JP6772052B2 - Image heating device - Google Patents

Description

The present invention relates to an image heating device used in a copier, a printer, or the like configured as an electrophotographic system.

An image heating device mounted on an image forming apparatus such as an electrophotographic copying machine or a printer has a configuration of a free belt nip fixing device. In this method, the nip portion is formed by pressing the heating member of the hard roller and the pressure pad and the pressure pad backed up by the metal stay to the heating member via the endless belt. As a problem of this configuration, when a recording material having a flap portion that is locally bent and thickened, such as an envelope, is passed through the paper, pressure concentration occurs in the flap portion and pressure release occurs around the concentrated portion. At the same time, there is a point that the pressure member may be damaged due to pressure concentration.

On the other hand, a method has been proposed in which an elastic member is sandwiched between a pressure pad and a metal stay to reduce pressure concentration and avoid pressure release around the concentration point and damage to the pressure member (Patent Documents). 1, 2).

Japanese Unexamined Patent Publication No. 2005-331574 Japanese Unexamined Patent Publication No. 2006-084655

However, as shown in FIG. 6, in the configuration in which the elastic member 75 is arranged under the pressure pad 159, the recording material transporting direction of the pressure pad 159 is particularly determined in order to accurately determine the position of the pressure pad 159 in the recording material transporting direction. A member that supports the pressure pad 159 from the downstream side is required. In this configuration, for example, when the elastic member 75 is compressively deformed by applying local pressure concentration, the pressure pad 159 also swings accordingly. That is, due to the paper passing, compression of the elastic member 75 due to the thickness of the paper is generated for each paper passing, 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. When 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 transport direction is shifted to the downstream side. As a result, the pressure at the nip portion by the downstream jaw member 74 is reduced. As a result, poor separation of the recording material occurs at the downstream end of the nip portion, and the hard roller is wound around the heating member (heat) roller.

An object of the present invention is to solve the above problems, and to provide an image heating device that suppresses poor separation of recording materials at the downstream end of the nip portion even after long-term use.

In order to achieve the above object, the image heating device according to the present invention includes a rotating body and an endless belt whose longitudinal direction is the longitudinal direction of the rotating body and which can rotate with the rotating body facing the rotating body. A pressurizing body that presses against the rotating body via the endless belt to form a nip portion that holds and conveys a recording material carrying a toner image together with the rotating body in a heated state. A pressurizing body including a separating member that supports an 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 L-shape in which a first region on the upstream side including the first region and a second region on the downstream side including the second end portion are bent at a predetermined position between the first end portion and the second end portion. The leaf spring member having a shape and supporting the pressurizing body in the second region, and the second end portion of the leaf spring member in a cross section orthogonal to the longitudinal direction are free ends. It is characterized by having a fixing member for fixing at least a part of the first region and fixing the separating member at a position upstream of the central position of the nip portion via the leaf spring member. ..

In addition, another image heating device according to the present invention includes a rotating body, an endless belt whose longitudinal direction is the longitudinal direction of the rotating body, and which can rotate with the rotating body facing the rotating body, and the endless belt. An elastic pad that is pressed as a pressurizing body that forms a nip portion that is pressed against the rotating body and holds and conveys a recording material carrying a toner image together with the rotating body in a heated state, and the nip portion. A separating member that separates the recording material from the rotating body on the downstream side, and a first region on the upstream side including the first end and a downstream including the second end in the cross section orthogonal to the longitudinal direction. A plate having an L-shape in which a second region on the side is bent at a predetermined position between the first end portion and the second end portion, and the elastic pad is supported by the second region. A fixing member that fixes at least a part of the first region of the leaf spring member in a state where the second end is fixed by the separating member in a cross section orthogonal to the longitudinal direction of the spring member. And, characterized by having.

According to the present invention, it is possible to suppress poor separation of the recording material at the downstream end of the nip portion even after long-term use.

Schematic configuration diagram of an image forming apparatus equipped with an image heating apparatus according to an embodiment of the present invention. Side model view of the main part of the image heating device according to the first embodiment Side model view of the pressure film unit in the first embodiment Perspective view of the pressure film unit in the first embodiment Frontal schematic view of the image heating device according to the first embodiment Schematic diagram of the side surface of the pressure film unit in the comparative example (first comparative example) Schematic diagram of the side surface of the pressure film unit in the second embodiment Schematic perspective view of the pressure film unit according to the third embodiment Configuration explanatory view 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 photoconductor drum as an image carrier, which is rotationally driven at a predetermined process speed (peripheral speed) in the clockwise direction indicated by the arrow. The photoconductor drum 101 is uniformly charged to a predetermined polarity and potential by the charging roller 102 in the rotation process.

