JP2024024836A - Fixing device and image forming device equipped with it - Google Patents

Abstract

[Problem] To provide a fixing device capable of suppressing a temperature drop in a paper passing area of a fixing belt and a temperature rise in a non-paper passing area while suppressing dispersion of cooling air, and an image forming apparatus including the fixing device. [Solution] The fixing device has an endless fixing belt heated by a heating device, a nip forming member, a pressure member, a duct, and an air blower, and fixes a toner image onto a sheet passing through a fixing nip portion. The nip forming member slides on the inner circumferential surface of the fixing belt. The pressure member is pressed against the nip forming member with the fixing belt sandwiched therebetween to form the fixing nip portion. The duct extends at least over the entire width of the fixing belt. A suction port is formed on the side of the duct, which communicates the inside and outside of the duct in the radial direction. By generating negative pressure by air flow inside the duct using the air blower, air around both ends of the fixing belt in the width direction is sucked into the duct through the suction port, thereby cooling both ends of the fixing belt in the width direction. [Selected Figure] Figure 8

Description

The present invention relates to a fixing device that is installed in an image forming apparatus such as a facsimile machine, a copier, or a printer and fixes a toner image transferred onto a recording medium, and an image forming apparatus equipped with the fixing device. The present invention relates to a method for discharging air to the outside.

In an image forming apparatus using an electrophotographic method, a toner image is formed by applying toner to an electrostatic latent image formed on a photoreceptor, and after the toner image is transferred to paper, a fixing device is used to transfer the toner image onto the paper. is firmly established.

When the size of the paper to be fixed in the fixing device is small, the paper passing area where the paper passes through the fixing member loses heat from the surface to the paper and becomes low in temperature, while the non-paper passing area where the paper does not pass through the fixing member. becomes high temperature. In particular, if the paper passing area of the fixing member is maintained at the fixing temperature (target temperature) during continuous printing, the temperature of the non-paper passing area of the fixing member will rise excessively, causing damage to the fixing member etc. if the temperature exceeds the heat resistance limit. Problems may occur. Specifically, in consideration of safety, the temperature of the thermostat provided for each heater becomes higher than the operating temperature, and the power supply to the heater is stopped and the temperature no longer rises. Additionally, if a large sheet of paper that covers the heated area is passed in a state where the temperature of the non-paper-passing area has risen excessively, the toner on the paper will over-melt and adhere to the fixing member, causing the toner to reappear on the following paper. Problems such as image deterioration due to adhered high-temperature offset and thermal deterioration of the rubber constituting the pressure member may also occur.

Therefore, various methods have been proposed for cooling the non-paper-passing area of the fixing device. For example, in Patent Document 1, in order to cool a predetermined area of the fixing member, an air blowing port and a cooling member are provided opposite to the fixing member. A cooling device having a cooling fan for blowing cooling air to the non-paper passing area cooling duct in which a wind guide portion is formed, a cooling device that makes the cooling device movable. A fusing device is presented.

Patent Document 2 describes an endless belt, a pressing member that contacts the inner circumferential surface of the belt, a pressing rotating body that is disposed opposite to the pressing member and forms a nip portion with the pressing member, and a heating member that heats the belt. A fixing device is disclosed that includes a heating section, a refrigerant supply section that cools the belt using a refrigerant, and a duct through which the refrigerant flows. In this fixing device, the duct includes a discharge section provided in an internal area surrounded by the belt, and the refrigerant is discharged from the discharge section toward the inner peripheral surface of the belt, and the refrigerant is discharged from the discharge section toward the width of the belt near the belt. flows out from the end side of the belt in the direction.

Japanese Patent Application Publication No. 2008-52031 JP 2019-128479 Publication

In the method of Patent Document 1, since the cooling air is applied from the outside of the belt, there is a problem that the cooling air is easily dispersed and temperature unevenness is likely to occur. In addition, TVOC (Total Volatile Organic Compounds) and UFP (Ultra Fine Particles) are generated when silicone rubber used as a heat-resistant member in the fixing device and wax components contained in toner are heated. However, the dispersion of the cooling air makes it difficult to collect TVOC and UFP. As a result, there is concern that TVOC and UFP will be discharged to the outside of the image forming apparatus, which may adversely affect the environment.

