JP2004170740A - Roller unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing roller 50 from which a coil spring 60 does not come off and where the winding pitch of the spring 60 does not fluctuate. <P>SOLUTION: Many projections 62 are formed at a part coming into contact with the inner circumferential surface 52a of a core bar 52 out of the outer circumferential surface of the coil spring 60 as shown in the figure. These projections 62 project in a direction where the spring 60 is prevented from shifting to one side when the core bar 52 is rotating (the fixing roller 50 rotates). That is, these projections 62 project in the same direction as the direction of the force in the longitudinal direction of the core bar 52 out of force acting on the spring 60 while the core bar 52 rotates. Therefore, these projections 62 are caught by the inner circumferential surface 52a of the core bar 52 when the spring 60 moves in the longitudinal direction of the core bar 52 during rotation of the roller 50. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a roller unit that conveys a recording medium or the like while nipping it with another roller.
[0002]
[Prior art]
2. Description of the Related Art As an output device of a computer or a workstation, an electrophotographic image forming apparatus that forms an image on a recording medium using a powder developer (toner) is known. In such an image forming apparatus, for example, an image carrier such as a photosensitive drum is irradiated with light (for example, laser light) carrying image information to form an electrostatic latent image, and a developing roller is applied to the electrostatic latent image. Is used to form a developed image, and the developed image is transferred to a recording medium using a transfer roller or the like to form a transferred image (developed image). The recording medium on which the transfer image has been formed is transported to a fixing device, where the transfer image is fixed on the recording medium. The fixing device is usually provided with a fixing roller having a built-in heater and a pressure roller which is in pressure contact with the fixing roller. When fixing the transferred image on the recording medium, the transferred image is heated at a predetermined fixing temperature while being conveyed while nipping and transporting the recording medium between a fixing roller and a pressure roller, and at the same time, pressure is applied. The transferred image is fixed on the recording medium by the heating and the pressing. The recording medium on which the transfer image is fixed is discharged while being nipped by a discharge roller or the like.
[0003]
The fixing device will be described with reference to FIG.
[0004]
FIG. 5 is a schematic diagram showing a schematic configuration of a conventional fixing device.
[0005]
The fixing device 100 is for permanently visualizing the toner (image) 102 on a recording medium 104 such as recording paper. The recording medium 104 conveyed in the direction of arrow A by the conveyance unit (not shown) is guided by the fixing entrance guide 106 and enters the nip 108 between the fixing roller 120 and the pressure roller 130.
[0006]
The fixing roller 120 is for heating and melting the toner 102. The thermistor 140 is in contact with the outer peripheral surface (front surface) of the fixing roller 120, and the thermistor 140 is configured to measure the temperature of the outer peripheral surface of the fixing roller 120. The fixing roller 120 has a built-in heat source (heating element) such as a halogen heater 122. A controller (not shown) controls the halogen heater 122 based on the outer peripheral surface temperature measured by the thermistor 140, whereby the outer peripheral surface temperature of the fixing roller 120 is maintained at a predetermined fixing temperature.
[0007]
As the fixing roller 120, a roller in which a fluororesin layer 126 having good releasability is coated on the outer peripheral surface of a cored bar 124 made of, for example, a pipe member made of iron or aluminum is used. The fixing roller 120 is rotated in the direction of arrow B by a driving source (not shown).
[0008]
The pressure roller 130 is for pressing the recording medium 104 against the fixing roller 120 at a predetermined pressure. As the pressure roller 130, a roller in which an outer peripheral surface of, for example, a metal core bar 132 is coated with an elastic layer 134 of, for example, silicone rubber or fluorine rubber to a predetermined thickness is used. While pressing the pressure roller 130 against the fixing roller 120 with a predetermined pressure and rotating in the direction of arrow C, a load for fixing the toner 102 to the recording medium 104 is applied.
[0009]
When the recording medium 104 enters the nip 108, the toner 102 on the recording medium 104 melts at the above-mentioned fixing temperature, and the melted toner 102 is pressed against the recording medium 104 with the above-mentioned load, and 104. The recording medium 104 on which the toner 102 has been fixed is separated from the fixing roller 120 by the separation claw 142, reaches a discharge roller (not shown), and is discharged outside the apparatus by the discharge roller.
[0010]
The fixing roller 120 is required to have a quick rise from the viewpoint of shortening the waiting time. For this reason, there is an image forming apparatus in which the time (rise time) from when the image forming apparatus body is completely cooled down to when the main switch is turned on and the first copy is discharged is 30 seconds or less. This rise time is getting shorter every year.
