JPH0226878B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to dot printers, and more particularly to print heads suitable for printing of various line widths or vector plots. For raster output, pin printer (impact printer),
It can be obtained using a thermal printer, an electrostatic printer, or an inkjet printer. Pin printers are noisy, slow, and subject to mechanical wear and failure. Thermal printers require special paper and dot characteristics are not stable. Electrostatic printers are very expensive and typically only use one color. Ink jet printers are unreliable, require pressurized ink systems, and have fairly low resolution (80 to 100 pixels per inch).
(about a dot). These aforementioned printing devices are either cumbersome to move in various directions or can only be moved at slow speeds. These systems also typically print dots only at the intersections of a two-dimensional orthogonal grid of points because the print head cannot be positioned at any arbitrary point on the paper.

The problem with the plotter is due to the pen used. The characteristics of plotter output are determined primarily by line quality and density. Current felt tip plotter pens are 2 in this regard.
There are two problems. Felt tip pens wear out, so the lines will gradually get thicker with use. Felt tip pens also dry out, so the quality of the line deteriorates over time. Carbide tips have been used to solve this problem, but they require specific pen pressure, are unreliable, and are difficult to use.
Another solution to these problems, using an entirely new rollerball pen, holds some promise. Ink jet pens have the advantage that the stylus does not come into contact with the paper and does not wear out with use. Thus, ink jet pens also hold promise as a solution to these problems.

It is desirable to be able to plot lines of various widths with a single pen. Usually the first one to get different line widths
One way to do this is to replace it with a pen of a different width. A second method is to repeatedly trace the pattern until a desired width is achieved.

The first method requires a plurality of pens,
and the printing or plotting process must be interrupted to change the pen. The second method not only requires extra time to draw the pattern multiple times, but also requires a retrace algorithm to be set up in the host computer.

According to embodiments of the present invention, the printer can print in either horizontal or vertical direction, can print characters of various sizes and line widths, and can print in raster mode, vector mode, with various line widths. -Can be used in any mode. Print·
The best head is that of a thermal ink jet printer/plotter. This is because a high resolution pattern of dots can be obtained. Accordingly, the embodiment described herein is an ink jet print head comprising a nozzle plate in which nozzles are formed and means for ejecting ink droplets through each of the nozzles. The nozzle pattern of the present invention can also be applied to other systems such as thermal printers. Generally, the nozzle and means for ejecting ink droplets may be replaced by a dot generator capable of forming dots under controlled conditions on a recording medium located at a suitable distance from the generator. The dot generator emits dots at points on the recording medium that correspond to the illustrated nozzle pattern for the ink jet embodiment.

The illustrated ink jet print head includes ink jet nozzles at selected points on a two-dimensional grid. The present invention provides a single raster scan in either horizontal or vertical direction.
To provide a print head capable of printing characters up to the width of the print head. To achieve this purpose, each column and each row of the grid is provided with at least one nozzle. It is also an object of the present invention to provide a print head which is as movable as possible and which can be quickly moved to any point on a page for printing or plotting. For this purpose, it is advantageous to reduce the number of connection lines to the print head. It is therefore preferred that there is only one nozzle in any column of the grid and only one nozzle in any row of the grid. For this purpose, the nozzle arrangement pattern is a basic nozzle pattern in which only one nozzle is arranged in any column or row.

In this case, the following two basic nozzle patterns are particularly simple configurations: The first basic nozzle pattern is a nozzle pattern with four nozzles arranged in a parallelogram, and the second is a nozzle pattern with seven nozzles arranged approximately in a hexagon. This nozzle pattern allows lines to be drawn that are 1, 2 1/2, and 4 times the nozzle diameter. In addition to the basic nozzle patterns, it is necessary to change the nozzle spacing relative to the nozzle diameter within a certain range in order to make each basic nozzle pattern bilaterally symmetrical so that a uniform line can be drawn in any direction. This makes it possible to draw lines in any direction with uniform line quality and dot spacing. The ejection of ink droplets from the nozzle is controlled to converge in an annular manner.

Hereinafter, the present invention will be explained in detail using examples.