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

Reference numeral 104 denotes a developing device, in which a developer (toner) is supplied from the developing roller 104a to the surface of the photoconductor drum 101, and the electrostatic latent image on the surface of the photoconductor drum 101 is sequentially developed as a toner image which is a transferable image. Will be done.

Reference numeral 105 denotes a paper feed cassette, in 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 materials P in the paper feed cassette 105 are separately fed one by one. Then, it is introduced at a predetermined timing into the transfer portion 108T, which is the contact nip portion with the transfer roller 108 that comes into contact with the photoconductor drum 101 and rotates drivenly via the resist roller pair 107. That is, the transfer of the recording material P is controlled by the resist roller 107 so that the tip of the toner image on the photoconductor drum 101 and the tip of the recording material P reach the transfer site 108T at the same time.

After that, the recording material P sandwiches and conveys the transfer portion 108T, and during that time, a transfer voltage (transfer bias) predeterminedly controlled 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 photoconductor drum 101 is electrostatically transferred to the surface of the recording material P at the transfer portion 108T. The recording material P after transfer is separated from the surface of the photoconductor drum 101, passes through the transport guide 109, and is introduced into the image heating device A.

The image heating device A undergoes heat fixing processing of the toner image. On the other hand, the surface of the photoconductor drum 101 after the toner image is transferred to the recording material P is cleaned by removing the transfer residual toner, paper dust, and the like by the cleaning device 110, and is repeatedly subjected to image drawing. The recording material P that has passed through the image heating device A is discharged onto the paper ejection tray 112 from the paper ejection port 111.

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

The thermal 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 raw tube 54 (cylindrical core metal) formed in a cylindrical shape having a predetermined length. Constitute. The raw pipe 54 of the thermal roller is made of a cylindrical body made of a metal having high thermal conductivity such as iron, aluminum, or SUS (here, a thin-walled high-tensile steel pipe is used). Further, as the heat-resistant elastic body layer 53 in the thermal roller 51, any material can be used 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), and specifically, silicone rubber, fluororubber or the like can be used.

Any resin may be used as the release layer 52 in the thermal roller 51 as long as it is a heat-resistant resin. For example, silicone resin, fluororesin, or the like can be used, but the release layer 52 is released from the toner. Fluororesin is suitable from the viewpoint of property and abrasion resistance. As the fluororesin, PFA, PTFE (polytetrafluoroethylene), FEP (fluorinated ethylene hexafluoropropylene copolymer) and 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 due to the distortion of the thermal roller 51, while if it exceeds 30 μm, the release layer 52 becomes hard and the image This is because the possibility of uneven gloss and the like increases, and both are not preferable.

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

The pressure film 56 as an endless belt that circulates (rotates) synchronously while being pressed against the thermal roller 51 is formed in an endless track shape (cylindrical shape having a predetermined length). The pressure film 56 is configured as an endless belt (endless belt) that can rotate facing the thermal roller 51, and includes a base layer 57 and a release layer 58 coated on the surface of the base layer 57 on the thermal 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 its thickness is about 30 to 200 μm, preferably about 50 to 100 μm.

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

The pressure film 56 configured in this way is rotatable (rotating operation) by slidingly contacting the pressure pad 59 as a pressurizing body that is in sliding contact with the inner peripheral surface thereof via the low friction sheet 72. It is supported freely). Then, the pressure film 56 is attached so that the fixing nip portion (nip portion) corresponding to the pressure pad 59 is transferred to the heat roller 51 at a predetermined pressure.

Next, the members arranged inside the pressure film 56 will be described with reference to FIG. The pressure pad 59 is inside the pressure film 56, presses the heat roller 51 with a predetermined pressure distribution through 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 while being elastically deformed, and is in the rotation direction of the pressure film 56 and the heat roller 51 (the transport direction of the recording paper 24). It has a predetermined length. Moreover, it refers to a substantially rectangular region in a plan view extending in the longitudinal direction of the pressure film 56 and the thermal roller 51.

The pressure pad 59 presses against the heat roller 51 via the pressure film 56 to form a nip portion that holds and conveys the recording material carrying the toner image together with the heat roller 51 in a heated state, and pressurizes the elastic pad. It is composed of a pad member 60 and a rectangular long body 63 for a pressure pad. Then, the pressure pad member 60 is configured by fixing the auxiliary member 60B formed of a long metal plate material to the bottom surface of the elastic material (elastic body) 60A formed in a prismatic shape. Further, the main body 63 for the pressure pad is configured to include a downstream jaw member 62 made of resin and an installation portion 62A of a rectangular groove-shaped pressure pad member 60 adjacent thereto.

