JP2010107914A - Image heating device, gloss increasing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image heating device which is wide in selection width of glossiness, prevents the occurrence of curl and does not require a separation means such as a separation pawl. <P>SOLUTION: In the image heating device thermally fixing an unfixed toner image on recording material by passing through a nip part, a heating member includes a first heating member that is a flexible belt type member 13 equipped with a heating source inside and pressured and heated by a flat surface from an inner surface, and a second heating member 30 that is a heat roller, wherein a pressure member includes a first pressure member 20 forming a fixing nip Nh with the first heating member 10, and a second pressure member 40 forming a heating nip Ng with the second heating member 30. The heating nip Ng is formed to have recessed shape in an opposite direction to an image forming surface of the recording material, and pressure force in unit area of the heating nip Ng of the second heating member 30 with the second pressure member 40 is made higher than pressure force per unit area of the fixing nip Nh of the first heating member 10 with the first pressure member 20. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is mounted on an image forming apparatus such as a printer, a copying machine, or a facsimile using an electrophotographic technique or an electrostatic recording technique, and is preferably used as a heat fixing apparatus for fixing an unfixed image on a recording material. The present invention relates to a heating device and an image forming apparatus using such an image heating device. The image heating apparatus can also be suitably used as a gloss increasing apparatus that increases the glossiness of an image by heating the image fixed on the recording material.

  An image forming apparatus such as a copying machine using an electrophotographic process includes an image heating device that heats an image (unfixed developer image) formed on a sheet (recording material) by a transfer method or a direct method.

  In recent years, as this image heating apparatus, an apparatus provided with a plurality of image heating means has been increasing along with the speeding up of paper passing and the improvement in image quality (for example, see Patent Documents 1, 2, and 3).

  This is because a plurality of image heating means having an image heating body for heating an image in contact with a recording material carrying an unfixed image is arranged along the recording material conveyance direction, and the recording material is arranged with the plurality of image heating means. The image is heated by sequentially passing.

  A characteristic of the apparatus having a plurality of image heating means is that the recording material carrying an unfixed image is passed once through the first image heating means on the most upstream side in the recording material conveyance direction, and the image is heated and fixed. The image is further reheated by passing the image through a second image heating means on the downstream side. In general, the first image heating means often secures a certain degree of fixability, and the second image heating means often aims for high image quality (high gloss). In particular, the glossiness (gross) of the image is greatly influenced by the second image heating unit on the downstream side in the recording material conveyance direction.

  Further, when both the first and second image heating means are of the heat roller type (see, for example, Patent Documents 1 and 2), in order to improve the separability when fixing the toner image on the recording material, It is effective to provide a separation member on the image heating body.

  By the way, when the separation claw is brought into contact with the image heating body, the separation can be remarkably improved. However, there is a problem of damaging the surface of the image heating body. Further, although the scratches can be reduced by reciprocating the separating claw to be brought into contact, the surface properties of the heating roller are changed depending on the endurance by rubbing the separating claw and the image surface, thereby causing uneven gloss. Therefore, the provision of the separation claw has the advantage of improving the separation property and the disadvantage of uneven gloss.

Also, as the first image heating means, a method is proposed in which the heat of the ceramic heater is applied to the first fixing nip portion from the inner surface of a flexible thin film, and the second image heating means is a heat roller system. (For example, see the second embodiment of Patent Document 3).
JP-A-6-258970 JP 2005-292567 A JP 2002-365967 A

  However, when the heat roller type image heating means is used for the first and second image heating means, there are the following disadvantages.

  For example, the time from when the main power supply of the image forming apparatus is turned on until the entire heat roller can be fixed by a halogen lamp or the like as a heating source contained in the cylindrical heat roller (hereinafter referred to as “ "Warm-up time") is long. In order to form a wide fixing nip portion, it is necessary to increase the outer diameter of each heat roller pair or to increase the thickness of the elastic layer, and the warm-up time may be several minutes.

  In particular, when the first image heating unit is a heat roller system, an appropriate nip width is required to ensure a certain degree of fixing without causing problems such as low temperature offset in the first image heating unit. To do.

  However, in the case of a heat roller, in order to secure a necessary nip width, the outer diameter of the heat roller must be kept large to a certain extent, a relatively thick elastic layer is required, and the applied pressure must be increased. As a result, in an image forming apparatus having a high recording material conveyance speed, the warm-up time of the first image heating means generally takes a long time.

  Further, the applied pressure per unit area in the fixing nip portion (hereinafter referred to as “linear pressure”) increases, and the glossiness of the image is increased to some extent by the first image heating means. Generally, the higher the linear pressure, the higher the glossiness. Therefore, the lower limit value of the glossiness is determined by the first image heating means, and the selection range of the glossiness that can be changed by the second image heating means is narrowed.

  In general, the second image heating unit has a great influence on the image on the recording material. When the surface of the heat roller in contact with the image surface of the second image heating unit is smooth, the glossiness tends to increase.

  Therefore, it is possible to some extent to adjust the smoothness of the surface of the heat roller in contact with the image surface on the recording material in the first and second image heating means. However, the surface property of the surface of the heat roller is closely related to the separation performance at the time of discharging from the fixing nip portion, and it is difficult to simultaneously achieve the improvement of the separation performance and the selection range of the glossiness. It was. Therefore, it is common to take a configuration that facilitates forcible separation with a separation claw, etc., but the surface of the heat roller is likely to be damaged by the separation claw, gloss unevenness is likely to occur, and the durability performance is extended. There were also issues such as difficulties.

  Also, when considering the pressure load on the recording material at the fixing nip portion of the first and second image heating means, the recording material in each image heating means is in a direction perpendicular to the conveying direction (whichever is sandwiched) In the circumferential direction of the roller, a load that is bent with heat and strong pressure is applied. As a result, the discharged recording material is easily deformed (hereinafter referred to as “curl”). This state will be described with reference to FIGS. 9A and 9B.

  FIG. 9A shows the case where the hardness of the pressure roller 70 is greater than the hardness of the fixing roller 60 in contact with the toner image T on the recording material P (the heating nip has a deformation of rubber on the fixing roller side). In the case of a large concave state). In this case, the recording material P is bent in the direction opposite to the printing surface of the toner image T in the direction perpendicular to the conveying direction by heat and pressure in the fixing nip portion.

  On the other hand, as shown in FIG. 9B, when the relationship between the hardnesses of the fixing roller 60 and the pressure roller 70 is reversed (when the elastic layer of the pressure roller is greatly deformed), The toner image T is discharged from the fixing nip while being bent toward the print surface side.

  Generally, there is a paper manufacturing direction as a paper manufacturing condition. However, in general, apart from the size of the curl, regardless of the fiber direction of the paper (the direction in which the paper fibers are easily arranged when paper is made and the same direction as the paper making direction), Depending on the shape, it is wound around the circumferential direction of one of the rollers of the heat roller pair and discharged without permission.

  Further, the fibers of the recording material forcibly bent by the first image heating means are weakened due to microscopic cutting of the fibers, and the recording material discharged from the first image heating means is It becomes easy to deform by external force. Therefore, the curl of the recording material is easily formed by the second image heating unit.

  By selecting the hardness of the elastic layer of the fixing roller and the pressure roller for the curl, it is possible to make the fixing nip portion substantially flat. However, it is difficult to keep the fixing nip portion flat through variations in hardness during manufacture and changes in hardness through durability. Further, in the case of the heat roller system that requires a high pressure as described above, the load on the recording material in the fixing nip portion becomes large due to some hardness difference between the upper and lower heat rollers. In addition, since the applied pressure is large, defects such as paper wrinkles are easily generated as deformations other than curling, and there are many restrictions such as the need to provide a reverse crown shape to the heat roller.

  From the above, when both the first and second image heating means are of the heat roller type, the selection range of the configuration is narrowed. Therefore, when the speed of the image forming apparatus is increased, the entire apparatus must be enlarged, for example, using a large-diameter heat roller, and the separation claws must be provided in both image heating means.

  On the other hand, the method in which the first image heating means is used as the image heating means for heating with a ceramic heater having a flat sliding surface from the inner surface of the flexible film-like heating member has the following advantages. .

  In other words, the warm-up time can be greatly reduced due to the low heat capacity, the formation of a flat fixing nip with the pressure member can be achieved without increasing the size of the apparatus and without increasing the linear pressure with the pressure member so much. There are advantages.

  However, on the other hand, it has been found that deformation at the fixing nip portion depending on the fiber direction of the recording material is likely to occur.

