JPH1195594A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of image noise such as oil streaks and the of an image, caused by the passage of a small-sized sheet, without complicating constitution and control by making a releasing agent coating quantity for a region serving as a nonpassage part when the small-sized sheet passes through smaller than that for a passage part. SOLUTION: An oil coating mechanism 40 is provided with a means 41 which is extended in the axial direction of a fixing roller 20 and for coating it with oil and a supplying nozzle 43 which is extended in the longitudinal direction of the coating means 41 and for supplying the oil to the coating means 41 through plural discharge holes 42. The oil coating mechanism 40 is provided with a distribution imparting means 70 and the quantity of the oil held by the oil-impregnated material 56 of an oil supplying roller 53 is made different to impart a prescribed distribution to an oil coating quantity on the fixing roller 20. In other words, the oil coating quantity for the region as the nonpassage part, when the small-sized sheet passes through, in the region in the axial direction of the fixing roller 20 is smaller than that for the passage region.

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.

A conventional oil application mechanism has a roller provided with an oil impregnating material made of a porous material on the outer periphery of a cored bar having a plurality of through holes, and impregnated and held in the oil impregnating material. A configuration in which the applied oil is applied to a fixing roller has been proposed (Japanese Utility Model Publication No. 3-10525).
Reference). In this oil application mechanism, the through holes of the cored bar are formed at substantially equal intervals, and the oil is impregnated uniformly in the oil impregnating material along the longitudinal direction. Thereby, the oil is uniformly applied along the axial direction of the fixing roller.

[0006]

In printers and copiers, the length of the fixing roller in the axial direction is set according to the maximum size of sheets that can be passed. A mode for passing a small so-called small size sheet is also frequently used.

When the small-size sheet is continuously passed, in a region along the axial direction of the fixing roller which is a non-sheet passing portion (for example, a region near both ends of the fixing roller), applied oil is applied. Since it is not consumed, excessive oil may be accumulated particularly in the nip portion. Then, when a large-size sheet is passed after continuous feeding of small-size sheets, there is a problem that excessive noise existing in the nip portion causes image noise such as oil streaks or cloudiness of an image.

The conventional oil application mechanism focuses only on the point that the oil is uniformly applied along the axial direction of the fixing roller, and a copy mode in which small size sheets are continuously passed is frequently used. In consideration of the above, no application mechanism was found in which the amount of oil applied on the fixing roller was considered.

Here, it is conceivable to provide a blade for removing excess oil applied to the non-sheet passing area of the fixing roller so as to be able to freely press and separate from the fixing roller. However, by providing a movable blade, the structure of the fixing device is increased. It becomes complicated,
There is a drawback that the control for moving the movable blade into and out of pressure is complicated.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems associated with the above prior art, and has a fixed idea that a release agent must be applied uniformly along the axial direction of a rotating body such as a fixing roller. It is an object of the present invention to provide a fixing device capable of preventing generation of image noise such as oil streaks or clouding of an image due to passing of a small-size sheet without complicating the configuration and control of the fixing device.

[0011]

According to a first aspect of the present invention, there is provided a rotating body for fixing a toner image held on a sheet by heat and pressure, and a rotating agent for rotating the release agent. A release agent applying mechanism for applying to the body, wherein the release agent applying mechanism includes a non-sheet passing portion when a small size sheet is passed in an area along the axial direction of the rotating body. The fixing device according to claim 1, further comprising a distribution providing unit configured to reduce the amount of the release agent applied to an area of the paper passing area to be smaller than the amount of the release agent applied to the paper passing area.

As a result of imparting the predetermined distribution to the release agent application amount on the rotating body, when small-size sheets are continuously passed,
Although the applied release agent is not consumed in the non-sheet passing area of the rotating body, an excessive amount of the release agent accumulates in the nip portion in the non-sheet passing area because the amount of application in the non-sheet passing area is originally small. Nothing. Therefore, even when the large-size sheet is passed after the continuous passing of the small-size sheet, image noise such as release agent streaks and image turbidity does not occur. Further, since a sufficient release agent is applied to the paper passing area of the rotating body regardless of the sheet size, image noise such as offset and uneven image gloss does not occur.

According to a second aspect of the present invention, the release agent application mechanism includes an application unit that includes a holding member that extends along an axial direction of the rotating body and holds the release agent. Supply means for supplying the release agent, and the distribution providing means, by varying the amount of the release agent held by the holding member of the application means along the longitudinal direction, The present invention is characterized in that a distribution is applied to the release agent application amount on the rotating body.