[0011]
Further, from the viewpoint of energy saving, it is required to reduce power consumption for keeping the fixing device warm in a standby state in which a main switch of the image forming apparatus main body is turned on. For this reason, in the standby state, it is necessary to completely turn off the heater of the fixing device. When the heater of the fixing device is completely turned off in the standby state as described above, in order to bring the surface of the fixing roller to a predetermined temperature almost simultaneously with turning on the heater, the thickness of the fixing roller is reduced and the heat capacity is reduced. You need to keep it small. For this reason, a fixing roller made of a thin aluminum alloy having good thermal conductivity is often used.
[0012]
In order to shorten the rise time, the thickness of the aluminum fixing roller 120 has recently been reduced to about 0.8 mm. When the thickness of the fixing roller 120 is further reduced, when the recording medium 104 is sandwiched between the fixing roller 120 and the pressure roller 130 (nip portion 108) and the developed image is fixed by heat and pressure, the fixing The roller 120 may be deformed.
[0013]
In order to solve the above-described problem, a technique has been proposed in which a helical coil spring is inserted inside the fixing roller 120 to reinforce the fixing roller 120 (for example, see Patent Document 1).
[0014]
This technique will be described with reference to FIGS.
[0015]
FIG. 6 is a cross-sectional view illustrating the fixing roller into which the coil spring is inserted. FIG. 7 is a schematic view showing a coil spring coming out of the cored bar. FIG. 8 is a cross-sectional view showing a core metal provided with a stopper. FIG. 9 is a cross-sectional view showing the coil spring in which the winding pitch has changed. In these drawings, the same components as those shown in FIG. 5 are denoted by the same reference numerals.
[0016]
As shown in FIG. 6, a spirally wound coil spring 150 is inserted into the inner space of the cored bar 124. The coil spring 150 extends in the longitudinal direction of the cored bar 124 and contacts the inner peripheral surface of the cored bar 124 to press the inner peripheral surface. Since the metal core 124 is very thin, the pressing force applied to the outer peripheral surface of the fixing roller 120 also affects the coil spring 150. Therefore, when the fixing roller 120 starts to rotate and the pressing roller 130 starts to rotate, the pressed fixing roller 120 and the coil spring 150 start to slightly move in the longitudinal direction. In this case, the movement of the fixing roller 120 is suppressed by a roller stopper (not shown), but since the coil spring 150 is merely inserted into the fixing roller 120, the coil spring 150 gradually moves in the direction of arrow D to It starts to get out of the gold 124 (see FIG. 7). When the fixing roller 120 and the pressure roller 130 continue to rotate, the coil spring 150 falls off from the metal core 124.
[0017]
Therefore, as shown in FIG. 8, a technique has been proposed in which stoppers 124a are formed at both ends in the longitudinal direction of the cored bar 124 so that the coil spring 150 does not fall out of the cored bar 124.
[0018]
[Patent Document 1]
JP 10-116675 A
[Problems to be solved by the invention]
However, in the technique shown in FIG. 8, although the coil spring 150 does not fall out of the cored bar 124, as shown in FIG. 9, the coil spring 150 may move inside the cored bar 124 and the winding pitch may fluctuate. . When the winding pitch of the coil spring 150 fluctuates in this manner, the strength for reinforcing the metal core 124 fluctuates in the longitudinal direction of the metal core 124 and the nip pressure changes. Occurs.
[0020]
SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a roller unit in which a wire does not come off and a winding pitch does not change.
[0021]
[Means for Solving the Problems]
The roller unit of the present invention for achieving the above object,
(1) a hollow cylindrical roller;
(2) a wire that extends in the longitudinal direction of the cylindrical roller while being spirally wound around the hollow portion of the cylindrical roller and that contacts the inner peripheral surface of the cylindrical roller and presses the inner peripheral surface outward; With
(3) The wire is characterized in that a projection is formed on a portion of the outer circumferential surface of the wire that contacts the inner circumferential surface of the cylindrical roller.
[0022]
here,
(4) The projection of the wire protrudes in a direction that prevents the wire from shifting when the cylindrical roller is rotating.
[0023]
Also,
(5) The projection of the wire protrudes in the same direction as the longitudinal force of the cylindrical roller among the forces acting on the wire while the cylindrical roller is rotating.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
The schematic structure of an image forming apparatus in which one embodiment of the roller unit of the present invention is incorporated will be described with reference to FIG.
[0025]
FIG. 1 is a schematic diagram showing a digital copying machine as an example of an image forming apparatus in which an embodiment of the roller unit of the present invention is incorporated.
