Spit-out device and method for determining spit-out timing

Abstract

To improve calculation accuracy of a discharge speed of an ink droplet.SOLUTION: Time from discharging of an ink droplet from a recording head 201 to detection of the ink droplet by a droplet detection sensor 205 is measured multiple times while changing a distance between the recording head 201 and the droplet detection sensor 205, and a discharge speed is calculated on the basis of a distance difference and a time difference.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a discharging device and a method for determining discharging timing.

Background Art

[0002] In an inkjet recording apparatus, as the use continues, the ejection speed of ink droplets may change due to individual differences in the recording apparatus and recording head, physical properties of the ink, and further usage conditions and environmental influences. When the ejection speed of ink droplets changes, for example, when an image is recorded by reciprocating scanning of the recording head, the landing positions of the ink droplets ejected in the forward path direction and the ink droplets ejected in the return path direction are shifted, affecting the image quality.

[0003] Patent Document 1 discloses a registration adjustment method for appropriately setting ejection timing from the moving speed of a recording head and the ejection speed by providing an optical detector for measuring the ejection speed of ejected ink, and based on the measurement result. Further, in this document, as a method for measuring the ejection speed of ink, the time from the ejection timing of the ink to the arrival of the light beam irradiated from the optical detector is measured, and the ejection speed is calculated based on the measurement result and the distance from the recording head to the light beam.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the method of calculating the ejection speed by setting the distance between the ejection head and the droplet detection sensor constant as in Patent Document 1, if there is an error in the distance between the ejection head and the droplet detection sensor, the ejection speed cannot be obtained with high accuracy.

[0006] The present invention aims to improve the ejection accuracy when recording an image.

Means for Solving the Problems

[0007] The present invention includes an ejection head that ejects droplets from a plurality of ejection ports formed on an ejection port surface, droplet detection means for detecting that the ejected droplets have reached a predetermined position, changing means for changing the distance between the ejection port surface of the ejection head and the predetermined position, and when the distance from the ejection port surface of the ejection head to the predetermined position is a first distance, the droplets ejected from the plurality of ejection ports are detected by the droplet detection means, and based on the result of detecting the droplets ejected from the plurality of ejection ports by the droplet detection means when the distance from the ejection port surface of the ejection head to the predetermined position is a second distance different from the first distance, determining means for determining the ejection timing when recording an image by the ejection head. The ejection head records a pattern for adjusting the ejection timing on a recording medium, the droplet detection means detects droplets ejected at a predetermined timing different from the timing when the pattern is recorded, and the determining means determines the ejection timing based on the pattern and the detection result of the droplet detection means.

Effects of the Invention

[0008] According to the present invention, by changing the distance between the ejection head and the droplet detection sensor and measuring multiple times the time from when an ink droplet is ejected from the ejection head until it is detected by the droplet detection sensor, the calculation accuracy of the ejection speed of the ink droplet can be improved.

Brief Description of the Drawings

[0009]

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Embodiments for Carrying Out the Invention

[0010] (First Embodiment) <Overall Outline of the Recording Apparatus> FIG. 1 is a diagram showing the appearance of an inkjet recording apparatus (hereinafter, recording apparatus) 100 as an example of a droplet ejection apparatus according to an embodiment.

[0011] The recording apparatus 100 shown in FIG. 1 includes a paper discharge guide 101 for loading the output recording medium, a display panel 103 for displaying various recording information, setting results, etc., and operation buttons 102 for setting recording modes, recording paper, etc. Further, the recording apparatus 100 includes an ink tank unit 104 that houses ink tanks for storing inks of colors such as black, cyan, magenta, and yellow, and supplies ink to a recording head 201 (FIG. 2) as an example of a droplet discharge head. The recording apparatus in FIG. 1 is a recording apparatus capable of recording on recording media of a plurality of widths up to a 60-inch size recording medium. As the recording medium 203, roll paper or cut paper can be used. Further, the recording medium 203 is not limited to paper, and may be, for example, cloth or vinyl.

[0012] FIG. 2 is a perspective view showing the internal configuration of the recording apparatus 100. The platen 212 is a member that supports the recording medium 203 positioned at a position facing the recording head 201. The recording medium 203 is conveyed in the conveyance direction (Y direction) by the paper conveyance roller 213 while being supported by the platen 212. The recording head 201 has a discharge port surface 201a (FIG. 5) in which discharge ports are formed. In the discharge port surface 201a, a discharge port row in which a plurality of discharge ports are arranged in the Y direction is formed for each ink color, and the discharge port rows are arranged in the X direction. The recording head 201 is mounted on the carriage 202. Further, the recording head 201 includes 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 (FIG. 8) that irradiates light onto the recording medium 203 and a light receiving element (FIG. 8) that receives the light reflected from the recording medium 203, and measures the distance from the change in the output of the light reception amount of the light receiving element. Details will be described with reference to FIG. 8. The droplet detection sensor 205 is a sensor that detects droplets, here ink droplets, discharged from the recording head. The droplet detection sensor 205 is an optical sensor including a light emitting element 401 (FIG. 5), a light receiving element 402 (FIG. 5), and a control circuit board 403 (FIG. 5). Details will be described with reference to FIG. 5. The main rail 206 supports the carriage 202, and 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 via the carriage conveyance belt 207. The linear scale 209 is disposed in the scanning direction, and position information is acquired by the encoder sensor 210 mounted on the carriage 202 detecting the linear scale 209. Further, the recording apparatus 100 includes a lift cam (not shown) for variably changing the height of the main rail 206 that supports the carriage 202 in steps and a lift motor 211 that drives the lift cam. By driving the lift cam with 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.It is possible to variably change the height in multiple steps with a predetermined accuracy based on the stop position of the lift cam, and since the variable amount of the height is driven relative to the height of a predetermined step, it is possible to set the variation distance between steps with high accuracy.

[0013] 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 speed and the thickness of the recording medium. The CPU 301, the sensor / motor control unit 302, and the memory 303 are connected to be communicable with each other. The sensor / motor control unit 302 controls the distance detection sensor 204, the droplet detection sensor 205, and the 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.

[0014] 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 block, controls the conveyance of the recording medium, controls the scanning of the carriage 202, and the like. The control of each functional block is executed by the sequence control unit 307 reading various programs from the memory 303 and executing them. The driver unit 306 generates control signals to the sensor / motor control unit 302, the memory 303, the head control circuit 305, etc. based on commands from the sequence control unit 307, and transmits input signals from each block to the sequence control unit 307.

