JPH11174884A - Heat roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact heat roller capable of easily changing a heating area corresponding to the size of a toner supporting body by providing a thermosnsitive feed switching part for switching a conduction path from a power source to a resistance heating element based on ambient temperature and generating resistance heat at a part of the heating area. SOLUTION: The thermosensitive feed switching parts 18a and 18b are composed of nearly ring-like electrode members 10a and 10b fixed on the inner peripheral surface of the resistance heating layer 2, and thermosensitive feed members 11a and 11b fixed on the members 10a and 10b and displaced and actuated toward the center axis of the heat roller 1 based o the ambient temperature. In order to change the heating area of the layer 2 corresponding to the size of paper on which toner is fixed, the switching parts 18a and 18b detect heat on the periphery and automatically switch the conduction path from a power source circuit 15 to the layer 2. Thus, hot offset due to the temperature rise of the paper non-passing part is prevented and the compact heat roller is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat roller for use in a copying machine, a facsimile, a printer, and the like, which heats and melts a toner on a toner support to fix the toner.

[0002]

2. Description of the Related Art In a copying machine, a facsimile, a printer, or the like, a toner support, for example, a toner supported on paper is heated and pressed to fix the toner on the paper. Specifically, in such an apparatus, a fixing device having a heat roller for heating and melting the toner and a pressure roller for applying pressure is used to form a sheet carrying toner according to an image to be formed. By passing between the heat roller and the pressure roller, the toner is fixed and a desired image is formed on the paper. The heat roller is in direct contact with paper, with a resistive heat generating layer for applying current and generating Joule heat, a cylindrical substrate for holding the resistive heat layer either outside or inside. And an offset prevention layer for preventing an offset phenomenon in which toner adheres to the heat roller. 2. Description of the Related Art In recent years, in copiers, facsimile machines, printers, and the like, it has been required to form images on sheets of different sizes according to various uses, in addition to energy saving and compactness. For this reason, in the conventional heat roller, the heat generation (heating) time in the resistance heating layer is shortened to improve energy saving by improving the heat generation efficiency in the resistance heating layer. Further, in the conventional heat roller, a portion that does not come into contact with the paper when fixing the toner (hereinafter, referred to as a “non-paper passing portion”).
In order to prevent the temperature rise and the occurrence of hot offset due to the temperature rise, the heat generation area in the resistance heat generation layer is changed according to the size of the paper on which the toner is fixed.

Here, as a conventional heat roller, for example, a heat roller of a heat fixing device disclosed in Japanese Patent Application Laid-Open No. 58-221875 will be specifically described with reference to FIG. FIG. 7 is a cross-sectional view illustrating a configuration of a conventional heat roller. In FIG. 7, a conventional heat roller 51 includes a rotating shaft 52 made of metal, a cylindrical base 54 having electrical insulation and held on the rotating shaft 52 via journal members 53a and 53b, A resistance layer 55 provided on the outer peripheral surface, an offset prevention layer 56 provided on the outer peripheral surface of the resistance layer 55, and a conductive layer provided on the outer side of each of the journal members 53a and 53b in the axial direction of the heat roller 51. It has ring members 57a and 57b. Further, the conventional heat roller 51 includes a power supply circuit 58 for supplying electric power to the resistance layer 55, and power supply brushes 59a, 59b, 59c which come into contact with the outer peripheral surfaces of the journal members 53a, 53b and the conductive ring members 57a, 57b, respectively. , 59d, the power supply circuit 58, and the power supply brushes 59a, 59b, 5
9c, 59d and connection lines 60a, 60b, 60
c, 60d.

[0004] The rotating shaft 52 is rotatably mounted on an outer container (not shown) of the fixing device. Insulating films 52a and 52b are provided around the rotation shaft 52,
And conductive ring members 57a, 57b and conductive members 61a,
61b is electrically insulated. The conductive member 61
Reference numerals a and 61b denote current-carrying members for changing (reducing) the heat generation area in the resistance layer 55 in accordance with the size of the paper on which the toner is fixed.
57b and a plurality of electrode layers 62a and 62b provided on the inner peripheral surface of the resistance layer 55 are connected respectively. The journal members 53a and 53b are made of metal,
Not only a holding (shaft-neck) member for rotatably holding the power supply circuit 58 but also a current-carrying member for supplying electric power from the power supply circuit 58 between both ends of the resistance layer 55. Each of the journal members 53a and 53b is formed by the conductive ring members 57a and 57b and the conductive members 61a and 61b by the insulating coatings 63a and 63b.
Electrically insulated from

[0005] The base 54 is formed of a ceramic having electrical insulation and heat resistance, and is configured to have a low thermal conductivity and heat capacity. A plurality of holes (not shown) are formed at both ends of the base 54 along the circumferential surface of the base 54. A plurality of projections 53a1, 53b1 provided on the outermost peripheral portions of the journal members 53a, 53b are fitted into these plurality of holes, and the base 54 is connected to the journal members 53a, 53b. Further, a plurality of electrode layers 64a, 64b are arranged between the plurality of projecting pieces 53a1, 53b1 and the inner peripheral surface of the resistance layer 55, and the resistance layer 5
5 and the journal members 53a and 53b are electrically connected. These electrode layers 64a and 64b are formed by the shape of the outer peripheral surface of each journal member 53a and 53b and the resistance layer 55.
For example, a strip-shaped copper plate is formed in an arc shape in conformity with the shape of the inner peripheral surface of the above, and is arranged in the plurality of holes. The resistance layer 55 is made of a metal such as nichrome or tungsten. On the inner peripheral surface of the resistance layer 55,
A plurality of electrode layers 62a and 62b are provided. Each of the electrode layers 62 a and 62 b is, for example, a strip-shaped copper plate formed in an arc shape in accordance with the shape of the inner peripheral surface of the resistance layer 55.
It is fixed to the inner peripheral surface at a predetermined interval. The length dimension of the resistance layer 55 in the axial direction of the heat roller 51 is set substantially equal to the width dimension of the paper (toner support) having a large width. Further, the distance between the electrode layer 62a and the electrode layer 62b in the axial direction is set to be substantially equal to the width of a sheet having a small width. Thus, the resistance layer 55 can form two large and small heat generating regions corresponding to two types of paper having different widths, and can heat and melt the toner on the paper. Offset prevention layer 5
6 is formed by applying Teflon or silicone rubber on the outer peripheral surface of the resistance layer 55.

