JP2013132801A - Droplet discharge detection device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a droplet discharge detection device, which is provided with a configuration such that measurement can be performed in the same time even in a state where optical systems cannot be disposed in line due to the larger width of an optical system than the width of laser beam to be projected, which results from small intervals of nozzle arrays.SOLUTION: The droplet discharge detection device includes a light emitting means 201, light adjusting means 211, 212, and a light receiving means 203. The device further includes a light reflecting means 213, and the light receiving means 203 is disposed on the downstream side of an end of a nozzle array 105b farthest from the position of the light emitting means 201 with respect to an optical beam 200a having the same advancing direction of an optical beam 200 emitted from the light emitting means 201, and disposed on the downstream side of an end of a nozzle array 105a closest to the position of the light emitting means 201 with respect to an optical beam 200c having an advancing direction opposite to that of the optical beam 200a emitted from the light emitting means 201.

Description

  The present invention relates to a droplet discharge detection device and an image forming apparatus, and more particularly to an apparatus for detecting a droplet discharge failure.

  Conventionally, one of image forming apparatuses such as a printer, a facsimile machine, a copying machine, a plotter, or a multifunction machine having these functions is an ink jet recording apparatus using a liquid discharge recording method using a recording head that discharges ink droplets. is there.

  This ink jet recording apparatus of the liquid discharge recording method ejects ink droplets from a recording head onto a conveyed paper to form an image (recording, printing, printing, and printing are also used synonymously), As its model, a serial type image forming apparatus that forms an image by ejecting droplets while the recording head moves in the main scanning direction, and a line type that forms images by ejecting droplets without the recording head moving There is a line type image forming apparatus using a head.

  The liquid discharge recording type image forming apparatus according to the present invention forms an image by landing ink on a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics. The image forming means that not only an image having a meaning such as a character or a figure is imparted to the medium but also an image having no meaning such as a pattern is imparted to the medium (simply It also means that a droplet is landed on a medium).

  Further, the ink used in the description of the present invention is not limited to what is referred to as ink, but can be used for image formation such as recording liquid, fixing processing liquid, resin, chemicals, and liquid. What is used as a general term for the liquids of

  In addition, the paper mentioned in the present invention is not limited to paper, but includes the above-described OHP sheet, cloth, and the like, and means that ink droplets adhere to the recording medium, recording medium, recording paper It is used as a generic term for what includes what is called recording paper.

  This liquid discharge recording type image forming apparatus is equipped with a large number of thermal or piezo-type inkjet heads to drive at high speed in the case of equipment-type inkjet printers used for bookbinding and small-scale production of various printed materials. However, an image can be formed only by paper conveyance without driving in the direction perpendicular to the paper conveyance direction (carriage driving). 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, in an ink jet recording apparatus, ink droplets are ejected from fine nozzles, so that the ink is easily dried when stopped, and the nozzle surface gets wet with ink, and dust such as paper dust tends to adhere to the nozzle surface. There is a problem that air may enter from the nozzle. These causes non-ejection, the ejection direction is bent, the droplet size is reduced, and ink droplet ejection failure occurs, resulting in missing dots or white streaks in the image, resulting in poor image quality. There was a problem that decreased.

  As a configuration for detecting the occurrence of such a problem, in the case of a small inkjet printer, the head is moved in a direction perpendicular to the paper direction through the drive mechanism to a position where a detection mechanism for detecting charges is arranged. An ink drop detection mechanism that emits later and detects an ink drop by a detection mechanism is already known.

  However, the detection mechanism employed in conventional small-sized ink jet printers requires driving in the direction perpendicular to the paper conveyance (carriage driving), and operates the driving mechanism to move the head to the position of the detection mechanism. There was a need.

  In Patent Document 1, as a configuration of a forward scattered light method, a droplet such as an ink droplet ejected from a nozzle on a head surface collides with an optical beam emitted from a light emitting means to generate scattered light, and the scattered light is received. There has been proposed a droplet discharge detecting device having a configuration in which light is received by an element and a droplet discharge defect is optically detected from the received light data.

  On the other hand, Patent Document 2 proposes a method for optically detecting a droplet discharge defect using a single optical beam for a configuration in which a head is provided with a plurality of rows, for example, two nozzle rows. ing.

  As disclosed in Patent Document 1, a line-type image forming apparatus using a line-type head uses a configuration that detects a droplet discharge failure due to scattered light for a configuration in which a large number of inkjet heads are arranged. .

