Fixing device

Abstract

To provide a configuration capable of suppressing a temperature sensor from becoming high temperature in a system for directly heating a belt by using a reflector and a heater and a configuration for detecting temperature of the belt by using a non-contact temperature sensor.SOLUTION: Heaters 110a and 110b are disposed in non-contact with an upper belt 30 to heat the upper belt 30. A reflector 115 has the heaters 110a and 110b disposed inside, and radiation heat of the heaters 110a and 110b is reflected toward a region of the upper belt 30. A temperature sensor 210 is disposed outside the reflector 115 and detects temperature of the region. The temperature sensor 210 is disposed on a flow path 160a through which airflow generated by a fan flows.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a fixing device that heats a sheet on which an image has been formed by ejecting ink, thereby fixing the image to the sheet. [Background technology]

[0002] Patent Document 1 describes a configuration in which a sensor disposed on a heater that heats a belt is used to measure the temperature of the heater, and when an abnormal temperature rise is detected, power supply control to the heater is changed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-136392 Summary of the Invention [Problem to be solved by the invention]

[0004] In the method of directly heating the belt with a heater, the belt temperature is sometimes detected using a non-contact temperature sensor (temperature detection unit). A configuration using a reflector (reflective member) has also been proposed to increase the efficiency of heating the belt with the heater. When this configuration is adopted, the temperature detection unit is placed outside the reflector to prevent damage caused by radiant heat.

[0005] However, even if the reflector blocks heat, the temperature detection unit may receive heat and may not be able to detect the temperature accurately. The reason for this is that in order to accurately detect the temperature of the target area, the temperature sensor must be placed in a location close enough to the belt or heater. Even when the above configuration is adopted, a configuration is required in which the temperature detection unit can detect the temperature accurately.

[0006] The present invention aims to provide a configuration that can prevent the temperature detection unit from becoming too hot in a system in which the belt is directly heated using a reflective member and a heater and the temperature of the belt is detected using a non-contact temperature detection unit. [Means for solving the problem]

[0007] One aspect of the present invention is a fixing device that heats a sheet on which an image has been formed by ejecting ink, thereby fixing the image to the sheet, and is characterized in that it comprises a rotating endless belt, a nip forming member that forms a nip between the belt and the belt to sandwich and transport the sheet, a heater that is arranged without contact with the belt and heats the belt, a reflective member on the inside of which the heater is arranged and that reflects the radiant heat of the heater toward an area of ​​the belt, a temperature detection unit that is arranged outside the reflective member and detects the temperature of the area, and a fan that generates an airflow, wherein the temperature detection unit is arranged in a flow path through which the airflow generated by the fan flows.

[0008] One aspect of the present invention is a fixing device that heats a sheet on which an image has been formed by ejecting ink, thereby fixing the image to the sheet, and is characterized by comprising: a rotating endless belt; a nip forming member that forms a nip between the belt and the belt to sandwich and transport the sheet; a heater that is arranged non-contact with the belt and along the width direction of the belt that intersects the rotation direction of the belt, and that heats the belt; a reflective member on the inside of which the heater is arranged, and that reflects the radiant heat of the heater toward an area of ​​the belt; and a temperature detection unit that is arranged outside the reflective member, outside the end of the heater in the width direction, and that detects the temperature of the area.

[0009] One aspect of the present invention is a fixing device that heats a sheet on which an image has been formed by ejecting ink, thereby fixing the image to the sheet, and is characterized by comprising: a rotating endless belt; a nip forming member that forms a nip between the belt and the belt to sandwich and transport the sheet; a heater that is arranged non-contact with the belt and along the width direction of the belt that intersects with the rotation direction of the belt, and that heats a position of the belt outside the nip portion; a reflective member that is arranged inside the heater and reflects the radiant heat of the heater toward the belt area; and a temperature detection unit that is arranged on the opposite side of the belt from the side on which the heater and the reflective member are arranged, and that detects the temperature of the back surface of the belt in the area. [Effects of the Invention]

[0010] According to the present invention, in a system in which the belt is directly heated using a reflective member and a heater and in a configuration in which the temperature of the belt is detected using a non-contact temperature detection unit, it is possible to prevent the temperature detection unit from becoming too high. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic cross-sectional view showing the configuration of an inkjet recording apparatus according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing the schematic configuration of a fixing module according to the first embodiment. [Figure 3] FIG. 2A is a schematic cross-sectional view showing an enlarged portion of the fixing belt unit according to the first embodiment, and FIG. 2B is a cross-sectional view of the heater and reflector of the fixing belt unit according to the first embodiment. [Figure 4] FIG. 2 is a perspective view showing the configuration of the periphery of the fan according to the first embodiment. [Figure 5] FIG. 2 is a cross-sectional view of the fixing belt unit according to the first embodiment, cut in the width direction at the fan and the flow path. [Figure 6](a) An oblique view showing a first state in which the upper door unit of the fixing module of the first embodiment is positioned in a closed position; (b) An oblique view showing a second state in which the upper door unit is positioned in an open position and the upper belt unit is positioned in an upper storage position; (c) An oblique view showing a third state in which the upper door unit is positioned in an open position and the upper belt unit is positioned in a maintenance position. [Figure 7] FIG. 4 is a block diagram relating to fixing control of an upper belt unit according to the first embodiment. [Figure 8] 6 is a flowchart relating to fixing control of the upper belt unit according to the first embodiment. [Figure 9] 1A is a plan view and a side view of a temperature sensor according to a first embodiment, FIG. 1B is a schematic diagram showing the viewing angle of the temperature sensor, and FIG. 1C is a graph showing the relationship between the viewing angle and measurement accuracy. [Figure 10] 1A is a schematic diagram showing the relationship between the heater and the belt in the width direction according to the first embodiment, and a diagram showing the distribution of radiation intensity of the heater in the width direction; FIG. 1B is a graph showing the relationship between heating time and belt temperature. [Figure 11] FIG. 3 is a diagram showing the distribution of the ambient temperature in a flow channel in which a temperature sensor according to the first embodiment is disposed. [Figure 12] FIG. 10 is a schematic cross-sectional view showing an enlarged portion of a fixing belt unit according to a second embodiment. [Figure 13] FIG. 10 is a block diagram relating to fixing control of an upper belt unit according to a second embodiment. [Figure 14] FIG. 10 is a cross-sectional view of a fixing belt unit according to a second embodiment, cut in the width direction at the fan and the flow path. [Figure 15] FIG. 11 is a schematic cross-sectional view illustrating a heating configuration with a portion of an upper belt unit omitted according to a third embodiment. [Figure 16] FIG. 10 is a schematic view of a temperature sensor, a reflector, and a belt according to a fourth embodiment, viewed from above the reflector. [Figure 17] FIG. 10(a) is a schematic side view of a temperature sensor, a reflector, and a belt according to a fourth embodiment, and FIG. 10(b) is a graph showing the relationship between heating time and belt temperature. [Figure 18]FIG. 11 is a schematic cross-sectional view illustrating the heating configuration with a portion of an upper belt unit omitted according to a fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] First Embodiment The first embodiment will be described with reference to Figures 1 to 11. First, the schematic configuration of an inkjet recording apparatus according to this embodiment will be described with reference to Figure 1.

[0013] [Inkjet recording device] The inkjet recording apparatus 1 as the image forming system of this embodiment uses an inkjet recording method in which ink is ejected to form an image on a sheet, and is a so-called sheet-fed inkjet recording apparatus that forms an ink image on a sheet using two liquids: a reaction liquid and ink. The sheet may be any recording material that can accept ink, such as paper such as plain paper or cardboard, plastic film such as an overhead projector sheet, specially shaped sheets such as envelopes or index paper, or cloth.

[0014] 1, the inkjet recording apparatus of this embodiment includes a feeding module 1000, a printing module 2000, a drying module 3000, a fixing module 4000, a cooling module 5000, an inverting module 6000, and a stacking module 7000. The sheet S supplied from the feeding module 1000 undergoes various processes as it is transported along the transport path within each module, and is finally discharged to the stacking module 7000.

[0015] The feeding module 1000, printing module 2000, drying module 3000, fixing module 4000, cooling module 5000, reversing module 6000, and stacking module 7000 may each have separate housings that are connected to form an inkjet recording apparatus, or the feeding module 1000, printing module 2000, drying module 3000, fixing module 4000, cooling module 5000, reversing module 6000, and stacking module 7000 may be arranged in a single housing.

[0016] The feeding module 1000 has storage cabinets 1100a, 1100b, and 1100c for storing sheets S, and the storage cabinets 1100a to 1100c are provided so that they can be pulled out toward the front of the apparatus to store the sheets S. The sheets S are fed one by one in each of the storage cabinets 1100a to 1100c by a separation belt and a transport roller, and are transported to the print module 2000. The number of storage cabinets 1100a to 1100c is not limited to three, and there may be one, two, four or more.

[0017] The print module 2000, which serves as an image forming unit, includes a pre-imaging registration correction unit (not shown), a print belt unit 2010, and a recording unit 2020. The sheet S conveyed from the feeding module 1000 has its tilt and position corrected by the pre-imaging registration correction unit before being conveyed to the print belt unit 2010. The recording unit 2020 is positioned opposite the print belt unit 2010 with respect to the conveyance path. The recording unit 2020 is an inkjet recording unit that forms an image by ejecting ink onto the conveyed sheet S from above using a recording head. Multiple recording heads that eject ink are arranged along the conveyance direction. In this embodiment, the unit has a total of five line-type recording heads corresponding to the four colors of Y (yellow), M (magenta), C (cyan), and Bk (black), as well as reaction liquids. The sheet S is adsorbed and conveyed by the print belt unit 2010, ensuring clearance between the sheet S and the recording heads.

[0018] The number of ink colors and recording heads is not limited to the five mentioned above. The inkjet method can be a method using a heating element, a piezoelectric element, an electrostatic element, or a MEMS (Micro Electro Mechanical Systems) element. Each color of ink is supplied to the recording head from an ink tank (not shown) via an ink tube. The ink contains 0.1% to 20.0% by mass of a resin component, water, a water-soluble organic solvent, coloring material, wax, additives, etc., based on the total mass of the ink.

[0019] When the sheet S on which an image is formed by the recording unit 2020 is transported by the print belt unit 2010, the misalignment and color density of the image formed on the sheet S are detected by an inline scanner (not shown) arranged downstream of the recording unit 2020 in the transport direction of the sheet S. Based on the misalignment and color density of the image, the image to be formed on the sheet S, its density, etc. are corrected.

[0020] The drying module 3000, which serves as a drying device, includes a decoupling section 3200, a drying belt unit 3300, and a hot air blowing section 3400. The drying module 3000 reduces the liquid content of the ink and reaction liquid applied to the sheet S to improve the fixation of the ink to the sheet S by the subsequent fixing module 4000. The sheet S on which an image has been formed is transported to the decoupling section 3200 disposed within the drying module 3000. In the decoupling section 3200, frictional force is generated between the sheet S and the belt by the wind pressure of air blown from above, causing the sheet S to be transported by the belt. In this way, the sheet S placed on the belt is transported by frictional force, thereby preventing the sheet S from shifting as it is transported between the print belt unit 2010 and the decoupling section 3200. The sheet S transported from the decoupling section 3200 is adsorbed and transported by the drying belt unit 3300, and the ink and reaction liquid applied to the sheet S are dried by blowing hot air from the hot air blowing section 3400 arranged above the belt.

[0021] In this way, the drying module 3000 heats the ink and reaction liquid applied to the sheet S, promoting evaporation of the water, thereby preventing so-called cockling, in which ink splatters on the sheet S and leaves a fringe-like line around the periphery. The drying module 3000 may be any device capable of heat drying, but a hot air dryer or heater is preferred. Heating by an electric heating wire or infrared heater is preferred from the standpoint of safety and energy efficiency. The drying method may also be a combination of a method of applying hot air, a method of irradiating the surface of the sheet S with electromagnetic waves (such as ultraviolet or infrared rays), or a conductive heat transfer method using contact with a heating element.

[0022] The fixing module 4000 as a fixing system has a fixing belt unit 4100 as a fixing device. The fixing belt unit 4100 fixes ink onto the sheet S by passing the sheet S conveyed from the drying module 3000 between a heated upper belt unit and a lower belt unit. The fixing belt unit 4100 will be described in detail later.

