JP2005301045A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device capable of preventing excessive temperature rise in a pressure member, and capable of preventing hot offset, and preventing a recording material from winding around the pressure member in forming images on both sides without using a complicated constitution. <P>SOLUTION: In the fixing device provided with a heat member heated by a heating means, the pressure member coming in contact with the heat member, and a backup member enclosed in the pressure member so as to pressurize the heat member through the pressure member, and for fixing an unfixed image on the recording material while holding/carrying the recording material between the heat member and the pressure member, the longitudinal length of the backup member is longer than the longitudinal length of the heat member, and the apparatus is provided with a means for cooling the part longer than the heat member of the backup member in the longitudinal direction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fixing device and an image forming apparatus.

  In an electrophotographic image forming apparatus (copier, facsimile, printer, etc.), a fixing device that heats and presses an unfixed toner image formed on a recording material and fixes the toner image on the recording material, an unfixed image Is used as an image heating device such as a hypothetical fixing device that temporarily fixes the toner on a recording material, and a surface modification device that modifies the surface property of a recording material carrying a fixed image.

  As a specific example of a heating apparatus that introduces a material to be heated to a mutual pressure nip between a heating unit having a heating element and a pressure unit that is in pressure contact with the heating unit, heats the material to be heated, For example, an image heat fixing apparatus such as a heat roller system or a belt fixing system incorporated in an image forming apparatus such as an electrophotographic copying machine, the same printer, or an electrostatic recording apparatus. Hereinafter, the image heat fixing apparatus will be described as an example.

  FIG. 6 is a cross-sectional model diagram showing a schematic configuration of an example of a heat roller type image heating and fixing apparatus.

  Reference numeral 10 denotes a fixing roller (heat roller, heat roller) as a heating unit, and 20 denotes a pressure roller as a pressure unit, which are arranged in parallel with each other in the vertical direction so that both ends are disposed between side plates of the apparatus frame 30. It is rotatably mounted and held via a sliding bearing (not shown). The fixing roller 10 is provided with a release layer 12 such as PFA or PTFE formed on the surface of a hollow aluminum core 11 and a halogen heater 13 as a heating element (heat source) inserted into the roller hollow. A temperature sensitive element 14 such as a thermistor is brought into contact with this.

  The pressure roller 20 includes a cored bar 21 and a heat-resistant elastic body layer 22 made of silicon rubber or the like formed concentrically with the cored bar 21 in a roller shape. A pressure nip portion (fixing nip portion) N having a predetermined width is formed between the fixing roller 10 and the pressure roller 20 by being pressed against the lower surface by a pressure spring (not shown) with a predetermined pressing force.

  The fixing roller 10 is rotationally driven at a predetermined peripheral speed in the clockwise direction a indicated by an arrow by a drive system (not shown), and the pressure roller 20 is rotated by being driven by the fixing roller 10.

  The halogen heater 13 of the fixing roller 10 is energized from an AC power supply circuit (not shown), and the halogen heater 13 generates heat, whereby the fixing roller 10 is heated, and the surface temperature of the fixing roller 10 is detected by the temperature sensitive element 14. The energization of the halogen heater 13 is controlled so that the detected temperature information is fed back to a control unit (main body control CPU) (not shown) and the detected temperature output of the temperature sensing element 14 becomes a predetermined constant. That is, the energization to the halogen heater 13 is controlled so that the surface temperature of the fixing roller 10 is maintained at a predetermined fixing temperature.

  Thus, in a state where the fixing roller 10 and the pressure roller 20 are rotated and the temperature of the fixing roller 10 is controlled to a predetermined fixing temperature, an unfixed toner image is displayed from the image forming mechanism section A (not shown). A recording material P as a heated material on which T is formed and conveyed is conveyed and introduced into the apparatus from the inlet guide 31, and enters the fixing nip portion N of the fixing roller 10 and the pressure roller 20. By being nipped and conveyed between 20, the unfixed toner image T on the recording material P is fixed as a permanently fixed image on the surface of the recording material P by heat and pressure at the fixing nip N. The recording material P that has undergone the image heating and fixing process exits the apparatus and is output as an image formed product (copy, print).

