JP3197967B2 - Fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, electrophotographic color copying machines have been actively commercialized, and in recent years, they have been applied to color printers and the like. In addition, there is a problem that it is difficult to reduce the size.

[0003] This is because the cost and size of the fixing device used in the color copying machine cannot be avoided. That is, in a fixing device of a color copying machine,
By heating both the toner and the recording material uniformly and stably, it is necessary to sufficiently melt and mix the multicolored thick toner image, and to provide a heater inside both the fixing roller and the pressure roller. In addition, it is necessary to use a roller having a large heat capacity. In addition, a thick rubber layer is required to have a wrapping effect on the unevenness of the multilayer toner. Further, in order to provide releasability and prevent oil swelling, rollers have been formed in multiple layers.

To solve this problem, a method has been proposed in which a heater is provided only in the fixing roller.

In addition to the above-described color copying machines, electrophotographic copying machines and printers are not limited to the above-described ones.
Conventionally, a thermal fixing method in which a recording material having an unfixed toner image is passed between a pair of heated and pressurized rollers to fix the recording material has been widely and generally used. The occurrence of the offset phenomenon in which the molten toner on the recording material adheres to the roller is mentioned. conventionally,
As a countermeasure, a heat-resistant release layer such as silicone rubber or fluororesin is provided on the surface of the roller, and a release agent such as silicone oil is applied. However,
Nevertheless, offset toner gradually accumulates on the surface of the roller, deteriorating the roller and shortening the service life.

Therefore, a method has been proposed in which a cleaning member such as a fibrous web pad is slid on the roller surface to perform cleaning by forced friction to remove the toner from the roller surface. The roller, silicone oil, cleaning member and the like are usually replaced or maintained one or several times as a consumable member by a serviceman or a user during the life of the main body machine of the image forming apparatus.

[0007] will be described with reference to another conventional example in FIG. In FIG. 8 , reference numeral 501 denotes a heater,
02. The fixing roller 502 has a silicone rubber layer 502 a on an aluminum core 504.
Similarly, it is disposed on the silicone rubber layer 504 so as to be in pressure contact with a pressure roller 503 having a silicone rubber layer 503a. Further, the fixing roller 50
2, a cleaning web 505 is disposed above the cleaning web 505.
07, the sponge roller 506 slidably contacts the surface of the fixing roller 502. Further, the fixing roller 502 includes an oil application roller 50.
8 is in contact with the fixing roller 50 in the following procedure.
2 Oil is applied to the surface.

First, after a suitable amount of silicone oil 512 is pumped from an oil tank 515 to an oil reservoir 511 by a pump 514, the pump roller 510 and the application roller 508 are rotated to apply the oil adhering to the surface of the pump roller 510. The oil is transferred to the surface of the roller 508, and the amount of oil adhering to the surface of the application roller 508 is passed by the regulating blade 509 only in a required amount, so that stable oil application is performed on the surface of the fixing roller 502.

[0009]

However, according to each of the above conventional examples, there are the following problems. First, according to the conventional example in which the heater is provided only in the fixing roller, there is a problem that the temperature of the pressure roller is reduced. In other words, when a full-color multiple transfer image is formed, since a certain long time is required for the transfer process, even a heater using only the fixing roller compensates for the temperature decrease of the pressure roller within the recording material conveyance interval in continuous paper feeding. It was possible for a while.
However, in the case of continuous printing of monocolor, since the transport interval is short, as the number of sheets is increased, the temperature drop of the pressure roller becomes remarkable, and the temperature drop of the pressure roller can be recovered within the transport interval. Did not.

Further, when a small fixing roller is used, the oil supply cannot keep up with the continuous paper feeding, and an offset may occur.

Further, in fixing a color image, the glossiness of the image is liable to change depending on the temperature condition. Therefore, when the temperature of the pressure roller is reduced as described above, the glossiness in the initial stage of continuous paper feeding is reduced. However, there is a problem that the glossiness gradually decreases as the number of sheets passed increases, and the image quality becomes non-uniform. In addition, the glossiness also changes due to a change in the amount of application on the surface of the fixing roller. In other words, when the amount of application is reduced, the effect of the oil layer covering the roughness of the roller surface is reduced, causing the occurrence of offset and a decrease in glossiness,
If the amount of application is too large, heat conduction from the roller surface to the toner and the recording material is hindered, and there is a problem that the glossiness is also lowered. Therefore, in order to maintain stable continuous image quality, it is necessary to always keep both the temperature of the pressure roller and the oil application of the fixing roller in a good state.

