JPH10198206A - Pressure roller, heating device, image forming device and inspection method for pressure roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a material to be heated from wrinkling by shaping a pressure roller forming a heating nip part by being made to press-contact with a heating member and interposing and carrying the material to be heated at the heating nip part like an inverted crown. SOLUTION: The pressure roller 11 is the rotary body integrally concentrically provided with an elastic body 11b at the outside circumference of a mandrel 11a. Besides, it is made to press-contact with a heater with prescribed pressure (nip pressure) by a spring by interposing the lower surface of the material to be heated, that means, a film so as to form the heating nip part. Then, the roller 11 is shaped like the inverted crown whose outside diameter is increased toward both end parts from the central part in the longitudinal direction thereof. By shaping the roller 11 like the inverted crown, the carrying speed of a material to be recorded at the heating nip part is increased at both end parts and reduced at the central part. Thus, since such an effect that the material to be recorded is pulled to both sides can be obtained, the material to be recorded is prevented from wrinkling.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a heating device for forming a heating nip by pressing a heating member and the heating member, and holding and heating the material to be heated in the heating nip. The present invention relates to a pressure roller, a heating device having the above configuration, and an image forming apparatus provided with the heating device.

[0002]

2. Description of the Related Art Conventionally, most of electrophotographic copying machines, printers, and the like employ a contact heating type heat roller fixing method having good thermal efficiency and safety as a fixing means, and an energy saving type film heating method. .

[0003] A heat fixing device of a heat roller fixing system basically includes a heating roller (fixing roller) as a heating rotating body and an elastic pressing roller as a pressing rotating body pressed against the heating roller. A recording material (transfer material sheet, electrostatic recording paper, or the like) as a material to be heated, in which an unfixed image (toner image) is formed and carried on the pressure contact nip portion (fixing nip portion) of the two roller pairs by rotating the rollers (Electro-fax paper, printing paper, etc.) is introduced and passed through the press-contact nip, and the unfixed image is permanently fixed to the recording material surface by the heat from the heating roller and the pressure of the press-contact nip. This is to fix by heat and pressure.

Further, a film heating type fixing device is disclosed in, for example, JP-A-63-313182, JP-A-2-57878, JP-A-4-44075 to 4-44083, and JP-A-4-204980 to 4- 20
A heat-resistant film (fixing film), which is a heating rotating body, is brought into close contact with a heating rotating body (elastic roller) and slid and conveyed. A transfer material carrying an unfixed image is introduced into a press-contact nip formed by a heating element and a pressing member, and is conveyed together with the heat-resistant film. Is a device for fixing an unfixed image as a permanent image on a transfer material by the heat of the pressure contacting nip.

A film heating type heating device can use a linear heating element having a low heat capacity as a heating element and a thin film having a low heat capacity as a film.
It is possible to shorten the wait time (improve the quick start performance).

In this type of fixing method, a driving roller is provided on the inner peripheral surface of the film in the driving method of the fixing film.
A method in which the film is driven while applying tension to the film, or a method in which the film is loosely fitted into the film guide and the rotating body for pressing is driven to rotate the film in accordance with the rotating body for pressing (the rotating body driving method for pressing) ) Is known, but in recent years, since the number of components is small, the latter type of rotating pressurizing member driving method is often adopted.

[0007]

Generally, in a heat fixing apparatus, paper is sandwiched and heated in a state where a strong pressure of about 10 kg is applied in a nip portion, and thus there is a problem that wrinkles are generated.

For this reason, in the heat fixing device of the heat roller type, in order to prevent wrinkles, the fixing roller itself has an inverted crown shape, and a wrinkle is generated by generating a force to pull the paper to both sides in the nip portion. It is well known that this was prevented.

On the other hand, in a fixing device of a film heating system, a film corresponding to the fixing roller is a film.
It is very difficult to form a shape such as an inverted crown on a fixing film due to a manufacturing method such as film dipping.

[0010] Therefore, the fixing film cannot generate a force for pulling the paper being conveyed through the fixing nip portion to both sides, and the effect of preventing the generation of wrinkles cannot be obtained. Therefore, it is difficult to prevent wrinkles. Met.

