JP2009244400A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device, reducing volatilization of a lubricant and improving heating efficiency. <P>SOLUTION: This fixing device includes: an endless fixing belt 2 rotatably disposed; heaters 3a, 3b provided inside the fixing belt 2 along the central axis direction to heat the fixing belt 2; a belt guide 4 supporting the fixing belt 2 from the inner surface side and having a sliding surface 40 slidable along the inner surface; and a pressure roller 5 for pressurizing the whole or a part of the sliding surface 40 across the fixing belt 2. The sliding surface 40 is formed so that after the lubricant for reducing the friction against the fixing belt 2 flows in from both end sides in the central axis direction on the inflow side where the lubricant flows in between the fixing belt 2 and the sliding surface 40 by the rotation of the fixing belt 2, the lubricant moves to the center side, and after the lubricant moved to the center side moves toward both ends at an outflow side where the lubricant flows out between the fixing belt 2 and the sliding surface 40, the lubricant flows out. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile, and a fixing device used therefor.

  Image forming apparatuses such as copying machines, printers, and facsimile machines that employ an electrophotographic system include a fixing device for fixing a toner image transferred onto a recording medium, such a fixing device. As a device, a two-roller type having a fixing roller and a pressure roller rotating in contact with each other is often used. By passing a recording medium such as paper having an unfixed toner image formed on the surface thereof through a nip formed by the fixing roller and the pressure roller, the toner is melted by heat and pressure, and the recording medium A toner image is fixed on the surface. This heating roller has an elastic layer and a release layer formed on a metal core having a heat source such as a halogen heater inside, and is heated from the inside by the heat source.

  In recent years, a fixing device has been able to instantaneously heat a heating member such as a heating roller from the viewpoint of saving energy and preventing the user from waiting at the time of use. ) As much as possible.

  In response to such a request, a technique using an endless belt-like fixing belt instead of a heating roller has been disclosed (for example, see Patent Document 1).

  FIG. 15 is a front view of a conventional fixing device. 15 includes a fixing belt 1036, a heater 1042 provided inside the fixing belt 1036, a pressure support body 1034 provided inside the fixing belt 1036, and pressure support via the fixing belt 1036. And a pressure roller 1038 provided to press the body 1034. In addition, a lubricant is applied to increase the slidability between the fixing belt 1036 and the pressing support 1034.

In such a fixing device, since the fixing belt 1036 having a small heat capacity is used, the time required for heating is shorter than that of a metal roller, and the warm-up time can be shortened.
JP 2006-243497 A

  However, in recent years, prevention of air pollution derived from volatile organic compounds (VOC) has been screamed, and the environment against ozone, dust, VOC, etc. discharged from image forming apparatuses such as copiers and printers used in offices, etc. Consideration from the aspect is becoming necessary. In particular, reduction of VOC emissions has been proposed, including German blue angels.

  Many of these VOCs are derived from toner and a fixing device. For the components derived from the fixing device, siloxane volatilized from silicon rubber used as a pressure roller or silicon oil used as a sliding lubricant. Is increasing.

  Thus, in the conventional fixing device, the sliding component (silicon oil) of the sliding lubricant heated at a very high temperature volatilizes and releases a volatile organic compound (siloxane).

  Further, since the sliding component is volatilized, the sliding property between the fixing belt 1036 and the pressing support 1034 is lowered.

  Further, since the radiant heat of the heater 1042 heats the slidable lubricant applied to the inner surface of the fixing belt 1036, the heat is absorbed by the lubricant and the heating efficiency of the fixing belt decreases.

  SUMMARY An advantage of some aspects of the invention is that it provides a fixing device and an image forming apparatus capable of reducing the volatilization of a lubricant and improving the heating efficiency in consideration of the problems of a conventional fixing device.

In order to achieve the above object, the first present invention provides:
An endless fixing belt disposed rotatably;
In order to heat the fixing belt, a heating unit provided along the central axis direction inside the fixing belt;
A support member supported from the inner surface side of the fixing belt and having a sliding surface slidable with the inner surface;
A pressing member that presses all or part of the sliding surface across the fixing belt,
The sliding surface is
Lubricant for reducing friction with the fixing belt flows from both ends in the central axis direction on the inflow side where the fixing belt rotates and flows into between the fixing belt and the sliding surface. Thereafter, the lubricant moves to the center side, the lubricant flows out from between the fixing belt and the sliding surface, and the lubricant moved to the center moves to the both end sides and then flows out. The fixing device is formed as described above.

The second aspect of the present invention is
The heating unit is
In the fixing device according to the first aspect of the present invention, the fixing device includes a heater disposed on both ends of the fixing belt so as to face a region between predetermined regions through which the lubricant flows out.

The third aspect of the present invention
The sliding surface is
An outflow groove formed on the outflow side so that the lubricant flows out from the center side to a predetermined region on both end sides of the fixing belt;
The fixing device according to the first or second aspect of the present invention includes an inflow groove formed on the inflow side so that the lubricant moves from each of the predetermined regions to the center side.

The fourth aspect of the present invention is
The inflow groove is
At least a first step formed from the position corresponding to the outside of each of the predetermined regions toward the center side so as to restrict the lubricant from moving along the rotation direction on the both end sides. Have
The outflow groove is
There is at least a second step formed from the center toward a position corresponding to the inside of each predetermined region so as to restrict the lubricant from moving along the rotation direction on the center side. The fixing device according to the third aspect of the present invention.

