JP7205771B2 - Fixing device and image forming device - Google Patents

Description

The present invention relates to a fixing device and an image forming apparatus having the same.

In an electrophotographic image forming apparatus such as a copier or printer, a recording medium such as paper on which an unfixed image is formed is conveyed between members such as rollers and belts facing each other (nip), and the recording medium is 2. Description of the Related Art A fixing device that applies heat to fix an unfixed image is known.

As such a fixing device, for example, the following Patent Document 1 (Japanese Patent Application Laid-Open No. 2008-233900) and Patent Document 2 (Japanese Patent Application Laid-Open No. 2016-145903) disclose a nip forming member arranged in the fixing belt as a heater. A fixing device is disclosed that heats a fixing belt through a nip forming member by heating with heat.

In the configuration in which the fixing belt is heated via the nip forming member as described above, a metal material such as copper is generally used as the material of the nip forming member to improve the thermal conductivity of the nip forming member. It shortens the first print time (heating time from standby to fixable state) and improves energy efficiency. Furthermore, in order to shorten the first print time and improve energy efficiency, it is desirable to reduce the heat capacity of the nip forming member by thinning it. However, since the nip forming member is a member that forms the nip portion by receiving pressure from the pressure roller, a certain degree of rigidity is required.

In the fixing device described in Patent Document 1, the cylindrical nip forming member is configured to receive the load mainly from the pressure roller. Since the rigidity of the nip forming member against the load of the pressure roller decreases, it becomes difficult to maintain the pressure at the nip portion.

Therefore, in order to improve energy efficiency and ensure the rigidity of the nip forming member, it is desirable to provide a stay for supporting the nip forming member in addition to the nip forming member, as shown in Patent Document 2. That is, in this case, since the nip forming member and the stay are separate members, the nip forming member can be made thin to improve energy saving, while the stay can be thickened to ensure rigidity that can withstand the load of the pressure roller. be able to

As described above, it is conceivable to further reduce the thickness of the nip forming member in order to improve energy efficiency. On the other hand, however, the nip forming member also needs to have strength enough to withstand pressure to some extent. In addition, in the structure disclosed in Patent Document 2, it is difficult to make the nip forming member thinner than before from the viewpoint of ensuring strength, and in order to improve the temperature rise property and energy saving property, other Countermeasures were necessary.

In order to solve the above problems, the present invention provides a cylindrical fixing member, a facing member that contacts the outer peripheral surface of the fixing member, a heating member disposed inside the fixing member, and a fixing member. A fixing device comprising: a nip forming member arranged inside and forming a nip portion with the opposing member sandwiching the fixing member; and a support member arranged inside the fixing member and supporting the nip forming member. The nip forming member has a through hole opening to the heating member side and the fixing member side in a region other than the nip portion within the passage width of the recording medium, and the nip portion region has a through hole that opens to the heating member side and the fixing member side. The support member is configured so as not to have a through hole, and the support member is arranged on the nip forming surface of the nip forming member on the upstream side and downstream side in the recording medium passage direction of the nip portion and the through hole portion of the nip forming member. and the distance between the through holes is set larger on the center side than on the end side of the nip forming member in the longitudinal direction of the fixing member .

According to the present invention, the nip forming member has a through-hole opening to the heating member side and the fixing member side in a region other than the nip portion, thereby reducing the heat capacity of the nip forming member and increasing the temperature of the nip forming member. performance and energy saving can be improved.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention; FIG. 2 is a side cross-sectional view of the fixing device; FIG. 2 is a perspective cross-sectional view of the fixing device; FIG. 2 is a front cross-sectional view of the fixing device; FIG. It is a perspective view of a belt support member. It is a perspective view showing a modification of a belt support member. 4 is a plan view of a nip forming member; FIG. FIG. 4 is a plan view of a nip forming member showing an example in which through holes are circular; FIG. 10 is a plan view of a nip forming member showing an example in which intervals between through-holes are different between the central portion side and the end portion side of the nip forming member; FIG. 4 is a side cross-sectional view of a fixing device showing an example in which a through-hole is provided downstream of a nip portion in a paper passing direction; FIG. 4 is a side cross-sectional view of a fixing device showing an example in which through holes are provided on the upstream side and downstream side of the nip portion in the paper passing direction; FIG. 5 is a cross-sectional view showing an example of arrangement of nip forming members when burrs are generated on the edge of a through hole; FIG. 5 is a cross-sectional view showing an example in which a lubricant is interposed between the nip forming member and the fixing belt; FIG. 3 is a diagram showing an example of a fixing device that conveys paper in a vertical direction; FIG. 5 is a plan view of a nip forming member according to a comparative example;

