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

Abstract

To improve accuracy of measurement, when a time from discharge to detection of droplets is detected.SOLUTION: A discharge device discharges a plurality of droplets including droplets continuously discharged from a discharge port of a recording head 201, and measures a plurality of times from start of the discharge of the respective discharged droplets to detection of the droplets by a droplet detection sensor 205. The discharge device determines a measurement condition, on the basis of the plurality of detected times. The discharge device measures a time used for calculating discharge speed according to the determined measurement condition.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] The present invention relates to a discharging device and a discharging Determination of Timing method.

Background Art

[0002] In an inkjet recording device, when it is continuously used, the ejection speed of ink droplets may change due to individual differences in the recording device and recording head, ink characteristics, 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 relationship between the landing positions of the ink droplets ejected in the forward path direction and the ink droplets ejected in the return path direction is shifted, which affects the image quality.

[0003] Patent Document 1 discloses an optical detector for measuring the ejection speed of ejected ink, and a registration adjustment method for appropriately setting the ejection timing based on the measurement result from the moving speed of the recording head and the ejection speed. 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 Patent Document 1, when attempting to reduce measurement error by increasing the number of measurements, the measurement error may instead increase. When attempting to increase the number of measurements by continuously ejecting ink droplets, as shown in FIG. 7(b), the amount of mist, which is ink separated from the main ink droplet, increases around the measurement environment. When ejecting ink droplets with an increased amount of mist in the surrounding environment, the ink droplets are more likely to separate into main droplets and satellites, and the main droplets tend to become smaller. Additionally, continuous ejection may not allow for timely refilling, and the main droplets of the ejected ink may become smaller. When the main droplets become smaller in this way, the ejection speed decreases, which may cause variations in the measurement results.

[0006] The present invention Improvement of Discharge Accuracy When Recording an Image has the following object.

Means for Solving the Problem

[0007] The present invention includes a discharge head having a discharge port for discharging droplets, a detection means for detecting that the droplets have reached a predetermined position, and a control means for controlling the discharge timing of the droplets of the discharge head when recording an image based on the detection result of the droplets by the detection means. Changing means for changing the distance between the discharge port surface on which the discharge port is formed and the predetermined position at the position where the droplet discharged from the discharge head passes through the predetermined position; It has The detection means detects the droplet discharged from the discharge port in a state where the distance between the discharge port surface and the predetermined position is a first distance, and the distance between the discharge port surface and the predetermined position is changed by the changing means to a second distance different from the first distance. The detection means detects the droplet discharged from the discharge port in the state; The control means in the state where the distance between the discharge port surface and the predetermined position is the first distance and in the state where the distance is the second distance, respectively controls the discharge head to discharge droplets from the discharge port a plurality of times, the detection means acquires a plurality of detection results, and the control means controls the discharge timing of the droplets of the discharge head when recording an image based on the detection results of the discharge of the droplets excluding the first predetermined number among the plurality of discharges of the discharge head.

Advantages of the Invention

[0008] According to the present invention, by determining the number of continuous discharges based on the measurement results, the measurement accuracy can be improved.

Brief Description of the Drawings

[0009]

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Mode 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 a plurality of widths of recording media up to a 60-inch size recording medium. The recording medium 203 can use roll paper or cut paper. Also, 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 located 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) on which discharge ports are formed. On 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. 3) that irradiates light onto the recording medium 203 and a light receiving element (FIG. 3) that receives the light reflected from the recording medium 203, and measures the distance from the change in the output of the light receiving amount of the light receiving element. Details will be described with reference to FIG. 3. 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 stages 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 stage, the variation distance between stages can be set with high accuracy. Also, a mist fan (not shown) for generating an air current for separating from the main droplets of the ink droplets ejected from the recording head 201 and recovering the mist floating between the recording head 201 and the platen 212 is provided below the platen 212. The mist fan is driven by a fan motor 214 (FIG. 4). The mist fan is driven during a recording operation of recording an image on the recording medium to recover the mist. The installation position is not limited to this, and any position may be used as long as the mist is moved to a place where it does not affect the recording.

[0013] FIG. 3 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 from the irradiation surface of the recording medium 203. As shown in FIG. 3(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 in 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. 3(b) shows the relationship between the distance, the output signal, and the distance information data. As shown in FIG. 3(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. 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 of 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 from the recording head 201 to the droplet detection sensor 205 at that time.

