Droplet ejection device

Abstract

To provide a droplet discharge device which can quickly and highly accurately acquire information about a distance between a discharge surface of a discharge head and a discharge object surface of a printing object medium.SOLUTION: The droplet discharge device comprises: a discharge head which discharges droplets from a nozzle hole provided on a discharge surface to a discharge object surface of a printing object medium; a TOF sensor which detects a distance between the discharge surface and the discharge object surface; a carriage on which the discharge head and the TOF sensor are mounted and which moves in the movement direction; a correction sensor which detects a distance between the discharge surface and the discharge object surface; and a control device. The control device acquires information about the distance between the discharge surface and the discharge object surface by correcting the detection result by the TOF sensor when moving the carriage in the movement direction on the basis of the detection result by the correction sensor.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a droplet ejection device used in an image forming apparatus such as an inkjet printer.

Background Art

[0002] As a technique for detecting the distance between a printing medium and the ejection surface of an ejection head, for example, in Patent Document 1, the time until light emitted toward the printing medium is reflected by the printing medium and returned is measured by a TOF (Time Of Flight) sensor, and a method for obtaining the above distance based on the measurement result is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in a TOF sensor, measurement errors are likely to occur due to the sensitivity of photoelectric conversion in the light receiving unit and noise during analog-digital conversion. Therefore, it has been difficult to accurately obtain information regarding the distance between the ejection surface of the ejection head and the ejection surface of the printing medium.

[0005] Therefore, an object of the present invention is to provide a droplet ejection device capable of quickly and accurately obtaining information regarding the distance between the ejection surface of the ejection head and the ejection surface of the printing medium.

Means for Solving the Problems

[0006] The droplet ejection device of the present invention comprises an ejection head that ejects droplets from nozzle holes provided on the ejection surface toward the ejection surface of a printing medium, a TOF sensor that detects the distance between the ejection surface and the ejection surface, a carriage that mounts the ejection head and the TOF sensor and moves in the direction of movement, a correction sensor that detects the distance between the ejection surface and the ejection surface, and a control device, wherein the control device corrects the detection result by the TOF sensor when the carriage is moved in the direction of movement based on the detection result by the correction sensor to obtain information regarding the distance between the ejection surface and the ejection surface.

[0007] According to the present invention, information regarding the distance between the discharge surface and the discharged surface can be quickly acquired using a TOF sensor. Furthermore, the control device corrects the detection result from the TOF sensor based on the detection result from a correction sensor. This results in a highly accurate numerical value for the detection result from the TOF sensor. As a result, it is possible to acquire information regarding the distance between the discharge surface and the discharged surface quickly and with high accuracy. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a droplet dispensing device that can quickly and accurately acquire information regarding the distance between the dispensing surface of the dispensing head and the dispensing surface of the printing medium. [Brief explanation of the drawing]

[0009] [Figure 1] This is a perspective view showing an image forming apparatus equipped with a droplet ejection device according to one embodiment of the present invention. [Figure 2] This is a plan view showing a droplet dispensing device according to one embodiment of the present invention. [Figure 3] Figure 1 is a cross-sectional view showing the configuration of the discharge head. [Figure 4] This is a block diagram showing the components of the image forming apparatus shown in Figure 1. [Figure 5] This diagram illustrates the detection of the distance between the ejection surface of the ejection head and the ejection surface of the printing medium. [Figure 6]This diagram illustrates a method for correcting detection results obtained using a TOF sensor. [Figure 7] This figure shows a head gap sensor as an example of a correction sensor. [Figure 8] This diagram shows an optical sensor as an example of a sensor used for correction. [Figure 9] This figure shows a method of detecting the distance to the same position on the discharge surface by moving the platen up and down. [Figure 10] This figure shows another example of an optical sensor used as a correction sensor. [Figure 11] This diagram shows an embodiment in which multiple TOF sensors are provided. [Modes for carrying out the invention]

[0010] Hereinafter, a droplet dispensing device according to an embodiment of the present invention will be described with reference to the drawings. The droplet dispensing device described below is merely one embodiment of the present invention. Therefore, the present invention is not limited to the following embodiments, and additions, deletions, and modifications are possible without departing from the spirit of the present invention.