Further, in the method disclosed in Patent Document 2, a duct is configured inside the fixing belt, and cooling air introduced by a fan is blown onto the inner surface of the belt outside the non-sheet passing area, and is discharged to the end of the fixing belt. In this configuration, the temperature of the cooling air is lowest before it contacts the fuser belt and highest immediately after it is discharged from the edge of the fuser belt, so the temperature is lowest in the area immediately outside the paper passing area that is hit by the cooling air. Become. Therefore, if the positional accuracy of the part to which the cooling air is applied is poor, it may cause fixing failure or the temperature of the non-sheet passing area may become too high, so accuracy in the positioning of the area to which the cooling air is applied is required. Furthermore, since the temperature on the downstream side of the cooling air tends to become high, more cooling air than necessary is required to lower the temperature in this area.

In view of the above-mentioned problems, the present invention provides a fixing device that can suppress a temperature drop in a paper passing area of a fixing belt and a temperature rise in a non-paper passing area while suppressing dispersion of cooling air with a simple configuration, and a fixing device equipped with the same. The object of the present invention is to provide an image forming apparatus with improved performance.

In order to achieve the above object, a first configuration of the present invention includes a fixing belt, a nip forming member, a pressure member, a duct, and an air blower, and heats a sheet passing through a fixing nip. and a fixing device that fixes the toner image formed on the sheet to the sheet by applying pressure. The fixing belt is endless and heated by a heating device. The nip forming member is arranged radially inside the fixing belt and slides on the inner circumferential surface of the fixing belt. The pressure member forms a fixing nip portion with the fixing belt by being pressed against the nip forming member with a predetermined pressure across the fixing belt. The duct has a cylindrical shape that extends at least across the entire width of the fixing belt and is open at both ends. The blower generates an air flow inside the duct. A suction port is formed on the side surface of the duct, which communicates between the inside and outside of the duct in the radial direction. By generating negative pressure inside the duct by the air flow, air around both ends of the fixing belt in the width direction is sucked into the duct through the suction port, thereby cooling both ends of the fixing belt in the width direction.

According to the first configuration of the present invention, by generating an air flow flowing inside the duct using the blower device, a force is generated to draw air near the suction port into the inside of the duct. Then, air near both ends in the width direction of the fixing belt is drawn along the inner circumferential surface of the fixing belt, and flows into the inside of the duct through the suction port while removing heat from the inner circumferential surface of the fixing belt. As a result, the air flow containing TVOC and UFP after cooling the fixing belt is collected in the duct, so that the air flow is more difficult to disperse than in a configuration in which the air flow is blown onto the outer peripheral surface of the fixing belt. Therefore, the configuration is such that TVOC and UFP contained in the airflow can be easily collected. In addition, even if the positional accuracy of the suction port in the axial direction is low, it is possible to effectively suppress the temperature rise in the non-paper passing area without reducing the temperature in the paper passing area, thereby reducing the occurrence of image defects such as poor fixing. Can be suppressed.

A side sectional view showing the internal structure of an image forming apparatus 100 equipped with a fixing device 15 of the present invention A side cross-sectional view of the fixing device 15 according to the first embodiment of the present invention taken along the paper insertion direction A side view of the fixing device 15 of the first embodiment viewed from the paper insertion direction A side sectional view taken along the axial direction of the fixing device 15 of the first embodiment Graph showing the temperature distribution in the width direction of the fixing belt 30 in the fixing device 15 of the first embodiment A side sectional view taken along the axial direction of a fixing device 15 according to a second embodiment of the present invention FIG. 7 is a side cross-sectional view taken along the axial direction of a fixing device 15 according to a third embodiment of the present invention, showing a state in which a suction port 37a is opened by a shutter 60; FIG. 7 is a side cross-sectional view taken along the axial direction of the fixing device 15 of the third embodiment, showing a state in which the suction port 37b is opened by the shutter 60;

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side sectional view showing the internal structure of an image forming apparatus 100 equipped with a fixing device 15 of the present invention. In the image forming apparatus (monochrome printer in this embodiment) 100, an image forming section P that forms a monochrome image through charging, exposure, development, and transfer steps is provided. The image forming section P includes a charging unit 4, an exposure unit (such as a laser scanning unit) 7, a developing unit 8, a transfer roller 14, and a cleaning device along the rotation direction of the photosensitive drum 5 (clockwise direction in FIG. 1). 19, and a static eliminator (not shown) are provided.

