Duct unit and image formation apparatus

Abstract

To provide a duct unit that achieves both device miniaturization and noise reduction of airflow sound generated by fan operation.SOLUTION: A sound-absorbing member 850 is placed outside a fan connection duct 710 which is connected to an imaging exhaust fan 410. The sound-absorbing member 850 consists of a perforated plate-shaped member 830 with multiple sound-absorbing holes and a sound-absorbing sheet 815 covering the multiple sound-absorbing holes. By arranging the sound-absorbing member 850, a noise reduction effect of the airflow sound generated by the operation of the imaging exhaust fan 410 is obtained. When a portion of the airflow sound passes through the sound-absorbing holes of the first-layer perforated plate-shaped member 830, a portion of the sound energy is converted into heat energy, and the airflow sound is reduced. Additionally, a portion of the sound energy of the sound that has passed through the sound-absorbing holes is further converted into heat energy by the second-layer sound-absorbing sheet 815, and the airflow sound is further reduced. Furthermore, the sound-absorbing member 850 can be installed in a small space.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a duct unit that forms an air passage through which air generated by a fan passes, and to an image forming apparatus including the duct unit. [Background technology]

[0002] The image forming apparatus includes a fan and a cylindrical duct for blowing air into the housing. The duct connects the fan to various devices, such as a corona charger that generates ozone, a developer that generates scattered toner, a fixing device that becomes hot, and a power supply, and forms an air passage through which the airflow generated by the fan passes. For example, by blowing air to the corona charger, the ozone generated by the charging of the photosensitive drum can be carried by the airflow to a filter and collected by the filter. In addition, by generating an airflow inside the housing, heat generated by the operation can be discharged outside the machine or dispersed within the housing.

[0003] Patent Document 1 proposes silencing airflow noise by providing multiple ducts of different lengths, or by providing a duct with a hollow tubular side branch with one closed end, thereby causing the sounds passing through them to interfere with each other. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 8-156367 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in recent years, there has been a demand for further miniaturization of image forming apparatuses, and the space available for installing fans and ducts within the image forming apparatus is limited. On the other hand, a relatively large space is required to use multiple ducts of different lengths or a duct with a side branch as described above. Therefore, conventional noise reduction techniques have the problem that it is difficult to miniaturize image forming apparatuses.

[0006] The present invention has been made in consideration of the above problems, and aims to provide a duct unit that can achieve both miniaturization of the device and silencing of airflow noise generated by fan operation, and an image forming device equipped with the duct unit. [Means for solving the problem]

[0007] A duct unit according to one embodiment of the present invention comprises a fan that generates an airflow, a duct having a cylindrical main body that forms an air passage through which the airflow generated by the fan passes, and a sound-absorbing material arranged on the outside of the main body along at least a portion of the air passage of the main body, wherein the sound-absorbing material includes a first layer and a second layer that is laminated with the first layer in a direction perpendicular to the outer surface of the main body and has sound-absorbing properties different from those of the first layer.

[0008] A duct unit according to one embodiment of the present invention comprises a fan that generates an airflow, a duct having a cylindrical main body that forms an air passage through which the airflow generated by the fan passes, and a sound-absorbing material arranged on the outside of the fan, wherein the sound-absorbing material includes a first layer and a second layer that is laminated with the first layer in a direction perpendicular to the outer surface of the main body and has sound-absorbing properties different from those of the first layer.

[0009] A duct unit according to one embodiment of the present invention comprises a fan that generates an airflow, a duct having a cylindrical main body that forms an air passage through which the airflow generated by the fan passes, and a sound-absorbing member arranged on the outside of the main body along at least a portion of the air passage of the main body, wherein the main body includes a wall portion having a non-through hole on the outside, and the sound-absorbing member is arranged on the outside of the wall portion.

[0010] An image forming apparatus according to one embodiment of the present invention comprises a housing, an image forming unit which forms an image on a recording material, a fan which generates an airflow, a duct provided in the housing and having a cylindrical main body which forms an air passage through which the airflow generated by the fan passes, and a sound-absorbing member fixed to the housing so as to be positioned outside the main body along at least a portion of the air passage of the main body, the sound-absorbing member including a first layer and a second layer which is stacked with the first layer in a direction perpendicular to the outer surface of the main body and has sound-absorbing properties different from those of the first layer. Effect of the Invention

[0011] According to the present invention, it is possible to achieve both miniaturization of the device and silencing of airflow noise generated by operation of the fan. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic diagram showing an image forming apparatus according to an embodiment of the present invention; [Diagram 2] FIG. 2A is a cross-sectional view showing an image forming transfer device, and FIG. 2B is an enlarged view showing an image forming station. [Diagram 3] FIG. [Figure 4] FIG. 4 is a block diagram showing an example of a fan air volume. [Diagram 5] FIG. 2A is a front view showing the appearance of an image forming / transfer device, and FIG. 2B is a right side view showing the appearance of the image forming / transfer device. [Figure 6] FIG. [Figure 7] FIG. [Figure 8] FIG. 4 is a perspective view showing a fan and a fan connection duct. [Figure 9] FIG. 2 is a perspective view showing a fan connection duct in which a sound absorbing member according to the first embodiment is arranged. [Figure 10] 1A is a perspective view showing a sound-absorbing member; FIG. 1B is an exploded perspective view showing the sound-absorbing member; FIG. 1C is an enlarged cross-sectional view showing an end portion of the sound-absorbing member; and FIG. [Figure 11] 6 is a graph showing the volume of airflow noise when no sound-absorbing member is arranged and when the sound-absorbing member of the first embodiment is arranged. [Figure 12] FIG. 4A is a perspective view showing the attachment / detachment mechanism, and FIG. [Figure 13] 1A is a perspective view showing a locking claw, FIG. 1B is an enlarged view showing the locking claw, FIG. 1C is a perspective view showing a claw holder, and FIG. [Figure 14] FIG. 13 is a perspective view showing a perforated type fan connection duct. [Figure 15] FIG. 13 is a cross-sectional view showing a perforated type fan connection duct. [Figure 16] (a) is a perspective view showing a recessed type fan connection duct, and (b) is a cutaway view taken along line AA. [Figure 17] FIG. 13 is a perspective view showing a case where a sound absorbing sheet is further arranged in addition to the sound absorbing member. [Figure 18] 11 is a graph showing the volume of airflow noise when the thickness of the sound-absorbing sheet is changed and in this embodiment in which a sound-absorbing member is arranged. [Figure 19] FIG. 11 is a perspective view showing a fan connection duct in which a sound absorbing member according to a second embodiment is arranged. [Figure 20] 13 is a graph showing the volume of airflow noise when using only one sound-absorbing sheet, when using two sound-absorbing sheets made of the same material, and when the sound-absorbing member of the second embodiment is arranged. [Figure 21] 1A is a top view showing a sound-absorbing member disposed on a fan, FIG. 1B is a perspective view, FIG. 1C is an exploded perspective view, and FIG. 1D is a top view showing a perforated plate-like member. [Figure 22]FIG. 1A is a schematic diagram showing a case in which a sound-absorbing member is supported by a bottom plate; FIG. 1B is a perspective view showing the sound-absorbing member supported by the bottom plate; and FIG. [Figure 23] FIG. 4A is a schematic diagram showing a case in which the sound-absorbing member is supported by the rear panel and the bottom panel, and FIG. 4B is a perspective view showing the fan, the fan connection duct, and the sound-absorbing member. [Figure 24] FIG. 4A is a diagram for explaining the attachment of the sound-absorbing material to the bottom plate, and FIG. 4B is a perspective view showing the sound-absorbing material after it has been attached to the bottom plate. [Diagram 25] 1A is a diagram showing the sound-absorbing member after it has been attached to the bottom plate, as viewed from the rear panel side; FIG. 1B is a diagram for explaining the attachment of the sound-absorbing member to the rear panel. [Figure 26] 1A is a perspective view showing the sound-absorbing member as viewed from the rear panel side, FIG. 1B is an exploded perspective view showing the sound-absorbing member, and FIG. 1C is a diagram showing a perforated plate-like member and double-sided tape. [Figure 27] FIG. 13 is a perspective view showing a case where a sound absorbing sheet is placed in a perforated type fan connection duct. [Figure 28] FIG. 1 is a schematic diagram showing a duct provided with a conventional side branch. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] [First embodiment] <Image forming system> The present embodiment will be described below. First, the image forming apparatus of the present embodiment will be described with reference to Fig. 1 to Fig. 2(b). The image forming system 1X shown in Fig. 1 includes an image forming apparatus 101, a large-capacity feeding apparatus 106 having a plurality of recording material storage units, and a sensing apparatus 107. The sensing apparatus 107 is disposed downstream of the image forming apparatus 101 with respect to the conveying direction of the recording material S by the large-capacity feeding apparatus 106 (from right to left in Fig. 1).

[0014] In this specification, the side on which a user stands when operating an operation unit 80 (described later) is referred to as the "front (or front)" and the opposite side is referred to as the "rear (or rear)". In addition, the left side as viewed from the front is referred to as the "left" and the right side as viewed from the front is referred to as the "right". Therefore, FIG. 1 shows the image forming system 1X as viewed from the front.

[0015] The large-capacity feeding device 106 and the sensing device 107 are not only physically connected to the image forming apparatus 101 so as to be able to convey the recording material S, but are also electrically connected so as to be able to transmit and receive electrical signals. The large-capacity feeding device 106 is a device that supplies the recording material S to the image forming apparatus 101. The sensing device 107 is a device that reads a fixed toner image formed on one side or both sides of the recording material S discharged from the image forming apparatus 101, and feeds it back to the image forming apparatus 101 as an image signal. The image forming apparatus 101 detects the image density and image position deviation based on the fed-back image signal, and corrects the image data based on the detected image density and image position deviation. Then, the image forming stations 200Y to 200K are controlled based on the corrected image data to form a toner image on the recording material S.

[0016] Instead of the large-capacity feeding device 106, a manual feeding device (not shown), a long-length feeding device capable of accommodating long-length recording materials, etc. can be selectively connected to the upstream side of the image forming apparatus 101 in the recording material conveying direction. Alternatively, a large-capacity feeding device, a manual feeding device, a long-length feeding device, etc. (not shown) may be selectively connected in a cascade connection to the further upstream side of the large-capacity feeding device 106. Also, although not shown, various post-processing devices such as an inserter, a puncher, a case binder, a large-capacity stacker, a folder, a finisher, a trimmer, etc. can be selectively connected in combination to the further downstream side of the image forming apparatus 101 or the sensing device 107. In this way, by selectively connecting various optional devices to the upstream and downstream of the image forming apparatus 101, it becomes possible to inline output products that have been subjected to various post-processing processes for recording materials S of various materials, and it is possible to provide an image forming system 1X that is highly productive, has high image quality, is highly stable, and is highly functional.

