JP2008065043A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

In a fixing device, the falling of a bearing member is reduced to prevent occurrence of abnormal noise or damage to durability of a rotating body or a bearing member.
The pressure roller bearing 31 is biased with a symmetrical force by a pressure roller biasing member 33 with respect to the center of gravity in the axial direction of the pressure roller bearing 31 so that no moment is generated in the pressure roller bearing 31, and the pressure roller The bearing 31 does not tilt. As described above, the pressure roller 18 and the pressure roller bearing 31 reduce the tilt and inclination of the pressure roller bearing 31, thereby generating abnormal noise and durability of the pressure roller 18 and the pressure roller bearing 31. It is possible to reduce the loss of sex.
[Selection] Figure 4

Description

  The present invention relates to a fixing device that performs an image fixing process on a recording medium having an unfixed image, and an image forming apparatus equipped with the fixing device.

  Conventionally, a fixing device performs recording by passing a recording medium having an unfixed image through a nip portion formed by a fixing rotator heated by a heat source and a pressure rotator pressed against the fixing rotator. An image fixing process is performed on the medium.

  In the fixing device having the above-described configuration, a ball bearing is generally used as a bearing that rotatably supports a fixing rotator and a pressure rotator. Further, in many cases, the ball bearing is biased so that the pressurizing rotating body is pressed against the fixing rotating body via the ball bearing.

  Further, the fixing rotator and the pressure rotator often have a heat source such as a halogen lamp inside, and these rotators become high temperature. For this reason, in consideration of the thermal expansion of the rotating body, the gap size of the fitting portion between the rotating body and the ball bearing is often larger than the portion where heat is not applied.

  Further, the value of the outer diameter of the rotating body at the time of thermal expansion is often calculated from the maximum reached temperature of the rotating body, and is not an assumed thermal expansion diameter at the time of actual use being heated, In many cases, the gap between the rotating body and the ball bearing is larger than usual.

In this case, since there is a gap in the fitting portion between the ball bearing and the rotating body, the ball bearing is likely to be inclined, and when the rotating body rotates in this inclined state, abnormal noise is generated, or the rotating body or There has been a problem that the durability of the ball bearing is impaired (see Patent Documents 1 and 2).
Japanese Patent No. 3097554 JP 2005-292644 A

  In the configuration of the conventional fixing device, there are several possible causes for the tilting of the bearing member such as a bearing. One of the major factors is which part of the bearing member the member that biases the bearing is. There is a problem of whether or not an energizing force is applied to the.

  For example, when a force is biased asymmetrically with respect to the axial center of gravity of the bearing member, a rotational moment is generated, and the bearing member is liable to fall down.

  The object of the present invention is to solve the above-mentioned conventional problems, devise the application of urging force to the bearing member, etc., reduce the collapse of the bearing member, generate abnormal noise, or durability of the rotating body and the bearing member It is an object of the present invention to provide a fixing device and an image forming apparatus that can alleviate the problem of damages.

  In order to achieve the object, the invention described in claim 1 includes a fixing rotator whose surface is heated by a heat source and a fixing rotator for performing a fixing process on a recording medium having an unfixed image. A pressure rotator that is in pressure contact, and a bearing member is fitted to outer peripheral surfaces of both ends of the fixing rotator and the pressure rotator, and the fixing rotator and the pressure rotator A biasing member that biases the bearing member of the fixing rotator or the pressing rotator with a force symmetrical to an axial center of gravity of the bearing member. Since the urging force can be uniformly applied to the bearing member by this configuration, the rotating member and its bearing member can reduce the tilt and inclination of the bearing member, and this is generated. Generation of abnormal bearing noise, It is possible to reduce problems such as the durability of the rotary member and the bearing member is impaired.

  According to a second aspect of the present invention, in the fixing device of the first aspect, when the axial center and the center of gravity of the bearing member are the same, the entire axial direction of the bearing member is uniformly biased by the biasing member. It is characterized by doing.