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

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

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

The downstream jaw member 62 can be formed from, for example, a heat-resistant resin such as PPS (polyphenylene sulfide), polyimide, polyester, or 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 in which the outer surface shape of the nip portion has a constant radius of curvature.

As described above, the downstream jaw member 62 is formed as a part of the main body 63 for the rectangular elongated pressure pad, and is connected to the installation portion 62A of the rectangular groove-shaped pressure pad member 60 at a position adjacent to the upstream side. It is integrally formed (integrated). Then, the pressure pad member 60 is fitted into the installation portion 62A with the installation portion 62A on the bottom side and integrally assembled. As a result, the pressure pad member 60 and the downstream jaw member 62 form one pressure pad 59 that is adjacent to each other in the longitudinal direction.

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

The leaf spring member 71 has a first region 71C on the upstream side including the first end V and a second region 71C on the downstream side including the second end H in a 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 leg (foot) 70D on the downstream side is formed shorter than the leg (foot) 70A on the upstream side in the recording material transport direction, and the second end H is set as a free end at a predetermined position M. At least a portion of the first region of the leaf spring member 71 is fixed so that it can be displaced around the. That is, of the first end V and the second end H of the leaf spring member 71, only one end side (only the first end 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 leg portion (foot) 70A on the upstream side, 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 at the installation portion with the leaf spring 71 indicated by 70C. Then, the leaf spring member 71 is fixed (coupled) to the side surface of the T stay 70 by a screw (not shown) in the region of the first region 71C on the upstream side. In this way, the pressure pad 59 is in contact (contact) with and supported by the leaf spring member 71 on the surfaces 59A and 59B.

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

In FIG. 2, when the recording paper 24 as a recording material invades the fixing nip portion, an additional pressure corresponding to the thickness of the recording paper 24 is applied to the pressure pad 59 via the pressure film 56, and the pressure is applied to FIG. As shown in the above, the region 71D received from the pressure pad 59 swings in the direction of the arrow. As a result, the additional pressure due to the recording paper 24 can be released, and the increase in pressure in the nip due to 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. With such a configuration, it is possible to make a state in which a plurality of finely divided regions 71D exist, not a state in which the region 71D exists over the entire longitudinal direction.

As a result, each of the divided regions 71D can swing independently. For example, when a recording paper having a short length in the longitudinal direction and a thick material such as an envelope invades 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 has a plurality of regions 71D each of which is a cantilever that swings independently 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 the situation where pressure is locally applied to the edges at both ends.

Further, in the configuration of the present embodiment, as shown in FIG. 3, the low friction sheet 72 is put on the pressure pad 59 in order to prevent the elastic material 60A 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 leaf spring member 71 in the vicinity of 71C where the leaf spring member 71 is fixedly supported by the T stay 70. .. Specifically, the low friction sheet 72 is fastened to the T stay 70 together with the leaf spring member 71 with screws (not shown) while stabilizing the shape by the pressing member 73. As a result, the low friction sheet 72 can be fixed with a simple structure.

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

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

In FIG. 5, the thermal 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 thermal roller 51. The flange members 12a and 12b shown in FIG. 5 are fitted onto 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. Then, when the thermal roller 51 rotates, it receives the end portion of the pressure film 56 and serves to regulate the lateral movement of the pressure film 56 along the longitudinal direction. As the material of the flange members 12a and 12b, a material having good heat resistance such as LCP resin is preferable.

When the halogen lamp 55 arranged inside the thermal roller 51 shown in FIG. 2 is energized, the recording paper 24 is placed on the fixing nip portion at the timing when the surface of the thermal roller 51 rises to a predetermined temperature due to heating by the halogen lamp 55. It will be carried in. As a result, the operation of fixing the toner image placed on the recording paper to the recording paper 24 is performed.

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

In FIG. 6, a pressure pad 159 is arranged inside the pressure film 56 in the same manner as the pressure pad 59 in FIG. The pressure pad 159 is composed of 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. Then, an elastic member 75 made of silicon rubber is arranged 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 for supporting and fixing the elastic member 75 is arranged on the lower surface of the elastic member 75, and the T stay 170 supports all the above-mentioned members via the resin stay 76. .. The resin stay 76 has a shape in which walls are erected on the upstream side and the downstream side in the transport direction of the recording paper, and also plays a role of fixing the positions of the pressure pad 159 and the elastic member 75 in the transport direction. There is.

