JP3197489B2 - Fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for an image forming apparatus such as a copying machine or a facsimile machine, and more particularly, to a fixing device for separating a fixed sheet adhered to a roller from a roller by a separating claw. About.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine or a facsimile machine, an image is formed by adhering toner on a sheet, and then the toner is fixed to the sheet by pressing the sheet from both sides while applying heat to the toner. Let me. Heating and pressing in the fixing device are performed by a pair of rollers. FIG. 6 shows a configuration of a main part of a conventional fixing device.

A heat roller 51 for heating and a pressure roller 52 for pressurization are provided in parallel with each other, and the pressure roller 52 is urged toward the heat roller 51 by a spring (not shown). The heat roller 51 and the pressure roller 52 rotate in directions indicated by arrows. Paper S with toner T on top
Is guided by the paper guide plate 53 and enters between the heat roller 51 and the pressure roller 52 from the upstream side A in the transport direction. The toner on the paper entering between the rollers 51 and 52 is
1 and pressurized by the pressure roller 52,
Stick to paper. The fixing is performed in this manner, and the sheet S after the fixing is discharged from the downstream side B in the transport direction to the outside of the fixing device.

In fixing, the sheet S may adhere to the heat roller 51 due to the adhesive force of the toner softened by heating, and a separation claw 56 is provided to separate the sheet from the heat roller 51. The separation claw 56 is provided rotatably about a shaft 57, and the sharp tip is
Is fixed by a spring 59 having one end fixed to the fixing device main body so as to contact the surface of the fixing device.

When toner adheres to the surface of the pressure roller 52, the paper S is pressed by the pressure roller 5 by the adhesive force of the toner.
2 is provided with a separation claw 62 for separating the paper adhered to the pressure roller 52. The separation claw 62 is disposed rotatably about a shaft 63, similarly to the separation claw 56 of the heat roller 51, and is attached to the main body of the apparatus such that a sharp tip contacts the surface of the pressure roller 52. One end is urged by a fixed spring 65.

[0006] Instead of the above-mentioned separating claw pivotally supported by a spring and biased by a spring, the separating claw is a plate spring, and the tip of the separating claw is brought into contact with the roller by the elasticity of the separating claw itself. There is also a fixing device.

The adhesion of the toner to the pressure roller 52 is determined by
This is caused by scattering of the toner before fixing on the upper surface of the sheet, that is, the surface in contact with the heat roller 51, but it is more likely to occur in an apparatus that forms an image on both sides of a sheet. In such an image forming apparatus, after forming and fixing an image on one side of a sheet, the sheet is turned over to form an image on the other side,
The fixing process is performed again. At this time, the surface on which the first image is formed comes into contact with the pressure roller, and the toner that has been insufficiently fixed is transferred from the paper to the pressure roller 52. In an apparatus for forming an image on both sides of a sheet, a pressure roller 5
Even when the toner is not attached to the surface of the second roller, the toner on the surface in contact with the pressure roller 52 may be softened by heating during the second fixing, and the sheet may adhere to the pressure roller 52 due to the adhesive force.

The separation claw 56 and the separation claw 62 are arranged near the contact position between the heat roller 51 and the pressure roller 52. The sheet adhered to the heat roller 51 or the pressure roller 52 is normally separated immediately after fixing by the separation claw 56 or the separation claw 62 and is normally discharged.

When the sheet adheres firmly to the heat roller 51 or the pressure roller 52, the sheet may not be separated even by the separation claws 56 and 62. The same applies when the tips of the separation claws 56 and 62 are deformed and the springs 59 and 65 are weakened. In this case, the paper is wound around the rollers and is not discharged, and paper jam occurs. The paper S is a pressure roller 52
FIG. 7 shows a state in which it is not separated from.

[0010] Such paper is manually removed by the user. Various devices for forming a toner image on a sheet are arranged on the upstream side A in the sheet conveying direction. Therefore, a normal fixing device is configured to remove the jammed sheet from the downstream side B in the sheet conveying direction. The user pulls the sheet S in the direction of arrow P in FIG. 7 to remove it.

