CN101093379A - Fixing device and image forming device - Google Patents

Abstract

A fixing device having a separation claw, the end of which is installed so as to be in contact with the outer peripheral surface of a pressing roller. The separating claw brings the end portion into contact with the outer peripheral surface of the pressing roller, thereby separating the paper from the pressing roller. The center axis of rotation of the separation claw is rotatably supported by the supporting member, and when a force for pressing the end of the separation claw into the pressing roller is applied, the center axis of rotation of the separation claw is guided so that the end of the separation claw Displaced in the direction of separation from the pressure roller.

Description

Fixing device and image forming device

This application is a divisional application of the patent application with the application number 200410063537.9, the filing date is July 9, 2004, and the invention title is "fixing device and image forming device".

Cross References to Related Applications

This application is based on, and claims priority to, the following patent application documents, Prior Japanese Patent Application No. 2003-195786 filed on July 11, 2003, Japanese Patent Application No. 2003- 196009, Japanese Patent Application No. 2003-195784 filed on July 11, 2003, and Japanese Patent Application No. 2003-195787 filed on July 11, 2003; the entire contents of which are incorporated herein by reference.

technical field

The present invention relates to a fixing device for an image forming apparatus for heating and pressurizing a toner image transferred onto a sheet-like recording medium and fixing it on the recording medium.

Background technique

There are known image forming apparatuses that transfer a toner image onto paper, and fix the transferred toner image onto the paper by means of a fixing device to form an image on paper.

As a fixing device installed in such an image forming apparatus, a fixing roller having a fixing roller for thermally fixing toner transferred onto transfer paper (recording paper), a pressing roller, separation claws, and a spring The devices are well known. The separation claw is biased by a spring so that its end is pressed to the outer periphery of the fixing roller. A long guide groove for guiding and supporting the rotation center shaft of the separating claw is installed on the main body side of the fixing device. The long guide groove is formed along a circumference coaxial with the outer circumference of the fixing roller. In addition, a detection sensor for detecting the movement of the rotation center shaft along the long guide groove is mounted on the main body side of the fixing device.

In this fixing device, as disclosed in Japanese Patent Application Laid-Open No. 10-74015, when clogging occurs, the separation claw moves along a long guide groove on a circumference coaxial with the outer circumference of the fixing roller. When the separating claw moves, the detection sensor is activated via a lever engaged with the central axis of rotation. In this way, a failure (occlusion) is detected.

Furthermore, in addition to the above-mentioned devices, there is also disclosed in Japanese Patent Application Laid-Open No. 2000-264520 a known fixing device having a claw shifting device for moving the separating claw so that The separation claw is separated from a position in contact with the surface of the processing roller.

However, according to the prior art disclosed in Japanese Patent Application Laid-Open No. 10-74015, the separation claw moves on a circumference coaxial with the outer circumference of the fixing roller along the guide groove. That is, the separation claw moves along the outer periphery of the fixing roller so as not to be separated from the outer periphery of the fixing roller. Therefore, with the jammed paper, a force for pressing it inward toward the fixing roller can be input to the end of the separation claw. In this case, the ends of the separation claws are pressed to the outer peripheral surface of the fixing roller, so that there is a risk of damaging the outer peripheral surface of the fixing roller.

Furthermore, in recent years, the hardness of the outer periphery of the pressure roller has been lowered (ie, softer) than before. Therefore, when the separating claw disclosed in Japanese Patent Application Laid-Open Document 10-74015 is applied to the pressing roller, its outer shaft is soft, and if the end of the separating claw is pressed to the pressing roller by the jammed paper On the peripheral surface, the peripheral surface of the pressing roller is easily damaged.

On the other hand, the prior art disclosed in Japanese Patent Application Laid-Open No. 2000-264520 is a construction in which the separation claw is separated from the surface of the processing roller by sliding the operation plate. That is, if the operator does not operate the operation plate, the separation claw will not be separated from the processing roller. Therefore, this technique is effective for clearing the jammed paper when a jam occurs, however, when the jammed paper presses the separation claw against the processing roller before the jammed paper is cleared, the separation claw may damage the processing roller.

Furthermore, in recent image forming apparatuses, a transfer unit and a fixing device are installed close to each other, thus miniaturizing the apparatus. Due to this miniaturization, transport distances between transfer and fusing processes are shortened so that paper often extends through multiple process steps.

Therefore, when a conveyance failure (hereinafter referred to as a jam) of a sheet occurs, especially when the jam occurs in the fixing device, the jammed sheet extends through a plurality of processes from the fixing device to the transfer unit, and is held at between multiple rollers.

At this time, the jammed paper closely adheres to the conveying surface between the fixing device and the transfer unit with substantially no gap. Therefore, a finger cannot substantially be inserted between the jammed paper and the conveying surface, and it is difficult to remove the jammed paper.

In particular, when the jam occurs near the fixing unit, the temperature of the conveying surface may be high due to the heat generated by the heating roller, making it more difficult to remove the jammed paper.

Therefore, for the case where clogging occurs near the fixing device, a method has been developed in which a rotary handle is installed on each of the heating roller and the pressing roller, and by rotating the handle, the heating roller and the pressing roller are rotated, thereby Remove any paper that is between the rollers.

Furthermore, in recent years, for example, as disclosed in Japanese Patent Application Laid-Open No. 7-157141, a method has been developed to stagger the timing of stopping the conveyance of sheets in the transfer unit and the fixing device when a jam occurs. A bend is thereby formed in a part of the sheet (the portion of the sheet separated from the conveying surface), the bend is maintained, and the sheet is removed.

However, in applying the method of rotating the heating roller and pressing roller by rotating the handle, the paper must be held between the heating roller and the pressing roller, and when it is not held, the paper cannot be held even if the rotating handle is rotated. Cleared.

Furthermore, in applying the method of forming a curved portion in the paper, the paper must extend over the distance between the transfer unit and the fixing device, and if such a distance is not extended, even for the timing of stopping the transfer of the transfer unit and the fixing device are staggered, and no curved portion is formed.

In recent years, as disclosed in Japanese Patent Application Laid-Open No. 2003-76202, a belt fixing device having a fixing belt stretched between a heating roller and a separating roller has been proposed. In this type of belt fixing device, the paper with the transferred toner image is heated under pressure by bringing the heat roller and the pressure roller into contact with each other via the belt under pressure. , to perform thermal fusing. Also, in the belt fixing device, the fixed paper is conveyed along the paper conveyance path via a conveyance belt that is stretched. The paper is separated from the conveyor belt by means of separation rollers. The separation roller portion is used as a separation point for separating the sheet from the transfer belt, so that a satisfactory image without claw marks can be obtained.

In the aforementioned belt fixing device, the relationship among the heating roller, separation roller, belt and pressing roller is important. For example, when such a structure is used that the belt fixing device applies driving force only to the heat roller, and the separation roller, the fixing belt and the pressing roller rotate following the heat roller, the separation roller is rotated by the heat roller via the fixing belt. . In this case, if the separation roller and the fixing belt slip, then a fixing belt driving failure in the fixing device or a sheet conveying failure occurs, and as a result, satisfactory image quality may not be obtained. Therefore, there is a need for a technique for efficiently and reliably driving each unit in the belt fixing device.

Furthermore, in the aforementioned belt fixing device, the separation roller and the heating roller support the fixing belt. Therefore, in the belt fixing device, when the relationship between the separation roller, the heating roller and the fixing belt is not ideal, malfunctions such as damage to the fixing belt may occur. Therefore, there is a need for a technique for assuring an ideal relationship among the fixing belt, the separation roller, and the heating roller.

Furthermore, a fixing device, such as that disclosed in Japanese Patent Application Document No. 2000-112283, may have a separating member for separating the paper from the rotating member. As the separating element, a separating element having an upstream side separating end and a downstream side separating end is known. In order to separate the paper passing through the nip, the upstream-side separating end is arranged on the upstream side of the downstream-side separating end on the paper conveying path, and is in contact with the surface-side rotating member, the nip being such a A region, that is, a region where the surface-side rotating member in contact with the surface of the sheet and the back-side rotating member in contact with the back side of the sheet are pressed against each other from the surface-side rotating member. In order to ensure that the paper passing through the nip is separated from the surface-side rotating member, the downstream-side separating end is installed in contact with the fixing roller. The purpose of installing the downstream side separating end is to prevent the paper from wrapping around the rotating member when a separating failure occurs.

