JP2019028151A - Fixing device and image forming apparatus - Google Patents

Abstract

To provide a fixing device that can guarantee the wettability of lubricant to improve sliding characteristics of a belt member.SOLUTION: A fixing device comprises: a circulating belt member; a pressure member that is in contact with the belt member and applies pressure to a recording medium moving between the belt member and pressure member; a lubricant that is interposed between an inner surface of the belt member and a heat source; and the heat source that has a plurality of resistance heating elements and an insulator covering 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 is formed to be convex toward the pressure member at the positions of the plurality of resistance heating elements.SELECTED DRAWING: Figure 5

Description

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

  A heating resistor and electrodes for supplying power to the heating resistor are formed in the longitudinal direction of a long flat substrate made of a heat-resistant and insulating material, and glass paste is printed on the substrate and the heating resistor. -In ceramic heaters with an overcoat layer formed by firing, the size of bubbles generated in the overcoat layer is made larger on the substrate than on the heating resistor, so that the surface roughness of the overcoat layer is reduced. A small 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 for connecting each pair of electrodes is provided, and a protective sheath covering the resistor and a part of the electrode is provided. Also known is a multiple resistance element structure in which a filling layer for filling a step between the resistor and the substrate surface is provided between the resistor and the resistor composed of each pair of electrodes and resistors. (Patent Document 2).

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

  The present invention provides a fixing device capable of ensuring the wettability of a lubricant and improving the sliding characteristics of a belt member.

In order to solve the above problem, a fixing device according to claim 1 is provided.
A circulating belt member;
A pressure member that presses a recording medium that contacts the belt member and moves between the belt member;
A lubricant interposed on the inner surface of the belt member;
A heating source that heats the inner surface of the belt member, having a plurality of resistance heating elements on the substrate, an insulator covering the gaps between the plurality of resistance heating elements and the plurality of resistance heating elements,
The heating source is formed to be convex toward the pressure member at the position of the plurality of resistance heating elements,
It is characterized by that.

According to a second aspect of the present invention, in the fixing device according to the first aspect,
The heating source supports the belt member from the inside so that a peak pressure is formed in a width of the gap between the plurality of resistance heating elements in a contact portion where the belt member and the pressure member are in contact with each other. ,
It is characterized by that.

According to a third aspect of the present invention, in the fixing device according to the second aspect,
A width of the gap between the plurality of resistance heating elements is longer than a width of the resistance heating element;
It is characterized by that.

According to a fourth aspect of the present invention, in the fixing device according to the first aspect,
The thickness of the insulator is thinner than the part covering the resistance heating element, the part covering the base material,
It is characterized by that.

According to a fifth aspect of the present invention, in the fixing device according to the first aspect,
The thickness of the insulator is thicker than the portion covering the resistance heating element.
It is characterized by that.

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

According to a seventh aspect of the present invention, in the fixing device according to any one of the first to sixth aspects,
The lubricant is interposed at least between the belt member and the gap;
It is characterized by that.

In order to solve the above problem, an image forming apparatus according to claim 8,
Image forming means for forming an image on a recording medium;
The fixing device according to claim 1, wherein the fixing device fixes the image on the recording medium on which the image is formed by the image forming unit.
It is characterized by that.

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

  According to the second aspect of the present invention, it is possible to form a plurality of regions where the lubricant is interposed between the inner surface of the belt member.

  According to the second aspect of the present invention, it is possible to form a plurality of regions where the lubricant is interposed between the inner surface of the belt member.

  According to the invention described in claim 3, it is possible to suppress a decrease in heat transfer efficiency to the belt member as compared with a configuration in which a portion covering the resistance heating element of the insulator is thicker than a portion covering the base material.

  According to invention of Claim 4, compared with the structure where the part which covers the resistance heating element of an insulator is thinner than the part which covers a base material, the fall of the slidability of a belt member can be suppressed.

