JPH10221992A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device having a fast rising time and sufficient mechanical strength, at a low cost by solving a problem generated because of reduction in the thickness of a fixing roller. SOLUTION: The fixing device is provided with the fixing roller 100 of a thin cylinder having a heat source inside, a pressure roller 300 coming into press-contact with the fixing roller 100 and a ring-like reinforcing member 101 for preventing the deformation of the fixing roller 100, thereinside. In the fixing device, the reinforcing member 101 is disposed in the outside position in an axial direction of the width of a maximum size paper passing through the fixing device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fixing device used for an image forming apparatus such as a copying machine, a printer, a facsimile, and the like.

[0002]

2. Description of the Related Art FIG. 10 is a sectional view of a general fixing device. A pressing roller 300 is pressed against a fixing roller 100 having a heat source 200 therein with a constant pressing force. As the heat source 200, a halogen lamp excellent in thermal response and durability is usually used. As the fixing roller, a fixing roller having a small heat capacity, such as a thin fixing roller, is being used from the viewpoint of saving power and shortening the rise time. As a result of using a thin fixing roller having a small amount of heat storage, the temperature of the paper passing portion and the temperature of the non-paper passing portion are significantly different when small size paper is continuously passed (commonly referred to as "end temperature rise"). As a result, large temperature unevenness occurs in the axial direction of the fixing roller. As a result, if small-size paper is continuously passed and then large-size paper is passed, fixing offset, winding, and jam occur. As a measure to prevent this trouble, it is known to use a total of two heaters, a heater having a heat generating portion corresponding to small-size paper and a heater for supplying heat to other portions (commonly referred to as "two heaters").

On the other hand, if the core of the fixing roller is made thinner, the mechanical strength is lost, causing problems such as bending of the roller as shown in FIG. 11 and crushing of the cross section as shown in FIG. These deformations cause poor fixing due to non-uniform nip width, and cause damage to the fixing roller due to extreme deformation. In addition, the fixing roller is required to have high outer diameter accuracy in order to guarantee the fixing property and the transportability, but machining of a thin metal core pipe having low mechanical strength, particularly, outer diameter turning is very difficult, Significantly impairs productivity.

As a means for solving these inconveniences, a method in which the fixing roller itself has a reinforcing rib shape is disclosed in Japanese Unexamined Patent Publication No. Sho.
No. 7-155571 and Japanese Utility Model Laid-Open No. 58-190660. However, when an integral reinforcing rib is provided on the inner surface of the fixing roller, the rib must be considerably high in order to obtain sufficient strength. as a result,
The processing cost increases, and economics becomes a major problem. Further, if the ribs are made higher, there is a problem of a delay in temperature rise at that portion, and extra waiting time is required until a uniform temperature distribution is obtained.

As another solution, loading of a member for reinforcing the fixing roller is disclosed in Japanese Patent Application Laid-Open No.
No. 6-7949. When the reinforcing member is loaded in the fixing roller, the mechanical strength of the fixing roller is improved, and the bending and the cross section of the fixing roller can be significantly reduced. As a result, it is possible to prevent defective fixing and damage to the fixing roller. At the same time, there is an advantage that, when turning the outer diameter of the thin metal core pipe, the deflection can be reduced and the accuracy can be easily secured.

[0006] However, there are some problems when loading the reinforcing member. First, it is difficult to fix the reinforcing member to the fixing roller. Since a large load is applied to the reinforcing member for preventing the deformation of the fixing roller, if the fixing member is not firmly fixed to the fixing roller, the reinforcing member will soon come off inside the fixing roller. When the reinforcing member is fixed in a shrink fit state, high accuracy is required for the reinforcing member, and a technique is required for the loading operation. In the case of fixing by welding or the like, not only is the processing cost increased, but also the load is concentrated on the welded portion, which causes ring damage.

Secondly, a gap is formed in a part of the contact surface between the fixing roller and the reinforcing member due to the pressurization, and as a result, a thrust force for the reinforcing member to slide and move on the inner surface of the fixing roller is generated. Has been confirmed. If the fixing of the reinforcing member is not sufficient, the reinforcing member will come off. If the strength of the reinforcing member is not sufficient, the reinforcing member will be damaged.

Lastly, installing a large supporting member for supporting the reinforcing ring inside the thin fixing roller is as follows.
This leads to a large increase in heat capacity, which causes a delay in temperature rise of the fixing roller. Further, when the core metal of the fixing roller is made of a metal such as Fe having a poor thermal conductivity, the temperature rise at the position of the reinforcing member is inevitably delayed because of the heat capacity of the reinforcing member. Even if the temperature of the fixing roller other than the reinforcing member position reaches the set temperature, if the temperature of the reinforcing member position does not reach the set temperature, the fixing property of that part cannot be satisfied, so the temperature of the reinforcing member position becomes the set temperature. The time it takes to reach this is the rise time of the entire fixing device.
Even with a reinforcing ring having a small heat capacity, the rise of the temperature of the fixing roller is slightly delayed, so that the rise time of the fixing device becomes somewhat longer. No matter how thin the fixing roller is, if the heat capacity of the reinforcing member is large, the temperature rise at the reinforcing member position is greatly delayed, and the rise time of the entire fixing device may be rather delayed.