[0011] Figure 1 is a perspective view showing an image forming apparatus 1 equipped with a droplet ejection device 1a according to one embodiment of the present invention. In Figure 1, mutually orthogonal directions are denoted as the first direction Ds, the second direction Df, and the third direction Dz. In this embodiment, for example, the first direction Ds is the direction of movement of the carriage 3, which will be described later, the second direction Df is the direction of transport of the printing medium W, which will be described later, and the third direction Dz is the vertical direction. In the following description, Ds will be referred to as the direction of movement, Df as the transport direction, and Dz as the vertical direction.

[0012] As shown in FIG. 1, the image forming apparatus 1 of the present embodiment includes a housing 2, operation keys 4, a display unit 5, a platen 6 on which a printing medium W is disposed, and an upper cover 7. Further, the image forming apparatus 1 includes a droplet ejection device 1a shown in FIG. 2 having a discharge head 10 and a controller unit 19 including a control device 20 (FIG. 4). The discharge head 10 is an inkjet head that discharges, as droplets, for example, ultraviolet curable ink droplets Dt (FIG. 5).

[0013] The housing 2 is formed in a box shape. The housing 2 has an opening 2a. The operation keys 4 are provided on the housing 2. Also, the display unit 5 is provided near the operation keys 4. The operation keys 4 receive operation inputs from the user. The display unit 5 is configured, for example, as a touch panel and displays predetermined information. A part of the display unit 5 also functions as an operation key. The controller unit 19 realizes a printing function based on an input from the operation keys 4 or an external input via a communication interface (not shown) and controls the display on the display unit 5.

[0014] The platen 6 is configured to be able to mount the printing medium W. The platen 6 has a predetermined thickness and is formed of, for example, a rectangular plate material having the conveyance direction Df as the longitudinal direction. The platen 6 is removably supported by a platen support (not shown). The platen support is configured to be movable in the conveyance direction Df between a printing position where printing on the printing medium W is executed by driving a conveyance motor 33 (FIG. 4) and a detachment position where the printing medium W is removed from the platen 6. Thereby, the platen 6 relatively moves the printing surface of the printing medium W in the conveyance direction Df with respect to the discharge head 10. Since the platen 6 moves in the conveyance direction Df during printing, the printing medium W placed on the platen 6 is conveyed along the conveyance direction Df. Also, the platen 6 is configured to be movable up and down by driving the above-described platen support.

[0015] The upper cover 7 is configured to rotate upward when its end is lifted. Thereby, the inside of the housing 2 is exposed.

[0016] As shown in FIG. 2, the droplet ejection device 1a includes a storage tank 62, a carriage 3 on which, for example, two ejection heads 10 (10A, 10B) and two ultraviolet irradiation devices 40 (40A, 40B) are mounted, and a pair of guide rails 67. Although two ejection heads 10 and two ultraviolet irradiation devices 40 are provided, the present invention is not limited to this, and one ejection head 10 and one ultraviolet irradiation device 40 may be provided.

[0017] The carriage 3 is supported by a pair of guide rails 67 extending in the moving direction Ds, and reciprocates in the moving direction Ds along the guide rails 67. Thereby, the two ejection heads 10 (10A, 10B) and the two ultraviolet irradiation devices 40 (40A, 40B) can reciprocate in the moving direction Ds. Further, the ejection head 10 is connected to the storage tank 62 via a tube 62a.

[0018] In the present embodiment, for example, the ejection head 10A ejects ink droplets Dt of each color of yellow (Y), magenta (M), cyan (C), and black (K), which may be collectively referred to as color ink. By ejecting the above four-color ink droplets Dt onto the printing medium W, a color image is printed on the printing medium W. On the other hand, the ejection head 10B ejects white (W) ink droplets Dt and clear (Cr) ink droplets Dt. When printing a color image on, for example, a fabric as the printing medium W, in order to reduce the influence on the color and material of the fabric, white ink droplets Dt are first ejected as the base ink, and color ink droplets Dt are ejected onto the white ink droplets Dt. Further, the clear ink droplets Dt are ejected when imparting gloss or protecting the printed portion.