  Conventionally, in such a heat roller system, a metal roller such as iron or aluminum is mainly used. However, in the case of using these materials, since the heat capacity is large, the temperature rises to a usable temperature of about 180 ° C. Heating requires a long heating time such as several minutes to several tens of minutes, and takes a so-called rise time.

  Therefore, in the above-described apparatus, when waiting for image formation, the rise time is shortened by maintaining the temperature of the fixing roller at a constant temperature slightly lower than a predetermined fixing temperature at which fixing is possible. However, in order to maintain a constant level of temperature even during standby, energy is always consumed.

  In recent years, energy conservation regulations have been established in each country due to increased awareness of environmental protection, and due to the demand for reducing energy consumption during standby as described above for power saving, power consumption can be reduced when the image forming device is not in use. It became necessary to reduce it.

  However, if the energy consumption is reduced during standby in the conventional fixing device configuration with a material having a large heat capacity, it takes time to bring the fixing roller up to a predetermined fixing temperature, and the user-friendliness deteriorates because the waiting time is long. End up.

  For this reason, a belt fixing method has attracted attention as a fixing device that can reduce energy consumption during standby and can immediately increase the fixing roller temperature to a predetermined fixing temperature during image formation.

  In Patent Document 1, the pressure member is made of a pressure film material and a backup roller, so that the nip width of the pressure nip portion with the heating portion is sufficiently secured and the heat capacity can be sufficiently reduced. Thus, it is possible to achieve both the rapid rise of the apparatus temperature and the improvement of the fixing performance immediately after the rise in the image heating and fixing apparatus.

Japanese Patent Laid-Open No. 07-129004

  When considering application to image forming apparatuses such as copiers and printers in the fixing device as described above, it has become possible to satisfy the fixing performance immediately after startup or during continuous paper passing, but the paper passing interval is If the length is longer, the heat capacity of the pressure member is small and the temperature becomes too high, which may cause a problem that the recording material is wound around the pressure member during hot offset or double-sided image formation.

  Although it may be possible to prevent the temperature of the lower belt from becoming too high by providing a desorption mechanism for the heating member and the pressure member, there is a problem that the configuration becomes complicated and the apparatus becomes large.

  Therefore, in the present invention, a fixing device capable of preventing an excessive temperature rise of the pressing member without using a complicated configuration and preventing a recording material from being wound around the pressing member during hot offset or double-sided image formation. It is another object of the present invention to provide an image forming apparatus including the same.

  In order to achieve the above object, the invention according to claim 1 is a heating member heated by a heating means, a pressure member in contact with the heating member, and the pressure member enclosed in the pressure member through the pressure member. A fixing member that presses the heating member and fixes a non-fixed image on the recording material by sandwiching and conveying the recording material between the heating member and the pressing member. The longitudinal length is longer than the length of the heating member, and means for cooling a portion longer than the heating member of the backup member in the longitudinal direction is provided.

  According to a second aspect of the present invention, in the first aspect of the present invention, the backup member is made of a heat conductive material.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the cooling means is a fan.

  According to a fourth aspect of the present invention, there is provided an image forming apparatus comprising: an image forming unit that forms and supports an unfixed image on a recording material; and a fixing device that heat-fixes the unfixed image on the recording material. The fixing device according to any one of? 3.

  According to a fifth aspect of the present invention, in the fourth aspect of the invention, there is provided a temperature detecting means for detecting or predicting at least the temperature of the pressure member during the fixing operation, and a drive control means for controlling the driving of the cooling means. The driving of the cooling means is controlled based on the detection result of the temperature detecting means.

  According to a sixth aspect of the present invention, in the fourth aspect of the invention, there is provided an interval detecting means for detecting or predicting an interval between the recording material and the preceding recording material passing through the fixing device, and the detection result of the interval detecting means. The driving of the cooling means is controlled based on the above.

