JP7346154B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus such as an electrophotographic copying machine, an electrophotographic printer (eg, a laser beam printer, an LED printer, etc.).

An electrophotographic image forming apparatus uses a developing section to apply toner to an electrostatic latent image formed on the surface of a photoconductor to form a toner image, thereby forming an image that is transferred to a sheet. .

Here, a configuration is known in which toner is stirred in the developing section in order to suppress toner aggregation. In such a configuration, frictional heat is generated as the toner is stirred, which may cause a change in the amount of charge of the toner or melting of the toner in the developing section, so it is desirable to cool the developing section.

On the other hand, there is an image forming apparatus that uses a fan and a duct to take in and exhaust air in order to cool the inside of the apparatus body, collect scattered substances, etc., as in the configuration of Patent Document 1, for example.

JP2007-233280A

In the duct described in Patent Document 1, the air flow path is bent at a substantially right angle in order to guide air to a desired position. FIG. 17(a) is an enlarged cross-sectional view of a bent portion of the duct 100 described in Patent Document 1. As shown in FIG. 17(a), the inner wall in the bending direction of the duct 100 of Patent Document 1 is bent at a right angle. When the wall of the bent portion is bent at right angles in this manner, a vortex 202 is generated downstream of the bent portion, the air becomes turbulent and stagnates, and a pressure loss of the air flowing through the duct 100 occurs.

On the other hand, as shown in FIG. 17(b), by forming the inside of the bent portion into a curved surface 101a, the generation of the vortex 202 can be suppressed, and the pressure loss of the air flowing through the duct 100 can be suppressed. However, many of the members installed in the image forming apparatus have an outer shape close to a rectangle in consideration of ease of arrangement. Therefore, in a configuration in which the inside of the bent portion is simply the curved surface 101a, the curved surface 101a and the other member 150 having a rectangular outer shape will interfere with each other. In order to avoid this interference, it is necessary to make the entire duct 100 protrude away from the other members 150. In this case, the image forming apparatus becomes larger.

In view of the current situation, it is an object of the present invention to provide an image forming apparatus that can both suppress the pressure loss of air flowing through a duct and suppress the increase in size of the image forming apparatus.

A typical configuration of an image forming apparatus according to the present invention for achieving the above object includes a photoreceptor that rotates around a rotation axis , a frame that supports at least the photoreceptor, and an exterior of the apparatus main body. an air intake port, a duct that guides the air taken in from the air intake port into the device , a first portion extending along the frame body , and a duct disposed downstream of the first portion in the direction in which the air flows. a duct that is bent from the first portion and includes a second portion that extends along the rotational axis direction of the photoreceptor ; and a fan that generates an airflow for taking in air from the intake port to the duct side. , which is on the inside in the bending direction from the first part to the second part, and at a connection part of the second part with the first part, protrudes toward the air flow path side of the duct, and A protruding portion made of a curved surface forming a concave portion is provided on the outside of the duct , and the duct includes a first duct portion and a second duct portion that constitute an air flow path by connecting with each other, and the first duct portion An engaging part that connects a duct part and the second duct part is included, and the engaging part is disposed in the recess .

According to the present invention, in an image forming apparatus, it is possible to simultaneously suppress pressure loss of air flowing through a duct and suppress the increase in size of the image forming apparatus.

