JP2007245658A - Ink-jet head unit mounted in image recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a conventional ink-jet head unit causes the formation positions of nozzle groups to be slightly misaligned when slight errors occur in the movement precision of the ink-jet head when the nozzle groups composed of a plurality of grouped nozzles are formed in the ink-jet head, white lines to occur on a recording medium, and an unevenness to occur in density. <P>SOLUTION: This invention provides the ink-jet head unit mounted in an image recording apparatus, having ink-jet heads 1a and 1b on which nozzle groups (20-1 to 20-8) having a plurality of nozzles 20a are formed and a cam member 54 for adjusting positions by shifting the ink-jet head 1a in a Y-axis direction with respect to the ink-jet head 1b even when the formation positions of the nozzle groups are misaligned, thereby suppressing the occurrences of white lines and suppressing an unevenness in density so as to record high-quality images. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inkjet head unit having a laminated structure in which a plurality of inkjet heads having the same structure are bonded together.

  In recent years, there has been a demand for an inkjet head that can record an image with higher resolution and less dot graininess at higher speed. In order to reduce the graininess, it is necessary to make the size of each ink droplet smaller and eject ink. Therefore, it is necessary to increase the arrangement density of the nozzles provided in the ink jet head in order to reduce the size of one ink droplet and to record a predetermined recording area at a high speed.

  In order to achieve such miniaturization of ink droplets and high-speed recording, Patent Document 1 discloses an inkjet head unit in which two inkjet heads are stacked. FIG. 22 is a schematic bottom view of the inkjet head unit disclosed in Patent Document 1. As shown in FIG. The ink jet head unit 100 is provided with ink jet heads 101a and 101b that discharge ink and a holding member 103 that holds the ink jet heads 101a and 101b. The inkjet heads 101a and 101b have the same structure using a piezoelectric body, and each is provided with a nozzle 120a. The nozzle 120a provided in the inkjet head 101a is shifted from the nozzle 120a provided in the inkjet head 101b by half the nozzle pitch P, that is, 1 / 2P along the nozzle arrangement direction (Y-axis direction). In this state, the ink jet heads 101 a and 101 b are bonded to each other through the holding member 103.

In the inkjet head unit 100 configured as described above, the nozzle arrangement density can be doubled.
JP 2004-058277 A

  In general, nozzle drilling is performed by, for example, irradiating an inkjet head with laser light from a laser processing machine to form holes. A large number of nozzles provided in the ink jet head cannot be formed by a single process. Therefore, a plurality of nozzles are divided into several groups, and processing is repeated a plurality of times along the longitudinal direction to form a nozzle row. If the feed accuracy of the inkjet head is low when forming the nozzle holes, the positions of the formed nozzles will not be uniform, and there will be a problem that gaps will be formed between the groups, resulting in deviations in the nozzle formation position. .

  This shift will be described with reference to FIGS. In FIG. 23 to FIG. 26, six nozzles are divided into one group, four nozzle groups (220-1 to 220-4) for the inkjet head 201a, and four nozzle groups (220-5) for the inkjet head 201b. ˜220-8) will be described as an example.

  FIG. 23 is a schematic bottom view of a conventional inkjet head showing the positional relationship when the nozzle groups provided in the inkjet heads 201a and 201b are accurately arranged. FIG. 24 is a solid image when ink is ejected onto a recording medium based on the arrangement shown in FIG. FIG. 25 shows a partial displacement of the nozzle arrangement shown in FIG. 23 (the nozzle group 220-2 provided in the inkjet head 201a is slightly displaced from the normal arrangement position in the −Y direction (left direction in the drawing) 26 is a schematic bottom view of the ink jet head showing a state in which the nozzle group 220-6 provided in the head 201b is slightly deviated in the + Y direction (right direction in the drawing) from the normal arrangement position. 6 is a solid image when ink is ejected onto a recording medium based on the arrangement shown in FIG.

  As shown in FIG. 23, the nozzle 220a provided in the ink jet head 201a is shifted by 1 / 2P in the nozzle arrangement direction with respect to the nozzle 220a provided in the ink jet head 201b, and as shown in FIG. In addition, ink is landed on the recording medium with high accuracy, and no white streak occurs between the landed ink dots.

  However, as described above, when a slight error occurs in the movement accuracy when the inkjet heads 201a and 201b are moved in the drilling process, as shown in FIG. 25, for example, the nozzle group 220-2 provided in the inkjet head 201a Slightly shifts in the -Y direction. Further, the nozzle group 220-6 provided in the inkjet head 201b is also slightly shifted in the + Y direction. As a result, the nozzle 220a provided in the inkjet head 201a and the nozzle 220a provided in the inkjet head 201b are not displaced by a distance of 1 / 2P, and when ink is ejected, as shown in FIG. In this case, white streaks occur in the width of the second group (nozzle group 220-2 and nozzle group 220-6), and density unevenness occurs.

  Therefore, in order to improve the drilling position accuracy of the nozzles, it is necessary to improve the feeding accuracy of the inkjet head when drilling the nozzles and to improve the accuracy of the nozzle pitch in the nozzle arrangement direction. However, in order to improve these accuracies, a feed mechanism with high feed accuracy of the ink jet head is required, and the equipment becomes expensive.

