Blower and image forming apparatus

Abstract

The present invention provides a blower and an image forming apparatus that can suppress condensation on the sheet contact member and suppress temperature rise at both ends of the fixing device in the sheet width direction. [Solution] The blower 60 comprises a duct 62 and a blower fan 61 that blows air into the duct 62. The duct 62 has a first discharge port 63 that discharges air to both ends in the width direction of the sheet of the fixing device 6, which heats and fixes the toner image formed on the sheet onto the sheet, and a second discharge port 64 that is located above the fixing device and discharges air to the paper discharge roller 26, which is a sheet contact member that contacts the sheet, and is equipped with a switching means to switch the destination of the air discharged from the duct.

Description

Technical Field

[0005]

[0001] The present invention relates to a blower device and an image forming apparatus.

Background Art

[0002] Conventionally, a blower device including a duct and a blower fan that blows air into the duct has been known.

[0003] In Patent Document 1, as the above-described blower device, for the purpose of changing the glossiness of a toner image fixed on a sheet, the air in the duct is discharged to a pair of conveying rollers disposed downstream in the sheet conveying direction with respect to a fixing device, or the air in the duct is discharged between the fixing device and the pair of conveying rollers. A device that switches between discharging and discharging is described.

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the sheet is heated by the fixing device, moisture contained in the sheet evaporates to generate water vapor, and the water vapor rises, and there is a risk of condensation on a guide member that guides the sheet disposed above the fixing device or a sheet contact member such as a discharge roller that discharges the sheet to a discharge tray. In addition, when small-sized sheets are continuously passed, there is also a risk that the temperatures at both ends in the width direction of the sheet of the fixing device will locally increase.

Means for Solving the Problems

[0005] In order to solve the above-described problems, the present invention provides a blower device including a duct and a blower fan that blows air into the duct, wherein the duct has at least a first discharge port that discharges the air to both ends in the width direction of the sheet of a fixing device that heats a toner image formed on the sheet and fixes it on the sheet, and a second discharge port that discharges the air to a sheet contact member that is disposed above the fixing device and contacts the sheet, and is characterized by including switching means for switching the discharge destination of the air in the duct.

Effects of the Invention

[0006] According to the present invention, condensation on the sheet contact member can be suppressed, and the temperature rise at both ends of the fixing device in the sheet width direction can be suppressed. [Brief explanation of the drawing]

[0007] [Figure 1] A schematic diagram of the image forming apparatus according to the present invention, viewed from the front. [Figure 2] A schematic diagram of an image forming apparatus with an image reading device mounted on top. [Figure 3] External perspective view of an image forming apparatus with an image reading device mounted on top. [Figure 4] A schematic diagram showing the smallest size of paper that can be transported by this image forming apparatus, as ejected from the output tray, and the fixing device. [Figure 5] A schematic diagram showing the vertical transport path and the blower. [Figure 6] Enlarged view of the area around the blower. [Figure 7] A schematic perspective view of the duct. [Figure 8] This diagram shows the fixing device being air-cooled on both axial sides. [Figure 9] This diagram shows how air is being sent near the paper output roller. [Figure 10] A diagram showing the exhaust of air from inside the aircraft. [Figure 11] Functional block diagram of the blower. [Figure 12] A control flow diagram for switching the destination of air discharged from a duct. [Modes for carrying out the invention]

[0008] The best mode for carrying out the present invention will be described below with reference to the drawings. It should be noted that a person skilled in the art will readily be able to modify or alter the present invention within the scope of the claims to create other embodiments, and such modifications and alterations are included within the scope of these claims. The following description is an example of the best mode in this invention and does not limit the scope of these claims.

[0009] An example of a color image forming apparatus to which the present invention is applied will be described with reference to Figure 1. Figure 1 is a schematic diagram of the image forming apparatus according to the present invention, viewed from the front. As shown in Figure 1, the image forming apparatus 1 of this embodiment is a full-color image forming apparatus that arranges in tandem multiple, four drum-shaped photoreceptors 10Y, 10C, 10M, and 10K as latent image carriers. These photoreceptors are configured as part of the respective image forming units 7Y, 7C, 7M, and 7K, which are the image forming means. These image forming units 7Y, 7C, 7M, and 7K correspond to the colors yellow, cyan, magenta, and black, respectively, and create images of these colors.

[0010] In the image forming apparatus shown in Figure 1, there is an intermediate transfer belt 14 as a surface moving member that rotates supported by five support rollers 15a, 15b, 15c, 15d, and 15e. Along the tension line on the lower side of this intermediate transfer belt 14, the image forming units 7Y, 7C, 7M, and 7K are arranged at intervals from the upstream side in the order of the movement direction of the intermediate transfer belt 14, as indicated by the arrows.

