JP5246253B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

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

2. Description of the Related Art Conventionally, some image forming apparatuses such as printers employ a fixing device using a fixing belt including a resistance heating layer, which can save energy compared to a fixing device using a halogen heater as a heat source. (For example, Patent Document 1)
FIG. 8A is a schematic perspective view showing a configuration example of such a fixing unit 500, and FIG. 8B is an enlarged cross-sectional view of the main part thereof.

As shown in FIG. 8A, the fixing unit 500 includes a fixing belt 554, a pressure roller 550, a pressure roller 560, a pair of power supply rollers 570 connected to an AC power source, and the like.
The pressure roller 550 has the surface of the rotary shaft portion 551 covered with an elastic layer 552 and is loosely inserted inside the rotation path of the fixing belt 554.

The pressure roller 560 is disposed outside the circulation path of the fixing belt 554 and presses the pressure roller 550 via the fixing belt 554 to form a fixing nip.
Further, the pressure roller 560 receives a driving force from a driving motor (not shown) and rotates in the direction of arrow P in FIG. When this driving force is transmitted to the pressing roller 550 via the fixing belt 554, the fixing belt 554 and the pressing roller 550 are driven to rotate in the direction of arrow Q in FIG.

  The fixing belt 554 is a cylindrical elastically deformable belt, and as shown in the sectional view of FIG. 8B, the release layer 554a, in order from the outer peripheral side, excluding both ends in the axial direction. It has a four-layer structure of a first insulating layer 554b, a resistance heating element layer 554c, and a second insulating layer 554d. Instead of the release layer 554a and the first insulating layer 554b at both ends in the axial direction, an electrode layer 554e is formed.

Here, the electrode layer 554e is made of a conductive material such as a metal foil, and is laminated on the resistance heating element layer 554c by plating or adhesion using a conductive adhesive.
The pair of power supply rollers 570 are configured to come into contact with the electrode 554e of the fixing belt 554 from the outer periphery of the fixing belt 554 and press downward (Z ′ direction) in FIG. 8B. Thus, power is supplied to the resistance heating layer 554c of the fixing belt 554.

Note that the width W1 of the power supply roller 570 is set to be smaller than the width W2 of the electrode layer 554e so that the power supply roller 570 does not ride on the release layer 554a to cause poor contact with the electrode layer 554e. ing.
In the above configuration, when power is supplied to the electrode 554e via the power supply roller 570 while the fixing belt 554 is driven to rotate, power is supplied to the resistance heating layer 554c of the fixing belt 554, and the entire resistance heating layer 554c is Fever.

  At this time, since the fixing belt 554 is not in contact with other members other than the portion pressed against the fixing nip and the power supply roller 570, the portion where heat is taken away is small, and the region of the fixing nip is caused by Joule heat generation. When the toner image formed on the recording sheet (not shown) passes through the fixing nip, the toner image is heated and pressurized to be thermally fixed to the recording sheet.

JP 2009-109997 A JP 2009-109998 A JP 2009-092785 A

However, when the fixing unit 500 having such a configuration is driven for a long period of time, only the portion of the electrode layer 554e of the fixing belt 554 that is in contact with the power supply roller 570 is pressed downward (in the Z ′ direction). Since such deformation is repeated, there is a problem that peeling easily occurs and the life of the fixing belt 554 is shortened.
The present invention has been made in view of the above problems, and an object of the present invention is to extend the life of a fixing belt in a resistance heating type fixing device and an image forming apparatus.

  In order to achieve the above object, a fixing device according to the present invention forms a fixing nip by pressing a pressure member on the outer peripheral surface of a heating rotator including a resistance heating layer, and forms a sheet on which an unfixed image is formed. A fixing device that heat-fixes paper by passing it through a fixing nip, wherein a bulk-shaped power supply member is attached to a pair of annular electrodes provided on a peripheral surface of the heating rotator with a sheet-passing range interposed therebetween. The surface of the power supply member facing the electrode is wider in the direction of the rotation axis of the heating rotator than the width of the electrode in the direction of the rotation axis; and In the contact position between the power supply member and the electrode, the entire region from one edge to the other edge in the width direction of the electrode is in contact with the power supply member.

