Image forming apparatus

Abstract

To provide an image forming apparatus that can efficiently exhaust air near the fuser. [Solution] The image forming apparatus 1 comprises a housing 2, an image forming unit 5 for forming an image on a sheet S, a fuser 60 for fixing a toner image on the sheet S, a first fan 71 for exhausting air from inside the housing 2, the first fan 71 located above the fuser 60, and a second fan 72 for exhausting air from inside the housing 2, the second fan 72 located below the fuser 60, and in a normal temperature and humidity environment, the exhaust volume of the first fan 71 is greater than the exhaust volume of the second fan 72.

Description

Technical Field

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

Background Art

[0002] Conventionally, as disclosed in Patent Document 1, there is known an image forming apparatus including a housing, an image forming unit that forms an image on a sheet, a fixing device that fixes a toner image on the sheet, a first fan located above the fixing device, and a second fan located below.

[0003] The first fan and the second fan are fans for exhausting the air inside the housing to the outside, and the first fan is configured to exhaust the air that has passed through the image forming unit and the fixing device.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, the miniaturization of image forming apparatuses has been progressing, and the distance between the adjacent image forming unit and the fixing device has become smaller, making it easier for the heat from the fixing device to be transmitted to the image forming unit. Further, in an image forming apparatus in which the fixing device is configured to be replaceable by a user, the occupied volume of the fixing device in the housing has increased, reducing the exhaust space and making it easier for the temperature of the electrical components near the fixing device to rise.

[0006] Therefore, there is a demand for efficiently exhausting the air near the fixing device, which is a heat source.

[0007] Thus, the present invention provides an image forming apparatus capable of efficiently exhausting the air near the fixing device. [Means for solving the problem]

[0008] The image forming apparatus that solves the above problems has the following features.

[0009] In other words, the image forming apparatus comprises a housing, an image forming unit for forming an image on a sheet, a fuser for fixing a toner image on the sheet, a first fan for exhausting air from inside the housing, the first fan located above the fuser, and a second fan for exhausting air from inside the housing, the second fan located below the fuser, and in a normal temperature and humidity environment, the exhaust volume of the first fan is greater than that of the second fan.

[0010] This allows the first fan to efficiently exhaust the heated air near the fuser that is rising upwards, thereby effectively dissipating heat from the vicinity of the fuser.

[0011] Furthermore, during printing in a normal temperature and humidity environment, the exhaust volume of the first fan is always greater than the exhaust volume of the second fan.

[0012] This allows for efficient exhaust of the air near the fuser during printing, when the temperature of the air near the fuser rises, thereby effectively dissipating the heat near the fuser.

[0013] Furthermore, in a normal temperature and humidity environment, the exhaust volume of the first fan is always greater than the exhaust volume of the second fan.

[0014] This allows the air near the fuser to be efficiently exhausted by the first fan at all times in a normal temperature and humidity environment, effectively dissipating heat near the fuser.

[0015] Furthermore, the first fan and the second fan are fans having the same specifications.

[0016] This makes it easier to control the exhaust volume between the first and second fans.

[0017] Also, the number of revolutions per unit time of the first fan is greater than the number of revolutions per unit time of the second fan.

[0018] Thereby, the exhaust volume of the first fan can be made larger than the exhaust volume of the second fan.

[0019] Also, the voltage applied to the first fan is greater than the voltage applied to the second fan.

[0020] Thereby, the exhaust volume of the first fan can be made larger than the exhaust volume of the second fan.

[0021] Also, the normal temperature and normal humidity environment is an environment where the temperature is 32.5 degrees or less and the humidity is 60% or less.

[0022] Thereby, in an environment where the temperature is 32.5 degrees or less and the humidity is 60% or less, the heat near the fixing device can be effectively exhausted.

[0023] Also, the normal temperature and normal humidity environment is an environment where the temperature is 10 degrees or more and the humidity is 20% or more.

[0024] Thereby, in an environment where the temperature is 32.5 degrees or less and the humidity is 60% or less, and further in an environment where the temperature is 10 degrees or more and the humidity is 20% or more, the heat near the fixing device can be effectively exhausted.

[0025] Also, the second fan is disposed at a position overlapping with a low-voltage substrate for converting an AC voltage applied from a commercial power source into a DC voltage when viewed from the axial direction of the second fan.

[0026] Thereby, the air around the low-voltage substrate can be efficiently exhausted by the second fan.

[0027] Also provided are a belt that is disposed opposite the image forming unit and conveys a sheet on which an image is formed by the image forming unit, a belt mark detection sensor that is disposed opposite the belt and detects a mark formed on the belt by the image forming unit, and a frame that supports the second fan. The frame has an opening that communicates with an accommodation space in which the belt mark detection sensor is accommodated at a position facing the second fan in the axial direction of the second fan.

[0028] Thereby, even when the exhaust volume of the second fan is smaller than the exhaust volume of the first fan, the air in the accommodation space of the belt mark detection sensor can be efficiently exhausted by the second fan.

[0029] Also, a part of the accommodation space is partitioned by a first resin sheet.

[0030] Thereby, the accommodation space of the belt mark detection sensor can be easily formed with a simple configuration.

[0031] Also, between the fixing device and the image forming unit, there is provided a second resin sheet having an upper end portion attached to the housing, the second resin sheet extending downward from the upper end portion.

[0032] Thereby, the air near the fixing device can be efficiently exhausted, and the heat near the fixing device can be effectively removed.

[0033] Also provided are a drawer that supports a developing cartridge having a developing roller and is movable between a mounting position where it is mounted to the housing and a drawing position where it is pulled out from the housing, and a positioning shaft for positioning the drawer at the mounting position. The lower end portion of the second resin sheet is sandwiched between the fixing device and the positioning shaft.

[0034] This allows for the stable formation of an exhaust path between the fuser and the second resin sheet, enhances the shielding effect of the second resin sheet between the fuser and the image forming unit, and efficiently exhausts the air near the fuser, effectively dissipating heat near the fuser. [Effects of the Invention]

[0035] According to the present invention, the heated air near the fuser that is rising upward can be efficiently exhausted by the first fan, thereby effectively dissipating heat near the fuser. [Brief explanation of the drawing]

[0036] [Figure 1] This is a central cross-sectional view showing an image forming apparatus. [Figure 2] This is a perspective view showing an image forming apparatus. [Figure 3] This is an exploded perspective view showing the fan fitted into the right frame, the ozone filter, and the louvers formed on the right side wall. [Figure 4] This is a block diagram showing the control board, the first fan, and the second stage. [Figure 5] This is a plan view showing the inside of an image forming apparatus. [Figure 6] This is a side cross-sectional view showing the belt device, detection sensor, fuser, substrate cover, and shielding sheet. [Figure 7] This is a perspective view showing the opening formed in the right frame. [Figure 8] This is a side cross-sectional view showing the opening formed in the right frame. [Figure 9] This is a side cross-sectional view showing a heat shield sheet attached to the paper output frame. [Figure 10] This is a perspective view showing the fuser with the fuser shutter closed. [Figure 11] This is a perspective view showing the fuser with the fuser shutter open. [Figure 12] This is a perspective view showing how the heat-shielding sheet is held in place by the fixing device and the positioning shaft. [Modes for carrying out the invention]

[0037] Next, embodiments for carrying out the present invention will be described with reference to the attached drawings.

