JP5609543B2 - Fixing device and image forming apparatus using the same - Google Patents

Description

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

As conventional fixing devices, for example, those described in Patent Documents 1 to 5 have already been proposed.
In Patent Document 1, a heating device is provided on one fixing roller of a pair of fixing rollers, and a flexible fixing belt having a longer circumference than the fixing roller is provided on the outer periphery of the fixing roller. A technique in which a slack portion is formed on the fixing belt at a downstream side in the recording medium feeding direction from the nip portion where the pair of fixing rollers are pressed against each other via the nip, and this slack portion is brought into contact with the outer peripheral surface of the other fixing roller. It is.
Patent Document 2 includes a fixing roller, a fixing belt, and a pressure roller. The fixing roller has a low hardness and a low bending rigidity. The fixing belt has a shape of the fixing roller at the exit of the nip portion. Therefore, the curvature of the exit of the nip portion is reduced. This is a technique for easily separating the paper using the waist of the paper.
In Patent Document 3, a fixing belt is installed between a heating roller and a winding roller, a pressure roller is urged to the winding roller via the fixing belt, and a fixing nip between the pressure roller and the fixing belt is detected. An auxiliary roller that is biased toward the winding roller is provided on the downstream side of the roller, and when pressed, the surface of the contact portion of the winding roller is recessed, and the fixing belt is wound between the fixing nip portion and the contact portion of the auxiliary roller. In this technique, a curved portion having a large curvature is formed while separating from the surface of the hanging roller, and the recording medium is peeled from the fixing belt by the curved portion.
Patent Document 4 discloses a fixing roller, a tension roller, an endless fixing belt stretched between the two, a pressure roller disposed outside the fixing belt and pressed against the fixing roller, and a fixing belt. And a pressing member for pressing the pressure roller downstream from the pressure contact portion where the pressure roller is brought into pressure contact with the fixing roller, and the nip width can be increased. This is a technique for increasing the curvature of the fixing belt on the exit side.
In Patent Document 5, a fixing belt module in which a fixing belt is stretched by a fixing roll and a stretching roll, and a press belt that is arranged so as to be pressed against the fixing belt module to form a nip portion between the fixing belt module and the fixing belt module. A pressure belt module, and the fixing belt module is disposed so as to be supported from the inside of the fixing belt on the downstream side in the recording material conveyance direction away from the nip portion, and a peeling pad for bending the advancing direction of the fixing belt; This is a technology that has

JP 2002-207380 A (Embodiment of the Invention, FIG. 2) JP 2002-268436 A (Embodiment of the Invention, FIG. 1) JP 2003-330310 A (Embodiment of the Invention, FIG. 1) Japanese Patent Laying-Open No. 2005-234103 (Best Mode for Carrying Out the Invention, FIG. 1) JP 2006-243471 A (Best Mode for Carrying Out the Invention, FIG. 2)

  The technical problem of the present invention is that a recording material is sandwiched and conveyed between a belt-shaped heating rotator and a pressure rotator, and a plurality of members are arranged opposite to the pressure rotator in order to secure a wide fixing area. In this manner, a fixing device and an image forming apparatus using the same that can prevent image disturbance caused by a deviation between a heating rotator and a recording material are provided.

The invention according to claim 1 has a belt-like heating rotator that has an elastic layer at least in part and rotates by heating, and is brought into pressure contact with the surface of the heating rotator and rolls together with the heating rotator. A pressure rotator that partially has an elastic layer and that heat-presses and fixes an unfixed toner image on the recording material, and that is disposed in contact with the back surface of the heating rotator facing the pressure rotator. An opposing rotator that rotates with the rotator and sandwiches and conveys the recording material on the heating rotator between the rotating rotator and extends in the width direction intersecting the moving direction of the heating rotator. Provided on the back surface of the heating rotator and adjacent to the downstream side of the first contact area between the counter rotator and the pressure rotator, and the heating rotator is Direction from the surface of the pressure rotator after being placed in contact with the pressure rotator So as to further bent shape, and a pressing member for pressing the heating rotating body, of the heating rotating body, from the first contact zone between the pressure rotating body and the counter rotator the second contact area set to be narrow with respect to the transporting direction of the recording material, and the heating rotating body and the pressure in the pressure rotating body side of the pressing member between the well and the pressing member and the pressure rotating body It is provided on the first contact area side with the rotating body, and the central portion projects in a convex shape toward the first contact area side from both ends with respect to the crossing direction intersecting the moving direction of the heating rotating body. A fixing device including a protruding portion .

The invention according to claim 2 is the fixing device according to claim 1, wherein the first pressure rotating body in the second contact zone in comparison with the maximum amount of bite opposing rotating member for pressurizing rotator in contact zone The fixing device is characterized in that the maximum biting amount of the pressing member with respect to is set small.
According to a third aspect of the present invention, in the fixing device according to the first or second aspect of the present invention, the second contact area is compared with the peak pressure between the pressure rotating body and the counter rotating body in the first contact area. The fixing device is characterized in that a peak pressure between the pressure rotator and the pressing member is set small.
The invention according to claim 4, in the fixing device according to any one of claims 1 to 3, the bent shape corners of provided pressure rotating body side and said heating rotary member the pressure rotating body of the pressing member it is the fixing device according to claim in which the heating rotating body is provided with a guide portion that is guided bite.

The invention according to claim 5 is the fixing device according to any one of claims 1 to 4, from the center portion toward the tip portion in the longitudinal direction of the provided and the pressing member on the surface of the pressure rotating body side of the pressing member according formed such that the surface away from the pressure rotating body, wherein a fixing device which is characterized in that it comprises a pressurizing part for pressurizing the heating rotating body with respect to pressure rotating body.
According to a sixth aspect of the present invention, in the fixing device according to any one of the first to fifth aspects, the counter rotating member has a heating source.

The invention according to claim 7 is an image forming apparatus for forming an unfixed toner image on a recording material, and an unfixed toner image on the recording material formed by the image forming apparatus is heated and pressure-fixed. An image forming apparatus comprising the fixing device according to any one of 6 to 6 .