  Since the entire region from one edge to the other edge in the width direction of the electrode is in contact with the power supply member at the contact position between the power supply member and the electrode, the stress generated in the electrode due to the contact The deformation is made uniform in the width direction, and local stress concentration and deformation do not occur and peeling is less likely to occur than in the conventional configuration in which the power supply member and the electrode are partially in contact in the width direction. be able to.

  The heating rotator is within a range between the inner peripheral surface and the outer peripheral surface of the heating rotator on the side where the pair of electrodes is provided and is sandwiched between the pair of electrodes. A non-heat-generating layer is laminated so as to cover the peripheral surface of the resistance heat-generating layer, and both edges in a direction parallel to the rotation axis of the non-heat-generating layer are respectively from the inner edge of the proximal electrode. It is desirable that the non-heat generating layer is formed so as to be located at a predetermined distance.

Furthermore, between the both edges of the non-heat generating layer of the resistance heating layer of the heating rotator and the inner edge of the electrode adjacent to each other, an insulating layer thinner than the thickness of the electrode is covered. It is desirable that
The heating rotator is within a range between the inner peripheral surface and the outer peripheral surface of the heating rotator on the side where the pair of electrodes is provided and is sandwiched between the pair of electrodes. When the non-heat generating layer is laminated so as to cover the peripheral surface of the resistance heating layer, and the pair of electrodes are present on the outer peripheral surface of the heating rotating body, the outer diameter of the electrodes is When the pair of electrodes are present on the inner peripheral surface of the heating rotating body, it is desirable that the inner diameter of the electrodes is smaller than the inner diameter of the non-heat generating layer.

The length and arrangement of the pressure member in a direction parallel to the rotation axis are preferably determined so as to contact within a range between the pair of electrodes of the heating rotator.
The pair of electrodes are preferably provided on an outer peripheral surface of the resistance heating layer in the heating rotator, and the non-heating layer preferably includes at least an elastic layer.
Alternatively, the pair of electrodes may be provided on the inner peripheral surface of the resistance heating layer in the heating rotator, and the non-heating layer may include at least a reinforcing layer.

Further, the pair of electrodes are provided on the inner peripheral surface side of the resistance heating layer in the heating rotator, and an insulating layer thinner than the thickness of the electrode is formed in a range sandwiched between the pair of electrodes. It is desirable that
Note that the present invention may be an image forming apparatus including the fixing device.

1 is a schematic diagram for explaining a configuration of a tandem type color printer which is an example of an image forming apparatus including a fixing device according to an embodiment of the present invention. FIG. 2 is a partially cutaway perspective view showing a configuration of the fixing device. It is a side view of the fixing device. It is sectional drawing when the said fixing device is cut | disconnected by the plane containing the roller axis | shaft. It is a fragmentary sectional view when the fixing device according to the modification is cut along a plane including the roller shaft. FIG. 6 is a cross-sectional view of a fixing device according to a modification when cut by a plane including the roller shaft. FIG. 10 is a cross-sectional view of a fixing device according to a modification. (A) is a perspective view of a fixing device in a conventional image forming apparatus, and (b) is an enlarged cross-sectional view of a main part thereof.

Hereinafter, embodiments of an induction heating unit, a fixing device, and an image forming apparatus according to the present invention will be described with reference to the drawings.
<Configuration of image forming apparatus>
FIG. 1 is a schematic diagram for explaining a configuration of a tandem type color printer (hereinafter simply referred to as “printer”) which is an example of an image forming apparatus including a fixing device according to an embodiment of the present invention.

  As shown in FIG. 1, the printer 1 includes an image processing unit 3, a paper feeding unit 4, a fixing unit 5, an optical unit 10, and a control unit 60. The printer 1 is connected to a network (for example, a LAN) and connected to an external device. When a print job execution instruction is received from a terminal device (not shown), a toner image composed of yellow, magenta, cyan and black is formed based on the instruction, and a full-color image is formed by multiple transfer of these toner images. .

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.
<Image process part>
The image processing unit 3 includes image forming units 30Y, 30M, 30C, and 30K corresponding to each of Y to K colors, an optical unit 10, an intermediate transfer belt 11, and the like.

