JPH09197870A - Thermal fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure sufficient deflection strength corresponding to a high speed machine and to simultaneously solve failure caused by heat transfer due to securing strength in the case of miniaturizing of a diameter and thinning(making small in volume) a heat generating roller so as to shorten the rising time of the heat generating roller for set temperature and to eliminate preliminary heating at standby time in a thermal fixing device having a surface heat generating type heat generating roller. SOLUTION: The thermal fixing device 2 is composed of the heat generating roller 4, a pressure roller 6 and a pressing means 8 making the pressure roller 6 in press-contact with the heat generating roller 4 in substance. The heat generating roller 4 consists of a substrate 10, an exothermic resistor 12 formed on its surface and being as a heat source, a heat-resistant resin layer 14 forming an outermost surface and having high mold releasability and a reinforcing pipe 16. Plural vertically long ribs 10b are formed at the inner wall surface 10a of the substrate 10, and support the reinforcing pipe 16 so as to be in a heat-insulating state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used in an electrophotographic recording device such as a copying machine, a facsimile, and an electrophotographic printer, and more specifically, it is heated and melted on the surface of a recording material such as paper or film. The present invention relates to a heat fixing device that heats an image made of a volatile toner to fix it as a permanently fixed image.

[0002]

2. Description of the Related Art In an image forming apparatus of an electrophotographic system such as a copying machine or a printer, a heat fixing device for fixing a developer (toner) adhered (transferred) to a recording sheet by heating and melting is generally used. ing. A typical fixing device based on this heat fixing method is such that a pressure roller is arranged in pressure contact with a heat roller having a halogen lamp inside, and the transfer paper is conveyed to a nip portion (mutual pressure contact portion) between the heat roller and the pressure roller. The heat and pressure of the halogen lamp melts and fixes the developer on the transfer paper.

However, in such a radiant heat type fixing device, 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. , The rise time (warm-up time) becomes longer. For this reason, in order to improve the usability of promptly starting recording (copying or printing) after the operation is started, power is supplied to the halogen lamp as a heat source to generate heat even in the standby state when no recording operation is performed. It is necessary to keep the roller 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, there has been proposed a heating roller in which a heating element pattern is attached to the outer surface of a cylindrical substrate made of metal or ceramic by a method such as printing or thermal spraying. . When such a heating roller is used, heat is generated on the roller surface,
The heating efficiency is increased, and 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, and the volume can be reduced by reducing its diameter and thickness.

However, in general, in order to efficiently fix the toner on the transfer paper, a large pressure contact force of the pressure roller to the heat roller is required in order to obtain a sufficient nip between the heat roller and the pressure roller. To do. For this reason, in the heat generating roller in which the volume of the base is simply reduced by the above-described method, the deflection of the base during pressurization is large, and the mechanical strength of the heat generating roller is reduced.

As a technique aiming at preventing the deflection of such a surface heating type heating roller, there is disclosed in Japanese Patent Laid-Open No. Sho 63-63.
A "heat fixing device" described in Japanese Patent No. 249875 is known. This heat fixing device is provided with a deflection preventing roller as a so-called backup roller so that the heat generating roller is sandwiched between the pressure roller and the heating roller. It is supposed to be suppressed by. Further, Japanese Patent Application Laid-Open No. 5-188810 discloses a structure in which a synthetic resin heat generating pipe is integrally formed on the outer periphery of a metal reinforcing pipe in order to improve the strength of the heat generating roller itself.

[0007]

However, in the one disclosed in Japanese Patent Laid-Open No. 63-249875, since the heat generating roller is sandwiched between the pressure roller and the deflection preventing roller from above and below, the heat generating roller itself has a corresponding strength. If the thickness of the base of the heat generating roller is reduced to reduce its heat capacity as described above, the heat generating roller itself is destroyed by the pressure of the sandwiching between the pressure roller and the deflection preventing roller. There's a problem. For this reason, it was not possible to expect a drastic reduction in the rise time, and it was difficult to cope with high-speed machines that require sufficient strength. Further, Japanese Patent Application Laid-Open No.
In the structure described in Japanese Patent No. 8810, since the heat generating pipe is integrally formed with the metal reinforcing pipe having good heat conductivity, heat escapes to the reinforcing pipe even if the heat capacity of the heat generating roller is reduced. However, a rapid temperature rise cannot be obtained.

In Japanese Patent Laid-Open No. 4-371984, in a radiant heat type fixing device using a halogen lamp, ribs extending in the axial direction are formed on the inner wall surface of the heat roller to make the wall surface area larger than the outer peripheral surface area. Techniques for increasing heat receiving efficiency are disclosed. This technique can suggest the improvement of strength of the heat-generating roller by forming ribs in the surface heat-generating heat-generating roller which is the object of the present invention. However, by merely providing the ribs, it is possible to achieve both rapid temperature increase and strength improvement. Can not.

