BACKGROUND

[0001] In an image forming device, a filter may be provided in an exhaust duct to reduce the number of particles such as ultrafine particles that are discharged to the outside. In addition, a baffle which blocks a part of an airflow may be provided in the exhaust duct to generate swirl or a turbulent flow inside the duct and to thus reduce the number of the particles.

BRIEF DESCRIPTION OF DRAWINGS

[0002] FIG. 1 is a schematic view of an image forming apparatus according to an example.

[0003] FIG. 2 is a schematic cross-sectional view of a collector including a valve, according to an example, illustrating a state where the valve is in a closed position.

[0004] FIG. 3 is a schematic cross-sectional view illustrating a state where the example valve is in an open position.

[0005] FIG. 4A is a schematic cross-sectional view illustrating an operational state of the example valve.

[0006] FIG. 4B is a schematic cross-sectional view illustrating another operational state of the example valve.

[0007] FIG. 4C is a schematic cross-sectional view illustrating another operational state of the example valve.

[0008] FIG. 5A is a schematic cross-sectional view of another example valve of the collector, illustrating an operational state of the valve.

[0009] FIG. 5B is a schematic cross-sectional view illustrating another operational state of the example valve.

[0010] FIG. 5C is a schematic cross-sectional view illustrating another operational state of the example valve.

[0011] FIG. 6 is a schematic cross-sectional view of another example valve of a collector, illustrating a state where the valve is in a closed position.

[0012] FIG. 7 is a schematic cross-sectional view illustrating a state where the example valve of the collector of FIG. 6, is in an open position.

[0013] FIG. 8 is a graph of a temperature measured over time, when a control unit controls the example collector illustrated in FIGS. 2 and 3.

[0014] FIG. 9 is a graph illustrating a control carried out over time, by a control unit on the example collector illustrated in FIGS. 6 and 7.

[0015] FIG. 10A is a schematic cross-sectional view of the example collector of FIG. 5A, illustrating a state where the example valve of the collector is in a closed position.

[0016] FIG. 10B is a schematic cross-sectional view of the example collector of FIG. 5B, illustrating a state where the example valve of the collector is in an open position.

[0017] FIG. 11 is a schematic cross-sectional view illustrating a collector of a another example.

[0018] FIG. 12 is a graph of the number of particles per unit time (ten seconds) measured in a first experiment.

[0019] FIG. 13 is a graph showing the cumulative number of particles measured in the first experiment.

[0020] FIG. 14 is a graph showing the number of particles measured in a second experiment.

[0021] FIG. 15A is a schematic diagram illustrating an example control operation of a main airflow generator.

[0022] FIG. 15B is a schematic diagram illustrating another example control operation of the main airflow generator.

[0023] FIG. 16 is a schematic cross-sectional view of a collector including a valve, according to another example, illustrating a state where the valve is in a closed position.

[0024] FIG. 17 is a schematic cross-sectional view illustrating a state where the example valve of FIG. 16 is in an open position.

[0025] FIG. 18 is a graph illustrating a control carried out over time, by the control unit on the example collector illustrated in FIGS. 16 and 17. [0026] FIG. 19 is a schematic cross-sectional view of a collector including a valve, according to another example, illustrating a state where the valve is in a closed position.

[0027] FIG. 20 is a schematic cross-sectional view illustrating a state where the example valve of FIG. 19, is in an open position.

[0028] FIG. 21 is a schematic cross-sectional view of a collector including a valve, according to another example, illustrating a state where the valve is in a closed position.

[0029] FIG. 22 is a schematic cross-sectional view illustrating a state where the example valve of FIG. 21 , is in an open position.

[0030] FIG. 23 is a graph showing an example of a relationship between the number of particles, the particle size distribution, and the collection efficiency of a filter.

DETAILED DESCRIPTION

[0031] The particles collection rate of a filter may be reduced, when the particle size of the particles collected are finer. Here, when a filter in which a filter material is folded or layered or a fine mesh filter is provided, the particle collection rate of the filter can be increased, however the pressure loss of an airflow passing through the filter is increased. In addition, when a baffle which blocks a part of the airflow is provided in an exhaust duct, the pressure loss of the airflow passing through the baffle is further increased. As a result, a large airflow generator is to generate an airflow, which may increase the product cost, the size of the device, the noise generation, and the power consumption. Therefore, a circulation flow path and a valve are provided in the duct, so that while an increase in pressure loss of the airflow is suppressed, the particle collection rate is increased.

[0032] According to an example, a collector includes a duct that directs an airflow from an inlet position to an outlet position, a filter that is disposed between the inlet position and the outlet position inside the duct to collect particles carried in the airflow, a circulation flow path which is formed between the inlet position and the filter and in which the airflow inside the duct circulates, and a valve that is disposed between the filter and the circulation flow path to be operable such that an opening degree of the duct is variable.

[0033] In addition, an example image forming system may include a fixing device that performs a fixing process to release particles, a duct that directs an airflow from the fixing device to an outlet position, a filter that is disposed between the fixing device and the outlet position of the duct inside the duct to collect the particles contained in the airflow, a circulation flow path which is formed between the fixing device and the filter and in which the airflow inside the duct circulates, and a valve that is disposed between the filter and the circulation flow path inside the duct to be operable such that an opening degree of the duct is variable.

[0034] Hereinafter, an image forming system of an example will be described with reference to the drawings. The image forming system may be an image forming apparatus (or image forming device) such as a printer or may be a device used in the image forming apparatus or the like. In the following description, with reference to the drawings, the same reference numbers are assigned to the same components or to similar components having the same function, and overlapping description is omitted.

[0035] With reference to FIG. 1 , an example image forming apparatus (or image forming device) 1 forms a color image, using four colors such as magenta, yellow, cyan, and black, which are represented by the characters "M", "Y", "C" and "K", respectively in the reference symbols. The image forming apparatus 1 includes a conveying device 10 that conveys a recording medium such as a paper (or sheet of paper) 3, image carriers 20M, 20Y, 20C, and 20K having respective surfaces (peripheral surfaces) that may form electrostatic latent images, developing devices 30M, 30Y, 30C, and 30K that develop the electrostatic latent images to form toner images, a transfer device 40 that transfers the toner images onto the paper 3, a fixing device 50 that fixes the toner images to the paper 3, an output device 60 that outputs the paper 3, and a control unit (or controller) 70.

[0036] The conveying device 10 conveys the paper 3, which is a recording medium on which an image is to be formed, along a conveyance path 11. The papers 3 are stacked and contained in a cassette 12, and are picked up from the cassette 12 and conveyed by a paper feeding roller 13 to the conveyance path 11.

[0037] Each of the image carriers 20M, 20Y, 20C, and 20K may also be referred to as an electrostatic latent image carrier, a photoconductor drum, or the like. The image carrier 20M forms an electrostatic latent image to generate a magenta toner image. The image carrier 20Y forms an electrostatic latent image to generate a yellow toner image. The image carrier 20C forms an electrostatic latent image to generate a cyan toner image. The image carrier 20K forms an electrostatic latent image to generate a black toner image. The image carriers 20M, 20Y, 20C, and 20K have similar configurations. Accordingly, the image carrier 20M will be described as a representative one among the image carriers 20M, 20Y, 20C, and 20K, unless otherwise described.

