JP2007130778A - Method of alignment between optical axis for detection of defective ejection of liquid and nozzle array, method and device for detecting defective ejection, and inkjet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of alignment between an optical axis for detection of defective ejection of a liquid from a light emission device to a photodetector and a nozzle array mounted on a liquid jet head in order to carry out the alignment without wasting a liquid. <P>SOLUTION: The liquid jet head 16y is moved in parallel by allowing a first nozzle Ny1 in the nozzle array 53y to eject ink droplets. The position of the first nozzle in the liquid ejection direction is aligned to the optical axis 31 for detection of defective ejection of the liquid based on the change between outputs of the light from the photodetector 40 before and after the ink droplets ejected from the first nozzle traverse the optical axis 31. A liquid defective ejection detection device 20 is rotated around the position O of the first nozzle in the liquid ejection direction aligned to the optical axis 31 by allowing a second nozzle Nyx to eject a liquid. The position of the second nozzle in the liquid ejection direction is aligned to the optical axis 31 based on the change between outputs of the light from the photodetector 40 before and after the ink droplets ejected from the second nozzle traverse the optical axis 31. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention has a configuration in which light is emitted from a light emitting element in a direction crossing the liquid ejection direction of the nozzles constituting the nozzle row, and the light is directed to the light receiving element. Liquid discharge failure detection device for detecting a failure, and in the liquid discharge failure detection device, a liquid discharge failure detection for aligning a liquid discharge failure detection optical axis from a light emitting element to a light receiving element and a nozzle row of a liquid discharge head A method for aligning the optical axis for the nozzle and the nozzle array, and a liquid for detecting a liquid ejection defect from the nozzles constituting the nozzle array after aligning the optical axis for detecting a liquid ejection defect and the nozzle array based on the alignment method The present invention relates to an ejection failure detection method and an inkjet recording apparatus that includes the liquid ejection failure detection device described above and records an image on a recording medium with ink droplets ejected from a liquid ejection head.

  Conventionally, an ink jet recording apparatus has a liquid discharge head that discharges fine ink droplets from fine nozzles, and discharges ink droplets from the nozzles while relatively moving the liquid discharge head and a recording medium such as paper. An image was recorded on the recording medium. This type of ink jet recording apparatus is widely used because it has advantages such as high speed and low noise, few restrictions on the type of recording medium, and easy colorization.

  However, since ink droplets are ejected from fine nozzles, the ink is easy to dry when stopped, the nozzle surface gets wet with ink, and dust such as paper dust tends to adhere to the nozzle surface, and air enters from the nozzle. This causes problems such as non-ejection and bending of the ejection direction, resulting in defective ejection of ink droplets, resulting in missing dots and white streaks in the image, resulting in poor image quality. There was a bug.

  In order to prevent the occurrence of such a problem, a conventional ink jet recording apparatus includes a light emitting element such as an LED and a light receiving element such as a photodiode, and a direction intersecting the ink droplet ejection direction from the light emitting element. Some of them include a liquid discharge failure detection device that optically detects a liquid discharge failure from a change in the light output of the light reception device.

  And when detecting liquid ejection failure, after emitting light from the light emitting element, ink droplets are ejected in order from the nozzles at the end, confirming the ejection of ink droplets from the decrease in light output of the light receiving element, and reducing to light output Insufficient ink droplet ejection was detected. When an ejection failure is detected, the liquid ejection head is moved to the recovery device position, and ink is sucked from the nozzle where the ejection failure is caused by the recovery device to eliminate the ink clogging and recover.

  Conventionally, there are ink jet recording apparatuses provided with such a liquid ejection defect detection apparatus, for example, those described in Patent Documents 1 to 3 below. In the ink jet recording apparatus described in Patent Literature 1, the liquid discharge failure detection optical axis from the light emitting element toward the light receiving element is disposed so as to have a predetermined angle with respect to the arrangement direction of the plurality of nozzles. The columns had a predetermined width with respect to the optical axis and were formed to be crossable.

  In addition, in the inkjet recording apparatus described in Patent Document 2 below, a light beam is emitted along the nozzle arrangement direction, and ink droplets are sequentially ejected in time series to identify defective ejection nozzles. Further, the ink jet recording apparatus described in Patent Document 3 below includes an automatic optical axis adjustment mechanism that adjusts the position of the shutter based on a signal of a change in the amount of light when the droplet passes through the light beam, and then the light receiving element. After adjusting the position, the optical axis was adjusted to adjust the position of the shutter again.

Japanese Patent No. 3178583 Japanese Patent No. 3501599 JP 2000-85140 A

  However, in the ink jet recording apparatus described in Patent Document 1, since the nozzle row is formed to intersect with the optical axis with a predetermined width, the problem in accuracy can be solved. It is merely a matter of determining whether or not there is ink ejection based on the level of a signal from the light emitting element by ejecting ink, and does not detect a liquid ejection failure of each nozzle.

  Further, in the ink jet recording apparatus described in Patent Document 2, in the case of a long liquid discharge head, in order to reliably detect liquid discharge defects, half of the distance from one end near the first beam receiving means to the center portion is obtained. Since the detection of the nozzle and the remaining half of the nozzle from the one end close to the second beam receiving means to the center is performed separately, the structure is complicated and position adjustment, in particular, alignment of the nozzle array and the optical axis is difficult. It seems that there is no description about this point.