The present invention will be described below with reference to the accompanying drawings. In addition, in each drawing for explaining the present invention, constituent elements such as members and constituent parts having the same function or shape are given the same reference numerals as much as possible, and once explained, the explanation will be repeated. omitted.

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to one embodiment of the present invention. First, referring to FIG. 1, the overall configuration and operation of the image forming apparatus will be described.

The image forming apparatus 1 shown in FIG. 1 is an electrophotographic monochrome laser printer. In addition to the printer, the present invention may be a copier, a facsimile machine, or a multifunction machine having two or three of these functions. Also, the image forming apparatus is not limited to a monochrome image forming apparatus, and may be a color image forming apparatus.

As shown in FIG. 1, the image forming apparatus 1 includes an image forming unit 2 for forming an image, a recording medium supply unit 3 for supplying paper P as a recording medium, and a printer for transferring an image onto the supplied paper P. A transfer section 4, a fixing device 5 for fixing the image transferred to the paper P, and a discharge section 6 for discharging the paper P with the image fixed thereon are provided.

The image forming unit 2 includes a drum-shaped photoreceptor 7, a charging roller 8 as charging means for charging the surface of the photoreceptor 7, and a latent image forming means for forming a latent image by exposing the surface of the photoreceptor 7. an exposure device 9, a developing roller 10 as developing means for supplying toner (developer) to the surface of the photoreceptor 7 to form a latent image into a visible image, and a cleaning means as cleaning means for cleaning the surface of the photoreceptor 7. a blade 11;

When there is an instruction to start the printing operation, the photoreceptor 7 in the image forming section 2 starts rotating, and the surface of the photoreceptor 7 is uniformly charged to a high potential by the charging roller 8 . Next, the exposure device 9 exposes the surface of the photoreceptor 7 based on the image information of the document read by the document reading device or the print information instructed to print from the terminal, thereby lowering the potential of the exposed portion. Then an electrostatic latent image is formed. Toner is supplied from the developing roller 10 to the electrostatic latent image, and a toner image is formed on the photosensitive member 7 .

The toner image formed on the photoreceptor 7 is transferred to the paper P at the transfer nip between the transfer roller 15 arranged in the transfer section 4 and the photoreceptor 7 . This paper P is supplied from the recording medium supply section 3 . In the recording medium supply unit 3 , the paper P accommodated in the paper feed cassette 12 is sent out one by one by the paper feed roller 13 . The sheet P sent out is conveyed to the transfer nip in timing with the toner image on the photosensitive member 7 by the timing roller pair 14 . Then, the toner image on the photoreceptor 7 is transferred to the paper P at the transfer nip. After the toner image is transferred, the toner remaining on the photoreceptor 7 is removed by the cleaning blade 11 .

The paper P onto which the toner image has been transferred is conveyed to the fixing device 5 . Then, in the fixing device 5 , the toner image is fixed on the paper P by being heated and pressurized when the paper P passes between the fixing belt 21 and the pressure roller 22 . After that, the paper P is conveyed to the discharge section 6 and discharged outside the apparatus by the paper discharge roller pair 16 to complete a series of printing operations.

Next, the configuration of the fixing device according to the first embodiment of the present invention will be described in detail with reference to FIGS. 2 to 6. FIG.

2 is a side sectional view of the fixing device, FIG. 3 is a perspective sectional view of the fixing device, and FIG. 4 is a front sectional view of the fixing device. 5 is a perspective view of a belt support member that supports the fixing belt, and FIG. 6 is a perspective view showing a modification of the belt support member.