[0038] The developing device 30M, a charging roller 22M, an exposure unit 23, and a cleaning unit 24M are provided adjacent the image carrier 20M. Similarly to the image carrier 20M, the respective developing devices 30Y, 30C, and 30K, respective charging rollers, the exposure unit 23, and respective cleaning units are also provided adjacent the respective image carriers 20Y, 20C, and 20K.

[0039] The charging roller 22M charges the surface of the image carrier 20M to a predetermined potential. The charging roller 22M rotates to follow a rotation of the image carrier 20M. The exposure unit 23 exposes the surface of the image carrier 20M to light according to the image to be formed on the paper 3, after the surface has been charged by the charging roller 22M. Accordingly, the potential of a portion of the surface of the image carrier 20M that is exposed to the light by the exposure unit 23, is changed, so that an electrostatic latent image is formed. The cleaning unit 24M recovers a toner remaining on the image carrier 20M.

[0040] The developing device 30M develops an electrostatic latent image with a toner supplied from a toner tank 21 M filled with a magenta toner and a carrier, to form a magenta toner image based on the electrostatic latent image formed on the image carrier 20M. The developing device 30Y develops an electrostatic latent image with a toner supplied from a toner tank 21 Y filled with a yellow toner and a carrier, to form a yellow toner image based on the electrostatic latent image formed on the image carrier 20Y. The developing device 30C develops an electrostatic latent image with a toner supplied from a toner tank 21 C filled with a cyan toner and a carrier, to form a cyan toner image based on the electrostatic latent image formed on the image carrier 20C. The developing device 30K develops an electrostatic latent image with a toner supplied from a toner tank 21 K filled with a black toner and a carrier, to form a black toner image based on the electrostatic latent image formed on the image carrier 20K. The developing devices 30M, 30Y, 30C, and 30K have similar configurations. Accordingly, the developing device 30M will be described as a representative one among the developing devices 30M, 30Y, 30C, and 30K, unless otherwise described.

[0041] The developing device 30M includes a developing roller 31 M that carries the toner to the image carrier 20M. The developing device 30M uses a two-component developer containing a toner and a carrier as a developer. Namely, in the developing device 30M, the toner and the carrier are adjusted to achieve a targeted mixing ratio and are further mixed and stirred to disperse the toner, so as to adjust the developer to have an optimal charge amount. In the developing device 30M, the developer is carried on the developing roller 31 M. Then, when the developer is conveyed to a region facing the image carrier 20M by the rotation of the developing roller 31 M, the toner of the developer carried on the developing roller 31 M transfers to the electrostatic latent image formed on a peripheral surface of the image carrier 20M, so that the electrostatic latent image is developed, thereby forming the toner image.

[0042] The transfer device 40 conveys the respective toner images, which have been formed by the developing devices 30M, 30Y, 30C, and 30K, and transfers the toner images onto the paper 3. The transfer device 40 includes a transfer belt 41 onto which the respective toner images are primarily transferred from the image carriers 20M, 20Y, 20C, and 20K, in a layered manner so as to form a single composite toner image on the transfer belt 41 , suspension rollers 44, 45, 46, and 47 that support (or suspend) the transfer belt 41 , primary transfer rollers 42M, 42Y, 42C, and 42K that are positioned to interpose the transfer belt 41 between the primary transfer rollers 42M, 42Y, 42C, and 42K and the image carriers 20M, 20Y, 20C, and 20K in order to primarily transfer the respective toner images from the image carriers 20M, 20Y, 20C, and 20K onto the transfer belt 41 , and a secondary transfer roller 43 that is positioned to interpose the transfer belt 41 between the secondary transfer roller 43 and the suspension roller 47 in order to secondarily transfer the toner images, as the composite toner image, from the transfer belt 41 onto the paper 3.

[0043] The transfer belt 41 is an endless belt which is rotated by the suspension rollers 44, 45, 46, and 47. Each of the suspension rollers 44, 45, 46, and 47 is a roller rotatable around an axis thereof. The suspension roller 47 is a drive roller that rotates around its axis, and the suspension rollers 44, 45, and 46 are driven rollers that are driven to rotate by the rotation of the suspension roller 47. The primary transfer rollers 42M, 42Y, 42C and 42K are pressed against the image carriers 20M, 20Y, 20C and 20K, respectively, from an inner peripheral side of the transfer belt 41 . The secondary transfer roller 43 is disposed parallel to the suspension roller 47 with the transfer belt 41 interposed between the secondary transfer roller 43 and the suspension roller 47, and pressed against the suspension roller 47 from an outer peripheral side of the transfer belt 41. Accordingly, a transfer nip region 14 where the toner images may be transferred from the transfer belt 41 onto the paper 3, is formed between the secondary transfer roller 43 and the transfer belt 41 .

[0044] The fixing device 50 is positioned to convey the paper 3 on which the composite toner image has been transferred, to pass through a fixing nip region where the paper 3 is subjected to heat and pressure, so as to attach and fix the composite toner image to the paper 3. The fixing device 50 includes a heating roller 52 that heats the paper 3, and a pressure roller 54 that is pressed against the heating roller 52 to drive the heating roller 52 to rotate. The heating roller 52 and the pressure roller 54 are formed in a cylindrical shape, and the heating roller 52 includes a heat source such as a halogen lamp thereinside. The fixing nip region which is a contact region is provided between the heating roller 52 and the pressure roller 54, and when the paper 3 passes through the fixing nip region, the composite toner image is melted to be fixed to the paper 3.

[0045] The output device 60 includes output rollers 62 and 64 that output the paper 3, to which the composite toner image has been fixed, to the outside of the apparatus.

[0046] The control unit (or controller) 70 is an electronic control unit including a central processing unit (CPU), a read-only memory (ROM), a randomaccess memory (RAM), and the like. In the control unit 70, a program which is stored in the ROM in the form of data and instructions, may be loaded onto the RAM to be executed by the CPU to execute various control operations. The control unit 70 may be formed of a plurality of electronic control units (electronic control devices) or may be formed of a single electronic control unit (electronic control device). The control unit 70 performs various control operation in the image forming apparatus 1 .

[0047] FIGS. 2 and 3 are schematic cross-sectional views of an example collector 80 of the example image forming apparatus 1 with reference to FIG. 1.

[0048] The collector 80 collects particles that may be floating (e.g., in suspension) in an internal space of the housing 2 of the image forming apparatus 1. The particles collected by the collector 80 may be, for example, ultrafine particles (UFP), where each particle has a size (particle size) of approximately 5 nm to 300 nm. The particles may be generated from, for example, the toner heated by the fixing device 50, the paper, the components of the fixing device 50, or other peripheral components. The fixing device 50 performs a fixing process which may cause particles to be released. In the fixing process, a toner image is fixed to the paper 3For example, as described above, when the paper 3 passes through the fixing nip region, the paper 3 is heated and pressed between the heating roller 52 and the pressure roller 54 to cause a layered toner image to be melted and fixed to the paper 3.

[0049] The collector 80 includes, for example, a duct 81 , a filter 82, a circulation flow path 83, a main airflow generator 84, a valve 85, an internal environment detection unit (or internal environment detector) 86, and a control unit (or controller) 70.

