Image formation apparatus

Abstract

To provide a configuration that can suppress the temperature rise of an intermediate transfer belt 21 without scattering toner on a surface of the intermediate transfer belt 21.SOLUTION: An intermediate transfer belt 21 is stretched by multiple stretching rollers including a first roller 251, a second roller 252 and a secondary transfer internal roller 23. The multiple stretching rollers are supported on a frame 26. A cooling fan 27 is supported on the frame 26 and is arranged inside the intermediate transfer belt 21. The cooling fan 27 is arranged so that a distance A between an inner peripheral surface 212a of the intermediate transfer belt 21 opposite to an exhaust port 27a of the cooling fan 27 and the exhaust port 27a becomes equal to or greater than a distance B between an inner peripheral surface 213a of the intermediate transfer belt 21 opposite to an air inlet 27b of the cooling fan 27 and the air inlet 27b with respect to the direction of the air flow generated by the cooling fan 27.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus such as a copier, a printer, a facsimile, or a multifunction machine having a plurality of these functions. [Background technology]

[0002] Conventionally known image forming apparatuses include a configuration in which a toner image is primarily transferred from a photosensitive drum to an intermediate transfer belt at a primary transfer section, and then the toner image is secondarily transferred from the intermediate transfer belt to a recording material at a secondary transfer section. The toner image transferred to the recording material is fixed to the recording material by heating it with a fixing device. In such a configuration, the intermediate transfer belt may be heated by the recording material passing through the secondary transfer section after having passed through the fixing device, or may be heated by radiant heat from the fixing device.

[0003] When the intermediate transfer belt is heated, the toner on the intermediate transfer belt may melt and adhere to the intermediate transfer belt, and heat may be transferred from the intermediate transfer belt to the photosensitive drum, causing the image forming unit, such as the photosensitive drum or the developing device, to overheat.

[0004] In response to this, a configuration for cooling the intermediate transfer belt has been proposed (Patent Document 1). In Patent Document 1, a cooling fan is provided outside the intermediate transfer belt to create an airflow on the outer circumferential surface of the belt (the surface on which the toner is placed). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2015-28563 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in a configuration in which an air flow is formed on the surface of the intermediate transfer belt from outside the intermediate transfer belt as in Patent Document 1, toner on the belt surface may be scattered, possibly contaminating the inside of the image forming apparatus body.

[0007] An object of the present invention is to provide a configuration capable of suppressing an increase in the temperature of a belt without scattering toner on the belt surface. [Means for solving the problem]

[0008] The image forming apparatus of the present invention comprises an endless belt which can rotate while carrying a toner image on its outer surface, a plurality of tension members which tension the belt, a frame which supports the tension members, and a fan which is supported by the frame and arranged inside the belt, wherein the fan is arranged so that, with respect to the direction of the airflow generated by the fan, the distance between the inner surface of the belt which faces the exhaust port of the fan and the exhaust port is greater than or equal to the distance between the inner surface of the belt which faces the intake port of the fan and the intake port. Effect of the Invention

[0009] According to the present invention, it is possible to suppress the temperature rise of the belt without scattering the toner on the belt surface. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic cross-sectional view of an image forming apparatus according to a first embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view of the intermediate transfer device according to the first embodiment. [Diagram 3] FIG. 11 is a cross-sectional view showing a schematic configuration of an intermediate transfer device according to a second embodiment. [Figure 4] FIG. 11 is a cross-sectional view showing a schematic configuration of an intermediate transfer device according to a third embodiment. [Diagram 5] FIG. 13 is a cross-sectional view showing a schematic configuration of an intermediate transfer device according to a fourth embodiment. [Figure 6] FIG. 13 is a cross-sectional view showing a schematic configuration of an intermediate transfer device according to a fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] <First embodiment> The first embodiment will be described with reference to Figures 1 and 2. First, a schematic configuration of an image forming apparatus according to the present embodiment will be described with reference to Figure 1.

[0012] [Image forming device] The image forming apparatus 100 is a tandem-type intermediate transfer type image forming apparatus in which image forming units 1Y, 1M, 1C, and 1K are arranged in series on the horizontal portion of an intermediate transfer belt 21. Such an image forming apparatus 100 forms a full-color image on a recording material S such as a sheet (paper, OHP sheet, etc.) by electrophotography in response to an image signal sent from an external device such as a personal computer or an image signal from a document reading device. Note that the order of these image forming units is merely an example, and the positions of these image forming units are not limited to these positions, and the number of these image forming units is not limited to these positions.

[0013] The image forming units 1Y, 1M, 1C, and 1K form yellow, magenta, cyan, and black toner images on the photosensitive drums 11Y, 11M, 11C, and 11K as image carriers, and primarily transfer the toner images to the same image positions on the intermediate transfer belt 21. The surface of the photosensitive drum 11Y is uniformly charged by the charging device 12Y. The exposure device 13Y irradiates the charged photosensitive drum 11Y with image light to form a latent image on the surface. The developing device 14Y transfers yellow toner to the latent image on the photosensitive drum 11Y to form a yellow toner image. The yellow toner image formed on the photosensitive drum 11Y is primarily transferred to the intermediate transfer belt 21 by applying a primary transfer bias to the primary transfer roller 35Y. The toner remaining on the photosensitive drum 11Y after the primary transfer of the toner image is removed by the cleaning member 15Y.

[0014] In the image forming units 1M, 1C, and 1K, magenta, cyan, and black toner images are formed on the photosensitive drums 11M, 11C, and 11K, respectively, in the same manner as in the image forming unit 1Y. Then, each toner image is transferred and superimposed on the yellow toner image on the intermediate transfer belt 21, and a full-color toner image is formed on the intermediate transfer belt 21. Note that the configurations of the image forming units 1M, 1C, and 1K are shown by replacing the suffix "Y" of the reference numerals attached to the configurations in the image forming unit 1Y with M, C, and K, respectively, and description thereof will be omitted.

[0015] The intermediate transfer belt 21 as an endless belt is stretched by a plurality of tension rollers including a first roller 251, a second roller 252, and a secondary transfer inner roller 23 as a plurality of tension members, and can be rotated by inputting a drive to any of these rollers. The primary transfer rollers 22Y, 22M, 22C, and 22K as primary transfer members are disposed at positions facing the photosensitive drums 11Y, 11M, 11C, and 11K through the intermediate transfer belt 21, and form primary transfer sections 220Y, 220M, 220C, and 220K. The toner images formed on the photosensitive drums 11Y, 11M, 11C, and 11K are primarily transferred onto the intermediate transfer belt 21 by applying a primary transfer voltage to the primary transfer rollers 22Y, 22M, 22C, and 22K.

[0016] At a position where the secondary transfer inner roller 23 contacts the intermediate transfer belt 21, a secondary transfer outer roller 24 is disposed as a secondary transfer member, forming a secondary transfer section 230. A secondary transfer voltage is applied to either the secondary transfer inner roller 23 or the secondary transfer outer roller 24, whereby the toner image on the intermediate transfer belt 21 is secondarily transferred to the recording material S. Residual toner remaining on the intermediate transfer belt 21 after the secondary transfer and unnecessary toner images are removed by a cleaning device 30.

