JP6098252B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

The present invention relates to a fixing device and an image forming apparatus for fixing an image on a recording material using rotating members that rotate in contact with each other.
Note that the recording material in this specification includes various sheet-like recording media such as plain paper, various coated papers, photosensitive paper, electrostatic recording paper, thick paper such as postcards, various films such as OHP films, and the like. To do.

In recent years, market demands for energy saving and high speed have been increasing for image forming apparatuses such as printers, copiers, and facsimiles.
In an image forming apparatus, an unfixed toner image is formed on a recording material by an image transfer method or a direct method by an image forming process such as electrophotographic recording, electrostatic recording, or magnetic recording. As a fixing device for fixing an unfixed toner image, a heat roller method using a roller as a rotating member of a fixing member, a belt method using a belt, and a contact heating method fixing device such as a film heating method and an electromagnetic induction heating method Is widely adopted.

  In recent years, such a fixing device is required to further shorten the warm-up time required to reach a predetermined printable temperature (reload temperature) from a normal temperature state such as when the power is turned on. This warm-up time is also related to the first print time from when a print request is received to when a print operation is performed through a print preparation and paper discharge is completed (Problem 1).

  Further, as the speed of the image forming apparatus is increased, the number of sheets to be passed per unit time is increased, and the required heat amount is increased. Problem 2).

  As a method for solving the problem of problem 1, surf fixing using a ceramic heater has been proposed. By this method, the heat capacity is reduced and the size is reduced as compared with a belt-type fixing device. However, since only the nip portion is locally heated in this method, the other portions are not heated, and the belt is in the coldest state at the entrance of the sheet or the like in the nip portion, and fixing failure is likely to occur. There is a problem. In particular, in a high-speed machine, there is a problem that fixing failure is more likely to occur because the belt rotates fast and the heat radiation of the belt outside the nip increases (problem 3).

There exists patent document 1 as a thing for solving the above problems 1-3. FIG. 12 is a schematic diagram of the fixing device disclosed in Patent Document 1.
A pipe-shaped metal heat conductor 202 is fixed inside the endless belt 201 so as to be able to guide the movement of the endless belt 201, and endlessly passed through the metal heat conductor 202 by the heat source 203 in the metal heat conductor 202. The belt 201 is heated. Furthermore, a pressure roller 204 that forms a nip portion 207 in contact with the metal heat conductor 202 via the endless belt 201 is provided, and the endless belt 201 is moved in the circumferential direction as the pressure roller 204 rotates. Let With this configuration, the entire endless belt 201 constituting the fixing device can be warmed, the first print time from the heating standby time can be shortened, and the lack of heat during high-speed rotation can be solved. ing.

  In order to further improve the energy saving and the first print time, it is necessary to further improve the thermal efficiency. For this reason, a configuration in which the endless belt 201 is directly heated without using a metal heat conductor is also known.

  In the above-described Patent Document 1 and the configuration in which the endless belt 201 is directly heated without using a metal heat conductor, the energy saving performance can be improved and the first print time from the heating standby time can be further shortened. However, by adopting such a configuration, the endless belt 201 passes through the nip portion 207 while sliding, and the endless belt 201 is rotated as compared with a conventional configuration in which a roller and a roller abut against each other. The problem that the torque for the increase increases.

  Further, the pressure roller 204 has an elastic layer 206, and this elastic layer 206 receives a shearing force as the endless belt 201 rotates. In order for the strength of the elastic layer 206 to have the increased rotational torque, the rubber hardness or sponge hardness of the elastic layer 206 tends to increase. Furthermore, in order to improve thermal efficiency, it is necessary to make this elastic layer 206 thin.

  In order to ensure the nip width in the recording material conveyance direction with such a configuration, an abutting method as shown in FIG. In this abutting method, as shown in FIG. 9A, a bearing 208 attached to both ends of the pressure roller 204 is urged toward the endless belt 201 by a pressing force F1 with a pressing force F1. The position of the pressure roller 204 is determined by abutting the bearing 208 against the abutting member 220 fixed to the frame of the fixing device.

