JP2019053246A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

To suppress pressure distribution variation without demanding high component accuracy compared to a constitution that supports a support with a whole area in a width direction of an endless belt-like member, in a constitution supporting the endless belt-like member by the support from an inner side.SOLUTION: A fixing apparatus (F) comprises: a counter member (1) that is arranged facing an endless belt-like member (11) rotating by contacting with a medium (S); a holding part (21) that is arranged corresponding to a region (Q6) in which the counter member (1) and the endless belt-like member (11) contact, that is the holding part (21) which holds an inner peripheral surface of the endless belt-like member (11), and that extends along a width direction of the endless belt-like member (11); and a supporting part (31) which is the supporting part (31) supporting the holding part (21), and in which a gap (35) is formed for the holding part (21) at a center part in the width direction.SELECTED DRAWING: Figure 2

Description

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

  In the image forming apparatus, the techniques described in Patent Documents 1 to 3 below are conventionally known with respect to a fixing apparatus that fixes an image transferred onto a medium.

  In Japanese Patent Application Laid-Open No. 2005-331574 as Patent Document 1, a pressure pad (64) is disposed inside a region where the fixing belt (54) contacts the heat roll (52), and the pressure pad (64) is a holder. The structure supported by the mounting plane of the attachment part (74) on the upper surface of the member (70) is described. It is also described that an elastic sheet material (76) is disposed between the attachment portion (74) and the pressure pad (64) corresponding to a portion where the pressure pad (64) receives pressure locally.

  In Japanese Patent Application Laid-Open No. 2005-037678 as Patent Document 2, an endless belt (510) of a fixing device (500) is supported by a soft pad (516) and a hard pad (514), and the hard pad (514) is disposed inside the belt. The structure supported by the support member (512) is described. In the configuration described in Patent Document 2, it is described that the dimensional accuracy is improved by forming the inner support member (512) by extrusion molding of aluminum.

  In Japanese Patent Application Laid-Open No. 2009-216910 as Patent Document 3, an endless belt (61) has a pad portion (65) and a head portion (64) from the inside in a pressure rotating body (6) of a fixing device (4). A configuration is described in which the head portion (64) is supported and supported by abutting the thin wall portions (upper long side portions 81a, 82a) of the side surfaces of the two support plates (81, 82). .

JP-A-2005-331574 ("0044"-"0049", "0060"-"0067", FIGS. 2 and 3) Japanese Patent Laying-Open No. 2005-037678 (“0121”-“0135”, FIG. 8) JP 2009-216910 A (“0038”-“0041”, “0052”-“0062”, FIG. 5 to FIG. 7)

  The present invention suppresses fluctuations in pressure distribution in a configuration in which an endless belt-shaped member is supported by a support from the inside, without requiring high component accuracy, compared to a configuration in which the support is supported in the entire width direction of the endless belt-shaped member. Doing this is a technical issue.

In order to solve the technical problem, a fixing device according to claim 1 is provided.
An endless belt-like member rotating in contact with the medium;
A facing member disposed to face the endless belt-shaped member;
A holding portion that presses the opposing member via the endless belt-like member by holding an inner peripheral surface of the endless belt-like member, the holding portion extending along a width direction of the endless belt-like member;
A support part for supporting the holding part, wherein the support part is formed with a gap with respect to the holding part at a central part in the width direction;
It is provided with.

According to a second aspect of the present invention, in the fixing device according to the first aspect,
The support part is formed integrally with the holding part.

According to a third aspect of the present invention, in the fixing device according to the first aspect,
The support part is configured separately from the holding part,
A convex part formed on at least one of the holding part and the support part, extending toward the other and contacting the other, the convex part disposed at both ends in the width direction; and
It is provided with.

According to a fourth aspect of the present invention, in the fixing device according to the third aspect,
The convex part provided on the support part;
It is provided with.

According to a fifth aspect of the present invention, in the fixing device according to the third or fourth aspect,
The tip of the convex part is formed in a curved surface.

According to a sixth aspect of the present invention, in the fixing device according to any one of the first to fifth aspects,
The holding portion is characterized in that a thickness in a direction in which the endless belt-like member and the facing member face each other in a region where the gap is present is thicker than the thickness in a region where the gap is not present.

