JPH0531838Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to a fixing heater for an electrophotographic copying machine that heats and fixes a visible toner image attached to the surface of a transfer member.

BACKGROUND TECHNOLOGY Conventional fuser heaters for copying machines are made of, for example, a straight metal pipe with both ends open, an insulating material filled in the pipe, and a spiral nichrome wire embedded in the insulating material. A device is known that includes a heating element and a pair of metal terminals that are inserted into both ends of a pipe, and whose inner ends are connected to the ends of the heating element and whose outer ends protrude from the pipe. However, both ends of such a fixing heater have metal terminals that do not generate heat even when energized, and heat is taken away from surrounding equipment.
The temperature will be lower than the center. For this reason,
There was a problem in that the heating at both ends of the transfer member in the width direction became weaker, resulting in poor fixing at those parts. In order to solve these problems, a conventional method has been proposed in which the winding density of the heating element is increased (the pitch is reduced) at both ends, thereby increasing the amount of heat generated at both ends of the fixing heater. Ta.

Problems to be Solved by the Invention However, in such a fixing heater, the temperature of the heating element in the area with high winding density is higher than the temperature of the heating element in other areas, so wire breakage is likely to occur. There is a problem that the lifespan is shortened. Furthermore, it is difficult to manufacture a heating element with partially different winding densities, and even if it could be manufactured, it would be expensive.

Means for Solving the Problems These problems are caused by a pipe that extends in a straight line almost perpendicular to the conveying direction of the transfer body and is open at both ends, an insulating material filled in the pipe, and an insulating material. a heating element embedded in the pipe, and a pair of metal terminals that are inserted into both ends of the pipe, the inner end side is connected to the end of the heating element, and the outer end protrudes from the pipe, and the metal terminal is inserted through the metal terminal. In the fixing heater of an electrophotographic copying machine, which heats and fixes the visible toner image adhered to the surface of the transfer member by applying electricity to the heating element, the end of the pipe is folded back so that it is almost parallel to the center of the heating element. This problem can be solved by forming an overlapping portion at the end of the heater, thereby increasing the amount of heat generated at the end of the heater.

Function In this design, the end of the pipe is folded back so that it is almost parallel to the center, so the metal terminal that does not generate heat even when energized is placed closer to the center of the heater, while the heating element that generates heat is placed at the end of the heater. As a result, the temperature of the heater becomes almost uniform in all parts (particularly even at the ends). here,
Since the heater pipe extends in a straight line almost perpendicular to the transfer direction of the transfer body, if the temperature of the heater becomes uniform in each part as mentioned above,
Heating of the transfer body also becomes uniform. Furthermore, due to the above-mentioned folding of the end of the pipe, the heating element inside the pipe is also folded back and overlaps at the end, so the amount of heat generated from the end of the heater increases compared to the center.
As a result, it is possible to replenish heat absorbed from surrounding equipment and make the heating of the transfer body more uniform.
Poor fixing is effectively prevented.

Embodiment Hereinafter, an embodiment of this invention will be described based on the drawings.

In FIG. 1, reference numeral 1 denotes a fixing conveyor that is run in the direction of the arrow by a drive mechanism (not shown).
A transfer body 2 made of a plastic sheet or the like is conveyed by its running. A radiation plate 6 is installed above the fixing conveyor 1.
is made of a material with high thermal conductivity. Reference numeral 7 denotes a plurality of heaters extending in the width direction of the transfer body 2, that is, extending in a straight line almost perpendicular to the conveyance direction of the transfer body 2. They are separated by a distance. Further, as shown in FIGS. 2 and 3, these heaters 7 are attached to the lower surface of the radiant plate 6 in close contact with a plurality of fasteners 8, and as a result, the radiant plate 6 conducts heat from the heaters 7. heat is transmitted by the Each of the heaters 7 has a hollow metal pipe 11, and the pipe 11 is filled with an insulating material 12 made of magnesia or the like. Inside this insulating material 12, a heating element 13 made of a spiral nichrome wire or the like with a constant pitch is installed inside the pipe 1.
It is buried over almost the entire length of 1. pipe 1
A pair of metal terminals 14 and 15 made of a conductive material are inserted into both ends of each metal terminal 1.
The outer ends of the pipes 4 and 15 protrude from the pipe 11 and are connected to a connector (not shown). Further, the inner ends of each of the metal terminals 14 and 15 are connected to both ends of the heating element 13, respectively. As a result, when electricity is applied to the heating element 13 through the metal terminals 14 and 15, the heating element 13 generates heat, but the metal terminals 14 and 15 hardly generate any heat. In addition, the pipe 11 and the metal terminal 14,
A barrier material 16 such as silicone that blocks moisture is filled between the inner end of the cap 15 and the inner end of the cap 15 to seal the opening. As shown in FIGS. 1, 2, and 4, the ends of the pipe 11, in this embodiment both ends, are folded back 180 degrees so that they are almost parallel to the center. As a result, the heating element inside the pipe 11 13 is also folded back together with the pipe 11. Thereby, both ends of the heat generating element 13 and the center part of the heat generating element 13 form an overlapping part 21 having a length L in which they overlap in a double manner. Further, both ends of the pipe 11 surrounding the metal terminals 14 and 15 are bent at right angles to a plane including the axis of the pipe 11 (in this embodiment, bent upward), and elongated holes are formed in the radiation plate 6. 2
2 and protrudes above the radiation plate 6. As a result, the metal terminals 14 and 15 which are live parts
are shielded from the working area by the radiation plate 6 to improve safety, and the metal terminals 14, 1
Connectors, lead wires, etc. connected to the heater 7 are thermally shielded from the heater 7.

