JP3163931B2 - 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 used in an image forming apparatus utilizing an electrophotographic process such as a copying machine, a printer or a facsimile.

[0002]

2. Description of the Related Art Conventionally, in a copying machine or the like utilizing an electrophotographic process, it is necessary to fix an unfixed toner image formed on a recording sheet into a permanent image. A pressure fixing method and a heat fixing method are known. The solvent fixing method has a drawback that the solvent vapor emanates and the problem of odor occurs, and the pressure fixing method has inferior fixability as compared with other methods, and the pressure-sensitive toner is expensive. At present, both have drawbacks and have not been widely used. For this reason, in order to fix an unfixed toner image, a heat fixing method in which a toner is generally melted by heating and fused on a recording sheet is widely used.

As a heat fixing device using this heat fixing method, as shown in FIG.
0, the recording sheet S on which the unfixed toner image S1 is formed is passed in the direction A between
A heating roller type which performs pressure fixing is known.
The heating roller 10 has a configuration in which a heater 12 is provided inside a cylindrical metal core 11 and a heat-resistant resin coating layer 13 is formed on an outer peripheral surface thereof. A heat-resistant elastic body 22 that is pressed against the resin coating layer 13 of the heating roller 10 is formed on the outer peripheral surface of the core 21. Such an apparatus has a higher thermal efficiency than other apparatuses using a hot air fixing method such as a hot air fixing method or an oven fixing method, so that it can be operated with low power, has a high speed, and has a fear of a fire due to a paper jam. It is currently the most widely used because there is no such thing.

Generally, in order to sufficiently fix the toner image S1, it is necessary to provide a nip portion P1 having a width (nip width) of at least about 4 mm. However, in the conventional heat fixing device, since both the heating roller 10 and the pressure roller 20 are cylindrical, in order to secure a sufficient nip width, the diameters of the heating roller 10 and the pressure roller 20 must be large. As a result, the entire apparatus becomes large and complicated, and it takes a long time of about 1 to 10 minutes to raise the temperature of the apparatus from room temperature to a temperature at which fixing can be performed (hereinafter referred to as a warm-up time). There is also.

Accordingly, the applicant of the present invention has proposed that a rotatable pressure roller 2 is placed under a heating roller 10 as shown in FIG.
A fixing device in which the heat-resistant elastic member 25 is fixedly disposed instead of 0 is proposed. In this heat-resistant elastic member 25, an elastic body 27 made of silicone rubber is housed in a support 26 having an open top, and a porous release agent permeation control film 28 is stretched on the upper surface of the elastic body 27. Things. here,
Unlike the cylindrical pressure roller 20, the heat-resistant elastic member 25
Can be freely set regardless of the size of the heat-resistant elastic member 25, so that the nip width P2 can be easily set.
Can be increased. Therefore, there is an advantage that the device can be reduced in size and simplified, and the warm-up time can be reduced.

The elastic body 27 is impregnated with a release agent, and the release agent is applied to the release agent permeation control film 28.
And is applied to the surface of the heating roller 10. The reason why the release agent is supplied to the surface of the heating roller 10 is to improve the performance of releasing the toner from the heating roller 10.

[0007]

However, this device has the following problems. For example, when silicone rubber is used as the elastic body 27 that is impregnated with and holds the release agent, and the elastic body 27 is gelled and impregnated with silicone oil as a release agent, the surface of the release agent permeation control film 28 is formed. It is not easy to control the amount of the release agent leached into a suitable amount, and the production cost is extremely high to do so. The hardness and rebound resilience of the elastic body 27 change according to the amount of the release agent impregnated, and as a result, a predetermined nip width cannot be obtained. For this reason, the fixing strength and the glossiness are insufficient, and it is impossible to fix a good toner image. Further, the passing characteristics of the recording sheet S may fluctuate, and the recording sheet S may not pass, or an image may be disturbed due to a speed change on the way.

