JPH05100594A - Thermal fixing device - Google Patents

Abstract

PURPOSE:To provide an inexpensive thermal fixing device which is excellent in the thermal responsiveness of a temperature fuse, whose actuation accuracy is excellent, and where abrasion scratch hardly occurs on a fixing roller. CONSTITUTION:The temperature fuse 5 is coated with a heat resistant member 8 made of a heat resistant material such as fluororesin and silicone rubber, etc., formed in a tube state, and it is arranged to contact with the surface 1a of the fixing roller 1 so that its axial direction is crossed with the axial direction of the roller 1. The fuse 5 and the roller 1 are always allowed to contact in a nearly point state even when there are a few errors at the attaching position to the frame.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing roller heated by heating means, a pressure roller pressed against the fixing roller, temperature detecting means for detecting the surface temperature of the fixing roller, and the fixing roller. A temperature fuse for preventing an excessive temperature rise, and the transfer material carrying the unfixed toner image is nipped and conveyed by the fixing roller and the pressure roller, and at that time, the unfixed toner image is fixed on the transfer material. The present invention relates to a heat fixing device.

[0002]

2. Description of the Related Art Thermal fixing devices of the above type are well known and are used in copying machines, printers, facsimiles and the like. As shown in FIG. 10, a conventional thermal fixing device of this type includes a fixing roller 51 heated by a halogen lamp 52 as a heating means, and a pressure roller 5 rotating in pressure contact with the fixing roller 51.
The transfer material carrying the unfixed toner image is nipped and conveyed by 3 and 3, and at this time, the unfixed toner image is melted and pressed to be fixed on the transfer material. The surface temperature of the fixing roller 51 is the temperature detection element 5
4, the surface temperature of which is detected by a predetermined set temperature,
For example, it is controlled by a control circuit (not shown) so as to hold it at 180 degrees Celsius.

If an abnormality occurs in the control circuit and the halogen lamp 52 is constantly lit, the temperature inside the fixing unit rises excessively, and the parts are smoked, ignited and burned.
Therefore, the temperature fuse 55 is connected in series with the halogen lamp 52 in the fixing unit, and when the temperature in the fixing unit rises to a dangerous temperature, the temperature fuse 55 is activated, that is, blown. As a result, the energization of the halogen lamp 52 is turned off, and the above burnout is prevented.

The above-mentioned conventional heat fixing device has a thermal fuse 5
5 is arranged apart from the surface of the fixing roller 51, and heat is transmitted by convective heat and radiant heat from the surface of the fixing roller. Therefore, the response tends to be delayed, and even if the surface temperature of the fixing roller 51 reaches the dangerous temperature, the temperature fuse 5
It is possible that 5 does not work. Further, the heat given to the temperature fuse 55 is heated by the convection heat and the radiant heat, and therefore has a large variation. Therefore, there is a problem that the surface temperature of the fixing roller 51 and the operating temperature of the thermal fuse 55 are not proportional.

As a means for alleviating this problem, Japanese Patent Laid-Open No. 63-169680 discloses a fixing device in which a thermal fuse is surrounded by an aluminum block and brought into contact with a fixing roller. In the fixing device, an aluminum block surrounding a thermal fuse is formed along the outer peripheral surface of the fixing roller and abutted on the fixing roller.

[0006]

The fixing device having the above-described structure has advantages that the thermal responsiveness of the thermal fuse is improved and the variation in the heat applied to the thermal fuse is reduced. However, in order to allow the aluminum block to follow the outer peripheral surface of the fixing roller, the aluminum block must be accurately curved, which increases the processing cost. further,
Since the contact area with the fixing roller is large, there is a problem that abrasion scratches easily occur.

The present invention solves the above-mentioned conventional problems,
An object of the present invention is to provide a thermal fixing device which is excellent in thermal responsiveness of a thermal fuse, has good operating accuracy, is inexpensive, and is less likely to cause abrasion damage to a fixing roller.

