JP2006007445A - Inkjet recorder and detection method of discharge defective nozzle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To carry out stable detection of nozzles in a short time by reducing effects of optical diffraction and conducting detection at once without moving a head for all nozzles in one nozzle array. <P>SOLUTION: There are provided a light emitting means for ejecting a detection light to intersect a trajectory of ink droplets discharged from the nozzles of a recording head which has the nozzle array with a plurality of the nozzles arranged, a light receiving means for detecting whether or not the ink droplets pass in an optical path of the detection light by receiving the detection light, a discharge control means for controlling to discharge the ink droplets sequentially in time series towards the optical path of the detection light from all of the nozzles of the recording head, and a discharge defective nozzle specifying means for specifying discharge defective nozzles by detecting a discharge state of the ink droplets from the nozzles on the basis of a timing of discharging of the ink droplets by the discharge control means and a passage detection timing of the ink droplets by the light receiving means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ink jet recording apparatus capable of performing stable detection over each nozzle of a recording head and a method for detecting defective ejection nozzles.

  In an inkjet recording apparatus that records an image by ejecting ink droplets from a nozzle provided in the recording head to a recording medium, each nozzle is periodically arranged so that high-quality and high-quality image recording can be maintained. The ink discharge state is detected by detecting whether or not the ink droplets are ejected from the nozzle (the presence or absence of clogging) and the flying speed of the ejected ink droplets.

  As such a detection method, a light emitting element (LED) that emits detection light and a light receiving element (photodiode) that receives the detection light are provided so as to cross the flight path of the ink droplet, and the detection light is on the optical path. Is generally performed by capturing the change in the amount of light of the light receiving element when the ink droplet passes through. Based on the timing at which the ink droplets are ejected and the timing at which the light receiving element detects a change in the amount of light, it is possible to detect the presence / absence of the ink droplets, that is, the presence / absence of the missing nozzle and the flying speed of the ink droplets.

  The distance between the light emitting element and the light receiving element becomes longer as the number of nozzles increases, so that all the nozzles in the nozzle array of the recording head are within the optical path of the detection light formed therebetween. From the viewpoint of space saving, they are arranged as close as possible to fit the nozzle row. On the other hand, since the detection light emitted from the light emitting element is divergent light, the shadow of the ink droplet ejected from the nozzle close to the light emitting element is easily affected by light diffraction.

  As a result, the detection output from the light receiving element tends to become weaker as the nozzle position is closer to the light emitting element due to the correlation between the distance from the light emitting element of the nozzle and the light diffraction. ), The nozzle position gradually decreases as the nozzle position approaches the light emitting element. In particular, due to the increase in the nozzle row length resulting from the increase in the number of nozzles in recent years, the optical path length of the detection light has become longer and the amount of ink droplets has become smaller. The detection output by the ejected ink droplets and the detection output by the ink droplets ejected from the nozzles on the light emitting element side end are greatly different, and there is a problem that uniform and stable detection cannot be performed across all the nozzles.

In order to cope with such a problem, Patent Document 1 provides two sets of light emitting elements and light receiving elements, and arranges the detection lights in parallel so that the emission directions are opposite to each other. Each half of the nozzles close to the light emitting element in one nozzle row is paused, and as shown in FIG. 11, the ink droplets for each of the half nozzles near the light receiving element whose detection output is higher than a predetermined threshold th. Discloses a method for performing detection that is not affected by light diffraction.
Japanese Patent Laid-Open No. 10-119307

  However, in the method described in Patent Document 1, two sets of light emitting elements and light receiving elements must be provided, and there is a problem of cost increase due to a complicated detection mechanism. Therefore, it is difficult to adjust the detection level to each other, and adjustment is necessary particularly when the flying speed of ink droplets and the amount of ink droplets are obtained.

  Further, since only half of the nozzles in one nozzle row can be detected by one detection light, the recording head itself can be detected between the two detection lights to detect all the nozzles in one nozzle row. Must be moved. The detection for each nozzle itself requires only a very short time of electrical control such as ejection control of ink droplets, whereas the movement of the recording head itself is the movement of the carriage on which the recording head is mounted in addition to the electrical control. It is necessary to repeatedly perform mechanical control such as optical axis coincidence detection operation and stop. Since this mechanical control takes much longer than the nozzle detection time by electrical control, there is a problem that the detection time increases accordingly.

  Therefore, the present invention reduces the influence of light diffraction and can detect nozzles stably in a short time by detecting at once without moving the head across all nozzles in one nozzle row. It is an object of the present invention to provide an inkjet recording apparatus and a method for detecting defective ejection nozzles.

  The other subject of this invention becomes clear by the following description.

  The above problems are solved by the following inventions.

  According to a first aspect of the present invention, there is provided an ink jet recording apparatus that performs recording by using a recording head having a nozzle array in which a plurality of nozzles are arranged and ejecting ink droplets from the nozzles toward a recording medium. A light emitting means for emitting detection light so as to cross the flight path; a light receiving means for detecting whether or not the ink droplet has passed through the optical path by receiving the detection light; and all of the recording heads An ejection control unit that sequentially controls ejection of ink droplets from the nozzle toward the optical path of the detection light, a timing of ejection of the ink droplets by the ejection control unit, and a timing of detection of passage of the ink droplets by the light receiving unit. A discharge failure nozzle specifying means for specifying a discharge failure nozzle by detecting a discharge state of ink droplets from the nozzle based on the light emission means, At least one light reflecting means that is arranged on the optical path of the emitted detection light and bends the detection light toward the light receiving means, and the nozzle row of the recording head is a detection range of ink droplet passage by the light receiving means. A plurality of moving means for moving the relative positions of the nozzle row and the detection light so as to coincide with the optical path of the detection light, and a plurality of light reaching from the light emitting means to the light receiving means via the light reflecting means. An ink jet recording apparatus characterized in that at least one of the optical paths excluding the optical path where the detection light emitted from the light emitting means first reaches the light reflecting means is set as a detection range of ink droplet passage by the light receiving means. It is.

