JP2000131984A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily insert a bearing under ordinary temperature by specifying press-contact load acting between a heating roll and a pressure roll and the ratio of the outside diameter of a shaft part to the inside diameter of the bearing. SOLUTION: When it is assumed that the press-contact load acting between the heating roll 2 and the pressure roll 3 is X and the dimension ratio of the outside diameter D of the shaft part 24 to the inside diameter(d) of the bearing is Y, they satisfy both expressions: Y>=(1/6000)X+99.86 and Y<=(-1.5/6000)X+100.1. Thus, appropriate clearance is kept in the case of fitting the bearing 4 in the shaft part 24, and the bearing 4 is easily inserted in the shaft part 24 of the heating roll 2 and/or the pressure roll 3 under the ordinary temperature, and the shaft part 24 is prevented from being worn in an early stage due to slippage caused between the shaft part 24 and the bearing 4. Besides, the shaft part 24 is prevented from being deformed due to the tact that the shaft part 24 and the bearing 4 get in a tight-fit state excessively at high temperature.

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 fixing a toner image transferred on a recording sheet to the recording sheet in an electrophotographic copying machine, a laser beam printer, or the like. The present invention relates to an improvement in a structure for rotatably supporting a pair of rolls to be inserted with respect to an apparatus frame.

[0002]

2. Description of the Related Art Conventionally, a so-called heat roll type fixing device has been known as a fixing device in an electrophotographic copying machine or the like. Specifically, a recording sheet on which a toner image has been transferred is inserted between a pair of a heating roll and a pressure roll that come into contact with each other at a predetermined pressure, and the toner is melted by a heater built in the heating roll. The toner image is fixed to the recording sheet with a predetermined fixing strength by pressing the formed toner against the image receiving surface of the recording sheet.

[0003] Further, the heating roll and the pressure roll include:
It is composed of a body portion that comes into contact with the recording sheet, and a pair of shaft portions projecting from both ends of the body portion, and is supported by a fixing device frame via a ball bearing fitted to the shaft portion. At the same time, it is rotationally driven by a gear mounted on the shaft. Here, the heating roll is formed of aluminum or the like having excellent thermal conductivity because it is necessary to efficiently transmit the heat of the heater incorporated therein to the toner on the recording sheet. The ball bearing fitted to the shaft of
It is formed of a material harder than aluminum such as US material.

[0004]

By the way, in order to easily fit the ball bearing to the shaft of the heating roll without using a press-fitting jig, the fitting tolerance between the shaft and the hole is taken into consideration. It is necessary to set the outer diameter of the shaft portion smaller than the inner diameter of the bearing. However, when the outer diameter of the shaft portion is determined in this way, slippage occurs between the shaft portion and the inner ring of the bearing, so that the bearing made of SUS material has a higher heating temperature than that of aluminum. Since it is harder than the shaft of the roll, there has been a problem that the shaft of the heating roll is extremely worn.

On the other hand, when the outer diameter of the shaft portion of the heating roll is set slightly larger than the inner diameter of the bearing, the slip does not occur as described above. Also, it was difficult to fit the shaft to the inner diameter of the bearing. Also, when the heat of the heater contained in the heating roll is conducted to the shaft and the bearing, aluminum has a larger thermal expansion coefficient than SUS material. In this state, the shaft portion loses to the inner ring and plastic deformation occurs. As a result, when the heating roll is cooled, there is a problem in that the aluminum shaft portion, which contracts more than the SUS material, becomes thin, and a gap is formed between the shaft and the bearing.

[0006] The present invention has been made in view of such problems, and an object of the present invention is to easily insert a bearing into the shaft of a heating roll and / or a pressure roll at room temperature. And no slippage occurs between the shaft portion and the bearing, and the shaft portion and the bearing are not excessively tightly fitted at a high temperature and the shaft portion is not deformed. An object of the present invention is to provide a fixing device.

[0007]

In order to achieve the above object, a fixing device according to the present invention comprises a heating roll and a pressure roll which rotate while being pressed against each other under a predetermined load. On the premise of a fixing device for inserting a recording sheet carrying a toner image and fixing the toner image to the recording sheet, the heating roll and / or the pressure roll are arranged such that the heating roll and / or the pressure roll are in contact with the body and the apparatus frame. And a pair of shaft portions integrally formed of the same material at both ends of the body portion, and a pressing load applied between the heating roll and the pressure roll is represented by X. When the dimensional ratio between the outer diameter of the shaft portion and the inner diameter of the bearing is Y, it is necessary to satisfy both of the following expressions: Y ≧ (1/6000) X + 99.86 Y ≦ (−1.5 / 6000) X + 100.1. It is an butterfly.

