JP5724320B2 - Droplet detection apparatus and ink jet recording apparatus - Google Patents

Description

  The present invention relates to a droplet detection apparatus and an ink jet recording apparatus, and more particularly to an apparatus for detecting a droplet discharge defect.

  As is well known, ink jet recording by a liquid discharge recording method using a recording head that discharges ink droplets in one of image forming apparatuses such as a printer, a facsimile machine, a copying machine, a plotter, or a multifunction machine having these functions. There is a device.

  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 device is equipped with a large number of thermal and piezo ink jet heads for high-speed driving in the case of equipment-type ink jet 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 easy to dry when stopped, and the nozzle surface gets wet with ink, and dust such as paper dust tends to adhere to the nozzle surface. The problem is that air may enter from the nozzles, resulting in non-ejection, bending of the ejection direction, and small droplet size, resulting in ink droplet ejection failure and dot in the image. There was a problem that image quality deteriorated due to missing or white streaks.

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 the position where the detection mechanism for detecting the charge is disposed. 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.

  Therefore, as a configuration that does not require the detection mechanism to be driven, a droplet such as an ink droplet ejected from a nozzle on the head surface collides with the light beam emitted from the light emitting element to generate scattered light, and the scattered light is generated by the light receiving element. There has been proposed a droplet discharge detection device having a configuration for receiving light and optically detecting a droplet discharge defect from the received light data (for example, Patent Document 1).

  As disclosed in Patent Document 1, in a configuration in which a droplet discharge defect due to scattered light is detected for a configuration in which a large number of inkjet heads used in a line-type image forming apparatus using a line-type head are arranged, A light receiving unit such as a photodiode is disposed at a position off the emission optical path of the ejected ink droplet, and the ejection failure is judged by the light reception state of the forward scattered light obtained from the emitted light impinging on the ink droplet. It has become. 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.

  An object of the present invention is to provide an ink droplet detection device and an ink jet recording apparatus having a configuration capable of shortening the time required for detecting the ejection state of ink droplets in view of the problems in the conventional droplet detection device. There is to do.

In order to achieve the above object, the present invention comprises the following arrangement.
(1) Ink liquid for nozzle heads in which a plurality of nozzles arranged in parallel are arranged in a staggered manner in which the nozzle rows are arranged in parallel and at right angles to the juxtaposition direction along the juxtaposition direction. In a device for detecting a droplet ejection failure,
A light emitting source using a laser or an LED, a lens for converging light emitted from the light source, an aperture disposed on the light exit side of the lens to remove excess light from the light converged by the lens, and A photodiode that receives forward scattered light generated when the emitted light hits an ink droplet ejected from a nozzle disposed in a direction perpendicular to the direction of light emission from the light emitting source;
The light emitting sources are provided on both sides in the emission direction of the emitted light in the one nozzle row, and the photodiodes are arranged at positions facing each other across the optical path of the emitted light at equal positions in the emission direction of the emitted light. And receiving the forward scattered light generated for each array with light emitted from one side of the light emitting source as a target.

(2) When the nozzle rows in which the plurality of nozzles are juxtaposed are two rows in a direction perpendicular to the nozzle juxtaposition direction, each light emitting source is targeted for one of the plurality of nozzles arranged in each nozzle row. The focus is adjusted so that the convergent light from the light passes through the center of the nozzle row arranged on one side of the two rows and is irradiated only with light from one of the light sources on both sides. (1) The droplet detection apparatus according to (1).

(3) When the number of nozzle rows in which the plurality of nozzles are juxtaposed is two in a direction perpendicular to the direction in which the nozzles are juxtaposed , each light emitting source is targeted for one of the plurality of nozzles arranged in each nozzle row The focus is adjusted so that the convergent light from the light passes through the center of the nozzle row arranged on one side of the two rows and is irradiated only with light from one of the light sources on both sides. (1) The droplet detection apparatus according to (1).

(4) A beam stopper capable of advancing and retreating with respect to the optical path of the irradiation light is provided between the head arrays, wherein one of (1) to (3) is provided. Droplet detection device.

(5) The droplet detecting device according to (4), wherein the beam stopper advances into the optical path of the irradiation light only when detecting the droplet.

