JP2005301185A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten the laying a bundled wire and to easily secure safety by individually arranging feeding routes to an abnormality detection means and a heating means in an image forming apparatus provided with a fixing device. <P>SOLUTION: A plurality of heaters 111-113 are driven by a first feeding part under the control of a system controller 101, thermo-SWs 115, 116 driven by a second feeding part and connected in series detect abnormality of respective heaters 111-113, and at the occurrence of abnormality, the first feeding part is cut off. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heater and a safety circuit configuration of a fixing device in an image forming apparatus.

  Conventionally, in a configuration of a fixing device having a plurality of heaters, each heater has an independent temperature detecting means, and a thermo SW is also independently installed in each heater as a means for interrupting power supply when a temperature abnormality is detected. It was.

  For the purpose of improving safety, if one of the plurality of heaters is in an abnormal state, the other heaters are also turned off.

  One conventional method of controlling multiple heaters is to connect multiple heaters with multiple SWs, switch between series / parallel connection by a combination of SW ON / OFF, efficiently control power, and flicker A technique for reducing this has been proposed (see, for example, Patent Document 1).

Further, the heater includes a plurality of heaters and a plurality of heater driving means for independently driving the plurality of heaters, and the inrush current preventing means, the failure detecting means, or the current interrupting means of the heater is shared by the plurality of heaters. A method of performing control by providing the current path is proposed (for example, see Patent Document 2).
JP 2001-142543 A Japanese Patent Laid-Open No. 9-16034

  In the above Japanese Patent Laid-Open No. 2001-142543, a configuration for ensuring safety is complicated when there are a plurality of power supply control SWs and the number of objects to be controlled causes a malfunction of the control means. Become.

  In Japanese Patent Laid-Open No. 9-16034, since the current interrupting means is connected through the same path as the power feeding path to the heater, when a plurality of heaters are mounted across a plurality of rollers, AC power feeding ( Since the bundle path on the primary side becomes long, various bundle processes have been required to ensure safety.

  In addition, there is an increasing demand for fixing images on various recording papers as current market needs. For example, paper that is very thick compared to normal recording paper (about 105 gsm or less) requires several times as much heat as fixing heat.

  Therefore, since it is necessary to further increase the number of heaters, the above-described technical problem will become more and more important in the apparatus main body in the future.

  According to the present invention, by solving the above-mentioned problems, it is possible to ensure further safety in an image forming apparatus including a fixing device having a plurality of heaters.

In a fixing device in an image forming apparatus,
Driving means for individually driving the plurality of heaters and the plurality of heaters driven by the first power supply means;
An abnormality detection means for detecting an abnormality in each of the plurality of heaters driven by the second power supply means;
Comprising
The plurality of abnormality detection means are connected in series, and when at least one of the abnormality detection means detects an abnormality, the first power supply means to the plurality of heaters is shut off.

In the above image forming apparatus,
The abnormality detecting means is a thermo SW.

  According to the present invention, in an image forming apparatus including a fixing device having a plurality of heaters, further safety can be ensured by a simpler wiring configuration.

  Embodiments of the present invention will be described below with reference to the drawings.

  An image forming apparatus embodying the present invention is an apparatus for forming an image image sent by an electric signal on plain paper, thermal paper, or the like by means of electrophotography, thermal sensitivity, thermal transfer, ink jet or the like.

  In this embodiment, an electrophotographic image forming unit using a laser beam exposure method will be described.

  FIG. 3 is a configuration diagram of the image forming apparatus.

  Reference numeral 301 denotes a photosensitive drum, on which an optical semiconductor layer whose electrical characteristics change by light irradiation is formed, and rotates at a constant speed during an image forming operation. Hereinafter, the image forming operation is performed according to the following steps.

  (1) Charging: The photo semiconductor layer of the photosensitive drum 301 is uniformly charged by a charger (charging roller) 302.

  (2) Laser exposure: An image pattern (electrostatic latent image) is irradiated by a laser optical system 303 toward the photosensitive drum.

  (3) Development: The developing device 304 attaches toner to the electrostatic latent image.

  (4) Transfer: Transfer is performed on a recording material (hereinafter referred to as recording paper) by a transfer roller 305.