Furthermore, as a fixing device, such as that disclosed in Japanese Patent Application Laid-Open No. 5-307336, has a separating claw for separating the sheet from the fixing roller. The separation claw is generally linear and consists of a support member having a rotational axis for bending only the fuser roller side in the event of a paper jam, and a claw end rotatably connected to the support element. In the separation claw, the rotation shaft of the support member is supported on the main body side, and the claw end of the claw end portion is in contact with the fixing roller with a predetermined pressure. In addition, in the claw end, on one side of the fixing roller side, when a paper jam occurs (when the supporting member is bent), a lever member is brought into contact with the surface of the fixing roller, and by leverage, the claw end is Separates from the surface of the fuser roller.

On the other hand, in addition to the heating roller and the pressing roller for applying pressure to the heating roller, the fixing device may have a separation roller installed opposite to the heating roller, and a tension roller between the heating roller and the separation roller. belt. In this fixing device, the paper is separated near the top end of the separation roller whose belt is stretched. Furthermore, in such a fixing device, in the case where paper sticks to the belt and cannot be separated, near the top end of the separation roller, a separation plate is installed.

However, a very thin sheet material constitutes the separation plate with a thickness of about 0.3 mm, so that when jamming occurs, the jammed paper comes into contact with the end surface of the separation plate, and the separation plate may be deformed or damaged.

An object of the present invention is to provide a fixing device capable of suppressing deformation and damage of a separation plate.

Contents of the invention

An object of the present invention is to provide a fixing device capable of preventing scratching and damage of a roller.

Furthermore, it is an object of the present invention to provide an image forming apparatus capable of simply removing a sheet of paper when a sheet conveyance failure occurs in the apparatus.

In addition, another object of the present invention is to provide a fixing device capable of reliably and efficiently driving each unit in the fixing device.

Furthermore, another object of the present invention is to provide a fixing device capable of preventing deformation and damage of a separation plate.

According to the present invention, there is provided a fixing device comprising: a heating roller whose outer peripheral surface is at least heated; a pressing roller configured to apply pressure to the heating roller; at least one separation claw having a a central axis of rotation on one end and a second end opposite to the first end, wherein the second end is arranged to contact the outer peripheral surface of the heating roller or the outer peripheral surface of the pressing roller, and the The second end is in contact with the outer peripheral surface of the roller, so that the recording medium is separated from the roller; and a support member configured to rotatably support the rotation center shaft, when pressure is applied to the second end Thus, when it comes into contact with the roller, the rotation center shaft is guided to separate the second end from the roller.

Furthermore, according to the present invention, there is provided an image forming apparatus for forming an image on the surface of a sheet conveyed in a conveyance path, comprising: a guide unit having a guide surface for guiding the sheet; and a separation member provided on the In the guide unit, protrudes from the guide surface, and extends from the guide surface into the transport path, thereby separating the paper from the guide surface.

Furthermore, according to the present invention, there is provided an image forming apparatus including: a transport path configured to transport a sheet on which an image is formed; And the sheet being conveyed in the conveying path is guided, and when the sheet is jammed, the member is lifted to the side of the conveying path, thereby releasing the sheet located in the conveying path.

In addition, according to the present invention, there is provided a fixing device including: a heating roller heated by a heat source; a separation roller arranged in the vicinity of the heating roller; a fixing belt supported in such a state that That is, the fixing belt is stretched between the heating roller and the separation roller; a pressure roller, which is in contact with the heating roller under a predetermined pressure on the fixing belt, wherein the heating roller is driven by the driving device, and the separation roller, the fixing belt and the The pressure roller rotates with the heating roller driven by the drive unit, and the surface of the separation roller is rougher than the contact surface of the fixing belt.

In addition, according to the present invention, there is provided a fixing device including: a heating roller heated by a heat source; a separation roller arranged near the heating roller; a fixing belt supported in such a state that That is, the fixing belt is stretched between the heating roller and the separation roller; a pressing roller, which is in contact with the heating roller under predetermined pressure on the fixing belt, wherein the separation roller has a width wider than that of the fixing belt.

In addition, according to the present invention, there is provided a fixing device including: a heating roller whose outer peripheral surface is heated at least; a pressing roller for applying pressure to the heating roller; and a separation roller arranged to face the heating roller. a certain image belt, which is stretched between the heating roller and the separation roller; a support member, which is rotatably arranged near the separation roller; and a separation plate, which has an end surface and is supported by the support member , so as to freely rotate between an approach position, in which the end surface is close to the fixing belt, and a displacement position, in which the end surface is pressed when the end surface is pressed. shifted so as to be separated from the fixing belt further than the close position.

Description of drawings

FIG. 1 is a schematic diagram showing an image forming apparatus to which a fixing device of the present invention is installed;

2 is a perspective view showing a part of the fixing device related to the first embodiment of the present invention;

FIG. 3 is a perspective view showing a pressure roller of the fixing device shown in FIG. 2;

FIG. 4 is a side view showing the fixing device shown in FIG. 2;

Fig. 5 is a side view showing the fixing device when clogging occurs;

6 is a perspective view showing the outer periphery of a guide unit installed on the downstream side of the fixing device;

7A and 7B show the outer circumference of the guide unit, FIG. 7A is a side view showing the state where the lifting and falling elements are pushed down, and FIG. 7B is a side view showing the state where the lifting and falling elements are raised. state;

8A and 8B show the situation when a paper jam occurs near the guide unit, FIG. 8A is a side view when a paper jam occurs, and FIG. 8B is a side view when the jammed paper is removed;

FIG. 9 is a perspective view showing a fixing device related to a second embodiment of the present invention;

Fig. 10 is a side view for explaining the pressing mechanism of the separation roller;

Fig. 11 is a side view for explaining the pressing mechanism of the separation roller;

Fig. 12 is a perspective view for explaining the pressing mechanism of the separation roller;

Fig. 13 is a perspective view for explaining the pressing mechanism of the separation roller;

Fig. 14 is a schematic diagram for explaining the relationship among the heating roller, the fixing belt and the separation roller;

15 is a perspective view showing a fixing device related to a third embodiment of the present invention;

FIG. 16 is a side view showing the fixing device shown in FIG. 15;

Fig. 17 is a side view showing the fixing device shown in Fig. 15, partially enlarged.

Detailed ways

A first embodiment of the fixing device of the present invention will be explained below with reference to FIGS. 1 to 4. FIG.

First, an electrophotographic copying machine of the present invention as an image forming apparatus equipped with a fixing device 1 will be described. This electrophotographic copier has a main body 1A, and an image forming unit 1 is installed in the main body 1A. The image forming unit 1 has a photosensitive drum 2 , a main charger 5 for charging the photosensitive drum 2 with a predetermined potential, and an exposure unit 4 for forming an electrostatic latent image on the charged photosensitive drum 2 .

The image forming unit 1 has a rotary developing device 8A for color for supplying toner as a developer to an electrostatic latent image formed on the photosensitive drum 2 by means of the exposure unit 4 and developing the toner, and for Color electrostatic developing device 8B. The rotary developing device 8A has a first developing unit 8a for supplying yellow toner, a second developing unit 8b for supplying cyan toner, and a third developing unit 8c for supplying magenta toner.

The image forming unit 1 has an intermediate transfer belt 3 for temporarily holding a toner image formed on a photosensitive drum 2 by means of developing units 8A and 8B. The image forming unit 1 has a cleaner 6 a for cleaning the intermediate transfer belt 3 , and a cleaner 6 b for cleaning residual toner on the photosensitive drum 2 .

The intermediate transfer belt 3 is stretched with a predetermined tension between the first to fourth rollers 3a to 3d, and the outer peripheral surface of the photosensitive drum 2 is pulled between the second and third rollers 3b and 3c against the intermediate transfer belt. tight part. The first transfer roller 12 is pressed to the top of the photosensitive drum 2 via the intermediate transfer belt 3 .

Below the image forming unit 1, paper feeding cassettes 18a and 18b for loading paper P of a predetermined size are installed. On the sheet feeding cassettes 18a and 18b, pickup rollers 7 are mounted, respectively. The sheets P are picked up by a pickup roller 7 , separated one by one by a feed roller 15 and a separation roller 16 , and conveyed by a conveyance unit 19 .