As a second problem of this film type fixing device, the heat capacity of the heater itself is small, and instead of instantly warming to a predetermined temperature, the nip portion floats due to the nip portion floating or the nip becomes abnormally thin or disappears, so that the heat release amount is reduced. When there is a portion having a small amount of heat, the portion immediately becomes high in temperature, which may cause burning of the film. This is likely to occur on both outer sides of the envelope when fixing a thick envelope or the like.

Accordingly, an object of the present invention is to provide a pressure roller, a heating device, and an image forming apparatus in which the pressure roller has an inverted crown shape to prevent wrinkles of a material to be heated. Further, in the pressure roller, the heating device and the image forming apparatus, it is checked whether or not the average value of the outer diameter of the pressure roller is within a predetermined range. It is an object of the present invention to provide a pressure roller inspection method capable of appropriately controlling the conveying force.

[0013]

SUMMARY OF THE INVENTION The present invention is a pressure roller, a heating device, an image forming apparatus, and a method for inspecting a pressure roller having the following features.

(1) A heating member and a pressure roller used in a heating device which presses against the heating member to form a heating nip portion, and sandwiches and conveys the material to be heated by the heating nip portion to heat the heating member. A pressure roller, wherein the pressure roller has an inverted crown shape.

(2) The pressure roller according to (1), wherein the central portion in the longitudinal direction of the roller has an inverted crown shape with a straight shape.

(3) In a heating device, a heating nip portion is formed by pressing the heating member against the heating member, and the heating nip portion sandwiches and conveys the material to be heated. A heating device characterized by having a crown shape.

(4) The heating device according to (3), wherein the pressure roller has an inverted crown shape having a straight central portion in the longitudinal direction of the roller.

(5) A heater for heating, a film sliding on the heater, and a pressure roller in pressure contact with the heater via the film are provided. A heating device for heating a material to be heated by nipping and transporting the material to be heated, wherein the pressure roller has an inverted crown shape.

(6) The heating device according to (5), wherein the pressing roller has an inverted crown shape in which a central portion in a longitudinal direction of the roller is straight.

(7) The pressure roller has an inverted crown shape having a straight central portion in the longitudinal direction of the roller, and the member to be heated is introduced into the heating nip portion by central reference conveyance. The heating device according to any one of (3) to (6).

(8) The heating member is an envelope carrying an unfixed image, and the straight portion at the center of the pressure roller is narrower than the envelope size. (7)
A heating device as described.

(9) The heating device according to any one of (3) to (8), wherein the pressure roller is driven to rotate.

(10) The heating device according to any one of (3) to (9), wherein the average value of the outer diameter of the pressure roller is set to a predetermined range.

(11) An image forming means for carrying a developer image on a recording material, and heating the developer image on the recording material according to any one of (3) to (10). An image forming apparatus comprising: a heating device.

(12) The image forming apparatus according to (11), wherein the average value of the outer diameter of the pressure roller is set to a predetermined range based on the image forming speed of the image forming means.

(13) In the pressure roller, the heating device or the image forming apparatus according to any one of (1) to (12), whether or not the average value of the outer diameter of the pressure roller is within a predetermined range. A method for inspecting a pressure roller, comprising:

(14) In the image forming apparatus described in (11) above, it is checked whether or not the average value of the outer diameter of the pressure roller is within a predetermined range obtained based on the image forming speed of the image forming means. A method for inspecting a pressure roller, comprising:

(15) The average value is obtained by measuring the outer diameter of the pressure roller at a plurality of locations and weighing the measurement results according to the respective measurement positions (13) or (13). The inspection method of the pressure roller according to 14).

<Function> The effect of pulling the recording paper P to both sides due to the fact that the conveying speed of the recording material in the heating nip portion is high at both ends and low at the center portion by forming the pressure roller in an inverted crown shape. And the occurrence of wrinkles on the recording paper P is prevented.

Further, it is checked whether or not the average value of the outer diameter of the pressure roller is within a predetermined range, and it is possible to suppress the occurrence of variation in the conveying force due to the variation in the outer diameter of the pressure roller. Even in the case of the shape, the conveyance speed of the recording material can be appropriately managed.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION

<First Embodiment> 1. First Embodiment FIG. 1 is a schematic sectional view of an image forming apparatus to which the present invention is applied.