  According to the present invention, the heating member heated by the heating means, the pressure member in contact with the heating member, and the backup member included in the pressure member and pressurizing the heating member via the pressure member. And a fixing device for fixing an unfixed image on the recording material by sandwiching and conveying the recording material between the heating member and the pressure member, wherein the length of the backup member is the length of the heating member Since the means for cooling the longer part of the backup member than the heating member in the longitudinal direction is provided, the temperature of the pressure member is prevented from excessively rising, and the pressure member of the recording material at the time of hot offset or double-sided image formation It is possible to prevent wrapping around.

  Embodiments of the present invention will be described below with reference to the accompanying drawings, but the present invention is not limited to these embodiments.

  FIG. 2 is a transverse cross-sectional model diagram showing a schematic configuration of a heating device (image heating and fixing device) according to the present embodiment, and FIG. 1 is a vertical cross-sectional model diagram. Constituent members / portions common to the apparatus shown in FIG.

  In the apparatus according to this embodiment, the heating unit 10 is a fixing roller (heat roller). Reference numerals 24, 25, and 26 denote a pressure film material, a pressure film guide, and a pressure roller that constitute the pressure unit 23, respectively.

  The pressure film guide 25 is a heat resistant mold member, and both ends thereof are fixedly supported between the side plates of the apparatus frame 30.

  The pressure film material 24 is a cylindrical heat-resistant film that is loosely fitted on the pressure film guide 25. As the pressurizing film material 24, a heat-resistant film similar to the fixing film in the film heating type heating apparatus can be used. For example, as shown in a layer configuration model diagram in FIG. 3, a composite layer comprising a heat-resistant resin film substrate layer 24a such as polyimide or PFA and a release layer 24b such as PTFE or PFA formed on the outer surface thereof. Film material and the like. In this example, when PFA is used as the film base layer 24a, it can be used as a single layer film.

  The pressure roller 26 is inserted into the inside of the cylindrical pressure film material 24 and both end shaft portions thereof are supported between the side plates of the apparatus frame 30 via bearings. The pressure roller 26 is constituted by a core metal 26a alone or a heat-resistant elastic body layer 26b concentrically integrated with the core metal, and silicon solid rubber, silicon sponge, fluorine rubber or the like is used as the heat-resistant elastic body layer 26b. A very soft grade having a roller hardness of 35 ° (ASKER-C, 500 gf load) or less is used. The cored bar 26a is preferably a good heat conductor such as Al so that the temperature distribution during end cooling is uniform.

  The bearings are attached to the side plates of the apparatus frame 30 with a degree of freedom of movement only in the vertical direction, and the bearings and lugs 25a and 25a at both ends of the pressure film guide 25 are provided. The pressurizing springs 27 and 27 are provided between the pressurizing springs 27 and 27 so that the pressurizing film 26 is sandwiched between the pressurizing roller 26 and the lower surface of the fixing roller 10 serving as a heating unit. A pressure nip portion (fixing nip portion) N having a predetermined width is formed by sandwiching the pressure film material 24 between the fixing roller 10 and the pressure roller 26.

  The fixing roller 10 is rotationally driven at a predetermined peripheral speed in the clockwise direction a in FIG. Further, the energization of the halogen heater 13 as a heating element is controlled by a temperature control system (not shown) including the temperature detecting element 14 so that the surface temperature is controlled to a predetermined fixing temperature.

  Further, as the fixing roller 10 is driven to rotate, the cylindrical pressure film material 24 is driven and rotated by a rotational force due to the frictional force between the fixing roller 10 and the outer surface of the film at the pressure nip N with the fixing roller 10. To do. The pressure roller 26 also rotates following the driven rotation of the cylindrical pressure film material 24.

  The pressure film guide 25 functions to facilitate the rotation of the film 24 and regulates the movement of the rotating film 24 in the circumferential direction and the longitudinal direction to prevent the film from being unnecessarily ramped or shifted. Yes.

  Thus, the recording material P as the heated material on which the unfixed toner image T is formed and supported is conveyed from the side of the image forming mechanism A (not shown) and introduced into the apparatus from the inlet guide 31, and the pressure film The recording material P enters between the fixing roller 10 and the pressure film material 24 of the fixing nip N formed between the fixing roller 10 and the pressure roller 26 with the material 24 interposed therebetween, and the fixing nip N Is heated and fixed to the recording material P of the unfixed toner image T.

