Image forming apparatus

Abstract

The present invention provides an image forming apparatus that allows for easy replacement of parts while maintaining the parallelism of the optical path in the floating detection section. [Solution] The image forming apparatus includes a print belt unit 2200 for transporting sheets, and a floating detection unit 2400 for detecting light-blocking objects B on the image forming surface 26 on which the sheets of the print belt unit 2200 are transported. The floating detection unit 2400 has an adjustment unit 80 for adjusting the light-emitting unit 31 so that the laser beam 33 is parallel to the image forming surface 26, and a fixing unit 28 for fixing the light-emitting unit 31 to the print belt unit 2200. The floating detection unit 2400 is removed from the print belt unit 2200 when the fixing unit 28 is removed from the print belt unit 2200, while the light-emitting unit 31 maintains the state adjusted by the adjustment unit 80.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus such as a printing machine, a copying machine, and a printer that performs image formation.

Background Art

[0002] In the printing industry, industrial inkjet printers that achieve high productivity and high-quality products are widespread. An industrial inkjet printer prints an image on a sheet being conveyed by a print head. The print gap, which is the distance between the print head and the sheet, greatly affects the image quality. In order to achieve high image quality, it is necessary to set the print gap to a short distance of about 1 [mm].

[0003] The sheet may float or be deformed such as being folded during conveyance. These cause the occurrence of head touch where the sheet contacts the print head. Head touch not only degrades the quality of the product but also leads to damage to the print head.

[0004] In order to prevent head touch, it is necessary to detect the floating and deformation of the sheet (hereinafter referred to as "floating etc."). The floating etc. of the sheet is detected by providing a floating detection unit for detecting the floating etc. of the sheet upstream of the print head in the conveyance direction of the sheet. The floating detection unit is realized, for example, using an optical sensor composed of a light emitting unit that emits laser light and a light receiving unit that receives the emitted laser light. Patent Document 1 discloses a paper conveyance device provided with a deterioration detection means for detecting the deterioration of a sheet conveyance belt that forms a conveyance path while detecting an abnormality of a sheet by such an optical sensor. Patent Document 2 discloses a sheet-fed printer in which a sensor system (floating detection unit) using an optical sensor can be adjusted so that the optical path of the laser light of the optical sensor is parallel to the sheet conveyance path.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] In Patent Document 1, the light-emitting and light-receiving parts of an optical sensor (float detection unit) are provided on either side of the sheet conveyor belt. Therefore, when replacing the sheet conveyor belt, the float detection unit must be temporarily removed. In Patent Document 2, when the sensor system is removed due to parts replacement or the like and then reinstalled, the optical path of the sensor system must be adjusted to be parallel to the conveyor path. Removing the float detection unit each time parts are replaced and adjusting the optical path of the laser beam to be parallel to the sheet conveyor path during reinstallation leads to a decrease in usability.

[0007] In view of the above-mentioned problems, the main objective of the present invention is to provide an image forming apparatus that allows for easy replacement of parts while maintaining the parallelism of the optical path of the floating detection unit. [Means for solving the problem]

[0008] The image forming apparatus of the present invention comprises a conveying means for conveying a sheet, an image forming means for forming an image on the sheet conveyed by the conveying means, and a detection means attached to the conveying means for detecting an object on the surface of the conveying means on which the sheet is conveyed, wherein the detection means comprises a light-emitting means for emitting laser light, a light-receiving means for receiving the laser light, an adjustment means for adjusting the light-emitting means so that the laser light is parallel to the surface, and a fixing means for fixing the light-emitting means to the conveying means, wherein the detection means is removed from the conveying means while the light-emitting means is maintained in the state adjusted by the adjustment means when the fixing means is removed from the conveying means. [Effects of the Invention]

[0009] According to the present invention, it is possible to easily replace parts while maintaining the parallelism of the optical path of the floating detection unit. [Brief explanation of the drawing]

[0010] [Figure 1] Configuration diagram of an inkjet recording device. [Figure 2] A diagram illustrating the configuration of a printed circuit board. [Figure 3] Diagram illustrating the control unit. [Figure 4] Diagram showing the configuration of the float detection unit. [Figure 5] Diagram showing the configuration of the float detection unit. [Figure 6] (a) and (b) are diagrams illustrating the state in which the laser beam is not parallel to the image-forming surface. [Figure 7] (a) to (c) are explanatory diagrams for adjusting the optical axis in the first embodiment. [Figure 8] (a) and (b) are explanatory diagrams for adjusting the optical axis in the second embodiment. [Figure 9] (a) and (b) are explanatory diagrams for adjusting the optical axis in the third embodiment. [Modes for carrying out the invention]

[0011] Preferred embodiments of the present invention will be described below with reference to the attached drawings.

[0012] Figure 1 is a configuration diagram of an inkjet recording device, which is an image forming apparatus of this embodiment. The inkjet recording device 1 ejects ink onto a sheet to form an image. The inkjet recording device 1 of this embodiment is a sheet-fed image forming apparatus that uses two liquids, a reaction solution and ink, to form an ink image on a sheet and produce a finished product. The sheet can be any recording material that can accept ink, such as plain paper, cardboard, plastic film for overhead projectors, specially shaped sheets such as envelopes and index paper, or cloth.

[0013] The inkjet recording device 1 comprises a paper feed module 1000, a print module 2000, a drying module 3000, a fixing module 4000, a cooling module 5000, an inversion module 6000, and a paper discharge and stacking module 7000. Sheets, which are cut-paper-like recording materials on which images are printed, are supplied from the paper feed module 1000, predetermined processing related to image formation is performed in each module, and the sheets are discharged to the paper discharge and stacking module 7000. In this embodiment, the inkjet recording device 1 is configured by each module having a separate housing, and these housings being connected. Alternatively, the inkjet recording device 1 may contain the functions of each module within a single housing.

