Patent Application
20240176269
This application claims priority from Japanese Patent Application No. 2022-190902 filed on Nov. 30, 2022. The entire content of the priority application is incorporated herein by reference.
There has been conventionally known a fixing device including a rotatable belt, a ceramic heater and a pressure roller. In the conventional fixing device, the ceramic heater and the pressure roller are configured to nip the belt in cooperation with each other. The ceramic heater includes a substrate and a resistance heating element. The ceramic heater has a nip surface in contact with the nip surface, and a back surface that is the opposite surface of the nip surface. A sheet-like thermal conductive member is arranged on the back surface and is in contact with the same. The thermal conductive member is configured to make uniform the temperature of the substrate.
Because the thermal conductive member has a heat capacity, it is desirable to minimize the size of the thermal conductive member in order to efficiently use heat generated by the heater to perform thermal fixing of an image.
In view of the foregoing, it is an object of the present disclosure to provide a fixing device in which the heat distribution of a heater can be made uniform while suppressing a thermal conductive member from removing heat greater than necessary.
In order to attain the above and other objects, the present disclosure provides a fixing device including a heating rotary body, a pressure rotary body, a heater, and a thermal conductive member. The pressure rotary body is configured to: form a nipping portion between the pressure rotary body and the heating rotary body; and convey a sheet in a conveying direction while nipping the sheet between the pressure rotary body and the heating rotary body. The heater is accommodated inside the heating rotary body. The heater includes a substrate, a first resistance heating element, and a second resistance heating element. The substrate has a first surface and a second surface opposite the first surface. The first resistance heating element extends in a crossing direction crossing the conveying direction. The first resistance heating element is provided on the first surface of the substrate. The second resistance heating element extends in the crossing direction. The second resistance heating element is provided on the first surface of the substrate. The second resistance heating element is positioned apart from the first resistance heating element by a predetermined distance in the conveying direction. The thermal conductive member is in contact with the second surface of the substrate. In the conveying direction, the thermal conductive member has a dimension that is greater than the predetermined distance and smaller than or equal to a dimension of the nipping portion.
In the above structure, since in the conveying direction the dimension of the thermal conductive member is greater than the dimension of the predetermined distance and smaller than or equal to the dimension of the nipping portion, the heat distribution of the heater can be made uniform while suppressing the thermal conductive member from removing heat greater than necessary.
According to another aspect, the present disclosure provides a fixing device including a heating rotary body, a pressure rotary body, a heater, and a thermal conductive member. The pressure rotary body is configured to: form a nipping portion between the pressure rotary body and the heating rotary body; and convey a sheet in a conveying direction while nipping the sheet between the pressure rotary body and the heating rotary body. The heater is accommodated inside the heating rotary body. The heater includes a substrate, a first resistance heating element, and a second resistance heating element. The substrate has a first surface and a second surface opposite the first surface. The first resistance heating element extends in a crossing direction crossing the conveying direction. The first resistance heating element is provided on the first surface of the substrate. The second resistance heating element extends in the crossing direction. The second resistance heating element is provided on the first surface of the substrate. The second resistance heating element is positioned apart from the first resistance heating element by a predetermined distance in the conveying direction. The thermal conductive member is in contact with the second surface of the substrate. In the conveying direction, the substrate has a dimension that is greater than a dimension of the nipping portion. In the conveying direction, the dimension of the nipping portion is greater than the predetermined distance and is greater than or equal to a dimension of the thermal conductive member.
According to still another aspect, the present disclosure provides a fixing device including a belt, a pressure roller, a heater, and a thermal conductive plate. The pressure roller is configured to: form a nipping portion between the pressure roller and the belt; and convey a sheet in a conveying direction while nipping the sheet between the pressure roller and the belt. The heater is accommodated inside the belt. The heater includes a substrate, a first resistance heating element, a second resistance heating element. The substrate having a first surface and a second surface opposite the first surface. The first resistance heating element extends in a crossing direction crossing the conveying direction. The first resistance heating element is provided on the first surface of the substrate. The second resistance heating element extends in the crossing direction. The second resistance heating element is provided on the first surface of the substrate. The second resistance heating element is positioned apart from the first resistance heating element by a predetermined distance in the conveying direction. The thermal conductive plate is in contact with the second surface of the substrate. In the conveying direction, the thermal conductive plate has a dimension that is greater than the predetermined distance and smaller than or equal to a dimension of the nipping portion.
In the above structures, the heat distribution of the heater can be made uniform while suppressing the thermal conductive member from removing heat greater than necessary.
A fixing device 1 according to a first embodiment is used with various apparatuses including an image forming apparatus and a device configured to thermally transfer foil onto a medium. As illustrated in
The heating unit 2 includes a belt B, a heater 10, a holder 20, and a thermal conductive member 30. The belt B is configured to heat a sheet S by rotating while the sheet S is nipped between the belt B and the pressure rotary body 3. The belt B is an example of the “heating rotary body”. The thermal conductive member 30 is an example of the “thermal conductive plate”.
