JPS6084560A - Fixing device - Google Patents

Abstract

PURPOSE:To improve separation of copying paper from a roller and to prevent jam by utilizing the difference of average surface roughness between a fixing roller and a pressing roller, allowing a toner attached to the fixing roller to be attached to the pressing roller to remove the toner from the fixing roller. CONSTITUTION:A fixing roller 1 is prepared by coating the outer circumference of a hollow roller core 1a made of a metal, such as aluminum, stainless steel, or copper, with a comparatively thin elastic layer 1b made of silicone rubber or fluororubber. An average roughness RZ of the peripheral surface of the layer 1b is in the range of 1-10mum. The pressing roller 2 is pressed into contact with the roller 1 at the time of fixing, and it is prepared by coating the outer circumference of a hollow metallic roller core 2a with a comparatively thick elastic layer 2b made of silicone rubber, fluororubber, fluorosilicone rubber, EPDM, hydrine rubber, or the like. An average surface roughness RZ of the peripheral surface of the layer 2b is controlled in the range of 6-25mum, and it is higher in roughness than that of the layer 1b of the roller 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fixing device for fixing an unfixed object to a support material, and preferably a fixing rotating body pair such as a roller or a belt for fixing an unfixed toner image to a recording material. The present invention relates to a fixing device having:

2. Description of the Related Art Conventionally, fixing devices have been used in image forming apparatuses such as printers, copying machines, and facsimiles, as well as in various devices for fixing objects to support materials.

In this fixing device, a heating roller serving as a fixing roller is used as the first rotating body, and a pressure roller that is in pressure contact with the first rotating body and rotates together with the first rotating body is used as the second rotating body. There are two types of heat roller type fixing devices.

In the first type, a so-called fluorine-based resin coated roller made of PTFE (polytetrafluoroethylene), PFA (perfluoroalcoquine), etc. is used as the fixing roller, and silicone rubber or fluorine rubber is used as the pressure roller. , E
There is a system using a roller covered with an elastic material such as PDM, hydrin rubber, fluorosilicone rubber, etc., and as a third type, a system using the above-mentioned elastic material-covered roller for both the fixing roller and the pressure roller. .

In the above one system, when the second type of elastic material coated roller is used as the fixing roller, compared to the case where the fluorine-based resin coated roller is used as the second type of fixing roller, the fixing It is very useful because it has good properties and image properties (image quality).

However, in the case of type No. 1, if the surface of the fixing roller is rough, the fixing roller is likely to be contaminated with toner after long use, and once toner adheres to the surface of the fixing roller, it is very difficult to remove. There were drawbacks. Additionally, once the toner adheres to the fixing roller, the adhering toner has a good affinity with the toner on the recording material, so toner offset increases rapidly, causing various problems such as jams. It became.

In addition, fixing rollers that are usually equipped with an internal heater and have an elastic surface have to have a thin elastic body for heat conduction. If a cleaning member such as the above is brought into contact with strong pressure, the elastic body may be damaged or problems may occur in terms of durability.

On the other hand, if the surface of the fixing roller, etc. is made smooth in order to eliminate the above-mentioned disadvantages, the electrostatic adsorption force and vacuum adsorption force of the recording material to the roller will increase, and the separation of the recording material from this roller will become worse. . Therefore, it is necessary to take measures such as bringing a claw-like member into contact with the fixing roller or the pressure roller with strong pressure, but this causes problems such as damage to the roller surface due to the separating member.

The present invention has been made in view of the above points and in order to improve the above drawbacks, and by specifying the average surface roughness of a fixing roller and a pressure roller whose surfaces are made of an elastic material,
It is an object of the present invention to provide a fixing device that has good fixing properties and image properties and can maintain its performance over a long period of time.

In the present invention, the average surface roughness Rz) of the fixing roller is set in the range of /~70μ, the average surface roughness RZ) of the pressure roller is set in the range O~2sμ, and the pressure roller The above object could be achieved by making the surface rougher than the surface of the fixing roller.