The power supply circuit 58 changes a power supply brush for supplying electric power in accordance with the width of a sheet on which toner is fixed. More specifically, when fixing toner on a sheet having a large width, the power supply circuit 58 supplies electric power to the power supply brushes 59a and 59b through the connection lines 60a and 60b. As a result, a predetermined voltage is applied between both ends of the resistance layer 55 via the journal members 57a and 57b and the electrode layers 64a and 64b, so that the entire resistance layer 55 generates Joule heat and the toner is fixed on the paper. Is done. When the toner is fixed on paper having a small width, the power supply circuit 58 is connected to the connection line 60.
Electric power is supplied to the power supply brushes 59c and 59d by c and 60d. As a result, a predetermined voltage is applied only between the electrode layers 62a and 62b via the conductive ring members 57a and 57b and the conductive members 61a and 61b.
The portion of the resistance layer 55 between a and 62b generates Joule heat and the toner is fixed on the paper. In this case, the non-sheet passing portion of the heat roller 51, that is, the electrode layers 62a and 62b
The power from the power supply circuit 58 is not supplied to the portion of the resistive layer 55 outside. For this reason, the non-sheet passing portion does not generate heat, and the temperature rise and the occurrence of hot offset can be prevented. As described above, in the conventional heat roller 51, by supplying the power from the power supply circuit 58 to the power supply brushes 59a and 59b or the power supply brushes 59c and 59d, the resistance layer 55 corresponding to the size of the paper on which the toner is fixed is provided. Had changed the heat generation area.

[0007]

In the conventional heat roller as described above, in order to change the heat generation area in the resistance layer to a smaller size in accordance with the size of the toner support, a pair of the heat rollers is disposed at an interval substantially equal to the size. It is necessary to provide the electrode layer on the resistance (heat generation) layer and to connect a dedicated energizing member for supplying power from the power supply circuit to the above-mentioned electrode layer. Specifically, in the conventional heat roller, it is necessary to dispose the connection wire, the power supply brush, the conductive ring member, and the conductive member between each electrode layer and the power supply circuit. For this reason, when the number of heat generating regions corresponding to the size of the toner support is increased, the conventional heat roller has a problem that the number of components increases, resulting in a large and complicated structure. Furthermore, since the conductive ring member and the conductive member are attached to the rotating shaft via the insulating coating, the conventional heat roller not only increases the number of components but also makes it difficult to make it compact. Further, in the conventional heat roller, since it is necessary to supply power by selecting a power supply brush or the like according to the size of the toner support, the power supply circuit has a complicated and large-scale configuration, and its control is also complicated. It became something.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the heat-generating region can be easily formed according to the size of the toner support without complicating the structure of the heat roller. It is an object of the present invention to provide a compact heat roller that can be changed to a heat roller.

[0009]

A heat roller according to the present invention comprises: a cylindrical base; a cylindrical resistance heating element provided on a surface of the base and formed with a plurality of heating regions; And a power supply that is provided inside the resistance heating element and switches an energization path from the power supply to the resistance heating element based on the ambient temperature to generate resistance heating in one of a plurality of heating regions. A thermal power supply switching unit is provided. With this configuration, even when the number of heat generating regions in the resistance heating element is increased, the occurrence of hot offset due to a rise in the temperature of the non-sheet passing portion is prevented, and a heat roller having a compact structure is configured. Can be. still,
The non-sheet passing portion is a portion that does not come into contact with the toner support when the toner is fixed by the heat roller.

According to another aspect of the present invention, there is provided a heat roller comprising: a cylindrical base having high thermal conductivity; a resistance heating element provided inside the base; and a resistance heating element provided inside the resistance heating element. A plurality of electrode members that divide the heating region in the axial direction of the base, a small-diameter cylindrical portion, and a large-diameter cylindrical portion provided with air holes, provided at both ends of the resistance heating element, First power supply means for supplying electric power to the largest heat generating region, toner intrusion prevention means provided near the air hole to prevent toner from entering the inside of the resistance heating element, and the first power supply A second power supply means connected to the first power supply means for supplying power from the first power supply means to each of the plurality of electrode members; and one end portion fixed to the electrode member, the other end being provided when an ambient temperature exceeds a predetermined temperature. The part is displaced in the axial direction of the base and makes contact with the second power supply means Te, and a thermal power supply member for supplying electric power through the electrode member from the second power supply means to the resistance heating element between the plurality of electrode members. With this configuration, even when the number of heat generating regions in the resistance heating element is increased, the occurrence of hot offset due to a rise in the temperature of the non-sheet passing portion is prevented, and a heat roller having a compact structure is configured. Can be.

In a heat roller according to another aspect of the present invention, a large-diameter cylindrical portion is inserted into both ends of the resistance heating element, and a second power supply device is connected within the small-diameter cylindrical portion. The total value of the resistance values of the power supply member and the electrode member is smaller than the total value of the resistance values of the resistance heating element from the large-diameter cylindrical portion and one end to the portion where the electrode member is provided.
With this configuration, when the heat-sensitive power supply member operates, the current supply path of the power supplied to the resistance heating element can be easily switched.

In a heat roller according to another aspect of the present invention, the toner intrusion preventing means has an opening smaller than the particle diameter of the toner, and is formed by a heat-resistant filter having good air permeability. With this configuration, it is possible to prevent the floating toner from entering the inside of the resistance heating element.

In the heat roller according to another aspect of the present invention, a toner intrusion preventing means is provided so as to close the air hole. With this configuration, it is possible to prevent the floating toner from entering the inside of the resistance heating element. Further, the installation area of the toner intrusion prevention means can be reduced.

In a heat roller according to another aspect of the present invention, the toner intrusion preventing means is provided inside a large-diameter cylindrical portion. With this configuration, it is possible to prevent the floating toner from entering the inside of the resistance heating element. Further, the positioning operation of the toner intrusion prevention means inside the resistance heating element can be omitted.

