JP5102471B2 - Fixing device and image forming apparatus using the same - Google Patents

Description

  The present invention relates to a fixing device provided in an image forming apparatus, and relates to a heating element that generates heat upon receiving power supply from an external power supply and an auxiliary power supply, a heating unit that is heated by the heating element, and the auxiliary power supply from the external power supply. The present invention relates to a fixing device including a charging device that charges the battery and an image forming apparatus using the same.

  An image forming apparatus such as a copying machine forms an image on a recording medium such as plain paper or OHP, and an electrophotographic method is often employed because of high speed image formation, image quality, cost, and the like. The electrophotographic method is a method in which a toner image is formed on a recording medium, and the formed toner image is fixed on the recording medium with heat and pressure. As the fixing method, the heat roller method is most often used from the viewpoint of safety and the like. In the heat roller method, a heat roller heated by a heating element such as a halogen heater and a pressure roller disposed opposite to the heat roller are pressed to form a mutual pressure contact portion called a nip portion, and a toner image is formed in the nip portion. The toner image is fixed on the recording medium by heating and pressing through the recording medium to which the toner is transferred.

  In recent years, in view of environmental problems, power saving of image forming apparatuses such as copiers and printers has been promoted. In order to save power in the image forming apparatus, it is effective to lower the temperature of the heating section of the fixing roller, the fixing belt, etc. of the fixing device when the image forming apparatus is not passing paper (for example, during standby).

  However, if the temperature of the heating unit is lowered when paper is not passed, the heating unit needs to be raised to a certain temperature again when the fixing device is used thereafter, and the user must wait during that time. As a result, it takes time for the apparatus to become ready for use, and the usability is deteriorated.

  Further, in order to save power in the image forming apparatus and to effectively reduce energy consumption during standby after image formation, the standby temperature of the fixing roller is suppressed to a low value as much as possible. Therefore, it is necessary to lower the heat capacity of the fixing roller so that the waiting time for the return of the toner is shortened. If the fixing roller with a small heat capacity is deprived of heat by the transfer material during image formation, the surface temperature of the fixing roller will drop relatively quickly, and the fixing roller will be below the lower limit temperature that satisfies the fixing property, so that fixing defects are likely to occur. There is a problem.

  In order to avoid such a situation, it is considered that the heating part heating time is shortened by auxiliary power supply from the auxiliary power source. A method has been proposed in which power is used more effectively by performing not only when returning from the off mode) but also when passing paper.

  Patent Document 1 discloses a technology that uses a large-capacitance capacitor called an electric double layer capacitor as the auxiliary power source, thereby realizing power saving of the image forming apparatus and preventing a temperature drop of the heating unit. Has been.

  Further, in Patent Document 2, when power is supplied from the main power supply to the main heating element, charging of the capacitor of the auxiliary power supply is stopped so that the main heating element has an allowable maximum capacity of the main power supply. There has been disclosed a technique for supplying electric power, supplying electric power from an auxiliary power supply device to an auxiliary heating element at the same time, and supplying a larger amount of electric power to the heating unit than when supplying electric power only by the main power supply device.

Patent Document 3 discloses a storage amount detection unit that detects a storage amount of an auxiliary power source, and a main power source only when a predetermined amount of power is not stored in the auxiliary power source based on the storage amount information from the storage amount detection unit. And a control device that switches to a main power mode that supplies power to at least two of the two or more auxiliary heating members with the power of the main heating member. A technique is disclosed that can supply stable power to the auxiliary heat generating member even when it is insufficient, and reduces temperature unevenness of the heating member.
Japanese Patent No. 3588006 JP2003-257590 JP 2004-200149 A

However, the environment in which the image forming apparatus is used varies, and particularly when a fixing roller having a small heat capacity is used for the reasons described above, if the temperature of the surrounding environment is low, the image forming apparatus is used as a transfer material during image formation. There is a problem that the heat of the fixing roller is easily taken away, and the temperature of the surface of the fixing roller is rapidly lowered, so that fixing failure is likely to occur.
Further, in the conventional fixing device using the auxiliary power source, the charging to the auxiliary power source is performed when the image forming apparatus is not in operation. Therefore, when image formation continues, from one image formation to the next image formation. In the meantime, the auxiliary power source is charged, and there is a problem that it takes a long time to wait for the next image formation.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device that realizes stable image fixing by heating a heating element with an auxiliary power source in accordance with the ambient temperature of the fixing device.