  Further, in the ink jet recording apparatus described in Patent Document 3, the position of the shutter is adjusted based on the signal of the light amount change when the droplet passes through the light beam while moving the carriage, and then the position of the light receiving element is adjusted. After that, since the optical axis adjustment for adjusting the shutter position again is performed, the adjustment is complicated, and it is necessary to adjust the timing of driving the carriage and ejecting ink from the nozzles, which increases the amount of ink ejected for adjustment. The waste of ink was uneconomical.

  Accordingly, a first object of the present invention is to easily align the liquid discharge failure detection optical axis from the light emitting element to the light receiving element and the nozzle array of the liquid discharge head without wasting liquid. Another object of the present invention is to provide a method for aligning the optical axis for detecting a liquid ejection failure and the nozzle row.

  A second object of the present invention is to perform liquid discharge for detecting a liquid discharge failure from the nozzles constituting the nozzle row after aligning the liquid discharge failure detection optical axis and the nozzle row based on such an alignment method. It is to provide a defect detection method.

  A third object of the present invention is to provide a liquid discharge defect detection device that makes it easy to align the liquid discharge defect detection optical axis and the nozzle row without wasting liquid.

  A fourth object of the present invention is to provide an ink jet recording apparatus that includes such a liquid discharge defect detection device and records an image on a recording medium with ink droplets discharged from a liquid discharge head.

Therefore, a first aspect of the present invention is a method for aligning a liquid ejection failure detection optical axis and a nozzle row in order to achieve the first object of the present invention described above.
While discharging a liquid, such as an ink droplet, from a first nozzle that is one of the nozzles constituting the nozzle row in a direction substantially orthogonal to the nozzle row, such as an ink jet head having a nozzle row, The liquid to be discharged moves in parallel so as to cross the optical axis for detecting liquid discharge failure from a light emitting element such as a semiconductor laser or LED toward a light receiving element such as a photodiode,
Detecting the optical output of the light receiving element before and after the liquid ejected from the first nozzle crosses the optical axis for liquid ejection failure detection;
Based on the change in the light output, after stopping the liquid discharge, the liquid discharge direction position of the first nozzle is aligned with the optical axis for liquid discharge failure detection,
Next, the liquid discharge failure detection device in which the light emitting element and the light receiving element are integrated into a single unit is used as a second nozzle which is another one of the nozzles constituting the nozzle row with the liquid discharge direction position of the first nozzle as the center. While discharging the liquid from the liquid, it rotates so that the liquid to be discharged crosses the optical axis for liquid discharge failure detection,
Detecting the optical output of the light receiving element before and after the liquid ejected from the second nozzle crosses the optical axis for liquid ejection failure detection;
Based on the change in the light output, the liquid discharge is stopped, and then the liquid discharge direction position of the second nozzle is aligned with the liquid discharge failure detection optical axis.

  At this time, a nozzle at one end of the nozzles constituting the nozzle row may be a first nozzle, and a nozzle at the other end may be a second nozzle. In addition, a plurality of liquid discharge heads are mounted on one carriage by positioning the nozzle rows so as to be parallel, and the liquid discharge heads are moved in parallel by moving the carriages. The liquid discharge direction position of the second nozzle of the same liquid discharge head is adjusted to the liquid discharge failure position by rotating the liquid discharge failure detection device while aligning the liquid discharge direction position of the first nozzle with the liquid discharge failure detection optical axis. It is good to match with the optical axis for detection.

  According to a second aspect of the present invention, in order to achieve the second object of the present invention described above, in the liquid discharge defect detection method, based on the above-described alignment method between the liquid discharge defect detection optical axis and the nozzle row, After aligning the liquid discharge failure detection optical axis and the nozzle row, liquid is discharged in order from the nozzles constituting the nozzle row, and the liquid discharge failure is detected based on the change in the light output of the light receiving element. To do.

According to a third aspect of the present invention, in order to achieve the third object of the present invention described above,
A light emitting element such as a semiconductor laser or LED emits light in a direction intersecting the liquid ejection direction of the nozzles constituting the nozzle row, and the light is directed to a light receiving element such as a photodiode. In a liquid ejection failure detection device that detects ejection failure of liquid such as ink droplets based on a change,
While integrating the light emitting element and the light receiving element into an integrated unit,
When a liquid discharge head such as an inkjet head having a nozzle row is translated in a direction substantially perpendicular to the nozzle row, the liquid discharge direction of the first nozzle that is one of the nozzles constituting the nozzle row is the light emitting element. It is characterized in that it is provided so as to be rotatable around a position crossing the optical axis for detecting liquid ejection failure from the light source to the light receiving element.