  However, in the configuration example shown in FIG. 9A, when the elastic layer 206 of the pressure roller 204 is increased in hardness and thickness as described above, the position of the abutting member 220, the pressure roller, and the like. The variation of the nip width due to the variation in the diameter of 204 increases. Further, in order to solve this problem, if the accuracy of each component used is increased, the cost increases.

On the other hand, in order to solve such a problem, a load method as shown in FIG. This adjusts the nip by adjusting the urging force of the pressure spring that urges the bearing 208 with the pressing force F1 without providing the abutting member 220 in the abutting method shown in FIG. 9A. It is.
In order to secure the nip, the fixing device has an adjusting mechanism for adjusting the pressing force F1, and the adjusting mechanism adjusts the pressing force F1 so that the nip width is secured at the time of factory production.

The problem of the configuration shown in FIG. 9B will be described below.
The pressure roller 204 is provided so as to be movable in the direction approaching the endless belt 201 and in the reverse direction D1. This is to make it easier for the user to remove the paper when a jam occurs. A driving gear 211 rotating coaxially is fixed to the shaft end of the pressure roller 204.

  Here, when the torque for rotating the endless belt 201 is increased in the configuration in which the endless belt 201 slides through the nip portion 207 as described above, the radial force in the drive gear 211 to which the torque is transmitted is increased. It cannot be ignored. That is, when the pressing force F3 due to the transmission torque transmitted to the drive gear 211 increases, the pressing force F2 that is the surface pressure at the nip portion 207 balances the influence. Since the pressing force F3 by the driving gear 211 is applied from one end of the shaft of the pressure roller 204, when the pressing force F3 increases, the pressing force F2 for forming the nip portion 207 is not uniform depending on the location, and the nip portion A surface pressure deviation of 207 occurs.

When a surface pressure deviation occurs in the nip portion 207, for example, the following problem may occur.
(1) Uneven wear of the member forming the nip portion 207 (2) Destruction of the elastic layer 206 of the pressure roller 204 (3) Skew of the recording material

  Furthermore, the rotational torque of the drive gear 211, which is a factor that increases the pressing force F3, tends to increase over time. For this reason, the surface pressure deviation at the nip portion 207 may also increase over time.

  The present invention has been made in view of such a situation, and an object thereof is to provide a fixing device that can effectively reduce the influence of the rotational torque on the nip surface pressure.

In order to achieve such an object, a fixing device according to the present invention includes a fixing member and a pressure member, which are rotating bodies that rotate in contact with each other, and a nip between the heated fixing member and the pressure member. A fixing device for fixing an image on a recording material by a portion, wherein the pressure member is engaged with a pressure member gear coaxially fixed to the pressure member on the upstream side in the recording material conveyance direction from the nip portion. A pressure member pressing means that is rotationally driven in response to a force from the transmission gear and presses the pressure member toward the fixing member, and a bearing that rotates coaxially with the pressure member by the pressure member pressing means. Opposing pressing means for pressing in a direction substantially opposite to the pressing direction is provided.

  As described above, according to the present invention, it is possible to effectively reduce the influence of the rotational torque on the nip surface pressure.

1 is a diagram illustrating a configuration example of an image forming apparatus 100 using a fixing device 80 as an embodiment of the present invention. FIG. 3 is a diagram illustrating a configuration example of a fixing device 80 according to the present embodiment. It is a figure which shows the other structural example of the fixing device 80 of this embodiment. FIG. 3 is a diagram schematically illustrating a configuration in which a pressing force is applied to the fixing device 80 of the present embodiment. FIG. 5 is a diagram schematically illustrating a configuration in which the pressing forces F1 and F4 in FIG. 4 are applied from an axial direction of a pressure roller 83. 4 is a diagram schematically showing a configuration for transmitting a rotational driving force to a shaft 97 of a pressure roller 83. FIG. It is a figure which shows roughly the relationship of the applied force about (a) this embodiment and (b) the conventional load system. FIG. 11 is a diagram illustrating a configuration example of a conventional fixing device. It is a figure which shows roughly the relationship of the force added to the conventional fixing device about (a) butting method and (b) load method.