[0038] [Image forming apparatus] The image forming apparatus 1 shown in Figure 1 is an embodiment of the image forming apparatus according to the present invention, and is a color laser printer that forms a multi-color image on a sheet S using an electrophotographic method.

[0039] In the following explanation, the left side of Figure 1 is defined as the front side of the image forming apparatus 1, and the right side of Figure 1 is defined as the rear side of the image forming apparatus 1. The front side of the paper in Figure 1 is defined as the right side of the image forming apparatus 1, and the back side of the paper in Figure 1 is defined as the left side of the image forming apparatus 1. Furthermore, the top and bottom sides of Figure 1 are defined as the top and bottom sides of the image forming apparatus 1, respectively.

[0040] The image forming apparatus 1 comprises a housing 2, a paper feeding unit 3 having a paper feeding tray 10 for supporting a sheet S and a sheet transport unit 30 for transporting the sheet S, and an image forming unit 5 for forming an image on the sheet S transported by the paper feeding unit 3.

[0041] The housing 2 is formed in a roughly rectangular parallelepiped shape and houses the paper feeding section 3 and the image forming section 5. The front of the housing 2 has a front opening 2A, and the housing 2 has a front cover 21 that can open and close the front opening 2A.

[0042] The front cover 21 is configured to rotate about a pivot axis 21a at its lower end, and by rotating about the pivot axis 21a, it can move between a closed position that closes the front opening 2A and an open position that opens the front opening 2A. A paper output tray 221 is formed on the upper surface of the housing 2, which slopes downward from the front to the rear. The housing 2 has a paper output frame 22 located at the upper and rear ends of the housing 2, and a portion of the paper output tray 221 is formed by the paper output frame 22.

[0043] A rear opening 2B is provided on the rear surface of the housing 2, and the housing 2 has a rear cover 23 that can open and close the rear opening 2B. The rear cover 23 is configured to rotate around a pivot axis 23a at its lower end, and by rotating around the pivot axis 23a, it can move between a closed position that closes the rear opening 2B and an open position that opens the rear opening 2B.

[0044] The paper feeding unit 3 is located at the bottom of the housing 2 and transports the sheet S, supported by the paper feeding tray 10, to the image forming unit 5 via the sheet transport unit 30. The paper feeding tray 10 is configured to slide in the front-rear direction and is movable between a storage position where it is housed in the housing 2 and a detached position where it is pulled forward from the storage position.

[0045] The sheet transport unit 30 includes a paper feed roller 32, a separation roller 33, a separation pad 33a, a transport roller pair 34, and a registration roller pair 35. Inside the housing 2, a transport path P for sheets S is configured, from the paper feed tray 10 through the image forming unit 5 to the paper output tray 221.

[0046] The sheets S supported in the paper feed tray 10 are separated one by one by the paper feed roller 32, the separation roller 33, and the separation pad 33a, and then sent to the transport path P. The paper feed roller 32 is a roller that transports the sheets S from the paper feed tray 10 toward the image forming unit 5. The separation roller 33 and the separation pad 33a constitute a separation means that separates the sheets S supported in the paper feed tray 10 one by one.

[0047] The sheet S, which has been sent onto the transport path P, is transported toward the image forming unit 5 by the transport roller pair 34 and the resist roller pair 35. The resist roller pair 35 restricts the movement of the leading edge of the transported sheet S, stopping it temporarily, and then transports the sheet S toward the image forming unit 5 at a predetermined timing.

[0048] The image forming unit 5 is located above the paper feeding unit 3 and includes four developing cartridges 50 arranged in a front-to-back direction, and a photosensitive drum 51 corresponding to each developing cartridge 50. Each developing cartridge 50 is provided to correspond to yellow, magenta, cyan, and black. Each developing cartridge 50 has a developing roller 52.

[0049] The developing cartridge 50 is detachably supported in a drawer 59. The drawer 59 is detachable from the housing 2 through the front opening 2A of the housing 2 by opening the front cover 21. The drawer 59 is movable between a mounting position where it is attached to the housing 2 and a pulled-out position where it is extended from the housing 2.

[0050] The housing 2 has a positioning shaft 29 for positioning the drawer 59 in the mounting position. The positioning shaft 29 extends in the left-right direction and is fixed to the housing 2. The drawer 59 has a positioning recess 592 at its rear end. The positioning recess 592 can be engaged with the positioning shaft 29 from the front, and the engagement of the positioning recess 592 and the positioning shaft 29 positions the drawer 59 in the mounting position.

[0051] The drawer 59 has a handle 591 for gripping when, for example, a user pulls the drawer 59 out of the housing 2 from its mounting position. The handle 591 is located at the front end of the drawer 59.

[0052] The photosensitive drum 51 is formed in a substantially cylindrical shape with its axis running in the left-right direction and is rotatably supported by the drawer 59. The developing roller 52 extends in the left-right direction and is rotatably supported by the developing cartridge 50. Toner is an example of a developer. The developing roller 52 supplies toner to the photosensitive drum 51.

[0053] The housing 2 has an exposure device 56 for exposing the surface of the photosensitive drum 51. The exposure device 56 includes a laser diode, a polarizer, a lens, and a mirror (not shown). The exposure device 56 is configured to emit a light beam to each photosensitive drum 51 and expose the surface of each photosensitive drum 51.

[0054] Below the transport path P of the photosensitive drum 51, a transfer belt 41 is positioned opposite. The transfer belt 41 is positioned opposite the image forming unit 5. The transfer belt 41 is in contact with the photosensitive drum 51. The transfer belt 41 is stretched between a drive roller 42 and a driven roller 43 positioned in front of the drive roller 42. Transfer rollers 44 are positioned opposite each photosensitive drum 51 on either side of the transfer belt 41. In the image forming unit 5, the belt device 40 is composed of the transfer belt 41, drive roller 42, driven roller 43, and transfer rollers 44, etc.

