JP2010078951A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device with reduced possibility of being damaged by preventing over-current. <P>SOLUTION: The fixing device 23 starts supply of a voltage by a voltage supply section 28 (S12). Then, the fixing device determines whether the detected supply voltage exceeds 100 V or not (S13). If determining that the supply voltage exceeds 100 V (YES in S13), the fixing device exerts control so that an output power has a constant value (S14). Meanwhile, if determining that the supply voltage is below 100 V (NO in S13), the fixing device exerts control so that the output power has a proportional relation with the supply voltage (S15). <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a fixing device and an image forming apparatus, and more particularly to a fixing device including a heating unit that heats a heat roller by induction heating and an image forming apparatus including such a fixing device.

  A general digital multi-function peripheral is provided with a fixing device that fixes toner onto a sheet. The fixing device includes a heat roller and a pressure roller in contact with the heat roller. The digital multi-function peripheral forms a visible image with toner on a photoconductor and then transfers the image onto a sheet. Then, the toner image is fixed on the sheet by the heat roller heated to a predetermined temperature and the pressure roller in contact with the heat roller.

The fixing device is provided with a heating device that heats the heat roller so as to keep the heat roller at a predetermined temperature. Here, induction heating type heating devices are widely used because they can control the temperature of the heat roller relatively efficiently. Japanese Unexamined Patent Publication No. 11-126678 (Patent Document 1) discloses a technique related to an induction heating type heating apparatus using an exciting coil. According to Japanese Patent Laid-Open No. 2004-260688, appropriate power feeding is performed by variably controlling the on time and off time of power feeding to the exciting coil according to the detected temperature information of the heat roller. In this way, universalization between different commercial power supply voltages is rationally achieved.
JP 11-126678 A

  In the technology disclosed in Patent Document 1, the output power output from the heating means is controlled by changing the on time and off time of power feeding to the exciting coil in accordance with the detected temperature information of the heat roller. Here, the following problems arise when performing control to keep the output power constant. That is, when control is performed to keep the output power constant, if the power supply voltage at the time of power supply decreases rapidly, a current excessively flows in the circuit including the heat roller. Such a state in which an overcurrent flows is very dangerous, and there is a possibility that the device or the like may be damaged.

  An object of the present invention is to provide a fixing device that can prevent the occurrence of overcurrent and reduce the risk of breakage.

  Another object of the present invention is to provide an image forming apparatus that can reduce the risk of breakage.

  A fixing device according to the present invention is a fixing device that fixes toner on a sheet, and includes a heat roller, a heating unit that heats the heat roller by induction heating, a voltage supply unit that supplies a voltage to the heating unit, and a voltage supply Detection means for detecting the supply voltage by the means, and control means for controlling the output power output to the heating means based on the detection result by the detection means.

  Preferably, the detection unit includes a determination unit that determines whether or not the supply voltage exceeds a predetermined value.

  More preferably, the control unit controls the output power to be a constant value when the determination unit determines that the supply voltage exceeds a predetermined value.

  The control means may control the output power so as to maintain a proportional relationship with the supply voltage if the determination means determines that the supply voltage does not exceed a predetermined value.

  In another aspect of the present invention, an image forming apparatus includes: an image forming unit that forms an image with toner; and any one of the above-described fixing devices that fixes an image formed by the toner formed by the image forming unit on a sheet. Is provided.

  According to this invention, the supply voltage supplied to the heating means by induction heating is detected, and the output power is controlled based on the detection result. As a result, the output power can be appropriately controlled according to the supply voltage, and even when the supply voltage rapidly decreases, it is possible to prevent an overcurrent from flowing in the circuit. Therefore, the occurrence of overcurrent can be prevented and the risk of breakage can be reduced.

  Such an image forming apparatus also includes a fixing device that can prevent the occurrence of overcurrent and reduce the risk of breakage, so that the risk of breakage can be reduced.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of a digital multifunction peripheral 10 when an image forming apparatus including a fixing device according to an embodiment of the present invention is applied to the digital multifunction peripheral 10. Referring to FIG. 1, a digital multifunction device 10 includes a CPU, a control unit 11 that controls the entire digital multifunction device 10, a DRAM 12 for writing and reading image data and the like, and a digital multifunction device 10. An operation unit 13 that serves as an interface with the user in the digital multifunction peripheral 10, a document feeder 14 that automatically transports a document to a predetermined document reading position, and a document feeder 14. An image reading unit 15 that reads an image of the conveyed document at a predetermined reading position, an image forming unit 16 that forms the image from the document read by the image reading unit 15, and a hard disk 17 that stores image data and the like. A FAX communication unit 18 connected to the public line 20 and a network IF (interface) for connecting to the network 21. ) And a section 19.