[0015] The image processing unit 308 performs image processing to decompose and convert the input image data from the host device 1 into recording data that can be recorded by the recording head 201. The timing control unit 309 transfers 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. Also, the timing control unit 309 controls the timing of discharging the recording data. The timing control is performed according to the discharging timing determined based on the discharging speed calculated in the discharging speed calculation process described later. The head control unit 310 functions as a discharging signal generation means, converts the recording data input from the timing control unit 309 into a discharging signal, and outputs it. Also, based on the command of the sequence control unit 307, the head control unit 310 outputs a control signal to such an extent that ink is not discharged, thereby controlling the temperature of the recording head 201. The head control circuit 305 functions as a driving pulse generation means, generates a driving pulse according to the discharging signal input from the head control unit 310, and applies it to the recording head 201.

[0016] Next, the adjustment of the discharging timing will be described with reference to FIG. 4. FIG. 4(a) is a schematic diagram showing the relationship between the discharging speed of ink droplets and the landing position. Let the distance in the Z direction between the discharge port surface 201a of the recording head 201 and the recording medium 203 be H. The recording head 201 reciprocates in the X direction at a speed Vcr while discharging ink to record an image on the recording medium 203. Let the discharging speed of the ink droplets discharged from the recording head 201 be Va. As shown in FIG. 4(a), since the scanning directions are different in the forward scanning direction and the return scanning direction, the landing positions of the ink are different with respect to the positions where the ink droplets are discharged. In order to align the landing positions of the ink droplets discharged by the recording head 201, the discharging timing of the ink droplets is adjusted. First, the distance Xa from the position where the ink droplet is discharged in the forward scanning direction to the position where the ink droplet lands on the recording medium 203 is described by the following calculation formula.

[0017] Xa =(H / Va)× Vcr Furthermore, the distance Xb from the position where the ink droplet is discharged in the return scanning direction to the position where the ink droplet lands on the recording medium 203 is described by the following calculation formula.

[0018] Xb = (H / Va) × (―Vcr) = ―Xa As described above, based on the distance between the recording head 201 and the recording medium 203 and the ejection speed of the ink droplets detected by the droplet detection sensor 205, the appropriate ejection timing for the position of the recording head 201 detected by the encoder sensor 210 is obtained. In the present embodiment, a default ejection speed and an ejection timing for the default ejection speed are determined in advance and stored in the memory 303. With the adjustment value for the ejection timing for this default ejection speed set to 0, the adjustment value is adjusted from -4 to +4 according to the ejection speed. The adjustment is performed in units of 1200 dpi. A table in which this ejection speed and the adjustment value of the ejection timing are associated is stored in the memory 303 in advance. Then, an adjustment value of the ejection timing corresponding to the speed obtained by the ejection speed calculation process of FIG. 7 described later is acquired from the table, and the ejection timing is adjusted.

[0019] Further, FIG. 4(b) shows a case where the ejection speed of the ink droplets detected by the droplet detection sensor 205 is lower than the ejection speed of the ink droplets shown in FIG. 4(a). At this time, the distance Xa' from the position where the ink droplets were ejected in the forward scan direction to the position where the ink droplets land on the recording medium 203 is described by the following calculation formula.

[0020] Xa’ = (H / Va’) × Vcr Assuming that the ejection speed of the ink droplets until the ink droplets ejected from the recording head 201 land on the recording medium 203 has decreased by 10%, the distance from the ejection position to the landing position can be obtained as follows.

[0021] Xa’ = (H / Va’) × Vcr = (H / (Va × 0.9)) × Vcr = 1.11 × Xa As described above, when the ejection speed decreases, the landing position shifts in the direction in which the recording head 201 scans. When the distance from the ejection position to the landing position is obtained, an adjustment value for appropriate ejection timing can be obtained based on the ejection speed, as in FIG. 4(a). In the first embodiment, it is assumed that the recording medium 203 is sufficiently thin, and the distance between the ejection port surface 201a of the recording head 201 and the recording medium 203 can be regarded as the same as the distance between the ejection port surface 201a and the platen 212.

[0022] Next, a method for calculating the ejection speed of the ink droplets ejected from the recording head 201 in the present embodiment will be described with reference to FIG. 5. FIG. 5 shows a schematic diagram of the recording head 201 and the droplet detection sensor 205 when the recording apparatus 100 is cut along the Y-Z plane. Also shown is a timing chart of the ejection signal for applying a drive pulse to the recording head 201 and the detection signal when the droplet detection sensor 205 detects the passage of an ink droplet.

[0023] As shown in Fig. 5(a), the recording head 201 has a discharge port surface 201a. The droplet detection sensor 205 is composed of a light emitting element 401, a light receiving element 402, a control circuit board 403, etc. The light emitting element 401 emits light 404, and the light receiving element 402 receives the light 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. When an ink droplet passes through the light 404, the amount of light received decreases, so the passage of the ink droplet can be detected. The droplet detection sensor 205 is installed such that the optical axis of the light 404 is at the same position in the Z direction as the surface of the platen 212 that supports the recording medium 203. Slits are provided near the light emitting element 401 and the light receiving element 402, respectively, to narrow down the incident light 404 and improve the S / N ratio. The position of the recording head 201 in the X direction where the ink droplet can be discharged so that the ink droplet passes through the light 404 is set as the detectable position. When detecting the ink droplet to calculate the discharge speed of the ink droplet, the sensor / motor control unit 302 controls the carriage motor 208 by the sequence control unit 307, and the recording head 201 moves to the detectable position. In this embodiment, the cross-sectional area of the light beam of the light 404 is about 1 (mm^2). And the parallel light projection area of the ink droplet when the ink droplet passes through the light 404 is about 2^-3 (mm^2).

