JP2024088387A - Recording device - Google Patents

Abstract

To determine with high accuracy the ejection state of ink droplets ejected from a recording head
A recording device that ejects droplets from nozzles of a recording head onto a recording medium while moving a carriage carrying the recording head relative to the recording medium detects droplets ejected from the nozzles, controls the ejection of droplets from the nozzles, and determines the nozzle ejection state based on the droplet detection results. The recording device ejects droplets from the nozzles while the carriage is moving, estimates an ejection state corresponding to a portion of the droplets from the detection results of the droplets ejected from the nozzles while the carriage is moving, and determines the nozzle ejection state based on a comparison between the ejection state corresponding to the portion of the droplets and a threshold value stored in a memory means.
[Selected figure] Figure 6

Description

The present invention relates to a recording device that records by ejecting droplets from a recording head.

Inkjet recording devices are intended for a variety of output items, including CAD (Computer Aided Design) line drawings, posters, and artwork, and are intended for a variety of usage environments, including different types of ink. In an inkjet recording device that performs reciprocating recording by ejecting ink while the recording head moves back and forth (scans), even if the recording head ejects ink at the same position, the deposition position of the ejected ink droplets may differ depending on the direction of recording head movement. In addition, the deposition position of the ejected ink droplets may vary depending on the condition of the recording head and the type of ink. As a result, the resolution of the image formed on the recording medium and the reproducibility of fine lines may deteriorate, and the overall image quality may deteriorate.

Patent document 1 discloses a registration adjustment method that includes a measuring means for measuring the ink ejection speed, and that uses the measurement results to appropriately set the ejection timing from the reciprocating recording movement speed and the ejection speed.

JP 2007-152853 A

In inkjet recording devices, ink droplets discharged from a head may be multiple droplets of different sizes discharged at different flight conditions, such as different discharge speeds. In such cases, conventional methods cannot distinguish between multiple droplets with different flight conditions and detect them, which can result in low detection accuracy for changes in the discharge condition of the head.

The present invention has been made in consideration of the above problems, and aims to provide a technology that makes it possible to determine with high accuracy the ejection state of ink droplets ejected from a recording head.

In order to achieve the above object, a recording apparatus according to the present invention comprises:
A recording apparatus that ejects droplets from nozzles of a recording head onto a recording medium while moving a carriage carrying the recording head relative to the recording medium,
A detection means for detecting droplets ejected from the nozzle;
a discharge control means for controlling the discharge of droplets from the nozzle;
a determination means for determining a discharge state of the nozzle based on a detection result of the detection means;
Equipped with
The ejection control means ejects droplets from the nozzles while the carriage is moving,
The determination means is
estimating an ejection state corresponding to a portion of the droplets from a detection result of the droplets ejected from the nozzles while the carriage is moving;
determining an ejection state of the nozzle based on a comparison between an ejection state corresponding to the portion of the droplet and a threshold value stored in a memory means;
It is characterized by:

According to the present invention, it is possible to determine with high accuracy the ejection state of ink droplets ejected from a recording head.

FIG. 1 is a diagram showing the appearance of a recording apparatus according to an embodiment of the present invention; FIG. 1 is a perspective view showing an internal configuration of a recording apparatus according to an embodiment of the present invention; FIG. 2 is a block diagram showing a control configuration of a printing apparatus according to the present embodiment. FIG. 4A is a diagram showing an example of ejection in a normal ejection state, and FIG. 4B is a diagram showing an example of ejection in a non-ejection state. 1A to 1D are diagrams showing changes in detection time corresponding to changes in the height of the recording head. A flowchart showing an example of a process executed by a recording device according to the present embodiment. Conceptual diagram of ejection detection while driving the CR FIG. 4A is a diagram showing droplet detection when the CR is driven, and FIG. 4B is a diagram showing droplet detection when the CR is not driven. 1A to 1D are schematic diagrams illustrating how to estimate a discharge speed and a discharge amount based on the amount of received light.

The following embodiments are described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe multiple features, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicate explanations are omitted.

In this specification, "recording" (sometimes called "printing") refers not only to the formation of meaningful information such as characters and figures, but also to the formation of images, designs, patterns, etc. on a recording medium, regardless of whether they are visible to humans or not.

The term "recording medium" refers not only to paper used in typical recording devices, but also broadly to anything that can accept ink, such as cloth, plastic film, metal plate, glass, ceramics, wood, leather, etc. In the following embodiment, the recording medium is described as recording paper, but as mentioned above, the recording medium can also be applied to other types of recording media and is not limited to recording paper. Furthermore, the term "recording device" refers to a device that records on the recording medium described above.

Furthermore, "ink" (sometimes called "liquid") should be interpreted broadly in the same way as the definition of "recording (print)" above. Therefore, it refers to a liquid that can be applied to a recording medium to form an image, design, pattern, etc., or to process the recording medium, or to process the ink (for example, to solidify or insolubilize the coloring agent in the ink applied to the recording medium).

Below, we will describe in detail one embodiment to which the present invention can be applied, with reference to the drawings.

<Overall Overview of Recording Device>
1 is an external view of an inkjet recording apparatus (hereinafter, recording apparatus) 100 according to this embodiment, which uses recording paper of 10 to 60 inches in size as a recording medium. Note that this embodiment is applicable to any recording apparatus that performs recording by ejecting ink onto any recording medium, as described above, and is not limited to any type or size of recording medium.

The recording device 100 shown in FIG. 1 includes a paper discharge guide 101 for stacking output recording paper, an operation panel section 102 for accepting operations for setting the recording mode and recording paper, and a display panel 103 for displaying various recording information and setting results. The recording device 100 further includes an ink tank unit 104 for housing one or more ink tanks, such as black, cyan, magenta, and yellow, and supplying ink to the recording head.