  Accordingly, in view of the above problems, the present invention provides an image recording apparatus capable of recording a high-quality image using an inkjet head unit in which a plurality of nozzle rows in which nozzles that are misaligned during nozzle formation are present. An object is to provide an inkjet head unit to be mounted.

  In order to achieve the object, the present invention provides an inkjet head having a plurality of nozzles arranged at a nozzle pitch P for ejecting ink and having a nozzle row formed by dividing a large number of nozzles into a plurality of nozzle groups. The inkjet head unit is configured so that the rows are arranged in a plurality of stages, and the nozzle row is shifted by 1 nozzle pitch P or more in the nozzle row direction with respect to the nozzles of the nozzle row arranged in the preceding stage or the subsequent stage. An inkjet head unit is provided that is fixed in quantity and mounted on an image recording apparatus.

  According to the present invention, an inkjet head unit mounted on an image recording apparatus capable of recording a high-quality image using an inkjet head unit in which a plurality of nozzle rows in which nozzles that have been misaligned are present at the time of nozzle formation. Can be provided.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In the following description, in the drawing, the conveyance direction of the recording medium is the X-axis direction or the sub-scanning direction, and the direction orthogonal to the conveyance direction is the Y-axis direction, the main scanning direction, or the width direction of the recording medium. A direction orthogonal to the X-axis and Y-axis directions is taken as a Z-axis direction or a vertical direction.

The first embodiment will be described with reference to FIGS.
FIG. 1 is a schematic bottom view of an inkjet head unit mounted on an image recording apparatus according to the present embodiment, FIG. 2 is a schematic perspective view of the inkjet head unit, and FIG. 3 is a schematic perspective view showing a bottom shape of a base plate of one inkjet head. 4 and 4 are schematic perspective views showing the positional relationship between the two base plates, the adjusting base, and the cam member, FIG. 5 is a side sectional view of the ink jet head unit, and FIG. 6 is a part of the base plate when aligned in the Y-axis direction. It is sectional drawing.

  The ink jet head unit 1 is provided with a first unit and a second unit. The first unit is provided with an ink jet head 1a that is the previous stage with respect to the X-axis direction and a base plate 30a that holds and fixes the ink jet head 1a. The second unit is provided with an inkjet head 1b that is a subsequent stage with respect to the X-axis direction and a base plate 30b that holds and fixes the inkjet head 1b. The first unit and the second unit are bonded and fixed with a displacement of approximately 2.5 P (the displacement of approximately 2.5 P will be described later). The first unit and the second unit have the same configuration.

  In addition, the inkjet head 1a divides six nozzles into one group to form four nozzle groups (20-1 to 20-4), and the nozzle groups 20-1, 20-2, 20-3, and 20-4. Are formed in order. Similarly, in the inkjet head 1b, six nozzles are divided into one group, and four nozzle groups (20-5 to 20-8) are formed, and the nozzle groups 20-8, 20-7, 20-6, and 20- It is formed gradually in the order of 5.

  In the inkjet head 1a and the inkjet head 1b, after four nozzle groups (20-1 to 20-4, 20-5 to 20-8) are formed, the inkjet head unit 1 includes the inkjet head 1a and the inkjet head 1b. Are pasted and fixed approximately 2.5P apart.

  In the X-axis direction, the nozzle groups 20-1, 20-2, 20-3, 20-4 are the front stage, and the nozzle groups 20-5, 20-6, 20-7, 20-8 are the rear stage. As described above, the nozzle rows in the inkjet head 1a and the inkjet head 1b are formed in a step shape. As with the nozzle groups 220-2 and 220-6 described above, the nozzle group 20-2 has a slight error in movement accuracy during the processing (feed movement) of the nozzle group, and the nozzle group 20-6 It is assumed that the nozzle group is formed with a slight deviation in the + Y direction as a slight error in movement accuracy during the processing (feed movement) of the nozzle group.

  Next, the configuration of the first unit and the second unit will be described in detail.

  The base plates 30a and 30b are made of a material having high thermal conductivity, such as aluminum. The base plates 30a and 30b formed of aluminum can efficiently dissipate heat generated from the piezoelectric body 10 and the IC 18b.

  The inkjet heads 1a and 1b are provided with a piezoelectric body 10, a nozzle plate 20, and the like. The piezoelectric body 10 is made of, for example, piezo, and a plurality of grooves 50 each having an arc shape along the Z-axis direction are formed in the piezoelectric body 10 up to the front surface 10b of the piezoelectric body 10. The nozzle plate 20 is bonded to the front surface 10b. In the nozzle plate 20, nozzles 20 a are formed at positions corresponding to the respective grooves 50, and the nozzles 20 a form nozzle rows arranged on a straight line in the Y-axis direction.

  The piezoelectric bodies 10 of the inkjet heads 1a and 1b are disposed on the upper surfaces of the base plates 30a and 30b, respectively, and ICs 18b that are drive circuits for driving the piezoelectric bodies 10 are also disposed on the upper surfaces of the base plates 30a and 30b, respectively. A flexible substrate 18 is fixedly disposed on the piezoelectric body 10 and the IC 18b. The piezoelectric body 10 is fixedly disposed on the base plates 30a and 30b by a fixing member, and the flexible substrate 18 is directly bonded on the base plates 30a and 30b by an adhesive.

