JP3440773B2 - Fixing device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device using a metal thin cylindrical body as a heating roll in a fixing process, and more particularly to a fixing device used in an electrophotographic copying machine, a printer, a facsimile or the like. The present invention relates to a fixing device that solves the problem of insufficient strength that occurs when a thin heating roll is used. .

[0002]

2. Description of the Related Art Conventionally, in a copying machine utilizing an electrophotographic process, it is necessary to fix an unfixed toner image formed on a recording sheet into a permanent image. As the fixing method, a heat fixing method in which a toner is melted by heating and then fused on a recording sheet is widely adopted.

A fixing device using such a heat fixing method will be described. FIG. 1 is a diagram illustrating the configuration of a heat fixing device. In FIG. 1, 11 is a heater for heating, and 12
Is a hollow metallic cylindrical core metal, 13 is a heat-resistant release layer, 1
4 is a fixing roller, 15 is a cylindrical core metal, 16 is a heat resistant elastic layer, 17 is a pressure roller, 18 is a toner image to be fixed, 1
9 is a sheet (recording paper).

As shown in FIG. 1, the heat fixing device includes a heater 11 for heating inside a cylindrical core metal 12, and a fixing roller 14 having a heat resistant release layer 13 formed on the outer peripheral surface thereof.
The pressure roller 17 is arranged in pressure contact with the fixing roller 14. The pressure roller 17 is formed by forming the heat resistant elastic body layer 16 on the outer peripheral surface of the cylindrical core metal 15.

In the fixing process by the fixing device having such a structure, the sheet (recording paper) 19 on which the unfixed toner image 18 is formed is inserted between the fixing roller 14 and the pressure roller 17 to perform fixing. This type of heat-fixing roller type fixing device has higher thermal efficiency than other heat-fixing methods such as flash fixing method and oven fixing method, so it consumes less electric power, has high speed, and has a flame due to paper jam. It is currently the most widely used due to its low risk.

Further, in the heat fixing roller type fixing device, it is desirable to shorten the time required for raising the surface temperature of the heating roll from room temperature to a predetermined set temperature (hereinafter referred to as warm-up time). However, it usually takes a long time of 1 to 10 minutes. This is because the roll heat capacity can be reduced only to some extent.
The warm-up time is determined by the relationship between the heat capacity of the roll and the input power, if a simple calculation is performed. For this reason, it is attempted to reduce the roll heat capacity in order to shorten the warm-up time, but there is a limit to the reduction of the roll heat capacity rather than the roll rigidity.

In a heat fixing roller type fixing device, the pressure in the contact area (nip area) between the heating roll and the pressure roll is generally 0.5 in order to ensure a predetermined fixing performance. A pressure of about 5.0 kg / cm ² is required. This is because if the pressure is lower than this, it is not possible to fill the gap due to the presence of irregularities on the paper or the roll surface, and it becomes impossible to efficiently transfer heat to the powder toner. In addition, the toner surface after fixing becomes mottled and the image quality deteriorates.

In order to obtain such a pressure in the nip region, the total load applied between both rolls reaches 20 to 200 kg. Therefore, the heating roll needs to be manufactured so as to have a strength capable of withstanding this load. In addition, there is a limit to the roll diameter reduction and the wall thickness reduction due to the necessity of rigidity of the heating roll.

On the other hand, various techniques have been developed for increasing the allowable stress of thin rolls. Next, regarding the case of utilizing the technique for increasing the allowable stress of these rolls, the technique for increasing the allowable stress up to now and the problem when applying them to the fixing device will be considered.

As a first method for increasing the allowable stress of the roll, there is a method of subjecting a thin metal roll to a heat treatment accompanied by transformation such as induction hardening or carburizing. According to the first method, the allowable stress of the roll increases, but the roll is warped or bent because the process for the roll is performed at a high temperature and transformation occurs in the material. Therefore, when applied to a fixing device, the shape of the pressure contact area (nip area) in the fixing process becomes non-uniform in the axial direction, or when the heat resistant elastic body layer is coated after heat treatment of the roll, the coating of the heat resistant elastic body is performed. It cannot be used as a heating roll because of problems such as uneven amount.

As a second method, for example, Japanese Patent Laid-Open No. 56-
As described in Japanese Patent No. 158359, there is a method of nitriding an iron roller material used as a fixing roller. According to this method, the nitriding treatment for the roller material is usually performed at a low temperature of 500 ° C. to 600 ° C., so that the shape deterioration such as the warp or bending of the roll is unlikely to occur.

[0012]

By the way, the fixing device has a structure in which both ends of a metallic heating roll serving as a fixing roll are pivotally supported. In the metallic heating roll having such a structure, the shafts at both ends are supported. In the place where it is supported, the working stress tends to increase. Therefore, the metallic heating roll has a structure in which both ends are reinforced. For example, as shown in FIG. 2, a metallic boss portion 3 is provided at both ends of the metallic heating roll core 1 and an offset prevention layer 2 is provided on the surface of the metallic heating roll core 1. It This is as described in the above-mentioned JP-A-56-158359.

