JPH09171321A - Fixing device for electrophotographic recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a failure in fixing caused by a shortage or surplus of heat applied to a recording paper by keeping the width of a nip formed on a pressure roller coming into press-contact with a fixing roller constant SOLUTION: A reinforcing roller 32 is made larger in diameter than a core metal 31b, when the reinforcing roller 32 is made of the same material as that of the core metal 31b, so that rigidity in a deflection direction is made sufficiently high, with respect to the core metal 31b of the pressure roller 31. Both end parts of a supporting frame 36 are notched to provide guide grooves 36a which are extended in radial directions centering on the center of the rotation of the fixing roller 21. The pressure roller 31 and the reinforcing roller 32 are supported to be movable along the guiding grooves 36 respectively. Energizing springs 38 connected by an energizing force adjusting mechanism 39 and a wire 40 exert energizing force F2 on pressure levers 37. The pressure levers 37 after receiving the energizing force F2 bring the reinforcing roller 32 into press-contact with the pressure roller 31.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to an electrophotographic recording apparatus such as a copying machine, a facsimile, a printer and the like using an electrophotographic system, and fixes a toner image formed on a recording paper by heating and pressing. It relates to the device.

[0002]

2. Description of the Related Art FIG. 4 is a side sectional view showing a schematic construction of a printer apparatus which is an example of an electrophotographic recording apparatus, and FIG.
FIG. 3 is a schematic configuration diagram of a conventional fixing device applicable to the electrophotographic recording apparatus shown in FIG. 1, where 1 is a photoconductor drum that is an electrophotographic photoconductor, 2 is a cleaning device, and 3 is a charging that uniformly charges the photoconductor drum 1. An optical writing unit 4 forms an electrostatic latent image on the photoconductor drum 1 by scanning the photoconductor drum 1 charged by the charger 3 with a laser beam L, and 5 is formed on the photoconductor drum 1. A developing device for developing the electrostatic latent image into a toner image by the toner T, 6 is a transfer roller in contact with the photoconductor drum 1, 7 is a discharge lamp, and 8 is a detachable mount on the main body of the apparatus to bundle the recording paper P. The paper feed cassette accommodated therein, 9 is a paper feed roller for separating and feeding one sheet of recording paper P from the paper feed cassette 8, 10 is a pair of registration rollers,
Reference numeral 11 denotes a pair of discharge rollers for discharging the recording paper P to the outside of the apparatus. Reference numeral 20 denotes a fixing device, which includes a fixing roller 21 having a heater, which will be described later, and a pressure roller 22 in pressure contact with the fixing roller 21, and the heater fixes the surface temperature of the fixing roller 21 to a predetermined value when the recording sheet P is fixed. It is controlled to reach the temperature. Further, the fixing roller 21 rotates in the conveying direction with respect to the recording paper P by transmitting the rotational force from a drive mechanism (not shown) to the drive gear 21b fixed to one roller shaft 21a.

Next, an image forming operation by the printer device shown in FIG. 4 will be briefly described. The charger 3 uniformly charges the photoconductor drum 1 rotating in the direction of the arrow, and the optical writing unit 4 scans the uniformly charged photoconductor drum 1 with the laser light L to cause the photoconductor drum 1 to move. Form an electrostatic latent image. The developing device 5 transfers the toner T to the photosensitive drum 1 to develop the electrostatic latent image into a toner image.

On the other hand, the recording paper P separated and fed from the paper feed cassette 8 is held by the registration roller pair 10, and the registration roller pair 10 synchronizes the recording paper P with the toner image on the photosensitive drum 1. Start transportation. The toner image on the photosensitive drum 1 is transferred onto the recording paper P by the transfer roller 6. After that, the recording paper P is conveyed to the fixing device 20,
In the fixing device 20, the toner image is fixed by being heated and pressed by the fixing roller 21 and the pressure roller 22,
The paper is discharged to the outside of the apparatus by the paper discharge roller pair 11. Also,
After the residual toner is removed by the cleaning device 2, the photoconductor drum 1 is irradiated with the charge-eliminating light by the charge-eliminating lamp 7 to neutralize the electric charge and prepare for the next image formation.