[0024] FIG. 5(a) shows a state where the distance in the height direction (Z direction) between the ejection port surface 201a of the recording head 201 and the light 404 emitted by the light-emitting element 401 is H1. When the distance between the ejection port surface 201a and the light 404 is not H1, the sensor-motor control unit 302 drives the lift motor 211 to move the height of the recording head 201 by the lift cam. When the state shown in FIG. 5(a) is reached, the ejection signal from the head control unit 310 in the CPU 301 is transmitted to the head control circuit 305 via the driver unit 306. The driver unit 306 transmits the timing at which the ejection signal is transmitted to the sequence control unit 307. The head control circuit 305 generates drive pulses according to the ejection signal and applies them to the recording head 201 to eject ink from the ejection port. When the amount of light received by the light-receiving element 402 changes as the ink droplet passes through the light 404 emitted by the light-emitting element 401, the timing at which the amount of light received changes is output as a detection signal by the control circuit board 403. The output detection signal is sent to the sequence control unit 307 via the sensor-motor control unit 302. Then, the sequence control unit 307 detects the detection time T1 from when the ejection signal is issued until the detection signal is output. As described above, the sequence control unit 307 functions as time detection means for detecting the time from the start of ink ejection until the ejected ink droplet is detected, and detects the detection time for calculating the ejection speed.

[0025] FIG. 5(b) shows a state where, after detecting the ink droplet in FIG. 5(a), the lift motor 211 is driven and the distance in the height direction (Z direction) between the ejection port surface 201a of the recording head 201 and the light 404 emitted by the light-emitting element 401 is set to H2. Similar to FIG. 5(a), the timing at which the amount of light received by the light-receiving element 402 changes when the ink droplet passes through the light 404 of the droplet detection sensor 205 is output as a detection signal. Then, the sequence control unit 307 detects the detection time T2 from when the ejection signal for ejecting the ink droplet onto the recording head 201 is issued until the detection signal is output.

[0026] When detecting the detection times T1 and T2 in the states of FIGS. 5(a) and 5(b), the sequence control unit 307 calculates the discharge speed V1 of the ink droplets passing between the distance H2 and the distance H1 based on the time difference between the detection time T1 and the detection time T2 and the distance difference between the distance H1 and the distance H2. The calculation formula is as follows.

[0027] V1=(H2-H1) / (T2-T1) When the discharge speed V1 is calculated, the lift motor 211 is driven to make the height-direction distance between the discharge port surface 201a and the light 404 be H3, which is further separated from the distance H2. The state at this time is shown in FIG. 5(c). Similar to FIGS. 5(a) and 5(b), ink droplets are discharged from the discharge port of the recording head 201, and the control circuit board 403 detects, as a detection signal, the timing when the light amount changes when the discharged ink droplets pass through the light 404 of the droplet detection sensor 205. Then, the sequence control unit 307 detects the detection time T3 from when the discharge signal for discharging the ink droplets to the recording head 201 is issued until the detection signal is output. Similar to the time described in FIGS. 5(a) and 5(b), based on the difference between the detection time T2 and the detection time T3 detected at the distances H2 and H3 respectively and the distance difference between the distance H2 and the distance H3, the discharge speed V2 of the ink droplets passing between the distance H3 and the distance H2 is calculated. The calculation formula is as follows.

[0028] V2=(H3-H2) / (T3-T2) When the ejection speed V2 is calculated, the lift motor 211 is further driven to set the distance in the height direction between the ejection port surface 201a and the light 404 to H4, which is further apart than the distance H3. The state at this time is shown in FIG. 5(d). Similar to FIGS. 5(a), 5(b), and 5(c), ink droplets are ejected from the ejection port of the recording head 201, and the control circuit board 403 detects the timing when the amount of light changes when the ejected ink droplets pass through the light 404 of the droplet detection sensor 205 and outputs a detection signal. Then, the sequence control unit 307 detects the detection time T4 from when the ejection signal for ejecting ink droplets is issued to the recording head 201 until the detection signal is output. Similar to the time described in FIGS. 5(a) to 5(c), based on the difference between the detection time T3 and the detection time T4 detected at the distances H3 and H4 respectively, and the distance difference between the distances H3 and H4, the ejection speed V3 of the ink droplets passing between the distance H4 and the distance H3 is calculated. The calculation formula is as follows.

[0029] V3=(H4-H3) / (T4-T3) As described above, the distance between the recording head 201 and the droplet detection sensor 205 is changed, and the detection time at each distance is detected to calculate the ejection speed V of the ink droplets. Above, the detection time was detected in order from the short distance, but the detection order is not limited to this. For example, it may be detected in order from the longer distance. In the present embodiment, the distance H to be separated is a distance between 1.2 mm and 2.2 mm.

[0030] Also, regarding the distance between the recording head 201 and the droplet detection sensor 205, the detection time at more distances may be measured and the ejection speed may be calculated. Since the ejection speeds corresponding to many distances can be calculated, the attenuation effect of the ejection speed (whether the ejection speed is constant or changes depending on the distance) can be obtained in more detail. As a result, it is possible to obtain the ejection speed of the ink droplets and the attenuation effect with higher accuracy.

[0031] Figures 6(a) and 6(c) are diagrams showing the distance between the discharge port surface 201a and the light 404 of the droplet detection sensor 205, which were described in FIG. 5, and the output results of the detection time at each distance. Figures 6(b) and 6(d) are diagrams showing the relationship between the discharge speed calculated from the distance and the detection time shown in Figures 6(a) and 6(c), respectively, and the difference between each distance.

[0032] In the graph shown in FIG. 6(a), the vertical axis represents the detection time detected by the sequence control unit 307, and the horizontal axis represents the distance between the discharge port surface 201a of the recording head 201 and the light 404 of the droplet detection sensor 205. The portion indicated by the shaded circles in FIG. 6(a) is the actually measured portion. Here, the detection is performed at distances H1 to H5. The distance H5 is a distance further away than the distance H4.

[0033] In the graph shown in FIG. 6(b), the vertical axis represents the discharge speed, and the horizontal axis represents the difference between the separated distances. At this time, the calculated discharge speed data may be non-linearly changing data due to various influences. Therefore, in order to calculate the discharge speed data shown for each distance difference more accurately, from the obtained discharge speed data, an approximation curve of a polynomial of the second degree or higher is obtained, and the polynomial of the obtained approximation curve is used as an expression representing the discharge speed. To obtain the approximation curve, three or more discharge speeds are used. In order to calculate three or more discharge speeds, it is necessary to detect the detection time at four or more distances. The method of obtaining the discharge speed is as described above.

[0034] Also, as a result of the inventors' experiments, it has been found that depending on the individual differences of the recording heads, the physical property differences for each ink color, and further the usage conditions and environmental influences, there may be a possibility of obtaining data that changes linearly. The data in such a linearly changing case is shown in FIG. 6(c). Also in this case, similar to the above, the ejection speed can be calculated from the detection time at each distance and the difference in the distance between the ejection port surface 201a and the light 404. A diagram showing the relationship between the calculated ejection speed and the difference in distance is shown in FIG. 6(d). As shown in FIG. 6(d), the ejection speed calculated for each difference in distance shows a constant ejection speed regardless of the difference in distance. When it is known that linearly changing data is obtained, since the ejection speed is constant regardless of the distance, only one ejection speed needs to be obtained. To calculate one ejection speed, it is sufficient to detect the detection times at two distances.

