JP2906511B2 - Fixing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device of a type that applies thermal energy to a recording material via a heat-resistant film.

This apparatus is composed of an image heating and fixing device in an image forming apparatus such as an electrophotographic copying machine, a printer, and a facsimile, that is, a resin or the like which is heated and melted by an appropriate image forming process means such as electrophotography, electrostatic recording, and magnetic recording. Unfixed toner corresponding to the target image information, formed on the surface of the recording material (electrofax sheet, electrostatic recording sheet, transfer material sheet, printing paper, etc.) using toner directly or indirectly (transferred) The present invention can be used as an image fixing device that heats and fixes an image as a permanently fixed image on a recording material surface carrying the image.

Further, the present invention is not limited to an image forming apparatus, and can be used as a means or a device for widely performing heat treatment of an image carrier, such as a device for heating a recording material carrying an image to improve the surface properties.

(Prior Art) Various types and configurations of an image heating and fixing device such as a heat roller method, a hot plate method, a belt fixing method, and a flash fixing method have been known and are in practical use.

Recently, fixedly supported heating elements (thermal heaters,
A heat-resistant film (fixing film) conveyed while being pressed against the heater, and a pressure member for depositing a recording material on the heater through the film. A fixing device (film heating method) has been devised in which a non-fixed image formed and carried on a recording material surface is heated and fixed on the recording material surface by applying the recording material to the recording material via the recording medium.

A method and apparatus disclosed in, for example, JP-A-63-313182 according to the earlier proposal of the present applicant belong to this, and a thin heat-resistant film (sheet), a moving driving means for the film,
A recording material to be image-fixed to the heater, which is fixedly supported and disposed on one side of the film with the film inside, and to the heater disposed opposite to the heater on the other side, via the film; The film has a pressurizing member for bringing the visible image bearing surface into close contact with the recording material to be conveyed and introduced between the film and the pressurizing member at the same speed in the forward direction at least during image fixing. The traveling image is passed through a fixing nip portion formed by pressing the heater and the pressing member with the traveling moving film and the recording material interposed therebetween, thereby moving the visible image carrying surface of the recording material through the film. Heat is applied by a heater to apply thermal energy to the visible image (unfixed toner image) to soften and melt it, and then separate the film and the recording material, or separate the film and the recording material after the toner is cooled and solidified. That A heating means or apparatus according to the present.

Such a film heating type fixing device has a low heat capacity heating element as a heater in comparison with other heat fixing type devices such as a heat roller type, a hot plate type, a belt fixing type, a flash fixing type, and an oven fixing type. Since it can be used, it saves power and shortens the wait time (quick start property), and since the fixing point and the separation point can be set separately, offset can be prevented. It has advantages such as being able to be solved and is effective.

A heater as a heating element is formed by coating a low-heat-capacity current-generating resistor in a linear or band shape on a heat-resistant and high-heat-conductive low-heat-capacity insulating substrate (base material) such as a ceramic, for example, an alumina substrate. A heater having a low heat capacity in which a surface protective layer made of a glass material or the like is coated thereon is used, and the heater has a small heat capacity of the resistor and the substrate by energizing the resistor, so that the surface has a required fixing temperature (for example, about 180 ° C.). ℃).

The heat capacity of the heat-resistant film in contact with the heater is also small, and the heat energy on the heater side is effectively transmitted to the recording material side in pressure contact with the film via the film, so that the image is heated and fixed well. .

The temperature control of the heater employs an energization control configuration in which the heater temperature is detected by a temperature detecting element, the energization to the energized heating resistor is controlled based on the temperature detection information, and the temperature of the heater is controlled to a predetermined fixing temperature. .

(Problems to be Solved by the Invention) In such a film heating type fixing device, a fixing nip portion formed by pressing a heating element and a pressing member with a film interposed therebetween has a fixing property and an offset property. Pressing with a certain amount of force. In addition, the fixing nip is heated to a high temperature. As a result, in the fixing nip portion, the back surface of the film (the surface in contact with the heating member) may adhere to the film sliding surface of the heating member and development may occur.

When sticking development occurs, the conveyed film is in a so-called stick-slip state, causing noise in the fixing nip portion, or even disturbing the image because the film cannot be fed smoothly. Further, in the case of extreme sticking development, a large increase in torque occurs at the time of starting the apparatus (at the start of film transport driving), and a part of the driving gear train may be damaged.

