阅读说明：本技术 排出状态检测装置、排出状态检测方法以及喷墨记录装置 (Discharge state detection device, discharge state detection method, and inkjet recording device ) 是由 稻叶康范 于 2020-03-16 设计创作，主要内容包括：本发明提供一种能够在不增加墨水消耗量的情况下精度良好地判别记录介质和墨水的排出状态检测装置、排出状态检测方法以及喷墨记录装置。本发明的排出状态检测装置包括：照射部,其相对于被从排出部排出了墨水的记录介质照射波长为比可见光区域短的短波长区域的波长的光作为照射光,该墨水吸收短波长区域的波长的光；受光部,其对短波长区域的波长的光的灵敏度比对可见光区域的波长的光高,接收基于照射光的经由记录介质的光；检测部,其基于接收到的光的强度,检测排出部对墨水的排出状态。(The invention provides a discharge state detection device, a discharge state detection method and an ink jet recording device, which can accurately judge a recording medium and ink without increasing ink consumption. The discharge state detection device of the present invention includes: an irradiation unit that irradiates, as irradiation light, light having a wavelength in a short wavelength region shorter than a visible light region with respect to a recording medium from which ink has been discharged by the discharge unit, the ink absorbing the light having the wavelength in the short wavelength region; a light receiving unit which has a higher sensitivity to light having a wavelength in a short wavelength region than light having a wavelength in a visible light region and receives light passing through a recording medium by irradiation light; and a detection unit that detects a discharge state of the ink by the discharge unit based on the intensity of the received light.)

1. A discharge state detection device is provided with:

an irradiation unit that irradiates, as irradiation light, light having a wavelength in a short wavelength region shorter than a visible light region with respect to a recording medium from which ink has been discharged by the discharge unit, the ink absorbing the light having the wavelength in the short wavelength region;

a light receiving unit which has a higher sensitivity to light having a wavelength in the short wavelength region than light having a wavelength in the visible light region and which receives light that has passed through the recording medium by the irradiation light;

and a detection unit that detects a discharge state of the ink by the discharge unit based on the intensity of the received light.

2. The discharge state detecting device according to claim 1,

the light receiving unit includes:

a light sensor that detects light having a wavelength from the short-wavelength region to the visible light region;

and a band-pass filter which is disposed between the recording medium and the optical sensor, and transmits light having a wavelength in the short wavelength region and blocks light having a wavelength in the visible light region.

3. The discharge state detecting device according to claim 2,

the band pass filter blocks light of a wavelength of at least a fluorescent light emitting region in the visible light region.

4. The discharge state detecting device according to any one of claims 1 to 3,

the intensity of the light received by the light receiving unit is an average value of the intensities of the lights received by the light receiving unit when the irradiation light is irradiated to each of a plurality of positions provided along the transport direction of the recording medium.

5. The discharge state detecting device according to any one of claims 1 to 4,

the ink is a white ink.

6. The discharge state detecting device according to any one of claims 1 to 4,

the ink is a transparent ink.

7. The discharge state detection device according to any one of claims 1 to 6, comprising:

a second irradiation unit that irradiates the recording medium from which the color ink is discharged with light having a wavelength in the visible light range;

and a control unit that controls the irradiation unit to irradiate the recording medium from which the white ink is discharged with light having a wavelength in the short wavelength region, and controls the second irradiation unit to irradiate the recording medium from which the color ink is discharged with light having a wavelength in the visible light region.

8. The discharge state detecting device according to claim 7,

the control unit controls the irradiation unit and the second irradiation unit in a time-sharing manner.

9. A discharge state detection method, wherein,

irradiating a recording medium from which ink is discharged from a discharge unit with light having a wavelength in a short wavelength region shorter than a visible light region as irradiation light, the ink absorbing the light having the wavelength in the short wavelength region,

receiving light passing through the recording medium based on the irradiation light, the light having a higher sensitivity to light having a wavelength in the short wavelength region than light having a wavelength in the visible light region,

detecting a discharge state of the ink by the discharge section based on the intensity of the received light.