[0055] The image forming unit 5 is equipped with a charger 54 for charging each photosensitive drum 51. The charger 54 is supported by a drawer 59. The photosensitive drums 51, uniformly charged by the charger 54, are selectively exposed by the exposure device 56. This exposure selectively removes charge from the surface of the photosensitive drum 51, forming an electrostatic latent image on the surface of the photosensitive drum 51.

[0056] The toner contained in the developing cartridge 50 is positively charged and carried on the surface of the developing roller 52. A developing bias is applied to the developing roller 52, and when the electrostatic latent image formed on the photosensitive drum 51 faces the developing roller 52, toner is supplied from the developing roller 52 to the electrostatic latent image due to the potential difference between the electrostatic latent image and the developing roller 52. As a result, a toner image is formed on the surface of the photosensitive drum 51.

[0057] When the sheet S, which has been transported toward the image forming unit 5, reaches the transfer belt 41, it is transported by the transfer belt 41 and passes sequentially between the transfer belt 41 and each photosensitive drum 51. Then, when the toner image supported on the surface of the photosensitive drum 51 comes into contact with the sheet S, it is transferred to the sheet S by the transfer bias applied to the transfer roller 44. The transfer belt 41 is an example of a belt that transports the sheet on which the image has been formed by the image forming unit.

[0058] In this embodiment, the transfer belt 41 is configured as a transport belt that transports the sheet S to which the toner image is transferred. However, it is also possible to configure it as an intermediate transfer belt to which the toner image is transferred to the belt itself, and the toner image transferred to the belt is further transferred to the sheet S.

[0059] The sheet S onto which the toner image has been transferred is transported to the fuser unit 60. The fuser unit 60 is located behind the transfer belt 41. In other words, the fuser unit 60 is located downstream of the transfer belt 41 in the sheet transport direction. The fuser unit 60 is detachably mounted on the main body 2 of the device. The fuser unit 60 is detachably mounted on the main body 2 through the rear opening 2B when the rear cover 23 is in the open position.

[0060] The fuser unit 60 includes a heating roller 61 and a pressure roller 62 that presses against the heating roller 61. The sheet S, transported to the fuser unit 60, has the toner image heat-fixed as it passes between the heating roller 61 and the pressure roller 62. In other words, the fuser unit 60 fixes the toner image to the sheet S. The fuser unit 60 has a fuser cover 63 that covers the heating roller 61 and the pressure roller 62.

[0061] The sheet S on which the toner image has been heat-fixed is transported downstream from the fuser 60 in the transport direction, and further transported by the intermediate paper discharge roller pair 66 and the paper discharge roller pair 67 located downstream of the intermediate paper discharge roller pair 66 in the transport direction, and discharged into the paper discharge tray 221.

[0062] In the image forming apparatus 1, a process unit PU is configured to form a toner image on the sheet S, comprising a drawer 59, a developing cartridge 50 supported by the drawer 59, a photosensitive drum 51, and a charger 54, etc. In the process unit PU, the drawer 59 may support the photosensitive drum 51 as in this embodiment, or the developing cartridge 50 may support the photosensitive drum 51.

[0063] The image forming apparatus 1 includes a low-voltage substrate 11 for converting an AC voltage applied from a commercial power source into a DC voltage, and a substrate cover 12 that covers the low-voltage substrate 11. The substrate cover 12 is made of a conductive sheet metal material and is grounded. The substrate cover 12 is located between the paper feed tray 10 and the belt device 40 at the rear of the housing 2.

[0064] The substrate cover 12 has an upper surface 12A facing upward. The upper surface 12A located at the rear of the substrate cover 12 faces the fuser 60, and the upper surface 12A located at the front of the substrate cover 12 faces the transfer belt 41. The substrate cover 12 has a recess 121 that is recessed downward from the upper surface 12A. The recess 121 is formed in the front-rear direction from the rear end of the transfer belt 41 to the front of the fuser 60. The housing 2 houses the process unit PU and the substrate cover 12.

[0065] [Left frame and right frame] As shown in Figure 2, the housing 2 contains a left frame 25 and a right frame 26. The left frame 25 and the right frame 26 are spaced apart in the left-right direction. The left frame 25 is located at the left end of the housing 2 and extends in the front-rear and up-down directions. The right frame 26 is located at the right end of the housing 2 and extends in the front-rear and up-down directions.

[0066] [First fan and second fan] As shown in Figures 1 to 3, the image forming apparatus 1 is equipped with a first fan 71 and a second fan 72 for exhausting the air inside the housing 2 to the outside of the housing 2.

[0067] The first fan 71 has a rotating shaft 711 whose axis extends along the left-right direction, blades 712 fixed to the rotating shaft 711, and a case 713 that rotatably supports the rotating shaft 711. The first fan 71 is an axial flow fan that sends out air along the axial direction of the rotating shaft 711. The axial direction of the first fan 71 is the left-right direction, which is perpendicular to the front-back direction. The first fan 71 exhausts the air inside the housing 2 along the axial direction.

[0068] The second fan 72 has a rotating shaft 721 whose axis extends along the left-right direction, blades 722 fixed to the rotating shaft 721, and a case 723 that rotatably supports the rotating shaft 721. The second fan 72 is an axial flow fan that sends out air along the axial direction of the rotating shaft 721. The axial direction of the second fan 72 is the left-right direction, which is perpendicular to the front-back direction. The second fan 72 exhausts the air inside the housing 2 along the axial direction.

[0069] The first fan 71 is positioned to the right and rear of the process unit PU within the housing 2. Furthermore, the first fan 71 is positioned above the fuser 60. The first fan 71 is configured to exhaust air that has passed through the process unit PU and fuser 60 inside the housing 2 to the outside of the housing 2. This allows the first fan 71 to effectively expel the air that has passed through the process unit PU and fuser 60.

[0070] However, the first fan 71 does not need to be located above the fuser 60, as long as it has the function of exhausting air that has passed through the fuser 60, such as by being connected to the fuser 60 through a duct.

[0071] The second fan 72 is positioned to the right of the circuit board cover 12 within the housing 2, and in the left-right direction, the projected surface of the second fan 72 towards the circuit board cover 12 overlaps with the rear of the circuit board cover 12. Furthermore, the second fan 72 is positioned so as to overlap with the low-voltage circuit board 11 when viewed from the left-right direction, which is the axis direction of the second fan 72. The second fan 72 is configured to exhaust the air inside the circuit board cover 12 within the housing 2 to the outside of the housing 2.

[0072] The second fan 72 is positioned so as to overlap with the low-voltage substrate 11 when viewed from the left and right directions, allowing for efficient exhaust of the air surrounding the low-voltage substrate 11. The second fan 72 is located below the first fan 71. The second fan 72 is located below the fuser 60.