An object of the present invention is to improve the reliability of the apparatus by strictly preventing the occurrence of film sticking development as described above.

(Means for Solving the Problems) According to the present invention, a heating body fixed and supported, and one surface slides on the heating body and the other surface moves together with a recording material bearing an unfixed image. And a fixing device for fixing an unfixed image on a recording material by heat from the heating element via the film, wherein a fluorine-based lubricant is provided between the heating element and the film. A fixing device characterized in that:

(Function) That is, since the above-mentioned fluorine-based lubricant is excellent in heat resistance, the characteristics of the lubricant remain unchanged regardless of the pressing force and the high temperature at the fixing nip due to the presence of the lubricant. A state in which the film slides smoothly with each other at all times is secured, and the occurrence of film sticking development to the heating body surface is strictly prevented. Problems such as the above-mentioned sound generation, image disorder, gear damage, etc. due to film sticking development are caused. Is eliminated.

(Example) (1) Example of fixing device I (FIG. 1) FIG. 1 shows a film heating type fixing device 11 according to the present invention.
1 shows a schematic configuration of an example.

Reference numeral 16 denotes an endless belt-shaped fixing film, which includes a left driving roller 17, a right driven roller 18, and a low heat capacity linear heating element fixedly supported and disposed below the rollers 17 and 18. The four members 17 parallel to each other of the heating element 12 and the guide roller 17a disposed below the drive roller 17
・ It is stretched between 18, 12, 17a.

The driven roller 18 is an endless belt-shaped fixing film 16.
Of the fixing film 16
Is a transfer material as an image carrier carrying an unfixed toner image Ta conveyed from the image forming unit (9) side at a predetermined peripheral speed in the clockwise direction accompanying the clockwise rotation of the drive roller 17; The sheet P is rotated at the same peripheral speed as the conveying speed of the sheet P without wrinkles, meandering, and speed delay.

Reference numeral 19 denotes a pressure roller having a rubber elastic layer having good releasability, such as silicon rubber, as a pressure member, and sandwiching the descending film portion of the endless belt-shaped fixing film 16 to form the heating element 12. The lower surface is brought into opposing pressure contact by a biasing means with a contact pressure of, for example, a total pressure of 4 to 7 kg,
The transfer material sheet P rotates counterclockwise in the forward direction in the transport direction.

Endless belt-shaped fixing film 16 that is driven to rotate
Is repeatedly used for heating and fixing of toner images, so it has excellent heat resistance, release property and durability, and generally has a total thickness of 100 μm.
Hereafter, preferably a thin material having a thickness of 40 μm or less is used.

For example, polyimide, polyetherimide, PES, PFA
(PTFE (tetrafluoroethylene resin)) on a single-layer film of a heat-resistant resin such as (tetrafluoroethylene-perfluoroalkylvinyl ether copolymer resin) or a composite layer film, for example, a 12 μm thick film at least on the image contacting surface side. 10μ of release coating layer with conductive material added to fluororesin such as PAF
and m-thick ones.

The low-heat-capacity linear heating element 12 as a heating element according to the present embodiment has a transversely long rigidity, high heat resistance, and heat insulating property whose longitudinal direction is in the transverse direction of the fixing film (the direction perpendicular to the running direction of the fixing film 16). A heater support 24, and a heating element 14, which is integrally attached and held on the lower surface side of the support along the length of the lower surface,
It has a heater substrate 13 provided with a temperature detecting element 15 and the like as means for detecting the temperature of the heating element 12.

The heater support 24 insulates and holds the heating body 12 and secures the overall strength. For example, PPS (polyphenylene sulfide), PAI (polyamide imide), PI (polyimide), PEEK (polyether ether ketone), liquid crystal It can be composed of a high heat-resistant resin such as a polymer, or a composite material of such a resin and a ceramic metal or glass.

The heater substrate 13 has a thickness of 1.0 mm, a width of 10 mm and a length of 2 as an example.
40mm alumina substrate.

The heating element 14 is, for example, a linear shape formed by coating an electric resistance material such as Ta ₂ N / silver palladium to a width of 1.0 mm (screen printing or the like) along a length thereof at a substantially central portion of a lower surface of the substrate 13. Or, it is a belt-shaped current-generating heating element having a low heat capacity.

