Image forming device

Abstract

To provide an image forming device that dispenses with work for adjusting a detection position where floating of a recording medium is detected.SOLUTION: An image forming device comprises: a conveying part that conveys a recording medium; an inkjet head that forms an image on the recording medium being conveyed; a height-moving part that moves the inkjet head so that a first height of the inkjet head with respect to a conveying surface of the conveying part is changed, depending on a kind of the recording medium; and a detecting part that detects floating of the recording medium with respect to the conveying surface at a second height with respect to the conveying surface, after the second height with respect to the conveying surface changes in tandem with the movement of the inkjet head.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] Known image forming devices include inkjet image forming devices that eject ink from nozzles in an inkjet head to form an image on a recording medium such as paper. In inkjet image forming devices, the distance from the nozzle surfaces of the nozzles that eject ink to the transport surface that transports the recording medium is short. Therefore, if the recording medium being transported floats above the transport surface due to the condition of the recording medium (such as tears, folds, wrinkles, or ripples), the quality of the image formation may deteriorate, or the recording medium may come into contact with the ejection surface, damaging the ejection surface.

[0003] For this reason, an inkjet image forming apparatus has been proposed that has a detector that detects floating of the recording medium being transported, and if the detector detects floating of the recording medium, the transport is stopped.

[0004] For example, Patent Document 1 discloses an image forming apparatus in which a light-projecting unit and a light-receiving unit are disposed as detectors facing each other with a recording medium sandwiched therebetween, and detection light is emitted from the light-projecting unit at a predetermined height from the conveying surface and detected by the light-receiving unit. Patent Document 1 also discloses an adjustment mechanism for adjusting the positions and angles of the light-projecting unit and the light-receiving unit. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-76872 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, when conveying recording media of different thicknesses in an inkjet image forming apparatus, it is necessary to change the height (detection position) of the detection light for detecting floating. In the technology disclosed in Patent Document 1, the height of the detection light can be changed by using the above-mentioned adjustment mechanism. However, each time the thickness of the recording medium changes, it is necessary to change the height of the detection light using the adjustment mechanism, and the height of the detection light cannot be easily changed.

[0007] SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that can eliminate the need for adjustment of the detection position for detecting floating of a recording medium. [Means for solving the problem]

[0008] The image forming apparatus according to the present invention comprises: a conveying unit that conveys the recording medium; an inkjet head for forming an image on the conveyed recording medium; a height moving unit that moves the inkjet head so as to change a first height of the inkjet head relative to a transport surface of the transport unit in accordance with the type of the recording medium; a detection unit that detects a floating of the recording medium from the transport surface at a second height that changes in conjunction with the movement of the inkjet head; a carriage that holds the inkjet head; Equipped with 、 The detection unit has a light-projecting unit that projects light parallel to the ink ejection surface of the inkjet head as detection light, and a light-receiving unit that receives the detection light, the light-projecting unit and the light-receiving unit being attached to both sides of the carriage that are outside both ends of the recording medium in a width direction perpendicular to the conveyance direction of the recording medium, and the detection unit detects floating of the recording medium based on the light-receiving result of the light-receiving unit. . The image forming apparatus according to the present invention comprises: a conveying unit that conveys the recording medium; an inkjet head for forming an image on the conveyed recording medium; a height moving unit that moves the inkjet head so as to change a first height of the inkjet head relative to a transport surface of the transport unit in accordance with the type of the recording medium; a detection unit that detects a floating of the recording medium from the transport surface at a second height that changes in conjunction with the movement of the inkjet head; Equipped with The detection unit has a light-projecting unit that projects light in a direction toward the transport surface, a first mirror that refracts the light from the light-projecting unit to change it into detection light parallel to the ink ejection surface of the inkjet head, a second mirror that refracts the detection light to change it into detection light in a direction away from the transport surface, and a light-receiving unit that receives the detection light from the second mirror, and detects floating of the recording medium based on the light-receiving result of the light-receiving unit. The image forming apparatus according to the present invention comprises: a conveying unit that conveys the recording medium; an inkjet head for forming an image on the conveyed recording medium; a height moving unit that moves the inkjet head so as to change a first height of the inkjet head relative to a transport surface of the transport unit in accordance with the type of the recording medium; a detection unit that detects a floating of the recording medium from the transport surface at a second height that changes in conjunction with the movement of the inkjet head; a plurality of carriages arranged side by side along the conveyance direction of the recording medium, each carriage holding an inkjet head; Equipped with The detection unit is attached to the carriage on the most upstream side in the transport direction. [Effects of the Invention]

[0009] According to the present invention, it is possible to eliminate the need for adjustment of the detection position for detecting floating of the recording medium. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention; [Figure 2] 2 is a block diagram showing a main part of a control system of the image forming apparatus shown in FIG. 1. FIG. [Figure 3A] FIG. 10 is a diagram illustrating a carriage that moves up and down depending on the thickness of the recording medium (when the thickness is 1 mm). [Figure 3B] FIG. 10 is a diagram illustrating a carriage that moves up and down depending on the thickness of the recording medium (when the thickness is 2 mm). [Figure 4] FIG. 2 is a diagram showing a carriage, a lift detection unit, a conveying belt, and a recording medium as viewed from the upstream side in the conveying direction. [Figure 5] 3A and 3B are diagrams illustrating the positional relationship between a carriage, a lift detection unit, a conveyor belt, and a recording medium. [Figure 6] 2 is a flowchart illustrating an image forming method in the image forming apparatus shown in FIG. [Figure 7] 7 is a flowchart illustrating a modification (modification 1) of the image forming method shown in FIG. 6. [Figure 8] 7 is a flowchart illustrating another modified example (modified example 2) of the image forming method shown in FIG. [Figure 9] 1. FIG. 4 is a diagram schematically illustrating a main part of a modification (modification 3) of the image forming apparatus shown in FIG. [Figure 10] FIG. 10 is a diagram showing a modification (modification 4) of the placement of the floating detection unit relative to the carriage. [Figure 11]FIG. 10 is a diagram showing another modified example (Modified Example 5) of the placement of the floating detection unit on the carriage. [Figure 12] FIG. 10 is a diagram showing another modified example (modified example 6) of the placement of the floating detection unit on the carriage. [Figure 13] FIG. 13 is a diagram showing an example in which a floating detection unit with a strip-shaped detection light is used in the modified example shown in FIG. [Figure 14] FIG. 11 is a perspective view showing a modified example (modified example 7) of the floating detection section. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0012] [Image forming device] 1 is a diagram showing a schematic configuration of an inkjet printer 100 (an image forming apparatus according to the present invention), and FIG. 2 is a block diagram showing the main parts of a control system of the inkjet printer 100.