  According to the invention of claim 5, compared to a configuration in which the portion covering the base material between the plurality of resistance heating elements of the insulator is thicker than the portion covering the base material outside the resistance heating element, A region where the lubricant is interposed between the inner surface of the belt member can be increased.

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

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

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

1 is a schematic cross-sectional view showing an internal configuration of an image forming apparatus. FIG. 3 is a schematic cross-sectional view illustrating a configuration of a fixing device. It is a plane schematic diagram which shows the structure of a heating source. It is an AA expanded sectional schematic diagram in FIG. 3 explaining the structure of a heating source. FIG. 3A is a schematic cross-sectional view showing a configuration of a heating source in the fixing device, and FIG. (A) is a schematic cross-sectional view showing a fixing nip when the distance between the resistance heat generation gaps is wide, and (b) is a diagram showing an example of a pressure distribution in the fixing nip. It is an expanded sectional schematic diagram of the heat source explaining the thickness of an insulator. (A) is a cross-sectional schematic diagram explaining the thickness of the insulator of the heat source according to the second modification, and (b) is a diagram showing an example of pressure distribution in the fixing nip. It is a cross-sectional schematic diagram explaining the thickness of the insulator of the heat source which concerns on the modification 2. FIG. It is a cross-sectional schematic diagram explaining the thickness of the insulator of the heat source which concerns on the modification 3. FIG.

Next, the present invention will be described in more detail with reference to the drawings with reference to embodiments and specific examples. However, the present invention is not limited to these embodiments and specific examples.
Also, in the description using the following drawings, it should be noted that the drawings are schematic and the ratio of each dimension and the like are different from the actual ones, and are necessary for the description for easy understanding. Illustrations other than the members are omitted as appropriate.
For easy understanding of the following description, in the drawings, the left-right direction is the X-axis direction, the front-rear direction is the Y-axis direction, and the vertical direction is 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 the 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, a discharge tray 1a for discharging and storing a sheet on which an image is recorded is formed.

  The control device 10 includes an image forming device control unit 11 that controls the operation of the image forming device 1, a controller unit 12 that prepares image data in response to a print processing request, an exposure control unit 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) into image information for forming a latent image, and outputs a drive signal to the exposure device LH at a preset timing. . The exposure apparatus LH of the present embodiment is configured by an LED head in which a plurality of light emitting elements (LEDs) are arranged linearly along the main scanning direction.

  A paper feeding device 20 is provided at the bottom of the image forming apparatus 1. The sheet feeding device 20 includes a sheet stacking plate 21, and a plurality of sheets P as recording media are stacked on the upper surface of the sheet stacking plate 21. The sheets P stacked on the sheet stacking plate 21 and positioned in the width direction by a regulating plate (not shown) are pulled out one by one from the upper side by the sheet pulling portion 22 (X direction), and then the registration roller pair. 23 is conveyed to the nip portion.

  The photoconductor unit 30 includes a photoconductor drum 31 that is provided in parallel above the paper feeding device 20 (in the Z direction) and serves as an image carrier that is rotationally driven. 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 for cleaning the surface of the charging roller 32 is disposed opposite to and in contact with the charging roller 32.

The developing device 40 includes a developing housing 41 in which a developer composed of toner and a carrier is accommodated. In the developing housing 41, a developing roller 42 as a developer holding member disposed facing the photosensitive drum 31, and the developer is stirred and conveyed to the developing roller 42 side obliquely below the back side of the developing roller 42. A pair of augers 44 and 45 are disposed. A layer regulating member 46 that regulates the layer thickness of the developer is disposed in proximity to the developing roller 42.
Each of the developing devices 40 is configured in a similar manner except for the developer contained in the developing housing 41, and each forms a yellow (Y), magenta (M), cyan (C), and black (K) toner image. .