According to the first aspect of the present invention, the recording material is sandwiched and conveyed between the belt-shaped heating rotator and the pressure rotator, and a plurality of members are provided to the pressure rotator in order to secure a wide fixing area. In the mode of being opposed to each other, it is possible to prevent image disturbance caused by a deviation between the heating rotator and the recording material.
Furthermore, when the recording material is peeled from the heating rotator, the pressure distribution at the peeled portion with respect to the recording material can be kept better as compared with the aspect without this configuration.
According to the second aspect of the present invention, the path in the fixing area of the recording material is a substantially S-shaped path, and the cause of the deviation between the heating rotator and the recording material in the second contact area of the fixing area. Even if the shearing force is easily generated, it is possible to effectively prevent image disturbance due to the deviation between the heating rotator and the recording material.
According to the third aspect of the present invention, the shearing force that causes the deviation between the heating rotator and the recording material is reduced in the second contact area of the fixing area as compared with the aspect without this configuration. Therefore, the image disturbance due to the shift between the heating rotator and the recording material can be effectively prevented.
According to the invention of claim 4, while ensuring the second contact area by the pressing member, the recording material passing through the contact area between the heating rotator and the pressure rotator is reliably peeled from the heating rotator. be able to.
According to the fifth aspect of the present invention, when the recording material passing through the contact area between the heating rotator and the pressurizing rotator is peeled from the heating rotator, the pressure distribution at the peeling site with respect to the recording material is better. Can be kept in .
According to the invention which concerns on Claim 6 , the heating efficiency to a fixing area can be improved.
According to the seventh aspect of the present invention, the recording material is sandwiched and conveyed between the belt-like heating rotator and the pressure rotator, and a plurality of members are attached to the pressure rotator in order to secure a wide fixing area. It is possible to prevent image disturbance due to the deviation between the heating rotator and the recording material in the face-to-face arrangement, and the recording material is removed from the heating rotator as compared to the aspect without this configuration. In peeling, it is possible to construct an image forming apparatus including a fixing device capable of maintaining a better pressure distribution at the peeling portion with respect to the recording material .

(A) is explanatory drawing which shows the outline | summary of embodiment of the fixing device to which this invention is applied, (b) is explanatory drawing which shows typically the state of the fixing area. 1 is an explanatory diagram illustrating an overall configuration of an image forming apparatus according to a first embodiment. 2 is an explanatory diagram illustrating details of a fixing device used in Embodiment 1. FIG. FIG. 3 is an explanatory diagram illustrating a peripheral structure of a fixing area of the fixing device used in the first embodiment. (A) is a perspective view which shows a press pad, (b) is the arrow line view seen from B direction in (a). In the figure, reference numerals x, y, and z indicate the directions of three axes (x axis, y axis, and z axis) in space. (A) is the perspective view of the peeling member which is one element of a press pad, (b) is the arrow view seen from B direction in (a), (c) is the arrow view seen from C direction in (b). (D) is sectional drawing equivalent to the DD line in (a), (e) is a perspective view which shows the peeling member which concerns on a comparison form. In the figure, reference numerals x, y, and z indicate the directions of three axes (x axis, y axis, and z axis) in space. (A) is explanatory drawing which shows an example of the attachment structure of a press pad, (b) is explanatory drawing which shows the other example of the attachment structure of a press pad. (A) is an explanatory view schematically showing the state of the fixing area of the fixing device used in Embodiment 1, and (b) is an explanatory view showing the relationship between the process direction position and the pressure in the fixing area. FIG. 3 is an explanatory diagram schematically illustrating a shift phenomenon that occurs between a fixing belt and a sheet in a fixing region of the fixing device used in the first exemplary embodiment. FIG. 4 is an explanatory diagram analyzing the behavior of a sheet in a fixing area of the fixing device used in the first embodiment. (A) is explanatory drawing which shows typically the relative positional relationship of a press pad and a press roll, (b) is explanatory drawing which shows the relationship between the process direction position and pressure of a press pad. (A) is explanatory drawing which shows the outline | summary of the comparative form which does not bite a press pad with respect to a pressure roll, (b) is explanatory drawing which expanded the B section in (a), (c) is in (b) It is explanatory drawing which shows typically the phenomenon which arises in the no-pressurization area | region. (A) is explanatory drawing which shows typically the layout which looked at the fixing apparatus from the upper part, (b) shows typically the pressure distribution of the fixing nip area | region of the aspect using the press pad whose pressurization area | region is planar. Explanatory drawing (c) is explanatory drawing which shows typically the pressure distribution of the fixing nip area | region of the aspect using the press pad to which the pressurization part was added. (A) is explanatory drawing which shows typically the pressure distribution of the aspect using the press pad to which the protrusion part was added, (b) is explanatory drawing which shows typically the pressure distribution of the aspect using the press pad without a protrusion part. FIG. (A) is explanatory drawing which shows an example of the conveyance state of the sheet | seat which passes through a fixing area, (b) is description which shows the effect | action to the sheet | seat by the aspect using the press pad to which the protrusion part was added in Embodiment 1. FIG. FIG. 4C is an explanatory diagram showing changes in the action on the paper according to the aspect in which the curvature of the leading edge curved edge of the protrusion is changed. (A) is a graph showing the nip pressure distribution in the fixing region of the fixing device according to Example 1, and (b) is a graph showing the nip pressure distribution in the fixing region of the fixing device according to the comparative example. FIG. 6 is a graph showing the relationship between the width dimension of a pressing pad and color noise using the fixing device according to Example 2. FIG. 10 is a graph showing the relationship between image density and color noise using a fixing device according to Example 3.

