JP5286919B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device that receives a driving force from the outside and a pressure member comes into contact with the fixing member to be in a pressurized state, and an image forming apparatus to which the fixing device is attached.

  Conventionally, an image forming apparatus using an electrophotographic system has been known. For example, an electrostatic latent image is formed on the surface of a photosensitive drum as an image carrier, and the electrostatic latent image on the photosensitive drum is developed with a toner as a developer to be visualized, and the developed image is transferred. The image is transferred onto the recording paper (sheet or recording medium) by the apparatus, the image is carried, the toner image on the recording paper is fixed by a fixing device using pressure, heat, etc., and the fixed recording paper passes through the paper discharge path, It is configured to be discharged out of the device.

  Here, the fixing device is provided with a fixing rotator constituted by opposing rollers or belts or a combination thereof, and sandwiches the recording paper and applies heat and pressure to fix the toner image on the recording paper. To do.

  The fixing rotator includes, for example, a fixing roller (fixing member (or fixing member)) including a heating roller having a heater as a heating unit and a fixing roller having a rubber layer on a surface layer, and an additional member that contacts the fixing belt. A pressure roller (pressure member (or pressure member)) is disposed. Alternatively, there is a configuration in which a fixing roller whose surface is heated and a pressure roller that contacts the fixing roller are arranged.

  The toner-transferred recording paper that has reached the fixing device enters the fixing nip portion where the fixing belt (or the fixing roller) and the pressure roller are in contact with each other, and is transferred while the recording paper passes through the fixing nip portion. The toner image is heated and pressed to be fixed.

  Here, in the process in which the recording paper passes through the fixing nip portion, the recording paper may be wrinkled. This is remarkable, for example, when the linear velocity of the recording paper is increased (when speeding up).

  Further, as described above, a method using an endless belt (or a film (hereinafter referred to as a belt)) is known as a fixing device used in an image forming apparatus. ) May occur (Problem a). Various techniques for regulating this shift have been proposed as follows.

(Prior Art 1) A belt-side regulating member is attached to the inner or outer peripheral surface of the endless belt end.
(Prior Art 2) A belt detent ring is provided at the end of the roller shaft.
(Prior Art 3) The meandering adjustment roller is tilted in a direction to control the shift (see Patent Documents 1 to 3).
(Prior Art 4) The belt support roller is mutated in the twist direction according to the variation amount of the deviation detecting member (see Patent Document 4).
(Prior Art 5) The static friction coefficient between the belt surface and the pressure roller surface is set to a predetermined value or less (see Patent Document 5).

However, these known techniques have the following problems.
For example, in the known technique 1, when a large shifting force is applied to the endless belt, the belt shifting regulating member is peeled off or the endless belt gets over the regulating member (problem b).

  Further, in the known technique 2, there is a problem that the end of the belt is damaged due to a buckling phenomenon of the endless belt when a large offset force acts on the endless belt (problem c).

  Further, in the known techniques 3 and 4, since a part for regulating the belt deviation is required, it has been an adverse effect of space saving and cost increase of the apparatus (problem d). Further, at least two rollers for stretching the belt are necessary, and a fixing device that does not apply tension to the belt like surf fixing cannot be implemented (Problem e). Further, since the number of components supporting the belt increases, the heat capacity increases, and the warm-up time of the fixing device becomes long (problem f).

  Further, in the known technique 5, even in this method, when the linear velocity is increased or the pressing force of the pressure roller (to the belt) is increased, the belt offset force increases, and therefore, a slight parallelism is caused. Deviations in degrees are not acceptable. In such a method, the effect of preventing the shifting force may be insufficient (Problem g). Further, in the fixing device in which the pressure roller is driven and the belt is rotated on the surface of the pressure roller, there is a problem that the belt slip frequently occurs by reducing the friction coefficient (problem h). . Further, when the pressure roller is inclined with respect to the paper feed roller of the image forming apparatus main body, the transfer material is also sent in an oblique direction when the paper is passed, and the transfer material is wrinkled (problem i). ).

Japanese Patent Publication No. 6-99055 Japanese Utility Model Publication No. 4-60916 JP 2002-173212 A Japanese Patent No. 3708826 JP 2002-173212 A

  SUMMARY An advantage of some aspects of the invention is that it provides a fixing device that suppresses wrinkling of a recording medium in the process of passing through a fixing nip portion. It is another object of the present invention to provide a fixing device that can eliminate the deviation of the endless belt and can simultaneously solve the problems a to i. It is another object of the present invention to provide an image forming apparatus using the fixing device.