The fifth aspect of the present invention is
The sliding surface is
An inflow surface in which the inflow groove is formed;
An outflow surface in which the outflow grooves are formed;
A pressure surface formed between the inflow surface and the outflow surface and pressed by the pressure member;
The pressure surface has a moving groove constituted by a third step formed in a longitudinal position corresponding to a nip portion with the pressure member,
The third step is a fixing device according to a fourth aspect of the present invention, which is connected to the first step.

The sixth aspect of the present invention
In the fixing device according to the fifth aspect of the present invention, the depths of the inflow groove, the movement groove, and the outflow groove are constant.

The seventh aspect of the present invention
The inflow groove is
A fourth step formed from the center of the end on the pressure surface side to a position corresponding to the inside of each predetermined region of the end on the inflow side;
The outflow groove is
The fixing according to the fifth aspect of the present invention, further comprising: a fifth step formed from the end on the outflow surface side of the third step to a position corresponding to the outside of each predetermined region of the end on the outflow side. Device.

Further, the eighth aspect of the present invention is
The sliding surface is
An inclination formed on the outflow side so that the lubricant flows out from the center side to a predetermined region on both ends of the fixing belt;
The fixing device according to the first or second aspect of the present invention has a slope formed on the inflow side so that the lubricant moves from each predetermined region to the center side.

The ninth aspect of the present invention provides
The sliding surface is
On the inflow side, the distance from the central axis is closer to the center side than the both end sides,
The fixing device according to the eighth aspect of the present invention is such that, on the outflow side, the distance from the central axis of the fixing belt is farther on the center side than on the both end sides.

The tenth aspect of the present invention is
The sliding surface is
A pressing surface pressed by the pressing member;
An inflow surface formed on the inflow side of the pressure surface;
An outflow surface formed on the outflow side of the pressure surface;
A first region formed on the central side, the distance from the central axis being constant in the central axis direction;
A fixing device according to a ninth aspect of the present invention, further comprising: a second region formed on each of the both end sides, the distance from the central axis being constant in the central axis direction.

The eleventh aspect of the present invention is
The first region is
In the inflow surface, both ends thereof are formed so as to gradually spread from the end on the inflow side to the end on the pressurization surface side, and in the pressurization surface, both ends thereof are on the end on the outflow surface side from the end on the inflow surface side. Is formed at a constant interval until the both ends of the outflow surface gradually spread from the end on the pressure surface side to the end on the outflow side,
The second region is
In the inflow surface, both ends thereof are formed so as to gradually spread from the end on the inflow side to the end on the pressurization surface side, and in the pressurization surface, both ends thereof are on the end on the outflow surface side from the end on the inflow surface side. The fixing device according to the tenth aspect of the present invention is formed at regular intervals until the both ends of the outflow surface gradually spread from the end on the pressure surface side to the end on the outflow side.

The twelfth aspect of the present invention is
An image forming unit for forming a developer image on the image carrier;
A transfer unit for transferring the developer image to a transfer material;
An image forming apparatus comprising: the fixing device according to claim 1, wherein the transferred developer image is fixed on the transfer material.

  According to the present invention, it is possible to provide a fixing device and an image forming apparatus capable of reducing the volatilization of the lubricant and improving the heating efficiency.

  Hereinafter, an embodiment of an image forming apparatus including a fixing device according to the present invention will be specifically described with reference to the drawings.

(Embodiment 1)
FIG. 1 illustrates the configuration of the image forming apparatus. The image forming apparatus 100 includes an image forming unit 101 for forming a toner image to be transferred to a recording medium. The image forming unit 101 includes a photosensitive drum 102 that is an image carrier, and a transfer belt 103 that conveys recording paper (transfer material) S is provided below the photosensitive drum 102. The photosensitive drum 102 is a drum in which a surface of a metal drum is coated with a photosensitive layer, for example, an A-SI (amorphous silicon) photosensitive drum, and rotates in the direction of arrow A in the figure.

  A charger 104 for uniformly charging the surface of the photosensitive drum 102, a laser irradiation device 105 for irradiating a photosensitive laser beam, and a developing device 107 are arranged along the rotation direction on the outer periphery of the photosensitive drum 102. Are arranged in order. It should be noted that the drum cleaner 109 and the surface of the photoconductive drum 102 are located downstream of the position where the photoconductive drum 102 and the recording paper S conveyed by the transfer belt 103 are in contact (transfer section) T in the rotation direction of the photoconductive drum 102. A static eliminator 110 is provided to neutralize the charges.

  The laser irradiation device 105 includes a laser light emitting unit and an optical device such as a mirror and a lens. An electrostatic latent image is formed on the surface of the photosensitive drum 2.

  The developing unit 107 is for attaching toner to a latent image formed on the surface of the photosensitive drum 102 to form a toner image. The developing unit 107 supplies an appropriate amount of toner in the toner container to the surface of the photosensitive drum 102. Develop the electrostatic latent image.

  The transfer belt 103 is an endless belt stretched between the driving roller 112 and the driven roller 113, and includes a resistance-controlled NBR base material. In order to ensure releasability, a PTFE coating dispersed in a high-resistance urethane binder is applied.

  The drive roller 112 and the driven roller 113 are supported in parallel with each other in rotation axis and in parallel with the axis of the photosensitive drum 102. When the driving roller 112 is driven to rotate, the transfer belt 103 circulates in a predetermined direction (in the direction of arrow B in the figure) at a predetermined speed. In addition to the driving roller 112 and the driven roller 113, a belt cleaner 114 for removing excess toner adhering to the transfer belt 103 is provided downstream of the driving roller 112 in the belt moving direction. A belt charger 118 for charging the belt and electrostatically adsorbing the recording paper S is provided on the upstream side of the transfer portion T of the transfer belt 103 in the moving direction. A neutralizer 119 for removing the charging of the transfer belt is provided immediately before the drive roller 112.