[0019] Ink is stored in the storage tank 62. The storage tank 62 is provided for each type of ink. For example, six storage tanks 62 are provided, and black, yellow, cyan, magenta, white, and clear inks are stored respectively.

[0020] Next, the detailed structure of the discharge head 10 will be described. As shown in Figure 3, the discharge head 10 has a plurality of nozzles 121 that discharge ink droplets Dt using ink from the storage tank 62. The discharge head 10 has a laminate of a flow channel forming body and a volume changing body. An ink flow channel is formed inside the flow channel forming body, and a plurality of nozzle holes 121a open on its lower surface, the discharge surface NM. The volume changing body is driven to change the volume of the ink flow channel. At this time, the meniscus vibrates in the nozzle holes 121a and ink is discharged.

[0021] The flow path forming body of the discharge head 10 is a laminate of multiple plates, and the volume changing section includes a diaphragm 155 and an actuator (piezoelectric element) 160. A common electrode 161, described later, is connected to the diaphragm 155.

[0022] Multiple plates are stacked, from bottom to top, including a nozzle plate 146, a spacer plate 147, a first channel plate 148, a second channel plate 149, a third channel plate 150, a fourth channel plate 151, a fifth channel plate 152, a sixth channel plate 153, and a seventh channel plate 154.

[0023] Each plate has holes and grooves of various sizes formed in it. Inside the flow channel forming body formed by stacking the plates, the holes and grooves are combined to form multiple nozzles 121, multiple individual flow channels 164, and a manifold 122 as ink flow channels.

[0024] The nozzle 121 is formed by penetrating the nozzle plate 146 in the stacking direction. On the discharge surface NM of the nozzle plate 146, multiple nozzle holes 121a, which are the tips of the nozzles 121, are arranged in the transport direction Df to form a nozzle row.

[0025] The manifold 122 supplies ink to the pressure chamber 128 to which discharge pressure is applied. The manifold 122 extends in the transport direction Df and is connected to one end of each of the multiple individual flow channels 164. In other words, the manifold 122 functions as a common flow channel for the ink. The manifold 122 is formed by through holes that penetrate the first flow channel plates 148 to the fourth flow channel plates 151 in the stacking direction, and recesses that are recessed from the lower surface of the fifth flow channel plate 152, overlapping in the stacking direction.

[0026] The nozzle plate 146 is positioned below the spacer plate 147. The spacer plate 147 is made of, for example, stainless steel. The spacer plate 147 has a recess 145 formed by, for example, half-etching, which causes a recess in the thickness direction of the spacer plate 147 from the surface facing the nozzle plate 146, thereby forming a thin-walled portion that forms a damper portion 147a and a damper space 147b. As a result, a damper space 147b is formed between the manifold 122 and the nozzle plate 146, acting as a buffer space.

[0027] A supply port 122a is connected to the manifold 122. The supply port 122a is formed, for example, in a cylindrical shape and is provided at one end in the conveying direction Df. The manifold 122 and the supply port 122a are connected by a flow path not shown in the figure.

[0028] Each individual flow path 164 is connected to the manifold 122. The upstream end of each individual flow path 164 is connected to the manifold 122, and the downstream end is connected to the base end of the nozzle 121. Each individual flow path 164 consists of a first communication hole 125, an individual throttling passage which is a supply throttling passage 126, a second communication hole 127, a pressure chamber 128, and a descender 129, and these components are arranged in this order.

[0029] The first communication hole 125 has its lower end connected to the upper end of the manifold 122, extends upward from the manifold 122 in the stacking direction, and penetrates the upper portion of the fifth flow path plate 152 in the stacking direction.

[0030] The upstream end of the supply throttling passage 126 is connected to the upper end of the first communication hole 125. The supply throttling passage 126 is formed, for example, by half-etching and consists of a groove recessed from the lower surface of the sixth flow channel plate 153. The second communication hole 127 has its upstream end connected to the downstream end of the supply throttling passage 126, extends upward from the supply throttling passage 126 in the stacking direction, and is formed by penetrating the sixth flow channel plate 153 in the stacking direction.

