JP2002106547A - Core bar structure and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a core bar structure capable of maintaining a high rigidity with a wall thinner than conventional one even when aluminum alloy is used. SOLUTION: The core bar structure relates to a hollow core bar with rounded section. The core bar structure is equipped with a group of central ribs 25 set at a central region of axial direction of an inner periphery 22b and at least each one periphery rib 26 set at both outsides of the central ribs 25. The group of the central ribs 25 is equipped with a central rib 25a located at an axial center and end rib 25b located at both sides of the group of the central ribs 25. A pitch S1 of the periphery rib 26 and the end rib 25b is equal to a pitch S1 between the end ribs.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cored metal structure having a hollow and circular cross section, and an image forming apparatus such as a copying machine, a facsimile, and a printer provided with a fixing roller having the cored metal structure.

[0002]

2. Description of the Related Art As shown in FIG.
The fixing roller 2 used in an electrophotographic image forming apparatus such as a facsimile has a halogen heater 2c in the roller.
And the like, and a nip portion N is formed by being pressed against the pressure roller 3. The fixing roller 2 melts and fixes the toner on the transfer paper P sent to the nip N by the pressure of the nip N and the radiant heat from the heat generating device.

[0003] Conventionally, a fixing roller has been made of an aluminum alloy as a material for securing the heat conductivity and rigidity of the core metal. The general configuration of such a fixing roller is a roller having a cylindrical thin metal core as a base, a powder coating of an outer peripheral surface thereof with a fluorine film or the like, followed by firing and coating a release layer.

In recent years, the thickness of the roller core of the fixing roller has been required to be further reduced in order to improve the thermal conductivity. That is, it is desired to shorten the time required to reach a temperature at which fixing can be performed by reducing the thickness of the roller core metal (rise time of the fixing roller) to promote power saving of a copying machine or the like.

[0005]

However, as described above, the fixing roller needs to have high rigidity in terms of its function, and the thickness of the roller core metal cannot be reduced unnecessarily.

That is, when the thickness of the roller core metal is reduced, as shown in FIG. 8A, the fixing roller 2 is bent or deformed by the pressing force from the pressing roller 3, or as shown in FIG.
As shown in (B), there is a possibility that the pressing force from the pressing roller 3 may cause a deformation such that the outer diameter of the fixing roller 2 is reduced from H1 to H2 and deformed.

[0007] The process limit point at which the thickness can be uniformly reduced by the diamond cutting tool is 0.8 mm in the conventional roller core, and at this thickness, the rise time of the fixing roller is almost the same. 30 seconds is the limit. It was also desired to increase the rise time. Therefore, there has been a demand for simultaneously achieving high rigidity and thinning.

Attempts have been made to use iron or stainless steel as an alternative material to the aluminum alloy material. The thermal conductivity is lower than that of the alloy material, and the uniformity of the temperature distribution is not sufficiently obtained.

It is an object of the present invention to provide an image forming apparatus having a cored metal structure which is thinner than conventional ones and which can ensure high rigidity even when an aluminum alloy material is used, and an image forming apparatus provided with a fixing roller having the cored metal structure. It is to provide a device.

[0010]

In order to achieve the above-mentioned object, a first aspect of the present invention relates to a hollow core metal structure having a circular cross section and a center provided in an axially central region of an inner peripheral surface. A plurality of ribs; and at least one peripheral rib provided on both outer sides of the center rib group. The center rib group includes a center rib located at an axial center, and both ends of the center rib group. And end ribs respectively located at
The pitch between the peripheral ribs and the end ribs is equal to the pitch between the end ribs.

According to a second aspect of the present invention, in the cored metal structure according to the first aspect, the cored bar has a drum shape.

According to a third aspect of the present invention, in the image forming apparatus provided with a fixing roller, the fixing roller is a hollow core metal structure having a circular cross section, and the axial direction of an inner peripheral surface of the core metal is provided. A central rib group provided in a central region of the central rib group and at least one peripheral rib provided on both outer sides of the central rib group. The central rib group has a center located at the center in the axial direction. Ribs, and end ribs located at both ends of the central rib group, respectively, and the peripheral ribs and the end ribs have a roller core having a pitch equal to the pitch between the end ribs. An image forming apparatus characterized in that:

According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the core metal structure has a drum shape.

