JP2001296770A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device where the deformation of a fixing roller such as deflection and the collapse of its cross section is restrained by regulating the deformation in a direction different from a pressuring direction. SOLUTION: This fixing device is provided with a reinforcing member 24 for correcting the deformation of the fixing roller 18 from the outside on the opposite side of the roller 18 to a pressure roller 19. The member 24 has plural small rollers 24a coming into contact with the outer periphery of the roller 18 on its opposite side to the roller 19. The rollers 24a are rotatably fixed on a holding member 25 having high rigidity and press the roller 18 in a reverse direction to the pressuring direction Y by the roller 19 so as to restrict the deformation. The deformation of the roller 18 is restrained even in directions perpendicularly or nearly perpendicularly crossing with the direction Y. Thus, a nip is prevented from being narrowed by the deformation of the roller 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used for an image forming apparatus such as a copying machine, a printer, and a facsimile.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a heat-fixing roller which is driven to rotate, and a pressure roller which is rotatable while being pressed against the heat-fixing roller at a predetermined pressure. There is a fixing device in which a fixing nip portion is formed, and a transfer material carrying a toner image is inserted into the fixing nip portion to heat and fuse the toner image to fix the toner image on the surface of the transfer material.

FIG. 1 is a configuration diagram of a laser printer as an example of an image forming apparatus. This printer supplies a charging unit 2, a cleaning device 3, a laser beam L by a laser optical system, and toner around a photoreceptor 1 rotating in the direction of an arrow to visualize a latent image on the photoreceptor 1. A developing unit 7 including a developing sleeve 5 and a transfer unit 6 are arranged. The sheet P in the sheet cassette 10 which can be attached and detached in the direction of the arrow a, which is disposed on the lower side, is supported by the middle plate 11 and is supplied to the sheet feeding roller 13 via the arm 12 by the urging force of a spring (not shown). Press. Then, when a control unit (not shown) issues a command, the paper feed roller 13 is rotated, and the uppermost sheet in the paper feed cassette 10 is prevented from being double fed by the separation pad 14 to the registration roller 15 on the downstream side in the transport direction. The sheet is conveyed and sent out to the transfer means 6 at a timing synchronized with the image on the photoconductor 1.

The paper on which the image from the photoreceptor 1 has been transferred by the transfer paper means 6 is further conveyed to the fixing means 16, passed between a nip formed by a fixing roller 18 and a pressure roller 19, and heated and pressed to form a toner. Fix the image. Thereafter, the sheet on which the image has been formed is discharged and placed on the discharge tray 22 from the discharge port 21 with the image side down by the discharge roller 20. In order to correspond to the size of the paper to be discharged, the paper discharge stopper is movable in the direction of arrow b.

In this printer, an operation surface is disposed on the right side in the figure, an operation panel 30 protrudes from an upper front surface of the exterior part 31 (right side on the apparatus in the figure), and a paper feed tray 32 is turned by a pin 33. Mounted movably. In a case 34 arranged on the left side of the drawing, electrical equipment such as a power supply 35 and a printed board 36 (engine driver board) and a control unit are housed. A controller board 37 is also stored. Cover 38 Constituting Output Tray 22
Can be opened around the rotation fulcrum 39.

FIG. 2 is a sectional view of a general example of the fixing device 16 used in the image forming apparatus as shown in FIG. The fixing device 16 has a halogen heater 23 as a heat source inside.
A pressing roller 19 made of an elastic member such as silicon rubber is pressed against the fixing roller 18 having a predetermined pressure. In such a fixing device, a device having a short rise time is desired from the viewpoint of power saving. For this reason, a fixing roller using a member having a small heat capacity such as a thin metal pipe as a core is often used as the fixing roller 18. It is being done.

However, when the core metal of the fixing roller 18 is made thinner, the mechanical strength is reduced, and problems such as deformation in the longitudinal direction of the fixing roller 18 and crushing of the cross section arise.
Due to such deformation of the fixing roller 18, the fixing roller 1
This is because the nip formed by the pressure roller 8 and the pressure roller 19 becomes narrow particularly in the central portion in the axial direction, and fixing failure occurs.

That is, in the case of a roller having a low mechanical strength such as a thin roller, the fixing roller 18 may cause an axial deflection as shown in FIG. 3 or a collapse in a radial cross section as shown in FIG. In particular, when the outer diameter of the fixing roller 18 is large, the cross section is significantly crushed, and the fixing roller 1
The deformation of 8 is such that only the central portion in the axial direction is crushed and bent as shown in FIG. At this time, the pressing force at the center of the fixing roller 18 in the axial direction becomes extremely small, and the width of the nip becomes narrow. Reference numerals 50 and 50 in FIGS. 3 and 5 denote fixing side plates.