  Here, a diaphragm member such as a collimator lens or a slit for narrowing the light beam emitted from the light emitting element, and a beam stopper for preventing light focused by the diaphragm member from entering the light receiving element as they are may be provided. When a liquid ejection failure is detected, the light emitted from the light emitting element is squeezed by the diaphragm member and guided to the light receiving element, while the liquid is ejected from the nozzle or the like. Here, when the liquid is normally ejected, the ejected liquid blocks the light beam and scatters the light, and a part of the scattered light enters the light receiving element from around the beam stopper. On the other hand, when the liquid is not ejected normally, the light beam squeezed by the diaphragm member is directly applied to the beam stopper without blocking the light beam with the ejected liquid, thereby preventing the light from the light emitting element from entering the light receiving element. . Thereby, since the amount of light received by the light receiving element is large, it is confirmed that the liquid is ejected. On the other hand, when the amount of received light is small, a liquid ejection failure is detected. That is, a liquid ejection failure is detected from a change in the amount of light received by the light receiving element.

  A semiconductor laser may be used as the light emitting element. Further, a light transmission window may be provided in a package that houses the light receiving element, and a light shielding portion may be formed on a light transmission member such as glass that closes the light transmission window, and the light shielding portion may be used as a beam stopper.

  According to a fourth aspect of the present invention, in order to achieve the above-described fourth object of the present invention, an ink jet recording apparatus is provided with the above-described liquid ejection defect detection device. The ink jet recording apparatus may be provided with a recovery device that sucks ink from a limited nozzle including a nozzle that has detected a discharge failure or a nozzle around it when there is a discharge failure of an ink droplet.

  According to the first aspect of the present invention, the liquid ejecting head having the nozzle row is translated while ejecting the liquid from the first nozzle, and the liquid ejected from the first nozzle is an optical axis for detecting a liquid ejection failure. Liquid discharge failure detection based on the change in the light output of the light receiving element before and after crossing the nozzle, aligning the position of the first nozzle in the liquid discharge direction with the optical axis for liquid discharge failure detection, and then discharging the liquid from the second nozzle The light receiving element before and after the liquid discharge failure detection device rotates around the position of the first nozzle in the liquid discharge direction aligned with the optical axis for use and the liquid discharged from the second nozzle crosses the liquid discharge failure detection optical axis Based on the change in the light output, the liquid discharge direction position of the second nozzle is aligned with the liquid discharge failure detection optical axis. Therefore, the liquid ejection failure detection optical axis and the nozzle row can be easily aligned with the liquid ejection failure detection optical axis and the nozzle row without complicating the structure or consuming liquid wastefully. Can be provided.

  At this time, assuming that the nozzle at one end of the nozzles constituting the nozzle row is the first nozzle and the nozzle at the other end is the second nozzle, liquid discharge from the two most distant nozzles constituting the nozzle row By aligning the direction position with the liquid discharge failure detection optical axis, the liquid discharge failure detection optical axis and the nozzle array can be more accurately aligned.

  In addition, a plurality of liquid discharge heads are mounted on one carriage by positioning the nozzle rows so as to be parallel, and first the liquid discharge heads are moved in parallel by moving the carriage. The liquid ejection direction position of one nozzle is aligned with the optical axis for liquid ejection failure detection, and then the liquid ejection head is rotated by rotating the carriage, and the liquid ejection direction position of the second nozzle of the same liquid ejection head is set. By aligning with the liquid discharge defect detection optical axis, even when a plurality of liquid discharge heads are provided as in a color recording apparatus, the nozzle row of each liquid discharge head is aligned with the liquid discharge defect detection optical axis. be able to.

  According to the second aspect of the present invention, in the liquid discharge failure detection method, the liquid discharge failure detection optical axis is based on the alignment method between the liquid discharge failure detection optical axis and the nozzle row as in the first aspect. After the alignment between the nozzle row and the nozzle row, liquid is discharged in order from the nozzles constituting the nozzle row, and a liquid discharge failure is detected based on the change in the light output of the light receiving element. Therefore, without complicating the structure or consuming liquid wastefully, the liquid discharge failure detection optical axis and the nozzle array are simply aligned, and then liquid discharge from each nozzle constituting the nozzle array is performed. It is possible to provide a liquid discharge defect detection method for accurately detecting defects individually.

  According to the third aspect of the present invention, in the liquid discharge failure detection device, the light emitting element and the light receiving element are integrated into a single unit, while the liquid discharge head having the nozzle row is parallel to a direction substantially perpendicular to the nozzle row. When moving, the first nozzle, which is one of the nozzles constituting the nozzle row, is provided so as to be rotatable about a position where the liquid discharge direction crosses the liquid discharge failure detection optical axis. Therefore, while the liquid is ejected from the first nozzle, the liquid ejection head having the nozzle array is translated, and the light output of the light receiving element before and after the liquid ejected from the first nozzle crosses the optical axis for detecting liquid ejection failure. Based on this change, the liquid discharge direction position of the first nozzle is aligned with the liquid discharge failure detection optical axis, and then the first nozzle is aligned with the liquid discharge failure detection optical axis while discharging the liquid from the second nozzle. Based on the change in the light output of the light receiving element before and after the liquid discharged from the second nozzle crosses the liquid discharge failure detection optical axis, the liquid discharge failure detection device rotates around the position of the nozzle in the liquid discharge direction. The position of the two nozzles in the liquid discharge direction can be aligned with the liquid discharge failure detection optical axis. Accordingly, it is possible to provide a liquid discharge failure detection device that can easily align the liquid discharge failure detection optical axis and the nozzle array without complicating the structure or consuming liquid wastefully. .

