Discharge state detection device

Abstract

The increasing image quality, higher speed, and greater variety of inks used in printers are leading to a trend of increasing the number of inspection nozzles. Furthermore, when the ejection speed of the ink droplets is slow, the distance the ejected droplets travel is shorter, and their flight path tends to be unstable. Therefore, when detecting the nozzle's ejection state, the number of pre-ejections required to stabilize the flight increases, leading to longer inspection times, which is a challenge. [Solution] This inkjet recording device, when inspecting the ejection state of the nozzles of the recording head, blocks the light beam of the droplet detection unit with multiple droplets, and the multiple droplets are composed of multiple nozzles, and the number of pre-ejected droplets is changed depending on the arrangement conditions of the multiple nozzles.

Description

Technical Field

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[0001] The present invention relates to an inkjet recording apparatus that ejects ink from a recording head to record an image, and more particularly to a recording apparatus provided with a recording head having a plurality of nozzles for recording and an ink ejection state detection method used in the recording apparatus.

Background Art

[0002] In an inkjet recording apparatus, in order to keep the quality of a printed image constant, the ejection state of ink droplets ejected from the nozzles of a recording head is grasped for each nozzle. Further, from the viewpoint of image formation, considering the differences in physical properties for each recording head and each ink color, the ejection speed and droplet volume of the ejected ink droplets are set to suitable values for each ink color. Also, it is known that the ejection state of the ejected ink droplets changes according to the usage situation and environmental influence of the recording apparatus. Specifically, it has been found that changes occur in the physical properties such as the ejection speed (flight speed), size, flight interval, and ejection direction of the ejected ink droplets (main droplets and satellite droplets formed by the splitting of main droplets). Therefore, before using the recording apparatus, it is desirable to detect the ejection state of the ejected ink droplets and determine that the ejection of the ink droplets is being performed normally.

[0003] As a technique for detecting non-ejection of droplets in an inkjet recording apparatus, there is a technique for detecting non-ejection using an optical detector composed of a pair of a light emitting element and a light receiving element (Patent Document 1). In Patent Document 1, a method has been proposed in which ink droplets are ejected in each nozzle unit so as to pass through the light beam irradiated from the light emitting element and reaching the light receiving element, and when a decrease in the amount of light received by the light receiving element is not detected, it is determined that the droplets are not ejected.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] However, Patent Document 1 assumes that the droplets reach the inspection area stably and does not consider cases where the flight state is unstable. Therefore, there is a risk that the detection accuracy will decrease.

[0006] This invention has been made in view of the above problems, and aims to provide a method for detecting the ejection state of ink droplets with high accuracy. [Means for solving the problem]

[0007] To achieve the above objective, the present invention comprises a recording head for ejecting ink droplets to print on recording paper, a droplet ejection control means for ejecting ink droplets from each nozzle arranged on the recording head, a droplet detection unit for detecting the ejection of ink droplets by blocking the beam of light from a light-emitting means to a light-receiving means at a position opposite to the recording head, and a ejection state inspection means for determining whether the ejection state is normal or abnormal based on the ejection timing by the droplet ejection control means and the output change of the droplet detection unit. The droplet ejection control means is capable of controlling the ejection of each arranged nozzle at a predetermined timing, and when inspecting the ejection state of the nozzles of the recording head, the beam of light from the droplet detection unit is blocked by multiple droplets, the multiple droplets are composed of multiple nozzles in the same nozzle row, and the number of droplets to be ejected before the inspection is determined from the arrangement conditions of the nozzles in the multiple droplet group. [Effects of the Invention]

[0008] According to the present invention, when nozzles are arranged in groups of multiple droplets and the groups are adjacent to each other that meet the arrangement conditions, airflow is generated by the discharged droplets from each other, stabilizing their flight. This allows for a reduction in the number of pre-inspection discharges compared to multiple nozzles that are not adjacent or single-discharge nozzles, thereby shortening the detection time. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows the external appearance of a recording device according to the first embodiment. [Figure 2] This is a perspective view showing the internal configuration of the recording device according to the first embodiment. [Figure 3] This is a block diagram showing the control configuration of a recording device according to the first embodiment. [Figure 4] This is a schematic diagram illustrating a method for detecting the discharge state. [Figure 5] This is a diagram illustrating the method for detecting the discharge state in the first embodiment. [Figure 6] This is a flowchart of the process for detecting the discharge state. [Figure 7] This figure shows the correlation between the flight distance of ink droplets and the arrangement of the ejection nozzles. [Figure 8] This figure shows the arrangement of the discharge nozzles in the first embodiment. [Figure 9] This is a flowchart of the process for detecting the discharge state in the first embodiment. [Figure 10] This is a table for determining the number of reserve discharges in the second embodiment. [Figure 11] This is a table for determining the number of reserve discharges in the third embodiment. [Figure 12] This is a diagram illustrating the method for determining the nozzle group in the first embodiment. [Modes for carrying out the invention]

[0010] <Overall overview of the recording device> Figure 1 shows the external appearance of an inkjet recording device (hereinafter referred to as "recording device") 100 as an example of a droplet ejection device according to this embodiment.