According to a fifth aspect of the present invention, in the image forming apparatus of the third aspect, the rib is continuous so that the rib and a flat surface adjacent to the rib have good thermal conductivity. It is characterized by having.

According to a sixth aspect of the present invention, in the image forming apparatus according to the third aspect, a minute concave portion for wrinkling the fixing paper is formed on an outer peripheral surface of the roller core. .

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a partial cross-sectional view showing a configuration of a roller core of a fixing roller provided in an electrophotographic image forming apparatus as an example of a core metal structure according to the first embodiment of the present invention.

As shown in FIG. 1, the roller mandrel 20 has a main body 22 wider than the paper passing area L and journals 27 and 28 smaller in diameter than the main body 22 formed integrally at both ends thereof.
And The roller core 20 is made of an aluminum alloy.

The main body 22 is formed in a drum shape. The volume of the main body 22 is set to, for example, about 0.08 mm, and is appropriately set according to product performance. The drum volume is defined as the outer diameter D2 outside the paper passing area L and the outer diameter D at the center.
It is a difference D1-D2 from 1.

The main body 22 has a space in which a heating device can be inserted, and has a circular cross section.
Further, on the inner peripheral surface 22b of the main body 22, a group of ribs for increasing rigidity is formed.

The rib group includes a central rib group 25 provided in a central region in the axial direction, and peripheral ribs 26 disposed on both outer sides of the central rib group 25 in the axial direction.

The central rib group 25 includes a central rib 25a located at the center in the axial direction, and end ribs 25b located at both axial ends of the central rib group 25, respectively.
a and the pair of left and right end ribs 25b are equally spaced S2.
Are located in

The peripheral rib 26 has a width S of the central rib group 25 from the axial center of the end rib 25b of the central rib group 25.
1 are provided on the inner peripheral surface 22b at the same distance from each other.

FIG. 2 is an enlarged view of a cross section of the rib, and FIG.
Indicates a semicircular rib, (B) indicates a semicircular rib that is smoothly continuous, (C) indicates an isosceles triangular rib, and (D) indicates a U-shaped rib. , (E) show trapezoidal ribs. Although FIG. 2 shows the case of the center rib 25a as a representative, the same applies to other ribs.

By forming the ribs on the inner peripheral surface of the roller core to increase the rigidity, the thickness of the roller core can be reduced. In particular, the density of the ribs is increased at the axial center of the roller core, which tends to bend and deform when pressure is applied from a pressure roller or the like, so that high strength can be obtained with a small number of ribs. In the present embodiment, even when the thickness of the flat surface of the roller core is reduced to 0.3 mm, the same rigidity as that of the 0.8 mm thick roller core without ribs can be maintained. .

Furthermore, since the density of the ribs is increased at the axial center of the roller core, which tends to bend and deform when pressure is applied from a pressure roller or the like, the volume of the roller core can be reduced, and the heat capacity can be reduced. Can be reduced, the temperature rise by the heat source can be speeded up, and power saving can be achieved.

Further, since the rib arrangement density at the central portion of the roller core is increased, the temperature distribution at which the temperature at the central portion is normally increased can be made uniform. In particular, FIG.
(B), (C), and (E), the rib and the inner peripheral surface 2
By smoothly connecting the flat surface 2b to the flat surface 2b, it is possible to smoothly change the temperature unevenness of the surface when the temperature is increased,
Fixing unevenness can be further reduced.

Further, since the main body portion 22 of the roller core 20 has a drum shape, a circumferential difference can be provided in the axial direction of the fixing roller, whereby the feed amount (linear speed) at the time of fixing by rotation is different. Can be provided. Since a difference can be provided in the feed amount in this way, tension can be applied in both width directions of the transfer paper, thereby preventing the transfer paper from being twisted or wrinkled.

FIG. 3 is a further enlarged view of the cross section of the rib.
As shown in FIG. 3, by forming a minute concave portion 22 c that forms an undulating shape on the outer peripheral surface of the main body portion 22 of the roller core metal 20, when used as a fixing roller, the transfer paper is less likely to be twisted and wrinkled. can do. The depth of the minute concave portion 22c is set, for example, to 1 to 10 μm, preferably 3 μm or less.

