Image forming apparatus and control apparatus

Abstract

To detect floating of a recording medium with high accuracy.SOLUTION: An image formation device is provided with: a conveying part that conveys a recording medium along a conveyance passage; a floatation detecting part that has a light emitting portion and a light receiving portion and detects floating of the recording medium, on the basis of a received result by the light receiving portion of light emitted from the light emitting portion and having passed on the conveyance passage; a temperature detecting part that detects a temperature in a light path of the light; a variable mechanism that changes an emitting direction of light emitted from the light emitting portion; and a control part that controls motion of the variable mechanism, on the basis of the detected temperature by the temperature detecting part.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to an image forming apparatus and a control apparatus.

Background Art

[0002] The recording apparatuses described in Patent Documents 1 and 2 include a light projecting unit that emits laser light and a light receiving unit that receives the laser light. The light projecting unit projects the laser light so as to pass through a conveyance path. The recording apparatus detects the lifting of the recording medium when it detects that the recording medium has blocked the laser light.

Summary of the Invention

Problems to be Solved by the Invention

[0003] However, when a temperature difference occurs in the optical path, the recording apparatuses described in Patent Documents 1 and 2 may not be able to accurately detect the lifting of the recording medium because the light bends.

[0004] An object of the present invention is to provide an image forming apparatus capable of accurately detecting the lifting of a recording medium. I

Means for Solving the Problems

[0005] An image forming apparatus according to an embodiment includes a conveyance unit that conveys a recording medium along a conveyance path, a light projecting unit and a light receiving unit, a lifting detection unit that detects the lifting of the recording medium based on a light reception result by the light receiving unit of light emitted from the light projecting unit and passing over the conveyance path, a temperature detection unit that detects the temperature in the optical path of the light, a variable mechanism that changes the emission direction of the light from the light projecting unit, and a control unit that controls the operation of the variable mechanism based on the temperature detected by the temperature detection unit.

Effects of the Invention

[0006] According to one embodiment, the effect of light bending can be suppressed by tilting the emission direction of light emitted from the light-emitting unit based on the temperature in the optical path. Therefore, an image forming apparatus capable of accurately detecting the lifting of the recording medium can be provided. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic diagram showing the overall configuration of an image forming apparatus according to one embodiment. [Figure 2] This is a schematic diagram showing the configuration of an inkjet recording module included in an image forming apparatus according to one embodiment. [Figure 3] This is a schematic diagram showing the arrangement of the recording medium floating detection sensors. [Figure 4] This is a schematic diagram showing a recording medium floating detection sensor. [Figure 5] This figure shows the distribution of laser light under normal conditions. [Figure 6] This figure shows the distribution of laser light when a temperature difference occurs. [Figure 7] This is a schematic diagram showing a variable mechanism that changes the direction of laser light emission from the light-emitting unit. [Figure 8] This figure shows the angle of the laser beam. [Figure 9] This table shows the relationship between the temperature difference within the optical path of a laser beam and the gradient of the laser beam. [Figure 10] This graph shows the relationship between the laser beam's arrival point and its height. [Figure 11] This is a block diagram showing the hardware configuration of an image forming apparatus according to one embodiment. [Figure 12] This block diagram shows the hardware configuration of the recording medium floating detection system. [Figure 13] This is a functional block diagram of an image forming apparatus according to one embodiment. [Figure 14] This is a flowchart showing the processing procedure in the recording medium floating detection system. [Figure 15]This is a block diagram showing the hardware configuration of the recording medium floating detection system according to Modification Example 1. [Figure 16] This flowchart shows the processing procedure in the recording medium floating detection system according to Modification 1. [Modes for carrying out the invention]

[0008] An embodiment of the present invention will be described below with reference to the drawings. In each figure, arrows indicating the three orthogonal directions, namely the X-axis, Y-axis, and Z-axis, may be shown. The X-axis direction is along the transport direction of the recording medium PP. The Y-axis direction is intersecting the transport direction and is along the width direction of the recording medium PP. The Z-axis direction is along the thickness direction of the recording medium PP.

[0009] <Overall configuration of the image forming apparatus 200> Figure 1 is a diagram showing the overall configuration of an image forming apparatus 200 according to one embodiment. The image forming apparatus 200 shown in Figure 1 is an on-demand line scanning inkjet recording apparatus. As shown in Figure 1, the image forming apparatus 200 according to one embodiment includes an image forming unit 210, a paper feeding unit 220, a resist adjustment unit 230, a drying unit 240, a recording medium inversion unit 250, and a paper discharge unit 290.

[0010] The paper feeding unit 220 picks up the recording media PP loaded on the paper feeding stack 221 one by one using the air separation unit 222 and sends them to the resist adjustment unit 230. The resist adjustment unit 230 corrects the tilt of the recording media PP sent from the paper feeding unit 220 using the resist roller pair 231. Then, the resist adjustment unit 230 sends the recording media PP, after the tilt correction has been performed, to the image forming unit 210.

[0011] The image forming unit 210 includes a head module 20 that ejects ink onto the recording medium PP. The head module 20 includes head modules 20K, 20C, 20M, 20Y, 20S, and 20P. When head modules 20K, 20C, 20M, 20Y, 20S, and 20P are not distinguished, they are referred to as head module 20.

[0012] The plurality of head modules 20 are arranged along the outer peripheral surface 10a of the drum 10. The head modules 20 are spaced apart from the outer peripheral surface 10a in the radial direction of the drum 10. The recording medium PP is disposed on the outer peripheral surface 10a of the drum 10 and is conveyed in the circumferential direction of the drum 10 as the drum 10 rotates.

[0013] A recording medium gripper 11 for holding the recording medium PP is provided on the outer peripheral surface 10a of the drum 10. In the image forming unit 210, with the recording medium gripper 11 sandwiching the leading end of the recording medium PP, as the drum 10 rotates, the recording medium PP is conveyed to a position facing the head module 20. The recording medium PP is disposed between the outer peripheral surface 10a of the drum 10 and the head module 20. The drum 10 is an example of a conveying unit that conveys the recording medium along the conveying path.

