Patent Application
20240280930
The present invention relates to a heater, a heating device and an image forming apparatus.
Image forming devices of electrophotographic printers, copiers, etc. are provided with a heating device which fixes toner to a recording material at a fixing nip portion which is formed by a fixing film and a pressing roller. A heater is arranged inside the fixing film. The heater includes a heat generating resistor which is provided on a substrate and a protective layer such as glass which protects the heat generating resistor. The heat which is generated from the heater is transferred to the fixing film, and the toner is fixed to the recording material which is nipped at the fixing nip portion. In such image forming apparatus, a technique which improves a sliding property of a fixing film and a heater by providing a groove on a surface of the heater's protective layer (sliding surface with the fixing film) is disclosed in Japanese Laid-Open Patent Application (JP-A) 2003-76178.
However, in a configuration in which the groove is provided in the protective layer, depending on an arrangement of the heat generating resistor and the groove, the heat from the heat generating resistor may be insulated by air in the groove and efficiency of heat transfer to the fixing film may be decreased.
In response to the above issue, it is an object of the present invention is to provide a heater, a heating device and an image forming apparatus which are capable of suppressing a decrease in efficiency of heat transfer.
According to an aspect of the present invention, there is provided a heater comprising: a substrate; a heat generating member provided on the substrate; and a protective layer configured to continuously cover a region in the substrate where the heat generating member is provided wherein when a direction of a longer side in a face of the substrate on which the heat generating member is provided is defined as a longitudinal direction, a direction perpendicular to the longitudinal direction in the face is defined as a short direction, and a direction perpendicular to the longitudinal direction and the short direction is defined as a thickness direction, the protective layer includes a recess toward the substrate in the thickness direction, and a first region where the heat generating member is provided and a second region where the recess is formed are not overlapped with each other as the protective layer is viewed in the thickness direction.
According to another aspect of the present invention, there is provided a heater comprising: a substrate; a heat generating member provided on the substrate; and a protective layer configured to continuously cover a region in the substrate where the heat generating member is provided, wherein when a direction of a longer side in a face of the substrate on which the heat generating member is provided is defined as a longitudinal direction, a direction perpendicular to the longitudinal direction in the face is defined as a short direction, and a direction perpendicular to the longitudinal direction and the short direction is defined as a thickness direction, the protective layer includes a recess toward the substrate in the thickness direction, a ratio of an area occupied by the recess to an area of a first region where the heat generating member is provided is smaller than a ratio of the area occupied by the recess to an area of a second region where the recess is provided is viewed in the thickness direction.
According to another aspect of the present invention, there is provided a heating device comprising: a rotatable cylindrical film; a substrate provided in an inner peripheral surface side of the film; a heat generating member provided on the substrate; an interposed member which is interposed between the heat generating member and an inner peripheral surface of the film, and slidable to the inner peripheral surface of the film while the film is rotated; and a pressing member configured to form a nip portion between itself and the protective layer via the film, wherein the heating device heats an unfixed toner image on a recording material nipped and conveyed in the nip portion by heat generated by the heat generating member and fixes on the recording material, and wherein when a direction of a longer side in a face of the substrate on which the heat generating member is provided is defined as a longitudinal direction, a direction perpendicular to the longitudinal direction in the face is defined as a short direction, and a direction perpendicular to the longitudinal direction and the short direction is defined as a thickness direction, a sliding surface with the film in the interposed member includes a recess toward the substrate in the thickness direction, a first region where the heat generating member is provided and a second region where the recess is formed are not overlapped with each other as the protective layer is viewed in the thickness direction.