[0014] The paper feed module 1000 is equipped with multiple (three in this embodiment) storage compartments 1100a to 1100c. Each storage compartment 1100a to 1100c is capable of storing a sheet. Each storage compartment 1100a to 1100c is designed to be pull out towards the front of the device, and a sheet is stored inside when it is pulled out towards the front of the device. The paper feed module 1000 feeds the sheets to the print module 2000 one by one. For this purpose, each storage compartment 1100a to 1100c is provided with a separation belt and a transport roller. The number of storage compartments 1100a to 1100c is just an example, and there may be one, two, or four or more levels.

[0015] The print module 2000 is an image forming unit that forms an image on a sheet fed from the paper feed module 1000. The print module 2000 includes a pre-image registration correction unit (not shown), a print belt unit 2200, and a recording unit 2300. The pre-image registration correction unit corrects the tilt and position of the sheet supplied from the paper feed module 1000 and transports it to the print belt unit 2200.

[0016] The print belt unit 2200 and the recording unit 2300 are arranged to face each other across the sheet conveyance path on the downstream side of the pre-imaging registration correction unit in the sheet conveyance direction. The print belt unit 2200 adsorbs and conveys the sheet conveyed from the pre-imaging registration correction unit. The recording unit 2300 is a sheet processing unit that forms an image by performing a recording process (printing) on the sheet conveyed by the print belt unit 2200 from above with a recording head. The recording head performs printing by ejecting ink onto the sheet. The sheet is adsorbed and conveyed by the print belt unit 2200, so that the clearance with the recording head is kept constant.

[0017] A plurality of recording heads are arranged along the sheet conveyance direction. The recording heads of the present embodiment are five line-type recording heads corresponding to the reaction liquid in addition to the four colors of Y (yellow), M (magenta), C (cyan), and K (black). Note that the number of colors and the number of recording heads are not limited to five. The inkjet method can adopt a method using a heating element, a method using a piezo element, a method using an electrostatic element, a method using a MEMS (Micro Electro Mechanical Systems) element, etc. The ink of each color is supplied from an ink tank (not shown) to the recording head through an ink tube. The ink contains, for example, a resin component of 0.1 mass% to 20.0 mass%, water, a water-soluble organic solvent, a colorant, a wax, an additive, etc. based on the total mass.

[0018] The sheet printed by the recording unit 2300 is conveyed by the print belt unit 2200. An in-line scanner (not shown) is arranged on the downstream side in the conveyance direction with respect to the recording unit 2300. The in-line scanner is used to detect the positional deviation and color density of the image formed on the sheet and correct the printed image.

[0019] The drying module 3000 dries the sheet on which the image has been formed by the printing module 2000 by blowing hot air onto the sheet. By drying the sheet, the drying module 3000 reduces the liquid component contained in the ink, thereby improving the adhesion between the sheet and the ink. The drying module 3000 comprises a decoupling unit 3200, a drying belt unit 3300, and a hot air blowing unit 3400.

[0020] The sheet printed in the recording unit 2300 of the print module 2000 is transported to the decoupling unit 3200 in the drying module 3000. The decoupling unit 3200 loosely holds and transports the sheet using the frictional force generated between the sheet and the belt by the pressure of the wind blown from above. As a result, the sheet straddles the decoupling unit 3200 and the print belt unit 2200, preventing any displacement of the portion remaining on the print belt unit 2200.

[0021] The sheet conveyed from the decoupling unit 3200 is adsorbed and conveyed to the drying belt unit 3300, and at the same time, hot air is blown from the hot air blowing unit 3400 located above the belt to dry the ink-applied surface (the printed surface of the image). The ink and reaction liquid applied to the sheet are heated, and the evaporation of moisture is promoted, so the sheet absorbs the applied ink, and the occurrence of so-called cockling, where the sheet stretches locally and wrinkles, can be suppressed. For the heater that heats the air, for example, an electric heating wire or an infrared heater is preferred from the viewpoint of safety and energy efficiency. In addition to the method of applying hot air, the drying method may also be a method that combines a method of irradiating the sheet surface with electromagnetic waves (ultraviolet rays or infrared rays, etc.) or a method of conduction heat transfer by contact with a heating element.

[0022] The fixing module 4000 fixes the image to the sheet by heating the sheet dried by the drying module 3000 to dry the ink. The fixing module 4000 includes a fixing belt unit 4100 having an upper belt unit and a lower belt unit. The fixing module 4000 passes the sheet conveyed from the drying module 3000 between the heated upper belt unit and the lower belt unit, thereby allowing the ink solvent to sufficiently penetrate (fix) into the sheet.

[0023] The cooling module 5000 cools the sheet on which the image has been fixed by the fixing module 4000, thereby solidifying the ink that has softened due to heating and suppressing temperature changes of the sheet caused by downstream equipment. The cooling module 5000 is equipped with multiple cooling units 5100. The multiple cooling units 5100 cool the high-temperature sheet conveyed from the fixing module 4000. Each cooling unit 5100 increases the pressure inside the cooling box by drawing in outside air with a fan. The air inside the cooling box is blown out from nozzles formed in the conveying path and directed onto the sheet, cooling the sheet. The multiple cooling units 5100 are arranged on both sides of the conveying path, allowing the sheet to be cooled from both sides.

[0024] A transport path switching unit is provided within the cooling module 5000. The transport path switching unit switches the transport path of the sheet depending on whether the sheet is being transported to the inversion module 6000 or to the double-sided transport path used during double-sided printing.