(6) By irradiating two nozzles of the head array for each convergent light from each light emitting source, two ink droplets are simultaneously detected for each arranged head array. (1) The droplet detection device according to one of (3).

(7) When ink droplets are detected for two nozzles in each of the arranged head arrays, forward scattered light generated in the two ink droplets is received by the light receiving unit, and the light receiving unit If the discharge state of the ink droplet is determined based on the output voltage of the nozzle and the output voltage is different based on the tendency of the output voltage, it is confirmed that one of the two nozzles has a change in the discharge state. (6) The droplet detection device according to (6), wherein the droplet detection device is detected.

(8) An ink jet recording apparatus using the droplet detection device according to any one of (1) to (7).

  According to the present invention, the light emission sources that emit the light emitted to the ink droplets are provided on both sides in the emission direction, and the detection lights emitted from the respective light emission sources are simultaneously irradiated on each side of the arranged nozzle rows. Therefore, it is possible to collectively detect the droplet discharge state at a plurality of locations. As a result, the time required for detection can be shortened by performing detection for a plurality of nozzles.

It is a schematic diagram for demonstrating an example of the inkjet recording device provided with the droplet detection apparatus by this invention. FIG. 2 is a schematic view of the ink jet recording apparatus illustrated in FIG. 1 in plan view. It is a schematic diagram for demonstrating operation | movement of the inkjet recording device shown in FIG. It is a figure for demonstrating the arrangement | sequence of the nozzle head used for the inkjet recording device shown in FIG. FIG. 5 is a view corresponding to FIG. 4 for explaining a main configuration of a droplet detection device according to the present invention. It is a schematic diagram for demonstrating a droplet detection principle. It is a figure for demonstrating the structure of the unit provided with the light emission source used for the droplet detection apparatus by this invention. It is a figure for demonstrating the structure of the unit provided with the light-receiving part used for the droplet detection apparatus by this invention. It is a figure for demonstrating the effect | action of the invention of Claim 1 and 2 using the structure shown in FIG. It is a figure for demonstrating the effect | action of the invention of Claim 3 using the structure shown in FIG. It is a figure for demonstrating the effect | action of the invention of Claim 4 and 5 using the structure shown in FIG. It is a figure for demonstrating the effect | action of the invention of Claim 6 using the structure shown in FIG. It is a figure for demonstrating the case where the effect | action shown in FIG. 12 is combined with the effect | action shown in FIG. It is a figure for demonstrating the effect | action of the invention of Claim 7. It is a figure for demonstrating the some modification of the effect | action shown in FIG. It is a figure for demonstrating the further another modification of a part of effect | action shown in FIG. 6 is a flowchart for explaining a detection procedure performed by the droplet detection device having the configuration shown in FIG. 5. It is a figure for demonstrating the effect | action at the time of the conventional droplet detection.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to embodiments shown in the drawings.
FIG. 1 is a diagram showing a configuration of an ink jet recording apparatus which is an example of an image forming apparatus using a droplet detecting apparatus according to the present invention. The structure will be described together with the operation as follows.

  In FIG. 1, an inkjet recording apparatus 1 is a line type that performs a droplet discharge operation by moving a paper P to be printed with respect to a fixed recording head during printing. A paper tray 2, a paper discharge tray 3 that discharges and stacks printed paper P, a transport unit 4 that transports the paper P from the paper feed tray 2 to the paper discharge tray 3, and a paper P that is transported by the transport unit 4 A head unit 5 that constitutes a recording head that discharges and prints droplets, a head maintenance device 6 that is a maintenance and recovery mechanism that performs maintenance and recovery of each recording head of the head unit 5 after printing is completed or at a required timing, and a head A cleaning device 7 for cleaning the cap member 61 and the wiper member (blade means not shown) of the maintenance device 6 is provided.

The ink jet recording apparatus 1 includes front and rear side plates and stays (not shown), and the paper P stacked on the paper feed tray 2 is fed to the transport unit 4 one by one by the separation roller 21 and the paper feed roller 22. Paper.
The transport unit 4 includes a transport drive roller 41A, a transport driven roller 41B, and an endless transport belt 43 wound around these rollers 41A and 41B. A plurality of suction holes (not shown) are formed on the surface of the transport belt 43, and a suction fan 44 that sucks the paper P is disposed below the transport belt 43. Further, conveyance guide rollers 42A and 42B are respectively held on guides (not shown) on the conveyance driving roller 41A and conveyance driven roller 41B and are in contact with the belt 43 by their own weight.
The conveyance belt 43 rotates around when the conveyance driving roller 41A is rotated by a motor (not shown), and the paper P is sucked onto the conveyance belt 43 by the suction fan 44 and is conveyed by the rotation movement of the conveyance belt 43. The transport driven roller 41 </ b> B and the transport guide rollers 42 </ b> A and 42 </ b> B rotate following the transport belt 43.

