Media condition detection device and image forming apparatus

Abstract

To correctly detect the state of a medium by excellently preventing the occurrence of fluctuations of laser light.SOLUTION: A medium state detection device 2 for detecting the state of a sheet-like medium conveyed along a prescribed conveyance path comprises: a medium holding part 21 which conveys a medium along a conveyance path in a state of holding the medium; a light projection part 5 which is arranged on one end side in the width direction of the conveyance path and irradiates a position at a prescribed height from a surface of the medium holding part 21 with laser light 7; a light reception part 6 which is arranged so as to face the light projection part 5 on the other end side in the width direction of the conveyance path and receives the laser light 7; a detection part which detects the state of the medium according to the light reception state of the laser light 7 by the light reception part 6; and a temperature adjustment mechanism 24 which raises the temperature of a space through which the laser light 7 passes to a prescribed temperature and holds the temperature.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a media condition detection device that detects the condition of sheet-like media such as printing paper, and an image forming apparatus equipped with the same. [Background technology]

[0002] Conventionally, among image forming devices that form images on sheet-like media such as printing paper using an inkjet recording method, there is one known device that holds the media on the surface of a cylindrical media holder and transports the media by rotating the media holder (see, for example, Patent Document 1). In this type of image forming device, in order to reduce misalignment when ink lands and form high-quality images, it is preferable to reduce the gap between the inkjet head and the media. For example, this gap may be set to about 1 mm.

[0003] However, media expands and contracts depending on the ambient temperature, the printing condition on the front side when printing on the back side, the condition of the transport path, and other factors. As a result, the media may lift up from the media holder and collide with the inkjet head. If the media collides with the inkjet head, the inkjet head may be damaged. To prevent such damage, it is necessary to detect whether the media has lifted up from the media holder before it enters the inkjet head.

[0004] The conventional image forming device disclosed in Patent Document 1 is configured to irradiate the surface of the media holding section with a parallel laser beam and detect whether the media is floating based on whether the laser beam is blocked. This image forming device also has a recessed portion on the surface of the media holding section, which is designed to easily create an air layer with a temperature difference in the recessed portion. When an air layer with a temperature difference forms in the recessed portion, the laser beam fluctuates, potentially resulting in a false detection of the media condition. Therefore, the conventional image forming device prevents false detection due to the laser beam by driving a fan to blow air into the recessed portion when the temperature of the media holding section exceeds a predetermined threshold. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-207559 Summary of the Invention [Problem to be solved by the invention]

[0006] However, simply driving a fan to blow air into the recessed portion, as in the conventional image forming apparatus described above, is not sufficient to completely prevent false detection due to laser light, for the following reasons.

[0007] First, when forming an image on media, the image forming device heats the media holding unit to maintain the surface temperature of the media holding unit at a temperature higher than the ambient temperature. Therefore, even if a fan is used to blow low-temperature ambient air onto the surface of the media holding unit, layers of high-temperature air and low-temperature air still form near the surface of the media holding unit, making it impossible to prevent fluctuations in the laser light and resulting in false detection.

[0008] Second, the surface temperature of the media holding unit, once heated to a high temperature, can vary due to various external factors. For example, if both ends of the media holding unit are exposed to the outside air, they tend to be cooler than the center. Furthermore, when printing multiple media continuously, heat generated by the fuser unit, which is located close to the media holding unit, can cause temperature variations on the surface of the media holding unit. However, simply using a fan to blow cool ambient air onto the surface of the media holding unit cannot adequately eliminate temperature variations near the surface of the laser light. As a result, it is still not possible to prevent laser light fluctuations, resulting in false detection.

[0009] The present invention has been made to solve the above problems, and aims to provide a media condition detection device that effectively prevents laser light fluctuations and enables accurate detection of the media condition, and an image forming apparatus equipped with the same. [Means for solving the problem]

[0010] In order to achieve the above object, the invention of claim 1 is a media condition detection device that detects the condition of sheet-like media transported along a predetermined transport path, comprising: a media holding unit that holds the media and transports the media along the transport path; a light projecting unit that is located on one end of the transport path in the width direction and that irradiates laser light at a position at a predetermined height from the media holding surface of the media holding unit; a light receiving unit that receives the laser light; a detection unit that detects the condition of the media in accordance with the state of reception of the laser light by the light receiving unit; and a temperature adjustment mechanism that raises the temperature of a space through which the laser light passes to a predetermined temperature and maintains that temperature. The temperature adjustment mechanism includes an optical path heating unit that heats air in a space around the optical path of the laser light, an air blowing unit that blows the air heated by the optical path heating unit toward the optical path of the laser light, and an air direction plate downstream of the air blowing unit that directs the air blown out from the air blowing unit in a width direction of the transport path. This is a configuration characterized by the above. The invention of claim 2 is a media condition detection device that detects the condition of sheet-like media transported along a predetermined transport path, and is characterized in that it comprises: a media holding unit that holds the media and transports the media along the transport path; a light projecting unit that is arranged on one widthwise end of the transport path and irradiates laser light at a position at a predetermined height from the media holding surface of the media holding unit; a light receiving unit that receives the laser light; a detection unit that detects the condition of the media based on the reception state of the laser light by the light receiving unit; and a temperature adjustment mechanism that raises the temperature of the space through which the laser light passes to a predetermined temperature and maintains it at that temperature, wherein the temperature adjustment mechanism comprises an optical path heating unit that heats the air in the space around the optical path of the laser light, and an air blowing unit that blows air heated by the optical path heating unit toward the optical path of the laser light, and the optical path heating unit comprises an upstream heater that heats the space upstream of the air blowing unit, and a downstream heater that heats the space downstream of the air blowing unit. The invention of claim 3 is a media condition detection device that detects the condition of sheet-like media transported along a predetermined transport path, and includes: a media holding unit that holds the media and transports the media along the transport path; a light projecting unit that is arranged at one widthwise end of the transport path and irradiates laser light at a position at a predetermined height from the media holding surface of the media holding unit; a light receiving unit that receives the laser light; a detection unit that detects the condition of the media according to the reception state of the laser light by the light receiving unit; a temperature detection unit that detects the temperature of the media or the media holding unit; and a temperature adjustment mechanism that raises and maintains the temperature of the space through which the laser light passes at a predetermined temperature according to the temperature detected by the temperature detection unit, wherein the temperature detection unit detects the temperature at multiple locations in the widthwise direction of the transport path, and the temperature adjustment mechanism includes an optical path heating unit that heats the air in the space around the optical path of the laser light, and the optical path heating unit has multiple heaters arranged along the widthwise direction, and the heating temperatures of the multiple heaters are individually adjusted based on the temperatures at the multiple locations detected by the temperature detection unit. The invention of claim 4 is a media condition detection device that detects the condition of sheet-like media transported along a predetermined transport path, and includes: a media holding unit that holds the media and transports the media along the transport path; a light projecting unit that is arranged on one widthwise end of the transport path and irradiates laser light at a position at a predetermined height from the media holding surface of the media holding unit; a light receiving unit that receives the laser light; a detection unit that detects the condition of the media according to the reception state of the laser light by the light receiving unit; a temperature detection unit that detects the temperature of the media or the media holding unit; and a temperature adjustment mechanism that raises and maintains the temperature of the space through which the laser light passes to a predetermined temperature according to the temperature detected by the temperature detection unit, wherein the temperature adjustment mechanism includes an optical path heating unit that heats air in the space around the optical path of the laser light, and an air blowing unit that blows air heated by the optical path heating unit toward the optical path of the laser light, and the air blowing unit adjusts the air volume according to the temperature detected by the temperature detection unit.

