JPH0968882A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of keeping a stable image for a long time and improving durability and reliability by preventing the reoffsetting of toner from a separating pawl to the fixing film and pressure member of a fixing device. SOLUTION: Two or more separating pawls 13 made of heat resistance resin or metal such as SUS are abutted on the outside surface of the fixing film 7 in a longitudinal direction, with pressure in such a degree that the front layer of the fixing film 7 is not peeled and can be separated from the film 7 by a mechanism using a solenoid, etc. For instance, when an A4R-size paper passes through and a temp. detected by a thermometric element becomes >=230 deg.C, the separating pawls 13 in a paper non-passing area are moved from a B-position to an A-position, to be separated from the film 7 and then, to the B-position again, when a copying operation is completed and the temp. detected by the thermometric element becomes <=150 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording material carrying a visible image (toner image) to be heat-fixed to a heating body via a fixing film, and the heating body to the fixing film. The present invention relates to a film heating type fixing device that applies heat energy to a recording material to heat and fix a toner image.

[0002]

2. Description of the Related Art The above heating device is used in an image forming apparatus such as a copying machine, a laser beam printer, a facsimile, a microfilm reader printer, an image display (display) device, and a recording machine. A recording material (electrofax sheet, electrostatic recording sheet, transfer material sheet, printing paper, etc.) as an image carrier is formed by using a toner made of a heat-meltable resin or the like by an appropriate image forming process means such as recording or magnetic recording. The image fixing device heat-fixes as a permanent fixed image on the surface of the recording material carrying the unfixed toner image corresponding to the target image, which is formed by the direct method or the indirect (transfer) method on the surface).

Conventionally, as such a fixing device, a heat roller system in which a recording material having an image supported by a heating roller and a pressure roller is nipped and conveyed has been widely used. Since the power consumption is large and the heat capacity of the heating roller is large, there is a problem that it takes a long time to reach the temperature at which the heating roller can be fixed.

Therefore, in order to solve the above problems, a fixing method using a heat resistant film as described in JP-A-63-313182 has been proposed.

This fixing device comprises a thin heat-resistant film (sheet), a means for moving the film, a heating element fixedly supported on one side of the film with the film inside, and a side of the other side. And a pressing member which is disposed so as to face the heating body and makes the developed image bearing surface of the recording material to be image-fixed adhere to the heating body through the film, and the film is used for at least image fixing. At this time, the heating member and the pressure member are pressed against each other with the traveling moving film sandwiched by traveling at the same speed in the forward direction as the recording material to be image-fixed which is conveyed and introduced between the film and the pressure member. By passing through the fixing nip portion formed by the above, the visible image bearing surface of the recording material is heated by the heating body through the film to impart thermal energy to the visible image (unfixed toner image) to soften it. , Melt, then film Separating the recording material, or after the toner is cooled and solidified, the heating means which is based on that to separate the film and the recording material is an apparatus.

As the heating element, a linear or strip-like shape is formed along the longitudinal direction of the film contact surface side of a horizontally elongated heat-resistant, insulating, low heat capacity heater substrate whose longitudinal direction is the width direction of the film. A low-heat-capacity energization heating resistor (heating element) is used for the heating element, and the heating element generates heat when power is supplied across the heating element, and the heater substrate is also heated. The entire body rapidly rises in temperature, and the heat of the heating body is applied to the recording material via the film.

The temperature control of the heating element is performed by a temperature sensor provided on the heating element, a microcomputer of the image forming apparatus main body and a heating element driving (normally heat generating) circuit, and the temperature is controlled to a predetermined fixable temperature. It Although the heating element is at a high temperature, the film is driven to move on the heating element at a predetermined speed at least when the heating element generates heat, so that local thermal deformation of the film does not occur and a stable image is obtained. Fixing is executed.

Such a film heating type fixing device has advantages such as a short wait time and is a fixing device that meets the demands of the times.