A head unit 5 composed of a head array unit that discharges droplets to be printed on the paper P is disposed above the transport unit 4 so as to be movable (here, moved up and down and movable in the left-right direction in the figure). During the maintenance and recovery operation (maintenance), the head unit 5 is lifted up to a height above the maintenance device 6 and then moved sideways up to the maintenance device 6. carry out.
FIG. 3 is a schematic diagram for explaining the movement path of the head unit 5 and the conveyance path of the paper P described above. In FIG. 3, the paper P serving as a print object is conveyed by the conveyance belt 43 and printed. The head unit 5 equipped with 101 is fixed during printing, and an image is formed by forming a matrix of ink droplets only by feeding the conveyor belt 43 and emitting the head unit 5.

As shown in FIG. 4B, which is a view as seen from the ejection surface side of the head array 101, the head section 5 includes head arrays 51 </ b> A to 51 </ b> F by a large number of head arrays 101 provided in the head array unit 50. A large number of head arrays 101 are also arranged in the paper width direction perpendicular to the paper feed direction corresponding to the up and down direction on the paper surface of FIG. 4B, and are arranged in nozzle rows (reference numerals 51K, 51M, 51C, 51Y, 51EP). (Shown) are connected.
As shown in FIG. 1, a suction fan is provided inside the rotation range of the transport belt 43, and the paper P is sucked by the transport belt 43 through holes formed in the transport belt 43 in the transport path shown in FIG. It is designed to be transported.
Note that the holes formed in the transport belt 43 are portions that are also used when the head 101 is dry-fired as a countermeasure against dryness. That is, when the thickened ink in the nozzle portion is discarded instead of image printing, when the paper P is not transported, for example, the transport belt 43 between the paper P to be punched and the succeeding paper P. When the surface of the ink is exposed, ink droplets are ejected at a timing when the position of the hole of the conveying belt matches the position of the nozzle, and the ejected ink droplet is discharged through the hole. .

In FIG. 1, a conveyance guide unit 45 that discharges the sheet P to the sheet discharge tray 3 is disposed on the downstream side in the conveyance direction of the sheet P with respect to the conveyance unit 4 (corresponding to the left side in FIG. 1). The paper P conveyed by the conveyance guide 45 is discharged to the paper discharge tray 3.
The paper discharge tray 3 includes a pair of side fences 31 that regulate the width direction of the paper P and an end fence 32 that regulates the front end of the paper P.

On the other hand, the above-described maintenance device 6 is provided on the side of the head unit 5 above the transport unit 4 and corresponds to each head row of the head array 101 shown in FIGS. ), A blade-like wiper member (wiper blade) (not shown) that wipes the nozzle surface corresponding to each head row of each head 101, and suction for cleaning the inside of the cap for one row by suction. A cleaning device 7 including means 63 is provided. In the maintenance device 6, the thickened ink is discharged from the nozzles 102 mounted on the head 101 by sucking with the suction means 63 on the cleaning device 7 side with the cap 61 sealing the nozzle surface of the head 101. The ejection performance of the head 101 is recovered. The wiper blade 62 is held by a blade holder 65.
Note that the suction means 63 and the flow path connecting the cap 61 and the suction means of the maintenance device 6 and other pressure chambers are arranged outside the rear side plate of the inkjet recording apparatus 1 and connected using a route such as a tube. You can also. Further, the inside of the head 101 may be pressurized by a pressurizing unit from the upstream side of the head 101 in place of or at the time of maintenance recovery.