The distribution providing means is specifically configured as follows. As described in claim 3, the coating means has a core member having a plurality of through holes formed therein and the holding member provided on the outer periphery thereof, and a release agent supplied into the core member from the supply means. Is held by the holding member through the through hole, and the distribution imparting means is configured by changing an opening ratio of the core member by the through hole along the longitudinal direction. In order to change the opening ratio of the core member along the longitudinal direction, the pitch at which the through holes of the core member are formed may be changed, or the diameter of the through holes may be changed. As the aperture ratio decreases along the longitudinal direction, the amount of the release agent passing through the through hole decreases, and the amount of the release agent held by the holding member also decreases along the longitudinal direction. For this reason, the predetermined distribution is given to the amount of the release agent applied to the rotating body, and the generation of image noise due to the passing of the small-sized sheet is prevented.

Further, as described in claim 4, the distribution imparting means may be constituted by forming an inner surface of the core member with a curved surface in a longitudinal direction. Since the release agent supplied into the core member flows toward the bottom region of the curved surface, the amount of the release agent passing through the through hole decreases as the distance from the bottom region increases, and the release agent is held by the holding member. Also, the amount of the releasing agent that decreases along the longitudinal direction decreases. For this reason, the predetermined distribution is given to the amount of the release agent applied to the rotating body, and the generation of image noise due to the passing of the small-sized sheet is prevented.

Further, as described in claim 5, the distribution applying means may be constituted by changing an amount of the release agent supplied from the supply means along a longitudinal direction of the coating means. Good. The supply means is a supply nozzle extending along the longitudinal direction of the application means and discharging the release agent from a plurality of discharge holes. In order to change the supply amount of the release agent along the longitudinal direction, the pitch for forming the discharge holes of the supply nozzle may be changed, or the diameter of the discharge holes may be changed. As the supply amount decreases along the longitudinal direction, the amount of the release agent held by the holding member also decreases along the longitudinal direction. For this reason, the predetermined distribution is given to the amount of the release agent applied to the rotating body, and the generation of image noise due to the passing of the small-sized sheet is prevented.

Further, as described in claim 7, the distribution applying means may be constituted by arranging a plurality of holding members having different abilities to hold the release agent along a longitudinal direction. In order to make the release agent holding capacity different for each holding member, the basis weight, density, hardness, pore diameter, and porosity of porous materials such as sponge, paper material, felt, and silicone rubber which form the holding member may be changed. . When the holding member or the coating member is formed from the same type of silicone rubber, the polishing direction of the rubber surface is reversed, and the release agent holding capability, in other words, the release agent transmission capability is made different in the longitudinal direction. You may.

[0018]

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

<< First Embodiment of Fixing Device >> FIG. 1 is a schematic configuration diagram showing a fixing device according to a first embodiment. The illustrated fixing device 100 is of a pressure heat fixing type, and is incorporated in an image forming apparatus such as a printer having a known image forming unit of an electrophotographic type. Fixing device 10
Reference numeral 0 denotes a fixing roller 20 provided rotatably in the direction of arrow a, and 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.
And heaters 21 and 31 for heating the respective rollers 20 and 30
And at least one of the rollers (the fixing roller 2 in the illustrated example).
0), an oil application mechanism 40 for applying a release agent for preventing offset. The fixing roller 20 and the pressure roller 30 are used for the toner 1 held on the sheet 10.
1 corresponds to a rotating body for fixing 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 (corresponding to a supply unit) 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 particular, this oil application mechanism 4
0 has a distribution applying unit 70 that makes the amount of oil applied to a region that is a non-sheet passing portion when a small-size sheet passes through the region along the axial direction of the fixing roller 20 smaller than the amount of oil applied to the sheet passing region. doing.

The application means 41 of the first embodiment includes an oil application roller 50 disposed on the side of the sheet 10 carrying the fixing roller 20 and pressed against the fixing roller 20, an oil supply roller 53 pressed against the oil application roller 50, It has.