On the conveying unit 19, a conveying roller pair 9, a registration roller 17, a second transfer roller 11, and a discharge roller pair 30 are sequentially installed along the conveying direction of the paper P (ie, arrow A shown in FIG. 1 ), and form A transport path 19 a that transports the paper P by means of rollers 9 , 11 , 17 and 30 . The registration roller 17 temporarily stops the conveyed paper P and aligns the inclination of the paper P to the conveying direction so that the end of the paper P coincides with the end of the toner image on the intermediate transfer belt 3 .

Between the second transfer roller 11 and the discharge roller pair 30 , a fixing device 13 for fixing the toner image transferred onto the paper P by means of heat is installed. The fixing device 13 has a heating roller 13a and a pressure roller 3b. On the downstream side of the heating roller 13a in the transport direction of the paper P, a separation roller 13c is installed. Between the heat roller 13a and the separation roller 13c, the fixing belt 14 is stretched. By rotating the separation roller 13c, the fixing belt 14 runs between the rollers 13a and 13b.

The pressing roller 13b is pressed against the outer peripheral surface of the heating roller 13a, and presses the paper P conveyed between the rollers 13a and 13b against the heating roller 13a.

On the downstream side of the separation plate 20 in the conveying direction of the paper P, a guide unit 22 for guiding the paper P separated from the fixing belt 14 by means of the separation plate 20 to the discharge roller pair 30 is installed.

On the downstream side of the discharge roller pair 30 in the conveying direction of the paper P, a receiving tray 31 for receiving the discharged paper P is installed.

On one side of the main body 1A, an automatic duplex device 29 used at the time of double-sided copying, and a manual paper feed unit 32 used at the time of manual paper feeding are installed.

The fixing device 13 shown in FIG. 2 has the electrophotographic copier shown in FIG. 1 . The fixing device 13 fixes the toner image on the paper P by passing the paper P, which is a sheet-like recording medium onto which the toner image is transferred, between the heating roller 13 a and the pressing roller 13 c.

The fixing device 13 of this embodiment is composed of a heating roller 13a, a separation roller 13c, a fixing belt 14, a pressing roller 13b, a separation claw 32, a supporting member 35, a stopper 36, a pressure spring 37 and a fixing member 40, and the heating At least the outer peripheral surface of the roller 13a is heated, the separating roller 13c is used to separate the paper P, the fixing belt 14 is stretched between the heating roller 13a and the separating roller 13c, and the pressing roller 13b is used to apply pressure to the heating roller. 13a exerts pressure, the separation claw 32 is used to separate the paper P from the pressing roller 13b, the support member 35 is used to support the separation claw 34, and the stopper 36 is used to prevent the end 43 of the separation claw 34 from passing Predetermined position and move along the direction of pressing into the pressing roller 13b, the pressure spring 37 is used as a pressing means for pressing the separating claw along the direction in which the end 43 of the separating claw 34 is in contact with the outer peripheral surface of the pressing roller 13b. 34 to apply pressure, and the fixing element 40 is used to fix the supporting element 35 .

As the heating roller 13a, for example, there may be employed one configured such that a heat lamp as a heat source is inserted into a cylindrical member or the outer peripheral surface of the cylindrical member is heated by IH (Induction Heating). As shown in the figure, in the direction indicated by arrow B, the heat roller 13a is rotated by a rotation driving unit not shown in the figure.

The separating roller 13c is installed near the heating roller 13a. In this embodiment, for example, a separating roller 13c is installed above the heating roller 13a. A shaft 13d extends from both ends of the separation roller 13c (only the shaft 13d is shown extending from only one end in the figure), and the shaft 13d is rotatably supported by bearings not shown in the figure. Between the separation roller 13c and the heating roller 13a, the fixing belt 14 is stretched. The rotation of the heat roller 13a is transmitted to the separation roller 13c via the fixing belt 14, so that the separation roller 13c rotates with the heat roller 13a.

The pressing roller 13b is mounted with a rotation shaft 33a and an elastic member 33b so as to cover the outer circumference of the rotation shaft 33a. The elastic member 33b may use, for example, a sponge made of synthetic resin. Under standard name SRISO101, test type, spring type ASKER C, the hardness of the elastic member 33b is set to ASKER C 55 or lower (55 degrees or lower).

The pressing roller 13b is installed so as to apply pressure to the heating roller 13a. The rotating shaft 33a is rotatably supported by a bearing not shown in the figure. The pressing roller 13b is rotated by an unshown rotation drive unit in the direction indicated by an arrow C in the figure, that is, in a direction opposite to that of the heating roller 13a.

For example, 1 to 5 separation claws 34 are installed. In this embodiment, five separating claws are installed side by side, spaced apart from each other in the longitudinal direction of the pressing roller 13b (refer to FIG. 3 ). The supporting member 35, the stopper 36 and the pressure spring 37 are mounted corresponding to the separating claws 34, respectively. In this embodiment, five support members 35 , stoppers 36 and pressure springs 37 are installed so as to correspond to the separating claws 34 one by one. The supporting element 35 , the stopper 36 and the compression spring 37 are mounted on the fixing element 40 .

The fixing member 40 is installed near the pressing roller 13b. In this embodiment, the fixing element 40 is mounted, for example, above the pressure roller 13b.

The fixing member 40 is formed into a long and narrow shape along the longitudinal direction of the pressing roller 13b, and is fixed to, for example, an outer wall of a stay 42 (refer to FIGS. 4 and 5 ) for supporting the fixing device 13 . The fixing element 40 has a first protruding wall 41a that protrudes almost flat from the strut 42 toward the pressure application roller 13b, and a side wall 41b that is bent almost vertically downward so that the end side of the first protruding wall 41a is close to the application roller 13b. For the pressing roller 13b, the second projecting wall 41c projects almost horizontally from the side wall 41b toward the heating roller 13a.

On the side wall 41b, five fixing members 40a for fixing the supporting member 35 are installed in the longitudinal direction so as to be spaced apart from each other. The stoppers 36 protrude horizontally from the edge of the second protruding wall 41c toward the heat roller 13a corresponding to the fixing parts 40a, respectively. In this embodiment, the actuator 36 is integrally formed with the fixing element 40 . However, the stopper 36 and the fixing member 40 may be formed separately.

Each separating claw 34 has a long side 34a and a short side 34b. In this embodiment, the angle formed by each long side 34a and each short side 34b is an obtuse angle. The end portion 43 of each separating claw 34, that is, the end portion of each long side 34a is formed in a knife-edge shape. The rotation center shaft 44 protrudes from the other end portion of each separation claw 34 , that is, both sides of the end portion of each short side 34 b.

Each supporting member 35 has a grooved notch portion 35 a for hook coupling and supporting the rotation center shaft 44 of each separating claw 34 . In this embodiment, each support member 35 forms a groove so as to open in the direction of a straight line M parallel to the center S passing through each rotation center shaft 44 and passing through the end 43 of each separating claw 34 and the applicator. The tangent line L to the tangent point T of the outer peripheral surface of the pressure roller 13b is located on the opposite side to the heat roller 13a, thus forming each notched portion 35a. The support member 7 rotatably supports the separation claw 34 when each notch portion 35 a is hooked by the rotation center shaft of each separation claw 34 . Each separation claw 34 is hooked to the notch portion 35 a of each support member 35 by means of the rotation center shaft 44 . Therefore, each separating claw 34 is movable along each notch portion 35a, that is, can be brought into contact with the outer peripheral surface of the pressing roller 13b, and can be disengaged from the outer shaft surface of the pressing roller 13b.

When a force for pressing the pressing roller 13b inward is given to the end portion 43 of each separating claw 34, the separating claw 34 moves the pressing roller 13b inwardly. Therefore, in this embodiment, a stopper 36 is installed between the long side 34a of each separating claw 34 and the second projecting wall 41c of the fixing member 40 . By the reaction force produced by each stopper 36 when each separation claw 34 is in contact with the stopper 36, the separation claw 34 is moved in the direction of separating from the pressing roller 13b, and the separation claw 34 and the stopper The position and shape of 36 are set separately. One end of each pressure spring 37 is engaged with the short side 34 b of each separation claw 34 , and the other end is engaged with each stopper 36 . Therefore, in a normal state, the end portion 43 of each separation claw 34 is urged by each pressure spring 37, and is in contact with the outer peripheral surface of the pressing roller 13b.

