JPH11119579A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly apply a releasing agent to a fixing roller though its quantity is small, to attain an excellent releasing property and to reduce the sticking of a foreign matter by setting the applying quantity of the releasing agent supplied from a roller to a rotary body in accordance with the center line average roughness of a roller surface. SOLUTION: This fixing device possesses the rotary body (fixing roller) 20 to fix a toner image held on a sheet 10 by thermal pressure and an oil applying mechanism 40 applying the releasing agent (silicone oil) to the fixing roller 20, and the oil applying mechanism 40 is provided with a roller 53 impregnated with oil and supplying the oil to the fixing roller 20. The applying quantity of the oil supplied from the roller 53 to the fixing roller 20 is set in accordance with the center line average roughness of the surface of the roller 53 at a fixing device 100. By this constitution, the desired uniformity of oil application for the fixing roller 20 is extremely efficiently obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device provided in an image forming apparatus such as an electrophotographic printer or a copying machine, and more particularly to a fixing device for fixing an image to a rotating body for heat and pressure fixing. The present invention relates to a fixing device provided with a mechanism for applying a release agent.

[0002]

2. Description of the Related Art Printers using an electrophotographic process,
2. Description of the Related Art An image forming apparatus such as a copying machine includes a fixing device for fixing an unfixed toner image held on a sheet as a recording medium. There are various fixing systems,
Generally, a pressure heating fixing method is widely used.

[0003] A fixing device based on this pressure heating fixing system,
The fixing roller and the pressure roller are arranged to face each other, and a tubular heating heater such as a halogen lamp is arranged, for example, on the center axis of the fixing roller. The heat generated from the halogen lamp is uniformly radiated to the inner wall of the fixing roller, and the temperature distribution on the outer wall of the fixing roller becomes uniform in the circumferential direction. The outer wall of the fixing roller is heated until its temperature reaches a temperature suitable for fixing (for example, 150 to 200 ° C.). In this state, the fixing roller and the pressure roller rotate in opposite directions while being pressed against each other, and sandwich the sheet holding the toner.
At the nip where the fixing roller and the pressure roller are in pressure contact, the unfixed toner on the sheet is melted by the heat conducted from the fixing roller, and the pressure acting on both rollers is further applied to be fixed on the sheet.

The fixing device using the pressure heating fixing method has a configuration in which the surface holding the toner among the two surfaces of the sheet is in direct contact with the surface of the fixing roller, so that a part of the unfixed toner image on the sheet is fixed to the fixing roller. Easy to transfer to the side.
For this reason, a so-called offset phenomenon occurs in which the toner fused to the fixing roller is transferred again to the rear end of the sheet to stain the sheet, or is transferred again to the next conveyed sheet to stain the sheet. There is a disadvantage that it is easy. Therefore, a fixing device using a pressure heating fixing method has a mechanism for applying a release agent for preventing offset to a fixing roller. Silicon oil (hereinafter, also simply referred to as "oil") is used as the release agent.

The conventional oil application mechanism includes an oil tank that stores oil and extends along the axial direction of the fixing roller, and a felt or roller that is disposed so as to be immersed in the oil in the oil tank. There is also known a device that supplies oil to an oil application roller that comes into contact with a fixing roller via the felt or the like (see Japanese Patent Publication No. 61-10069).

In such an oil application mechanism, if there is uneven oil application, the following problems occur. First, when the amount of oil applied is small, a part of the toner on the sheet is transferred to the portion where the oil is small, and the offset phenomenon is likely to occur. On the other hand, when the oil application amount increases, not only does the oil consumption amount increase, but also oil stains occur on the sheet. Therefore, it is necessary to make the oil application to the fixing roller uniform and to stabilize the application amount. Therefore, conventionally, a configuration in which a blade made of metal, rubber, or the like is brought into contact with the oil application roller has been generally adopted.

[0007]

However, since a blade is used for uniform oil application, foreign matter adheres to the edge of the blade. When foreign matter adheres to the blade, the amount of oil applied is small in the area where the foreign matter is adhered and increases around the area. Will happen. For this reason, an offset phenomenon and oil contamination are caused.