The position of the pressure pad 159 in the recording paper transport direction is determined by abutting 74A (downstream side), which is one surface of the downstream jaw member 74, against 76A, which is one surface of the resin stay 76. When the recording paper has entered the fixing nip portion of the image heating device 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. As a result, the additional pressure due to the recording paper 24 can be released, and the increase in pressure in the nip portion due to the recording paper 24 can be reduced.

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

Specifically, every time 500 sheets of SpringHill 199 g paper are passed, 5 sheets of recording paper CS520 which is left in a high temperature and wet environment (temperature 30 ° C., humidity 80%) and contains water (moisture content 9%) is passed. Paper. CS520 is a thin paper having a low basis weight, has a thickness of about 67 μm, and becomes a recording paper in which wrapping around the thermal roller 51 is likely to occur because the rigidity is lowered by containing a larger amount of water. When passing the CS520 paper, a solid image was drawn with toner near the tip of the paper to make it easier to wrap.

Through the above experiments, it was compared whether or not the wrapping of CS520 occurs in the configuration of this embodiment and the comparative example. In the present embodiment, the CS520 does not wrap even when 500 sheets of SpringHill 199 paper are passed through 20 cycles (10000 sheets in total). After that, the cycle was switched to 5 CS520 sheets for every 10000 sheets of SpringHill199 paper, and the experiment was continued until the cumulative number of sheets of SpringHill199 paper reached 100,000 sheets, but the CS520 was wrapped around the heat roller 51. There wasn't.

On the other hand, in the comparative example, when 500 sheets of SpringHill 199 paper were passed 5 times, a corner fold began to occur at the tip of the CS520. This occurs because the separability from the thermal roller 51 deteriorates and the heat roller is slightly wrapped and discharged from the fixing nip portion, so that the heat roller 51 is caught by a guide near the paper path behind the fixing nip portion. Then, when 500 sheets of SpringHill 199 paper were passed 5 times (10 cycles in total), the CS520 wound around the thermal roller 51, jammed, and stopped the printing operation.

When the image heating device of the comparative example after the experiment was disassembled and examined, the surface 74A (FIG. 6) on the downstream side of the downstream jaw member 74 was scraped off, and the surface 74A was in contact with the downstream jaw member 74 to position the downstream jaw member 74. The surface 76A (FIG. 6) of the resin stay 76 in which the above is performed was also scraped in the same manner.

This is because the elastic member 75 is compressed by the thickness of the paper due to the passing of SpringHill 199g paper, the pressure pad 159 swings, and the surface 74A of the downstream jaw member 74 and the 76A of the resin stay 76 slide. It is probable that it has been rubbed and worn. As a result, the position of the pressure pad 159 in the recording paper transport 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. Then, the force for separating the CS520 was weakened, and the heat roller 51 was wrapped around the heat roller 51.

Here, the total amount of wear 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 the shift is made by 1 mm, the pressure in the nip portion becomes weak and the CS520 separation failure 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 (surface 71P in FIG. 4), so that the recording paper transport direction The position of is decided. The place supporting the surface 59B is located upstream of the center position (center) of the nip portion in the recording material transport direction, and approaches the fulcrum (predetermined position M) when the leaf spring member 71 swings. This is a portion where there is almost no displacement even when the leaf spring member 71 swings. Therefore, since rubbing hardly occurs between the leaf spring member 71 and the surface 59B of the pressure pad 59, the surface 59B of the pressure pad 59 does not wear.

Therefore, in the present embodiment, even when a large amount of SpringHill 199 g paper is passed and the leaf spring member 71 swings so as 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. The pressure does not fluctuate and no wrapping occurs.

As described above, if the pressure pad is supported near the fulcrum of the leaf spring member having the structure of the cantilever as in the present embodiment, even when a large amount of thick recording paper is passed, the inside of the fixing nip portion is provided. The nip pressure does not decrease, and good separability can be maintained.

<< Second Embodiment >>
Next, the configuration of the second embodiment of the present invention will be described with reference to FIG. In the image heating device of the present embodiment, the shape of the downstream jaw member constituting the pressure pad 259 as the pressurizing body is different from that of the first embodiment. This part will be described with reference to FIG. 7, and the other parts including the T-stay 70 are the same as those in the first embodiment, and thus the description thereof will be omitted.