[0031] The pressure chamber 128 has its upstream end connected to the downstream end of the second communication hole 127. The pressure chamber 128 is formed by penetrating the seventh flow channel plate 154 in the stacking direction.

[0032] The descender 129 is formed by penetrating the spacer plate 147, the first flow path plate 148, the second flow path plate 149, the third flow path plate 150, the fourth flow path plate 151, the fifth flow path plate 152, and the sixth flow path plate 153 in the stacking direction. The upstream end of the descender 129 is connected to the downstream end of the pressure chamber 128, and the downstream end is connected to the base end of the nozzle 121. The nozzle 121 overlaps the descender 129 in the stacking direction, for example, and is positioned in the center of the descender 129 in the width direction.

[0033] The diaphragm 155 is laminated on the seventh flow path plate 154 and covers the upper end opening of the pressure chamber 128.

[0034] The actuator 160 includes a common electrode 161, a piezoelectric layer 162, and individual electrodes 163, arranged in this order. The common electrode 161 covers the entire surface of the diaphragm 155. The piezoelectric layer 162 covers the entire surface of the common electrode 161. Individual electrodes 163 are provided for each pressure chamber 128 and are arranged on the piezoelectric layer 162. One actuator 160 is composed of one individual electrode 163, the common electrode 161, and the portion of the piezoelectric layer 162 sandwiched between the two electrodes.

[0035] The individual electrodes 163 are electrically connected to a driver IC. This driver IC receives a control signal from the control device 20, generates a drive signal (voltage signal), and applies it to the individual electrodes 163. In contrast, the common electrode 161 is always kept at ground potential. In this configuration, the active portion of the piezoelectric layer 162 expands and contracts in the planar direction together with the common electrode 161 and the individual electrodes 163 in response to the drive signal. Accordingly, the diaphragm 155 deforms in cooperation, changing the volume of the pressure chamber 128 in a direction that increases or decreases it. As a result, the discharge pressure that causes the ink droplet Dt to be ejected from the nozzle 121 is applied to the pressure chamber 128.

[0036] In the ejection head 10, ink flows into the manifold 122 via the supply port 122a, then flows from the manifold 122 into the supply throttling passage 126 via the first communication hole 125, and from the supply throttling passage 126 into the pressure chamber 128 via the second communication hole 127. The ink then flows through the descender 129 and into the nozzle 121. At this point, when ejection pressure is applied to the pressure chamber 128 by the actuator 160, ink droplets Dt are ejected from the nozzle hole 121a.

[0037] As shown in Figure 4, in addition to the components described above, the image forming apparatus 1 includes a reading device 26, motor driver ICs 30 and 31, head driver ICs 32 and 35, transport motor 33, carriage motor 34, irradiation device driver ICs 36 and 37, TOF (Time Of Flight) sensor 38, and correction sensor 39.

[0038] The controller unit 19 includes a control device 20 composed of a CPU, a storage unit (ROM 21, RAM 22, EEPROM 23, HDD 24), and an ASIC 25. The control device 20 is connected to each of the above-mentioned storage units and controls the driver ICs 30-32, 35-37, the display unit 5, the TOF sensor 38, and the correction sensor 39.

[0039] The control device 20 performs various functions by executing a predetermined processing program stored in the ROM 21. The control device 20 may be implemented as a single processor in the controller unit 19, or as multiple processors working together. The processing program is read by the reader 26 from a recording medium KB such as a computer-readable magneto-optical disk or USB flash memory and stored in the ROM 21. The RAM 22 stores image data received from an external source and the calculation results of the control device 20. The EEPROM 23 stores various initial setting information entered by the user. The HDD 24 stores specific information, etc.

[0040] The ASIC25 is connected to motor driver ICs 30 and 31, head driver ICs 32 and 35, irradiation device driver ICs 36 and 37, TOF sensor 38, and correction sensor 39. When the control device 20 receives a print job from the user, it outputs an image recording command to the ASIC25 based on the processing program. The ASIC25 drives each of the driver ICs 30-32 and 35-37 based on the image recording command. The control device 20 moves the platen 6 in the transport direction Df by driving the transport motor 33 with the motor driver IC 30. The control device 20 moves the carriage 3 in the movement direction Ds by driving the carriage motor 34 with the motor driver IC 31.

