JP2008139666A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device which is excellent in power saving properties, that is, is configured so that heat is more efficiently transferred to toner by enlarging a nip width, while maintaining adhesion, in concrete terms. <P>SOLUTION: The fixing device is configured so that the heat is applied to the toner and a recording material through a heat transmit plate adhering to a roller through a film, by using a halogen lamp as a heat source. The heat transmit plate has spring properties and is deformed into a shape along the roller and adhered, to form a wide nip, when pressure is applied. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heat fixing device in an image forming apparatus employing an electrophotographic image forming process such as a copying machine or a printer.

  In an image forming apparatus employing an electrophotographic image forming process, a film heating type fixing device is used in a fixing unit that fixes a toner image transferred onto a transfer object such as a recording paper by heating and pressing. (See Patent Documents 1 and 2).

  This film heating system is a system in which a heater is adhered to one surface side of a heat resistant film and a heated material is adhered to the other surface side, and the heat energy of the heater is applied to the heated object via the heat resistant film.

  FIG. 5 shows a schematic diagram of a fixing device employing a film heating method.

  This apparatus is a thin-walled cylindrical film 5 made of a ceramic heater 5-1 as a heating element, a stay 5-2 that supports and insulates this heater, and a heat-resistant resin material wound around the stay that supports the heater. -3 and film 5-3, and a pressure roller 5-4 that presses against the heater 5-1 to form a nip portion N5. A temperature detection element 5-5 is arranged on the back surface of the heater 5-1.

  The pressure roller is driven to rotate, and the film 5-3 is driven to rotate. The heater 5-1 is energized, and the temperature is adjusted to a predetermined temperature. -6 recording material 5-7 is transported, introduced into the nip N5, and the nip N5 is sandwiched and transported together with the film 5-3, so that the heat of the heater 5-1 passes through the film 5-3. To the recording material 5-7 to fix the unfixed toner image 5-6.

  Because the heat capacity of film 5-3 and heater 5-1 is small, it takes a short time to energize heater 5-1 and adjust the temperature to the specified temperature, and it has excellent quick start and power saving. It is a fixing method.

  In recent years, environmental problems have attracted attention, and power saving performance has been regarded as important in electrical products in various fields.

  Copiers and printers that employ an electrophotographic image forming process are no exception, and products with lower power consumption are required.

  Various methods have been studied in order to provide a fixing device with excellent energy saving even in a film heating type fixing device.

  Among them, a method of reducing the fixing temperature and reducing the power consumption by increasing the fixing strength by increasing the nip and heating time is considered.

  However, it is necessary to increase the width of the heater substrate in order to increase the nip in the configuration of the film heating type heat fixing device.

  A ceramic substrate made of alumina or aluminum nitride is used for a heater substrate used in a current film heating type heat fixing apparatus.

  If the heater substrate width is increased in order to widen the nip, the substrate using aluminum nitride is very expensive. In addition, a substrate using alumina having poor thermal conductivity makes it difficult to accurately detect the temperature in the nip, which causes a defect such as poor fixing in which fixing strength is reduced.

  Therefore, Japanese Patent Laid-Open No. 11-305578 (Patent Document 3) proposes a method of increasing the nip width by arranging a heat transfer plate having a shape along the surface of the pressure roller between the heater and the pressure roller. Yes.

  According to this proposal, the nip width becomes wide as a curved surface along the pressure roller surface, and the heating time can be increased.

Further, since the nip is widened by using a low-cost metal material having good thermal conductivity between the heater and the pressure roller, it is not necessary to widen the heater substrate width.
Japanese Unexamined Patent Publication No. 2-157878 JP-A-4-44075 Japanese Patent Laid-Open No. 11-305578

  In the film heat fixing method in which the nip is widened by using a curved heat transfer plate along the pressure roller, there is a problem in the adhesion between the pressure roller and the heat transfer plate.

  In the contact between the conventional flat surface heater and the pressure roller, the pressure roller is compressed and deformed and comes into contact with the heater, so that the pressure inside the nip is high and the heater and the pressure roller are in good contact. Sex was obtained.

  However, in the film heating and fixing method in which the nip shape is formed along the pressure roller using a curved heat transfer plate, the nip can be formed without compressing the pressure roller so much, so the pressure in the nip is low, and the heater And the adhesion of the pressure roller is lowered. In such a state, the thermal conductivity is deteriorated, and efficient fixing cannot be performed.

