JP7302212B2 - EJECTION STATE DETECTION DEVICE, EJECTION STATE DETECTION METHOD, AND INKJET RECORDING APPARATUS - Google Patents

Description

The present invention relates to an ejection state detection device, an ejection state detection method, and an inkjet recording apparatus.

2. Description of the Related Art In an inkjet recording apparatus, an image is formed on a recording medium by ejecting ink onto a recording medium from a plurality of nozzles arranged in an inkjet head. In this inkjet recording apparatus, nozzle clogging and failure of the ejection mechanism (ink ejection failure) may occur.

Such clogging of the nozzles and failure of the ejection mechanism cause blurring and unevenness in the image, thus degrading the image quality. In order to detect ink ejection failures, the inkjet recording apparatus is capable of distinguishing between the recording medium and the colored inks, for example, based on the read density difference between the recording medium and the colored inks (CMYK inks). Image reading sensor (inline sensor) is installed.

Further, for example, in Patent Document 1, colored ink is ejected onto a blank sheet of paper, and an inspection pattern of white ink is ejected onto the colored ink. A technique for detecting the ejection failure of the ink is disclosed.

JP 2010-125605 A

However, with the above-described image reading sensor, for example, when white ink is applied to a blank sheet of paper, it is difficult to produce a reading density difference between the blank sheet and the white ink, making it difficult to distinguish between the blank sheet and the white ink. There was a problem.

Further, in the technique described in Patent Document 1, it is necessary to apply colored ink as a base to white paper in order to detect ejection failures of white ink, so there is a problem that the consumption of colored ink increases. be.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ejection state detection device, an ejection state detection method, and an inkjet printing apparatus capable of accurately discriminating ink from a printing medium without increasing ink consumption.

In order to achieve the above object, the ejection state detection device of the present invention comprises:
Irradiation that irradiates a recording medium onto which ink that absorbs light in a short wavelength region, which is a wavelength region shorter than the wavelength in the visible light region, is ejected from the ejection unit with the light in the short wavelength region as irradiation light. Department and
a light-receiving unit that has a higher sensitivity to light with a wavelength in the short wavelength range than light with a wavelength in the visible light range and that receives light based on the irradiation light that has passed through the recording medium;
a detection unit that detects an ink ejection state of the ejection unit based on the intensity of the received light;
with
The intensity of the light received by the light receiving unit is the intensity of each light received by the light receiving unit when the irradiation light is applied to each of a plurality of locations provided along the conveying direction of the recording medium. is the average value of

The ejection state detection method according to the present invention includes:
For each of the plurality of locations provided along the conveying direction of the recording medium onto which the ink that absorbs light in the short wavelength region, which is a wavelength region shorter than the wavelength in the visible light region, is ejected from the ejection unit, irradiating light with a wavelength in the wavelength range as irradiation light,
Sensitivity to light with a wavelength in the short wavelength range is higher than light with a wavelength in the visible light range, and each light is received through each of the plurality of locations based on the irradiation light,
The ink ejection state of the ejection section is detected based on the average value of the intensity of each light received.

The inkjet recording apparatus of the present invention includes
The ejection state detection device and the ejection section are provided.

According to the present invention, it is possible to accurately discriminate between the recording medium and the ink without increasing the amount of ink consumed.

1 is a diagram showing a schematic configuration of an inkjet recording apparatus according to an embodiment of the invention; FIG. 1 is a block diagram showing the main functional configuration of an inkjet printing apparatus according to an embodiment of the invention; FIG. FIG. 3 is a diagram showing spectral reflectance of a recording medium and spectral reflectance of white ink; 6 is a flowchart showing an example of ejection state detection processing;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an inkjet recording apparatus 1 according to this embodiment. The inkjet recording apparatus 1 includes a paper feed section 10, an image recording section 20, a paper discharge section 30, and a control section 40 (see FIG. 2).

