JP2018105963A - Image heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image heating device for suppressing a separation failure of a recording material at a downstream end of a nip part even for long-term use.SOLUTION: The image heating device includes: a pressure body coming into press-contact with a rotation body through an endless belt to form a nip part and including an elastic pad and a separation member supporting the elastic pad to separate a recording material from the rotation body on a downstream side of the nip part; an L-shaped plate spring member with a first area of an upstream side including a first end part and a second area of a downstream side including a second end part bent at a prescribed position between the first end part and the second end part to support the pressure body in the second area; and fixing member for fixing at least a portion of the first area with the second end part in the plate spring member is in a state of a free end in a cross section perpendicular to a longer direction and fixing the separation member at a position closer to an upstream side than the center position of the nip part through the plate spring member.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image heating apparatus used for a copying machine or a printer configured as an electrophotographic system.

  An image heating apparatus mounted on an image forming apparatus such as an electrophotographic copying machine or a printer has a configuration called a free belt nip fixing device. In this method, a pressure pad and a pressure pad backed up by a metal stay are brought into pressure contact with the heating member via a heating member of the hard roller and an endless belt, thereby forming a nip portion. As a problem of this configuration, for example, when a recording material having a flap portion which is locally bent and thickened like an envelope is passed, pressure concentration occurs in the flap portion, and pressure loss occurs around the concentrated portion. In addition, the pressure member may be damaged due to pressure concentration.

  On the other hand, a method has been proposed in which pressure concentration is reduced by sandwiching an elastic member between the pressure pad and the metal stay, and pressure loss around the concentrated location and damage to the pressure member are avoided (Patent Literature). 1, 2).

JP 2005-331574 A JP 2006-084655 A

  However, as shown in FIG. 6, in the configuration in which the elastic member 75 is disposed under the pressure pad 159, in order to accurately determine the position of the pressure pad 159, particularly in the recording material conveyance direction, the recording material conveyance direction of the pressure pad 159. A member for supporting the pressure pad 159 from the downstream side is necessary. In this configuration, for example, when the elastic member 75 is compressed and deformed due to local pressure concentration, the pressure pad 159 also swings accordingly. That is, the compression of the elastic member 75 due to the thickness of the paper occurs each time the paper is passed, and the pressure pad 159 swings.

  At this time, the pressure pad 159 is rubbed against the resin stay 76 supported from the downstream side. That is, the surface 74A of the downstream jaw member 74 and 76A of the resin stay 76 are rubbed. If this is repeated, the downstream side of the pressure pad 159 is worn by rubbing, and the position of the pressure pad 159 in the recording material conveyance direction is shifted to the downstream side. Thereby, the pressure in the nip portion by the downstream jaw member 74 is lowered. As a result, the separation failure of the recording material at the downstream end of the nip portion occurs, and the hard roller is wound around the heating member (heat) roller.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image heating apparatus that solves the above-described problems and suppresses a recording material separation failure at the downstream end of a nip portion even over a long period of use.

  In order to achieve the above object, an image heating apparatus according to the present invention includes a rotating body, an endless belt that has the longitudinal direction of the rotating body as its longitudinal direction, and is rotatable with the rotating body so as to face the rotating body. A pressure member that presses against the rotating body via the endless belt and forms a nip portion for nipping and conveying the recording material carrying a toner image together with the rotating body, the elastic pad; and A pressure member that includes a separation member that supports the elastic pad and separates the recording material from the rotating body on the downstream side of the nip portion; and a first end portion in a cross section orthogonal to the longitudinal direction. An upstream L-shaped region including a second end region including a second end portion is bent at a predetermined position between the first end portion and the second end portion. Having a shape and supporting the pressurizing body in the second region A spring member, and at least a part of the first region is fixed in a state where the second end of the leaf spring member is a free end within a cross section orthogonal to the longitudinal direction, and the leaf spring member is And a fixing member that fixes the separation member at a position upstream of the center position of the nip portion.

  Another image heating apparatus according to the present invention includes a rotating body, an endless belt that can be rotated together with the rotating body, with the longitudinal direction of the rotating body being the longitudinal direction, and facing the rotating body, and the endless belt. An elastic pad that is pressed as a pressurizing member that forms a nip portion that is in pressure contact with the rotating body and forms a nip portion for nipping and conveying the recording material bearing a toner image together with the rotating body; A separation member for separating the recording material from the rotating body on the downstream side, and a downstream including a first region on the upstream side including a first end and a second end in a cross section orthogonal to the longitudinal direction. A plate having an L shape bent at a predetermined position between the first end and the second end, and supporting the elastic pad in the second region A spring member and the second member within a cross section perpendicular to the longitudinal direction; In a state where the end portion is fixed by the separating member, and having a fixing member for fixing at least a portion of said first region in said plate spring member.