[0073] However, the second fan 72 does not have to be located below the fuser unit 60. Also, the second fan 72 may not be used to exhaust air around the low-voltage substrate 11, but rather for other purposes, such as exhausting air around the process unit PU.

[0074] [Support from first and second-tier fans] The enclosure 2 has a right side wall 24 that covers the right side of the right frame 26. The right side wall 24 has a first opening 24a and a second opening 24b that penetrate the right side wall 24 in the left-right direction. The first opening 24a and the second opening 24b are located at the rear of the right side wall 24, and the first opening 24a is located above the second opening 24b.

[0075] The right frame 26 has a first duct 27 that penetrates in the left-right direction. The first duct 27 extends along the left-right direction. The first fan 71 is fitted into the first duct 27 and supported by the right frame 26. The first duct 27 is configured to allow air to flow in the axial direction of the first fan 71.

[0076] The first fan 71 is positioned such that the projection plane of the first fan 71 projected toward the right wall 24 in the left-right direction coincides with the first opening 24a. When the first fan 71 is driven, an airflow is generated in the direction from left to right, and the airflow created by the first fan 71 exhausts the air inside the process unit PU and the air near the fuser 60 to the outside of the housing 2 through the first opening 24a.

[0077] The right frame 26 has a second duct 28 that penetrates in the left-right direction. The second duct 28 extends along the left-right direction. The second duct 28 is located below the first duct 27. The second fan 72 is fitted into the second duct 28 and supported by the right frame 26. The second duct 28 is configured to allow air to flow in the axial direction of the second fan 72.

[0078] The second fan 72 is positioned such that the projection plane of the second fan 72 projected toward the right wall 24 in the left-right direction coincides with the second opening 24b. The right frame 26 is an example of a frame that supports the second fan 72. When the second fan 72 is driven, an airflow is generated from left to right, and the airflow created by the second fan 72 exhausts the air inside the circuit board cover 12 to the outside of the housing 2 through the second opening 24b.

[0079] [First fan's first louver and first ozone filter] The right side wall 24 of the enclosure 2 has a first louver 241 that covers the first opening 24a. The first louver 241 connects the inside and outside of the enclosure 2. The first louver 241 is located to the right of the first fan 71. In other words, the first louver 241 is positioned downstream of the first fan 71 in the exhaust direction of the first fan 71.

[0080] The image forming apparatus 1 includes a first ozone filter 73 located between the first fan 71 and the first louver 241 in the left-right direction. The first ozone filter 73 is composed of, for example, a honeycomb filter in which the filter material is formed in a honeycomb shape.

[0081] As the filter material constituting the first ozone filter 73, for example, paper supporting an ozone decomposition catalyst such as manganese dioxide or activated carbon, a metal such as aluminum, or ceramics can be used.

[0082] Inside the enclosure 2, ozone may be generated by components that generate discharges into the atmosphere, such as the charger 54 provided in the process unit PU. The air inside the process unit PU is drawn to the rear of the process unit PU by the first fan 71, then flows to the right, passes through the first ozone filter 73 to remove ozone and dust, and is then exhausted to the outside of the enclosure 2 through the first louver 241.

[0083] Furthermore, the air near the fuser 60 housed in the housing 2 is heated by the heating roller 61 and tends to rise from the vicinity of the fuser 60. The heated air rising from the vicinity of the fuser 60 is drawn in by the first fan 71, circulates to the right, passes through the first ozone filter 73 to remove ozone and dust, and is then exhausted to the outside of the housing 2 through the first louver 241. By exhausting the air near the fuser 60 to the outside of the housing 2 by the first fan 71, it is possible to dissipate the heat near the fuser 60 and lower the temperature near the fuser 60.

[0084] [Second fan's second louver and second ozone filter] The right side wall 24 of the enclosure 2 has a second louver 242 that covers the second opening 24b. The second louver 242 connects the inside and outside of the enclosure 2. The second louver 242 is located to the right of the second fan 72. In other words, the second louver 242 is positioned downstream of the second fan 72 in the exhaust direction of the second fan 72.

[0085] The image forming apparatus 1 includes a second ozone filter 74 located between the second fan 72 and the second louver 242 in the left-right direction. The second ozone filter 74 is composed of, for example, a honeycomb filter in which the filter material is formed in a honeycomb shape.

[0086] As the filter material for the second ozone filter 74, for example, paper supported with an ozone decomposition catalyst such as manganese dioxide or activated carbon, a metal such as aluminum, or ceramics can be used.

[0087] The air inside the circuit board cover 12 housed in the enclosure 2 is easily heated and warmed by the electronic components mounted on the low-pressure circuit board 11. The air inside the circuit board cover 12 is circulated from left to right by the second fan 72, passes through the second ozone filter 74 to remove ozone and dust, and is then exhausted to the outside of the enclosure 2 through the second louver 242. By exhausting the air inside the circuit board cover 12 to the outside of the enclosure 2 by the second fan 72, it is possible to lower the temperature of the air inside the circuit board cover 12.

[0088] [Specifications of the first and second fans] The first fan 71 has an electric motor that rotates the blades 712, and the electric motor is driven by power supplied from the low-voltage circuit board 11. The rotational speed of the blades 712 changes according to the magnitude of the voltage applied to the first fan 71. For example, if the voltage applied to the first fan 71 is small, the rotational speed of the blades 712 decreases, and if the voltage applied to the first fan 71 is large, the rotational speed of the blades 712 increases.

[0089] Furthermore, the exhaust volume of the first fan 71 changes according to the rotational speed of the blades 712. For example, when the rotational speed of the blades 712 is low, the exhaust volume of the first fan 71 decreases, and when the rotational speed of the blades 712 is high, the exhaust volume of the first fan 71 increases.

[0090] The second fan 72 has an electric motor that rotates the blades 722, and the electric motor is driven by power supplied from the low-voltage circuit board 11. The rotational speed of the blades 722 changes depending on the magnitude of the voltage applied to the second fan 72. For example, if the voltage applied to the second fan 72 is small, the rotational speed of the blades 722 decreases, and if the voltage applied to the second fan 72 is large, the rotational speed of the blades 722 increases.

[0091] Furthermore, the exhaust volume of the second fan 72 changes according to the rotational speed of the blades 722. For example, if the rotational speed of the blades 722 is low, the exhaust volume of the second fan 72 decreases, and if the rotational speed of the blades 722 is high, the exhaust volume of the second fan 72 increases.

[0092] The first fan 71 and the second fan 72 have identical specifications. That is, the shape and size of the blades 722, the performance of the electric motors that drive the blades 712 and 722, and the shape and size of the cases 713 and 723 are all configured similarly in the first fan 71 and the second fan 72.