[0011] In forming a full-color image, toner images of each color are formed on the photoreceptors 10Y, 10C, 10M, and 10K provided in the image-forming units 7Y, 7C, 7M, and 7K, as described later. Next, these toner images of different colors are sequentially transferred onto the intermediate transfer belt 14 as the intermediate transfer belt 14 moves, by the function of the primary transfer rollers 16, which are positioned opposite each photoreceptor with the intermediate transfer belt 14 in between. Specifically, the points on the intermediate transfer belt 14 where the primary transfer rollers 16 are in contact are called transfer positions, and transfer takes place at these transfer positions.

[0012] The four overlapping toner images are transferred simultaneously to the sheet of paper P at the secondary transfer nip section between the support roller 15a and the secondary transfer roller 9. The paper P, on which the toner images have been transferred at the secondary transfer nip section, is passed between the fuser rollers 6a and 6b of the fuser unit 6, and then discharged onto the discharge tray 19 from the discharge roller 26. In this way, a full-color image is obtained on the paper.

[0013] Furthermore, in order to adapt to the single-color black image formation mode, the intermediate transfer belt 14 is configured to be in constant contact with the photoreceptor 10K by the primary transfer roller 16, while the intermediate transfer belt 14 is configured to move toward and away from the other photoreceptors by the function of a movable tension roller.

[0014] The lower part of the image forming apparatus is provided with a paper feed cassette 5 for storing multiple sheets of paper P on which the output image is recorded, and a paper feed unit 40 for feeding the paper P from the paper feed cassette 5. The paper feed unit 40 includes a pickup roller 41 that is supported so as to be able to move toward and away from the paper loaded in the paper feed cassette 5, and a pair of separation rollers 42 that separates the multiple sheets of paper fed by the pickup roller 41 and feeds only the top sheet of paper. The pair of separation rollers 42 consists of a feed roller 42a and a reverse roller 42b. The feed roller 42a is driven by the driving force of a drive motor and rotates at the separation nip of the pair of separation rollers 42 to move the paper in the paper feeding direction. On the other hand, the reverse roller 42b is driven by the driving force of a drive motor via a torque limiter and rotates at the separation nip to move the paper in the direction of returning the paper to the paper feed cassette (in the opposite direction to the paper feeding direction).

[0015] When a sheet of paper is held in the separation nip, or when no paper is held in it, the rotational load on the reverse roller 42b is relatively large. Therefore, in this case, the torque applied to the reverse roller 42b exceeds the specified value, and the torque limiter cuts off the driving force from the motor. As a result, the reverse roller 42b rotates freely relative to the torque limiter and is carried along by the feed roller 42a.

[0016] On the other hand, when a plurality of sheets of paper are sandwiched between the separation nip, the rotational load applied to the reverse roller 42b due to the slippage between the sheets of paper is relatively small. Therefore, at this time, the torque applied to the reverse roller 42b becomes less than the specified value, and the torque limiter transmits the driving force from the motor to the reverse roller 42b. As a result, the reverse roller 42b moves in the direction of returning the paper to the paper feed cassette at the separation nip by the driving force from the motor, and among the plurality of sheets of paper sandwiched between the separation nip, the lower sheets except the top sheet are returned to the paper feed cassette 5.

[0017] The paper that has passed through the separation nip is conveyed by the relay conveyance roller 24 disposed in the paper feed path 43 toward the registration roller 25.

[0018] In addition, a manual feed tray 21 for manually feeding paper is provided on the left side surface (corresponding to the front of the image forming apparatus) in the drawing of the image forming main body. Further, between the writing device 4 which is a latent image writing means and a detachable component and the paper feed cassette 5, there is provided a manual relay conveyance path 23 which is a manual conveyance path for conveying the paper P fed from the manual feed tray 21 by the manual feed roller 22 to the confluence portion with the paper feed path 43. Three manual relay conveyance rollers 23a, 23b, 23c are disposed in the manual relay conveyance path 23. The manual relay conveyance path 23 merges into the paper feed path 43 in front of the relay conveyance roller 24.

[0019] In addition, on the right side in the drawing from the fixing device 6 of the image forming apparatus main body, there is provided a reverse conveyance path 30 for conveying the paper P to the secondary transfer nip portion again during double-sided printing. A reverse conveyance roller 31 is disposed in the reverse conveyance path 30.

[0020] In FIG. 1, each image forming unit 7Y, 7C, 7M, 7K only has a different toner color, and the mechanical configuration and image forming process are common. Therefore, the same reference numerals are given to each component member other than the photoreceptor, and the configuration and image forming process are described for any one of the image forming units, for example, the image forming unit 7Y.