  According to the present invention, it is possible to suppress a recording material separation failure at the downstream end of the nip portion even over a long period of use.

1 is a schematic configuration diagram of an image forming apparatus equipped with an image heating apparatus according to an embodiment of the present invention. Side surface model diagram of main part of image heating apparatus according to first embodiment Side model diagram of the pressure film unit in the first embodiment The perspective view of the pressurization film unit in a 1st embodiment. 1 is a schematic front view of an image heating apparatus according to a first embodiment. Side surface schematic diagram of pressure film unit in comparative example (first comparative example) Side surface schematic diagram of the pressure film unit in 2nd Embodiment Schematic perspective view of a pressure film unit in the third embodiment Configuration explanatory diagram of local pressure avoidance in the third embodiment

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<< First Embodiment >>
(Image forming device)
FIG. 1 is a schematic configuration diagram of an image forming apparatus 100 equipped with an image heating apparatus according to an embodiment of the present invention. The image forming apparatus 100 is an electrophotographic laser beam printer. Reference numeral 101 denotes a photosensitive drum as an image carrier, which is driven to rotate in a clockwise direction indicated by an arrow at a predetermined process speed (circumferential speed). The photosensitive drum 101 is uniformly charged to a predetermined polarity and potential by the charging roller 102 during the rotation process.

  Reference numeral 103 denotes a laser beam scanner as image exposure means. Then, a laser beam L input from an external device such as a computer (not shown) and modulated on / off in response to a digital image signal generated by the image processing means is output to charge the photosensitive drum 101. Scanning exposure. By this scanning exposure, the charge of the exposed bright portion on the surface of the photosensitive drum 101 is removed, and an electrostatic latent image corresponding to the image signal is formed on the surface of the photosensitive drum 101.

  A developing device 104 supplies developer (toner) to the surface of the photosensitive drum 101 from the developing roller 104a, and the electrostatic latent image on the surface of the photosensitive drum 101 is sequentially developed as a toner image which is a transferable image. Is done.

  Reference numeral 105 denotes a paper feed cassette on which the recording material P is loaded and stored. The paper feed roller 106 is driven based on the paper feed start signal, and the recording material P in the paper feed cassette 105 is separated and fed one by one. Then, the toner is introduced at a predetermined timing into a transfer portion 108T that is a contact nip portion with the transfer roller 108 that is rotated by contact with the photosensitive drum 101 via the registration roller pair 107. That is, the conveyance of the recording material P is controlled by the registration roller 107 so that the leading edge of the toner image on the photosensitive drum 101 and the leading edge of the recording material P reach the transfer portion 108T at the same time.

  Thereafter, the recording material P is nipped and conveyed at the transfer portion 108T, and during that time, a transfer voltage (transfer bias) controlled to a predetermined level is applied to the transfer roller 108 from a transfer bias application power source (not shown). A transfer bias having a polarity opposite to that of the toner is applied to the transfer roller 108, and the toner image on the surface side of the photosensitive drum 101 is electrostatically transferred onto the surface of the recording material P at the transfer portion 108T. The recording material P after the transfer is separated from the surface of the photosensitive drum 101, passes through the conveyance guide 109, and is introduced into the image heating apparatus A.

  In the image heating apparatus A, the toner image is subjected to heat fixing processing. On the other hand, the surface of the photosensitive drum 101 after the transfer of the toner image to the recording material P is cleaned by the cleaning device 110 after removal of transfer residual toner, paper dust, and the like, and is repeatedly used for image formation. The recording material P that has passed through the image heating apparatus A is discharged from the paper discharge port 111 onto the paper discharge tray 112.

(Image heating device)
The image heating apparatus A in this embodiment is a heat roller system. 2 is a cross-sectional side view of the main part of the image heating apparatus A, FIG. 3 is a side view of the main part (pressure film unit), and FIG. 4 is a perspective view of the main part (pressure film unit). In the following description, a direction orthogonal to the recording material conveyance direction is referred to as a longitudinal direction.

  A heat roller 51 as a rotating body is formed by laminating a heat-resistant elastic body layer 53 and a release layer 52 around a metal base tube 54 (cylindrical cored bar) formed in a cylindrical shape having a predetermined length. Configure. The base tube 54 of the heat roller is formed of a cylindrical body made of a metal having high thermal conductivity such as iron, aluminum, SUS (here, a thin high-tensile steel pipe is used). Furthermore, any material can be used for the heat resistant elastic layer 53 in the heat roller 51 as long as it is an elastic body having high heat resistance. In particular, it is preferable to use an elastic body such as rubber or elastomer having a rubber hardness of about 25 to 40 degrees (JIS A). Specifically, silicone rubber, fluorine rubber, or the like can be used.