In FIG. 3, a print head nozzle pattern suitable for printing or plotting various line widths in raster or vector scan modes is shown with a two-dimensional orthogonal grid.
Each circle represents a dot to be printed, with the dot in the center of the circle representing the center of the nozzle. The two-dimensional grid is divided into 30 x ³⁰ squares with ^sides measuring 4 mils x 4 mils. Hereinafter, a set of squares in the y-axis direction will be called a column, and a set of squares in the x-axis direction will be called a row. 1/8 inch (approximately 0.32 cm) in a single raster scan in either the x-axis direction (hereinafter referred to as horizontal direction) or the y-axis direction (hereinafter referred to as vertical direction)
Each column and each row is equipped with at least one nozzle in order to be able to print characters. To allow rapid movement of the print head during printing or plotting, one nozzle is placed in each column and row, reducing the number of electrical connections to the print head.

The nozzle pattern shown in Figure 3 is as shown in Figure 1A.
It is formed by the small basic nozzle pattern shown in FIGS. 1B, 2A, and 2B. Each of these basic nozzle patterns includes a single nozzle in each column and row. Figure 1A is
There are seven basic nozzle patterns arranged in a roughly hexagonal pattern. This nozzle pattern will hereinafter be referred to as a 7-nozzle basic nozzle pattern. The hexagonal pattern is modified to some degree to center each nozzle in the grid square. Each nozzle in this pattern has a point (0,
0), (3, -1), (1, -3), (-2, -2),
(−
3,1), (-1,3) and (2,2). However, the coordinates are 4 mils (approximately 10.16×
10 ^-3 cm).

Each printed dot has a diameter of 8 mils (20.32 x 10 ^-3 cm) in both the x and y directions, so
Each dot overlaps the dot in its adjacent column by 1/2 the dot diameter (for example, in the direction parallel to the rows,
Dots in this direction overlap by half the diameter between adjacent dots). Similarly, adjacent dots on a row each overlap by 1/2 of the dot diameter.
This 50% overlap prevents the print head output from appearing stair-stepped. In a horizontal raster scan, each row of nozzles is controlled to eject a single scan of 1/8 inch character drops. In a vertical raster scan, each row of nozzles is 1/8 of a single scan.
It is controlled to eject ink droplets of inch (approximately 0.32 cm) characters. In continuous horizontal scan,
50% of the upper dot overlaps with the lower dot of the previous scan. A similar superposition is performed for vertical scans. Therefore, characters larger than 1/8 inch (approximately 0.32 cm) can be generated by performing multiple raster scans in either the horizontal or vertical direction.

The basic nozzle pattern shown in FIG. 1B is a 7-nozzle pattern different from the one described above,
One nozzle is arranged in each column and row.
This pattern is obtained by folding the pattern shown in FIG. 1A along the x or y axis.
Such a symmetrical pattern is called a conjugate pattern, and the nozzle pattern shown in FIG. 1B is called a conjugate seven-nozzle basic nozzle pattern.

Although the basic nozzle pattern shown in FIG. 1B has 50% overlapping dots, it is not possible to draw straight lines in all directions. In the same figure, the tangent line 18 of nozzles 110 and 111 and the nozzles 112, 1
The tangents 19 of 13 and 114 are parallel. 1st B
If a straight line is drawn in substantially the same direction as the lines 18 and 19 using the nozzle shown in the figure, the straight line cannot be drawn. In this case, the line has a gap along its length. If the line were drawn with a vector movement along the direction of lines 18 and 19, this gap would have a width equal to the distance perpendicular to lines 18 and 19. Therefore, FIGS. 1A and 1B
None of the basic patterns shown in the figure can be used to draw straight lines in all directions. However, in the basic pattern shown in Figure 1A, the dots
Since the patterns overlap by 50%, they can be used to draw straight lines in directions that cannot be used with the basic pattern of FIG. 1B. As a practical matter,
The basic nozzle pattern of Figure 1A is
Straight lines can be drawn in all directions that could not be used with the basic nozzle pattern of FIG. 1B. In view of this, the print head shown in FIG. 3 includes these two basic patterns.

A basic nozzle pattern using four nozzles, one nozzle in each row and column, is shown in FIGS. 2A and 2B. The basic nozzle pattern of FIG. 2B can be obtained by folding the basic nozzle pattern of FIG. 2A in either the x-axis or the y-axis. These two patterns can be called conjugate elementary nozzle patterns. The nozzle pattern shown in FIG. 2A can be referred to as a four-nozzle basic nozzle pattern, and the pattern shown in FIG. 2B can be called a conjugate four-nozzle basic nozzle pattern. The dotted line in Figure 2A indicates that if you try to draw a straight line in this vicinity using the basic nozzle pattern,
It shows the direction in which the gap occurs. The basic nozzle pattern shown in Figure 2B has straight lines in all directions which could not be used with the nozzle pattern shown in Figure 2A because dots in adjacent columns and rows overlap each other by 50%. can be drawn. Therefore, the nozzle pattern of FIG. 3 includes both four-nozzle basic nozzle patterns.