  (5) Fixing: The fixing device 306 heats and presses the recording paper to fix the toner on the recording paper, and the recording paper is discharged onto the paper discharge tray 307.

  (6) Cleaning: Toner remaining on the drum without being completely transferred onto the recording paper is scraped off by the blade 308, and the scraped toner is accumulated in the waste toner container 309.

  An image forming operation is performed according to the above steps. The recording paper or the recording material is stacked on the paper feed cassette 311 or the manual feed tray 312 and is conveyed to the drum surface by the paper feed roller 310 (broken line portion A in the figure).

  FIG. 4 is a configuration diagram showing a fixing device (upper 306 in FIG. 3) according to the embodiment of the present invention.

  The fixing device includes a fixing roller 401 serving as a fixing member having a fixing main heater 111 serving as a first heating source and a fixing sub-heater 112 serving as a second heating source therein, and a pressure roller 402 serving as a pressure member. However, the fixing device is configured so as to be rotatable while being pressed against each other by a pressure mechanism (not shown).

  The fixing roller 401 and the pressure roller 402 rotate by receiving a driving force from a fixing motor (not shown) that is a rotation driving unit. Driving / stopping of the fixing motor is controlled by the system controller 101 (see FIG. 1) according to the operation mode of the image forming apparatus, the surface temperature condition of the fixing roller, and the like.

  The thermistors 107 and 108 as temperature detecting means are in contact with the end portions and the central portion of the fixing roller 401 in the fixing roller 401 incorporating the heater, and the thermistors 107 and 108 detect the surface temperature of the fixing roller 401. Is done.

  The fixing roller 401 is provided with an HTV (high temperature vulcanization type) silicone rubber layer on the outer periphery of an aluminum cored bar, and an RTV (room temperature vulcanization type) silicone rubber as a heat resistant elastic layer on the outer periphery of the HTV silicone rubber layer. A layer is provided, and the layer has a thickness of 3 [mm] and a diameter of 40 [mm].

  On the other hand, the pressure roller 402 is provided with an HTV silicone rubber layer having a thickness of 1 [mm] on the outer periphery of an aluminum core, and further provided with a fluororesin layer on the outer periphery of the HTV silicone rubber layer and having a diameter of 40 [mm]. ]. By combining the fixing roller 401 and the pressure roller 402 configured as described above, the releasability with respect to the toner is further enhanced.

  Further, an external heating roller 403 incorporating an external heater 113 is configured to be able to contact and separate on the outer peripheral surface of the fixing roller 401.

  The external heating roller 403 is connected to the outer periphery of the fixing roller 401 by the system controller 101 via the contact / separation means (not shown) based on a signal from the contact / separation sensor (not shown) as contact / separation detection means. It comes in contact with the surface. The contact / separation sensor is a sensor that detects whether the external heating roller 403 is in a contact position or a separation position with respect to the fixing roller 401.

  When the external heating roller 403 comes into contact with the fixing roller 401, the external heating roller 403 is pressed by a spring or the like, and rotates following the fixing roller 401. The external heating roller 403 is supported by a support rod such as a heat insulating bush. Then, the support bar is moved by the contact / separation means, so that the contact with the separation roller 401 is performed. This contact / separation is achieved using a known technique such as a motor, a spring clutch, and a solenoid.

  For example, the outer surface of the external heating roller 403 is formed by coating the metal surface with a metal such as aluminum, iron, or stainless steel having a high thermal conductivity, or rubber or resin having a high releasability. As a result, the external heating roller 403 generally has a smaller heat capacity than the fixing roller 401, and the warm-up time is shorter than that of the fixing roller 401.

  The thermistors 109 and 110 as temperature detecting means are in contact with the end and the center of the external heating roller 403 in the same manner as the fixing roller 401, and the thermistors 109 and 110 detect the surface temperature of the external heating roller 403. Is done.

  In addition, thermo SWs 115 and 116 are installed in the vicinity of the fixing roller 401 and the external heating roller 403 as abnormality detection means.