  The surface of the rotating photosensitive drum 31 is charged by the charging roller 32, and an electrostatic latent image is formed by the 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 includes an intermediate transfer belt 51 to which each color toner image formed on the photoconductive drum 31 of each photoconductor unit 30 is transferred, and each color toner image formed on each photoconductor unit 30 to the intermediate transfer belt. 51, a primary transfer roller 52 that sequentially transfers (primary transfer) to 51, and a secondary transfer roller 53 that collectively transfers (secondary transfer) each color toner image transferred on the intermediate transfer belt 51 onto the paper P. Yes.

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

  The superimposed toner image on the intermediate transfer belt 51 is conveyed to a region (secondary transfer portion T) where the secondary transfer roller 53 is disposed as the intermediate transfer belt 51 moves. When the superimposed toner image is conveyed to the secondary transfer unit T, the paper P is supplied from the paper feeding device 20 to the secondary transfer unit T in accordance with the timing. A predetermined transfer voltage is applied to the secondary transfer roller 53 from the power supply device 70 controlled by the image forming apparatus control unit 11, and the intermediate transfer medium P is fed from the registration roller pair 23 and guided by the conveyance guide. Multiple toner images on the transfer belt 51 are collectively transferred.

  Residual toner on the surface of the photosensitive 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 that rotates in contact with the charging roller 32.

  The fixing device 60 includes a heating module 61 including a heating source and a pressure module 62, and a fixing nip N (fixing area) is formed by a pressure contact area between the heating module 61 and the pressure module 62.

The sheet P on which the toner image is transferred in the transfer device 50 is conveyed to the fixing device 60 via the conveyance guide in a state where the toner image is not fixed. The toner image is fixed on the sheet P conveyed to the fixing device 60 by a pair of heating module 61 and pressure module 62 by the action of pressure bonding and heating.
The sheet P on which the fixing toner image is formed is discharged from the discharge roller pair 69 to the discharge tray 1 a on the upper surface of the image forming apparatus 1 via the conveyance roller pair 68.

(2) Configuration of Fixing Device 60 FIG. 2 is a schematic sectional view showing the configuration of fixing device 60, FIG. 3 is a schematic plan view showing the configuration of heating source 612, and FIG. 4 is a diagram illustrating the configuration of heating source 612 in FIG. FIG. 5A is a schematic enlarged cross-sectional view, FIG. 5A is a schematic cross-sectional view illustrating a configuration of a heating source 612 in the fixing device 60, and FIG. 5B is a diagram illustrating an example of a pressure distribution in the fixing nip N.

(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 onto the paper P. The fixing belt 611 rotates counterclockwise in the figure (see arrow R in FIG. 2).

  The fixing belt 611 is an endless belt member having both ends opened, and a polytetrafluoroethylene (PTFE) or the like is formed on the surface of a belt base material formed in a thin cylindrical shape with a heat-resistant resin such as polyimide (PI). It has a multilayer structure in which a release layer containing a fluororesin is formed.

  As shown in FIG. 3, a plate-shaped heating 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 inside the fixing belt 611. It has been. The heating source 612 is a planar heating element, and the fixing belt 611 is heated to a predetermined temperature by the heating source 612.

  The heat source 612 is made of heat-resistant synthetic resin having heat resistance such as polyethylene terephthalate (PET) through a heat receiving plate 613 that 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 a high bending strength.

Further, the heating module 61 is provided with a temperature sensor SNR. The temperature sensor SNR is disposed in contact with the heating source 612 through the holding member 614 and the heat receiving plate 613, and detects the temperature of the heating source 612.
A pair of belt guide members 616 (not shown) that rotatably support the inner peripheral surfaces of both ends of the fixing belt 611 are provided at both ends of the holding member 614 and the support member 615.

  In the heating module 61 configured as described above, the lubricant S is interposed between the heating source 612 and the fixing belt 611 between the inner surfaces (see FIG. 5A), so that the fixing belt 611 and the heating source 612 are slid. Ensures mobility. The lubricant S contains a lubricating oil (amine lubricating oil) having an amine equivalent of 50,000 g / mol or less as a main component (50% by mass or more) of the lubricant from the inner peripheral surface of the fixing belt 611. This is preferable in that the separation can be suppressed and the wear of the fixing belt 611 can be suppressed.