  According to a second aspect of the present invention, the light emitting unit includes a light source converging lens, and a distance between the light emitting unit and a nozzle closest to the light emitting unit on the optical path of the detection light is determined by the light source converging lens. 2. The ink jet recording apparatus according to claim 1, wherein the ink jet recording apparatus has a focal length of not less than twice.

  A third aspect of the invention is the ink jet recording apparatus according to the first or second aspect, wherein the recording head is provided with a plurality of heads such that the nozzle rows between the heads are parallel to each other.

  A fourth aspect of the present invention is the ink jet recording apparatus according to the first, second, or third aspect, wherein the recording head has a plurality of nozzle rows parallel to each other.

  According to a fifth aspect of the present invention, the plurality of optical paths bent by the light reflecting means are parallel to each nozzle row at the same interval except for the optical path where the detection light emitted from the light emitting means first reaches the light reflecting means. A plurality of optical paths formed in parallel at the same intervals as the nozzle rows are used as a detection range of ink droplet passage by the light receiving means corresponding to the nozzle rows. The inkjet recording apparatus according to claim 3 or 4.

  According to a sixth aspect of the invention, the ejection control means can change the number of ink droplets ejected from each nozzle at the time of detection, and the output level by the light receiving means extends over all nozzles on the optical path of the detection light. 6. The number of ink droplets is controlled to be ejected more at the light emitting means side than at the light receiving means side on the optical path of the detection light so as to be substantially the same. An inkjet recording apparatus according to any one of the above.

  According to a seventh aspect of the present invention, in the optical path of the detection light, an aperture for restricting the passage of the detection light is disposed at least immediately before the light receiving means. Inkjet recording apparatus.

  The invention according to claim 8 has a nozzle row in which a plurality of nozzles are arranged, and uses a head that discharges droplets from the nozzles, and emits detection light so as to cross the flight path of the droplets. In the method of detecting a discharge failure nozzle by detecting the discharge state of the droplet by means and a light receiving unit that detects whether or not the droplet has passed through the optical path by receiving the detection light, A plurality of optical paths are formed by bending the detection light emitted from the light emitting means toward the light receiving means by at least one light reflecting means, and among the plurality of optical paths, the detection light emitted from the light emitting means The at least one optical path excluding the optical path that first reaches the light reflecting means is set as a detection range of droplet passage by the light receiving means, and the nozzle array of the head is used for the droplet passage by the light receiving means. The relative positions of the nozzle array and the detection light are moved so as to coincide with the optical path of the detection light that is the detection range of the liquid, and droplets are directed from all the nozzles of the head toward the optical path of the detection light. By sequentially controlling the ejection in time series, the ejection failure nozzle is detected by detecting the ejection state of the droplet from the nozzle based on the ejection timing of the droplet and the passage detection timing of the droplet by the light receiving means. This is a method for detecting defective ejection nozzles.

  According to a ninth aspect of the present invention, the light emitting unit includes a light source converging lens, and the distance between the light emitting unit and the nozzle closest to the light emitting unit on the optical path of the detection light is determined by the light source converging lens. 9. The method for detecting defective ejection nozzles according to claim 8, wherein the focal length is at least twice the focal length.

  The invention according to claim 10 is the ejection failure nozzle detection method according to claim 8 or 9, wherein the head is provided with a plurality of heads so that the nozzle rows between the heads are parallel to each other. is there.

  The invention described in claim 11 is the ejection failure nozzle detection method according to claim 8, wherein the head has a plurality of nozzle rows parallel to each other.

  According to a twelfth aspect of the present invention, the plurality of optical paths bent by the light reflecting means are parallel to each nozzle row at the same interval except for the optical path where the detection light emitted from the light emitting means first reaches the light reflecting means. A plurality of optical paths formed in parallel at the same intervals as the nozzle rows are used as a detection range of droplet passage by the light receiving means corresponding to the nozzle rows. The method for detecting a defective ejection nozzle according to claim 10 or 11.

  In the invention described in claim 13, the number of droplets ejected from each nozzle can be changed, and the output level by the light receiving means is substantially the same over all nozzles on the optical path of the detection light. 13. The ejection failure nozzle detection according to claim 8, wherein the number of ejections of the nozzles on the light emitting unit side is controlled to be larger than that on the light receiving unit side on the optical path of the detection light. Is the method.

  The invention according to claim 14 is characterized in that an aperture for restricting the passage of the detection light is arranged at least immediately before the light receiving means on the optical path of the detection light. This is a method for detecting defective ejection nozzles.

  According to the first and eighth aspects of the invention, by bending the optical path of the detection light by the light reflecting means, the most light emitting means side end nozzle in one nozzle row can be obtained without particularly increasing the size of the detection mechanism. Since the distance between the light emitting means can be increased, the influence of light diffraction can be reduced, and the head can be detected at once without any need for moving the head. Thus, stable detection of all nozzles can be realized in a short time.

  Further, since the optical path of the detection light is bent by the light reflecting means, the arrangement of the light emitting means and the light receiving means is not restricted, and the degree of freedom in designing the detection device is increased.

  According to the second and ninth aspects of the invention, the effect of reducing the influence of light diffraction is high, the detection output does not vary, and more stable nozzle detection can be performed.