Outline of Embodiment FIG. 1A is an explanatory diagram showing an outline of an embodiment of a fixing device to which the present invention is applied. This type of fixing device is, for example, an image forming apparatus employing an electrophotographic system. Used for. FIG. 1B shows details of the fixing area of the fixing device.
In this case, the image forming apparatus includes a toner image producing device that forms an unfixed toner image on a recording material, a fixing device that fixes an unfixed toner image on the recording material produced by the toner image producing device, and Is provided.
As shown in FIGS. 1A and 1B, the fixing device includes a belt-like heating rotator 1 that has at least a part of an elastic layer 1a and is heated and rotated, and the heating rotator 1 includes: A pressure rotator 2 that is brought into pressure contact with the surface and rolls together with the heating rotator 1, has an elastic layer 2 a at least in part, and heat-presses and fixes an unfixed toner image T on the recording material 6; The recording material on the heating rotator 1 is placed in contact with the back surface of the heating rotator 1 facing the pressurizing rotator 2 and rotates together with the heating rotator 1 and between the pressurizing rotators 2. The counter rotator 3 that sandwiches and conveys 6, and is provided so as to extend long along the width direction intersecting the moving direction of the heating rotator 1. Adjacent to the downstream side of the first contact area N ₁ between the pressurizing rotating body 2 and arranged in contact A pressing member 4 that presses the heating rotator 1 so that the heating rotator 1 has a bent shape whose direction is changed from the surface of the pressing rotator 2 after the heating rotator 1 is placed in contact with the pressurizing rotator 2. Of the heating rotator 1, the first contact area N ₁ between the counter rotator 3 and the pressurizing rotator 2 is more than the first contact area N ₁ between the pressing member 4 and the pressurizing rotator 2. The contact area N ₂ of ₂ is set narrower than the conveyance direction of the recording material 6.
In FIG. 1A, reference numeral 5 denotes a heating source that sandwiches and conveys the heating rotator 1 to and from the pressurizing rotator 2 and heats the heating rotator 1. In FIG. Although it is built in the rotator 3, the method of heating the heating rotator 1 is not limited to this. For example, a heating source is added to the surface of the counter rotator 3, or the heating rotator 1 is stretched. Of course, other stretching members to be transported and heating members arranged in contact with or non-contact with the heating rotator 1 may be used as the heating source.

In such technical means, the belt-like heating rotator 1 may be a belt-like rotator heated by the heating source 5, and may be at least driven across the counter rotator 3 and rotated, An appropriate number of stretching members other than the counter-rotating body 3 may be used for the rotation, and the counter-rotating body 3 or the stretching member may be used as a drive source for rotational driving.
Further, the heating source 5 of the heating rotator 1 may be one that heats from the front surface or the back surface of the heating rotator 1, and the heating rotator 1 itself incorporates the heating source itself or a part of the heating source (for example, A mode in which a thin metal layer such as copper that generates heat due to a change in magnetic flux is provided in the heating rotator 1 and the magnetic flux generated by the magnetic flux generator is applied to the thin layer is also possible.
Further, from the viewpoint that the recording material 6 is nipped and conveyed between the pressure rotator 2 and the heating rotator 1, the pressure rotator 2 needs to roll together with the heating rotator 1.
Here, when the elastic layer 2a of the pressurizing rotator 2 has a lower elastic modulus (easily elastically deformed) than the elastic layer 1a of the heating rotator 1, the heating rotator 1 is pressed against the counter rotator 3 and pressed. It moves via the path | route which bites into the pressurization rotary body 2 side between the bodies 2. FIG.

Further, as the pressing member 4, a recording material is provided at a bent corner portion provided along a contact surface between a supported member supported by a predetermined supporting portion and the heating rotator 1 of the supported member. The aspect which has the peeling member which peels 6, and the aspect which fixedly supports via the supporting member with respect to the holding member which the heating rotary body 1 can hold | maintain may be selected suitably.
Further, in this embodiment, the size relationship to the transport direction of the recording material 6 in the first contact zone N ₁ and the second contact zone N ₂ have been identified.
That is, in the present embodiment, since the first contact area N ₁ > the second contact area N ₂ , the first contact area N ₁ and the second contact area are used as the fixing area path of the recording material 6. A route with N ₂ and a non-contact zone N ₀ between them is obtained.
At this time, in the first contact area N ₁ and the second contact area N ₂ , a shear force is generated between the heating rotator 1 and the recording material 6 in the second contact area N ₂ due to a change in curvature and direction. There is a concern that the distortion will occur. In this state, in the second contact area N ₂ , the distortion tends to be larger in the outlet section than in the inlet section along the conveyance direction of the recording material 6. In this example, however, the second contact area N because ₂ is narrower than the first contact zone N _1, the elastic layer 1a of the heating rotating body 1 absorbs the strain.
In this respect, if the second contact area N ₂ becomes wider than the first contact area N ₁ , the elastic layer 1a of the heating rotator 1 cannot absorb the strain in the second half of the second contact area N ₂ , and heating is performed. There is a possibility that a deviation occurs between the rotating body 1 and the recording material 6.

Next, representative aspects or preferred aspects of the present embodiment will be described.
First, facing the rotating body 3 with respect to pressure rotating body 2, for the bite amount of the pressing member 4, FIG. 1 (b), the opposite rotating body 3 with respect to pressure rotating body 2 in the first contact zone N ₁ it is preferable to set a small maximum bite amount h ₂ of the pressing member 4 with respect to pressure rotating body 2 in the second contact zone N ₂ as compared with the maximum bite amount h ₁ of.
In this aspect, when such a biting amount is set, the fixing area path of the recording material 6 is substantially S-shaped by the first contact area N ₁ , the second contact area N _2, and the non-contact area N ₀ between them. Path is obtained. In this substantially S-shaped path, since the curvature and the direction change are large in the first contact area N ₁ and the second contact area N ₂ , the shearing force is generated between the heating rotator 1 and the recording material 6. Works and distortion is likely to occur. However, in the case of this aspect, in the second contact area N ₂ , since the maximum biting amount h ₂ by the pressing member 4 is reduced, the pressing force by the pressing member 4 is reduced, and the shearing force that causes the deviation correspondingly. It can be made smaller.
Further, both the contact region N _1, N ₂ Preferred pressure conditions, as shown in FIG. 1 (b), between the first contact zone N pressurizing rotator 2 in ₁ and the counter rotor 3 and the like can be set small peak pressure p ₂ between the pressure rotating body 2 and the pressing member 4 in the contact zone N ₂ the second compared to the peak pressure p _1. Setting the peak pressure in this context, in the fixing zone the second contact zone of N _2, the peak pressure p ₂ is smaller amount, it is possible to reduce the pressing force by the pressing member 4, the heating rotator 1 and the recording material 6 can be reduced in shearing force.