  A bias applying transfer roller 115 is provided at a position facing the photosensitive drum 102 with the transfer belt 103 interposed therebetween. The transfer roller applies a charge having a reverse polarity to the toner on the surface of the photosensitive drum 102 to the transfer belt 103, and causes the toner image on the photosensitive drum 102 to be transferred to the recording paper S on the surface of the transfer belt 103 by this charge. Thus, a high voltage is applied from the high-voltage power supply 116 and the spring 117 is pressed against the back surface of the transfer belt 103.

  The transfer belt 103, the driving roller 112, the driven roller 113, the belt cleaner 114, the transfer roller 115, the high voltage power source 116, the spring 117, and the belt charger 118 correspond to an example of the transfer unit of the present invention.

  A fixing device 1 according to the present invention is provided on the downstream side of the transfer belt 103 in the sheet conveyance direction.

  Hereinafter, the configuration of the fixing device 1 of the present embodiment will be described.

  FIG. 2 is a front sectional configuration diagram of the fixing device 1 according to the present embodiment. As shown in FIG. 2, the fixing device 1 sandwiches the fixing belt 2, two heaters 3 a and 3 b provided inside the fixing belt 2, a belt guide 4 that supports the fixing belt 2, and the fixing belt 2. And a pressure roller 5 that presses the belt guide 4 to form the nip portion 10. Note that the length of the nip portion 10 in the sheet conveyance direction is 10 W.

  The fixing belt 2 is a flexible belt formed in an endless shape, and has appropriate rigidity and elasticity. The material of the fixing belt 2 is, for example, fluorine on the surface of a belt-like thin metal (stainless steel, nickel, etc.) substrate. A coating with a heat absorbing paint applied to the inner peripheral surface can be suitably used.

  The fixing belt 2 circulates on a substantially circular locus, and heaters 3a and 3b are installed therein as radiant heat sources. The heaters 3a and 3b are for melting the toner on the recording sheet S and securely adhering it to the recording sheet. For example, a halogen lamp is used as the heaters 3a and 3b.

  The belt guide 4 is formed to have the same length as that of the fixing belt 2 in the axial direction. The belt guide 4 is formed in the shape of a bowl having a concave cross section, and the surface on the fixing belt 2 side is the fixing belt 2 side. It becomes the sliding surface 40 which slides with the inner peripheral side. The belt guide 4 is for maintaining the shape of the portion of the flexible fixing belt 2 facing the pressure roller 3 in a predetermined shape (in the illustrated example, a straight line) and securing the nip portion 10, and has an appropriate rigidity. For example, a metal material such as stainless steel.

  Further, since the belt guide 4 is formed to be thin in order to reduce the heat capacity, a backup member 6 is provided on the heater 3a, 3b side of the belt guide 4 in order to suppress bending in the longitudinal direction. Yes. The backup member 6 is used to apply a back pressure so that the belt guide 4 can withstand the pressure of the pressure roller 3, and is formed of a high strength material such as stainless steel. Further, as shown in FIG. 2, the backup member 6 has a plate-like member 6a facing the belt guide 4, and a rib-like member 6b rising up at a right angle on the opposite side of the belt-like member 4a of the plate-like member 6a. In the figure, it is formed in an inverted T shape. The rib-like member 6b is attached to a housing not shown. In FIG. 2, the paper transport direction is indicated as V.

  The pressure roller 5 is rotated at a predetermined speed in the direction of arrow X by a driving device (not shown). When the pressure roller 5 is rotated, the fixing belt 2 in contact with the pressure roller 5 is driven and rotated in the direction of the arrow Y in a rotating manner. As the pressure roller 5, for example, a material in which an elastic layer such as silicon rubber is formed on a core metal material such as iron and a surface release layer such as a PFA tube is formed on the elastic layer can be used. .

  Further, silicone oil as a lubricant is applied to the inner peripheral surface side of the fixing belt 2 in order to improve the slidability with the sliding surface 40. Since this lubricant has viscosity, it rotates according to the rotation of the fixing belt 2 in the direction of the arrow Y, and flows between the sliding surface 40 and the fixing belt 2 from the inflow end 40a shown in FIG. It passes through and flows out from the outflow end 40b.

  FIG. 3 is a front configuration diagram showing only the belt guide 4. As shown in FIG. 3 and FIG. 2, the sliding surface 40 of the belt guide 4 is formed on the upstream side of the pressing surface 41 with the pressing surface 41 pressed by the pressing roller 5 and the paper transport direction V as a reference. The inflow surface 42 on the side into which the lubricant flows is formed, and the outflow surface 43 on the side from which the lubricant flows out is formed on the downstream side of the pressure surface 41.

  FIG. 4 is a perspective view of the belt guide 4 as seen from the pressure roller 5 side. In FIG. 4, the fixing belt 2 is indicated by a dotted line. 5A, 5B, and 5C are plan views of the belt guide 4 as viewed from above, in front, and below in FIG.

  As shown in FIGS. 4 and 5, the inflow surface 42 is formed with inflow grooves 42 a having inflow ports 42 b for the lubricant to flow in at two locations near both ends in the axial direction of the fixing belt 2. . Each end (outer) step 42t forming the two inflow grooves 42a is slanted from both ends toward the center so that the distance between the two steps 42t is narrowed toward the pressure surface 41. Is formed. Further, each step 42 s on the central side forming the two inflow grooves 42 a is formed in a V shape in FIG. 5 from the center to both ends in the direction opposite to the conveyance direction V.

