JPH09197871A - Surface heat generating roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize and thin (make small in volume) a substrate at a surface heat generating roller, to simultaneously improve rupture strength, to shorten rising time for set temperature and to reduce the power consumption of an entire image forming device by unnecessitating preliminary heating. SOLUTION: A fixing device 2 is provided with the surface heat generating roller 4 having a cylindrical substrate 10 where an exothermic resistor 12 and a mold-released layer which is not shown in figure are formed on a surface, a pressure roller 6 arranged to be in press-contact and pressing means 8 and 8 as press-contacting force sources, and the end part of the surface heat generating roller 4 is rotatably supported by a bearing member 14. A reinforced area 16 whose thickness is larger than that at the inside of a paper-passing area and where the width of a thick part in the direction of a roller shaft is wider than the thickness at the inside of the paper-passing area is formed at a part other than the range of the paperpassing area at the substrate 10.

Description

Detailed Description of the Invention TECHNICAL FIELD OF THE INVENTION

The present invention mainly relates to a fixing device, and more particularly to a heating roller of a toner fixing device used in an image forming apparatus such as a copying machine, facsimile machine, electrophotographic printer and the like.

[0002]

2. Description of the Related Art Generally, an electrophotographic image forming apparatus such as a copying machine or a printer adopts a heating roller fixing method in which a developer (toner) adhered (transferred) to a recording sheet is heated and melted to perform fixing. Has been done. The typical configuration of this heating roller fixing system is that a pressure roller is arranged in pressure contact with a heating roller equipped with a halogen lamp inside, and the transfer paper is conveyed to the nip portion (mutual pressure contact portion) between the heating roller and the pressure roller. The heat of the halogen lamp and the pressure between the rollers melt and fix the developer on the transfer paper.

However, in such a so-called radiant heat type heating structure, since the heating efficiency (heat conduction characteristic) is low,
It takes several minutes for the heating roller to heat up to the temperature required for melting the developer, and the rising time (warm-up time) becomes long. For this reason, in order to realize comfortable operability or usability such as prompt start of recording (copying or printing) after the start of operation, even if the recording operation is not performed, the halogen lamp as a heat source is powered by electricity. Must be supplied and the heating roller must be kept at a constant temperature at all times. However, in such a system in which the power is constantly supplied to the heat source, the standby power consumption occupies a large proportion of the power consumption of the entire image forming apparatus, which hinders reduction of the power consumption of the image forming apparatus.

Therefore, for the purpose of solving such a problem, it may be called a self-heating type in which a heating element pattern is attached to the outer surface of a cylindrical substrate made of metal or ceramic by printing or thermal spraying. Surface heating rollers have been proposed. When such a surface heating roller is used, heat is generated on the roller surface, so that the heating efficiency is increased,
The rise time can be greatly shortened. However, even in such a heat generating roller, in order to avoid power supply during the standby time, it is necessary to speed up the rising thereof, and for that purpose, it is known that reducing the heat capacity of the substrate is effective. Has been. The heat capacity of the substrate can be reduced by reducing its volume.
In order to reduce the volume, the diameter may be reduced and the thickness may be reduced.

[0005]

However, in general, in order to fix the toner efficiently and reliably on the transfer paper, in order to obtain a sufficient nip between the surface heating roller and the pressure roller, the surface heating roller is provided. A large pressure contact force of the pressure roller with respect to is required. For this reason, in the surface heating roller in which the volume of the substrate is simply reduced by the above-described method, the mechanical strength is low, and the strain or bending of the substrate at the time of pressurization or the accompanying breakdown is likely to occur. Therefore, in the conventional surface heating roller, although it is known that the rise time to the set temperature can be shortened, it is not possible to reduce the diameter and the wall thickness (reduce the volume) in consideration of the destruction phenomenon. The rise time has not been significantly shortened.

