JPH0535141A - Fixing device - Google Patents

Abstract

PURPOSE:To maintain excellent cleaning performance over a long term by providing a simple pressure means in the center part of a member for holding a cleaning blade so that proper press-contact force may be obtained. CONSTITUTION:The cleaning blade 12 is allowed to press-contact to a fixing roller 1 by a pressure spring and the center part of the blade 12 in the longitudinal direction is also pressed in a direction where the fixing roller 1 is pressed by a pressure spring 17 which engages with the holding member 10. By pressing the center part of the holding member, the press-contact force distribution of the blade 12 to the roller 1 is adjusted. By setting the press-contact force distribution in an axial direction so that it may be larger in the center part than at both end parts, the accumulated toner lump advances to both ends of the blade along the blade and drops downward from both ends without passing through the blade and going round to the back surface of the blade, thereby maintaining the excellent cleaning performance over a long term.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat roller fixing device for an electrophotographic recording device.

[0002]

2. Description of the Related Art In an electrophotographic recording apparatus such as a laser printer, a facsimile or an electrophotographic copying machine, a toner image formed on a photoconductor by an electrophotographic process is transferred onto a transfer paper and fixed to complete recording. To do. A heat roller fixing device is widely used as a fixing device for performing this fixing.

A general structure of a heat roller fixing device is shown in FIG.
Will be described.

In the figure, reference numeral 1 is a heating source 1 inside thereof.
9 shows a fixing roller having a. This fixing roller 1
A pressure roller 2 having an elastic surface is brought into press-contact with each other, and they are rotationally driven in the directions of the arrows. Fusing roller 1
The cleaning mechanism 3 is abutted on the outer peripheral surface of so as to be separable. The cleaning mechanism 3 is held by a movable side plate 4 (only one is shown) rotatably supported by a support shaft 5 on a front side plate and a rear side plate (not shown) that rotatably support the rollers. There is. Cleaning mechanism 3
Is composed of a cleaning unit 6 and a release agent applying mechanism 7. The cleaning mechanism 6 includes a pair of brackets 9 (only one of which is shown) rotatably fitted to a pin 8 fixed to the movable side plate 4, a holding member 10 having both ends fixed to the brackets 9, It is held by a holding member 10 via an elastic plate 11, and its leading edge 12a is fixed to the fixing roller 1.
The cleaning blade 12 is made of an elastic material that is brought into contact with and separated from the peripheral surface of the cleaning blade 12 over the entire length. As a means for pressing the cleaning blade against the fixing roller, in this example, a biasing spring 9a is stretched between the bracket 9 and the movable side plate 4 as disclosed in Japanese Utility Model Laid-Open No. 60-107968. , The cleaning blade 12 is urged in the clockwise direction, and when the movable side plate 4 is at the predetermined position shown in the drawing, the cleaning blade is brought into pressure contact with the peripheral surface of the fixing roller 1 with a predetermined pressure contact force.

The releasing agent applying mechanism 7 applies an oil applying felt 13 for applying oil pumped up from a tank (not shown) storing a releasing agent (not shown), such as silicone oil, to the outer peripheral surface of the fixing roller 1; It is composed of a blade 14 for uniformly leveling the oil applied by the felt 13 and scraping off excess oil. The blade 14 is held by a holder 16 via a spring plate 15. The cleaning mechanism 3 shown in FIG.
The oil application felt 13 and the blade 14 are attached to the fixing roller 1.
It shows a state in which the peripheral surface is contacted with a predetermined pressure contact force.

Copy paper P carrying an unfixed toner image T
Is fed to the nip portion between the rollers 1 and 2 by a conveying unit (not shown), and the unfixed toner image is fixed on the fixing roller 1.
It is fixed by heating and welding. A portion Ta of the toner image transferred from the paper P adheres to the surface of the fixing roller 1, and this toner Ta is blocked by the edge 12a of the cleaning blade 12 that is in pressure contact with the roller surface and is held together with the silicone oil. It is deposited as a toner mass Tb.

By the way, as described above, in the apparatus in which the cleaning blade holding member is brought into pressure contact over the entire length of the surface of the fixing roller by the spring force of the spring hung between the both ends and the side plate, the holding member is completely Since it is not a rigid body, the pressure contact force of the cleaning blade with respect to the fixing roller tends to appear strong at both ends in the axial direction of the roller and weakly appear at the center, as shown by the curve B in FIG.

The pressure contact force is measured by cutting a certain transfer paper into a strip shape with a width of 10 mm, impregnating the tip with silicone oil, and immediately scraping off the excess oil at the tip of the strip with the same transfer paper. A method was used in which the tip was sandwiched between a fixing roller and a cleaning blade, a strip was pulled in the tangential direction of the fixing roller, and the pulling force was measured.