[0021] Around the photoreceptor 10Y of the image-forming unit 7Y, in the diagram, in the order of clockwise rotation, are the charging roller 11 as a means of charging the photoreceptor 10Y, the irradiation position of the light beam L, the developing device 12 as a means of developing, the primary transfer roller 16, the cleaning device 13, and so on.

[0022] The light beam L is emitted from the writing device 4, which is equipped with a semiconductor laser as a light source, a coupling lens, an fθ lens, a toroidal lens, a mirror, a rotating polyface mirror, and other components. The writing device 4 emits a light beam L for each color toward each photoreceptor, and irradiates the writing position on the photoreceptor 10Y with the light beam L to form an electrostatic latent image.

[0023] For example, the developing device 12 of the imaging unit 7Y contains a yellow developer, and the latent image is made visible as a yellow image. Other imaging units also contain developers of their respective colors, and the latent image is made visible using the color of the developer stored in them.

[0024] During image formation, the photoreceptor 10Y rotates and is uniformly charged by the charging roller 11. At the writing position, it is irradiated with a light beam L containing information for the yellow image, forming an electrostatic latent image. This latent image is then revealed by the yellow toner as it passes through the developing device. The yellow toner image on the photoreceptor 10Y is transferred to the intermediate transfer belt 14 by the primary transfer roller 16. This yellow toner image on the intermediate transfer belt 14 is then sequentially transferred over with a cyan toner image by the imaging unit 7C, a magenta toner image by the imaging unit 7M, and a black toner image by the imaging unit 7K. This forms a full-color toner image. After the transfer, the photoreceptor is cleaned by the cleaning device 13 to remove residual toner, and then discharged by the static elimination lamp to prepare it for the next image formation.

[0025] The paper P is transported from either the paper feed cassette 5 or the manual feed tray 21 and stops once it reaches the registration roller 25. Then, at a predetermined timing, the registration roller 25 rotates to feed the paper P toward the nip between the support roller 15a and the secondary transfer roller 9.

[0026] The full-color toner image superimposed on the intermediate transfer belt 14 is secondarily transferred to the paper P at the secondary transfer nip between the support roller 15a and the secondary transfer roller 9. This forms a toner image on the paper P. The paper P on which the full-color toner image has been secondarily transferred is transported toward the fuser unit 6 and clamped in the fuser nip. The toner image on the paper P is heated and fixed by the heat from the fuser roller 6a in the fuser nip. In the case of single-sided printing, the paper P on which the toner image has been fixed is discharged from the machine by the paper discharge roller 26. On the other hand, in the case of double-sided printing, after the image has been formed on the paper P as described above, it is switched back by the paper discharge roller 26 and transported to the inversion transport path 30. Then, with the front and back sides reversed, it is transported to the paper feed path 43, and after the image has been formed on the back side opposite to the front side on which the image was previously formed, it is discharged from the machine.

[0027] Furthermore, the image forming apparatus 1 may also be equipped with an image reading device 2 at the top, which includes a scanner unit 2b and an automatic document feeder (ADF) 2a, as shown in Figures 2 and 3. As shown in Figure 3, the image forming apparatus 1 is equipped with an operation panel 50, which is an operation input unit consisting of a touch panel or the like that receives input from the operator. In addition, an air intake port 1b for taking in outside air is provided on the side of the image forming body.

[0028] The image forming apparatus of this embodiment had the following two problems. First, let me explain the first problem. Because paper P is hygroscopic, water vapor is generated from the paper when it is heated by the fuser unit 6. The water vapor generated from the paper by the fuser unit 6 rises, increasing the humidity around the paper discharge roller 26, which is a sheet contact member located above the fuser unit 6. At this time, if the internal temperature of the machine is low and the temperature of the paper discharge roller 26 located above the fuser unit 6 is low, condensation may form on the paper discharge roller 26, and water droplets from the paper discharge roller 26 may adhere to the toner image on the paper, potentially causing image defects such as blurring. In addition, water droplets from the paper discharge roller 26 may adhere to the paper, causing it to become wet and wrinkle, or the wet paper may stick to the paper discharge roller 26, potentially causing paper discharge problems. This is the first problem.

[0029] Next, I will explain the second task. Figure 4 is a schematic diagram showing the smallest size of paper that can be transported by this image forming apparatus, which is ejected into the output tray 19, and the fuser unit 6. In this embodiment, the image forming apparatus transports paper using a central reference, and when continuously printing the smallest size paper Ps shown in Figure 4, the temperature of the non-paper-passing area on the surface of the fuser roller 6a tends to rise. When such a temperature rise occurs in the non-paper-passing area, the heat can cause the axial sides of the fuser unit 6, enclosed by the dashed lines in Figure 4, to heat up, potentially damaging the components of the fuser unit 6. This is the second problem.