On the other hand, an oil supply roller for applying oil to the fixing roller is brought into contact with an oil supply roller for supplying oil to the oil application roller, and foreign matter is transferred by a difference in surface energy between the two rollers. (See Japanese Patent Publication No. 59-29874).

[0009] However, the above-described method of treating foreign matter is a so-called post-treatment treatment of removing the foreign matter after it has adhered, and cannot eliminate the cause of foreign matter adhesion. In addition, foreign matter adhering to the oil application roller only moves to the oil supply roller located upstream of the oil supply that comes into contact with the oil application roller, and the oil carried from the oil supply roller to the oil application roller is not uniform. Brings the sex. As a result, there is a problem that uneven application of oil on the fixing roller occurs.

The present invention has been made in order to solve the problems associated with the above-mentioned prior art, and enables uniform application to a fixing roller even with a small amount of a release agent, and has excellent release properties and adheres to foreign matters. It is an object of the present invention to provide a fixing device that can reduce the image quality.

[0011]

The object of the present invention is achieved by the following means.

(1) A rotary member for fixing a toner image held on a sheet by heat and pressure, and a release agent applying mechanism for applying a release agent to the rotary member, wherein the release agent The coating mechanism includes a roller that impregnates the release agent and supplies the release agent toward the rotating body, and is supplied from the roller to the rotating body according to a center line average roughness of the roller surface. This is a fixing device in which a coating amount of a release agent is set. In this fixing device, the desired oil application uniformity to the rotating body can be obtained very efficiently. That is, it is possible to ensure uniform oil application without using a blade for uniform oil application and even when the amount of oil applied is very small.

(2) When the center line average roughness of the roller surface is Ra (μm) and the amount of the release agent supplied to the rotating body from the roller is M (mg / m ² ) It is preferable to set the fixing device so that 0 ≦ −0.6 · ln (Ra) + 0.4 · ln (M) ≦ 3. In this case, while avoiding an excessive amount of oil application and an increase in manufacturing cost, a desired oil application to the rotating body necessary to reliably prevent a situation in which toner is transferred to the rotating body and an offset phenomenon occurs. Uniformity is obtained and good image quality is obtained.

(3) Further, 1 ≦ −0.6 · ln (R
a) It is more preferable to set the fixing device so that + 0.4 · ln (M) ≦ 2. In this case, an acceptable level of image gloss unevenness, oil contamination of the sheet, and an increase in cost are eliminated, and better image quality can be obtained.

(4) The roller includes a core having a plurality of through-holes communicating with the inner and outer surfaces, a release agent impregnating material that is coated on the outer periphery of the core and impregnates a release agent, May be provided. In this case, the release agent is efficiently and entirely impregnated into the impregnating material from its inner surface.

(5) Further, the release agent applying mechanism may have a release agent supply means disposed inside the roller to supply the release agent. In this case, a required amount of oil can be supplied.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing a fixing device according to an embodiment of the present invention. Illustrated fixing device 100
Is based on a pressure heat fixing method, and is incorporated in an image forming apparatus such as a printer having a known image forming means of an electrophotographic type. The fixing device 100 includes a fixing roller 20 provided rotatably in the direction of arrow a, a pressure roller 30 provided in pressure contact with the fixing roller 20, and driven to rotate with the rotation of the fixing roller 20. 2
Heaters 21 and 31 for heating 0 and 30; an oil application mechanism 40 for applying a release agent for preventing offset to at least one of the rollers (the fixing roller 20 in the illustrated example);
Having. The fixing roller 20 and the pressure roller 30
Corresponds to a rotator for fixing the toner 11 held on the sheet 10 by heat and pressure. Silicon oil is used as the release agent.

The fixing roller 20 is a hollow metal pipe 2.
2 is a roller having an outer peripheral surface coated with a fluororesin to form a release layer 23 having good releasability and heat resistance to toner. On the central axis of the fixing roller 20, a tubular heating heater such as a halogen lamp 21 is arranged. The fixing roller 20 has a driving gear (not shown) fixed to one end thereof, and is driven to rotate by a driving source (not shown) such as a motor connected to the driving gear.

