JP6132956B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer having a function of forming an image on a recording material such as a sheet.

In the image forming apparatus, since an image forming operation is performed using a precise technique, there is an element that has an influence when the temperature in the apparatus is excessively increased due to the continuous operation. Among these, an image forming unit (image forming unit, process cartridge, toner cartridge, image forming unit) related to the formation of a toner image is particularly important.
The image forming unit includes elements that generate heat due to rubbing friction, such as a developing blade that regulates the amount of toner supplied to the developing roller and a cleaning blade that collects untransferred toner remaining on the photosensitive drum after the transfer process. . Since the toner melts when heated, if the temperature of these elements is not maintained below the specified temperature, the physical properties of the toner will change as the temperature rises, causing a lump of toner to fuse to the blade tip, drum surface, etc. There is. This phenomenon hinders the image forming process, and is surfaced in the form of image defects.
The same problem applies to all areas related to toner storage and supply in the image forming unit, and it prevents overheating, including the influence of heat from the surroundings, such as the drive unit, fixing unit, and electric board of the image forming apparatus. Without it, it is difficult to guarantee image quality throughout the life of these cartridges.

In the case of a monochrome product having only one image forming unit, since there are few spatial restrictions around the image forming unit, the degree of freedom in configuring the cooling air passage is high, and the above problem can be avoided relatively easily.
On the other hand, in the case of a color product in which a plurality of image forming units are arranged, if it is assumed that the image forming unit 70 is a rectangular parallelepiped as shown in FIG. That is, of the six surfaces surrounding the periphery of the image forming portion, two surfaces (71, 72) are adjacent by the image forming portion, one surface (73) is the intermediate transfer belt, and one surface (74) is the laser scanner. One surface (75) and a total of five surfaces are closed by the drive unit that drives the. For this reason, the restriction | limiting on an air path structure becomes very large.

With the recent miniaturization of image forming apparatuses, the spatial density of components and units constituting the apparatus has increased, and this restriction has become more severe. There are roughly two types of design philosophy for preventing overheating in the machine. One of them is a method of “providing sufficient in-flight cooling performance that does not exceed a safe temperature even when continuously operated under any condition in an operation guarantee environment”. The other one is a method of “detecting the in-machine temperature state by the in-machine temperature detection means and switching to a safe operation mode in which the temperature rise does not proceed further before exceeding the safe temperature”. The former design philosophy is adopted when the image forming apparatus has sufficient cooling capacity, and the latter design philosophy is adopted otherwise.
In recent color products, as mentioned above, restrictions on the air path configuration have increased, but the printing speed that affects the heat generation of the drive unit and the rubbing unit has gradually increased, and sufficient cooling capacity for the amount of heat generated It has become difficult to ensure. As a result, the latter method is often selected. Even when the latter design philosophy is selected, how to suppress the reduction in image formation throughput (productivity) when switching to a safe operation mode is very important as product performance. It is required to increase to the limit.

Under these limitations surrounding the problem of temperature rise in color products, conventionally, the image forming unit is cooled using two types of methods as described below. One of them is a method of forming a wind flow in one direction along the photosensitive drum 85 inside the image forming unit 80 as shown in FIG. In this method, a configuration in which cooling air is supplied by a fan from one end side in the longitudinal direction of the image forming unit and exhausted by another fan from the other end side (see Patent Document 1) is typical. There is a configuration in which the fan is arranged only on one side. The other one is a method of dissipating heat from both ends by providing heat dissipating means at both ends of the image forming section and applying cooling air to the heat dissipating means (see Patent Document 2).

JP 2008-268528 A JP 2005-173335 A

  However, these conventional technologies have a low cooling efficiency of the image forming unit, and it is difficult to satisfy the cooling performance required for the product. In order to compensate for the low cooling efficiency with the air volume, many fans There is a problem that is necessary. This will be specifically described below.