Next, an embodiment to which a fixing device according to the present invention is applied will be described in detail with reference to the drawings.
The present embodiment relates to a fixing device used in an electrostatic recording image forming apparatus such as a copying machine, a facsimile machine, or a printer. More specifically, a fixing device that forms a nip portion between an endless fixing member that is a rotating body and a pressure member and performs fixing processing on a material to be fixed that passes through the nip portion, and the fixing device are mounted. The present invention relates to an image forming apparatus.

FIG. 1 shows a configuration example of an image forming apparatus 100 according to the present embodiment.
The image forming apparatus shown in FIG. 1 is a color printer using a tandem system in which image forming units for forming a plurality of color images are juxtaposed along the belt extending direction, but this embodiment is limited to this system. It is not a thing. Further, this embodiment can be applied not only to a printer but also to various image forming apparatuses such as a copying machine and a facsimile machine.

  As shown in FIG. 1, the image forming apparatus 100 includes a photosensitive drum 20Y as an image carrier that can form an image as an image corresponding to each color separated into yellow, cyan, magenta, and black. 20C, 20M, 20Bk. Thus, the image forming apparatus 100 of the present embodiment employs a tandem structure in which the photosensitive drums 20Y, 20C, 20M, and 20Bk are arranged in parallel.

  In the image forming apparatus 100 having the configuration shown in FIG. 1, the visible image formed on each of the photoconductive drums 20Y, 20C, 20M, and 20Bk faces the photoconductive drums 20Y, 20C, 20M, and 20Bk, and the intermediate transfer member. The primary transfer process is executed for the transfer belt 11. The transfer belt 11 is an endless belt that can move in the arrow A1 direction. In this way, the images of the respective colors are superimposed and transferred onto the transfer belt 11, and then transferred in a batch by executing a secondary transfer process on the recording material S on which a recording sheet or the like is used.

  Around each photosensitive drum, an apparatus for image forming processing is arranged according to the rotation of the photosensitive drum. For this reason, the photosensitive drum 20Bk that performs black image formation will be described as an object. Is arranged. For the writing performed after charging, the optical writing device 8 is used.

  In the superimposing transfer to the transfer belt 11, the visible image formed on each of the photoconductive drums 20 </ b> Y, 20 </ b> C, 20 </ b> M, and 20 </ b> Bk is superimposed on the same position on the transfer belt 11 in the process in which the transfer belt 11 moves in the direction of arrow A <b> 1. Transcribed. The transfer of each color visible image is performed by voltage application by the primary transfer rollers 12Y, 12C, 12M, and 12Bk, and the timing is shifted from the upstream side to the downstream side in the arrow A1 direction. The primary transfer rollers 12Y, 12C, 12M, and 12Bk respectively transfer the photosensitive drums 20Y, 20C, and 20M across the transfer belt 11 so that the respective color visible images to be transferred are transferred to the same position on the transfer belt 11. , 20Bk.

  The photosensitive drums 20Y, 20C, 20M, and 20Bk are arranged in this order from the upstream side in the arrow A1 direction. Each of the photosensitive drums 20Y, 20C, 20M, and 20Bk is provided in an image station for forming yellow, cyan, magenta, and black images.

  The image forming apparatus 100 includes four image stations that perform image forming processing for each color, a transfer belt unit 10, a secondary transfer roller 5, an intermediate transfer belt cleaning device 13, and an optical writing device 8. doing.

  The transfer belt unit 10 is disposed so as to oppose each of the photosensitive drums 20Y, 20C, 20M, and 20Bk, and includes a transfer belt 11 and primary transfer rollers 12Y, 12C, 12M, and 12Bk.

  The secondary transfer roller 5 is a transfer roller as a transfer member that is disposed to face the transfer belt 11 and is driven by the transfer belt 11.

  The cleaning device 13 is disposed to face the transfer belt 11 and cleans the surface of the transfer belt 11.

  The optical writing device 8 is disposed below the four image stations and includes a semiconductor laser as a light source, a coupling lens, an fθ lens, a toroidal lens, a folding mirror, a rotating polygon mirror as a deflecting unit, and the like. . With such a configuration, the optical writing device 8 emits the writing light Lb corresponding to each color to each of the photosensitive drums 20Y, 20C, 20M, and 20Bk, and electrostatically applies the photosensitive drums 20Y, 20C, 20M, and 20Bk. A latent image is formed. In FIG. 1, for the sake of convenience, reference numerals are given only to the image stations for black images, but the same applies to other image stations.