The present invention provides a surface heating roller which can reduce the power consumption of the entire image forming apparatus without the need for preheating and has a large breaking strength.
With that purpose.

[0007]

According to the present inventors' consideration of the cause of destruction, as shown in FIG. 8, a pressing roller 52 and a biasing means 53 are applied to a conventional simple cylindrical base model 50. When a load is applied through (when fixing operation),
As shown in (b), the strain at the opening end portion becomes maximum in relation to the bearing portion 54 as compared with the central portion. (A) shows the state when there is no load. With glass or ceramics used from a practical point of view as the material of the substrate, chipping is likely to occur at the end portion in the manufacturing process due to its material characteristics or handling characteristics, but as shown in FIG. If there are chippings 56 such as the one shown in FIG.
Tends to occur. From the above, it can be concluded that when the substrate 50 is made of glass or ceramic, breakage is likely to occur.

Based on the above consideration, it is the gist of the present invention to effectively reinforce only the end portion of the base body and, under such backing, to sufficiently reduce the volume so as to significantly shorten the rising time. is there. Specifically, in the invention according to claim 1, in a portion outside the range of the paper passing area on at least one end side of the base body, the thickness is formed to be thicker than the thickness in the paper passing area of the base body, and Reinforcing area (for example, ring-shaped) whose width in the roller axial direction is formed wider than the wall thickness in the paper passing area
Is adopted.

According to a second aspect of the present invention, in the structure according to the first aspect, the reinforcement region has a width extending inward in the axial direction from the terminal end of the base body in order to facilitate manufacture. There is. According to a third aspect of the present invention, in the structure according to the first or second aspect, a reinforcing region is combined with a base member that is a separate body from the base member in order to facilitate manufacturing and uniformize product accuracy. It has a structure of forming. According to a fourth aspect of the invention, in the structure of the third aspect, at least a part of the reinforcing member is formed of the same or the same material as the substrate in order to suppress the strain during heating due to the difference in the coefficient of thermal expansion. Is adopted. In the invention of claim 5, claim 1 or 2 or 3
Or in the configuration described in 4, in order to efficiently perform the reinforcement,
At least a part of the reinforced region is in a position where the reinforced region and the bearing portion supporting the roller are overlapped with each other.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention (application example to a toner fixing device) will be described below with reference to FIGS. The toner fixing device 2 includes a surface heating roller 4 and the surface heating roller 4.
The pressure roller 6 is arranged to face the surface heating roller 4 by urging means 8 such as a spring. Fixing is performed by passing a material to be heated having a toner image between the surface heating roller 4 and the pressure roller 6. Surface heating roller 4
Is composed of a cylindrical substrate 10 that is longer than the maximum paper passing area W, a heating resistor 12 formed on the surface of the substrate 10, and a release layer on the outermost surface (not shown). A portion (end portion) outside the range of the paper region W is rotatably supported by the bearing members 14, 14.

The base 10 is made of a metal such as aluminum (Al), iron (Fe), or an alloy thereof, and a ceramic layer, a heat-resistant polymer layer, an insulating layer such as an oxide film such as alumite, or ceramic. Insulators such as glass and heat-resistant plastic. Heating resistor 12
Is a ceramic heating element, nichrome, Ta ₂ N, RuO
₂ , spraying a heating resistor such as Ag / Pd on the surface of the substrate 10,
It is formed in a planar shape or a linear shape by a method such as coating or printing. When the heating resistor 12 is energized, the surface heating roller 4 generates heat. It is also possible to use a heating resistor as it is as the substrate 10 such as by forming the heating ceramics in a cylindrical shape, and generate heat by energizing. The release layer not shown is PFA, PTF
It is formed of a material such as A.