The pressure roller 30 is a hollow metal pipe 3
2, a roller having a silicon rubber layer 33 provided on the outer periphery thereof, and the halogen lamp 31 is arranged on the center axis of the roller. The silicone rubber layer 33 is a rubber layer having releasability from which the sheet 10 is easily separated from the surface and having heat resistance. The pressure roller 30 is pressed in a direction toward the fixing roller 20 by a spring material (not shown). If the toner can be sufficiently fixed only by the halogen lamp 21 built in the fixing roller 20, the pressure roller 30
The halogen lamp 31 on the side may be omitted.

In the fixing operation, first, a predetermined voltage is applied to the halogen lamps 21 and 31, and the radiant heat generated from the halogen lamps 21 and 31 causes the outer wall temperatures of the fixing roller 20 and the pressure roller 30 to be fixed. Heat to the appropriate temperature. The sheet 10 holding the unfixed toner 11 is conveyed from the right as indicated by an arrow b in FIG. 1 and is sent toward a nip 12 which is a contact portion between the fixing roller 20 and the pressure roller 30. Sheet 1
0 is conveyed while being nipped by the nip portion 12 while the heat from the fixing roller 20, the heat from the pressure roller 30, and the pressure applied from the pressure roller 30 are applied. As a result, the unfixed toner 11 is fixed on the sheet 10. The toner 11 is held on the side of the sheet 10 that contacts the fixing roller 20. The sheet 10 that has passed through the nip portion 12 is naturally separated from the fixing roller 20 by a curvature according to the strength of the sheet 10 itself, and is conveyed leftward in FIG. The sheet 10 is conveyed by a discharge roller (not shown) and discharged onto a discharge tray (not shown).

Next, the configuration of the oil application mechanism 40 will be described. The oil application mechanism 40 extends along the axial direction of the fixing roller 20 and applies an oil to the fixing roller 20. The oil applying mechanism 40 extends from the plurality of discharge holes 42 while extending along the longitudinal direction of the application means 41. A supply nozzle 43 for supplying oil to the application unit 41.
As shown in FIG. 2, the oil application mechanism 40 further includes a closed type oil tank 45 that holds the oil 44, an oil conveyance unit 46 that sends the oil 44 stored in the oil tank 45 to the supply nozzle 43, have. In the supply nozzle 43, the opening cross-sectional areas of the plurality of discharge holes 42 are formed to be substantially the same.

The application means 41 includes an oil application roller 50 which is arranged on the side of the fixing roller 20 carrying the sheet 10 and is in pressure contact with the fixing roller 20, and an oil supply roller 53 which is in pressure contact with the oil application roller 50.

As shown in FIG. 1, the oil application roller 50 is a roller in which a silicon rubber layer 52 is provided on the outer periphery of a metal pipe 51.

As shown in FIG. 2, the oil supply roller 53 is a roller in which an outer periphery of a cylindrical metal core 55 having a plurality of through holes 54 is covered with an oil impregnating material 56. Further, a supply nozzle 43 is arranged on the central axis in a non-rotating state so that a required amount of oil is supplied. The through holes 54 are small holes having a predetermined diameter and are formed at substantially equal intervals. This through hole 54
The inner and outer surfaces of the cored bar 55 communicate with each other via. Oil 44 supplied from supply nozzle 43 to the inner surface of cored bar 55
Reaches the outer surface of the metal core 55 through the through hole 54 of the metal core 55 and is impregnated with the oil impregnating material 56.

The oil application roller 50 is supported so as to be able to rotate with the rotation of the fixing roller 20, while the oil supply roller 53 is supported so as to be able to rotate with the rotation of the oil application roller 50. By such a rotation, the oil 44 supplied from the supply nozzle 43 is transmitted from the oil impregnating material 56 of the oil supply roller 53 to the oil application roller 50, and from the oil application roller 50 to the outer periphery of the release layer 23 of the fixing roller 20. Applied to the surface.

As shown in FIG. 1, the oil application roller 50
Is in contact with an oil recovery blade 57 for removing oil not applied to the fixing roller 20. The oil recovery blade 57 has a length substantially equal to the axial length of the oil application roller 50. Oil recovery blade 5
7 is received by an oil pan 58 and is passed through an oil tank 45 via a recovery path (not shown).
Is returned to. Thus, the oil recovery blade 57
Is not used to make the oil on the oil application roller 50 uniform, but is used to fulfill the function of scraping off the oil remaining on the oil application roller 50 without being applied to the fixing roller 20.

