JP5808547B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device and an image forming apparatus using the fixing device, and more particularly to a technique for preventing deterioration of the belt in a fixing device using a belt including a resistance heating element layer.

In recent years, a fixing device using a belt including a layer of a resistance heating element that generates Joule heat has been used as a fixing device of an image forming apparatus such as a printer or a copying machine.
Usually, such a fixing device is configured such that power is supplied to the resistance heating element layer by bringing a power supply member connected to an external power source into sliding contact with the peripheral surface of the belt (for example, patents). Reference 1).

FIG. 9 is a schematic diagram for explaining the configuration of the fixing device disclosed in Patent Document 1. In FIG.
As shown in the figure, the fixing device 200 includes an endless belt 201 including a resistance heating element layer, a pressure roller 202 that presses the outer peripheral surface of the belt 201 to form a nip portion N, and a pressure roller 202. A C-shaped backing member 203 that receives the pressure applied from the belt 201, a power supply member 204 that is slidably contacted with the outer peripheral surface of the belt 201, and a pressing roller 205 that is disposed on the opposite side of the power supply member 204 with the belt 201 interposed therebetween. The urging unit 206 is provided.

The power supply member 204 is electrically connected to an external power supply (not shown), and power from the external power supply is supplied to the resistance heating element layer of the belt 201 via the power supply member 204.
The pressing roller 205 presses the belt 201 to the power supply member 204 side by the urging force from the urging unit 206 so that the contact state between the belt 201 and the power supply member 204 becomes good.

JP-A-9-16013 JP 2009-109997 A

However, in the fixing device 200 shown in FIG. 9, a gap is generated between the power supply member 204 and the belt 201, and the contact state may be deteriorated.
Specifically, for example, when a foreign matter such as paper dust on a recording sheet or wear powder on a part adheres to and accumulates on a path on the outer peripheral surface of the belt 201 where the power feeding member 204 is in sliding contact, FIG. As shown, the foreign matter F adhering to the belt 201 reaches the power supply member 204 as the belt 201 rotates. The belt 201 is not urged by the pressing roller 205 in this portion, and there is a gap g (see FIG. 9).

  Therefore, when the foreign matter F collides with the end surface of the power supply member 204, the belt 201 is deformed so that the belt 201 bends inward at a portion where the belt 201 is not backed up (a portion corresponding to the gap g) (FIG. 10B). The foreign substance F enters between the belt 201 and the power supply member 204 as it is (FIG. 10C). In FIG. 10B, the belt deformation is exaggerated for easy understanding.

When the foreign matter F is sandwiched between the belt 201 and the power supply member 204, a minute gap is generated between the power supply member 204 and the belt 201. As a result, a spark discharge (spark) occurs between the belt 201 and the power supply member 204, and the belt 201 is damaged by the spark discharge and deteriorates.
The present invention has been made in view of the above-described problems, and provides a fixing device and an image forming apparatus capable of suppressing the deterioration of the belt and extending the life of the belt. With the goal.

In order to achieve the above object, a fixing device according to the present invention includes a resistance heating element layer, presses a pressure member on a circumferential surface of an endless belt that rotates and forms a nip portion, and the nip portion includes A fixing device that heats and fixes a recording sheet on which an unfixed image is formed, and that is electrically connected to an external power source and extends in the circumferential direction at both ends of the peripheral surface of the belt A power supply member that slidably contacts a layer and supplies power; a support member that is disposed on the opposite side of the power supply member across the belt; and that supports the belt in contact with the belt; and at least one member of the power supply member and the support member the a biasing means for urging the other member, in a cross section perpendicular to the rotation axis of the belt, the sectional shape of the sliding contact sliding surface on the electrode layer of the belt of the feed member, said support member and a cross-sectional shape of the contact surface between the belt Together are formed to have a heart circular arcs, angles formed edge portion in the end surface of the upstream side in the rotational direction and the sliding surface of the belt of said feeding member is less than 90 °, And when viewed from a direction parallel to the urging direction by the urging means, the shape of the power supply member and the support member is such that the sliding contact surface of the power supply member is included in the contact surface of the support member. And the size is determined.

  Here, the “belt rotation axis” means a virtual axis that becomes the center of rotation when the belt is rotated.

According to the fixing device configured as described above, the cross-sectional shape of the sliding surface of the power supply member is formed to be a circular arc concentric with the cross-sectional shape of the contact surface of the support member with the belt, and the power supply member The angle of the edge portion constituted by the end surface on the upstream side in the rotation direction of the belt and the sliding contact surface is less than 90 °, and when viewed from a direction parallel to the urging direction by the urging means, Since the sliding contact surface of the power supply member is included in the contact surface of the support member, the entire surface of the electrode layer of the belt that is in sliding contact with the power supply member is reliably supported by the support member.
As a result, deformation of the belt is less likely to occur in the sliding contact area with the power supply member, and even if foreign matter adheres to the surface of the electrode layer of the belt, the foreign matter is Most of them are removed from the electrode layer in contact with the end of the power supply member.