Embodiments of the fixing device according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of a fixing device according to the present invention. This figure shows a device in which a toner image T formed by electrophotography is fixed onto plain paper P using a heating roll type fixing device.

/ is a fixing roller that has a heating heater 3 such as a halogen heater inside and comes into contact with the unfixed toner image T, and rotates in the direction of the arrow shown in the figure in response to driving force from a drive motor (not shown). Reference numeral ``Y'' is a pressure roller having a built-in heater 3' for low heating, and rotates in sliding contact with the fixing roller. This fixing roller has a hollow roller core made of metal such as aluminum, stainless steel, copper, etc., and the outer circumferential surface of the roller is made of silicone rubber, for example.
A relatively thin elastic layer /b made of one of fluorine rubber, fluorosilicone rubber, etc. is provided, and the average surface roughness Rz) of the circumferential surface of this elastic layer /b is /~
It is within the range of 10μ.

The pressure roller is rotatably supported by a bearing (not shown), and is pressed against the fixing roller by a known pressure means at least during fixing, and is coated with silicone rubber, for example, on the outer peripheral surface of the hollow metal roller core 2. , fluorine rubber, fluorosilicone rubber, EPDM, hydrin rubber, etc., is provided with a relatively thick elastic layer 2b, and the surface average roughness of the circumferential surface of the elastic layer 2b is R.
z) is set within the range of O to 2 Sμ, and this roughness is rougher than the average surface roughness of the elastic layer/b of the fixing roller/. By heat conduction from the part that supports the pressure roller etc., the driving force of the motor is transmitted to prevent the heat of the fixing roller/pressure roller etc. from escaping and to obtain a uniform temperature surface. The fixing roller, pressure roller, etc. are thermally floated by using heat insulating materials such as glass for the gears and roller bearings. However,
When a large number of sheets are continuously passed through the mass production of the fixing roller/pressure roller Ω, the heat at the center of these rollers is taken away by the paper passing, and the temperature at the center of the roller decreases. At the ends of the rudder roller, less heat is transferred to the passed paper than at the center. Therefore, the temperature drop at the ends of the roller is less than the temperature drop at the center of the roller. At this time, heat from the ends of the roller is conducted toward the center of the roller, and the entire surface of the roller becomes uniform, but this results in poor fixing in the center, resulting in poor fixing performance.

Therefore, in order to eliminate this influence, the heat generation distribution of the heater 3 provided inside the fixing roller is such that the amount of heat generated at the center of the fixing roller is nearly twice as large as that at the ends. Therefore, the roller surface exhibits a good uniform temperature suitable for fixing, not only in normal conditions but also even when the sheets are continuously passed. A temperature-sensitive element such as a thermistor or thermocouple is placed in contact with the outer circumferential surface of the fixing roller, and its detection signal is guided to a known control means (not shown) to control the temperature of the outer circumferential surface of the fixing roller. The toner image is maintained at the melting temperature by controlling the output of the heater 3 or the voltage applied thereto.

B is an anti-offset liquid application member that also serves as a cleaning member to remove foreign matter such as offset toner and paper dust attached to the surface of the fixing roller;
Dimethyl silicone oil, methylphenyl silicone oil,
It is a mixture of anti-offset liquids such as fluorosilicone oil and amino-modified silicone oil.

The cleaning web Oa is brought into contact with the heating roller by an elastic pressing roller Otsu C.

Moreover, this web Oa is driven by a winding roller 1. The supply roller B is moved gradually by changing its abutting position by e, and the cleaning web B is constantly
The new surface of the fixing roller comes into contact with the fixing roller. This web Ot a moves on the roller Ot d interposed after the pressing roller O C, is reversed to the side toward the supply roller O, and is wound around the winding roller O with the front side and the back side reversed.