The maximum paper passing area W at both ends of the substrate 10
A reinforcing region 16 is formed in a portion outside the range of (1) in correspondence with the position of the bearing member 14 as a reinforcing portion. As is clear from FIG. 2, the reinforcing region 16 has a wall thickness t ₂ larger than the wall thickness t ₁ in the maximum paper passing region W and a width L wider than the wall thickness t _1. It is integrally molded in a ring shape (claim 1). Further, in this embodiment, the width L of the reinforcing region 16 is set to be slightly wider than the width G of the bearing member 14.

Under the above construction, a model of a fixing device for A3 recording paper as shown below was prepared, and a large load was applied to measure the breaking strength of the substrate 10. -Material of the base 10: Pyrex glass-Outer diameter D of the base 10: 30 mm-Thickness t _{1 of the} base 10: 0.5 mm-Maximum paper passing area W: 305 mm-Distance M between the bearing members 14: 330 mm-Reinforcing area Thickness t _{2 of} 16: 10 mm The reinforcing region 16 was formed by inserting another component formed in a ring shape into the pipe by post-processing. For comparison, the breaking strength of a glass pipe having a uniform thickness over the entire region (other conditions are the same as above) was also measured. As a result, the loads where more than half of the samples remained without being broken are as follows. -Without reinforced area: 55 kgf-With reinforced area: 75 kgf These experimental facts show that the breaking strength of the substrate 10 according to the present invention is improved by about 50%. From the direction in which the glass cracks, the observation by high-speed camera photography, etc., the breakdown of the substrate often occurs from the end of the cylinder. The strength of the base 10 itself can be improved.

FIG. 3 shows the reinforced region 16 shown in the above embodiment.
This shows a modification of the first embodiment. (A) shows the case where the reinforcement region 16 is integrally formed on the outside of the base body 10, (b) shows the case where the reinforcement region 16 is formed integrally on the inside and outside of the base body 10, and (c) shows the reinforcement region 16. As a wall,
When the rigidity in the cylinder collapse direction is increased, (d) shows that when the reinforcing region 16 is partially formed under the heating resistor 12,
(E) shows (f) when the reinforcing region 16 is tapered.
Shows a case where the reinforcing region 16 has a stiff rod-like auxiliary piece 16a due to the deformation of (c). In the case of the taper (e), the wall thickness changes little by little, but the stress is not locally concentrated and the strain amount of the substrate 10 becomes uniform in the vicinity of the center of the surface heating roller 4 and on the outside. Thus, it is preferable that the thickness increases toward the end. Auxiliary piece 1
In the case of (f) having 6a, it is not necessary to have a uniform wall thickness in the circumferential direction of the wall thickness region as in the above embodiment.

FIG. 4 shows the reinforced region 16 shown in the above embodiment.
The modified example (corresponding to claim 2) of the above is shown, which is located at the end of the base body 10. (A) shows the case where it is formed in a ring shape, and (b) shows the case where it is formed as a closed wall. In the case of (b), the rigidity against strain is increased.

FIG. 5 shows a modification of the reinforcing region 16 (claim 3).
In contrast to the case where the above-described respective embodiments are integrally molded with the base body 10, the reinforcing member formed as a separate component is formed in combination with the base body 10. (A) shows a case where the ring-shaped reinforcing member 18 is installed inside the base body 10, and (b) shows a ring-shaped reinforcing member 20.
Is installed outside the substrate 10, (c) is closed by the disc-shaped reinforcing member 22, and (d) is the auxiliary piece 24a.
When it is closed by a disc-shaped reinforcing member 22 having
When the ring-shaped reinforcing member 26 having a step is butted against the end of the base 10 and a part thereof is projected outward,
(F) shows a case where a ring-shaped reinforcing member 28 having steps of different diameters on both sides is butted against the end of the base 10 and a part thereof is projected outward.