JP-A-8-106228 and JP-A-8-106228
JP-A-171299 also discloses a fixing device in which a reinforcing member is inserted into a fixing roller, but the method of fixing the reinforcing member to the inner surface of the fixing roller has not been solved and remains as a problem.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to solve these problems and to provide a fixing device having a fast rise time, low cost, and sufficient mechanical strength.

[0011]

According to the present invention, there is provided a thin cylindrical fixing roller having a heat source therein, and a pressing roller which is in pressure contact with the fixing roller. In a fixing device having a ring-shaped reinforcing member for preventing deformation of the fixing roller, the reinforcing member is disposed at a position axially outside a width of a maximum sheet passed through the fixing device. It is solved by being.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described based on the illustrated embodiment. FIG. 1 is a diagram showing a first embodiment according to the present invention. The fixing roller 100 is fixed to the fixing side plate 400 via a heat insulating bush 401 and a bearing 402.
a, 400b, and is rotationally driven by a drive source (not shown) via a gear 404. As the core metal material of the fixing roller 100, Al and Fe that are well balanced in terms of thermal conductivity, mechanical strength, and cost are used. The thickness of the core metal in the thin fixing roller is about 0.3 to 0.8 mm. The outer diameter of the cored pipe is about 20 to 40 mm. The heat-insulating bush 401 is for minimizing heat dissipation (heat conduction) from the fixing roller to the side plate and the like, thereby saving power, reducing temperature unevenness of the fixing roller, and improving the durability of the bearing 402. Fixing roller 100 with constant pressure
The pressure roller 300 pressed against is rotated by the rotation of the fixing roller 100. One ring-shaped reinforcing member 101 is fixed to the inner surface of the fixing roller 100 at each of the side plates 400a and 400b located outside the maximum sheet passing range. As shown in FIG.
Reference numeral 01 has a cylindrical portion 101a at an outer edge portion that engages with the inner surface of the fixing roller, and has a shape that is hardly distorted in the fixing roller 100. At this time, the outer diameter of the tip of the cylindrical portion 101a of the reinforcing member 101 has a cylindrical portion 101a.
From the outer diameter of the transition portion to the flat portion 101b
Advantageously, the tapered shape is 0.8 mm larger. The material of the reinforcing member is desirably the same as the fixing roller core from the viewpoint of thermal expansion, and the thickness is desirably 0.2 to 0.8 mm, which is about the same as the fixing roller core from the relationship between strength and heat capacity. The fixing of the reinforcing member 101 to the inner surface of the fixing roller 100 is performed as follows. That is, in the fixing roller 100, the reinforcing member 101 is pressed into the fixing member 102 (FIG. 3) with a predetermined load and fixed, and the reinforcing member 101 is caused to expand to the outside of the fixing member 102 due to the force. The fixing by friction is formed between the fixing member 102 and the inner surface of the fixing roller (FIG. 4).

As a comparative example, FIG. 5 shows a fixing device in which a reinforcing member is provided at the center of the fixing roller. Hereinafter, the fixing device in FIG. 5 is referred to as a fixing device A, and the fixing device according to the first embodiment of the present invention illustrated in FIG. 1 is referred to as a fixing device B.

In the fixing device B, by arranging the reinforcing member outside the maximum sheet passing range, a delay in temperature rise at the position of the reinforcing member does not directly affect the fixing performance and the rise of the fixing device. . Since the reinforcing member is provided near the end rather than at the center where the cross-section of the fixing roller is most crushed, the effect of reinforcing is smaller than when the fixing member is provided at the center (the fixing device A). However, as shown in FIG. 6, the thickness of the fixing roller is increased, for example, the thickness of the fixing roller of the fixing device B is set to 0.35 mm with respect to the thickness of the fixing roller of the fixing device A 0.3 mm. However, since there is no delay in the rise time due to the installation of the reinforcing member, the rise time of the fixing device B is shorter in the fixing device B as a whole.
Even if the reinforcing member is installed outside the paper passing area, the temperature rise at the reinforcing member position will certainly be delayed, but the delay in temperature rise within the paper passing area that affects the rise time can be very small. is there. Also, the thickness is 0.05 mm from the fixing device A.
Since the strength of the fixing roller is increased by the increased thickness, sufficient strength can be obtained even when the installation position of the reinforcing member is not at the center.

FIG. 7 shows another embodiment according to the present invention. Since the crushing of the cross section of the fixing roller becomes more conspicuous near the center of the roller, it is advantageous to arrange the reinforcing member 101 as close to the center as possible to prevent deformation of the cross section of the fixing roller. Therefore, in this embodiment, the reinforcing member 1
01 is outside the maximum sheet passing range and the pressure roller 30
At positions inside the two ends of the elastic layer 0, the fixing layer 100 is fixed to the inner surface of the fixing roller 100. Other configurations are the same as those in the first embodiment. In the case of the second embodiment, as a result of disposing the reinforcing member outside the maximum sheet passing range, the delay in temperature rise at the time of rising by the reinforcing member is the same as in the first embodiment. Does not affect rise time. In addition, as a result of the arrangement of reinforcing members near both ends of the pressure roller elastic layer where the load is concentrated,
A larger reinforcing effect can be obtained.