[0017] Meanwhile, the image forming apparatus 100 has a plurality of feeding cassettes 61, 62 that store recording materials S. The recording materials S stored in each cassette are transported to a recording material transport path 81 by the rotation of either feeding rollers 71, 72, and reach a registration roller 74. The registration roller 74 feeds the recording material S to a secondary transfer unit 230 in synchronization with the toner image on the intermediate transfer belt 21. Then, the toner image on the intermediate transfer belt 21 is transferred to the recording material S at the secondary transfer unit 230.

[0018] Next, the recording material S onto which the toner image has been transferred is conveyed to the fixing device 5 arranged downstream of the secondary transfer section 230 in the conveying direction of the recording material, where the full-color toner image is fixed to the surface by heating and pressing in the fixing device 5. Then, the recording material S onto which the toner image has been fixed is sent to the discharge tray 64 via the discharge conveying path 82. In the case of double-sided printing, the recording material S is reversed in the reversing conveying path 83, and is conveyed again to the secondary transfer section 230 via the double-sided conveying path 84, where the toner image is transferred. Thereafter, the recording material S is conveyed to the fixing device 5, where the toner image is fixed, and is sent to the discharge tray 64 via the discharge conveying path 82.

[0019] The positions and the number of the feeding cassettes in Fig. 1 are merely examples, and are not limited to these positions and numbers. In Fig. 1, the fed recording material S is conveyed from right to left, but the direction is not limited to this, and the recording material may be conveyed from left to right.

[0020] [Configuration of intermediate transfer device] Next, the intermediate transfer device 20 including the intermediate transfer belt 21 will be described with reference to Fig. 2. The intermediate transfer device 20 includes the intermediate transfer belt 21, a plurality of tension rollers including a first roller 251, a second roller 252, and a secondary transfer inner roller 23, primary transfer rollers 22Y, 22M, 22C, and 22K, and a frame 26 supporting each of these rollers. The frame 26 has a pair of side plates (not shown) arranged on both sides of the intermediate transfer belt 21 with respect to the rotation axis direction of each roller (the width direction intersecting the rotation direction of the intermediate transfer belt 21), and a first connecting portion 261 and a second connecting portion 262 connecting the pair of side plates to each other. Both ends of each of the above-mentioned rollers are rotatably supported by the pair of side plates.

[0021] When double-sided printing is performed in the image forming apparatus 100, the recording material S, which has passed through the fixing device 5 once and is in a heated state, is conveyed to the secondary transfer section 230, and the intermediate transfer belt 21 is heated by the heat of the recording material S in the secondary transfer section 230. Furthermore, in order to reduce the size of the device, the fixing device 5 is often disposed in the vicinity of the downstream side of the secondary transfer section 230 in the conveying direction of the recording material S. In that case, the intermediate transfer belt 21 is also heated by radiant heat from the fixing device 5. In this way, the third surface 213 of the intermediate transfer belt 21, which is downstream of the secondary transfer section 230 in the rotation direction of the intermediate transfer belt 21, which will be described later, is likely to become hotter than other portions.

[0022] The tension rollers include a first roller 251 and a second roller 252. The first roller 251 is located upstream of the most upstream primary transfer roller 22Y among the multiple primary transfer rollers 22Y, 22M, 22C, and 22K. The second roller 252 is located downstream of the most downstream primary transfer roller 22K. The first roller 251 and the second roller 252 are arranged so that the winding angle of the intermediate transfer belt 21 is larger than that of the other tension rollers. In the configuration shown in FIG. 1, a roller 251a is arranged between the primary transfer roller 22Y and the first roller 251, but this roller 251a may be omitted as shown in FIG. 2. In addition, as shown in FIGS. 1 and 2, a roller 252a is arranged between the primary transfer roller 22K and the second roller 252, but this roller 252a may also be omitted.

[0023] The primary transfer rollers 22Y, 22M, 22C, and 22K are arranged in a straight line in the rotation direction of the intermediate transfer belt 21, and this arrangement direction is defined as a first direction. That is, in the configuration shown in FIG. 1, the first direction is a direction parallel to a tension surface of the outer peripheral surface of the intermediate transfer belt 21 stretched by the roller 251a and the roller 252a, and in the configuration shown in FIG. 2, the first direction is a direction parallel to a tension surface of the outer peripheral surface of the intermediate transfer belt 21 stretched by the first roller 251 and the roller 252a. Then, toner images are transferred from the photosensitive drums 11Y, 11M, 11C, and 11K to the tension surface 21a of the intermediate transfer belt 21 along the first direction. In this embodiment, the first direction is a substantially horizontal direction.

[0024] Furthermore, of the outer peripheral surface of the intermediate transfer belt 21, a region sandwiched between the most upstream primary transfer roller 22Y and the most downstream primary transfer roller 22K in the rotation direction of the intermediate transfer belt 21 is defined as a first surface 211. This first surface 211 includes the above-mentioned tension surface 21a. Of the intermediate transfer belt 21, a region sandwiched between the second roller 252 and the inner secondary transfer roller 23 is defined as a second surface 212, and a region sandwiched between the inner secondary transfer roller 23 and the first roller 251 is defined as a third surface 213. Note that these surfaces may not be flat because another roller is present between each roller.

[0025] In this embodiment, in order to cool the third surface 213 of the intermediate transfer belt 21 from the inner circumferential surface side of the intermediate transfer belt 21, that is, the opposite side to the surface on which the toner image is formed, a cooling fan 27 that generates an airflow is disposed inside the intermediate transfer belt 21. The cooling fan 27 is an axial fan supported by the frame 26, and in this embodiment, generates an airflow substantially parallel to the first direction. Since the cooling fan 27 is an axial fan, the direction in which the airflow flows is the direction of the rotation axis of the cooling fan 27.

[0026] The cooling fan 27 is positioned such that, with respect to the direction of the airflow generated by the cooling fan 27 (i.e., the direction of the rotational axis of the cooling fan 27), the distance A between the exhaust port 27a and the inner surface 212a of the intermediate transfer belt 21 that faces the exhaust port 27a of the cooling fan 27 downstream in the exhaust direction is greater than or equal to the distance B (A≧B) between the intake port 27b and the inner surface 213a of the intermediate transfer belt 21 that faces the intake port 27b of the cooling fan 27 upstream in the intake direction.

[0027] Particularly in this embodiment, the cooling fan 27 is positioned such that, with respect to the direction of the airflow, the distance A between the inner surface 212a of the intermediate transfer belt 21 facing the exhaust port 27a and the exhaust port 27a is longer than the distance B between the inner surface 213a of the intermediate transfer belt 21 facing the intake port 27b and the intake port 27b (A>B).

[0028] Here, the inner peripheral surface 212a of the intermediate transfer belt 21 facing the exhaust port 27a is the inner peripheral surface of the intermediate transfer belt 21 whose outer peripheral surface is the second surface 212, and the inner peripheral surface 213a of the intermediate transfer belt 21 facing the intake port 27b is the inner peripheral surface of the intermediate transfer belt 21 whose outer peripheral surface is the third surface 213. That is, the inner peripheral surface 213a of the intermediate transfer belt 21 facing the intake port 27b is in a range downstream of the secondary transfer portion 230 and upstream of the primary transfer portion 220Y with respect to the rotation direction of the intermediate transfer belt 21. Therefore, the cooling fan 27 is disposed close to the inner peripheral surface side of the third surface 213, and is adapted to suck in air from the inner peripheral surface side of the third surface 213 and exhaust it to a larger space inside the intermediate transfer device 20.