In the inkjet recording apparatus 1, under the control of the control unit 40, the recording medium P stored in the paper feeding unit 10 is conveyed to the image recording unit 20, and the image recording unit 20 records an image on the recording medium P, thereby printing the image. The recorded recording medium P is conveyed to the paper discharge section 30 . As the recording medium P, in addition to paper such as plain paper and coated paper, it is possible to use various media such as cloth or sheet-like resin, on which ink that has landed on the surface can be fixed.

The paper feed unit 10 has a paper feed tray 11 that stores the recording medium P, and a medium supply unit 12 that conveys and supplies the recording medium P from the paper feed tray 11 to the image recording unit 20 . The medium supply unit 12 includes a ring-shaped belt whose inner side is supported by two rollers, and the recording medium P is fed from the paper feed tray 11 by rotating the rollers while the recording medium P is placed on the belt. It is conveyed to the image recording section 20 .

The image recording section 20 has a conveying drum 21 , a transfer unit 22 , a heating section 23 , a head unit 24 , a fixing section 25 and a delivery section 26 .

The conveying drum 21 rotates around a rotating shaft extending in a direction perpendicular to the drawing of FIG. , the recording medium P is conveyed in the conveying direction along the conveying surface. The conveying drum 21 has claws and suction units (not shown) for holding the recording medium P on its conveying surface. The recording medium P is held on the conveying surface by having its end portion pressed by the claw portion and by being attracted to the conveying surface by the suction portion. The transport drum 21 has a transport drum motor (not shown) for rotating the transport drum 21, and rotates by an angle proportional to the amount of rotation of the transport drum motor.

The delivery unit 22 delivers the recording medium P conveyed by the medium supply section 12 of the paper supply section 10 to the conveyance drum 21 . The delivery unit 22 is provided at a position between the medium supply section 12 of the paper supply section 10 and the transport drum 21 , and holds one end of the recording medium P transported from the medium supply section 12 with the swing arm section 221 and picks it up. , to the transfer drum 21 via the delivery drum 222 .

The heating unit 23 is provided between the placement position of the transfer drum 222 and the placement position of the head unit 24, and heats the transport drum 21 so that the temperature of the recording medium P transported by the transport drum 21 falls within a predetermined temperature range. and the recording medium P are heated. The heating unit 23 has, for example, an infrared heater or the like, and energizes the infrared heater based on a control signal supplied from the control unit 40 (see FIG. 2) to cause the infrared heater to generate heat.

The head unit 24 ejects the ink onto the recording medium P from nozzle openings provided on the ink ejection surface facing the conveying surface of the conveying drum 21 at appropriate timing according to the rotation of the conveying drum 21 holding the recording medium P. An image is recorded by ejecting ink. The head unit 24 is arranged such that the ink ejection surface and the transport surface are separated by a predetermined distance.

In the inkjet recording apparatus 1 according to the present embodiment, five head units 24 corresponding to five color inks of white (W), yellow (Y), magenta (M), cyan (C), and black (K) are provided. The colors W, Y, M, C, and K are arranged at predetermined intervals in order from the upstream side in the conveying direction of the recording medium P. As shown in FIG.

Each head unit 24 includes a recording head 242 (see FIG. 2, corresponding to the "ejection section" of the present invention). The print head 242 is provided with a plurality of print elements each having a pressure chamber for storing ink, a piezoelectric element provided on the wall surface of the pressure chamber, and a nozzle. When a driving signal for deforming the piezoelectric element is input to the recording element, the pressure chamber is deformed by the deformation of the piezoelectric element, the pressure in the pressure chamber is changed, and ink is ejected from a nozzle communicating with the pressure chamber.

The arrangement range in the orthogonal direction of the nozzles included in the recording head 242 covers the width in the orthogonal direction of the area on which the image is recorded on the recording medium P transported by the transport drum 21 . The head unit 24 is used with its position fixed with respect to the rotating shaft of the conveying drum 21 when recording an image. That is, the inkjet recording apparatus 1 is a single-pass type inkjet recording apparatus.