  According to the third, fourth, fifth, tenth, eleventh and twelfth aspects, the influence of light diffraction can be reduced and the head can be reduced by setting a plurality of optical paths formed in parallel by the light reflecting means as the detection range. There is no need to move it, and detection can be performed at once for all the nozzles of a plurality of nozzle rows, and the detection time can be greatly shortened.

  According to the inventions of claims 6 and 13, the influence of light diffraction can be further reduced, the detection output by the light receiving means can be made almost uniform over all nozzles, and more stable nozzle detection is performed. Can do.

  According to the seventh and fourteenth aspects of the present invention, it is possible to limit the incident of the reflected light to the light receiving means when the detection light is reflected by the nozzle surface of the head, and to reduce erroneous detection.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view showing a schematic configuration of a main part for detecting an ejection failure nozzle in the ink jet recording apparatus, FIG. 2 is a block diagram showing the configuration of the main part, and FIG. 3 is a plan view showing an optical path of detection light. It is.

  In the figure, reference numeral 1 denotes a recording head, which is mounted on a carriage (not shown) provided so as to be reciprocally movable along the main scanning direction by a moving means (not shown) including a guide rail and a main scanning motor. . A large number of nozzles 12 are arranged on the nozzle surface 11 on the lower surface of the recording head 1 along a direction orthogonal to the main scanning direction, and the large number of nozzles 12 form a single nozzle row. The recording head 1 is controlled by a driving circuit 7 under predetermined driving conditions (driving voltage, driving frequency) by a controller (CPU) 6 shown in FIG. 2 in the process in which the carriage reciprocates along the main scanning direction by the moving means. Thus, a desired image is recorded on a recording medium (not shown) by ejecting ink droplets a in the form of fine droplets from each nozzle 12 at a predetermined timing in the downward direction in FIG.

  Reference numeral 2 denotes a light emitting element composed of an LED, which emits detection light L for detecting the passage of the ink droplet a ejected from each nozzle 12 of the recording head 1. Although the light emitting element 2 is not shown in detail, lighting / extinguishing is controlled by the controller 6 shown in FIG.

  Reference numeral 3 denotes a light receiving element made of a photodiode, which receives the detection light L emitted from the light emitting element 2.

  A light reflecting member 4 forms a plurality of optical paths by bending the detection light L emitted from the light emitting element 2 toward the light receiving element 3. As the light reflecting member 4, a reflecting mirror or prism having a function of bending the detection light L can be used. Among them, the prism is preferable in that incident light can be emitted without loss.

  Here, two light reflecting members 41 and 42 each consisting of a prism are arranged on the optical path of the detection light L, and the detection light L emitted from the light emitting element 2 is first reflected by the first light reflecting member 41. The light is reflected toward the light 42 and then reflected by the light reflecting member 42 to reach the light receiving element 3. Thereby, the optical path of the detection light L is the optical path L1 from the light emitting element 2 to the first light reflecting member 41, the optical path L2 from the light reflecting member 41 to the light reflecting member 42, and the light reflecting member 42 to the light receiving element 3. And the optical path L3 to reach.

  Here, of the three optical paths L1 to L3 of the detection light L, at least the optical path L3 closest to the light receiving element 3 is orthogonal to the main scanning direction of the recording head 1 and parallel to the arrangement direction of the nozzles 12 of the recording head 1. In this case, the height position along the ejection direction of the ink droplet a is formed to be lower than the position of the nozzle surface 11 of the recording head 1. In addition, the light receiving element 3 and the light reflecting member 42 are arranged at a distance that allows all the nozzles 12 of the recording head 1 to be entirely accommodated on the optical path L3. Thereby, when the nozzle row of the recording head 1 is positioned on the optical path L3 in the detection light L, the traveling path of the ink droplet a ejected from each nozzle 12 crosses the optical path L3. Accordingly, here, the optical path L3 between the light receiving element 3 and the light reflecting member 42 is set as a detection range of the ink droplet passage by the light receiving element 3 as shown by the oblique lines in FIG.

  Reference numeral 5 denotes an ink tray that is provided so as to face the nozzle surface 11 of the recording head 1 disposed on the optical path L3 of the detection light L, and receives the ink droplet a ejected from the recording head 1 at the time of detection. It is like that.

  The light emitting element 2, the light receiving element 3, the light reflecting member 4, and the ink receiving tray 5 are provided in a non-recording area where the recording head 1 does not record on the recording medium. The ink droplet a is detected from the controller 6 when the recording head 1 is moved to the non-recording area along the main scanning direction by the moving means and the nozzle row is stopped on the optical path L3 of the detection light L. The drive circuit 7 is controlled by the output ejection start signal (FIRE-M), and the ink droplet a is ejected from each nozzle 11 of the recording head 1, whereby the shadow of the ink droplet a passing through the optical path L3 is received by the light receiving element. This is done by detecting by 3.

  The light receiving element 3 detects the shadow when the ink droplet a passes through the optical path L3 in this way as a change in the amount of light, and sends this detection signal to the detection unit 8 shown in FIG. The detection unit 8 includes a current amplification unit 81 that amplifies the detection signal of the light receiving element 3, an AC amplification unit 82 that amplifies only the variation of the detection signal amplified by the current amplification unit 81, and the AC amplification unit 82. And a comparator 84 that compares the output signal with a reference signal generated through the low-pass filter 83 and outputs a signal exceeding the reference signal level to the controller 6 as a defect-out signal. .

  Next, a detection flow of ejection failure nozzles in the ink jet recording apparatus will be described with reference to the flowchart shown in FIG.