[0014] Each of the head modules 20 forms an image on the surface of the recording medium PP by discharging ink onto the recording medium PP. The image forming unit 210 sends out the recording medium W1 after the image is formed to the drying unit 240.

[0015] The drying unit 240 includes a heater 241 for drying the recording medium PP. The recording medium PP is heated by the heater 241 while being conveyed. The drying unit 240 sends out the dried recording medium PP to the paper discharge unit 290. When performing double-sided printing, the drying unit 240 sends out the recording medium PP to the recording medium reversing unit 250.

[0016] The recording medium reversing unit 250 includes a recording medium reversing mechanism 251 for reversing the recording medium PP and a reversing conveyance unit 252 for conveying the reversed recording medium PP. The recording medium reversing unit 250 reverses the recording medium PP sent out from the drying unit 240 by the recording medium reversing mechanism 251 and sends it to the image forming unit 210 by the reversing conveyance unit 252. A registration roller 253 provided inside the image forming unit 210 corrects the inclination of the recording medium W1 sent out from the recording medium reversing unit 250 and conveys it to the drum 10.

[0017] The paper output unit 290 stacks multiple PP recording media sent from the drying unit 240 in an aligned state.

[0018] <Configuration of Head Module 20> Next, the head module 20 will be described with reference to Figure 2. As shown in Figure 2, the head module 20 comprises a drive control board 21, a cable 22, and an inkjet recording head 23. Hereinafter, "inkjet recording head" may be abbreviated as "recording head". The head module 20 comprises a plurality of recording heads 23. The plurality of recording heads 23 are arranged in the Y-axis direction to form a line head.

[0019] The drive control board 21 is equipped with a drive control unit 25, a drive waveform generation unit 26, and a storage unit 24. The drive control unit 25 controls the drive elements for ejecting ink. The drive waveform generation unit 26 generates pulse signals supplied to the drive elements. The storage unit 24 stores various information.

[0020] Cable 22 has connectors 27 and 28. Connector 27 is connected to the drive control board 21. Connector 28 is connected to the recording head 23. Cable 22 transmits analog and digital signals between the drive control board 21 and the recording head 23.

[0021] The recording head 23 includes a residual vibration detection module 29, a head substrate 30, an in-head ink tank 31, a head drive IC substrate 32, and a rigid plate 33. The recording head 23 includes an ink channel through which ink flows, a drive element for ejecting ink, a pressure chamber for applying pressure to the ink, and a nozzle plate on which nozzles for ejecting ink are formed. The drive element is, for example, a piezoelectric element. The ink in the in-head ink tank 31 flows through the ink channel and is supplied to the pressure chamber. The pressure of the ink in the pressure chamber increases when the drive element is driven, and the ink is ejected from the nozzle. The ink droplets ejected from the nozzle land on the recording medium.

[0022] The residual vibration detection module 29 detects residual vibrations of the ink in the ink flow path within the recording head 23. The head board 30 is electrically connected to the drive control board 21 and receives the drive waveform. The head drive IC board 32 is electrically connected to the head board 30. The head drive IC board 32 drives the drive elements according to the drive waveform.

[0023] The rigid plate 33 is positioned below the head drive IC board 32 to increase the rigidity of the recording head 23. The rigid plate 33 constitutes part of the housing of the recording head 23. The pressure chamber, drive element, and nozzle are arranged within the area enclosed by the rigid plate 33. The ink ejected from the nozzle flies along the Z-axis direction and adheres to the recording medium PP.

[0024] The image forming apparatus 200 in this embodiment is an on-demand line-scanning inkjet recording apparatus. Therefore, the multiple recording heads 23 of the head module 20 are arranged in a direction perpendicular to the transport direction of the recording medium PP. The image forming apparatus 200 is not limited to line-scanning inkjet recording apparatuses, but can also be applied to recording apparatuses using other methods. An example of a recording apparatus using other methods is a serial scanning printer, in which the recording head moves in the main scanning direction while forming an image on the surface of the recording medium.

[0025] <Recording medium buoyancy detection system> Next, the recording medium floating detection system 40 will be described with reference to Figures 3 to 6. Figure 3 is a schematic diagram showing the arrangement of the recording medium floating detection sensors. Figure 4 is a schematic diagram showing the recording medium floating detection sensors. The image forming apparatus 200 includes a recording medium floating detection system 40 that detects the floating of the recording medium PP from the transport path. As shown in Figure 3, the recording medium floating detection system 40 is located upstream of the head module 20 in the transport path of the recording medium PP. The recording medium floating detection system 40 is located in the radial direction of the drum 10, close to the outer circumferential surface 10a of the drum 10. Part of the transport path is formed along the outer circumferential surface 10a of the drum 10. The recording medium PP is transported in the circumferential direction of the drum 10 as the drum 10 rotates.

[0026] As shown in Figure 4, the recording medium floating detection system 40 includes a recording medium floating detection sensor 41. The recording medium floating detection sensor 41 has a light-emitting unit 42 that emits laser light 44 and a light-receiving unit 43 that receives the laser light 44. The light-emitting unit 42 includes a light-emitting element that emits laser light 44, and the light-receiving unit 43 includes a light-receiving element that receives the laser light 44. The light-emitting unit 42 emits laser light 44, for example, along the Y-axis. The laser light 44 passes above the outer circumferential surface 10a of the drum 10. The outer circumferential surface 10a forms a transport surface along the transport path of the recording medium PP. The laser light 44 has a predetermined width in the Z-axis direction. In Figure 4, the transport direction of the recording medium PP is shown linearly along the X-axis, but in reality, the transport direction of the recording medium PP is curved along the outer circumferential surface 10a of the drum 10.

