JP2001022221A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a safe direct heating type fixing device capable of preventing a situation that breakdown strength gets insufficient because a heating roller is locally abnormally overheated to rupture a proximate insulating layer and preventing short circuit between a core bar and a heating element. SOLUTION: This fixing device is provided with the heating roller, which is provided with the core bar 1, and the insulating layer 2 and the heating element 3 successively laminated on the inner peripheral surface. In the device, the core bar 1 is connected to either side of a power source, and the device is equipped with a detection means for detecting a current from the core bar 1 to the power source when insulating property is ruptured and a cutoff means 10 for cutting off the supply of the current to the heating element 3 when the detection means detects the current. Thus, firing and fuming are prevented from occurring because the core bar and the heating element are short-circuited and the power supply to the heating element is cut off.

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 apparatus utilizing an electrophotographic process, such as an electrophotographic copying machine, a facsimile, a printer, and the like.

[0002]

2. Description of the Related Art As a fixing method of a toner image, a heat fixing method, a pressure fixing method, and a solvent fixing method are known.
The heat fixing method is widely adopted as a method in which toner is melted by heat and the paper is fixed by applying pressure. Among the heat fixing methods, the most common one is a method of heating from the inner surface of a metal roller with a halogen lamp.

[0003]

However, such a system has a drawback that the radiant heat is used, so that the energy conversion efficiency is low, the power consumption is large, and the warm-up time is long. Therefore, as one of means for solving such a defect, a heating roller of a direct heating type in which a heating element made of a linear or foil-shaped resistor is disposed inside or outside a metal core via an insulating layer is provided. A fixing device has been proposed.

As such a fixing device, there is a fixing device having the same configuration as that shown in FIG. 5 as a comparative example with the present invention, and this will be described with reference to FIG. The fixing device is provided with a heat generating roller having a cored bar 1 as shown in FIG. 1, an insulating layer 2 sequentially laminated on an inner peripheral surface thereof, a heating element 3, and a release layer 4 laminated on an outer peripheral surface thereof. I have. The heating element 3 is heated by being supplied with electricity from a power source 5, and a thermistor 6 is arranged near the center of the heating roller. Based on the temperature detected by the thermistor 6, the heating element 3 is heated by a temperature control circuit 7.
The fixing temperature is controlled by turning on and off the power to the fixing device.

[0005]

However, in such a heating roller, if the layers are not in close contact with each other, uniform and efficient heat conduction cannot be achieved, and the heating element 3 may be separated from the insulating layer 2. However, in that portion, the temperature of the roller surface does not rise, so that temperature unevenness occurs or the temperature rise time becomes long. Further, if the release of the heating element 3 expands, the generated heat itself is not taken away by the insulating layer 2 and the cored bar 1, causing abnormal overheating locally and, in the worst case, destroying the adjacent insulating layer 2. Under the Electrical Appliance and Material Control Law, 100 kV equipment is required to have a withstand voltage of 1 kV as basic insulation, but is insufficient in withstand voltage. If such a state continues, a short circuit occurs between the cored bar 1 and the heating element 3, and a partial abnormal heat generation occurs due to a current from the short section, resulting in a dangerous state such as ignition or smoking. There is a problem of fear.

The present invention solves the problems of the conventional fixing device as described above, and prevents the heat generating roller from locally overheating abnormally, destroying the adjacent insulating layer and causing insufficient pressure resistance. To provide a safe direct heating type fixing device in which a short circuit does not occur between gold and a heating element, and there is no danger of a dangerous state such as ignition or smoking due to partial abnormal heat generation. The purpose is to:

[0007]

In order to achieve the above object, the present invention has a heating roller, and the heating roller comprises a cored bar and an insulating layer sequentially laminated on the inner peripheral surface thereof.
In a fixing device having a heating element, the invention according to claim 1, wherein the core is connected to one of the power sources, and a detecting means for detecting a current from the core to the power source when the insulation property is broken. And interrupting means for interrupting the supply of the current to the heating element when the detecting means detects the current.

According to a second aspect of the present invention, the core is connected to one of the power supplies, and a detection heating element is disposed in a connection circuit between the core and the power supply, and the detection is performed when the insulation property is broken. When the temperature of the heating element rises due to the current flowing from the core to the power supply,
It is characterized by comprising a shutoff means for detecting this and shutting off the supply of current to the heating element.