[0017] <Image forming device> The image forming apparatus 101 is largely divided into an image forming and transferring device 500 and a fixing and conveying device 600, which are configured separately. In the present embodiment, the image forming and transferring device 500 as an image forming means includes image forming stations 200Y, 200M, 200C, and 200K, which realize a transfer process of transferring a toner image to a recording material S, and an intermediate transfer belt unit 800. On the other hand, the fixing and conveying device 600 includes a fixing device 8 and a cooler 302, which realize a fixing process of fixing the toner image to the recording material S. The image forming and transferring device 500 and the fixing and conveying device 600 are connected so as to be able to deliver the recording material S.

[0018] The image forming and transferring device 500 and the fixing and conveying device 600 have independent housings 500A and 600A, respectively, and can be moved by a plurality of casters provided on each. As a result, even if the image forming and transferring device 500 and the fixing and conveying device 600 are large devices, they can be packaged and transported in a state separated into the housings 500A and 600A, improving the workability until installation. In addition, the housing 500A is provided with a document reading device 160 that reads image information of a document, a display unit that can display various information, an operation unit 80 having keys that can input various information according to user operations, and the like.

[0019] The housings 500A and 600A each include a front plate on the front side, a rear plate on the rear side that supports the image forming stations 200Y-200K, the intermediate transfer belt unit 800, the fixing unit 8, the cooler 302, etc. together with the front plate, and a plurality of frames such as supports that connect the front plate and the rear plate and support the front plate. The housings 500A and 600A are fitted with resin exterior covers that form the exterior. The image forming and transferring device 500 and the fixing and conveying device 600 may be provided in one housing instead of separate housings (500A, 600A).

[0020] <Image forming and transferring device> Next, the image forming and transferring device 500 will be described with reference to Fig. 2(a) and Fig. 2(b). The image forming and transferring device 500 as an image forming section is an intermediate transfer type device in which image forming stations 200Y, 200M, 200C, and 200K that form yellow, magenta, cyan, and black toner images housed in a housing 500A (inside the housing) are arranged facing an intermediate transfer belt 208. The image forming and transferring device 500 forms a toner image on a recording material S according to image data from a document reading device 160 (see Fig. 1) provided above the housing 500A or an external device (not shown) such as a personal computer. Examples of the recording material S include sheet materials such as paper, plastic film, and cloth.

[0021] The conveying process of the recording material S in the image forming and transferring device 500 will be described. The recording material S is stored in a stacked form in one or more (here, two) cassettes 212, and is supplied one sheet at a time by a supply roller 220 in accordance with the image forming timing. The recording material S supplied by the supply roller 220 is conveyed to a registration roller 213 arranged in the middle of a conveying path 250. Then, the registration roller 213 performs skew correction and timing correction on the recording material S, and the recording material S is sent to a secondary transfer section ST. The secondary transfer section ST is formed by a secondary transfer inner roller 214 and a secondary transfer outer roller 215 that face each other with the intermediate transfer belt 208 in between, and is a transfer nip section that transfers a toner image from the intermediate transfer belt 208 onto the recording material S by applying a predetermined pressure and secondary transfer voltage.

[0022] The process of forming an image sent to the secondary transfer station ST at the same timing as the process of conveying the recording material S to the secondary transfer station ST described above will be described. First, the image forming stations 200Y to 200K will be described. However, since the image forming stations 200Y to 200K for each color are basically the same except for the color of the toner, the following description will be given by taking the black image forming station 200K as an example.

[0023] The image forming station 200K includes a photosensitive drum 201K, a charger 202K, a laser scanner 203K, a developer 204K, etc. The surface of the rotating photosensitive drum 201K is uniformly charged in advance by the charger 202K, and then an electrostatic latent image is formed on the surface by the laser scanner 203K driven based on image data. Next, the developer 204K develops the electrostatic latent image formed on the photosensitive drum 201K with toner contained in the developer, and a toner image is formed on the photosensitive drum 201K.

[0024] Thereafter, a predetermined pressure and a primary transfer voltage are applied by a primary transfer roller 207K disposed opposite the image forming station 200K with the intermediate transfer belt 208 sandwiched therebetween, and the toner image formed on the photosensitive drum 201K is primarily transferred onto the intermediate transfer belt 208. Primary transfer residual toner remaining on the photosensitive drum 201K after the primary transfer is removed by a drum cleaner 209K. The removed primary transfer residual toner is collected in a recovered toner container 211 via a toner recovery path 210.

[0025] The intermediate transfer belt 208 is an endless belt that is stretched by a plurality of tension rollers and a secondary transfer inner roller 214 and moved by a motor (not shown) at a speed corresponding to the rotation speed of the photosensitive drums 201Y to 201K. The image forming process of each color, which is processed in parallel by the image forming stations 200Y to 200K of each color, is performed at a timing to sequentially superimpose the toner image of the color that has been primarily transferred onto the intermediate transfer belt 208 upstream in the moving direction. As a result, a full-color toner image is finally formed on the intermediate transfer belt 208 and conveyed to the secondary transfer section ST. Secondary transfer residual toner remaining on the intermediate transfer belt 208 after passing through the secondary transfer section ST is collected from the intermediate transfer belt 208 by a belt cleaner device 216. The primary transfer rollers 207Y to 207K, the intermediate transfer belt 208, the plurality of tension rollers, the secondary transfer inner roller 214, the belt cleaner device 216, and the like may be integrally provided as an intermediate transfer belt unit 800.

[0026] Through the above-described conveying process and image forming process, the timing of the recording material S and the toner image coincides at the secondary transfer portion ST, and secondary transfer is performed in which the toner image is transferred from the intermediate transfer belt 208 to the recording material S. Thereafter, the recording material S is conveyed by pre-fixing conveying belts 217a and 217b to the fixing conveying device 600, which fixes the toner image onto the recording material S.

[0027] The image forming and transferring device 500 can form a full-color image using all the image forming stations 200Y to 200K described above, as well as a black-and-white image using only the black image forming station 200K. When forming a black-and-white image, the primary transfer rollers 207Y to 207C and the primary transfer auxiliary roller 218 are displaced vertically downward by a separation mechanism (not shown). This separates the photosensitive drums 201Y to 201C from the intermediate transfer belt 208, and the image forming stations 200Y to 200C are stopped. In this way, by stopping the image forming stations 200Y to 200C, it is possible to prevent wear of parts due to unnecessary driving, thereby increasing the life of the image forming stations 200Y to 200C.

[0028] In the image forming station 200K that is not separated from the intermediate transfer belt 208, the photosensitive drum 201K is configured to have a larger diameter suitable for a longer life than the photosensitive drums 201Y to 201C. The charger 202K of the image forming station 200K is a corona charger of a non-contact charging type, and the chargers 202Y to 202C of the image forming stations 200Y to 200C are roller chargers of a contact charging type using a charging roller. As a result, even for a user who frequently uses black-and-white image formation, the maintenance interval of the image forming station 200K that is used frequently is not shorter than the maintenance interval of the image forming stations 200Y to 200C that are used less frequently, and the two are almost the same. In addition, the large-diameter drum configuration using a corona charger can provide a wider charging width in the direction of the rotation axis of the photosensitive drum than the small-diameter drum configuration using a roller charger, and is suitable for high-speed charging, thereby improving productivity during black-and-white image formation.

[0029] In the image forming and transferring device 500 in which the image forming stations 200Y to 200C and the image forming station 200K are partially different as described above, there may be a difference in the amount of toner charge on the photosensitive drums 201Y to 201C and the photosensitive drum 201K due to differences in shape and wear. If a difference in the amount of toner charge occurs, the toner image is not transferred uniformly from the intermediate transfer belt 208 to the recording material S in the secondary transfer process, and transfer failure may occur. Therefore, the photosensitive drum 201K is provided with a pre-transfer charger 219 made of a corona charger in order to equalize the amount of toner charge on the photosensitive drums 201Y to 201C. The pre-transfer charger 219 performs charge control (specifically, charge application) on the photosensitive drum 201K before it reaches the transfer nip portion formed by the photosensitive drum 201K and the primary transfer roller 207K, and equalizes the amount of toner charge on the toner image formed on the photosensitive drum 201K.

[0030] The above-described configuration provides an image forming and transferring device 500 that is excellent in terms of high productivity, high image quality, high stability, and long life, not only in full-color image formation but also in black-and-white image formation.

[0031] <Fixing conveying device> Next, the fixing and conveying device 600 will be described. As shown in FIG. 1, the fixing and conveying device 600 has a fixing unit 8 and a cooling unit 302. The fixing unit 8 has a fixing roller 8a heated by a heater (not shown), and a pressure roller 8b that presses the recording material S against the fixing roller 8a. The recording material S on which a toner image is formed and conveyed from the image forming and transferring device 500 is heated and pressurized while being nipped and conveyed in a fixing nip portion N1 formed by the fixing roller 8a and the pressure roller 8b. As a result, the toner image is fixed to the recording material S.

[0032] In this embodiment, the fixing device 8 is configured by a pair of rollers, the fixing roller 8a and the pressure roller 8b, but is not limited to this. For example, the fixing device may have a fixing belt instead of the fixing roller 8a, and fix the toner image on the recording material S by applying heat and pressure to the recording material S while sandwiching and conveying it in a fixing nip formed by the fixing belt heated by a heater and the pressure roller 8b.

[0033] The recording material S heated by the fixing device 8 is transported towards the cooler 302. The cooler 302 has cooling belts 302a and 302b and a heat sink 303. The cooling belts 302a and 302b come into contact with each other to form a cooling nip portion N2 that sandwiches and transports the recording material S. The heat sink 303 is arranged in contact with the inner circumferential surface of the cooling belt 302a, and the heat sink 303 cools the cooling belt 302a. As a result, the recording material S heated by the fixing device 8 is cooled when it is sandwiched and transported in the cooling nip portion N2.

[0034] The recording material S cooled by the cooler 302 is sandwiched between a pair of cooling outlet rollers 601 and conveyed. In the case of a single-sided mode in which a toner image is formed only on one side of the recording material S, the recording material S cooled by the cooler 302 is guided to a discharge conveying path 304 and discharged from the housing 600A toward the sensing device 107. On the other hand, in the case of a double-sided mode in which a toner image is formed on both sides of the recording material S, the recording material S cooled by the cooler 302 is inverted on a reversing conveying path 305, and then returned to the image forming and transferring device 500 through a double-sided conveying path 306. Thereafter, the recording material S undergoes the same process as in the single-sided mode, a toner image is formed on the other side by the fixing device 8, and after being cooled by the cooler 302, it is guided to a discharge conveying path 304 and finally discharged from the housing 600A toward the sensing device 107.

