JPH07129019A - Heat fixing device - Google Patents

Abstract

(57) [Abstract] [Purpose] Regardless of the type of paper, it consumes less power, has a good response to the rise of heat, and has a thermal adverse effect on the components and various components near the heat fixing unit. The present invention provides a heat fixing device having a compact structure, which employs a heating roller having a simple structure capable of properly performing heat fixing and stops the heat fixing at a timely timing when there is an abnormality in a sheet. [Structure] The heating roller 30 has a central portion 31 and a base portion 3
2, electrode layer 33 having each electrode portion 33a, each electrode 33a
The elastic layer 34 having the through holes 34a into which the holes are inserted, the resistance layer 35, the common electrode layer 36, and the fusion preventing layer 37 are sequentially fitted in a cylindrical shape. When an abnormal pressure is applied to the nip portion between the heating roller 30 and the pressure roller, the microcomputer stops the driving of the heating roller 30 and the application of the DC voltage of the DC power supply based on the pressure detection signal of the pressure sensor 80a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal fixing device for thermally fixing toner used in electrophotographic printers, copying machines and the like onto paper.

[0002]

2. Description of the Related Art Conventionally, a heat roller using a halogen heater has been mainly used in a heat fixing device for fixing toner onto a sheet. The heat roller is composed of a hollow cylindrical roller made of a material having good heat conductivity such as aluminum or stainless steel. The heat roller is configured to rotate along the outer circumference of the halogen heater fixed in the hollow portion. Thus, the heat and adhesion required for fixing the paper and the toner are obtained. In addition, a pressure roller composed of heat-resistant silicone rubber is used, and the nip area necessary to obtain an appropriate pressure contact force and adhesiveness is sandwiched between the heat roller and the paper on which the toner image is transferred. To form.

Further, in such a heat fixing device,
A temperature sensor is provided in contact with the heat roller,
The amount of heat supplied from the halogen heater is controlled by adjusting the electric power applied to the halogen heater in accordance with the detection result, and the surface temperature of the heat roller is kept constant. In addition, a thermal fuse is installed near the heat roller to shut off the electric power applied to the halogen heater when it becomes difficult to control the amount of heat emitted from the halogen heater due to some trouble in the heat fixing device, and to prevent fire. It is designed to prevent it.

[0004]

However, in the thermal fixing device having such a configuration, the heating roller portion and the heating roller portion other than the portion in contact with the paper or the toner are heated by the halogen heater at the time of fixing and before and after fixing. The bearings, and even the air around the halogen heater are heated and exposed to high temperature. Therefore, there are various problems as described below. First, there is a problem in that members such as the heat roller, the pressure roller, the bearing that supports the temperature sensor and the temperature fuse, and the like must be made of resin or metal having high heat resistance. In particular,
There is a problem that high heat resistance is required for bearings of the rotating portion of the heat roller. In addition, the heating as described above keeps almost the entire heat fixing device in a high temperature state, so that when a paper jam occurs during fixing, the user tries to remove the paper near the heat fixing device or the user It is necessary to completely cover the outer periphery of the heat fixing device with a cover made of a heat insulating protection member so as to prevent injury such as burns when the heat fixing device is accidentally touched. Otherwise, the heat fixing device must be installed in a place that cannot be touched by the user's hand, which has a drawback that the structure of the heat fixing device becomes complicated and the device itself becomes large. .

Secondly, in order to prevent each constituent member located on the outer periphery of the thermal fixing device from being affected by heat from the same thermal fixing device, each constituent member is installed separately from the thermal fixing device. Alternatively, it is necessary to provide a heat insulating member, an exhaust fan, or the like with another device (photoreceptor, developing device, scanner, toner, etc.). Therefore, there is a drawback that the structure of the printer or the copying machine becomes complicated and the size becomes large. Third, after the power is turned on from the initial state and before the surface temperature of the heat roller reaches the actual fixing temperature, the heat of the halogen heater is transmitted to the inner circumferential surface of the heat roller after the halogen heater is turned on. It was necessary to raise the temperature. For this reason, a certain amount of rising time is required between turning on the power and starting the fixing, which is inconvenient for the user. Fourth, as described above, the heat generated from the heat roller as a whole includes unnecessary heat generated for purposes other than the original purpose. Therefore, there is a disadvantage in that the power consumed is very large.