In FIG. 1, reference numeral 1 denotes a photosensitive drum serving as an image carrier, which is formed by forming a photosensitive material such as OPC or amorphous silicon on a cylindrical substrate such as aluminum or nickel. First, the surface of the photosensitive drum 1 is uniformly charged by a charging roller 2 as a charging device. The charged surface is irradiated with a laser beam L from an exposing unit 3, and the exposing unit 3 performs scanning exposure by controlling ON / OFF of the laser beam L in accordance with image information. A latent image is formed. This electrostatic latent image is developed by the developing device 4 and visualized. As a developing method, a jumping developing method, a two-component developing method, or the like is used, and in many cases, a combination of image exposure and reversal developing is used.

The recording material P is taken out of the manual tray 21 or the cassette 26 by the paper feed rollers 22 and 27, and the size of the recording material is detected by the trailing end detection sensor 23.
The sheet is sent to the registration roller 24. The size of the recording material may be determined by the registration sensor 25. The recording material P is supplied by a registration roller 24 to a transfer nip t formed by the photosensitive drum 1 and the transfer roller 5 in synchronization with the toner image formed on the surface of the photosensitive drum 1. At the transfer nip portion t, the toner image on the photosensitive drum 1 is transferred to the recording material P by the action of a transfer bias from a power supply (not shown).
The recording material P holding the toner image is conveyed to the fixing device 6, where the toner image is fixed on the recording material P by heating and pressing at the nip portion of the fixing device 6 to form a permanent image. And discharged out of the machine. On the other hand, the transfer residual toner remaining on the photosensitive drum 1 after the transfer is removed from the surface of the photosensitive drum 1 by the cleaning device 7.

2. Schematic Configuration of Fixing Device (Heating Device) FIG. 2 is a schematic sectional view of a film heating fixing device as an example of the heating fixing device of the present embodiment. Hereinafter, the configuration and operation will be described.

In FIG. 2, reference numeral 13 denotes a heat-resistant film (fixing film) in the form of an endless belt, which has a total thickness of 100 μm or less, preferably 40 μm or less and 20 μm to reduce the heat capacity and improve the quick start property.
As described above, P having heat resistance, release property, strength, durability, etc.
It is a single-layer film of TFE, PFA, PPS, or the like, or a composite layer film in which a film of polyimide, polyamideimide, PEEK, PES, or the like is coated with PTFE, PFA, FEP, or the like as a release layer.

Reference numeral 12 denotes a ceramic heater, which is made of Al ₂
A ceramic substrate made of O ₃ , AlN, SiC or the like, a heating element having a heating paste printed on the ceramic substrate, a glass coating layer for protecting the heating element and ensuring insulation. Then, the power-controlled AC current is supplied to the heating element on the heater 12 to generate heat. Further, a temperature detecting element (chip thermistor) 14 is adhered to the back of the ceramic substrate, and detects a temperature change within a time when power supply to the heater is turned off or on for a certain period of time when paper is not passed. The target temperature of the heater 12 is determined based on the detection result, and a heater driving unit (not shown) is controlled to control the power to the heater 12 so that the heater temperature is maintained at the target temperature (print temperature). ing.

Reference numeral 10 denotes a film guide member having a substantially semi-circular cross-sectional shape. The film guide member 10 holds a heater 12 on a lower surface of the film guide member facing downward, and a film 13 is externally fitted with the heater 12 held. The film guide 10, the heater 12,
The assembly of the films 13 and the like constitutes the heating member R of the present example.

Reference numeral 11 denotes a pressing roller as a pressing member, which is a rotating body having an elastic body 11b provided concentrically and integrally on the outer periphery of a cored bar 11a. The elastic body 11b is composed of an elastic layer b1 formed by molding a heat-resistant rubber such as silicone rubber or foaming the silicone rubber, and the like, and is formed on the elastic layer b1 by a fluororesin such as PFA, PTFE, and FEP. A heat-resistant release layer b2 may be formed.

The pressure roller 11 is heated by a spring (not shown) with the heater 12 sandwiching the lower surface of the heating member R, that is, the film 13.
At a predetermined pressure (nip pressure) against the heating nip N
Is formed. The pressure roller 11 is driven to rotate clockwise as indicated by an arrow in the figure by a pressure roller driving means 15 to rotate the fixing film 13 in a driven manner, and to move the recording material P introduced into the nip N into the fixing film 13. 13 and is conveyed in a state of being brought into close contact therewith. As the recording paper P is conveyed in the nip portion N, the unfixed toner image formed and carried on the recording paper P as described above is transferred to the heating member R.
The fixing process is performed by the heat and the nip pressure.