According to a seventh aspect of the present invention, in the fixing device according to the sixth aspect,
The thickness of the holding part is formed so as to increase toward the center part in the width direction.

According to an eighth aspect of the present invention, in the fixing device according to the sixth aspect,
In the state where the endless belt-like member is not in contact with the opposing member, the shape of the holding portion is formed so that both end portions in the width direction of the holding portion have a gap with respect to the endless belt-like member. And

The invention according to claim 9 is the fixing device according to any one of claims 1 to 8,
The convex portion disposed outside the maximum width of the medium that can be transported in the width direction,
It is provided with.

In order to solve the technical problem, an image forming apparatus according to claim 10 is provided.
An image carrier,
A latent image forming apparatus for forming a latent image on the image carrier;
A developing device for developing a latent image of the image carrier into an image;
A transfer device for transferring the image held by the image carrier to a medium;
A fixing device according to any one of claims 1 to 9, wherein an image transferred on a medium is fixed.
It is provided with.

According to invention of Claim 1, 10, in the structure which supports an endless belt-shaped member with a support body from the inside, compared with the structure which supports a support body in the whole area of the width direction of an endless belt-shaped member, high component precision is obtained. The pressure distribution fluctuation can be suppressed without obtaining it.
According to the second aspect of the present invention, it is possible to easily assemble the fixing device as compared with a case where the fixing device is configured separately.
According to the third aspect of the present invention, it is possible to select a material corresponding to the rigidity and strength required for the support portion and the holding portion.
According to invention of Claim 4, compared with the case where a convex part is provided in a holding | maintenance part, the thickness by the side of a holding | maintenance part can be made more highly flexible.

According to the invention described in claim 5, it is possible to reduce the contact area of the convex portion and to easily suppress fluctuations in the pressure distribution as compared with the case where the convex shape is not formed.
According to the sixth aspect of the present invention, even if the holding portion bends under pressure, the pressure distribution in the width direction can be made to be uniform.
According to the seventh aspect of the invention, the pressure distribution can be made uniform in the width direction even if the pressing force is applied at both ends.
According to the eighth aspect of the present invention, it is possible to suppress the deviation of the endless belt-like member and the generation of wrinkles as compared with the case where there are no gaps at both ends in the width direction.
According to the ninth aspect of the present invention, it is possible to suppress the occurrence of local pressure fluctuations in the width direction as compared with the case where the convex portion is disposed inside the maximum width of the medium.

FIG. 1 is an overall explanatory view of an image forming apparatus according to a first embodiment. FIG. 2 is a schematic explanatory diagram of the fixing member of the first embodiment. FIG. 3 is an explanatory diagram of a support portion and a holding portion of the pressure belt of the first embodiment. FIG. 4 is an explanatory diagram of a relationship in length in the width direction of the pressure belt according to the first embodiment. FIG. 5 is an explanatory diagram of the fixing device according to the second embodiment. FIG. 6 is an explanatory diagram of the fixing device according to the third embodiment.

Next, specific examples of embodiments of the present invention (hereinafter referred to as examples) will be described with reference to the drawings, but the present invention is not limited to the following examples.
In order to facilitate understanding of the following description, in the drawings, the front-rear direction is the X-axis direction, the left-right direction is the Y-axis direction, the up-down direction is the Z-axis direction, and arrows X, -X, Y, -Y, The direction indicated by Z and -Z or the indicated side is defined as the front side, the rear side, the right side, the left side, the upper side, the lower side, or the front side, the rear side, the right side, the left side, the upper side, and the lower side, respectively.
In the figure, “•” in “○” means an arrow heading from the back of the page to the front, and “×” in “○” is the front of the page. It means an arrow pointing from the back to the back.
In the following description using the drawings, illustrations other than members necessary for the description are omitted as appropriate for easy understanding.