The belt B is an endless belt and made of metal or resin. The belt B is configured to rotate around the heater 10 while being guided by the holder 20. The belt B has an outer circumferential surface and an inner circumferential surface. The outer circumferential surface is configured to contact the sheet S to be subjected to heating. The inner circumferential surface is in contact with the heater 10.
The heater 10 includes a substrate 11, a resistance heating element 12, and a cover 13. The heater 10 is accommodated inside the belt B. Note that, in the present disclosure, the expression “the heater 10 is accommodated inside the belt B” does not necessarily denote that the entire heater 10 is accommodated inside the belt B but specifies that at least part of the heater 10 is accommodated inside the belt B. As illustrated in
The resistance heating element 12 is provided on the substrate 11. The resistance heating element 12 is a heating resistor, for example. The resistance heating element 12 is formed on one surface of the substrate 11 by printing. The resistance heating element 12 includes a first terminal 12A, a second terminal 12B, a first heating pattern 121, and a second heating pattern 122. The first terminal 12A is provided at one end of the first heating pattern 121. The first terminal 12A is a terminal used for supplying electric power to the resistance heating element 12. The second terminal 12B is provided at one end of the second heating pattern 122. The second terminal 12B is a terminal used for supplying electric power to the resistance heating element 12. The first heating pattern 121 extends in the crossing direction crossing the conveying direction of the sheet S. The second heating pattern 122 extends in the crossing direction. The other end of the first heating pattern 121 and the other end of the second heating pattern 122 are electrically connected to each other. The second heating pattern 122 is positioned downstream relative to the first heating pattern 121 in the conveying direction. The second heating pattern 122 is positioned apart from the first heating pattern 121 in the conveying direction by a predetermined distance D1. The first heating pattern 121 is an example of the “first resistance heating element”. The second heating pattern 122 is an example of the “second resistance heating element”.
The cover 13 covers the resistance heating element 12. The cover 13 is made of glass, for example.
As illustrated in
The thermal conductive member 30 has a thermal conductivity that is greater than the thermal conductivity of the substrate 11. The thermal conductive member 30 has a plate-like shape or a sheet-like shape. The thermal conductive member 30 is a member for making uniform the temperature of the heater 10 in directions along the surface of the substrate 11 by conducting heat in directions parallel to the surface of the substrate 11, i.e., in the directions along the surface of the substrate 11. The thermal conductive member 30 is positioned between the heater 10 and the supporting portion 21 of the holder 20. When the sheet S is nipped by the heating unit 2 and the pressure rotary body 3, the thermal conductive member 30 is nipped by the heater 10 and the supporting portion 21.
The thermal conductive member 30 has a thermal conductivity in the directions along the surface of the substrate 11 that is greater than the thermal conductivity of the substrate 11 in the directions along the surface of the substrate 11. While there is no particular restriction on the material of the thermal conductive member 30, for example, the thermal conductive member 30 may be made of metal having a high thermal conductivity such as aluminum, aluminum alloy, or copper. Also, the thermal conductive member 30 may be a graphite sheet. In this case, the graphite sheet has a greater thermal conductivity in directions orthogonal to the thickness direction of the graphite sheet than in the thickness direction. In other words, the thermal conductivity of the graphite sheet in the directions orthogonal to the thickness direction is greater than the thermal conductivity of the graphite sheet in the thickness direction. Further, although there is no limitation on the thickness of the thermal conductive member 30, for example, the thermal conductive member 30 may be a film-like member that is thinner than 0.1 mm, or a plate-like member that is thicker than 1 mm.
The pressure rotary body 3 is a rotatable roller. The pressure rotary body 3 includes a shaft 3A and an elastic layer 3B. The shaft 3A has a columnar shape and is made of metal. The shaft 3A extends in the crossing direction. The elastic layer 3B is configured of an elastically deformable member and covers the shaft 3A. The pressure rotary body 3 is configured to form a nipping portion NP between the pressure rotary body 3 and the belt B by nipping the belt B in cooperation with the heater 10 between the pressure rotary body 3 and the heater 10. The nipping portion NP is a portion for applying heat and pressure to the sheet S. The nipping portion is a contact portion between the belt B and the pressure rotary body 3, i.e., a portion in which the belt B and the pressure rotary body 3 contact each other.
The pressure rotary body 3 is configured to be driven to rotate by receiving a driving force of a motor (not illustrated). When the pressure rotary body 3 is driven and rotates, the belt B rotates following the rotation of the pressure rotary body 3 by the friction force generated between the pressure rotary body 3 and the belt B (or the sheet S). Hence, the pressure rotary body 3 conveys the sheet S between the pressure rotary body 3 and the belt B. Accordingly, for example, when the sheet S having a toner image transferred thereon is conveyed between the pressure rotary body 3 and the heated belt B, the toner image is thermally fixed to the sheet S.