The apparatus of this embodiment has a configuration in which the recording paper P is introduced into the heating nip N by the central reference conveyance as shown in FIG.

3. Shape of Pressure Roller 11 In the present embodiment, the pressure roller 11 has an inverted crown shape whose outer diameter increases from a central portion to both ends in the longitudinal direction of the roller. FIG. 4 is a schematic explanatory view showing the shape (inverted crown shape) of the pressure roller 11 used in the present embodiment.

In the apparatus of this embodiment, the maximum size of the recordable paper that can be passed is LTR, and the paper passing width at this time is 21 LTR.
6 mm, the length (rubber length) L3 of the elastic body 11b
Used was 220 mm.

Both ends L0 to L1, L of the pressure roller 11
2 to L3 have a tapered shape, and the positions at 0 mm and 220 mm are the thickest, and their outer diameters are D1 = D3 = φ20.
2 mm. Further, the central portion L1 of the pressure roller 11
L2 has a straight shape and an outer diameter D2 = φ20.0. Differences D1-D2, D between the outer diameter of the both ends and the outer diameter of the center.
3-D2 is called an inverse crown amount.

As described above, in this embodiment, the pressure roller 11
Has an inverted crown shape, the effect of pulling the recording paper P to both sides due to the fact that the recording paper conveyance speed at the nip portion N is high at both ends and low at the center portion can be obtained. The occurrence of wrinkles on the paper P is prevented.

In this embodiment, L0 to L1 and L2 to L2
Although L3 is connected in a tapered shape, that is, in a straight line, L3 is not limited to this shape, but may be in a parabolic shape.

4. Inspection Method of Outer Diameter of Pressure Roller As described above, in order to form the pressure roller 11 into an inverted crown shape, an inverse crown shape is provided on the inner surface of a mold at the time of molding the pressure roller. If the amount varies, the paper transport speed (abbreviated as fixing speed) of the fixing device will be different. This is because the variation in the amount of the inverse crown causes the outer diameter of the end to be different, resulting in a difference in the conveying force.

In the image forming apparatus, the paper transport speed must be a predetermined speed (process speed) corresponding to the rotation of the photosensitive drum 1 and the transfer roller 5. If the (fixing speed) is significantly different, the formed image may be disturbed. For example, if the fixing speed is high, a problem occurs in that the image in the transfer nip t is pulled by pulling the paper. Conversely, if the fixing speed is extremely slow, the paper may sag between the transfer portion t and the fixing portion N, hit the inside of the apparatus, and again disturb the image.

FIG. 5 specifically shows the conveying speed of the recording paper P when the shape of the pressure roller 11 is changed.

In the figure, the term "straight" refers to a straight pressing roller 11 having the same outer diameter over the entire longitudinal area as in the prior art.

The inverted crown A has a length of 0 to L1 and L2 to L3 of 80 mm and an inverted crown amount of 200 μm.

The inverse crown B has the same length of 0 to L1 and L2 to L3 of 80 mm, but has a large inverse crown amount of 30 mm.
0 μm. It can be seen that at the same central outer diameter as the inverted crown A, the transport speed is faster than the inverted crown A.

The inverted crown C has a length of 0 to L1 and L2 to L3 longer than that of the inverted crown A and is 100 mm, and the central straight portion is only 20 mm. The reverse crown amount is reverse crown A
200 μm, which is the same as

FIG. 5 shows that, even if the center outer diameter is the same, if the amount of the inverted crown or the length of the inverted crown portion is different, the transport speed changes. In this case, the fixing speed cannot be specified, and as described above, there is a problem in that the image is blurred due to the tension between the transfer portion t and the fixing portion N, and the image is rubbed in the apparatus by sagging.

Therefore, in the present embodiment, the outer diameter of the molded pressure roller 11 is measured at several places so that the conveyance speed can be regulated even if the pressure roller 11 has an inverted crown shape, and the average is determined within a predetermined range. Is selected (outside diameter average value management).

