JPH064006A - Fixing device - Google Patents

Abstract

PURPOSE:To obtain an excellent transferred image regardless of the size of a transfer paper to suppress the wear of a releasing material of a heating roller and to improve the durability of the roller by disposing a heater pipe extending over both contact areas of the small and the large transfer papers in the axial direction of the end parts of the heating roller. CONSTITUTION:A fixing device 1 is constituted of the heating roller 3 obtained by disposing a xenon lamp as a heater 2 inside, the stick-like heat pipe 4 disposed in a hollow space S inside the core bar 3A of the roller 3 and a press- contact roller 5 arranged adjacent to the roller 3. The outer-shell 4a of the pipe 4 is formed by a hollow cylinder constituted of a shape memory alloy. Besides, the cavity part 4b thereof is sealed with a specific amount of a solvent. Then, the pipe 4 is supported by a bracket 10 welded and fixed to both side surfaces of the roller 3 and disposed at an optional short section extending over the small contact area L2 and the large contact area L1 of the roller 3. Therefore, the thermal transfer of the surface of the roller is quickened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat fixing device in an image forming apparatus such as a fax machine or a printer.

[0002]

2. Description of the Related Art Generally, a heat roll fixing device coats a core metal with a release member (for example, PTFE), and a heating roller provided with a heater inside the core metal, and the heating roller is pressed. In order to form a nip portion, a pressure roller whose surface is covered with an elastic body (for example, Si rubber) is used. Then, the toner image is fixed on the transfer paper by passing the transfer paper carrying the toner image through the formed nip portion.

By the way, when the surface temperature of the heating roller is low, insufficient fixing occurs on the transfer paper, and when the surface temperature is too high, the release material on the roller surface deteriorates, so that the surface temperature of the heating roller becomes axial. It is desirable to keep it uniform.

However, in a high-speed image forming apparatus (high-speed copying machine), when copying small size transfer paper continuously, the roller surface through which the transfer paper passes is controlled by measuring the temperature with a temperature detecting member such as a thermistor. Therefore, the temperature of the transfer paper is maintained at a constant temperature range, but at the roller surface area that exceeds the width of the small size transfer paper, the transfer paper does not carry heat and the heat quantity continues to be high, resulting in high temperature. .

Therefore, in many image forming apparatuses, the release material at the end of the heating roller, which is in contact with the small-sized transfer paper, deteriorates, wear of the roller surface is promoted, and durability becomes a problem.

[0006]

Therefore, for example, in the device disclosed in Japanese Utility Model Laid-Open No. 58-38165, a heat pipe is embedded in a core metal of a heating roller to make the surface temperature of the roller uniform. However, in such a device, there are problems that the response speed of the temperature moving on the roller is slow and the cost of the heat pipe itself is high.

Further, in the invention described in Japanese Utility Model Laid-Open No. 54-76239, there is proposed a method for making the temperature distribution on the heating roller surface uniform while the heat supply amount of the heat generation source is in the standby state of the equipment. If this is done, the temperature of the roller surface will be uniform in the standby state, but when continuously copying small size transfer paper, etc., the temperature of the end of the heating roller that is not in contact with the small size transfer paper will rise and The release material on the roller surface deteriorates.

[0008]

In view of the above, the present invention comprises a heating roller having a built-in heater and a pressure roller which is in pressure contact with the heating roller, and at least one heat pipe is provided inside the heating roller. In the fixing device having the heat pipe, the heat pipe is arranged over both the contact area with the small size transfer paper and the contact area with the large size transfer paper in the axial direction of the end portion of the heating roller, or With respect to the heat pipe arranged over the entire axial direction of the heating roller, the thickness of the core metal of the pressure roller may be different between the contact area with the large size transfer paper and the contact area with the small size transfer paper. With respect to the light emission distribution of the heater, the amount of heat in the contact area with the small-size transfer paper was increased and the amount of heat in the contact area with the large-size transfer paper was decreased.

Further, the core metal material in the contact area of the heating roller with the large size transfer paper is made of a material having high thermal conductivity, and the core metal material of the contact area of the heating roller with the small size transfer paper is heated. It was made of a material with low conductivity.