[0027] The light-receiving unit 43 receives the laser light 44 emitted from the light-emitting unit 42. The light-receiving unit 43 outputs a voltage value based on the amount of received laser light 44. In the recording medium levitation detection system 40, the height position of the recording medium PP in the Z-axis direction can be detected from the voltage value based on the amount of received light. As the laser light 44 is shielded by the recording medium PP, the amount of laser light 44 received by the light-receiving unit 43 changes depending on the position of the recording medium PP in the Z-axis direction. When there is a large overlap between the laser light 44 and the recording medium PP in the Z-axis direction, the amount of light received by the light-receiving unit 43 is smaller compared to when there is a small overlap between the laser light 44 and the recording medium PP. The recording medium levitation detection sensor 41 is an example of a levitation detection unit that detects the levitation of the recording medium PP. "Levitation of the recording medium PP" refers to, for example, the levitation of the recording medium PP from the outer peripheral surface 10a of the drum 10. "Voltage value based on the amount of received light" is an example of the light reception result by the light-receiving unit.

[0028] Next, the distribution of laser light in the ideal case will be explained with reference to Figure 5. Figure 5 is a diagram showing the distribution of laser light in the ideal case. The ideal case is when the effect of temperature difference in the optical path of the laser light is small and the laser light 44 travels in a straight line along the Y axis. The laser light 44 has a predetermined width in the Z axis direction. In the Z axis direction, the direction away from the outer surface 10a of the drum 10 will be described as the up and down direction. The height is along the Z axis direction. In the radial direction of the drum 10, the side closer to the outer surface 10a is considered down, and the side away from the outer surface 10a is considered up.

[0029] In an ideal case, the laser beam 44 is not tilted with respect to the Y-axis direction. The recording medium floating detection system 40 can calculate the detection height h1 in the Z-axis direction of the recording medium PP based on the voltage value output from the light receiving unit 43. The detection height h1 may be a range of heights in which the laser beam 44 is not received by the light receiving unit 43. The light receiving unit 43 cannot receive the laser beam 44 in the range overlapping with the recording medium PP from the lower end of the light receiving element. This range in which reception is not possible becomes the detection height h1.

[0030] Next, with reference to Figure 6, the distribution of laser light when a temperature difference occurs in the optical path of the laser beam 44 will be explained. Figure 6 is a diagram showing the distribution of laser light when a temperature difference occurs in the optical path. As shown in Figure 6, a temperature difference may occur in the optical path of the laser beam 44. In Figure 6, a temperature difference occurs in the Z-axis direction, resulting in a temperature distribution. For example, the temperature T2 at position A2, which is close to the outer surface 10a of the drum 10, is higher than the temperature T1 at position A1, which is further away from the outer surface 10a (T2 > T1).

[0031] Thus, when a temperature difference occurs within the optical path of the laser beam 44, the laser beam 44 bends towards the lower temperature side. The laser beam 44 bends towards the lower temperature side so as to move away from the outer peripheral surface 10a on the higher temperature side. In Figure 6, the laser beam 44 bends and tilts in the Z-axis direction so as to move away from the outer peripheral surface 10a. In Figure 6, the tilted laser beam 44a is shown by a solid line, and the lower end 44b of the laser beam 44 passing over the recording medium PP when it travels ideally without tilting is shown by a dashed line. The detection height h1 when the laser beam 44 travels ideally corresponds to the height position of the lower end 44b of the laser beam 44 passing over the recording medium PP.

[0032] When the laser beam 44 is tilted, the detection height h2 will be higher than the detection height h1. In this case, the light receiving unit 43 will output a voltage value based on the detection height h2, which is higher than the actual detection height h1 of the recording medium PP. The laser beam 44 that has passed over the recording medium PP curves upward, for example, so that the light receiving unit 43 outputs a voltage value corresponding to the detection height h2, which is higher than the detection height h1. Therefore, in the cases shown in Figures 5 and 6, the height of the recording medium PP is the same, but in the case of Figure 6, the detection height h2 is higher, so the recording medium PP may be perceived as being at a higher position than the predetermined transport path. The recording medium floating detection sensor 41 may falsely detect that the recording medium PP is floating.

[0033] Note that "temperature in the optical path" refers to the temperature in the optical path through which light passes, and may also refer to the temperature of the space in which the optical path is formed. For example, the temperature in the optical path may be detected by detecting the temperature of the space in which the optical path is formed, or by detecting the temperature of the space adjacent to the optical path, or by detecting the temperature of the recording medium that has passed through the space in which the optical path is formed, or by detecting the temperature of the outer surface 10a of the drum 10 adjacent to the optical path. In addition, the temperature in the optical path may be detected by detecting other factors that affect the temperature in the optical path.

[0034] <Variable mechanism> Next, with reference to Figure 7, the variable mechanism 60 for tilting the laser beam emission direction will be described. Figure 7 is a schematic diagram showing the tilt mechanism for tilting the laser beam emission direction. The recording medium floating detection system 40 is equipped with a variable mechanism 60 for tilting the laser beam emission direction 44.

[0035] The variable mechanism 60 includes a support base 61 that supports the light-emitting unit 42, a worm gear 62 that changes the orientation of the support base 61, a rotating shaft 63, and a motor 64. The light-emitting unit 42 is mounted on the support base 61 and fixed to the support base 61.

[0036] The worm gear 62 has a worm 62a mounted on a rotating shaft 63 and a worm wheel 62b that meshes with the worm 62a. The worm wheel 62b is fixed to the bottom surface of, for example, a support base 61. The rotating shaft 63 extends in the Y-axis direction. A motor 64 rotates the rotating shaft 63. The motor 64 may be, for example, a stepping motor. By rotating the rotating shaft 63, the worm wheel 62b that meshes with the worm 62a rotates around an axis along the X-axis direction. As a result, the support base 61 and the light-emitting unit 42 rotate together with the worm wheel 62b. In this way, the direction of emission of the laser beam 44 can be adjusted by changing the orientation of the light-emitting unit 42. The variable mechanism 60 can tilt the direction of emission of the laser beam 44 with respect to the Y-axis direction.

[0037] <Relationship between temperature difference and gradient> Next, with reference to Figures 8 and 9, the relationship between the temperature difference in the optical path of the laser beam 44 and the tilt amount θ of the laser beam 44 will be explained. Figure 8 is a diagram showing the tilt amount of the laser beam. Figure 9 is a table showing the relationship between the temperature difference in the optical path of the laser beam and the tilt amount of the laser beam. As shown in Figure 8, the tilt amount θ of the laser beam 44 is the inclination angle of the laser beam 44 with respect to a reference line LA that extends along the Y-axis direction. For example, the tilt amount θ when tilted downward with respect to the reference line LA is considered positive. The tilt amount of the light-emitting unit 42 may also be used as the tilt amount θ of the laser beam 44. Downward with respect to the reference line LA means closer to the outer surface 10a of the drum 10.