As shown in FIG. 2, the fixing device 5 includes a fixing belt 21, a pressure roller 22, a halogen heater 23, a nip forming member 24, a stay 25, a reflecting member 26, a guide member 27, and a temperature sensor. 28 and.

The fixing belt 21 is a cylindrical fixing member that fixes the unfixed image T on the paper P, and is arranged on the side of the unfixed image bearing surface of the paper P. As shown in FIG. In this embodiment, the fixing belt 21 is composed of a base material on the inner peripheral side formed of a metal material such as nickel or SUS or a resin material such as polyimide, and PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) or It is composed of an endless belt (including a film) having a release layer on the outer peripheral side made of PTFE (polytetrafluoroethylene) or the like. An elastic layer made of a rubber material such as silicone rubber, foamed silicone rubber, or fluororubber may be interposed between the substrate and the release layer. If the thickness of the elastic layer is set to about 100 μm, the elastic deformation of the elastic layer when the unfixed image (unfixed toner) is crushed and fixed can absorb minute irregularities on the belt surface, resulting in uneven glossiness. can be avoided. Further, in the present embodiment, a thin and small-diameter belt is used as the fixing belt 21 from the viewpoint of reducing the heat capacity of the fixing belt 21 . Specifically, the thickness of each of the base material and the release layer constituting the fixing belt 21 is set within the ranges of 20 to 50 μm and 10 to 50 μm, and the thickness of the fixing belt 21 as a whole is set to 1 mm or less. are doing. Moreover, when the fixing belt 21 has an elastic layer, the thickness of the elastic layer is preferably set to 100 to 300 μm. In order to further reduce the heat capacity, the thickness of the fixing belt 21 as a whole is desirably 0.2 mm or less, and more desirably 0.16 mm or less. Further, in this embodiment, the diameter of the fixing belt 21 is set to 20 to 40 mm. It is desirable that the fixing belt 21 have a diameter of 30 mm or less.

The pressure roller 22 is a facing member that faces and contacts the outer peripheral surface of the fixing belt 21 . In this embodiment, the pressure roller 22 is composed of a metal core, an elastic layer made of foamed silicone rubber or fluororubber provided on the surface of the metal core, and PFA or PTFE provided on the surface of the elastic layer. A release layer consisting of Further, in this embodiment, the pressure roller 22 is a solid roller, but it may be a hollow roller. In the case of a hollow roller, it is also possible to arrange a heating member such as a halogen heater inside the pressure roller 22 . The elastic layer of the pressure roller 22 may be made of solid rubber, but if a heating member is not arranged inside, it is desirable to use sponge rubber for the elastic layer to enhance the heat insulation of the pressure roller 22 . As a result, the heat of the fixing belt 21 is less likely to be lost to the pressure roller 22, and the heat efficiency of the fixing belt 21 is improved.

Further, the pressure roller 22 is configured to be rotationally driven in the direction indicated by the arrow A in FIG. 2 by a drive source provided in the main body of the image forming apparatus. On the other hand, when the pressure roller 22 is driven to rotate, the fixing belt 21 is driven to rotate in the direction of arrow B in FIG. As shown in FIG. 2, when the sheet P onto which the unfixed image T has been transferred enters the nip portion N from the nip entrance side (the right side in FIG. 2), the sheet P is moved by the rotating fixing belt 21 and pressure roller 22. is conveyed and passes through the nip portion N. At this time, the unfixed image T is fixed on the paper P by applying heat and pressure to the paper P. FIG. Then, the paper P is discharged from the nip exit side (left side in FIG. 2) by the rotating fixing belt 21 and pressure roller 22 .

Further, the pressure roller 22 and the fixing belt 21 are configured so as to approach and separate from each other. In the unlikely event that paper is jammed in the nip portion N, the pressure roller 22 and the fixing belt 21 are separated from each other to open the nip portion N, making it possible to perform maintenance work such as clearing the jammed paper. is. The pressure roller 22 and the fixing belt 21 may be configured to move one of them toward and away from the other, or may be configured to move both toward and away from each other.

