166546, JP-A-63-166548, JP-A-63-321157, JP-A-2-184443, JP-A-3-200199, JP-A-4-296562, JP-A-4-296563, JP-A-4-356328, JP-A-5
-278218, JP-A-2-184443, etc.) have been proposed. This method has the feature that it does not require nozzles for each individual dot or partition walls of the ink flow path, and it has an effective structure for prevention and restoration of clogging, which was a major obstacle in making a line head. have. In addition, since ink droplets having a very small diameter can be stably ejected, it is also suitable for high resolution.

However, in the conventional print head using such an ink jet printer system, since the ink nozzles are linearly arranged, unless the special and complicated driving method is adopted, the print resolution in the nozzle arrangement direction is the nozzle. There was a problem that it was substantially determined by the interval of. For example, in an ink jet printer of a variable capacity type using a piezoelectric material, as shown in FIG.
Ink ejection elements including the piezoelectric body 2, the ink chamber 3, and the nozzle 4 were linearly arranged at equal intervals. Therefore, the recording resolution in the arrangement direction of the nozzles 4, in other words, the recording paper 7 conveyance direction must be equal to the nozzle arrangement interval.

[0006]

As described above, in the conventional serial scanning type ink jet printer using a plurality of ink nozzles, the recording resolution in the paper conveying direction, in other words, the direction in which a plurality of ink nozzles are arranged is set. Has a problem that it is substantially determined by the distance between the nozzles. Therefore, it was difficult to manufacture a recording head having a high resolution due to problems in processing technology.

Similarly, the serial scanning type ink jet printer using the ultrasonic wave having the slit-shaped nozzle also has a problem that the resolution in the slit direction is substantially determined by the interval of the transducer array.

The present invention solves the above-mentioned problems of the related art, and does not require a high processing technique or a complicated driving method,
An object of the present invention is to provide an inkjet printer capable of recording a recording image point with high resolution.

[0009]

SUMMARY OF THE INVENTION The present invention provides an ink jet recording apparatus for recording an image on a recording medium by ejecting ink droplets from a plurality of ink droplet ejection points and flying them on the recording medium. An ink jet recording apparatus comprising means for defining a flight direction of the ink droplet so that an interval between arrival points of ink droplets on the recording medium is smaller than an interval between the plurality of ink droplet ejection points. It is provided.

In a preferred embodiment of the present invention,
In an ink jet recording apparatus that records an image on a recording medium by ejecting ink droplets from a plurality of ink droplet ejection points and flying the recording medium, a plurality of ink droplet ejection points arranged on a concave surface An ink jet head for ejecting ink droplets ejected from the ink jet head toward the geometric center of the concave surface, and a convex surface having a radius of curvature smaller than that of the concave surface of the ink jet head to form the recording medium. An inkjet recording apparatus is provided, which is provided with a supporting member that is supported from the back surface.

[0011]

According to the present invention, the distance between the ink droplet ejection points on the recording medium is smaller than the distance between the plural ink droplet ejection points of the ink jet head or the ink ejection groove. In addition, since the flight direction of the ink droplets is defined, it is possible to record the recording image points at intervals narrower than the intervals between the plurality of ink droplet ejection points.

Further, according to a preferred aspect of the present invention, since the ink droplets ejected from the individual ink droplet ejection points respectively fly toward the geometric center of the concave surface, the distance between the ink droplets is different according to the flying distance. Becomes narrower. Therefore, the distance between the ink droplets when they adhere to the recording medium is
It becomes narrower than the initial interval discharged from the inkjet head.

Further, in a particularly preferred embodiment of the present invention, the concave surface and the convex surface have substantially the same geometric center. At this time, the flight distance of the ink between the concave surface and the convex surface is substantially equal. For this reason, the intervals of the respective ink droplets when they are attached to the recording medium are evenly narrower than the initial intervals of ejection from the inkjet head.

Further, Ra is the distance between the convex surface of the supporting member for supporting the recording paper from the back and the geometric center, Rb is the distance between a plurality of ink droplet ejection points and the geometric center, and the thickness of the recording paper is Letting Tp be the distance between ink droplets that can fly from the nozzle surface of the recording head, and Dn, the distance Dr between the ink image points that can be recorded on the recording paper can be expressed by Equation 1.

Dr = {(Ra + Tp) / Rb} .Dn ... Equation 1 Here, since (Ra + Tp) <Rb, Dr <Dn, so that the distance between ink droplets that can fly from the recording head It can be seen that it is possible to record the recording image points at narrow intervals. For example, (Ra + Tp): Rb =
If it is 1: 2, it is possible to perform recording with a resolution twice that of ink droplets that can fly from the surface of the recording head.

As described above, according to a particularly preferred aspect of the present invention, the intervals between the ink droplet arrival points on the recording medium are uniformly narrowed with respect to the intervals between the plurality of ink droplet ejection points. Therefore, it is easy to control the resolution.

