JP2011048233A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To uniformly apply a lubricant to a fixing belt in order to reduce the sliding resistance of the fixing belt, in a belt fixation system fixing device configured to press the fixing belt against a fixing member by means of a pressure member. <P>SOLUTION: With a pressurizing force of the pressure member against the fixing belt which is made lower than that at a fixation step, the fixing belt is driven, and then, the lubricant is applied to the fixing belt. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fixing device in an image forming apparatus that forms an image by electrophotography.

  A belt-fixing type fixing device that pinches and conveys a recording material between a fixing member and a fixing belt and fixes a toner image has been developed and put into practical use.

The belt fixing type fixing device has the following advantages because the fixing nip for heating the toner image can be lengthened.
(1) The speed can be increased.
(2) Since a fixing member such as a fixing roller can be made of a small diameter and the heat capacity of the fixing member can be reduced, the warm-up time can be shortened.
(3) Suitable for fixing a color image having a large amount of toner for forming an image.

  In the belt fixing type fixing device, the fixing belt is pressed against the fixing member by the pressing member, and the fixing belt slides with respect to the pressing member. Thus, since the fixing belt slides in a state of being pressed by the pressing member, sliding resistance of the fixing belt is generated, and there is a problem due to this sliding resistance.

  In the belt fixing method, a fixing member is used as a driving member, and the fixing member drives the fixing belt with a frictional force. However, since the sliding between the fixing belt and the pressing member becomes resistance, if the sliding resistance is high, the fixing belt does not follow the fixing member faithfully, and image displacement occurs. Further, there arises a problem that the pressing member and the fixing belt are worn and deteriorated.

  In order to improve the slidability between the fixing belt and the pressing member, the pressing member is constituted by a pressing pad and a sliding member covering the pressing pad, and a lubricant is applied to the fixing belt. 2nd and so on.

  In Patent Document 1, in order to uniformly apply the lubricant, the lubricant application member is disposed upstream of the pressing member.

JP-A-11-45018 JP 2007-79036 A

  To reduce the sliding resistance between the fixing belt and the pressing member covered with the sliding member, press the pressing member and the fixing belt with the lubricant film formed on both the inner surface of the fixing belt and the sliding member. It is necessary to. However, the lubricant application mechanism of Patent Documents 1 and 2 cannot stably form a lubricant film on the surface of the sliding member.

  In the prior art including Patent Documents 1 and 2 and the like, a lubricant is applied to the fixing belt in the fixing process. For example, when a new device is started, the lubricant is applied to the pressing member and the fixing belt. There is no lubricant film on the fixing belt and the sliding member. For this reason, when the new device is started, a high sliding resistance of the fixing belt is generated, and the fixing belt and the pressing member are worn. As described above, when the pressing member is pressed against the fixing belt in the fixing step to attach the lubricant to the surface of the sliding member, the wear progresses at the same time, and the lubricant is sufficiently adsorbed on the surface of the sliding member to form the lubricant film. Cannot be formed. In the fixing process, the pressing member presses the fixing belt against the fixing member with a high pressure in order to obtain sufficient fixing performance. If sliding continues in such a state, the fixing belt and the sliding member on the surface of the pressing member are worn, and wear powder generated by the wear further increases the sliding resistance. In this way, the sliding resistance increases rapidly.

  In order to avoid such a problem, it is conceivable to apply a lubricant to the fixing belt by rotating the fixing belt without pressing the pressing member.

  However, in this case, the lubricant is not applied to the sliding member on the surface of the pressing member, and the sliding resistance is not reduced.

  The present invention has problems that cannot be solved by the prior art even by using a lubricant, that is, an increase in sliding resistance between the fixing belt and the pressing member, deterioration due to wear of the sliding member on the surface of the fixing belt and the pressing member, etc. An object of the present invention is to provide a belt-fixing type fixing device that solves this problem and operates stably over a long period of time.

  The object is achieved by the following invention.