[0035] Also, even if the change in the ejection speed is non-linear, when recording is performed only when the distance between the ejection port surface 201a and the recording medium 203 is a constant distance, it is not always necessary to calculate an approximate curve. In that case, it is sufficient to detect the detection times at two distances that include the distance at the time of recording.

[0036] FIG. 7 corresponds to FIGS. 5 and 6 and shows a flowchart of the process for calculating the ejection speed.

[0037] The ejection speed calculation process in FIG. 7 is a process performed when the user of the recording apparatus 100 operates the recording apparatus 100 for the first time during initial installation, or when the recording head 201 is replaced with a new one and installed. Also, it may be performed regularly as maintenance or in accordance with a user's instruction. The process in FIG. 7 is a process performed by the sequence control unit 307 of the CPU 301 according to a program stored in the memory 303, for example.

[0038] First, in step S601, the sequence control unit 307 drives the lift motor 211 to separate the recording head 201 and the droplet detection sensor 205 by a predetermined distance. The separation distance is set in advance in the memory 303 and is the distances H1 to H4 described in FIG. 5 in this embodiment. The order of the separation distances is the same as that described in FIG. 5, i.e., in the order of distances H1, H2, H3, and H4.

[0039] Next, proceed to step S602 and execute the preprocessing necessary to detect the ejection speed. Specifically, it includes the preliminary setting of the optimal ejection control for detecting the ejection speed, the preliminary ejection operation for the stable ejection of ink droplets, and further the suction fan stop operation for stabilizing the air flow control inside the recording device.

[0040] Next, proceed to step S603 and execute an ejection operation to eject inspection ink droplets from the recording head 201 with respect to the light 404 emitted by the light emitting element 401 of the droplet detection sensor 205. Specifically, at the distance separated in step S601, the detection time, which is the time from the start of the ejection of ink droplets from a predetermined nozzle of the recording head 201 until the light receiving element 402 of the droplet detection sensor 205 detects that the ink droplet has passed through the light 404, is detected. At this time, the detection time is detected for a plurality of detection times using a plurality of nozzles of the recording head 201. It is desirable that the nozzles for which the detection time is measured are selected from a wide range of nozzles including both ends and the center in order to accurately detect the ejection speed.

[0041] Next, proceed to step S604 and execute data processing on the detection time data obtained in step S603 to calculate the detection time for the distance separated in step S601. Specifically, data processing such as averaging processing based on the number of acquisition samples necessary for stabilizing the measurement of the detection time and deleting data outside the upper and lower error ranges to prevent the mixing of abnormal values in the data is executed.

[0042] Next, proceed to S605 to determine whether the detection time has been detected for all the distances set in the memory 303. In the present embodiment, it is determined whether the distance between the current ejection port surface 201a and the light 404 of the droplet detection sensor 205 is the distance H4, which is the distance to be separated last. If the distance is not the distance H4, return to step S601, separate by the next set distance, and execute the subsequent data acquisition and processing. In step S605, if it is determined that the current distance is the distance H4, it is considered that the acquisition of the detection time at all distances is completed, and proceed to S606.

[0043] In step S606, calculate the ejection speed. Specifically, as described with reference to FIGS. 5 and 6, calculate the ejection speed based on the difference between each distance and the detection time at each distance. After calculating the ejection speed, proceed to step S607 and save the information of the ejection speed calculated in step S606 in the memory 303. The ejection speed information saved here is used for data processing and driving control of the recording head 201 according to necessary processing hereinafter.

[0044] Next, proceed to step S608 to perform end processing. Specifically, since the calculation of the ejection speed is completed, retract the recording head 201 to a predetermined position, shift to a standby state for the next recording operation process, or further shift to a cleaning process of the recording head 201 based on the obtained ejection speed information, etc., and then this process ends.

[0045] When the ejection speed in FIG. 7 ends, based on the table in which the ejection speed saved in the memory 303 in advance is associated with the adjustment value of the ejection timing, and the ejection speed obtained by the process in FIG. 7, obtain the adjustment value of the ejection timing from the table and perform the adjustment of the ejection timing. When printing an image, the timing control unit 309 controls the timing of ejecting ink according to the recording data.

[0046] As described above, in the present embodiment, the distance between the recording head 201 and the droplet detection sensor 205 was changed, and the time from the ejection to the detection of the ink droplets was detected for each of a plurality of distances. Then, the ejection speed is calculated based on the difference between each distance and the difference in the detection time. Thereby, even when not in a state assembled with high precision, the ejection speed of the ink droplets can be calculated with high precision. Further, by detecting the detection times of four or more distances, it is possible to more accurately obtain the individual differences of the recording apparatus and the recording head, the physical properties for each ink color, and further the attenuation effect of the ejection speed for each separated distance with respect to the usage status and environmental influence. Furthermore, by adjusting the ejection timing based on the ejection speed, it is possible to suppress a decrease in image quality due to a landing position shift.

[0047] In the above-described embodiment, the recording head 201 is configured to move with respect to the droplet detection sensor 205 to change the distance. However, it is only necessary that the distance in the Z direction between the droplet detection sensor 205 and the recording head 201 changes relatively. Therefore, for example, the droplet detection sensor 205 may be moved in the Z direction to change the distance.

[0048] In the above-described embodiment, regarding the calculation of the ejection speed by the droplet detection sensor 205, a method of calculating the ejection speed from the difference between each distance and the difference in the detection time was shown. However, a method of obtaining the detection time at a plurality of distances and calculating the ejection speed based on each distance and the corresponding detection time may also be used.

[0049] Also, it has been shown that the target nozzles for measuring the detection time of the ejection speed are set more widely. However, depending on the usage status of the user, it may be configured to measure the ejection speed for nozzles that are more frequently used in printing. (Second Embodiment) Next, the first embodiment will be described. In the first embodiment, the thickness of the recording medium 203 was not considered. However, in reality, since the recording medium 203 has a thickness, the distance between the ejection port surface 201a and the platen 212 is different from the distance between the ejection port surface 201a and the recording medium 203. In particular, when recording is performed using a particularly thick recording medium, there is a risk that the ejection position will shift because the distance between the ejection port surface 201a and the recording medium 203 is different from the adjustment value determined based on the distance between the ejection port surface 201a and the platen 212. In this embodiment, the ejection timing is adjusted based on the distance between the ejection port surface 201a and the recording medium 203.