However, when a thin metal roll is used as the metallic heating roll core metal, it is difficult to provide the boss portions 3 at both ends of the heating roll core metal because of its thin thickness. Therefore, instead of providing such a boss portion 3, for example, as shown in FIG. 3, a heating roll core metal 4 subjected to a drawing process is used as a fixing roll. It is effective to apply a drawing process to a metallic roll to reinforce both ends, but when applying a drawing process, a certain amount of wall thickness is required and when the metal roll is thin. However, it is difficult to implement due to the problems of deformation and manufacturing tolerances. In FIG. 3, reference numeral 4 indicates a heating roll core bar subjected to drawing processing, and 2 indicates an offset prevention layer.

By the way, when a metallic roll is used as a fixing roll, if surface heat treatment without transformation such as nitriding treatment is performed, the fatigue strength can usually be increased by hardening the surface portion. In the thin metal heating roll, since a large stress amplitude is applied to the inside in the fixing process of the fixing device, the surface heat treatment only by surface hardening does not increase the fatigue strength so much.

The present invention has been made in view of the above problems, and an object of the present invention is to use a thin-walled heating roll capable of significantly shortening the warm-up time without increasing the manufacturing cost. It is to provide a fixing device.

[0016]

In order to achieve the above-mentioned object, the fixing device of the present invention has, as a first feature, a pressurizing member which is in pressure contact with a heating roll whose both ends are axially supported. In a fixing device in which a transfer material carrying an unfixed toner image is passed through a pressure area to be heat-fixed, a nitrogen diffusion layer by soft nitriding is formed on the entire area of the heating roll core bar in the thickness direction thereof. Nitriding treatment (including soft nitriding treatment)
It is characterized by performing. That is, in a fixing device that heats and presses a recording medium carrying a toner image to melt and press the toner image on the recording medium, a heating fixing roll that heats the recording medium and a rotation that drives the heating fixing roll to rotate. A driving unit and a pressurizing member that is disposed on the opposite side of the recording medium from the heat fixing roll and presses the heat fixing roll, wherein the heat fixing roll is a thin-walled metal cylindrical body and the metal. Having a heat-resistant release layer provided on the outer peripheral surface of the cylindrical body made of metal, the metal cylindrical body is a cylindrical body having a diffusion layer of nitrogen formed by soft nitriding treatment throughout the thickness direction thereof. Characterize.

As a second feature, in the fixing device of the present invention, a nitrogen diffusion layer is provided in the entire area of the thin metal roll core metal. As a third feature, the fixing device of the present invention is characterized in that the thickness of the thin metallic roll core metal is 1 mm or less. That is, the wall thickness of the metal cylindrical body is in the range of 0.1 mm to 1 mm.

A fourth feature of the fixing device of the present invention is that the pressing body is a pressing roll, and when the heating roll using a thin metal roll and the pressing roll are brought into pressure contact with each other, The pressure rolls should be bent in the same direction. Therefore, the pressure roll, a hollow cylindrical body,
A pressing member that is inserted into the hollow cylindrical body and has a central portion whose diameter is larger than that of both end portions that press the hollow cylindrical body against the heating and fixing roll is provided.

A fifth feature of the fixing device of the present invention is that the pressure body is a fixed pressure member such as a pad, and the portion of the fixed pressure member that is in pressure contact with the heating roll has an axial direction. When a fixing roller and the fixed pressure member are brought into pressure contact with each other, the bending direction of the heating roll and the direction of the convex shape of the fixed pressure member are in the same direction.

As a sixth feature, in the transfer device to which the fixing device according to the present invention is applied, an endless belt or an endless belt is sandwiched between the heating roller and the pressurizing member, and the belt is It is an intermediate transfer member to which a toner image formed on the image carrier is transferred.

As a seventh feature, in the fixing device or the transfer fixing device of the present invention, the image glossiness is changed by changing the set temperature of the heating roll.

As described above, the conventional thick heating roll can have a structure for reinforcing the end portion as shown in FIG. 2 or FIG. It is difficult to use a structure that reinforces the end portion by providing a boss portion or the like. Therefore, in the fixing device of the present invention, a heating roll driving type heating roll is used. In this case, in the heating roll driving type heating roll, as shown in FIG. A notch (key groove) 43 is provided in the notch 43 and a drive gear is connected to the notch 43. The cutout portion 43 is close to the support portion at the end portion and serves as a stress concentration portion. However, as will be described later, a roll core having a nitrogen diffusion layer formed by nitriding treatment is used so as to have sufficient fatigue strength. To In FIG. 4, 42 is a release layer.

Although the nitriding treatment varies depending on the treatment conditions, it is basically a thin compound layer (several .mu.m to tens of .mu.m) made of iron nitride or the like on the surface of steel, and solid solution hardening or precipitation by nitrogen underneath. Hardened diffusion layer (several 100 μm
Up to several mm). The hardness of the compound layer is H
v500-600, and the diffusion layer has Hv300.

