JPH08241002A - Fixing device - Google Patents

Abstract

PURPOSE: To prevent a slip between a driving roller and a fixing film from being caused by worn particle generated by the rub of a heating body and the film without deteriorating the film because of overheating in a device fixing a toner image by using the heating body through the fixing film. CONSTITUTION: This fixing device is provided with the fixing film 7 driven by the driving roller 8 and the heating body 1 and a pressure member 10 interposing the film 7 between them and pressing it and constituted so that unfixed toner is heated and fixed at a fixing nip part. Then, one or both of the pressure force adjusting action of the pressure member and the attaching and detaching action thereof can be executed. By adjusting the pressing force of the pressuring member and/or attaching and detaching the pressurizing member according to the heating state of the heating body 1 or the supply state of electric power supplied to a heat generation part in the heating body, the generation of the worn particle caused by the rub is reduced and the slip is prevented from occurring by the roller 10 while the nip part is prevented from being excessively heated and the film is prevented from being deteriorated when the electric power is not supplied.

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 member via a fixing film so that the recording material is heated from the heating member via the fixing film. The present invention relates to a film heating type fixing device that applies heat energy to the toner to heat and fix a toner image.

[0002]

2. Description of the Related Art Conventionally, a heat roller is known as a means for fixing a visible image on a recording sheet, but it consumes a large amount of power and takes a long time to reach a fixing temperature. There were drawbacks such as.

On the other hand, a fixing method using a heat-resistant film for improving the above-mentioned drawbacks is described in JP-A-63-313182.

The fixing device described in the above-mentioned publication has a thin heat-resistant film (sheet), a drive means for moving the film, and a heating device arranged so as to be fixedly supported on one side of the film with the film inside. And a pressing member which is disposed on the other surface side so as to be opposed to the heating body, and which closely adheres the developed image bearing surface of the recording material to be image-fixed to the heating body via the film, At least during image fixing, the film travels 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, and sandwiches the running moving film to form a heating body. By passing through the fixing nip portion formed by pressure contact with the pressure member, the developed image bearing surface of the recording material is heated by the heating body through the film to heat the developed image (unfixed toner image). Apply energy to soften and melt Then, separating the film and the recording material,
Alternatively, it is a heating means and a device that basically separates the film and the recording material after the toner is cooled and solidified. As the heating element, a horizontally long heat resistance having a widthwise direction of the film as a longitudinal direction, an insulating property, a film contact surface side of a heater substrate of a low heat capacity, which has a low heat capacity linearly or in a strip shape along the length of the surface. An energization heating resistor (heating element) is used, and the heating element generates heat when electric power is supplied between both ends of the heating element, and the heater substrate is also heated, so that the entire heating element is heated. The temperature is rapidly raised, and the heat of the heating body is applied to the recording material via the film.

The temperature of the heating element is controlled by a temperature sensor provided in the heating element, a microcomputer of the image forming apparatus main body and a heating element driving (energizing heat generation) 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 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 advantages such as a short wait time and is a fixing device that meets the demands of the times.

[0007]

However, in the above-mentioned conventional film heating type fixing device, the inner surface of the fixing film is slid against the heating member due to the pressure contact between the heating member and the pressing member due to long-term use. Abrasion is caused by abrasion, and the abrasion powder adheres to the surface of the driving roller via the inner surface of the fixing film, and the wear coefficient between the inner surface of the fixing film and the driving roller decreases, and eventually slippage occurs. , The drive of the film is stopped, or the like occurs, and therefore, the recording material carrying the unfixed image conveyed from the image forming unit side is not introduced into the fixing nip in the fixing device, or the fixing film, While the pressure member and the recording material are stopped, only the fixing nip portion is heated, so that the fixing film, the pressure member, the recording material, and the heating body are thermally damaged, and the image is deteriorated.

Therefore, it is conceivable to release the pressure applied to the pressure member except when fixing is being performed. By releasing the pressure, the friction between the inner surface of the fixing film and the heating body is reduced, and the reduction of wear can be expected.

However, when the pressurization member is depressurized at the time of supplying power to the heating element in the heating element, the temperature of the heating element instantaneously rises due to the separation of the pressing element which is also an element to be heated. However, a problem such as damage to the heating body occurs.