FIGS. 6A and 6B show the displacement of the upper and lower surfaces of the fixing roller 18 having a diameter of φ40 mm and a thickness t = 0.3 mm, and the change in the diameter of the fixing roller 18 in the pressing direction. As the load increases, the fixing roller 18 is bent in the axial direction, and the position of the lower surface rises, whereas the cross section in the radial direction is remarkably crushed, so that the position of the upper surface conversely decreases with the load. . Due to this deformation, the pressure is reduced at the center in the roller axis direction as described above, and the nip is narrowed, so that a uniform nip cannot be formed, thus causing a fixing failure.

As means for solving these problems, Japanese Patent Application Laid-Open No. 09-171321 and Japanese Patent Application Laid-Open No.
As disclosed in Japanese Patent Publication No. 28-28, a structure in which a reinforcing member is provided outside or inside a fixing roller has been proposed.

The technique disclosed in Japanese Patent Application Laid-Open No. 09-171321 is intended to eliminate the deflection in the longitudinal direction of the fixing roller. The reinforcing roller is brought into contact with the pressure roller from the outside, and the deflection is reduced by a spring. To reinforce the pressure roller. There is also disclosed a technique in which an auxiliary roller is provided only at the center of the pressure roller. Further, the technique disclosed in Japanese Patent Application Laid-Open No. 09-171321 is intended to eliminate crushing in the cross-sectional direction, and is configured by mounting a plurality of reinforcing rings in a fixing roller.

By mounting a reinforcing ring in the fixing roller, it is possible to greatly reduce the deflection and the crushing of the cross section of the fixing roller. However, when a reinforcing member is mounted, some new members are required. Problems can arise. That is,
(1) It is difficult to fix the reinforcing member to the fixing roller. (2) Since a large load is applied to the reinforcing member for preventing deformation of the fixing roller, it must be firmly fixed to the fixing roller. (3) When the reinforcing member is fixed in the fixing roller in a shrinking state, the reinforcing member requires high precision, and the loading operation requires skill, (4) welding, etc. When fixing inside the fixing roller, not only the processing cost is increased but also the load is concentrated on the welded part, which may cause damage to the reinforcing ring,
(5) Since another member is placed inside the fixing roller, the heat capacity is locally increased, and the temperature rise in that portion is slowed down. (6) The configuration of the heat source of the fixing roller is limited due to the reinforcing member (for example, when the fixing roller is heated by an internal halogen heater, the inner reinforcing member is heated before conducting heat to the core metal. And a delay in thermal response occurs), and so on.

In view of these problems and the fact that the thickness of the fixing roller will continue to be reduced in the future, it is necessary to improve the technology of reinforcing means for restricting roller deformation from the outside. When the deformation of the fixing roller having the diameter of φ40 mm and the thickness t of 0.3 mm is actually observed when the fixing roller is pressed, the displacement of the upper surface of the fixing roller (opposite to the pressing roller) due to the collapse in the cross-sectional direction is small. The displacement of the lower surface (pressure roller side) is large,
The nip becomes uneven. To prevent this, see Japanese Patent Application Laid-Open
It is not possible by means for controlling the deformation of the upper surface of the fixing roller as in the technique disclosed in Japanese Patent Application Publication No.

Accordingly, the present invention is to solve the above-mentioned conventional problems by suppressing the deformation of the roller by restricting the deformation in the direction different from the pressing direction.

[0015]

According to a first aspect of the present invention, there is provided a fixing device comprising: a thin cylindrical fixing roller having a heat source inside or outside; and a pressure contact with the fixing roller. In a fixing device having a pressure roller,
A fixing member that restricts deformation of the fixing roller from outside the fixing roller, the reinforcing member having an outer diameter swelling in a direction perpendicular to a direction in which the pressing roller applies pressure to the fixing roller; It is characterized by including means for limiting at least the above.

According to a second aspect of the present invention, in order to achieve the above object, the reinforcing member has an outer diameter of the fixing roller in a direction perpendicular to a direction in which the pressure roller applies pressure to the fixing roller. And a means for restricting the fixing roller from bending in the direction in which the pressure roller presses the fixing roller.

According to a third aspect of the present invention, in order to achieve the above object, the reinforcing member is an elastic roller which can rotate in contact with the fixing roller.

According to a fourth aspect of the present invention, in order to achieve the above object, the reinforcing member can be positioned by the fixing roller.

According to a fifth aspect of the present invention, in order to achieve the above object, the reinforcing member is provided at a central portion in the axial direction of the fixing roller.