[0093] Therefore, when the same voltage is applied to the first fan 71 and the second fan 72, the blades 712 of the first fan 71 and the blades 722 of the second fan 72 rotate at the same speed, and the exhaust volume of the first fan 71 and the exhaust volume of the second fan 72 become the same.

[0094] Furthermore, if a higher voltage is applied to the first fan 71 than to the second fan 72, the rotational speed of the blades 712 of the first fan 71 will be greater than the rotational speed of the blades 722 of the second fan 72, and the exhaust volume of the first fan 71 will be greater than that of the second fan 72.

[0095] Furthermore, if a lower voltage is applied to the first fan 71 than to the second fan 72, the rotational speed of the blades 712 of the first fan 71 becomes lower than the rotational speed of the blades 722 of the second fan 72, and the exhaust volume of the first fan 71 becomes lower than the exhaust volume of the second fan 72.

[0096] [Operation of the first and second fans] As shown in Figure 4, the image forming apparatus 1 includes a control board 91 that controls the driving of the first fan 71 and the second fan 72.

[0097] The control board 91 can adjust the magnitude of the voltage applied to the first fan 71 and the second fan 72, and in a normal temperature and humidity environment, it applies a higher voltage to the first fan 71 than to the second fan 72. In other words, in a normal temperature and humidity environment, the voltage applied by the control board 91 to the first fan 71 is greater than the voltage applied to the second fan 72.

[0098] Here, a normal temperature and humidity environment is defined as an environment where the temperature is 32.5 degrees Celsius or lower and the humidity is 60% or lower. Alternatively, a normal temperature and humidity environment is defined as an environment where the temperature is 10 degrees Celsius or higher and the humidity is 20% or higher. In other words, normal temperature is 32.5 degrees Celsius or lower and 10 degrees Celsius or higher, and temperatures above 32.5 degrees Celsius are considered high temperature. Also, normal humidity is 60% or lower and 20% or higher, and humidity above 60% is considered high humidity.

[0099] The image forming apparatus 1 is equipped with a temperature and humidity sensor (not shown), and the ambient temperature and humidity are measured by the temperature and humidity sensor provided in the image forming apparatus 1. The temperature and humidity sensor may be formed as an integrated unit with the temperature sensor and humidity sensor, or it may be formed as a separate unit with the temperature sensor and humidity sensor. The control board 91 controls the driving of the first fan 71 and the second fan 72 based on environmental conditions such as ambient temperature and ambient humidity.

[0100] When a voltage greater than that applied to the second fan 72 is applied to the first fan 71, the rotational speed per unit time of the first fan 71 becomes greater than the rotational speed per unit time of the second fan 72. Note that the rotational speed of the first fan 71 refers to the rotational speed of the blades 712 of the first fan 71, and the rotational speed of the second fan 72 refers to the rotational speed of the blades 722 of the second fan 72.

[0101] If the rotational speed per unit time of the first fan 71 is greater than that of the second fan 72, the displacement of the first fan 71 will be greater than that of the second fan 72. In other words, by making the rotational speed per unit time of the first fan 71 greater than that of the second fan 72, the displacement of the first fan 71 can be made greater than that of the second fan 72.

[0102] In this way, by controlling the control board 91, in a normal temperature and humidity environment, the exhaust volume of the first fan 71 is made larger than that of the second fan 72, thereby efficiently exhausting the heated air near the fuser 60 that is rising upwards with the first fan 71, and effectively dissipating the heat near the fuser 60.

[0103] In this case, a normal temperature and humidity environment is an environment where the temperature is 32.5 degrees Celsius or lower and the humidity is 60% or lower. Therefore, in an environment where the temperature is 32.5 degrees Celsius or lower and the humidity is 60% or lower, it is possible to effectively dissipate heat from the vicinity of the fuser unit 60.

[0104] In addition, since a normal temperature and humidity environment is an environment where the temperature is 10 degrees Celsius or higher and the humidity is 20% or higher, it is possible to effectively dissipate heat near the fuser unit 60 in an environment where the temperature is 32.5 degrees Celsius or lower and the humidity is 60% or lower, and furthermore, in an environment where the temperature is 10 degrees Celsius or higher and the humidity is 20% or higher.

[0105] If the exhaust volume of the first fan 71 is made greater than that of the second fan 72, then, in particular, during printing in a normal temperature and humidity environment of the image forming apparatus 1, the exhaust volume of the first fan 71 can always be made greater than that of the second fan 72.

[0106] During printing by the image forming apparatus 1, the fuser 60 operates, causing the temperature of the air near the fuser 60 to rise. Therefore, during printing, when the temperature of the air near the fuser 60 rises, by increasing the exhaust volume of the first fan 71 to that of the second fan 72, it is possible to efficiently exhaust the air near the fuser 60 and effectively dissipate the heat near the fuser 60.

[0107] Note that "printing in progress" in the image forming apparatus 1 refers to the state in which a print job has been entered into the image forming apparatus 1.

[0108] Furthermore, in the image forming apparatus 1, regardless of whether printing is in progress or not, the exhaust volume of the first fan 71 can always be made greater than that of the second fan 72 in a normal temperature and humidity environment. This makes it possible to efficiently exhaust the air near the fuser 60 by the first fan 71 at all times in a normal temperature and humidity environment, and to effectively dissipate the heat near the fuser 60.

[0109] Furthermore, in the image forming apparatus 1, when the temperature of the air surrounding the low-pressure substrate 11 (hereinafter referred to as ambient temperature) rises above a predetermined temperature, the exhaust volume of the second fan 72 can be controlled to be greater than that of the first fan 71, or the exhaust volumes of the second fan 72 and the first fan 71 can be controlled to be the same. Moreover, when the ambient temperature of the low-pressure substrate 11 is below the predetermined temperature, the exhaust volume of the first fan 71 can always be controlled to be greater than that of the second fan 72.

[0110] This allows for efficient heat dissipation from the vicinity of the fuser 60 when the ambient temperature of the low-voltage substrate 11 is below a predetermined temperature, while also increasing the heat dissipation efficiency around the low-voltage substrate 11 when the ambient temperature of the low-voltage substrate 11 rises above the predetermined temperature.

[0111] Furthermore, when the control board 91 controls the exhaust volume of the first fan 71 and the second fan 72, the first fan 71 and the second fan 72 are configured to the same specifications, making it easier to control the exhaust volume of the first fan 71 and the second fan 72.

[0112] Furthermore, the first fan 71 and the second fan 72 can be driven so that the exhaust volume of the first fan 71 is greater than that of the second fan 72, even when the ambient temperature is high and exceeds room temperature.