  The pressing surface 41 is formed with one moving groove 41a for the lubricant to move. The step 41t on both ends forming the moving groove 41a is formed continuously with the step 42t on the end of the two inflow grooves 42a. The interval between the steps 41 t corresponds to the axial length of the pressure roller 5.

  The outflow surface 43 is formed with two outflow grooves 43a through which the lubricant flows out. Each step (outer side) step 43t that forms the outflow groove 43a is formed obliquely from the step 42t toward both ends so that the interval widens toward the outflow end 40b. Moreover, each level | step difference 43s of the center side which forms the two outflow grooves 43a is formed in the reverse V shape in FIG. 5 toward the both end sides from the center side. In FIG. 5, a portion where the lubricant moves is hatched, and the moving direction of the lubricant is indicated by an arrow.

  6 is a cross-sectional view taken along the line AA ′ of FIG. As shown in FIG. 6, the heater 3a has a plurality of light emitting section filaments 30 arranged at predetermined intervals in the axial direction. The fixing belt 2 is heated by the radiant heat of the light emitting filament 30. In the present embodiment, the position in the longitudinal direction where the light emitting unit filament 30 is arranged corresponds to the width in the longitudinal direction of the pressure roller 5. In other words, the plurality of light emitting unit filaments 30 are disposed at positions corresponding to the region 2 b in which the region 2 a is spaced from both ends of the fixing belt 2. Since the radiant heat of the light emitting section filament 30 is radiated in the direction perpendicular to the axis, the radiant heat is radiated strongly to the region 2b. Since this region 2b also corresponds to the axial length of the nip portion 10 between the pressure roller 5 and the fixing belt 2, the paper passing through the nip portion 10 can be efficiently heated. The heater 3b has the light emitting filament 30 as in the case of the heater 3a. However, the heater 3b is used for fixing a small size sheet, and a plurality of light emitting filaments 30 are arranged inside the heater 3a. ing.

  Further, FIG. 6 illustrates a portion of the belt guide 4 having the outflow surface 43, and two outflow grooves 43a are indicated by dotted lines. The outlet 43b of the outflow groove 43a is formed within the width of the region 2a on both ends in the axial direction of the fixing belt 2. Although not shown, the inlet 42 b of the inflow groove 42 a is also formed within the width of the region 2 a of the fixing belt 2. The belt guide 4 has an edge 44 formed upward from the inflow end 40a and an edge 45 formed upward from the outflow end 40b. The edge 44 and the edge 45 are It may not be formed.

  An example of the heating unit of the present invention corresponds to the heaters 3a and 3b of the present embodiment, and an example of the support member of the present invention corresponds to the backup member 6 of the present embodiment. An example of the pressure member of the present invention corresponds to the pressure roller 5 of the present embodiment. An example of the first step of the present invention corresponds to the two steps 42t of the present embodiment, and an example of the second step of the present invention corresponds to the two steps 43s of the present embodiment. An example of the third step of the present invention corresponds to the two steps 41t of the present embodiment. An example of the fourth step of the present invention corresponds to the two steps 42s of the present embodiment, and an example of the fifth step of the present invention corresponds to the two steps 42t of the present embodiment.

  Next, the operation of the fixing device of this embodiment will be described.

  During the fixing operation, the fixing belt 2 rotates in the direction indicated by the arrow Y in FIG. 2 together with the heating by the radiant heat of the heaters 3a and 3b. Due to this rotation, the lubricant applied to the inner peripheral surface of the fixing belt 2 has viscosity, so that the lubricant moves with the rotation of the fixing belt 2 and flows between the sliding surface 40 and the intermediate transfer belt 2. It flows out through the outlet 43b and into the width of the region 2a near both ends of the fixing belt 2 (see FIG. 5C). The lubricant that has flowed out moves as the fixing belt 2 rotates.

  Then, it flows between the sliding surface 40 and the fixing belt 2 from the inlet 42b formed within the width of the region 2a. As shown in FIG. 5A, the lubricant that has flowed in is prevented from moving along the rotational direction by the step 42t and moves toward the center as shown in FIG.

  Next, as shown in FIG. 5B, the lubricant spreads over the entire area (groove 41 a) pressed by the pressure roller 5 on the pressure surface 41. Here, since the lubricant has spread throughout the nip portion 10, the fixing belt 2 rotates smoothly. Subsequently, the lubricant is prevented from moving along the rotation direction by the step 43S on the outflow surface 43, and moves from the center to both ends.

  Finally, as shown in FIG. 5C, the lubricant flows out from the outlets 43b formed at both ends.

  In this fixing operation, a region 2s through which the lubricant flows on the fixing belt 2 is indicated by hatching in FIG. Further, the region 2s is indicated by hatching in FIG. The region 2s corresponds to an example of the “predetermined region from which the lubricant flows out” according to the present invention, and an example of the “region inside the predetermined region at both ends” according to the present invention is shown in FIG. This corresponds to the region 2b between the two regions 2s. Further, the boundary 21s on both ends of the two regions 2s corresponds to an example of the outside of the predetermined region of the present invention, and the boundary 22s on the center side of the two regions 2s corresponds to an example of the inside of the predetermined region of the present invention. (See FIG. 6).