[0020]

Embodiments and examples of the present invention will be described below with reference to the drawings. In the following, portions common to the related art are denoted by the same reference numerals, and redundant description is omitted.

FIG. 7 is a radial sectional view (A) and an axial sectional view (B) of the first embodiment of the fixing device according to the present invention. The fixing roller 18 is mounted on the fixing side plates 50, 50 via heat insulating bushes 51, 51, bearings 52, 52, and a gear 53 mounted on an end of the fixing roller 18 meshes with a driving source (not shown) to receive a rotational driving force. Has become. Further, the fixing roller 18 has a thin pipe of Al or Fe as a base,
The thickness is about 0.3 to 2.0 mm, a surface release layer is formed on the outer periphery, and a halogen heater 23 is provided on the inner side.

Although not shown, the fixing roller 18
A temperature sensor is in contact with, and energization to the halogen heater 23 is controlled based on the temperature of the fixing roller 18 detected by the temperature sensor. Normally, when the power of the image forming apparatus is turned on, a current flows to the halogen heater 23,
The temperature of the fixing roller 18 rapidly rises to a set temperature of about 180 ° C. On the opposite side of the pressure roller 19 of the fixing roller 18, a reinforcing member 24 for externally correcting deformation of the fixing roller 18 is provided.

The reinforcing member 24 is provided with a plurality of small rollers 24a arranged so as to be in contact with the outer periphery of the fixing roller 18 on the side opposite to the pressing roller 19. These rollers 24a are:
The fixing roller 18 is rotatably fixed to the holding member 25 having high rigidity, and presses the fixing roller 18 in a direction opposite to the pressing direction Y in the pressing direction of the pressing roller 19 (the arrow Y direction in the drawing) to limit the deformation. In addition, the deformation is suppressed by pressing the fixing roller 18 in a direction perpendicular to or substantially perpendicular to the pressing direction Y, thereby preventing the nip from being narrowed by the deformation of the fixing roller 18.

FIG. 8 is a radial sectional view of a fixing device according to a second embodiment of the present invention. This embodiment has the same basic structure as that of the previous embodiment, but three elastic rollers 24b made of silicon rubber or the like are provided so as not to damage the surface release layer of the fixing roller. Member 25
It is fixed to be rotatable. One elastic roller 24b presses the fixing roller 18 in a direction opposite to the pressing direction of the pressing roller 19 (the direction indicated by the arrow Y in the drawing) to limit the deformation, and the other two elastic rollers 24b, 24b The fixing roller 18 is pressed in a direction perpendicular to the pressing direction Y to suppress the deformation of the fixing roller 18, thereby preventing the nip from being narrowed by the deformation of the fixing roller 18.

FIG. 9 is a radial sectional view of a third embodiment of the fixing device according to the present invention. This embodiment has the same basic structure as the second embodiment, but
The holding member 25 is pressed against the fixing roller 18 with a predetermined load by a spring 26 from a direction opposite to the pressing direction Y of the pressing roller 19. The elastic roller 24b is provided so as to restrict only deformation in the direction perpendicular to the pressing direction Y,
There is no restriction on the deflection of the fixing roller 18 in the direction opposite to the pressing direction Y. For this reason, the holding member 25 and the elastic roller 24b also move together with the deflection of the fixing roller 18, so that the deformation of the fixing roller 18 is always suppressed at the optimum position, and in order to prevent the diameter of the fixing roller 18 from expanding, There is no need to strictly set the positional accuracy between the holding member 25, the elastic roller 24b, and the fixing roller 18.

FIG. 10 is a radial sectional view of a fourth embodiment of the fixing device according to the present invention. In this embodiment, two elastic rollers 24b made of silicon rubber or the like are provided, and the outer diameter of the fixing roller 18 is suppressed by being opposed in a direction perpendicular to the pressing direction Y when viewed from the center of the fixing roller 18. You can do it. The elastic roller 24 (reinforcing member) is pressed against the fixing roller by a spring 26. As described above, the outer diameter of the fixing roller 18 is φ40.
When the diameter is equal to or greater than 2 mm, the deformation in the radial direction cross section is more remarkable than the axial deflection of the roller. Therefore, the radial deformation is reinforced by two reinforcing members (elastic roller 24b).

FIG. 11 is a radial sectional view of a fixing device according to a fourth embodiment of the present invention. This embodiment is applicable to all the previous embodiments. As shown in the figure, the reinforcing member 24 is disposed at the axial center where the deformation of the fixing roller 18 is most remarkable. However, the deformation of the fixing roller 18 can be sufficiently suppressed by a short reinforcing member.