  The release layer 52 in the heat roller 51 may be any resin as long as it is a heat-resistant resin. For example, a silicone resin, a fluorine resin, or the like can be used. From the viewpoints of wear resistance and wear resistance, fluororesin is suitable. As the fluororesin, PFA, PTFE (polytetrafluoroethylene), FEP (tetrafluoroethylene hexafluoropropylene copolymer), or the like can be used. The thickness of the release layer 52 is preferably 10 to 50 μm, more preferably 10 to 30 μm.

  If the thickness of the release layer 52 is less than 10 μm, wrinkles are likely to occur on the recording paper 24 as a recording material based on the distortion of the heat roller 51, while if it exceeds 30 μm, the release layer 52 becomes hard and an image is formed. This is because there is an increased possibility of uneven luster and the like, both of which are undesirable.

  Inside the heat roller 51, a halogen lamp 55 is disposed as a heat source (heating source). A temperature sensor is brought into contact with the surface of the heat roller 51, and the control unit of the image forming apparatus controls lighting of the halogen lamp 55 based on a temperature measurement value by the temperature sensor, so that the surface temperature of the heat roller 51 is predetermined. The temperature is adjusted so as to maintain the set temperature (for example, 170 ° C.).

  The pressure film 56 as an endless belt that rotates in a synchronized manner while being pressed against the heat roller 51 is formed in an endless track shape (cylindrical shape of a predetermined length). The pressure film 56 is configured as an endless belt (endless belt) that can rotate to face the heat roller 51, and includes a base layer 57 and a release layer 58 covered on the surface of the base layer 57 on the heat roller 51 side. It is composed of The base layer 57 is formed of a polymer such as polyimide, polyamide, or polyamideimide, or a metal such as SUS, nickel, or copper, and has a thickness of about 30 to 200 μm, preferably about 50 to 100 μm.

  The release layer 58 covered on the surface of the base layer 57 is made of a fluororesin such as PFA, PTFE, or FEP, and has a thickness of about 5 to 100 μm, preferably about 10 to 30 μm.

  The pressure film 56 configured in this manner is freely rotatable (circulating operation) by being slidably slidably contacted via a low friction sheet 72 with a pressure pad 59 as a pressure member that is slidably contacted with the inner peripheral surface thereof. Freely). The pressure film 56 is mounted so that the fixing nip portion (nip portion) corresponding to the pressure pad 59 is brought into rolling contact with the heat roller 51 with a predetermined pressure.

  Next, the member arrange | positioned inside the pressurizing film 56 is demonstrated using FIG. The pressure pad 59 is inside the pressure film 56 and presses the heat roller 51 with a predetermined pressure distribution via the pressure film 56, and forms a nip portion with the heat roller 51. Here, the nip portion is a region where the pressure film 56 and the heat roller 51 are in rotational contact with each other while being elastically deformed, and is in the rotation direction of the pressure film 56 and the heat roller 51 (the conveyance direction of the recording paper 24). It has a predetermined length. And it shall mean the area | region of a substantially planar view rectangular shape covering the longitudinal direction of the pressure film 56 and the heat roller 51. FIG.

  The pressure pad 59 is in pressure contact with the heat roller 51 via the pressure film 56, and forms a nip portion for nipping and conveying the recording material carrying the toner image with the heat roller 51 in a heated state. It comprises a pad member 60 and a rectangular elongated main body 63 for a pressure pad. The pressure pad member 60 is configured by adhering an auxiliary member 60B formed of a metal long plate material to the bottom surface of an elastic material (elastic body) 60A formed in a prismatic shape. Further, the pressure pad main body 63 is configured to include a downstream jaw member 62 made of resin and an installation portion 62A of the pressure pad member 60 having a rectangular groove shape adjacent thereto.

  Here, the downstream jaw member 62 functions as a separation member that supports the pressure pad member 60 and separates the recording material from the heat roller 51 on the downstream side of the nip portion.

  The pressure pad member 60 is disposed on the inlet side in the recording material conveyance direction of the nip portion, and secures a wide nip portion with respect to the conveyance direction of the recording paper 24 as a recording material (recording medium). It is configured so that the required pressure can be applied by heating to a temperature of. The elastic material 60A can be made of a heat-resistant elastic material such as silicone rubber or fluorine rubber.

  In this printer, as described above, the pressure pad member 60 is configured by adhering the auxiliary member 60B formed of a metal long plate material to the bottom surface of the elastic material 60A formed in a prismatic shape. The upper surface of the elastic material 60 </ b> A is formed in a substantially concave shape that follows the outer peripheral surface of the heat roller 51. The downstream jaw member 62 of the pressure pad 59 is disposed on the downstream side in the conveyance direction of the nip portion, and is strongly pressed against the heat roller 51 to elastically heat the heat-resistant elastic layer 53 and the release layer 52 provided around the base layer 54. Deform. As a result, the recording paper 24 is peeled (separated) from the surface of the heat roller 51.