Figure 2 is a perspective view showing an example of the internal configuration of the recording device 100. The recording head 201 is mounted on a carriage (hereinafter also referred to as CR) 202. The recording head 201 also includes a paper detection sensor 204 for detecting the distance between the recording paper 203 and the recording head 201. The CR 202 or the recording head 201 also includes an ink tank unit 104 equipped with one or more ink tanks. The recording device 100 also includes a droplet detection sensor 205 for detecting ink droplets ejected from the recording head 201. The main rail 206 supports the carriage 202 and limits the movement direction of the carriage 202 to the horizontal direction (perpendicular to the conveying direction of the recording paper), thereby causing the carriage to scan back and forth.

The carriage 202 is driven by a carriage motor 208 via a carriage conveyor belt 207 and is scanned back and forth in the horizontal direction. This allows the recording head 201 to move relative to the recording paper. In this embodiment, the direction in which the recording paper is conveyed is referred to as the conveying direction (Y direction in FIG. 2), and the direction in which the carriage moves back and forth is referred to as the scanning direction (X direction). An encoder sensor 210 mounted on the carriage 202 detects a linear scale 209 arranged in the scanning direction to obtain position information of the carriage 202. The recording device 100 also includes a lift motor 211 for varying the height of the carriage 202 in stages. The lift motor 211 can move the recording head 201 closer to or farther away from the recording paper 203 by varying the height of the carriage 202. The recording paper 203 is also supported by a platen 212 and conveyed in the conveying direction by a paper conveying roller 213. Here, the recording paper 203 will be described using roll paper as an example, but this is not limited to roll paper, and cut paper, for example, may also be used. The width of the recording paper 203 may also be configured to accommodate multiple paper widths.

Figure 3 is a diagram showing an example of the internal configuration of the recording device 100. The recording device 100 includes a (Central Processing Unit) 301, a control interface (I/F) 302, and a memory 303. The CPU 301 executes programs stored in the memory 303 to control the entire device. The control I/F 302 is controlled by the CPU 301 and controls a detection unit including the paper detection sensor 204, the droplet detection sensor 205, and the encoder sensor 210, and a drive unit including the carriage motor 208 and the lift motor 211. The memory 303 stores various information such as the programs executed by the CPU 301 and the ejection speed and thickness of the recording paper used by the programs. The CPU 301, the control I/F 302, and the memory 303 are connected to each other so that they can communicate with each other via a bus 304.

The control I/F 302 acquires the results detected by the paper detection sensor 204 and the droplet detection sensor 205. The control I/F 302 also controls the carriage motor 208 that scans the carriage 202. Furthermore, the control I/F 302 drives the head control circuit 305 based on the position information detected by the encoder sensor 210. In the above configuration, the print data from the host device (not shown) is converted into a head control signal, and printing is performed on the print paper 203 by the print head 201.

The CPU 301 reads and executes various programs stored in the memory 303, thereby functioning as a driver unit 306, a sequence control unit 307, an image processing unit 308, a timing control unit 309, and a head control unit 310. In the following description, the driver unit 306, the sequence control unit 307, the image processing unit 308, the timing control unit 309, and the head control unit 310 may be referred to as functional blocks without distinction.

The sequence control unit 307 performs general recording control, specifically starting and stopping each functional block, controlling the transport of recording paper, and controlling the scanning of the carriage 202.

The driver unit 306 controls the detection unit and the drive unit by outputting each control signal to the control interface 302 based on an instruction from the sequence control unit 307 via the bus 304. The driver unit 306 also acquires input signals from the detection unit and the drive unit via the control interface 302 and the bus 304, and transmits them to the sequence control unit 307.

The image processing unit 308 performs image processing to separate and convert the color of the input image data from the host device. Here, the input image data from the host device is passed to the driver unit 306 via an input interface such as a communication unit (not shown) connected to the bus 304 or a universal serial bus (USB), and is then sent to the image processing unit 308. The timing control unit 309 transmits the recording data converted and generated by the image processing unit 308 to the head control unit 310 in conjunction with the position of the carriage 202 or the recording head 201. The timing control unit 309 also controls the timing of the ejection of the recording data by the recording head 201 based on the distance between the recording head 201 and the recording paper 203 detected by the paper detection sensor 204. Furthermore, the timing control unit 309 also controls the timing of the ejection of the recording data by the recording head 201 based on the ejection speed information of the droplets determined based on the timing of each ink droplet detected by the droplet detection sensor 205. The head control unit 310 converts the print data input from the timing control unit 309 into a head control signal and outputs it to the print head 201, and controls the temperature of the print head 201 based on commands from the sequence control unit 307. In other words, the head control unit 310 functions as an ejection control unit that controls the ejection of the print head 201.

Next, a method for detecting the ejection state of ink droplets ejected from the recording head 201 in this embodiment will be described with reference to Figures 4(a) and 4(b). Figure 4(a) shows an example of ejection in a normal ejection state, and Figure 4(b) shows an example of ejection in a non-ejection state, i.e., an ejection in a state where ejection is not performed normally. The upper part of Figure 4(a) and the upper part of Figure 4(b) show cross-sectional views of the recording head 201 and the droplet detection sensor 205 in the YZ plane of the recording device 100. The YZ plane is a plane that passes through the Y direction, which is the conveying direction of the recording paper, and the Z direction, which is the vertical direction. As shown in Figures 4(a) and 4(b), the ejection port surface 201a of the recording head 201 has ejection ports (hereinafter also referred to as nozzles) 216 for ejecting ink droplets for each ink color for image formation. The droplet detection sensor 205 includes a light-emitting element 401, a light-receiving element 402, a control circuit board 403, and an ejection 405. The light emitting element 401 is disposed so that ink droplets discharged from the nozzle 216 in the discharge direction pass through the light beam 404, and the light receiving element 402 is disposed in a position to receive the light beam 404 emitted from the light emitting element 401. In order to improve the S/N ratio by narrowing the light beam 404 incident on the light receiving element 402 from the light emitting element 401, an aperture is formed near each element, and the amount of light beam 404 incident on the light receiving element 402 from the light emitting element 401 is read by the light receiving element 402.