This prevents foreign matter and the like from entering between the electrode layer of the belt and the power supply member as much as possible, thereby preventing the occurrence of spark discharge. It becomes possible to prevent.
Further, it is possible to the angle of the sheet collecting member as compared with the case where an obtuse angle of 90 [°] greater, enhance the effect of removing foreign matter adhered to the electrode layer surface of the belt.

Moreover, it is desirable that the cross-sectional shape of the contact surface of the support member is an R shape.
Further, it is desirable that a pressure roller that is pressed by a pressure member via the belt is disposed inside the rotation path of the belt, and the pressure roller is also configured to serve as a support member.
Moreover, it is desirable that the portion of the support member that contacts the belt is formed of an elastic body. Thereby, the support member is brought into elastic contact with the belt, the contact pressure (surface pressure) is prevented from being biased, and the support force for supporting the belt can be made uniform.

The elastic body is preferably a foam. In this case, since the foam also functions as a heat insulating material, it is possible to suppress the heat of the belt from being radiated through the support member.
Further, the invention of the present application may be an image forming apparatus provided with the fixing device having the above-described configuration, whereby the same effect as that of the fixing device having the above-described configuration can be obtained.

1 is a schematic diagram illustrating a configuration of a printer according to a first embodiment of the present invention. FIG. 2 is a perspective view illustrating a configuration of a main part of a fixing device in the printer. 2A is a partial cross-sectional view of the fixing device of FIG. 2 as viewed from the Y ′ direction when cut by a virtual plane V, and FIG. 2B is an enlarged view of a portion surrounded by a broken line in FIG. is there. FIG. 3 is a partial cross-sectional view for explaining a laminated structure of a fixing belt. FIG. 9 is a schematic diagram for explaining a mechanism for preventing foreign matter from entering between the power supply member and the fixing belt, and (a) shows a state in which foreign matter adheres to and accumulates on the surface of the fixing belt; ) Shows a state in which foreign matter is removed from the surface of the fixing belt. (A) is a figure which shows the case where the angle of the edge part of a power feeding member is an acute angle less than 90 [degree], (b) is a figure which shows the case where the angle of the edge part of a power feeding member is 90 [degree]. (C) is a figure which shows the case where the angle of the edge part of an electric power feeding member is an obtuse angle exceeding 90 [°]. (A) is a figure which shows the structure of the principal part of the fixing | fixed part which concerns on the 2nd Embodiment of this invention, (b) is a power supply member when it sees from a direction parallel to an urging | biasing direction. It is a figure explaining the magnitude | size and positional relationship of a sliding contact surface and the support surface of a supporting member. FIG. 7A is a diagram illustrating an example of a configuration of a fixing device according to a modification, in which FIG. 9A illustrates an example in which a support member is used instead of a pressing roller, and FIG. 9B illustrates a power supply member disposed inside the fixing belt. It is a figure which shows an example. FIG. 10 is a schematic diagram for explaining a configuration of a fixing device according to a conventional example. (A) is a figure which shows the state in which the foreign material adhered to the belt, (b) is a figure which shows the state which the foreign material collided with the electric power feeding member and the belt deform | transformed, (c) is a belt It is a figure which shows the state which the foreign material approached between the electric power feeding members.

<First Embodiment>
Hereinafter, a first embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings by taking a tandem type full color printer (hereinafter simply referred to as “printer”) as an example.
<Overall configuration of printer>
FIG. 1 is a schematic diagram illustrating a configuration of a printer.

  As shown in FIG. 1, the printer 1 includes an image process unit 3, a paper feed unit 4, a fixing unit 5, and a control unit 60. When the printer 1 is connected to a network (for example, a LAN) and receives a print job execution instruction from an external terminal device (not shown), each of the colors of yellow, magenta, cyan, and black is received based on the instruction. After a toner image is formed and these are multiplex-transferred to form a full-color image, a printing process on a recording sheet is executed.

Hereinafter, the reproduction colors of yellow, magenta, cyan, and black are represented as Y, M, C, and K, and Y, M, C, and K are added as subscripts to the numbers of the components related to the reproduction colors.
The image processing unit 3 includes image forming units 3Y, 3M, 3C, and 3K corresponding to each of Y to K colors, an optical unit 10, an intermediate transfer belt 11, and the like.
The image forming unit 3Y includes a photosensitive drum 31Y, a charger 32Y, a developing unit 33Y, a primary transfer roller 34Y, a cleaner 35Y for cleaning the photosensitive drum 31Y, and the like disposed around the photosensitive drum 31Y. A Y-color toner image is formed on the drum 31Y. The other image forming units 3M to 3K have the same configuration as the image forming unit 3Y, and the reference numerals are omitted in FIG.