  Even if the total load applied between the heater and the pressure roller is increased in order to increase the pressure, the pressure at the edge of the curved heat transfer plate increases and the pressure inside the nip decreases, resulting in good adhesion. Sex cannot be obtained.

  The present invention proposes a heat-fixing apparatus that solves such problems and enables more efficient fixing.

  The present invention is a fixing device having the following configuration.

(1) an image carrier, a charging device for charging the image carrier, a means for writing information by creating an electrostatic latent image on a charging surface of the image carrier, and the electrostatic latent image with toner Development means for visualizing and means for transferring the visualized toner image onto the image recording medium, applying heat to the toner image transferred onto the image recording medium and applying pressure to the image recording medium In a fixing device of an image forming apparatus having a fixing means,
The fixing device has a structure in which a pressure roller and a heating means for applying heat to the pressure roller are in pressure contact with each other;
The heating means includes a heat source and a heat transfer member that transfers heat from the heat source to a nip portion between the fixing roller, the heat transfer member has a larger curvature than the outer periphery of the pressure roller, and has a spring property. A fixing device which is made of a material and can be deformed into a shape along a pressure roller by applying pressure.

(2) an image carrier, a charging device for charging the image carrier, a means for writing information by creating an electrostatic latent image on a charging surface of the image carrier, and the electrostatic latent image with toner Development means for visualizing and means for transferring the visualized toner image onto the image recording medium, applying heat to the toner image transferred onto the image recording medium and applying pressure to the image recording medium In a fixing device of an image forming apparatus having a fixing means,
The fixing device has a structure in which two fixing rollers as pressure means brought into pressure contact with each other, and a heating means for applying heat to one fixing roller are in pressure contact with each other,
The heating means includes a heat source and a heat transfer member that transfers heat from the heat source to a nip portion with the fixing roller, the heat transfer member has a larger curvature than the outer periphery of the pressure roller, and has a spring property. A fixing device characterized in that the fixing device can be deformed into a shape along the pressure roller by applying pressure.

  By adopting the configuration according to the present invention, it is possible to improve the adhesion in a nip having a curvature and form a fixing device excellent in power saving.

  In the present invention, a radiant heat source such as a halogen lamp or a carbon lamp is used as the heat source, and this heat source is covered with a reflector that opens to the pressure roller side, and the opening of the reflector has a black surface and has a spring property. It has a structure covered with a heat transfer member made of a metal having high thermal conductivity.

  As the metal used for the heat transfer member, phosphor bronze, stainless steel or the like is desirable. The thickness of the heat transfer member is preferably about 100 μm to 500 μm, more preferably about 70 μm to 300 μm from the viewpoint of strength and deformation.

  When the heat source is a heat source capable of performing radiant heat transfer, such as a halogen lamp or a carbon lamp, the heat transfer member can be freely deformed, and the configuration is easy.

  Further, by providing a black surface on at least the halogen lamp side surface of the heat transfer plate, it becomes possible to efficiently absorb the radiant heat.

  When this heating element is pressed against the pressure roller, the black heat transfer member having spring property is deformed along the outer peripheral surface of the pressure roller, and is applied to the pressure roller through a film that wraps around and slides on the heating element. Adhere and form a nip.

  At this time, since the black heat transfer member is deformed while applying pressure to the pressure roller, the pressure in the nip can be increased.

  For this reason, adhesiveness is high and a wide nip width can be obtained.

  Further, even if the total load applied between the heat transfer plate and the pressure roller is increased, the pressure is applied from the center of the nip, so that the problem that the pressure is concentrated only on the edge portion of the curved nip does not occur.

  When a halogen lamp or carbon lamp as a radiant heat source is energized, heat is supplied to the nip portion through a black heat transfer member having a shape along the roller due to a radiant heat transfer effect from the heat source.

  Since it has a high nip width with high adhesion, heat can be efficiently applied to the unfixed toner image on the recording material when the recording material passes, and the fixing strength can be increased.

  As a result, the fixing temperature can be reduced and more power-saving printing can be performed.

  As described above, according to the present invention, it is possible to form a nip having high adhesion and a wide width, and it is possible to provide a heat fixing device with higher thermal efficiency.

(Example 1)
Hereinafter, the present invention will be described in detail.

