JP2010002471A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device wherein induction heating is surely stopped as the rotations of a heat roller and a fixing belt are stopped, and to provide an image forming apparatus. <P>SOLUTION: The fixing device 5 is provided with a generator 80 that is connected to the heat roller 53 that is rotated by a driving force transmitted through a fixing belt 52 stretched to be laid between the heat roller 53 and a fixing roller 51 rotationally driven by a prescribed driving means, for generating the power in accordance with the rotation of the heat roller 53. An IGBT gate drive circuit 72 for switching to input or not to input a switching signal to an IGBT 73 that controls the power supply to the induction coil 54a of an induction heating part 54 is driven by the power generated by the generator 80. Accordingly, in the state where the heat roller 53 is not rotated, the drive of the IGBT gate drive circuit 72 is surely stopped, then, the input of the switching signal to the IGBT 73 is surely stopped. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an induction heating type fixing device and an image forming apparatus including the same, and more particularly to a technique for forcibly stopping induction heating when abnormal heating occurs.

Conventionally, an image forming apparatus such as a printer, a copying machine, a facsimile machine, or a complex machine of these is heated by a fixing belt stretched between a heating roller and a fixing roller, and the fixing belt is pressed against a sheet of paper. A fixing device that melts and fixes toner on paper may be used.
The fixing belt in the fixing device is provided with an induction coil, a magnetic core, or the like that heats the heating roller or the fixing belt by applying an induced current to a rotating heating roller or a part of the fixing belt. An electromagnetic induction heating device is used (see, for example, Patent Document 1). In such a fixing device, when the fixing belt and the heating roller are not normally rotated, the fixing belt and the heating roller may be heated locally and reach an abnormally high temperature.
Therefore, for example, in the fixing device described in Patent Document 1, it is proposed to prevent abnormal heating by stopping the output of the inverter circuit when it is detected that the rotation of the heating roller or the fixing belt is stopped. Yes. Specifically, in Patent Document 1, the output of the inverter circuit is stopped by stopping the input of the pulse signal input to the inverter circuit or by an enable signal for switching the enable / disable of the inverter circuit.
JP 2004-279661 A

However, as disclosed in Patent Document 1, in the configuration in which the output of the inverter circuit is stopped by stopping the pulse signal or enable signal input to the inverter circuit, the rotation of the heating roller or the fixing belt is abnormal. If an abnormality has occurred in the control circuit that outputs the pulse signal or enable signal when it stops, the output of the inverter circuit cannot be stopped, and the safety measures against abnormal heating cannot be said to be perfect. It was.
Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fixing device and an image forming apparatus that can reliably stop induction heating when the rotation of a heating roller or a fixing belt is stopped. Is to provide.

In order to achieve the above object, the present invention provides a fixing roller which is rotationally driven by a predetermined driving means, and a driving force transmitted from the fixing roller via a fixing belt stretched between the fixing roller. A heating roller that is rotationally driven, an induction heating unit that induction-heats the heating roller and / or the fixing belt, a switching unit that controls power supplied to the induction heating unit based on an input switching signal, The present invention is applied to a fixing device comprising switching drive control means for switching presence / absence of input of a switching signal to the switching means, comprising power generation means for generating electric power by rotation of the heating roller, and the switching drive The control means is driven by the power generated by the power generation means, and the switching signal is switched to the switch Configured as a fixing device, characterized in that it is used to input to the means.
According to the present invention, when the power generation means is not generating power, that is, the heating roller rotates due to some abnormality occurring during transmission of driving force from the fixing roller to the fixing belt and the heating roller. Otherwise, the switching drive control means is not driven, and the input of the switching signal to the switching means is surely stopped, so that the heating roller and the fixing belt by the induction heating means are locally Abnormal heating can be reliably prevented and safety can be improved.
Further, it is conceivable that the power generation means supplies power to the switching drive control means when the power generated by the rotation of the heating roller is equal to or higher than a predetermined power set in advance. As a result, even when the rotation speed of the heating roller is not sufficient, the driving of the switching drive control means can be stopped. In addition, an unstable operation of the switching drive control means due to a halfway power supply can be prevented.
By the way, the present invention can also be understood as an image forming apparatus including the fixing device. At this time, the switching means and the switching drive control means may be provided as constituent elements of the image forming apparatus, not as constituent elements of the fixing device. That is, it is only necessary that the above-described components are embodied in the image forming apparatus.