  That is, as shown in FIG. 7, even in the flat fixing nip portion Nh, the recording material P is deformed by evaporation of water contained in the recording material P in order to heat the recording material P in the fixing nip portion. Happens.

  FIG. 7 is an enlarged view of a fixing nip portion of a film heating system, and includes a heater 80 and a fixing film 85 as fixing members. In the figure, the heater 80 is formed with an energization heating resistance layer 82 and a sliding layer 83 formed on one side of a ceramic substrate 81 and is held by a heater holding member 84.

  By introducing a flexible thin fixing film 85 into the fixing nip portion Nh and applying pressure between the heater 80 and the pressure roller 90, the elastic layer 91 of the pressure roller 90 is deformed. A fixing nip portion Nh is formed.

  Heat fixing is performed by introducing the recording material P on which the toner image T is formed in the fixing nip portion Nh. Generally, the fixing film 85 is substantially horizontal in the upstream and downstream regions of the fixing nip portion Nh. Drive to.

  On the other hand, the pressure roller surface rotates in a direction away from the fixing nip portion on the downstream side of the fixing nip portion Nh. The recording material P is nipped and conveyed by the fixing film 85 and the pressure roller 90 in the fixing nip portion Nh, but is not restrained downstream of the fixing nip portion Nh. Therefore, the recording material P can be deformed only in the direction of the arrow.

  As a result, as shown in FIG. 8A, for example, when the conveyance direction of the recording material P and the fiber direction are the same, deformation due to the shrinkage of the recording material in the direction perpendicular to the fiber direction occurs. Deformation occurs in the direction opposite to the surface in a direction perpendicular to the fiber direction of the recording material P (hereinafter referred to as “vertical curl”). This is because contraction in the width direction of the fibers occurs when moisture evaporates from the fibers of the recording material. Further, when the conveyance direction of the recording material P and the fiber direction are orthogonal to each other, as shown in FIG. 8B, deformation occurs in a direction in which the pressure roller 90 is wound in the circumferential direction (hereinafter, “horizontal”). "Curl".)

  Therefore, when the first image heating means is a film heating method, at least the fixing member on the image forming surface side of the first image heating means does not require a means such as a separation claw as a recording material separation means. On the other hand, curling occurred due to shrinkage of paper fibers.

  Further, the second image heating unit disposed on the downstream side of the first image heating unit serves to control the glossiness of the toner image on the recording material. However, depending on the settings of the outer diameter, heat capacity, nip width, and linear pressure of the fixing roller and pressure roller of the second image heating unit, the recording material can be wound around the fixing roller or pressure roller of the second image heating unit. A separation claw is required to prevent sticking. Also, it takes time to warm up. Further, the curl generated by the first image heating means may be promoted or deteriorated.

  As a result, the recording material discharged from the second image heating unit has a complicated structure, such as having a deformation correction unit such as a curl removing unit before the recording material is discharged to the outside of the image forming apparatus, and the size of the image forming apparatus is increased. Was forced to result.

  Further, the film type image heating means does not include the second image heating means, and a protrusion in the direction of the fixing nip portion of the heater holding member is provided so that a pressure peak is generated downstream in the fixing nip. Have been put to practical use. However, in these cases, the glossiness is generally high, but it is difficult to control the glossiness widely, and a load is applied to the traveling film, so that a highly durable film type image heating apparatus is provided. Has become difficult. In addition, the effect of the pressure method downstream of the fixing nip on the curling of the recording material is large, and it has been difficult to suppress the occurrence of curling on all types of recording materials.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image heating apparatus, an image forming apparatus, and a gloss increase which have a wide selection range of glossiness of a toner image on a recording material, prevent curling, and do not require a separation means such as a separation claw Is to provide a device.

  Another object of the present invention is that the first and second image heating means each having a heating member and a pressure member can form a toner image on a recording material in a wide range of glossiness, and a warm-up time. An object of the present invention is to provide an image heating apparatus, an image forming apparatus, and a gloss increasing apparatus that have a short time, can effectively remove curling of the recording material, and are excellent in separation between the recording material and the image heating means.

The above object is achieved by the image heating apparatus, the image forming apparatus, and the gloss increasing apparatus according to the present invention. In summary, according to the first aspect of the present invention, an unfixed toner image on a recording material is heated as a fixed image on the recording material by passing through a nip formed by a heating member and a pressure member. In an image heating apparatus for fixing,
The heating member includes a first heating member that is a flexible belt-like member that includes a heating source therein and is pressurized and heated on a surface flatter than an inner surface, and a second heating member that is a heat roller. With
The pressure member includes a first pressure member that forms a fixing nip portion with the first heating member, and a second pressure member that forms a heating nip portion with the second heating member. ,
The heating nip portion has a heating nip shape having a concave shape in a direction opposite to the image forming surface of the recording material,
The heating nip portion of the second heating member with respect to the second pressure member is applied to the pressing force per unit area of the fixing nip portion with respect to the first pressure member of the first heating member. The applied pressure per unit area can be increased.
An image heating apparatus is provided.

According to a second aspect of the present invention, in an image forming apparatus comprising: an image forming unit that forms an unfixed toner image on a recording material; and a fixing device that thermally fixes the unfixed toner image on the recording material.
An image forming apparatus is provided in which the fixing device is an image heating device having the above-described configuration.

According to the third aspect of the present invention, in the gloss increasing device that increases the glossiness of the image by heating the image fixed on the recording material with the image heating device,
A gloss increasing device is provided, wherein the image heating device is an image heating device configured as described above.

  According to the present invention, an image heating apparatus and an image forming apparatus that have a wide selection range of glossiness of a toner image on a recording material, prevent occurrence of curling, and do not require a separation unit such as a separation claw, and gloss increase An apparatus can be provided. In particular, the first and second image heating means each having a heating member and a pressure member can form the glossiness of the toner image on the recording material in a wide range, and the warm-up time is short, and the recording material Can be effectively removed. In addition, it is possible to provide an image heating apparatus, an image forming apparatus, and a gloss increasing apparatus that are excellent in separation between the recording material and the image heating means.

  Hereinafter, the image heating apparatus, the image forming apparatus, and the gloss increasing apparatus according to the present invention will be described in more detail with reference to the drawings.

Example 1
Exemplary embodiments of the present invention will be described below in detail with reference to the drawings. However, the configuration, dimensions, material, shape, and relative arrangement of the image forming apparatus until the recording material is supplied to the image heating apparatus described in this embodiment are the configuration of the apparatus to which the present invention is applied and various types. It should be changed appropriately according to conditions. It is not intended to limit the scope of the present invention to the following examples.

(1) Overall Configuration of Image Forming Apparatus FIG. 1 shows a schematic configuration of a color image forming apparatus which is an embodiment of an image forming apparatus according to the present invention. In this embodiment, the color image forming apparatus is an electrophotographic tandem type full color printer.

  The image forming apparatus 100 of the present embodiment includes four image forming units (image forming units) 1 (1Y, 1M, 1C, 1Bk), and these four image forming units 1Y, 1M, 1C, 1Bk are They are arranged in a line at regular intervals. That is, in this embodiment, the image forming unit includes an image forming unit 1Y that forms a yellow image, an image forming unit 1M that forms a magenta image, and an image forming unit 1C that forms a cyan image. And an image forming unit 1Bk that forms a black image.

  Photosensitive drums 2a, 2b, 2c, and 2d are installed in the image forming units 1Y, 1M, 1C, and 1Bk, respectively. Around each photosensitive drum 2a, 2b, 2c, 2d, charging rollers 3a, 3b, 3c, 3d, developing devices 4a, 4b, 4c, 4d, transfer rollers 5a, 5b, 5c, 5d, drum cleaning device 6a, 6b, 6c and 6d are respectively installed. Exposure devices 7a, 7b, 7c, and 7d are installed above the charging rollers 3a, 3b, 3c, and 3d and the developing devices 4a, 4b, 4c, and 4d, respectively. Each developing device 4a, 4b, 4c, 4d contains yellow toner, magenta toner, cyan toner, and black toner, respectively.

  An endless belt-like intermediate transfer member 50 as a transfer medium is in contact with each primary transfer portion N of each of the photosensitive drums 2a, 2b, 2c, and 2d of the image forming portions 1Y, 1M, 1C, and 1Bk. The intermediate transfer belt 50 is stretched between a drive roller 51, a support roller 52, and a secondary transfer counter roller 53, and is rotated (moved) in the arrow direction (clockwise) by the drive of the drive roller 51.

