JP2009139437A - Image heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image heating device capable of stably rotating a belt even in a case where a lubricant is applied to the internal face of the belt. <P>SOLUTION: The image heating device includes: a pressure roll 14 and a tension roll 15 that suspend the belt 731 and apply rotating force to the belt 731; a belt separating mechanism 75 that brings the belt 13 and a heat roll 11 into contact with each other and separate them; an oil application member 735 that supplies a lubricant to the internal face of the belt 731; and a belt drive roller 17 that applies rotating force to the belt 731 by coming into contact with the external face of the belt 731 when the belt 731 separates from a rotation body. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image heating apparatus that heats an image formed on a recording material by a belt member.

  In an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, a toner image is formed on a sheet, and the image is formed by heating and pressurizing and fixing the toner image. As an image heating device used as such a fixing device, a roller fixing method in which a fixing nip is formed by pressing a pressure roller against a fixing roller having a heater therein to perform fixing is conventionally employed.

  By the way, in order to increase the glossiness of the image and increase the speed of image formation, it is preferable to lengthen the sheet nip passage time and sufficiently melt the toner. However, in the case of the roller fixing method, in order to achieve this, the roller diameter must be increased, and the fixing device becomes larger.

  Therefore, a belt fixing method has been proposed that can obtain a sufficient nip width (length in the sheet conveying direction) while achieving a reduction in size and speed of the apparatus as compared with the roller fixing method. In this belt fixing system, as shown in FIG. 9a, a member that presses the sheet against the fixing roller 11 is constituted by a pressure belt 13 made of an endless belt, and the sheet is nipped and conveyed between the fixing roller 11 and the pressure belt 13. In this configuration, fixing is performed. Therefore, a sufficient nip width can be obtained as compared with the roller fixing method. This achieves higher image quality and higher speed in image formation.

  In the fixing device using the belt fixing system, since the pressure is high, the fixing roller is locally deformed when the fixing roller 11 and the pressure belt 13 are kept in pressure contact with each other. For this reason, at the time of standby other than the time of image formation, as shown in FIG. 9B, the fixing roller 11 and the pressure belt 13 are separated from each other. Even during this separation, the pressure belt 13 is rotated by the driving means that suspends the pressure belt 13. This is because the heating by the heating means is made uniform over the entire pressure belt 13, and the temperature of the pressure belt 13 is made uniform.

  As described above, since the pressure belt 13 rotates even during standby, wear occurs with the rollers 14 and 15 that stretch the belt. Further, during image formation, the pressure pad 18 is pressed against the inner surface of the belt and the pressure belt 13 is pressed against the fixing roller 11, and wear occurs between the pressure pad 18.

  Therefore, oil is continuously applied to the inner surface of the pressure belt 13 by an oil application member 16 such as an oil application roller in order to prevent a decrease in durability due to wear and to reduce a load during durability. (Patent Document 1).

JP 2005-292713 A

  However, in the case of the conventional belt fixing method, there is a limit to the amount of oil applied to the inner surface of the pressure belt.

  That is, if the amount of oil applied to the inner surface of the belt is small, the sliding resistance between the inner surface of the pressure belt 13 and the member in contact with the inner surface of the belt is increased. Further, the motor load is increased due to the increase of the driving torque. Therefore, the amount of oil to be applied cannot be reduced.

  However, when the amount of oil applied to the inner surface of the belt increases, the pressure belt 13 easily slips on the rollers 14 and 15 when the pressure belt 13 is separated from the fixing roller 11. . As a result, the rotational movement speed of the pressure belt 13 becomes uneven or stops.

  In addition, if the rotation of the pressure belt 13 is not stable, the temperature of the entire circumference of the belt with respect to the conveyance direction will be uneven, such as uneven glossiness of the image and toner offset when the image is formed again from the standby state. It will cause problems.

  The present invention has been made in view of the above points, and an object thereof is to provide an image heating apparatus capable of stably rotating a belt even when a lubricant is applied to the inner surface of the belt. is there.