  The image forming unit 30Y includes a photosensitive drum 31Y, a charger 32Y disposed around the photosensitive drum 31Y, a developing unit 33Y, a primary transfer roller 34Y, a cleaner 35Y for cleaning the photosensitive drum 31Y, and the like. A Y-color toner image is formed on the drum 31Y. The other image forming units 30M to 30K have the same configuration as that of the image forming unit 30Y, and the reference numerals are omitted in FIG.

The intermediate transfer belt 11 is an endless belt, is stretched around a driving roller 12 and a driven roller 13, and is rotationally driven in the direction of arrow A.
The optical unit 10 includes a light emitting element such as a laser diode, emits a laser beam L for forming an image of Y to K colors by 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 superimposed on the same positions on the intermediate transfer belt 11 and primarily transferred onto the photosensitive drums 31Y to 31K. It is executed at different timings.
The toner images of the respective colors are sequentially transferred onto the intermediate transfer belt 11 by the electrostatic force acting on the primary transfer rollers 34Y to 34K to form a full-color toner image, and further move toward the secondary transfer position 46.

  On the other hand, the paper feed unit 4 includes a paper feed cassette 41 that stores the recording sheets S, a feed roller 42 that feeds the recording sheets S in the paper feed cassette 41 one by one onto the transport path 43, and a fed recording sheet S. Are provided with a timing roller pair 44 for taking the timing of feeding the toner to the secondary transfer position 46, and the recording sheet S is transferred from the paper feeding unit 4 to the secondary transfer position in accordance with the movement timing of the toner image on the intermediate transfer belt 11. The toner images on the intermediate transfer belt 11 are collectively transferred onto the recording sheet S by the action of the secondary transfer roller 45.

The recording sheet S that has passed the secondary transfer position 46 is conveyed to the fixing unit 5, and the toner image (unfixed image) on the recording sheet S is fixed to the recording sheet S by heating and pressurization in the fixing unit 5. Thereafter, the sheet is discharged onto the discharge tray 72 via the discharge roller pair 71.
<Fixing part>
FIG. 2 is a partial cross-sectional perspective view showing the configuration of the fixing unit 5, and FIG.

As shown in FIG. 2, the fixing unit 5 includes a fixing belt 154, a pressing roller 150, a pressure roller 160, and a power supply member 170.
The pressure roller 150 is arranged with play on the inner side of the circulation path of the fixing belt 154.
Further, the pressure roller 160 is disposed outside the circulation path of the fixing belt 154, and is driven to rotate in the direction of arrow D by a driving mechanism (not shown) and is pressed from the outside of the fixing belt 154 via the fixing belt 154. The roller 150 is pressed.

As a result, the fixing belt 154 and the pressing roller 150 are driven to rotate in the direction of arrow E, and a fixing nip N is formed between the surface of the fixing belt 154.
When a recording sheet (not shown) passes through the fixing nip N while the fixing nip N is maintained at the target temperature, an unfixed toner image on the recording sheet is heated, pressurized, and thermally fixed. .

Hereinafter, the configuration of each part of the fixing unit 5 will be described in detail.
<Pressing roller>
As shown in FIG. 2, the pressing roller 150 is formed by forming an elastic layer 152 around a long and cylindrical rotating shaft portion 151.
The rotating shaft portion 151 is a solid shaft made of, for example, aluminum, iron, stainless steel or the like, and has an outer diameter of 20 mm. Both end portions in the axial direction rotate to bearing portions of the main body side frame of the fixing portion 5 (not shown). It is supported freely.

Instead of such a solid shaft, a hollow shaft having a thickness of 0.1 mm to 10 mm, or a structure having a reinforcing rib having a Y-shaped cross section inside the hollow may be used.
The elastic layer 152 is made of a material having high heat resistance and high heat insulation, for example, a foamed elastic body such as silicone rubber or fluorine rubber, and has a thickness of 1 mm to 20 mm. , 20 mm or more and 100 mm or less, but here it is set to 30 mm.
(After that, please fill in the underlined brackets.)
The length of the elastic layer 152 in the Y-axis direction is 374 mm.