[0035] <Airflow unit> Next, the airflow units arranged in the housings 500A and 600A in the image forming apparatus 101 to blow air will be described with reference to Figs. 3 and 4 while also referring to Figs. 1 to 2(b). First, the airflow unit of the image forming and transferring apparatus 500 will be described. As shown in Fig. 3, the airflow units of the image forming and transferring apparatus 500 include an image forming airflow 401, a pre-fixing transport airflow 402, and a power supply airflow 403.

[0036] The imaging air flow 401 has a charger intake fan 408, developer intake fans 409Y, 409M, and 409C, an imaging exhaust fan 410, and a duct unit 700. The charger intake fan 408 supplies outside air for ventilation to the charger 202K. A charger intake filter 411 is disposed at the intake port of the charger intake fan 408 to collect dust floating in the outside air in order to supply purified air to the charger 202K. The air volume of the charger intake fan 408 is, for example, 0.27 m 3 / min".

[0037] The developing unit intake fans 409Y, 409M, and 409C supply outside air for cooling to the developing units 204Y, 204M, and 204C. The air volume of the developing unit intake fans 409Y to 409C is, for example, 0.11 m 3 / min".

[0038] The imaging exhaust fan 410 exhausts ozone, which is a dischargeable substance generated by corona discharge performed by the charger 202K and the pre-transfer charger 219, from the image forming station 200K. The imaging exhaust fan 410 also exhausts heat generated in the developing devices 204Y, 204M, and 204C due to friction during rotational driving from the image forming station 200. The imaging exhaust fan 410 also exhausts heat accumulated inside from the toner recovery path 210. In this embodiment, polyester resin is used as the binder resin of the toner, and if the temperature in the vicinity of the developing devices 204Y to 204C becomes 40°C or higher, there is a risk of image defects occurring, and if the temperature in the vicinity of the toner recovery path 210 becomes 45°C or higher, there is a risk of toner clogging occurring. Therefore, in this embodiment, heat is exhausted in order to keep the temperature in the vicinity of the developing devices 204Y to 204C at 40°C or lower and the temperature in the vicinity of the toner recovery path 210 at 45°C or lower. Furthermore, the imaging exhaust fan 410 exhausts scattered toner during the image forming process from the image forming stations 200Y to 200K. The air volume of the imaging exhaust fan 410 is, for example, 1.13 m 3 The air volume of the image forming exhaust fan 410 is the total air volume of the charger intake fan 408 and the developing unit intake fans 409Y, 409M, and 409C, which is 0.60 m 3 / min".

[0039] An imaging exhaust filter 412 that collects ozone and scattered toner discharged from the image forming stations 200Y to 200K is disposed upstream of the airflow direction (arrow Y direction) of the imaging exhaust fan 410. The imaging exhaust filter 412 collects the ozone and scattered toner, thereby preventing the ozone and scattered toner from being discharged outside the housing 500A.

[0040] In this embodiment, the air currents generated by the charger intake fan 408, the developer intake fans 409Y to 409C, and the imaging exhaust fan 410 are exhausted to the outside of the housing 500A (outside the housing) through a cylindrical duct unit 700 provided in the housing 500A. The imaging exhaust filter 412 is disposed in the duct unit 700. The duct unit 700 will be described later (see FIGS. 6 and 7).

[0041] According to the imaging airflow 401 described above, ozone, scattered toner, and heat can be efficiently discharged to the outside of the housing 500A without being retained in the housing 500A. Therefore, it is possible to prevent poor charging such as uneven charging caused by ozone or scattered toner adhering to the photosensitive drum or charger, poor development caused by toner overheating and deteriorating fluidity, operational malfunction such as clogging of the toner transport path, and poor transfer caused by ozone or scattered toner adhering to the pre-transfer charger 219.

[0042] A pre-fixing conveyance suction fan 413 is provided on the inner periphery of the pre-fixing conveyance belts 217a and 217b for suctioning the recording material S to the outer periphery of the pre-fixing conveyance belts 217a and 217b through a suction port directed toward the pre-fixing conveyance belts 217a and 217b. The pre-fixing conveyance suction fans 413 are arranged, for example, two for each of the pre-fixing conveyance belts 217a and 217b in the conveying direction, for a total of four. These pre-fixing conveyance suction fans 413 constitute a pre-fixing conveyance air flow 402. The pre-fixing conveyance suction fan 413 is adjusted to an optimal air volume according to the material and shape of the conveyed recording material S by a control circuit (not shown). With this configuration, it is possible to stably convey recording materials S of various materials without disturbing the toner image on the recording material S before fixing. The air volume of the pre-fixing conveyance suction fan 413 is set to, for example, "0.25 m. 3 / min".

[0043] The power supply airflow 403 has a power supply exhaust fan 415 that exhausts heat generated in the power supply board 414 to the outside of the housing 500A. As the power supply exhaust fan 415 exhausts heat, outside air for cooling is supplied from the power supply intake port 416, and the power supply board 424 can be efficiently cooled. This configuration makes it possible to prevent malfunctions and breakdowns of the image forming and transferring apparatus 500 caused by a drop in output due to an overheating of the power supply board 414. The air volume of the power supply exhaust fan 415 is, for example, 1.23 m 3 / min".

[0044] Next, a description will be given of the airflow units of the fixing conveying device 600. As shown in Fig. 3, the airflow units of the fixing conveying device 600 include a fixing airflow 404, a cooler airflow 405, a power supply airflow 406, and an electrical equipment airflow 407. The fixing airflow 404 has a fixing exhaust heat fan 417, a fixing pressurized intake fan 418, a fixing pressurized exhaust fan 419, and a moisture exhaust fan 420.

[0045] The fixing heat exhaust fan 417 mainly exhausts heat generated in the fixing roller 8a of the fixing unit 8 to the outside of the housing 600A. In the present embodiment, three fixing heat exhaust fans 417 are arranged side by side in the left-right direction. When the parts constituting the fixing unit 8 or the release agent (wax, etc.) contained in the toner are heated, VOCs (Volatile Organic Compounds), UFPs (Ultra Fine Particles), etc. may be generated. Therefore, a fixing upper exhaust filter 421 for collecting VOCs, UFPs, etc. is disposed downstream (here, on the rear side) of the airflow generated by the fixing heat exhaust fan 417. The air volume of the fixing heat exhaust fan 417 is, for example, "0.55 m 3 / min".

[0046] The fixing pressure intake fan 418 supplies outside air for cooling to the pressure roller 8b of the fixing unit 8. The fixing pressure exhaust fan 419 exhausts heat generated on the pressure roller 8b side of the fixing unit 8 to the outside of the housing 600A. The moisture exhaust fan 420 exhausts water vapor that may be generated when the recording material S containing moisture is heated by the fixing unit 8 to the outside of the housing 600A. The air volume of the fixing pressure intake fan 418 is, for example, 1.74 m 3 / min, and the air volume of the fixing pressure exhaust fan 419 is, for example, "0.50 m 3 The air volume of the moisture exhaust fan 420 is, for example, 0.28 m 3 / min".

[0047] A fixing lower exhaust filter 422 for collecting VOCs, UFPs, and the like is disposed downstream (here, on the left side) of the airflow generated by the fixing pressurization exhaust fan 419 and the moisture exhaust fan 420.

[0048] It should be noted that the above-mentioned pre-fixing transport suction fan 413 may suck VOCs, UFPs, and the like from the housing 600A into the housing 500A. Therefore, in this embodiment, the air sucked by the pre-fixing transport suction fan 413 is also collected by the lower fixing exhaust filter 422 to collect VOCs, UFPs, and the like.

[0049] According to the above-described configuration of fixing airflow 404, heat, moisture, VOCs, UFPs, and the like generated in the fixing process can be efficiently discharged to the outside of housing 600A without being retained in housing 600A. In other words, fixing failures and operational failures caused by the temperature rise of toner and parts due to heat being retained in housing 600A can be prevented.

[0050] Also, it is possible to prevent poor fixing caused by the excessive heat given to the toner in the fixing process due to the pressure roller 8b of the fixing unit 8 rising too high, or poor separation of the recording material S from the fixing roller 8a and the pressure roller 8b. It is also possible to prevent condensation on the conveying guide (not shown) caused by water vapor adhering, and poor conveying and fixing caused by condensed water droplets adhering to the recording material S during conveying. Furthermore, it is possible to prevent malfunctions and conveying problems caused by the release agent (wax) vaporized by heating solidifying again and adhering to parts, etc.

[0051] The cooler airflow 405 has a cooler exhaust fan 423 for discharging heat released by the heat sink 303 of the cooler 302 to the outside of the housing 600A. The heat sink 303 of the cooler 302 is a heat exchanger that absorbs heat from the recording material S after fixing via the cooling belt 302a and releases the absorbed heat. With this configuration, the recording material S heated by the fixing device 8 is efficiently cooled, so that the amount of heat released from the recording material S in the conveying path (304, 305, 306, see FIG. 1) can be reduced. In other words, it is possible to prevent image defects and operational defects caused by the toner being overheated due to the heat released from the recording material S. In addition, when a large amount of deliverables are stacked in the post-processing device (here, the sensing device 107), it is possible to prevent the recording materials S from sticking to each other via the toner.

[0052] The power supply airflow 406 includes power supply exhaust fans 425, 426 that exhaust heat generated in the power supply board 424 to the outside of the housing 600A. As the power supply exhaust fans 425, 426 exhaust air, air for cooling is supplied from the power supply intake port 427, and the power supply board 424 can be efficiently cooled. This configuration makes it possible to prevent malfunctions and failures caused by the power supply board 424 overheating and reducing its output.

[0053] The electrical component airflow 407 includes an electrical component exhaust fan 430 that exhausts heat generated in the electrical component boards 428 and 429 to the outside of the housing 600A. As the electrical component exhaust fan 430 exhausts air, air for cooling is supplied from the electrical component intake port 431, and the electrical component boards 428 and 429 can be efficiently cooled. This makes it possible to prevent malfunctions and breakdowns caused by a drop in output due to an overheating of the electrical component boards 428 and 429.

[0054] <Duct unit> Next, the duct unit 700 will be described with reference to FIGS. 5(a) to 7 and with reference to FIGS. 2(a) to 3. As shown in FIGS. 5(a) and 5(b), resin exterior covers (60a to 60e) that cover the housing 500A and constitute the exterior are attached to the housing 500A. In this embodiment, the exterior covers include a front cover 60a on the front side, a right side cover 60b on the right side, a left side cover 60c on the left side, a top cover 60d on the top, and a rear cover 60e on the rear. In order to take air into the housing 500A, an air intake 61 is formed in the front cover 60a, and an air intake 62 is formed in the right side cover 60b.

[0055] The above-mentioned developing unit intake fans 409Y to 409C draw air into the housing 500A from outside the housing 500A through the intake port 61. The charger intake fan 408 draws air into the housing 500A from outside the housing 500A through the intake port 62, and blows the drawn air toward the photosensitive drum 201K from above the charger 202K.