  As shown in FIG. 3, grooves 34 are formed on the bottom surfaces of the base plates 30a and 30b (however, only the base plate 30b is shown in FIG. 3).

  As shown in FIG. 4, the base plate 30a is provided with a round hole 31a for adjusting the position of the base plate 30a in the Y-axis direction with respect to the base plate 30b and two long holes 32a. Similarly, the base plate 30b is also provided with a round hole 31b provided at a position corresponding to the round hole 31a and two round holes 32b provided at positions corresponding to the two long holes 32a, respectively.

The diameter of the round hole 31b is smaller than the diameter of the round hole 31a. A cam member 54, which is a fixing member described later, is inserted into the round hole 31a and the round hole 31b. In addition, a positioning pin 53, which is a fixing member described later, is inserted into each of the long hole 32a and the round hole 32b. Furthermore, two pins 33a and 33b for positioning in the Z-axis direction are provided on the upper surfaces of the base plates 30a and 30b.
The effects of these adjustment round holes 31a and 31b, the long hole 32a, the round hole 32b, the pins 33a and 33b, and the positioning pin 53 will be described later.

  As shown in FIG. 2, the fixing member 40 is provided with a leaf spring 41. The leaf spring 41 fixes the inkjet heads 1a and 1b to the base plates 30a and 30b, and elastically presses the inkjet heads 1a and 1b toward the upper surfaces of the base plates 30a and 30b (X-axis direction). The leaf springs 41 are provided at both ends in the Y-axis direction of the inkjet heads 1a and 1b, respectively, and elastically urge and fix the inkjet heads 1a and 1b along the X-axis direction with respect to the base plates 30a and 30b. ing. The leaf spring 41 elastically biases the piezoelectric body 10 of the ink jet heads 1a and 1b only from the X-axis direction, and does not bias the Y-axis direction at all. The reason for not energizing in the Y-axis direction is that when the inkjet heads 1a and 1b are driven, even if the piezoelectric body 10 expands in the Y-axis direction due to heat radiation generated from the piezoelectric body 10, the dimensional change of the piezoelectric body 10 is allowed. This is to make it possible.

  Next, a method for positioning the inkjet heads 1a and 1b on the base plates 30a and 30b and a method for bonding and fixing the base plates 30a and 30b to each other will be described.

  First, when the inkjet heads 1a and 1b are fixed on the base plates 30a and 30b, the rear surface 10c of the piezoelectric body 10 (the end surface opposite to the front surface 10b to which the nozzle plate 20 is bonded) is provided on the base plates 30a and 30b. The ink jet heads 1a and 1b are fixed by the fixing member 40 in this state. As a result, positioning in the Z-axis direction is performed.

  The piezoelectric body 10 in the ink jet heads 1a and 1b usually has high rigidity and is processed with a dicing saw or the like, so that it can be processed with high accuracy. For this reason, the front surface 10b (strictly the nozzle plate 20) and the rear surface 10c of the piezoelectric body 10 and the distance between the surfaces are kept in parallel with each other, and the accuracy is extremely high. Therefore, if the positions of the two pins 33a, 33b, the two long holes 32a, and the two round holes 32b provided on the base plates 30a, 30b in the Z-axis direction are highly accurate, the piezoelectric elements of the inkjet heads 1a, 1b can be used. By simply bringing the rear surface 10c of the body 10 into contact with the two pins 33a and 33b of the base plates 30a and 30b, the inkjet heads 1a and 1b can be positioned in the Z-axis direction.

  Next, the base plates 30a and 30b to which the inkjet heads 1a and 1b are fixed are bonded to each other by the bonding surfaces 51a and 51b, and placed on the adjustment table 52 as shown in FIGS.

  The positioning table 52 is provided with two positioning pins 53. The two positioning pins 53 are inserted into two round holes 32b provided in the base plate 30b and two long holes 32a provided in the base plate 30a, respectively. The diameter of the positioning pin 53 is substantially the same as the diameter of the round hole 32b provided in the base plate 30b. Therefore, when the positioning pin 53 is inserted into the round hole 32b, the base plate 30b is positioned and fixed on the adjustment base 52, and is positioned in the X, Y, and Z axis directions.

  The diameter of the positioning pin 53 is substantially the same as only the dimension in the Z-axis direction of the long hole 32a provided in the base plate 30a. Therefore, when the positioning pin 53 is inserted into the long hole 32a, the base plate 30a is positioned and fixed with respect to the Z-axis direction. The base plate 30a is movable in the Y axis direction (nozzle arrangement direction).

  Next, in order to position the base plate 30a in the Y-axis direction, cam members 54 that adjust the movement of the base plate 30a by a small amount are inserted into the round holes 31a and 31b. The cam member 54 is a round bar-shaped pin, and an eccentric cam 56 is formed at the center of the pin. The diameter of the round bar portion 55 of the cam member 54 is substantially the same as the diameter of the round hole 31b provided in the base plate 30b. The diameter of the eccentric cam 56 of the cam member 54 is large enough to be inserted into the round hole 31a provided in the base plate 30a. The eccentric cam 56 is inserted into the round holes 31a and 31b formed in the base plates 30a and 30b, and then rotated, so that the base plate 30a extends along the Y-axis direction with respect to the base plate 30b as shown in FIG. Can be moved and positioned. When positioning in the Y-axis direction by the cam member 54, the base plates 30a and 30b are urged toward the eccentric cam 56 from the arrow direction by the urging means 5 shown in FIG. As a result, the end surfaces of the inkjet heads 1a and 1b abut against the cam member 54 without any gap, and the position of the base plate 30a can be adjusted easily and with high accuracy. Details of positioning in the Y-axis direction will be described later.