In a heat roller according to another aspect of the present invention, the toner intrusion prevention means is made of a heat-resistant rubber elastic body. With this configuration, the toner intrusion prevention unit can be deformed in accordance with the expansion and contraction of the air inside the resistance heating element.

A heat roller according to another aspect of the present invention includes a support member for supporting the second power supply means, and an insulator for fixing the support member to the inner peripheral surface of the resistance heating element. With this configuration, the second power supply unit can be stably held inside the resistance heating element.

In a heat roller according to another aspect of the invention, the other end of the heat-sensitive power supply member is fixed to the electrode member so as to project toward the center of the resistance heating element. With this configuration, the heat-sensitive power supply member and the electrode member can be inserted into the resistance heating element without damaging the heat-sensitive power supply member.

According to another aspect of the present invention, when the ambient temperature exceeds a predetermined temperature, the other end of the heat-sensitive power supply member is displaced in the radial direction of the heat roller and comes into contact with the second power supply means. I do. With this configuration,
The installation space for the heat-sensitive power supply member inside the resistance heating element can be reduced.

In a heat roller according to another aspect of the present invention, the width of the heat-sensitive power supply member is smaller than that of the electrode member, and the heat-sensitive power supply member is provided on the electrode member so as not to protrude from the surface of the electrode member. With this configuration, the heat-sensitive power supply member and the electrode member can be inserted into the resistance heating element without damaging the heat-sensitive power supply member.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment showing a heat roller of the present invention will be described with reference to the drawings.

<< First Embodiment >> FIG. 1 is a sectional view showing the structure of a heat roller according to a first embodiment of the present invention, and FIG. 2 shows the structure of a heat-sensitive power supply switching section shown in FIG. It is a perspective view. In the following description, for the sake of simplicity, a toner support for fixing the toner, for example, a heat roller capable of changing the heating area in the resistance heating layer to one of two sizes, large or small, according to the size of the paper. explain.

<< Structure >> In FIGS. 1 and 2, the heat roller 1 of this embodiment comprises a cylindrical resistance heating layer 2, an electric insulating layer 3 provided on the outer peripheral surface of the resistance heating layer 2, and A base 4 is provided on the outer peripheral surface of the electrical insulating layer 3, and an offset prevention layer 5 is provided on the outer peripheral surface of the base 4. Further, the heat roller 1 includes two cylindrical portions having different diameters (hereinafter, referred to as “large-diameter cylindrical portions 6a1 and 6b1”).
First power feeding portions 6a and 6b in which the large-diameter cylindrical portions 6a1 and 6b1 are fitted and inserted into both ends of the resistance heating layer 2, and one end is a small-diameter cylindrical portion. The second power supply sections 7a and 7b inserted into the sections 6a2 and 6b2 and the other ends thereof are held inside the resistance heating layer 2 and the inside of the resistance heating layer 2 are provided. There is a heat-sensitive power supply switching unit 18a, 18b for changing. In order to generate Joule heat for heating and melting the toner on the paper in the resistance heating layer 2, the heat roller 1 includes a power supply circuit 1 for supplying a predetermined power to the resistance heating layer 2.
5. Sliding contacts 16a and 16b which are in sliding contact with the outer peripheral surfaces of the small-diameter cylindrical portions 6a2 and 6b2, respectively, and a power supply circuit 15.
Connection line 17 for connecting the sliding contacts 16a and 16b
a and 17b are provided.

The outer peripheral surface of the offset prevention layer 5 at the outermost peripheral portion of the heat roller 1 is supported by a bearing portion 1a constituted by a bearing or a slide bearing, and is rotatable by an outer container (not shown) of the fixing device. Held and mounted. A pressure roller 20 is arranged near the heat roller 1 so as to be in contact with the offset prevention layer 5. The paper is supplied to the offset prevention layer 5 and the pressure roller 2 by a paper feeding mechanism (not shown).
0, the toner on the sheet is heated and melted by the heat roller 1, and further pressed by the pressure roller 20 to be fixed on the sheet. The length dimension of the contact surface between the offset prevention layer 5 and the pressure roller 20 constitutes the nip width of the fixing device.
This is the maximum size at which the toner can be fixed. The pressure roller 20 has a central shaft 20a made of metal such as iron.
And a heat-resistant cylindrical elastic body 20b provided around the central axis 20a. The elastic body 20b is made of a heat-resistant rubber made of silicone, fluorine, or the like. In order to further improve the abrasion resistance, the rubber constituting the elastic body 20b may be coated with a heat-resistant resin such as a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether (PFA; Perfluoroalkoxy). . Further, a silicone oil, a fluorine oil or the like may be applied on the elastic body 20b in order to improve the releasability of the paper.

The resistance heating layer 2 is made of nichrome, tungsten, molybdenum, palladium silver, a mixed material of palladium silver and lead glass, or a combination of these materials. Occurs. The thickness dimension of the resistance heating layer 2 is about 5 μm to 200 μm. The length dimension of the resistance heating layer 2 is set to 300 mm (= 297 mm + 3 mm) with a margin so that the toner can be fixed on a large-size sheet, for example, a B4 portrait or A3 portrait size sheet. The electrical insulating layer 3 is for electrically insulating the resistance heating layer 2 and the base 4 from each other, and is made of a heat-resistant resin such as polyimide or polyphenylene sulfide at 200 ° C. or higher, or an inorganic material such as glass or ceramic. I have.
The above-mentioned material having a high thermal conductivity is preferable for the electric insulating layer 3, and the thinner the better. The specific thickness dimension of the electric insulating layer 3 is about 10 μm to 200 μm, preferably 2 μm.
It is about 0 μm to 100 μm. Further, as a material of the electric insulating layer 3, a polyimide resin is particularly desirable.