Of course, the length of the elastic layer 152 in the Y-axis direction is set to be larger than the maximum sheet passing width of the recording sheet S.
<Configuration of pressure roller>
As shown in FIG. 2, the pressure roller 160 includes a rotating shaft portion 161 and an elastic body layer 162 that covers a portion excluding both ends thereof.

The rotating shaft portion 161 is rotationally driven by a drive mechanism (not shown), and is a solid shaft made of, for example, aluminum, iron, stainless steel or the like and having an outer diameter of 30 mm.
Instead of such a solid shaft, a hollow shaft having a thickness of 0.1 mm to 10 mm, or a structure having a reinforcing rib having a Y-shaped cross section inside the hollow portion may be used.

The elastic body layer 162 is a cylindrical body made of silicone rubber, and the thickness is desirably 1 mm or more and 20 mm or less.
In the present embodiment, the elastic layer 162 has a thickness of 3 mm and an outer diameter of 36 mm.
Further, the length of the elastic body layer 162 in the Y-axis direction is 330 mm.
<Power supply member>
The power supply member 170 is electrically connected to an external AC power supply 180 via a lead wire 175, and is in sliding contact with a pair of electrode layers 154e (described later) of the fixing belt 154 to supply power thereto. is there.

The lead wire 175 is connected to an AC power source 180 via a switch circuit (not shown), and the control unit 60 controls the switch circuit based on the surface temperature of the fixing belt 154 detected by a temperature sensor (not shown). By performing ON / OFF control, the fixing belt 154 has a predetermined target temperature.
The power supply member 170 includes a brush portion 171 and a leaf spring 172.

The brush portion 171 is, for example, a bulky conductor having a thickness of 30 mm in the Z-axis direction, a width of 20 mm in the Y-axis direction, and a depth of 5 mm, and has both slidability and conductivity. This is a so-called carbon brush made of these materials.
In the brush portion 171 in the present embodiment, the width in the Y-axis direction is set larger than the width in the Y-axis direction of the electrode layer 154e. The reason will be described later.

The leaf spring 172 is a rectangular plate body such as phosphor bronze having conductivity and elasticity, and one end portion is fixed to an insulator on the main body side (not shown) of the printer 1 and the other end portion. Is joined to the brush portion 171 with an adhesive or the like having conductivity.
As shown in FIG. 3, the leaf spring 172 forms a power feeding path for the brush portion 171 and presses the brush portion 171 against the outer periphery of the electrode layer 154e.
<Fixing belt>
FIG. 4 is a schematic cross-sectional view in the direction of the rotation axis of the pressure roller 160 of the fixing device according to the present embodiment.

The fixing belt 154 is an endless belt that is elastically deformable and has a laminated structure.
As shown in FIG. 4, in the fixing belt 154, an elastic layer 154c and a release layer 154d are laminated in this order in a region excluding both ends of the outer peripheral surface of the resistance heating layer 154b. The electrode layer 154e and the insulating layer 154f are both laminated so that the insulating layer 154f is on the elastic layer 154c side.

Hereinafter, each layer constituting the fixing belt 154 will be described in detail.
The resistance heating layer 154b is a cylindrical heating element that generates Joule heat when current flows due to a potential difference at both ends in the Y-axis direction.
More specifically, the resistance heating layer 154b has a thickness of 5 μm or more and 100 μm or less, and one or more kinds of conductive fillers having different electrical resistivity are uniformly dispersed in PI (polyimide) resin. Become.

The length of the resistance heating layer 154b in the Y-axis direction is 374 mm.
In addition, PPS, PEEK, and the like can be used as a base material (hereinafter referred to as “base material”) used for the resistance heating layer 154b.
Here, as the conductive filler, metal powder such as Ag, Cu, Al, Mg and Ni, or carbon compound powder such as graphite, carbon black, carbon nanofiber and carbon nanotube, or silver iodide, copper iodide. Examples thereof include high ionic conductors in inorganic compounds, and the shape thereof is preferably fibrous to increase the probability of contact between the conductive fillers per unit content.