  When the operator rotates the cam member 54, the base plate 30a moves in the Y-axis direction. When moved, the nozzle row of the inkjet head 1a provided on the base plate 30a reached a position shifted by about 2.5 times the nozzle pitch P with respect to the nozzle row of the inkjet head 1b provided on the base plate 30b. In other words, when the positioning in the Y-axis direction is completed, the base plates 30a and 30b and the cam member 54 are fixed with an adhesive and attached together. Alternatively, the base plates 30a and 30b are fixed by screwing or the like.

  Next, the position adjustment in the Y-axis direction of the inkjet head unit will be described in detail with reference to FIG. FIG. 7 shows a schematic view around the inkjet heads 1a and 1b without the base plates 30a and 30b holding the inkjet heads 1a and 1b. Here, in order to simplify the description, in order to form six nozzles in four nozzle groups (nozzle groups 20-1 to 20-4) in the inkjet head 1a, as described above, one group of processing is performed. This will be described assuming an ink jet head in which nozzle processing is completed by repeating the above four times. The same applies to the inkjet head 1b.

  When each nozzle pitch is P, the length of one nozzle group to be processed is 6P. Here, a description will be given of a method in which the inkjet head 1a is fixed by being attached to the inkjet head 1b with a position shifted by 2.5P, which is about half the nozzle group length (1/2).

  As shown in FIG. 7, the inkjet head 1a forms nozzle groups 20-1 to 20-4, and the inkjet head 1b forms nozzle groups 20-5 to 20-8.

  First, the inkjet head 1a is urged from the direction of the arrow to the cam member 54 by the urging means 5 shown in the drawing while the inkjet head 1a freely moves in the Y-axis direction along the long hole 32a with respect to the inkjet head 1b. The Next, the inkjet head 1a is moved by the cam member 54 so as to be shifted by about 2.5 P with respect to the inkjet head 1b.

  Next, the image capturing means 6 such as a CCD camera captures image information of the nozzles at both ends of the inkjet head 1a and the inkjet head 1b. The image information of the nozzles at both ends includes the peripheral area image information of the nozzle located at the leftmost end provided in the nozzle group 20-1 and the nozzle group 20-5, the nozzle group 20-4, and the nozzle group 20-8. It is the peripheral area image information of the nozzle located in the provided rightmost end. After calculating the position coordinates of the leftmost nozzles provided in the nozzle group 20-1 and the nozzle group 20-5 from the peripheral area image information, the image processing means 7 calculates the displacement amount A in the Y-axis direction between the nozzles. To do. Further, the image processing means 7 calculates the position coordinates of the rightmost nozzles provided in the nozzle group 20-4 and the nozzle group 20-8 from these peripheral area image information, and then calculates the deviation amount B in the Y-axis direction between the nozzles. calculate. Based on the calculation result, the operator rotates the cam member 54 so that the deviation amount A and the deviation amount B are close to about 2.5P, and the deviation amount A = the deviation amount B.

  As a result, the inkjet head 1a can be adjusted so as to be displaced by about 2.5 P with respect to the inkjet head 1b, and the inkjet head 1a is positioned in the Y-axis direction. After the positioning in the Y-axis direction is completed, the base plates 30a and 30b and the cam member 54 (the ink-jet head 1a and the ink-jet head 1b in FIG. 7) are then moved in the Y-axis direction by using, for example, screws or the adhesive described above. Fix and paste together.

  FIG. 8 is a schematic bottom view of the ink jet heads 1a and 1b that have been adjusted in position as described above (base plates 30a and 30b are not shown). FIG. 9 is a solid image when ink is ejected to a recording medium based on the arrangement shown in FIG.

  As described above in the present embodiment, the nozzles provided in the nozzle groups 20-2 and 20-6 have a slight error in the movement accuracy when the ink-jet heads 1a and 1b are moved and moved. The other nozzle groups are not displaced in the Y-axis direction. Further, as shown in FIG. 8, the inkjet heads 1a and 1b are attached by being fixed in two steps in the X-axis direction by being shifted about 2.5P in the Y-axis direction by the cam member 54 as described above. As a result, the nozzle rows formed in the inkjet heads 1a and 1b are stepped in the X-axis direction.

  In this embodiment, ink ejected from three nozzles on the −Y (left) side formed on the nozzle group 20-6 slightly shifted in the + Y direction and landed on the recording medium, and nozzles not shifted in the Y-axis direction The ink ejected from the three nozzles on the + Y (right) side of the group 20-1 and landed on the recording medium is adjacent to each other, so that there are almost no white stripes and human recognition becomes difficult.