[0029] The distance between exhaust port 27a and inner circumferential surface 212a is the distance between the center position of the opening surface where exhaust port 27a of cooling fan 27 is formed, i.e., the exhaust surface, and the position where a line extending from this center position downstream in the exhaust direction along the rotation axis direction of cooling fan 27 intersects with inner circumferential surface 212a. Similarly, the distance between intake port 27b and inner circumferential surface 213a is the distance between the center position of the opening surface where intake port 27b of cooling fan 27 is formed, i.e., the intake surface, and the position where a line extending from this center position upstream in the intake direction along the rotation axis direction of cooling fan 27 intersects with inner circumferential surface 213a.

[0030] The reason why the cooling fan 27 draws in air from a narrow space and exhausts it to a wide space is that it is more efficient at ventilation than blowing air into a narrow space. That is, by making the space on the side where the cooling fan 27 blows air wider than the side where the cooling fan 27 sucks air, ventilation inside the intermediate transfer device 20 is promoted. Even if the distance A between the exhaust port 27a and the inner circumferential surface 212a and the distance B between the intake port 27b and the inner circumferential surface 213a are equal, the ventilation inside the intermediate transfer belt 21 is promoted, so the distances A and B may be equal. However, since the ventilation inside the intermediate transfer belt 21 is promoted when the distance A is longer than the distance B, it is preferable to arrange the cooling fan 27 so that the distance A is longer than the distance B.

[0031] In order to prevent heat from building up, the exhaust side of the cooling fan 27 communicates with the exhaust port 27a of the cooling fan 27 and the inner circumferential surface 212a of the intermediate transfer belt 21 facing the exhaust port 27a. As described above, the frame 26 has the first connecting portion 261 and the second connecting portion 262. The first connecting portion 261 and the second connecting portion 262 are arranged across the rotation axis direction of each tension roller so as to connect a pair of side plates. The first connecting portion 261 is arranged so as to extend substantially parallel to the first direction below the primary transfer rollers 22Y to 22K, and the second connecting portion 262 is arranged substantially parallel to the first connecting portion 261 and below the first connecting portion 261. In this embodiment, the cooling fan 27 is attached to the second connecting portion 262. Specifically, the cooling fan 27 is supported on the upper surface of the second connecting portion 262 between the first connecting portion 261 and the second connecting portion 262 .

[0032] The second connecting portion 262 is formed with a bent portion 263 to increase its strength. As shown in Fig. 2, the bent portion 263 may be integral with the second connecting portion 262 and extend in an angled direction, such as perpendicular to the first direction and the rotation axis direction of the tension roller, or may be a pipe extending in the rotation axis direction. In the former case, the first connecting portion 261 and the second connecting portion 262 may not be connected, or the first connecting portion 261 and the second connecting portion 262 may be connected, but the bent portion 263 may have an opening hole or a louver hole.

[0033] This allows the space between the first connecting portion 261 and the second connecting portion 262 to communicate with the space between the first connecting portion 261 and the intermediate transfer belt 21. That is, the exhaust port 27a of the cooling fan 27 can communicate with the inner circumferential surface 212a of the intermediate transfer belt 21 facing the exhaust port 27a. Even in the latter case where the second connecting portion 262 is reinforced with a reinforcing material such as a pipe, the space between the first connecting portion 261 and the second connecting portion 262 and the space between the first connecting portion 261 and the intermediate transfer belt 21 can communicate with each other through the gaps in the reinforcing material.

[0034] Furthermore, the pair of side plates of the frame 26 are not in contact with the intermediate transfer belt 21, and a gap is provided between the pair of side plates and the intermediate transfer belt 21. Therefore, the internal space surrounded by the pair of side plates and the intermediate transfer belt 21 communicates with the space outside the intermediate transfer belt 21 via this gap. Note that an opening may be further provided in the pair of side plates, and the internal space surrounded by the pair of side plates and the intermediate transfer belt 21 may communicate with the space outside the intermediate transfer belt 21 via this opening.

[0035] Also, a cooling roller 29 may be arranged so as to be in contact with the inner circumferential surface 213a of the intermediate transfer belt 21 facing the intake port 27b of the cooling fan 27. The cooling roller 29 is a metal roller having high thermal conductivity, such as an aluminum pipe. By arranging the cooling roller 29 on the inner circumferential surface 213a, the third surface 213 can be cooled more efficiently.

[0036] In addition, when the heating element 28, such as a high-voltage board for applying a secondary transfer voltage or a resistor electrically connected to the high-voltage board, is disposed in the intermediate transfer device 20, it is preferable to dispose it between the inner circumferential surface 213a of the intermediate transfer belt 21 and the intake port 27b of the cooling fan 27, or between the exhaust port 27a of the cooling fan 27 and the inner circumferential surface 212a of the intermediate transfer belt 21. For example, as shown in FIG. 2, the heating element 28 is supported by the second connecting portion 262 of the frame 26 and disposed near the intake port 27b. Even when the heating element 28 is disposed on the exhaust port 27a side, it is preferable to dispose it near the exhaust port 27a. This allows the heating element 28 to be cooled efficiently. In order to intensively blow air to the heating element 28, a cooling duct (not shown) connected to the cooling fan 27 may be provided.

[0037] In this manner, in this embodiment, it is possible to suppress the temperature rise of the intermediate transfer belt 21 without scattering toner on the surface of the intermediate transfer belt 21. That is, since the cooling fan 27 is disposed inside the intermediate transfer belt 21, it is possible to suppress scattering of toner on the outer circumferential surface of the intermediate transfer belt 21 due to the airflow generated by the cooling fan 27. In addition, since the distance A between the exhaust port 27a of the cooling fan 27 and the inner circumferential surface 212a of the intermediate transfer belt 21 is set to be equal to or greater than the distance B between the intake port 27b and the inner circumferential surface 213a, preferably the distance A is set to be longer than the distance B, it is possible to efficiently cool the intermediate transfer belt 21.

[0038] In addition, since the space surrounded by the exhaust port 27a of the cooling fan 27, the first connecting portion 261, the second connecting portion 262, and the inner circumferential surface 212a is larger than the space surrounded by the intake port 27b of the cooling fan 27, the first connecting portion 261, the second connecting portion 262, and the inner circumferential surface 213a of the third surface 213, the heat of the third surface 213, which is relatively high, can be caused to flow to a larger space by the cooling fan 27, and the intermediate transfer device 20 can be efficiently ventilated. This makes it possible to level the temperature gradient in the intermediate transfer device 20, and to prevent the intermediate transfer belt 21, the photosensitive drums 11Y to 11K, and the developing units 14Y to 14K from becoming overheated.