Fifth, in order to shorten the rise time of the heat fixing device as much as possible, it is necessary to keep the temperature of the heat roller at a certain temperature during the time after the power is turned on and before the actual start of fixing. Heat treatment is required. As a result, there is a serious drawback that a large amount of electric power is consumed even though the actual fixing by the heat fixing device is not performed. Sixth, in addition to normal copy paper and high-quality paper, paper with a rough surface such as envelopes and bond paper and thick paper still have problems in their fixing quality. That is, these rough papers and thick papers have a lot of extra air layers, and as a result, they act as a heat insulating layer. Compared to the fixing energy required for high-quality paper, it had to be fixed with a larger amount of energy. Therefore, if the fixing energy of the heat fixing device is set to a large value so that it can be sufficiently fixed on paper or paper having a rough surface, the surface temperature of the heat roller will be overheated when fixing on ordinary paper. There was a risk of causing problems in fixing quality and the like. Seventh,
In the process of fixing the paper, if the paper has protrusions, large deposits, excessive bends or jams, there is a risk of local overheating of the heat roller and damage to the heat fixing device. . Therefore, in order to deal with the above, the present invention provides a low power consumption, a good response of the rise of heat generation, and a component or various components near the heat fixing unit regardless of the type of paper. Adopting a heating roller with a simple structure that can properly perform heat fixing without adversely affecting heat,
It is an object of the present invention to provide a heat fixing device having a compact structure, which can stop the heat fixing at a timely timing when a sheet is abnormal.

[0007]

In order to solve the above-mentioned problems, the structure of the present invention is rotatably supported by a stationary member and is provided substantially concentrically with the rotating shaft to form a plurality of through holes. A cylindrical insulating elastic layer, a cylindrical electrode layer having respective electrode portions fitted substantially concentrically to the insulating elastic layer and inserted into the through holes, respectively, and the electrode via the insulating elastic layer. A heating roller composed of a cylindrical resistance layer fitted substantially concentrically with the insulating elastic layer so as to face the layer, and a nip portion for sandwiching a sheet under contact with the heating roller are formed. So that the stationary member is rotatably supported by a pressure roller, and a power supply means for supplying power between the electrode layer and the resistance layer of the heating roller, the heating roller and the Generated by contact with the pressure roller By elastically deforming the portion corresponding to the nip portion, each portion of the electrode layer and the resistance layer corresponding to the nip portion are electrically connected to each other by each electrode portion corresponding to the nip portion. A thermal fixing device for generating heat necessary for fixing in a nip portion, wherein pressure detecting means for detecting a pressure generated in the nip portion, and electric power from the power supply means when the detected pressure becomes abnormal. And a control unit for controlling the supply and the driving of the driving unit with respect to the heating roller to be stopped.

[0008]

With the above-described structure of the present invention, the heating roller is driven by the driving means to rotate together with the pressure roller while forming the nip portion,
Further, the power source supplies electric power to the electrode layer and the resistance layer of the heating roller so as to secure electrical connection in a region corresponding to the nip portion. As a result, the sheet is conveyed in a state of being supported by the nip portion according to each rotation of the heating roller and the pressure roller, and the resistance value of the resistance layer is in an area corresponding to the nip portion. Generates heat according to. Then, the heat energy due to this heat generation is transmitted to the paper through the area corresponding to the nip portion of the resistance layer, is used for melting the toner on the paper, and is ready for heat fixing. Therefore, as the paper is conveyed as described above, the toner is thermally fixed on the paper. In addition, when the paper is a paper that exceeds a specified thickness, when a paper jam occurs at the nip portion, or when foreign matter or the like adheres to the paper,
Since an abnormal pressure is generated in the nip portion, this abnormal pressure is detected by the pressure detecting means, and the control means stops the supply of electric power from the power source and the driving of the driving means with respect to the heating roller. To control.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows an example of a heat fixing device to which the present invention is applied. The thermal fixing device includes upper and lower covers 10 and 20 each having a substantially U-shaped cross section, and the respective covers 10 and 20 are arranged so that their openings are opposed to each other. The heat fixing device includes a heating roller 30 assembled in the cover 10 and a pressure roller 40 assembled in the cover 20.
Is rotatably and coaxially supported on the inner wall of the cover 10 by a central shaft 31 via both bearings (not shown).