[0010]

According to the first aspect of the invention, the heat transfer on the roller surface is accelerated by arranging a short heat pipe at a portion having a large temperature drop without using a long heat pipe extending over the entire core of the heating roller. According to the second aspect of the present invention, the outer shape of the heat pipe is made of a shape memory alloy, so that the temperature movement of the roller surface is promoted by reacting at high temperature and extending the heat pipe itself toward the low temperature portion. It

Further, according to the invention of claim 3, the thickness of the core metal of the heater for the heat pipe in the heating roller is different between the end portion and the central portion of the heating roller. You can adjust the amount of heat that arrives at the heat pipe. Also, when the copy speed is high, the heat capacity of the heat pipe may become insufficient, but even at this time, the heat quantity is intensively and rapidly supplied to the portion where the heat consumption on the roller surface is large due to the difference in the thickness of the core metal. . Further, in the invention of claim 4, the thickness of the core metal is thin at the center and thick at the ends, and in addition, the light emission distribution of the heater disposed inside the heating roller is set so that the center is large and the ends are small. With this configuration, the amount of heat is more intensively supplied from the heater to the heat pipe.

According to the fifth aspect of the present invention, the end material in the axial direction of the core of the heating roller is made of a material having a high thermal conductivity, so that the end temperature generated during continuous copying of small size transfer paper can be controlled. The rise can be prevented by transferring heat to the central part of the roller. Further, in the invention of claim 6, the heat pipe is formed in the heating roller core metal, so that the heat amount is more intensively supplied from the heater to the heat pipe. It

[0013]

Embodiments of the present invention will be described below in order. FIG. 1 shows a first embodiment, and reference numeral 1 shows the entire fixing device. The fixing device 1 includes a heating roller 3 in which a xenon lamp 2 is arranged as a heater, a stick-shaped heat pipe 4 arranged in a hollow space S inside a core metal 3A of the heating roller 3, and a heating roller 3 And a pressure roller 5 disposed adjacent to the pressure roller 5.

The surface of the heating roller 3 is made of Teflon, and the surface of the pressure contact roller 5 is made of silicon rubber. Both are pressed against each other to form a nip portion. A bearing 6 is arranged in the journal portion 3a of the heating roller 3 via a heat insulating bush member 7, and the bearing 6 holds the heating roller 3 rotatably on the unit side plate 8. A plurality of hollow spaces S are formed in the core metal 3A on the front surface side of the heating roller 3 in the circumferential direction. A drive gear 9 is provided on one side of the journal portion 3a to rotate the heating roller 3.

On the other hand, the pressure roller 5 is rotatably supported by the unit side plate 8 and is moved in the direction of the arrow at a suitable time by a pressing mechanism (not shown). Reference numeral L1 indicates a contact area (hereinafter, referred to as “large contact area L1”) on the surface of the heating roller 3 with the large-sized transfer paper, and L2 indicates a contact area with the small-sized transfer paper (hereinafter, “small contact”). Region L2 ”).

The heat pipe 4 will be described below.
The heat pipe 4 has a hollow cylindrical shape whose outer shell 4a is made of a shape memory alloy, and has a hollow portion 4b.
A predetermined amount of solvent is enclosed, and is supported by brackets 10 that are welded and fixed to both side surfaces of the heating roller 3, and is arranged in an arbitrary short section extending from the small contact area L2 and the large contact area L1 of the heating roller 3. .

FIG. 2 is a diagram showing the gradient of the surface temperature in the axial direction of the heating roller 3 when a small size transfer paper is continuously passed. The broken line shows the surface temperature gradient of the conventional heating roller, the thin line shows the surface temperature gradient of the heating roller provided with the heat pipe 4, and the thick solid line shows the small contact area of the heat pipe 4 using the shape memory alloy of this embodiment. The heating roller 3 when disposed near the boundary between L2 and the large contact area L1
The surface temperature gradient of each is shown.