In the present embodiment, a conductive filler having a fibrous shape, for example, Ni, is uniformly dispersed in the base material.
Here, the volume resistivity of the resistance heating layer 154b is desirably about 10 × 10 ^ −6 to 1.0 × 10 ^ −2 Ω · m. Further, in the specification of the fixing unit 5 in the present embodiment, It is desirable to set the volume resistivity to 1.0 × 10 ^ −5 to 5.0 × 10 ^ −3 Ω · m.

The elastic layer 154c is made of a material having elasticity and heat resistance, such as silicone rubber, and has a thickness of about 200 μm.
The material of the elastic layer 154c may be fluorine rubber or the like in addition to silicone rubber.
The release layer 154d is made of a material having releasability such as fluorine resin such as PTFE or PFA, and has a thickness of 5 μm or more and 100 μm or less.

Here, both ends of the elastic layer 154c and the release layer 154d are provided at positions separated by a predetermined distance from the inner ends of the adjacent electrode layers 154e in order to avoid interference with the power supply member 170. Yes.
The electrode layer 154e is formed so as to go around the outer periphery of both ends in the Y-axis direction of the resistance heating layer 154b, and functions as a pair of annular electrodes for supplying power to the resistance heating layer 154b.

The electrode layer 154e is formed by, for example, chemically plating Cu, Al, Ni, brass, phosphor bronze, or the like having a lower electrical resistivity than the resistance heating layer 154b on both ends of the outer periphery of the resistance heating layer 154b, It is formed by performing plating or the like.
When electroplating is performed after chemical plating is performed in advance and a thin film is formed on the resistance heating layer 154b, the plating time can be shortened, which is efficient.

In addition, a belt-like sheet made of the above-described material may be attached to both ends of the resistance heating layer 154b in the Y-axis direction with the conductive adhesive or the like.
The width of the electrode layer 154e (the length in the Y-axis direction) is 18 mm.
Furthermore, the thickness of the electrode layer 154e is preferably 5 μm or more and 100 μm or less in order to ensure flexibility necessary to follow the deformation of the belt in the fixing nip N while having an appropriate strength. It is set to 20 μm.

  Here, as shown in FIG. 4, the electrode layer 154e passes through the fixing nip N so that a large stress is not generated due to the nip pressure applied with the rotation of the fixing belt 154. Is not provided in the area to be pressed (hereinafter referred to as “pressing area”), but is an area other than the pressing area located on both outer sides of the pressing area in the Y-axis direction (hereinafter referred to as “non-pressing area”). It is desirable to provide in.

Therefore, in the fixing unit 5 in the present embodiment, the length W3 of the elastic body layer 162 of the pressure roller 160 is longer than the length W1 of the fixing belt 154, as shown in FIG. It is set to be smaller than those obtained by subtracting the length W2.
<Relationship Between Width of Electrode Layer of Fixing Belt and Width of Brush Portion>
Further, the brush portion 171 of the power supply member 170 in the present embodiment has a width W5 in the Y-axis direction set to be larger than a width W2 in the Y-axis direction of the electrode layer 154e, and the power supply member 170 and the electrode layer At the contact position of 154e, the entire area from one edge to the other edge in the width direction (Y-axis direction) of the electrode layer 154e is in contact with the power supply member 170 in the Y-axis direction. The position has been determined.

  Thereby, the brush portion 171 contacts the entire width direction (Y-axis direction) of the electrode layer 154e, and stress and deformation generated in the electrode layer 154e due to the contact are made uniform in the Y-axis direction. As compared with the conventional configuration in which the brush portion and the electrode layer are partially in contact with each other in the Y-axis direction, local stress concentration and deformation hardly occur, so that peeling is less likely to occur. Therefore, the durability of the electrode layer 154e is greatly improved, and the life of the fixing belt 154 can be extended.

The insulating layer 154f is thinner than the electrode layer 154e, is adjacent to the electrode layer 154e, and is provided on the outer peripheral surface side of the fixing belt 154 so as to cover the resistance heating layer 154b.
With this configuration, the brush portion 171 rides on the insulating layer 154f and does not cause poor contact with the electrode layer 154e, and power is directly supplied between the brush portion 171 and the resistance heating layer 154b. There is no risk of abnormal heat generation.