[0013] As shown in Figures 1 and 2, the inkjet printer 100 includes a conveying unit 10, a supplying unit 20, a discharging unit 30, an operation display unit 40, an input / output interface 50, an image forming unit 60, a lifting unit 70, a float detecting unit 80, a control unit 90, and the like.

[0014] Although the conveying unit 10 is shown in a simplified diagram in FIG. 1 , it has multiple components related to conveyance, such as a conveying belt 11, a driving roller 12, and a driven roller 13. The conveying unit 10 conveys the recording medium M by the conveying action of the multiple components, such as the conveying belt 11. Specifically, in the conveying unit 10, the conveying belt 11 is stretched over the driving roller 12 and the driven roller 13. By driving the driving roller 12, the recording medium M supplied from the supplying unit 20 is conveyed to the image forming unit 60 while being placed on the conveying surface 11a of the conveying belt 11, and the recording medium M on which an image has been formed (printed) in the image forming unit 60 is conveyed to the discharging unit 30.

[0015] The recording medium M can be any of various media capable of fixing ink ejected from the inkjet head 63 described below, such as sheet-like paper, cloth (woven fabric), etc. Note that the recording medium M is not limited to sheet-like media, and may also be roll-like media such as paper or cloth.

[0016] Here, as an example, a conveying unit 10 that conveys the recording medium M using a conveying belt 11 is shown, but the conveying unit 10 is not limited to a conveying belt 11 and may be configured to convey the recording medium M using a drum or roller.

[0017] The supply unit 20 has a supply stacking unit 21 that stacks and stores a plurality of recording media M, and a supply conveying unit 22 that conveys and supplies the recording media M from the supply stacking unit 21 to the conveying unit 10. The supply stacking unit 21 is configured to be able to rise and fall, and when the topmost recording medium M is conveyed to the conveying unit 10 by the supply conveying unit 22, the supply stacking unit 21 rises so that the recording medium M that has become the topmost after the conveying can be conveyed to the supply conveying unit 22.

[0018] The discharge section 30 has a discharge stacking section 31 that stores a stack of multiple recording media M, and a discharge conveying section 32 that conveys the recording media M discharged from the conveying section 10 to the discharge stacking section 31. The discharge stacking section 31 is configured to be able to move up and down, and when the recording media M is conveyed from the discharge conveying section 32 to the discharge stacking section 31, the discharge stacking section 31 descends.

[0019] The supply conveying section 22 and the discharge conveying section 32 have, for example, a plurality of rollers, and convey the recording medium M by rotating the rollers. The supply conveying section 22 and the discharge conveying section 32 are not limited to rollers, and may be configured with a belt, or may be configured with a combination of rollers and belts.

[0020] When a roll-shaped medium is used as the recording medium M, an unwinding roller on which the roll-shaped medium is stored in a wound state and a winding roller that winds up the roll-shaped medium are used instead of the supply stacking unit 21 and the discharge stacking unit 31. The roll-shaped medium is transported to the transport unit 10 by rotating the unwinding roller, and is wound up onto the winding roller by rotating the winding roller.

[0021] Furthermore, a post-processing device may be provided between the conveying unit 10 and the discharging unit 30 to perform post-processing on the recording medium M on which an image has been formed by the image forming unit 60. One example of the post-processing device is a fixing device that fixes the ink to the recording medium M. When ultraviolet-curable ink is used as the ink, a fixing device is used that irradiates ultraviolet light onto the recording medium M to fix the ink to the recording medium M. When aqueous ink or solvent ink is used as the ink, a fixing device is used that fixes the ink to the recording medium M by a method such as drying. Furthermore, a device other than a fixing device, such as a cutting device that cuts the recording medium M to a desired length, may also be used as the post-processing device.

[0022] The image forming unit 60 includes a carriage 61, a head driving unit 62, an inkjet head (hereinafter simply referred to as a head) 63, and the like (see FIGS. 1 and 2).

[0023] The carriage 61 is a housing that holds therein a head drive unit 62, a head 63, and devices and members required for image formation by the head 63.

[0024] As an example, the carriage 61 is configured to function as a one-pass inkjet printer that forms an image in one scan. Therefore, in a direction perpendicular to the conveyance direction T of the recording medium M (a width direction W of the recording medium M shown in FIG. 3 described later), the width of the carriage 61 is longer than the width of the recording medium M, and the carriage 61 is disposed so as to straddle the recording medium M.

[0025] Although detailed illustration of the inside of the carriage 61 is omitted, the carriage 61 has heads 63 arranged therein in the width direction W, the number of which corresponds to the image formation width (see FIG. 3).

[0026] Furthermore, here, the number of carriages 61 corresponding to the number of ink colors is arranged in parallel along the transport direction T. As an example, four carriages 61 corresponding respectively to four ink colors, yellow (Y), magenta (M), cyan (C), and black (K), are arranged at predetermined intervals from the upstream side in the transport direction in the order of Y, M, C, and K, for example.

[0027] Based on the control of the control unit 90, the head driving unit 62 outputs a driving signal to the head 63 according to the image data of the image to be formed, thereby causing the nozzles of the head 63 to eject an amount of ink according to the image data.

[0028] Although detailed illustration is omitted, the head 63 has a pressure chamber that stores ink, a piezoelectric element provided on the wall of the pressure chamber, and a nozzle that communicates with the pressure chamber. The head 63 also has a nozzle surface 63a (ink ejection surface in the present invention) on the bottom side (conveyor belt 11 side) of the carriage 61, and a plurality of nozzles are provided on the nozzle surface 63a. The nozzle surface 63a is arranged so as to be flush with the bottom surface of the carriage 61. The head 63 has a pressure chamber and a piezoelectric element corresponding to each nozzle.

[0029] When a drive signal is input from the head drive unit 62 to the head 63, the drive signal deforms the piezoelectric element, which in turn deforms the pressure chamber, which in turn changes the pressure within the pressure chamber, causing ink to be ejected from the nozzles communicating with the pressure chamber. In this way, ink is ejected from the nozzles of the head 63 to form an image on the recording medium M being transported.

[0030] Although detailed illustration is omitted, the lifting / lowering unit 70 (height moving unit in the present invention) includes a lifting / lowering control unit 71, a lifting / lowering motor 72, etc., as shown in FIG. 2. The lifting / lowering control unit 71 outputs a lifting / lowering signal to the lifting / lowering motor 72 based on the control of the control unit 90. The lifting / lowering motor 72 is driven based on the lifting / lowering signal input from the lifting / lowering control unit 71, and raises and lowers the carriage 61 relative to the conveying surface 11a of the conveyor belt 11. Here, the lifting / lowering unit 70 raises and lowers multiple (four in FIG. 1) carriages 61 collectively.