1. A fixing member that heats and fixes the toner image to the recording material;
A fixing belt,
A pressing member that presses the fixing belt against the fixing member;
Lubricant application means for applying a lubricant to the surface of the fixing belt that contacts the pressing member;
Driving means for driving the fixing belt;
A pressing force changing means for changing the pressing force of the pressing member;
A fixing step for fixing the toner image;
A lubricant application step of applying a lubricant to the pressing member and the fixing belt;
In the lubricant application step, the driving means relatively moves the fixing belt and the lubricant application means to apply the lubricant to the fixing belt, and in the lubricant application step, the pressing force A fixing device, wherein the pressing member is pressed against the fixing belt by a changing unit with a pressing force lower than that in the fixing step.

  2. 2. The fixing device according to 1 above, wherein the pressing member includes a pressing pad and a sliding member that covers the pressing pad, and a lubricant layer is formed on the sliding member in the lubricant application step.

  3. 3. The fixing device according to 1 or 2, further comprising a heating unit configured to heat the fixing belt, wherein the heating unit operates at least in the lubricant application step.

  In the present invention, the pressing force of the pressing member is made lower than that in the fixing step so that the fixing belt and the pressing member are brought into contact with each other and the lubricant is applied, so that a sliding member surface lubricant film covering the pressing member is formed. be able to. As a result, the sliding resistance between the fixing belt and the pressing member is sufficiently reduced, the deterioration of the image quality that occurs during fixing can be prevented, and deterioration due to wear of the fixing belt and the pressing member can be prevented.

1 is a diagram illustrating a color image forming apparatus using a fixing device according to an embodiment of the present invention. 1 is a diagram illustrating a configuration of a fixing device 100 according to an embodiment of the present invention. It is a figure which shows the press member. It is a figure which shows the drive mechanism of a fixing device. It is a figure which shows the state of the fixing device in the fixing process, at rest, and at the time of lubricant application. 6 is a graph showing changes in driving torque of the fixing belt.

  FIG. 1 shows a color image forming apparatus using a fixing device according to an embodiment of the present invention. The color image forming apparatus shown in FIG. 1 transfers a toner image formed on a photosensitive member onto an intermediate transfer member and superimposes it, and transfers the superimposed toner images onto a recording material all at once. The image forming unit is constituted by an image reading unit SC and an image forming unit A, and a plurality of image forming units 10Y, 10M, 10C, and 10K, an intermediate transfer unit 7, a sheet feeding and conveying device, and a fixing device. 100.

  An image forming unit 10Y that forms a yellow image includes a photoreceptor 1Y, and includes a charging device 2Y, an exposure device 3Y, a developing device 4Y, a primary transfer device 5Y, and a cleaning device 6Y disposed around the photoreceptor 1Y. Have. An image forming unit 10M that forms a magenta image includes a photoreceptor 1M, and includes a charging device 2M, an exposure device 3M, a developing device 4M, a primary transfer device 5M, and a cleaning device 6M disposed around the photoreceptor 1M. Have. An image forming unit 10C for forming a cyan image has a photoreceptor 1C, and includes a charging device 2C, an exposure device 3C, a developing device 4C, a primary transfer device 5C, and a cleaning device 6C arranged around the photoreceptor 1C. Have. The image forming unit 10K that forms a black image includes a photoreceptor 1K, and also includes a charging device 2K, an exposure device 3K, a developing device 4K, a primary transfer device 5K, and a cleaning device 6K disposed around the photoreceptor 1K. In each image forming unit, charging, exposure, and development are performed, and a toner image of each color is formed on the photoreceptor.

  The intermediate transfer unit 7 includes a semiconductive endless belt-shaped intermediate transfer body 70 that is wound around a plurality of rollers and is rotatably supported.

  The toner images of the respective colors formed by the image forming units 10Y, 10M, 10C, and 10K are transferred onto the rotating intermediate transfer body 70 by the primary transfer devices 5Y, 5M, 5C, and 5K, and are sequentially superimposed and combined. A color toner image is formed. The recording material P accommodated in the paper feeding cassette 20 is fed by the paper feeding device 21 and is conveyed to the secondary transfer device 5A through a plurality of intermediate rollers 22A, 22B, 22C, 22D and a registration roller 23. The color toner images superimposed on the recording material P are collectively transferred. The recording material P onto which the color toner image has been transferred is fixed by the fixing device 100, is sandwiched between the paper discharge rollers 25, and is placed on a paper discharge tray 26 outside the apparatus.

