JP3093561B2 - 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 a recording material carrying a visible image to be heat-fixed (hereinafter referred to as a toner image) which is brought into close contact with a heating member via a 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.

This apparatus is used in image forming apparatuses such as copying machines, laser beam printers, facsimile machines, microfilm reader printers, image display devices, and recording paper.
A recording material (electrofax sheet, electrostatic recording sheet, transfer material sheet) as an image carrier using an appropriate image forming process means such as electrophotography, electrostatic recording, or magnetic recording using a toner made of a heat-meltable resin or the like. , Printing paper, etc.)
The image fixing apparatus can be used as an image fixing device for heating and fixing an unfixed toner image corresponding to target image information formed on the surface of the recording material directly or indirectly as a permanently fixed image on a recording material surface carrying the image.

[0003]

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 pressure roller having an elastic layer and pressing against the heating roller. A fixing device of a heat roller fixing type, which heats a recording material while nipping and transporting the recording material, is often used.

However, the fixing device of the heat roller fixing method firstly 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. Is required, a relatively large power is required. Third, because the roller temperature is high, a heat-resistant special bearing is required for the rotating roller, and fourthly, the roller is in direct contact with the hand, Fifth, there is a drawback that there is a danger or a protective member is required, and fifthly, the recording material is wound around due to the fixing temperature and the curvature of the roller to cause a jam.

In view of the above, as a fixing device of a heating system which does not have the above-mentioned disadvantages, a fixing device of a film heating system as described above has recently attracted attention, and research and development for practical use thereof have been promoted.

A method and apparatus disclosed in, for example, Japanese Patent Application Laid-Open No. 63-313182 according to the applicant's earlier proposal belong to this, and include a thin heat-resistant film (sheet), a moving driving means for the film, and A heating element fixedly supported and arranged on one side of the film with the film inside, and a recording arranged on the other side of the heating element opposite to the heating element to fix an image to the heating element via the film; A pressurizing member for bringing the visible image bearing surface of the material into close contact with the recording material, which is transported and introduced between the film and the pressurizing member at least at the time of performing image fixing, and is the same in the forward direction as the recording material to be image-fixed By moving the film at a speed and passing it through a fixing nip formed by pressing a heating element and a pressing member across the film, the visible image bearing surface of the recording material is heated through the film. Heated by the body and revealed image (to be determined The heating means and the device are based on applying thermal energy to the toner image) to soften and melt it, and then separating the film and the recording material, or separating the film and the recording material after the toner is cooled and solidified. .

As the heating element, a horizontally long heat-resistant, insulating, low-heat-capacity heater substrate having a length in the width direction of the film is linearly or narrowly stripped along the length of the surface. A type having a low-heat-capacity energizing heat-generating resistor (heat-generating element) is used, and when power is supplied between both ends of the heat-generating element, the heat-generating element generates heat. Temperature rises rapidly, and the heat of the heating element 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 (electric heating) circuit to control the temperature to a predetermined fixing temperature. You. Although the heating element is at a high temperature, at least when the heating element generates heat, the film is moved and driven on the heating element at a predetermined temperature, so that local thermal deformation of the film does not occur and stable image fixing is performed. Is executed.

Such a film heating type fixing device has features such as a short wait time, and is a fixing device that has been desired in the times.

[0010]

However, in the above-mentioned conventional example, the nip portion of the pressure roller may be dented and deformed during a long period of time. In some cases, a defect that image fixing failure occurs occurs.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a movable film, a heating element which is in contact with the film and generates heat by being energized, and a pressurizing apparatus which presses the heating element via the film. And an energization to the heating element is started after receiving an image formation start signal, and a recording material carrying an unfixed image is nipped and conveyed by a nip formed by the film and the pressure roller. In a fixing device for fixing an unfixed image on a recording material, power is supplied to the heating element during the pre-rotation of the pressure roller immediately after the main power of the apparatus main body is turned on.

[0012]

【Example】

Embodiment 1 (1) Example of Image Apparatus FIG. 3 shows a schematic configuration of an example of an image forming apparatus using a fixing device 60 described later according to the present invention.

The image forming apparatus of this embodiment is an electrophotographic copying apparatus of a document table fixed-optical system moving type, a rotating drum type, and a transfer type.