The above-described maintenance device 6 is disposed above the transport unit 4 so as to be movable in the vertical direction with respect to the paper transport direction. During head maintenance, the head unit 5 is lifted and slid and moved above the maintenance device 6. The maintenance part at the lower part of the head part 5 rises and performs maintenance. During printing, the head 5 is moved to the position shown in FIG.
A cleaner device 7 for cleaning droplets (waste liquid) adhering to the cap 61 and the wiper blade 62 is disposed on the maintenance device 6.
The cleaner device 7 is arranged so as to be vertically movable with respect to the sheet conveying surface by a cleaner moving means (not shown).
When the maintenance of the head array 101 is completed, the maintenance device 6 moves downward, and the cleaner device 7 moves downward to clean the cap 61 and the wiper blade 62.

On the other hand, FIG. 4 shows the configuration of the head array unit 50 constituting the head unit 5, where (A) is a front view and (B) is a view as seen from the nozzle surface.
In the head array unit 50 constituting the head unit 5, a head in which a plurality of nozzles 102 are juxtaposed (for convenience, each head is collectively indicated by reference numeral 101) is in a direction parallel to and perpendicular to the juxtaposition direction of the nozzles 102. In the configuration shown in FIG. 4, six rows are arranged in a direction perpendicular to the juxtaposition direction, and each head 101 has a plurality of nozzles as described above, and in the configuration shown in FIG. Since it looks like a nozzle, it looks like a two-row nozzle in the figure.
Among the head rows, the head rows 51A and 51B having the nozzle row 51K are for ejecting black ink, and the eight nozzle rows constitute one nozzle row corresponding to the paper width, and other colors. The resolution is doubled than that of the nozzle.
With respect to nozzle rows for ejecting ink droplets for colors other than black, two nozzle rows (51M, 51C, 51Y) that eject ink droplets of the same color are used, and nozzles for one row corresponding to the paper width. A column is configured. That is, in FIG. 4, head rows 51 </ b> A to 51 </ b> F arranged in a row are configured by using six heads denoted by reference numeral 101 in FIG. 1.

  Each head row is provided with a plurality of parallel nozzles 102 as shown in FIG. Among these nozzles 102, the nozzle 51K (see FIG. 4) in the head row indicated by reference numerals 51A and 51B in FIG. 1 is used for black ink, and one nozzle in the head row indicated by reference numerals 51C and 51D in FIG. The column 51M (see FIG. 4) is for magenta and the other nozzle row 51C is for cyan. In FIG. 1, one nozzle row 51Y (see FIG. 4) of the head row indicated by reference numerals 51E and 51F is for yellow and the other nozzle row 51C is for the other. The nozzle row 51EP (see FIG. 4) is set as an alternative when there is a nozzle defect (a variety of alternative methods are not described here).

  In the head unit 5, branch members (not shown) that supply ink to the respective heads 101 of the head array unit 50 are arranged for each color, and a sub tank is arranged on the upstream side of the branch member, and due to a water head difference between the sub tank and the head. A negative pressure appropriate to hold the meniscus of the nozzle 102 of the head 101 is formed. Further, a replaceable main tank for storing ink is disposed on the upstream side of the sub tank.

The characteristics of the present invention will be described below with the above configuration as an object.
A feature of the present invention is that light emitting sources are provided on both sides of the nozzle array, and light receiving portions that receive forward scattered light generated by the irradiation light impinging on the droplets are arranged on both sides of the optical path of the irradiation light in both nozzle arrays. The point is that droplets at different locations can be detected simultaneously.

  Conventionally, droplet detection has been developed based on head drive (hereinafter referred to as carriage drive) in a direction perpendicular to the paper transport direction. After moving to a detection position outside the print range on the paper P by carriage drive, Detection is implemented. On the other hand, the ink jet recording apparatus 1 used as equipment is mainly a line ink jet head, and there is no carriage, and it is desirable to detect ink droplets without driving the head 101.

  In the case of a line ink jet recording apparatus, a head array in which a large number of nozzle rows 51 are arranged requires a large amount of time only by ink droplet detection. For this reason, it is necessary to omit other time (here, time required for driving the carriage). Therefore, it is desired to shorten the time required for detecting a droplet.