[0009]

However, in the above-mentioned conventional film heating type fixing device, when a small size paper is used, the temperature of the film and the pressure member in the non-paper feed area increases, and In some cases, the toner on the separating claw that adheres with use is melted and is offset again on the film or the pressing member, and the offset toner adheres to the recording material to cause image deterioration.

Therefore, the first invention according to the present application prevents re-offset of toner from the separating claw to the fixing film or the pressing member of the fixing device, and keeps a stable image for a long period of time.
An object of the present invention is to provide a fixing device capable of improving durability and reliability.

In addition to the above-mentioned object, the second invention of the present application aims at providing a fixing device which can prevent the re-offset of the toner from the separation claws more reliably.

Further, according to the third invention of the present application, due to the constitution different from that of the first invention, re-offset of the toner from the separating claw to the fixing film and the pressing member of the fixing device is prevented and the stability is stabilized. It is an object of the present invention to provide a fixing device capable of maintaining a formed image for a long period of time and improving durability and reliability.

[0013]

According to the first invention of the present application, the above object is to provide a film member arranged to be movable endlessly, and to contact the film member inside the film member. And a pressure member arranged so as to be in pressure contact with the heating member through the film member, and the heating member and the pressing member formed through the film member. A fixing device that sandwiches and conveys a recording material carrying an unfixed developer image at a pressing portion of a member, and applies thermal energy to the recording material and the unfixed developer image on the recording material from the heating body through the film member. In the above, the recording material is disposed on the discharge side of the recording material so as to be able to come into contact with and separate from the film member and the pressure member more than the pressure contact portion between the heating body and the pressure member formed through the film member. A plurality of separation claws and the recording material of the heating body And a temperature detecting means for detecting the temperature of the passing area, the separation claw is achieved by the detected temperature by the temperature sensing means is moved away from the film member or the pressure member when it exceeds a predetermined temperature.

According to a second aspect of the present invention,
In the first aspect of the invention, the temperature detecting means is divided into a central portion and an end portion in the width direction of the recording material, and the temperature of the recording material non-passing area is detected by the temperature detecting means on the end portion side. It is achieved by

Further, according to the third invention of the present application, the above object is to provide a film member movably arranged endlessly, and to arrange the film member inside the film member so as to contact the film member. And a pressure member arranged so as to be in pressure contact with the heating member via the film member, and a pressure contact portion between the heating member and the pressure member formed via the film member. In the fixing device, the recording material carrying the unfixed developer image is nipped and conveyed, and thermal energy is applied to the recording material and the unfixed developer image on the recording material from the heating body through the film member. A plurality of separation claws that are arranged so as to come into contact with and separate from the film member and the pressure member on the recording material discharge side with respect to the pressure contact portion between the heating body and the pressure member formed via the member. And the recording material size detection means For example, the detection size by said detecting means, if less than the predetermined size is achieved by separating the separating claw from the film member or the pressure member.

Therefore, according to the first invention of the present application, when the temperature of the recording material non-passing area detected by the temperature detecting means exceeds the predetermined temperature, the separation claw is separated from the film member or the pressing member. Since they are separated from each other, the separation claw that is in contact with the area is not heated to a high temperature, and the developer attached to the separation claw is not melted.

According to the second aspect of the present invention,
In the first invention, the temperature of the recording material non-passage area is
The temperature of the recording material non-passing area is accurately detected because it is detected by the temperature detecting means arranged on the end side in the width direction of the recording material.

Further, according to the third invention of the present application, when the recording material size detected by the recording material size detecting means is less than the predetermined size, the separation claw is separated from the film member or the pressing member. Since they are separated from each other, even if the recording material of a small size passes through the pressure contact portion of the heating member and the pressure member formed through the film member and the non-passage area of this recording material becomes high temperature, Since the separating claws that are in contact with each other are separated from each other, the separating claws are not heated to a high temperature and the developer attached to the separating claws is not melted.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a sectional view showing a schematic configuration of an example of an image forming apparatus using the fixing device of the present invention. As shown in FIG. 4, the image forming apparatus of the present embodiment is an electrophotographic copying apparatus of fixed optical platen type, movable optical system, rotary drum type, and transfer type.