  The downstream jaw member 62 can be formed using, for example, a heat-resistant resin such as PPS (polyphenylene sulfide), polyimide, polyester, polyamide, or a metal such as iron, aluminum, or SUS. The shape of the downstream jaw member 62 is formed into a convex curved surface shape having a constant radius of curvature at the outer surface shape at the nip portion.

  As described above, the downstream jaw member 62 is formed as a part of the rectangular elongated pressure pad main body 63, and the installation portion 62 </ b> A of the rectangular groove-shaped pressure pad member 60 is positioned adjacent to the upstream side. It is formed integrally (integrated). Then, the pressure pad member 60 is fitted into the installation portion 62A so as to be integrally assembled with the installation portion 62A at the bottom side. Thereby, the pressure pad member 60 and the downstream jaw member 62 constitute one pressure pad 59 adjacent to each other in the longitudinal direction.

  Next, a member that supports the pressure pad 59 will be described with reference to FIG. The pressure pad 59 is constituted by a T stay 70 as a fixing member having a certain degree of rigidity and a leaf spring member 71 provided to the pressure pad 59 so that a pressing force for forming a nip portion in the longitudinal direction is applied. Supported. The T-stay 70 is a stay member formed of a steel plate having a U-shaped cross section (a cross section orthogonal to the longitudinal direction), and is a galvanized steel plate such as a brand name gin coat (manufactured by Nippon Steel) or stainless steel 304. Formed of steel material. Of the U shape, the downstream leg (foot) 70D in the recording material conveyance direction is formed shorter than the upstream leg (foot) 70A.

  The leaf spring member 71 has a first region 71C on the upstream side including the first end V and a second downstream side including the second end H within the cross section orthogonal to the longitudinal direction shown in FIG. The region (region 71B) has an L shape bent at a predetermined position M between the first end V and the second end H. In FIG. 3, the pressure pad 59 is supported in the second region.

  Further, in the T stay 70, the downstream leg (foot) 70D is formed shorter than the upstream leg (foot) 70A in the recording material conveyance direction, and the second end H is a free end and a predetermined position M. At least a part of the first region of the leaf spring member 71 is fixed so as to be displaceable around. That is, of the first end portion V and the second end portion H of the leaf spring member 71, only one end side (only the first end portion V side) is fixedly supported by the T stay 70.

  The T stay 70 has a chamfered portion 70B formed at the tip of the upstream leg portion (foot) 70A, and has a shape that avoids interference with the curved portion 71A of the leaf spring member 71. The T stay 70 supports a part (upstream side) of the region 71B of the leaf spring 71 in the installation portion with the leaf spring 71 indicated by 70C. The leaf spring member 71 is fixed (coupled) to the side surface of the T stay 70 by screws (not shown) in the region of the first region 71C on the upstream side. In this manner, the pressure pad 59 is supported by contacting (contacting) the leaf spring member 71 on the surfaces 59A and 59B.

  Further, the leaf spring member 71 will be described with reference to FIG. As shown in FIG. 4, the leaf spring member 71 has a shape formed in a comb shape in the longitudinal direction. The region 71D at the end in the longitudinal direction is a portion corresponding to the teeth of the comb teeth, and the adjacent 71E indicates a portion without the teeth of the comb teeth (notched portion). In FIG. 4, the region 71 </ b> D at the longitudinal end portion of the leaf spring 71 is a cantilever where a portion (upstream side) of the region 71 </ b> B of the leaf spring 71 is supported by the leaf spring support portion 70 </ b> C of the T stay 70. ing.

  In FIG. 2, when the recording paper 24 as a recording material enters the fixing nip portion, an additional pressure corresponding to the thickness of the recording paper 24 is applied to the pressure pad 59 through the pressure film 56, and the pressure is shown in FIG. As shown, the region 71D received from the pressure pad 59 swings in the direction of the arrow. Thereby, the additional pressure by the recording paper 24 can be released, and the increase in the pressure in the nip by the recording paper 24 can be reduced.

  As described above, the leaf spring member 71 has a notch shape indicated by 71E in the longitudinal direction as shown in FIG. By adopting such a configuration, it is possible to make a state where there are a plurality of finely divided regions 71D, instead of a state where the region 71D exists over the entire longitudinal direction.

  Thereby, each divided | segmented area | region 71D can rock | fluctuate independently. For example, when a recording paper having a short width in the longitudinal direction and having a large width, such as an envelope, enters the fixing nip portion, a high pressure may be locally applied to both end edges of the recording paper. In such a case, if the configuration includes a plurality of regions 71D each of which is a cantilever that independently swings as in the present embodiment, the swing amount of the region 71D can be changed according to the pressure applied in the longitudinal direction. It is possible to avoid a situation in which pressure is locally applied to both end edges.