The invention of claim 1
A fixing device provided in an image forming apparatus,
A first heating element that generates heat upon receiving power from an external power source;
A second heating element that generates heat upon receiving power from an auxiliary power source;
A main heating part heated by the first heating element;
An auxiliary heating unit heated by the second heating element;
A charging device for charging the auxiliary power source from the external power source;
In the fixing device provided with
Temperature sensing means for sensing the ambient temperature around the fixing device;
Control means for switchingly controlling whether to charge the auxiliary power source from the external power source or to supply power to the second heating element from the auxiliary power source,
The charging device is for charging the auxiliary power supply in a standby state,
When the environmental temperature sensed by the temperature sensing means is lower than a predetermined value during image formation immediately after returning from the standby state, the auxiliary power supply is used when power is not supplied to the heating element during the image formation. The control means sets two threshold temperatures T1 and T2 with respect to the temperature information from the temperature sensing means, and the specified charge amount V1 which becomes the voltage value of the auxiliary power supply for each of the threshold temperatures. And V2 to control charging time of the auxiliary power supply ,
The threshold temperatures T1 and T2 are T1> T2, the charge amounts V1 and V2 are V1 <V2, the threshold temperature T1 corresponds to the charge amount V1, and the threshold temperature T2 is equal to the charge amount V2. Corresponding,
The fixing device is characterized in that.

According to a second aspect of the invention, in the fixing device according to claim 1, when the environmental temperature sensed by said temperature sensing means before Kiga image being formed is higher than a predetermined value, power to the heating element during the image forming There characterized in that it does not charge the pre Symbol auxiliary power when not being supplied.

The invention according to claim 3, in the fixing device according to claim 1 or 2, a front Kiga image formation in, said charging of the auxiliary power supply when the power to the heating element is not supplied, the maximum that allowed and controlling to a predetermined value less than the charging amount.

A fourth aspect of the present invention, in the fixing device according to claim 3, in accordance with the prior SL temperature sensing means temperature sensed by, and adjusting the charge amount for the auxiliary power supply.

The invention of claim 5, that the fixing device according to claim 4, before SL depending on the temperature sensed by the temperature sensing means, one of a plurality of charge amount determined in advance, supplied to the auxiliary power supply It is characterized by.

According to a sixth aspect of the present invention, in the fixing device according to any one of the first to fifth aspects, an electric double layer capacitor is used as the auxiliary power source.

According to a seventh aspect of the present invention, there is provided an image forming apparatus using the image forming portion and the fixing device according to any one of the first to sixth aspects.

  According to the present invention, the amount of power supplied to the heating element by the auxiliary power source can be adjusted according to the ambient environment temperature of the fixing device, so that stable image fixing and image formation can be achieved without being affected by changes in the ambient environment temperature. Can be planned.

  The best mode for carrying out the present invention will be described below with reference to the embodiments shown in the drawings.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view conceptually showing an image forming apparatus such as an electrophotographic copying machine or printer provided with a fixing device according to the present invention. The image forming apparatus according to the present embodiment is capable of, for example, 100 continuous sheets (75 CPM (CPM: copy speed)), and mainly includes a reading unit 11 for reading a document, and image formation for forming an image. Unit 12, automatic document feeder (ADF) 13, document discharge tray 14 for stacking documents sent from ADF 13, sheet feed unit 19 having sheet cassettes 15 to 18, and sheet discharge unit (sheet discharge) for stacking recording sheets It is constituted by a tray 20). For example, the ADF 13 has a maximum stacking number of 100 sheets, and the reading unit 11 sets the reading time of 100 originals to 60 seconds.