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 has an oil impregnated material 56 on the outer periphery of a cylindrical metal core 55 (corresponding to a core member) having a plurality of through holes 54 formed therein.
The supply nozzle 43 is arranged on the central axis of the roller in a non-rotating state. Through hole 54
Is a small hole having a predetermined diameter.
The inner and outer surfaces of the cored bar 55 communicate with each other via. The oil impregnating material 56 is formed of a porous material such as sponge, paper, felt, and silicone rubber. The oil impregnating material 56 is a holding member included in the application unit 41 and corresponds to a holding member extending along the axial direction of the fixing roller 20 and holding oil. Supply nozzle 43
The oil 44 supplied to the inner surface of the core metal 55 from the
5 to the outer surface of the cored bar 55 through the through hole 54, and is impregnated and held in 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.

Since the oil tank 45 is of 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. A supply port 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 diameters of the through hole 68 and the tube pipe 69 are substantially the same along the longitudinal direction, it is not necessary to increase the diameter of the pipe 65 even if the nozzle length is increased. Can be avoided. Also,
Since the hole diameters are substantially the same, the formation of the discharge holes 42 does not become complicated, and an increase in manufacturing cost can be suppressed. Therefore, the fixing device 100 has a compact configuration and is excellent in cost.

The oil 44 in the tank 45 is conveyed from the supply port 66 into the pipe 65 via the oil conveying means 46, and is discharged as droplets from each discharge hole 42. Also,
Since the discharge holes 42 of the supply nozzle 43 are provided at a predetermined pitch, the oil 44 is not supplied in a planar shape, but is supplied in a dot shape.

As described above, the oil application mechanism 40 has the distribution applying means 70. The distribution providing means 70 in the present invention is provided with the oil impregnating material 56
The amount of oil retained in the fixing roller 20 is varied along the longitudinal direction so as to give a predetermined distribution to the amount of oil applied on the fixing roller 20. Divided as follows. That is, (A)
(B) a configuration in which the opening ratio of the core bar 55 by the through hole 54 is changed along the longitudinal direction, (B) a configuration in which the inner surface of the core bar 55 is formed into a curved cross section along the longitudinal direction, and (C) the supply nozzle 43.
And (D) a plurality of oil-impregnated materials (holding members) having different oil holding abilities arranged along the longitudinal direction. Divided into Hereinafter, specific examples of the distribution providing unit 70 will be sequentially described.

In the image forming apparatus such as a printer, the sheet may be conveyed on the basis of the center position in the width direction orthogonal to the sheet conveying direction irrespective of the sheet size. There is a form in which a sheet is conveyed based on one side edge position of the sheet. In the former conveyance mode, two areas near the both ends of the fixing roller 20 are formed in the area along the axial direction of the fixing roller 20, which is a non-sheet passing area when a small-size sheet is passed. Also,
In the latter transport mode, the non-sheet passing area is formed only at one position near one end of the fixing roller 20. In the following description,
A description will be given of a distribution applying unit applied when a sheet is passed in the former transport mode and a non-sheet passing area is formed at two positions near both ends of the fixing roller 20.

<< Example A of Distribution Assigning Means >> First, the above (A)
An example of the distribution providing means 70 in which the opening ratio of the cored bar 55 is changed will be described. As shown in FIG.
Reference numerals 4 have the same diameter but are not formed at equal intervals, and have a small pitch in the central region and a large pitch in an end region corresponding to the non-sheet passing region of the fixing roller 20. Since the presence of the through holes 54 is “dense” in the center region and “coarse” in the end regions, the opening ratio O of the cored bar 55 is
It changes along the longitudinal direction, and becomes smaller toward the end region.

According to the distribution providing means 70, the core metal 5
5, the opening ratio O becomes smaller and the amount of oil passing through the through hole 54 becomes smaller as it goes to both ends in the longitudinal direction. For this reason, as shown in FIG. 4, the amount of oil retained in the oil impregnating material 56 decreases toward both ends (distribution d), and the amount of oil applied to the fixing roller 20 via the oil application roller 50 is reduced. The amount is given a predetermined distribution D such that it is the largest in the central region of the fixing roller 20 and decreases as it goes to the end region.

When the predetermined distribution D is applied to the amount of oil applied on the fixing roller 20, when the small size sheet is continuously passed, the applied oil is not consumed in the non-sheet passing area of the fixing roller 20. Since the application amount in the non-sheet passing area is originally small, the nip portion 1 in the non-sheet passing area
There is no excess oil accumulated in 2. Therefore, even when the large-size sheet is passed after the continuous passing of the small-size sheet, generation of image noise such as oil streaks and image turbidity is prevented. Also, regardless of the sheet size, the fixing roller 20
Since sufficient oil is applied to the paper passing area, no image noise such as offset or uneven image gloss occurs.