  First, after the light emitting element 2 is turned on (S1), the controller 6 drives a moving unit (not shown) to move the carriage in the main scanning direction so that the nozzle row of the recording head 1 is included in the detection light L. It is adjusted on the optical path L3 which becomes the detection range (S2).

  Next, the controller 6 outputs a discharge start signal (FIRE-M) to the drive circuit 7, and discharges a plurality of ink droplets a continuously from all the nozzles 12 of the recording head 1 as a measure for discharging normal ink droplets a. (Preliminary discharge) is performed (S3).

  After this preliminary ejection, the controller 6 specifies the first nozzle that ejects the ink droplet a for nozzle detection among all the nozzles 12 of the recording head 1 (nozzle No. n = 1) (S4). ). Then, an ejection start signal (FIRE-M) is output to the first nozzle No. 1 nozzle (hereinafter referred to as No. 1 nozzle), and the ink droplet a for detection is ejected ( S5).

  Here, when the ink droplet a is normally ejected from the No. 1 nozzle and the ink droplet a passes through the optical path L3 of the detection light L, a part of the incident light is blocked by the light receiving element 3, whereby the light amount signal is temporarily transmitted. To decrease. When the decrease in the light amount signal exceeds a predetermined level, the detection unit 8 outputs a defect-out signal as shown in FIG. 5 on the assumption that the passage of the ink droplet a has been detected.

  The controller 6 determines whether or not the defect-out signal is input from the detection unit 8. After the ejection start signal (FIRE-M) is output and the ink droplet a is ejected from the No. 1 nozzle, the ink droplet a is ejected from the predetermined time-out period, that is, the ink droplet a is the optical path L3 of the detection light L Is detected and the defect-out signal is not output from the detection unit 8 even after the time-out period has elapsed (indicated by a dotted line in FIG. 5). The No. 1 nozzle is determined as a missing nozzle in which the ink droplet a is not ejected due to clogging or the like, and the nozzle number is stored in a predetermined storage area (S6). As a result, it is possible to specify a defective ejection nozzle of a missing nozzle.

  On the other hand, when the controller 6 receives a defect-out signal within a predetermined time-out period due to the normal ejection of the ink droplet a from the No. 1 nozzle, the ejection start signal ( FIRE-M) is detected from the timing when the defect-out signal is detected (Tn time in FIG. 5), and this detection time and the nozzle surface 11 of the recording head 1 which is known in advance are detected. The flying speed of the ink droplet a is calculated based on the distance between the light L and the optical path L3, and is stored in a predetermined storage area (S6). By comparing the flying speed stored at this time with a predetermined value stored in advance, a speed abnormality can be detected. As a result, it is possible to identify a discharge failure nozzle having an abnormal flight speed.

  Thereafter, the controller 6 sequentially repeats the same processing for all the nozzles 12 of the recording head 1 in a time-sequential manner (No. 2 nozzle, No. 3 nozzle, etc.) (S5 to S8). When the detection of the nozzle 12 is completed, the controller 6 turns off the light emitting element 2 (S9) and ends the ejection failure detection operation.

  In this manner, the detection light L formed between the light emitting element 2 and the light receiving element 3 is bent by the light reflecting member 4 to form a plurality of optical paths L1 to L3, and the optical path L3 closest to the light receiving element 3 among them is formed. Is the detection range of the ejection failure of the nozzle 12 by the light receiving element 3, as shown in FIG. 3A, the distance on the optical path of the detection light L from the light emitting element 2 to the detection range (from the light emitting element 2 to the light emitting element). In the case of the conventional detection mechanism shown in FIG. 3B in which the distance between the light emitting element 2 and the light receiving element 3 is only a distance corresponding to the detection range. Compared to the optical paths L1 and L2, it becomes longer.

  Thereby, even when the ink droplet a ejected from the nozzle 12 on the side close to the light emitting element 2 on the optical path of the detection light L in the nozzle array of the recording head 1 is detected, the distance from the light emitting element 2 becomes long. As a result, the detection output of the light receiving element 3 is totally amplified as shown by the solid line graph (a) in FIG. 11, and the slope of the detection output graph with respect to the nozzle position is shown in FIG. 11 can be laid down compared to the conventional one shown by the dot-dash line graph (a). Accordingly, the influence of light diffraction can be reduced and ink can be detected at a time without moving the recording head 1 across all the nozzles 12 in one nozzle row, and the ink from all the nozzles 12 can be stabilized in a short time. Detection of the droplet a can be realized.

  The number of the light reflecting members 4 is not limited to two as shown in FIGS. 1 and 3A, and the detection light L emitted from the light emitting element 2 is bent toward the light receiving element 3 to be at least 2 There may be at least one on the optical path of the detection light L so that the optical path of the book can be formed. Then, among the plurality of optical paths formed by the at least one light reflecting member 4 in this way, at least one optical path excluding the optical path where the detection light L emitted from the light emitting element 2 first reaches the light reflecting member 4, A detection range for detecting the passage of the ink droplet a by the light receiving element 3 may be used. Therefore, for example, among the three optical paths L1 to L3 shown in FIG. 1 and FIG. 3A, the optical paths L2 and L3 excluding the optical path L1 can be set as the detection range, so that besides the illustrated optical path L3, The optical path L2 can also be used as a detection range.