The substrate 4 is a member having a function of conducting Joule heat generated in the resistance heating layer 2 to the offset prevention layer 5, and is made of a material having high heat conductivity and rigidity, specifically, a heat conductivity of 30 W. / (M * K) or more iron, nickel,
It is made of aluminum, copper, silver, or a material combining these. In particular, the base 4 is made of aluminum.
It is desirable to constitute. By forming the base 4 using a material having high thermal conductivity, even when the amount of heat generation is small in a part of the resistance heating layer 2, the base 4 can reduce the Joule heat generated in the part around the part by the offset prevention layer. 5 can be conducted. As a result, it is possible to prevent a temperature drop in the portion of the offset prevention layer 5 above the resistance heating layer 2 that generates a small amount of heat, thereby preventing a cold offset from being caused by the temperature drop. The specific numerical value of the outer diameter of the base 4 is about 8 mm to 60 mm, and the thickness is about 0.3 mm to 2.5 mm. In order to shorten the rise time of the temperature in the offset prevention layer 5, the thickness of the base 4 must be 1.5 mm.
It is desirable to be less than. More specifically, the maximum A3
In the heat roller 1 capable of fixing the toner to the vertical size paper, when the base 4 is made of aluminum, the outer diameter of the base 4 must be set to 20 seconds or less at a power of 1 kW. The thickness and the thickness are desirably 35 mm or less and 1.3 mm or less, respectively.

The anti-offset layer 5 is in direct contact with the paper carrying the toner based on the image to be formed, and uses the Joule heat from the resistance heating layer 2 conducted through the electric insulating layer 3 and the base 4. Then, the toner is heated and melted and fixed on the paper. The anti-offset layer 5 is made of a material having heat resistance and releasability from the toner and having high thermal conductivity, specifically, polytetrafluoroethylene (PTFE; Polytetr).
a fluoroethylene), PFA, fluorine resin such as fluorine rubber, silicone resin containing silicone rubber, or the like, or a mixture of these materials with carbon. The specific thickness dimension of the offset prevention layer 5 is about 10 μm to 500 μm. As a material of the offset prevention layer 5, PTFE is particularly preferable,
The thickness dimension is desirably 5 μm to 50 μm. still,
A temperature detection unit (not shown) is disposed at the center of the offset prevention layer 5, and the power supply circuit 15 is controlled so that the surface temperature of the offset prevention layer 5 becomes a predetermined temperature, for example, 180 ° C.
Supplies power to the resistance heating layer 2.

The first power supply units 6a and 6b are connected to the power supply circuit 15
Is a current-carrying member for supplying power from both ends of the resistance heating layer 2 to generate heat in the largest heating area in the resistance heating layer 2, and has high conductivity copper, brass, brass, copper alloy, It is made of a metal material such as a silver alloy. The first power supply units 6a and 6b are stably fixed to the inner peripheral surface of the resistance heating layer 2,
In order to easily align the center axis of the resistance heating layer 2 (heat roller 1) with the center axis of the first power supply units 6a and 6b,
It is preferable to increase the contact width (dimension) between the inner peripheral surface of the resistance heating layer 2 and the first power supply portions 6a and 6b. That is, it is desirable to increase the length of each of the large-diameter cylindrical portions 6a1 and 6b1, and more specifically, it is preferable that the length be about 2 to 20 mm. The resistance heating layer 2 and the first power supply portions 6a, 6b are fixed by injecting a conductive adhesive between the inner peripheral surface of the resistance heating layer 2 and the large-diameter cylindrical portions 6a1, 6b1, or fixed by screws. It is fixed using.

The second power supply units 7a and 7b are connected to the power supply circuit 15
Is a current-carrying member for supplying the electric power from the heater to the resistance heating layer 2 via the heat-sensitive power supply switching units 18a and 18b, respectively.
It is made of a rod-shaped metal material such as copper, brass, brass, copper alloy, and silver alloy having high conductivity. As described above, each of the second power supply portions 7a and 7b has one end having a small-diameter cylindrical portion 6a.
a2, 6b2, and the other end is held inside the resistance heating layer 2. At one end of the second power supply portions 7a and 7b, fixing members 12a and 12b made of metal screws are inserted into screw holes provided in the small-diameter cylindrical portions 6a2 and 6b2, respectively, and the fixing members 12a and 12b are tightened. , And is fixed to the first power supply units 6a and 6b. Further, supporting members 8a and 8b for holding the inside of the resistance heating layer 2 are provided at the other end portions of the second power supply portions 7a and 7b, respectively. The supporting members 8a and 8b
a and 7b are stably held inside the resistance heating layer 2 along the central axis of the heat roller 1, respectively.
It is made of a leaf spring-like elastic body made of copper, phosphor bronze, or the like. Each of the support members 8a and 8b is provided on the inner peripheral surface of the resistance heating layer 2 in plural numbers, for example, three. These support members 8a and 8b are fixed to the inner peripheral surface of the resistance heating layer 2 via ring-shaped insulators 9a and 9b made of, for example, polyimide.

The thermal power supply switching units 18a and 18b detect ambient heat (ambient temperature) and change the power supply circuit in order to change the heating area of the resistance heating layer 2 in accordance with the size of the paper on which the toner is fixed. The current path from 15 to the resistance heating layer 2 is automatically switched. Specifically, the heat-sensitive power supply switching units 18a, 1
8b is a substantially ring-shaped electrode member 10a, 10b fixed to the inner peripheral surface of the resistance heating layer 2, and the electrode members 10a, 10b.
And heat-sensitive power supply members 11a and 11b which are displaced and operated in the direction of the central axis of the heat roller 1 based on the ambient temperature.
It is composed of Also, the second power supply unit 7a
Is the sum of the resistance value of the large-diameter cylindrical portion 6a1 and the resistance value of the large-diameter cylindrical portion 6a1.
The resistance value is set to be much smaller than the sum of the resistance values of the resistance heating layer 2 from the one end where is connected to the portion where the heat-sensitive power supply switching portion 18a is fixed. Similarly, the resistance value of the second power supply unit 7b and the heat-sensitive power supply switching unit 18
The sum of the resistance values of the large-diameter cylindrical portion 6b1 and the resistance heating layer 2 from one end where the large-diameter cylindrical portion 6b1 is connected to the portion where the heat-sensitive power supply switching portion 18b is fixed is obtained.
The resistance value is set to be much smaller than the sum of the resistance values. This makes it possible to easily switch the current path from the power supply circuit 15 to the resistance heating layer 2 when the heat-sensitive power supply switching units 18a and 18b operate.