[0011]

However, the separation claw 62
Are arranged so that the direction from the shaft 63 toward the leading end 62a is opposite to the take-out direction P of the sheet S, so that when removing the sheet S wound around the pressure roller 52,
The upper surface of the paper is caught on the tip 62 a of the separation claw 62. For this reason, the separation claw 62 rotates in the direction opposite to the biasing direction of the spring 65, and the spring 65 is extended by receiving a strong tensile force. If the pulling force is excessive, the spring 65 is damaged and the original urging force cannot be given to the separation claw 62 even after the paper is removed.

When the urging force given by the spring 65 is weakened, the function of the separation claw 62 is reduced, and the paper is easily wound around the pressure roller 52. As a result, a vicious cycle occurs in which the paper is wound around the pressure roller 52 and the spring 65 is damaged due to the removal of the paper, so that the separation claw 62 does not function at all and paper jams frequently occur.

When the sheet is removed, the leading end 62a hooked on the sheet may be deformed. This deformation is
This occurs in the direction in which a gap is formed between the pressure roller 52a and the surface of the pressure roller 52. Therefore, the function of the separation claw 62 is reduced, and the paper is easily wound around the pressure roller 52. Also in this case, a vicious cycle of winding of the paper and deformation of the leading end 62a occurs, and finally the separation claw 62 does not function at all.

Even when the separation claw itself is a leaf spring in place of the separation claw 62, the sheet is caught on the tip of the leaf spring when the sheet is removed, so that the elasticity of the leaf spring is reduced or deformed. Also in this case, the separating claw eventually stops functioning.

On the other hand, the sheet S stuck on the separation claw 62
Is easily broken from the hooked portion, and sometimes it is cut off and remains partially adhered to the pressure roller 52.
It is difficult to remove such a sheet, and a great deal of labor and time are required for the sheet removing operation.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing device capable of easily removing paper adhered to a pressure roller without damaging a separation claw.

[0017]

In order to achieve the above-mentioned object, the present invention provides a heat roller which generates heat and a heat roller under the heat roller.
A pressure roller that is disposed on the other side and presses against the heat roller, and a separation claw whose tip abuts on the pressure roller by a resilient force. A sheet carrying an unfixed toner image is transferred between the heat roller and the pressure roller. To fix the toner image on the paper
A fixing device for separating a sheet from the pressure roller by the separation claw when the sheet adheres to the pressure roller,
The separating claw is made of a metal leaf spring, and its tip is supported so as to be in contact with the vicinity of the lowermost end of the pressure roller, and its fulcrum is moved in the paper transport direction more than the contact point between the tip and the pressure roller. And above the contact point.

According to this, the paper adhered to the pressure roller
Rotates with the pressure roller, so the tip of the separation claw is
The paper enters between the paper and the pressure roller to separate the paper from the pressure roller. Although the paper jam can not separation occurs when the tip of the separating claw does not enter between the paper adhering thereto and pressure roller, conveying the fulcrum of the separating claw of the sheet than the contact point between the tip and the pressure roller On the upstream side in the direction
When the sheet is pulled out from the downstream side in the sheet conveyance direction and is taken out, the direction from the fulcrum of the separation claw toward the leading end and the moving direction of the sheet taken out are forward. For this reason, the jammed paper does not get caught on the tip of the separation claw.

Further, according to the present invention, there is provided a heat roller which generates heat,
A pressure roller disposed below the heat roller and pressed against the heat roller, a separation claw whose tip abuts the pressure roller by a resilient force, a shaft rotatably pivoting the separation claw, and A spring for urging the separation claw toward the pressure roller, wherein a sheet carrying an unfixed toner image is passed between the heat roller and the pressure roller to fix the toner image on the sheet; In a fixing device that separates a sheet from the pressure roller by the separation claw when adhered to a roller, the separation claw is made of resin, and a tip of the separation claw is pivotally supported so as to abut on a vicinity of a lowermost end of the pressure roller. The shaft is provided upstream of a contact point between the front end and the pressure roller in the sheet transport direction and above the contact point.