  That is, if an optical path serving as a detection range among a plurality of optical paths is formed in parallel with the nozzle row, other optical paths can be arbitrarily formed. Therefore, for example, the light emitting element 2 is perpendicular to the light reflecting member 41 in FIG. It can be arranged to emit the detection light L from the direction, or a light reflecting member can be added immediately before the light receiving element 3 to form the optical path to the light receiving element 3 in the vertical direction. The arrangement of the light emitting element 2 and the light receiving element 3 is not restricted and the degree of freedom in designing the detection mechanism can be increased. Of course, in order to increase the distance of the nozzle 12 from the light emitting element 2, it is not necessary to dispose the light emitting element 2 straightly away from the light receiving element 3, so that the detection mechanism is not significantly enlarged.

  Further, when detecting the flying speed of the ink droplet a from the nozzle 12, for example, by interposing a plurality of light reflecting members 41 to 43 between the light emitting element 2 and the light receiving element 3, as shown in FIG. A plurality of optical paths L1 to L4 are formed, and the optical paths L2 and L4 are used as detection ranges. The inks are parallel to each other along the nozzle row of the recording head 1, and both of the optical paths L2 and L4 are ejected from the nozzle 12. By providing the ink droplets a so as to intersect with the traveling path of the droplet a, the timing at which the ink droplet a ejected from one nozzle 12 passes through the point P1 intersecting the first optical path L4 and below It is also possible to obtain the flying speed of the ink droplet a based on the time difference from the timing of passing through the point P2 that intersects the optical path L2 and the distance between the optical paths L2 and L4.

  Usually, when the flight speed is obtained by the time difference between the timings of passing through the two optical paths, the two optical paths must be formed in parallel by using two pairs of the light emitting element and the light receiving element. By using a plurality of light reflecting members 4 as in the invention, it is possible to easily form the two optical paths L2 and L4 by using only one set of the light emitting element 2 and the light receiving element 3. In the example shown in FIG. 6, the detection light L emitted from the light emitting element 2 does not use the optical path L1 reaching the first light reflecting member 41 for detection, so that the influence of light diffraction can be reduced and the direction of the light reflecting member 41 The light emitting element 2 can be freely arranged by appropriately adjusting.

  As described above, according to the present invention, the detection light L emitted from the light emitting element 2 is bent toward the light receiving element 3 by the at least one light reflecting member 4 to form a plurality of optical paths. By setting at least one optical path excluding the optical path where the detected light L first reaches the light reflecting member 4 as a detection range, the detection mechanism is not increased in size, and the inside of the nozzle array of the recording head 1 from the light emitting element 2 can be reduced. The distance D between the nozzle 12a closest to the light emitting element 2 can be increased and the influence of light diffraction can be reduced. This distance D is a light emission as schematically shown in FIG. It is preferably at least twice the focal length of the light source focusing lens 21 provided in the element 2. Thereby, the influence of light diffraction can be further reduced, and more stable detection can be performed.

  By the way, as shown in FIG. 3A, an aperture 9 that restricts the passage of the detection light L is interposed on the optical paths L <b> 1 to L <b> 3 of the detection light L from the light emitting element 2 to the light receiving element 3.

  Details of the aperture 9 are shown in FIG. An opening 91 is formed in the aperture 9, and the passage of the detection light L is restricted to the opening 91. The opening 91 has a horizontally long shape, and more specifically, the diameter (major axis) d2 along the direction perpendicular to the diameter (minor axis) d1 along the direction perpendicular to the nozzle surface 11 of the recording head 1 is. It is formed long. In general, the opening 91 has a narrower width along the direction perpendicular to the nozzle surface 11 of the recording head 1, that is, the ejection direction of the ink droplet a, and improves detection accuracy when detecting the passage of the ink droplet a. This is advantageous in that On the other hand, if the width in the direction perpendicular to this is narrowed, the output of the signal detected by the light receiving element 3 is reduced, and the margin for the optical axis deviation of the recording head 1 in the main scanning direction is reduced, and thus the stability is reversed. Therefore, the ink droplet a can be formed by setting the opening shape to be a horizontally long shape and having the short diameter d1 along the direction perpendicular to the nozzle surface 11 of the recording head 1. This makes it possible to improve both the detection accuracy and reduce the detection error. An example of the shape of the opening 91 is d1 = 1.5 mm and d2 = 3 mm.

  In FIG. 8, the horizontally-long substantially rectangular opening 91 is shown, but the opening 91 may be a horizontally long elliptical shape formed so as to satisfy d1 <d2.

  In FIG. 3A, the positions of the apertures 9 are provided at two locations, immediately before the light receiving element 3 and immediately before the light reflecting member 41, along the emission direction of the detection light L, but at least immediately before the light receiving element 3. It is preferable to provide it. By providing the aperture 9 immediately before the light receiving element 3, it is possible to reduce the problem of erroneous detection caused by the reflected light of the detection light L reflected by the nozzle surface 11 or the like of the recording head 1 entering the light receiving element 3. .

The recording head 1 in FIG. 1 shows a mode in which one nozzle row is provided in a single recording head 1, but the number of recording heads provided in the ink jet recording apparatus is not limited to one, such as YMCK. Some have a plurality of heads each having a dedicated recording head for each of a plurality of ink colors. FIG. 9A shows a state in which four recording heads 1A to 1D each having one nozzle row 1a to 1d are mounted on a carriage (not shown) so that the nozzle rows 1a to 1d are parallel to each other. It is the figure seen from the nozzle surface side. Some recording heads have a plurality of nozzle rows in one recording head. FIG. 9B shows two recording heads 10A and 10B each having two nozzle rows 10a ₁ , 10a ₂ and 10b ₁ and 10b ₂ which are parallel to each other, and each nozzle row 10a _{1 to} 10b ₂ is parallel to each other. It is the figure which looked at the state mounted in the carriage which is not illustrated so that it may become from the nozzle surface side.

