JP2000089596A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce power consumption required for heating by preventing the heat radiation from a fixing roll incorporating a heat source, in a fixing device capable of fixing a toner image carried on recording material by heating and pressurizing. SOLUTION: This fixing device is allowed, to arrange a heat insulating member 8 close to a periphery of a fixing roll 1, on a range excluding a nip part where the fixing roll 1 and a pressure roll 2 are held in press contact with each other. The heat insulating member 8 has a structure laminating outer heat insulating material 11 over inner heat insulating material 10 consisting of mutually different elastic material, and the whole inner surface of the inner heat insulating material 10 is provided with a metallic thin surface layer 9 furnished with heat reflection property. On the upstream side and the downstream side of the nip part of the heat insulating member 8, a thin layer film 13 held in contact with the periphery of the fixing roll 1 is supported. In such a manner, air layer is hermetically sealed between the heat insulating member 8 and the fixing roll 1 by the thin layer film 13, therefore the excellent heat insulating effect can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in an image forming apparatus such as a copying machine, a recording device, a printer, a micro-reader printer, etc., and is carried on a recording material such as a transfer material, a photosensitive paper, an electrostatic recording paper or the like. The present invention relates to a fixing device that fixes an unfixed toner image by applying heat and pressure.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine or a printer using an electrophotographic system, it is necessary to fix an unfixed toner image formed on a recording sheet to a permanent image. As such a fixing means, a solvent fixing method, a pressure fixing method, a heat fixing method and the like are conventionally known.

[0003] However, the solvent fixing method has a problem of odor and hygiene because the solvent vapor is emitted. Further, the pressure fixing method has disadvantages in that the fixing property is poor as compared with other fixing methods, and the pressure-sensitive toner is expensive. For this reason, the heat fixing method is generally widely used.

[0004] In the heat fixing method, an unfixed toner image is melted by heating, and the image is fixed by heat fusion on a recording sheet. As such a heating and fixing device, a heating roll type is widely known. For example, as shown in FIG. 3, a fixing roll 101 having a heat source and a pressure roll disposed in pressure contact with the fixing roll 101 are provided. A main part is constituted by 102 and a frame body 110 for accommodating them. The fixing roll 101 is a cylindrical cored bar 1 made of aluminum or the like.
11, a heat source 113 such as a halogen heater is provided,
A fluororesin layer 112 such as PTFE is laminated on the outer peripheral surface of the metal core in order to prevent the occurrence of an offset phenomenon. An oil supply device 103 for supplying oil to the surface of the fixing roll 101 is provided in the frame 110.
A temperature sensor 104 for detecting the temperature of the surface of the fixing roll 101; an abnormal temperature detecting device 105 for preventing overheating of the fixing roll 101; and a separation for separating the recording material from the fixing roll 101 after heating and fixing the toner image. And a claw 106. The shaft portions at both ends of the fixing roll 101 are held on side plates via heat insulating bushes and bearings (not shown).

[0005] The pressure roll 102 is formed by coating an outer peripheral surface of a cylindrical cored bar 121 made of aluminum or the like with an elastic layer 122 made of rubber or the like. This pressure roll 10
The shafts at both ends of the two are also held on the side plates via bearings (not shown).

The fixing roll 101 and the pressure roll 102
Is pressed by an appropriate pressure to form a clamping portion (hereinafter, referred to as a nip portion), and the fixing roll 101 is rotated by driving means (not shown). This fixing roll 10
The pressure roller 103 is driven to rotate with the rotation of 1.

In such a fixing device, a recording material carrying an unfixed toner image is fixed to a fixing roll 101 and a pressure roll 1.
The sheet is conveyed while being sandwiched in a nip portion with the sheet No. 02. The recording material carrying the toner image is heated and pressurized while passing through the nip portion, and the toner image melted by the heat is fixed on the recording material. Such a fixing device is currently most widely used because it has a higher thermal efficiency than a heat radiation fixing method, which is another heat fixing method, and has less risk of burning of a paper due to a paper jam.