  According to a third aspect of the present invention, in the fixing device according to the first or second aspect, the urging position of the urging member in the axial direction of the bearing member is set according to the configuration of the urging member and the bearing member. It is characterized by.

  According to a fourth aspect of the present invention, in the fixing device according to the first aspect, the fixing rotator is composed of an endless belt that is stretched and moved by at least two fixing side rotators, and the pressurizing rotator includes: It is characterized by comprising at least one pressure side rotator that is pressed against at least one of the fixing side rotators via an endless belt.

  According to a fifth aspect of the present invention, there is provided an image forming apparatus including a fixing unit that performs fixing processing by pressing and heating an unfixed image image of a recording medium at a nip portion formed by a plurality of rotating bodies. The fixing device according to any one of claims 1 to 4 is installed as the fixing unit, and by mounting the fixing device according to the present invention, a highly reliable fixing process is performed. High-quality image formation is realized.

  According to the fixing device of the present invention, the biasing force is uniformly applied to the bearing member in the rotating body that constitutes the fixing device, thereby reducing the tilt and inclination of the bearing member in the rotating body and the bearing member. Therefore, it is possible to prevent the occurrence of abnormal bearing noise and the deterioration of the durability of the rotating body and the bearing member. As a result, stable fixing processing is performed, and fixing reliability is improved.

  According to the image forming apparatus according to the present invention, by mounting the fixing device according to the present invention, a fixing process with excellent reliability is performed, and high-quality image formation is realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of an embodiment of an image forming apparatus according to the present invention. Reference numeral 1 denotes an electrophotographic image forming unit that includes an intermediate transfer belt 2 and a plurality of photoreceptors 3 and forms a toner image. 4 is a transfer roller for transferring the toner image formed on the intermediate transfer belt 2 onto a transfer sheet P as a recording medium, and 5 is a fixing process by applying pressure and heating to the transfer sheet P on which the toner image is transferred. Fixing units to be performed, 6, 6 are a plurality of paper feed trays in which transfer paper P as a recording medium is stored, 7, 7 are paper feed rollers provided corresponding to the respective paper feed trays 6, and 8 is an intermediate A registration roller 9 for transporting the transfer paper P to the nip between the transfer belt 2 and the transfer roller 4 with timing is a manual feed tray.

  Further, 10 is a paper discharge roller for discharging the fixed transfer paper P to the paper discharge tray 11, 12 is a reversing unit for reversing the front and back surfaces of the fixed transfer paper P, and 13 is a transfer paper P from the reversing unit 12. It is a double-sided conveyance unit that conveys to the registration roller 8.

  The transfer paper P in the paper feed tray 6 is picked up by the paper feed roller 7 and conveyed to the registration roller 8, and the toner image is transferred by the transfer roller 4, and sent to the fixing unit 5 while carrying an unfixed toner image. . After the toner image is fixed to the transfer paper P in the fixing unit 5, the toner image is discharged onto the paper discharge tray 11 by the paper discharge roller 10.

  When the double-sided image forming mode is set, the transfer paper P on which the image is formed on one side and subjected to the fixing process by the fixing unit 5 is sent to the reversing unit 12 so that the front and back sides are reversed, and the double-sided transport unit 13, and again conveyed to the registration roller 8. Then, the toner image on the other side of the transfer paper P is transferred by the transfer roller 4, and is transferred to the fixing unit 5 after the transfer. After the fixing process is performed, the transfer paper P is discharged to the paper discharge tray 11 by the paper discharge roller 10. The

  FIG. 2 is a configuration diagram of the fixing unit in the present embodiment. The fixing unit 5 includes an endless fixing belt 15 for conveying the transfer paper P on which fixing processing is performed, and a fixing belt 15 stretched over the fixing belt 15. A heating roller 16 and a fixing roller 17 that drive the belt 15 in the direction of the arrow, a pressure roller 18 that presses against the fixing roller 17 via the fixing belt 15, and a heating roller 16 and a pressure roller 18, respectively. It consists of heaters 19 and 20.