  Representative means in the present invention for solving the above problems are an endless belt and a rotating body for heating a recording material carrying a toner image while nipping and conveying the recording material at its press contact portion, and the belt from the inner surface thereof to the rotating body. In the image heating apparatus, comprising: a pressure pad that pressurizes the belt; a lubricant supply unit that supplies a lubricant to an inner surface of the belt; and a contact / separation unit that contacts and separates the belt and the rotating body. And a driving means for abutting against the outer surface of the belt and rotating the belt when the rotating body is separated from the belt.

  According to the present invention, even if the amount of lubricant supplied to the inner surface side of the endless belt is increased, a rotational force is applied to the belt by the driving means that contacts the outer surface side of the belt. For this reason, the belt does not slip, and the occurrence of uneven rotation speed and the stop of rotation are prevented. Accordingly, it is possible to provide a high-quality image free from image defects such as uneven gloss of the image and toner offset.

  Further, since the lubricant supplied to the inner surface side of the belt can be increased, the belt sliding resistance between the belt inner surface and the member in contact with the belt inner surface can be reduced, and the durability and reliability of the image heating apparatus can be improved. Is possible.

  Next, an image heating apparatus according to an embodiment of the present invention will be described with reference to the drawings together with an image forming apparatus including the image heating apparatus.

[First Embodiment]
First, the overall configuration of the image forming apparatus will be described together with the image forming operation with reference to FIG.

[Entire configuration of image forming apparatus]
The image forming apparatus shown in FIG. 6 is an image forming apparatus that employs an electrophotographic system.

  The image forming apparatus 100 is roughly divided into an image forming unit that forms a toner image on a sheet as a recording material, and an image heating apparatus that fixes an unfixed image by heating and pressurizing the toner image formed on the sheet. A fixing device is provided.

  First, the image forming means is provided with a device described below. A charger 103 as a charging unit is provided around the photosensitive drum 102 as an image carrier, and the surface of the photosensitive drum 102 is uniformly charged by the charger 103. An electrostatic latent image is formed on the photosensitive drum 102 by irradiating a laser beam 105 corresponding to the image from an exposure device 104 serving as an exposure unit. This electrostatic latent image is developed by a developing device 106 as developing means to form a toner image.

  On the other hand, the sheet S as a recording material is stored in a feeding cassette 109 at the lower part of the apparatus and is fed by a feeding roller 110. The sheet is conveyed in synchronism with the toner image on the photosensitive drum 102 by a pair of registration rollers 111 as conveying means.

  The toner image on the photosensitive drum is electrostatically transferred onto the sheet by a transfer roller 107 as a transfer unit, and is conveyed to the fixing device 114. Thereafter, the toner remaining on the photosensitive drum 102 is removed by a cleaning device 108 as a cleaning unit.

  The toner image formed on the sheet S by the image forming unit is fixed on the sheet by being heated and pressed by a fixing device 114 as an image heating device. Thereafter, the sheet S on which the toner image is fixed is conveyed and discharged by a discharge roller pair 112 to a discharge tray 113 at the top of the apparatus.

[Fixing device]
Next, the fixing device 7 will be described with reference to FIG. As shown in FIG. 1, the fixing device of this embodiment is a diagram showing a first embodiment of the present invention. The fixing device 7 includes a fixing roller portion 70 and a fixing belt portion 73.

  The fixing roller 71, which is a rotating body, is provided with an elastic layer 712 made of silicon rubber on the surface layer of a metal core 711 made of aluminum or the like, and the surface layer is a release roller for improving the releasability between the fixing roller made of a PFT tube and toner. Layer 713 is provided. A heater 721 is disposed in the vicinity of the central portion inside the fixing roller.

  The fixing belt 73 is an endless belt. The fixing belt 731 is stretched by an entrance roller 732, a separation roller 733, and a steering roller 734 as support members for supporting the fixing belt 731.

  The fixing roller 71 is driven to rotate by a driving motor. Then, the fixing belt 731 is pressed against the fixing roller 71 and rotated.

