JP2006184598A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the possibility of the occurrence of accident in an inductive heating fixing device having a plurality of induction coils, due the possibility of wrong connections of the induction coils in the assembly process thereof. <P>SOLUTION: A resonant circuit, including a drive circuit and the induction coils, is driven by a current of constant electric power, and the wrong connections are detected, by detecting input to the drive circuit at that time. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrophotographic image forming apparatus and a fixing device used in the image forming apparatus, and more particularly to an induction heating type fixing device.

  Conventionally, in an electrophotographic image forming apparatus, a fixing device using a halogen lamp as a heat source has been used. However, in such a fixing device, the temperature of the heat fixing member is increased from a power-on to a temperature capable of fixing. It took a long warm-up time of about several minutes. Therefore, an image forming apparatus that turns on the power supply when performing image formation such as copying or printing waits for several minutes for each image formation, and is extremely inefficient. In order to avoid this, in the conventional image forming apparatus, the power supply of the fixing device is maintained in an on state in a standby state where it is not used.

  However, since the fixing device consumes several hundred watts of power, an image forming apparatus that keeps the fixing device in an always-on state is not desirable from the viewpoint of energy saving, and an improvement is desired.

  As a technique for answering such needs, an induction heating type fixing technique having a feature of a short warm-up time has been developed (for example, Patent Document 1).

In Patent Document 1, a plurality of induction coils are arranged in the axial direction in order to make the temperature distribution in the rotation axis direction of the fixing roller uniform.
JP-A-9-106207

  In a heating induction type fixing device using a plurality of induction coils, for example, an induction coil arranged at the center and an induction coil arranged at the end have different characteristics such as different impedances. However, the induction coil may be misconnected in the assembly process. If it is connected by mistake, the impedance of each induction coil is different and the power to be passed through each coil is different, so that the fixing device does not operate normally, and in some cases, the fixing device is damaged. It becomes.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device that can detect such erroneous connection and prevent malfunction or damage, and an image forming apparatus including the fixing device.

The object is achieved by the following invention.
(Claim 1)
In a fixing device for fixing a toner image by induction heating,
A plurality of induction coils having different impedances;
A drive circuit for supplying a high-frequency current to the induction coil;
An input detection unit for detecting an input of the drive circuit; and
And a control means for operating the resonance circuit having the induction coil and the drive circuit with a predetermined power and outputting an erroneous connection signal when the input detected by the input detection unit at the time of operation is not a predetermined value. A fixing device characterized.
(Claim 2)
The fixing device according to claim 1, wherein the control unit operates the resonance circuit at a predetermined frequency and a predetermined duty ratio when detecting an erroneous connection.
(Claim 3)
3. The fixing according to claim 1, wherein the input detection unit includes a current detection circuit, and the control unit outputs the erroneous connection signal based on a detection current of the current detection circuit. apparatus.
(Claim 4)
3. The fixing according to claim 1, wherein the input detection unit includes a power detection circuit, and the control unit outputs the erroneous connection signal based on detection power of the power detection circuit. apparatus.
(Claim 5)
The fixing device according to claim 1, wherein the control unit stops oscillation of the drive circuit in response to the erroneous connection signal.
(Claim 6)
The fixing device according to claim 1, further comprising a relay that cuts off an input of the driving circuit in response to the erroneous connection signal.
(Claim 7)
An image forming apparatus having the fixing device according to claim 1, further comprising a display unit that displays an erroneous connection based on the erroneous connection signal. .

  According to any one of the first to sixth aspects of the present invention, when the induction coil is erroneously connected, the erroneous connection can be detected prior to the operation, so that the cause of the malfunction of the assembled fixing device is immediately In addition, it is possible to prevent damage to the device that occurs when a misconnected fixing device is operated.

  According to the invention of claim 5 or claim 6, damage to the apparatus that occurs when a misconnected fixing apparatus is operated is completely prevented.

  According to the seventh aspect of the present invention, it is immediately known that there is a misconnection in the fixing device, and accidents such as damage to the device due to misconnection can be prevented.

  FIG. 1 shows a mechanical configuration of an image forming apparatus according to an embodiment of the present invention.

  The image forming apparatus includes an automatic document feeder A, an image reading unit B, and an image forming unit C. In the image forming portion C, reference numeral 1 denotes a photoreceptor, and an organic photoreceptor having a photosensitive layer in which an organic photoconductor is dispersed in a resin is preferable as the photoreceptor from the viewpoints of environment and cost, but is not limited thereto. Any known photoreceptor can be used.

  The photosensitive member 1 is not limited to the drum-shaped photosensitive member illustrated, and may be a belt-shaped photosensitive member. Reference numeral 2 denotes a charging device that charges the photoreceptor 1 and forms a uniform potential on the photoreceptor 1. As the charging device, a scorotron charger having a control grid and a discharge electrode or a contact charging type charger using a roller to which a voltage is applied is preferable.