[0023] The cooling module 5000 has a plurality of cooling sections 5001, which cool the high-temperature sheet S transported from the fixing module 4000. The cooling sections 5001, for example, use a fan to draw outside air into a cooling box to increase the pressure inside the cooling box, and then cool the sheet S by blowing air out of the cooling box through a nozzle due to the pressure onto the sheet S. The cooling sections 5001 are arranged on both sides of the transport path of the sheet S, and cool both sides of the sheet S.

[0024] The cooling module 5000 is provided with a transport path switching unit 5002. The transport path switching unit 5002 switches the transport path of the sheet S depending on whether the sheet S is transported to the reversing module 6000 or to a double-sided transport path for double-sided printing, in which images are formed on both sides of the sheet S.

[0025] The reversing module 6000 has a reversing section 6400. The reversing section 6400 reverses the sheet S being conveyed, changing the orientation of the sheet S when it is discharged to the stacking module 7000. The stacking module 7000 has a top tray 7200 and a stacking section 7500, and stacks the sheet S conveyed from the reversing module 6000.

[0026] During double-sided printing, the sheet S is conveyed to a conveyance path below the cooling module 5000 by the conveyance path switching unit 5002. The sheet S then passes through a double-sided conveyance path including the fixing module 4000, the drying module 3000, the print module 2000, and the feeding module 1000, and is returned to the print module 2000. The double-sided conveyance section of the fixing module 4000 is provided with an inverting unit 4200 that inverts the sheet S. An image is formed with ink on the other side of the sheet S that has been returned to the print module 2000, and the sheet S is then discharged to the stacking module 7000 via the drying module 3000, the fixing module 4000, the cooling module 5000, and the inverting module 6000.

[0027] [Fixing module] Next, the fixing module 4000 will be described in detail with reference to FIG. 2. FIG. 2 is a schematic diagram showing the fixing module 4000. A fixing belt unit 4100 serving as a fixing device is provided above the fixing module 4000. The fixing belt unit 4100 has a substantially linear sheet transport path 4100a for receiving the sheet S discharged from the drying module 3000, performing fixing, and then delivering the sheet S to the cooling module 5000 (see FIG. 1). In each drawing, the front side of the inkjet recording system 100 is represented as the front direction F, the rear side as the rear direction B, the right side as the right direction R, the left side as the left direction L, the upper side as the upward direction U, and the lower side as the downward direction D. An operation unit (not shown) operated by an operator is provided at the front side of the inkjet recording system 100.

[0028] The fixing belt unit 4100 includes an upper belt unit 10 and a lower belt unit 20. The upper belt unit 10 is disposed vertically above the lower belt unit 20. The upper belt unit 10 includes an upper belt 30, which is an example of a belt and a first belt, and a tension roller 410 (a tension member, a first tension member) that applies tension to the upper belt 30. That is, the upper belt unit 10 is an example of a belt unit (a first belt unit) and detachably includes the upper belt 30 that conveys the sheet S. The lower belt unit 20 is an example of a second belt unit and includes a lower belt 40, which is an example of a nip portion forming member and a second belt, a tension roller 420 (a second tension member) that applies tension to the lower belt 40, and a pad 428 with an arc-shaped curved surface. The pad 428 is disposed so as to form a nip with the upper belt 30 via the lower belt 40.

[0029] The sheet S is conveyed while being sandwiched in the nip between the upper belt unit 10 and the lower belt unit 20. That is, as will be described later, the lower belt 40 is disposed opposite the upper belt unit 10 when the upper door unit 43 is in the closed position and the upper belt unit 10 is in the upper storage position. At this time, the lower belt 40 sandwiches and conveys the sheet S together with the upper belt 30. The pressure of the nip is determined by the tension and thickness of the upper belt 30 and the curvature of the pad 428. If the pressure of the nip is too high, ink on the sheet S may adhere to the upper belt unit 10 and peel off from the sheet S. Therefore, the pressure is preferably 1 Pa to 2000 Pa, and more preferably 1 Pa to 200 Pa.

[0030] If the curvature of the pad 428 becomes large, the difference in the conveyance path between the front and back of the sheet S becomes large, which may cause friction between the sheet S and the belt. If the curvature of the pad 428 becomes large, there is a risk that the sheet S itself may memorize the curved shape and curl, so the radius of curvature of the pad 428 is desirably 50 mm or more. Furthermore, from the viewpoint of manufacturing precision, the radius of curvature of the pad 428 is desirably 100,000 mm or less. Due to these constraints, in this embodiment, the tension of the upper belt 30 is set to 200 N, the thickness is set to 0.3 mm, the curvature of the pad 428 is set to 30,000 mm, and the nip pressure is set to approximately 16 Pa.

[0031] This configuration enables uniform pressure application even in a wide nip. As a result, even when the temperature of the upper belt unit 10 is set to the melting point of wax or the boiling point of water, sufficient heat transfer to the sheet S can be achieved by increasing the contact time between the sheet S and the upper belt unit 10. However, if the nip continues to form after sufficient heat transfer, ink may adhere to the upper belt 30 and peel off from the sheet S, or the upper belt 30 may rub against the sheet S, causing image distortion. Therefore, a long contact time is not desirable. Therefore, the time required for the leading edge of the sheet S to enter the nip entrance and exit the nip exit is preferably 0.5 to 4 seconds. In this embodiment, a pad 428 with a length of 900 mm in the sheet transport direction is used, the sheet S is transported at 700 mm / s, and the time required for the leading edge of the sheet S to completely exit the nip exit is approximately 1.3 seconds. Since moisture is necessary for ink to penetrate into the sheet S, it is preferable that the upper belt 30 and the lower belt 40 are impermeable to moisture so that when the sheet becomes hot, the moisture evaporated from the surface of the sheet S does not escape through the upper belt 30 or the lower belt 40 that they come into contact with. In this embodiment, the upper belt 30 and the lower belt 40 are made of a belt material with a thickness of approximately 0.4 mm, which is made of a glass fiber base material with a PTFE (polytetrafluoroethylene) coating on the surface, taking into consideration heat resistance, sliding properties, airtightness, and durability.

[0032] [Fusing belt unit] As described above, the fixing belt unit 4100 as a fixing device includes the upper belt unit 10 and the lower belt unit 20, and the upper belt 30 of the upper belt unit 10 and the lower belt 40 of the lower belt unit 20 are pressed together to form a nip portion N. The sheet S1 is nipped and conveyed at the nip portion N, and pressure and heat are applied thereto, so that an image formed with ink is fixed to the sheet S1.

[0033] The upper belt unit 10 includes an endless upper belt 30 serving as a belt and a first belt, a plurality of tension rollers serving as a plurality of first tension members for tensioning the upper belt 30, and a first heating unit 300. The plurality of tension rollers are an entrance roller 411, an exit roller 412, a drive roller 610, a tension roller 410, a guide roller 413, a guide roller 414, and a steering roller 415. These rollers are arranged in order from upstream of the nip portion N in the rotation direction of the upper belt 30, and a rotation locus of the upper belt 30 is formed thereby.

[0034] A nip portion N exists between the inlet roller 411 and the outlet roller 412. That is, the inlet roller 411 and the outlet roller 412 are arranged to sandwich the nip portion N in the rotation direction of the upper belt 30. The upper belt 30 is stretched by the inlet roller 411 and the outlet roller 412 to form a first tension surface 30a. Each roller is supported by an upper frame 416, which serves as a first frame and is a housing of the upper belt unit 10.

[0035] The lower belt unit 20 includes an endless lower belt 40 as a belt and a second belt, a plurality of tension rollers as second tension members that tension the lower belt 40, and a second heating unit 400. The plurality of tension rollers are a nip upstream guide roller 421, a nip upstream roller 422, a nip downstream roller 423, a drive roller 620, a tension roller 420, a guide roller 424, and a steering roller 426. These rollers are arranged in order from upstream of the nip portion N in the rotation direction of the lower belt 40.

[0036] Furthermore, a nip portion N exists between the nip upstream roller 422 and the nip downstream roller 423, and a pad 428 is disposed therebetween. That is, the nip upstream roller 422 and the nip downstream roller 423 are disposed so as to sandwich the nip portion N in the rotation direction of the lower belt 40. The pad 428, which serves as a support member, abuts against the inner circumferential surface of the lower belt 40 in the region of the nip portion N to support the lower belt 40. In other words, the nip upstream roller 422 and the nip downstream roller 423 are disposed on both sides of the pad 428 in the rotation direction of the lower belt 40. The lower belt 40 is tensioned by the nip upstream roller 422 and the nip downstream roller 423, thereby forming a second tension surface 40a. The nip portion N is formed between the first tension surface 30a and the second tension surface 40a of the upper belt 30. A rotational locus of the lower belt 40 is formed by these rollers and the pad 428. Each roller and pad 428 are supported by a lower frame 427 serving as a second frame that is a housing of the lower belt unit 20.

[0037] The upper belt 30 and the lower belt 40 are driven to rotate by the friction between the roller surface and the inner surface of the belt as the drive rollers 610 and 620 of each belt unit rotate their respective motors (not shown). Furthermore, rotation detection sensors 413a and 424a are disposed on the rotation axes of guide rollers (driven rollers) 413 and 424, which are driven to rotate by the rotation of the upper belt 30 and the lower belt 40. The rotation detection sensors 413a and 424a are elements formed by magnets whose magnetic force switches in the direction of rotation of the guide rollers 413 and 424. The rotation detection sensors 413a and 424a detect the rotation of the upper belt 30 and the lower belt 40 by detecting the change in N-pole and S-pole caused by the rotation using a hall sensor (not shown). While the rotation detection sensors are magnetic elements in this embodiment, transmission-type sensors that detect changes in light blocking and light transmission using a physical flag with an edge in the rotation direction of the driven roller may also be used.

[0038] Next, the first heating unit 300 and the second heating unit 400 of each belt unit will be described. The first heating unit 300 is disposed inside the upper belt 30 and has heating sections 117, 127, and 137. Each heating section has heaters 110a, 110b, 120a, 120b, 130a, and 130b, and reflectors (reflecting plates) 115, 125, and 135 as reflective members (see FIG. 3(a)). The first heating unit 300 is detachable from the first belt unit main body 10a that has the upper belt 30.

[0039] The heaters 110a, 110b, 120a, 120b, 130a, and 130b of the heating units 117, 127, and 137 are arranged in a non-contact manner with the upper belt 30 and along the width direction of the upper belt 30, which intersects with the rotation direction of the upper belt 30, and radiate heat to heat the upper belt 30. The reflectors 115, 125, and 135 are arranged along the width direction and reflect the radiant heat of the heaters 110a, 110b, 120a, 120b, 130a, and 130b toward certain regions of the upper belt 30.

[0040] In this embodiment, the first heating unit 300 of the upper belt unit 10 is disposed inside the upper belt 30 and above the nip portion N, and heats the upper belt 30 from the inside. The first heating unit 300 has a plurality of heating sections 117, 127, and 137. In this embodiment, the three heating sections 117, 127, and 137 are disposed side by side in the rotation direction of the upper belt 30.

[0041] Further, reflectors 115, 125, and 135 are arranged to cover the peripheries of the heaters 110a, 110b, 120a, 120b, 130a, and 130b, respectively, except for the sides facing the upper belt 30. That is, the reflectors 115, 125, and 135 are formed so that the nip portion N sides of the heaters 110a, 110b, 120a, 120b, 130a, and 130b are open and so as to cover both widthwise ends of the heaters 110a, 110b, 120a, 120b, 130a, and 130b. This allows the reflectors 115, 125, and 135 to efficiently irradiate radiant heat from the heaters 110a, 110b, 120a, 120b, 130a, and 130b toward the nip portion N.

[0042] That is, in the upper belt unit 10, a certain region is a region within the range of the nip portion N on the inner circumferential surface of the upper belt 30, and the nip portion N is directly heated by the multiple heating sections 117, 127, and 137. This allows heat to be efficiently transferred to the sheet S passing through the nip portion N. In this embodiment, the region within the range of the nip portion N heated by the multiple heating sections 117, 127, and 137 is the inner circumferential surface (lower surface) of the upper belt 30, and is a region located upstream of the center position of the nip portion N in the conveying direction of the sheet S passing through the nip portion N. Furthermore, the input power of the heating sections 117, 127, and 137 is controlled based on a value detected by a temperature sensor 310 that detects the surface temperature of the upper belt 30, and temperature control is performed to maintain the temperature of the upper belt 30 at a predetermined temperature.