[0011] Claim 5 The invention according to claim 1 or 2The media condition detection device further comprises a temperature detection unit that detects the temperature of the media or the media holding unit, and the temperature adjustment mechanism is configured to set the predetermined temperature according to the temperature detected by the temperature detection unit.

[0012] Claim 6 The invention according to claim 5 In the media condition detection device, the temperature adjustment mechanism is configured to set the temperature detected by the temperature detection unit to the predetermined temperature.

[0014] Claim 7 The invention according to claim 3 In the media condition detection device, the temperature adjustment mechanism further comprises an air blower that blows air heated by the optical path heating unit toward the optical path of the laser light.

[0015] Claim 8 The invention according to claim 1, 2, 4, or 7 In the media condition detection device, the air blowing unit blows air toward the media holding surface from a position higher than the height at which the laser light passes.

[0020] Claim 9 The invention according to claim 4 In the media condition detection device, the optical path heating unit adjusts the heating temperature in accordance with the temperature detected by the temperature detection unit.

[0021] Claim 10 The invention according to claim 4 or 9 In the media condition detection device, the temperature detection unit detects the temperature at multiple locations in a width direction perpendicular to the transport path, and the air blowing unit has multiple fans arranged along the width direction, and is configured to individually adjust the air volume of the multiple fans based on the temperatures at the multiple locations detected by the temperature detection unit.

[0022] Claim 11 The invention according to claim 1 to 10 The media condition detection device according to any one of the above items 1 to 4 further comprises a media holding and heating unit that heats the media holding unit.

[0023] Claim 12 The invention relates to an image forming apparatus, comprising claims 1 to 11 the light-emitting unit and the light-receiving unit, and an inkjet head that ejects ink onto the media; and a control unit that drives the inkjet head to perform a printing operation.

[0024] Claim 13 The invention according to claim 12 In the image forming apparatus, the control unit is configured to stop the printing operation when the detection unit of the media state detection device detects that the media is floating above the media holding unit.

[0025] Claim 14 The invention according to claim 12 or 13 In the image forming apparatus, the control unit sets the temperature of the media holding unit based on print settings.

[0026] Claim 15 The invention according to claim 12 ~ 14 In any one of the image forming apparatuses, the control unit sets the predetermined temperature in the temperature adjustment mechanism based on a print setting.

[0027] Claim 16 The invention according to claim 14 or 15 In the image forming apparatus, the print settings include a print ratio of the image to be printed.

[0028] The invention according to claim 17 is 14 ~ 16 In any one of the image forming apparatuses, the print settings include the type of media.

[0029] Claim 18 The invention according to claim 14 ~ 17 In any one of the image forming apparatuses, the print settings include a designation of either single-sided printing or double-sided printing.

[0030] Claim 19 The invention according to claim 14 ~ 18 In any one of the image forming apparatuses, the print settings include a print speed. [Effects of the Invention]

[0031] According to the present invention, it is possible to effectively prevent fluctuations in the laser light and accurately detect the state of the media. [Brief explanation of the drawings]

[0032] [Figure 1] 1 is a schematic diagram illustrating an example of the overall configuration of an image forming apparatus. [Figure 2] 10A and 10B are diagrams illustrating examples of how a light-emitting unit and a light-receiving unit are installed relative to a media holding unit. [Figure 3] 10A and 10B are diagrams illustrating how a temperature adjustment mechanism and a temperature detection unit are installed relative to a media holding unit. [Figure 4] FIG. 2 is a cross-sectional view showing the internal structure of a temperature adjustment mechanism. [Figure 5] FIG. 2 is a cross-sectional view showing the internal structure of a temperature adjustment mechanism. [Figure 6] FIG. 10 is an enlarged view of a wind direction plate provided below the blower unit. [Figure 7] FIG. 4 is a diagram showing an example of temperatures detected by each of a plurality of temperature detection sensors. [Figure 8]FIG. 2 is a block diagram showing an example of a control mechanism of the image forming apparatus. [Figure 9] 4 is a flowchart showing an operation procedure of the image forming apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0033] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. Elements common to the embodiments described below are designated by the same reference numerals, and redundant description thereof will be omitted.

[0034] (First embodiment) Fig. 1 is a schematic diagram showing an example of the overall configuration of an image forming apparatus 1 in this embodiment. This image forming apparatus 1 is an apparatus that transports sheet-like media such as printing paper along a predetermined transport path and forms an image on the media using an inkjet recording method as the media passes a predetermined position. Note that Fig. 1 illustrates an apparatus that is capable of forming a color image on the media using four colors of ink: yellow (Y), magenta (M), cyan (C), and black (K).

[0035] 1, image forming apparatus 1 has a media supply unit 10, an image forming unit 20, a media discharge unit 30, and a control unit 40. This image forming apparatus 1 is connected to an external terminal device (not shown) via a network, obtains print data to be printed from such terminal device, and forms an image on sheet-like media 9.

[0036] The media supply unit 10 has a media tray 11 and a supply mechanism 12. The media tray 11 is a plate-shaped member that can hold multiple media 9. The media tray 11 is movable vertically depending on the number of media 9 placed on it. Of the multiple media 9 placed on the media tray 11, the media 9 that is at the top in the vertical direction is removed one by one by the supply mechanism 12 and held in a position where it can be transported along the transport path.

[0037] The supply mechanism 12 has multiple (two in this example) rollers 12a and 12b and a conveyor belt 12c. The conveyor belt 12c is formed as an endless belt with both longitudinal ends connected. The conveyor belt 12c is stretched over the rollers 12a and 12b. When one of the rollers 12a and 12b is driven to rotate, the conveyor belt 12c moves in a circular motion between the two rollers 12a and 12b. As a result, a single sheet of media 9 placed on the conveyor belt 12c is conveyed downstream along the conveyance path.

[0038] The supply mechanism 12 also has a drive unit (not shown) that rotates the rollers 12a and 12b, and a pickup mechanism that picks up the topmost sheet of media 9 from among the multiple sheets of media 9 placed on the media tray 11 and passes it to the conveyor belt 12c. The supply mechanism 12 then conveys the media 9 placed on the conveyor belt 12c toward the image forming unit 20 and supplies it to the image forming unit 20.

[0039] The image forming section 20 has a media holding section 21, a transfer unit 22, a temperature detection section 23, a media state detection device 2, a printing unit 25, a fixing section 26, a discharge mechanism 27, and a media inversion section 28.

[0040] The media holding unit 21 is formed as a cylindrical drum. It rotates in the direction of arrow R by a drive motor (not shown). The media 9 supplied from the media supply unit 10 is held on the outer circumferential surface of the media holding unit 21. Specifically, the media 9 is held in a state where it is attached to the outer circumferential surface of the media holding unit 21. Therefore, the surface (outer circumferential surface) of the media holding unit 21 functions as a media holding surface that holds the media 9. The media holding unit 21 then rotates in the direction of arrow R, transporting the media 9 along an arc-shaped transport path formed by the outer circumferential surface of the media holding unit 21. Therefore, the transport direction of the media 9 held by the media holding unit 21 coincides with the rotation direction R of the media holding unit 21. In addition, the temperature detection unit 23, the media condition detection device 2, the printing unit 25, and the fixing unit 26 are arranged facing the outer circumferential surface of the media holding unit 21.