Further, when the heater is provided only on the fixing roller, there is another problem that the life of the roller is shortened. In other words, if the fixing roller temperature is set higher than before in order to obtain a sufficient amount of heat, deterioration of the roller material is accelerated,
In addition, since the melt viscosity of the toner directly adhered to the roller surface becomes lower, offset easily occurs and the life of the roller is shortened.

On the other hand, in order to reduce the size of the developing device, it is necessary to realize a non-magnetic one-component system. At the time, when the toner abuts on the photosensitive drum or when cleaning is performed, fusing due to frictional friction is very likely to occur. Therefore, it is necessary that the glass transition point of the toner be 60 ° C. or higher to prevent fusing.

However, a hardened toner having a glass transition point of 60 ° C. or higher is different from a soft toner having a glass transition point lower than 60 ° C.
There has been a problem that the surface gloss of the image is reduced and the translucency of the OHT sheet is also deteriorated.

Therefore, the toner has a softening point of 130 ° C. or less and a viscosity of 100 ° C.
At it it was thought that use of the following toner 1.5 × 10 ⁵ poise, although color mixing property and translucency was slightly improved is insufficient as still lead to prevent the occurrence of the offset Did not.

Further, in the above-mentioned conventional apparatus provided with a cleaning member for a web or a pad, an oil application mechanism,
These necessitate a cleaning mechanism, which hinders miniaturization of the apparatus. Furthermore, replacement and maintenance of rollers, oils, and cleaning materials are not preferable from the viewpoint of safety and hygiene for the user side, and there is also a problem that maintenance costs are increased if the manufacturer performs the service. . Although the above-mentioned problem is currently being solved to some extent in a monochrome / two-color type fixing device, it remains as an essential problem in a color fixing device. One of the reasons is that a color image needs to fix a multicolored thick toner layer of yellow, cyan, magenta, black, etc. There is
That is, the endurance load is significantly higher than that of the single color or the two colors. In addition, since the color developing property and the color mixing property cannot be enhanced unless they are completely melt-mixed, the toner resin used is made of a material having a small viscoelasticity that is sharply melted at a relatively low temperature. This resin has much worse releasability from the roller than that of the monochrome resin.

Therefore, in order to maintain the releasability of a roller having a silicone rubber / fluororesin surface, the surface of the roller is always covered with silicone oil to provide a releasing effect to prevent offset phenomenon and roller deterioration. It was necessary to prevent it. At that time, there is a demand that the amount of oil used be reduced to a small amount as much as possible, to save the trouble of replacement, to reduce the size of the large-capacity oil tank, and to simplify the application mechanism.

Further, in the conventional apparatus shown in FIG. 8 , it is difficult to obtain a sufficient oil reservoir container due to restrictions on the size of the apparatus, and the following problems occur.

1) When the apparatus is not used on a horizontal table or the entire apparatus is tilted when the apparatus is moved, oil overflows from the oil reservoir.

2) If the liquid level of the oil is too low, sufficient coating cannot be performed, and if the liquid level is too high, the oil overflows beyond the wall of the container, and it is necessary to control the liquid level at a position intermediate between the two. Yes, the smaller the container, the narrower the latitude and the more difficult it is to control.

[0021] 3) the number of components is increased, to be diversified heat-resistant material, high cost.

An object of the present invention is to solve the above-mentioned problems and to provide a fixing device having a mechanism for applying oil which has no oil spill, can easily control the oil level, and has a low fixing cost. Is to do.

[0023]

According to the present invention, an object of the present invention is to provide a fixing roller, and a releasing agent applying means for applying a releasing agent to the fixing roller. means, in the fixing device having a coating member for applying a release agent in contact with the fixing roller, and a dropping portion for dropping a release agent, and a supply unit for supplying a release agent to the dropping unit, the coating
The member is in the form of a roller, and the drip portion is the fixing roller
Has multiple micro holes along the axial direction of
Release agent is the contact position of the application member and the constant roller
This is achieved by dropping the liquid at different positions on the application member .

[0024]

According to the present invention, the release agent is supplied to the release agent dropping section by the release agent supply section, and is dropped onto the coating member from the fine holes formed in the release agent dropping section. Since the micropores are formed along the axial direction of the fixing roller, the release agent is uniformly dropped along the axial direction of the fixing roller, and the release agent is applied by an application member disposed so as to contact the surface. It is evenly distributed on the surface.