[0031] When forming an image on a recording medium M, if the thickness of the recording medium M varies, the carriage 61 is raised and lowered by the lifting unit 70 so that the height (gap) of the nozzle surface 63a relative to the surface of the recording medium M is a predetermined height to prevent a decrease in the quality of the image formation.

[0032] The carriage 61 that moves up and down depending on the thickness of the recording medium M will be described with reference to Figures 3A and 3B. Figure 3A is a diagram illustrating the carriage 61 that moves up and down depending on the thickness of the recording medium M (when the thickness is 1 mm). Figure 3B is a diagram illustrating the carriage 61 that moves depending on the thickness of the recording medium M (when the thickness is 2 mm).

[0033] The height (gap) of the nozzle surface 63a relative to the surface of the recording medium M is set to 2 mm. As shown in Fig. 3A, when a recording medium M having a thickness of 1 mm is placed on the conveyance surface 11a of the conveyance belt 11 and conveyed, the lifting unit 70 lifts and lowers the carriage 61 so that the height of the nozzle surface 63a relative to the surface Ma of the recording medium M becomes 2 mm. As a result, the lifting unit 70 lifts and lowers the carriage 61 so that the height of the nozzle surface 63a relative to the conveyance surface 11a of the conveyance belt 11 (first height in the present invention) becomes 3 mm.

[0034] 3B, when a recording medium M having a thickness of 2 mm is placed on the conveying surface 11a of the conveyor belt 11 and conveyed, the lifting unit 70 lifts and lowers the carriage 61 so that the height of the nozzle surface 63a relative to the surface Ma of the recording medium M becomes 2 mm. As a result, the lifting unit 70 lifts and lowers the carriage 61 so that the height of the nozzle surface 63a relative to the conveying surface 11a of the conveyor belt 11 becomes 4 mm.

[0035] In this way, the lifting unit 70 raises and lowers the carriage 61 in accordance with the thickness of the recording medium M (one example of the type of recording medium M), and changes the height of the nozzle surface 63a relative to the conveying surface 11a of the conveyor belt 11 so that the gap is 2 mm. Note that the thicknesses of the recording medium M of 1 mm and 2 mm and the gap of 2 mm are examples for the purpose of explanation.

[0036] Here, as an example, the lifting unit 70 that raises and lowers the carriage 61 using the lifting motor 72 is shown, but the lifting unit 70 is not limited to the lifting motor 72 and may be configured to raise and lower the carriage 61 using another actuator.

[0037] The lift detection unit 80 (detection unit in the present invention), the details of which will be described later, detects lifting of the recording medium M from the conveying surface 11a as it is conveyed by the conveyor belt 11. When the lift detection unit 80 detects that the conveyed recording medium M has lifted, the control unit 90 performs a predetermined process, such as a process to stop the conveyance of the recording medium M.

[0038] The operation display unit 40 is, for example, a flat panel display such as a liquid crystal display with a touch panel or an organic electroluminescence (EL) display. The operation display unit 40 displays an operation menu for the user, information related to image data, various states of the inkjet printer 100, etc. The operation display unit 40 also has a plurality of keys and accepts various input operations from the user.

[0039] The input / output interface 50 mediates the transmission and reception of data between the external device 200 and the control unit 90. The input / output interface 50 is configured, for example, by any one of various serial interfaces, various parallel interfaces, or a combination of these.

[0040] The external device 200 is, for example, a personal computer or a facsimile machine, and supplies print jobs, image data, and the like to the control unit 90 via the input / output interface 50 .

[0041] The control unit 90 includes a CPU (Central Processing Unit) 91, a RAM (Random Access Memory) 92, a ROM (Read Only Memory) 93, a storage unit 94, and the like.

[0042] The CPU 91 reads out various control programs and setting data stored in the ROM 93, stores them in the RAM 92, and executes the programs to perform various arithmetic processing. For example, the control unit 90 generates a drive signal for an image to be formed based on image data received from the input / output interface 50, and outputs the drive signal to the head 63.

[0043] The RAM 92 provides a working memory space for the CPU 91 and stores temporary data. The RAM 92 may include a non-volatile memory.

[0044] The ROM 93 stores various control programs and setting data executed by the CPU 91. Note that, instead of the ROM 93, a rewritable non-volatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory may be used.

[0045] The storage unit 94 stores print jobs (image formation process commands) and image data related to the print jobs input from the external device 200 via the input / output interface 50. As the storage unit 94, for example, an HDD (Hard Disk Drive) is used, and a DRAM (Dynamic Random Access Memory) or the like may also be used in combination.

[0046] The control unit 90 is connected to the conveying unit 10, the supplying unit 20, the discharging unit 30, the operation and display unit 40, the input / output interface 50, the image forming unit 60, the lifting unit 70, and the float detection unit 80. The control unit 90 controls the overall operation of the inkjet printer 100. The conveying unit 10, the supplying unit 20, the discharging unit 30, the operation and display unit 40, the input / output interface 50, the image forming unit 60, the lifting unit 70, and the float detection unit 80 are controlled by the control unit 90 to execute predetermined processes.

[0047] The inkjet printer 100 having the above configuration supplies the recording medium M from the supply unit 20 to the conveying unit 10 under the control of the control unit 90, forms an image on the recording medium M conveyed to the conveying unit 10 in the image forming unit 60, and conveys the recording medium M with the image formed thereon to the discharge unit 30.

[0048] Incidentally, when conveying recording media of different thicknesses in an inkjet printer, it is necessary to change the height (detection position) of the detection light of the lift detection unit that detects lifting. The technology shown in Patent Document 1 makes it possible to change the height of the detection light by using an adjustment mechanism for the lift detection unit. However, every time the thickness of the recording medium changes, it is necessary to change the height of the detection light using the adjustment mechanism, and the height of the detection light cannot be easily changed.

[0049] Therefore, in this embodiment, the inkjet printer 100 is provided with a lift detection unit 80 that changes a second height relative to the transport surface 11a of the transport belt 11 in conjunction with the movement of the head 63 and detects lifting of the recording medium M relative to the transport surface 11a at the second height. More specifically, the second height is the height (second height) of the detection light B of the lift detection unit 80 relative to the transport surface 11a (see FIG. 4 described later). In FIG. 4, the second height is "the thickness h of the recording medium M + the height d2 of the detection light B relative to the surface Ma of the recording medium M."

[0050] In this embodiment, the lift detection unit 80 is attached to the carriage 61 on the most upstream side in the transport direction T. When the lift unit 70 raises and lowers the carriage 61, the lift detection unit 80 moves together with the head 63, so that the height (first height) of the nozzle surface 63a changes and the second height of the lift detection unit 80 also changes. Note that as long as the lift detection unit 80 can move together with the head 63, the head 63 and the lift detection unit 80 may be configured to move in conjunction with each other using a member other than the carriage 61.