  Then, when the document D is set on the document table 21 of the ADF 13 and an operation on an operation unit (not shown), for example, a press operation of a print key is performed, the uppermost document D is sent out in the direction of the arrow B1 by the rotation of the pickup roller 22 Then, by the rotation of the document conveying belt 23, the paper is fed onto the contact glass 24 fixed to the image reading unit 11, and stops there. The image of the document D placed on the contact glass 24 is read by a reading device 25 located between the image forming unit 12 and the contact glass 24. The reading device 25 includes a light source 26 that illuminates the document D on the contact glass 24, an optical system 27 that forms an image of the document, a photoelectric conversion element 28 that includes a CCD that forms an image of the document, and the like. After the image reading is completed, the document D is transported in the direction of the arrow B2 by the rotation of the document transport belt 23 and discharged onto the document discharge tray 14. In this way, the document D is fed one by one onto the contact glass 24 and the document image is read by the image reading unit 11.

  On the other hand, inside the image forming unit 12, a photoconductor 30 as an image carrier is disposed. The photosensitive member 30 is driven to rotate clockwise in the drawing, and the surface is charged to a predetermined potential by the charging device 31. Further, the writing unit 32 emits a laser beam L that is light-modulated in accordance with image information read by the reading device 25, and the surface of the charged photoreceptor 30 is exposed with the laser beam L, whereby the photoreceptor is exposed. An electrostatic latent image is formed on the surface 30. When the electrostatic latent image passes through the developing device 33, the electrostatic latent image is transferred to the recording medium P fed between the photosensitive member 30 and the transfer device 34 by the opposing transfer device 34. The surface of the photoconductor 30 after the toner image is transferred is cleaned by a cleaning device 35.

  A plurality of paper feed cassettes 15 to 18 arranged below the image forming unit 12 contain recording media P such as paper, and the recording media P is fed from any of the paper feed cassettes 15 to 18 in the direction of arrow B3. The toner image formed on the surface of the photoreceptor 30 as described above is transferred onto the surface of the recording medium P. Next, the recording medium P is passed through the fixing device 36 in the image forming unit 12 as indicated by an arrow B4, and the toner image transferred to the surface of the recording medium P by the action of heat and pressure is fixed. The recording medium P that has passed through the fixing device 36 is conveyed by the discharge roller pair 37, discharged to the discharge tray 20 as indicated by an arrow B5, and stacked.

  Next, a fixing device according to an embodiment of the present invention will be described. FIG. 2 is a cross-sectional view conceptually showing an enlarged detail of the fixing device shown in FIG. In the figure, a fixing device 200 includes a fixing roller 201, a pressure roller 202 disposed opposite thereto, two heaters (a main heater 203 and an auxiliary heater 204) disposed in the fixing roller 201, and a fixing roller 201. A temperature detection unit 205 that detects the surface temperature and a separation claw 206 whose tip is pressed against the fixing roller 201 are provided.

  The fixing roller 201 is configured by disposing a release layer on a cylindrical metal tube, and is heated to a predetermined temperature by two heaters 203 and 204 disposed along the inner longitudinal direction thereof. . The pressure roller 202 is configured by arranging a rubber layer and a release layer on a metal tube, and is in pressure contact with the fixing roller 201. The fixing roller 201 and the pressure roller 202 are rotationally driven by a driving unit (not shown), and pass through the transfer device 34 between the nips to pass the recording medium P having a toner unfixed image on the surface thereof. Thus, heating and pressurization are simultaneously applied to the image to fix the image. The heaters 203 and 204 are controlled to be turned on based on the surface temperature of the fixing roller detected by the temperature detecting unit 205, and thereby the surface temperature of the fixing roller 201 is controlled to a temperature suitable for image fixing. The recording medium P that has passed through the nip portion between the fixing roller 201 and the pressure roller 202 is preferably discharged toward the discharge tray without being attached to the fixing roller 201 by the separation claw 206.

  Of the two heaters, the main heater 203 is connected to an external power supply (commercial power supply) in a power supply circuit, which will be described later, and thus receives power supply, and the auxiliary heater 204 is connected to an auxiliary power supply in a power supply circuit, which will be described later. Connected and thereby powered, they are driven independently. These heaters 203 and 204 are preferably composed of a halogen heater, a nichrome wire heater, an IH heater or the like.