[0008] Such a problem is not caused by supplying the release agent from the heat-resistant elastic member 25 constituting the nip portion P2, but by separately supplying the release agent supply member 29 as shown by a virtual line in FIG. It seems to be solved by providing. However, in this case, even if the release agent is supplied, a very small amount of the offset toner adhering to the surface of the heating roller 10 is transferred to the release agent supply member 29 and gradually accumulates. After fixing of the deposited toner on the recording sheet S, the heating roller 10 is cooled, and when the heating roller 10 is reheated for fixing to the next recording sheet, the toner is transferred to the heating roller 10 again. This is because when the deposited toner starts to melt, the heating roller 10 starts to rotate, a large shearing force is applied to the toner, the toner is separated, and the heating roller 1
This is because they are re-adhered to 0. Then, the re-adhered toner is further melted on the heating roller 10 and transferred to the recording sheet S. As a result, a black streak-like image defect occurs on the recording sheet S to be fixed. In order to prevent this, it is conceivable to provide a cleaning means for removing the toner from the release agent supply member 29, but this requires a complicated structure and increases the manufacturing cost.

The present invention has been made in consideration of the above circumstances, and stably supplies a releasing agent for preventing toner offset to a fixing roll, while conveying a recording sheet and fixing toner. It is an object of the present invention to provide a fixing device that does not hinder the image formation and does not cause a defect in an image due to offset toner.

[0010]

A fixing device according to the present invention has a heating unit and a pressing unit which are disposed to face each other and at least one of which is movable, and presses the pressing unit and the heating unit together. a nip portion therebetween by providing, in the fixing device is passed to heat and pressure pressure fixing the toner image on the recording sheet recording sheet to the nip portion, a release agent supplied to a position different from the above nip disposed member, the toner offset to at least one of said heating means and pressurizing means from the recording sheet, is adhered to the release agent supplying member, the recording passing through the nip portion
When the sheet comes into contact with the release agent supply member,
The toner adhered to the release agent supply member is adhered to the recording sheet .

[0011]

According to the fixing device of the present invention, the release agent supply member is provided at a position different from the nip portion, thereby irrespective of the configuration of the heating means and the pressing means for forming the nip part. It is possible to stably supply the release agent. Further, since the heating means and the pressing means are not impregnated with the release agent, the hardness and rebound resilience of these means do not change. Therefore, the nip width can be made constant, and a good toner image having desired fixing strength and glossiness can be fixed. Further, it is possible to prevent the recording sheet from being unable to pass without changing the passage characteristic of the recording sheet, or to prevent problems such as an image being disturbed due to a speed change on the way.

In the case where a very small amount of offset toner adhering to the surface of the heating means or the pressure means is transferred to and deposited on the release agent supply member, the recording sheet to be fixed passes through the nip portion. Each time, the toner is transferred from the release agent supply member to the leading end of the recording sheet. As a result, the surface of the release agent supply member is cleaned, and the toner does not transfer to the moving heating means or the pressing means again, and does not stain the center of the recording sheet. Further, each time the recording sheet passes through the nip portion, the surface of the release agent supply member is cleaned, so that the amount of toner adhering to the leading end of the recording sheet is always very small and is recognized as being dirty. Very few things. This is the same even when the heating unit is cooled after the fixing to the recording sheet and the heating unit is reheated to fix the recording sheet to the next recording sheet. It is possible to prevent a black streak-like image defect from occurring on the top. Therefore, there is no need to provide a cleaning unit for removing the toner from the release agent supply member, the structure is simple, and the manufacturing cost does not increase.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. (1) First Embodiment FIG. 1 shows a fixing device according to a first embodiment. This fixing device includes a heating roller (heating means) 30 and a fixed heat-resistant elastic member (pressing means) 40 disposed below and opposed to the heating roller 30. Reference symbol S denotes a recording sheet, T denotes unfixed toner transferred onto the recording sheet S, arrow A denotes a conveying direction of the recording sheet S, and arrow B denotes a rotation direction of the heating roller 30. Here, the nip portion N through which the recording sheet S is passed is provided between the heating roller 30 and the heat-resistant elastic member 40 by being pressed against each other.

The heating roller 30 dip-coats a silicone-based rubber such as silicone LTV rubber to a thickness of about 30 μm on the outer peripheral surface of a cylindrical iron core 31 having an outer diameter of 15 mm, a thickness of 0.3 mm, and a length of 225 mm. Thus, the release layer 33 is formed. Inside the iron core 31, a heater 32 which is an infrared lamp with an output of 100V and 300W is provided. The surface temperature of the heating roller 30 heated by the heater 32 is constantly controlled to 150 ° C. by a temperature controller (not shown). Symbol 46 is
4 shows a thermocouple for monitoring the surface temperature of the heating roller 30 with a temperature controller.