As the ink ejected from the recording head 242, an ink having a property of changing phase to gel or sol depending on temperature and being cured by irradiation with energy rays such as ultraviolet rays is used. Further, in the present embodiment, an ink is used which is gel at room temperature and becomes sol when heated. The head unit 24 includes an ink heating section (not shown) that heats ink stored in the head unit 24 . The ink heating section operates under the control of the control section 40, and heats the ink to a sol-like temperature. The head unit 24 ejects ink that has been heated and turned into a sol. When this sol-like ink is ejected onto the recording medium P, after the ink droplets land on the recording medium P, the ink quickly turns into gel and solidifies on the recording medium P due to natural cooling.

The fixing section 25 has a light emitting section arranged across the width of the conveying drum 21 in the orthogonal direction. The fixing unit 25 irradiates the recording medium P placed on the conveying drum 21 with energy rays such as ultraviolet rays from the light emitting unit, thereby imparting predetermined energy to the ink ejected onto the recording medium P. , thereby curing and fixing the ink. The light emitting section of the fixing section 25 is arranged to face the conveying surface of the conveying drum 21 between the arrangement position of the recording head 242 and the arrangement position of the transfer drum 261 (delivery section 26) in the conveying direction.

The delivery unit 26 has a belt loop 262 having a ring-shaped belt whose inner side is supported by two rollers, and a cylindrical delivery drum 261 that delivers the recording medium P from the transport drum 21 to the belt loop 262. The recording medium P transferred from the conveying drum 21 onto the belt loop 262 by the transfer drum 261 is conveyed by the belt loop 262 and delivered to the paper discharging section 30 .

The paper ejection section 30 has a plate-shaped paper ejection tray 31 on which the recording medium P delivered from the image recording section 20 by the delivery section 26 is placed.

FIG. 2 is a block diagram showing the main functional configuration of the inkjet recording apparatus 1. As shown in FIG. The inkjet recording apparatus 1 includes a heating unit 23, a recording head driving unit 241 and a recording head 242 included in the head unit 24, a fixing unit 25, a detection unit 27A, a control unit 40, a transport driving unit 51, an input/output and an interface 52 .

Under the control of the control unit 40, the recording head driving unit 241 supplies drive signals to the recording elements of the recording head 242 at appropriate timings to deform the piezoelectric elements according to the image data. The amount of ink corresponding to the pixel value of the image data is ejected from the nozzles.

The control unit 40 has a CPU 41 (Central Processing Unit), a RAM 42 (Random Access Memory), a ROM 43 (Read Only Memory) and a storage unit 44 .

The CPU 41 reads various control programs and setting data stored in the ROM 43, stores them in the RAM 42, and executes the programs to perform various arithmetic processing. Further, the CPU 41 centrally controls the overall operation of the inkjet recording apparatus 1 .

The RAM 42 provides working memory space to the CPU 41 and stores temporary data. Note that the RAM 42 may include a nonvolatile memory.

The ROM 43 stores programs for various controls executed by the CPU 41, setting data, and the like. Instead of the ROM 43, a rewritable non-volatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or flash memory may be used.

The storage unit 44 stores a print job (image recording command) input from the external device 2 via the input/output interface 52 and image data related to the print job. As the storage unit 44, for example, an HDD (Hard Disk Drive) is used, and a DRAM (Dynamic Random Access Memory) or the like may be used together.

The transport drive unit 51 supplies a drive signal to the transport drum motor of the transport drum 21 based on the control signal supplied from the control unit 40 to rotate the transport drum 21 at a predetermined speed and timing. In addition, the transport drive unit 51 supplies drive signals to motors for operating the medium supply unit 12, the delivery unit 22, and the delivery unit 26 based on control signals supplied from the control unit 40, thereby feeding the recording medium P. Supply to the transport drum 21 and discharge from the transport drum 21 are performed.