[0050] The distance between the ejection port surface 201a and the recording medium 203 is measured by the distance detection sensor 204. Then, the ejection timing control is performed based on the distance between the recording head 201 and the recording medium 203 detected by the distance detection sensor 204 and the ejection speed information calculated in the ejection speed calculation process.

[0051] FIG. 8 is a diagram showing the internal configuration of the distance detection sensor 204 and the change in the amount of light (output) in the irradiation area and the light reception area that changes according to the distance between the irradiation surface of the recording medium 203. As shown in FIG. 8(a), inside the distance detection sensor 204, a control board 701 that performs lighting and extinguishing processes of a light source is provided at a position where the recording medium 203 is conveyed, a light emitting unit 702 for irradiating the light, a light receiving unit 703 for receiving the reflected light, and a light receiving unit 704 are mounted. In the present embodiment, the surface of the distance detection sensor 204 facing the recording medium 203 is at the same position in the Z direction as the discharge port surface 201a of the recording head 201. Therefore, the distance to the recording medium 203 measured by the distance detection sensor 204 corresponds to the distance between the discharge port surface 201a of the recording head 201 and the recording medium 203. Further, the intensity of the reflected light obtained by the light receiving units 703 and 704 is converted into an output signal of a current value or a voltage value, a predetermined arithmetic process is performed on the output signal, and the result is stored in the memory 303. For example, it is stored as distance information data indicating the relationship between the ratio value of the output signals obtained by the light receiving units 703 and 704 and the distance from the recording head 201 to the recording medium 203. FIG. 8(b) shows the relationship between the distance, the output signal, and the distance information data. As shown in FIG. 8(b), when the distance from the irradiation surface of the recording medium 203 is M1, the amount of reflected light to the light receiving unit 704 becomes maximum, and the amount of reflected light to the light receiving unit 703 becomes minimum. Therefore, the ratio value of the output signal of the distance detection sensor 204, that is, the distance information data also shows the minimum. Also, when the irradiation surface of the recording medium is M3, the amount of reflected light to the light receiving units 703 and 704 becomes about half of the peak value respectively. Therefore, as the output distribution of the distance detection sensor, the light receiving unit 703 and the light receiving unit 704 become equal, and the ratio value of the output signal of the distance detection sensor 204, that is, the distance information data becomes 1. Further, when the irradiation surface of the recording medium is M5, the amount of reflected light to the light receiving unit 704 becomes minimum, and the amount of reflected light to the light receiving unit 703 becomes maximum. Therefore, as the output distribution of the distance detection sensor, the light receiving unit 704 shows the minimum and the light receiving unit 703 shows the maximum, and the ratio value of the output signal of the distance detection sensor 204, that is, the distance information data also shows the maximum. Here, regarding the relationship between the position of the reference irradiation surface and the proportional value of the output signal of the distance detection sensor 204, it may be obtained in advance and stored in the memory 303.For example, a value detected for a recording medium with a predetermined thickness can be held as a reference value. Further, it is also possible to store the position of the recording head 201 when the distance from the recording head 201 to the recording medium 203 is M1 to M5, and the distance between the recording head 201 and the droplet detection sensor 205 at that time.

[0052] FIG. 9(a) is a diagram showing the distances H1 to H5 at which the droplet detection sensor 205 and the recording head 201 are separated from each other, and the output results of the detection times detected by the droplet detection sensor 205 at each distance. FIG. 9(b) is a diagram showing the relationship between the distances shown in FIG. 9(a) and the ejection speed calculated from the detection times. The detection time and the ejection speed are obtained by the same method as the method described in FIG. 6 of the first embodiment. In FIG. 9, the detection speeds at the distances of H1 to H5 are obtained, and the corresponding ejection speeds V1 to V5 are calculated. After obtaining the ejection speed, an approximate curve representing the ejection speed is obtained from the obtained ejection speed in the same manner as in the first embodiment.

[0053] To determine the adjustment value of the ejection timing, first, the recording medium 203 is conveyed onto the platen 212, and the distance between the conveyed recording medium 203 and the ejection port surface 201a is measured by the distance detection sensor 204. Then, the speed corresponding to the measured distance between the ejection port surface 201a and the recording medium 203 is obtained from the approximate curve of the ejection speed. In this way, by calculating the ejection speed of the ink droplets from the actually measured distance between the ejection port surface 201a and the recording medium 203, a more accurate ejection speed can be calculated.

[0054] In FIG. 9(a), the measurement points are indicated by hatched circles. FIG. 9(a) shows the detection times of ink droplets when the distances between the recording head 201 and the droplet detection sensor 205 are separated from distance H1 to distance H5 respectively. FIG. 9(b) shows the relationship between the ejection speed calculated based on FIG. 9(a) and the difference in each distance. At this time, by complementing on the approximate curve from the output results of the detection times measured at distances H1 to H5, it is possible to predict the detection time and ejection speed for distances (such as H0, H6, etc.) other than the measured distances H1 to H5. Also, in addition to distances far from the section of distances H1 to H5 such as distances H0 and H6, the speed at the distance between H1 and H2 can also be obtained.

[0055] For example, assume that the ejection speeds when the distance between the ejection port surface 201a and the droplet detection sensor 205 is 1.0 mm and 1.5 mm have been calculated. In this case, when the distance between the ejection port surface 201a and the recording medium 203 measured by the distance detection sensor 204 is 1.1 mm, the ejection speed at a distance of 1.1 mm can be calculated by linearly complementing the calculated ejection speed.

[0056] In the above, the distance between the ejection port surface 201a and the recording medium 203 is measured by the distance detection sensor 204, but other methods may also be used. For example, the thicknesses of various target recording media are stored in the memory 303 respectively, and the user selects the target recording medium from the operation panel on the recording apparatus 100, and a configuration for setting the corresponding distance may be adopted. In the case of such a configuration, it is not necessary to mount a distance detection sensor.

[0057] When the ejection speed at the distance between the ejection port surface 201a and the recording medium 203 is calculated, an adjustment value for the ejection timing is obtained based on the table held in the memory 303 and the calculated ejection speed in the same manner as in the first embodiment.