  Further, the ink ejected from the three nozzles on the + Y (right) side formed in the nozzle group 20-6 that is slightly displaced in the + Y direction is slightly displaced in the + Y direction and landed on the recording medium, and the −Y direction. The ink ejected from the three nozzles on the −Y side of the nozzle group 20-2 slightly deviated slightly deviates in the −Y direction and lands on the recording medium. As a result, there are many portions that overlap each other when landing, and white streaks occur (the white streaks of the landing ink are conspicuous), which makes it easier for humans to recognize.

  Also, ink ejected from the three nozzles on the + Y side formed in the nozzle group 20-2 and landed on the recording medium, and ejected from the three nozzles on the −Y side of the nozzle group 20-7 not displaced in the Y-axis direction. Since the ink that lands is next to each other, there are almost no white streaks, making it difficult for humans to recognize.

  When the ink is landed on the recording medium in this way, as shown in FIG. 9, the white stripes that are easily recognized by humans are generated by the nozzle groups 20-2 and 20-6 whose processing is shifted in the reverse direction in the Y-axis direction described above. This occurs only in the overlapping portion, and as a result, the width of the white streak is minimized as compared with FIG.

  Normally, recognition of density unevenness tends to be easier for humans to recognize as the width of the white stripe increases. In this embodiment, as shown in FIG. 8, the inkjet heads 1a and 1b are attached and fixed while being shifted by about 2.5 P. Therefore, when ink is ejected, the width of the white stripe is minimized as shown in FIG. Can be suppressed. Thereby, recognition of density unevenness can be minimized and a high-quality image can be recorded.

  More specifically, in the present embodiment, the two inkjet heads 1a and 1b are fixed to the base plates 30a and 30b, respectively, and two positioning pins 53 and a cam member 54, which are common positioning members, are used, and about 2. After positioning by shifting 5P, it is stuck and fixed. By displacing in this way, it is possible to minimize the white stripes that are easily recognized by humans due to the landing ink, and to eject a high-density ink and record a high-quality image. Can be configured. Further, the shift amount is about 2.5 P, but is not limited, and may be about 3.5 P, for example, and may be adjusted appropriately.

  Further, in this embodiment, when the inkjet head is moved during nozzle processing, even if a slight error occurs in the movement accuracy and the pitch between the nozzle groups is shifted, it is shifted by about 2.5 P in the Y-axis direction. By adjusting the position, the width of white stripes that can be easily recognized by humans due to deviations in the pitch between nozzle groups can be suppressed. It is possible to record high-quality images while minimizing image quality.

  In addition, since the tolerance of nozzle position deviation can be relaxed in nozzle processing, it is not necessary to introduce expensive high-precision processing equipment, and recognition of density unevenness is minimized as shown in FIG. A quality image can be recorded.

  In addition, in an inkjet head having a different nozzle length, when the shift amount is adjusted only at one end of the inkjet head, the shift amount may be different at one end and the other end of the inkjet head. However, since the position of the nozzle is detected by detecting the position of the nozzle at both ends of the ink jet head as in the present embodiment, an optimum shift amount can be set for the entire width of the nozzle line.

  In the present embodiment, by adjusting the position in the Y-axis direction from the deviation amounts A and B at both ends, the deviation amount can be set to about 2.5 P over the entire nozzle line even in an inkjet head having a different nozzle length. it can.

  In the present embodiment, the cam member 54 is applied as the position adjusting means. However, the present invention is not limited to this, and for example, a dial gauge with a rotating means may be applied.

Further, the image information acquired by the image capturing means 6 is not limited to the image information at both ends described above. For example, the nozzle groups of the inkjet head 1a and the inkjet head 1b (nozzle group 20-1 and nozzle group 20-4). , The nozzle group 20-5 and the nozzle group 20-8) may be image information, and the center value of each nozzle group in the Y-axis direction is calculated from the captured image information using, for example, pattern matching. A method of calculating the shift amount of the inkjet head 1a and the inkjet head 1b from the shift amount of the center value of each nozzle group may be used.
When the deviations A and B are calculated based on the position information of one nozzle described above, erroneous calculation may occur if dust such as a processed pattern or dust adheres to the edge portion of the nozzle. However, since the shift amount is calculated from the plurality of nozzle position information (the inkjet head 1a and the entire inkjet head 1b) as described above, the shift amount can be calculated to about 2.5P with higher accuracy.

  Further, in order to minimize the error of the positional deviation of the nozzles provided in each nozzle group, the image capturing means 6 is scanned over the entire area of the nozzles, and the positional information of all the nozzles is captured. An average value (center value) is calculated, and the center value in the Y-axis direction of the nozzle provided in the inkjet head 1a and the center value in the Y-axis direction of the nozzle provided in the inkjet head 1b are set to about 2.5P. Accordingly, it is possible to adjust the displacement amount to about 2.5 P over the entire area of the nozzle lines of the inkjet head 1a and the inkjet head 1b.

  Further, as a method for improving the acquisition accuracy of the image information, the amount of the peripheral image area information that can be temporarily captured by the image capturing means 6 is decreased, and the resolution is increased. Next, the image capturing means 6 is gradually scanned over the nozzles to obtain peripheral image area information, and the high resolution image information is captured into the image processing means 7 so that the positions of both ends of the inkjet head 1a and the inkjet head 1b are obtained. Information can be calculated with higher accuracy.