[0011] The recording device 100 includes a paper output guide 101 for loading the output recording medium, operation buttons 102 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 also has an ink tank unit 104 that houses ink tanks for storing color inks such as black, cyan, magenta, and yellow, and supplies ink to a recording head 201 (see Figure 2), which is an example of a droplet ejection head. Note that the recording device 100 shown in Figure 1 is a recording device capable of recording on recording media of multiple widths up to 60 inches in size. Roll paper or cut paper can be used as the recording medium recorded by the recording device 100. Furthermore, the recording medium is not limited to paper, but may also be cloth or vinyl, for example.

[0012] Figure 2 is a perspective view showing the internal configuration of the recording device 100. The platen 212 is positioned opposite the recording head 201 and is a component that supports the recording medium 203 when it is transported to that position. The recording medium 203 is supported by the platen 212 and transported in the transport direction (Y direction) by the paper transport roller 213. The recording head 201 is mounted on the carriage 202.

[0013] Furthermore, the recording head 201 has a distance detection sensor 204 for detecting the distance between the recording medium 203 on the platen 212 and the recording head 201. The distance detection sensor 204 is an optical sensor that has a light-emitting element that illuminates the recording medium 203 with light and a light-receiving element that receives light reflected from the recording medium 203, and measures the distance from the change in the output of the amount of light received by the light-receiving element. The droplet detection sensor 205 is an optical sensor that detects droplets (in this case, ink droplets) ejected from the recording head. As shown in Figure 4, which will be described later, the droplet detection sensor 205 has a light-emitting element 401, a light-receiving element 402, and a control circuit board 403. Details of the droplet detection sensor 205 will be described later.

[0014] The main rail 206 is for supporting the carriage 202. The carriage 202 reciprocates in the X direction (a direction orthogonal to the conveyance direction of the recording medium) along the main rail 206. The scanning of the carriage 202 is performed by driving the carriage motor 208 to move the carriage conveyance belt 207. The linear scale 209 is disposed in the scanning direction in which the carriage 202 scans. The position information of the carriage 202 is acquired by the encoder sensor 210 mounted on the carriage 202 detecting the linear scale 209. The recording apparatus 100 has a lift cam (not shown) for stepwise displacing the height of the main rail 206 that supports the carriage 202 and a lift motor 211 for driving the lift cam. By moving the lift cam by driving the lift motor 211, the recording head 201 can be moved up and down, and the distance between the recording head 201 and the recording medium 203 can be made closer or farther apart.

[0015] The recording head 201 has an ejection port surface (so-called face surface) 201a in which ejection ports are formed. Inside the ejection port surface 201a, there is a heater that generates energy for ejecting liquid such as ink, and a member for forming the ejection ports. A common liquid chamber 214 is provided for each ink color on the ejection port surface 201a. Ink is supplied to the multiple ejection ports arranged via an ink flow path 215. Then, the pressure generated by driving the heater ejects the ink from the ejection ports, forming an image. On the ejection port surface 201a, multiple ejection ports 216 are arranged along the Y direction, forming a row of ejection ports for each ink color. Multiple such rows of ejection ports are arranged in the X direction. Furthermore, each row of arranged ejection ports has 2048 nozzles. In this embodiment, the nozzles are arranged in a staggered pattern rather than a simple single row. Therefore, when numbers are assigned sequentially to the ejection ports from one end of each nozzle row, the rows are divided into two: ejection port row 217, where the ejection ports are numbered odd-numbered, and ejection port row 218, where the ejection ports are numbered even-numbered. Here, the ejection port row with odd-numbered ports is called the "odd nozzle row," and the ejection port row with even-numbered ports is called the "even nozzle row." Thus, each odd-numbered nozzle row and even-numbered nozzle row consists of 1024 nozzles, and the distance between them is approximately 0.6 mm. Furthermore, a recording resolution of 1200 dpi (dots / inch) is achieved by combining both the odd-numbered and even-numbered nozzle rows in each nozzle row, and the nozzle spacing in each of the odd-numbered and even-numbered nozzle rows is 600 dpi. In addition, the amount of ink droplets ejected from the ejection port surface 201a of the recording head 201 is mainly around 4 pl to 6 pl.

[0016] FIG. 3 is a block diagram showing the control configuration of the recording apparatus 100. The recording apparatus 100 includes a CPU 301 that controls the entire apparatus, a sensor-motor control unit 302 that controls each sensor and motor, and a memory 303 that stores various information such as the ejection state and the thickness of the recording medium. The CPU 301, the sensor-motor control unit 302, and the memory 303 are connected to each other so as to be able to communicate with each other. The sensor-motor control unit 302 controls a distance detection sensor 204, a droplet detection sensor 205, and a carriage motor 208 that scans the carriage 202. Further, the sensor-motor control unit 302 controls the head control circuit 305 based on the position information detected by the encoder sensor 210, and ejects ink from the recording head 201.