  The fixing belt 15 is pressed outward by a belt stretching member 21 and a fixing belt urging member 22 so as to have a predetermined tension. 2, 23 is a cleaning roller that contacts the pressure roller 18 to clean the surface, 24 is an inlet guide plate for guiding the transfer of the transfer paper P, and 25 is an outlet guide plate.

  In the fixing unit 5 configured as described above, the fixing belt 15 receives heat from the heating roller 16 heated by the heater 19, and is pressed against the pressure roller 18 also heated by the heater 20 on one side of the fixing roller 17. Thus, a nip N is formed. When the transfer paper P having an unfixed toner image is sent to the nip N, the transfer paper P is heated and pressurized, and the toner image is fixed to the transfer paper P.

  FIG. 3 is an explanatory view showing the front structure of the fixing roller and the pressure roller in the fixing unit of the present embodiment. In this example, only the bearing structure of the pressure roller 18 is shown. The bearing structure 17 may be similar.

  In FIG. 3, a pressure roller bearing 31 as a bearing member is fitted on each of the rotating shafts 30 protruding from both ends of the pressure roller 18 as a pressure rotating body, and the pressure roller 18 is rotatably supported. ing. The pressure roller bearing 31 is pressurized by a pressure roller urging member 33 that receives the urging force of the spring 32, and the urging force is applied to the pressure roller 18 through the pressure roller bearing 31, thereby In this manner, the pressure roller 18 is pressed against the fixing roller 17 via the fixing belt 15, and a nip N necessary for fixing the toner image on the transfer paper P is formed between the pressure roller 18 and the fixing belt 15.

  Further, as described in the background art, a gap is formed in the fitting portion between the pressure roller 18 and the pressure roller bearing 31 in consideration of the influence of thermal expansion of the pressure roller 18. Therefore, as shown in FIG. 4A, when a force is urged asymmetrically with respect to the center of gravity of the pressure roller bearing 31 in the axial direction by the pressure roller urging member 33, the pressure roller bearing 31. In FIG. 4B, a rotational moment is generated and tilted as shown in FIG.

  However, as shown in FIG. 4C, if the pressure roller urging member 33 urges the center of gravity of the pressure roller bearing 31 in the axial direction with a symmetric force, the above moment is generated. First, as shown in FIG. 4D, the pressure roller bearing 31 does not tilt.

  In the case where the axial center and the center of gravity of the pressure roller bearing 31 are at the same position, the inclination of the pressure roller bearing 31 is reduced by applying a symmetric force to the center. be able to.

  Thus, by uniformly applying a biasing force to the pressure roller bearing 31, the pressure roller bearing 31 and the pressure roller bearing 31 can reduce the tilt and inclination of the pressure roller bearing 31. It is possible to reduce the occurrence of abnormal noise caused by this and the deterioration of the durability of the pressure roller 18 and the pressure roller bearing 31.

  Further, when the axial center and the center of gravity of the pressure roller bearing 31 are at the same position, as shown in FIG. 5, a uniform force is applied to the entire area of the pressure roller bearing 31 in the axial direction. The pressure roller bearing 31 is biased with a force symmetrical to the axial center of gravity, so that the inclination of the pressure roller bearing 31 can be reduced.

  At this time, by making the length of the pressure roller 18 in the axial direction of the pressure roller urging member 33 longer than the length of the pressure roller bearing 31 in the axial direction, the positional accuracy of the pressure roller urging member 33 is increased. Can be energized without making it highly accurate.

  6A and 6B, the position of the pressure roller urging member 33 with respect to the axial direction of the pressure roller bearing 31 is determined according to the shape of the pressure roller urging member 33 and the pressure. It can be determined by the shape of the roller bearing 31.

