JP2006003693A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus having a fixing device which copes with various types of transfer materials and whose down time is lessened and with which energy can be saved. <P>SOLUTION: The image forming apparatus has a fixing device for fixing a toner image onto a transfer material by passing the transfer material through a nip formed from two rotary bodies disposed in contact with each other, at least one of the rotary bodies being rotated by receiving drive force from a drive source. In the image forming apparatus, one of the two rotary bodies is such a roller that incorporates no heating means and is pressed against the other rotary body heated by the heating means or released from its being pressed against the rotary body. The rotary body can be replaced while it is released from its being pressed against it. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine having a toner image fixing device, a printer, and a FAX, and in particular, fixing processing is performed by sandwiching, pressing, and heating a transfer material between two rotating bodies. The present invention relates to an image forming apparatus having a fixing device.

  In a conventional fixing device, there is a method in which a transfer material holding a toner image is passed through a nip formed by pressing rollers, which are two rotating bodies, and heated and pressed to fix the toner image on the transfer material. It is common.

  In the case of a color image forming apparatus, since the toner adhesion amount on the transfer material increases, there is a problem that the transfer material is easily wound around the heating rotator contacting the toner image. (Not concave on the unfixed toner image side). In such a case, the hardness of the rotator on the back side of the transfer material (the rotator on the side where the toner image does not contact) needs to be somewhat higher than the hardness of the rotator on the unfixed toner image side. The nip width required for transfer materials with poor fixability cannot be secured. When fixing transfer materials with poor fixability, it is possible to increase the fixing temperature or reduce the process speed. There is a problem that time is increased and print productivity is lowered. In addition, a highly rigid transfer material such as thick paper also has a problem in that the shape when discharged after the fixing device follows the nip shape and the curl becomes large. Cardboard has high rigidity, and it is not necessary to make the nip shape convex on the roller side of the unfixed toner image side. Therefore, the hardness of the roller on the back side of the transfer material is reduced to ensure the nip width and curl is reduced. As described above, the nip portion can be made flat. However, under such a condition, there is a problem that the thin paper is wound around the roller on the unfixed toner image side.

In response to the problem that the combination of one type of roller pair as described above cannot be applied to various transfer materials, (1) the optimal roller temperature, diameter, peripheral speed, etc. depending on the moisture content, thickness, etc. of the transfer material A technology that makes it possible to select conditions such as surface hardness using a plurality of rollers (see, for example, Patent Document 1), and (2) color toner on envelope wrinkles or OHT (transparent paper) carrying a toner image A technique for selecting a roller according to the type of transfer material (for example, see Patent Document 2) has been disclosed for measures such as ensuring image transparency. In addition, (3) a plan to manually replace a plurality of fixing units has been attempted.
JP-A-54-95246 JP-A-4-166878

  However, in the technique (1) described above, the temperatures of a plurality of rollers must be controlled at the same time, and there is a problem that the power consumption during standby becomes very large. Also, if you do not control the temperature of multiple rollers to reduce power consumption during standby, it takes time for the rollers to heat up after switching the rollers, and the first print takes a very long time. May occur. In addition, it is not preferable to reduce the peripheral speed of the roller because it affects print productivity. Furthermore, there is a problem that it is difficult to optimize the temperature distribution during paper wrinkling, waving, and paper passing only by changing the temperature, diameter, peripheral speed, and surface hardness. Similarly, the technique (2) cannot solve the above-described problem. In the technique (3), there is a problem that the waiting time is long until the temperature of the fixing device rises, and in particular, when the device is large, it takes time to replace the user.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus having a fixing device that can cope with various transfer materials, has a small downtime, and can save energy.

  At least one of the two rotating bodies that rotate by obtaining a driving force from a driving source is pressed against each other to form a nip portion, and the transfer material is passed through the nip portion, thereby fixing the toner image on the transfer material. In the image forming apparatus having the fixing device, one of the two rotating bodies is a roller that does not have a heating unit on the inside, and can pressurize and release the pressure on the other rotating body heated by the heating unit. An image forming apparatus, wherein the roller is replaceable in a pressure release state.

  By simply replacing the roller member that does not have an internal heat source, it can be used for various transfer materials, and when the roller member is replaced, the temperature is controlled to the heating means, so the downtime can be reduced. Printing can be started without spending waiting time.