In the case of the former conventional configuration (one-way cooling along the drum), the following two points are the main causes of cooling efficiency reduction. (See Figure 8)
・ Air velocity / air volume reduction on the downstream side of the air passage ・ Temperature rise of cooling air on the downstream side of the air passage Inside the image forming section is a space for laser irradiation from the laser scanner 84 and a space for contacting and separating the developing device Many open parts exist, and a closed air passage cannot be formed. Therefore, the cooling air A supplied to one end of the image forming unit 80 is diffused from these open portions into the apparatus, and a clean flow cannot be formed throughout the photosensitive drum 85. In addition, when the drive unit 81 of the image forming unit is located on the downstream side of the air passage, it becomes difficult to secure an ideal exhaust route due to spatial restrictions, so the drive unit 81 promotes the diffusion of the cooling air. It becomes wind path resistance. Due to these influences, the wind speed and the air volume are reduced toward the downstream side of the air passage.
As a method for alleviating this problem, a method is known in which a fan is provided on the exhaust side in addition to the intake side to suppress wind diffusion, as in the embodiment of Patent Document 2. However, since the fan on the exhaust side also sucks heat in the area other than the image forming unit, it is not easy to obtain the expected cooling effect.

  Further, the temperature of the cooling air gradually increases in the process of taking the heat of the image forming unit. In the configuration in which cooling is performed with a unidirectional wind flow, the temperature of the cooling air becomes higher toward the downstream side, so that the cooling effect is reduced, and a large temperature distribution gradient is generated in the axial direction of the image forming unit. This maximum difference in temperature distribution corresponds to the temperature difference (front temperature difference) between the frames 82 and 83 constituting the image forming apparatus. In general, the image forming unit 80 is positioned on the frames 82 and 83 of the image forming apparatus at both axial ends of the drum. The difference between the front and back temperature of the frame leads to a difference in thermal expansion amount of the image forming unit positioning unit, and a front-rear difference occurs in the interval of the positioning unit between adjacent image forming units. This difference appears in the output image as a “color shift problem” in the color product. Here, in FIG. 8, 86 is an intermediate transfer belt unit, 87 is a primary transfer roller, and 88 is an intermediate transfer belt.

Even in the latter conventional configuration (heat radiation from both ends of the image forming unit), it is difficult to increase the cooling efficiency for the following two reasons.
・ Each element of the imaging unit is difficult to enhance the heat transfer effect due to its shape. ・ It is difficult to secure sufficient heat radiation at both ends of the imaging unit. In contrast, the cross-sectional area is an “elongate shape” that is very small. For this reason, the heat generated in the longitudinal center is not efficiently transmitted to both ends, and it is difficult to obtain a cooling effect due to heat radiation. The wider the media width of the image forming apparatus, the more pronounced this effect becomes, and the heat radiation from both ends becomes difficult.
In addition, although it is necessary to provide a heat dissipation member having a surface area that contributes to heat dissipation in the heat dissipation part, it is easy to provide a sufficiently large heat dissipation member in an image forming part where many elements are densely arranged. is not. In particular, on the interface side between the image forming unit and the drive unit, many drive couplings and electrical contacts are laid out, so the spatial restrictions are very large, and at the same time it is easy to supply cooling air there is not.
As described above, since there is a great limitation in increasing the cooling efficiency in the prior art, development of a cooling method that can solve this problem is required.
The present invention has been made in view of the above circumstances, and in an image forming apparatus in which a plurality of image forming units are arranged side by side along a belt, a temperature difference generated inside the apparatus is reduced, and cooling efficiency that is significantly higher than that of the related art. The purpose is to improve.

In order to achieve the above object, the present invention provides:
A plurality of image forming units each including a rotatable image carrier, and an image forming unit for forming a toner image on the image carrier;
A belt unit having a belt for transferring toner images formed on the plurality of image carriers onto a recording material;
Two frames facing each other with the belt unit in between,
Two guide rails are provided on the belt unit side of the two frames, and guide the belt unit in a detachable manner;
A blower means for generating a wind for cooling the image forming unit of multiple,
In an image forming apparatus for forming a toner image on a recording material,
Each of the two guide rails is provided with a plurality of openings along the arrangement direction of the plurality of image forming units at positions facing the spaces between the plurality of image forming units and the belt,
The wind generated by the blowing means is provided to each guide rail through a space between one of the frames and the one guide rail and a space between the other frame and the other guide rail. The plurality of openings are blown out from the openings, and flow from both ends of the image forming unit toward the center in the rotation axis direction of the image carrier.

