JP2011053411A - Heat fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ensure satisfactory fixability, even while ensuring on-demand performance of a heat fixing device of a belt heating system. <P>SOLUTION: The heat fixing device is configured such that a heat-resistant endless belt is slid and conveyed while kept in close contact with a heating element by means of a pressing member, a material to be heated is introduced between the belt and pressing member forming a pressure contact nip, and the pressure contact nip is sandwiched and conveyed together with the belt, thereby applying the heat of the heating element to the material. In the heat fixing device, the average value of the pressure on the rear half of the pressure contact nip is higher than that on the front half thereof. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a heating apparatus for heating a heated body, for example, a heat fixing apparatus used for fixing a toner image in electrophotography to the heated body.

  Conventionally, as a fixing device for fixing an unfixed image on a recording material in an image forming apparatus such as an electrophotographic copying machine, a printer, or a fax machine, a contact heating type fixing device having excellent thermal efficiency and safety is widely used. A belt heating type fixing device that heats through a belt (film) with a small heat capacity as a method (on-demand) that has high heat transfer efficiency and a quick start-up of the device from the viewpoint of promoting energy saving, especially in recent years. Is attracting attention.

  This belt heating type fixing device is disclosed in, for example, JP-A-2-157878, 4-44075, 4-204980 and the like, and a heat-resistant resin which is a heating rotator as a heating body (heater). A belt (fixing belt) is brought into close contact with a pressure rotating body (elastic roller) and is slid and conveyed, and a non-fixed image is carried on a pressure nip formed by a heating body and a pressure member with the belt interposed therebetween. A recording material as a heating material is introduced and conveyed together with the heat-resistant resin belt, and an unfixed image is formed on the recording material by heat from the heating body applied through the belt and pressure applied at the pressure nip portion. It is a device for fixing as an image.

  FIG. 3 is a schematic sectional view of an example of a belt heating type fixing device. In FIG. 3, 1 is an endless belt member, 2 is a heating body, 3 is a belt guide member that supports the heating body 2 and guides the movement of the belt 1. The belt 1 is externally fitted to the assembly of the heating body 2 and the support member 3 with a margin. Since the belt 1 rotates while rubbing against the internal heating body 2 and the support member 3, it is necessary to suppress the frictional resistance between the heating body 2 and the support member 3 and the belt 1. For this reason, a small amount of lubricant such as heat-resistant grease is interposed between the heating element 2 and the support member 3 and the belt 1.

  The belt 1 is an endless belt member having a heat-resistant resin such as polyimide or a metal base layer such as nickel, and the outermost layer is formed with a release layer such as a fluororesin in order to ensure the release property of the toner. Yes. In addition, a heat-resistant elastic layer containing silicone rubber or fluororubber as a component may be formed in order to ensure the fixability of color toner or the like.

The heating element 2 is formed on a substrate formed of a highly insulating ceramic such as alumina or aluminum nitride, or a metal such as SUS, along the longitudinal direction (direction perpendicular to the moving direction of the material to be heated), for example, Ag / Pd. It is a member for energization heat generation formed by applying a heating element such as (silver palladium), RuO ₂ , Ta ₂ N or the like into a linear or narrow strip having a thickness of about 10 μm and a width of about 1 to 5 mm by screen printing or the like.

  Reference numeral 4 denotes a pressure roller as a pressure member that is rotatably supported and presses against the heating body 2 via the belt 1. The pressure roller 4 is driven to rotate by driving means (not shown) and drives the belt 1. Also serves as a roller. The pressure roller 4 is provided with a heat-resistant elastic layer 4b formed by foaming silicone rubber, fluorine rubber, or silicone rubber on a metal core 4a such as aluminum, and fluorine as a release layer on the outer periphery of the rubber layer 4b. A layer 4c of resin or the like is provided.

  The belt 1 is a heated material carrying a predetermined peripheral speed, that is, an unfixed toner image 6 while sliding on the lower surface of the heating body 2 in the clockwise direction by the counterclockwise rotation of the pressure roller 4 at least during image fixing. The recording material 5 is rotationally driven at substantially the same speed as the conveyance speed of the recording material 5.