The inventors of the present invention have made extensive studies based on the following ideas in order to study the above problems, and have come to achieve the present invention.
First, when the driving force received from the image forming apparatus main body is transmitted to the fixing device, the force twists the entire fixing device, the fixing frame is deformed, and a roller (or fixing roller) that supports the fixing belt or a pressure roller It has been found that the inclination and the parallelism with the conveying system roller in the image forming apparatus main body are out of order. For example, there is a fixing device in which a pressure roller is brought into contact with the fixing belt by power applied from the image forming apparatus main body and put into a pressure state. By adjusting the pressure state of the pressure roller, the nip width is made variable. It is also possible to add a function of controlling the optimum fixing conditions and improving the removability of jammed paper (reducing resistance when taking out jammed paper). When this pressure member is brought into a pressurized state, a force that deforms the fixing frame acts to tilt the roller in the fixing device, thereby causing a belt shift. As a result, sheet wrinkles in the process of passing through the fixing nip occurred. Alternatively, in the known techniques 1, 2, and 5, there are cases where the effect of the means against the belt is insufficient. In order to solve such a problem, known techniques 3 and 4 and methods for increasing the rigidity of the structure (frame) of the fixing device are conceivable. In these methods, the problems d, e, and f are simultaneously solved as described above. It cannot be solved. Therefore, in the present invention, in order to solve the above-described problems with an inexpensive and compact configuration, a position reference member such as a position reference pin of the fixing device when set in the image forming apparatus main body is added to a pressure arm or the like. The support shaft that supports the member that holds the pressure state (pressure holding member) is provided integrally. As a result, even if an external force is applied to the support shaft that supports the pressure holding member, the position reference pin integrated therewith is fitted and fixed to the image forming apparatus main body, so that the frame is deformed. Generation of moments can be suppressed.
If the position reference pin is inclined with respect to the side plate of the frame of the fixing device, the roller in the fixing device supported by the frame is also inclined with respect to the transfer material conveying roller on the image forming apparatus main body side. , Paper wrinkles and other problems will occur. Therefore, in the present invention, the support shaft is a single through shaft and both ends are supported by the frame so that the position reference pin and the support shaft are not easily tilted. Accordingly, it is possible to prevent the position reference pin (member) of the fixing device from being inclined (relative to the side plate of the fixing frame) when receiving a driving force from the image forming apparatus main body.

That is, the present invention provided to solve the above problems is as follows.
[1] A fixing device that is mounted on the main body of the image forming apparatus and allows a non-fixed toner to be fixed onto the sheet by passing the sheet, and a fixing member that is rotatably provided, and fixed in contact with the fixing member It is supported by a pressure member that forms a nip portion, a frame that supports the fixing member and the pressure member at both ends in the width direction, and a support shaft that is provided on the frame. When the fixing device is mounted on the main body of the image forming apparatus and the pressure holding member that is driven to act on the pressure member and brings the pressure member into contact with the fixing member to make a pressure state. At least one position reference member supported by the forming apparatus body, wherein at least one of the position reference members is integrally provided at an end of the support shaft, and the support shaft is The pressure holding member is A fixing device that is a rotation center of the pressure holding member when the pressure member is brought into contact with the fixing member by receiving an external driving force to be in a pressure state .
[2] The fixing device according to [1], wherein the support shaft is formed by spanning one through shaft extending in the width direction of the pressure member over the frame.
[3] The fixing device according to [1], wherein the position reference member provided integrally with an end portion of the support shaft is a cylindrical member whose central axis is coaxial with the axial center of the support shaft.
[4] An image forming apparatus comprising: the fixing device according to any one of [1] to [3]; and a support member that is fitted to a position reference member of the fixing device and supports the fixing device.

  According to the fixing device of the present invention, even when the pressure member is brought into contact with the fixing member to be in a pressurized state, the roller and the image forming apparatus main body side regarding the conveyance mechanism of the sheet (recording medium) such as the pressure member in the fixing device Since the parallelism with the roller can be maintained, it is possible to prevent the sheet from being wrinkled when passing through the fixing nip portion.

The fixing device according to the present invention will be described below.
As shown in FIG. 1, a fixing device 100 according to the present invention includes a fixing member (fixing belt 12) spanned between a fixing roller 11 and a heating roller 14 within a fixing cover 100 c with a constant tension, and the fixing device 100. A pressure member (pressure roller 13) that forms a fixing nip portion N by being pressed against the member (fixing belt 12) so as to be rotatable downward, and a leading end of the fixing nip portion N on the sheet discharge side. A separation claw 16a that is disposed in the vicinity of the fixing member (fixing belt 12) and prevents the sheet P from being wrapped around the fixing member (fixing belt 12), and a leading end on the sheet discharge side of the fixing nip N. A separation claw 16b that is disposed in contact with the pressure member (pressure roller 13) and prevents the sheet P from being wrapped around the pressure member (pressure roller 13), and a cleaning web is pressed against the cleaner belt 12 to clean the fixing belt 12. A cleaning mechanism 17 for packaging, a.