  FIG. 2 shows the fixing belt unit 73. In the fixing belt unit 73, the front side plate 110 and the rear side plate 120 are fixed to the pressure pad portion 740. An inlet roller 732 is rotatably supported by the front side plate 110 and the rear side plate 120. Bearings 733c and 733d are attached to both ends 733a and 733b of the separation roller 733. A bearing 734 c is provided at the end 734 a of the steering roller 734 and is attached to the elongated hole 153 a of the front pressure arm 153. The steering roller 734 moves in the direction of arrow B with respect to the elongated hole 153a of the pre-pressing arm 153. Further, the front pressure arm 153 presses the steering roller 734 in the direction of arrow C by the pressure spring 154a, thereby applying tension to the fixing belt. Similarly, on the rear plate 120 side, a bearing 734d is provided at the end 734b of the steering roller 734, and is attached to the elongated hole 155a of the rear pressure arm 155. Thereafter, the steering roller 734 moves in the direction of arrow B with respect to the elongated hole 155a of the pressure arm 155. Further, the rear pressure arm 155 presses the steering roller 734 in the direction of arrow C by a pressure spring (not shown), thereby applying tension to the fixing belt 731. When the belt unit 73 is separated from the fixing roller 71, the steering roller 734 is pressurized in the direction of arrow C by a pressure spring. For this reason, the steering roller 734 moves in the direction of the arrow C to apply tension to the fixing belt 731. Therefore, even if the belt unit 73 is separated from the fixing roller 71, the fixing belt 731 is stretched by the fixing entrance roller 732, the separation roller 733, and the steering roller 734 without sagging. One end of the steering roller 734 is movable in the direction of arrow B, and corrects the deviation of the fixing belt 731.

  The pressure pad portion 740 includes a base 741 made of a metal such as SUS, a pressure pad 742 made of silicon rubber, and a sliding made of a PI film or the like disposed between the pressure pad 742 and the fixing belt 731. It is composed of a sheet 743.

  An oil application roller 735 that is an oil application member is provided between the entrance roller 732 and the pressure pad unit 740.

  Further, a lubricant supply means for supplying a lubricant to the inner surface side of the fixing belt 731 is provided. In this embodiment, oil is used as a lubricant, and an oil application roller 735 as a lubricant supply means is in contact with the inner surface side of the fixing belt 731. As a result, oil is applied to the inner surface of the fixing belt 731 and the sliding resistance between the inner surface side of the fixing belt 731 and the pressure pad 742 is reduced.

  Here, the fixing belt 731 may be appropriately selected as long as it has heat resistance. The belt 431 of this embodiment uses a stainless steel belt having a thickness of 75 μm, a width of 380 mm, and a circumferential length of 150 mm coated with silicon rubber having a thickness of 300 μm.

    [Belt Contacting / Separating Means] Next, referring to FIGS. 3 and 4, the contacting / separating means for contacting and separating the fixing belt portion 73 with respect to the fixing roller 71 will be described.

  Contact and separation means 75 are provided at both ends of the fixing belt portion 73. Both sides have substantially the same configuration, and FIG. 4 shows only one side. A bearing 732 a is provided at the end of the fixing entrance roller 732, and the bearing 732 a is disposed in the roller pressure holder 751.

  An end of the base 741 of the pressure pad unit 740 is disposed in a pad pressure holder 752.

  A pressure holder 753 is disposed below the roller pressure holder 751 and the pad pressure holder 752. The roller pressure holder 751, the pad pressure holder 752, and the pressure holder 753 are configured to be rotatable about a rotation shaft 754.

  In addition, a roller pressure spring 757 is disposed between the pressure holder 753 and the roller pressure holder 751, and a guide shaft 755 fixed to the pressure holder 753 passes through the roller pressure spring and passes through the roller pressure holder 751. And is arranged through the hole.

  A pad pressurizing spring 758 is disposed between the pressurizing holder 753 and the pad pressurizing holder 752, and a guide shaft 756 fixed to the pressurizing holder 753 passes through the pad pressurizing spring, and the pad pressurizing holder 752. And is arranged through the hole.

  A receiving portion 759 is provided on the side surface of the pressure pad holder 753, and a pressure cam 761 is provided on the rotating shaft 760 below the receiving portion 759.