[0041] Furthermore, a heater 29 is provided inside the media holding unit 21. This heater 29 is a media holding and heating unit for heating the media holding unit 21. The image forming apparatus 1 forms an image on the media 9 by discharging ink that has been heated to a predetermined temperature (e.g., approximately 80°C) and melted. The way the ink that lands on the media 9 spreads varies depending on the temperature of the media 9. Therefore, in order to maintain a constant ink dot diameter, it is necessary to heat the media 9 to a predetermined temperature (e.g., approximately 43°C) before discharging the ink onto the media 9. If the temperature of the media 9 is lower than the predetermined temperature, the ink that has adhered to the media 9 hardens immediately, resulting in a small dot diameter. Conversely, if the temperature of the media 9 is higher than the predetermined temperature, the ink that has adhered to the media 9 spreads too much, resulting in a large dot diameter. Therefore, in order to maintain a constant ink dot diameter, the heater 29 generates heat inside the media holding unit 21 to heat the surface of the media holding unit 21, thereby heating the media 9 to a predetermined temperature (e.g., approximately 43°C).

[0042] The transfer unit 22 is located between the supply mechanism 12 of the media supply unit 10 and the media holding unit 21. The transfer unit 22 includes a claw 22a and a cylindrical transfer drum 22b. The claw 22a holds one end of the media 9 transported by the supply mechanism 12. The transfer drum 22b guides the media 9 held by the claw 22a toward the media holding unit 21. As a result, the media 9 is transferred from the supply mechanism 12 to the outer circumferential surface of the media holding unit 21 via the transfer unit 22.

[0043] A media condition detection device 2 that detects the condition of the media 9 held by the media holding unit 21 is located downstream of the transfer drum 22b in the media 9 transport direction. The media condition detection device 2 includes a temperature detection unit 23, a light-emitting unit 5, a light-receiving unit 6, and a temperature adjustment mechanism 24. The temperature detection unit 23 is located upstream of the light-emitting unit 5, the light-receiving unit 6, and the temperature adjustment mechanism 24 in the media 9 transport direction. The temperature detection unit 23 detects the temperature of the media 9 held and transported by the media holding unit 21 or the temperature of the surface (outer periphery) of the media holding unit 21. The temperature detection method used by the temperature detection unit 23 may be contact or non-contact. The light-emitting unit 5, the light-receiving unit 6, and the temperature adjustment mechanism 24 are located downstream of the temperature detection unit 23 in the media 9 transport direction. The light-projecting unit 5 and the light-receiving unit 6 use laser light to detect whether the media 9 held by the media holding unit 21 is floating above the surface of the media holding unit 21. The temperature adjustment mechanism 24 raises the temperature of the space through which the laser light passes to a predetermined temperature and maintains it there. This prevents fluctuations in the laser light and prevents erroneous detection when detecting the state of the media 9. Details of the media state detection device 2 will be described later.

[0044] A printing unit 25 is provided downstream of the media condition detection device 2 in the transport direction of the media 9. The printing unit 25 has, arranged in order from upstream in the transport direction of the media 9, an inkjet head 25Y that ejects yellow (Y) ink, an inkjet head 25M that ejects magenta (M) ink, an inkjet head 25C that ejects cyan (C) ink, and an inkjet head 25K that ejects black (K) ink.

[0045] The inkjet heads 25Y, 25M, 25C, and 25K are each set to a length (width) sufficient to cover the entire medium 9 in the axial direction of the medium holding unit 21 (the width direction of the transport path). In other words, the image forming apparatus 1 is a one-pass line-head inkjet recording device. The inkjet heads 25Y, 25M, 25C, and 25K heat the ink of each color to a predetermined temperature (e.g., approximately 80°C) and hold it in a melted state. Driven by the control unit 40, the inkjet heads 25Y, 25M, 25C, and 25K eject the melted ink toward the surface of the medium 9 being transported by the medium holding unit 21. To minimize misalignment of the ink that lands on the medium 9, the distance between the inkjet heads and the medium is small, for example, approximately 1 to 3 mm.

[0046] A fixing unit 26 is disposed downstream of the printing unit 25 in the transport direction of the medium 9. The fixing unit 26 hardens the ink ejected onto the medium 9 to fix it to the medium 9. For example, a fixing unit 26 that irradiates the medium 9 with ultraviolet light can be used as this fixing unit 26. In this case, the fixing unit 26 irradiates the medium 9 being transported by the media holding unit 21 with ultraviolet light to harden the ink ejected onto the medium 9. In this way, the fixing unit 26 can fix the image formed on the medium 9.

[0047] The fixing unit 26 is not limited to one that irradiates ultraviolet rays, but may be one that irradiates energy rays having properties that harden ink according to the properties of the ink, and the light source is also appropriately replaced depending on the wavelength of the energy rays, etc. The fixing unit 26 is also not limited to one that irradiates light such as ultraviolet rays. For example, the fixing unit 26 may fix the image to the medium 9 by applying heat to the medium 9 to dry the ink or by applying a liquid that causes a chemical change in the ink.

[0048] A discharge mechanism 27 and a media inverting unit 28 are provided downstream of the fixing unit 26 in the transport direction of the media 9.

[0049] The discharge mechanism 27 transports the media 9 transported by the media holding unit 21 toward either the media discharge unit 30 or the media inversion unit 28. The discharge mechanism 27 has a cylindrical separation drum 27a and a discharge belt 27b. The separation drum 27a separates the media 9 held by the media holding unit 21 from the outer surface of the media holding unit 21. The separation drum 27a then guides the media 9 to the discharge belt 27b or the media inversion unit 28.

[0050] The separation drum 27a guides the medium 9 to the discharge belt 27b when performing face-up discharge during single-sided printing. The separation drum 27a also guides the medium 9 to the media inversion unit 28 when performing face-down discharge during single-sided printing or double-sided printing.

[0051] The discharge belt 27b is formed as an endless belt, similar to the conveyor belt 12c of the supply mechanism 12. The discharge belt 27b is rotatably supported by multiple rollers. The discharge belt 27b sends the medium 9 passed from the separation drum 27a to the media discharge unit 30.

[0052] The media inverting unit 28 has multiple inverting rollers 28a, 28b and an inverting belt 28c. When performing face-down paper discharge, the media inverting unit 28 inverts the media 9 guided from the separation drum 27a and transports it to the discharge mechanism 27. As a result, the media 9 is transported to the media discharge unit 30 with the side on which the image is formed facing downward in the vertical direction.

[0053] Furthermore, when double-sided printing is performed, the media inverting unit 28 inverts the media 9 guided from the separation drum 27a and transports it again to the outer circumferential surface of the media holding unit 21. As a result, the media 9 is transported while being held by the media holding unit 21, and passes through the temperature detection unit 23, the media state detection device 2, the printing unit 25, and the fixing unit 26 again.

[0054] The media discharge unit 30 stores the media 9 sent out from the image forming unit 20 by the discharge mechanism 27. The media discharge unit 30 has a flat collection tray 31. The media discharge unit 30 places the media 9 on which an image has been formed onto the collection tray 31.

[0055] When forming an image on the media 9 in the image forming device 1 described above, the distance between the inkjet heads 25Y, 25M, 24C, 25K and the media 9 is small, so before the media 9 transported by the media holding section 21 reaches the printing unit 25, the media state detection device 2 detects whether the media 9 is floating above the surface of the media holding section 21.