[0025] During double-sided printing, the sheet is transported to a transport path below the cooling module 5000 and then transported through the double-sided transport path of the fuser module 4000, drying module 3000, print module 2000, and paper feed module 1000. The double-sided transport section of the fuser module 4000 is provided with a first inversion section 4200 that inverts the front and back sides of the sheet. After being transported to the first inversion section 4200, the sheet is inverted and transported to the drying module 3000, thereby inverting the printed side of the image. By passing through the first inversion section 4200, printing on the back side of the sheet becomes possible. After that, the sheet is transported again to the pre-image registration correction section, print belt unit 2200, and recording section 2300 of the print module 2000 for printing.

[0026] The inversion module 6000 includes a second inversion unit 6400. The inversion module 6000 can invert the front and back sides of the conveyed sheets using the second inversion unit 6400. This allows the orientation of the front and back sides of the discharged sheets to be changed. The output and stacking module 7000 includes a top tray 7200 and a stacking tray 7500. The output and stacking module 7000 aligns and stacks the sheets conveyed from the inversion module 6000 onto the top tray 7200 or the stacking tray 7500.

[0027] (Print Module) Figure 2 is a diagram of the print module 2000. As described above, the print module 2000 comprises a pre-image registration correction unit, a print belt unit 2200, and a recording unit 2300. The sheet S, whose orientation has been corrected by the pre-image registration correction unit, is printed by the recording unit 2300 directly below the recording head 10. The sheet S is transported by suction and adsorption from the print belt unit 2200, so that its transport behavior is stable directly below the recording head 10.

[0028] The printed belt unit 2200 comprises an endless printed belt 25 stretched over tension rollers 21, 22, 23, and 24. The tension roller 21 is a drive roller that rotates the printed belt 25 and is movable in the roller axis direction (front-rear direction in the figure). The tension roller 22 is a tension roller that applies force to the printed belt 25 from the inner surface outward to tension the belt. The tension roller 23 is a steering roller that can be tilted by moving one of its axis ends to suppress meandering of the printed belt 25. The tension roller 24 is a driven roller that moves in accordance with the rotation of the printed belt and is movable in the roller axis direction. Each of the tension rollers 21, 22, 23, and 24 is rotatably supported by bearings provided on the front frame and rear frame of the printed belt unit 2200.

[0029] The belt surface of the print belt 25, which is stretched by tension rollers 21 and 24, becomes an image forming surface 26 for image formation directly below the recording head 10. The print belt 25 rotates so that the image forming surface 26 moves in the direction of conveying the sheet S. The print belt 25 is provided with numerous suction holes (not shown) for attracting the sheet S. The suction holes have a diameter of, for example, about 0.3 mm.

[0030] The print belt 25 attracts and holds the sheet S through suction holes located on the image forming surface 26, and transports the held sheet S by rotating. For this purpose, a suction device (not shown) is provided in the area surrounded by the print belt 25 to attract and hold the sheet S through the suction holes on the image forming surface 26. The print belt 25 is manufactured, for example, by forming suction holes in a single PET sheet wound into a roll, cutting it to a predetermined length, and then joining the ends by laser welding.

[0031] By operating the tension roller 22, the tension on the print belt 25 is released. This causes the print belt 25 to flex, creating a gap between it and each of the tension rollers 21-24. As a result, the print belt 25 becomes movable in the roller axis direction and can be removed from the print belt unit 2200. Print belts 25 that need to be replaced due to aging or other reasons are removed from the print belt unit 2200 through this process and replaced with new print belts.

[0032] The sheet S, which is adsorbed onto the image forming surface 26, is transported with a predetermined print gap between it and the recording head 10. In this embodiment, the print gap is approximately 1.0 mm. As described above, the recording head 10 has five line-type recording heads arranged along the transport direction of the sheet S, corresponding to the reaction solution in addition to the four colors Y (yellow), M (magenta), C (cyan), and K (black).

[0033] A floating detection unit 2400 is positioned upstream of the recording head 10 in the direction of sheet S transport. The floating detection unit 2400 detects objects on the image forming surface 26 and can detect objects located a predetermined distance away from the image forming surface 26 towards the recording unit 2300. In other words, the floating detection unit 2400 can detect objects that have floated a predetermined distance above the image forming surface 26. By providing such a floating detection unit 2400, it is possible to prevent various problems that may occur due to collisions (head touches) between the sheet S that have floated above the image forming surface 26 and the recording head 10. Details of the floating detection unit 2400 will be described later.

[0034] Upstream of the floating detection unit 2400 in the sheet transport direction, a sheet presence / absence detection unit 40 is positioned to detect the presence or absence of sheet S. The recording unit 2300 starts printing the image after a predetermined time has elapsed, starting from the detection of sheet S by the sheet presence / absence detection unit 40.

[0035] (Image formation process) Figure 3 is an explanatory diagram of the control unit that controls the operation of the inkjet recording device 1. The control unit 70 is connected to each module and controls the operation of each module to form an image on the sheet S. The control unit 70 is also connected to the operation unit 50 and the notification unit 60. The operation unit 50 is an input interface such as a keyboard or touch panel. The notification unit 60 is an output interface that provides notifications such as image displays on a display or voice notifications on a speaker. The operation unit 50 and the notification unit 60 may be an integrated touch panel display.

[0036] The control unit 70 is an information processing device having processing units such as a CPU (Central Processing Unit) and an MPU (Microprocessor Unit). The control unit 70 controls the operation of the inkjet recording device 1 by executing a predetermined computer program. The control unit 70 may also be provided as a dedicated control device for the inkjet recording device 1 using an ASIC (Application Specific Integrated Circuit).

[0037] The production of the deliverable (image formation on the sheet S) by the inkjet recording device 1 begins when the control unit 70 receives a job start instruction. The user inputs sheet information such as the type and size of the sheet S to be used for the deliverable, image data representing the image to be formed on the sheet S, and the quantity of deliverables using the operation unit 50. This information is input from the operation unit 50 to the control unit 70. The user then inputs a job start instruction from the operation unit 50 to the control unit 70.