  Next, a second embodiment according to the present invention will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected in the structure part similar to 1st Embodiment mentioned above, and the detailed description is abbreviate | omitted. In the present embodiment, the ink jet head unit includes four ink jet heads. Similarly to the first embodiment described above, six nozzles are formed in one nozzle group, and the nozzle rows are stepped.

  FIG. 10 is a schematic bottom view of a conventional inkjet head showing a positional relationship when nozzles provided in four inkjet heads are accurately arranged. FIG. 11 is a solid image when ink is ejected to a recording medium based on the arrangement shown in FIG. 12 shows a partial displacement of the nozzle arrangement shown in FIG. 10 (nozzle group 20-2 is slightly displaced in the + Y (right) direction, and nozzle group 20-11 is slightly displaced in the -Y (left) direction. It is a schematic bottom view of the ink-jet head showing the state. FIG. 13 is a solid image when ink is ejected to a recording medium based on the arrangement shown in FIG. FIG. 14 is a schematic bottom view of an ink jet head that is attached and fixed by adjusting the shift amount. FIG. 15 is a solid image when ink is ejected onto a recording medium based on the arrangement shown in FIG.

  As shown in FIG. 10, four inkjet heads 1a, 1b, 1c, and 1d are bonded and fixed, and each of the inkjet heads 1a, 1b, 1c, and 1d has three nozzle groups (20-1 to 20-3). 20-4 to 20-6, 20-7 to 20-9, 20-10 to 20-12). As described above, when the inkjet head is fed and moved to process nozzles in the inkjet head, if the movement accuracy is high and there is no variation in the nozzle position of the nozzle group, unevenness does not appear in the landing as shown in FIG.

  However, the movement accuracy is low. For example, as shown in FIG. 12, the nozzles provided in the nozzle group 20-2 of the inkjet head 1a are displaced in the + Y direction, and the nozzle group 20- provided in the inkjet head 1d. When the positions of the 11 nozzles are shifted in the −Y direction, white streaks are conspicuous in the ink landing areas corresponding to the two nozzle areas as shown in FIG. 13, and density unevenness occurs.

  Therefore, the present embodiment is shifted in the same manner as the first embodiment so that the overlapping of the processing sections of the respective inkjet heads is reduced when the inkjet head 1a, the inkjet head 1b, the inkjet head 1c, and the inkjet head 1d are bonded together. Adjust the amount (adjust the position in the Y-axis direction) and fix it.

  The deviation amount in this embodiment at that time is a value approximate to a value obtained by dividing the number of nozzles formed in the nozzle group (6 in this embodiment) by the number of ink jet heads (4 in this embodiment). The inkjet head 1b is displaced with respect to the inkjet head 1a by about 1.25P, the inkjet head 1c is displaced with respect to the inkjet head 1b, and the inkjet head 1d is displaced with respect to the inkjet head 1c. FIG. 14 shows a state in which they are displaced and fixed in such a manner. When ink is ejected onto the recording medium in this state, as shown in FIG. 15, the right three nozzles of the nozzle group 20-2 and the left three nozzles of the nozzle group 20-11 as in the first embodiment described above. White streaks that are easily recognized by humans are generated only in the overlapping portions of the ink ejected from the ink, and as a result, the generation of white streaks can be minimized as compared with FIG.

  As described above, in the present embodiment, when the nozzles are formed in the nozzle groups of the inkjet heads 1a, 1b, 1c, and 1d by adjusting the shift amount based on the approximate value, the movement accuracy due to the feed movement of the inkjet head is low. Even if there are variations in the nozzle formation position of the nozzle group, the white stripe width of 6 nozzles shown in FIG. Can be suppressed. Thereby, recognition of density unevenness can be minimized and a high-quality image can be recorded.

In the present embodiment, the number of nozzles formed in the nozzle group is six, but the number of nozzles is not limited to this number.
For example, when the number of nozzles formed in a nozzle group is 12, when 12/4 = 3 and 4 inkjet heads are bonded and fixed, the displacement amount between the inkjet heads is about 3.25P. . Further, the shift amount may be not the same pitch but unevenly, for example, a shift amount of about 2.25P, about 1.25P, or about 2.25P.

  Dividing the number of nozzles formed in approximately one nozzle group in this way by the number of heads to be combined, shifting the adjacent inkjet heads by the divided value (distance), and adhering them together to fix 3 or more inkjet heads Even if it is fixed, recognition of density unevenness can be minimized and a high-quality image can be recorded.

  Next, a third embodiment according to the present invention will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected in the structure part similar to 1st Embodiment mentioned above, and the detailed description is abbreviate | omitted. In the present embodiment, the inkjet head unit includes two inkjet heads. The inkjet head is provided with three nozzle groups, and one nozzle group is formed with 12 nozzles, and the nozzle row is stepped.