[0028]

As described above, the fixing device according to the first aspect of the present invention has a reinforcing member that restricts deformation of a thin cylindrical fixing roller having a heat source inside or outside from outside, and Since the reinforcing member includes means for at least restricting the outer diameter of the fixing roller from expanding in the direction perpendicular to the direction in which the pressure roller applies pressure to the fixing roller, at least the direction perpendicular to the pressing direction is at least increased. Since deformation of the fixing roller can be suppressed by limiting deformation, the deformation of the fixing roller can be suppressed while reducing costs with the minimum reinforcement member, and the fixing performance can be improved by making the nip formed with the pressure roller uniform. There is an effect that improvement can be achieved.

In the fixing device according to the second aspect, as described above, the reinforcing member restricts expansion of the outer diameter of the fixing roller in a direction perpendicular to the direction of pressing by the pressing roller; Since it includes means for restricting the fixing roller from bending in the pressing direction by the pressure roller, there is an effect that deformation of the fixing roller can be further suppressed.

According to the third aspect of the present invention, as described above, the reinforcing member is constituted by the elastic roller which is rotatable in contact with the fixing roller. This has the effect of not damaging the layer.

In the fixing device according to the fourth aspect, as described above, since the reinforcing member can be positioned by the fixing roller, the positional accuracy between the fixing roller and the reinforcing member is taken into consideration in addition to the above common effects. There is no effect, and there is an effect that reinforcement can be performed at a position where the outer diameter is always maximum even if the fixing roller is bent.

In the fixing device according to the fifth aspect, as described above, the reinforcing member is provided at the central portion in the longitudinal direction where the deformation of the fixing roller is remarkable. Is minimized, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a laser printer as an example of an image forming apparatus.

FIG. 2 is a radial sectional view of a general fixing device.

FIG. 3 is an explanatory diagram of a deflection in a longitudinal direction of a fixing roller.

FIG. 4 is an explanatory diagram of a collapse of a radial cross section of a fixing roller.

FIG. 5 is an explanatory diagram of a longitudinal deflection of a fixing roller.

FIG. 6 is an explanatory diagram of a deflection in a longitudinal direction showing a deformation of a central portion of the fixing roller.

FIGS. 7A and 7B are a sectional view in the radial direction and a sectional view in the axial direction of the fixing device according to the first embodiment of the present invention;

FIG. 8 is a radial sectional view of a second embodiment of the fixing device according to the present invention.

FIG. 9 is a radial sectional view of a third embodiment of the fixing device according to the present invention.

FIG. 10 is a radial sectional view of a fixing device according to a fourth embodiment of the present invention.

FIG. 11 is a radial sectional view of a fixing device according to a fourth embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor 2 charging means 3 cleaning device 5 developing sleeve 6 transfer means 7 developing device 10 paper feed cassette 11 middle plate 12 arm 13 paper feed roller 14 separation pad 15 registration roller 16 fixing means 18 fixing roller 19 pressure roller 20 paper discharge Roller 21 Discharge port 22 Discharge tray section 23 Halogen heater 24 Reinforcement member 25 Reinforcement member holding member 26 Spring 30 Operation panel 31 Exterior part 32 Paper feed tray 33 Pin 34 Case 35 Power supply 36 Print board 37 Controller board 38 Cover 39 Rotation Supporting point 50 Side plate 51 Insulated bush 52 Bearing 53 Gear L Laser beam

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Jun Nakato 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (Reference) 2H033 AA06 BB01 BB28 BB34 BB39 3J103 AA02 AA41 BA03 CA52 DA05 FA03 GA57 GA58 GA60

Claims (5)

[Claims] 1. A fixing device having a thin cylindrical fixing roller having a heat source inside or outside and a pressure roller pressed against the fixing roller, wherein reinforcement for restricting deformation of the fixing roller from outside the fixing roller is provided. A fixing member, wherein the reinforcing member includes means for at least restricting the outer diameter of the fixing roller from expanding in a direction perpendicular to a direction in which the pressing roller applies pressure to the fixing roller. apparatus. 2. The fixing member according to claim 1, wherein the reinforcing member restricts expansion of an outer diameter of the fixing roller in a direction perpendicular to a direction in which the pressing roller applies pressure to the fixing roller. Means for restricting the fixing roller from bending in a direction in which the roller is pressed. 3. The fixing device according to claim 1, wherein the reinforcing member is an elastic roller that can rotate in contact with the fixing roller. 4. The fixing member according to claim 1, wherein said reinforcing member can be positioned by said fixing roller.
Any of the fixing devices. 5. The fixing device according to claim 1, wherein the reinforcing member is provided at a central portion in an axial direction of the fixing roller.