  By the fixing device 306 having the above-described configuration, an unfixed image formed of a developer such as toner transferred onto the recording paper is heated and pressed through the nip portion between the fixing roller 401 and the pressure roller 402. It is fixed on the recording paper.

  FIG. 1 shows a block diagram of the control system of this apparatus.

  All the devices are controlled by the system controller 101 in a centralized manner. The system controller 101 mainly plays a role of driving each load in the apparatus and collecting and analyzing information of sensors. The CPU 101a is mounted on the internal configuration of the system controller 101, and the CPU 101a executes various sequences based on predetermined image forming sequences in accordance with programs stored in the ROM 101b mounted on the system controller 101. . At that time, a RAM 101c is also mounted to store rewritable data that needs to be stored temporarily or permanently.

  The AC driver 117 for controlling the heater in the fixing device 306 is provided with switch means 104, 105, and 106 for electrically connecting and disconnecting the fixing main heater 111, the fixing sub heater 112, and the external heater 113, respectively. On / off of each switch is controlled by a control signal output from the system controller 101. Such heater switches 104, 105, and 106 can be configured by semiconductor switch means such as SSR or triac, for example, but are not limited thereto.

  In addition, an AC relay 118 that energizes / cuts off the power supply to the heater for heating each roller is provided. The AC relay 118 is controlled based on an on / off control signal from the system controller 101. When the apparatus is abnormal, the AC relay 118 cuts off the power supply to all the heaters to protect the image forming apparatus. Here, the AC relay 118 constitutes a common switch means.

  Further, the thermo SWs 115 and 116 disposed in the vicinity of the fixing roller and the external heating roller are connected in series as shown in the figure and also serve as a power feeding unit to the AC relay 118.

  The AC power source 119 supplies AC power to the AC driver 117 and the DC power source 114, and the DC power source 114 supplies power to the system controller 101 and the thermo SW.

  A method for controlling the temperature of the fixing device 306 in the above configuration will be described.

  In the fixing roller 401 and the external heating roller 403 in the apparatus 3, the system controller 101 detects the detected values of the thermistors 107, 108, 109, and 110 according to the temperature changes of the rollers 401 and 403 by the A / D converter 103. The resistance value change of the thermistor 104 is converted into a voltage value and then input to the system controller 101 as a digital value.

  The system controller 101 controls the surface temperature of each roller to maintain a predetermined value by turning on / off the switch means on the AC driver 110 based on the input value.

  FIG. 2 shows a control flow when at least one of the thermo SWs 115 and 116 detects an abnormality in the above circuit and device configuration.

  As shown in FIG. 2, when one of at least one of the thermo SWs 115 and 116 is turned off (S201), the power supply to the AC relay 118 is cut off (the SW attractive force by the coil in the AC relay is turned off (S202). Since the SW of the AC relay 118 is turned off, the supply of AC power to all the heaters 111, 112, 113 is cut off (S203).

  Further, when the thermo SW is turned off, the DC current interruption detection circuit 102 in the system controller 101 detects the interruption (S204), the CPU 101a turns off the on / off control switches 104, 105, 106, and after the interruption detection. Is stopped (S205).

1 is a block diagram showing a control system of a fixing device of the present invention. Operation flow diagram when detecting abnormality of fixing device embodying the present invention 1 is a configuration diagram of an image forming apparatus including a fixing device according to the present invention. Schematic showing the configuration of the fixing device according to the present invention.

Explanation of symbols

101 System Controller 107 Thermistor 108 Thermistor 109 Thermistor 110 Thermistor 111 Fixing Main Heater 112 Fixing Subheater 113 External Heater 115 Thermo SW
116 Thermo SW
306 Fixing device

Claims (2)

In a fixing device in an image forming apparatus,
Driving means for individually driving the plurality of heaters and the plurality of heaters driven by the first power supply means;
An abnormality detection means for detecting an abnormality in each of the plurality of heaters driven by the second power supply means;
Comprising
The image forming apparatus, wherein the plurality of abnormality detection units are connected in series, and when at least one of the abnormality detection units detects an abnormality, the first power supply unit to the plurality of heaters is shut off.   The image forming apparatus according to claim 1, wherein the abnormality detection unit is a thermo SW.

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