As described above, according to the present invention, the ink jet printer which enables the recording of higher resolution by applying the conventional recording head processing technique without using the advanced processing technique or the complicated driving method. Can be provided.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings. FIG. 1 is a schematic view showing an embodiment of a variable capacity ink jet printer using a piezoelectric element according to the present invention. FIG. 2 is a diagram showing an inkjet head of the inkjet printer shown in FIG. As shown in FIGS. 1 and 2, the recording head 1 includes a piezoelectric body 2 and an ink chamber 3.
An ink ejecting element including a nozzle 4 is provided for each recording dot. The tips of the nozzles 4 of each ink ejection element are arranged on the concave surface at regular intervals. The recording head 1 is provided with a cylindrical recording paper support roll 5 so as to face the concave surface and the geometric center point of the concave surface exists on the central axis of the cylinder. Further, the recording paper 7 is closely supported by the two auxiliary support rolls 6 on the peripheral surface of the recording paper support roll 5, and the recording paper is moved by the rotation of the recording paper support roll 5 and the auxiliary support roll 6. Has become. In addition, the recording head 1 includes a recording paper support roll 5
It has a mechanism that moves mechanically in the longitudinal direction.

Since the ink droplets ejected from each nozzle 4 fly toward the center point of the concave surface where the nozzle 4 is arranged, the distance between them becomes narrower according to the flying distance. On the recording paper 7 on the side surface of the recording paper support roll 5 having a central axis where the geometric center of the concave surface where the nozzles 4 are arranged is present, ink droplets are attached at intervals narrower than the intervals of the nozzles 4. At this time, the ratio of narrowing the intervals becomes almost equal.

Let Ra be the radius of the recording paper support roll 5, Rb be the radius of the concave array of a plurality of nozzles 4, Tp be the thickness of the recording paper, and Dn be the distance between the nozzles 4 on the concave surface. The distance Dr between the ink image points recorded on the image No. 7 is represented by the above-mentioned formula 1. In this embodiment, the radius (Ra) of the recording paper fixing roll 5 is 2.9 mm, the radius (Rb) of the arcuate array of the plurality of nozzles 4 is 6 mm, and the thickness (Tp) of the recording paper is
) Is 0.1 mm and the nozzle interval (Dn) on the arc is 0.071 mm, the ink image dot interval (Dr) recorded on the recording paper is 0.035 mm. That is, the distance between the image points on the recording paper 7 is half the distance between the nozzles 4 of the recording head 1. In a conventional inkjet printer, the nozzle spacing of the recording head is the same as the resolution in the paper feed direction. Therefore, when the recording head is manufactured with the same nozzle spacing as in this embodiment, the resolution is 360 dpi (d).
However, a printer according to the present invention can obtain a resolution of 720 dpi.

Further, since the geometric center of the arrangement on the concave surface of the nozzle 4 exists on the central axis of the recording paper supporting roll 5, the image point interval on the recording paper can be constant without distortion. further,
Since the nozzles 4, the ink chambers 3, and the ink ejection elements including the piezoelectric bodies 2 are arranged in a radial pattern, the arrangement intervals of the piezoelectric bodies 2 located at the rearmost portion can be set wider than the arrangement intervals of the nozzles. .

FIG. 3 is a schematic view showing an embodiment of an ultrasonic ink jet printer using the piezoelectric vibrator array according to the present invention. FIG. 4 is a diagram showing the inkjet head. As shown in FIGS. 3 and 4, the recording head 21 is provided with a plurality of piezoelectric vibrators 8 on a concave substrate 9. An acoustic lens 20 having a plano-concave shape is provided above the piezoelectric vibrator 8.
By 0, the generated ultrasonic waves are focused in the direction orthogonal to the arrangement of the piezoelectric vibrator array. The acoustic lens 20 can be omitted by processing each piezoelectric vibrator into a concave shape in the longitudinal direction. Further, the ink chamber 3 and the slit-shaped nozzle 10 are provided on the acoustic lens 20, and the slit-shaped nozzle 10 and the concave substrate 9 are
It has such a structure that its geometric center lies on the central axis of the cylindrical recording paper support roll 5. Multiple piezoelectric vibrators 8
By controlling the phase of a part of the piezoelectric vibrator group in the inside and driving them simultaneously, the ultrasonic waves are focused on the ink liquid surface in the slit-shaped nozzle 10 to cause the ink droplet to fly.

The ink droplets ejected from the nozzle 10 fly toward the center point of the concave surface where the nozzle 10 is arranged. Therefore, like the ink jet printer shown in FIG. 1, the distance between them becomes narrower according to the flight distance thereof, and on the recording paper 7 on the side surface of the recording paper support roll 5, an interval narrower than the distance between the ink droplet ejection points of the nozzles 10. Ink drops adhere to the surface. In addition, at this time, the ratio of the narrowed intervals becomes substantially equal.

At this time, the discharge interval of the ink droplets from the slit-shaped nozzle 10 is Db, and the radius of the recording paper support roll 5 is R.
Letting a be the radius of curvature of the slit-shaped nozzle 10 be Rb and the thickness of the recording paper be Tp, the distance Dr between the ink image points recorded on the recording paper 7 can be expressed by Equation 1. In this embodiment, the distance between the image points on the recording paper 7 is 1/2 of the ink discharge distance from the slit nozzle 10 of the recording head 1.