In FIG. 5, reference numeral 23 is a heater which is a heating means disposed inside the fixing roller 21, 24 is rotatably supporting the fixing roller 21 and the pressure roller 22, and the pressure roller 22 is fixed to the fixing roller 21. 21 is a supporting frame that is supported so as to be able to come into contact with and separate from each other, and 25 is a biasing spring that locks roller shafts 22a protruding from both end surfaces of the pressure roller 22,
The biasing spring 25 exerts a biasing force F ₁ on the roller shaft 22a in the direction (pressure direction) of the fixing roller 21 to bring the pressure roller 22 into pressure contact with the fixing roller 21. The pressure roller 22 has a roller surface formed by an elastic member 22c wound around the outer peripheral surface of a metal cored bar 22b.
A deformed nip is formed along the roller surface of the fixing roller 21 at the portion in pressure contact with 21. In this way, by forming a nip on the roller surface of the pressure roller 22, the fixing roller 21
A contact area corresponding to the width of the nip of the pressure roller 22 is generated between and the recording paper P. In the fixing device 20, a nip having a width corresponding to the amount of heat required to fix the toner image is formed in the pressure roller 22, so that the recording paper is transferred from the roller surface of the fixing roller 21 heated to a predetermined fixing temperature. The amount of heat required to fix the toner image on P is applied.

[0006]

However, in the fixing device 20 described above, the biasing force F ₁ acts on the roller shafts 22a respectively arranged at both ends of the pressure roller 22,
The cored bar 22b formed integrally with the roller shaft 22a is flexibly deformed in the direction (arrow B direction) in which the central portion is separated from the fixing roller 21. As a result, the pressure roller against the fixing roller 21
The pressure contact force of the pressure roller 22 gradually decreases from the end to the center of the roller surface, and the width of the nip formed on the surface of the pressure roller 22 in accordance with the change in the pressure contact force also changes.
The width gradually narrows from the end portion to the central portion, and changes to become the narrowest at the central portion of the pressure roller 22.

The amount of heat per unit width applied to the recording paper P by the fixing roller 21 is substantially proportional to the nip width formed on the pressure roller 22. Therefore, the amount of heat applied to the recording paper P by the fixing roller 21 at the time of fixing is distributed so as to gradually decrease from the roller end portion to the central portion. When the fixing temperature of the fixing roller 21 is set on the basis of the amount of heat applied to the recording paper P by the end portion of the fixing roller 21 during fixing on the recording paper P, the recording paper P is set by the central portion of the fixing roller 21. The amount of heat applied to the fixing roller 21 may be insufficient to fix the toner image, and the fixing temperature of the fixing roller 21 is set on the basis of the amount of heat applied to the recording paper P by the central portion of the fixing roller 21. If the fuser roller 21
The amount of heat applied to the recording paper P may become excessive due to the end portions of the toner and the toner may be melted.

In order to solve the above problems, an object of the present invention is to provide means for making the width of a nip formed in a pressure roller that is in pressure contact with a fixing roller constant, and to prevent the amount of heat applied to recording paper from being insufficient or excessive. It is an object of the present invention to provide a fixing device for an electrophotographic recording device that prevents fixing failure.

[0009]

In order to solve the above-mentioned problems, the fixing device for an electrophotographic recording apparatus according to claim 1 of the present invention has a heating means arranged therein, and the heating means is used for fixing the recording paper. A fixing roller for applying heat generated from the means to the recording paper, and a pressure roller for forming a roller surface by an elastic member wound around the outer peripheral surface of the core metal, and nipping and conveying the recording paper together with the fixing roller. In a fixing device of an electrophotographic recording apparatus that heats and presses a toner image on a recording paper at a sandwiching portion between the fixing roller and the pressure roller to fix the toner image, a rigidity higher than a core metal of the pressure roller in a bending direction is provided. A reinforcing roller that is driven to rotate in contact with the pressure roller, and the reinforcing roller that is arranged outside the pressure roller in a radial direction centered on the axis of the pressure roller and the fixing roller,
The frame member movably supported in the radial direction and both ends of the reinforcing roller are urged toward the fixing roller to bring the reinforcing roller into pressure contact with the pressure roller, and the pressure roller causes the pressure roller to contact the pressure roller. An urging unit that presses the fixing roller is provided.