  First, a fixing device according to the present invention and an image forming apparatus on which the fixing device is mounted will be described.

  In the description of the embodiment of the present invention, the technical scope of the present invention is not limited by the terms used in this specification.

  FIG. 1 is a schematic diagram illustrating an example of the overall configuration of the image forming apparatus.

  In FIG. 1, 10 is a photoconductor, 11 is a scorotron charger as charging means, 12 is a writing device as image writing means, 13 is a developing device as developing means, and 14 is for cleaning the surface of the photoconductor 10. A cleaning device, 15 a cleaning blade, 16 a developing sleeve, and 20 an intermediate transfer belt. The image forming unit 1 includes a photoconductor 10, a scorotron charger 11, a developing unit 13, a cleaning device 14, and the like. Since the mechanical configuration of the image forming unit 1 for each color is the same, in FIG. Reference numerals are given to configurations of only the (yellow) series, and reference symbols are omitted for the constituent elements of M (magenta), C (cyan), and K (black).

  The arrangement of the image forming means 1 for each color is in the order of Y, M, C, K with respect to the running direction of the intermediate transfer belt 20, and each photoconductor 10 contacts the stretched surface of the intermediate transfer belt 20. The contact point rotates in the same direction as the traveling direction of the intermediate transfer belt 20 and at the same linear speed.

  The intermediate transfer belt 20 is stretched around a driving roller 21, an earth roller 22, a tension roller 23, a static elimination roller 27, and a driven roller 24. The belt unit 3 includes these rollers, the intermediate transfer belt 20, a transfer device 25, a cleaning device 28, and the like. Configure.

  The intermediate transfer belt 20 is driven by rotation of the driving roller 21 by a driving motor (not shown).

  The photosensitive member 10 is formed by forming a photosensitive layer such as a conductive layer, an a-Si layer, or an organic photosensitive member (OPC) on the outer periphery of a cylindrical metal base formed of, for example, an aluminum material, and the conductive layer is grounded. In the state, it rotates counterclockwise as indicated by the arrow in FIG.

  An electrical signal corresponding to the image data from the reading device 80 is converted into an optical signal by the image forming laser, and is projected onto the photoconductor 10 by the writing device 12.

  The developing unit 13 is a developing sleeve formed of a cylindrical nonmagnetic stainless steel or aluminum material that keeps a predetermined interval with respect to the circumferential surface of the photoconductor 10 and rotates in the same direction as the rotation direction of the photoconductor 10. 16.

The intermediate transfer belt 20 is an endless belt having a volume resistivity of 10 ⁶ to 10 ¹² Ω · cm. For example, the intermediate transfer belt 20 may be an engineering plastic such as modified polyimide, thermosetting polyimide, ethylene tetrafluoroethylene copolymer, polyvinylidene fluoride, and nylon alloy. It is a semiconductive seamless belt having a thickness of 0.04 to 0.10 mm in which a conductive material is dispersed.

  A transfer unit 25 has a function of transferring a toner image formed on the photoreceptor 10 onto the intermediate transfer belt 20 by applying a direct current having a polarity opposite to that of the toner. As the transfer unit 25, a transfer roller can be used in addition to the corona discharger.

  Reference numeral 26 denotes a transfer roller which can be brought into contact with and released from the earth roller 22 and retransfers the toner image formed on the intermediate transfer belt 20 onto the transfer material P.

  A cleaning device 28 is provided to face the driven roller 24 with the intermediate transfer belt 20 interposed therebetween. After the toner image is transferred to the transfer material P, the intermediate transfer belt 20 has the charge of the residual toner weakened by the neutralizing roller 27 to which an AC voltage superimposed with a DC voltage having the same or opposite polarity as that of the toner is applied. The toner remaining on the peripheral surface is cleaned. A fixing device 4 according to the present invention will be described in detail later.

  70 is a paper feed roller, 71 is a timing roller, 72 is a paper cassette, and 73 is a transport roller. 81 is a paper discharge roller, and 82 is a paper discharge tray. Reference numeral 85 denotes an operation panel. B1 is a control unit which is a control means.

  Here, the fixing device 4 according to the present invention will be described.

  FIG. 2 is a view for explaining the pressure mechanism of the replaceable pressure roller.

  3 is a cross-sectional view taken along arrow XX in FIG.