[0050] The duct 81 is a member that is disposed in the housing 2 to direct an airflow from an inlet position 81a to an outlet position 81 b. The duct 81 may extend linearly, curvedly, or in a bending manner. An extending direction of the duct 81 is referred to as a longitudinal direction D1. When the duct 81 extends linearly, the longitudinal direction D1 also is a linear direction, and when the duct 81 extends curvedly or in a bending manner, the longitudinal direction D1 is a direction curved or bent along the duct 81 . In an internal space of the duct 81 , an inlet position 81 a side relative to the outlet position 81 b (or a relative position toward the inlet position 81 a) may be referred to as an upstream side, and an outlet position 81 b side relative to the inlet position 81a (or a relative position toward the outlet position 81 b) is referred to as a downstream side. The inlet position 81a is disposed, for example, in the vicinity of a particle generation source. The particle generation source may be located inside the duct 81 , in some examples. In the example of FIGS. 2 and 3, the fixing device 50 is disposed in the vicinity of the inlet position 81 a inside the duct 81 , as the particle generation source. As an example, the outlet position 81 b is disposed in the housing 2 in order to discharge an airflow to the outside of the housing 2.

[0051] The filter 82 is disposed between the inlet position 81 a and the outlet position 81 b inside the duct 81. The filter 82 is disposed downstream of the fixing device 50 inside the duct 81 to collect particles generated from the fixing device 50. The filter 82 can be produced, for example, by layering a plurality of sheet-shaped filter materials or by folding a sheet-shaped filter material.

[0052] The circulation flow path 83 is a flow path that is formed inside the duct 81 , between the inlet position 81a and the filter 82 (or in some examples, between the fixing device 50 and the filter 82), to cause an airflow to circulate inside the duct 81 . Namely, the circulation flow path 83 is disposed upstream of the filter 82 and downstream of the fixing device 50. The circulation flow path 83 may be formed by a partition wall 87 disposed in the duct 81 . The partition wall 87 is provided in the circulation flow path 83 to form a first flow path 83a and a second flow path 83b inside the duct 81 , and extends between the fixing device 50, the inlet position 81 a and the filter 82, the outlet position 81 b substantially in the longitudinal direction D1 of the duct 81 . The partition wall 87 partitions off the internal space of the duct 81 in a direction orthogonal to the longitudinal direction D1 . One side of the internal space of the duct 81 is the first flow path 83a, the internal space being partitioned off by the partition wall 87, and the other side of the internal space of the duct 81 is the second flow path 83b, the internal space being partitioned off by the partition wall 87. The first flow path 83a and the second flow path 83b form a part of the circulation flow path 83. The partition wall 87 is disposed such that the first flow path 83a narrows in a downstream direction of the duct 81 (e.g., toward the filter 82 and the outlet position 81 b). The partition wall 87 may be formed in a flat plate shape, may be formed in a curved shape, or may be formed in a bent shape.

[0053] The main airflow generator 84 directs air in the first flow path 83a toward the outlet position 81 b of the duct 81 . Namely, the main airflow generator

84 sends the air in the first flow path 83a from the inlet position 81 a side to the outlet position 81 b side. For example, a fan can be provided as the main airflow generator 84. The main airflow generator 84 may be disposed in the first flow path 83a in some examples, may be disposed upstream of the first flow path 83a in other examples, or may be disposed downstream of the first flow path 83a in yet other examples.

[0054] The valve 85 is disposed between the circulation flow path 83 and the filter 82 and is operable such that the opening degree of the duct 81 is variable. As will be described, the example valve 85 may be switched between a closed position and an open position. FIG. 2 illustrates a state where the valve 85 is in the closed position, and FIG. 3 illustrates a state where the valve 85 is in the open position.

[0055] As illustrated in FIG. 2, when the valve 85 is in the closed position, the valve 85 prevents an airflow from passing from the circulation flow path 83 to the filter 82 such that the airflow circulates in the circulation flow path 83. Namely, when the valve 85 is in the closed position, the airflow is prevented from reaching the filter 82 such that the airflow is restricted to circulate in the circulation flow path 83. In addition, as illustrated in FIG. 3, when the example valve 85 is in the open position, the valve 85 allows the airflow to pass from the circulation flow path 83 to the filter 82. Namely, when the valve 85 is in the open position, the valve

85 is operable to cause the airflow to travel toward the outlet position 81 b of the duct 81 from the circulation flow path 83 through the filter 82. In addition, the valve 85 can also change in the opening degree when the valve 85 is in the open position. The opening degree is the opening ratio of the valve 85, and can be expressed as, for example, a percentage where the fully closed state of the valve 85 is 0% and the fully open state of the valve 85 is 100%.

[0056] For example, as illustrated in FIGS. 4A, 4B, and 4C, the example valve 85 may include a plurality of louvers 91 that may be opened and closed inside the duct 81 , to switch between the open position and the closed position. The valve 85 includes, for example, a fixation portion 92 fixed to the duct 81 and the plurality of louvers 91 . Then, the plurality of louvers 91 may be opened and closed with respect to the fixation portion 92, to switch between an open position and a closed position. In this case, for example, the degree of opening of the plurality of louvers 91 with respect to the fixation portion 92 can be changed or the number of the louvers 91 which are opened with respect to the fixation portion 92 can be changed to change the opening degree in the open position.

[0057] FIG. 4A illustrates a state where the valve 85 is in the closed position (fully closed state). FIGS. 4B and 4C illustrate a state where the valve 85 is in the open position. FIG. 4B illustrates a state where all the louvers 91 are fully opened with respect to the fixation portion 92 to be associated with an opening degree of the valve 85 of 100%. FIG. 4C illustrates a state where the louvers 91 are half-open with respect to the fixation portion 92 to be associated with an opening degree of the valve 85 to be 50%.

[0058] In addition, with reference to FIGS. 5A, 5B, and 5C, another example valve 85 may be pulled in and out from the duct 81 to switch between the open position and the closed position. The example valve 85 includes, for example, a valve main body 93 forming a main portion of the valve 85, and a pivot 94 that supports the valve main body 93 so as to be swingable (or rotatable) with respect to the duct 81 . Then, the valve main body 93 is pulled in and out from the duct 81 by rotating the valve main body 93 around the pivot 94, so that the valve 85 switches between the open position and the closed position. In this case, for example, the valve main body 93 may be rotated around the pivot 94, so that the opening degree in the open position can be changed.

[0059] FIG. 5A illustrates a state where the valve 85 is in the closed position (fully closed state). FIGS. 5B and 5C illustrate a state where the valve 85 is in the open position. FIG. 5B illustrates a state where the valve main body 93 is rotated around the pivot 94 such that the entirety of the valve main body 93 is pulled out from the duct 81 , so as to be associated with an opening degree of the valve 85 of 100%. FIG. 5C illustrates a state where the valve main body 93 is rotated around the pivot 94 such that the valve main body 93 is pulled half-way out from the duct 81 , so as to be associated with an opening degree of the valve 85 to be 50%.

[0060] The example valve 85 illustrated in FIGS. 4A, 4B, and 4C will be described.