FIG. 5 is a schematic view showing another embodiment in which high speed recording is performed by using the recording head 1 of the variable capacity ink jet printer shown in FIGS. In this example,
The recording paper 7 is fixed on the entire side surface of the recording paper support roll 5. In most conventional serial scanning printers, the movement of the recording paper 7 is temporarily stopped while the recording head 1 moves in the longitudinal direction of the recording paper support roll 5. But Figure 5
In the embodiment shown in (1), it is possible to record the image on the recording paper by constantly rotating the recording paper support roll 5 at the time of printing and simultaneously moving the recording head 1 in the longitudinal direction of the recording paper support roll 5. As a result, high-speed recording can be realized.

FIG. 6 is a schematic view showing a modified example of the variable capacity ink jet printer shown in FIG. In this example, as shown in FIG. 6, instead of the recording paper support roll 5, a recording paper support member 15 having a partially convex surface is provided. The recording paper support member 15 is separated from the recording paper when the recording paper 7 is first conveyed. After that, the recording paper support member 15 is pressed against the recording paper 7 when recording is performed. When the recording paper 7 is pressed, the recording portion is deformed according to the convex surface. By providing such a moving mechanism of the recording paper supporting member, it is possible to prevent the paper jam at the initial stage of conveying the recording paper.

FIG. 7 is a schematic diagram showing a modification of the ultrasonic ink jet printer shown in FIG. An example of this is shown in FIG.
As shown in FIG.
And the recording paper 7 that receives ink have a flat shape. In this case, the recording paper 7 is conveyed in a flat state,
Since the recording is stopped, the recording paper support roll 5 shown in FIG.
It is not necessary to provide a support member that deforms the recording paper into a convex shape by pressing the recording paper from the side opposite to the recording surface. The feature of this printer is that, when a part of a plurality of piezoelectric vibrators is phase-controlled and driven, it is generated by a part of each piezoelectric vibrator. It is to have a means for controlling so that the phases of the sound waves match at a position deviated from the center line of the piezoelectric vibrator group. That is, focusing of ultrasonic waves is controlled so as to occur asymmetrically. By adopting such a driving method, it becomes possible to make the ink droplets fly obliquely. In this printer, by applying this driving method, the flight direction of the ink droplets can be controlled so that the distance between the ink droplet arrival points on the recording medium is smaller than the distance between the plurality of ink droplet ejection points. This enables higher density recording.

[0028]

As described above, according to the present invention, recording image points are formed at intervals narrower than the intervals of a plurality of ink droplet ejection points of the recording head, without requiring a high-level processing technique or a complicated driving method. There is provided an inkjet printer capable of recording an image.

[Brief description of drawings]

FIG. 1 is a diagram showing the structure of an embodiment of a variable capacity inkjet printer using a piezoelectric element according to the present invention.

FIG. 2 is a diagram showing the inkjet head of FIG.

FIG. 3 is a diagram showing the structure of an embodiment of an ultrasonic inkjet printer using a piezoelectric vibrator array according to the present invention.

FIG. 4 is a diagram showing the inkjet head of FIG.

FIG. 5 is a diagram showing a structure of a modified example of the variable capacity inkjet printer shown in FIG. 1.

FIG. 6 is a diagram showing the structure of another modified example of the variable capacity inkjet printer shown in FIG. 1.

7 is a diagram showing the structure of a modification of an ultrasonic inkjet printer using the piezoelectric vibrator array shown in FIG.

FIG. 8 is a diagram showing a structure of a conventional variable-capacity inkjet printer using a piezoelectric element.

[Explanation of symbols]

 1, 21, 31 ... Recording head 2 ... Piezoelectric body 3 ... Ink chamber 4 ... Nozzle 5 ... Recording paper fixing roll 6 ... Auxiliary fixing roll 7 ... Recording paper 8 ... Piezoelectric vibrator 9 ... Substrate 10 ... Slit nozzle 11 ... Support roll

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Chiaki Tanuma 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Incorporated Toshiba Research and Development Center

Claims (2)

[Claims] 1. An ink jet recording apparatus for recording an image on a recording medium by ejecting ink droplets from the plurality of ink droplet ejection points to fly on the recording medium. An ink jet recording apparatus comprising means for defining a flight direction of the ink droplet so that the distance between the arrival points of the ink droplet on the recording medium is smaller than the distance. 2. An ink jet recording apparatus for recording an image on a recording medium by ejecting ink droplets from a plurality of ink droplet ejection points and flying the recording medium on a recording medium. An ink jet head for ejecting ink droplets ejected from the ink droplet ejection point toward the geometric center of the concave surface, and a convex surface arranged facing the concave surface of the ink jet head and having a radius of curvature smaller than the concave surface. An ink jet recording apparatus comprising: a support member that supports the recording medium from the back side.