In the apparatus of this embodiment, when the original 19 is placed on the fixed original glass 20 and the required copying conditions are set and the copy start key is pressed, the photosensitive drum 39 is moved to the arrow mark. It is rotationally driven at a predetermined peripheral speed in the clockwise direction indicated by. In addition, the light source 21 (22 is a reflective shade) and the first
The mirror 23 moves forward along the lower surface of the platen glass 20 from the home position on the left side of the glass to the right side of the glass at a predetermined speed V, and the second mirror 24 and the third mirror 25 move in the same direction at V / 2. By moving forward, the downward image surface of the document 19 placed on the document glass 20 is illuminated and scanned from the left side to the right side, and the reflected light of the illumination scanning light on the document surface is fixed to the imaging lens 29 and the fixed fourth side. Image formation exposure (slit exposure) is performed on the surface of the photosensitive drum 39 via the mirror 26, the fifth fixed mirror 27, and the sixth fixed mirror 28.

Before the exposure, the surface of the rotating photosensitive drum 39 is uniformly charged to a predetermined positive or negative potential by the primary charger 30, and the above-mentioned exposure is performed on the charged surface. By doing so, an electrostatic latent image having a pattern corresponding to the original image is sequentially formed on the surface of the photosensitive drum 39. The electrostatic latent image formed on the surface of the photosensitive drum 39 is visualized as a toner image by the developing roller 32 of the developing device 31.

On the other hand, the recording material sheet P is fed by a paper feeding means (not shown) and is introduced into the transfer portion between the photosensitive drum 39 and the transfer charger 34 at a predetermined timing through the guide 33. The toner image on the surface of the photosensitive drum 39 is sequentially transferred to the surface of the recording material sheet P by receiving the transfer corona.

The sheet P which has passed through the image transfer portion is separated by a separating means,
For example, it is sequentially separated from the surface of the photosensitive drum 39 by a separation belt (not shown) arranged at the end of the drum, and the charge removal needle 35 removes the charges on the back surface of the transfer guide 38.
It is introduced into the fixing device 60 by the guide 18, undergoes toner image fixing as described later, and is ejected outside the machine as an image formed product.

After the transfer, the surface of the photosensitive drum 39 is cleaned and removed by the cleaning blade 37 of the cleaning device 36 to remove stains such as residual toner, and is repeatedly used for image formation.

The moving optical section (light source 2) that has moved forward as described above
When 1, the reflection shade 22, the first mirror 23, the second mirror 24, and the third mirror 25) reach a predetermined forward movement end point, they are returned to the original home position and return to the initial home position to start the next copy cycle. Wait until (this step is called a back step of the optical system).

Next, the fixing device 60 mounted on the apparatus of this embodiment will be described in detail with reference to FIGS.
In the figure, 7 is an endless fixing film which is a film member. The fixing film 7 includes a driving roller 8 on the left side and a driven roller 9 on the right side of FIG.
It is suspended and stretched between the heating element 1 having a low heat capacity and arranged in the lower part of the space 9.

The driven roller 9 also serves as a tension roller for applying tension in a direction in which the endless fixing film 7 is stretched outward. The fixing film 7 is rotated in a clockwise direction by a predetermined amount in accordance with the clockwise rotation of the driving roller 8. Peripheral speed,
That is, the unfixed toner image Ta conveyed from the image forming portion side is rotationally driven at the same peripheral speed as the conveying speed of the recording material sheet P carrying the upper surface without wrinkles, meandering, or speed delay.

Reference numeral 10 denotes a pressure roller having a rubber elastic layer 12 having a good releasability such as silicone rubber as a pressure member. The lower film portion of the fixing film 7 is sandwiched between the heating body 1 and the heating film 1. , A total pressure of 4 to 7 kg / cm by a biasing means (not shown) such as a spring against the lower surface of the heating body 1.
The recording material sheet P
It rotates about the shaft 11 in the counterclockwise direction, which is the forward direction of the transport direction.