Further, in the fixing device according to the second aspect, the biasing means is provided with an adjusting mechanism for changing the magnitude of the biasing force applied to both ends of the reinforcing roller according to an operation from the outside. It is characterized by

A fixing device for an electrophotographic recording apparatus according to a third aspect of the present invention is provided with a heating means inside thereof, and a fixing roller for applying heat generated from the heating means to the recording paper at the time of fixing to the recording paper. A roller surface is formed by an elastic member wound around the outer peripheral surface of the core metal, and a pressure roller for sandwiching and conveying the recording paper together with the fixing roller, and both ends of the pressure roller are urged toward the fixing roller. And a biasing unit for pressing the pressure roller against the fixing roller, wherein the holding unit between the fixing roller and the pressure roller heats and presses the toner image on the recording paper to fix the toner image. An auxiliary roller which is formed to have a roller width narrower than that of the pressure roller and is driven to rotate in contact with the pressure roller, and the auxiliary roller which is arranged outside the pressure roller in a radial direction around the axis of the fixing roller. , The frame member movably supported in the radial direction and the auxiliary roller are urged in the direction of the fixing roller to be pressed against the widthwise central portion of the pressure roller. And a biasing means for preventing bending in the direction.

Further, in the fixing device of the electrophotographic recording apparatus according to the fourth aspect, the biasing means is provided with an adjusting mechanism for changing the magnitude of the biasing force applied to the auxiliary roller according to an operation from the outside. It is characterized by being provided.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a perspective view of a first embodiment of a fixing device of the present invention used in an electrophotographic recording apparatus, and FIG. 2 is a sectional view of a biasing force adjusting member for a pressure roller in the fixing device of the first embodiment. 4 and FIG. 5, the members corresponding to the members described with reference to FIG.
The description is omitted. In the fixing device 30 of the present embodiment, 31 is a pressure roller, 32 is a reinforcing roller that is driven by the pressure roller 31 while being in contact with the pressure roller 31, and a roller shaft protruding from both end surfaces of the fixing roller 21. Bearings 33 are arranged on the respective 21a, and the roller shafts 31a and 32a protruding from both end surfaces of the pressure roller 31 and the reinforcing roller 32 are also respectively bearings.
34 and 35 are arranged. Reference numeral 36 denotes a support frame that supports the fixing roller 21, the pressure roller 31, and the reinforcing roller 32 via bearings 33, 34, and 35, and 37 is arranged on both side surfaces of the support frame 36 and is swingably supported by the support frame 36. The pressing lever 38 is an urging spring connected to the swing end of the pressing lever 37, and 39 is an urging force adjusting member that connects the urging springs 38, 38 together with the pair of wires 40, 40. is there.

The pressure roller 31 comprises a cored bar 31b integrally formed with the roller shaft 31a and an elastic member 31c wound around the outer peripheral surface of the cored bar 31b to form a roller surface. In order to sufficiently increase the rigidity of the pressure roller 31 in the bending direction with respect to the cored bar 31b, the pressure roller 31 has a larger diameter than the cored bar 31b when it is made of the same material as the cored bar 31b. Further, the support frame 36 is provided with guide grooves 36a extending in the radial direction around the rotation center of the fixing roller 21 at both ends thereof, and the pressure roller 31 and the reinforcing roller 32 are provided along the guide grooves 36a. Movably support each. In the support frame 36, the pressure roller 31 is arranged at a position in contact with the fixing roller 21, and the reinforcing roller 32 is arranged outside the pressure roller 31 in the radial direction and at a position in contact with the pressure roller 31. ing.