10. The discharge state detecting method according to claim 9,

detecting light having a wavelength from the short-wavelength region to the visible light region;

and a light sensor for transmitting light having a wavelength in the short wavelength region and blocking light having a wavelength in the visible light region between the recording medium and the light sensor.

11. The discharge state detecting method according to claim 10,

and shielding light of at least the wavelength of the fluorescent light-emitting region in the visible light region.

12. The discharge state detecting method according to any one of claims 9 to 11,

the intensity of the received light is an average value of intensities of the received lights when the irradiation light is irradiated to each of a plurality of positions provided along a conveying direction of the recording medium.

13. The discharge state detecting method according to any one of claims 9 to 12,

the ink is white ink.

14. The discharge state detecting method according to any one of claims 9 to 12,

the ink is a transparent ink.

15. The discharge state detecting method according to any one of claims 9 to 14,

the recording medium from which the white ink is discharged is irradiated with light having a wavelength in the short wavelength region, and the recording medium from which the colored ink is discharged is irradiated with light having a wavelength in the visible light region.

16. An ink jet recording apparatus, comprising:

the discharge state detecting device according to any one of claims 1 to 8;

the discharge portion.

Technical Field

The invention relates to a discharge state detection device, a discharge state detection method, and an inkjet recording apparatus.

Background

In an inkjet recording apparatus, ink is discharged onto a recording medium from a plurality of nozzles arranged in an inkjet head, and an image is formed on the recording medium. In this inkjet recording apparatus, nozzle clogging or a failure of a discharge mechanism (defective discharge of ink) may occur.

Such clogging of the nozzle and failure of the discharge mechanism cause blurring and unevenness of an image, and thus the image quality is degraded. In order to detect an ink discharge failure, an inkjet recording apparatus is provided with an image reading sensor (built-in sensor) that can discriminate between a recording medium and color ink (CMYK ink) based on, for example, a difference in reading density between the recording medium and the color ink.

For example, patent document 1 discloses a technique of detecting a discharge failure of white ink by discharging colored ink onto white paper and discharging a white ink-based inspection pattern onto the colored ink so that the white ink is applied in a superimposed state onto the colored ink.

Patent document 1: japanese unexamined patent application publication No. 2010-125605

However, in the image reading sensor, for example, when white ink is applied to white paper, there is a problem that a difference in reading density between the white paper and the white ink is difficult to occur, and it is difficult to distinguish the white paper from the white ink.

In addition, in the technique described in patent document 1, in order to detect a discharge failure of white ink, it is necessary to coat white paper with color ink as a ground color, and therefore there is a problem that the amount of consumption of the color ink increases.

Disclosure of Invention

The invention aims to provide a discharge state detection device, a discharge state detection method and an ink jet recording device which can accurately distinguish a recording medium and ink without increasing the consumption of the ink.

In order to achieve the above object, a discharge state detection device according to the present invention includes:

an irradiation unit that irradiates, as irradiation light, light having a wavelength in a short wavelength region shorter than a visible light region with respect to a recording medium from which ink has been discharged by the discharge unit, the ink absorbing the light having the wavelength in the short wavelength region;

a light receiving unit which has a higher sensitivity to light having a wavelength in the short wavelength region than light having a wavelength in the visible light region and which receives light that has passed through the recording medium by the irradiation light;

and a detection unit that detects a discharge state of the ink by the discharge unit based on the intensity of the received light.

The discharge state detecting method of the present invention irradiates a recording medium, on which ink is discharged from a discharge unit, with light having a wavelength in a short wavelength region shorter than a visible light region as irradiation light, the ink absorbing the light having the wavelength in the short wavelength region,

receiving light passing through the recording medium based on the irradiation light, the light having a higher sensitivity to light having a wavelength in the short wavelength region than light having a wavelength in the visible light region,

detecting a discharge state of the ink by the discharge section based on the intensity of the received light.

The ink jet recording apparatus of the present invention includes the discharge state detecting device and the discharge unit.

According to the present invention, the recording medium and the ink can be discriminated with high accuracy without increasing the amount of ink consumed.