However, in the above fixing device, the fixing roll 1
01 has a large design heat capacity, so that it is difficult to rapidly warm it, and a warm-up time for heating from room temperature to a set temperature is required. For this reason, usually, the temperature of the fixing roll is maintained at the set temperature and is kept on standby. But,
The power consumption during the standby is large, which poses a major problem in energy saving. Further, even during the copying operation, considerable heat energy is radiated from the surfaces of the fixing roll and the pressure roll.

As a countermeasure against such a problem, for example, Japanese Patent Application Laid-Open No. 61-107276 discloses that the entire apparatus including a fixing roll and a pressure roll is covered with a heat insulating material to reduce heat radiation from the surface of the fixing roll. A fixing device has been proposed. Also, JP-A-62-150278 discloses that
There has been proposed a fixing device provided with a reflector for reflecting infrared rays at a position close to the outer peripheral surface of the fixing roll.

[0010]

However, the above fixing device has the following problems. All the above fixing devices reduce heat radiation by disposing a heat insulating material or a heat reflection plate around the fixing device or the fixing roll,
This is to increase the thermal efficiency. In order to maximize the effect of preventing heat radiation, it is most effective to completely seal or cover the vicinity of the surface of the fixing roll or the pressure roll heated to a high temperature with a heat insulating material. However, the entrance and exit for transporting the recording material must be secured in the fixing device, and the entire fixing device cannot be sealed.

A number of devices such as a recording material peeling device, a cleaning device, an oil supply device, a temperature sensor, and an abnormal temperature detection device are provided around the fixing roll, and these devices are surrounded by a heat insulating material. Covering increases the gap between the fixing roll and the surrounding heat insulating material. If the air layer formed in the gap portion is thick, there is a problem that air in the frame causes convection, heat of the fixing roll is taken away, and thermal efficiency of the roll portion is significantly reduced. In addition, the heat insulation effect is exerted only after all of the internal equipment covered with heat insulation has been heated to the saturation temperature, so during warm-up and for a while,
Energy saving effect is not fully exhibited.

Further, it is necessary to separately provide an exhaust device for preventing the temperature rise of the entire apparatus in the fixing device. However, high-temperature air in the fixing device is discarded and power consumption is increased. Further, there is a problem that the size of the device becomes large and it is difficult to miniaturize the device. If the heat insulation and the exhaust are incomplete, the temperature inside the machine such as the photoconductor and the developing device in the copying machine becomes high. In this case, the performance of the copying machine is deteriorated. Therefore, the fixing device, the photosensitive member, and the developing device must be installed separately in the copying machine. In this case as well, the miniaturization of the device is hindered.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to minimize the heat radiation from a fixing unit for heating an unfixed toner image, and to provide a heating source. An object of the present invention is to provide a fixing device capable of reducing power consumption.

[0014]

According to a first aspect of the present invention, there is provided an image forming apparatus comprising: a first fixing member having a built-in heat source and having an endless peripheral surface moving around; And a second fixing member which moves circumferentially while being pressed against the circumferential surface of the first fixing member, and the unfixed toner image is carried on a nip portion where the two fixing members are pressed against each other. In a fixing device that conveys a sheet and heats and presses the unfixed toner image to fix the unfixed toner image on the recording sheet, a portion of the peripheral surface of the first fixing member that is pressed against the second fixing member. In the range excluding the vicinity, the first
A heat insulator that blocks heat radiation from the fixing member is disposed in close proximity, and at both ends in the circumferential direction of the gap between the heat insulator and the first fixing member, air between the outside of the heat insulator and It shall have a shielding member that blocks entry and exit.

In the above fixing device, the heat insulator is disposed so as to be close to the peripheral surface of the first fixing member containing the heat source, and the shielding member for blocking air from flowing between the inside and the outside of the heat insulator. Since the air layer is provided, the air layer in the gap between the heat insulator and the fixing roll becomes thin, and this air layer is in a closed state. Since such an air layer has a very small heat capacity, it is rapidly heated as the surface temperature of the first fixing member rises, and the heat insulating effect is immediately exhibited. Further, even if the first fixing member moves around, the air layer is stationary without being convected by the shielding member, so that it acts as a heat insulating air layer on the peripheral surface of the fixing member, and the heat insulating effect is increased.