  The transfer rollers 5a, 5b, 5c, and 5d for primary transfer are in contact with the photosensitive drums 2a, 2b, 2c, and 2d via the intermediate transfer belt 50 at the primary transfer nip portions N, respectively.

  The secondary transfer counter roller 53 is in contact with the secondary transfer roller 54 via the intermediate transfer belt 50 to form a secondary transfer portion M. The secondary transfer roller 54 is installed so as to be able to contact and separate from the intermediate transfer belt 50.

  A belt cleaning device 55 that removes and collects transfer residual toner remaining on the surface of the intermediate transfer belt 50 is installed in the vicinity of the driving roller 51 outside the intermediate transfer belt 50.

  An image heating device 200 is installed on the downstream side of the secondary transfer portion M in the conveyance direction of the recording material P. The image heating device 200 will be described in detail later.

  In addition, an environmental sensor 57 and a media sensor 58 are installed in the image forming apparatus 200.

  When the image forming operation start signal is issued, the photosensitive drums 2a, 2b, 2c, and 2d of the image forming units 1Y, 1M, 1C, and 1Bk that are rotationally driven at a predetermined process speed are respectively charged with the charging rollers 3a, 3b, and 3c. 3d is uniformly charged to negative polarity in this embodiment.

  Then, the exposure devices 7a, 7b, 7c, and 7d respectively convert the input color-separated image signals into optical signals at a laser output unit (not shown), and convert the laser light that is the converted optical signal. Scanning exposure is performed on each of the charged photosensitive drums 2a, 2b, 2c, and 2d. Thereby, an electrostatic latent image is formed on each of the photosensitive drums 2a, 2b, 2c, and 2d.

  Next, first, yellow toner is applied to the surface of the photoreceptor by the developing device 4a in which a developing bias having the same polarity as the charging polarity (negative polarity) of the photosensitive drum 2a is applied onto the photosensitive drum 2a on which the electrostatic latent image is formed. The electrostatic latent image is visualized by electrostatic attraction according to the charging potential, and a developed image is obtained. This yellow toner image is primarily transferred onto the rotating intermediate transfer belt 50 by a transfer roller 5a to which a primary transfer bias (a polarity opposite to that of toner (positive polarity)) is applied at the primary transfer portion N. Is done. The intermediate transfer belt 50 to which the yellow toner image is transferred is rotated toward the image forming unit 1M.

  Also in the image forming unit 1M, the magenta toner image formed on the photosensitive drum 2b in the same manner as described above is superimposed and transferred onto the yellow toner image on the intermediate transfer belt 50 by the primary transfer unit N. The

  In the same manner, cyan and black toner images formed by the photosensitive drums 2c and 2d of the image forming units 1C and 1Bk on the yellow and magenta toner images superimposed and transferred onto the intermediate transfer belt 50 in the same manner are respectively used as the primary. The images are sequentially overlapped at the transfer portion N. As a result, a full-color toner image is formed on the intermediate transfer belt 50.

  Then, the recording material (transfer material) P is conveyed to the secondary transfer portion M by the registration roller 56 in accordance with the timing at which the front end of the full color toner image on the intermediate transfer belt 50 is moved to the secondary transfer portion M. A full-color toner image is secondarily transferred collectively to the recording material P by a secondary transfer roller 54 to which a secondary transfer bias (opposite polarity (positive polarity) with respect to toner) is applied.

  The recording material P on which a full-color toner image is formed is conveyed to a fixing device 200 that is an image heating device. In this embodiment, the fixing device 200 includes a first image heating unit (first image heating device) 200A and a second image heating unit (second image heating device) 200B. The first image heating device 200A includes a first heating member (that is, a fixing member) 10 and a first pressure member 20, and the second image heating device 200B includes a second heating member (that is, a fixing member). A fixing member 30 and a second pressure member 40.

  The full-color toner image of the recording material P is heated and pressed at the fixing nip portions of the first and second image heating devices 200A and 200B to be melted and fixed on the surface of the recording material P, and then discharged to the outside for image formation. It becomes an output image of the apparatus 100. Then, a series of image forming operations is completed.

  The image forming apparatus 100 includes an environmental sensor 57, and charging, developing, primary transfer, secondary transfer bias and fixing conditions are in accordance with the atmospheric environment (temperature, humidity) in the image forming apparatus. Can be changed. The environmental sensor 57 is used for adjusting the density of the toner image formed on the recording material P and for achieving optimum transfer and fixing conditions.

  Further, the image forming apparatus 100 includes a media sensor 57, and by determining the recording material P, the transfer bias and the fixing conditions can be changed according to the recording material. Used to achieve optimum transfer and fixing conditions for P.

  During the primary transfer described above, the primary transfer residual toner remaining on the photosensitive drums 2a, 2b, 2c, and 2d is removed and collected by the drum cleaning devices 6a, 6b, 6c, and 6d. Further, the secondary transfer residual toner remaining on the intermediate transfer belt 50 after the secondary transfer is removed and collected by the belt cleaning device 55.

(2) Image Heating Device FIGS. 2 to 4 show an embodiment of the image heating device according to the present invention. As described above, in this embodiment, the image heating apparatus is the fixing apparatus 200 that thermally fixes the unfixed toner image transferred to the recording material to the recording material.

  FIG. 2 is a schematic cross-sectional view of the fixing device 200 of the present embodiment, and FIGS. 3 and 4 illustrate the first image heating device 200A and the second image heating device 200B that constitute the fixing device 200, respectively. It is a figure which shows a longitudinal direction schematic structure.

  The fixing device 200 according to the present exemplary embodiment includes a first image heating device 200A of a fixing belt heating method and a pressure rotating body driving method (tensionless type), and a second image heating composed of a fixing roller and a pressure roller. Device 200B. These first and second two image heating devices 200A and 200B have a permuted device configuration.

  As described above, in the present embodiment, the first image heating apparatus 200A includes the first fixing member 10 and the first pressure member 20, and the second image heating apparatus 200B includes the second fixing member. A member 30 and a second pressure member 40 are provided.

(Overall configuration of first image heating apparatus 200A)
2 and 3, the first fixing member 10 in the first image heating apparatus 200A includes a fixing belt 13. The fixing belt 13 has an elastic layer on a heat-resistant belt-like member having flexibility. A cylindrical (endless belt-shaped) member provided. The fixing belt 13 will be described in detail later.

  The first image heating apparatus 200A is further provided with a heater holder 14 having a substantially semicircular arc-shaped saddle-like cross section as a heating body holding member, and a lower surface of the heater holder 14 along the length of the holder. And a fixing heater 11 as a heating body (heating source). The fixing belt 13 is loosely fitted on the heater holder 14. The fixing heater 11 is a ceramic heater as will be described in detail later.

  The heater holder 14 and end flanges 15 disposed at both ends in the longitudinal direction are formed of liquid crystal polymer resin, phenol resin, PPS or the like having high heat resistance, and serve to hold the fixing heater 11 and guide the fixing belt 13. In this example, DuPont Zenite 7755 (trade name) was used as the liquid crystal polymer. The maximum usable temperature of Zenite 7755 is about 270 ° C.

  The pressure member 20 in the first image heating apparatus 200A is a pressure roller. The pressure roller 20 is formed by forming a silicone rubber layer 22 having a thickness of about 3 mm on a cored bar 21 made of aluminum, stainless steel, or SUM (grinding steel) by injection molding. The layer 23 is formed by covering a PFA resin tube having a thickness of about 50 μm.

  The pressure roller 20 is arranged such that both ends of the cored bar 21 are rotatably held by bearings 24 between the back and front side plates of the apparatus frame (not shown). A rotation drive gear 25 is attached to the end of the pressure roller 20 and can rotate at a predetermined rotation speed.

  On the upper side of the pressure roller 20, a fixing belt unit including the fixing heater 11, the heater holder 14, the fixing belt 13, the end flange 15 and the like is arranged in parallel with the pressure roller 20 so that the fixing heater 11 side faces downward. Deploy. Then, end flanges 15 at both ends fitted to the heater holder 14 are urged in the axial direction of the pressure roller 20 with a predetermined pressure by a pressure spring 16 as a pressure mechanism. As a result, the downward surface of the fixing heater 11 is brought into pressure contact with the elastic layer 22 of the pressure roller 20 through the fixing belt 13 against the elasticity of the elastic layer 22 with a predetermined pressing force, and a predetermined width required for heat fixing. The fixing nip portion Nh is formed.

