JPH09193368A - Ink jet printer and ink jet printing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out good printing to a solid having a slope or curved surface by an ink jet printing method. SOLUTION: A distance from an ink jet print head to a printing area of a solid is measured for every discharge point, a displacement of a measured distance in relation to an interval between discharge points is obtained and an amount of ink to be discharged is changed. Thus, in a section where the degree of inclination is large in a slope or curved surface, for instance, any gap among dots formed by ink can be prevented from occurring by increasing the amount of ink to be discharged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printing apparatus and an ink jet printing method, and particularly to an ink jet printing apparatus for printing on a print medium having a slope, a curved surface or an uneven surface instead of a sheet-shaped print medium. And an inkjet printing method.

[0002]

2. Description of the Related Art With the recent development of information processing technology and communication technology, information processing devices such as copying machines, word processors, and computers, and communication devices such as facsimile machines have become widespread. Along with this, as one of the information output devices in those devices, a printing device that forms a digital image using a print head of an inkjet system is rapidly becoming widespread. In such a printing apparatus, many use an inkjet print head in which a plurality of ejection ports for ejecting ink are integrated, or use a plurality of ink jet heads in accordance with recent color compatibility. Can be seen. Further, in such an apparatus, due to technological progress, the degree of integration of the ejection openings and the color reproducibility during color printing are improved, and the image quality of printing and silver halide photography is imminent.
Furthermore, the price reduction is progressing.

On the other hand, paying attention to the simple printing principle, easy colorization, and non-contact printing,
There is growing interest in applying and expanding inkjet technology not only to the above-mentioned information and communication devices but also to other fields. Examples of such applications include:
Examples include printing on cloth, printing lot numbers and manufacturing dates in various production processes, and the like.

In particular, since it is a non-contact type printing method, in addition to a sheet-like material such as paper which is generally used as a print medium in the past, an object including a slope, a curved surface or an unevenness (hereinafter, simply referred to as "three-dimensional"). It is also being developed to print on the surface of the object. As a print on such a three-dimensional object, for example, Japanese Patent Laid-Open No. 5-29395.
5, JP-A-5-318715, JP-A-6-9187.
No. 8 and other publications.

[0005]

By the way, the ink jet system forms dots by ejecting liquid ink droplets from an ejection port and landing them on a print medium. Therefore, flying ink droplets land on the print medium. The intervals of the dots formed are likely to change depending on the relative direction of time. Therefore, in order to print a desired image faithfully, it is preferable that the ejection direction of the ink droplets is always perpendicular to the print surface of the print medium and the intervals of the dots formed are uniform.

If the print medium is a sheet,
Although it is possible to make the ink fly perpendicular to the print surface by scanning the inkjet print head in a certain fixed posture as in a commonly used printing apparatus, the print medium is a three-dimensional object. In this case, the perpendicularity of the ejection direction cannot be realized unless the ejection direction of the ink is adjusted to the direction corresponding to the slope or the curved surface. In this case, the method for fixing the inkjet print head and the method for scanning become complicated, and it is difficult to carry out the method.

Further, the ink jet print head is
The ink droplets ejected from the ejection port may actually have a slight deviation in the flight direction for each ejection port due to variations and the like that occur during manufacturing of the inkjet print head. In this case, when the printed surface is a curved surface or the like, the print result may be adversely affected.

With respect to such problems, the conventional examples described in the above-mentioned publications disclose the following configurations. First, the one disclosed in Japanese Patent Application Laid-Open No. 5-293955 controls to eject ink while operating a print medium three-dimensionally. The device is relatively large and complicated. Need control. Next, in Japanese Unexamined Patent Publication No. 5-318715, a three-dimensional object serving as a print medium is limited to a rotating body having a different diameter, and a first supporting member rotatable about its axis and an inkjet print head are arranged in this axial direction. It is described that the movable support includes a second supporting member and has a setting unit capable of variably setting the facing distance between the print medium and the inkjet print head. That is, the apparatus of the publication has some restrictions on the shape of the print medium. In addition, Japanese Unexamined Patent Publication No.
Japanese Patent No. 91878 discloses a continuous charge control type ink jet, which is provided with a distance sensor near the ink jet print head for measuring a distance between the ink jet print head and a print medium.
It discloses that the deflection amount of flying ink droplets is controlled based on the measurement result of the distance sensor.