  Reference numeral 3 denotes an exposure apparatus that exposes the photoreceptor 1. As the exposure apparatus, a scanning exposure apparatus having a scanning optical system composed of a polygon mirror, a lens, and a mirror using a laser diode as a light source, and a scanning optical apparatus having a light emitting diode array and an imaging optical fiber are preferable. Any known exposure apparatus can be used. The exposure device 3 performs dot exposure of the photoreceptor 1 according to the image data.

  A developing device 4 accommodates a two-component developer or a one-component developer, develops an electrostatic latent image on the photoreceptor 1, and forms a toner image on the photoreceptor 1. A transfer device 5 includes a corona charger. The transfer device 5 charges the recording material P with a polarity opposite to that of the toner on the photoreceptor 1, and transfers the toner image to the recording material P. Reference numeral 6 denotes a separation device including a corona charger, which performs AC corona charging on the recording material P to remove the charge from the recording material P and separate it from the photoreceptor 1.

  A fixing device 7 fixes the toner image on the recording material P by induction heating. The heating roller 7A as a heating member, the pressure roller 7B as a pressure member, and an induction coil unit that generates an induction current in the heating roller 7A. 7C. The fixing device 7 will be described later.

  Reference numeral 8 denotes a cleaning, and 9 denotes a paper feeding unit that supplies the recording material P to the transfer unit. The paper feeding unit 9 has a paper feeding tray for storing the recording material P and a paper feeding / conveying unit for feeding the recording material P from the paper feeding tray. Reference numeral 10 denotes a display unit.

  FIG. 2 is a circuit diagram of the fixing device and the image forming apparatus according to the embodiment of the present invention.

  The circuit includes a drive substrate CB1, a main body substrate CB2, and an induction heating unit IH. The power supplied from the AC power supply 71 is input to drive circuits 72A and 72B composed of IGBTs (Insulated Gate Bipolar Transistors) that are switching elements and resonant capacitors, and the drive circuits 72A and 72B use the induction coils 73A and 73B at frequencies. It is driven by a high frequency current of about 5 to 200 kHz. Reference numeral 7A denotes a heating roller as a heating member for heating the toner image, which is made of a heating element that generates Joule heat by an induced current caused by a magnetic field generated by a high frequency current, that is, iron, stainless alloy, nickel, carbon steel, aluminum alloy, or the like. Become.

  The induction coil 73A is disposed at the center of the heating roller 7A, and the induction coil 73B is disposed at both ends of the heating roller 7A. The induction coil 73A and the induction coil 73B have different inductances. 75 is a main body control unit of the image forming apparatus controlled by the CPU, and 76 is a fixing control unit as a control unit controlled by the CPU. 77A is a temperature sensor that detects the temperature of the central portion of the heating roller 7A, and 77B is a temperature sensor that detects the temperature of the end of the heating roller 7A. Reference numeral 78 is a reference voltage power source that is a power source of the fixing control unit 76, and 79 is an input detection unit that detects input current or input power of the drive circuits 72A and 72B, and detects a current detection circuit or input power that detects the input current. Power detection circuit.

  The drive circuits 72A and 72B output high-frequency currents to drive the induction coils 73A and 73B, causing the heating roller 7A to generate heat. The fixing control unit 76 feedback-controls the drive circuits 72A and 72B based on the output of the current / power detection unit 79, and controls the power supplied to the induction coils 73A and 73B. The main body control unit 75 controls the drive circuits 72A and 72B via the fixing control unit 76 based on the outputs of the temperature sensors 77A and 77B, so that the surface of the heating roller 7A has a fixed fixing temperature of about 150 ° C. to 200 ° C. To maintain. The center portion and the end portion of the fixing roller 7A do not always change in temperature. Therefore, the main body control unit 76 controls the drive circuits 72A and 72B separately based on the outputs of the temperature sensors 77A and 77B. An input signal CONT1 to the fixing control unit 76 is a control signal for ON / OFF control of driving of the induction coil 73A, and CONT2 is a control signal for ON / OFF control of driving of the induction coil 73B. The input signal “switching signal” of the fixing control unit 76 is a control signal that causes the induction coil 73A and the induction coil 73B to operate alternately instead of simultaneously. The output CONT3 of the fixing controller 76 controls the drive circuit 72A, and the output CONT4 controls the drive circuit 72B.

  The induction coil 73A is connected to the drive circuit 72A through the connection terminal portion 80A, and the induction coil 3B is connected to the drive circuit 72B at the connection terminal portion 80B. Although the drawing shows a circuit when correct connection is made, in the assembly process, the induction coil 3A may be connected to the drive circuit 2B, and the induction coil 3B3B may be connected to the drive circuit 2B. As shown in the figure, there is a fixing device in which a large number of induction coils and a large number of drive circuits are connected instead of two sets of drive circuits and induction coils, and a combination of a different number of induction coils and drive circuits. Some fixing devices are configured.