[0030] The first problem mentioned above can be solved by using a blower fan to circulate air around the paper discharge roller 26 and remove moisture. The second problem mentioned above can be solved by using a blower fan to circulate air to the area enclosed by the dashed line in Figure 4 and air-cooling that area.

[0031] If a fan is provided to circulate air near the paper discharge roller 26 and another fan is provided to air-cool the fixing unit 6, the cost will increase due to the increased number of parts, the image forming apparatus will become larger, and the noise will increase due to the wind noise from multiple fans.

[0032] Therefore, in this embodiment, a single blower fan is used to supply air to both the condensation site and the end of the fuser. The features of this embodiment will be described below with reference to the drawings.

[0033] Figure 5 is a schematic diagram showing the vertical transport path and the blower 60. As shown in Figure 5, the image forming apparatus of this embodiment is equipped with a blower 60 that blows air on both sides in the axial direction of the fixing unit 6 and near the paper discharge roller 26. The blower 60 comprises a blower fan 61 and a duct 62. The image forming apparatus also includes an internal temperature sensor 71 for measuring the internal temperature and an external temperature sensor 72 for measuring the external temperature. The internal temperature sensor 71 is located near the center of the image forming apparatus body, and the external temperature sensor 72 is located on the outer circumferential surface of the image forming apparatus body, below the apparatus body. Note that the arrangement of the internal temperature sensor 71 and the external temperature sensor 72 is just an example. It is preferable to place the internal temperature sensor 71 in a location where the average temperature inside the machine can be measured, excluding areas that are hotter than other areas due to the influence of heat-generating components inside the image forming apparatus or areas where the temperature differs significantly from other areas due to the influence of the external temperature. It is preferable to place the external temperature sensor 72 in a location where the ambient temperature can be measured well.

[0034] Figure 6 is an enlarged view of the area around the blower 60, and Figure 7 is a schematic perspective view of the duct 62. Figure 8 shows the air cooling of both axial sides of the fixing device 6, Figure 9 shows the air being sent to the vicinity of the paper discharge roller 26, and Figure 10 shows the exhaust of air from inside the machine.

[0035] As shown in Figures 8 to 10, the duct 62 has its central axial portion (X direction, left-right direction of the device, width direction of the paper) located further from the fuser 6 than the ends in the axial direction (+Y direction, front side of the device). Third outlets 65 for exhausting air from inside the machine to the outside are provided at both ends in the axial direction of the duct, and these outlets are opposite the outlets 1a provided on each side perpendicular to the axial direction (X direction, left-right direction of the device) of the image forming apparatus body. First outlets 63 are also provided at the locations on both sides of the duct 62 that are opposite the axial ends of the fuser 6. The central axial portion of the duct 62 extends upward, and a second outlet 64 is provided on an inclined surface of this upwardly extending portion that is inclined to face the paper discharge roller 26. An air intake port 69 for taking in air from a blower fan 61 is also provided in the central axial portion of the duct 62, and the blower fan 61 is positioned opposite this air intake port 69.

[0036] As shown in Figures 8 to 10, the duct 62 is provided with a first shutter 66, which is a first opening / closing member; a second shutter 67, which is a second opening / closing member; and a third shutter 68, which is a third opening / closing member. The first shutter 66 and the third shutter 68 are installed inside the duct so as to be able to take on a first closed position that blocks the third outlet 65 shown in Figure 8; a second closed position that blocks the first outlet 63 shown in Figure 10; and a blocked position shown in Figure 9 that is closer to the center than the first outlet 63 and blocks the airflow from the center to the end of the duct 62. The second shutter 67 is installed inside the duct so as to be able to take on a closed position that blocks the second outlet 64 shown in Figures 8 and 10; and an open position that opens the second outlet 64 as shown in Figure 9.

[0037] As shown in Figure 8, when air-cooling both sides of the fixing device 6 in the axial direction, the first shutter 66 and the third shutter 68 are positioned in the first closed position, blocking the third outlet 65, and the second shutter 67 is positioned in the closed position, blocking the second outlet 64. As a result, the air taken in from the intake port 69 is discharged from the first outlet 63, air-cooling both sides of the fixing device 6 in the axial direction. This prevents the temperature on both sides of the fixing device 6 in the axial direction from becoming too high.