The downstream jaw member 77 shown in FIG. 7 has a configuration in which the leaf spring member 71 is incorporated into a mold and integrally molded at the time of resin molding, so that the downstream jaw member 77 is directly attached to the downstream edge of the leaf spring member 71. As shown in FIG. 7, in the T-stay 70, the leg (foot) 70D on the downstream side is formed shorter than the leg (foot) 70A on the upstream side in the recording material transport direction so as not to interfere with the downstream jaw member 77. It is configured in.

The pressurizing pad 60, which is pressurized as the main pressurizing body in the present embodiment, is arranged so as to be directly supported by the leaf spring member 71 via the sheet metal 60B. In this way, the pressure pad 60 is positioned in the recording paper transport direction by being supported by the downstream jaw member 77 integrally molded with the leaf spring member 71 from the downstream side in the recording paper transport direction.

Further, a guide member 78 for guiding the leaf spring member 71 is arranged 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.

As in the first embodiment, the T-stay 70 supports a part (upstream side) of the area 71B of the leaf spring 71 at the installation portion with the leaf spring 71 shown by 70C. Then, the leaf spring member 71 is fixed (coupled) to the side surface of the T stay 70 by a screw (not shown) in the region of the first region 71C on the upstream side. In this way, the pressure pad 259 contacts (contacts) with the leaf spring member 71 and is supported.

In this embodiment as described above, an experiment was conducted to see if good separation performance could be maintained through paper. In the experiment, in order to greatly swing the leaf spring member 71 as described in the first embodiment, continuous printing was performed using SpringHill 199 g paper having a thickness of 240 μm as the recording paper.

Every time 500 sheets of SpringHill 199 g paper were passed, the sheet was left in a high temperature and wet environment (temperature 30 ° C., humidity 80%), and 5 sheets of recording paper CS520 containing water (moisture content 9%) were passed. The CS520 is a thin paper having a low basis weight, has a thickness of about 67 μm, and becomes a recording paper in which wrapping around the thermal roller 51 is likely to occur because the rigidity is lowered by containing a larger amount of water. When passing the CS520 paper, a solid image was drawn with toner near the tip of the paper to make it easier to wrap.

In the present embodiment, the CS520 does not wrap even when 500 sheets of SpringHill 199 paper are passed through 20 cycles (10000 sheets in total). After that, the cycle was switched to 5 CS520 sheets for every 10000 sheets of SpringHill199 paper, and the experiment was continued until the cumulative number of sheets of SpringHill199 paper reached 100,000 sheets, but the CS520 was wrapped around the heat roller 51. There wasn't.

Further, in the present embodiment, the downstream jaw member 77 is directly fixed to the leaf spring member 71. When the leaf spring member 71 swings, there is no place where rubbing occurs, so even if a thick recording paper such as SpringHill 199g passes through the nip, there are no parts that wear. Therefore, since the pressure of the fixing nip is not affected, good separation performance can be maintained through long-term paper passing.

As described above, even if the downstream jaw member 77 is directly fixed to the leaf spring member 71 as in the present embodiment, the image heating device that does not impair the separation performance can be formed.

<< Third Embodiment >>
Next, the configuration of the third embodiment of the present invention will be described with reference to FIG. In the present embodiment, the following improvements have been made to the leaf spring 71 in order to realize an image heating device that does not cause poor separation of the recording paper even after long-term use of the leaf spring 71. That is, not only is there little fluctuation in the nip pressure due to the fact that the position of the pressure pad in the transport direction does not fluctuate, but also the pressure pad portion fluctuates and local pressure can be avoided even when thick recording paper enters the fixing nip portion. It was made like this. Since the parts other than the leaf spring 71 including the T-stay 70 are the same as those in the first embodiment or the second embodiment, the description thereof will be omitted.

The leaf spring 71 in the present embodiment has a plurality of notch shapes 71E in the longitudinal direction orthogonal to the recording material transport direction. As shown in FIG. 8, the notch shape is arranged at a position corresponding to the size of the paper to be passed through the image heating device A. 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 notch shapes 71E_A4 is set to be about 2 to 3 mm larger than the paper width of 210 mm.

The configuration of local pressure avoidance in the present embodiment will be described with reference to FIG. 9 viewed from the downstream side in the recording material transport direction by comparison with a comparative example (second comparative example). FIG. 9A shows a schematic view of the image heating device of the comparative example (second comparative example) as viewed from the downstream side in the transport direction when the A4 paper has entered the nip portion. The A4 paper P is sandwiched between a thermal roller 51 and a pressure film 56 (FIG. 2) (not shown in FIG. 9). There is a downstream jaw member 62 under the pressure film 56, and the substantial heat roller 51 and the downstream jaw member 62 are strongly pressed against each other to elastically deform the release layer of the heat roller 51 and release the recording paper. There is.