On the other hand, the heat-resistant elastic member 40 is composed of a rigid support 41 having a substantially U-shaped cross section, a leaf spring 43 supported by one upper part of the support 41, and It is composed of a laminated elastic body 44 and a film 45 stretched on the surface of the elastic body 44 on the heating roller 30 side. The leaf spring 43 is made of, for example, an elastic metal plate such as spring steel, and has a thickness of 0.1 to 0.3.
mm is preferable, and most preferably 0.15 mm.

The elastic body 4 is provided on the upper surface of the leaf spring 43.
4 are adhered. The elastic body 44 is made of a silicone LTV rubber having a rubber hardness of 20 mm measured according to JIS-K6301 and formed into a flat plate having a thickness of 1.5 mm, and is elastically deformed by receiving a pressing load of the heating roller 30. I do. Note that the width of the elastic body 44 and the leaf spring 43 (the length in the traveling direction of the recording sheet S) is 8 mm.

Heating roller 30 and heat-resistant elastic member 40
Are pressed against each other, and the plate spring 43 is slightly bent downward due to the pressing load at this time, and the elastic body 44 is elastically deformed. As a result, the elastic body 44 has a thickness of only 1.
The nip width can be reduced to 3 mm while the width is 5 mm and the width is only 8 mm. The pressing load is 2 kgf, and the deformation of the heating roller 30 can be almost ignored.

The film 45 is made of a low friction material having a very small coefficient of friction with the recording sheet S as compared with the release layer 33 of the heating roller 30. Further, since this material receives a high temperature of 150 ° C. from the heating roller 30, it is necessary to have heat resistance. As such a material, for example, a fluorine-based resin, specifically, polytetrafluoroethylene is used.

In FIG. 1, a release agent supply member 60 is disposed at a position immediately before the nip portion N, and is fixed by a fixture (not shown). The release agent supply member 60 includes:
It is a porous impregnated body capable of impregnating a liquid. In this embodiment, dimethyl silicone oil having a viscosity of 10,000 centistokes is used as a release agent. In this case, it is preferable to use a heat-resistant felt made of aromatic polyamide having a density of 0.3 g / cm ³ (trade name: “NOMEX”) as the impregnated body constituting the release agent supply member 60. The release agent supply member 60 is brought into contact with the surface of the heating roller 30 at a predetermined pressure, from which the release agent is leached and applied to the surface of the heating roller 30.

The release agent needs to be uniformly applied to the entire surface of the heating roller 30. From this viewpoint, a test for examining a suitable thickness (length along the traveling direction of the recording sheet S) of the release agent supply member 60 was performed. Table 1 shows the results of the test.

[0021]

[Table 1]

In Table 1, the symbol ○ indicates that supply unevenness did not occur on the surface of the heating roller 30, and the symbol x indicates that supply unevenness occurred. As is clear from this table, when the thickness of the release agent supply member 60 is 0.8 mm or more, the release agent is uniformly applied to the surface of the heating roller 30. This is presumably because the thickness error of the release agent supply member 60 at the time of molding is relatively large when the thickness is less than 0.8 mm. The suppression plate 62 in the table will be described later.

B. Operation and Effect of Embodiment Next, the operation of the fixing device having the above configuration will be described. First, the heating roller 30 is rotated in the direction of arrow B while being heated by the heater 32. Then, the recording sheet S on which the image with the unfixed toner T is formed passes through the nip portion N from the direction of the arrow A. In the case of this embodiment, the recording sheet S first passes between the heating roller 30 and the release agent supply member 60, and then passes through the nip N. In the nip portion N, the unfixed toner T is transferred from the heater 32 to the iron core 31 and the release layer 33.
The recording medium S is fixed on the recording sheet S by receiving heat given through the heating roller 30 and a pressing load acting between the heating roller 30 and the heat-resistant elastic member 40.

