JP2005081714A - Method for detecting ejection velocity of ink drop and ink jet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for detecting the velocity of an ink drop being ejected from a nozzle with high accuracy through a simple arrangement without requiring highly accurate adjustment of the distance between a recording head a velocity detecting means, and to provide an ink jet recorder. <P>SOLUTION: A recording head ejecting an ink drop and a pair of light emitting element and a light receiving element having an optical axis on the passage of ink drop are moved relatively so that the distance between the recording head and the pair of elements can be altered. After a first distance is sustained between the recording head and the pair of elements and a first time after ejecting an ink drop from the recording head before detecting the pair of elements is measured, distance between the recording head and the pair of elements is altered to a second distance different from the first distance and a second time after ejecting an ink drop from the recording head before detecting the pair of elements is measured. Ink drop ejection velocity is measured based on the time difference between the first and second times and the difference between the first and second distances. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ink droplet ejection speed detection method and an ink jet recording apparatus, and more specifically, the speed of ink droplets ejected from a recording head without the need to adjust the distance between the recording head and the speed detection means with high accuracy. The present invention relates to an ink droplet ejection speed detection method and an ink jet recording apparatus that can be easily detected.

  The ink jet recording apparatus ejects ink from each of a large number of nozzles formed on the recording head as fine droplet-shaped ink droplets, and lands on a recording medium arranged to face the nozzle surface of the recording head. A desired image is recorded and formed on a recording medium while the recording head performs bidirectional main scanning.

  In such an ink jet recording apparatus, a malfunction caused by nozzle ejection causes a serious image recording problem such as missing pixels or streaks in a recorded image. Therefore, a light emitting element is provided at one end of the scanning path of the recording head. It is known that a light receiving element is provided to detect ejection and non-ejection of a plurality of nozzles (Patent Document 1).

  However, image recording defects due to malfunctioning nozzles that eject ink droplets may appear not only as non-ejections but also as abnormal ejection speeds, and thus cannot be solved sufficiently by simply detecting ejection or non-ejection. Further, if it is attempted to detect a malfunction of the nozzle only by non-ejection, a future non-ejection cannot be detected in advance.

Therefore, it is conceivable to detect the speed of the ink droplet and detect the future non-ejection in advance due to the abnormality of the speed.
Japanese Patent Laid-Open No. 11-17984

  In order to detect the speed of such ink droplets, it is possible to measure the time from when the ejection pulse signal is applied to the recording head to the detection of the ink droplets by the sensor, and to detect the speed of the ink droplets from the measurement results. Conceivable.

  However, in order to perform measurement with high accuracy, it is necessary to assemble the position of the recording head and the position of the sensor in the apparatus main body in a state where the accuracy is maintained in advance. Usually, the recording head is provided so as to be capable of reciprocating along the main scanning direction, and the sensor is fixedly provided at a position corresponding to the home position of the recording head, and is disposed at a separate location on the apparatus main body. It was extremely difficult to adjust and assemble the distance between them with high accuracy, and it was difficult to detect speed with high accuracy.

  Therefore, the present invention does not need to adjust the distance between the recording head and the speed detection means with high accuracy, and can detect the speed of ink droplets ejected from the nozzles with high accuracy with a simple configuration. It is an object of the present invention to provide an ink droplet ejection speed detection method and an ink jet recording apparatus.

  The above problems are solved by the following inventions.

  According to a first aspect of the present invention, the recording head is configured by relatively moving a recording head that ejects ink droplets and a pair of light-emitting elements and light-receiving elements that have an optical axis on a passage path of the ink droplets. The distance between the recording head and the element pair is changeable, the first distance is maintained between the recording head and the element pair, and from the ejection of the ink droplets of the recording head to the detection by the element pair. After measuring the first time, the distance between the recording head and the element pair is relatively changed to a second distance different from the first distance, and the recording head discharges the ink droplets to the element. An ink droplet is measured based on a time difference between the first time and the second time and a distance difference between the first distance and the second distance. Measuring the discharge speed of ink droplets It is out speed detection method.