The present invention is intended to shorten the time required for detecting a droplet by providing the above-described characteristics based on the current situation.
The configuration of the droplet detection mechanism is as follows. For each of the plurality of nozzle arrays shown in FIGS. The photodiodes (hereinafter also referred to as PD for convenience) are alternately arranged. In such a configuration, it is the light emitting source (LD) and the light receiving unit (PD) unit that are divided into two on both sides of the head array that detect the liquid droplet ejection failure. The detection light is irradiated in accordance with the timing when the hole of the belt 43 faces the nozzle, and the forward scattered light generated when the irradiated light hits the liquid droplet is arranged at a position facing the light emitting part (LD). The detection is performed by the light receiving unit (PD).

  Based on such a configuration, the configuration of the droplet detection apparatus used in this embodiment will be described with reference to FIG. 5A is a view from the upstream side in the paper transport direction, FIG. 5B is a plan view of the head portion, and FIG. 5C is a view from a direction perpendicular to the paper transport direction. Each figure is shown.

As described above, in the head array unit 50, eight head rows 51A to 51F are arranged on the base member 52, and the adjacent head rows are arranged in a staggered manner with their positions shifted in the nozzle arrangement direction.
For each head row 51, an LD unit 202 that is a light emitting means including a laser diode (LD) 201 as a light emitting element that emits the laser light 200 along the nozzle arrangement direction, and scattered light of the laser light 200 generated by the liquid droplets. A PD unit 204 that is a light receiving means including a photodiode (PD) 203 that receives light is attached to the base member 52 and disposed. Each of the LD unit 202 and the PD unit 204 includes two LD 201 and PD 203 corresponding to each adjacent nozzle row of the four nozzle rows of one head row. In addition, the light emitting source may be an LED.

In FIG. 5B, between the head rows 51 adjacent in the vertical direction, the LD unit 202 and the PD unit 204 are arranged on the opposite sides. Specifically, for example, with respect to the head row 51A, the LD unit 202 is disposed on one end side, the PD unit 204 is disposed on the other end side, and the head row 51A is arranged adjacent to the head row 51A in a nozzle arrangement direction. For the matching head row 51B, the PD unit 204 is disposed on one end side, and the LD unit 202 is disposed on the other end side. The other head rows are also arranged in the same relationship.
That is, for example, when the head row 51A is the first head row and the head row 51B arranged with the head array 51 shifted in the nozzle arrangement direction is the second head row, the first head row and the second head row In between, the LD unit 202 and the PD unit 204 are arranged on the opposite side (in the opposite positional relationship).
Since the planar shape (viewed from above) is rectangular as the base member 52, the LD unit 202 is mounted on the side where the distance between the nozzle array direction end of the head row and the base member is short. The PD unit 203 is arranged on the side where the distance between the nozzle arrangement direction end of the row and the base member is long.

  By configuring in this way, the length of the head array unit 50 in the nozzle array direction can be shortened compared to a configuration in which the LD unit 202 and the PD unit 204 are arranged on the same side in each head row.

FIG. 6 is a diagram for explaining detection of scattered light ink droplets.
First, when ink droplet detection is performed by the scattered light method, the light emitted from the LD 202 is converged by the collimator lens 211 from the LD unit 202 arranged on one side and is extraneous through the aperture 212 as shown in FIG. As a laser beam 200 from which extra light has been removed, the laser beam 200 is emitted toward the droplet 300 ejected from the head 101.

The laser beam 200 receives scattered light generated when the laser beam 200 hits the droplet 300 by the PD 204 of the PD unit 204 arranged at a position separated from the optical axis of the laser beam 200 on the other side. Whether or not the droplet 300 is discharged is detected.
In this scattered light method, unless the PD 204 is arranged at a fixed distance from the optical axis of the laser beam 200, the laser beam 200 is directly received or affected.

  Therefore, in this embodiment, in order to secure this distance, the position of the PD 204 in the nozzle arrangement direction is separated from the nozzle (droplet discharge position) of the head 101 by a predetermined distance (reference numerals S, in FIG. 6). A position having a distance indicated by H). As a result, the PD unit used in the light receiving unit is arranged at equal positions along the emission direction of the emitted light from the LD unit and at opposite positions across the optical path of the emitted light.

The configurations of the LD unit and the PD unit used in this embodiment are as shown in FIGS.
As shown in FIG. 7, two laser diodes are built in one LD unit, and in FIG. 8, two photodiodes are built in one PD unit.
The semiconductor laser (LD) and photodiode (PD) mounted inside the unit are adjacent to the nozzle row in the head row (in the example shown in FIGS. There are two nozzle rows in the short distance, for a total of four rows.), And each laser beam path passes through the center of the adjacent nozzle row 51. Has been adjusted.