The halogen heater 23 is a heating member that is arranged inside the fixing belt 21 and heats the fixing belt 21 via the nip forming member 24 with radiant heat by radiating infrared light. A carbon heater, a ceramic heater, or the like can be used as the heating member other than the halogen heater 23 . In this embodiment, only one halogen heater 23 is arranged in the fixing belt 21, but a plurality of halogen heaters 23 having different heat generating areas according to the width size of the paper may be used.

The nip forming member 24 is longitudinally arranged inside the fixing belt 21 along the longitudinal direction (hereinafter referred to as the “longitudinal direction of the belt”), which is also the direction of the rotational axis of the fixing belt 21 . A nip portion N is formed by sandwiching the fixing belt 21 between them. As shown in FIG. 2, the nip forming member 24 includes a nip forming portion 24a facing the pressure roller 22 via the fixing belt 21, a nip entrance side (the right side in FIG. 2) and a nip exit side of the nip forming portion 24a. (left side in FIG. 2) and a pair of bent portions 24b bent to the side opposite to the pressure roller 22 side. The nip forming portion 24a is provided with a through hole 24c that opens to the halogen heater 23 side and the fixing belt 21 side.

In the nip forming portion 24a, the nip forming surface 24d on the side of the fixing belt 21 is anodized or coated with a fluororesin material in order to improve wear resistance and slidability when the fixing belt 21 rotates. good too. Furthermore, in order to ensure slidability over time, a lubricant such as fluorine-based grease may be applied to the nip forming surface 24d of the nip forming portion 24a on the fixing belt 21 side. Although the nip forming member 24 has a flat plate shape in this embodiment, it may have another shape. For example, by forming the nip forming member 24 into a recessed shape that is recessed on the side opposite to the pressure roller 22 side, the exit portion of the nip portion N is closer to the pressure roller 22, and the separation of the paper from the fixing belt 21 is improved. improves.

Also, the nip forming member 24 is made of a material having a higher thermal conductivity than the stay 25 . For example, the material of the nip forming member 24 is preferably copper (thermal conductivity: 398 W/mk) or aluminum (thermal conductivity: 236 W/mk). Since the nip forming member 24 is made of a material having a high thermal conductivity, the radiant heat from the halogen heater 23 is absorbed by the nip forming member 24 and efficiently transmitted to the fixing belt 21 . For example, by setting the thickness of the nip forming member 24 to 1 mm or less, the heat transfer time from the nip forming member 24 to the fixing belt 21 can be shortened, and the startup speed of the fixing device 5 can be increased. Conversely, when the thickness of the nip forming member 24 is set to be greater than 1 mm and 5 mm or less, the heat storage property of the nip forming member 24 can be enhanced.

The stay 25 is a support member that supports the nip forming member 24 against the pressing force of the pressure roller 22 . Like the nip forming member 24 , the stay 25 is longitudinally arranged inside the fixing belt 21 along the longitudinal direction of the belt. As shown in FIG. 2, in this embodiment, the stay 25 includes a pair of side wall portions 25a arranged parallel to each other with the halogen heater 23 interposed therebetween, and a bottom wall connected to the upper end portion of each side wall portion 25a. It is formed in a substantially U-shaped cross section having a portion 25b. Since each side wall portion 25a of the stay 25 is in contact with the surface of the nip forming member 24 opposite to the nip forming surface 24d via the reflecting member 26, both end portions in the belt rotation direction B are in contact with each other. A nip forming member 24 is supported by a stay 25 . In addition, since each side wall portion 25a extends in the pressing direction of the pressure roller 22 (vertical direction in the figure), the rigidity in the pressing direction is increased, and the nip forming portion 24 due to the pressing force of the pressure roller 22 is suppressed. As the material of the stay 25, it is preferable to use an iron-based metal material such as SUS or SECC in order to ensure rigidity.

The reflecting member 26 is arranged inside the fixing belt 21 so as to face the halogen heater 23 , and reflects infrared light (radiant heat) emitted from the halogen heater 23 toward the nip forming member 24 . As shown in FIG. 2, in the present embodiment, the reflecting member 26 includes a reflecting portion 26a having a curved surface such as an arc or an elliptical shape, and a reflecting portion 26a extending in directions away from both ends of the reflecting portion 26a in the belt rotation direction B. As shown in FIG. and a pair of bent portions 26b. The reflecting member 26 is held by sandwiching each bent portion 26 b between each side wall portion 25 a of the stay 25 and the nip forming portion 24 a of the nip forming member 24 .