[0010]

In order to achieve the above-mentioned object, the present invention significantly reduces the wear caused by frictional rubbing with the heating body on the inner surface of the fixing film and eliminates the thermal damage of the heating body. It is an object of the present invention to provide a fixing device capable of improving durability and reliability. According to the present invention, an endless fixing film that is driven and driven by a driving roller and a fixing film sandwiching the fixing film are provided. A heating member and a pressure member that are in pressure contact with each other, and the fixing film is sandwiched between the fixing film and the pressing member in the fixing nip portion formed by pressing the heating member and the pressing member. The recording material carrying the deposited toner is introduced and runs through the fixing nip portion together with the running fixing film, and thereby heat energy is applied to the recording material from the heating body through the fixing film to heat and fix the toner image. In the fixing device, it is possible to adjust either the pressing force of the pressure member or the contact and separation of the pressure member, preferably both, and to supply the heating state of the heating element or the heating section in the heating element. For example, the pressurizing force is adjusted and / or contacted / separated in accordance with the supply state of electric power, and preferably, the pressurization is performed by a predetermined pressurizing force when the recording material is heat-fixed, and the pressure is applied at least at a part other than when the heat-fixing is executed. The adjustment and / or the contact / separation reduce wear of the inner surface of the fixing film without causing damage due to overheating of the heating element.

[0011]

【Example】

<Embodiment 1> FIG. 7 is a sectional view showing an example of an image forming apparatus using a fixing device 60, which will be described later, according to the first embodiment of the present invention.

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

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 rotary photosensitive drum 39 is rotated in the clockwise direction indicated by the arrow. It is driven to rotate at the peripheral speed.

Further, 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, and the second mirror. 24, the third mirror 25 is V in the same direction
By moving forward at a speed of / 2, the downward image surface of the document 19 placed on the document table glass 20 is illuminated and scanned from the left side to the right side, and the reflected light from the illumination scanning light on the document surface forms the imaging lens 2
Image formation exposure (slit exposure) is performed on the surface of the rotating photoconductor drum 39 via the 9, fourth fixed mirror 26, fifth fixed mirror 27, and sixth fixed mirror 28.

Prior to this 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 charged surface is subjected to the above-mentioned exposure. An electrostatic latent image having a pattern corresponding to the original image is sequentially formed on the surface of the drum 39. The drum 3
The electrostatic latent image formed on the nine surfaces 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 drum 39 and the transfer charger 34 at a predetermined timing through the guide 33 and transferred. The drum 39 by receiving corona
The toner visible image on the surface of the drum 39 is sequentially transferred to the surface of the recording sheet P.

The sheet P which has passed through the image transfer portion is sequentially separated from the surface of the drum 39 by a separating means (not shown), for example, a separating belt arranged at the end of the drum,
The charge of the back surface is removed by the charge removal needle 35, the toner is introduced into the fixing device 60 by the transport guide 38 and the guide 18, the toner image is fixed as described later, and the toner is discharged as an image-formed product to the outside of the apparatus.

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

When the moving optical section (the light source 21, the reflection shade 22, the first mirror 23, the second mirror 24, and the third mirror 25) that has moved forward has reached a predetermined forward movement end point, it is turned to forward movement. , Return to the first home position and wait until the start of the next copy cycle (back stroke of the optical system).

Next, a first embodiment of the fixing device 60 will be described with reference to FIGS. 1, 2 and 3.

In the figure, 7 is an endless fixing film, which is a driving roller 8 on the left side in FIG. 1, a driven roller 9 on the right side, and a low heat capacity linear film arranged below the rollers 8 and 9. The heating body 1 is 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 film 7 is driven by the drive roller 8 in the clockwise direction.
With a predetermined peripheral speed in the clockwise direction, that is, with the same peripheral speed as the conveying speed of the recording material sheet P having the unfixed toner image Ta conveyed from the image forming portion side on its upper surface, it rotates without wrinkles, meandering, or speed delay. It is driven dynamically.

Reference numeral 10 is a pressure roller having a rubber elastic layer 12 such as silicon rubber having a good releasability as a pressure member. The pressure roller 10 is provided on the lower surface of the heating body 1 with the lower film portion of the fixing film 7 sandwiched therebetween. On the other hand, for example, they are pressed against each other with a contact pressure of 4 to 7 kg in total, and rotate about the shaft 11 in a counterclockwise direction that is a forward direction in the conveying direction of the recording material sheet P.

In this embodiment, the roller diameter is 25 mm, the rubber length is 330 mm, and the P. F.
A thin film with a thickness of 50 μm is formed and the roller hardness is 50 °.
Using (Asker C), the total pressure was 7 kg and the nip width was about 4 to 5 mm.

The heating element 1 is of a linear shape having a low heat capacity and has a longitudinal direction in a direction crossing the surface 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, etc., and is attached and held to the heater support 2 and solidified.

The heater support 2 fixes the heating body 1 to the fixing device 60.
And those having heat insulating properties, high heat resistance, and rigidity for thermally supporting the image forming apparatus, such as PPS (polyphenylene sulfide), PAI (polyamide imide), PI (polyimide), PEEK (polyether ether ketone), It can be made of a highly heat-resistant resin such as 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, insulation and low heat capacity, and as an example, the thickness is 1.0 mm and the width is 16 m.
It is an alumina substrate having a length of m and a length of 340 mm.