[0039] In this embodiment, the secondary transfer inner roller 23 is disposed upstream in the rotation direction of the intermediate transfer belt 21 with respect to the center position of the intermediate transfer belt 21 in the first direction, that is, in the vicinity of the primary transfer roller 22Y in FIG. 2 (between the primary transfer roller 22Y and the primary transfer roller 22M with respect to the first direction). As a result, the space under the first connecting portion 261 is larger on the upstream side in the rotation direction of the intermediate transfer belt 21 in the first direction than on the downstream side. Accordingly, the second connecting portion 262 can be easily disposed closer to the upstream side in the rotation direction of the intermediate transfer belt 21 in the first direction with respect to the first connecting portion 261, and the inner circumferential surface 213a of the third surface 213 and the opening surface of the intake port 27b of the cooling fan 27 can be brought closer to each other in parallel, so that air can be widely taken in from the third surface 213 side. With this configuration, the third surface 213 can be efficiently cooled. However, the arrangement of the secondary transfer inner roller 23 and the shape of the frame 26 are not limited to this and can be changed as appropriate.

[0040] 2 are merely examples, and the shape of the frame 26, the mounting location of the cooling fan 27, and the like can be changed as appropriate. For example, the first connecting portion 261 may be disposed so as to be substantially perpendicular to the third surface 213, the cooling fan 27 may be attached to the first connecting portion 261, and the exhaust port 27a of the cooling fan 27 may be opposed to the inner circumferential surface 211a of the first surface 211. In short, it is only necessary to dispose the intake port 27b of the cooling fan 27 near the inner circumferential surface 213a of the third surface 213, and to dispose the intake port 27b so that the distance between the inner circumferential surface of the intermediate transfer belt 21 facing the exhaust port 27a and the exhaust port 27a is equal to or greater than the distance between the intake port 27b and the inner circumferential surface 213a.

[0041] <Second embodiment> The second embodiment will be described with reference to Fig. 3. In the first embodiment described above, an axial fan was used as the cooling fan 27, but in this embodiment, a sirocco fan is used as the cooling fan 270. Accordingly, the shape of the frame 26A supporting the tension roller is changed. Since the other configurations and functions are the same as those of the first embodiment described above, the same reference numerals are used for the configurations similar to those of the first embodiment, and the description and illustrations are omitted or simplified. The following description will focus on the points that are different from the first embodiment.

[0042] In the intermediate transfer device 20A of this embodiment, the frame 26A has a pair of side plates that rotatably support a plurality of tension rollers including the first roller 251, the second roller 252, and the secondary transfer inner roller 23, and a connecting portion 264 that connects the pair of side plates, as in the first embodiment. The connecting portion 264 includes a first frame portion 264a, a second frame portion 264b, a third frame portion 264c, and the like. The first frame portion 264a is provided so as to extend in the rotation axis direction of each tension roller, and is disposed below the primary transfer roller 22Y and the primary transfer roller 22M so as to extend substantially parallel to the first direction. The second frame portion 264b is disposed substantially parallel to the first frame portion 264a and below the first frame portion 264a. The second frame portion 264b is disposed below the primary transfer roller 22C and the primary transfer roller 22K. The third frame portion 264c is disposed above the second frame portion 264b and on the same plane as the first frame portion 264a. The third frame portion 264c is disposed below the roller 252a.

[0043] The first frame portion 264a, the second frame portion 264b, and the third frame portion 264c are continuous via the upright plate portion 264d. As a result, the cross section of the frame 26A perpendicular to the rotation axis direction of each tension roller has a concave shape as shown in Fig. 3. Note that the shape of the frame 26A shown in Fig. 3 is only an example, and the frame 26A may have a different configuration from that shown in Fig. 3, for example, the first frame portion 264a may be discontinuous.

[0044] In addition, the end of the frame 26A is provided with a bent portion 263 to increase strength. Also in the case of the present embodiment, the pair of side plates of the frame 26A and the intermediate transfer belt 21 are not in contact with each other, and the internal space surrounded by the pair of side plates and the intermediate transfer belt 21 is in communication with the space outside the intermediate transfer belt 21.

[0045] In this embodiment, a cooling fan 270 is attached to the lower part of the second frame part 264b in order to cool the third surface 213 of the intermediate transfer belt 21 from the inner side. An opening communicating with an exhaust port 270a of the cooling fan 270 is formed in the second frame part 264b, and the air blown out from the exhaust port 270a flows above the second frame part 264b. The cooling fan 270 may be attached to another position in the frame 26A, for example, to the first frame part 264a.

[0046] The cooling fan 270 is a sirocco fan, and is arranged such that, with respect to the direction of the airflow generated by the cooling fan 270, the distance C between the inner surface 211a of the intermediate transfer belt 21 facing the exhaust port 270a of the cooling fan 270 and the exhaust port 270a is greater than or equal to the distance D between the inner surface 213a of the intermediate transfer belt 21 facing the intake port 270b of the cooling fan 270 and the intake port 270b (C≧D).

[0047] Particularly in this embodiment, the cooling fan 270 is positioned such that, with respect to the direction of the airflow, a distance C between the inner surface 211a of the intermediate transfer belt 21 facing the exhaust port 270a and the exhaust port 270a is longer than a distance D between the inner surface 213a of the intermediate transfer belt 21 facing the intake port 270b and the intake port 270b (C>D).

[0048] Here, the inner peripheral surface 211a of the intermediate transfer belt 21 facing the exhaust port 27a is the inner peripheral surface of the intermediate transfer belt 21 whose outer peripheral surface is the first surface 211, and the inner peripheral surface 213a of the intermediate transfer belt 21 facing the intake port 27b is the inner peripheral surface of the intermediate transfer belt 21 whose outer peripheral surface is the third surface 213. In addition, in the present embodiment, since the cooling fan 270 is a sirocco fan, the direction of the airflow sucked in from the intake port 270b is different from the direction of the airflow blown out from the exhaust port 270a. Therefore, unlike the first embodiment, the direction of the airflow blown out from the exhaust port 270a is inside the first surface 211 of the intermediate transfer belt 21.

[0049] The distance between the exhaust port 270a and the inner circumferential surface 211a is defined as the distance between the center position of the opening surface where the exhaust port 270a of the cooling fan 270 is formed, i.e., the exhaust surface, and the position where a line extending from this center position along the airflow direction on the exhaust side of the cooling fan 270 intersects with the inner circumferential surface 211a. The distance between the intake port 270b and the inner circumferential surface 213a is defined as the distance between the center position of the opening surface where the intake port 270b of the cooling fan 270 is formed, i.e., the intake surface, and the position where a line extending from this center position along the rotation axis direction of the cooling fan 270 intersects with the inner circumferential surface 213a. Here, in the case of a sirocco fan, the airflow direction on the exhaust side is defined as the normal direction of the opening surface where the exhaust port of the cooling fan 270 is formed.

[0050] In this embodiment, too, the cooling fan 270 is positioned close to the inner circumferential surface side of the third surface 213, and is configured to draw in air from the inner circumferential surface side of the third surface 213 and exhaust it to a larger space within the intermediate transfer device 20A.

[0051] In addition, since the space surrounded by the exhaust port 270a of the cooling fan 270, the first frame portion 264a, the second frame portion 264b, the third frame portion 264c, the standing plate portion 264d, and the inner peripheral surface 211a of the first surface 211 is larger than the space surrounded by the intake port 270b of the cooling fan 270, the second frame portion 264b, and the inner peripheral surface 213a of the third surface 213, the heat of the third surface 213, which is relatively high, can be diverted to a larger space by the cooling fan 270, and the intermediate transfer device 20A can be efficiently ventilated. This makes it possible to level the temperature gradient in the intermediate transfer device 20A, and to prevent the intermediate transfer belt 21, the photosensitive drums 11Y to 11K, and the developing units 14Y to 14K from being overheated.