The heating element 1 is of a low heat capacity type having a longitudinal direction in a direction crossing the plane moving direction of the fixing film 7 (width direction of the fixing film 7). ) 4, a temperature measuring element 5, a heat-resistant glass layer 6 and the like, which are attached and held and fixed to the heater support 2.

The heater support 2 includes the heating body 1 and the fixing device 6
0, which has a heat insulating property, a high heat resistance, and a rigidity for adiabatically supporting the image forming apparatus such as PPS (polyphenylene sulfide), PAI (polyamide imide), P
It can be made of high heat resistant resin such as I (polyimide), PEEK (polyether ether ketone), liquid crystal polymer, or a composite material of these resins and ceramics, metal, glass or the like.

The heater substrate 3 is a member having heat resistance and low heat capacity, and has a thickness of 1.0 mm, a width of 10 mm, and a width of 16 m, for example.
It is an alumina substrate having a length of m and a length of 340 mm.

The heating element 4 is made of, for example, Ag and Pd (silver-palladium), Ta ₂ N, or another electrical resistance material along the lengthwise direction substantially in the center of the lower surface of the heater substrate 3 (opposite side of the fixing film 7). A film having a thickness of 10 μm and a width of 1 to 3 mm is applied by screen printing or the like, and a heat-resistant glass 6 as a surface protection layer is coated thereon to a thickness of about 10 μm.

As an example, the temperature detecting element 5 serving as the temperature detecting means is located substantially at the center (first temperature detecting element) and end (second side) of the upper surface of the heater substrate 3 (the surface opposite to the surface on which the heating element 4 is provided). It is a side temperature resistor having a low heat capacity such as a Pt film provided by coating the temperature measuring element) by screen printing or the like. Temperature measuring element 5
Alternatively, a thermistor or the like having a low heat capacity may be arranged in contact with the heater substrate 3.

In the case of the heating element 1 of this embodiment, the heating element 4 having a linear or strip shape is energized from both ends in the longitudinal direction thereof to cause the heating element 4 to generate heat over substantially the entire length. The energization is 100 V AC, and the energization power is controlled by controlling the energizing phase angle by an energization control circuit (not shown) including a triac according to the temperature detected by the temperature detecting element 5.

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

FIG. 3 is a schematic diagram of a layer constitution of an example in which the fixing film 7 is a composite film, and this embodiment is a two-layer constitution film. 7b is a heat-resistant layer as a base layer (base film) of the fixing film 7, and 7a is a release layer laminated on the outer surface (the surface facing the toner image) of the heat-resistant layer 7b.

The heat-resistant layer 7b is made of, for example, a highly heat-resistant resin film such as polyimide, polyetheretherketone, polyethersulfone, polyetherimide, or polyparabanic acid, or a metal such as Ni, SUS, or Al. It can be used with excellent properties.

The release layer 7a is preferably, for example, a fluororesin such as PTFE (polytetrafluoroethylene), PFA, FEP, or a silicone resin. The resistance value of the surface of the fixing film 7 can be lowered by mixing a conductive agent such as carbon black, graphite or conductive whiskers into the release layer 7a. Accordingly, the toner contact surface of the fixing film 7 can be prevented from being charged.

The release layer 7a is laminated on the heat-resistant layer 7b by adhesion lamination of the release layer film, electrostatic coating (coating) of the release layer material, lamination by a film forming technique such as vapor deposition, CVD, heat-resistant layer material and the like. 2 by co-extrusion of release layer material
It can be performed with a layer film or the like.

Further, in FIG. 1, reference numeral 13 is a separation claw for separating the fixing film 7 and the recording material sheet P after fixing, which will be described later.