When a force for internally pressing the pressing roller 13b is supplied to the end portion 43 of each separation claw 34, the separation claw 34 operates as shown below.

When a force for pressing the pressing roller 13 b inwardly is given to the end 43 of each separation claw 34 , the separation claw 34 moves toward the corresponding stopper 36 with the long side 34 a in contact with the stopper 36 . Therefore, a reaction force is given to the separation claw 34 from the stopper 36 . However, the direction of movement of the rotation center shaft 44 of each separation claw 34 is limited by the corresponding notch portion 35a, so that the rotation center shaft 44 moves in the direction of the notch portion 35a rather than in the direction in which the stopper 36 reacts. .

In this embodiment, each notch portion 35a opens in the direction of the straight line M, that is, opens in the direction of separation from the heating roller 23a, and therefore, the moving direction of the center S of each rotation center shaft 44 is the direction of the straight line M. direction, and the direction of separation from the heating roller 13a. Therefore, by the component of the reaction force from the stopper 36, the rotation center shaft 44 of the separation claw 34 is in contact with the notch portion 35a, and is guided, and is separated from the pressure roller 13b along the end portion 43 of the separation claw 34. direction to move.

On the other hand, when the end portion 43 of each separating claw 34 is to move along a square spaced apart from the pressing roller 13b, the movement position of the center S of the corresponding rotation center shaft 44 is preferably set on the straight line M, which The straight line M is parallel to the tangent line L passing through the center S of the rotation center shaft 44 and passing through the tangent point T of the end portion 43 of the separation claw 34 and the outer peripheral surface of the pressing roller 13b, or is set at a midpoint passing through the rotation center shaft 44 On the horizontal line N of S, or within the range of the angle θ defined by the straight line M and the horizontal line N, more preferably in the direction of the straight line M. In this way, the ends of the separation claws 34 can move in the direction of separation from the pressing roller 13b. Therefore, the direction of the corresponding notch portion 35a is preferably set within the range of the angle θ defined by the straight line M and the horizontal line N, preferably on the straight line M. As shown in FIG.

The fixing device constructed as described above operates in the following manner. The heating roller 13a rotates in a direction indicated by an arrow B in the figure, and the pressing roller 13b rotates in a direction indicated by an arrow C in the figure. Accordingly, the paper sheet P is guided from below between the heating roller 13a and the pressing roller 13b for pressing the heating roller, and is conveyed upward in the direction indicated by arrow A in FIG. 2 . And the paper P that is guided to the fixing belt 14 and conveyed to the separation roller 13c is separated from the fixing belt 14 near the top end of the separation roller 13c (refer to FIG. 2 ). It is guided to a conveying mechanism not shown in the figure, and discharged.

On the other hand, usually the paper P is conveyed as described above, but it may also be adhered to the pressing roller 13b and conveyed so as to be wound around the pressing roller 13b. Also, in this case, the separating claw 34 acts between the paper P and the pressing roller 13b, and separates the paper P from the pressing roller 13b, so that the paper P can return to the normal transport path again (refer to FIG. 4 ) .

On the other hand, when a jam or a paper jam occurs, the jammed paper PG presses the end 43 of the separation claw 34 to press it into the pressing roller 13b, and the separation claw 34 is pressed by the jammed paper PG and moves along the The direction of contact with the stopper 36 moves. With the component of the reaction force from the stopper 36, the separation pawl 34 pressed by the jammed paper PG is guided to the notch portion 35a, and moves in the direction of the arrow D shown in FIG. 4) and move in the direction of separation from the heating roller 13a. Therefore, the end portion 43 of the separating claw 34 is separated from the heating roller 13a, and does not penetrate the heating roller 13a.

In addition, when the jammed paper PG is cleared, the separation claw 34 returns to its normal position by the pressure spring 37 (refer to FIG. 4).

As described above, according to the fixing device 13 of the present invention, since it has the separating claw 34, the paper P adhered to the pressing roller 13b and conveyed so as to be wound around the pressing roller 13b can be separated from the pressing roller 13b. In addition, even when the end 43 of the separation claw 34 is pressed by the outer peripheral surface of the pressure roller 13b due to the jammed paper PG, the separation claw 34 guides the rotation center shaft 44 to the supporting member 35 and displaces it so that the end 43 is separated from the outer peripheral surface of the pressing roller 13b, so that the pressing roller 13b can be prevented from being damaged and scratched.

A plurality of separation claws 34 are installed and supported by the supporting member 35 so as to work independently of each other, so that the paper P can be satisfactorily separated from the pressing roller 13b. In addition, only the separation claw 34 pressed onto the outer peripheral surface of the pressing roller 13b by the jammed paper PG can be displaced so as to be separated from the pressing roller 13b.

The fixing device 13 of this embodiment is very effective when the hardness of the outer periphery of the pressing roller 13b is Asker C 55 or lower of the SRISO101 spring type and the ASKER C type, and even if the outer periphery of the pressing roller 13b is soft as described above, It is possible to prevent the pressing roller 13b from being damaged by the separation claw 34 .

In addition, the fixing device 13 of the present embodiment has the stopper 36 for preventing the end portion 43 of the separation claw 34 from passing a predetermined position and moving in the direction of pressing the pressing roller 13b, so that the separation claw 34 can be prevented from moving. The end portion 43 passes through a predetermined position and is pressed into the pressing roller 13b. In addition, by the reaction force generated by the stopper 36 when the separation claw 34 is in contact with the stopper 36, the separation claw 34 is moved in the direction of separation from the pressing roller 13b, the positions and shapes of the separation claw 34 and the stopper 36 are set separately. Therefore, when a force that presses the end portion 43 of the separating claw 34 into the pressing roller 13b is applied to the separating claw 34, the end portion 43 of the separating claw 34 can be separated from the pressing roller 13b.

Further, when the end portion 43 of the separation claw 34 is displaced in the direction of separation from the pressing roller 13b, the movement position of the center S of the rotation center shaft 44 is set on a straight line M parallel to the direction passing through the rotation center. The center S of the shaft 44 and the tangent line L passing through the tangent point T of the end portion 43 of the separation claw 34 and the outer peripheral surface of the pressing roller 13b are set on the horizontal line N passing through the center S of the rotation center shaft 44, or Set within a range defined by a straight line M parallel to a tangent L passing through the tangent point T and a horizontal line N. Therefore, unless the end portion 43 of the separation claw 34 is pierced into the heat roller 13a, the end portion 43 can be separated from the heat roller 13a.

In addition, the number of separation claws 34 may be set to be one or more. Furthermore, in this embodiment, the separating claw 34 is installed so as to be in contact with the outer peripheral surface of the pressing roller 13b. However, the separation claw 34 may be installed so as to be in contact with the outer peripheral surface of the heat roller 13a, and to be in contact with the separation roller 13c. In addition, when a plurality of separation claws 34 are installed, the separation claws 34 may be installed to correspond to a plurality of rollers of the pressing roller 13b, the heating roller 13a, and the separation roller 13c. Furthermore, the separation roller 13c and the fixing belt 14 may be omitted.

Furthermore, in this embodiment, the plurality of separating claws 34 are supported by the supporting member 35 so as to work independently of each other. However, the plurality of separating claws 34 may be connected to each other so as to work in connection with each other. The support element 35 and the separation claw 34 may not have a one-to-one correspondence with each other, and one support element 35 can support a plurality of separation claws 34.

In addition, the direction of movement of the separating claw 34 is not limited to a direction parallel to the tangent passing between the end portion 43 of the separating claw 34 and the outer peripheral surfaces of the rollers (the pressing roller 13b, the heating roller 13a and the separating roller 13c). Any direction in which the ends 43 of the separation claws 34 separate from the rollers is acceptable. Furthermore, the stopper 36 and the pressure spring 37 as pressure means can be omitted.

Next, the configuration of the fixing device 13, the guide unit 22 for guiding the paper P to be conveyed through the fixing device 13, and its surroundings will be explained.

Figure 6 is a perspective view showing the surroundings of the guide unit 22, Figures 7A and 7B are schematic side views showing the surroundings of the guiding unit 22, Figure 7A shows the lifting and falling elements 24 being pushed down 7B shows the state in which the lifting and falling member 24 is raised.