[0061] With reference to FIGS. 2 and 3, the example valve 85 is formed in a concave plate shape, as an example, in which an inlet surface 85a facing the inlet position 81 a of the duct 81 is formed in a concave surface shape. The expression "facing the inlet position 81a of the duct 81" refers to an orientation that faces the inlet position 81 a of the duct 81 in the longitudinal direction D1 (which is the extending direction of the duct 81 ). The inlet surface 85a is formed downstream of the circulation flow path 83. Namely, the circulation flow path 83 is formed by an inner wall surface (or surfaces) of the duct 81 , the partition wall 87, and the inlet surface 85a of the valve 85. Accordingly, the inlet surface 85a is formed in a concave surface shape, to facilitate a circulation of an airflow in the circulation flow path 83.

[0062] The internal environment detection unit 86 detects an internal environment of the housing 2. Examples of the internal environment of the housing 2 include temperature, the number of particles, humidity, and the like. For example, a temperature sensor 86A that measures temperature, a particle counter 86B that counts the number of particles, and the like can be used as the internal environment detection unit 86. In the example collector 80 illustrated in FIGS. 2 and 3, the temperature sensor 86A is provided as the internal environment detection unit 86, and in an example collector 80A illustrated in FIGS. 6 and 7, the temperature sensor 86A and the particle counter 86B are used as the internal environment detection unit 86. The collector 80A illustrated in FIGS. 6 and 7 similar to the collector 80 illustrated in FIGS. 2 and 3, with the exception that the particle counter 86B is provided. [0063] The temperature sensors 86A can be disposed, for example, in the circulation flow path 83, in the fixing device 50, outside the duct 81 in the housing 2, and/or the like, depending on examples. In the collector 80 illustrated in FIGS.

2 and 3 and the collector 80A illustrated in FIGS. 6 and 7, the temperature sensors 86A are disposed downstream of the partition wall 87, in the fixing device 50, and outside the duct 81 in the housing 2, respectively.

[0064] The particle counter 86B can be disposed, for example, in the circulation flow path 83 or the like. In the collector 80A illustrated in FIGS. 6 and 7, the particle counter 86B is disposed downstream of the partition wall 87.

[0065] According to examples, the control unit 70 is electrically connected to the main airflow generator 84 and the valve 85 to control the main airflow generator 84 and the valve 85. The control unit 70 may control the main airflow generator 84 and the valve 85 based on the internal environment detected by the internal environment detection unit 86. Examples of control of the main airflow generator 84 include operation and stop of the main airflow generator 84, adjustment of the operation amount (drive amount) of the main airflow generator 84, and the like. Examples of control of the valve 85 include switching between the open position and the closed position, adjustment (setting) of the opening degree of the valve 85, and the like. Switching of the valve 85 from the closed position to the open position is also referred to as opening of the valve 85, and switching of the valve 85 from the open position to the closed position is also referred to as closing of the valve 85.

[0066] An example operation of the collector 80 illustrated in FIGS. 2 and

3 will be described.

[0067] With reference to FIG. 2, the control unit 70 controls the main airflow generator 84 to operate and the valve 85 to be closed such that the valve 85 is in the closed position. Then, an airflow containing particles P released from the fixing device 50 circulates in the circulation flow path 83 inside the duct 81. Namely, the main airflow generator 84 directs the air to flow in the first flow path 83a toward the outlet position 81 b of the duct 81 , so that the airflow which has passed through the fixing device 50 and that contains the particles P flows through the first flow path 83a in the downstream direction of the duct 81 (e.g., from the inlet position 81 a side to the outlet position 81 b side), to further flow from a first flow path 83a side to a second flow path 83b side along the inlet surface 85a of the valve 85 on a downstream side of the partition wall 87, to further flow through the second flow path 83b in an upstream direction of the duct 81 (e.g., from the outlet position 81 b side to the inlet position 81 a side), and then, to flow from the second flow path 83b side to the first flow path 83a side on an upstream side of the partition wall 87.

[0068] When the airflow circulates in the circulation flow path 83 in such a manner, a turbulent flow or swirl is generated in the airflow to cause a large number of the particles P contained in the airflow to collide with each other or to collide with the inner wall surfaces of the duct 81 , the inlet surface 85a of the valve 85, the partition wall 87, and the like (hereinafter, referred to as "inner wall surfaces and the like"). Accordingly, the large number of particles P contained in the airflow aggregate with each other and/or adhere to the inner wall surfaces and the like. In addition, as the time during which the airflow circulates in the circulation flow path 83 is increased, the particles P are further caused to aggregate with each other or to adhere to the inner wall surfaces of the duct 81 or the like. Consequently, the particle sizes of the particles P are increased by such aggregation or adhesion of the particles P, so that the number of the particles P is reduced.

[0069] Subsequently, with reference to FIG. 3, when a predetermined time has elapsed or the temperature measured by the temperature sensor 86A increases to reach a predetermined threshold temperature, from the viewpoint of suppressing temperature inside the duct 81 , namely the temperature of the fixing device 50, from increasing excessively, the control unit 70 controls the valve 85 to be opened such that the valve 85 is in the open position. Then, the airflow circulating in the circulation flow path 83 passes through the valve 85 to toward the filter 82 inside the duct 81 . The main airflow generator 84 causes air in the first flow path 83a to pass through the valve 85 toward the filter 82. Due to a scavenging effect of the airflow formed when the main airflow generator 84 causes the air of the first flow path 83a to be directed toward the filter 82, air in the second flow path 83b passes through the valve 85 to toward the filter 82. Then, the particles P contained in the airflow are collected by the filter 82, and the airflow which has passed through the filter 82 is discharged from the outlet position 81 b to the outside of the duct 81 . Accordingly, the temperature inside the duct 81 and of the fixing device 50 disposed inside the duct 81 is lowered. Further, the airflow discharged to the outside of the duct 81 is discharged to the outside of the housing 2, so that the temperature inside the housing 2 is also lowered. At this time, due to the circulation of the airflow in the circulation flow path 83, the particle sizes of the particles P contained in the airflow are increased, and the number of the particles P is reduced. Accordingly, the collection efficiency of the filter 82 for the particles P may be increased, and clogging of the filter 82 caused by the collection of the particles P having small particle sizes is suppressed.

[0070] FIG. 8 shows an example where the control unit 70 controls the collector 80 illustrated in FIGS. 2 and 3. In the example shown in FIG. 8, first, the control unit 70 controls the main airflow generator 84 to operate. Then, until the temperature measured by the temperature sensor 86A reaches a threshold temperature T2, the valve 85 is closed such that the valve 85 is in the closed position. When the temperature measured by the temperature sensor 86A reaches the threshold temperature T2, the valve 85 is opened such that the opening degree of the valve 85 is set to 50%. Further, when the temperature measured by the temperature sensor 86A reaches a threshold temperature T3 which is greater than the threshold temperature T2, the opening degree of the valve 85 is set to 100%. Then, when the temperature measured by the temperature sensor 86A reaches a threshold temperature T1 that is less than the threshold temperature T2, the valve 85 is closed such that the valve 85 is in the closed position.

[0071] An example operation of the example collector 80A illustrated in FIGS. 6 and 7 will be described.