FIG. 4 is a longitudinal sectional view of a fixing device provided with a fixing roller having the roller core of FIG. As shown in FIG. 4, the fixing device 1 includes a fixing roller 2 having a surface layer 21 formed on the outer surface of the roller core shown in FIG. 1, a pressing roller 3 for pressing the transfer paper against the fixing roller, and a roller. It comprises a bearing 2a for supporting the journal of the cored bar, a drive gear for driving the fixing roller, and a heat generating device having a halogen heater 2c mounted inside the fixing roller.

In the fixing roller, a surface layer 21 is formed by coating an outer peripheral surface of a roller core with a release layer made of a fluororesin layer. The surface layer 21 is formed to a thickness of, for example, 10 to 30 μm.

FIG. 5 is a partial sectional view showing a roller core of a fixing roller according to a second embodiment of the present invention. As shown in FIG. 5, this roller core differs from the roller core of FIG. 1 in that the center rib group 25 has an intermediate rib 25c between the center rib 25a and the end rib 25b. This is the point that the peripheral rib 26 is composed of the outer peripheral rib 26a and the inner peripheral rib 26b.

In this case, the width S1 of the central rib group 25
S1 between the end rib 25b and the inner peripheral rib 26b
And the width S between the inner peripheral rib 26b and the outer peripheral rib 26a
1 is equal.

As described above, the center rib group 25 includes the center rib 2
5a and the end rib 25b, the center rib 2
One or more intermediate ribs 25c may be formed between 5a and the end rib 25b.

The peripheral ribs 26 may be formed from a plurality of ribs. In this case, the distance between the innermost peripheral rib 26b and the next outer peripheral rib 26a is the width S
It is preferably set to 1.

FIG. 6 is an explanatory view showing the main structure of an image forming apparatus provided with a fixing roller having a roller core as a core metal structure of the present invention. As shown in FIG. 6, the image forming apparatus includes a photosensitive drum 4a on which an electrostatic latent image is formed,
A charging roller 4b for performing charging processing in contact with or in proximity to the photosensitive drum 4a; a developing roller 4e for attaching toner to an electrostatic latent image on the photosensitive drum 4a; and a DC roller for applying a DC voltage to the charging roller 4e. Power supply 4h, photosensitive drum 4
a transfer roller 4f for transferring the toner image on the transfer paper P to the transfer paper P conveyed from the paper supply unit, and a cleaning device 4 for removing and collecting residual toner on the surface of the photosensitive drum 4a.
g, a surface potential meter 4 d for measuring the surface potential of the photosensitive drum 4 a, and the fixing device 1 having the fixing roller 2 and the pressure roller 3. Reference numeral 4c indicates exposure such as laser light or light reflected from a document.

An image forming operation in the image forming apparatus configured as described above will be described. First, a DC voltage is supplied from a power supply 4h to the charging roller 4b in contact with the photosensitive drum 4a, so that the photosensitive drum 4a
Is uniformly charged to a high potential.

Immediately thereafter, the surface of the photosensitive drum 4a is exposed to light 4
When c is applied, the potential of the exposed portion decreases. Since the exposure 4c has a light amount distribution corresponding to the image density, the exposure 4c forms a potential distribution with respect to the recorded image, that is, an electrostatic latent image on the surface of the photosensitive drum 4a.

Next, when the portion where the electrostatic latent image is formed passes through the developing roller 4e, toner adheres according to the level of the potential, and a toner image is formed by visualizing the electrostatic latent image. You. Next, the transfer paper P is conveyed at a predetermined timing to a portion where the toner image is formed, and overlaps the toner image. After the toner image is transferred onto the transfer sheet P by the transfer roller 4f, the transfer sheet P is separated from the photosensitive drum 4a.

Next, the separated transfer paper P is conveyed through a conveyance path, is subjected to heat and pressure fixing by the fixing roller 2 and the pressure roller 3, and is then discharged out of the apparatus. After the completion of the transfer, the surface of the photosensitive drum 4a is
g, and the residual charge is erased by a residual charge erasing means (not shown) to prepare for the next image forming process.

At this time, since a fixing roller having a thinned roller core is used as the fixing roller, the rate of temperature rise of the fixing roller can be improved, the rise time can be greatly reduced, and power saving can be achieved. Can also be achieved. That is, both the warm-up time and the lighting time of the halogen heater can be reduced.