[0038] The table in Figure 9 shows the relationship between the temperature difference ΔT and the slope θ. The temperature difference ΔT is, for example, the difference between the high-temperature side temperature T2 and the low-temperature side temperature T1, as shown in Figure 6 (ΔT = T2 - T1).

[0039] The recording medium levitation detection system 40 sets the slope amount θ to 0° (deg) when the temperature difference ΔT is 0 degrees. The recording medium levitation detection system 40 can set the slope amount θ to +1° when the temperature difference ΔT is less than 2°C. The recording medium levitation detection system 40 can set the slope amount θ to +2° when the temperature difference ΔT is 2° or more and less than 8°C. The recording medium levitation detection system 40 can set the slope amount θ to +3° when the temperature difference ΔT is 8° or more and less than 14°C. The recording medium levitation detection system 40 can set the slope amount θ to +4° when the temperature difference ΔT is 14°C or more and less than 20°C. The recording medium levitation detection system 40 can set the slope amount θ to +5° when the temperature difference ΔT is 20°C or more. Note that these values ​​are arbitrary and can be changed as appropriate. For example, the table shown in Figure 9 classifies the slope amount into 5 stages, but it may be classified into 4 stages or less, or into 6 stages or more. When the temperature difference ΔT is large, the amount of tilt θ required to correct the tilt of the laser beam 44's emission direction becomes larger compared to when the temperature difference ΔT is small.

[0040] <Relationship between the laser beam's arrival point and its height> Next, with reference to Figure 10, the relationship between the arrival position of the laser beam 44 and the height position of the laser beam 44 will be explained. Figure 10 is a graph showing the relationship between the arrival position of the laser beam and the height position of the laser beam. In Figure 10, the horizontal axis shows the arrival position of the laser beam 44 [mm], and the vertical axis shows the height position of the laser beam 44. The emission point of the laser beam 44 in the light-emitting unit 42 is the laser arrival position 0 mm, and the laser height is 10.000 mm. The arrival position of the laser beam 44 is the position in the Y-axis direction. The height position of the laser beam 44 is the position in the Z-axis direction. The height position of the laser beam 44 may be, for example, the height position from the outer surface 10a of the drum 10. Figure 10 shows the position of the laser beam 44 at its lowest height. The lowest height is the position closest to the outer surface 10a of the drum 10.

[0041] Graph L1 shows the height of the laser beam 44 when the light-emitting unit 42 is tilted and there is no temperature difference. Graph L2 shows the height of the laser beam 44 when the light-emitting unit 42 is tilted and there is a temperature difference. The case where the light-emitting unit 42 is tilted means that the direction of emission of the laser beam 44 is tilted with respect to the Y-axis direction by tilting the light-emitting unit 42. The tilt of the light-emitting unit 42 is the same in the cases of graphs L1 and L2.

[0042] Graph L3 shows the height of the laser beam 44 when there is no slope in the light-emitting unit 42 and no temperature difference. The case shown in Graph L3 is the ideal case. Graph L4 shows the height of the laser beam 44 when there is no slope in the light-emitting unit 42 and there is a temperature difference. When there is no slope in the light-emitting unit 42, it means that the laser beam 44 is emitted along the Y-axis.

[0043] Graphs L1 and L3 show cases where there is no temperature difference, and the laser beam 44 travels straight in the direction of emission. Graphs L2 and L4 show cases where there is a temperature difference, and the laser beam 44 bends upward. In the case shown in graph L2, the light-emitting unit 42 is tilted downward, thereby tilting the emission direction of the laser beam 44, which suppresses the positional displacement of the laser beam 44. In the case shown in graph L4, the light-emitting unit 42 is not tilted, so the laser beam 44 emitted along the Y-axis bends upward. In the case shown in graph L4, the positional displacement is larger compared to the case shown in graph L2.

[0044] Figure 10 shows the regions R1 and R2 where the lifting of the recording medium cannot be detected. Hereafter, the "region where the lifting of the recording medium cannot be detected" will be referred to as the "undetectable region." Undetectable region R1 is the case for graph L2, and undetectable region R2 is the case for graph L1. Undetectable region R1 is less than half the size of undetectable region R2.

[0045] For example, in the case of graphs L2 and L4, if the recording medium PP is located above this line, the laser beam 44 is blocked, allowing the recording medium levitation detection system 40 to recognize the location of the recording medium PP. The above-mentioned "regions R1 and R2 where recording medium levitation cannot be detected" may also be "regions where recording medium PP is falsely detected as being levitated" even though it is not. Furthermore, if the laser beam 44 bends and creates regions where the laser beam 44 is absent, these regions where the laser beam 44 is absent are regions where the recording medium PP cannot be detected.

[0046] <Hardware configuration of image forming apparatus> Next, the hardware configuration of the image forming apparatus 200 will be described with reference to Figure 11. Figure 11 is a block diagram showing the hardware configuration of an image forming apparatus according to one embodiment. The hardware configuration shown in Figure 11 may include additional components as needed. The hardware may not include the components shown in Figure 11 as needed.

[0047] The image forming apparatus 200 is equipped with a control device 500. The control device 500 has a CPU (Center Processing Unit) 501, a ROM (Read Only Memory) 502, a RAM (Random Access Memory) 503, an NVRAM (Random Access Memory) 504, and an HDD (Hard Disk Drive) 508. The CPU 501 is responsible for the overall control of the image forming apparatus 200. The ROM 502 stores various programs for the CPU 501 to execute liquid ejection control, as well as various data necessary for painting.

[0048] RAM 503 temporarily stores various data. NVRAM 504 is a non-volatile memory that can retain data even when the power supply to the image forming apparatus 200 is cut off. The control device 500 has a main control unit 500A, which includes a CPU 501, ROM 502, and RAM 503.

