JPH0331973Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention consists of a rotatable heat roller, a means for heating the heat roller by applying electricity, an auxiliary roller that can rotate while holding paper in cooperation with the heat roller, and The present invention relates to a fixing device including a current cutoff element that senses high temperature and cuts off the above current flow.

Prior Art The above fixing device is mainly used in copying machines, facsimile machines, and the like. Its action is to transport the copy paper carrying an unfixed image between a heat roller and an auxiliary roller, press the copy paper appropriately, and use the heat from the heat roller to fix the unfixed image onto the copy paper. It's about doing.

The heat roller generally includes a heater inside and is heated by the heater. The heating temperature is set at a temperature that allows good fixing and does not cause any trouble to the copy paper or the heat roller itself. Normally, good fusing is performed in this state, but if some abnormality occurs and the temperature of the heat roller exceeds the set value above, the power to the heater is cut off and the heat roller is turned off. Heating must be stopped. For this purpose, a temperature fuse is provided as a current cutoff element in the power supply path to the heater, and the temperature fuse is placed near the heat roller.When the heat roller becomes abnormally high temperature, the temperature fuse melts and the current is turned on. There is a fixing device designed to cut off the

In this fixing device, as long as the quality of the temperature fuse is constant, that is, it always melts at a predetermined temperature, and the distance between the temperature fuse and the heat roller is always maintained at a predetermined length, the above-mentioned effect can be achieved. be able to achieve the objectives of the term. However, it is extremely difficult to use temperature fuses of uniform quality all the time. It is also difficult to maintain a constant distance between the temperature fuse and the heat roller in any device. For this reason, it is extremely dangerous if the temperature fuse does not blow out even if the temperature reaches a predetermined abnormally high temperature. Particularly in abnormal situations, the temperature rises rapidly, so if the timing of cutting off the power is even slightly delayed, the damage to the fixing device and the copy paper to be fixed will be very large.

Purpose In view of the above points, it is an object of the present invention to ensure the safety and reliability of a fixing device by making it possible to immediately interrupt the heating of a heat roller when an abnormally high temperature occurs.

Configuration The present invention will be explained below based on drawings showing examples thereof.

FIG. 1 is a diagram showing a first embodiment of the present invention.
In the figure, two side plates 1a and 1b that form the machine frame are each provided with one bearing 2a and 2b made of a material that changes thermally at abnormally high temperatures, such as a pylon. roller 3
is supported. General bearings 4a and 4b are provided below the thermal deformation bearings 2a and 2b, and the auxiliary roller 5 is supported by these bearings. The bearings 4a, 4b are pushed upward by springs 6a, 6b from below, so that the auxiliary roller 5 pushes the heat roller 3 with an appropriate pressure, as shown in FIG. A temperature fuse 7 as a current cutoff element is fixedly disposed at an appropriate distance from the heat roller 3 in the direction in which the auxiliary roller 5 pushes the heat roller 3. Any means for fixing the temperature fuse 7 may be used, but in any case, the distance between the temperature fuse 7 and the heat roller 3 is determined by the fixing means and the thermal deformation bearings 2a, 2b. held at a certain distance. This temperature fuse 7 is
It is placed on the power supply path 9 to the heater 8 provided inside the heat roller 3, and is fused to cut off the power supply path 9 when the ambient temperature reaches a predetermined abnormally high temperature.

In FIG. 2, copy paper 1 carrying an unfixed image
1 is guided by a guide plate 12 and sent to the contact area between the heat roller 3 and the auxiliary roller 5, that is, the so-called nip area. The copy paper thus sent to the nip section is nipped by both rollers under appropriate pressure, undergoes a fixing operation by receiving heat from the heat roller 3, and is discharged through the guide plate 13.

When the heat roller 3 reaches an abnormally high temperature due to some reason such as abnormal heating of the heater 8, the thermal deformation bearings 2a and 2b become deformable due to the heat. At this time, as described above, the heat roller 3 is biased in the direction of the temperature fuse 7 by the auxiliary roller 5, so the heat roller 3 is biased by its shaft portions 3a and 3b as shown in FIG. Approach the temperature fuse 7 while deforming the thermally deformable bearings 2a and 2b (section A).
As a result, the temperature fuse 7 accurately senses the temperature of the heat roller 3 and blows it out, and as a result, the power supply to the heater 8 is cut off and heating to the heat roller 3 is interrupted. In this way, when the temperature is abnormally high, the distance between the temperature fuse and the heat roller 3 is automatically adjusted, so even if the distance between the two is greater than necessary, we can quickly and accurately close the temperature fuse. 7 can be melted.