When performing an image forming operation, the photosensitive drum 5, which rotates in a clockwise direction, is uniformly charged by the charging unit 4. Next, an electrostatic latent image is formed on the photoreceptor drum 5 by a laser beam from the exposure unit 7 based on the original image data. Then, a developer (hereinafter referred to as toner) is attached to the electrostatic latent image by the developing unit 8 to form a toner image.

Toner is supplied to the developing unit 8 from a toner container 9. Note that the image data is transmitted from a personal computer (not shown) or the like. Further, a static eliminator (not shown) for removing residual charges on the surface of the photoreceptor drum 5 is provided downstream of the cleaning device 19 with respect to the rotational direction of the photoreceptor drum 5.

The paper S is conveyed at a predetermined timing from the paper feed cassette 10 (or manual paper feed device 11) via the registration roller pair 23 toward the photoconductor drum 5 on which the toner image has been formed as described above, and the toner image is transferred. The toner image formed on the surface of the photoreceptor drum 5 is transferred onto the paper S by the roller 14 . The paper S on which the toner image has been transferred is separated from the photoreceptor drum 5 and conveyed to the fixing device 15, where the toner image is fixed. The paper S that has passed through the fixing device 15 is transported to the upper part of the apparatus by a paper transport path 16, and when an image is to be formed on only one side of the paper S (during single-sided printing), the paper S is ejected to an ejection tray 18 by a pair of ejection rollers 17. Ru.

On the other hand, when forming images on both sides of the paper S (during double-sided printing), the conveyance direction is reversed after the trailing edge of the paper S passes through the branch section 20 of the paper conveyance path 16. As a result, the paper S is sorted from the branching section 20 to the reversing conveyance path 21 that branches off, and is conveyed again to the image forming section P with the image surface reversed. Then, the next toner image formed on the photosensitive drum 5 is transferred by the transfer roller 14 to the surface of the paper S on which the image is not formed. The sheet S on which the toner image has been transferred is conveyed to a fixing device 15 and the toner image is fixed thereon, and then is discharged onto a discharge tray 18 by a pair of discharge rollers 17 .

An edge detection sensor 25 is arranged upstream of the pair of registration rollers 23 in the paper conveyance direction. The edge detection sensor 25 detects the edge position (edge position) of the paper S in the width direction (perpendicular to the paper conveyance direction). As the edge detection sensor 25, for example, a PI (photo interrupter) sensor is used, which has a detection section having a light emitting element such as an LED and a light receiving element such as a photodiode, and is opposed to both ends of the paper S in the width direction. placed in position.

Further, a control section 90 is arranged inside the image forming apparatus 100. The control unit 90 centrally controls the image forming apparatus 100.

FIG. 2 is a side sectional view of the fixing device 15 according to the first embodiment of the present invention, which is installed in the image forming apparatus 100, taken along the paper insertion direction. FIG. 3 is a side view of the fixing device 15 of the first embodiment viewed from the paper insertion direction. The fixing device 15 is of a belt fixing type, and includes a fixing belt 30, a pressure roller (pressure member) 31, a heater (heating device) 33, a support stay 37, a nip plate 39, and a blower device 50. Be prepared. Note that the housing of the fixing device 15 is not shown in FIGS. 2 and 3.

The fixing belt 30 is an endless belt made of a plurality of laminated layers including a base layer provided on the innermost side (on the heater 33 side) and a release layer provided on the outermost side (on the pressure roller 31 side). be. A predetermined tension is applied to the fixing belt 30 by a nip plate 39 and a belt support guide (not shown).

Further, the dimension of the fixing belt 30 in the width direction (rotation axis direction, left-right direction in FIG. 3) is set to be wider than the maximum paper width that passes through the fixing nip portion N. Thereby, the fixing belt 30 can cover the entire surface of the paper S regardless of the paper size, so that unfixed toner can be prevented from adhering to the nip plate 39.