[0049] The control device 500 includes an ASIC (Application Specific Integrated Circuit) 505. The ASIC 505 processes input and output signals for controlling the overall operation of the image forming apparatus 200. The ASIC 505 can also perform various signal processing operations on image data. The ASIC 505 can perform image processing on image data input to the control device 500.

[0050] The control device 500 is equipped with an external interface (external I / F) 506 that enables the transmission and reception of data, etc., with an external device, such as a PC.

[0051] Furthermore, the control device 500 includes an input / output (I / O) unit 507 for receiving detection signals output from the sensors 18. The sensors 18 may include various temperature sensors.

[0052] The control device 500 includes a head control device 510 that controls the drive of the head module 20. The head control device 510 can control the drive device of the head module 20. The head control device 510 can control the drive elements of the head module 20 to perform liquid discharge. The head control device 510 can perform various controls related to the head module 20.

[0053] The control device 500 includes a detection system control device 511. The detection system control device 511 controls the operation of the recording medium floating detection sensor 41 and the variable mechanism 60 according to commands from the CPU 501.

[0054] <Recording medium buoyancy detection system> Next, the hardware configuration of the recording medium levitation detection system 40 will be described with reference to Figure 12. Figure 12 is a block diagram showing the hardware configuration of the recording medium levitation detection system. The hardware configuration of the recording medium levitation detection system 40 shown in Figure 12 is part of the hardware configuration of the image forming apparatus 200 shown in Figure 11. The hardware configuration shown in Figure 12 may include additional components as needed. The hardware may not have to include the components shown in Figure 12 as needed.

[0055] The recording medium floating detection system 40 includes a recording medium floating detection sensor 41 and a variable mechanism 60. The control device of the recording medium floating detection system 40 comprises a detection system control device 511 and a temperature detection unit 80. The detection system control device 511 is electrically connected to a CPU 501 and a storage unit 509. The storage unit 509 may include a ROM 502, RAM 503, NVRAM 504, and HDD 508. The detection system control device 511 is an example of a control unit that controls the operation of the variable mechanism 60. The control device of the recording medium floating detection system is

[0056] The recording medium buoyancy detection sensor 41 comprises a light-emitting unit 42, a light-receiving unit 43, a communication unit 46, and an amplifier unit 47. The recording medium buoyancy detection sensor 41 uses the communication unit 46 as an interface to receive information regarding the detection threshold from the detection system control device 511. The detection threshold is a threshold for determining whether the recording medium PP is buoyant.

[0057] The amplifier unit 47 recognizes the detection height h1 based on the information output from the light receiving unit 43. The amplifier unit 47 determines whether the recording medium PP is lifting based on the detection threshold and the detection height h1. The amplifier unit 47 determines that the recording medium PP is lifting if the detection height h1 is higher than the detection threshold. The recording medium lifting detection sensor 41 outputs the determination result regarding the lifting of the recording medium PP to the detection system control device 511.

[0058] The detection system control device 511 recognizes the temperature in the optical path of the laser beam 44 based on the information output from the temperature detection unit 80. Based on the temperature in the optical path of the laser beam 44, the detection system control device 511 determines the tilt amount of the light-emitting unit 42. The detection system control device 511 transmits data regarding the tilt amount to the motor 64 of the variable mechanism 60 and drives the motor 64 to change the tilt of the light-emitting unit 42. This allows the direction of emission of the laser beam 44 by the light-emitting unit 42 to be changed. The detection system control device 511 may also recognize the temperature distribution in the optical path of the laser beam 44 based on the information output from the temperature detection unit 80. The detection system control device 511 may also determine the tilt amount of the light-emitting unit 42 based on the temperature distribution in the optical path of the laser beam 44.

[0059] <Temperature detection unit> The temperature detection unit 80 includes a temperature detection sensor (temperature sensor) 81 capable of detecting the ambient temperature inside the device, and can detect the ambient temperature using this temperature detection sensor 81. Based on the detected ambient temperature, the temperature detection unit 80 may also detect the temperature distribution in the optical path of the laser beam 44. The temperature detection sensor may be, for example, a thermocouple. The temperature detection sensor 81 is located near the recording medium floating detection sensor 41.

[0060] <Functional Configuration> Next, the functional configuration of the image forming apparatus 200 will be described with reference to Figure 13. Figure 13 is a functional block diagram of the image forming apparatus 200. The CPU 501 shown in Figure 11 executes programs stored in a storage unit such as the ROM 502 to realize the functions of the system control unit 121, memory control unit 122, communication control unit 123, ejection control unit 124, transport control unit 125, temperature recognition unit 131, tilt amount determination unit 132, tilt amount control unit 133, detection system control unit 134, and lift-up determination unit 135 shown in Figure 13. External devices and sensors connected to the control device 500 may perform some of these functions.

[0061] The system control unit 121 controls the overall operation of the image forming apparatus 200. The memory control unit 122 controls the operation of memory such as ROM 502, RAM 503, NVRAM 504, and HDD 508. The communication control unit 123 controls communication with external devices connected to the control device 500.

[0062] The discharge control unit 124 controls the discharge of liquid by the head module 20. The transport control unit 125 controls the transport of the recording medium PP by the transport unit. The transport unit includes rollers for transporting the recording medium PP and a motor for driving the rollers.

[0063] The temperature recognition unit 131 recognizes the temperature within the optical path of the laser beam 44 based on the information output from the temperature detection unit 80. The temperature recognition unit 131 can determine whether or not there is a temperature difference within the optical path.

[0064] The tilt amount determination unit 132 can determine the tilt amount of the light-emitting unit 42 according to the temperature in the optical path of the laser beam 44. The tilt amount determination unit 132 may also determine the tilt amount θ according to the temperature difference ΔT by referring to the table shown in Figure 9.

[0065] The tilt control unit 133 controls the variable mechanism 60 to tilt the light-emitting unit 42 so that the tilt amount θ corresponds to the temperature in the optical path. This allows the tilt control unit 133 to change the direction of emission of the laser light 44. The tilt control unit 133 may also control the variable mechanism 60 to tilt the light-emitting unit 42 so that the tilt amount θ corresponds to the temperature difference ΔT in the optical path.