The present invention is not limited to the above embodiment. For example, in the above-described embodiment, the case where the number of the central rib groups is three and the case where the number is five are described. Further, in the above embodiment, the case of one peripheral rib and the case of two peripheral ribs have been described, but three or more peripheral ribs may be used. That is, various modifications can be made without departing from the gist of the present invention.

[0042]

As described above, according to the core metal structure of the present invention, it is possible to obtain a core metal structure that can be reduced in thickness while maintaining rigidity.

When a fixing roller is formed using this core metal structure, since the roller core metal has a convex rib on the inner peripheral surface, the rigidity of the roller is ensured and the thickness of the roller surface is reduced. Therefore, the rise time of the fixing roller can be significantly reduced.

Further, according to the image forming apparatus provided with the fixing roller using the metal core structure of the present invention, the rise time of the fixing roller can be greatly reduced, so that the image forming time can be reduced. Power saving can be achieved.

Further, when undulation is formed by providing a minute dent on the outer peripheral surface of the roller core, it is possible to almost completely prevent wrinkles, twists, and the like of the fixing paper, and to minimize fixing unevenness. it can.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing a configuration of a roller core of a fixing roller included in an electrophotographic image forming apparatus as an example of a core metal structure according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of a cross section of a rib, (A) shows a semicircular rib, (B) shows a semicircular rib that is smoothly continuous, and (C) shows an isosceles triangular shape. The ribs of
(D) shows a U-shaped rib, and (E) shows a trapezoidal rib.

FIG. 3 is a further enlarged view of a cross section of a rib.

FIG. 4 is a longitudinal sectional view of a fixing device provided with a fixing roller having the roller core of FIG. 1;

FIG. 5 is a partial sectional view showing a roller core of a fixing roller according to a second embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a main configuration of an image forming apparatus including a fixing roller having a roller core as a core metal structure of the present invention.

FIG. 7 is a diagram illustrating a fixing roller used in an electrophotographic image forming apparatus.

FIG. 8 is a diagram showing a technical problem of a thin fixing roller;
(A) shows the case of the bending deformation, and (B) shows the case of the crushing deformation.

[Explanation of symbols]

 2 Fixing Roller 20 Roller Core (Core Metal Structure) 22 Main Body 22b Inner Peripheral Surface 22c Small Concave 25 Central Rib Group 25a Central Rib 25b End Rib 26 Peripheral Rib S1 Width (Pitch) S2 Width (Pitch)

Continued on the front page (72) Inventor Makoto Murata 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (Reference) 2H033 AA21 BB03 BB13 3J103 AA02 AA07 AA12 AA14 AA41 AA51 AA72 AA73 BA03 BA17 BA34 CA03 FA01 FA03 FA20 GA02 GA57 GA58 GA60 GA66 HA03 HA04 HA15 HA37 HA43 HA54

Claims (6)

[Claims] 1. A core metal structure having a hollow and circular cross section, a central rib group provided in an axially central region of an inner peripheral surface, and at least a central rib group provided on both outer sides of the central rib group. A central rib group located at the center in the axial direction;
A core metal structure, comprising: end ribs located at both ends of a central rib group, wherein a pitch between the peripheral ribs and the end ribs is equal to a pitch between the end ribs. 2. The core metal structure according to claim 1, wherein the core metal has a drum shape. 3. An image forming apparatus provided with a fixing roller, wherein the fixing roller is a hollow core metal structure having a circular cross section, and is provided in an axial central region of an inner peripheral surface of the core metal. A central rib group, and at least one peripheral rib respectively provided on both outer sides of the central rib group. The central rib group includes a central rib located at the center in the axial direction, and a central rib group. An image forming apparatus, comprising: an end rib located at each of both ends, wherein a pitch between the peripheral rib and the end rib is equal to a pitch between the end ribs. . 4. The image forming apparatus according to claim 3, wherein the core metal structure has a drum shape. 5. The image forming apparatus according to claim 3, wherein the rib is continuous so that the rib and a flat surface adjacent to the rib have good thermal conductivity. 6. The image forming apparatus according to claim 3, wherein a fine concave portion for wrinkling the fixing paper is formed on an outer peripheral surface of the roller core.