[0052] In this embodiment, the secondary transfer inner roller 23 is disposed downstream in the rotation direction of the intermediate transfer belt 21 with respect to the center position of the intermediate transfer belt 21 in the first direction, that is, in the vicinity of the primary transfer roller 22K in FIG. 3. As a result, the space below the first frame portion 264a and the third frame portion 264c is larger on the downstream side in the rotation direction of the intermediate transfer belt 21 in the first direction than on the upstream side. Accordingly, it becomes easy to dispose the second frame portion 264b closer to the downstream side in the rotation direction of the intermediate transfer belt 21 in the first direction with respect to the first frame portion 264a, and the space sandwiched between the inner circumferential surface 213a of the third surface 213 and the intake port 270b of the cooling fan 270 can be made wider, making it easier to dispose the cooling fan 270. However, the disposition of the secondary transfer inner roller 23 and the shape of the frame 26A are not limited to this and can be changed as appropriate.

[0053] When the heating element 28, such as a high-voltage board for applying a secondary transfer voltage or a resistor electrically connected to the high-voltage board, is disposed in the intermediate transfer device 20A, it is installed near the exhaust port 270a of the cooling fan 270, for example, on the vertical plate portion 264d, so that the air from the cooling fan 270 hits it. This makes it possible to efficiently cool the heating element 28. Also, in order to intensively blow air to the heating element 28, a cooling duct (not shown) connected to the cooling fan 270 may be provided.

[0054] In this manner, in the case of this embodiment, as in the first embodiment, the temperature rise of the intermediate transfer belt 21 can be suppressed without scattering the toner on the surface of the intermediate transfer belt 21. That is, since the cooling fan 270 is disposed inside the intermediate transfer belt 21, scattering of the toner on the outer peripheral surface of the intermediate transfer belt 21 due to the airflow generated by the cooling fan 270 can be suppressed. In addition, the distance C between the exhaust port 270a of the cooling fan 270 and the inner peripheral surface 211a of the intermediate transfer belt 21 is set to be equal to or greater than the distance D between the intake port 270b and the inner peripheral surface 213a, and preferably the distance C is set to be longer than the distance D, so that the intermediate transfer belt 21 can be efficiently cooled.

[0055] <Third embodiment> The third embodiment will be described with reference to FIG. 4. In the first and second embodiments described above, the intake port of the cooling fan faces the inner circumferential surface 213a of the third surface 213, but in this embodiment, the exhaust port of the cooling fan faces the inner circumferential surface 213a of the third surface 213. In addition, in this embodiment, an axial fan is used as the cooling fan 27, as in the first embodiment. Since the other configurations and functions are the same as those of the first embodiment described above, the same reference numerals are used for the configurations similar to those of the first embodiment, and explanations and illustrations are omitted or simplified, and the following description will focus on the points that are different from the first embodiment.

[0056] In the intermediate transfer device 20B of this embodiment, the frame 26B has a pair of side plates that rotatably support a plurality of tension rollers including the first roller 251, the second roller 252, and the secondary transfer inner roller 23, and a first connecting portion 261A and a second connecting portion 262A that connect the pair of side plates, as in the first embodiment. The first connecting portion 261A is disposed so as to extend substantially parallel to the first surface 211. The second connecting portion 262A is disposed substantially parallel to the first connecting portion 261A and below the first connecting portion 261A. Note that the shape of the frame 26B shown in FIG. 4 is an example, and the frame 26B may have a different configuration from that shown in FIG. 4, for example, the first connecting portion 261A may be discontinuous.

[0057] The first connecting portion 261A is formed with a bent portion 263 to increase strength. The bent portion 263 is configured to communicate the space between the first connecting portion 261A and the second connecting portion 262A and the space between the first connecting portion 261A and the intermediate transfer belt 21 to prevent heat from being trapped in one area. For example, as in the first embodiment, the bent portion 263 is configured to have an opening hole or a louver hole. In addition, the pair of side plates of the frame 26B and the intermediate transfer belt 21 are not in contact with each other, and the internal space surrounded by the pair of side plates and the intermediate transfer belt 21 is both in communication with the space outside the intermediate transfer belt 21.

[0058] In this embodiment, a cooling fan 27 is attached to the second connecting part 262A in order to cool the third surface 213 from the inner surface side. The cooling fan 27 may be attached to another position in the frame 26B, for example, to the first connecting part 261A. The cooling fan 27 is an axial flow fan, and is disposed close to the inner circumferential surface 212a side of the second surface 212 so as to draw in air from the inside of the second surface 212 and blow the air toward the inner circumferential surface 213a side of the third surface 213.

[0059] The cooling fan 27 is positioned such that, with respect to the direction of the airflow generated by the cooling fan 27 (i.e., the direction of the rotational axis of the cooling fan 27), the distance E between the inner surface 213a of the intermediate transfer belt 21 facing the exhaust port 27a of the cooling fan 27 and the exhaust port 27a is greater than or equal to the distance F between the inner surface 212a of the intermediate transfer belt 21 facing the intake port 27b of the cooling fan 27 and the intake port 27b (E≧F).

[0060] In particular, in this embodiment, the cooling fan 27 is positioned in such a way that, with respect to the direction of the airflow, the distance E between the inner surface 213a of the intermediate transfer belt 21 facing the exhaust port 27a and the exhaust port 27a is longer than the distance F between the inner surface 212a of the intermediate transfer belt 21 facing the intake port 27b and the intake port 27b (E>F).

[0061] In this embodiment, the cooling fan 27 is positioned close to the inner circumferential surface of the second surface 212, and draws in air from the inner circumferential surface of the second surface 212 and exhausts it to a larger space within the intermediate transfer device 20A.

[0062] In addition, since the space surrounded by the exhaust port 27a of the cooling fan 27, the first connecting portion 261A, the second connecting portion 262A, and the inner circumferential surface 213a of the third surface 213 is larger than the space surrounded by the intake port 27b of the cooling fan 27, the first connecting portion 261A, the second connecting portion 262A, and the inner circumferential surface 212a of the second surface 212, the air near the second surface 212, which is relatively low temperature, can be efficiently circulated to the third surface 213, which is relatively high temperature, by the cooling fan 27, and the intermediate transfer device 20B can be efficiently ventilated. In addition, when the fixing device 5 is disposed relatively close to the intermediate transfer device 20B (downstream of the secondary transfer portion 230), the air warmed by the fixing device 5 is not taken into the intermediate transfer device 20B, so that the intermediate transfer belt can be cooled more efficiently. This makes it possible to level out the temperature gradient within the intermediate transfer device 20A, and to prevent the intermediate transfer belt 21, the photosensitive drums 11Y to 11K, and the developing units 14Y to 14K from becoming overheated.