[0051] The floating detection unit 80 attached to the carriage 61 will be described below with reference to Fig. 4. Fig. 4 is a diagram of the carriage 61, floating detection unit 80, conveyor belt 11, and recording medium M as viewed from the upstream side in the conveyance direction.

[0052] The floating detection unit 80 has a light-projecting unit 81 and a light-receiving unit 82. The light-projecting unit 81 is attached to one side surface 61a of the carriage 61 in the width direction W, and the light-receiving unit 82 is attached to the other side surface 61b of the carriage 61 in the width direction W. The light-projecting unit 81 and the light-receiving unit 82 are disposed below the side surfaces 61a, 61b of the carriage 61 so as to face each other. In the width direction W, the width of the carriage 61 is longer than the width of the recording medium M, and therefore the light-projecting unit 81 and the light-receiving unit 82 are disposed outside both ends of the recording medium M.

[0053] The light-projecting unit 81 has a light-emitting element such as an LED (Light Emitting Diode) or a laser that projects light. The light-receiving unit 82 has a photoelectric conversion element that outputs an electrical signal according to the amount of light received (light-receiving result). The light-projecting unit 81 and the light-receiving unit 82 may be configured to project and receive light via optical fiber (fiber sensor). Because the fiber sensor uses optical fiber for projecting and receiving light, it can be installed even in narrow spaces.

[0054] Detection light B, condensed into a point, is projected from the light projecting unit 81 toward the light receiving unit 82. The detection light B is parallel to the nozzle surface 63a and passes between the nozzle surface 63a and the surface Ma of the recording medium M transported on the conveyor belt 11 in the height direction. When the recording medium M floats up from the transport surface 11a of the conveyor belt 11 and approaches the nozzle surface 63a, part or all of the detection light B transmitted from the light projecting unit 81 to the light receiving unit 82 is blocked by the recording medium M, and the amount of light received by the light receiving unit 82 decreases. Therefore, by comparing whether the amount of light received detected by the light receiving unit 82 is equal to or less than a preset threshold, it is possible to detect floating of the recording medium M.

[0055] As described above, in the inkjet printer 100, when conveying recording media M of different thicknesses, it is necessary to change the height (second height) of the detection light B of the lift detection unit 80. In this embodiment, the lift detection unit 80 is attached to the carriage 61, and the carriage 61 is raised and lowered by the elevator unit 70 according to the thickness of the recording medium M. Therefore, the height (second height) of the detection light B of the lift detection unit 80, which moves together with the carriage 61 (head 63), automatically changes according to the thickness of the recording medium M.

[0056] The lift detection unit 80 is arranged on the carriage 61 so that the range of the height (second height) of the detection light B, which is changed by the movement of the carriage 61 (head 63), includes the detection position of the lift of the recording medium M, which changes depending on the thickness of the recording medium M.

[0057] In this way, by attaching the lift detection unit 80 to the carriage 61 that is raised and lowered according to the thickness of the recording medium M, it is possible to easily change the height (detection position) of the detection light B of the lift detection unit 80 that detects the lift of the recording medium M according to the thickness of the recording medium M. As a result, there is no need to adjust the detection position that detects the lift of the recording medium.

[0058] Basically, there is no need to change the height position of the detection light B relative to the nozzle surface 63a of the carriage 61. However, for example, a detection light position changer (not shown) may be provided that changes the height position of the detection light B depending on the distance between the surface Ma of the recording medium M and the nozzle surface 63a, the type of recording medium M (for example, thickness, material, etc.), etc. The detection light position changer may be configured to have, for example, an actuator that changes the height position of the floating detection unit 80 (light-emitting unit 81 and light-receiving unit 82).

[0059] 5 is a diagram for explaining the positional relationship between the carriage 61, the lift detection unit 80, the conveyor belt 11, and the recording medium M. As shown in FIG.

[0060] In Figure 5, distance D is the distance between the surface Ma of the recording medium M and the nozzle surface 63a (the height of the nozzle surface 63a relative to the surface Ma). Distance d1 is the distance between the nozzle surface 63a and the detection light B, and distance d2 is the distance between the surface Ma and the detection light B (the height of the detection light B relative to the surface Ma). Furthermore, thickness h is the thickness of the recording medium M. Distance D + thickness h corresponds to the first height described above, and distance d2 + thickness h corresponds to the second height described above.

[0061] For example, when the distance D increases, the detection light position changing unit may increase the distance d1 to bring the height position of the detection light B closer to the surface Ma of the recording medium M, thereby preventing a decrease in the detection sensitivity for the lifting of the recording medium M. Furthermore, when the recording medium M (type) is one that can tolerate some lifting, the detection light position changing unit may decrease the distance d1 to move the height position of the detection light B away from the surface Ma of the recording medium M, thereby preventing a increase in the detection sensitivity for the lifting of the recording medium M.

[0062] [Image forming method] An image forming method in the inkjet printer 100 having the above-described configuration will be described with reference to Fig. 6. Fig. 6 is a flowchart illustrating the image forming method in the inkjet printer 100.

[0063] (Step S11) The control unit 90 controls the conveyance unit 10 to convey the recording medium M.

[0064] (Step S12) The control unit 90 acquires the amount of light received by the lift detection unit 80.

[0065] (Step S13) The control unit 90 determines whether the amount of received light acquired from the lift detection unit 80 is equal to or less than a preset threshold. If the amount of received light is not equal to or less than the threshold (NO), the process proceeds to step S14, and if the amount of received light is equal to or less than the threshold (YES), the process proceeds to step S16.

[0066] When the recording medium M floats up from the conveying surface 11a of the conveyor belt 11 and the detection light B transmitted from the light projecting unit 81 to the light receiving unit 82 of the floating detection unit 80 is partially or completely blocked by the recording medium M, the amount of light received by the light receiving unit 82 decreases. Therefore, by comparing whether the amount of light detected by the light receiving unit 82 is equal to or less than a threshold value, it is possible to determine whether the recording medium M has floated up.

[0067] As described above, when the carriage 61 is raised or lowered in accordance with the thickness of the recording medium M, the lift detection unit 80 moves together with the carriage 61, and the height of the detection light B of the lift detection unit 80 also changes automatically. Therefore, even if the thickness of the recording medium M changes, the lift detection unit 80 can appropriately detect the lift of the recording medium M.

[0068] (Step S14) In step S13, if the amount of received light is not equal to or less than the threshold (NO), that is, if the recording medium M is not floating, the control unit 90 executes image forming processing on the recording medium M by the image forming unit 60.

[0069] (Step S15) The control unit 90 determines whether the image forming process is complete. For example, it can determine whether the image forming process is complete based on the number of processed recording media M input from the operation display unit 40. If the image forming process is not complete (NO), the process returns to step S11, and if the image forming process is complete (YES), the series of procedures ends.