[0072] With reference to FIG. 6, the control unit 70 controls the main airflow generator 84 to operate and the valve 85 to be closed such that the valve 85 is in the closed position. Then, similarly to the case illustrated in FIG. 2, an airflow containing particles P released from the fixing device 50 circulates in the circulation flow path 83 inside the duct 81 . When the airflow circulates in the circulation flow path 83, a turbulent flow or swirl is generated in the airflow, and accordingly, aggregation or adhesion of the particles P contained in the airflow is promoted.

[0073] Subsequently, with reference to FIG. 7, when a predetermined time has elapsed or the temperature measured by the temperature sensor 86A increases to reach a predetermined threshold temperature, in order to prevent or inhibit a temperature inside the duct 81 , namely the temperature of the fixing device 50, from increasing excessively, the control unit 70 controls the valve 85 to be opened such that the valve 85 is in the open position. Then, similarly to the case illustrated in FIG. 3, inside the duct 81 , the airflow circulating in the circulation flow path 83 passes through the valve 85 to toward the filter 82 and the particles P contained in the airflow are collected by the filter 82, and then the airflow is discharged from the outlet position 81 b to the outside of the duct 81 .

[0074] Additionally, even when the predetermined time has not elapsed or even when the temperature measured by the temperature sensor 86A does not reach the predetermined threshold temperature, if the number of particles counted by the particle counter 86B is less than a predetermined threshold number, as illustrated in FIG. 7, the control unit 70 controls the valve 85 to be opened such that the valve 85 is in the open position. When the number of particles counted by the particle counter 86B is less than the predetermined threshold number, the temperature inside the duct 81 , namely, the temperature of the fixing device 50, can be further prevented or inhibited from increasing excessively.

[0075] FIG. 9 illustrates an example where the control unit 70 controls the example collector 80A of FIGS. 6 and 7. In the example shown in FIG. 9, the control unit 70 initially controls the main airflow generator 84 to operate. Then, until the temperature measured by the temperature sensor 86A reaches a threshold temperature T2, the valve 85 is closed such that the valve 85 is in the closed position. When the temperature measured by the temperature sensor 86A reaches the threshold temperature T2, the valve 85 is opened such that the opening degree of the valve 85 is set to 50%. Subsequently, even when the temperature measured by the temperature sensor 86A does not reach the threshold temperature T3 which is greater than the threshold temperature T2, if the number of particles counted by the particle counter 86B is reduced to a threshold number N, the opening degree of the valve 85 is set to 100%. According to examples, the threshold number N can be set at a value at which even when the valve 85 is opened at an opening degree of 100%, the number of particles discharged to the outside of the housing 2 is a predetermined reference or less. Then, when the temperature measured by the temperature sensor 86A reaches a threshold temperature T1 that is less than the threshold temperature T2, the valve 85 is closed such that the valve 85 is in the closed position.

[0076] Here, an image forming apparatus with the collector 80 of an example illustrated in FIGS. 10A and 10B and an image forming apparatus with a collector 180 of another example illustrated in FIG. 11 were produced, and a first experiment was performed on the image forming apparatuses to measure a relationship between print time and the number of particles contained in an airflow discharged from the duct 81. The example collector 80 illustrated in FIGS. 10A and 10B includes the valve 85 illustrated in FIGS. 5A, 5B, and 5C. The collector 180 of the example illustrated in FIG. 11 is similar to the example collector 80, with some exceptions in that the valve 85 and the main airflow generator 84 are not provided and a fan 184 disposed inside the duct 81 is provided. A printing operation was performed for t seconds with the example collector 80 and with the example collector 180. In the example collector 80, the valve 85 was closed at the start of print corresponding to a start time of the printing operation, the valve 85 was opened after t1 seconds from the start time, the valve 85 was closed after t2 seconds from the start time, the valve 85 was opened after t3 seconds from the start time, and the valve was closed after t4 seconds from the start time. The printing time and the number of particles contained in the airflow discharged from the duct 81 were measured by the particle counter 86B disposed in the vicinity of the outlet position 81 b of the duct 81 . FIG. 12 shows the number of particles per unit time measured during the experiment, and FIG. 13 shows the cumulative number of particles. In FIG. 12, a dotted line represents a number of particles that is expected to be initially present, in a space where the experiment is performed. [0077] Based on FIGS. 12 and 13, in the example collector 80, the number of particles was temporarily increased by opening and closing of the valve 85, but the cumulative number of particles after the elapse of t seconds from the start of printing was reduced by 40% in comparison to that in the example collector 180. [0078] As described above, in the collector 80 illustrated in FIGS. 2 and 3 and in the collector 80A illustrated in FIGS. 6 and 7, the circulation flow path 83 and the valve 85 are provided inside the duct 81 , such that when the valve 85 is in the closed position, the airflow circulates in the circulation flow path 83, so as to promote the particles contained in the airflow to aggregate with each other or to adhere to the inner wall surfaces and the like, so that the particle sizes of the particles are increased and the number of the particles is reduced. Subsequently, when the valve 85 is in the open position, the particles contained in the airflow are collected by the filter. At this stage, the particle sizes of the particles has been increased by the circulation of the airflow in the circulation flow path 83.

[0079] In addition, the partition wall 87 is provided in the circulation flow path 83, to allow the airflow to more easily circulate in the circulation flow path 83. Moreover, the partition wall 87 is disposed such that the first flow path 83a narrows in the downstream direction of the duct 81 (e.g., toward the filter 82 and the outlet position 81 b), to direct the airflow circulating in the circulation flow path 83 to more easily reach the inlet surface 85a of the valve 85. Accordingly, the particles contained in the airflow are further caused to adhere to the inlet surface 85a, and the generation of a turbulent flow or swirl is further promoted in the vicinity of the inlet surface 85a.

[0080] In addition, the main airflow generator 84 directs the air in the first flow path 83a toward the outlet position 81 b of the duct 81 is provided, such that when the valve 85 is in the closed position, the airflow can circulate in the circulation flow path 83, and when the valve 85 is in the open position, the airflow can be directed toward the filter 82 from the circulation flow path 83 through the valve 85.

[0081] In addition, the control unit 70 controls the valve 85 based on the internal environment detected by the internal environment detection unit 86, so as to achieve a suitable control according to the internal environment in the housing 2. For example, the valve 85 may be opened when a predetermined time has elapsed or when the temperature measured by the temperature sensor 86A increases to a predetermined threshold temperature. Accordingly, the temperature inside the duct 81 , namely, the temperature of the fixing device 50, can be inhibited from increasing excessively. In addition, when the valve 85 is closed, if the number of particles counted by the particle counter 86B is less than the predetermined threshold number, the valve 85 is controlled to be opened. Accordingly, in addition to inhibiting a reduction of the collection efficiency of the filter 82 for collecting the particles, the temperature inside the duct 81 , namely, the temperature of the fixing device 50, can be inhibited from increasing excessively.

[0082] Using the image forming apparatus with the collector 80 of the example illustrated in FIG. 10A and 10B, the main airflow generator 84 was operated in a first case, at a predetermined reference air volume while the valve 85 was in an open state, and the main airflow generator 84 was operated in a second case, at an air volume twice the reference air volume while the valve 85 was in the open state. Then, a second experiment was performed for 10 minutes after printing was performed during a predetermined time, for each of the first case and the second case, to measure the number of particles contained in the airflow discharged from the duct 81. FIG. 14 shows results of the second experiment for each of the first case (operation at reference air volume) and the second case (operation at twice the reference air volume).