FIG. 1 is an overall explanatory view of an image forming apparatus according to a first embodiment.
In FIG. 1, a printer U as an example of an electronic apparatus according to the first exemplary embodiment of the present invention, which is an example of an image forming apparatus, is an example of an apparatus main body, and includes a printer main body U1 as an example of an image forming apparatus main body. Have. A front cover U1a as an example of an opening / closing member is disposed on the front surface of the printer body U1. The front cover U1a is supported so as to be openable and closable around the center of rotation. Further, a discharge tray TRh as an example of a discharge unit is formed on the upper surface of the printer U. Further, a rear cover U1b as an example of an opening / closing member is rotatably supported on the rear surface of the printer body U1. The rear cover U1b is rotatably supported between a closed position indicated by a solid line and an open position indicated by a broken line. The rear cover U1b as an example of an opening / closing member can open the rear surface of the printer main body U1 when a paper jam or an internal inspection is performed.

The printer U according to the first embodiment includes a controller C as an example of a control unit. The controller C is electrically connected to an image processing unit IPS, a laser drive circuit DL as an example of a latent image forming circuit, and a power supply circuit E. Therefore, the controller C can output a control signal to the image processing unit IPS and the like.
At the rear of the printer U, a photosensitive member PR as an example of an image holding member that is rotationally driven is supported. Around the photoconductor PR, along the rotation direction of the photoconductor PR, a charging roll CR, a latent image forming device LH, a developing device G, a transfer roll Tr as an example of a transfer device, and a cleaning device for an image carrier. As an example, a photoreceptor cleaner CL is arranged.

In FIG. 1, a charging roll cleaner CRc, which is an example of a cleaning device for a charging device, is disposed opposite to and in contact with the charging roll CR.
The latent image forming apparatus LH according to the first embodiment is an apparatus in which LEDs (Light Emitting Diodes) as an example of a latent image writing element are linearly arranged at predetermined intervals along a horizontal direction, a so-called LED head. It is configured.
The developing device G has a developing container V in which a developer is accommodated. In the developing container V, a developing roll Ga as an example of a developer holding member is disposed to face the photosensitive member PR. In the developing container V, a pair of circulation conveyance members Gb and Gc and a supply member Gd are disposed in order from the developing roll Ga. Further, a layer thickness regulating member Ge is disposed in the developing container V so as to face the developing roll Ga.

  A developer replenishing port V1 as an example of a replenishing portion is formed on the front upper surface of the developing container V. A developer supply path V3 as an example of a developer transport path is connected to the developer supply port V1. The developer supply path V3 is formed in a cylindrical shape extending forward. A supply auger V4 as an example of a developer conveying member is rotatably supported in the developer supply path V3. A toner cartridge TC as an example of a developer container is detachably supported at the front end of the developer supply path V3. The toner cartridge TC is formed with an outlet TC1 so that the developer can flow into the developer supply path V3 from the toner cartridge TC.

In FIG. 1, a paper feed tray TR <b> 1 as an example of a medium storage unit is disposed below the printer U. A pickup roll Rp as an example of a medium take-out member is disposed at the rear of the paper feed tray TR1. A separation roll Rs as an example of a medium separation member is disposed behind the pickup roll Rp. Above the separating roll Rs, a registration roll Rr as an example of a timing adjusting member is disposed.
A fixing device F is disposed above the transfer region Q4 where the photoconductor PR and the transfer roll Tr face each other. The fixing device F includes a heating roll Fh and a pressure belt Fp as examples of a fixing member. A fixing region Q6 is formed by the contact region of the pair of fixing members Fh and Fp.
Above the fixing device F, sheet guides SG1 and SG2 as examples of medium guide members are arranged. A discharge roll R1 as an example of a discharge member is disposed in front of the sheet guides SG1 and SG2.

(Description of image forming operation)
Print information is transmitted to the controller C of the printer U from a host computer or the like as an example of an external information transmission apparatus. When the controller C receives the print information, the image forming operation is started. The controller C outputs print information to the image processing unit IPS. The image processing unit IPS converts the print information into image information for forming a latent image, and outputs it to a laser driving circuit DL as an example of an image writing circuit at a preset time, that is, at a timing. The laser drive circuit DL outputs a drive signal to the latent image forming apparatus LH according to the input image information.

When the image forming operation is started, the photoconductor PR starts to rotate.
A charging voltage is applied from the power supply circuit E to the charging roll CR. In the charging region Q1 where the charging roll CR and the photoconductor PR face each other, the charging roll CR charges the surface of the photoconductor PR.
The charging roll cleaner CRc cleans the surface of the charging roll CR.
The latent image forming apparatus LH forms an electrostatic latent image corresponding to the image information on the surface of the photoconductor PR in the writing area Q2.