According to another aspect of the present invention, there is provided a heating device comprising: a rotatable cylindrical film; a substrate provided in an inner peripheral surface side of the film; a heat generating member provided on the substrate; an interposed member which is interposed between the heat generating member and an inner peripheral surface of the film, and slidable to the inner peripheral surface of the film while the film is rotated, and a pressing member configured to form a nip portion between itself and the protective layer via the film, wherein the heating device heats an unfixed toner image on a recording material nipped and conveyed in the nip portion by heat generated by the heat generating member and fixes on the recording material, and wherein when a direction of a longer side in a face of the substrate on which the heat generating member is provided is defined as a longitudinal direction, a direction perpendicular to the longitudinal direction in the face is defined as a short direction, and a direction perpendicular to the longitudinal direction and the short direction is defined as a thickness direction, a sliding surface with the film in the interposed member includes a recess toward the substrate in the thickness direction a ratio of an area occupied by the recess to an area of a first region where the heat generating member is provided is smaller than a ratio of the area occupied by the recess to an area of a second region where the heat generating member is not provided as the protective layer is viewed in the thickness direction.
According to the present invention, it is possible to provide a heater, a heating device and an image forming apparatus which are capable of suppressing a decrease in efficiency of heat transfer.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Part (a) of
Part (a) of
Part (a) of
Part (a) of
In the following, with reference to figures, embodiments of the present invention will be exemplarily described in detail, based on the embodiments. However, dimensions, materials, shapes, relative arrangements, etc. of component parts which are described in the embodiments may be appropriately changed, according to configurations and various conditions of devices to which the present invention is applied. That is, it is not intended to limit scope of the present invention to the following embodiments. Further, terms which indicates geometrical shapes or relationships, such as parallel, perpendicular, center, straight, circle, etc., are not limited to mathematically exact meanings unless otherwise specified, and are to be interpreted as including ranges which are allowed by manufacturing tolerances, etc.
When a print instruction is received, a scanner unit 3 emits laser light L according to image information. A photosensitive member 1, which is an image bearing member which is charged to a predetermined polarity by a charging roller 2 which is a charging means, is scanned by the laser light L which is an exposure means according to the image information. In this way, an electrostatic latent image on a surface of a photosensitive member 1 in accordance with the image information is formed. After that, a developing device 4 which is a developing means supplies toner to the photosensitive member 1, and develops the electrostatic latent image on the photosensitive member 1 into a toner image. The toner image which reaches a transfer position which is formed by the photosensitive member 1 and a transfer roller 5 which is a transfer means by rotation of the photosensitive member 1 in a direction of an arrow R1 is transferred to a recording material P which is fed by a pickup roller 7 from a cassette 6. The surface of the photosensitive member 1 which has passed the transfer position is cleaned by a cleaner 8.
The recording material P on which the toner image has been transferred is heated and pressed in a heating device 9 and the toner image is fixed. After that, the recording material P is discharged by a discharging roller 10 to a discharge tray 11.
The heating device 9 will be described in detail in a next section (2).
In the following, the heating device 9 will be described. The heating device 9 applies a film heating method of a tensionless type. The heating device 9, which applies the film heating method of the tensionless type, uses an endless belt shape (or cylindrical shape) as a heat resistant film. At least part of film circumference is always tension-free (no tension is applied), and the film is rotationally driven by rotational driving force of a pressing member. In the following, the heating device 9 which applies the film heating method will be described in detail.
With reference to the sectional view in
A reinforcing member 24 is made of metal such as iron and presses the heater 22 via a film guide 21 toward a side of the pressing roller 30. The reinforcing member 24 is a member which has enough strength to prevent significant deformation even when pressure is applied to form the nip portion N by pressing the heater 22 to the side of the pressing roller 30. The film guide 21 has a function as a guide which guides to rotate the film 23. The film guide 21 is a molded product of a heat resistant resin such as PPS (polyphenylene sulfide) or liquid crystal polymer, for example. The pressing roller 30 receives power from a motor M via an unshown power transmission mechanism such as a gear and rotates in a direction of an arrow b. As the pressing roller 30 rotates, the film 23 is driven to rotate in the direction of the arrow a. Rotational directions which are indicated by the arrow a and the arrow b are rotational directions which are same directions as a direction of conveying of the recording material P at the nip portion N.
