JP3072791B2 - Fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a fixing device for fixing an unfixed image using a fixing film.

[0002]

2. Description of the Related Art Conventionally, as a heating-type fixing device, an unfixed toner image is formed by a heating roller maintained at a predetermined temperature and a pressing roller having an elastic layer and pressing against the heating roller. A fixing device of a heat roller fixing type for heating the recording material while nipping and conveying the recording material is often used.

However, this heat roller fixing type fixing device requires a large heat capacity of the heat roller, and requires a time until the temperature rises to a predetermined temperature (a time during which the image forming operation is prohibited), that is, a so-called wait time.

In order to solve such a problem of the heat roller fixing method, the applicant has disclosed in Japanese Patent Application Laid-Open Nos. 63-313182 and 2-1577878 a fixed heater having a small heat capacity and a thin film film. We have proposed a heat fixing device using.

In this fixing device, heat can be concentrated on the toner side, the wait time is short, and power saving can be achieved.

In an image forming apparatus using such a fixing device, it is preferable that the discharge side of the fixing device can be opened for jam processing.

[0007]

When the discharge side is opened in the fixing device using the above-mentioned fixing film, the operator may touch the film because the fixing film is exposed.

[0008] This film is a thin film, and the film may be damaged or damaged.

[0009]

In order to solve the above problems, the present invention has a film which moves in contact with a recording material carrying an unfixed image, and the unfixed image is transferred onto the recording material by heat from the film side. In a fixing device that fixes the film, a protective member that protects the film, an openable and closable member, and a release agent applying member that contacts and separates from the film in conjunction with the opening and closing operation of the openable and closable member, In conjunction with the opening operation of the opening / closing member, the protection member moves to a position covering the film portion with which the release agent applying member has contacted.

[0010]

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

FIG. 1 is a sectional view of an electrophotographic image forming apparatus according to an embodiment of the present invention.

In FIG. 1, 101 is a photosensitive drum, 102 is a developing device, and 103 is a developing sleeve. Reference numeral 104 denotes a cassette for loading copy paper, and 1
05 is a paper feed roller, 106 is a guide, 107 is a registration roller, 108 is a heat exhaust fan, and 109 is a fixing device.
Reference numeral 113 denotes an optical system. When a document on a document glass is exposed by a document lamp, the exposure light passes through a lens from a first mirror, is irradiated on a photosensitive drum 1 via a sixth mirror.

The exhaust fan 108 is located downstream of the photosensitive drum 101 and its cleaner unit 114, and is located upstream of the fixing unit 109. Therefore, the exhaust fan 108 has a function of exhausting ozone generated when the photosensitive drum is primarily charged and ozone generated when transferring the toner developed on the drum onto copy paper from the paper discharge side through the filter 116. I have.

Next, the operation of the apparatus shown in FIG. 1 will be described. In a normal copying operation, a main motor (not shown) starts operating immediately after the start key is turned on. Then, the paper feed roller 105, to which the drive is transmitted through a one-rotation clutch constituted by a solenoid and a spring clutch, performs one rotation, so that the copy paper is fed from the cassette 104. The fed copy sheet is guided to the registration roller 7 through the guide 106. Since the registration roller 107 is stationary, the copy paper is in a state where the leading end is sandwiched between the nip portions of the registration roller, and is further conveyed only at the rear portion of the paper, thereby forming a loop and temporarily stopping.
Thus, the copy sheet is sent to the transfer position after being aligned.

On the other hand, the optical system starts scanning at a timing such that the leading edge of the copy sheet fed from the registration roller and the latent image formed on the drum are synchronized by a dedicated stepping motor (not shown). After the scanning, the original image is sequentially exposed on the drum 1 through the first to sixth mirrors. The latent image is developed with unfixed powder toner in a subsequent process, and this image is transferred to copy paper.

The copy sheet on which the unfixed toner is transferred is conveyed to a fixing device, and is fixed by being heated and pressed during the conveyance. Reference numeral 120 denotes a left side plate of the main body, reference numeral 20 denotes a fixing discharge door, and both members are substantially on the same plane.

When the discharge door is opened, the main power is turned off by detection by a sensor (not shown).

Next, the fixing section will be described in detail.

2 and 3 are enlarged sectional views of the fixing unit.
2 shows a state in which the discharge door is closed, and FIG. 3 shows a state in which the discharge door is open. FIG. 4 is a partial perspective view.