  Further, in the configuration of the present embodiment, as shown in FIG. 3, the low friction sheet 72 is placed on the pressure pad 59 in order to avoid the elastic material 60 </ b> A of the pressure pad 60 from directly rubbing against the pressure film 56. Deploy. The low friction sheet 72 is a flexible sheet member formed of a heat-resistant resin such as polyimide, and is fixed to the plate spring member 71 in the vicinity of 71C where the plate spring member 71 is fixedly supported by the T stay 70. . Specifically, the low friction sheet 72 is fastened to the T stay 70 with a screw (not shown) together with the leaf spring member 71 while the shape is stabilized by the pressing member 73. Thereby, the low friction sheet 72 can be fixed with a simple configuration.

  The low friction sheet 72 is provided to reduce the rubbing resistance (friction resistance), and is a material having a small friction coefficient and excellent wear resistance and heat resistance (for example, a sheet formed of a fluororesin woven fabric. Or a sheet made of polyimide thin film).

  Here, as shown in FIG. 5, both end portions in the longitudinal direction of the pressure film unit described above are fixed to movable metal plates 80 a and 80 b that are movably disposed via a T stay 70. Then, pressure springs 17a and 17b are respectively contracted between the movable metal plates 80a and 80b and the spring receiving members 18a and 18b on the apparatus chassis side. As a result, a pushing force is applied to the movable metal plates 80a and 80b, and the pressure film unit is pressed against the heat roller 51 to form a fixing nip portion. In the image heating apparatus A of the present embodiment, a pressing force of about 100 N to 250 N (about 10 kgf to about 25 kgf) is applied.

  In FIG. 5, the heat roller 51 is rotationally driven by a driving means (not shown), and a rotational force is applied to the pressure film 56 by a frictional force with the outer surface of the heat roller 51. The flange members 12a and 12b shown in FIG. 5 are fitted around the left and right ends of the pressure film 56, and the left and right positions are fixed by the regulating members 13a and 13b. When the heat roller 51 rotates, the end of the pressure film 56 is received, and the shift of the pressure film 56 along the longitudinal direction is restricted. The material of the flange members 12a and 12b is preferably a material having good heat resistance such as LCP resin.

  When the energization of the halogen lamp 55 disposed inside the heat roller 51 shown in FIG. 2 is started, the recording paper 24 is placed at the fixing nip portion at the timing when the surface of the heat roller 51 rises to a predetermined temperature due to heating by the halogen lamp 55. It is brought in. Thereby, the fixing operation of the toner image placed on the recording paper to the recording paper 24 is performed.

(3) Confirmation of effect of this embodiment In order to confirm the effect of this embodiment, two types of image heating apparatuses of this embodiment and a comparative example (first comparative example) are prepared, and a comparison experiment is performed. went. FIG. 3 is a schematic cross-sectional view of the image heating apparatus of the present embodiment, and FIG. 6 is a schematic cross-sectional view of the image heating apparatus of the comparative example. Since the description of the image heating apparatus of the present embodiment is as described above, the description is omitted. Since the image heating apparatus of the comparative example has a different configuration for holding the pressure pad 159, this part will be described with reference to the drawings.

  In FIG. 6, a pressure pad 159 is disposed inside the pressure film 56 in the same manner as the pressure pad 59 in FIG. 3. The pressure pad 159 includes a pressure pad 60 and a downstream jaw member 74, and the pressure pad 60 is supported by the downstream jaw member 74 as shown in FIG. An elastic member 75 made of silicon rubber is disposed under the pressure pad 159. The elastic member 75 supports the pressure pad 159 from the lower surface of the downstream jaw member 74.

  A resin stay 76 that supports and fixes the elastic member 75 is disposed on the lower surface of the elastic member 75, and the T stay 170 supports all the above-described members via the resin stay 76. . The resin stay 76 has such a shape that walls are built on the upstream side and the downstream side in the conveyance direction of the recording paper, and also plays a role of fixing the position of the pressure pad 159 and the elastic member 75 in the conveyance direction. Yes.

  The pressure pad 159 has its position in the recording paper conveyance direction determined by abutting 74 A (downstream side), which is one surface of the downstream jaw member 74, against 76 A, which is one surface of the resin stay 76. When the recording paper enters the fixing nip portion of the image heating apparatus of the comparative example described above, an additional pressure corresponding to the thickness of the recording paper is applied to the pressure pad 159 via the pressure film 56. Then, by receiving the pressure via the pressure pad 159, the elastic member 75 is compressed in the direction (downward) shown in FIG. Thereby, the additional pressure by the recording paper 24 can be released, and the increase in the pressure in the nip portion by the recording paper 24 can be reduced.