[0058] As described above, by calculating the ejection speed of ink droplets based on the distance between the ejection port surface 201 of the recording head 201 and the recording medium 203, a more accurate ejection speed can be calculated. By adjusting the ejection timing based on such a highly accurate ejection speed, landing position deviation can be further suppressed. (Third Embodiment) Next, the third embodiment will be described. The ejection speed of ink droplets gradually decreases when the recording head is used over a long period of time. If the ejection speed decreases after the adjustment value of the ejection timing is set, there is a possibility that the landing position of the ink droplets will deviate from the set adjustment value. Therefore, in this embodiment, a form in which the adjustment value of the ejection timing is reset at a predetermined timing after the adjustment value of the ejection timing is set once will be described. In this embodiment, parts similar to those in the above-described embodiment will be omitted.

[0059] FIG. 10 is a flowchart showing a process of determining the adjustment value of the ejection timing from an adjustment pattern and calculating the ejection speed from the determined adjustment value. The process of FIG. 10 is a process performed by the sequence control unit 307 of the CPU 301 according to a program stored in the memory 303, for example. This process starts when the recording apparatus is initially installed or when the recording head is replaced with a new one. Further, the process may be started by the user instructing to print an adjustment pattern from the operation panel of the recording apparatus 100 and adjust the ejection timing. The ejection speed of the ink droplets calculated by the process of FIG. 10 is used as the reference ejection speed.

[0060] First, at step S1101, an inspection of the adjustment pattern for the ejection timing is performed. Specifically, an adjustment pattern for obtaining the adjustment value of the ejection timing is printed, and the adjustment value is determined from the adjustment pattern.

[0061] FIG. 11 shows a pattern for adjusting the recording position shift in the forward and reverse directions in this embodiment. The vertical grid line 901 is a grid line pattern recorded by 64 nozzles in each nozzle row during forward scanning, and the vertical grid line 902 is a grid line pattern recorded by 64 nozzles in each nozzle row during reverse scanning. In recording these patterns, the recording conditions are a carriage speed of 25 inches / second and a driving frequency of 30 KHz. The patterns are five patterns in which the discharge timing during reverse scanning is changed so that the recording position of the vertical grid line 902 changes in five steps from "-2" to "+2" in units of 1 / 1200 inch with respect to the vertical grid line 901. Note that the "-" direction indicates that the recording timing is advanced with respect to the reference, and the "+" direction indicates that the recording timing is delayed. From among such adjustment patterns, the pattern with the smallest shift between the two grid lines is selected, and the selected adjustment value is stored in the memory 303. Based on the selected adjustment value, the discharge timing in the scanning direction in which the non-reference side grid line is recorded is determined. If it is a recording apparatus provided with an optical sensor on the carriage, the detection of the pattern with the smallest shift between the two vertical grid lines may be automatically performed. Also, the user may look at the recording paper on which the adjustment pattern is recorded and input the value of the pattern with the smallest shift between the two vertical grid lines from the operation unit.

[0062] Next, proceed to step S1102, and calculate the discharge speed at the time when the adjustment pattern is printed from the adjustment value obtained in S1101. Hereinafter, the discharge speed when the adjustment pattern is printed is referred to as the reference discharge speed. The method for calculating the reference discharge speed will be described with reference to FIG. 4.

[0063] First, when the adjustment value is determined, the amount of landing position deviation from the adjustment value of the reference ejection timing (here, "0") can be determined. As described in FIG. 4, the amount of deviation is deviation amount = Xa’ - Xa. For example, when the adjustment value is determined to be "-1", the deviation is reduced by shifting 1 / 1200 inch from the reference. Since this is the combined deviation amount in the reciprocating direction, the deviation amount Xa’ - Xa due to one-way scanning is 1 / 2400 inch. Note that the distance Xa between the ejection position at the reference ejection speed and the landing position is stored in the memory 303 in advance. As described above, since the deviation amount and Xa are known, the distance Xa’ from the ejection position at the current reference ejection speed can be calculated.

[0064] As described in FIG. 4, the distance Xa’ from the ejection position to the landing position at the current reference ejection speed is Xa’ = (H / Va’) × Vcr. From this equation, the current reference ejection speed Va’ is calculated by the following equation.

[0065] Va’ = (H × Vcr) / Xa’ The distance H between the ejection port surface 201a and the recording medium 203 is measured by the distance detection sensor 204. Also, the scanning speed Vcr of the recording head 201 is stored in the memory 303 in advance. Then, as described above, from the distance Xa and the deviation amount obtained from the adjustment value determined from the pattern, the distance Xa’ from the ejection position to the landing position at the current reference ejection speed is calculated. By substituting each value into the equation, the current reference ejection speed Va’ can be calculated. The calculated current reference ejection speed Va’ is stored in the memory 303. In this embodiment, patterns are printed when the distance between the ejection port surface 201a and the recording medium 203 is distance M1, distance M3, and distance M5, and the respective ejection speeds are calculated. By the above processing, the adjustment value is determined and the reference ejection speed is calculated from the adjustment pattern.

[0066] When using the recording head 201, the ejection speed decreases over time. When the ejection speed decreases, a deviation occurs in the landing position when printing is performed with the adjustment value determined by the adjustment pattern. Therefore, at a predetermined timing after printing the adjustment pattern, the ejection speed is calculated using the droplet detection sensor 205 described in the first and second embodiments, and the attenuation rate of the ejection speed since the previous ejection speed was calculated is obtained. Based on this attenuation rate, an adjustment value for the ejection timing is set. Details will be described with reference to FIG. 13.

[0067] FIG. 12 is a diagram for explaining the reference ejection speed and the ejection speed calculated based on the detection time detected by the droplet detection sensor 205. Here, the detection of the detection time by the droplet detection sensor 205 is performed at a timing later than the timing of printing the adjustment pattern for calculating the reference ejection speed.

[0068] FIG. 12(a) is a diagram showing the distance between the ejection port surface 201a and the platen 212 or the recording medium 203, and the output results of the detection time at each distance. The horizontal axis indicates the distance (such as H1 to H5) between the ejection port surface 201a of the recording head 201 and the light 404 of the droplet detection sensor 205 or the distance (M1 to M5) between the ejection port surface 201a and the recording medium 203. The vertical axis indicates the detection time detected by the droplet detection sensor 205. FIG. 12(b) shows the ejection speed corresponding to the detection time and distance in FIG. 12(a).