The temperature detecting element 15 is, for example, a Pt film or the like provided by coating (screen printing, etc.) along the length at a substantially central portion of the upper surface of the substrate 13 (the surface opposite to the side on which the heating element 14 is provided). It is a low-heat-capacity resistance thermometer. In this example, the temperature of the substrate 13 is
The temperature 12 is detected by the temperature detecting element 15.

The lower surface side of the heating element 12, that is, the substrate surface on which the heating element 14 is provided is a contact surface with the film, and this surface is covered with a protective layer 22 made of a glass material to protect the surface.

The heating element 12 is attached to a heat-insulating heater support 24 with a heat-resistant double-sided tape or a heat-resistant adhesive. The support 24 is attached to and supported by a stay 23 of the fixing device, and the stay 23 is made of a material and a structure that does not cause a large deflection at the center in the longitudinal direction even when the heating body 12 is pressed by the pressing roller 19. belongs to.

In the case of this example, the linear or belt-like heating element 14 is energized from both longitudinal ends thereof to generate heat over the entire length. The energization has a pulse-like waveform of 100 V DC and a cycle of 20 msec, and has an energization control circuit configuration for giving a pulse corresponding to a desired temperature and energy release amount controlled by the temperature detecting element 15 by changing the pulse width. The pulse width is approximately 0.5 to 5 msec.

In this embodiment, a sensor for detecting the leading and trailing edges of the sheet (not shown) is provided closer to the fixing device on the upstream side in the sheet conveying direction of the transfer material than the fixing device 11, and the heating element 14 is energized by a sheet detection signal of the sensor. The period of the sheet P is the fixing device 11
Is controlled only for the necessary period of passing.

The leading end of the transfer material sheet P carrying the unfixed toner image Ta on the upper surface, which is conveyed from the transfer unit (9) side to the fixing device 11 by the image forming device performing the image forming operation in response to the image forming start signal, is closer to the fixing device. The above-mentioned sensor (not shown) arranged in
, The rotation of the fixing film 16 starts,
The transfer material sheet P is guided by a guide 21 and a fixing film at a pressure contact portion N (fixing nip portion) between the heating body 12 and the pressure roller 19.
16 between the pressure roller 16 and the pressure roller 19, the unfixed toner image surface comes into close contact with the lower surface of the fixing film 16 which is moving in the same direction at the same speed as the conveyance speed of the sheet P, and the surface misalignment occurs. The sheet passes through the fixing nip portion N between the heating element 12 and the pressure roller 19 while receiving the pinching pressure in an overlapping state with the fixing film 16 without causing deviation.

w is the width dimension of the heating element 14 provided on the lower surface of the heating element, and the heating element 14 is in the mutual pressure contact width region between the lower surface of the heating element 12 and the upper surface of the pressure roller 19, that is, the width of the fixing nip N. Exist in the area.

In the process of passing through the fixing nip N in a state where the toner image carrying surface of the sheet P is pressed and adhered to the fixing film surface, a heating element is formed.
14 is received via the fixing film 16, the toner image is melted at a high temperature and softened and adhered Tb to the sheet P surface.

In the case of this apparatus, a sheet P as a recording material and a fixing film are used.
The separation from the sheet 16 is performed when the sheet P passes through the fixing nip N and exits.

At the time of the separation, the temperature of the toner Tb is still higher than the glass transition point of the toner, and therefore, the bonding force (adhesive force) between the sheet P and the fixing film 16 at the time of the separation.
Since the sheet P is small, the sheet P hardly causes toner offset on the surface of the fixing film 16, and the sheet P is always smoothly separated without being wound and jammed while the sheet P adheres to the surface of the fixing film 16 due to poor separation. Go.

And since the toner Tb in a state higher than the glass transition point has an appropriate rubber property, the toner image surface at the time of separation has an appropriate uneven surface property without following the fixing film surface. Is maintained, and the toner image is cooled and solidified. Therefore, excessive image gloss is not generated on the fixed toner image surface, and high quality image is obtained.

The sheet P separated from the fixing film 16 is guided by the guide 25 and naturally reaches a temperature lower than the glass transition point because the temperature of the toner Tb higher than the glass transition point naturally lowers (natural cooling) before reaching the paper discharge portion. As a result, the sheet P on which the image has been fixed is output.