In the developing device G, the pair of circulation conveyance members Gb and Gc circulate and convey the developer inside the developing container V while stirring. The supply member Gd conveys the developer stirred by the circulation conveyance members Gb and Gc to the developing roll Ga. When the developer on the surface of the developing roll Ga passes through a region facing the layer thickness regulating member Ge, the layer thickness is regulated. A developing voltage is applied from the power supply circuit E to the developing roll Ga. In the developing region Q3 where the developing roll Ga and the photoconductor PR face each other, the electrostatic latent image on the photoconductor PR is developed into a visible image with the developer of the developing roll Ga.
The replenishment auger V4 is driven according to the amount of developer consumed in the developing device G, and the developer is replenished from the toner cartridge TC to the developing device G.

The pickup roll Rp sends out the recording sheet S accommodated in the paper feed tray TR1.
The separation rolls Rs are separated one by one when the pickup roll Rp sends out a plurality of recording sheets S. The recording sheets S separated one by one by the separating roll Rs are sent to the registration roll Rr. The registration roll Rr conveys the recording sheet S to the transfer area Q4 at a preset timing.
A transfer voltage is applied from the power supply circuit E to the transfer roll Tr. The transfer roll Tr transfers the toner image on the photoreceptor PR to the recording sheet S that passes through the transfer region Q4.
The photoconductor cleaner CL removes residual toner on the surface of the photoconductor PR in a cleaning region Q5 as an example of a cleaning region set on the downstream side of the transfer region Q4.

The recording sheet S on which the toner image is transferred in the transfer area Q4 is conveyed to the fixing device F in a state where the toner image is not fixed.
In the fixing device F, a fixing region Q6 is formed by the pressure contact region of the fixing members Fh and Fp. The recording sheet S conveyed to the fixing device F is fixed with a toner image by a pair of fixing members Fh and Fp in the fixing region Q6.
The recording sheet S on which the toner image is fixed is guided by sheet guides SG1 and SG2.
The discharge roll R1 discharges the recording sheet S to the discharge tray TRh.

(Description of fixing device)
FIG. 2 is a schematic explanatory diagram of the fixing member of the first embodiment.
1 and 2, in the fixing device F according to the first embodiment, the heating roll Fh includes a hollow cylindrical roll body 1 as an example of a counter member. Inside the roll body 1, a heater 2 as an example of a heat source is accommodated. The heater 2 extends in the axial direction and is turned on during image formation to control the temperature of the fixing area Q6 to a preset fixing temperature. Note that a gear (not shown) is supported at the end of the roll body 1, and driving is transmitted from a motor (not shown).

FIG. 3 is an explanatory diagram of a support portion and a holding portion of the pressure belt according to the first embodiment.
FIG. 4 is an explanatory diagram of a relationship in length in the width direction of the pressure belt according to the first embodiment.
In FIG. 2, the pressure belt Fp has a belt body 11 as an example of an endless belt-like member. Inside the belt main body 11, a pad 21 as an example of a holding portion is disposed corresponding to the fixing region Q6. The pad 21 according to the first embodiment includes a pad body 22 that contacts the inner peripheral surface of the belt body 11 as an example of a contact portion. The pad main body 22 is supported by a holder 23 as an example of a holding unit main body. 3 and 4, the pad 21 extends in the width direction of the recording sheet S in the first embodiment.

In FIG. 4, in Example 1, the pad 21 is formed so that the thickness in the facing direction of the heating roll Fh and the pressure belt Fp increases as it goes to the center in the width direction. That is, in FIG. 4, the pad 21 is formed in a kamaboko shape. Note that the thickness of the pad 21 in the facing direction can be easily changed by changing the thickness of the pad main body 22, but is not limited to this, and the thickness of the holder 23 can be changed, It is also possible to change both of the holders 23.
In particular, as shown in FIG. 4, in the state where the belt main body 11 is not in contact with the heating roll Fh, the shape of the pad 21 is such that the width direction both ends of the pad 21 have a gap 24 with respect to the belt main body 11. Is formed.