[0070] (Steps S16 and S17) In step S13, if the amount of received light is equal to or less than the threshold value (YES), that is, if the recording medium M is in a floating state, the control unit 90 stops the conveyance unit 10 from conveying the recording medium M. Then, the control unit 90 notifies the user, for example, using the operation display unit 40, that the recording medium M has floated, and ends the series of procedures.

[0071] By the above procedure, if the recording medium M floats up, the conveyance of the recording medium M can be stopped to prevent the recording medium M from contacting the head 63, and damage to the head 63 can be prevented.

[0072] As described above, in this embodiment, the inkjet printer 100 is equipped with a lift detection unit 80 that changes a second height relative to the conveying surface 11a in conjunction with the movement of the head 63 and detects lifting of the recording medium M relative to the conveying surface 11a at that second height.

[0073] According to this embodiment configured as described above, the height of the lift detection unit 80 (height of the detection light B) that detects lift of the recording medium M can be easily changed according to the thickness of the recording medium M. As a result, there is no need to adjust the detection position that detects lift of the recording medium M. Furthermore, according to this embodiment, the carriage 61 is raised and lowered according to the thickness of the recording medium M, and the lift detection unit 80 moves together with the head 63, and the height of the detection light B of the lift detection unit 80 also changes automatically. Therefore, even if the thickness of the recording medium M changes, the lift of the recording medium M can be appropriately detected by the lift detection unit 80.

[0074] <Variation 1> FIG. 7 is a flowchart illustrating a modified example of the image forming method shown in FIG.

[0075] In this modification, the configuration of the inkjet printer 100 may be the same as that described in the above embodiment, and therefore a description of that configuration will be omitted here.

[0076] (Steps S21 to S24) Steps S21 to S24 are the same as steps S11 to S14 in the flowchart of the image forming method shown in FIG. 6, so a duplicated description will be omitted here.

[0077] (Step S25) In step S23, if the amount of received light is equal to or less than the threshold value (YES), that is, if the recording medium M is in a floating state, the control unit 90 temporarily stops the image forming process by the image forming unit 60.

[0078] (Step S26) The control unit 90 moves the carriage 61 (head 63) from the image forming position to the retracted position using the elevator unit 70. The image forming position is a position where the head 63 forms an image on the recording medium M, and the retracted position is a position where the recording medium M does not come into contact with the head 63 even if the recording medium M is lifted up.

[0079] (Step S27) The control unit 90 determines whether the recording medium M has passed the carriage 61. For example, an optical sensor (not shown) may be used to determine whether the recording medium M has passed the carriage 61. If the recording medium M has not passed the carriage 61 (NO), step S27 is repeated, and if the recording medium M has passed the carriage 61 (YES), the process proceeds to step S28.

[0080] (Step S28) The control unit 90 controls the elevator unit 70 to move the carriage 61 (head 63) from the retracted position to the image forming position.

[0081] (Step S29) The control unit 90 determines whether the image forming process is complete. For example, it may determine whether the image forming process is complete based on the number of processed recording media M input from the operation display unit 40. If the image forming process is not complete (NO), the process returns to step S21, and if the image forming process is complete (YES), the series of procedures is completed.

[0082] If the image forming process is not completed in step S29 (NO), the process returns to step S21, and the control unit 90 causes the conveying unit 10 to convey the recording medium M. Then, if the amount of received light is not equal to or less than the threshold value in step S23 (YES), that is, if the recording medium M is not floating, the control unit 90 causes the image forming unit 60 to execute the image forming process, that is, to resume the image forming process.

[0083] By following the above procedure, when the recording medium M has floated up, the carriage 61 (head 63) is moved from the image forming position to the retracted position, preventing the recording medium M from contacting the head 63 and preventing damage to the head 63. Furthermore, image formation processing can be continued for recording media M other than the floating recording medium M. The procedure shown in Fig. 7 is an effective method when it is desirable to avoid stopping the image formation processing as much as possible.

[0084] In addition, when the carriage 61 (head 63) is continuously moved to the retracted position, as described in steps S16 and S17 of Figure 6, the transport of the recording medium M by the transport unit 10 may be stopped and the user may be notified that the recording medium M has floated up.

[0085] <Variation 2> FIG. 8 is a flowchart illustrating another modified example of the image forming method shown in FIG.

[0086] In this modification, the inkjet printer 100 may have the same configuration as that described in the above embodiment, and therefore a description of that configuration will be omitted here.

[0087] (Steps S31 to S34) Steps S31 to S34 are the same as steps S11 to S14 in the flowchart of the image forming method shown in FIG. 6, so a duplicated description will be omitted here.

[0088] (Step S35) In step S33, if the amount of received light is equal to or less than the threshold value (YES), that is, if the recording medium M is in a floating state, the control unit 90 moves the carriage 61 (head 63) from the image forming position to the retracted position by the elevator unit 70. The image forming position is a position where the head 63 forms an image on the recording medium M, and the retracted position is a position where the recording medium M does not come into contact with the head 63 even if the recording medium M is floating.

[0089] (Step S36) The control unit 90 causes the image forming unit 60 to perform image formation processing on the recording medium M. At this time, the image formation processing is performed with the carriage 61 (head 63) at the retracted position.

[0090] (Step S37) The control unit 90 determines whether the recording medium M has passed the carriage 61. For example, an optical sensor (not shown) may be used to determine whether the recording medium M has passed the carriage 61. If the recording medium M has not passed the carriage 61 (NO), step S37 is repeated, and if the recording medium M has passed the carriage 61 (YES), the process proceeds to step S38.

[0091] (Step S38) The control unit 90 controls the elevator unit 70 to move the carriage 61 (head 63) from the retracted position to the image forming position.

[0092] (Step S39) The control unit 90 determines whether the image forming process is complete. For example, it may determine whether the image forming process is complete based on the number of processed recording media M input from the operation display unit 40. If the image forming process is not complete (NO), the process returns to step S31, and if the image forming process is complete (YES), the series of procedures is completed.

[0093] If the image forming process is not completed in step S39 (NO), the process returns to step S31, and the control unit 90 conveys the recording medium M by the conveying unit 10. Then, if the amount of received light is not equal to or less than the threshold value in step S33 (YES), that is, if the recording medium M is not floating, the control unit 90 executes the image forming process with the carriage 61 (head 63) at the image forming position.

[0094] By the above procedure, when the recording medium M is lifted up, the carriage 61 (head 63) is moved from the image forming position to the retracted position, preventing the recording medium M from contacting the head 63 and preventing damage to the head 63. Furthermore, the image forming process can be continued, including the lifted recording medium M. The procedure shown in Fig. 8 is also an effective method when it is desirable to avoid stopping the image forming process as much as possible.