According to a third aspect of the present invention, there is provided a connection circuit in which a detection heating element is disposed in parallel with a connection circuit between a heating element and a power supply, and when the insulation property is broken, the detection heating element is provided therewith. When the temperature rises due to a current flowing through the heating element, the temperature detecting device detects the temperature rise and shuts off the supply of the current to the heating element.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. In this description, the same reference numerals are given to members common to the above-described conventional example and each embodiment, so that the description will not be repeated. FIG. 1 shows a cross section of a heating roller according to the present invention. The heating roller includes a cored bar 1, an insulating layer 2, a heating element 3, and a release layer 4 sequentially laminated on an inner peripheral surface thereof. ,
The fixing device is supported by an insulating resin bearing (not shown).

FIG. 2 shows a first embodiment included in the first aspect. In the first embodiment, the heat generating roller has an outer diameter of 30 mm, the core 1 has an iron thickness of 0.4 mm, and the paper passing width is 300 mm.
mm, insulation layer 2 is 50 μm polyimide film, heating element 3
Is formed by bonding 50μm SUS430 in a meandering pattern so that the resistance becomes 8.3Ω, and reaches the required temperature of 180 ° C for about 8 seconds in about 8 seconds. ing.

In this embodiment, the metal core 1 is connected to one of the power supplies 5 via a metal bearing 8 (other sliding electrodes may be used) and a current detection circuit 9. When the current of the current detection circuit 9 becomes 100 mA or more, the setting is made so that the cutoff means 10 is activated to cut off the current supply to the heating element 3.

When an electric current test was performed in this embodiment, the leakage current from the heating element 3 through the insulating layer 2 was 3 mA, and the current detection circuit 9 did not operate, so that normal use was possible. Therefore, the short section 15 which is 30 mm apart from the center of the roller at both ends was short-circuited. When the power supply is started in this state, a short circuit causes a large current of 100 mA or more to flow, so that the power supply to the heating element 3 is instantaneously interrupted, and there is no danger of ignition or smoking.

FIG. 3 shows a second embodiment of the present invention. The metal core 1 is connected to one of the power sources 5 and the detection heating element 11 via a metal bearing 8 (other sliding electrodes may be used).
Connected through. A thermostat 12 (which may be a temperature fuse) operating at 100 ° C., which is clearly higher than the normal internal temperature of 50 ° C., is arranged close to the detection heating element 11, and the thermostat 12 is connected in series with the heating element 3. The thermostat 12 is activated by the heat generated by the detection heating element 11,
The power supply to the heating element 3 can be cut off.

In this embodiment, when an energization test is performed, the detection heating element 11 is not energized, and the thermostat 12 does not operate, so that normal use is possible. Therefore, the short section 15 which is 30 mm apart from the center of the roller at both ends was short-circuited.
When current is started in this state, a large current flows through the detection heating element 11 due to short-circuiting, and the detection heating element 11
It reached within a few seconds as described above, and the thermostat 12 was activated to cut off the power supply to the heating element 3 and there was no danger of ignition or smoking.

FIG. 4 shows a third embodiment of the present invention. The detection heating element 13 was connected in parallel with the heating element 3. A thermostat 14 operating at 100 ° C., which is reached when the detection heating element 13 is continuously energized for 14 seconds or more, which is sufficiently longer than the heating time of the fixing device for 8 seconds, is close to the detection heating element 13 (a temperature fuse may also be used). Good), the thermostat 14 is connected in series with the heating element 3
The device is activated by the heat generated by the thirteenth heat source so that the power supply to the heat generating element 3 can be cut off.

In this embodiment, when an energization test is performed, energization control of the detected heating element 13 is controlled in the same manner as the heating element 3, the temperature does not reach 100 ° C., and the thermostat 14 does not operate, so that normal use is possible. . Therefore, the short section 15 which is 30 mm apart from the center of the roller at both ends was short-circuited. When the power supply is started in this state, the short-circuit causes the temperature of the thermistor 6 of the heating roller not to rise, and the current flows to both the heating element 3 and the detection heating element 13 for at least 14 seconds. 100 ℃
As a result, the thermostat 14 was activated to cut off the power supply to the heating element 3, and there was no danger of ignition or smoking.