A first thermistor 35a and a second thermistor 35b are provided to face the outer peripheral surface of the fixing belt 30. The first thermistor 35a is disposed at the center of the fixing belt 30 in the width direction, and detects the surface temperature of the paper passing region R1 (see FIG. 4) of the fixing belt 30 in a non-contact manner. The second thermistor 35b is disposed at one end of the fixing belt 30 in the width direction, and detects the surface temperature of the non-sheet passing region R2 (see FIG. 4) of the fixing belt 30 in a non-contact manner.

The surface temperature of the paper passing region R1 of the fixing belt 30 is detected by the first thermistor 35a, and the fixing temperature is controlled by turning the heater 33 on or off. Further, the second thermistor 35b detects the surface temperature of the non-paper passing region R2 of the fixing belt 30, and the non-paper passing region R2 of the fixing belt 30 is cooled by turning on or off a blower device 50, which will be described later.

The pressure roller 31 has an elastic layer 31b made of silicone rubber or the like laminated on the outer circumferential surface of a cylindrical core 31a made of a material such as metal, and a release layer (such as a fluororesin coat) coated on the surface of the elastic layer 31b. (not shown) is used. The pressure roller 31 is pressed against the fixing belt 30 with a predetermined pressure.

The support stay 37 is a hollow rectangular cylindrical member made of metal. A nip plate 39, which will be described later, is supported on the lower surface of the support stay 37. Both ends of the support stay 37 are fixed to housing side plates (not shown) of the fixing device 15.

A blower device 50 is connected to one end of the support stay 37. The blower device 50 is, for example, a sirocco fan or an axial fan, and generates an air flow from one end of the support stay 37 to the other end. An exhaust port 51 is provided at the other end of the support stay 37. The airflow that has passed through the support stay 37 is exhausted to the outside of the image forming apparatus 100 through the exhaust port 51. The support stay 37 extends at least across the entire width of the fixing belt 30 and also serves as a cylindrical duct with both ends open.

The nip plate 39 comes into contact with the pressure roller 31 via the fixing belt 30 to form a fixing nip N through which the sheet S is inserted. The nip plate 39 is made of a heat-resistant resin such as a liquid crystal polymer or an elastic material such as silicone rubber, and an elastomer may be disposed on the surface facing the fixing belt 30 in some cases.

The heater 33 is a planar heater in which a resistance layer is coated on a ceramic base material and generates heat by applying electricity to the resistance layer. The heater 33 is disposed between the fixing belt 30 and the nip plate 39, and a glass layer is laminated on the surface of the resistance layer facing the inner peripheral surface of the fixing belt 30. The heat generated in the resistance layer heats the fixing belt 30 through the glass layer. The glass layer is in contact with the inner peripheral surface of the fixing belt 30 to ensure electrical insulation and slidability with the inner peripheral surface of the fixing belt 30. Note that in place of the heater 33, an induction heating type heating section may be used.

A drive input gear 41 is fixed to one end of the core metal 31a. When the pressure roller 31 rotates counterclockwise in FIG. 2 due to driving force being transmitted from the fixing drive motor (not shown) via the drive input gear 41, the outer periphery of the pressure roller 31 and the fixing belt 30 rotates. The nip plate 39 (heater 33) and the inner circumferential surface of the fixing belt 30 slide due to the frictional force between the nip plate 39 (heater 33) and the fixing belt 30, and the fixing belt 30 rotates clockwise in FIG. A fixing nip portion N is formed at a portion where the fixing belt 30 and the pressure roller 31 contact each other while rotating in opposite directions.

The paper S is transported from the upstream side in the paper transport direction (right side in FIG. 2) to the fixing nip N, and in the fixing nip N, the paper S is heated and pressurized by the fixing belt 30 and the pressure roller 31. The powdered toner above is thermally melted and fixed. The sheet S after the fixing process is separated from the surface of the fixing belt 30 by a separation claw (not shown), and then conveyed to the downstream side of the fixing device 15 (to the left side in FIG. 2) in the sheet conveyance direction.

