JP4257171B2 - Fixing device and image forming apparatus using the same - Google Patents

Description

The present invention relates to a fixing device employing an electromagnetic induction heating method and an image forming apparatus using the same, which are used in image forming apparatuses such as copying machines, facsimiles, and printers.

  In recent years, there has been an increasing demand for speeding up image forming apparatuses such as copying machines, and as one means for achieving this, fixing having a heating means for heating a belt having heat generation by electromagnetic induction by electromagnetic induction. A device has been proposed.

  Such a fixing device that performs electromagnetic induction heating is a form in which a heating element of a thin belt having heat generation is directly heated by electromagnetic induction by using an eddy current generated by electromagnetic induction. It is said that the heat conversion efficiency is high and the temperature of the fixing roller can be rapidly raised to the fixing temperature with less power.

  By the way, among fixing devices that perform electromagnetic induction heating, an electromagnetic induction heating means is provided on the outside of the roller or belt, and a structure that heats about a half circumference of the roller of the belt wound around the roller locally (for example, Patent Document 1). In the reference), it is necessary to start the electromagnetic induction heating in a state where the belt is rotated. When electromagnetic induction heating is started in a state where the belt is not rotating, the portion of the belt facing the electromagnetic induction heating means is locally heated, and the temperature of the portion rises abnormally, resulting in smoke generation or belt melting. This is to prevent this.

  For that purpose, means to detect the rotation of the belt is necessary, but in the past, instead of directly detecting the rotation, the rotation of the roller and other rollers that wrap around the belt is detected and used as a substitute for belt rotation detection. I was trying. However, in such a detection method, the belt and the roller around which it is slipped slip, and even if the roller is rotating but the belt is stopped, it is erroneously detected that the belt is rotating. become.

Therefore, a technique has been proposed in which at least one detection hole is provided in the belt and this is detected by a transmission type sensor (see, for example, Patent Document 2). There is also known a reflection type sensor instead of a transmission type sensor, in which a reflection part for detection is provided on a belt, and rotation is detected by the reflection.
JP 11-297462 A JP 2002-40839 A

  However, in the detection using light, the sensor has to be arranged in the vicinity of the heating element, and it is difficult to satisfy the use temperature condition of the sensor, and development of a different detection method has been desired. In addition, opening a hole in the belt as in the technique disclosed in Patent Document 2 has a problem such as a decrease in strength, and the belt is sandwiched between tension applied by a roller or a pressure roller. In view of the applied pressure, it is not very desirable, and improvement of this point has been desired.

  The present invention has been made in view of the above-described conventional problems, and in an electromagnetic induction heating type fixing device, it is possible to detect rotational running without using a photosensor and without providing a hole or the like in the belt. It is an object of the present invention to provide an image forming apparatus using the same.

Fixing device according to claim 1 of the present invention, an electromagnetic induction heating means, and a belt having a heat generating layer which generates heat Ri by the electromagnetic induction on a substrate, a fixing roller that the belt is Kai over, the fixing roller in the fixing device and a pressure roller for pressing through the belt and the belt is not the end of the detected portion, wherein the heat generating layer on said substrate is not provided in the axial direction of the fixing roller It has at least one or more locations in the image area, and includes an infrared temperature sensor that is not in contact with the belt and detects rotation of the belt by detecting the detected portion.

Fixing device according to the claim 2 is the fixing device according to claim 1, comprising a support roller which the belt together with the fixing roller is Kai over, the electromagnetic induction heating means, the outer peripheral surface of the support rollers closely be arranged, characterized in Rukoto.

The fixing device according to claim 3 is the fixing device according to claim 1 , wherein the belt is wound around the fixing roller without using another roller, and the fixing roller connects the pressure roller and the belt . It is characterized by being pressed through .

Temperature fixing apparatus according to the claim 4, in the fixing device according to any one of claims 1 to 3, wherein the infrared temperature sensor which detects the infrared temperature sensor while detecting the rotational travel of the belt It characterized that you control the energization of the electromagnetic induction heating means based on.

Fixing device according to the claim 5 is the fixing device according to any one of claims 1 to 4, wherein the infrared temperature sensor, wherein the Oh Rukoto thermopile.

An image forming apparatus according to claim 6 includes the fixing device according to any one of claims 1 to 5 .

  The present invention relates to a fixing device having a heating means for heating a belt by electromagnetic induction, and is not influenced by ambient temperature conditions as in an optical sensor, and is structured as a belt such as a hole for detecting rotational running on the belt. There is an effect that it is possible to detect rotational running without providing a portion that impairs uniformity.