  Here, if a diaphragm member for narrowing the light beam emitted from the light emitting element and a beam stopper for preventing the light narrowed by the diaphragm member from entering the light receiving element as they are, the structure is simple and the scattered light is received. Since the amount of light received by the light receiving element is large, the discharge of liquid is confirmed. On the other hand, since the amount of received light is small by blocking light with the beam stopper, defective liquid discharge is detected. The ratio of the amount of received light can be increased, and the liquid discharge failure can be reliably detected.

  If a semiconductor laser is used as a light emitting element, it can cope with downsizing and cost reduction, and it has good coherence and is easy to make parallel light, so it is effective in detecting liquid discharge defects that are effective for long liquid discharge heads, for example. An apparatus can be provided.

  If a light-transmitting window is provided in the package that houses the light-receiving element, a light-shielding part is formed on the light-transmitting member that closes the light-transmitting window, and the light-shielding part is used as a beam stopper, the beam stopper is integrated with the light-receiving element to reduce the number of parts. In addition to the reduction, the optical axis alignment can be simplified and the size can be reduced.

  According to the fourth aspect of the present invention, since the ink jet recording apparatus includes the liquid discharge defect detecting device as in the third aspect, the structure is simplified, and the liquid discharge defect is detected without wasting liquid. Accordingly, it is possible to provide an ink jet recording apparatus that includes a liquid ejection failure detection device that can easily align the optical axis for the nozzle and the nozzle row and that can reliably detect ejection failure of ink droplets.

  When there is a defective ejection of ink droplets, wasteful consumption of ink can be prevented by providing a recovery device that sucks ink from a limited nozzle including the nozzle that detected the ejection failure or the surrounding nozzles.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1A shows an ink jet printer provided with a liquid ejection failure detection device according to a third aspect of the present invention as viewed from the front, and FIG.

  Reference numeral 10 in the figure denotes a housing. A guide shaft 13 and a guide plate 14 are provided in parallel on the left and right side plates 11 and 12 of the housing 10. The guide shaft 13 and the guide plate 14 support one carriage 15. An endless belt (not shown) is attached to the carriage 15. The endless belt is wound around a driving pulley and a driven pulley (not shown) provided on the left and right sides of the housing 10. The endless belt travels while the driven pulley rotates following the rotation of the driving pulley, and the carriage 15 is slidable left and right as indicated by arrows in the figure.

  On the carriage 15, yellow, cyan, magenta, and black ink jet heads 16 y, 16 c, 16 m, and 16 b are mounted side by side in the movement direction of the carriage 15. Although not shown in FIG. 1, each inkjet head 16 that is a liquid discharge head has an ink row formed by arranging a plurality of nozzles in a straight line, and is positioned so that the ink rows are parallel.

  When the carriage 15 is at the rightmost home position shown in the figure, each inkjet head 16 faces the recovery device 18 installed on the bottom plate 17 in the housing 10. The recovery device 18 is a device that recovers defective ejection by sucking ink from nozzles that are defective in ejecting ink droplets.

  On the bottom plate 17 in the housing 10, a liquid ejection failure detection device 20 according to the third aspect of the present invention is provided next to the recovery device 18. The liquid discharge failure detection device 20 will be described later in detail with reference to FIG.

  A plate-like platen 22 is installed at a position adjacent to the liquid discharge failure detection device 20. On the back side of the platen 22 when viewed from the front, a paper feed base 24 for supplying the paper 23 as a recording medium is provided on the platen 22 in an oblique manner. Although not shown, a paper feed roller for feeding the paper 23 on the paper feed tray 24 onto the platen 22 is provided. Further, a transport roller 25 is provided for transporting the paper 23 on the platen 22 in the direction of the arrow and discharging it to the front side.

  On the bottom plate 17 in the housing 10, a driving device 26 is further installed at the left end. The driving device 26 drives a feed roller (not shown), a conveying roller 25, and the like, and drives the above-described driving pulley to travel the endless belt and move the carriage 15.

  At the time of recording, the paper 23 is transported and moved onto the platen 22 by being driven by the driving device 26, positioned at a predetermined position, and the carriage 15 is moved to scan on the paper 23 in the left direction. While moving, ink droplets are ejected from the nozzles of the respective ink rows in order using the four-color inkjet heads 16y, 16c, 16m, and 16b, and an image is recorded on the paper 23. After image recording, the carriage 15 is returned to the right and the sheet 23 is conveyed by a predetermined amount in the direction of the arrow.

  Next, while moving the carriage 15 to the left again, ink droplets are sequentially ejected from the nozzles of the respective ink rows using the four-color inkjet heads 16y, 16c, 16m, and 16b on the forward path to record an image on the paper 23. To do. Similarly, after image recording, the carriage 15 is returned to the right and the paper 23 is conveyed by a predetermined amount in the direction of the arrow. Thereafter, the same is repeated, and an image is recorded on one sheet of paper 23.

  FIG. 2 shows a state in which ink droplet ejection failure is detected from each nozzle of a nozzle row provided in one inkjet head 16 using the liquid ejection failure detection device 20, and the axial direction of the guide shaft 13 from the left side. To see.

  In the figure, n 1, n 2, n 3, n 4, n 5,... Nx represents the liquid ejection direction from each nozzle of the ink row provided in one inkjet head 16 mounted on the carriage 15. The liquid discharge failure detection device 20 is configured to emit light from the light emitting element 30 in a direction crossing the liquid discharge direction n and direct the light toward the light receiving element 40.