However, even if any of the above-mentioned known examples is directly applied to an on-demand type ink jet printing apparatus which is currently the mainstream of general-purpose ink jet printers, it is possible to print on a three-dimensional object by a relatively simple mechanism. It is difficult to implement. Further, as the mechanism becomes complicated, the size of the device also becomes large and the cost becomes high.

[0010]

In view of some of the problems described above, the present inventor has conducted diligent research and, as a result, has found a new direction from the viewpoint of conventional inkjet printing for curved surfaces. The above problems have been solved. Then, they have invented an inkjet printing apparatus and method capable of expressing a high-quality image on a print medium composed of a three-dimensional object.

That is, according to a first aspect of the present invention, in an inkjet printing apparatus that uses an inkjet print head to eject ink onto a print medium for printing, the inkjet head is scanned in a predetermined direction with respect to the print medium. And a head scanning unit for discharging the ink of the inkjet print head according to a displacement amount of a distance between the inkjet print head and a print medium measured at predetermined intervals in the scanning direction during scanning by the head scanning unit. And a discharge control means for performing printing by changing the amount or the discharge interval.

According to this structure, when an image is formed on the print medium of the three-dimensional object by the ink jet print head, the displacement amount of the distance from the ejection portion of the ink jet print head to the surface of the print medium with respect to a predetermined interval is always recognized. Since this is done, it is possible to arbitrarily set the method of driving the inkjet print head according to this distance, that is, the ink ejection amount and the ink ejection interval. As a result, it is possible to obtain the same quality image output as when the sheet-shaped one is used, regardless of the unevenness of the surface of the print medium.

According to a second aspect of the present invention, in addition to the above-described first aspect, the ejection control means performs the forward scanning of the ink jet print head and the distance measuring means by the head scanning means. A feature is that the distance is measured and ink is ejected in the backward scanning.

According to the second aspect of the present invention, in the serial type printing apparatus in which the ink jet print head is scanned to achieve image formation, it is noted that the ink jet print head is reciprocating. Ink ejection is detected when the inkjet print head is moved, and the state of the surface of the print medium, which is a three-dimensional object, is detected when the other inkjet print head is moved. With such a configuration, it is not necessary to add a special mechanism or control to the scanning unit that moves the inkjet print head, and therefore the cost does not increase.

Further, as the concrete control of ink ejection in the above-mentioned first and second aspects of the present invention, the distance from the ink jet print head to the print medium is determined based on the measurement result of the distance measuring means. Is controlled so as to increase the amount of ink discharged from the inkjet print head, or based on the measurement result of the distance measuring unit, the time of ink discharge from the inkjet print head is changed. When the displacement amount of the distance between two different points exceeds a predetermined value, the above 2
It is characterized in that control is performed so as to perform ink ejection that complements pixels between points.

As a method for determining whether or not the displacement amount between the above two points exceeds a predetermined value, a conventionally known method can be adopted, and either software or hardware method can be used. But it can be judged. With this method, it is possible to determine the degree of inclination of the slope on the surface of the print medium on which ink is to be ejected, and it is possible to appropriately control the ink ejection method. Then, if it is determined from the result of this determination that it has a certain gradient, ink ejection control can be performed in accordance with the configurations described in the first and second aspects of the invention, and proper image quality can be maintained.

In addition to the first and second aspects of the present invention described above, the ink jet printing apparatus has a substantially constant distance between the ink jet print head and the print medium based on the measurement result of the distance measuring means. Head displacement control means for displacing the ink jet print head in the ink ejection direction so as to maintain the above condition.

Here, displacing the position of the ink jet print head so as to keep the distance from the ink jet print head to the print medium substantially constant,
It is possible to use a well-known technique known in the related art. For example, it is possible to displace the ink jet print head in the ink jet direction through a gear in a mounting portion of the ink jet print head.

As described above, in particular, when forming an image on the print medium of a three-dimensional object by the ink jet method, the distance measuring means for measuring the distance from the moving print head to the print medium as the ink jet print head scans is provided. In addition, based on the information from the distance measuring means, it is an inkjet printing system that variably controls the ink ejection amount or the ink ejection interval from the inkjet print head.
Sufficient image quality can be obtained in image formation for a three-dimensional object, which has been difficult in the past.