The image forming apparatus 100 further includes a sheet feeding device 61 and a registration roller pair 4.
The sheet feeding device 61 is a paper feeding cassette in which recording materials S conveyed between the photosensitive drums 20Y, 20C, 20M, and 20Bk and the transfer belt 11 are stacked.

The registration roller pair 4 transfers the recording material S conveyed from the sheet feeding device 61 to each of the photosensitive drums 20Y, 20C, 20M, and 20Bk at a predetermined timing in accordance with the toner image formation timing by the image station. It is fed out toward the transfer part between the belt 11.
The image forming apparatus 100 also includes a sensor (not shown) that detects that the leading edge of the recording material S has reached the registration roller pair 4.

  The image forming apparatus 100 further includes a fixing device 80, a discharge roller 7, a discharge tray 17, and toner bottles 9Y, 9C, 9M, and 9Bk.

The fixing device 80 fixes the toner image on the recording material S on which the toner image is transferred.
The discharge roller 7 discharges the fixed recording material S to the outside of the main body of the image forming apparatus 100.
The paper discharge tray 17 is disposed at the upper part of the main body of the image forming apparatus 100 and stacks the recording material S discharged to the outside of the main body of the image forming apparatus 100 by the discharge roller 7.
The toner bottles 9Y, 9C, 9M, and 9Bk are arranged on the lower side of the paper discharge tray 17, and are filled with toner of each color of yellow, cyan, magenta, and black.

In addition to the transfer belt 11 and primary transfer rollers 12Y, 12C, 12M, and 12Bk, the transfer belt unit 10 includes a drive roller 72 and a driven roller 73 around which the transfer belt 11 is wound.
The driven roller 73 also has a function as a tension urging unit for the transfer belt 11. For this reason, the driven roller 73 is provided with an urging unit using a spring or the like. Such a transfer belt unit 10, the primary transfer rollers 12Y, 12C, 12M, and 12Bk, the secondary transfer roller 5, and the cleaning device 13 constitute a transfer device 71.

  The sheet feeding device 61 is disposed at the lower part of the main body of the image forming apparatus 100, and includes a feeding roller 3 as a paper feeding roller that contacts the upper surface of the uppermost recording material S. The sheet feeding device 61 feeds the uppermost recording material S toward the registration roller pair 4 when the feeding roller 3 is rotationally driven in the counterclockwise direction.

  Although not shown in detail, the cleaning device 13 provided in the transfer device 71 includes a cleaning brush and a cleaning blade disposed so as to face and contact the transfer belt 11. With this configuration, the cleaning device 13 cleans the transfer belt 11 by scraping and removing foreign matters such as residual toner on the transfer belt 11 with a cleaning brush and a cleaning blade. The cleaning device 13 further includes discharge means (not shown) for carrying out and discarding the residual toner removed from the transfer belt 11.

Next, a configuration example of the fixing device 80 of the present embodiment will be described with reference to FIG.
A fixing device 80 shown in FIG. 2 has a pressure rotating body as a rotating body that rotates in contact with each other and a fixing belt 81, and the fixing belt 81 is directly heated by radiant heat from the inner peripheral side by a heat source 82. It has become. In the example of FIG. 2, a configuration example is shown in which a pressure roller 83 is used as the pressure rotator and a halogen heater is used as the heat source 82.

  2 is provided with a nip forming member 86 that forms a nip portion N with a pressure roller 83 that is opposed to the fixing belt 81 through the fixing belt 81, and is slid directly on the inner surface of the fixing belt 81 or not shown. It slides indirectly through the sheet. In this way, the fixing belt 81 and the pressure roller 83, which are rotating bodies that rotate in contact with each other, are configured to be rotatable about parallel axes, whereby the nip portion N is formed.

  In the example of FIG. 2, the shape of the nip portion N is flat, but may be a concave shape or other shapes. When the nip portion N has a concave shape, the discharge direction of the leading end of the recording material is closer to the pressure roller 83 and the separation is improved, so that the occurrence of jam is suppressed.