According to this, the paper adhered to the pressure roller
Rotates with the pressure roller, so the tip of the separation claw is
Enter between the paper and the pressure roller to separate the paper from the pressure roller.
Let go. Separation claw tip with pressure roller and paper attached to it
If the paper does not enter between, paper cannot be separated and paper jams may occur.
The shaft that pivots the separation claw and the tip of the separation claw are
Upstream and forward of the paper transport direction from the contact point with the
Because it is provided above the contact point,
When pulling out the paper from the downstream side in the direction
To the tip of the separation claw from the
The moving direction is forward. Therefore, jammed paper is separated
It does not catch on the tip of the nail.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a fixing device according to the present invention will be described with reference to FIGS. FIG. 1 is a front view showing a schematic configuration of a main part of the fixing device. The fixing device includes a heat roller 11, a pressure roller 12, a paper guide plate 1
3. Discharge roller pair 14, 15, separation roller 1 for heat roller 11
6 and a separation claw 20 for the pressure roller 12.

Both ends of the heat roller 11 are pivotally supported by front and rear walls (not shown) of the fixing device main body, and provide a driving force via a gear (not shown) provided at the rear end. Given, it rotates in the direction of arrow R1. The heat roller 11 is formed by coating an aluminum tube with a fluorine resin, and has a heater inside to generate heat. The pressure roller 12 is formed by covering a metal tube with silicon rubber and further covering with a fluororesin. The pressure roller 12 is disposed in parallel with the heat roller 11, and is urged by a spring from below and is in pressure contact with the heat roller 11. The pressure roller 12 rotates in the direction of the arrow R <b> 2 following the rotation of the heat roller 11.

FIG. 2 shows a configuration for supporting the pressure roller 12. A thin shaft 24 protrudes from both ends of the pressure roller 12, and a cylinder 25 is provided around the shaft 24. The shaft 24 and the cylinder 25 are rotatably connected by a ball bearing 26. On both sides of the cylinder 25, a pair of pressure roller guides 27 fixed to the apparatus main body are provided. The pressure roller guide 27 is provided in parallel with a plane including the rotation center of the heat roller 11 and the rotation center of the pressure roller 12 and symmetrically with respect to the plane. The cylinder 25 can slide and move on the pressure roller guide 27. It has become. When the cylinder 25 moves along the pressure roller guide 27, the pressure roller 12 also moves.

Below the cylinder 25, a pair of springs 28, 29
Are arranged in parallel with a plane including the rotation center of the heat roller 11 and the rotation center of the pressure roller 12, and symmetrically with respect to the plane. A spring cap 30 is provided so as to cover from the upper ends of the springs 28 and 29 to the middle of the side surfaces.
The lower ends of 8, 29 are supported by a plate 31 fixed to the apparatus body. The upper part of the spring cap 30 is formed as a plane perpendicular to the plane including the rotation center of the heat roller 11 and the rotation center of the pressure roller 12, and this upper surface contacts the lower end of the outer surface of the cylinder 25. The springs 28 and 29 are compressed, and urge the pressure roller 12 toward the heat roller 11 via the spring cap 30 and the cylinder 25 by the restoring force.

In the above-described structure for supporting the pressure roller 12, the number of springs for biasing each end is two instead of one.
Variations in the strength of the spring are averaged, so that substantially equal forces can always be applied to both ends of the pressure roller 12. Further, even if an assembly error occurs in the mounting positions and mounting directions of the springs 28 and 29, a uniform force is applied to the upper portion of the spring cap 30, so that the force applied to the end of the pressure roller 12 is substantially constant. Therefore, the pressure roller 12 is pressed against the heat roller 11 with uniform pressure from one end to the other end.

The paper guide plate 13 guides the paper S having the toner T adhered on its upper surface between the heat roller 11 and the pressure roller 12 on the upstream side A in the paper transport direction. The sheet S that has entered between the heat roller 11 and the pressure roller 12 is heated from above by the heat roller 11 and is pressed from both sides by the heat roller 11 and the pressure roller 12. The heated toner T is softened to increase the adhesive strength, and is fixed to the sheet S by being pressed. At the time of this fixing, a uniform fixing pressure is applied to the paper, so that there is no uneven fixing.