[0020]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

(Embodiment 1) FIG. 1 is a diagram schematically showing a printing mechanism of an ink jet printing apparatus according to an embodiment of the present invention. Mainly, an ink jet print head and a carriage for mounting and scanning the same. The side of is shown. 2 is a block diagram showing a configuration for controlling data processing and printing in the apparatus shown in FIG.

First, before explaining the basic operation of ink jet printing on a three-dimensional object with reference to FIGS. 1 and 2, for comparison, FIG. 10 shows a case of printing on a three-dimensional object by a conventional ordinary ink jet printing apparatus. And explain. Compared with the case of printing on a sheet-shaped object in a normal inkjet printing apparatus, when an image is formed by ejecting ink onto a print medium of a three-dimensional object, not only a flat part horizontal to the surface to be printed However, due to the presence of a sloped surface, a curved surface, or a height difference, the intervals of the landing positions of the ejected inks are not uniform, and the intervals of the dots formed are not uniform, resulting in image distortion. May occur.

This state is schematically shown in FIG. In addition,
In the following description, an inclined surface will be represented as the surface of the three-dimensional object. This can be said to be appropriate since, when considering a relatively small range on a curved surface, the range can be approximated as a slope.

When printing is performed at a constant ejection timing, the landing point of each ejected ink droplet is on the ink landing surface 302, as shown in FIG.
As indicated by the intervals of 01, 502, 503, 504, and 505, the intervals change according to the inclination angle of the slope 302. This is a sheet, that is, Fig. 1
This is because the ink droplets are ejected in the direction perpendicular to the virtual surface 303 indicated by the broken line 0, and the landed ink is properly arranged on this surface. That is, the distance d shown in FIG.
This is because when the ink is ejected, the ink ejection amount and the ink ejection cycle are set so that dots of uniform size are formed at equal intervals on a surface perpendicular to the ejection direction.

In the present embodiment, in order to cope with such a problem, when printing on the slope portion, the ink droplets 506 and 5 are ejected as shown in FIG.
By increasing the size of 07, 508, 509, and 510, the increase in the interval of each landed ink drop is compensated. The rate at which the size of each ink drop is increased can be determined as a function of the inclination angle of the slope with respect to the scanning direction of the inkjet print head. Generally speaking, including the case of printing on a curved surface, this can be determined as a function of the ratio of the amount of displacement of the distance from the inkjet print head to the surface of the print medium to the pixel pitch d.

Further, in addition to increasing the size of the ink droplet with respect to the state of FIG. 10, as a modified example, an ink droplet may be further added to the gap between the ink droplets to complement the pixel. , It is possible to compensate for the increase in the interval of each landed ink drop. For example, as shown in FIG. 12, ink droplets 511 and 511 are also formed at a point of d / 2 with respect to the ink discharge interval d.
512, 513, and 514 are added. In this case, the ink droplets may be of a normal size, but control for ejecting the ink droplets other than the portion corresponding to the image signal is performed.
The distance from the tip of the ejection port of the inkjet print head to the surface of the print medium is variably controlled as a function of the amount of displacement.

In the control described above, means for detecting the distance e from the ejection tip of the ink jet print head 301 to the print medium 302 is installed in parallel with the ink jet print head, and feedback control is performed based on the detection result. It is something to do.

Next, a specific structure of this embodiment will be described.

The image data formed by the host computer 101 shown in FIG. 2 is sent to the ink jet printing apparatus and input to the image data processing unit 102. The image data processing unit 102 performs image processing such as color conversion, masking, γ correction, etc. on the sent image data, and also performs binarization processing using a predetermined dither pattern, and the ink of the ink jet print head. It is converted into an on / off signal (image signal) that determines ejection. Subsequently, the converted binary image signal is input to the image signal correction unit 103. Here, for the image data sent from the host computer, the edge portion of the image, the degree of density, or the connecting portion of the scan at the time of printing is detected, and the appropriate ink ejection correction is performed for each. In addition, the ink discharge amount is determined by the inkjet print head / print medium distance detection unit 105 and the RAM.
106 and the ROM 107 by referring to the contents. Through these processes, a signal (driving signal) finally given to each ejection port of the inkjet print head can be obtained. This drive signal is subsequently input to the inkjet print head drive unit 104 together with the above image signal, where information obtained from inside the printing apparatus stored in the RAM 108, that is, ambient temperature and humidity,
Information such as the history of the inkjet printhead, the type of ink, the remaining amount, and the like are added, and based on the drive information in the ROM 109, the pulse signal is converted to a pulse signal that is appropriate for each ejection port of the inkjet printhead.