  According to the present invention, in an image forming apparatus in which a plurality of image forming units are arranged side by side along a belt, it is possible to reduce a temperature difference generated inside the apparatus and to significantly improve cooling efficiency as compared with the prior art. It becomes.

Sectional drawing which shows schematic structure of the image forming apparatus which concerns on Example 1. FIG. Schematic diagram in section X when cut along the one-dot chain line in FIG. The figure which shows the way of the cooling air flow around the process cartridge of Example 1. Sectional drawing which shows schematic structure of the image forming apparatus which concerns on Example 2. FIG. Schematic diagram in section Y when cut along the one-dot chain line in FIG. The figure which shows how the cooling air flows around the process cartridge of Example 2. The figure explaining the spatial restrictions around the image forming unit in the prior art The figure which shows the cooling composition of the image formation section in the prior art Schematic diagram in section X when cut along the one-dot chain line in FIG. Perspective view showing how cooling air flows around the process cartridge

  DETAILED DESCRIPTION Exemplary embodiments for carrying out the present invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the scope to the following embodiments.

A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view illustrating a schematic configuration of the image forming apparatus according to the present embodiment.
On the upper part of the printer main body (image forming apparatus main body) 1, a yellow, magenta, cyan, and black (hereinafter abbreviated as Y, M, C, and K) primary image for forming a total of four colors is prepared. The image station is laid out.
Print data transmitted from an external device such as a PC is received by a controller that controls the printer body 1 and is output to the laser scanner 10 as write image data. The laser scanner 10 irradiates the photosensitive drum 12 with a laser and draws an optical image according to the written image data. The image forming apparatus according to the present embodiment employs a configuration in which laser irradiation is performed on each of the Y, M, C, and K photosensitive drums with one laser scanner 10.

  In the image forming station, a process cartridge 42 (42Y, 42M, 42C, 42D in the figure) as an image forming unit (image forming unit) for forming a primary image corresponding to each color Y, M, C, K is provided. 42K) is arranged. The plurality of process cartridges are arranged side by side along the moving direction of the intermediate transfer belt 34. In this embodiment, the intermediate transfer belt 34 is disposed above the plurality of process cartridges. Here, the configuration and operation of each process cartridge are substantially the same except that the color of the toner used is different. Therefore, in FIG. 1, only members constituting the process cartridge 42Y are denoted by reference numerals, and the configuration and operation of the process cartridge will be described below.

The process cartridge 42 includes a photosensitive drum 12 as a rotatable image carrier, a charger 13, a developing device 14, a cleaner (not shown), and the like. Here, the charger 13 is for uniformly charging the surface of the photosensitive drum 12. Further, the developing device 14 converts the electrostatic latent image created by the laser scanner 10 to draw an optical image on the surface of the photosensitive drum 12 charged by the charger 13 into a toner image to be transferred to the intermediate transfer belt 34. It is for developing. The cleaner is for removing the toner remaining on the photosensitive drum 12 after transferring the toner image. Here, the charger 13, the laser scanner 10, the developing device 14, and the cleaner constitute image forming means (process means acting on the photosensitive drum 12, image forming unit) for forming a toner image on the photosensitive drum 12. Is. As the process cartridge 42, at least one of the process means and the photosensitive drum 12 may be integrally formed into a cartridge and detachable from the printer main body 1.
A primary transfer roller 33 as a transfer member for transferring the toner image developed on the surface of the photosensitive drum 12 to the intermediate transfer belt 34 is disposed at a position facing the photosensitive drum 12.