Drawings

FIG. 1 is a view showing a schematic configuration of an ink jet recording apparatus according to an embodiment of the present invention;

FIG. 2 is a block diagram showing the main functional configuration of an ink jet recording apparatus according to an embodiment of the present invention;

FIG. 3 is a graph showing the spectral reflectance of a recording medium and the spectral reflectance of white ink;

FIG. 4 is a flowchart showing an example of the discharge state detection process;

description of the marks

1: ink jet recording apparatus

2: external device

10: paper feeding part

11: paper feeding tray

12: medium supply unit

20: image storage unit

21: conveying roller

22: handover unit

23: heating part

24: head unit

25: fixing unit

26: delivery unit

27A: detection unit

27: irradiation part

28: light receiving part

30: paper discharging part

40: control unit

242: recording head

281: optical sensor

282: band-pass filter

Detailed Description

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 the present embodiment. The ink jet recording apparatus 1 includes a paper feed unit 10, an image recording unit 20, a paper discharge unit 30, and a control unit 40 (see fig. 2).

In the ink jet recording apparatus 1, the recording medium P stored in the paper feed unit 10 is conveyed to the image storage unit 20 under the control of the control unit 40, an image is recorded on the recording medium P in the image recording unit 20, and the recording medium P on which the image is recorded is conveyed to the paper discharge unit 30. As the recording medium P, various media capable of fixing ink dropped on the surface, such as cotton cloth or sheet-like resin, can be used in addition to plain paper and coated paper.

The paper feed unit 10 includes a paper feed tray 11 that stores a recording medium P, and a medium feed unit 12 that conveys the recording medium P from the paper feed tray 11 to the image storage unit 20 and feeds the recording medium P. The medium feeding unit 12 includes a wheel-shaped belt supported on the inside by two rollers, and conveys the recording medium P from the paper feed tray 11 to the image storage unit 20 by rotating the rollers while the recording medium P is placed on the belt.

The image storage section 20 includes a conveying roller 21, a delivery unit 22, a heating section 23, a head unit 24, a fixing section 25, and a delivery section 26.

The conveying roller 21 conveys the recording medium P in a conveying direction along a conveying surface by rotating about a rotation axis extending in a direction perpendicular to the drawing surface of fig. 1 (hereinafter referred to as an "orthogonal direction") while holding the recording medium P on a cylindrical outer peripheral curved surface (conveying surface). The conveying roller 21 has a claw portion and an air inlet portion, not shown, for holding the recording medium P on the conveying surface. The recording medium P is held by the conveyance surface by the claw portion pressing the end portion and by the suction portion sucking to the conveyance surface. The conveyance roller 21 has a conveyance roller motor, not shown, for rotating the conveyance roller 21, and rotates by an angle proportional to the amount of rotation of the conveyance roller motor.

The delivery unit 22 delivers the recording medium P conveyed by the medium supply unit 12 of the paper feed unit 10 to the conveying roller 21. The delivery unit 22 is provided at a position between the medium supply portion 12 of the paper feed portion 10 and the transport roller 21, and holds and lifts one end of the recording medium P transported from the medium supply portion 12 by the swing arm portion 221, and delivers the recording medium P to the transport roller 21 via the delivery roller 222.

The heating unit 23 is provided between the position where the delivery roller 222 is disposed and the position where the head unit 24 is disposed, and heats the conveyance surface of the conveyance roller 21 and the recording medium P so that the recording medium P conveyed by the conveyance roller 21 has a temperature within a predetermined temperature range. The heating unit 23 includes, for example, an infrared heater, and generates heat by energizing the infrared heater based on a control signal supplied from the control unit 40 (see fig. 2).

The head unit 24 discharges an ink recording image onto the recording medium P from nozzle openings provided on an ink discharge surface facing the conveyance surface of the conveyance roller 21 at an appropriate timing according to the rotation of the conveyance roller 21 held by the recording medium P. The head unit 24 is disposed so that the ink discharge surface and the conveyance surface are separated by a predetermined distance.

In the inkjet recording apparatus 1 of the present embodiment, five colors of white (W), yellow (Y), red (M), blue (C), and black (K) are arranged at predetermined intervals in order of wylck colors from the upstream side in the conveyance direction of the recording medium P.