As shown in FIGS. 6, 7A and 7B, the fixing device 13 has a heating roller 13a and a pressing roller 13b. On the downstream side of the heating roller 13 a in the conveying direction of the sheet P, a separation roller 13 c is arranged. The fixing belt 14 is stretched between a heat roller 13a and a separation roller 13c. The fixing belt 14 rotates the separation roller 13c so as to run between the rollers 13a and 13c.

The separation roller 13c has a built-in heating unit (not shown). When the heating unit is operated, the fixing belt 14 may be heated to about 200° C. via the separation roller 13 c. The pressing roller 13b is pressed to the outer peripheral surface of the heating roller 13a, and the paper P conveyed between the rollers 13a and 13c is pressed against the heating roller 13a.

On the downstream side of the heat roller 13c in the conveying direction of the paper P, a separation plate 20 is arranged. One end of the separation plate 20 extends toward the outer peripheral surface of the separation roller 13c with a slight gap therebetween so that the paper P discharged from the fixing device 13 can be separated from the fixing belt 14 .

On the downstream side of the separation plate 20 in the conveying direction of the paper P, a guide unit 22 for guiding the paper P separated from the fixing belt 14 by the separation plate 20 is installed to discharge the pair of rollers 30 .

The guide unit 22 is configured such that a plurality of guide plates 23 are installed side by side at predetermined intervals. Each guide plate 23 has a curved surface 23a curved with a predetermined curvature, and since the guide plates are installed side by side, a smoothly curved guide surface 22a is formed by each curved surface 23a. The sheet P discharged from the fixing device 13 is smoothly guided toward the pair of discharge rollers 30 in a state of being in close contact with the guide surface 22 a. Furthermore, the center of curvature of the curved surface 23a and the guide surface 22a are positioned on opposite sides of the conveyance path 19a across the curved surface 23a and the guide surface 22a.

On the portion of the guide unit 22 on the upstream side of the sheet P in the conveying direction, a shaft member 25a constituted by a round bar is mounted almost perpendicularly to each guide plate 23, and is rotatable. On the shaft member 25a, a plurality of lift-up and drop members 24 (separation members) are mounted at predetermined intervals, one end surface 24a of which is formed in the shape of the guide surface 22a. The lift-up and drop members 24 are made of resin, and each of them is provided in the guide plate 23 and in the gap between the guide plates 23 .

The lever 25 is fixed at one end of the shaft member 25a. When the lever 25 is fixed and the shaft member 25a is rotated, the guide plate 23 can be raised and lowered.

When the raising and lowering member 24 is pushed down by the lever 25, the raising and lowering member 24 is completely held in the gap between the guide plates 23 (indicated by the solid line in FIG. 6). Furthermore, when the raising and lowering member 25 is raised by the lever 25, the raising and lowering member 24 is protruded from the guide surface 22b into the conveying path 19a (indicated by the dotted line in FIG. 6).

Next, the operation of the aforementioned electrophotographic copying machine will be explained.

First, the optical image reading device 26 reads a document loaded on the document table 28 . At this time, the surface of the photosensitive drum 2 is uniformly charged by the main charger 5 . According to the read information, the charged photosensitive drum 2 is exposed by the exposure unit 4, and an electrostatic latent image is formed. By rotating the photosensitive drum 2 , the electrostatic latent image is conveyed to and faces the developing unit 8B from which black toner is supplied to be developed. The developed toner image is conveyed onto the intermediate transfer belt 3 by the rotation of the photosensitive drum 2 , and is first transferred by the first transfer roller 12 . After passing through the transfer area, the photosensitive drum 2 is discharged by a discharger (not shown in the drawing). The toner remaining on the photosensitive drum 2 is cleaned by the cleaner 6b.

At this time, the paper P taken out from the paper feeding cassettes 18a and 18b is conveyed between the intermediate transfer belt 3 and the second transfer roller 11, and the toner image on the intermediate transfer belt 3 is subsequently transferred to the paper on p. After the transfer, the paper P is separated from the intermediate transfer belt 3 and conveyed to the fixing device 13 by which the toner image is fixed by heating and pressing. After fixing, the paper P is guided by the guide unit 22 and discharged by the discharge roller pair 30 . The discharged sheets P are sequentially loaded onto the delivery tray 31 . At this time, the lifting and lowering element 24 is pushed down and held in the gap between the guide plates 23 . In this way, the conveyance of the paper P is not hindered by the lift-and-drop element 24 .

When a jam due to the paper P occurs near the fixing device 13, particularly when the jammed paper P is nipped between the fixing device 13 and the discharge roller pair 30, as shown in FIG. 8A, since the guide surface 22a is Therefore, the paper P can be closely attached to the guide surface 22a substantially without gaps.

In this case, it is difficult to insert a finger between the guide surface 22a and the paper P, so it is very difficult to remove the jammed paper P. However, as shown in FIG. 8B, when the lever 25 is rotated and the lift-up and drop member 24 is lifted for the guide surface 22a, the jammed paper P can be separated from the guide surface 22a. By this separation, a space can be formed between the guide surface 22a and the paper P. As shown in FIG. A finger can be inserted into the space, so that the jammed paper P can be easily removed.

In this way, the operator can remove the jammed paper P with fingers without touching the guide unit 22 . Therefore, even if the guide surface 22 a is at a high temperature due to the heating of the fixing device 13 , the jammed paper P can be quickly removed without fear of burns.

In addition, in order to separate the jammed paper P from the guide surface 22a by the lift-up and drop member 24, a space for inserting a finger may be formed at a fixed position. Therefore, the jammed paper P can be reliably removed.

According to this embodiment, even if the jammed paper P is held only by the fixing device 13 or by the discharge roller pair 30, a gap can be formed between the guide surface 22a and the jammed paper P.

Furthermore, when the lever 25 is rotated and the lift-and-drop member 24 is held in the gap between the guide plates 23 after the jammed paper P is cleared, the copying operation can be resumed quickly.

One end surface 24 a of each lift-up and drop member 24 is formed in substantially the same shape as the curved surface 23 a of each guide plate 23 . Each lifting and lowering element 24 is positioned such that the end face 24a is flush with the guide face 22a. Thus, the guide surface 22a is composed of the curved surface 23a of each guide plate 23 and the end surface 24a of each lifting and lowering member 24 . Therefore, compared with the case of only the guide plate 23, the area for supporting the paper P is increased, and the paper P can be guided more reliably.

In the foregoing embodiments, the raising and lowering member 24 is installed in the guide unit 22 whose guide surface 22a is smoothly curved. However, even if the lift-up and drop member 24 is installed in, for example, a guide unit having an almost planar-shaped guide surface, the jammed paper can be removed quickly and reliably. Between the fixing device 13 and the second transfer roller 11 or between the conveying roller pair 9 and the paper supply roller 15, such components may be considered.

By increasing the number of lifting and lowering elements 24, the guide unit 22 can be omitted. That is, when the copying operation is performed, the lift-and-drop member 24 is pushed down, and forms the guide surface 22A for guiding the paper P only with its end surface 24a. When a paper jam occurs, the lift-and-drop member 24 can be lifted, and the jammed paper can be released in the transport path 19a.

A lift and drop mechanism is installed in the guide unit 22, and the guide unit 22 lifts and drops so that it can be used as a guide during copying operation, and the paper P can be released when a paper jam occurs.

Next, a second embodiment of the fixing device of the present invention will be explained.

In FIG. 9 , a fixing device 50 is composed of a heating roller 51 , a pressing roller 52 , a fixing belt 53 and a separating roller 54 .

The heat roller 51 is rotated in the direction shown in the figure (right-hand direction) by an unillustrated drive motor as a drive means. The heat roller 51 has an embedded heat source. With this heat source, the surface of the heat roller 51 is heated to a fixing temperature. A heating element such as an IH coil or a halogen lamp is used as a heating source for the heating roller 51 .

For example, when an IH coil is used as a heat source in the heat roller 51, a conductive material such as iron is formed in a cylindrical shape, and furthermore, the outer peripheral surface of the iron is coated with, for example, fluoroplastic such as tetrafluoroethylene plastic. Furthermore, when an IH coil is used as a heating source, high-frequency power is supplied to the IH coil, and a high-frequency magnetic field for induction heating is generated. When a high-frequency magnetic field is generated, eddy currents are generated in the heating roller 51 , and due to the eddy currents, the heating roller 51 itself generates heat due to Joule heat.