  FIG. 4 a shows a state where the fixing belt 71 is pressed, and FIG. 4 b shows a state where the fixing belt 73 is retracted from the fixing roller 71.

  In FIG. 4a, when the pressure cam 761 is rotated by a drive system (not shown) around the rotation shaft 760 and the major diameter 761a of the pressure cam 761 is positioned at the top, the receiving portion 759 is pushed upward, and the rotation shaft The pressure holder 753 rotates in the direction of arrow V around 754. As a result, the roller pressure spring 757 causes the roller pressure holder 751 to rotate about the rotation shaft 754 so that the separation roller 733 is pressed against the fixing roller 71 with the applied pressure SF. Similarly, the pad pressurizing holder 752 is rotated about the rotation shaft 754 by the pad pressurizing spring 758 so that the fixing pad portion 740 is pressed against the fixing roller 71 with the applied pressure PF.

    While the recording material is conveyed from the direction of the arrow H and is conveyed narrowly to the pressure contact portion N between the fixing roller 71 and the fixing belt 731, the toner on the recording material is melted by the heat of the fixing roller 71 and the fixing belt 731, The toner is pressed against the recording material by the pressure of the fixing pressure pad unit 740 and fixed.

  In FIG. 4b, when the pressure cam 761 is rotated by a drive system (not shown) around the rotation shaft 760 so that the short diameter 761b of the pressure cam 761 is located at the top, the receiving portion 759 is lowered downward from the above state. Then, the pressure holder 753 rotates in the arrow W direction around the rotation shaft 754. Therefore, the urging force of the roller pressure spring 757 is not applied by the stopper portion of the guide shaft 755, the roller pressure holder 751 rotates about the rotation shaft 754, and the separation roller 733 is separated from the fixing roller 71. Similarly, the urging force of the pad pressure spring 758 is no longer applied by the stopper portion of the guide shaft 756, the pad pressure holder 752 rotates about the rotation shaft 754, and the fixing pad portion 740 is fixed to the fixing roller 71. Separate from. At this time, as can be seen from FIG. 4b, the oil application roller 735 is not in contact with the inner surface of the fixing belt.

  In the standby state where there is no recording material or waiting for image output, the fixing belt 731, the separation roller 733, and the pressure pad unit 740 are separated from the fixing roller 71 as shown in FIG. Here, when the fixing belt 731 is stopped, the temperature of the fixing belt 731 becomes high only at the contact portion of the entrance roller 780 due to the heat from the belt heater 781, and therefore the fixing belt 731 is rotated as described later. At this time, even if the oil application roller 735 is not in contact with the inner surface of the fixing belt and oil is not supplied to the inner surface of the fixing belt, the pressure pad portion 740 is separated from the fixing roller. For this reason, the sliding resistance generated on the inner surface of the fixing belt 731 is small, and no large wear occurs on the inner surface of the fixing belt 731.

[Belt rotation means]
In the belt fixing system, it is necessary to make the temperature distribution in the circumferential direction of the belt 731 uniform and to make the gloss of the image uniform. Therefore, it is necessary to always rotate the fixing belt 731 so that the fixing belt 731 is uniformly heated in the circumferential direction by the fixing inlet roll 732 incorporating the halogen heater.

  The fixing device of the present embodiment is provided with a belt rotating unit that abuts on the outer surface side of the fixing belt 731 and applies a rotational force to the fixing belt 731 when the fixing belt 731 is separated from the fixing roller 71. .

  Specifically, as shown in FIG. 1B, when the fixing belt 731 is separated from the fixing roller 71 by the above-described belt separation mechanism, the belt driving roller 17 as a belt rotating unit comes into contact with the outer surface of the fixing belt 731. Is arranged.

  As shown in the plan view of the fixing device in FIG. 5, the belt driving roller 17 is disposed so as to contact an end portion in the belt width direction orthogonal to the rotation direction of the fixing belt 731. This contact position is outside the conveyance area L of the maximum width sheet conveyed by the image forming apparatus.