  For example, a semiconductor laser is used for the light emitting element 30, and a photodiode is used for the light receiving element 40, for example. A collimating lens 32 is provided as a diaphragm member on the liquid discharge failure detection optical axis 31 from the light emitting element 30 to the light receiving element 40 before crossing the liquid discharge direction n of n1 to nx. A disk-shaped beam stopper 33 is provided after traversing. Therefore, the light emitting element 30, the collimating lens 32, the beam stopper 33, and the light receiving element 40 are provided in order on the straight optical axis 31. In the case of the short inkjet head 16, the cost can be reduced by using an LED as the light emitting element 30.

  As a result, the light beam emitted from the light emitting element 30 is collimated by the collimator lens 32, and the collimated lens 32 is prevented from entering the light receiving element 40 by collimating the parallel light to the beam stopper 33. In this example, the collimating lens 32 is used as a diaphragm member, and the light beam 34 from the light emitting element 30 is made parallel light. However, the light beam 34 from the light emitting element 30 may be narrowed by the diaphragm member, and the parallel light is not necessarily used. It is not limited to.

At this time, if the diameter of the light beam 34 focused by the collimating lens 32 is Φd, the outer diameter of the beam stopper 33 is Φds, and the effective light receiving surface diameter of the light receiving surface 41 of the light receiving element 40 is ΦD,
Φd <Φds <ΦD
Set to be.

  By the way, in the illustrated inkjet printer, recording is performed on a certain number of sheets of paper 23 when the power is turned on, when a certain time has elapsed since the previous detection of liquid discharge failure, or after the previous detection of liquid discharge failure. When it is performed, the detection of liquid discharge failure is automatically started. Further, when the user operates the detection switch, detection of liquid discharge failure is started.

  The light emitted from the light emitting element 30 is collimated by the collimator lens 32 to be converted into parallel light, and guided to the light receiving element 40. On the other hand, ink droplets are sequentially ejected from one end of a plurality of nozzles of the ink row of the inkjet head 16y. In this case, when the ink droplets are normally ejected, the ejected liquid blocks the light beam 34 to scatter the light, and a part of the scattered light is received from around the beam stopper 33 as indicated by a chain line in the figure. Place in element 40.

Here, when the ink droplet diameter is several μm to several tens of μm, for example, as shown in the figure, it is scattered like S1, S2, S3, S4, S5, S6, S7, S8, and the scattering intensity is
S1> S2, 3> S4, 5> S6, 7> S8
The forward scattered light (S1-5) becomes stronger than the backscattered light (S6-8).

  On the other hand, when the ink droplets are not ejected normally, the light beam 34 squeezed by the collimating lens 32 is directly applied to the beam stopper 33 without blocking the light beam 34 with the ejected liquid, and the light from the light emitting element 30 is received by the light receiving element. Block entry into 40. As a result, the scattered light that protrudes from the outer diameter of the beam stopper 33 is received and the light output of the light receiving element 30 is increased. Therefore, while confirming the ejection of the ink droplet, the light is blocked by the beam stopper 33 and almost no light output. Since it is as small as 0, an ink droplet ejection failure is detected. That is, the ejection failure of the ink droplet is detected from the change in the light output of the light receiving element 30.

  When ink droplet ejection defects are detected in order from one end of a plurality of nozzles constituting the ink row of the yellow inkjet head 16y, the carriage 15 is moved to connect the cyan inkjet head 16c to the liquid ejection defect detection device 20 next. Similarly, the ink droplet ejection failure is detected sequentially from one end of a plurality of nozzles provided in the cyan inkjet head 16c, and then the magenta inkjet head 16m and the black inkjet head 16b are sequentially detected. Detect discharge failure.

  When there is an ink droplet ejection defect, in this example, the carriage 15 is returned to the home position, and the recovery device 18 sucks ink from the nozzles of the inkjet head 16 to eliminate clogging of the nozzles. At this time, wasteful consumption of ink can be prevented by sucking ink not from all nozzles but from a limited nozzle including nozzles that have detected ejection failure or surrounding nozzles.

  The light receiving element 40 is housed and installed in a can-like package 42. The package 42, for example, closes the circular light transmission window 43 with a light transmission member 44 made of plate glass. The scattered light is applied to the light receiving surface 41 of the light receiving element 40 through the light transmitting member 44.

  FIG. 3 shows the beam stopper 33 and the light receiving element 40 as viewed from the light emitting element 30 side in the direction of the liquid ejection defect detecting optical axis 31.

FIG. 4 shows another example of the beam stopper 33.
In the above-described example, the beam stopper 33 is disposed in front of the light receiving element 40 as a separate body from the light receiving element 40 so as to prevent the light focused by the collimating lens 32 from entering the light receiving element 40 as it is. However, for example, as shown in FIG. 4, a light transmission window 43 is provided in a package 42 that houses the light receiving element 40, and a light shielding portion is formed on the light transmission member 44 that closes the light transmission window 43 by metal vapor deposition or the like. The portion may be a beam stopper 33.