  The fixing belt 81 is composed of a metal belt such as nickel or SUS (stainless steel) or an endless belt or film using a resin material such as polyimide. The surface layer of the belt has a release layer such as a PFA or PTFE layer, and has a release property so that toner does not adhere. There may be an elastic layer formed of a silicone rubber layer or the like between the belt substrate and the PFA or PTFE layer. When there is no silicone rubber layer, the heat capacity is reduced and the fixability is improved, but when the unfixed image is crushed and fixed, minute irregularities on the belt surface are transferred to the image, and the image has a crusty skin shape. There arises a problem that the gloss unevenness (zudder skin image) remains. In order to improve this, it is necessary to provide a silicone rubber layer of 100 μm or more. Due to the deformation of the silicone rubber layer, fine irregularities are absorbed and the skin image is improved.

  A support member 87 by a stay for supporting the nip portion N is provided inside the fixing belt 81 to prevent the nip forming member 86 that receives pressure from the pressure roller 83 from bending, and the nip portion N in the recording material conveyance direction. The width of the is made uniform in the axial direction. The support member 87 is held and fixed to a holding member 88 by flanges at both ends. In addition, a reflection member 89 is provided between the heat source 82 and the support member 87, and wasteful energy consumption due to the support member 87 being heated by radiant heat from the heat source 82 or the like is suppressed. Here, instead of providing the reflecting member 89, the same effect can be obtained even if the surface of the supporting member 87 is heat-insulated or mirror-finished.

  The heat source 82 may be the illustrated halogen heater, but may be IH, a resistance heating element, a carbon heater, or the like.

  The pressure roller 83 is provided with an elastic layer 84 made of elastic rubber or the like on the outer periphery of the cored bar 85, and further provided with a release layer (PFA or PTFE layer) on the surface in order to obtain releasability. The pressure roller 83 is rotated by a driving force transmitted through a gear from a driving source such as a motor provided in the image forming apparatus. Further, the pressure roller 83 is pressed against the fixing belt 81 by a pressure spring or the like which will be described later, and has a predetermined nip width when the elastic layer 84 is crushed and deformed.

  The pressure roller 83 may be a hollow roller, and the pressure roller 83 may have another heat source such as a halogen heater. The elastic rubber constituting the elastic layer 84 may be solid rubber, but if there is no heater inside the pressure roller 83, sponge rubber may be used. Sponge rubber is more desirable because it increases heat insulation and makes it difficult for the fixing belt 81 to lose heat.

  The fixing belt 81 is rotated by the pressure roller 83. In the case of FIG. 2, the pressure roller 83 is rotated by a driving source (not shown), and the driving force is transmitted to the belt at the nip portion N, whereby the fixing belt 81 is rotated. The fixing belt 81 is sandwiched and rotated at the nip portion N, and travels while being guided by the holding member 88 (flange) at both ends other than the nip portion N.

  Further, a fixing separation member 90 for separating the recording material from the fixing belt 81 which is a rotating body to be separated is provided downstream of the nip portion N in the recording material conveyance direction.

  In this embodiment, such a configuration makes it possible to realize a fixing device 80 that is inexpensive and has a fast warm-up.

FIG. 3 is a diagram illustrating another configuration example of the fixing device 80 of the present embodiment.
In the configuration example of FIG. 2, the heat source 82 is configured by one halogen heater, whereas the configuration example of FIG. 3 is different in that the heat source 82 is configured by three halogen heaters.

  Next, the configuration around the shaft 97 of the pressure roller 83 including the main features of the present embodiment will be described with reference to FIGS. FIG. 4 schematically shows the configuration of the fixing device 80 of the present embodiment from a direction perpendicular to the axial direction of the pressure roller 83. 5 shows a mechanism for adjusting the pressing force F1 applied to the shaft 97 of the pressure roller 83, and FIG. 6 shows a configuration for transmitting the rotational driving force to the shaft 97 of the pressure roller 83.