At the bottom of Figures 4(a) and 4(b), a timing chart is shown showing the timing of sending an ejection signal (instruction signal) that instructs the recording head 201 to eject ink by applying a drive pulse, and the detection signal of the light receiving element 402 that changes when the droplet detection sensor 205 detects an ink droplet. The droplet detection sensor 205 is composed of a light emitting element 401, a light receiving element 402, a control circuit board 403, and the like. The light emitting element 401 emits a light beam 404, and the light receiving element 402 receives the light beam 404 emitted by the light emitting element 401. In this embodiment, the light emitting element 401 and the light receiving element 402 are described as being arranged in the Y direction, but they may be arranged in the X direction. In other words, the light emitting element 401 emits a light beam 404 in a direction intersecting the ejection direction (Z direction) of the nozzle 216, and the light receiving element 402 is arranged in a position where it can receive the light beam 404 sent from the light emitting element 401, and is not limited to the example of Figure 4. The light receiving element 402 outputs an output signal corresponding to the amount of light received to the control circuit board 403, and the control circuit board 403 detects the amount of light received by the light receiving element 402.

On the control circuit board 403, a current-voltage conversion circuit that converts the current flowing according to the amount of light received by the light receiving element 402 into a voltage signal and outputs it, and an amplifier circuit for the level of the detection signal of the ink droplet are provided. Furthermore, the control circuit board 403 is provided with a clamp circuit for holding the level of the signal output from the amplifier circuit at a predetermined value (clamp voltage) until ejection detection is performed. This makes it possible to avoid output saturation and a decrease in S/N due to fluctuations in the level of the detection signal of the light receiving element 402 caused by disturbances. These circuits ensure the level of the detection signal due to the desired ejection in order to detect minute changes such as the ejection of ink droplets. In other words, the control circuit board 403 is provided with a circuit element for detecting the output signal of the light receiving element 402 that changes due to the ejection of ink droplets. As a result, when an ink droplet passes through the light beam 404 of the droplet detection sensor 205, the amount of light received by the light receiving element 402 changes, and the ejection state of the nozzle to be detected is determined based on the result of comparing the level of the output detection signal with a predetermined reference voltage.

The droplet detection sensor 205 is installed so that the optical axis of the light beam 404 is at the same position in the Z direction as the surface of the platen 212 that supports the recording paper 203. Slits are provided near the light emitting element 401 and the light receiving element 402, respectively, to narrow the incident light beam 404 and improve the S/N ratio. The detection position is the position of the recording head 201 in the X direction where ink droplets can be ejected so that the ink droplets pass through the light beam 404. When detecting ink droplets to determine the ejection state of the ink droplets, the sequence control unit 307 controls the carriage motor 208 via the control I/F 302, and the recording head 201 moves to the detection position. The detection position is the position where the recording head 201 is located vertically above the droplet detection sensor 205.

In this embodiment, as shown in FIG. 2, the detection position is located outside the range in which the recording paper is transported in the movement direction (X direction) of the carriage 202. However, the detection position may be located within the range in which the recording paper is transported. In such a case, the recording device 100 performs processes such as cutting, transporting, and discharging the recording paper, and ejects ink droplets when no recording paper is located vertically above the detection position (X direction), thereby making it possible to determine the ink ejection state in the same way as in this embodiment.

In this embodiment, the cross-sectional area of the light beam 404 in the XZ plane is about 2 mm×2 mm. The parallel light projection area of the ink droplet when the ink droplet passes through the light beam 404 is about 2 ⁻³ [mm ² ]. The ejection port array and the light beam 404 are arranged in a parallel relationship with each other, and the creeping distance in the height direction (Z direction) is 2 to 10 mm. When the creeping distance between each ejection port and the light beam 404 is made close to each other, the passage of the ink droplet can be detected at a position where the light beam 404 is close to the flight distance of the ejected ink droplet, so that the ejection state can be detected stably. However, when the ejection port array and the light beam 404 are close to each other, the diffused light component emitted from the light emitting element 401 is reflected by the ejection port surface 201a of the recording head 201, and a light amount component is generated that is received by the light receiving element 402. As a result, the noise component is superimposed on the detection signal for the ejection state detection, and there is a possibility that the detection accuracy is reduced. Therefore, the surface distance between the light beam 404 of the droplet detection sensor 205 and the row of ejection openings of the recording head 201 is determined taking these correlations into consideration. Also, in order to match the conditions for detecting ink droplets by the droplet detection sensor 205 with the ejection state of ink droplets onto the recording paper 203 during image formation, the light beam 404 and the platen 212 supporting the recording paper 203 are disposed at approximately the same position (height) in the vertical direction (Z direction).

Next, the configuration for determining the ejection state and non-ejection of the ejected ink droplets will be described. The configuration shown in FIG. 4(a) is a schematic diagram showing the detection result when the ejection port 216 (hereinafter, the Nth nozzle) that is the object of detection of the ejection state of the recording head 201 by the droplet detection sensor 205 is ejecting normally. Ink droplets are ejected toward the droplet detection sensor 205 based on an ejection signal via the head control unit 310 and head control circuit 305 in the CPU 301. The aforementioned clamp circuit is operated by a control signal synchronized with the ejection of the ink droplets, and the signal level output is held at a predetermined clamp voltage value just before the ejection of the ink droplets is detected.

The CPU 301 releases the clamp circuit operation when the ejection of ink droplets begins and immediately before the ink droplets ejected toward the light beam 404 are blocked. Furthermore, if it detects that the change in the amount of light caused by the ejected ink droplets passing through the light beam 404 of the droplet detection sensor 205 is smaller than a reference voltage value determined according to the amount of change when the ink droplets block the light beam 404, it determines that the ejection state is normal. As a result, it is determined that the nozzle to be detected (nozzle number N) has ejected normally. Here, the results of ejection from nozzle number N to be detected multiple times are shown in order to obtain more reliable detection results of the ejection state by the droplet detection sensor 205.