Furthermore, as a preferable aspect of the pressing member 4, the heating rotator 1 is provided on the pressing rotator 2 side of the pressing member 4 and the bent shape corners of the heating rotator 1 bite into the pressing rotator 2. The aspect provided with the guide part (not shown) which is guided is mentioned. In this aspect, the guide portion may be appropriately selected as long as the guide portion bites into the pressure rotator 2 so that the bent corner portion of the heating rotator 1 is buried.
Further, as another preferable aspect of the pressing member 4, the pressing member 4 is provided on the surface of the pressing member 4 on the side of the pressing rotator 2, and the surface is added to the pressing member 4 from the center to the end in the longitudinal direction. The aspect provided with the pressurization part (not shown) formed so that it may leave | separate from the pressure rotary body 2, and pressurizes the heating rotary body 1 with respect to the said pressurization rotary body 2 is mentioned. At this time, the pressure distribution at the peeled portion with respect to the recording material 6 corresponding to the central portion of the pressing member 4 is increased, and the insufficient pressurization at the central portion due to the loosening of the pressing member 4 is eliminated.
Further, from the viewpoint of maintaining a good pressure distribution at the peeled portion of the recording material 6, another preferable embodiment of the pressing member 4 is the pressure rotating body 2 side of the pressing member 4 and the heating rotating body 1. wherein provided in the first contact zone N ₁ side of the pressure rotating body 2, the contact center portion than both end portions of the first to a direction crossing the moving direction of the heating rotating body 1 region N ₁ side The aspect provided with the protrusion part (not shown) which protrudes in convex shape toward is mentioned. The protruding portion here does not necessarily need to be curved. It may be protruding in a mountain shape, or may be appropriately selected as long as the central portion protrudes.

The fixing device described above is used as one component of the image forming apparatus.
That is, the image forming apparatus forms an unfixed toner image T (not shown) on the recording material 6 and an unfixed toner image T on the recording material 6 formed by the image forming apparatus. It is only necessary to include the above-described fixing device that performs heat and pressure fixing.
Here, as an image forming apparatus, any apparatus such as an electrophotographic system or an electrostatic recording system may be appropriately selected as long as it forms an unfixed toner image T on the recording material 6 using toner.

Embodiment 1
<Image forming apparatus>
FIG. 2 is an explanatory diagram showing Embodiment 1 of the image forming apparatus to which the present invention is applied.
In FIG. 1, an image forming apparatus 20 is an intermediate transfer type image forming apparatus called a so-called tandem type, and each color component (in this example, yellow (Y), magenta (M), cyan (C), A plurality of image forming units 22 (22a to 22d) on which black (K) toner images are formed, and belt-like intermediate transfer members 23 are arranged at positions corresponding to the respective image forming units 22. In addition, a primary transfer unit 24 (for example, a primary transfer roll) is disposed on the back surface of the intermediate transfer member 23 corresponding to each image forming unit 22, and each image forming unit is formed on a part of the intermediate transfer member 23. A secondary transfer device (for example, a secondary transfer roll) 25 is provided for each color component toner image primarily transferred from the unit 22 to the intermediate transfer body 23 by the primary transfer device 24 to be secondarily transferred to the paper P as a recording material. Each color component toner image was transferred The downstream side of the paper P is disposed a fixing device 60 is intended to fix the unfixed toner image on the sheet P.

Here, each image forming unit 22 includes a drum-shaped photoconductor 30 that rotates in a predetermined direction. Around the photoconductor 30, a charger 31 that charges the photoconductor 30, and this charger An exposure device 32 such as a laser scanning device for writing an electrostatic latent image on the photosensitive member 30 charged by 31, and a color toner corresponding to the electrostatic latent image written on the photosensitive member 30 by the exposure device 32 The developing unit 33 that develops the toner and the toner image developed by the developing unit 33 are cleaned of the residue on the photoreceptor 30 after the toner image developed by the primary transfer unit 24 is primarily transferred onto the intermediate transfer member 23. And a cleaning device 34.
The intermediate transfer member 23 is stretched around a plurality of stretching rolls 41 to 45. For example, the intermediate transfer body 23 circulates and rotates along a predetermined direction using the stretching roll 41 as a driving roll. Further, the stretching roll 44 also serves as an opposing roll of the secondary transfer roll as the secondary transfer device 25, and generates a secondary transfer electric field necessary for secondary transfer between the secondary transfer roll and the opposing roll. It has become. Further, an intermediate transfer cleaner 46 is disposed on the surface of the intermediate transfer member 23 corresponding to the stretching roll 45.
Further, a paper supply device 50 is provided below the intermediate transfer body 23, and the paper P supplied from the paper supply device 50 is conveyed along a conveyance path 51 that reaches the fixing device 60 through the secondary transfer device 25. It has become so. Note that an appropriate number of transport rollers 52, a transport belt 53 transported from the secondary transfer device 25 to the fixing device 60, a secondary transfer portion by the secondary transfer device 25, and a fixing device 60 are provided in the transport path 51. Guide plates 54 and 55 for guiding the paper P to the fixing part, a discharge roll 56 for discharging the paper P to a paper discharge unit (not shown), and the like are provided.

<Fixing device>
Next, the fixing device 60 used in this embodiment will be described with reference to FIGS.
In the drawing, a fixing device 60 includes a fixing belt 66 that is looped over a plurality of stretching rolls 61 to 65 and circulates while being heated, and one of the stretching rolls 61 to 65 of the fixing belt 66 is an opposing roll. (61 in this example), and a nip area between the pressure roller 67 and the pressure roller 67 that pressurizes and conveys the fixing belt 66 to and between the counter roller 61 and the pressure roller 67 inside the fixing belt 66. provided (a first contact zone) downstream of the N _1, and a peeling apparatus 70 for peeling after further nip conveying the sheet that has passed through the nip region N _1.
Here, in this example, the opposing roll 61 that also serves as a stretching roll has a heat source 61a such as a halogen lamp, and is driven to rotate by a driving force from a driving motor (not shown). Further, the opposing roll 61 and the stretching rolls 62, 64 and 65 are arranged inside the fixing belt 66, and the stretching roll 63 is arranged outside the fixing belt 66 between the stretching rolls 62 and 64.
In addition, in this example, although the opposing roll 61 is the structure which has the heat source 61a, in addition to this or separately, about the part of the stretching rolls 62-65, for example as needed, An auxiliary heating roll having the heat source 61a may also be used.
And in this example, the opposing roll 61 coat | covers the protective layers, such as a fluororesin, on the surface of the cylindrical metal core which consists of aluminum, for example. The pressure roll 67 is formed by using, for example, an aluminum core as a base 67a, and an elastic layer 67b such as silicone rubber, and a release layer 67c such as a PFA tube are laminated on the base 67a. Further, the fixing belt 66 may be selected as appropriate. For example, the fixing belt 66 has a base layer 66a made of polyimide resin or the like, an elastic layer 66b made of silicone rubber or the like on the surface side of the base layer 66a, and a release layer made of a PFA tube. 66c is laminated. Each of the tension rolls 62 to 65 is, for example, an aluminum metal roll.