[0038] When removing moisture near the paper discharge roller 26, as shown in Figure 9, the first shutter 66 and the third shutter are positioned in a blocking position that blocks the flow path of the duct 62, and the second shutter 67 is positioned in an open position that opens the second outlet 64. As a result, the air taken in from the intake port 69 is blown from the second outlet 64 towards the vicinity of the paper discharge roller 26. The air flowing towards the vicinity of the paper discharge roller 26 diffuses the moisture near the paper discharge roller 26 into the image forming apparatus, suppressing condensation on the paper discharge roller 26.

[0039] When exhausting air from inside the image forming apparatus, as shown in Figure 10, the first shutter 66 and the third shutter 68 are positioned in the second closed position, blocking the first exhaust port 63, and the second shutter 67 is positioned in the closed position, blocking the second exhaust port 64. As a result, the air inside the machine is discharged outside through the third exhaust port 65 and the exhaust port 1a of the image forming apparatus, and outside air is drawn into the machine through the intake port 1b shown in Figure 3, thereby suppressing the temperature rise inside the image forming apparatus.

[0040] Furthermore, if the second shutter 67 is positioned in an open position that opens the second outlet 64, such as by providing the second outlet 64 on a vertical surface in the vertical direction of the duct, the flow path can be blocked, then the second shutter 67 and the first shutter 66, or the second shutter 67 and the third shutter 68, may be positioned in a blocking position.

[0041] Figure 11 is a functional block diagram of the blower 60. The image forming apparatus 1 includes a control unit 70 that controls a blower 60, which is composed of a computer device such as a microcomputer. The control unit 70 includes a CPU (Central Processing Unit) 70a. It also includes a ROM (Read Only Memory) 70c and a RAM (Random Access Memory) 70b as storage means connected to the CPU 70a via a bus line. The CPU 70a controls the blower 60 by executing a control program, which is a pre-installed computer program. The ROM 70c stores fixed data such as computer programs and control data in advance. The RAM 70b functions as a work area, etc., that stores various data in a rewritable manner.

[0042] The user inputs information about the paper size and the number of sheets to be printed into the operation panel 50. The control unit 70 obtains the paper size and number of sheets to be printed from the operation panel 50 and determines whether air cooling is necessary at both ends of the fuser unit 6 in the axial direction based on the obtained paper size and number of sheets (number of continuous prints). The control unit 70 also determines whether it is necessary to send air near the paper discharge roller based on the ambient temperature detected by the ambient temperature sensor 72 and the internal temperature detected by the internal temperature sensor 71. Based on these determinations, the control unit 70 controls the shutter drive unit 73 that drives the first to third shutters 66 to 68 and switches the destination of the air discharged in the duct. In other words, in this embodiment, the first to third shutters 66 to 68, the shutter drive unit 73, and the control unit 70 function as switching means.

[0043] Figure 12 is a control flow diagram showing the control of switching the destination of the air discharged from the duct. The control unit 70 determines that if the difference between the internal temperature Ti detected by the internal temperature sensor 71 and the outside temperature To detected by the outside temperature sensor 72 (Ti-To) is less than a specified value δ, and the internal temperature Ti is less than the condensation threshold temperature T1 (Y in S1), then the temperature of the paper discharge roller 26 is low, and there is a risk that water vapor from the paper evaporated by heating in the fuser unit 6 may condense on the paper discharge roller 26. Therefore, if (Ti-To) is less than a specified value δ, or if the internal temperature Ti is less than the condensation threshold temperature T1 (Y in S1), the control unit 70 sets the control unit to "condensation prevention mode" (S2).

[0044] When set to "condensation prevention mode," the control unit 70 positions the first shutter 66 and the third shutter in the third position, which closes the inside of the duct, as shown in Figure 9, and positions the second shutter 67 in the open position, which opens the second outlet 64. As a result, the destination of the air in the duct is switched to the second outlet 64, and the air in the duct is discharged through the second outlet 64 to the vicinity of the paper discharge roller 26, which removes moisture near the paper discharge roller 26 and prevents condensation on the paper discharge roller 26.

[0045] If the above (Ti-To) is greater than or equal to the specified value δ, or if the internal temperature Ti is greater than or equal to the dew threshold temperature T1 (No. in S1), and the number of continuous prints N of small-sized paper exceeds the edge temperature rise threshold number N1 (Y in S3, Y in S4), then the axial ends of the fuser unit 6 may become hot. Therefore, in this case, the control unit is set to the "edge temperature rise suppression mode" which air-cools both axial sides of the fuser unit 6 (S5).

[0046] When set to "end temperature rise suppression mode," the control unit 70 positions the first shutter 66 and the third shutter 68 in a first position that blocks the third outlet 65, as shown in Figure 8, and positions the second shutter 67 in a position that blocks the second outlet 64. As a result, the destination of the air in the duct is switched to the first outlet 63, and the air in the duct is discharged to both sides in the axial direction of the fixing device 6 via the first outlet 63, thereby air-cooling both sides in the axial direction of the fixing device 6. This prevents both ends in the axial direction of the fixing device 6 from becoming hot and suppresses damage to the components of the fixing device 6 due to heat.