  The best mode for carrying out the present invention will be described below with reference to the embodiments shown in the drawings.

  FIG. 1 is a schematic cross-sectional view of an embodiment of an image forming apparatus including a fixing device according to the present invention. In the figure, 1 is an image carrier, 2 is a charging means, 3 is a laser writing unit, 4 is a developing device, 5 is a transfer roller, and 6 is a cleaning device. In the figure, reference numeral 7 denotes a paper feed unit, 8 denotes a paper feed roller, 9 denotes a registration roller pair, 10 denotes a fixing device, 11 denotes a paper discharge unit, and 12 denotes an image forming apparatus main body.

  The image carrier 1 is rotationally driven in the direction of the arrow in the figure by a driving unit (not shown), the surface of the image carrier 1 is uniformly charged by the charging unit 2, and then a latent image is formed on the surface by exposure from the laser writing unit 3. The latent image is visualized by the developing device 4 and the toner image is transferred by the transfer device 5 to a transfer body P such as paper supplied from the paper supply unit 7 via the paper supply roller 8 and the registration roller pair 9. . The toner remaining on the surface of the image carrier 1 after the transfer of the toner image is removed by the cleaning device 6.

  The transfer body P to which the image has been transferred is introduced into the fixing device 10, the toner image is fixed to the transfer body P by heating and pressurization, and then discharged to the paper discharge unit 11. Of course, the present invention is not limited to the illustrated image apparatus, and can be applied to various types.

  FIG. 2 is a schematic sectional view (A) and an enlarged side view (B) showing an embodiment of the fixing device according to the present invention. The fixing device 10 is wound around the support roller 21, the fixing roller 22 arranged so that the axis of the support roller 21 is parallel to the support roller 21, and the electromagnetic induction of the induction heating means 20. An endless heat generating belt 23 heated by heat, a pressure roller 24 that rotates in pressure contact with the fixing roller 22 via the heat generating belt 23, and a thermopile 30 for detecting the rotation of the heat generating belt 23. It is. In the figure, reference numeral 40 denotes a temperature sensor, which is disposed in the vicinity of the nip portion N so that the temperature in the vicinity of the nip portion N can be detected. Note that one of the support roller 21 and the fixing roller 22 is driven to rotate by a motor or the like so that the heat generating belt 23 is driven by the rotating roller. However, since this type of configuration is well known, the illustration is omitted.

  FIG. 3 is a cross-sectional view (A) and a side view (B) showing the configuration of the induction heating means 20. The induction heating means 20 heats the heat generating belt 23 by electromagnetic induction, and includes an excitation coil 25 that is a magnetic field generation means, a coil guide plate 26 around which the excitation coil 25 is wound, and an excitation coil 25 that is not shown. An exciting coil core made of a ferromagnetic material such as ferrite disposed on the outside and an exciting coil core support member for fixing and supporting the exciting coil core. The excitation coil 25 is connected to a driving power supply (not shown) (for example, an oscillation circuit whose frequency is variable).

  The coil guide plate 26 has a semi-cylindrical shape arranged close to the outer peripheral surface of the support roller 21, and the excitation coil 25 is formed by passing one excitation coil wire along the coil guide plate 26 as shown in FIG. Thus, a so-called “kura” shape is wound alternately in the axial direction of the support roller 21. A magnetic field is generated in a direction perpendicular to the axis of the coil, and the heat generating belt 23 is heated by electromagnetic induction. The coil is wound in an area that substantially covers the half circumference of the support roller 21 where the heat generating belt 23 and the support roller 21 are in contact with each other, so that the area of the heat generating belt 23 that performs electromagnetic induction heating can be made as large as possible to increase the heating efficiency. It is.

  The support roller 21 has a heat insulating property, for example, a heat insulating material such as ceramic, a heat insulating material in which a balloon (hollow body) such as phenol resin or glass is dispersed and mixed in a super engineering plastic, or a silica-made material. It is preferable to use a cylindrical material made of a low thermal conductivity material or the like. This is because the heat transfer from the heat generating belt 23 is substantially blocked by the heat insulating or low heat conductive material. However, the support roller 21 may be made of a magnetic metal member such as iron, cobalt, nickel, or an alloy thereof, and the support roller 21 may be induction-heated by the induction heating means 20 as well as the heat generating belt 23. .

  The fixing roller 22 is configured by, for example, using a metal core such as stainless steel as a metal heat generating layer and coating a heat-resistant silicone rubber in a solid or foamed form. The pressure roller 24 is configured by providing an elastic member having high heat resistance and high toner releasability on the surface of a metal core made of a cylindrical member made of a metal having high thermal conductivity such as copper or aluminum. In addition to the above metal, SUS or the like can be used for the core metal. The fixing roller 22 and the pressure roller 24 are pressed against each other via the heat-resistant belt 23 to form a nip portion N for fixing the transfer body P and the toner T thereon by heating and pressurization. The structure is thick.