Each head unit 24 includes a recording head 242 (see fig. 2, corresponding to the "discharge unit" of the present invention). The recording head 242 includes a plurality of recording elements each including a pressure chamber for storing ink, a piezoelectric element provided on a wall surface of the pressure chamber, and a nozzle. When a drive signal for deforming the piezoelectric element is input to the recording element, the pressure chamber is deformed in accordance with the deformation of the piezoelectric element to change the pressure in the pressure chamber, and ink is discharged from a nozzle communicating with the pressure chamber.

The nozzles included in the recording head 242 are arranged in a range orthogonal to the direction so as to cover the width of the area in the orthogonal direction in which the image is recorded in the recording medium P conveyed by the conveying roller 21. The head unit 24 is used at a fixed position with respect to the rotation axis of the conveying roller 21 when recording an image. That is, the inkjet recording apparatus 1 is a one-pass inkjet recording apparatus.

As the ink discharged from the recording head 242, an ink is used which undergoes a phase change in a gel or sol state depending on the temperature and is cured by irradiation with an energy ray such as ultraviolet light. In the present embodiment, an ink that is in a gel state at normal temperature and forms a sol state by heating is used. The head unit 24 includes an ink heating unit (not shown) that heats ink stored in the head unit 24. The ink heating unit operates under the control of the control unit 40 to heat the ink to a sol temperature. The head unit 24 discharges the ink in a gel state after heating. When such a solution-like ink is discharged onto the recording medium P, the ink is ejected onto the recording medium P, and then, the ink rapidly turns into a gel-like state and solidifies on the recording medium P due to natural cooling.

The fixing unit 25 includes a light emitting unit disposed across the width of the conveying roller 21 in the orthogonal direction. The fixing unit 25 applies a predetermined energy to the ink discharged onto the recording medium P by irradiating the recording medium P placed on the conveying roller 21 with an energy ray such as ultraviolet light from the light emitting unit, thereby curing and fixing the ink. The light emitting section of the fixing section 25 is disposed to face the conveying surface of the conveying roller 21 from the position where the recording head 242 is disposed in the conveying direction to the position where the delivery roller 261 (delivery section 26) is disposed.

The delivery unit 26 includes a belt 262 of a wheel-shaped belt supported by 2 rollers on the inside, and a cylindrical delivery roller 261 for delivering the recording medium P from the conveying roller 21 to the belt 262, and the recording medium P delivered from the conveying roller 21 to the belt 262 by the delivery roller 261 is conveyed by the belt 262 and delivered to the paper discharge unit 30.

The sheet discharging unit 30 includes a sheet-shaped sheet discharging tray 31 on which the recording medium P fed from the image storage unit 20 by the feeding unit 26 is placed.

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

The recording head driving unit 241 supplies a driving signal for deforming the piezoelectric element in accordance with the image data to the recording element of the recording head 242 at an appropriate timing based on the control of the control unit 40, and discharges an amount of ink corresponding to the pixel value of the image data from the nozzle of the recording head 242.

The control Unit 40 includes a CPU41(Central Processing Unit), a RAM42(random access Memory), a ROM43 (read only Memory), and a storage Unit 44.

The CPU41 reads various control programs and setting data stored in the ROM43, stores the programs in the RAM42, and executes the programs to perform various arithmetic operations. The CPU41 controls the overall operation of the inkjet recording apparatus 1.

The RAM42 provides the CPU41 with a storage space for jobs, storing temporary data. The RAM42 may also include nonvolatile memory.

The ROM43 stores programs for various controls executed by the CPU41, setting data, and the like. In place of the ROM43, a rewritable nonvolatile memory such as an eeprom (electrically Erasable Programmable Read Only memory) or a flash memory may be used.

The storage section 44 stores a print job (image storage command) input from the external apparatus 2 via the input/output interface 52 and image data relating to the print job. For example, hdd (hard disk drive) may be used as the storage unit 44, and dram (dynamic Random Access memory) may be used in combination.