[0014] <Block Diagram> FIG. 4 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, a carriage motor 208 that scans the carriage 202, and a fan motor 214 for driving the mist fan. 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.

[0015] The image data transmitted from the host device 1 is converted into ejection signals by the CPU 301, and ink is ejected from the recording head 201 according to the ejection signals 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 so on. The control of each functional block is executed by the sequence control unit 307 reading various programs from the memory 303 and executing them. Based on commands 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.

[0016] The image processing unit 308 performs image processing that color-separates and converts 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 ejection timing of the recording data. The timing control is performed according to the ejection timing determined based on the ejection speed calculated in the ejection speed calculation process described later. The head control unit 310 functions as ejection signal generation means, converts the recording data input from the timing control unit 309 into ejection signals, and outputs them. Also, based on commands from the sequence control unit 307, it outputs control signals to such an extent that ink is not ejected to control the temperature of the recording head 201. The head control circuit 305 functions as drive pulse generation means, generates drive pulses according to the ejection signals input from the head control unit 310, and applies them to the recording head 201.

[0017] <Adjustment of ejection timing> Next, the adjustment of the ejection timing will be described with reference to FIG. 5. FIG. 5(a) is a schematic diagram showing the relationship between the ejection speed of ink droplets and the landing position. Let the distance in the Z direction between the ejection 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 ejecting ink to record an image on the recording medium 203. Let the ejection speed of the ink droplets ejected from the recording head 201 be Va. As shown in FIG. 5(a), since the scanning directions are different in the forward scan and the return scan, the landing positions of the ink are different with respect to the positions where the ink droplets are ejected. In order to align the landing positions of the ink droplets ejected by the recording head 201, the ejection timing of the ink droplets is adjusted. First, the distance Xa from the position where the ink droplet is ejected in the forward scan to the position where the ink droplet lands on the recording medium 203 is described by the following calculation formula.

[0018] Xa =(H / Va)× Vcr Furthermore, the distance Xb from the position where the ink droplet is ejected in the return scan to the position where the ink droplet lands on the recording medium 203 is described by the following calculation formula.

[0019] Xb =(H / Va)×(―Vcr) = ―Xa Based on the above, an appropriate ejection timing with respect to the position of the recording head 201 detected by the encoder sensor 210 is obtained 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. In this embodiment, a default ejection speed and an ejection timing corresponding to the default ejection speed are determined in advance and stored in the memory 303. With the adjustment value of 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 associating this ejection speed and the adjustment value of the ejection timing 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. 11 described later is obtained from the table, and the ejection timing is adjusted.

[0020] Further, FIG. 5(b) shows a case where the ejection speed of the ink droplets detected by the droplet detection sensor 205 has decreased from the ejection speed of the ink droplets shown in FIG. 5(a). At this time, the distance Xa' from the position where the ink droplets were ejected in the forward scanning direction to the position where the ink droplets land on the recording medium 203 is described by the following calculation formula.

[0021] Xa' = (H / Va') × Vcr Assuming that the ejection speed of the ink droplets has decreased by 10% from the ejection position of the ink droplets ejected from the recording head 201 until they land on the recording medium 203, the distance from the ejection position to the landing position can be obtained as follows.

[0022] 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, similar to FIG. 5(a), an appropriate adjustment value for the ejection timing can be obtained based on the ejection speed. 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 distance as the distance between the ejection port surface 201a and the platen 212.

[0023] <Calculation of ejection speed> 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. 6. FIG. 6 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.

[0024] As shown in FIG. 6, 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, and the like. 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 received light decreases, so that 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 in the same position in the Z direction as the surface of the platen 212 that supports the recording medium 203. Slits are provided in the vicinity of 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. In the X direction, the positional relationship between the droplet detection sensor 205 and the recording head 201 is defined as a detection positional relationship such that the ink droplets ejected from the recording head 201 pass through the light 404 of the droplet detection sensor 205. When detecting an ink droplet to calculate the ejection 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 a 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).

[0025] FIG. 6 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 from 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. 6 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 sent 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 from 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 sent from the driver unit 306 to the head control circuit 305 until the detection signal is output, taking the timing at which the ejection signal is sent as the start timing of ejection. 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. In this embodiment, the timing at which the ejection signal is sent to the head control circuit 305 is taken as the start timing of ejection. However, depending on the structure of the recording head 201 and the like, it may take time from when the ejection signal is input to the head control circuit 305 until the ink droplet is actually ejected. In such a configuration, the time from a predetermined time after the timing at which the ejection signal is sent until the detection signal is output can be taken as the detection time.