[0113] In this case, the operation of the first fan 71 can be controlled so that the exhaust volume of the first fan 71 at high temperatures is greater than the exhaust volume of the first fan 71 at normal temperatures. Similarly, the operation of the second fan 72 can be controlled so that the exhaust volume of the second fan 72 at high temperatures is greater than the exhaust volume of the second fan 72 at normal temperatures.

[0114] However, it is also possible to control the operation of the first fan 71 so that its exhaust volume at high temperatures is the same as its exhaust volume at normal temperatures. Similarly, it is also possible to control the operation of the second fan 72 so that its exhaust volume at high temperatures is the same as its exhaust volume at normal temperatures.

[0115] Furthermore, the first fan 71 and the second fan 72 can be driven so that the exhaust volume of the first fan 71 is greater than that of the second fan 72, even when the ambient humidity is high, exceeding normal humidity.

[0116] In this case, the operation of the first fan 71 can be controlled so that the exhaust volume of the first fan 71 at high humidity is greater than the exhaust volume of the first fan 71 at normal humidity. Similarly, the operation of the second fan 72 can be controlled so that the exhaust volume of the second fan 72 at high humidity is greater than the exhaust volume of the second fan 72 at normal humidity.

[0117] However, it is also possible to control the operation of the first fan 71 so that the exhaust volume of the first fan 71 in high humidity conditions is the same as the exhaust volume of the first fan 71 in normal humidity conditions. Furthermore, it is also possible to control the operation of the second fan 72 so that the exhaust volume of the second fan 72 in high humidity conditions is the same as the exhaust volume of the second fan 72 in normal humidity conditions.

[0118] (Examples of operation of the first and second fans) The first fan 71 and the second fan 72 can be configured to operate at three rotational speeds, for example, low speed, medium speed, and full speed. The rotational speed of the first fan 71 and the second fan 72 is greater at medium speed than at low speed, and greater at full speed than at medium speed.

[0119] When the first fan 71 and the second fan 72 are driven at a low speed, for example, a voltage of 12V is applied to the first fan 71 and the second fan 72. When the first fan 71 and the second fan 72 are driven at a medium speed, for example, a voltage of 18V is applied to the first fan 71 and the second fan 72. Furthermore, when the first fan 71 and the second fan 72 are driven at full speed, for example, a voltage of 24V is applied to the first fan 71 and the second fan 72.

[0120] The displacement of the first fan 71 and the second fan 72 rotating at medium speed is greater than the displacement of the first fan 71 and the second fan 72 rotating at low speed. The displacement of the first fan 71 and the second fan 72 rotating at high speed is greater than the displacement of the first fan 71 and the second fan 72 rotating at medium speed.

[0121] [Table 1]

[0122] As shown in Table 1 for drive speed 1, in a normal temperature and humidity environment with a temperature of 32.5 degrees Celsius or less and a humidity of 60% or less, the first fan 71 can be driven at a medium speed and the second fan 72 can be driven at a low speed. In this way, a voltage higher than that applied to the second fan 72 can be applied to the first fan 71, allowing the first fan 71 to rotate at a higher rotational speed than the second fan 72. This makes it possible to increase the exhaust volume of the first fan 71 compared to that of the second fan 72. Note that when the first fan 71 and the second fan 72 are driven at drive speed 1, the ambient temperature of the low-voltage substrate 11 does not exceed a predetermined temperature.

[0123] Furthermore, as shown in the drive speed 2 in Table 1, in high-temperature environments where the temperature exceeds 32.5 degrees Celsius, the first fan 71 can be driven at full speed and the second fan 72 can be driven at medium speed. In this way, a voltage greater than that applied to the second fan 72 can be applied to the first fan 71, allowing the first fan 71 to rotate at a higher rotational speed than the second fan 72. This makes it possible to increase the exhaust volume of the first fan 71 compared to that of the second fan 72.

[0124] Furthermore, when the first fan 71 and the second fan 72 are driven at drive speed 2, the ambient temperature of the low-voltage substrate 11 does not exceed a predetermined temperature. Also, the rotational speed of the first fan 71 at drive speed 2 is greater than the rotational speed of the first fan 71 at drive speed 1. Similarly, the rotational speed of the second fan 72 at drive speed 2 is greater than the rotational speed of the second fan 72 at drive speed 1.

[0125] Furthermore, as shown in the drive speed 3 in Table 1, in a high-humidity environment where the humidity exceeds 60%, the first fan 71 can be driven at a medium speed and the second fan 72 at a low speed. In this way, a voltage greater than that applied to the second fan 72 can be applied to the first fan 71, allowing the first fan 71 to rotate at a higher rotational speed than the second fan 72. This makes it possible to increase the exhaust volume of the first fan 71 compared to that of the second fan 72.

[0126] Furthermore, at drive speed 3, the temperature of the air surrounding the low-voltage substrate 11 does not exceed a predetermined temperature. Also, the rotational speed of the first fan 71 at drive speed 3 is the same as the rotational speed of the first fan 71 at drive speed 1. In addition, the rotational speed of the second fan 72 at drive speed 3 is the same as the rotational speed of the second fan 72 at drive speed 1.

[0127] Furthermore, as shown in the drive speed 4 in Table 1, when the ambient temperature of the low-voltage substrate 11 is higher than a predetermined temperature, the second fan 72 can be driven at full speed. In this case, the first fan 71 can be driven at, for example, medium speed or full speed. In this way, by applying a voltage of 24V to the second fan 72, the second fan 72 can be rotated at a higher rotational speed than the first fan 71, or at the same rotational speed as the first fan 71. This makes it possible to make the exhaust volume of the second fan 72 larger than that of the first fan 71, or to make the exhaust volume of the second fan 72 the same as that of the first fan 71.

[0128] As shown in the drive speeds 1, 2, and 3 in Table 1, under normal conditions where the ambient temperature of the low-voltage substrate 11 is below a predetermined temperature, the first fan 71 and the second fan 72 are driven so that the rotation speed of the first fan 71 is greater than the rotation speed of the second fan 72, not only in a normal temperature and pressure environment, but also in high-temperature and high-humidity environments.

[0129] On the other hand, as shown in the drive speed 4 of Table 1, in the unusual situation where the ambient temperature of the low-voltage substrate 11 is higher than a predetermined temperature, the second fan 72 is driven at full speed, causing the second fan 72 to rotate at a higher rotational speed than the first fan 71, or at the same rotational speed as the first fan 71.

[0130] (First variation of the operation of the first and second fans) In the image forming apparatus 1, the operation of the first fan 71 and the second fan 72 can be controlled based solely on the ambient temperature, for example, by using only a temperature sensor without using a humidity sensor.