The conveyance drive unit 51 supplies a drive signal to the conveyance roller motor of the conveyance roller 21 based on the control signal supplied from the control unit 40, and rotates the conveyance roller 21 at a predetermined speed and timing. The conveyance drive unit 51 supplies a drive signal to the motor for operating the medium supply unit 12, the delivery unit 22, and the delivery unit 26, based on the control signal supplied from the control unit 40, and supplies and discharges the recording medium P to and from the conveyance roller 21 and the conveyance roller 21.

The input/output interface 52 is used for data transmission and reception between the external device 2 and the control unit 40. The input/output interface 52 is constituted by, 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 storage command (print job), image data, and the like to the control section 40 via the input/output interface 52.

With the above configuration, the recording medium P stored in the paper feed unit 10 is conveyed to the image recording unit 20, and the image is recorded in the image recording unit 20 by the ink discharged from the nozzles, and is sent to the paper discharge unit 30 by the delivery unit 26. However, due to nozzle clogging and a failure of the discharge mechanism, ink may not be discharged to a predetermined area on the recording medium P. Since clogging of the nozzles causes a reduction in image quality, it is necessary to perform an inspection (nozzle defect inspection) as to whether or not ink is reliably discharged from the nozzles.

Next, the nozzle defect inspection will be described. Here, a case where the recording medium P is a white paper and white ink is discharged on the white paper will be described. The white ink contains a wavelength λ in the visible light region of the absorption ratio_rShort wavelength region, i.e. wavelength λ of short wavelength region_swOf (e.g., titanium oxide). Here, the wavelength λ in the visible light region_rAt 400[ nm ]]The above. In addition, the wavelength λ of the short wavelength region_swLess than 365[ nm ]]Or 400[ nm ]]. When the white ink discharged from the nozzles is dropped on the white paper, the region of the recording dots is referred to as a "drop portion".

The nozzle defect inspection is performed by the discharge state detection device. The discharge state detection device of the present embodiment includes a detection unit 27A and a control unit 40. The detection unit 27A includes an irradiation unit 27 and a light receiving unit 28.

The irradiation unit 27 and the light receiving unit 28 are disposed to face the conveying surface of the conveying roller 21 from the position where the fixing unit 25 is disposed to the position where the delivery roller 261 (delivery unit 26) is disposed in the conveying direction.

The irradiation unit 27 operates under the control of the control unit 40, and irradiates the irradiation light to the droplet landing unit.

The irradiation part 27 irradiates the dripping part with the wavelength lambda of the short wavelength region_swOf the light of one wavelength.

Light receiving unit 28 is configured to be able to receive light via a drop unit based on irradiation light.

The light receiving unit 28 has a photosensor 281, and the photosensor 281 receives light from a short wavelength region to a visible light region. The optical sensor 281 is, for example, an internal line sensor. The internal line sensor is formed of an image line sensor such as a CCD or a CMOS.

The light receiving unit 28 operates the light sensor 281 under the control of the control unit 40. Thus, the light sensor 281 detects the intensity of light passing through the drop portion based on the irradiation light in accordance with the timing when the irradiation light is irradiated from the irradiation portion 27 to the drop portion.

The irradiation unit 27 irradiates irradiation light of a predetermined wavelength to the dropping unit, and when the light sensor 281 detects light of a predetermined wavelength, a ratio of the intensity of the irradiated light of the predetermined wavelength to the intensity of the detected light of the predetermined wavelength is referred to as "spectral reflectance".

There are cases where black ink is not dropped on white paper or where white ink that has been discharged does not drop on a predetermined drop portion due to a discharge failure of white ink. The spectral reflectance of the white ink at the time of dropping at the dropping portion is a ratio of the intensity of the light irradiated to the white ink to the intensity of the light received, that is, the spectral reflectance of the white ink. On the other hand, the spectral reflectance when the white ink does not drop on the drop portion is the spectral reflectance of the white paper, which is the ratio of the intensity of the light irradiated to the white paper (the texture of the white paper) and the intensity of the light received. The spectral reflectance of white ink is different from that of white paper. Therefore, whether or not the discharge of the white ink is defective can be determined based on the spectral reflectance.