The nip forming member 24 is heated by being irradiated with the infrared light reflected by the reflecting member 26 . In this manner, the nip forming member 24 is irradiated not only with the infrared light directly irradiated from the halogen heater 23 but also with the infrared light reflected by the reflecting member 26, so that the nip forming member 24 is effectively heated. In addition, the reflecting member 26 is interposed between the halogen heater 23 and the stay 25 and also has a function of blocking infrared light irradiation to the stay 25 . As a result, wasteful consumption of thermal energy due to heating of the stay 25 is suppressed. Furthermore, in the present embodiment, since the gap S (air layer) is interposed between the stay 25 and the reflecting member 26, heat is further transferred to the stay 25 due to the heat insulation effect of the air layer in this gap S. Suppressed.

The surface of the reflecting member 26 on the side of the halogen heater 23 is subjected to mirror finishing or surface treatment to increase the reflectance. In this embodiment, the reflectance is measured using a spectrophotometer (UV-visible-infrared spectrophotometer UH4150 manufactured by Hitachi High-Tech Science Co., Ltd.) at an incident angle of 5°. In general, halogen heaters have different color temperatures depending on their uses, and those having a color temperature of about 2500K are used for heating fixing devices. The reflectance of the reflecting member 26 should be 70% or more with respect to the wavelength of the halogen heater 23 having a high emission intensity, specifically the wavelength of 900 to 1600 nm, more preferably the wavelength of 1000 to 1300 nm.

Further, the stay 25 may have the function of reflecting the reflecting member 26 and heat insulating. For example, the inner surface of the stay 25 (the surface on the halogen heater 23 side) can be heat-insulated or mirror-finished so that the stay 25 also functions as the reflecting member 26 . In this case, the reflecting member 26, which is separate from the stay 25, can be omitted. The reflectance of the mirror-finished stay 25 is desirably equal to the reflectance of the reflecting member 26 .

The guide member 27 is in contact with the inner peripheral surface of the rotating fixing belt 21 and guides the fixing belt 21 . As shown in FIG. 2, in this embodiment, guide members 27 are provided on both the nip position opening side and the nip exit side. The guide member 27 has an attachment portion 27 a fixed to the stay 25 or the like, and a curved guide portion 27 b that contacts the inner peripheral surface of the fixing belt 21 . Further, as shown in FIG. 3, a plurality of ribs (projections) 27c are provided at regular intervals along the longitudinal direction of the fixing belt 21 (guide surface) of the guide portion 27b. By guiding the fixing belt 21 along the guide surface having the plurality of ribs 27c, the fixing belt 21 can be smoothly rotated without large deformation.

The temperature sensor 28 is arranged to face the outer peripheral surface of the fixing belt 21 and detects the temperature of the fixing belt 21 . In the present embodiment, the temperature sensors 28 are arranged at two locations on the fixing belt 21, namely, the central portion and one end portion of the fixing belt 21 in the longitudinal direction of the belt. The surface temperature of the fixing belt 21 is detected by the temperature sensor 28, and the output of the halogen heater 23 is controlled based on the detection result, thereby controlling the temperature of the fixing belt 21 to a desired temperature (fixing temperature). be done. Also, the temperature sensor 28 may be either a contact type or a non-contact type. As the temperature sensor 28, a known temperature sensor such as a thermopile, thermostat, thermistor, NC sensor, etc., can be applied.

As shown in FIG. 4, cylindrical belt support members 30 are inserted at both ends of the fixing belt 21, respectively. Since the belt support members 30 are inserted into both ends of the fixing belt 21 in this manner, the fixing belt 21 basically does not generate tension in the circumferential direction with respect to the fixing belt 21 when it is not rotating. It is supported by a so-called free belt system.