The urging spring 38 connected to the urging force adjusting member 39 via the wire 40 is stretched between the arm portion 36b formed on the support frame 36 and the pressure lever 37 so that the pressure lever 37 is extended. The urging force F ₂ is applied to it. The pressure lever 37, which receives the urging force F ₂ , presses the bearing 35 of the reinforcing roller 32 to urge the bearing 35 toward the fixing roller 21. Reinforcing roller 32
When both ends thereof are urged in the direction of the fixing roller 21 via the bearings 35, the pressure roller 31 is pressed against the pressure roller 31 and the force transmitted from the pressure lever 37 is applied. Pressure roller 31
Receives the pressure contact force from the reinforcing roller 32 and presses against the fixing roller 21, and at the pressure contact portion with the fixing roller 21, the fixing roller 21
To form a nip along the roller surface of the. Here, the reinforcing roller 32 that is in pressure contact with the pressure roller 31 is the core metal 31 of the pressure roller 31.
By having a rigidity sufficiently higher than that of b, the bending generated in the reinforcing roller 32 by the pressing force from the pressure lever 37 becomes minute. As a result, the pressure contact force that the reinforcing roller 32 exerts on the pressure roller 31 becomes substantially constant at any position in the roller width direction, so that the core metal 31b of the pressure roller 31 is flexibly deformed. This can be suppressed, and the pressure contact force applied by the pressure roller 31 to the fixing roller 21 can be made substantially constant in the roller width direction. The pressure contact force exerted by the pressure roller 31 on the fixing roller 21 becomes substantially constant in the roller width direction, so that the pressure roller 31
The width of the nip formed on the surface of the recording paper P becomes constant at an arbitrary position in the roller width direction, and the recording paper P is fixed by the fixing roller 21.
Since the amount of heat applied to the recording paper P can be made uniform in the roller width direction, the amount of heat applied to the central portion of the recording paper P becomes insufficient and the fixing of the toner image becomes insufficient. It is possible to prevent the toner from being melted due to an excessive amount of heat applied to the part.

Further, the biasing force adjusting member 39 connecting the pair of wires 40, 40 is inserted into the inner cylinder 39a having a thread groove formed on the outer peripheral surface thereof and the inner cylinder 39a, as shown in FIG. And an outer cylinder 39c screwed to the inner cylinder 39a while being pressed by the coil spring 39b. Wires are provided at the end of the inner cylinder 39a and the end of the outer cylinder 39c, respectively. 40 is fastened. Here, the outer cylinder 39c is replaced with the inner cylinder 3
By rotating in one direction (extension direction) with respect to 9a, the entire length of the biasing force adjusting member 39 is extended, and by rotating the outer cylinder 39c in the other direction (contraction direction) with respect to the inner cylinder 39a, the biasing force is adjusted. The total length of the member 39 is shortened. That is, since the user or the service person rotates the outer cylinder 39c in the extension direction to extend the biasing force adjusting member 39, the elastic deformation amount of the biasing spring 38 is reduced, so that the pressure lever 37 is used to reinforce the reinforcing roller.
The pressure roller 31 is reduced by reducing the urging force acting on both ends of 32.
The pressure contact force of the fixing roller 21 against the fixing roller 21 can be reduced, and the elastic deformation amount of the biasing spring 38 is increased by rotating the outer cylinder 39c in the contracting direction to shorten the biasing force adjusting member 39. Reinforcing roller 32 by pressure lever 37
It is possible to increase the pressing force of the pressure roller 31 against the fixing roller 21 by increasing the urging force acting on both ends of the fixing roller 21. As described above, the pressing force of the pressure roller 31 to the fixing roller 21 is adjusted by operating the biasing force adjusting member 39, so that the width of the nip formed on the roller surface of the pressure roller 31 can be easily adjusted. It becomes possible to do.

FIG. 3 is a schematic configuration diagram of a second embodiment of the fixing device of the present invention used in an electrophotographic recording apparatus, and FIG.
The members corresponding to the members described with reference to FIG. 5 are designated by the same reference numerals, and the description thereof will be omitted. In the fixing device 50 of the present embodiment, 51 has a roller width narrower than the pressure roller 22, and the pressure roller 22 is in contact with the pressure roller 22.
The auxiliary roller 52 is driven to rotate, and 52 is a support frame that rotatably supports the fixing roller 21, the pressure roller 22, and the auxiliary roller 51. The pressure roller 22 and the pressure roller 22 are arranged in the radial direction around the rotation center of the fixing roller 21. Each of the auxiliary rollers 51 is movably supported. In the support frame 52, the pressure roller 22 is arranged at a position in contact with the fixing roller 21,
The auxiliary roller 51 is arranged outside the pressure roller 22 in the radial direction, and is supported by the support frame 52 so as to come into contact with the central portion of the pressure roller 22. 53 is a movable fulcrum which is arranged on the support frame 52 and whose position can be adjusted in the roller width direction, 54 is a pressure lever which is swingably supported by the movable fulcrum 53, and 55 is the rear end of the pressure lever 54. It is an urging spring that presses against the portion and applies an urging force F ₃ .