Next, the spectral reflectance of the white paper and the spectral reflectance of the white ink will be described with reference to fig. 3. Fig. 3 is a graph showing the spectral reflectance of white paper and the spectral reflectance of white ink. In the following description, as an example of the white paper, Maricote and Invercote (registered trademark) manufactured by beige paper mill are mentioned. The horizontal axis in fig. 3 represents the wavelength [ nm ] of light received by the light receiving unit 28, and the vertical axis in fig. 3 represents the spectral reflectance [% ]. In fig. 3, the spectral reflectance of Maricote is indicated by a solid line, the spectral reflectance of Invercote is indicated by a chain line, and the spectral reflectance of white ink is indicated by a two-dot chain line. In fig. 3, the difference between the spectral reflectance of Maricote and the spectral reflectance of white ink is shown by a broken line, and the difference between the spectral reflectance of Invercote and the spectral reflectance of white ink is shown by a dotted line.

First, a difference (spectral reflectance difference) between the spectral reflectance of Maricote and the spectral reflectance of the white ink indicated by a dotted line in fig. 3 will be described. When the wavelength of the irradiation light is 380[ nm ], the difference in spectral reflectance is 18%. When the wavelength of the irradiated light is 390[ nm ], the difference in spectral reflectance is 23%. When the wavelength of the irradiated light is 400[ nm ], the difference in spectral reflectance is 32%. When the wavelength of the irradiated light is 410[ nm ], the difference in spectral reflectance is 20%. On the other hand, when the wavelength region 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 is found that the spectral reflectance difference is large when the wavelength region of the irradiation light is 380[ nm ] to 410[ nm ].

Next, a difference (spectral reflectance difference) between the spectral reflectance of Invercote and the spectral reflectance of white ink shown by a dotted line in fig. 3 will be described. When the wavelength of the irradiation light is 380[ nm ], the difference in spectral reflectance is 15%. When the wavelength of the irradiation light is 390[ nm ], the spectral reflectance difference is 12%. When the wavelength of the irradiated light is 400[ nm ], the difference in spectral reflectance is 8%. When the wavelength of the irradiated light is 410[ nm ], the difference in spectral reflectance is 2%. From this, it is found that the spectral reflectance difference is large when the wavelength region of the irradiation light is 380[ nm ] or more and less than 400[ nm ].

From the above, it is known that, when the wavelength region of the irradiation light is a short wavelength region of 380[ nm ] or more and less than 400[ nm ], the difference between the spectral reflectance of white paper (Maricote, Invercote) and the spectral reflectance of white ink is large.

In the present embodiment, the irradiation unit 27 irradiates the wavelength λ in the short wavelength region_swOf a specified wavelength (e.g. 380[ nm ])]Ultraviolet light of (b) as irradiation light, and the light sensor 281 receives the wavelength λ of the short wavelength region_swOf (2) is detected. The control unit 40 calculates the spectral reflectance from the intensity of the received light, determines whether the spectral reflectance is that of white ink or white paper (texture of white paper), and functions as a checking unit for checking discharge failure of the nozzles.

In addition, the white ink containing fluorescent dye is irradiated with the wavelength lambda of the short wavelength region_swThe fluorescent substance (2) produces a fluorescent light-emitting effect. Similarly, the white paper containing the fluorescent whitening agent is irradiated with a wavelength λ in the short wavelength region_swThe fluorescent substance (2) produces a fluorescent light-emitting effect. The wavelength range of the light generated by fluorescence is 400[ nm ]]Above and 450[ nm ]]The following. On the other hand, the wavelength λ based on the short wavelength domain_swThe spectral reflectance of the white paper and the spectral reflectance of the white ink can be discriminated. However, the light sensor 281 not only detects the wavelength λ of the short wavelength domain_swAnd the wavelength λ in the visible light region is detected_rThe intensity of the light of (1). Thus, the wavelength λ of the short wavelength region_swThe detection accuracy of the intensity of light of (2) is degraded. As a result, it is difficult to distinguish the spectral reflectance of the white paper from the spectral reflectance of the white ink.