Here, the function of the thermal power supply switching units 18a and 18b will be specifically described with reference to FIG. FIG.
FIG. 3 is a block diagram showing a configuration of an equivalent electric circuit of the resistance heating layer 2, the power supply circuit 15, and the heat-sensitive power supply switching units 18a and 18b shown in FIG. In FIG. 3, the resistance heating layer 2
Are represented by resistors 2a, 2b, and 2c connected in series. One ends of the heat-sensitive power supply switching units 18a and 18b, which are switching members, are connected to the power supply circuit 15,
The other end is connected to a connection point B between the resistor 2a and the resistor 2b and a connection point C between the resistor 2b and the resistor 2c. Points A and D indicating both ends of the resistance heating layer 2 are connected to the power supply circuit 15. Thermal power supply switching units 18a, 18b
Is not operating (OFF state), the power supply circuit 15
Is applied between points A and D, and supplied to the resistors 2a, 2b and 2c connected in series. As a result, the entire resistive heat generating layer 2 generates heat as a heat generating area, and the toner can be fixed on a large-sized sheet. The state in which the thermal power supply switching units 18a and 18b are operated (ON state)
Then, the electric power from the power supply circuit 15 is supplied to the heat-sensitive power supply switching unit 18.
A voltage is applied between the connection points B and C via a and 18b, and power is supplied to the resistor 2b. At this time, the power from the power supply circuit 15 is not supplied to the resistors 2a and 2c due to the action of the resistance values of the resistors 2a and 2c and the large-diameter cylindrical portions 6a1 and 6b1 (FIG. 1), as described above. As a result, only the resistor 2b of the resistance heating layer 2 generates heat as a heating area, and the toner can be fixed on a small-sized sheet.

Returning to FIG. 1, the electrode members 10a, 10b
Is made of a metal such as copper or brass having high conductivity, or an alloy material obtained by mixing other metals such as silver and nickel with these metals, and supplies power from the power supply circuit 15 to the resistance heating layer 2. This divides the heat generation area in the resistance heat generation layer 2 in the axial direction of the base 4. Electrode members 10a, 10
The interval of b is 220 mm (= 210 mm) in view of the margin of the width of a small-size sheet, for example, A4 size sheet.
mm + 10 mm). Also, the electrode member 1
0a and 10b have a thickness dimension and a width dimension of 5
It is about 300 μm and about 0.1 to 10 mm. As a material of the electrode members 10a and 10b, a copper-based metal is particularly preferable. These electrode members 10a and 10b are connected to the large-diameter cylindrical portions 6a1 and 6b1 and the supporting member 8 by a conductive adhesive.
a and 8b are fixed to the inner peripheral surface of the resistance heating layer 2.

The heat-sensitive power supply members 11a and 11b are made of two kinds of metals having different coefficients of thermal expansion, for example, a plate-shaped bimetal in which a copper alloy and an amber (nickel-iron alloy) are bonded. Each thermal power supply member 11a, 11b
One end is fixed to the inner peripheral surfaces of the electrode members 10a and 10b such that the surface of the copper alloy having a large coefficient of thermal expansion is closer to the inner peripheral surface of the resistance heating layer 2 than the surface of the amber. Also,
When the heat-sensitive power supply switching units 18a and 18b are fixed to the inner peripheral surface of the resistance heating layer 2, the other ends are connected to the second power supply units 7a and 7b.
When the ambient temperature exceeds the set temperature, as shown by an arrow “P” in FIG. 2, the actuator is displaced so as to contact the second power supply units 7a and 7b. The shortest distance between the other end portions of the heat-sensitive power supply members 11a and 11b and the second power supply portions 7a and 7b is specifically 1 μm to 10 mm. The thickness of the heat-sensitive power supply members 10a and 10b is 10 μm.
５5 mm, and the width dimension is 10 μm〜20 mm.
The heat-sensitive power supply members 11a and 11b are fixed to the electrode members 10a and 10b such that the other end portions protrude toward the center of the resistance heating layer 2 with respect to the electrode members 10a and 10b.

The above-mentioned ambient temperature rises, for example, when the toner is continuously fixed on a small-sized sheet, and is not contacted with the sheet at the time of fixing the toner, that is, at the non-sheet passing portion of the heat roller 1. It rises based on the temperature rise. Before the heat-sensitive power supply members 11a and 11b reach a temperature (for example, 240 ° C.) at which a hot offset occurs due to an ambient temperature exceeding a predetermined set temperature (for example, 200 ° C.), the other end portion is heated by a heat roller. It is displaced and actuated in the direction of the central axis 1 and comes into contact with the second power supply units 7a and 7b. As a result, the current path from the power supply circuit 15 to the resistance heating layer 2 is formed by the small-diameter cylindrical portions 6a2, 6a of the first power supply portions 6a, 6b.
b2 and the heat-sensitive power supply switching section 18a, 1 from the current path to the resistance heating layer 2 via the large-diameter cylindrical sections 6a1, 6b1 via the small-diameter cylindrical sections 6a2, 6b2 and the second power supply sections 7a, 7b.
The path is switched to the current path to the resistance heating layer 2 via 8b. As a result, the resistance heating layer 2 between the electrode members 10a and 10b
Only the portion generates heat, and the heat generation area in the resistance heat generation layer 2 is changed from that corresponding to the large-size paper to that corresponding to the small-size paper. Further, the current from the power supply circuit 15 does not flow to the large-diameter cylindrical portion 6a1 and the electrode member 10a and to the resistance heating layer 2 between the large-diameter cylindrical portion 6b1 and the electrode member 10b. 2 does not generate Joule heat. Thus, it is possible to prevent the temperature in the non-sheet passing portion from further increasing. As a result, for example, after continuously fixing toner on small-size paper,
It is possible to completely prevent hot offset that occurs when fixing toner on a large-size sheet. In order to easily attach the heat-sensitive power supply switching sections 18a and 18b to the inner peripheral surface of the resistance heating layer 2, for example, as shown in FIG.
0a1 is provided on the electrode member 10a.