The heating element 4 is the lower surface of the substrate 3 (fixing film 7
Along the length in the substantially central part (on the side facing with), for example,
An electric resistance material such as Ag, Pd (silver palladium), Ta ₂ N, etc. is applied to the thickness of 10 μm and the width of 1 to 3 mm by screen printing or the like, and a heat-resistant glass 6 as a surface protective layer is applied thereto by about 10 μm. is there. In the present embodiment, the one having a width of 2.25 mm was used. The pressure roller 1
Regarding the nip with 0, the center of the nip band is located at the center of the heating element.

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

In the case of the heating element 1 of this embodiment, electricity is applied to the linear or strip-shaped heating element 4 from both ends in the longitudinal direction, and the heating element 4 is caused to generate heat over substantially the entire length. The energization is AC 100V, 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.

Reference numeral 13 is a pressure roller supporting member for supporting the pressure roller 10 according to the present invention and performing pressure and position adjustment, and is adjusted by a contacting / separating means (not shown).

Reference numeral 14 is a pressure spring which is a pressure roller pressure member. In the figure, an arrow A indicates a direction in which the pressure roller support member 13 can be pressed and its position can be adjusted, that is, a direction in which the pressure roller 10 moves. Arrows B indicate the respective moving directions.

FIG. 1 is a cross-sectional view of the fixing device according to the present embodiment, in which fixing is performed by applying pressure, heating, and fixing. The pressure roller 10 is pressurized by a predetermined pressing force necessary for fixing and rotates to perform fixing.

FIG. 2 is a cross-sectional view of the fixing device when releasing the pressure in this embodiment. The pressure roller 10 is separated from the surface of the fixing film 7 by adjusting the position of the pressure roller support member 13.

FIG. 3 is a cross-sectional view of the fixing device when pressure is applied at a pressure lower than that applied when fixing is performed in this embodiment. The pressure roller 10 rotates by being pressed with a pressure lower than that at the time of fixing by adjusting the pressure roller support member.

In this embodiment, at low pressure, the applied pressure was reduced to a total pressure of 4 to 5 kg and a nip width of 2 to 3 mm.
Further, by setting the nip width to be 2 to 3 mm, the heating element is in contact with the heating element over almost the entire area.

With this structure, it is possible to prevent abrupt temperature rise of the heating element when the heating element is energized at low pressure.

In this embodiment, the fixing material is pressed by a predetermined fixing pressure at all fixing operations of the recording material, and at least a part other than the fixing operation at the time of energization of the heating element, the fixing operation is performed. The pressure is lower than the predetermined pressure.

Then, the pressure contact of the pressure roller was released at least in a part of the time when the heating element was not energized.

In the present embodiment, the pressing force and the adjustment contact / separation adjustment are executed according to the energized state of the heating element.

FIG. 4 shows the timing of energizing the heating element, adjusting the pressure of the pressure roller, and adjusting the contact / separation during continuous copying, and FIG. 5 shows at least one interval between the end of fixing and the start of next fixing. The part shows the timing when the non-energized state is used for the heating element. It is a matter of course that the timings of pressure adjustment and contact / separation adjustment in the present invention take into consideration the temperature rising characteristics of the heating element and the specific heat of the heater substrate, the heater support, the fixing film, the pressure roller, and the like. .

According to the present embodiment, the number of durable sheets is normally 100,000 (A4), and it is possible to endure long-term use up to 15 to 200,000.

In this embodiment, both the pressurizing force adjustment and the contact / separation adjustment are performed, but it goes without saying that only one of them may be adjusted.

<Embodiment 2> As another embodiment, in this embodiment, the pressing force of the pressure roller is adjusted and the pressure is released according to the heating state of the heating body of the fixing device.

Since the image forming apparatus, the fixing apparatus, and the set values for adjusting the pressing force are the same as those in the first embodiment, the sectional view is omitted.

For example, a normal copy paper size (A4,
In the case of recording paper (such as postcards) of a smaller size than B4 etc., the temperature of the non-sheet passing portion such as the heating element of the fixing device during continuous copying rises, the pressure roller etc. is damaged, and the fixing film is damaged. Can occur.

Therefore, in the case of continuous copying of small-sized paper, a method of switching the temperature control temperature between the end of recording paper fixing and the start of the next recording paper fixing (hereinafter referred to as paper interval) by detection of a thermistor or the like. Is generally performed to prevent the temperature rise of the non-sheet passing portion.

