JP7187766B2 - Fixing device and image forming device - Google Patents

Description

The present invention relates to fixing devices and image forming apparatuses.

A heating resistor and an electrode for supplying power to the heating resistor are formed in the longitudinal direction of a long flat plate-shaped substrate made of a heat-resistant and insulating material, and glass paste is printed on the substrate and the heating resistor.・In a ceramic heater with an overcoat layer formed by firing, by making the size of air bubbles generated in the overcoat layer larger on the substrate than on the heating resistor, the unevenness of the surface of the overcoat layer is smoothed out. A smaller ceramic heater is known (Patent Document 1).

In a multiple resistance element structure in which a pair of electrodes are arranged side by side at regular intervals on a substrate, a resistor connecting each pair of electrodes is provided, and a protective sheath covering a part of the resistor and the electrode is applied There is also known a multiple resistance element structure in which a filling layer is provided between each resistance element composed of each pair of electrodes and a resistance element to fill the step between the resistance element and the substrate surface. (Patent document 2).

JP-A-2006-92831 JP-A-5-251220

SUMMARY OF THE INVENTION The present invention provides a fixing device capable of ensuring wettability of a lubricant and improving sliding characteristics of a belt member.

In order to solve the above problems, the fixing device according to claim 1 comprises:
a circulating belt member;
a pressing member that contacts the belt member and presses the recording medium moving between the belt member;
a lubricant interposed on the inner surface of the belt member;
a heating source that has a plurality of resistance heating elements on a base material, and an insulator that covers the plurality of resistance heating elements and gaps between the plurality of resistance heating elements, and heats the inner surface of the belt member;
The heat source forms a convex shape toward the pressure member at the positions of the plurality of resistance heating elements, and is wider than the convex shape in the gap between the plurality of resistance heating elements and extends in the direction in which the resistance heating elements extend. a continuous concave shape along the gap and a convex shape at the center of the gap ,
It is characterized by

The invention according to claim 2 is the fixing device according to claim 1, wherein:
The heating source is configured such that, in the contact portion where the belt member and the pressure member are in contact, the pressure in the gap between the plurality of resistance heating elements is higher than that on the downstream side and the upstream side in the moving direction of the recording medium. supporting the belt member from the inside so as to be relatively high;
It is characterized by

The invention according to claim 3 is the fixing device according to claim 2,
the width of the gap of the plurality of resistance heating elements is longer than the width of the resistance heating elements;
It is characterized by

The invention according to claim 4 is the fixing device according to claim 1, wherein:
The thickness of the insulator is such that a portion covering the resistance heating element is thinner than a portion covering the base material.
It is characterized by

The invention according to claim 5 is the fixing device according to claim 1,
The thickness of the insulator is such that a portion covering the resistance heating element is thicker than a portion covering the base material.
It is characterized by

The invention according to claim 6 is the fixing device according to claim 4 or 5, wherein
The thickness of the insulator is such that a portion covering the base between the plurality of resistance heating elements is thinner than a portion covering the base outside the resistance heating elements.
It is characterized by

The invention according to claim 7 is the fixing device according to any one of claims 1 to 6,
the lubricant intervenes at least between the belt member and the gap ;
It is characterized by

In order to solve the above problems, the image forming apparatus according to claim 8 includes:
an image forming means for forming an image on a recording medium;
and a fixing device according to any one of claims 1 to 7 for fixing the image on the recording medium on which the image is formed by the image forming means,
It is characterized by

According to the first aspect of the invention, the wettability of the lubricant is ensured compared to the configuration in which the heating source is not formed in a convex shape toward the pressure member at the positions of the plurality of resistance heating elements. As a result, the sliding characteristics of the belt member can be improved.

According to the second aspect of the invention, it is possible to form a plurality of regions in which the lubricant intervenes between the inner surface of the belt member.

According to the second aspect of the invention, it is possible to form a plurality of regions in which the lubricant intervenes between the inner surface of the belt member.

According to the third aspect of the invention, it is possible to suppress a decrease in the efficiency of heat transfer to the belt member compared to a configuration in which the portion of the insulator covering the resistance heating element is thicker than the portion covering the base material.