By the way, since the predetermined distribution is given to the oil application amount, it is conceivable that the oil in the end region of the fixing roller 20 may be insufficient when the large size sheet is passed. However, since the unfixed toner image 11 held near the edge of the sheet 10 is generally smaller than that at the center, the occurrence of offset and image gloss unevenness is sufficiently prevented even when a large-size sheet is passed.

The pitch of the through holes 54 is changed to change the
Although the case where the aperture ratio of No. 5 is changed along the longitudinal direction is illustrated, the aperture ratio of the cored bar 55 may be changed as follows. That is, the diameter of the through hole 54 may be changed along the longitudinal direction while keeping the distance between the through holes 54 the same.

<< Example B of Distribution Assigning Means >> Next, the above (B)
An example of the distribution imparting means 70a in which the inner surface of the cored bar 55a is formed into a curved cross-sectional surface will be described. As shown in FIG. 5, the distribution imparting means 70a is formed by forming the inner surface 71 of the cored bar 55a into a curved cross section along the longitudinal direction. The curved surface 71 is formed such that an oil holding space formed inside the cored bar 55a expands in a central region and has a crown shape (convex shape) which is deflated in an end region.
The through holes 54a of the core bar 55a have the same diameter and are formed at substantially equal intervals.

According to the distribution applying means 70a, since the oil 44 supplied to the inner surface of the core metal 55a easily flows toward the central region of the oil holding space (broken line in the figure), both ends of the core metal 55a in the longitudinal direction are provided. The amount of the oil passing through the through-hole 54a decreases as going to the portion. Therefore, the amount of oil retained in the oil impregnating material 56 a decreases toward both ends, and the amount of oil applied to the fixing roller 20 via the oil application roller 50, similarly to the distribution applying unit 70 described above. Is a predetermined distribution D in which the central region of the fixing roller 20 is the largest and decreases toward the end region.
Is given.

Therefore, even if small-size sheets are continuously passed, excessive oil does not accumulate in the nip portion 12 in the non-sheet-passing area, and even if large-size sheets are subsequently passed, oil streaks and the like are not generated. The occurrence of image noise is prevented.

<< Example C of Distribution Assigning Means >> Next, (C)
An example of the distribution providing means 70b in which the amount of oil supplied from the supply nozzle 43b of the above-described nozzle is changed along the longitudinal direction will be described. As shown in FIG. 6, the discharge holes 4 of the supply nozzle 43b
2b have the same diameter but are not formed at equal intervals, and have a small pitch in the central area and a large pitch in the end area corresponding to the non-sheet passing area of the fixing roller 20. The presence of the ejection holes 42b is “dense” in the central region,
Since the oil becomes “coarse” in the end region, the amount of oil supplied from the supply nozzle 43b changes along the longitudinal direction, and becomes smaller toward the end region. The through holes 54b of the cored bar 55b have the same diameter and are formed at substantially equal intervals.

According to the distribution imparting means 70b, since the amount of oil supplied to the inner surface of the cored bar 55b is smaller in the end region, the oil passing through the through-hole 54b increases toward both ends in the longitudinal direction of the cored bar 55b. The amount of is reduced. Therefore, the amount of oil retained in the oil impregnating material 56b decreases toward both ends similarly to the distribution applying means 70, 70a described above, and the oil applied to the fixing roller 20 via the oil application roller 50 The amount of the fixing roller 20
A predetermined distribution D is given such that the central region is the largest and decreases toward the end region.

Therefore, even if small-size sheets are continuously passed, excessive oil does not accumulate in the nip portion 12 in the non-sheet-passing area. The occurrence of image noise is prevented.

<< Example D of Distribution Assigning Means >> Next, the above (D)
Providing means 70c having a plurality of types of oil impregnating materials
An example will be described. As shown in FIG. 7, the distribution providing means 70c has different oil holding capacities and the core metal 55c.
Are arranged along the longitudinal direction of the oil supply roller 53c. The oil holding capacity is set to be high in the first oil impregnating material 75 arranged in the central region and to be low in the two second oil impregnating materials 76 arranged in the end regions. Each of the oil impregnating materials 75 and 76 is formed of a porous material such as sponge, paper, felt, and silicone rubber. As a specific example in which the oil holding ability is made different, a porous material having a large basis weight and density is used for the first oil impregnating material 75, and a small porous material is used for the second oil impregnating material 76. In addition, the core metal 55c
Have the same diameter and are formed at substantially equal intervals.