Since the oil tank 45 is a closed type, no oil spills even when a large amount of oil 44 is stored, and no oil spills even when vibration is applied or inclined.

As shown in FIG. 2, the oil transfer means 46 includes an oil pump 60, a tube 61 having one end connected to the oil pump 60 and the other end immersed in the oil 44 in the oil tank 45, and one end connected to the oil pump 45. Tube 62 connected to oil pump 60 and the other end connected to supply nozzle 43
And is composed of

The supply nozzle 43 has a pipe 65 made of stainless steel or the like, and a supply hole 66 is formed by opening one end of the pipe 65. The other end of the pipe 65 is closed by a plug member 67 and the like. A plurality of through holes 68 are formed in the pipe 65 at a predetermined pitch, and a tube pipe 69 made of stainless steel or the like is inserted and attached to each of the through holes 68. The lower end of the tube pipe 69 in the figure is the oil discharge hole 42, and the hole diameter of each tube pipe 69 is substantially the same, whereby the cross-sectional area of each of the plurality of discharge holes 42 is substantially the same. Since the hole diameters are substantially the same, the formation of the discharge holes 42 is not complicated, and an increase in manufacturing cost can be suppressed.

The oil 44 in the tank is conveyed from the supply hole 66 into the pipe 65 via the oil conveying means 46.
Each of the discharge holes 42 is discharged as a droplet. Further, since the discharge holes 42 of the supply nozzle 43 are provided at a predetermined pitch, the oil 44 is supplied in a point-like manner.
Further, the supply nozzle 43 is provided with a uniforming means for making the amount of oil discharged from each of the discharge holes 42 uniform.

As the uniformizing means, for example, (A)
Regulating the cross-sectional area of the opening per discharge hole and the dimension between the discharge holes located at both ends to make the pressure of oil acting on each discharge hole 42 substantially constant; (B) opening both ends of the nozzle;
(C) An oil supply port is provided in a range where the discharge hole 42 is formed, or (D) An effective opening cross-sectional area substantially related to oil discharge in each of the discharge holes 42 having substantially the same opening cross-sectional area. Adjustments and other means,
Thereby, the amount of oil discharged from each discharge hole 42 can be made uniform. It is also possible to configure so that the diameters of the discharge holes are different along the longitudinal direction.

By adopting the means for equalizing the oil discharge amount in this manner, the oil is uniformly discharged from each discharge hole 42.

In the present embodiment, in addition to the above, the center of the surface of the oil supply roller 53 is provided so that the uniformly discharged oil can be applied evenly to the fixing roller 20 even if the amount of the oil is very small. The amount of oil supplied from the oil supply roller 53 to the fixing roller 20 is set according to the line average roughness.

More specifically, the center line average roughness of the surface of the oil supply roller 53 is Ra (μm), and the amount of the release agent supplied from the oil supply roller 53 to the fixing roller 20 is M (mg / m ² ), 0 ≦ −0.6 · ln (Ra) + 0.4 · ln (M) ≦ 3 (1) Alternatively, it is preferable to set 1 ≦ −0.6 · ln (Ra) + 0.4 · ln (M) ≦ 2 (2).

The above equations (1) and (2) are obtained by experiments. As will be described later, the lower limit is
It is determined from the viewpoint of preventing the occurrence of offset phenomenon and image unevenness in gloss by ensuring uniform oil application to 0. On the other hand, the upper limit is determined from the viewpoints of the occurrence of paper stains due to excessive oil, a decrease in fixability, and an increase in manufacturing costs due to a reduction in surface roughness and the possibility of manufacturing.

FIG. 3 is a diagram showing the relationship between the oil application uniformity and the oil application amount, and FIG. 4 is a diagram showing the relationship between the oil application uniformity and the surface roughness of the oil supply roller surface.