The types of nitriding treatment are gas nitriding,
There are methods of salt bath nitriding, gas soft nitriding, and ion nitriding.
In gas nitriding, the processing temperature is 500 ° C. to 560 ° C., the processing time is 50 to 100 hours, and the thickness of the nitrided layer is 1 mm.
Reach a degree. However, since the processing time becomes long, the production efficiency becomes low. Further, as an applicable metal material, nitrided steel is required, so that the applicable range is narrow. Since brittle Fe ² N is generated on the surface after the treatment, peeling problem occurs when the heat-resistant release material or the heat-resistant elastic layer is provided on the heating roll.

On the other hand, in the salt bath nitriding, the treatment temperature is 500 to 600 ° C., the treatment time is 0.5 to 20 hours, and the thickness of the nitride layer is 0.3 to 0.5 mm.

Further, in the gas soft nitriding, the processing temperature is 55.
0 to 600 ° C., the treatment time is 0.5 to 20 hours,
The nitride layer has a thickness of 0.3 to 0.5 mm.

In ion nitriding, the processing temperature is 35.
The treatment time is 2 to 20 hours at 0 ° C. or lower, and the thickness of the nitride layer is 0.3 to 0.5 mm.

Therefore, when these nitriding methods (1) to (3) are used, the processing time is short and the productivity is high. Further, the treated material can be all steel materials, and even non-ferrous materials such as aluminum can be treated by ion nitriding. Therefore, it is preferable to use the nitriding methods (1) to (3). The temperature distribution of the heating roll, especially for the image quality, as a treatment of the core metal of the heating roll of the color fixing device, which is a problem,
It is very effective. Further, in the ion nitriding, the treatment temperature is the lowest, which is a more preferable treatment method for the thin metal roll.

When a thin heating roll is attached to a fixing device and used, a problem of destruction due to fatigue occurs. In a thin-walled heating roll, the break start position is often a stress concentration portion such as a cutout portion at the end. Then, when performing the nitriding treatment, usually, to prevent fatigue fracture is considered to prevent the occurrence of cracks in the compound layer of the outermost layer of high hardness, in the case of a thin heating roll It was found from the experimental results that the role of the nitrogen diffusion layer having the increased hardness is important because it receives a large stress amplitude inside.

Therefore, in the fixing device according to the present invention,
A nitrogen diffusion layer is formed by soft nitriding treatment on the entire area of the metal cylinder used as the fixing roll in the thickness direction. It is of course necessary that the stress diffusion area of the notch at the end of the heating roll be covered with the global diffusion layer, but the global diffusion layer also extends inside, which significantly increases the fatigue strength of the thin heating roll. . The nitrogen diffusion layer here is the same as the practical hardened layer depth (practical, ND-P) defined by JSHS1001 (Japan Heat Treatment Technology Association Standard), and is determined from the hardness of the base material. HV5
0 Depth up to high hardness.

On the contrary, when the diffusion layer does not reach the inside, the fatigue limit is almost the same as in the case where the thin heating roll is not treated, which is not preferable.

As a method used for nitriding the core of the heating roll, salt bath nitriding, gas soft nitriding, or ion nitriding in which a fragile Fe ² N layer is not deposited on the outermost layer is preferable. To form
The core thickness of the heating roll is preferably 1 mm or less. Further, from the viewpoint of manufacturing the metal roll core, in order to satisfy the roundness of the roll and the runout, it is preferably 0.1 mm or more. Therefore, it is assumed that the wall thickness of the metal cylindrical body is in the range of 0.1 mm to 1 mm. In this case, the warm-up time can be shortened to about 5 seconds to 2 minutes.

Further, when a steel material is used as a heating roll, "rust" which lowers the fatigue limit and causes peeling of the offset prevention layer and the rubber layer on the roll surface becomes a serious problem. It turned out that "rust" can be prevented by applying it. This is more remarkable by using a nitriding method such as salt bath nitriding, gas soft nitriding, or ion nitriding in which a fragile Fe ² N layer is not deposited on the outermost layer.

If the stress-concentrated portion such as the notch portion is processed before the nitriding treatment, rust will be generated from the machined portion. Therefore, rust prevention treatment is required for the machined part and it becomes expensive, but the rust prevention effect of the soft nitriding treatment is maintained by processing the stress concentration part such as the notch after the soft nitriding treatment. . In this case, it is possible to omit the rust-prevention treatment which has been conventionally required, and it is possible to reduce the manufacturing cost.

In the fixing device according to the present invention,
When a thin metal roll is used as the heating roll core metal, the material allowable stress is increased by nitriding treatment, but since the elastic modulus of the heating roll core metal does not change, the thin metal roll is used as a heating roll for the fixing device. When it is mounted on the heating roll and a load is applied, the heating roll may be deformed in the axial direction. If the amount of this deflection increases significantly, the contact area (nip area) between the heating roll and pressure roll becomes uneven, and when unfixed paper is passed, paper wrinkles occur and the fixing strength at the center of the paper is increased. Causes a weak offset and stains the next copy sheet, or the image is missing. On the other hand, in the fixing device of the present invention, such a problem is solved by adding a mechanism for correcting the axial deflection of the heating roll.