[0008]

The structure of the present invention for achieving the above object is as follows. (1) A fixing roller heated by a heating means, a pressure roller pressed against the fixing roller, a temperature detecting means for detecting a surface temperature of the fixing roller, and a temperature for preventing an excessive temperature rise of the fixing roller. A thermal fixing device having a fuse, wherein a transfer material carrying an unfixed toner image is nipped and conveyed by the fixing roller and a pressure roller, and the unfixed toner image is fixed to the transfer material at that time. The thermal fuse is covered with a heat resistant member and is formed into a substantially cylindrical shape, and the thermal fuse is arranged in contact with the surface of the fixing roller so that the axial direction of the thermal fuse and the axial direction of the fixing roller intersect. A heat fixing device characterized by the above.

(2) The angle at which the axis line of the thermal fuse and the axis line of the fixing roller intersect at a distance of 30 degrees to 1
The thermal fixing device as described in (1) above, which is in a range of 50 degrees.

(3) The above-mentioned (1), wherein the heat resistant member covering the thermal fuse is a fluororesin.
The heat fixing device according to.

(4) The heat fixing device as described in (1) above, wherein the heat resistant member covering the thermal fuse is silicone rubber.

(5) The thermal fixing device as described in (1) above, wherein a position of the thermal fuse, which comes into contact with the surface of the fixing roller, is a non-sheet passing portion of the fixing roller.

(6) The fixing roller heated by the heating means, the pressure roller pressed against the fixing roller, the temperature detecting means in contact with the fixing roller for detecting the surface temperature thereof, and the temperature excess of the fixing roller. A thermal fuse which has a temperature fuse for preventing rising, and which conveys the transfer material carrying the unfixed toner image between the fixing roller and the pressure roller while fixing the unfixed toner image on the transfer material. In the fixing device, the thermal fuse is attached to a supporting member that supports the temperature detecting means.

[0014]

According to the above configuration (1), since the thermal fuse contacts the surface of the fixing roller, the thermal responsiveness and operating accuracy of the thermal fuse are good, and the axial direction of the thermal fuse and the axial direction of the fixing roller are good. I arranged them so that they intersect,
Since the thermal fuse contacts the fixing roller in a state close to point contact, it is possible to prevent the fixing roller from being easily scratched.

According to the above configuration (6), since the temperature fuse is attached to the support member that supports the temperature detecting means, the temperature fuse and the fixing roller can be kept close to each other in a constant width. it can.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a cross-sectional explanatory view showing a fixing roller of a thermal fixing device according to the present invention. In FIG. 1, the fixing roller 1
A pressure roller (not shown) is brought into pressure contact with and a halogen lamp 2 as a heating means is incorporated therein. The halogen lamp 2 turns on the power supply 3 and the halogen lamp 2
Solid state relay 4 (hereinafter, SS
Call it R. ) And a control circuit having a temperature fuse 5 for preventing the temperature of the fixing roller 1 from rising excessively. The surface 1a of the fixing roller 1 is provided with a temperature detecting element 6 as a temperature detecting means so as to be in contact therewith.
SR4 is ON / OFF controlled.

As shown in FIGS. 2 and 3, the thermal fuse 5 is formed in a cylindrical shape, and is covered with a heat resistant member 8 formed in a tube shape. The heat-resistant member 8 is made of a heat-resistant material such as fluororesin or silicone rubber. Since the heat-resistant member 8 of the thermal fuse 5 covered with the heat-resistant member 8 has a tubular shape, its outer shape is also substantially cylindrical. It has become. The thermal fuse 5 is supported by a frame (not shown) and arranged so as to be pressed against the surface 1 a of the fixing roller 1. If the heat-resistant member 8 is a fluororesin tube, it is excellent in heat resistance, wear resistance, and insulation, and if it is a silicone rubber tube, it is excellent in heat resistance and insulation.

The thermal fuse 5 is disposed in contact with the surface 1a of the fixing roller 1 so that the axial direction of the thermal fuse 5 and the axial direction of the fixing roller 1 intersect. That is, as shown in FIG. 2, the axis L1 of the thermal fuse 5 and the axis L2 of the fixing roller 1 intersect at a distance, and the intersecting angle θ is approximately 90 degrees in this example. The intersection angle θ is 30 to 15 degrees
It is convenient to set it within the range of 0 degrees. If the intersecting angle θ is out of the range, the fixing roller 1 and the thermal fuse 5 are in a state of being almost in line contact with each other, and as shown in FIG. 4, one end of the thermal fuse 5 may be attached floating.