The pressure roller 40 is constructed by forming an elastic roller portion 42 made of a heat resistant elastic material such as silicon rubber on the outer circumference of a central shaft 41. The pressure roller 40 is provided on the bottom wall of the cover 20. , Both bearings 43, 43 at both ends of the central shaft 41 (only one bearing 43 is shown in FIG. 1B), both holders 44 having a substantially H-shaped cross section,
44 (only one holder 44 is shown in FIG. 1 (B))
Also, it is rotatably supported by both coil springs 45, 45 (only one coil spring 45 is shown in FIG. 1B) so that the outer peripheral surface of the elastic roller portion 42 contacts the outer peripheral surface of the heating roller 30. Touching. In such a case, each holder 44 can move up and down through the coil spring 45 in the lower recess 44a of the protrusion 21 of the cover 20 (see FIG. 1).
In (B), only one of the protrusions 21 is shown), and the bearings 43 are received in the upper recesses 44b of these holders 44 at their lower outer circumferences so as not to rotate. Further, since each coil spring 45 plays a role of pressing the outer peripheral surface of the elastic roller portion 42 against the outer peripheral surface of the heating roller 30 via each bearing 43, the pressure roller 40
A nip portion A (see FIG. 4) is formed at both abutting portions of the heating roller 30 and the heating roller 30, as described later.

In this heat fixing device, however, the toner 51 placed on the paper 50 is melted by the heat generated by the heating roller 30 as will be described later, so that the paper 5 is melted.
It is heat-fixed to 0. Further, in this heat fixing, the heating roller 30 and the pressure roller 40 are rotated in the direction of the arrow shown in FIG. Therefore, the thermal fixing device described in this embodiment generally has two functions: a function of transporting the sheet 50 and a function of melting the toner 51 by heat and fixing the toner on the sheet 50. In such a case, the pressure roller 40 is
It is rotatably connected to a central shaft 31 of the heating roller 30 via a gear (not shown). In FIG. 2, reference numerals 60a and 60b respectively denote paper guides for guiding the paper 50 to a predetermined position, and reference numeral 7
Reference numerals 0a and 70b respectively denote paper discharge rollers that discharge the paper 50 to the outside of the apparatus.

Next, the structure of the heating roller 30 is shown in FIG.
It will be described in detail with reference to FIGS. This heating roller 3
0 has two functions of conveying the sheet 50 and generating two heats in the nip portion A to melt the toner 51 and fix it on the sheet 50. The heating roller 30 is
A cylindrical base portion 32, which is concentrically and axially supported, is provided on the outer periphery of a central shaft 31 made of a metal material, and the base portion 32 is made of a slightly elastic insulating material such as rubber or resin. In addition, the heating roller 30 has a cylindrical electrode layer 33.
The electrode layer 33 is mainly made of a metal conductive material such as aluminum, and is concentrically fitted to the outer periphery of the base portion 32. On the outer peripheral surface of the electrode layer 33, as shown in FIG. 3, a plurality of columnar electrode portions 33a are discretely provided in a predetermined array. In this case, the electrode layer 33 and each electrode portion 33a can be electrically connected to each other. In this embodiment, each electrode portion 33a is formed of a heat-resistant metal material such as tungsten, which has excellent heat resistance and wear resistance, because its tip is exposed to high temperature and high pressure conditions. The respective electrode portions 33a are not limited to the columnar shape, and may be formed in various shapes such as a cubic columnar shape or a hemispherical shape, and each electrode portion 33a may be formed of the same material as the electrode layer 33. Alternatively, it may be formed integrally with the electrode layer 33.

The elastic layer 34 is formed of an insulating elastic material into a cylindrical shape, and the elastic layer 34 is concentrically fitted on the outer peripheral surface of the electrode layer 33 as shown in FIG. ing. In this elastic layer 34, each cylindrical through hole 34a is formed.
3 is formed so as to face each electrode portion 33a, and each electrode portion 3 is formed in each through hole 34a.
3a is inserted almost concentrically. In this case, the depth of each through hole 34a is deeper than the height of each electrode portion 33a, and when the elastic layer 34 and the electrode layer 33 are adhered to each other, the outer end surface of each electrode portion 33a and the outer side of the elastic layer 34 are separated. A gap is formed between the surface, that is, the outer end opening surface of each through hole 34a. In addition, the inner diameter of each through hole 34a is equal to each electrode portion 3
It is larger than the outer diameter of 3a.

