JP2015068981A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can appropriately stop heating even when a part (center part) of a fixing belt is damaged.SOLUTION: An image forming apparatus includes: image forming means (11) for forming toner images on recording media (P); fixing means (10) for holding and conveying the recording media with an endless fixing belt (16) heated by heating means (40) and a pressure roller (12) to fix unfixed toner formed on the recording media with the image forming means; peeling means (30) for peeling the recording media from the fixing belt; detection means 32 for detecting the movement of the peeling means; and control means (50). When the detection means has detected the movement of the peeling means, the control means stops the heating of the fixing belt by the heating means.

Description

  The present invention relates to an image forming apparatus accompanied by a heat fixing process when an image is formed on recording paper or the like.

In an image forming apparatus such as a copying machine, a facsimile machine, or a multi-function machine using a dry electrophotographic method, an image is generally formed on a surface of a photoconductor using a toner (toner, a fine color developer). After the transfer to the recording paper or the like, the toner is fixed to the recording paper or the like by heating and pressurizing the recording paper or the like.
As a method of heating and pressurizing, a method of heating from the inside of the heating roller with a heater (a halogen lamp that easily transmits heat has been used), a belt is heated with the heating roller, and the belt is pressed with a pressure roller. There are a method of sandwiching the belt, a method of generating heat with an energy efficient IH (Induction Heating), and a method of sandwiching the belt with a pressure roller.

  That is, the fixing process is to bring the molten component of the toner into close contact with the recording paper or the like. At the same time, the molten component of the toner is also fused to the heating belt (heating roller) as described above, and the recording paper or the like is adhered. I will. For this reason, conventionally, such an image forming apparatus has a structure for peeling off a recording paper or the like attached by toner.

JP 2006-171551 A JP 2007-304666 A JP 2008-122431 A JP2012-16883A

For example, Japanese Patent Laid-Open No. 2006-171551 discloses a metal separation for separating the fixing belt and the recording paper at a portion where the recording paper is sandwiched between the pressure roller and the fixing belt (hereinafter referred to as a nip portion). A structure and a manufacturing method of the plate, and Japanese Patent Application Laid-Open No. 2007-304666 show a configuration for enhancing the effect of the separation plate.
Japanese Patent Application Laid-Open No. 2008-122431 discloses the shape of the separation plate, and Japanese Patent Application Laid-Open No. 2012-168383 discloses separation by gas injection.

Now, in a fixing unit using a fixing belt (IH belt), when the fixing belt is torn or damaged, the roller on which the fixing belt is stretched does not rotate. Therefore, in general, a control structure is provided that stops heating when the rotation stop of the stretching roller is detected.
However, for example, when the central portion of the fixing belt is damaged, the stretching roller may continue to rotate. In such a case, since the heating does not stop, the temperature continues to rise.

In such a fixing unit that performs heating and pressure fixing, a temperature detection element such as a thermistor and a position detection element are arranged, and the temperature of each part and the position of the recording paper are predicted so that the recording paper is wound around a roller or the like. JAM (paper jam) such as sticking is detected.
However, there are cases where JAM recording paper cannot be found even during maintenance in the fixing unit, or when the JAM is removed, the recording paper is torn and some of it remains in the fixing unit. As described above, when the central portion of the fixing belt is damaged, if JAM-recorded recording paper or the like remains in the fixing unit, this may overheat, leading to an unexpected accident.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an image forming apparatus capable of appropriately stopping heating even when a part (central portion) of the fixing belt is damaged. It is to provide.

According to the present invention, the image forming unit forms a toner image on the recording medium, and the recording medium is sandwiched and conveyed by an endless fixing belt heated by the heating unit and a pressure roller. An image forming apparatus including a fixing unit that fixes unfixed toner formed on a recording medium, the peeling unit configured to peel the recording medium from the fixing belt, and a detection unit configured to detect movement of the peeling unit. And control means for stopping heating of the fixing belt by the heating means when the movement of the peeling means is detected by the detection means.
The heating means is supplied with high frequency power from a power supply means controlled by the control means, and the fixing belt generates eddy currents by electromagnetic induction generated by the high frequency power supplied to the heating means, It has a conductor layer that can generate heat by the eddy current.