  In a fixing device in which a plurality of induction coils are incorporated, the currents to be supplied to the induction coils are not necessarily the same and are often different. Therefore, if the connection between the induction coil and the drive circuit is made by mistake, the device will not operate normally. In addition, when the mismatch between the induction coil and the drive circuit is significant, the circuit may overheat and cause a failure when a current is supplied to the induction coil.

  In the present invention, the following measures are taken to prevent erroneous connection between the induction coil and the drive circuit.

  By driving the resonance circuit composed of the drive circuit 72A and the induction coil 73A and the resonance circuit composed of the drive circuit 72B and the induction coil 73B with a predetermined power, and reading the current or power detected by the input detection unit 79 at that time, Detects misconnection.

  There are an infinite number of combinations of the frequency and duty ratio of the current of constant power flowing through the resonant circuit, but the combination of the frequency and duty ratio that provides constant power is determined in advance.

  At the stage of detecting an erroneous connection, the fixing controller 76 drives the resonance circuit including the drive coil 72A and the induction coil 72A and the resonance circuit including the drive circuit 72B and the induction coil 73B with the determined frequency and duty ratio. In this case, the input detection unit 79 detects the input current or power of the drive circuits 72A and 72B. The input detection unit 79 outputs the detection result as voltage information VOUT.

  The fixing control unit 76 reads the voltage information VOUT, and if the detected current or power matches the value in the case of normal connection, the fixing control unit 76 determines that the circuit connection is normal, and the detected current or power is the normal value. If they are different, it is determined that the induction coils 73A and 73B are connected by mistake, and an erroneous connection signal is output.

  The fixing control unit 76 outputs an erroneous connection signal as the control signal CONT3 or CONT4, and prohibits the operation of the drive circuit 72A or 72B. Further, the fixing control unit 76 outputs an erroneous connection signal ANS to the main body control unit 75, and the main body control unit 75 receives the erroneous connection signal ANS and is erroneously connected to the display unit 10 (shown in FIG. 1) of the image forming apparatus. Display.

  The detection of the erroneous connection described above is performed when the image forming apparatus is activated. That is, before the main switch of the image forming apparatus is turned on and power is supplied from the AC power source 71 to start warming up of the fixing device, the above-described erroneous connection detection step is performed. As the predetermined power for operating the resonance circuit, an appropriate value within the rated power is set. For example, the predetermined power of about ½ of the rated power is set, and the frequency and duty ratio in that case are set. Is set.

  FIG. 3 shows a main part of another example of the fixing device according to the embodiment of the present invention.

  Since this example has the same configuration as that shown in FIG. 2 except for the portion shown in FIG. 3, the illustration of the portion having the same configuration is omitted.

  In FIG. 3, a relay 81 is provided in the AC input unit. The relay 81 is driven by an erroneous connection signal ANS of the fixing control unit 76, and operates when the fixing control unit 76 determines that the connection is incorrect, and interrupts input to the drive circuits 72A and 72B.

1 is a schematic view of an image forming apparatus according to an embodiment of the present invention. 1 is a circuit diagram of an image forming apparatus including a fixing device according to an embodiment of the present invention. It is a figure which shows the principal part of the other example of embodiment of this invention.

Explanation of symbols

72A, 72B Drive circuit 73A, 73B Inductive coil 7A Heating roller 75 Main body control unit 76 Fixing control unit 81 Relay 80A, 80B Connection terminal unit

Claims (7)

In a fixing device for fixing a toner image by induction heating,
A plurality of induction coils having different impedances;
A drive circuit for supplying a high-frequency current to the induction coil;
An input detection unit for detecting an input of the drive circuit; and
And a control means for operating the resonance circuit having the induction coil and the drive circuit with a predetermined power and outputting an erroneous connection signal when the input detected by the input detection unit at the time of operation is not a predetermined value. A fixing device characterized. The fixing device according to claim 1, wherein the control unit operates the resonance circuit at a predetermined frequency and a predetermined duty ratio when detecting an erroneous connection. 3. The fixing according to claim 1, wherein the input detection unit includes a current detection circuit, and the control unit outputs the erroneous connection signal based on a detection current of the current detection circuit. apparatus. 3. The fixing according to claim 1, wherein the input detection unit includes a power detection circuit, and the control unit outputs the erroneous connection signal based on detection power of the power detection circuit. apparatus. The fixing device according to claim 1, wherein the control unit stops oscillation of the drive circuit in response to the erroneous connection signal. The fixing device according to claim 1, further comprising a relay that cuts off an input of the driving circuit in response to the erroneous connection signal. An image forming apparatus having the fixing device according to claim 1, further comprising a display unit that displays an erroneous connection based on the erroneous connection signal. .

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