After the original 19 is placed on the fixed original platen glass 20 and the necessary copy conditions are set, the copy start key is pressed, and the photosensitive drum 39 is rotated at a predetermined peripheral speed in the clockwise direction indicated by the arrow. Is driven to rotate.

The light source 21 (22 is a reflection shade) and the first mirror 23 move forward along the lower surface of the original table 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. When the third mirrors 24 and 25 move in the same direction at a speed of V / 2, the downward image surface of the placed document 19 on the platen glass 20 is illuminated and scanned from the left side to the right side, and the illumination scan is performed. The light reflected from the original surface is an imaging lens 2
9. Image formation exposure (slit exposure) is performed on the surface of the rotating photosensitive drum 39 via the fixed fourth to sixth mirrors 26, 27, 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-described exposure is performed on the charged surface. Thus, an electrostatic latent image having a pattern corresponding to the original image is sequentially formed on the surface of the drum 39. The formed electrostatic latent image on the surface of the photosensitive drum 39 is applied to the developing roller 32 of the developing device 31.
Is developed as a toner image.

On the other hand, a transfer material sheet P as a recording material is fed by a paper feeding means (not shown), and is guided into a transfer portion between the drum 39 and the transfer charger 34 at a predetermined timing through a guide 33. Drum 3 by receiving transfer corona
9, the toner-visible image on the drum 39 side is sequentially transferred to the sheet P side.

The sheet P that has passed through the image transfer section is sequentially separated from the surface of the drum 39 by separation means (not shown) (for example, a separation belt disposed at the end of the drum). The toner image is introduced into the fixing device 60 by the transport unit 38 and the guide 18, and is fixed to the toner image as described later, and is discharged out of the apparatus as an image formed product.

The surface of the drum 39 after the transfer is the cleaning device 3
The cleaning blade 37 of No. 6 removes stains such as residual toner and cleans the surface, and is repeatedly used for image formation.

When the moving optical members 21 to 25 that have moved forward have reached the predetermined end point of the forward movement, they are turned to the backward movement, return to the first home position, and wait until the start of the next copy cycle (back of the optical system). Process).

(2) Example of Fixing Device a) Device Configuration FIG. 1 is a side view of an example of a fixing device 60 according to the present invention, and FIG.
FIG. 3 is a schematic diagram of a layer structure of a fixing film.

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

The driven roller 9 also serves as a tension roller for the endless belt-shaped fixing film 7, and the fixing film 7 is rotated at a predetermined peripheral speed in a clockwise direction by the clockwise rotation of the driving roller 8, ie, the image forming section. The recording material P carrying the unfixed toner image Ta conveyed from the 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, which sandwiches the descending film portion of the endless belt-shaped fixing film 7 and 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 total pressure of 4 to 7 kg, for example. Rotate around 11.

The heating element 1 is a low-heat-capacity linear heating element whose longitudinal direction is the direction (width direction of the film) that intersects with the plane movement direction of the film 7, and includes a heater substrate 3, an energized heating resistor (heating element) 4, It is composed of a temperature detecting element 5 and the like, and is fixedly supported by being attached to and held by the heater support 2.

The heater support 2 is used to fix the heating element 1 to the fixing device 60.
And a material having heat insulation, high heat resistance and rigidity for heat-insulating and supporting the image forming apparatus, such as PPS (polyphenylene sulfide), PAI (polyamide imide), PI
(Polyimide), PEEK (polyetheretherketone), high-heat-resistant resins such as liquid crystal polymers, and composite materials of these resins with ceramics, metals, glasses, and the like.

The heater substrate 3 is a member having heat resistance, insulation, and low heat capacity. For example, the thickness is 1.0 mm and the width is 16 m.
m, an alumina substrate having a length of 340 mm.

The heating element 4 is formed on the substrate 3 at a substantially central portion of the lower surface (the side facing the film 7) along the length thereof, for example, Ag / P.
An electric resistance material such as d (silver palladium) or Ta ₂ N is applied by screen printing or the like to a thickness of about 10 μm and a width of 1 to 3 mm.
It was coated with 0 μm.

As an example, the temperature detecting element 5 has a low heat capacity such as a Pt film coated by screen printing or the like on 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. As the temperature detecting element, a thermistor having a low heat capacity or the like may be arranged so as to be in contact with the substrate 3.