Next, a mechanism in which the inkjet printing apparatus actually operates after the driving pulse is applied to the inkjet print head will be described with reference to FIG.

When a print start command is issued, the carriage 3 at the home position before the start of printing receives a driving force for scanning the carriage from a driving source (not shown) such as a stepping motor via a timing belt, and the carriage 3 By moving in the main scanning direction (direction perpendicular to the paper surface of FIG. 1) along the shaft 4 and the carriage shaft 5, and in synchronization with that, the ink is ejected from each ejection port of the inkjet print head 1 to form a three-dimensional object. Is printed on the print medium 8. The inkjet print head 1 has nozzle groups capable of ejecting black ink, cyan ink, magenta ink, and yellow ink, respectively, arranged in parallel along the main scanning direction of the carriage 3, and inks of each color are ejected. The dots are sequentially discharged to form dots on the print medium 8 to enable color image formation. Then, when the movement of the carriage 3 is completed up to the other end facing the home position, the rotation of the stepping motor becomes reverse rotation, and the carriage 3 returns to the original home position accordingly. On the other hand, both ends of the carriage shaft 5 have a helical gear shape and mesh with the lead screw 6. Then, the helical gear is rotated by a predetermined angle by a drive source (not shown), thereby moving the carriage 3 in the t direction in the figure, that is, the sub-scanning direction. By repeating the above operation, image formation on the print medium 8 is completed.

In FIG. 1, reference numeral 7 denotes a distance detection sensor for detecting the distance between the surface of the print medium 8 and the ink ejection surface of the ink jet print head 1. The distance detection sensor 7 is provided on the surface of the print medium 8 with a relatively small load. It is composed of contact needles that come into contact with each other. Since this contact needle has a slight load,
The print medium 8 is smoothly moved up and down along the irregularities of the print medium 8 without damaging the surface of the print medium 8, and the vertical movement is read one by one and converted into an electric signal. This reading interval is synchronized with the ink ejection cycle. The sensor 7 is provided for one of the plurality of ejection ports arranged in the sub-scanning direction in each print head. The distance used in the discharge control described below is similar to the distance detected by the sensor 7 for other non-corresponding discharge ports. However, the present invention is not limited to such a configuration, and it goes without saying that a plurality of sensors 7 may be provided at predetermined intervals.

Next, an operation example will be described in which the printing operation is carried out using the inkjet printing apparatus of FIG. 1 while detecting the distance from the inkjet print head 1 to the print medium 8 by the distance detection sensor 7.

FIG. 3 shows the control state of the operation. Here, (A) shows the result of measuring the distance from the ink ejection port of the inkjet print head 1 to the print surface of the print medium 8 in one line in the main scanning direction, that is, the moving direction of the carriage, and (B) calculates the displacement amount of the distance with respect to the pitch of the pixel (dot forming position) based on the result of the distance detection shown in (A), and changes the amount of ink to be ejected by 1 based on the calculation result. Is shown for one discharge port,
Further, (C) shows a state in which the dots formed by the respective inks that have landed on the print medium 8 as a result of this ink ejection are viewed in the p direction in FIG.

As is clear from these figures, in the portion where the surface of the print medium is sloped, the reference ink ejection amount V0 is larger than the reference ink ejection amount, and in other portions, it is almost the same as this reference amount V0. And Then, the ink ejection amount is increased as the degree of inclination increases. With such a structure, it is possible to obtain a clear and uniform image in a printed matter without creating gaps between the dots formed on the surface of the printed matter, and to obtain the same image as when printing on a flat surface. Is possible.

The ink ejection amount is determined by the image signal correction unit 103 in FIG. 2. The process of the determination will be described with reference to FIGS. 4 and 5.