[0056] FIG. 2 is a diagram illustrating an example of the placement of the light-projecting unit 5 and the light-receiving unit 6 relative to the media holding unit 21. Note that FIG. 2 only illustrates the media holding unit 21, the light-projecting unit 5, and the light-receiving unit 6, and does not illustrate other components that are arranged around the media holding unit 21. As shown in FIG. 2, the light-projecting unit 5 is located at one end of the media holding unit 21 in the axial direction (width direction of the transport path) and irradiates laser light 7 parallel to the surface of the media holding unit 21 at a position at a predetermined height from the surface of the media holding unit 21. The light-receiving unit 6 is located at the other end of the media holding unit 21 in the axial direction (width direction of the transport path) and receives the laser light 7 irradiated from the light-projecting unit 5.

[0057] 2, if the media 9 has a portion 9a that is raised above the surface of the media holding unit 21, and the height of the raised portion 9a exceeds the height position through which the laser light 7 passes, the raised portion 9a will block the laser light 7 as it passes between the light-emitting unit 5 and the light-receiving unit 6. This allows the media-state detection device 2 to detect that the media 9 is raised above the media holding unit 21.

[0058] 3 is a diagram showing the installation of the temperature adjustment mechanism 24 and temperature detection unit 23 relative to the media holding unit 21. Note that FIG. 3 illustrates the media holding unit 21, temperature detection unit 23, light projector 5, light receiver 6, and temperature adjustment mechanism 24, but does not illustrate other components arranged around the media holding unit 21. As shown in FIG. 3, the temperature detection unit 23 includes multiple temperature detection sensors 23a, 23b, 23c, 23d, and 23e arranged at predetermined intervals along the axial direction of the media holding unit 21 (the width direction of the transport path). Therefore, the temperature detection unit 23 can simultaneously detect the temperature of the media holding unit 21 or the media 9 at multiple locations along the width direction of the transport path.

[0059] The temperature adjustment mechanism 24 is provided at the same position as the light projecting unit 5 and the light receiving unit 6 in the rotation direction R of the media holding unit 21. This temperature adjustment mechanism 24 has a casing 50 that covers the space through which the laser light 7 passes between the light projecting unit 5 and the light receiving unit 6 (space around the optical path). An air introduction unit 51 for introducing air into the casing 50 is provided at the top of the casing 50. For example, the air introduction unit 51 is made up of a plurality of openings formed at the top of the casing 50. The temperature adjustment mechanism 24 blows air heated to a predetermined temperature onto the part of the casing 50 through which the laser light 7 passes.

[0060] Figure 4 is a cross-sectional view showing the internal structure of the temperature adjustment mechanism 24. Note that Figure 4 shows a cross section in the transport direction of the media 9. As shown in Figure 4, the laser light 7 emitted from the light projector 5 is positioned at a predetermined height H above the surface 21a of the media holding unit 21. This height H is set to be the same as or lower than the distance between the inkjet heads 25Y, 25M, 24C, and 25K and the media holding unit 21. This makes it possible to detect media 9 that has risen to the point where it may collide with the inkjet heads 25Y, 25M, 24C, and 25K.

[0061] As shown in FIG. 4 , the temperature adjustment mechanism 24 includes a casing 50, a light path heating unit 53 for heating the optical path of the laser beam 7, and a blower 52 for blowing air heated by the light path heating unit 53 toward the optical path of the laser beam 7. The temperature adjustment mechanism 24 also includes a partition wall 57 that divides the interior of the casing 50 into two spaces, an upper space and an lower space. The partition wall 57 has an opening 58 that connects the two spaces. The blower 52 is located in the partition wall 57 at the position where the opening 58 is formed. The blower 52 is configured by a blower, such as a fan or blower, and blows air from the upper space to the lower space. Therefore, the two spaces provided inside the temperature adjustment mechanism 24 are divided into an upper upstream space R1 and a lower downstream space R2. The air introduction unit 51 described above is connected to the upstream space R1. Therefore, when the blower 52 is activated, external air flows from the air introduction section 51 into the upstream space R1 of the temperature adjustment mechanism 24. The air that has flowed into the upstream space R1 is then forced by the blower 52 to flow from the upstream space R1 into the downstream space R2, and is then released to the outside through the gap with the media holding section 21.

[0062] The optical path heating unit 53 heats the air blown onto the optical path of the laser beam 7 in each of the upstream space R1 and the downstream space R2. To this end, the optical path heating unit 53 includes an upstream heater 54 disposed in the upstream space R1 and a downstream heater 55 disposed in the downstream space R2. The upstream heater 54 heats the air in the upstream space R1. The downstream heater 55 heats the air in the downstream space R2. Therefore, the temperature adjustment mechanism 24 can primarily heat the air flowing in from the air introduction unit 51 in the upstream space R1 and then secondarily heat it in the downstream space R2. The heating temperature (heater temperature) when the upstream heater 54 heats the air and the heating temperature (heater temperature) when the downstream heater 55 heats the air can be controlled separately.

[0063] The air blower 52 blows air from the normal direction of the media holding unit 21 toward the surface 21a of the media holding unit 21. At this time, the air blower 52 can send air that has been primarily heated by the upstream heater 54 and has a temperature higher than the external environmental temperature into the downstream space R2. The air sent into the downstream space R2 is then secondarily heated by the downstream heater 55 before reaching the optical path of the laser beam 7, further increasing its temperature. Therefore, the air blower 52 can maintain the space in the downstream space R2 through which the laser beam 7 passes at a predetermined temperature higher than the external environmental temperature.

[0064] Furthermore, the temperature adjustment mechanism 24 can adjust the temperature of the space through which the laser beam 7 passes by controlling the optical path heating unit 53 and the air blower 52, respectively. For example, the temperature of the space through which the laser beam 7 passes can be increased by increasing the heating temperatures of the upstream heater 54 and the downstream heater 55. In this case, the heating temperatures of both the upstream heater 54 and the downstream heater 55 may be increased, or only one of them may be increased. The temperature of the space through which the laser beam 7 passes can also be increased by decreasing the airflow rate of the air blower 52. Conversely, the temperature of the space through which the laser beam 7 passes can be decreased by decreasing the heating temperatures of the upstream heater 54 and the downstream heater 55. In this case, the heating temperatures of both the upstream heater 54 and the downstream heater 55 may be decreased, or only one of them may be decreased. The temperature of the space through which the laser beam 7 passes can also be decreased by increasing the airflow rate of the air blower 52.

[0065] The temperature adjustment mechanism 24 also includes an air deflector 56 located below the air blower 52 in the downstream space R2. The air deflector 56 is supported below the air blower 52 by, for example, a support member 561 provided on the casing 50. The air deflector 56 deflects a portion of the air blown from the air blower 52 toward the surface 21a of the media holding unit 21 in the width direction of the transport path, thereby distributing temperature-adjusted air throughout the entire optical path of the laser light 7.

[0066] FIG. 5 is a cross-sectional view showing the internal structure of the temperature adjustment mechanism 24, showing a cross section in a direction perpendicular to the transport direction of the medium 9 (the width direction of the transport path). As shown in FIG. 5, the upstream heaters 54 and downstream heaters 55 are installed at multiple locations in the width direction of the transport path. That is, the optical path heating unit 53 is configured to include multiple upstream heaters 54 and downstream heaters 55 along the width direction of the transport path. These multiple upstream heaters 54 and downstream heaters 55 are installed at approximately equal intervals in the width direction of the transport path. Note that FIG. 5 shows an example in which five upstream heaters 54 and downstream heaters 55 are installed in the width direction of the transport path, but the number of upstream heaters 54 and downstream heaters 55 is not limited to this. Also, FIG. 5 shows an example in which the upstream heater 54 and downstream heater 55 are installed in the same position in the width direction of the transport path, but the upstream heater 54 and downstream heater 55 do not necessarily have to be installed in the same position in the width direction of the transport path.