Normally, as shown in FIG.
In the vicinity of both ends of the elastic layer of the pressure roller, the outer diameter is formed to be about 0.05 mm to 0.2 mm larger than that of the center, so that the linear velocity at both ends is slightly higher than that at the center. The paper is pulled outward, thereby preventing the paper from wrinkling during paper passing. However, as described above, it is very difficult to perform the outer diameter turning of the thin cored pipe, and processing the fixing roller into such a special shape also hinders productivity.

On the other hand, the reinforcing member 1
When the fixing member 01 is fixed to the fixing roller, as shown in FIG. 9, the reinforcing member 101 spreads the fixing member 102 and is fixed to the inner surface of the fixing roller by friction, so that an outward load is applied to the inner surface of the fixing roller. As a result, the outer diameter of the fixing roller is about 0.01 to 0.1 mm at the position where the reinforcing member is provided.
growing. That is, by using such a fixing method of the reinforcing member 101, the weakness of the mechanical strength, which is generally a weak point of the thin fixing roller, can be reversed even if the fixing roller is not previously formed into a drum shape. By utilizing this, a drum-shaped fixing roller having a large outer diameter at both end portions of the pressure roller elastic layer can be inevitably obtained. Therefore, it is possible to significantly reduce the processing cost due to grinding or the like, and obtain good transportability in which wrinkles are prevented from occurring during paper passing.

[0018]

According to the first aspect of the present invention, since the reinforcing member is disposed axially outside of the maximum sheet passing width, a delay in temperature rise at the position where the reinforcing member is provided causes a delay in the rise time of the fixing device. It has no effect and therefore the rise time of the fixing device can be reduced. Accordingly, even if the thickness of the fixing roller is made larger than before, the rise time is shortened, and the mechanical strength of the fix roller can be improved without delaying the rise time.

In the fixing device according to the second aspect, since the reinforcing member is disposed axially inside both ends of the elastic layer of the pressure roller, the reinforcing effect is increased. In the fixing device according to the third aspect,
By using the fixing member, the reinforcing member can be easily and reliably fixed. Also, when the reinforcing member is fixed by using the fixing member, the fixing member pushes the fixing roller outward in the radial direction, so that the fixing roller itself does not have to be formed into a special shape, and the occurrence of wrinkles at the time of paper passing is reduced. This can be prevented. Therefore, workability and productivity are significantly improved.

[Brief description of the drawings]

FIG. 1 is a schematic view of a first embodiment of a fixing device according to the present invention.

FIG. 2 is a cross-sectional view, a front view, and a perspective view of a reinforcing member from the left.

FIG. 3 is a sectional view, a front view, and a perspective view of a fixing member for a reinforcing member from the left.

FIG. 4 is a principle view showing a method of fixing a reinforcing member.

FIG. 5 is a schematic diagram of a fixing device A as a comparative example, in which a reinforcing member is provided at the center.

6 is a graph and a table comparing the temperature changes at the time of rising between the fixing device A shown in FIG. 5 and the fixing device B of the first embodiment of the present invention shown in FIG.

FIG. 7 is a schematic view of a second embodiment of the fixing device according to the present invention.

FIG. 8 is a schematic view of a conventionally used fixing roller having a drum shape.

FIG. 9 is a principle diagram illustrating an increase in the outer diameter of the fixing roller when the reinforcing member is fixed.

FIG. 10 is a schematic sectional view of a general fixing device.

FIG. 11 is an explanatory view schematically showing a flexing state of a fixing roller.

FIG. 12 is a schematic cross-sectional view illustrating a crushed state of a fixing roller.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 fixing roller 101 reinforcing member 101 a cylindrical portion of reinforcing member 101 b flat portion of reinforcing member 102 fixing member for reinforcing member 200 heat source 300 pressure roller 400 a, 400 b fixing side plate 401 heat insulating bush 402 bearing 404 gear

Claims (3)

[Claims] 1. A fixing device comprising: a thin cylindrical fixing roller having a heat source therein; and a pressing roller for pressing against the fixing roller.
In a fixing device having a ring-shaped reinforcing member for preventing deformation of the fixing roller inside the fixing roller, the reinforcing member is located outside the maximum width of the paper passing through the fixing device in the axial direction. A fixing device, wherein the fixing device is disposed at a position. 2. The fixing device according to claim 1, wherein the reinforcing member is disposed at a position axially inward of both ends of the elastic layer of the pressure roller. 3. The reinforcing member has a tapered outer edge portion, and when the reinforcing member is pushed in with a predetermined load, the reinforcing member expands in a radial direction and presses against the inner surface of the fixing roller to place the reinforcing member on the inner surface of the fixing roller. 3. The fixing device according to claim 1, wherein the fixing member to be fixed is used as fixing means for the reinforcing member.