  The toner image (primary image) transferred (primary transfer) to the intermediate transfer belt 34 is then retransferred (secondary transfer) onto a recording material such as a sheet in a secondary transfer portion. In other words, the toner image transferred onto the intermediate transfer belt is recorded at the secondary transfer portion composed of the secondary transfer roller 31 that also serves as a driving roller for the intermediate transfer belt 34 and the opposing secondary transfer outer roller 24. Re-transferred onto the material. The toner remaining on the intermediate transfer belt 34 without being transferred to the recording material in the secondary transfer portion is collected by the intermediate transfer belt cleaner 18.

  The feeding unit 20 is located in the uppermost stream of the recording material conveyance, and is provided in the lower part of the printer main body 1. When the recording material loaded and stored in the feeding tray 21 is fed by the feeding unit 20, the recording material passes through the conveyance path 22 and is conveyed downstream. A registration roller pair 23 is disposed in the conveyance path 22, where final skew correction of the recording material, and timing adjustment of image writing and recording material conveyance in the image forming unit are performed.

A fixing roller 25 for fixing the toner image on the recording material as a permanent image is provided on the downstream side of the image forming unit. Downstream thereof, a discharge conveyance path that continues to the discharge roller 26 for discharging the recording material from the printer main body 1 and a reversal path having a reversing roller 35 for reversing the conveyance direction of the recording material during double-sided printing are provided. Is provided. The path to which the recording material is guided can be selected by switching the reverse flapper 36.
For the second side of single-sided printing and double-sided printing, the recording material is guided to the discharge conveyance path and discharged outside the apparatus by the discharge roller 26. The discharged recording material is stacked on a discharge tray 27 provided on the upper portion of the printer main body 1.

  On the other hand, the recording material on the first side of double-sided printing is guided to the reversal path, and then the conveyance direction is reversed by the reversing roller 35 and conveyed to the double-sided conveyance path 28 for returning to the image forming unit. The double-sided conveyance path 28 is provided with a double-sided conveyance roller 29 for re-feeding the recording material reversely conveyed by the reverse roller 35 to the image forming unit.

The cooling configuration around the process cartridge in this embodiment will be described below. One fan 40 is provided on the left side surface of the printer main body 1 (the left side surface in FIG. 1), and outside air can be taken into the apparatus. The position of the fan 40 in the longitudinal direction of the process cartridge 42 is a position corresponding to the approximate center of the intermediate transfer belt 34 in the longitudinal direction. A duct 41 as a branch member is provided between the discharge tray 27 and the intermediate transfer belt 34 downstream of the fan 40. A rectifying plate (not shown) is provided inside the duct 41, and the cooling air is branched in two directions toward the front and back of the apparatus, and the air flow to the periphery of each process cartridge is regulated appropriately. doing. By disposing the fan 40 as described above and branching in two directions, the front and back of the device, the amount of cooling air flowing in front of the device and the amount of cooling air flowing in the back of the device after branching are made substantially the same. This prevents uneven cooling in the front of the device.
Here, “front” with respect to the printer main body 1 refers to the front side of the sheet of FIG. 1 (one side of the rotation axis direction of the photosensitive drum 12 (longitudinal direction of the photosensitive drum 12 and the process cartridge 42)). Further, “back (back)” refers to the back side of the paper surface of FIG. 1 (the other side in the longitudinal direction of the photosensitive drum 12). When the printer main body 1 is viewed from the right side in FIG. 1, the left side is “front” and the right side is “back”. The fan 40 and the duct 41 generate air (cooling air, wind) toward both ends in the longitudinal direction of the photosensitive drum 12 in spaces existing between the intermediate transfer belt 34 and the plurality of photosensitive drums 12. The fan 40 and the duct 41 constitute a blowing unit that generates wind for cooling the plurality of process cartridges 42.