[0069] The values indicated by white circles in FIG. 12(b) are the reference ejection speeds when the distances between the ejection port surface 201a and the recording medium 203 calculated in the process of FIG. 10 are M1, M3, and M5, respectively. Although not actually calculated, the detection times when the reference ejection speeds corresponding to FIG. 12(b) are obtained are indicated by white circles in FIG. 12(a). By obtaining an approximate curve of the speed from the speeds indicated by the white circles in FIG. 12(b), the ejection speeds corresponding to the distances H1 to H5 can be calculated. The detection time and ejection speed at this time are indicated by hatched circles surrounded by dotted lines.

[0070] Next, at a predetermined timing, in the same manner as in the first embodiment, the detection times at distances H1 to H5 are detected by the droplet detection sensor 205, and the detected times are denoted as detection times T1' to T5', which are shown by hatched circles enclosed by a solid line in FIG. 12(a). The ejection speeds V1' to V4' calculated from the detection times T1' to T5' are shown by hatched circles enclosed by a solid line in FIG. 12(b). An approximate curve of the ejection speed can be obtained from the ejection speeds V1' to V4'.

[0071] FIG. 13 shows the correction process for the ejection timing. As described above, this process is performed at a timing after the timing when the adjustment pattern for calculating the reference ejection speed of the detection time is printed. For example, it is when a predetermined time has elapsed since the previous ejection speed was calculated, when a predetermined number of ink droplets are ejected, or when a predetermined number of sheets are printed. In this embodiment, it is assumed that the process of FIG. 10 is completed before the process of FIG. 13 is started. The process of FIG. 13 is a process performed by the sequence control unit 307 of the CPU 301 according to a program stored in the memory 303, for example.

[0072] First, in step S1201, in the same manner as the ejection speed detection process of FIG. 7 in the first embodiment, the ejection speed of the ink droplets ejected from the recording head 201 is calculated. The speeds to be calculated are the ejection speeds V1' to V4' shown in FIG. 12(b).

[0073] Next, in step S1202, the ejection speed calculated in step S1201 is compared with the reference ejection speed obtained in the process of FIG. 10, and it is determined whether the ejection speed has changed. The determination is made based on whether the difference between the reference ejection speed and the speed calculated in step S1201 is equal to or greater than a threshold value previously stored in the memory 303. If the difference is equal to or greater than the threshold value, the process proceeds to step S1203. If the difference is not equal to or greater than the threshold value, the process proceeds to step S1205.

[0074] When the process proceeds to step S1203, the reduction rate of the ejection speed of the ink droplets obtained in step S1201 with respect to the reference ejection speed is calculated.

[0075] Next, proceed to step S1204 and execute correction processing for the adjustment value of the ejection timing from the reduction rate with respect to the reference ejection speed calculated in step S1203. Based on the attenuation rate, the adjustment value can be corrected by calculating how much the adjustment value is shifted from the adjustment value when the ejection speed of the ink droplets is the reference ejection speed.

[0076] Next, proceed to step S1205, and store the calculated ejection speed and the result of the correction processing in the memory 303. Then, end processing is performed in step S1206. The end processing is the same as the processing in step S608 of FIG. 7 in the first embodiment.

[0077] As described above, by correcting the adjustment value of the ejection timing, an appropriate adjustment value of the ejection timing can be set for the current ejection speed of the ink droplets, and a decrease in image quality can be suppressed.

[0078] Also, the ejection speed may be calculated using the droplet detection sensor 205 at the timing when the processing of FIG. 13 ends and a further predetermined time has elapsed, or when a predetermined number of sheets are printed. In that case, an appropriate adjustment value of the ejection timing can be set by performing the processing of FIG. 13 with the ejection speed calculated in step S1201 of FIG. 13 as the reference speed.

[0079] In the processing of FIG. 13, in step S1204, the misalignment of the landing position of the ink is corrected by correcting the adjustment value of the ejection timing, but other methods may also be used. For example, the pulse width of the drive pulse applied to the recording head 201 for ejecting ink may be increased. By increasing the pulse width according to the attenuation rate of the ejection speed, the ejection speed can be increased and the ejection speed can be corrected.

[0080] In the above, the initial reference ejection speed is calculated from the adjustment pattern, but the ejection speed may be calculated using the droplet detection sensor 205 at the timing when the adjustment pattern is printed. Also, the adjustment value may be determined based on the ejection speed calculated using the droplet detection sensor 205 at first, and then the adjustment value may be updated by printing the pattern.

[0081] Moreover, the present embodiment is applicable even to a configuration that does not have a function of printing an adjustment pattern for obtaining an adjustment value of the ejection timing, as long as the first adjustment value is set based on the ejection speed calculated using the droplet detection sensor 205.

Explanation of Signs

[0082] 100 Recording apparatus 201 Recording head 203 Recording medium 204 Distance detection sensor 205 Droplet detection sensor 301 CPU 302 Sensor / motor control unit 303 Memory

Claims

1. a discharge head that discharges droplets from a plurality of discharge ports formed on a discharge port surface; A droplet detection means for detecting when the discharged droplet reaches a predetermined position; a change unit that changes the distance between the ejection port surface of the ejection head and the predetermined position; a determination means for determining a discharge timing when an image is recorded by the discharge head, based on a result of detection by the droplet detection means of droplets discharged from the plurality of discharge ports when a distance from the discharge port face of the discharge head to the predetermined position is a first distance, and a result of detection by the droplet detection means of droplets discharged from the plurality of discharge ports when a distance from the discharge port face of the discharge head to the predetermined position is a second distance different from the first distance; having The ejection head records a pattern for adjusting the ejection timing on a recording medium, the droplet detection means detects droplets discharged at a predetermined timing different from the timing at which the pattern is recorded; The ejection device according to claim 1, wherein the determining means determines the ejection timing based on the pattern and the detection result of the droplet detecting means.

2. The ejection device described in claim 1, characterized in that the determination means determines the ejection timing when recording an image with the ejection head based on a result of detection by the droplet detection means of droplets ejected from the multiple ejection ports when the distance from the ejection port face to the predetermined position is the first distance, a result of detection by the droplet detection means of droplets ejected from the multiple ejection ports when the distance from the ejection port face to the predetermined position is the second distance, and a result of detection by the droplet detection means of droplets ejected from the multiple ejection ports when the distance from the ejection port face to the predetermined position is a third distance different from the first distance and the second distance.