According to the distribution providing means 70c, the first
The first amount is larger than the amount of oil held in the oil impregnating material 75.
Second oil impregnating material 7 located on both sides of oil impregnating material 75
6, the amount of oil applied to the fixing roller 20 via the oil applying roller 50 is smaller in the central region of the fixing roller 20 and is larger in the end region. A predetermined distribution D that decreases is provided.

Therefore, even if small-size sheets are continuously passed, excessive oil does not accumulate in the nip portion 12 in the non-sheet-passing area, and even if a large-size sheet is subsequently passed, oil streaks and the like are not generated. The occurrence of image noise is prevented.

Other specific examples for differentiating the oil holding capacity are as follows. That is, the first oil impregnating material 75
May be a porous material having a large pore diameter or porosity, and the second oil impregnating material 76 may be a small porous material. Alternatively, a porous material having low hardness may be used for the first oil impregnating material 75, and a high porous material may be used for the second oil impregnating material 76, and the nip width may be different.

Further, when the first and second oil impregnating materials 75 and 76 are formed from the same type of silicone rubber, the first and second oil impregnating materials are reversely polished on the rubber surface. It is also possible to vary the oil holding capacity of the impregnating material. As shown conceptually in FIG. 8, when the rubber surface is polished, the surface becomes very fuzzy and fuzzy. First and second oil impregnating material 7
5 and 76 are both rotated by the rotation of the oil application roller 50, but as shown in FIG. 3A, the first and the second are rotated in a direction (upside-down direction) such that the raised portion 77 rises. The oil impregnating material 75 is arranged, and the second oil impregnating material 76 is arranged so as to rotate in a direction (a forward direction) in which the flared portion 77 is pushed down.

When the oil impregnating material rotates in the reverse direction, the raised portion 77 rises and the oil application roller 5 is raised.
The oil held between the squeezed portions 77 is transmitted to the oil application roller 50 in a large amount because of the contact with the oil application roller 50. For this reason, the first oil impregnating material 7 rotating in the reverse direction
The amount of oil that the second oil impregnating material 76 rotating in the forward direction transmits to the oil application roller 50 is smaller than the amount of oil that 5 transmits to the oil application roller 50. As a result, as described above, the amount of oil applied to the fixing roller 20 via the oil applying roller 50 has a predetermined distribution D.
Is added, and the occurrence of image noise such as oil streaks is prevented.

As is clear from this example, "the ability to hold oil" is synonymous with "the ability to easily transmit oil".

Since the silicon rubber layer 52 of the oil application roller 50 also corresponds to the oil holding member of the application means, the polishing direction of the silicon rubber layer 52 is reversed between the center region and the end region as described above. By doing so, the oil holding ability, in other words, the oil transmitting ability may be different in the longitudinal direction.

<< Second Embodiment of Fixing Device >> FIG. 9 is a schematic configuration diagram showing a fixing device according to a second embodiment. In the fixing device 400 according to the second embodiment, the oil applying mechanism 40 has the distribution applying unit 70 as in the first embodiment.
Embodiment 41 differs from Embodiment 1 in that the specific configuration of the embodiment 41 is modified.

The application means 441 of the second embodiment includes an oil application roller 50 pressed against the fixing roller 20 and an oil impregnated material 456 impregnated with the oil 44 dropped from the supply nozzle 43 and brought into contact with the oil application roller 50. . The oil impregnating material 456 is formed of a porous material such as sponge, felt, or the like.
Is in contact with The distribution providing unit 70 includes the supply nozzle 43
Is configured to change the amount of oil supplied from the machine along the longitudinal direction (see FIG. 6).

Corresponding to the fact that the amount of oil supplied from the supply nozzle 43 decreases toward the end region, the amount of oil retained in the oil impregnating material 56 decreases toward the both ends. The amount of oil transmitted to the oil application roller 50 rotating while contacting the lower surface side of 56 also decreases as going to both ends. As a result, similar to the first embodiment,
A predetermined distribution D is given to the amount of oil applied to the fixing roller 20, and the occurrence of image noise such as oil streaks is prevented.