Specifically, in the roller shown in FIG. 4, the outer diameter is measured every 10 mm from L = 0 mm to L = 220 mm in the longitudinal direction of the roller. For example, the outer diameter d1 when L = 0 mm, the outer diameter d2 when L = 10 mm, the outer diameter d3 when L = 20 mm, and the outer diameter d23 when L = 220 mm.
Outer diameters were measured at 23 locations up to that point, and the average value D _ave was determined. That is, D _ave = (d1 + d2 +... + D23)
/ 23.

FIG. 6 is a graph showing the conveying speed when the average value D _ave is changed for each roller used in FIG.

In FIG. 5, the actual transport speed and the outer diameter value did not match one-to-one because the attempt was made to specify only the center outer diameter. However, in FIG. 6, the average value of the outer diameter according to the present invention was managed. Therefore, it can be seen that the actual transport speed and the outer diameter average value correspond one-to-one.

Therefore, in this embodiment, the average value is controlled so that the average value of the outer diameter is within a predetermined range, that is, 20.0 ± 0.1 mm so that the required conveyance speed of 94.2 mm / sec is obtained. . Note that the predetermined range is appropriately determined based on a required speed (for example, an image forming speed) and the configuration of the recording material P conveyance path so that the recording material P does not hit the inside of the apparatus even if the recording material P becomes loose. Just set it.

Table 1 shows the results of actual printing using the apparatus that has performed average value management according to the present embodiment.

[0060]

[Table 1] As shown in Table 1, the outer diameter of the straight roller is 20.0 m.
With the roller of m, the transport speed was not a problem, but wrinkles were observed. On the other hand, when the average outer diameter of the inverted crown roller is controlled according to the present invention, the average outer diameter Dave is 20.0%.
By adjusting the distance to mm, the transfer speed was the same as that of a straight roller, and no problem such as wrinkles could be prevented.

In the present embodiment, the outer diameter measurement for controlling the average value was performed every 10 mm. However, in actuality, when a large amount is manufactured, the measurement interval can be slightly widened to simplify the measurement. It is.

As described above, according to the present embodiment, as a method of inspecting the pressure roller 11 having an inverted crown shape, by controlling the average value of the outer diameter, it is easy to control the paper conveyance speed by the pressure roller 11. This can prevent wrinkles from occurring when recording paper is conveyed without causing disturbance in the formed image.

<Second Embodiment> In this embodiment, the first embodiment
Compared with the embodiment, the method of measuring the outer diameter average value is not simply measured at equal intervals, but is characterized in that only the predetermined position is measured and approximated by the outer diameter shape of the pressure roller 11, and the other The configuration is substantially the same.

FIG. 7 shows a cross-sectional view of the inverted crown roller of this embodiment. The hatched portion is the rubber portion, and the length L1 is 70 mm at the portion with the inverted crown. The length of the central straight portion is 70 mm, and the amount of the inverted crown is 200 μm. Since the amount of the inverse crown is indicated by the diameter, the size of d is 100 μm.

In this embodiment, D1, D2,
The average value of the outer diameter is obtained by measuring three points of D3.

The length of the portion with the inverted crown is 14
0 mm, the straight part is 70 mm, the ratio is 2: 1, and the range where the outer diameter is thickened by the inverted crown is longer, but the actual transport speed is larger at both ends as shown by the ratio. Is not dominated by.

Therefore, in the present embodiment, the outer diameters at both ends are weighted by the ratio of the area of the triangle indicated by the base L1 and the height d to the area indicated by the horizontal L / 2 and the vertical d. I tried to average. That is, if the area ratio h = (L1 × d / 2) / (d × L / 2), Dave = (h × D1 + D2 + h × D3) / (1 + h +
h) It is as follows.

FIG. 8 is a graph showing the manner of averaging and the transfer speed.

The average A is a simple three-point average, and the average B is an average according to the above equation. In the simple average, the outer diameter average value does not match the transport speed, but the average B according to the present embodiment shows the same value as the method according to the first embodiment.

As described above, when the outer diameter shape is known in advance, the transfer speed can be easily indicated without measuring the outer diameter at a fine pitch.