The holder 23 is formed with a recess 23a for supporting the pad body 22 on the surface on the fixing region Q6 side. Further, the holder 23 is formed with two groove portions 23b extending in parallel with the width direction on the surface opposite to the fixing region Q6.
In addition, the bad main body 22 of Example 1 is comprised by the silicone rubber as an example, and the holder 23 is comprised by the resin material whose rigidity is higher than the pad main body 22. FIG.

The pad 21 is supported by a frame 31 as an example of a support portion. The frame 31 according to the first exemplary embodiment includes a first frame 32 as an example of a first support unit disposed on the upstream side in the conveyance direction of the recording sheet S, and an example of a second support unit disposed on the downstream side. The second frame 33. The first frame 32 is formed in a flat plate shape extending in the width direction of the recording sheet S and in the opposing direction of the heating roll Fh and the pressure belt Fp. Similar to the first frame 32, the second frame 33 is bent to the first frame 32 from a flat plate portion 33a extending in the width direction and the opposing direction of the recording sheet S and an end portion of the flat plate portion 33a opposite to the fixing region Q6. And a bent portion 33b.
Note that the frame 31 of the first embodiment is made of a sheet metal having higher rigidity than the pad 21.

2 to 4, the end portions 32c and 33c on the pad 21 side of the frames 32 and 33 of the first embodiment are formed to be thin enough to fit in the width of the groove portion 23b. Convex portions 34 are formed at the left and right end portions in the width direction at the end portions 32c and 33c. The convex portion 34 is formed in a semi-cylindrical shape. Therefore, the convex part 34 is formed in a curved surface at the tip part (end part on the fixing region Q6 side). The convex part 34 contacts the groove part 23b and supports the pad 21. The term “both ends” as used herein does not mean the true end of the frame like the both ends 36 in FIG. 4, but means that they are positioned at least closer to the end than the center.
Therefore, in the first embodiment, the pad 21 is supported on the frame 31 by the two convex portions 34. Therefore, a gap 35 is formed between the frame 31 and the pad 21 in the range on the inner side in the width direction than the convex portion 34.

In addition, the convex part 34 of Example 1 is arrange | positioned on the outer side in the width direction rather than the width L1 of the recording sheet S of the largest magnitude | size which can be used with the printer U, ie, the maximum width L1 of the recording sheet S.
In FIG. 4, both end portions 36 of the frame 31 of the first embodiment extend outside the width of the belt body 11. Both ends of the frame 31 are supported by arms (not shown) and are pressed by springs 37 as an example of an elastic member. Therefore, the belt main body 11 is pressed toward the heating roll Fh by the pad 21 supported by the frame 31.
In FIG. 2, the frame 31 supports a lubricant application material 41 and support portions 42 and 43 that support the belt body 11 from the inside.

(Operation of Example 1)
In the printer U according to the first embodiment having the above-described configuration, the unfixed image on the recording sheet S receives heat and pressure when passing through the fixing region Q6 sandwiched between the heating roll Fh and the pressure belt Fp. Is done. In the fixing region Q6, the belt body 11 is pressed by the pad 21 to form a predetermined pressure distribution.
Here, the pad 21 is supported by the frame 31, and the shape of the portion supported by the frame gives distortion to the pad 21. When the pad is distorted, uneven pressure distribution in the fixing region Q6 may occur, and fixing failure may occur, the recording sheet S may skew, or wrinkles may occur in the recording sheet S. As in the techniques described in Patent Documents 1 and 2, in a configuration in which a member corresponding to a pad is supported by a “surface” such as a mounting surface of a member corresponding to a frame, the accuracy of the surface is improved over the entire width direction. It is necessary to secure. Therefore, there is a problem that the manufacturing cost increases and becomes an obstacle in mass production. As in Patent Document 1, in the configuration in which the elastic sheet is arranged, the number of parts increases, the manufacturing cost increases, and it is necessary to secure a space for arranging the elastic sheet, which is not suitable for downsizing. .