The oil application uniformity in FIGS. 3 and 4 was determined by the following evaluation method. First, as shown in FIG.
Then, the oil is applied to the oil detection sheet 10a by passing the oil detection sheet 10a. Next, visualization (brightness conversion) of the oil applied to the oil detection sheet 10a is performed. That is, the amount of oil adhering to the oil detection sheet 10a is converted into luminance.

Then, as schematically shown in FIG. 6, the variation of the luminance was evaluated, and levels 1 to 6 were given to the smaller variation. In this case, level 3
If it is less than 5, an uncoated portion of oil is formed, and an offset phenomenon is likely to occur. On the other hand, if the level is lower than 4, the unevenness of oil application is large, and uneven gloss of the image occurs. On the other hand, when the level exceeds 5, the oil application amount increases, image noise such as oil stains (oil streaks) occurs on the sheet, and the oil consumption increases, so that the running cost increases. In addition, the manufacturing cost increases because the surface roughness is reduced. Further, when the level exceeds 6, the applied amount of oil is too large, and the fixing property is reduced, thereby causing an offset phenomenon. In addition, the surface roughness becomes extremely small and cannot be manufactured by ordinary processing. In reality, it can be said that it is extremely difficult to reduce the surface roughness to Ra 0.1 μm or less.

The measurement of the oil application amount is performed, for example, as shown in FIG.
As shown in FIG. 1, an OHP (overhead projector) sheet 10 is provided between the fixing roller 20 and the pressure roller 30.
b, the amount of oil transferred to the OHP sheet 10b (mg / m ² ) is measured. Thus, the amount of oil applied to the fixing roller 20 can be measured indirectly. As the OHP sheet, a sheet having a polyester film as a base material is generally used.

On the other hand, the surface roughness of the surface of the oil supply roller 53, that is, the surface of the oil impregnated material 56 can be measured by a surface roughness meter.

The oil impregnating material 56 of the oil supply roller 53 is formed of a porous material such as sponge, paper, felt, and silicone rubber. Here, in order to reduce the surface roughness of the surface of the oil impregnated material 56, when the oil impregnated material 56 is a rubber (including a solid or a sponge), the roughness of the grindstone is reduced when polishing is performed, When molding with a mold, the roughness of the inner surface of the mold is reduced and the particle size of the filler is reduced. On the other hand, the oil impregnated material 56
When is a sheet (including paper or felt) wound, the surface roughness of the surface of the oil impregnated material 56 can be reduced by increasing the density or decreasing the fiber diameter.

As can be seen from FIG. 3, the greater the amount of oil applied to the fixing roller, the higher the uniformity of oil application.
However, as described above, if the amount of oil applied increases,
This results in oil stains on the sheet, high running cost, and offset phenomenon due to a decrease in fixability. Also,
As can be seen from FIG. 4, the smaller the surface roughness of the oil supply roller surface, the higher the uniformity of oil application. However, as described above, as the surface roughness is reduced, manufacturing difficulties and manufacturing costs increase.

Thus, regarding the uniformity of oil application,
The amount of oil applied and the surface roughness of the oil supply roller surface can be cited as factors of the variation.

FIG. 8 is a diagram showing the relationship between the oil application amount, the surface roughness of the oil supply roller surface, and the oil application uniformity. This is obtained by integrating the relationships shown in FIGS. 3 and 4 under various conditions, and in the figures, the uniformity level of oil application is shown in a three-dimensional plane. Note that the uniformity level is on the vertical axis (in FIG. 8, described as uniformity rank), and the meaning of the numerical value is as described above.

Considering the relational expressions from the viewpoint of satisfying the relation of FIG. 8 comprehensively, the uniformity level Y, the center line average roughness Ra (μm) of the surface of the oil supply roller 53 and the oil application amount M (mg) / m ²⁾ relationship with can be expressed by Y = -0.6 · ln (Ra) +0.4 · ln (M).

Here, as described above, the uniformity level Y of the oil application needs to satisfy 3 to 6, preferably 4 to 5. Therefore, as a result, the amount of oil supplied from the oil supply roller 53 to the fixing roller 20 is adjusted according to the center line average roughness of the surface of the oil supply roller 53 so as to satisfy the above equation (1) or (2). By setting, it has been found that a desired oil application uniformity can be obtained very efficiently.