[0038] When the control unit 70 receives a job start instruction, it instructs each module to perform preparatory operations before job execution in order to stably execute the sheet S transport operation and the image formation operation on the sheet S. In response to this instruction, each module performs preparatory operations. The preparatory operations mainly involve activating the sheet S transport section, including the print belt unit 2200, to stabilize the transport speed, and heating the fixer belt unit 4100 to stabilize image formation by thermal fixing. Since these operations require a predetermined amount of time, the feeding of the sheet S is not started during this time.

[0039] After the preparation operation is complete, the control unit 70 instructs the paper feed module 1000 to start feeding sheets S according to the sheet information acquired from the operation unit 50. The paper feed module 1000 starts feeding sheets S in response to this command. The sheets S fed from the paper feed module 1000 are transported to the print module 2000. After the sheet S transported to the print module 2000 has its tilt and position corrected by the pre-image registration correction unit, it is detected by the sheet presence detection unit 40. The sheet presence detection unit 40 transmits a signal to the control unit 70 indicating that a sheet S has been detected.

[0040] The control unit 70 instructs the recording unit 2300 to start the image formation operation after a predetermined time has elapsed since the sheet presence detection unit 40 detected the sheet S. This predetermined time is the transport time required for the sheet S to be transported from the sheet presence detection unit 40 to the printing position by the recording head 10. The control unit 70 calculates this predetermined time based on the size of the sheet S included in the sheet information and the transport speed of the sheet S.

[0041] The sheet S on which the image has been formed is finally discharged into the paper output and stacking module 7000. The control unit 70 repeats this series of operations until the specified quantity of deliverables is reached. When the specified quantity of deliverables is reached, the control unit 70 notifies the user of the completion of the job via the notification unit 60. The control unit 70 also notifies the user via the notification unit 60 in the event of an error or abnormal termination.

[0042] (Float detection unit) The floating detection unit 2400 detects objects on the image forming surface 26, including the sheet S that is adsorbed to and transported by the image forming surface 26. The floating detection unit 2400 detects objects a predetermined amount above the image forming surface 26 and transmits the detection result to the control unit 70. Based on the detection result of the floating detection unit 2400, various problems that would occur if an object a predetermined amount above the image forming surface 26 (for example, a floating sheet S) collides with the recording head 10 (head touch) are prevented.

[0043] The recording head 10 may become contaminated due to head contact. As a specific example, we will explain the contamination of the recording head 10 by a recording head that ejects yellow (Y) ink (for convenience, referred to as "10Y") and a recording head that ejects magenta (M) ink (for convenience, referred to as "10M"). When the sheet S collides with the recording head 10Y, yellow ink adheres to the sheet S. Subsequently, when the sheet S collides with the following recording head 10M, yellow ink adheres to the recording head 10M that ejects magenta ink. In this state, a mixture of magenta and yellow ink is ejected onto the sheet S, making it impossible to perform normal printing.

[0044] Furthermore, the recording head 10 may be damaged if the sheet S collides with it. For example, repeated collisions of the sheet S with the recording head 10 can cause the ink ejection nozzles on the recording head 10 to become damaged, making it impossible to perform normal printing.

[0045] To prevent these problems, it is necessary to detect head touch in advance and then perform a process to prevent head touch or a process to ensure that no problems occur even if head touch occurs. In this embodiment, the possibility of head touch is detected in advance using the float detection unit 2400. When the control unit 70 detects the possibility of head touch, it sends an instruction to the print belt unit 2200 or the recording unit 2300 to perform processes such as stopping ink ejection, stopping the transport of the sheet S, and retracting the recording head 10.

[0046] Figures 4 and 5 are configuration diagrams of the float detection unit 2400 as viewed from the upstream side in the conveying direction of the sheet S. Figure 4 shows a state in which no float or deformation has occurred in the sheet S and it is determined that no head contact will occur. Figure 5 shows a state in which float or deformation has occurred in the sheet S and it is determined that a head contact will occur. The float detection unit 2400 is an optical sensor comprising a light-emitting unit 31 that emits laser light and a light-receiving unit 32 that receives the laser light emitted from the light-emitting unit 31.

[0047] The light-emitting unit 31 is positioned at one end in the direction intersecting the conveying direction of the sheet S conveyed by the print belt 25 (hereinafter referred to as the "width direction"), and the light-receiving unit 32 is positioned at the other end in the width direction of the print belt 25. In this embodiment, one end is the front side of the print module 2000, and the other end is the back side of the print module 2000. From the front side of the print module 2000, users can process jammed paper and maintenance workers can replace the print belt 25.

[0048] The light-emitting unit 31 emits laser light 33 in the width direction of the print belt 25. The laser light 33 is a line laser with a predetermined width (e.g., 10 mm) in the height direction. Here, the height direction is the direction perpendicular to the width direction of the image forming surface 26 (print belt 25) and also perpendicular to the conveying direction of the sheet S. The laser light 33 is irradiated from the light-emitting unit 31 on the front side of the print module 2000 toward the light-receiving unit 32 on the back side of the print module 2000. Therefore, exposure to the eyes of users and maintenance workers is prevented.

[0049] The light-receiving unit 32 has multiple light-receiving elements. The multiple light-receiving elements are arranged in the height direction. Each light-receiving element outputs an electrical signal corresponding to the amount of laser light 33 received (received intensity). The electrical signals output from each light-receiving element are transmitted to an amplifier (not shown) provided in the floating detection unit 2400. The amplifier amplifies the electrical signals acquired from the light-receiving elements. Based on the comparison result of the amplified electrical signal value with a predetermined threshold, the floating detection unit 2400 determines which of the multiple light-receiving elements are receiving the laser light 33 or not.