  The heat generating belt 23 wound between the support roller 21 and the fixing roller 22 has a base material (metal heat generating layer) made of a magnetic metal such as iron, cobalt, nickel, or an alloy thereof, and the surface thereof is a silicone rubber. Or a composite layer belt formed by covering with a release layer made of an elastic member such as fluorine rubber. For example, nickel electroforming with a thickness of 40 μm is applied to the base material, and the upper layer is covered with a release layer such as an elastic layer or Teflon (registered trademark), or a multilayer metal heating layer is provided on the polyimide layer. Various composite belt materials such as those provided with an elastic layer and a release layer can be used.

  As is well known, the thermopile 30 is an infrared sensor and is a non-contact sensor, which is configured by connecting many thermocouples in series. The infrared ray emitted from an object is transmitted by an optical system such as a lens. When the light is collected and infrared rays are incident on the thermopile light-receiving part (hot junction), a temperature difference is generated between the hot junction and the cold junction according to the amount of incident infrared rays, and a thermoelectromotive force corresponding to the difference is generated. . Such a thermopile 30 can be detected even if it is, for example, about 60 mm away from the surface of the heat generating belt 23 that is a heat source, and heat countermeasures are easier than an optical sensor.

  As a temperature detection target of the thermopile 30, in the vicinity of the edge of the heat generating belt 23, a portion (hereinafter referred to as a detected portion) 31 where no metal heat generating layer is provided is provided at an appropriate interval in the circumferential direction. FIG. 4 is a conceptual plan view showing how to provide the detected portion 31 on the heat generating belt 23. FIG. 4A shows a case where a metal layer is provided on the entire heat generating belt 23 (the hatched portion 23a in the drawing is a portion where the metal layer is present), and the portion without the metal heat generating layer is individually formed in the vicinity of the edge, in other words, an island shape. An example is shown in which a plurality of parts are formed in the form of notches, and these are used as detected parts 31. FIG. 4B shows an example in which a portion without the metal heat generating layer is provided in a form including the edge of the heat generating belt 23 and the island-shaped detected portions 31 are continuously arranged. Further, FIG. 4 (C) shows a portion 23b without a belt-like metal heat generating layer including the edge of the heat generating belt 23 and the vicinity thereof, and a portion 23c having a metal layer in the portion 23b without the metal heat generating layer is formed as an island. An example is shown in which a portion to be detected 31 is formed between a portion 23c where a plurality of adjacent metal layers are formed. Of course, the detected part of the present invention may be other than the forms of these examples. Such a detected part 31 is naturally different in temperature from other parts. The size and arrangement interval of the detected parts 31 may be set as appropriate in consideration of the specifications of the image forming apparatus and the fixing apparatus, the specifications of the thermopile 30 and the processing means for the output signal, and the like.

  Therefore, if the support roller 21 or the fixing roller 22 is rotationally driven, and the heat generating belt 23 travels in a required state, the detected portion 31 sequentially passes through the detection portion by the thermopile 30. Correspondingly, the detected value of the thermopile 30 indicates a low value or a high value, so that the rotational running of the heat generating belt 23 can be detected. The rotational traveling speed of the heat generating belt 23 can also be detected by the arrangement form of the detected parts 31 and the detection value processing of the thermopile 30.

  Of course, it is necessary to set so that the change in output value is larger than the change due to noise. Even if only one detected part 31 is provided, the output value of the thermopile 30 changes at a certain time interval, so that the rotational running of the heat generating belt 23 can be detected.

  It should be noted that the part where the detected part 31 is provided is preferably a non-image forming region such as a part near the edge of the heat generating belt 23. Further, both the temperature and the rotational traveling detection can be performed by using only one thermopile 30, but two or more thermopiles can be used to perform the temperature detection and the rotational traveling detection separately. In this case, a thermopile can be used instead of the temperature sensor 40 for detecting the temperature of the nip portion N described above. Of course, two or more thermopile can be configured to detect both temperature and rotational travel.

  The operation of the fixing device of this embodiment will be described with reference to the flowchart of FIG. 5 assuming that the image forming apparatus of FIG. 1 is a printer. When the printer receives a print start signal, it first sends a motor ON signal to the fixing drive motor (S1). Next, it is confirmed whether the heat generating belt 23 is rotating based on the detection result of the detected portion 31 by the thermopile 30 (S2). Energization is started to start electromagnetic induction heating (S3). If the rotation state of the heat generating belt 23 cannot be confirmed, it is detected as an error (S10) and the printing operation is cancelled.