Reference numeral 7 denotes a curved reflection plate having heat reflection properties, which is provided close to the periphery of the fixing roller 1 over the entire longitudinal direction of the fixing roller l. Further, the reflecting plate 7 has a width so as to cover the space between the position of the fixing roller/circumferential pressing roller B C and the entrance opening for the paper P. Reference character g denotes a thick cover for preventing heat radiation, which is provided in close contact with the entire convex surface of the reflecting plate 7 to prevent wasteful radiation of heat from the reflecting plate 7.

/B is a casing member on the upper side of the fixing device, which surrounds the cleaning member B, the reflection plate 7, the cover g, and the temperature sensing element q. The temperature sensing portion of the temperature sensing element q is located closer to the roller than the reflecting plate 7.

On the other hand, on the pressure roller side, a reflector w similar to the reflector 7 and a cover 70 similar to the cover g are provided so as to cover most of the circumferential surface of the pressure roller.

By providing these reflective plates 7.9 and covers g and 10, it is possible to reduce the heat wasted from the surfaces of the fixing roller and the pressure roller, and also to improve the temperature measurement performance of the temperature sensing element g. It can be stabilized. Furthermore, it is possible to stabilize the temperature control for the set temperature of the fixing roller and to reduce power consumption.

A guide plate 22 guides the paper P toward the fixing roller, and is provided close to the fixing roller so as to be located between the reflecting plate 7 and one end of each of the reflecting plates.

Reference numeral 21I denotes a support plate that supports the pressure roller 2, and the pressure roller is pressed against the fixing roller by a spring 23.

Now, plain paper P having an unfixed toner image T is used for fixing,
The pressure cylinder is held and conveyed between rollers/1 and 2, and
The "C" toner image T is fixed by applying heat due to the surface temperature of the paper, and is then ejected from the apparatus while being held by a paper ejection roller 2θ2/.The plain paper P is fixed on the ejection port side of this fixing roller. A plurality of separation claws 5a are provided in contact with the surface of the roller along the axial direction of the roller to ensure separation from the roller.

Further, a separation claw 5b is also provided on the discharge port side of the pressure roller in contact with the surface of the roller.

The separation claw 5a is held by a support plate /gh that is spaced from the casing member /B, and the separation claw 5b is also held by a support plate 1gb that is spaced from the casing member /7 on the lower side of the fixing device. The casing member/7 is a reflection plate 9 of the pressure rollerco,
It is provided so as to be spaced apart from the cover 10 and cover them.

A cleaning member 2S is pressed against the pressure roller by means not shown, and is made of, for example, felt, and is used to clean toner offset from the pressure roller.

The reflective plate 7.9 is preferably made of a metal with a glossy surface, such as an aluminum or copper plate with a polished surface, or an iron plate with a surface treatment such as CR plating.

The shape of the reflecting plate 7.9 is preferably one having a curvature concentric with the circumferential surface of the roller, and the thickness thereof is preferably relatively thin.

The covers g and 10 are preferably made of glass wool, rock wool, ceramic fiber, or foam such as phenol foam or epoxy foam, or are made of a composite material.

Next, the present invention will be explained in detail by citing more specific members and numerical values.

Example/In a fixing device having the above configuration, an aluminum core bar with an outer diameter box and a wall thickness of S- is used as the hollow metal roller core/a of the fixing roller/, and the elastic layer/b is θ3tun.
A thick HTV (thermovulcanized) silicone rubber coating was used. This fixing roller had an inverted crown shape in which the diameter at the center was 730 μm smaller than that at the ends. As the hollow metal roller core 2a of the pressure roller, the outer diameter is 0.
At the end, an iron core with a wall thickness of 70 mm is used, and the elastic layer 2b is
Rubber hardness lIO degree (Japanese Industrial Standards), wall thickness 5mm
A heat vulcanizable (HTV) silicone rubber coating was used.

Furthermore, as the heater 3 inside the fixing roller, a halogen heater with a power consumption of 50 W is used.The surface temperature of the fixing roller is detected by a temperature sensing element, and this heater 3 is turned on by a control circuit (not shown). - Turn off and maintain the surface temperature of the fixing roller at 70°C. Further, the recording paper processing speed of the fixing device is 11110 tay'sea, that is, it is possible to process 60 sheets of A4 size recording paper per 7 minutes.