  The shaft 97 of the pressure roller 83 of this embodiment is provided with a bearing 91 and a drive gear 92 that rotate coaxially. One bearing 91 is disposed on each side of the pressure roller 83 in the axial direction. The drive gear 92 is fixed near the end of the shaft 97 of the pressure roller 83. The drive gear 92 is a pressure member gear that meshes with an idler gear 111 that is a gear provided adjacently and receives a rotational driving force to rotate the pressure roller 83.

  The pressure roller 83 is provided so as to be movable in the direction approaching the fixing belt 81 and in the reverse direction D1. This is to make it easier for the user to remove the paper when a jam occurs. Therefore, the shaft 97 of the pressure roller 83 is attached to the frame 110 of the fixing device 80 so as to be rotatable and movable in the direction approaching the fixing belt 81 and in the reverse direction D1.

  Further, around the bearing 91, an adjustment mechanism that is a pressing member pressing unit that presses the bearing 91 in a direction from the pressure roller 83 toward the fixing belt 81 with a pressing force F1, and a pressing force in a substantially opposite direction. And an opposing pressing means for pressing with F4. The substantially reverse direction of pressing with the pressing force F4 is most preferably the direction opposite to the pressing direction by the pressing member pressing means, and a nip portion N is formed between the pressing roller 83 and the fixing belt 81 to reduce the pressing force. The direction according to the design or the like may be used as long as the balance can be maintained.

The configuration of the pressing member pressing means and the opposing pressing means will be described with reference to FIG.
The bearing 91 is held by the bearing holder 93 and rotatably attaches the shaft 97 to the bearing holder 93. The bearing holder 93 is made of sheet metal. Further, bearing holders 93 provided for the respective bearings 91 provided on both sides in the axial direction of the pressure roller 83 are fixed and integrated by a stay 94 made of sheet metal.

  For this reason, the adjusting mechanism that presses the bearing 91 from the pressure roller 83 to the fixing belt 81 is configured so that the two bearings 91 provided on both sides in the axial direction of the pressure roller 83 can be pressed with the same pressing force F1. The Therefore, the nip portion N can be formed by pressing from the pressure roller 83 to the fixing belt 81 with a uniform surface pressure over the entire axial direction of the shaft 97.

  The bearing holder 93 is attached to the frame 110 of the fixing device 80 so as to be rotatable around an axis 105 parallel to the axial direction of the pressure roller 83. Further, the pressure arm 104 is attached to the frame 110 of the fixing device 80 so as to be rotatable around the same axis 105.

  A pressure spring 95 whose restoring force is adjusted by the adjusting screw 101 and the abutting member 102 is disposed between the pressure arm 104 and the bearing holder 93. A rotatable pressure cam 106 is disposed on the back side of the pressure arm 104 where the bearing holder 93 is disposed. The pressure arm 104 is configured such that the position in the rotation direction D3 around the shaft 105 shown in FIG.

  Further, by adjusting the position in the direction D2 shown in FIG. 5 by rotating the adjustment screw 101, the urging force by the pressure spring 95 from the pressure arm 104 to the bearing holder 93 is adjusted. Further, in this adjustment mechanism, the distance from the shaft 105 at the position where the bearing 91 is pressed from the bearing holder 93 is made shorter than the distance from the shaft 105 at the position where the biasing force by the pressure spring 95 is applied to the bearing holder 93. Arrange so that. By arranging in this way, it is possible to apply a pressing force F <b> 1 in which the urging force by the pressure spring 95 is increased to the bearing 91. In the example of FIG. 5, by placing the bearing 91 at a position half the distance from the shaft 105 to the pressure spring 95, the urging force of the pressure spring 95 is doubled to obtain the pressing force F <b> 1 to the bearing 91. A configuration example is shown.

  With such an adjustment mechanism, the pressing force F1 in the direction from the pressure roller 83 toward the fixing belt 81 can be finely adjusted so as to be suitable for the formation of the nip portion N, and can be held at an adjusted constant value.

  Further, as shown in FIG. 5, a counter spring 96 is provided on the side facing the adjustment mechanism that applies the pressing force F <b> 1 to the bearing 91, and is pressed by the pressing force F <b> 4 in the substantially reverse direction. Yes. The opposing spring 96 is fixed to the frame 110 of the fixing device 80, and is configured to bias the bearing 91 when the shaft 97 of the pressure roller 83 is attached. Further, by pressing the bearing 91 with the pressing force F <b> 1 in the direction from the pressure roller 83 toward the fixing belt 81 by the adjusting mechanism described above, the pressing force F <b> 4 by the opposing spring 96 acts on the bearing 91.