  According to the present invention, when the power generation means is not generating power, that is, the heating roller rotates due to some abnormality occurring during transmission of driving force from the fixing roller to the fixing belt and the heating roller. If not, the switching drive control means does not drive and the input of the switching signal to the switching means is surely stopped, so that the heating roller and the fixing belt by the induction heating means are locally Abnormal heating can be reliably prevented and safety can be improved.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
FIG. 1 is a block diagram showing a schematic configuration of the copying machine X according to the embodiment of the present invention, and FIG. 2 is a block diagram showing a schematic configuration of the fixing device 5 according to the embodiment of the present invention.
First, a schematic configuration of the copying machine X according to the embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 1, a copying machine X according to an embodiment of the present invention includes an operation display unit 1, an image reading unit 2, an image processing unit 3, an image forming unit 4, a fixing device 5, a control unit 6, and the like. In general, it is structured. The copying machine X has various other constituent elements that a general electrophotographic copying machine has, but since these are not different from the conventional ones, description thereof is omitted here. The present invention is not limited to the copying machine X, and can also be applied to, for example, an electrophotographic image forming apparatus such as a printer apparatus, a facsimile apparatus, and a multifunction machine having these functions and a scanner function.

The control unit 6 includes a CPU and peripheral devices such as a ROM and a RAM, and controls the copier X in an integrated manner by executing processing according to a predetermined program stored in the ROM. When the invention is regarded as an invention of the image forming apparatus, a processing function of a CPU 71 of a heating control unit 7 described later provided in the fixing device 5 may be achieved by the control unit 6.
The operation display unit 1 includes a liquid crystal display that displays various types of information according to instructions from the control unit 6, a touch panel for performing operation input to the control unit 6, and the like.
The image reading unit 2 reads an image of a document set on a document table or an ADF (automatic conveyance device), and the image data read by the image reading unit 2 is input to the image processing unit 3. The
The image processing unit 3 performs various operations on image data of a document read by the image reading unit 2 and image data of a document input from an information processing apparatus (not shown) via a communication network such as a LAN. Image processing is performed. The image data that has been subjected to image processing by the image processing unit 3 is input to the image forming unit 4.
The image forming unit 4 includes a photosensitive drum, a charger, a developing device, an LSU, and the like. A toner image (developer) is applied to a sheet based on image data of a document input from the image processing unit 3. To form.
The fixing device 5 melts and fixes the toner image on the paper on which the toner image is formed by the image forming unit 4. The copying machine X according to the embodiment of the present invention is characterized by the configuration and operation related to the fixing device 5 and will be described in detail below.

As shown in FIG. 2, the fixing device 5 includes a fixing roller 51 and a pressure roller that rotate while pressing a sheet conveyed on the sheet conveying path 50 after the toner image is transferred in the image forming unit 4. 51a and a heating roller 53 that is rotationally driven by a driving force transmitted from the fixing roller 51 via a fixing belt 52 stretched between the fixing roller 51, and induction that heats the heating roller 53 An induction heating unit 54 (an example of induction heating means) having a coil 54a and a magnetic core 54b and a heating control unit 7 for controlling the heating operation by the induction heating unit 54 are provided.
The fixing roller 51 is connected to predetermined driving means such as a stepping motor (not shown) that is driven and controlled by a CPU 71 of the heating control unit 7 described later, and is rotationally driven by the predetermined driving means. When the fixing roller 51 is rotationally driven, the fixing belt 52 travels by the driving force, and the heating roller 53 rotates by the driving force transmitted from the fixing belt 52.
The induction coil 54 a and the magnetic core 54 b are formed to have substantially the same width as that of the heating roller 53 in the longitudinal direction, and are arranged to face a part of the outer peripheral surface of the heating roller 53. The heating roller 53 is composed of a magnetic member, whereby a magnetic circuit (magnetic path) is formed between the magnetic core 54 b and the surface of the heating roller 53.
In the fixing device 5, a magnetic flux generated by passing an alternating current through the induction coil 54 a acts on a magnetic circuit formed between the magnetic core 54 b and the heating roller 53, so that the heating roller The heating roller 53 is heated (induction heating) by the eddy current (induction current) generated on the surface of 53. As a result, the fixing belt 52 stretched around the heating roller 53 is heated, and the adhered toner is melted and fixed on the sheet in contact with the fixing belt 52. In the case where the fixing belt 52 is made of a magnetic member, the fixing belt 52 is heated by a magnetic flux acting from the magnetic core 54b.