In the thermal fixing device thus constructed, even if there is some error in the mounting position of the thermal fuse 5 with respect to the frame, the thermal fuse 5 and the fixing roller 1 are always in contact with each other in a state close to a point. A large contact area can be obtained. Therefore, since the thermal fuse 5 contacts the fixing roller 1 via the heat resistant member 8, the thermal response is good and the contact area is uniform, so that the operation accuracy is good. Further, since the thermal fuse 5 and the fixing roller 1 have a small point contact and a small contact area, the surface 1a of the fixing roller 1 is less likely to be scratched. Further, the contact position of the temperature fuse 5 may be set outside the sheet passing area of the fixing roller 1 so that the fixed image is not affected even if the fixing roller 1 is damaged by the contact of the temperature fuse 5. ..

FIG. 5 shows the temperature when the halogen lamp is constantly turned on and the fixing roller is raised from room temperature, and the thermal fuses 5, 55 of the thermal fixing device of the present invention and the conventional thermal fixing device shown in FIG. 3 is a graph showing the relationship with the above, and when the thermal fuses 5 and 55 are in operation. In this graph, a is the surface temperature of the fixing roller, b is the temperature of the thermal fuse 5 of the present invention, c is the temperature of the conventional thermal fuse 55, and b ′ is c ′ when the thermal fuse 5 of the present invention is in operation. Indicates the operation of the conventional thermal fuse 55. The thermal fuses 5, 5
No. 5 used the same manufacturer and the same rating.

As is apparent from the graph of FIG. 5, when the conventional temperature fuse 55 is operating, c'is when the surface temperature of the fixing roller is 373 ° C., and when the temperature fuse 5 of the present invention is operating, b'is fixing. The surface temperature of the roller was 298 ° C. Therefore, the thermal response of the thermal fuse 5 of the present invention is
It is clear that it is superior to the conventional one.

By the way, in order to improve the thermal responsiveness and operation accuracy of the thermal fuse, the thermal fuse may be applied to the surface 1a of the fixing roller without being covered with the heat-resistant member 8 and contacting the surface 1a of the fixing roller. It would be good if they could be placed close together. However, it is difficult to arrange the thermal fuse close to the surface of the fixing roller and always dispose it with a constant creepage distance.

Therefore, the present invention also proposes a thermal fixing device in which the thermal fuse 5 can be arranged close to the surface 1a of the fixing roller 1 and can always be arranged with a constant creepage distance. FIG. 6 is a perspective view of a fixing roller showing another embodiment of the present invention, and the same members as those in FIG. 1 are designated by the same reference numerals.

In FIG. 6, the temperature detecting element 6 provided in contact with the surface 1a of the fixing roller 1 is supported by a supporting member 9. As shown in FIGS. 7 to 9, the support member 9 is formed of a substrate 12 fixed to a leaf spring 10 by an eyelet 11 and an elastic body sealed by a heat-resistant thin polyimide film 13 and bonded to the substrate 12. And the temperature detection element 6 is supported by the foamed silicone 14 on the fixing roller 1 side. Further, the supporting member 9 is attached to the frame of the fixing unit by attaching the plate spring 10 so that the temperature detecting element 6 is pressed against the surface 1a of the fixing roller 1 by the spring force of the plate spring 10.
It is held in place.

In the present invention, the thermal fuse 5 is attached to the substrate 12. According to this structure, the thermal fuse 5 can be arranged close to the surface 1a of the fixing roller 1 with a constant creepage distance. That is, even if there is an error in mounting the leaf spring 10 on the frame of the fixing unit, as long as the temperature detecting element 6 is in pressure contact with the surface 1a of the fixing roller 1, the substrate 12 of the supporting member 9 and the surface 1a of the fixing roller 1 are provided. Is a compressed width of the foamed silicone 14 and is a substantially constant distance. Since the thermal fuse 5 is attached to the substrate 12, the thermal fuse 5
Therefore, the distance d of the surface 1a of the fixing roller 1 can be made substantially constant.