The input/output interface 52 mediates transmission and reception of data between the external device 2 and the control unit 40 . The input/output interface 52 is composed of, for example, various serial interfaces, various parallel interfaces, or a combination thereof.

The external device 2 is, for example, a personal computer, and supplies an image recording command (print job), image data, etc. to the control section 40 via the input/output interface 52 .

According to the above configuration, the recording medium P stored in the paper feeding section 10 is conveyed to the image recording section 20, and an image is recorded by the ink ejected from the nozzles in the image recording section 20. It is delivered to the paper ejection section 30 . However, ink may not be ejected to a predetermined area on the recording medium P due to nozzle clogging or failure of the ejection mechanism. Since nozzle clogging and the like cause deterioration in image quality, it is necessary to perform an inspection (nozzle missing inspection) as to whether or not ink is surely ejected from the nozzles.

Next, the missing nozzle inspection will be described. Here, a case where the recording medium P is a blank sheet and white ink is ejected onto the blank sheet will be described. The white ink contains a component (for example, titanium oxide) that absorbs light with a wavelength λ _sw in the short wavelength region, which is shorter than the wavelength λ _r in the visible light region. Here, the wavelength _λr in the visible light region is assumed to be 400 [nm] or more. Also, the wavelength λ _sw in the short wavelength region is set to 365 [nm] or more and less than 400 [nm]. An area where dots are recorded when the white ink ejected from the nozzle lands on the white paper is referred to as a ``landing portion''.

The missing nozzle inspection is performed by an ejection state detection device. The ejection state detection device according to the present embodiment includes a detection unit 27A and a control section 40. As shown in FIG. The detection unit 27A has an irradiation section 27 and a light receiving section 28 .

The irradiating section 27 and the light receiving section 28 are arranged to face the conveying surface of the conveying drum 21 between the arrangement position of the fixing section 25 and the arrangement position of the transfer drum 261 (delivery section 26) in the conveying direction.

The irradiation unit 27 operates under the control of the control unit 40 and irradiates the landing portion with irradiation light.

The irradiation unit 27 irradiates the landing portion with irradiation light having one wavelength in the wavelength λ _sw in the short wavelength region.

The light-receiving part 28 is arranged so as to be able to receive light through the landing part based on the irradiation light.

The light receiving section 28 has an optical sensor 281 that receives light ranging from the short wavelength range to the visible light range. For example, an in-line sensor is used as the optical sensor 281 . The in-line sensor is composed of image line sensors such as CCD and CMOS.

The light receiving section 28 operates the optical sensor 281 under the control of the control section 40 . As a result, the optical sensor 281 detects the intensity of the light that has passed through the landing portion based on the irradiation light in accordance with the timing at which the irradiation portion 27 irradiates the landing portion with the irradiation light.

In addition, when the irradiation unit 27 irradiates the landing portion with irradiation light of a predetermined wavelength and the optical sensor 281 detects the light of the predetermined wavelength, the intensity of the irradiated irradiation light of the predetermined wavelength and the detected predetermined wavelength The ratio of wavelength to light intensity is called "spectral reflectance."

There are cases where the white ink does not land on the white paper or the discharged white ink does not land on the predetermined landing portion due to the ejection failure of the white ink. The spectral reflectance when the white ink lands on the landing portion is the spectral reflectance of the white ink, which is the ratio between the intensity of the irradiation light applied to the white ink and the intensity of the received light. On the other hand, the spectral reflectance when white ink does not land on the landing area is the spectral reflectance of white paper, which is the ratio of the intensity of the irradiated light to the intensity of the light received on the white paper (background of the white paper). is. The spectral reflectance of white ink is different from the spectral reflectance of white paper. Therefore, based on the spectral reflectance, it is possible to determine whether or not there is an ejection failure of the white ink.