[0083] As shown in FIG. 14, even if the air volume of the main airflow generator 84 is increased when the valve 85 is in an open state, the number of particles contained in the airflow discharged from the duct 81 remains substantially unchanged. Meanwhile, when the air volume of the main airflow generator 84 is increased when the valve 85 is in an open state, the temperature inside the duct 81 and the temperature of the fixing device 50 disposed inside the duct 81 is reduced more quickly. Accordingly, the control unit 70 may for example, increase the ratio of the time during which the valve 85 is in a closed state to the time during which the valve 85 is in an open state, so as to further facilitate aggregation and adhesion of the particles. In addition, when the valve 85 is in an open state, the air volume of the main airflow generator 84 is increased, so that temperature inside the duct 81 , namely, the temperature of the fixing device 50, can be more quickly reduced.

[0084] When the valve 85 is in a closed state, a change in speed of the airflow circulating in the circulation flow path 83 facilitates the generation of a turbulent flow or swirl. Accordingly, with reference to FIGS. 15A and 15B, when the valve 85 is in a closed state, the control unit 70 may change the operation of the main airflow generator 84 so as to vary the amount of airflow generated. Arrows illustrated in FIGS. 15A and 15B indicate the magnitudes of the operation amount (e.g., air volume) of the main airflow generator 84. Namely, FIG. 15A illustrates a state where the operation amount of the main airflow generator 84 is relatively high, and FIG. 15B illustrates a state where the operation amount of the main airflow generator 84 is relatively low. According to examples, when the valve 85 is in a closed state, the control unit 70 may control the main airflow generator 84 such that the state where the operation amount of the main airflow generator 84 is high as illustrated in FIG. 15A and the state where the operation amount of the main airflow generator 84 is low as illustrated in FIG. 15B, are continuously repeated in alternation, so as to further promote aggregation and/or adhesion of the particles contained in the airflow. For ease of understanding, the internal environment detection unit 86 is not illustrated in FIGS. 15A and 15B.

[0085] FIGS. 16 and 17 are schematic cross-sectional views of a collector 80B of another example. According to examples, in the image forming apparatus 1 illustrated in FIG. 1 , the collector 80B may be used instead of the collector 80. With reference to FIGS. 1 , 16, and 17, the collector 80B includes, for example, a duct 81 B, the filter 82, the circulation flow path 83, the main airflow generator 84, an auxiliary airflow generator 84B, the valve 85, the internal environment detection unit 86, and the control unit 70. The collector 80B illustrated in FIGS. 16 and 17 is similar to the collector 80A illustrated in FIGS. 6 and 7, with some exceptions, in that the shape of the duct is different and the auxiliary airflow generator 84B is provided.

[0086] The duct 81 B is disposed in the housing 2 to direct an airflow from an inlet position 81 Ba to an outlet position 81 Bb. The duct 81 B includes a main pipe 81 Be and a branch pipe 81 Bd.

[0087] The main pipe 81 Be corresponds to the duct 81 of the collector 80A illustrated in FIGS. 6 and 7, and the inlet position 81 Ba and the outlet position 81 Bb are located at both ends of the main pipe 81 Be. The main pipe 81 Be may extend linearly, curvedly, or in a bending manner. An extending direction of the main pipe 81 Be is referred to as the longitudinal direction D1 . In an internal space of the main pipe 81 Be, an inlet position 81 Ba side with respect to the outlet position 81 Bb is referred to as an upstream side, and an outlet position 81 Bb side with respect to the inlet position 81 Ba is referred to as a downstream side. Similarly to the collector 80A illustrated in FIGS. 6 and 7, the fixing device 50, the circulation flow path 83, the valve 85, and the filter 82 are disposed in this order, in a downstream direction of the duct 81 B (e.g., from the inlet position 81 Ba side (upstream side) toward the outlet position 81 Bb side (downstream side) inside the main pipe 81 Be).

[0088] The branch pipe 81 Bd communicates with the main pipe 81 Be to direct the airflow from an intermediate opening 81 Be to the main pipe 81 Be. The intermediate opening 81 Be is located on an opposite end of the branch pipe 81 Bd from the main pipe 81 Be. The branch pipe 81 Bd may be connected to the main pipe 81 Be in the second flow path 83b of the circulation flow path 83 according to some examples, or between the circulation flow path 83 and the fixing device 50 according to other examples. For this reason, the intermediate opening 81 Be is located between the inlet position 81 Ba of the duct 81 B and the filter 82. A connection portion of the branch pipe 81 Bd adjacent to the main pipe 81 Be is angled with respect to a direction orthogonal to the longitudinal direction D1 to extend toward the main pipe 81 Be and toward an upstream of the main pipe 81 Be such that an airflow flowing from the branch pipe 81 Bd to the main pipe 81 Be is directed downstream into the main pipe 81 Be.

[0089] The auxiliary airflow generator 84B introduces outside air into the duct 81 B from outside the duct 81 B. Namely, the auxiliary airflow generator 84B introduces air outside the duct 81 B into the second flow path 83b of the circulation flow path 83, or between the circulation flow path 83 and the fixing device 50 from the intermediate opening 81 Be, depending on examples. Accordingly, the auxiliary airflow generator 84B directs air of the circulation flow path 83, namely, air of the second flow path 83b from the inlet position 81 Ba side to the outlet position 81 Bb side. For example, a fan can be provided as the auxiliary airflow generator 84B.

[0090] An example operation of the collector 80B illustrated in FIGS. 16 and 17 will be described.

[0091] With reference to FIG. 16, the control unit 70 controls the main airflow generator 84 to operate and controls the valve 85 to be closed such that the valve 85 is in the closed position. At this time, the auxiliary airflow generator 84B is stopped. Then, similar to the case illustrated in FIG. 6, an airflow containing particles P released from the fixing device 50 circulates in the circulation flow path 83 inside the duct 81 B. When the airflow circulates in the circulation flow path 83, a turbulent flow or swirl is generated in the airflow, and accordingly, aggregation or adhesion of the particles P contained in the airflow is promoted.

[0092] Subsequently, with reference to FIG. 17, when a predetermined time has elapsed or the temperature measured by the temperature sensor 86A increases to a predetermined threshold temperature, in order to suppress the temperature inside the duct 81 B, namely , the temperature of the fixing device 50 from increasing excessively, the control unit 70 controls the valve 85 to be opened such that the valve 85 is in the open position, and controls the auxiliary airflow generator 84B to operate.