According to the fourth aspect of the present invention, it is possible to suppress deterioration of the slidability of the belt member compared to a configuration in which the portion of the insulator covering the resistance heating element is thinner than the portion covering the base material.

According to the fifth aspect of the invention, compared to the configuration in which the portion of the insulator covering the substrate between the plurality of resistance heating elements is thicker than the portion covering the substrate outside the resistance heating elements, It is possible to increase the area where the lubricant intervenes between the inner surface of the belt member.

According to the sixth aspect of the invention, wettability of the lubricant to the inner surface of the belt member can be ensured.

According to the seventh aspect of the invention, a gap for retaining lubricant can be formed between the resistance heating elements.

According to the eighth aspect of the invention, the wettability of the lubricant is ensured compared to the configuration in which the heating source is not formed in a convex shape toward the pressure member at the positions of the plurality of resistance heating elements. As a result, the sliding characteristics of the belt member can be improved.

2 is a schematic cross-sectional view showing the internal configuration of the image forming apparatus; FIG. 1 is a schematic cross-sectional view showing the configuration of a fixing device; FIG. It is a plane schematic diagram which shows the structure of a heat source. 4 is an enlarged schematic cross-sectional view taken along line AA in FIG. 3 for explaining the configuration of a heat source; FIG. 3A is a schematic cross-sectional view showing the configuration of a heat source in the fixing device, and FIG. 3B is a view showing an example of pressure distribution in the fixing nip; FIG. FIG. 8A is a schematic cross-sectional view showing a fixing nip when the distance between resistive heat generation gaps is wide, and FIG. 8B is a view showing an example of pressure distribution in the fixing nip; It is an enlarged cross-sectional schematic diagram of a heat source explaining the thickness of an insulator. 9A is a schematic cross-sectional view for explaining the thickness of an insulator of a heat source according to Modification 2, and FIG. 9B is a view showing an example of pressure distribution within a fixing nip; FIG. FIG. 10 is a schematic cross-sectional view for explaining the thickness of the insulator of the heat source according to Modification 2; FIG. 11 is a schematic cross-sectional view illustrating the thickness of the insulator of the heat source according to Modification 3;

Next, with reference to the drawings, the present invention will be described in more detail with reference to embodiments and specific examples, but the present invention is not limited to these embodiments and specific examples.
In addition, in the explanation using the drawings below, it should be noted that the drawings are schematic, and the ratio of each dimension is different from the actual one. Illustrations other than members are omitted as appropriate.
To facilitate understanding of the following description, in the drawings, the horizontal direction is defined as the X-axis direction, the front-rear direction as the Y-axis direction, and the vertical direction as the Z-axis direction.

"First Embodiment"
(1) Overall Configuration and Operation of Image Forming Apparatus FIG. 1 is a schematic cross-sectional view showing the internal configuration of an image forming apparatus 1 according to this embodiment.
Hereinafter, the overall configuration and operation of the image forming apparatus 1 will be described with reference to the drawings.

The image forming apparatus 1 includes a control device 10 , a paper feeding device 20 , a photosensitive unit 30 , a developing device 40 , a transfer device 50 , a fixing device 60 and a power supply device 70 . On the upper surface (Z direction) of the image forming apparatus 1, there is formed a discharge tray 1a for discharging and containing sheets of paper on which images are recorded.

The control device 10 includes an image forming device control section 11 that controls the operation of the image forming device 1, a controller section 12 that prepares image data according to a print processing request, an exposure control section 13 that controls lighting of the exposure device LH, and the like. have

The controller unit 12 converts print information input from an external information transmission device (for example, a personal computer, etc.) into image information for forming a latent image, and outputs a drive signal to the exposure device LH at preset timing. . The exposure apparatus LH of this embodiment is configured by an LED head in which a plurality of light emitting elements (LEDs: Light Emitting Diodes) are linearly arranged along the main scanning direction.

A paper feeding device 20 is provided at the bottom of the image forming apparatus 1 . The paper feeding device 20 has a paper stacking plate 21 on which a large number of papers P as recording media are stacked. Sheets P stacked on the sheet stacking plate 21 and positioned in the width direction by a regulating plate (not shown) are pulled out forward (in the X direction) one by one from the upper side by the sheet drawer 22, and then passed through a pair of registration rollers. 23 nip portion.