  In this way, it is possible to provide the liquid ejection defect detection device 20 that integrates the beam stopper 33 with the light receiving element 40 to reduce the number of parts, simplify the optical axis alignment, and enable miniaturization.

  As described above, light is emitted from the light emitting element 30 in a direction crossing the liquid ejection direction n and the light is directed to the light receiving element 40, and a liquid ejection failure is detected from a change in the light output of the light receiving element 30. In the liquid ejection failure detection device 20, a collimator lens 32 as a diaphragm member for narrowing the light beam 34 emitted from the light emitting element 30 between the light emitting element 30 and the light receiving element 40, and the light focused by the collimator lens 32 is directly received by the light receiving element. Since only a beam stopper 33 that prevents entry into 30 is provided, the structure is simple.

  In addition, since the scattered light is received and the light output of the light receiving element 30 is large, the discharge of the liquid is confirmed. On the other hand, since the light output is small by shielding the light with the beam stopper 33, the liquid discharge failure is detected. The light output ratio of the light receiving element 40 with and without the light can be increased, and the detection of the liquid discharge failure can be ensured.

  FIG. 5 shows experimental data showing the relationship between the position between the light emitting element 30 and the light receiving element 40 and the light output ratio of the light receiving element 40 with and without ink droplets.

  As can be seen from FIG. 5, in both cases where the diameter of the beam stopper 33 is Φ1.5 and Φ3.0, the nozzle arrangement length of the inkjet head 16, that is, the length of the ink row (550 mm) is twice or more light. The output ratio could be obtained. Also from this experimental data, it can be seen that the detection threshold value of the liquid discharge failure can be set to 2 or more to reliably detect the liquid discharge failure.

  By the way, in the liquid discharge failure detection device 20 as described above, if the parallelism between the liquid discharge failure detection optical axis 31 and the nozzle row is deviated, the detection of the liquid discharge failure becomes inaccurate. Therefore, in the present invention, before ejecting liquid in order from the nozzles constituting the nozzle row and detecting the liquid ejection failure based on the change in the light output of the light receiving element 40, the liquid ejection failure detection optical axis 31 and the nozzle row are previously detected. And align with.

  In the liquid ejection failure detection device 20 shown in FIG. 6, the light emitting element 30 and the collimating lens 32 are integrated to form the light emitting side unit 50, while the light receiving element 40 and the beam stopper 33 are integrated as shown in FIG. Using the light receiving side unit 51, the light emitting side unit 50 and the light receiving side unit 51 are fixed on the same rotating plate 52, and the light emitting element 30 and the light receiving element 40 are integrated into a single unit.

  On the other hand, the nozzle rows 53y, 53c, 53m, and 53b are positioned so as to be parallel, and the four inkjet heads 16y, 16c, 16m, and 16b are mounted on one carriage 15, and the carriage 15 is moved in the L direction. Thus, the inkjet heads 16y, 16c, 16m, and 16b having the nozzle rows 53y, 53c, 53m, and 53b can be translated in a direction substantially orthogonal to the nozzle row 53. In this example, any one of the inkjet heads 16 may be used for the parallel movement, but in this example, the first nozzle that is one of the nozzles Ny constituting the nozzle row 53y of the first yellow inkjet head 16y, for example, one end portion The liquid discharge failure detection device 20 is provided so as to be rotatable in the R direction with the liquid discharge direction n1 of the nozzle Ny1 centering on a position O that crosses the liquid discharge failure detection optical axis 31.

  FIG. 7 shows a flow chart when aligning the liquid discharge failure detection optical axis 31 with the nozzle rows 53y, 53c, 53m, and 53b.

  When performing alignment, first, in step S1, the carriage 15 is moved in the L direction to move the inkjet heads 16y, 16c, 16m, and 16b in parallel, and one of the nozzles Ny constituting the nozzle row 53y. Ink droplets are ejected from one nozzle Ny1. Then, the ink jet head 16y is moved in a direction substantially orthogonal to the nozzle row 53y while ejecting ink droplets from the first nozzle Ny1, so that the ejected ink droplets traverse the liquid ejection failure detection optical axis 31. To do.

  Then, in step S2, the optical outputs LT1 to LT7 of the light receiving elements 40 at positions L1 to L7 before and after the ink droplet ejected from the first nozzle Ny1 crosses the liquid ejection failure detection optical axis 31 are detected, and step S3 is performed. And remember them. At this time, when the light outputs LT1 to LT7 cannot be detected, it is desirable to detect the light outputs LT1 to LT7 by changing the nozzle Ny1 to the next Ny2, Ny3,. In addition, it is preferable to improve the reliability of detection by ejecting not only one ink droplet but also several droplets. Then, after detecting the light outputs LT1 to LT7, in step S4, the ejection of ink droplets from the first nozzle Ny1 is stopped.

  FIG. 9 is a graph showing the relationship between the movement positions L1 to L7 of the carriage 15 and the detected light outputs LT1 to LT7. As can be seen from this figure, the peak value LT4 of the light outputs LT1 to LT7 is the position L4 at which the scattered light is received most. Based on the change of the light outputs LT1 to LT7, in step S5, the carriage 15 is moved to the position L4, and the position of the first nozzle Ny1 in the liquid discharge direction n1 is aligned with the liquid discharge failure detection optical axis 31.