[0025]

EXAMPLES Examples 1 to 3 of the present invention are referred to as reference examples.
Both will be described with reference to the drawings.

[0026] <Example 1> First, a description will be given of a first embodiment of the present invention in FIG. Incidentally, the same parts of the conventional example device shown in FIG. 8 will not be described are denoted by the same reference numerals. FIG. 1 shows a schematic configuration of an apparatus according to a first embodiment of the present invention. In this embodiment, as shown in FIG. 1 , a pump having a pumping roller and an oil reservoir is provided.
In addition, a nozzle 516 for uniformly dropping oil in the axial direction of the roller is provided on the surface of the application roller 508 as an application member .

Accordingly, the procedure for applying oil to the surface of the fixing roller is as follows. First, the conveyance of the oil 512 from the oil tank 515 to the nozzle 516 is started by the pump 514 immediately before the recording material is conveyed and the fixing is started, and stopped when the fixing is completed. At this time,
Improve the accuracy of the pump to control the oil transport, by increasing the fine pore diameter of the nozzle and axial uniformity, 8
The regulating blade 509 may be omitted perform uniform coating, such as. The configuration shown in FIG. 2 is a reference example of the present invention in which the oil drop position is on the fixing roller. Also,
In the above method, even if the supply amount of oil becomes excessive and an oil pool occurs in the nip portion between the application roller and the fixing roller and the oil overflows, the oil starts to overflow from both ends of the roller due to the configuration. The danger of oil falling on the material passage is much less than in the prior art.

<Reference Example 1 > Next, Reference Example 1 according to the present invention will be described with reference to FIG. The same parts as those in the first embodiment are denoted by the same reference numerals, and the description is omitted.

FIG. 3 shows the first embodiment. In this reference example, in addition to the pumping roller and the oil reservoir, the application roller is omitted, and a new leveling blade 517 is provided. The blade is pressed against the surface of the fixing roller, and the oil dripped from the nozzle onto the surface of the fixing roller is discharged. The roller is evenly distributed in the axial direction.

[0030] Therefore, as the procedure of oil application to the fixing roller surface in the present reference example, except that there is no rotation of the application roller is the same as in Example 1, carried out for the case where the oil supply becomes excessive Examples As in the case of 1 , the risk of oil falling on the recording material passage area is extremely low. However, in the case of using the stomach as a pressing method of the blade, the blade tip is set to be in point contact with the surface of the fixing roller in order to prevent the tip of the blade from separating from the fixing roller and causing oil dripping from the tip of the blade. It is necessary, and more desirably, the contact position between the blade and the fixing roller is set above the center horizontal line of the fixing roller. When the durability of the fixing roller is important, there is a method of providing a fluororesin layer on the surface of the leveling blade in order to reduce the friction between the blade and the roller.On the contrary, it is necessary to finely regulate the oil application amount. When emphasis is placed, there is a method of providing fluororubber on the leveling blade surface.

[0031] <Example 2> Next, a second embodiment of the present invention will be described with reference to FIG. Incidentally, the same parts of the first embodiment will not be described are denoted by the same reference numerals.

[0032] Figure 4 illustrates a second embodiment of the present invention. In this embodiment, the oil from the nozzle 516 is applied to the application roller.
508. In this embodiment, the oil tank 515 is newly deformed to provide an opening under the pressure roller, and the oil applied at the time of fixing is transferred to the pressure roller side without being adsorbed by the recording material. The structure is such that the oil falling from the pressure roller can be collected. By adopting such a configuration, it is also possible to reuse the unconsumed oil collected by using the pump 514 provided for oil application, and to provide processing means for absorbing and discarding oil falling from the pressure roller. This eliminates the need and increases the efficiency of oil use, which is advantageous in terms of simplification of the size of the device, extension of the oil supply cycle, and the like.

[0033] <Reference Example 2> Next, a description will be given of a reference example 2 of the present invention in FIGS. 5 to 7. Incidentally, the same parts of the first embodiment will not be described are denoted by the same reference numerals.

[0034] FIG. 5 shows a reference example 2 of the present invention. In this reference example, the application roller, the pumping roller, the oil reservoir and the regulating blade are not provided, and the oil drop position of the nozzle is set at the boundary between the cleaning member and the sponge roller, and more preferably, the cleaning roller is fixed to the fixing roller. Set the area in contact with the surface,
The cleaning web and the sponge roller are also used as an oil leveling member. In this configuration, a silicone rubber roller may be used in place of the sponge roller, similarly to the application roller, particularly when the amount of oil absorbed by the sponge roller affects the oil application amount.