  The heating body temperature is detected by the temperature detecting element 8 pressed against the center of the back surface of the heating body, and the detected temperature is fed back to a temperature control circuit (not shown) to maintain the heating body back surface temperature at a predetermined temperature. The energization is controlled so that.

  In a state where the belt 1 is rotationally driven, a recording material 5 is introduced between the belt 1 and the pressure roller 4 in the press nip portion 7 formed by deformation of the belt 1 and the pressure roller 4, and the recording is performed. The material 5 is brought into close contact with the outer peripheral surface of the belt 1 and passed through the pressure nip portion 7 while being overlapped with the belt, and the heat generated by the heating body 2 is applied to the recording material 5 through the belt 1 together with it. By applying pressure, the unfixed toner image 6 on the recording material 5 is heated and melted and fixed. The recording material 5 subjected to the fixing process is separated from the belt 1 after passing through the press-contact nip portion 7 and discharged outside the apparatus.

  Recently, as the speed of the electrophotographic process is increasing, high-speed fixability is required as a requirement for the fixing device. Under high-speed conditions, the time during which the heated material is present in the pressure nip (short time in the nip) is short, so the heat from the heated body is not sufficiently transferred to the toner and heated material, making it difficult to obtain satisfactory fixing properties. Become. For this reason, a method has been proposed in which a wide pressure nip portion is provided to increase the residence time in the nip as disclosed in Japanese Patent Application Laid-Open No. 2001-356625.

  On the other hand, from the viewpoint of energy saving in recent years, by using a metal such as nickel or SUS instead of a heat-resistant resin as a base layer of the belt in this belt heating type heat fixing device, by increasing the thermal conductivity of the belt base layer, A method for reducing the power consumption of the heating element is described in JP-A-9-16004.

Japanese Patent Laid-Open No. 2-157878 JP-A-4-44075 JP-A-4-204980 JP 2001-356625 A JP-A-9-16004

  However, in the configuration in which the pressure nip portion is widely provided as in the above-described conventional example, it takes a lot of energy and time until the apparatus can be fixed because the entire roller is heated (decrease in on-demand property). There is a fear.

  In addition, when the metal base layer is used, the rigidity of the belt is increased, and therefore, there is a problem that the apparatus becomes larger when a wide pressure nip portion is provided.

  The present invention has been made in order to solve the above-described problems in the belt heating type heat fixing device, and the object of the present invention is to ensure good fixability while ensuring the on-demand property of the fixing device. It is to be.

  The present invention is a heat fixing apparatus characterized by the following constitution as means for achieving the above object.

  (1) A heat-resistant endless belt is brought into close contact with a heating body with a pressure member and slid and conveyed, and heated between the belt and the pressure member in a pressure nip formed by the belt and the pressure member. In the heat fixing device in which the heat of the heating body is applied to the heated material through the belt by introducing the material and causing the pressure nip portion to be nipped and conveyed together with the belt, the pressure in the latter half of the pressure nip portion The heating fixing device is characterized in that the average value of is higher than the average value of the pressure in the first half.

  (2) A heat-resistant endless belt is brought into close contact with a heating member with a pressure member and slid and conveyed, and heated between the belt and the pressure member in a pressure nip formed by the belt and the pressure member. In the heat fixing device in which the heat of the heating body is applied to the heated material through the belt by introducing the material and causing the pressure nip portion to be nipped and conveyed together with the belt, in the pressure direction of the pressure member On the other hand, a heating fixing device characterized in that the vertical direction of the belt contact side surface of the heating body has an inclination.

  (3) The heat fixing apparatus according to any one of (1) to (2), wherein the belt contact surface of the heating body is closer to the pressure member on the downstream side than the upstream side in the conveyance direction of the heated material.

  (4) The angle formed by the perpendicular direction of the belt contact surface of the thermal body and the pressure direction of the pressure member is 0.5 degrees or more and less than 20 degrees, (1) to (3), Heat fixing device.

  (5) The heating according to any one of (1) to (4), characterized in that the downstream end of the heating body in the conveying direction of the heated material is in the pressure nip, and the upstream end is outside the pressure nip. Fixing device.