[0047] On the other hand, if the paper being printed is not small-sized paper and the temperature does not rise on both sides of the fuser unit 6 in the axial direction (N in S3), or if the number of sheets of small-sized paper printed continuously is less than or equal to the edge temperature rise threshold number N1, and the temperature at both ends of the fuser unit 6 in the axial direction is low, then the system is set to "heat dissipation mode" (S6).

[0048] When set to "heat dissipation mode," the control unit 70 positions the first shutter 66 and the third shutter 68 in a second position that blocks the first exhaust port 63, as shown in Figure 10, and positions the second shutter 67 in a position that blocks the second exhaust port 64. As a result, the heated air inside the machine is discharged outside the machine through the third exhaust port 65 and the exhaust port 1a of the image forming apparatus, and outside air cooler than the temperature inside the machine is taken in through the intake port 1b shown in Figure 3. This suppresses the temperature rise inside the image forming apparatus.

[0049] Thus, in this embodiment, the destination of the airflow generated by a single blower fan 61 can be switched to the vicinity of the paper discharge roller, both sides in the axial direction of the fixing device, and outside the machine. This reduces the number of fans compared to a system that has separate fans for blowing air near the paper discharge roller, for blowing air to both sides in the axial direction of the fixing device, and for discharging internal air to the outside of the machine. This reduces the number of parts and lowers the cost of the device. In addition, since only one fan is needed, noise caused by fan noise can be suppressed. Furthermore, the power consumption of the image forming apparatus can be reduced.

[0050] In the above, the device environment is determined based on the internal temperature and the outside temperature to determine whether condensation is likely to occur on the paper discharge roller 26. However, a humidity sensor is also provided around the paper discharge roller to detect humidity, and the device environment is determined based on the humidity around the paper discharge roller and the internal temperature to determine whether condensation is likely to occur on the paper discharge roller 26.

[0051] In this embodiment, air is blown onto the paper discharge roller 26, but air may also be blown onto a component that is positioned above the fuser device and comes into contact with the paper, such as a paper transport guide. Alternatively, air may be blown onto the paper discharge roller 26 and a component that comes into contact with the paper, such as a paper transport guide, positioned between the fuser device 6 and the paper discharge roller 26.

[0052] Although preferred embodiments of the present invention have been described above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the spirit of the present invention as described in the claims, unless otherwise specifically limited in the above description.

[0053] The above is just one example; each of the following embodiments produces its own unique effects. (Aspect 1) In a blower 60 comprising a duct 62 and a blower fan 61 for blowing air into the duct 62, the duct 62 has at least a first discharge port 63 that discharges air to both ends in the sheet width direction of a fixing device 6 that heats and fixes a toner image formed on a sheet such as paper onto the sheet, and a second discharge port 64 that is positioned above the fixing device 6 and discharges air to sheet contact members such as a paper discharge roller 26 that contact the sheet, and is equipped with a switching means (composed of first to third shutters 66 to 68, a shutter drive unit 73 and a control unit 70) for switching the destination of the air discharged from the duct. According to this, as described in the embodiment, when there is a risk of condensation of moisture evaporated from the sheet in the fuser unit 6 onto a sheet contact member such as the paper discharge roller 26 that contacts the sheet such as paper P located above the fuser unit 6, the moisture around the sheet contact member can be removed by discharging air from the duct 62 through the second discharge port 64. This suppresses condensation of water vapor evaporated from the sheet in the fuser unit 6 onto the sheet contact member, and prevents image defects such as blurring of the image caused by water droplets condensed on the sheet contact member adhering to the toner image on the sheet. On the other hand, when small-sized sheets are fed continuously and there is a risk of the temperature of the ends of the fuser unit 6 rising locally, the ends of the fuser unit 6 in the width direction can be air-cooled by discharging air from the duct 62 through the first discharge port 63, thereby suppressing the temperature rise at both ends of the fuser unit 6 in the width direction and preventing heat damage. Furthermore, compared to a case where a blower fan is provided to blow air onto the sheet contact member and blower fans are provided to blow air onto both ends in the width direction of the fixing device, the number of parts can be reduced, and the enlargement of the image forming apparatus and the increase in the cost of the image forming apparatus can be suppressed.