These are all cases having a plurality of nozzle rows. In such a case, by sequentially moving the carriage using one detection range constituted by one optical path L3 shown in FIG. 3A, the nozzle rows 10a to 1d or the nozzle rows 10a. _Although detection can be performed sequentially every _{1 to} 10b _2, there is a problem that it takes time for mechanical control by moving the carriage. Therefore, when detecting a plurality of nozzle rows, it is preferable to be able to detect a plurality of nozzle rows simultaneously by bending the detection light L by the light reflecting member 4 to form a plurality of optical paths in parallel.

  FIG. 10 is a plan view showing an optical path by the detection light L of such a detection mechanism. Here, nine light paths L1 to L9 are formed by sequentially bending the detection light L from the light emitting element 2 to the light receiving element 3 by the eight light reflecting members 41 to 48.

Of these, the optical paths L3, L5, L7, and L9 are parallel to each other. These optical paths L3, L5, L7, and L9 correspond to the nozzle rows 1a to 1d of the recording heads 1A to 1D shown in FIG. 9A or the nozzle rows of the recording heads 10A to 10B shown in FIG. 8B. 10a ₁ ~10b ₂ and a same number (four) are formed and as the spacing W1, W2, W3 of each nozzle array 1a~1d or _10a 1 _{~10b 2} becomes the same interval. By this, these optical path L3, L5, L7, L9 all detection range (1) to (4), to correspond the detection range of which the (1) to the nozzle array 1a or 10a _1, detection range (2) Corresponding to the nozzle row 1b or 10a ₂ , the detection range (3) corresponds to the nozzle row 1c or 10b ₁ , and the detection range (4) corresponds to the nozzle row 1d or 10b ₂ .

According to this, the carriage is moved in the main scanning direction by a moving means (not shown), and the nozzle rows 1a to 1d of the recording heads 1A to 1D or the nozzle rows 10a _{1 to} 10b _{2 of the} recording heads 10A to 10B are respectively provided. By stopping at a position that coincides with the optical path of the corresponding detection range (1) to (4), it is possible to execute detection for all the nozzles of the plurality of nozzle rows at a time. Therefore, the detection time can be greatly shortened. Further, in this case, among the plurality of optical paths L <b> 1 to L <b> 9, at least the detection light L emitted from the light emitting element 2 does not use the optical path L <b> 1 that first reaches the light reflecting member 41 for detection, so that the influence of light diffraction can be reduced. Of course.

  In the embodiment shown in FIG. 9A, the number of recording heads is not limited to four, and a plurality of nozzle arrays can be formed as long as the number is two or more. In the mode shown in FIG. 9B, the number of recording heads is not limited to two or more, and even if only one is provided, a plurality of (two) nozzle rows are provided. In these cases, the number of light paths that become the detection range may be formed by the number corresponding to the number of nozzle rows by appropriately adjusting the number of light reflecting members 4 disposed.

  Further, as a detection method in the case of having a plurality of nozzle rows, the detection time can be shortened by forming the same number of optical paths as the plurality of nozzle rows and detecting all of the plurality of nozzle rows all at once as described above. However, it is not always necessary to be able to detect at one time, and at least at the same interval as each nozzle row except for the optical path where the detection light L emitted from the light emitting element 2 first reaches the light reflecting member 4. It is only necessary to include a plurality of optical paths formed in parallel. For example, in the case of four nozzle rows 1a to 1d by the four recording heads 1A to 1D shown in FIG. 9A, only the detection ranges (1) and (2) by the two optical paths L9 and L7 are used (that is, The other optical paths do not necessarily correspond to the nozzle rows.) After the detection of the nozzle rows 1a and 1b, the carriage is moved to detect the nozzle rows 1c and 1d. Good. In this case, compared with the above-described case where all the nozzle rows 1a to 1d are detected at a time without moving the carriage, it takes extra time for mechanical control of the carriage. The detection time can be shortened compared to the case where only one optical path is set as the detection range as in a).

  Next, a preferred ejection form of the ink droplet a when detecting ejection failure of the nozzle will be described.

  As already described, the detection output output from the light receiving element 3 becomes weaker as it approaches the light emitting element 2 due to the influence of light diffraction. In particular, since the size of one ink droplet has become very small with the recent increase in image quality of printing, a weak signal in which the shadow of the small droplet is captured by the light receiving element 3 when detecting ejection failure. Must be amplified and the S / N of the detection signal tends to decrease.

  For this reason, when a defective ejection nozzle is detected, the controller 6 changes the number of ink droplets ejected from each nozzle 12 of the recording head 1 by appropriately changing the application timing of the ejection start signal output to the drive circuit 7. However, the number of ink droplets at the time of detection is not the same over all the nozzles 12 positioned on the optical path of the detection light L to be detected, and the level of the detection output by the light receiving element 3 is on the optical path of the detection light L. It is preferable to control the ejection of more nozzles located on the light emitting element 2 side than the nozzles located on the light receiving element 3 side in the optical path of the detection light L so that the nozzles 12 are substantially the same. .

  The ink droplets at the time of detection can be controlled by changing the number of ink droplets with each nozzle 12, thereby making a lump of ink droplets a or a group of two or more ink droplets a that are continuously ejected. The ink is ejected from each nozzle 12 in the form of an ink droplet group G.

  FIG. 12A shows a state of a group of ink droplet groups G composed of three ink droplets a ejected continuously from one nozzle 12. Here, in order to ensure the detection reliability, a single ink droplet group G is continuously ejected from a single nozzle 12 at regular intervals, such as ink droplet groups G1, G2,.