FIG. 4 shows a second embodiment of the invention.
In this example, the auxiliary roller 5 is placed on the upper side and the heat roller 3 is placed on the lower side. The heat roller 3 is supported by heat deformation bearings 2a, 2b, and the temperature fuse 7 is fixedly arranged, which is the same as in the first embodiment.
In this embodiment, when the heat roller 3 reaches an abnormally high temperature, the bearings 2a and 2b become thermally deformable, and as a result, the heat roller 3 descends as shown by the chain line 3' due to its own weight, and was previously placed at a lower position. Approach temperature fuse 7. As in the case of the first embodiment, the temperature fuse 7 can be appropriately blown out by this. Incidentally, if necessary, the spring 6 can be replaced as in the first embodiment.
The auxiliary roller 5 may be pressed against the heat roller 3 by a and 6b.

FIG. 5 shows a third embodiment of the invention.
In this example, the heat roller 3 and the auxiliary roller 5 are both supported by general bearings 14 and 15, so that the heat roller 3 will not move even if the temperature becomes high. Instead, in this embodiment, the pivot 1 is mounted on the machine frame 16 as shown by arrow B.
By fixing the temperature fuse 7 to the tip of a link 18 that is rotatable within the plane of the paper about 7, the temperature fuse 7 is moved relative to the heat roller 3. The temperature fuse 7 tends to move downward due to its own weight, and therefore in the direction of the heat roller 3, but a support member 19 made of a thermally deformable material of an appropriate length is sandwiched between them.
Normally, the distance between the temperature fuse 7 and the heat roller 3 is kept constant. In this example, when the heat roller 3 becomes abnormally high temperature, the support member 19 can be deformed, and the temperature fuse 7 is caused by the heat roller 3 due to its own weight.
As a result, it receives the temperature of the heat roller 3 appropriately and is fused.

Effects As described above, according to the present invention, the distance between the current cutoff element (temperature fuse 7) and the heat roller 3 is maintained constant using the thermally deformable support members 2a, 2b, and 19, and the distance between the current cutoff element (temperature fuse 7) and the heat roller 3 is maintained constant. Since either one of them is biased in advance so that they approach each other, when the heat roller becomes abnormally high temperature, the support member is thermally deformed and the gap between the current cutoff element and the heat roller is pinched, resulting in The current cutoff element immediately melts and the power supply to the heat roller is interrupted.

Unlike in the past, there is no variation in the temperature at the time of fusing due to variations in the distance between the current cutoff element and the heat roller, or variations in the product quality of the current cutoff element such as temperature fuses, thus improving safety. and reliability is improved.

[Brief explanation of the drawing]

Fig. 1 is a front view showing a first embodiment of the fixing device according to the present invention, Fig. 2 is a side view of the embodiment, and Fig. 3 is a case where the heat roller temperature becomes abnormally high in the embodiment. Figure 4 is an explanatory diagram of the second invention of the present invention.
FIG. 5 is a side view showing the main parts of the third embodiment of the present invention. 3... Heat roller, 8... Heater (heating means), 11... Paper (copy paper), 5... Auxiliary roller,
7...Temperature fuse (current cutoff element), 2a, 2
b, 19... Support member, 6a, 6b... Spring (biasing means), 18... Link (biasing means).

Claims (1)

[Scope of utility model registration request] A rotatable heat roller, a shaft portion having a smaller diameter than the heat roller and rotatably supporting the heat roller, a means inserted into the shaft portion and heating the heat roller by energization, and cooperating with the heat roller. In a fixing device that includes an auxiliary roller that can rotate while sandwiching paper, and a current cutoff element that detects an abnormally high temperature and cuts off the power supply, the heat roller and the current cutoff element are maintained at a constant interval. A fixing device comprising: a support member that supports the shaft portion and includes a material that undergoes thermal change at high temperatures; and means that biases the heat roller so that the heat roller and the current cutoff element approach each other.