  Next, an experiment performed using the image heating apparatus of the present embodiment and the comparative example will be described. In the experiment, first, SpringHill 199g paper having a thickness of 240 μm was used as the recording paper in order to largely swing the leaf spring member 71 (FIG. 3) of the present embodiment and the elastic member 75 (FIG. 6) of the comparative example. To print continuously.

  Specifically, every time 500 sheets of SpringHill 199g paper are passed through, 5 sheets of recording paper CS520 containing moisture (water content 9%) are allowed to stand in a high temperature and humidity environment (temperature 30 ° C., humidity 80%). Paper. CS520 is a thin paper having a low basis weight, and has a thickness of about 67 μm. Since the rigidity is reduced by containing more moisture, the recording paper is likely to be wound around the heat roller 51. When the CS 520 was passed, a solid image was drawn with toner near the front end of the paper, making it easier to wrap.

  Based on the above experiment, whether the winding of CS520 occurs in the configurations of the present embodiment and the comparative example was compared. In this embodiment, the winding of CS520 did not occur even when 500 cycles of Spring Hill 199 paper were repeated 20 cycles (total of 10,000 sheets). After that, the cycle was switched to a cycle in which 5 sheets of CS 520 were passed for every 10000 sheets of Spring Hill 199 paper, and the experiment was continued until the cumulative number of sheets of Spring Hill 199 sheets reached 100,000 sheets. There wasn't.

  On the other hand, in the comparative example, when 500 pieces of Spring Hill 199 sheets were passed five times, corner breakage started to occur at the tip of CS520. This occurs because the separation from the heat roller 51 is deteriorated and the paper is discharged from the fixing nip portion with a slight winding, and is caught by a guide near the paper path behind the fixing nip portion. Further, when 500 sheets of Spring Hill 199 paper were passed five times (total 10 cycles), CS520 was wound around the heat roller 51 and jammed to stop the printing operation.

  When the image heating apparatus of the comparative example after the experiment was disassembled and examined, the downstream surface 74A (FIG. 6) of the downstream jaw member 74 has been scraped, and the downstream jaw member 74 is positioned in contact with the surface 74A. The surface 76A (FIG. 6) of the resin stay 76 that is performing the cutting was also cut in the same manner.

  This is because the Spring Hill 199g paper passes, and the compression of the elastic member 75 due to the thickness of the paper occurs every time the paper is passed, the pressure pad 159 swings, and the surface 74A of the downstream jaw member 74 and 76A of the resin stay 76 slide. It is thought that they have been rubbed and worn. As a result, the position of the pressure pad 159 in the recording sheet conveyance direction is shifted to the downstream side, and as a result, the pressure at the fixing nip portion by the downstream jaw member 74 is lowered. And the force which isolate | separates CS520 became weak and the winding to the heat roller 51 had generate | occur | produced.

  Here, the total wear amount of 74A and 76A is about 1 mm, and the position of the pressure pad 59 is shifted 1 mm downstream due to wear due to rocking. When shifted by 1 mm, the pressure in the nip portion becomes weak, and separation failure of CS520 occurs.

  On the other hand, in the present embodiment, the surface 59B of the pressure pad 59 (the surface on the upstream side of the downstream jaw member 62 in FIG. 3) is supported by the leaf spring member 71 (the surface 71P in FIG. 4). The position of is determined. The place where the surface 59B is supported is closer to the fulcrum (predetermined position M) when the leaf spring member 71 swings at a position upstream of the center position (center) of the nip portion in the recording material conveyance direction. This is the position where there is almost no displacement even when the leaf spring member 71 swings. Therefore, almost no friction is generated between the leaf spring member 71 and the surface 59B of the pressure pad 59, so that the surface 59B of the pressure pad 59 is not worn.

  For this reason, in this embodiment, even when a large amount of Spring Hill 199g paper is passed and the leaf spring member 71 swings to reduce the pressure due to its thickness, the position of the pressure pad 59 does not change, and the nip in the fixing nip portion is not changed. The pressure does not fluctuate and no wrapping occurs.

  As described above, when the pressure pad is supported near the fulcrum of the leaf spring member having a cantilever structure as in this embodiment, even when a large amount of thick recording paper is passed, Nip pressure does not drop, and good separability can be maintained.

<< Second Embodiment >>
Next, the structure of the 2nd Embodiment of this invention is demonstrated using FIG. The image heating apparatus according to the present embodiment is different from the first embodiment in the shape of the downstream jaw member constituting the pressure pad 259 as a pressurizing body. This portion will be described with reference to FIG. 7, and the other portions including the T stay 70 are the same as those in the first embodiment, and thus the description thereof is omitted.