FIG. 6 shows the timings of temperature control switching and pressure roller contact pressure adjustment. For temperature control switching,
In the present embodiment, the temperature control temperature during normal copying is 225 ° C. for the first to fourth sheets, 210 ° C. for the fifth to eighth sheets, and 20 after the ninth sheet.
The temperature control temperature is set to 0 ° C., and the temperature control temperature at the time of continuous copying of small size paper is set to 20 ° C. lower than the normal temperature, and this is set as the special temperature control.

Therefore, the temperature control is switched as shown in FIG. 6, and the pressing force of the pressure roller is controlled corresponding to the temperature control switching.

According to this embodiment, the fixing film has a long service life, and despite the switching of the special temperature control and the like,
The fixability was sufficiently satisfactory.

<Embodiment 3> As another embodiment, in this embodiment, the pressure roller pressing force is adjusted in multiple stages in accordance with the temperature control temperature and the energizing power, and the timing shown in FIG. Same setting as.

Table 1 shows the correspondence between the temperature control temperature and the switching of the nip width instead of the pressing force of the pressure roller.

[0054]

[Table 1]

When the temperature control temperature is relatively low, the degree of decreasing the nip width can be increased to a large extent. Therefore, since the pressing force can be set lower, the life of the fixing film can be further extended.

[0056]

As described above, according to the present invention,
Either the pressure of the pressure member is adjusted, or the pressure member is brought into contact with or separated from the pressure member, or both are performed, for example, in accordance with the heating state of the heating body or the supply state of electric power or the like supplied to the heating portion in the heating body. Adjust the pressing force and / or bring it into and out of contact. Then, preferably, the recording material is pressurized with a predetermined pressing force at the time of executing the heat fixing, and the pressing force is adjusted and / or the contact / separation is performed at least at a part other than the time of the heat fixing is performed.
Abrasion of the inner surface of the fixing film is reduced without causing damage to the heating body, slipping of the fixing film due to abrasion powder and stopping of driving of the fixing film are prevented, and stable image formation is achieved even in long-term use. be able to.

[Brief description of drawings]

FIG. 1 is a sectional view of a fixing device during execution of fixing according to a first exemplary embodiment of the present invention.

FIG. 2 is a cross-sectional view of the fixing device when releasing pressure according to the first exemplary embodiment of the present invention.

FIG. 3 is a cross-sectional view of a fixing device according to a first exemplary embodiment of the present invention at low pressure.

FIG. 4 is a diagram showing timing regarding pressing of a pressing roller and energization of a heating element during continuous copying.

FIG. 5 is a diagram showing timing regarding pressurization of a pressure roller and energization of a heating element when a non-energized state is provided after completion of fixing.

FIG. 6 is a diagram showing timings of temperature control switching, pressure application of a pressure roller, and contact / separation adjustment.

FIG. 7 is a diagram showing an example of an image forming apparatus using the fixing device according to the first embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heating body 7 ... Fixing film 8 ... Driving roller 10 ... Pressure roller 13 ... Pressure roller supporting member 14 ... Pressure spring 60 ... Fixing device P ... Recording material sheet

Claims (2)

[Claims] 1. An endless fixing film that is driven and driven by a driving roller, a heating body and a pressing member that press-contact with the fixing film sandwiched therebetween, and the heating body and the pressing member sandwich the fixing film. The recording material carrying unfixed toner is introduced between the fixing film and the pressure member in the fixing nip portion formed by pressurization of the fixing nip portion and the fixing film is moved to pass through the fixing nip portion. In a fixing device for applying heat energy to a recording material from a heating body through a fixing film to heat and fix a toner image, either one of pressure adjustment of the pressure member or contact and separation of the pressure member, or both. The fixing device is characterized in that the pressing force is adjusted and / or the contact / separation is performed in accordance with the heating state of the heating body or the supply state of electric power or the like supplied to the heating section in the heating body. . 2. An endless fixing film that is driven and driven by a driving roller, a heating body and a pressing member that sandwich the fixing film and are in pressure contact, and the heating body and the pressing member sandwich the fixing film. The recording material carrying unfixed toner is introduced between the fixing film and the pressure member in the fixing nip portion formed by pressurization of the fixing nip portion and the fixing film is moved to pass through the fixing nip portion. In a fixing device for applying heat energy to a recording material from a heating body through a fixing film to heat and fix a toner image, either one of pressure adjustment of the pressure member or contact and separation of the pressure member, or both. It is possible to perform, and pressurizing with a predetermined pressing force when the recording material heat fixing is performed,
Pressure adjustment and / or contact / separation is performed in at least a part other than when heat fixing is performed, in accordance with the heating state of the heating body or the supply state of electric power or the like supplied to the heating portion in the heating body. Alternatively, a fixing device characterized by contact and separation.