[0050] In the example shown in Figure 4, the laser beam 33 is shielded by the thickness of the printed belt 25 and the sheet S. As a result, the multiple light-receiving elements of the light-receiving unit 32 are such that the light-receiving elements below position D1 in the height direction do not receive the laser beam 33, while the light-receiving elements above position D1 in the height direction do receive the laser beam 33. Based on this light-receiving state of the light-receiving unit 32, the floating detection unit 2400 determines that the shielded position is position D1.

[0051] The light-shielding position indicates the boundary position between light-receiving elements that receive the laser light 33 and those that do not, in an array of multiple light-receiving elements, and can also be called the light-receiving position. The floating detection unit 2400 has a detection threshold DS set in advance to determine the height of the light-shielding object. The floating detection unit 2400 compares the light-shielding position with the detection threshold DS, and if the light-shielding position is above the detection threshold DS in the height direction, it transmits a detection signal to the control unit 70 indicating that a light-shielding object (object) that may cause head contact has been detected on the image forming surface 26.

[0052] In this embodiment, the detection threshold DS is a value that indicates the possibility of an object above that position touching the head. The detection threshold DS is set to an appropriate value considering factors such as the clearance between the image forming surface 26 and the recording head 10, and variations in the dimensional tolerances of each component.

[0053] In this manner, the floating detection unit 2400 transmits a detection signal to the control unit 70 when it detects a floating object on the image forming surface 26 based on the light-shielding position and the detection threshold DS. In the example shown in Figure 4, since the position D1 in the height direction is below the detection threshold DS, no detection signal is transmitted. Even if there is a floating object on the image forming surface 26, there is no possibility of head contact if the light-shielding position does not exceed the detection threshold DS. Therefore, in Figure 4, no detection signal is transmitted, and the normal sheet transport operation and image forming operation are not stopped.

[0054] In Figure 5, the deformation portion Sf of the sheet S determines that position D2 is the light-shielding position. Since the light-shielding position is above the detection threshold DS in the height direction, the floating detection unit 2400 transmits a detection signal to the control unit 70. In response to the detection signal, the control unit 70 causes the print belt unit 2200 and the recording unit 2300 to perform image formation stop processing when floating is detected, such as stopping ink ejection, stopping the transport of the sheet S, and retracting the recording head 10.

[0055] In Figure 5, the deformed portion Sf of the sheet S is located on the side of the light-emitting portion 31. The deformed portion Sf may occur at any position in the width direction, or it may occur across the entire width direction. In any case, if the deformed portion Sf blocks the laser light 33 and it is detected that the blocking position is above the detection threshold DS in the height direction, the floating detection unit 2400 transmits a detection signal to the control unit 70. In this embodiment, it is possible to detect head touch in advance by the floating detection unit 2400.

[0056] Figure 6 is an explanatory diagram of a state in which the laser beam 33 is not parallel to the image forming surface 26. Figure 6(a) shows the case where the deformed portion Sf of the sheet S is near the light-emitting portion 31. Figure 6(b) shows the case where the deformed portion Sf of the sheet S is near the light-receiving portion 32. The height of the deformed portion Sf from the image forming surface 26 is the same in Figure 6(a) and Figure 6(b). The inclination of the laser beam 33 with respect to the image forming surface 26 is the same in Figure 6(a) and Figure 6(b).

[0057] In Figure 6(a), position D3 is detected as a light-shielding position by the deformation part Sf. Since position D3 is below the detection threshold DS in the height direction, the floating detection unit 2400 does not transmit a detection signal to the control unit 70. In Figure 6(b), position D4 is detected as a light-shielding position by the deformation part Sf. Since position D4 is above the detection threshold DS in the height direction, the floating detection unit 2400 transmits a detection signal to the control unit 70.

[0058] When the laser beam 33 is not parallel to the image forming surface 26, the detection result of the buoyancy detection unit 2400 fluctuates depending on the position of the deformed portion Sf of the sheet S. As a result, the buoyancy detection unit 2400 becomes unable to reliably detect the deformed portion Sf (buoyancy detection). In order to perform stable buoyancy detection without being affected by the position of the deformed portion Sf of the sheet S, it is necessary to achieve a state in which the laser beam 33 is parallel to the image forming surface 26, as shown in Figure 5.

[0059] Furthermore, "parallel" does not mean a state in which the laser beam 33 is perfectly parallel to the image forming surface 26, but also a state in which the deformation portion Sf is non-parallel to such an extent that it is detected that the light-shielding position in the height direction is above the detection threshold DS, regardless of the position of the deformation portion Sf in the width direction.

[0060] Here, the float detection unit 2400 may be removed when replacing parts such as the print belt 25. Therefore, the print module 2000 is equipped with a configuration that allows adjustment of the parallelism of the laser beam 33 of the float detection unit 2400 with respect to the image forming surface 26 (hereinafter referred to as "optical axis adjustment"). This allows the parallelism of the laser beam 33 to be adjusted when reinstalling the float detection unit 2400, even if it is removed when replacing parts such as the print belt 25.

[0061] (Example 1 of optical axis adjustment) Figure 7 is an explanatory diagram of the optical axis adjustment in the first embodiment. Figure 7(a) illustrates a state in which the laser beam 33 is parallel to the image forming surface 26. Figure 7(b) illustrates a state in which the laser beam 33 is not parallel to the image forming surface 26. Figure 7(c) illustrates a state in which the buoyancy detection unit 2400 has been released from the print belt 25.

[0062] The float detection unit 2400 has a light-emitting unit 31 and a light-receiving unit 32 connected by a connecting unit 34. The light-emitting unit 31 and the light-receiving unit 32 are provided between the front frame and the rear frame of the print belt unit 2200.