Here, a method of attaching the heat-sensitive power supply switching units 18a and 18b to the heat roller 1 will be specifically described with reference to FIG. FIG. 4 is an explanatory diagram showing a method of attaching the thermal power supply switching unit shown in FIG. As shown in FIG.
The method of mounting the heat-sensitive power supply switching unit 18b to the heat roller 1 is as follows. First, the heat-sensitive power supply switching unit 18b is accommodated and arranged in a cylindrical mounting member 30 smaller than the inner diameter of the resistance heating layer 2. Subsequently, the extruding member 31 is operated in the direction of the arrow “Q” in the figure to insert the heat-sensitive power supply switching unit 18 b into the inside of the resistance heating layer 2 and mounted on the inner peripheral surface of the resistance heating layer 2. Since the notch illustrated in FIG. 2 is provided in the electrode member 10b, the electrode member 10b is elastically deformed in conformity with the inner peripheral surface of the mounting member 30, and the heat-sensitive power supply switching unit 18b is easily inserted into the mounting member 30. Can be inserted into In addition, heat-sensitive power supply member 1
The heat-sensitive power supply switching unit 18b is attached to the mounting member 3 so that the other end of the protrusion 1b is on the opposite side of the pushing member 31.
By arranging the heat-sensitive power supply switching member 18b inside the resistance heating layer 2, the heat-sensitive power supply switching portion 18b can be inserted into the resistance heating layer 2 without damaging the heat-sensitive power supply member 11b by the pushing member 31.
The heat-sensitive power supply switching unit 18a is also mounted on the inner peripheral surface of the resistance heating layer 2 and mounted on the heat roller 1 in the same manner.

Returning to FIG. 1, the cylindrical resistance heating layer 2
The openings at both ends are sealed by the first power supply units 6a and 6b. Therefore, in the heat roller 1 of the present embodiment, the air holes 1 are formed in the flange surfaces of the large-diameter cylindrical portions 6b1 and 6b2.
3a and 13b are provided to allow air to flow out of the resistance heating layer 2;
It is configured to allow inflow. This allows
In the heat roller 1 of the present embodiment, the heat roller 1 is not affected by the thermal expansion and contraction of the air in the resistance heating layer 2 which is generated by the heating and cooling of the heat roller 1, and the heat roller 1 is not deformed such as distortion. This can be prevented. Further, toner intrusion preventing members 14a, 14b are provided inside the resistance heating layer 2 of the air holes 13a, 13b.
b is provided. These toner intrusion prevention members 14
a and 14b are heat-resistant filters having good air permeability,
It is made of a heat-resistant rubber elastic body such as fluorine rubber or silicone rubber, or a metal mesh or silicone sponge, and has an opening (for example, 3 μm or less) smaller than the particle diameter of the toner. By providing the toner intrusion prevention members 14a and 14b, in the heat roller 1 according to the present embodiment, when the air in the resistance heating layer 2 thermally contracts, the toner floating near the heat roller 1 is removed by the resistance heating layer. 2 and further into the second power supply units 7a, 7
b, and can prevent the conduction between the second power supply units 7a and 7b and the heat-sensitive power supply members 11a and 11b.

Each of these toner intrusion prevention members 14
a and 14b are large-diameter cylindrical portions 6 made of a curable adhesive, for example.
It is preferable to adhere to the insides of a1 and 6b1 so as to close the air holes 13a and 13b. By doing so, the installation area of the toner intrusion prevention members 14a and 14b can be reduced. Further, by previously adhering the toner intrusion prevention members 14a and 14b inside the large-diameter cylindrical portions 6a1 and 6b1, the positioning operation of the toner intrusion prevention members 14a and 14b in the resistance heating layer 2 can be omitted. The man-hour for manufacturing the heat roller 1 can be reduced. Also,
Toner intrusion prevention members 14a and 14b and first power supply unit 6
By providing an adhesive surface with the a and 6b inside the resistance heating layer 2, the influence of contaminants such as silicone oil applied to the pressure roller 20 can be reduced, and the toner intrusion prevention members 14a and 14a due to the contaminants can be reduced. 14b can be prevented from peeling off. Further, the toner intrusion prevention members 14a, 14
It is desirable that b is made of a heat-resistant rubber elastic material such as fluorine rubber or silicone rubber. The reason is that the use of these rubber elastic bodies can completely prevent toner and silicone oil from entering the inside of the resistance heating layer 2, and furthermore, the above-described expansion and expansion of the internal air due to heating and cooling of the heat roller 1. Since the elastic member can be elastically deformed in accordance with the contraction, it is possible to prevent the destruction of the toner intrusion prevention members 14a and 14b themselves.

The power supply circuit 15 includes a DC power supply and a control unit for controlling the DC power supply. Based on the surface temperature of the offset prevention layer 5 detected by the temperature detection unit, the resistance heating layer 2
To supply power. The sliding contacts 16a and 16b have good wear resistance with the first power supply portions 6a and 6b, and are made of a material having high conductivity, such as tough pitch copper, phosphor bronze, brass, carbon, and silver alloy. Connection lines 17a, 17
“b” is formed of a metal wire with an insulating coating. In the heat roller 1 of the present embodiment, the heat-sensitive power supply switching unit 1
8a and 18b operate based on the ambient temperature and automatically change the heating area in the resistance heating layer 2 according to the size of the paper on which the toner is fixed.
The number of heat generating regions in the resistance heat generating layer 2 can be increased without changing the configurations of the a and 16b and the connection lines 17a and 17b.

<Operation> Next, the operation of the heat roller of this embodiment will be described. First, referring to FIG.
The operation of the heat roller 1 in the case where the toner is fixed on a large-size sheet such as a portrait or A3 portrait will be described. The power supply circuit 15 supplies predetermined power to the connection lines 17a and 17
b to the sliding contacts 16a and 16b. As a result, the first power supply unit 6 can be moved from the sliding contacts 16a and 16b.
a, 6b small diameter cylindrical portions 6a2, 6b2 and large diameter cylindrical portion 6a
Electric power is supplied to the first and sixth b1 and the large-diameter cylindrical portions 6a1 and 6b1 supply electric power between both ends of the resistance heating layer 2, that is, the largest heating region of the resistance heating layer 2. As a result, Joule heat is generated on the entire surface of the resistance heating layer 2, and the Joule heat is transmitted to the entire surface of the offset prevention layer 5 via the electric insulating layer 3 and the base 4. After that, the power supply circuit 15
Power is supplied to the resistance heating layer 2 until the surface temperature of the offset prevention layer 5 reaches a predetermined temperature. Subsequently, a large-sized sheet is supplied between the heat roller 1 and the pressure roller 20, and the toner carried on the sheet is fixed. In this case, since the ambient temperature of the heat-sensitive power supply switching units 18a and 18b does not exceed the set temperature at which the heat-sensitive power supply members 11a and 11b are displaced and operated, the current path from the power supply circuit 15 to the resistance heating layer 2 is not changed.