  In the lump ink droplet group G, the relationship between the discharge interval between the ink droplets a and the discharge interval between successive lump ink droplet groups G is the discharge between the adjacent ink droplets a in the lump ink droplet group G. The interval is α, and the ejection interval between the ink droplet group G1 ejected first and the ink droplet group G2 ejected next (the last ink droplet a of the ink droplet group G1 and the first ink droplet a of the ink droplet group G2) Where α <β. At this time, it is more preferable that the sum of α in the group of ink droplets G is set to a value smaller than the distance in the vertical direction within the range in which the shadow is captured by the light receiving element 3. Even if each of a is composed of very small droplets, the ink droplet group G can be detected as one large integrated signal.

  In addition, when the ejection of the ink droplet group G from one nozzle 12 is completed and the transition to the ejection from the adjacent nozzle 12 is performed, the ink ejected from the previous nozzle 12 as shown in FIG. The ejection interval β between the droplet group G1 and the ink droplet group G2 ejected from the next nozzle 12 is related to the interval α between adjacent ink droplets a in the lump of ink droplet group G, and α < If β is set, each ink droplet group G can be regarded as one lump even when ejected continuously from each nozzle 12.

  As an example of a specific mode for changing the number of ink droplets, all nozzles 12 on a plurality of optical paths constituted by one detection light L are divided into a plurality of groups, and the number of ink droplets is changed for each group. Can be mentioned. FIG. 13 shows that all nozzles 12 positioned on the optical path of the detection light L are divided into three groups, and an ink droplet group Gf composed of three ink droplets a from a plurality of nozzles 12 on the side closer to the light receiving element 3. Are controlled so as to eject an ink droplet group Gm consisting of four ink droplets a from a plurality of nozzles located in the middle, and a plurality of nozzles on the side closer to the light emitting element 2 are controlled. A case is shown in which control is performed so that an ink droplet group Gn consisting of five ink droplets a is ejected from the nozzle. The group to be divided is arbitrary as long as it is 2 or more according to the level of the detection output by the light receiving element 3, and the number of ink droplets is also appropriately determined according to the size of one drop of the ink droplet a and the level of the detection output by the light receiving element 3. Can be adjusted.

  In this way, the number of ink droplets is changed and controlled in accordance with the position of the nozzle 12 positioned on the optical path of the detection light L from the light emitting element 2, and the nozzle 12 on the light emitting element 2 side is compared with the nozzle 12 on the light receiving element 3 side. By controlling the amount of discharge more, the output level of the light receiving element 3 is made substantially uniform over all the nozzles on the optical path of the detection light L, as shown by the two-dot chain line (c) in FIG. Can do.

  As shown in FIGS. 9 and 10, when there are a plurality of nozzle rows to be detected and the plurality of nozzle rows are simultaneously detected by a plurality of optical paths, the nozzle row on the side close to the light emitting element 2 is detected. Increasing the number of ink droplets ejected from each nozzle 12 and decreasing the number of ink droplets ejected from each nozzle 12 of that nozzle row as the nozzle row approaches the light receiving element 3, etc. You may make it vary the number of drops.

  Data on the number of ink droplets at the time of detection of each nozzle 12 positioned on the optical path of the detection light L is stored in advance in a predetermined area in the controller 6 corresponding to each nozzle 12 or each set of a plurality of nozzles 12. When detecting defective nozzles, the number of ink droplets of each nozzle 12 may be controlled based on the stored data.

  In the above description, the light emitting element 2 is an LED. However, the present invention is not limited to this, and the present invention can also be applied to a case where an LD (laser) is used as a light emitting means for emitting the detection light L.

  Although the recording head 1 mounted on the carriage can be moved along the main scanning direction by the moving means and the recording head 1 moves to the detection light L has been described here, the recording head 1 has been described. And the detection light L may be moved relatively. Therefore, the detection light L side may be movable toward the recording head 1, or both may be moved relative to each other.

  The ejection failure nozzle detection method according to the present invention is not limited to an inkjet recording apparatus that records various images such as characters and photographs on a recording medium such as recording paper or film by ejecting ink droplets. For example, an inkjet printing apparatus that forms a desired pattern by ejecting ink droplets onto a fabric from a nozzle, an organic EL element manufacturing apparatus that forms a light emitting layer by ejecting droplet-like luminescent material from the nozzle, and a nozzle By applying to a device having a nozzle row in which a large number of nozzles are arranged and a head for discharging droplets from each nozzle, such as a silk printing device that discharges ink droplets for silk printing from Similarly to the above, it is possible to detect a defective ejection nozzle stably in a short time.

The perspective view which shows schematic structure of the principal part of an inkjet recording device Block diagram showing the configuration of the main part of an inkjet recording apparatus Plan view showing optical path of detection light Flow diagram showing the detection flow for defective nozzles Diagram showing discharge control signal and detection signal The perspective view which shows schematic structure of the principal part of the inkjet recording device which concerns on another aspect. The figure which shows the positional relationship of a light emitting element and a nozzle typically. Front view of aperture (A) is a view of four recording heads each having one nozzle row viewed from the nozzle surface side, and (b) is a view of two recording heads each having two nozzle rows parallel to each other from the nozzle surface side. Figure Plan view showing optical path of detection light Graph showing the relationship between nozzle position and detection output (A) (b) is a figure which shows the mode of the lump group of ink droplets discharged from a nozzle, respectively. The figure which shows the aspect which changed the ink droplet number of the ink droplet group by the nozzle position.