  The fixing nip portion is formed with a width W1 with respect to the longitudinal direction, and among these, the recording material maximum conveyance width L is formed. The pressurization mechanism has a pressure release mechanism, and is configured to release the pressurization and remove the recording material P at the time of jam processing or the like.

  In the first image heating apparatus 200A, a thermistor 12 as a temperature detecting means is arranged. The thermistor 12 as temperature detecting means is disposed in contact with the fixing nip Nh of the fixing heater 11 with a predetermined pressure and is connected to a control circuit unit (CPU) (not shown). The control circuit unit determines the temperature control content of the fixing heater 11 based on the output of the thermistor 12, and controls energization to the fixing heater 11 as a power supply unit (heating means). Alternatively, a method may be used in which the thermistor 12 is elastically brought into contact with the inner surface of the fixing belt 13, the temperature of the inner surface of the fixing belt 13 is detected, and energization to the fixing heater 11 is controlled.

  A fixing inlet guide 101 is disposed as a member for guiding the recording material P on which the unfixed toner image T1 is formed in the fixing nip portion Nh formed by the fixing member 10 and the pressure member 20 in the first image heating apparatus 200A. Has been. As the inlet guide 101, a heat resistant resin such as polyphenylene sulfide (PPS) resin is used.

  The pressure roller 20 is driven to rotate at a predetermined peripheral speed in a counterclockwise direction indicated by an arrow by a driving unit. A rotational force acts on the cylindrical fixing belt 13 by the pressure frictional force at the fixing nip portion Nh between the outer surface of the pressure roller 20 and the fixing belt 13 by the rotational driving of the pressure roller 20. Therefore, the inner surface of the fixing belt 13 is in close contact with the downward surface of the fixing heater 11 and slides around the outer periphery of the heater holder 14 in the clockwise direction indicated by the arrow. Grease is applied to the inner surface of the fixing belt 13 to ensure slidability between the heater holder 14 and the inner surface of the fixing belt 13.

  The pressure roller 20 is rotationally driven, and the cylindrical fixing belt 13 is driven and rotated accordingly. In addition, the fixing heater 11 is energized, and the fixing heater 11 is heated to a predetermined temperature and the temperature is adjusted. In this state, the recording material P carrying the unfixed toner image T1 is guided and introduced along the entrance guide 101 between the fixing belt 13 and the pressure roller 20 in the fixing nip portion Nh.

  At the fixing nip portion Nh, the toner image carrying surface side of the recording material P is brought into close contact with the outer surface of the fixing belt 13 and is nipped and conveyed together with the fixing belt 13 along the fixing nip portion Nh. In this nipping and conveying process, heat of the fixing heater 11 is applied to the recording material P via the fixing belt 13, and the unfixed toner image T1 on the recording material P is heated and pressurized on the recording material P to be melted and fixed. The

  The recording material P that has passed through the fixing nip portion Nh is separated from the fixing belt 13 while keeping the fixed toner image T2, and is conveyed to a heating nip portion of a second image heating apparatus described later.

(Fixing heater 11)
The fixing heater 11 as the heat source uses a ceramic heater in this embodiment. The ceramic heater is made of a pressure-resistant glass after a resistance heating element is formed on a substrate of alumina or aluminum nitride by applying a conductive paste containing silver / palladium alloy into a film of uniform thickness by screen printing. A glass coat is applied.

The fixing heater 11
(1) A horizontally long substrate (alumina or aluminum nitride) whose longitudinal direction is a direction orthogonal to the paper passing direction,
(2) A thickness of 10 μm of a conductive paste containing silver palladium (Ag / Pd) alloy which is applied to one side of the above substrate in a linear or belt shape by screen printing along the length and generates heat when current flows. A resistance heating element layer having a width of about 1 to 5 mm,
(3) As a power supply pattern for the resistance heating element layer, the first and second electrode portions, which are similarly patterned by screen printing of silver paste on one side of the alumina substrate,
(4) A thin glass-coated sliding layer (or about 50 μm thick) that can withstand the rubbing against the fixing belt 13 formed on the resistance heating element layer to ensure protection and insulation. In the case of using a high thermal conductive substrate such as aluminum nitride, a resin sliding layer such as a polyimide layer as a sliding surface formed on the substrate opposite to the resistance heating element layer may be used).
(5) a thermistor 12 provided on the surface opposite to the fixing nip side of the substrate;
Etc.

  The fixing heater 11 is supported by being fixed to the heater holder 14 with its sliding surface exposed downward. A power supply connector (not shown) is attached to the electrode portion of the fixing heater 11. When the power is supplied from the heater drive circuit unit to the electrode unit via the power supply connector, the resistance heating element layer generates heat and the fixing heater 11 is quickly heated. The heater drive circuit unit is controlled by a control circuit unit (CPU).

  In normal use, the rotation of the fixing belt 13 starts as the pressure roller 20 starts rotating, and the temperature of the inner surface of the fixing belt 13 increases as the temperature of the fixing heater 11 increases. The energization of the fixing heater 11 is controlled by PID control, and the input power is controlled so that the temperature of the fixing heater 11 or the inner surface temperature of the fixing belt 13, that is, the temperature detected by the thermistor 12 becomes a predetermined temperature.

  Further, in the fixing nip portion Nh, as shown in FIG. 7 described in the above-described conventional method, the fixing belt 13 travels in contact with the substantially flat heater sliding surface, and the toner image T on the recording material P is transferred. Fix by heating. Note that the fixing nip having a substantially flat surface as described above reduces the load on the fixing belt, which will be described later, and makes it possible to achieve a long life of the fixing belt.

(Fixing belt 13)
In this embodiment, the fixing belt 13 is a cylindrical (endless belt-shaped) member in which an elastic layer is provided on a belt-shaped member. Specifically, as shown in FIG. 6, SUS is used as a material, and a silicone rubber layer (elastic layer) 13b having a thickness of about 300 μm is formed on an endless belt (belt base material) 13a formed in a cylindrical shape having a thickness of 30 μm. Is formed by a ring coat method. Further, a PFA resin tube (outermost surface layer) 13c having a thickness of 20 μm is coated thereon.

When the heat capacity of the fixing belt 13 produced in such a configuration was measured, it was 0.12 J / cm ² · K (2.9 × 10 ⁻² cal / cm ² · ° C., heat capacity per 1 cm ^{2 of} the fixing belt). It was.

  FIG. 6 shows the configuration of each layer of the fixing belt 13 and how the toner image is fixed in the fixing nip portion Nh.

(1) Fixing belt base layer 13a
Polyimide or the like can be used for the base layer 13a of the fixing belt 13, but SUS has a thermal conductivity approximately 10 times larger than polyimide, and higher on-demand characteristics can be obtained. Therefore, in this embodiment, SUS is used for the base layer 13 a of the fixing belt 13.

(2) Elastic layer 13b of the fixing belt
A rubber layer having high thermal conductivity is used for the elastic layer 13 b of the fixing belt 13. This is to obtain higher on-demand characteristics. The material used in this example has a specific heat of about 1.21 J / g · K (2.9 × 10 ⁻¹ cal / g · ° C.).

(3) Releasable layer 13c of fixing belt
By providing a release layer 13c such as a fluororesin layer on the surface of the fixing belt 13, the surface release property is improved, and the toner once adheres to the surface of the fixing belt 13 and moves to the recording material P again. Therefore, the offset phenomenon that occurs can be prevented. In addition, by using a PFA tube as the fluororesin layer on the surface of the fixing belt 13, it is possible to more easily form a fluororesin layer having a uniform and good surface property.

(4) Heat Capacity of Fixing Belt Generally, when the heat capacity of the fixing belt 13 is increased, the temperature rise becomes dull and the on-demand property is impaired. For example, although it depends on the configuration of the fixing device, the heat capacity of the fixing belt 13 is about 0.51 J / cm ² · K (0.123 cal / cm ² ) when it is assumed that there is no standby temperature control and rises within 20 seconds. • ° C) or less.