Next, with reference to FIGS. 1 and 5, the operation of the heat roller 1 in the case where the toner is fixed on a sheet of a small size such as A4 portrait size will be described. FIG.
FIG. 2 is an explanatory diagram illustrating an operation of a heat roller in a state after a heat-sensitive power supply switching unit illustrated in FIG. 1 operates. Power supply circuit 15
Supplies a predetermined power to the sliding contacts 16a and 16b via the connection lines 17a and 17b in the same manner as in the case of fixing the toner on the large-size paper. This allows
Electric power is supplied from the sliding contacts 16a, 16b to the small-diameter cylindrical portions 6a2, 6b2 and the large-diameter cylindrical portions 6a1, 6b1 of the first power feeding portions 6a, 6b, and both ends of the resistance heating layer 2 are supplied by the large-diameter cylindrical portions 6a1, 6b1. Electric power is supplied to the space, that is, to the largest heating area of the resistance heating layer 2. As a result, the resistance heating layer 2
Joule heat is generated on the entire surface, and the Joule heat is transmitted to the entire surface of the offset prevention layer 5 via the electrical insulating layer 3 and the base 4. Thereafter, the power supply circuit 15 supplies power to the resistance heating layer 2 until the surface temperature of the offset prevention layer 5 reaches a predetermined temperature. Next, a sheet of small size is supplied between the heat roller 1 and the pressure roller 20, and the toner carried on the sheet is fixed.

Subsequently, when small-sized sheets are continuously supplied, the temperature rises in the non-sheet passing portion of the heat roller 1. The heat due to the temperature rise in the non-sheet passing portion is transmitted from the offset prevention layer 5 to the resistance heating layer 2 via the base 4 and the electric insulating layer 3, and raises the ambient temperature of the heat-sensitive power supply switching sections 18a and 18b. As a result, the thermal power supply switching unit 18a,
The heat-sensitive power supply members 11a and 11b of 18b are displaced and operated, and the heat-sensitive power supply members 11a and 11b come into contact with the second power supply portions 7a and 7b as shown in FIG. As a result, the conduction path from the power supply circuit 15 to the resistance heating layer 2 is switched to a path corresponding to a small-sized sheet, and the current from the power supply circuit 15 is, for example, as indicated by "I" in FIG.
Connecting wire 17a, sliding contact 16a, small-diameter cylindrical portion 6a2, second power supply portion 7a, thermal power supply switching portion 18a, resistance heating layer 2, thermal power supply switching portion 18b, second power supply portion 7b, small-diameter cylindrical portion 6b2, It flows in the order of the sliding contact 16b and the connection line 17b. Therefore, in the resistance heating layer 2, only the portion between the electrode members 10a and 10b of the heat-sensitive power supply switching units 18a and 18b generates Joule heat by the current. The Joule heat passes through the electrical insulating layer 3 and the base 4 and passes through the offset prevention layer 5 on the portion between the electrode members 10a and 10b.
(Shown as a "heat generation area" in FIG. 5), and the toner on the paper in contact with this portion is fixed.

As described above, the heat roller 1 of this embodiment
In the first embodiment, the heat-sensitive power supply switching units 18a and 18b are provided inside the cylindrical resistance heating layer 2, and the heating area in the resistance heating layer 2 is changed according to the size of the toner support on which the toner is fixed. For this reason, even when the number of heat generating regions in the resistance heat generating layer 2 is increased, it is possible to prevent the occurrence of hot offset due to a rise in the temperature of the non-sheet passing portion and to configure the heat roller 1 having a compact structure.

Second Embodiment FIG. 6 is a perspective view showing a configuration of a heat-sensitive power supply switching unit in a heat roller according to a second embodiment. In this embodiment, in the configuration of the heat roller, a heat-sensitive power supply member that operates in the radial direction of the heat roller is provided on the inner surface of the electrode member. The other parts are the same as those of the first embodiment, and the duplicated description thereof will be omitted. As shown in FIG. 6, the thermal power supply switching unit 18a '
Is a substantially ring-shaped electrode member 1 having a notch 10a1.
0a and the heat-sensitive power supply member 1 fixed to the inner peripheral surface of the electrode member 10a and displaced and operated in the radial direction (the direction of arrow "R" in the figure) of the heat roller 1 (FIG. 1) based on the ambient temperature.
1a '. Thermal power supply member 11a '
Are different from each other in the thermal expansion coefficient in the same manner as in the first embodiment.
It is composed of a plate-shaped bimetal made of various metals, for example, a copper alloy and amber. However, unlike the first embodiment, the amber surface having a small coefficient of thermal expansion is closer to the inner peripheral surface of the resistance heating layer 2 than the copper alloy surface.
The surface of the amber is fixed to the inner peripheral surface of the electrode member 10a. By using the heat-sensitive power supply member 11a 'that operates in the radial direction of the heat roller 1, the heat-sensitive power supply switching unit 18a' is installed inside the resistance heating layer 2 (FIG. 1) as compared with the first embodiment. The space can be reduced, and the number of heating regions in the resistance heating layer 2 can be increased without increasing the size of the heat roller 1. Also,
The heat-sensitive power supply member 11a 'is configured so that the width of the heat-sensitive power supply member 11a' is smaller than that of the electrode member 10a, and the heat-sensitive power supply member 11a 'is attached to the electrode member 10a so as not to project from the inner peripheral surface of the electrode member 10a. Deploy. With this configuration, when the heat-sensitive power supply switching unit 18a is inserted into the resistance heating layer 2, the heat-sensitive power supply member 11a 'can be installed inside the heat roller 1 without being damaged.