FIG. 4 is a side cross-sectional view of the fixing device 15 of the first embodiment taken along the axial direction. As shown in FIG. 4, a suction port 37a is formed in the upper part of the support stay 37 (on the opposite side to the nip plate 39). A pair of suction ports 37a are formed at symmetrical positions with respect to the center portion of the fixing belt 30 in the width direction.

The suction port 37a is formed at a position corresponding to the outside of the paper passing region R1 through which the smallest size (for example, A5 size) paper S inserted into the fixing nip N passes. In the present embodiment, a pair of holes are formed at positions corresponding to the innermost portions of both ends of the paper passing region R1 through which the paper S of the most frequently used size (for example, A4 portrait size) passes in the image forming apparatus 100.

When the temperature detected by the second thermistor 35b reaches a predetermined temperature or higher, the blower device 50 is activated by a control signal from the control section 90 (see FIG. 1) to generate an air flow inside the support stay 37. At this time, by increasing the speed of the air flow inside the support stay 37 to a predetermined speed or higher (for example, 10 m/sec), the space inside the fixing belt 30 is brought into a negative pressure state.

As a result, a force is generated that draws the air near the suction port 37a into the support stay 37. Then, the air near both ends in the width direction of the fixing belt 30 is drawn in along the inner circumferential surface of the fixing belt 30 (indicated by dotted arrows in FIG. 4), and while removing heat from the inner circumferential surface of the fixing belt 30, It flows into the inside of the support stay 37 via 37a. Thereby, it is possible to suppress the temperature rise in the non-sheet passing region R2 of the fixing belt 30.

The airflow after cooling the inner peripheral surface of the fixing belt 30 contains TVOC and UFP. After the fixing belt 30 has been cooled, the air flow containing the TVOC and UFP is drawn inside the support stay 37 by the negative pressure generated by the suction port 37a. Thereafter, the air flow joins the air flow in the support stay 37 along with the TVOC and UFP, and after the TVOC and UFP are removed by the filter 53 disposed on the downstream side, the air flow is discharged to the outside of the image forming apparatus 100.

FIG. 5 is a graph showing the temperature distribution in the width direction of the fixing belt 30 in the fixing device 15 of the first embodiment. In FIG. 5, the temperature distribution when the blower device 50 is activated is shown by a solid line, and the temperature distribution when the blower device 50 is not activated is shown by a broken line.

When the blower device 50 is operated, the temperature of the fixing belt 30 is lowest at the ends in the width direction of the fixing belt 30, which are strongly influenced by the air flow drawn along the inner peripheral surface of the fixing belt 30. Then, since the air flow is gradually heated toward the suction port 37a, the temperature reduction effect near the outer side in the width direction of the paper passing region R1 of the fixing belt 30 becomes smaller.

As a result, as shown by the solid line in FIG. 5, the temperature gradient in the width direction of the fixing belt 30 when the air blower 50 is operated becomes gentler as it approaches the air intake port 37a from the widthwise end of the fixing belt 30. . Therefore, even if the accuracy of the axial position of the suction port 37a or the insertion position of the paper S is low, the temperature of the fixing belt 30 does not drop significantly near the outside of the paper passing area R1 in the width direction, resulting in poor fixing, etc. It is possible to suppress the occurrence of quality defects.

Furthermore, since the air flow containing TVOC and UFP after cooling the fixing belt 30 is collected in the support stay 37, compared to a configuration in which the air flow is blown onto the outer peripheral surface of the fixing belt 30, the air flow containing TVOC and UFP is collected in the supporting stay 37. Airflow becomes difficult to disperse. Therefore, the configuration is such that TVOC and UFP contained in the airflow can be easily collected.

Furthermore, by controlling the wind speed of the blower 50 according to the widthwise size of the paper S and the temperature detected by the second thermistor 35b, it is possible to change the temperature gradient from the widthwise end of the fixing belt 30 to the suction port 37a. can. For example, when an output signal from the edge detection sensor 25 (see FIG. 1) is transmitted to the control section 90 (see FIG. 1), the control section 90 determines the width of the sheet S to be conveyed based on the transmitted output signal. Detect the directional size. The control unit 90 controls the wind speed of the air blower 50 based on the detected widthwise size of the paper S and the temperature detected by the second thermistor 35b.

