JPS5971073A - Fixation device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of an offset by prolonged stable destaticizing and prevent the coiling of copying paper by providing a destaticizing member near either the first rotating body or the second rotating body of a fixation device. CONSTITUTION:The fixation device having a heating roll 1 and a pressure roll 2 fixes toner T on copying paper P by a heat source 3. A destaticizer B has an earth supporting part 8 and a conductive aciculate member 7 and provided on the paper P discharge side of the pressure contact part of the two rolls 1, 2. The staticizer B is not brought into contact with the surface of the roll and the member 7 is provided entirely along the rolls 1, 2 longitudinally. Its tip C is near the pressure contact part and close to a part where the paper P is discharged along the roll 1. The tip C of the member 7 is positioned in a space formed by a straight line A connecting the tip 9 of a guide member G and the center of pressure contact or the straight line A and the roll 1, and near the pressure contact part. By this way, charge caused by the friction or the separation of the rolls 1, 2 can be electrostatically discharged.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fixing device installed in a recording device such as an electrophotographic device or an electrostatic recording device, and more specifically, a fixing device for fixing an object to be fixed, such as an unfixed image, to a recording material. The present invention relates to a fixing device that extremely effectively prevents offset of an object to be fixed that occurs in a rotating body for heat treatment, pressure treatment, or heating and pressure treatment.

2. Description of the Related Art Conventionally, fixing devices for image forming apparatuses that fix unfixed images onto the surface of plain paper often use a fixing roller and a pressure roller to sandwich and convey a recording material such as plain paper.

This type of roller has a problem in that frictional electrification occurs due to contact between the plain paper and the roller, and the plain paper wraps around the roller surface. In order to solve this problem, as disclosed in Japanese Utility Model Publication No. 57-41793 and 1% Japanese Patent Publication No. 56-143474, an AC bias is applied via a static eliminating brush that is simply brought into contact with the roller surface. There is something to do.

However, in either case, if the tip of the static elimination brush becomes contaminated with toner or paper powder, the static elimination efficiency will drop sharply.

That is, it deteriorated significantly over time and had poor durability.

Furthermore, although the static elimination effect of the static elimination method described above is effective to some extent in terms of preventing the toner from being wrapped around the recording roller, it is not effective in preventing the toner from being offset to the fixing roller because it rapidly (decreases). This makes it difficult to obtain offset toner, and generates offset toner that cannot be cleaned by cleaning means (blades, felts, etc.) of the fixing roller.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to provide a fixing device that can maintain a high performance static elimination effect over a long period of time and can significantly prevent the offset phenomenon.

In order to achieve the above object, the present invention includes a charge eliminating member having a tip disposed in a non-contact manner with the rotating body in the vicinity of a position where the rotating body, which is the body to be neutralized, contacts the recording material. This is a unique fixing device.

This improves the static eliminating property of the static eliminating blades, provides an exceptional static eliminating effect that cannot be obtained conventionally, and improves fixing performance.

Examples of the present invention will be described in detail below.

FIG. 1 shows an apparatus in which a toner image T formed by electrophotography is fixed onto plain paper P using a heat fixing device.

A heating roller 1 has a heating heater 6 such as a halogen heater inside, and rotates in the direction of the arrow in response to driving force from a drive motor (not shown). 2 is a heater for low heating
! A pressure roller with a built-in I presses against the heating roller 1 and rotates by sliding.

This heating roller 1 has a heat-resistant mold release resin layer 11 such as tetrafluoroethylene resin provided on the outer peripheral surface of a hollow roller core 12 made of metal such as aluminum, stainless steel, or copper to a thickness of 20 to 100 μm. The pressure roller 2 is rotatably supported by a bearing (not shown).

This roller 2 is pressed against the heating roller 1 by a known pressure means at least during fixing, and the outer circumferential surface of a metal roller core 22 is coated with silicone rubber, fluoro rubber, or fluorine.

