Image forming apparatus

Abstract

The present invention provides an image forming apparatus that can reduce the influence of airflow on temperature detection of a sensing element. [Solution] The image forming apparatus comprises a main body housing 10, a fixing device 80, and an exhaust fan F for expelling air from inside the main body housing 10. The fixing device 80 comprises a heating roller 81 heated by a heater, a pressure roller 82, a first cover 140 covering the heating roller 81, and a first temperature sensor S1 disposed between the heating roller 81 and the first cover 140, the first temperature sensor S1 having a detection element S11 disposed with a gap between it and the surface of the heating roller 81. The first cover 140 has a first cover hole 142 that connects the space between the first cover 140 and the heating roller 81 with the space of the first cover 140 opposite to the heating roller 81. The exhaust fan F is disposed on one side of the main body housing 10 in the direction of the rotation axis, and the first cover hole 142 is disposed on the other side of the first temperature sensor S1 in the direction of the rotation axis.

Description

Technical Field

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

Background Art

[0002] Conventionally, as an image forming apparatus, there is known one including a heating rotator heated by a heater, a pressure rotator that nips a sheet with the heating rotator, and a temperature sensor that detects the temperature of the heating rotator (Patent Document 1). In this technology, the temperature sensor is a thermistor and is arranged with a gap from the surface of the heating rotator.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in a non-contact temperature sensor, an error may occur in the result of temperature detection due to the influence of the air flow around the detection element. Therefore, it is desired to be able to reduce the influence of the air flow on the temperature detection of the detection element.

Means for Solving the Problems

[0005] The image forming apparatus includes a main body housing, an image forming unit, a fixing device, and an exhaust fan. The image forming unit forms a toner image on a sheet. The fixing device fixes the toner image on the sheet. The exhaust fan discharges the air inside the main body housing to the outside. The fixing device includes a heating rotator, a pressure rotator, a first cover, and a temperature sensor. The heating rotator extends in the axial direction of the rotation axis and is heated by a heater. The pressurized rotating body extends in the direction of the rotation axis and nips the sheet between itself and the heated rotating body. The first cover extends in the direction of the rotation axis and covers the heated rotating body. The temperature sensor is positioned between the heating rotating body and the first cover. The temperature sensor has a sensing element positioned with a gap between it and the surface of the heating rotating body. The first cover has a first through-hole that connects the space between the first cover and the heating rotating body with the space of the first cover opposite the heating rotating body. The exhaust fan is located on one side of the main casing in the direction of its rotational axis. The first through-hole is located to the other side of the temperature sensor in the direction of the rotation axis.

[0006] In the direction of the rotation axis, the exhaust fan is positioned on one side of the main housing, and the first through-hole of the first cover is positioned on the other side of the temperature sensor. This allows the airflow formed by the exhaust fan to escape through the first through-hole from the space between the first cover and the heating rotating body to the space on the opposite side of the heating rotating body of the first cover. This reduces the influence of airflow on temperature detection of the sensing element.

[0007] The first cover may have a cover body and ribs. The cover body encloses the heating rotating body. The ribs protrude from the cover body toward the heating rotating body. When viewed from the direction of the rotation axis, the opposing surface of the ribs that faces the heating rotating body has a concave shape that corresponds to the outer shape of the heating rotating body.

[0008] The first cover has ribs that protrude from the cover body toward the heating rotating body, and these ribs act as resistance, reducing the airflow formed in the space between the first cover and the heating rotating body.

[0009] The rib may be positioned on the other side of the temperature sensor in the direction of the rotation axis.

[0010] In the direction of the rotation axis, the exhaust fan is positioned on one side of the main housing, and the ribs are positioned on the other side of the temperature sensor. This allows the ribs to act as resistance, reducing the airflow in the space between the first cover and the heating rotating body toward the temperature sensor.

[0011] The rib may protrude from one edge of the first through-hole in the direction of the rotational axis.

[0012] The rib protrudes from one edge of the first through-hole in the direction of the rotation axis, allowing airflow to flow along the rib into the first through-hole.