  (6) The heat-fixing apparatus according to any one of (1) to (5), wherein the heat-resistant belt has at least a metal layer.

  According to the present invention, the pressure distribution in the pressure nip can be controlled by adjusting the angle of the belt contact side surface of the heating body, and the pressure average value in the latter half is higher than that in the first nip. In addition, it is possible to provide a belt-heating-type heat fixing device that ensures sufficient fixing performance even under high speed conditions.

It is a cross-sectional schematic diagram of the example of the heat fixing apparatus of this invention. It is a cross-sectional schematic diagram around the heating body in this invention. It is a cross-sectional schematic diagram of an example of a heating type fixing device.

  Hereinafter, the present invention will be described in detail.

  Since the vertical direction of the belt contact side of the heating element is inclined with respect to the pressure direction of the pressure roller, the pressure distribution in the pressure nip can be controlled. As a result, sufficient fixing performance can be achieved even when the residence time in the nip is short. Can be secured.

  FIG. 1 is a schematic cross-sectional view of an example of a heat fixing apparatus according to the present invention. The vertical direction of the belt contact side surface of the heating element is adjusted to a desired angle depending on the shape of the support member and the shape of the heating element itself, and a load is applied between the support member supporting the heating element and the shaft of the pressure roller. In this case, the pressure average value on the upstream side in the conveyance direction of the heated material inside the nip formed by the contact between the belt and the pressure roller is different from the pressure average value on the downstream side.

  The pressure average value was measured in a stationary state using a “roller pressure measurement system” manufactured by Nitta Corporation. The pressure value calculation method employs the average of the upstream pressure value and the average of the downstream pressure value excluding the center point when there are an odd number of measurement points in the heated material conveyance direction in the pressure nip. When the number of measurement points is an even number, the average value on the upstream side and the average value on the downstream side are taken, and the average value of 10 measurements is calculated to obtain the pressure average value. The pressure distribution can also be predicted and calculated by static stress analysis using a finite element method or the like.

  The angle of the heating body with respect to the load direction perpendicular to the belt contact surface is set to 0.5 ° or more from the viewpoint of fixability. On the other hand, it is preferably less than 20 degrees from the viewpoint of the heating element strength and belt strength, and practically less than 15 degrees is preferred from the viewpoint of sliding resistance.

  While the heated material carrying the toner passes through the first half of the pressure nip, it is in a relatively low pressure state, and the heat supplied from the belt is applied to the toner and the heated material, so the solid toner melts. And changes to a semi-liquid state. The toner melted in this manner is further conveyed through the pressure nip and enters the latter half of the high pressure, where it is pushed into the material to be heated and fixed.

  In addition to the heating member, the heating and fixing device is provided with a belt that slides on the heating member and presses the developer onto the material to be heated. However, the heat conductivity of the belt can be improved and the fixing device can be started up. A laminated belt having at least a metal layer is desirable from the viewpoint of speed (ensuring on-demand performance).

  The heating element 1 formed by forming a heating element with Ag / Pd (silver palladium) in the longitudinal direction of the aluminum nitride sintered body having a width of 12.3 mm and providing a thin glass coat on the surface is used as the load direction of the pressure member. The substrate was bonded to the support member at an angle of 5 degrees. Further, a belt 1 for a heat fixing device was prepared by providing a fluororesin release layer on a belt base layer mainly composed of polyimide (thickness 50 μm, belt inner diameter 24 mm). The belt 1 is externally fitted to a support member, both ends of the pressure member are pressed toward the center of the heating body with a total pressure of 120 N, and the pressure in the pressure nip is measured. The pressure average value on the upstream side in the transport direction was 52 KPa, whereas the pressure average value on the second half (downstream side) was 64 KPa, and the pressure value in the second half could be set higher. A state in the vicinity of the nip portion is shown in FIG. In this state, the pressure roller is rotated at a speed of 150 mm / sec. At the same time, power (900 W) is applied to the heating body, and the temperature of the temperature detection element on the back surface of the heating body is controlled so as not to exceed 230 ° C. When the temperature reached 180 ° C., the paper on which an unfixed image of black toner was formed was passed through, and the fixability of the toner fixed image discharged from the downstream side was evaluated. The evaluation of the fixing property was judged by rubbing the transfer paper a predetermined number of times with a predetermined load, and the density decrease at that time. In this example, a practically sufficient level (◯) of fixability was exhibited. In this example, the time required to reach the fixing temperature (start-up time) was 9.3 seconds, which was a practically sufficient level (◯). The results are shown in Table 1.