  FIG. 16 is a schematic bottom view of a conventional inkjet head showing the positional relationship when the nozzles provided in the inkjet heads 1a and 1b are accurately arranged. FIG. 17 is a solid image when ink is ejected to a recording medium based on the arrangement shown in FIG. 18 shows a partial displacement of the nozzle arrangement shown in FIG. 16 (nozzle group 20-2 is slightly displaced in the + Y direction (right direction) and nozzle group 20-6 is minutely displaced in the -Y direction (left direction). It is a schematic bottom view of the inkjet head which shows the state which has shifted | deviated. FIG. 19 is a solid image when ink is ejected to a recording medium based on the arrangement shown in FIG. FIG. 20 is a schematic bottom view of an ink jet head that is attached and fixed by adjusting the shift amount. FIG. 21 is a solid image when ink is ejected onto a recording medium based on the arrangement shown in FIG.

  As shown in FIG. 16, inkjet heads 1a and 1b are bonded and fixed, and each of the inkjet heads 1a and 1b has three nozzle groups (20-1 to 20-3 and 20-4 to 20-6). Is provided. Twelve nozzles are formed in these nozzle groups. When the inkjet head is fed and moved to process nozzles in the inkjet head, if the movement accuracy is high and there is no variation in the nozzle position of the nozzle group, unevenness does not appear in the landing as shown in FIG.

  However, the movement accuracy is low. For example, as shown in FIG. 18, the nozzles provided in the nozzle group 20-2 of the inkjet head 1a are displaced in the + Y direction, and the nozzles provided in the nozzle group 20-5 of the inkjet head 1b. When the position is shifted in the -Y direction, white streaks are conspicuous in the ink landing areas corresponding to the two nozzle areas described above, as shown in FIG.

  For this reason, in this embodiment, the nozzle group formed in each nozzle group is divided into two times, the first nozzle group that processes the nozzle first, and the second nozzle group that is processed later. The order of processing is that the odd-numbered nozzles (first nozzle group) from the nozzle group 20-1 to the nozzle group 20-3 are processed in order from the nozzle group 20-1 to the nozzle group 20-3 in the first of the inkjet head 1a. Second, even-numbered nozzles (rear nozzle groups) from the nozzle group 20-1 to the nozzle group 20-3 are sequentially processed from the nozzle group 20-1 to the nozzle group 20-3. At that time, even-numbered nozzles are formed between the odd-numbered nozzles, that is, even-numbered nozzles and odd-numbered nozzles are alternately formed as shown in FIG. Similarly, in the inkjet head 1b, even-numbered nozzles and odd-numbered nozzles are alternately formed.

  After processing in this way, the inkjet heads 1a and 1b are adjusted so as to be displaced by about ½ P by the cam member 54 as in the first embodiment, and are bonded and fixed.

  FIG. 20 shows the state of being bonded and fixed in this way. When ink is ejected onto the recording medium in this state, the result is as shown in FIG.

  As described above, according to the present embodiment, the nozzle processing is performed twice in the same nozzle group. In the processing, even if the nozzle processing position is shifted due to the low movement accuracy of the ink jet head, the white streaks do not continue and one line skips (alternate). For this reason, when the ink jet head 1a and the ink jet head 1b are bonded and fixed, and the ink is landed on the recording medium, the white streaks due to the landing deviation become inconspicuous, recognition of density unevenness is minimized, and a high quality image is obtained. Can be recorded.

  Although the shift amount is about 1 / 2P, a higher quality image can be recorded by calculating in the same manner as in the first embodiment. Specifically, the white streaks due to landing deviation are less noticeable by minimizing the recognition of density unevenness by shifting the nozzle group length 12P, about 5.5P, which is about half the nozzle group length, and fixing them together. As a result, a high-quality image can be recorded.

  In the present embodiment, even-numbered nozzle processing was performed after odd-numbered nozzle processing, but this order may be reversed, and the nozzle processing in the nozzle group was divided into even-numbered and odd-numbered two times, but this is limited to this. The processing may be performed a plurality of times, for example, by dividing the nozzles every third to three times.

  In each of the above-described embodiments, the number of nozzles of a nozzle group that is processed at a time may be appropriately selected in consideration of a processing range, processing accuracy, and the like. Further, the amount of displacement of the nozzles between the inkjet heads is usually 1 pitch or less, but may be an amount of displacement larger than 1 pitch and smaller than the length of the nozzle group (6P or 12P). In other words, if the nozzles formed at both ends of the nozzle group of one inkjet head do not overlap with the nozzles formed at both ends of the nozzle group of the other inkjet head on the same straight line in the X-axis direction, the width of the white stripe is increased. Smaller image quality can be improved.