According to the present invention having such technical means, the outer diameter of the shaft portion and the inner diameter of the bearing are adjusted according to the pressing load applied between the heating roll and the pressing roll which are pressed against each other. By controlling the ratio within the range shown in the above formula, an appropriate clearance is maintained when the bearing is fitted to the shaft, and the slip between the shaft and the bearing can be prevented. Deformation can be prevented. Further, the shaft can be easily inserted into the bearing at room temperature.

In the present invention, a collar may be interposed between the shaft and the bearing in order to improve the wear resistance of the shaft of the heating roll and the pressure roll with respect to the bearing. However, in this case, when the pressing load applied between the heating roll and the pressure roll is X, and the dimensional ratio between the outer diameter of the shaft portion and the inner diameter of the bearing is Y, Y ≧ (1/6000) X + 99. 84 Y ≦ (−1.5 / 6000) X + 100.1.

Further, when a collar is interposed between the shaft portion and the bearing, the collar is substantially C-shaped having a sectional shape smaller than the inner diameter of the shaft portion in consideration of the mountability of the collar to the shaft portion. Preferably, it is formed in a shape and is configured to be elastically fitted to the shaft portion.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a fixing device according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing a fixing device to which the present invention is applied. In the figure, reference numeral 1 denotes a recording sheet carrying an unfixed toner image T, reference numeral 2 denotes a heating roll that comes into contact with the surface of the recording sheet 1, and reference numeral 3 denotes a pressure roll that is disposed to face the heating roll 2. The fixing roll 2 and the pressure roll 3 are configured to abut against each other under a predetermined pressing load F to nip the recording sheet 1 to be inserted.

The fixing roll 2 is provided with a Teflon (registered trademark) coat layer 21 on the surface of a hollow roll 20 made of aluminum. Inside the hollow roll 20, a heater 22 for heating and melting the toner T is provided. Built-in. On the other hand, the pressure roll 3 is provided with an insulating elastic layer 31 made of silicon rubber or the like around the shaft 30, and when pressed against the heating roll 2, the elastic layer 31 is crushed, so that the recording sheet is pressed. It is configured to form one nip width.

As shown in FIG. 2, a hollow roll 20 constituting the heating roll 2 is formed with a body 23 for holding the recording sheet 1 in combination with the pressure roll 3, and is formed at both ends of the body 23. A shaft portion 24 supported via a ball bearing 4 to a frame (not shown) of the fixing device
The body 23 is made of an aluminum material (JIS 6063) in order to efficiently transfer the heat of the heater 22 to the recording sheet 1.
Further, if the body 23 and the shaft 24 are formed of different materials, the manufacturing cost of the heating roll 2 is increased and the assembly of the body 23 and the shaft 24 is troublesome. Is formed of the same aluminum material as the body 23,
The body 23 and the shaft 24 are integrally formed by cutting.

In order to rotatably support the heating roll 2 with respect to the apparatus frame, the ball bearing 4 is required.
Is required to be fitted to the shaft portion 24 of the hollow roll 20. Generally, the ball bearing 4 is formed of a wear-resistant stainless steel (SUS). Is also hard, the slippage between the fitted shaft portion 24 and the inner ring of the ball bearing 4 causes a disadvantage that the shaft portion 24 is unilaterally worn. Further, since the thermal expansion coefficient (23.0 × 10 ⁻⁶ ) of the aluminum material is larger than the thermal expansion coefficient (11.7 × 10 ⁻⁶ ) of the stainless steel material, the heat of the heater 22 is increased during the operation of the fixing device. Shaft 2
If the temperature of the shaft portion 24 rises due to the flow into the shaft 4, the shaft portion 24 is excessively tightened by the inner ring of the bearing 4, and there is a disadvantage that plastic deformation occurs and the outer diameter cannot return to the original outer diameter.

Therefore, in fitting the shaft portion 24 of the heating roll 2 and the ball bearing 4, the dimensional ratio in fitting the two is important, and if such a dimensional ratio is appropriate, the early It is considered that the heating roll 2 can be used for a long period of time by preventing abrasion and deformation. Therefore, the inventors of the present application changed the pressing load F between the heating roll 2 and the pressing roll 3, and
The ratio of the outer diameter D of the roller to the inner diameter d of the bearing 4 is changed.
An experiment was conducted to determine the lifespan before the device became unusable.
The results are shown in Table 1 below. In the table, ○ indicates that the heating roll 2 was usable even when 600 × 10 ³ or more recording sheets were passed.
The symbol x indicates the case where the heating roll 2 becomes unusable after passing 00 × 10 ³ sheets, and the symbol x indicates the case where the heating roll 2 becomes unusable after passing less than 100 × 10 ³ sheets.