  FIG. 1 shows the structure of the heat fixing apparatus of the present invention.

  The heating unit 1-1 is a radiation heating source of a halogen lamp or a carbon lamp, and the heating unit 1-1 has a structure covered with a reflecting member 1-2 and a heat transfer member 1-3.

  More specifically, a halogen lamp having a diameter of 6 mm, a rated voltage of 120 V, and a power consumption of 700 W is used as the heating unit 1-1, and the surface on the heating unit 1-1 side as the reflecting member 1-2 is mirror-finished to achieve a reflection efficiency. And a heat transfer plate made of phosphor bronze with a width of 15 mm and a thickness of 300 μm having a black surface with the surface processed on the surface of the heating means 1-1 as the heat transfer member 1-3 Thus, the heating means 1-1 is enclosed.

  The ends of the reflecting member 1-2 and the heat transfer member 1-3 are bonded to each other, so that the light from the halogen lamp as the heating means 1-1 does not leak to the outside.

  Further, a cylindrical fixing film 1-5 is wound around the reflecting member 1-2 and the heat transfer member 1-3.

  The pressure roller 1-4 is a heat-resistant and elastic roller in which an aluminum cored bar 1-4a is coated with sponge silicon rubber 1-4b foamed as an elastic body layer. The mold layer has a structure coated with fluororesin 1-4c.

  In this embodiment, a pressure roller having a diameter of about 20 mm having a sponge silicon rubber 1-4b having a thickness of 3.5 mm and a fluororesin layer 1-4c having a thickness of 30 μm on an aluminum core metal 1-4a having a diameter of 13 mm. Was used.

  The pressure roller 1-4 is pressed against the heat transfer member 1-3 with a predetermined pressure across the fixing film 1-5. At this time, the heat transfer member 1-3 is deformed into a shape along the pressure roller 1-4 by being in pressure contact with the pressure roller 1-4, and is transferred to the pressure roller 1-4 via the fixing film 1-5. Adheres closely to form a nip portion N1.

  The fixing film 1-5 rotates in conjunction with the rotation of the pressure roller 1-4, and when the recording material 1-6 is introduced into the nip portion N1, the recording material 1-6 is nipped and conveyed. To do. In this embodiment, the conveyance speed of the recording material was 118 mm / s.

  The unfixed toner image 1-7 on the recording material 1-6 that has entered the nip portion N1 is heated in the nip portion N1, melted, penetrated, and fixed to the recording material 1-6.

  Since the nip portion N1 is curved along the pressure roller 1-4, the nip portion N1 is wide and more heat can be applied to the unfixed toner image 1-7.

  In Example 1, Examples 1-1 and 1-2 were performed by changing the load applied between the heat transfer member 1-3 and the pressure roller, and the fixing temperature, the rise time, and the power during printing were evaluated. went. In addition, Comparative Examples 1-1 and 1-2 were performed for comparison with Examples.

  When the fixing temperatures were compared in Examples and Comparative Examples, the fixing temperatures when the fixing strengths were at the same level were compared.

  The fixing strength indicates how much force the fixed image is fixed on the recording material by fixing the unfixed image with a fixing device, and is expressed as a density reduction rate (unit:%). Next, a method for measuring the concentration reduction rate will be described.

  As the unfixed image, black and halftone (gray) 5 mm square images are arranged on 9 letter size papers.

  The halftone pattern of the unfixed image is a pattern in which a pixel density of 600 dpi is formed by a 3 × 3 matrix, and this is formed in a staggered pattern with one dot and one space.

  After measuring the halftone density of the image after passing through the fixing device with a density meter (Macbeth), rub the image with a dedicated rubbing tester and measure the halftone density after rubbing again. Calculate the rate of decline.

  The rubbing tester has a structure in which a 200g metal weight is placed on a 5mm square black and halftone pattern placed on nine places on a table that fixes the sheet by static electricity. Silbon C paper (manufactured by Ozu Sangyo Co., Ltd.) is sandwiched between the paper and the weight. The table for fixing the paper can reciprocate in the longitudinal direction of the paper. At this time, the image is rubbed against the Sylbon C paper and is lost. In this example, the image was rubbed after 5 reciprocations.

  The density reduction rate is calculated for all nine halftone images on letter-size paper, and an average value is calculated as an index representing the fixing strength under the conditions.