Next, the spectral reflectance of white paper and the spectral reflectance of white ink will be described with reference to FIG. FIG. 3 is a diagram showing the spectral reflectance of white paper and the spectral reflectance of white ink. In the following description, Maricoat and Invercoat (registered trademarks) manufactured by Hokuetsu Kishu Paper Co., Ltd. are used as examples of white paper. The horizontal axis of FIG. 3 indicates the wavelength [nm] of the light received by the light receiving section 28, and the vertical axis of FIG. 3 indicates the spectral reflectance [%]. In FIG. 3, the spectral reflectance of Maricoat is indicated by a solid line, the spectral reflectance of Invercoat is indicated by a one-dot chain line, and the spectral reflectance of white ink is indicated by a two-dot chain line. In FIG. 3, the dashed line indicates the difference between the spectral reflectances of Maricoat and white ink, and the dotted line indicates the difference between the spectral reflectances of Invercoat and white ink.

First, the difference (spectral reflectance difference) between the spectral reflectance of the maricoat and the spectral reflectance of the white ink indicated by the dashed line in FIG. 3 will be described. When the wavelength of the irradiation light is 380 [nm], the spectral reflectance difference is 18%. Moreover, when the wavelength of the irradiation light is 390 [nm], the spectral reflectance difference is 23%. Moreover, when the wavelength of the irradiation light is 400 [nm], the spectral reflectance difference is 32%. Also, when the wavelength of the irradiation light is 410 [nm], the spectral reflectance difference is 20%. On the other hand, when the wavelength range of the irradiation light is 420 [nm] or more and 470 [nm] or less, the spectral reflectance difference is 4% or less. From this, it can be seen that the spectral reflectance difference is relatively large when the wavelength range of the irradiation light is 380 [nm] or more and 410 [nm] or less.

Next, the difference (spectral reflectance difference) between the spectral reflectance of Invercoat and the spectral reflectance of white ink indicated by the dotted line in FIG. 3 will be described. When the wavelength of the irradiation light is 380 [nm], the spectral reflectance difference is 15%. Moreover, when the wavelength of the irradiation light is 390 [nm], the spectral reflectance difference is 12%. Also, when the wavelength of the irradiation light is 400 [nm], the spectral reflectance difference is 8%. Also, when the wavelength of the irradiation light is 410 [nm], the spectral reflectance difference is 2%. From this, it can be seen that the spectral reflectance difference is relatively large when the wavelength range of the irradiation light is 380 [nm] or more and less than 400 [nm].

What can be said in common from the above is that when the wavelength range of the irradiation light is a short wavelength range of 380 [nm] or more and less than 400 [nm], the spectral reflectance of white paper (Maricoat, Invercoat) and the spectral reflectance of white ink It can be seen that the difference from the reflectance is relatively large.

In the present embodiment, the irradiation unit 27 irradiates light having a predetermined wavelength (for example, ultraviolet light of 380 [nm]) in the wavelength λ _sw in the short wavelength region as irradiation light, and the optical sensor 281 emits light having a short wavelength. It receives light of wavelength λ _sw in the wavelength range. The control unit 40 calculates the spectral reflectance based on the intensity of the received light, and determines whether the spectral reflectance is the spectral reflectance of white ink or the spectral reflectance of white paper (background of white paper). It has a function as a detection unit that determines ejection failures of nozzles by discriminating .

By the way, when white ink containing a fluorescent dye is irradiated with light having a wavelength λ _sw in a short wavelength range, fluorescence emission occurs. Similarly, when white paper containing a fluorescent brightening agent is irradiated with light having a wavelength of λ _sw in the short wavelength region, fluorescence emission occurs. The wavelength range of light generated by fluorescence emission is 400 [nm] or more and 450 [nm] or less. On the other hand, it is possible to distinguish between the spectral reflectance of white paper and the spectral reflectance of white ink based on the spectral reflectance of the wavelength λ _sw in the short wavelength region. However, the optical sensor 281 detects not only the intensity of light with a wavelength λ _sw in the short wavelength region, but also the intensity of light with a wavelength λ _r in the visible light region. Therefore, the detection accuracy of the light intensity of the wavelength λ _sw in the short wavelength region is lowered. As a result, it becomes difficult to distinguish between the spectral reflectance of white paper and the spectral reflectance of white ink.