Figure 4(b) is a schematic diagram showing the detection result when the nozzle (assumed to be Nth here) of the recording head 201 that is the object of detection of the ejection state described in Figure 4(a) is not ejecting normally, that is, it is in a non-ejection state. As in the diagram shown in Figure 4(a), ink droplets are ejected toward the droplet detection sensor 205 based on an ejection signal via the head control unit 310 and head control circuit 305 in the CPU 301. However, in this case, the ink droplets are not ejected correctly, and the ink droplets are not ejected sufficiently. As a result, the ink droplets cannot block the light beam 404, and the reduction in the amount of light that occurs when ejection is performed correctly in advance is not obtained. As a result, even if the detection signal exceeds the clamp voltage and an instruction to eject ink droplets is issued, the voltage does not fall below the reference voltage. In such a case, the CPU 301 determines that the Nth nozzle that is the object of detection is not ejecting normally and is in a non-ejection state.

Figure 5 (a) is a diagram showing an example of the internal configuration of the droplet detection sensor 205 for detecting the ejection speed of ink droplets ejected from the recording head 201. The CPU 301 drives the lift motor 211, ejects ink droplets while separating the recording head 201 from the droplet detection sensor 205 by a predetermined distance (first distance), and detects the ejected ink droplets.

A detailed description will be given of the configuration for detecting the ejected ink droplets and calculating their speed. In the configuration shown here, ink droplets are ejected from the recording head 201 towards the droplet detection sensor 205 based on an ejection signal via the head control unit 310 and head control circuit 305 in the CPU 301. The timing at which the amount of light changes when the ink droplet passes through the light beam 404 incident from the droplet detection sensor 205 is output as a detection signal. At this time, a first detection time T1 is detected, which is the time from when an ejection signal is issued for the distance H1 from the recording head 201 to the droplet detection sensor 205 until the detection signal is output.

Next, FIG. 5(b) is a diagram showing an example of an internal configuration for detecting the ink droplet ejection speed by driving the lift motor 211 to further increase the distance between the recording head 201 and the droplet detection sensor 205 (second distance) in comparison with FIG. 5(a). As in FIG. 5(a), the timing of the change in the amount of light when the ink droplet passes through the light beam 404 incident from the droplet detection sensor 205 is output as a detection signal. At this time, a second detection time T2 is detected, which is the time from when an ejection signal for the distance H2 from the recording head 201 to the droplet detection sensor 205 is issued until the detection signal is output.

Here, with respect to Figures 5(a) and 5(b), a first ejection velocity V1 of the ink droplet is calculated based on the distance difference in the section from the first distance to the second distance and the difference between the first and second detection times.
V1=(H2-H1)/(T2-T1)
Next, Fig. 5C is a diagram showing an example of an internal configuration for detecting the ejection speed of ink droplets by driving the lift motor 211 to further increase the distance between the recording head 201 and the droplet detection sensor 205 compared to Figs. 5A and 5B. As in Figs. 5A and 5B, the timing of the change in the amount of light when the ink droplet passes through the light beam 404 incident from the droplet detection sensor 205 is output as a detection signal. At this time, a third detection time T3 is detected, which is the time from when an ejection signal for a third distance H3 from the recording head 201 to the droplet detection sensor 205 is generated to when a detection signal is output.

Here, similar to the first and second distances, with respect to Figures 5 (b) and 5 (c), a second ejection velocity V2 of the ink droplet is calculated based on the distance difference in the section from the second distance to the third distance and the difference between the second and third detection times.
V2=(H3-H2)/(T3-T2)
5(d) is a diagram showing an example of an internal configuration for detecting the ejection speed of ink droplets by driving the lift motor 211 to further increase the distance between the recording head 201 and the droplet detection sensor 205 compared to FIGS. 5(a), 5(b), and 5(c). As in FIGS. 5(a), 5(b), and 5(c), the timing of the change in the amount of light when the ink droplet passes through the light beam 404 emitted from the light emitting element 401 is output as a detection signal. At this time, a fourth detection time T4 from the emission of an ejection signal for a fourth distance H4 from the recording head 201 to the droplet detection sensor 205 to the output of a detection signal is detected.

Here, similarly to the first, second, and third distances, with respect to Figures 5C and 5D, a third ejection velocity V3 of the ink droplet is calculated based on the distance difference in the section from the third distance to the fourth distance and the difference between the third and fourth detection times.
V3 = (H4 - H3) / (T4 - T3)
As described above, the ejection speed of ink droplets is determined based on the change in the detection time of ink droplets when the distance between the print head 201 and the droplet detection sensor 205 is changed.

Furthermore, according to the configuration described above, it is also possible to further increase the distance between the recording head 201 and the droplet detection sensor 205 using the lift motor 211. With this configuration, it is possible to measure even greater separation distances and the detection time for each ink droplet, and to more accurately calculate the ink droplet ejection speed. On the other hand, according to the configuration described above, it is also possible to reduce the distance and section by which the lift motor 211 separates the recording head 201 and the droplet detection sensor 205, thereby shortening the time it takes to detect the ink droplet ejection speed.

As described above, it is possible to provide a lifting means for varying the distance from the recording head 201 to the recording paper in multiple stages, and a highly accurate ink ejection detection means for detecting the ink ejection speed fluctuations at each stage.

The ejection state may change by ejecting droplets from the nozzle 216. On the other hand, the change caused by ejecting droplets several times is small. Therefore, as a guideline, it is sufficient to monitor the ejection state once for several pages. In one example, the head control unit 310 may count the number of ejections of each nozzle 216 of the recording head 201 as a dot count, and determine the ejection state of a nozzle 216 whose dot count exceeds a predetermined threshold before recording on the recording paper. Note that the ejection state determination may be performed after receiving an instruction for the recording process and before recording on the recording paper. In another example, when a recording process spanning multiple pages is performed, the determination may be performed while the recording medium is being transported between pages or between scans of the recording head 201, thereby reducing the impact on the recording process on the recording medium. Note that the processing timing is not limited to this.