[0066] The detection system control unit 134 controls the operation of the recording medium floating detection sensor 41. The detection system control unit 134 emits laser light 44 from the light emitting unit 42. The detection system control unit 134 can acquire information regarding the detected height h1 output from the light receiving unit 43.

[0067] The lifting determination unit 135 determines whether or not the recording medium PP is lifting based on the information regarding the detected height h1 obtained from the recording medium lifting detection sensor 41. The lifting determination unit 135 can determine that the recording medium PP is lifting if it is lifted away from the outer peripheral surface 10a of the drum 10.

[0068] The transport control unit 125 can change the transport path of the recording medium PP so that the recording medium PP is not supplied to the head module 20 if it is lifting up. The transport control unit 125 can change the transport path of the recording medium PP by driving a guide for changing the transport path of the recording medium PP.

[0069] Furthermore, the system control unit 121, memory control unit 122, communication control unit 123, discharge control unit 124, transport control unit 125, temperature recognition unit 131, tilt amount determination unit 132, tilt amount control unit 133, detection system control unit 134, and floating determination unit 135 can be implemented in software by programs stored in the memory unit. However, all or part of these system control unit 121, memory control unit 122, communication control unit 123, discharge control unit 124, transport control unit 125, temperature recognition unit 131, tilt amount determination unit 132, tilt amount control unit 133, detection system control unit 134, and floating determination unit 135 may be implemented in hardware such as an IC (Integrated Circuit).

[0070] Furthermore, the program may be recorded as installable or executable file information on a recording medium readable by a computer device, such as a CD-ROM or flexible disk (FD), and provided to the image forming apparatus 200 via such a recording medium. Alternatively, the program may be recorded on a recording medium readable by a computer device, such as a CD-R, DVD (Digital Versatile Disk), Blu-ray® disc, or semiconductor memory, and provided to the image forming apparatus 200 via such a recording medium. The program may also be provided to the image forming apparatus 200 by installation via a network such as the Internet. Furthermore, the program may be pre-installed in ROM or the like within the image forming apparatus 200.

[0071] Furthermore, the control device 500 may perform functions that are executed by a computer connected to the control device 500. Similarly, a computer connected to the control device 500 may perform functions that are executed by the control device 500.

[0072] <Change the amount of inclination> Next, we will describe the modification of the tilt amount θ of the laser beam 44 performed in the recording medium floating detection system 40. Figure 14 is a flowchart showing the processing procedure in the recording medium floating detection system.

[0073] The temperature recognition unit 131 of the control device 500 recognizes the temperature in the optical path of the laser beam 44 (step S11). The temperature recognition unit 131 obtains information regarding the temperature in the optical path from the temperature detection unit 80. The temperature recognition unit 131 obtains information regarding the temperatures T1 and T2 in the optical path, as shown in Figure 6.

[0074] Next, the temperature recognition unit 131 determines whether or not there is a temperature difference ΔT between temperature T1 and temperature T2 (step S12). The temperature recognition unit 131 determines that there is a temperature difference ΔT if the temperature difference ΔT is equal to or greater than a determination threshold (first determination threshold). If there is a temperature difference ΔT (step S12; YES), the process proceeds to step S13; if there is no temperature difference ΔT (step S12; NO), the process proceeds to step S14. The temperature recognition unit 131 may also recognize that a temperature distribution has occurred in the optical path if there is a temperature difference ΔT. The temperature recognition unit 131 may also determine whether or not the temperature in the optical path is equal to or greater than a predetermined determination threshold. The temperature recognition unit 131 may also determine that the temperature difference ΔT is equal to or greater than the determination threshold if the temperature in the optical path is equal to or greater than the predetermined determination threshold.

[0075] In step S13, the temperature recognition unit 131 determines whether the temperature difference ΔT is small or not. The temperature recognition unit 131 can determine that the temperature difference ΔT is small if the temperature difference ΔT is less than the determination threshold (second determination threshold). If the temperature difference ΔT is small (step S13; YES), the process proceeds to step S15; if the temperature difference ΔT is large (step S13; NO), the process proceeds to step S16. The temperature recognition unit 131 may also determine whether the temperature in the optical path is less than a predetermined determination threshold. The temperature recognition unit 131 may also determine that the temperature difference ΔT is less than the determination threshold if the temperature in the optical path is less than the predetermined determination threshold.

[0076] In step S14, the tilt control unit 133 of the control device 500 does not change the tilt amount θ of the laser beam 44. Alternatively, if the tilt amount θ of the laser beam 44 has already been changed, the tilt control unit 133 controls the variable mechanism 60 so that the laser beam 44 is emitted along the Y-axis, thereby returning the tilt amount θ to zero.

[0077] In step S15, the tilt control unit 133 controls the variable mechanism 60 to change the tilt amount θ to a smaller value. In step S16, the tilt control unit 133 controls the variable mechanism 60 to change the tilt amount θ to a larger value. The magnitude of the tilt amount θ can be determined by referring to the table shown in Figure 9. The larger the temperature difference ΔT, the larger the tilt amount θ will be, and the smaller the temperature difference ΔT, the smaller the tilt amount θ will be.

[0078] After steps S14 to S16 are completed, the control device 500 proceeds to step S17 to determine whether the print job is finished or not. If the print job is finished (step S17; YES), the process here is terminated. If the print job is not finished (step S17; NO), the process returns to step S11 and steps S11 to S17 are repeated.

[0079] In steps S14 to S16, the example shows a case where the inclination is classified into three stages, such as "no change in inclination," "small inclination," and "large inclination," but it may also be classified into two stages or four or more stages. Furthermore, the control device 500 may perform the processes in steps S11 to S17 periodically, for example, by performing the processes every minute to adjust the inclination amount θ.