FIG. 1 is a schematic cross-sectional view of an image forming apparatus. FIG. 1 is a schematic perspective view showing the internal configuration of an image forming apparatus. FIG. 2 is a perspective view showing the configuration of a duct of the image forming apparatus. FIG. 3 is a perspective view of a developing duct. FIG. 3 is a schematic cross-sectional view of the image forming section cut horizontally. FIG. 3 is an enlarged perspective view of the periphery of a portion of the developing duct that bends from the main stream portion to the branch portion. FIG. 2 is an enlarged cross-sectional view of the periphery of a portion of the developing duct that bends from the main stream portion to the branch portion. FIG. 7 is a diagram and a graph for explaining the verification results of the pressure loss reduction effect of the protrusion. FIG. FIG. 7 is a diagram showing the results of calculating the air pressure distribution in the developing duct using fluid analysis software. FIG. 3 is a diagram of a developing duct with a different bending angle from a main stream portion to a branch portion. FIG. 3 is a diagram of a developing duct with a different bending angle from a main stream portion to a branch portion. It is a graph for explaining the verification result of the pressure loss reduction effect of the protruding part. FIG. 7 is a schematic cross-sectional view of a developing duct according to a modification. FIG. 7 is a schematic cross-sectional view of a developing duct according to a modification. FIG. 7 is a schematic cross-sectional view of a developing duct according to a second comparative example and a third comparative example. It is a graph for explaining the verification result of the pressure loss reduction effect of the protruding part. FIG. 2 is a schematic diagram of a duct for explaining a conventional problem.

(First embodiment)
<Image forming device>
Hereinafter, first, the overall configuration of an image forming apparatus A according to a first embodiment of the present invention will be described with reference to the drawings together with the operation during image formation. It should be noted that the dimensions, materials, shapes, relative arrangements, etc. of the component parts described below are not intended to limit the scope of the present invention only thereto, unless otherwise specified.

FIG. 1 is a schematic cross-sectional view of an image forming apparatus A. As shown in FIG. 1, the image forming apparatus A includes an image forming section that transfers a toner image onto a sheet to form an image, a sheet feeding section that supplies the sheet toward the image forming section, and a toner image forming section on the sheet. A fixing section is provided to fix the image.

The image forming section includes photosensitive drums 102 (102Y, 102M, 102C, 102K), charging rollers 103 (103Y, 103M, 103C, 103K), and developing devices 105 (105Y, 105M, 105C, 105K). It also includes primary transfer rollers 106 (106Y, 106M, 106C, 106K), a secondary transfer roller 113, a secondary transfer opposing roller 112, a laser scanner unit 104, and the like.

The developing device 105 includes a developing sleeve 30 (30Y, 30M, 30C, 30K) as a developer carrier, and a developing screw 126 (126Y, 126M, 126C, 126K) as a stirring member. The developing screw 126 stirs toner, which is a developer inside the developing device 105 , and conveys the toner to the developing sleeve 30 . The developing sleeve 30 includes a magnet (not shown), carries toner by the magnetic force of the magnet, and supplies the toner to the photosensitive drum 102 (photosensitive member). Furthermore, when the amount of toner inside the developing device 105 becomes low, toner is replenished from the toner bottles 109 (109Y, 109M, 109C, 109K) to the developing device 105.

Furthermore, when the toner is stirred by the developing screw 126, frictional heat is generated. When the temperature inside the developing device 105 increases due to this frictional heat, the toner inside the developing device 105 may melt. Therefore, in order to avoid melting of the toner due to frictional heat, a developing duct 127 for cooling the developing device 105 is provided between the laser scanner unit 104 and the developing device 105. The configuration of the developing duct 127 will be described later.

Next, the image forming operation will be explained. First, when a control unit (not shown) receives an image forming job signal, the sheet S stored in the sheet cassette 110 is conveyed to the registration rollers 111 by the feed roller 114 while being guided by the conveyance guide 118 . The registration rollers 111 convey the sheet S to a secondary transfer section formed by a secondary transfer roller 113 and a secondary transfer opposing roller 112 at a predetermined timing.

On the other hand, in the image forming section, the surface of the photosensitive drum 102Y is first charged by the charging roller 103Y. Thereafter, the laser scanner unit 104 scans the surface of the photosensitive drum 102Y according to image data input from an external device such as a personal computer or from an image reading device 35 provided at the top of the image forming apparatus A. Irradiate with laser light. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 102Y according to the image data.