The photoreceptor units 30 are arranged in parallel above the paper feeding device 20 (in the Z direction), and include photoreceptor drums 31 as rotationally driven image carriers. A charging roller 32 , an exposure device LH, a developing device 40 , a primary transfer roller 52 and a cleaning blade 34 are arranged along the rotation direction of the photosensitive drum 31 . A cleaning roller 33 that cleans the surface of the charging roller 32 is arranged to face and contact the charging roller 32 .

The developing device 40 has a developing housing 41 in which a developing agent made up of toner and carrier is accommodated. In the developing housing 41, there are provided a developing roller 42 as a developer holding member disposed facing the photosensitive drum 31, and a developing roller 42 disposed obliquely below the back side of the developing roller 42 for agitating and conveying the developer toward the developing roller 42 side. A pair of augers 44, 45 are provided. A layer regulating member 46 that regulates the layer thickness of the developer is arranged close to the developing roller 42 .
Each developing device 40 has the same configuration except for the developer accommodated in the developing housing 41, and forms yellow (Y), magenta (M), cyan (C), and black (K) toner images, respectively. .

The surface of the rotating photosensitive drum 31 is charged by the charging roller 32, and an electrostatic latent image is formed by latent image forming light emitted from the exposure device LH. The electrostatic latent image formed on the photosensitive drum 31 is developed as a toner image by the developing roller 42 .

The transfer device 50 has an intermediate transfer belt 51 onto which the toner images of each color formed by the photoreceptor drums 31 of the photoreceptor units 30 are multiple-transferred, and the toner images of each color formed by each photoreceptor unit 30 are transferred onto the intermediate transfer belt 51 . 51, and a secondary transfer roller 53 for collectively transferring (secondary transfer) the toner images of each color superimposed and transferred onto the intermediate transfer belt 51 onto the paper P. there is

Each color toner image formed on the photosensitive drum 31 of each photosensitive unit 30 is transferred to the intermediate transfer belt 51 by the primary transfer roller 52 to which a predetermined transfer voltage is applied from the power supply device 70 controlled by the image forming apparatus control section 11 . A superimposed toner image is formed by sequentially electrostatically transferring (primary transfer) onto the toner image, and the toners of the respective colors are superimposed.

As the intermediate transfer belt 51 moves, the superimposed toner image on the intermediate transfer belt 51 is conveyed to an area (secondary transfer portion T) where the secondary transfer roller 53 is arranged. When the superimposed toner image is conveyed to the secondary transfer portion T, the paper P is supplied to the secondary transfer portion T from the paper feeding device 20 in accordance with the timing. A predetermined transfer voltage is applied to the secondary transfer roller 53 from the power supply 70 controlled by the image forming apparatus control section 11, and the intermediate transfer roller 53 is sent out from the registration roller pair 23 and transferred to the paper P guided by the conveyance guide. The multiple toner images on the transfer belt 51 are collectively transferred.

Residual toner on the surface of the photoreceptor drum 31 is removed by the cleaning blade 34 and collected in the waste developer container. The surface of the photosensitive drum 31 is recharged by the charging roller 32 . Residues that cannot be completely removed by the cleaning blade 34 and adhere to the charging roller 32 are captured and accumulated on the surface of the cleaning roller 33 rotating in contact with the charging roller 32 .

The fixing device 60 has a heating module 61 provided with a heat source and a pressure module 62 , and a pressure contact area between the heating module 61 and the pressure module 62 forms a fixing nip N (fixing area).

The paper P onto which the toner image has been transferred by the transfer device 50 is transported to the fixing device 60 via a transport guide while the toner image is not yet fixed. A pair of heating module 61 and pressure module 62 presses and heats the sheet P conveyed to the fixing device 60 to fix the toner image thereon.
The paper P on which the fixed toner image is formed is discharged from the discharge roller pair 69 via the transport roller pair 68 to the discharge tray 1 a on the upper surface of the image forming apparatus 1 .