[0080] <Effects and Effects of Image Forming Apparatus> In this image forming apparatus 200, a laser beam 44 is emitted from a light-emitting unit 42, and the laser beam 44 that has passed above the transport path is received by a light-receiving unit 43, thereby detecting the lifting of the recording medium PP. The image forming apparatus 200 can detect the temperature in the optical path of the laser beam 44 using a temperature detection unit 80. The image forming apparatus 200 can tilt the emission direction of the laser beam 44 emitted from the light-emitting unit 42 using a variable mechanism 60. The image forming apparatus 200 can control the variable mechanism 60 based on the temperature in the optical path detected by the temperature detection unit 80. The control device 500 of the image forming apparatus 200 can drive the variable mechanism 60 to change the tilt of the light-emitting unit 42 when the temperature in the optical path is above a predetermined threshold. This allows the image forming apparatus 200 to change the amount of tilt θ in the emission direction of the laser beam emitted from the light-emitting unit 42.

[0081] With this image forming apparatus 200, even if the temperature in the optical path is above a predetermined judgment threshold and the laser beam 44 is bent, the direction of emission of the laser beam can be adjusted by tilting the light-emitting unit 42 using the variable mechanism 60. This reduces the measurement error of the detection height h1. The "predetermined judgment threshold" here is a judgment threshold that can detect that a temperature difference occurs in the optical path and that this temperature difference causes the laser beam to bend.

[0082] The image forming apparatus 200 is equipped with a temperature detection sensor 81 that detects the internal temperature of the image forming apparatus 200, thereby enabling the detection of the temperature of the space within the optical path of the laser beam 44. This allows the detection system control device 511 to recognize whether or not a temperature difference has occurred within the optical path. As shown in Figure 6, the detection system control device 511 can recognize whether or not a temperature distribution has occurred based on the temperature difference between temperature T1 and temperature T2.

[0083] In the image forming apparatus 200, if a lifting of the recording medium PP is detected, the recording medium PP can be prevented from being supplied to the head module 20. This prevents the recording medium PP that has lifted above a predetermined height from hitting the head module 20. As a result, damage to the head module 20 (head attack) can be prevented.

[0084] For example, the image forming apparatus 200 may be a commercial inkjet printer. In such commercial printers, the distance between the head module 20 and the recording medium PP is sometimes set to about 1 mm in order to achieve high image quality. In such commercial printers, even if the recording medium PP lifts slightly, it may come into contact with the recording medium PP and the head module 20, potentially damaging the head module 20.

[0085] In the image forming apparatus 200, the lifting of the recording medium PP can be detected with high accuracy, and the occurrence of head attacks is suppressed, allowing the head module to be positioned closer to the transport path of the recording medium PP. Therefore, high image quality can be achieved in the image forming apparatus 200.

[0086] <Example 1> Next, an image forming apparatus 200 according to Modification 1 will be described. The image forming apparatus 200 may be configured to include a temperature detection unit 80B according to Modification 1 instead of the temperature detection unit 80 described above. Figure 15 is a block diagram showing the hardware configuration of the recording medium floating detection system according to Modification 1. In the description of the image forming apparatus 200 according to Modification 1, the same descriptions as those for the image forming apparatus 200 according to the above embodiment will be omitted.

[0087] As shown in Figure 15, the temperature detection unit 80B according to Modified Example 1 includes a temperature sensor 82 capable of detecting the temperature of the recording medium PP after printing, and the temperature of the recording medium PP can be detected using this temperature sensor 82. An infrared thermometer can be used as a thermometer capable of detecting the temperature of the recording medium PP. The temperature detection unit 80 can detect the temperature in the optical path of the laser beam 44 based on the temperature of the recording medium PP after printing.

[0088] The temperature recognition unit 131 of the image forming apparatus 200 according to Modification 1 can detect the temperature in the optical path of the laser beam 44 based on the temperature of the recording medium PP after printing, which is output from the temperature sensor 82. The temperature recognition unit 131 can determine whether or not there is a temperature difference in the optical path. For example, the storage unit 509 stores in advance data showing the relationship between the temperature of the recording medium PP after printing and the temperature difference ΔT in the optical path. The data showing the relationship with the temperature difference Δ in the optical path may also be data related to the occurrence of temperature distribution.

[0089] Figure 16 is a flowchart showing the processing procedure in a recording medium levitation detection system according to Modification 1. The image forming apparatus 200 detects the temperature of the recording medium PP after printing (step S21). The temperature recognition unit 131 detects the temperature in the optical path of the laser beam 44 based on the temperature of the recording medium PP after printing.

[0090] Next, the temperature recognition unit 131 determines whether the temperature of the recording medium PP after printing is equal to or greater than the determination threshold Tb1 (step S22). If the temperature of the recording medium PP is equal to or greater than the determination threshold Tb1 (step S22; YES), the unit proceeds to step S23. If the temperature of the recording medium PP is less than the determination threshold Tb1 (step S22; NO), the unit proceeds to step S14. The temperature recognition unit 131 can recognize that a temperature difference ΔT has occurred in the optical path when the temperature of the recording medium PP after printing is equal to or greater than the determination threshold Tb1.

[0091] In step S23, the temperature recognition unit 131 determines whether the temperature difference ΔT is small or not. The temperature recognition unit 131 can determine that the temperature difference ΔT is small if it is less than the determination threshold (second determination threshold). If the temperature difference ΔT is small (step S13; YES), the process proceeds to step S15; if the temperature difference ΔT is large (step S13; NO), the process proceeds to step S16. As a result, the image forming apparatus 200 can recognize the occurrence of a temperature difference Δ in the optical path according to the temperature of the recording medium PP and change the tilt amount θ.

[0092] The image forming apparatus 200 according to this modified example 1 also provides the same effects and advantages as the image forming apparatus 200 according to the above embodiment. The image forming apparatus 200 according to modified example 1 is transported by a transport unit and includes a temperature sensor 82 that detects the temperature of the recording medium PP after printing, and can detect the temperature in the optical path based on the detected temperature of the recording medium PP.

[0093] <Modification 2> Next, an image forming apparatus 200 according to Modification 2 will be described. The image forming apparatus 200 may be configured to include a temperature detection unit 80 according to Modification 2 instead of the temperature detection unit 80 described above. In the description of the image forming apparatus 200 according to Modification 2, the same descriptions as those for the image forming apparatus 200 according to the above embodiment will be omitted. The image forming apparatus 200 according to Modification 2 may be equipped with a print count detection unit for detecting the number of printed sheets.