[0013] The heating rotating body is a cylindrical roller, and the ribs may have an arc shape where the opposing surface, when viewed from the direction of the rotation axis, is concentric with the roller.

[0014] When viewed from the direction of the rotation axis, the opposing surface of the rib forms a concentric arc shape with the cylindrical roller, which allows the gap between the heated rotating body and the rib to be kept constant. This further reduces the airflow formed in the space between the first cover and the heated rotating body.

[0015] The fixing device may further include a first side frame, a second side frame, and a metal connecting frame. The first side frame is positioned on one side of the heated rotating body in the direction of the rotation axis. The second side frame is positioned on the other side of the heating rotating body in the direction of the rotation axis. The connecting frame connects the first side frame and the second side frame. The first cover may be made of resin and may be positioned between the connecting frame and the heating rotating body.

[0016] Since the first cover is made of resin, the degree of freedom in the shape of the first cover can be improved. As a result, the air flow formed in the space between the first cover and the heating rotator can be effectively reduced. Further, since the resin-made first cover is disposed between the connection frame and the heating rotator, heat from the heating rotator can be suppressed from escaping to the metal-made connection frame.

[0017] The connection frame may have a second through hole facing the first through hole.

[0018] Since the connection frame has the second through hole facing the first through hole, the air flow that has escaped from the first through hole to the outside of the first cover can be further escaped from the second through hole to the outside of the connection frame.

[0019] The fixing device may further include a second cover that extends in the direction of the rotation axis and covers the first cover. The first cover may be disposed between the heating rotator and the second cover. The second cover may be disposed with a gap between the second cover and the first cover.

[0020] Since the second cover is disposed with a gap between the second cover and the first cover, a flow path for the air flow that has escaped from the first through hole can be formed between the first cover and the second cover.

[0021] The second cover may have a third through hole that communicates the space between the second cover and the first cover and the space of the second cover opposite to the first cover.

[0022] Since the second cover has the third through hole, the air flow that has escaped from the first through hole to the outside of the first cover can be further escaped from the third through hole to the outside of the second cover.

Advantages of the Invention

[0023] <Element ID= The influence of the air flow on the temperature detection of the detection element can be reduced.

Brief Description of the Drawings

[0024] [Figure 1] This is a cross-sectional view showing an image forming apparatus. [Figure 2] This diagram shows the fixing device and exhaust fan. [Figure 3] This is a perspective view of the first side frame, the second side frame, and the connecting frame, viewed from one direction in the first direction. [Figure 4] This is a cross-sectional view of the fixing device from one side in the first direction. [Figure 5] This is a perspective view of the first side frame, second side frame, connecting frame, and first cover, viewed from one direction in the first direction. [Figure 6] This is a perspective view of the first side frame, second side frame, connecting frame, and first cover as seen from the other side in the first direction. [Figure 7] This is a cross-sectional view of the fixing device, seen from one side in the direction of the rotation axis. [Figure 8] This is a cross-sectional view showing an enlarged view of the area around the first cover hole in Figure 4. [Figure 9] This is a perspective view showing the fixing device. [Modes for carrying out the invention]

[0025] Next, embodiments will be described. As shown in Figure 1, the image forming apparatus 1 comprises a main body housing 10, a sheet supply unit 20, an image forming unit 30, a fixing device 80, and a sheet discharge unit 90.

[0026] The main casing 10 includes a front cover 11, an output tray 12, and a rear cover 13. The front cover 11 opens and closes the opening on the front side of the main casing 10. The rear cover 13 opens and closes the opening on the rear side of the main casing 10.

[0027] The sheet supply unit 20 comprises a sheet tray 21 and a supply mechanism 22. The sheet tray 21 holds sheets S such as paper. The supply mechanism 22 supplies the sheets S in the sheet tray 21 to the image forming unit 30.

[0028] The image forming unit 30 forms a toner image on the sheet S. The image forming unit 30 comprises an exposure apparatus 40, a process unit PU, and a transfer unit 70.

[0029] The exposure apparatus 40 is located above the process unit PU. The exposure apparatus 40 emits a light beam as shown by the dashed line to expose the surface of the photosensitive drum 51.