[0063] The print belt unit 2200 is equipped with a pivot support portion 27 on the rear frame of the print belt unit 2200 on the light-receiving portion 32 side. The pivot support portion 27 has a groove portion 27a that is open to the print belt 25 side. A pivot shaft 35 extending in the direction of conveying the sheet S is provided in the groove portion 27a. The pivot shaft 35 can be inserted into the groove portion 27a from the print belt 25 side, and the movement of the groove portion 27a in the height direction is restricted. The pivot shaft 35 passes through the end of the connecting portion 34 on the light-receiving portion 32 side. In this configuration, the floating detection portion 2400 is positioned in the height direction by the pivot support portion 27 on the light-receiving portion 32 side. The connecting portion 34 is freely rotatable around the pivot shaft 35.

[0064] The float detection unit 2400 is equipped with a fixing part 28 on the front frame of the print belt unit 2200 on the light-emitting unit 31 side. An adjustment part 80 is provided above the fixing part 28 in the height direction. The adjustment part 80 is one or more spacer sheets. The adjustment part 80 is held between the end of the connecting part 34 on the light-emitting unit 31 side and the fixing part 28 by an adjustment holding member 81. The adjustment holding member 81 is, for example, a screw or a biasing spring. The fixing part 28 is fixed to the print belt unit 2200 by a fixing member 29. The fixing member 29 is, for example, a screw. In this way, the light-emitting unit 31, the adjustment part 80, and the fixing part 28 are fixed together to the print belt unit 2200.

[0065] The floating detection unit 2400 has its position in the height direction restricted on the light-emitting unit 31 side by the adjustment unit 80 and the fixing unit 28, and its rotation around the pivot axis 35 on the light-receiving unit 32 side is restricted. The thickness of the adjustment unit 80 can be increased or decreased by changing (increasing or decreasing) the number or thickness of the spacer sheets. Insertion of the spacer sheets can be performed by a service technician (or customer engineer). By increasing or decreasing the thickness of the adjustment unit 80, it is possible to change the restricted position in the height direction on the light-emitting unit 31 side of the floating detection unit 2400.

[0066] As shown in Figure 7(b), the rotation of the floating detection unit 2400 (connecting unit 34) around the pivot axis 35 causes the laser beam 33 to tilt, resulting in a loss of parallelism of the laser beam 33 with respect to the image forming surface 26. As described above, by increasing or decreasing the thickness of the adjustment unit 80, the height restriction position on the light-emitting unit 31 side of the floating detection unit 2400 (connecting unit 34), i.e., the rotation restriction position of the floating detection unit 2400, can be changed. Therefore, by changing the thickness of the adjustment unit 80, it is possible to adjust the tilt of the laser beam 33 with respect to the image forming surface 26. Accordingly, by increasing or decreasing the thickness of the adjustment unit 80, it is possible to adjust the optical axis so that the laser beam 33 in the state shown in Figure 7(b) becomes a laser beam 33 parallel to the image forming surface 26, as shown in Figure 7(a).

[0067] Next, we will explain the optical axis adjustment that makes the laser beam 33 parallel to the image forming surface 26. As explained in Figure 6, when the laser beam 33 is not parallel to the image forming surface 26, the detection result may change depending on the position in the width direction where the deformed portion Sf of the sheet S is located.

[0068] In Figure 7(b), the light-shielding object B, which corresponds to the deformed portion Sf of the sheet S, is located above the image-forming surface 26. When the light-shielding object B is near the light-emitting portion 31, the light-shielding position is position D5. When the light-shielding object B is near the light-receiving portion 32, the light-shielding position is position D6, which is higher than position D5. The difference between position D5 and position D6 is caused by the inclination of the laser beam 33 with respect to the image-forming surface 26.

[0069] As shown in Figure 7(a), when the laser beam 33 is parallel to the image forming surface 26, positions D5 and D6 are the same. To make the laser beam 33 parallel to the image forming surface 26, the tilt of the laser beam 33 is adjusted by the adjustment unit 80. The number and thickness of the spacer sheets in the adjustment unit 80 are increased or decreased so that positions D5 and D6 are the same. The thickness of the adjustment unit 80 is adjusted by increasing or decreasing the number and thickness of the spacer sheets. The optical axis is adjusted by adjusting the thickness of the adjustment unit 80, so that the laser beam 33 is parallel to the image forming surface 26.

[0070] Once the optical axis adjustment is complete, the adjustment unit 80 maintains its thickness by the adjustment holding member 81. As long as the holding state by the adjustment holding member 81 is not released, the optical axis of the laser beam 33 is maintained in the adjusted state.

[0071] The float detection unit 2400 is removed from the printed belt unit 2200 when replacing parts such as the printed belt 25. In this case, the fixing member 29 is removed as shown in Figure 7(c). As a result, the float detection unit 2400 is released from the printed belt unit 2200 on the side of the light-emitting unit 31.

[0072] When the light-emitting part 31 of the float detection unit 2400 is released from its fixed position, the connecting part 34 becomes rotatable above the print belt unit 2200. As the connecting part 34 rotates above the print belt unit 2200, the light-emitting part 31, the adjustment part 80, and the fixing part 28 move together above the print belt unit 2200. After the connecting part 34 has rotated above the print belt unit 2200, moving the connecting part 34 in the width direction releases the restriction on the position of the pivot axis 35 by the groove 27a. This allows the float detection unit 2400 to be removed from the print belt unit 2200.

[0073] Subsequently, the tension roller 22 is operated to release the tension on the print belt 25, and the print belt 25 is moved in the width direction, thereby removing the print belt 25 from the print belt unit 2200. This makes it possible to replace the print belt 25.

[0074] At this time, the fixing part 28, the light-emitting part 31, and the adjustment part 80 move together with the connecting part 34, and the adjustment part 80 is fixed to the fixing part 28 by the adjustment holding member 81. As a result, the optical axis of the laser beam 33 is maintained as it was during adjustment. In this state, when attaching the float detection part 2400 to the print belt unit 2200 after replacing the print belt 25, it is not necessary to adjust the optical axis again.