  According to a second aspect of the present invention, there is provided a first element pair composed of a light emitting element and a light receiving element, each of which has an optical axis on a passage path of the ink droplet along a direction of ink ejection of a recording head that ejects the ink droplet. The second element pair is disposed at a different distance from the recording head, the first time from the ejection of the ink droplet of the recording head to the detection by the first element pair, and the second A second time until detection by the first element pair is measured, and a distance between the first element pair and the second element pair and a time difference between the first time and the second time are measured. An ink droplet ejection speed detection method is characterized in that an ink droplet ejection speed is measured based on the ink droplet ejection speed.

  According to a third aspect of the present invention, there is provided a recording head that ejects ink droplets, an element pair including a light emitting element and a light receiving element that have an optical axis on a passage path of the ink droplet, and the recording head and the element pair. A changing means for relatively changing the distance between the first distance and a second distance different from the first distance, and when the distance between the recording head and the element pair is at the first distance. After measuring the first time from the ejection of the ink droplets of the recording head to the detection by the element pair, the recording head of the recording head when the distance between the recording head and the element pair is at the second distance is measured. A second time from ink droplet ejection to detection by the element pair is measured, a time difference between the first time and the second time, and a distance difference between the first distance and the second distance. Measuring means for measuring the ejection speed of ink droplets based on It is an inkjet recording apparatus characterized.

  According to a fourth aspect of the present invention, there is provided a recording head for ejecting ink droplets, a first element pair comprising a light emitting element and a light receiving element having an optical axis on a passage path of the ink droplet, and the first element pair. Is a second element pair consisting of a light emitting element and a light receiving element which are arranged at different distances from the recording head along the ink ejection direction of the recording head and which have an optical axis on the passage path of the ink droplets. Measuring a first time from the ejection of the ink droplets of the recording head to detection by the first element pair and a second time from detection by the second element pair; Measuring means for measuring an ink droplet ejection speed based on a distance between a pair of elements and the second element pair and a time difference between the first time and the second time. Inkjet recording apparatus.

  According to the present invention, it is not necessary to adjust the distance between the recording head and the speed detection unit with high accuracy, and the speed of the ink droplets ejected from the nozzle can be detected with high accuracy by a simple configuration. An ink droplet ejection speed detection method and an ink jet recording apparatus can be provided.

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

  FIG. 1 is a schematic configuration diagram showing a main part of a first embodiment of an ink jet recording apparatus for carrying out the ink droplet ejection speed detection method of the present invention, and FIG. 2 is a configuration block diagram relating to the ejection speed detection.

  In FIG. 1, reference numeral 1 denotes a recording head, and a lower surface thereof is a head surface 11 in which a large number of nozzles (not shown) are arranged along the horizontal direction in the drawing. A plurality of recording heads 1 such as YMCK are held in parallel by a carriage (not shown) with high accuracy, and the carriage reciprocates in a direction orthogonal to the nozzle arrangement direction, thereby moving the main scanning direction. A desired inkjet image is recorded by ejecting ink droplets a toward a recording medium (not shown) at a predetermined timing in the process. 1A and 1B have the same configuration except that the height of the recording head 1 along the ink ejection direction is changed.

  Reference numeral 2 denotes an element pair in which a light emitting element 21 that emits detection light and a light receiving element 22 that receives the detection light are opposed to each other. In the ink jet recording apparatus, when the recording head 1 is stopped at a predetermined position such as a home position where image recording on the recording medium is not performed, the element pair 2 stops the optical axis X of the detection light at the predetermined position. The ink droplets a are ejected from the recording head 1 so as to exist on the passage path (so that the traveling path of the ink droplets a and the optical axis X of the detection light intersect).

  The light emitting element 21 and the light receiving element 22 are both mounted in housings 23 and 24 that optically shield light. The housing 23 on the light emitting element 21 side receives detection light from the light emitting element 21. A light emitting opening 23a for emitting light toward the side 22 is formed. Further, the housing 24 on the light receiving element 22 side is formed with a light receiving opening 24 a for receiving the detection light from the light emitting element 21 so that the light receiving element 22 can detect it.