[0041] The control device 20 converts image data acquired from an external device into ejection data for ejecting ink droplets Dt onto the ejection surface. Based on the converted ejection data, the control device 20 uses head driver ICs 32 and 35 to eject ink droplets Dt from the ejection head 10. The control device 20 also uses irradiation device driver ICs 36 and 37 to irradiate ultraviolet light from the light-emitting diode chips of the ultraviolet irradiation devices 40A and 40B.

[0042] Figure 5 is a diagram illustrating the detection of the distance between the ejection surface NM of the ejection head 10 and the ejection surface WM of the printing medium W. As shown in Figure 5, the ejection surface WM of the printing medium W includes, for example, an ejection surface parallel to a first direction parallel to the ejection surface NM of the ejection head 10 and an inclined surface intersecting with respect to the first direction.

[0043] As described above, carriage 3 is equipped with a discharge head 10 and an ultraviolet irradiation device 40, as well as a TOF sensor 38 and a correction sensor 39. The TOF sensor 38 is positioned adjacent to the discharge head 10 in the direction of movement Ds of carriage 3. The correction sensor 39 is also positioned adjacent to the TOF sensor 38 in the direction of movement Ds.

[0044] The control device 20 causes the TOF sensor 38 to detect the distance Dh between the ejection surface NM of the ejection head 10 and the ejection surface WM of the printing medium W as the carriage 3 moves in the direction Ds. The TOF sensor 38 measures the time it takes for the emitted laser light to reflect off the ejection surface WM and return, and converts this measured time into distance. The TOF sensor 38 detects the heights of multiple parts of the printing medium W on the ejection surface WM that have different heights.

[0045] Furthermore, the control device 20 causes the correction sensor 39 to detect the distance Hh between the ejection surface NM and the ejection surface WM. In this case, the correction sensor 39 detects the distance Hh when the printing medium W is transported in the transport direction Df by the platen 6. The correction sensor 39 detects the heights of multiple parts of the printing medium W on the ejection surface WM that have different heights.

[0046] The control device 20 receives the detection results from the TOF sensor 38 and the correction sensor 39. The control device 20 then corrects the distance Dh, which is the detection result from the TOF sensor 38, based on the distance Hh, which is the detection result from the correction sensor 39. As a result, the control device 20 obtains information about the distance between the discharge surface NM and the discharged surface WM, that is, information about the corrected distance. This will be explained in detail below.

[0047] Figure 6 is a diagram illustrating the correction method for the detection results obtained by the TOF sensor 38. First, the control device 20 obtains a provisional profile Pz relating to the distance Dh between the ejection surface NM and the ejected surface WM from the detection results of the TOF sensor 38. The provisional profile Pz corresponds to provisional information. The provisional profile Pz is a collection of multiple distances Dh between the ejection surface NM and the ejected surface WM in the movement direction Ds, obtained based on the detection results of the TOF sensor 38. Since the height of the ejection surface NM of the ejection head 10 is constant, the trajectory of the provisional profile Pz almost coincides with the shape of the printed medium W in the movement direction Ds. In Figure 6, the provisional profile Pz is, for example, an arc shape. The control device 20 also obtains a peak value Vbp from among the provisional values ​​Vb in the provisional profile Pz. This peak value Vbp is the value corresponding to the highest point of the ejected surface WM of the printed medium W.

[0048] Next, the control device 20 acquires the peak value Vap from the distance Hh information detected by the correction sensor 39. In this case, the control device 20 acquires the peak value Vap when the printing medium W is transported in the transport direction Df before detection by the TOF sensor 38 begins. This peak value Vap corresponds to the highest point on the ejection surface WM of the printing medium W. The control device 20 calculates the difference Gv between the acquired peak value Vap and the peak value Vbp in the provisional profile Pz.