The separation claw 3a has a contact width of 2 cm to the fixing roller.
The curvature of the tip edge is 0. /R sharp edge shape, polyamideimide coated with a modified Teflon coating was used. In addition, the rotation fulcrum position of this separation claw SaO is
This is a so-called 1-biting position located on the outside opposite to the fixing roller from the contact edge at the contact point of the separating claw 5a to the fixing roller.

The fixing roller/
The paper was passed while applying 10 g of dimethyl silicone oil per AII size onto the surface of the paper. Further, as the fixing roller, a roller whose surface average roughness RZ) was processed to be gu μ was used, and as the pressure roller, a roller whose surface average roughness Rz) was processed to be /g μ was used.

Furthermore, the contact pressure of the separating claw 5a on the fixing roller is set to 7011, and the A cylinder is used, and the contact pressure of the separating claw and tb on the pressure roller is set to 10 I. Three of these were used. Then, 700,000 sheets of AII size plain paper P were continuously fed with toner images T placed on the entire iss area, but no troubles such as jams occurred.

In addition, when I visually observed the state of separation, it was found that the copy paper after fixing hardly relied on the separation claw Sa or 5b,
It was separated from 2. In addition, the toner that has been offset by a small amount on the fixing roller may be offset due to the difference in surface roughness between the fixing roller and the pressure roller when they rotate and come into pressure contact between paper passes. It was observed that the toner was transferred to the pressure roller side.The cleaning member 25, which was pressed against the pressure roller, transferred the toner transferred to the pressure roller.
It was possible to remove it with a cleaning felt. Here, the elastic layer 2b of the pressure roller is as thick as 3 tm and has sufficient elasticity, so it is not damaged by external pressure and can press the cleaning member 2S against the pressure roller with strong pressure. Ta.

After passing 30,000 sheets of 3θ paper, the pressure roller was completely smeared with toner, but the surface of the fixing roller was hardly stained at all, and more paper could be fed. Met.

Comparative Example/Except that both the fixing roller and the pressure roller were processed to have an average surface roughness (RZ) of RZ=4μ.
The conditions were the same as in Example.

When paper was fed continuously, jam occurred // times out of 1000 sheets. When observing the separation process, it was found that most copy paper was separated by relying on the separation claw, and sometimes the paper would slip through the separation claw, resulting in a jam. This seems to be because the electrostatic adsorption force and vacuum adsorption force of the paper to the fixing roller change due to the difference in the average surface roughness of the pressure roller.

Further, since the toner on the jammed paper is in contact with the roller for a long time, it tends to be offset to the roller, and once the toner has been offset, it may not be able to be removed by a cleaning web pressed with light pressure. Even when both rollers rotate under pressure, if the surface roughness is the same, the offset toner on the fixing roller will not transfer to the pressure roller side and will remain on the fixing roller side, and that toner will further cause the paper to As a result, winding around the roller and offset are more likely to occur.

Comparative Example Conditions were the same as in the examples except that the fixing roller and the pressure roller were both processed to have an average surface roughness (RZ) of Rz=/gμ. When paper was passed continuously, it showed good separation and fixing properties at first, but when the number of sheets passed was about 10,000, local stains appeared on the fixing roller that could not be cleaned with the web. As the sheets were passed, the stains on the fixing roller increased, and when about 30,000 sheets were passed, copy paper jams occurred frequently due to the stains.

Next, replace the fixing roller with a new one (the surface average roughness is also RZ = 15μ), and increase the web feed speed to 10
I doubled the amount of dimethyl silicone oil applied by 10 times (Aq size/per sheet, /X10 g) and continuously fed the paper, but after 30,000 sheets passed, the fixing roller etc. became slightly dirty and then became dirty. The number of paper jams increased rapidly, with the number of sheets being passed at 70,000 and jams occurring frequently.