Referring to the flow chart of FIG. 4, when a print start command is detected in step S1030, first, in step S1031, the ink is changed by a distance change between the ink jet print head and the print medium which is stored in the ROM 107 as a standard value in advance. The value e _s that does not need to be changed and the reference ink discharge amount V ₀ at that time are set in the RAM 106. Then, in the next step S1032, the initial value of the change rate m of the ink ejection amount, which will be described later, is set to 1. Next, proceeding to step S1032, the data sent from the inkjet printhead-print medium distance detection unit 105 at that time is set in the RAM 106 as the reference distance e ₀ between the inkjet printhead and print medium, and then at step S1033. , Then the detector 1
The data sent from 05 is set in the RAM 106 as the distance e between the inkjet print head and the print medium. In the next step S1034, the initial value of the change rate m of the ink ejection amount is set to 1. The absolute value of the difference between the above-mentioned e ₀ and e in step S1035, i.e., calculates the absolute value of the displacement amount of the distance to the pixel pitch, therewith to determine the magnitude relationship between the reference of e _s. As a result, | e-e ₀ | it is larger than the e _s step S1
If it is not, the process proceeds to step S1036.

In step S1036, the current value of e is reset as the reference distance e ₀ between the inkjet print head of the next pixel (ejection timing) and the print medium. Then, in step S1037, the ink ejection amount is set. In this portion, the ink ejection amount V for the dot is set by the rate m of change with respect to the reference ink ejection amount V ₀ that has been set previously, and becomes a signal for the inkjet print head drive unit. Then, in step S1038, ink is ejected.

Then, in step S1039, it is determined whether or not the printing for one line is completed. If the printing for one line is not completed, the process returns to step S1033 to print for the next pixel, 1 If the line ends, the data ends (step S104
Until 0), printing is sequentially performed line by line.

On the other hand, in the determination of step S1035, | e-
When it is determined that e ₀ | is larger than the reference value e _s , the ratio of the distance displacement | e−e ₀ | to e _{s is} calculated in step S1041, and then in step S1041, the ROM 107 is stored in the ROM 107 based on this ratio. After obtaining an appropriate value of m by referring to the table set as above, the process proceeds to steps S1036 and S1037 to appropriately determine the ink ejection ejection amount as described above.

FIG. 5 is a diagram schematically showing the contents of the above table. As shown in FIG. 5, m is set in accordance with the range of the ratio e _t.
The value of is set. That is, for each ejection timing (each pixel), the ink ejection amount increases as the displacement amount with respect to the distance e ₀ between the inkjet print head and the print medium at the time of the immediately preceding ejection increases.
Set a large value for m.

Incidentally, regarding the first embodiment of the present invention, FIG.
Although the processing shown in (1) is performed by software, the processing speed can be further improved by using this as a hardware configuration.

As the processing for dot complementation described as a modification of this embodiment, for example, the number of dots required for complementation (the number of ejections) is set according to the value of m, and
Based on this, it is possible to perform control so that ejection is performed at ejection timings obtained by dividing a predetermined ejection interval.

As a method of varying the ink ejection amount described above, various conventionally known methods can be applied. For example, when a piezoelectric element is used for ejecting ink, there is a method in which the voltage applied to the piezoelectric element is changed to directly change the ejection pressure of ink to change the ejection amount. When used, a method is used in which a plurality of voltage pulses are applied to the heating element provided in the nozzle and the preceding pulse is changed, or two or more types of heating elements of large and small sizes are provided in the same nozzle and used properly. Is mentioned. For these, a preferable method may be selected according to the system used.

By performing the drive control with the above-mentioned structure, an image of the same quality as the image obtained by the conventional sheet-like image can be obtained with a simple device structure without spending extra time for processing. It is possible to obtain a three-dimensional object.

(Second Embodiment) FIG. 6 is a block diagram showing a data processing configuration according to another embodiment when printing is performed on a print medium of a three-dimensional object using the ink jet printing apparatus shown in FIG.

Generally, in the case of an ink jet printing apparatus using an on-demand type print head, there are many so-called serial type in which the print head is scanned in the main scanning direction. In order to maintain good landing accuracy, that is, image quality, it is common to perform the printing operation only in one scanning direction. That is, among the above-mentioned reciprocating movements, a slight deviation from the same ink landing position may occur in each of the forward path and the backward path. Therefore, a complicated mechanism and cost are required to improve the accuracy. Due to. The subtle deviation from this ink landing position is
When switching the direction during reciprocating movement, it is necessary to decelerate, reverse rotate, and accelerate the drive source of the scanning means.
It occurs in these cases. On the other hand, if the ink is ejected only in one direction of the scanning means of the ink jet print head, the above deviation is unlikely to occur and the image quality is less likely to be impaired.