For example, as a pressure roll of the fixing device, a hollow cylinder is inserted into the hollow cylinder and the inside of the hollow cylinder, and the center of the hollow cylinder is more than the both ends pressing the heat fixing roll. A pressing member having an enlarged diameter is used (FIG. 7). Further, as the pressure body of the fixing device, a non-rotating fixed pressure body, in which the portion of the fixed pressure body that presses the fixing roll is convex in the axial direction of the heat fixing roll, is used. (FIG. 9).

Further, particularly in a color fixing device or a color transfer fixing device, when a thin metal roll such as the fixing device of the present invention is used, a heating roll having a very small heat capacity can be realized, and the roll surface The temperature can be changed in a relatively short time. Therefore, the image glossiness (a ratio of reflected light of 75 degrees to incident light of 75 degrees; this screen glossiness is hereinafter referred to as “gloss”) can be easily controlled.

By constructing the fixing device as described above, in the fixing device using the metallic thin heating roll, the warm-up time can be greatly shortened, and the energy consumption during standby can be greatly reduced. It becomes possible. Also, when applied to a fixing device of a color copying machine, it is possible to use a heating roll with a small heat capacity, the set temperature of the heating roll can be changed in a short time, and the gloss of the image can be appropriately changed. Becomes

[0039]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, modes for carrying out the present invention will be specifically described with reference to the drawings. Figure 4
FIG. 3 is a cross-sectional view showing the shape of a thin heating roll used in the fixing device according to the embodiment of the present invention. As the heating roll, an iron roll core 41 having a diameter of 35 mm, a wall thickness of 0.4 mm, and a length of 380 mm was used, and PFA (perfluoroalkyl vinyl ether copolymer resin) was formed as a release layer 42 on the surface of the roll core 41 by 25 μm. It was done. The roll core 41 has a wall thickness of 0.4 mm and a length of 380 m.
m STKM11A blank tube through centerless grinding,
It is manufactured. Length 19mm, width 5mm at the end
Is formed with a key groove 43. The key groove 43 and a gear (not shown) are connected to drive the heating roll by a drive motor. The roll core 41 is nitrided.

For the roll core 41 of the heating roll having such a structure, the following three types of roll cores were prepared and tested for the purpose of comparison between the embodiment of the present invention and the conventional example. 1. Untreated (A roll), 1. 2. Nitrogen diffusion layers having 0.1 mm on both sides (B roll), A nitrogen diffusion layer having 0.2 mm on both sides (a nitrogen diffusion layer covers the entire area) (C roll) was prepared. Note that the B roll and the C roll were subjected to nitriding treatment using a salt bath nitriding treatment method called tuftride. B
The roll was treated at 560 ° C. for 0.5 hours, while the C roll was treated at 560 ° C. for 2 hours.

The heating rolls of these three types of roll cores were mounted on a fixing device (not shown), and idle rotation without paper passing was carried out as a real mode fatigue test. As conditions for the fixing device during the test, the set temperature was 180 ° C. and the process speed was 300 mm / sec. The total load was changed between 10 kgf and 100 kgf. The result of the fatigue test in that case is as shown in FIG. In this test, the elapsed time was measured,
In the graph shown in FIG. 5, it is displayed as the number of cycles of repeated stress of compressive tension.

As is clear from the graph of FIG. 5, there is almost no difference in the fatigue strength between the A roll and the B roll, and cracks occur at the notches due to almost the same load. On the other hand, the fatigue strength of the C roll is significantly increased. This indicates that the thin metal heating roll cannot obtain the strengthening effect by the nitriding treatment unless the nitrogen diffusion layer extends over the entire area.

Next, a fixing device according to an embodiment of the present invention will be described. FIG. 6 is a diagram showing an example of a pressure roll used in the fixing device of the present invention. The structure of the fixing device is shown in FIG.
In the fixing device having such a structure as shown in FIG.
A roll 61 supported at the center is coated with a heat resistant release layer 62. As a result, when the fixing roller 14 for heating is pressed by the pressure roller 17, the bending directions of the pressure roller 17 and the fixing roller (heating roll) 14 are the same.

The pressure roller used in the fixing device of the present invention is
A roll 61 supported at the center is covered with a heat-resistant release layer 62 of silicon rubber having a thickness of 4 mm. As the heating roll 14, as described above, the heating roll shown in FIG. 4 was used. A total load of 70 kg is applied from the bearings at both ends. In this state, the deflection at the central portion of the heating roll reached 0.5 (mm), but as shown in FIG. 6, the deflection was corrected by the pressure roll using the roll 61 supported at the center. Then, when the nip formed by the heating roll and the pressure roll is measured, the roll end nip is 7.0 mm and the roll center nip is 6.4 mm. According to such a configuration, the nip shape index (center nip amount) / End nip amount) 0.9 could be obtained. In this state, Fuji Xerox Co., Ltd. copy machine "Vi
When the unfixed toner image imaged with "Vace 550 (trade name)" is fixed, sufficient fixing property is obtained and paper wrinkles are not generated at all.

FIG. 7 is a diagram showing another example of the pressure roll used in the fixing device of the present invention. As a pressure roll,
As shown in FIG. 7, the same effect can be obtained by using a roll having a convex central portion. That is, the pressure roll having the structure shown in FIG. 7 has a structure in which the pressure applying roll 73 having a convex central portion is provided inside the pressure rotating body 72.