  Thus, the lubricant passes through the region 2s within the width of the region 2a at both ends of the fixing belt 2, and the light emitting section filament 30 is not disposed at a position corresponding to the region 2a. Compared with the case where it passes through the entire inner peripheral surface, the radiant heat is not directly received, so that the volatilization of the lubricant can be reduced. Further, since the lubricant does not pass through the region 2b of the fixing belt 2 where the radiant heat is strongly irradiated, the radiant heat absorbed by the lubricant is reduced and the heating efficiency of the fixing belt 2 can be improved.

(Example)
In the present embodiment, the above-described configurations are set under the following conditions.

  The outer diameter of the fixing belt 2 is set to 30 mm, the thickness of the stainless steel substrate is set to 0.03 mm, and the thickness of the fluorine coating is set to 20 μm. For example, the outer diameter of the pressure roller 5 is set to 25 mm, and the thickness of the surface release layer is set to 50 μm. The thickness of the belt guide is, for example, 0.5 mm, and the depths of the inflow groove 42a, the movement groove 41a, and the outflow groove 43a are set to 50 μm. The thickness of the plate-like member 6a of the backup member 6 described above is set to 1.2 mm, and the height of the rib-like member 6b is set to 20 mm. Further, as the heater 3a, for example, a heater with 900 W output can be used, and as the heater 3b, a heater with 450 W can be used. The length 10 W in the paper conveyance direction of the nip portion 10 is set to 8.5 mm. Silicon oil used as a lubricant volatilizes at about 240 ° C. or higher.

  Under such a configuration, the heaters 3a and 3b were controlled so that the surface temperature of the fixing belt 2 was 180 ° C., and the fixing belt 2 was rotated at an outer peripheral speed of 250 mm / sec under the condition of a fixing load of 120 N. In this case, the temperature in the area 2 b on the inner peripheral surface of the fixing belt 2 was about 270 ° C., and the temperature in the area 2 a was about 180 ° C.

  From this, it can be seen that the volatilization amount can be reduced by allowing the lubricant to pass through the region 2a which is lower than the temperature at which the silicon oil volatilizes without passing through the region 2b.

  The sliding surface 40 of the present embodiment has two steps 42 s and two steps 43 t, but after the lubricant flows from both ends on the inflow side due to the rotation of the fixing belt 2. Since the lubricant that has moved to the center side and moved to the center side on the outflow side needs to flow out after moving to both ends, the step 42 s and the step 43 t may not be formed. In this case, the gap between the steps 42t is the inflow port.

  Further, in the present embodiment, the position of the light emitting unit filament 30 is provided at a position corresponding to the region 2s, and is not provided at the position corresponding to the region 2s. The part may be arranged in the region 2s. Even in such a case, since the radiant heat is relatively weaker at both ends than at the center, the amount of volatilization can be reduced as compared with the conventional case.

(Embodiment 2)
The fixing device according to the second embodiment of the present invention will be described below. The basic configuration of the fixing device of the second embodiment is the same as that of the first embodiment, but the configuration of the belt guide is different. Therefore, this difference will be mainly described.

  FIG. 7 is a front sectional view showing the belt guide 7 of the fixing device according to the second embodiment, a backup member 6 that suppresses the bending of the belt guide 7, and a part of the fixing belt 2.

  As shown in FIG. 7, the belt guide 7 is provided with a sliding surface 70 for sliding with the inner peripheral surface of the fixing belt 2. Further, the overall schematic shape of the belt guide 7 is formed in the same length as the length of the fixing belt 2 in the axis 2e direction as in the first embodiment, and the cross-sectional shape is curved in a concave shape upward. Is formed. FIG. 8 shows a perspective view of the belt guide 7 in a state where the curve is extended. In FIG. 8, the belt guide 7 is illustrated so that the upper side is the sliding surface 70. 9A, 9B, and 9C are a plan view, a front view, and a side view of the belt guide 7 in the state shown in FIG. 6 to 9 show the paper transport direction V. Further, in FIG. 9C, the fixing belt 2 which is not curved so as to correspond to the extended belt guide 7 is indicated by a dotted line for the purpose of explanation. As shown in FIG. 7, the belt guide 9 has edge portions 701 and 702 at the upstream end and the downstream end, respectively, like the belt guide 4 of the first embodiment. 702 may not be formed. Note that the edges 701 and 702 are omitted in the drawings after FIG.

  As shown in FIGS. 8 and 9, the belt guide 7 is a flat surface formed so that the axial width on the downstream side is wider than the upstream side at the center in the axial direction on the upstream side of the sliding surface 70. A region 74, a region 75 formed so that the downstream side is wider than the upstream side at both axial ends of the sliding surface 70, and a region formed between the region 74 and the region 75 73. Note that the line in the region 73 in FIG. 8 is for representing a change in inclination.

  As shown in FIG. 9A, the sliding surface 70 includes a pressing surface 76 that is pressed by the pressing roller 5, an inflow surface 77 that is formed on the upstream side of the pressing surface 76, and a downstream side of the pressing surface 76. And an outflow surface 78 formed on the side.

  As shown in FIGS. 8 and 9, in the region 74, the width 74L is widened at the inflow surface 77, the width 74L is constant at the pressurization surface 76, and the width 74L is widened at the outflow surface in the paper transport direction V. Is formed. Further, the region 75 is formed so that the width 75L is widened at the inflow surface 77, the width 75L is constant at the pressurization surface 76, and the width 75L is widened at the outflow surface 78 as it goes in the transport direction V.

  Further, as shown in FIG. 9C, the region 74 is formed so that the distance from the fixing belt 2 becomes smaller from the upstream side toward the downstream side, and the region 75 is fixed from the upstream side toward the downstream side. 2 is formed so as to widen the distance between the two.