The resistance layer 35 is made of a material in which carbon is dispersed in a polycarbonate film, and is formed into a cylindrical shape with a film thickness of about 20 micrometers so as to have a predetermined volume resistance value. Figure 1
As shown in (A), they are concentrically fitted to the outer peripheral surface of the elastic layer 34. The common electrode layer 36 is vacuum-deposited in a cylindrical shape with a thickness of 1000 angstrom to 0.2 mm from a material such as aluminum, and the common electrode layer 36 is concentric with the outer peripheral surface of the resistance layer 35. Is fitted to. The anti-fusing layer 37 is formed of a material such as tetrafluoroethylene into a cylindrical shape, and the anti-fusing layer 37 is concentrically fitted on the outer peripheral surface of the common electrode layer 36. Constitutes the outer peripheral surface of the heating roller 30,
Toner 5 on the outer peripheral surface of the heating roller 30 during heat fixing
1 fusion prevention. However, the fusion preventing layer 37 has a right end portion 37a shown in FIG.
The elastic layer 34, the resistance layer 35, and the common electrode layer 36 are shortened together with the right end portions thereof so as to expose b, and the positive electrode 38a is provided on the right end portion 33b of the electrode layer 33 at its tip portion. Are in contact. Further, the fusion preventing layer 37 is short so as to expose the left end portion 36a of the common electrode layer 36 at the left end portion 37b shown in FIG. The negative electrode 38b is in contact with its tip. Both electrodes 38a and 38b are
Each base is fixed in place.

In the heating roller 30 thus constructed, the heating roller 30 is the pressure roller 40.
At the contact portion with the outer peripheral portion of the pressure roller 40,
Since the elastic layer 34 is pressed by the elastic layer 34, the elastic layer 34 is elastically deformed and crushed at the abutting portion under the same pressure. Similarly, the elastic roller portion 42 of the pressure roller 40 is elastically deformed under the pressure of the heating roller 30 and is crushed at the contact portion with the heating roller 30. As a result, at the contact portion between the heating roller 30 and the pressure roller 40, the nip portion A is formed so as to ensure the area and pressure required for heat fixing.
Are formed as shown in FIG.

In such a case, at the non-contact portion between the heating roller 30 and the pressure roller 40, the elastic layer 34 described above is used.
Since elastic deformation of the electrode layer 3 does not occur, each electrode portion 3 of the electrode layer 33
3a and the resistance layer 35 are maintained in a non-contact state with each other (see FIG. 6A). Therefore, the electrode layer 33 and the resistance layer 35
No direct current will flow between and. On the other hand, in the nip portion A, the heating roller 30 and the pressure roller 4
Since the elastic layer 34 described above is crushed by its elastic deformation at the contact portion with 0, each electrode portion 33 of the electrode layer 33.
a and the resistance layer 35 are kept in contact with each other (FIG. 6).
(See (B)). Therefore, the respective electrode portions 33a of the electrode layer 33 and the resistance layer 35 are in a state capable of mutually conducting electricity in the region corresponding to the nip portion A. It should be noted that each facing surface between the central axis 31, the base portion 32, the electrode layer 33, the elastic layer 34, the resistance layer 35, the common electrode layer 36, and the fusion preventing layer 37 described above is formed of an appropriate adhesive or vapor deposition force. Are evenly bonded by.

Next, the electric circuit configuration of the device of the present invention will be described with reference to FIGS. 1, 7 and 8. Pressure sensor 8
0a is one holder 4 as shown in FIG. 1 (B).
The pressure sensor 80a is sandwiched between the bottom wall of the upper recess 44b of the pressure roller 4 and the lower portion of the bearing 43. The pressure sensor 80a operates under the elastic action of the coil spring 45.
The pressure applied from 0 through the bearing 43 is detected and a pressure detection signal is generated. As shown in FIG. 2, the temperature sensor 80b is supported at the lower end opening of the cover 10 via the leaf spring 11 so as to come into contact with the outer peripheral surface of the heating roller 30 with a fine force. The temperature of the outer peripheral surface of the roller 30 is detected and a temperature detection signal is generated.