  Thereby, according to the present invention, when a part of the IH fixing belt or the like is damaged in the fixing unit, even if the recording paper or the like remains in the fixing unit, an accident caused by overheating of the recording paper or the like is suppressed. There is an effect that.

FIG. 2 is a block diagram relating to an image forming unit and a fixing unit according to the image forming apparatus of the present invention, and their control, and a diagram showing a relationship between them. FIG. 4 is a view around the nip portion in the present embodiment, and is a diagram illustrating an example of a state in which breakage of the fixing belt is detected. FIG. 5 is a view around the nip portion in the present embodiment, and is a diagram illustrating another example of a state in which breakage of the fixing belt is detected. FIG. 5 is a view around the nip portion in the present embodiment, and is a diagram illustrating another example of a configuration for detecting breakage of the fixing belt.

  Next, embodiments of the present invention will be specifically described with reference to the drawings. The image forming apparatus of the present invention is a copying machine or the like using an electrophotographic (dry electrophotographic) system. In this embodiment, as shown in FIG. 1, an image formed on the surface of a recording sheet P as an example of a recording medium by a toner in an image forming unit 11 as an example of an image forming unit is used as a fixing unit as an example of a fixing unit. 10 is fixed to the recording paper P.

  The image forming unit 11 creates a toner image based on the image data and transfers a transfer drum to the recording paper P, a transport roller for transporting the recording paper P, etc. (None of which is a feature of the present invention. The toner image is formed on the recording surface of the recording paper P taken from the lower part of the image forming unit 11 in FIG. 1, and the recording paper P on which the toner is not fixed is transferred to the fixing unit 10. Transport.

The fixing unit 10 has a structure in which the cylindrical pressure roller 12 is pressed toward the fixing roller 14 at the nip portion N.
At least the outer edge side of the fixing roller 14 is made of an elastic material, and the fixing belt 16 and the recording paper P are sandwiched between the pressure roller 12 and pressed from the pressure roller 12 side. As a result, the fixing belt 16 and the recording paper P are in close contact with each other in the nip portion N.

  The fixing belt 16 is made of a material in which an eddy current is generated by electromagnetic induction and an electric resistance component is generated by the eddy current. The fixing belt 16 is stretched endlessly through the roller 18 and the roller 20 in addition to the fixing roller 14. It rotates in the direction of the chain line arrow. The roller 18 is a tensioner that adjusts the tension of the fixing belt 16.

  The recording paper P is sandwiched between the pressure roller 12 and the fixing roller 14 in a state where the recording surface on which toner is not fixed and the outer surface of the fixing belt 16 face each other, and is heated and pressed. For this reason, the toner as the color former is melted and fixed on the recording paper P (the recording surface thereof). At the same time, the recording paper P adheres to the fixing belt 16 by the melted toner. In order to peel off the stuck recording paper P and the fixing belt 16, a separation plate 30 as an example of a peeling unit is provided in the vicinity of the nip portion N.

  One end (support end) of the separation plate 30 is rotatably supported by a part of the fixing unit 10 by a support member 30a. Further, the separating plate 30 is urged in the direction of arrow A by an elastic member 30b such as a spring fixed to a part of the fixing unit 10, so that the rotation end which is the other end abuts the fixing belt 16. .

In general, in the image forming apparatus as shown in the present embodiment, an image is not formed at the end of the recording surface of the recording paper P in order to facilitate separation of the recording paper P and the fixing belt 16. A margin is provided.
Accordingly, the blank portion of the recording paper P does not stick to the fixing belt 16, so that it floats up from the fixing belt 16 and a gap is formed. The rotating end of the separation plate 30 enters the gap between the recording paper P discharged from the nip portion N and the fixing belt 16, thereby peeling the stuck recording paper P and the fixing belt 16. The recording paper P peeled from the fixing belt 16 in this way is conveyed in the direction of the two-dot chain line arrow.