Thus, the thermal fuse 5 is attached to the fixing roller 1.
Can be arranged with a constant creepage distance close to the surface 1a of the fixing roller 1, and if the distance d from the temperature fuse 5 to the surface 1a of the fixing roller 1 is set to 3 mm or less, the temperature fuse 5
The thermal response and operating accuracy of can be improved. Moreover, since the thermal fuse 5 is not brought into contact with the surface 1a of the fixing roller 1,
The surface 1a of the fixing roller 1 does not have abrasion scratches,
It is advantageous.

[0027]

According to the above construction, since the thermal fuse is arranged in contact with the surface of the fixing roller in the present invention, the thermal responsiveness and operating accuracy of the thermal fuse are improved, and moreover, the axial direction of the thermal fuse and the fixing roller are fixed. Since the thermal fuse is arranged so as to intersect with the axial direction and contacts the fixing roller in a state close to point contact with the fixing roller, it is possible to prevent abrasion damage to the fixing roller. Further, when the temperature fuse is attached to the support member that supports the temperature detecting means, the width of the temperature detecting means can be used to keep the temperature fuse and the fixing roller in a constant width in close proximity to each other.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view of a fixing roller of a heat fixing device according to the present invention.

FIG. 2 is a plan sectional view of FIG.

FIG. 3 is a side sectional view of FIG.

FIG. 4 is an explanatory diagram showing a state in which a problem occurs when the intersection angle θ is out of the range.

FIG. 5 is a graph showing the relationship between the temperature when the halogen lamp is constantly turned on and the fixing roller is raised, the relationship between the present invention and the conventional thermal fuse, and its operation.

FIG. 6 is a perspective view of a fixing roller according to another embodiment of the present invention.

FIG. 7 is a plan view showing a main part of FIG.

FIG. 8 is a front view showing the main part of FIG.

9 is a cross-sectional view showing a main part of FIG.

FIG. 10 is a cross-sectional explanatory view of a conventional heat fixing device.

[Explanation of symbols]

 1 Fixing Roller 2 Halogen Lamp 5 Thermal Fuse 6 Temperature Sensing Element 8 Heat Resistant Member 9 Supporting Member L1 Thermal Fuse Axis L2 Fusing Roller Axis θ Crossing Angle

Claims (6)

[Claims] 1. A fixing roller heated by heating means, a pressure roller pressed against the fixing roller, a temperature detecting means for detecting a surface temperature of the fixing roller, and an excessive temperature rise of the fixing roller. A thermal fixing device that has a temperature fuse and that holds the transfer material carrying the unfixed toner image between the fixing roller and the pressure roller and fixes the unfixed toner image on the transfer material. The thermal fuse is formed into a substantially cylindrical shape by being covered with a heat-resistant member, and the thermal fuse is arranged in contact with the surface of the fixing roller so that the axial direction of the thermal fuse and the axial direction of the fixing roller intersect. The heat fixing device is characterized in that 2. The angle at which the axis line of the thermal fuse and the axis line of the fixing roller intersect at a distance of 30 to 150 degrees.
The heat fixing device according to claim 1, wherein the heat fixing device is in a range of degrees. 3. The heat fixing device according to claim 1, wherein the heat resistant member covering the thermal fuse is a fluororesin. 4. The heat fixing device according to claim 1, wherein the heat resistant member covering the thermal fuse is a silicone rubber. 5. The thermal fixing device according to claim 1, wherein a position of the thermal fuse, which is in contact with the surface of the fixing roller, is a non-sheet passing portion of the fixing roller. 6. A fixing roller heated by heating means, a pressure roller pressed against the fixing roller, a temperature detecting means for contacting the surface of the fixing roller and detecting the surface temperature thereof, and a temperature excess of the fixing roller. A thermal fuse which has a temperature fuse for preventing rising, and which conveys the transfer material carrying the unfixed toner image between the fixing roller and the pressure roller while fixing the unfixed toner image on the transfer material. In the fixing device, the thermal fuse is attached to a supporting member that supports the temperature detecting means.