JPH0962140A - Abnormal temperature rising prevention device for fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To forcedly interrupt energizing of a heating roll when the temperature of the heating roll arranged in a fixing device rises to an abnormal temperature. SOLUTION: The heating roll 10 arranged in the fixing device is rotated in the direction of the arrow R, and a heating lamp 12 is disposed at the inside of the roll 10. The heating lamp 12 is connected to a controller 30 through circuits L1 and L2 , and is electrically heated. A bimetal 40 is attached on the outer peripheral surface of the heating roll 10 by a fixing part 42 and a switch 50 is provided opposed to the bimetal 40. When the temperature of the heating roll 10 rises to an abnormal temperature set, the bimetal 40 is thermally deformed and pushes the lever 52 of the switch 50, so that a contact 54 is opened and the circuit L2 for the heating lamp is opened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for preventing a heating roll in a fixing device equipped with an image forming apparatus by heating and pressing from rising to an abnormal temperature.

[0002]

2. Description of the Related Art In an apparatus having a heating roller and a pressure roller having a heater built therein and passing a sheet between the rollers to fix an image, the temperature of the heating roller rises to an abnormal temperature. Need a mechanism to prevent.

For example, Japanese Patent Laid-Open No. 4-136971 discloses a mechanism in which thermostats are provided on both sides of a fixing roller. Further, Japanese Patent Laid-Open No. 5-2355 discloses an apparatus provided with a thermostat which separates from the roller surface when the fixing roller rotates and contacts the surface of the roller when the roller is stopped to detect the surface temperature of the roller.
Furthermore, Japanese Utility Model Laid-Open No. 58-141266 discloses a structure in which a thermostat is supported by a heat insulating material.

[0004]

The above-mentioned problems are all intended to improve the thermal response and to shut off the power source of the heat source as soon as possible when the abnormal temperature rises. Both use regulated thermostats (structures that have snap-action bimetals and electrical contacts for power interruption). In order to transmit the temperature change of the heating roller to the thermostat bimetals, the parts that make up the thermostat are also heated. Therefore, there is a problem that the thermal response becomes slower by that amount. The present invention provides an apparatus for preventing an abnormal temperature rise of a fixing device that solves this problem.

[0005]

The fixing device of the present invention has a structure in which a bimetal is attached to the outside of the paper passing area of the heating roll. The bimetal deforms at the set temperature, and one end of the bimetal separates from the heating roll. A blocking device is provided on the frame side of the fixing device. When the deformed bimetal comes into contact with the fixing device, the heating roll is turned off.
Prevent the heating roll from rising to an abnormal temperature.

[0006]

1 is a front view showing a main part of a fixing device of the present invention, and FIG. 2 is a side view of a heating roll and an explanatory view of a control circuit. The fixing device, generally designated by reference numeral 1, has a heating roll 10 rotatably supported by bearings 20 and 22 on a frame 2 and a pressure roll (not shown) forming a nip between the heating roll 10. . The heating roll 10 has a gear 14 and is driven via a gear mechanism that meshes with the gear 14. A heating lamp 12 is built in the heating roll 10 and is connected to a power source through lines L ₁ and L ₂ .

The sheet passing area of the heating roll 10 is designated by W ₁
In the heating roll 10 of the present invention, the bimetal 40 is attached to the outside of the paper passage area W ₁ . The bimetal 40 is a plate-shaped one, and the heating roll 1
With respect to the rotation direction R of 0, one end, which is the tip, is fixed
2 is attached to the heating roll 10.

FIG. 2 shows a side surface of the heating roll 10, and a switch 50 is arranged so as to face the bimetal 40 attached to the heating roll 10. The switch 50 is the heating lamp 12
Of the heating lamp 12 and is connected in series to the control device 30 of the heating lamp 12. The bimetal 40 normally maintains the shape in contact with the surface of the heating roll 10, but when the heating roll 10 rises to an abnormal temperature, the bimetal whose temperature is set to the working temperature is deformed and fixed as shown in FIG. Point 42
The opposite side of the roll 10 is separated from the surface of the roll 10.

The switch 50 has a lever 52, and the deformed bimetal 40 contacts the lever 52 and pushes the lever 52. By this action, the contact 5 of the switch 50
4 opens and the power to the heating lamp 12 is cut off. This configuration prevents an abnormal temperature rise of the fixing device. Less than,
The other Example of this invention is shown.

In FIG. 4, the switch 50 is connected to the relay 60, and the relay 60 disconnects the circuit connecting the control device 30 and the heating lamp. That is, when the bimetal 40 of the heating roll 10 pushes the lever 52 of the switch 50 to open the contact 54, the circuit of the power supply 62 opens, the relay 60 opens, and the power supply to the heating lamp is cut off.

In the embodiment of FIG. 5, the heating roll 10 is connected to ground and the other circuit L ₂ connects the control device 30 and the heating lamp 12. Bimetal 40 of heating roll 10
Is connected to the contact switch 70, the circuit of the relay 60 is closed and the relay 60 is activated to cut off the power supply to the heating lamp.

In the embodiment of FIG. 6, the heating roll 10
Is not connected to the ground, but a DC power supply 62, a relay 60 or an AC power supply 64, a relay 66, and a contact switch 70 are connected in series. When the bimetal 40 comes into contact with the contact switch 70, the circuit is closed and the relay is activated to cut off the circuit L ₂ connecting the control device 30 and the heating lamp.