In the above-described first and second embodiments, a configuration has been described in which a pair of heat-sensitive power supply switching sections is provided inside the resistance heating layer, and the heating area in the resistance heating layer can be changed into two large and small areas. However, a configuration may be adopted in which a plurality of pairs of heat-sensitive power supply switching units corresponding to the size of the toner support are provided inside the resistance heating layer so that the heating area in the resistance heating layer can be further divided.
Also, the resistance heating layer provided over the entire inner surface of the heat roller has been described. In the circumferential direction of the heat roller, a resistance heating layer in which the resistance heating layer is partially removed to adjust the resistance value is used. Is also good. Also, the configuration has been described in which the resistance heating layer between the pair of thermal power supply switching units generates heat as one heating area. However, one thermal power supply switching unit is fixed to the inner peripheral surface of the resistance heating layer. A configuration in which a portion of the resistance heating layer between the switching section and one end of the resistance heating layer is used as one heating region to generate heat may be adopted. Further, although the configuration in which the resistance heating layer is provided on the inner peripheral side of the base has been described, the configuration may be such that the base is provided on the inner peripheral side of the resistance heating layer.

[0044]

As described above, in the heat roller according to the present invention, the heat-sensitive power supply switching section is provided inside the cylindrical resistance heating layer, and the resistance heating layer corresponds to the size of the toner support on which the toner is fixed. Has changed the heating area. For this reason,
Even when the number of heating regions in the resistance heating layer is increased, it is possible to prevent the occurrence of hot offset due to a rise in the temperature of the non-sheet passing portion, and to configure a heat roller having a compact structure. Furthermore, in the heat roller of the present invention, the heat-sensitive power supply switching unit operates based on the ambient temperature, and automatically changes the heat generation area in the resistance heat generation layer according to the size of the paper on which the toner is fixed. The number of heat generating regions in the resistance heat generating layer can be increased without changing the configuration of a power supply circuit or the like that supplies power to the heat generating layer.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a heat roller according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a configuration of a thermal power supply switching unit shown in FIG. 1;

FIG. 3 is a block diagram showing a configuration of an equivalent electric circuit of a resistance heating layer, a power supply circuit, and a heat-sensitive power supply switching unit shown in FIG. 1;

FIG. 4 is an explanatory view showing a method of mounting the thermal power supply switching unit shown in FIG. 1;

FIG. 5 is an explanatory diagram showing an operation of the heat roller in a state after the heat-sensitive power supply switching unit shown in FIG. 1 is operated.

FIG. 6 is a perspective view showing a configuration of a heat-sensitive power supply switching unit in a heat roller according to a second embodiment of the present invention.

FIG. 7 is a cross-sectional view showing a configuration of a conventional heat roller.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heat roller 2 Resistance heating layer 4 Substrate 6a, 6b 1st power supply part 6a1, 6b1 Large diameter cylindrical part 6a2, 6b2 Small diameter cylindrical part 7a, 7b Second power supply part 8a, 8b Support member 9a, 9b Insulator 10a, 10b Electrode member 11a, 11b, 11a 'Thermally sensitive power supply member 13a, 13b Air hole 14a, 14b Toner intrusion prevention member 15 Power supply circuit 18a, 18b, 18a' Thermally sensitive power supply switching unit

Claims (11)

[Claims] 1. A cylindrical substrate, a cylindrical resistance heating element provided on a surface of the substrate and formed with a plurality of heating areas, a power supply for supplying power to the resistance heating element, and the resistance heating element A heat-sensitive power supply switching unit that is provided inside the body and that switches a current path from a power supply to a resistance heating element based on an ambient temperature and generates resistance heating in one of a plurality of heating regions. A heat roller. 2. A cylindrical base having high thermal conductivity; a resistance heating element provided inside the base; and a heating area provided inside the resistance heating element, wherein a heating area of the resistance heating element is set in an axial direction of the base. A plurality of electrode members, a small-diameter cylindrical portion, and a large-diameter cylindrical portion provided with air holes, provided at both ends of the resistance heating element, for supplying power to the largest heating area of the resistance heating element. A first power supply unit that is connected to the first power supply unit; a toner intrusion prevention unit that is provided near the air hole and that prevents toner from entering the inside of the resistance heating element; A second power supply unit for supplying electric power from the power supply unit to each of the plurality of electrode members, one end of which is fixed to the electrode member, and the other end of which is displaced in the axial direction of the base when the ambient temperature exceeds a predetermined temperature. Second
A heat roller, comprising: a heat-sensitive power supply member that is in contact with the power supply unit and supplies electric power from the second power supply unit to the resistance heating element between the plurality of electrode members via the electrode member. 3. A large-diameter cylindrical portion is inserted into both ends of the resistance heating element, and a second power supply means is connected in the small-diameter cylindrical portion, so that the resistance of the second power supply means, the heat-sensitive power supply member, and the resistance of the electrode member are increased. The heat roller according to claim 2, wherein the total value of the values is smaller than the total value of the resistance values of the resistance heating element from the large-diameter cylindrical portion and one end to the portion where the electrode member is provided. . 4. The heat roller according to claim 2, wherein the toner intrusion prevention means has an opening smaller than the particle diameter of the toner, and is constituted by a heat-resistant filter having good air permeability. 5. The heat roller according to claim 2, wherein a toner intrusion prevention means is provided so as to close the air hole. 6. A heat roller according to claim 5, wherein said toner intrusion prevention means is provided inside a large-diameter cylindrical portion. 7. The heat roller according to claim 2, wherein said toner intrusion prevention means is made of a heat-resistant rubber elastic body. 8. The heat according to claim 2, wherein a supporting member for supporting the second power supply means and an insulator for fixing the supporting member to an inner peripheral surface of the resistance heating element are provided. roller. 9. The heat roller according to claim 2, wherein the other end of the heat-sensitive power supply member is fixed to the electrode member so as to project toward the center of the resistance heating element. 10. When the ambient temperature exceeds a predetermined temperature, the other end of the heat-sensitive power supply member is displaced in the radial direction of the heat roller and comes into contact with the second power supply means. 3. The heat roller according to 2. 11. The heat-sensitive power supply member has a width dimension smaller than that of the electrode member, and is provided on the electrode member so that the heat-sensitive power supply member does not protrude from the surface of the electrode member. Heat roller.