[0026]
On the top surface of the copying machine 10, a document pressing plate 12 having a rectangular parallelepiped shape which can be opened and closed is arranged. An image reading device 14 that reads an image recorded on a document is arranged below the document pressing plate 12. The upper surface (upper wall) of the image reading device 14 is a platen glass (not shown) on which a document is placed.
[0027]
An operation panel (not shown) for inputting the number of copies and the like is arranged on the front side (front side) of the original cover 12. At the lower part of the copying machine 10, a cassette 16 for accommodating a plurality of cut sheets is provided so as to be able to be taken in and out of the copying machine 10. A space is formed on the left side of the copying machine 10, and a discharge tray 18 on which discharged recording paper is stacked is formed.
[0028]
A procedure for forming an image in the copying machine 10 will be described.
[0029]
In order to form an image recorded on a document on a recording medium, the document pressure plate 12 is opened, and the document is placed on the upper surface of a platen glass (not shown) so that the image surface faces down. The original is pressed and fixed by the original cover 12. Next, by pressing a predetermined operation button or the like, the image recorded on the document is read by the image reading device 14. The read image is converted into a digital signal, and this digital signal is transmitted to the laser scanner 20.
[0030]
The signal transmitted to the laser scanner 20 is converted into a laser beam, and this laser beam is applied to the photosensitive drum 22 via a scanner mirror 20a rotating at a high speed and a folding mirror 20b. The photosensitive drum 22 is uniformly charged by the charger 24, and an electrostatic latent image is formed on the photosensitive drum 22 irradiated with the laser beam. This electrostatic latent image is developed with the developer supplied from the developing roller 26 to form a developed image.
[0031]
On the other hand, a recording medium such as recording paper is fed from the cassette 16 in the direction of arrow E (feeding direction) by the feed roller 28 and is transported to the transfer roller 34 by the transport roller 30 and the registration roller 32. The transfer roller 34 transfers the developed image of the photosensitive drum 22 to the recording medium while holding the recording medium together with the photosensitive drum 22. The recording medium on which the developed image has been transferred is guided to the fixing device 40 by the transport guide 36. The fixing device 40 includes a fixing roller 50 (an example of a roller unit according to the present invention) and a pressure roller 70. The pressure roller 70 is pressed against the fixing roller 50 by a pressure spring 72 (see FIG. 2). The recording medium is conveyed while being nipped by the two rollers 50 and 70, and the developed image is fixed on the recording medium. The recording medium on which the developed image has been fixed in this manner is discharged by the discharge roller 80 and stacked on the discharge tray 18.
[0032]
The basic configuration of the fixing device 40 described above is the same as the configuration of the conventional fixing device 100 shown in FIG. The fixing device 40 differs from the fixing device 100 in a fixing roller 50. The structure of the fixing roller will be described with reference to FIGS.
[0033]
FIG. 2 is a schematic diagram showing the fixing device cut in the longitudinal direction. FIG. 3 is an enlarged view showing the inside of the fixing roller of FIG. FIG. 4 is a perspective view showing the inside of the fixing roller of FIG.
[0034]
The fixing roller 50 includes a pipe-shaped (hollow cylindrical) cored bar 52 (an example of a cylindrical roller according to the present invention) made of an alloy of aluminum and magnesium. The outer diameter of the central portion of the core bar 52 in the longitudinal direction is smaller than the outer diameter of both ends in the longitudinal direction. For this reason, the cored bar 52 has an inverted crown shape. Since the cored bar 52 has an inverted crown shape in this manner, the pinching force of both ends in the longitudinal direction of the fixing roller 50 in the nip formed by the fixing roller 50 and the pressure roller 70 (pressing the recording medium against the recording medium) Force) is greater than the longitudinal center. Therefore, the recording medium conveyed while being nipped between the fixing roller 50 and the pressure roller 70 does not have a warp or a wrinkle. The outer diameter of both ends in the longitudinal direction of the cored bar 52 is larger by about 0.07 mm to 0.13 mm than the central part in the longitudinal direction.
[0035]
The core 52 is cut so that its thickness is about 0.3 to 0.4 mm over the entire area. A release layer 54 is formed on the outer peripheral surface of the cored bar 52. The release layer 54 is formed by forming a fluororesin layer on the surface of a fluororesin, an oil-impregnated silicone rubber, or a silicone rubber layer having a high release property.