[0095] In addition, when the carriage 61 (head 63) is continuously moved to the retracted position, as described in steps S16 and S17 of Figure 6, the transport of the recording medium M by the transport unit 10 may be stopped and the user may be notified that the recording medium M has floated up.

[0096] <Variation 3> FIG. 9 is a diagram schematically showing the main parts of a modified example of the image forming apparatus (inkjet printer 100) shown in FIG.

[0097] The inkjet printer shown in Figure 9 has the same configuration as the inkjet printer 100 shown in Figure 1, except for some components. Figure 9 shows only the main parts of the inkjet printer, and for example, the supply section 20 and the discharge section 30 are not shown.

[0098] In the above embodiment, the float detection unit 80 is attached to the carriage 61 on the most upstream side, but the float detection unit 80 may be attached to a carriage 61 other than the most upstream carriage 61. For example, as shown in FIG. 9, the float detection unit 80 may be attached to all carriages 61.

[0099] In this case, the lifting unit 70 may be configured to lift and lower all of the carriages 61 together, or may be configured to lift and lower the carriages 61 individually. When the lifting unit 70 is configured to lift and lower the carriages 61 individually, the lifting unit 70 may, for example, lift and lower only the carriage 61 to which the lift detection unit 80 that detected the lifting of the recording medium M is attached. Alternatively, the lifting unit 70 may lift and lower the carriage 61 to which the lift detection unit 80 that detected the lifting of the recording medium M is attached, and the carriage 61 downstream in the transport direction from the carriage 61.

[0100] When an image is formed by ejecting ink Ik from the head 63 onto the recording medium M, the ejected ink Ik may moisten the recording medium M, causing wrinkles in the recording medium M and resulting in wavy floating of the recording medium M. When the printing rate for the recording medium M is high, the wavy floating described above is likely to occur.

[0101] In this modified example, as described above, the lifting detection unit 80 is attached to all carriages 61. Therefore, even if there is no lifting of the recording medium M during image formation on a certain carriage 61, if the lifting of the recording medium M occurs on a carriage 61 that passes after that image formation, the lifting of the recording medium M can be detected.

[0102] When floating of the recording medium M is detected in the carriage 61 passing after image formation, as described above, the carriage 61 on which the floating detection unit 80 that detected the floating of the recording medium M is attached and the carriage 61 downstream of that are raised and lowered. This makes it possible to prevent the recording medium M from coming into contact with the head 63, and to prevent damage to the head 63.

[0103] <Variation 4> FIG. 10 is a diagram showing a modified example of the placement of the lift detection unit 80 relative to the carriage 61. In FIG.

[0104] In the above embodiment, the light-emitting unit 81 and the light-receiving unit 82 are attached to both side surfaces 61a, 61b of the carriage 61 in the width direction W, respectively, and are arranged below the side surfaces 61a, 61b of the carriage 61 so as to face each other.

[0105] Considering the size of the light-emitting unit 81 and the light-receiving unit 82 and the height of the nozzle surface 63a relative to the conveying surface 11a of the conveyor belt 11, it is desirable to configure the light-emitting unit 81 and the light-receiving unit 82 so that they do not come into contact with the conveying surface 11a.

[0106] Therefore, in this modified example, the floating detection unit 80 has spacer members 83 and 84 (first spacer members in the present invention) extending in the width direction W. The spacer members 83 and 84 extend in the width direction W so that the light projecting unit 81 and the light receiving unit 82 are located outside both end portions of the conveyor belt 11 in the width direction W.

[0107] Using such spacer members 83, 84, the light-projecting unit 81 and the light-receiving unit 82 are attached to the side surfaces 61a, 61b, respectively, of the carriage 61. Specifically, the light-projecting unit 81 is attached to one side surface 61a of the carriage 61 via the spacer member 83, and the light-receiving unit 82 is attached to the other side surface 61b of the carriage 61 via the spacer member 83, and are arranged to face each other.

[0108] In this modified example, as described above, the light projecting unit 81 and the light receiving unit 82 are attached to the side surfaces 61a and 61b of the carriage 61 via the spacer members 83 and 84, respectively, and are arranged so as to be outward from both ends in the width direction W of the conveyor belt 11. Therefore, even if the height of the lift detection unit 80 changes as the carriage 61 moves, the light projecting unit 81 and the light receiving unit 82 do not come into contact with the conveying surface 11a of the conveyor belt 11, and the lift of the recording medium M can be properly detected.

[0109] Furthermore, the light projecting unit 81 and the light receiving unit 82 are positioned away from the surface Ma of the recording medium M by the spacer members 83 and 84. Therefore, the influence of the mist of ink ejected from the head 63 onto the surface Ma of the recording medium M on the light projecting unit 81 and the light receiving unit 82 can be suppressed.

[0110] <Variation 5> FIG. 11 is a diagram showing another modified example of the placement of the floating detection unit 80 relative to the carriage 61. In FIG.

[0111] In the above embodiment, the light-emitting unit 81 and the light-receiving unit 82 are attached to both side surfaces 61a, 61b of the carriage 61 in the width direction W, respectively, and are arranged below the side surfaces 61a, 61b of the carriage 61 so as to face each other.

[0112] Considering the size of the light-emitting unit 81 and the light-receiving unit 82 and the height of the nozzle surface 63a relative to the conveying surface 11a of the conveyor belt 11, it is desirable to configure the light-emitting unit 81 and the light-receiving unit 82 so that they do not come into contact with the conveying surface 11a.

[0113] Therefore, in this modified example, the floating detection unit 80 has mirrors 85 and 86 (first and second mirrors in the present invention) that change the optical path of the light. The mirrors 85 and 86 refract the optical path of the detection light B from the light projecting unit 81 to the light receiving unit 82.

[0114] Such mirrors 85 and 86 are disposed, using mounting members not shown, near the lower corners of the side surfaces 61a and 61b of the carriage 61. Specifically, the mirror 85 is attached near the lower corner of one side surface 61a of the carriage 61, and the mirror 86 is attached near the lower corner of the other side surface 61b of the carriage 61, and are disposed so as to face each other.

[0115] In this way, the mirrors 85, 86 are disposed near the lower corners of the side surfaces 61a, 61b, so that the light-projecting unit 81 and the light-receiving unit 82 can be attached to the side surfaces 61a, 61b of the carriage 61 at positions above the mirrors 85, 86. Once the optical path of the detection light B from the light-projecting unit 81 to the light-receiving unit 82 is set, there is no need to change the position of the optical path, and therefore the optical path can be refracted even if the mirrors 85, 86 are relatively small in size.