Figure 6 shows an example of a process executed by the recording device 100 according to this embodiment. The process shown in Figure 6 is realized by the CPU 301 executing a program stored in the memory 303.

In processing step S601 (also referred to as S601; the same applies to subsequent processing steps), the CPU 301 scans the CR 202 under the same conditions as the recording process, passes ink droplets over the droplet detection sensor 205, and ejects ink droplets onto the droplet detection sensor 205 so that the ink droplets pass through the light beam 404 (S602).

Here, the same conditions as in the recording process include using the same parameters for driving the CR202 and the recording head 201 as in the recording process. Driving the CR202 includes the height, driving speed, and control of the CR202. For example, the carriage driving speed includes an acceleration region where the carriage accelerates, a constant speed region where the carriage moves at a constant speed, and a deceleration region where the carriage decelerates while moving, but most printing is performed in the constant speed region. For this reason, ejection monitoring is also performed in the constant speed region. The deceleration region is a region where the acceleration of the CR202 is less than a negative predetermined value a1, the acceleration region is a region where the acceleration of the CR202 is equal to or greater than a positive predetermined value a2, and the constant speed region is a region where the acceleration of the CR202 is equal to or greater than a1 and less than a2. In other words, the constant speed region is any region where the speed of the CR202 is within a predetermined range. In addition, the head driving includes using the same parameters for block driving and ejection pulse width as those in the recording process.

To monitor changes in the landing state of the ejected droplets formed on the recording paper, the CR202 is driven under the same conditions as those used in the recording process. The conditions here include the distance between the CR202 and the recording paper (carriage height) and the scanning speed of the CR202.

Figure 7 shows a conceptual diagram of ejection detection while driving the CR. Depending on the ejection conditions, ink droplets ejected from the recording head 201 are ejected separately into main droplets and small droplets other than the main droplets (hereinafter referred to as satellites or satellites). When ejected, the main droplets and satellites are ejected from the same ejection port 216, but due to differences in ejection speed, the landing positions on the recording paper may differ. In order to detect changes in the landing positions on the recording paper and the landing dot shapes, ejection monitoring is performed under the same conditions as the recording process. Note that in this embodiment, the same conditions as the recording process are used, but in order to detect changes in the ejection state of the ink droplets, they do not necessarily have to match, and driving conditions different from those of the actual recording process may be used.

As a supplement to the explanation of detection during CR driving, the difference between ejection in the CR driving state and ejection in the CR non-driving state will be explained using Figures 8(a) and 8(b). Figure 8(a) shows the ejection and detection unit that performs ejection detection while driving CR202. Figure 8(b) shows the ejection and detection unit that performs ejection detection with CR202 stopped. The droplets ejected from nozzle 216 are different in size and ejection speed between the main droplet and the satellite. In one example, the ejection speed of the satellite is smaller than that of the main droplet. That is, the main droplet moves more in the vertical direction (Z direction) than the satellite during the same period. On the other hand, the movement amount in the movement direction (-X direction) of CR202 is equal for the main droplet and the satellite. Therefore, when ejection detection is performed while driving CR202, the main droplet flies on a trajectory 802 with a different inclination in the XZ plane compared to the trajectory 801 on which the satellite flies. The head control unit 310 controls the ejection timing so that one of the trajectories 801 and 802 passes through the light beam 404, i.e., the droplet detection range, allowing the CPU 301 to separate the main droplet and the satellite and determine the detection timing.

On the other hand, as shown in FIG. 8(b), when CR202 ejects droplets in a non-driven state, the trajectory of the satellite droplets and the trajectory of the main droplets are the same, so the main droplets and the satellite droplets cannot be detected separately.

In this way, by performing ejection and detection while driving CR202, it is possible to detect changes in the ejection size and ejection speed of the main droplet, and changes in the ejection size and ejection speed of the satellite. Note that in the example of FIG. 8(a), the trajectory 802 is shown passing through the irradiation range of the light beam 404 in order to detect the main droplet, but a method of shifting the ejection timing and detecting only the satellite may also be implemented.

The main droplet and the satellite droplet may be simultaneously passed through the detection unit and separated depending on the timing of detection by the detection unit. In such a case, ejection may be performed when CR202 is not driven, as shown in FIG. 8(b).

In S603 of FIG. 6, the CPU 301 calculates the ejection speed and droplet size of the main droplet and the satellite droplet from the waveform detected by the light receiving element 402.

As described above with reference to FIG. 4A, when a droplet passes through the light beam 404, the amount of light received by the light receiving element 402 changes, and the signal output by the light receiving element 402 changes according to the amount of light received. FIGS. 9A and 9B are schematic diagrams showing the calculation of the ejection speed and ejection amount in this embodiment. FIG. 9A shows a detection signal 901 output according to the amount of light received detected by the light receiving element 402. The signal that changes when the main droplet and the satellite pass through the light beam 404 affects the distribution of droplets passing through the light beam 404. The change in the ejection speed is correlated with the number of times each nozzle 216 ejects for recording. Therefore, when droplets ejected from multiple nozzles 216 are used for detection, the bias in the distribution of the ejection speed is reduced by selecting nozzles 216 with a similar number of ejections.

In the example shown in FIG. 9B, function approximation is performed assuming that the ejection speeds of the main droplet and the satellite follow a normal distribution. Since the main droplet always has an ejection speed equal to or greater than that of the satellite, of the two normal distribution results, the waveform at the top on the time axis is taken as the main droplet waveform, and the other is taken as the satellite waveform. In one example, the CPU 301 may detect a minimum value in a predetermined period after sending an ejection start signal, and determine that the minimum value at the top on the time axis corresponds to the main droplet waveform, and the second minimum value on the time axis corresponds to the satellite waveform. In another example, the detected amount in a predetermined range on the time axis may be determined to be the waveform corresponding to the main droplet. This is because the main droplet is a liquid of a predetermined size or larger, and is detected within a predetermined time.