Note that, since the fixing belt 154 may meander in the width direction (Y-axis direction), even if it is meandering, a pair of elastic body layers 162 may be prevented from pressing the electrode layer 154e. It is desirable to set the distance between the portions where the brush portions 171 of the power supply member 170 and the elastic body layer 162 of the pressing roller 150 are close to each other to 2 mm or more.
For this reason, it is desirable to set the width of the insulating layer 154f in the Y-axis direction to be larger than 2 mm. The upper limit is naturally determined by the size of the image forming apparatus, but need not exceed 20 mm.
<Modification>
The present invention is not limited to the above-described embodiment, and the following modifications can be implemented.

(1) In the above embodiment, the fixing belt 154 includes the resistance heating layer 154b, the elastic layer 154c, the release layer 154d, the electrode layer 154e, and the insulating layer 154f. I can't.
For example, in some cases, the elastic layer 154c and the release layer 154d may be omitted.

Alternatively, for example, a new layer may be added, such as providing an insulating layer made of a non-conductive material such as PI (polyimide) on the inner peripheral surface side of the resistance heating layer 154b.
(2) In the above-described embodiment, the power supply member 170 has the bulk brush portion 171 in contact with the electrode layer 154e of the pressure roller 160. For example, instead of the brush portion 171, the metal roller Such a bulk conductor may be used to maintain electrical contact with the electrode layer 154e while reducing friction.

Even in this case, in order to suppress the occurrence of peeling of the electrode layer 154e, the width of the metal roller in the Y-axis direction is made wider than the width of the electrode layer 154e in the Y-axis direction, and the width of the electrode layer 354e. The entire region from one edge portion to the other edge portion in the direction (Y-axis direction) needs to be brought into contact with the power supply member 170.
(3) In the above embodiment, it has been described that the thickness of the electrode layer 154e is preferably 5 μm or more and 100 μm or less from the viewpoint of durability and followability, but the electrode layer 154e is sufficiently separated from the pressing region of the fixing nip. Under the condition that the cross-sectional shape of the electrode layer 154e is not significantly deformed during rotation, such as being provided at a position, the thickness of the electrode layer 154e may be set to be larger than this.

FIG. 5 is a diagram illustrating the configuration of the fixing belt 254 having such a configuration.
The fixing belt 254 includes an elastic layer 254c and a release layer so as to fill a portion sandwiched between the pair of electrode layers 254e and the resistance heating layer 254b, the electrode layers 254e provided at both ends of the outer peripheral surface thereof. 254d are laminated in this order, and the thickness t2 of the electrode layer 254e is set to be larger than the total thickness t3 of the elastic layer 254c and the release layer 254d.

That is, when the power feeding member 170 is brought into contact with the electrode layer 154e, the facing portion between the end of the brush portion 171 and the release layer 254d is separated by a separation distance L2 so that the brush portion 171 does not interfere with the release layer 254d. It is set to be.
With such a configuration, it is not necessary to provide the insulating layer 154f like the fixing belt 154 in the above embodiment, and the structure can be simplified.

Since the brush portion 171 wears the contact portion during long-term use, even if such wear occurs during the service life, the brush portion 171 does not contact the release layer 254d. The separation distance L2 in the initial state is desirably set to 50 μm or more.
(4) In the above embodiment, the electrode layer 154e is provided at both ends of the outer peripheral surface of the fixing belt 154. However, the present invention is not limited to this configuration.

For example, as shown in FIG. 6, the electrode layer 354e is provided at both ends of the inner peripheral surface of the fixing belt 354, and accordingly, the power supply member 170 is also arranged on the inner peripheral side of the fixing belt 354. Power may be supplied by bringing the power supply member 170 into contact with the electrode layer 354e.
At this time, in the fixing belt 354, a release layer 354d, an elastic layer 354c, and a resistance heating layer 354b are laminated in order from the outer peripheral side, and electrode layers are formed at both ends on the inner peripheral surface side of the resistance heating layer 354b. A structure in which 354e is stacked may be used.

