JPH08248791A - Heating device - Google Patents

Abstract

PURPOSE: To provide a heating device for the use of a fixing device capable of eliminating defects, such defects as taking the long time for temp. rising and consuming the much energy, in the heat roller type fixing system, and in the case of a surf type fixing system, there are the defects that only a low speed machine is available and the constitution is complicated. CONSTITUTION: This heating device 2 equipped with an endless belt 15 and permitting a paper sheet 5 to pass through in-between a pressure roller 3 arranged opposite thereto, is provided with the first frame 6, the second frame 7 disposed inside the first frame, the heater 8 arranged inside the second frame, a metal plate 14 disposed on an opening part of the paper sheet passage side of the second frame 7, and a guide roller 10 pivotally supported by a bearing member 11 fitted in parallel grooves 9 disposed on the first frame 6, while permitted for sliding. The endless belt 15 is extended over an outer periphery of the first frame 6, the metal plate 14 and the guide roller 10, and the metal plate 14 is elastically bent by the pressure roller 3 held in press contact, and thus a nip is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device provided with an endless belt and passing a sheet between the endless belt and a pressure roller arranged facing the endless belt, and more particularly, a copying machine, a printer, a facsimile and the like. The heating device used in the fixing device of the image forming apparatus.

[0002]

2. Description of the Related Art A fixing device of an image forming apparatus of an electronic process can be roughly classified into two types, a heat roller type fixing device and a surf type fixing device. Most of the fixing devices still employ the former heat roller type, but the latter surf type fixing system is rapidly becoming widespread especially in low-speed fields due to recent environmental and energy problems. Both fixing methods have the following advantages and disadvantages.

The heat roller type fixing system has an advantage that it has a large heat capacity and can handle from low speed to high speed, and has a simple structure, but it has a disadvantage that it takes a long time to heat up and consumes a large amount of energy. . On the other hand, the surf-type fixing method has the advantages that the heat capacity is small, the start-up is fast, and the energy consumption is low, but it has the drawbacks that it is limited to low-speed, popular layer image forming apparatuses, and the configuration is complicated.

In the heat roller type fixing system, a rigid metal roller is used as the heat roller, and in the surf type fixing system, the pressure roller is pressed against the heat-resistant endless film and the sheet to be fixed. Is a ceramic heater, the surface of which is a rigid body. Therefore, in any of the fixing methods, it is necessary to use an elastic roller made of silicon rubber for the pressure roller to form the nip, which inevitably results in an increase in cost. Formation of the nip N by the elastic pressure roller in the heat roller type fixing system is shown in FIG.

Further, in the heat roller type fixing system, it is already known to use the thin heat roller 20 in which the thickness t of the cored bar 20a shown in FIG. 5 is thinned in order to shorten the rising time (temperature rising time). Is. 30 is a pressure roller, and 5
Is a sheet that passes through a nip N between both rollers.

However, such a thin heat roller 20 is
Since the distance L from the cored bar 20a to the heater 21 and hence the space therebetween is large and the surface of the heat roller is open, heat loss is large. Furthermore, the wall thickness t needs to be 0.6 mm or more. For this reason, the energy consumption is large and the wall thickness does not become small, so it takes time to raise the temperature, and the desired effect is not obtained.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to propose a heating device which has the advantages of both fixing systems described above and eliminates the disadvantages.

[0008]

According to the present invention, the above-mentioned problem is solved in the heating device of the type initially mentioned, the first frame, the second frame provided inside the first frame, and the second frame. A heater disposed inside the frame, and a flexible metal plate disposed in an opening provided on the paper passage side of the second frame are provided, and the outer peripheral surface of the first frame and the outside of the metal plate are endless. It is solved by sliding the belt.

In order to solve the above problems more effectively, the present invention provides a parallel groove in the first frame, and a roller bearing member joined to an endless belt is slidably mounted in the parallel groove. It is also proposed to arrange between the bottom of the groove and the bearing member a spring which biases the roller to join the endless belt.

In order to solve the above problems more effectively, the present invention proposes that the first frame and the second frame are integrally formed of a heat resistant resin.

Further, in order to solve the above problems more effectively, the present invention proposes that at least the outer peripheral portion of the roller is made of heat resistant rubber. Further, the present invention proposes to use a heat resistant film-like sheet as the endless belt in order to more effectively solve the above problems.

Furthermore, the present invention proposes that the metal plate is attached to the opening of the second frame with a gap in order to solve the above problems more effectively. Further, in order to solve the above problems more effectively, the present invention proposes to apply a resin coating to any one or both surfaces of the metal plate and the endless belt which are in contact with each other.