The amplifier circuit 90a amplifies the pressure detection signal from the pressure sensor 80a and generates a pressure amplification signal. The amplifier circuit 90b amplifies the temperature detection signal from the temperature sensor 80b and generates a temperature amplification signal. Current detection circuit 100
Detects a DC current flowing from the DC power supply 110 to the exposed end portion 33b of the electrode layer 33 of the heating roller 30 via the positive electrode 38a and generates a current detection signal. DC power supply 110
Is connected to the positive electrode 38a through the current detection circuit 100 at its positive terminal, and the negative electrode 3 is connected at its negative terminal.
It is connected to 8b. Then, this DC power supply 110
Under the control of the microcomputer 120,
A DC voltage is selectively applied between the exposed end portion 33b of the electrode layer 33 and the exposed end portion 36a of the common electrode layer 36 of the heating roller 30 via the current detection circuit 100 and both electrodes 30a and 38b.

The microcomputer 120 follows both the amplifier circuits 90a and 90b according to the flow chart shown in FIG.
The computer program is executed in cooperation with the current detection circuit 100 and the DC power supply 1 during execution of the computer program.
The arithmetic processing required to control the driving of the heating roller driving circuit 10 and the heating roller driving circuit 130 is performed. The computer program described above is stored in advance in the ROM of the microcomputer 120.

In the present embodiment configured as described above,
A case where thermal fixing is actually performed by the apparatus of the present invention will be described. When the device of the present invention is put into operation, the microcomputer 120 starts execution of the computer program in step 200 according to the flowchart of FIG. At this time, in the heating roller 30, as shown in FIG.
It is assumed to be supported by a nip portion A formed by the heating roller 30 and the pressure roller 40. In such a case, in the nip portion A, as shown in FIG. 4B, each electrode portion 33a of the electrode layer 33 is elastically deformed into an elastic layer 34.
Through the through-holes 34a to contact the corresponding portions of the resistance layer 35. At the present stage, the temperature of the outer peripheral surface of the heating roller 30, the pressure roller 40 and the holder 44
Both pressures applied to the heating roller 30 are normal.
It is assumed that no DC voltage is applied to the.

After the execution of the computer program in step 200, the microcomputer 120 determines "YES" based on the temperature detection signal from the temperature sensor 80b in step 210, and the pressure sensor in step 220. It is determined to be "YES" based on the pressure detection signal from 80a, and "YES" is determined based on the current detection signal from the current detection circuit 100 in step 230.
To determine. In such a case, each of the determinations of “YES” is made when the value T of the temperature detection signal from the temperature sensor 80b is less than the predetermined temperature To and the value P of the pressure detection signal from the pressure sensor 80a is less than the predetermined pressure Po. It is premised that the value I of the current detection signal from the current detection circuit 100 is less than the predetermined current Io. However, the predetermined temperature To
Represents the lower limit of the abnormal heat generation temperature of a part of the heating roller 30, the predetermined pressure Po represents the lower limit of the abnormal pressure from the pressure roller 40 to the pressure sensor 80a, and the predetermined current Io represents the abnormality flowing through the heating roller 30. Indicates the lower limit of current. The predetermined temperature To, the predetermined pressure Po, and the predetermined current Io are the R of the microcomputer 120.
Pre-stored in the OM.

As described above, in step 230, "YE
If it is determined to be "S", the microcomputer 12
In the next step 240, 0 outputs the drive command signal required for driving the heating roller 30 to the heating roller drive circuit 130, and outputs the application command signal required for applying the DC voltage from the DC power supply 110 to the DC power supply 110. To do. Therefore, the heating roller 30 is driven by the heating roller drive circuit 130 to rotate together with the pressure roller 40,
Further, the DC power source 110 applies a DC voltage to the right exposed end 33b of the electrode layer 33 and the left exposed end 36a of the common electrode layer 36 of the heating roller 30 via the electrodes 38a and 38b in a region corresponding to the nip portion A. Apply. This allows the paper 5
0 is conveyed in a state of being nipped by the nip portion A in accordance with each rotation of the heating roller 30 and the pressure roller 40, and the DC power source 110, the current detection circuit 100, and the positive electrode 3
8a, the electrode layer 33 of the heating roller 30 and each electrode portion 3 thereof
A direct current flows through a closed circuit composed of 3a (the electrode portion corresponding to the nip portion A), the resistance layer 35, and the negative electrode 38b. In such a case, in the area corresponding to the nip portion A,
When the DC current flows into the resistance layer 35 as described above, the resistance layer 35 generates heat according to its resistance value. Then, the heat energy due to this heat generation is transmitted from the resistance layer 35 to the sheet 50 through the area corresponding to the nip portion A of the common electrode layer 36 and the fusion preventing layer 37. Therefore, the transferred heat energy is used for melting the toner 51 on the sheet 50 at the nip portion A, and the heat fixing is possible. Therefore,
As the paper 50 is conveyed as described above, the heat fixing of the toner 51 on the paper 50 is smoothly performed with high quality.