  As shown in FIG. 2, when the ink droplet a ejected from a nozzle of the recording head 1 passes on the optical axis X of the element pair 2 and blocks the detection light, the control unit 100 generates a detection signal for the ink droplet a. Is input. In addition, the control unit 100 controls the ejection signal generation unit 101 to control the application of the ejection signal to the recording head 1.

  In FIG. 2, reference numeral 102 denotes a distance changing unit, which will be described in detail later. The distance between the recording head 1 and the element pair 2 is relatively changed by being controlled by the control unit 100.

  Reference numeral 103 denotes an arithmetic unit that measures the ejection speed of the ink droplet a based on the detection signal from the element pair 2. This measurement will be described later.

  Here, the detection method of the ejection speed of the ink droplet a in the first embodiment is that the recording head 1 and the element pair 2 are moved by relatively moving the recording head 1 and the element pair 2 that eject the ink droplet a. Between the ink droplet a before and after the relative distance is changed and the amount of change in the relative distance from the time difference between the ejection of the ink droplet a and the detection by the element pair 2. The purpose is to measure the velocity v1.

  A preferred mode of measuring the ink droplet ejection speed v1 will be described. In the first mode, as shown in FIG. 1, the height of the head surface 11 is changed by changing the height of the recording head 1 along the ink ejection direction without changing the position of the optical axis X. It is.

  In this case, the control unit 100 generates an ejection signal while the recording head 1 shown in FIG. 1A is at a low position and the distance between the element pair 2 is relatively short (first distance). By controlling the unit 101 to apply the ejection signal P1 to the recording head 1 and eject the ink droplet a from any one of the nozzles, as shown in FIG. 3, after the elapse of time t1 (first time), as shown in FIG. The ink droplet a passes on the optical axis X of the light emitting element 21 and the light receiving element 22 and is detected as the detection signal S1. The detection signal S1 is input to the control unit 100.

  Next, the control unit 100 controls the distance changing unit 102, so that the distance between the element pair 2 is relatively long (first) as shown in FIG. 2), and then the ejection signal generator 101 is controlled again to apply the ejection signal P2 to the recording head 1 and eject the ink droplet a from the same nozzle as described above. At (second time), the ink droplet a passes on the optical axis X of the light emitting element 21 and the light receiving element 22 and is detected as the detection signal S2. The detection signal S2 is also input to the control unit 100.

  In FIG. 3, for convenience of explanation, the discharge signals P1 and P2 are collectively shown as one discharge signal, and the detection signals S1 and S2 are shown separately.

  Here, the difference in height between the head surfaces 11 of the recording heads 1 in FIGS. 1A and 1B, that is, the distance difference between the first distance and the second distance is referred to as d1 (see FIG. 1B). ), The ejection speed v1 of the ink droplet a is v1 = d1 / (t2-t1) = d1 / t3, which is calculated and measured by the calculation unit 103, as can be seen from FIG. Similarly, the ejection speed v1 of the ink droplet a from each nozzle is also measured.

  In this embodiment, the means for changing the recording head 1 from the position shown in FIGS. 1A to 1B is not particularly limited, and examples thereof include those shown in FIG.

  In FIG. 4, reference numeral 3 denotes a carriage provided so as to be slidable along a slide bar 4 by a driving means (not shown). The slide bar 4 extends along a direction (main scanning direction) orthogonal to the conveyance direction (sub-scanning direction) of the recording medium, and the carriage 3 holds the recording head 1 along the slide bar 4. By reciprocating, the recording head 1 functions to reciprocate in the main scanning direction.

  The carriage 3 is divided into a recording head mounting portion 31 on which the recording head 1 is mounted and a slide portion 32 that is slidably attached to the slide bar 4. The recording head mounting portion 31 is a slide. The part 32 is provided so as to be capable of linearly reciprocating along the arrow A direction along the ink ejection direction of the recording head 1.