  In the present embodiment, the pressure roller 26 has a longer length than the fixing roller 10, and the pressure roller 26 is cooled at the longitudinal end of the pressure roller 26 in order to cool the portion that is not in contact with the fixing roller 10. A fan 17 is provided as a means. FIG. 1 shows the relationship of the longitudinal length, which is a feature of this embodiment. As the cooling means, a Peltier element or a fan can be used, but it is desirable to use a fan in consideration of power consumption and the like.

  The test results of the apparatus according to this example and the conventional apparatus are shown below.

Example apparatus (FIGS. 1 and 2)
a. Fixing roller 10
An outer diameter φ: 30 mm, a wall thickness t: 0.7 mm, and a length of 320 mm. The surface of the iron hollow roller 11 having a PFA coating surface layer 12 of 30 μm. Halogen heater 13; 100V / 800W
Temperature control during printing; 185 ° C
b. Pressurized film material 24
Base material 24a; 40 μm (made of polyimide), surface layer 24b; PFA coating 10 μm (including primer layer), film outer diameter: φ35 mm, film width: 325 mm
c. Pressure roller 26
Outer diameter φ: 20 mm, diameter φ of core metal 26a: 12 mm, core metal length: 385 mm, elastic layer: silicon rubber, 1.0 mm, roller hardness: 25 ° (ASKER-C, 500 gf load), roller rubber length: 325 mm. As shown in FIG. 1, a cooling fan 40 is provided at the end of the pressure roller 26.

d. Pressurizing force and nip width Total pressure: 30 kgf, nip N width: 8.0 mm
e. Process speed: 140mm / sec
f. A recording material (transfer material) P; plain paper, is formed with toner having a basis weight of 64 g / m weight rests A4 paper leading 5cm wide as the non-fixed image ² 0.2mg / cm ^2.
[Experiment 1]
In the apparatus 1 of the present embodiment described above, recording is performed in which the fixing roller 10 is idly rotated from when the heater is energized and the temperature is adjusted to 185 ° C., and then unfixed images are placed at intervals of 30 seconds. The material was passed through. At this time, it is evaluated whether the toner offset to the fixing roller 10 appears at a position corresponding to the second circumference of the fixing roller 10 on the recording material P.

  Table 1 shows the relationship between the idling time and the temperature of the pressure roller 26 together with the result of the visual evaluation. As a comparative example, an end cooling fan 40 is turned off.

  From Table 1, in this embodiment, the temperature of the pressure roller 26 does not increase, and an image defect that can be recognized visually does not occur. In the comparative example, it can be seen that as the idling time becomes longer, the temperature of the pressure film material 24 increases, and a visible offset occurs.

  From the above results, according to the configuration of the present embodiment, the temperature rise of the pressure roller 26 can be suppressed, and the occurrence of image defects due to hot offset can be suppressed.

  FIG. 4 is a cross-sectional model diagram showing a schematic configuration of the apparatus of the present embodiment.

  The apparatus of this embodiment is the same as the apparatus of the first embodiment (FIGS. 1 and 2) except that the pressure roller 26 of the pressure unit 23 is changed to a non-rotating fixed pressure pad 26A. The same as in the first embodiment.

  The fixed pressure pad 26 </ b> A is an elongated heat-resistant elastic member having a cross-sectional kamaboko shape that is fixed to the upper surface of the pressure film guide 25 along the longitudinal direction.

  When the pressure pad support member 25 is assembled between the side plates of the apparatus frame 30, the pressure pad 26A presses against the lower surface of the fixing roller 10 as the pressure portion against the elasticity with the pressure film member 24 interposed therebetween. Thus, a predetermined pressure and nip width can be obtained at the pressure nip N by the elastic reaction force of the pressure pad 26A.

  As with the pressure roller 26 of the first embodiment, the pressure pad support member 25 is preferably made of a material having a high thermal conductivity such as Al in order to make temperature unevenness in the longitudinal direction uniform.

