JP2003329030A - Roller unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a roller unit for preventing a deformation resulting from a bearing arranged at both ends of the lengthwise direction. <P>SOLUTION: A winding pitch P1 of a coil spring 60 in a part where a bearing 56 is located is made shorter than a winding pitch P2 of a coil spring in a part where the bearing 56 is not located out of an external wall surface 52b of a cored bar. Therefore, the winding pitch P1 of lengthwise body ends 62 and 62 of the coil spring 60 is made shorter than the winding pitch P2 of a lengthwise center 64. Then, the lengthwise both ends of the external surface 52 is pressed outwards with the force stronger than that of the lengthwise center. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roller unit that conveys a recording medium while sandwiching it with another roller.

[0002]

2. Description of the Related Art As an output device of a computer or a workstation, an electrophotographic image forming apparatus for forming an image on a recording medium using a powdery developer (toner) is known. In such an image forming apparatus, for example, light (for example, laser) carrying image information is applied to an image carrier such as a photosensitive drum to form an electrostatic latent image, and a developing roller is used for the electrostatic latent image. To supply toner to form a developed image,
This developed image is transferred onto 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 is formed is conveyed to the fixing device, and the transfer image is fixed on the recording medium by the fixing device. The fixing device is usually provided with a fixing roller having a built-in heater and a pressure roller in pressure contact with the fixing roller. When fixing the transfer image to the recording medium, the transfer image is heated at a predetermined fixing temperature and simultaneously pressed while the recording medium is sandwiched and conveyed by a fixing roller and a pressure roller. The transfer image is fixed on the recording medium by the heating and pressing. The recording medium on which the transfer image is fixed is ejected while being sandwiched by a paper ejection roller or the like.

The fixing device will be described with reference to FIG.

FIG. 4 is a schematic diagram showing a schematic structure of a conventional fixing device.

The fixing device 100 is for permanently making a toner (image) 102 visible on a recording medium 104 such as recording paper. The recording medium 104 transported in the direction of arrow A by a transport unit (not shown) is guided by the fixing inlet guide 106 and enters the nip portion 108 between the fixing roller 120 and the pressure roller 130.

The fixing roller 120 is for heating and melting the toner. 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. Further, the fixing roller 120 has a heat source (heating element) such as a halogen heater 122 built therein. 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.

As the fixing roller 120, there is generally used one in which a metal core 124 made of, for example, a pipe-shaped member made of iron or aluminum is coated with a fluororesin layer 126 having a good releasability on the outer peripheral surface. The fixing roller 120 rotates in the direction of arrow B by a drive source (not shown).

The pressure roller 130 is for pressing the recording medium 104 against the fixing roller 120 with a predetermined pressure. As the pressure roller 130, for example, a metal cored bar 1
The outer peripheral surface of 32 is generally coated with an elastic layer 134 such as silicone rubber or fluororubber having a predetermined thickness. The pressure roller 130 is pressed against the fixing roller 120 with a predetermined pressure to rotate in the direction of arrow C, and a load for fixing the toner 102 to the recording medium 104 is applied.

When the recording medium 104 enters the nip portion 108, the toner 102 on the recording medium 104 melts at the above fixing temperature and the melted toner 102 is pressed against the recording medium 104 by the above load. The recording medium 104 is fixed. The recording medium 104 on which the toner 102 is fixed is fixed to the fixing roller 120 by the separation claw 142.
Then, it is separated from the pressure roller 130 and reaches a paper discharge roller (not shown), and is discharged to the outside of the machine by this paper discharge roller.

The fixing roller 120 is required to have a quick start-up from the viewpoint of energy saving. For this reason, there is an image forming apparatus in which the time (rise time) from when the image forming apparatus main body is completely cooled 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 year by year.

Further, it is required to reduce power consumption as much as possible for keeping the fixing device warm in a standby state where the main switch of the image forming apparatus main body is turned on.
Therefore, in the above standby state, it is necessary to completely turn off the heater of the fixing device. In this way, when the heater of the fixing device is completely cut off in the standby state, in order to bring the fixing roller to a predetermined temperature almost at the same time when the heater is turned on, the thickness of the fixing roller is reduced to reduce its heat capacity. Need to be kept. For this reason, a fixing roller made of an aluminum alloy having a good thermal conductivity is often used.

In order to shorten the rise time described above, the thickness of the fixing roller 120 made of aluminum has recently been reduced to 0.
It is as thin as about 8 mm. When the thickness of the fixing roller 120 is further reduced, the recording medium 104 is provided between the fixing roller 120 and the pressure roller 130 (nip portion 108).
The fixing roller 120 may be deformed when the developed image is fixed by sandwiching the sheet with heat and pressure.