The heating control unit 7 includes a CPU 71, an IGBT gate drive circuit 72 (an example of switching drive control means), an IGBT 73 (an insulated gate bipolar transistor, an example of switching means), a fixing high temperature detection circuit 74, a protection operation circuit 75, and a relay coil 76. , Relay contact 77, thermistor 78, thermostat 79, generator 80 (an example of power generation means), voltage stabilization circuit 81, and the like.
In the heating control unit 7, the CPU 71 executes predetermined control processing (arithmetic processing) based on a control program and various parameters stored in a ROM or RAM (not shown) to control each component. Is done.
Specifically, when starting the induction heating by the induction heating unit 54, the CPU 71 switches the relay contact 77 by energizing the relay coil 76, thereby providing a direct current (not shown) provided in the fixing device 5. Power supply from the power source (primary power source) to the IGBT 73 is started. The CPU 71 controls the power supplied from the IGBT 73 to the induction coil 54 a of the induction heating unit 54 by inputting a switching signal to the IGBT 73 via the IGBT gate drive circuit 72. The CPU 71 is driven by power supplied from a DC power source (not shown) provided in the copying machine X, and controls the heating operation based on a control instruction from the control unit 6.

The IGBT gate drive circuit 72 includes drive elements such as transistors and IGBTs, and switches whether or not a switching signal input from the CPU 71 is input to the IGBT 73. Specifically, the IGBT gate drive circuit 72 is driven by power supply from a generator 80, which will be described later, to input a switching signal input from the CPU 71 to the IGBT 73, and from the CPU 71 when the drive is stopped. The input of the input switching signal to the IGBT 73 is stopped.
For example, the IGBT gate drive circuit 72 has a collector terminal connected to a power supply path from the generator 80, an emitter terminal connected to the gate terminal of the IGBT 73, and a base terminal connected to a switching signal from the CPU 71. As an example, a transistor, FET, IGBT, or the like is inputted. In this case, in the IGBT gate drive circuit 72, when the power is supplied from the generator 80 to the collector terminal, the switching signal is input to the base terminal, so that the emitter is generated according to the switching signal. A switching signal is input to the IGBT 73 connected to the terminal. On the other hand, when the power from the generator 80 is not supplied to the collector terminal, even if a switching signal is input to the base terminal, the switching signal is not output to the IGBT 73 connected to the emitter terminal.
The drive of the IGBT 73 is controlled based on a switching signal input from the CPU 71 to the gate terminal via the IGBT gate drive circuit 72, and a switching operation of energizing the induction coil 54a of the induction heating unit is performed. The power supplied to the induction coil 54a is controlled. Specifically, the IGBT 73 establishes an energization path of the induction coil 54a from a DC power source (primary power source) (not shown) provided in the fixing device 5 when a current is input to the gate terminal. The IGBT 73 is an example of a switching means, and for example, a switching element such as a transistor or FET may be used.

The thermistor 78 detects the temperature of the fixing belt 52 in the vicinity of the fixing roller 51, and the detected temperature is input to the CPU 71 and the fixing high temperature detection circuit 74. The CPU 71 performs control for maintaining the temperature of the fixing belt 52 at a predetermined fixing temperature by controlling a switching signal output to the IGBT 73 based on the temperature detected by the thermistor 78.
The fixing high temperature detection circuit 74 determines whether the temperature detected by the thermistor 78 has reached a preset abnormal high temperature, and the determination result is input to the protection operation circuit 75. The
The protection operation circuit 75 switches the establishment / cutoff of the input path of the switching signal to the IGBT 73 according to the determination result input from the fixing high temperature detection circuit 74. Specifically, the protection operation circuit 75 inputs a switching signal to the IGBT 73 when the fixing high temperature detection circuit 74 determines that the temperature detected by the thermistor 78 has reached a preset abnormal high temperature. The induction heating is forcibly stopped by blocking the path.
Further, the thermostat 79 is provided in the vicinity of the fixing belt 52 together with the thermistor 78, and operates when the temperature of the fixing belt 52 reaches a preset upper limit temperature, from the primary power source to the IGBT 73. This switch forcibly cuts off the power supply path. In general, the upper limit temperature is set higher than the abnormally high temperature of the fixing high temperature detection circuit 74. That is, the thermostat 79 is provided in order to ensure the minimum safety in the fixing device 5.

Here, in the fixing device 5, safety measures when a high temperature abnormality occurs are taken by the fixing high temperature detection circuit 74, the protection operation circuit 75, the thermostat 79, and the like. Or the temperature of the fixing belt 52 at the position where the thermostat 79 is disposed.
Therefore, in the fixing device 5, slipping or the like occurs between the fixing roller 51 and the fixing belt 52, and the driving force of the fixing roller 51 is not normally transmitted to the fixing belt 52, so that the heating roller 53 When the fixing belt 52 and the heating roller 53 are locally concentrated and heated by the induction heating unit 54 because they are not normally rotated, the heating unit 54 is disposed at a position far from the heating unit. There is a problem that the abnormal heating cannot be detected by the temperature detected by the thermistor 78 or the thermostat 79.