In the case of the heating element 1 of the present embodiment, electricity is supplied to the linear or band-shaped heating element 4 from both ends in the longitudinal direction, and the heating element 4 generates heat over substantially the entire length. Energization is A
The power is controlled by controlling the phase angle to be energized by an unillustrated energization control circuit including a triac according to the temperature detected by the temperature detecting element 5.

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

FIG. 2 is a schematic diagram of a layer structure of an example of a composite layer film, and this example is a two-layer film. 7b is a heat-resistant layer as a base layer (base film) of the fixing film;
a is a release layer laminated on the outer surface of the heat-resistant layer 7b (the surface facing the toner image).

The heat-resistant layer 7b is made of a high heat-resistant resin film such as polyimide, polyetheretherketone (PEEK), polyethersulfone (PES), polyetherimide (PEI), polyparabanic acid (PPA), or N
Materials having excellent strength and heat resistance, such as metals such as i, SUS, and Al, can be used.

The release layer 7a is made of, for example, a fluororesin such as PTFE (polytetrafluoroethylene), PFA, FEP, or the like.
Silicon resin or the like is preferable (in this example, PTFE). The resistance value of the surface of the fixing film 7 can be reduced by, for example, mixing a conductive material such as carbon black, graphite, or a conductive whisker into the release layer 7a. As a result, charging of the toner contact surface of the fixing film 7 can be prevented.

The laminating property of the release layer 7a with respect to the heat-resistant layer 7b is as follows: adhesive lamination of the release layer film, electrostatic coating (coating) of the release layer material, lamination by a film forming technique such as CVD, and heat-resistant layer material. Can be performed by co-extrusion into a two-layer film.

B) Fixing execution operation The image forming apparatus (FIG. 3) of the above-described example performs an image forming operation in response to an image forming start signal, and a recording material sheet carrying on its upper surface an unfixed toner image Ta conveyed to the fixing device 60. P is guided by the guide 18 and enters between the fixing film 7 and the pressure roller 10 at the pressure contact portion (fixing nip portion) between the heating body 1 and the pressure roller 10 so that the unfixed toner image surface is a sheet. The heating element 1 and the pressure roller are in close contact with the lower surface of the fixing film 7 which is rotated in the same direction and the same direction as the conveying speed of P without causing any surface shift, wrinkling or twisting. It passes between the mutually press-contact parts with 10 while receiving a clamping pressure.

The heating element 1 is energized and heated at a predetermined timing by an image forming start signal, so that the toner image Ta
Is heated at the pressure contact portion to be softened and becomes a fused image Tb.

The fixing film 7 is formed at the edge portion S (having a radius of curvature of about 2 mm) of the heater support 2 where the curvature is large.
The running direction is turned at a steep angle (the bending angle θ is about 45 degrees). Therefore, the sheet P conveyed through the pressure contact portion while overlapping the fixing film 7 is separated in curvature from the fixing film 7 at the edge portion S, and is discharged to the 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 heating element 1 at the pressure contact portion is quickly reduced to the melting point of the toner (or the sheet P).
(The temperature at which the heater 1 can be fixed), the heating element 1 does not need to be heated in advance (so-called standby temperature control), and energy saving can be realized.
In addition, the temperature inside the machine can be prevented from rising.

C) Heater control immediately after the main power supply is turned on After the main power supply of the apparatus main body is turned on, the fixing film 7 and the pressure roller 10 also start to rotate forward as the main motor (not shown) rotates forward. In the system of this embodiment, it takes 1.5 seconds for the fixing film 7 to make one rotation.

After confirming that one rotation has been made 1.5 seconds after the start of rotation in the rotation sensor (not shown), the power supply to the heating element 1 is started. The energizing time to the heating element 1 is 5 seconds. This is to synchronize with the pre-rotation time, and the power supply to the heating element 1 is stopped at the same time as the main motor is stopped. That is, the pre-rotation time is 6.5 seconds.

The temperature control temperature at the time of energizing the heating element 1 is controlled as follows. Temperature sensor 5 immediately after turning on the main power
The temperature control temperature is controlled in three stages according to the detected temperature of the fixing film 7 detected by the above. The detected temperature immediately after turning on the main power is 11
When the temperature is 0 ° C. or less, the temperature control temperature is 225 ° C. Similarly, when the detected temperature is between 110 ° C. and 140 ° C. or less, the controlled temperature is set to 200 ° C. When the detected temperature is higher than 140 ° C., the controlled temperature is set to 180 ° C. and controlled.