The pair of pressure levers 54, 54 receive the urging force F ₃ from the urging spring 55, so that the lever tips are brought into pressure contact with the roller shafts 51a, 51a protruding from the both end surfaces of the auxiliary roller 51. Urges the auxiliary roller 51 in the direction of the fixing roller 21. As a result, the auxiliary roller 51 comes into pressure contact with the pressure roller 22 and exerts a pressure contact force C in the direction of the fixing roller 21 on the central portion of the pressure roller 22.
The magnitude of the pressure contact force C is set according to the magnitude of the urging force F ₁ applied by the urging spring 25 to the roller shafts 22a, 22a of the pressure roller 22. By applying a pressure contact force C which corresponds to the biasing force F ₁ in the central portion of the pressing roller 22, the pressing roller 22 press-contact force C to balance the force to the core metal 22b is flexibly deformed by the biasing force F ₁ Therefore, it is possible to prevent the core metal 22b of the pressure roller 22 from being bent and deformed, and to make the pressure contact force applied by the pressure roller 22 to the fixing roller 21 constant in the roller width direction. You can By making the pressure contact force applied by the pressure roller 22 to the fixing roller 21 constant in the roller width direction,
Since the width of the nip formed on the surface of the pressure roller 22 becomes constant at any position in the roller width direction, the amount of heat applied to the recording paper P by the fixing roller 21 can be made uniform in the roller width direction. The amount of heat applied to the central portion of the recording paper P is insufficient and fixing of the toner image is insufficient, or the amount of heat applied to the end portion of the recording paper P is excessive and toner melting occurs. Can be prevented.

Further, the user or the like can move the movable fulcrum 53 to the arrow C ₁
Urging force F ₃ acting on the roller shaft 51a of the auxiliary roller 51 by the pressure lever 54 can be increased by moving the movable fulcrum 53 in the arrow C ₂ direction. Since the biasing force F ₃ acting on the roller shaft 51a of the auxiliary roller 51 can be reduced by the lever 54, the pressure roller 22 can be made to correspond to the magnitude of the biasing force F _1.
It is possible to adjust the magnitude of the pressure contact force C of the auxiliary roller 51 with respect to.

[0020]

As described above, according to the fixing device of the electrophotographic recording apparatus of the first aspect, the reinforcing roller pressed against the pressure roller has higher rigidity in the bending direction than the core metal of the pressure roller. Since the flexure generated in the reinforcing roller can be made extremely small by having the above, the pressure contact force applied by the reinforcing roller to the pressure roller can be made substantially constant at any position in the roller width direction. can do. As a result, the core metal of the pressure roller can be prevented from flexing and deforming, and the pressure contact force applied to the fixing roller by the pressure roller can be made constant in the roller width direction. The width of the nip formed in the roller is constant in the roller width direction, and the amount of heat applied to the recording paper by the fixing roller can be made uniform in the roller width direction.

Further, according to the fixing device of the electrophotographic recording apparatus of the second aspect, the urging means changes the magnitude of the urging force applied to both ends of the reinforcing roller in response to an operation from the outside. Thus, the user or the like can reduce the pressure contact force of the pressure roller against the fixing roller by reducing the magnitude of the biasing force by the biasing means, and increase the magnitude of the biasing force by the biasing means. As a result, since the pressure contact force of the pressure roller with respect to the fixing roller can be increased, the width of the nip formed on the roller surface of the pressure roller can be easily adjusted.

According to the fixing device of the electrophotographic recording apparatus of the third aspect, the auxiliary roller applies a pressing force in the direction of the fixing roller to the central portion of the pressure roller, so that the biasing means applies the force. Since it is possible to exert a pressure contact force on the pressure roller that balances the force of the core metal of the pressure roller about to bend and deform due to the force, it is possible to prevent the core metal of the pressure roller from bending and deforming. Therefore, the pressure contact force applied by the pressure roller to the fixing roller can be made constant in the roller width direction. As a result, the core metal of the pressure roller can be prevented from flexing and deforming, and the pressure contact force applied to the fixing roller by the pressure roller can be made constant in the roller width direction. The width of the nip formed in the roller is constant in the roller width direction, and the amount of heat applied to the recording paper by the fixing roller can be made uniform in the roller width direction.