The light receiving section 28 in this embodiment has a bandpass filter 282 . The bandpass filter 282 is arranged between the conveying surface of the conveying drum 21 and the optical sensor 281 . The band-pass filter 282 transmits light of wavelength λ _sw in the short wavelength region and blocks light of wavelength λ _r (400 [nm] or more) in the visible light region. Thereby, the bandpass filter 282 blocks light of wavelength λ _f in the fluorescence emission region.

When the impact portion is irradiated with light of wavelength λ _sw in the short wavelength region to cause fluorescence emission, the band-pass filter 282 blocks light of wavelength λ _f in the fluorescence emission region. Since the optical sensor 281 detects light of the wavelength _λsw in the short wavelength region and does not detect light of the wavelength _λf in the fluorescence emission region, the detection accuracy of the light intensity of the wavelength _λsw in the short wavelength region is reduced. can be suppressed.

The optical sensor 281 detects the intensity of light with a wavelength λ _sw in the short wavelength range under the control of the controller 40 . The control unit 40 (detection unit) detects the ejection state of the white ink based on the detected intensity of the light having the wavelength λ _sw in the short wavelength region.

Specifically, the control unit 40 controls the intensity of the light with the wavelength λ _sw in the short wavelength region that is irradiated from the irradiation unit 27 to the landing portion, and the intensity of the light with the wavelength λ _sw in the short wavelength region that is detected by the optical sensor 281 . Spectral reflectance at a predetermined wavelength is calculated from the intensity. When the spectral reflectance of the predetermined wavelength is close to the spectral reflectance of the blank paper, the control unit 40 regards the spectral reflectance of the predetermined wavelength as the spectral reflectance of the blank paper, and determines that there is a white ink ejection failure. Further, when the spectral reflectance difference of the predetermined wavelength is close to the spectral reflectance of the white ink, the control unit 40 determines that the white ink is not defectively ejected by using the spectral reflectance of the predetermined wavelength as the spectral reflectance of the white ink. In other words, the white paper and the white ink are discriminated from the reading contrast difference between the white paper and the white ink due to the spectral reflectance.

More specifically, when the recording medium P is Maricoat, the control unit 40 determines the intensity of the ultraviolet light with a wavelength of 380 [nm] irradiated to the landing portion and the intensity of the ultraviolet light with a wavelength of 380 [nm] detected by the optical sensor 281. The spectral reflectance is calculated from the intensity of the ultraviolet light of the wavelength. If the spectral reflectance is closer to the spectral reflectance of the maricoat than that of the white ink, the control unit 40 regards it as the spectral reflectance of the white paper (see FIG. 3) and determines that there is a white ink ejection failure. Further, when the spectral reflectance difference is closer to the spectral reflectance of white ink than that of Maricoat, the control unit 40 determines that it is the spectral reflectance of white ink (see FIG. 3), and determines that there is no ejection failure of white ink. .

In addition, when the recording medium P is Invercoated, the control unit 40 controls the intensity of the ultraviolet light with a wavelength of 380 [nm] irradiated to the landing portion and the ultraviolet light with a wavelength of 380 [nm] detected by the optical sensor 281. The spectral reflectance is calculated from the intensity of light. When the spectral reflectance is closer to the spectral reflectance of Invercoat than that of white ink, the control unit 40 regards it as the spectral reflectance of white paper (see FIG. 3), and determines that there is a discharge failure of white ink. Further, when the light reflectance difference is closer to the spectral reflectance of white ink than that of Invercoat, the control unit 40 determines that it is the spectral reflectance of white ink (see FIG. 3), and determines that there is no ejection failure of white ink. do.