[0030] The process unit PU is located between the sheet tray 21 and the exposure device 40. The process unit PU is detachable from the main housing 10 through an opening in the main housing 10, which is opened by opening the front cover 11. The process unit PU comprises a drum cartridge 50 and multiple toner cartridges 60.

[0031] The drum cartridge 50 comprises a plurality of photosensitive drums 51, a plurality of chargers 52 corresponding to the plurality of photosensitive drums 51, and a drum frame 53. The drum frame 53 supports the photosensitive drums 51 and the chargers 52. The drum frame 53 is movably supported in the main body housing 10. A toner cartridge 60 can be attached to and removed from the drum frame 53.

[0032] Multiple toner cartridges 60 each contain toner of a different color. Each toner cartridge 60 includes a developer roller 61, a supply roller 62, a layer thickness regulating blade 63, a toner storage section 64 for storing toner, and an agitator 65. The agitator 65 agitates the toner in the toner storage section 64. The agitator 65 supplies toner to the supply roller 62. The supply roller 62 supplies toner to the developer roller 61. The layer thickness regulating blade 63 regulates the toner on the developer roller 61 to a constant thickness.

[0033] The transfer unit 70 is located between the sheet tray 21 and the process unit PU. The transfer unit 70 comprises a drive roller 71, a driven roller 72, a conveyor belt 73, and a plurality of transfer rollers 74. The conveyor belt 73 is an endless belt for conveying the sheet S. The drive roller 71 and the driven roller 72 rotate the conveyor belt 73. The transfer rollers 74 are located inside the conveyor belt 73. The transfer rollers 74 sandwich the conveyor belt 73 between themselves and the photosensitive drum 51.

[0034] The fixing device 80 is detachable from the main housing 10 through an opening in the main housing 10, which is opened by opening the rear cover 13. The fixing device 80 includes a heating roller 81 as a heating rotating body and a pressure roller 82 as a pressurizing rotating body.

[0035] The heating roller 81 is a cylindrical roller. The heating roller 81 heats the sheet S. Two heaters 81A are arranged inside the heating roller 81. The heating roller 81 is heated by the heaters 81A. The heating roller 81 rotates under the driving force of a drive source (not shown). The pressure roller 82 nips the sheet S between itself and the heating roller 81. The pressure roller 82 rotates in conjunction with the heating roller 81.

[0036] The charger 52 charges the surface of the photosensitive drum 51. The exposure device 40 exposes the charged surface of the photosensitive drum 51 with a light beam. This forms an electrostatic latent image on the photosensitive drum 51. The developing roller 61 supplies toner to the photosensitive drum 51 on which the electrostatic latent image has been formed. This forms a toner image on the photosensitive drum 51.

[0037] The photosensitive drum 51 and transfer roller 74 transport the sheet S supplied from the sheet supply unit 20, thereby transferring the toner image formed on the photosensitive drum 51 to the sheet S. The fixing device 80 transports the sheet S, on which the toner image has been transferred, using the heating roller 81 and the pressure roller 82, thereby fixing the toner image to the sheet S.

[0038] The sheet discharge unit 90 has a conveyor roller 91 and a discharge roller 92. The conveyor roller 91 conveys the sheet S to the discharge roller 92. The discharge roller 92 discharges the sheet S onto the discharge tray 12.

[0039] The image forming apparatus 1 is further equipped with an exhaust fan F. The exhaust fan F is a fan that expels air from inside the main housing 10 to the outside. By expelling air from inside the main housing 10 with the exhaust fan F, heat generated inside the main housing 10 can be expelled to the outside of the main housing 10, for example.

[0040] As shown in Figure 2, the exhaust fan F is located on one side of the main body housing 10 in the direction of the rotation axis. More specifically, the main body housing 10 has a first main body side frame 14 and a second main body side frame 15. The first main body side frame 14 is a frame located at one end of the main body housing 10 in the direction of the rotation axis. The second main body side frame 15 is a frame located at the other end of the main body housing 10 in the direction of the rotation axis. The fixing device 80 is located between the first main body side frame 14 and the second main body side frame 15. The exhaust fan F is located on the first main body side frame 14.