According to FIG. 2, it can be seen that the conventional heating roller not provided with the heat pipe 4 has a large temperature gradient in the axial direction when the small size transfer paper is continuously fed. This takes heat when a small-sized transfer sheet passes over the heating roller 3, and also makes a generally known temperature detecting member contact the small contact area L2 of the heating roller to cause the fixing roller 3 to move. Since the surface temperature is controlled, the small contact region L2 is kept at a constant temperature, but the large contact region L1 has a high temperature because there is no heat transfer.

The surface temperature gradient of the fixing roller 3 in which the heat pipe 4 is axially arranged over the small contact region L2 and the large contact region L1 has a significantly relaxed axial temperature gradient. That is, it can be said that there is no temperature difference between the large contact area L1 and the small contact area L2. Further, in the present embodiment in which the heat pipe 4 is made of a shape memory alloy and is arranged near the boundary between the large contact region L1 and the small contact region L2, it can be seen that the temperature gradient is further alleviated. this is,
Since the heat transfer ability of the heat pipe 4 is a shape memory alloy, the higher the surface temperature gradient of the heating roller 3, the greater the expansion of the heat pipe 4 (shape memory alloy), and the faster the heat transfer rate (heat transfer ability). It indicates that
That is, when a small size transfer paper is continuously copied, only the heat of the small contact area L2 is taken and the temperature of the large contact area L1 rises. Then, the temperature rise causes the shape-memory alloy heat pipe 4 to move to the small contact region L2 side, and the heat amount that has been mainly provided to the large contact region L1 until now is supplied to the contact region L2. The temperature rise of L1 in the relatively large contact area is suppressed.

In the following embodiments, those having the same operations as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 3 shows a second embodiment of the present invention. In the second embodiment, the material of the core metal 3A of the heating roller 3 is changed in the axial direction in order to quickly supply the amount of heat of the xenon lamp 2, which is a heater, to the heat amount insufficient portion on the surface of the heating roller 3.

That is, in the core metal 3A of the heating roller 3, the material 3A1 having a high thermal conductivity is provided in the vicinity of both ends (the contact area L1 with the large size transfer paper) and the central part (the contact area L2 with the small size transfer paper). 3A2, which has a low thermal conductivity, is used for each of 3) and 3A1 and 3A having different thermal conductivities.
2 are welded together.

Further, heat insulating bush members 7 are provided between the journal portion 3a of the heating roller 3 and the bearing 6 and between the journal portion 3a and the driving gear 9, respectively. It has a structure that makes it hard to escape.

According to this structure, the surface temperature of the heating roller 3 when the apparatus is on standby or standing up is such that the heat conduction from the both ends of the heating roller 3 to the bearing 6 or the unit side plate 8 is blocked by the heat insulating bush member 7. Therefore, it is kept constant.

On the other hand, when the apparatus is activated and the large-sized transfer paper is continuously copied, the large-sized transfer paper uniformly takes heat from the entire surface of the heating roller 3, that is, the axial length (L1 + L2 + L1) of the roller surface. Therefore, the temperature gradient on the surface of the heating roller 3 is kept uniform.

Further, when continuous copying is performed with the small-size transfer paper, in the conventional copy, the small-size transfer paper comes into contact only with the central portion, that is, the small contact area L2, so that only the heat of the area L2 is taken away. Because of this, the heat accumulated in the L1 portion, which is a large contact area located at both ends of the roller, becomes abnormally high temperature. However, as in this embodiment, the core metal material at both ends of the roller is the material 3A1 having high thermal conductivity. As a result, the heat storage at both ends can be moved to the center, and the temperature gradient on the surface of the heating roller 3 can be kept uniform.

FIG. 5 shows a heat pipe 4 which is long in the axial direction, added to the second embodiment. A plurality of heat pipes 4 are arranged over both the member 3A1 having a high thermal conductivity and the member 3A2 having a low thermal conductivity of the heating roller 3 and along the circumferential direction of the roller 3. By disposing the heat pipe 4 in this manner, the temperature gradient on the surface of the heating roller 3 can be made uniform more quickly even during continuous copying of small size transfer paper.