Next, the ejection state detection process will be described with reference to FIG. FIG. 4 is a flowchart showing an example of ejection state detection processing. Here, it is assumed that the irradiation unit 27 irradiates the landing portion with light having a wavelength λ _sw in a short wavelength region as irradiation light. In addition, the band-pass filter 282 cuts off light with a wavelength _λr in the visible light region (including the fluorescence emission region) among the light that has passed through the landing portion based on the irradiated light, and the optical sensor 281 cuts off light in the short wavelength region. Assume that light of wavelength λ _sw is received. This flow starts when a print job is executed.

First, in step S100, the control unit 40 (detection unit) acquires the intensity of light through the landing portion based on the irradiation light. The control unit 40 calculates the spectral reflectance of the predetermined wavelength based on the acquired light intensity.

Next, in step S110, the control unit 40 determines whether the spectral reflectance of the predetermined wavelength is close to the spectral reflectance of white ink or the spectral reflectance of white paper. If the spectral reflectance of the predetermined wavelength is close to the spectral reflectance of white ink (step S110: YES), the process transitions to step S120. If the spectral reflectance of the predetermined wavelength is not the spectral reflectance of white ink but is close to the spectral reflectance of white paper (step S110: NO), the process transitions to step S130.

In step S120, the controller 40 determines that there is no ejection failure of the white ink. After that, the processing shown in FIG. 4 ends.

In step S130, the controller 40 determines that there is a white ink ejection failure. After that, the processing shown in FIG. 4 ends.

According to the ejection state detection device in the above embodiment, the irradiation unit 27 irradiates the white paper on which the white ink that absorbs ultraviolet light of a predetermined wavelength is ejected from the recording head 242 with ultraviolet light as irradiation light, and the visible light. The light receiving unit 28, which has a higher sensitivity to light with a wavelength in the ultraviolet region than light with a wavelength _λr in the light region, receives light based on the irradiation light through a white paper, and the intensity of the received light is used for recording. and a control unit 40 that detects the ejection state of the white ink from the head 242 . As a result, since it is not necessary to apply colored ink as a base, it is possible to accurately detect blank paper and white ink without increasing the consumption of colored ink. As a result, it becomes possible to determine the ejection failure of the white ink.

Further, according to the ejection state detection device of the above-described embodiment, when white ink ejected from the recording head 242 is irradiated with ultraviolet light to cause fluorescence emission, the band-pass filter 282 becomes visible. Blocks light of wavelength _λr in the optical region. As a result, the optical sensor 281 does not detect the light generated by the fluorescence emission action, so that the influence of the fluorescence emission action on the intensity of the light received by the light receiving section 28 can be reduced. As a result, it is possible to suppress deterioration in detection accuracy of the ejection state of the white ink.

In addition, the above-described embodiments are merely examples of specific implementations of the present invention, and the technical scope of the present invention should not be construed to be limited by these. Thus, the invention may be embodied in various forms without departing from its spirit or essential characteristics.

For example, in the above-described embodiments, the detection of the ink ejection state is performed based on the intensity of the light that passes through one landing portion based on the irradiation light, but the present invention is not limited to this. Alternatively, the determination may be performed based on the average value of the intensity of light passing through the section. Note that the plurality of landing portions may be provided along the conveying direction of the recording medium P, for example. Since the SN ratio can be increased by averaging the light intensity, the detection accuracy of the ink ejection state can be increased.

Further, for example, in the above-described embodiment, the discharge state is detected for white ink. Any ink may be used as long as it causes a rate difference. For example, transparent ink may be used.