[0094] The temperature detection unit 80 of the image forming apparatus 200 according to Modification 2 may output information regarding the temperature in the optical path based on print job information such as the number of printed sheets. The temperature detection unit 80 may output information regarding the temperature in the optical path based on, for example, the number of printed sheets per unit time. The temperature detection unit 80 may output information regarding the temperature difference ΔT in the optical path based on the number of printed sheets per unit time.

[0095] The storage unit 509 of the image forming apparatus 200 stores data showing the relationship between the number of prints per unit time and the temperature inside the housing of the image forming apparatus 200. The temperature recognition unit 131 can determine whether or not a temperature difference ΔT occurs in the optical path based on the number of prints per unit time and output the determination result.

[0096] The image forming apparatus 200 according to this modified example 2 also provides the same effects and advantages as the image forming apparatus 200 according to the above embodiment. The image forming apparatus 200 according to modified example 2 is equipped with a print count detection unit that detects the number of prints on the recording medium PP, and can detect the temperature in the optical path based on the number of prints on the recording medium PP. The image forming apparatus 200 can change the direction of light emission from the light emitting unit 42 by controlling the operation of the variable mechanism 60 based on the temperature in the optical path.

[0097] Furthermore, the present invention is not limited to the embodiments described above, and various modifications are possible without departing from or altering the technical concept of the present invention.

[0098] In the above embodiment, the case where the light-emitting unit 42 and the light-receiving unit 43 are arranged facing each other in the Y-axis direction across the transport path of the recording medium PP is described, but the light-emitting unit 42 and the light-receiving unit 43 are not limited to this. For example, the light-emitting unit 42 and the light-receiving unit 43 may be arranged as a single module at the same position in the Y-axis direction. The recording medium floating detection sensor with this configuration may also include a mirror arranged facing the module having the light-emitting unit 42 and the light-receiving unit 43 across the transport path. Light emitted from the light-emitting unit 42 passes over the transport path and is reflected by the mirror. The light-receiving unit 43 receives the laser light that has been reflected by the mirror and has passed over the transport path again. Due to characteristics such as light diffraction, by mounting the light-emitting unit and the light-receiving unit so that light is emitted and received at a small angle, it may be possible to suppress variations in the detection of the recording medium PP.

[0099] The above embodiment describes a case in which a variable mechanism 60 having a worm gear 62 and a motor 64 is provided, but the tilting mechanism is not limited to this. The tilting mechanism may also be configured to include other guide mechanisms and actuators. The tilting mechanism may also be configured to include, for example, a hinge mechanism, a ball screw, an air cylinder, etc. Furthermore, the direction of light emission may be changed using mirrors or the like.

[0100] Furthermore, in the above embodiment, the temperature detection unit 80 detects the temperature in the optical path, but the temperature detection unit 80 may also detect the temperature distribution in the optical path in the Z-axis direction. The temperature detection unit 80 may, for example, detect the temperature distribution in the optical path in the Y-axis direction, or it may detect the temperature distribution in a direction tilted with respect to the Z-axis and Y-axis directions. The temperature detection unit 80 may detect a position where a temperature difference occurs in the Y-axis direction and change the tilt amount θ of the laser beam 44 according to the detected position.

[0101] Of the functions of the embodiments described above, the portion executed by the control unit can be realized by one or more processing circuits. Here, "processing circuit" as used herein includes processors programmed to execute each function by software, such as processors implemented by electronic circuits, as well as devices such as ASICs (Application Specific Integrated Circuits), DSPs (digital signal processors), FPGAs (field programmable gate arrays), and conventional circuit modules designed to execute each of the functions described above. [Explanation of symbols]

[0102] 10 Drum (Conveyor Unit) 10a Outer surface 20 Head Modules 40 Recording medium floating detection system 41 Recording medium floating detection sensor (floating detection unit) 42. Light-emitting section 43 Light receiving part 44 Laser light 60 Variable Mechanism 80 Temperature detection unit 81 Temperature detection sensor 82 Temperature Sensor 131 Temperature recognition section 200 Image forming apparatus 500 Control Device 511 Detection system control device (control unit for media floating detection system) PP recording medium [Prior art documents] [Patent Documents]

[0103] [Patent Document 1] Specification of Patent No. 6076848 [Patent Document 2] Specification of Patent No. 5444079

Claims

1. A transport unit that transports the recording medium along the transport path, A floating detection unit having a light-emitting unit and a light-receiving unit, which detects the floating of the recording medium based on the light-receiving result of the light emitted from the light-emitting unit and passing over the transport path by the light-receiving unit, A temperature detection unit for detecting the temperature within the optical path of the light, A variable mechanism for changing the direction of light emission from the light-emitting unit, An image forming apparatus comprising: a control unit that controls the operation of the variable mechanism based on the temperature detected by the temperature detection unit; and other components.

2. The device further includes a temperature sensor that detects the ambient temperature inside the device. The image forming apparatus according to claim 1, characterized in that the temperature detection unit detects the temperature in the optical path based on the ambient temperature inside the apparatus.

3. The system further includes a temperature sensor that detects the temperature of the recording medium transported by the transport unit, The image forming apparatus according to claim 1, characterized in that it detects the temperature in the optical path based on the temperature of the recording medium.

4. The system further includes a print count detection unit that detects the number of printed pages on the aforementioned recording medium, The image forming apparatus according to claim 1, characterized in that it detects the temperature in the optical path based on the number of printed sheets of the recording medium.

5. The transport unit has a drum that rotates while holding the recording medium on its outer surface, The image forming apparatus according to any one of claims 1 to 4, characterized in that the lift detection unit detects lifting of the recording medium from the outer peripheral surface.

6. A control device for a media levitation detection system that detects the levitation of a recording medium based on the light reception result by a light receiving unit of light emitted from a light emitting unit and passing over the transport path of the recording medium, A temperature detection unit for detecting the temperature within the optical path of the light, A control device for a media floating detection system, comprising: a control unit that controls the operation of a variable mechanism that changes the direction of light emission from the light emission unit based on the temperature detected by the temperature detection unit.

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