In the fixing device 1 having the heating roller 3 configured as described above, the surface temperature gradient in the axial direction of the heating roller 3 during continuous copying with a small size transfer paper is shown in FIG.
Shown in.

In FIG. 4, the broken line shows the temperature gradient on the surface of the conventional heating roller shown in FIG. 2, and the thin solid line shows the core metal material of the second embodiment shown in FIG. , 3A2, and thick solid lines indicate the respective surface temperature gradients of the heating roller 3 to which the heat pipe 4 according to the third embodiment shown in FIG. 5 is added.

It can be seen from FIG. 4 that the third embodiment using the heat pipe 4 with different core metal materials is remarkably excellent in equalizing the temperature gradient on the surface of the heating roller 3 as compared with the conventional heating roller. I understand.

Next, FIG. 6 shows a fourth embodiment in which the thickness of the core metal 3A of the heating roller 3 is changed in the axial direction.

All transfer contact areas, ie (L1 + L2 +
Around the heat pipe 4 disposed over L1), the central portion 30A of the core metal 3A facing the xenon lamp 2 side is
It is configured to be thicker than both end portions 30B, and heat transfer from the xenon lamp 2 at both end portions 30B is slower than that at the central portion 30A. Further, in this embodiment, the bearing 6
Is disposed directly on the journal portion 3a of the heating roller 3 without interposing a heat insulating bush material, and the heat of the heating roller 3 escapes to the unit side plate 8 by the bearing 6 and the drive gear 9 when the equipment is standing up or in standby. Has become.

In such a structure, when a large-sized transfer sheet is continuously copied, the thickness of the core metal portion 30B located at the end portion of the heating roller 3 is made thinner than that of the central portion 30A, so that the heat quantity is insufficient. The amount of heat of the xenon lamp 2 can be quickly supplied to the end portion of the heating roller 3. That is, it is possible to prevent insufficient fixing of the portion of the large-sized transfer paper that comes into contact with the end of the heating roller 3 due to the insufficient amount of heat generated when the core metal 3A has the same thickness.

Next, FIG. 7 shows that the thickness of the cored bar 30A located in the central portion of the heating roller 3 which is the contact area L2 with the small size transfer paper is thicker than both sides 30B of the cored bar. It is a fifth embodiment of the present invention. In the present embodiment, the drive gear 9 and the bearing 6 are arranged in the journal portion 3a via the heat insulating bush material 7 so that heat is unlikely to escape. In addition, the light emission distribution of the xenon lamp 2 has a small contact area L as compared with both ends of the heating roller 3 located in the large contact area L1.
The light is distributed so that the amount of light emission increases in the central portion of the heating roller located at 2.

In such a structure, the amount of heat escaping from the end portion of the heating roller 3 can be reduced by providing the heat insulating bush materials 7 and 7 ', so that the surface temperature of the heating roller 3 is kept uniform and a large-sized transfer paper can be obtained. Even when continuous copying is performed, it is possible to prevent insufficient fixing of the image on the large-sized transfer paper that comes into contact with the L2 portion, which is the end portion, and obtain a good image.

Further, since the core metal end portion 30B is thicker than the central portion 30A, it is possible to delay the arrival time of heat quantity from the xenon lamp 2 to the heat pipe 4, and further, the light emission distribution from the central portion to both end portions. Since the light distribution reduces the amount of heat generated on the side, even when continuous copying of small-size transfer paper is performed, the amount of heat supplied to the end portion 30B is relatively low. It is possible to suppress abnormal heating of the L1 region, which is the end portion of the heating roller 3, and to keep the surface temperature of the heating roller 3 uniform.

Since the heat insulating bush materials 7 and 7'are not used in the low-grade model because of the cost, the configuration of Example 1 is often used, but in the low-grade model, the copying speed is not so high, and thus the small size is used. The temperature rise at the end of the heating roller 3 which is a problem during continuous copying of transfer paper does not occur.