An elastic layer 21 made of silicone rubber or the like is provided relatively thickly. One purpose of this configuration is to secure a pressure contact area with the heating roller. A temperature sensing element 4 such as a thermistor or thermocouple is disposed in contact with the outer peripheral surface of the heating roller 1, and its detection signal is guided to a known control means (not shown) to control the temperature of the outer peripheral surface of the heating roller 1. is maintained at the toner image melting temperature (by controlling the output of the heater 3, the applied voltage, etc.). Separation claws 5 and 51 are used to reliably separate the fixed copy paper from each roller.

Reference numeral 6 denotes a cleaning member for removing foreign matter such as offset toner and paper dust adhering to the heating roller surface from the roller surface, and a cleaning web 61 made of heat-resistant non-woven fabric such as Nomex or Hyflon 9 is used.

The cleaning web 61 is brought into contact with the heating roller by an elastic pressing roller 65 made of silicone rubber, fluorosilicone rubber, fluorosilicone rubber, silicone rubber sponge, or the like. Further, this web 61 is moved from the supply roller 62 by a small amount by a driven take-up roller 65, so that a new surface of the cleaning web 61 always comes into contact with the surface of the heating roller 1.

G is a guide member that guides the plain paper P to the pressure contact portion between the heating roller 1 and the pressure roller 2, and its leading end 9 is close to the heating roller 1 side. Therefore, the plain paper P is guided along the surface of the heating roller 1 to the pressure contact portion of the rollers 1 and 2.

Reference numeral B designates a static eliminator that does not contact the roller surface, and has a grounded support portion 8 and a conductive needle member 7, and is provided with pressure on the discharge side of the plain paper P at the pressure contact portion. This conductive needle-like member 7 is provided over the entire longitudinal direction of the rollers 1 and 2, and its tip C
is near the pressure contact portion and is close to the portion where the plain paper P is discharged along the surface of the heating roller 1. Further, to explain the position of the tip C in detail, the position of the tip 9 of the guide member q and the center of the pressure contact width of the pressure contact portion of the roller 1.2 is a straight line A (or a surface formed by this), or this straight line The tip portion C of the conductive needle-like member 7 is located in the space formed by the surface of the heating roller 1 and the tip portion C of the conductive needle-like member 7 near the pressure contact portion. or,
This static eliminator B is located between the separation claws 5 and 510 described above.

Now, the plain paper P bearing the toner image T by a known means is guided toward the heating roller 1 side by the guide member G.
The toner image is heated and melted and fixed at the pressure contact portion. After passing through the pressure contact part, the plain paper P is heated by the heating roller 1 due to the adhesiveness of the toner image.
As shown in the figure, it is separated from the surface of the heating roller 1 at the part of the roller surface where the separation claw 5 comes into contact with the separation claw 5, and is sent along the lower guide surface of the separation claw 5 to a conveyance roller or a discharge roller (not shown). Sent. In this way, whether the rotating body that contacts the toner image on the plain paper and performs the fixing action is heated or pressurized, the plain paper P is usually ejected from the pressure contact section in a state wrapped around it due to the adhesiveness of the toner. It is.

This phenomenon is particularly noticeable in a heat fixing device, and is also noticeable when a pressure roller having a higher elastic modulus than the surface of the rotating body that contacts the toner applies pressure from the back side of the plain paper.

In this embodiment, the heater 3 of the heating roller 1 (200W)
The surface temperature is determined by the pressure roller 2's heater'! 1 (90W
) to improve fixing performance. As a result, the plain paper P reaches the separating claw 5 while forming a curl along the surface side of the heating roller 1. Furthermore, the curvature of the elastic pressure roller 2 having a radius R2 (':R1) which is in pressure contact with the rigid heating roller 1 having a radius R1 is large near the discharge side of the nip portion (radius The direction of the curvature curl of the passing paper P caused by r2 < R1, R2) and the direction of the toner adhesive curl due to the toner image T on the plain paper P are both the direction in which the plain paper P moves along the heating roller 1. matches.