In the above fixing device, when a heat source is provided inside the second fixing member, it is desirable to provide the heat insulator and the shielding member also around the second fixing member. Thus, similarly to the first fixing member, a closed thin air layer can be formed on the peripheral surface of the second fixing member, and a good heat insulating effect can be obtained.

[0017] The shielding member may be set to an appropriate member and structure as long as it can block air from entering and exiting between the air layer in the gap between the heat insulator and the first fixing member and the outside thereof. Can be. For example, as described in claim 2, on the upstream side or the downstream side in the conveying direction of the recording sheet, the first
And a film-like member supported so as to contact the peripheral surface of the fixing member. In other words, by installing a film-shaped member in contact with the peripheral surface of the fixing member in the gap between the heat insulator and the fixing member, it is possible to prevent the inflow or outflow of air from the outside. By sealing the air layer in the gap between the heat insulator and the fixing member in this way, it is possible to prevent the convection of the heated air and the generation of the boundary layer flow of the air accompanying the orbital movement of the fixing member, A stationary heat-insulating air layer can always be formed on the surface of the fixing member.

Further, in the invention according to claim 3, the shielding member has a tip of the film-shaped member facing the nip portion so as to peel off the recording sheet attached to the first fixing member. It is assumed that the tip is attached so as to abut on the first fixing member.

In the conventional fixing device, a plurality of peeling claws are attached in the axial direction of the fixing member as means for peeling the recording sheet, but a heat insulator must be provided so as to avoid the peeling claws. However, the heat insulator on the transport outlet side had to be provided in a state of being opened to the fixing member. On the other hand, in the present invention, since the film-shaped member on the transport outlet side has a function as a peeling device, the air layer between the fixing device and the heat insulator is almost completely sealed, and the air layer is formed in the air layer. Convection can be prevented.

According to a fourth aspect of the present invention, the heat insulator has a notch at a position facing the first fixing member, and the surface temperature of the first fixing member is adjusted in the notch. It is assumed that a temperature detecting element or an abnormal temperature rise detecting element for performing the operation is provided.

Conventionally, the temperature detecting element and the abnormal temperature rise detecting element, which are the minimum components of the fixing device, are provided in the space between the inner peripheral surface of the heat insulator and the fixing member. Until the heat insulating effect is not sufficiently exerted, the space between the inner peripheral surface of the heat insulator and the fixing member must be large. On the other hand, in the present invention, by providing a cutout portion in the heat insulator, the temperature detection element and the abnormal temperature rise detection element are installed in a state surrounded by the heat insulator, so that the heat insulation space and the heat capacity thereof are reduced. Therefore, a very excellent heat insulating effect can be obtained.

In the invention described in claim 5, the heat insulator has a multilayer structure in which a plurality of heat insulators are laminated. When the heat insulator has a multilayer structure, the inner surface layer and the outer layer of the heat insulator can be formed of different types of materials. For example, when a resin foam which is frequently used as a heat insulator is used, the inner layer is made of a material having heat resistance in consideration of heat resistance and heat insulation (low heat conductivity), and the outer layer is made of excellent heat insulation. And materials having excellent characteristics can be used in combination. This makes it possible to satisfy the required specifications of the fixing device as a heat insulator at a high level.

According to a sixth aspect of the present invention, a high gloss metal layer is provided on the inner surface of the heat insulator. The high gloss metal layer functions as a reflector for returning infrared rays radiated from the fixing member to the fixing member. Therefore, in combination with the above-described heat insulator placed close to and around the peripheral surface of the fixing member, high heat dissipation is prevented. The effect can be achieved.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing one embodiment of a fixing device according to the present invention. This fixing device
A fixing roll 1 having a built-in heating source, a pressing roll 2 pressed against the fixing roll 1, a heat insulating member 8 arranged at a slight interval on the outer peripheral surface of the fixing roll 1, The main part is constituted by the frame 15 supported so as to surround the periphery.

