JP3486285B2 - Fixing device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for an image forming apparatus.

[0002]

2. Description of the Related Art Recently, a fixing device having a short rise time has been desired from the viewpoint of power saving, and it is achieved to achieve this.
As one of the means, a fixing roller in which the core metal of the fixing roller is formed of a thin metal and has a small heat capacity and a short rise time is being used. As shown in FIG. 9, such a fixing device has a fixing roller 1 having a heater 3 as a heat source therein and a pressure roller 2 in pressure contact with the fixing roller 1, and includes a core metal 1 a of the fixing roller 1. The material of A is well balanced in terms of thermal conductivity, mechanical strength and cost.
l, Fe, etc. are used, and the wall thickness is 0.3 to 0.8 mm.
The outer diameter of the core metal 1a is about 20 to 40 mm.

In the above-mentioned one, the fixing roller 1
Since the core metal 1a of 1 is thinned, the mechanical strength is insufficient, and as shown in FIG.
As exaggeratedly shown in FIG. 11, the cross-section is crushed, and these deformations cause fixing failure or damage of the fixing roller 1. Further, the accuracy of the outer diameter of the fixing roller 1 is required to be high in order to ensure the fixability and the transportability.
There is a problem that machining of thin-walled cored pipes having low mechanical strength, especially outer diameter turning, is very difficult and remarkably hinders productivity. Therefore, as a measure to solve this problem,
As shown in FIG. 1, a ring-shaped reinforcing member 4'in the fixing roller 1 and a supporting rod 5 for supporting the reinforcing member 4 '.
The fixing roller 1 and the fixing roller 1 are provided in the fixing roller 1 and the mechanical strength of the fixing roller 1 is increased.

However, in the above-mentioned one, it causes a large increase in heat capacity and delays the temperature rise of the fixing roller 1, and the support rod 5 for preventing the bending of the fixing roller 1 is the heater 3. There is a problem in that the heat generated from the fixing roller 1 is blocked, and the fixing roller 1 has uneven temperature. As a measure for solving this problem, although not shown, it is proposed to remove the support rod and fix the ring-shaped reinforcing member to the fixing roller in a tight fit state. The temperature rising characteristics are as shown in FIG. 13, and the temperature rise of the portion where the reinforcing member is attached causes a considerable delay compared to the portion where the reinforcing member is not attached.

[0005]

The above-mentioned conventional reinforcing member which is fixed to the fixing roller in a tightly fitted state requires high precision and requires a high level of skill in the loading operation. If the strength is insufficient, the reinforcing member cannot withstand the stress concentrated on the top and bottom of its inner edge when it is pressed by the pressure roller, and the reinforcing member itself deforms or
As shown in FIG. 14, a crack is generated and damaged, or a thermal expansion of the fixing roller causes a gap between the fixing roller and the reinforcing member to fall off. If the strength is too strong, the fixing roller may be deformed or damaged due to thermal expansion of the reinforcing member, so that it is difficult to set the strength of the reinforcing member, and further, the heat capacity is increased by loading the reinforcing member. Therefore, there is a problem that the rise time is delayed, the fixing roller has a sufficient mechanical strength at a low cost, and the fixing device that does not deform cannot be easily obtained.

Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional fixing device and to design the reinforcing member.
To provide a fixing device that is easy to manufacture, has a fast rise time, has a high productivity of a fixing roller equipped with the reinforcing member, is low in cost, has sufficient mechanical strength, and does not deform. is there.

[0007]

SUMMARY OF THE INVENTION The present invention, in order to accomplish the above objects, the invention according to claim 1, the inner
Fixing roller that has a heat source in its part and pressure contact with this fixing roller
A pressure roller, and a reinforcing portion inside the fixing roller.
In the fixing device having the material, the thickness t _ri of the reinforcing member is larger than the wall thickness t _ro of the fixing roller core metal ,

[Number 1] Ri t _ro ≦ t _ri ≦ 3t _ro der, reinforcing member, it size of thermal expansion than the fixing roller
It is formed of a material that is a fixing apparatus according to claim Rukoto. The invention according to claim 2 is a fixing device having a heat source inside.
A roller and a pressure roller that is in pressure contact with this fixing roller are provided.
In the fixing device having the reinforcing member inside the fixing roller , the reinforcing member is formed of a material having a coefficient of thermal expansion larger than that of the fixing roller, and the thermal expansion of the reinforcing member at about 150 to 200 ° C. When the thermal stress in the radial direction due to is σ _th , the inner diameter of the fixing roller is D _in , and the yield stress of the material of the fixing roller core metal is σ _s , the wall thickness t _ro of the fixing roller core metal is

[Equation 2] Is a fixing device .