  However, in this configuration, a light receiving unit such as a photodiode is arranged at a position off the emission light path to the ink droplets ejected from the nozzles, and light reception of forward scattered light obtained from the emitted light impinging on the ink droplets is received. The ejection failure is judged according to the state. For this reason, if the number of nozzles in the head is large, detection must be performed sequentially for each nozzle, which causes a problem that it takes time to detect.

  On the other hand, when adopting a forward scattered light type discharge detection method for a head having a large number of nozzle rows as disclosed in Patent Document 2, it is possible to cope with a plurality of nozzle rows by widening the laser beam. However, if the laser beam to be projected is made wider, the amount of light of the optical beam incident on the droplet will be reduced and the detection output at the light receiving unit will decrease, so a plurality of optical systems should be arranged side by side. become. However, since the width of the optical system is wider than the width of the laser beam to be projected, there is a problem that the optical systems cannot be arranged side by side.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical system in which the width of the optical system is wider than the width of laser light to be projected because the distance between nozzle rows is small. An object of the present invention is to provide a droplet discharge detection device having a configuration capable of measuring in the same time even in a state where they cannot be arranged side by side.

  In order to achieve this object, the present invention has the following features.

  The droplet discharge detecting device according to the present invention includes a light emitting means for generating an optical beam, a light adjusting means for adjusting an intensity distribution and a divergence or convergence state of the optical beam emitted by the light emitting means, and the plurality of nozzles. A liquid having light receiving means for irradiating the optical beam parallel to the row so as to intersect with the trajectory of the ink droplet ejected from the nozzle and detecting scattered light generated when the optical beam hits the ink droplet. A droplet discharge detection device comprising: a plurality of optical beams including a single head or an optical path of the optical beam parallel to a plurality of nozzle arrays configured by the plurality of heads by sequentially bending the optical beam; A plurality of light reflecting means for forming an optical path are provided, and the light receiving means is the same as the traveling direction of the optical beam emitted from the light emitting means. On the other hand, with respect to the optical beam opposite to the traveling direction of the optical beam emitted from the light emitting means, disposed downstream of the plurality of nozzle row end portions farthest from the light emitting means position. Is characterized in that it is arranged downstream from the end of the plurality of nozzle rows closest to the light emitting means position.

  According to the present invention, for the optical beam parallel to the plurality of nozzle rows that is the same as the traveling direction of the optical beam emitted from the light emitting means, the light receiving means is from the end of the plurality of nozzle rows farthest from the light emitting means position. Also, the end of the plurality of nozzle rows closest to the light emitting means position for the optical beam parallel to the plurality of nozzle rows opposite to the traveling direction of the optical beam emitted from the light emitting means By adopting a configuration arranged on the downstream side, the optical beam from the light emitting means via the light adjusting means is moved in the horizontal direction with respect to the head nozzle surface by a plurality of light reflecting means, and at the same time the traveling direction is reversed. The light emitted from the light emitting means and the optical beam parallel to the same plurality of nozzle rows as the traveling direction of the optical beam emitted from the light emitting means from the nozzles provided in the plurality of nozzle rows by bending. The discharge state of each ink droplet of an optical beam parallel to a plurality of nozzle rows opposite to the beam traveling direction can be detected simultaneously, and the distance between the nozzle rows is small, so the opticalness is greater than the width of the laser beam to be projected. Even in a state where the optical system cannot be arranged side by side due to the wider width of the system, measurement can be performed in the same time.

1 is a schematic configuration diagram illustrating a configuration of an image forming apparatus according to an exemplary embodiment. It is a top view which shows an example of a head array unit. It is a figure which shows the structure which attached each one LD unit and PD unit to 1 head row, (a) is a front view, (b) is a top view. It is a figure explaining the droplet detection by a laser beam, (a) is a top view, (b) is a front view. It is a top view of a head array unit including a droplet discharge detection device according to the present embodiment.

  Hereinafter, the present embodiment will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram illustrating a configuration of an image forming apparatus according to the present embodiment.

  The image forming apparatus includes a head unit 5 that constitutes a recording head that discharges and prints droplets on a sheet P conveyed by the conveyance unit 4, and a head maintenance device 6 that is a maintenance recovery mechanism of the head unit 5. . The maintenance device 6 is arranged to be slidable along the paper transport direction above the transport unit 4, and after the head unit 5 is lifted during head maintenance, it moves to the lower part of the head unit 5, and during printing, FIG. Retreat to the position.