[0054] (Aspect 2) In embodiment 1, the sheet contact member is an output roller such as an output roller 26 that outputs a sheet of paper P to an output tray such as an output tray 19. According to this, as described in the embodiment, it is possible to suppress condensation on the paper discharge roller 26 due to water vapor generated from the sheet in the fixing device 6, and to suppress image defects such as blurring of the image caused by water droplets on the paper discharge roller 26 adhering to the image on the sheet. In addition, it is possible to suppress the sheet from sticking to the paper discharge roller 26 and causing ejection problems, and to suppress the occurrence of wrinkles on the sheet due to water droplets on the paper discharge roller 26 adhering to the sheet.

[0055] (Aspect 3) In embodiment 1 or 2, the switching means includes an opening / closing member (in this embodiment, first and third shutters 66 and 68) that opens and closes the first discharge port 63, and an opening / closing member such as a second shutter 67 that opens and closes the second discharge port 64, and the destination of the air discharge is switched by controlling the opening and closing of the opening / closing members. According to this, as described in the embodiment, by opening the first discharge port 63 with an opening / closing member that opens and closes the first discharge port 63 and closing the second discharge port 64 with an opening / closing member that opens and closes the second discharge port 64, the destination of the air can be made to the first discharge port 63, and both sides in the width direction of the fixing device can be air-cooled. On the other hand, by closing the first discharge port 63 with an opening / closing member that opens and closes the first discharge port 63 and opening the second discharge port 64 with an opening / closing member that opens and closes the second discharge port 64, the destination of the air can be made to the second discharge port 64, which can blow away moisture around sheet contact members such as the paper discharge roller 26, and condensation on the sheet contact members can be suppressed.

[0056] (Aspect 4) In embodiment 1 or 2, the blower fan 61 blows air from inside the image forming apparatus on which the blower device 60 is mounted into the duct 62, the duct 62 has a third outlet 65 for discharging air outside the image forming apparatus, and the switching means (composed of first to third shutters 66 to 68, shutter drive unit 73 and control unit 70) selectively switches the destination of the air discharge between the first outlet 63, the second outlet 64 and the third outlet 65. According to this, as described in the embodiment, the heated air inside the image forming apparatus can be discharged from the third outlet 65, and the temperature rise of the image forming apparatus can also be suppressed.

[0057] (Aspect 5) In embodiment 4, the third outlet 65 is provided at both ends of the duct 62 in the width direction, the first outlet 63 is provided on both sides of the duct in the width direction, and an intake port 69 for taking in air from a blower fan 61 is provided in the center of the duct 62 in the width direction. The switching means includes a first opening / closing member such as a first shutter 66 that opens and closes the first outlet 63 on one side in the width direction and the third outlet 65 on the other side in the width direction, a second opening / closing member such as a second shutter 67 that opens and closes the second outlet 64, and a third opening / closing member such as a third shutter 68 that opens and closes the first outlet 63 on the other side in the width direction and the third outlet 65 on the other side in the width direction. Two of the first opening / closing member, the second opening / closing member and the third opening / closing member are configured to be in a blocking position that blocks the flow of air flowing toward the end in the width direction, located closer to the center in the width direction than the first outlet 63. According to this, as described in the embodiment, when discharging air from the second outlet 64, by positioning two of the first opening / closing member, the second opening / closing member, and the third opening / closing member in the blocking position, it is possible to prevent air from being discharged from the first outlet and the third outlet even when they are open. As a result, the opening / closing member can be used for both the third outlet and the first outlet, and the number of parts can be reduced compared to a system that has separate opening / closing members for the third outlet and the first outlet.

[0058] (Aspect 6) In any of embodiments 1 to 5, the switching means switches the destination of the air discharge based on the internal environment of the image forming apparatus on which the blower is installed and the sheet transport conditions. According to this, when the internal environment of the image forming apparatus is such that condensation may occur on sheet contact members such as the paper discharge roller 26, the air can be automatically switched to the second outlet 64, and when the sheet transport conditions are such that both sides in the width direction of the fixing device 6 may become hot, the air can be automatically switched to the first outlet 63.

[0059] (Aspect 7) In embodiment 6, the image forming apparatus has an internal temperature sensor 71 for detecting the temperature inside the image forming apparatus and an external temperature sensor 72 for detecting the external temperature outside the image forming apparatus. The switching means sets the air outlet to the second outlet 64 when the difference (Ti-To) between the internal temperature Ti detected by the internal temperature sensor 71 and the external temperature To detected by the external temperature sensor 72 is less than a specified value δ, and the internal temperature Ti is below a specified temperature such as the condensation threshold temperature T1. The air outlet to the first outlet 63 is set when the difference (Ti-To) between the internal temperature Ti and the external temperature To is equal to or greater than a specified value δ, or when the internal temperature Ti is above a specified temperature, the width of the sheet being transported is less than a specified width, and the number of continuous prints N to the fuser is equal to or greater than a specified number such as the edge temperature rise threshold number N1. According to this, as described in the embodiment, when the internal environment of the image forming apparatus is such that condensation may occur on sheet contact members such as the paper discharge roller 26, the air can be automatically switched to the second outlet 64, and when the sheet transport conditions are such that both sides in the width direction of the fixing device 6 may become hot, the air can be automatically switched to the first outlet 63.