According to the fixing device, the coefficient of friction between the heating roller 30 and the heat-resistant elastic member 40 is reduced by the film 45 made of a heat-resistant low-friction material provided on the surface of the elastic body 44 on the heating roller 30 side. Decrease. Therefore, the driving force for rotating the heating roller 30 can be reduced. Furthermore, wear of the surface of the heating roller 30 and the surface of the heat-resistant elastic member 40 is reduced, and the life of the apparatus can be improved.

Moreover, the recording sheet S slides on the heat-resistant elastic member 40, so that the leading end of the recording sheet S easily enters the nip portion.
The recording sheet S is conveyed due to the friction between the recording sheet S and the running property of the recording sheet S.

Further, since the surface of the heat-resistant elastic member 40 becomes concave due to bending of the leaf spring 43 and elastic deformation of the elastic body 44, it is possible to obtain a large nip width even if the pressing load by the heating roller 30 is low. Can be. Therefore, the device can be reduced in size and simplified, and the warm-up time can be reduced.

Now, the surface of the heating roller 30 is
And the release agent supply member 6
By releasing the release agent from 0 and applying the release agent to the surface of the heating roller 30, the unfixed toner T is prevented from offsetting to the heating roller 30 as much as possible. However, even in this case, it is inevitable that a very small amount of the unfixed toner T adheres to the heating roller 30.

The offset toner is supplied to the heating roller 30
With the rotation of, it makes a complete rotation and transfers to the release agent supply member 60. Thereby, the surface of the heating roller 30 is cleaned. Then, when the recording sheet S on which the toner T is to be fixed is conveyed toward the nip portion N, the toner is transferred from the release agent supply member 60 to the leading end of the recording sheet S.

By repeating the above process,
Each time the recording sheet S to be fixed passes through the nip portion N, the release agent supply member 60 is attached to the leading end of the recording sheet S.
Is transferred from the toner T. As a result, the surface of the release agent supply member 60 is always cleaned, and the toner T does not transfer to the heating roller 30 again and does not stain the center of the recording sheet S. Further, each time the recording sheet S passes through the nip portion N, the surface of the release agent supply member 60 is cleaned, so that the amount of toner T adhering to the leading end of the recording sheet S is always very small and becomes dirty. Is rarely recognized as being This is the same even when the heating roller 10 is cooled after the fixing to the recording sheet S and the heating roller 30 is reheated for fixing to the next recording sheet. Occasionally, black streak-like image defects on the recording sheet S can be prevented. Therefore, there is no need to provide a cleaning unit for removing the toner T from the release agent supply member 60, the structure is simple, and the manufacturing cost does not increase.

By disposing the release agent supply member 60 at a position different from the nip portion N, regardless of the configurations of the heating roller 30 and the heat-resistant elastic member 40 forming the nip portion N, It is possible to supply the release agent stably. In addition, since the heating roller 30 and the heat-resistant elastic member 40 are not impregnated with the release agent, the hardness and rebound resilience of these members do not change. Therefore, the width of the nip portion N can be made constant, and a good toner image having desired fixing strength and glossiness can be fixed. In addition, it is possible to prevent the recording sheet S from being unable to pass without causing the passage characteristic of the recording sheet S to fluctuate, or to prevent the image from being disturbed due to a speed change in the middle.

During the time when the recording sheet S passes between the heating roller 30 and the release agent supply member 60 (that is, during almost the entire fixing time), the release agent supply member 60 heats the recording sheet S. It will come into contact with the surface opposite to the roller 30. Therefore, the supply of the release agent to the surface of the heating roller 30 is temporarily interrupted. However, the heating roller 3
0 is rotating, and when the recording sheet S is not between the heating roller 30 and the release agent supply member 60, a sufficient amount of release agent is supplied from the release agent supply member 60; There is no problem if the supply is temporarily cut off.

(2) Second Embodiment FIG. 2 shows a fixing device according to a second embodiment of the present invention. Unlike the first embodiment, in the present embodiment, the release agent supply member 60
Are disposed immediately after the nip portion N. Other configurations are completely the same as those of the first embodiment. In the present embodiment, the same effects as in the first embodiment can be obtained. In this case, the toner offset to the heating roller 30 comes into contact with the film 45 before attaching to the release agent supply member 60 with the rotation of the heating roller 30, but the film 45 is made of polytetrafluoroethylene having a high release property. By forming the film 45 with ethylene or the like, the toner is prevented from adhering to the film 45 and transferred to the release agent supply member 60. Then, the toner is carried away to the leading end of the recording sheet S that has passed through the nip portion N next.