Next, the fixing execution operation will be described.
The image forming apparatus of FIG. 4 performs an image forming operation in response to an image forming start signal, and the recording material sheet P having the unfixed toner image Ta conveyed to the fixing device 60 on the upper surface is guided by the guide 1.
8 is guided by the heating member 1 and the pressure roller 10 into the pressure contact portion (fixing nip portion) between the fixing film 7 and the pressure roller 10, and the unfixed toner image surface conveys the sheet P. The heating body 1 and the pressure roller 10 are brought into close contact with the lower surface of the fixing film 7 which is rotated in the same direction at the same speed as the heating member 1 and the pressure roller 10 in an overlapping state with the fixing film 7 without causing wrinkles or deviations. Passing through the mutual pressure contact parts while receiving clamping pressure.

Since the heating element 1 is electrically heated by the image formation start signal at a predetermined timing, the toner image Ta
Is softened by being heated at the press contact portion and becomes a fusion image Tb.

The fixing film 7 has a large curvature at the edge portion S (having a radius of curvature of about 2 mm) of the heater support 2.
The traveling direction turns at a steep angle (the bending angle θ is approximately 45 °). Therefore, the sheet P conveyed through the pressure contact portion while being overlapped with the fixing film 7 is curvature-separated from the fixing film 7 at the edge portion S and is discharged to the discharge tray. The toner is sufficiently cooled and solidified by the time it is discharged, and is completely fixed on the sheet P (toner image T
c).

Further, in the present embodiment, the heat capacity of the heating element 4 and the substrate 3 of the heating element 1 is small, and these are heat-insulated and supported by the heater support 2.
The surface temperature of the heating element 1 at the pressure contact portion is raised to a sufficiently high temperature with respect to the melting point of the toner (or the temperature at which the recording material sheet P can be fixed) in a short time. (So-called standby temperature control) is not required, energy can be saved, and the temperature rise inside the machine can be prevented.

Further, the separation claw 13 will be described. As shown in FIG. 1, the separation claw 13 is made of heat-resistant resin or S.
The separation claws 13 are made of a metal such as US, and two or more separating claws 13 are brought into contact with the outer surface of the fixing film 7 in the longitudinal direction with a pressure that does not separate the surface layer of the fixing film 7.

Further, as shown in FIG. 2, the separation claw 13 is
The fixing film 7 can be separated from the fixing film 7 by a mechanism (not shown) using a solenoid or the like. In the present embodiment, for example, when passing a sheet of A4R size and the temperature detected by the second temperature detecting element becomes 230 ° C. or higher, the separation claw 13 in the non-sheet passing area moves from the position B to the position A, It is separated from the fixing film 7. After that, the copy operation ends, and the temperature detected by the second temperature sensing element is 150 ° C.
When it becomes the following, it moves to the B position again. However, this temperature differs depending on the control temperature of the heating element 1 and the toner material.

By doing so, the deterioration of the image due to the re-offset of the toner from the separation claw can be prevented, and the durability and reliability of the fixing device 60 can be improved.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. In the present embodiment, paper is used as a recording material, and a paper width detecting means (not shown) is provided as a means for detecting the size of the recording material, and the separation and contact of the separation claws are controlled according to the paper width.

FIG. 5 and Table 1 show the correspondence between the paper size and the separating claw to be separated according to the second embodiment of the present invention.

[0051]

[Table 1]

For example, when the paper width L is L <l ₁ , the separation claws a, b, c and d are separated. When L <l ₂ , the separating claws a, b and c are separated. The paper size is detected by a detection unit (not shown) in both cases of cassette paper feed and manual paper feed, and the separation claw that is always in the non-paper feed area is
It is designed to be separated from the fixing film or the pressure roller. By doing so, the same effect as that of the first embodiment can be obtained.

(Third Embodiment) FIG. 6 shows a third embodiment of the present invention. In this case, the pressure roller separation claws are separated according to the surface temperature of the pressure roller. The surface temperature of the pressure roller is detected by the temperature detecting element 20 which is a temperature detecting means that is brought into contact with the end portion of the surface of the pressure roller, and the separating claws are separated in the same temperature range as in the first embodiment. By doing so, the same effect as in the first embodiment can be obtained.