In this embodiment, the lower surface of the heating element 12 in the fixing nip portion N,
That is, the protective layer 22 of the heating element 12 and the endless film 16
, A lubricant 27 is interposed between the back side, that is, the side in contact with the toner image and the opposite side.

The lubricant 27 does not disappear or deteriorate even when used at a high temperature, and also has a heat insulating support 24 made of another contact member, for example, a rubber material of the drive roller 17 or a heat-resistant resin. It is necessary not to make mistakes. According to experiments by the present inventors, a remarkable effect was observed with a lubricant comprising perfluoropolyether oil and PTFE.

The lubricant 27 may be applied to the lower surface of the heating element 12 in advance when assembling the fixing device.

In this way, when the lubricant is interposed between the surface of the heating element and the surface of the film, the protective layer 22 on the surface of the heating element and the surface of the film 16 do not stick together, and the film 16 always slides smoothly on the surface of the heating element. As a result, it is possible to prevent the generation of noise and vibration.

(2) Example of fixing device II (FIG. 2) The fixing film 16 is not limited to the endless belt shape.
As shown in the example, the end-fixed film 16 wound around a feed shaft 40 in a roll form is locked between the heating body 12 and the pressure roller 19, under the guide roller 17a, and on the winding shaft 41. Then, the transfer material sheet P is moved from the delivery shaft 40 side to the take-up shaft 41 side.
May be configured to run at the same speed as the transport speed of the vehicle.

Also in this device, a lubricant is provided between the lower surface of the heater 12 in the fixing nip N, that is, the protective layer 22 of the heater 12 and the back surface of the fixing film 16, that is, the surface opposite to the side in contact with the toner image. 27 is interposed. The lubricant 27 may be applied to the lower surface of the heating element 12 in advance when assembling the fixing device.

(3) Fixing Device Example III (FIG. 3) In this example, an endless belt type fixing film 16 is used as in the fixing device example I (FIG. 1), and the guide roller 17a is omitted. In this point, the configuration is different from that of the example in FIG.

Also in this device, the lower surface of the heater 12 in the fixing nip portion N, that is, the protective layer (22) of the heater 12 and the fixing film 16
, A lubricant 27 is interposed between the back side, that is, the side in contact with the toner image and the opposite side. The lubricant 27 may be applied to the lower surface of the heating element 12 in advance when assembling the fixing device.

(4) Example of fixing device IV (FIG. 4) In the above examples I to III, the example in which the lubricant 27 is applied to the surface of the heating body at the time of assembling the device has been described. It is desirable to provide a supply device for the agent 27. FIG. 4 shows this embodiment.

In FIG. 4, the lubricant 27 in the tank 30 is sent to the grease applying roller 31, and is applied to the surface of the heat-resistant endless film 16 opposite to the surface in contact with the toner image (the back surface of the film). The roller 31 continues to supply the lubricant to the back surface of the film.
The lubricant 24 attached to the back surface of the film intervenes between the back surface of the film and the lower surface of the heating body at the fixing nip N, and
As in III, sticking of the heated body surface to the film and stick-slip development can be prevented.

Grease application roller 31 that supplies lubricant 27 with corn
Is preferably upstream of the fixing nip portion N in the film moving direction and downstream of the driving roller in the film moving direction. In this case, the excess grease does not flow into the drive roller, and the film temperature is sufficiently lowered, so that the heat resistance of the material of the grease applying roller 31 is low, so that an inexpensive material can be used. is there.

(5) Example of fixing device V (FIG. 5) In this example, the lubricant 27 in the tank 32 is heated
The film 12 is supplied to the back surface of the film from a small hole formed in the lower surface portion of the support on the upstream side in the film movement direction of the fixing nip portion N through a thin supply path 33 provided in the heater support 24 which supports the heat insulating member 12. .

In the case of this embodiment, the structure is simple, and the lubricant can be supplied more easily.

(6) Example of Image Forming Apparatus (FIG. 6) FIG. 6 shows a fixing device 11 according to the present invention (of the example in FIG. 1).
1 shows a schematic configuration of an example of an image forming apparatus in which is incorporated. The image forming apparatus of the present embodiment is an electrophotographic copying apparatus of a reciprocating platen type, a rotating drum type, and a transfer type.