Further, in this embodiment, the release agent supply member 6
By disposing 0 at a position immediately after the nip portion N,
The recording sheet S easily enters the nip portion N.
Therefore, it is considered that the transportability of the recording sheet S is better than in the first embodiment.

(3) Third Embodiment Next, FIG. 3 shows a fixing device according to a third embodiment of the present invention. In this apparatus, in addition to the configuration of the second embodiment, a suppression plate 62 is disposed behind the release agent supply member 60 along the rotation direction of the heating roller 30. The upper end of the restraining plate 62 is substantially at the same height as the upper end of the release agent supply member 60, thereby preventing the release agent supply member 60 from falling over with the rotation of the heating roller 30. You.

However, the suppression plate 62 is arranged at a distance from the heating roller 30 so as not to excessively remove heat from the heating roller 30 and to prevent the release layer 3 on the surface of the heating roller 30 from being removed.
3 is not damaged. As the restraining plate 62, any material may be used as long as it can support the release agent supply member 60 against the rotational torque of the heating roller 30 and has sufficient heat resistance. In the present embodiment, a stainless steel plate having a thickness of 0.1 mm was used as the suppression plate 62.

The depressing plate 62 is particularly effective when the release agent supply member 60 having a thickness of 2.0 mm or less is used. Is used, the problem that the release agent supply member 60 falls down due to the rotation of the heating roller 30 and the release agent cannot be applied to the surface of the heating roller 30 is solved.

(4) Fourth Embodiment FIG. 4 shows a fixing device according to a fourth embodiment of the present invention. In this apparatus, in addition to the configuration of the third embodiment, the surface of the release agent supply member 60 is made of a porous film 63 made of a heat-resistant material.
It is covered with. As the porous film 63, a film in which a number of holes are formed in a polytetrafluoroethylene resin film, for example, a trade name “Goretex GT sheet” manufactured by Japan Goretex Co., Ltd. can be used.

Table 2 shows the results of a test in which a large number of recording sheets S were successively subjected to image fixing and the release agent supply state was compared between the case where the porous film 63 was provided and the case where the porous film 63 was not provided. Is shown. In the above two cases, the release agent supply member 6
Zero was impregnated with an equal amount of release agent. As the recording sheet S, Fuji Xerox's A-4 size L
The paper was transported in the portrait direction. In addition, two types of recording sheets S were prepared, a so-called fresh paper sheet whose package was just opened, and a sheet whose water content was adjusted to about 10% under a high humidity environment.

[0039]

[Table 2]

In this table, the symbol ○ indicates that the amount of release agent supplied per A4 sheet was 0.1 mg or more, and the symbol △ indicates that the amount of release agent supplied per A4 sheet was 0 mg. .
X was less than 0.1 mg, and X was A
This indicates that the release agent supply amount per one sheet of paper was less than 0.05 mg. In the case of a fixing temperature of 150 ° C. as in the present embodiment, the release agent supply amount per A4 sheet is 0.1%.
mg or more is considered suitable. When the porous film 63 was not provided, the release agent supply amount per A4 sheet was 0.05 m at the time of fixing 8000 sheets.
g, the fixing of 10,000 sheets was not performed.

As is clear from Table 2, when the porous film 63 is not provided, a sufficient amount of release agent cannot be supplied at the time of fixing 5,000 sheets.
This is because if the porous film 63 is not provided, the release agent supply member 60 comes into direct contact with the surface of the heating roller 30 and supplies a large amount of the release agent at an initial stage.
On the other hand, when the porous film 63 is provided, since the porous film 63 regulates the amount of supply from the release agent supply member 60 to the heating roller 30, the release agent lasts longer, and
The release agent can be stably supplied even when the number of sheets fixed is 00 or more.