3. 2. The ejection device according to claim 1, further comprising a measuring means for measuring a distance between the ejection head and the recording medium.

4. 2. The ejection device according to claim 1, wherein the determination means determines the ejection timing in accordance with a table showing the relationship between the ejection speed of the droplets and the ejection timing.

5. a time detection means for detecting a time from when the discharge head starts discharging the droplet to when the droplet detection means detects that the droplet has reached the predetermined position; a calculation means for calculating a discharge speed of the droplet based on the time detected by the time detection means and the distance from the discharge port face to the predetermined position; having the ejection head records a pattern for adjusting the ejection timing on a recording medium; the calculation means calculates a droplet ejection speed based on the ejection timing determined based on the pattern; the time detection means detects a time from when the ejection head starts ejecting the droplets at a predetermined timing different from a timing at which the pattern is recorded to when the droplet detection means detects that the droplets have reached the predetermined position; The calculation means calculates a discharge speed based on the time detected by the time detection means, The ejection device according to any one of claims 1 to 4, characterized in that the determination means determines the ejection timing from an ejection speed calculated by the calculation means based on the ejection timing determined based on the pattern and an ejection speed calculated based on the time detected by the time detection means.

6. 6. The ejection device according to claim 1, wherein the ejection head records the pattern when the ejection head is attached to the ejection device.

7. A time detection means for detecting a time from when the ejection head starts ejecting the droplet to when the droplet detection means detects that the droplet has reached the predetermined position; a calculation means for calculating a discharge speed of the droplet based on the time detected by the time detection means and the distance from the discharge port face to the predetermined position, 7. The ejection device according to claim 1, wherein the predetermined timing is a timing when a predetermined time has elapsed since the ejection speed was calculated by the calculation means.

8. A time detection means for detecting a time from when the ejection head starts ejecting the droplet to when the droplet detection means detects that the droplet has reached the predetermined position; a calculation means for calculating a discharge speed of the droplet based on the time detected by the time detection means and the distance from the discharge port face to the predetermined position, 8. The ejection device according to claim 1, wherein the predetermined timing is a timing at which a predetermined number of droplets have been ejected after the ejection speed has been calculated by the calculation means.

9. An ejection signal generating means for generating an ejection signal; a drive pulse generating unit that generates a drive pulse for ejecting the droplets from the ejection opening of the ejection head in accordance with an input of the ejection signal, The ejection head ejects droplets from the ejection opening when the drive pulse is applied to the ejection head.

6. The ejection device according to claim 5, wherein the time detection means detects the timing at which the ejection signal generating means inputs the ejection signal to the drive pulse generating means as the timing at which the ejection of the droplets from the ejection port begins.

10. The detecting means further includes a light emitting unit that emits light and a light receiving unit that receives the light emitted by the light emitting unit, The ejection device according to any one of claims 1 to 9, wherein the droplet detection means detects that a droplet ejected from the ejection head has reached the predetermined position, which is the light emitted by the light-emitting element, based on the amount of light received by the light-receiving element.

11. a discharge head that discharges droplets from a plurality of discharge ports formed on a discharge port surface by applying a driving pulse; A droplet detection means for detecting when the discharged droplet reaches a predetermined position; a change unit that changes the distance between the ejection port surface of the ejection head and the predetermined position; a determination means for determining a length of a drive pulse to be applied to the ejection head when an image is recorded by the ejection head, based on a result of detection by the droplet detection means of droplets ejected from the plurality of ejection ports when the distance from the ejection port face of the ejection head to the predetermined position is a first distance, and a result of detection by the droplet detection means of droplets ejected from the plurality of ejection ports when the distance from the ejection port face of the ejection head to the predetermined position is a second distance different from the first distance; having The ejection head records a pattern for adjusting the length of a drive pulse on a recording medium, the droplet detection means detects droplets discharged at a predetermined timing different from the timing at which the pattern is recorded; The ejection device according to claim 1, wherein the determining means determines the length of the drive pulse based on the pattern and the detection result of the droplet detecting means.

12. The ejection device described in claim 11, characterized in that the determination means determines the length of the drive pulse to be applied to the ejection head when recording an image using the ejection head based on a result of detection by the droplet detection means of droplets ejected from the multiple ejection ports when the distance from the ejection port face to the predetermined position is the first distance, a result of detection by the droplet detection means of droplets ejected from the multiple ejection ports when the distance from the ejection port face to the predetermined position is the second distance, and a result of detection by the droplet detection means of droplets ejected from the multiple ejection ports when the distance from the ejection port face to the predetermined position is a third distance different from the first distance and the second distance.

13. 12. The ejection device according to claim 11, further comprising a measuring unit for measuring a distance between the ejection head and the recording medium.

14. 12. The ejection device according to claim 11, wherein the determining means determines the length of the drive pulse in accordance with a table indicating the relationship between the ejection speed of the droplets and the ejection timing.

15. 15. The ejection device according to claim 11, wherein the ejection head records the pattern when the ejection head is attached to the ejection device.

16. A platen is provided to support a recording medium transported in a transport direction and is disposed in a position opposite the ejection head, 16. The ejection device according to claim 1, wherein the droplet detection means is provided beside the platen in a direction intersecting the transport direction.

17. 17. The ejection device according to claim 16, further comprising a measuring unit for measuring a distance between the ejection head and the recording medium.

18. Detecting that droplets discharged from a plurality of discharge ports formed on a discharge port surface of the discharge head have reached a predetermined position; detecting that the droplet has reached the predetermined position after the ejection head has started ejecting the droplet; detecting that the droplets discharged from the plurality of discharge ports have reached the predetermined position when a distance from the discharge port surface of the discharge head to the predetermined position is a first distance; changing a distance from the ejection head to the predetermined position to a second distance different from the first distance; detecting that the droplets discharged from the plurality of discharge ports have reached the predetermined position when the distance from the discharge port surface of the discharge head to the predetermined position is the second distance; determining a discharge timing when an image is recorded by the discharge head based on the detection results of the droplets detected at the first distance and the second distance; The ejection head records a pattern for adjusting the ejection timing on a recording medium, Detecting droplets ejected at a predetermined timing different from the timing at which the pattern was recorded; A method for determining ejection timing, comprising determining the ejection timing based on the pattern and a detection result that detects when the droplet has reached the specified position after the ejection head has started ejecting the droplet.

Images