Actually, when the pressure roller 11 is mass-produced, the pressure roller 11 is finished in a shape following the inner surface shape of the mold. Therefore, the numerical values shown in FIG. Can be used.

<Third Embodiment> The configuration of the image forming apparatus of this embodiment is the same as that of the first embodiment shown in FIG. In the present embodiment, a central straight portion is provided on the pressure roller 11 having an inverted crown shape, and the length L1-L2 of the straight portion is provided.
Is slightly narrower than the width H of the envelope (including the thick recording paper P such as a postcard). In this embodiment, L1-L2 is 90 mm, and the envelope used is Monar.
The channel size width H is 98.4 mm.

FIG. 10 shows a state in which an envelope is passed through the fixing device 6. For simplicity, only the fixing film 13 and the pressure roller 11 are shown. In the present invention, even if the envelope is sandwiched between the nip portions N, the nips at both ends of the envelope are properly removed. However, in the comparative example, a portion where the nip cannot be removed occurs at both ends of the envelope due to the thickness of the envelope.

FIG. 11 is a graph showing the temperature distribution in the longitudinal direction of the nip portion N. This shows the temperature distribution when the temperature reaches a peak by printing an envelope.

The dotted line indicates that both ends of the envelope are floated due to the thickness of the envelope as in the comparative example shown in FIG.
When the elastic layer 11b of the pressure roller 11 is buried and there is a portion where the nip disappears, the heat of the heater is not removed any more, so that the temperature rises rapidly and reaches about 400 ° C.

On the other hand, according to the present invention, the pressure roller 11 has an inverted crown shape, and the outer diameter of the roller gradually increases from slightly inside to the outside of the end of the envelope. The gap between the end and the surface of the film 13 can be reduced, the nip does not become thinner or disappears, and the temperature does not rise abnormally at both ends of the envelope as shown by the solid line.

In the apparatus of this embodiment, the fixing temperature is adjusted to 18
Since the temperature is set to 0 ° C., the temperature is 180 ° C. in the paper passing area, but the temperature rises to about 290 ° C. in the non-paper passing area outside the envelope because the envelope does not have heat. But,
Even in this case, if the pressure roller is in contact with the fixing nip properly, the temperature does not rise to 400 ° C. as in the comparative example.

In the case of the present embodiment, the temperature rise was about 290 ° C., so there was no problem with the fixing device. However, in the comparative example, the pressure roller caused by the film scorch or the pressure roller 11 being stretched by heat was used. Non-paper passing wrinkles occurred.
These may cause problems such as shortening of the life of the fixing device 6 and deterioration of image quality.

As described above, the effect of the present invention can be obtained by reducing the central straight portion of the pressure roller with respect to the paper passing width of the envelope (the minimum paper passing width in this example).

In this embodiment, the paper width of the envelope is set to the envelope Mon.
Although the arch size width is 98.4 mm, the present invention is not limited to this, and the effect of the present invention can be obtained by reducing the center linear portion of the pressure roller with respect to the paper passing width of the envelope in each model.

<Others> In the heating device of the present invention, the heating member R is not limited to the film heating type device using the ceramic heater described in the above embodiment, but may have another configuration.

For example, as a heater for heating, an exciting coil and a conductive member are provided, and the magnetic force of the exciting coil acts on the conductive member, and the conductive member generates heat by induced current (for example, heat generated by eddy current loss). ) May be used.

FIG. 12A is a schematic configuration diagram of such a heating device 6 of the electromagnetic heating system.

[0084] In the figure, 10 is a stay holder cross section substantially trough-shaped, is composed of a liquid crystal polymer phenol resin, the inner core material (iron core) 12a ₁ the winding 12
The exciting coil 12a constituted by winding a a ₂ are allowed to housing.

Reference numeral 12b denotes a flat conductive member (ferromagnetic metal or the like), which is held on the lower surface of the stay holder 10. The conductive member 12b and the exciting coil 12a
An electromagnetic heating type heater 12 for generating heat in the conductive member by applying a magnetic force from the excitation coil 12b to the conductive member 12b is configured.

The stay 1 holding the heater 12 for heating
At 0, the pressure roller 11 is pressed against a heating member R formed by loosely fitting the fixing film 13 to the outside.