In this embodiment, when the power is started up in the morning, 700 W of power is supplied to the fixing heater 11 so that the surface of the fixing belt 13 rises from room temperature to 190 ° C. within 20 seconds. The silicone rubber layer 13b is made of a material having a specific heat of about 1.21 J / g · K (2.9 × 10 ⁻¹ cal / g · ° C.). At this time, the thickness of the silicone rubber must be 500 μm or less. I must. The heat capacity of the fixing belt 13 needs to be about 0.19 J / cm ² · K (4.5 × 10 ⁻² cal / cm ² · ° C.) or less. On the other hand, if the pressure is set to 0.042 J / cm ² · K (1.0 × 10 ⁻² cal / cm ² · ° C.) or less, the rubber layer 13 b of the fixing belt 13 becomes extremely thin. Therefore, in terms of image quality such as OHT permeability and gloss unevenness, it becomes equivalent to an on-demand fixing device having no elastic layer.

In this example, the thickness of the silicone rubber necessary for obtaining a high-quality image such as OHT permeability and gloss setting was 180 μm or more. The heat capacity at this time was 0.088 J / cm ² · K (2.1 × 10 ⁻² cal / cm ² · ° C.).

That is, in the configuration of the same fixing device as this embodiment, the heat capacity of the fixing belt 13 0.042J / cm ² · K or more 0.51J / cm ² · K or less is generally subject. Among them, a fixing belt of 0.088 J / cm ² · K or more and 0.19 J / cm ² · K or less that can achieve both on-demand properties and high image quality is used.

  In addition, about specific gravity, measuring apparatuses, such as AUW-SGM series (brand name, Shimadzu Corporation Corp.) and an electronic hydrometer (model number SD-200L, Alpha Mirage Co., Ltd.), can be used. The specific heat can be measured using a measuring device such as DSC6200 (trade name, manufactured by Seiko Instruments Inc.) or a differential scanning calorimeter (model number DSC8240, manufactured by Rigaku Corporation). The heat capacity is obtained from these measurement results.

  The manner of fixing the toner image on the recording material in the fixing nip portion Nh will be described with reference to FIG.

  As described above, since the fixing belt 13 includes the elastic layer 13b, the surface of the fixing belt 13 is elastic in accordance with the level difference of the toner image at the fixing nip portion Nh with respect to the toner image T on the recording material P. It becomes possible to deform. Therefore, there is an effect of enveloping the toner image T1, and uniform fixing performance is achieved. For this reason, the hardness of the elastic layer 13b of the fixing belt 13 is closely related to the fixing uniformity. 1 to 50 in terms of hardness (hereinafter referred to as “ASKER-C hardness”) measured using an ASKER-C type hardness meter (trade name, manufactured by Kobunshi Keiki Co., Ltd.) according to JIS K7312 and SRIS0101 standards. The one at a time is preferred. By setting the ASKER-C hardness of the elastic layer within this range, the elastic layer of the heat fixing member can easily follow the unevenness of the recording material and the toner image, and sufficient image uniformity can be ensured. In addition, in the sample which cannot ensure sufficient thickness for measuring ASKER-C hardness, it measures by cutting out only an elastic layer and measuring several sheets.

  The above is the details of the overall configuration of the first image heating apparatus and the configuration of the main part. Depending on the speed of the image forming apparatus and the type of toner, each configuration is appropriately selected in shape and material. , Not uniquely determined. However, the outer diameter of the fixing belt 13 is set to a diameter of about 16 to 30 mm, the ASKER-C hardness of the elastic layer 13 b is about 15 to 30 degrees, the thickness is 180 to 350 μm, and the thickness of the PFA tube 13 c is about 12 to 35 μm. Further, the fixing heater 11 has a substrate width of about 6 to 13 mm and a fixing nip width Nh of about 5 to 10 mm to ensure the fixing performance, the size of the image heating apparatus, the conveyance stability of the recording material, and the separation. From the viewpoint of property, it is a good range.

  Further, the outer diameter of the pressure roller as the pressure member 20 is in an appropriate range from the viewpoint of the heat capacity that a diameter of about 20 to 30 mm ensures on-demand characteristics. Further, the ASKER-C hardness of the elastic rubber alone is 15 to 40 °, and the hardness of about 45 to 65 ° after the release layer coating is a good range from the viewpoint of securing the nip width Nh and the recording material transportability.

  Further, when the first various image heating devices 200A are configured within the above range and toner images on various recording materials P are heated and fixed, the recording material P discharged from the fixing nip portion Nh is shown in FIG. Curled deformation as in a) and (b) occurred. These curls are generated when the moisture contained in the fibers in the recording material P evaporates as described above. Therefore, there is a large correlation with the amount of heat that the recording material P receives at the fixing nip portion Nh. . Further, no great damage (fiber breakage as seen with a heat roller) was observed on the fibers of the recording material P itself.

(Overall configuration of second image heating apparatus 200B)
With reference to FIG.2 and FIG.4, the 2nd image heating apparatus 200B which concerns on a present Example is demonstrated.

  In the present embodiment, the second image heating apparatus 200 </ b> B includes a fixing member 30 and a pressure member 40. A second heating nip portion Ng is formed by the respective members 30 and 40 so that the toner image on the recording material can be heated.

  The fixing member 30 of the second image heating apparatus 200B is a hollow fixing roller, and a halogen heater 31 is disposed inside the hollow fixing roller 30 as a heating source for heating from the inside of the roller. The halogen heater 31 is a heating source having a rating of about 350 W to 600 W. In addition, the halogen heater 31 emits tungsten by supplying power to the power supply electrode 31b connected to the outside from the sealing portions 31a at both ends, and generates radiant heat.

  The fixing roller 30 is a SUM material having a diameter of 8 to 16 mm or a metal sleeve such as stainless steel to ensure on-demand property and separability of the recording material, and is formed to be as thin as 0.4 to 1.0 mm. The hollow cored bar 31 is formed. Further, in order to increase the strength, a cylindrical body in which a nitrogen diffusion layer by soft nitriding treatment is formed in the entire thickness direction, or a rib for strength up may be formed inside. Black coating (material Okitsumo 8000; made by Mitsui Yuka Co., Ltd.) is applied to the inner surface as a hatching process to increase the radiation heater's radiant heat absorption efficiency.

  A fluororesin layer having a thickness of about 10 to 30 μm is formed as the releasable layer 32 a on the outermost surface of the cored bar 32 constituting the fixing roller 30. Examples of the fluororesin layer include polytetrafluoroethylene resin (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA), fluorinated ethylene polypropylene copolymer resin (FEP), and polyvinylidene fluoride resin (PVDF). ) And polyvinyl fluoride resin (PVF).

  Moreover, a member having high thermal conductivity may be added to the above material to form a release layer having high thermal conductivity. For example, as one method, a layer in which 10 vol% to 50 vol% of a fibrous or flaky high thermal conductive filler made of a material having a thermal conductivity of at least 10.0 W / m · K or more is mixed in PFA has a thickness of 10 to 30 μm. Form with. However, the surface of the fixing roller 30 provided in the second image heating apparatus 200B in order to widen the glossiness selection range of the target toner image has a higher glossiness when the surface is a smooth surface with less roughness. It is suitable for achieving high thermal conductivity in a state where the surface property is kept good.

  The above fibrous or flaky high thermal conductive filler is, for example, metal oxides such as AlN, graphite, and alumina, metals such as carbon nanotube, diamond, aluminum, titanium alloy, copper alloy, boron nitride, silicon nitride, Examples thereof include silicon carbide and crystalline silica.

  Alternatively, a method of covering a PFA tube having a thickness of 10 to 30 μm as a release layer having a good surface property may be used. Of course, the filler for improving heat conduction may be mixed in the PFA tube.

  Further, an extremely thin elastic rubber may be interposed between the cylindrical metal core 32 constituting the fixing roller 30 and the releasable layer 32a. However, in order to obtain the curl removing effect described later, it is preferable that the thickness is 1 mm or less and the ASKER-C hardness of the elastic rubber is 30 ° or more. As a result, the amount of bending of the rubber of the fixing roller 30 is less than the amount of bending of the elastic layer 42 of the pressure roller 40 in bending with the elastic layer 42 of the pressure roller as the pressure member 40 described later. A removal effect is obtained.

The heat capacity per unit area of the fixing roller 30 needs to be 0.35 J / cm ² · K or less so that the surface temperature of the fixing roller reaches a predetermined temperature within 20 seconds in consideration of on-demand characteristics. . For this reason, the fixing roller 30 having a smaller diameter is suitable. Further, in order to satisfy the mechanical strength against a certain pressure, a heat capacity of 0.13 J / cm ² · K or more is required. Therefore, it is desirable to form the fixing roller in the following heat capacity 0.13J / cm ² · K or more 0.35J / cm ² · K.