  On the other hand, after the color toner image is transferred to the recording material P by the secondary transfer device 5A, the residual toner is removed by the cleaning device 6A from the intermediate transfer body 70 which has separated the curvature of the recording material P.

  During the image forming process, the primary transfer device 5K is always in pressure contact with the photoreceptor 1K. The other primary transfer devices 5Y, 5M, and 5C are in pressure contact with the corresponding photoreceptors 1Y, 1M, and 1C, respectively, only during color image formation.

  The secondary transfer device 5A comes into pressure contact with the intermediate transfer member 70 only when the recording material P passes through the secondary transfer device 5A and secondary transfer is performed.

  As a fixing device for fixing a toner image, a belt fixing type fixing device 100 is used in which a recording material is nipped and conveyed by a fixing belt and a fixing member, and the toner image is heated and fixed on the recording material during nipping and conveying. FIG. 2 is a diagram showing a configuration of the fixing device 100 according to the embodiment of the present invention.

  The fixing device 100 includes a fixing roller 101 as a fixing member that heats and fixes a toner image, and a fixing belt 105 that sandwiches and conveys the recording material P by the fixing roller 101.

  The fixing roller 101 includes a core metal 101a made of SUS pipe, an elastic layer 101b made of silicon rubber formed on the core metal 101a, and a releasable surface made of PFA formed on the elastic layer 101b (not shown). Consists of layers.

  As shown in FIG. 2B, the fixing belt 105 includes a PI (polyimide) base layer 105a, an elastic layer 105b made of silicon rubber formed on the base layer 105a, and a PFA formed on the elastic layer 105b. And the surface layer 105c. The surface layer 105c contacts the recording material P.

  The fixing belt 105 is stretched around the entrance roller 102, the separation roller 103, and the steering roller 104.

  The entrance roller 102, the separation roller 103, and the steering roller 104 are each made of SUS. The separation roller 103 and the steering roller 104 are non-hollow rod-like members as shown in the figure, but the inlet roller 102 is a pipe-like member, and a heater 107 is provided in the inlet roller 102 to heat the fixing belt 105. . The separation roller 103 presses the fixing belt 105 against the fixing roller 101 to deform the elastic layer 101 b and bites into the fixing roller 101.

  Below the fixing roller 101, the pressing member 106 presses the fixing belt 105 against the fixing roller 101, and the pressing member 106 and the separation roller 103 form a fixing nip N.

  The pressing member 106 includes a support member 106a, a spacer 106b, a pressing pad 106c, a base member 106d, and a sliding member 106e. The pressing pad 106c is made of an elastic body such as silicon rubber and is covered with a sliding member 106e made of a PI sheet as shown in FIG. The portion where the pressing pad 106 c contacts the fixing roller 101 is formed in a curved shape that matches the outer periphery of the fixing roller 101 as shown in the figure. The base member 106d is made of aluminum and is formed integrally with the pressing pad 106c at the time of molding.

  The fixing roller 101 and the separation roller 103 are connected by a power transmission mechanism, and rotate as indicated by an arrow by driving a motor (not shown) as a driving unit. When the fixing belt 105 is pressed by the fixing roller 101, the fixing belt 105 is driven by the fixing roller 101 and also driven by the separation roller 103. When it is not pressed, it is driven only by the separation roller 103 and goes around. The entrance roller 102 and the steering roller 104 are driven to rotate by the fixing belt 105.

  A heater 108 is a halogen lamp that heats the fixing roller 101, and the toner image is fixed by the fixing roller 101 heated by the heater 108.

  In the image formation, the recording material P is introduced into the fixing device 100 as indicated by an arrow W1, the fixing roller 101 and the separation roller 103 rotate as indicated by the arrow, and the recording material P is sandwiched between the fixing roller 101 and the fixing belt 105. In the fixing nip N, the toner image is heated and fixed on the recording material P.