The LD unit 202 in FIG. 7 has a collimating lens 211 placed at a certain distance from the semiconductor laser (LD) 201 soldered to the substrate 221. This positional relationship is assembled with a jig and is adjusted for individual differences in the LD 201.
An aperture 212 is disposed on the opposite side of the collimating lens 211 from the LD 201. The aperture 212 is made of a thin plate having a thickness of about 1 mm, and has a hole in order to cut only an extra portion of the laser beam 200 and allow the laser beam 200 having a certain diameter to pass through. Is fixed at a certain interval.
Except for the exposed portion of the aperture 212, the substrate 211 on which the LD 201 is disposed covers the front and back so that extra mist generated when ink is ejected from the head 101 enters and does not impair the function of each component.

  The PD unit 204 shown in FIG. 8 is provided by soldering a photodiode (PD) 203 to the substrate 231. Except for the exposed portion of the photodiode (PD) 203, the substrate 231 is covered with front and back so that extra mist generated when ink is ejected from the head 101 enters and the function of each component is not impaired.

  The operation of the present embodiment will be described using the above configuration as follows. In FIG. 9 and subsequent figures, (A) is a diagram showing the arrangement of the head array and the droplet detection device in front view, and (B) is a diagram showing from the ejection surface side of the nozzle. Preface.

  FIG. 9 is a layout diagram of each member when the droplet detection apparatus 250 having the configuration shown in FIG. 5 is used. In FIG. 9, the laser irradiation light 200 emitted from the LD unit 202 is a collimating lens 211. The excess light is removed by the aperture 212 and irradiated onto the droplet. The irradiation light directed to the droplets at this time is light from both sides in the emission direction, and corresponds to droplets ejected from nozzle rows at different positions.

  The forward scattered light generated by the irradiation light hitting the droplet is targeted for the scattered light generated by irradiation of each LD unit 204 from one side, and the PD unit disposed at a relative position across the optical path of the irradiation light. Light is received by a photodiode, and a droplet discharge failure is determined based on the received light data. Thereby, it is possible to determine the discharge state from the nozzles at two locations at the same time.

By the way, as shown in FIG. 18, the irradiation light emitted from the LD unit is converged by the lens and does not target droplets from all the nozzles in the head row. In FIG. 18, only nozzles located in the left head row are targeted.
In this way, the state shown in FIG. 9 allows the discharge state to be determined for the nozzle located in the converged light by converging the emitted light. That is, by limiting the region that can be irradiated with convergent light and selecting a plurality of regions in the head row arrangement direction, it is possible to simultaneously determine the discharge state of nozzles for a plurality of nozzle rows.
This action corresponds to the action in the embodiment according to the first aspect of the invention.

  In addition, the beam waist position of the convergent light can be adjusted, so that the position of the liquid droplet is only on the light emission source (LD unit) on either side of the light emitted from the LD unit (in FIG. 9, the left-right direction on the paper surface). The emitted light is irradiated from the light emitting sources (LD units) at different positions at the same time so that the liquid droplets are irradiated or almost all the droplet positions are irradiated only by the light emitting sources (LD) on either side of the emitting direction. In this case, it is possible to prevent light interference when droplets are discharged at the same time.

Further, it is possible to adjust the focus so that the convergent light from the light source (LD unit) passes through the center of the nozzle array in the arrangement direction and is irradiated only from one side. That is, in FIG. 9, the light converging direction is defined. As shown in FIG. 9B, the light is divided into two nozzle rows of odd and even (two adjacent rows of the four nozzle rows of the head 101). 9B), in FIG. 9B, by adjusting the focal point so that it passes through the center between the nozzle row including the measurement slur and the parallel nozzle row, It is possible for the droplet to receive only the irradiation of the emitted light.
This action corresponds to the action according to the embodiment of the second aspect of the invention.

Next, the operation of the embodiment according to the third aspect of the present invention will be described with reference to FIG.
In the case where there are two nozzle rows, when the convergent light from the lens is in the same prescribed condition as in FIG. 9, the emitted light 100 from both LD units 202 is directed to one nozzle in the nozzle row. Each is irradiated so that the droplet receives only light from the LD unit 202 on one side.
As a result, by adjusting the focal point, individual droplets are irradiated from only one side of both LD units 202, and the ejection states at a plurality of nozzles are detected simultaneously.