  The fixing roller 30 is the second image heating device 200B, and increases the glossiness by heating the outermost surface of the toner image on the recording material P that has already been heated by the first image heating device 200A. Objective. Therefore, as the heating nip portion Ng of the fixing roller 30, a width of 3 mm or less is sufficient for the sheet passing direction (recording material conveyance direction). Further, by reducing the heating nip width Ng, it becomes possible to give a sufficient linear pressure in the heating nip portion Ng with respect to the applied pressure, thereby effectively increasing the glossiness of the toner image on the recording material. be able to.

  Further, the fixing roller 30 has a small diameter of 16 mm or less (8 mm or more), so that curl removal can be effectively achieved by the curvature of the fixing roller 30 even in a narrow heating nip portion Ng.

  In particular, the recording material enters the second image heating device 200B in a stable state in which moisture in the recording material has evaporated by the first image heating device 200A. Therefore, by making the fixing roller 30 have a small diameter, it is possible to perform curl correction that does not contribute to the amount of moisture in the recording material, and thus it is possible to perform very stable curling correction of the recording material. Further, since the fixing roller 30 has a small diameter, the recording material discharged from the heating nip portion Ng is naturally separated from the fixing roller 30 only by the waist of the recording material itself due to curvature separation. Therefore, there is no need to arrange a member that may damage the surface of the fixing roller 30 such as a separation claw, and the image heating apparatus has a long life.

  A thermistor as a temperature detecting element 33 is disposed on the surface of the fixing roller 30 and is controlled so that the surface of the fixing roller is maintained and heated to a predetermined temperature.

  Further, as shown in FIG. 4, a driving gear 34 is fixed to the longitudinal end portion of the cylindrical metal core constituting the fixing roller 30 and is driven to rotate by receiving the drive of the image forming apparatus. It has become.

  Further, the pressure roller as the pressure member 40 has an outer surface of a metal cored bar 41 made of aluminum, stainless steel, SUM, or the like, and an elastic layer 42 made of silicone rubber or the like. The elastic layer 42 is preferably covered with silicone rubber with a thickness of about 1 to 3 mm. The setting is such that the pressure roller side that is effective for removing the curling of the recording material between the fixing roller 30 has a concave shape. It is preferable to have a concave shape in the direction opposite to the image forming surface of the recording material P. The elastic rubber has an ASKER-C hardness of about 15 to 40 °. The ASKER-C hardness of the entire pressure roller is preferably about 50 to 65 ° with a load of 1 kgf.

  Further, it is also effective to make the heat insulating elastic layer as the elastic layer 42 in order to increase the temperature of the fixing roller.

  As the heat insulating elastic layer 42, a silicone rubber composition obtained by blending 0.1 to 200 parts by weight of a hollow filler having an average particle diameter of 500 μm or less to 100 parts by weight of a thermosetting organopolysiloxane composition is heated and cured. It is formed.

  Here, as the hollow filler, there is a microballoon material or the like that reduces the thermal conductivity like sponge rubber by having a gas portion in the cured product. As such a material, any glass balloon, silica balloon, carbon balloon, phenol balloon, acrylonitrile balloon, vinylidene chloride balloon, alumina balloon, zirconia balloon, shirasu balloon, etc. may be used.

  Specific examples of the inorganic microballoon are listed below, but the present invention is not limited thereto. Examples of the Shirasu balloon include winlite manufactured by Ijichi Kasei Co., Ltd. and Sankilite manufactured by Sanki Kogyo Co., Ltd. Examples of the glass balloon include Caloon made by Nippon Sheet Glass Co., Ltd., Cellstar made by Asahi Glass Co., Ltd., and Glass Bubbles Filler made by 3M Co., Ltd. Examples of the silica balloon include Q-CEL manufactured by Asahi Glass Co., Ltd. Examples of the fly ash balloon include CEROSHERES manufactured by PFAMARKETING. As the alumina balloon, BW manufactured by Showa Denko KK can be mentioned. Examples of the zirconia balloon include HOLLOW ZIRCONIUM SPHEES manufactured by ZIRCOA. Examples of the carbon balloon include Kureha Fair, Kureha Fair.

  The hollow filler itself is preferably elastic. For example, a hollow balloon made of a thermoplastic resin, particularly a vinylidene chloride, acrylonitrile, methacrylonitrile, acrylic acid ester, a polymer of acrylate ester or a copolymer of two or more of these is suitable.

  Furthermore, examples of the thermally expandable microballoon material include Matsumoto Microsphere-F series from Matsumoto Yushi Seiyaku Co., Ltd., and Expandance series from Expancel.

  Further, a release layer such as a PFA tube may be formed on the outermost layer of the pressure roller 40.

  As the outer diameter of the pressure roller 40, it is desirable to configure it with a small diameter of about 10 to 20 mm. Accordingly, the heat capacity can be suppressed to ensure the on-demand property of the fixing roller 30, and only the outermost surface of the toner image on the recording material that is already heated is used as the second image heating device 200B. Further, it can be melted to smooth the toner surface.

  As shown in FIG. 4, the pressure roller 40 receives an end shaft 41 a by a bearing 43, and a pressure spring 44 can be attached to the bearing 43. By fixing the other end of the pressure spring 44 to a fixing frame (not shown), a predetermined pressure is applied to the fixing roller 30. As a result, a heating nip portion Ng is formed between the fixing roller 30 and the pressure roller 40 with a length in the longitudinal direction W2.

  In contrast to the second image heating apparatus 200B constituted by the fixing roller 30 and the pressure roller 40, the recording material P discharged from the first image heating apparatus 200A is continuously continuously fed to the second image heating apparatus 200B. To introduce. At this time, the toner image T2 on the recording material P discharged from the first image heating device 200A is further heated on the surface of the toner image by the second image heating device 200B to become a fixed image T3, and the paper discharge guide 102. It is guided and discharged. The paper discharge guide 102 is formed of a heat resistant resin such as PPS.

  In the above configuration, the curl generated by the first image heating apparatus 200A was removed, and it was confirmed how much the glossiness of the toner image on the recording material can be increased.

  The image forming apparatus 100 used in the experiment is an electrophotographic tandem full-color printer with a process speed of 180 mm / sec, and is an apparatus capable of passing 30 cut sheets (LTR size, A4 size) per minute. .

  The image forming apparatus 100 can also pass through at a half speed of 90 mm / sec, and is selected by performing a panel operation of the image forming apparatus when passing thick paper, rough paper, or gloss paper. It has possible functions.

  The image forming apparatus 100 is mounted with an image heating apparatus (fixing apparatus) 200 of the present embodiment described below.

  In the first image heating apparatus 200A, the aluminum nitride heater 11 having a width of 10 mm and a thickness of 0.6 mm is brought into contact with the fixing belt 13 having an outer diameter of 24 mm having the above-described configuration (SUS 30 μm, silicone rubber 300 μm, PFA tube 20 μm). The fixing member 10 is provided. The pressing member 20 is formed by forming a 3 mm thick silicone rubber 22 having an ASKER-C hardness of 25 ° on the outer side of a solid core 21 made of a SUM material having an outer diameter of 18 mm, and a PFA having a thickness of 50 μm on the outermost layer 23. A pressure roller with a diameter of 25 mm coated with a tube was used.

The ASKER-C hardness after the pressure roller 20 is covered with the PFA tube is 56 ° with a 1 kg load. Further, in the aluminum nitride heater 11, a resistance heating element was formed on the surface opposite to the nip, and a polyimide layer having a thickness of 6 μm was formed on the nip surface side. The fixing belt 13 was interposed between the aluminum nitride heater 11 and the pressure roller 20, and the applied pressure was 24 kgf. The longitudinal dimension of the pressure area is 230 mm, and the width of the fixing nip portion Nh in the recording material conveyance direction is 6.7 mm. Therefore, the linear pressure per unit area is about 15.6 g / mm ² .

  Next, the second image heating apparatus 200B includes a halogen heater 31 having a diameter of 6 mm and an output of 500 W inside a fixing roller 30 in which a surface of a hollow core metal 32 having a thickness of 0.6 mm is covered with a PFA tube 32a having a thickness of 20 μm. It was a thing. As the pressure roller 40, a 50 mm thick PFA tube is formed after forming a 2 mm thick silicone rubber 42 having an ASKER-C hardness (1 kgf load) of 15 to 40 ° on a solid core metal 41 made of SUM and having a diameter of 14 mm. It was coated. As the hardness of the entire roller, samples in which the ASKER-C hardness (1 kgf load) was shaken in various ways from 45 to 70 ° were prepared.