<Peeling device>
-Press pad-
In this embodiment, as shown in FIG. 4, the peeling device 70 is provided so as to extend long along the width direction intersecting the moving direction of the fixing belt 66, and the fixing belt 66 contacts the pressure roll 67 side. A pressing pad 71 is provided to press the fixing belt 66 so that the direction of the pressing roll 67 is changed from the surface of the pressing roll 67 after being disposed.
In this example, as shown in FIGS. 4 and 5A and 5B, the pressing pad 71 is formed of a rigid body such as a metal such as carbon steel or a ceramic, and is supported on a predetermined supporting portion. Peeling member provided along a contact surface between the supported member 72 to be fixed and the fixing belt 66 of the supported member 72 and formed in a substantially L-shaped cross section with a rigid body such as a metal such as SUS or ceramics. 73, and fixing member 73 is fixed to supported member 72 with a stopper (not shown) through a plurality of mounting holes 74 provided in vertical wall portion 73a extending in the vertical direction of peeling member 73. It is.
-Guide section-
In this example, the peeling member 73 that is one element of the pressing pad 71 has a curved corner 73 c at a bent portion having a substantially L-shaped cross section, and the pressing pad 71 is in the lateral direction of the peeling member 73. The fixing belt 66 is guided so that the fixing belt 66 is caused to bite into the pressure roll 67 using the lateral wall portion 73b and the curved corner portion 73c extending in the direction of the guide portion 75 as a guide portion 75.
In this example, the guide portion 75 bites the bent portion of the fixing belt 66 that is bent and arranged corresponding to the curved corner portion 73 c of the peeling member 73 to the extent that the pressure roller 67 is buried.
Therefore, in this example, as shown in FIG. 4, for example, the fixing belt 66 includes a nip area (corresponding to a first contact area) N ₁ between the opposing roll 61 and the pressure roll 67 and the pressing pad 71. The fixing belt 66 is placed in contact with the pressure roll 67 in a nip area (corresponding to a second contact area) N ₂ with the pressure roll 67, and the fixing belt 66 is fixed to the fixing nip area N (specifically, the nip area). After the sheet P is heated and pressurized and conveyed to and from the pressure roll 67 over the area N ₁ + the nip area N ₂ ), the curved surface of the peeling member 73 of the pressing pad 71 located on the outlet side of the nip area N ₂ It is separated from the pressure roll 67 along the shape of the corner portion 73c. For this reason, the sheet P is likely to be peeled off at a portion corresponding to the curved corner 73c of the peeling member 73 of the pressing pad 71 after passing through the fixing nip region N between the fixing belt 66 and the pressure roll 67. It has become. A non-contact area N ₀ exists between the nip area N ₁ and the nip area N ₂ of the fixing nip area N corresponding to the gap between the opposing roll 61 and the pressing pad 71.

-Pressure part-
Further, in the present embodiment, as shown in FIGS. 6A to 6D, the peeling member 73 that is one element of the pressing pad 71 has a surface of the lateral wall portion 73b that is centered with respect to the longitudinal direction of the pressing pad 71. It is formed so as to be separated from the pressure roll 67 as it goes from the section toward the end, and is configured as a pressure section 76 that presses the fixing belt 66 against the pressure roll 67. The protrusion amount h (see FIG. 6D) of the pressure unit 76 toward the pressure roll 67 side is the addition of the central portion in the width direction of the paper P in the pressure distribution in the nip region N ₂ by the pressure pad 71. It is set appropriately considering the pressure deficiency.
-Protrusion-
Further, in the present embodiment, the peeling member 73 that is one element of the pressing pad 71 further protrudes on the leading end side of the lateral wall portion 73 b, that is, on the nip region N ₁ side between the opposing roll 61 and the pressure roll 67. The projecting portion 77 is formed so that the center portion projects in a convex shape toward the nip region N ₁ side from both ends with respect to the width direction intersecting with the conveyance direction (corresponding to the process direction) of the paper P. .
In particular, in this example, the leading edge of the protruding portion 77 is formed as a curved edge 78 that is symmetrical and curved around the central portion in the width direction of the paper P.
As described above, in this embodiment, the peeling member 73 that is one element of the pressing pad 71 is a peeling member 73 ′ (a substantially rectangular flat plate having a substantially L-shaped cross section) of the comparative form shown in FIG. The embodiment is characterized in that it has a guide portion 75, a pressurizing portion 76, and a protruding portion 77.

-Peeling device mounting structure-
In the present embodiment, as shown in FIG. 7A, the attachment structure of the peeling device 70 is such that a holder 68 that holds the opposing roll 61 is fixed to an image forming apparatus housing (not shown), and the holder 68 is fixed to the holder 68. On the other hand, a supported member 72 that is one element of the pressing pad 71 is fixed by a supporting member 80.
Note that the attachment structure of the peeling device 70 is not limited to this, and for example, as shown in FIG. A supported member 72, which is one element of the pressing pad 71, is fixed to the support member 81, and the supported member 72 is biased by a biasing spring 82 in a direction against the swinging direction of the support member 81. It may be.
Regarding the mounting structure of such a peeling device 70, the method shown in FIG. 7A is relative to the pressure roll 67 of the pressing pad 71 of the peeling device 70 as compared to the method shown in FIG. 7B. Is preferable in that it is uniquely determined.