The heater 22 includes a substrate 22a which is made of ceramics. The heater 22 includes the substrate 22a which is a long and narrow rectangular plate shape, a heat generating resistor 22c which generates heat when it is energized, and a protective layer 22d which continuously covers and protects a surface of the heat generating resistor 22c. In the following, a longitudinal direction on a rectangular surface on which the heat generating resistor 22c is formed on the substrate 22a is defined as a Y direction, a short direction which is perpendicular to the longitudinal direction on the surface is defined as an X direction, and a thickness direction which is perpendicular to the longitudinal direction and the short direction is defined as a Z direction. In the first embodiment, a conveying direction of the recording material P at the nip portion N (sliding direction of the heater 22 and the film 23 at the nip portion N) is parallel to the X direction, and directions of rotational axes of the film 23 and the pressing roller 30 are parallel to the Y direction. In the first embodiment, the protective layer 22d is configured of a glass coat layer. The protective layer 22d is an interposed member which is interposed between the heat generating resistor 22c and the inner peripheral surface of the film 23 and is slidable with the inner peripheral surface of the film 23 when the film 23 is rotated. A groove 22h is formed as a recess on a surface of the protective layer 22d. It is possible to fix an unfixed toner image on the recording material which is nipped and conveyed at the nip portion N on the recording material by heating it with heat which is generated by the heat generating resistor 22c which is a heating member via the film 23. The heater 22 will be described in detail in a section (3).
A thermistor 25 which is a temperature detecting portion is abutted with the substrate 22a on a side which contacts the film guide 21. The energization of the heat generating resistor 22c is controlled according to temperature which is detected by the thermistor 25.
Thickness of the film 23 may preferably be 20 μm or more and 100 μm or less in order to ensure good thermal conductivity. The film 23 may preferably be a single layer film which is made of materials such as PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether), PPS, as a base layer 23a, or a composite layer film in which a surface of materials such as PI (polyimide), PAI (polyamideimide), PEEK (polyetheretherketone), PES (polyethersulfone), etc., is coated with PTFE, PFA, FEP (tetrafluoroethylene-perfluoroalkyl ether), etc., as a release layer 23b. Further, it may also preferable that a pure metal or alloy such as SUS, Al, Ni, Cu, Zn, etc., which have high thermal conductivity, is used for the base layer 23a, and the coating treatment which is described above and fluororesin tube coating are applied to the release layer 23b.
In the first embodiment, PI with a thickness of 60 μm is used as the base layer 23a, and PFA with a thickness of 12 μm is coated as for the release layer 23b, considering both wear of the release layer 23b due to sheet passing and thermal conductivity. The longitudinal length of the film 23 is 240 mm.
The pressing roller 30 as a pressing member includes a core metal 30a which is made of material such as iron or aluminum, an elastic layer 30b which is made of material such as silicone rubber, and a release layer 30c which is made of material such as PFA. The pressing roller 30 receives power from the motor M via an unshown gear and rotates in the direction of the arrow b. An unfixed toner image T on the recording material P is thermally fixed to the recording material P, when the recording material P is nipped and conveyed at the nip portion N and heated and pressurized. The recorded material P which has passed through the nip portion N is conveyed to the discharge tray 11.
Next,
Both end portions of the reinforcing member 24 protrude from both ends of the film 23, a flange member 26 is fitted to each of the ends and, as a whole, they are assembled as a film assembly unit 20.
A power supply terminal of the heater 22 is also protruded from one side end of the film 23 and is engaged with a power supply connector 27. The power supply connector 27 contacts an electrode portion of the heater 22 at a predetermined pressure and forms a power supply passage.
A heater clip 28 is formed from a metal plate which is bent in a U shape and has spring property.
Next,
The film assembly unit 20 is provided opposing the pressing roller 30, restricted to move in a horizontal direction (Y direction) in the figure, and supported by a casing 41 on a top side of the heating device 9 so that its movement in a vertical direction (X direction) is movable freely. A pressure spring 45 is mounted in the casing 41 on the top side of the heating device 9 in a compressed state. Pressing force of the pressure spring 45 is received by both end portions of the reinforcing member 24 via the flange member 26, the reinforcing member 24 is pressed toward a side of the pressing roller 30, and the entire film assembly unit 20 presses toward the side of the pressing roller 30.