In the image heating device of the comparative example (second comparative example), the notch shape 71E of the A4 paper edge and the leaf spring 71 are not aligned, and the notch shape 71E is inside the A4 paper edge. Have been placed. The downstream jaw member 62 is pushed by the outer leaf spring 71D portion as shown in FIG. 9A, and an extra load is applied to the A4 paper edge portion. As a result, some local pressure concentration is generated at the edge of the A4 paper of the downstream jaw member 62, although it is less than that of the conventional example.

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

(Modification example 1)
In the above-described embodiment, the fixing device for fixing the unfixed toner image to the sheet has been described as an example of the image heating device, but the present invention is not limited to this, and is assumed to be attached to the sheet in order to improve the gloss of the image. The same applies to a device that heats and pressurizes a toner image.

(Modification 2)
In the above-described embodiment, the recording paper has been described as the recording material, but 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, a standard or irregular plain paper, thick paper, thin paper, envelope, postcard, sticker, resin sheet, transparency, etc. Glossy paper and the like are included. In the above-described embodiment, for convenience, the handling of the recording material S has been described using the terms paper, paper passing, paper feeding, and paper ejection, but the recording material in the present invention is not limited to paper. Absent.

51 ... Thermal roller, 56 ... Pressurized film, 59 ... Pressure pad, 60 ... Pressurized pad member, 62 ... Downstream jaw member (separation member), 70 ... T stay, 71 ... Leaf spring, 77 ... Downstream jaw member (separation member), V ... 1st end, H ... 2nd end, M ... predetermined position

Claims (11)

With a rotating body,
An endless belt whose longitudinal direction is the longitudinal direction of the rotating body and which can rotate with the rotating body facing the rotating body.
A pressurizing body that presses against the rotating body via the endless belt to form a nip portion that holds and conveys a recording material carrying a toner image together with the rotating body in a heated state, and is an elastic pad and the elastic. A pressurizing body including a separating 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, the first region on the upstream side including the first end portion and the second region on the downstream side including the second end portion are the first end portion and the first region. A leaf spring member having an L-shape bent at a predetermined position between the two ends and supporting the pressurizing body in the second region.
Within the cross section orthogonal to the longitudinal direction, at least a part of the first region is fixed in a state where the second end portion of the leaf spring member is a free end, and the nip is inserted through the leaf spring member. A fixing member that fixes the separating member at a position upstream of the center position of the portion,
An image heating device characterized by having. The image heating device according to claim 1, wherein the position for fixing at least a part of the first region is a position close to the predetermined position. With a rotating body,
An endless belt whose longitudinal direction is the longitudinal direction of the rotating body and which can rotate with the rotating body facing the rotating body.
An elastic pad that is pressed against the rotating body via the endless belt and is pressurized as a pressurizing body that forms a nip portion that holds and conveys a recording material carrying a toner image together with the rotating body in a heated state.
A separating member that separates the recording material from the rotating body on the downstream side of the nip portion, and
Within the cross section orthogonal to the longitudinal direction, the first region on the upstream side including the first end portion and the second region on the downstream side including the second end portion are the first end portion and the first region. A leaf spring member having an L-shape bent at a predetermined position between the two ends 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 where the second end is fixed by the separating member in a cross section orthogonal to the longitudinal direction.
An image heating device characterized by having. The image heating device according to claim 3, further comprising a guide member that guides the leaf spring member on the upstream side of the nip portion. Any one of claims 1 to 4, 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 device according to the section. The image heating device according to any one of claims 1 to 5, wherein the rotating body is a heating member having a heating source inside. The image heating device according to any one of claims 1 to 6, wherein the separating member is made of a material having a hardness higher than that of the elastic pad. The image heating device according to any one of claims 1 to 7, wherein the fixing member is a metal stay. The image heating device according to any one of claims 1 to 8, wherein the leaf spring member includes notches at one or more positions in the longitudinal direction. The image heating device according to claim 9, wherein the position of the notch is provided so as to be on the end side of the recording material in the longitudinal direction. The image heating device according to any one of claims 1 to 10, wherein the fixing member is supported by a spring receiving member via a pressure spring at both ends in the longitudinal direction.