  In this measurement, a rough paper (Fox River Paper manufactured by Fox River Paper) with a grammage of 90 g was used as a recording material in a laboratory maintained at room temperature 23 ° C and humidity 50%, 15 seconds after the fixing device was started up. The fixing temperature was measured such that the density reduction rate when passing through the fixing device was 10%.

  A density reduction rate of 10% is a level at which an image is not lost even if the image is strongly rubbed with a finger, and is sufficiently high for practical use.

  Table 1 summarizes the evaluation results of Examples and Comparative Examples.

実施例1-1ではハロゲンランプに通電が開始されると700Wの電力がハロゲンランプに投入され、定着装置の立上が始まった。定着の温調温度は160℃で、温調が始まるまでに要した時間は6.0secであった。電力測定の結果、プリント中に消費された電力は平均でおよそ400Wであった。

In Example 1-1, when energization of the halogen lamp was started, 700 W of electric power was supplied to the halogen lamp, and the fixing device started up. The temperature control temperature for fixing was 160 ° C., and the time required for the temperature control to start was 6.0 sec. As a result of the power measurement, the average power consumed during printing was about 400 W.

  In Example 1-2, when energization of the halogen lamp was started, 700 W of power was supplied to the halogen lamp, and the start-up of the fixing device was started. The temperature control temperature for fixing was 175 ° C., and the time required for the temperature control to start was 7.0 sec. As a result of the power measurement, the average power consumed during printing was approximately 440 W.

  Since the total load decreased and the nip width narrowed as compared with Example 1-1, the fixing temperature increased, the rise time, and the power consumed during printing increased.

  As Comparative Example 1-1, a similar evaluation was performed using a film heating unit used in a conventional film heating type fixing device (see FIG. 2). The pressure roller was a roller 1-4 shown in FIG.

  The temperature control temperature for fixing was 195 ° C., and the time required for the temperature control to start was 8.0 sec. As a result of power measurement, the average power consumed during printing was approximately 500W.

  The total load applied between the heater and the pressure roller is 13 kg, which is the same as in Example 1-1. However, since a ceramic heater having a flat surface is used, the nip width is determined in Examples 1-1 and 1- It is narrower than 2. As a result, the fixing temperature increased, and the rise time and power consumed during printing also increased.

  Furthermore, as Comparative Example 1-2, in a fixing device having a configuration in which a heat transfer plate having a curvature equivalent to that of a pressure roller is provided in a film heating unit used in a conventional film heating type fixing device (see FIG. 2). Similar evaluations were made. The pressure roller was a roller 1-4 shown in FIG. FIG. 2 shows the configuration of Comparative Example 1-2.

  Ceramic heater 2-1 as a heating element, stay 2-2 which is a support body that supports and insulates this heater, and a thin cylindrical film 2-3 made of a heat-resistant resin material wound around a stay supporting the heater, It consists of a pressure roller 2-4 that presses against the heater 2-1 across the film 2-3 to form a nip portion N2. Reference numeral 2-5 denotes a temperature detecting element, which is arranged on the back surface of the heater 2-1.

  A heat transfer plate 2-6 having a curved surface having the same curvature as that of the pressure roller 2-4 is disposed between the ceramic heater 2-1 and the film 2-3, and the pressure roller 2-4 and the film 2-3 are interposed therebetween. Close contact.

  When the total load applied between the ceramic heater 2-1 and the pressure roller 2-4 was 13 kg, a nip width of 15 mm equivalent to that of Example 1-1 was obtained. However, when the pressure distribution was measured, the pressure at the edge portion of the nip was high and the pressure inside the nip was low. Since the adhesiveness between the ceramic heater 2-1 and the pressure roller 2-4 is low inside the nip, the temperature adjustment temperature is 175 ° C, which is 15 ° C higher than that of Example 1-1. I have. As a result, both the rise time and power during printing were high.

  Compared to Example 1-1, an equivalent nip width was obtained, but because the adhesion between the heater and the pressure roller was low, heat could not be transferred efficiently.

  From the above comparison, the configuration of the present invention can widen the nip width compared to the conventional film fixing method, and can sufficiently transfer heat because the adhesion between the heat transfer plate and the pressure roller can be sufficiently increased. It has been found that a more efficient fixing device can be provided.