[0075] As described above, the adjustment unit 80 makes it easy to adjust the optical axis so that the laser beam 33 is parallel to the image forming surface 26. The adjustment unit 80 is fixed to the fixing unit 28. The adjustment unit 80 and the fixing unit 28 are retracted above the print belt 25 when the float detection unit 2400 is removed, and are fixed to the print belt unit 2200 when the float detection unit 2400 is installed. Therefore, the optical axis of the laser beam 33 can be maintained while the float detection unit 2400 can be attached and detached.

[0076] When removing the float detection unit 2400 to replace any necessary parts, optical axis adjustment is not required even when detaching the float detection unit 2400 from the printed belt unit 2200, as described above. This makes parts replacement easy.

[0077] (Second embodiment of optical axis adjustment) Figure 8 is an explanatory diagram of the optical axis adjustment in the second embodiment. Figure 8(a) illustrates a state in which the laser beam 33 is parallel to the image forming surface 26. Figure 8(b) illustrates a state in which the laser beam 33 is not parallel to the image forming surface 26.

[0078] In the second embodiment, the light-emitting section 31 is attached to the light-emitting support section 91. The light-emitting support section 91 is rotatably supported on the fixed section 93 via a pivot shaft 92. The fixed section 93 is fixed to the printed belt unit 2200 by a fixing member 94. The light-emitting support section 91 and the fixed section 93 are connected by an adjustment and holding member 95, which is a tension spring. The adjustment and holding member 95 biases the light-emitting support section 91 toward the fixed section 93.

[0079] The printed belt unit 2200 is provided with an adjustment section 90. The adjustment section 90 has a stopper section 90a that can be translated in the direction of the adjustment holding member 95. The adjustment section 90 is implemented, for example, by a micrometer head. The light-emitting support section 91 is biased toward the fixed section 93 by the adjustment holding member 95 and rotates around the pivot axis 92 until it contacts the stopper section 90a. That is, the stopper section 90a is a rotation restricting member of the light-emitting support section 91, and the rotation restricting position of the light-emitting support section 91 can be changed by the translation of the stopper section 90a.

[0080] Since the light-emitting unit 31 is attached to the light-emitting support unit 91, the inclination of the laser beam 33 with respect to the image-forming surface 26 changes as the light-emitting support unit 91 rotates. Therefore, by translating the abutment unit 90a of the adjustment unit 90, the angle of the surface to which the light-emitting unit 31 is attached to the light-emitting support unit 91 can be changed, thereby changing the inclination of the laser beam 33 with respect to the image-forming surface 26. In this way, optical axis adjustment becomes possible to adjust the laser beam 33 to be parallel to the image-forming surface 26.

[0081] When the light-emitting unit 31 is removed from the print belt unit 2200 for replacement of parts such as the print belt 25, the fixing member 94 is removed, and the fixing part 93 is removed from the print belt unit 2200. As a result, the light-emitting unit 31, the light-emitting support part 91, the pivot shaft 92, the fixing part 93, and the adjustment holding member 95 are removed. The adjustment part 90 remains attached to the print belt unit 2200. Therefore, as long as the abutment part 90a is not translated, the result of the optical axis adjustment performed earlier is maintained.

[0082] When the light-emitting unit 31 is reattached to the print belt unit 2200, the light-emitting unit 31, light-emitting support unit 91, pivot shaft 92, fixing unit 93, and adjustment holding member 95 are placed on the print belt unit 2200 and fixed by the fixing member 94. The light-emitting support unit 91 to which the light-emitting unit 31 is attached is rotated by the adjustment holding member 95 until it contacts the abutment unit 90a of the adjustment unit 90, which has been adjusted for optical axis. This reproduces the state in which the laser beam 33 is parallel to the image forming surface 26, and there is no need to perform the optical axis adjustment work again. In this way, even when the light-emitting unit 31 is removed and parts are replaced, optical axis adjustment is not required when reattaching the light-emitting unit 31, making parts replacement easy.

[0083] (Third embodiment of optical axis adjustment) Figure 9 is an explanatory diagram of the optical axis adjustment in the third embodiment. Figure 9(a) illustrates a state in which the laser beam 33 is parallel to the image forming surface 26. Figure 9(b) illustrates a state in which the laser beam 33 is not parallel to the image forming surface 26. The configuration and function of the light-emitting unit 31, light-emitting support unit 91, pivot shaft 92, fixing unit 93, fixing member 94, and adjustment holding member 95 are the same as in the second embodiment in Figure 8.

[0084] In the third embodiment, the adjustment unit 90 having abutment portion 90a in the second embodiment is replaced with an adjustment unit 100 composed of a rotatable eccentric cam. The light-emitting support unit 91 is biased by the adjustment holding member 95 and rotates around the pivot axis 92 until it contacts the contact position 100a of the adjustment unit 100. That is, the contact position 100a becomes the rotation restriction position of the light-emitting support unit 91. By rotating the adjustment unit 100, the contact position 100a (rotation restriction position) can be changed.

[0085] Since the light-emitting unit 31 is attached to the light-emitting support unit 91, the inclination of the laser beam 33 with respect to the image forming surface 26 changes as the light-emitting support unit 91 rotates. Therefore, by rotating the adjustment unit 100 and displacing the contact position 100a, it is possible to change the angle of the surface to which the light-emitting unit 31 is attached on the light-emitting support unit 91, thereby changing the inclination of the laser beam 33 with respect to the image forming surface 26. In this way, optical axis adjustment is possible to adjust the laser beam 33 to be parallel to the image forming surface 26.