  The slide portion 32 is provided with a cam 5 that is rotated by a cam motor (not shown).

  On the other hand, the recording head mounting portion 31 is urged toward the direction opposite to the ink discharge direction (upward direction in the drawing) by an urging means made of a resilient member such as a spring 6 between the recording portion mounting portion 31 and the slide portion 32. As a result, the upper end 31 a of the recording head mounting portion 31 is always in contact with the cam 5.

  Accordingly, the cam motor is rotated as a function of the distance changing unit 102, and the cam 5 is rotated to guide the recording head mounting unit 31 relative to the slide unit 32 in the direction of arrow A. The recording head 1 can be changed to the position shown in FIGS. 1A to 1B.

  The distance between the recording head 1 and the element pair 2 is detected as the number of drive pulses of the cam motor, or the rotation amount of the cam 5 and the height position of the recording head mounting portion 30 are detected by an encoder or the like. Can be done. Further, by restricting the vertical movement distance of the recording head mounting portion 31 with a stopper or the like in advance, only the two points regulated in advance are moved, so that the first distance and the second distance can be increased. The distance may be regulated.

  In general, such a carriage 3 can accurately change the distance between the head surface 11 of the recording head 1 and the recording medium for measures such as thick paper. That is, by using such a carriage 3 to change the distance between the recording head 1 and the element pair 2, the distance from the optical axis X of the element pair 2 can be adjusted with high accuracy. Therefore, it is possible to measure the ejection speed of the ink droplet a with high accuracy by the above method without requiring the trouble of assembling each of the recording head 1 and the optical axis X by the element pair 2 in advance in the apparatus main body. Can be done easily.

  In addition, since the speed of the ink droplet a can be detected with high accuracy, it is possible to identify in advance the nozzle that will not discharge in the future by detecting the discharge speed for all the nozzles of the recording head 1 by the above method.

  Further, since the speed of the ink droplet a can be detected with high accuracy, it is possible to perform control such as equalizing the ink discharge speed for each of a plurality of recording heads with high accuracy from the data of the discharge speed of each nozzle. Become.

  Next, a second mode of measuring the ink droplet ejection speed v1 will be described. This is a mode in which the position of the optical axis X is changed without changing the height of the head surface 11 of the recording head 1 as shown in FIG.

  In this case, as shown in FIG. 5A, the optical axis X1 is located near the head surface 11 of the recording head 1 and the distance between the element pair 2 is relatively close (first distance). In a state, when the control unit 100 controls the ejection signal generation unit 101 to apply the ejection signal P3 to the recording head 1 and eject the ink droplet a from any one of the nozzles, as shown in FIG. After the time t4 has elapsed (first time), the ink droplet a reaches the optical axis X1 of the light emitting element 21 and the light receiving element 22, and is detected as the detection signal S3. The detection signal S3 is input to the control unit 100.

  Next, the control unit 100 controls the distance changing unit 102 to move the optical axis X1 downward from the head surface 11 of the recording head 1 along the ink discharge direction by a distance d2, as shown in FIG. 5B. The position is changed to the position of the optical axis X2 shifted to, and then the ejection signal is again sent to the recording head 1 in a state where the distance between the recording head 1 and the element pair 2 is relatively long (second distance). When the ejection signal P4 is applied to the recording head 1 and the ink droplet a is ejected from the same nozzle as described above by controlling the generator 101, the ink droplet a is emitted from the light emitting element after time t5 has elapsed (second time). 21 and the light receiving element 22 reach the optical axis X2, and are detected as a detection signal S4. The detection signal S4 is input to the control unit 100.

  Accordingly, in this case, the ejection speed v1 of the ink droplet a is v1 = d2 / (t2−t1) = d2 / t3, which is calculated and measured by the calculation unit 103. Similarly, the ejection speed v1 of the ink droplet a from each nozzle is also measured.

  Here, in FIG. 6, for convenience of explanation, the discharge signals P3 and P4 are collectively described as one discharge signal, and the detection signals S3 and S4 are described separately.