By using the method described above, the CPU 301 can separate a normal distribution 911 that approximates the detection amount of the main droplet and a normal distribution 912 that approximates the detection amount of the satellite based on the detection signal 901. However, the function approximation does not necessarily have to be performed using a normal distribution, and a polynomial may also be used. In such a case, the results of function approximation such as the normal distributions 911 and 912 are called the main droplet approximation function 911 and the satellite approximation function 912, respectively.

The peak fitting method is known as a method for separating detection signals. This is a method in which peak values and half-widths are given to Gaussian and Lorentzian functions, and calculations are repeated until the composite spectrum of the waveforms calculated with each function matches the actual spectrum. For example, when the detection signal of the main droplet alone or the satellite alone can be approximated by a Gaussian function, the waveforms can be separated as shown in Figure 9(b) by peak fitting using a Gaussian function. After waveform separation, the ejection speed and ejection amount can be calculated from the time difference from the ejection start signal to the time it takes to reach the peak and the peak value for the main droplet detection signal and the satellite detection signal, respectively.

The approximation function of the detection signal is not limited to a Gaussian function, but may be a Lorentz function, a polynomial function, or the like. The method of approximating and separating the detection signal is also not limited to the peak fitting method, but may be a nonlinear least squares method, or the like.

9(c) is a conceptual diagram of calculating the ejection speed and ejection amount from the separated main droplet. The CPU 301 calculates the time from the start of ejection of the ink droplet to its detection based on the approximation functions 911 and 912 described with reference to FIG. 9(b). Since the distance between the CR 202 and the droplet detection sensor 205 is known, the ejection speed can be calculated. In addition, the ejection monitoring detects the difference in the time from the start of ejection of the ink droplet to its detection, which was calculated last time. Therefore, if the distance between the CR 202 and the droplet detection sensor 205 is the same as the last detection, the CPU 301 does not need to accurately grasp the absolute value of the distance. For example, if the initial ejection speed is 18 m/s, it is not necessary to have high detection accuracy of 18 m/s, and it is sufficient to be able to detect a change of 0.5 m/s as the amount of change after use. The CPU 301 may also determine the ejection amount from the amount of change in the detection signal. This ejection amount can be determined based on a correspondence relationship between the amount of change in the detection signal of the light receiving element 402 and the amount of ejection, which is defined in advance. FIG. 9D is a conceptual diagram of calculating the ejection speed and ejection amount from the separated satellite. The CPU 301 can determine the ejection speed and ejection amount of the satellite in the same way as the main droplet. If the ejection speed from the nozzle 216 changes, the landing position of the droplet on the recording paper will shift. In that case, for example, when recording a single vertical line, the line may become thicker, one line may become two lines, or the position of the line may shift, resulting in recording defects. Similarly, if the size of the droplet changes, the density of the dots formed on the recording paper will change. For example, when forming an image by overlapping magenta and cyan, a change in the droplet size of one nozzle will change the color density balance, which may result in recording defects. The CPU 301 calculates the ejection speed and ejection amount based on the detection value of the droplet detection sensor 205.

In S604, it is determined whether the droplet ejection amount and ejection speed are within a predetermined range. For example, in S604, it is determined whether the droplet ejection amount is equal to or greater than a first threshold value associated with the ejection amount. It is also determined whether the ejection speed is equal to or greater than a second threshold value associated with the ejection speed. If the ejection amount and ejection speed are equal to or greater than the first and second threshold values, respectively (Yes in S604), the CPU 301 determines that there is no change in the ejection state and ends the process shown in FIG. 6. On the other hand, if it is determined that the droplet ejection amount is less than the first threshold value or the ejection speed is less than the second threshold value (No in S504), the CPU 301 determines that there is a change in the ejection state and proceeds to S605. Note that only one of the ejection amount and the ejection speed may be compared with the threshold value.

In addition, in S604, it may be determined whether the change in the ejection amount and the change in the ejection speed of the droplets when compared with the past detection results are equal to or less than a third threshold associated with the change in the ejection amount and a fourth threshold associated with the change in the ejection speed, respectively. In this case, the past detection results are recorded in the memory 303. If the change in the ejection amount is equal to or less than the third threshold and the change in the ejection speed is equal to or less than the fourth threshold (Yes in S504), the CPU 301 determines that no change in the ejection state has occurred and ends the process shown in FIG. 6. The CPU 301 can determine the change by comparing the initial or past ejection state with the current ejection state. On the other hand, if the change in the ejection amount and the ejection speed when compared with the past detection results are greater than the third threshold or the fourth threshold (No in S604), the CPU 301 determines that a change in the ejection state has occurred and proceeds to S605.

The ejection speed and ejection volume of the main droplets or satellites are compared with the first and second thresholds described above, and if any one of them falls below the threshold, the recording process may be affected. In addition, if the amount of change in the ejection speed and the amount of change in the ejection volume of the main droplets or satellites is greater than the third and fourth thresholds, the recording process may also be affected. For this reason, in S605, the CPU 301 turns on the detection NG flag stored in the memory 303 and ends the process. The detection NG flag is a flag that indicates that the ejection state of the print head 201 was not detected to be normal.

In addition, in S605, a recovery process for the print head 201 may be performed automatically. The recovery process includes continuous ejection into a cap (not shown) multiple times in succession, such as 1000 times or more, for example 10,000 times. The recovery process may include suctioning the nozzle 216 with a cap (not shown), or may include a cleaning process such as wiping the nozzle 216, or a foreign matter removal process using an electric potential. After performing these recovery processes, the ejection state is detected in a similar manner, so that it can be determined whether the ejection state has been restored by the recovery process.

In this embodiment, the first to fourth thresholds used as reference values for the ejection state are described as values that are pre-registered at the time of product manufacture. However, in one example, the first to fourth thresholds may be updated based on the detection results of the droplet detection sensor 205. For example, of the ejection speeds and ejection amounts detected in S603, the ejection amounts or ejection speeds that are determined to be equal to or greater than the thresholds may be stored in the memory 303 as new first to fourth thresholds.