[0041] The direction of the rotation axis is the direction in which the rotation axis of the heating roller 81 extends. The heating roller 81 and the pressure roller 82 each extend in the direction of the rotation axis. The heating roller 81 and the pressure roller 82 are long in the direction of the rotation axis. In this embodiment, the direction of the rotation axis is the direction along the left-right direction of the image forming apparatus 1. One side of the rotation axis direction corresponds to the right side of the image forming apparatus 1, and the other side of the rotation axis direction corresponds to the left side of the image forming apparatus 1. In the referenced drawings, the arrows indicating direction point to one side in that direction.

[0042] The fixing device 80 further includes a first temperature sensor S1, a second temperature sensor S2, and a thermostat TM, all of which are temperature sensors.

[0043] The first temperature sensor S1 is a sensor that detects the temperature of the heating roller 81. The first temperature sensor S1 is a non-contact type temperature sensor. The first temperature sensor S1 is positioned with a gap between it and the surface of the heating roller 81. The first temperature sensor S1 has a detection element S11 that detects temperature. The detection element S11 is positioned with a gap between it and the surface of the heating roller 81. The detection element S11 is, for example, a thermistor. The first temperature sensor S1 is positioned facing the vicinity of the center of the heating roller 81 in the direction of the rotation axis.

[0044] The second temperature sensor S2 is a sensor that detects the temperature of the heating roller 81. The second temperature sensor S2 includes a thermistor as an example. The second temperature sensor S2 is positioned in contact with the surface of the heating roller 81. The second temperature sensor S2 is positioned in contact with the other end of the heating roller 81 in the direction of the rotation axis.

[0045] The thermostat TM is an element that cuts off the power supply to the heater 81A (see Figure 1) when the surface temperature of the heating roller 81 exceeds a predetermined temperature. The thermostat TM is positioned with a gap between it and the surface of the heating roller 81. The thermostat TM is positioned facing the vicinity of the center of the heating roller 81 in the direction of the rotation axis. In this embodiment, the first temperature sensor S1 is positioned on the other side of the thermostat TM in the direction of the rotation axis.

[0046] As shown in Figure 3, the fixing device 80 further comprises a first side frame 110, a second side frame 120, and a connecting frame 130. The first side frame 110, the second side frame 120, and the connecting frame 130 are metal frames. More specifically, the first side frame 110, the second side frame 120, and the connecting frame 130 are made of metal plates.

[0047] The first side frame 110 is positioned on one side of the heating roller 81 in the direction of the rotation axis. The first side frame 110 holds one end of the heating roller 81 in the direction of the rotation axis. The second side frame 120 is positioned on the other side of the heating roller 81 in the direction of the rotation axis. The second side frame 120 holds the other end of the heating roller 81 in the direction of the rotation axis.

[0048] The connecting frame 130 connects the first side frame 110 and the second side frame 120. The connecting frame 130 extends in the direction of the rotation axis. In the direction of the rotation axis, one end of the connecting frame 130 is fixed to the first side frame 110 by a screw SC1. In the direction of the rotation axis, the other end of the connecting frame 130 is fixed to the second side frame 120 by a screw SC2.

[0049] The first temperature sensor S1 is fixed to the connecting frame 130 by a screw SC3. The second temperature sensor S2 is fixed to the connecting frame 130 by a screw SC4.

[0050] As shown in Figure 4, the fixing device 80 further comprises a first cover 140. The first cover 140 is a resin cover that covers the heating roller 81. The first cover 140 is positioned between the connecting frame 130 and the heating roller 81. The first cover 140 extends in the direction of the rotation axis. The first temperature sensor S1 is positioned between the heating roller 81 and the first cover 140.

[0051] As shown in Figure 5, the first cover 140 has a cover body 141, a first cover hole 142 as a first through hole, a second cover hole 143, and a third cover hole 144. The cover body 141 is the part that covers the heating roller 81. The cover body 141 includes a first cover wall 141A, a second cover wall 141B, and a third cover wall 141C.