  The downstream jaw member 77 shown in FIG. 7 is configured to be directly attached to the downstream edge of the plate spring member 71 by incorporating the plate spring member 71 into a mold and integrally molding it during resin molding. As shown in FIG. 7, in the T stay 70, the downstream leg (foot) 70D is shorter than the upstream leg (foot) 70A in the recording material conveyance direction so as not to interfere with the downstream jaw member 77. It is configured.

  And the press pad 60 pressed as a main press body in this embodiment is arrange | positioned so that it may be directly supported by the leaf | plate spring member 71 via the sheet metal 60B. As described above, the pressure pad 60 is positioned in the recording paper conveyance direction by being supported by the downstream jaw member 77 integrally formed with the leaf spring member 71 from the downstream side in the recording paper conveyance direction.

  Further, a guide member 78 for guiding the leaf spring member 71 is disposed on the upstream side of the pressure pad 60, and the low friction sheet 72 is configured to cover the pressure pad 259 while gently curving.

  Similar to the first embodiment, the T stay 70 supports a part (upstream side) of the region 71B of the leaf spring 71 in the installation portion with the leaf spring 71 indicated by 70C. The leaf spring member 71 is fixed (coupled) to the side surface of the T stay 70 by screws (not shown) in the region of the first region 71C on the upstream side. In this way, the pressure pad 259 comes into contact (contact) with the leaf spring member 71 and is supported.

  In the present embodiment as described above, an experiment was conducted to see whether good separation performance can be maintained through paper. In the experiment, in the same manner as described in the first embodiment, in order to largely swing the leaf spring member 71, the printing paper was subjected to continuous printing using Spring Hill 199g paper having a thickness of 240 μm.

  Each time 500 sheets of Spring Hill 199 g paper were passed, the paper was left in a high temperature and humidity environment (temperature 30 ° C., humidity 80%), and 5 sheets of recording paper CS520 containing moisture (water content 9%) were passed. CS520 is a thin paper with a low basis weight, and has a thickness of about 67 μm. Since the rigidity is reduced by containing more moisture, the recording paper is likely to be wound around the heat roller 51. When the CS 520 is passed, a solid image is drawn with toner near the front end of the paper to make it easier to wrap.

  In this embodiment, the winding of CS520 did not occur even when 500 cycles of Spring Hill 199 paper were repeated 20 cycles (total of 10,000 sheets). After that, the cycle was switched to a cycle in which 5 sheets of CS 520 were passed for every 10000 sheets of Spring Hill 199 paper, and the experiment was continued until the cumulative number of sheets of Spring Hill 199 sheets reached 100,000 sheets. There wasn't.

  In the present embodiment, the downstream jaw member 77 is directly fixed to the leaf spring member 71. When the leaf spring member 71 is swung, there is no portion where rubbing occurs. Therefore, even if a thick recording sheet such as Spring Hill 199g passes through the nip, there is no part to be worn. For this reason, since the pressure of the fixing nip is not affected, it is possible to maintain good separation performance through a long period of paper passing.

  As described above, an image heating apparatus that does not impair the separation performance can be formed even when a configuration in which the downstream jaw member 77 is directly fixed to the leaf spring member 71 as in the present embodiment is used.

<< Third Embodiment >>
Next, the structure of the 3rd Embodiment of this invention is demonstrated using FIG. In the present embodiment, the following improvements are made with respect to the leaf spring 71 in order to realize an image heating apparatus that does not have poor recording paper separation even after long-term use. That is, not only does the nip pressure change due to the pressure pad transport direction position not changing, but even when a thick recording sheet enters the fixing nip part, the pressure pad part swings and local pressure can be avoided. It is what I did. Since the portions other than the leaf spring 71 including the T stay 70 are the same as those in the first embodiment or the second embodiment, description thereof will be omitted.

  The leaf spring 71 in the present embodiment has a plurality of cutout shapes 71E in the longitudinal direction orthogonal to the recording material conveyance direction. The cutout shape is arranged at a position corresponding to the paper size to be passed through the image heating apparatus A as shown in FIG. Taking the A4 size as an example, the paper width of the A4 size is 210 mm, but the inner dimension of the pair of cutout shapes 71E_A4 is set to be about 2 to 3 mm larger than the paper width 210 mm.

  With reference to FIG. 9 viewed from the downstream side in the recording material conveyance direction, a configuration for avoiding local pressure in the present embodiment will be described by comparison with a comparative example (second comparative example). FIG. 9A is a schematic view of the image heating apparatus of the comparative example (second comparative example) as viewed from the downstream side in the transport direction when A4 paper enters the nip portion. The A4 paper P is sandwiched between the heat roller 51 and a pressure film 56 (FIG. 2) not shown in FIG. A downstream jaw member 62 is provided below the pressure film 56, and the substantial heat roller 51 and the downstream jaw member 62 are pressed strongly to elastically deform the release layer of the heat roller 51 and release the recording paper. Yes.