[0049] Next, the control device 20 corrects each provisional value Vb in the provisional profile Pz based on the calculated difference Gv. In this case, the control device 20 performs a correction by adding the difference Gv to each provisional value Vb in the provisional profile Pz. Through this correction, the control device 20 obtains each value Va, which is the provisional value Vb with the difference Gv added to it. This makes it possible to obtain a profile Ps, which is a collection of multiple values ​​Va that represent information about the distance between the discharge surface NM and the discharged surface WM. By correcting the provisional profile Pz in this way, the profile Ps can be obtained.

[0050] Figure 7 shows a head gap sensor 50 as an example of a correction sensor 39. The correction sensor 39 may be a head gap sensor 50, which is an example of a contact-type sensor that detects the distance Hh between the ejection surface NM and the ejection surface WM by contacting the ejection surface WM. The head gap sensor 50 is used to adjust the distance between the ejection head 10 and the printing medium W, and is a sensor that is usually provided in the droplet ejection device 1a of the image forming apparatus 1.

[0051] As shown in Figure 7, the head gap sensor 50 has a rotating shaft 51 that rotates in the same direction as the transport direction Df and a contact portion 52 connected to the rotating shaft 51. The rotating shaft 51 is provided with an encoder that detects the rotation angle of the rotating shaft 51. The position where the contact portion 52 is aligned with the vertical direction Dz is taken as the reference position. When the contact portion 52 comes into contact with the ejection surface WM of the printing medium W, it rotates away from the reference position. The control device 20 obtains the distance Hh between the ejection surface NM and the ejection surface WM based on the rotation angle obtained from the encoder when the contact portion 52 rotates.

[0052] Figure 8 shows an example of a correction sensor 39, specifically an optical sensor 55. As shown in Figure 8, the correction sensor 39 may be an optical sensor 55 that detects the distance Hh between the discharge surface NM and the discharge surface WM by emitting light perpendicular to the discharge surface NM relative to the discharge surface WM. In this case, the optical sensor 55 includes, for example, a laser diode and a photodetector diode. Laser light emitted from the laser diode is reflected at the discharge surface WM, and the reflected light is received by the photodetector diode. The time from when the laser light is emitted until the reflected light reflected from the discharge surface WM is received varies depending on the position of the discharge surface WM. Therefore, the distance Hh can be obtained by detecting the time from when the laser light is emitted until the reflected light reflected from the discharge surface WM is received.

[0053] Figure 9 shows a method of detecting the distance Hh at the same position on the discharge surface WM by moving the platen 6 up and down.

[0054] As shown in Figure 9, the optical sensor 55, which serves as the correction sensor 39, may detect the distance to the same position Wp on the discharge surface WM as the platen 6 moves up and down. In this case, the optical sensor 55 emits a laser beam to position Wp on the discharge surface WM when the platen 6 is positioned at its normal height, thereby detecting the distance Hh1 between the discharge surface NM and position Wp. The optical sensor 55 also emits a laser beam to position Wp on the discharge surface WM when the platen 6 is positioned higher than its normal height, thereby detecting the distance Hh2 between the discharge surface NM and position Wp. The TOF sensor 38 also detects the distance between the discharge surface NM and position Wp when the platen 6 is positioned at its normal height, and the distance between the discharge surface NM and position Wp when the platen 6 is positioned higher than its normal height. The control device 20 corrects the detection result from the TOF sensor 38 based on the distances Hh1 and Hh2, which are the detection results from the optical sensor 55. Specifically, the control device 20 compares the difference between two distances Hh1 and Hh2 detected by the optical sensor 55 with the difference between the same two distances detected by the TOF sensor 38 and corrects the detection result from the TOF sensor 38. For example, if the difference detected by the optical sensor 55 is 1.0 mm and the difference detected by the TOF sensor 38 is 0.9 mm, the control device 20 performs a correction by adding a correction value of 0.1 mm (= 1.0 mm - 0.9 mm) to the detection result from the TOF sensor 38.