  Next, a transmission mechanism using a gear that rotates the pressure roller 83 will be described with reference to FIG.

  A drive gear 92 that is a pressure member gear that rotates the pressure roller 83 meshes with an idler gear 111 that is a gear provided adjacently. The idler gear 111 is attached to the frame 110 such that the idler gear 111 can rotate about the axis and the axial position is fixed to the frame 110 of the fixing device 80.

  Further, the pressure roller 83 is provided so as to be movable in the direction approaching the fixing belt 81 and in the reverse direction D1 as described above. Therefore, the idler gear 111 is disposed upstream of the drive gear 92 in the recording material conveyance direction so as to avoid the movable range of the drive gear 92 movable in the forward and reverse directions D1. The idler gear 111 functions as a transmission gear that transmits the rotational driving force from the main body side gear 112 attached to the main body of the image forming apparatus 100 to the driving gear 92 by meshing the gears.

Since the pressure roller 83 and the fixing belt 81 are rotated by the rotation of the drive gear 92 and the recording material is conveyed at the nip portion N, the rotation direction of the drive gear 92 is counterclockwise in FIG. The rotation direction of the idler gear 11 is clockwise in FIG.
Therefore, the rotational driving force for rotating the driving gear 92 acts between the driving gear 92 and the idler gear 11 in the right direction in FIG. 6 and the pressing force F3. For this reason, when the rotational torque for rotating the drive gear 92 increases, the pressing force F <b> 3 acts on the drive gear 92 in the direction from the pressure roller 83 toward the fixing belt 81.

  The relationship of the force applied by the present embodiment configured as described above will be described with reference to FIG. FIG. 7A shows the relationship of the force applied according to the present embodiment, and FIG. 7B shows the relationship of the force applied by the configuration of the conventional load method.

  In the conventional configuration shown in FIG. 7B, the pressing force F <b> 2 applied to the elastic layer of the pressure roller 204 for forming the nip portion 207 and the bearing 208 is pressed from the pressure roller 204 toward the endless belt 201. The pressing force F1 has an equal relationship. For this reason, when the rotational torque for rotating the drive gear 211 increases and the pressing force F3 acting on the drive gear 211 due to the rotational torque increases, the pressing force F3 acts from one end in the axial direction of the pressure roller 204. . For this reason, the pressing force F <b> 2 that forms the nip portion 207 is not uniform in the axial direction of the pressure roller 204, and a surface pressure deviation of the nip portion 207 may occur.

  On the other hand, in the configuration of this embodiment shown in FIG. 7B, the pressing force F <b> 1 that presses the bearing 91 in the direction from the pressure roller 83 to the fixing belt 81 is the pressing force F <b> 2 for forming the nip portion N. And the pressing force F4 by the opposing spring 96. For this reason, even when the pressing force F3 acting on the driving gear 92 is increased by the rotational torque for rotating the driving gear 92, the influence of the pressing force F3 is opposed to the pressing force F2 of the nip portion N. Dispersed in the pressing force F4 by the spring 96. For this reason, the influence which it has on the pressing force F2 which forms the nip part N can be made small.

  As shown in FIGS. 2 and 3 described above, the configuration in which the fixing belt 81 rotates while sliding on the surface of the nip forming member 86 is different from the conventional configuration in which the rollers are abutted against each other. Thus, the torque for rotating the fixing belt 81 tends to increase. According to the present embodiment, even when the rotational torque for rotating the drive gear 92 is increased in this way, the influence of the pressing force F3 due to the rotating torque is caused by the pressing force F2 of the nip portion N and the opposing spring 96. The pressure can be distributed to the pressing force F4. For this reason, the influence which it has on the pressing force F2 which forms the nip part N can be made small. For this reason, the pressing force F2 for forming the nip portion N can be made uniform over the entire nip portion N, and the surface pressure deviation of the nip portion N can be prevented.