In this case, in order to suppress the occurrence of peeling of the electrode layer 354e, the width of the power supply member 170 in the Y-axis direction is made larger than the width of the electrode layer 354e in the Y-axis direction, and the width direction of the electrode layer 354e (Y It is necessary to bring the entire region from one edge to the other edge in the axial direction into contact with the power supply member 170.
In such a configuration, the end of the power supply member 170 near the elastic layer 252 of the brush portion 171 approaches the resistance heating layer 354b, so there is a possibility that a short circuit due to discharge or contact may occur in this portion. Here, as shown in the figure, in the resistance heating layer 354b, a range where such a short circuit may occur is covered with an insulating layer 354f.

At this time, it is desirable that the thickness of the insulating layer 354f is set to be thinner than the thickness of the electrode layer 354e so that the brush portion 171 of the power feeding member 170 rides on the insulating layer 354f so that good power feeding is not hindered.
Note that when the brush portion 171 of the power supply member 170 is pressed against the electrode layer 354e, the electrode layer 354e is provided on the side where the electrode layer 354e is provided so that the electrode layer 354e does not retract and the contact surface pressure decreases. It is desirable that the elastic layer 162 of the pressure roller 360 is in contact with the opposite surface.

Therefore, in the same figure, the length of the elastic layer 262 in the pressure roller 360 in the axial direction is longer than that of the elastic layer 252 of the pressing roller 350.
As shown in FIG. 6, in the configuration in which the electrode layer 354e is provided on the inner peripheral surface of the fixing belt 354, it is on the inner peripheral surface side of the resistance heating layer 354b and is sandwiched between the pair of electrode layers 354e. A configuration in which a reinforcing layer for improving the strength is laminated in a range that can be considered.

Since the reinforcing layer normally has insulating properties, when the thickness of the reinforcing layer can be set to be thinner than the electrode layer 354e, the insulating layer 354f does not need to be provided. When the thickness cannot be set smaller than 354e, an insulating layer 354f needs to be provided between the reinforcing layer and the electrode layer 354e.
(5) In the above embodiment, the power supply member 170 that contacts the electrode layer 154e is on the extension of the fixing nip N in the Y-axis direction, as shown in FIG. However, when viewed from the direction of the rotation axis of the pressure roller 150, the position may be shifted from the position on the extension of the fixing nip N in the Y-axis direction.

When the amount of displacement is large, when a fixing member that is long in the Y-axis direction is applied to the fixing belt 154 from the side opposite to the side where the power supply member 170 is present, It is desirable that large deformation does not occur in the electrode layer 154e.
(6) In the above embodiment, the pressing roller 150 is arranged with play inside the circulation path of the fixing belt 154, but it is arranged inside the circulation path of the fixing belt 154 without play. It does not matter.

(7) In the above-described embodiment, the fixing belt 154 is sandwiched to form the fixing nip, and each of them is constituted by a rotating body such as the pressure roller 150 or the pressure roller 160. Only one of the two may be replaced with a member that is fixed without rotating the other.
FIG. 7 is a diagram illustrating an example of a configuration when the fixing device in such a case is viewed from the Y direction.

In this example, a pressing member 350 is loosely inserted inside the rotation path of the fixing belt 154 instead of the pressing roller 150.
Here, the pressing member 350 includes an elastic member 351 that is long in the direction perpendicular to the paper surface of the drawing and a sliding sheet 352 that is provided so as to cover a part of the outer periphery of the member 351 and has a small friction coefficient. doing.

(8) Further, as in the above-described embodiment, the pressure roller 160 is driven to rotate and the pressure roller 150 is driven to rotate. However, the present invention is not limited to this configuration.
For example, the pressure roller 150 may be driven to rotate, and the pressure roller 160 may be driven to rotate.
(9) In the above-described embodiment, an example in which the image forming apparatus according to the present invention is applied to a tandem color digital printer has been described. However, the present invention is not limited to this, and the first and the first rotating one of them. A fixing device in which a first pressing member among the two pressing members is disposed inside the fixing belt and is pressed by the second pressing member through the fixing belt to form a fixing nip; In addition, the present invention can be applied to general image forming apparatuses including the fixing device.

  The contents of the above embodiment and the above modification may be combined.