  The nip portion 10 shown in FIG. 6 is included in the pressure surface 76, and the length 10W in the conveying direction V is the same as the pressure surface 76, but the width 10L in the longitudinal direction is within the pressure surface 76. This corresponds to a portion between the two regions 75 at both ends.

  Next, FIG. 10A, FIG. 10B, and FIG. 10C schematically showing only the cross-sectional portion between AA ′, BB ′, CC ′, DD ′, and EE ′ shown in FIG. The positional relationship between the fixing belt 2 and the sliding surface 70 in each cross section will be described using FIGS. FIG. 6 is a cross-sectional view taken along line FF ′ in FIGS. 10 (a), 10 (b), 10 (c), and 10 (d). For the sake of explanation, FIGS. 10B, 10 </ b> C, and 10 </ b> D show a state in which the fixing belt 2 is not pressed by the pressure roller 5.

  6 corresponds to the upstream end of the sliding surface 70 and is an inflow end 70a through which the lubricant flows into the sliding surface 70 as the fixing belt 2 rotates in the Y direction. As shown in FIG. 10A, the inflow end 70 a is inclined in the region 73 so that the distance t from the fixing belt 2 is wide at the center 71 and narrows toward the both ends 72. That is, at the inflow end 70 a, a triangular inflow port 79 is formed between the fixing belt 2 and the sliding surface 70 for allowing the lubricant to flow in.

  Between BB 'is a position corresponding to the upstream side of the nip part 10 shown in FIG. As shown in FIG. 10B, the sliding surface 70 is formed such that the interval t with the fixing belt 2 is wide on the center 71 side and narrows toward both ends 72 between BB ′. A region 74 having a constant interval t with the fixing belt 2 is formed on the center 71 side, and a region 75 having a constant interval t with the fixing belt 2 is formed at both ends. A region 73 that is inclined so as to connect the region 74 and the two regions 75 is formed.

  Between CC 'is a position corresponding to the center of the nip part 10 shown in FIG. As shown in FIG. 10C, the sliding surface 70 is formed so that the distance t from the fixing belt 2 is constant between CC ′. That is, the intervals t between the areas 73, 74, and 75 and the fixing belt 2 are all equal.

  Between DD 'is a position corresponding to the downstream side of the nip part 10 shown in FIG. As shown in FIG. 10D, between DD ′, the sliding surface 70 has a narrow interval t between the central region 74 and the fixing belt 2 and a wide interval t between the region 75 and the fixing belt 2. It is formed to become. That is, the region 73 is formed from the region 74 toward the region 75 so that the distance t from the fixing belt 2 becomes wider, and is inclined in the direction opposite to BB ′.

  Between EE ′ corresponds to the outflow end 70 b from which the lubricant flows out of the sliding surface 70. As shown in FIG. 10E, at the outflow end 70 b, the sliding surface 70 is formed so that a gap with the fixing belt 2 is generated in the region 75 and there is no gap with the fixing belt 2. . A region 73 connecting the region 74 and the region 75 is formed substantially perpendicular to the regions 74 and 75, and an outlet 70 e through which the lubricant flows out is formed by the region 73 and the region 74.

  In addition, since the pressure roller 5 actually presses the fixing belt 2 and the belt guide 7 between the above-described BB ′, CC ′, and DD ′, there is a gap between the belt guide 7 and the fixing belt 2. It has not occurred.

  FIG. 11 is a diagram showing the moving part of the lubricant on the belt guide 7 in the state of FIG. 8 by arrows. As shown in FIG. 11, when the fixing belt 2 is rotated as in the first embodiment, the lubricant existing between the sliding surface 70 and the fixing belt 2 is formed in the region 75 of the outflow end 70b. It flows out from 70e. Since the outlet 70e is formed in the region 2a of the fixing belt 2, the lubricant flows out into the region 2a.

  As the fixing belt 2 rotates, the lubricant is moved to the inflow end 70 a of the belt guide 7. At the inflow end 70a, as shown in FIG. 10A, the interval t between the fixing belt 2 and the sliding surface 70 is wider at the center than at both ends. Therefore, the lubricant moves from both ends 72 toward the center 71 side.

  Then, the lubricant flows from the inflow surface 77 to the pressure surface 76. Here, as shown in FIG. 10B, the conveyance surface 70 is formed between the BB ′ so that the interval t between the fixing belt 2 and the sliding surface 70 is wider at the center than at both ends. 10, there is actually no gap between the fixing belt 2 and the sliding surface 70 due to pressing by the pressure roller 5. However, since the center 71 side is set wider than the distance between the ends 72, the pressure applied by the pressure roller 5 is higher at the ends 72 than at the center 71. Therefore, the lubricant that has flowed in from both end portions also moves between the BB's of the pressing surface 76 (nip portion 10) toward the center side and spreads over the entire area in the longitudinal direction. Further, as shown in FIG. 10D, when the rotation is performed, the interval t on the center 71 side becomes narrower and the interval t on both ends 72 side becomes wider, so that the pressure applied by the pressure roller 5 is closer to the ends 72 side than the center 71 side. As a result, the lubricant moves from the center 71 side to both ends 72 side.

  Then, the lubricant further moves toward the both ends 72 on the outflow surface 78, and finally the lubricant flows out from the outlet 70 e formed at the both ends 72.