  Next, in step S6, the liquid discharge failure detecting device 20 is rotated in the R direction around the liquid discharge direction n1 position O of the first nozzle Ny1, and another one of the nozzles Ny constituting the nozzle row 53y. Ink droplets are ejected from the second nozzle, for example, the nozzle Nyx at the other end of the nozzle row 53y. Then, the ink droplet ejected from the nozzle Nyx rotates so as to cross the liquid ejection failure detection optical axis 31.

  Then, in step S7, the optical outputs RT1 to RT7 of the light receiving elements 40 at positions R1 to R7 before and after the ink droplet ejected from the second nozzle Nyx crosses the liquid ejection failure detection optical axis 31 are detected, and step S8 is performed. And remember them. At this time, even when the light outputs RT1 to RT7 cannot be detected, it is desirable to detect the light outputs RT1 to RT7 by changing the nozzle Nyx. In addition, it is preferable to improve the reliability of detection by ejecting not only one ink droplet but also several droplets. After detecting the light outputs RT1 to RT7, in step S9, the ejection of ink droplets from the second nozzle Nyx is stopped.

  In FIG. 10, the graph which shows the relationship between rotation position R1-R7 of the liquid discharge defect detection apparatus 20 and detected light output RT1-RT7 is shown. As can be seen from this figure, the peak value RT4 of the light outputs RT1 to RT7 is when the scattered light is received most at the position R4. Based on the change of the light outputs RT1 to RT7, in step S10, the liquid discharge failure detecting device 20 is rotated to the position R4, and the liquid discharge direction nx position of the first nozzle Nyx is set as the liquid discharge failure detecting optical axis 31. Match. Thereby, the liquid discharge failure detection optical axis 31 and the ink row 53y can be accurately aligned, and the liquid discharge failure detection optical axis 31 and the other ink rows 53c, 53m, 53b can also be aligned. .

  Then, after alignment of the liquid discharge failure detection optical axis 31 and the nozzle rows 53y, 53c, 53m, and 53b, ink droplets are discharged in order from the nozzles constituting the nozzle rows 53y, 53c, 53m, and 53b to receive light. A liquid discharge failure is detected based on the change in the light output of the element 40.

  That is, as shown in FIG. 8, in step S11, ink droplets are first ejected in order from the nozzles Ny1, Ny2,... Nyx of the yellow inkjet head 16y, and in step S12, the light output of the light receiving element 40 is detected. Then, it is determined whether or not the light output is equal to or greater than the threshold value, and the ejection check is performed. If the threshold value is not reached, the non-ejection nozzle is stored in step S13 as ejection failure.

  After detecting the ejection failure of the yellow inkjet head 16y, in step S14, the carriage 15 is moved in the L direction by the pitch P, and then in step S15, the nozzles Nc1, Nc2 of the cyan inkjet head 16c are detected. In this case, the ink droplets are ejected in order from Ncx, and in step S16, the light output of the light receiving element 40 is detected to determine whether the light output is equal to or greater than a threshold value, and an ejection check is performed. If the threshold value is not reached, the non-ejection nozzle is stored in step S17 as ejection failure.

  After detecting the ejection failure of the cyan inkjet head 16c, in step S18, the carriage 15 is moved again in the L direction by the pitch P, and then in step S19, the nozzle Nm1 of the magenta inkjet head 16m, Nm2,..., Nmx are ejected in order from Nmx, and in step S20, the light output of the light receiving element 40 is detected to determine whether the light output is equal to or greater than a threshold value, and an ejection check is performed. If the threshold value is not reached, the non-ejection nozzle is stored in step S21 as ejection failure.

  After detecting the ejection failure of the magenta inkjet head 16m, the non-ejection nozzles are stored in the same manner for the black inkjet head 16b. Then, the carriage 15 is moved under this data, the non-ejection nozzle to be stored is opposed to the recovery device 18, and the recovery device 18 sucks ink from, for example, the non-ejection nozzle to be stored to eliminate the nozzle clogging. To do.

  After the nozzle clogging or the like is eliminated by the recovery device 18, for example, only the non-ejection nozzles to be stored are checked again for liquid ejection defects. When there is a liquid discharge failure, the recovery device 18 again performs the discharge failure elimination operation.

(A) is a front view of an ink jet printer provided with the liquid discharge failure detection device which is the 3rd mode of this invention, and (B) is a perspective view which shows a part seen from the slanting top. It is a figure which shows the state which has detected the discharge failure of the ink droplet from the nozzle of one inkjet head using the liquid discharge failure detection apparatus from the left side in the axial direction of a guide shaft. It is a figure which shows the beam stopper and light receiving element of the liquid discharge defect detection device as seen from the light emitting element side in the optical axis direction. It is the front view and partially broken side view of the light receiving element accommodation package which show the other example of the beam stopper. It is an experimental data figure which shows the relationship between the position between a light emitting element and a light receiving element, and the light output ratio of a light receiving element with and without an ink drop. FIG. 5 is a plan view for explaining alignment between a liquid ejection defect detection device and an ink column of an ink jet head mounted on a carriage. It is a flowchart when performing the alignment. It is a flowchart when performing liquid discharge defect detection after the alignment. FIG. 5 is a relationship diagram between the movement position of the carriage and the light output of the light receiving element when the liquid discharge direction position of the first nozzle in the nozzle row crosses the optical axis during the alignment. FIG. 5 is a relationship diagram between a rotation position of a liquid discharge defect detection device and a light output of a light receiving element when a liquid discharge direction position of a second nozzle in a nozzle row crosses an optical axis during alignment.