Therefore, in the embodiment described above, due to a number of overlapping factors, the plain paper P is reliably conveyed along the surface of the heating roller 1 even after passing through the pressure contact portion. Although the separating claw 51 is provided in this example for safety, it is not necessarily necessary. In other words, it is possible to bring the static eliminator B as close as possible to the vicinity of the press-contact part.

During transport, when the plain paper P passes through the nip section as described above, the plain paper P, pressure roller 2. The heating roller 1 is charged due to friction and peeling, which is a major cause of offset of charged toner and wrapping of plain paper around the roller. However, in this embodiment, since the static eliminator B is arranged as described above, this cause can be removed and the balance of these three surface potentials can be kept in an appropriate state. In other words, the toner offset phenomenon can be largely prevented, and a superior static elimination effect can be achieved over a long period of time compared to the conventional method.

Next, the effects of the present invention will be explained in detail by giving specific numerical examples. FIG. 2 shows positions C1 to C7 when the position of the tip C of the conductive needle member 7 of the static eliminator B is variously changed in the fixing device configured as shown in FIG. The effects are summarized in the table below. Note that 0 indicates a positive angle toward the rotation direction of the pressure roller with respect to the straight line connecting the non-fixing end F of the pressure contact portion and the center of the pressure roller,
d indicates the distance from the pressure roller surface.

The position C1 is located approximately in the extending direction of the pressure contact portion, and is close to the pressure roller 2 and close to the surface of the heating roller 1 via the plain paper P passage area.

Position flt, C2 is near position C1, but position 111c
1, but the distance from the pressure roller 2 is the same as position C1.

Position C3 is lower than pressure roller 2. than position C2. heating roller 1
They are located at a very large distance from each other.

Further, position C4 is provided on the above-mentioned straight line A, and is close to the surface of pressure roller 2 at the same distance as positions C1 and C2. These positions C1 to C4 are located within the space created by the straight line A and the surface of the heating roller.

Further, position C5 is located downstream in the rotational direction of the pressure roller 2 from the abutment position of the separation claw 51 (omitted in this figure), and is a contact type static eliminator (1983-1983). 41793
(disclosed in the above publication) is normally installed. Position C6 is located further downstream than position C5, and position C7
is located further downstream than position C6, and heater 6
This is the position of the pressure welding part and the anteroposterior position with 1 as the center.

The values in the table above are based on the roller configuration explained in Figure 1.
The outer diameters R1 and R2 of each roller 1.2 are both 60 mm,
Rollers 1 and 2 are pressed together at a total pressure of 60 to 9 to meet Japanese Industrial Standards A.
26 sheets of 6 size paper per minute (roller peripheral speed 270 mrn)
Fixing was performed at a speed of 7/sec). In addition, a negatively charged toner (negative toner) is used as the toner, and the amount of offset toner is expressed as a weight ratio (%) to the amount of unfixed toner on plain paper P, and the surface potential of the pressure roller (
Since v) directly affects the negative toner,
This is added to the table as it is an important comparative element.

In FIGS. 1 to 6, D is a common external tangent (plane) between the heating roller 1 and the pressure roller 2 on the plain paper discharge section side, and the above positions C1 to C4 are this common external tangent (plane). I)
It is located in the space created by the surface of the heating roller and the surface of the pressure roller.

Comparing the effects based on the table above, when the static eliminator B having a conductive needle-like member is not used at all, the offset toner is 0.60 < 1), and the pressure roller surface potential is also < 50.
It is extremely large, exceeding 00 (V). Needless to say, many problems arise at this time.

Now, when the tip C is provided in a non-contact state at the positions C1 to C4 according to the present invention, that is, near the pressure contact part, the offset toner and the surface potential of the pressure roller are lowered compared to the case where the top 85 is not used. We were able to reduce it to less than one-fourth. Of course, no wrapping of the plain paper P around the roller was observed.

On the other hand, if the offset toner is provided at position C5 or position C7 located outside the vicinity of the pressure contact part, the offset toner can be reduced slightly and the pressure roller surface potential can also be reduced, but if the offset toner is 0.3 inch or more, The pressure roller surface potential is also -2
000 (IL is larger than V+ at the out-of-light value. In this case, the surface potential is such that the offset toner increases temporarily, so the toner image T on the plain paper P may be disturbed. was often seen and lacked reliability.