In the basic nozzle pattern shown in Figure 1B, the nozzles are brought close together and the overlapping ratio is set by line
Even if the perpendicular distance between the nozzles and 19 is increased sufficiently until it disappears, a small distance still remains between the nozzles. By increasing the overlapping portion in this manner, the seven-nozzle basic nozzle pattern can be made to draw uniform lines in all directions. In this case, the nozzle pattern need only include one of the two conjugate 7-nozzle basic nozzle patterns. However, this is not applicable to the four-nozzle basic nozzle pattern shown in FIGS. 2A and 2B. This is because nozzles cannot be brought closer together until adjacent dots touch. Therefore, it is necessary to eliminate the gap in all directions of the vector by simply increasing the dot diameter. Therefore, if the dot diameter is not increased,
Both of these four-nozzle basic nozzle patterns must be used as arbitrary nozzle patterns.

In general, a combination using n nozzles and placing only one nozzle in each column and row is n! There is a street. However, to obtain good line characteristics, the basic nozzle pattern must have nozzles adjacent to each other (i.e., no gaps along their length for any vector direction); It is necessary that there be little variation in line width as a function of direction. The width of the resulting line along a given direction is equal to the distance between two straight lines,
parallel to the direction of print head movement and tangential to the outside of the nozzle pattern (i.e., line 11 in the direction of vector V in FIG.
5 and 116). These properties can be investigated by drawing a circle and observing whether the line width changes with angle and whether an arbitrary gap is obtained in the radial or circumferential direction of the line. Up to the case of the 9-nozzle pattern, the basic nozzle pattern described above shows only a slight change in line width due to the change in angle, and the line can be filled by using both conjugate nozzle patterns. The slight change in line width with angle indicates that the outer nozzles of these four patterns (i.e., the nozzles touching parallel lines such as lines 18 and 19 above) are approximately circular focal points (i.e., the circle is the pattern circle containing the outer nozzles). (drawn by passing through each quadrilateral of ).

Another feature of the basic nozzle pattern according to the invention is that no two nozzles in adjacent columns are also in adjacent rows. This allows sufficient room for the spacing between adjacent nozzles to act as a barrier between the nozzles, reducing fluid crosstalk between the nozzles.
If such a barrier is not formed, a certain
Pressure waves and liquid flow of ink droplets ejected from one nozzle affect ink droplets ejected from other nozzles. In this way, 4 and 7 mentioned above
Nozzle basic nozzle pattern can be used with other basic nozzle patterns.
Especially better than using patterns.

4 and 7 nozzle basic nozzles shown in Figure 3.
Patterns and using these conjugate nozzle patterns, the nozzle pattern can be 8 mils (approximately 20.32 x 10 ^-3 cm), 20 mils (approximately 50.8 x 10 ^{-3 cm} ) in any direction.
cm) and a line width of 32 mils (approximately 81.28 x 10 ^-3 cm). 8 mil (approximately 20.32×
10 ^-3 cm) wide lines can be drawn using any one of the 30 nozzles in the pattern. 20
A line of 32 mils (approximately 81.28 x ^{10 -3 cm} ) is created using a 7-nozzle basic nozzle pattern and its conjugate pattern. It can be drawn by using conjugate nozzle patterns. The 6 basic nozzle patterns shown in Figure 3 are 6! /4×6! /4 combinations, which must satisfy the requirement of placing a unique nozzle in each row and column of the pattern. In this regard, 6! A combination of arranging the nozzles on two diagonal lines is preferred. In a thermal ink drop generator, these diagonal patterns can simplify the wiring patterns required to control ink drop ejection.