Light receiving unit 28 in the present embodiment includes a band pass filter 282. The belt filter 282 is disposed between the conveying surface of the conveying roller 21 and the optical sensor 281. Band pass filter 282 transmits wavelength λ of short wavelength region_swLight of wavelength lambda of the shielded visible light region_r(400[nm]Above). Thus, the band pass filter 282 blocks the wavelength λ of the fluorescent light emitting region_fOf (2) is detected.

At a wavelength lambda of irradiating the dripping part with a short wavelength region_swWhen the fluorescence emission effect is generated by the light of (3), the band pass filter 282 blocks the wavelength λ of the fluorescence emission region_fOf (2) is detected. Since the light sensor 281 detects the wavelength λ of the short wavelength domain_swWithout detecting fluorescence emissionWavelength λ of region_fSo that the wavelength λ of the short wavelength region can be suppressed_swThe detection accuracy of the light intensity of (2) is lowered.

The optical sensor 281 detects a wavelength λ in a short wavelength region under the control of the control unit 40_swThe intensity of the light of (1). The control unit 40 (detection unit) detects the wavelength λ of the short wavelength region based on the detection_swThe discharge state of the white ink is detected.

Specifically, the control unit 40 controls the wavelength λ of the short wavelength region irradiated from the irradiation unit 27 to the droplet deposition unit_swAnd the wavelength λ of the short wavelength region detected by the optical sensor 281_swThe spectral reflectance at a predetermined wavelength is calculated from the intensity of the light of (1). When the spectral reflectance at the predetermined wavelength is close to that of the white paper, the control unit 40 determines that the white ink discharge is defective by setting the spectral reflectance at the predetermined wavelength as the spectral reflectance of the white paper. When the spectral reflectance difference at the predetermined wavelength is close to the spectral reflectance of the white ink, the control unit 40 determines that the discharge failure of the white ink is not present, using the spectral reflectance at the predetermined wavelength as the spectral reflectance of the white ink. In other words, the white paper and the white ink are discriminated from each other based on the difference in the read contrast between the white paper and the white ink based on the spectral reflectance.

More specifically, when the recording medium P is Maricote, the control unit 40 calculates the spectral reflectance from the intensity of the ultraviolet light having a wavelength of 380[ nm ] irradiated to the droplet landing part and the intensity of the ultraviolet light having a wavelength of 380[ nm ] detected by the photosensor 281. When the spectral reflectance is closer to the spectral reflectance of Maricote than the white ink, the control unit 40 determines that the white ink discharge is defective as the spectral reflectance of the white paper (see fig. 3). When the spectral reflectance difference is closer to the spectral reflectance of the white ink than the Maricote, the control unit 40 determines that the discharge failure of the white ink is not the spectral reflectance of the white ink (see fig. 3).

When the recording medium P is a reverse-coated layer, the control unit 40 calculates the spectral reflectance from the intensity of the ultraviolet light having a wavelength of 380 nm irradiated to the drop portion and the intensity of the ultraviolet light having a wavelength of 380 nm detected by the photosensor 281. When the spectral reflectance is closer to that of the opposite coat layer than the white ink, the control unit 40 determines that the white ink discharge is defective as the spectral reflectance of the white paper (see fig. 3). When the difference in light reflectance is closer to the spectral reflectance of the white ink than the reverse coat layer, the control unit 40 determines that the white ink discharge failure is not the spectral reflectance of the white ink (see fig. 3).

Next, the discharge state detection process will be described with reference to fig. 4. Fig. 4 is a flowchart showing an example of the discharge state detection processing. Here, the irradiation section 27 irradiates the wavelength λ of the short wavelength region_swThe light of (2) is irradiated as irradiation light to the droplet landing part. The band pass filter 282 filters a wavelength λ in a visible light region (including a fluorescent light emitting region) of light passing through the drop portion based on the irradiation light_rLight is blocked, and the light sensor 281 receives the wavelength λ of the short wavelength region_swOf (2) is detected. The present flow starts with the execution of a print job.

First, in step S100, the control unit 40 (detection unit) obtains the intensity of light passing through the drop unit based on the irradiation light. The control unit 40 calculates the spectral reflectance at a predetermined wavelength from the intensity of the acquired light.