[0052] The first cover wall 141A is a wall that extends in the direction of the rotation axis and in the first direction. The first direction is the direction that intersects with the direction of the rotation axis. In this embodiment, the first direction is the direction perpendicular to the direction of the rotation axis. The first direction is the direction along the front-rear direction of the image forming apparatus 1. One end of the first direction corresponds to the front side of the image forming apparatus 1, and the other end of the first direction corresponds to the rear side of the image forming apparatus 1.

[0053] The second cover wall 141B is a wall that extends from one end of the first cover wall 141A in the first direction toward one end of the second direction. The second direction is a direction that intersects both the rotation axis direction and the first direction. In the embodiment, the second direction is a direction perpendicular to both the rotation axis direction and the first direction. The second direction is a direction along the vertical direction of the image forming apparatus 1. One end of the second direction corresponds to the lower side of the image forming apparatus 1, and the other end of the second direction corresponds to the upper side of the image forming apparatus 1.

[0054] The third cover wall 141C is a wall that extends from one end of the second cover wall 141B in the second direction toward one end in the first direction.

[0055] The first cover hole 142, the second cover hole 143, and the third cover hole 144 are holes that connect the space between the first cover 140 and the heating roller 81 to the space of the first cover 140 opposite the heating roller 81. The first cover hole 142, the second cover hole 143, and the third cover hole 144 are located near the center of the first cover 140 in the direction of the rotation axis.

[0056] The first cover hole 142 is formed across the first cover wall 141A and the second cover wall 141B.

[0057] The second cover hole 143 is formed in the first cover wall 141A. The second cover hole 143 is located to one side of the first cover hole 142 in the direction of the rotation axis. The second cover hole 143 is positioned to overlap with the detection element S11 of the first temperature sensor S1 (see Figure 4) in the direction of the rotation axis and in the first direction. In other words, the second cover hole 143 is positioned to overlap with the detection element S11 when viewed from the second direction.

[0058] The third cover hole 144 is the hole in which the first temperature sensor S1 (see Figure 3) is placed. The third cover hole 144 is formed in the second cover wall 141B. The third cover hole 144 and the second cover hole 143 are located to one side of the first cover hole 142 in the direction of the rotation axis. The third cover hole 144 is located in a position that overlaps with the second cover hole 143 in the direction of the rotation axis.

[0059] The connecting frame 130 includes a first frame wall 131A, a second frame wall 131B, a third frame wall 131C, and a fourth frame wall 131D.

[0060] The first frame wall 131A is a wall that extends in the direction of the rotation axis and in the first direction. The first frame wall 131A overlaps with the first cover wall 141A of the first cover 140. The second frame wall 131B is a wall that extends from one end of the first frame wall 131A in the first direction toward one end in the second direction. The second frame wall 131B overlaps with the second cover wall 141B of the first cover 140.

[0061] The third frame wall 131C is a wall that extends from one end of the second frame wall 131B in the second direction toward one end in the first direction. The third frame wall 131C overlaps with the third cover wall 141C of the first cover 140. The fourth frame wall 131D is a wall that extends from one end of the third frame wall 131C in the first direction toward one end in the second direction.

[0062] The connecting frame 130 has a first frame hole 132, a second frame hole 133, and a third frame hole 134, which serve as second through holes. The first frame hole 132, the second frame hole 133, and the third frame hole 134 are holes that connect the side of the connecting frame 130 facing the first cover 140 to the side opposite the first cover 140.

[0063] The first frame hole 132 is formed across the first frame wall 131A and the second frame wall 131B. The first frame hole 132 faces the first cover hole 142 of the first cover 140.

[0064] The second frame hole 133 is formed in the first frame wall 131A. The second frame hole 133 faces the second cover hole 143 of the first cover 140. The second frame hole 133 and the second cover hole 143 are positioned so that the sensing element S11 (see Figure 4) of the first temperature sensor S1 is exposed to the other side in the second direction. This allows the distance between the sensing element S11 and the heating roller 81 to be measured when manufacturing the fixing device 80. The second frame hole 133 and the second cover hole 143 may be sealed with heat-resistant tape or the like after the manufacturing of the fixing device 80 is completed.