(Example 2)
Hereinafter, the present invention will be described in detail.

  FIG. 3 shows the structure of the fixing device of the present invention.

  The fixing device in this embodiment mainly includes a fixing roller 3-1, a pressure roller 3-2 pressed against the fixing roller 3-1, and an external heating unit 3-3 for heating the fixing roller 3-1 from the outside. ing.

  The fixing roller 3-1 is a porous ceramic whose roller base 3-1a has an outer diameter of 20 mm and an inner diameter of 13 mm, and a silicon rubber layer 3-1b having a thickness of about 1 mm as an elastic layer on the outer peripheral surface of the roller base 3-1a. Further, a fluororesin layer 3-1c having a thickness of 30 μm is provided on the outer peripheral surface as a release layer.

  In the pressure roller 3-2, the roller base 3-2a is a porous ceramic having an outer diameter of 20 mm and an inner diameter of 13 mm, and a silicon rubber layer 3-2b having a thickness of approximately 0.3 mm as an elastic layer on the outer peripheral surface of the roller base, Further, a fluororesin layer 3-2c having a thickness of 30 μm is provided on the outer peripheral surface as a release layer.

The porous ceramic used in this example is based on silica, has a density of 0.2 to 1.0 g / cm ² , more preferably 0.3 to 0.7 g / cm ² , and a thermal conductivity of 0.1 to 0.2 W / mK. I used something.

  The pressure roller 3-2 is arranged in parallel under the fixing roller 3-1, and is pressed and pressed with a pressure of 40 kg to form a nip portion N3-1 having a width of 3 mm.

  The pressure roller 3-2 rotates following the rotation direction of the fixing roller 3-1, and is fixed when the recording material 3-4 on which the unfixed toner image 3-3 is placed is introduced into the nip portion N3-1. The recording material 3-4 is nipped and conveyed in cooperation with the roller 3-1. In this embodiment, the conveyance speed of the recording material 3-4 is 118 mm / sec.

  The external heating means 3-3 is a means for heating the fixing roller 3-1 from the outside.

  The heat source 3-3a is a radiation heating source of a halogen lamp or a carbon lamp, and the heat source 3-3a is covered with a reflecting member 3-3b and a heat transfer member 3-3c.

  More specifically, a halogen lamp with a diameter of 6 mm, a rated voltage of 120 V, and a power consumption of 700 W is used as the heat source 3-3a, and the surface on the heat source 3-3a side as the reflecting member 3-3b is mirror-finished to increase the reflection efficiency. A heat reflecting plate made of phosphor bronze having a black surface with a surface processed on the surface of the heat source 3-3a side as a heat reflecting member 3-3c and a heat transfer plate made of phosphor bronze having a black surface The structure is wrapped around 3-3a.

  The ends of the reflecting member 3-3b and the heat transfer member 3-3c are bonded to each other so that light from the halogen lamp as the heat source 3-3a does not leak to the outside.

  Further, a cylindrical fixing film 3-3d is wound around the reflecting member 3-3b and the heat transfer member 3-3c.

  The external heating means 3-3 has heat transfer members 3-3c arranged in parallel with the fixing roller 3-1, and is in pressure contact with the fixing roller 3-1 with a total pressure of 13 kg.

  At this time, the heat transfer member 3-3c is deformed into a shape along the fixing roller 3-1 by being pressed against the fixing roller 3-1, and is in close contact with the fixing roller 3-1 through the fixing film 3-3d. Nip part N3-2 is formed.

  Even in the case where the roller base is made of a material having high hardness such as porous ceramics as in this embodiment, the heat transfer member is deformed into a shape along the roller, so that it can be efficiently heated.

  As the fixing roller 3-1 is driven to rotate, the film 3-3d of the external heating means 3-3 is rotated while sliding and friction with the heat transfer member 3-3c. Thereafter, the heat source 3-3a is energized to generate heat, and the surface of the fixing roller 3-1 is heated via the heat transfer member 3-3c.

  A temperature detecting means 3-6, more specifically an NTC thermistor is in contact with the circumference between the external heating means 3-3 and the nip portion N3-2 of the fixing roller 3-1, and the surface temperature of the fixing roller 3-1 Configured to monitor. By this temperature detection means 3-6, the surface temperature of the fixing roller 3-1 is adjusted to a predetermined temperature.