(2) Configuration of Fixing Device 60 FIG. 2 is a schematic cross-sectional view showing the configuration of the fixing device 60, FIG. 3 is a schematic plan view showing the configuration of the heat source 612, and FIG. 5A is an enlarged schematic cross-sectional view taken along line AA, FIG. 5A is a schematic cross-sectional view showing the configuration of a heat source 612 in the fixing device 60, and FIG.

(2.1) Overall Configuration of Fixing Device The fixing device 60 includes a heating module 61 and a pressure module 62 .
The heating module 61 is provided with a fixing belt 611 as an example of a belt member used for fixing the toner image on the paper P. As shown in FIG. The fixing belt 611 rotates counterclockwise in the figure (see arrow R in FIG. 2).

The fixing belt 611 is an endless belt member whose both ends are open. The surface of a thin cylindrical belt base material made of a heat-resistant resin such as polyimide (PI) is coated with polytetrafluoroethylene (PTFE) or the like. It has a multi-layer structure in which a release layer containing fluororesin is formed.

Inside the fixing belt 611, as shown in FIG. 3, a plate-like heat source 612 extending along the moving direction (X direction) of the fixing belt 611 and the width direction (Y direction) of the fixing belt 611 is provided. It is The heating source 612 is a planar heating element, and the heating source 612 heats the fixing belt 611 to a predetermined temperature.

The heat source 612 is composed of a heat-resistant synthetic resin such as polyethylene terephthalate (PET) via a heat-receiving plate 613 which is made of aluminum oxide, which is a heat-resistant and electrically insulating material, and receives heat from the heat source 612 . It is held by a holding member 614 . The holding member 614 is supported by a support member 615 made of synthetic resin and having high bending strength.

Furthermore, the heating module 61 is provided with a temperature sensor SNR. The temperature sensor SNR penetrates the holding member 614 and the heat receiving plate 613 and is arranged in contact with the heat source 612 to detect the temperature of the heat source 612 .
A pair of belt guide members 616 (not shown) are provided at both ends of the holding member 614 and the support member 615 to rotatably support the inner circumferential surfaces of the open ends of the fixing belt 611 .

In the heating module 61 configured in this manner, a lubricant S is interposed between the heat source 612 and the inner surface of the fixing belt 611 (see FIG. 5A), thereby preventing friction between the fixing belt 611 and the heat source 612 . Ensures mobility. Lubricant S contains lubricating oil (amine lubricating oil) having an amine equivalent of 50,000 g/mol or less as its main component (50% by mass or more). This is preferable in that it is possible to suppress detachment and wear of the fixing belt 611 .

The pressure module 62 is composed of a pressure roller 621 and a pressure mechanism (not shown) including a pressure spring (not shown) that presses the pressure roller 621 against the heating module 61 .
The pressure roller 621 includes, for example, a cylindrical core member 622 made of metal, a heat-resistant elastic layer 623 (for example, a silicone rubber layer, a fluororubber layer, etc.) covering the outer peripheral surface of the core member 622, and further , and if necessary, a surface release layer 624 coated with a heat-resistant resin such as PFA or a heat-resistant rubber is laminated.

Both ends of the pressure roller 621 are pressed against the heat receiving plate 613 via the fixing belt 611 by pressing springs (not shown) to form a fixing nip N. As shown in FIG. Further, it is supported by a moving mechanism (not shown) so as to be able to come into contact with and separate from the outer peripheral surface of the fixing belt 611 . During the fixing operation, the fixing belt 611 rotates in the direction of arrow R in FIG. The image is fixed on the paper P.

(2.2) Configuration of Heat Source As shown in FIG. 4, the heat source 612 is configured by laminating an insulating layer 612B, a plurality of resistance heating elements 612C, and an insulator 612D on a base material 612A.
The base material 612A is a long flat plate made of, for example, stainless steel (SUS) or ceramic, and serves as a support for the heat source 612 . A resistance heating element 612C is provided on the surface side of the base material 612A via an insulating layer 612B formed by printing and baking glass paste, and the resistance heating element 612C is further covered with an insulator 612D.