Next, in step S110, the control unit 40 determines whether or not the spectral reflectance at a predetermined wavelength is close to that of the white ink or close to that of the white paper. When the spectral reflectance at the predetermined wavelength is close to that of the white ink (step S110: YES), the process proceeds to step S120. When the spectral reflectance of the predetermined wavelength is not the spectral reflectance of the white ink but is close to the spectral reflectance of the white paper (no in step S110), the process proceeds to step S130.

In step S120, the control unit 40 determines that the white ink has not been discharged. Then, the processing shown in fig. 4 is ended.

In step S130, the control unit 40 determines that the white ink discharge is defective. Then, the processing shown in fig. 4 is ended.

Discharge state detection device according to the above embodimentComprises the following steps: an irradiation section 27 for irradiating white paper, which discharges white ink absorbing ultraviolet light of a predetermined wavelength from the recording head 242, with ultraviolet light; sensitivity ratio of light in ultraviolet region to wavelength lambda in visible region_rThe light receiving unit 28 has high sensitivity and receives light through the white paper based on the irradiation light; and a control unit 40 for detecting the discharge state of the white ink from the recording head 242 based on the intensity of the received light. Thus, since it is not necessary to apply a color ink as a primer, white paper and white ink can be detected with high accuracy without increasing the amount of consumption of the color ink. As a result, a discharge failure of the white ink can be discriminated.

In addition, according to the discharge state detecting apparatus in the above embodiment, when the white paper from which the white ink is discharged from the recording head 242 is irradiated with the ultraviolet light to generate the fluorescence emission action, the band pass filter 282 blocks the wavelength λ in the visible light region_rOf (2) is detected. Thus, since the light sensor 281 does not detect light generated by the fluorescence emission action, the influence of the fluorescence emission action on the intensity of light received by the light receiving unit 28 can be reduced. As a result, a decrease in detection accuracy of the discharge state of the white ink can be suppressed.

In addition, the above embodiments are merely specific examples of the implementation of the present invention, and the technical scope of the present invention cannot be construed in a limiting manner by these embodiments. That is, the present invention may be implemented in various forms as long as it does not depart from the gist or main features thereof.

For example, in the above-described embodiment, the detection of the ink discharge state is performed based on the intensity of light having passed through one of the drop portions based on the irradiation light, but the present invention is not limited to this, and may be performed based on, for example, an average value of the intensities of light having passed through a plurality of drop portions. The plurality of dropping units may be provided along the transport direction of the recording medium P, for example. By averaging the intensity of light, the SN ratio can be increased, and the detection accuracy of the discharge state of ink can be improved.

For example, in the above-described embodiment, the detection of the discharge state is performed with respect to the white ink, but the present invention is not limited to this, and any ink may be used as long as the difference in reading density from the recording medium P is small and the difference in spectral reflectance from the recording medium P occurs. For example, it may be a transparent ink.

For example, in the above embodiment, the ink jet recording apparatus may further include a second irradiation unit that irradiates the droplet landing portions of the respective color inks of yellow, red, cyan, and black with a wavelength λ in the visible light range_rOf (2) is detected. The control unit 40 controls the irradiation unit 27 and the 2 nd irradiation unit in a time-division manner so as to irradiate the drop portion of the white ink with the wavelength λ of the short wavelength region_swAnd irradiating the drop portion of the color ink with a wavelength λ in the visible light region_rOf (2) is detected. Thus, for example, the spectral reflectance of white paper and the spectral reflectance of white ink can be discriminated, and the spectral reflectance of colored paper and the spectral reflectance of colored ink can be discriminated by one built-in sensor.

In the above-described embodiment, the irradiation light to be irradiated to the droplet landing part is ultraviolet light, but the present invention is not limited to this, and may be light having a wavelength λ in a short wavelength range as long as it absorbs a component (for example, titanium oxide) contained in white ink_swFor example 390 nm]Etc. of light.

In the above embodiment, the band pass filter 282 blocks the wavelength λ in the visible light region_rHowever, the present invention is not limited thereto. For example, as long as the wavelength λ of the luminescent light emitting region is blocked_fMay be used. This can reduce the influence of the fluorescence emission action on the intensity of light received by light receiving unit 28.