[0056] In this embodiment, the duct unit 700 is provided in the housing 500A in order to merge the airflow generated by the charger intake fan 408, the airflow generated by the developer intake fans 409Y to 409C, and the airflow generated by the image formation exhaust fan 410 into one and exhaust the merged airflow. However, when multiple airflows are merged, if the merging points of the multiple airflows overlap and the pressure loss increases, there is a risk that the overall exhaust efficiency will decrease. Therefore, in this embodiment, the duct unit 700 is used, which can suppress the decrease in exhaust efficiency while merging multiple airflows.

[0057] 6 and 7, the duct unit 700 has a developing exhaust duct 701, an ozone exhaust duct 702, an imaging exhaust duct 703, and a fan connection duct 710. In this embodiment, the fan connection duct 710 is connected downstream of the imaging exhaust fan 410 in the airflow direction, and a sound absorbing member 850, which will be described later, is arranged on the outside of the fan connection duct 710.

[0058] The developer exhaust duct 701 is a developer exhaust section 701a and a cooling exhaust section 701b that are integrally provided by resin. The developer exhaust section 701a is formed with developer exhaust ports 71Y, 71M, and 71C. The developer exhaust ports 71Y to 71C are formed at positions corresponding to the developers 204Y to 204C so that air passing near the developers 204Y, 204M, and 204C due to the intake by the developer intake fans 409Y, 409M, and 409C can be taken into the developer exhaust section 701a. That is, the air near the developers 204Y to 204C flows from the developer exhaust ports 71Y to 71C into the developer exhaust section 701a, and the developer exhaust section 701a joins the air flowing from the developer exhaust ports 71Y to 71C. The vicinity of the developing units 204Y to 204C refers to the area around the developing units 204Y to 204C through which the air sucked by the developing unit intake fans 409Y to 409C flows.

[0059] The cooling and exhausting section 701b is formed with a pre-transfer charging exhaust port 72 and an imaging cooling port 73. The pre-transfer charging exhaust port 72 is formed to take in air containing ozone generated by the pre-transfer charger 219 from the vicinity of the pre-transfer charger 219 into the cooling and exhausting section 701b. The imaging cooling port 73 is formed to take in air near the toner recovery path 210 into the cooling and exhausting section 701b. In this embodiment, air flows into the cooling and exhausting section 701b from the pre-transfer charging exhaust port 72 and the imaging cooling port 73 with the operation of the imaging exhaust fan 410. The vicinity of the pre-transfer charger 219 refers to the area around the pre-transfer charger 219 where air is exhausted with the operation of the imaging exhaust fan 410. The vicinity of the toner recovery path 210 refers to the area around the toner recovery path 210 where air is exhausted with the operation of the imaging exhaust fan 410. By forming an air flow in the cooling exhaust section 701b, the ozone generated by the pre-transfer charger 219 can be collected by the imaging exhaust filter 412, and the heat retained in the toner recovery path 210 can be discharged.

[0060] In this way, the developing exhaust duct 701 merges the air taken in from the developing exhaust ports 71Y to 71C, the pre-transfer charging exhaust port 72, and the imaging cooling port 73 by one imaging exhaust fan 410, and then passes the air through the imaging exhaust filter 412. This makes it possible to reduce the number of fans, thereby realizing space saving in the housing 500A.

[0061] The ozone exhaust duct 702 is a duct for taking in air containing ozone generated by the charger 202K from the vicinity of the charger 202K. The imaging exhaust duct 703 is a duct for combining the airflow from the development exhaust duct 701 and the airflow from the ozone exhaust duct 702 into one airflow.

[0062] In this embodiment, in order to efficiently take in air from a narrow space, even though the opening areas of the development exhaust ports 71Y to 71C, the pre-transfer charging exhaust port 72, and the imaging cooling port 73 are relatively small, a sirocco fan with high static pressure is used as the imaging exhaust fan 410. The sirocco fan is a multi-blade blower with many rectangular fins attached in a circle, and can generate a large amount of airflow because it can generate high static pressure even though it is small. The imaging exhaust fan 410 is disposed inside the duct unit 700.

[0063] However, centrifugal fans are prone to produce particularly loud fan noise, which is unpleasant to the ears of users. Causes of fan noise include aerodynamic noise generated by the rotation of the fins, airflow noise generated by turbulence in the flowing air, and mechanical noise such as creaking of bearings. In order to reduce fan noise, it is possible to consider silencing the airflow noise. As one example, a side branch type silencing device can be used to silence the airflow noise using the Helmholtz principle. Silencing of airflow noise using a side branch type silencing device will be explained using FIG. 28.

[0064] As shown in FIG. 28, in the side branch type noise suppressor, a fan 2 is fixed to the end of a duct 1 attached to a housing (not shown). In addition, downstream of the airflow direction, which is the direction in which the air generated in the duct 1 flows, a side branch 4 is provided that protrudes from the side of the duct 1 in a direction intersecting the airflow direction. In this case, the airflow sound of the airflow generated by the fan 2 is divided into a first path from point A to point B and a second path from point A to point B via point C. The length L of the side branch 4 is set so that the waveform phase of the sound passing through the first path (point A-point B) and the sound passing through the second path (point A-point C-point B) is shifted by 180°. Therefore, the sound passing through the first path and the sound passing through the second path interfere with each other at point B, and the airflow sound is reduced.

[0065] However, in recent years, there has been a demand for further miniaturization of the image forming apparatus 101, and the space available for installing fans and ducts is limited. Specifically, the speed of sound in air is approximately 331000 mm / s, so if the frequency of the airflow sound is assumed to be 1000 Hz, the distance λ that the airflow sound travels in one cycle is 331000 / 1000=331 mm. In this case, to reduce the airflow sound, it is necessary to install a duct 1 provided with a side branch 4 with a length L of 2L=λ / 2, L=λ / 4=82.75 mm. However, some image forming apparatuses 101 may not have a large enough space to install the desired number and size of side branches 4.

[0066] Therefore, in this embodiment, instead of or in addition to the side branch, a configuration is adopted in which a sound absorbing member 850 is arranged on the outside of the fan connection duct 710 that constitutes an air passage through which the airflow passes, so that the airflow noise generated by the operation of the fan can be silenced. The fan connection duct 710 and the sound absorbing member 850 will be described with reference to Figures 8 to 10(d).

[0067] <Fan connection duct> The opening of the imaging exhaust fan 410 is formed to have a rectangular cross section. Accordingly, as shown in Fig. 8, the fan connection duct 710 has a main body 740 formed to have a rectangular cross section. Here, the main body 740 is formed to have a rectangular shape in which the short sides of the non-porous walls 730 and 731, which are two faces perpendicular to the rotation axis 410a of the imaging exhaust fan 410, are longer than the short sides of the non-porous walls 732 and 733, which are the other two faces. Note that the main body 740 is not limited to having a rectangular cross section, and may have a plurality of faces (three or more faces) whose cross sections are polygonal.

[0068] The main body 740 is formed with a duct inlet 720 through which air flows in as the imaging exhaust fan 410 operates, and a duct outlet 721 through which the air that flows in from the duct inlet 720 flows out. The fan connection duct 710 is connected to an opening of the imaging exhaust fan 410 via the duct inlet 720, and the main body 740 forms an air passage through which the air that flows in from the duct inlet 720 passes to the duct outlet 721. The fan connection duct 710 is made of metal or resin.

[0069] <Sound absorbing materials> Fig. 9 is a perspective view showing a fan connection duct 710 in which a sound absorbing member 850 of the first embodiment is arranged. As shown in Fig. 9, on both sides of the non-porous walls 730, 731 of the fan connection duct 710, the sound absorbing members 850 are arranged along at least a part of the air passage of the main body 740. The sound absorbing members 850 are adhered to the non-porous walls 730, 731 by, for example, an adhesive double-sided tape (not shown) as an adhesive member.

[0070] As shown in FIG. 10(a), the sound absorbing member 850 includes at least a perforated plate-like member 830 and a sound absorbing sheet 815. The sound absorbing sheet 815 has a different sound absorbing property from that of the perforated plate-like member 830. In this embodiment, the sound absorbing sheet 815 is formed of a material different from that of the perforated plate-like member 830. The perforated plate-like member 830 and the sound absorbing sheet 815 are laminated in a direction perpendicular to the non-perforated walls 730, 731 of the main body 740. In other words, the sound absorbing member 850 of this embodiment includes a two-layer member constituted by the sound absorbing sheet 815 and the perforated plate-like member 830.

[0071] <Perforated plate member> As shown in Fig. 9, the sound absorbing member 850 is disposed so that the perforated plate-like member 830 as the first layer is located on the main body 740 side (main body side). The perforated plate-like member 830 is a plate-like member made of resin or metal. As shown in Fig. 10(b), the perforated plate-like member 830 has sound absorbing properties due to the formation of a plurality of sound absorbing holes 811 which are through holes. That is, when airflow sound generated by the operation of the imaging exhaust fan 410 passes through the fan connection duct 710, part of the airflow sound enters the sound absorbing holes 811 via the non-perforated walls 730, 731 and vibrates, so that part of the sound energy is converted into thermal energy, resulting in the effect of silencing the airflow sound.

[0072] <Sound absorbing sheet> As shown in FIG. 10(a), a sound absorbing sheet 815 is disposed on the surface of the perforated plate-like member 830 opposite to the surface facing the main body 740 so as to cover the multiple sound absorbing holes 811. The sound absorbing sheet 815 is formed in a sheet shape from a porous material such as an ethylene propylene diene rubber (EPDM) or urethane foam, or a glass wool material made of glass fiber, or a mineral rock wool material. By covering the sound absorbing holes 811 of the perforated plate-like member 830 with the porous sound absorbing sheet 815, when a part of the airflow sound entering the sound absorbing holes 811 is diffused in the sound absorbing sheet 815, a part of the sound energy is converted into thermal energy, and the sound can be reduced. The perforated plate-like member 830 and the sound absorbing sheet 815 have different sound absorbing properties. More strictly, when the perforated plate-like member 830 and the sound absorbing sheet 815 of the same thickness are disposed alone, they have different sound absorbing properties. As an example of different sound absorption properties, there is a difference in sound absorption coefficient for each frequency. For example, the perforated plate-like member 830 can reduce sounds in a low frequency band (bass side) in the audible range compared to the sound absorbing sheet 815. The sound absorbing sheet 815 can reduce sounds in a high frequency band (treble side) in the audible range compared to the perforated plate-like member 830. Alternatively, the difference in sound absorption properties may occur depending on whether or not there is sound absorption.

[0073] Generally, a thicker sound absorbing sheet 815 is preferable because it is more adaptable to sounds of a wider frequency band and is more likely to provide a silencing effect. In this embodiment, in order to obtain a higher effect at a low cost, a sound absorbing sheet 815 formed of an EPDM foam with a thickness of "5 mm" is used. Note that when an EPDM or urethane sound absorbing sheet 815 is used, if the sound absorbing sheet 815 is crushed, it becomes difficult to obtain a silencing effect. Therefore, the duct unit 700 is installed in the housing 500A so that the sound absorbing sheet 815 of the sound absorbing member 850 arranged in the fan connection duct 710 is not crushed.