Further, the offset toner in this case could not be completely removed by ordinary or simple leaning means, and it was often seen that the offset toner was re-offset onto the surface of the plain paper.

As is clear from the table, positions C1 to C4 are located at position C.
Compared to positions 5 to C7, the amount of K offset toner can be reduced by 115 to 1/4, and the surface potential of the pressure roller can also be reduced to about 1/2.
We were able to reduce it to below. Furthermore, by comparing these, it can be estimated that until the rollers 1 and 2 are charged and the surface potential of the plain paper is formed, the surface is relatively unstable and non-uniform in the longitudinal direction of the rollers. In the above positions C1 to C4, since it is possible to eliminate the frictional charge and peeling charge under this unstable and non-uniform condition, these charges can be efficiently removed before forming a firm surface potential. It is thought that static electricity can be removed well. On the other hand, it is considered that at positions C5 to C7, the surface potential becomes relatively stable, so that the static elimination efficiency decreases, and eventually the surface potential is allowed to increase in the negative direction.

The effective effects of the present invention can be explained from such a point of view, and the above positions C1 to C4 are also particularly effective at positions CI,
It is understood why C2 has a particularly high static elimination effect.

Furthermore, the potential of the plain paper P after being ejected is + at positions C5 to C7.
What was 1000 V or more becomes +200 V due to the settings such as positions C1 to C4 of the tip C of the conductive needle-like member.
It was possible to reduce the voltage to below V, and good effects were obtained in terms of electric shock and copy paper formulation. As a result, it is possible to eliminate the need for a copy paper neutralization member, which has conventionally been provided with a copy paper ejection trap outside the machine in many copying machines.

Further, especially when the entrance guide G is not provided, it is also possible to consider the approach line of the copy paper by assuming that the end of the copy paper conveying section is the tip of the entrance guide. The surface potential of the heating roller is -100 to -150 in all cases.Other embodiments of the present invention will be described with reference to FIGS. 3 to 7. The features of these embodiments are that the tip C of the conductive needle-like member is provided near the plain paper P discharge side of the press-contact portion, and that the conductive needle-like member is integrated with the separating claw. Furthermore, from another perspective, a technique is disclosed in which the static eliminating member can be installed at any desired location by integrating the static eliminating member with the separation claw. In this technique, the static eliminating member may be of a contact type or a non-contact type.

FIG. 6 shows the static eliminator B of the embodiment described in FIG. This is an example. The separating claw 5o is made of a heat-resistant and insulating material in order to concentrate the electric field on the tip 0 of the conductive needle member 7 and to enhance the static elimination effect. Examples of this material include polyimide sheet, polyamide, polyamideimide, Teflon, etc., and sheet-like materials or metal surfaces coated with the above-mentioned heat-resistant and insulating materials are suitable. If this purpose is not used, even if the separation claw 5C is conductive, a sufficient static elimination effect can be obtained since it is near the pressure contact portion.

By the way, the following can be obtained from the above technique by focusing on the point that the static eliminator B1 and the separation member are integrated. Conventionally, the separation claw on the pressure roller side is generally used for plain paper P.
However, when a static eliminator is provided to prevent winding, the area in which it is disposed has to be limited due to the presence of separation claws. Specifically, the separation claw requires a certain degree of strength and uses a relatively large space on the peripheral surface of the roller, so the static eliminating member must be provided at a distance from the separation claw. This has made it difficult to provide the static eliminating member at a position suitable for achieving an appropriate static eliminating effect. Therefore, since the static eliminating member is disposed at a large distance from the press-contact portion, few static eliminating members can provide a sufficient static eliminating effect. Further, when a sheet-like separating claw is used and an attempt is made to dispose a conductive needle-like member immediately after the sheet-like separating claw, the method of supporting the sheet-like separating claw is difficult and has not been realized yet.