  Further, as the fixing roller 30, the surface temperature is adjusted to 150 ° C. and the outer diameter is swung from 7 mm to 20 mm so that the high temperature offset does not occur, thereby improving the curl correction effect, the separation property of the recording material, and the glossiness. The effect was confirmed. The applied pressure was varied as appropriate, and the nip width and linear pressure were adjusted to confirm the respective characteristics. As a method for measuring the glossiness, a measurement value at an incident angle of 75 ° using PG-3D manufactured by Nippon Denka Co., Ltd. was used.

  As a method for measuring each nip width, a recording material (a recording material having the maximum longitudinal width that can be conveyed by the image forming apparatus) on which a solid black image is formed in a heated state is conveyed and stopped for 10 seconds or more in the nip. Then, the nip width is measured from the difference in gloss on solid black when removed.

  In this experiment, the nip width was measured five times by the above method including the fixing nip width of the first image heating apparatus 200A, and the average value was defined as each nip width.

  Further, the linear pressure of each of the image heating apparatuses 200A and 200B is determined based on the nip widths W1 and W2 in the longitudinal direction shown in FIGS. 3 and 4 and the nip width in the recording material conveyance direction measured by the nip width measuring method. The total area of the nip was calculated, and the total applied pressure was divided by this total area.

The recording material used was LTR paper having a basis weight of 60 g / m ² , 75 g / m ² , 90 g / m ² , 105 g / m ² , 120 g / m ² , and 160 g / m ² . Regarding the paper quality, ordinary copy paper, recycled paper, and gloss paper (coated paper) were prepared and confirmed in 36 types of recording materials in which the fiber direction was parallel and perpendicular to the transport direction. The confirmation results are shown in Table 1.

The curl correction in the table is
(1) A circle indicates that no curl is reduced by the second image heating apparatus 200B in all recording materials, and there is no problem.
(2) Δ is curl reduced with 70% or more of the recording material, but there is no problem, but the remaining paper type has a slightly large curl and an unacceptable level.
(3) × indicates that curling is not improved with 30% or more of the recording material,
Indicates.

In addition, the separability of the recording material is determined when the toner image is printed in a solid state on the leading edge of the recording material.
(1) ○ indicates that all paper types have passed without any problem.
(2) △ is a case where a failure such as a corner break of the recording material apex generated by hitting the guide on 1 to 5 types of recording materials occurs.
(3) X indicates that at least one paper type has been wound around the fixing roller,
Indicates.

Further, the effect of improving the glossiness is a value obtained by measuring a gloss value when heated and fixed only by the first image heating apparatus 200A with a gloss meter “PG-1” (manufactured by Nippon Denka Co., Ltd., 75 ° incident angle). Against
(1) The case where the gross value can be increased by a factor of 2 or more for all types of paper with the second image heating device.
(2) When the gloss improvement of 2 times or more was achieved with 70% of the paper types, but it did not reach 2 times with the remaining paper types, the speed of the image forming apparatus was reduced to 90 mm / sec. △ (allowable range) when the gross improvement of
(3) When the paper type of 30% or more does not reach twice, even if the speed is reduced to 90 mm / sec, the case where double or more cannot be achieved in all ×,
As evaluated.

  From the above results, it can be seen that when the linear pressure of the heating nip portion Ng in the second image heating apparatus 200B is lower than that in the first image heating apparatus 200A, the effect of improving the glossiness is small. When the linear pressure is the same, the gloss can be sufficiently improved by reducing the speed of the image forming apparatus.

  Therefore, in order to widen the selection range of the glossiness with the second image heating apparatus 200B, the second image is at least based on the pressing force (linear pressure) per unit area of the fixing nip portion in the first image heating apparatus 200A. The applied pressure (linear pressure) per unit area of the heating nip portion in the heating device 200B needs to be high. This is important in terms of firmly transferring the smooth surface shape on the surface of the fixing roller of the second image heating apparatus 200B to the toner image on the recording material.

  It can also be seen that curl correction is effective if the linear pressure is firmly applied by the small-diameter fixing roller 30.

  On the other hand, it can be seen that with the large fixing roller 30 having an outer diameter of 17 mm or more, the curl correction effect is reduced even when the linear pressure is applied, and the separability tends to be significantly deteriorated. In particular, the second image heating apparatus 200B shown in the above experiment forms the heating nip portion Ng by the elastic layer 42 of the pressure roller 40 being bent by the applied pressure. Heating is performed in a form in which a concave depression is generated on the roller side.

  On the other hand, since the first image heating device 200A is curled and discharged in the direction opposite to the toner image forming surface of the recording material as described above, the effect of correcting the curl by the second image heating device 200B of this system is effective. You can see that it appears.

  In order to confirm this, in the above experiment, an elastic layer having a thickness of 2 mm was formed outside the hollow core metal 32 of the fixing roller 30 in the second image heating apparatus 200B, and the elastic layer 42 of the pressure roller 40 was deleted. The same experiment was conducted by making a prototype. As a result, it was confirmed that the curling of the recording material was promoted and worsened as the linear pressure increased in all cases.

  From the above, the effect of improving the gloss of the toner image on the recording material by increasing the linear pressure of the second image heating device 200B as compared with the average linear pressure in the image heating device 200A of the first film type. It becomes high and it turns out that the selection range of glossiness spreads. The experiment was conducted with the temperature of the fixing roller 30 adjusted to 150 ° C., and it was confirmed that the glossiness of the toner image on the recording material can be easily changed by shaking from room temperature to 150 ° C. .

  Further, the outer diameter of the fixing roller 30 of the second image heating apparatus 200B is set to 16 mm or less, and the heating nip portion Ng having a concave shape on the pressure roller side is formed to ensure the linear pressure. Thus, the curl correction can be reliably performed. Furthermore, separability could be ensured.

  That is, the selection range of the glossiness of the image can be widened by increasing the linear pressure at the nip portion in the second image heating apparatus 200B from the first image heating apparatus 200A. Further, as described above, in the second image heating apparatus 200B, the fixing roller 30 has a diameter of 16 mm or less, and the heating nip Ng having a concave shape is formed on the pressure roller side, thereby reliably achieving curl correction and separation. It becomes possible to do. Accordingly, it is not necessary to provide a separation means such as a configuration of the curl correction means on the downstream side of the image heating apparatus 200B or a separation claw for ensuring separation.

  For this reason, it is not necessary to increase the size of the image forming apparatus or the image heating apparatus, and no flaws on the surface of the fixing roller due to the separation claw or the like occur. Furthermore, since the fixing nip portion is substantially flat in the first image heating apparatus 200A, an image heating apparatus with a small load on the fixing belt 13 and a long durability life is configured.

  Furthermore, since the load applied to the fibers of the recording material is substantially only from the second image heating apparatus 200B, the waist of the recording material discharged from the image forming apparatus does not become extremely low.

  In this embodiment, the first and second image heating devices 200A and 200B are provided as the image heating devices, and the first and second heating members 10, 30 and the first and second pressure members 20 are respectively provided. , 40 has been described. However, the pressure members 20 and 40 can be shared. That is, although the first pressure member 20 and the second pressure member 40 are different and separate pressure members, they may be the same pressure member.

  That is, the first heating member 10 is configured to heat the flexible fixing belt 13 from the inner surface with a substantially flat heater. The second heating member 30 has a heat roller shape, and the heating nip formed between the pressure member and the pressure member forms a heating nip portion on the opposite side to the image forming surface of the recording material. If there is, the same effect can be obtained.

  As described above, according to the image heating apparatus of the present embodiment, in the first heating member, the flexible belt is heated from the inner surface by the flat heating surface, and the flat heating surface and the pressure member are In between, pressure is applied through the belt. Therefore, the unfixed toner image on the recording material is heated and fixed with flat pressure. Therefore, no bending load is applied to the recording material, and only deformation due to evaporation of moisture in the recording material occurs.

  On the other hand, in the second heating member and the pressure member, since heating and pressurization are performed in the heating nip portion having a concave shape in a direction opposite to the image forming surface of the recording material, the first heating portion is formed. It is possible to correct the deformation of the recording material. Further, the unit of the heating nip formed between the second heating member and the pressure member with respect to the pressure per unit area of the fixing nip formed between the first heating member and the pressure member. The pressure per area is set high. As a result, an effect of increasing the glossiness of the toner image on the recording material by the second heating member is obtained by pressing and heating the outermost surface of the toner image on the recording material in a heated state with a strong linear pressure. Furthermore, by forming the diameter of the heat roller as the second heating member to be small, the curl correction capability is improved, the recording material is further separated, and no separation means such as a separation claw is required.