  Here, means for changing the distance from the recording head 1 by moving the position of the optical axis X by the element pair 2 to X1 and X2 is not particularly limited. For example, means for moving up and down simultaneously for each of the casings 23 and 24. Alternatively, a means for moving only the light emitting element 21 and the light receiving element 22 in the casings 23 and 24 up and down may be employed. As the means for moving up and down, various means such as a pinion-rack can be adopted in addition to the means using the cam as described above. The change of the distance in this case is also performed by the control unit 100 controlling the distance change unit 102.

  Also in this aspect, similarly to the above, high-precision measurement of the ink droplet ejection speed is easily performed without the need for assembling the apparatus main body in advance so that the distance between the recording head 1 and the element pair 2 is high-precision. be able to.

  FIG. 7 is a schematic configuration diagram showing a main part of a second embodiment of the ink jet recording apparatus for carrying out the ink droplet ejection speed detection method of the present invention, and FIG. 8 is a configuration block diagram relating to the ejection speed detection. Here, the same reference numerals as those in FIG. 1 denote the same components, and detailed description thereof will be omitted unless there is a particular difference.

  In this embodiment, two element pairs are provided, and the ejection speed of the ink droplet a is measured by the detection difference between the two element pairs 7 and 8.

  In the element pair 7, a light emitting element 71 that emits detection light and a light receiving element 72 that receives the detection light are disposed to face each other, and the element pair 8 includes a light emitting element 81 that similarly emits detection light and the detection A light receiving element 82 that receives light is disposed opposite to the light receiving element 82. These element pairs 7 and 8 are arranged such that the height along the ink ejection direction is varied in the order of the element pair 7 and the element pair 8 from the side close to the head surface 11 of the recording head 1 so that the recording head 1 can image the recording medium. When stopping at a predetermined position such as a home position where recording is not performed, the optical axes Xa and Xb of the respective detection lights are on the passage path of the ink droplet a ejected from the recording head 1 stopped at the predetermined position. (The traveling path of the ink droplet a and the optical axes Xa and Xb of the detection light intersect with each other).

  Each of the light emitting elements 71 and 81 and each of the light receiving elements 72 and 82 are mounted in casings 73 and 74 that optically shield light, and the casing 73 on the light emitting elements 71 and 81 side has a light emitting element. A light emitting opening 731 for emitting detection light from 71 and 81 toward the light receiving elements 72 and 82 is formed. The housing 74 on the side of the light receiving elements 72 and 82 is formed with a light receiving opening 74a for taking in the detection light from the light emitting elements 71 and 81 so that the light receiving elements 72 and 82 can detect them.

  Then, the control unit 200 controls the ejection signal generation unit 201 to apply the ejection signal P5 to the recording head 1 and eject the ink droplet a from any one of the nozzles, as shown in FIG. The droplet a sequentially passes on the optical axis Xa and the optical axis Xb of the light emitting element 21 and the light receiving element 22. At this time, as shown in FIG. 9, the detection signals S <b> 5 and S <b> 6 are detected by the element pairs 7 and 8 and input to the control unit 200.

  The calculation unit 202 measures the ejection speed v1 of the ink droplet a based on the detection signals S5 and S6. The measurement of the ink droplet ejection speed v1 will be described. Since each element pair 7 and 8 is separated by a distance d3 as shown in FIG. 7, as shown in FIG. 8, it is detected from the ejection signal P5. Similar to the time to the signal S5 (first time), the time from the ejection signal P5 to the detection signal S6 (second time) is shifted by the time t7. Since the distance d3 is an invariable distance that is set in advance when the element pairs 7 and 8 are manufactured, the ejection speed v1 of the ink droplet a is measured as v1 = d3 / t7.

  According to the second embodiment, when the distance between the element pair 7 and 8 is adjusted in advance with high accuracy, the apparatus is arranged so that the distance between the recording head 1 and the element pair 7 and 8 becomes high accuracy in advance. It is possible to measure the ink droplet ejection speed with high accuracy without the need for assembling the main body. The adjustment of the distance between the element pairs 7 and 8 can be performed much more easily than the adjustment of the distance from the recording head 1 by, for example, assembling in the same housing. The same effects as described above, such as high-accuracy measurement of the discharge speed, can be achieved.