[0043] The second heating unit 4060b is disposed inside the lower belt 40 and has heating parts 147 and 157. Each heating part has heaters 140a, 140b, 150a, and 150b, and reflectors (reflecting plates) 145 and 155 as reflective members (see FIG. 3(a)). The second heating unit 400 is detachable from the second belt unit main body 20a having the lower belt 40.

[0044] The heaters 140a, 140b, 150a, and 150b of the heating units 147 and 157 are arranged in a non-contact manner with the lower belt 40 and along the width direction of the lower belt 40, which intersects with the rotation direction of the lower belt 40, and radiate heat to heat the lower belt 40. The reflectors 145 and 155 are arranged along the width direction and reflect the radiant heat of the heaters 140a, 140b, 150a, and 150b toward a certain region of the lower belt 40.

[0045] In this embodiment, the second heating unit 400 of the lower belt unit 20 is disposed inside the lower belt 40 and below the nip portion N, and heats the lower belt 40 from the inside. The second heating unit 400 has a plurality of heating sections 147, 157. In this embodiment, the two heating sections 147, 157 are disposed side by side in the rotation direction of the lower belt 40.

[0046] Furthermore, reflectors 145 and 155 are arranged to cover the peripheries of the heaters 140a, 140b, 150a, and 150b except for the sides facing the lower belt 40. That is, the reflectors 145 and 155 are formed so that the bottoms of the heaters 140a, 140b, 150a, and 150b are open and so that they cover both widthwise ends of the heaters 140a, 140b, 150a, and 150b. This allows the reflectors 145 and 155 to efficiently irradiate the radiant heat from the heaters 140a, 140b, 150a, and 150b toward the lower portion of the lower belt 40.

[0047] That is, in the lower belt unit 20, a certain region is a region of the inner circumferential surface of the lower belt 40 that is outside the nip portion N, and in this embodiment, this region is the lower portion of the lower belt 40. Specifically, the region heated by the multiple heating sections 147, 157 is the inner circumferential surface (lower surface portion) of the lower belt 40 between the guide roller 424 and the guide roller 425 with respect to the rotation direction of the lower belt 40. That is, the certain region of the lower belt unit 20 is the surface on which the lower belt 40 is stretched in a substantially horizontal direction between the guide roller 424 and the guide roller 425. As described above, the lower belt unit 20 is provided with the pad 428 at a position corresponding to the nip portion N, and therefore cannot directly heat the nip portion N as in the upper belt unit 10. For this reason, by arranging the multiple heating sections 147, 157 facing the above-mentioned region of the lower belt 40, the lower belt 40 is efficiently directly heated.

[0048] The region of the lower belt 40 heated by the multiple heating sections 147, 157 is located downstream of the center position between the guide roller 425 and the tension roller 420, which tension the lower portion of the lower belt 40, in the rotation direction of the lower belt 40. Therefore, the multiple heating sections 147, 157 can heat the lower belt 40 at a position relatively close to the nip portion N, and can efficiently transfer heat to the sheet S passing through the nip portion N. Furthermore, the input power of the heating sections 147, 157 is controlled based on the value detected by a temperature sensor 320 that detects the surface temperature of the lower belt 40, and temperature control is performed to maintain the temperature of the lower belt 40 at a predetermined temperature.

[0049] Furthermore, when the rotation detection sensors 413a and 424a detect that the belts have stopped rotating, the heating units 117, 127, 137, 147 and 157 are set to stop heating. This makes it possible to prevent localized heating that would occur if the upper belt 30 and the lower belt 40 are heated while stopped.

[0050] [Heating section] Next, the heating units 117, 127, 137, 147, and 157 will be described in detail with reference to Figures 3(a) and (b). Figure 3(a) is an enlarged cross-sectional view of the periphery of the heating units 117, 127, 137, 147, and 157 of the fixing belt unit 4100, and Figure 3(b) is a cross-sectional view of the heaters 110a and 110b and the reflector 115. Note that the heating units 117, 127, 137, 147, and 157 provided in the upper belt unit 10 and the lower belt unit 20, respectively, basically have the same configuration, and therefore the common configuration will be described by using the heating unit 117 as a representative.

[0051] The heating unit 117 has two heaters 110a and 110b with different maximum powers. The heaters 110a and 110b have their widthwise ends supported by support parts (not shown). In this embodiment, the heaters 110a and 110b are halogen heaters, and the heater 110a is a heater that can be supplied with higher power than the heater 110b. That is, the heater 110a corresponds to a first heater, and the heater 110b corresponds to a second heater that has lower power than the heater 110a.

[0052] The heaters 110a and 110b are covered with reflectors 115, and heat the upper belt 30 directly below the heaters 110a and 110b. The reflectors 115 are made of, for example, a mirror-finished aluminum member, and reflect the light generated from the heaters 110a and 110b to concentrate the light on a certain area of ​​the upper belt 30.

[0053] As shown in FIG. 3(b), the reflector 115 has a shape that is a part of a parabola. The reflector 115 is a parabola with a reflector vertex 115a as its vertex. The parabolic shape formed from the reflector vertex 115a toward the upper belt 30 extends to the reflector parabola end point 115c, and then extends almost vertically toward the upper belt 30 to form a reflector straight portion 115b. The shape of the reflector 115 may be approximated by a polygonal shape consisting of multiple line segments due to constraints on component manufacturing. It is preferable to arrange the reflector straight portion 115b as short as possible (even to zero), but it is provided to ensure space for arranging the temperature sensor 210, which will be described later.

[0054] The heaters 110a and 110b are arranged closer to the upper belt 30 than the reflector focus 115d of a parabola formed by the reflector vertex 115a and the reflector parabola end point 115c, and are arranged with a difference in height in the vertical direction. Also, the heater 110a, which can be turned on and has high power, is arranged at a position shifted downward from the heater 110b.

[0055] That is, the cross-sectional shape of the reflector 115 has a reflector apex 115a, a reflector parabola end point 115c, and a reflector straight portion 115b extending from the reflector parabola end point 115c toward the upper belt 30. With respect to a focus 115d of an approximate parabola that passes through the reflector apex 115a and the reflector parabola end point 115c, the two heaters 110a and 110b are each disposed closer to the upper belt 30 than the focus 115d, and the two heaters 110a and 110b are each located at a different distance from the upper belt 30.

[0056] The positions of the heaters 110a and 110b can be defined as follows. Note that the heaters 110a and 110b each satisfy the following requirements, and therefore the heater 110b will be described below as a representative. First, let us define an incident ray λ1 as a line drawn from the heater 110b toward the reflector 115 in a direction that is perpendicular to a perpendicular line dropped from the heater 110b to the upper belt 30 and perpendicular to the width direction of the upper belt 30, which intersects with the rotation direction of the upper belt 30. Let us define a first intersection P1 as the point where the incident ray λ1 intersects with the inner surface of the reflector 115. Let us define a reflected ray λ2 as a line drawn from the first intersection P1 so that the angle of incidence and the angle of reflection are the same in relation to the incident ray λ1. Let us define a second intersection P2 as the point where the reflected ray λ1 intersects with the upper belt 30. A third intersection point P3 is a point where a perpendicular line V dropped from the first intersection point P1 to the upper belt 30 intersects with the upper belt 30. In this case, the heater 110b is disposed such that the second intersection point P2 is closer to the heater 110b than the third intersection point P3 in the rotation direction of the upper belt 30.

[0057] By arranging the heaters 110a and 110b at a position closer to the upper belt 30 than the reflector focal point 115d, it is possible to reduce the proportion of light generated from the heaters 110a and 110b that is reflected by the reflector 115, thereby improving the heating efficiency of the upper belt 30. On the other hand, if the heaters are arranged too close to the upper belt 30, the heating efficiency can be improved, but the unevenness of the intensity distribution of the light irradiated onto the upper belt 30 becomes large. Furthermore, by arranging the two heaters 110a and 110b at different heights in the vertical direction, it is possible to differentiate the unevenness of the light concentration distribution when the heaters 110a and 110b are turned on individually, and therefore it is possible to prevent the light concentration distribution from concentrating locally at one location when the two heaters 110a and 110b are turned on simultaneously.

[0058] Furthermore, in this embodiment, there is provided a temperature sensor 210, which is a safety sensor that detects the temperature of the area of ​​the upper belt 30 heated by the heaters 110a and 110b and detects whether the temperature exceeds a threshold value of 200°C. The temperature sensor 210 is arranged near the outside of the reflector 115 because it is necessary to directly detect the temperature of the area (belt area) of the upper belt 30 heated by the heaters 110a and 110b. That is, the temperature sensor 210 as a temperature detection unit is arranged at a position where it can detect the temperature of a certain area of ​​the upper belt 30 from the outside of the reflector 115, and detects the temperature of the upper belt 30.

[0059] The threshold temperature of 200°C is set to prevent deformation of the upper belt 30 and is determined depending on the material of the upper belt 30, so this is not a limiting factor. Normally, when the upper belt 30 is rotating and the heaters 110a and 110b are temperature-controlled, the temperature sensor 210 maintains a temperature below approximately 130°C and does not detect temperatures above 200°C. On the other hand, if the rotation detection sensor 413a malfunctions and the upper belt 30 stops rotating, the area around the detection position of the temperature sensor 210 continues to heat locally, resulting in a high temperature. Therefore, by providing the temperature sensor 210, even in the event of such a malfunction, the temperature sensor 210 can directly detect the hottest point on the upper belt 30. This allows the device to be stopped before the upper belt 30 is damaged by deformation or other factors, resulting in a safer fixing device.

[0060] Although the reflector 115 is subjected to the above-mentioned mirror finish or the like to increase reflection efficiency, a portion of the light irradiated by the heaters 110a and 110b is absorbed by the reflector 115 itself, causing the temperature of the reflector 115 to rise. Therefore, there is a risk that the temperature of the reflector 115 will eventually rise to approximately 300°C. Meanwhile, the reflector 115 heated to a high temperature also heats the surrounding atmosphere, and the temperature of the temperature sensor 210 arranged near the reflector 115 may also rise to approximately 200°C. The temperature sensor 210 has a heat resistance temperature of approximately 110°C, and if the temperature sensor 210 arranged near the reflector 115 becomes too high, there is a risk that the temperature detection accuracy of the temperature sensor 210 will decrease. For this reason, in this embodiment, the following measures are implemented to suppress the temperature rise of the temperature sensor 210.

[0061] [Temperature sensor position relative to heater] 3(a), in this embodiment, temperature sensors 210, 220, 230, 240, and 250 serving as temperature detection units are disposed adjacent to reflectors 115, 125, 135, 145, and 155, respectively. That is, temperature sensor 210 is disposed adjacent to reflector 115, temperature sensor 220 is disposed adjacent to reflector 125, temperature sensor 230 is disposed adjacent to reflector 135, temperature sensor 240 is disposed adjacent to reflector 145, and temperature sensor 250 is disposed adjacent to reflector 155. Furthermore, detection windows are formed in the reflectors 115, 125, 135, 145, and 155 so that the temperature sensors 210, 220, 230, 240, and 250 can detect the temperature of the upper belt 30 or the lower belt 40 in a non-contact manner. The detection window is, for example, an opening or a notch, and is formed so that the detection surface of each temperature sensor faces the belt in a direction oblique to the surface of the belt.

[0062] Furthermore, the temperature sensor 210 is disposed at a position closer to the heater 110b, which has lower power than the heater 110a, than to the heater 110a. That is, in this embodiment, the temperature sensor 210 is disposed on one of the side surfaces of the reflector 115 that is closer to the heater 110b. Because the heater 110b has lower input power than the heater 110a, a temperature rise on the side surface of the reflector 115 closer to the heater 110b is suppressed. Therefore, by disposing the temperature sensor 210 near this side surface, a temperature rise in the temperature sensor 210 can be suppressed.