(Fourth Embodiment) In the third embodiment, the separation claws are separated according to the temperature detected by the second detection element. In this case, the temperature detecting element for detecting the surface temperature of the pressure roller is not required, and the cost can be reduced.
Moreover, it is possible to obtain the same effect as that of the third embodiment.

[0055]

As described above, the first embodiment according to the present application is described.
According to the invention, in the film heating type fixing device, by separating the separation claw from the film member or the pressure member according to the temperature of the non-passage area of the recording material, the toner adhered to the separation claw due to long-term use. Can be prevented from being re-offset to the fixing film or the pressure roller and adhering to the recording material to deteriorate the image, maintain a stable image for a long time, and improve high durability and reliability. You can

According to the second invention of the present application,
In the first invention, the temperature of the recording material non-passage area is
Since the temperature is detected by the temperature detecting means provided on the end side in the width direction of the recording material, the temperature of the recording material non-passing area can be accurately detected, and the re-offset can be appropriately prevented.

Further, according to the third invention of the present application, the separating claw is separated from the film member or the pressing member, or is separated from the pressing member depending on the size of the recording material. It is possible to prevent the toner attached to the separation claws from being offset again to the fixing film or the pressure roller due to use and to attach to the recording material to deteriorate the image, maintain a stable image for a long time, and have high durability. In addition, reliability can be improved.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a fixing device according to a first embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view showing a part of FIG.

FIG. 3 is an enlarged sectional view of the fixing film of FIG.

FIG. 4 is a sectional view of the image forming apparatus including the fixing device according to the first embodiment of the present invention.

FIG. 5 is a partial cross-sectional view of a fixing device according to a second embodiment of the present invention.

FIG. 6 is a partial cross-sectional view of a fixing device according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating body 5,20 Temperature detecting element (temperature detecting means) 7 Fixing film (film member) 10 Pressure roller (pressurizing member) 13 Separation claw 60 Fixing device a, b, c, d Separation claw

Claims (3)

[Claims] 1. A film member movably arranged in an endless manner, a heating member arranged inside the film member so as to come into contact with the film member, and a heating member disposed on the heating member via the film member. A pressure member arranged so as to be in pressure contact with each other, and a recording material carrying an unfixed developer image is nipped and conveyed at a pressure contact portion of the heating member and the pressure member formed via the film member. A heating device and a pressure member formed through the film member in a fixing device for applying thermal energy from the heating member to the recording material and the unfixed developer image on the recording material through the film member. Detecting the temperature of the recording material non-passing area of the heating body and a plurality of separation claws arranged so as to be able to come into contact with and separate from the film member and the pressing member on the recording material discharge side with respect to the pressure contact portion. And a temperature detecting means, A fixing device characterized in that when the temperature detected by the temperature detecting means exceeds a predetermined temperature, it is separated from the film member or the pressure member. 2. The temperature detecting means is separated into a central portion and an end portion in the width direction of the recording material, and the temperature of the recording material non-passing area is detected by the temperature detecting means on the end portion side. The fixing device according to 1. 3. A film member arranged so as to be capable of endless movement, a heating member arranged inside the film member so as to come into contact with the film member, and a heating member provided on the heating member via the film member. A pressure member arranged so as to be in pressure contact with each other, and a recording material carrying an unfixed developer image is nipped and conveyed at a pressure contact portion of the heating member and the pressure member formed via the film member. A heating device and a pressure member formed through the film member in a fixing device for applying thermal energy from the heating member to the recording material and the unfixed developer image on the recording material through the film member. A plurality of separation claws that are arranged so as to come into contact with and separate from the film member and the pressure member on the recording material discharge side with respect to the press contact portion and a recording material size detecting means are provided. The detection size is less than the specified size A fixing device characterized by separating the separation claw from the film member or the pressure member when not present.