Incidentally, in order to uniformly apply the release agent to the surface of the heating roller 30, it is necessary to bring the release agent supply member 60 into contact with the heating roller 30 with a certain load.
However, if this load is applied too much, the release agent supply member 60
The recording sheet S is jammed between the recording sheet S and the heating roller 30. This phenomenon is particularly remarkable in the case of thin paper such as tracing paper. Therefore, a test was conducted to examine the relationship between the load between the release agent supply member 60 and the heating roller 30 and the clogging of the recording sheet S. In this test, the heating roller 3
The pressure contact load between 0 and the heat-resistant elastic member 40 was 3 kgf. Table 3 shows the results of this test.

[0043]

[Table 3]

In Table 3, the symbol ○ indicates that the recording sheet S is 1
00 indicates that no sheet was clogged after passing, 00 indicates that clogging occurred in less than 3 out of 100 sheets, and x indicates that clogging occurred in 3 or more out of 100 sheets. Indicates that an event has occurred. According to this table, the heating roller 3
It can be seen that if the pressure load between the heating roller 30 and the release agent supply member 60 is smaller than the pressure load between the heat-resistant elastic member 40 and the recording sheet S, clogging of the recording sheet S is less likely to occur.

The heating roller 30 and the heat-resistant elastic member 4
A similar test was performed with a pressure contact load between 0 and 3 kgf. In this case, if the pressing load between the heating roller 30 and the release agent supply member 60 was less than 3 kgf, the recording sheet S was hardly clogged. Therefore, if the pressing load between the heating roller 30 and the release agent supplying member 60 is smaller than the pressing load between the heating roller 30 and the heat-resistant elastic member 40, the recording sheet S is less likely to be clogged. That was confirmed.

Further, when the image is continuously fixed using the water-containing paper, the water vapor evaporated from the recording sheet S by being heated in the nip portion N is supplied to the nip portion N and the release agent supply member. Between 60 and the recording sheet S
It turned out to generate muscle. This phenomenon is
This occurred both when the release agent supply member 60 as shown in FIG. 3 was not covered with the porous film 63 and when the release agent supply member 60 as shown in FIG. 4 was covered with the porous film 63.

This is because the nip N and the release agent supply member 60
Since the recording sheet S is not sandwiched between the heating roller 30 and the heat-resistant elastic member 40, water vapor escapes, and the heat-resistant elastic member 40 downstream of the nip portion N has a low temperature. This is considered to be because the steam that has flowed into the recording sheet S as water droplets here. Therefore, a test was performed in which the gap between the nip portion N and the release agent supply member 60 was changed to check whether or not dew condensation would occur. Table 4
Indicates the results of this test.

[0048]

[Table 4]

As is apparent from Table 4, when the gap between the nip portion N and the release agent supply member 60 is 1 mm or less, the above-mentioned problem of dew condensation does not occur. This test was performed for both cases where the release agent supply member 60 was not covered with the porous film 63 and for cases where the release agent supply member 60 was covered with the porous film 63, and similar results were obtained. This is because, when the gap is small, the recording sheet S comes into close contact with the heating roller 30 and the heat-resistant elastic member 40, so that there is no escape space for water vapor, and the temperature of the heat-resistant elastic member 40 in the gap hardly decreases. This is probably because even when the water vapor escapes, dew condensation hardly occurs.

(5) Fifth Embodiment FIG. 5 shows a fifth embodiment of the present invention. This embodiment can also avoid the above-mentioned problem of dew condensation.
Here, the porous film 63 is bridged from the release agent supply member 60 to the upper surface of the elastic body 44 of the heat resistant elastic member 40,
The film 45 was laminated thereon. According to this, even if the recording sheet S passes through the nip portion N, the porous film 6
3, the recording sheet S is pressed to the heating roller 30 side. Therefore, the recording sheet S is brought into close contact with the heating roller 30 and the porous film 63 until the recording sheet S has passed through the release agent supply member 60, and even in the gap between the nip portion N and the release agent supply member 60, Since the temperature of the recording sheet S hardly decreases and the dew condensation hardly occurs on the porous film 63, the problem that water droplets flow on the recording sheet S is solved.