In this embodiment, by integrating the sheet-like separating claw and the conductive needle-like member, the separating claw can be easily supported, and the distance between the tip of the separating claw and the conductive needle-like member 7 can be easily supported. It becomes possible to bring them very close to each other. Therefore, the separating claw and the tip C of the member 7 can be arranged close to the nip portion, so that stable separation of the transfer paper and effective static elimination of the pressure row 22 can be realized.

In this embodiment, a metal plate such as aluminum or copper is used as the material of the support part 8 of the conductive needle-like member 7, and the member 7
and a separating claw 5o, as shown in FIG. 4. In FIG. 4, one side of the bendable metal plate 5e is provided with several punched out protrusions 50' in the longitudinal direction, and corresponding holes are provided at positions opposite the punched out convex parts 50' on the other side. 50' is provided. Further, a hole is provided in the separation claw 5o at a position corresponding to the metal plate 5eK, and the punched-out convex portion 50' is fitted into this hole, so that a conductive needle (not shown in FIG. 4) is attached to the metal plate 5e. It can be completely fixed in a connected state with the shaped member 7.

Further, by coating the surface portion of the metal plate 5e constituting the support portion 8 with an electrically insulating material, the electric field can be further concentrated on the tip portion C as described above, and the static elimination effect can be further improved. Note that FIG. 5 is a top view of the pressure roller 2 shown in FIG.
The point of contact with 2 is shown.

As another embodiment, FIG. 6 shows one in which a conductive needle-like member is integrally provided on the upper part of the separating claw. The shape of the separating claw has a sharp tip 8& for separating the plain paper P by coming into contact with the pressure row 22, and a slope 8b for guiding the separated paper P. It is placed on the separation claw 8 and its tip end is the slope 8b.
A conductive needle-like member 7 is disposed at a position below the top. When the paper P is ejected by the two pairs of fixing rollers so that it is wrapped around the pressure p-22, the paper P is separated by the separation claw 5.
It is separated by the tip 8a of the slanted surface 8b, and is guided and conveyed along the slope 8b. The tip O of the conductive needle member is the guide 8
Since the uppermost part of the paper P is also arranged at the lower part, the paper P will not come into contact with the conductive needle member 7 and jam. With this configuration, the tip C of the conductive needle-like member 7 can be positioned above the tip 8a of the separating claw 50, so that the tip 8a can be placed above the fixing 4-2. It becomes possible to arrange it near the end of the pair of nip sections.

Moreover, this separation claw 5c and the support part 8 which integrally constitutes this
The static elimination effect is improved if at least one of them is made insulating, but as mentioned above, even if the tip C of the conductive needle member 7 is hidden at the separation claw 5o, both sides of the separation claw 5c The needle-like member located at the position ensures that static electricity is removed from the portion where the v separation claw 5o contacts, and uniform static electricity removal can be performed in the axial direction of the pressure roller 2. Incidentally, FIG. 7 shows a top view of the pressure roller 2 of FIG. 6 viewed from above.

In any case, by integrating the separation claw and the static eliminating member, the static eliminating member can be positioned at an arbitrary and appropriate location, and the static eliminating performance can also be stabilized, which is particularly preferable.

Next, while explaining FIG. 8, supplementary information about the embodiment of the present invention will be provided. Specifically, terms used in the present invention will be explained.

The region where the tip of the static eliminating member in the present invention is located is the first region.
This is explained using the phrase "near the press-contact part" of the second rotating body. The vicinity of the pressure contact portion is the discharge side of the recording material and is referred to as the above-mentioned first part. The common external tangent line D of the second rotating bodies 1 and 2 (which is actually a common circumscribing surface, but will be explained below when looking at FIG. 8 as a cross-sectional view) and the respective circumferential surfaces of the first and second rotating bodies form If a static eliminating member is provided that has a tip or a tip close to the surface of the rotating body in a space where the terminal end F of the press contact part and the common external tangent in normal (non-fixing) and the common external tangent follow this fixed line, the charge eliminating member is provided. It is good that the effect can be obtained.