Further, the present invention proposes to provide a plurality of small holes in the metal plate in order to solve the above problems more effectively. In addition, the present invention proposes that the metal plate be attached to the opening of the second frame with a gap in order to more effectively solve the above problems.

Further, in order to solve the above problems more effectively, the present invention proposes to apply a resin coating to any one or both surfaces of the metal plate and the endless belt which are in contact with each other.

[0015]

In the present invention, a flexible metal plate is provided in the opening provided on the paper passage side of the second frame in which the heater is arranged, and the outer peripheral surface of the first frame and the outer side of the metal plate are set to The endless belt is designed to slide.
Since the heater can be arranged relatively close to the metal plate, the loss of heat dissipation is small. As a result, the fixing temperature is rapidly reached, and quick start is possible. In the conventional heat roller type fixing method, the heater is always turned on, whereas in the present invention, it is not necessary. Even when the paper is not passed, the heater is turned off, and the heater is turned on only when the print signal arrives. Energy saving can be achieved because you can start up in sufficient time.

Further, although the surf-type fixing system starts up quickly, since the heat capacity of the heater portion is small, the temperature drop is remarkable for high-speed copying, and at present, it is only used for low-speed machines. It was Since the heating device of the present invention is a system in which the heater is turned on, the amount of heat generated is large and there is no temperature drop, so it can also be applied to high speed machines.

Further, in the present invention, since the nip between the metal plate and the pressure roller is formed by elastically bending the metal plate, the pressure roller can be a rigid body. The cost can be reduced. In some cases, a tubular body can be used as the pressure roller.

Further, in the present invention, since the metal plate is provided with a plurality of small holes, the heat from the heater can heat the endless belt by direct radiation, and the heat transfer rate can be increased.
It is effective for quick start.

Furthermore, since the metal plate is attached to the opening of the second frame with a gap, the metal plate absorbs deformation during assembly and thermal expansion, and is pressed against the pressure roller to form a metal. It is also possible to absorb the contraction of the metal plate in the width direction when the plate is bent.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2, the fixing device 1 is provided with a heating device 2 constructed according to the present invention and a pressure roller 3 arranged to face the heating device 2, and a sheet 5 carrying an unfixed toner image 4 is provided. It passes between the heating device 2 and the pressure roller 3 in the direction of the arrow, at which time the unfixed toner image 4 is fixed.

The heating device 2 has a first outer side which is substantially circular.
The frame 6 is a main body, and a second frame 7 having a substantially semicircular shape is provided inside the first frame 6. The first frame 6 and the second frame 7 are integrally formed of heat resistant resin in order to prevent thermal loss. The second frame 7 is open on the paper-passing side of the paper 5, and a heater 8 is arranged inside the second frame 7.

A parallel groove 9 is formed in the first frame 6 in the longitudinal direction thereof so as to extend parallel to the surface of the paper 5. The parallel groove 9 has an opening on the opposite side of the first frame 6 from the side where the paper 5 passes, that is, on the upper side in the figure, and extends inward from this opening to reach the second frame 7. There is. A bearing member 11 of a guide roller 10 is slidably inserted in the parallel groove 9. In the parallel groove 9, the bearing member 11
And a compression spring 12 is arranged between the bottom of the parallel groove 9 and
The bearing member 11 and thus the guide roller 10 are constantly provided with the habit of outward movement of the parallel groove 9.

The flange portion 13 at the open end of the second frame 7
A metal plate 14 is attached to the. The metal plate 14 can be elastically bent and has a thickness of 0.2 to 0.3 mm. Both ends of the metal plate 14 are U-shaped and engage with the flange portion 13. In that case, a gap C is particularly provided between the metal plate 14 and the flange portion 13 as shown in FIG. It is possible to absorb the deformation at the time of installation and assembly, at the time of thermal expansion, and at the time of bending of the metal plate due to pressure contact with a pressure roller described later. If there is no problem of deformation at the time of assembly or thermal expansion, it is possible to eliminate the gap C and fix the gap.

An endless belt 15 is wound around the outer periphery of the first frame 6 of the heating device 2, the guide roller 10 and the metal plate 14. For the endless belt 15, it is advantageous to use a heat resistant film-like sheet. Furthermore, the endless belt 15
Slides on the metal plate 14 at a high speed. Therefore, in order to prevent wear of both and improve slidability, either one of the surfaces of the metal plate and the endless belt which are in contact with each other, or both surfaces are coated with a resin. Is good. As a result, the life of both is improved.