According to the present invention, the rise time until the heat roller reaches a predetermined temperature can be shortened, and thus desired heat generation can be obtained with low power consumption and high economical efficiency, and sufficient strength can be obtained for a high speed machine. It is an object of the present invention to provide a heat fixing device capable of dealing with the above.

[0010]

According to the present invention, the adverse effects of small diameter and thinning (reduction in volume) are covered by a reinforcing member, and heat transfer to the reinforcing member is limited as much as possible to quickly raise the temperature and increase the strength. It is based on the idea of achieving both improvement. Specifically, in the invention according to claim 1, in a heat fixing device including a hollow heat generating roller integrally having a heat source near the surface and a pressure roller arranged in pressure contact with the heat generating roller, A convex portion is formed on at least a part of the inner wall surface of the heat generating roller, and a reinforcing member is inserted in the heat generating roller with a distance from the inner wall surface being maintained by the convex portion. .

According to a second aspect of the present invention, in the structure according to the first aspect, a gap in which the convex portions are arranged in the circumferential direction of the heat roller is a nip formed between the heat roller and the pressure roller. The width is less than or equal to the width. According to a third aspect of the invention, in the configuration of the first or second aspect, the reinforcing member is formed in a coil shape. According to a fourth aspect of the present invention, in a heat fixing device provided with a hollow heat generating roller integrally having a heat source near the surface and a pressure roller arranged in pressure contact with the heat generating roller, the heat fixing device is provided inside the heat generating roller. The structure is such that a coil-shaped reinforcing member is inserted.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention (corresponding to claims 1 and 2) will be described below with reference to FIGS. As shown in FIGS. 1 and 2, the heat fixing device 2 includes a heat generating roller 4 and a pressure roller 6 provided along the axis of the heat generating roller 4.
And a biasing means 8 for pressing the pressure roller 6 against the heat roller 4.

The heating roller 4 includes a hollow substrate 10, a heating resistor 12 as a heat source formed in a planar or linear shape on the surface of the substrate 10, and a heating resistor formed on the surface of the heating resistor 12. It is composed of a heat-resistant resin layer 14 as an outer layer and a reinforcing pipe 16 as a reinforcing member inserted in the base body 10 (claim 1). On the other hand, the pressure roller 6 is composed of a cored bar 18 made of a metal round bar and a rubber layer 20 such as silicon rubber having a good releasability. Biasing means 8
, Which is simply shown in the drawing, employs a conventional pressing mechanism such as a coil spring or a leaf spring. The heat generating roller 4 and the pressure roller 6 are brought into pressure contact with each other by the pressing force F by the urging means 8, whereby a nip portion (mutual pressure contact portion) n is formed between both rollers.

As is apparent from FIG. 3, a plurality of ribs 10b as convex portions are axially formed on the inner wall surface 10a of the base body 10 at intervals in the circumferential direction.
6 is pressed into contact with the tips of these ribs 10b. Therefore, the heat insulating space 22 exists between the inner wall surface 10a of the base body 10 and the reinforcing pipe 16 except for the contact portion with the rib 10b. Further, the tip of the rib 10b is formed in a curved shape having a large curvature, and the reinforcing pipe 16 is in line contact with the rib 10b.

As the material of the substrate 10, glass, ceramics, resin, or metal such as Al or SUS can be used. However, when a metal is used, it is necessary to provide an insulating layer made of a resin material such as SiO ₂ or polyimide (PI) for electrical insulation with the heating resistor 12. The heating resistor 12 is a ceramic heating element, nichrome,
The heat generating resistance of Ta ₂ N, RuO ₂ , Ag / Pd, etc.
It can be formed on the surface of No. 0 by a method such as thermal spraying, coating, or printing. The heat-resistant resin layer 14 improves the releasability from the toner, prevents the heat-generating resistor 12 from being damaged by the contact of the heat-generating resistor 12 with other members, and also heat-generating resistor 1
It is provided for the purpose of electrically insulating 2, and Teflon or the like can be adopted. The material of the reinforcing pipe 16 may be ceramics, resin, or metal such as SUS or aluminum. Desirably, the substrate 10 has a coefficient of thermal expansion.
The one that does not change much is better.