Next, the operation of the embodiment according to the fourth and fifth aspects of the present invention will be described with reference to FIG.
In FIG. 11, a beam stopper 400 capable of moving back and forth with respect to the optical path of the irradiation light is provided between the heads 101 of the head array. The beam stopper 400 is configured to advance into the optical path only when a droplet is detected. By providing such a beam stopper 400, only the irradiation light 200 from the LD unit 202 on one side is arranged in one of the head rows arranged in plural without requiring the beam waist adjustment operation described in FIG. It is possible to irradiate the nozzle row without interfering with each other. According to such an operation, even when parallel light as well as convergent light is used, the irradiation light 200 of only the LD unit 202 from one side is different at the same time without causing interference with the irradiation light 200 from the other LD unit 202. Since the nozzle row of the head row can be irradiated, it is possible to detect the ejection state of the nozzles at different head rows at the same time.
Since the beam stopper 400 advances into the optical path of the irradiation light only when a droplet is detected, it can be stored in a position that does not interfere with the maintenance of the head.

Next, the operation of the embodiment according to the sixth and seventh aspects of the present invention will be described with reference to FIGS.
The embodiment shown in FIG. 12 is characterized in that two nozzles are irradiated for each converged light unlike the embodiment described above. That is, two nozzles can be detected simultaneously by the convergent light from the LD unit 202 on one side. When these two nozzles are detected at the same time, it is possible to determine the discharge state by determining whether or not there is a difference (gain difference) in the gain of the obtained detection data.
In this way, if a method of simultaneously detecting two nozzles in one head row is used, two nozzles can be detected together on each side as shown in FIG. 13, so in the case shown in FIG. In comparison, the detection time can be reduced by a factor of two.

In order to shorten the detection time, FIG. 14 shows two nozzles for each converged light, which are the contents described in FIG. 12, when detecting two nozzles simultaneously with the light emitted from the LD unit on one side. In the case of irradiation as a target, an example is shown in which the arrangement order of the nozzle rows to be irradiated is set to the opposite phase (indicated by round numerals on the measurement nozzle in FIG. 14).
As a result, in the PD unit that receives forward scattered light from the simultaneously irradiated droplets, for example, in the storage unit that stores output data from the PD unit, the nozzle position is addressed, so that an output corresponding to the address ( Take advantage of different gains. As a result, the time required for simultaneous detection of a plurality of slurs can be reduced without reducing the accuracy of determining the nozzles to be detected.

  Further, as a modification of the present embodiment, as shown in FIG. 15, a detection optical system including a light emitting source (LD) and a light receiving unit (PD) used in a droplet detecting device is targeted for each head row. In this way, by providing a plurality of stages and shifting the droplet discharge timing from the nozzles in each head row (the movement position after droplet discharge is different in FIG. 15A), nozzles only for individual head rows ( It is also possible to detect the discharge state of the droplets targeting the first and second measurement nozzles). According to this, it is possible to determine the droplet state independently in the head row without incurring interference between the detection light paths with respect to the nozzles in each head row. Further, as an application of the modified example shown in FIG. 15, as shown in FIG. 16, head arrays may be arranged in a staggered manner, and a detection optical system may be provided for each head.

The droplet detection as described above is executed based on the procedure shown in FIG.
17A and 17B, first, in FIG. 17A, when the power is turned on, the head unit including the head array unit is moved from the capping position by the maintenance device to the printing position, and the conveying belt is driven.

  After that, the operation of detecting the ink droplet ejection state is performed to determine whether or not the ink droplet is normally ejected. When the ink droplet is detected, the operation proceeds to the printing operation and the ink droplet is detected. If not, that is, if an ejection failure is detected, an idle ejection operation is performed to eject droplets that do not contribute to image formation. In this idle ejection operation, droplets are ejected toward the suction holes of the conveyor belt.

  After the idle ejection operation, the ink droplet ejection state detection operation is performed again to determine whether or not the ink droplet is detected. When the ink droplet is detected, the operation proceeds to the printing operation.