[0026] When detecting the detection time T1, the sequence control unit 307 calculates the ejection speed V from the detection time T1 and the distance H1. The calculation formula is as follows.

[0027] V = H1 / T1 The ejection speed can be calculated as described above.

[0028] <Determination of measurement conditions> Next, the determination of the measurement conditions for the detection time will be described. In this embodiment, in order to calculate the ejection speed, the detection time is measured a plurality of times, here a total of 1000 times, and the ejection speed is calculated based on the measured detection time. In this embodiment, when measuring the detection time, the mist fan is not driven in order to avoid the ejected ink droplets being affected by the airflow.

[0029] FIG. 7 shows a schematic diagram showing the state of the measurement environment near the recording head 201 and the droplet detection sensor 205 when measuring the detection time. FIG. 7(a) shows the case where there is not much mist in the measurement environment, and FIG. 7(b) shows the case where there is a lot of mist in the measurement environment. Immediately after starting the ejection of ink droplets for measurement, there is not much mist as shown in FIG. 7(a). However, as the number of ejections increases, as shown in FIG. 7(b), a state where a lot of mist is generated. When ejection is performed in an environment where such a large amount of mist is generated, the ejected ink droplets are likely to separate into main droplets and satellites, and the ejection speed decreases, so the detected detection time becomes longer. Also, even when there is no mist, if continuous ejection causes the refilling to be insufficient, the detected detection time becomes longer because the ejected ink droplets become smaller.

[0030] FIG. 8 shows a graph showing the relationship between the detection time and the number of measurements. FIG. 8(a) shows the detection time when ejection is performed continuously 1000 times. As shown in FIG. 8(a), the detection time becomes longer as the number of measurements increases. Also, the tendency of the increase in the detection time varies depending on the composition of the ink and the characteristics of the recording head due to manufacturing variations.

[0031] Therefore, in the present embodiment, measurement conditions are determined such that stable detection time can be detected. Here, the number of consecutive discharges from the same discharge port is determined. In the present embodiment, during the period when the detection time of a predetermined discharge port is being measured, the detection time of another discharge port is not measured. FIG. 9 shows a flowchart for determining the timing for determining the measurement conditions. This process is a process performed when the recording head 201 is attached to the recording apparatus 100, and is, for example, a process performed by the sequence control unit 307 of the CPU 301 according to a program stored in the memory 303.

[0032] First, in step S501, it is determined whether the attached recording head 201 is the recording head 201 that is attached to the recording apparatus 100 for the first time. The determination is made by reading the memory in the recording head 201. If it is determined that it is the first time of attachment, the process proceeds to step S502, and the measurement condition determination process is performed. In this process, it is determined how many times to discharge continuously in the measurement of the detection time. The measurement condition determination process will be described in detail with reference to FIG. 10. If it is determined in step S501 that it is not the recording head attached for the first time, the measurement conditions stored in the memory 303 are selected.

[0033] Next, in step S504, the discharge speed calculation process is performed. The detection of the detection time used for calculating the discharge speed is performed based on the measurement conditions determined in step S502 or step S503. The discharge speed calculation process will be described in detail with reference to FIG. 11.

[0034] FIG. 10 shows a flowchart of the measurement condition determination process.

[0035] First, in step S601, as the first measurement condition, the detection time when 1000 ink droplets are continuously discharged is measured. Note that the first to fourth measurement conditions used in this process are stored in advance in the memory 303.

[0036] Next, in step S602, it is determined whether or not the detection time measured in step S601 is stable. Whether or not it is stable is determined by the variation in the measured detection time. For example, the variance is obtained from the measured values, and if the obtained variance is within a predetermined value, it is determined to be stable. Also, if the detection times falling within the range of ±5% from the average value of the measured values are 80% or more, it may be determined to be stable. Additionally, for example, an approximate curve equation of the time-series data of the measured detection time is obtained, and if its coefficient is below a predetermined value, it can also be determined to be stable. Also, the setting of the range may be a fixed value instead of a ratio. If it is determined to be stable, the process proceeds to step S603, and if it is determined not to be stable, the process proceeds to step S604.