[0017] The image data transmitted from the host device 1 is converted into an ejection signal by the CPU 301, and ink is ejected from the recording head 201 according to the ejection signal to perform printing on the recording medium 203. The CPU 301 includes 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. The sequence control unit 307 controls overall recording control. Specifically, it starts and stops the image processing unit 308, the timing control unit 309, and the head control unit 310, which are each functional blocks, controls the conveyance of the recording medium, controls the scanning of the carriage 202, and the like. The control of each functional block included in the CPU 301 is executed by the sequence control unit 307 reading out various programs from the memory 303 and executing them. The driver unit 306 functions as an I / O control unit that controls input and output. For example, based on a command from the sequence control unit 307, the driver unit 306 generates control signals to the sensor-motor control unit 302, the memory 303, the head control circuit 305, etc., and transmits input signals from each block to the sequence control unit 307.

[0018] The image processing unit 308 performs image processing that separates the input image data from the host device 1 into colors, converts the data obtained from the color separation, and converts it into recordable data that can be recorded by the recording head 201. The timing control unit 309, in conjunction with the position of the carriage 202, transfers the recordable data generated by the conversion in the image processing unit 308 to the head control unit 310. The timing control unit 309 also controls signals synchronized with the ejection from each nozzle to determine the ejection state of ink droplets. The head control unit 310 functions as a generation means for generating ejection signals, converting the recordable data input from the timing control unit 309 into ejection signals and outputting them. The head control unit 310 also controls the temperature of the recording head 201 by outputting a control signal that does not eject ink based on the command of the sequence control unit 307. The head control circuit 305 functions as a generation means for generating drive pulses, generating drive pulses according to the ejection signals input from the head control unit 310 and applying them to the recording head 201.

[0019] <Method for detecting the ink droplet ejection state> Figure 4 illustrates a method for detecting the ejection state of ink droplets ejected from the recording head 201. The upper diagrams of Figure 4(a) and 4(b) respectively show schematic diagrams of the recording head 201 and droplet detection sensor 205 when the recording device 100 is cut in the YZ cross section. As shown in Figures 4(a) and 4(b), the ejection port surface 201a of the recording head 201 is provided with ejection ports (also called nozzles) 216 for ejecting ink droplets of each ink color for image formation.

[0020] Furthermore, the lower diagrams in Figure 4(a) and Figure 4(b) respectively show timing charts of the ejection signal for applying a drive pulse to the recording head 201 and the signal detected when the droplet detection sensor 205 detects the passage of an ink droplet ejected from the ejection port 216. As shown in Figures 4(a) and 4(b), the recording head 201 has an ejection port surface 201a. The droplet detection sensor 205 includes a light-emitting element 401, a light-receiving element 402, and a control circuit board 403. 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. The control circuit board 403 detects the amount of light received by the light-receiving element 402. The control circuit board 403 is provided with a current-voltage conversion circuit that converts the current flowing due to the amount of light received by the light-receiving element 402 into a voltage signal and outputs it, and an amplification circuit for the level of the ink droplet detection signal. Furthermore, external disturbances can cause fluctuations in the level of the detection signal for ink droplet ejection, leading to output saturation and a decrease in the signal-to-noise ratio. To eliminate these effects, a clamp circuit is provided to maintain the level of the signal output from the amplification circuit at a predetermined value (clamp voltage) until immediately before ejection observation. These circuits ensure a desired level of detection signal for ejection, enabling detection of minute changes such as ink droplet ejection. In this configuration, 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 level of the output detection signal changes. The ejection state of the nozzle under inspection is determined by comparing the output detection signal level with a predetermined reference voltage. In this specification, the nozzle under inspection is also referred to as the "target nozzle."

[0021] Furthermore, the droplet detection sensor 205 is positioned such that the optical axis of the light beam 404 is in the same position in the Z direction as the surface of the platen 212 that supports the recording medium 203. In addition, 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 signal-to-noise ratio. The X-direction position of the recording head 201 capable of ejecting ink droplets so that the ink droplets pass through the light beam 404 is defined as the "detectable position". When detecting ink droplets in order to detect the ejection state of the ink droplets, the sensor / motor control unit 302 controls the carriage motor 208 according to the command of the sequence control unit 307, and the recording head 201 moves to the detectable position.