[0074] As shown in Fig. 10(b) and Fig. 10(c), the perforated plate-like member 830 and the sound-absorbing sheet 815 are laminated with the double-sided tape 816 sandwiched therebetween. The sound-absorbing sheet 815 is adhered to the perforated plate-like member 830 by the adhesive double-sided tape 816 as an adhesive member. However, if the double-sided tape 816 blocks the sound-absorbing holes 811, the noise reduction effect may be reduced compared to when the holes are not blocked. Therefore, as shown in Fig. 10(d), it is desirable that the double-sided tape 816 adheres the perforated plate-like member 830 and the sound-absorbing sheet 815 to the non-forming area 810a where the sound-absorbing holes 811 are not formed, in other words, outside the area 810b where the sound-absorbing holes 811 are formed. Here, since the non-forming area 810a is provided on the outer peripheral edge of the perforated plate-like member 830, for example, a ring-shaped double-sided tape 816 is used.

[0075] In order to strengthen the adhesive strength of the double-sided tape 816, it is advisable to adhere the sound absorbing sheet 815 to a plurality of locations other than the non-forming region 810a (other than the outer periphery) in addition to the non-forming region 810a. In this case, some of the sound absorbing holes 811 may be blocked by the double-sided tape 816.

[0076] The sound absorbing holes 811 formed in the perforated plate-like member 830 preferably occupy an area of ​​"35% or more" relative to the surface area of ​​the perforated plate-like member 830. However, taking into consideration the workability of the sound absorbing holes 811 in the perforated plate-like member 830 and the ease of attachment of the double-sided tape 816, the area of ​​the multiple sound absorbing holes 811 may be "10% to 40%" relative to the surface area of ​​the perforated plate-like member 830. The sound absorbing holes 811 are preferably round holes with a hole diameter of "3 mm to 12 mm". It is not necessary for all the sound absorbing holes 811 to have the same hole diameter, but in this embodiment, the hole diameter of all the sound absorbing holes 811 is "6.4 mm". The sound absorbing holes 811 are preferably evenly distributed in the main body 740.

[0077] <Silence effect> 11 shows the results of comparing the volume of airflow noise when the imaging exhaust fan 410 is operated alone and when the sound absorbing member 850 is arranged in the fan connection duct 710 and when the sound absorbing member 850 is not arranged. As can be seen from FIG. 11, the volume of airflow noise when the sound absorbing member 850 is not arranged is "6.97 sones", and the volume of airflow noise when the sound absorbing member 850 is arranged is "6.64 sones". That is, by using the fan connection duct 710 arranged with the sound absorbing member 850 of this embodiment, a noise reduction effect of "0.33 sones" was obtained. Since a high noise reduction effect can be obtained by the sound absorbing member 850 having a thickness of several mm to several tens of mm, the device can be made compact.

[0078] The noise reduction configuration using the side branch shown in FIG. 28 is a configuration that reduces vibrations of a specific frequency by interference. Therefore, it has a high reduction effect on the specific frequency. On the other hand, in the noise reduction configuration using the side branch, there may be a frequency band where resonance occurs. In contrast, according to the sound absorbing member 850 of this embodiment, the two-layer structure of the perforated plate-like member 830 and the sound absorbing sheet 815, which have different sound absorbing properties, can reduce sounds in a wide frequency band in the audible range, so that the resonance phenomenon is unlikely to occur. In addition, since there is no need to change the shape to match a specific frequency, even if the fan is changed to one with a higher rotation speed or one fan is used while changing the rotation speed, one sound absorbing member 850 can be used.

[0079] As described above, in this embodiment, a two-layered sound absorbing member 850 having a perforated plate-like member 830 in which a plurality of sound absorbing holes 811 are formed and a sound absorbing sheet 815 covering the plurality of sound absorbing holes 811 is disposed outside the fan connection duct 710, thereby obtaining a silencing effect for airflow noise. That is, when part of the airflow noise generated with the operation of the imaging exhaust fan 410 passes through the sound absorbing holes 811 of the first layer of the perforated plate-like member 830, part of the sound energy is converted to thermal energy, and the airflow noise is silenced. In addition, part of the sound energy of the sound that has passed through the sound absorbing holes 811 is further converted to thermal energy by the second layer of the sound absorbing sheet 815, so that the airflow noise is further silenced.

[0080] Furthermore, according to this embodiment, the configuration allows for placement in a small space, making it possible to reduce the airflow noise that occurs with the operation of the fan.

[0081] In addition, generally, when the sound-absorbing sheet 815 having sound absorption properties is used alone, the sound-absorbing sheet 815 has a characteristic that it exhibits a sound-absorbing effect at a certain frequency. For example, when the horizontal axis is frequency and the vertical axis is sound absorption coefficient, a central high characteristic is observed. The sound absorption coefficient of low frequency band sounds (bass side) in the audible range can be improved by increasing the thickness of the sound-absorbing sheet, but it is difficult to obtain an effect of improving the sound absorption coefficient for sounds in the main frequency bands in the audible range even if the thickness of the sound-absorbing sheet is increased. In contrast, in this embodiment, by using a two-layered sound-absorbing member 850 having a perforated plate-like member 830 and a sound-absorbing sheet 815, it is possible to reduce sounds in a wide frequency band including sounds in the main frequency bands in the audible range.

[0082] In addition, when the imaging exhaust fan 410 is a sirocco fan that generates an airflow by rotating fins around the rotation axis 410a (see FIG. 8), a high noise reduction effect can be obtained by arranging the sound absorbing members 850 on the outside of the two non-porous walls 730, 731 perpendicular to the rotation axis 410a of the fan as described above. The noise reduction effect can also be obtained when the sound absorbing members 850 are arranged only on the other non-porous walls 732, 733. However, in this case, the noise reduction effect is relatively small compared to when the sound absorbing members 850 are arranged only on the non-porous walls 730, 731. In order to obtain a higher noise reduction effect than the configuration in which the sound absorbing holes 811 are formed only on the non-porous walls 730, 731, the noise reduction effect may be improved by arranging the sound absorbing members 850 on all four non-porous walls 730, 731, 732, 733. In order to obtain the sound absorbing effect of this embodiment, when the cross section of the main body 740 is polygonal, the sound absorbing member 850 needs to be disposed on at least one of the multiple faces. Even when the cross section of the main body 740 is circular, the sound absorbing member 850 can be disposed on at least a part of the outer side of the wall surface to obtain the noise absorbing effect.

[0083] <Detachable mechanism> In the above-described embodiment, the sound absorbing member 850 is attached to the fan connection duct 710 (specifically, the non-porous walls 730, 731) by double-sided tape (not shown) as an example, but the present invention is not limited to this. The sound absorbing member 850 may be provided detachably to the fan connection duct 710. An attachment / detachment mechanism for making the sound absorbing member 850 detachable from the fan connection duct 710 will be described with reference to Figs. 12(a) to 13(d). In the following, an example will be described in which the sound absorbing member 850 is detachably provided to the non-porous wall 730 of the fan connection duct 710.

[0084] As shown in Fig. 12(a), the sound absorbing member 850 is detachably attached to the fan connecting duct 710 by snap fits 907. The snap fits 907 are provided at four locations in the longitudinal direction of the fan connecting duct 710, two on the duct inlet 720 side and two on the duct outlet 721 side. As shown in Fig. 12(b), the snap fits 907 as an attachment / detachment mechanism have a locking claw 901 as a first locking portion and a claw holder 902 as a second locking portion. When the sound absorbing member 850 is attached to the main body 740, the locking claw 901 is locked to the claw holder 902, and when the sound absorbing member 850 is removed from the main body 740, the locking claw 901 and the claw holder 902 are released from their locked state.

[0085] As shown in Fig. 13(a), the locking claws 901 are provided on the non-perforated walls 732, 733 of the main body 740. As shown in Fig. 13(b), the locking claws 901 have elastically deformable hooking portions 901a, which protrude beyond the non-perforated wall 730. On the other hand, as shown in Fig. 13(c), the claw holder 902 is provided on the perforated plate-like member 830. As shown in Fig. 13(d), the claw holder 902 is formed with a hooking hole 902a through which the hooking portion 901a of the locking claw 901 can pass. When the sound absorbing member 850 is attached to the main body 740, the hooking portion 901a is inserted into the hooking hole 902a while being elastically deformed, and after passing through, is hooked in the hooking hole 902a, so that it does not come out of the hooking hole 902a (locked state). As a result, the sound absorbing member 850 is attached to the fan connection duct 710 as shown in FIG. 12(a).

[0086] <Perforated fan connection duct> In the above-described embodiment, the sound absorbing member 850 is arranged in the non-perforated fan connection duct 710 having non-perforated walls 730-733 with no holes formed in the wall surface, but the present invention is not limited to this. The fan connection duct in which the sound absorbing member 850 is arranged may be a perforated fan connection duct 710A having a number of through holes formed in the wall surface. Figures 14 and 15 show the perforated fan connection duct 710A. The configuration of the sound absorbing member 850 is the same as that shown in Figures 9 and 10, except for the parts where differences are described.

[0087] 14, perforated type fan connection duct 710A has, as perforated wall surface portions, a perforated wall 730A in which a plurality of sound absorbing holes 711 that are through holes are formed, and a perforated wall 731A that is provided at a position opposite to perforated wall 730A and in which a plurality of sound absorbing holes 711 that are through holes are formed. Note that fan connection duct 710A may have sound absorbing holes 711 formed in wall surfaces (732A, 733A) out of four surfaces (730A, 731A, 732A, 733A), or may have sound absorbing holes 711 formed in all or only one of the four surfaces (730A to 733A).

[0088] In the fan connection duct 710A, when airflow sound generated by the operation of the imaging exhaust fan 410 passes through the main body 740A, a part of the airflow sound enters the sound absorption holes 711 and vibrates, so that a part of the sound energy is converted into thermal energy, which has the effect of silencing the airflow sound. Since the imaging exhaust fan 410 is a sirocco fan, a high sound silencing effect can be obtained by forming the sound absorption holes 711 in the two perforated walls 730A and 731A perpendicular to the rotation axis 410a of the fan as described above. When the sound absorption holes 711 are formed only in the other perforated walls 732A and 733A, the sound silencing effect is relatively small compared to when the sound absorption holes 711 are formed only in the perforated walls 730A and 731A. However, if a sufficient noise absorbing effect cannot be obtained by forming the sound absorbing holes 711 only in the perforated walls 730A and 731A, the noise absorbing effect may be improved by forming the sound absorbing holes 711 in all four perforated walls 730A to 733A.