The intermediate transfer belt 11 is an endless belt, and is stretched around the driving roller 12 and the driven roller 13 to circulate in the direction of arrow A.
The optical unit 10 includes a light emitting element such as a laser diode. The optical unit 10 emits laser light L for forming images of Y to K colors according to a drive signal from the control unit 60, and exposes and scans the photosensitive drums 31Y to 31K.

By this exposure scanning, electrostatic latent images are formed on the photosensitive drums 31Y to 31K charged by the chargers 32Y to 32K.
The electrostatic latent images are developed by developing units 33Y to 33K, and Y to K color toner images are formed on the photosensitive drums 31Y to 31K.
Each of the formed toner images is primarily transferred onto the intermediate transfer belt 11 by an electrostatic force generated by a voltage applied to the primary transfer rollers 34Y to 34K. At this time, the image forming operation in the image forming units 3Y, 3M, 3C, and 3K is performed by the intermediate transfer belt 11 so that the toner images of the respective colors are transferred to the same position on the intermediate transfer belt 11 that is traveling. It is executed with the timing shifted from the upstream side to the downstream side.

After the primary transfer, the toner image on the intermediate transfer belt 11 is collectively transferred onto the recording sheet S conveyed from the paper feeding unit 4 by the electrostatic force generated by the voltage applied to the secondary transfer roller 45. Is done.
The paper feeding unit 4 stores the recording sheet S, the feeding roller 42 that feeds the recording sheet S in the paper feeding cassette 41 one by one onto the conveying path 43, and the fed recording sheet S to the secondary. A timing roller pair 44 and the like for taking the timing of sending to the transfer position 46 are provided. The recording sheet S is conveyed from the paper feeding unit 4 to the secondary transfer position 46 in accordance with the timing of the toner image on the intermediate transfer belt 11.

The recording sheet S on which the toner image (unfixed image) is formed by the secondary transfer is further conveyed to the fixing unit 5. In the fixing unit 5, the toner image on the recording sheet S is heated and pressurized to be thermally fixed. Thereafter, the recording sheet S is discharged onto the discharge tray 72 by the discharge roller pair 71.
The control unit 60 controls the operations of the image processing unit 3, the paper feeding unit 4, and the fixing unit 5.
<Configuration of fixing unit>
Next, the configuration of the fixing unit 5 will be described with reference to FIGS. 2 and 3.

FIG. 2 is a perspective view showing the configuration of the main part of the fixing unit 5, and FIG. 3 is a cross-sectional view seen from the Y ′ direction when cut along the virtual plane V of FIG.
The fixing unit 5 includes an endless fixing belt 51 having a resistance heating element layer, a pressure roller 52 loosely fitted inside the fixing belt 51, a pressure roller 53 disposed outside the fixing belt 51, and fixing. Power supply members 54a and 54b for supplying power to the belt 51 and urging portions 56a and 56b are provided. In the fixing unit 5, the pressure roller 53 is pressed against the pressing roller 52 via the fixing belt 51, and a fixing nip N (see FIG. 3A) is provided between the fixing belt 51 and the pressure roller 53. ) Is formed.

  The pressure roller 53 is rotationally driven through a power transmission mechanism such as a gear gear or a belt using a motor (not shown) as a power source. The pressure roller 52 and the fixing belt 51 are driven to rotate by the rotation of the pressure roller 53 and are interlocked with each other. The pressure roller 53 rotates in the arrow B direction (see FIG. 2), and the pressing roller 52 and the fixing belt 51 rotate in the arrow C direction. 2 is a plane orthogonal to the virtual axis at the center of rotation when the fixing belt 51 is driven to rotate, in other words, orthogonal to the rotation axis of the pressing roller 52 or the pressure roller 53. It is also a surface.

Hereinafter, each component in the fixing unit 5 will be described in detail.
(Fixing belt)
The fixing belt 51 is elastically deformable when a certain amount of external force is applied in the radial direction, and is capable of retaining its own shape that returns to its original state by its own restoring force when the application of the external force is stopped from the deformed state.

Electrode layers 515a and 515b that receive power supply in contact with the power supply members 54a and 54b are provided on the outer peripheral surfaces of both ends t1 and t2 (FIG. 2) in the width direction of the fixing belt 51.
FIG. 4 is a partial cross-sectional view including an end portion on the electrode layer 515b side for explaining the laminated structure of the fixing belt 51.
As shown in FIG. 4, in the area where the electrode layer of the fixing belt 51 is not provided, the insulating layer 511, the resistance heating element layer 512, the elastic layer 513, and the release layer 514 are laminated in this order. ing. On the other hand, in the region of the electrode layer, the elastic layer 513 and the release layer 514 are not provided, and the electrode layer 515 b is formed directly on the outer peripheral surface of the resistance heating element layer 512. The end of the fixing belt 51 on the electrode layer 515a side has the same configuration.