[0063] In this embodiment, a plurality of heating units 117, 127, and 137 are provided in parallel to the upper belt unit 10. Therefore, a temperature sensor 210 serving as a temperature detection unit provided in the heating unit 117 and a temperature sensor 220 provided in the heating unit 127 are both disposed between the reflectors 115 and 125. The temperature sensors 210 and 220 are disposed near the side surfaces of the reflectors 115 and 125, respectively, close to the heaters 110b and 120b, which have low power consumption.

[0064] A more detailed description will be given. First, the reflector 115 serving as the first reflecting member of the heating unit 117 reflects radiant heat from the heaters 110a and 110b serving as the first and second heaters toward the first region of the upper belt 30. The temperature sensor 210 serving as the first temperature detecting unit is disposed at a position where it can detect the temperature of the upper belt 30 in the first region. On the other hand, the heater 120a serving as the third heater and the heater 120b serving as the fourth heater of the heating unit 127 are disposed in a non-contact state with the upper belt 30 and heat the upper belt 30 by radiating heat. The heater 120b has lower power than the heater 120a. The reflector 125 serving as the second reflecting member has the heaters 120a and 120b disposed inside and reflects radiant heat from the heaters 120a and 120b toward the second region of the upper belt 30. The temperature sensor 220 as the second temperature detection unit is disposed at a position where it can detect the temperature of the upper belt 30 in the second region from outside the reflector 125, and detects the temperature of the upper belt 30.

[0065] In this configuration, the temperature sensor 210 of the heating unit 117 is disposed between the reflectors 115 and 125 in relation to the rotation direction of the upper belt 30, at a position closer to the heater 110b than to the heater 110a, and closer to the heater 120b than to the heater 120a. The temperature sensor 220 of the heating unit 127 is disposed between the reflectors 115 and 125 in relation to the rotation direction of the upper belt 30, at a position closer to the heater 110b than to the heater 110a, and closer to the heater 120b than to the heater 120a. In other words, the temperature sensors 210 and 220 are disposed between the reflectors 115 and 125, and the heaters 110b and 120b are disposed closer to the region between the reflectors 115 and 125 than the heaters 110a and 120a, respectively. This makes it possible to suppress the temperature rise of the temperature sensors 210 and 220.

[0066] On the other hand, temperature sensor 230 as a temperature detection unit provided in heating unit 137 is disposed between reflectors 125 and 135. Temperature sensor 230 is disposed near the side surface of reflector 135, close to heater 130b, which has lower power than heater 130a. That is, temperature sensor 230 is also disposed at a position closer to heater 130b, which serves as a second heater and has lower power than heater 130a, than to heater 130a, which serves as a first heater. However, between temperature sensor 230 and the heaters 120a and 120b of heating unit 127 adjacent to it, the one closest to it is heater 120a, which has higher power.

[0067] As described above, in this embodiment, when three or more heating units are installed side by side, it is not possible to arrange all the temperature sensors so that they are close to the heaters on the low-power side, but they are arranged so that at least the heaters of the heating units 127, 137 that are closest to the temperature sensor 230 are not both high-power heaters 120a, 130a. In other words, by designating at least one of the heaters of the heating units 127, 137 that are close to the temperature sensor 230 as a low-power heater, it is possible to suppress the temperature rise of the temperature sensor 230.

[0068] Note that, similarly to the relationship between the heating sections 117 and 127, the heating sections 147 and 157 arranged in the lower belt unit 20 are also provided with temperature sensors 240 and 250 as temperature detection sections. That is, the temperature sensor 240 provided in the heating section 147 and the temperature sensor 250 provided in the heating section 157 are both arranged between the reflectors 145 and 155. The temperature sensors 240 and 250 are also arranged near the side surfaces of the reflectors 145 and 155, closer to the heaters 140b and 150b, which have lower power than the heaters 140a and 140a. This makes it possible to suppress the temperature rise of the temperature sensors 240 and 250.

[0069] [Blowing air into the space where the temperature sensor is located] In this embodiment, in addition to the above-mentioned measures, fans 1500, 1501, and 1502 are used to blow air into the spaces in which the temperature sensors 210, 220, 230, 240, and 250 are disposed, thereby suppressing the temperature rise of the temperature sensors 210, 220, and 230. This point will be explained using FIGS. 3(a), 4, and 5. The fans 1500, 1501, and 1502 that generate airflow are connected to the front side plates 38 and 48, respectively, as shown in FIG. 4. In this embodiment, the fans 1500, 1501, and 1502 are disposed outside the upper belt 30 and the lower belt 40 in the width direction. Furthermore, the fans 1500, 1501, and 1502 are disposed only on one side of both ends of the upper belt 30 and the lower belt 40 in the width direction. The front side plate 38 is the side plate on the front side of the upper belt unit 10. The front side plate 38 is provided with a grip portion 38a, and as will be described later, a user grips the grip portion 38a to perform operations when clearing a jammed sheet S or performing maintenance on the device. The front side plate 48 is a side plate on the front side of the lower belt unit 20.

[0070] As shown in FIG. 3A, the upper belt unit 10 and the lower belt unit 20 are provided with flow path forming portions 161a, 161b, and 161c that form flow paths 160a, 160b, and 160c through which airflows generated by fans 1500, 1501, and 1502 flow. Temperature sensors 210, 220, 230, 240, and 250 are disposed in the flow paths 160a, 160b, and 160c, respectively. That is, the temperature sensors 210 and 220 are disposed in the flow path 160a, the temperature sensor 230 in the flow path 160b, and the temperature sensors 240 and 250 in the flow path 160c. The flow path forming portions 161a, 161b, and 161c may each be formed of a single member or multiple members. Furthermore, a portion of the reflector of the adjacent heating unit may also function as a flow path forming portion. In this embodiment, each flow path forming member is configured as follows.

[0071] The flow path forming portion 161a that forms the flow path 160a has a front side plate 38 as a first cover portion, a lower side plate 162 as a second cover portion, an upper side plate 163 as a third cover portion, and a rear side plate 37 (FIG. 5) as a fourth cover portion. The front side plate 38 covers the upstream side of the temperature sensors 210 and 220 in terms of the direction of the airflow flowing through the flow path 160a. The lower side plate 162 covers the surface of the upper belt 30 that is irradiated with radiant heat from the heaters 110a, 110b, 120a, and 120b (the nip portion N side, the lower side in FIGS. 3(a) and 5) rather than the temperature sensors 210 and 220. The upper plate 163 covers the side opposite the surface of the upper belt 30 from the temperature sensors 210 and 220 (the opposite side to the nip portion N, the upper side in FIGS. 3(a) and 5). The rear side plate 37 is a side plate on the rear side of the upper belt unit 10, and covers the downstream side of the temperature sensors 210 and 220 in the direction of the airflow flowing through the flow path 160a.

[0072] The side surfaces of the reflectors 115, 125 facing the temperature sensors 210, 220 constitute a flow path forming portion 161a. The reflectors 115, 125 and the upper plate 163 are connected by connecting plates 116, 126, respectively, and the connecting plates 116, 126 also constitute the flow path forming portion 161a. The lower plate 162, the upper plate 163, and the connecting plates 116, 126 are each arranged along the width direction of the upper belt 30 and connected to the front plate 38 and the rear plate 37. Therefore, the flow path forming portion 161a is formed by the front plate 38, the rear plate 37, the lower plate 162, the upper plate 163, the reflectors 115, 125, and the connecting plates 116, 126, and the space surrounded by these components constitutes a flow path 160a. The lower plate 162 , the upper plate 163 , and the connecting plates 116 and 126 do not necessarily have to be connected to the rear plate 37 .

[0073] Similarly, the flow path forming portion 161b that forms the flow path 160b has a front side plate 38 as a first cover portion, a lower side plate 164 as a second cover portion, an upper plate 163 as a third cover portion, and a rear side plate 37 as a fourth cover portion (FIG. 5). The front side plate 38 covers the upstream side of the temperature sensor 23 in the direction of the airflow flowing through the flow path 160b. The lower plate 164 covers the surface of the upper belt 30 that is irradiated with radiant heat from the heaters 130a and 130b more than the temperature sensor 230 (the nip portion N side, the lower side in FIGS. 3(a) and 5). The upper plate 163 is in communication with the flow path forming portion 161a and covers the opposite side of the surface of the upper belt 30 from the temperature sensor 230 (the opposite side from the nip portion N, the upper side in FIGS. 3(a) and 5). The rear side plate 37 covers the downstream side of the temperature sensor 230 in the direction of the airflow flowing through the flow path 160b.

[0074] The side surfaces of the reflectors 125, 135 facing the temperature sensor 230 constitute the flow path forming portion 161b. The reflector 135 and the upper plate 163 are connected by a connecting plate 136, and the connecting plate 136 also constitutes the flow path forming portion 161b. The connecting plate 126 also constitutes the flow path forming portion 161b. The lower plate 164, the upper plate 163, and the connecting plate 136 are each arranged along the width direction of the upper belt 30 and connected to the front plate 38 and the rear plate 37. Therefore, the flow path forming portion 161b is formed by the front plate 38, the rear plate 37, the lower plate 164, the upper plate 163, the reflectors 125, 135, and the connecting plates 136, 136, and the space surrounded by these components constitutes the flow path 160b. The connecting plate 136 does not have to be connected to the rear plate 37 either. Furthermore, the connecting plate 126 may be omitted, and the flow paths 160a and 160b may be communicated between the reflector 125 and the upper plate 163.

[0075] Similarly, the flow path forming portion 161c that forms the flow path 160c has a front side plate 48 as a first cover portion, a lower plate 165 as a second cover portion, an upper plate 166 as a third cover portion, and a rear side plate (not shown) as a fourth cover portion. The front side plate 48 is a side plate on the front side of the lower belt unit 20, and covers the upstream side of the temperature sensors 240 and 250 in terms of the direction of the airflow flowing through the flow path 160c. The lower plate 165 covers the surface of the lower belt 40 that is irradiated with radiant heat from the heaters 140a, 140b, 150a, and 150b relative to the temperature sensors 240 and 250 (the opposite side to the nip portion N, the lower side in FIGS. 3(a) and 5). The upper plate 166 covers the opposite side of the surface of the lower belt 40 relative to the temperature sensors 240 and 250 (the nip portion N side, the upper side in FIGS. 3(a) and 5). The rear side plate is a side plate on the rear side of the lower belt unit 20, and covers the downstream side of the temperature sensors 240 and 250 in the direction of the airflow flowing through the flow path 160c.

[0076] The side surfaces of the reflectors 145, 155 facing the temperature sensors 240, 250 constitute the flow path forming portion 161c. The reflectors 145, 155 and the upper plate 166 are connected by connecting plates 146, 156, respectively, and the connecting plates 146, 156 also constitute the flow path forming portion 161c. The lower plate 165, the upper plate 166, and the connecting plates 146, 156 are each arranged along the width direction of the lower belt 40 and connected to the front plate 48 and the rear plate. Therefore, the flow path forming portion 161c is formed by the front plate 48, the rear plate, the lower plate 165, the upper plate 166, the reflectors 145, 155, and the connecting plates 146, 156, and the space surrounded by these components constitutes the flow path 160c. The lower plate 165, the upper plate 166, and the connecting plates 146, 156 do not necessarily have to be connected to the rear plate.

[0077] Fans 1500, 1501, and 1502 are connected to front side plates 38 and 48, respectively. Fan 1500 is connected to flow path forming portion 161a and sends air to flow path 160a. Fan 1501 is connected to flow path forming portion 161b and sends air to flow path 160b. Fan 1502 is connected to flow path forming portion 161c and sends air to flow path 160c.

[0078] A first flow path inlet unit 167a serving as a second duct unit is connected to the upstream side (front side) of the flow path forming portion 161a in the airflow direction, i.e., the front side plate 38. The first flow path inlet unit 167a is connected to a second flow path inlet unit 168a serving as a first duct unit provided on the upper frame 416. A fan 1500 is connected to the second flow path inlet unit 168a. The second flow path inlet unit 168a is connected to the fan 1500 and directs the airflow generated by the fan 1500. The first flow path inlet unit 167a is connected to the front side plate 38 and the second flow path inlet unit 168a and directs the airflow generated by the fan 1500 into the flow path forming portion 161a.