As shown in FIGS. 4 and 5, the belt support member 30 includes a C-shaped support portion 30a that is inserted inside the fixing belt 21 to support the fixing belt 21, and an end surface of the fixing belt 21 that is in contact with the fixing belt 21 to perform fixing. and a flange-like restricting portion 30b that restricts longitudinal movement (deviation) of the belt 21. As shown in FIG. In addition, as in the example shown in FIG. 6, the support portion 30a may have a cylindrical shape that is continuous over the entire circumference. Each belt support member 30 is fixed to a pair of side plates 31 (see FIG. 4) which are frame members constituting the fixing device 5 . Further, the belt support member 30 is provided with an opening 30c (see FIG. 5), and both ends of the halogen heater 23 and the stay 25 are fixed to the respective side plates 31 through the opening 30c. Halogen heater 23 and stay 25 may be fixed to belt support member 30 .

Hereinafter, regarding the fixing device according to the present embodiment, a configuration that is advantageous in terms of temperature rise and energy saving will be described.

As described above, in the present embodiment, the nip forming member 24 is provided with the through hole 24c that opens to the halogen heater 23 side and the fixing belt 21 side. Further, as shown in FIG. 7 which is a plan view of the nip forming member 24, a plurality of through holes 24c are provided across the longitudinal direction of the nip forming member 24 (or the longitudinal direction of the fixing belt 21). As described above, in the present embodiment, since the plurality of through holes 24c are provided in the nip forming member 24, the heat capacity of the nip forming member 24 is reduced compared to the case where such through holes 24c are not provided. can be reduced. This makes it easier for the nip forming member 24 to rise in temperature, so that the temperature rise rate of the nip forming member 24 can be increased, and the first print time can be shortened and energy saving can be improved.

Further, since the nip forming member 24 is provided with a plurality of through holes 24c, as shown in FIG. A part of the infrared light reflected by is irradiated to the fixing belt 21 through each through hole 24c. Alternatively, radiant heat emitted from the halogen heater 23 is applied to the fixing belt 21 through each through hole 24c. Further, as shown in FIG. 7, the through-hole 24c is provided within the paper passage width W (the passage width of the recording medium) of the nip forming member 24. A region within the sheet passing width W is irradiated. As described above, in the present embodiment, the fixing belt 21 is irradiated with infrared light or radiant heat is applied through the plurality of through holes 24c, so that the fixing belt 21 can be effectively heated. Become. As a result, the heating speed of the fixing belt 21 can be increased, and the first print time can be shortened and the energy saving can be improved. Note that the position where the through hole 24c is formed may be appropriately changed according to the size of the paper passing width W (paper size). Further, in the present embodiment, a so-called center-based transport method is adopted in which the paper is transported while the center position in the width direction of the paper is aligned with the center position in the longitudinal direction of the nip portion N. A so-called edge-based transport method may be employed in which the paper is transported in accordance with the position of one end of the nip portion N in the longitudinal direction.

Further, in this embodiment, the stay 25 and the reflecting member 26 are arranged so as to surround the nip portion N of the nip forming member 24 and the portions of the through holes 24c. It is possible to suppress the heat diffusion of the halogen heater 23 and effectively apply the heat of the halogen heater 23 to the nip portion N and the vicinity thereof. That is, in the present embodiment, as shown in FIG. 7, the region E of the nip portion of the nip forming member 24 and the portions of the through holes 24c are the portions where the stay 25 or the reflecting member 26 contacts the nip forming member 24. It is sandwiched by F in the paper passing direction G. Further, as shown in FIG. 2, the space opposite to the nip forming member 24 with respect to the halogen heater 23 (the space above the halogen heater 23 in FIG. 2) is closed by a stay 25 and a reflecting member 26. .

Thus, in this embodiment, the stay 25 and the reflecting member 26 are arranged upstream and downstream in the paper passing direction G from the nip portion N of the nip forming member 24 and the portions of the through holes 24c. Since the stay 25 and the reflecting member 26 are also arranged on the opposite side of the nip forming member 24 with the halogen heater 23 interposed therebetween, the heat of the halogen heater 23 held by the stay 25 and the reflecting member 26 is transferred to form the nip. It can be effectively applied to the nip portion N of the member 24, and can be effectively applied to the fixing belt 21 through the through holes 24c. As a result, the nip portion N and the vicinity thereof can be efficiently heated, and energy saving can be improved.