-Pressure conditions in the fixing nip area-
Fixing belt 66 in the fixing nip area N, as shown in FIG. 8 (a), received a driving force F ₁ by a frictional force between the counter roll 61 which is driven, together with the pressure contact with the sheet P, the pressure roll Rotate and move 67 while rotating.
At this time, in the latter half of the fixing nip region N (nip region N ₂ ), the fixed pressing pad 71 and the back surface of the fixing belt 66 are rubbed, and this frictional force is a braking force ( the braking force) _{F 2.} When the braking force F ₂ increases, where the change in curvature of the fixing nip area N, with the fixing belt 66 the paper P is easily deformed, the fixing belt 66 and the sheet P is is likely to leave slack easily occurs. Braking force F ₂ of the pressing pad 71, those determined by the pressure pad 71 surface and the coefficient of friction between the fixing belt 66 backside, the pressing force F ₃ exerted thereto, it is the pressing force F ₃ small braking force F ₂ is small, and the fixing belt 66 and the paper P are conveyed well in the fixing nip area N.
In order to reduce the friction coefficient between the surface of the pressing pad 71 and the back surface of the fixing belt 66, a lubricating layer such as glass fiber is formed on the contact surface of the peeling member 73, which is an element of the pressing pad 71, with the fixing belt 66. It is preferable to reduce the frictional resistance between the pressing pad 71 and the fixing belt 66.
In the present embodiment, the pressurizing condition in the fixing nip area N is set as follows (see FIGS. 4 and 8).
(1) The nip area N ₁ between the opposing roll 61 and the pressure roll 67 and the nip area N ₂ between the pressing pad 71 and the pressure roll 67 are N _{1 with} respect to the width dimension in the paper transport direction. > N ₂ is satisfied. For example, when the fixing nip area N is 23 mm, the nip area N ₁ is set to 15 mm, the nip area N ₂ is set to 7 mm, and the non-nip area N (non-contact area) is about 1 mm.
(2) the maximum amount of bite of _{h 1} of the pressure roll 67 in the nip region _{N 1,} the maximum amount of biting pressure roll 67 in the nip zone _{N 2} When _{h 2,} satisfy the relationship of h 1> _{h 2.}
(3) pressure pressure distribution of the fixation nip zone N is 8 shown in (b) has a tendency, p ₁ the peak pressure at the nip region N _1, p ₂ the peak pressure in the nip area N ₂ If so, the relationship of p ₁ > p ₂ is satisfied. In particular, the peak pressure _{p 2} of the nip zone _{N 2} is preferably set low to an extent less than half of the peak pressure _{p 1} of the nip region _{N 1.}

<Peeling assist device>
In this embodiment, the fixing device 60 includes the peeling device 70 inside the fixing belt 66, but is downstream of the fixing nip region N between the fixing belt 66 and the pressure roll 67 of the fixing device 60. A peeling assisting member 90 (see FIG. 3) is provided on the side.
The peeling assisting member 90 peels off the paper P that is arranged in a non-contact manner so that the front end faces the fixing belt 66 in the rotational direction and sticks to the fixing belt 66. For example, a plate-like baffle plate is used. .
The peeling assisting member 90 is preferably provided with its tip as close to the fixing belt 66 as possible. The installation distance from the fixing belt 66 is at least 1.0 mm or less, preferably 0.3 mm or less.
However, if the installation distance of the peeling assisting member 90 is too close to the fixing belt 66, the peeling assisting member 90 may be thermally expanded due to radiant heat from the fixing belt 66, and the fixing belt 66 may be damaged or corrugated. There is also a concern that it may cause image defects. For this reason, in this example, it is preferable to use a material (for example, Invar) having a small thermal expansion for the peeling assisting member 90.

<Operation of image forming apparatus>
Next, the operation of the image forming apparatus according to the present embodiment will be described.
In the image forming apparatus shown in FIG. 2, each color component toner image is formed on the photoreceptor 30 by the image forming unit 22 (22 a to 22 d) for each color component, and each color toner image is sequentially primary transferred onto the intermediate transfer body 23. Thereafter, the color toner images on the intermediate transfer body 23 are collectively transferred to the paper P supplied from the paper supply device 50, and the paper P holding the color toner images transferred in batch is carried into the fixing device 60 and fixed. After fixing each color toner image on the paper P by the device 60, the fixed paper P is discharged from the fixing device 60.
An operation process of the peeling device 70 of the fixing device 60 in such an image forming process will be described.

<Operation process of peeling device>
-Paper behavior in the fixing nip area-
First, the behavior of the paper P in the fixing nip area N will be described.
Now, as shown in FIGS. 8A and 9, the fixing nip area N includes a nip area N ₁ between the opposing roll 61 and the pressure roll 67, and between the pressing pad 71 and the pressure roll 67. Nip area N ₂ and a non-nip area N ₀ provided therebetween, and the sheet P is nipped and conveyed along the path of the fixing nip area N between the fixing belt 66 and the pressure roll 67. .
At this time, as shown in FIG. 9, since the nip area N ₁ and the nip area N ₂ have different curvatures and width dimensions along the paper conveyance direction, the path between the fixing belt 66 and the paper P in the nip area N _1. The difference α (for example, + 1%) acts as a shear stress in the nip area N ₂ with the inflection point between the nip areas N ₁ and N ₂ as a boundary. This shear stress, the path difference between the fixing belt 66 and the sheet P in the nip area N ₂ beta (e.g. - a few percent) acts in a direction to reduce. In such an operation process, when the nip region N ₂ is too long, there is a concern that the deviation occurs between them after the path difference between the two β is exhausted by the shear stress. Therefore, in the present embodiment, by setting the length along the compared to the nip region N ₁ nip area N ₂ in the sheet conveying direction (process direction) shorter, the fixing belt 66 and the sheet at the nip region N ₂ It is preferable to consider so as to suppress the deviation generated between P and the P as much as possible.
This paper behavior will be described in more detail. As shown in FIG. 10, the curvature of each nip area is between a nip area N ₁ and a non-nip area N ₀ (A area) and a nip area N ₂ (B area). Assuming that the directions are different from each other, the speed difference (Δv = v ₁ −v ₂ ) of the paper P between the nip areas N ₁ and N _{2 is the} difference in the sheet feed amount, and the non-nip area N ₀ Then, the slack M of the paper P is observed. Actually, since the paper P is pressed by the nip pressure, the force to loosen the paper P becomes the shearing force Fs between the fixing belt 66 and the paper P interface. Now, assuming that the radius of the opposing roll 61 is r ₁ , the radius of the pressing pad 71 is r ₂ , and the sheet thickness is d, the difference s in the sheet feed amount is the amount L of the fixing belt 66 conveyed in t seconds.
s = d · L · (r ₁ + r ₂ ) / r ₁ · r ₂
It can be expressed as
In other words, towards the radius r ₂ of the pressure pad 71 is small slack M increases. That is, the sheet P tends to be loosened as the pressing pad 71 bites into the pressure roll 67 side. As other paper conveyance conditions, for example, it is understood that the thicker the paper P, the larger the slack M, and the longer the conveyance distance L, the more slack.
Further, when these are viewed in terms of the parameters of the nip region, it is possible to obtain a result that the pressure of the pressing pad 71 is preferably small and the width dimension of the pressing pad 71 along the paper conveyance direction is preferably short.