  The fixing roller 3-1 and the pressure roller 3-2, which are made of porous ceramic with high hardness as a roller base, are in pressure contact with each other with a high linear pressure, and an unfixed toner image 3-5 on the recording material 3-4. On the other hand, a pressure exceeding the compression yield pressure of the toner is applied to cause plastic deformation.

  The conveyed recording material 3-4 enters the nip portion N3-1 between the fixing roller 3-1 and the pressure roller 3-2. The fixing roller 3-1 receives heat from the external heating unit 3-3 and is heated.

  Although the fixing roller 3-1 has high hardness, heat is efficiently transferred by forming the heat transfer plate and the nip N3-2 along the curvature.

  The unfixed toner image 3-5 that has entered the nip portion N3-1 between the fixing roller 3-1 and the pressure roller 3-2 is crushed by receiving a high linear pressure and is heated and melted by the fixing roller 3-1. , Penetrates and is fixed on the recording material 3-4.

  In Example 2, Examples 2-1 and 2-2 are performed by changing the pressure applied between the heat transfer member 3-3c and the pressure roller 3-1, and the fixing temperature, the rise time, and the power during printing are changed. Was evaluated. Comparative Example 2-1 was also performed.

  When the fixing temperatures were compared in Examples and Comparative Examples, the fixing temperatures when the fixing strengths were at the same level were compared.

  Since the fixing strength was described in Example 1, it will not be described here.

In this measurement, the density reduction rate when passing rough paper (Fox River Paper manufactured by Fox River Paper) with a grammage of 90g as the recording material in a laboratory maintained at room temperature 23 ° C and humidity 50%. The fixing temperature was measured so as to be 10%.
The results are summarized in Table 2.

実施例2-1ではハロゲンランプに通電が開始されると700Wの電力がハロゲンランプに投入され、定着装置の立上が始まった。定着の温調温度は150℃で、温調が始まるまでに要した時間は5.5secであった。電力測定の結果、プリント中に消費された電力は平均でおよそ350Wであった。

In Example 2-1, when energization of the halogen lamp was started, 700 W of power was supplied to the halogen lamp, and the fixing device started to start. The temperature control temperature for fixing was 150 ° C., and the time required for the temperature control to start was 5.5 seconds. As a result of the power measurement, the average power consumed during printing was about 350 W.

  In Example 2-2, when energization of the halogen lamp was started, 700 W of power was supplied to the halogen lamp, and the fixing device started to start. The temperature control temperature for fixing was 150 ° C., and the time required for the temperature control to start was 8.0 sec. As a result of the power measurement, the average power consumed during printing was approximately 370 W.

  First, the fixing mechanism in this embodiment will be described.

  In this embodiment, a load of 40 kg is applied between the fixing roller 3-1 and the pressure roller 3-2, and the nip is as narrow as 3 mm, so that the pressure in the nip is higher than that in the conventional example. When the pressure increases, the toner is more flattened between the roller and the recording material, and the contact area between the roller and the recording material increases.

  In this state, since the thermal conductivity of the toner is improved as compared with the normal time, the heat is well transmitted to the entire toner by applying a small amount of heat, and the toner can be melted.

  That is, in the configuration of this embodiment, the heat transfer dependency of the factor for fixing the toner is reduced, and the pressure dependency is increased.

  Therefore, the amount of heat consumed during fixing can be kept low.

  In the configuration of this embodiment, the temperature required for fixing is 150 ° C. This is, for example, a lower temperature than in Example 1 (see Table 1).

  In Example 2-2, the load applied between the heat transfer member 2-3c and the fixing roller 2-1 was reduced compared to Example 2-1, the nip width was narrowed, and heat transfer was slowed down. Time and power consumed during printing also increased.

  In Comparative Example 2-1, the same evaluation was performed using a film heating unit used in a conventional film heating type fixing device (see FIG. 4) as the external heating device 3-3. The fixing roller was the same as the rollers 3-1 and 3-2 shown in FIG. FIG. 4 shows a configuration diagram of Comparative Example 2-1.

  The fixing device in Comparative Example 2-1 mainly includes a fixing roller 4-1, a pressure roller 4-2 pressed against the fixing roller 4-1, and an external heating unit 4-3 for heating the fixing roller 4-1 from the outside. It is configured.