In FIG. 7, 71 is a heating roll.
The load applied to the heating roll 71 of the fixing device having such a structure is applied to the load applying roll 73 via the pressure rotator 72.
It is configured to be applied from. In the above configuration, even if the heating roll (fixing roll) 71 is bent, the surface shape of the load applying roll 73 is changed to a drum shape in consideration of the amount of bending of the heating roll 71 and the rigidity of the pressurizing rotary member 72. Since the pressure rotator 72 bends following the deflection curve of the heating roll (fixing roll), a substantially uniform nip shape can be obtained.

FIG. 8 is a transverse sectional view for explaining the structure of the fixing device of another embodiment of the present invention. As shown in FIG. 8, in the fixing device of this embodiment, the heating roll 81 applies a salt bath nitriding treatment called a tuftride to the iron core 83 having a diameter of 35 mm, a wall thickness of 0.4 mm and a length of 335 mm for 560 The iron core 83 is coated with a fluororesin (trade name of Teflon / DuPont Co., Ltd.) in a thickness of 30 μm as the release layer 84.

At the center of the heating roll 81, a 100v, 1000w infrared lamp is provided as a heating source 85, and a temperature sensor 93 provided on the side of the heating roll 81 keeps the temperature constantly at 150 ° C. , Controlled by a temperature controller. The warm-up time at this time can reach 10 seconds. In addition, the heating roll 81 is 250 m by a drive motor (not shown).
It is driven at a speed of m / s.

The pressure rotator 82 is an aerial roll in which a stainless steel core 86 having an outer diameter of 30 mm, a wall thickness of 0.2 mm and a length of 310 mm is coated with a silicon rubber 87 having a wall thickness of 2.0 mm. The load applying roll 88 arranged inside the pressure rotating body 82 has an outer diameter of 20 mm and a length of 320 mm.
Roll end wall thickness of 1.0 mm on stainless steel core 89 of
Silicon rubber 90 so that the center of the roll is 1.6 mm
Is a drum-shaped roll. A total load of 50 kg is applied from the bearings at both ends, and the pressure rotor 82 is loaded from the center.

At this time, the amount of deflection of the heating roll (fixing roll) is about 0.5 mm. Compared with 0.1 mm, which was considered to be the limit of the conventional deflection amount, even with such a large deflection amount, the roll end nip is 6.0 mm and the roll center nip is 5.4 mm. The fixing device can obtain a nip shape index of 0.9. In this state, Fuji Xerox Co., Ltd. copy machine "Vivac"
e550 (trade name) ”unfixed toner image 9
When No. 1 was fixed on the recording paper 92, sufficient fixability was obtained and no paper wrinkles occurred. Moreover, even in the idle rotation mode in which the stress amplitude is 10 ⁶ cycles,
No breakage of the fuser roll was observed.

FIG. 9 is a view for explaining the structure of a fixing device according to still another embodiment of the present invention. The fixing device according to this embodiment is a fixing device that uses a pressure pad type pressing member provided with a convex shape in the axial direction so that the bending direction matches the heating roll, instead of the pressing roll. As shown in FIG. 9, the fixing device of this embodiment includes a fixing roll 20, a thin film endless belt 30, and a pressure pad 50 disposed inside the endless belt 30. As a result, the pressure pad 50 is pressed against the fixing roll 20, and a nip portion through which the recording sheet is passed is formed between the fixing roll 20 and the endless belt 30.

The fixing roll 20 has an outer diameter of 30 mm, a wall thickness of 0.35 mm, and a length of 360 mm, which is a cylindrical iron metal core 21 made of iron and subjected to salt bath nitriding treatment called tuftride at 560 ° C. for 2 hours. The outer surface of the iron core 21 is treated with silicone HTV as the elastic layer 22.
Rubber (rubber hardness 45 degrees: JIS-A) is coated to a thickness of 500 μm, and further, fluororubber is dip-coated to a thickness of 30 μm as a release layer 23 on the surface, and the surface is a mirror surface. Finished to a surface close to the state. Further, the fixing roll 20 has a halogen lamp 24 of 600 w as a heating source arranged therein. The surface temperature of the fixing roll 20 is detected by a temperature sensor 25, and the temperature controller controls the energization of the halogen lamp 24. , Its surface temperature is controlled at 150 ° C. Further, as the release agent, amino-modified silicone oil having a viscosity of 300CS is uniformly supplied to the release layer 23 of the fixing roll by an oil supply system (not shown).

On the other hand, the endless belt 30 has a circumference of 94.
The base layer 31 is a thermosetting polyimide having a thickness of 75 mm, a thickness of 75 μm, and a length of 320 mm, and PFA is coated on the outer peripheral surface to a thickness of 30 μm to form a release layer 32.

