KR20000030111A - Working fluid cycling structure of heat-piped image fixing heat roller - Google Patents

Abstract

PURPOSE: A working liquid circling structure of a heat roller is to reduce the energy consumed by the heat roller at the standby time. CONSTITUTION: A heat roller(10) comprises an outer roller-sided sheath(11) made of stainless steel or aluminum, an end plate(12) attached both ends of the sheath to form a sealed cavity filled with a working liquid and a vapor of the working liquid. A heater-sided sheath(13) is provided in its inside with a heater lamp(15). A space formed by the heater-sided sheath and the heater lamp is filled with a thermal greese to enhance the heat transfer. The inside of the heat roller is provided with a wick(14) and a working liquid cycling device(16) for returning the working liquid to the wick. The wick encloses the heater-sided sheath and is concentric with the heater-sided sheath about a rotating shaft(20).

Description

WORKING FLUID CYCLING STRUCTURE OF HEAT-PIPED IMAGE FIXING HEAT ROLLER}

The present invention adopts a watermill-type hydraulic fluid conveying device in a heating roller made of a heat pipe, the heating roller itself for fixing an image in a device such as a copier, a facsimile, a laser printer, or the like for recording an image on recording paper such as paper. This aims to greatly reduce the energy consumed by the heating roller during the waiting time.

Devices that form images on recording paper such as paper, such as copiers, laser printers, and facsimiles, generate static electricity on the drum to coat the toner, and then transfer the toner to a recording medium such as paper passing therethrough, and then As the toner melts, the toner is melted and fixed on the recording medium. The heating roller is in contact with the contact roller so that the recording paper, such as paper, passes between these two rollers to fix the image. The most consuming part of the electric energy in the image forming apparatus is a heating roller for fixing the image. The heating roller generally provides a heater lamp in the center of the roller in the axial direction thereof to heat the roller from the inside. By the way, the heater lamp not only is not uniform heat generated in each part, but also heat transfer occurs in each part even in the process of heat transfer, the surface temperature of the roller is different from each other according to the part. This can cause the toner to dissolve less in some areas and spread to the side when a person touches it, and in other areas, the toner melts too much and sticks to the contact roller that is in contact with the heating roller. In this way, when the toner adheres to the contact roller, a problem occurs in that the toner is buried in the shape of a band on the output recording medium and degrades the image quality. In addition, since these image forming apparatuses require preheating of the heating roller in order to operate normally, there is a disadvantage of having to wait for a considerable time even after switching the image forming apparatuses such as a copying machine.

In order to remedy this problem, efforts have been made to use heat pipes in heating rollers. Heat pipes have the advantage of being able to even the surface temperature in all areas, save energy due to the high heat transfer rate, and reduce the waiting time for operation. For example, US Pat. No. 5,426,495, 5,596,397, 3,952,798, and the like. However, as shown in FIG. 5, although U.S. Patent 5,426,495 made the entire heating roller as a heat pipe, it took up a lot of space because it was made to install the heater outside the roller body, and the heat loss of the heater lamp was practically not much. There was a disadvantage that did not help. Meanwhile, US Patent 5,596, 397 adopts a method of inserting a plurality of heat pipes into the body of the roller as shown in FIG. This method has the advantage of better thermal efficiency and smaller size than US Patent 5,426,495. However, in order to achieve full isothermal at the surface of the roller, several heat pipes must be installed, and the thickness of the heating roller is too thick to mount the heat pipe. In addition, materials such as aluminum suitable for this structure have the disadvantage that the heat capacity is large and consequently a very large heat capacity. This greatly increases the preheating time and makes it difficult to control the temperature in detail. This is because a small amount of heat must be supplied even if a small temperature difference is corrected. Moreover, there also exists a problem of temperature nonuniformity at the beginning of a heating. For example, when four heat pipes are mounted, heat transfer in the axial direction of the heat roller is very rapid due to the nature of the heat pipe, while heat is transferred only by the heat conduction of the roller body back to the middle region between the four heat pipes. As a result, a temperature nonuniformity may occur in part in the axial direction. Particularly in the short period of time when power is supplied to the image forming apparatus, this disadvantage is inevitable. In addition, U.S. Patent 3,952,798, such as FIG. 6, takes advantage of heat pipes, but has an excessively complex structure, high manufacturing costs, and a limitation in that an excellent heating element such as a halogen lamp cannot be used. Proposed to improve this disadvantage is the application number 10-1999-0055037 of FIG. 7 has the advantage of excellent heat transfer efficiency and simplified overall structure, but because heat is transferred through the partition wall connecting the central axis and the outer wall For example, a copier or a laser printer has a power switch, but it has a disadvantage in that the heater roller easily loses heat during standby time without using it.