As shown in FIG. 3, the resistance heating element 612C is parallel to the longitudinal direction (Y direction) crossing (perpendicular to) the moving direction of the fixing belt 611 on the surface side of the base material 612A. A band-shaped resistance heating element having a predetermined resistance value by printing and baking a metal paste containing a /palladium (Pd) alloy as a main component.
The resistance heating element 612C has a power supply electrode 612E made of, for example, a good conductive film made of Ag/Pd alloy with one end layered, and is connected to a power source (not shown) to receive power.

As shown in FIG. 4, the width L of the gap G between the plurality of resistance heating elements 612C is formed longer than the width W of each resistance heating element 612C. An insulator 612D is formed by printing a thick film of glass paste and baking it on the plurality of resistance heating elements 612C and the gaps G between the plurality of resistance heating elements 612C, leaving the power supply electrodes 612E. The insulator 612D is formed so that only the region covering the resistance heating element 612C protrudes toward the inner surface of the fixing belt 611. As shown in FIG.

As a result, the heat source 612 comes into stronger contact with the inner surface of the fixing belt 611 in the area of the resistance heating element 612C, and as shown in FIG. The area of the resistive heating element 612C that is in the shape of two peaks is higher than the other areas.

As a result, the lubricant S is held in the area of the gap G between the plurality of resistance heating elements 612C, and the wettability of the inner surface of the fixing belt 611 is effectively ensured. The sliding property of the inner peripheral surface of 611 can be improved.

In addition, the projecting insulator 612D in the region covering the resistive heating elements 612C has a protrusion height H in relation to the width L of the gap G between the plurality of resistive heating elements 612C. : α=60 to 240) and L≧insulation distance.
As an example, when the width L of the gap G is 2 mm and the constant α is in the range of 100 to 150, the protrusion height H is 13 μm to 20 μm. The pressure distribution is relatively stronger than the surrounding area, and the adhesion to the inner surface of the fixing belt 611 is improved.

"Variation"
FIG. 6A is a schematic cross-sectional view showing the fixing nip N when the width L of the gap G of the resistance heating element 612C is wide, FIG. 8A is a cross-sectional schematic diagram showing a heat source 612 according to a modification, FIG. 8B is a diagram showing an example of pressure distribution in the fixing nip N, and FIG. It is an enlarged cross-sectional schematic diagram.

When the width L of the gap G between the plurality of resistance heating elements 612C is large, the pressure roller 621 presses the inner peripheral surface of the fixing belt 611 toward the heat source 612, and the inner peripheral surface of the fixing belt 611 fills the gap G. The pressure distribution within the fixing nip N in contact with the central portion of the covering insulator 612D has a three-peak shape in which the region of the resistive heating element 612C that generates heat and the central portion of the gap G are higher than the other regions. Therefore, the lubricant S can be retained in the plurality of regions G1 and G2 of the gaps G between the plurality of resistance heating elements 612C, and the sliding characteristics of the inner peripheral surface of the fixing belt 611 can be further improved.

On the other hand, when the heat source 612 is small, the width L of the gap G between the plurality of resistance heating elements 612C is also narrow, and the pressure distribution within the fixing nip N is less likely to be triangular.
As shown in FIG. 7A, in the heat source 612 according to the modification, an insulator 612D is formed in a convex shape at the center of the gap G between a plurality of resistance heating elements 612C.
Therefore, as shown in FIG. 7B, the pressure distribution in the fixing nip N has a three-peak shape in which the region of the heat-generating resistance heating element 612C and the central portion of the gap G are higher than the other regions. Lubricant S can be held in a plurality of regions G1 and G2 of gaps G between a plurality of resistance heating elements 612C. As a result, the sliding characteristics of the inner peripheral surface of the fixing belt 611 can be improved more reliably.

As shown in FIG. 8, the thickness of the insulator 612D is such that the thickness t1 of the portion covering the resistance heating element 612C is thinner than the thickness t2 of the portion covering the base material 612A.
As a result, the heat transfer efficiency of the insulator 612D from the heat source 612 to the fixing belt 611 is higher than in the case where the thickness t1 of the portion covering the resistance heating element 612C is thicker than the thickness t2 of the portion covering the base material 612A. can be suppressed.