Further, as in the technique described in Patent Document 3, the configuration in which the upper long side portion of the plate-shaped frame is abutted is configured to support the pad with a “line” extending in the width direction. It is necessary to ensure the accuracy of the side in the width direction. Therefore, there are the same problems as in Patent Documents 1 and 2.
On the other hand, in the first embodiment, the pad 21 that supports the belt main body 11 from the inside is supported with respect to the frame 31 by two convex portions 34 in the width direction. In other words, the pad 21 is supported by “dots”. Therefore, it is sufficient to ensure the accuracy of two portions of the convex portion 34, and it is easy to ensure the accuracy as compared with the configurations described in Patent Documents 1 to 3. Therefore, the shape of the convex part 34 of the frame 31 hardly distorts the pad 21, and the adverse effect on the pressure distribution is reduced. Therefore, in the configuration in which the belt main body 11 is supported by the pad 21 from the inside, the pressure distribution fluctuation is suppressed without requiring high component accuracy compared to the configuration in which the pad 21 is supported in the entire width direction of the belt main body 11. .

Further, in the fixing device F according to the first exemplary embodiment, the pad 21 and the frame 31 are configured separately. Therefore, it is possible to select the material of the pad 21 and the frame 31 according to purposes such as required strength, rigidity, shape, and heat resistance, as compared with the case where they are integrally formed. Therefore, the degree of freedom in design is improved.
Further, in the fixing device F of the first embodiment, the convex portion 34 is provided not on the pad 21 but on the frame 31. Therefore, by providing no protrusion on the side of the pad 21 that is to be bent, the thickness on the side of the pad 21 can be made more flexible. That is, if the protrusions 34 are provided on the pad 21 side, the thickness of the portion where the protrusions 34 at the end portions are increased, which may cause the deflection to vary, but this is solved in the first embodiment.

  Furthermore, in the fixing device F of the first embodiment, the pad 21 and the frame 31 can be assembled simply by abutting the convex portion 34 against the groove portion 23b. Therefore, the assembly is easier than in the case of screwing or the like. Moreover, in Example 1, the edge parts 32c and 33c of each flame | frame 32 and 33 are fitting in the groove part 23b. The pad 21 is pushed downstream in the rotation direction of the belt main body 11 with the rotation of the belt main body 11 in contact. Even if a force pushed downstream is applied, the end portions 32c and 33c are fitted in the groove portion 23b, thereby preventing the circumferential position of the pad 21 from fluctuating. Therefore, as compared with a configuration in which the end portions 32c and 33c and the convex portion 34 are not fitted in the groove portion 23b, fluctuations in the position of the pad 21 in the circumferential direction (conveyance direction of the recording sheet S) are suppressed, and the pressure distribution in the fixing region Q6. Fluctuations are suppressed. The clearance (gap) between the end portions 32c and 33c and the groove portion 23b is desirably secured so that the end portions 32c and 33c do not distort the groove portion 23b.

  Further, in the fixing device F according to the first exemplary embodiment, the tip of the convex portion 34 is a curved surface. The shape of the convex portion 34 may not be a semi-cylindrical shape, but may be a polygonal column shape such as a quadrangular column, and the contact portion with the groove 23b may be a planar shape. However, when the shape is a polygonal column, the area of the contact portion with the groove 23b is increased, and the surface accuracy is required. On the other hand, if the tip of the convex portion 34 is a curved surface, when viewed in the width direction, it contacts the groove 23b at one point (a line when viewed in the rotational direction of the belt body 11). Therefore, the contact area with the groove 23b is reduced, and fluctuations in pressure distribution due to processing accuracy are easily suppressed.

Further, in the fixing device F of the first embodiment, a gap 35 is formed between the pad 21 and the frame 31 inside the convex portion 34 with respect to the width direction. Therefore, as shown by the broken line in FIG. 4, in a state where the heating roll Fh and the pressure belt Fp are in contact and pressure is applied to the fixing region Q <b> 6, the pad 21 bends but the pad 21 does not contact the frame 31. A gap 35 is secured. When the pad 21 is bent and touches the frame 31, the deflection of the pad 21 is affected by the accuracy of the contacted portion, and the pressure distribution may not be a predetermined distribution. On the other hand, in the first embodiment, the gap 35 is secured, and even if the pad 21 is bent, fluctuations in the pressure distribution are suppressed.
In the first embodiment, the convex portion 34 is disposed outside the maximum width (paper passing range) L1 of the recording sheet S. When the convex part 34 is arrange | positioned inside the maximum width L1, the pressure of the fixing area Q6 may rise locally in the position where the convex part 34 contacts. On the other hand, in the configuration in which the convex portion 34 is disposed outside the maximum width L1, a local increase in pressure is suppressed.