  Here, the fixing belt 12 is an endless belt and has a two-layer structure in which an elastic layer such as a silicon rubber layer is formed on a base material such as nickel, stainless steel, or polyimide. The fixing roller 11 has a metal core and silicon rubber. In order to shorten the warm-up time, foamed silicon rubber may be used so that the heat of the fixing belt 12 is not easily absorbed. The heating roller 14 is an aluminum or iron hollow roller and has a heat source including a heater 14h such as a halogen heater. The heat source may be an induction heating mechanism (IH). A plurality of hollow pipes are formed in the thick portion of the hollow roller of the heating roller 14 so that the longitudinal direction thereof is the width direction of the heating roller 14, and a heat pipe 14a embedded uniformly in the circumferential direction of the heating roller 14 is provided. Have. The heat pipe 14a improves the heat transfer from the heater 14h to the roller surface, and the fixing belt 12 is heated quickly and uniformly.

  When the fixing device 100 is driven, for example, the pressure roller 13 is driven by a driving force input from the outside and rotates counterclockwise in the drawing. As a result, the fixing roller 11 is rotated in the clockwise direction in the drawing. As a result, the fixing belt 12 discharges the sheet P in a state where an appropriate tension is applied by the pressing of the tension roller 15 (in FIG. Rotate in the rotation direction). Further, at the time of fixing, the fixing belt 12 is heated to a predetermined temperature (for example, a temperature suitable for toner fixing) detected by a thermistor (not shown) due to heat generated by a heater 14 h disposed inside the heating roller 14. Is done. In the present invention, the fixing belt 12 (endless belt) shown in FIG. 1 is shown as the fixing member. However, the fixing member is not limited to this and may be a hollow cylindrical roller (fixing roller).

  The pressure roller 13 is a cylindrical roller in which an elastic layer such as silicon rubber is usually provided on a core metal such as aluminum or iron. When necessary, such as during fixing, the pressure roller 13 is heated to a predetermined temperature by the heat generated by the heater 13h disposed therein.

  Further, the pressure roller 13 can be switched between a pressure state in contact with the fixing belt 12 and a pressure-release state after being separated by the pressure-decompression means 30.

FIG. 2 shows the configuration of the pressure depressurizing means of the pressure roller 13.
The pressurizing and depressurizing means 30 includes a pressurizing cam 31 that is rotated by a driving force input from the outside, a first pressurizing arm 32, a second pressurizing arm 33 that is a pressurizing holding member (shaded portion in the figure), a first The elastic members 34 fixed to the respective end portions of the first pressure arm 32 and the second pressure arm 33, and the first pressure arm 32 and the second pressure arm 33 fixed to the frame of the fixing device 100 are common. A support shaft 35 is provided.

  Here, the pressurizing / depressurizing means 30 moves the pressure roller 13 toward the fixing belt 12 to apply pressure, and moves the pressure roller 13 in the direction away from the fixing belt 12 to depressurize as follows. Is called.

(Pressurizing operation)
First, when the pressure cam 31 is rotated by a constant rotation angle in the direction of the arrow in the figure by an external driving force, the pressure cam 31 pushes up the top portion of the first pressure arm 32 (( 1) Arrow direction of part).
When the top portion of the first pressure arm 32 is pressed, the first pressure arm 32 rotates around the support shaft 35 (counterclockwise direction in FIG. 2). Then, the elastic member 34 fixed to the end of the first pressure arm 32 opposite to the support shaft 35 also rotates, and the elastic member 34 is fixed to the end of the second pressure arm 33 with a constant pressure. Is pushed up (in the direction of the arrow in FIG. 2 (2)).
Next, when the end of the second pressure arm 33 on the elastic member 34 side is pushed up, the second pressure arm 33 rotates about the support shaft 35 (counterclockwise direction in FIG. 2).
Next, the pressure portion 33a located between the end of the second pressure arm on the elastic member 34 side and the support shaft 35 abuts against the shaft 13j of the pressure roller 13 and acts to push toward the fixing roller 11 ( FIG. 2 (3) portion arrow direction).
Finally, the pressure roller 13 comes into contact with the fixing roller 11 via the fixing belt 12 and is in a state of being pressed with a constant pressure based on the elastic force of the elastic member 34, thereby forming the fixing nip portion N (FIG. 2 ( 4) Arrow direction of part).
As described above, when the fixing device 100 is driven, the pressing / depressurizing unit 30 presses the pressing roller 13 against the fixing belt 12 with a constant pressure in the direction of the fixing belt 12.