  That is, in the configuration example shown in FIG. 6 (a), the pressing roller urging member 33 has a urging surface with the pressing roller bearing 31, and the center is supported by the protruding portion. Thus, the point of application of the pressure roller bearing 31 to the center of gravity can be determined only by the dimensions of the pressure roller bearing 31 and the pressure roller urging member 33.

  Further, in the example shown in FIG. 6B, the urging surface of the pressure roller urging member 33 with the pressure roller bearing 31 is formed in a concave shape, and the pressure roller bearing 31 is fitted and supported in this concave portion. Thus, when a force parallel to the radial direction of the pressure roller bearing 31 is applied, the direction of the force is determined only by the dimensions of the pressure roller bearing 31 and the pressure roller urging member 33. Can do.

  6A and 6B, if the position of the center of gravity of the pressure roller bearing 31 is known, a contact portion between the pressure roller urging member 33 and the pressure roller bearing 31; The position necessary for matching the center of gravity of the pressure roller bearing 31 can be determined only by the size and shape of the pressure roller bearing 31 and the pressure roller urging member 33, and more accurately with respect to the center of gravity. It can be energized symmetrically.

  Further, regarding the application of force parallel to the radial direction of the pressure roller bearing 31, the direction of the urging force can be determined only by the size and shape of the pressure roller bearing 31 and the pressure roller urging member 33. The force parallel to the radial direction can be urged accurately, and the inclination of the pressure roller bearing 31 can be reduced.

  The present invention is applied to an image forming unit such as a laser printer, a copying machine, and a facsimile machine, and is particularly effective for a heat fixing device using a heat roller system.

1 is a schematic configuration diagram of an embodiment of an image forming apparatus according to the present invention. Configuration diagram of the fixing unit in the present embodiment Explanatory drawing which shows the front structure of the fixing roller and pressure roller in the fixing unit of this embodiment. (A)-(d) Explanatory drawing of the urging | biasing force addition state to the pressure roller bearing by the pressure roller urging member in this embodiment, and generation | occurrence | production of the inclination of a pressure roller bearing Explanatory drawing which shows the other structural example of the pressure roller urging member and pressure roller bearing in this embodiment. (A), (b) is explanatory drawing which shows the other structural example of the pressure roller urging member and pressure roller bearing in this embodiment.

Explanation of symbols

5 Fixing unit 15 Fixing belt 16 Heating roller 17 Fixing roller (rotating body for fixing)
18 Pressure roller (rotating body for pressure)
19, 20 Heater 30 Rotating shaft 31 Pressure roller bearing (bearing member)
32 Spring 33 Pressure roller biasing member N Nip

Claims (5)

A fixing rotator whose surface is heated by a heat source; and a pressing rotator which is pressed against the fixing rotator to perform a fixing process on a recording medium having an unfixed image. In a fixing device in which bearing members are fitted on outer peripheral surfaces of both ends of the body and the pressing rotator, and the fixing rotator and the pressing rotator are rotatably supported.
A fixing device comprising: an urging member that urges the bearing member of the fixing rotator or the pressurizing rotator with a symmetric force with respect to an axial center of gravity of the bearing member.   2. The fixing device according to claim 1, wherein when the axial center and the center of gravity of the bearing member are the same, the entire axial direction of the bearing member is uniformly urged by the urging member.   The fixing device according to claim 1, wherein a biasing position of the bearing member in the axial direction by the biasing member is set according to a configuration of the biasing member and the bearing member.   The fixing rotator comprises an endless belt that is stretched and moved by at least two fixing-side rotators, and the pressing rotator is connected to at least one of the fixing-side rotators via the endless belt. The fixing device according to claim 1, comprising at least one pressure-side rotating body that is in pressure contact.   An image forming apparatus provided with a fixing unit that performs fixing processing by pressing and heating an unfixed image image of a recording medium at a nip formed by a plurality of rotating bodies as the fixing unit. 4. An image forming apparatus comprising the fixing device according to claim 1.

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