The pressure pad 50, which serves as a pressurizing member, is the support member 5.
1, an elastic body 52 disposed on the support 51, a low-friction film 54 stretched on the surface serving as a contact surface between the elastic body 52 and the endless belt 30, and a belt provided so as to rotate smoothly. The belt running guide 55 is provided. The elastic body 52 has a width of 10 mm and a wall thickness of 5 m.
A glass fiber sheet impregnated with a Teflon resin is used for the low-friction film 54, which is a silicone rubber having a length of m and a length of 320 mm and arranged on the surface thereof. A rib in the belt rotation direction is provided on the surface of the belt running guide 55,
The contact area with the inner peripheral surface of the endless belt 30 is reduced. Further, at both ends of the belt running guide 55, a brim-shaped member (not shown) for restricting the deviation of the belt is provided.

In order to obtain a predetermined fixing performance, the pressure pad 50 of the heat resistant fixing member is pressed against the fixing roll 20 by a compression coil spring (not shown) through the thin film endless belt 30 with a load of 40 kg. It In this case, as shown in FIG. 9 (b), the elastic body 52 has a height of the convex portion of 0.4 mm. Further, in this embodiment,
Although the convex portion is provided on the elastic body 52, it goes without saying that the convex portion may be provided on the support body 51. The winding angle of the endless belt 30 around the fixing roll 20 is about 45.
And the nip width is about 10 mm at this time. The driving force from the motor serving as a driving source is transmitted to the fixing roll 20 and the fixing roll 20 and the thin film endless belt 30.
Rotates in the direction of the arrow at a speed of 160 mm / sec.

As described above, the low friction sheet 54 is provided on the surface of the pressure pad 50. As the low friction sheet 54, for example, a glass fiber sheet (FGF) impregnated with Teflon manufactured by Chukoh Chemical Industries, Ltd. is used. -400-4) is used to cover the elastic body 52. This pressure pad 50
Amino-modified silicone oil is interposed as a lubricant between the surface of the endless belt 30 and the inner surface of the endless belt 30.

In this state, when the unfixed toner image imaged by the color copying machine "A-color 935 (trade name)" manufactured by Fuji Xerox Co., Ltd. is fixed, sufficient fixing property is obtained and No paper wrinkles occurred, and no breakage of the fixing roll was observed even in the idle rotation mode in which the stress amplitude was 10 ⁶ cycles.

Further, under the above conditions, "50" was obtained as the gloss average value for the single colors of yellow, magenta and cyan. Set the temperature of the heating roll to 145 ℃, 155 ℃
Then, the gross average values are "40" and "58", respectively.
Can be obtained. At that time, the core temperature of 150
The time required to change the temperature from ℃ to the set temperature (145 ° C., 155 ° C.) was 8 seconds in the former cooling and 4 seconds in the latter heating. Thus, the set temperature can be changed in a very short time, and the gloss can be easily controlled.

Further, the fixing device according to the present invention can be suitably applied as a heating roll of a transfer fixing device. Such an embodiment will be described. FIG. 10 is a diagram illustrating the configuration of an image forming apparatus according to still another embodiment of the present invention. In FIG. 10, 101 is an intermediate transfer medium, and an arrow 10
Rotate in the direction 2 at a speed of 300 mm / s. The intermediate transfer medium 101 needs to have heat resistance. As the base material, a film sheet of polyester, polyimide, polyamideimide, polyacrylate, polyetherimide, polyether sulfone, polyether ketone, polyparabanic acid or the like can be used.

In the transfer-fixing device of this embodiment, the intermediate transfer medium 101 has a peripheral length of 800 mm and a width of 320 m.
A substrate of polyamide having a thickness of 12 m and a thickness of 12 m coated with PFA fluororesin having a good releasability of 3 m was used. Further, in consideration of electrostatic transfer performance, carbon is used by dispersing carbon in the base material to have a resistance value of 10 ¹⁰ (Ωcm).

An image forming unit 104 for each color of a color image corresponding to the running direction 102 of the intermediate transfer medium 101.
Y, 104M, 104C, 104K are arranged,
A heating member 105 and a pressure member 106 are arranged on the downstream side.

The heating member 105 and the pressure member 106 are
The intermediate transfer medium 10 includes a heating roller 107 and a pressure roller 108 which are arranged to face each other.
1 is sandwiched between the heating area nip portion PA and the transfer fixing area to form a nip portion PB. In the heating area nip portion PA, the heating roller 107 is attached to the intermediate transfer medium 101.
The nip portion PA of 78.5 mm is formed by winding the nip portion PA 80 degrees.

The heating member 105 uses a heating roll obtained by subjecting a hollow core made of steel having a diameter of 49.5 mm and a wall thickness of 0.4 mm to salt bath nitriding treatment called tuftride at 560 ° C. for 2 hours. Further, the surface has a thickness of 250 μm.
Of 0.75 × 10 ⁻³ cal / ° C. · sec · cm, which is coated with silicone rubber. Heating member 105
Two types of halogen lamps 109A and 109B of 650 W and 550 W are built in at the center of the heat source.
With such a configuration, a startup time of about 20 seconds is achieved by turning on both lamps when the temperature of the initial operation when the power is turned on is raised.

The pressing member 106 is arranged so as to face the heating roller 107 and presses the heating roller 107 with a pressing force of 35 kg. The pressure member 106 uses, as the outer roll 108, a roll made by coating a heat-resistant hard resin such as polyimide on a steel pipe having an outer diameter of 30 mm and a wall thickness of 0.3 mm and further forming a 20 μm PFA tube on the surface thereof. , As the load applying roll 111,
A crown having a taper of 00 μm is provided.