The uneven pressure contact force is caused by the cleaning blade scraping toner from the peripheral surface of the fixing roller, toner such as silicone oil as an anti-offset liquid, especially in the central portion in the longitudinal direction of the blade, and it is gradually increased by repeating the copying operation. It grows and solidifies over time. The solidified toner or the like is heat-shrinked to make the pressure contact force between the blade and the roller non-uniform, thereby causing a phenomenon that the toner or the like that has flowed in later cannot be removed. When this phenomenon occurs, toner or the like exists on the peripheral surface of the fixing roller, and is retransferred (offset) to the sheet to be fixed and appears as "black streaks" on the copy, greatly impairing the copy quality. Therefore, in order to improve the cleaning effect, if you strengthen the spring, the work of attaching and detaching the spring when replacing the cleaning blade becomes troublesome,
There is a problem that the service cost increases.

Further, in Japanese Patent Laid-Open No. 186884/1985, as shown in FIG. 10, the cleaning blade 3 is held by a holding member 34 fixed to the apparatus frame via a leaf spring 35.
1 and holds the free end 31a of the cleaning blade 31.
One end of the leaf spring 32 is fixed to the holding member 34 on the back surface of the leaf spring 32.
There is disclosed a fixing roller cleaning device in which the free end is pressed against the fixing roller over the entire length thereof and the cleaning blade 31 is pressed against the peripheral surface of the fixing roller to stably remove excess oil over a long period of time.

The leaf spring 32 of this apparatus is provided with corrugated cross-sections at the intermediate portion between the fixed end and the free end and at the free end to enhance the rigidity in the longitudinal direction, and the tip portion 3 of the cleaning blade 31.
It is considered that the back surface of 1a abuts with a relatively uniform pressing force.

In the case of the method of pressing the back surface of the cleaning blade directly with the spring material and pressing it against the fixing roller, the pressing force of the blade is determined by the elastic modulus of the spring, but the elastic modulus of the spring varies widely, and therefore the blade has a large elastic modulus. The pressure contact force of the fixing roller also varies, and it is difficult to obtain a stable pressure contact force. If you try to keep the variation within a certain range, the manufacturing cost will be high. If the pressure contact force is weak, the desired cleaning effect cannot be obtained. Conversely, if the pressure contact force is too strong,
The release coating on the surface of the fixing roller may be peeled off, which has the opposite effect.

Further, in order to press the entire length of the tip of the blade against the fixing roller, the back surface of the blade tip is pressed uniformly by the spring material having the same length as the blade. Only the both end portions are strongly pressed against the roller, and the pressure contact force distribution in the axial direction has the same tendency as in the case where the both end portions of the holding member are biased by the spring, and the same problem occurs.

[0014]

SUMMARY OF THE INVENTION In view of the above-mentioned problems caused by the pressure distribution of the cleaning blade with respect to the fixing roller of the conventional heat roller fixing device, the present invention maintains good cleaning performance for a long period of time. It is an object of the present invention to provide a fixing device capable of increasing the maintenance interval and reducing the maintenance cost.

[0015]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is designed such that a sheet carrying an unfixed toner image is inserted between a fixing roller and a pressure roller which rotate in pressure contact with each other. In a fixing device having a cleaning blade made of an elastic material for fixing an unfixed toner image and cleaning the surface of the fixing roller while being pressed against the outer peripheral surface of the fixing roller over the entire length, the cleaning blade is held. There is provided a rigid pressing means for pressurizing the central portion of the holding member in a direction in which the cleaning blade is pressed against the fixing roller so that the pressing force can be adjusted, and the pressing contact force between the cleaning blade and the fixing roller is applied from both ends in the axial direction. Is also characterized in that the central part is enlarged.

[0016]

Since the fixing device of the present invention is constructed as described above, it is possible to adjust the pressure contact distribution of the cleaning blade to the fixing roller by pressing the central portion of the holding member by the pressing means. . By setting the axial pressure contact force distribution so that the central portion is larger than both end portions, toner, oil, etc. adhering to the peripheral surface of the fixing roller is scraped off by the tip edge of the blade, and gelled. It is deposited as a toner mass over the entire length of the cleaning blade. In this case, since the pressure contact force at the central portion of the blade is larger than the both end portions, the accumulated toner lumps do not pass through the blade and go around to the back surface thereof, but fall toward both end portions of the blade along the blade and fall downward from both end portions. .