[0116] In this arrangement, the light-projecting unit 81 projects light in a direction toward the conveying surface 11a, and the mirror 85 refracts the light from the light-projecting unit 81 to change it into detection light B that is parallel to the nozzle surface 63a. The mirror 86 refracts the detection light B from the mirror 85 to change it into detection light B that is directed away from the conveying surface 11a, and the light-receiving unit 82 receives the detection light B from the mirror 86.

[0117] In this modified example, as described above, the mirrors 85 and 86 are attached near the lower corners of the side surfaces 61a and 61b, and the light-projecting unit 81 and the light-receiving unit 82 are attached to the side surfaces 61a and 61b of the carriage 61 at positions above the mirrors 85 and 86. Therefore, even if the height of the lift detection unit 80 changes as the carriage 61 moves, the light-projecting unit 81 and the light-receiving unit 82 and the mirrors 85 and 86 do not come into contact with the conveying surface 11a of the conveyor belt 11, and the lift of the recording medium M can be detected appropriately.

[0118] Furthermore, due to the above-described configuration, the light projecting unit 81 and the light receiving unit 82 are positioned away from the surface Ma of the recording medium M. Therefore, the influence of mist from the ink ejected from the head 63 onto the surface Ma of the recording medium M on the light projecting unit 81 and the light receiving unit 82 can be suppressed.

[0119] <Variation 6> Fig. 12 is a diagram showing another modified example of the installation of the lift detection unit 80 on the carriage 61. Fig. 13 is a diagram showing an example in which the modified example shown in Fig. 12 uses a lift detection unit 80-1 that emits strip-shaped detection light.

[0120] In the above embodiment, the light-emitting unit 81 and the light-receiving unit 82 are attached to both side surfaces 61a, 61b of the carriage 61 in the width direction W, respectively, and are arranged below the side surfaces 61a, 61b of the carriage 61 so as to face each other.

[0121] When the floating detection unit 80 detects floating of the recording medium M, it performs avoidance processing (for example, stopping transport or retracting the carriage 61) to prevent the recording medium M from contacting the head 63. In order to reliably prevent the recording medium M from contacting the head 63, it is desirable to ensure that there is a predetermined distance (hereinafter, "predetermined distance") or more from the floating detection unit 80 to the closest head 63 in the transport direction T.

[0122] For this reason, in this modified example, the lift detection unit 80 has a spacer member 87 (second spacer member in the present invention) that extends in the transport direction T. The spacer member 87 extends in the transport direction T so that the distance from the lift detection unit 80 to the closest head 63 is equal to or greater than a predetermined distance FD that reliably prevents the recording medium M from contacting the head 63. Here, the predetermined distance FD is a distance that is set so that the head 63 can avoid contact with the lifted portion from the time that the lift detection unit 80 detects the lifted portion of the recording medium M until the lifted portion reaches the head 63.

[0123] The predetermined distance FD is set in consideration of image formation conditions, such as the response time of the floating detection unit 80, the conveying speed of the conveying unit 10 (recording medium M), and the response time for the avoidance process (for example, the distance (time) until the conveying belt 11 stops conveying, the time until the carriage 61 retracts, etc.).

[0124] As an example, if the response time of the floating detection unit 80 is 1 ms, the conveying speed of the conveying unit 10 (recording medium M) is 1 m / s, and the distance until the conveying belt 11 stops conveying is 50 mm, the predetermined distance FD is 51 mm.

[0125] Further, for example, the predetermined distance FD may be calculated by assuming the image forming conditions under which the predetermined distance FD is maximized, and the spacer member 87 extending the predetermined distance FD in the transport direction T may be used.

[0126] Using such a spacer member 87, the floating detection unit 80 (light-emitting unit 81 and light-receiving unit 82) is attached to the side surface 61c on the upstream side of the carriage 61 in the conveying direction, and is positioned at a position at least a predetermined distance FD upstream of the nearest head 63 in the conveying direction T.

[0127] In this modified example, as described above, the lift detection unit 80 is attached to the side surface 61c of the carriage 61 via a spacer member 87 that extends a predetermined distance FD in the transport direction T. Therefore, for example, if the recording medium M is a sheet of paper, the above-mentioned avoidance processing can be performed from the time the lift detection unit 80 detects that the sheet has lifted up until the sheet reaches the head 63. Also, if the recording medium M is roll paper, the above-mentioned avoidance processing can be performed from the time the lift detection unit 80 detects that a portion of the roll paper has lifted up until the portion reaches the head 63. In this way, it is possible to reliably prevent the recording medium M from coming into contact with the head 63.

[0128] Furthermore, the spacer member 87 positions the lift detection unit 80 away from the surface Ma of the recording medium M. This makes it possible to suppress the influence of mist from the ink ejected from the head 63 onto the surface Ma of the recording medium M on the lift detection unit 80.

[0129] The spacer member 87 may be configured so that its length in the transport direction T is changeable, in which case the spacer member 87 functions as a distance changer that changes the predetermined distance FD based on the image formation conditions. For example, the transport speed of the transport unit 10 (recording medium M) can be changed by settings, etc. In such a case, the spacer member 87, which functions as a distance changer, changes the predetermined distance FD, thereby reliably avoiding contact of the recording medium M with the head 63.

[0130] Furthermore, instead of the float detector 80 in which the detection light B is focused in a point shape, a float detector 80-1 in which the detection light B-1 is focused in a line (band shape) may be used, as shown in Fig. 13. A fiber sensor having a slit for emitting and receiving the detection light B-1 can be used as this float detector 80-1. When using this float detector 80-1, the float detector 80-1 is attached to the side surface 61c of the carriage 61 on the upstream side in the transport direction via a spacer member 87 so that the plane of the detection light B-1 is parallel to the nozzle surface 63a.

[0131] In the lift detection unit 80-1, the detection light B-1 is focused linearly (in a band), so the detection width of the detection light B-1 is wide, enabling stable detection of lift of the recording medium M. Furthermore, on the upstream side in the transport direction, a distance (predetermined distance FD) can be set from the nearest head 63 to the lift detection unit 80-1. Furthermore, because the predetermined distance FD has a certain width, lift of the recording medium M can be stably detected even if, for example, the transport speed of the transport unit 10 (recording medium M) changes slightly.

[0132] <Variation 7> FIG. 14 is a perspective view showing a modified example of the floating detector 80. In FIG.

[0133] When ink is ejected from the head 63 onto the surface Ma of the recording medium M, the ink generates mist. When the lift detection unit 80 is attached to the carriage 61, the lift detection unit 80 is positioned close to the surface Ma of the recording medium M, so it is desirable to configure the lift detection unit 80 so that it is not affected by the generated mist.

[0134] Therefore, in this modified example, the floating detection unit 80 has covers 88 and 89 that cover the light-emitting unit 81 and the light-receiving unit 82 except for the portions through which light passes.