Specifically, when the paper S to be conveyed is the smallest size (A5 size), or when the temperature detected by the second thermistor 35b is higher than a predetermined temperature, the speed of the air blower 50 is increased to blow the fixing belt. The temperature gradient from the widthwise end of the tube 30 to the suction port 37a is increased. On the other hand, if the paper S to be conveyed is large size (B4 size), or if the temperature detected by the second thermistor 35b is lower than the predetermined temperature, the air speed of the blower 50 is reduced to increase the width of the fixing belt 30. The temperature gradient from the direction end to the suction port 37a is reduced. Thereby, depending on the size of the sheet S in the width direction and the temperature of the non-sheet passing area R2 of the fixing belt 30, the non-sheet passing area R2 can be cooled just enough. Note that when the paper S is the maximum size (A3 size), the entire width direction of the fixing belt 30 becomes the paper passing region R1, so the blower device 50 is stopped.

Further, a filter 53 is disposed downstream of the support stay 37 with respect to the flow direction of the air flow, and after collecting TVOC and UFP contained in the air flow flowing inside the support stay 37, the air flow is directed to the outside of the image forming apparatus 100. discharge. Thereby, the negative impact on the environment caused by TVOC and UFP can be reduced.

FIG. 6 is a side cross-sectional view taken along the axial direction of the fixing device 15 according to the second embodiment of the present invention. In this embodiment, the blower device 50 is disposed on the downstream side of the support stay 37 in the direction of air flow. The blower device 50 is a suction fan that sucks air inside the support stay 37. Further, a blowing fan 55 is arranged to blow air onto both ends of the outer peripheral surface of the fixing belt 30 in the width direction. The configuration of other parts of the fixing device 15 is similar to that of the first embodiment.

As shown in FIG. 6, a blowing fan 55 disposed on the outside of the fixing belt 30 can cool the outer circumferential surface of both ends of the fixing belt 30 in the width direction. Therefore, in addition to the cooling of the inner peripheral surface of both ends of the fixing belt 30 in the width direction by the air blower 50, the cooling function of both ends of the fixing belt 30 in the width direction is improved.

Further, the airflow after being blown onto the fixing belt 30 by the blowing fan 55 and cooling the fixing belt 30 contains TVOC and UFP. After the fixing belt 30 has been cooled, the airflow containing the TVOC and UFP is drawn into the inside of the support stay 37 from the widthwise ends of the fixing belt 30 by the negative pressure generated by the suction port 37a. Thereafter, the airflow joins the airflow in the support stay 37 together with the TVOC and UFP, passes through the air blower 50 disposed on the downstream side, and after the TVOC and UFP are removed by the filter 53, the airflow is transferred to the image forming apparatus 100. Expelled to the outside.

In this embodiment, the blower device 50 is disposed on the downstream side in the direction of air flow inside the support stay 37, and the air inside the support stay 37 is sucked by the blower device 50. In this configuration, the flow velocity (wind speed) of the air flow inside the support stay 37 is difficult to increase compared to the configuration of the first embodiment in which the blower device 50 is disposed on the upstream side and air is blown into the support stay 37 by the blower device 50. . Therefore, it is necessary to use a blower device 50 with a larger output than that in the first embodiment.

FIG. 7 is a side cross-sectional view of the fixing device 15 according to the third embodiment of the present invention, cut along the axial direction. In this embodiment, a pair of suction ports 37a and a pair of suction ports 37b are formed at the upper part of the support stay 37. The pair of suction ports 37b are located at symmetrical positions with respect to the center portion of the fixing belt 30 in the width direction, and are formed one each on the outer side of the pair of suction ports 37a in the axial direction. More specifically, a pair of suction ports 37b are provided at positions corresponding to the inner side of both ends in the width direction of the sheet passing region R1' through which a large-sized sheet S (for example, B4 size) to be inserted into the fixing nip N passes. It is formed.