[0055] Instead of the optical sensor 55 described above, a correction sensor 39 shown in Figure 10 may be used. This correction sensor 39 includes a light-emitting unit 56 that emits laser light and a light-receiving unit 57 that receives the laser light. The light-receiving unit 57 is positioned on the opposite side of the light-emitting unit 56 with respect to the printing medium W. In this configuration, the platen 6 supporting the printing medium W is lowered while the laser light is emitted from the light-emitting unit 56. The distance Hh between the ejection surface NM and the ejected surface WM may be detected from the height position of the platen 6 at the moment when the laser light is not reflected from the printing medium W and passes over the printing medium W, that is, at the moment the laser light is received by the light-receiving unit 57. Alternatively, instead of lowering the platen 6 as described above, the light-emitting unit 56 and the light-receiving unit 57 may be lowered. Alternatively, the distance Hh between the top of the printing medium W and the ejection surface NM may be detected based on the amount of light that was blocked from the laser light emitted from the light source.

[0056] Figure 11 shows an embodiment in which multiple TOF sensors 38 are provided. As shown in Figure 11, multiple TOF sensors 38 may be arranged in a straight line in the transport direction Df. The distance between one TOF sensor 38 and another TOF sensor 38 arranged along the transport direction Df is the same. In Figure 11, four TOF sensors 38 are provided, but the number of TOF sensors 38 arranged in the transport direction Df is not limited to the above.

[0057] As explained above, the droplet dispensing device 1a allows for the rapid acquisition of information regarding the distance Dh between the dispensing surface NM and the dispensing surface WM using the TOF sensor 38. The detection results from the TOF sensor 38 are generally prone to measurement errors due to factors such as the sensitivity of the photoelectric conversion in the light-receiving section and noise during analog-to-digital conversion. Therefore, the control device 20 corrects the detection results from the TOF sensor 38 based on the detection results from the correction sensor 39. This results in highly accurate detection results from the TOF sensor 38. As a result, it becomes possible to rapidly and accurately acquire information regarding the distance between the dispensing surface NM and the dispensing surface WM.

[0058] Furthermore, in this embodiment, by using the peak value Vap from the detection results of the correction sensor 39 as a correction criterion, each provisional value Vb in the detection results of the TOF sensor 38 can be easily corrected.

[0059] Furthermore, in this embodiment, by using a head gap sensor 50, which is a contact-type sensor, as the correction sensor 39, the distance Hh between the discharge surface NM and the discharged surface WM can be detected with high accuracy. In addition, by using the head gap sensor 50, which is originally provided in the droplet discharge device 1a, as the correction sensor 39, it becomes unnecessary to install a new correction sensor, and costs can be reduced.

[0060] Furthermore, in this embodiment, by using optical sensors 55 and 56 as correction sensors 39, the distance Hh between the discharge surface NM and the discharged surface WM can be detected with high accuracy.

[0061] Furthermore, in this embodiment, the TOF sensor 38 is positioned adjacent to the discharge head 10 in the movement direction Ds of the carriage 3. This allows the TOF sensor 38 to continuously detect the distance Dh between the discharge surface NM and the discharged surface WM as the carriage 3 moves in the movement direction Ds.

[0062] Furthermore, in this embodiment, the correction sensor 39 detects the heights of multiple parts with different heights on the discharge surface WM, and the control device 20 corrects the detection result from the TOF sensor 38 based on the detection results from the correction sensor 39. This makes it possible to obtain a more accurate correction result.

[0063] Furthermore, in this embodiment, the optical sensor 55 detects distances Hh1 and Hh2 for the same position Wp on the discharge surface WM as the platen 6 moves up and down, and the control device 20 corrects the detection result from the TOF sensor 38 based on the detection results from the optical sensor 55. This makes it possible to obtain information regarding the distance between the discharge surface NM and the discharge surface WM with higher accuracy.

[0064] Furthermore, in this embodiment, multiple TOF sensors 38 may be arranged in a straight line along the transport direction Df. In this case, the distance Dh between the discharge surface NM and the discharged surface WM can be detected over a wide area along the transport direction Df.