Further, according to the fixing device of the electrophotographic recording apparatus of the fourth aspect, the urging means changes the magnitude of the urging force applied to the auxiliary roller according to the operation from the outside, thereby applying the force. Since it is possible to adjust the pressure contact force of the auxiliary roller according to the force applied to both ends of the pressure roller, the pressure contact force of the auxiliary roller corresponds to the force of the biasing means. By doing so, it is possible to adjust the size so that the bending deformation of the pressure roller is prevented.

[Brief description of the drawings]

FIG. 1 is a perspective view of a first embodiment of a fixing device of the present invention used in an electrophotographic recording device.

FIG. 2 is a cross-sectional view of a biasing force adjusting member for a pressure roller in the fixing device according to the first exemplary embodiment.

FIG. 3 is a schematic configuration diagram of a second embodiment of a fixing device of the present invention used in an electrophotographic recording device.

FIG. 4 is a side sectional view showing a schematic configuration of a printer device which is an example of an electrophotographic recording device.

5 is a schematic configuration diagram of a conventional fixing device applicable to the electrophotographic recording apparatus shown in FIG.

[Explanation of symbols]

21 ... Fixing roller, 22,31 ... Pressing roller, 22b, 31b ...
Core bar, 22c, 31c ... elastic member, 23 ... heater, 25 ... biasing spring, 30, 50 ... fuser, 36, 52 ... support frame, 37, 54 ... pressure lever, 38, 55 ... biasing spring, 39 ... biasing force adjusting member, 51 ... auxiliary roller.

Claims (4)

[Claims] 1. A roller surface comprising a fixing roller having a heating means disposed therein, which applies heat generated from the heating means to the recording paper at the time of fixing to the recording paper, and an elastic member wound around the outer peripheral surface of the core metal. And a pressure roller that holds and conveys the recording paper together with the fixing roller, and an electrophotographic recording in which a toner image on the recording paper is heated and pressed and fixed by a sandwiching portion between the fixing roller and the pressure roller. In the fixing device of the apparatus, a reinforcing roller that has a rigidity higher than that of the core metal of the pressure roller in the bending direction and is driven to rotate in contact with the pressure roller is centered around the axis of the pressure roller and the fixing roller. A frame member that movably supports the reinforcing roller disposed radially outside the pressure roller in the radial direction, and urges both ends of the reinforcing roller toward the fixing roller to apply the reinforcing roller. Pressure A fixing device for an electrophotographic recording apparatus, comprising: a biasing unit that presses the pressure roller against the fixing roller by a pressure contact force from the reinforcing roller. 2. The urging means is provided with an adjusting mechanism for changing the magnitude of the urging force applied to both ends of the reinforcing roller according to an operation from the outside. Fixing device for electrophotographic recording device. 3. A roller surface including a fixing roller having a heating means disposed therein, which applies heat generated from the heating means to the recording paper at the time of fixing to the recording paper, and an elastic member wound around the outer peripheral surface of the cored bar. And a pressing roller for sandwiching and conveying the recording paper together with the fixing roller, and a pressing means for pressing both ends of the pressing roller toward the fixing roller to press the pressing roller against the fixing roller. In a fixing device comprising: a fixing unit configured to heat and press the toner image on the recording paper at a sandwiching portion between the fixing roller and the pressure roller, the roller width is narrower than that of the pressure roller, An auxiliary roller that is in contact with and driven to rotate, and a frame member that movably supports the auxiliary roller, which is arranged outside the pressure roller in the radial direction around the axis of the fixing roller, so as to be movable in the radial direction; And a biasing means for preventing the pressure roller from bending in the radial direction due to the pressure contact force from the auxiliary roller, by biasing the roller in the direction of the fixing roller to pressure-contact the widthwise center of the pressure roller. A fixing device for an electrophotographic recording device, which is characterized in that 4. The electrophotographic recording according to claim 3, wherein the urging means is provided with an adjusting mechanism for changing the magnitude of the urging force applied to the auxiliary roller according to an operation from the outside. Fixing device of the device.