These reinforcing members include metals such as iron (Fe), aluminum (Al) and copper (Cu) and alloys thereof, or heat resistant resins such as phenol, polyimide and liquid crystal polymer, or ceramics and glass. However, in order to prevent destruction due to a difference in thermal expansion coefficient, it is desirable that the thermal expansion coefficient is substantially the same as that of the base 10. If the material of the base body 10 is glass, it is necessary to melt the end portions in order to integrally form the reinforcing region 16, which makes it difficult to perform the processing at this time, and the cost also increases. On the other hand, when it is formed as a separate component, there is a merit that the reinforcing region 16 can be formed accurately and inexpensively.

FIG. 6 shows a modification of the reinforced region 16 (corresponding to claim 4). The reinforcing member 30 includes a ring-shaped main body portion 32 having a step and a ring-shaped auxiliary portion 34 made of a material different from that of the ring-shaped main body portion 32, and is butt-assembled with the end portion of the base body 10. The main body 32 is
In order to prevent breakage due to a difference in thermal expansion coefficient, it is formed of the same or the same material as the substrate 10, and it is desirable to use an adhesive having substantially the same thermal expansion coefficient for bonding. Here, an example in which a part of the reinforcing member 30 has the same or the same material as the base body 10 is shown, but it goes without saying that the entire reinforcing member 30 may be made of the same or the same material as the base body 10. By the way, the substrate of the surface heating roller may reach a temperature of about 200 degrees when fixing the toner. Linear expansion coefficient of the material is approximately glass 3.0 [10- ⁶ / d
eg], about 90 [10- ⁶ / de Examples of the heat-resistant resin
g] etc., and with these materials, the size of φ30 is 200
When a temperature rise occurs, the change in diameter is about 0.02 mm for glass and the change for heat resistant resin is 0.54 mm.
As described above, when the coefficient of thermal expansion of the base material and the material of the reinforcing member are significantly different, the base is destroyed. Therefore, by making the material of the reinforcing member the same as or the same as the material of the substrate (including a part), it is possible to prevent damage due to a difference in linear expansion coefficient.

FIG. 7 shows a modification of the reinforcing region 16 (claim 5).
The present invention is characterized in that the reinforced region 16 and the bearing member 14 are in a position where they overlap each other. (A)
When the bearing member 14 completely enters the reinforcing region 16 formed by the ring-shaped reinforcing member 36 having steps,
In (b), when the bearing member 14 partially overlaps the reinforcing region 16 formed by the ring-shaped reinforcing member 38 having steps, (c) is formed by the ring-shaped reinforcing member 40 having steps. When the bearing member 14 is completely inserted into the reinforced region 16 at the end of the base body 10, (d) shows the base body 10.
The case where the bearing member 14 is overlapped on the ring-shaped reinforcing member 42 installed on the outer side of FIG.

The reinforcing region 16 is formed at a position where it does not overlap with the bearing member 14, and as in the first embodiment, the following A3 is used.
A model of a fixing device for recording paper was prepared, and a large load was applied to measure the breaking strength of the substrate 10. -Material of the base 10: Pyrex glass-Outer diameter D of the base 10: 30 mm-Thickness t _{1 of the} base 10: 0.5 mm-Maximum paper passing area W: 305 mm-Distance M between the bearing members 14: 330 mm-Reinforcing area The thickness t _{2 of} 16: 10 mm As a result, the loads where more than half of the samples remained without being broken are as follows. -Reinforcement region does not overlap with the bearing member: 62 kgf-Reinforcement region overlaps with the bearing member: 75 kgf According to this experimental fact, the structure in which the reinforcement region 16 overlaps with the bearing member 14 improves the breaking strength of the base body 10. I understand.

Since a glass substrate can have a smaller heat capacity than a metal substrate, it has great practical utility in that the temperature rising time is fast and the cost is very low, but it is problematic in strength. There is. In order to obtain a desired temperature rising time by setting the substrate material to be glass and the paper passing size to be A3, the thickness of the glass needs to be 1 mm or less. In the case of the reinforcing structure according to the present invention, the strength of the substrate made of brittle material such as ceramics, particularly glass, is improved, so that it is possible to realize a glass substrate having a wall thickness of 1 mm or less that can withstand the actual fixing operation.