  The fixed pressure pad 26 </ b> A is a heat-resistant elastic body and has a surface that contacts the inner surface of the pressure film material 24 with low friction.

  Specifically, what is used as a single material is, for example, a pad member made of a PTFE non-woven fabric (trade name: Nomex) or a porous body of PTFE (trade name: fluoropore).

  Also, when separating the elastic body and the surface low-friction function, use silicon solid rubber, silicon sponge, fluorine rubber or the like as the elastic layer, and cover the surface with glass cloth, PFA tape or Kapton tape, etc. Can be used.

  The pressure film material 24 is driven to rotate while the inner surface slides on the surface of the pressure pad 26A as the fixing roller 10 rotates.

  By using the pressure pad 26A as a fixing member of a heat-resistant elastic body, the configuration can be simplified as compared with the case of using a roller-type pressure member, and the heat capacity on the pressure unit 23 side can be further reduced. Further, it is possible to further shorten the wait time and improve the fixing property in the morning.

  In this embodiment, the pressure pad support member 25 </ b> A is longer than the fixing roller 10, and the pressure member 23 is configured to cool the portion where the pressure pad support member 25 </ b> A is not in contact with the fixing roller 10. A fan 17 as a cooling means is provided at the longitudinal end of the pressure pad support member 25A. FIG. 5 shows the positional relationship between the longitudinal length and the fan 17, which is a feature of the present embodiment.

  The apparatus of the present embodiment can obtain the same effects as the apparatus of the first embodiment.

  FIG. 7 shows a schematic configuration of an example of an image forming apparatus incorporating the image heating and fixing apparatus 50 as a heating apparatus of the heating system of the first embodiment described above.

FIG. 7 is a schematic configuration model diagram of an example of an image forming apparatus provided with a heating device according to the present invention as a fixing device. The image forming apparatus of this embodiment is
A full-color printer having an automatic duplex printing function using an electrophotographic process.

  The photosensitive drum 101 as an image carrier is driven in the direction of the arrow in the figure by a driving unit (not shown) and is uniformly charged by the primary charger 102. Next, the exposure device 103 irradiates the photosensitive drum 101 with laser light L according to the yellow image pattern, and a latent image is formed on the photosensitive drum 101. Further, when the photosensitive drum 101 advances in the direction of the arrow, the developing device 104a containing yellow toner among the developing devices 104a, 104b, 104c, and 104d supported by the rotary support 111 rotates so as to face the photosensitive drum 101. And is visualized by the selected developing device 104a.

  The intermediate transfer belt 105 rotates in the direction of the arrow at substantially the same speed as the photosensitive drum 101, and the intermediate transfer belt 105 applies a toner image formed and supported on the photosensitive drum 101 by a primary transfer bias applied to the primary transfer roller 108 a. Primary transfer is performed on the outer peripheral surface of the belt 105. By performing the above steps for yellow, magenta, cyan, and black, toner images of a plurality of colors are formed on the intermediate transfer belt 105.

  Next, the transfer material is fed from the transfer material cassette 112 by the pickup roller 113 at a predetermined timing. At the same time, a secondary transfer bias is applied to the secondary transfer roller 108b, and the toner image is transferred from the intermediate transfer belt 105 to the transfer material. Further, the transfer material is conveyed to the fixing device 106 by the conveyance belt 114 and melted and fixed, whereby a color image is obtained.

  Further, the transfer residual toner on the intermediate transfer belt 105 is charged by the intermediate transfer cleaning roller 115 and is reversely transferred onto the photosensitive drum at the next primary transfer. On the other hand, the untransferred toner on the photosensitive drum 101 is cleaned by a known blade unit cleaning device 107.

  The image forming apparatus according to the present exemplary embodiment has an output speed of A4 horizontal feed of 40 sheets / minute in the monochrome image forming mode. However, in the color image forming mode, the four colors of yellow, magenta, cyan, and black are formed on the intermediate transfer member 105 by one photosensitive drum 101 and transferred onto the transfer material P all at once. The A4 horizontal feed output speed in the image forming mode is 7 sheets / minute, which is 1/4 or less.