[0063] In this embodiment, the secondary transfer inner roller 23 is disposed downstream in the rotation direction of the intermediate transfer belt 21 with respect to the center position of the intermediate transfer belt 21 in the first direction, that is, in the vicinity of the primary transfer roller 22K in FIG. 4. As a result, the space below the first connecting portion 261A is larger on the downstream side in the rotation direction of the intermediate transfer belt 21 in the first direction than on the upstream side. Accordingly, it becomes easier to dispose the second connecting portion 262A closer to the downstream side in the rotation direction of the intermediate transfer belt 21 in the first direction with respect to the first connecting portion 261A, and it becomes easier to secure the distance E, so that the third surface 213 can be cooled more efficiently. However, the arrangement of the secondary transfer inner roller 23 and the shape of the frame 26B are not limited to this and can be changed as appropriate.

[0064] When the heating element 28, such as a high-voltage substrate for applying a secondary transfer voltage or a resistor electrically connected to the high-voltage substrate, is disposed inside the intermediate transfer device 20B, the heating element 28 can be efficiently cooled by disposing the heating element 28 near the exhaust port 27a of the cooling fan 27. Also, in order to blow air intensively to the heating element 28, a cooling duct (not shown) connected to the cooling fan 27 may be provided.

[0065] Also in this embodiment, the cooling fan may be a sirocco fan as in the second embodiment. In this case, for example, the cooling fan is attached to the first connecting part 261A, and the intake port 27b faces the inner circumferential surface 211a of the first surface 211, and the exhaust port 27a faces the inner circumferential surface 213a of the third surface 213.

[0066] In this manner, in the case of this embodiment, as in the first embodiment, the temperature rise of the intermediate transfer belt 21 can be suppressed without scattering the toner on the surface of the intermediate transfer belt 21. That is, since the cooling fan 27 is disposed inside the intermediate transfer belt 21, scattering of the toner on the outer circumferential surface of the intermediate transfer belt 21 due to the airflow generated by the cooling fan 27 can be suppressed. In addition, the distance E between the exhaust port 27a of the cooling fan 27 and the inner circumferential surface 213a of the intermediate transfer belt 21 is set to be equal to or greater than the distance F between the intake port 27b and the inner circumferential surface 212a, and preferably the distance E is set to be greater than the distance F, so that the intermediate transfer belt 21 can be efficiently cooled.

[0067] <Fourth embodiment> The fourth embodiment will be described with reference to FIG. 5. In the first to third embodiments described above, the intermediate transfer device is arranged so that the first surface 211 of the intermediate transfer belt 21 is in a substantially horizontal direction. In this embodiment, however, the intermediate transfer device is arranged so that the first surface 211 of the intermediate transfer belt 21 is in a substantially vertical direction. In addition, in this embodiment, an axial fan is used as the cooling fan 27, as in the first embodiment. Since the other configurations and functions are the same as those of the first embodiment described above, the same reference numerals are used for the same configurations as those of the first embodiment, and explanations and illustrations are omitted or simplified. The following description will focus on the points that are different from the first embodiment.

[0068] In this embodiment, the image forming apparatus is configured such that the photosensitive drums 11Y-11K are arranged in a line in a substantially vertical direction, and therefore the first direction in which the primary transfer rollers 22Y-22K are arranged is also substantially vertical (the direction of gravity). When connecting a device that performs various processes such as cutting and folding the recording material S after forming a full-color image on the recording material S to the image forming apparatus, the connection direction is usually the left-right direction (horizontal direction), and it is also desirable that the conveying direction of the recording material S is the left-right direction in the figure.

[0069] As described above, in the intermediate transfer device 20C of this embodiment, the first direction is the direction of gravity, and when the recording material S is transported in the left-right direction, the secondary transfer section 230 is positioned below the intermediate transfer device 20C, so that the recording material S can be transported in the left-right direction without bending significantly. That is, the position of the secondary transfer inner roller 23 for forming the secondary transfer section 230 is located below the intermediate transfer device 20C. For example, the recording material S enters the secondary transfer section 230 from the diagonally lower left of the secondary transfer section 230 in FIG. 5, and after passing through the secondary transfer section 230, it is transported in a substantially horizontal direction to the left of FIG. 5. Note that the arrangement of the secondary transfer inner roller 23 and the shape of the frame 26C are not limited to these and can be changed as appropriate.

[0070] Between the secondary transfer inner roller 23 and the first roller 251, a third roller 253 is disposed such that the downstream surface of the secondary transfer inner roller 23 in the rotation direction of the intermediate transfer belt 21 is approximately parallel to the first surface 211. The third roller 253 is also a tension roller that tensions the intermediate transfer belt 21. In this embodiment, the outer circumferential surface from the downstream of the secondary transfer inner roller 23 to the upstream of the third roller 253 in the rotation direction of the intermediate transfer belt 21 is the third surface 213, and the outer circumferential surface from the downstream of the third roller 253 to the upstream of the first roller 251 is the fourth surface 214.

[0071] The frame 26C has a pair of side plates that rotatably support a plurality of tension rollers including the first roller 251, the second roller 252, the third roller 253, and the secondary transfer inner roller 23, and a first connecting portion 261B and a second connecting portion 262B that connect the pair of side plates. The first connecting portion 261B and the second connecting portion 262B are intermittently arranged substantially parallel to the first surface 211. The second connecting portion 262B is arranged closer to the third surface 213 than the first connecting portion 261B. The shape of the frame 26C shown in FIG. 5 is an example, and for example, the first connecting portion 261B and the second connecting portion 262B may be formed continuously.

[0072] The first connecting portion 261B and the second connecting portion 262B each have a bent portion 263 formed therein in order to increase strength. The pair of side plates of the frame 26C are not in contact with the intermediate transfer belt 21, and the internal space surrounded by the pair of side plates and the intermediate transfer belt 21 is in communication with the space outside the intermediate transfer belt 21.

[0073] As described above, the secondary transfer portion 230 is likely to become relatively hot because heat is carried thereto by the recording material S that has passed through the fixing device 5. In this embodiment, the cooling fan 27 is attached to the second connecting portion 262B in order to cool the vicinity of the secondary transfer inner roller 23. The cooling fan 27 may be attached to another position in the frame 26C. The cooling fan 27 is an axial fan, and is disposed close to the secondary transfer inner roller 23 and the inner circumferential surface 212a side of the second surface 212 so as to draw in air from the vicinity of the secondary transfer inner roller 23 and the inner circumferential surface 212a and blow out the air toward the inner circumferential surface 214a side of the fourth surface 214.

[0074] The cooling fan 27 is positioned such that, with respect to the direction of the airflow generated by the cooling fan 27 (i.e., the direction of the rotational axis of the cooling fan 27), the distance G between the inner surface 213a of the intermediate transfer belt 21 facing the exhaust port 27a of the cooling fan 27 and the exhaust port 27a is greater than or equal to the distance H between the inner surface 212a of the intermediate transfer belt 21 facing the intake port 27b of the cooling fan 27 and the intake port 27b (G≧H).

[0075] Particularly in this embodiment, the cooling fan 27 is positioned such that, with respect to the direction of the airflow, the distance G between the inner surface 214a of the intermediate transfer belt 21 facing the exhaust port 27a and the exhaust port 27a is longer than the distance H between the inner surface 212a of the intermediate transfer belt 21 facing the intake port 27b and the intake port 27b (G>H).