[0089] However, when the fan connection duct 710A is manufactured by injection molding using a mold made of resin, the mold capable of forming the sound absorbing holes 711 on all four sides is complicated and costly. Therefore, it is conceivable to prepare separate molds to create parts into which the fan connection duct 710A is divided and then assemble them. However, in such a case, gaps are likely to be formed between the divided parts, so a separate member is required to close the gaps. In addition, a step is generated between the parts, and the airflow noise generated by the operation of the imaging exhaust fan 410 becomes large, so that in the end, even if the sound absorbing holes 711 are formed, a sufficient sound silencing effect cannot be obtained. Therefore, it is preferable to form the sound absorbing holes 711 only in the perforated walls 730A and 731A perpendicular to the rotation axis 410a of the fan as much as possible.

[0090] In contrast, when fan connection duct 710A is made of metal, sound absorption holes 711 can be easily formed on all four sides, and the distance between sound absorption holes 711 can be narrower than when made of resin, which has the advantage of allowing the number of sound absorption holes 711 to be increased. However, as will be described later, there is a disadvantage that it costs more to manufacture fan connection duct 710A with the downstream side of duct inlet 720 formed in an inclined shape in order to reduce the cross-sectional area of ​​the air passage in the area where sound absorption holes 711 are provided, if the duct is made of metal, it is more costly than if the duct is made of resin. Taking these advantages and disadvantages into consideration, it is better to manufacture fan connection duct 710A from resin rather than metal.

[0091] 15, if there is a step between the blowout port 410b of the imaging exhaust fan 410 and the duct inlet 720 of the fan connection duct 710A, a loud airflow noise will be generated. Therefore, it is preferable that there is no step, but it is difficult to form the imaging exhaust fan 410 and the fan connection duct 710A, which are different parts, so that they can be connected without a step. Therefore, the duct inlet 720 is made slightly wider than the blowout port 410b of the imaging exhaust fan 410.

[0092] The shape of the fan connection duct 710A downstream of the duct inlet 720 in the airflow direction is preferably such that the airflow spreads inside the fan connection duct 710A and some of the airflow sound is easily incident on the sound absorption holes 711. To achieve this, the downstream side of the duct inlet 720 is inclined, and the cross-sectional area of ​​the air passage in sound absorption hole region 725A where the sound absorption holes 711 are provided is made smaller than the cross-sectional area of ​​the air outlet 410b.

[0093] The main body 740A has a first main body 741A whose cross-sectional area narrows from upstream to downstream in the airflow direction (arrow Y direction) in which air flows, and a second main body 742A formed continuously on the downstream side of the first main body 741A and whose cross-sectional area widens from upstream to downstream. In the first main body 741A, the perforated wall 730A and the perforated wall 731A are inclined at a gradient of, for example, about 1 degree so that the duct cross-sectional area narrows from the duct inlet 720 to the minimum cross-sectional area part 722A, which is the boundary between the first main body 741A and the second main body 742A. In the second main body 742A, the perforated wall 730A and the perforated wall 731A are inclined at a gradient of, for example, about 1 degree so that the duct cross-sectional area widens from the minimum cross-sectional area part 722A to the duct outlet 721. In this way, fan connection duct 710A is formed such that the air passage at duct center portion 723A including minimum cross-sectional area portion 722A is narrower in the airflow direction than the air passage at upstream duct inlet 720. Also, fan connection duct 710A is formed such that the air passage at downstream duct outlet 721 is wider in the airflow direction than the air passage at duct center portion 723A.

[0094] The reason for inclining first main body portion 741A in this manner is to facilitate the incidence of part of the airflow sound into sound absorbing holes 711, as described above. On the other hand, the reason for inclining second main body portion 742A is to increase the cross-sectional area of ​​duct outlet 721. This is to prevent the airflow sound flowing out from main body portion 740A from becoming louder if the cross-sectional area of ​​duct outlet 721 is narrow. Note that in perforated wall 730A and perforated wall 731A, sound absorbing holes 711 are not formed in duct central portion 723A.

[0095] The sound absorbing holes 711 formed in the perforated wall 730A and the sound absorbing holes 711 formed in the perforated wall 731A are preferably formed at positions where they do not overlap each other when viewed from the perforated wall 730A to the perforated wall 731A. By shifting the sound absorbing holes 711 between the perforated wall 730A and the perforated wall 731A, a part of the airflow sound in the fan connection duct 710A is more likely to enter the sound absorbing holes 711 in both the perforated wall 730A and the perforated wall 731A, and the silencing effect of the airflow sound is further improved. The sound absorbing holes 711 are preferably round holes with a hole diameter of "3 mm or more and 12 mm or less". It is not necessary to make the hole diameter of all the sound absorbing holes 711 the same, but in this embodiment, the hole diameter of all the sound absorbing holes 711 is "6.4 mm". In addition, it is preferable that the sound absorbing holes 711 are evenly distributed and arranged in the main body part 740A.

[0096] The above-mentioned sound absorbing member 850 is disposed on the perforated walls 730A, 731A in which the sound absorbing holes 711 are formed in the perforated fan connection duct 710A. In this case, a part of the sound energy of the sound that passes through the sound absorbing holes 711 in the fan connection duct 710A is further converted into thermal energy by the two-layered sound absorbing member 850, so that the airflow sound can be quieter than in the case of the non-perforated fan connection duct 710 (see FIG. 8). Note that the sound absorbing member 850 may also be disposed on the perforated walls 732A, 733A in which the sound absorbing holes 711 are not formed in the fan connection duct 710A.

[0097] <Fan connection duct with recessed section> Alternatively, the fan connection duct in which the sound absorbing member 850 is arranged may be a recessed fan connection duct 710B in which a number of recesses are formed on the wall surface. Figures 16(a) and 16(b) show the recessed fan connection duct 710B. The configuration of the sound absorbing member 850 is the same as that shown in Figures 9 and 10, except for the parts where differences are described.

[0098] 16(a) and 16(b), the recess-formed fan connection duct 710B has a wall surface portion 730B (wall portion) in which a large number of recesses 715 that are non-through holes are formed, and a wall surface portion 731B (wall portion) that is provided at a position opposite to the wall surface portion 730B and in which a large number of recesses 715 that are non-through holes are formed. The recesses 715 are depressions in the outer surface of the main body portion 740B, and the shape of the recesses 715 is not limited to a circular shape and may be a polygonal shape, etc.

[0099] In the fan connection duct 710B, when airflow sound generated by the operation of the imaging exhaust fan 410 passes through the main body 740B, a part of the airflow sound enters the recess 715 and vibrates, so that a part of the sound energy is converted into thermal energy, which has the effect of silencing the airflow sound. The sound absorbing member 850 is disposed on the wall surface portions 730B and 731B where the recess 7015 is formed in the recess-formed fan connection duct 710B. Therefore, a part of the sound energy of the sound that passes through the recess 715 of the fan connection duct 710B is further converted into thermal energy by the two-layered sound absorbing member 850, so that the airflow sound can be silenced more than in the case of the non-hole type fan connection duct 710 (see FIG. 8). The fan connection duct 710B is different from the above-mentioned perforated type fan connection duct 710A in that the wall surface has a recess 715 formed therein, and the wall surface has a sound absorbing hole 711 formed therein, and other configurations may be the same, so a description thereof will be omitted here.

[0100] <Sound-absorbing material + sound-absorbing sheet> In the above-described embodiment, an example in which only the sound absorbing member 850 is disposed in the fan connection duct 710 (710A, 710B) has been shown, but the present invention is not limited to this. For example, a sound absorbing sheet may be further disposed between the sound absorbing member 850 and the fan connection duct 710 (710A, 710B). FIG. 17 shows a case in which a sound absorbing sheet 900 is further disposed in addition to the sound absorbing member 850. FIG. 17 shows a case in which the sound absorbing member 850 is disposed on the sound absorbing sheet 900 disposed on the perforated wall 731A, using the perforated type fan connection duct 710A (see FIG. 14) as an example. For example, it is considered to use an EPDM foam for the sound absorbing sheet 815 and the sound absorbing sheet 900 to reduce costs.

[0101] As shown in FIG. 17, the sound absorbing sheet 900 as the second sound absorbing member is attached to the perforated wall 731A with double-sided tape so as to cover all of the sound absorbing holes 711 formed in the perforated wall 731A. The above-mentioned two-layered sound absorbing member 850 (first sound absorbing member) is attached to the outside of the sound absorbing sheet 900 with double-sided tape 860. The double-sided tape 860 adheres the perforated plate-like member 830 so as not to block the sound absorbing holes 811. In this way, the double-sided tape (not shown), the sound absorbing sheet 900, the double-sided tape 860, the perforated plate-like member 830, the double-sided tape 816, and the sound absorbing sheet 815 are laminated on the perforated wall 731A in this order from the perforated wall 731A side in the direction intersecting with the perforated wall 731A. In other words, the perforated plate-like member 830 is sandwiched between the sound absorbing sheet 900 and the sound absorbing sheet 815.

[0102] In the fan connection duct 710A, when airflow sound generated by the operation of the imaging exhaust fan 410 passes through the main body 740A, a part of the airflow sound enters the sound absorbing hole 711 and vibrates, so that a part of the sound energy is converted into thermal energy, and the airflow sound can be silenced. In addition, by covering the sound absorbing hole 711 with the sound absorbing sheet 900, a part of the sound energy is converted into thermal energy when a part of the airflow sound that passed through the sound absorbing hole 711 is diffused in the sound absorbing sheet 900. Furthermore, the sound that passed through the sound absorbing sheet 900 is silenced by the sound absorbing member 850. As described above, in the sound absorbing member 850, a part of the sound energy of the sound that passed through the sound absorbing sheet 900 is converted into thermal energy when it passes through the sound absorbing hole 811, and a part of the sound energy of the sound that passed through the sound absorbing hole 811 is further converted into thermal energy by the sound absorbing sheet 815. In this way, the airflow sound is silenced in stages as it passes through sound absorbing hole 711, sound absorbing sheet 900, sound absorbing hole 811, and sound absorbing sheet 815.

[0103] <Silence effect> 18 shows the volume of airflow noise when imaging exhaust fan 410 is operated alone, with the following cases: only sound absorbing sheet 900 with a thickness of 5 mm is arranged; only sound absorbing sheet 900 with a thickness of 10 mm is arranged; and sound absorbing sheet 900 with a thickness of 5 mm and sound absorbing member 850 are arranged. Note that sound absorbing sheet 815 of sound absorbing member 850 is made of the same material as sound absorbing sheet 900 and is 5 mm thick (EPDM foam).