Thereafter, yellow toner is attached to the electrostatic latent image formed on the surface of the photosensitive drum 102Y by the developing sleeve 30Y of the developing device 105Y, thereby forming a yellow toner image on the surface of the photosensitive drum 102Y. The toner image formed on the surface of the photosensitive drum 102Y is primarily transferred onto the intermediate transfer belt 107 by applying a bias to the primary transfer roller 106Y.

By a similar process, magenta, cyan, and black toner images are also formed on the photosensitive drums 102M, 102C, and 102K. Then, by applying a bias to the primary transfer rollers 106M, 106C, and 106K, these toner images are transferred onto the yellow toner image on the intermediate transfer belt 107 in a superimposed manner. As a result, a full-color toner image is formed on the surface of the intermediate transfer belt 107.

The intermediate transfer belt 107 rotates as a result of the rotation of the secondary transfer opposing roller 112 by the driving force of a motor (not shown). When the intermediate transfer belt 107 carrying the toner image rotates, the toner image is sent to the secondary transfer section. Then, by applying a bias to the secondary transfer roller 113 in the secondary transfer section, the toner image on the intermediate transfer belt 107 is transferred onto the sheet S.

Next, the sheet S onto which the toner image has been transferred is subjected to heating and pressure processing in the fixing device 115, whereby the toner image on the sheet S is fixed to the sheet S. Thereafter, the sheet S with the toner image fixed thereon is discharged to a discharge section 117 by a discharge roller 116.

<Internal configuration of image forming apparatus>
Next, the internal configuration of image forming apparatus A will be explained.

FIG. 2 is a schematic perspective view showing the internal configuration of the image forming apparatus A. Here, FIG. 2(b) shows a state in which an exterior cover 120 and a front side plate 121 are provided from the state of FIG. 2(a). As shown in FIG. 2, the image forming apparatus A includes a front plate 121 and a rear plate 119 as a frame. The front side plate 121 and the rear side plate 119 are covered with an exterior cover 120.

The front side plate 121 and the rear side plate 119 together support the toner bottle 109, the photosensitive drum 102, the developing device 105, the charging roller 103, the intermediate transfer belt 107, and the like. The rear plate 119 also supports a controller board 195 (FIG. 4) on which a CPU and other electronic components are mounted. Electronic components mounted on the controller board 195 (FIG. 5) convert the image data of the document read by the image reading device 35 into electrical digital signals.

Furthermore, an opening 120a is formed on the right side surface of the exterior cover 120. If the sheet S is jammed and a jam occurs while the sheet S is being conveyed, the user opens a door (not shown) and accesses the opening 120a. This allows the user to access the conveyance guide 118 and the fixing device 115 located inside the opening 120a, and remove the sheet S causing the jam.

Further, the front side plate 121 has four openings 121a formed therein. The four openings 121a are arranged at the bottom of each of the four developing devices 105. As will be described later, a developing duct 127 for cooling the developing device 105 is inserted into the opening 121a.

<Duct>
Next, the configuration of a duct for cooling the inside of image forming apparatus A will be described.

FIG. 3 is a perspective view showing the configuration of the duct of the image forming apparatus A. As shown in FIG. 3, the image forming apparatus A is provided with a developing duct 127 that cools the developing device 105, and an exhaust duct 160 that exhausts air exhausted from the developing duct 127 to the outside of the image forming apparatus A. There is. The developing duct 127 is inserted through an opening 121a (FIG. 2(b)) formed in the front plate 121, and a portion of the developing duct 127 is disposed at the lower part of the developing device 105. The exhaust duct 160 is fixed to the rear side plate 119. Further, the exhaust port 160b of the duct 160 communicates with a vent (not shown) formed in the exterior cover on the back side of the image forming apparatus A.