In the embodiment shown in FIG. 7, a fuse 80 is provided in the middle of a circuit L ₂ connecting the control device 30 and a heating lamp. The fuse 80 is sheared by the bimetal 40 to cut off the power supply to the heating lamp.

The embodiment shown in FIG. 8 shows a modified bimetal. The bimetal 100 is attached to the outer peripheral surface of the heating roll 10 by fixing points 102. The bimetal 100 has a curved shape of a disc and generates a so-called click action. Therefore, when heated to the deformation temperature, it is instantly deformed as shown in (B) of the figure, and the tip projects from the roll surface by the distance D ₂ . This dimension D ₂ has a larger value than the height dimension D ₁ before deformation.

In the embodiment shown in FIG. 9, a disc-shaped bimetal 1 is used.
A protruding portion 114 is provided at the tip of 10. When this bimetal 110 is deformed, it projects from the outer peripheral surface of the roll 10 by a distance D ₃ . This dimension D ₃ is larger than the dimension D ₂ of the embodiment shown in FIG.

The embodiment shown in FIG. 10 has a ring-shaped member 122.
Is fitted to a heating roll, and only the tip portion of the ring-shaped member is made of the bimetal 120 so as to be deformed. A hook portion 124 is provided as necessary to ensure the attachment to the roll.

The embodiment shown in FIG. 11 is an arc-shaped bimetal 1.
The fixing hook portions 132 and 134 are inserted into the heating roll 10 using the No. 30 and attached. One end of the bimetal 130 turns back at the set temperature.

The embodiment of FIG. 12 is similar to the above-described embodiment in that the bimetal 200 is attached to the heating roll 10, but the deformed bimetal 200 has a stepped portion 7 provided on the frame 6 of the fixing device. It is configured to hit.

FIG. 13 shows a drive motor 18 for the heating roller 10.
The driving circuit of FIG. 2 is shown, and an outline of being connected to the power supply 230 via the switch 220 of the control device 210 is shown. When the heating roller 10 is forcibly stopped, the motor 18 is forcibly stopped. The control device detects that the motor is overloaded, determines that an abnormality has occurred, and shuts off the power supply to the motor 18 and the heating lamp.

[0020]

As described above, according to the present invention, the bimetal is attached to the outer peripheral surface of the heating roll, and the switch is arranged at a position facing the bimetal so that the bimetal detects that the heating roll is overheated. Then, it is deformed, and the switch is operated to cut off the power supply to the heating roll. Since the power supply circuit is mechanically cut off, reliable operation can be achieved.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a circuit of an embodiment of the present invention.

FIG. 3 is an explanatory view showing the operation of the embodiment of the present invention.

FIG. 4 is an explanatory view showing another embodiment of the present invention.

FIG. 5 is an explanatory view showing another embodiment of the present invention.

FIG. 6 is an explanatory view showing another embodiment of the present invention.

FIG. 7 is an explanatory view showing another embodiment of the present invention.

FIG. 8 is an explanatory view showing an embodiment in which the structure of bimetal is changed.

FIG. 9 is an explanatory view showing an embodiment in which the structure of bimetal is changed.

FIG. 10 is an explanatory view showing an embodiment in which the bimetal structure is changed.

FIG. 11 is an explanatory view showing an embodiment in which the bimetal structure is changed.

FIG. 12 is an explanatory view showing still another embodiment of the present invention.

13 is an explanatory diagram showing a circuit of the device of FIG.

[Explanation of symbols]

10 heating roll, 12 superheat lamp, 30 control device, 40 bimetal, 50 switch, 6
0,66 relay, 70 contact switch, 80 fuse, 100,110,120,130 bimetal.

Claims (7)

[Claims] 1. A fixing device having an electric heater, a heating roll that is rotationally driven, a pressure roll that forms a nip between the heating roll, and a controller for controlling the electric heater. There is a bimetal that is attached to the outside of the paper passage area on the outer peripheral surface of the heating roll and that deforms in the direction away from the heating roll when heated to a set temperature. A device for preventing an abnormal temperature rise in a fixing device, which comprises a shutoff device for shutting off the electric power to the electric heater. 2. The abnormal temperature rise prevention device in the fixing device according to claim 1, wherein the cutoff device is a switch whose contact is opened when the bimetal comes into contact with the cutoff device. 3. The abnormal temperature rise prevention device in the fixing device according to claim 1, wherein the cutoff device is a relay that operates when a bimetal comes into contact with the cutoff device. 4. The abnormal temperature rise prevention device in a fixing device according to claim 1, wherein the breaking device is a fuse that is sheared by the contact of the bimetal. 5. The abnormal temperature rise prevention device in a fixing device according to claim 1, wherein the bimetal has a disc shape having a click function. 6. The abnormal temperature rise prevention device in a fixing device according to claim 1, wherein the bimetal has a ring shape with a part thereof separated, and is fitted to the outer peripheral portion of the heating roll. 7. A heating roll incorporating an electric heater, a drive motor for the heating roll, a pressure roll arranged to form a nip between the heating roll, and a controller for controlling the electric heater and the drive motor. A fixing device having a bimetal attached to the outer peripheral surface of the heating roll outside the paper passage area and deformed in a direction of separating from the heating roll when heated to a set temperature, and provided on the frame side of the fixing device. An abnormal temperature rise prevention device in the fixing device, which includes a stop member for suppressing the deformed bimetal, and the control device detects that the heating roll has stopped abnormally and shuts off the power of the device.