A bearing member 31 is provided to support the core metal 30a of the pressing roller 30 on its axis. The bearing member 31 receives the pressing force from the film assembly unit 20 via the pressing roller 30. In order to rotatably support the core metal 30a of the pressing roller 30 which becomes relatively high temperature, it is preferable that material of the bearing member 31 is heat resistant and has excellent sliding properties. The bearing member 31 is mounted on a casing 43 on a bottom side of the heating device 9.
Next, materials which configure the heater 22, manufacturing method, etc. according to the first embodiment will be described by using part (a) and part (b) of
The substrate 22a according to the first embodiment is made of ceramics. A type of ceramics is not specially limited, and it may be selected appropriately considering required mechanical strength, coefficient of linear expansion to match a formation of the heat generating resistor 22c, availability of a plate material in a market, etc.
A thickness of the substrate 22a may be determined by considering strength, thermal capacity, and heat radiation performance. In a case that the thickness of the substrate 22a is thin, it is advantageous for quick start since its heat capacity is small, however, when it is too thin, it is more likely to occur distortion problems during heat forming of the heat generating resistor 22c. On the other hand, in a case that the thickness of the substrate 22a is thick, it is advantageous in terms of distortion during heat forming of the heat generating resistor 22c, however, when it is too thick, it is not advantageous for quick start since the heat capacity is large. The thickness of the substrate 22a may preferably be from 0.3 mm to 2.0 mm in a case of taking the balance of mass production, cost, and performance into consideration.
In the first embodiment, an alumina substrate which is 10 mm in width, 300 mm in length, and 1 mm in thickness is used as the substrate 22a.
The heat generating resistor 22c is made by printing a heat generating resistor paste which is a mixture of conductive composition, glass composition, and organic binding component, on the substrate 22a and then firing (baking) it.
When the heat generating resistor paste is fired, the organic binding component is burned off and the conductive component and the glass component remain, so the heat generating resistor 22c which includes the conductive component and the glass component.
Here, silver-palladium (Ag—Pd), ruthenium oxide (RuO2), semiconducting barium titanate (BaTiO3), etc. are used alone or in combination as the conductive component. Further, it is preferable that a sheet resistance of it is from 0.1 [Ω/sq.] to 100 [kΩ/sq.].
Further, other materials other than the conductive component, the glass component, and the organic binding component may be included in the heat generating resistor paste, when they are such a very small quantity that they do not deteriorate its properties of the present invention.
In the first embodiment, silver-palladium (Ag—Pd) is used as the conductive component, and the heat generating resistor paste which is mixed with the glass component and the organic binding component is used, and after coating on the substrate 22a by screen printing, the heat generating resistor 22c is formed, followed by drying at 180° C. and firing at 850° C. After firing, the thickness of the heat generating resistor 22c is set as 15 μm, its length is set as 220 mm, and its width is set as 1.1 mm. A distance between an end portion (longer side) of the substrate 22a in the X direction and the heat generating resistor 22c is set as 1.0 mm.
A power supplying electrode 22f and a conductive pattern 22g which are shown in part (a) of
The power supplying electrode 22f and the conductive pattern 22g are provided in order to supply power to the heat generating resistor 22c, and their resistances are sufficiently low relative to the heat generating resistor 22c.
Here, as for the heat generating resistor paste, the power supplying electrode paste, and the conductive pattern paste, which are described above, a material which is soften and melt at a temperature lower than a melting point of the substrate 22a is chosen, and a material which is heat resistant in consideration of a practical temperature is chosen.
In the first embodiment, silver is used as the conductive component, and the power supplying electrode paste and the conductive pattern paste in which the glass component and the organic binding component are mixed with it are used. After coating the substrate 22a by screen printing, the power supplying electrode 22f and the conductive pattern 22g are formed followed by drying at 180° C. and firing at 850° C.