(Decompression operation)
First, when the pressure cam 31 is further rotated by a fixed rotation angle from the angular position when the pressure is applied by an external driving force, the pressure cam 31 moves the top portion of the first pressure arm 32. Pushing up is released (in the direction opposite to the arrow in part (1) in FIG. 2).
When the push-up of the first pressure arm 32 is released, the first pressure arm 32 is applied with the support shaft 35 as the central axis with a repulsive force via the fixing nip portion N, the pressure portion 33a, and the elastic member 34. It rotates in the opposite direction to the pressure (clockwise direction in FIG. 2). Next, the end of the second pressure arm 33 together with the elastic member 34 fixed to the end of the first pressure arm 32 opposite to the support shaft 35 is pulled in the direction opposite to that in the case of pressurization ( (The direction opposite to the arrow in part (2) of FIG. 2).
Next, when the end of the second pressure arm 33 on the elastic member 34 side is pulled down, the second pressure arm 33 moves in the direction opposite to the direction of pressure with the support shaft 35 as the central axis. It rotates (clockwise direction in FIG. 2).
Next, the pressing portion 33a in the middle of the end of the second pressing arm on the elastic member 34 side and the support shaft 35 rotates in the opposite direction to the pressurizing direction, so that it is away from the shaft 13j of the pressing roller 13. (In the direction opposite to the arrow in part (3) in FIG. 2).
As a result, the pressure roller 13 is released from being pressed, so that the pressure roller 13 moves away from the fixing roller 11, and the formation of the fixing nip portion N is eliminated and the pressure is released (see FIG. (The direction opposite to the arrow in the portion (4) in FIG. 2).
As described above, when the driving of the fixing device 100 is stopped, the pressing / depressurizing unit 30 releases the pressing of the pressure roller 13 to the fixing belt 12, and the separation from the fixing belt 12 (depressurized state).

  The separation claw 16b comes into contact with the pressure roller 13 when the pressure roller 13 contacts the fixing belt 12 and enters the pressure state, and the pressure roller 13 moves away from the fixing belt 12 and is released from the pressure state. When it becomes, it is separated from the pressure roller 13.

  Further, in the present invention, the form of the pressure roller 13 (roller type) shown in FIG. 1 is shown as the pressure member. However, the present invention is not limited to this, and an endless belt shape spanned between two rollers is used. It is good also as a pressurizing member (belt type).

  In the fixing device 100, the surface of the fixing belt 12 is heated to a predetermined temperature while the fixing belt 12 and the pressure roller 13 are driven to rotate, and unfixed toner T is formed in the fixing nip portion N. The sheet P is passed (paper passing from the right side to the left side in FIG. 1), and fixing is performed by thermally fusing the unfixed toner on the sheet P by pressurization and heating at the fixing nip N.

  In FIG. 1, the toner-fixed sheet P is discharged from the fixing nip portion N. At this time, the sheet P may come out while being wound around the fixing belt 12 or the pressure roller 13. As countermeasures, an oil application device 21 that improves the releasability by applying oil to the fixing belt 12 and an oil application device 22 that improves the releasability by applying oil to the pressure roller 13 are provided. The oil used here is preferably a heat-resistant and non-volatile oil, such as silicone oil. Further, when the leading ends of the separation claws 16 a and 16 b come into contact with the leading end of the sheet P, the sheet P is separated from the fixing belt 12 or the pressure roller 13. The sheet P discharged from the fixing nip portion N passes through a predetermined discharge path and is sent out from the fixing device 100.

By the way, the fixing device 100 includes a positioning pin for mounting at an appropriate position in the image forming apparatus main body when the fixing apparatus 100 is mounted on the image forming apparatus main body.
FIG. 3 is a configuration diagram of the fixing device 900 of the comparative example, and is a view (front view) of the fixing device 900 viewed from the front.
The fixing device 900 has a belt-type roller configuration shown in FIG. 1, and left and right side plates 100f1 and 100f2 erected on the bottom plate 100f3 are provided with a fixing roller 11, a heating roller 14, Each pressure roller 13 is supported. Further, the fixing belt 12 is stretched around the fixing roller 12 and the heating roller 14.

  Further, the pressure release means 30 is provided on each of the left and right side plates 100f1 and 100f2, and the pressure cam 31 is rotated by receiving a driving force from the image forming apparatus main body, and the left and right side plates 100f1 are rotated by the mechanism described above. , 100 f 2, the second pressure arms supported by the respective support shafts 95 push up the shafts at both ends of the pressure roller 13.