Therefore, if the mechanism for ejecting ink only in such one scanning direction does not eject ink when the other ink jet print head is moved, the ink jet print head is simply used as the original reference. It just returns it to the position. That is, in the conventional printing apparatus, ink is ejected while moving the ink jet print head from the home position as the reference position, and when the ink ejection for one scan is completed, then the ink jet print head is returned to the reference position. When the direction of movement of these inkjet print heads is called the forward path and the opposite direction is the return path,
By repeating this reciprocating movement, ink is ejected in the forward pass, then immediately before switching to the return pass, simultaneously with the return pass, or after the return pass is completed, the print medium is moved in the sub-scanning direction by a predetermined amount, and the movement direction is set to the return pass. When switching, the inkjet print head is moved to the home position, and printing is completed in sequence.

On the other hand, in the present embodiment, ink is not ejected in the so-called outward path in which the carriage 3 shown in FIG. 1 moves from the home position to the other end opposite thereto, and the distance detection sensor 7 prints. Medium 8
The distance from the surface to the ink ejection surface of the inkjet print head 1 is measured, and the measurement results are sequentially stored in the memory. This measurement is performed by providing measurement points at a resolution that is substantially the same as the resolution in the scanning direction during printing, but here the resolution of the print image is 3
60 dpi, and the measurement interval of the distance from the surface of the print medium 8 to the ink ejection surface of the inkjet print head 1 is the same as the distance of 360 dpi (70.5).
μm). The measurement result is sequentially stored in the RAM 110 as the carriage 3 advances. While performing this operation, when the carriage 3 has reached the end, the rotation of the stepping motor is reversed as in the first embodiment, and then the carriage 3 is moved in the home position direction, that is, in the return path, and ink is ejected. To print. When this printing is completed, the carriage 3 is moved in the t direction (sub scanning direction) of FIG. 1 by the combination of the helical gear and the lead screw 6.
Printing by one scanning is completed by moving to.

The printing operation in this reciprocal scanning will be described with reference to the flowchart of FIG.

When a print start command is issued, the process first proceeds to step S1111 and the number of lines in the main scanning direction is n.
The initial value of is set to 0. Subsequently, in step S1112, the carriage 3 is moved from the home position in the outward direction. In synchronization with the movement of the carriage 3, step S
In 1113, after increasing the number of lines n in the main scanning direction by 1, the process proceeds to step S1114, the distance between the inkjet print head and the print medium at that point is measured by the distance detection sensor 7 shown in FIG. Is set as e (n). And step S11
In step 15, it is determined whether or not the current n is the end of the line in the main scanning direction, and if it is not the end, the process returns to step 1113 to repeat the above-described e (n) setting. On the other hand, if the current n is the end of the line, the process advances to step S1115 to stop the movement of the carriage 3. Thereafter, in step S1117, the ink ejection amount corresponding to each line in the main scanning direction is determined as V (n) in the same manner as in the first embodiment, and is stored in the RAM 106 in the next step S1118. Then, in step S1119, the carriage 3 is moved in the backward direction, and in step S1120, ink is ejected based on the data V (n) determined as described above to perform printing.

With such a configuration, conventionally, printing is performed in one scanning direction of the carriage, then the carriage is returned without printing (without ejecting ink), and the next actual printing is performed as before. In contrast to the method in which the same scanning direction is used, it is possible to control the ink ejection amount without increasing the time required for printing and according to the displacement amount of the distance between the inkjet print head and the print medium with respect to the pixel pitch. With respect to a three-dimensional object, sufficiently high-quality image formation can be achieved as in the first embodiment.