[0037] When proceeding to step S603, it is determined to perform the measurement by continuously discharging ink droplets 1000 times in the measurement, and in step S611, the measurement conditions determined in step S603 are stored in the memory 303.

[0038] When the process of step S611 is completed, the process proceeds to step S612, and it is determined whether or not the measurement conditions have been determined for all ink colors. If it is determined that the measurement conditions for all ink colors have been determined, this process ends. If it is determined that the measurement conditions for all ink colors have not been determined, the process is performed from step S601 for the ink colors for which the measurement conditions have not yet been determined.

[0039] When proceeding to step S604, as the second measurement condition, the operation of continuously discharging 100 times and then waiting is repeated 10 times, and the detection time when 1000 times have been discharged is measured.

[0040] Then, in step S605, it is determined whether the detection time measured in step S604 is stable. The determination is made based on the variation of the 1000 detection times measured in step S604. The method for obtaining the variation can be calculated in the same way as in step S602. In evaluating whether improvement has been seen in detection by changing the number of consecutive discharges, it is desirable that the calculation method and the determination criteria be the same as in step S602, but they can be changed as appropriate. If it is determined that it is stable, then in step S606, it is decided to repeat the continuous discharge 100 times 10 times to measure the detection time, and in step S611, the measurement conditions determined in step S606 are stored in the memory 303.

[0041] If it is determined in step S604 that it is not stable, then the process proceeds to step S607, and the operation of continuously discharging 10 times and then waiting is repeated 100 times as the third measurement condition, and the detection time when discharging 1000 times is measured.

[0042] Next, in step S608, it is determined whether the detection time measured in step S607 is stable. The determination is made based on the variation of the 1000 detection times measured in step S607. The method for obtaining the variation can be calculated in the same way as in step S602. In evaluating whether improvement has been seen in detection by changing the number of consecutive discharges, it is desirable that the calculation method and the determination criteria be the same as in step S602 and step S604, but they can be changed as appropriate. The determination method is the same as the method in step S602. If it is determined that it is stable, then in step S609, it is decided to repeat the continuous discharge 10 times 100 times to measure the detection time, and in step S611, the measurement conditions determined in step S609 are stored in the memory 303.

[0043] If it is determined in step S608 that it is not stable, the process proceeds to step S610. In step S610, it is determined to insert a wait every time a fourth measurement condition, that is, a single ejection, is performed, and to measure the detection time by performing 1000 ejections. In step S611, the measurement conditions determined in step S610 are stored in the memory 303.

[0044] In the above manner, the measurement conditions for the detection time for each ink color are determined. When the same conditions can be set depending on the ink color, the process of FIG. 10 may be executed for one ink color to determine the measurement conditions, and for other ink colors, the measurement conditions determined for one ink color may be used. Also, in the present embodiment, conditions are set such that a total of 1000 detection times can be measured under all the measurement conditions to be determined. However, since a wait time is included in the second to fourth measurement conditions, the measurement takes time. Measurement conditions may be set such that the total number of detections is reduced in order to shorten the measurement time.

[0045] Also, in FIG. 10, the stability of the detection time was determined, but the ejection speed may be calculated and the measurement conditions may be obtained by determining the stability of the ejection speed.

[0046] In the present embodiment, during the period in which the detection time for a predetermined ejection port is measured, the detection time for another ejection port is not measured. However, the detection times for a predetermined ejection port and another ejection port may be measured during the same period. When two ejection ports are located such that they are affected by each other's mist, the measurement conditions may be set in consideration of the two ejections.

[0047] <Ejection speed calculation process> FIG. 11 shows a flowchart of the ejection speed calculation process, which corresponds to the ejection speed calculation method described in FIG. 6 and is the process of S504 in FIG. 9.

[0048] The calculation process of the ejection speed in FIG. 11 is a process performed during the initial installation operation when the user of the recording device 100 operates the recording device 100 for the first time, or when the recording head 201 is replaced with a new one and installed. Further, it may be performed regularly as maintenance, or may be performed according to the user's instructions. 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.

[0049] 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 in this embodiment, it is the distances H1 to H4 described in FIG. 5. The order of the separation distances is as described in FIG. 5, in the order of distances H1, H2, H3, and H4.

[0050] Next, proceed to step S602 and execute the preprocessing necessary for detecting the ejection speed. Specifically, it includes the preliminary setting of the optimal ejection control for detecting the ejection speed, the preliminary ejection operation for stable ejection of ink droplets, and further the mist fan stop operation for stabilizing the air flow control inside the recording device.