The oil regulating blade 4 of the second embodiment
57 is in contact with the fixing roller 20 so as to remove excess oil 44 from the oil applied from the oil applying roller 50 to the fixing roller 20. The oil 44 removed from above the fixing roller 20 is received by the oil pan 58 and returned to the oil tank 45 via the recovery path 458.

Although the oil is slightly diffused in the axial direction of the fixing roller 20 by the oil regulating blade 457, the pitch of the discharge holes 42 formed in the supply nozzle 43 is set in consideration of the amount of diffusion. Fixing roller 20
The distribution of the amount of applied oil applied to the surface can be a predetermined distribution D.

[0060]

As described above, according to the present invention, the stereotype that the release agent must be uniformly applied along the axial direction of the rotating body such as the fixing roller is broken, and the structure and the control are controlled. It is possible to provide a fixing device that prevents generation of image noise such as oil streaks and clouding of an image due to passing of a small-sized sheet without causing complication.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a fixing device according to a first embodiment.

FIG. 2 is a configuration diagram partially showing an oil application mechanism of a fixing device.

FIG. 3 is a configuration diagram illustrating an example of a distribution providing unit.

FIG. 4 is a diagram showing a distribution state of an oil amount held by an oil impregnating material of an oil supply roller as an application unit and a distribution state of an oil amount applied to a fixing roller as a rotating body.

FIG. 5 is a configuration diagram illustrating another example of a distribution providing unit.

FIG. 6 is a configuration diagram showing still another example of a distribution providing unit.

FIG. 7 is a configuration diagram showing still another example of a distribution providing unit.

FIG. 8 is a conceptual diagram for explaining a case where the oil holding capacity is changed by reversing the polishing direction of the rubber surface.

FIG. 9 is a schematic configuration diagram illustrating a fixing device according to a second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Sheet 11 ... Unfixed toner 20 ... Fixing roller (rotating body) 30 ... Pressurizing roller (rotating body) 40 ... Oil application mechanism 41 ... Application means 42 ... Discharge hole 43 ... Supply nozzle (supply means) 50 ... Oil application Roller (coating means) 52 ... Silicon rubber layer (holding member) 53 ... Oil supply roller (coating means) 54 ... Through hole 55 ... Core metal (core member) 56 ... Oil impregnated material (holding member) 70 ... Distribution applying means 71 ... inner surface of core metal, curved surface 75, 76 ... first and second oil impregnated materials (plurality of holding members)

Claims (7)

[Claims] 1. A fixing device comprising: a rotating body 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 rotating body. The release agent applying mechanism is configured to determine the amount of the release agent applied to an area that becomes a non-sheet passing portion when a small-size sheet is passed among the areas along the axial direction of the rotating body, and to calculate the amount of the release agent applied to the sheet passing area by A fixing device comprising a distribution providing means for reducing the number of distributions. 2. The release agent application mechanism includes: an application unit that extends along an axial direction of the rotating body and includes a holding member that holds the release agent; and supplies the release agent to the application unit. Supply means, and the distribution applying means makes the amount of the release agent held by the holding member of the application means different along the longitudinal direction, thereby releasing the mold on the rotating body. The fixing device according to claim 1, wherein the fixing device is configured to impart a distribution to the amount of the applied agent. 3. The coating means has a core member having a plurality of through-holes formed therein and the holding member provided on the outer periphery thereof, and the release agent supplied into the core member from the supply means is passed through the coating member. The holding member is configured to be held by the holding member through a hole, and the distribution imparting unit is configured by changing an opening ratio of the core member by the through hole along a longitudinal direction. 3. The fixing device according to 2. 4. The coating means has a core member having a plurality of through holes formed therein and the holding member provided on an outer periphery thereof, and the mold release agent supplied from the supply means into the core member. 3. The structure according to claim 2, wherein the holding member is held by the holding member through a hole, and the distribution imparting means is formed by forming an inner surface of the core member into a curved cross section along a longitudinal direction. 3. The fixing device according to claim 1. 5. The apparatus according to claim 2, wherein the distribution providing unit is configured to change an amount of the release agent supplied from the supply unit along a longitudinal direction of the application unit. The fixing device as described in the above. 6. The supply device according to claim 5, wherein the supply device is a supply nozzle extending along a longitudinal direction of the application device and discharging the release agent from a plurality of discharge holes.
3. The fixing device according to claim 1. 7. The method according to claim 2, wherein the distribution providing unit is configured by arranging a plurality of holding members having different abilities to hold the release agent along a longitudinal direction. Fixing device.