Further, in the vicinity of the pressure contact portion, the pressure contact portion itself changes as the recording material passes between the rotating bodies during fixing. In other words, the terminal end F of the pressure contact part in the recording material ejection direction widens by several millimeters.
After the recording material passes, it returns to its original state. Further, frictional electrification of the rotating body and the recording material occurs at the pressure contact portion, and the first. Separation and electrification when the second rotating body is separated is particularly responsible for the occurrence of offset.

Therefore, it is only necessary to provide the above-mentioned static eliminating member within the peeling area, particularly in a range where the influence of the peeling electrostatic voltage can be prevented. The term "separation area" refers to the distance i1r distance (in one example, 5mm
A tangent line Dλ and a horse of the opposing rotating body are drawn through each of the first rotating body 1' circumferential surface H1 and the second rotating body 2' circumferential surface H1 (mm to 2 mm), and the common external tangent line and the tangent line D are drawn. Engineering, D■
means the spatial area surrounded by The pick peeling area is such that the part that causes peeling electrification (near the terminal end F) is in contact with the tangential line outside the ring of the distal end C of the static eliminating member. At the respective intersections with J Ds and Di, the dot is the contact point of the 20th-22' tangent line D1, and the dot l is the contact point of the 10th-21' tangent line D1. By setting it within this range, more efficient static elimination can be achieved.

Further, within this peeling region or in the vicinity of the pressure contact portion, there is a range that satisfies the above-mentioned positions C1 to C4 of the tip portion C, where the static elimination effect is particularly high and the generation rate of offset toner can be further reduced by one rank.

This is an angle θ (-60
It was found that it is sufficient if the circumferential angle is within 1°). When the boundary line M with the angle θ (-60°) is a common circumference, the point S where it intersects with D, the point N where it intersects with the tangent D1, and the point where it intersects with the outer circumference of the second rotating body is defined, then this is surrounded. It means an area or something that includes the IN, NL, and LI areas.

Also, within this range or region, it is preferable to provide the neutralizing member on the one of the first and second rotating bodies that is more likely to be charged, and in the above description, the second rotating body is assumed to be more likely to be charged.

In any case, the present invention provides a long-term stable static elimination effect that cannot be obtained from conventional contact-type static elimination members, can prevent the occurrence of offset, and provides excellent static elimination that cannot be obtained from conventional non-contact static elimination members. It is something that can be effective.

It has now become possible to obtain a fixing device that has very little offset over a long period of time and is also very good in terms of wrapping of copy paper.

Further, although negative toner was used in all of the examples, it is also effective when using positive toner.

The present invention is particularly effective for heat fixing devices, but also for pressure fixing devices, and is particularly effective for processing objects to be fixed such as toner images.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of one embodiment of the present invention, FIG. 2 is an explanatory diagram for detailed explanation of the present invention, FIG. 5 is an explanatory diagram of another embodiment of the present invention, and FIG. 4 is an explanatory diagram of another embodiment of the present invention. An explanatory diagram of the static eliminator according to the present invention, FIG. 5 is a top view of the pressurizing device 22 in FIG. 6, FIG. 6 is an explanatory diagram of another embodiment of the present invention, and FIG. A top view of the pressure roller 2, FIG. 8, is an explanatory view for explaining the position range related to the present invention. 1 is heating row 2.2 is pressure row 2%515+ is separation claw,
7 is a conductive needle member, 8 is a support portion, B is a static eliminator, C is a tip portion, D is a common external tangent line, G is a guide member, F is a terminal end (of the pressure contact portion), and θ is an angle. Applicant: Canon Co., Ltd.

Claims (1)

Claims: The invention includes a first rotating body and a second rotating body that is in pressure contact with the first rotating body, the first rotating body. In the fixing device that fixes an object to be fixed onto a recording material by sandwiching and conveying the recording material between the second rotating bodies, the above-described first. In the vicinity of the recording material discharge side of the pressure contact portion of the second rotating body, the first. A fixing device comprising a static eliminating member having a tip disposed close to one of the surfaces of the second rotating body.