When printing characters in raster scan mode in either the vertical or horizontal direction, ink drops are ejected only in the center of selected pixels. When drawing a vector (ie, a line with a predetermined direction) in vector mode, a given nozzle is driven at a set frequency to eject ink drops at evenly spaced intervals along the length of the vector. This is in contrast to typical ink drop ejectors that can only draw graphs by ejecting ink drops in the center of selected pixels in raster scan mode. In vector graph mode, more uniform lines can be drawn by making the spacing between ink drops uniform along the length of the vector. The distance between the dots along the vector allows the firing frequency to be adjusted in relation to the print head travel speed. For typical recording media, the ink drop spacing is 7 mils (approx.
17.78×10 ^-3 cm), the best line is obtained.
The best uniformity is achieved by having 12.5% overlap between dots along the length of the vector, since some of the ink is allowed to flow to smooth the edges of the lines. When the interval is narrow, the amount of ink that adheres increases, which causes bleeding on most common recording media.

When using a 7-nozzle basic nozzle pattern to generate a line with a line width of 32 mils, ^the resulting boundaries of the line segments are , it looks uneven. This drawback is shown in Figure 4, when all the nozzles of the 7-nozzle basic nozzle pattern 41 are actuated simultaneously in a horizontal vector, they rotate to the left and right boundaries of the line shown in the figure. A shaped part occurs.

To eliminate this line segment boundary imperfection, all nozzles are configured so that they do not start and end printing at the same time. In the case of displacement along the vector length of adjacent columns and rows, the operation timing of a 7-nozzle basic nozzle pattern of 50% overlapping nozzles will be explained using FIG. When heading in the vector direction shown in the figure, first the nozzle 52
is driven first, two cycles after nozzle 52 is driven, nozzle 57 is driven to eject an ink droplet, three cycles after nozzle 52 is driven, nozzle 51 is driven to eject an ink droplet, and nozzle 52 is driven to eject an ink droplet. After four cycles of driving, the nozzle 53 is driven to eject an ink drop, and the nozzle 5
After six cycles of driving No. 2, the nozzles 54-56 are activated to eject ink droplets. These preceding ink drops are indicated by dotted circles in the figure.
For example, circles 53' and 53'' indicate that nozzle 53 ejects an ink drop two cycles ahead of nozzles 54-56. The number of cycles that are driven before or after the nozzles is selected so that the circle 58 is formed as smoothly as possible. This can be achieved by controlling the jet so that it ejects as close to as possible.

In a thermal ink drop generator, ink drops are not ejected from the nozzles simultaneously. This is because a common ground point within the drive causes large current spikes in the emitter resistance. To avoid this, each nozzle has its ink drop ejection cycle slightly offset from the other nozzles, so that in thermal ink ejection, the timing at which each nozzle is activated is different from that of the other nozzles. The relative offset of a particular nozzle's ejection cycle relative to the In embodiments of the present invention, these relative offsets between firing cycles do not normally affect line segment boundaries, so it is important to note how many firing cycles one nozzle starts before or after another nozzle. It can be simplified and ignored with simple calculations.
In the exemplary embodiment, the relative offset between successive ink drop ejections from different nozzles is 5 microseconds, and the maximum offset between different nozzle ejection cycles is 150 microseconds.
In contrast, during vector scan, the time between ink drop ejections from a given nozzle at print head movement speed and dot spacing is 833 microseconds. Therefore, the offset is a small enough value to be ignored. In other embodiments, the number of ejection cycles that a particular nozzle initiates before or after other nozzles must be calculated and taken into account. In these embodiments, a standard number of ejection cycles in which one nozzle starts before or after another may still be used. This is because the initial ink drop from each nozzle should be as close to circle 59 as possible.

The delay in driving one nozzle relative to the other nozzles to form a rounded boundary can cause printing problems.
The path that the head follows to generate a predetermined pattern becomes complex. This is shown in FIG. Draw a line from point 61 to point 62 and then point 6
3, the print head must actually follow the trajectory from point 61 to 64 to point 65 and finally to point 63. The overshoot from point 62 to point 64 occurs even though the print head forms a rounded boundary for the line segment from point 61 to point 62 as described in FIGS. minimally sufficient. Similarly,
The overshoot from point 65 to point 62 is minimally sufficient to produce a rounded line segment boundary for the line segment from point 62 to point 63 at point 62.

As mentioned above, the conjugate basic nozzle patterns 31 ^and 36 shown in FIG. 3 cannot each draw a vector 32 mils wide in all directions. Alternatively, a nozzle pattern 31 can be used in a range of directions, while nozzle patterns 31 can be used in all other directions.
Pattern 36 can be used. Switching from nozzle pattern 31 to nozzle pattern 36 interrupts the firing cycle of the nozzles of nozzle pattern 31 and moves the print head from the center of nozzle pattern 36 toward the center of nozzle pattern 31. , may be performed by initiating a firing cycle of the nozzles of nozzle pattern 36.