In order to solve the above problems, a technique has been proposed in which a spiral coil spring is inserted into the fixing roller 120 to reinforce the fixing roller 120 (see Japanese Patent Laid-Open No. 10-116675). .

This technique will be described with reference to FIG.

FIG. 5 is a sectional view showing a fixing roller having a coil spring inserted therein. In this figure, the same components as those shown in FIG. 4 are designated by the same reference numerals.

A coil spring 150 wound in a spiral shape is inserted into the inner space of the core metal 124. The coil spring 150 extends in the longitudinal direction of the core metal 124, contacts the inner peripheral surface of the core metal 124, and presses the inner peripheral surface outward. The fixing roller 120 is provided with bearings 128 that come into contact with the outer peripheral surface of the cored bar 124 and rotatably support both longitudinal ends of the cored bar 124. This bearing 128
Are arranged at positions outside the paper passing area (area where the recording medium passes).

[0017]

As described above, when the recording medium is conveyed, the pressure roller 130 is fixed to the fixing roller 12.
Press it to 0 with a predetermined pressure. In this way, the pressure roller 13
When 0 is pressed against the fixing roller 120, the fixing roller 1
Since 20 is strongly pressed against the bearing 128, the portion of the fixing roller 120 that is in contact with the bearing 128 (the portion of the outer peripheral surface where the bearing 128 is located) and its vicinity may be deformed. Fixing roller 120
Is deformed, the fixing roller 120 does not rotate smoothly, resulting in poor rotation.

By the way, when the fixing roller 120 and the pressure roller 130 are quickly rotated to increase the speed of image formation,
The fixability may decrease. In order to prevent the deterioration of the fixing property, the pressure roller 130 may be strongly pressed against the fixing roller 120 to increase the nip portion (the portion where the fixing roller 120 and the pressure roller 130 are in contact with each other). In this case, the above deformation is more likely to occur.

In view of the above circumstances, it is an object of the present invention to provide a roller unit in which deformation due to bearings arranged at both ends in the longitudinal direction is prevented.

[0020]

A first roller unit of the present invention for achieving the above object comprises (1) a hollow cylindrical roller, and (2) a spiral shape in a hollow portion of the cylindrical roller. (3) a wire rod that extends from one end in the longitudinal direction of the cylindrical roller to the other end in the longitudinal direction while being wound and that contacts the inner peripheral surface of the cylindrical roller and presses the inner peripheral surface outward. And a bearing that rotatably supports both ends in the longitudinal direction of the linear roller, and (4) the wire is stronger in a portion of the outer circumferential surface where the bearing is located than in other portions. It is characterized in that it is pressed outward by pressure.

Further, the second roller unit of the present invention for achieving the above object comprises (5) a hollow cylindrical roller, and (6) a hollow cylindrical roller wound around the hollow portion of the cylindrical roller in a spiral shape. (7) A wire rod that extends from one end in the longitudinal direction of the cylindrical roller to the other end in the longitudinal direction and that contacts the inner peripheral surface of the cylindrical roller and presses the inner peripheral surface to the outside, (7) The outer periphery of the cylindrical roller (8) The wire rod has a winding pitch of a portion of the outer peripheral surface in which the bearing is located more than a winding pitch of other portions. Is also short.

Here, (9) the portion of the outer peripheral surface of the cylindrical roller where the portion where the winding pitch of the wire is not short is located may be a portion for sandwiching the recording medium.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A schematic structure of an image forming apparatus incorporating an embodiment of a roller unit of the present invention will be described with reference to FIG.

FIG. 1 is a schematic view showing a digital copying machine which is an example of an image forming apparatus in which an embodiment of the roller unit of the present invention is incorporated.

On the top surface of the copying machine 10 is arranged a rectangular parallelepiped original document pressure plate 12 which can be opened and closed. An image reading device 14 that reads an image recorded on a document is arranged below the document pressure plate 12. The upper surface (upper wall) of the image reading device 14 is a document table glass (not shown) on which a document is placed.

An operation panel (not shown) for inputting the number of copies and the like is provided on the front side (front side) of the original pressure plate 12.
Are arranged. A cassette 16 for accommodating a plurality of cut sheets is provided in the lower part of the copying machine 10 so that it can be freely taken in and out of the copying machine 10. A space is formed on the left side of the copying machine 10, and a paper discharge tray 18 on which discharged recording paper is stacked is formed.

A procedure for forming an image with the copying machine 10 will be described.

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 document table glass (not shown) with the image side facing down. Then, the original is pressed and fixed by the original pressure plate 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.

The signal transmitted to the laser scanner 20 is converted into laser light, and this laser light is applied to the photosensitive drum 22 via the scanner mirror 20a and the folding mirror 20b which rotate at high speed. 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 light. This electrostatic latent image is developed with the developer supplied from the developing roller 26 to form a developed image.