(6) Sixth Embodiment FIG. 6 shows a sixth embodiment of the present invention. In this example,
A heat-resistant elastic member (pressing means) 70 is used in place of the heat-resistant elastic member 40 of the above embodiment. The heat-resistant elastic member 70 is the same as the heat-resistant elastic member 40 except that the support 71 is different.

The storage section 72 is provided at the bottom of the support 71.
The release unit L is stored in the storage unit 72. Further, the release agent supply member 60 is elongated, and extends from the heating roller 30 to the storage unit 72.
The release agent supply member 60 is formed of a heat-resistant felt, sucks up the release agent L from the storage unit 72 by a capillary phenomenon, and supplies the release agent L to the heating roller 30.

According to the present embodiment, the release agent L
Is stored, it is possible to continuously supply the release agent L for a long time regardless of the volume of the release agent supply member 60. Further, the release agent L in the storage unit 72
Is insufficient, the initial function can be restored only by replenishing the release agent L into the storage section 72, and compared with the case where the release agent is directly replenished to the release agent supply member 60. hand,
There is an advantage that work is easy.

(7) Modification In the above embodiment, the fixed type heat-resistant elastic member 40 is used as the pressing means. However, the present invention is not limited to this. It is also possible to apply the present invention to a fixing device having a nip portion with a roll, and to provide the release agent supply member 60 immediately before or immediately after the nip portion.

When the unfixed toner T is fixed on the recording sheet S by the pressure roll and the heating roll, the recording sheet S can be conveyed with the unfixed toner T facing the pressure roll. . In this case, since the toner is offset to the pressure roller, the release agent supply member 60 is pressed against the pressure roller in order to remove the offset toner from the pressure roller.

Further, even when the fixed type heat-resistant elastic member 40 is used, the leaf spring 43 is not limited to a metal flat plate made of spring steel as in the above-described embodiment, but may be made of an elastically deformable material. Any material can be used. In the above embodiment, the elastic body 44 and the leaf spring 4
Although 3 is formed in a flat plate shape, it may be curved so as to be convex or concave toward the heating roller 30 side. By making the upper surface of the heat-resistant elastic member 40 concave, a wider nip width can be obtained. Further, instead of the leaf spring 43, a flexible member such as a silicone sponge or the like can be filled in the support body 41, and the flexible member can be compressed and deformed by a pressing load.

[0057]

As described above, according to the first aspect of the present invention, the heating means for forming the nip portion by disposing the release agent supply member at a position different from the nip portion. Regardless of the configuration of the pressurizing means, the release agent can be stably supplied. Further, since the heating means and the pressing means are not impregnated with the release agent, the hardness and rebound resilience of these means do not change. Therefore, the nip width can be made constant, and a good toner image having desired fixing strength and glossiness can be fixed. Further, it is possible to prevent the recording sheet from being unable to pass without changing the passage characteristic of the recording sheet, or to prevent problems such as an image being disturbed due to a speed change on the way.

Further, when a very small amount of offset toner adhering to the surface of the heating means or the pressing means is transferred to and deposited on the release agent supplying member, the recording sheet to be fixed passes through the nip portion. Each time, the toner is transferred from the release agent supply member to the leading end of the recording sheet. As a result, the surface of the release agent supply member is cleaned, and the toner does not transfer to the moving heating means or the pressing means again, and does not stain the center of the recording sheet. Further, each time the recording sheet passes through the nip portion, the surface of the release agent supply member is cleaned, so that the amount of toner adhering to the leading end of the recording sheet is always very small and is recognized as being dirty. Very few things. This is the same even when the heating unit is cooled after the fixing to the recording sheet and the heating unit is reheated to fix the recording sheet to the next recording sheet. It is possible to prevent a black streak-like image defect from occurring on the top. Therefore, there is no need to provide a cleaning unit for removing the toner from the release agent supply member, the structure is simple, and the manufacturing cost does not increase.

According to the second aspect of the invention, by setting the distance between the nip portion and the release agent supply member to 1 mm or less, the adhesion between the recording sheet and the heating means and the pressing means is improved. Since there is no escape point for water vapor and the temperature of the pressurizing means is less reduced, even if the water vapor escapes, it is difficult for dew condensation to occur, thereby preventing the formation of streaks on the recording sheet due to water droplets. According to the third aspect of the present invention, it is possible to reduce the occurrence of clogging of the recording sheet between the release agent supply member and the movable heating means or pressurizing means. Further, in the invention according to claim 4, since the release amount of the release agent is long because the porous film regulates the supply amount to the heating means or the pressurization means which can be moved from the release agent supply member, the porous film has a long life. Even when fixing one recording sheet, the release agent can be stably supplied.