  The fixing roller 4-1 is a porous ceramic having a roller base 4-1a having an outer diameter of 20 mm and an inner diameter of 13 mm, and a silicon rubber layer 4-1b having a thickness of about 1 mm as an elastic layer on the outer peripheral surface of the roller base 4-1a. Further, a fluororesin layer 4-1c having a thickness of 30 μm is provided as a release layer on the outer peripheral surface thereof.

  The pressure roller 4-2 is a porous ceramic with a roller base 4-2a having an outer diameter of 20 mm and an inner diameter of 13 mm, and a silicon rubber layer 4-2b having a thickness of approximately 0.3 mm as an elastic layer on the outer peripheral surface of the roller base, Further, a fluororesin layer 4-2c having a thickness of 30 μm is provided on the outer peripheral surface as a release layer.

The porous ceramic used in this example is based on silica, has a density of 0.2 to 1.0 g / cm ² , more preferably 0.3 to 0.7 g / cm ² , and a thermal conductivity of 0.1 to 0.2 W / mK. I used something.

  The pressure roller 4-2 is arranged in parallel to the lower side of the fixing roller 4-1 and is press-contacted with a pressure of 40 kg to form a nip portion N4-1 having a width of 3 mm.

  The pressure roller 4-2 rotates following the rotation direction of the fixing roller 4-1, and is fixed when the recording material 4-4 on which the unfixed toner image 4-3 is placed is introduced into the nip portion N4-1. The recording material 4-4 is nipped and conveyed in cooperation with the roller 4-1. In Comparative Example 2-1, the conveyance speed of the recording material 4-4 is 118 mm / sec.

  The external heating unit 4-3 is a unit for heating the fixing roller 4-1 from the outside.

  The external heating means 4-3 includes a ceramic heater 4-3a as a heating body, a stay 4-3b that is a support body that supports the heater, and a thin cylinder made of a heat-resistant resin material wound around a stay that supports the heater. It is made of a shaped film 4-3c or the like.

  This external heating means 4-3 is arranged so that the heater 4-3a side is parallel to the fixing roller 4-1, and is in pressure contact with the fixing roller 4-1 with a total pressure of 13 kg.

  At this time, a nip portion N4-2 is formed by the fixing roller 4-1 and the heater 4-3a.

  As the fixing roller 4-1 is driven to rotate, the film 4-3b of the external heating means 4-3 is rotated while sliding and friction with the heater 4-3a and the stay 4-3b. Thereafter, the heater 4-3a is energized to generate heat, and the surface of the fixing roller 4-1 is heated.

  A temperature detecting means 4-6, more specifically an NTC thermistor, is in contact with the circumference between the external heating means 4-3 and the nip portion N4-1 of the fixing roller 4-1, and the surface temperature of the fixing roller 4-1 Configured to monitor. By this temperature detecting means 4-6, the surface temperature of the fixing roller 4-1 is adjusted to a predetermined temperature.

  The fixing roller 4-1 and the pressure roller 4-2, which are made of high-hardness porous ceramics as a roller base, are in pressure contact with each other at a high linear pressure, and an unfixed toner image 4-5 on the recording material 4-4 On the other hand, a pressure exceeding the compression yield pressure of the toner is applied to cause plastic deformation.

  The conveyed recording material 4-4 enters the nip portion N4-1 between the fixing roller 4-1 and the pressure roller 4-2. The fixing roller 4-1 receives heat from the external heating unit 4-3 and is heated.

  The unfixed toner image 4-5 that has entered the nip portion N4-1 between the fixing roller 4-1 and the pressure roller 4-2 is crushed by receiving a high linear pressure, and is heated and melted by the fixing roller 4-1. , Penetrates and is fixed on the recording material 4-4.

  In this configuration, the time required from the start of heater energization to the start of temperature control was 40 seconds. As a result of the power measurement, the average power consumed during printing was approximately 550 W.

  The total load applied between the heater and the pressure roller is 13 kg, which is the same as in Example 2-1. However, since a ceramic heater having a flat surface is used, the nip width is in Examples 2-1 and 2- It is narrower than 2. Since the fixing roller 4-1 in Comparative Example 2-1 uses porous ceramics with high hardness as a base, the roller hardly deforms and a wide nip cannot be formed. In Comparative Example 2-1, the nip width between the heat transfer member 4-3c and the fixing roller 4-1 was 3 mm.