[0104] As can be seen from FIG. 18, a higher airflow noise silencing effect is obtained by arranging the sound absorbing member 850 in addition to the sound absorbing sheet 900 having a thickness of 5 mm, rather than by increasing the thickness of the sound absorbing sheet 900 from 5 mm to 10 mm. This is because, as described above, the frequency band of sound at which sound energy is converted into thermal energy differs between the sound absorbing sheet 900 and the sound absorbing sheet 815 and the sound absorbing holes 811 of the perforated plate-like member 830. That is, when the sound absorbing member 850 is arranged in addition to the sound absorbing sheet 900, the sound silencing effect is more easily obtained by adapting to a wider frequency band of sound than when the sound absorbing sheet 900 is made thicker, so the sound volume is smaller (6.23 sone). Note that, in order to obtain a higher airflow noise silencing effect, it is preferable to use different materials for the sound absorbing sheet 900 and the sound absorbing sheet 815. This is because the frequency band of sound at which sound energy is converted into thermal energy differs depending on the material of the sound absorbing sheet.

[0105] The sound absorbing member 850 may be disposed with a gap (for example, 3 mm) between it and the sound absorbing sheet 900. For example, the thickness of the double-sided tape 860 that bonds the sound absorbing sheet 900 and the sound absorbing member 850 may be increased to ensure a gap between the sound absorbing member 850 and the sound absorbing sheet 900. By providing a gap between the sound absorbing member 850 and the sound absorbing sheet 900, the frequency band of sound that can be reduced by the sound absorbing holes 811 of the perforated plate-like member 830 can be adjusted. For example, by widening the gap between the sound absorbing member 850 and the sound absorbing sheet 900, the sound absorbing holes 811 can reduce sounds in a low frequency band (low frequency side) in the audible range compared to before the gap is widened. However, a higher airflow noise silencing effect can be obtained by not providing a gap between the sound absorbing member 850 and the sound absorbing sheet 900.

[0106] 17, the sound absorbing sheet 900 may be considered to be included in the sound absorbing member 850. In other words, the sound absorbing member 850 may be considered to include three layers, namely, the sound absorbing sheet 900, the perforated plate-like member 830, and the sound absorbing sheet 815, which are laminated in this order from the side of the main body 740. It can be said that the noise reduction effect of this embodiment can be obtained according to the configuration of the wall of the main body 740 and the combination of the number, material, and shape of the layers arranged on the outside of the wall.

[0107] [Second embodiment] Next, the second embodiment will be described with reference to Figs. 19 and 20. Fig. 19 is a perspective view showing a fan connection duct 710A in which a sound absorbing member 850A of the second embodiment is arranged. That is, the sound absorbing member 850A is arranged outside the fan connection duct 710A instead of the sound absorbing member 850 of the first embodiment described above. Note that, here, an example in which the sound absorbing member 850A is arranged in the fan connection duct 710A of a perforated type (see Fig. 14) is given, but the sound absorbing member 85A may be arranged in the fan connection duct 710 of a non-perforated type (see Fig. 8) or the fan connection duct 710B of a recessed type (see Fig. 16(a)). Hereinafter, the second embodiment will be described, but the same reference numerals are used for the same configurations as those of the first embodiment described above, and the description will be simplified or omitted.

[0108] <Sound absorbing materials> As shown in Fig. 19, a sound absorbing member 850A of the second embodiment includes a sound absorbing sheet 815 and a sound absorbing sheet 825. The sound absorbing sheet 815 and the sound absorbing sheet 825 are laminated in a direction perpendicular to the perforated walls 730A, 731A. The sound absorbing member 850A is arranged such that the sound absorbing sheet 825 as a first layer covers the multiple sound absorbing holes 711 (see Fig. 14) formed in the perforated walls 730A, 731A. The sound absorbing sheet 815 as a second layer is laminated on the sound absorbing sheet 825 and adhered to the sound absorbing sheet 825 by double-sided tape (not shown) or the like.

[0109] By covering sound absorbing hole 711 with sound absorbing sheet 825, when a part of the airflow sound that has passed through sound absorbing hole 711 is diffused in sound absorbing sheet 825, a part of the sound energy is converted into heat energy. Also, when a part of the sound that has passed through sound absorbing sheet 825 is diffused in sound absorbing sheet 815, a part of the sound energy is converted into heat energy. Sound absorbing sheet 815 and sound absorbing sheet 825 are porous members made of different materials, and sound absorbing sheet 825 can reduce sounds in a lower frequency band (low frequency side) in the audible range compared to sound absorbing sheet 815. Sound absorbing sheets 815 and 825 are, for example, ethylene propylene diene rubber (EPDM) or urethane foam, glass wool material made of glass fiber, mineral rock wool material, or the like.

[0110] <Silence effect> 20 shows the volume of airflow noise when imaging exhaust fan 410 is operated alone, with one sound absorbing sheet (5mm thick Eptsealer), two sound absorbing sheets of the same material stacked together (5mm thick Eptsealer + 5mm thick Eptsealer), and sound absorbing member 850A. Sound absorbing member 850A is made by laminating 5mm thick Eptsealer and 5mm thick Moltoprene.

[0111] As can be seen from FIG. 20, when there was one 5 mm thick Eptsealer, the sound level was 6.39 sones. When a 5 mm thick Eptsealer was stacked with a 5 mm thick Eptsealer, the sound level was 6.3 sones. This is the same as when a single sound absorbing sheet is made thicker by stacking sound absorbing sheets of the same material, and is a sound silencing effect obtained by the difference in thickness. In contrast, when sound absorbing member 850A was used, the sound level was 6.08 sones, and a higher sound silencing effect was obtained by using sound absorbing member 850A, which has a two-layer structure in which sound absorbing sheets of different materials are stacked together even though they are the same thickness.

[0112] In this way, when the sound absorbing member 850A in which the sound absorbing sheet 815 and the sound absorbing sheet 825 made of different materials are stacked is used, a higher sound silencing effect can be obtained compared to the case where two sound absorbing sheets made of the same material are stacked, even if the total thickness of the two sound absorbing sheets is the same. This is because, as described above, the frequency band of sound that changes sound energy into heat energy differs depending on the material of the sound absorbing sheet. In general, when one sound absorbing sheet is arranged, the sound absorption coefficients of sound absorbing sheets made of different materials are compared, and a sound absorbing sheet made of a material that can provide a high sound silencing effect overall is selected in consideration of all frequency bands. However, rather than stacking two sound absorbing sheets that have a high sound silencing effect when viewed as a single type (or increasing the thickness), stacking the sound absorbing sheets 815 and 825 made of different materials can provide a sound silencing effect in a wider frequency band. In other words, in the case of the sound absorbing member 850A, the same sound silencing effect can be obtained even if the thickness of the two sound absorbing sheets 815 and 825 stacked is thinner than the thickness of the two sound absorbing sheets stacked together made of the same material.

[0113] In the second embodiment, as in the first embodiment, an additional sound absorbing sheet may be placed between the sound absorbing member 850A and the fan connection duct 710A. That is, a higher noise reduction effect can be obtained by stacking three or more sound absorbing sheets. However, the material of the sound absorbing sheet placed between the sound absorbing member 850A and the fan connection duct 710A must be different from that of the sound absorbing sheet 825 on the fan connection duct 710A side of the sound absorbing member 850A. All three or more sound absorbing sheets may be made of different materials.

[0114] [Third embodiment] Next, a third embodiment will be described with reference to Fig. 21(a) to Fig. 21(d). As shown in Fig. 21(a) and Fig. 21(b), in the third embodiment, the above-mentioned two-layered sound absorbing member 850 (850A) is disposed outside the imaging exhaust fan 410, not outside the fan connection duct 710 (710A, 710B). The third embodiment is different from the first and second embodiments in that the sound absorbing member 850 (850A) is disposed outside the imaging exhaust fan 410, and other points may be the same as those of the first and second embodiments. Therefore, the same reference numerals are used for the same configurations, and the description thereof will be simplified or omitted.

[0115] As shown in FIG. 21(c), the sound absorbing member 850 is a two-layered member having a perforated plate-like member 830 in which a plurality of sound absorbing holes 811 are formed and a sound absorbing sheet 815 made of a material different from that of the perforated plate-like member 830, and these sound absorbing members are laminated in the direction of the rotation axis 410a of the imaging exhaust fan 410. The perforated plate-like member 830 is provided with a self-tapping hole 880 as an insertion hole for inserting a screw 909. On the surface of the perforated plate-like member 830 opposite to the surface facing the imaging exhaust fan 410, a sound absorbing sheet 815 is attached with a double-sided tape 816 so as to cover the sound absorbing holes 811 of the perforated plate-like member 830. However, if even a part of the sound absorbing holes 811 are blocked with the double-sided tape 816, the silencing effect of the sound absorbing holes 811 is reduced compared to when they are not blocked. 21(d), the double-sided tape 816 adheres the sound absorbing sheet 815 to a non-forming area 810a where the sound absorbing holes 811 are not formed, in other words, outside the area 811b where the sound absorbing holes 811 are formed. The self-tapping hole 880 is also provided outside the area 811b. The sound absorbing member 850 is attached to the imaging exhaust fan 410 by fastening the sound absorbing member 850 with a screw 909 inserted into a fastening hole of the imaging exhaust fan 410 and the self-tapping hole 880 of the perforated plate-like member 830. Although not shown in the figure, an insert nut is press-fitted into the self-tapping hole 880.

[0116] In this way, even if the sound absorbing member 850 is disposed outside the imaging exhaust fan 410, the airflow sound is silenced because part of the sound energy is converted to thermal energy when part of the airflow sound generated by the operation of the imaging exhaust fan 410 passes through the sound absorbing holes 811. Also, part of the sound energy of the sound that passes through the sound absorbing holes 811 is further converted to thermal energy by the sound absorbing sheet 815, further silencing the airflow sound.

[0117] [Fourth embodiment] Next, a fourth embodiment will be described with reference to Fig. 22(a) to Fig. 27(c). As shown in Fig. 22(a), the duct unit 700 and the imaging exhaust fan 410 are supported by a frame 501 and a bottom plate 502 that constitute a housing 500A. As shown in Fig. 22(b) and Fig. 22(c), the above-mentioned two-layered sound absorbing member 850 (850A) is attached to the bottom plate 502 in advance with a double-sided tape 870 or the like, with the sound absorbing sheet 815 facing the bottom plate 502 side.

[0118] The location of the sound absorbing member 850 (850A) on the bottom plate 502 may be a location that faces either or both of the fan connection duct 710 (710A, 710B) and the imaging exhaust fan 410 when the duct unit 700 is installed in the housing 500A. In addition, when the duct unit 700 is supported by the housing 500A, the sound absorbing member 850 (850A) may be in contact with the fan connection duct 710 (710A, 710B) or the imaging exhaust fan 410, or there may be a gap (for example, 3 mm) therebetween. When the sound absorbing member 850 (850A) comes into contact with the fan connection duct 710 (710A, 710B) or the imaging exhaust fan 410, the sound absorbing member 850 (850A) may be adhered to the fan connection duct 710 (710A, 710B) or the imaging exhaust fan 410 with double-sided tape (not shown) or the like.