[0067] Furthermore, the air blowers 52 are also installed at multiple locations in the width direction of the transport path. That is, the temperature adjustment mechanism 24 is configured to include multiple air blowers 52 along the width direction of the transport path. These multiple air blowers 52 are installed at approximately equal intervals in the width direction of the transport path. FIG. 5 shows an example in which multiple air blowers 52 are installed at approximately the same positions in the width direction of the transport path as the upstream heater 54 and the downstream heater 55 are installed. However, this is not limited to this, and the positions of the air blowers 52 do not necessarily have to coincide with the positions of the upstream heater 54 and the downstream heater 55. Furthermore, FIG. 5 shows an example in which five air blowers 52 are installed in the width direction of the transport path, but the number of air blowers 52 is not limited to this.

[0068] 5, the above-mentioned air direction vane 56 is provided below each air blower 52. That is, the air direction vane 56 is provided below each of the plurality of air blowers 52.

[0069] Fig. 6 is an enlarged view of an airflow direction plate 56 provided below one of the air blowing sections 52. As shown in Fig. 6, the airflow direction plate 56 provided below the air blowing section 52 includes a pair of plate members 56a, 56b that are inclined in different directions. The pair of plate members 56a, 56b are arranged below the air blowing section 52 at a predetermined distance.

[0070] Plate member 56a is provided below blower 52 and closer to light-projecting unit 5, and is inclined toward light-projecting unit 5 so as to deflect the airflow blown from blower 52 toward light-projecting unit 5. Therefore, the air blown from blower 52 and striking plate member 56a flows in the direction toward light-projecting unit 5, as shown by arrow F2. Plate member 56b is provided below blower 52 and closer to light-receiving unit 6, and is inclined toward light-receiving unit 6 so as to deflect the airflow blown from blower 52 toward light-receiving unit 6. Therefore, the air blown from blower 52 and striking plate member 56b flows in the direction toward light-receiving unit 6, as shown by arrow F3. Furthermore, the pair of plate members 56a, 56b are arranged at a predetermined interval in the width direction of the transport path. Therefore, as shown by arrow F1, the air passing between the pair of plate members 56a, 56b can be blown perpendicularly to the surface of the medium holding unit 21. Therefore, the air direction plate 56 can blow the air flowing into the downstream space R2 from the blower 52 almost evenly toward the optical path of the laser light 7.

[0071] The media condition detection device 2 then sets the temperature of the space inside the casing 50 through which the laser beam 7 passes, based on the temperature of the media holding unit 21 or the media 9 detected by the temperature detection unit 23, and drives the optical path heating unit 53 and the air blower 52 to achieve the set temperature. For example, the media condition detection device 2 sets the temperature of the space through which the laser beam 7 passes to match the temperature of the media holding unit 21 or the media 9. As a result, the temperature of the air blown by the air blower 52 into the space through which the laser beam 7 passes inside the casing 50 matches the surface temperature of the media holding unit 21 or the media 9. Therefore, the air blown evenly along the optical path of the laser beam 7 by the air blower 52 and the air direction plate 56 can prevent air convection from occurring near the surface of the media holding unit 21. A single air layer consisting only of air heated to a predetermined temperature and blown by the air blower 52 can be formed near the optical path of the laser beam 7. In other words, it is possible to effectively prevent the formation of multiple air layers with different temperatures near the optical path of the laser light 7, and to prevent fluctuations in the laser light 7. This effectively prevents erroneous detection when detecting the state of the media 9.

[0072] To prevent fluctuations in the laser light 7, it is sufficient to blow air that is hotter than the temperature of the media holding unit 21 or the media 9. Therefore, when setting the temperature of the space through which the laser light 7 passes, it is not necessarily limited to setting it to a temperature that matches the surface temperature of the media holding unit 21 or the media 9. For example, the media state detection device 2 may set the temperature of the space through which the laser light 7 passes to a temperature that is higher than the surface temperature of the media holding unit 21 or the media 9.

[0073] As described above, the temperature detection unit 23 is equipped with multiple temperature detection sensors 23a, 23b, 23c, 23d, and 23e arranged in the width direction of the transport path. Therefore, the temperature detection unit 23 can detect the temperature at multiple locations along the width direction of the transport path. If there are temperature variations along the width direction of the transport path, the media condition detection device 2 can individually control the multiple optical path heating units 53 and air blowers 52 arranged along the width direction to eliminate the temperature variations and prevent fluctuations in the laser light 7.

[0074] FIG. 7 shows an example of temperatures detected by each of the temperature detection sensors 23a, 23b, 23c, 23d, and 23e. For example, as shown in FIG. 7(a), if the temperatures detected by the temperature detection sensors 23a, 23b, 23c, 23d, and 23e are approximately the same, the media holding unit 21 is heated evenly across the width of the transport path at both ends and the center. In this case, the media condition detection device 2 sets the same heating temperature for the multiple upstream heaters 54 arranged across the width of the transport path, and also sets the same heating temperature for the multiple downstream heaters 55, based on the temperatures detected by the temperature detection sensors 23a, 23b, 23c, 23d, and 23e. Furthermore, in this case, the media condition detection device 2 sets the same airflow rate for the multiple air blowers 52 arranged across the width of the transport path. In other words, if there is no temperature unevenness across the surface of the media holding unit 21, the media condition detection device 2 blows air that has been heated evenly across the width of the media holding unit 21 into the optical path of the laser light 7. This makes it possible to prevent erroneous detection when detecting the state of the medium 9.

[0075] In contrast, as shown in FIG. 7B, the temperatures detected by the temperature detection sensors 23a, 23b, 23c, 23d, and 23e may not be substantially the same, and the temperatures at both ends of the media holding unit 21 may be lower than the temperature at the center. In this case, temperature variations occur across the width of the surface of the media holding unit 21. When such temperature variations occur, the media condition detection device 2 adjusts the temperature based on the temperatures detected by the temperature detection sensors 23a, 23b, 23c, 23d, and 23e to raise the temperatures at both ends of the width of the transport path higher than the center. Specifically, this temperature variation can be eliminated by applying a higher amount of heat to both ends of the width of the transport path than to the center. For example, the media condition detection device 2 sets the heating temperature of the upstream heater 54 located at the end of the width of the transport path to a higher temperature than the heating temperature of the upstream heater 54 located in the center. The media condition detection device 2 also sets the heating temperature of the downstream heater 55 located at the widthwise end of the transport path to a higher temperature than the heating temperature of the downstream heater 55 located in the center. Furthermore, the media condition detection device 2 reduces the airflow rate of the air blower 52 located at the widthwise end of the transport path to a lower airflow rate than the air blower 52 located in the center. This makes it possible to raise the temperature at both ends of the width of the transport path in the space through which the laser beam 7 passes to approximately the same temperature as the center, eliminating temperature variations. This prevents fluctuations in the laser beam 7 and prevents erroneous detection when detecting the state of the media 9.