At this time, the pressure contact line between the cleaning blade and the fixing roller is provided so as to incline downward from the back side of the apparatus, so that the toner scraped off by the blade tip portion naturally becomes the front end portion of the apparatus. Since it collects and falls on the surface, processing becomes easy.

The pressing means is a stainless steel stepped screw, and if the tip edge of the screw is rounded, the fixing member may be damaged or metal powder may be generated to fix the fixing roller. Since the end of the side that is touched when releasing pressure is made of a heat-resistant resin with low thermal conductivity, it will not be affected by heat during maintenance and can be operated safely. .

The problems other than the above of the present invention and the structure for solving the same will be apparent from the description of the embodiments described in detail below with reference to the drawings.

[0020]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a sectional view of the fixing roller in the vicinity of the center in the axial direction, showing one embodiment in which the present invention is applied to the fixing device described above with reference to FIG. Therefore, members having the same functions as those of the conventional fixing device are designated by the same reference numerals,
Focus on different points.

In this embodiment, the cleaning blade 1
2 is not pressed against the fixing roller only by the biasing spring 9a, but the central portion in the longitudinal direction is also the holding member 1.
The fixing screw 1 that engages with 0 urges the fixing roller 1 in a direction to press the fixing roller 1. The structure will be described with reference to FIGS. 2 and 3. In these figures, the movable side plates 4 on both sides
A pressure screw 17 as a pressure applying means is screwed into a substantially central portion of the stay 18 spanned between the two. The tip portion 17a of the pressure screw 17 is positioned so as to be engageable with the contact portion 10a formed in the central portion of the holding member 10. Then, when the pressure screw 17 is screwed in, the central portion of the holding member 10 is bent, and the cleaning blade 12 held by this is brought into pressure contact with the peripheral surface of the fixing roller 1.

The distribution of the pressure contact force of the cleaning blade 12 under pressure in the roller axis direction is shown by a curve A in FIG. As shown in the figure, the central portion of the cleaning blade 12 pressed by the pressure screw 17 has a pressure contact force of about 70 g per unit area by the pressure screw 17, and both end portions (the front portion and the rear portion of the fixing device) are The contact pressure is about 30g. The stay 18 can have high rigidity by appropriately selecting the sectional shape and dimension, and the pressure screw 17 has high rigidity, and both can be considered as substantially rigid bodies. The amount of deformation of the screw and stay due to the jamming can be ignored, and the pressure contact force can be stabilized. Such a distribution of the pressure contact force is appropriately determined according to the material of the cleaning blade 12, the material of the elastic layer forming the surface of the fixing roller 1, and the like. Pressure screw 17
The pressure contact force can be adjusted by adjusting the screw-in length. Further, when the pressurizing screw 17 is screwed in by the length l (see FIG. 3), if the optimum pressure contact force distribution as shown by the curve A in FIG. 6 is obtained, the effective length of this screw is set to the length l. If set to, it is only necessary to screw the screw under the neck, and the specified pressure contact force can be reproduced without troublesome adjustment work.

As shown by line A in FIG. 6, when the pressure contact force between the cleaning blade 12 and the fixing roller 1 is set, the toner, oil, etc. adhering to the peripheral surface of the roller is scraped off by the tip edge 12a of the blade. As a result, the toner lumps are accumulated as indicated by the symbol Tb. The toner and the like scraped off are accumulated over the entire length of the cleaning blade 12. In this case, the lumps of toner and the like blocked by the blade have a large pressure contact force at the central portion of the blade, and therefore cannot pass through the blade and go around to the back surface thereof. Therefore, the lump Tb of the toner or the like that gradually grows is generated at both ends 12 of the blade.
Inevitably, we have to go to b and 12c, and in FIG.
As indicated by, the roller 1 moves toward both ends of the roller 1 and flows downward from both ends of the fixing roller. As a result, the toner or the like that has passed through the cleaning blade 12 and remains on the peripheral surface of the fixing roller 1 is eliminated, and the roller surface used when the next toner image is fixed is maintained in a clean state.

The tip of the pressure screw 17 is securely attached to the predetermined contact portion 10a of the holding member 10 by preventing the pressure screw 17 from falling.
It is desirable to provide a burring (protruding seat) 18a in the threaded hole drilling portion of the stay 18 as shown in FIG. 3 so that the 7b is engaged and stably abuts with a large abutment area.

Further, when there is a burr or a sharp portion at the time of processing at the edge portion of the tip 17b of the pressure screw 17, the holding member 1
When the pressure of 0 is applied, the holding member may be scraped and metal powder may be generated. When the metal powder falls on the surface of the fixing roller 1, the release coating material on the fixing roller 1 is scraped off, or the tip of the blade 12 is scratched. Black streaks are generated on the paper, which is not preferable. So pressure screw 1
The tip 17b of 7 is preferably rounded to remove burrs and sharp points.