[0079] 5, the airflow generated by the fan 1500 is sent into the flow path forming portion 161a via the second flow path inlet unit 168a and the first flow path inlet unit 167a, and flows through the flow path 160a as shown by arrow 1500a. Meanwhile, a flow path outlet 169b is provided on the downstream side (rear side) of the flow path forming portion 161a in the direction of the airflow, i.e., on the rear plate 37, so that the air that has passed through the flow path 160a can be discharged to the outside of the upper belt unit 10. Also, at least a portion of the temperature sensors 210 and 220 is disposed inside the flow path forming portion 161a.

[0080] Similarly, a first flow path inlet unit 167b serving as a second duct unit is connected to the upstream side (front side) of the flow path forming unit 161b in the airflow direction, i.e., the front side plate 38. The first flow path inlet unit 167b is connected to a second flow path inlet unit 168b serving as a first duct unit provided on the upper frame 416. A fan 1501 is connected to the second flow path inlet unit 168b. The configuration for directing airflow from the fan 1501 into the interior of the flow path forming unit 161b is the same as the configuration for directing airflow from the fan 1500 into the interior a of the flow path forming unit 161a. On the upper belt unit 10 side, the flow path inlet configuration connected to the fans 1500 and 1501 is composed of two members. This is because the first flow path inlet units 167a, 167b and the second flow path inlet units 168a, 168b can be separated from each other during device maintenance, as will be described in detail later.

[0081] On the other hand, on the lower belt unit 20 side, a fan 1502 is connected directly or via a duct to the upstream side (front side) of the flow path forming portion 161b in the airflow direction, i.e., to the front side plate 48. Note that the flow path inlet configuration connected to the fan 1502 on the lower belt unit 20 side may also be configured with two members, similar to the flow path inlet configuration connected to the fans 1500 and 1501 on the upper belt unit 10 side.

[0082] The temperature sensor 210, which detects the temperature of the upper belt 30 heated by the heaters 110a and 110b, is located between the reflectors 115 and 125 and is positioned close to the fan 1500, which will be described later, with respect to the center 2200 of the width direction of the upper belt 30. That is, the temperature sensor 210 is positioned upstream of the center 2200 of the width direction of the upper belt 30 in the direction of airflow caused by the fan 1500. FIG. 5 shows the region (detection region) α of the upper belt 30 detected by the temperature sensor 210. In this embodiment, this detection region α is also positioned upstream of the center 2200 of the width direction of the upper belt 30 in the direction of airflow caused by the fan 1500, which will be described later. The same applies to the other temperature sensors 220, 230, 240, and 250.

[0083] As described above, the temperature sensors 210, 220, 230, 240, and 250 are disposed in the flow paths 160a, 160b, and 160c, respectively. The fans 1500, 1501, and 1502 respectively take in air and send it into the flow path forming portions 161a, 161b, and 161c, forming airflows in the flow paths 160a, 160b, and 160c. The formed airflows then cool the temperature sensors 210, 220, 230, 240, and 250. This makes it possible to suppress a rise in temperature of the temperature sensors 210, 220, 230, 240, and 250.

[0084] Furthermore, when multiple heating units are arranged in the rotation direction of the upper belt 30 or the lower belt 40 as in this embodiment, the temperature sensor is also supplied with heat from the adjacent reflectors, causing the temperature to rise. Therefore, by arranging two temperature sensors 210, 220 or two temperature sensors 240, 250 in one flow path 160a or one flow path 160c as described above, it becomes possible to efficiently cool the temperature sensors with a small number of fans.

[0085] Although the temperature sensors are arranged as described above to minimize the number of fans used and reduce the cross-sectional size of the device, the arrangement of the temperature sensors and the number of fans and flow paths are not limited to the above, and for example, each temperature sensor may have its own flow path. For example, the temperature sensors 240 and 250 of the heating unit 147 or 157, or both, may be arranged on the opposite side from the above (outside the reflector on the opposite side to the position shown in FIG. 3(a)), and a fan and flow path may be added. Furthermore, the temperature sensors 210 and 230 of the heating unit 117 or 137, or both, may be arranged on the opposite side, and a fan and flow path may be added.

[0086] As described above, by appropriately positioning the temperature sensor relative to the heater and blowing air into the space in which the temperature sensor is placed, for example, the amount of heat received by reflector 115 from heaters 110a and 110b is reduced, and by cooling temperature sensor 210 with airflow, the temperature of temperature sensor 210 can be suppressed to approximately 95°C. As a result, temperature sensor 210 can detect temperatures with high accuracy. The same applies to the other temperature sensors 220, 230, 240, and 250.

[0087] In the above description, the fans 1500, 1501, and 1502 are arranged upstream of the flow paths 160a, 160b, and 160c in the airflow direction and are fans that supply air to the flow paths 160a, 160b, and 160c. However, at least one of the fans 1500, 1501, and 1502 may be arranged downstream of the corresponding flow path 160a, 160b, and 160c in the airflow direction and may be a fan that exhausts air from the flow path. Also, at least one of the flow paths may be provided with both a supply fan and an exhaust fan.

[0088] [Jam removal and maintenance] Next, jam removal and maintenance in the fixing module 4000 of this embodiment will be described with reference to FIGS. 6(a) to 6(c). When a sheet becomes jammed or slips in the sheet transport path 4100a (FIG. 1) and the transport timing deviates from the predetermined timing, the device detects the jam. In this case, the sheet S remaining in the sheet transport path 4100a is automatically discharged to a purge tray, but if the remaining sheet cannot be discharged to the purge tray, the user must remove the remaining sheet. The sheet S is conveyed while being sandwiched between the nip portion N of the upper belt unit 10 and the lower belt unit 20. If a sheet S remains in the nip portion N when a jam occurs, the user must open the nip portion N and remove the remaining sheet.

[0089] For this reason, either the upper belt unit 10 or the lower belt unit 20 is movable relative to the other belt unit between a nip position where the upper belt 30 and the lower belt 40 form a nip portion N, and a spaced position where the upper belt 30 and the lower belt 40 are spaced apart from the nip position. In this embodiment, the upper belt unit 10 is movable relative to the lower belt unit 20 between the nip position and the spaced position. This will be described in detail below.

[0090] As shown in FIGS. 6(a) to 6(c), the fixing module 4000 has a housing that can be opened in the upward direction U and an upper door unit 43 that serves as a first housing. The upper belt unit 10 of the fixing belt unit 4100 can be housed inside the upper door unit 43, and the upper door unit 43 is configured to be able to open in the upward direction U together with the upper belt unit 10. The upper door unit 43 is rotatably connected to the device main body 44 that serves as a second housing by a support shaft 45 that is provided on the rear side B of the device main body 44. The support shaft 45 that serves as a second rotation support part is provided on the rear side of the device main body 44 in the width direction (front-rear direction) and is provided along the sheet conveying direction (left-right direction). The upper door unit 43 is rotatable relative to the device main body 44 around the support shaft 45.

[0091] The upper door unit 43 has a handle 431 on the front side F of the device body 44, and is rotated and opened by pulling up the handle 431 in the upward direction U. The upper door unit 43 is freely rotatable relative to the device body 44 between a closed position (FIG. 6(a)) and an open position (FIG. 6(b)). In the closed position, the upper belt 30 and the lower belt 40 are in a nip position where they form a nip portion N, and in the open position, the upper belt 30 and the lower belt 40 are in a separated position where they are further apart than the nip position. In this embodiment, the upper door unit 43 is made up of a top plate and side plates, and functions as an upper cover for the device body 44.

[0092] If a jam occurs, the user can lift up the handle 431 of the upper door unit 43 to open the upper door unit 43 upward to the separated position, and remove the sheets S remaining inside the apparatus main body 44 from the front of the apparatus. In this embodiment, to improve the operability when the user opens and closes the upper door unit 43, a gas spring (not shown) is provided, and the gas spring urges the upper door unit 43 toward the open position, thereby maintaining the upper door unit 43 in the open position. When the apparatus is in use, the upper door unit 43 is maintained in the closed position by its own weight, and the nip portion N is formed as described above.

[0093] The upper belt unit 10 is rotatably supported by a support shaft 46 at a first position and a second position relative to the upper door unit 43. The support shaft 46 as the rotation support portion and the first rotation support portion is provided on the rear side in the width direction (front-rear direction) of the upper door unit 43 and is provided along the sheet conveying direction (left-right direction), as shown in FIG. 6(c). The first position (upper storage position) is a position where the upper belt unit 10 is stored inside the upper door unit 43 (FIG. 6(b)). The second position (maintenance position) is a position where at least a part of the upper belt unit 10 is exposed outside the upper door unit 43 more than at the first position (FIG. 6(c)). The upper belt unit 10 is movable from the first position to the second position in the above-mentioned separated position.

[0094] When the device is in use, the upper belt unit 10 is held in the upper storage position by being fixed near the front side of the upper door unit 43 with a holding member such as a screw (not shown). When performing maintenance on the upper belt unit 10, the upper door unit 43 is set to the open position, and the upper belt unit 10 is lowered from the upper door unit 43 around the support shaft 46 by, for example, gripping the grip portion 38a provided on the front side plate 38, and moved to the maintenance position. The maintenance position is a state in which, for example, attachment and detachment of the upper belt 30 to and from the upper belt unit 10 is permitted.

[0095] As described above, on the upper belt unit 10 side, the flow path inlet configuration connected to the fans 1500 and 1501 is composed of two members. That is, the flow path inlet configuration is composed of the first flow path inlet units 167a and 167b and the second flow path inlet units 168a and 168b. If all of the flow path inlet configurations connected to the fans 1500 and 1501 were fixed to the upper frame 416 of the upper belt unit 10, it would be necessary to lower the upper belt unit 10 including the fans 1500 and 1501 during maintenance (FIG. 6(c)), which could result in an increase in the size of the device or a decrease in maintainability.

[0096] 5, in this embodiment, the fans 1500 and 1501 and the second flow path inlet units 168a and 168b are fixed to the upper frame 416, and the second flow path inlet units 168a and 168b and the first flow path inlet units 167a and 167b can be separated by the connection portion 169 during maintenance. That is, the connection portion 169 connects the second flow path inlet units 168a and 168b and the first flow path inlet units 167a and 167b at the upper storage position, and can separate the second flow path inlet units 168a and 168b and the first flow path inlet units 167a and 167b when the upper belt unit 10 moves from the upper storage position to the maintenance position. As a result, during maintenance, the upper belt unit 10 can be lowered from the upper storage position while leaving the fans 1500 and 1501 on the upper door unit 43 side.

[0097] In this embodiment, the joint surface 169a between the second flow path inlet units 168a, 168b and the first flow path inlet units 167a, 167b is inclined in a direction perpendicular to the first tension surface 30a of the upper belt 30 (FIG. 2, sheet conveying direction) in the upper storage position, toward the upstream side of the airflow direction through the flow paths 160a, 160b as it approaches the first tension surface 30a. That is, in FIG. 5, the joint surface 169a at the connection portion 169 is inclined toward the front as it approaches the bottom. By making the joint surface 169a inclined in this way, even if the positions of the second flow path inlet units 168a, 168b and the first flow path inlet units 167a, 167b are slightly misaligned during joining, this misalignment in the direction of inclination can be absorbed, allowing for stable joining. A seal or the like may be provided on the joint surface 169a to improve sealing performance.

[0098] In the present embodiment, the lower belt unit 20 does not need to be separated for maintenance, as described above, and therefore the fan 1502 is directly attached to the front plate 48 of the lower belt unit 20.

[0099] The fans 1500 and 1501 are disposed obliquely above the intake ports of the second flow path inlet units 168a and 168b, and form an airflow obliquely downward. Part of the air blown by the fans 1500 and 1501 leaks out from parts of the flow path forming portions 161a and 161b (for example, the front ends of the reflectors 115 and 125) and hits the lower and side portions of the front plate 38 and the gripping portion 38a. As a result, it is possible to reduce the temperature of the gripping portion 38a, which is gripped and operated when clearing jammed sheets S or performing maintenance on the device.