  In the second embodiment, the pressure at the nip portion 10 when the fixing operation was performed under the same conditions as in the above example was measured. FIG. 12A is a graph showing a pressure distribution graph in the longitudinal direction between BB ′ in FIG. 6. FIG. 12B is a graph showing a pressure distribution graph in the longitudinal direction between DD ′ in FIG. FIG. 12C is a graph showing a pressure distribution graph in the circumferential direction at the central portion in the longitudinal direction of the nip portion 10. FIG. 12D is a graph showing a pressure distribution graph at the end of the nip portion 10 in the longitudinal direction (region 75). According to each graph, it can be seen that the pressure applied by the pressure roller 5 is lower when the distance t is formed wider.

  As described above, since the lubricant can be moved into the regions 2a at both ends of the fixing belt 2 in this embodiment, it is possible to avoid receiving the radiant heat of the heaters 3a and 3b directly. The effect of reducing the volatilization amount can be exhibited.

  In addition, the inflow side and the outflow side of the present invention can be divided on the basis of, for example, the above-mentioned CC ′, and “the lubricant is applied from the center side to a predetermined region on the both end sides of the fixing belt of the present invention. An example of the “inclination formed on the outflow side so as to flow out” corresponds to the inclination of the regions 73, 74, and 75 on the downstream side from the CC ′ that is the center of the nip portion 10 in the transport direction V. An example of the “inclination formed on the inflow side so that the lubricant moves from the respective predetermined regions to the center side” corresponds to the inclinations of the regions 73, 74, and 75 on the upstream side from CC ′.

  In addition, an example of “the distance from the central axis of the fixing belt on the outflow side is farther on the center side than the both end sides” of the present invention is an interval t between DD ′ and EE ′. This is equivalent to being wider on both ends 72 than on the center 71. This is because the wider distance t, which is the distance from the inner peripheral surface of the fixing belt 2, is closer to the central axis 2e. In addition, an example of “in the inflow side, the distance from the central axis on the inflow side is closer to the center side than the both end sides” is an example in which the distance t between AA ′ and BB ′ is the center 71 side. This corresponds to the narrowness at both ends 72 side. This is because the smaller distance t, which is the distance from the inner peripheral surface of the fixing belt 2, is a position farther from the central axis 2e. In FIG. 10A, the central axis 2e is indicated by a dotted line. An example of the first region of the present invention corresponds to the region 74 of the present embodiment, and an example of the second region of the present invention corresponds to the region 75 of the present embodiment.

  Further, the shape of the belt guide 7 according to the second embodiment is not limited to the shape, and may be, for example, a belt guide 8 as shown in FIG. As with the belt guide 7 of FIG. 8, the sliding surface 80 of the belt guide 8 has a region 84 formed at the center in the longitudinal direction, a region 85 formed at both ends in the longitudinal direction, and a region 84 between the regions 84 and 85. And a region 83 formed in the region. Unlike the region 74 of the belt guide 7 shown in FIG. 8, the region 84 does not have a constant width at the nip portion 10, and the width 84L gradually increases in the transport direction. That is, the region 84 has a triangular shape in plan view. Also, the regions 85 at both ends in the longitudinal direction are different from the region 75 in that the width is not constant in the nip portion, and the width 85L is widened in the transport direction, and has a triangular shape in plan view. This region 84 corresponds to an example of the first region of the present invention, and the region 85 corresponds to an example of the second region of the present invention.

  FIG. 14 is a perspective view showing a belt guide 9 according to another modification. The belt guide 9 includes a region 94 formed in a triangular shape in plan view so that the width 94L is widened in the conveying direction from the center in the longitudinal direction on the upstream side, the center 91 and the end 92a on the upstream side, and the end 92b on the downstream side. And a region 93 formed between the region 94 and the region 95. In this case, the outlet 90e through which the lubricant flows out has a triangular shape. The belt guide 9 does not include the above-described second region of the present invention, but in short, an inclination formed on the outflow side so that the lubricant flows out from the central side to the predetermined region on both ends, and the predetermined region. If there is an inclination formed on the inflow side so that the lubricant moves from the center side to the center side, the lubricant can be conveyed in the vicinity of both ends of the fixing belt 2, so that the effect of reducing the volatilization amount can be exhibited. I can do it.

  In the belt guide described above, the sliding surface is formed by changing the thickness. However, the sliding surface may be formed by molding a plate member having a constant thickness. In any case, it is more preferable that the thickness is smaller from the viewpoint of reducing the heat capacity.

  In the first and second embodiments, the lengths of the pressure surfaces 41 and 76 in the paper conveyance direction coincide with the length 10 W of the nip portion 10 in the conveyance direction. May be longer than the length 10 W of the nip portion 10. The axial length of the pressure roller 10 is shorter than the length of the pressure surfaces 41 and 76 in the longitudinal direction, but may be the same or longer.

  The fixing device and the image forming apparatus of the present invention have the effect of reducing the volatilization of the lubricant and improving the heating efficiency, and are useful as a copying machine, a facsimile, a printer, and the like.