  In addition, according to the second embodiment, since only one ejection signal needs to be given in order to detect the ejection speed of one ink droplet a, the detection time can be shortened. It is.

(A) (B) is a schematic block diagram which shows the principal part of the one aspect | mode of the inkjet recording device which concerns on 1st Embodiment. Configuration block diagram related to the discharge speed detection Timing chart showing the relationship between ejection pulse signal and sensor output Schematic configuration diagram showing a configuration example of the carriage (A) (B) is a schematic block diagram which shows the principal part of the other aspect of the inkjet recording device which concerns on 1st Embodiment. Timing chart showing the relationship between ejection pulse signal and sensor output Schematic configuration diagram showing the main part of an ink jet recording apparatus according to a second embodiment Configuration block diagram related to the discharge speed detection Timing chart showing the relationship between ejection pulse signal and sensor output

Explanation of symbols

1: Recording head 11: Head surface 2, 7, 8: Element pair 21, 71, 81: Light emitting element 22, 72, 82: Light receiving element 3: Carriage 31: Recording head mounting part 31a: Upper end 32: Slide part 4 : Slide bar 5: Cam 6: Spring 100, 200: Control unit 101, 201: Discharge signal generation unit 102: Distance changing unit 103, 202: Calculation unit

Claims (4)

  By relatively moving a recording head for ejecting ink droplets and an element pair consisting of a light-emitting element and a light-receiving element having an optical axis on the passage path of the ink droplet, the recording head and the element pair are moved between each other. After the distance between the recording head and the element pair is maintained at a first distance, and a first time from the ejection of the ink droplet of the recording head to the detection by the element pair is measured The recording head and the element pair are relatively changed to a second distance different from the first distance, and a second period from the ink droplet ejection of the recording head to the detection by the element pair is changed. Measuring time, and measuring an ink droplet ejection speed based on a time difference between the first time and the second time and a distance difference between the first distance and the second distance. A method for detecting the ejection speed of ink droplets.   A first element pair and a second element pair each composed of a light emitting element and a light receiving element, each having an optical axis on the passage path of the ink droplets along the ink ejection direction of the recording head that ejects the ink droplets, The recording heads are arranged at different distances, and the first time from the ejection of the ink droplets of the recording head to the detection by the first element pair and the first time from the detection by the second element pair. 2 is measured, and based on the distance between the first element pair and the second element pair and the time difference between the first time and the second time, the ejection speed of the ink droplets A method for detecting the ejection speed of ink droplets, characterized in that:   A distance between the recording head for ejecting ink droplets, an element pair composed of a light emitting element and a light receiving element having an optical axis on the passage of the ink droplets, and the distance between the recording head and the element pair is a first distance. And a change means for relatively changing to a second distance different from the first distance, and an ink droplet of the print head when the gap between the print head and the element pair is at the first distance. After measuring a first time from ejection to detection by the element pair, from the ejection of ink droplets of the recording head when the distance between the recording head and the element pair is at the second distance, the element pair A second time until detection by the ink droplet is measured, and an ink droplet is ejected based on a time difference between the first time and the second time and a distance difference between the first distance and the second distance. Measuring means for measuring speed Jet recording apparatus.   A recording head that ejects ink droplets, a first element pair that includes a light emitting element and a light receiving element that have an optical axis on a passage path of the ink droplets, and the first element pair are ink ejection of the recording head. A second element pair comprising a light emitting element and a light receiving element which are arranged at different distances from the recording head along the direction and have an optical axis on the passage path of the ink droplet, and an ink droplet of the recording head A first time from the ejection of the first element to the detection by the first element pair and a second time from the detection by the second element pair to measure the first element pair and the second element pair And a measuring unit for measuring the ejection speed of the ink droplets based on the distance between the first time and the time difference between the first time and the second time.

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