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the embodiments of the present invention shown in FIGS. 1 to 4, the same parts as in the prior art will be designated by the same reference numerals and the description thereof will be omitted, and mainly different parts will be described. In the first embodiment of the present invention, a plurality of ring-shaped reinforcing members 4 are mounted inside the fixing roller 1. Set the thickness t _ri of the reinforcing member 4 in t _ro ≦ t _ri ≦ 3t _ro the relationship with respect to the thickness t _ro of the fixing roller, ensuring the strength of the reinforcing member 4, arrangement and the and the heat capacity is not too large It was done. 3a is a central heater, 3b is an end heater, 6a and 6b are side plates, 7 is a heat insulating bush, 8 is a bearing, and 9 is a gear.

[0009]

[Example of the first embodiment] This example has a diameter of 40 mm.
Then, the fixing roller 1 of Fe whose core metal 1a has a thickness of 0.3 mm
In addition, a reinforcing member 4 of Fe having a thickness _tri of 0.5 mm that satisfies the above relationship is mounted. In such a case, the temperature change at the time of rising is as shown in FIG. 5, and the delay of the temperature rise at the time of rising in the portion without the reinforcing member 4 and a certain portion is the same as that of the conventional one (see FIG. (Refer to 11), and the temperature is uniform even after reaching the set temperature. Further, the mounting of the reinforcing member 4 not only improves the mechanical strength of the fixing roller 1 to prevent fixing failure and damage of the fixing roller 1 due to heat, but also eliminates the bending when the outer diameter of the thin cored bar pipe is turned. It is easy to ensure accuracy

The second embodiment differs from the first embodiment in that
Although not shown, the reinforcing member 4 is made of a material having a smaller specific heat capacity than the fixing roller 1.

[0011]

Example of Second Embodiment In this example, the fixing roller 1 is used.
Of the core metal 1a is made of Fe, and the reinforcing member 4 is made of Fe.
It is formed of an Al alloy, which is a material having a smaller specific heat capacity than that. In such a case, the heat capacity is determined by the specific heat of the member, the density and the volume, but the specific heat capacity per unit volume obtained by multiplying the specific heat and the density is a constant peculiar to the material, and Al is Fe. In comparison, the specific heat capacity is about double and the density is about one third, so the specific heat capacity is about 60% of that of Fe. In such a case, the heat capacity of the reinforcing member 4 is reduced, the rising time of the fixing roller 1 can be shortened, and Al has a very high thermal conductivity. The temperature unevenness on the surface of the fixing roller 1 becomes small.

The third embodiment differs from the first embodiment in that
As shown in FIGS. 6 to 8, a flat cylindrical tongue portion 11 is provided on the inner edge portion 10 of the reinforcing member 4, and the cylindrical tongue portion 11 is provided.
And the inner wall of the core metal 1a of the fixing roller 1 are engaged with each other in a tight fit state, and the reinforcing member 4 is fixed to the fixing roller 1.

In such a case, when the reinforcing member 4 is mounted in the fixing roller 1 and pressure is applied from below by the pressure roller 2, the reinforcing member 4 is against the stress concentrated on the upper and lower sides of the inner edge portion 10. As a result, sufficient strength can be ensured and strength and durability are improved, there is no possibility of cracks from the inner edge portion 10 and damage of the reinforcing member 4, and the shape of the reinforcing member 4 The sheet metal can be manufactured with high precision at a low cost by drawing, and the reinforcing member 4 thus manufactured is mounted on the fixing roller 1 to
It improves the workability and productivity.

The fourth embodiment is the same as the first embodiment.
The reinforcing member 4 is formed of a material having a thermal expansion coefficient larger than that of the fixing roller 1, and the core metal 1 a of the fixing roller 1 is the reinforcing material 4.
The thickness is limited to withstand the thermal stress due to the thermal expansion. That is, the circumferential stress σ _θ of the core metal 1a of the fixing roller is t _{ro for} the wall thickness of the core metal 1a and D for the inner diameter thereof.
_{When we say in} ,

[Equation 3] In order to prevent the fixing roller 1 from being deformed, the safety factor is set to 3, and this σ _θ is relative to the yield stress σ _s .

## EQU4 ## It is necessary to satisfy sθ <3s _s ... (Equation 2). From the first and second equations, in order that the circumferential stress of the fixing roller 1 is within the range of the yield stress of the core metal 1a at the safety factor 3,

[Equation 2] It is necessary to be.