The reference values (first to fourth thresholds) for the ejection speed and ejection amount stored in memory 303 may be the ejection speed and ejection amount during printer adjustment, specifically after registration adjustment (also called landing position adjustment) or density adjustment (called color calibration). The ejection speed and ejection amount when the adjustment is performed are detected and stored in memory 303. Thereafter, a comparison with the above starting point is performed at the timing detected during ejection monitoring. The starting point is updated at the timing when registration adjustment or density adjustment is performed.

In addition, in S605, the CPU 301 may notify the user of the change in the discharge state. In such a case, the CPU 301 may send a message to the user or administrator via the network instructing them to adjust the discharge, or may display the message on the display panel 103 of the recording device 100.

In addition, in S605, the CPU 301 may execute a registration adjustment process (registration adjustment) based on the detection result. For example, if there is no change in the ejection volume but a change in the ejection speed occurs, the CPU 301 may be able to respond to the change in the ejection state by changing the ejection timing since only the landing position on the recording paper has changed. For this reason, the CPU 301 adjusts the registration to determine the ejection timing for ejecting the ink at the landing position. In addition, a density adjustment may be executed in the recording process of the recording device 100. In addition, a process may be executed to change the distance between the recording head 201 and the recording medium in the recording process of the recording device 100. In other words, in S605, different processes may be executed depending on the changed ejection state.

As a method for automatic adjustment when ejection fluctuations are detected, a method of adjusting the ejection landing position is considered. This can be achieved by recording on a recording medium and detecting the recorded pattern. Another method is to calculate the ejection timing based on the amount of ejection fluctuation. The amount of deviation in the landing position caused by fluctuations in the ejection speed can be calculated from the head-to-paper distance, the carriage operation speed, and the ejection speed. Using this method, it is possible to reduce paper waste caused by printing.

An additional explanation will be given of the operation of scanning the CR202 under the same conditions as the image formation shown in S601 of Figure 6 and passing it over the ejection monitoring sensor.

The ejection monitoring sensor has a different optical system configuration and a different intended function than the droplet detection sensor 205 that detects ejection failures, but it is preferable to use it in combination with the droplet detection sensor 205 shown in FIG. 2 in terms of the number of hardware parts. Therefore, in one embodiment, detection is performed by the droplet detection sensor 205 that is placed outside the recording area where recording is performed on the recording medium.

On the other hand, this ejection monitoring can also be performed during the printing operation. In such a case, the movement of the CR 202 to the droplet detection sensor 205 located outside the printing area can cause a decrease in the throughput of the printing process. For this reason, the ejection monitoring sensor can also be used as a spare ejection port located immediately adjacent to the printing area. By locating the ejection monitoring sensor in an area that is passed through during printing, ejection monitoring can be performed without decreasing the printing throughput.

When a droplet passes the ejection monitoring sensor and splits into a main droplet and a satellite, the main droplet and the satellite will interrupt the light beam a short time after the main droplet interrupts the light beam. As a result, the detection signal of the ejection monitoring sensor will have a waveform with two peak values (local minimum values), as shown in Figure 8(a). This can be considered to be a combination of the detection signal of the main droplet and the detection signal of the satellite. In order to calculate the ejection speed and droplet size of each of the main droplet and the satellite, it is necessary to separate the detection signal of the main droplet from the detection signal of the satellite.

Additional explanation will be given regarding the determination of change in the ejection state shown in S604 in FIG. 6. The purpose of ejection monitoring is to detect changes from an ejection state that has been determined to be correct. A possible starting point for determining that the state is correct is the state of the recording device 100 when it is initially installed or at the time of shipment. Other possible starting points are the state immediately after the recording head 201 is replaced, and the state after adjustment of the ejection landing position (registration adjustment). In each state, the ejection state is detected, and this value is stored as the default ejection state. When the amount of change from this default ejection state exceeds a certain amount, the ejection state is determined to be poor.

As described above, according to this embodiment, the droplet ejection state of the recording device can be determined with high accuracy, so the ejection state can be monitored with high accuracy. This makes it possible to prevent recording defects caused by aging or unintended changes in ejection.

<Other embodiments>
The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions.

Summary of the embodiment
The disclosure of this embodiment is as follows.

(Item 1)
A recording apparatus that ejects droplets from nozzles of a recording head onto a recording medium while moving a carriage carrying the recording head relative to the recording medium,
A detection means for detecting droplets ejected from the nozzle;
a discharge control means for controlling the discharge of droplets from the nozzle;
a determination means for determining a discharge state of the nozzle based on a detection result of the detection means;
Equipped with
The ejection control means ejects droplets from the nozzles while the carriage is moving,
The determination means is
estimating an ejection state corresponding to a portion of the droplets from a detection result of the droplets ejected from the nozzles while the carriage is moving;
determining an ejection state of the nozzle based on a comparison between an ejection state corresponding to the portion of the droplet and a threshold value stored in a memory means;
A recording device comprising:

(Item 2)
The detection means includes:
A light emitting means for irradiating light;
a light receiving means for receiving the light emitted from the light emitting means and outputting a signal in accordance with the amount of received light;
Equipped with
2. The recording apparatus according to item 1, wherein the ejection control means controls the droplets ejected from the recording head so as to block light from the light emitting means to the light receiving means.

(Item 3)
The determination means is
determining a detection timing of the droplet based on a change in a signal output from the light receiving means, the change occurring when the droplet blocks the light;
3. The recording apparatus according to item 2, wherein the ejection control means determines an ejection speed of droplets based on a transmission timing of an instruction signal for instructing the recording head to eject droplets.

(Item 4)
The nozzle further includes an adjustment unit for adjusting a distance from the nozzle to the light in a discharge direction of the nozzle,
The recording device described in item 3, characterized in that the ejection speed of the droplets is determined based on a first time from the transmission timing to the detection timing when the distance from the nozzle to the light is a first distance, and a second time from the transmission timing to the detection timing when the distance from the nozzle to the light is a second distance.