[0131] When the control board 91 controls the operation of the first fan 71 and the second fan 72 using only ambient temperature as an environmental condition, it can control the exhaust volume of the first fan 71 to be greater than that of the second fan 72 in a normal temperature environment.

[0132] (Second variation of the operation of the first and second fans) In the image forming apparatus 1, the operation of the first fan 71 and the second fan 72 can be controlled based solely on ambient humidity, for example, by using only a humidity sensor without using a temperature sensor.

[0133] When the control board 91 controls the operation of the first fan 71 and the second fan 72 using only ambient humidity as the environmental condition, it can control the exhaust volume of the first fan 71 to be greater than that of the second fan 72 in a normal humidity environment.

[0134] [Detection Sensor] As shown in Figure 5, in the image forming apparatus 1, when performing registration such as density correction and color shift correction of the image formed on the sheet S, toner is transferred from the photosensitive drum 51 to the surface of the transfer belt 41 to form a mark M.

[0135] As shown in Figures 1, 5, and 6, the image forming apparatus 1 is equipped with a detection sensor 13 for detecting marks M formed on the surface of the transfer belt 41, and registration is performed by reading the marks M on the surface of the transfer belt 41 with the detection sensor 13. The detection sensor 13 is an example of a belt mark detection sensor that detects marks formed on the belt by the image forming unit. The fuser 60 is located behind and above the detection sensor 13.

[0136] The detection sensor 13 is an optical detection device that detects the mark M by irradiating the surface of the transfer belt 41 with light emitted from the light-emitting element and receiving the reflected light from the transfer belt 41 with a light-receiving element.

[0137] When performing registration in the image forming apparatus 1, for example, light from the light-emitting element of the detection sensor 13 is shone onto the transfer belt 41 on which a mark M has been formed by the image forming unit 5, and the reflected light from the shone is received by the light-receiving element of the detection sensor 13. Furthermore, the difference in light reflectivity between the surface of the transfer belt 41 and the mark M is read from the output of the received light from the detection sensor 13, and the position of the mark M is detected. In addition, color shift correction is performed based on the detection result of the position of the mark M.

[0138] The detection sensor 13 is located below and behind the drive roller 42 in the transfer unit 40. In other words, the detection sensor 13 is located at the rear end and below the transfer belt 41. Furthermore, the detection sensor 13 is positioned between the transfer belt 41 and the fuser 60, facing the transfer belt 41.

[0139] Therefore, the detection sensor 13 can easily irradiate the surface of the transfer belt 41 with light and receive reflected light from the transfer belt 41, and can easily read the mark M formed on the transfer belt 41.

[0140] In the transfer unit 40, multiple marks M are formed along the front-to-back direction at two locations, the left end and the right end of the transfer belt 41. The detection sensors 13 are provided at two locations, on the left and right sides, corresponding to the positions of the marks M formed on the transfer belt 41.

[0141] Mark M is detected by the detection sensor 13 when the transfer unit 40 is mounted on the main body 2 of the device. In this case, by providing two marks M spaced apart in the left-right direction, it is possible to improve the accuracy of corrections when performing density correction and color shift correction of the image formed on the sheet S.

[0142] The detection sensor 13 is located in a recess 121 of the substrate cover 12. A portion of the lower part of the detection sensor 13 is located inside the recess 121, and a portion of the upper part protrudes above the upper surface 12A of the substrate cover 12.

[0143] However, if the detection sensor 13 is capable of irradiating the surface of the transfer belt 41 with light and receiving reflected light from the transfer belt 41, it is also possible to position the entire sensor within the recess 121 so as not to protrude upward from the upper surface 12A. In other words, the detection sensor 13 can be positioned such that at least a portion of it is located within the recess 121.

[0144] The detection sensor 13 is attached to the holder 131. The holder 131 is made of a sheet metal member with its longitudinal direction in the left-right direction. The holder 131 is positioned between the left frame 25 and the right frame 26 in the left-right direction and is supported by the left frame 25 and the right frame 26.

[0145] The image forming apparatus 1 is equipped with a shielding sheet 14. The shielding sheet 14 is a shielding member formed in the shape of a rectangular sheet. The shielding sheet 14 is constructed, for example, by forming a resin member into a sheet. The shielding sheet 14 is an example of a first resin sheet.

[0146] The shielding sheet 14 is attached to the upper surface 12A of the substrate cover 12 and covers the detection sensor 13 from above. By covering the detection sensor 13 from above with the shielding sheet 14, it is possible to prevent a user from accessing and touching the detection sensor 13 through the rear opening 2B, for example, when the fuser 60 is removed from the housing 2.

[0147] The detection sensor 13 is housed inside a housing space V formed by the recess 121 of the substrate cover 12 and the shielding sheet 14. The upper part of the housing space V is separated from the outside by the shielding sheet 14. The lower, front, and rear parts of the housing space V are separated from the outside by the recess 121 of the substrate cover 12. In other words, a portion of the housing space V is separated by the shielding sheet 14. By separating a portion of the housing space V with the shielding sheet 14, the housing space V for the detection sensor 13 can be easily formed with a simple configuration.

[0148] [Opening in the right frame] As shown in Figures 7 and 8, the right frame 26 has an opening 261 that communicates in the left-right direction. The opening 261 is positioned opposite the second fan 72 in the left-right direction, which is the axial direction of the second fan 72. In the left-right direction, the opening 261 is opposite the housing space V in which the detection sensor 13 is housed, and the opening 261 and the housing space V are in communication.

[0149] Thus, since the right frame 26 has an opening 261 that communicates with the housing space V at a position opposite the second fan 72, even if the exhaust volume of the second fan 72 is smaller than that of the first fan 71, the air in the housing space V of the detection sensor 13 can be efficiently exhausted by the second fan 72. This makes it possible to effectively cool the housing space V partitioned by the substrate cover 12 and the shielding sheet 14.

[0150] [Fuser] As shown in Figures 6 and 9, the fixing frame 63 of the fixing unit 60 has a heating roller 61 and a first opening 63a formed on the upstream side in the sheet conveying direction of the heating roller 61, and a second opening 63b formed on the downstream side in the sheet conveying direction of the heating roller 61.

[0151] The sheet S, which has been transported to the fuser unit 60, enters the interior of the fuser frame 63 through the first opening 63a, passes between the heating roller 61 and the pressure roller 62, and is then discharged to the outside of the fuser frame 63 through the second opening 63b.

[0152] The fuser 60 includes a fuser shutter 64 that can open and close the first opening 63a, and an opening / closing arm 65 for operating the fuser shutter 64. The opening / closing arm 65 is movable in the front-rear direction and is biased forward by a spring (not shown).