The upper discharge roller 14 is pivotally supported at a front portion and a rear portion of the apparatus main body, is provided with a driving force via a gear (not shown) provided at the rear side, and rotates in the same direction as the heat roller 11. I do. Although not shown, downstream side B in the paper transport direction
Is provided with a door that opens around the lower end in the left direction in the figure, and the lower discharge roller 15 is provided on this door. The discharge roller 15 is formed by a discharge roller 1 by a spring.
4 and rotates following the rotation of the discharge roller 14. Paper after toner fixing
4 and 15 and is discharged by the rollers 14 and 15 to the outside of the apparatus.

The above-mentioned door is normally closed, and at this time, the discharge roller 15 is at the position shown in the figure. When the door is opened, the discharge roller 15 also moves together with the door, and the discharge roller 15 does not exist at the position shown in the drawing, so that the paper jammed in the apparatus can be removed from the downstream side B in the paper transport direction. .

The separation claw 16 of the heat roller 11 is a resin molded body formed so that the tip portion becomes gradually thinner, and is rotatably supported by a shaft 17 provided in the front-rear direction of the apparatus. A spring 19 is provided between an upper portion of the separation claw 16 and a hook 18 fixed to the apparatus, and the separation claw 16 is urged by a pulling force of the spring 19, and a sharp tip is formed on the surface of the heat roller 11. Abut. Paper S for fixing
Is attached to the surface of the heat roller 11, the tip of the separation claw 16 enters between the sheet S and the heat roller 11 by the rotation of the heat roller 11, and the sheet is separated from the heat roller 11.

The separation claw 20 of the pressure roller 12 is made of a thin metal plate having elasticity and is a leaf spring. Separation claw 20
A plate 21 is fixedly mounted on the apparatus main body on the upstream side A in the sheet conveying direction relative to the pressure roller 12 to support
A plate 22 having a substantially horizontal upper surface is fixed to the plate 21. The separation claw 20 is attached to the upper surface of the plate 22 with a screw 23. The separation claw 20 protrudes from the plate 22 toward the downstream side B in the sheet conveying direction.
At a position slightly lower than the upper surface of the pressure roller 12. That is, the separation claw 20 is in a state of being pressed down by the pressure roller 12, and is in contact with the pressure roller 12 by its own elasticity. This contact pressure is set small enough not to damage the surface of the pressure roller 12.

FIG. 3 shows a view from above of the pressure roller 12 and its peripheral portion. In FIG. 3, the upper side is the upstream side A in the sheet transport direction. As described above, the pressure roller 12 has the cylinders 25 at both ends, and the springs 28, 2
9 is energized. The distal end 20a of the separation claw 20 has a reduced width, and the base 20
A punch 20c is formed at the center of a portion protruding from the b toward the pressure roller 12. In this fixing device, four separating claws 20 are arranged at equal intervals.

When the sheet S adheres to the pressure roller 12 during fixing, the leading end moves to the contact point between the leading end 20 a of the separation claw 20 and the pressure roller 12 according to the rotation of the pressure roller 12. Since the separation claw 20 is thin, its leading end 20a enters between the leading end of the sheet and the pressure roller 12, and the sheet is separated from the pressure roller 12. When the sheet adheres strongly to the pressure roller 12, the contact pressure of the separation claw 20 against the pressure roller 12 is small, so that the sheet enters between the leading end 20a of the separation claw 20 and the pressure roller 12, thereby causing a paper jam. . This state is shown in FIG.

The paper S is manually removed by the user. As described above, the user opens the door on the downstream side B in the paper transport direction and retracts the lower discharge roller 15,
Grasp the paper and pull in the direction of arrow P in FIG. At this time,
The moving direction of the sheet S at the leading end 20a of the separation claw 20 is as follows.
As shown by the arrow Q, the tangential direction of the pressure roller 12 is set. The direction Q is from the base 20b of the separation claw 20 to the tip 20b.
a is a forward direction with respect to the direction toward
It is removed without getting caught on zero. Therefore, no force is applied to the separation claw 20, and the elasticity is not impaired and the tip 20a is not deformed. Also, the paper is not easily torn and the paper is very easy to remove.