[0022] In this embodiment, the cross-sectional area of ​​the luminous flux 404 is approximately 2 mm × 2 mm. The parallel light projection area of ​​the ink droplet when it passes through the luminous flux 404 is approximately 2^-3 (mm^2). The ejection port row and the luminous flux 404 are arranged in a relationship parallel to each other, and the creepage distance in the height direction (Z direction) is 2 to 10 mm. When the creepage distance between each ejection port and the luminous flux 404 is made close, the passage of the ejected ink droplet can be detected at a position close to the flight distance of the ejected ink droplet, thus enabling stable detection of the ejection state. However, when the ejection port row and the luminous flux 404 are in close proximity, a light component is generated when the diffuse light component emitted from the light-emitting element 401 is reflected off the ejection port surface 201a of the recording head 201 and received by the light-receiving element 402. As a result, it may be superimposed on the detection signal as a noise component in the detection of the ejection state, making it difficult to perform good detection. Therefore, the creepage distance between the luminous flux 404 of the droplet detection sensor 205 and the discharge port row of the recording head 201 is set considering these correlations. It is desirable to detect the discharge state under a more suitable arrangement.

[0023] Furthermore, it is desirable to position the light beam 404 of the droplet detection sensor 205 and the platen 212 supporting the recording medium 203 at approximately the same height (in the Z direction). This is because the conditions for detecting the ink droplet ejection state by the droplet detection sensor 205 should be matched with the ink droplet ejection state onto the recording medium 203 during image formation.

[0024] Next, the configuration for detecting the ejection status and non-ejection status of ejected ink droplets will be described in detail. Figure 4(b) is a graph showing the detection result when the ejection port 216 (referred to here as "Nozzle N"), which is the target of inspection for detecting the ejection status of the recording head 201, is ejecting ink normally, in the configuration shown at the top of Figure 4(a). Based on the ejection signal output by the head control unit 310 and the head control circuit 305, an ink droplet is ejected toward the droplet detection sensor 205. A control signal synchronized with the ejection of the ink droplet operates the clamp circuit described above, and just before observing the ejection of the ink droplet, the output signal level is held at a predetermined clamp voltage value.

[0025] Subsequently, ink droplet ejection begins, and the clamp circuit is released just before the ejected ink droplets, directed towards the light beam 404, block the light. Furthermore, the change in the amount of light when the ink droplets block the light beam 404 is used to determine whether the ejection state is normal or not. Specifically, a normal ejection state is determined by detecting (indicated by 406) that the light intensity drops below a predetermined reference voltage value due to the decrease in light intensity that occurs when the ejected ink droplets pass through the light beam 404 of the droplet detection sensor 205. In this case, it is determined that the N nozzle being inspected ejected normally. Figure 4(a) shows the results of performing multiple ejections (1st and 2nd shots) from the N nozzle being inspected in order to obtain more reliable results regarding the detection of the ejection state by the droplet detection sensor 205.

[0026] The lower part of Figure 4(b) is a graph showing the detection result when the Nth nozzle, which is the subject of inspection for detecting the ejection status of the recording head 201, is not ejecting ink properly, that is, when the Nth nozzle is in a non-ejecting state, as shown in the upper part of Figure 4(b). Similar to Figure 4(a), based on the ejection signal output by the head control unit 310 and the head control circuit 305, ink droplets are ejected toward the droplet detection sensor 205. However, in the example of Figure 4(b), the ink droplets are not ejected correctly, and the ink droplets do not fly toward the light beam 404. As a result, the ink droplets cannot block the light beam 404, and the decrease in light intensity that occurs when ejection is performed correctly is not obtained (reference numeral 407). Therefore, the signal output does not fall below the reference voltage value, and the ejection status cannot be detected. Thus, the Nth nozzle, which is the subject of inspection, is determined to be in a non-ejecting state (also called an abnormal state) where ink droplets are not ejected properly. A nozzle that is determined to not eject ink droplets properly is also called a non-ejecting nozzle or an abnormal nozzle.

[0027] <Method for detecting discharge status on a nozzle group basis> Figure 5 illustrates a method for detecting the ejection state on a nozzle group basis. Using Figure 5, we will explain how to detect the ejection state of ink droplets ejected from the recording head 201. Figure 5(a) shows a schematic diagram of the recording head 201 and droplet detection sensor 205 when the recording device 100 is cut in a YZ cross section, similar to the example described in Figure 4. Figure 5(a) also shows a timing chart of the ejection signal for applying a drive pulse to the recording head 201 and the detection signal detected when the droplet detection sensor 205 detects the passage of an ink droplet. Figure 5(b) is a diagram showing a cross-section of the light beam 404.

[0028] In this embodiment, nozzles are used as nozzles in groups, each consisting of multiple nozzles, as the nozzles to be inspected. That is, in this embodiment, the nozzles provided on the recording head 201 are divided into a certain number of groups. Then, a process is performed to detect the ejection state for each divided group. More specifically, the nozzles belonging to the nozzle group to be inspected (hereinafter also referred to as the "inspection nozzle group") are sequentially driven to eject ink droplets so that the ink droplets ejected from each nozzle simultaneously block the light beam 404 of the droplet detection sensor 205. That is, as shown in Figure 5(b), the nozzles of the inspection nozzle group are sequentially driven so that each ink droplet ejected from each nozzle simultaneously blocks the light beam 404 of the droplet detection sensor 205.