  The recording material P after the fixing process is separated from the fixing roller 101 by the straightness of the recording material P because the radius of curvature of the separation roller 103 is small. That is, since the separation roller 103 bites into the fixing roller 101, when the recording material P exits the fixing nip N, the recording material P advances in a direction away from the fixing roller 101 and is reliably separated from the fixing roller 101.

  In the fixing process, the fixing belt 105 slides around the sliding member 106e, and the sliding member 106e is a member that reduces the sliding resistance of the fixing belt 105. A heat-resistant sheet is used. In addition, in order to reduce the sliding resistance, an uneven surface having a height of about 0.2 mm is formed on the surface of the sliding member 106e (the surface in contact with the fixing belt 105) by embossing to reduce the contact area with the fixing belt 105. ing.

  In order to reduce sliding resistance, a lubricant is further used. In other words, the lubricant is applied by the application member 114 to the inner peripheral surface that is the surface of the fixing belt 105 that is in contact with the sliding member 106e. As the application member 114, a blade or a roller made of heat-resistant fiber such as aramid fiber or PTFE fiber is used. As the lubricant, dimethyl silicone oil, amino-modified silicone oil, fluorine-modified oil or the like is used.

  FIG. 4 shows a drive system of the fixing device 100.

  M1 is a motor as driving means for rotationally driving the fixing roller 101 and the separation roller 103, and a fixing process and a lubricant application process described later are executed by driving the motor M1.

  The entrance roller 102, the separation roller 103, and the pressing member 106 are supported by a support frame 110. The rotation shaft of the entrance roller 102 is fixed to the support frame 110, the separation roller 103 is supported by the support arm 111a, and the pressing member 106 is supported by the support arm 111b. The support arms 111a and 111b are supported by a support base 110b which is a part of the support frame 110 via springs 115a and 115b, respectively. Thus, the separation roller 103 and the pressing member 106 are pressed against the fixing roller 101 via the fixing belt 105 by the elastic force of the springs 115a and 115b.

  The support frame 110 is rotatable around a shaft 110a and is rotated by rotation of a cam 113 as pressing force changing means that is rotationally driven by a motor M2.

  FIG. 5 shows the state of the fixing device in the fixing process (FIG. 5A), the state of the fixing device in the resting state [FIG. Fig. 5 shows the state of the fixing device in Fig. 5 (c). The states shown in FIGS. 5A, 5B, and 5C are set by setting the cam 113 to a predetermined angle by the rotation of the motor M2. In the fixing process in the state of FIG. 5A, the fixing roller 101 and the separation roller 103 are rotated by the motor M1, and the fixing belt 105 is mainly driven by the fixing roller 101 and rotates. During the rest in the state of the part 5 (b), the fixing roller 101 and the separation roller 103 are stopped, and thus the fixing belt 105 is also stopped. In the lubricant application process of FIG. 5C, the fixing roller 101 and the separation roller 103 are rotated by the motor M1, and the fixing belt 105 is driven mainly by the separation roller 103 and circulates.

  5A, the toner image on the recording material is fixed on the recording material. The pressing member 106 and the separation roller 103 press the fixing belt 105 against the fixing roller 101 with a high pressure that can provide sufficient fixing strength. In the state shown in FIG. 5A, the recording material is nipped and conveyed to the fixing nip N to be fixed. The application member 114 as a lubricant application unit contacts the fixing belt 105, and the lubricant is applied to the inner peripheral surface of the fixing belt 105 by the rotation of the fixing belt 105.

  In the rest state of FIG. 5B, the separation roller 103 and the pressing member 106 are separated from the fixing roller 101. The fixing belt 105 is slightly in contact with the fixing roller 101. In the rest state, it is important that the separation roller 103 and the pressing member 106 are separated from the fixing roller 101, thereby preventing permanent deformation of the fixing roller 101 and the pressing member 106. In the rest state, the fixing belt 105 may be separated from the fixing roller 101 or may be in contact therewith.