[0100] [Upper belt unit heater control configuration] Next, a control configuration of the heaters 110a, 110b, 120a, 120b, 130a, and 130b of the upper belt unit 10 will be described with reference to Fig. 7. Fig. 7 is a hardware block diagram of the upper belt unit 10 of this embodiment. The control configuration of the upper belt unit 10 includes a CPU (Central Processing Unit) 1100 as a control unit, a Relay 1200, a power supply 1300 as a power supply unit, a motor 1400 as a drive unit, FETs (Field Effect Transistors) 111, 121, and 131 as voltage adjustment units, overheat detection HW (hardware) 211, 221, and 231 as a threshold determination unit, the heaters 110a, 110b, 120a, 120b, 130a, and 130b, protective temperature sensors 210, 220, and 230, a temperature adjustment temperature sensor 310, and a rotation detection sensor 413a.

[0101] The CPU 1100 controls the driving of the motor 1400. The motor 1400 is a motor that drives the upper belt 30 to rotate, and in this embodiment, drives the drive roller 610 via a drive transmission path (not shown). The motor 1400 starts and stops driving in response to instructions from the CPU 1100.

[0102] The CPU 1100 controls the power supplied to the heaters 110a, 110b, 120a, 120b, 130a, and 130b by driving the FETs 111, 121, and 131 through ON / OFF control. Power is supplied to each of the heaters 110a, 110b, 120a, 120b, 130a, and 130b from a power supply 1300. The FETs 111, 121, and 131 are arranged between the power supply 1300 and the heaters 110a, 110b, 120a, 120b, 130a, and 130b, and adjust the voltage applied to each heater from the power supply 1300 based on the control by the CPU 1100.

[0103] The CPU 1100 adjusts the power supplied to the heaters 110a, 110b, 120a, 120b, 130a, and 130b by feeding back temperature information from the temperature adjustment temperature sensor 310. That is, the CPU 1100 controls the temperature of the upper belt 30 by driving the FETs 111, 121, and 131 based on the temperature detected by the temperature sensor 310 (detection result).

[0104] The overheating detection HWs 211, 221, and 231 can switch between an energized state in which the FETs 111, 121, and 131 can be energized from the power supply 1300 to the heaters 110a, 110b, 120a, 120b, 130a, and 130b, and a cutoff state in which the power supply 1300 is cut off from the heaters 110a, 110b, 120a, 120b, 130a, and 130b. The overheating detection HWs 211, 221, and 231 switch from an energized state to a cutoff state when the temperatures detected by the temperature sensors 210, 220, and 230 are equal to or higher than a threshold. That is, the overheating detection HWs 211, 221, and 231 stop driving the FETs 111, 121, and 131 when the temperatures detected by the temperature sensors 210, 220, and 230 are equal to or higher than a threshold. The threshold value of the excessive temperature rise is a temperature set in accordance with the material of the belt to prevent deformation, and is set to 200° C. in this embodiment, but is not limited to this.

[0105] When any of the overheat detection HWs 211, 221, and 231 detects a temperature of 200°C or higher, it stops control of the corresponding FET 111, 121, or 131. For example, when the overheat detection HW 211 detects the temperature of the temperature sensor 210, it stops control of the FET 111, but the control of the other FETs 121 and 131 is not stopped by the hardware circuit. The CPU 1100 detects the interrupt signal from the overheat detection HW 211 and stops the FETs 121 and 131 by software. Note that, although the FETs are stopped by the CPU in the above explanation, they may also be stopped by the hardware circuit. The rotation detection sensor 413a detects the stop of rotation of the upper belt 30 and shuts off the relay 1200, thereby stopping the heating of the heaters 110a, 110b, 120a, 120b, 130a, and 130b. The CPU 1100 is connected to an operation unit 1401 as a notification unit. The operation unit 1401 is used to operate the inkjet recording apparatus 1 and is, for example, an operation panel with a touch panel that can input and display information. The operation unit 1401 may also be provided with physical buttons such as a start button in addition to the touch panel. In this embodiment, the display unit of the operation unit 1401 has a function of notifying the user of various information, such as error information. Examples of error information include a stop due to excessive temperature rise of the upper belt 30. The CPU 1100 may also notify an external terminal, such as a personal computer connected to the inkjet recording apparatus 1, of various information, such as error information about the fixing belt unit 4100. In this case, the CPU 1100 functions as a notification unit.

[0106] [Upper belt unit fixing control] Next, the fixing control of the upper belt unit 10 will be described with reference to Fig. 8. When the fixing control is started, the CPU 1100 controls the motor 1400 of the upper belt 30 to rotate the upper belt 30. The CPU 1100 also turns on the RELAY 1200 (S101). The CPU 1100 determines whether the upper belt 30 is rotating using the rotation detection sensor 413a (S102). If the CPU 1100 determines that the upper belt 30 is rotating (Y in S102), the process proceeds to S103, and if it determines that the upper belt 30 is not rotating (N in S102), the process proceeds to S105.

[0107] If the answer is Y in S102, the CPU 1100 controls the temperatures of the heaters 110a, 110b, 120a, 120b, 130a, and 130b (S103) based on the temperature values ​​read from the temperature sensor 310. In this embodiment, the CPU 1100 controls the temperatures of the heaters 110a, 110b, 120a, 120b, 130a, and 130b by controlling the duty width of the PWM control signal for the FETs 111, 121, and 131.

[0108] Next, the CPU 1100 determines whether the temperature values ​​read from the temperature sensors 210, 220, and 230 are equal to or greater than the threshold temperature (S104). If the value of at least one of the temperature sensors 210, 220, and 230 is equal to or greater than the threshold temperature (Y in S104), the process proceeds to S105. On the other hand, if the temperature values ​​read by the CPU 1100 from the temperature sensors 210, 220, and 230 are lower than the threshold temperature (N in S104), the process proceeds to S102. In S105, the CPU 1100 turns off the FETs 111, 121, and 131, thereby stopping the heaters 110a, 110b, 120a, 120b, 130a, and 130b.

[0109] If the rotation detection sensor 413a fails and the upper belt 30 stops rotating, it may be determined in S102 that the upper belt 30 is rotating even though it has stopped rotating. In this case, the process proceeds to S103. In S103, the CPU 1100 controls the temperatures of the heaters 110a, 110b, 120a, 120b, 130a, and 130b based on the temperature value read by the temperature sensor 310. Since the upper belt 30 is not rotating, the temperature value read by the temperature sensor 310 remains almost unchanged, and only the temperatures of the portions of the upper belt 30 facing the heating units 117, 127, and 137 rise.

[0110] As a result, in S104, the temperature values ​​read by the CPU 1100 from the temperature sensors 210, 220, and 230 become equal to or greater than the threshold temperature, and the process proceeds to S105. In S105, the CPU 1100 turns off the FETs 111, 121, and 131 to stop the heaters 110a, 110b, 120a, 120b, 130a, and 130b. This makes it possible to stop the heaters from driving before the temperature of the upper belt 30 rises above the threshold temperature.

[0111] [Temperature sensor configuration] Next, the configurations of temperature sensors 210, 220, and 230 will be described using Figures 9(a) to (c). Since temperature sensors 210, 220, and 230 have the same configuration, the following description will focus on temperature sensor 210. Figure 9(a) is an external view of temperature sensor 210, with the upper figure being a plan view and the lower figure being a side view. Figures 9(b) and 9(c) are diagrams explaining the viewing angle of temperature sensor 210.

[0112] Sensor module 3801 is a package with a sensor module built in, mounted on substrate 3800, and has detection window 3802 at the top. Temperature sensor 210 absorbs infrared rays emitted from the object to be measured through detection window 3802 and converts the absorbed infrared energy into an electrical signal, enabling non-contact temperature detection. Temperature sensor 210 is also capable of outputting the results detected by sensor module 3801 from connector 3806. In this embodiment, sensor module 3801, which actually detects temperature, is arranged at the edge of substrate 3800 among the components mounted thereon.

[0113] 9(b) is a diagram schematically showing the field of view of the temperature sensor 210. The detection window 3802 not only allows infrared rays to pass into the sensor module 3801, but also functions as a lens. That is, the temperature sensor 210 has a fixed field of view 3804, and detects the temperature of the measurement object 3803 within the field of view 3804 without contact.

[0114] 9(c) is a diagram for explaining the definition of the viewing angle 3804. The temperature measurement accuracy is defined as 100% when the measurement object 3803 is located on the center line 3805 of the viewing angle 3804. Next, the measurement object 3803 is moved from the center line 3805 without changing the distance from the temperature sensor 210. When the temperature measurement accuracy drops to 50% due to the movement, the angle θ formed by the measurement object 3803 and the center line 3805 is defined as the viewing angle 3804. Note that the value of 50% in this embodiment is merely an example and is not limited to 50%.

[0115] [Heater configuration] Next, the configurations of heaters 110a, 110b, 120a, 120b, 130a, and 130b will be described using Figures 10(a) and 10(b). In this embodiment, heaters 110a, 110b, 120a, 120b, 130a, and 130b have the same back color and only differ in power between the two heaters in one heating unit. Therefore, heater 110a will be described below as a representative. Figure 10(a) is a schematic diagram of heater 110a and upper belt 30 viewed from upstream to downstream in the sheet conveying direction, and a graph showing the radiation intensity of heater 110a at various positions in the belt width direction. The belt width direction is the direction perpendicular to the sheet conveying direction and is shown as the x-axis in the figure. The sheet conveying direction is shown as the y-axis, and the height direction is shown as the z-axis. In this embodiment, the heater 110a is arranged to distribute light so that the radiation intensity is higher in end regions 2501 and 2503 in the belt width direction than in a central region 2502 in the belt width direction, thereby suppressing uneven heating in the belt width direction.

[0116] FIG. 10(b) is a graph showing the relationship between heating time and the temperature of the upper belt 30 when the upper belt 30 is continuously heated by a heater. The horizontal axis represents time, and the vertical axis represents the temperature of the upper belt 30. Graph 2504 shows the temperature increase in end regions 2501 and 2503 in the belt width direction, and graph 2505 shows the temperature increase in the central region 2502 in the belt width direction. Because the light is distributed so that the radiation intensity is higher in the end regions 2501 and 2503 than in the central region 2502, the temperature increase in graph 2504 has a steeper slope. The dashed line 2506 shown in the figure is the limit temperature set to prevent the belt from deforming, and is a temperature determined depending on the material of the belt. For this reason, the threshold for detecting excessive temperature rise is set so that the belt does not exceed the limit temperature of dashed line 2506. Although the heaters 110a, 110b, 120a, 120b, 130a, and 130b have the same configuration, they may have different configurations. For example, of the two heaters in one heating unit, one heater may have the above-mentioned light distribution, and the other heater may have a light distribution with a flat radiation intensity in the belt width direction. Alternatively, both heaters may have a light distribution with a flat radiation intensity. Alternatively, both heaters may have a flat radiation intensity, but may have different lengths.

[0117] [Temperature distribution] Next, the distribution of the ambient temperature in the flow paths where temperature sensors 210, 220, and 230 are located will be described. As described above, temperature sensors 210 and 220 are located between reflectors 115 and 125, and temperature sensor 230 is located between reflectors 125 and 135. Fig. 11 shows the ambient temperature distribution between reflectors 115 and 125. As described in Fig. 5, an airflow is formed between reflectors 115 and 125 from fan 1500 in the direction of arrow 1500a, so that outside air is blown into the area near fan 1500. Therefore, the ambient temperature near fan 1500 becomes lower. Each time the air moves in the direction of the arrow 1500a, the air is heated by the heat of the heaters 110a, 110b and heaters 120a, 120b transmitted through the reflectors 115, 125, so that the ambient temperature at positions farther from the fan 1500 becomes higher.

[0118] Therefore, in this embodiment, as described above, the temperature sensor 210 is disposed upstream of the center 2200 in the width direction of the upper belt 30 in the direction of the airflow generated by the fan 1500. This allows low-temperature air to be directed at the temperature sensor 210, thereby efficiently cooling the temperature sensor 210. The same applies to the other temperature sensors. As described above, in this embodiment, the belt is directly heated using a reflector and a heater, and the temperature of the belt is detected using a non-contact temperature sensor. However, since the temperature sensor is disposed in the airflow path, the temperature sensor can be prevented from becoming too high. As a result, it is possible to prevent a decrease in the detection accuracy of the temperature sensor, which could result in a decrease in the quality of the product, or a decrease in the safety of the device when the temperature sensor is used as a sensor for detecting overheating.