[0076] Furthermore, if there are temperature variations as shown in Figure 7(b), when ink is ejected onto the media 9 held by the media holding unit 21, the ink will spread differently at both ends of the media 9 than at the center, which could result in image quality degradation. However, as described above, the media condition detection device 2 raises the temperature at both ends of the width of the transport path to approximately the same temperature as the center, thereby raising the temperature at both ends of the media 9 to approximately the same temperature as the center. As a result, it is possible to eliminate temperature variations on the surface of the media 9 before the media 9 enters the inkjet heads 25Y, 25M, 24C, and 25K, and to prevent image quality degradation when ink is ejected onto the surface of the media 9.

[0077] Although the above describes temperature unevenness when the temperature at both ends of the width of the transport path is lower than the temperature at the center, temperature unevenness can also occur when the temperature at the center of the width of the transport path is lower than the temperature at both ends. Even in such a case, the media condition detection device 2 can raise the temperature at the center of the width of the transport path in the space through which the laser light 7 passes to approximately the same temperature as at both ends, thereby eliminating temperature unevenness.

[0078] Next, the control mechanism of the image forming apparatus 1, which includes the media condition detection device 2 described above, will be described. FIG. 8 is a block diagram showing an example of the control mechanism of the image forming apparatus 1. The image forming apparatus 1 includes a control unit 40 for controlling the media supply unit 10, image forming unit 20, media discharge unit 30, and media condition detection device 2. The control unit 40 includes a hardware processor, such as a CPU (not shown), and memory. The hardware processor executes a predetermined program, causing the control unit 40 to function as a job control unit 41, a temperature setting unit 45, and a detection unit 46. Of these, the temperature setting unit 45 and the detection unit 46 are functions included in the media condition detection device 2.

[0079] The job control unit 41 controls the execution of print jobs in the image forming device 1. In other words, the job control unit 41 comprehensively controls the image forming operation on the medium 9 by controlling the operation of the medium supply unit 10, the image forming unit 20, and the medium discharge unit 30. The job control unit 41 includes a print data acquisition unit 42, a print setting analysis unit 43, and a job execution unit 44.

[0080] The print data acquisition unit 42 acquires print data to be printed. For example, the print data acquisition unit 42 acquires print data from an external terminal device via a network.

[0081] The print setting analysis unit 43 analyzes the setting information included in the print data and, based on the setting information, determines the print settings to be applied to each of the media supply unit 10, image forming unit 20, and media discharge unit 30. The print setting analysis unit 43 then performs a process to apply the print settings to each unit. For example, the print settings determined by the print setting analysis unit 43 include the print ratio of the image to be printed, the type of media 9, whether single-sided printing or double-sided printing is selected, the print speed, and the target temperature of the media holding unit 21. Of these, the type of media 9 is specified in advance in the setting information included in the print data, and the selection of either single-sided printing or double-sided printing is also included in advance in the setting information. Therefore, the print setting analysis unit 43 determines the type of media 9 and whether single-sided printing or double-sided printing is selected based on the setting information. The print setting analysis unit 43 also determines the print ratio by calculating the print ratio of the image to be printed based on the print data, and determines the print speed and the target temperature of the media holding unit 21 based on the type of media 9. Here, the printing speed is the speed at which the medium 9 is transported along the transport path. Furthermore, when the print setting analysis unit 43 determines the print settings, it not only reflects the print settings in each unit, but also outputs the print settings to the temperature setting unit 45.

[0082] The job execution unit 44 controls the operation of each unit when execution of a print job begins. That is, the job execution unit 44 synchronously drives the media supply unit 10, image forming unit 20, and media discharge unit 30 while the print settings are reflected, thereby controlling the operation of supplying media 9 from the media supply unit 10, forming an image on the media 9 in the image forming unit 20, and discharging the image-formed media 9 to the media discharge unit 30. At this time, the job execution unit 44 drives the heater 29 of the media holding unit 21 and controls it so that the surface temperature of the media holding unit 21 reaches the target temperature specified in the print settings. The job execution unit 44 also sets the fixing strength of the fixing unit 26 according to the print rate. Note that the stronger the fixing strength of the fixing unit 26, the greater the amount of heat generated by the fixing unit 26 and the higher the temperature of the media holding unit 21. Furthermore, when the medium 9 being transported along the transport path passes through the printing unit 25, the job execution unit 44 drives the inkjet heads 25Y, 25M, 24C, and 25K to eject ink onto the surface of the medium 9 to form an image.

[0083] Furthermore, during execution of a print job, the job execution unit 44 acquires the temperature of the media holding unit 21 or the media 9 detected by the temperature detection unit 23 and controls the heater 29 of the media holding unit 21 based on that temperature. Even if the surface temperature of the media holding unit 21 is maintained at a target temperature when execution of a print job begins, the surface temperature of the media holding unit 21 will fluctuate as execution of the print job continues. To reduce such fluctuations, the job execution unit 44 performs feedback control of the heater 29 of the media holding unit 21 based on the temperature detected by the temperature detection unit 23 during execution of the print job. For example, when double-sided printing is performed on the media 9, the media 9 with an image formed on its first side is turned over in the media inversion unit 28 and transported again toward the printing unit 25. At this time, the temperature of the media 9 rises due to the image being formed on the first side. Therefore, the job execution unit 44 may control the heater 29 to lower the heating temperature based on the temperature of the media 9 detected by the temperature detection unit 23, so as to lower the surface temperature of the media holding unit 21.

[0084] The temperature setting unit 45 sets a temperature for the temperature adjustment mechanism 24. Before the job execution unit 44 starts executing a print job, the temperature setting unit 45 acquires print settings from the print setting analysis unit 43. Therefore, the temperature setting unit 45 initially sets the temperature of the space through which the laser light 7 passes for the temperature adjustment mechanism 24 based on the print settings. For example, the temperature setting unit 45 performs the initial setting so that the temperature of the space through which the laser light 7 passes matches the target temperature of the media holding unit 21. As described above, the target temperature of the media holding unit 21 is determined according to the type of media 9. Therefore, the temperature setting unit 45 may initially set the temperature of the space through which the laser light 7 passes based on the type of media 9. This initial setting is performed before the execution of the print job starts.

[0085] Furthermore, after the job execution unit 44 starts executing a print job, the temperature setting unit 45 changes the temperature setting based on the temperature of the media holding unit 21 or the media 9 detected by the temperature detection unit 23. For example, the temperature setting unit 45 changes the temperature setting of the temperature adjustment mechanism 24 so that it matches the temperature of the media holding unit 21 or the media 9. By changing the temperature setting in this way, even if the temperature of the media holding unit 21 or the media 9 fluctuates during job execution, the temperature of the air blown into the space through which the laser light 7 passes can be appropriately adjusted in accordance with the temperature detected by the temperature detection unit 23. This makes it possible to effectively prevent fluctuations in the laser light 7 during job execution. Furthermore, for example, if the temperature detection unit 23 detects temperature unevenness, the temperature setting unit 45 changes the temperature setting to eliminate the temperature unevenness. This makes it possible to blow air whose temperature has been adjusted to eliminate the temperature unevenness into the space through which the laser light 7 passes, making it possible to effectively prevent fluctuations in the laser light 7 due to temperature unevenness.

[0086] The temperature setting unit 45 can also change the temperature setting based on the print settings after the job execution unit 44 starts executing a print job. For example, if the print rate of the previously transported medium 9 is higher than a predetermined value, the temperature of the media holding unit 21 may be higher than the target temperature when the next medium 9 is transported. Therefore, the temperature setting unit 45 may change the temperature setting of the temperature adjustment mechanism 24 when the next medium 9 is transported, based on the print rate of the previously transported medium 9.