[0029] In this embodiment, control is performed to sequentially drive the nozzles belonging to the inspection nozzle group. In this case, a predetermined time difference occurs in the ink droplet ejection start timing for each nozzle belonging to the group. Therefore, it is possible to create a time difference in the timing when the ejected ink droplets reach the light beam 404 of the droplet detection sensor 205 and block the light, and the decrease in light intensity that occurs when passing through the light beam 404 is cumulatively added along with the time difference. As a result, it becomes possible to observe the ejection of ink droplets with a time difference from the control signal synchronized with the ejection. However, if ink droplets are ejected at exactly the same timing without a time difference, ink droplets from nozzles closer to the light-emitting element may block ink droplets from nozzles closer to the light-receiving element, making proper detection impossible. For this reason, in this embodiment, ejection control is performed so that multiple ink droplets block the light beam 404 simultaneously with a predetermined time difference. This will be referred to as "approximately simultaneous" from now on.

[0030] In Figure 5, based on the ejection signal transmitted via the head control unit 310 and head control circuit 305 within the CPU 301, an ink droplet is ejected from the recording head 201 toward the droplet detection sensor 205. In the configuration shown in Figure 5, the multiple nozzles belonging to the inspection nozzle group are nozzles in the same ejection port row. The ejection state is then detected for the group N to be inspected (here, group N consists of nozzles a, b, c, and d). Figure 5 is a schematic diagram showing the detection result when ejection is performed normally in group N. Following nozzle a, which belongs to inspection nozzle group N, ejection control is performed for nozzles b, c, and d. As described above, a control signal synchronized with the ejection of the ink droplet is used to hold the output signal level at a predetermined clamp voltage value just before observing the ejection of the ink droplet. The clamp operation is released just before the ink droplet ejected toward the light beam 404 is blocked after the ejection of the ink droplet has started. As a result, a predetermined change in the detection signal occurs due to the decrease in light intensity that occurs when the ink droplet ejected from nozzle a begins to pass through the light beam 404, relative to a reference voltage value determined by the amount of change when the ink droplet blocks the light beam 404.

[0031] Furthermore, the decrease in light intensity that occurs when ink droplets ejected from nozzle b, with a predetermined time difference from the ejection from nozzle a, pass through the light beam 404 is added and cumulatively added as the change in the detection signal. Similarly, the decrease in light intensity that occurs when ink droplets ejected from nozzles c and d pass through the light beam 404 is added and cumulatively added as the change in the detection signal. As a result, if it is detected that the voltage falls below a predetermined reference voltage value, the inspection nozzle group N is determined to be in a normal ejection state. Similar to the result shown in Figure 4, in the example in Figure 5, the inspection nozzle group N, which is the subject of inspection, is determined to have performed normal ejection. That is, it is determined that each nozzle belonging to the inspection nozzle group N performed normal ejection.

[0032] In the example shown in Figure 5, the nozzles belonging to inspection nozzle group N are shown as being composed of nozzles spaced one apart within the same nozzle row, but this is not limited to this. Any nozzles belonging to the same nozzle row can be divided into a nozzle group. Any nozzle whose discharge timing can be controlled so that it passes through the light beam 404 with a staggered discharge timing is acceptable. In addition, if the distance between nozzles is extremely large, the effect on the light shielding of one dot may differ, so it is preferable to have multiple closely spaced nozzles belong to the same inspection nozzle group N. Also, in the example in Figure 5, an example in which the number of nozzles belonging to the nozzle group is four is described, but it is acceptable as long as it includes multiple nozzles, and it is not limited to this number.

[0033] Figure 6 is a diagram showing an example of a control flowchart for detecting the discharge state in this embodiment. As shown in Figure 5, Figure 6 is an example of detecting the discharge state in units of inspection nozzle groups including multiple nozzles. The process shown in Figure 6 is a process performed by the sequence control unit 307 of the CPU 301 according to a program stored in memory 303, for example. The symbol "S" in the description of each process means a step in the sequence diagram.

[0034] The ejection state detection control shown in Figure 6 is a process performed during the initial setup when the user first operates the recording device 100, or immediately after the recording head 201 is replaced with a new one and installed. It may also be performed periodically as maintenance after the user has used the recording device for a certain period of time. Furthermore, the control shown in Figure 6 may be executed as appropriate according to the user's instructions.