The angular positions of the respective vectors used in nozzle patterns 31 and 36 are shown in FIG. This figure plots vector line width as a function of direction when nozzles in adjacent columns and rows overlap by 28%. Due to this superposition, the nozzle pattern 31 is 0 to 29 degrees, 61 to 90 degrees
degrees, 119-151 degrees, 180-209 degrees, 241-270 degrees, and
Straight lines (i.e., lines with no gaps in the length direction) can be drawn only in directions between 299 and 331 degrees. Similarly, nozzle pattern 36 can be straight only in the remaining directions. Therefore, 32
In order to draw a line with a width of mil (approximately 81.28 x 10 ^-3 cm), an appropriate nozzle pattern 31 and 36 is selected depending on the range of the direction of the vector to be drawn.
select. These directional ranges can also be used for nozzles with over 28% overlap.

Similarly, change the direction of the vector from 0 to 45 degrees, 90 to
By limiting to 135 degrees, 180-225 or 270-315 degrees, either nozzle pattern 32 or 34 can be used to draw a ²⁰ mil wide vector. Nozzle pattern 33 or 35 is 20 mils (approximately 50.8×
10 ^-3 cm) wide line. The choice of which nozzle pattern to use at the end of these ranges is arbitrary and therefore
For example, if you select nozzle pattern 31, you can use this pattern at both the 0 and 29 degree end points, but you can use it at either point or neither point at your discretion. . 4
There is a similar degree of freedom in the choice of termination for the nozzle basic nozzle pattern.

Because nozzle patterns 32 and 34 are identical, each can be used to achieve a 20 mil (approximately ^50.8
cm) width can be chosen to draw a given segment of the line. In order to equalize the amount of consumption of the ink droplet ejecting portion corresponding to each of these patterns, it is preferable to equalize the usage amount of each of these patterns. Complex algorithms must be used to equalize the usage times of the nozzle patterns, including remembering the usage times of each, but within the range of values allowed when using nozzle patterns 32 and 34. For a 20 mil (about 50.8 x 10 ^-3 cm) wide vector segment (i.e., drawing a continuous line using the same basic nozzle pattern for all segments) with a direction of This can be easily carried out by using them alternately. Patterns 33 and 35 can also be made equal by a similar method. Furthermore, to equalize the use of each spout, 8 mils (approximately 20.32 x 10 ^-3 cm)
If a single nozzle is used to draw the width vector, the nozzles may be used in different order according to the order in which they are used.

[Brief explanation of drawings]

1A, 1B, 2A, 2B, and 3 are diagrams showing the pen positions of the print head of the present invention. 4th, 5th,
6 and 7 are explanatory views of the operation of the print head of the present invention. 31-36: Nozzle: Pattern.

Claims (1)

[Scope of Claims] 1. A print head comprising the following (a) and (b). (a) means for forming a first basic pattern on a medium without rotating or translating the print head; The first basic pattern has its dots on a first two-dimensional orthogonal grid, the dots substantially approximating a regular polygon plate, and the axis of symmetry of the regular polygon paralleling the first two-dimensional orthogonal grid. The grid is arranged so as not to coincide with the orthogonal axes of the two-dimensional orthogonal grid. (b) means for forming a second basic pattern on the medium without rotation or translation of the print head; The second basic pattern consists of dots arranged on a second two-dimensional orthogonal grid having an orthogonal axis parallel to the orthogonal axis of the first two-dimensional orthogonal grid, and is a conjugate of the first basic pattern. This is a translation of the pattern. 2. The dots forming the first basic pattern are (0, 0), (3, -1),
(1, -3), (-2, -2), (-3, 1), (-1
,
3) and (2, 2), and the dots forming the second basic pattern are located at (0, 0), (3, 1), (1, 3), (-2) of the second orthogonal grid. ,2)
,
The prints according to claim 1 arranged at (-3, -1), (-1, -3) and (2, -2)
Head. 3. The dots forming the first basic pattern are (3, -1), (-1, -3),
The dots arranged at (-3, 1) and (1, 3) and forming the second basic pattern are (3, 1), (-1, 3), (-3, -1)
and (1, -3).