"Modification 2"
FIG. 9 is a schematic cross-sectional view illustrating the thickness of the insulator 612D of the heat source 612 according to Modification 2. As shown in FIG. As shown in FIG. 9, in the heat source 612 according to Modification 2, the insulator 612D is formed so that the thickness t1 of the portion covering the resistance heating element 612C is thicker than the thickness t2 of the portion covering the base material 612A. ing.

As a result, the lubricant S is applied to the regions of the gaps G of the plurality of resistance heating elements 612C, compared to the case where the thickness t1 of the portion covering the resistance heating elements 612C is thinner than the thickness t2 of the portion covering the base material 612A. is formed, the wettability of the inner surface of the fixing belt 611 is effectively ensured, and the sliding property of the inner peripheral surface of the fixing belt 611 that moves around can be improved.

"Modification 3"
FIG. 10 is a schematic cross-sectional view for explaining the thickness of the insulator 612D of the heat source 612 according to Modification 3. As shown in FIG. As shown in FIG. 10, in the heat source 612 according to Modification 3, the thickness of the insulator 612D is such that the thickness t2 of the portion covering the gap G of the resistance heating element 612C is greater than the thickness t2 of the base material 612A outside the resistance heating element 612C. is formed thinner than the thickness t3 of the portion covering the .

As a result, the thickness t2 of the portion covering the gap G of the resistance heating element 612C is thicker than the thickness t3 of the portion covering the base material 612A outside the resistance heating element 612C. By increasing the number of recesses that can hold the lubricant S formed in the region of the gap G of the body 612C, the wettability of the inner surface of the fixing belt 611 is more effectively ensured, and the inner peripheral surface of the fixing belt 611 that moves in a circular motion is increased. Sliding properties can be improved.

DESCRIPTION OF SYMBOLS 1... Image forming apparatus 10... Control apparatus 20... Paper feeder 30... Photoreceptor unit 31... Photoreceptor drum 40... Developing device 42... Developing roller 50... Transfer device 51 Intermediate transfer belt 53 Secondary transfer roller 60 Fixing device 61 Heating module 611 Fixing belt 612 Heating source 612A Base material 612B Insulating layer 612C Resistance heating element 612D Insulator G Gap S Lubricant N Fixing nip

Claims (8)

a circulating belt member;
a pressing member that contacts the belt member and presses the recording medium moving between the belt member;
a lubricant interposed on the inner surface of the belt member;
a heating source that has a plurality of resistance heating elements on a base material, and an insulator that covers the plurality of resistance heating elements and gaps between the plurality of resistance heating elements, and heats the inner surface of the belt member;
The heat source forms a convex shape toward the pressure member at the positions of the plurality of resistance heating elements, and is wider than the convex shape in the gap between the plurality of resistance heating elements and extends in the direction in which the resistance heating elements extend. a continuous concave shape along the gap and a convex shape at the center of the gap ,
A fixing device characterized by: In the contact portion where the belt member and the pressure member are in contact with each other, the heat source is configured such that the pressure in the gap between the plurality of resistance heating elements is relatively higher than that on the downstream side and the upstream side in the moving direction of the recording medium. supporting the belt member from the inside so as to be relatively high;
2. The fixing device according to claim 1, wherein: the width of the gap of the plurality of resistance heating elements is longer than the width of the resistance heating elements;
3. The fixing device according to claim 2, wherein: The thickness of the insulator is such that a portion covering the resistance heating element is thinner than a portion covering the base material.
2. The fixing device according to claim 1, wherein: The thickness of the insulator is such that a portion covering the resistance heating element is thicker than a portion covering the base material.
2. The fixing device according to claim 1, wherein: The thickness of the insulator is such that a portion covering the base between the plurality of resistance heating elements is thinner than a portion covering the base outside the resistance heating elements.
6. The fixing device according to claim 4, wherein: the lubricant intervenes at least between the belt member and the gap ;
The fixing device according to any one of claims 1 to 6, characterized in that: an image forming means for forming an image on a recording medium;
and a fixing device according to any one of claims 1 to 7 for fixing the image on the recording medium on which the image is formed by the image forming means,
An image forming apparatus characterized by:

Images