[0035] First, in S601, the sequence control unit 307 sets the inspection nozzle groups. Here, in order to inspect the discharge state of all nozzles on the recording head 201, each nozzle is assigned to one of the inspection nozzle groups. That is, multiple nozzles are grouped together, and it is set which nozzles are assigned to each group. In the case of a new recording head 201 that has just been put into use, the nozzles are assigned to each group in order from the nozzles at the end of the discharge port 217. This will be explained using Figure 12(a). When assigning the nozzle port row 217 to groups, nozzles 1201, 1202, 1203, and 1204 are assigned to nozzle Gr.1 in Figure 12(b). However, nozzles that become non-discharging nozzles while using the recording head are registered as non-discharging nozzles in memory 303. Therefore, registered non-discharging nozzles are not assigned to groups, and discharge inspections may be performed individually, or they may be assigned to a group consisting only of non-discharging nozzles. If non-discharge nozzles are removed from the group assignment, the nozzle order may skip one position, or nozzles that are separated by more than one position may be formed into a nozzle group. In nozzle Gr.2 in Figure 12(b), non-discharge nozzles 14 and 16 are removed and the next nozzle, 18, is assigned.

[0036] Next, in S602, the sequence control unit 307 drives the carriage motor 208 to drive and control the recording head 201 and carriage 202, moving the recording head 201 to a position detectable by the droplet detection sensor 205.

[0037] Next, in S603, the sequence control unit 307 performs pre-processing necessary to detect the ejection state. Specifically, this includes pre-setting the optimal ejection control for detecting the ejection state, a preliminary ejection operation for stable ejection of ink droplets, and a suction fan stop operation for stabilizing the airflow control inside the recording device.

[0038] Next, in S604, the sequence control unit 307 performs the ejection drive setting operation when ejecting ink droplets for inspection from the recording head 201. Specifically, it stabilizes the ejection state of the ink droplets from the nozzles to be inspected and sets the ejection drive so that the ink droplets ejected from multiple nozzles pass through the light beam 404 almost simultaneously.

[0039] Next, in S605, the sequence control unit 307 executes an operation to eject an ink droplet for inspection from the recording head 201 so that it passes through the light beam 404 emitted by the light-emitting element 401 of the droplet detection sensor 205. Specifically, it starts ejecting ink droplets from each nozzle of the inspection nozzle group of the recording head 201. Then, the light-receiving element 402 of the droplet detection sensor 205 detects a detection signal indicating that the ink droplet has passed through the light beam 404. At this time, a reference voltage for detecting the ejection state according to the number of nozzles used is also set based on the ejection drive settings of the multiple nozzles set in S604. The reference voltage and the detection signal are compared and judged to detect the ejection state of the inspection nozzle group to be inspected. In other words, here, the ejection state is detected on a unit basis of the inspection nozzle group, rather than detecting the ejection state of individual nozzles.

[0040] Next, in S606, the sequence control unit 307 determines whether the waveform of the detection signal 501 falls below a predetermined reference voltage value. If it falls below the reference voltage, the process proceeds to S607, where the sequence control unit 307 determines that the ejection of all nozzles in the inspection nozzle group is normal. On the other hand, if it does not fall below the reference voltage, the process proceeds to S608, where the sequence control unit 307 determines that there is an abnormality in one of the nozzles in the inspection nozzle group. If the process proceeds to S608, in S609, the method is switched to inspecting each nozzle individually in the inspection nozzle group currently being processed. In detail, as explained in Figure 4, the reference voltage value is switched to a value that allows for the detection of ejection from one nozzle, and the process of ejecting ink from each nozzle is performed. In S609, each nozzle belonging to the inspection nozzle group is set as the nozzle to be inspected.

[0041] Following S609, in S610 the sequence control unit 307 determines whether it was able to detect a detection signal from the single discharge of the nozzle under inspection. That is, it determines whether the waveform of the detection signal 501 falls below the reference voltage. If the waveform of the detection signal 501 falls below the reference voltage, the process proceeds to S611, and the sequence control unit 307 determines that the nozzle under inspection is a normal nozzle. On the other hand, if the waveform of the detection signal 501 does not fall below the reference voltage, the process proceeds to S612, and the sequence control unit 307 determines that the nozzle under inspection is a non-discharging nozzle and stores the nozzle number in memory 303. Following S611 or S612, in S613 the sequence control unit 307 determines whether processing of all nozzles in the inspection nozzle group has been completed, and if there are any unprocessed nozzles, it returns to S610 and repeats the process. If processing of all nozzles in the inspection nozzle group has been completed, the process proceeds to S614. Furthermore, the loop processing from S610 to S613 is performed when it is determined that there is a non-discharging nozzle in the inspection nozzle group, but it is also possible that the nozzles will be able to discharge normally when discharging is performed again on an individual nozzle basis. For this reason, in the loop processing from S610 to S613, it is possible that the process will proceed all the way to S611, and all of the target nozzles in the inspection nozzle group will be determined to be normal nozzles.