  Furthermore, the pressurizing force can be adjusted so that a nip is produced during manufacturing in a factory. An example of adjustment is given below.

For example, the pressure roller 83 is φ25, the rubber thickness is 3.5 mm, and the rubber material is foamed silicone rubber. Further, it is assumed that the spring multiplier of the pressure spring 95 is 80 N / mm, the lever ratio of the lever mechanism by the bearing holder 93 is 2, and the pressing force F1 is doubled. Further, it is assumed that the spring multiplier of the opposing spring 96 is 40 N / mm.
In nip formation under these conditions, the following force relationship is generally obtained.
Pressing force F1: Pressing force F4 = 280N: 80N

As described above, the fixing device according to the present embodiment described above includes a fixing member and a pressure member, which are rotating bodies that are in contact with each other and rotating, a heating source that directly heats the fixing member by radiant heat, and an internal heating unit. A nip forming member facing the pressure member and forming a nip. The fixing member is driven to rotate by friction with the pressure member, and slides on the nip forming member.
In addition to such a configuration, the fixing device of the present embodiment includes a pressing member pressing unit that biases the pressing member toward the fixing member, and an opposing pressing unit that biases the pressing member in a substantially reverse direction. Prepare.

  For this reason, even when the rotational torque for rotating the fixing belt 81 as a fixing member is increased, the influence of the rotational torque on the nip surface pressure can be reduced.

  Further, according to the image forming apparatus provided with the fixing device according to the above-described embodiment, it is possible to provide an image forming apparatus that can obtain the respective effects of the fixing device according to the above-described embodiment.

  Each of the above-described embodiments is a preferred embodiment of the present invention, and the present invention is not limited to this, and various modifications can be made based on the technical idea of the present invention.

For example, the configuration of the opposing pressing means by the opposing spring 96 is not limited to the above-described embodiment as long as the pressing force F4 can be applied in a direction substantially opposite to the pressing force F1 that presses the pressure roller 83 toward the fixing belt 81. .
For example, as long as the shaft 97 of the pressure roller 83 can be pressed, the pressing force F <b> 4 may be applied at a position other than the position of the bearing 91. Moreover, the structure further provided with the adjustment mechanism which adjusts pressing force F4 may be sufficient.

  Further, regarding the configuration in which the pressure roller 83 is pressed by the pressure spring 95 and the configuration of the adjustment mechanism that adjusts the pressing force F <b> 1 to the bearing 91, the configuration of the above-described embodiment is possible as long as the nip portion N can be formed. However, the present invention is not limited to this, and an arbitrary configuration may be used.

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 80 Fixing apparatus 81 Fixing belt 82 Heat source 83 Pressure roller 84 Elastic layer 85 Core metal 86 Nip forming member 87 Support member 88 Holding member 89 Reflecting member 90 Fixing separation member 91 Bearing 92 Drive gear 93 Bearing holder 94 Stay 95 Pressure spring 96 Opposing spring 97 Shaft 101 Adjustment screw 102 Abutting member 104 Pressure arm 105 Shaft 106 Pressure cam 110 Frame 111 Idler gear 112 Body side gear N Nip part

Japanese Patent No. 4818826

Claims (4)

A fixing device that includes a fixing member and a pressure member that are rotating bodies that are in contact with each other and rotate, and that fixes an image on a recording material by a nip portion between the heated fixing member and the pressure member. And
The pressure member is rotationally driven in response to a force from a transmission gear meshing with the pressure member gear coaxially fixed to the pressure member on the upstream side in the recording material conveyance direction from the nip portion ,
A pressing member pressing means for pressing the pressing member toward the fixing member;
A fixing device comprising: an opposing pressing means for pressing a bearing rotating coaxially with the pressing member in a direction substantially opposite to a pressing direction by the pressing member pressing means. The pressure member of claim 1 Symbol mounting of the fixing device is characterized in that movable in the direction and the opposite direction approaching the fixing member. It said pressing means for the pressure member, the fixing device according to claim 1, wherein further comprising an adjusting mechanism for adjusting the force for pressing the pressure member to the fixing member. An image forming apparatus comprising the fixing device according to any one of claims 1 to 3.

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