The fixing roll 1 is formed by forming a heat-resistant resin layer 1b around a cylindrical cored bar 1a made of aluminum. The resin layer 1b is made of ethylene tetrafluoride resin and has a thickness of Are formed at 20 μm to 80 μm. A heating heat source 3 including a halogen heater is provided inside the cylindrical cored bar 1a. In addition, the core metal 1a
As a material other than aluminum, a metal material such as stainless steel or copper can be used. Further, as the resin layer 1b, another material can be used as long as the material has releasability and heat resistance.

The pressure roll 2 has a relatively thick heat-resistant elastic layer 2b made of silicone rubber provided on the peripheral surface of an iron core 2a. The pressure roll 2 is rotatably supported by a bearing (not shown), and is pressed against the fixing roll 1 by pressure means such as a spring. The heat-resistant elastic layer 2b is elastically deformed by this pressing, and the heat roll 1
And a pressure contact area is secured between them. The core 2a may be made of metal such as stainless steel or copper, instead of iron, and the elastic layer 2b may be made of fluorine rubber or fluorosilicone rubber.

The heat insulating member 8 is supported so as to be close to the fixing roll 1 and cover the outer peripheral surface thereof in a range other than a nip portion where the fixing roll 1 and the pressure roll 2 are pressed against each other. The heat insulating member 8 has a structure in which heat insulating materials made of different elastic materials are laminated, and includes an inner heat insulating material 10, an outer heat insulating material 11 bonded to the outside thereof, and an inner surface of the inner heat insulating material 10 on the fixing roll 1 side. It is composed of a thin metal surface layer 9 formed as a whole and a frame body 12 that tightly supports and integrally supports them. The surface of the elastic member 8 facing the fixing roll 1 has a curvature such that it is close to the peripheral surface of the fixing roll at a distance of 0.2 mm to 2.0 mm.

As the inner heat insulating material 10 of the heat insulating member 8, 2
A 2.0 mm thick polyethylene terephthalate foam (Cell Pet: manufactured by Sekisui Chemical Co., Ltd.) having a high heat-resistant temperature up to 20 ° C. is used. As the outer heat insulating material 11, the average thickness is 4 mm. A polypropylene foam (PFB: Sekisui Chemical Co., Ltd.) having a low thermal conductivity of 0.03 Kcal / mHr ° C. or less is used. As the thin metal surface layer 9, a 15 μm-thick highly smooth aluminum foil having heat reflectivity is used.

The heat insulating member 8 has the thin metal surface layer 9, the inner heat insulating material 10 and the outer heat insulating material 11 in close contact with each other.
, The heat conduction and heat radiation from the thin metal surface layer 9 as a reflection member can be significantly reduced. Further, the thickness of the thin metal surface layer 9 is 5 μm or more.
When the thickness is within the range of 20 μm, the heat capacity itself becomes small, and the heat reflection efficiency becomes very good.

At a position facing the peripheral surface of the fixing roll 1, a heat sensing element 4 and an abnormal temperature rise prevention device 5 are provided by hollowing out two portions of a heat insulating member 8. Thermal element 4
Is composed of a thermistor, a thermocouple, and the like, and measures the temperature of the surface of the fixing roll 1. Then, the heat source 3 is feedback-controlled by a temperature controller (not shown) based on the measurement signal of the warming element 4, and the surface of the fixing roll 1 is adjusted to 180 ° C. The abnormal temperature rise prevention device 5 is made of a thermostat, and the disk-shaped bimetal inside the device is deformed in response to the abnormal temperature rise of the fixing roll 1, and cuts off the electrical contact for supplying power to the heat source 3. .