  In the lubricant application step of FIG. 5C, the lubricant is applied to the sliding member 106e on the surface of the pressing member 106 to form a lubricant film. The fixing belt 105 and the sliding member 106e of the pressing member 106 are in contact with each other with a pressure smaller than that in the fixing process. At this time, the entire surface of the sliding member 106e in contact with the fixing belt may be in contact with the fixing belt 105. The application member 114 as the lubricant application means is in contact with the fixing belt 105 and is in a state of applying the lubricant. The state shown in FIG. 5C, that is, the state in which the fixing belt 105 and the pressing member 106 are brought into contact with each other with a low pressure is set by bringing the pressing member 106 into contact with the fixing belt 105 with a smaller pressing force than in the fixing step. Is done. The separation roller 103 is separated from the fixing roller 101 in the state of FIG.

  In the state of FIG. 5C, the fixing roller 101 and the separation roller 103 rotate by driving of the motor M <b> 1 (see FIG. 4), so that the fixing belt 105 rotates mainly by driving of the separation roller 103, and the fixing belt. A lubricant is applied to the inner peripheral surface of 105. By applying the lubricant in a light pressure contact state between the fixing belt 105 and the pressing member 106, the lubricant on the inner peripheral surface of the fixing belt 105 adheres to the surface of the sliding member 106e, and evenly on the surface of the sliding member 106e. A lubricant film is formed. Further, it is desirable that the fixing member 105 is rotated to some extent and a lubricant film is formed on the inner peripheral surface of the fixing belt 105, and then the pressing member 106 is pressed.

  2 is a heating means for heating the fixing belt 105 in the fixing step and the lubricant applying step. In the fixing process, the fixing belt 105 is heated by the heater 107 to heat the recording material P from the back surface. Also in the lubricant application step, when the fixing belt 105 is heated by the heater 107, the temperature of the lubricant adhering to the inner peripheral surface of the fixing belt 105 increases, so that the viscosity is reduced and more uniform lubricant application is performed. Further, since the lubricant film is easily formed at a high temperature, it is preferable to heat the inner peripheral surface of the fixing belt 105 and the surface of the sliding member 106e. It is desirable to set the temperature of the fixing belt to 100 ° C. or higher. In the lubricant application step, the fixing belt 105 is heated by the heater 107, whereby the fixing belt 105 and the sliding member 106e are sufficiently heated to form a good lubricant film.

  In the state of FIG. 5C, the fixing belt 105 and the sliding member 106e are in contact with each other at a pressure lower than that in the fixing step. The low contact pressure prevents wear of the fixing belt 105 and the sliding member 106e, and a lubricant is applied to the surface of the sliding member 106e to form a lubricant film. When pressed at a high pressure in the fixing process, the lubricant is applied to the sliding member 106e and wear proceeds more than the lubricant film is formed, and the lubricant film is not formed. Once the lubricant film is formed, even if a high pressure is applied in the fixing process in the state of FIG. 5A, it is difficult to wear and the sliding resistance is low.

  The lubricant application in the state of FIG. 5C is executed prior to the start of the image forming process. In particular, prior to the operation of a new unused device, the lubricant application is performed in the state shown in FIG. In an unused new article, since the lubricant is not yet applied to the fixing belt 105 and the pressing member 106, when the fixing process is performed in this state, a large sliding resistance between the fixing belt 105 and the sliding member 106e is obtained. Will occur. As a result, the fixing belt 105 and the sliding member 106e are worn, and these components deteriorate early.

  Further, prior to the start of image formation after a period of time longer than a predetermined time, the lubricant application in the state of FIG. 5C is executed. Further, prior to the start of image formation in a low temperature environment lower than a predetermined temperature, lubricant application in the state of FIG. 5C is executed. The sliding resistance of the fixing belt 105 may become high when it is rested for a long time or in a low temperature environment. This is because even when the fixing roller 101 and the fixing belt 105 reach the set temperature of the fixing process, the surface temperature of the sliding member 106e is low and the viscosity μ of the lubricant film is high, or the state of the lubricant film has changed. It is thought that. When the fixing device is operated in such a state of high sliding resistance, the same wear as in the case of a new article proceeds. However, by performing the lubricant application process in the state of FIG. Such wear is prevented by increasing the temperature of the agent film or forming a new lubricant film.