[0065] The third frame hole 134 is the hole in which the first temperature sensor S1 (see Figure 3) is placed. The first frame hole 132 is formed across the first frame wall 131A and the second frame wall 131B. The third frame hole 134 faces the third cover hole 144 of the first cover 140. In this embodiment, the first frame hole 132 and the third frame hole 134 are connected to each other and form a single hole.

[0066] As shown in Figure 6, the first cover 140 further has a plurality of ribs 145. The ribs 145 protrude from the cover body 141 toward the heating roller 81 (see Figure 7). The plurality of ribs 145 are aligned in the direction of the rotation axis.

[0067] As shown in Figure 7, each rib 145 extends along the circumferential direction of the heating roller 81 when viewed from the direction of the rotation axis. The rib 145 has an opposing surface 146. The opposing surface 146 is the surface of the rib 145 that faces the heating roller 81. When viewed from the direction of the rotation axis, the opposing surface 146 of the rib 145 has a concave shape corresponding to the outer shape of the heating roller 81. In this embodiment, when viewed from the direction of the rotation axis, the opposing surface 146 of the rib 145 has a circular arc shape concentric with the heating roller 81.

[0068] As shown in Figure 8, the rib 145 includes multiple ribs 145A and multiple ribs 145B (see also Figures 4 and 6).

[0069] Multiple ribs 145A are aligned in the direction of the rotation axis. The ribs 145A are positioned to one side of the first temperature sensor S1 in the direction of the rotation axis. In other words, the ribs 145A are closer to the exhaust fan F (see Figure 2) than to the first temperature sensor S1 in the direction of the rotation axis.

[0070] Multiple ribs 145B are aligned in the direction of the rotation axis. The ribs 145B are positioned further to the other than the first temperature sensor S1 in the direction of the rotation axis. In other words, the ribs 145B are further from the exhaust fan F (see Figure 2) than the first temperature sensor S1 in the direction of the rotation axis.

[0071] The first cover hole 142 of the first cover 140 and the first frame hole 132 of the connecting frame 130 are located on the other side of the first temperature sensor S1 in the direction of the rotation axis. The first cover hole 142 and the first frame hole 132 are in communication when the first cover 140 and the connecting frame 130 are overlapping.

[0072] The second cover hole 143 and the second frame hole 133 are positioned to overlap with the first temperature sensor S1 in the direction of the rotation axis. The second cover hole 143 and the second frame hole 133 are in communication with the first cover 140 and the connecting frame 130 when they are overlapping.

[0073] Rib 145B includes rib 145C. Rib 145C is located in the rotational axial direction to the other of the first temperature sensor S1 and to the other of the first cover hole 142. In other words, rib 145C is located between the first temperature sensor S1 and the first cover hole 142 in the rotational axial direction. Rib 145C protrudes from one edge of the first cover hole 142 toward the heating roller 81 in the rotational axial direction.

[0074] As shown in Figure 9, the fixing device 80 further comprises a second cover 150. The second cover 150 is a resin cover. In this embodiment, the second cover 150 constitutes the exterior of the fixing device 80. The second cover 150 extends in the direction of the rotation axis.

[0075] As shown in Figure 4, the second cover 150 covers the connecting frame 130 and the first cover 140. The connecting frame 130 and the first cover 140 are positioned between the heating roller 81 and the second cover 150. The second cover 150 is positioned with a gap between it and the first cover 140. Also, the second cover 150 is positioned with a gap between it and the connecting frame 130.

[0076] The second cover 150 has a ventilation hole 151 which serves as a third through-hole. The ventilation hole 151 connects the space between the second cover 150 and the first cover 140 with the space on the second cover 150 opposite to the first cover 140. Specifically, the ventilation hole 151 connects the space inside the second cover 150 with the space outside the second cover 150 (fixing device 80).