  The belt drive roller 17 is provided on the drive shaft 17a, and becomes a pair of drive transmission portions that come into contact with regions at both ends in the belt width direction when the fixing belt 731 is separated from the fixing roller 71. The belt drive roller 17 is controlled so as to be driven to rotate in a state where the rotational force is transmitted from the drive source M1 to the drive shaft 17a and in contact with the fixing belt 731. The outer surface of the fixing belt 731 is μ1 when the friction coefficient between the surface of the belt driving roller 17 and the outer surface of the fixing belt 731 is μ1, and the friction coefficient between the inner surface of the fixing belt 731 and the separation roller 733 is μ2. It is made of a material having a relationship of> μ2. In the present embodiment, the belt driving roller 17 is made of a metal or heat-resistant resin roller.

  By providing the belt driving roller 17 as described above, when the fixing belt 731 is separated from the fixing roller 71, the belt driving roller 17 rotates as the belt driving roller 17 is driven. Accordingly, stable rotation can be performed regardless of the amount of oil on the inner surface side of the belt 731. For this reason, the amount of oil impregnated in the oil application roller 735 can be increased, and the wear of the inner surface of the fixing belt 731 and the member rubbed against the inner surface of the fixing belt 731 can be reduced, and the durability can be improved.

  Further, since the belt driving roller 17 abuts outside the sheet conveyance area of the fixing belt 731, in the sheet conveyance area L, dust or the like is present at the contact portion between the belt driving roller 17 and the surface of the fixing belt 731. The fixing belt 731 is not damaged such as a scratch or a dent. For this reason, a high quality image can be output.

[Second Embodiment]
Next, an apparatus according to a second embodiment will be described with reference to FIGS. Note that the basic configuration of the apparatus of the present embodiment is the same as that of the above-described embodiment, and thus redundant description is omitted. Here, a configuration different from the first embodiment will be described. Moreover, the same code | symbol is attached | subjected to the member which has the same function as embodiment mentioned above.

  In this embodiment, an endless belt (hereinafter referred to as “belt”) 30 is used in place of the fixing roller 71 of the first embodiment, and a lubricant supply means for reducing the sliding resistance on the inner surface side of the belt 30 is provided. .

  In general, the belt member has a smaller heat capacity than the roller member. For this reason, there is an advantage that the temperature rise at the start of the fixing device is quickened and the rise time is quickened. In addition, since the pressure contact portion (nip portion) is formed by two belts, a wide nip width can be secured, so that there is an advantage that speeding up is easy.

  The fixing device of the present embodiment includes a belt 731 (first belt member), a separation roller 733, a fixing entrance roller 732, a steering roller 734, an oil application roller 735, and a belt drive that is a belt rotating unit described in the first embodiment. It has a roller 17 (first belt rotating means).

  And it has the belt 30 (2nd belt member) as a rotary body which can contact | abut to the said belt 731 and can be separated | separated. Further, belt suspension means for suspending the belt 30, lubricant supply means for supplying a lubricant to the inner surface of the belt 30, and second belt rotation means for applying a rotational force to the belt 30 are provided.

  Specifically, as shown in FIG. 4, the heating belt 30 having a metal layer such as nickel inside is suspended by a pressure roll 31 and a tension roll 32 which are suspension means. The pad stay 37 forms a nip together with the pressure roll 14, the pressure roll 31, and the pressure pad 742. Reference numeral 35 denotes an induction heating coil, which heats the metal layer inside the heating belt 30.

  Further, as a lubricant supply means for supplying lubricant to the inner surface side of the belt 30 to reduce sliding resistance, an oil application roller 33 for applying oil to the inner surface of the belt is in contact with the inner surface side of the belt 30. .

  The belt driving roller 34 as the second belt rotating means is in contact with the outer surface side of the heating belt 30 regardless of the pressure contact and separation state of the belt 731 and the heating belt 30 and is pressed by an unillustrated pressing means (for example, spring bias). The pressure roll 31 is pressed via the heating belt 30. As shown in FIG. 8, the belt driving roller 34 receives rotational driving from a motor M2 that is a driving source.

  The surface of the heating belt 30 has a friction coefficient between the surface of the belt driving roller 34 and the outer surface side of the heating belt 30 as μ3, and a friction coefficient between the inner surface side of the belt 30 and the pressure roll 31 as μ4. Then, it is made of a material having a relationship of μ3> μ4.