Next, the operation of one embodiment of this invention will be explained.

Now, assume that the electrophotographic copying machine is in operation and a visible toner image is attached to the surface of the transfer member 2 by transfer from the photosensitive drum. Such a transfer body 2 is then
The transfer body 2 is conveyed in the direction of the arrow by the fixing conveyor 1, and during this conveyance, the transfer body 2 is heated by heat from the heater 7 and the radiation plate 6, and the visible toner image is fixed thereon. Here, the metal terminal 14,
15 has an extremely low resistance value, so it does not generate heat even when energized, but such metal terminals 14, 1
5 is placed closer to the center of the heater 7 due to the folding, while the heating element 13 that generates heat is positioned up to both ends of the heater 7, so that the temperature of the heater 7 is almost uniform in each part (even at the ends). becomes. Here, the pipe 11 of the heater 7 is connected to the transfer body 2.
Since the transfer member 2 extends linearly substantially orthogonally to the conveyance direction, the transfer member 2 is heated uniformly.
Furthermore, as described above, since the heating elements 13 overlap each other at both ends of the heater 7, the amount of heat generated from both ends of the heater 7 increases. This replenishes the amount of heat absorbed from surrounding devices, uniformizes the heating of the transfer body 2, and prevents defective fixing. Furthermore, in this case, since it is sufficient that the heating elements 13 have the same pitch throughout, the heater 7 has a long life and the manufacturing cost is reduced.

In the above embodiment, both ends of the pipe 11 are folded back, but in this invention, only one end or the other end of the pipe 11 may be folded back. Further, in the above-mentioned embodiment, both ends of the pipe 11 are folded back once to form the double overlapping part 21, but in this invention, the pipe 11 may be folded back twice or more to form a triple or more overlapping part. Furthermore, in the above-mentioned embodiment, the case was explained in which the heater 7 was attached to the radiation plate 6 in close contact with the radiation plate 6, but in this invention, the heater 7 is installed inside a reflective shade with a substantially U-shaped cross section, and the radiant heat from the heater is transmitted to the radiation plate 6. The transfer body may be heated by reflection and dispersion using a reflective shade.

Effects of the Invention As explained above, according to this invention, the amount of heat generated at the end of the heater increases, so that heating of the transfer member is made uniform, and fixing defects can be prevented. Furthermore, since the heating elements need only be of the same pitch throughout, the life of the heater is extended and manufacturing costs are reduced.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view of the fixing structure of an electrophotographic copying machine showing one embodiment of this invention, and FIG.
A sectional view taken along the line I-I in the figure, and Figure 3 is a - of Figure 2.
FIG. 4 is a sectional view taken along the - arrow in FIG. 2. 2... Transfer body, 11... Pipe, 12... Insulating material, 13... Heating element, 14, 15... Metal terminal,
21...Overlapping part.

Claims (1)

[Scope of utility model registration request] A pipe that extends linearly substantially perpendicularly to the transfer direction of the transfer body and is open at both ends, an insulating material filled in the pipe, and a heating element embedded in the insulating material.
A pair of metal terminals are inserted into both ends of the pipe, the inner end is connected to the end of the heating element, and the outer end protrudes from the pipe, and by supplying electricity to the heating element through the metal terminal, In the fixing heater of an electrophotographic copying machine that heats and fixes the visible toner image attached to the surface of the transfer body, the end of the pipe is folded back so that it is almost parallel to the center, and the overlapping part of the heating element forms the end of the heater. A fixing heater for a copying machine, characterized in that the amount of heat generated at the end of the heater is increased by this.