[0077] Next, the effects of the embodiment will be described. As shown in Figure 8, in the direction of the rotation axis, the exhaust fan F is located on one side of the main housing 10 (the exhaust fan side), and the first cover hole 142 of the first cover 140 is located on the other side of the first temperature sensor S1. This allows the airflow formed by the exhaust fan F to escape through the first cover hole 142 from the space between the first cover 140 and the heating roller 81 to the space on the opposite side of the heating roller 81 of the first cover 140 (see the thick solid arrow). This reduces the influence of the airflow on the temperature detection of the sensing element S11.

[0078] The first cover 140 has ribs 145 that protrude from the cover body 141 toward the heating roller 81, so that the ribs 145 act as resistance and reduce the airflow formed in the space between the first cover 140 and the heating roller 81.

[0079] In the direction of the rotation axis, the exhaust fan F is positioned on one side of the main housing 10, and the rib 145B is positioned on the other side of the first temperature sensor S1. As a result, the rib 145B acts as resistance, reducing the airflow in the space between the first cover 140 and the heating roller 81 toward the first temperature sensor S1.

[0080] Since the rib 145C protrudes from one edge of the first cover hole 142 that is close to the first temperature sensor S1 in the direction of the rotation axis, airflow can be directed along the rib 145C into the first cover hole 142.

[0081] When viewed from the direction of the rotation axis, the opposing surface 146 of the rib 145 (see Figure 7) is concentric with the cylindrical heating roller 81, forming a circular arc shape. This allows the gap between the heating roller 81 and the rib 145 to be kept constant. As a result, the airflow formed in the space between the first cover 140 and the heating roller 81 can be further reduced. Furthermore, turbulence in the airflow can be suppressed.

[0082] The fact that the first cover 140 is made of resin allows for greater freedom in the shape of the first cover 140 compared to, for example, the case where the first cover is made of metal. This effectively reduces the airflow formed in the space between the first cover 140 and the heating roller 81. Furthermore, because the resin first cover 140 is positioned between the connecting frame 130 and the heating roller 81, heat from the heating roller 81 is prevented from escaping to the metal connecting frame 130.

[0083] The connecting frame 130 has a first frame hole 132 that faces the first cover hole 142, which allows the airflow that escapes to the outside of the first cover 140 through the first cover hole 142 to escape further to the outside of the connecting frame 130 through the first frame hole 132.

[0084] The second cover 150 is positioned with a gap between it and the first cover 140, which allows a flow path for the airflow escaping from the first cover hole 142 to be formed between the first cover 140 and the second cover 150.

[0085] The second cover 150 has ventilation holes 151, which allows the airflow that escaped from the first cover hole 142 to the outside of the first cover 140 to escape further to the outside of the second cover 150 (fixing device 80) through the ventilation holes 151 (see thick dashed arrows).

[0086] Although embodiments have been described above, the image forming apparatus can be modified as appropriate, as illustrated below.

[0087] In this embodiment, the second cover 150 had a ventilation hole 151 (third through hole), but for example, the second cover does not have to have a third through hole. Also, the fixing device does not have to include a second cover that covers the first cover.

[0088] In this embodiment, the rib 145 included a rib 145C, but for example, the rib does not have to include a rib that protrudes from one edge of the first through hole in the direction of rotational axis. Also, the rib may be located only on the other side of the temperature sensor in the direction of rotational axis, or only on one side of the temperature sensor in the direction of rotational axis.

[0089] Furthermore, in this embodiment, the opposing surface 146 of the rib 145 was concentric with the heating roller 81 when viewed from the direction of the rotation axis, but for example, the opposing surface of the rib may be concave, such as part of the outer shape of a polygon when viewed from the direction of the rotation axis. Also, the first cover does not have ribs.

[0090] In this embodiment, the connecting frame 130 had a first frame hole 132 (second through hole), but for example, the connecting frame does not have to have a second through hole. Also, the fixing device does not have to have a metal connecting frame.

[0091] In this embodiment, the first cover 140 was made of resin, but for example, the first cover may be made of metal.

[0092] In this embodiment, a thermistor is exemplified as the first temperature sensor S1 (temperature sensor), but for example, the temperature sensor may be a temperature sensor other than a thermistor.