The insulating layer 511 is made of a heat resistant insulating resin such as PI (polyimide), PPS (polyphenylene sulfide), PEEK (polyetheretherketone).
The resistance heating element layer 512 is formed by dispersing a conductive filler in a resin material, and generates Joule heat upon receiving power supply. As the resin material, a heat-resistant resin such as PI, PPS, and PEEK can be used. Conductive fillers include metals such as silver, copper, aluminum, magnesium and nickel, carbon-based materials such as carbon nanotubes, carbon nanofibers, and carbon microcoils, and those mixed and dispersed in two or more of these. Can be used.

The conductive filler is preferably in the form of a fiber in order to increase the probability of contact between fillers with the same content. Moreover, the electrical resistivity of the conductive filler is 1.0 × 10 ^{−5 to} 5.0 × 10 ⁻³ [Ωm].
The elastic layer 513 is made of a heat-resistant, elastic, and insulating rubber material or resin material such as silicone rubber. By providing the elastic layer 513, it is possible to prevent the toner image from being crushed or the toner image from being melted non-uniformly, thereby preventing the occurrence of image noise.

The release layer 514 is an insulating layer for enhancing the releasability from the recording sheet S after fixing, and is made of a resin material having heat resistance and excellent releasability. As the resin material, for example, a fluororesin such as PFA (tetrafluoroethylene / perfluoroalkoxyethylene copolymer) can be used.
The electrode layers 515a and 515b are made of a metal material such as gold, silver, copper, aluminum, zinc, tungsten, nickel, brass, or phosphor bronze. The electrode layers 515a and 515b are formed in an annular shape by plating the metal material, for example, along the outer peripheral surface of the resistance heating element layer 512. Each width of the electrode layers 515a and 515b is set to 15 [mm], for example.

The thickness of each said layer is uniform over the perimeter. Specifically, the insulating layer 511 is 5 to 100 [μm], the resistance heating element layer 512 is 5 to 100 [μm], the elastic layer 513 is 10 to 800 [μm], and the release layer 514 is 5 to 100 [μm]. The electrode layers 515a and 515b are 0.1 to 20 [μm].
For example, the width dimension of the fixing belt 51 is set to 366 [mm], which is larger than the total value of the maximum sheet passing width (A3 lengthwise) of the recording sheet S and the widths of the electrode layers 515a and 515b. The inner diameter of the fixing belt 51 is set to 30 [mm].
(Pressing roller)
2 and 3, the pressing roller 52 has an elastic layer 522 formed around a long and cylindrical cored bar 521.

  The cored bar 521 is made of, for example, aluminum, iron, stainless steel, and the like, and at both axial ends thereof, shaft portions 521a, which are rotatably supported by bearing portions of the fixing portion 5 provided in a housing (not shown). 521b. The elastic layer 522 is made of a material having high heat resistance and high heat insulation, such as a foamed elastic body such as silicone rubber or fluororubber. By providing the elastic layer 522, the pressing roller 52 and the fixing belt 51 are in elastic contact so that the contact pressure is not biased as much as possible and the contact state is improved. Further, since the elastic layer 522 also functions as a heat insulating material, heat generated in the fixing belt 51 can be suppressed from being radiated through the pressing roller 52. The thickness of the elastic layer 522 is desirably 1 to 20 [mm].

Here, the outer diameter of the core metal 521 (excluding the shaft portions 521a and 521b) is about 18 [mm], and the thickness of the elastic layer 522 is about 5 [mm]. The inner diameter of the fixing belt 51 is set to be smaller than 30 [mm]. Further, the length of the pressing roller 52 excluding the shaft portions 521 a and 521 b is equal to the width dimension of the fixing belt 51.
(Pressure roller)
In the pressure roller 53, an elastic layer 532 and a release layer 533 are laminated in this order around a long and cylindrical cored bar 531.

The metal core 531 is made of, for example, aluminum, iron, stainless steel, and the like, and shaft portions 531a, which are rotatably supported by bearing portions provided in a housing (not shown) of the fixing unit 5 at both axial ends thereof. 531b. The elastic layer 532 is made of, for example, silicone rubber, and the release layer 533 is made of, for example, a fluorine resin such as PFA. By providing the elastic layer 532, the pressure roller 53 and the fixing belt 51 are in elastic contact so that the contact pressure is as small as possible and the contact state is improved.
The thickness of the elastic layer 532 is desirably 1 to 20 [mm], and the thickness of the release layer 533 is desirably 10 to 50 [μm].