Air from outside the image forming apparatus A is taken into the developing duct 127 . The air taken into the developing duct 127 is conveyed to the lower part of the developing device 105 through the inside of the developing duct 127 and cools the developing device 105. Furthermore, the air warmed by the developing device 105 is taken into the exhaust duct 160 through the intake port 160a of the exhaust duct 160. A fan (not shown) is provided inside the exhaust duct 160. The air taken into the exhaust duct 160 by the airflow generated by the fan is carried to the back side of the image forming apparatus A through the inside of the exhaust duct 160. Thereafter, this air is discharged to the outside of the image forming apparatus A from a vent (not shown) formed in the exterior cover on the back side of the image forming apparatus A via the exhaust port 160b.

<Developing duct>
Next, the configuration of the developing duct 127 will be explained in detail.

FIG. 4 is a perspective view of the developing duct 127. As shown in FIG. 4, the developing duct 127 is a rectangular member made of ABS resin and has a cross section of 10 mm x 10 mm, and is manufactured by injection molding using a mold. In this embodiment, the developing duct 127 has a rectangular shape in order to ensure a large air flow path, but the cross-sectional shape may be other shapes. Further, the developing duct 127 is not limited to being made of resin, but may be made of metal such as steel.

Due to limitations of the mold, the developing duct 127 is divided into two parts: an upper duct 127x arranged on the upper side in the vertical direction and a lower duct 127y arranged on the lower side in the vertical direction. The upper duct 127x and the lower duct 127y are connected and integrated by engaging each other with claw portions 144 (engaging portions) provided on both.

The developing duct 127 includes one linear main stream portion 127a, and four branch portions 127b (127b1 ~127b4). The main stream portion 127a extends in a direction along the front side plate 121 that supports the developing sleeve 30, and the branch portion 127b extends in the direction of the rotation axis of the developing sleeve 30.

Further, one opening 127c (communication hole) for taking air into the developing duct 127 is formed in the main stream portion 127a. Further, each of the four branch portions 127b is formed with an opening portion 127d (127d1 to 127d4) having an open upper surface for discharging air from the developing duct 127.

FIG. 5 is a schematic cross-sectional view of the image forming section of the image forming apparatus A cut horizontally. As shown in FIG. 5, the main stream portion 127a of the developing duct 127 is disposed further forward of the image forming apparatus A than the front side plate 121. As shown in FIG. The main stream portion 127a of the developing duct 127 is fixed to the front plate 121 by screws 199 at a flange portion (not shown).

The four branch portions 127b of the developing duct 127 are inserted into the main body of the image forming apparatus A through the opening 121a (FIG. 2) of the front side plate 121. The four branch parts 127b are below the four developing devices 105, and are respectively arranged at positions between the four developing devices 105 and the laser scanner unit 104.

An air intake port 120b is provided on the right side of the exterior cover 120 of the image forming apparatus A. An opening 127c formed in the main stream portion 127a of the developing duct 127 is arranged to communicate with the intake port 120b of the exterior cover 120. As a result, the outside of the image forming apparatus A and the inside of the developing duct 127 are communicated with each other, and outside air can be taken into the developing duct 127. Note that by providing the air intake port 120b on the side surface of the exterior cover 120 instead of the front side, it is possible to suppress the operating noise inside the apparatus from being directly transmitted to the user standing in front of the image forming apparatus A. I can do it.

Further, an axial fan 128 is provided inside the developing duct 127 near the opening 127c. The axial fan 128 is an airflow for drawing air from outside the image forming apparatus A into the developing duct 127 side, and generates an airflow in the direction of arrow K1 shown in FIG. When air is taken into the developing duct 127 by the axial fan 128, the air flows from the main flow section 127a to the branch section 127b. Then, air is discharged toward the bottom surface of the developing device 105 from the opening 127d of the branching portion 127b. The developing duct 127 cools the developing device 105 by sending the air outside the image forming apparatus A into the developing device 105 in this way.

<Protrusion>
Next, the protrusion 137 provided on the developing duct 127 will be explained.