The outer surface of the load applying roll 111 is covered with a hard silicone rubber having a thickness of 1.0 mm. With such a structure of the pressing member 106, the central portion is 1.5 m.
A transfer fixing nip shape with m and 1.6 mm at both ends is obtained. The dwell time when passing through this nip is 0.
It is 005 seconds, and the intermediate transfer medium is hardly heated in the transfer fixing area in this short time.

A drive roller 112 for moving the intermediate transfer medium 101 is disposed downstream of the heating member 105 and the pressure member 106 in the running direction of the intermediate transfer medium 101. Recording support (image recording paper) 103
Is separated from the intermediate transfer medium 101 by the peeling device 113 near the nip outlet. In addition, the intermediate transfer medium 1
01 is hooked on a pulling roller 114 for giving a constant tension.

In the transfer and fixing device having such a structure, the intermediate transfer medium 101 and the toner image 110 thereon are transferred from the heating roller 107 at the heating area nip portion PA where the intermediate transfer medium 101 and the heating roller 107 are in close contact with each other. Heat is transferred. As a result, the toner image 110 on the intermediate transfer medium 101 has a reduced viscosity, which causes an appropriate mixing of the uppermost toner layer and the lowermost toner layer, and further, the transparency of the toner layer itself is rapidly increased, The fixing process proceeds with good subtractive mixing.

At the exit of the nip portion PA, 200 ° C. which is 2.0 times the toner softening point temperature equal to the set temperature of the heating roller.
Is heated up. The heating roll is 2 with the temperature sensor 115.
Controlled to 00 ° C. After that, the intermediate transfer medium 101 on which the color toner image is transferred is superposed on the recording support 103 at the entrance of the transfer fixing nip PB, and is nipped and pressed by the heating roller 107 and the pressure roller 108. The toner image is brought into pressure contact with the recording support 103, is cooled and solidified while penetrating into the fibers of the recording material, and the transfer fixing is completed. At the nip outlet, the toner temperature becomes lower than the softening point temperature, so the toner cohesive force increases and the toner returns to the solid state. Further, the cohesive force of the toner of the toner image 110 is increased, and the toner image 110 is integrally moved from the intermediate transfer medium 101 to the recording support 103 having a large adhesive force with the toner and permeated. In this way, the color toner image on the intermediate transfer medium 101 is transferred onto the recording support 103 and simultaneously fixed.

Under these conditions, when the unfixed toner image imaged by the color copying machine "A-color 935 (trade name)" manufactured by Fuji Xerox Co., Ltd. is fixed, sufficient fixing property is obtained. As it was obtained, there were no paper wrinkles. Further, even in the idling mode in which the stress amplitude was 10 ⁶ cycles, the heating roll was not broken.

[0070]

As described above, the heating roll used in the fixing device and the transfer fixing device of the present invention is a thin metal roll, and has a much shorter warm-up time than the conventional one. The present invention can solve the problem of heating roll destruction that occurs due to insufficient strength of thin metal rolls, and at the same time solve the rust problem that was a conventional problem when using iron rolls. Further, since the strength of the heating roll is improved, it is possible to provide a heating roll core having a long life even in a high speed copying machine or a color copying machine using a high load. Further, since it is possible to use a heating roll having a small heat capacity in a color copying machine or a color printer, it is possible to change the set temperature in a short time and easily change the gloss of the image. . Considering the above effects, the industrial utility value of the present invention is very large.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a configuration of a heat fixing device,

FIG. 2 is a diagram showing an example of a structure of a conventional fixing roll;

FIG. 3 is a diagram showing another example of the structure of a conventional fixing roll;

FIG. 4 is a cross-sectional view showing the shape of a thin heating roll used in the fixing device according to the embodiment of the present invention.

FIG. 5 is a diagram showing the results of an actual mode fatigue test performed by mounting a heating roll with three types of roll cores on a fixing device.

FIG. 6 is a diagram showing an example of a pressure roll used in the fixing device of the present invention,

FIG. 7 is a diagram showing another example of a pressure roll used in the fixing device of the present invention,

FIG. 8 is a cross-sectional view illustrating the configuration of a fixing device according to another embodiment of the present invention,

FIG. 9 is a diagram illustrating a configuration of a fixing device according to still another embodiment of the present invention,

FIG. 10 is a diagram illustrating a configuration of an image forming apparatus according to still another embodiment of the present invention.