[0119] Alternatively, as shown in Fig. 23(a) and Fig. 23(b), the above-mentioned two-layered sound absorbing member 850 (850A) may be fixed to the rear plate 503 and the bottom plate 502 with the sound absorbing sheet 815 facing the rear plate 503 of the housing 500A. The sound absorbing member 850 (850A) may be disposed at a position on the rear plate 503 and the bottom plate 502 that faces either or both of the fan connection duct 710 (710A, 710B) and the imaging exhaust fan 410 when the duct unit 700 is installed in the housing 500A. When the duct unit 700 is supported by the housing 500A, there is a gap between the sound absorbing member 850 (850A) and the fan connection duct 710 (710A, 710B) or the imaging exhaust fan 410.

[0120] 24(a) and 24(b), a part of the end of the perforated plate-like member 830 on the bottom plate 502 side is bent at a right angle to the opposite side from the rear plate 503 to provide a bottom plate fixing part 830A for fixing the sound absorbing member 850 (850A) to the bottom plate 502. A screw insertion hole 8301 is formed in the bottom plate fixing part 830A, and a tap part 502a for screw fastening is formed in the bottom plate 502. The sound absorbing member 850 (850A) is fixed to the bottom plate 502 by fastening a screw 909 inserted from the screw insertion hole 8301 of the bottom plate fixing part 830A to the tap part 502a of the bottom plate 502.

[0121] The perforated plate-like member 830 is provided with a protrusion 831 for fixing the sound absorbing member 850 (850A) to the rear plate 503, protruding from an end opposite to the bottom plate fixing portion 830A toward the rear plate 503. In order to ensure an area for contacting the rear plate 503, as shown in FIG. 25(a), the tip of the protrusion 831 is bent at a right angle so as not to overlap with 815, and a tap portion 832 for screw fastening is formed there. On the other hand, the rear plate 503 is formed with a screw insertion hole 5031 as shown in FIG. 25(b). The sound absorbing member 850 (850A) is fixed to the rear plate 503 by fastening a screw 909 inserted from the screw insertion hole 5031 of the rear plate 503 to the tap portion 832 of the protrusion 831.

[0122] As shown in FIG. 26(a), it is preferable that all of the sound absorbing holes 811 of the perforated plate-like member 830 are covered with the sound absorbing sheet 815. That is, as shown in FIG. 26(b), the sound absorbing sheet 815 is attached to the perforated plate-like member 830 with a double-sided tape 816. However, if even a part of the sound absorbing holes 811 is blocked with the double-sided tape 816, the sound silencing effect of the sound absorbing holes 811 is reduced compared to when the holes are not blocked. Therefore, as shown in FIG. 26(c), the double-sided tape 816 bonds the sound absorbing sheet 815 to a non-forming area 810a in which the sound absorbing holes 811 are not formed in the perforated plate-like member 830. In addition, the double-sided tape 816 may bond the sound absorbing sheet 815 to a non-forming area 810a provided at the end of the perforated plate-like member 830, and also to a non-forming area 810c provided inside the end.

[0123] As described above, the sound absorbing member 850 (850A) is provided in advance in the housing 500A, and is located at a position facing either or both of the fan connection duct 710 (710A, 710B) and the imaging exhaust fan 410 when the duct unit 700 is installed in the housing 500A. In this way, even if there is not enough space available for installing the duct unit 700 in the housing 500A, there is less risk of damaging the sound absorbing member 850 (850A) when installing the duct unit 700 in the housing 500A, compared to when the sound absorbing member 850 (850A) is bonded to the fan connection duct 710 (710A, 710B).

[0124] <Other embodiments> It is to be noted that only the sound absorbing sheet 815 may be disposed in the fan connection duct 710 (710A, 710B). Fig. 27 shows an example in which the sound absorbing sheet 815 is disposed in the perforated type fan connection duct 710A. Here, the sound absorbing sheet 815 is adhered by double-sided tape 816 to both sides of the perforated wall 730A and the perforated wall 731A in which the sound absorbing holes 711 are formed.

[0125] As described above, in the case of the perforated type fan connection duct 710A, when airflow sound generated by the operation of the imaging exhaust fan 410 passes through the main body 740A, part of the airflow sound enters the sound absorption holes 711 and vibrates, converting part of the sound energy into thermal energy and silencing the airflow sound. Then, by using the sound absorbing sheet 815 to further convert part of the energy of the sound that has passed through the sound absorption holes 811 into thermal energy, the airflow sound can be further silenced.

[0126] Similarly, a configuration may be adopted in which a sound absorbing sheet 815 is arranged in the fan connection duct 710B shown in FIG. 16. When the airflow passes through the main body 740B, part of the airflow sound enters the recess 715 and vibrates, so that part of the sound energy is converted into thermal energy, which has the effect of silencing the airflow sound. The sound absorbing sheet 815 is arranged on the wall surface parts 730B and 731B in which the recess 7015 is formed in the recess-formed fan connection duct 710B. Therefore, part of the sound energy of the sound that has passed through the recess 715 of the fan connection duct 710B is further converted into thermal energy by the sound absorbing sheet 815, so that the airflow sound can be silencing.

[0127] In each of the above-described embodiments, a case has been described in which a centrifugal fan is used as the imaging exhaust fan 410. However, this is not limited to this, and airflow noise is also generated by other fans such as axial fans. Therefore, each of the above-described embodiments may be applied without being limited to the type of fan.

[0128] The above-mentioned fan connection duct 710 (710A, 710B) is not limited to use as a duct disposed downstream in the airflow direction of the imaging exhaust fan 410 in the imaging airflow 401, but may be used as a duct disposed upstream in the airflow direction of the imaging exhaust fan 410. Furthermore, the fan connection duct 710 (710A, 710B) is not limited to use in the imaging airflow 401, but may be used in other airflows as described above (see FIG. 3). [Explanation of symbols]

[0129] 101...image forming apparatus, 410...fan (imaging exhaust fan), 500...image forming section (image forming transfer device), 500A...housing, 710 (710A, 710B)...duct (fan connection duct), 711...through hole (sound absorbing hole), 720...inlet (duct inlet), 721...outlet (duct outlet), 730A (731A)...perforated wall surface section (perforated wall), 730B (731B)...wall section (wall surface portion), 740 (740A, 740B)...main body portion, 811...through hole (sound absorbing hole), 815...second layer (sound absorbing sheet), 825...first layer (sound absorbing sheet), 830...first layer (perforated plate-like member), 850 (850A)...sound absorbing member (first sound absorbing member), 900...second sound absorbing member (sound absorbing sheet), 901...first locking portion (locking claw), 902...second locking portion (claw holding portion), S...recording material

Claims

1. A fan that generates airflow; a duct having a cylindrical main body that forms an air passage through which the airflow generated by the fan passes; a sound absorbing member disposed on the outside of the main body along at least a portion of the air passage of the main body, The sound absorbing member includes a first layer and a second layer laminated with the first layer in a direction perpendicular to an outer surface of the main body and having a sound absorbing property different from that of the first layer. A duct unit characterized by:

2. the first layer is a perforated plate-like member having a plurality of through holes formed therein; The second layer is a porous member arranged to overlap the plurality of through holes. The duct unit according to claim 1 .

3. the sound absorbing member is a first sound absorbing member, The second sound absorbing member is disposed between the outer surface of the main body and the first sound absorbing member in a direction perpendicular to the outer surface of the main body, and has a sound absorbing property different from that of the first layer. The duct unit according to claim 1 .

4. The first layer of the sound absorbing member is disposed so as to be located on the main body side with respect to the second layer, the first layer is a perforated plate-like member having a plurality of through holes formed therein; the second layer is a porous member arranged to overlap the plurality of through holes, The second sound absorbing member is a porous member arranged so as to overlap the plurality of through holes. The duct unit according to claim 3 .

5. The first sound absorbing member and the second sound absorbing member are in contact with each other. The duct unit according to claim 3 .

6. The first sound absorbing member and the second sound absorbing member are disposed with a gap therebetween. The duct unit according to claim 3 .

7. The first layer and the second layer are porous members made of different materials. The duct unit according to claim 1 .

8. The body portion has a perforated wall having a plurality of through holes formed therein, The sound absorbing member is disposed on the outer side of the perforated wall in a direction perpendicular to the perforated wall. The duct unit according to claim 1 .

9. The body portion has a perforated wall having a plurality of recesses formed therein, The sound absorbing member is disposed on the outer side of the perforated wall in a direction perpendicular to the perforated wall. The duct unit according to claim 1 .

10. The main body has a plurality of faces that form a polygonal cross section, The sound absorbing member is disposed on at least one of the plurality of surfaces. The duct unit according to claim 1 .

11. The main body and the sound absorbing member are provided detachably, The main body portion has a first locking portion, The sound absorbing member has a second locking portion that locks with the first locking portion when the sound absorbing member is attached to the main body. The duct unit according to claim 1 .

12. The duct is disposed downstream of the fan in an airflow direction in which the air flows, The duct has an inlet through which air flows in the main body and an outlet through which air flows out, The fan is connected to the inlet of the main body. The duct unit according to claim 1 .

13. The fan is a sirocco fan. The duct unit according to claim 1 .

14. an image forming section for forming an image on a recording material; The duct unit according to any one of claims 1 to 13, 1. An image forming apparatus comprising:

15. A fan that generates airflow; a duct having a cylindrical main body that forms an air passage through which the airflow generated by the fan passes; a sound absorbing member disposed on the outside of the fan, The sound absorbing member includes a first layer and a second layer laminated with the first layer in a direction perpendicular to an outer surface of the main body and having a sound absorbing property different from that of the first layer. A duct unit characterized by:

16. an image forming section for forming an image on a recording material; The duct unit according to claim 15, 1. An image forming apparatus comprising:

17. A fan that generates airflow; a duct having a cylindrical main body that forms an air passage through which the airflow generated by the fan passes; a sound absorbing member disposed on the outside of the main body along at least a portion of the air passage of the main body, The body portion includes a wall portion having a non-through hole provided on an outer side thereof, The sound absorbing member is disposed on the outer side of the wall portion. A duct unit characterized by:

18. an image forming section for forming an image on a recording material; The duct unit according to claim 17, 1. An image forming apparatus comprising:

19. A housing and an image forming section for forming an image on a recording material; A fan that generates airflow; a duct provided in the housing and having a cylindrical main body that forms an air passage through which the airflow generated by the fan passes; a sound absorbing member fixed to the housing so as to be disposed outside the main body along at least a portion of the air passage of the main body, The sound absorbing member includes a first layer and a second layer laminated with the first layer in a direction perpendicular to an outer surface of the main body and having a sound absorbing property different from that of the first layer.

1. An image forming apparatus comprising:

Images