  As shown in FIG. 2, the head unit 5 is a head array unit (recording unit) having eight head rows 51 </ b> A to 51 </ b> H composed of a plurality of (in this example, five) heads 101 arranged in a row on the base member 52. Head) 50. In the head 101, a plurality of nozzles 102 for discharging droplets are arranged in two rows on the nozzle surface 104.

  Then, black (K) liquid droplets are ejected from the two nozzle arrays of the heads 101 of the head arrays 51A and 51B, and magenta (M) liquid droplets are ejected from the two nozzle arrays of the heads 101 of the head arrays 51C and 51D. And the cyan (C) droplets are discharged from the two nozzle rows of the heads 101 of the head rows 51E and 51F, and the yellow (Y) droplet is discharged from the two nozzle rows of the head rows 51G and 51H. Is discharged. That is, in the head unit 5, one nozzle row corresponding to the paper width is constituted by four nozzle rows, and one nozzle row corresponding to the paper width is constituted by two head rows 51.

  The line configuration of each color is not limited to the above, and the arrangement of each color is not particularly limited. Further, the configuration of the head portion is not limited to this example.

  Next, an embodiment of a head array unit including a droplet discharge detection device in this image forming apparatus will be described with reference to FIGS. Hereinafter, in order to simplify the illustration, one head row 51A will be described with three heads. In the head array unit 50, a head row 51 is arranged on a base member 52.

  In the arrangements shown in FIGS. 3A and 3B, a laser diode (hereinafter referred to as “LD”) that emits laser light 200 parallel to the nozzle arrangement direction in units of one row on one side of the head row 51. An LD unit 202 including 201 is attached, and a PD unit 204 including a photodiode (hereinafter referred to as “PD”) 203 which is a light receiving means for receiving the scattered light of the laser light 200 generated by the droplet is provided. It is attached to the base member 52.

  Here, one LD unit 202 has one row of heads, two LDs 201 corresponding to two nozzle rows, and one PD unit 204 has one row of heads, ie, two nozzle rows corresponding to two nozzle rows. A PD 203 is provided.

  By using a laser diode as the light emitting means, an optical beam with strong directivity can be created, and an optical beam can be irradiated onto the ink droplets of the multiple nozzle rows, so that it is possible to receive multiple rows of forward scattered light with fewer light emitting means. Since it can be detected by means, the number of parts can be reduced. Further, by using a photodiode as the light receiving means, it is possible to detect weak scattered light, so that reliable droplet discharge detection can be performed.

  Here, an ink droplet ejection method will be described with reference to FIGS. 4A and 4B. When the droplet discharge detection is performed by the scattered light method, the emitted light of the LD 201 arranged on one side of the base member 52 is emitted toward the droplet 300 as the laser light 200 through the lens 211 and the aperture 212. The

  By using a collimator lens as the light adjustment means, it is possible to create the optical path of the optical beam with the converged or divergent state of the optical beam changed, and the outer periphery where the output of the optical beam is unstable due to the aperture is deleted. can do. Therefore, the state of the optical beam is set to a converged state so that the width of the optical beam does not become larger than the distance between the nozzle rows, so that the optical beam is in an unstable state. As a result, since the optical beam can be irradiated to the ink droplets of the plurality of nozzle arrays, it is possible to reliably detect the droplet discharge.

  The scattered light 301 generated when the laser beam 200 strikes the droplet 300 is received by the PD 203 disposed at a position separated from the laser beam 200 disposed on the other side of the base member 52, whereby the droplet 300 is ejected. It is designed to detect whether or not it has been done. As described above, it is possible to detect droplet discharge by arranging one optical system side by side for each nozzle row.

  Here, by increasing the laser beam width W1, it is possible to handle two or more nozzle rows with one laser beam. However, when the laser beam width W1 to be projected is increased, there is a problem that the light amount of the optical beam incident on the droplet is reduced, and the detection output at the light receiving unit is reduced.

  Further, when the distance D1 between the nozzle rows shown in FIG. 3B is small, there is a problem that the optical systems cannot be arranged side by side because the width of the optical system is wider than the width of the laser beam to be projected. Therefore, the present embodiment is characterized in that the above-described problems are solved by using the configuration of addition of the reflecting means and arrangement of the light receiving means shown in FIG.