  2 and 3, reference numeral 41 denotes a heating roller, and a heat-resistant layer 412 that is an elastic body is lined on a cylindrical cored bar 413 made of aluminum, and a release layer 411 is coated on the outer periphery of the heat-resistant layer 412. And receives power from a driving source (not shown) via a gear 415. The heating roller 41 is heated to a predetermined temperature by a halogen heater 46 that is a heating means disposed in the hollow portion of the heating roller 41 via a support contact piece 461, and the temperature is set near the surface of the heating roller 41. Detected by the non-contact temperature sensor 414 and transmitted to the control unit B1, the control unit B1 controls the surface temperature of the heating roller 41 to be a specified temperature by turning the halogen heater 46 on and off. .

  Reference numeral 42 denotes a roller-shaped pressure roller that does not have a heating means on the inside, and a silicone rubber (heat conductivity of 0.25 W / m · K) with a low-heat-conducting heat-resistant layer formed on a cylindrical rigid cored bar made of aluminum. The following is lined, and the surface layer is made of a PFA resin thin layer as a release layer.

  41A is an external heating roller that heats the pressure roller 42 from the outside, and a fluororesin is applied to the surface of the aluminum base tube, and encloses a halogen heater 46A supported by a support contact piece (not shown). .

  Reference numeral 43 denotes an exchange unit on which the pressure roller 42 is mounted, and is placed as a unit on a pressure mechanism 44 described later. A plurality of exchange units 43 are provided, and the pressure roller 42 of each exchange unit is of a different type, and each roller hardness, heat capacity, outer diameter shape, rubber thickness, or heat capacity in the direction perpendicular to the moving direction of the transfer material. At least one of the distributions is made of different materials.

  The replacement unit 43 may be configured to engage with the coupling so that the rotational force is transmitted to the pressure roller 42 while being mounted on the pressure mechanism 44.

  FIG. 4 is a view showing a pressure roller replacement unit.

  FIG. 4A is a perspective view of the entire replacement unit.

  FIG. 4B is a view of the rear end portion 435 viewed from the direction F in FIG.

  4A and 4B, reference numeral 431 denotes a support frame that supports the pressure roller 42 via a bearing 432, and a guide portion 434 that is inserted into a guide rail 423 of a swing frame 441 described later. Have. The rear end 435 of the support frame 431 is provided with a light transmission hole 424, which engages with an optical sensor 437 comprising a light emitting part and a light receiving part attached to a pressurizing mechanism 44 described later, and a pressure roller 42 types are identified. The position of the light transmitting hole 424 varies depending on the type of the pressure roller 42 made of at least one different material. If light from the light emitting part of the optical sensor 437 passes, the electric light from the light receiving part correspondingly corresponds. The signal is transmitted to the control unit B1, and automatically switches to the optimum control temperature of the transfer material to be used depending on the position of the light transmission hole 424.

  Reference numeral 433 denotes a handle integrally attached to the support frame body 431. The operator holds the handle 433 and inserts and pulls out the guide portion 434 of the support frame body 431 along the guide rail 423 of the swing frame 441. To do.

  Next, the pressurizing mechanism will be described.

  The pressurizing mechanism 44 includes a swing frame 441 that supports the replacement unit 43, a support shaft 443 that supports the swing frame 441, an eccentric cam 445 that is integral with a rotation shaft 447 that is rotated by a power source (not shown), Crimping with a drag force that causes the swing frame 441 to rotate clockwise with the dowel 446, the rotation restricting dowel 449, the bearing 448, and the rotation shaft 443 on the swing frame 441 engaged with the eccentric cam 445 as fulcrums. It consists of a spring 444 and the like. Both ends of the crimp spring 444 are fixed so as not to buckle to the horizontal portion B of the fixing device frame 4 </ b> C and the swing frame 441.

  The swing frame 441 is provided with a guide rail 423 that engages with the replacement unit 43, and when the replacement unit 43 is inserted along the guide rail 423 in the longitudinal direction, a predetermined stopper is used to prevent a predetermined movement. The position is determined and fixed by a clamp member (not shown).