[0119] <Second embodiment> The second embodiment will be described with reference to Figures 12 to 14. In the first embodiment described above, a configuration was described in which one temperature sensor for each heater was used to detect the temperature directly below each heater. In contrast, in this embodiment, a configuration is used in which multiple temperature sensors are used for temperature detection for each heater. Since the other configurations and operations are the same as those of the first embodiment described above, the same configurations are assigned the same reference numerals, and explanations and illustrations will be omitted or simplified. The following description will focus on the points that are different from the first embodiment.

[0120] 12 is an enlarged cross-sectional view showing a portion of the upper belt unit 10A and the lower belt unit 20A of the fixing belt unit 4100A in the inkjet recording apparatus of this embodiment. The difference from the fixing belt unit 4100 (FIG. 2) of the first embodiment is that there are three temperature sensors (temperature sensors 210a, 210b, 210c, 220a, 220b, 220c, 230a, 230b, 230c, 240a, 240b, 240c, 250a, 250b, 250c) for each heater that detect the belt temperature directly below each heater (area irradiated with radiant heat from the heater). That is, in this embodiment, multiple temperature sensors (temperature sensors 210a, 210b, 210c) that detect the temperature of the upper belt 30 directly below the heaters 110a and 110b are arranged along the width direction. Similarly, multiple temperature sensors for detecting the temperatures of the upper belt 30 or the lower belt 40 directly below the other heaters are arranged along the width direction (temperature sensors 220a, 220b, 220c, 230a, 230b, 230c, 240a, 240b, 240c, 250a, 250b, 250c). The rest of the configuration is the same as in the first embodiment.

[0121] [Upper belt unit heater control configuration] 13 is a hardware block diagram of the upper belt unit 10A of this embodiment. Three temperature sensors are provided for each heater to detect the belt temperature directly below the heater. Compared to the block diagram of the first embodiment (FIG. 7), the overheat detection hardware 211, 221, and 231 are modified so that they can control the power supply to the heaters based on inputs from the three temperature sensors.

[0122] [Temperature sensor and fan placement] 14 is a diagram showing the arrangement of the temperature sensors 210a, 210b, and 210c in this embodiment, and the arrangement of the fan 1500. The same applies to the other temperature sensors 220a, 220b, 220c, 230a, 230b, 230c, 240a, 240b, 240c, 250a, 250b, and 250c, so below, only the arrangement of the temperature sensors 210a, 210b, and 210c and the arrangement of the fan 1500 will be described as representative examples.

[0123] The difference from the first embodiment is that the number of temperature sensors that detect the belt temperature directly below each heater has been increased. As in the first embodiment, the temperature sensors 210a, 210b, and 210c are arranged closer to the fan 1500 in the front-to-rear direction (width direction), thereby suppressing temperature increases in the temperature sensors 210a, 210b, and 210c. That is, in this embodiment, all of the temperature sensors 210a, 210b, and 210c are arranged closer to the fan 1500 than the center 2200 of the upper belt 30 in the width direction.

[0124] However, when the lengths of the substrates constituting the temperature sensors 210a, 210b, and 210c are taken into consideration, when arranging the multiple temperature sensors 210a, 210b, and 210c side by side in the width direction, it may be difficult to arrange all of the temperature sensors 210a, 210b, and 210c closer to the fan 1500 than the center 2200 in the width direction of the upper belt 30. In this case, the multiple temperature sensors 210a, 210b, and 210c may be arranged in greater numbers upstream of the center in the width direction of the upper belt 30 than downstream of the center in the width direction with respect to the direction of the airflow flowing through the flow path 160a.

[0125] Furthermore, when the regions of the upper belt 30 detectable by the temperature sensors 210a, 210b, 210c are defined as detection regions αa, αb, αc, the temperature sensors 210a, 210b, 210c may be arranged so that, of the total area of ​​the detection regions αa, αb, αc of the temperature sensors 210a, 210b, 210c, the area upstream of the center in the width direction of the upper belt 30 with respect to the direction of the airflow flowing through the flow path 160a is larger than the area downstream of the center in the width direction. The detection region is the region of the upper belt 30 within the range of the viewing angle 3804 described in FIGS. 9(a) to 9(c).

[0126] Furthermore, if there is a temperature distribution in the width direction of the upper belt 30, a configuration that detects the temperature at the hottest point in the temperature distribution makes it possible to set a threshold that does not directly exceed the limit temperature of the upper belt 30. If it is difficult to detect the hottest point in the temperature distribution, the heater can be stopped before the belt's limit temperature is reached by setting the detection threshold to a different value from the temperature at the temperature sensor position so that the belt's limit temperature is not exceeded. An example of a case in which it is difficult to detect the hottest point in the temperature distribution is when, in a configuration such as this embodiment in which multiple temperature sensors are arranged in the width direction, the temperature sensors are arranged at close intervals, making it physically difficult to detect the temperature at the hottest point in the temperature distribution.

[0127] In this embodiment, by arranging multiple temperature sensors, the heater can be safely stopped even if one temperature sensor fails or experiences other problems. Even in this configuration of this embodiment, the fan 1500 is arranged upstream of the flow path 160a in the direction of the arrow 1500a, and is a fan that supplies air to the flow path 160a. However, the fan may also be a fan that exhausts air downstream in the direction of the arrow 1500a, or both a fan that supplies air and a fan that exhausts air may be provided. When a fan that exhausts air is arranged downstream in the direction of the arrow 1500a, the same effect can be achieved by arranging the temperature sensor far from the fan.

[0128] <Third embodiment> The third embodiment will be described with reference to Fig. 15. In the first embodiment described above, a configuration was described in which a heating unit having heating sections 117, 127, and 137 was arranged inside the upper belt 30. In contrast, in this embodiment, the heating unit is arranged outside the upper belt 30. Since the other configurations and functions are the same as those of the first embodiment described above, the same reference numerals are used for similar configurations, and explanations and illustrations will be omitted or simplified. The following description will focus on the points that are different from the first embodiment.

[0129] 15 is an enlarged cross-sectional view of a portion of the upper belt unit 10B in this embodiment. Since the upper belt unit 10B and the lower belt unit in this embodiment have the same configuration and function, a description of the lower belt unit will be omitted.

[0130] In this embodiment, the heating unit having the heating portions 117, 127, and 137 is disposed outside the upper belt 30. By disposing the heating unit having the heating portions 117, 127, and 137 outside the upper belt 30, it is possible to secure space inside the upper belt unit 10, and the degree of freedom in arranging various components can be increased. On the other hand, there are disadvantages such as an increase in the size of the device and an inability to arrange the nip portion N so as to directly heat it.

[0131] The components (heater, reflector, flow path, temperature sensor) that make up the heating units 117, 127, and 137 are the same as those in the first embodiment. Even when the heating units 117, 127, and 137 are arranged outside the upper belt 30, the same effect as in the first embodiment can be obtained with respect to the temperature rise of the temperature sensors 210, 220, and 230. In the configuration of this embodiment, multiple temperature sensors may be arranged in the width direction, as in the second embodiment.

[0132] <Fourth embodiment> The fourth embodiment will be described with reference to FIGS. 16 to 17(b). In the first embodiment described above, the temperature sensors 210, 220, and 230 are arranged in the flow paths 160a and 160b through which the airflow flows. In contrast, in this embodiment, the temperature sensors 210, 220, and 230 are arranged outside the ends of the heaters in the width direction. Since the other configurations and functions are the same as those of the first embodiment described above, the same components are denoted by the same reference numerals, and their description and illustration will be omitted or simplified. The following description will focus on the differences from the first embodiment. Note that, although the following description will be given of the case where this embodiment is applied to the upper belt unit 10, it can also be applied to the lower belt unit 20.

[0133] In the first embodiment described above, fans 1500 and 1501 are used to create airflows between reflector 115 and reflector 125 and between reflector 125 and reflector 135 where temperature sensors 210, 220, and 230 are disposed, and temperature sensors 210, 220, and 230 are disposed in positions close to fans 1500 and 1501, thereby enabling the temperature sensors to stably detect the temperature of upper belt 30. In this embodiment, such an airflow is not formed, allowing the temperature sensors to stably detect the temperature of upper belt 30. Note that, since no airflow is formed in this embodiment, flow path forming portions 161a and 161b as described in the first embodiment are not provided.

[0134] 16 shows the arrangement of the upper belt 30, heaters 110, 120, 130, and temperature sensors 210, 220, and 230 when viewing the upper belt unit 10C of this embodiment from above. The heaters 110, 120, and 130 correspond to the heaters 110a, 110b, 120a, 120b, 130a, and 130b of the first embodiment, but for ease of explanation, multiple heaters are shown as a single heater. Note that in this embodiment, the temperature sensors 210, 220, and 230 are not arranged between the reflector 115 and the reflector 125 or between the reflector 125 and the reflector 135. Therefore, the arrangement of the heaters 110a, 110b, 120a, 120b, 130a, and 130b may differ from that of the first embodiment. For example, heaters with high power and heaters with low power can be arranged more freely than in the first embodiment. In this embodiment, each heating unit may have one heater.

[0135] The temperature sensors 210, 220, and 230 are arranged to detect the temperatures directly below the heaters 110, 120, and 130, respectively. That is, the temperature sensors 210, 220, and 230 are arranged outside the ends of the heaters 110, 120, and 130 in the width direction, at positions where they can detect the temperature of a certain region of the upper belt 30 from outside a reflector (not shown), and detect the temperature of the upper belt 30.

[0136] 17(a) is a diagram showing the positional relationship between the upper belt 30 and the temperature sensor 210 when viewed from the upstream side to the downstream side in the sheet conveying direction. The temperature sensor 210 is disposed outside the end of the upper belt 30 so as to detect an end region 2501 of the upper belt 30 at an angle. In order to directly view the heating region directly below the heater 110, the temperature sensor 210 is disposed so as not to allow the heater 110 to enter a detection region 2101. The detection region 2101 is the region of the upper belt 30 within the range of the viewing angle 3804 described in FIGS. 9(a) to 9(c).

[0137] When the temperature sensor 210 is positioned in this manner, the depression angle of the temperature sensor 210 relative to the upper belt 30 becomes larger. When the depression angle of the temperature sensor 210 becomes larger, a wider belt area is included in the detection area 2101. Therefore, it is necessary to use a temperature sensor 210 with a narrower detection area 2101, or to provide a margin for detecting excessive temperature rise, taking into account that a wide range of belt temperature is being detected.

[0138] 17(b) is a graph showing the relationship between heating time and belt temperature at each position in the width direction of the upper belt 30 when the upper belt 30 is continuously heated by the heater 110. The horizontal axis represents time, and the vertical axis represents belt temperature. Graph 2201 shows the temperature rise at the end position 2102 (FIG. 16) directly below the heater 110. Graph 2202 shows the temperature rise at the center position 2103 (FIG. 16) directly below the heater 110. The difference in the slope of the temperature rise between graph 2201 and graph 2202 is due to the difference in heater light distribution (the diagram on the right side of FIG. 16).

[0139] In this embodiment, the temperature sensor 210 detects the temperature at the end position 2102, which is the area with the highest rate of temperature increase. Therefore, the limit temperature 2006 of the upper belt 30 and the overheating detection threshold temperature 2204 are the same temperature. Note that the relationship between the limit temperature and the overheating detection threshold temperature in this embodiment is merely an example and is not limited to this. For example, it is also possible to provide a safety margin in the overheating detection threshold temperature 2204 and set it to a value lower than the limit temperature 2206. The configuration of the temperature sensor 210 described above is similar to that of the other temperature sensors 220 and 230.

[0140] <Fifth embodiment> The fifth embodiment will be described with reference to FIG. 18. In the first embodiment described above, the temperature sensors 210, 220, and 230 are arranged inside the upper belt 30 in the flow paths 160a and 160b through which the airflow flows. In contrast, in this embodiment, the temperature sensors 210, 220, and 230 are arranged on the side of the upper belt 30 opposite to the side on which the heater and reflector are arranged. Since the other configurations and functions are the same as those of the first embodiment described above, the same components are denoted by the same reference numerals, and their description and illustration will be omitted or simplified. The following description will focus on the differences from the first embodiment. Note that the following description will be given for the case where this embodiment is applied to the upper belt unit 10, but it can also be applied to the lower belt unit 20.