In particular, in the fixing device F of the first embodiment, as shown in FIG. 4, when the belt main body 11 is not in contact with the heating roll Fh, both end portions in the width direction of the pad 21 have a gap 24 with respect to the belt main body 11. The shape of the pad 21 is formed so as to have Therefore, even if the pressure rises at the position where the convex portion 34 contacts, the pressure rise is suppressed by the gap 24 minutes. Therefore, even at the portion where the convex portion 34 comes into contact, the local increase in pressure is suppressed and the width becomes nearly uniform in the width direction. If the pressure is locally increased at both ends in the width direction, there is a risk that the belt main body 11 may be offset or wrinkles may be generated in the belt main body 11, and the transportability may be reduced. Is done.
Further, in the fixing device F according to the first exemplary embodiment, the pad 21 is formed thicker toward the center in the width direction. Therefore, as shown by the broken lines in FIG. 4, even if the center portion of the pad 21 is bent by the pressing of the springs 37 at both ends, the pressure distribution in the fixing region Q6 can be made uniform in the width direction.

Next, a second embodiment of the present invention will be described. In the description of the second embodiment, components corresponding to the components of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. To do.
This embodiment is different from the first embodiment in the following points, but is configured in the same manner as the first embodiment in other points.
FIG. 5 is an explanatory diagram of the fixing device according to the second embodiment.
In FIG. 5, the fixing device F according to the second embodiment has a heating belt Fh ′ and a pressure roll Fp ′, unlike the combination of the heating roll Fh and the pressure belt Fp according to the first embodiment. Therefore, the heating belt Fh ′ of the second embodiment includes the belt main body 11 ′, the pad 21 ′, and the frame 31 ′ similar to the belt main body 11, the pad 21, and the frame 31 of the first embodiment, and the heater 2 is built in. Yes.

(Operation of Example 2)
In the fixing device F according to the second embodiment having the above-described configuration, similarly to the first embodiment, it is possible to suppress fluctuations in the pressure distribution in the fixing region Q6 without requiring a high parts system for the frame 31 ′.

Next, the third embodiment of the present invention will be described. In the description of the third embodiment, the same reference numerals are given to the components corresponding to the components of the first and second embodiments, and the detailed description thereof will be given. Is omitted.
This embodiment is different from the first and second embodiments in the following points, but is configured similarly to the first and second embodiments in other points.
FIG. 6 is an explanatory diagram of the fixing device according to the third embodiment.
In FIG. 6, the fixing device F according to the third embodiment includes a heating belt Fh ′ and a pressure roll Fp ′ as in the second embodiment. In the heating belt Fh ′ of the third embodiment, instead of the heater 2 and the pad 21 ′ of the second embodiment, a plate heater 51 as an example of a holding unit and an example of a heat source is disposed. Accordingly, the plate heater 51 is supported on the frame 31 ′ by the convex portion 34. Note that the present invention is not limited to this configuration, and the plate heater 51 may be supported by the holder 23 and the holder 23 may be supported by the frame 31 ′.

(Operation of Example 3)
In the fixing device F of the third embodiment having the above-described configuration, as in the first embodiment, it is possible to suppress fluctuations in the pressure distribution in the fixing region Q6 without requiring a high parts system for the frame 31 ′ and the like. .

(Example of change)
As mentioned above, although the Example of this invention was explained in full detail, this invention is not limited to the said Example, A various change is performed within the range of the summary of this invention described in the claim. It is possible. Modification examples (H01) to (H08) of the present invention are exemplified below.
(H01) In the above-described embodiment, the printer U as an example of the image forming apparatus is illustrated. However, the present invention is not limited to this. For example, the printer U is configured by a copying machine, a FAX, or a multifunction machine having a plurality or all of these functions. It is also possible to do.