FIG. 6 is an enlarged perspective view of a portion of the developing duct 127 that bends from the main stream portion 127a to the branch portion 127b4. FIG. 7 is an enlarged cross-sectional view of a portion of the developing duct 127 that bends from the main stream portion 127a to the branch portion 127b4. Here, in FIG. 6, in order to show the internal structure of the developing duct 127, a part of the side wall of the developing duct 127 is shown with a chain double-dashed line, and the top surface and other parts of the developing duct 127 are not shown.

As shown in FIGS. 6 and 7, the inside of the developing duct 127 in the bending direction from the main flow part 127a to the branch part 127b4, and the connection part with the main flow part 127a of the branch part 127b4, are provided with air in the developing duct 127. A protrusion 137 having a curved surface protruding toward the flow path is provided. Note that a curved surface with a radius of 10 mm is provided on the outer side in the bending direction of the bending portion from the main stream portion 127a to the branch portion 127b4.

The specific shape of the protrusion 137 is as follows. A point P1 is defined as a point at which the protrusion 137 in the main flow part 127a begins to be formed in the portion where the main flow part 127a bends to the branch part 127b4. Further, in the direction in which the air flows, the downstream end of the protrusion 137 at the branch portion 127b4 is defined as a point P2. Further, the part of the protruding portion 137 that protrudes most toward the air flow path side is defined as a point P3. Further, the inner diameter of the developing duct 127 shown in FIG. 7 is assumed to be X.

At this time, point P2 is located at a position moved a distance of X from point P1 to the downstream side in the direction in which the air flows. In addition, point P3 is moved a distance of X/2 from point P1 to the downstream side in the direction in which the air flows, and a distance of X/2 × (√2-1) in the direction perpendicular to the direction in which the air flows. will be placed in the specified position. The protrusion 137 has an arc shape passing through these three points P1, P2, and P3. Further, the angle between the direction in which the main stream portion 127a extends along the front side plate 121 and the straight line connecting the points P1 and P3 is defined as θ1, and the direction in which the main stream portion 127a extends along the front side plate 121 and the point P2 and the point P3 are defined as θ1. Let θ2 be the angle formed by the straight line connecting . At this time, θ1=67.5° and θ2=67.5° are set.

By providing such a protruding portion 137, generation of a vortex can be suppressed in the bending portion from the main stream portion 127a to the branch portion 127b4, and pressure loss of the air flowing through the developing duct 127 can be suppressed. Further, the portion that bends from the main flow portion 127a to the branch portion 127b4 is not simply a curved surface, but a protrusion portion 137 that is a curved surface that protrudes toward the air flow path is provided at the branch portion 127b4. Accordingly, when another member having a rectangular outer shape is placed near the protrusion 137, the other member can be placed while avoiding interference between the curved surface portion and the other member. Therefore, there is no need to make the entire developing duct 127 protrude in a direction to retreat from other members, and it is possible to suppress the image forming apparatus A from increasing in size.

Furthermore, a claw portion 144 is provided on the outer peripheral portion of the protruding portion 137 to connect the upper duct 127x and the lower duct 127y. By providing the claw portion 144 on the protruding portion 137 that protrudes inward of the developing duct 127 in the branch portion 127b4 in this manner, it is possible to prevent the overall width of the outer peripheral portion of the branch portion 127b4 from increasing due to the claw portion 144. . Therefore, the width of the opening 121a of the front plate 121 can be narrowed, and the rigidity of the front plate 121 can be increased, compared to a configuration in which the claw part 144 is provided in another part of the branch part 127b4.

<Verification results of pressure loss reduction effect of protrusions>
Next, the results of verifying the effect of reducing pressure loss by the protrusion 137 formed in the developing duct 127 will be explained. Here, the developing duct 127 of this embodiment is compared with the developing duct 177 of a first comparative example shown in FIG. The effectiveness is being verified.