Further, a shutter 60 for switching the suction ports 37a, 37b between an open state and a closed state is arranged adjacent to the upper surface of the support stay 37. The shutter 60 is formed with a pair of first openings 60a and a pair of second openings 60b. The distance between the pair of first openings 60a is the same as the distance between the pair of suction ports 37a. The distance between the pair of second openings 60b is the same as the distance between the pair of suction ports 37b. Further, when the first opening 60a overlaps the suction port 37a, the second opening 60b does not overlap the suction port 37b, and when the second opening 60b overlaps the suction port 37b, the first opening 60a overlaps the suction port 37a. The positions are such that they do not overlap.

Further, a shutter drive gear 61 for reciprocating the shutter 60 is arranged. The shutter drive gear 61 is connected to a shutter drive motor 62. The shutter drive gear 61 rotates forward or backward while meshing with a rack gear (not shown) formed on the top surface of the shutter 60. As a result, the shutter 60 is moved to a position (first position) where the suction port 37a is in the open state and the suction port 37b is in the closed state, and a position (second position) where the suction port 37a is in the closed state and the suction port 37b is in the open state. position) and place it selectively.

When the output signal from the edge detection sensor 25 (see FIG. 1) is transmitted to the control section 90 (see FIG. 1), the control section 90 determines the width direction size of the sheet S to be conveyed based on the transmitted output signal. Detect. The control unit 90 transmits a control signal to the shutter drive motor 62, rotates the shutter drive gear 61 by a predetermined amount in a predetermined direction, and places the shutter 60 in either the first position or the second position.

FIG. 7 shows a state in which the shutter 60 is placed at the first position. When passing a paper S having a small widthwise size (A4 lengthwise size), as shown in FIG. By sucking more air, the temperature rise in the paper non-passing region R2 is suppressed.

FIG. 8 is a diagram showing the shutter 60 in the second position. When passing a sheet S having a large widthwise size (B4 size), as shown in FIG. 8, the suction port 37b located immediately inside the sheet passing area R1' of the sheet S is opened, By sucking more air, the temperature rise in the paper non-passing region R2 is suppressed.

According to the configuration of this embodiment, by switching the opening/closing state of the suction ports 37a and 37b according to the widthwise size of the paper S, it is possible to efficiently cool the non-paper passing region R2, which varies depending on the widthwise size of the paper S. Therefore, it is possible to effectively suppress the temperature rise in the paper non-passing region R2 without lowering the temperature of the paper passing region R1 as much as possible.

Here, two pairs of suction ports 37a and 37b corresponding to small size (A4 vertical size) and large size (B4 size) paper S are provided, and a first opening 60a corresponding to the arrangement of the suction ports 37a and 37b is provided. , the shutter member 60 in which the second opening 60b is formed is used, but three or more pairs of suction ports are provided according to the size of the paper S in the width direction, and three or more pairs of suction ports are provided corresponding to the arrangement of the respective suction ports. It is also possible to use a shutter member 60 in which an opening is formed. According to this configuration, the non-sheet passing area can be cooled with higher accuracy.

In addition, the present invention is not limited to the above-mentioned embodiments, and various changes can be made without departing from the spirit of the present invention. For example, in each of the above embodiments, the support stay 37 is configured to also serve as a duct that is a distribution path for the air flow generated by the blower device 50, but a duct is provided inside the fixing belt 30 in the radial direction separately from the support stay 37. It may be provided.

Further, in the second embodiment, the blowing fan 55 that blows air is disposed at both ends in the width direction of the outer circumferential surface of the fixing belt 30, but the blowing fan 55 may be combined with the first or third embodiment.

Further, in each of the above embodiments, an example is shown in which two PI sensors are arranged at both ends in the width direction as the edge detection sensor 25, but other sensors such as CIS may be used. Furthermore, without using the edge detection sensor 25, for example, a paper size detection mechanism (not shown) provided in the paper feed cassette 10 or manual paper feeder 11 of the image forming apparatus 100, or an operation panel (not shown) of the image forming apparatus 100 may be used. Alternatively, the size of the paper S may be detected based on the size information of the paper S input from a personal computer (not shown) or a personal computer.

Further, in each of the above embodiments, a monochrome printer has been described as an example of the image forming apparatus 100, but the present invention is not limited to monochrome printers, but can be applied to color printers, monochrome and color copying machines, digital multifunction devices, facsimile machines, etc. The present invention can be applied to various electrophotographic image forming apparatuses in which an image is transferred onto paper (recording medium) and the transferred unfixed toner is fixed by a fixing device.