[0087] Furthermore, when double-sided printing is performed on the medium 9, the temperature of the medium 9 rises when an image is formed on the first side. Therefore, when double-sided printing is specified in the print settings, the temperature setting unit 45 may change the temperature setting of the temperature adjustment mechanism 24 after an image is formed on the first side.

[0088] Furthermore, if the printing speed during execution of a print job is slower than a predetermined value, the temperature of the medium holding unit 21 is likely to rise. Therefore, the temperature setting unit 45 may be configured to appropriately change the temperature setting of the temperature adjustment mechanism 24 based on the printing speed included in the print settings.

[0089] The detection unit 46 detects the state of the media 9 based on the laser light 7 received by the light receiving unit 6. Specifically, the detection unit 46 detects that the media 9 has been raised a predetermined amount above the surface of the media holding unit 21 when the light receiving unit 6 is no longer receiving the laser light 7. When the detection unit 46 detects that the media 9 has been raised a predetermined amount, it outputs the detection result to the job control unit 41.

[0090] When the detection unit 46 detects that the medium 9 has been lifted a predetermined amount during job execution, the job control unit 41 forcibly stops execution of the job by the job execution unit 44. In other words, the job control unit 41 stops execution of the job before the medium 9 that has lifted from the media holding unit 21 enters the printing unit 25. This stops the transport of the medium 9, so that the medium 9 that has lifted from the media holding unit 21 will not collide with the inkjet heads 25Y, 25M, 24C, and 25K. This prevents damage to the inkjet heads 25Y, 25M, 24C, and 25K.

[0091] Next, a description will be given of the operation of the image forming apparatus 1 configured as described above. Fig. 9 is a flowchart showing the operation procedure of the image forming apparatus 1. The operation procedure based on the flowchart of Fig. 9 is realized by the hardware processor of the control unit 40 executing a predetermined program.

[0092] When the image forming apparatus 1 starts this process, it first acquires print data (step S10). The image forming apparatus 1 analyzes the setting information included in the print data and determines print settings based on the setting information (step S11). Next, the image forming apparatus 1 performs initial settings based on the print settings. That is, the image forming apparatus 1 sets a target temperature for the media holding unit 21 (step S12) and sets the temperature for the temperature adjustment mechanism 24 (step S13). For example, the image forming apparatus 1 sets the temperature for the temperature adjustment mechanism 24 to the same temperature as the target temperature for the media holding unit 21. The image forming apparatus 1 also reflects other print settings in each section (step S14).

[0093] The image forming apparatus 1 then starts executing the print job (step S15). This starts the transport of the medium 9, and an image is formed in ink as the medium 9 passes through the printing unit 25. When the print job starts, the image forming apparatus 1 detects the temperature using the temperature detection unit 23 and measures the temperature of the medium holding unit 21 or the medium 9 (step S16). The image forming apparatus 1 then determines whether or not the temperature setting of the temperature adjustment mechanism 24 needs to be changed based on the temperature detected by the temperature detection unit 23 (step S17). If the temperature setting of the temperature adjustment mechanism 24 needs to be changed (YES in step S17), the image forming apparatus 1 changes the temperature setting of the temperature adjustment mechanism 24 (step S18). For example, if there is temperature unevenness on the surface of the medium holding unit 21 or the medium 9, the image forming apparatus 1 changes the temperature setting of the temperature adjustment mechanism 24 to eliminate the temperature unevenness. At this time, the image forming apparatus 1 may change the temperature setting differently at both ends and the center of the width direction of the transport path. Then, based on the changed temperature setting, the image forming apparatus 1 changes the heating temperature of the optical path heating unit 53 (step S19), and further changes the air volume of the air blower unit 52 (step S20). However, the image forming apparatus 1 may change only the heating temperature of the optical path heating unit 53, or may change only the air volume of the air blower unit 52. Furthermore, when changing the heating temperature of the optical path heating unit 53, the image forming apparatus 1 may change the heating temperatures of both the upstream heater 54 and the downstream heater 55, or may change only one of the heating temperatures.

[0094] On the other hand, if there is no need to change the temperature setting of temperature adjustment mechanism 24 (NO in step S17), image forming apparatus 1 skips steps S18 to S20. In this case, the temperature setting of temperature adjustment mechanism 24 is not changed. For example, if the surface temperature of media holding unit 21 or media 9 has reached a preset target temperature and no temperature unevenness has occurred, image forming apparatus 1 does not change the temperature setting of temperature adjustment mechanism 24, and continues the operation of blowing air heated to the same temperature as the surface temperature of media holding unit 21 or media 9 into the space through which laser light 7 passes.

[0095] After that, the image forming apparatus 1 determines whether the execution of the print job has finished (step S21). If the execution of the print job has not finished (NO in step S21), the image forming apparatus 1 determines whether the detection unit 46 has detected that the media 9 is floating (step S22). If the detection unit 46 has not detected that the media 9 is floating (NO in step S22), the processing by the image forming apparatus 1 returns to step S16. The above-described processing is then repeated. Therefore, if temperature unevenness occurs on the media holding unit 21 or the surface of the media 9 during the execution of the print job, the temperature setting of the temperature adjustment mechanism 24 is changed each time to eliminate the temperature unevenness.

[0096] Furthermore, if the detection unit 46 detects that the medium 9 is floating during execution of a print job (YES in step S22), the image forming device 1 forcibly stops execution of the print job (step S23). That is, the image forming device 1 stops the printing operation based on the print job before the medium 9, which is floating from the media holding unit 21, enters the printing unit 25. This prevents damage to the inkjet heads 25Y, 25M, 24C, and 25K.

[0097] On the other hand, if the execution of the print job ends without the detection unit 46 detecting that the medium 9 is floating (YES in step S21), the processing by the image forming apparatus 1 ends normally.

[0098] As described above, the image forming apparatus 1 of this embodiment is equipped with a media condition detection device 2 that detects the condition of sheet-like media 9 transported along a predetermined transport path to prevent damage to the inkjet heads 25Y, 25M, 24C, and 25K. As described above, the media condition detection device 2 is equipped with a media holding unit 21 that holds the media 9 and transports the media along the transport path, a light projecting unit 5 that is located at one widthwise end of the transport path and irradiates laser light 7 at a predetermined height from the surface of the media holding unit 21, a light receiving unit 6 that is located at the other widthwise end of the transport path facing the light projecting unit 5 and receives the laser light 7, a detection unit 46 that detects the condition of the media 9 based on the state of reception of the laser light 7 by the light receiving unit 6, and a temperature adjustment mechanism 24 that raises the temperature of the space through which the laser light 7 passes to a predetermined temperature and maintains that temperature.

[0099] This type of media condition detection device 2 raises and maintains the temperature of the space through which the laser light 7 passes at a predetermined temperature, preventing the formation of hot and cold air layers near the surface of the media holding unit 21. As a result, fluctuations in the laser light 7 are effectively prevented, allowing the detection unit 46 to accurately detect the condition of the media 9.

[0100] Furthermore, if there is temperature unevenness across the width of the transport path, the media condition detection device 2 is configured to eliminate temperature unevenness across the width of the transport path by individually controlling each of the optical path heating units 53 and air blowers 52 located at multiple locations across the width of the transport path. This effectively prevents fluctuations in the laser light 7 due to temperature unevenness, making it possible to accurately detect the condition of the media 9.