(Item 5)
a memory means for storing a first threshold value associated with the droplet ejection speed;
5. The recording apparatus according to item 3 or 4, wherein the determining unit determines that the ejection state has changed when the ejection speed of the droplets determined by the determining unit falls below the first threshold value.

(Item 6)
6. The recording apparatus according to item 5, further comprising a first setting unit that sets the first threshold value in the storage unit based on a detection result of the detection unit.

(Item 7)
7. The recording apparatus according to any one of items 2 to 6, wherein the determining unit determines the ejection amount of the droplet based on an amount of change in a signal output from the light receiving unit when the droplet blocks the light.

(Item 8)
The inkjet recording device further includes a memory means for storing a second threshold value associated with the droplet ejection amount,
8. The recording apparatus according to item 7, wherein the determining unit determines that the ejection state has changed when the ejection amount of droplets determined by the determining unit falls below the second threshold value.

(Item 9)
9. The recording apparatus according to item 8, further comprising a second setting unit that sets the second threshold value in the storage unit based on a detection result of the detection unit.

(Item 10)
10. The recording apparatus according to any one of items 1 to 9, wherein the determination means determines the ejection state of the nozzle based on a detection result of droplets ejected from the nozzle while the carriage is moving at a constant speed.

(Item 11)
11. The recording apparatus according to any one of items 1 to 10, wherein the ejection control means selects a nozzle from which droplets are ejected, based on a dot count of a recording process, from among a plurality of nozzles provided in the recording head.

(Item 12)
12. The recording apparatus according to any one of items 1 to 11, wherein the determining means has a notifying means for notifying a user that the ejection state has changed.

(Item 13)
A recording device described in any one of items 1 to 12, characterized in that the droplets from the nozzle include multiple droplets including a main droplet and a satellite, and the main droplet ejected from the nozzle while the carriage is moving is ejected on a trajectory different from that of the satellite.

(Item 14)
14. The recording apparatus according to any one of items 1 to 13, further comprising an execution unit that executes a recovery process when the determination unit determines that the ejection state determined by the determination unit has changed.

The invention is not limited to the above-described embodiment, and various modifications and variations are possible without departing from the spirit and scope of the invention. Therefore, the following claims are appended to disclose the scope of the invention.

100 Recording device, 201 Recording head, 203 Recording paper, 205 Droplet detection sensor, 301 CPU, 302 Control I/F, 303 Memory, 401 Light emitting element, 402 Light receiving element, 403 Control board, 404 Light beam

Claims (14)

A recording apparatus that ejects droplets from nozzles of a recording head onto a recording medium while moving a carriage carrying the recording head relative to the recording medium,
A detection means for detecting droplets ejected from the nozzle;
a discharge control means for controlling the discharge of droplets from the nozzle;
a determination means for determining a discharge state of the nozzle based on a detection result of the detection means;
Equipped with
The ejection control means ejects droplets from the nozzles while the carriage is moving,
The determination means is
estimating an ejection state corresponding to a portion of the droplets from a detection result of the droplets ejected from the nozzles while the carriage is moving;
determining an ejection state of the nozzle based on a comparison between an ejection state corresponding to the portion of the droplet and a threshold value stored in a memory means;
A recording device comprising: The detection means includes:
A light emitting means for irradiating light;
a light receiving means for receiving the light emitted from the light emitting means and outputting a signal in accordance with the amount of received light;
Equipped with
2. The recording apparatus according to claim 1, wherein said ejection control means controls the droplets ejected from said recording head so as to block light from said light emitting means to said light receiving means. The determination means is
determining a detection timing of the droplet based on a change in a signal output from the light receiving means, the change occurring when the droplet blocks the light;
3. The recording apparatus according to claim 2, wherein the ejection control means determines the ejection speed of the droplets based on a transmission timing of an instruction signal for instructing the recording head to eject the droplets. The nozzle further includes an adjustment unit for adjusting a distance from the nozzle to the light in a discharge direction of the nozzle,
The recording device according to claim 3, characterized in that the ejection speed of the droplets is determined based on a first time from the transmission timing to the detection timing when the distance from the nozzle to the light is a first distance, and a second time from the transmission timing to the detection timing when the distance from the nozzle to the light is a second distance. the storage means stores a first threshold value associated with an ejection speed of the droplet;
4. The recording apparatus according to claim 3, wherein the determining unit determines that the ejection state has changed when the ejection speed of the droplets determined by the determining unit falls below the first threshold value. The recording device according to claim 5, further comprising a first setting means for setting the first threshold value in the storage means based on the detection result of the detection means. The recording device according to claim 2, characterized in that the determining means determines the amount of the droplet discharged based on the amount of change in the signal output from the light receiving means when the droplet blocks the light. the storage means stores a second threshold value associated with the ejection amount of the droplet;
8. The recording apparatus according to claim 7, wherein the determining unit determines that the ejection state has changed when the ejection amount of the droplets determined by the determining unit falls below the second threshold value. The recording device according to claim 8, further comprising a second setting means for setting the second threshold value in the storage means based on the detection result of the detection means. The recording device according to claim 1, characterized in that the determination means determines the ejection state of the nozzle based on the detection result of droplets ejected from the nozzle while the carriage is moving at a constant speed. The recording device according to claim 1, characterized in that the ejection control means selects nozzles from among the multiple nozzles of the recording head that eject droplets based on the dot count of the recording process. The recording device according to claim 1, characterized in that the determination means has a notification means for notifying a user that the ejection state has changed. The recording device according to claim 1, characterized in that the droplets from the nozzles include multiple droplets including main droplets and satellites, and the main droplets ejected from the nozzles while the carriage is moving are ejected on a trajectory different from that of the satellites. The recording device according to any one of claims 1 to 13, further comprising an execution means for executing a registration adjustment process when it is determined by the determination means that the ejection state determined has changed.

Images