15 Fixing device 25 Edge detection sensor (sheet size detection mechanism)
30 Fixing belt 31 Pressure roller (pressure member)
33 Heater (heating device)
35a First thermistor 35b Second thermistor 37 Support stay (support member, duct)
37a, 37b Suction port 39 Nip plate (nip forming member)
50 Air blower 55 Blow fan 60 Shutter 60a First opening 60b Second opening 61 Shutter drive gear (shutter drive mechanism)
62 Shutter drive motor (shutter drive mechanism)
90 Control unit 100 Image forming device P Image forming unit S Paper (sheet)
R1 Paper passing area R2 Non-paper passing area

Claims (8)

an endless fixing belt heated by a heating device;
a nip forming member disposed radially inside the fixing belt and sliding on an inner peripheral surface of the fixing belt;
a pressure member that forms a fixing nip portion between the fixing belt and the fixing belt by being pressed against the nip forming member with a predetermined pressure across the fixing belt;
A fixing device that fixes a toner image formed on the sheet to the sheet by heating and pressurizing the sheet passing through the fixing nip,
a cylindrical duct extending at least across the entire width of the fixing belt and having both ends open;
a blower device that generates airflow inside the duct;
Equipped with
At least one pair of suction ports communicating between the inside and outside of the duct in the radial direction are formed on the side surface of the duct at symmetrical positions with respect to the center in the width direction of the fixing belt,
By generating negative pressure inside the duct by the air flow, air around both ends of the fixing belt in the width direction is sucked into the inside of the duct through the suction port, and the air around both ends of the fixing belt in the width direction is sucked into the duct. A fixing device characterized by cooling its parts. 2. The fixing device according to claim 1, wherein the suction port is formed at a position corresponding to an outer side of both ends in the width direction of an insertion area of the sheet of a minimum size to be inserted into the fixing nip. A plurality of pairs of the suction ports are formed at positions immediately adjacent to the inner side of both ends in the width direction of the insertion area of the sheets of different sizes to be inserted into the fixing nip portion,
a shutter member capable of reciprocating along the duct and having a plurality of pairs of openings having the same spacing as the plurality of pairs of suction ports;
a shutter moving mechanism that reciprocates the shutter member;
Equipped with
The fixing device according to claim 1, wherein one of the pair of suction ports is opened and the other suction port is closed. 2. The fixing device according to claim 1, further comprising a blowing fan that blows an air flow from the outside in the radial direction of the fixing belt to both ends in the width direction of the fixing belt. a support member disposed inside the fixing belt in the radial direction and supporting the nip forming member;
The fixing device according to claim 1, wherein the support member also serves as the duct, and the suction port is formed on a side surface of the support member opposite to the nip forming member. The fixing device according to claim 1, further comprising a filter provided on the downstream side of the duct with respect to the flow direction of the air flow. an image forming section that forms a toner image on a sheet;
The fixing device according to claim 1, wherein the fixing device is arranged downstream of the image forming unit and fixes the toner image formed on the sheet to the sheet.
a sheet size detection mechanism that detects the size of the sheet;
a thermistor that detects the temperature of a region of the fixing belt where the sheet is not inserted;
a control unit that controls driving of the blower;
Equipped with
The control unit increases the wind speed of the blower as the size in the width direction of the sheet detected by the sheet size detection mechanism becomes smaller or as the temperature of the non-inserted region increases as detected by the thermistor. An image forming apparatus characterized by: an image forming section that forms a toner image on a sheet;
The fixing device according to claim 3, wherein the fixing device is arranged downstream of the image forming unit and fixes the toner image formed on the sheet to the sheet.
a sheet size detection mechanism that detects the size of the sheet;
a control unit that controls driving of the shutter moving mechanism;
Equipped with
The control unit causes the shutter moving mechanism to reciprocate the shutter to open the pair of suction ports located immediately inside both ends in the width direction of the insertion area of the sheet detected by the sheet size detection mechanism. An image forming apparatus characterized in that the other suction ports are closed.