[0016]

[Table 1]

As is apparent from this result, even when the dimensional ratio between the outer diameter D of the shaft portion 24 and the inner diameter d of the bearing 4 is the same, the pressure contact load F between the heating roll 2 and the pressing roll 3 varies. Then, the progress of the wear and deformation of the shaft portion 24 is different. Therefore, the inventors of the present application set Table 1 in a graph in which the horizontal axis represents the pressure-contact load F and the vertical axis represents the axial dimension ratio.
Among the experimental results, those in which the result was good (○) were plotted. FIG. 3 shows this graph.

The experimental examples plotted on this graph are gathered in the range surrounded by the two approximate straight lines and the line shown in the graph. If it is located in the region between the approximate straight lines, it is estimated that wear and deformation of the shaft portion 24 of the heating roll 2 are suppressed, and that the heating roll 2 can be used for a long time. When these approximate straight lines are expressed by mathematical formulas, where the pressing load is X and the axial dimension ratio is Y, the range expressed by the following expression and the expression is a region suitable for long-term use of the heating roll 2. ... Y≥ (1/6000) X + 99.86 ... Y≤ (-1.5 / 6000) X + 100.1

In view of the above points, in the fixing device actually configured, the outer diameter D of the shaft portion 24 of the heating roll 2 is set to 29.975 to 29.993 mm including the tolerance, while the inner diameter of the bearing 4 is set. Dimension d is 29.990-30.
000 mm, and the pressing load F was set to 350 kgf. Further, in order to prevent the bearing 4 from burning, the temperature of the heating roll 2 is controlled to 200 ° C. or less.

Next, in order to improve the wear resistance of the shaft portion 24 of the heating roll 2, the present inventors made use of stainless steel (SUS).
A collar 5 having a substantially C-shaped cross section was mounted on the outer peripheral surface of the shaft portion 24. 4 shows a state before the collar 5 is mounted on the shaft 24, FIG. 5 shows a state after the collar 5 is mounted on the shaft 24, and FIG. 6 shows a state of the collar 5 viewed from the axial direction. It is a figure each shown.

As shown in FIGS. 4 and 5, a concave ring groove 25 for mounting the collar 5 is formed on the outer peripheral surface of the shaft portion 24 of the heating roll 2. The collar 5 enters, and the outer peripheral surface of the collar 5 and the outer peripheral surface of the shaft portion 24 form the same outer diameter. The ball bearing 4 is fitted on the outer peripheral surface of the collar 5, and the inner race of the bearing 4 is made of an aluminum shaft 2.
4 and not with the SUS collar 5.

Further, as shown in FIG. 6, the collar 5 is formed in a substantially C shape having a part cut out on the circumference and having an inner diameter smaller than the cross section of the shaft part 24. By expanding the portion 50, the collar 5 can be easily mounted on the shaft portion 24. Further, the collar 5 can be easily fitted into the concave annular groove 25 of the shaft portion 24 by utilizing the elastic force that attempts to restore the original shape. Can be combined.

The inventors of the present application also conducted an experiment in the case where the collar 5 was fitted to the shaft portion 24 of the heating roll 2 in the same manner as in the above-described case where the collar 5 was not used. As a result of plotting, two approximate straight lines and the one shown in the graph of FIG. 7 were obtained. Therefore, the SUS collar 5 is fitted to the shaft portion 24 and the shaft portion 2 is
When the wear resistance of No. 4 is improved, the following formula and the range represented by the formula are regions suitable for long-term use of the heating roll 2. ... Y≥ (1/6000) X + 99.84 ... Y≤ (-1.5 / 6000) X + 100.1

In view of the above, in the fixing device actually configured, the plate thickness of the collar 5 is 0.3 mm and the plate width is 12.5 mm.
mm, and sets the inside diameter d ₁ to 28mm, the color is fitted in a snap-fit with respect凹環groove 25 of nominal dimensions 29.4 mm, inner diameter of the outer diameter and the bearing 4 of the collar 5 after installation The ratio with the size is 99.900 to 10.
0.010%. And the pressure contact load 40
When the recording sheet 1 was passed between the heating roll 2 and the pressure roll 3 under 0 kgf, the life of the heating roll 2 was 2
000 × 10 ³ sheets or more, and it was possible to achieve 600 × 10 ³ sheets or more under the pressure load of 600 kgf.