Here, the outer diameter of the core metal 531 (excluding the shaft portions 531a and 531b) is about 30 [mm], and the thickness of the elastic layer 532 is about 3 [mm]. The length excluding the shaft portions 531a and 531b of the pressure roller 53 is set to a size 330 [mm] which is larger than the maximum sheet passing width of the recording sheet S and does not contact the electrode layers 515a and 515b. .
(Power supply member)
The power feeding members 54a and 54b are block-like carbon brushes, and are made of a material such as copper graphite or carbon graphite having slidability and conductivity. The power feeding members 54a and 54b are electrically connected to an external power source 500 through lead wires 55, respectively. One power supply member 54a is in sliding contact with the electrode layer 515a of the fixing belt 51, and the other power supply member 54b is in sliding contact with the electrode layer 515b.

The sizes of the power supply members 54a and 54b are set to, for example, 10 [mm] in the vertical direction (Y-axis direction), 5 [mm] in the horizontal direction (X-axis direction), and 15 [mm] in the Z-axis direction. .
The power source 500 is, for example, a household power source having a voltage of 100 [V] and a frequency of 50 [Hz] or 60 [Hz]. Note that a known relay (relay switch) (not shown) that performs ON / OFF control of power supply based on an input signal from the control unit 60 is inserted into the lead wire 55.
(Energizing Department)
The power supply member 54a is held so as to be movable in the direction of arrow E (see FIG. 3A) by a guide member (not shown), and is urged toward the fixing belt 51 by the urging portion 56a.

The urging portion 56 a includes a base 57 and a compression coil spring 58 having one end attached to the base 57. The base 57 is attached to a housing or frame (not shown) of the fixing unit 5, and a compression coil spring 58 is inserted between the base 57 and the power supply member 54 a in a compressed state.
Inside the fixing belt 51, the pressing roller 52 functions as a support member that supports the outer peripheral surface 52 a in contact with the inner peripheral surface of the fixing belt 51. Accordingly, the fixing belt 51 is sandwiched between the power supply member 54a and the pressing roller 52. Here, the biasing direction E by the compression coil spring 58 is a direction toward the center G side in the radial direction of the pressing roller 52, and as much as possible, the bias of the contact pressure between the power supply member and the belt is eliminated. It tries to prevent partial wear.

Here, also in the contact between the pressing roller 52 and the fixing belt 51, the elastic layer 522 of the pressing roller 52 is in elastic contact with the fixing belt 51, so that the pressing roller 52 and the fixing belt 51 contact as much as possible. The bias of pressure is eliminated, and the supporting force for supporting the fixing belt 51 of the pressing roller 52 is made uniform.
The urging portion 56b is similarly configured. Therefore, the power supply member 54b is also urged by the compression coil spring of the urging portion 56b, and the fixing belt 51 is sandwiched between the urged power supply member 54b and the pressing roller 52. .

FIG.3 (b) is the figure which expanded the part enclosed with the broken line of Fig.3 (a).
The sliding contact surface S1 that is in sliding contact with the electrode layer 515a of the power supply member 54a shown in FIG. 3B is formed along the outer peripheral surface 52a of the pressing roller 52 with the fixing belt 51 interposed therebetween. Specifically, the cross-sectional shape of the sliding contact surface S1 of the power supply member 54a is the same as the cross-sectional shape of the outer peripheral surface 52a of the pressing roller 52 in consideration of the thickness of the end t1 where the electrode layer 515a of the fixing belt 51 is provided. It is formed to be a concentric circular arc.

Thus, when the sliding contact surface S1 of the power supply member 54a is urged by the urging portion 56a to the end t1 of the fixing belt 51 and is sandwiched between the sliding contact surface S1 and the outer peripheral surface 52a of the pressing roller 52. In addition, there is no gap between the slidable contact surface S1 and the fixing belt 51 and between the region R1 pressed against the slidable contact surface S1 of the fixing belt 51 and the outer peripheral surface 52a.
At this time, a part of the outer peripheral surface 52a of the pressing roller 52 is in contact with the fixing belt 51 to form the contact surface S2, and the sliding contact surface S1 of the power supply member 54a is smaller than the size of the contact surface S2. When viewed in the urging direction E, the entire sliding contact surface S1 is included in the contact surface S2.

This is because when the power supply member 54a is pressed against the fixing belt 51, the fixing belt 51 is elastically deformed not only in the region R1 pressed against the sliding contact surface S1 of the power supply member 54a but also in the peripheral region inside the belt. This is to contact the outer peripheral surface 52 a of the pressing roller 52.
Thus, since the fixing belt 51 is supported by the contact surface S2 of the pressing roller 52 in a range wider than the region R1 of the fixing belt 51, the fixing belt 51 cannot be deformed inward within the contact range, and the power supply member 54a In the entire sliding surface, the surface pressure (contact pressure) due to the urging of the power supply member 54a can be set to a certain value or more.