-Pressure distribution by the guide-
In the present embodiment, as shown in FIG. 11A, the peeling device 70 guides the fixing belt 66 so that the fixing belt 66 bites into the pressure roll 67 side by the guide portion 75 of the pressing pad 71. To do.
In particular, in this example, the guide portion 75 of the pressing pad 71 bites into the pressure roll 67 so that the bent portion 66 a of the fixing belt 66 that is bent and arranged corresponding to the curved corner portion 73 c of the peeling member 73 is buried in the pressure roll 67. since that is way to, pressure distribution between the fixing belt 66 and the pressure roller 67 by the pressure pad 71 (corresponding to the pressurizing pressure distribution in the nip zone N ₂ shown in FIG. 4) is, and FIG. 11 (b) As shown in FIG. 5, the pressure is applied substantially uniformly from the lateral wall portion 73b of the peeling member 73 to the curved corner portion 73c with respect to the process direction position corresponding to the moving direction of the paper P.
Incidentally, pressurizing pressure distribution shown in FIG. 11 (b) shows the pressure distribution at the fixing nip region N of Fig. 4, in which the left area corresponds to the nip area N _1, right area corresponds to the nip area N ₂ is there.

In this regard, as in the comparative example shown in FIG. 12A, the pressing pad 71 ′, which is one element of the peeling device 70 ′, presses the fixing belt 66 against the pressure roll 67 without being bitten. In the present embodiment, as shown in FIG. 12B, a non-pressurized region J in which the fixing belt 66 is not pressed against the pressure roll 67 between the pressure pad 71 ′ and the pressure roll 67 is generated. There is a concern.
At this time, in a state where the fixing belt 66 is pressed by the pressure roll 67, the toner layer T on the paper P is pressed by the fixing belt 66 as shown in FIG. Even if the bubbles K in the layer T try to expand, the relationship of the pressing force U> the water vapor pressure in the bubbles K is satisfied, and the bubbles K in the toner layer T are kept as they are.
On the other hand, as described above, when the non-pressurized region J exists, the bubbles K in the toner layer T expand as shown in FIG. 12C, and the pressing force U <the water vapor pressure in the bubbles K. In relation, there is a concern that the expanded bubble K destroys the toner layer T and disturbs the surface of the toner layer T.
Therefore, according to the present embodiment, since the above-described non-pressurized region J does not exist, the phenomenon that the expanded bubble K destroys the toner layer T is suppressed.

-Pressure distribution by the pressurizing part-
FIG. 13A is a schematic view of the fixing device 60 used in the present embodiment as viewed from above.
At this time, if the pressing portion 71 is not provided on the pressing pad 71 of the peeling device 70 (corresponding to a mode in which the pressing portion is planar), as shown in FIG. As for the pressure distribution in FIG. 4, a sufficiently strong pressure is obtained in the nip area N ₁ (corresponding to P / R Nip in the figure) shown in FIG. 4, but the nip area N ₂ (corresponding to Pad Nip in the figure) shown in FIG. In this case, the central portion in the paper width direction intersecting the process direction tends to be weaker than both ends.
In such a situation, in the present embodiment, the pressing portion 76 of the pressing pad 71 has a surface that moves away from the pressing roll 67 as it goes from the center portion to the end portion in the paper width direction. of the pressure distribution in the nip region N, the nip region N ₂ corresponding to the pressure pad 71 _{(corresponding} to figure pad nip), will be pressurized shortage amount of the central portion is supplemented, the nip region N ₂ the pressure in the sheet width direction central portion also becomes the pressure of the end portions substantially uniform toner layer T of the paper P is heated and fixed with a substantially uniform pressure distribution even in the nip area N ₂ of the fixing nip area N. For this reason, the fixability of the paper P to the toner layer T is kept substantially uniform in the paper width direction.

-Pressure distribution due to protrusion-
In this embodiment, the pressure pad 71, since the relative sheet width direction and has a protruding portion 77 which center portion is protruded in a convex shape toward the nip region N ₁ side from both end portions, the The pressing area at the center portion in the width direction of the pressing pad 71 is increased by the amount of the protruding portion 77. For this reason, the pressurization distribution by the press pad 71 shows the tendency which increases in the part corresponding to the protrusion part 77, as shown to Fig.14 (a).
In particular, in this example, the pressure distribution by the pressing pad 71 has a pressing force (nip pressure) higher than the water vapor pressure of bubbles at a portion corresponding to the protruding portion 77 as shown in FIG. Therefore, the toner layer is unlikely to break due to the expansion of the bubbles at the location corresponding to the protruding portion 77.
In this respect, in the embodiment in which the protrusion 77 is not provided on the pressing pad 71, no pressing force is applied to the portion corresponding to the protrusion 77 of the pressing pad 71. Therefore, as shown in FIG. There is a concern that a non-pressurized region (pressing force <bubble water vapor pressure) that is hardly pressurized on the pressure roll 67 side is formed between the opposing roll 61.

-Suppression of paper wrinkles by protrusions-
When the paper P passes through the fixing nip area N (see FIG. 4) of the fixing device 60, wrinkles Z are likely to occur on the paper P as shown in FIG.
In the present embodiment, the leading edge of the protrusion 77 of the pressing pad 71 is formed as a curved edge 78 that is symmetrical and curved around the center in the width direction of the paper P. As shown, a force Fb that pushes the paper P toward the normal direction of the curved edge 78 acts on the curved edge 78 of the protruding portion 77, and the ridge Z of the paper P is spread and generated. It becomes difficult.
In particular, if the curvature (1 / R) of the curved edge 78 of the protrusion 77 is set large, the force Fc in the normal direction of the curved edge 78 has a small curvature as shown in FIG. As compared with the above, the action of pushing the paper P is further strengthened.