(H02) In the above embodiment, the printer U has exemplified the configuration in which a single color developer is used. However, the present invention is not limited to this. For example, the printer U can be applied to a multicolor image forming apparatus having two or more colors. .
(H03) In the above embodiment, the case where one of the fixing members Fh and Fp has a roll configuration and the other has a belt configuration is exemplified, but the present invention is not limited to this. For example, both belt configurations are possible.

(H04) In the above-described embodiment, it is desirable that the pads 21, 21 'and the frames 31, 31' are configured separately, but they can also be configured integrally. At this time, the portion of the convex portion 34 is integrally formed with the pads 21 and 21 'while securing the gap 35. If the accuracy of the portion of the convex portion 34 is ensured, the frame 31, 31' side adversely affects the pressure distribution. Giving is suppressed.
(H05) In the above-described embodiment, the convex portion 34 is exemplified to be provided on the side of the frames 31, 31 ′, but is not limited thereto. It can also be provided on the pads 21 and 21 'side. Moreover, it is also possible to provide a convex part in both.
(H06) In the above embodiment, the pad main body 22 and the holder 23 are illustrated as separate structures, but may be integrated.

(H07) In the above-described embodiment, the configuration in which two convex portions 34 are provided at both end portions in the width direction is exemplified, but three or more convex portions 34 may be provided. However, as the number of the convex portions 34 increases, it becomes difficult to ensure the accuracy between the convex portions 34, so two is most desirable. Moreover, although the structure which provides the convex part 34 in the both ends of the flame | frame 31 is desirable, it is not limited to this. It is possible to arrange at least closer to the end than the center. Further, although it is preferable to dispose outside the maximum sheet passing width, it is also possible to dispose inside the maximum sheet passing width.
(H08) In the above embodiment, it is desirable that the pad 21 has a thick central portion in the width direction, but the thickness may be constant depending on the required pressure distribution or the like. Further, the shape is not limited to the kamaboko shape having a continuous curved surface, and a stepped shape including a stepped surface may be used.

1 ... Opposing member,
11, 11 '... endless belt-like member,
21, 21 ′, 51... Holding part,
24: A gap with respect to the endless belt-like member at both ends in the width direction,
31, 31 '... support part,
34 ... convex part,
35 ... Gap,
F: Fixing device,
G: Developing device,
L1 ... the maximum width of the medium,
LH ... latent image forming device,
PR: Image carrier,
Q6 ... contact area,
S ... medium,
Tr: Transfer device,
U: Image forming apparatus.

Claims (10)

An endless belt-like member rotating in contact with the medium;
A facing member disposed to face the endless belt-shaped member;
A holding portion that presses the opposing member via the endless belt-like member by holding an inner peripheral surface of the endless belt-like member, the holding portion extending along a width direction of the endless belt-like member;
A support part for supporting the holding part, wherein the support part is formed with a gap with respect to the holding part at a central part in the width direction;
A fixing device comprising: The fixing device according to claim 1, wherein the support portion is integrally formed with the holding portion. The support part is configured separately from the holding part,
A convex part formed on at least one of the holding part and the support part, extending toward the other and contacting the other, the convex part disposed at both ends in the width direction; and
The fixing device according to claim 1, further comprising: The convex part provided on the support part;
The fixing device according to claim 3, further comprising: The fixing device according to claim 3 or 4, wherein a tip portion of the convex portion is formed on a curved surface. The thickness of the holding portion in a direction in which the endless belt-like member and the facing member face each other in a region where the gap is present is thicker than the thickness in a region where the gap is not present. The fixing device according to any one of the above. The fixing device according to claim 6, wherein the thickness of the holding portion is formed so as to increase toward a central portion in the width direction.   In the state where the endless belt-like member is not in contact with the opposing member, the shape of the holding portion is formed so that both end portions in the width direction of the holding portion have a gap with respect to the endless belt-like member. The fixing device according to claim 6. The convex portion disposed outside the maximum width of the medium that can be transported in the width direction,
The fixing device according to claim 1, further comprising: An image carrier,
A latent image forming apparatus for forming a latent image on the image carrier;
A developing device for developing a latent image of the image carrier into an image;
A transfer device for transferring the image held by the image carrier to a medium;
A fixing device according to any one of claims 1 to 9, wherein an image transferred on a medium is fixed.
An image forming apparatus comprising:

Images