Explanation of symbols

15 Carriage 16, 16y, 16c, 16m, 16b Inkjet head (liquid ejection head)
DESCRIPTION OF SYMBOLS 18 Recovery apparatus 20 Liquid discharge defect detection apparatus 30 Light receiving element 31 Optical axis for liquid discharge defect detection 32 Collimating lens (aperture member)
33 Beam stopper 34 Light beam 40 Light receiving element 42 Package 43 Light transmitting window 44 Light transmitting member 50 Light emitting side unit 51 Light receiving side unit 52 Rotating plate 53, 53y, 53c, 53m, 53b Nozzle array LT1 to LTx Light output of light receiving element RT1 to RTx Light output of light receiving element Ny, Nc, Nm, Nb Nozzle Ny1 First nozzle Nyx Second nozzle n, n1, n2, n3, n4, n5, ... nx Liquid discharge direction

Claims (10)

While discharging a liquid from a first nozzle which is one of the nozzles constituting the nozzle row in a direction substantially orthogonal to the nozzle row, the liquid to be discharged is a light emitting element. Parallel to move across the optical axis for liquid discharge failure detection from the
Detecting the light output of the light receiving element before and after the liquid ejected from the first nozzle crosses the liquid ejection failure detection optical axis;
Based on the change in the light output, after stopping the liquid discharge, the liquid discharge direction position of the first nozzle is adjusted to the liquid discharge failure detection optical axis,
Next, the liquid discharge failure detection device in which the light emitting element and the light receiving element are integrated into one unit is another one of the nozzles constituting the nozzle row with the liquid discharge direction position of the first nozzle as the center. While ejecting liquid from the second nozzle, the ejected liquid rotates so as to cross the liquid ejection failure detection optical axis,
Detecting the light output of the light receiving element before and after the liquid discharged from the second nozzle crosses the optical axis for liquid discharge failure detection;
Based on the change in the light output, after stopping the liquid discharge, the liquid discharge direction position of the second nozzle is aligned with the liquid discharge failure detection optical axis.
A method of aligning a liquid discharge failure detection optical axis and a nozzle row, characterized in that:   2. The liquid ejection failure according to claim 1, wherein a nozzle at one end of the nozzles constituting the nozzle row is the first nozzle and a nozzle at the other end is the second nozzle. A method for aligning the detection optical axis with the nozzle array.   A plurality of the liquid discharge heads are mounted on one carriage by positioning so that each nozzle row is parallel, and the liquid discharge heads are moved in parallel by moving the carriages, and the liquid discharge heads of the one liquid discharge head are moved. The liquid discharge direction position of the second nozzle of the same liquid discharge head is adjusted by rotating the liquid discharge defect detection device while matching the liquid discharge direction position of the first nozzle with the liquid discharge defect detection optical axis. 3. The method for aligning a liquid ejection failure detecting optical axis and a nozzle array according to claim 1, wherein the liquid ejection failure detection optical axis is aligned with the liquid ejection failure detection optical axis.   4. After aligning the liquid discharge failure detection optical axis and the nozzle row based on the method for aligning the liquid discharge failure detection optical axis and the nozzle row according to any one of claims 1 to 3, the nozzle row A liquid discharge failure detection method, wherein a liquid discharge failure is detected on the basis of a change in light output of the light receiving element by sequentially discharging liquid from the nozzles constituting the light receiving element. The light emitting element emits light in a direction intersecting the liquid ejection direction of the nozzles constituting the nozzle row, and the light is directed to the light receiving element, and a liquid ejection failure is detected based on a change in the light output of the light receiving element. In the liquid discharge defect detection device,
While making the light emitting element and the light receiving element into an integral unit,
When the liquid discharge head having the nozzle row is translated in a direction substantially orthogonal to the nozzle row, the liquid discharge direction of the first nozzle which is one of the nozzles constituting the nozzle row is changed from the light emitting element. A liquid discharge failure detection apparatus, wherein the liquid discharge failure detection device is provided so as to be rotatable about a position crossing the optical axis for liquid discharge failure detection toward the light receiving element.   The liquid ejection according to claim 5, further comprising: a diaphragm member that narrows a light beam emitted from the light emitting element; and a beam stopper that prevents light narrowed by the diaphragm member from entering the light receiving element as it is. Defect detection device.   The liquid ejection defect detection device according to claim 5, wherein a semiconductor laser is used as the light emitting element.   8. A light-transmitting window is provided in a package that houses the light-receiving element, a light-blocking portion is formed on a light-transmitting member that closes the light-transmitting window, and the light-blocking portion is used as the beam stopper. The liquid discharge defect detection device according to 1.   An ink jet recording apparatus comprising the liquid discharge failure detecting device according to claim 5.   The inkjet recording apparatus according to claim 9, further comprising a recovery device that sucks ink from a limited nozzle including a nozzle that has detected an ejection failure or a nozzle around the nozzle when ejection failure of the ink droplet is present. .

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