Example 2
With reference to FIG. 5, a second embodiment of the fixing device 200 which is an image heating device according to the present invention will be described.

  The configuration of the fixing device 200 of the present embodiment is the same as that shown in FIGS. 2 to 4 shown in the first embodiment, and members having the same configuration and function are denoted by the same reference numerals. Assistance will be omitted.

  This embodiment is characterized in that the pressure applied between the fixing member 30 and the pressure member 40 in the second image heating apparatus 200B is variable according to the purpose.

  With reference to FIG. 5, the structure of the second image heating apparatus 200B in the present embodiment will be described.

  In FIG. 5, shafts 41 a at both ends of the pressure roller 40 are provided with levers 46 for changing the applied pressure. The lever 46 is attached to be rotatable about the rotation shaft 45, and is in contact with the pressure change cam 48 at the end of the lever 46 opposite to the end of the pressure roller shaft 41 a. As a result of one end of the lever 46 being moved up and down by the circumferential position of the pressure change cam 48, the other end of the lever 46 is moved up and down, and the pressure applied between the fixing roller 30 and the pressure roller 40 is applied to the pressure spring. It is changed by the expansion / contraction of 44.

  The pressure change cam 48 is rotatable in the circumferential direction of the rotary shaft 47 so that a predetermined pressure is applied between the fixing roller 30 and the pressure roller 40 at the apexes 48a, 48b, and 48c. It has become. The fixing roller 30 and the pressure roller 40 can be separated from each other, and the vertex 48c is the farthest from the rotation shaft 47. At this time, the fixing roller 30 and the pressure roller 40 are completely separated from each other. .

  In addition, the fact that each apex of the pressure change cam 48 has come to a position directly below the lever 46 means that the position of a sensor lever (not shown) fixed to the encoder or pressure change cam is detected by a photo interrupter or the like. It can be detected by a method such as detection by an element. The detection method may be any method.

  As a result, when each apex of the pressure change cam 48 is located directly below the lever 46, the applied pressure can be adjusted in three stages: no load (48c), light load (48b), and heavy load (48a). become. In this embodiment, the three-stage pressurization state has been described. However, the pressurization state may be changed more finely, or the two-stage pressurization state change method may be used. As long as it is a method that achieves a multi-stage pressurization state according to the method, the form is not limited.

  Various recording materials are sold in the market, and user preferences vary widely for color images. Some people like the picture quality of silver-salt photos with high gloss even if they take a single photographic image, while others prefer matte images with no gloss. In addition, some people feel that the glossy character image is more noticeable, while others feel that the matte is better because it is flickering and difficult to read.

  Therefore, the wide selection range of the glossiness of the toner image on the recording material in accordance with the user's preference can cope with various users and applications. As shown in the first embodiment, in the first image heating apparatus 200A, the toner image on the recording material is discharged with a low glossiness. Therefore, when the user wants to output a matte image, the low pressure mode is selected from the operation panel or the like of the image forming apparatus, whereby the pressure change cam 48 can be rotated to be in a no-load state. .

  Or, in which mode the pressurizing force in the second image heating apparatus 200B is set when the user forms a color image using each recording material from the operation panel or personal computer in advance according to the type of each recording material. It can also be determined and stored in the image forming apparatus.

  By making it possible to select the glossiness of the toner image preferred by the user by the above method, it is possible to form images with various image quality.

  Further, the pressure in the second image heating apparatus 200B can be automatically set by utilizing the environment sensor 57 and the media sensor 58 in FIG. 1 shown in the first embodiment.

  That is, when the environment sensor 57 detects a high-temperature and high-humidity environment, the applied pressure of the second image heating apparatus 200B can be increased and the curl correction can be strengthened.

  Further, when the media sensor 58 detects a cardboard that is unlikely to be curled by the first image heating device 200A, the pressurizing force of the second image heating device 200B is lowered to reduce the second image heating device 200B. It is also possible to set the curl removal effect by.

  In particular, for cardboard and the like that are unlikely to curl in the first image heating apparatus 200A, the quality of the discharged recording material is higher when the second image heating apparatus 200B does not apply bending force to the recording material. There is also. For this reason, in such a case, it is possible to select to discharge a high-quality recording material by lowering the pressure of the second image heating apparatus 200B.

  As described above, in this embodiment, the pressure of the second image heating device 200B can be changed, so that the glossiness of the toner image on the recording material can be selected in a wide range, or the first image heating device 200A. The curl correction force of the curl generated in can be changed according to the usage environment and recording material. As a result, it is possible to form an image according to the preference of the user to be used and improve the quality of the discharged recording material.

Example 3
The image heating device described in the first and second embodiments, that is, the fixing device 200 is the fixing device 200 that heat-fixes the transferred unfixed toner image formed on the image forming unit on the recording material P. .

  However, the image heating apparatus 200 of the above embodiment can also be used as a gloss increasing apparatus that increases the glossiness of an image by heating the image fixed on the recording material.

  That is, according to the present embodiment, the recording material having the fixed image manufactured by the image forming apparatus and fixed by the fixing device is again heated through the gloss increasing device of the present embodiment, The glossiness of the image on the recording material can be increased.

  Of course, also in this embodiment, the same effects as those of the image heating apparatus in Embodiments 1 and 2 can be achieved.

1 is a schematic cross-sectional view of an embodiment of an image forming apparatus according to the present invention. It is a schematic structure sectional view of one example of an image heating device concerning the present invention. It is a longitudinal direction schematic structure front view of one Example of the image heating apparatus which concerns on this invention. It is a longitudinal direction schematic structure sectional view of one example of an image heating device concerning the present invention. It is a schematic structure side view explaining the applied pressure change of the second image heating apparatus in another embodiment of the image heating apparatus according to the present invention. FIG. 6 is a schematic diagram illustrating toner image fixing in a fixing nip portion. FIG. 6 is a schematic diagram illustrating a recording material conveyance direction of a fixing nip portion. FIG. 5 is a schematic diagram illustrating deformation of a recording material after heat fixing. It is the schematic explaining the deformation | transformation of the recording material in the heat fixing apparatus in a prior art example.

Explanation of symbols

10 First heating member (fixing member)
11 Heater (heating source)
12 Temperature detection means 13 Fixing belt (film-like member)
14 Insulating stay holder 20 Pressure rotating body 30 Second heating member (fixing member)
32 Fixing roller 33 Temperature detection means 40 Pressure rotator Ng Heating nip Nh Fixing nip T Toner P Recording material

Claims (8)

In an image heating apparatus that heat-fixes an unfixed toner image on a recording material as a fixed image on the recording material by passing through a nip formed by a heating member and a pressure member.
The heating member includes a first heating member that is a flexible belt-like member that includes a heating source therein and is pressurized and heated on a surface flatter than an inner surface, and a second heating member that is a heat roller. With
The pressure member includes a first pressure member that forms a fixing nip portion with the first heating member, and a second pressure member that forms a heating nip portion with the second heating member. ,
The heating nip portion has a heating nip shape having a concave shape in a direction opposite to the image forming surface of the recording material,
The heating nip portion of the second heating member with respect to the second pressure member is applied to the pressing force per unit area of the fixing nip portion with respect to the first pressure member of the first heating member. The applied pressure per unit area can be increased.
An image heating apparatus.   The image heating apparatus according to claim 1, wherein an outer diameter of the heat roller is 16 mm or less.   The image heating apparatus according to claim 1, wherein a heating source of the first heating member is a ceramic heater.   The image heating apparatus according to any one of claims 1 to 3, wherein a pressing force between the second heating member and the second pressure member is variable.   The image heating apparatus according to claim 4, wherein the second heating member is separable from the second pressure member.   The said 1st pressurization member and said 2nd pressurization member are respectively different separate pressurization members, or are the same one pressurization member, The any one of Claims 1-5 characterized by the above-mentioned. An image heating apparatus according to any one of the above items. In an image forming apparatus comprising: an image forming unit that forms an unfixed toner image on a recording material; and a fixing device that thermally fixes the unfixed toner image on the recording material.
The image forming apparatus according to claim 1, wherein the fixing device is an image heating device according to claim 1. In a gloss increasing device that increases the glossiness of an image by heating the image fixed on the recording material with an image heating device,
The gloss increasing device according to claim 1, wherein the image heating device is the image heating device according to claim 1.

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