Between the heating roller 51 and the separation roller 54 , the fixing belt 53 is stretched. The fixing belt 53 must efficiently conduct heat from the heating roller 51, so it is formed of a metal such as nickel. Especially when an IH coil is used as the heating source of the heating roller 51, the heat from the heating roller 51 must be efficiently transferred to the fixing belt 53, so the fixing belt 53 is preferably formed of metal.

Force is applied to the separation roller 54 in a direction of separation from the heat roller 51 by means of a pressing mechanism which will be described later. On the other hand, the shaft of the heating roller 51 is fixed. Accordingly, the fixing belt 53 is stretched with a predetermined pressure applied to the separation roller 54 from the pressure applying mechanism. That is, the force applied to the fixing belt 53 is a force applied by the pressing mechanism in the direction of separating the separation roller 54 from the heating roller 51 .

The driving force of the heat roller 51 is transmitted to the separation roller 54 via the fixing belt 53 . That is, the separation roller 54 rotates with the heating roller 51 via the fixing belt 53 .

The pressing roller 52 passes the fixing belt 53 and is pressed against the heating roller 51 with a predetermined pressure (for example, about 20 kg) by means of a pressing mechanism not shown in the figure. The surface of the pressing roller 52 is formed of, for example, a heat-resistant elastic member such as sponge or rubber. Therefore, at a position opposed to the heating roller 51 , the pressing roller 52 is in contact with the outer peripheral surface of the fixing belt 53 in a pressed state. The contact portion of the pressing roller 52 and the fixing belt 53 are constructed so as to have a fixed nip width.

The driving force of the heating roller 51 is also transmitted to the pressing roller 52 via the fixing belt 53 , and the pressing roller 52 also rotates with the heating roller 51 . That is, the fixing device 50 is constructed such that only the heating roller 51 is driven by the driving means, and the pressing roller 52 , the fixing belt 53 and the separation roller 54 rotate along with the heating roller 51 .

In the fixing device 50 , paper as an image forming medium onto which a toner image is transferred is supplied to a nip portion between a pressing roller 52 and a fixing belt 53 . When heat is supplied from the heating roller 51 to the paper on which the toner image is transferred, pressure is applied to the nip portion at a predetermined pressure. In this way, the toner on the paper as the image forming medium is melted and fixed on the paper.

The separation roller 54 is installed so as to separate the sheet fixed by the pressing roller 52 , the fixing belt 53 and the nip portion formed by the fixing belt 53 . The separation roller 54 separates the paper with its curved surface. In addition, paper that cannot be separated even by the curved surface of the separation roller 54 and adheres to the fixing belt 53 is separated from the fixing belt 53 by a separation plate.

The separation roller 54 is formed of a ceramic piece. The ceramic used as the separation roller 54 has, for example, a bulk density of 0.7±0.1 g/cm and a porosity of 69% to 77%. The separation roller 54 must separate the fixed sheet from the fixing belt 53 by virtue of the curvature of its roller portion. Therefore, the diameter of the roller portion of the separating roller 54 is designed to be at least smaller than the diameter of the roller portion of the heating roller 51 .

By applying the above configuration, in the fixing device 50 , the heating roller 51 is driven by a driving device not shown in the drawing, and the pressure roller 52 , the fixing belt 53 and the separation roller 54 are driven by the rotation of the heating roller 51 .

Next, the mechanism in the vicinity of the separation roller 54 will be explained.

10 to 13 show the mechanism in the vicinity of the separation roller 54 . 10 and 15 show the mechanism when the separation roller 54 is viewed from the direction of the rotation axis. In addition, FIGS. 12 and 13 show the mechanism in the vicinity of the separation roller 54 .

As shown in FIGS. 10 and 12 , the plate 55 is fixed to the shaft 54 a of the separation roller 54 . Furthermore, as shown in FIGS. 11 and 13 , a movable plate 56 is fixed to the plate 55 . The movable plate 56 applies an upward force (a force in a direction to separate from the heating roller 51 ) by means of a pressing member 57 such as an elastic member.

As shown in FIGS. 11 and 13, since the upper end of the pressing member 57 is fixed to the frame 58 mounted on the main body of the image forming apparatus, and the lower end thereof is fixed to the movable plate 56, the pressing member 57 can be Moving plate 56 exerts an upward force. Furthermore, the plate 56 moves upward and downward according to the force exerted by the pressing member 57 . The upward force applied to the movable plate 56 by the pressing member 57 is transmitted to the shaft 54 a of the separation roller via the fixed plate 55 . That is, by means of a pressing mechanism having a fixed plate 55, a movable plate 56 and a pressing member 57, a force in a direction separating from the heat roller 51 (upward force in FIGS. 10 to 13) is applied to the separation roller 54.

Next, the relationship between the fixing belt 53 and the separation roller 54 will be explained.

As described above, the fixing belt 53 stretched by the separation roller 54 and the heating roller 51 is pressed by the aforementioned pressing mechanism. Here, assuming that the position of the heating roller 51 is fixed, the force applied to the fixing belt 53 is the force applied to the separation roller 54 by the pressing mechanism.

When a large force is applied to the separation roller 54 by means of the pressing mechanism, the force applied to the fixing belt 53 is also large, thus possibly causing the fixing belt 53 to be damaged. Therefore, the force to tighten the fixing belt 53 must be within a predetermined allowable range. However, when the force of tensioning the fixing belt 53 is too small, the resistance between the fixing belt 53 and the separation roller 54 is reduced, and the possibility of slippage between the surface of the separation roller 54 and the inner surface of the fixing belt 53 becomes high. big. Therefore, the force applied to the separation roller 54 is set to be about 2 to 3 kg.

By using the aforementioned structure, the separation roller 54 and the fixing belt 53 are held by the pressure provided by the pressing mechanism, and the coefficient of static friction between the separation roller 54 and the inner surface of the fixing belt 53 is also held by the pressure. On the other hand, in the heating roller 51 and the fixing belt 53, the surface of the heating roller 51 and the inner surface of the fixing belt 53 are pressed by the aforementioned tension force for the fixing belt 53 and the pressure provided by the pressing roller 52. .

As described above, the force applied by the pressing roller 52 to the nip portion of the fixing belt 53 on the heating roller 51 is much larger than the force applied to the separation roller 54 . For example, the force applied to the separation roller 54 is about 2 to 3 kg, and the force applied by the pressing roller 52 is about 10 times that, ie, about 20 kg. In addition, the diameter of the heat roller 51 is larger than that of the separation roller 54 . That is, the size of the contact surface between the surface of the heating roller 51 and the inner surface of the fixing belt 53 is larger than the size of the contact surface between the surface of the separation roller 54 and the inner surface of the fixing belt 53 .

Thus, when the heating roller 51 is driven by the driving means, even if the surface of the heating roller 51 is smooth, the inner surfaces of the heating roller 51 and the fixing belt 53 rarely slip.

On the other hand, when the heat roller 51 is driven by the driving means, the separation roller 54 rotates with the heat roller 51 via the fixing belt 53 . Factors for securing the separation roller 54 and the fixing belt 53 from slipping include: the force applied to the separation roller 54 in the direction of separation from the heating roller 51, the surface resistance between the surface of the separation roller 54 and the inner surface of the belt, and the diameter of the separation roller 54 (the size of the contact surface between the surface of the separation roller 54 and the inner surface of the belt).

As described above, in order to prevent the fixing belt 53 from being damaged, the force applied to the separating roller 54 in the direction of separating from the heating roller 51 cannot exceed a predetermined allowable range. In addition, in order to ensure the function of separating sheets from the fixing belt 53, the diameter of the separation roller 54 is preferably as small as possible so that it cannot be increased.

Therefore, in order to prevent the separation roller 54 and the fixing belt 53 from slipping when the heat roller 51 is driven, the fixing device 50 is designed such that the surface of the separation roller 54 is rough and the surface of the separation roller 54 and the inner surface of the fixing belt 53 are increased. surface resistance between them.

For example, as described above, the surface of the separation roller 54 is made rougher than the inner surface of the fixing belt 53 formed of metal such as nickel. In addition, the separation roller 54 is formed of the above-mentioned ceramics as described above, thus making its surface rough. In addition, the separation roller 54 is formed of ceramics, so that the warm-up time of the fixing device 50 can be shortened. The reason is that the heat capacity of ceramics is smaller than that of metals such as aluminum.