When the sheet adhered to the pressure roller 12 is separated by the separation claw 20, the leading end of the sheet is directed not to the downstream side B but to the upstream side A in the conveying direction, so that the sheet is jammed. Also in this case, the user needs to manually remove the paper, but the removal is very easy.

FIG. 5 shows a schematic configuration of a second embodiment of the fixing device of the present invention. This fixing device uses a separation claw 32 of a resin molded body as a pressure roller. The other components except the separation claw 32 and its supporting structure are the same as those of the first embodiment.

The separation claw 32 is formed so that the tip portion becomes gradually thinner, and is rotatably supported by a shaft 33 provided in the front-rear direction of the apparatus upstream of the pressure roller 12 in the paper transport direction. ing. A spring 35 is disposed between the upper portion of the separation claw 32 and the hook 34 fixed to the apparatus, and the separation claw 32 is urged by the pulling force of the spring 35, and its tip is located near the lowermost end of the pressure roller 12. In contact with the surface.

Also in this configuration, when the sheet not separated from the pressure roller 12 by the separation claw 32 is taken out, the sheet is not caught by the separation claw 32. Therefore, the spring 35 is not damaged and the tip of the separation claw 32 is not deformed, and the paper is not torn and the removal is difficult.

[0038]

As is apparent from the above description, when the fixing device of the present invention is used, the paper adhered to the pressure roller is removed.
The separation claw can be removed without damage. Further, there is no possibility that the sheet is torn, and the sheet can be removed very easily. Since the separation claw is not damaged, it functions stably for a long period of time, and maintenance work such as replacement is reduced.

[0039]

[0040]

[Brief description of the drawings]

FIG. 1 is a front view showing a schematic configuration of a first embodiment of a fixing device of the present invention.

FIG. 2 is a front view showing a support structure of the pressure roller according to the first embodiment.

FIG. 3 is a plan view showing a pressure roller and a peripheral portion thereof according to the first embodiment;

FIG. 4 is a diagram illustrating a state in which a sheet adheres to a pressure roller according to the first embodiment.

FIG. 5 is a front view illustrating a schematic configuration of a fixing device according to a second embodiment of the invention.

FIG. 6 is a front view showing a configuration of a main part of a conventional fixing device.

FIG. 7 is a diagram illustrating a state in which a sheet adheres to a pressure roller of a conventional fixing device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 heat roller 12 pressure roller 13 paper guide plate 14, 15 discharge roller pair 16 separation claw (for heat roller) 20 separation claw (for pressure roller) 32 separation claw (for pressure roller) 33 shaft 35 spring

Claims (2)

(57) [Claims] 1. A heat roller that generates heat and a portion below the heat roller
A pressure roller disposed in contact with the heat roller, and a separation claw having a distal end contacting the pressure roller by a resilient force,
A sheet carrying an unfixed toner image is passed between the heat roller and the pressure roller to fix the toner image on the sheet, and when the sheet adheres to the pressure roller, the sheet is separated from the pressure roller by the separation claw. In the fixing device for separating, the separation claw is made of a metal leaf spring, and a tip of the separation claw is supported so as to be in contact with a vicinity of a lowermost end of the pressure roller, and a fulcrum of a contact point between the tip and the pressure roller. A fixing device provided on the upstream side in the sheet conveyance direction and above the contact point. 2. A heat roller that generates heat and a portion below the heat roller.
A pressure roller disposed in contact with the heat roller, a separation claw whose tip abuts on the pressure roller by a resilient force, a shaft rotatably supporting the separation claw, and A spring for urging the roller side, a sheet carrying an unfixed toner image is passed between the heat roller and the pressure roller to fix the toner image on the sheet, and the sheet adheres to the pressure roller. A fixing device that separates a sheet from the pressure roller by the separation claw, wherein the separation claw is made of resin, and a tip of the separation claw is pivotally supported so as to abut on a vicinity of a lowermost end of the pressure roller; A fixing device provided upstream of a contact point between the pressure roller and the pressure roller in a sheet conveying direction and above the contact point.