Reference numeral 100 denotes an apparatus housing, and 1 denotes a reciprocating type document placing table made of a transparent plate member such as a glass plate disposed on an upper plate 100a of the apparatus housing. Reciprocatingly driven at a predetermined speed in the direction a and the left side a ′.

G is an original, which is placed on the upper surface of the original placing table 1 with the image side to be copied facing downward according to a predetermined placing reference;
The original is set by placing the original cover 1a on top of the cover.

Reference numeral 100b denotes a slit opening serving as a document illuminating unit which is opened on the surface of the casing upper surface plate 100a with a direction perpendicular to the reciprocating movement direction of the document placing table 1 (a direction perpendicular to the paper surface) as a longitudinal direction. The downward image surface of the document G placed and set on the document table 1 sequentially passes through the position of the slit opening 100b from the right side to the left side during the reciprocating movement of the document table 1 to the right side a. During the passage of the light, the light L of the lamp 3 is received through the slit opening 100b and the transparent document table 1, and is scanned by illumination. The reflected light of the illumination scanning light on the document surface is image-formed and exposed on the surface of the photosensitive drum 4 by the short-focus small-diameter imaging element array 2.

The photosensitive drum 4 is coated with a photosensitive layer such as a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer, and is driven to rotate clockwise as indicated by an arrow b at a predetermined peripheral speed around a center support shaft 4a. The charging device 5 receives a uniform charging process of positive or negative polarity, and the uniformly charged surface receives image forming exposure (slit exposure) of the original image, thereby forming an image on the surface of the photosensitive drum 4. An electrostatic latent image corresponding to a document image is sequentially formed.

The electrostatic latent image is successively visualized by a toner made of a resin or the like which is softened and melted by heating by the developing device 6, and the developed toner image is transferred to a portion where a transfer discharger 9 as a transfer portion is provided. I will do it.

S denotes a cassette in which transfer material sheets P as recording materials are stacked and stored, and the sheets in the cassette are fed out one by one by the rotation of the feed roller 7, and then the toner on the drum 4 is transferred by the registration roller 8. When the leading end of the image forming section reaches the transfer discharger 9, the leading end of the transfer material sheet P also reaches the position between the transfer discharger 9 and the photosensitive drum 4, and the timing is synchronized so that they coincide with each other. Will be fed. Then, the transfer discharger 9 is applied to the surface of the sheet.
Accordingly, the toner images on the photosensitive drum 4 side are sequentially transferred.

The sheet to which the toner image has been transferred in the transfer unit is sequentially separated from the surface of the photosensitive drum 4 by a separation unit (not shown),
The unfixed toner image Ta guided by the fixing device 11 and carried by the fixing device 10 is subjected to a heat-fixing process, and is passed through a guide 25 and a discharge roller 36 as an image formed product (copy), and is set on a discharge tray 37 outside the apparatus. Is discharged on top.

On the other hand, the surface of the photosensitive drum 4 after the transfer of the toner image is subjected to removal of contaminants such as untransferred toner by the cleaning device 20, and is repeatedly used for image formation.

(Effects of the Invention) As described above, the present invention relates to a fixing device of a film heating type, in which a surface of a heating body and a surface where a heat-resistant film is in contact with the heating body, that is, a film surface opposite to a film surface in contact with a toner image. By interposing a lubricant in
This has the effect of preventing sticking and stick-slip development between the surface of the heating element and the film surface. As a result, it is possible to prevent sound and vibration, disturbance of an image due to the sound and vibration, and damage to gears.

[Brief description of the drawings]

1 to 5 are schematic diagrams of fixing device examples I to V according to the present invention, respectively, and FIG. 6 is a schematic diagram of an image forming apparatus. Numeral 11 denotes a fixing device, 12 denotes a heating element, 16 denotes a heat-resistant fixing film, 17 and 18 denote film driving rollers and driven rollers, 19 denotes a pressure roller, N denotes a fixing nip, 27 denotes a lubricant,
30 and 32 are lubricant tanks and 31 is a coating roller.

Claims (1)

(57) [Claims] A heating member fixedly supported; and a film having one surface sliding with the heating member and the other surface moving in contact with a recording material carrying an unfixed image. A fixing device for fixing an unfixed image on a recording material by heat from the heating member via a film, comprising a fluorine-based lubricant between the heating member and the film.