  FIG. 3 is a circuit diagram showing a configuration of an embodiment of the fixing device according to the present embodiment. In the figure, a main power supply 301 is supplied in the form of a main heater 203 and an auxiliary 204 of the fixing device and an external power supply (commercial power supply), and supplies power to the main heater 203. A control switch 302 for turning on and off, an auxiliary power source 303 for supplying power to the auxiliary heater 204, a charger 304 for charging the auxiliary power source 303, charge / discharge switching means 305, and an image forming apparatus provided with this fixing device. A temperature measurement unit 306 that measures the ambient temperature and a control unit 307 that switches and controls the charge / discharge switching unit 305 based on the temperature measured by the temperature measurement unit 306 and other control information are shown.

  The main power supply 301 supplies power to the main heater 203, and this power supply is controlled by turning on / off the control switch 302. The fixing roller 201 described above maintains a specified temperature mainly by heating of the main heater 203 driven by the main power supply 301.

  The auxiliary power supply 303 is a power supply that can be charged by a charger 304 that receives power supply from the main power supply 301, and has a role of assisting heating of the fixing roller 201 by the main heater 203 by supplying power to the auxiliary heater 204. is doing. Therefore, the auxiliary heater 204 is driven when the image forming apparatus starts up or returns from the standby state, and when power supply exceeding the maximum power from the main power supply is required, thereby accelerating the start-up of the apparatus or fixing. The temperature of the roller 201 can be stably adjusted.

  In the preferred embodiment, an electric double layer capacitor is used as the auxiliary power source 303. Due to its characteristics, the electric double layer capacitor can be charged quickly for several minutes, and can be supplied with a high voltage at the beginning of discharge. Is effectively utilized. The electric double layer capacitor is also most suitable for use as an auxiliary power source in the present invention because its lifetime is almost unlimited and little deterioration occurs due to repeated charge and discharge.

  The auxiliary power source 303 can be charged from the charger 304 and discharged to the auxiliary heater 204 by switching the charge / discharge switching means 305. In this circuit configuration, the charger 304 is charged when the main power supply 301 is not energized to the main heater 203, and charges the auxiliary power supply 303 when the auxiliary power supply 303 is not energized to the auxiliary heater 204. Do.

  The temperature measuring unit 306 measures the ambient temperature of the image forming apparatus including the fixing device. When the fixing roller 201 having a small heat capacity is used in the fixing device, there is a risk of causing a fixing defect if the ambient temperature around the image forming apparatus is low. In the embodiment, when the control unit 307 determines that the temperature measured by the temperature measurement unit 306 is lower than the specified temperature and there is a risk of causing poor fixing, the two heaters 203 and When the power supply to 204 is not performed, the charge / discharge switching means 305 is operated to charge the auxiliary power source 303 by the charger 304. The additional charging operation for the auxiliary power supply 303 increases the amount of power supplied to the auxiliary heater 204, and the temperature of the fixing roller 201 can be suitably maintained even when the environmental temperature is low.

  In the embodiment, the control unit 307 sets two threshold temperatures T1 and T2 with respect to the temperature information from the temperature measurement unit 306, and the specified charge amounts V1 and V2 (this is the voltage of the auxiliary power supply) with respect to the threshold temperatures, respectively. The charging time of the auxiliary power source 303 is controlled so as to be given a value. That is, when T1> T2, the auxiliary power supply 303 is given a charge amount of V1 <V2. By such control, when the environmental temperature is extremely low, a large charge amount corresponding to the environmental temperature is given, and when the environmental temperature is not so low, a small charge amount corresponding to the environmental temperature is given. The temperature of the fixing roller 201 can be stably maintained regardless of the temperature. Note that the control unit 307 performs control so that these charge amounts V1 and V2 are less than the allowable maximum charge amount necessary for fully charging the auxiliary power source 303. As a result, electric power less than the maximum electric power is supplied to the auxiliary heater 204, and an excessive amount of heat is prevented from being applied to the fixing roller 201, and problems such as toner and transfer material blocking after image formation occur. Can be avoided.