(Third Embodiment) FIG. 8 shows an example in which a mechanism for making the distance from the ink ejection port of the ink jet print head to the surface of the print medium substantially constant is added to the ink jet printing apparatus shown in FIG. Is shown. Here, 11 is an inkjet print head,
12 is an ink tank, 13 is a carriage, 14 is a carriage shaft, 15 is a carriage shaft with helical gears on both ends, 16 is a lead screw, 17 is a distance detection sensor,
Reference numeral 18 denotes a print medium, and since each configuration and each function are the same as the elements denoted by reference numerals 1 to 8 in FIG. 1, their description will be omitted here. In the embodiment shown in FIG. 8, the inkjet print head 11 is used.
Further, a gear 19 is further provided in order to have a mechanism capable of moving in the p direction or the −p direction in a state where the ink tank 12 is coupled, and a corresponding portion of the inkjet print head 11 is engaged with the gear 19 so as to mesh with the gear 19. Also has teeth. In addition, this mechanism is based on the distance detection sensor 17
The gear 19 and the gear 20 are rotatably incorporated in association with the output result of 1., and the ink jet print head can be freely moved in the p direction and the -p direction.

By adding such a mechanism,
In addition to the controls described in the first and second embodiments, the inkjet print head 11 and the print medium 1 are further added.
It is possible to keep the distance between 8 and 8 constant with the movement of printing. As a result, it is possible to reduce the influence of the image disturbance caused by the deviation of the ink landing points on the print medium due to the variation in the ink ejection direction at the time of ink ejection, and it is possible to form a higher quality image.

(Fourth Embodiment) In contrast to the mechanism described in the third embodiment, in the present embodiment, the movement of the combined body of the ink jet print head 11 and the ink tank 12 in the p direction and the -p direction is movable in the apparatus. When the range is exceeded, the control range of the ink ejection amount can be further expanded. In the case of this embodiment, when the print surface is extremely inclined, the image formation can be sufficiently achieved even in the case where the above-described embodiments are not applicable, and specifically, FIG. In the table shown in, the value of m can be set up to 8.

(Embodiment 5) FIG. 9 is the same as the ink jet printing apparatus described in Embodiment 1 except that the control for changing the ink ejection amount at each ink ejection point is not performed as shown in FIG. When the print surface of the print medium is a slope and the slope shows a predetermined value or more, that is, the distance difference (distance difference between the inkjet print head and print medium) at the ink ejection point exceeds the predetermined value. In this case, dot complementation is added between the ink ejection points.

In FIG. 9, the complemented dots are indicated by white circles and the original dots are indicated by black circles. In addition, the inkjet print head
The predetermined value of the distance difference between the print media is set to 2 mm. Even when the drive control of the inkjet print head is performed as described above, when the print surface is an inclined surface, there is no gap between the dots, and a normal image can be formed.

Needless to say, even if the variable control of the ink ejection amount is used together with this operation, a larger effect is produced. In addition, it is also an effective method to incorporate the mechanisms described in the second and third embodiments at the same time.

Further, in the above-mentioned embodiments, the image formation on all three-dimensional objects has been described as an example. However, even if this system is applied to a sheet-shaped print medium, no problem will occur. it is obvious.

(Embodiment 6) In Embodiment 1 and Embodiment 2, after detecting the distance from the ejection port of the ink jet print head to the surface of the print medium, the predetermined pixel interval is set to two points and the difference in distance therebetween is used. The ink ejection amount is variably controlled. In addition to this, it is also possible to make the distance between these two points wider and variably control the ink ejection amount based on the distance difference between the two points. With such a configuration, it is effective when the print surface of the print medium is relatively smooth, and the interval for detecting the distance from the ejection port of the inkjet print head to the surface of the print medium can be made coarse. Becomes For example, even if the resolution of the image is 360 dpi, the detection interval can be set to a half corresponding to 180 dpi (141 μm).

[0061]

As described above, according to the ink jet printing system of the present invention, a sloped surface, a curved surface or an uneven state of the surface of a three-dimensional object which is a target of a print medium is always detected, and the detection result is obtained. Based on the above, variable control of ink ejection amount, control of ink ejection timing, and control to keep the distance between the inkjet print head and print medium constant are performed. High-definition images, which could only be obtained, can now be obtained for three-dimensional objects as well. The present invention can be similarly applied to an ink jet print head having one ejection port or plural ejection ports.

Further, these things also broaden the range of application of the ink jet system, and contribute to various small-quantity multi-type printing.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an inkjet printing apparatus and a print medium according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of data processing and the like in the inkjet printing apparatus shown in FIG.

FIG. 3 is an explanatory diagram illustrating a print state according to the first embodiment of the present invention.

FIG. 4 is a flowchart illustrating a printing operation of the first embodiment.