1 is a schematic bottom view of an ink jet head unit mounted on an image recording apparatus according to a first embodiment of the present invention. It is a schematic perspective view of an inkjet head unit. It is a schematic perspective view which shows the bottom face shape of the base plate of one inkjet head. It is a schematic perspective view which shows the positional relationship of two base plates, an adjustment stand, and a cam member. It is side surface sectional drawing of an inkjet head unit. It is a partial sectional view of a base plate when aligning in the Y-axis direction. FIG. 3 is a schematic view of the periphery of an inkjet head without a base plate that holds the inkjet head. It is a schematic bottom view of an inkjet head that has been adjusted, pasted and fixed. FIG. 9 is a solid image when ink is ejected to a recording medium based on the arrangement shown in FIG. 8. It is a schematic bottom view of the conventional inkjet head which shows the positional relationship when the nozzle provided in four inkjet heads is arrange | positioned accurately. 11 is a solid image when ink is ejected to a recording medium based on the arrangement shown in FIG. FIG. 11 is a schematic bottom view of the ink jet head showing a state where a part of the nozzle arrangement shown in FIG. 10 is shifted. 13 is a solid image when ink is ejected onto a recording medium based on the arrangement shown in FIG. FIG. 6 is a schematic bottom view of an ink-jet head that is attached and fixed by adjusting a shift amount in an ink-jet head unit mounted on an image recording apparatus according to a second embodiment of the present invention. FIG. 15 is a solid image when ink is ejected to a recording medium based on the arrangement shown in FIG. 14. It is a schematic bottom view of the conventional inkjet head which shows the positional relationship when the nozzle provided in the inkjet head is arrange | positioned accurately. FIG. 17 is a solid image when ink is ejected to a recording medium based on the arrangement shown in FIG. 16. FIG. 17 is a schematic bottom view of the ink jet head showing a state in which a part of the nozzle arrangement shown in FIG. 16 is displaced. 19 is a solid image when ink is ejected to a recording medium based on the arrangement shown in FIG. FIG. 10 is a schematic bottom view of an ink jet head that is attached and fixed by adjusting a shift amount in an ink jet head unit mounted on an image recording apparatus according to a third embodiment of the present invention. 21 is a solid image when ink is ejected to a recording medium based on the arrangement shown in FIG. It is a schematic bottom view of the conventional inkjet head unit. It is a schematic bottom view of the conventional inkjet head which shows the positional relationship when the nozzle provided in the inkjet head is arrange | positioned accurately. 24 is a solid image when ink is ejected to a recording medium based on the arrangement shown in FIG. FIG. 24 is a schematic bottom view of the inkjet head showing a state in which a part of the nozzle arrangement shown in FIG. 23 is shifted. 26 is a solid image when ink is ejected to a recording medium based on the arrangement shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Inkjet head unit, 1a, 1b, 1c, 1d ... Inkjet head, 2 ... Recording medium, 5 ... Energizing means, 6 ... Image taking means, 7 ... Image processing means, 10 ... Piezoelectric body, 10b ... Front surface, 10c ... rear surface, 18 ... flexible substrate, 18b ... IC, 20 ... nozzle plate, 20a ... nozzle, 20-1, 20-2, 20-3, 20-4, 20-5, 20-6, 20-7, 20-8, 20-9, 20-10, 0-11, 20-12 ... Nozzle group, 30a, 30b ... Base plate, 31a, 31b, 32b ... Round hole, 32a ... Long hole, 33a, 33b ... Pin, 34 DESCRIPTION OF SYMBOLS ... Groove, 40 ... Fixing member, 41 ... Leaf spring, 50 ... Groove, 51a, 51b ... Bonding surface, 52 ... Adjustment stand, 53 ... Pin, 54 ... Cam member, 55 ... Round bar part, 56 ... Eccentric cam.

Claims (7)

An inkjet head having a plurality of nozzles arrayed at a nozzle pitch P for ejecting ink, the nozzles being divided into a plurality of nozzle groups and gradually formed so as to be stacked in a plurality of stages. An inkjet head unit configured as follows:
The nozzle row is fixed with a deviation amount of 1 nozzle pitch P or more in the nozzle row direction with respect to the nozzles of the nozzle row arranged in the front stage or the rear stage, and is mounted on the image recording apparatus. Inkjet head unit.   The inkjet head unit is configured by stacking two inkjet heads, and the displacement amount of the nozzle between the nozzle row provided in one of the inkjet heads and the nozzle row provided in the other inkjet head is The inkjet head unit mounted on the image recording apparatus according to claim 1, wherein the inkjet head unit is less than or equal to ½ of the nozzle group length.   The ink jet head unit is configured by stacking three or more ink jet heads, and the displacement amount between the adjacent nozzle rows is the number of the ink jet heads constituting the ink jet head unit by the nozzle group length. The inkjet head unit mounted on the image recording apparatus according to claim 1, wherein the inkjet head unit is an approximate value of a value divided by. The inkjet head is composed of a plurality of nozzles that eject ink onto a recording medium, and the nozzles are divided into a plurality of nozzle groups and gradually formed. An inkjet head unit,
The nozzle group is
A tip nozzle group having a plurality of the nozzles formed in the nozzle row direction first;
A rear nozzle group having a plurality of the nozzles formed later in the nozzle row direction;
Comprising
The nozzles formed in the rear nozzle group are formed between the nozzles formed in the front nozzle group after the nozzles formed in the front nozzle group are formed first. An inkjet head unit mounted on an image recording apparatus.   The formation positions of the nozzles formed in the front nozzle group and the nozzles formed in the rear nozzle group are alternately arranged in the nozzle row direction. An inkjet head unit mounted on an image recording apparatus.   The said front nozzle group has the said odd-numbered said nozzle in the said inkjet head, and the said back nozzle group has the said even-numbered said nozzle in the said inkjet head. An inkjet head unit mounted on an image recording apparatus.   5. The front nozzle group includes the even-numbered nozzles in the inkjet head, and the rear nozzle group includes the odd-numbered nozzles in the inkjet head. An inkjet head unit mounted on an image recording apparatus.

Images