Explanation of symbols

1,1A~1D, 10A~10B: recording head 11: the nozzle surface 12: nozzle _{1a~1d, 10a 1, 10a 2,} 10b 1, 10b 2: nozzle array 2: light emitting element 21: light source converging lens 3: light Element 4: Light reflecting member 5: Ink tray 6: Controller 7: Drive circuit 8: Detection unit 9: Aperture 91: Opening L: Detection light L1 to L9: Optical path g: Ink droplet group a: Ink droplet

Claims (14)

In an inkjet recording apparatus that performs recording by using a recording head having a nozzle row in which a plurality of nozzles are arranged, and ejecting ink droplets from the nozzles toward a recording medium,
A light emitting means for emitting detection light so as to cross the flight path of the ink droplets;
A light receiving means for detecting whether the ink droplet has passed through the optical path by receiving the detection light;
An ejection control unit that sequentially ejects ink droplets from all the nozzles of the recording head toward the optical path of the detection light in a time-series manner;
Identification of defective ejection nozzles that identify ejection failure nozzles by detecting the ejection state of ink droplets from the nozzles based on the timing of ejection of ink droplets by the ejection control means and the detection timing of ink droplet passage by the light receiving means Means,
At least one light reflecting means disposed on the optical path of the detection light emitted from the light emitting means and bending the detection light toward the light receiving means;
Moving means for moving the relative positions of the nozzle row and the detection light so that the nozzle row of the recording head coincides with the optical path of the detection light that is a detection range of ink droplet passage by the light receiving means; ,
Among the plurality of optical paths from the light emitting means to the light receiving means via the light reflecting means, at least one optical path excluding the optical path where the detection light emitted from the light emitting means first reaches the light reflecting means An ink jet recording apparatus having a detection range of ink droplet passage by means.   The light emitting means includes a light source converging lens, and a distance between the light emitting means and a nozzle closest to the light emitting means on an optical path of the detection light is at least twice a focal length of the light source converging lens. The inkjet recording apparatus according to claim 1.   The inkjet recording apparatus according to claim 1, wherein the recording head is provided with a plurality of heads such that nozzle rows between the heads are parallel to each other.   4. The ink jet recording apparatus according to claim 1, wherein the recording head has a plurality of nozzle rows parallel to each other.   The plurality of optical paths bent by the light reflecting means are a plurality of optical paths formed in parallel at the same intervals as the nozzle rows except for the optical path where the detection light emitted from the light emitting means first reaches the light reflecting means. The plurality of optical paths that are formed in parallel with each nozzle row at the same interval are used as a detection range of ink droplet passage by the light receiving unit corresponding to each nozzle row. Inkjet recording device.   The ejection control means can change the number of ink droplets ejected from each nozzle at the time of detection, and the output level by the light receiving means is substantially the same over all nozzles on the optical path of the detection light. 6. The ink jet recording apparatus according to claim 1, wherein the number of ink droplets is controlled to be ejected more by the light emitting means side nozzles than the light receiving means side nozzles on the optical path of the detection light. .   The inkjet recording apparatus according to claim 1, wherein an aperture for restricting the passage of the detection light is disposed at least immediately before the light receiving unit on the optical path of the detection light. Using a head that has a nozzle row in which a plurality of nozzles are arranged and discharges droplets from the nozzles, a light emitting means for emitting detection light so as to cross the flight path of the droplets, and receiving the detection light In the method for detecting a defective ejection nozzle by detecting the ejection state of the droplet by a light receiving means that detects whether or not the droplet has passed through the optical path,
A plurality of optical paths are formed by bending detection light emitted from the light emitting means toward the light receiving means by at least one light reflecting means,
Among the plurality of optical paths, at least one optical path excluding the optical path where the detection light emitted from the light emitting means first reaches the light reflecting means is set as a detection range of droplet passage by the light receiving means,
The relative positions of the nozzle row and the detection light are moved so that the nozzle row of the head coincides with the optical path of the detection light that is a detection range of droplet passage by the light receiving means, and all the heads By sequentially controlling the discharge of the droplets from the nozzle toward the optical path of the detection light, the droplets from the nozzle are controlled based on the discharge timing of the droplets and the detection timing of the passage of the droplets by the light receiving means. A defective discharge nozzle detection method, wherein a defective discharge nozzle is specified by detecting a discharge state of a droplet.   The light emitting means includes a light source converging lens, and a distance between the light emitting means and the nozzle closest to the light emitting means on the optical path of the detection light is at least twice the focal length of the light source converging lens. The method for detecting a defective ejection nozzle according to claim 8.   10. The ejection failure nozzle detection method according to claim 8, wherein the head is provided with a plurality of heads so that nozzle rows between the heads are parallel to each other.   11. The method for detecting defective ejection nozzles according to claim 8, wherein the head has a plurality of nozzle rows parallel to each other.   The plurality of optical paths bent by the light reflecting means are a plurality of optical paths formed in parallel at the same intervals as the nozzle rows except for the optical path where the detection light emitted from the light emitting means first reaches the light reflecting means. 12. A plurality of optical paths that are formed in parallel with each nozzle row at the same interval are used as a detection range of droplet passage by the light receiving means corresponding to each nozzle row. Detection method of defective nozzles.   The number of droplets ejected from each nozzle can be changed, and the number of droplets on the optical path of the detection light is set so that the output level by the light receiving means is substantially the same across all nozzles on the optical path of the detection light. The ejection failure nozzle detection method according to claim 8, wherein ejection control is performed more for the light emitting means side nozzles than for the light receiving means side nozzles.   The method for detecting a defective ejection nozzle according to any one of claims 8 to 13, wherein an aperture for restricting the passage of the detection light is disposed at least immediately before the light receiving means on the optical path of the detection light.

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