The specific configuration of this embodiment is as follows. -Diameter D of heating roller 4 = 30 mm (Fig. 1) -Thickness of substrate 10 = 1 mm (Fig. 3) -Material of substrate 10: liquid crystal polymer-Height h of rib 10b formed on substrate 10 = 1 mm (Fig. 3) -Power supplied to the heating resistor 12: 800 W-Width L of the heating portion of the heating roller 4 = 305 mm (Fig. 1) -Set temperature of the heating roller 4: 180 ° C

Under the above structure, the heat roller 4 is driven (the pressure roller 6 is driven to rotate) and the transfer paper (not shown) having the toner image formed thereon is passed through the nip portion n. It was possible to satisfactorily fix the toner image on the transfer sheet without disturbing the toner image without causing any bending. Deflection of the heat generation roller 4 is basically caused by the reinforcement pipe 1
Although it is due to the bending strength of No. 6, the rib 10b formed on the base body 10 also functions as a reinforcing member, and this is a result of the strength function of the reinforcing pipe 16 and the rib 10b being combined.

In this embodiment, the time from when the print start switch is turned on to when the temperature of the heat generating roller 4 reaches the set temperature of 180 ° C., that is, the rising time is measured and it is 5 seconds. . Incidentally, the base 1
The case where the rib 10b was not formed in 0 (reinforcing pipe 16 only) was prepared as a comparative example, and the rise time was measured for this, and it was 12 seconds. From the above results,
By forming the rib 10b on the base 10 and holding the reinforcing pipe 16 in a heat insulating state by the rib 10b, heat transfer to the reinforcing pipe 16 can be suppressed as much as possible, and the function of the reinforcing pipe 16 is Literally, it turns out that it can be stopped only by reinforcement. Therefore, it is possible to solve the contradictory problems of the reinforcement due to the smaller diameter and thinner wall (smaller volume) of the base body 10 and the heat radiation due to the presence of the reinforcing member.

Further, the arrangement interval P of the ribs 10b in this embodiment is, as shown in FIG. 4 (a), the width N of the nip portion n.
Is set so as to satisfy the condition of P ≦ N (Claim 2). Assuming that the arrangement interval condition is P> N, FIG.
As shown in (c), the reinforcing portion (rib 10b) of the heat-generating roller 4 may not enter the nip portion n, and the pressure-contact force F deforms the thinned heat-generating roller 4 (and thus the portion of the heat-generating resistor 12). There is a concern that the surface temperature distribution may become uneven due to the change in the static resistance value.
As shown in (b), the reinforcing portion is always applied to the nip portion n, and the above-mentioned problem can be avoided.

FIG. 5 and FIG. 6 show an embodiment corresponding to claim 3. The thermal fixing device 24 shown in this example is
The heat generating roller 26, a pressure roller 6 provided along the axis of the heat generating roller 26, and urging means 8 for pressing the pressure roller 6 against the heat generating roller 4 are generally configured. . The heating roller 26 is different from the above example in that
That is, the coil spring 28 is used as the reinforcing member (claim 3). The coil spring 28 may be wound continuously by the length of the heat generating roller 26, but in this embodiment, it is shown in FIG.
As shown in FIG. 3, in consideration of the strength improvement by the ribs 10b of the base body 10, the heat-generating roller 26 is formed in an intermittent winding shape having dense portions at both end portions and the central portion to reduce the weight and efficiently use the material. Since each coil (unit loop) of the coil spring 28 is substantially in point contact with the rib 10b, a heat transfer suppressing function from the base body 10 to the coil spring 28 can be obtained as in the above example.

7 to 9 show an embodiment corresponding to the fourth aspect. The thermal fixing device 30 shown in this example is
The heat generating roller 32, a pressure roller 6 provided along the axis of the heat generating roller 32, and urging means 8 for pressing the pressure roller 6 against the heat generating roller 4 are generally configured. . The heat generating roller 32 is different from the above-mentioned examples in that the rib is not formed on the base body 34 and a continuously wound coil spring 36 is used as a reinforcing member.
When the coil spring 36 is press-fitted into the base body 34, as shown in FIG. 9, each coil linearly contacts the inner wall surface 34a of the base body 34, and a heat insulating space 38 is formed between the coils. Therefore, similarly to each of the above-described examples, a heat transfer suppressing function from the base body 34 to the coil spring 36 is obtained, and the coil spring 36 is provided.
Does not hinder the temperature rise by the heating resistor 12 and functions only as a reinforcing member. In this example, it is not necessary to form ribs on the base body 34, and the continuous winding coil spring 3
In the case of No. 6, since a commercially available coil spring can be used as it is, there is an advantage that the heating roller 32 can be manufactured easily and at low cost.