According to the fifth aspect of the present invention, even when the recording sheet passes through the nip portion, the recording sheet is pressed toward the heating means by the porous film. Therefore, the recording sheet is brought into close contact with the heating means and the porous film until the recording sheet has passed through the release agent supply member, and the temperature of the porous film hardly decreases even in the gap between the nip portion and the release agent supply member. In addition, since dew condensation hardly occurs on the porous film, the problem that water droplets flow on the recording sheet to generate streaks is solved. Further, in the invention according to claim 6, by storing the release agent in the storage unit, the release agent can be continuously supplied for a long time regardless of the volume of the release agent supply member. It is possible. In addition, if the release agent in the storage section becomes insufficient, it is possible to recover the initial function simply by replenishing the release section with the release section, and directly replenish the release agent to the release agent supply member. There is an advantage that work is easier than in the case where

[Brief description of the drawings]

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

FIG. 2 is a schematic side view showing a fixing device according to a second embodiment of the present invention.

FIG. 3 is a schematic side view showing a fixing device according to a third embodiment of the present invention.

FIG. 4 is a schematic side view showing a fixing device according to a fourth embodiment of the present invention.

FIG. 5 is a schematic side view showing a fixing device according to a fifth embodiment of the present invention.

FIG. 6 is a schematic side view showing a fixing device according to a sixth embodiment of the present invention.

FIG. 7 is a schematic side view illustrating an example of a conventional fixing device.

FIG. 8 is a schematic side view showing another example of a conventional fixing device.

[Explanation of symbols]

S recording sheet, T unfixed toner, L release agent, 30
Heating roller (heating means), N nip portion 40, 70
Heat-resistant elastic member (pressing means), 41, 71 support, 4
3, leaf spring, 44, elastic body, 45, film, 60 release agent supply member, 62 deterring plate, 63 porous film,
72 Storage

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-36298 (JP, A) JP-A-6-19357 (JP, A) JP-A-57-147674 (JP, A) (58) Investigation Field (Int.Cl. ⁷ , DB name) G03G 13/20 G03G 15/20

Claims (6)

(57) [Claims] 1. A heating means and a pressure means, which are opposed to each other and at least one of which is movable, has a nip between them by pressing the pressure means and the heating means under pressure. In a fixing device that passes a recording sheet through the nip portion and heats and presses the toner image on the recording sheet, a release agent supply member is provided at a position different from the nip portion,
The toner offset to at least one of said heating means and pressurizing means from the recording sheet, is adhered to the release agent supplying member, the recording sea passing through the nip portion
The contact between the mold release agent supply member and the
A fixing device, wherein the toner adhered to the mold agent supply member is adhered to the recording sheet . 2. The method according to claim 1, wherein the release agent supply means is in contact with the heating means, and a distance between the nip portion and the release agent supply member is 1 mm or less.
3. The fixing device according to claim 1. 3. The method according to claim 1, wherein a force for bringing the release agent supply member into contact with at least one of the movable heating means and the pressurizing means is smaller than a pressure contact force between the pressurizing means and the heating means. The fixing device according to claim 1. 4. The release agent supply member is made of a material having heat resistance and capable of impregnating a liquid, and the surface thereof is covered with a porous film made of a heat resistant material. The fixing device according to any one of 1 to 3, above. 5. The release agent supply member is disposed immediately before or immediately after the nip portion in the traveling direction of the recording sheet, and the porous film is continuously provided from the release agent supply member to the pressurizing unit. The fixing device according to claim 4, wherein the fixing device is bridged and is in close contact with the heating unit. 6. The pressurizing means is a fixed heat-resistant elastic body, is supported by a support, and the release agent is stored in a storage section provided on the support. The fixing device according to claim 1, wherein the fixing device penetrates into the release agent supply member by a capillary phenomenon.