Furthermore, in this embodiment, a gap S (see FIG. 2) is provided between the stay 25 and the reflecting member 26 in order to improve energy saving. By providing the gap S between the stay 25 and the reflecting member 26 in this manner, the air layer in the gap S can suppress the heat transfer from the reflecting member 26 to the stay 25 . As a result, application of unnecessary heat to the stay 25 can be reduced, and energy saving can be improved.

Here, as in the comparative example shown in FIG. 15, when the through hole 24c is provided in the region E of the nip portion of the nip forming member 24, the rigidity of the nip forming member 24 particularly at the nip portion is reduced. As a result, a uniform nip width and nip pressure cannot be sufficiently obtained, and there is a possibility that fixing failure may occur. Further, if the through hole 24c is provided in the region E of the nip portion, unevenness is generated in the nip portion, which may cause paper wrinkles.

On the other hand, in the present embodiment, as shown in FIG. 7, the through hole 24c is provided outside the region E of the nip portion of the nip forming member 24. As shown in FIG. Thus, by not providing the through hole 24c in the region E of the nip portion, the rigidity of the nip forming member 24 in the nip portion can be secured, and the nip portion has a uniform width and pressure. can be formed.

Further, since the nip forming member 24 and the stay 25 are separate members as in the present embodiment, it is easy to configure the nip forming member 24 and the stay 25 with different thicknesses. As a result, the stay 25 can be formed thick to ensure its rigidity, while the nip forming member 24 can be formed thin to improve energy efficiency. Both improvements can be achieved.

As described above, according to the configuration of the present embodiment, by providing the through hole 24c only in the region other than the nip portion of the nip forming member 24, the nip forming member can be 24 rigidity can be secured. As a result, it is possible to provide a highly reliable fixing device in which poor fixing and paper wrinkles are less likely to occur.

The shape of the through-hole 24c is not limited to a rectangle (see FIG. 7) as in this embodiment, but may be circular as shown in FIG. Moreover, the intervals between the through-holes 24c are not limited to equal intervals, and may be different intervals. For example, when the nip forming member 24 is likely to be bent at the central side in the longitudinal direction of the nip forming member 24, as in the example shown in FIG. It is desirable to increase the distance between the through holes 24c on the side (D1>D2). By doing so, it is possible to suppress a decrease in rigidity due to the formation of the through hole 24c on the central side of the nip forming member 24, and it is difficult for the nip forming member 24 to bend.

Further, in the present embodiment, the through hole 24c is provided upstream of the nip portion N in the paper passing direction (see FIG. 2). It may be provided on the downstream side in the paper passing direction. Furthermore, as in the example shown in FIG. 11, the through holes 24c can be provided on both the upstream side and the downstream side of the nip portion N in the paper passing direction. As shown in FIG. 2, when the through-hole 24c is provided on the upstream side of the nip portion N in the paper passing direction, the fixing belt 21 can be effectively heated at the timing when the amount of heat is most required. Therefore, fixability can be improved.

Further, the through-holes 24c may be arranged symmetrically in the longitudinal direction (horizontal direction in FIGS. 7 to 9) or in the lateral direction (vertical direction in FIGS. 7 to 9) of the nip forming member 24, or may be arranged asymmetrically. may be placed in The arrangement and number of the through-holes 24c may be appropriately determined according to the required rigidity of the nip forming member 24 and the required temperature rise property or energy saving property.

Also, the size (opening width) of the through holes 24c may be the same or may be different. Various processing methods such as press processing and cutting processing can be employed for processing the through holes 24c. For example, when the opening width of the through-hole 24c is desired to be 50 μm or more, cutting with a drill can be applied, and when the opening width is desired to be less than 50 μm, laser processing is preferably applied, and when the opening width is desired to be less than 5 μm. is preferably applied by a chemical etching method.

If burrs (projections) are generated when the through holes 24c are formed, as shown in FIG. It is desirable to place them on opposite sides. In this way, by projecting the burr 240 formed on the edge of the through hole 24c to the side opposite to the side contacting the fixing belt 21, contact between the fixing belt 21 and the burr 240 can be avoided. can be done. As a result, it is possible to prevent the fixing belt 21 from slightly floating due to contact of the fixing belt 21 with the burrs 240, and it is possible to maintain excellent heat transfer from the nip forming member 24 to the fixing belt 21. . Further, it is possible to prevent the fixing belt 21 from being scratched due to contact with the burr 240, and to reduce the risk of the fixing belt 21 being damaged.