In this case, since the common electrode layer 36 and the fusion preventing layer 37 are both formed of extremely thin layers, the thermal resistance of the common electrode layer 36 and the fusion preventing layer 37 is extremely small. Therefore, the thermal energy generated in the resistance layer 35 can be very efficiently transferred to the outer surface of the heating roller 30.
As a result, the heat-fixable state described above is quickly achieved, and the waiting time for starting heat-fixing can be shortened to the minimum. Further, since the heat generated by the heating roller 30 and its transmission are limited to the nip portion A, it is of course possible to extremely reduce the thermal adverse effect on the other components of the heat fixing device, and of course, the power consumption. The amount can be extremely reduced, and this type of heat fixing device can be made compact.

By the way, in the heat fixing process as described above, when a conveyance problem such as jamming of the sheet 50 at the nip portion A occurs, or when the sheet 50 is a sheet having a thickness exceeding the specified thickness. A very large pressure is applied to the nip portion A between the heating roller 30 and the pressure roller 40. Therefore, the contact area between the electrode layer 33 and the resistance layer 35 in the nip portion A, that is, the number of contacts of each electrode portion 33a with the resistance layer 35, abnormally increases, and the amount of the direct current described above abnormally increases. This abnormal increase in DC current is detected by the current detection circuit 100 as a current detection signal.

When a narrow foreign matter or the like is attached to the paper 50, the current amount is locally abnormal only in a part of the nip portion A, although the amount of the direct current is normal. It increases and causes partial abnormal heating of the heating roller 30. Such abnormal heating is detected as a temperature detection signal by the temperature sensor 80b. In addition, as described above, when the paper 50 is a paper that exceeds the specified thickness,
Abnormal pressure is applied to the pressure roller 40 from the nip portion A and is transmitted to the pressure sensor 80a via the bearing 43. Further, as described above, when a narrow foreign matter or the like is attached to the sheet 50, even if the foreign matter is located at a position where the temperature sensor 80b cannot detect, the foreign matter passes through the pressure roller 40 and the bearing 43. Abnormal pressure is applied to the pressure sensor 80a. Abnormal pressures such as these are detected as pressure detection signals by the pressure sensor 80a.

When abnormal heating is detected as the temperature detection signal as described above, the microcomputer 120 determines in step 210 that the value T of the temperature detection signal is equal to or higher than the predetermined temperature To. Based on this, "NO" is determined. Further, when the abnormal pressure is detected as the pressure detection signal as described above, the microcomputer 12
In step 220, "NO" is determined based on the value P of the pressure detection signal being equal to or higher than the predetermined temperature Po. When the abnormal current is detected as the current detection signal as described above, the microcomputer 120
In step 230, it is determined to be "NO" based on the value I of the current detection signal being equal to or higher than the predetermined temperature Io.

In this way, when the determination of "NO" is made in any of steps 210, 220 and 230,
The microcomputer 120, at step 250,
A drive stop command signal required to stop driving the heating roller 30 is output to the heat roller drive circuit 130, and an application stop command signal required to stop applying a DC voltage from the DC power supply 110 is output to the DC power supply 110. Therefore, the heating roller 30 stops rotating together with the pressure roller 40,
Further, the DC power supply 110 stops applying the DC voltage to the heating roller 30. As a result, it is possible to prevent the occurrence of damage or destruction of the component members due to heat abnormality or pressure abnormality in the heat fixing device in good timing. In carrying out the present invention, the central shaft 31 of the heating roller 30 and the base 32 may be integrally formed, or the base 32 may be formed in a hollow shape and the central shaft 31 may be coaxial with the hollow. You may make it fit. Further, in implementing the present invention, the heating roller 30 may be configured such that the electrode layer 33 and the resistance layer 35 are replaced with each other, and each electrode portion 33a of the electrode layer 33 is provided on the resistance layer 35. You may