  During continuous image formation in the black and white image forming mode, the transfer material P continuously passes through the nip portion and takes heat from the pressure member, so that the temperature rise of the pressure member can be suppressed.

  However, in the color image forming mode, since the interval between the recording material P and the recording material P that passes through the nip portion next becomes long, the heat of the fixing roller 10 is transmitted to the pressure film material 24, and the pressure film material 24 The temperature will rise.

In the image forming apparatus of FIG. 7 provided with the conventional fixing device, 500 sheets of full-color black images were continuously output on both sides on a basis weight of 64 g / m ² in the color image forming mode. For comparison, the same output was made when the fan 17 at the end of the pressure roller 26 was not driven.

  In the state where the fan 17 is turned off, the temperature of the pressure film material 24 becomes too high and the recording material P is wound around the pressure film material 24 on both sides.

  However, in this embodiment, since the cooling fan 17 is provided at the end of the pressure roller 26, the above problem does not occur.

  In this embodiment, the driving of the cooling fan 17 is controlled by the temperature of the pressure member 23 or the sheet passing interval in the image forming mode in the image forming apparatus of the third embodiment.

  As described above, in the continuous output in the black and white image forming mode, the recording material P takes away the temperature of the pressurizing member. Therefore, it is not necessary to consider the temperature increase of the heating member 23 as in the color image forming mode. Therefore, by controlling the driving of the cooling fan 17 from the temperature of the pressure member 23 or the sheet passing interval in the image forming mode, it is possible to efficiently cool only when the pressure member 23 is heated.

  The fixing device according to the present invention is also used as an image heating device such as a hypothetical fixing device that temporarily fixes an unfixed image on a recording material, and a surface modification device that modifies the surface property of a recording material carrying a fixed image.

It is a longitudinal cross-sectional model figure which shows schematic structure of the heating apparatus of Example 1 of this invention. It is a cross-sectional model figure which shows schematic structure of the heating apparatus of Example 1 of this invention. It is a layer structure model figure of a pressurization film material of a composite layer type. It is a cross-sectional model figure which shows schematic structure of the heating apparatus of Example 2 of this invention. It is a longitudinal cross-section model diagram which shows schematic structure of the heating apparatus of Example 2 of this invention. It is a cross-sectional model figure which shows schematic structure of an example of the heating apparatus of a heat roller system. It is the schematic of the image forming apparatus of Example 3 of this invention.

Explanation of symbols

10 Heat roller (fixing roller)
20, 23 Pressure roller or pressure film mechanism 13, 15 Halogen heater 14 Temperature sensor (thermistor)
16, 25 Film inner surface guide member 17 Fan as cooling means 24 Pressure film material 26, 26A Pressure roller or fixed pressure member N Pressure nip (fixing nip)
P Heated material (recording material, transfer material)
T Toner image

Claims (6)

A heating member that is heated by a heating means; a pressure member that contacts the heating member; and a backup member that is contained in the pressure member and pressurizes the heating member via the pressure member. In a fixing device for fixing an unfixed image on the recording material by sandwiching and conveying the recording material between the pressure member and the pressure member,
A fixing device comprising: means for cooling a portion of the backup member having a longitudinal length longer than that of the heating member and longer than the heating member of the backup member in the longitudinal direction.   The fixing device according to claim 1, wherein the backup member is made of a heat-conductive material.   The fixing device according to claim 1, wherein the cooling unit is a fan. In an image forming apparatus having an image forming means for forming and supporting an unfixed image on a recording material, and a fixing device for heating and fixing an unfixed image on the recording material,
An image forming apparatus, wherein the fixing device is the fixing device according to claim 1.   A temperature detecting means for detecting or predicting at least the temperature of the pressure member during the fixing operation; and a drive control means for controlling the driving of the cooling means, and driving the cooling means based on the detection result of the temperature detecting means. 5. The image forming apparatus according to claim 4, wherein the image forming apparatus is controlled.   An interval detection unit that detects or predicts an interval between the recording material and the previous recording material passing through the fixing device, and controls driving of the cooling unit based on a detection result of the interval detection unit. Item 5. The image forming apparatus according to Item 4.

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