[0015]

[Example of Fourth Embodiment] When the core metal 1a is Fe and the material of the reinforcing member 4 is Al whose thermal expansion coefficient is larger than that of Fe, the linear expansion coefficient of Fe is 1.16 × 10 ⁵ / K, The linear expansion coefficient of Al is 2.38 / 10 to ⁵ K, and the outer diameter of the fixing roller 1 is 40 m.
m, the core metal wall thickness is 0.4 mm, the outer diameter of the reinforcing member 4 is the same as the inner diameter of the fixing roller 1, and the temperature is 185 ° C. (room temperature is 25 ° C.)
If heated up to, the inner diameter of the fixing roller 1 becomes 39.48 mm due to thermal expansion. Since the Al reinforcing member 4 also tries to expand further, thermal stress σ is generated on the inner surface of the fixing roller 1.
_It takes _th and the value is 0.17kgf / mm ² , and the core metal 1
The circumferential tensile stress of a is 8.4kgf / mm ² from the first formula, and F
If the yield stress of e is 30 kgf / mm ² , then the third equation is satisfied.

For those satisfying such conditions,
During the fixing operation, the fixing roller 1 is heated to about 150 by the internal heat source.
When the temperature of the fixing roller 1 is kept at a temperature of up to 200 ° C., the reinforcing member 4 does not fall off due to this temperature.
Will not be deformed.

[0017]

The present invention is as described above, and the invention according to claim 1 is a fixing roller having a heat source inside.
And a pressure roller in pressure contact with this fixing roller,
In the fixing device having the reinforcing member inside the fixing roller , the thickness t _ri of the reinforcing member is larger than the thickness t _ro of the fixing roller core metal ,

Since t _ro ≦ t _ri ≦ 3t _ro and the reinforcing member is formed of a material having a thermal expansion coefficient higher than that of the fixing roller, it is easy to design and manufacture the reinforcing member. There is an effect that it is possible to obtain a fixing device which has a fast rise time, good productivity and low cost, has sufficient mechanical strength, and does not deform the fixing roller. The invention according to claim 2 has a heat source inside.
Fixing roller and pressure roller that is in pressure contact with this fixing roller
And a reinforcing member inside the fixing roller, wherein the reinforcing member is formed of a material having a coefficient of thermal expansion larger than that of the fixing roller, and is about 150 to 200 ° C.
When the radial thermal stress due to the thermal expansion of the reinforcing member is σ _th , the inner diameter of the fixing roller is D _in , and the yield stress of the material of the fixing roller core metal is σ _s , the wall thickness t _{ro of the} fixing roller core metal is
But,

[Equation 2] Therefore, the workability and productivity of the fixing roller can be improved, and the fixing roller can be prevented from being deformed due to thermal expansion.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of a first embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view of the reinforcing member of the first embodiment.

FIG. 3 is a front view of the reinforcing member of the above-described first embodiment.

FIG. 4 is a perspective view of a reinforcing member according to the first embodiment of the above.

FIG. 5 is a surface temperature characteristic diagram of the fixing roller according to the first embodiment.

FIG. 6 is a vertical sectional view of a reinforcing member according to a third embodiment of the present invention.

FIG. 7 is a front view of a reinforcing member of the above third embodiment.

FIG. 8 is a perspective view of a reinforcing member according to a third embodiment of the above.

FIG. 9 is a schematic vertical sectional view of a conventional fixing device.

FIG. 10 is a diagram showing a bending state of the above fixing roller.

FIG. 11 is a diagram showing a crushed state of the above fixing roller.

FIG. 12 is a schematic vertical sectional view of a fixing device having the same reinforcing member.

FIG. 13 is a surface temperature characteristic diagram of the above fixing roller.

FIG. 14 is a view showing a damaged state of the reinforcing member of the above.

[Explanation of symbols]

1 fixing roller 1a core metal 2 pressure roller 3 heater 4 Reinforcement member 10 Inner edge 11 Cylindrical tongue

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyuki Shibaki 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) Reference JP-A-57-155571 (JP, A) JP Sho 59-30571 (JP, A) Patent 3397934 (JP, B2) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 13/20 G03G 15/20

Claims (2)

(57) [Claims] 1. A fixing device having a fixing roller having a heat source therein and a pressure roller in pressure contact with the fixing roller, and having a reinforcing member inside the fixing roller, wherein the reinforcing member has a thickness _{tri of} that of the fixing roller. the thickness t _ro, Equation 1] ri t _ro ≦ t _ri ≦ 3t _ro der, reinforcing member, it size of thermal expansion than the fixing roller
A fixing device which is characterized that you have been formed by material. 2. A fixing device having a fixing roller having a heat source inside and a pressure roller in pressure contact with the fixing roller, and having a reinforcing member inside the fixing roller, wherein the reinforcing member has a coefficient of thermal expansion higher than that of the fixing roller. Of the material of the fixing roller is σ _th , the thermal stress in the radial direction due to the thermal expansion of the reinforcing member at about 150 to 200 ° C. is σ _th , the inner diameter of the fixing roller is D _in , and the yield stress of the material of the core of the fixing roller is σ. _{When s} , the wall thickness t _ro of the fixing roller core metal is Is a fixing device.