[0051] Next, proceed to step S603 and execute the ejection operation of ejecting inspection ink droplets from the recording head 201 according to the conditions determined in the measurement condition determination process of FIG. 10 for the light 404 emitted by the light emitting element 401 of the droplet detection sensor 205. Specifically, at the distance H1 separated in step S601, the detection time, which is the time from the start of 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.

[0052] Next, proceed to step S604, execute data processing on the detection time obtained in step S603, and calculate the detection time for the distance separated in step S601. Specifically, execute data processing such as averaging processing based on the number of acquisition samples required for stabilizing the measurement of the detection time and deleting data outside the upper and lower error ranges to prevent abnormal data from being mixed in.

[0053] In step S605, calculate the ejection speed. Specifically, as described with reference to FIG. 6, calculate the ejection speed based on the detection time measured at the distance H1. After calculating the ejection speed, proceed to step S606 and store the information on the ejection speed calculated in step S605 in the memory 303. The ejection speed information stored here is used for data processing and driving control of the recording head 201 according to necessary processing hereafter.

[0054] Next, proceed to step S607 and 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 cleaning processing of the recording head 201 based on the obtained ejection speed information, etc., and then this process ends.

[0055] When the ejection speed calculation process in FIG. 11 ends, obtain the adjustment value of the ejection timing from the table in which the ejection speed pre-stored in the memory 303 is associated with the adjustment value of the ejection timing, and based on the obtained ejection speed obtained by the process in FIG. 11. Then, adjust the ejection timing based on the obtained adjustment value. When printing an image, the timing control unit 309 controls the timing of ejecting ink according to the recording data.

[0056] As described above, according to the present embodiment, by determining the measurement conditions of the detection time measured to calculate the ejection speed, it is possible to stably measure the detection time while suppressing the influence of the ink composition and the characteristics of the recording head due to manufacturing variations. Thereby, the calculation accuracy of the ejection speed can be improved. Further, when continuous ejection is possible, measurement can be performed while suppressing an increase in measurement time by performing continuous ejection for measurement.

[0057] In addition, in the present embodiment, the mist fan was stopped while measuring the detection time. However, in the case of measurement conditions with a wait during measurement, the mist fan may be driven during the wait to collect the mist.

[0058] Also, in the above embodiment, when the detection time was stable in the continuous 1000 - time ejection which is the first measurement condition, the first measurement condition was used as the measurement condition. Alternatively, the detection time may be measured under all measurement conditions, and the most stable condition may be selected therefrom.

[0059] (Second Embodiment) In the first embodiment, the ejection speed was calculated from the detection time when the distance from the ejection port surface of the recording head 201 to the droplet detection sensor 205 was H1. In the present embodiment, the detection time in the case of a plurality of distances is measured, and the ejection speed is calculated. Parts similar to the first embodiment are omitted.

[0060] (Calculation of ejection speed) A method for calculating the ejection speed of ink droplets ejected from the recording head 201 in the present embodiment will be described with reference to FIG. 12. FIG. 12 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.

[0061] FIG. 12(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 of the droplet detection sensor 205 is H1. The detection time is detected in the same manner as in the first embodiment. First, 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 light quantity 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 light quantity 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.

[0062] FIG. 12(b) shows a state where, after ejecting an ink droplet in FIG. 12(a), the lift motor 211 is driven and the distance in the height direction (Z direction) between the ejection port surface 201a and the light 404 emitted by the light-emitting element 401 is H2. Similar to FIG. 12(a), when the ink droplet passes through the light 404 of the droplet detection sensor 205, the timing at which the light quantity received by the light-receiving element 402 changes 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.

[0063] In this embodiment, when detecting the detection times T1 and T2 in the states of FIGS. 12(a) and 12(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.

[0064] 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. 12(c). Similar to FIGS. 12(a) and 12(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 is issued to the recording head 201 until the detection signal is output. Similar to the time described in FIGS. 12(a) and 12(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.

[0065] 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 separated from the distance H3. The state at this time is shown in FIG. 12(d). Similar to FIGS. 12(a), 12(b), and 12(c), ink droplets are ejected from the ejection port of the recording head 201. Then, 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 detection time T4 from when the ejection signal for ejecting ink droplets to the recording head 201 is issued until the detection signal is output is detected by the sequence control unit 307. Similar to the time described in FIGS. 12(a) to 12(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.