The pressure screw 17 may be a total screw threaded from under the neck to the tip, but as shown in FIG. 3, a step is formed in the intermediate portion and a portion 17a from the step portion to the tip side is provided. When the pressure screw 17 is screwed into the screw hole of the stay 18 by using a stepped screw that is not threaded but is threaded only from the step to the enlarged head side, the length of the pressure screw 17 is Even if the length is increased, the screwing work from the step portion is unnecessary, and the work efficiency can be improved.

As a material for the pressure screw 17, stainless steel is more suitable than mild steel which is usually used for many screws. The reason is as follows. The temperature of the upper part of the fixing roller 1 is 180 to 190 ° C. when the fixing device is in operation.
Becomes high temperature. With mild steel, the coefficient of thermal expansion is large, and pressure screw 1
As the temperature of 7 becomes higher, the length thereof becomes longer, so that the pressing force increases, which is different from the adjusted pressing force in the unheated state, which is not preferable. On the other hand, stainless steel is preferable because it has a small coefficient of thermal expansion, has little influence on the applied pressure even when subjected to temperature change, and is stable with respect to temperature. In addition to this, a ceramic material or the like can be used as the material that is not easily affected by the temperature change.

In the embodiment of the pressurizing device shown in FIGS. 2 and 3, the pressurizing force is obtained by screwing the pressurizing screw, but the optimum pressurizing force distribution is experimentally obtained and cleaning is performed. If the desired pressure contact force distribution can be obtained only by bringing the mechanism into contact with the fixing roller 1, the adjustment work using the pressure screw is not particularly necessary.

This example will be described with reference to FIGS. The stay 18, which is stretched between the movable side plates on both sides, is provided with a pressurizing unit corresponding to substantially central portions of the fixing roller 1 and the cleaning roller 12 in the longitudinal direction. This pressurizing means
A pressure lever 21 is rotatably supported on the stay 18 via a bracket 19 and a support shaft 20, and a spring 22 for urging the lever in one direction. Pressure lever 21
Has a bent piece 21a formed at its tip to lock one end of the spring 22 and contact part 1 of the holding member 10.
A member 21a is provided that forms an L-shaped surface 21b that engages 0a. The other end of the spring 22 is locked to one flange of the stay 18. The base end portion 21c of the pressure lever 21 abuts the lower surface 18b of the stay 18 when the lever is swung. FIG. 4 shows a state where the cleaning blade 12 is separated from the peripheral surface of the fixing roller 1, and the holding member 10 and the pressure lever 21 are placed at positions separated from each other. Now, as shown in FIG. 5, when the cleaning blade 12 is swung so as to be brought into pressure contact with the fixing roller 1, the upper surface 10a of the holding member 10 enters into the space sandwiched by the L-shaped surfaces, and the pressure lever 21 is swung. To move. And the cleaning blade 12
When the front end of the pressure roller 21 is pressed against the peripheral surface of the fixing roller 1, the base end portion 21c of the pressure lever 21 is attached to the lower surface 18c of the stay 18.
The sway is regulated by abutting against. At this time, the pressing lever 21 generates the same pressing force as pressing the central portion of the holding member 10 using the pressing screw having the screwing depth 1 (see FIG. 3). In other words, the pressure lever 21 is shown in FIG.
The member 21a is formed at a position where the pressure contact force distribution can be obtained as indicated by the curve A in FIG. Needless to say, when the cleaning blade 12 is brought into contact with or separated from the fixing roller 1, the release agent applying mechanism 7 is also moved in conjunction with this. Since the embodiment shown in FIG. 4 does not require screwing adjustment of the pressure screw, the maintenance work for blade replacement is simplified and the reproducibility of the predetermined pressure contact force distribution is good.

When the above two examples or other pressure applying means are used, the pressure applying means may be released for maintenance of the fixing device immediately after the fixing device is operated. In that case,
Since the pressurizing means is hot and cannot be touched, it is necessary to wait until it is cooled. However, if the time until cooling is prolonged, the downtime (non-operation time) of the entire electrophotographic recording apparatus is prolonged, which is not preferable. Therefore,
To reduce the heat transferred to the operator's hand by covering the end of the pressing means that is touched when releasing the pressure with a heat-resistant resin material whose thermal conductivity is lower than that of metal, or by integrally molding the entire resin. It is possible to facilitate the releasing operation of the pressurizing means. As the heat resistant resin for this purpose, polyphenylene sulfide, polyimide amide and the like are considered.