[0135] Although not shown, the cover 88 has a passage hole that allows the detection light B from the light projecting unit 81 to pass through. Note that a film that allows the detection light B to pass through may be provided in the passage hole.

[0136] The cover 89 also has a passage hole 89a that allows the detection light B from the light projecting unit 81 to pass through. A film that allows the detection light B to pass through may also be provided in the passage hole 89a.

[0137] In this way, the light-projecting unit 81 and the light-receiving unit 82 are housed inside the covers 88 and 89 so as to be covered by the covers 88 and 89 except for the portions through which the detection light B passes. Therefore, the influence of the mist of ink ejected from the head 63 onto the surface Ma of the recording medium M on the light-projecting unit 81 and the light-receiving unit 82 can be suppressed.

[0138] The above-described embodiment and modifications 1 to 7 are merely examples of specific embodiments of the present invention, and the technical scope of the present invention should not be construed as being limited by these. In other words, the present invention can be embodied in various forms without departing from the gist or main features thereof.

[0139] For example, in the above-described embodiment and modifications 1 to 7, an optical sensor-type detection sensor is used as the lift detection unit 80, but instead, a contact-type detection sensor may be used. [Explanation of symbols]

[0140] 10 Conveying section 11 Conveyor belt 11a Conveying surface 12 Drive roller 13 Driven roller 20 Supply section 21 Supply loading section 22 Supply and conveying section 30 Discharge section 31 Discharge loading section 32 Discharge and conveyance section 40 Operation display section 50 Input / Output Interface 60 Image forming unit 61 Carriage 61a, 61b, 61c side 62 Head drive unit 63 Inkjet head 63a Nozzle surface 70 Lifting section 71 Lift control section 72 Lifting motor 80, 80-1 Float detection unit 81 Light projector 82 Light receiving section 83, 84, 87 Spacer members 85, 86 mirror 88, 89 Cover 89a Passing hole 90 Control Unit 100 Inkjet Printer 200 External device

Claims

1. a conveying unit that conveys the recording medium; an inkjet head for forming an image on the conveyed recording medium; a height moving unit that moves the inkjet head so as to change a first height of the inkjet head relative to a transport surface of the transport unit in accordance with the type of the recording medium; a detection unit that detects a second height relative to the transport surface that changes in conjunction with movement of the inkjet head and detects floating of the recording medium relative to the transport surface at the second height; a carriage that holds the inkjet head; Equipped with the detection unit has a light-projecting unit that projects light parallel to the ink ejection surface of the inkjet head as detection light, and a light-receiving unit that receives the detection light, the light-projecting unit and the light-receiving unit being attached to both sides of the carriage that are outside both ends of the recording medium in a width direction perpendicular to the conveyance direction of the recording medium, and the detection unit detects floating of the recording medium based on the light-receiving result of the light-receiving unit. Image forming device.

2. A conveying unit that conveys a recording medium; an inkjet head for forming an image on the conveyed recording medium; a height moving unit that moves the inkjet head so as to change a first height of the inkjet head relative to a transport surface of the transport unit in accordance with the type of the recording medium; a detection unit that detects a second height relative to the transport surface that changes in conjunction with movement of the inkjet head and detects floating of the recording medium relative to the transport surface at the second height; Equipped with the detection unit has a light-projecting unit that projects light in a direction toward the transport surface, a first mirror that refracts the light from the light-projecting unit to change it into detection light parallel to the ink ejection surface of the inkjet head, a second mirror that refracts the detection light to change it into detection light in a direction away from the transport surface, and a light-receiving unit that receives the detection light from the second mirror, and detects floating of the recording medium based on the light-receiving result of the light-receiving unit. Image forming device.

3. A conveying unit that conveys a recording medium; an inkjet head for forming an image on the conveyed recording medium; a height moving unit that moves the inkjet head so as to change a first height of the inkjet head relative to a transport surface of the transport unit in accordance with the type of the recording medium; a detection unit that detects a second height relative to the transport surface that changes in conjunction with movement of the inkjet head and detects floating of the recording medium relative to the transport surface at the second height; a plurality of carriages arranged side by side along the conveyance direction of the recording medium, each carriage holding an inkjet head; Equipped with the detection unit is attached to the carriage on the most upstream side in the conveying direction; Image forming device.

4. a carriage for holding the inkjet head; the detection unit is attached to the carriage, the height movement unit moves the carriage to move the inkjet head, thereby changing the first height of the inkjet head and changing the second height of the detection unit; The image forming apparatus according to claim 1 .

5. the detection unit has a light-projecting unit that projects light parallel to the ink ejection surface of the inkjet head as detection light, and a light-receiving unit that receives the detection light, and detects floating of the recording medium based on the light-receiving result of the light-receiving unit. The image forming apparatus according to claim 3 .

6. a carriage that holds the inkjet head; a first spacer member for attaching the light projecting unit and the light receiving unit to both sides of the carriage so that the light projecting unit and the light receiving unit are located outside both ends of the transport unit in a width direction perpendicular to the transport direction of the recording medium; Equipped with The image forming apparatus according to claim 5 .

7. A first spacer member is provided to attach the light-emitting unit and the light-receiving unit to both sides of the carriage so that they are outside both ends of the conveying unit in the width direction. The image forming apparatus according to claim 1 .

8. the detection unit is disposed so that the range of the height of the detection light, which is changed by the movement of the inkjet head, includes a detection position of the floating of the recording medium, which changes depending on the type of the recording medium. The image forming apparatus according to claim 1 , 2 , 5 to 7 .

9. a carriage that holds the inkjet head; a second spacer member that attaches the light projecting unit and the light receiving unit to the carriage so as to be located upstream of the inkjet head in the conveying direction of the recording medium; Equipped with The image forming apparatus according to claim 8 .

10. the detection unit is disposed at a position spaced a predetermined distance or more upstream from the inkjet head in the transport direction by the second spacer member; the predetermined distance is a distance set so that the inkjet head can avoid contact with the raised portion from when the detection unit detects the raised portion of the recording medium until the raised portion reaches the inkjet head. The image forming apparatus according to claim 9 .

11. a distance change unit that changes the predetermined distance based on image formation conditions; The image forming apparatus according to claim 10.

12. a detection light position changing unit that changes the height position of the detection light relative to the ink ejection surface in accordance with the type of the recording medium; 12. The image forming apparatus according to claim 1, 2, or 5 to 11.

13. a cover for covering the light-emitting unit and the light-receiving unit except for the portion through which light passes; 13. The image forming apparatus according to claim 1, 2, or 5 to 12.

14. the detection unit is attached to the carriage downstream of the carriage located most upstream in the conveying direction; The image forming apparatus according to claim 3 .

15. the recording medium is any one of a sheet of paper, a roll of paper, a sheet of cloth, and a roll of cloth; The image forming apparatus according to claim 1 .

Images