[0038]

According to the present invention, by shortening the length of the heat pipe and disposing it over both the small size region and the large size region, the cost of the heat pipe can be reduced and the heat pipe can be reduced. It is possible to have the same heat transfer capacity as the one arranged in a shaft. Further, since the thickness of the core metal of the heating roller is set to be different depending on the size of the transfer paper, the surface temperature of the heating roller at the time of rising and standby can be made uniform, and the large-sized transfer paper and the small-sized transfer paper can be made uniform. The image fixability during copying can be improved, the temperature rise at the roller end can be suppressed, wear of the release material of the heating roller can be prevented, and the life of the heating roller can be improved.

That is, since the surface temperature of the heating roller can be kept uniform in the axial direction at a low cost regardless of the size of the transfer paper, a good transferred image can be obtained and the durability and durability of the heating roller can be improved. Wear of the release material can be suppressed.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view illustrating a schematic configuration of a fixing device that is a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a temperature gradient characteristic of a heating roller surface in the first embodiment and a surface temperature gradient of a conventional heating roller.

FIG. 3 is a partial cross-sectional view illustrating a schematic configuration of a fixing device that is a second embodiment of the present invention.

FIG. 4 is a characteristic diagram showing surface temperature gradients of a heating roller in the second and third embodiments and a conventional heating roller.

FIG. 5 is a partial cross-sectional view showing a schematic configuration of a fixing device that is a third embodiment of the present invention.

FIG. 6 is a partial cross-sectional view illustrating a schematic configuration of a fixing device that is a fourth embodiment of the present invention.

FIG. 7 is a partial cross-sectional view showing a schematic configuration of a fixing device that is a fifth embodiment of the present invention.

[Explanation of symbols]

 1 Fixing device 2 Heater (xenon lamp) 3 Heating roller 3A Core metal 3A1 Material with high thermal conductivity 3A2 Material with low thermal conductivity 4 Heat pipe 5 Pressure roller L1 Contact area with large size transfer paper L2 Small size transfer paper Contact area

Front page continuation (72) Inventor Jun Okamoto 1-3-6 Nakamagome, Ota-ku, Tokyo, stock company Ricoh (72) Inventor Masahiko Sato 1-3-6 Nakamagome, Ota-ku, Tokyo stock company In Ricoh (72) Inventor Yutaka Fukuchi 1-3-6 Nakamagome, Ota-ku, Tokyo ・ In Ricoh Co., Ltd.

Claims (6)

[Claims] 1. A fixing device comprising a heating roller having a built-in heater and a pressure roller in pressure contact with the heating roller, wherein at least one heat pipe is provided inside the heating roller. A fixing device, characterized in that the fixing device is arranged over both the contact area with the small size transfer paper and the contact area with the large size transfer paper in the axial direction of the end portion of the roller. 2. The heat pipe is made of a shape memory alloy, is arranged in a contact area with the large-sized transfer paper, and is expandable and contractable to the contact area with the small-sized transfer paper. The fixing device according to 1. 3. A fixing device comprising a heating roller having a built-in heater and a pressure roller in pressure contact with the heating roller, the fixing roller having at least one heat pipe inside the heating roller, in the axial direction of the heating roller. The thickness of the core metal of the pressure roller is different between the contact area with the large-size transfer paper and the contact area with the small-size transfer paper with respect to the heat pipe arranged over the entire area. Fixing device. 4. In the core metal of the heating roller, the thickness of the core metal located in the contact area with the small size transfer paper and facing the heater is set to the thickness of the core metal located in the contact area with the large size transfer paper and facing the heater. Is smaller than the thickness of the core metal, and the light emission distribution of the heater is such that the amount of heat in the contact area with the small-size transfer paper is large and the amount of heat in the contact area with the large-size transfer paper is small. Item 3. A fixing device according to item 3. 5. A fixing device comprising a heating roller having a built-in heater and a pressure roller in pressure contact with the heating roller, wherein at least one heat pipe is provided inside the heating roller. The core metal material of the contact area with the transfer paper is made of a material having high thermal conductivity, and the core metal material of the contact portion of the heating roller with the small size transfer paper is made of a material having low thermal conductivity. And fixing device. 6. The fixing device according to claim 5, wherein at least one heat pipe is disposed over at least two kinds of core metal materials having different thermal conductivities.