[0093] The auxiliary airflow generator 84B introduces the air outside the duct 81 B into the second flow path 83b of the circulation flow path 83 or between the circulation flow path 83 and the fixing device 50 from the intermediate opening 81 Be. Then, the main airflow generator 84 and the auxiliary airflow generator 84B cause the airflow, which circulates in the circulation flow path 83, to pass through the valve 85 toward the filter 82 inside the main pipe 81 Be. Namely, the main airflow generator 84 causes the air of the first flow path 83a to pass through the valve 85 toward the filter 82. In examples where the branch pipe 81 Bd is connected to the main pipe 81 Be between the circulation flow path 83 and the fixing device 50, the main airflow generator 84 and the auxiliary airflow generator 84B cause the air of the first flow path 83a to pass through the valve 85 toward the filter 82. In addition, the auxiliary airflow generator 84B causes the air of the second flow path 83b to pass through the valve 85 toward the filter 82. In examples where the branch pipe 81 Bd is connected to the main pipe 81 Be in the second flow path 83b of the circulation flow path 83, a part of air which has passed through the fixing device 50 is also directed toward the second flow path 83b due to scavenging effect of the airflow formed when the auxiliary airflow generator 84B directs the air of the second flow path 83b toward the filter 82. The particles P contained in the airflow are collected by the filter 82, and the airflow which has passed through the filter 82 is discharged from the outlet position 81 Bb to the outside of the duct 81 B.

[0094] FIG. 18 illustrates an example operation where the control unit 70 controls the collector 80B illustrated in FIGS. 16 and 17. With reference to FIG. 18, first, the control unit 70 controls the main airflow generator 84 to operate, and the auxiliary airflow generator 84B to stop. Until the temperature measured by the temperature sensor 86A reaches a threshold temperature T2, the valve 85 remains closed, such that the valve 85 is in the closed position. When the temperature measured by the temperature sensor 86A reaches the threshold temperature T2, the valve 85 is opened such that the opening degree of the valve 85 is set to 50%. Subsequently, even when the temperature measured by the temperature sensor 86A does not reach the threshold temperature T3 which is greater than the threshold temperature T2, if the number of particles counted by the particle counter 86B is reduced to the threshold number N, the opening degree of the valve 85 is set to 100%, and the auxiliary airflow generator 84B is operated. Then, when the temperature measured by the temperature sensor 86A reaches the threshold temperature T1 which is less than the threshold temperature T2, the valve 85 is closed such that the valve 85 is in the closed position, and the auxiliary airflow generator 84B is stopped.

[0095] As described above, the collector 80B illustrated in FIGS. 16 and 17 includes the auxiliary airflow generator 84B that introduces outside air into the main pipe 81 Be from outside the duct 81 B via the intermediate opening 81 Be. Accordingly, when the valve 85 is in the open state, the amount of the airflow discharged from the duct 81 B can be increased, so that the temperature inside the duct 81 B, namely, the temperature of the fixing device 50, can be reduced more quickly. Accordingly, the control unit 70 may for example, increase the ratio of the time during which the valve 85 is in a closed state to the time during which the valve 85 is in an open state, so as to further promote aggregation and/or adhesion of the particles, and so as to more quickly reduce the temperature inside the duct 81 B, namely, the temperature of the fixing device 50.

[0096] In addition, since the auxiliary airflow generator 84B directs outside air to the second flow path 83b toward the outlet position 81 b of the duct 81 B, when the valve 85 is in an open state, the airflow heading downstream in the second flow path 83b is more easily generated.

[0097] FIGS. 19 and 20 are schematic cross-sectional views of a collector 80C of another example. According to examples, in the image forming apparatus 1 illustrated in FIG. 1 , the collector 80C may be used instead of the collector 80. With reference to FIGS. 1 , 19, and 20, the collector 80C includes, for example, the duct 81 , the filter 82, the circulation flow path 83, the main airflow generator 84, the valve 85, the internal environment detection unit (e.g., internal environment detection unit 86 in FIGS. 2, 16), an interference member 88, and the control unit 70. The collector 80C illustrated in FIGS. 19 and 20 similar to the collector 80 illustrated in FIGS. 2 and 3, with exceptions in that the interference member 88 is provided. For ease of understanding of the figures, the internal environment detection unit and particles are not illustrated in FIGS. 19 and 20.

[0098] The interference member 88 is provided in the circulation flow path 83 to generate turbulence in the airflow. The interference member 88 generates turbulence in the airflow passing through the circulation flow path 83 to promote the generation of a turbulent flow or swirl. The interference member 88 extends in a substantially transversal direction of the duct 81 , namely, a direction that is substantially lateral to the longitudinal direction of the duct 81 (e.g., a direction perpendicular to the view of FIGS. 19 and 20), and end portions of the interference member 88 are held or supported by the duct 81 . The interference member 88 may be formed in, for example, a rod shape, a plate shape, a wave shape, or the like. According to examples, a plurality of the interference members 88 are provided in the circulation flow path 83. The interference members 88 may be provided in the first flow path 83a, may be provided in the second flow path 83b, or may be provided in positions other than the first flow path 83a and the second flow path 83b, according to example. In the example illustrated in FIGS. 19 and 20, eight interference members 88 are provided in the circulation flow path 83, each having a rod shape.

[0099] An example operation of the collector 80C illustrated in FIGS. 19 and 20 will be described.

[00100] First, as illustrated in FIG. 19, the control unit 70 controls the main airflow generator 84 to operate and the valve 85 to be closed such that the valve 85 is in the closed position. Similarly to the case illustrated in FIG. 2, an airflow containing particles released from the fixing device 50 circulates in the circulation flow path 83 inside the duct 81 . When the airflow circulates in the circulation flow path 83, a turbulent flow or swirl is generated in the airflow, and accordingly, aggregation and/or adhesion of the particles contained in the airflow is promoted. At this time, the airflow circulating in the circulation flow path 83 collides with the interference members 88, so as to promote the generation of a turbulent flow or swirl. Accordingly, aggregation or adhesion of the particles contained in the airflow is further promoted.

[00101] Subsequently, with reference to FIG. 20, when a predetermined time has elapsed or the temperature measured by the temperature sensor of the internal environment detection unit (cf. 86 in FIG. 2) increases to a predetermined threshold temperature, from the viewpoint of suppressing the temperature inside the duct 81 , namely, the temperature of the fixing device 50 from increasing excessively, the control unit 70 controls the valve 85 to be opened such that the valve 85 is in the open position. Then, similarly to the case illustrated in FIG. 3, inside the duct 81 , the airflow circulating in the circulation flow path 83 passes through the valve 85 toward the filter 82 and the particles contained in the airflow are collected by the filter 82, and then the airflow is discharged from the outlet position 81 b to the outside of the duct 81 .

[00102] As described above, in the collector 80C illustrated in FIGS. 19 and 20, the interference members 88 are provided in the circulation flow path 83, so as to promote the generation of a turbulent flow or swirl in the circulation flow path 83. Accordingly, aggregation or adhesion of the particles contained in the airflow is further promoted, so that the particle sizes of the particles are increased and the number of the particles is reduced. Consequently, the collection efficiency of the filter 82 for the particles can be further increased.

[00103] FIGS. 21 and 22 are schematic cross-sectional views of a collector 80D of another example. According to examples, in the image forming apparatus 1 illustrated in FIG. 1 , the collector 80D may be used instead of the collector 80. With reference to FIGS. 1 , 21 , and 22, the collector 80D includes, for example, the duct 81 , the filter 82, a circulation flow path 83D, a main airflow generator 84D, the valve 85, the internal environment detection unit (e.g., internal environment detection unit 86 in FIGS. 2, 16), and the control unit 70. The collector 80D illustrated in FIGS. 21 and 22 is similar to the collector 80 illustrated in FIGS. 2 and 3, with exceptions, in that the main airflow generator and the circulation flow path are different. For ease of understanding of the figures, the internal environment detection unit and particles are not illustrated in FIGS. 21 and 22.