Reference numeral 7 denotes an endless belt-shaped fixing film, which includes a driving roller 8 on the left side, a driven roller 9 on the right side,
The linear heating element 1 having a constant heat capacity as a heating element disposed between the rollers 8 and 9 is suspended between the three members 8, 9 and 1.

The driven roller 9 also serves as a tension roller for the endless belt-shaped fixing film 7, and the fixing film 7 has a predetermined peripheral speed, ie, an image, in a clockwise direction accompanying the clockwise rotation of the driving roller 8. The recording material P carrying the unfixed toner image Ta conveyed from the forming unit side is rotated at the same peripheral speed as the conveying speed of the recording material P without wrinkles, meandering, and speed delay.

Reference numeral 10 denotes a pressure roller having a rubber elastic layer 12 of silicon rubber or the like having good releasability as a pressure member, and the endless belt-shaped fixing film 7 sandwiching the descending film portion therebetween. The lower surface of the heating element 1 is pressed against the lower surface of the heating element 1 by a biasing means (not shown) with a contact pressure of, for example, a total pressure of 4 to 7 kg. To rotate.

The heating element 1 is a low-heat-capacity linear heating element whose longitudinal direction is the direction intersecting with the plane moving direction of the film 7 (the width direction of the film). A heating element 4, a temperature detecting element 5, etc., are fixed to and supported by the heater support 2.

The heater support 2 has a heat insulating property, a high heat resistance and a rigidity for heat-insulating and supporting the heater 1 and is made of, for example, PPS.
(Polyphenylene sulfide), PAI (polyamide imide), PI (polyimide), PEEK (polyether ether ketone), high heat resistant resin such as liquid crystal polymer, and composite of these resins with ceramics, metal, glass, etc. It can be composed of materials.

The heater substrate 3 is a member having heat resistance, insulation, and low heat capacity. As an example, the thickness is 1.0 mm and the width is 16 mm.
-A 340 mm long alumina substrate.

The heating element 4 is, for example, Ag / Pd at a substantially central portion of the lower surface of the substrate 3 (facing the film 7) along the longitudinal direction.
(Silver palladium), an electric resistance material such as Ta ₂ N or the like is applied by screen printing or the like to a thickness of about 10 μm and a width of 1 to 7 mm.
m-coated.

As an example, the temperature detecting element 5 has a low heat capacity such as a Pt film or the like provided by applying a screen printing or the like to a substantially central portion of the upper surface of the substrate 3 (the surface opposite to the surface on which the heating element 4 is provided). Is a resistance thermometer. Alternatively, a low-heat-capacity thermistor or the like may be arranged in contact with the substrate 3 as the temperature detecting element.

In the case of the heating element 1 of this embodiment, electricity is supplied to the linear or band-shaped heating element 4 from both ends in the longitudinal direction.
The heating element 4 is heated over substantially the entire length. Energization is AC1
The power supply is controlled by controlling the phase angle to be supplied by a power supply control circuit (not shown) including a triac according to the temperature detected by the temperature detection element 5.

The fixing film 7 has heat resistance, releasability, durability and the like, and generally has a total thickness of 100 μm or less, preferably 40 μm or less.
A single-layer or multi-layer film of μm or less can be used.

The film protection member 13 is made of sheet metal or heat-resistant resin, and has pins 15 attached to both ends. The pins 15a and 15b are supported by the support plates 14a and 14b.
It is fitted in the long hole. The support plate 14 is attached to the upper fixing stay 17, and by removing the upper fixing stay 17, the film protection member 13 can be removed, so that the film can be easily cleaned. Thus, the film protection member 13 is rotatably and slidably mounted, and is urged by the spring 16 to the left in FIGS. The discharge door 20 is rotatably supported by the side plate 26,
The pressing plate 27 and the oil application roller 21 are attached. The fixed film protection member 29 is attached to the side plate 26 and does not move even when the discharge door 20 is opened, and overlaps with the film protection member 13 to completely cover the film 7.

When the discharge door 20 shown in FIG. 2 is closed, the oil application roller impregnated with the release oil comes into contact with the fixing film 7 at a position facing the drive roller 8 to apply oil to the surface. I have.