As a result, even if foreign matter such as paper dust of the recording sheet or wear powder of parts adheres and accumulates on the surface of the fixing belt 51, the fixing belt 51 partially escapes and deforms inward as in the past. Thus, foreign matter does not enter between the power supply member 54a and the fixing belt 51.
Most of the foreign matter is removed from the fixing belt 51 by the front edge portion of the power supply member 54a (intersection formed by the end surface of the power supply member 54a on the upstream side of the rotation direction of the fixing belt 51 and the sliding contact surface S1). , Accumulated at the edge portion.

FIG. 5 is a schematic diagram for explaining a mechanism for preventing foreign matter from entering between the power supply member 54 a and the fixing belt 51, and FIG. 5A shows a foreign matter F attached to the surface of the fixing belt 51. FIG. 4B shows a state where the foreign matter F has been removed from the surface of the fixing belt 51.
As shown in FIG. 5A, when the foreign matter F adheres to the surface of the fixing belt 51, the foreign matter F collides with the front end surface 541a of the power supply member 54a as the fixing belt 51 rotates.

  As described above, since the entire region R1 of the fixing belt 51 is supported by the peripheral surface of the pressing roller 52, the fixing belt 51 is not allowed to be partially elastically deformed by foreign matter, and the power supply member 54a and the fixing belt 51 are not allowed. There is no room for foreign matter F to enter between the two. Therefore, the foreign matter F cannot enter between the power supply member 54a and the fixing belt 51, and the foreign matter F is peeled off from the fixing belt 51 by the shearing force applied by the edge portion on the front end surface 541a of the power supply member 54a. It is removed (FIG. 5 (b)).

In order to effectively apply such a shearing force applied to the foreign matter F, the power supply member 54a shown in FIG. 5A includes an end surface 541a on the upstream side in the rotation direction of the fixing belt 51 and a sliding contact surface S1. The angle θ1 of the edge portion K to be applied is preferably 90 [°] or less.
This is because, first, if the angle θ1 is an acute angle of less than 90 [°], the shearing force can be concentrated on the tip of the edge portion K, so that the effect of removing the foreign matter F can be enhanced. In this case, as the angle θ1 becomes sharper, the effect of peeling off becomes higher. For example, as shown in FIG. 6A, the power supply member 114 having an angle θ2 sharper than the angle θ1 of FIG. In this case, the effect of removing the foreign matter F is higher than that of the power supply member 54a of FIG.

Even if the angle θ1 is 90 [°], as shown in FIG. 6B, the shearing force P is applied only in the direction of the tangent L that contacts the surface of the fixing belt 51 with respect to the foreign matter F. When the angle θ3 shown in (c) is an obtuse angle exceeding 90 °, the shear force P is dispersed into the component p1 perpendicular to the upstream end surface 124a of the power supply member 124 and the component p2 parallel thereto. This is because the effect of removing the foreign matter F is higher than that. Even in the case of an obtuse angle exceeding 90 [°], the effect of removing the foreign matter F can be obtained depending on the magnitude of the urging force for urging the power supply member and the specifications of the power supply member and the fixing belt.
<Second Embodiment>
The fixing unit according to the second embodiment has a configuration in which a support member other than the pressure roller is separately arranged inside the fixing belt, and the fixing belt is sandwiched between the support member and the power supply member. This is different from the first embodiment.

Other configurations are basically the same as those of the fixing unit 5 of the first embodiment. Therefore, only the above differences will be described, and descriptions of other configurations will be omitted. In addition, the same reference numerals are used for the same components as those of the fixing unit 5 of the first embodiment.
FIG. 7A is a diagram illustrating a configuration of a main part of the fixing unit 150 according to the second embodiment, and is a schematic side view of the fixing belt 51 included in the fixing unit 150 as viewed from the rotation axis direction. .

As shown in FIG. 7A, the fixing unit 150 includes a pressing roller 152 and a support member 153 arranged inside the fixing belt 51, a pressure roller 53 and a power feeding member 154 arranged outside the fixing belt 51. , And an urging portion 155.
The outer diameter of the pressing roller 152 is set to be smaller than that of the pressing roller 52 of the first embodiment in order to secure a space for arranging the support member 153 inside the fixing belt 51.

  The support member 153 has a support surface 153a having an arcuate cross section, and is supported by a frame (not shown) or the like so that the support surface 153a is in sliding contact with the inner peripheral surface of the fixing belt 51. Has been. The curvature of the support surface 153 a is formed to have an R shape with substantially the same curvature as the inner peripheral surface of the fixing belt 51, and the entire surface is in sliding contact with the inner peripheral surface of the fixing belt 51.