  In the longitudinal direction of the aluminum nitride sintered body having a width of 9.6 mm, a heating element is formed in the same manner as in Example 1 and a glass coat layer is provided to prepare a heating element 2. As shown in FIG. The heating element was arranged so that the downstream side was in the nip, and similarly, an angle of 5 degrees was provided and adhered to the support member. The belt 1 was externally fitted and pressurized with 12 kgf in the same manner as in Example 1, and the pressure was measured. As a result, the average value of the pressure in the first half was 52 KPa, and the pressure average value in the second half was 78 KPa. Therefore, as in Example 1, the fixing property of the toner fixed image discharged from the downstream side was evaluated by passing paper on which an unfixed image of black toner was formed. As a result, the fixability was better than that in Example 1, and was particularly good (◎). The startup time was 9.5 seconds, which was a practically sufficient level (◯) as in Example 1. The results are shown in Table 1.

  A belt 2 for a heat fixing device was prepared by providing a fluororesin release layer on a metal base layer (thickness 30 μm, inner diameter 24 mm) mainly composed of nickel (Ni) formed into a cylindrical shape by electroforming. When the pressure was measured under the same conditions as in Example 2, the average value of the pressure in the first half was 54 KPa, and the pressure average value in the second half was 82 KPa. In this example as well, the fixing property was evaluated in the same manner. The startup time was 6.8 seconds, which was a particularly good level (◎). The results are shown in Table 1.

[Comparative Example 1]
The heating element 1 used in Example 1 was bonded without being inclined with respect to the load direction of the pressure member, and the belt 1 was externally fitted and pressed (FIG. 2-c). When the pressure was measured, the average value of the pressure in the first half and the average value of the pressure in the second half were almost equal, and both were 57 KPa. The start-up time was 9.6 seconds, and a practically sufficient level (○) was secured. However, when the fixability was evaluated under the same conditions as in Example 1, the density was drastically lowered and practically impossible (×). It was. The results are shown in Table 1.

DESCRIPTION OF SYMBOLS 1 Belt 2 Heating body 3 Support member 4 Pressure roller 5 Heated material (recording material)
6 Unfixed toner image 7 Pressure nip 8 Temperature detector

Claims (6)

A heat-resistant endless belt is brought into close contact with a heated body with a pressure member and slid and conveyed, and a material to be heated is introduced between the belt and the pressure member in a pressure nip formed by the belt and the pressure member. In the heating and fixing apparatus in which the heat of the heating body is applied to the material to be heated via the belt by nipping and conveying the pressure nip portion together with the belt,
A heating and fixing apparatus, wherein an average value of pressure in the latter half in the press nip is higher than an average value of pressure in the first half. A heat-resistant endless belt is brought into close contact with a heated body with a pressure member and slid and conveyed, and a material to be heated is introduced between the belt and the pressure member in a pressure nip formed by the belt and the pressure member. In the heating and fixing apparatus in which the heat of the heating body is applied to the material to be heated via the belt by nipping and conveying the pressure nip portion together with the belt,
A heating and fixing apparatus, wherein a vertical direction of a belt contact side surface of a heating body is inclined with respect to a pressure direction of the pressure member.   3. The heat fixing apparatus according to claim 1, wherein the belt contact surface of the heating body is closer to the pressure member on the downstream side than the upstream side in the conveyance direction of the heated material.   The heat fixing apparatus according to claim 1, wherein an angle formed by a direction perpendicular to a belt contact surface of the heat body and a pressure direction of the pressure member is 0.5 degrees or more and less than 20 degrees.   5. The heat fixing apparatus according to claim 1, wherein a downstream end portion of the heating member in a conveyance direction of the heated material is in the press nip portion and an upstream end portion is outside the press nip portion.   6. The heat fixing device according to claim 1, wherein the heat resistant belt has at least a metal layer.

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