On the other hand, a recording medium such as a recording sheet is fed from the cassette 16 by the paper feed roller 28 in the direction of arrow D (paper feed direction), and the transport roller 30 and the registration roller 32.
And is conveyed to the transfer roller 34. Transfer roller 34
Holds the recording medium together with the photosensitive drum 22, and transfers the developed image of the photosensitive drum 22 to the recording medium. The recording medium onto which the developed image is transferred is guided to the fixing device 40 by the transport guide 36. The fixing device 40 includes a fixing roller 50.
A pressure roller 70 (which is an example of the roller unit according to the invention) is arranged. 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 sandwiched between the two rollers 50 and 70, and the developed image is fixed on the recording medium.
The recording medium on which the developed image is fixed in this manner is discharged by the paper discharge rollers 80 and stacked on the paper discharge tray 18.

The basic structure of the fixing device 40 is as follows.
The configuration is the same as that of the conventional fixing device 100 shown in FIG. The fixing device 40 is different from the fixing device 100 in the fixing roller 50. The structure of the fixing roller will be described with reference to FIGS. 2 and 3.

FIG. 2 is a perspective view showing the fixing roller.
FIG. 3 is a schematic diagram showing the inside of the fixing roller.

The fixing roller 50 is a pipe-shaped (hollow cylindrical) core metal 5 made of an alloy of aluminum and magnesium.
2 (which is an example of a cylindrical roller according to the present invention). The outer diameter of the central portion of the core metal 52 in the longitudinal direction is smaller than the outer diameter of both end portions in the longitudinal direction. Therefore, the cored bar 52 has a so-called inverted crown shape. In this way, since the cored bar 52 has an inverted crown shape, the nipping portion formed between the fixing roller 50 and the pressure roller 70 has a clamping force at both ends in the longitudinal direction of the fixing roller 50 (pressing a recording medium into pressure contact). Force) is larger than the central portion in the longitudinal direction. Therefore, the recording medium conveyed while being nipped by the fixing roller 50 and the pressure roller 70 does not become twisted or wrinkled. The diameter of both end portions of the cored bar 52 in the longitudinal direction is 0.07 mm larger than that of the central portion in the longitudinal direction.
It is about 0.13 mm large.

The cored bar 52 is cut so that the thickness of the cored bar 52 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 a fluororesin having a high release property, an oil-impregnated silicone rubber, or a silicone resin layer on which a fluororesin layer is formed. Also,
The fixing roller 50 is provided with bearings 56 that come into contact with the outer wall surface 52b of the cored bar 52 and rotatably support both longitudinal ends of the cored bar 52. The bearing 56 is arranged at a position (outside the paper passing area) that is out of the paper passing area (the area through which the recording medium passes). As described above, both ends of the pressure roller 70 in the longitudinal direction are pressed toward the fixing roller 50 by the pressure springs 72. Therefore, the pressure roller 70 is pressed against the fixing roller 50 to form a nip portion (a portion where the rollers 50 and 70 contact each other to sandwich the recording medium).

A coil spring 60 (which is an example of a wire rod according to the present invention) wound in a spiral shape is arranged in the hollow portion of the cored bar 52 (inside the fixing roller 50). The outer diameter of the coil spring 60 is 0.1 mm to 0.
It is as large as 5 mm. Therefore, the coil spring 60 contacts the inner wall surface 52a (which is an example of the inner peripheral surface according to the invention) 52a surrounding the hollow portion of the cored bar 52 and pushes (presses) the inner wall surface 52a to the outside. ). The coil spring 60 is fixed to the cored bar 52 by this pressing force and rotates together with the cored bar 52.

The winding pitch P1 of the coil spring 60 in the portion of the outer wall surface 52b (which is an example of the outer peripheral surface in the present invention) of the core metal 52 where the bearing 56 is located is determined by the outer wall surface 52b.
Of the coil spring 6 in a portion of the bearing 56 where the bearing 56 is not located
It is shorter than the winding pitch P2 of 0. That is, the coil spring 60
The winding pitch P1 of the longitudinal end portions 62, 62 of the coil spring 60 is
Shorter than. Therefore, the coil spring 60 causes the outer wall surface 5 to
Both longitudinal end portions of 2 are pressed outward with a stronger force than the longitudinal central portion thereof.

When the pressure roller 70 is strongly pressed against the fixing roller 50, the cored bar 52 is strongly pressed against the bearing 56. However, since the longitudinal ends 62, 62 of the coil spring 60 sufficiently reinforce the longitudinal ends of the cored bar 52, the longitudinal ends of the cored bar 52 are not deformed.
Therefore, the winding pitch P1 is
It does not deform due to the bearing 56. If the winding pitch P2 of the central portion 64 of the coil spring 60 in the longitudinal direction is made too short, the core 52 is less likely to be heated by the halogen heater 122 (see FIG. 4). Therefore, the winding pitch P2 cannot be shortened.