[0153] As shown in Figure 10, when the fuser 60 is removed from the housing 2, the opening / closing arm 65 moves forward due to the biasing force of the spring, and the fuser shutter 64 is moved to the closed position by the opening / closing arm 65 that has moved forward.

[0154] On the other hand, as shown in Figures 9 and 11, when the fuser 60 is mounted on the housing 2, the opening / closing arm 65 moves backward against the biasing force of the spring, and the fuser shutter 64 is moved to the open position by the opening / closing arm 65 that has moved backward. In this case, the opening / closing arm 65 moves backward by contacting the positioning shaft 29 from behind when the fuser 60 is mounted on the housing 2 from behind.

[0155] [Heat-shielding sheet] As shown in Figures 1, 9, and 12, the image forming apparatus 1 is equipped with a heat-shielding sheet 15. The heat-shielding sheet 15 is a heat-shielding member formed in the shape of a rectangular sheet. The heat-shielding sheet 15 is constructed, for example, by forming a resin member into a sheet. The heat-shielding sheet 15 is an example of a second resin sheet.

[0156] The heat shield sheet 15 has its upper end attached to the paper output frame 22 of the housing 2, and extends downward from the upper end attached to the paper output frame 22. The heat shield sheet 15 extending downward from the paper output frame 22 is located behind the drawer 59 that constitutes the image forming unit 5 and in front of the fuser 60. In other words, the heat shield sheet 15 is located between the drawer 59 of the image forming unit 5 and the fuser 60, and the heat shield sheet 15 separates the image forming unit 5 from the fuser 60.

[0157] Because the space between the fuser 60 and the drawer 59 is narrow in the front-to-back direction, when attempting to exhaust the air near the fuser 60 with the first fan 71, it may also draw in air from in front of the fuser 60, making it difficult to efficiently exhaust the air near the fuser 60.

[0158] Therefore, in the image forming apparatus 1, a heat shield sheet 15 is placed between the image forming unit 5 and the fuser 60, and an exhaust path is formed between the fuser 60 and the heat shield sheet 15, from the vicinity of the fuser 60 to the first fan 71.

[0159] As a result, the first fan 71 can efficiently exhaust the air near the fuser 60 through the exhaust path, and effectively dissipate the heat near the fuser 60.

[0160] Furthermore, by placing the heat shield sheet 15 between the image forming unit 5 and the fuser 60, it is possible to suppress the transfer of heat generated in the fuser 60 to the image forming unit 5.

[0161] Furthermore, the heat shield sheet 15 extending downward from the paper output frame 22 passes between the fuser unit 60 and the positioning shaft 29, and the lower end of the heat shield sheet 15 is held between the opening / closing arm 65 of the fuser unit 60 and the positioning shaft 29.

[0162] By sandwiching the heat shield sheet 15 between the fuser 60 and the positioning shaft 29, a stable exhaust path can be formed between the fuser 60 and the heat shield sheet 15 when the fuser 60 is mounted on the housing 2. In addition, the shielding effect of the heat shield sheet 15 between the fuser 60 and the image forming unit 5 can be enhanced. As a result, the air near the fuser 60 can be efficiently exhausted through the exhaust path, and the heat near the fuser 60 can be effectively dissipated. [Explanation of Symbols]

[0163] 1. Image forming apparatus 2 cabinets 5 Image forming unit 11 Low-voltage substrate 13 Detection Sensors 14. Shielding sheet 15 Heat-shielding sheet 26 Right frame 29 Positioning shaft 41 Transfer Belt 50 developing cartridges 52 Developing roller 59 drawers 60 Fuser 71 First Fan 72 Second Fan 261 Aperture M mark S Seat V dwelling space

Claims

1. The casing and An image forming unit that forms an image on a sheet, A fuser that fixes the toner image onto the sheet, A first fan for exhausting air from inside the housing, the first fan being located above the fuser, A second fan for exhausting air from inside the housing, the second fan being located below the fuser, An image forming apparatus in which, under normal temperature and humidity conditions, the exhaust volume of the first fan is greater than the exhaust volume of the second fan.

2. The image forming apparatus according to claim 1, wherein, during printing in a normal temperature and humidity environment, the exhaust volume of the first fan is always greater than the exhaust volume of the second fan.

3. The image forming apparatus according to claim 1, wherein, in a normal temperature and humidity environment, the exhaust volume of the first fan is always greater than the exhaust volume of the second fan.

4. The image forming apparatus according to any one of claims 1 to 3, wherein the first fan and the second fan are fans having the same specifications.

5. The image forming apparatus according to any one of claims 1 to 3, wherein the rotational speed per unit time of the first fan is greater than the rotational speed per unit time of the second fan.

6. The image forming apparatus according to any one of claims 1 to 3, wherein the voltage applied to the first fan is greater than the voltage applied to the second fan.

7. The image forming apparatus according to any one of claims 1 to 3, wherein the aforementioned normal temperature and humidity environment is an environment in which the temperature is 32.5 degrees Celsius or less and the humidity is 60% or less.

8. The image forming apparatus according to claim 7, wherein the ambient temperature and humidity environment is an environment with a temperature of 10 degrees Celsius or higher and a humidity of 20% or higher.

9. The image forming apparatus according to any one of claims 1 to 3, wherein the second fan is positioned so as to overlap with a low-voltage substrate for converting an AC voltage applied from a commercial power supply to a DC voltage, when viewed from the axial direction of the second fan.

10. A belt positioned opposite the image forming unit and transporting the sheet on which the image has been formed by the image forming unit, A belt mark detection sensor is positioned opposite the belt and detects marks formed on the belt by the image forming unit, The frame supporting the two fans mentioned above, The image forming apparatus according to any one of claims 1 to 3, wherein the frame has an opening at a position opposite to the second fan in the axial direction of the second fan that communicates with a housing space in which the belt mark detection sensor is housed.

11. The image forming apparatus according to claim 10, wherein a portion of the aforementioned containment space is partitioned by a first resin sheet.

12. An image forming apparatus according to any one of claims 1 to 3, comprising a second resin sheet between the fuser and the image forming unit, the second resin sheet having an upper end attached to the housing, and the second resin sheet extending downward from the upper end.

13. A drawer that supports a developing cartridge having a developing roller and is movable between a mounting position where it is mounted on the housing and a pull-out position where it is pulled out from the housing, The drawer further comprises a positioning shaft for positioning the drawer in the mounting position, The image forming apparatus according to claim 12, wherein the lower end of the second resin sheet is held between the fuser and the positioning shaft.

Images