The present invention improves these problems with the conventional method, while heating to the required temperature in a short time, while maintaining an even temperature on the surface of the heating roller, reducing the energy required for initial heating and maintaining the proper temperature, while at the same time Edo aims to create a structure that does not lose much heat.

1 is a conceptual diagram of a working fluid circulation structure of a heating roller for fixing an image using a heat pipe.

2 is a longitudinal cross-sectional view thereof,

3 is its cross section.

4 is a conceptual diagram of the technology used in US Patent 5,596,397

5 is a conceptual diagram of the technology used in US Pat. No. 5,426,495.

6 is a conceptual diagram of the technology used in US Patent 3,952,798,

7 is a conceptual diagram of the technique used in the application No. 10-1999-0055037.

* Explanation of symbols for main parts of the drawings

DESCRIPTION OF SYMBOLS 11: Outer-contact outer side of a heating roller. 12: Both finishing boards. 13: Outer-side of a heating lamp. 14: Wick 15: Heater lamp. 16: Watermill-type fluid conveying apparatus. Cold internal space 18: Temperature sensor 19: Temperature control device 20: Rotating shaft 31: Closer roller side shell of heating roller 32: Heater lamp side outer shell of heating roller 33: Wick 34: Bulkhead

2 shows a cross section of the present invention. In the heating roller according to the present invention, the outer cylindrical adhesive roller-side outer shell 11 made of thin stainless steel or aluminum and the heater-side outer shell 13 surrounding the heater are concentric about the rotating shaft 20 of the heating roller. The left and right sides of these envelopes are attached with a closing plate 12 to form a completely enclosed interior space filled only with the working liquid and the vapor of the working liquid. The finishing plates are welded to the two shells 11 and 13 with no gaps. The heater lamp 15 which heats a heating roller is inserted in the inner space (the side with a rotation center axis | shaft) of 13 outer skins. The free space created by the heater lamps and the jacket of 13 can also be filled with thermal grease (grease with excellent heat transfer performance) to promote heat transfer. The inner space of the heating roller is filled with a wick (14, also known as a wick), a water mill-type hydraulic fluid delivery device (16) consisting of 8-12 pieces, and a vapor of the hydraulic fluid and the hydraulic fluid. The wick 14 wraps the envelope 13 from the inside, as shown in FIG. This wick is concentric with the shell 13 with the axis of rotation 20 as the axis.

The working principle of the heating roller having such a structure will now be described in detail. When the switch is turned on for the operation of an image forming apparatus such as a copying machine or the like, the heater lamp 15 starts to be heated while being supplied with power, and at the same time, the heating roller starts to rotate in the rotational direction shown in FIG. The heater lamp 15 supplies heat to the heater lamp side shell 13. In this case, the space between the heater lamp 15 and the heater lamp side shell 13 may be filled with a thermal grease or the like to increase the heat transfer speed in order to increase the heat transfer efficiency. The heat supplied to the heater lamp side shell 13 heats the wick 14 surrounding the shell, which is moistened with the working fluid. Therefore, the working liquid is evaporated, the vapor of the evaporated working liquid is quickly spread out, the heat is taken away from the contact roller side shell 11 of the roller and condensed. The condensed hydraulic fluid is operated when the heating roller is rotating, while the watermill type fluid transfer device 16 collects the condensed hydraulic fluid as the roller rotates and is inclined backwards, as shown in FIG. Pour the liquid into the wick (14). The working fluid returned to the wick 14 is evaporated again to transfer heat due to the heat received from the heater lamp 15, and condensed back to the wick 14 through the watermill-type working fluid transfer device 16. In this way, a closed circulation cycle of heat transfer is formed inside the heater roller. This heat transfer method is a so-called 'heat pipe' method. This is based on the thermodynamic equilibrium theory that the vapor filling the confined space is almost completely at a constant pressure, and therefore its evaporation and condensation temperatures are constant at any point. (12) Due to the material's thermal conductivity limit, it operates with a temperature difference of less than about 1 degree as a whole. This temperature difference is very small, and it can be said that it operates while maintaining a constant temperature. Theoretically, it can be seen that the most ideal heating roller is implemented. In addition, the heat pipe method has an advantage that heat transfer speed is 100 to 1,000 times faster than heat transfer by conduction or convection. Therefore, the time to reach the target temperature is very short. In addition, it is necessary to make the overall configuration so that the heat capacity is small in order to reduce the target temperature reaching time to a minimum. It is necessary to use a material such as stainless steel with low heat capacity and sufficient rigidity, or to maintain an optimal size. The heating roller according to the present invention does not require an unnecessary extra heating roller length because the temperature is constant in all parts, and may be adapted to the size of the recording paper using the size of the heating roller. Therefore, the heat capacity can be designed smaller than any other method. For example, the aforementioned U.S. Patent 5,426,495 or U.S. Patent 5,596,397 have a fairly large margin and have a large heat capacity and a lot of space.