  In the image heating apparatus of the comparative example (second comparative example), the alignment of the notch shape 71E of the A4 sheet end and the leaf spring 71 is not performed, and the notch shape 71E is located inside the end of the A4 sheet. Has been placed. As shown in FIG. 9A, the downstream jaw member 62 is pushed by the outer leaf spring 71D, and an extra load is applied to the end of the A4 sheet. As a result, some local pressure concentration occurs at the end of the A4 sheet of the downstream jaw member 62 although it is less than in the conventional example.

  On the other hand, in the present embodiment shown in FIG. 9B, the notch shape 71E_A4 and the end portion of the leaf spring 71D_A4 are arranged outside (end portion side) the end portion of the A4 sheet. As a result, the load of the outer leaf spring 71D_LTR is not applied to the end of the A4 sheet, and the local pressure concentration can be further reduced.

(Modification 1)
In the above-described embodiment, the fixing device that fixes an unfixed toner image to a sheet has been described as an example of the image heating device. The present invention can be similarly applied to an apparatus that heats and presses the toner image.

(Modification 2)
In the embodiment described above, the recording paper has been described as the recording material. However, the recording material in the present invention is not limited to paper. Generally, a recording material is a sheet-like member on which a toner image is formed by an image forming apparatus. For example, regular or irregular plain paper, cardboard, thin paper, envelope, postcard, seal, resin sheet, OHP sheet, Includes glossy paper. In the embodiment described above, for the sake of convenience, the handling of the recording material S has been described using terms such as paper, paper passing, paper feed, and paper discharge. However, the recording material in the present invention is not limited to paper. Absent.

51 .. Heat roller 56 ..Pressure film 59 ..Pressure pad 60 ..Pressure pad member 62 ..Downstream jaw member (separating member) 70 ..T stay 71. 77 ··· Downstream jaw member (separating member), V ··· First end portion, H ··· Second end portion, M ··· Predetermined position

Claims (11)

A rotating body,
An endless belt that can be rotated together with the rotating body in the longitudinal direction of the rotating body, facing the rotating body,
A pressure member that presses against the rotating body via the endless belt and forms a nip portion for nipping and conveying the recording material carrying a toner image together with the rotating body, the elastic pad; A pressure member comprising: a separation member that supports the pad and separates the recording material from the rotating body on the downstream side of the nip portion;
Within the cross section orthogonal to the longitudinal direction, an upstream first region including a first end and a downstream second region including a second end include the first end and the first A leaf spring member having an L shape bent at a predetermined position between the two end portions and supporting the pressurizing body in the second region;
Within the cross section perpendicular to the longitudinal direction, at least a part of the first region is fixed with the second end of the leaf spring member being a free end, and the nip is interposed via the leaf spring member. A fixing member that fixes the separation member at a position upstream of the central position of the part;
An image heating apparatus comprising:   The image heating apparatus according to claim 1, wherein a position where at least a part of the first region is fixed is a position close to the predetermined position. A rotating body,
An endless belt that can be rotated together with the rotating body in the longitudinal direction of the rotating body, facing the rotating body,
An elastic pad that is pressed against the rotating body via the endless belt and is pressed as a pressing body that forms a nip portion for nipping and conveying the recording material carrying the toner image together with the rotating body; and
A separating member for separating the recording material from the rotating body on the downstream side of the nip portion;
Within the cross section orthogonal to the longitudinal direction, an upstream first region including a first end and a downstream second region including a second end include the first end and the first A leaf spring member having an L shape bent at a predetermined position between the two end portions and supporting the elastic pad in the second region;
A fixing member that fixes at least a part of the first region of the leaf spring member in a state in which the second end is fixed by the separation member within a cross section perpendicular to the longitudinal direction;
An image heating apparatus comprising:   The image heating apparatus according to claim 3, further comprising a guide member that guides the leaf spring member on an upstream side of the nip portion.   5. The fixing member according to claim 1, wherein the fixing member has a U-shape in a cross section orthogonal to the longitudinal direction, and the length of the foot on the downstream side is shorter than the length of the foot on the upstream side. The image heating apparatus according to Item.   The image heating apparatus according to claim 1, wherein the rotating body is a heating member provided with a heating source therein.   The image heating apparatus according to claim 1, wherein the separation member is made of a material having a hardness higher than that of the elastic pad.   The image heating apparatus according to claim 1, wherein the fixing member is a metal stay.   The image heating apparatus according to claim 1, wherein the leaf spring member includes a notch at one or more positions in the longitudinal direction.   The image heating apparatus according to claim 9, wherein a position of the notch is provided so as to be closer to an end portion side than an end portion in the longitudinal direction of the recording material.   11. The image heating apparatus according to claim 1, wherein the fixing member is supported by a spring receiving member via a pressure spring at both ends in the longitudinal direction.