Further, in order to rotate the fixing roller 50 and the pressure roller 70 quickly to increase the speed of image formation, even if the pressure roller 70 is strongly pressed against the fixing roller 50, as described above, the coil spring 60 is pressed. Longitudinal ends 62, 62
Since the winding pitch P1 of 1 is short, both ends of the cored bar 52 in the longitudinal direction are not deformed.

When manufacturing the fixing roller 50 described above,
A coil spring 60 having an outer diameter larger by 0.1 mm to 0.5 mm than the inner diameter of the core metal 52 is prepared, and the coil spring 60 is contracted in a diameter reducing direction (direction in which winding becomes tight, direction in which outer diameter becomes smaller). In the twisted state, it is inserted into the hollow part of the cored bar 52. After the insertion is completed, the twist of the coil spring 60 is released. As a result, the outer peripheral surface of the coil spring 60 becomes the inner wall surface 5
The inner wall surface 52a is pushed outward by coming into contact with 2a.

[0040]

As described above, in the first roller unit of the present invention, the portion of the outer peripheral surface where the bearing is located is pressed outward with a stronger pressure than the other portions, so that the cylindrical roller is used as the bearing. Even if it is strongly pressed against, the part of the outer peripheral surface where the bearing is located does not deform.

In the second roller unit of the present invention, the winding pitch of the portion of the outer peripheral surface where the bearing is located is shorter than the winding pitch of the other portion of the outer peripheral surface. It is pressed outward with a stronger pressure than the part. Therefore, even if the cylindrical roller is strongly pressed against the bearing, the portion of the outer peripheral surface where the bearing is located does not deform.

Here, in the case where the portion of the outer peripheral surface of the cylindrical roller where the portion where the winding pitch of the wire is not short is located is a portion for sandwiching the recording medium, the cylindrical roller and other rollers. In order to increase the nip part (the part where both rollers come into contact with each other) when the recording medium is nipped and conveyed between and, even if other rollers are strongly pressed against the cylindrical roller, the bearing on the outer peripheral surface The positioned part does not deform.

[Brief description of drawings]

FIG. 1 is a schematic view showing a digital copying machine which is 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 perspective view showing a fixing roller.

FIG. 3 is a schematic diagram showing the inside of the fixing roller of FIG.

FIG. 4 is a schematic diagram showing a schematic configuration of a conventional fixing device.

FIG. 5 is a cross-sectional view showing a fixing roller having a coil spring inserted therein.

[Explanation of symbols]

50 fixing roller 52 core metal 52a Inner wall surface of core metal 52b Core wall outer wall 56 bearing 60 coil spring P1, P2 Coil spring winding pitch

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tsukasa Teshima             6-3-3 Shimorenjaku, Mitaka City, Tokyo             Within the corporation (72) Inventor Kazuhiro Murakami             6-3-3 Shimorenjaku, Mitaka City, Tokyo             Within the corporation F term (reference) 2H033 AA21 AA31 BA08 BA10 BA11                       BB13 BB30                 3F049 CA04 CA14 CA16 CA17 DA11                       LA01 LB03                 3J059 AA03 BA06 GA50                 3J103 AA02 AA42 CA66 FA03 FA26                       GA66 GA74

Claims (3)

[Claims] 1. A hollow cylindrical roller, which extends from one end in the longitudinal direction of the cylindrical roller to the other end in the longitudinal direction while being spirally wound in the hollow portion of the cylindrical roller, and within the cylindrical roller. A wire rod that comes into contact with the circumferential surface and presses the inner circumferential surface outward, and a bearing that comes into contact with the outer circumferential surface of the cylindrical roller and rotatably supports both longitudinal ends of the cylindrical roller; A roller unit, wherein a portion of the outer peripheral surface where the bearing is located is pressed outward with a stronger pressure than other portions. 2. A hollow cylindrical roller, which extends from one end in the longitudinal direction to the other end in the longitudinal direction of the cylindrical roller while being spirally wound in the hollow portion of the cylindrical roller and within the cylindrical roller. A wire rod that comes into contact with the circumferential surface and presses the inner circumferential surface outward, and a bearing that comes into contact with the outer circumferential surface of the cylindrical roller and rotatably supports both longitudinal ends of the cylindrical roller; A roller unit, wherein a winding pitch of a portion of the outer peripheral surface where the bearing is located is shorter than a winding pitch of other portions. 3. The portion of the outer peripheral surface of the cylindrical roller in which a portion where the winding pitch of the wire is not short is located is a portion for sandwiching a recording medium. Roller unit.