  The fixing device 900 includes a positioning pin 98 that is a positioning reference member that fits with a support member of the image forming apparatus main body in order to be attached to and detached from the image forming apparatus main body. Although only one position reference member 98 is shown in FIG. 3, at least one positioning pin 98 is provided on the left side plate 100f1. These positioning pins 98 are fixed to the left side plate 100f1 so that the end portions protrude from the fixing cover 100c (not shown).

  Here, when the fixing device 900 is mounted on the image forming apparatus main body, the fixing device 900 is moved in the axial direction of the positioning pin 98 so that the surface on which the positioning pin 98 is provided is in the back, thereby forming an image. It is installed at a predetermined location (positioning hole 200a) in the apparatus. At this time, the axis of the positioning pin 98 of the fixing device 900 is set in parallel to the transfer roller and the paper feeding registration roller in the image forming apparatus, and each roller in the fixing device 900 is parallel to the axis of the positioning pin 98. By maintaining the sheet, the sheet is normally conveyed.

  At this time, since the positioning pin 98 is fixed to the left side plate 100f1, the positioning pin 98 may not be perpendicular to the left side plate 100f1. That is, the axis of the positioning pin 98 is inclined, and the fixing roller 11 and the pressure roller 13 forming the fixing nip portion N are not parallel to the transfer roller and the registration roller on the image forming apparatus main body side. Meandering, leading to paper wrinkles and left / right image magnification deviations.

  In the fixing device 900 of FIG. 3, when the pressure cam 31 receives a driving force from the image forming apparatus main body, the second pressure arm pushes up the shafts at both ends of the pressure roller 13 by the mechanism described above. Force is transmitted to the left and right side plates 100f1 and 100f2 via the support shaft 95, and acts as a force for pushing the entire fixing device 900 upward in the drawing. At this time, since the fixing device 900 is supported and fixed to the image forming apparatus main body at the position of the positioning pin 98, the fixing device 900 receives a rotational moment with the positioning pin 98 as the center of rotation by the pushing-up force. When the rigidity of the positioning pin 98 on the left side plate 98 is insufficient, the fixing frame is twisted and deformed so that only the right side plate 100f2 side is slightly lifted. Therefore, the parallelism of the rollers in the fixing device 900 positioned on the fixing frame is incorrect, and the fixing belt 12 is deviated.

  As described above, since the fixing device of the comparative example has such a problem, even if the rollers in the fixing device are accurately configured, the parallelism is not correct when the fixing belt rotates, and each roller of the image forming apparatus main body Also, there is a problem that paper wrinkles, an image magnification error, or a belt shift occurs. Therefore, the inventors have intensively studied to solve this problem, and as a result, have come to achieve the present invention. Hereinafter, the fundamental part of the present invention will be described.

4 and 5 show the configuration of the fixing device 100 of the present invention. 4 is a front view of the fixing device 100, and FIG. 5 is a side view seen from the left side plate 100f1 side.
The fixing device 100 has a belt-type roller configuration shown in FIG. 1, and right and left side plates 100f1 and 100f2 erected on a bottom plate 100f3 are provided with a fixing roller 11, a heating roller 14, Each pressure roller 13 is supported. In FIG. 5, the axes of the fixing roller 11, the heating roller 14, and the pressure roller 13 are visible from the left side plate 100f1. Further, the fixing belt 12 is stretched over the fixing roller 11 and the heating roller 14. At this time, the left and right side plates 100f1 and 100f2 may be made of metal or resin, but are preferably made of metal having high rigidity. Further, the left and right side plates 100f1 and 100f2 are reinforced by a bottom plate 100f3, a stay (not shown) or the like so as to maintain rigidity in order to keep the parallelism of the rollers from shifting. Hereinafter, a structure including the side plates 100f1 and 100f3, the bottom plate 100f3, and the stay is referred to as a frame.

  Further, the pressure release means 30 is provided on each of the left and right side plates 100f1 and 100f2, and the pressure cam 31 is rotated by receiving a driving force from the image forming apparatus main body, and the left and right side plates 100f1 are rotated by the mechanism described above. , 100 f 2, the second pressure arm 33 supported by the support shaft 35 pushes up the shafts at both ends of the pressure roller 13. At this time, one through shaft extending in the width direction of the pressure roller 13 (width direction of the fixing device 100) is spanned from the left side plate 100f1 to the right side plate 100f2.

  Further, the fixing device 100 has positioning pins 18a and 18b which are positioning reference members for fitting with the support member (positioning hole 200a) of the image forming apparatus main body in order to be attached to and detached from the image forming apparatus main body. (FIG. 5). Here, as an example, a position reference member (reference pin) of a cylindrical columnar shaft made of metal will be described, but other resin bosses or sheet metal brackets may be used. The positioning hole 200a may be a simple through hole, but may be a sliding bearing.