In each of the above examples, the heating resistor 12 as a heat source is formed on the surfaces of the bases 10 and 34, but the bases 10 and 34 themselves may be used as the heat source. For example, a ceramic material in which a conductive material is dispersed, a conductive fiber formed in a tubular shape, or the like. In each of the above examples, the heating roller 4, 26, 32 is driven to drive the pressure roller 6 to rotate, but the pressure roller 6 is driven to generate the heat roller 4, 26, 32.
The same fixing function can be obtained even if the drive system is driven to rotate.

[0023]

According to the first aspect of the present invention, even if the heat generating roller is made smaller in diameter and thinner (smaller in volume), the convex portion formed on the inner wall surface and the reinforcing member placed in the heat generating roller are provided. Due to the combined reinforcing effect of, it is possible to obtain sufficient flexural strength for high speed machines. Moreover, since the reinforcing member is held in a heat-insulating state by the convex portion, heat transfer to the reinforcing member is suppressed, thereby shortening the temperature rising time of the heat generating roller and preheating during standby is required. There is no.
Therefore, the power consumption of the entire image forming apparatus can be significantly reduced. Further, since it is not necessary to provide a backup roller for preventing the heat roller from bending, it is possible to downsize the configuration of the heat fixing device, and further downsize the image forming apparatus.

According to the second aspect of the present invention, since the arrangement interval of the convex portions is less than or equal to the nip width,
The reinforcing portion (convex portion) of the heat generating roller always exists in the nip portion. Therefore, even if the heating roller is made smaller in diameter and thinner in order to shorten the rising time, it is possible to obtain sufficient strength to withstand the high pressure contact force required for a high-speed machine.

According to the third aspect of the present invention, since the reinforcing member is formed in a coil shape, the contact area between the heat generating roller and the reinforcing member is further reduced, so that heat transfer from the heat generating roller to the reinforcing member is suppressed. Further, the rise time can be further shortened.

According to the invention described in claim 4, since the reinforcing member is formed in a coil shape, each coil (unit loop) does not have a convex portion formed on the inner wall surface of the heat generating roller, and each coil (unit loop) has a line on the inner wall surface. An adiabatic space is formed between the coils and the inner wall surface between the coils. Therefore, the manufacturing of the heat generating roller can be facilitated, and the function of suppressing heat transfer from the heat generating roller to the reinforcing member can be obtained without forming the convex portion.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of a heat fixing device showing an embodiment (corresponding to claims 1 and 2) of the invention.

FIG. 2 is an enlarged sectional view taken along line II-II of FIG.

FIG. 3 is an enlarged cross-sectional view of a main part of a heat generating roller.

FIG. 4 is a cross-sectional view showing the relationship between the arrangement of convex portions (ribs) and the nip width in the heat roller.

FIG. 5 is a schematic vertical sectional view showing an embodiment corresponding to claim 3;

6 is an enlarged cross-sectional view taken along line VI-VI in FIG.

FIG. 7 is a schematic vertical sectional view showing an embodiment corresponding to claim 4.

8 is an enlarged cross-sectional view taken along the line VIII-VIII in FIG.

9 is an enlarged cross-sectional view of an essential part showing a contact state between the inner wall surface of the base body and the coil spring in FIG. 7.

[Explanation of symbols]

 4,32 Heat generating roller 6 Pressure roller 10a, 34a Inner wall surface 10b Rib as a convex portion 12 Heat generating resistor as a heat source 16 Reinforcing pipe as a reinforcing member 28,36 Coil spring as a reinforcing member N Nip width P Convex portion (rib ) Arrangement interval

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Shinichi Adachi 1-3-3 Nakamagome, Ota-ku, Tokyo, Ricoh Co., Ltd. (72) Kazuto Kishi 1-3-6 Nakamagome, Ota-ku, Tokyo Issue / Stock Company Ricoh

Claims (4)

[Claims] 1. A heat fixing device comprising a hollow heat generating roller integrally having a heat source near a surface thereof, and a pressure roller arranged in pressure contact with the heat generating roller, wherein at least one inner wall surface of the heat generating roller is provided. The heat fixing device is characterized in that a convex portion is formed on the portion, and the reinforcing member is inserted in the heat generating roller with the convex portion maintaining a distance from the inner wall surface. 2. The arrangement interval of the convex portions in the circumferential direction of the heat generating roller is less than or equal to the nip width formed between the heat generating roller and the pressure roller.
The heat fixing device described. 3. The heat fixing device according to claim 1, wherein the reinforcing member is formed in a coil shape. 4. A heat fixing device comprising a hollow heat generating roller integrally having a heat source near the surface thereof, and a pressure roller arranged in pressure contact with the heat generating roller. A heat fixing device characterized by containing a reinforcing member.