  The image forming unit 16 includes a transfer unit (not shown) that transfers an image of toner formed on a photoreceptor (not shown) to a sheet. In addition, the digital multifunction machine 10 includes a fixing device 23 that fixes the toner transferred onto the paper by the transfer unit onto the paper. That is, the digital multi-function peripheral 10 includes a fixing device 23 that fixes an image formed by the toner formed by the image forming unit 16 onto a sheet. The details of the fixing device 23 will be described later.

  The control unit 11 compresses and writes the original data output from the image reading unit 15 in the DRAM 12, reads the data written in the DRAM 12, decompresses and encodes the data, and outputs it by the image forming unit 16.

  The digital multi-function peripheral 10 operates as a copier by forming an image in the image forming section 16 via the DRAM 12 using the document read by the image reading section 15. Further, the digital multifunction peripheral 10 forms an image in the image forming unit 16 via the DRAM 12 using the image data transmitted from the personal computer 22 connected to the network 21 through the network IF unit 19, thereby serving as a printer. Operate. Further, the digital multifunction peripheral 10 forms an image in the image forming unit 16 through the DRAM 12 using the image data transmitted from the public line 20 through the FAX communication unit 18, and also by the image reading unit 15. The image data of the read original is transmitted to the public line 20 through the FAX communication unit 18 to operate as a facsimile machine.

  In FIG. 1, thick arrows indicate the flow of image data, and thin arrows indicate the flow of control signals or control data.

Here, details of the fixing device 23 will be described. FIG. 2 is a schematic cross-sectional view showing the main part of the fixing device 23. With reference to FIGS. 1 and 2, the fixing device 23 includes a cylindrical heat roller 24 that is heated to a predetermined temperature suitable for fixing, and a cylindrical pressure roller 25 that contacts the heat roller 24. The pressure roller 25 has elasticity. The heat roller 24 and the pressure roller 25 are in contact with each other so as to nip at a predetermined pressure. The part which is niped in the area | region 26 in FIG. 2 is shown. At the time of fixing, the heat roller 24 and the pressure roller 25 rotate in the directions indicated by arrows A ₁ and A ₂ in FIG.

  The fixing device 23 conveys the sheet on which the toner image is transferred from the image forming unit 16 in the direction indicated by the arrow B in FIG. Supply. Then, the toner is fixed on the sheet by the heat roller 24 and the pressure roller 25 heated to a predetermined temperature suitable for fixing.

  The fixing device 23 detects a voltage supplied by a heating device 27 as a heating unit that heats the heat roller 24, a voltage supply unit 28 as a voltage supply unit that supplies a voltage to the heating device 27, and a voltage supply unit 28. And a voltage detection unit 29 as detection means. The heating device 27 is indicated by a one-dot chain line in FIG. The heating device 27 is provided on the inner side of the cylindrical heat roller 24. A circuit is formed by the heating device 27 and the voltage supply unit 28.

  Further, the fixing device 23 includes a thermistor (not shown) as temperature detecting means for detecting the temperature of the heat roller 24. The thermistor is provided so as to contact a part of the surface of the heat roller 24. The heat roller 24 is controlled to be maintained within a predetermined temperature range by heat supplied from the heating device 27 at the time of fixing. The pressure roller 25 is also heated by heat transfer from the contacting heat roller 24.

  The heating device 27 includes an exciting coil 30 therein. The heating device 27 causes the exciting coil 30 to generate heat by induction heating with output power corresponding to the supply of voltage from the voltage supply unit 28. The heat roller 24 is heated by this heat generation.

  Here, the control unit 11 includes control means for controlling the output voltage output to the heating device 27 based on the detection result of the supply voltage by the voltage detection unit 29. The voltage detection unit 29 includes a determination unit that determines whether or not the supply voltage from the voltage supply unit 28 exceeds a predetermined value.

  Next, the case where the output power is controlled in the digital multi-function peripheral 10 according to one embodiment of the present invention will be described. FIG. 3 is a flowchart showing the operation in this case. FIG. 4 is a graph showing the relationship between the supply voltage supplied by the voltage supply unit 28 and the output power. In FIG. 4, the vertical axis represents output power (W), and the horizontal axis represents supply voltage (V). In this embodiment, the maximum output power is 1300 W, and the supply voltage at this time is 100 V. Further, the predetermined value of the supply voltage is set to 100 V corresponding to the maximum output voltage.