FIG. 5 shows a comparative example for the present invention. This comparative example is similar to the conventional example as described above,
The present embodiment is configured in the same manner as the above-described three embodiments of the present invention, except for the parts that constitute the gist of the present invention. In this comparative example, the cored bar 1 is in a float state in which it is not electrically connected to any part, and short-circuit portions 15 which are 30 mm away from the center of the heat roller at both ends are short-circuited. Thermistor 6 does not heat up, and only both ends generate abnormal heat. And the center is 18
At 0 ° C., energization was continuous for 28 seconds, and both ends reached a maximum of 770 ° C., and ignition and smoke were generated from a pressure roller (not shown).

[0019]

The present invention is as described above. According to the first aspect of the present invention, when a short circuit occurs between the cored bar and the heating element, it is detected that a large leakage current is generated, and the power to the heating element is detected. Since the power supply is cut off, there is an effect that ignition and smoke do not occur.

According to the second aspect of the present invention, when a short circuit occurs between the cored bar and the heating element, it is detected that a large leakage current is generated, and the power supply to the heating element is cut off. There is no need for a secondary circuit such as a current detection circuit, so that there is an effect that the safety is further enhanced.

According to the third aspect of the present invention, when a short circuit occurs between the core metal and the heating element, an abnormally long continuous energization is detected and the energization to the heating element is cut off, so that no ignition or smoking occurs. Further, since a secondary circuit such as a current detection circuit is not required, there is an effect that the safety is further improved.

[Brief description of the drawings]

FIG. 1 is a vertical sectional front view of a heat generating roller of the present invention.

FIG. 2 is a control circuit diagram according to the first embodiment of the present invention.

FIG. 3 is a control circuit diagram according to a second embodiment of the present invention.

FIG. 4 is a control circuit diagram according to a third embodiment of the present invention.

FIG. 5 is a control circuit diagram of a comparative example of a fixing device of the same type as the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Core metal 2 Insulating layer 3 Heating element 4 Release layer 5 Power supply 6 Thermistor 7 Temperature control circuit 8 Bearing 9 Current detection circuit 10 Cut-off means 11 Detection heating element 12 Thermostat 13 Detection heating element 14 Thermostat 15 Short section

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Jun Yura 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (reference) 2H033 AA42 BA25 BA32 BA34 BB03 BB04 BB13 BB14 BB18 BB22 CA06 CA07 CA23 CA34 CA43 3K058 AA13 AA16 BA18 CA04 CA23 CA41 CA61 CE17 DA03 DA21 5H323 AA36 FF01 GG04 HH02 JJ04 KK05 MM02 QQ06 RR02 RR04 SS01 SS03 SS10 TT06 TT20

Claims (3)

[Claims] 1. A fixing device having a heating roller, a heating roller, and an insulating layer and a heating element sequentially laminated on an inner peripheral surface of the heating roller, wherein the core is connected to one of power sources. Detecting means for detecting a current from the metal core to the power supply when the insulation property is broken, and interrupting means for interrupting the supply of the current to the heating element when the detecting means detects the current. A fixing device characterized by the above-mentioned. 2. A fixing device having a heat generating roller, wherein the heat generating roller includes a core metal, an insulating layer sequentially laminated on an inner peripheral surface thereof, and a heat generating element, wherein the core metal is connected to one of power sources. , Arrange the detection heating element in the connection circuit between the core metal and the power supply,
When insulation is destroyed, when the temperature of the detection heating element rises due to the current flowing from the metal core to the power supply, the detection heating element detects the temperature rise and has a shutoff means for interrupting the supply of current to the heating element. Fixing device. 3. A fixing device having a heating roller, wherein the heating roller includes an insulating layer and a heating element sequentially laminated on a core metal, an inner peripheral surface thereof, and a fixing circuit in parallel with a connection circuit between the heating element and a power supply. A connection circuit with a detection heating element is provided, and if the insulation heating is broken and the temperature of the detection heating element rises due to the current flowing through it, this is detected and the supply of current to the heating element is cut off. A fixing device comprising a blocking unit that performs a fixing operation.