Hereinafter, the dimensions of the substrate 11, thermal conductive member 30 and nipping portion NP will be described. The thermal conductive member 30 has a dimension D3 in the conveying direction. The predetermined distance D1 described above is the distance in the conveying direction between an inward end edge 121A of the first heating pattern 121 and an inward end edge 122A of the second heating pattern 122. In the conveying direction, the dimension D3 of the thermal conductive member 30 is greater than the predetermined distance D1. Note that the inward end edge 121A of the first heating pattern 121 denotes the downstream end edge of the first heating pattern 121 in the conveying direction. The inward end edge 122A of the second heating pattern 122 denotes the upstream end edge of the second heating pattern 122 in the conveying direction.
Also, in the conveying direction, the dimension D3 of the thermal conductive member 30 is greater than a distance D2. The distance D2 is the distance in the conveying direction between an outward end edge 121B of the first heating pattern 121 (i.e., the upstream end edge of the first heating pattern 121 in the conveying direction) and an outward end edge 122B of the second heating pattern 122 (i.e., the downstream end edge of the second heating pattern 122 in the conveying direction).
The nipping portion NP has a dimension D4 in the conveying direction. In the conveying direction, the dimension D3 of the thermal conductive member 30 is smaller than or equal to the dimension D4 of the nipping portion NP. Note that, when a configuration is employed that can change the dimension D4 of the nipping portion NP by moving at least one of the heating unit 2 and the pressure rotary body 3, the above-described comparison between the dimensions D3 and D4 is based on the assumption that the dimension D4 is the maximum dimension of the nipping portion NP in the conveying direction.
The substrate 11 has a dimension D5 in the conveying direction. In the conveying direction, the dimension D3 of the thermal conductive member 30 is greater than or equal to 40% (forty percent) of the dimension D5 of the substrate 11. Also, in the conveying direction, the dimension D3 of the thermal conductive member 30 is smaller than or equal to the dimension D5 of the substrate 11.
In the conveying direction, the dimension D5 of the substrate 11 is greater than the dimension D4 of the nipping portion NP.
As illustrated in
In the fixing device 1 according to the first embodiment described above, the following technical advantages can be attained. In the fixing device 1, in the conveying direction, the dimension D3 of the thermal conductive member 30 is greater than the predetermined distance D1 and is smaller than the dimension D4 of the nipping portion NP. This configuration can suppress the thermal conductive member 30 from conducting heat to the outside of the nipping portion NP, thereby making the heat distribution of the heater 10 uniform while suppressing the thermal conductive member 30 from removing heat greater than necessary. Hence, the heater 10 is suppressed from losing heat greater than necessary, thereby resulting in saving electric power.
Also, in the crossing direction, the dimension L2 of the thermal conductive member 30 is smaller than the dimension L1 of the substrate 11. This configuration can suppress the thermal conductive member 30 from removing heat greater than necessary from the heater 10.
While the invention has been described in conjunction with various example structures outlined above and illustrated in the figures, various alternatives, modifications, variations, improvements, and/or substantial equivalents, whether known or that may be presently unforeseen, may become apparent to those having at least ordinary skill in the art. Accordingly, the example embodiments of the disclosure, as set forth above, are intended to be illustrative of the invention, and not limiting the invention. Various changes may be made without departing from the spirit and scope of the disclosure. Therefore, the disclosure is intended to embrace all known or later developed alternatives, modifications, variations, improvements, and/or substantial equivalents. Some specific examples of potential alternatives, modifications, or variations in the described invention are provided below:
For example,
In the second embodiment, since in the conveying direction the dimension D4 of the nipping portion NP is greater than or equal to the dimension D3 of the thermal conductive member 30A, the thermal conductive member 30A can be suppressed from conducting heat to the outside of the nipping portion NP. Accordingly, the thermal conductive member 30A can be suppressed from removing heat greater than necessary from the heater 10 while making uniform the heat distribution in an appropriate region of the heater 10 that corresponds to the nipping portion NP.
For example,
For example,
In the embodiments described above, the resistance heating element 12 includes the two heating patterns extending in the crossing direction. However, the number of the heating patterns is not limited to a particular number, but may be three or more.
For example,
In the resistance heating element 12 in the above-mentioned embodiments, the first terminal 12A is provided at one end portion of the first heating pattern 121, the second terminal 12B is provided at one end portion of the second heating pattern 122, and the other end portion of the first heating pattern 121 and the other end portion of the second heating pattern 122 are electrically connected to each other. However, the resistance heating element 12 is not limited to this configuration.
For example,
In the embodiments described above, the thermal conductive member 30 is configured of a single sheet-like member, but the thermal conductive member 30 may be configured of a combination of a plurality of sheet-like members. In this case, the material, thermal conductivity, and shape of the plurality of sheet-like members may be different from one another. Also, the material, thermal conductivity, and shape of the plurality of sheet-like members may be the same as one another.
In the embodiments described above, the substrate 11 of the heater 10 is the ceramic plate having the rectangular shape elongated in the crossing direction. However, provided that the substrate 11 has a thermal conductivity that is smaller than the thermal conductivity of the thermal conductive member 30, the substrate 11 may be a slender metal plate (e.g., a slender stainless plate) having an elongated rectangular shape.
The elements described in connection with the embodiments and modifications thereto may be combined as appropriate.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-190902 | Nov 2022 | JP | national |