  Such a support member 153 can be composed of, for example, a main body portion having a semicircular cross section and an elastic layer formed on the outer surface of the main body portion. The main body portion is made of, for example, a resin such as polyphenylene sulfide, polyimide, or a liquid crystal polymer, a metal such as aluminum or iron, or a material such as ceramic. The elastic layer is made of a material having high heat resistance and high heat insulation, such as a foamed elastic body such as silicone rubber or fluororubber. It is desirable to provide a low friction layer on the surface of this elastic layer for reducing friction with the fixing belt 51. The low friction layer can be formed, for example, by coating a glass cloth base material with a heat-resistant resin such as PTFE (polytetrafluoroethylene), and using a material such as a porous fluororesin. Can do.

In the present embodiment, the support surface 153a of the support member 153 has an R shape with substantially the same curvature as the inner peripheral surface of the fixing belt 51. However, the present invention is not limited to this, and the support surface 153a is not limited thereto. The curvature can be appropriately selected according to the specifications of the fixing belt 51, the support member 153, and the like.
The power supply member 154 is disposed on the opposite side of the support member 153 across the fixing belt 51, and is urged by the compression coil spring 158 included in the urging portion 155 and is in sliding contact with the fixing belt 51. The slidable contact surface S11 slidably contacting the fixing belt 51 of the power supply member 154 is formed along the support surface 153a of the support member 153.

  FIG. 7B shows the size and positional relationship between the sliding contact surface S11 of the power supply member 154 and the support surface 153a of the support member 153 when viewed from a direction parallel to the biasing direction E by the biasing portion 155. It is a figure explaining. As shown in FIG. 7B, the sliding contact surface S11 of the power supply member 154 is smaller than the support surface 153a (sliding contact surface) of the support member 153, and the entire sliding contact surface S11 is included in the support surface 153a. It has a configuration.

As described above, in the present embodiment, the sliding contact surface S11 of the power supply member 154 is formed along the support surface 153a of the support member 153, and is pressed by the sliding contact surface S11 of the power supply member 154 of the fixing belt 51. Since the entire region R2 is supported by the support member 153 and the fixing belt 51 is sandwiched between the power supply member 154 and the support member 153, the same effect as in the first embodiment can be obtained. it can.
[Modification]
As described above, the present invention has been described based on the embodiment. However, the present invention is not limited to the above-described embodiment, and the following modifications can be implemented.

(1) In the first embodiment, the configuration in which the pressing roller 52 that sandwiches the fixing belt 51 is loosely fitted inside the fixing belt 51 is shown. However, the present invention is not limited to this. The configuration may be such that 52 is squeezed and fitted inside the fixing belt 51.
Further, as shown in FIG. 8A, instead of the pressing roller 52, a long support member 162 provided with an arcuate sliding contact surface S21 that is in sliding contact with the inner peripheral surface of the fixing belt 51 is provided. You may use. In this case, the pressure roller 53 is pressed against the support member 162 via the fixing belt 51 to form the fixing nip portion N, and the entire region pressed against the power supply member 54 of the fixing belt 51 is supported. By adopting a configuration that is supported by the sliding contact surface S21 of the member 162, it is possible to obtain the same effect as that of the first embodiment.

  (2) In the above embodiment, the electrode layers 515a and 515b for supplying power to the resistance heating element layer 512 of the fixing belt 51 are provided on the outer peripheral surface of the resistance heating element layer 512. The configuration is not limited, and the electrode layer may be provided on the inner peripheral surface of the resistance heating element layer. In this case, for example, as shown in FIG. 8B, a power supply member 174 is arranged inside the fixing belt 171, and a support member 173 is arranged outside the fixing belt 171, and these power supply member 174 and the support member are arranged. By configuring so that the fixing belt 171 is sandwiched between the 173 and the 173, the same effect as in the first embodiment can be obtained.

  In this case as well, the entire area where the sliding contact surface S22 of the power supply member 174 is formed along the sliding contact surface S23 of the support member 173 and is pressed by the sliding contact surface S11 of the power supply member 154 of the fixing belt 171. Is supported by the sliding contact surface S22 of the support member 173. In this case, a biasing portion 175 that biases the support member 173 toward the constant belt 51 is provided.

(3) In the above embodiment, the configuration in which the fixing belt 51 is provided with the electrode layers 515a and 515b for supplying power to the resistance heating element layer 512 has been described. However, the present invention is not limited to this. It is also possible to supply power directly to the resistance heating element layer without providing an electrode layer on the belt.
In this case, since the resistance heating element layer has a higher electrical resistivity than the electrode layer made of a metal material, there is a possibility that spark discharge may occur even if a part of the power supply member is separated. By adopting the configuration as in the above-described embodiment, it is possible to prevent a gap from being generated between the resistance heating element layer and the power feeding member, and it is possible to prevent the occurrence of spark discharge. Therefore, the same effect as the above embodiment can be obtained.