[0066] 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 this embodiment, the separation distance H is a distance between 1.2 mm and 2.2 mm.

[0067] 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 changing 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.

[0068] Figures 13(a) and (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. 12, and the output results of the detection time at each distance. Figures 13(b) and (d) are diagrams showing the relationship between the discharge speed calculated from the distance and the detection time shown in Figures 13(a) and (c), respectively, and the difference between each distance.

[0069] In the graph shown in FIG. 13(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. 13(a) is the actually measured portion. Here, detection is performed at distances H1 to H5. The distance H5 is farther than the distance H4.

[0070] In the graph shown in FIG. 13(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 more accurately calculate the discharge speed data shown for each distance difference, 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 the 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 for obtaining the discharge speed is as described above.

[0071] Also, as a result of the inventors' experiments, it has been found that there is a possibility that data that changes linearly may be obtained depending on individual differences in the recording head, differences in physical properties for each ink color, and furthermore, usage conditions and environmental influences. The data in the case of such linear change is shown in FIG. 13(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. 13(d). As shown in FIG. 13(d), the ejection speed calculated at 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 only necessary to detect the detection times at two distances.

[0072] 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 only necessary to detect the detection times at two distances that include the distance at the time of recording.

[0073] The ejection speed calculation process of this embodiment is executed by performing the processes of steps S601 to S603 for distances H1 to H4 in the process of FIG. 11 of the first embodiment, and calculating the ejection speed as described above in step S605.

[0074] The adjustment of the ejection timing is adjusted by the same method as in the first embodiment.

[0075] <Determination of measurement conditions> The determination process for the timing of setting the measurement conditions performs the same process as in FIG. 9 of the first embodiment.

[0076] Regarding the measurement condition determination process in step S502, the same processing as in FIG. 10 of the first embodiment is performed to determine the measurement conditions. At this time, the distance between the discharge port surface 201a for measuring the detection time and the light 404 emitted by the light emitting element 401 is a preset distance stored in the memory 303, and is any one of the distances H1 to H4. Further, the detection time may be measured at a plurality of distances, the stability may be determined for each, and the measurement conditions may be determined to be those with the fewest number of consecutive discharge times among them.

[0077] As described above, in this embodiment, the distance between the recording head 201 and the droplet detection sensor 205 is changed, and the time from the discharge of the ink droplet to the detection is detected for each of a plurality of distances. Then, the discharge speed is calculated based on the difference in each distance and the difference in the detection time. Thereby, even when not in a state assembled with high precision, the discharge speed of the ink droplet 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 device and the recording head, the physical properties of each ink color, and further the usage conditions and environmental influences, as well as the attenuation influence of the discharge speed at each separated distance.

[0078] In the above-described processing, the recording head 201 is configured to move with respect to the droplet detection sensor 205 to change the distance, but 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.

[0079] (Third Embodiment) When there has been no ink discharge for a while since the previous discharge, the moisture of the ink evaporates from the portion in contact with the atmosphere through the discharge port, and the viscosity of the ink near the discharge port decreases. Discharging in such a state may affect the discharge amount and the discharge speed. In this embodiment, the discharge speed is calculated in consideration of such an influence. The same parts as in the above-described embodiment are omitted.

[0080] The following description can be applied to the determination process of the measurement conditions in step S502 of FIG. 9 and the ejection speed calculation process of FIG. 11.

[0081] FIG. 14 is a graph showing the relationship between the detection time and the number of measurements when starting to measure the detection time from a state where ink has not been ejected for a while. The measurement of the detection time at this time is performed under measurement conditions such that the influence of mist is reduced. As shown in FIG. 14, the detection times measured from the 1st to the 10th measurement times have large data variations and are not stable. Therefore, a predetermined number of data until the state where the detection time can be measured in a state where the ejection state is stable are excluded from the data used for calculating the ejection speed. The number of data to be excluded is a number preset by those skilled in the art through experiments or the like in advance. Also, the number of data to be excluded may be changed according to the elapsed time from the previous ejection. The ejection speed is calculated by the method described in the above embodiment.