[0036]
A helically wound coil spring 60 (an example of a wire according to the present invention) is disposed in a hollow portion of the cored bar 52 (inside the fixing roller 50). The outer diameter of the coil spring 60 is about 0.1 mm to 0.5 mm larger than the inner diameter of the cored bar 52. For this reason, the coil spring 60 is in contact with the inner wall surface (which is an example of the inner peripheral surface in the present invention) 52a surrounding the hollow portion of the cored bar 52 and presses (presses) the inner wall surface 52a outward. ). Therefore, the coil spring 60 rotates together with the metal core 52. At both ends in the longitudinal direction of the core bar 52, stoppers 52b are formed to fix both ends in the longitudinal direction of the coil spring 60 so that the coil spring 60 does not come off from the core bar 52. Note that the stopper 52b need not be formed.
[0037]
As shown in FIG. 4, a large number of projections 62 are formed on a portion of the outer peripheral surface of the coil spring 60 which contacts the inner peripheral surface 52a of the cored bar 52. The tip of each projection 62 is slightly pointed. These many projections 62 protrude in a direction that prevents the coil spring 60 from being biased when the cored bar 52 is rotating (the fixing roller 50 is rotating). That is, the large number of projections 62 protrude in the same direction as the direction of the force in the longitudinal direction of the core 52 among the forces acting on the coil spring 60 while the core 52 rotates. Therefore, when the coil spring 60 attempts to move in the longitudinal direction of the metal core 52 while the fixing roller 50 is rotating, a large number of protrusions 62 are caught on the inner peripheral surface 52 a of the metal core 52. For this reason, the coil spring 60 cannot move in the longitudinal direction of the cored bar 52. As a result, since the coil spring 60 does not shift or jump out of the core bar 52 inside the core bar 52, the rigidity of the fixing roller 50 can be kept uniform in the longitudinal direction. When inserting (inserting) the coil spring 60 into the metal core 52, the coil spring 60 is inserted into the metal core 52 from a direction opposite to the direction in which the numerous protrusions 62 protrude.
[0038]
In the above embodiment, the fixing roller is described as an example, but the present invention can be applied to a cylindrical thin roller such as a photosensitive drum or a developing sleeve.
[0039]
【The invention's effect】
As described above, in the roller unit of the present invention, when the wire attempts to move in the longitudinal direction of the cylindrical roller, the projection of the wire is caught on the inner peripheral surface of the cylindrical roller, and thus the wire is formed in the longitudinal direction of the cylindrical roller. Cannot move in the direction. Therefore, since the wire does not shift or jump out of the cylindrical roller inside the cylindrical roller, the rigidity of the cylindrical roller can be kept uniform in the longitudinal direction.
[0040]
Here, when the projection of the wire is protruding in a direction that prevents the wire from shifting when the cylindrical roller is rotating, the wire may shift inside the cylindrical roller. It is possible to more reliably prevent the wire from jumping out of the cylindrical roller.
[0041]
Further, when the protrusion of the wire rod is one that projects in the same direction as the longitudinal force direction of the cylindrical roller among the forces acting on the wire rod during rotation of the cylindrical roller, It is possible to more reliably prevent the wire rod from leaning or jumping out of the cylindrical roller inside the cylindrical roller.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a digital copying machine as an example of an image forming apparatus in which an embodiment of a roller unit of the present invention is incorporated.
FIG. 2 is a schematic diagram showing a fixing device cut in a longitudinal direction thereof.
FIG. 3 is an enlarged view showing the inside of the fixing roller of FIG. 2;
FIG. 4 is a perspective view showing the inside of the fixing roller of FIG. 2;
FIG. 5 is a schematic diagram illustrating a schematic configuration of a conventional fixing device.
FIG. 6 is a sectional view showing a fixing roller into which a coil spring is inserted.
FIG. 7 is a schematic view showing a coil spring coming out of a cored bar.
FIG. 8 is a cross-sectional view showing a core metal on which a stopper is formed.
FIG. 9 is a cross-sectional view showing a coil spring in which a winding pitch is changed.
[Explanation of symbols]
50 fixing roller 52 core metal 52a inner peripheral surface of core metal 60 coil spring 62 protrusion

Claims (3)

A hollow cylindrical roller,
A wire that extends in the longitudinal direction of the cylindrical roller while being spirally wound around the hollow portion of the cylindrical roller and contacts the inner peripheral surface of the cylindrical roller to press the inner peripheral surface outward,
The wire is
A roller unit, wherein a projection is formed on a portion of the outer peripheral surface of the wire that contacts the inner peripheral surface of the cylindrical roller. The protrusion of the wire is
2. The roller unit according to claim 1, wherein the wire protrudes in a direction that prevents the wire from shifting when the cylindrical roller is rotating. 3. The protrusion of the wire is
The roller according to claim 1, wherein the cylindrical roller protrudes in the same direction as the longitudinal direction of the cylindrical roller among the forces acting on the wire during rotation. unit.

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