FIG. 8B is a graph showing the results of calculating the pressure loss of air in the developing duct 127 of this embodiment and the developing duct 177 of the first comparative example using fluid analysis software. The fluid analysis software used here was ``Fluent'' by Ansys, and the turbulence model was ``Standard k-ε'', the wall function was ``Standard Wall Function'', and the calculation scheme was ``SIMPLE method''. . FIG. 9 is a diagram showing the results of calculating the air pressure distribution in the developing duct 127 of this embodiment and the developing duct 177 of the first comparative example using fluid analysis software.

As shown in FIG. 8B, in the developing duct 127 of this embodiment, the air pressure loss is lower than in the developing duct 177 of the first comparative example. This is because, as shown in FIG. 9, in the developing duct 177 of the first comparative example, there is no protrusion at the bending part from the main flow part 177a to the branch part 177b, so turbulent flow occurs around the bending part and a vortex is generated. This is thought to be due to pressure loss occurring. On the other hand, in the developing duct 127 of the present embodiment, the protrusion 137 suppresses the generation of vortices around the bent portion from the main stream section 127a to the branch section 127b, suppresses the generation of turbulence, and airs the air. This is thought to be because the pressure loss is reduced.

Next, the results of verifying the pressure loss reduction effect of the protrusion 137 will be described with respect to a configuration in which the bending angle from the main stream portion 127a to the branch portion 127b4 of the developing duct 127 according to the present embodiment is ±10 degrees from a substantially right angle. Here again, the pressure loss reducing effect of the protrusion 137 is verified by comparing the developing duct 127 of this embodiment and the developing duct 177 of the first comparative example.

FIG. 10A is a diagram showing the configuration of the developing duct 127 of this embodiment when the bending angle from the main stream portion 127a to the branch portion 127b4 is set to 100°. FIG. 10B is a diagram showing the configuration of the developing duct 177 of the first comparative example when the bending angle from the main stream portion 177a to the branch portion 177b is set to 100°. FIG. 10(c) is a graph showing the results of calculating the pressure loss of these developing ducts 127 and 177 using fluid analysis software. As shown in FIG. 10C, even in the configuration in which the bending angle is 100°, the air pressure loss in the developing duct 127 of this embodiment is lower than the air pressure loss in the developing duct 177 of the first comparative example. It's getting smaller.

FIG. 11A is a diagram showing the configuration of the developing duct 127 of this embodiment when the bending angle from the main stream portion 127a to the branch portion 127b4 is 80°. FIG. 11B is a diagram showing the configuration of the developing duct 177 of the first comparative example when the bending angle from the main stream portion 177a to the branch portion 177b is set to 80°. FIG. 11(c) is a graph showing the results of calculating the pressure loss of these developing ducts 127 and 177 using fluid analysis software. As shown in FIG. 11(c), even in the configuration where the bending angle is 80 degrees, the air pressure loss in the developing duct 127 of this embodiment is lower than the air pressure loss in the developing duct 177 of the first comparative example. It's getting smaller.

In addition, in the developing duct 127 of this embodiment and the developing duct 177 of the comparative example, pressure loss is reduced by the protrusion 137 regarding the configuration in which each of the four corners of the square cross-sectional shape of 10 mm x 10 mm is provided with an arc shape with a radius of 3 mm. We verified the effectiveness. As a result, as shown in FIG. 12, the air pressure loss in the developing duct 127 of this embodiment is smaller than the air pressure loss in the developing duct 177 of the first comparative example.

As described above, according to the configuration of the present embodiment, by providing the protruding portion 137 in the portion of the developing duct 127 that bends from the main stream portion 127a to the branch portion 127b4, pressure loss of the air flowing through the developing duct 127 can be suppressed, and the image It is possible to suppress the enlargement of the main body of the forming apparatus A at the same time.

<Modified example>
Next, as a modification, a configuration in which the position and shape of the protrusion 137 in the developing duct 127 are changed will be described.