That is, to satisfy the above equation (1),
By setting the center line average roughness of the surface of the oil supply roller 53 and the amount of oil supplied from the oil supply roller 53 to the fixing roller 20, the blade for uniformizing oil application is not used, and Even if the amount of oil applied is very small, uniformity of oil application can be ensured. Thereby, the surface of the fixing roller has excellent releasability and adhesion of foreign matters is reduced, so that uniform application with a stable application amount can be realized over a long period of time. Therefore, it is possible to efficiently prevent a situation in which the toner is transferred to the fixing roller and the offset phenomenon occurs, and it is possible to obtain good image quality.

By setting the center line average roughness of the surface of the oil supply roller 53 and the amount of oil supplied from the oil supply roller 53 to the fixing roller 20 so as to satisfy the above expression (2), It is also possible to eliminate an acceptable level of image gloss unevenness that can occur near the lower limit of the above equation (1), and an allowable level of oil contamination of the sheet and an increase in cost that can occur near the upper limit of the above equation (1). Becomes possible.

It should be noted that the present invention is not limited to only the above-described embodiment, and various modifications can be made within the technical concept of the present invention.

[0051]

As described above, according to the present invention, the desired uniformity of oil application to the rotating body can be obtained very efficiently. That is, it is possible to ensure uniform oil application without using a blade for uniform oil application and even when the amount of oil applied is very small. Thereby, the surface of the fixing roller has excellent releasability and adhesion of foreign matters is reduced, so that uniform application with a stable application amount can be realized over a long period of time. Therefore, it is possible to efficiently prevent a situation in which the toner is transferred to the fixing roller and the offset phenomenon occurs, and it is possible to obtain good image quality. It is also possible to eliminate an acceptable level of image gloss unevenness, oil stain on the sheet, and an increase in cost.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a fixing device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a mechanism for sending oil to an inner surface of an oil supply roller.

FIG. 3 is a diagram showing the relationship between oil application uniformity and oil application amount.

FIG. 4 is a diagram showing a relationship between oil application uniformity and surface roughness of an oil supply roller surface.

FIG. 5 is a diagram for explaining a method for evaluating uniformity of oil application.

FIG. 6 is a schematic diagram in which the amount of oil adhesion is converted into luminance.

FIG. 7 is a diagram for explaining measurement of an oil application amount.

FIG. 8 is a diagram showing a relationship between an oil application amount, a surface roughness of an oil supply roller surface, and oil application uniformity.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Sheet, 11 ... Toner, 20 ... Fixing roller (rotating body), 30 ... Pressurizing roller (rotating body), 40 ... Oil application mechanism (release agent application mechanism), 41 ... Application means, 43 ... Supply nozzle ( Release agent supply means), 50: oil application roller, 53: oil supply roller (roller), 54: through hole, 55: cored bar, 56: oil impregnated material (release agent impregnated material).

Claims (5)

[Claims] A rotating body for fixing the toner image held on the sheet by heat and pressure; and a release agent applying mechanism for applying a release agent to the rotating body. The mechanism includes a roller that impregnates the release agent and supplies the release agent toward the rotating body. The release roller that is supplied to the rotating body from the roller according to a center line average roughness of the roller surface. A fixing device in which the amount of mold agent applied is set. 2. The center line average roughness of the roller surface is Ra
(Μm), and when the application amount of the release agent supplied from the roller to the rotating body is M (mg / m ² ), 0 ≦ −0.6 · ln (Ra) + 0.4 · ln The fixing device according to claim 1, wherein (M) ≦ 3. 3. A roller having a center line average roughness of Ra
(Μm) and the amount of the release agent supplied from the roller to the rotating body is M (mg / m ² ): 1 ≦ −0.6 · ln (Ra) + 0.4 · ln The fixing device according to claim 1, wherein (M) ≦ 2. 4. The roller has a core having a plurality of through holes communicating the inner and outer surfaces thereof, and a release agent impregnated material which is coated on an outer periphery of the core and impregnates a release agent. The fixing device according to claim 1, further comprising: 5. The fixing device according to claim 4, wherein the release agent applying mechanism includes release agent supply means disposed inside the roller to supply the release agent.