[0101] (Variation) The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications are possible.

[0102] For example, in the above embodiment, the media holding unit 21 is formed as a cylindrical drum, and is rotated by a drive motor to transport the media 9 along an arc-shaped transport path. However, the media holding unit 21 is not necessarily limited to being formed as a cylindrical drum, and the transport path for the media 9 is not necessarily limited to an arc-shaped path. For example, the media holding unit 21 may transport the media 9 along a linear transport path.

[0103] In the above embodiment, the temperature adjustment mechanism 24 is provided with the optical path heating unit 53 and the air blower 52. However, the temperature adjustment mechanism 24 may be configured to include only the optical path heating unit 53, as long as it can raise and maintain the temperature of the space through which the laser light 7 passes at a predetermined temperature. [Explanation of symbols]

[0104] 1. Image forming device 2 Media status detection device 5 Light projector 6 Light receiving part 7. Laser light 9. Media 21 Media holder 23 Temperature detection unit 24 Temperature adjustment mechanism 25 printing units 25Y, 25M, 24C, 25K inkjet heads 29 Heater (media holding and heating section) 46 Detection unit 52 Blower 53 Optical path heating section 54 Upstream heater 55 Downstream heater 56 Wind direction board

Claims

1. A media condition detection device that detects the condition of a sheet of media transported along a predetermined transport path, comprising: a media holding unit that holds the medium and transports the medium along the transport path; a light projecting unit that is disposed at one end of the transport path in the width direction and that projects laser light at a position at a predetermined height from the media holding surface of the media holding unit; a light receiving unit that receives the laser light; a detection unit that detects the state of the medium according to the state of reception of the laser light by the light receiving unit; a temperature adjustment mechanism that raises the temperature of the space through which the laser light passes to a predetermined temperature and maintains it at that temperature; Equipped with The temperature adjustment mechanism includes: an optical path heating unit that heats the air in a space around the optical path of the laser light; a blower that blows the air heated by the optical path heating unit toward the optical path of the laser light; a wind direction plate disposed downstream of the blower unit for directing the air blown out from the blower unit in the width direction of the transport path; A media condition detection device comprising:

2. A media condition detection device that detects the condition of a sheet of media transported along a predetermined transport path, comprising: a media holding unit that holds the medium and transports the medium along the transport path; a light projecting unit that is disposed at one end of the transport path in the width direction and that projects laser light at a position at a predetermined height from the media holding surface of the media holding unit; a light receiving unit that receives the laser light; a detection unit that detects the state of the medium according to the state of reception of the laser light by the light receiving unit; a temperature adjustment mechanism that raises the temperature of the space through which the laser light passes to a predetermined temperature and maintains it at that temperature; Equipped with The temperature adjustment mechanism includes: an optical path heating unit that heats the air in a space around the optical path of the laser light; a blower that blows the air heated by the optical path heating unit toward the optical path of the laser light; Equipped with The optical path heating unit includes: an upstream heater that heats a space upstream of the blower; a downstream heater that heats a space downstream of the blower; A media condition detection device comprising:

3. A media condition detection device that detects the condition of a sheet of media transported along a predetermined transport path, comprising: a media holding unit that holds the medium and transports the medium along the transport path; a light projecting unit that is disposed at one end of the transport path in the width direction and that projects laser light at a position at a predetermined height from the media holding surface of the media holding unit; a light receiving unit that receives the laser light; a detection unit that detects the state of the medium according to the state of reception of the laser light by the light receiving unit; a temperature detection unit that detects the temperature of the medium or the medium holding unit; a temperature adjustment mechanism that raises the temperature of the space through which the laser light passes to a predetermined temperature and maintains the temperature in accordance with the temperature detected by the temperature detection unit; Equipped with the temperature detection unit detects temperatures at a plurality of locations in a width direction of the conveying path, the temperature adjustment mechanism includes an optical path heating unit that heats air in a space around the optical path of the laser light, The optical path heating unit has a plurality of heaters arranged along the width direction, and the media condition detection device is characterized in that the heating temperatures of the plurality of heaters are individually adjusted based on the temperatures of the plurality of locations detected by the temperature detection unit.

4. A media condition detection device that detects the condition of a sheet of media transported along a predetermined transport path, comprising: a media holding unit that holds the medium and transports the medium along the transport path; a light projecting unit that is disposed at one end of the transport path in the width direction and that projects laser light at a position at a predetermined height from the media holding surface of the media holding unit; a light receiving unit that receives the laser light; a detection unit that detects the state of the medium according to the state of reception of the laser light by the light receiving unit; a temperature detection unit that detects the temperature of the medium or the medium holding unit; a temperature adjustment mechanism that raises the temperature of the space through which the laser light passes to a predetermined temperature and maintains the temperature in accordance with the temperature detected by the temperature detection unit; Equipped with The temperature adjustment mechanism includes: an optical path heating unit that heats the air in a space around the optical path of the laser light; a blower that blows the air heated by the optical path heating unit toward the optical path of the laser light; Equipped with The media condition detection device is characterized in that the air blowing unit adjusts the air volume in accordance with the temperature detected by the temperature detection unit.

5. a temperature detection unit that detects the temperature of the medium or the medium holding unit; Further provided with 3. The media condition detection device according to claim 1, wherein the temperature adjustment mechanism sets the predetermined temperature in accordance with the temperature detected by the temperature detection unit.

6. 6. The media condition detection device according to claim 5, wherein the temperature adjustment mechanism sets the temperature detected by the temperature detection unit to the predetermined temperature.

7. 4. The media condition detection device according to claim 3, wherein the temperature adjustment mechanism further comprises a blower that blows air heated by the optical path heating unit toward the optical path of the laser light.

8. 8. The media state detection device according to claim 1, wherein the air blowing unit blows air toward the media holding surface from a position higher than the height at which the laser light passes.

9. 5. The media condition detection device according to claim 4, wherein the optical path heating unit adjusts the heating temperature in accordance with the temperature detected by the temperature detection unit.

10. the temperature detection unit detects temperatures at a plurality of locations in a width direction perpendicular to the conveying path, The media condition detection device described in claim 4 or 9, characterized in that the blower unit has multiple fans arranged along the width direction, and the air volume of the multiple fans is individually adjusted based on the temperatures at the multiple locations detected by the temperature detection unit.

11. a media holding and heating unit that heats the media holding unit; 11. The media condition detection device according to claim 1, further comprising:

12. A media condition detection device according to any one of claims 1 to 11; an inkjet head that is provided downstream of the light projecting unit and the light receiving unit on the transport path and that ejects ink onto the medium; a control unit that drives the inkjet head to perform a printing operation; An image forming apparatus comprising:

13. 13. The image forming apparatus according to claim 12, wherein the control unit stops the printing operation when the detection unit of the media state detection device detects that the media is floating above the media holding unit.

14. 14. The image forming apparatus according to claim 12, wherein the control unit sets the temperature of the media holding unit based on a print setting.

15. 15. The image forming apparatus according to claim 12, wherein the control unit sets the predetermined temperature in the temperature adjustment mechanism based on a print setting.

16. 16. The image forming apparatus according to claim 14, wherein the print settings include a print ratio of an image to be printed.

17. 17. The image forming apparatus according to claim 14, wherein the print settings include the type of the media.

18. 18. The image forming apparatus according to claim 14, wherein the print settings include a designation of either single-sided printing or double-sided printing.

19. 19. The image forming apparatus according to claim 14, wherein the print settings include a print speed.

Images