[0076] In this embodiment, the cooling fan 27 is positioned close to the inner circumferential surface of the second surface 212, and draws in air from the inner circumferential surface of the second surface 212 and exhausts it to a larger space within the intermediate transfer device 20C.

[0077] In addition, since the space surrounded by the exhaust port 27a of the cooling fan 27, the first connecting portion 261B, the second connecting portion 262B, the inner peripheral surface 213a of the third surface 213, and the inner peripheral surface 214a of the fourth surface 214 is larger than the space surrounded by the intake port 27b of the cooling fan 27, the second connecting portion 262B, the inner peripheral surface 212a of the second surface 212, and the inner peripheral surface 213a of the third surface 213, the air near the second surface 212, which is relatively low temperature, can be made to flow into a larger space by the cooling fan 27, and the intermediate transfer device 20 can be efficiently ventilated. This makes it possible to level the temperature gradient in the intermediate transfer device 20A, and to prevent the intermediate transfer belt 21, the photosensitive drums 11Y to 11K, and the developing units 14Y to 14K from being in an overheated state.

[0078] When the heating element 28, such as a high-voltage substrate for applying a secondary transfer voltage or a resistor electrically connected to the high-voltage substrate, is disposed inside the intermediate transfer device 20C, the heating element 28 can be efficiently cooled by disposing the heating element 28 near the exhaust port 27a or near the intake port 27b of the cooling fan 27. Also, in order to blow air intensively to the heating element 28, a cooling duct (not shown) connected to the cooling fan 27 may be provided.

[0079] In this manner, in the case of this embodiment, as in the first embodiment, the temperature rise of the intermediate transfer belt 21 can be suppressed without scattering the toner on the surface of the intermediate transfer belt 21. That is, since the cooling fan 27 is disposed inside the intermediate transfer belt 21, scattering of the toner on the outer peripheral surface of the intermediate transfer belt 21 due to the airflow generated by the cooling fan 27 can be suppressed. In addition, the distance G between the exhaust port 27a of the cooling fan 27 and the inner peripheral surface 214a of the intermediate transfer belt 21 is set to be equal to or greater than the distance H between the intake port 27b and the inner peripheral surface 212a, and preferably the distance G is set to be greater than the distance H, so that the intermediate transfer belt 21 can be efficiently cooled.

[0080] <Fifth embodiment> The fifth embodiment will be described with reference to FIG. 6. In the above-described fourth embodiment, an axial fan was used as the cooling fan 27, but in this embodiment, a sirocco fan is used as the cooling fan 270. Accordingly, the shape of the frame 26D supporting the tension roller is changed. Since the other configurations and functions are the same as those of the above-described fourth embodiment, the same reference numerals are used for the configurations similar to those of the fourth embodiment, and the description and illustrations are omitted or simplified. The following description will focus on the points that are different from the fourth embodiment.

[0081] In the intermediate transfer device 20D of this embodiment, the frame 26D has a pair of side plates that rotatably support a plurality of tension rollers including the first roller 251, the second roller 252, the third roller 253, and the secondary transfer inner roller 23, a first connecting portion 265 that connects the pair of side plates, and a second connecting portion 266. The first connecting portion 265 includes a first frame portion 265a, a second frame portion 265b, a third frame portion 265c, and the like that are intermittently arranged substantially parallel to the first surface 211. The second connecting portion 266 is substantially parallel to the first connecting portion 265 and is arranged on the third surface 213 side with respect to the first connecting portion 265. Note that the shape of the frame 26D shown in FIG. 6 is an example, and the frame 26D may have a configuration different from that shown in FIG. 6, for example, the first connecting portion 265 may be continuous, or the second connecting portion 266 may not exist.

[0082] Further, the ends of the first frame portion 265a, the second frame portion 265b, and the third frame portion 265c are provided with bent portions 263 to increase strength. Also, the space sandwiched between the first connecting portion 265 and the second connecting portion 266 is made to communicate with the space sandwiched between the first connecting portion 265 and the intermediate transfer belt 21. Also in the case of this embodiment, the pair of side plates of the frame 26D and the intermediate transfer belt 21 are not in contact with each other, and the internal spaces surrounded by the pair of side plates and the intermediate transfer belt 21 are both in communication with the space outside the intermediate transfer belt 21.

[0083] In this embodiment, in order to cool the third surface 213 of the intermediate transfer belt 21 from the inner surface side, a cooling fan 270 is attached to the second connecting part 266. An opening communicating with the intake port 270b of the cooling fan 270 is formed in the second connecting part 265, and air can be taken in from the intake port 270b via this opening. The cooling fan 270 may be attached to another position in the frame 26D, for example, to the first connecting part 265.

[0084] Cooling fan 270 is a sirocco fan, and is disposed close to inner circumferential surface 213a of third surface 213 so as to draw air in from near third surface 213 and blow the air toward inner circumferential surface 214a of fourth surface 214.

[0085] In this embodiment, with respect to the direction of the airflow generated by the cooling fan 270, the distance J between the inner surface 214a of the intermediate transfer belt 21 facing the exhaust port 270a of the cooling fan 270 and the exhaust port 270a is set to be equal to or greater than the distance K between the inner surface 213a of the intermediate transfer belt 21 facing the intake port 270b of the cooling fan 270 and the intake port 270b (J≧K).

[0086] Particularly in this embodiment, the cooling fan 270 is disposed such that, with respect to the direction of the airflow, a distance J between the inner circumferential surface 214a of the intermediate transfer belt 21 facing the exhaust port 270a and the exhaust port 270a is longer than a distance K between the inner circumferential surface 213a of the intermediate transfer belt 21 facing the intake port 270b and the intake port 270b (J>K). The relationship of the distance between the inner circumferential surface of the intermediate transfer belt 21 and the exhaust port 270a and intake port 270b of the cooling fan 270 is the same as in the second embodiment.

[0087] In this embodiment, too, the cooling fan 270 is positioned close to the inner circumferential surface side of the third surface 213, so as to draw in air from the inner circumferential surface side of the third surface 213 and exhaust it to a larger space within the intermediate transfer device 20D.

[0088] In addition, since the space surrounded by the exhaust port 270a of the cooling fan 270, the first connecting portion 265, the second connecting portion 266, the inner peripheral surface 213a of the third surface 213, and the inner peripheral surface 214a of the fourth surface 214 is larger than the space surrounded by the intake port 270b of the cooling fan 270, the second connecting portion 266, and the inner peripheral surface 213a of the third surface 213, the relatively high-temperature air of the third surface 213 can be made to flow into a larger space by the cooling fan 270, and the intermediate transfer device 20D can be efficiently ventilated. This makes it possible to level the temperature gradient of the intermediate transfer device 20D and prevent the intermediate transfer belt 21, the photosensitive drums 11Y to 11K, and the developing units 14Y to 14K from overheating.

[0089] In addition, in Figure 6, the secondary transfer inner roller 23 is arranged in the opposing vicinity between the primary transfer roller 22K and the second roller 252 in the first direction, but the arrangement of the secondary transfer inner roller 23 and the shape of the frame 26D are not limited to this.