[0082] Also, as the number of ejections increases, the temperature of the recording head 201 rises, so the viscosity of the ink decreases. Therefore, even when a certain amount of driving energy is applied to the recording head 201, the amount of ink droplets ejected varies depending on the temperature of the recording head and the temperature of the ink, and the ejection speed changes. In order to further improve the stability of the detection time used for calculating the ejection speed, a simple moving average may be used for every predetermined number of measurements based on the measured time-series data. In that case, among the detection times obtained by the simple moving average, the data in the section determined to be stable is used to calculate the ejection speed.

[0083] Also, a configuration using a weighted moving average by performing weighting in consideration of the characteristics of the ink color to be measured and the influence of changes due to environmental changes around is also applicable.

Explanation of Signs

[0084] 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 having a discharge port for discharging droplets; A detection means for detecting when a droplet reaches a predetermined position; a control unit that controls a timing at which the ejection head ejects droplets when an image is recorded, based on a result of the detection of the droplets by the detection unit; a changer for changing a distance between a discharge port face, on which the discharge ports are formed, and the predetermined position at a position where the droplets discharged from the discharge head pass the predetermined position; having the detection means detects the droplets discharged from the discharge port when the distance between the discharge port face and the predetermined position is a first distance, and the detection means detects the droplets discharged from the discharge port when the distance between the discharge port face and the predetermined position is changed by the change means to a second distance different from the first distance, the control means controls the discharge head to discharge droplets from the discharge port a plurality of times when the distance between the discharge port face and the predetermined position is the first distance and when the distance is the second distance, and the detection means obtains a plurality of detection results, The control means controls the timing of droplet ejection from the ejection head when recording an image based on the detection results of droplet ejection, excluding the first predetermined number of droplets, out of multiple ejections from the ejection head.

2. 2. The ejection device according to claim 1, wherein the predetermined number is a number of times that is set in advance.

3. 3. The ejection device according to claim 2, wherein the predetermined number is ten times.

4. 2. The ejection device according to claim 1, wherein the control means determines the predetermined number based on an elapsed time from a previous ejection.

5. The ejection device according to claim 1 , further comprising an acquisition unit that acquires the time from when the ejection head starts ejecting the droplets until the detection unit detects that the droplets have reached the predetermined position.

6. The ejection device according to claim 5, characterized in that when the acquisition means acquires the time from when the ejection of the droplets from the ejection head of the multiple ejections begins to when the detection means detects that the droplets have reached the specified position, the control means controls the ejection head to continuously eject droplets from the ejection head.

7. 7. The ejection device according to claim 6, wherein the number of consecutive ejections is 1000.

8. a time detection means for detecting a time from when the discharge head starts discharging the droplet to when the detection means detects that the droplet has reached the predetermined position; the time detection means detects a first time from when the ejection of droplets from the ejection port begins to when the detection means detects the droplets in a state where the distance between the ejection port face of the ejection head and the predetermined position is a first distance, and detects a second time from when the ejection of droplets from the ejection port begins to when the detection means detects the droplets in a state where the distance between the ejection port face of the ejection head and the predetermined position is a second distance different from the first distance by the changing means, a calculation unit that calculates an ejection speed of the droplet based on the first distance, the second distance, the first time, and the second time; 2. The ejection device according to claim 1, wherein the control means controls the ejection timing based on a result of the calculation 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.

9. The ejection device according to claim 8, wherein the time detection means detects the timing at which the ejection signal generation means inputs the ejection signal to the drive pulse generation means as the timing at which the ejection of the droplets from the ejection port begins.

10. The detection means has a light emitting portion that emits light and a light receiving portion that receives the light emitted by the light emitting portion, The ejection device according to claim 1 , wherein the predetermined position is light emitted from the light emitting portion.

11. a detection step of detecting whether a droplet discharged from a discharge port of a discharge head having the discharge port has reached a predetermined position; a changing step of changing a distance between an ejection port face, on which the ejection ports are formed, and the predetermined position at a position where the droplets ejected from the ejection head pass the predetermined position; In the detection step, a plurality of droplets discharged from the discharge port are detected when a distance between the discharge port face and the predetermined position is a first distance; In the changing step, the distance between the ejection port surface and the predetermined position is set to a second distance different from the first distance, In the detection step, a plurality of droplets discharged from the discharge port are detected when the distance between the discharge port face and the predetermined position is the second distance; a determination step of determining a timing for ejecting droplets from the ejection head when recording an image based on a detection result of the ejection of droplets excluding an initial predetermined number of the plurality of ejections detected in the detection step; 13. A method for determining ejection timing comprising the steps of:

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