In addition, unlike the application No. 10-1990-0055037, the working fluid transfer device 16 according to the present invention does not use the partition wall 34, so that the rotation of the roller is stopped because a device such as a copier or a laser printer is in a standby state. Even in this state, heat loss through the partition does not occur. In the standby state, the inside of the roller is filled with the working liquid on the bottom surface and only the vapor of the working liquid in the empty space, so that the heat on the wick 14 side is hardly transferred to the outer shell 11. If there is a partition 34, heat is conducted and transferred through the partition 34, but since they are separated from each other by steam, heat loss is inevitably small due to the nature of the gas, which is much slower in heat transfer. In addition, when only the minimum working fluid required to achieve the heat transfer rate required by the system is injected, the roller is almost vacuum thermos because the interior of the roller remains close to vacuum. Therefore, heat loss in the standby state is minimized. Similar experiments with heat pipes in cookware have shown that the heat loss is reduced to a quarter.

When the heating roller reaches a constant temperature, the temperature sensor 18 detects the temperature. Since heat pipes have a constant temperature of less than 1 degree on all surfaces, it is sufficient to sense the temperature in only one place, simplifying the control and reducing the number of parts. The temperature sensor sends a signal to the temperature controller 19 to perform 'on-off' control to maintain an appropriate temperature. Since the heat capacity of the entire roller is much smaller than in the case of the aforementioned U.S. patents, the time required for heating is reduced and thus precise temperature control is possible.

On the other hand, when the working liquid is operated near the optimum temperature (about 180 degrees) at which the heating roller operates, the heating roller operates near 1 atm, thereby preventing the internal pressure from rising excessively. On the other hand, a solution suitable for these conditions is preferable because the working liquid transfers heat only when the latent heat of evaporation is large. In addition, the suction function by the wick should be good to shorten the circulation cycle, for this purpose, the surface tension is good.

Due to these various features, the working fluid circulation structure of the heat pipe type image fixing heating roller according to the present invention has an effect of significantly reducing energy than the heat roller type image fixing heating roller.

Heat rollers for image fixing using heat pipes make the heating roller itself a heat pipe structure, so heat transfer is fast, greatly reducing the waiting time, the temperature is constant on the surface of all heating rollers, greatly reducing the energy required for heating, In addition, by reducing the size of the heating roller and the overall heat capacity, it is possible to make an image forming apparatus that is energized, and it is easy to precisely control the temperature and minimize the heat loss in the waiting time.

Claims (2)

A heating roller of a fixing apparatus for fixing an image onto a recording sheet, the heating roller being integrated with a heat pipe in the following manner. A) The cylindrical outer shell 11 on the contact roller side made of a thin metal material in contact with the contact roller and the cylindrical outer shell 13 on the heater side surrounding the heater 15 provided on the rotating shaft are centered on the rotating shaft of the heating roller. Are concentric, and at the same time B) At both ends of these shells a closing plate 12 is attached to form an enclosed interior space 17 filled with the working liquid and the vapor of the working liquid. C) The wick 14 surrounds the heater-side cylindrical shell 13 in the sealed space 17, and at the same time D) Inside the heater-side cylindrical shell 13, a watermill type fluid transfer device 16 is isolated from the wick 14 on the central axis so that the fluid is wicked by gravity when the heating roller rotates. 14) heating roller to feed. An image forming apparatus such as a copying machine for fixing an image on a recording sheet having a heat pipe integrated heating roller as follows. A) The cylindrical outer shell 11 on the contact roller side made of a thin metal material in contact with the contact roller and the cylindrical outer shell 13 on the heater side surrounding the heater 15 provided on the rotating shaft are centered on the rotating shaft of the heating roller. Are concentric, and at the same time B) At both ends of these shells a closing plate 12 is attached to form an enclosed interior space 17 filled with the working liquid and the vapor of the working liquid. C) The wick 14 surrounds the heater-side cylindrical shell 13 in the sealed space 17, and at the same time D) Inside the heater-side cylindrical shell 13, a watermill type fluid transfer device 16 is isolated from the wick 14 on the central axis so that the fluid is wicked by gravity when the heating roller rotates. 14) heating roller to feed.