The pressure module 62 includes a pressure roller 621 and a pressure mechanism (not illustrated) including a pressure spring (not illustrated) that presses the pressure roller 621 against the heating module 61.
The pressure roller 621 includes, for example, a metal cylindrical core material 622, a heat-resistant elastic body layer 623 (for example, a silicone rubber layer or a fluororubber layer) coated on the outer peripheral surface of the core material 622, and If necessary, for example, a surface release layer 624 with a heat-resistant resin coating such as PFA or a heat-resistant rubber coating is laminated.

  Both ends of the pressure roller 621 are pressed against the heat receiving plate 613 via a fixing belt 611 by a pressing spring (not shown) to form a fixing nip N. Further, it is supported by a moving mechanism (not shown) so as to be able to contact and separate from the outer peripheral surface of the fixing belt 611. At the time of the fixing operation, the sheet is rotated in the direction of arrow R in FIG. 2 following the fixing belt 611, and the sheet P holding the unfixed toner image is passed through the fixing nip N. 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 612A is a long flat plate made of, for example, stainless steel (SUS) or ceramic and serves as a support for the heating source 612. A resistance heating element 612C is provided on the surface side of the substrate 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 formed of silver (Ag) in parallel along the longitudinal direction (Y direction) intersecting (orthogonal) with the moving direction of the fixing belt 611 on the surface side of the base 612A. / A strip-like resistance heating element having a predetermined resistance value by printing and baking a metal paste mainly composed of a palladium (Pd) alloy.
The resistance heating element 612C has a power supply electrode 612E made of a good conductor film made of, for example, an Ag / Pd alloy, one end of which is formed as a multilayer, 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 and baking a glass paste as a thick film on the gap G between the plurality of resistance heating elements 612C and the plurality of resistance heating elements 612C with the feeding electrode 612E left. The insulator 612D is formed so that only the region covering the resistance heating element 612C is convex toward the inner surface of the fixing belt 611.

  As a result, the heating source 612 comes into stronger contact with the inner surface of the fixing belt 611 in the region of the resistance heating element 612C, and the pressure distribution in the fixing nip N is generated as shown in FIG. The area of the resistance heating element 612C to be formed is a double mountain shape higher than the other areas.

  As a result, the lubricant S is held in the region of the gap G between the plurality of resistance heating elements 612C to effectively ensure the wettability of the inner surface of the fixing belt 611, and the fixing belt moves around while contacting the heating source 612. The sliding characteristics of the inner peripheral surface of 611 can be improved.

Further, the convex insulator 612D in the region covering the resistance heating element 612C has a protrusion height H of L ≦ α · H (α is a predetermined constant in relation to the width L of the gap G between the plurality of resistance heating elements 612C. : Α = 60 to 240), and L ≧ insulation distance is preferable.
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 a protrusion amount of 13 μm to 20 μm, and in the fixing nip N in the region of the resistance heating element 612C that generates heat. The pressure distribution is relatively stronger than the surrounding area, and the adhesion to the inner surface of the fixing belt 611 is improved. In the region of the gap G, the pressure distribution is lowered, thereby suppressing an increase in frictional resistance.

"Modification"
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. 6B is a view showing an example of the pressure distribution in the fixing nip N, and FIG. FIG. 8A is a schematic cross-sectional view showing a heat source 612 according to a modified example, FIG. 8B is a view showing an example of a pressure distribution in the fixing nip N, and FIG. It is an expanded sectional schematic diagram.