[0035] Note that the nozzle used in each of the above embodiments there are two as shown in FIG. 6 and FIG. 7 roughly.

FIG. 6A shows a structure in which a tube is connected to the center of a nozzle 516 provided with micro holes 518 in a heat-resistant container, and is an effective structure when importance is placed on the symmetry of the application distribution. In the figure, the tip of the nozzle is divided to further improve the uniformity of coating.

FIG. 7 shows that the tip of the tube is sealed and micro holes 518 are provided in the area of the paper passing area. This reduces the number of parts and improves workability, and is effective when cost reduction is important. It is. Regarding the uniformity of the application distribution, if the diameter of the micropores is too large compared to the viscosity of the oil, the amount of oil dripping on the root side from the tube tip tends to increase, but the oil is easily made using the surface tension of the oil. By making the hole diameter small enough to prevent free fall, and increasing the hole diameter toward the tip of the tube, the coating can be made uniform.

Regardless of which nozzle is used, the smaller the volume of the nozzle, as opposed to the conventional example which requires a certain amount or more, the better the response of the oil to the control of the pump, and It is better to reduce the volume of the nozzle as much as possible because the amount of oil can be reduced.

Finally, in Examples 1 and 2 , the fixing roller and the pressure roller were fixed at a diameter of 40 mm, a fixing temperature of 175 ° C., and a fixing speed of 86 mm / sec. 0.2m diameter at 1mm intervals
m holes are arranged in A4 paper width.
Using a tube pump that can control oil conveyance of about 0 mg, oil is conveyed at a speed of 10 mg / sec, and about 30 mg per A4 sheet without causing oil dripping.
Achieved uniform oil application. Further, it is also effective to use a slit instead of the minute hole of the nozzle or to provide a porous film in the opening.

[0040]

As described above, according to the present invention,
The dropping portion has a micro-hole formed along the axial direction of the fixing roller, because the release agent from the micropores of the dropper were to be dropped into the coating member, a release agent Multiple
Of the coating member in the longitudinal direction
Mold release agent can be applied evenly, and
The release agent is applied at a different coating
Since it is dropped on the cloth member, the release agent dropped on the coating member
More evenly before moving to the position where it contacts the fuser roller
Become.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic configuration of an apparatus according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a fixing device according to a reference example of the invention.

FIG. 3 is a cross-sectional view illustrating a schematic configuration of an apparatus according to a first embodiment of the present invention.

FIG. 4 is a sectional view showing a schematic configuration of an apparatus according to a second embodiment of the present invention.

5 is a cross-sectional view showing a schematic configuration of Example 2 according to the present invention.

FIG. 6 is a perspective view showing an example of a release agent dropping unit used in the apparatus shown in FIGS. 1 to 5;

FIG. 7 is a perspective view showing another example of a release agent dropping portion used in the apparatus shown in FIGS. 1 to 5;

FIG. 8 is a cross-sectional view illustrating a schematic configuration of a fixing device having a conventional release agent applying unit.

[Explanation of symbols]

 502 Fixing roller 508 Application roller (application member) 512 Silicone oil (release agent) 513 Tube (release agent supply unit) 514 Pump (release agent supply unit) 515 Oil tank (release agent supply unit) 516 Nozzle (release) Molding agent dropping part)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 13/20 G03G 15/20

Claims (3)

(57) [Claims] 1. A fixing device comprising: a fixing roller; and a release agent applying unit for applying a release agent to the fixing roller, wherein the release agent applying unit contacts the fixing roller and applies the release agent. In a fixing device having an application member, a dropping section for dropping a release agent, and a supply section for supplying a release agent to the dropping section, the coating member is in the form of a roller, and the dropping section is fixed.
It has a plurality of micro holes along the axial direction of the
The release agent from the small hole contacts the coating member and the fixed roller.
A fixing device , wherein the liquid is dropped onto a position on the application member different from the position . 2. A small hole of the dropping unit, a fixing device according to claim 1, characterized in that a slit formed small width along the axial direction of the fixing roller. 3. A small hole of the dropping unit, the fixing roller
The fixing device according to claim 1, wherein the fixing device is a plurality of small diameter round holes formed along the axial direction of the fixing device.