In other words, if the roller surface is rough, the toner that has entered the recesses will accumulate without being completely removed by the web of the cleaning member, and the toner that has entered the roller recesses will further promote toner offset, which can cause jams. It has become.

This was somewhat alleviated by increasing the amount of dimethyl silicone oil applied, but it was still incomplete even after applying 70 times this amount. In other words, if the surface of the fixing roller is rough, the electrostatic adsorption force and vacuum adsorption force are weak, and separation is good, but toner offset is likely to occur, and the offset toner is transferred to the fixing roller. The above-mentioned inconvenience occurs because it is difficult to remove from the surface.

If the average surface roughness (Rz) of the fixing roller surface is rougher than /, 2μ (this is approximately the same as the average particle diameter of toner), the roller surface is likely to be stained by offset toner, and the dirt can be removed by a cleaning member. Because it was difficult to do so, problems such as jams occurred. Furthermore, it is not economical to produce a smooth surface with an average surface roughness (Rz) of lμ or less due to high manufacturing costs.

Further, as described above, the toner offset in small amounts on the surface of the fixing roller may not be completely removed by the web that is brought into contact with the fixing roller with light pressure. Once toner offset occurs on the fixing roller, the toner offset increases rapidly due to the affinity between the toners. Therefore, if the average surface roughness of the pressure roller is made rougher than that of the fixing roller, It was confirmed that the offset toner was successfully transferred to the pressure roller due to the difference in surface average roughness. In addition, the pressure roller has a relatively thick elastic body and is strong, so it is possible to contact a cleaning member such as a cleaning felt or a cleaning web with strong pressure, so that the toner on the pressure roller can be removed.

It is also possible to apply toner little by little to the back side of the copy paper every day, and in this case it is not necessary to bring the cleaning member into contact with the pressure roller.

Further, it is preferable that the direction of polishing during manufacture of the fixing roller and the pressure roller be in the same direction as the direction of rotation during operation after assembly into a machine.

As shown schematically and exaggeratedly in the enlarged cross-section in FIG.
When the surface of the fixing roller / and the surface of the pressure roller come into contact, the angle of the convex portions on the peripheral surfaces of these elastic layers /b and 2b is steep with respect to the outer peripheral reference plane of both rollers / and 2. It is shown that the fixing roller and the pressure roller rotate while being in pressure contact with each other so that they come into contact with each other from the soft side to the gentle side. Although the present invention is effective for heat fixing devices, it can also be applied to pressure fixing devices that can fix with light pressure.

As described above in detail about the present invention, the toner to be offset to the fixing roller is attached to the pressure roller side by utilizing the difference in average surface roughness, and the attached toner is removed by pressing the cleaning member against this. By doing this, the fixing roller side is always kept clean, and toner offset to the pressure roller side is prevented as much as possible, which improves the separation between the copy paper and the roller after the paper passes, and prevents jams, etc. The result is a fixing device that prevents troubles and has excellent durability.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a fixing device according to the present invention, and FIG. 2 is an explanatory diagram showing a cross-sectional state of a roller. / is a fixing roller, 2 is a pressure roller, 3 is a heater, /a
, /b is an elastic layer, 2a and 2b are metal hollow roller cores,
Part B is the offset prevention liquid coating member. Ot a is the cleaning web, and 5 a and 5 b are the separation claws. KO S: Cleaning member.

Claims (1)

[Claims] In order to fix an unfixed object to a recording material, a fixing roller that pinches and conveys the recording material and comes into contact with the object to be fixed on the recording material is opposite to the side of the object to be fixed of the recording material. A fixing device having a pressure roller in contact with a side surface, wherein the fixing roller and a surface layer of the pressure roller are both formed of an elastic material. The average surface roughness of the circumferential surface is /~72 μ, the average surface roughness of the circumferential surface of the pressure roller is in the range of 6 to 2 S μ, and the circumferential surface of the pressure roller is in the range of A fixing device characterized by having a rougher surface than the surface.