[0086] When the light-emitting unit 31 is removed from the print belt unit 2200 for replacement of parts such as the print belt 25, the fixing member 94 is removed, and the light-emitting unit 31, light-emitting support unit 91, pivot shaft 92, fixing part 93, and adjustment holding member 95 are removed. This is the same as in the second embodiment. The adjustment unit 100 remains attached to the print belt unit 2200. Therefore, unless the adjustment unit 100 is rotated to displace the contact position 100a, the result of the previously performed optical axis adjustment is maintained.

[0087] When the light-emitting unit 31 is reattached to the print belt unit 2200, the light-emitting unit 31, light-emitting support unit 91, pivot shaft 92, fixing unit 93, and adjustment holding member 95 are placed on the print belt unit 2200 and fixed by the fixing member 94. This is the same as in the second embodiment. The light-emitting support unit 91 to which the light-emitting unit 31 is attached is rotated by the adjustment holding member 95 until it contacts the adjustment unit 100, which has been adjusted for optical axis alignment, at the contact position 100a. This reproduces the state in which the laser beam 33 is parallel to the image forming surface 26, and there is no need to perform the optical axis adjustment work again. In this way, even when the light-emitting unit 31 is removed and parts are replaced, optical axis adjustment is not required when reattaching the light-emitting unit 31, making parts replacement easy.

[0088] As described above, in this embodiment, the adjustment units 80, 90, and 100 perform optical axis adjustment to make the laser beam 33 parallel to the image forming surface 26. The floating detection unit 2400 is fixed to the print belt unit 2200 by the fixing units 28 and 94. Because the adjustment units 80, 90, and 100 and the fixing units 28 and 94 are separate, the floating detection unit 2400 can be attached to and detached from the print belt unit 2200 while maintaining the results of the optical axis adjustment. Therefore, even if the floating detection unit 2400 is removed from the print belt unit 2200 and reattached when replacing parts such as the print belt 25, it is not necessary to perform optical axis adjustment again, making parts replacement easy.

[0089] In this embodiment, an example in which the sheet S is transported by a printed belt 25 has been described, but the sheet S may also be transported by a drum-shaped member. In this case as well, the float detection unit 2400 can be attached and detached while maintaining the adjusted optical axis of the laser beam.

[0090] The buoyancy detection unit 2400 of this embodiment is configured to detect buoyancy or deformation of the sheet S using a line-shaped laser beam 33, but the laser beam 33 may be spot-shaped or area-shaped. The light receiving unit 32 has a detection threshold DS set for detecting the light-shielding position, but the detection threshold DS may also be set according to the amount of light received. The buoyancy detection unit 2400 only needs to be able to set the detection threshold DS and distinguish between detected and undetected states based on that setting.

Claims

1. A conveying means for transporting sheets, An image forming means for forming an image on the sheet that is transported by the transport means, The transport means is equipped with a detection means for detecting an object on the surface of the transport means on which the sheet is transported, The aforementioned detection means is A light-emitting means that emits laser light, The light receiving means for receiving the laser light, An adjustment means for adjusting the light-emitting means so that the laser beam is parallel to the surface, The light-emitting means is fixed to the transport means, The detection means is characterized in that when the fixing means is removed from the transport means, the light-emitting means is removed from the transport means while maintaining the state adjusted by the adjustment means. Image forming apparatus.

2. The light-emitting means is positioned on one end of the conveying means in a direction intersecting the conveying direction of the sheet. The light receiving means is positioned on the other end side of the conveying means in a direction intersecting the conveying direction of the sheet. The detection means is characterized by detecting the object on the surface when the light receiving means does not receive the laser light. The image forming apparatus according to claim 1.

3. The detection means includes, on the side where the light-receiving means is provided, a pivot shaft extending in the transport direction, and a connecting means for connecting the light-emitting means and the light-receiving means. The pivot shaft passes through the end of the connecting means on the side where the light receiving means is provided, The connecting means is freely rotatable about the pivot axis, The adjusting means and the fixing means are provided on the side of the connecting means where the light-emitting means is provided. The light-emitting means, the adjustment means, and the fixing means are characterized by rotating in conjunction with the rotation of the connecting means. The image forming apparatus according to claim 2.

4. The adjustment means is characterized by adjusting the optical axis of the laser beam by changing the thickness. The image forming apparatus according to claim 3.

5. The adjustment means is one or more spacer sheets, and the thickness is changed by changing the number or thickness of the spacer sheets, thereby adjusting the optical axis of the laser beam. The image forming apparatus according to claim 4.

6. A light-emitting support portion to which the light-emitting means is attached and which is rotatably supported by the fixing means, The device includes a biasing means for biasing the light-emitting support portion toward the fixing means, The adjustment means is characterized by having a stopper portion that abuts against the light-emitting support portion and is capable of translating in the direction of the light-emitting support portion. The image forming apparatus according to claim 2.

7. The adjustment means is characterized by changing the angle of the surface to which the light-emitting means is attached to the light-emitting support portion by translating the abutment portion, thereby adjusting the optical axis of the laser beam. The image forming apparatus according to claim 6.

8. The adjustment means is characterized by being a rotatable eccentric cam. The image forming apparatus according to claim 6.

9. The adjustment means is characterized by adjusting the optical axis of the laser beam by changing the angle of the surface of the light-emitting support to which the light-emitting means is attached, by displacing the contact position of the eccentric cam with the light-emitting support by rotating the eccentric cam. The image forming apparatus according to claim 8.

10. The aforementioned conveying means is An endless belt, It has a plurality of tension rollers for tensioning the belt, The surface of the belt stretched by two of the aforementioned tension rollers is the surface on which the sheet is conveyed. One of the plurality of tension rollers is a tension roller that applies tension to the belt from the inner surface outward to stretch the belt. The belt can be removed from the plurality of tension rollers when the tension applied by the tension rollers is released. The image forming apparatus according to claim 1.

Images