By energizing for 5 seconds immediately after turning on the main power,
The pressure roller 10 can also be warmed, and it is possible to apply a sufficient amount of heat to restore the dent-deformed portion. The reason why the temperature control temperature is divided into three stages is that when the temperature detected by the temperature detection element 5 immediately after the main power is turned on is high, the temperature of the pressure roller 10 is assumed to be high, and the amount of dent deformation is small. It is not necessary to raise it.

FIG. 4 shows a timing chart of the pre-rotation after the main power supply of the main body is turned on and the energization of the heating element.

As described above, in this embodiment, since heat is applied to the pressure roller during the pre-rotation, the dent of the pressure roller can be corrected, and defective fixing can be prevented.

Embodiment 2 The system is the same as that of Embodiment 1 except for the heater control immediately after the main power is turned on.

Heater control immediately after the main power is turned on A timer (not shown) is provided in the image forming apparatus. The timer counts the time from the end of copying. This timer operates even after the main power is turned off.

Next, when the main power is turned on, the value of the counter is first read. Thereby, the time from when the pressure roller 10 is stopped can be known. The amount of dent deformation in the nip portion of the pressure roller 10 is closely related to the stop time of the pressure roller 10, and the amount of dent deformation can be estimated from the stop time. That is, by knowing the stop time of the pressure roller 10, it is possible to determine the time for energizing the heating element 1 required to recover the dent deformation.

The control of the actual energization time is performed as follows.

In the case of 0 to 1 hour after the end of the final copy, the energization of the heating element 1 is not performed because the dent has not been deformed. In the case of more than 1 hour and less than 24 hours after the end of the final copy, the heating element 1 is energized for 5 seconds during the pre-rotation. If the time exceeds 24 hours after the end of the final copy, the heating element 1 is energized for 10 seconds during the pre-rotation.

The control of the temperature control temperature is the same as in the first embodiment.

FIG. 5 is a graph showing the relationship between the elapsed time after the end of the final copy and the energization time to the heating element.

As described above, according to the present embodiment, it is possible to more accurately correct the deformation of the pressure roller without waste, and to prevent a defective fixing.

[0054]

As described above, according to the present invention, the dent deformation generated at the nip portion of the pressure roller can be recovered during the pre-rotation. Therefore, it is possible to solve an image fixing defect that occurs in the pressing roller cycle due to the dent deformation.

Further, by controlling the amount of current supplied to the heating element in accordance with the amount of dent deformation of the pressure roller, the required amount of current can be reduced.

Further, by energizing the heating element during the pre-rotation, there is also an effect of warming the inside of the apparatus at the time of start-up, and the temperature rise during copying is accelerated accordingly, and an effect of improving the fixing property is obtained.

[Brief description of the drawings]

FIG. 1 is a side view of a fixing device according to a first embodiment and a second embodiment.

FIG. 2 is a model diagram of an example of a layer configuration of a fixing film in Examples 1 and 2.

FIG. 3 is a schematic diagram illustrating an example of an image forming apparatus according to the first and second embodiments.

FIG. 4 is a timing chart of pre-rotation after the main power supply of the main body is turned on and power supply to the heating body in the first embodiment.

FIG. 5 is a graph showing the relationship between the elapsed time after the end of the final copy and the energization time to the heating element in the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating element 3 Heater board 4 Heating element 5 Temperature measuring element 7 Fixing film 10 Pressure roller

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hisaaki Senba 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-5-35150 (JP, A) JP-A-4 -179980 (JP, A) JP-A-4-251266 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 13/20 G03G 15/20

Claims (3)

(57) [Claims] 1. An image forming apparatus comprising: a movable film; a heating element which is in contact with the film and generates heat when energized; and a pressure roller which presses the heating element via the film. From the energization to the heating body is started, in the fixing device for fixing the unfixed image on the recording material by nipping and conveying the recording material carrying the unfixed image in the nip formed by the film and the pressure roller, A fixing device characterized in that the heating element is energized during the pre-rotation of the pressure roller immediately after the main power supply of the apparatus main body is turned on. 2. The fixing device according to claim 1, wherein the energization of the heating element performed during the pre-rotation is performed after the movement of the film. 3. A measuring means for counting a time from the end of the fixing operation to the next turning on of the main power supply, and an output from the measuring means controls an energizing time to the heating element during pre-rotation. The fixing device according to claim 1, wherein