FIG. 2 is a schematic diagram of a cross section X when cut along a one-dot chain line in FIG. The arrow shown in FIG. 2 represents the flow of cooling air.
The cooling air branched inside the duct 41 is guided to the following space (gap, air passage) from the duct opening 41a, and is centered in the longitudinal direction from both longitudinal ends (rotational axis both ends) of the process cartridge 42. Supplied toward the center (center of rotation axis). It is a gap (space, air passage) 37 that is configured by three members of the front side plate 44 and the rear side plate 45, the intermediate transfer belt unit 30, and the process cartridge 42. It is a space (including a gap 37 and a gap 38 described later) between two adjacent process cartridges 42. Here, the front side plate 44 and the rear side plate 45 are side plates arranged so as to sandwich the process cartridge 42 from both ends in the longitudinal direction among the side plates constituting the frame (frame body) of the printer main body 1. As shown in FIG. 1, the duct opening 41 a is provided to face each of the spaces between two adjacent process cartridges 42. As a result, the cooling air can be efficiently delivered to the gap 37. Further, the duct 41 is used as an air path through which cooling air is supplied to the gap 37 through the outside of both ends of the intermediate transfer belt unit 30 in the longitudinal direction of the process cartridge 42. With such an air path, since the cooling air does not directly hit the portion constituting the gap 37 of the intermediate transfer belt 34, the toner image on the intermediate transfer belt 34 is hardly disturbed.

When the cooling air passes through this space, it also cools the front side plate 44 and the rear side plate 45 to suppress the temperature difference between them. Thereby, the color shift of the color image resulting from the thermal expansion difference of the front and back side plates 44 and 45 can be suppressed.
Further, the front and rear side plates 44 and 45 are provided with positioning portions for positioning the process cartridge 42, and the cooling air blown by the fan 40 is supplied to the positioning portions. As a result, it is possible to suppress the occurrence of a difference in the amount of thermal expansion in the positioning portion, and thus it is possible to suppress the occurrence of a front-back difference in the interval between the positioning portions between adjacent process cartridges. Deviation can be suppressed.
The amount of cooling air to be supplied to which position for the process cartridge of each image forming station is optimized according to the heat distribution characteristics in the printer main body 1 and the like.

  Between the process cartridges adjacent to each other (adjacent), a stay member 43 for connecting the front side plate 44 and the rear side plate 45 is provided at a position facing the intermediate transfer belt 34. The stay member 43 is provided so as to form a gap with the process cartridge 42. The stay member 43 functions as a guide portion when the process cartridge 42 is attached to and detached from the apparatus main body. Further, an exhaust space 46 for exhausting the cooling air sent by the fan 40 from the gap 37 to the outside of the apparatus (outside the apparatus) is formed between the process cartridges 42 adjacent to each other.