[0093] In this embodiment, a heating roller 81 is exemplified as the heating rotating body, but for example, the heating rotating body may be an endless belt that rotates around the heater. Also, in this embodiment, a pressure roller 82 is exemplified as the pressure rotating body, but for example, the pressure rotating body may be an endless belt that is sandwiched between a pad placed on the inside and the heating rotating body.

[0094] In this embodiment, the image forming unit 30 was equipped with an exposure device 40 that exposed the photosensitive drum 51 with a light beam. However, for example, the image forming unit may be equipped with an exposure device that exposed the photosensitive drum with light emitted from an LED.

[0095] In this embodiment, the fixing device 80 was detachable from the main housing 10, but for example, the fixing device does not necessarily have to be detachable from the main housing.

[0096] In this embodiment, the image forming apparatus 1 was a printer capable of forming color images, but for example, the image forming apparatus may be a printer capable of forming only monochrome images. Alternatively, the image forming apparatus may be a copier, a multifunction printer, or the like.

[0097] The elements described in the above embodiments and modifications may be implemented in any combination. [Explanation of Symbols]

[0098] 1. Image forming apparatus 10 Main Unit 30 Image forming unit 80 Fixing device 81. Heating roller (heating rotating body) 81A Heater 82 Pressure roller (pressure rotating body) 140 First Cover 142 1st cover hole (1st through hole) F Exhaust fan S Seat S1 First temperature sensor (temperature sensor) S11 Detection element

Claims

1. The main casing and An image forming unit that forms a toner image on a sheet, A fixing device that fixes the toner image onto the sheet, The main body housing is equipped with an exhaust fan that expels air from inside the housing to the outside, The fixing device is A heating rotating body extending in the direction of the rotational axis and heated by a heater, A pressurizing rotating body extending in the direction of the rotation axis and nipping the sheet between itself and the heating rotating body, A first cover extending in the direction of the rotation axis and covering the heating rotating body, A temperature sensor is disposed between the heating rotating body and the first cover, and the temperature sensor has a sensing element that is positioned with a gap between it and the surface of the heating rotating body. The first cover has a first through-hole that connects the space between the first cover and the heating rotating body with the space of the first cover opposite to the heating rotating body. The exhaust fan is positioned on one side of the main housing in the direction of the rotation axis, The image forming apparatus is characterized in that the first through-hole is located to the other side of the temperature sensor in the direction of the rotation axis.

2. The first cover is, A cover body that covers the aforementioned heating rotating body, The image forming apparatus according to claim 1, further comprising a rib protruding from the cover body toward the heating rotating body, wherein the rib has a concave shape corresponding to the outer shape of the heating rotating body, with the opposing surface facing the heating rotating body when viewed from the direction of the rotation axis.

3. The image forming apparatus according to claim 2, characterized in that the rib is positioned to the other side of the temperature sensor in the direction of the rotation axis.

4. The image forming apparatus according to claim 2, characterized in that the rib protrudes from one edge of the first through hole in the direction of the rotation axis.

5. The aforementioned heating rotating body is a cylindrical roller, The image forming apparatus according to claim 2, characterized in that the rib has an arc shape concentric with the roller when viewed from the direction of the rotation axis.

6. The fixing device is A first side frame is positioned on one side of the heating rotating body in the direction of the rotation axis, A second side frame is positioned on the other side of the heating rotating body in the direction of the rotation axis, The system further comprises a metal connecting frame that connects the first side frame and the second side frame, The image forming apparatus according to claim 1, characterized in that the first cover is made of resin and is disposed between the connecting frame and the heating rotating body.

7. The image forming apparatus according to claim 6, characterized in that the connecting frame has a second through hole facing the first through hole.

8. The fixing device further comprises a second cover that extends in the direction of the rotation axis and covers the first cover, The first cover is positioned between the heating rotating body and the second cover. The image forming apparatus according to claim 1, characterized in that the second cover is arranged with a gap between it and the first cover.

9. The image forming apparatus according to claim 8, characterized in that the second cover has a third through-hole that connects the space between the second cover and the first cover with the space of the second cover opposite to the first cover.

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