Further, for example, in the above-described embodiment, a second irradiating section that irradiates light of wavelength _λr in the visible light region onto the landing sections of the colored inks of yellow, magenta, cyan, and black may be provided. The control unit 40 controls so that the landing portion of the white ink is irradiated with light having a wavelength λ _sw in the short wavelength region, and the landing portion of the colored ink is irradiated with light having a wavelength λ _r in the visible light region. , the irradiation unit 27 and the second irradiation unit are controlled in a time division manner. As a result, for example, with one in-line sensor, it is possible to distinguish between the spectral reflectance of white paper and the spectral reflectance of white ink, and to distinguish between the spectral reflectance of colored paper and the spectral reflectance of colored ink. can be determined.

Further, in the above-described embodiment, the irradiation light irradiated to the landing portion is ultraviolet light, but the present invention is not limited to this, and any light that absorbs the component (for example, titanium oxide) contained in the white ink can be used. Well, it may be light with a wavelength λ _sw in the short wavelength range, such as 390 [nm].

Further, in the above embodiment, the bandpass filter 282 blocks the wavelength _λr in the visible light region, but the present invention is not limited to this. For example, any material may be used as long as it blocks light of wavelength _λf in the fluorescence emission region. As a result, the influence of the fluorescent emission action on the intensity of the light received by the light receiving section 28 can be reduced.

Reference Signs List 1 inkjet recording device 2 external device 10 paper feeding section 11 paper feeding tray 12 medium feeding section 20 image recording section 21 conveying drum 22 delivery unit 23 heating section 24 head unit 25 fixing section 26 delivery section 27A detection unit 27 irradiation section 28 light receiving section 30 paper discharge unit 40 control unit 242 recording head 281 optical sensor 282 bandpass filter

Claims (8)

Irradiation that irradiates a recording medium onto which ink that absorbs light in a short wavelength region, which is a wavelength region shorter than the wavelength in the visible light region, is ejected from the ejection unit with the light in the short wavelength region as irradiation light. Department and
a light-receiving unit that has a higher sensitivity to light with a wavelength in the short wavelength range than light with a wavelength in the visible light range and that receives light based on the irradiation light that has passed through the recording medium;
a detection unit that detects an ink ejection state of the ejection unit based on the intensity of the received light;
with
The intensity of the light received by the light receiving unit is the intensity of each light received by the light receiving unit when the irradiation light is applied to each of a plurality of locations provided along the conveying direction of the recording medium. , which is the average value of the discharge state detector. The light receiving unit is
an optical sensor that detects light with wavelengths ranging from the short wavelength range to the visible light range;
a band-pass filter disposed between the recording medium and the optical sensor, which transmits light of wavelengths in the short wavelength range and blocks light of wavelengths in the visible light range;
The ejection state detection device according to claim 1, comprising: The bandpass filter blocks light of wavelengths in at least the fluorescence emission region in the visible light region,
The ejection state detection device according to claim 2. The ink is white ink,
The ejection state detection device according to any one of claims 1 to 3. a second irradiating unit that irradiates a recording medium on which colored ink is to be ejected with light having a wavelength in the visible light region;
The irradiation unit is controlled so as to irradiate the recording medium onto which the white ink is ejected with the light of the wavelength in the short wavelength region, and the recording medium onto which the colored ink is ejected is irradiated with the light of the wavelength in the visible light region. A control unit that controls the second irradiation unit to irradiate light,
The ejection state detection device according to any one of claims 1 to 4 . The control unit controls the irradiation unit and the second irradiation unit in a time-sharing manner,
The ejection state detection device according to claim 5 . For each of the plurality of locations provided along the conveying direction of the recording medium onto which the ink that absorbs light in the short wavelength region, which is a wavelength region shorter than the wavelength in the visible light region, is ejected from the ejection unit, irradiating light with a wavelength in the wavelength range as irradiation light,
Sensitivity to light with a wavelength in the short wavelength range is higher than light with a wavelength in the visible light range, and each light is received through each of the plurality of locations based on the irradiation light,
detecting the ejection state of the ink by the ejection unit based on the average value of the intensity of each light received;
Discharge state detection method. An inkjet recording apparatus comprising the ejection state detection device according to claim 1 and the ejection section.

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