[0022]

As described above, according to the first aspect of the present invention, since the reinforcing region is provided at the end portion of the substrate outside the range of the sheet passing area, the end portion that is apt to start the occurrence of breakage. It is possible to prevent the maximum strain from appearing and improve the breaking strength. Further, by doing so, it is possible to reduce the volume in the paper passing area, shorten the rise time to the set temperature, and eventually reduce the power consumption of the entire image forming apparatus by eliminating the need for preheating. .

According to the second aspect of the invention, since the reinforcing region is provided at the outermost end of the substrate, the reinforcing region can be easily manufactured and processed, and a cheaper energy-saving fixing device can be realized. it can.

According to the third aspect of the present invention, since the reinforcing region is formed by combining the reinforcing members as separate parts, the reinforcing region can be formed in various shapes easily and accurately. In addition, it is possible to reduce the manufacturing cost and suppress variations in accuracy among products.

According to the invention described in claim 4, since at least a part of the reinforcing member is made of the same or the same material as the substrate, it is possible to prevent the destruction due to the difference in the coefficient of thermal expansion during heat generation. . As a result, it is possible to improve the durability and reliability of the surface heating roller.

According to the fifth aspect of the present invention, at least a part of the reinforced region overlaps with the bearing member in position, so that the surface heating roller receives a load at a high strength part, and is thus destroyed. The strength has been improved, making it possible to support high-speed machines.

[Brief description of drawings]

FIG. 1 is a schematic vertical cross-sectional view of a usage state of a fixing device according to an embodiment of the present invention.

FIG. 2 is a perspective view of a main part of a base body.

FIG. 3 is a cross-sectional perspective view showing a modified example of the reinforcing region corresponding to claim 1.

FIG. 4 is a cross-sectional perspective view showing a modified example of the reinforcing region corresponding to claim 2;

FIG. 5 is a cross-sectional perspective view showing a modified example of the reinforcing region corresponding to claim 3;

FIG. 6 is a sectional perspective view showing a modified example of the reinforcing region corresponding to claim 4;

FIG. 7 is a cross-sectional perspective view showing a modified example of the reinforcing region corresponding to claim 5;

FIG. 8 is a schematic cross-sectional view showing strain at the time of pressurization by a conventional model.

FIG. 9 is a diagram showing a state in which cracking occurs when the substrate has chipping.

[Explanation of symbols]

10 Base 14 Bearing Member 16 Reinforcing Area 18, 20, 22, 24, 26, 28, 30, 38, 4
0,42 Reinforcement member t ₁ Thickness in the paper passing area

Front page continuation (72) Inventor Shinichi Adachi 1-3-6 Nakamagome, Ota-ku, Tokyo, stock company Ricoh (72) Inventor Yumiko Suzuki 1-3-6 Nakamagome, Ota-ku, Tokyo stock company In Ricoh

Claims (5)

[Claims] 1. A hollow surface heating roller having a cylindrical base body formed to have a length wider than the paper passing area, and integrally having a heat source within the entire thickness including the base body, wherein at least the base body is provided. A portion outside the paper passing area on one end side is formed to be thicker than the wall thickness in the paper passing area of the base body, and the width in the roller axial direction of the thick portion is formed to be wider than the wall thickness in the paper passing area. A surface heating roller having a reinforced region. 2. The surface heating roller according to claim 1, wherein the reinforcing region has a width extending inward in the axial direction from the end of the base body. 3. The surface heating roller according to claim 1, wherein the reinforcing region is formed by combining a reinforcing member separate from the base and the base. 4. The surface heating roller according to claim 3, wherein at least a part of the reinforcing member is made of the same or the same material as the base material. 5. The surface heating roller according to claim 1, wherein at least a part of the reinforcing region overlaps with a bearing portion that supports the roller.