[0028]

As a result of the above-described structure and operation of the present invention, the thermal energy generated in the portion of the resistance layer corresponding to the nip portion is transferred to the sheet through the area corresponding to the nip portion. . Therefore, the transferred heat energy is used for melting the toner on the paper at the nip portion, and the heat fixing is possible. As a result, as the above-mentioned sheet is conveyed, the heat fixing of the toner on the sheet is smoothly performed with high quality. In such a case, the thermal energy generated in the resistance layer is transferred to the paper through the nip portion,
A very efficient heat transfer is possible. As a result, the heat-fixable state described above is quickly achieved, and the waiting time for starting heat-fixing can be shortened to the minimum. Further, as described above, since the heat generation and the transmission thereof are limited to the nip portion, it is needless to say that the thermal adverse effect given to other constituent members of the heat fixing device can be made extremely small.
The power consumption can be extremely reduced, and this type of heat fixing device can be provided as a reliable heat fixing device with a compact structure. Further, by stopping the rotation of the heating roller and the pressure roller and stopping the supply of the electric power from the power source, it is possible to prevent the occurrence of the damage or the destruction of the constituent members due to the heat abnormality and the pressure abnormality in the heat fixing device in a timely manner. .

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of a heating roller of FIG. 2 and an enlarged cross-sectional view of a bearing component portion of a pressure roller.

FIG. 2 is a schematic sectional view showing an embodiment of the present invention.

3 is an enlarged perspective view of a main part showing a configuration of an electrode layer and an elastic layer of the heating roller of FIG.

FIG. 4 is an enlarged cross-sectional view of a main part for showing a nip portion formed by the heating roller and the pressure roller of FIG.

FIG. 5 is a perspective view showing the appearance of a heating roller.

6 is an enlarged sectional view of an essential part showing the states of an electrode layer, an elastic layer and a resistance layer in a non-nip portion taken along line 6A-6A in FIG. 4 and an electrode in a nip portion taken along line 6B-6B in FIG. FIG. 3 is an enlarged cross-sectional view of a main part showing the states of a layer, an elastic layer and a resistance layer.

FIG. 7 is an electric circuit diagram for driving a heating roller and applying a DC voltage.

8 is a flowchart showing the operation of the microcomputer of FIG.

[Explanation of symbols]

30 ... Heating roller, 31 ... Central axis, 33 ...
Electrode layer, 33a ... Electrode part, 34 ... Elastic layer, 34
a ... through hole, 35 ... resistance layer, 40 ... pressure roller, 50 ... paper, 51 ... toner, 8
0a ... Pressure sensor, 110 ... DC power supply, 120
... Microcomputer, 130 ... Heating roller drive circuit, A ... Nip portion.

Claims (1)

[Claims] 1. A rotary member is rotatably supported by a stationary member, and
A cylindrical insulating elastic layer which is provided substantially concentrically on the rotation shaft and forms a plurality of through holes, and electrodes which are substantially concentrically fitted to the insulating elastic layer and inserted into the through holes, respectively. A heating roller comprising a cylindrical electrode layer having a portion, a cylindrical resistance layer substantially concentrically fitted to the insulating elastic layer so as to face the electrode layer through the insulating elastic layer, and the heating roller. Between the electrode layer and the resistance layer of the heating roller, which is rotatably supported by the stationary member so as to form a nip portion for nipping the sheet under the contact of An electrode layer and a resistance layer corresponding to the nip portion according to elastic deformation of a portion corresponding to the nip portion caused by contact between the heating roller and the pressure roller. Each part of this A thermal fixing device that generates heat necessary for fixing in the nip portion by electrically connecting the corresponding electrode portions to each other, and pressure detecting means for detecting a pressure generated in the nip portion. A thermal fixing device comprising: a control unit that controls the supply of electric power from the electric power supply unit and the driving of the driving unit with respect to the heating roller when the detected pressure becomes abnormal.