  FIG. 5 is a plan view of a head array unit including the droplet discharge detection device according to the present embodiment. The nozzle rows 105a and 105b installed at the interval D1 provided in the simplified head row, the LD 201 as the light emitting means for emitting the laser light 200 parallel to the nozzle row 105a, and the scattered light 301b generated by the laser light 200c are received. An LD / PD unit 206 including a PD 203b, a PD 203a that receives scattered light 301a generated by the laser light 200a, and a PD / mirror unit 205 including mirrors 213a and 213b that reflect the laser light 200a and 200b are attached to the base member 52.

  Light emitted from the LD 201 disposed on one side of the base member 52 is emitted toward the droplet 300a as a laser light 200a parallel to the nozzle row 105a via the lens 211 and the aperture 212. The scattered light 301a generated when the laser beam 200a strikes the droplet 300a is received by the PD 203a disposed at a position separated from the laser beam 200a disposed on the other side of the base member 52, whereby the droplet 300a is ejected. It is designed to detect whether or not it has been done.

  At the same time, the laser beam 200a bent by the mirror 213a disposed on the other side of the base member 52 changes its direction, and the laser beam 200b bent by the mirror 213b is parallel to the nozzle row 105b. The laser beam 200c is emitted toward the droplet 300b.

  The scattered light 301b generated when the laser beam 200c strikes the droplet 300b is received by the PD 203b disposed at a position separated from the laser beam 200c disposed on one side of the base member 52, whereby the droplet 300b is ejected. It is designed to detect whether or not it has been done. In the above configuration, the end portion of the laser beam 200c is processed so as not to cause disturbance to the PD after passing through the LD / PD unit 206.

  According to the present embodiment, the forward scattered light is detected by the light receiving means, and it is not necessary to install the light receiving means in the optical path of the optical beam, so that the same plural traveling directions of the optical beam emitted from the light emitting means are provided. A light receiving means is arranged for each of the optical beams parallel to the nozzle rows and the optical beams parallel to the plurality of nozzle rows opposite to the traveling direction of the optical beams emitted from the light emitting means. It becomes possible to measure.

  In addition, according to the present embodiment, with the above configuration, the distance between the nozzle rows D1 is small, and therefore the optical system is wider than the width of the laser beam to be projected, and the optical system cannot be arranged side by side. It is possible to adopt a configuration in which ejection detection is performed in the same manner as in the state where the optical system is arranged for each nozzle row without increasing the laser beam width W1 to be emitted.

102 Nozzle 105 Nozzle Row 200 Laser Light 201 Laser Diode 203 Photodiode 205 PD / Mirror Unit 206 LD / PD Unit 211 Lens 212 Aperture 213 Mirror 300 Droplet 301 Scattered Light

JP 2008-194825 A JP 2011-37201 A

Claims (6)

A light emitting means for generating an optical beam;
Light adjusting means for adjusting the intensity distribution and divergence or convergence state of the optical beam emitted by the light emitting means;
Light receiving means for irradiating the optical beam parallel to the plurality of nozzle rows so as to intersect with the trajectory of the ink droplet ejected from the nozzle, and detecting scattered light generated when the optical beam hits the ink droplet; A droplet discharge detection device comprising:
By sequentially bending the optical beam, a plurality of optical paths for forming the plurality of optical beams including a single head or a plurality of optical paths of the optical beam parallel to a plurality of nozzle arrays composed of the plurality of heads are formed. Providing light reflecting means,
The light receiving means is disposed downstream of the plurality of nozzle row end portions farthest from the light emitting means position for the same optical beam as the traveling direction of the optical beam emitted from the light emitting means, The optical beam that is opposite to the traveling direction of the optical beam emitted from the light emitting means is arranged on the downstream side of the end of the plurality of nozzle rows that is closest to the light emitting means position. A droplet discharge detection device characterized by the above.   2. The droplet discharge detection device according to claim 1, wherein the light receiving means is installed at a position away from the optical path of the optical beam.   The droplet discharge detection device according to claim 1, wherein the light emitting means is a laser diode.   The droplet discharge detection device according to claim 1, wherein the light adjustment unit includes a collimator lens and an aperture.   5. The droplet discharge detection device according to claim 1, wherein the light receiving means is a photodiode.   An image forming apparatus comprising the droplet discharge detection device according to claim 1.

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