[0065] Furthermore, in this embodiment, the correction sensor 39 detects the distance Hh between the ejection surface NM and the ejected surface WM when the printing medium W is transported in the transport direction Df by the platen 6, and the TOF sensor 38 detects the distance Dh when the carriage 3 moves in the movement direction Ds. This makes it possible to obtain highly accurate information regarding the distance between the ejection surface NM and the ejected surface WM for the entire printing medium W.

[0066] (modified version) The present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. For example, the following:

[0067] In the above embodiment, a head gap sensor 50 and optical sensors 55 and 56 were used as the correction sensor 39, but the invention is not limited to these. For example, a radio wave sensor such as a millimeter-wave radar or an ultrasonic sensor may be used as the correction sensor 39.

[0068] Furthermore, in the above embodiment, the control device 20 corrected each provisional value Vb in the provisional profile Pz based on the difference Gv between the peak value Vap and the peak value Vbp in the provisional profile Pz. However, it is not limited to this. The control device 20 can also correct each provisional value Vb in the provisional profile Pz based on the difference between a value other than the peak value Vap (i.e., the height value of a part of the printing medium W that is not the highest point) and the peak value Vbp. [Explanation of symbols]

[0069] 1a Droplet discharge device 3 carriages 6 Platen 10 Discharge heads 20 Control device 38 TOF sensors 39. Correction sensor 50 Head gap sensor 55, 56 Optical sensors 121a Nozzle hole Df Conveying direction Dh Distance between the discharge surface and the discharged surface Ds moving direction Dt Inkdrop Gv difference Hh Distance between the discharge surface and the discharged surface NM discharge surface Pz Provisional Profile Vap peak value Vbp peak value W Printing medium WM discharged surface

Claims

1. A dispensing head that dispenses droplets from nozzle holes on its dispensing surface onto the dispensing surface of the printing medium, A TOF sensor for detecting the distance between the discharge surface and the discharge surface, A carriage is provided, which is equipped with the discharge head and the TOF sensor and moves in the direction of movement, A correction sensor for detecting the distance between the discharge surface and the surface to be discharged, A control device is provided, The control device acquires information regarding the distance between the discharge surface and the discharged surface by correcting the detection result by the TOF sensor when the carriage is moved in the direction of movement, based on the detection result by the correction sensor.

2. The control device is Provisional information regarding the distance between the discharge surface and the discharge surface is obtained from the detection results of the TOF sensor, and, The droplet dispensing device according to claim 1, wherein the provisional information is corrected based on the difference between the peak value of the distance detected by the correction sensor and the peak value in the provisional information obtained from the detection result of the TOF sensor to obtain information regarding the distance between the dispensing surface and the surface to be dispensed.

3. The droplet dispensing device according to claim 1, wherein the correction sensor is a contact-type sensor that detects the distance between the dispensing surface and the dispensing surface by contacting the dispensing surface.

4. The droplet ejection device according to claim 1, wherein the correction sensor is a head gap sensor used to adjust the distance between the ejection head and the printing medium.

5. The droplet dispensing device according to claim 1, wherein the correction sensor is an optical sensor that detects the distance between the dispensing surface and the surface to be dispensed by emitting light parallel to the dispensing surface to the surface to be dispensed.

6. The droplet dispensing device according to claim 1, wherein the TOF sensor is arranged adjacent to the dispensing head in the direction of movement of the carriage.

7. The correction sensor detects the heights of multiple parts on the discharge surface that have different heights, The droplet dispensing device according to claim 1, wherein the control device corrects the detection result from the TOF sensor based on the detection results from the correction sensor.

8. The system further comprises a platen that supports the printing medium and is movable up and down. The correction sensor detects the distance at the same position on the discharge surface as the platen moves up and down. The droplet dispensing device according to claim 1, wherein the control device corrects the detection result from the TOF sensor based on the detection results from the correction sensor.

9. The system further comprises a platen for transporting the printing medium in the transport direction, The droplet dispensing device according to claim 1, wherein a plurality of TOF sensors are arranged in a linear fashion in the transport direction.

10. The correction sensor detects the distance between the discharge surface and the discharge surface when the printing medium is transported in the transport direction by the platen. The droplet dispensing device according to claim 9, wherein the TOF sensor detects the distance when the carriage moves in the direction of movement.

Images