Example 1
The fixing device according to Embodiment 1 is defined as Example 1, the fixing nip area N is configured to be 23 mm, the nip area N ₁ is 15 mm, the nip area N ₂ is 7 mm, the non-nip area N ₀ is 1 mm, and When the pressure distribution in the fixing nip region N was examined under the condition that the maximum biting amount of the pressing pad 71 was set smaller than the maximum biting amount of the opposing roll 61 with respect to the pressure roll 67, FIG. The results shown are obtained.
On the other hand, as a comparative example, the fixing nip area N is configured to be 25 mm, the nip areas N ₁ and N ₂ are set to be substantially equal, and the pressing pad 71 has a maximum biting amount compared to the pressure roll 67. When the pressure distribution in the fixing nip region N was examined under the condition that the maximum biting amount was set to approximately the same level, the result shown in FIG. 16B was obtained.
When 100 continuous image forming processes were performed using the fixing device according to Example 1, an image without image distortion was obtained.
In this regard, when the image forming process was continuously performed for 100 sheets using the fixing device according to the comparative example, image disturbance was confirmed in some images.

Example 2
When the fixing device according to the first embodiment is in Example 2 and two parameters are used as the pressing force of the pressing pad 71 and the relationship between the pad width of the pressing pad 71 and the color noise is examined, the result shown in FIG. Obtained.
Here, the color noise is used as an index indicating the graininess. In this method, a color image is captured by a scanner, converted into a scanner RGB signal, and decomposed into lightness, saturation, and hue in a uniform color space (CIELAB). Next, the two-dimensional color space is converted into a two-dimensional frequency arc space. In the two-dimensional frequency space, VTF (Visual Transfer Function) is multiplied. The amplitude of the two-dimensional frequency space that has been subjected to VTF processing is subjected to circular integration for each frequency to calculate a color noise vector. A color noise value is calculated using a predicted model of subjectiveness from the obtained color noise vector. The larger the color noise value, the greater the noise and the worse the graininess.
According to FIG. 17, it is understood that the smaller the pad width of the pressing pad 71, the smaller the color noise and the better the graininess.

Example 3
An image measured with a colorimeter X-Rite 938 manufactured by X-Rite Co., Ltd., in which the fixing device according to the first embodiment is set to Example 3, the pad width of the pressing pad 71 is set to 4 mm, and the pressing force is set to ² kgf / cm ^2. When the color noise with respect to the density L ^* was measured, the result shown in FIG. 18 was obtained.
The fixing condition of the measurement sample at this time is that the fixing belt 66 is fixed under the condition that the temperature of the fixing belt 66 is set to a temperature that is + 10 ° C. lower than the lowest temperature at which the toner on the low temperature side does not come off (so-called cold offset does not occur). A fixed image was obtained.
As a comparative example, a pad having a pressing pad width of 11 mm and a pressing force of 4 kgf / cm ² was used.
According to FIG. 18, when the target value of color noise is set to 5, for example, it is understood that in Example 3, color noise is suppressed to a low level for all density images and the graininess is good.
In this respect, in the comparative example, it was confirmed that the color noise increases and the graininess deteriorates in a region where the image density L ^* is medium density.
As described above, according to this embodiment (or embodiment 2), it is possible to obtain an image with good graininess as the fixing performance of the fixing device. Of course, for example, even when image forming processing was performed on embossed paper (for example, trade name: Rezac 66), there was no image displacement between the embossed paper and the fixing belt, and an image without image distortion was obtained.

1 ... strip heating rotator, 1a ... elastic layer, 2 ... pressure rotating body, 2a ... elastic layer, 3 ... facing the rotary body, 4 ... pressing member, 5 ... heat source, 6 ... recording medium, N 0 _... noncontact Area, N ₁ ... first contact area, N ₂ ... second contact area, h ₁ ... maximum amount of biting by the opposed rotating body with respect to the pressure rotating body, h ₂ ... maximum amount of biting by the pressing member with respect to the pressing rotating body , P ₁ ... peak pressure in the first contact area, p ₂ ... peak pressure in the second contact area, T ... unfixed toner image

Claims (7)

A belt-like heating rotator having an elastic layer at least in part and rotating by being heated;
A pressure rotator which is brought into pressure contact with the surface of the heating rotator and rolls together with the heating rotator, and has an elastic layer at least partially and heat-presses and fixes an unfixed toner image on the recording material;
An opposing surface that is disposed in contact with the back surface of the heating rotator facing the pressure rotator, rotates together with the heating rotator, and sandwiches and conveys the recording material on the heating rotator. A rotating body,
A first contact area between the opposing rotating body and the pressure rotating body of the back surface of the heating rotating body, which is provided to extend long along a width direction intersecting the moving direction of the heating rotating body; The heating rotator is pressed in such a manner that the heating rotator is arranged in contact with the downstream side, and has a bent shape whose direction is changed from the surface of the pressure rotator after the heating rotator is disposed in contact with the pressure rotator. A pressing member,
Among the heating rotator, the recording material and the second contact zone between the first the pressing member than the contact area between the pressure rotating body between the pressure rotating body and the counter rotator Set narrower in the transport direction ,
Provided on the pressure rotating body side of the pressing member and on the first contact area side of the heating rotating body and the pressure rotating body, and a central portion with respect to the intersecting direction intersecting the moving direction of the heating rotating body. A fixing device comprising: a protruding portion that protrudes in a convex shape toward both sides of the first contact area . The fixing device according to claim 1.
The fixing is characterized in that the maximum biting amount of the pressing member with respect to the pressure rotating body in the second contact region is set smaller than the maximum biting amount of the counter rotating body with respect to the pressure rotating body in the first contact region. apparatus. The fixing device according to claim 1 or 2,
Setting the peak pressure between the pressure rotator and the pressing member in the second contact area to be smaller than the peak pressure between the pressure rotator and the counter rotator in the first contact area. A fixing device characterized. The fixing device according to any one of claims 1 to 3,
And wherein the pressure provided on the rotary body side and the heating rotating body the heating rotating body so bent shape corner portion bites into the pressure rotating body of the pressing member is provided with a guide portion to be guided Fixing device to do. The fixing device according to any one of claims 1 to 4,
Wherein said face toward the end from the central portion in the longitudinal direction of the pressing member and the pressurizing a surface on the rotary body side and the pressing member is formed away from the pressure rotating body, the pressure rotating body A fixing device comprising a pressurizing unit that pressurizes the heating rotator. The fixing device according to any one of claims 1 to 5 ,
The fixing device according to claim 1, wherein the counter rotating body includes a heating source. An image forming device for forming an unfixed toner image on a recording material;
An image forming apparatus comprising the fixing device according to any one of claims 1 to 6, heating pressure fixing an unfixed toner image on the recording material formed by the image forming apparatus.

Images