In the present invention, the separation plate 30 also has a role of detecting breakage of the fixing belt 16. In the fixing unit 10, a photo interrupter 32 as an example of a detecting unit is fixed in the vicinity of the separation plate 30.
In the present embodiment, the photo interrupter 32 is, for example, a reflection type photo interrupter. This irradiates the separating plate 30 with infrared rays or the like emitted by itself, and measures the incident intensity of reflected infrared rays.

  In one separation plate 30, the part irradiated with the infrared rays has a predetermined reflectance. Alternatively, a reflection member having a predetermined reflectance or reflection pattern is attached to the separation plate 30. Accordingly, the amount of reflected infrared light incident on the photo interrupter 32 changes as the separation plate 30 moves or the angle of opposition to the photo interrupter 32 changes.

Another example of the photo interrupter 32 includes a lens that focuses on the light receiving unit when infrared rays or the like emitted by the photo interrupter 32 are reflected by an object at a predetermined distance. That is, if the photo interrupter 32 is fixed at a predetermined distance from the separation plate 30, the reflected infrared rays are not focused on the photo interrupter 32 when the distance to the separation plate 30 changes, and the incident intensity is reduced. Become.
In this way, it can be determined by the photo interrupter 32 that the separation plate 30 has been rotated by a predetermined angle or more.

  In the fixing unit 10 of the present embodiment, an IH coil unit 40 as an example of a heating unit is provided so as to substantially cover a portion where the fixing belt 16 is stretched around the roller 20. The IH coil unit 40 is supplied with high frequency power (alternating current power) having a predetermined frequency and a predetermined current (predetermined power), and generates an eddy current due to electromagnetic induction in an opposing portion of the adjacent fixing belt 16. Is to generate heat.

In the image forming apparatus to which the present invention is applied, for example, a control unit 50 as an example of a control unit is provided outside the fixing unit 10. In general, the IH coil unit 40 includes an inverter 60 for supplying high-frequency power of a predetermined frequency (for example, about 40 kHz).
The inverter 60 as an example of the power supply means includes the oscillation circuit 62 having the above-described predetermined frequency and is supplied with power for driving the IH coil unit 40 (a DC power source or an AC power source may be used). The This power is turned on / off by a switch element 64 such as an IGBT (Insulated Gate Bipolar Transistor) based on the oscillation signal of the oscillation circuit 62, so that power having a predetermined frequency, a predetermined waveform, or a predetermined duty ratio is obtained. Supplied to the IH coil unit 40.

  In the inverter 60 in the present embodiment, for example, an AND gate (logic operation element) 66 is provided between the oscillation circuit 62 and the switch element 64 described above. As a result, the control unit 50 forcibly turns off the switch element 64 by the IH control signal when the photo interrupter 32 detects that the separation plate 30 is displaced by a predetermined angle or more. The high frequency power supplied to 40 is cut off.

Next, the behavior when the fixing belt 16 is damaged will be described with reference to FIG. In FIG. 2, the periphery of the nip portion N shown in FIG.
The fixing belt 16 is continuously or intermittently bent by the fixing roller 14 (nip portion N), the roller 18, and the roller 20, and a force to peel off the recording paper P adhered by the toner is applied, so that the fixing belt 16 deteriorates with time of use. Advances. For this reason, as an example, in FIG. 2, a part of the fixing belt 16 is broken, and the broken portion 16 a is folded and superimposed on the fixing belt 16.

  In this state, when the fixing belt 16 rotates in the direction of the one-dot chain line and the damaged portion 16a passes through the part of the separating plate 30, the damaged portion 16a pushes up the separating plate 30 biased in the direction of arrow A. . Therefore, the separating plate 30 moves (rotates) in the direction of arrow B, and the distance and the facing angle with the photo interrupter 32 change.