[0090] Furthermore, when a heating element 28 such as a high-voltage substrate for applying a secondary transfer voltage or a resistor electrically connected to the high-voltage substrate is disposed inside the intermediate transfer device 20D, the cooling fan 270 is installed so that the air from the cooling fan 270 hits the cooling fan 270 near the exhaust port 270a of the cooling fan 270. This allows efficient cooling of the heating element 28. Furthermore, in order to intensively blow air to the heating element 28, a cooling duct (not shown) connected to the cooling fan 270 may be provided.

[0091] In this manner, in the case of this embodiment, as in the first embodiment, the temperature rise of the intermediate transfer belt 21 can be suppressed without scattering the toner on the surface of the intermediate transfer belt 21. That is, since the cooling fan 270 is disposed inside the intermediate transfer belt 21, scattering of the toner on the outer peripheral surface of the intermediate transfer belt 21 due to the airflow generated by the cooling fan 270 can be suppressed. In addition, the distance J between the exhaust port 270a of the cooling fan 270 and the inner peripheral surface 214a of the intermediate transfer belt 21 is set to be equal to or greater than the distance K between the intake port 270b and the inner peripheral surface 213a, and preferably the distance J is set to be longer than the distance K, so that the intermediate transfer belt 21 can be efficiently cooled.

[0092] The disclosure of this embodiment also includes the following configuration. (Configuration 1) a rotatable endless belt carrying a toner image on its outer circumferential surface; A plurality of tension members for tensioning the belt; A frame supporting the tension member; a fan supported by the frame and disposed inside the belt; The fan is disposed such that, with respect to the direction of the airflow generated by the fan, the distance between the inner circumferential surface of the belt facing the exhaust port of the fan and the exhaust port is equal to or greater than the distance between the inner circumferential surface of the belt facing the intake port of the fan and the intake port. 1. An image forming apparatus comprising: (Configuration 2) The fan is disposed such that, with respect to the direction of the airflow, a distance between the exhaust port and an inner circumferential surface of the belt facing the exhaust port is longer than a distance between the intake port and an inner circumferential surface of the belt facing the intake port. 2. The image forming apparatus according to claim 1, (Configuration 3) a rotatable image carrier carrying a toner image; a primary transfer member for primarily transferring a toner image from the image carrier to the belt in a primary transfer portion; a secondary transfer member for secondarily transferring the toner image from the belt to a recording material in a secondary transfer portion, The inner circumferential surface of the belt facing the intake port is in a range downstream of the secondary transfer unit and upstream of the primary transfer unit with respect to the rotation direction of the belt. 3. The image forming apparatus according to claim 1, wherein the first and second components are arranged in a same plane. (Configuration 4) The belt further includes a metal roller that contacts the inner peripheral surface of the belt in the range. 4. The image forming apparatus according to claim 3, (Configuration 5) The toner image is transferred to the recording material by the secondary transfer unit. The toner image is fixed to the recording material by the secondary transfer unit. 5. The image forming apparatus according to claim 3 or 4. (Configuration 6) a rotatable image carrier carrying a toner image; a primary transfer member for primarily transferring a toner image from the image carrier to the belt in a primary transfer portion; a secondary transfer member for secondarily transferring the toner image from the belt to a recording material in a secondary transfer portion, The inner circumferential surface of the belt facing the exhaust port is in a range downstream of the secondary transfer portion and upstream of the primary transfer portion with respect to the rotation direction of the belt. 3. The image forming apparatus according to claim 1, wherein the first and second components are arranged in a same plane. (Configuration 7) The toner image is transferred to the recording material by the secondary transfer unit. The toner image is fixed to the recording material by the secondary transfer unit. 7. The image forming apparatus according to configuration 6, (Configuration 8) The heater further includes a heating element supported by the frame and disposed between the intake port and an inner circumferential surface of the belt facing the intake port with respect to the direction of the air flow. 8. The image forming apparatus according to any one of configurations 1 to 7, (Configuration 9) The heater further includes a heating element supported by the frame and disposed between the exhaust port and an inner circumferential surface of the belt facing the exhaust port with respect to the direction of the air flow. 8. The image forming apparatus according to any one of configurations 1 to 7, (Configuration 10) The fan is an axial fan. 10. The image forming apparatus according to any one of configurations 1 to 9, (Configuration 11) The fan is a sirocco fan. 10. The image forming apparatus according to any one of configurations 1 to 9, [Explanation of symbols]

[0093] 5. Fixing device 11Y, 11M, 11C, 11K...Photosensitive drum (image carrier) 21... Intermediate transfer belt (belt) 22Y, 22M, 22C, 22K: Primary transfer roller (primary transfer member) 23 Secondary transfer roller (secondary transfer member, tension member) 27, 270... Cooling fan (fan) 28 Heating element 29 Cooling roller (metal roller) 100 Image forming apparatus 211a, 212a, 213a, 214a...inner surface 220Y, 220M, 220C, 220K...Primary transfer section 230 Secondary transfer unit 251... First roller (tension member) 252... Second roller (tension member) 253...Third roller (tension member)

Claims

1. A rotatable endless belt carrying a toner image on its outer circumferential surface; a plurality of tension members that tension the belt; a frame supporting the tension member; a transfer member to which a transfer voltage is applied, which transfers the toner image carried on the belt onto a recording material; a voltage application unit disposed inside the belt and configured to apply a voltage for generating the transfer voltage; a fan supported by the frame, disposed inside the belt, and configured to cool the voltage application unit; a distance between a region of the belt facing the fan on a downstream side of the fan in an exhaust direction of the fan and the fan is a first distance; a distance between a region of the belt facing the fan on the upstream side of the fan in the intake direction and the fan is a second distance; the first distance is greater than or equal to the second distance; An image forming apparatus characterized by:

2. The fan is an axial flow fan, the first distance is a distance from an intersection of a rotation axis of the fan and the belt to an exhaust port of the fan on the exhaust side of the fan, the second distance is a distance from an intersection of the rotation axis of the fan and the belt to an air intake port of the fan on the intake side of the fan; 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

3. The fan is a sirocco fan, the first distance is a distance from an intersection point of an imaginary line extending from an exhaust port of the fan along an exhaust direction of the fan and the belt to the exhaust port, the second distance is a distance from an intersection of the rotation axis of the fan and the belt to an air intake port of the fan on the intake side of the fan; 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

4. The voltage application unit is a high-voltage substrate.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

5. The voltage application unit includes a resistor electrically connected to a high-voltage substrate.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

6. A toner image is primarily transferred to the belt at a primary transfer section, and secondarily transferred from the belt to a recording material at a secondary transfer section, and the intake surface side of the fan faces the belt downstream of the secondary transfer section and upstream of the primary transfer section in the direction of rotation of the belt.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

7. A toner image is primarily transferred to the belt at a primary transfer section, and secondarily transferred from the belt to a recording material at a secondary transfer section, and the exhaust surface side of the fan faces the belt downstream of the primary transfer section and upstream of the secondary transfer section in the direction of rotation of the belt.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

8. The voltage application unit is provided on the intake side of the fan.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

9. The voltage application unit is provided on the exhaust side of the fan, and in the exhaust direction of the fan, the distance between the exhaust port of the fan and the voltage application unit is shorter than the distance between the voltage application unit and the belt.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

Images