As described above, in the fixing device, the belt is held by the heating roller 51 and the separation roller 54, which rotates with the heating roller 51, and the surface roughness of the separation roller 54 is made larger than that of the inner surface of the fixing belt 53. The surface roughness, thus, the surface resistance between the surface of the separation roller 54 and the inner surface of the fixing belt 53 is increased.

Thus, the contact surface resistance between the separation roller and the surface of the belt can be increased, and the separation roller can be reliably rotated with the heating roller, and the separation roller and the belt can be effectively rotated together.

In addition, the separation roller is made of ceramics, so that the warm-up time of the fixing device is shortened, and the contact surface resistance between the surface of the separation roller and the belt surface can be increased, enabling efficient driving of the fixing device.

Next, the relationship among the heating roller 51, the fixing belt 53 and the separation roller 54 will be explained.

FIG. 14 shows the relationship among the heating roller 51 , the fixing belt 53 and the separation roller 54 .

In the example shown in FIG. 14 , the width of the fixing belt 53 is 310 mm, the width of the separation roller 54 is 313 mm, and the width between the belt guide members 59 a and 59 b of the heating roller 51 is 313 mm.

The width of the fixing belt 53 is designed according to the size of the paper fixed by the fixing device 50 as an image forming medium. That is, in the fixing device 50, the width of the fixing belt 53 is designed to be larger than the maximum paper size to be fixed. For example, in the example shown in FIG. 14 , a paper of 304 mm is assumed as the maximum paper size to be fixed, and the tolerance of the maximum paper size is about 6 mm.

The reason is that, when the paper is fed to the nip portion between the pressing roller 52 and the fuser 53 , the paper may be displaced horizontally. Therefore, the width of the fixing belt is designed based on the range of horizontal displacement assumed to be the maximum size of the sheet. In the example shown in FIG. 14, a stable fixing process can be achieved by providing a tolerance of about 3 mm for the maximum dimension of the sheet in the lateral direction.

In addition, the width of the separating roller 54 and the width between the belt guide members of the heating roller 51 are designed in accordance with the width of the fixing belt 53 . That is, in the fixing device 50, the width of the separation roller 54 and the width between the belt guide members of the heating roller 51 are designed to be wider than at least the width of the fixing belt 53, for example, in the example shown in FIG. The width of the strap 53 is designed to be 310 mm, thus providing a tolerance of about 3 mm for the strap.

The reason for making the width of the separation roller 54 larger than the width of the belt is to protect the end of the fixing belt 53 . That is, when the fixing belt 53 moves and the end of the fixing belt 53 reaches the end of the separation roller 54, a large force is applied to the portion, so the fixing belt 53 may break due to fatigue.

Therefore, the width of the separation roller 54 may be a width to reliably support both ends of the fixing belt 53 , and may be wider than the width of the fixing belt 53 . In addition, as shown in FIG. For example, in the example shown in FIG. 14, the width of the separation roller 54 is equal to the width between the belt guide members 59a and 59b of the heating roller 51, however, the width of the separation roller 54 may be larger than the belt guide member 59a of the heating roller 51. and widths between 59b.

As described above, in the fixing device 50, the width of the separation roller is wider than the width of the belt designed based on the maximum size of the sheet. In this way, at the end of the separation roller, fatigue fracture of the end of the belt can be prevented.

In addition, when the width of the separation roller is equal to or wider than that between the belt guide members mounted on the heating roller, the entire belt can be reliably supported by the separation roller, and the belt can be prevented from malfunctioning such as fatigue fracture.

Next, a third embodiment of the fixing device of the present invention will be explained.

In FIG. 15 , the first transfer guide 65 , which will be described below and in FIGS. 16 and 17 , is omitted, and the hinge member 20 b , which will be described below, is also omitted.

In the fixing device 60 shown in FIG. 15, the paper P as a sheet-like recording medium on which the toner image is transferred passes between the heating roller 61 and the pressing roller 64, so that the toner image is Fixed on paper P.

The fixing device 60 of the present embodiment has: a heating roller 61 at least whose outer peripheral surface is heated, a separation roller 62 for separating the paper P from the heating roller 61 , a fixing belt stretched between the heating roller 61 and the separation roller 62 63 , a pressing roller 64 for applying pressure to the heating roller 61 , a support member 69 rotatably installed near the separation roller 62 , and a separation plate 71 supported by the support member 69 .

As the heat roller 61, there may be used one configured such that, for example, a heater lamp is inserted into the cylindrical member as a heat source, or the outer peripheral surface of the cylindrical member is heated by IH (induction heating). The heat roller 61 is driven to rotate in the direction of arrow B1 as shown in the figure by means of a rotary drive unit not shown in the figure.

The separation roller 62 is arranged near the heating roller 61 . For example, in this embodiment, the separating roller 62 is arranged above the heating roller 61 . A shaft 62a (only the shaft 3a extending from one end is shown in FIGS. 15 to 17 ) extends from both ends of the separation roller 62, and the shaft 62a is rotatably supported by bearings not shown in the drawings. The fixing belt 63 is stretched between the separation roller 62 a and the heating roller 61 . The rotation of the heat roller 61 is transmitted to the separation roller 62 via the fixing belt 63 , so that the separation roller 62 rotates in the direction of the arrow B2 described in the figure along with the rotation of the heat roller 61 .

The pressing roller 64 has a rotation shaft 64a, and an elastic member 64b is installed so as to cover the outer circumference of the rotation shaft 64a. The elastic member 64b may employ a sponge made of synthetic resin. The pressing roller 64 is installed so as to apply pressure to the heating roller 61 . The rotary shaft 64a is rotatably supported by bearings not shown in the figure. The pressing roller 64 is driven in a direction indicated by an arrow C in the drawing to rotate at a predetermined speed, ie, in a direction opposite to that of the heating roller 61 , by a rotational driving unit not shown in the drawing. The rollers 61, 62, and 64 are respectively formed to have substantially equal lengths slightly wider than the width of the paper P. As shown in FIG.

In the vicinity of the separation roller 62, a support member 69 is rotatably mounted. In more detail, the supporting member 69 has an elongated member 69a, a pair of hinge members 69b (in the figure, only the hinge member 20b mounted on one side is shown), and a cylindrical hinge catch 69c. The elongated member 69 a is formed in a long and narrow shape along the longitudinal direction of the separation roller 62 . The elongated member 69a has a flat surface 70 and a through hole (not shown in the figure) formed along the longitudinal direction, through which the hinge clasp 69c passes. Paired hinge members 69b are installed on both sides of the elongated member 69a, and are fixed to, for example, a bracket (not shown) for supporting the fixing device 60 . The elongate member 69a is rotatably connected to a pair of hinge members 69b via a hinge clasp 69c.

In this embodiment, as shown in FIG. 17 , in a normal state, the flat surface 70 of the elongated member 69a is supported by a pair of hinge members 69b so that the center T1 connecting the heating roller 61 and the center T2 of the separating roller 62 A straight line, inclined at an initial angle θ1. In addition, the elongated member 69a is mounted to be rotatable in a direction in which the plane 70 forms a predetermined angle θ2 with the straight line L, and θ2 is larger than the initial angle θ1.

As shown in FIG. 15 , the separation plate 71 is formed in a long and narrow shape along the longitudinal direction of the separation roller 62 . The separation plate 71 can use a plate member formed of, for example, stainless steel. The thickness of the separation plate 71 is, for example, about 0.2 mm to 0.5 mm.

As shown in Figure 17, the separating plate 71 is mounted such that one side thereof is in contact with the flat surface 70 of the elongated member 69a. At this time, when the elongated member 69a is in the state of the initial angle θ1, the separating plate 71 is installed nearby so that the gap between the end surface 71a and the fixing belt 63 becomes about 0.4 mm to 0.5 mm. Furthermore, in the initial state, the plane 70 of the elongated element 69a is inclined relative to the straight line L by an initial angle θ1. Therefore, in the initial state, the side surface of the separation plate 71 is also inclined relative to the straight line L by an initial angle θ1.

Therefore, the separation plate 71 is arranged such that the square portion formed by the end face 71a and the side contacting the flat surface 70 of the elongated member 69a approaches near the top end of the separation roller 62 on which the fixing belt 63 is stretched.