13 and 14 are schematic cross-sectional views of a developing duct 127 according to a modification. Note that the cross-sectional shape of the developing duct 127 according to the modification is a rectangular shape of 60 mm x 10 mm, and the length X of the inner diameter shown in FIG. 13 is 60 mm. Further, a curved surface with a radius of 60 mm is provided on the outer side in the bending direction at the bending portion from the main stream portion 127a to the branch portion 127b4.

As shown in FIG. 13(a), the protrusion 137 of the first modification is arranged at a position where the point P2 is moved a distance X from the point P1 to the downstream side in the direction in which the air flows. Also, point P3 moves a distance of X/2 downstream from point P1 in the direction in which the air flows, and moves a distance of (√2-1)×X÷2 in the direction perpendicular to the direction in which the air flows. It is placed in the specified position. The protrusion 137 has an arc shape passing through points P1, P2, and P3. The angles θ1 and θ2 are set at 67.5° and 67.5°, respectively.

As shown in FIG. 13(b), the protrusion 137 of the second modification has the shape of the upstream half of the protrusion 137 of the first modification in the direction in which air flows. It is set to θ1=67.5° and θ2=0°.

As shown in FIG. 13(c), the protrusion 137 of the third modification has a shape in which the position of point P3 in the protrusion 137 of the second modification is moved 100 mm downstream in the direction of air flow. . It is set to θ1=67.5 degrees and θ2=82.9 degrees.

As shown in FIG. 14(a), the protrusion 137 of the fourth modification has a shape in which the position of point P3 in the protrusion 137 of the second modification is moved 200 mm downstream in the direction of air flow. . It is set to θ1=67.5° and θ2=86.4°.

As shown in FIG. 14(b), the protrusion 137 of the fifth modification is arranged at a position where the point P2 is moved a distance X from the point P1 to the downstream side in the direction in which the air flows. In addition, point P3 is moved from point P1 to the downstream side in the direction in which the air flows by a distance of X/2, and in a direction perpendicular to the direction in which the air flows by a distance of (√2-1) It is placed in the same position. The protruding portion 137 has a triangular prism shape passing through three points P1, P2, and P3. The angles θ1 and θ2 are set at 67.5° and 67.5°, respectively.

As shown in FIG. 14(c), the protruding portion 137 of the sixth modification is arranged at a position where the point P2 is moved a distance of X/2 from the point P1 to the downstream side in the direction in which the air flows. In addition, point P3 is moved from point P1 to the downstream side in the direction in which the air flows by a distance of X/2, and in a direction perpendicular to the direction in which the air flows by a distance of (√2-1) It is placed in the same position. The protruding portion 137 has a triangular prism shape passing through three points P1, P2, and P3. It is set to θ1=67.5° and θ2=0°.

Next, the results of verifying the effect of reducing pressure loss by the protrusion 137 formed on the developing duct 127 according to the first to sixth modifications will be explained. Here, the developing duct 127 according to the first to sixth modified examples, the developing duct 277 of the second comparative example shown in FIG. 15(a), and the developing duct 377 of the third comparative example shown in FIG. 15(b) are compared. The pressure loss reducing effect of the protrusion 137 was verified. The configuration of the second comparative example is a configuration in which the protrusion 137 is removed from the configuration of the first modification. The configuration of the third comparative example differs from the configuration of the second comparative example in that a curved surface 377c with a radius of 1 mm is provided on the inner side in the bending direction at the bent portion from the main stream portion 377a to the branch portion 377b.