  With reference to FIGS. 1 to 4, first, image formation is started in response to a user request. (In FIG. 3, step S11, hereinafter, steps are omitted). Here, the fixing device 23 starts supply of voltage by the voltage supply unit 28 (S12). Then, the supply voltage is detected by the voltage detector 29, and it is determined whether or not the supply voltage exceeds 100V (S13). Here, the control unit 11 operates as a determination unit. If it is determined that the detected supply voltage exceeds 100 V (YES in S13), control is performed so that the output power becomes a constant value (S14). In this case, as shown by the line 31a shown in FIG. 4, the output power is controlled to be a maximum value of 1300 W as a constant value. On the other hand, if it is determined that the detected supply voltage does not exceed 100 V (NO in S13), control is performed so that the output power is proportional to the supply voltage (S15). In this case, the output power is controlled so as to maintain the relationship of output power P = a × supply voltage + b as indicated by a line 31b shown in FIG. Here, a and b are arbitrary constants. In the case shown in FIG. 4, a = 13 and b = 0.

  In this way, the output power is controlled until the voltage supply is stopped and the image formation is completed (S16, S17).

  With this configuration, it is possible to appropriately control the output power according to the supply voltage, and it is possible to prevent an overcurrent from flowing in the circuit even when the supply voltage rapidly decreases. Therefore, it is possible to prevent the occurrence of overcurrent and reduce the possibility of the fixing device 23 being damaged.

  In addition, since the digital multifunction machine 10 includes the fixing device 23 that can prevent the occurrence of overcurrent and reduce the risk of breakage, the risk of breakage can be reduced.

  In the above embodiment, the heat roller is heated by the heating device including the exciting coil. However, the present invention is not limited to this, and the heat roller is heated using other heating means employing an induction heating method. You may decide.

  In the above embodiment, if it is determined that the supply voltage does not exceed the predetermined value, the output power is controlled to maintain a proportional relationship with the supply voltage. If it is determined that the voltage does not exceed a predetermined value, the output voltage may be controlled to change stepwise according to the supply voltage. For example, if the supply voltage is 80 V to 100 V, the output power is controlled to be 1200 W, and if the supply voltage is 60 V to 80 V, the output power is controlled to be 1100 W.

  In the above embodiment, the fixing device is controlled by the control unit included in the digital multi-function peripheral. However, the present invention is not limited to this, and the fixing device has its own control unit. The entire fixing device may be controlled.

  As mentioned above, although embodiment of this invention was described with reference to drawings, this invention is not limited to the thing of embodiment shown in figure. Various modifications and variations can be made to the illustrated embodiment within the same range or equivalent range as the present invention.

1 is a block diagram illustrating an overall configuration of a digital multi-function peripheral including a fixing device according to an embodiment of the present invention. 1 is a schematic cross-sectional view showing a main part of a fixing device according to an embodiment of the present invention. It is a flowchart which shows the operation | movement in the case of controlling output electric power. It is a graph which shows the relationship between output electric power and supply voltage.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Digital multifunction device, 11 Control part, 12 DRAM, 13 Operation part, 14 Document feeder, 15 Image reading part, 16 Image formation part, 17 Hard disk, 18 FAX communication part, 19 Network IF part, 20 Public line, 21 Network , 22 PC, 23 fixing device, 24 heat roller, 25 pressure roller, 26 area, 27 heating device, 28 voltage supply unit, 29 voltage detection unit, 30 excitation coil, 31a, 31b wire.

Claims (5)

A fixing device for fixing toner on paper,
A heat roller;
Heating means for heating the heat roller by induction heating;
Voltage supply means for supplying a voltage to the heating means;
Detection means for detecting a supply voltage by the voltage supply means;
And a control unit that controls output power output to the heating unit based on a detection result of the detection unit. The fixing device according to claim 1, wherein the detection unit includes a determination unit that determines whether or not the supply voltage exceeds a predetermined value. The fixing device according to claim 2, wherein the control unit controls the output power to be a constant value when the determination unit determines that the supply voltage exceeds a predetermined value. 4. The control unit according to claim 2, wherein, when the determination unit determines that the supply voltage does not exceed a predetermined value, the control unit controls the output power so as to maintain a proportional relationship with the supply voltage. 5. Fixing device. An image forming unit that forms an image with toner;
An image forming apparatus comprising: the fixing device according to claim 1, wherein the toner image formed by the image forming unit is fixed on a sheet.

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