  FIG. 5 is a plan view of the fixing device in the second embodiment, and shows the positional relationship between the heating belt driving roller 34 and the heating belt 30 in the longitudinal direction. As shown in FIG. 8, the belt driving roller 34 is disposed so as to contact an end portion in the belt width direction orthogonal to the rotation direction of the belt 30. This contact position is outside the conveyance area of the maximum width sheet conveyed by the image forming apparatus.

  The belt driving roller 34 is controlled so as to be driven to rotate while being in contact with the belt 30 by receiving a rotational force from the motor M2.

  In this embodiment, not only the belt 731 but also the belt 30 can stably rotate regardless of the amount of oil on the inner surface of the belt. For this reason, by increasing the amount of oil impregnated in the oil application roller 33, it is possible to reduce the wear of the inner surface of the heating belt 30 and the members that are rubbed against the inner surface of the heating belt 30, and improve the durability.

  Furthermore, the belt driving roller 34 also abuts outside the sheet conveyance area of the belt 30 in the same manner as the belt driving roller 17, so that no damage is caused in the sheet conveyance area of the belt 30 and a high-quality image is output. Can do.

FIG. 3 is a cross-sectional view illustrating a state in which a pressure roll and a belt of the fixing device according to the first embodiment are in contact with each other. FIG. 3 is a cross-sectional view illustrating a state where a pressure roll and a belt of the fixing device according to the first embodiment are separated from each other. 1 is a perspective view illustrating a configuration of a belt fixing device according to a first embodiment. FIG. 2 is a diagram illustrating a belt fixing device contacting / separating unit according to the first embodiment. FIG. 3 is a diagram showing a belt pressurization state of the first embodiment. FIG. 3 is a diagram illustrating a belt retracted state according to the first embodiment. 1 is a plan view of a fixing device according to a first embodiment. 1 is a cross-sectional view of an image forming apparatus. FIG. 6 is a cross-sectional view of a fixing device according to a second embodiment in a state where belts are in contact with each other. FIG. 6 is a cross-sectional view of a fixing device according to a second embodiment in a state where belts are separated from each other. FIG. 6 is a plan view of a fixing device according to a second embodiment. It is sectional drawing of the state which the pressure roll and belt of the fixing device based on a prior art contact | abutted. FIG. 6 is a cross-sectional view showing a state where a pressure roll and a belt of a fixing device according to a conventional technique are separated from each other.

Explanation of symbols

S ... Sheet
7 ・ ・ ・ Fixing device
17… Belt drive roller
71… Fixing roller
73… Fixing belt
100 ... Image forming apparatus
102… Photosensitive drum
103… Charger
104 Exposure apparatus
105 ... Laser light
106… Developer
107… Transfer roller
108… Cleaning device
109… feed cassette
110… feed roller
111… Registration roller pair
113… discharge tray
731 Fusing belt
732… Fixing entrance roller
733… Separation roller
735… Oil application roller
740… Pressure pad

Claims (4)

An endless belt and a rotating body for heating a recording material carrying a toner image while being nipped and conveyed at the press contact portion, a pressure pad for pressing the belt from the inner surface toward the rotating body, and an inner surface of the belt are lubricated. In an image heating apparatus having a lubricant supply means for supplying an agent, and a contact / separation means for contacting and separating the belt and the rotating body,
An image heating apparatus, comprising: a driving unit that abuts on an outer surface of the belt and rotationally drives the belt when the belt and the rotating body are separated from each other.   The image heating apparatus according to claim 1, further comprising a support member that supports the belt from an inner surface, wherein the driving unit rotationally drives the belt while being sandwiched between the support member.   3. The image heating apparatus according to claim 1, wherein the pressure pad is separated from the belt in accordance with an operation of separating the belt and the rotating body.   The drive means includes a drive shaft and a pair of drive transmission portions that are provided on the drive shaft and transmit the drive by contacting the regions at both ends in the width direction of the belt. The image heating apparatus according to any one of 1 to 3.