  Now, when replacing the pressure roller 42 in the fixing device in the heating control state, the operator opens the front door (not shown) of the image forming apparatus, manually pulls out the replacement unit 43, and then from the replacement unit 43. Select one and insert it. Since the notch W is penetrated through the fixing device frame 4A, the pressure roller 42 (exchange unit 43) can be pulled out and inserted. As soon as the replacement unit 43 is completely inserted, the optical sensor 437 operates to automatically switch to the optimum control temperature. When it is detected that the temperature switching is completed, a print is accepted. In this state, when the print button is pressed, the eccentric cam 445 obtains rotational force from a power source (not shown), pushes up the swing frame 441, rotates 180 °, stops, and reaches the position indicated by the solid line. The replaced pressure roller 42 is in pressure contact with the heating roller 41 and the external heating roller 41A. Then, the heating roller 41 is rotated to pass the transfer material P through the nip portion. When the passage is completed, the rotation of the heating roller 41 is stopped, and the eccentric cam 445 obtains a rotational force from a power source (not shown), pushes up the swing frame 441 against the compression spring 444, rotates 180 ° and stops. The pressure roller 42 is in a position separated from the heating roller 41 and the external pressure roller 41A. Even in this state, the energization control of the halogen heaters 46 and 46A is performed and the engine is in the idling state, and the pressure roller 42 can be replaced in this heating control state. Even during the replacement operation of these pressure rollers 42, the energization to the heating source is continued.

  Therefore, according to the present invention, even when the pressure roller is released from pressure, the control to the heating source is continued, the pressure roller can be replaced, and the control temperature of the heating source is automatically switched after the replacement. If the roller member and the heat capacity are set to be small, printing can be started without spending a waiting time.

  The embodiment is not limited to the one shown in FIG. 2, but the pressure roller in contact with the heating belt as shown in FIG. 5 may be exchanged. The heat source may not be disposed inside the roller, and the external heating roller may be in contact with the surface of the heating roller so that the pressure can be released from the heating roller and the external heating roller.

  FIG. 5 is a diagram showing an embodiment in which a heating belt is used as one rotating body.

  In FIG. 5, the heating belt is made of polyimide rubber coated with silicone rubber and coated with fluororesin on the surface. However, the belt heating roller is made of aluminum base tube with cored metal and coated with fluororesin on the surface. The roller is made by lining a silicone sponge rubber with an aluminum base tube as a core metal.

  The operation of the pressurizing mechanism and the temperature control are omitted because they are almost the same as those described in FIG.

1 is a schematic diagram illustrating an example of an overall configuration of an image forming apparatus. It is a figure for demonstrating the pressurization mechanism of the pressure roller which can be replaced | exchanged. It is sectional drawing of the XX arrow of FIG. It is a figure which shows the unit for replacement | exchange of a pressure roller. It is a figure which shows embodiment using a heating belt for one rotary body.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image formation means 41 Heating roller 41A External heating roller 42 Pressure roller 423 Guide rail 43 Replacement unit 431 Support frame 437 Optical sensor 44 Pressure mechanism 441 Swing frame 444 Crimp spring 445 Eccentric cam 4A, 4B, 4C Fixing device Frame

Claims (5)

At least one of the two rotating bodies that rotate by obtaining a driving force from a driving source is pressed against each other to form a nip portion, and the transfer material is passed through the nip portion, thereby fixing the toner image on the transfer material. In the image forming apparatus having the fixing device, one of the two rotating bodies is a roller that does not have a heating unit on the inside, and can pressurize and release the pressure on the other rotating body heated by the heating unit. An image forming apparatus, wherein the roller is replaceable in a pressure release state. In addition to the other rotating body heated by the heating means, the roller contacts the external heating roller, and when the pressure is released from the other rotating body, the roller is also separated from the external heating roller. The image forming apparatus according to claim 1. 3. The image according to claim 1, comprising a plurality of replaceable rollers having a configuration in which a rigid metal core, a silicone rubber coated thereon, and a PFA resin are attached to a surface layer thereof. 4. Forming equipment. The replaceable rollers are made of materials different from each other in at least one of roller hardness, heat capacity, outer diameter shape, and thickness or heat capacity distribution of the silicone rubber in the direction perpendicular to the moving direction of the transfer material. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. When the roller is replaced, the heating unit is energized, temperature control is continued, and the control temperature of the heating unit is automatically switched after the roller is replaced. Item 5. The image forming apparatus according to any one of Items 1 to 4.

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