  The positioning pin 18a is provided integrally with the support shaft 35 at the end of the support shaft 35 on the left side plate 100f1, and the end protrudes from the fixing cover 100c. Further, the positioning pin 18b is erected at another position on the same left side plate 100f1 and fixed so that its end protrudes from the fixing cover 100c.

  Further, the positioning pin 18 a provided integrally with the end portion of the support shaft 35 may be a cylindrical member whose central axis is coaxial with the axial center of the support shaft 35. In this way, the positioning pin 18 a is a columnar (or cylindrical) member, and it is only necessary to provide the central axis of the positioning pin 18 a so as to be coaxial with the axial center of the support shaft 35. It is realizable in the aspect which extends an axis | shaft so that it may protrude. That is, the positioning pin 18a and the support shaft 35 can be covered with a single component. As a result, since the number of parts can be reduced, a space-saving and inexpensive configuration can be achieved.

FIG. 6 shows how the fixing device 100 is mounted on the image forming apparatus main body 200.
When the fixing device 100 is mounted on the image forming apparatus main body, the fixing device 100 is moved in the axial direction of the positioning pins 18a and 18b so that the surface on which the pressure cam 31 is provided is in the back, thereby forming an image. Insert into a predetermined place in the apparatus 200.
On the other hand, the image forming apparatus 200 includes a main body frame 200f for assembling a transfer roller and a photoreceptor, and the main body frame 200f is provided with two sleeve-like positioning holes 200a (support members). When the fixing device 100 is inserted, each of the positioning pins 18a and 18b is slid from the inlet of the positioning hole 200a toward the back using the positioning hole 200a as an introduction rail, and finally, the positioning pin 200a is positioned at the end of the positioning hole 200a. By fixing the pins 18a and 18b, the fixing device 100 is installed at a predetermined location in the image forming apparatus 200, and the positional relationship with the transfer roller, the photosensitive member, and the paper feeding registration roller is determined with high accuracy. ing. That is, the axes of the positioning pins 18a and 18b of the fixing device 100 are installed in parallel with the transfer roller and the paper feeding registration roller in the image forming apparatus 200, and each roller in the fixing device 100 is connected to the positioning pins 18a and 18b. By keeping parallel to the axis, the sheet is normally conveyed.

  The positioning hole 200a and the positioning pins 18a and 18b are fitted to each other by, for example, fixing the positioning pins 18a and 18b by a resin pressing lever. Alternatively, screwing may be used.

  Further, as shown in FIG. 6, there is a main body driving unit 200 b behind the positioning hole 200 a of the main body frame 200 f, and when the fixing device 100 is disposed at a predetermined location in the image forming apparatus 200, the pressure cam 31. So that a driving force is input to the pressurizing cam 31 from the main body driving unit 200b.

  Here, the pressure cam 31 receives a driving force from the main body driving unit 200b on the image forming apparatus side, and a part of the force received by the pressure cam 31 is a support shaft 35 of the second pressure arm 33, and further a positioning pin. 18a, the support shaft 35 is firmly supported by the left and right side plates 100f1 and 100f2 as one through shaft, and the positioning pin 18a integrated with the support shaft 35 is a positioning hole of the image forming apparatus 200. Since it is a portion supported by 200a, the rotational moment as generated in the fixing device 900 of the comparative example does not occur, the deformation of the fixing frame is prevented, and the above problem can be solved. In addition, by using the positioning pin 18a as the fulcrum (support shaft 35) of the pressure arm 33, it is possible to reduce the accumulation of tolerances of components, and the positioning accuracy between the image forming apparatus main body and the fixing nip portion is improved. Accordingly, the correct position of the fixing device 100 in the image forming apparatus 200 is maintained even when receiving a driving force from the main body of the image forming apparatus 200, and transfer material conveyance failure (paper wrinkles) due to poor parallelism can be prevented. I can do it.