When the discharge door 20 is opened from this state,
When the pressing plate 27 escapes in conjunction with the opening operation of the discharge door 20, the film protection member 13 moves to a position covering the fixing film 7 on the discharge door 20 side shown in FIG. Then, the contact portion of the oil application roller is covered.

Further, since the oil application roller is provided integrally with the paper discharge door 20, when the paper discharge door 20 is opened, it is separated from the fixing film.

For this reason, maintenance work such as replacement of the oil application roller can be easily performed, the consumption of oil is reduced, and the fixing is performed by preventing the film portion having a relatively large amount of release agent from touching. Facilitates equipment maintenance.

When the discharge door 20 is closed while the discharge door 20 shown in FIG. 3 is open, the tip of the pressing plate 27 hits the pin 15 and moves the film protection member 13 rightward. At this time, the film protection member 13 is regulated by the bent portion 14c of the support plate 14 while moving to the right,
Rotate clockwise around. By the movement of the film protection member 13 as described above, the film protection member 13 can be stored in a small space.

Also, during normal fixing, the film protection member moves to a position where the downstream portion of the nip is opened as shown in FIG. 2, so that water vapor generated from the copy paper at the time of fixing may stay around the drive roller and condense on the film. Absent.

Further, since the film protection member moves mechanically in conjunction with the paper discharge door, it functions even when the power is turned off because it moves. Particularly in the configuration in which the main power supply is turned off when the paper discharge door is opened as in this embodiment. It is valid.

Next, the fixing operation will be described.

A recording material sheet carrying an unfixed toner image on its upper surface, which has been conveyed to the fixing device by the image forming apparatus of the above-described example in response to an image forming start signal and which has been conveyed to the fixing device, is guided by the guide 18 to the heating element 1. The fixing film 7 and the pressure roller 1 at the pressure contact portion (fixing nip portion) between the pressure film 10 and the pressure roller 10
0, and the unfixed toner image surface is rotated in the same direction at the same speed as the sheet conveying speed.
The heating member 1 passes through the mutual press contact portion between the heating element 1 and the pressure roller 10 in the overlapping state with the fixing film 7 without causing surface deviation, wrinkling, and deviation, by being closely attached to the lower surface of the fixing member 7.

The heater 1 is energized and heated at a predetermined timing by the image formation start signal, so that the toner image Ta
Is heated at the pressure contact portion and becomes a softened / melted image Tb.

The fixing film 7 is provided at an edge portion S (having a radius of curvature of about 2 mm) of the heater support 2 having a large curvature.
The running direction is turned at a steep angle (the bending angle θ is approximately 45 °). Accordingly, the sheet P conveyed through the pressure contact portion in a state of being overlapped with the fixing film 7 is separated from the fixing film 7 at the edge portion by a curvature, and is discharged to a discharge tray. By the time the sheet is discharged, the toner is sufficiently cooled and solidified, and is in a state of being completely fixed on the sheet P (toner image Tc).

In the present embodiment, the heat capacity of the heating element 4 and the substrate 3 of the heating element 1 is small,
, The surface temperature of the heater 1 at the press contact portion rises to a sufficiently high temperature in a short time with respect to the melting point of the toner (or the temperature at which the toner can be fixed to the sheet). There is no need to raise the temperature (so-called standby temperature control), energy can be saved, and the temperature inside the machine can be prevented.

[0043]

As described above, according to the present invention, the film is not damaged during the jam processing.

Further, maintenance of the fixing device can be easily performed.

[Brief description of the drawings]

FIG. 1 is a sectional view of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a fixing unit, showing a state in which a sheet discharge door is closed.

FIG. 3 is an enlarged cross-sectional view of a fixing unit, showing a state in which a discharge door is opened.

FIG. 4 is a partial perspective view of a fixing unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating body 13 Film protection member 16, 23, 25 Spring 15, 24, 28 Pin 29 Fixed film protection member

Claims (2)

(57) [Claims] A fixing member for fixing the unfixed image on the recording material by heat from the film side, the fixing member having a film that moves in contact with the recording material carrying the unfixed image; And an opening and closing member that can be opened and closed, and a release agent applying member that comes into contact with and separates from the film in conjunction with the opening and closing operation of the opening and closing member. A fixing device, wherein the fixing agent moves to a position covering a film portion with which the release agent applying member has contacted. 2. The fixing device according to claim 1, wherein the release agent applying member is provided on the opening / closing member.