(4) In the above embodiment, the configuration in which the compression coil spring 58 is used as the biasing member that biases the power supply members 54a and 54b has been described. However, the present invention is not limited to this. It is good also as a structure which supports
(5) In the said embodiment, the magnitude | size, shape, arrangement | positioning, etc. of an electric power feeding member are not limited. The shape of the slidable contact surface that contacts the fixing belt of the power supply member only needs to be configured as shown in the above embodiment, and the size, shape, arrangement, and the like of the power supply member depend on the specifications of the fixing unit. Can be appropriately selected.

  (6) Although the sliding contact surface of the power supply member is smaller than the contact surface of the pressing roller or the sliding contact surface of the support member in the above embodiment, the same size may be used. The size of the slidable contact surface of the power supply member should not be larger than the contact surface of the pressure roller or the slidable contact surface of the support member, and when viewed from a direction parallel to the direction of urging the power supply member, It is sufficient that the entire sliding contact surface is included in the contact surface of the pressing roller or the sliding contact surface of the support member. Here, “included in the plane” means, in other words, not protruding from the plane.

(7) In the above embodiment, the fixing belt 51 has a laminated structure in which the insulating layer, the resistance heating element layer, the elastic layer, and the release layer are laminated in this order. However, the present invention is limited to this. Instead, the configuration of the fixing belt can be appropriately selected according to the specifications of the fixing unit.
(8) In the above embodiment, a tandem full-color printer has been described as the image forming apparatus. However, the scope of the present invention is not limited to this, and a copying machine having a fixing unit using a resistance heating element, The present invention can be applied to a facsimile machine, a printer, and the like.

  Further, the contents of the above-described embodiment and modification examples may be combined as much as possible.

  The present invention relates to a fixing device and an image forming apparatus using the fixing device, and particularly to a fixing device using a belt including a resistance heating element layer, and can be used as a technique for preventing deterioration of the belt.

DESCRIPTION OF SYMBOLS 1 Printer 3 Image process part 3 Image forming part 4 Paper feed part 5 Fixing part 10 Optical part 11 Intermediate transfer belt 12 Drive roller 13 Driven roller 31 Photoreceptor drum 32 Charger 33 Developer 34 Primary transfer roller 35 Cleaner 41 Paper feed cassette 42 Roller 43 Conveying path 44 Timing roller pair 45 Secondary transfer roller 46 Secondary transfer position 51 Fixing belt 52 Pressing roller 53 Pressure roller 54 Power supply member 54a, 54b Power supply member 56a, 56b Energizing portion 58 Compression coil spring 114, 124, 154,174 Power supply member 153,162,173 Support member 153a Support surface (sliding contact surface)
155 Energizing portion 158 Compression coil spring 500 Power source 511 Insulating layer 512 Resistance heating element layer 513 Elastic layer 514 Release layer 515a, 515b Electrode layer 541a, 124a End surface (end surface on the upstream side of the power supply member)
S1 sliding surface (sliding surface of the power feeding member)
S2 Contact surface (contact surface of the pressure roller)
S11, S22 Sliding contact surface (sliding contact surface of power supply member)
S21, S23 Sliding contact surface (sliding contact surface of support member)

Claims (6)

A pressure member is pressed against the circumferential surface of an endless belt that rotates and includes a resistance heating element layer to form a nip portion, and a recording sheet on which an unfixed image is formed is passed through the nip portion and heated. A fixing device for fixing,
A power supply member that is electrically connected to an external power source and that slidably contacts an annular electrode layer extending in the circumferential direction at both ends of the peripheral surface of the belt;
A support member disposed on the opposite side of the power feeding member across the belt, and supporting the belt in contact with the belt;
A biasing means for biasing at least one of the power supply member and the support member toward the other member;
In a cross section perpendicular to the rotation axis of the belt, the sectional shape of the sliding contact sliding surface on the electrode layer of the belt of the feeding member, the cross-sectional shape and concentric arc of contact surface with the belt of the supporting member And the angle of the edge portion constituted by the end surface on the upstream side in the rotation direction of the belt of the power feeding member and the sliding contact surface is less than 90 °,
And when viewed from a direction parallel to the urging direction by the urging means, the shape of the power supply member and the support member is such that the sliding contact surface of the power supply member is included in the contact surface of the support member. A fixing device characterized in that the size is determined. The fixing device according to claim 1 , wherein a cross-sectional shape of the contact surface of the support member is an R shape in a cross section orthogonal to the rotation axis of the belt. A pressure roller that is pressed by the pressure member via the belt is disposed inside the rotation path of the belt,
The pressing roller is configured to serve also as the support member by pressing the power feeding member from the outer side of the rotating track of the belt toward the peripheral surface of the pressing roller via the belt. The fixing device according to claim 1 or 2 . The fixing device according to any one of the belt portions in contact of the support member, claims 1 to 3, characterized in that it is formed of an elastic body. The fixing device according to claim 4 , wherein the elastic body is a foam. An image forming apparatus comprising the fixing device according to any one of claims 1 to 5.

Images