[Explanation of symbols]

1 ... Metallic heating roll core metal, 2 ... Offset prevention layer, 3
... Boss portion, 4 ... Heating roll core metal, 11 ... Heating heater, 12 ... Cylindrical core metal, 13 ... Heat resistant release layer, 14 ... Fixing roller, 15 ... Cylindrical core metal, 16 ... Heat resistant elastic body Layer, 1
7 ... Pressure roller, 18 ... Toner image to be fixed, 19 ... Sheet (recording paper), 20 ... Fixing roll, 21 ... Iron core,
22 ... Elastic layer, 23 ... Release layer, 24 ... Halogen lamp,
25 ... Temperature sensor, 30 ... Endless belt, 31 ...
Base material, 32 ... Release layer, 41 ... Roll core, 42 ... Release layer, 43 ... Key groove, 50 ... Pressure pad, 51 ... Support,
52 ... Elastic body, 54 ... Low friction film, 55 ... Belt running guide, 61 ... Roll supported at the center, 62 ... Heat-resistant release layer, 71 ... Heating roll, 72 ... Pressurizing rotating body, 73
... load applying roll, 81 ... heating roll, 82 ... pressure rotator, 83 ... iron core, 84 ... release layer, 85 ... heating source, 8
6 ... Stainless steel core, 87 ... Silicon rubber, 88 ... Load application roll, 89 ... Stainless steel core, 90 ... Silicon rubber, 91 ... Unfixed toner image, 92 ... Recording paper, 93 ...
Temperature sensor, 101 ... Intermediate transfer medium, 102 ..., 10
3 ... Recording support (image recording paper), 104 ..., 105 ...
106 ... Pressure member, 107 ... Heating roller, 108 ... Pressure roller, 110 ... Toner image, 111 ... Load applying roll, 112 ... Drive roller, 113 ... Peeling device, 114 ...
Tension roller, 115 ... Temperature sensor.

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-6-3995 (JP, A) JP-A-9-68883 (JP, A) JP-A-8-137310 (JP, A) JP-A-59- 77470 (JP, A) JP 59-183007 (JP, A) JP 61-13064 (JP, A) JP 5-285820 (JP, A) JP 10-176258 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G03G 13/16 G03G 13/20 G03G 15/16 G03G 15/20 F16C 13/00

Claims (8)

(57) [Claims] 1. A fixing device for heating and pressurizing a recording medium carrying a toner image to melt and press the toner image on the recording medium, wherein a heating fixing roll for heating the recording medium and rotating the heating fixing roll. A rotary drive means for driving; and a pressurizing member that is arranged on the opposite side of the recording medium from the heat fixing roll and presses the heat fixing roll, wherein the heat fixing roll is a thin metal cylindrical body, A heat-resistant release layer is provided on the outer peripheral surface of the metal cylinder, and the metal cylinder is a cylinder in which a nitrogen diffusion layer is formed by soft nitriding treatment in the entire thickness direction. A fixing device characterized by the above. 2. The fixing device according to claim 1, wherein the metal cylinder has a wall thickness in the range of 0.1 mm to 1 mm. 3. The fixing device according to claim 1, wherein the pressure body is a pressure roll, and the pressure roll and the heating roll are pressed when the heat fixing roll is pressed by the pressure roll. A fixing device in which the fixing rolls are bent in the same direction. 4. The fixing device according to claim 3, wherein the pressure roll is inserted into a hollow cylinder and the inside of the hollow cylinder, and the hollow cylinder is pressed against the heating fixing roll. And a pressing member in which the diameter of the central portion is larger than that of both end portions of the fixing device. 5. The fixing device according to claim 1, wherein the pressure body is a non-rotating fixed pressure body, and a portion of the fixed pressure body that presses the heat fixing roll is the heat fixing roll. A fixing device having a convex shape in the axial direction. 6. A transfer device for transferring and fixing a toner image held on a toner image holding member to an image receiving member, a heating fixing roll for heating the toner image on the toner image holding member, and the toner image holding member. With respect to the heat fixing roll, and a pressurizing member for pressing the heat fixing roll via the toner image holding member, wherein the heat fixing roll is at least a thin metal cylindrical body. A transfer device, wherein the metal cylinder is a cylinder having a nitrogen diffusion layer formed by soft nitriding treatment throughout the thickness direction. 7. A toner image holding member holding a toner image, a toner image on the toner image holding member and a recording medium are brought into contact with each other, and the toner image is heated and transferred onto the recording medium and fixed. An image forming apparatus including a transfer fixing unit, wherein the transfer fixing unit heats a toner image on the toner image holding member, a rotation driving unit that rotationally drives the heat fixing roll, and the toner image. A heating member arranged on the opposite side of the holding member from the heat fixing roll and pressing the heat fixing roll via the toner image holding member, wherein the heat fixing roll is at least a thin metal cylinder An image forming apparatus having a body, wherein the metal cylindrical body is a cylindrical body having a nitrogen diffusion layer formed by soft nitriding treatment formed over the entire thickness direction thereof. 8. A toner image carrier for holding a toner image, a recording medium, a transfer unit for transferring the toner image on the toner image carrier to the recording medium, and a toner image transferred to the recording medium. Fixing means for fixing, wherein the fixing means heats and heats the recording medium, a rotation driving means for rotationally driving the heating fixing roll, and a side of the recording medium opposite to the heat fixing roll. And a pressurizing body for pressing the heat fixing roll, wherein the heat fixing roll has at least a thin-walled metal cylindrical body, and the metal cylindrical body is nitrocarburized over its entire thickness direction. An image forming apparatus comprising a cylindrical body having a nitrogen diffusion layer formed by a treatment.