[0141] In the case of this embodiment, as in the above-described fourth embodiment, an air flow is not formed, so that the temperature sensor can stably detect the temperature of the upper belt 30. Note that, since an air flow is not formed in this embodiment, the flow path forming portions 161a and 161b described in the first embodiment are not provided.

[0142] FIG. 18 is an enlarged cross-sectional view of a portion of the upper belt unit 10D in this embodiment. The configurations and operations of the upper belt unit 10D and the lower belt unit in this embodiment are similar, so a description of the lower belt unit will be omitted. In this embodiment, the temperature sensors 210, 220, and 230 are not disposed between the reflectors 115 and 125 or between the reflectors 125 and 135. Therefore, similar to the fourth embodiment, the relative positions of the heaters 110a, 110b, 120a, 120b, 130a, and 130b may be different from those in the first embodiment. For example, heaters with high power and heaters with low power can be more freely disposed than in the first embodiment. For example, the heaters may be disposed as shown in FIG. 18.

[0143] In this embodiment, the heating units having the heating sections 117, 127, and 137 heat the inner surface of the upper belt 30 on the opposite side (upper side) from the nip portion N. The temperature sensors 210, 220, and 230 are disposed at locations on the outer surface of the upper belt 30 that face the heaters 110a, 110b, 120a, 120b, 130a, and 130b of the heating sections 117, 127, and 137, respectively, across the upper belt 30. That is, the temperature sensors 210, 220, and 230 are disposed on the opposite side from the side on which the heaters 110a, 110b, 120a, 120b, 130a, and 130b and the reflectors 115, 125, and 135 of the upper belt 30 are disposed, and detect the temperature of the rear surface of the upper belt 30 in a certain region.

[0144] In this embodiment, the heating units 117, 127, and 137 are arranged to heat the inner surface of the upper belt 30 except for the nip portion N, and the temperature sensors 210, 220, and 230 are arranged to detect the temperature of the outer surface of the upper belt 30. As a result, the temperature sensors 210, 220, and 230 are not arranged near the reflectors 115, 125, and 135, so that an increase in the temperature of the temperature sensors 210, 220, and 230 can be suppressed. However, this has disadvantages such as an increase in the size of the device and an inability to arrange the temperature sensors in a way that directly heats the nip portion N. Note that in the configuration of this embodiment, multiple temperature sensors may be arranged in the width direction as in the second embodiment.

[0145] <Other embodiments> In the above-described embodiments, the present invention has been described as being applied to a fixing device (fixing belt unit) of an inkjet recording apparatus, but the present invention is not limited to this. For example, the present invention can also be applied to a fixing device of an electrophotographic image forming apparatus that uses toner, and the same effects as those of the embodiments can be obtained.

[0146] In the above-described embodiments, the temperature sensors 210, 220, 230, 240, and 250 are used as sensors that detect excessive temperature rise in the belt and stop power to the heater. These temperature sensors 210, 220, 230, 240, and 250 may also be used for controlling the temperature of the heater. [Explanation of symbols]

[0147] 1. Inkjet recording device 30···Upper belt (belt, first belt) 40 Lower belt (nip forming member, second belt) 43 Upper door unit (chassis, first chassis) 44 Device main body (second housing) 110a, 110b, 120a, 120b, 130a, 130b... heater 115, 125, 135... Reflector (reflective material) 140a, 140b, 150a, 150b heater 145, 155... Reflector (reflective member) 160a, 160b, 160c... Flow path 161a, 161b, 161c... Flow path forming portion 167a, 167b... First flow path inlet unit (second duct portion) 168a, 168b... Second flow path inlet unit (first duct portion) 210, 220, 230, 240, 250...Temperature sensor (temperature detection part) 210a, 210b, 210c...Temperature sensors (temperature detection units) 211, 221, 231... Overheat detection hardware (threshold judgment unit) 220a, 220b, 220c...Temperature sensor (temperature detection unit) 230a, 230b, 230c...Temperature sensors (temperature detection units) 1300...Power supply (power supply section) 1500, 1501, 1502... Fan 4100, 4100A... Fusing belt unit (fusing device) N...Nip section

Claims

1. A fixing device that heats a sheet on which an image is formed by ejecting ink, thereby fixing the image to the sheet, A rotating endless belt, a nip portion forming member that forms a nip portion between the belt and the nip portion to nip and convey a sheet; a heater disposed in a non-contact state with the belt and configured to heat the belt; a reflecting member inside which the heater is disposed and which reflects radiant heat from the heater toward the belt area; a temperature detection unit disposed outside the reflecting member and detecting the temperature of the area; a fan that generates an airflow, The temperature detection unit is disposed in a flow path through which the airflow generated by the fan flows. A fixing device characterized by:

2. a flow path forming section that forms the flow path through which the airflow generated by the fan flows, The temperature detection unit is disposed in the flow path.

2. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image onto a recording medium.

3. The temperature detection unit is disposed adjacent to the reflecting member in the rotation direction of the belt.

2. The fixing device according to claim 1, wherein the fixing device is a fixing device.

4. the heater is a first heater, a second heater that is disposed inside the reflecting member together with the first heater and does not come into contact with the belt, and that heats the belt by radiating heat, the second heater having a lower electric power than the first heater; the reflecting member reflects radiant heat from the first heater and the second heater toward the region of the belt; The temperature detection unit is disposed at a position closer to the second heater than to the first heater.

2. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image onto a recording medium.

5. the reflecting member is a first reflecting member that reflects radiant heat from the first heater and the second heater toward a first region of the belt, the temperature detection unit is disposed at a position where it can detect the temperature of the belt in the first region, a third heater disposed in a non-contact state with the belt and configured to heat the belt by radiating heat; a fourth heater that is disposed in a non-contact state with the belt and heats the belt by radiating heat, the fourth heater having a lower electric power than the third heater; the third heater and the fourth heater are disposed inside a second reflecting member that reflects radiant heat from the third heater and the fourth heater toward a second region of the belt, The temperature detection unit is disposed between the first reflecting member and the second reflecting unit in the rotation direction of the belt, at a position closer to the second heater than to the first heater, and closer to the fourth heater than to the third heater.

5. The fixing device according to claim 4.

6. the temperature detection unit is a first temperature detection unit, a second temperature detector disposed at a position where the temperature of the belt in the second region can be detected from outside the second reflecting member, and configured to detect the temperature of the belt; The second temperature detection unit is disposed between the first reflecting member and the second reflecting unit in the rotation direction of the belt, at a position closer to the second heater than to the first heater, and closer to the fourth heater than to the third heater.

6. The fixing device according to claim 5,

7. the heater and the reflecting member are arranged along a width direction of the belt that intersects with a rotation direction of the belt, The temperature detection units are arranged in plurality along the width direction.

2. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image onto a recording medium.

8. The fan is disposed on the outer side of the belt in the width direction.

8. The fixing device according to claim 7,

9. The flow path is formed along the width direction, When a region of the belt that can be detected by the temperature detection unit is defined as a detection region, the plurality of temperature detection units are arranged such that, of the total area of ​​the detection regions of the plurality of temperature detection units, an area on the upstream side of the center in the width direction of the belt in relation to the direction of the airflow flowing through the flow path is larger than an area on the downstream side of the center in the width direction.

8. The fixing device according to claim 7,

10. The flow path is formed along the width direction, The plurality of temperature detection units are arranged more on the upstream side of the center in the width direction of the belt than on the downstream side of the center in the width direction with respect to the direction of the airflow flowing through the flow path.

9. The fixing device according to claim 8, wherein the fixing member is a fixing member.

11. The fan is disposed only at one of both end portions in the width direction. The fixing device according to claim 10 .

12. In the case where a line drawn from the heater to the reflecting member in a direction perpendicular to a perpendicular line dropped from the heater to the belt and perpendicular to the width direction of the belt that intersects with the rotation direction of the belt is defined as an incident ray segment, a point where the incident ray segment intersects the inner surface of the reflecting member is defined as a first intersection point, a line drawn from the first intersection point so that the angle of incidence and the angle of reflection are the same in relation to the incident ray segment is defined as a reflected ray segment, a point where the reflected ray segment intersects with the belt is defined as a second intersection point, and a point where the perpendicular line dropped from the first intersection point to the belt intersects with the belt is defined as a third intersection point, The heater is disposed such that the second intersection is closer to the heater than the third intersection in the rotation direction of the belt.

2. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image onto a recording medium.

13. The flow path forming section has a first cover section that covers the upstream side of the temperature detection section in the direction of the airflow flowing through the flow path, a second cover section that covers the side of the belt surface that is irradiated with the radiant heat more than the temperature detection section, and a third cover section that covers the side of the belt surface opposite to the temperature detection section.

3. The fixing device according to claim 2, wherein the fixing device is a fixing device.

14. A part of the reflecting member constitutes the flow path forming portion.

14. The fixing device according to claim 13.

15. The fan is connected to the first cover.

14. The fixing device according to claim 13.

16. a belt unit including the belt, the heater, the reflecting member, the temperature detecting unit, and the flow path forming unit; a housing capable of accommodating the fan and the belt; a rotation support portion that supports the belt unit rotatably with respect to the housing at a first position where the belt unit is accommodated inside the housing and at a second position where at least a portion of the belt unit is exposed to the outside of the housing further than at the first position; a first duct portion connected to the fan and through which the airflow generated by the fan flows; a second duct portion connected to the first cover portion and the first duct portion and configured to send the airflow generated by the fan into the flow path forming portion; a connection portion that connects the first duct portion and the second duct portion at the first position and that can separate the first duct portion and the second duct portion when the belt unit moves from the first position to the second position, 16. The fixing device according to claim 15.

17. the belt is a first belt stretched by a plurality of first tension members, the nip portion forming member is a second belt stretched by a plurality of second tension members, the nip portion is formed between a first tension surface of the first belt stretched by the plurality of first tension members and a second tension surface of the second belt stretched by the plurality of second tension members; the housing is a first housing, the rotation support portion is a first rotation support portion, a second housing that houses the second belt; a second rotation support portion that supports the first housing relative to the second housing so that the first housing can rotate between a nip position where the first belt forms the nip portion between the first belt and the second belt and a spaced position where the first belt is spaced apart from the second belt with respect to the nip position, The belt unit is movable from the first position to the second position when in the separated position.

17. The fixing device according to claim 16.

18. At the first position, a joint surface between the first duct portion and the second duct portion is inclined in a direction perpendicular to the first tensioning surface, toward an upstream side of the direction of the airflow flowing through the flow path as the joint surface approaches the first tensioning surface.

18. The fixing device according to claim 17.

19. a power supply unit that supplies power to the heater; and a threshold determination unit that stops the power supply from the power supply unit when the temperature detected by the temperature detection unit is equal to or higher than a threshold.

19. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image.

20. The heater, the reflecting member, and the temperature detector are disposed inside the belt.

2. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image onto a recording medium.

21. The heater, the reflecting member, and the temperature detector are disposed outside the belt.

2. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image onto a recording medium.

22. A fixing device that heats a sheet on which an image is formed by ejecting ink, thereby fixing the image to the sheet, A rotating endless belt, a nip portion forming member that forms a nip portion between the belt and the nip portion to nip and convey a sheet; a heater that is disposed in a non-contact manner with the belt and along a width direction of the belt that intersects with a rotation direction of the belt, and that heats the belt; a reflecting member disposed inside the heater and reflecting radiant heat from the heater toward the belt area; a temperature detection unit that is disposed outside the reflecting member and outside the end of the heater in the width direction and detects the temperature of the region; A fixing device characterized by:

23. A fixing device that heats a sheet on which an image is formed by ejecting ink, thereby fixing the image to the sheet, A rotating endless belt, a nip portion forming member that forms a nip portion between the belt and the nip portion to nip and convey a sheet; a heater that is disposed in a non-contact manner with the belt and along a width direction of the belt that intersects with a rotation direction of the belt, and that heats a position of the belt that is out of the nip portion; a reflecting member disposed inside the heater and reflecting radiant heat from the heater toward the belt area; a temperature detection unit that is disposed on the opposite side of the belt from the side on which the heater and the reflecting member are disposed, and that detects the temperature of the back surface of the belt in the region; A fixing device characterized by:

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