[0042] In S614, the sequence control unit 307 determines whether all inspections of the inspection nozzle group have been completed. If the inspection of all inspection nozzle groups has not been completed, the process proceeds to S614, sets the next inspection nozzle group to be inspected, and proceeds to S605. If the inspection of all inspection nozzle groups has been completed, the process proceeds to S616. In S616, the sequence control unit 307 saves the ejection status results of all nozzles provided on the recording head 201 to the memory 303. That is, if the ejection status result for an inspection nozzle group is normal, all nozzles belonging to that inspection nozzle group will be considered normal. On the other hand, if the ejection status of an inspection nozzle group is abnormal, the inspection results for each individual nozzle belonging to that inspection nozzle group will be saved to the memory 303. The ejection status information saved here (also called nozzle information) is used for data processing and drive control of the recording head 201 as needed thereafter.

[0043] Next, the process proceeds to S617, where the sequence control unit 307 performs termination processing. Specifically, since the detection of the ejection state is complete, the recording head 201 is moved to a predetermined position, or the system is switched to a standby state for the next recording operation. Furthermore, based on the acquired ejection state information, the system proceeds to cleaning the recording head 201, and this process is completed.

[0044] Once the processing shown in Figure 6 for one row of nozzles, as described above, is complete, the recording head 201 moves to a position where ink droplets from the nozzles of the next row of nozzles to be inspected enter the light beam 404, and the processing shown in Figure 6 for the next row of nozzles to be inspected begins. Note that the termination process in S617 may be performed after the processing of all nozzle rows has been completed.

[0045] (First Embodiment) Using Figures 7, 8, and 9, we will explain how to determine the number of preliminary ejections performed before inspection to stabilize ejection when detecting the ejection state of ink droplets ejected from the recording head 201 in this embodiment, based on the nozzle arrangement conditions of group non-ejection detection that are ejected approximately simultaneously.

[0046] It has been found that when the ejection speed of ink droplets ejected from the recording head 201 is low, the flight distance of the ejected ink becomes shorter, and the flight state tends to become unstable. Therefore, in an optical ejection state detector that prevents droplet ejection, the behavior of ink droplets ejected towards the irradiated light beam becomes unstable, and they may not be able to reach the detection area at the desired speed.

[0047] The graph in Figure 7 shows that in a recording head that ejects ink droplets at a low speed, controlling the ejection of nearby nozzles, including the nozzle being detected, almost simultaneously changes the flight distance of the ejected ink droplets. When the nozzle being detected is driven and controlled alone, the flight distance of the ejected ink droplet is 7.9 mm. In contrast, when ejection control is performed using nearby nozzles, in this case adjacent nozzles, in addition to the nozzle being detected, the flight distance of the ejected ink droplet is 14.9 mm. Furthermore, even when using nozzles separated by one nozzle length instead of adjacent nozzles, the flight distance of the ejected ink droplet is 12.4 mm. The experimental results show that, in the case of a recording head 201 with a nozzle arrangement that forms a recording resolution of 600 dpi, controlling the ejection of nearby nozzles, including adjacent nozzles or nozzles separated by one nozzle length, when controlling the ejection of the nozzle being detected, makes it possible to extend the flight distance of the ejected ink droplets, indicating that the position of nozzles ejecting almost simultaneously contributes to stabilizing the ejection state. Furthermore, this is not limited to adjacent nozzles in the direction of the optical axis, but also applies to adjacent nozzles in a direction perpendicular to the optical axis, as long as they are arranged at the same interval as the nozzles described above.

[0048] Figure 8 illustrates the arrangement of the target nozzles. Figure 8(a) shows an arrangement where the target nozzles 801 that discharge almost simultaneously are adjacent to each other.

[0049] Furthermore, Figure 8(b) shows that the target nozzles 802 that eject ink almost simultaneously are not adjacent to each other, but are spaced apart. If ink droplets are ejected simultaneously at exactly the same timing without any time difference, ink droplets from nozzles closer to the light-emitting element may block ink droplets from nozzles closer to the light-receiving element, making proper detection impossible. Therefore, almost simultaneous ejection is necessary to create a time difference in the timing when the ejected ink droplets reach the light beam 404 of the droplet detection sensor 205 and block the light.

[0050] Using the flowchart in Figure 9, the sequential drive setting for detection nozzle Gr. discharge in step S604 of the flowchart in Figure 6 will be explained. In step S901, the multiple target nozzle groups shown in Figure 12(b), which were assigned in step S601, are sequentially set to be driven as target nozzle groups to be discharged almost simultaneously, in the order of the nozzle arrangement. In step S902, the arrangement of the set target nozzles is determined, and the number of pre-inspection reserve discharges is determined. Specifically, as shown in Figure 8(b), if the target nozzles are not adjacent, the normal number of pre-inspection reserve discharges for group non-discharge detection, 30, is set. Also, as shown in Figure 8(a), if the target nozzles are adjacent, the number of pre-inspection reserve discharges is set to 17, which is fewer than the normal number.