As described above, according to the fixing device of the present invention, the following effects can be obtained.
That is, in the fixing device that receives driving force from the image forming apparatus, in the fixing device 900 of the comparative example in which the positions of the support (support shaft) of the positioning pin 98 and the pressure arm 33 are different, the driving input rotating body receives the driving force. Then, a moment is generated such that the fixing frame with the positioning pin 98 as the center of rotation is deformed. Due to this force, the parallelism of the support roller (fixing roller 11) of the fixing belt 12 and the pressure roller 13 that forms a nip opposite to the belt is lost, and the wrinkles of the sheet (recording medium) (in the case of a fixing belt) (Belt side) occurred. On the other hand, in the configuration of the present invention, since the pressing arm 33 is supported by the support shaft 35 that is integral with the positioning pin 18a, the support shaft 35 is interposed via the positioning pin 18a even when receiving a driving force. Since the image forming apparatus 200 is fixed to the main body, the moment as described above does not act, and deformation of the fixing frame is prevented. Accordingly, the positional relationship of the fixing roller 11 (fixing belt 12) with the main body of the image forming apparatus 200 does not get out of order, so that the conveyance direction of the sheet (recording medium) is stabilized and the occurrence of image wrinkles can be prevented. Further, in the case of the fixing belt 12, the belt can be prevented from being shifted.

  Here, the configuration example in which the fixing member (fixing belt 12) is arranged on the upper side of the fixing device and the pressure member (pressure roller 13) is arranged on the lower side is shown, but the present invention is not limited to this. A roller-type fixing member may be disposed, and a belt-type pressing member may be disposed below the roller-type fixing member. FIG. 7 shows an example of the configuration. Here, a fixing roller 12a that is rotatably arranged on the upper side and a pressure belt 13a that is rotatably supported by rollers R11, R14, and R15 below the roller 12a are brought into contact with each other to be in contact with the pressure belt 13a. The fixing nip portion N is arranged so as to be formed by a backup member 13b which is a pressure pad on the back surface of the toner. In this case, the pressure depressurizing means 30 is arranged so as to act on the roller R14 or R15, for example.

Next, the image forming apparatus according to the present invention will be described.
FIG. 8 shows a configuration of a tandem type color copying machine which is an image forming apparatus according to the present invention.
The color copying machine 200 includes an image forming unit 200A positioned at the center of the apparatus main body, a paper feeding unit 200B positioned below the image forming unit 200A, and an image reading unit (not shown) positioned above the image forming unit 200A. The fixing device 100 of the present invention is incorporated in the image forming unit 200A.

  The image forming unit 200A is provided with a transfer belt 210 having a transfer surface extending in the horizontal direction, and a configuration for forming an image of a color complementary to the color separation color on the upper surface of the transfer belt 210. Is provided. That is, photoconductors 205Y, 205M, 205C, and 205K as image carriers that can carry images of toners of complementary colors (yellow, magenta, cyan, and black) are juxtaposed along the transfer surface of the transfer belt 210. ing.

  Each of the photoconductors 205Y, 205M, 205C, and 205K is configured by a drum that can rotate in the same direction (counterclockwise direction), and around the optical writing device 201 that performs image forming processing in the rotation process, Charging devices 202Y, 202M, 202C and 202K, developing devices 203Y, 203M, 203C and 203K, primary transfer devices 204Y, 204M, 204C and 204K and a cleaning device are arranged. Each developing device 203Y, 203M, 203C, 203K contains a respective color toner.

  The transfer belt 210 is configured to be able to move in the same direction at a position facing the photoconductors 205Y, 205M, 205C, and 205K by being wound around a driving roller and a driven roller. Further, a transfer roller 212 is provided at a position facing a roller 211 that is one of the driven rollers. Further, the conveyance path of the sheet P from the transfer roller 212 to the fixing device 100 is a horizontal path.

  Note that an oil tank 251 that collects oil for improving the releasability of the sheet P used in the fixing device 100 attached to the fixing device 100, and oil that supplies oil in the oil tank 251 to the fixing device 100 again. An oil circulation mechanism such as a pump 252 is provided.

  The sheet feeding unit 200B separates the sheet P in the sheet feeding tray 220 one by one from the top in order from the top to the position of the transfer roller 212. It has a transport mechanism for transporting.

  In image formation in the image forming apparatus 200 of the present invention, the surface of the photoreceptor 205Y is uniformly charged by the charging device 202Y, and an electrostatic latent image is formed on the photoreceptor 205Y based on image information from the image reading unit. Is done. The electrostatic latent image is visualized as a toner image by a developing device 203Y containing yellow toner, and the toner image is primarily transferred onto the transfer belt 210 by a primary transfer device 204Y to which a predetermined bias is applied. Is done. The other photoconductors 205M, 205C, and 205K also form similar images only with different toner colors, and the toner images of the respective colors are sequentially transferred onto the transfer belt 210 by the electrostatic force and superimposed.

  Next, the toner image T primarily transferred from the photoconductors 205Y, 205M, 205C, and 205K onto the transfer belt 210 is transferred to the sheet P conveyed by the rollers 211 and 212. The sheet P to which the toner image T has been transferred is further conveyed to the fixing device 100 and is fixed at a fixing nip N between the fixing belt 12 and the pressure roller 13. At this time, for example, the sheet P passes through the fixing nip portion N while the parallelism of the fixing roller 11 and the pressure roller 13 with respect to the driven roller 211 and the transfer roller 212 is maintained in a good state. Normal fixing is carried out without doing so.