Of the space between the two adjacent process cartridges 42, the gap 38 provided between the stay member 43 and the process cartridge 42 is directed from the intermediate transfer belt 34 side (gap 37 side) to the exhaust space 46 side. It is a wind path. By providing the stay member 43, air (cooling air) flows over the entire length in the longitudinal direction of the gap 37 and the gap 38, and the central portion in the longitudinal direction of the process cartridge 42 can be cooled by the cooling air.
In this manner, the stay member 43 regulates the amount of air flowing from the gap 37 through the gap 38 to the exhaust space 46 so as to be constant throughout the longitudinal direction of the exhaust space 46. Further, the stay member 43 regulates the flow rate of the wind generated by the fan 40 so that the wind generated by the fan 40 flows to the central portion in the longitudinal direction of the gap 37 and the gap 38. Here, the stay member 43 corresponds to a flow rate regulating member. Further, with respect to two adjacent image forming units provided with a stay member 43 therebetween, the stay member 43 includes a facing portion (facing surface) that faces each other with a gap between the facing portion and the image. The flow rate of the wind flowing between the forming unit is regulated.
With this stay member 43, the shape of the gap 37 and the gap 38 is such that the temperature distribution of each element (component) constituting the process cartridge 42 is as long as possible in the longitudinal direction (rotational axis direction of the photosensitive drum 12). It is designed to be equalized. In this embodiment, the entire area is made uniform with a sufficiently narrow dimension with respect to the supply air volume of the cooling air so that the cooling air flows evenly in the entire longitudinal direction of the gap 37 and the gap 38. As described above, the stay member 43 that is a flow rate regulating member regulates the flow rate of the cooling air that has flowed toward the lower cartridge on both sides of the belt unit 30 by regulating the flow rate of the wind. The direction has changed. In this way, by changing the direction in which the cooling air flows, the cooling air flows evenly in the entire longitudinal direction of the gap 37 and the gap 38. In other words, the stay member 43 also functions as a wind direction changing member that changes the direction in which the cooling air flows.
Further, as shown in FIGS. 9 and 10, it is possible to make the cooling air easily flow into the central portion in the longitudinal direction by widening the gap in the central portion in the longitudinal direction with respect to both ends in the longitudinal direction.
9 is a cross-sectional view taken along a cross-section X in FIG. As shown in this figure, an intermediate transfer belt facing portion (belt facing portion, facing surface) 43a facing the intermediate transfer belt of the stay member 43 is formed between the intermediate transfer belt 34 and the intermediate transfer belt 34 from both ends in the longitudinal direction toward the central portion. A tapered portion is provided to increase the distance. Thereby, the clearance gap 37 becomes a clearance gap which becomes wide as it goes to a longitudinal direction center part from the longitudinal direction both ends.
FIG. 10 is a perspective view showing how the cooling air flows around the process cartridge. As shown in this figure, the distance between the stay cartridge 43 and the process cartridge 42 increases from the cartridge facing portion (image forming unit facing portion, facing surface) 43b facing the cartridge toward the central portion from both longitudinal ends. A tapered portion is provided. Thereby, the clearance gap 38 becomes a clearance gap which becomes wide as it goes to a longitudinal direction center part from the longitudinal direction both ends.
Even in this case, air (cooling air) flows in the entire longitudinal direction of the gap 37 and the gap 38, and the central portion in the longitudinal direction of the process cartridge 42 can be cooled by this cooling air. The taper shape of the stay member 43 described above may be provided in the intermediate transfer belt facing portion 43a and the cartridge facing portion 43b. Further, a taper shape may be provided on the process cartridge 42 side so that the distance between the process cartridge 42 and the cartridge facing portion 43b is increased.

  The cooling air that has flowed out into the exhaust space 46 is exhausted outside the apparatus through gaps between units and parts inside the printer main body 1. The front side (front side, indicated by F in the figure) of the printer main body 1 is discharged through a cartridge replacement door and a gap in the exterior. Further, the back side of the printer body 1 (rear side, indicated by R in the figure) is an exhaust louver provided on the back cover with the exhaust heat of these heat sources passing through the device drive unit 47 and the electrical unit. Discharged from. Note that inflow of air from the exhaust space 46 to the peripheral space of the laser scanner 10 is restricted from the viewpoint of preventing scattered toner from adhering to the optical system of the laser scanner 10. For example, the air movement in this direction can be prevented by maintaining the air pressure in the laser scanner space high by another fan (not shown).

  FIG. 3 shows how the cooling air flows around the process cartridge 42 (cooling air path) in the image forming unit cooling configuration of the present embodiment. First, the cooling air flows to the vicinity of the center in the longitudinal direction of the process cartridge 42 along the periphery of the photosensitive drum 12 where the self-temperature rising elements are concentrated. At this time, the cooling air directly takes away the heat of the elements around the photosensitive drum 12, so that more efficient cooling is performed. In addition, the flow of cooling air suppresses the temperature difference in the front in the longitudinal direction, and the temperature distribution in the longitudinal direction is made uniform by the heat dissipation effect from the vicinity of both ends of the element.

  The air flow from the intermediate transfer belt 34 side toward the exhaust space 46 side through the gap between the process cartridge 42 and the stay member 43 flows so as to wrap the entire process cartridge 42. Further, the flow from the exhaust space 46 to the outside of the apparatus forms a longitudinal flow from the longitudinal center of the process cartridge 42 toward the front and back directions, that is, “a flow of air from the inside of the printer main body 1 to the outside”. The flow of these cooling airs produces the effect of cooling the entire process cartridge evenly, and at the same time, blocks the flow of heat toward the process cartridge 42 from adjacent external units such as a fixing device, an apparatus drive unit, and an electrical unit. .