Further, as is apparent from the comparison between the above-mentioned equations and the equations, when the SUS collar 5 is interposed between the outer diameter of the shaft portion 24 and the inner diameter of the bearing 4, the shaft dimensional ratio Can be slightly relaxed, and there is an advantage that the bare link 4 can be easily fitted to the shaft portion 24 of the heating roll 2 by that much.

In the above embodiment, the shaft 2 of the heating roll 2 is used.
The present invention is applied to the fitting between the bearing 4 and the bearing 4,
In exactly the same way, the present invention can be applied to the fitting between the shaft of the pressure roll 3 and the bearing.

[0027]

As described above, according to the fixing device of the present invention, the outer diameter of the shaft and the bearing are adjusted according to the pressing load applied between the heating roll and the pressing roll which are pressed against each other. By controlling the ratio of the inner diameter to the inner diameter within a range shown by a predetermined formula, an appropriate clearance is maintained when the bearing is fitted to the shaft portion, and the heating roll and / or the pressure roll at normal temperature are maintained. The bearing can be easily inserted into the shaft, and the shaft does not wear out early due to slippage between the shaft and the bearing. The shaft portion is not deformed due to an excessive interference fit between the bearing and the bearing, so that the service life of the heating roll and the pressure roll can be extended.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of a fixing device to which the present invention is applied.

FIG. 2 is an enlarged view of a main part showing a relationship between a shaft portion and a bearing of the heating roll according to the embodiment.

3 is a graph showing a result of examining a life of a heating roll in a fitting mode of a shaft portion of a heating roll and a bearing shown in FIG. 2;

FIG. 4 is an enlarged view of a main part showing a state before a SUS collar is mounted on a heating roll and a shaft part.

FIG. 5 is an enlarged view of a main part showing a state after a SUS collar is attached to a heating roll and a shaft.

FIG. 6 is a view showing a SUS collar according to the embodiment.

FIG. 7 is a graph showing the results of examining the life of the heating roll with respect to the manner of fitting the shaft of the heating roll and the bearing shown in FIGS. 4 and 5;

[Description of sign]

DESCRIPTION OF SYMBOLS 1 ... Recording sheet, 2 ... Heating roll, 3 ... Pressure roll, 4
... bearing, 23 ... trunk, 24 ... shaft, T ... toner image

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tomoki Kobayashi 2274 Hongo, Ebina-shi, Kanagawa Prefecture, F-Term in Fuji Xerox Co., Ltd. BA53 BA70 EA06 FA46 GA53

Claims (3)

[Claims] 1. A heating roll and a pressure roll that rotate while being pressed against each other under a predetermined load, and a recording sheet carrying a toner image is inserted between these rolls.
In the fixing device for fixing a toner image on a recording sheet, the heating roll and / or the pressure roll are supported via a bearing to a body portion abutting on the recording sheet and an apparatus frame, and the body portion And a pair of shafts integrally formed from the same material at both ends of the shaft, X represents a pressing load applied between the heating roll and the pressure roll, and the dimensions of the outer diameter of the shaft and the inner diameter of the bearing. A fixing device, wherein when the ratio is Y, both the following expressions are satisfied: Y ≧ (1/6000) X + 99.86 Y ≦ (−1.5 / 6000) X + 100.1. 2. A heating roll and a pressure roll which rotate while being pressed against each other under a predetermined load, and a recording sheet carrying a toner image is inserted between these rolls.
In the fixing device for fixing a toner image on a recording sheet, the heating roll and / or the pressure roll are supported via a bearing to a body portion abutting on the recording sheet and an apparatus frame, and the body portion A pair of shafts integrally formed of the same material at both ends of the shaft, and a collar interposed between the shaft and a bearing. When the load is X and the dimensional ratio between the outer diameter of the collar mounted on the shaft and the inner diameter of the bearing is Y, Y ≧ (1/6000) X + 99.84 Y ≦ (−1.5 / 6000) X + 100. A fixing device satisfying both of the formulas (1) and (2). 3. The fixing device according to claim 2, wherein the collar has an inner diameter smaller than the inner diameter of the shaft of the heating roll and / or the pressure roll, and has a substantially C-shaped cross section. A fixing device characterized by being elastically fitted.