1 is a front configuration diagram of an image forming apparatus according to a first embodiment of the present invention. 1 is a cross-sectional configuration diagram of a fixing device according to a first embodiment of the present invention. 1 is a cross-sectional configuration diagram of a belt guide 4 of a fixing device according to a first embodiment of the present invention. The perspective view of the belt heater 4 in Embodiment 1 concerning this invention. (A)-(c) Top view of the belt guide 4 in Embodiment 1 concerning this invention. Sectional view between AA 'in FIG. FIG. 6 is a partial cross-sectional configuration diagram of a fixing device according to a second embodiment of the present invention. The perspective view of the state which extended the curve of the belt guide in Embodiment 2 concerning this invention. (A) The top view of the belt guide in the state of FIG. 8, (b) The front view of the belt guide in the state of FIG. 8, (c) The side view of the belt guide in the state of FIG. (A) Schematic diagram of only the cross-sectional portion between AA 'in FIG. 7, (b) Schematic diagram of only the cross-sectional portion between BB' in FIG. 7, (c) Schematic diagram of only the cross-sectional portion between CC 'in FIG. (D) Schematic diagram of only the cross-sectional portion between DD ′ in FIG. 7, (e) Schematic diagram of only the cross-sectional portion between EE ′ in FIG. The perspective view of the state which extended the curve of the belt guide in Embodiment 2 concerning this invention. (A) The figure which shows the graph of the pressure distribution of the longitudinal direction in the position of BB ', (b) The figure which shows the graph of the pressure distribution of the longitudinal direction in the position of CC', (c) The longitudinal direction center part of the nip part 10 FIG. 4 is a diagram showing a graph of the pressure distribution in the circumferential direction of FIG. 3D. FIG. The figure which shows the modification of the belt guide in Embodiment 2 concerning this invention. The figure which shows the other modification of the belt guide in Embodiment 2 concerning this invention. Cross-sectional configuration diagram of a conventional fixing device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixing device 2 Fixing belt 3a, 3b Heater 4, 7, 8, 9 Belt guide 5 Pressure roller 6 Backup member 6a Plate-like member 6b Rib-like member 30 Light emission part filament 40, 70, 80, 90 Sliding surface 40a, 70a Inflow end 40b, 70b Outflow end 41, 76 Pressurization surface 42, 77 Inflow surface 43 78 Outflow surface 41a, 42a, 43a Groove 41t, 42s, 42t, 43s, 43t Step 42b Inlet 43b Outlet

Claims (12)

An endless fixing belt disposed rotatably;
In order to heat the fixing belt, a heating unit provided along the central axis direction inside the fixing belt;
A support member supported from the inner surface side of the fixing belt and having a sliding surface slidable with the inner surface;
A pressing member that presses all or part of the sliding surface across the fixing belt,
The sliding surface is
Lubricant for reducing friction with the fixing belt flows from both ends in the central axis direction on the inflow side where the fixing belt rotates and flows into between the fixing belt and the sliding surface. Thereafter, the lubricant moves to the center side, the lubricant flows out from between the fixing belt and the sliding surface, and the lubricant moved to the center moves to the both end sides and then flows out. The fixing device is formed as follows. The heating unit is
The fixing device according to claim 1, further comprising a heater disposed so as to face a region between predetermined regions through which the lubricant flows out on both ends of the fixing belt. The sliding surface is
An outflow groove formed on the outflow side so that the lubricant flows out from the center side to a predetermined region on both end sides of the fixing belt;
The fixing device according to claim 1, further comprising an inflow groove formed on the inflow side so that the lubricant moves from each of the predetermined regions to the center side. The inflow groove is
At least a first step formed from the position corresponding to the outside of each of the predetermined regions toward the center side so as to restrict the lubricant from moving along the rotation direction on the both end sides. Have
The outflow groove is
There is at least a second step formed from the center toward a position corresponding to the inside of each predetermined region so as to restrict the lubricant from moving along the rotation direction on the center side. The fixing device according to claim 3. The sliding surface is
An inflow surface in which the inflow groove is formed;
An outflow surface in which the outflow grooves are formed;
A pressure surface formed between the inflow surface and the outflow surface and pressed by the pressure member;
The pressure surface has a moving groove constituted by a third step formed in a longitudinal position corresponding to a nip portion with the pressure member,
The fixing device according to claim 4, wherein the third step is connected to the first step.   The fixing device according to claim 5, wherein depths of the inflow groove, the moving groove, and the outflow groove are constant. The inflow groove is
A fourth step formed from the center of the end on the pressure surface side to a position corresponding to the inside of each predetermined region of the end on the inflow side;
The outflow groove is
6. The fixing device according to claim 5, further comprising: a fifth step formed from an end of the third step on the outflow surface side to a position corresponding to an outside of the respective predetermined region of the outflow side end. . The sliding surface is
An inclination formed on the outflow side so that the lubricant flows out from the center side to a predetermined region on both ends of the fixing belt;
The fixing device according to claim 1, further comprising an inclination formed on the inflow side so that the lubricant moves from each of the predetermined regions to the center side. The sliding surface is
On the inflow side, the distance from the central axis is closer to the center side than the both end sides,
The fixing device according to claim 8, wherein, on the outflow side, the distance from the central axis of the fixing belt is farther on the center side than on the both end sides. The sliding surface is
A pressing surface pressed by the pressing member;
An inflow surface formed on the inflow side of the pressure surface;
An outflow surface formed on the outflow side of the pressure surface;
A first region formed on the central side, the distance from the central axis being constant in the central axis direction;
The fixing device according to claim 9, further comprising: a second region formed on each of the both end sides, wherein a distance from the central axis is constant in the central axis direction. The first region is
In the inflow surface, both ends thereof are formed so as to gradually spread from the end on the inflow side to the end on the pressurization surface side. Is formed at a constant interval until the both ends of the outflow surface gradually spread from the end on the pressure surface side to the end on the outflow side,
The second region is
In the inflow surface, both ends thereof are formed so as to gradually spread from the end on the inflow side to the end on the pressurization surface side. The fixing device according to claim 10, wherein both ends of the outflow surface are formed so as to gradually spread from an end on the pressure surface side to an end on the outflow side. An image forming unit for forming a developer image on the image carrier;
A transfer unit for transferring the developer image to a transfer material;
An image forming apparatus comprising: the fixing device according to claim 1, wherein the transferred developer image is fixed to the transfer material.

Images