As described above, for an image forming apparatus having a plurality of image forming units, by applying the present invention to the cooling configuration of the image forming unit, it is possible to achieve a significant improvement in cooling efficiency than before, The adverse effects of the conventional technology can also be eliminated.
Then, cooling air is supplied from both ends of the image forming unit to the space between the image forming unit and the transfer unit, and exhaust is performed while restricting the air volume with respect to the exhaust air path provided between the adjacent image forming units. As a result, a cooling air passage having the following characteristics can be formed.
・ Cooling air can be supplied to the vicinity of the central part in the longitudinal direction of the image forming unit, enabling balanced cooling (preventing heat stagnation in the central part)
-The elements around the photosensitive drum (developing blade, cleaning blade, etc.) that are the main heat generating part of the image forming unit can be cooled directly.
-The flow of air that wraps around the entire image forming unit makes it possible to cool the image forming unit evenly and eliminate heat stagnation between adjacent image forming units.
Regarding the exhaust route, a flow “inside to outside” from the center of the image forming unit toward the outside of the image forming apparatus is formed by a pressure difference between the inside and the outside of the image forming apparatus. Thereby, the entrance of heat from the external heat source to the image forming unit is blocked.

Due to these features of the cooling air passage according to the present invention, the following effects can be obtained.
-Greater cooling effect can be obtained even with a small air volume.
-The front difference in the longitudinal direction of the temperature around the image forming part on the side plate, which causes color misalignment, can be eliminated.
-Since one fan can be used, the number of fans can be reduced as compared with the conventional case where a plurality of fans are used, which contributes to miniaturization, power saving, and noise reduction.
While the image forming apparatus is strongly required to achieve both environmental performance such as downsizing, power saving, and noise reduction and operation performance, the effect of the present invention is great.

Hereinafter, Example 2 will be described with reference to FIGS. The configuration of the image forming apparatus according to the present embodiment is the same as that of the first embodiment except for the cooling configuration of the image forming unit. For this reason, explanation of these parts is omitted, and the same reference numerals are used for common elements.
FIG. 4 is a cross-sectional view illustrating a schematic configuration of the image forming apparatus according to the present embodiment. FIG. 5 shows a schematic view in a cross section Y when cut along a one-dot chain line in FIG. FIG. 6 is a diagram illustrating how the cooling air flows around the process cartridge 42 in the image forming unit cooling configuration of the present embodiment.

ITB guide rails 51 for attaching and detaching the intermediate transfer belt unit 30 are respectively provided on the front side plate 44 and the rear side plate 45 constituting the frame of the printer main body 1 (in this embodiment, the right direction in FIG. 4). Adopting a removable structure).
A duct 51 a is formed between the ITB guide rail 51 and each of the front side plate 44 and the rear side plate 45. The duct 51a is provided with a plurality of openings 51b toward the space (gap 37) between the intermediate transfer belt 34 and the process cartridge 42. One fan 40 is provided on the left side surface of the printer main body 1 so that outside air can be taken into the apparatus. The air blown by the fan 40 is branched and sent toward the duct 51a in the ITB guide rail 51 provided on the front and rear side plates 44 and 45, respectively.

The cooling air is guided to the plurality of openings 51b while the air volume is regulated, and is supplied to the space between the intermediate transfer belt 34 and the process cartridge 42 from the plurality of openings 51b. When the cooling air passes through the duct 51a, it cools the front side plate 44 and the rear side plate 45, and suppresses the temperature difference between them. Thereby, the color shift of the color image resulting from the thermal expansion difference of the front and back side plates 44 and 45 can be suppressed.
The ratio of the cooling air supplied to each process cartridge 42 at which ratio is optimized according to the heat distribution characteristics in the printer main body 1 and the like.

In this embodiment, in the process cartridges 42 adjacent to each other, restriction shapes (opposing portions) 53a and 53b are provided at positions facing the intermediate transfer belt 34 to restrict the gap 38 between them to a predetermined size. ing. Here, the regulation shapes 53 a and 53 b are opposed to each other with a gap 38 in the space between two adjacent process cartridges 42.
The gap 38 regulated (formed) by the regulation shapes 53a and 53b of the adjacent process cartridges 42 is an air path from the intermediate transfer belt 34 side to the exhaust space 46 side, and its flow rate is regulated. Yes. As in the first embodiment, the gap shape is such that the temperature distribution of each element of the process cartridge during the image forming operation is made as uniform as possible in the longitudinal direction.
The cooling air that has flowed into the exhaust space 46 is exhausted outside the apparatus through gaps between units and parts inside the printer body 1 as in the first embodiment.