  On the other hand, another example when the fixing belt 16 is damaged will be described with reference to FIG. In the example shown in FIG. 3, the damaged portion 16 b becomes a wrinkle and floats from the surface of the fixing roller 14. Also in this example, when the fixing belt 16 continues to rotate in the direction of the one-dot chain line and the damaged portion 16b passes through the part of the separating plate 30, the damaged portion 16b pushes up the separating plate 30 biased in the arrow A direction. . Therefore, the separating plate 30 moves in the direction of arrow B, and the distance and the facing angle with the photo interrupter 32 change.

  The photo interrupter 32 determines that the separation plate 30 has moved in the direction of arrow B based on a change in incident intensity such as reflected infrared rays, and outputs this as a detection signal. The control unit 50 receives the detection signal from the photo interrupter 32, determines that the fixing belt 16 is damaged, and turns off the IH control signal. When the IH control signal is “OFF”, the high frequency power supplied from the inverter 60 to the IH coil unit 40 is cut off, and the heat generation of the fixing belt 16 is stopped.

  FIG. 4 is another example of the separation plate. In the example shown in FIG. 4, the separation plate 31 as another example of the peeling means is sandwiched between the support members 31 a-1 and 31 a-1 and the support members 31 a-2 and 31 a-2 in the direction of arrow C or arrow D. It is slidable. The separation plate 31 is urged from one end by the elastic member 31b in the direction of arrow C, and the other end is normally in contact with the fixing belt 16, but at this time, reflected infrared rays are not incident on the photo interrupter 32. It has become.

  In this example, a part of the fixing belt 16 is damaged in the vicinity of the nip portion N, and the damaged portion 16c jumps to the opposite side to the fixing roller 14 and is folded and is in contact with the other end portion of the separation plate 31. As described above, when the fixing belt 16 continues to rotate in the direction of the one-dot chain line, the separation plate 31 moves in the direction of the arrow D by the force. Thereby, the reflected infrared light enters the photo interrupter 32.

  The photo interrupter 32 determines that the separation plate 31 has moved in the direction of arrow D based on a change in incident intensity such as reflected infrared rays, and outputs this as a detection signal. The control unit 50 receives the detection signal from the photo interrupter 32, determines that the fixing belt 16 is damaged, and turns the IH control signal “OFF”. When the IH control signal is “OFF”, the high frequency power supplied from the inverter 60 to the IH coil unit 40 is cut off, and the heat generation of the fixing belt 16 is stopped.

In this way, in the image forming apparatus of the present invention, it is detected that a part of the fixing belt is broken, and heat generation related to fixing is appropriately blocked. This avoids a failure that may be caused by overheating of each part of the fixing unit and the recording paper due to breakage of the fixing belt.
Note that the present invention is not limited to the above-described embodiments, and it is obvious that the embodiments can be appropriately changed within the scope of the technical idea of the present invention.
Further, the number, position, shape, and the like of the constituent members are not limited to the above-described embodiment, and can be set to a number, position, shape, and the like that are suitable for carrying out the present invention. In each figure, the same numerals are given to the same component.

DESCRIPTION OF SYMBOLS 10 Fixing unit 11 Image forming unit 12 Pressure roller 14 Fixing roller 16 Fixing belt 30, 31 Separation plate 32 Photo interrupter 40 IH coil unit 50 Control part 60 Inverter 62 Oscillation circuit 64 Switch element P Recording paper

Claims (2)

Image forming means for forming a toner image on a recording medium;
A fixing unit that fixes the unfixed toner formed on the recording medium by the image forming unit by sandwiching and transporting the recording medium by an endless fixing belt heated by a heating unit and a pressure roller. An image forming apparatus,
Peeling means for peeling the recording medium from the fixing belt;
Detecting means for detecting movement of the peeling means;
An image forming apparatus comprising: a control unit that stops heating of the fixing belt by the heating unit when the detection unit detects the movement of the peeling unit. The heating means is supplied with high frequency power from a power supply means controlled by the control means,
The image forming apparatus according to claim 1, wherein the fixing belt has a conductor layer that generates eddy current by electromagnetic induction generated by the high-frequency power supplied to the heating unit and can generate heat by the eddy current. apparatus.

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