A thin film 13 is supported on the frame 12 of the heat insulating member 8 at the entrance side and the exit side in the conveying direction of the recording paper so as to be in contact with the peripheral surface over the entire area of the fixing roll 1 in the axial direction. ing. This thin film 13
Is a 75 μm thick polyimide film coated with a 10 μm thick fluororesin. In addition, the thin film 13 on the outlet side is, as shown in FIG.
The leading end thereof is in contact with the peripheral surface of the fixing roll 1 with the nip side facing, and the recording paper on which the toner image has been fixed is peeled off from the peripheral surface of the fixing roll 1. The air layer adjacent to the outer peripheral surface of the fixing roll 1 is hermetically closed by the two thin film films 13 and the heat insulating member 8, so that the inflow and outflow of air from the outside are blocked.

Next, the operation of the fixing device will be described. The fixing roll 1 is driven to rotate, and the pressure roll 2 rotates following the fixing roll 1. Then, the recording paper 30 onto which the unfixed toner image 31 has been transferred is introduced into the nip where the fixing roll 1 and the pressure roll 2 are pressed against each other from the direction of the arrow shown in the drawing. The recording paper 30 moves as the fixing roll 1 rotates, and the toner image 31 on the recording paper 30 is melted by the heat of the fixing roll 1 and fixed on the recording paper. Thereafter, the recording paper on which the toner image has been fixed is discharged outside the apparatus while being nipped by the discharge rolls 20 and 21. A thin film 13 is in contact with the surface of the fixing roll 1 on the discharge port side of the fixing roll 1, and the recording paper 30 is separated from the fixing roll 1.

In such a fixing device, a heat insulating member 8 in which a thin metal surface layer 9, an inner heat insulating material 10, and an outer heat insulating material 11 are laminated is provided close to the peripheral surface of the fixing roll 1. 8, the function of each member is improved to exhibit an excellent heat radiation preventing effect. That is, the air layer between the heat insulating member 8 and the fixing roll 1 is thin and sealed, and the heat capacity of the air layer is extremely small. Is done. At this time, the thin metal surface layer 9 inside the inner heat insulating material 10
As a result, infrared rays emitted from the fixing roll 1 are reflected, so that the space between the fixing roll 1 and the heat insulating member 8 acts as a heat insulating air layer.

Further, it is possible to prevent the convection of the heated air between the heat insulating member 8 and the fixing roll 1 and the generation of the boundary layer flow of the air due to the orbital movement of the fixing roll 1. It is possible to form a constantly insulated air layer on the surface. Thereby, the toner image can be fixed by effectively using the heat of the fixing roll 1. Further, since the heat radiation from the fixing roll 1 is significantly reduced, the time required for the fixing roll 1 to be heated to reach a predetermined temperature can be reduced.

Next, a description will be given of an experiment in which a change in heat release with time was measured using the fixing device of the present invention and a fixing device for comparison. In this experiment, the case where the heat insulating member 8 shown in FIG. 1 is arranged close to both the fixing roll and the pressure roll (the present invention and a thin film is provided) and the case where the thin film is not used under the same conditions ( The present invention and the case where the thin film is not used), the case where the entire conventional fixing device shown in FIG. 3 is covered with the same heat insulating material as in the above embodiment, and the case where no heat insulating member is used are compared. The heat radiation amount of these fixing devices was measured every two minutes for 20 minutes immediately after warm-up, with the fixing roll rotated at a speed of 150 mm / s. Table 1 shows the results of this experiment. Below margin

[0036]

[Table 1]

According to Table 1, when the heat insulating member is arranged close to the surface of the fixing roll as in the present invention, the heat insulating effect appears immediately after warm-up, whereas the heat insulating member appears as in the prior art. When the whole is covered with the heat insulating material or when no heat insulating material is provided, the heat radiation amount is not stable even after 20 minutes. Therefore, when the oil supply device, the peeling device, the temperature sensor, and the abnormal temperature rise prevention device are excluded from the space inside the heat insulating member, and the heated portion is only the air layer near the surface of the fixing roll, it is extremely difficult. It can be seen that an excellent heat insulating effect can be obtained. For this reason, the fixing device of the present invention is particularly effective when the operation of a small number of parts is large like a small machine.