The flow of cooling air around the process cartridge in the image forming unit cooling configuration of the present embodiment is basically the same as that of the first embodiment. Further, similarly to the first embodiment, the shape of the process cartridge 42 may be devised so that the gap 37 between the process cartridge 42 and the intermediate transfer belt 34 becomes wider from both longitudinal ends toward the longitudinal center. Good.
Further, the shape of the process cartridge 42 may be devised so that the gap 38 between two adjacent process cartridges 42 becomes wider from the both ends in the longitudinal direction toward the center in the longitudinal direction.
In the first exemplary embodiment, the flow of air that wraps the entire process cartridge from the intermediate transfer belt 34 toward the exhaust space 46 is generated through the gap defined by the stay member 43 and the process cartridge 42. On the other hand, in the configuration of the present embodiment, the above-described flow of the air that envelops the entire process cartridge is generated through the gap defined by the restriction shapes 53 a and 53 b provided in the process cartridge 42.
Also in this embodiment, the same effect as that described in the first embodiment can be obtained.

[Other Examples]
The configuration to which the present invention can be applied is not limited to the configurations of the above two embodiments.
In the above-described embodiment, the configuration in which the air from one fan is branched and supplied to both ends in the longitudinal direction of the process cartridge 42 is shown. However, the present invention is not limited to this. The structure which ventilates by may be sufficient. In the first embodiment, the configuration in which the air duct 41 is provided in the space between the discharge tray 27 and the intermediate transfer belt 34 is shown, but the configuration is limited to the configuration in which the cooling air is isolated from the intermediate transfer belt 34 and the air is blown. It is not something. For example, the surface of the intermediate transfer belt 34 may also serve as the air path wall of the duct 41. According to such a configuration, since the surface of the intermediate transfer belt 34 is exposed to the cooling air, the intermediate transfer belt 34 is cooled and the temperature rise of the process cartridge 42 during the printing operation is further suppressed. can do.

  In the above-described embodiment, the intermediate transfer type image forming apparatus has been described. However, the present invention is not limited to this. That is, the present invention can also be suitably applied to an image forming apparatus that transfers toner images respectively formed on a plurality of image carriers onto a recording material carried and conveyed by a recording material conveyance belt. .

  DESCRIPTION OF SYMBOLS 10 ... Laser scanner 12 ... Photosensitive drum 13 ... Charger 14 ... Developing device 37, 38 ... Gap 40 ... Fan 42 ... Process cartridge

Claims (3)

A plurality of image forming units each including a rotatable image carrier, and an image forming unit for forming a toner image on the image carrier;
A belt unit having a belt for transferring toner images formed on the plurality of image carriers onto a recording material;
Two frames facing each other with the belt unit in between,
Two guide rails are provided on the belt unit side of the two frames, and guide the belt unit in a detachable manner;
A blower means for generating a wind for cooling the image forming unit of multiple,
In an image forming apparatus for forming a toner image on a recording material,
Each of the two guide rails is provided with a plurality of openings along the arrangement direction of the plurality of image forming units at positions facing the spaces between the plurality of image forming units and the belt,
The wind generated by the blowing means is provided to each guide rail through a space between one of the frames and the one guide rail and a space between the other frame and the other guide rail. An image forming apparatus characterized in that it blows out from the plurality of openings and flows from both ends of the image forming unit toward the center in the rotation axis direction of the image carrier. The image forming apparatus according to claim 1, wherein a gap between the belt and the image forming unit becomes wider from both ends in the rotation axis direction toward the center. Gap between the image forming unit adjacent to an image forming apparatus according to claim 1, characterized in that is wider toward the center from both ends of the rotation axis direction.

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