Further, an appropriate amount of oil is applied to the fixing belt 12 and the pressure roller 13 by the oil applying devices 21 and 22, respectively, and if necessary, separation claws 16a and 16a disposed on the exit side of the fixing nip N. Since 16b functions, the sheet P is discharged to the exit side of the fixing nip portion N without being wound around the fixing belt 12 and the pressure roller 13.
Next, the sheet P discharged from the fixing nip N is sent out to the stacker 215 along the discharge path.

  As described above, the image forming apparatus having the fixing device 100 according to the present invention can provide a more advanced fixing separation function without causing wrinkles on the sheet P, and can be used for various types of paper (from thin paper to thick paper). It is possible to cope with an image (it is possible to reduce the leading edge margin of the image).

  Although the present invention has been described with the embodiments shown in the drawings, the present invention is not limited to the embodiments shown in the drawings, and other embodiments, additions, modifications, deletions, etc. Can be changed within the range that can be conceived, and any embodiment is included in the scope of the present invention as long as the effects and advantages of the present invention are exhibited.

FIG. 2 is a cross-sectional view illustrating a configuration of a fixing device according to the present invention. FIG. 3 is a schematic diagram illustrating a configuration of a pressure depressurizing unit in the fixing device according to the present invention. FIG. 2 is a schematic diagram illustrating a configuration of a fixing device of a comparative example. FIG. 2 is a front view illustrating a configuration of a fixing device according to the present invention. FIG. 2 is a side view illustrating a configuration of a fixing device according to the present invention. FIG. 2 is a schematic diagram illustrating a state in which the fixing device according to the present invention is mounted on the image forming apparatus main body. FIG. 6 is a cross-sectional view showing another configuration example of a pressure member and a fixing member in the fixing device according to the present invention. 1 is a cross-sectional view illustrating a configuration of an image forming apparatus according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11, 12a Fixing roller 12 Fixing belt 13 Pressure roller 13a Pressure belt 13b Backup member 13j Pressure roller shaft end 13h, 14h Heater 14 Heating roller 14a Heat pipe 15 Tension roller 16a, 16b Separation claw 17 Cleaning mechanism 18a, 18b , 98 Positioning pin (position reference member)
21, 22 Oil application device 30 Pressure depressurizing means 31 Pressure cam 32 First pressure arm 33 Second pressure arm 33a Pressure portion 34 Elastic member 35,95 Support shaft 100,900 Fixing device 100c Fixing cover 100f1 Left side Plate 100f2 Right side plate 100f3 Bottom plate 200 Image forming device 200A Image forming unit 200B Paper feeding unit 200a Positioning hole 200b Main body driving unit 200f Main body frame 201 Optical writing device 202Y, 202C, 202M, 202K Charging device 203Y, 203M, 203C, 203K Developing device 204Y, 204M, 204C, 204K Primary transfer device 205Y, 205C, 205M, 205K Photoconductor 210 Transfer belt 211 Driven roller 212 Transfer roller 215 Stacker 220 Paper feed tray 250 Oil circulation mechanism 25 Oil tank 252 oil pump O Oil P sheet (recording medium)
R11, R14, R15 Roller T Toner

Claims (4)

A fixing device that is attached to an image forming apparatus main body, passes a sheet, and fixes unfixed toner on the sheet,
A fixing member that is rotatably provided;
A pressure member that contacts the fixing member to form a fixing nip portion;
A frame that supports the fixing member and the pressure member at both ends in the width direction;
It is supported by a support shaft provided on the frame, is driven by an external driving force and acts on the pressure member, and the pressure member is brought into contact with the fixing member to be in a pressurized state. A pressure holding member;
At least one position reference member supported by the image forming apparatus main body when the fixing device is mounted on the image forming apparatus main body;
With
At least one of the position reference members is integrally provided at an end of the support shaft ,
The support shaft is a rotation center of the pressure holding member when the pressure holding member receives a driving force from the outside and brings the pressure member into contact with the fixing member to be in a pressure state. Fixing device.   2. The fixing device according to claim 1, wherein the support shaft is configured such that one through shaft extending in a width direction of the pressure member is stretched over the frame.   The fixing device according to claim 1, wherein the position reference member provided integrally with an end portion of the support shaft is a columnar member whose central axis is coaxial with the axial center of the support shaft.   An image forming apparatus comprising: the fixing device according to claim 1; and a support member that is fitted to a position reference member of the fixing device and supports the fixing device.

Images