[0060] (Pattern 8) An image forming apparatus comprising an image forming means (in this embodiment, consisting of an image forming unit, an intermediate transfer belt 14, a primary transfer roller 16, and a secondary transfer roller 9, etc.) for forming a toner image on a sheet such as paper, and a fixing device 6 for heating and fixing the toner image formed on the sheet, wherein the apparatus is further equipped with a blower device according to any of embodiments 1 to 7. According to this method, image defects can be suppressed, and damage to the fixing device can also be suppressed. [Explanation of symbols]

[0061] 1: Image forming apparatus 1a: Outlet 1b: Air intake 2: Image reading device 4: Writing device 5: Paper feed cassette 6: Fixing device 19: Paper output tray 26: Paper output roller 50: Control Panel 60: Blower 61: Blower fan 62: Duct 63:First outlet 64:Second outlet 65:Third outlet 66: First shutter 67: Second shutter 68: Third shutter 69: Air intake 70: Control Unit 71: In-flight temperature sensor 72: Outdoor temperature sensor 73: Shutter drive unit P:Paper Ps: Minimum paper size [Prior art documents] [Patent Documents]

[0062] [Patent Document 1] Patent No. 5414765

Claims

1. Ducts and, In a blower device comprising a blower fan for blowing air into the duct, The duct has at least a first discharge port that discharges the air to both ends in the width direction of the sheet of a fixing device that heats and fixes a toner image formed on the sheet onto the sheet, and a second discharge port that is positioned above the fixing device and discharges the air to a sheet contact member that contacts the sheet. A blower characterized by comprising a switching means for switching the destination of the air discharged from the duct.

2. In the blower according to claim 1, The blower is characterized in that the sheet contact member is a discharge roller that discharges the sheet to a discharge tray.

3. In the blower according to claim 1, The switching means comprises an opening / closing member for opening and closing the first outlet and an opening / closing member for opening and closing the second outlet, and the blower is characterized in that the destination of the air is switched by controlling the opening and closing of the opening / closing members.

4. In the blower according to claim 1, The aforementioned blower fan blows air from within the image forming apparatus on which the blower device is installed into the duct. The duct has a third outlet for discharging the air outside the image forming apparatus. The switching means is characterized by selectively switching the destination of the air discharged between the first outlet, the second outlet, and the third outlet.

5. In the blower according to claim 4, The third outlet is provided at both ends of the duct in the width direction, The first outlet is provided on both sides of the duct in the width direction, An air intake port is provided in the center of the duct in the width direction for taking in air from the blower fan. The switching means includes a first opening / closing member that opens and closes a first discharge port on one side in the width direction and a third discharge port on the other side in the width direction, a second opening / closing member that opens and closes a second discharge port, and a third opening / closing member that opens and closes a first discharge port on the other side in the width direction and a third discharge port on the other side in the width direction. A blower device characterized in that two of the first opening / closing member, the second opening / closing member, and the third opening / closing member are configured to take a blocking position that blocks the flow of air that flows toward the end in the width direction, located on the central side in the width direction of the first outlet.

6. In the blower according to claim 1, The switching means is characterized by switching the destination of the air discharge based on the internal environment of the image forming apparatus on which the blower is installed and the sheet transport conditions.

7. In the blower according to claim 6, An internal temperature sensor for detecting the temperature inside the image forming apparatus, The image forming apparatus has an ambient temperature sensor that detects the ambient temperature outside the image forming apparatus. The switching means is characterized in that, when the difference between the internal temperature detected by the internal temperature sensor and the outside temperature detected by the outside temperature sensor is less than a specified value, and the internal temperature is below the specified temperature, the air is discharged to the second outlet; and when the difference between the internal temperature and the outside temperature is equal to or greater than the specified value, or when the internal temperature is equal to or greater than the specified temperature, and the width of the sheet being transported is less than a specified width, and the number of sheets continuously fed to the fixing device is equal to or greater than the specified number, the air is discharged to the first outlet.

8. Image forming means for forming a toner image on a sheet, An image forming apparatus comprising a fixing device that heats and fixes a toner image formed on the sheet onto the sheet, An image forming apparatus characterized by comprising the blower device described in claim 1.

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