[0051] As described above, in this embodiment, when detecting the ejection state of ink droplets ejected from the recording head 201, multiple nozzles are grouped together, and the ejection from multiple nozzles is detected by the droplet detection sensor 205 to determine whether all nozzles in the group are able to eject. The number of pre-ejections performed to stabilize the ejection before detection is determined by the arrangement conditions of the multiple nozzles ejecting almost simultaneously. This allows the number of pre-inspection pre-ejections to be set according to the conditions, thereby reducing the number of pre-inspection pre-ejections and further reducing the inspection time.

[0052] (Second embodiment) Next, a second embodiment will be described. In the first embodiment, the number of pre-inspection pre-discharges was determined by the nozzle arrangement conditions for group non-discharge inspections that were discharged almost simultaneously. The difference from the first embodiment is that in step S902, the arrangement relationship of the target nozzles is recorded as an adjacent table in Figure 10.

[0053] (Third embodiment) Next, a third embodiment will be described. In the first and second embodiments, the nozzle arrangement conditions were adjacent and non-adjacent. However, as shown in the graph in Figure 7, even when nozzles separated by one nozzle length are used instead of adjacent nozzles, the flight distance of the ejected ink droplets is 12.4 mm. Therefore, this is designated as the proximity condition, and in step S902, a table like Figure 11 is used to show the arrangement relationship of the target nozzles and the number of pre-emptive ejections.

[0054] (Fourth embodiment) Next, a fourth embodiment will be described. The ejection characteristics of ink droplets differ depending on the ink color. There are various types, such as yellow which has a slower ejection speed than other colors, and cyan which has high ejection stability. In step S902, the number of pre-inspection pre-dispense droplets is calculated for each color by multiplying the values ​​in the adjacent table, which shows the arrangement relationship of the target nozzles and the number of pre-dispense droplets, by a certain coefficient.

[0055] (Fifth embodiment) Next, a fifth embodiment will be described. In the first to fourth embodiments, the target nozzle arrangement conditions and adjacent tables were held in advance by the recording device 100. However, in order to take into account the characteristics that change for each recording head 201, measurements may be taken when the recording head is replaced, and this may be set in step S902 as an individual-specific table showing the arrangement relationship of the target nozzles and the number of pre-emptive discharges.

[0056] As described above, in this embodiment, when detecting the ejection state of ink droplets ejected from the recording head 201, the number of pre-ejections performed to stabilize the ejection before detection is determined based on the arrangement conditions of multiple nozzles ejecting approximately simultaneously and the ink color. This allows the number of pre-inspection pre-ejections to be set according to the conditions, thereby reducing the number of pre-inspection pre-ejections and further reducing the inspection time. [Explanation of Symbols]

[0057] 100 Recording device 201 Recording head 203 Record Sheet 205 Droplet detection sensor 301 CPU 302 Sensor / Motor Control Unit 303 memory 401 Light-emitting part 402 Light receiving part 403 Control board 404 Luminous flux

Claims

1. A recording head having a nozzle for ejecting droplets, A droplet ejection control means that controls the recording head and ejects ink droplets from each nozzle provided on the recording head, A droplet detection unit detects the ejection of the droplet by blocking the beam of light from the light-emitting means to the light-receiving means at a position opposite to the recording head, The system includes a discharge state inspection means that determines whether the discharge state is normal or abnormal based on the output change of the droplet detection unit, The droplet ejection control means enables the ejection of droplets from each nozzle at a predetermined timing, and ejects droplets from multiple nozzles in such a manner that the droplets obstruct the light beam. An inkjet recording apparatus characterized by determining the number of pre-extraction nozzles based on the arrangement conditions of the aforementioned multiple nozzles.

2. The inkjet recording apparatus according to claim 1, characterized in that the droplet ejection control means sequentially drives each nozzle and ejects ink droplets continuously, so that the ink droplets ejected to the droplet detection unit block the light beam with a time difference, thereby allowing the ejection state inspection means to perform a determination.

3. The inkjet recording apparatus according to claim 1, characterized in that the plurality of nozzles are capable of blocking the light beam and the distance between the nozzles is within a predetermined distance range.

4. The inkjet recording apparatus according to claim 1, characterized in that the plurality of nozzles are composed of nozzles in the same discharge port row of the recording head.

5. An inkjet recording apparatus characterized in that the conditions for determining the number of preliminary ejections before inspection are configured in a table.

6. The arrangement condition for the multiple nozzles is that the nozzles are arranged adjacent to each other, characterized in that the inkjet recording apparatus.

7. The arrangement condition for the multiple nozzles is that the nozzles are located in close proximity to each other, characterized in that the inkjet recording apparatus.

8. The inkjet recording apparatus is characterized in that the conditions for determining the number of preliminary ejections before inspection differ depending on the ink color.

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