[00104] The main airflow generator 84D includes a cross flow fan 84Da and a regulation plate 84Db.

[00105] The cross flow fan 84Da is a fan in which a plurality of blades 84Dc extending in an axial direction are arranged in a cylindrical shape and an introduction space 84Dd is formed in a central portion of the plurality of blades 84Dc. The cross flow fan 84Da is disposed inside the duct 81 such that an axis direction of the cross flow fan 84Da is orthogonal to the longitudinal direction D1 of the duct 81 . The cross flow fan 84Da is configured such that when the cross flow fan 84Da rotates around an axis thereof, air is suctioned into the introduction space 84Dd from end surfaces in the axis direction of the cross flow fan 84Da, and the air suctioned into the introduction space 84Dd is discharged from between the plurality of blades 84Dc in directions orthogonal to the axis direction. Accordingly, a space around the cross flow fan 84Da, the introduction space 84Dd of the cross flow fan 84Da, spaces between the plurality of blades 84Dc, and a space around the cross flow fan 84Da form the circulation flow path 83D.

[00106] The regulation plate 84Db regulates the direction of discharge from the cross flow fan 84Da. The regulation plate 84Db is disposed to cover a downstream side in a rotational direction D2 of the cross flow fan 84Da, on a valve 85 side of the cross flow fan 84Da. Namely, the regulation plate 84Db is disposed such that the air discharged from the cross flow fan 84Da is directed upstream of the valve 85 side of the cross flow fan 84Da side in the rotational direction D2 of the cross flow fan 84Da.

[00107] An operation example of the collector 80D illustrated in FIGS. 21 and 22 will be described.

[00108] First, as illustrated in FIG. 21 , the control unit 70 controls the cross flow fan 84Da of the main airflow generator 84D to operate and the valve 85 to be closed such that the valve 85 is in the closed position. An airflow containing particles released from the fixing device 50 circulates in the circulation flow path 83D inside the duct 81 . When the airflow circulates in the circulation flow path 83D, a turbulent flow or swirl is generated in the airflow, and accordingly, aggregation or adhesion of the particles contained in the airflow is promoted.

[00109] Subsequently, with reference FIG. 22, when a predetermined time has elapsed or when the temperature measured by the temperature sensor cf. 86 in FIG. 2 increases to a predetermined threshold temperature, from the viewpoint of suppressing temperature inside the duct 81 , particularly, the temperature of the fixing device 50 from increasing excessively, the control unit 70 controls the valve 85 to be opened such that the valve 85 is in the open position. Then, inside the duct 81 , the airflow discharged from the cross flow fan 84Da passes through the valve 85 toward the filter 82 and the particles contained in the airflow are collected by the filter 82, and then the airflow is discharged from the outlet position 81 b to the outside of the duct 81 .

[00110] As described above, even when the cross flow fan 84Da is used, since aggregation or adhesion of the particles contained in the airflow can be promoted, while an increase in pressure loss of the airflow is suppressed, the particle collection rate can be increased.

[00111] It should be appreciated that all the aspects, advantages, and features described in the specification are not necessarily achieved by or included in any one specific example. In effect, various examples have been described in the specification, and it is apparent that the arrangements and details can be also changed in other examples.

[00112] In some examples, the valve may be operable such that the opening degree of the duct is variable, without being operable in a closed position. Namely, the valve may not be configured to fully close the duct. For example, the valve may be operable such that the opening degree of the duct is variable to an opening degree between the states illustrated in FIG. 4B and FIG. 4C, or may be operable such that the opening degree of the duct is variable to an opening degree between the state illustrated in FIG. 5B and FIG. 5C. Even when the duct is not closed, if the opening degree is minimal, the airflow may sufficiently circulate in the circulation flow path, so that the particles contained in the airflow suitably aggregate with each other and/or to adhere to the inner wall surfaces and the like. Accordingly, the particle sizes of the particles are increased, and the number of the particles is reduced.

[00113] In some examples, an airflow generator or the like provided outside the collector may enable the airflow to circulate sufficiently in the circulation flow path, without providing a main airflow generator. In addition, the circulation flow path can be formed by an airflow generator such as a fan, without providing a partition wall. In addition, in the collector 80B illustrated in FIGS. 16 and 17, the auxiliary airflow generator 84B may be provided in the main pipe 81 Be, while omitting the branch pipe 81 Bd. In addition, opening and closing control of the valve by the control unit may be optimized according to power consumption of the fixing device and the like, temperature, humidity, a print mode, a paper thickness, a paper size, or the like.

[00114] In some examples, the control unit may control the opening degree of the valve based on a particle size and number distribution of particles, or may control the opening degree of the valve in consideration of a particle size and number of particles. For example, as shown in FIG. 23, particles generated in the housing 2 have a predetermined particle size and number distribution. In addition, as the particle sizes of the particles are increased, the collection efficiency of the filter is further increased. Therefore, for example, particles may be classified and counted by the particle counter disposed inside the duct, and a particle number distribution representing the number of particles in each of predetermined particle size ranges, may be generated. A detection value A shown in FIG. 23 shows an example of the particle number distribution, and the area of a portion surrounded by the line of the detection value A indicates the total number of particles counted by the particle counter. Next, the number of particles in each of the predetermined particle size ranges is integrated by the collection efficiency of the filter, and the integrated values for all the particle size ranges are added to estimate a particle number distribution of particles contained in the airflow which passes through the filter to be discharged from the duct. An estimation value B shown in FIG. 23 shows an example of the estimated particle number distribution, and the area of a portion surrounded by the line of the estimation value B indicates the estimated total number of particles contained in the airflow discharged from the duct. Then, for example, similarly to the control shown in FIG. 9, even when the temperature measured by the temperature sensor 86A does not reach the threshold temperature T3 that is greater than the threshold temperature T2, if the total number of the particles counted by the particle counter or the estimated total number of the particles contained in the airflow discharged from the duct is reduced to the predetermined threshold number N, the control unit sets the opening degree of the valve to 100%. In this case, the number of particles discharged to the outside of the housing 2, which is one example of the reference of the threshold number N, may be determined based on the particle size and number distribution of the particles, or may be determined in consideration of the particle size and number distribution of the particles, depending on examples.

[00115] In some examples, the control unit may determine the opening degree of the valve or the ratio of the time during which the valve is in a closed state to the time during which the valve is in an open state, based on the estimation value of the amount of particles generated. In this case, the control unit determines the opening degree of the valve or the ratio such that the estimation value of the amount of particles generated is reduced in the short term or in the long term. For example, the collector or the image forming system may include a particle-generation-amount estimation device that estimates the amount of particles generated, based on a print mode, a paper thickness, single-sided printing and double-sided printing, the duty ratio of the heat source of the fixing device, the number of printed sheets, and the like, and the control unit may determine the opening degree of the valve or the ratio based on the estimation value of the amount of particle generated, which has been estimated by the particle-generation-amount estimation device.

[00116] It is to be understood that not all aspects, advantages and features described herein may necessarily be achieved by, or included in, any one particular example. Indeed, having described and illustrated various examples herein, it should be apparent that other examples may be modified in arrangement and detail is omitted.