  In the embodiment, the amount of charge to the auxiliary power source 303 can be finely adjusted by setting a plurality of threshold temperatures. In addition, regarding the temperature information from the temperature measuring unit 306, two threshold temperature ranges T1a to T1b and T2a to T2b are set, and prescribed charge amounts V1 and V2 are given to the threshold temperature ranges, respectively. You can also Moreover, in the said Example, although the electric double layer capacitor was mentioned as an example as an auxiliary power supply, it is not restricted to this, The battery which can be charged / discharged repeatedly can be used.

1 is a cross-sectional view conceptually showing an image forming apparatus such as an electrophotographic copying machine or printer provided with a fixing device according to the present invention. FIG. 2 is a cross-sectional view conceptually showing an enlarged detail of a fixing device according to an embodiment of the present invention. 1 is a circuit diagram illustrating a configuration of a fixing device according to an embodiment of the present invention.

Explanation of symbols

11 Reading unit 12 Image forming unit 13 Automatic document feeder (ADF)
14 Document discharge trays 15 to 18 Paper feed cassette 19 Paper feed unit 20 Paper discharge tray 21 Document tray 22 Pickup roller 23 Document transport belt 24 Contact glass 25 Reading device 26 Light source 27 Optical system 28 Photoelectric conversion element 30 Photoconductor 31 Charging device 32 unit 33 developing device 34 transfer device 35 cleaning device 36 fixing device 37 discharging roller 200 fixing device 201 fixing roller 202 pressure roller 203 main heater 204 auxiliary heater 205 temperature detecting means 206 separation claw 301 main power supply 302 control switch 303 auxiliary power supply 304 Charger 305 Charge / discharge switching means 306 Temperature measurement unit 307 Control unit

Claims (7)

A fixing device provided in an image forming apparatus,
A first heating element that generates heat upon receiving power from an external power source;
A second heating element that generates heat upon receiving power from an auxiliary power source;
A main heating part heated by the first heating element;
An auxiliary heating unit heated by the second heating element;
A charging device for charging the auxiliary power source from the external power source;
In the fixing device provided with
Temperature sensing means for sensing the ambient temperature around the fixing device;
Control means for switchingly controlling whether to charge the auxiliary power source from the external power source or to supply power to the second heating element from the auxiliary power source,
The charging device is for charging the auxiliary power supply in a standby state,
When the environmental temperature sensed by the temperature sensing means is lower than a predetermined value during image formation immediately after returning from the standby state, the auxiliary power supply is used when power is not supplied to the heating element during the image formation. The control means sets two threshold temperatures T1 and T2 with respect to the temperature information from the temperature sensing means, and the specified charge amount V1 which becomes the voltage value of the auxiliary power supply for each of the threshold temperatures. And V2 to control charging time of the auxiliary power supply ,
The threshold temperatures T1 and T2 are T1> T2, the charge amounts V1 and V2 are V1 <V2, the threshold temperature T1 corresponds to the charge amount V1, and the threshold temperature T2 is equal to the charge amount V2. Corresponding,
A fixing device.
  When the environmental temperature sensed by the temperature sensing means during the image formation is higher than a predetermined value, the auxiliary power source is not charged when power is not supplied to the heating element during the image formation. The fixing device according to claim 1.   The charging to the auxiliary power supply during the image formation and when the power is not supplied to the heating element is controlled to be a predetermined value less than the maximum allowable charge amount. Item 3. The fixing device according to item 1 or 2.   The fixing device according to claim 3, wherein a charge amount to the auxiliary power source is adjusted according to a temperature sensed by the temperature sensing unit.   5. The fixing device according to claim 4, wherein one of a plurality of predetermined charging amounts is supplied to the auxiliary power source according to the temperature sensed by the temperature sensing unit. The fixing device according to claim 1, wherein an electric double layer capacitor is used for the auxiliary power source . An image forming unit, an image forming apparatus comprising the fixing device according to any one of claims 1 to 6.