The protective layer 22d which is shown in part (a) and part (b) of
In the first embodiment, the protective layer glass paste is used, and after coating the protective layer glass paste on the heat generating resistor 22c and the conductive pattern 22g by screen printing, the protective layer 22d is formed followed by drying at 180° C. and firing at 850° C.
The groove 22h which is shown in part (a) of
As shown in
As shown in part (b) of
Further, in the first embodiment, a depth of the groove 22h is set to be 5 μm. When the groove 22h is too deep, the grease 60 may accumulate in the groove 22h, and it may become difficult to supply the grease 60 to a contact surface (sliding surface) of the film 23 and the protective layer 22d. In this case, sliding property between the film 23 and the protective layer 22d may be reduced. From this viewpoint, it is desirable that the depth of the groove 22h may not be limited to 5 μm as in the first embodiment, but the depth of the groove 22h may be set appropriately based on a configuration of the heating device 9 and each configuration such as and the type of the grease 60. Further, in the first embodiment, the groove 22h which is a linear shape is used as a recess which is provided on the sliding surface of the protective layer 22d, however, the recess is not limited to a linear groove, but it may be various shapes such as a dot shape.
By using the heater 22 which is shown in part (a) and part (b) of
As a result, it is possible to maintain good rotation of the film 23 and good print quality over a long period of time (the number of prints is approximately 150,000 sheets in the case of the first embodiment).
By reducing the sliding resistance between the inner peripheral surface of the film 23 and the protective layer 22d, an effect of reducing torque of the motor M which rotationally drives the pressing roller 30. Further, since it is possible to reduce the contact area between the inner peripheral surface of the film 23 and the protective layer 22d, an effect of reducing wear on the inner peripheral surface of the film 23 is obtained.
Incidentally, as shown in
Further, in the first embodiment, a case that the protective layer 22d which configures the heater 22 is interposed between the heat generating resistor 22c and the inner peripheral surface of the film 23 and is an interposed member which is slidable against the inner peripheral surface of the film 23 when the film 23 is rotated is described. The interposed member of the present invention is not limited to this case, however, it may be configured to include another member such as a heat transfer member between the heater 22 and the film 23, for example, as an interposed member. In this case, the groove 22h which is similar to that in the first embodiment is provided on the sliding surface between the interposed member and the film 23. Heat from the heater 22 is indirectly transferred to the film 23 via the interposed member.
A comparative example 1 in order to compare with the first embodiment will be described below. The configurations of the image forming apparatus and the heating device other than a heater 22X in the comparative example 1 is the same as in the first embodiment, so descriptions will be omitted. Part (a) of
In the heater 22X according to the comparative example 1, the groove is not existed directly under the heat generating resistor 22c on the sliding surface of the protective layer 22dX similar to the first embodiment. Therefore, it is possible to efficiently transfer heat of the heat generating resistor 22c to the film 23 via the protective layer 22d, and it is possible to thermally fix the toner image T on the recording material P in good condition. However, since the groove is not provided on the sliding surface of the protective layer 22dX, contact area between the film 23 and the protective layer 22dX is large and sliding resistance is high, so rotational torque of the film 23 according to the comparative example 1 is higher than that according to the first embodiment.
As a result, rotatability of the film 23 is decreased when the number of prints exceeded approximately 80,000 sheets. When the recording material P is nipped and conveyed in the nip portion N, discrepancy between rotational speed of the film 23 and conveying speed of the recording material P which is conveyed by the pressing roller 30 may occur, and the toner image T on the recording material P may be thermally fixed on the recording material P in a disturbed state.
A second embodiment of the present invention will be described below. The configurations of the image forming apparatus and the heating device other than a heater 22Y in the second embodiment is the same as in the first embodiment, so descriptions will be omitted. Part (a) of
Here, as shown in part (a) of
On the other hand, as shown in part (a) of
Incidentally, as shown in part (a) of
Therefore, although the detected temperature of the thermistor 25 is affected somewhat by the grease 60 in the groove 22h, it is possible to sufficiently reduce degree of its influence.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2023-025431 filed on Feb. 21, 2023, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-025431 | Feb 2023 | JP | national |