Therefore, in the fixing device 5 according to the embodiment of the present invention, the IGBT gate driving circuit 72 is driven by the power supplied from the generator 80.
The generator 80 is connected to the rotating shaft of the heating roller 53 and generates electric power as the heating roller 53 rotates. The electric power generated by the generator 80 is the voltage stabilizing power source. 81. Note that various known generators may be used for the generator 80.
The voltage stabilization power supply 81 has a smoothing circuit, a filter, and the like, stabilizes the power input from the generator 80 to a predetermined voltage, and then outputs it to the IGBT gate drive circuit 72.
In the fixing device 5 configured as described above, when the heating roller 53 is not driven to rotate for some reason, the generator 80 does not generate power, so that the IGBT gate drive circuit 72 is reliably turned off. The driving state is entered, and the switching signal output from the CPU 71 is not output from the IGBT gate driving circuit 72. Thereby, the power supply to the induction coil 54a of the induction heating unit 54 by the IGBT 73 is forcibly stopped, the abnormal heating of the fixing belt 52 and the heating roller 53 is prevented, and the safety of the fixing device 5 is improved. Secured. That is, in the fixing device 5, when the rotation of the heating roller 53 is stopped, the induction heating of the fixing belt 52 and the heating roller 53 by the induction heating unit 54 can be stopped quickly and reliably. According to such a configuration, in the configuration in which a switch element or the like for switching whether or not to supply power to the IGBT gate drive circuit 72 is provided, the energization to the IGBT gate drive circuit 72 is performed as in the case where the switch element is short-circuited. Can be eliminated.

In addition, the voltage stabilization power supply 81 is provided only when the power generated by the generator 80 is equal to or higher than a predetermined power set in advance as power that can drive the IGBT gate drive circuit 72, for example. Is preferably supplied to the IGBT gate driving circuit 72. At this time, the predetermined power may be set to a power value obtained when the heating roller 53 is rotating normally. As a result, even when the heating roller 53 is in a rotationally driven state but the rotational speed is not sufficient, it is determined that the heating roller 53 is not rotating normally and the IGBT gate driving circuit 72 is driven. Can be stopped. In addition, an unstable operation of the IGBT gate driving circuit 72 due to halfway power supply can be prevented.
Further, if the power generated by the generator 80 is also input to the CPU 71 from the voltage stabilization circuit 81 (broken line in FIG. 2), the voltage stabilization circuit 81 is connected to the CPU 71. It is possible to determine the presence / absence of power generation by the power generator 80 and the amount of power generation, that is, the presence / absence of rotation of the heating roller 53, the rotational speed, and the like based on the input voltage from. Thereby, the CPU 71 performs corresponding processing such as displaying a warning on the operation display unit 1 by transmitting to the control unit 6 that the heating roller 53 is not normally rotated, for example. Is possible.

1 is a block diagram showing a schematic configuration of a copier according to an embodiment of the present invention. 1 is a block diagram showing a schematic configuration of a fixing device according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Operation display part 2 ... Image reading part 3 ... Image processing part 4 ... Image forming part 5 ... Fixing device 51 ... Fixing roller 51a ... Pressure roller 52 ... Fixing belt 53 ... Heating roller 54 ... Induction heating part (induction heating means) Example)
54a ... induction coil 54b ... magnetic core 6 ... control unit 7 ... heating control unit 71 ... CPU
72 ... IGBT gate drive circuit (an example of switching drive control means)
73 ... IGBT (an example of switching means)
74 ... High-temperature fixing detection circuit 75 ... Protection operation circuit 76 ... Relay coil 77 ... Relay contact 78 ... Thermistor 79 ... Thermostat 80 ... Generator (an example of power generation means)
81 ... Voltage stabilization circuit X ... Copier (an example of an image forming apparatus)

Claims (3)

A fixing roller that is rotationally driven by a predetermined driving means; a heating roller that is rotationally driven by a driving force transmitted from the fixing roller via a fixing belt stretched between the fixing rollers; and the heating roller And / or induction heating means for induction heating of the fixing belt, switching means for controlling power supplied to the induction heating means based on an input switching signal, and whether or not a switching signal is input to the switching means. A fixing device comprising switching drive control means for switching,
Comprising power generation means for generating power by rotation of the heating roller;
The fixing device, wherein the switching drive control means is driven by the electric power generated by the power generation means and inputs the switching signal to the switching means.   The fixing device according to claim 1, wherein the power generation unit supplies power to the switching drive control unit when power generated by rotation of the heating roller is equal to or higher than a predetermined power set in advance.   An image forming apparatus comprising the fixing device according to claim 1.

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