As shown in FIGS. 7 and 8, the pressure contact line between the fixing roller 1 and the tip 12a of the cleaning blade 12 is pressed so that the front side of the recording apparatus is lower than the rear side of the recording apparatus.
When the central portion of the cleaning blade is pressed so as to have a larger pressure contact force than the both ends, the toner and the like scraped off the surface of the fixing roller 1 by the cleaning blade 12 is dammed by the blade 12 and gelled. The lumps Tb and Tc are formed, and along a line of intersection that is inclined so that the front side of the blade 12 and the outer peripheral surface of the fixing roller 1 is lowered,
It flows from the back side to the front side and flows downward from the front end portion 12b of the blade 12. Therefore, the provision of a means for receiving the toner lumps on the front side facilitates the processing of the toner lumps.

[0033]

As described above, according to the first aspect of the invention, a desired pressure contact force can be obtained only by providing the pressing means having a simple structure in the central portion of the holding member of the cleaning blade, and the blade can be used. The scraped toner or oil can flow down to both ends in the axial direction of the roller, and good cleaning performance can be maintained for a long period of time.

Further, since the pressing means is a rigid body, deformation of the stay, screws, etc. due to tightening of the pressing screw is reduced.

According to a second aspect of the present invention, by using a stainless steel stepped screw as the pressurizing means and removing the sharpened portion at the tip, it is advantageous for thermal expansion and the time required for the screwing operation can be shortened. Further, generation of abrasion powder from the tip of the screw is prevented, and damage to the surface of the fixing roller due to this is prevented.

By using part or all of the pressurizing means made of a heat-resistant resin as described in claim 3, the heat transmitted from the pressurizing means to the worker at the time of releasing the pressurizing means for maintenance of the fixing device is prevented. Decrease and improve safety.

Further, by setting the pressure contact line between the cleaning blade and the fixing roller so that the front side is lowered as described in claim 4, the lump of toner or oil can be made to flow only to the front side, and the processing is facilitated. Become.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts of an embodiment of a fixing device including a cleaning device according to the present invention.

FIG. 2 is a perspective view showing a main part of a fixing device including a central part of the cleaning blade.

FIG. 3 is a cross-sectional view of the cleaning blade central portion pressing means.

FIG. 4 is a cross-sectional view showing the configuration of another embodiment of the cleaning blade central portion pressing means.

FIG. 5 is a cross-sectional view illustrating the operation thereof.

FIG. 6 is a curve diagram showing a comparison of a pressing force distribution curve of the cleaning blade against the fixing roller when a central portion of the cleaning blade according to the present invention is pressed against a similar pressing force distribution curve of a conventional fixing device. .

FIG. 7 is a perspective view showing a cleaning blade and a fixing roller of a fixing device in which the pressure contact line between the cleaning blade and the fixing roller is set such that the front side is lower than the back side.

FIG. 8 is a front view thereof.

FIG. 9 is a sectional view of a main part of an example of a fixing device including a conventional cleaning mechanism.

FIG. 10 is a perspective view showing another example of a conventional fixing roller cleaning mechanism.

[Explanation of symbols]

1 fixing roller 3 cleaning mechanism 4 movable side plate 5 Support shaft 6 Cleaning section 8 pin 9 bracket 10 Blade holding member 11 Elastic plate 12 cleaning blade 17 Pressure screw (pressurizing means) 18 stay 19 bracket 21 Pressure lever (pressurizing means) 22 spring

Claims (4)

[Claims] 1. An unfixed toner image is fixed by inserting a sheet carrying an unfixed toner image between a fixing roller and a pressure roller which rotate in pressure contact with each other, and the entire length of the outer peripheral surface of the fixing roller. In a fixing device provided with a cleaning blade made of an elastic body for cleaning the surface of the fixing roller in a state of being pressed against the fixing roller, the central portion of the holding member holding the cleaning blade is pressed against the fixing roller. A fixing device characterized in that a rigid pressurizing means for pressurizing the pressurizing force in the direction is provided, and the pressure contact force between the cleaning blade and the fixing roller is made larger in the central portion than in both end portions in the axial direction. 2. The fixing device according to claim 1, wherein the pressurizing means is a stepped screw made of stainless steel, and the tip edge portion thereof is rounded. 3. The fixing device according to claim 1, wherein at least the end of the pressing means on the side where the hand is touched is made of a heat resistant resin. 4. The fixing device according to claim 1, wherein a pressure tangent line between the cleaning blade and the fixing roller is inclined so as to be lower on a front side than a back side of the device.