  On the other hand, unlike the case described above, when the ink droplet is not detected again, the conveying belt is stopped and the head unit including the head array unit is moved to the maintenance position by the maintenance device. Then, the maintenance and recovery operation is performed by the maintenance device, and after the maintenance and recovery operation until the predetermined number of times of the maintenance and recovery operation, the above-described processing is repeated, and the operation is performed when the ink droplets cannot be detected even after the predetermined number of times of the maintenance and recovery operation. Stop and display error, capping head and wait.

Next, processing relating to detection of a droplet discharge state after the end of printing will be described with reference to FIG.
In FIG. 17B, when printing is completed, an ink droplet discharge state detection operation is performed to determine whether ink droplets are detected (normal discharge), and ink droplets are detected. Sometimes the head moves to the capping position by the maintenance device and enters a standby state. When no ink droplets are detected (discharge failure is detected), an empty discharge operation is performed to discharge droplets that do not contribute to image formation. To do.

  After this idle ejection operation, the ink droplet ejection state detection operation is performed again to determine whether or not the ink droplet is detected. When the ink droplet is detected, the head is moved to the capping position by the maintenance device. And enter a standby state.

  On the other hand, when the ink droplet is not detected again, the head unit is moved to the maintenance position by the maintenance device. Then, the maintenance and recovery operation is performed by the maintenance device, and the above-described processing is repeated after the maintenance and recovery operation until the predetermined number of maintenance and recovery operations are performed. An error is displayed and the head is capped to enter a standby state.

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 5 Head part 51A-51F Head row | line | column 51K-51 Nozzle row | line | column 202 LD unit used as a light emission source 204 PD unit used as a light-receiving part 211 Collimator lens 212 Aperture

JP 2008-194825 A

Claims (8)

Ink droplet ejection for nozzle heads in which a plurality of nozzles are arranged side by side in a direction parallel to and perpendicular to the juxtaposition direction and shifted along the juxtaposition direction. In an apparatus for detecting defects,
A light emitting source using a laser or an LED, a lens for converging light emitted from the light source, an aperture disposed on the light exit side of the lens to remove excess light from the light converged by the lens, and A photodiode that receives forward scattered light generated when the emitted light hits an ink droplet ejected from a nozzle disposed in a direction perpendicular to the direction of light emission from the light emitting source;
The light emitting sources are provided on both sides in the emission direction of the emitted light in the one nozzle row, and the photodiodes are arranged at positions facing each other across the optical path of the emitted light at equal positions in the emission direction of the emitted light. And receiving the forward scattered light generated for each array with light emitted from one side of the light emitting source as a target. When there are two nozzle rows in which the plurality of nozzles are juxtaposed in a direction perpendicular to the juxtaposition direction of the nozzles, convergence from each light source is targeted for one of the plurality of nozzles arranged in each nozzle row. The focal point is adjusted so that light passes through the center of the nozzle row arranged on one side of the two rows and is irradiated only with light from the light source on one side of the light sources on both sides. The droplet detection device according to claim 1. When there are two nozzle rows in which the plurality of nozzles are juxtaposed in a direction perpendicular to the juxtaposition direction of the nozzles, convergence from each light source is targeted for one of the plurality of nozzles arranged in each nozzle row. The focal point is adjusted so that light passes through the center of the nozzle row arranged on one side of the two rows and is irradiated only with light from the light source on one side of the light sources on both sides. The droplet detection device according to claim 1.   4. The droplet detection device according to claim 1, wherein a beam stopper capable of advancing and retreating with respect to the optical path of the irradiation light is provided between the head arrays.   5. The droplet detection device according to claim 4, wherein the beam stopper advances into the optical path of the irradiation light only when the droplet is detected.   2. Two ink droplets are simultaneously detected for each head array arranged by irradiating two nozzles of the head array for each convergent light from each light emitting source. 4. The droplet detection device according to any one of 1 to 3.   When ink droplets are detected for two nozzles in each of the arranged head arrays, forward scattered light generated in the two ink droplets is received by the light receiving unit, and the output voltage at the light receiving unit If the output voltage is different based on the tendency of the output voltage based on the determination of the discharge state of the ink droplet, the change in the discharge state of any of the two nozzles is detected. The droplet detection device according to claim 6.   An ink jet recording apparatus using the droplet detection device according to claim 1.

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