When the lubricant 40 is interposed between the fixing belt 21 and the nip forming member 24 as in the example shown in FIG. The presence of the burr 240 prevents the lubricant 40 from flowing out to the halogen heater 23 side (lower side in the figure) by the height of the burr 240 . Further, by reducing the size of the through hole 24c (to several μm), the surface tension of the lubricant 40 can suppress the outflow of the lubricant 40 to the halogen heater 23 side. By adjusting the direction of the burr 240 and the size of the through hole 24c in this manner, the lubricant 40 is less likely to flow out to the halogen heater 23 side, and the adhesion of the lubricant 40 to the halogen heater 23 and the fixing belt 21 are prevented. It is possible to prevent poor lubrication with the nip forming member 24 from occurring.

As described above, in each embodiment of the present invention, by providing the nip forming member 24 with the through hole 24c, the heat capacity of the nip forming member 24 can be reduced and the temperature of the nip forming member 24 can be easily increased. However, if the nip forming member 24 is thin and has low rigidity, the nip forming member 24 may be thermally deformed due to a sudden temperature rise. In such a case, by rotating the fixing belt 21 before heating the halogen heater 23 (before energization), the heat of the nip forming member 24 can be dispersed and transmitted in the circumferential direction of the fixing belt 21 . . As a result, thermal deformation of the nip forming member 24 due to a sudden temperature rise can be avoided.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

Further, the fixing device according to the present invention is not limited to the fixing device 5 for horizontally conveying the paper as shown in FIG. The installation direction of the fixing device 5 can be changed as appropriate, and the present invention can also be applied to a fixing device 5 that conveys paper in the vertical direction as shown in FIG.

REFERENCE SIGNS LIST 1 image forming apparatus 2 image forming section 5 fixing device 21 fixing belt (fixing member)
22 pressure roller (opposing member)
23 Halogen heater (heating member)
24 nip forming member 24c through hole 24d nip forming surface 25 stay (support member)
40 Lubricant 240 Burr D1 Width between through holes on the center side D2 Width between through holes on the end side N Nip portion P Paper (recording medium)
W Paper width

Japanese Patent Application Laid-Open No. 2008-233900 JP 2016-145903 A

Claims (7)

a cylindrical fixing member;
a facing member that contacts the outer peripheral surface of the fixing member;
a heating member disposed inside the fixing member;
a nip forming member that is disposed inside the fixing member and forms a nip portion with the opposing member sandwiching the fixing member;
a support member disposed inside the fixing member and supporting the nip forming member;
A fixing device comprising:
The nip forming member has a through hole opening to the heating member side and the fixing member side in a region other than the nip portion within the passage width of the recording medium, and has the through hole in the nip portion region. is configured not to
The support member is arranged on the upstream side and the downstream side in the recording medium passage direction of the nip portion and the through hole portion of the nip forming member and on the side opposite to the nip forming surface of the nip forming member ,
A fixing device according to claim 1, wherein the interval between the through-holes is larger on the central portion side than on the end portion side of the nip forming member in the longitudinal direction of the fixing member . The fixing device according to claim 1, wherein the nip forming member and the support member are separate members. 3. The fixing device according to claim 1, wherein the through hole is provided on the upstream side in the recording medium passage direction of the nip portion. The fixing device according to any one of claims 1 to 3, wherein the edge of the through-hole is provided with a protrusion that protrudes in a side opposite to the side that contacts the fixing member . 5. The fixing device according to claim 4, wherein a lubricant is interposed between said fixing member and said nip forming member . The fixing device according to any one of claims 1 to 5, wherein the fixing member is controlled to rotate before heating the heating member . an image forming unit that forms an image on a recording medium;
a fixing device for fixing an image formed by the image forming unit onto the recording medium;
In an image forming apparatus comprising
An image forming apparatus comprising the fixing device according to claim 1 as the fixing device .

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