FIG. 16 shows the results of calculating the air pressure loss in the developing duct 127 of the first to sixth modified examples, the developing duct 277 of the second comparative example, and the developing duct 377 of the third comparative example using the fluid analysis software described above. This is a graph showing. As shown in FIG. 16, in the developing ducts 127 of the first to sixth modified examples, the air pressure loss is lower than that of the developing duct 277 of the second comparative example and the third comparative example 377. This is because in the developing ducts 277 and 377 of the second and third comparative examples, turbulent flow occurs around the bent portions from the main flow portions 277a and 377a to the branch portions 277b and 377b, generating vortices, resulting in pressure loss. This is thought to be due to the occurrence of On the other hand, in the developing ducts 127 of the first to sixth modifications, the protrusion 137 suppresses the generation of vortices around the bent portion from the main stream section 127a to the branch section 127b, and suppresses the generation of turbulent flow. This is thought to be because the pressure loss of the air is reduced.

Although the present embodiment and the first to sixth modifications have been described by way of example in which the cross-sectional shape of the developing duct 127 is square or rectangular, the present invention is not limited to this. That is, the same effect as described above can be obtained even if the cross-sectional shape of the developing duct 127 is triangular, circular, or the like.

Further, in this embodiment, the protruding portion 137 is provided only at the branch portion 127b4 of the developing duct 127. This is because among the four branch parts 127b1 to 127b4, the branch part 127b4 is located at the farthest position from the opening 127c through which air is taken into the developing duct 127, and the pressure of the air flowing through the branch part 127b4 is the lowest. It is. However, a configuration may also be adopted in which the protruding portions 137 are provided in the other branch portions 127b1 to 127b3, respectively. This suppresses a decrease in the pressure of the air flowing through the branch portions 127b1 to 127b3, and improves the cooling effect of the developing device 105.

30...Developing sleeve (developer carrier)
102...Photosensitive drum (photosensitive member)
105...Developing device (developing section)
120...Exterior cover (exterior)
120b...Intake port 121...Front side plate (frame body)
121a...Opening part 126...Developing screw (stirring member)
127...Developing duct (duct)
127a...Main stream section (first section)
127b1 to 127b4... Branch part (second part)
127c...Opening (communication hole)
127x...Upper duct 127y...Lower duct 128...Axial flow fan (fan)
137...Protrusion part 144...Claw part (engaging part)
A...Image forming device

Claims (7)

A photoreceptor that rotates around a rotation axis ,
a frame that supports at least the photoreceptor;
An air intake port provided on the exterior of the device body;
A duct that guides air taken in from the intake port into the inside of the device , the duct having a first portion extending along the frame , and a duct arranged downstream of the first portion in the direction in which the air flows; a second portion bent from the second portion and extending along the rotation axis direction of the photoreceptor ;
a fan that generates an airflow for taking in air from the intake port to the duct side;
Equipped with
The inner side in the bending direction from the first part to the second part, and the connecting part of the second part with the first part protrudes toward the air flow path side of the duct, and the outer side of the duct. A protrusion consisting of a curved surface forming a concave portion is provided for the
The duct includes a first duct part and a second duct part that configure an air flow path by being connected to each other, and an engaging part that connects the first duct part and the second duct part,
The image forming apparatus is characterized in that the engaging portion is disposed in the recess . a developing section including a developer carrier that carries a developer and causes the developer to adhere to the electrostatic latent image formed on the surface of the photoreceptor; and a stirring member that stirs the developer;
2. The image forming apparatus according to claim 1, wherein the duct guides air sucked in from the air intake port around the developing section. A plurality of the photoreceptors and the developing section are each provided,
3. The image forming apparatus according to claim 2 , wherein the duct includes a plurality of the second portions for respectively guiding air taken in from the intake port to the plurality of developing units. 4. The image forming apparatus according to claim 1, wherein the first portion of the duct is provided with a communication hole that communicates with the air intake port of the apparatus main body. 5. The image forming apparatus according to claim 1, wherein the duct has a rectangular cross -sectional shape. The image forming apparatus according to any one of claims 1 to 5 , wherein the first portion of the duct is fixed to the frame. 7. The image forming apparatus according to claim 6 , wherein the frame body is provided with an opening through which the second portion passes.

Images