  In the case where the width L of the gap G between the plurality of resistance heating elements 612C is wide, the inner peripheral surface of the fixing belt 611 is pressed toward the heating source 612 by the pressure roller 621, and the inner peripheral surface of the fixing belt 611 passes through the gap G. The pressure distribution in the fixing nip N in contact with the central portion of the covering insulator 612D becomes a triple shape in which the region of the resistance 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 held in the plurality of regions G1 and G2 of the gap 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 heating source 612 is small, the width L of the gap G between the plurality of resistance heating elements 612C is also narrowed, and the pressure distribution in the fixing nip N is unlikely to be in a mountain shape.
As shown to Fig.7 (a), as for the heat source 612 which concerns on a modification, insulator 612D is formed in the convex part in the center part of the gap | interval G of several resistance heating element 612C.
Therefore, as shown in FIG. 7B, the pressure distribution in the fixing nip N has a triangular shape in which the region of the resistance heating element 612C that generates heat and the central portion of the gap G are higher than the other regions. The lubricant S can be held in the plurality of regions G1 and G2 of the gap G between the plurality of resistance heating elements 612C. Thereby, the sliding characteristic of the inner peripheral surface of the fixing belt 611 can be improved more reliably.

As shown in FIG. 8, the insulator 612D is formed 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.
Accordingly, the heat transfer efficiency by the insulator 612D from the heating source 612 to the fixing belt 611 is larger than the case where the thickness t1 of the portion covering the resistance heating element 612C is formed 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 heating source 612 according to Modification 2. As shown in FIG. 9, in the heating source 612 according to the second modification, the thickness of the insulator 612D is formed such 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.

  Accordingly, the lubricant S is formed in the region of the gap G between the plurality of resistance heating elements 612C as compared with the case where the thickness t1 of the part covering the resistance heating element 612C is formed thinner than the thickness t2 of the part covering the base material 612A. Is formed so that the wettability of the inner surface of the fixing belt 611 is effectively secured, and the sliding characteristics 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 illustrating the thickness of the insulator 612D of the heating source 612 according to Modification 3. As shown in FIG. 10, in the heating source 612 according to the 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 outside the resistance heating element 612C. Is formed to be thinner than the thickness t3 of the portion covering.

  As a result, a plurality of resistance heatings are generated as compared with the case where 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 612A outside the resistance heating element 612C. By increasing the depression 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 around is rotated. Sliding characteristics can be improved.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 10 ... Control apparatus 20 ... Paper feeding apparatus 30 ... Photoconductor unit 31 ... Photoconductor drum 40 ... Developing apparatus 42 ... Developing roller 50 ... Transfer device 51 ... Intermediate transfer belt 53 ... Secondary transfer roller 60 ... Fixing device 61 ... Heating module 611 ... Fixing belt 612 ... Heat 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 pressure member that presses a recording medium that contacts the belt member and moves between the belt member;
A lubricant interposed on the inner surface of the belt member;
A heating source that heats the inner surface of the belt member, having a plurality of resistance heating elements on the substrate, an insulator covering the gaps between the plurality of resistance heating elements and the plurality of resistance heating elements,
The heating source is formed to be convex toward the pressure member at the position of the plurality of resistance heating elements,
A fixing device. The heating source supports the belt member from the inside so that a peak pressure is formed in a width of the gap between the plurality of resistance heating elements in a contact portion where the belt member and the pressure member are in contact with each other. ,
The fixing device according to claim 1. A width of the gap between the plurality of resistance heating elements is longer than a width of the resistance heating element;
The fixing device according to claim 2. The thickness of the insulator is thinner than the part covering the resistance heating element, the part covering the base material,
The fixing device according to claim 1. The thickness of the insulator is thicker than the portion covering the resistance heating element.
The fixing device according to claim 1. The thickness of the insulator is thinner than the portion covering the base material, the portion covering the base material between the plurality of resistance heating elements,
The fixing device according to claim 4, wherein the fixing device is any one of the fixing devices. The lubricant is interposed at least between the belt member and the gap;
The fixing device according to claim 1, wherein Image forming means for forming an image on a recording medium;
The fixing device according to claim 1, wherein the fixing device fixes the image on the recording medium on which the image is formed by the image forming unit.
An image forming apparatus.

Images