  Therefore, it is considered that heat transfer is greatly delayed, leading to a delay in rise time and an increase in power consumption during printing.

  From the above comparison, it can be seen that, for example, a roller with high hardness can be contacted with a curved surface, so that the configuration of the present invention can efficiently transfer heat.

  In addition, it was found that by fixing two rollers with high hardness and applying high pressure to a narrow nip, the fixing temperature can be reduced and fixing can be performed more efficiently.

  This configuration can be quickly heated by using a heating device capable of forming a nip along the outer periphery of the roller as in the present invention as an external heating device, and can be proposed as an example of an effective fixing device according to the present invention.

Schematic diagram of fixing device of the present invention (Example 1) Conceptual diagram of the fixing device of Comparative Example 1-2 Conceptual diagram of the fixing device of the present invention (Example 2) Conceptual diagram of the fixing device of Comparative Example 2-1 Schematic diagram of a fixing device using a conventional film heating method

Explanation of symbols

1-1 Halogen lamp
1-2 reflector
1-3 Black curved heat transfer member
1-4 Pressure roller
1-4a Core
1-4b Elastic layer
1-4c Release layer
1-5 film
1-6 Unfixed toner image
1-7 Recording material
N1 nip
2-1 Ceramic heater
2-2 Stay
2-3 film
2-4 Pressure roller
2-5 Temperature sensing element
2-6 Heat transfer plate
N2 Nip part
3-1 Fixing roller
3-1a Porous ceramics
3-1b Elastic layer
3-1c Release layer
3-2 Pressure roller
3-2a Elastic layer
3-2b Elastic layer
3-2c Release layer
N3-1 Nip between fixing roller 3-1 and pressure roller 3-2
3-3 External heating means
3-3a Halogen lamp
3-3b Reflector
3-3c Black curved heat transfer member
3-3d film
N3-2 Nip between heat transfer member 3-3d and fixing roller 3-1
3-4 Recording material
3-5 Unfixed toner image
3-6 Temperature sensing element
4-1 Fixing roller
4-1a Porous ceramics
4-1b Elastic layer
4-1c Release layer
4-2 Pressure roller
4-2a Porous ceramics
4-2b Elastic layer
4-2c Release layer
N4-1 Nip between fixing roller 3-1 and pressure roller 3-2
4-3 External heating means
4-3a Ceramic heater
4-3b Stay
4-3c film
N4-2 Nip part between ceramic heater 4-3a and fixing roller 4-1
4-4 Recording material
4-5 Unfixed toner image
4-6 Temperature sensing element
5-1 Heater
5-2 Stay
5-3 Film
5-4 Pressure roller
5-5 Temperature sensing element
5-6 Unfixed toner image
5-7 Recording material
N5 Nip part

Claims (2)

An image carrier, a charging device for charging the image carrier, a means for writing information by creating an electrostatic latent image on a charging surface of the image carrier, and development for visualizing the electrostatic latent image with toner And means for transferring the visualized toner image onto the image recording medium, applying heat to the toner image transferred onto the image recording medium, and fixing the image on the image recording medium by applying pressure. In the fixing device of the image forming apparatus having
The fixing device has a structure in which a pressure roller and a heating means for applying heat to the pressure roller are in pressure contact with each other;
The heating means includes a heat source and a heat transfer member that transfers heat from the heat source to a nip portion between the pressure roller, the heat transfer member has a larger curvature than the outer periphery of the pressure roller, and has a spring property A fixing device characterized in that it can be deformed into a shape along the pressure roller by applying pressure. An image carrier, a charging device for charging the image carrier, a means for writing information by creating an electrostatic latent image on a charging surface of the image carrier, and development for visualizing the electrostatic latent image with toner And means for transferring the visualized toner image onto the image recording medium, applying heat to the toner image transferred onto the image recording medium, and fixing the image on the image recording medium by applying pressure. In the fixing device of the image forming apparatus having
The fixing device has a structure in which a roller pressed against each other and a heating unit that applies heat to at least one of the rollers are pressed against each other,
The heating means has a heat transfer member that transfers heat from the heat source to the nip portion with the roller, and the heat transfer member has a larger curvature than the outer periphery of the roller to which the heating means is pressed, The fixing device is made of a material having a spring property and can be deformed into a shape along the roller by applying pressure.

Images