  The predetermined time and the predetermined temperature are set in advance.

-Device condition fixing roller: outer diameter 65 mm,
1.5mm thick silicon on 5mm thick metal core
Rubber layer, 30 μm thick PFA surface layer separation roller:: outer diameter 23 mm
Metal rod fixing belt made of SUS: a silicon rubber layer having a thickness of 200 μm on a PI having a thickness of 70 μm,
30 μm thick PFA layer pressing pad: 3 mm thick 3 mm on an aluminum base plate
Hardness JISA 20 ° silicon rubber layer lubricant application member: Application blade sliding member made of non-woven fabric of aramid fiber: Embossed PI sheet lubricant: Dimethyl silicon oil, viscosity 300 cs
-Process condition paper: plain paper (basis weight 80 g / m ² ), A4 size lateral feed paper speed: 65 sheets / min. Press member pressing load: fixing process 50 kg
Lubricant application process 5kg
Lubricant application process time: 5 minutes Environmental temperature: 23-26 ° C
Example 1: Lubricant application process only for 0 sheets Example 2: Comparison example of lubricant application process at the time of starting image formation after 0 sheets and overnight standing No lubricant application process The test results are shown in FIG. In FIG. 6, the vertical axis represents the load torque applied to the fixing drive motor, and the horizontal axis represents the number of printed sheets.

  The image forming apparatus is adjusted so that the initial state operates normally. Therefore, the initial state of the comparative example was set to the normal state, and the load torque in the initial state of the comparative example was set to 1, which is the reference value.

  25,000 prints were repeatedly executed per day, and the torque applied to the drive motor at the start of printing and at the end of printing was measured. In the graph of FIG. 6, ▪ represents data of Example 1, ▲ represents data of Example 2, and ◆ represents data of Comparative Example. A part of the data shown in FIG. 6 is shown as a pair arranged vertically, but the data shown by the pair is data at the end of image formation and at the start of image formation. This indicates that there was no difference that appears on the graph between the end of image formation and the start of image formation.

  In FIG. 6, the allowable range is below level L, and if it is higher than level L, a problem such as image displacement has occurred. As shown in the figure, Examples 1 and 2 were good through printing of 30 kp, but in the comparative example, there was an increase in torque exceeding level L, and image displacement occurred. Further, in the comparative example, the rate of increase in torque is high, and the deterioration of the fixing belt and the pressing member is progressing.

DESCRIPTION OF SYMBOLS 100 Fixing device 101 Fixing roller 102 Entrance roller 103 Separation roller 104 Steering roller 105 Fixing belt 106 Pressing member 107, 108 Heater 113 Cam 114 Coating member M1, M2 Motor

Claims (3)

A fixing member that heats and fixes the toner image to the recording material;
A fixing belt,
A pressing member that presses the fixing belt against the fixing member;
Lubricant application means for applying a lubricant to the surface of the fixing belt that contacts the pressing member;
Driving means for driving the fixing belt;
A pressing force changing means for changing the pressing force of the pressing member;
A fixing step for fixing the toner image;
A lubricant application step of applying a lubricant to the pressing member and the fixing belt;
In the lubricant application step, the driving means relatively moves the fixing belt and the lubricant application means to apply the lubricant to the fixing belt, and in the lubricant application step, the pressing force A fixing device, wherein the pressing member is pressed against the fixing belt by a changing unit with a pressing force lower than that in the fixing step.   The fixing device according to claim 1, wherein the pressing member includes a pressing pad and a sliding member that covers the pressing pad, and a lubricant layer is formed on the sliding member in the lubricant application step. .   The fixing device according to claim 1, further comprising a heating unit configured to heat the fixing belt, wherein the heating unit is operated at least in the lubricant application step.

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