  The present invention forms a fixing nip by pressing a pressure member on the outer peripheral surface of a heating rotator including a resistance heating layer and an electrode for supplying power thereto, and a sheet on which an unfixed image is formed is connected to the fixing nip. The present invention can be widely applied to a fixing device and an image forming apparatus in which heat is fixed by passing paper.

DESCRIPTION OF SYMBOLS 1 Printer 3 Image process part 4 Paper feed part 5,105,205 Fixing part 11 Intermediate transfer belt 30Y, 30M, 30C, 30K Image formation part 31 Photosensitive drum 32 Charger 33 Developer 34 Primary transfer roller 45 Secondary transfer roller 46 Secondary transfer position 60 Control section 71 Discharge roller pair 72 Discharge tray 150,250 Press roller 151 Rotating shaft section 152,252 Elastic layer 154,254,354 Fixing belt 154b, 254b, 354b Resistance heating layer 154c, 254c, 262, 354c Elastic layer (non-heat generating layer)
154d, 254d, 354d Release layer (non-heat generation layer)
154e, 254e, 354e Electrode layer 160, 260 Pressure roller 161 Rotating shaft portion 162 Elastic body layer 170 Power supply member 171 Brush portion 172 Leaf spring 175 Lead wire 180 Power source 175 Lead wire 180 AC power source 350 Press member 351 Long member 352 Sliding sheet

Claims (9)

A fixing device that forms a fixing nip by pressing a pressure member on an outer peripheral surface of a heating rotator including a resistance heating layer, and heat-fixes a sheet on which an unfixed image is formed by passing the sheet through the fixing nip. ,
It has a configuration in which a bulk-shaped power supply member is brought into contact with a pair of annular electrodes provided across the sheet passing range on the peripheral surface of the heating rotator to supply power,
The width of the surface of the power supply member facing the electrode in the rotation axis direction of the heating rotator is wider than the width of the electrode in the rotation axis direction, and the contact position between the power supply member and the electrode The fixing device, wherein the entire region from one edge to the other edge in the width direction of the electrode is in contact with the power supply member. Of the inner peripheral surface and the outer peripheral surface of the heating rotator, the peripheral surface on the side where the pair of electrodes is provided, and within the range sandwiched between the pair of electrodes, the resistance of the heating rotator A non-heat generating layer is laminated so as to cover the peripheral surface of the heat generating layer,
The non-heat-generating layer is formed such that both edges of the non-heat-generating layer in the direction parallel to the rotation axis are at a predetermined distance from the inner edge of the proximal electrode. The fixing device according to claim 1.   The resistance heating layer of the heating rotator is covered with an insulating layer that is thinner than the thickness of the electrode between both edges of the non-heating layer and the inner edge of each proximal electrode. The fixing device according to claim 2, wherein: Of the inner peripheral surface and the outer peripheral surface of the heating rotator, the peripheral surface on the side where the pair of electrodes is provided, and within the range sandwiched between the pair of electrodes, the resistance of the heating rotator A non-heat generating layer is laminated so as to cover the peripheral surface of the heat generating layer,
When the pair of electrodes are present on the outer peripheral surface of the heating rotator, the outer diameter of the electrodes is larger than the outer diameter of the non-heat generating layer,
2. The fixing device according to claim 1, wherein when the pair of electrodes are present on an inner peripheral surface of the heating rotator, an inner diameter of the electrodes is smaller than an inner diameter of the non-heat generating layer. The length and arrangement of the pressurizing member in a direction parallel to the rotation axis are determined so as to abut within a range between the pair of electrodes of the heating rotator. 5. The fixing device according to any one of items 4 to 4. The pair of electrodes are provided on an outer peripheral surface of a resistance heating layer in the heating rotator,
The fixing device according to claim 1, wherein the non-heat generating layer includes at least an elastic layer. The pair of electrodes are provided on an inner peripheral surface of a resistance heating layer in the heating rotator,
The fixing device according to claim 1, wherein the non-heat generating layer includes at least a reinforcing layer. The pair of electrodes are provided on the inner peripheral surface side of the resistance heating layer in the heating rotator,
The fixing device according to claim 1, wherein an insulating layer thinner than a thickness of the electrode is formed in a range between the pair of electrodes.   An image forming apparatus comprising the fixing device according to claim 1.

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