  If heating is started in step S3, it is determined whether the temperature of the heat generating belt 23 detected by the temperature sensor 40 has reached the printing start temperature (S4). If it has reached, the heat generating belt 23 is controlled at the control temperature. The printing is started (S5). If the print start temperature is not reached within a predetermined time, an error is detected (S11), and the print operation is canceled. By detecting this error, it can be seen that there is a possibility of malfunction such as rotation stop of the heat generating belt 23, abnormality of the temperature sensor 40, and abnormality of the induction heating means 20. Of course, the slip of the heat generating belt 23 can be detected by the detection mode of the detected portion 31 of the heat generating belt 23 by the thermopile 30. Various known methods may be used for slip detection.

  When printing is finished (S6), the induction heating means 20 is turned off (S7), the temperature of the heat generating belt 23 is detected by the temperature sensor 40, and the detected temperature reaches a predetermined drive stop temperature. Whether or not (S8). If the detected temperature reaches the drive stop temperature, a motor OFF signal is sent to the fixing drive motor (S9), and the printing operation is terminated. Further, if the drive stop temperature is not reached within a predetermined time, since the energization to the induction heating means 20 may not be turned off, it is detected as an error (S12), and the steps described above Returning to S7, the subsequent steps are repeated.

  That is, when the rotation state of the heat generating belt 23 cannot be confirmed, or when an abnormality in the rotation state is detected, it is detected as an error. In such a state, the heat generating belt 23 is continuously heated by the induction heating means 20 to generate heat. It is possible to avoid a situation in which the temperature of the belt 23 is abnormally increased.

  The present invention is not limited to the fixing device of the type shown in the figure as long as the heating roller and the heating belt are heated from the outside, and one piece is used without using a pair of rollers to wrap around the heating belt. The present invention can also be applied to an apparatus in which a heat generating belt is hung around a roller to directly form a nip portion together with a pressure roller, and overheating of these types of fixing devices can be prevented.

1 is a schematic cross-sectional view of an embodiment of an image forming apparatus including a fixing device according to the present invention. 1A and 1B are a schematic cross-sectional view (A) and an enlarged side view (B) showing an embodiment of a fixing device according to the present invention. It is sectional drawing (A) which shows the structure of an induction heating means, a side view (B), and an expanded sectional view (C). It is a conceptual top view which shows how to provide the to-be-detected site | part to a heat generating belt. 3 is a flowchart illustrating an operation of an embodiment of a fixing device according to the present invention.

Explanation of symbols

1: image carrier 2: charging means 3: laser writing unit 4: developing device 5: transfer roller 6: cleaning device 7: paper feeding unit 8: paper feeding roller 9: registration roller pair 10: fixing device 11: paper ejection unit 12: Image forming apparatus body 20: Induction heating means 21: Support roller 22: Fixing roller 23: Heat generating belt 24: Pressure roller 25: Excitation coil 26: Coil guide plate 27: Excitation coil core 28: Excitation coil core support member 30: Thermopile 31: Detected part 40: Temperature sensor P: Transfer body T: Toner

Claims (6)

Electromagnetic induction heating means;
A belt having a heat generating layer which generates heat Ri by the electromagnetic induction on a substrate,
A fixing roller that the belt is Kai over,
A pressure roller in pressure contact with the fixing roller via the belt ;
In a fixing device comprising:
The belt has at least one detected portion where the heat generation layer is not provided on the base material in a non-image region at one end in the axial direction of the fixing roller ,
Fixing device characterized by comprising an infrared temperature sensor of the belt and a non-contact for detecting the rotation travel of the belt by detecting the該被detection site. The fixing device according to claim 1,
A supporting roller which said belt is Kai over together with the fixing roller,
It said electromagnetic induction heating means, the fixing device characterized that you have placed close to the outer peripheral surface of the support rollers. The fixing device according to claim 1 ,
A fixing device , wherein the belt is wound around the fixing roller without using another roller, and the fixing roller is in pressure contact with the pressure roller via the belt. The fixing device as claimed in any one of claims 1 to 3,
The infrared temperature sensor, a fixing device which is characterized that you control the energization of the electromagnetic induction heating means based on the detected temperature of the infrared temperature sensor while detecting the rotational travel of the belt. In the fixing device according to any one of claims 1 to 4 ,
The infrared temperature sensor, a fixing device according to claim Oh Rukoto thermopile. An image forming apparatus comprising the fixing device according to any one of claims 1 to 5.

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