When the air heat insulating layer is sealed by the thin film, it is possible to reduce the electric power by about 10% as compared with the case where no thin film is provided. This is because the air heat insulation layer having a closed structure can prevent the heated air inside the heat insulation member from leaking outside due to convection. Therefore, it is understood that the energy saving effect by the shielding member such as a thin film is large.

Further, the fixing device of the present invention can reduce the electric power by about 4.5% as compared with the case where no heat insulating means is used, and the electric energy can be reduced by 75 watts. This means that the fixing speed can be increased from 30 sheets per minute to 36 sheets per minute with the same power consumption.

[0040]

As described above, in the fixing device according to the present invention, the heat insulator is arranged close to the peripheral surface of the first fixing member, and the heat insulator is disposed between the heat insulator and the first fixing member. An excellent heat insulating effect can be obtained by forming a stationary heat insulating air layer. For this reason, the heat radiation from the first fixing member can be significantly reduced, and the energy can be effectively used. Further, since the heat-insulating air layer does not convect, the amount of heat exhausted to peripheral members is reduced, and the problem of temperature rise in the apparatus is greatly reduced. Further, by reducing the heat capacity of the heat-insulating air layer, the heat-insulating effect can be exerted immediately after warm-up, which is also effective for a small device.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a fixing device according to an embodiment of the present invention.

FIG. 2 is a partially enlarged view showing a thin film used in the fixing device.

FIG. 3 is a schematic configuration diagram illustrating an example of a conventional fixing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing roll 2 Pressure roll 3 Heat source 4 Heat sensing element 5 Abnormal temperature rise prevention device 8 Heat insulating member 9 Thin metal surface layer 10 Inner heat insulating material 11 Outer heat insulating material 12 Frame 13 Thin film 15 Frame 20 Discharge roll 21 Discharge Roll 30 Recording paper 31 Toner image

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H033 BA05 BA32 BB38 2H071 BA23 DA12 5H323 AA36 BB12 BB20 CA08 CB03 DA01 DA10 EE01 FF01 GG04 HH02 KK05

Claims (6)

[Claims] 1. A first fixing member having a built-in heat source and having an endless peripheral surface moving around, and a second fixing member having an endless peripheral surface being pressed against the peripheral surface of the first fixing member to move around. The two fixing members convey a recording sheet carrying an unfixed toner image in a nip portion where the two fixing members are pressed against each other, and heat and pressurize the unfixed toner image to press the recording sheet on the recording sheet. In the fixing device for fixing, a heat insulator that blocks heat radiation from the first fixing member is provided on a peripheral surface of the first fixing member, excluding a portion near a portion that is pressed against the second fixing member. It is characterized by having shielding members arranged in close proximity to each other in the circumferential direction at both ends of the gap between the heat insulator and the first fixing member to block air from flowing into and out of the heat insulator. Fixing device. 2. The image forming apparatus according to claim 1, wherein the shielding member is a film-shaped member supported on an upstream side or a downstream side in a conveying direction of the recording sheet so as to be in contact with a peripheral surface of the first fixing member. The fixing device according to claim 1. 3. The image forming apparatus according to claim 1, wherein the shielding member peels off the recording sheet adhered to the first fixing member, with the leading end of the film-shaped member facing the nip portion, and the leading end of the first fixing member facing the first fixing member. The fixing device according to claim 2, wherein the fixing device is attached so as to contact the member. 4. The heat insulator has a notch at a position facing the first fixing member, and a temperature detecting element for adjusting a surface temperature of the first fixing member in the notch. 4. The fixing device according to claim 1, further comprising an abnormal temperature rise detecting element. 5. The fixing device according to claim 1, wherein the heat insulator has a multilayer structure in which a plurality of heat insulating materials are stacked. 6. The fixing device according to claim 1, wherein a high-gloss metal layer is provided on an inner surface of the heat insulator.