Furthermore, the separation plate 71, together with the supporting member 69, rotates between the initial angle θ1 and the predetermined angle θ2. That is, the separation plate 71 is supported by the support member 69 and is free to rotate between an approach position where the end surface 71 a approaches the fixing belt 63 and a displaced position where the end surface 71 a is displaced so as to be separated from the fixing belt 63 further from the closer position.

In the conventional sheet conveyance as shown in FIG. 16, the sheet P is in contact with the side of the separation plate 71 opposite to the side in contact with the flat surface 70 of the elongated member 69a. Therefore, in the separation plate 71, as shown in FIG. 16, force is applied to the other side toward the left side. On the other hand, the separation plate 71 is positioned so as not to rotate beyond the initial angle θ1 in the direction in which the end portion contacts the surface of the separation roller 62 (clockwise in FIG. 16 ). Therefore, in the normal sheet conveyance path, as shown in FIG. 16 , the end portion of the separation plate 71 will not move leftward beyond the initial angle θ1.

On the other hand, as shown in FIG. 17 , when a paper jam occurs, the jammed paper Pg comes into contact with the end surface 71 a of the separation plate 71 . And, the jammed paper Pg is jammed, so that the end surface 71 a of the separation plate 71 is pressed. In this way, the separating plate 71 rotates in a direction to increase the initial angle θ1 (counterclockwise in FIG. 17 ). That is, in this embodiment, only when a force is applied to the end surface 71a, the separation plate 71 rotates, as shown in FIG. 17, so that the end thereof moves rightward.

In the drawings, reference numeral 65 denotes a first conveying guide, 66 denotes a second conveying guide, 67 denotes a third conveying guide, and 68 denotes a pair of discharge rollers.

The first transport guide 65 is formed along the longitudinal direction of the pressing roller 64 . In the first transport guide 65 , one edge side is positioned above the pressing roller 64 and is bent over the separation roller 62 , and the other edge side extends over the support element 69 . That is, the first transport guide member 65 is arranged to partially cover the fixing belt 63 , the separation roller 62 and the supporting member 69 . In addition, the first transport guide 65 has a plurality of separating claws 65a (only one is shown in FIGS. . The separating claws 65a are arranged in the longitudinal direction of the pressing roller 64 so as to be separated from each other. The end portion of the separation claw 65a is formed in a knife-edge shape.

In the second transport guide 66 , for example, a plurality of plate members 66 a made of metal having almost the same shape are arranged in the longitudinal direction of the separation roller 62 so as to be separated from each other. In the second transport guide 66, there are provided a plurality of plate members 66a, one edge side being positioned above the support member and bent so as to approach the support member horizontally, and the other edge side being formed to approach the discharge roller. In the third transport guide 67 , for example, a plurality of plate members 67 a made of synthetic resin and having almost the same shape are arranged to be separated from each other along the longitudinal direction of the separation roller 62 . The third transport guide 67 , that is, the plurality of plates 67 a is arranged opposite to the second transport guide 66 .

The fixing device 60 constructed as described above operates as follows. The heating roller 61 rotates in the direction indicated by the arrow B1 in the figure, and the pressing roller 64 rotates in the direction indicated by the arrow C in the figure. Therefore, the sheet P guided from below between the heating roller 61 and the pressing roller 64 for applying pressure to the heating roller 61 is conveyed upward in the direction indicated by the arrow A1 in FIG. 16 . In a normal state, the separation plate 71 is positioned at a position where the end surface 71 a is close to the fixing belt 63 , so that the paper guided by the fixing belt 63 and conveyed to the separation roller 62 between the fixing belt 63 and the first conveying guide 65 P is separated from the fixing belt 63 by the separation plate 71 near the top end of the fixing belt 63 at the separation roller 62 where it is stretched. And as shown by arrow A2 in FIG.

Furthermore, as shown in FIG. 17 , when a jam occurs near the end of the separation plate 71 , the jammed paper Pg comes into contact with the end surface 71 a of the separation plate 71 . Further, when the separation roller 62 is driven to rotate in this state, the jammed paper Pg pushes up the end surface 71 a of the separation plate 71 from below. When pressure (thrusting force from the jammed paper Pg) is thus applied to the end surface 71a, as shown by arrow E in FIG. Closer locations are farther away. Therefore, due to the pressure from the jammed paper Pg, the separation plate 71 is prevented from being deformed and damaged.

As described above, according to the fixing device 60 of the third embodiment, the separation plate 71 is supported by the supporting member 69 so that the end surface 71a is close to the fixing belt 63 at an approach position, and when pressure is applied to the end surface 71a along the end surface 71a. The shift position moves farther from the closer position in the direction of belt separation, with free rotation in between. Therefore, even if the jammed paper Pg comes into contact with the end surface 71 a of the separation plate 71 and is pushed upward, the separation plate 71 can be displaced in the direction of separation from the outer surface of the separation roller 62 . Therefore, deformation and damage of the separation plate 71 can be prevented.

According to the present invention, it is possible to obtain a fixing device capable of preventing the roller from being scratched or damaged.

Furthermore, according to the present invention, when a paper jam occurs in or near the fixing device of the apparatus, the jammed paper can be easily removed.

Furthermore, according to the present invention, it is possible to provide a fixing device capable of reliably and efficiently driving each unit in the fixing device. In addition, it is also possible to provide a fixing device capable of maintaining a satisfactory relationship among the fixing belt, the separation roller, and the heating roller, and suppressing the frequency of malfunctions such as damage of the belt.

According to the present invention, it is possible to obtain a fixing device capable of preventing deformation and damage of the separation plate.

Claims (11)

1. An image forming apparatus for forming an image on a surface of a sheet conveyed in a conveyance path, comprising: a guide unit having a guide surface for guiding the paper; and A separation element, which is provided in the guide unit, can protrude from the guide surface and extend from the guide surface into the transport path, thereby separating the paper from the guide surface. 2. The image forming apparatus according to claim 1, wherein the guide surface is a curved surface having a center of curvature on the opposite side of the transport path. 3. The image forming apparatus according to claim 1, wherein the separation member enters the guide unit, and goes upward to a position where the separation member is flush with the guide surface. 4. The image forming apparatus according to claim 1, wherein the separation member completely enters the guide unit. 5. An image forming apparatus comprising: a transport path configured to transport the paper on which the image is formed; and a lift-up and drop element for guiding the paper that is pushed down and conveyed in the conveyance path during conveyance of the paper and is lifted on the conveyance path side when said paper is jammed , to release the paper in the transport path. 6. A fixing device comprising: a heating roller heated by a heating source; a separation roller, which is arranged in the vicinity of the heating roller; a certain fixing belt, which is supported in such a state that the fixing belt is stretched between the heating roller and the separating roller; and a pressure roller which contacts the heating roller under a predetermined pressure on the fixing belt, Wherein, the heating roller is driven by the driving device, and the separation roller, the fixing belt and the pressure roller rotate with the heating roller driven by the driving device, and the surface of the separation roller is rougher than the contact surface of the fixing belt. 7. The fixing device according to claim 6, wherein the fixing belt is formed of a metal member, the separation roller is formed of a member having a small heat capacity, and a surface of the member is ground to a predetermined roughness. 8. The fixing device according to claim 7, wherein the separation roller is formed of ceramics. 9. A fixing device comprising: a heating roller heated by a heating source; a separation roller, which is arranged in the vicinity of the heating roller; a certain fixing belt, which is supported in such a state that the fixing belt is stretched between the heating roller and the separating roller; and a pressure roller which contacts the heating roller under a predetermined pressure on the fixing belt, Wherein, the width of the separation roller is wider than the width of the fixing belt. 10. The fixing device according to claim 9, wherein a guide unit for guiding both ends of the fixing belt is provided on the heating roller, and the separation roller has a width equal to or wider than the guide of the heating roller. Spacing between cells. 11. A fixing device comprising: a heating roller, at least the outer peripheral surface of which is heated; a pressure roller, which is used to apply pressure to the heating roller; a separation roller arranged opposite to the heating roller; A certain film belt, which is tensioned between the heating roller and the separation roller; a support element, which is rotatably disposed adjacent to the separation roller; and a separation plate having an end surface and supported by the supporting member to freely rotate between an approach position in which the end surface is close to the fixing belt and a displacement position in which Positionally, when the end surface is pressed, the end surface is displaced to be separated from the fixing belt further than the close position.

Images