The pressure roller 3 is rotatably supported by a pressure roller bearing 16, and the pressure roller bearing 16 is pushed upward by the action of a spring 17, so that the pressure roller 3 is pressed. The la 3 is in pressure contact with the metal plate 14 via the conveyed paper 5. Since the surface of the pressure roller 3 is made rigid, the metal plate 14 is pressed by the pressure roller 3 as shown in FIG.
It will elastically bend into the second frame 7. As a result, a nip N is formed between the metal plate 14 and the pressure roller 3. The bending of the metal plate 14 is caused by the above-mentioned clearance C.
It becomes easier and the pressure roller 3 is returned to the original state when the pressure contact of the pressure roller 3 is released. The size of the nip N can be easily adjusted by changing the plate thickness of the metal plate or the strength of the spring 17.

In particular, as shown in FIG. 2, the guide roller 10
Shaft 10a penetrates through the bearing hole 11a of the bearing member 11, and a gear 18 is fixed to the shaft end thereof, and is connected to a drive means (not shown) via the gear 18. Thereby, the guide roller 10 is rotated at the same peripheral speed as the conveying speed of the paper 5. The outer peripheral portion of the guide roller 10 is made of rubber to prevent slippage with the endless belt 15. As described above, when the gear 18 is rotationally driven by the driving means, the guide roller 10 is in close contact with the endless belt 15 due to the action of the compression spring 12, so the endless belt 15
Rotates at the same speed as the conveyance speed of the paper 5.

Innumerable small holes 17 are provided in the metal plate 14 'shown in FIG. These small holes 17 also allow direct heating of the endless belt 15 by radiant heat from the heater 8, increasing the heat transfer rate of the heater 8 and contributing to a quick start. The small hole 17 may be a round hole or a long hole, and a size and a shape that do not affect the fixing property can be selected.

The mode of operation of the above heating device will be described below. When the main switch or print signal is output and the heater 8 is turned on, the heater emits light. In the heating device according to the present invention, the space between the heater 8 and the metal plate 14 is narrow, and since the parts other than the metal plate 14 are made of resin, the loss of heat radiation is small and the temperature of the metal plate 14 rises rapidly. The fixing temperature is reached.

At the same time when the heater 8 is turned on, the guide roller 10
Rotates to rotate the endless belt 15 at the same speed as the conveyance speed of the paper 5. As described above, the pressure roller 3 is in pressure contact with the metal plate 14, and the nip N is formed between the metal plate 14 and the pressure roller 3, and the sheet carrying the unfixed toner image 4 thereon. 5 is guided by the endless belt 15 having the same speed and passes through the nip N. At this time, the unfixed toner image carried on the paper 5 is fixed conveniently.

[Brief description of drawings]

FIG. 1 is a fixing device showing a heating device according to the present invention in cross section.

FIG. 2 is an exploded perspective view of the fixing device in FIG.

FIG. 3 is an explanatory diagram showing nip formation by bending of a metal plate.

FIG. 4 is a perspective view showing a modified example of a metal plate.

FIG. 5 is an illustration of a conventional heat roller type fixing device.

[Explanation of symbols]

 1 Fixing Device 2 Heating Device 3 Pressurizing Roller 5 Paper 6 First Frame 7 Second Frame 8 Heater 9 Parallel Groove 10 Guide Roller 12 Compression Spring 14, 14 'Metal Plate 17 Small Hole C Clearance

Claims (8)

[Claims] 1. A heating device comprising an endless belt and a sheet passing between the endless belt and a pressure roller arranged so as to face the endless belt, wherein the first frame is provided inside the first frame. A second frame, a heater disposed inside the second frame, and a flexible metal plate disposed in an opening provided on the sheet passage side of the second frame,
The heating device, wherein the endless belt slides on the outer peripheral surface of the first frame and the outer side of the metal plate. 2. A parallel groove is provided in the first frame, a bearing member of a roller joined to the endless belt is slidably mounted in the parallel groove, and the roller is provided between the bottom of the groove and the bearing member. The heating device according to claim 1, further comprising a spring for urging the endless belt so as to bond the endless belt. 3. The heating device according to claim 1, wherein the first frame and the second frame are integrally formed of a heat resistant resin. 4. The heating device according to claim 2, wherein at least an outer peripheral portion of the roller is made of heat resistant rubber. 5. The heating device according to claim 1, wherein a heat resistant film-like sheet is used as the endless belt. 6. The heating device according to claim 1, wherein the metal plate is provided with a plurality of small holes. 7. The metal plate is attached to the opening of the second frame with a clearance.
A heating device according to one of claims 6 to 7. 8. A resin coating is applied to any one or both surfaces of the metal plate and the endless belt which are in contact with each other, and a resin coating is applied.
The heating device described in 1.