FIG. 5 is a diagram schematically showing a table used in the processing shown in the above flow chart and for determining an ink ejection amount during printing.

FIG. 6 is a block diagram showing a configuration such as data determination according to a second embodiment of the present invention.

FIG. 7 is a flowchart illustrating a print operation of the second embodiment.

FIG. 8 is a diagram schematically showing an inkjet printing apparatus and a print medium according to a third embodiment of the present invention.

FIG. 9 is a diagram illustrating a print state according to a fifth embodiment of the present invention.

FIG. 10 is a diagram illustrating a landing state of ink when printed on a three-dimensional object by a conventional method.

FIG. 11 is a schematic diagram illustrating an example of an ink landing state when a three-dimensional object is printed by the inkjet printing apparatus of the present invention.

FIG. 12 is a schematic diagram illustrating an example of an ink landing state when a three-dimensional object is printed by an inkjet device according to another embodiment of the present invention.

[Explanation of symbols]

 1,11 Inkjet print head 2,12 Ink tank 3,13 Carriage 4,14 Carriage shaft 5,15 Carriage shaft with helical gears carved at both ends 6,16 Lead screw 7,17 Distance detection sensor 8,18 Print medium 19,20 Gears 501,502,503,504,505 Landing ink

Claims (13)

[Claims] 1. An inkjet printhead is used,
In an inkjet printing apparatus that ejects ink onto a print medium to perform printing, a head scanning unit for scanning the inkjet print head in a predetermined direction on the print medium, and the scanning between the scanning by the head scanning unit. And an ejection control unit that performs printing by changing the ink ejection amount or the ejection interval of the inkjet print head according to the displacement amount of the distance between the inkjet print head and the print medium measured at every predetermined interval in the direction. An inkjet printing device characterized by the above. 2. The ink jet printing apparatus, in the scanning direction of the head scanning means, distance measuring means for measuring the distance at the predetermined intervals, and based on the measurement result by the distance measuring means, for each of the predetermined intervals. The inkjet printing apparatus according to claim 1, further comprising a calculation unit that obtains the displacement amount. 3. The ink jet printing apparatus according to claim 1, wherein the ejection control unit increases the ink ejection amount or decreases the ejection interval as the displacement amount increases. 4. The distance measuring means has a scanning means for scanning in the scanning direction, and the distance is measured during the scanning by the scanning means. The inkjet printing apparatus described. 5. The scanning means included in the distance measuring means comprises:
5. The head scanning means comprises the head scanning means.
5. The inkjet printing apparatus according to claim 1. 6. The ejection control unit changes the ink ejection amount or the ejection interval while performing the scanning by the scanning unit together with the scanning by the head scanning unit. The inkjet printing apparatus according to any one of claims. 7. The ink jet printing apparatus further comprises storage means for storing the displacement amount at each of the predetermined intervals, and the ejection control means stores the ink ejection amount or the ink ejection amount according to the displacement amount stored in the storage means. The inkjet printing apparatus according to claim 1, wherein the ejection interval is changed. 8. The inkjet printing apparatus according to claim 1, wherein the print medium is a three-dimensional object having a slope and / or a curved surface. 9. The inkjet printing apparatus according to claim 1, wherein the predetermined interval is an interval between pixels formed on the print medium in a scanning direction of the inkjet print head. . 10. The ink jet printing apparatus according to claim 1, wherein the ejection control unit reduces the ejection interval and complements the pixels when the displacement amount exceeds a predetermined value. . 11. The inkjet printing apparatus comprises:
A head displacement control means for displacing the inkjet print head in the ink ejection direction so as to keep the distance between the inkjet print head and the print medium substantially constant based on the measurement result of the distance measurement means. The inkjet printing apparatus according to claim 1, wherein the inkjet printing apparatus is a printing apparatus. 12. The ejection control means measures the distance in the forward scan of the inkjet print head and the distance measuring means by the head scanning means, and ejects ink in the backward scan. The inkjet printing device according to claim 5. 13. An inkjet printing method for performing printing by ejecting ink onto a print medium using an inkjet print head, comprising: scanning the print medium in a predetermined direction with the inkjet print head; According to the displacement amount of the distance between the inkjet print head and the print medium measured at predetermined intervals in the scanning direction, the ink ejection amount or the ejection interval of the inkjet head is changed to perform printing. Characteristic inkjet printing method.