Then, the pressure roller 11 is driven by the pressure roller driving means 15 to rotate the film 13, and a voltage is applied from an excitation circuit (not shown) to the excitation coil 12 a, and the conductive film is formed by electromagnetic induction. The member 12b generates heat, the recording material P on which the unfixed image t is formed is introduced into the press-contact nip N, and the press-contact nip N is formed together with the film 13 in a state where the recording paper P is in close contact with the lower surface of the film. , Heat from the conductive member 42 is applied, and the unfixed toner image t is fixed.

Further, another heating device 6 of the electromagnetic heating type is used.
As shown in FIG. 12 (b), a conductive member 12b of a heater is provided on a film 13, and a magnetic force from an exciting coil 12a is applied to the film 13 to generate heat. Recording paper P introduced into N
And a heat fixing process.

As shown in FIG. 12C, the film 13 is made of polyimide, polyamide imide, PEEK, PE
A heat-resistant resin such as S / PTFE / FEP is used as the base layer 13a of the endless film, and a metal layer such as iron, cobalt, nickel, copper, or chromium is formed on the outer periphery of the base layer 13a as the conductive layer (conductive member) 12b. Has formed. Further, the outer peripheral surface of the conductive layer 12b is mixed or independently coated with a heat-resistant resin having good toner release such as PTF, PTFE, and FEP to form a release layer 13c. In this example, the film base layer 13a and the conductive layer 12b are separate layers, but the film base layer itself may be a conductive layer.

The heating member R is not limited to the film heating system, but may be a device using a heat roller.

[0091] The heating device of the present invention is not limited to the fixing device shown in the embodiment, but also a device for heating a recording material carrying an image to improve the surface properties (such as gloss), a device for temporarily attaching, a drying process, and the like. It can be widely used as a heating device such as a device for thermal lamination.

[0092]

As described above, according to the present invention, there is provided a pressure roller, a heating device, and an image forming apparatus in which a pressure roller has an inverted crown shape to prevent wrinkles of a material to be heated. be able to.

In the pressure roller, the heating device and the image forming apparatus, it is checked whether the average value of the outer diameter of the pressure roller is within a predetermined range. It is possible to provide a method of inspecting a pressure roller in which the conveying force of a heating material can be appropriately managed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an image forming apparatus of the present invention.

FIG. 2 is a schematic diagram of a heating device of the present invention.

FIG. 3 is an explanatory diagram of a paper passing reference position.

FIG. 4 is a schematic explanatory view of a pressure roller shape.

FIG. 5 is a graph of the outer diameter of a central portion of a pressure roller and a recording paper conveyance speed.

FIG. 6 is a graph of an average outer diameter of a pressure roller and a recording paper conveyance speed.

FIG. 7 is a schematic explanatory view of a pressure roller shape.

FIG. 8 is a graph of an average outer diameter of a pressure roller and a recording paper conveyance speed.

FIG. 9 is a diagram showing a relationship between a central linear portion of the pressure roller and an envelope width.

FIG. 10 is an explanatory diagram of a fixing nip portion when passing an envelope.

FIG. 11 is a graph of a temperature distribution in a fixing nip portion when an envelope is passed through the paper.

FIG. 12 is a schematic view of another configuration example of the heating member.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging roller 3 Exposure means 4 Developing device 5 Transfer roller 6 Fixing device (heating device) 7 Cleaner 10 Film guide 12 Heating heater 13 Film R Heating member P Heated material

Claims (15)

[Claims] 1. A pressure roller used for a heating member and a heating device which presses and contacts the heating member to form a heating nip portion, and pinches and conveys a material to be heated in the heating nip portion to perform heating. A pressure roller wherein the pressure roller has an inverted crown shape. 2. The pressure roller according to claim 1, wherein the pressure roller has an inverted crown shape having a straight central portion in the longitudinal direction of the roller. 3. A heating device, comprising: a heating member; a heating nip portion formed by pressing against the heating member; a heating nip portion for nipping and transporting a material to be heated by the heating nip portion; A heating device characterized by having a shape. 4. The heating device according to claim 3, wherein the pressure roller has an inverted crown shape having a straight central portion in the roller longitudinal direction. 5. A heating heater, a film that slides on the heater, and a pressure roller that is in pressure contact with the heater via the film, wherein a coating is provided between the film and the pressure roller. A heating device for heating a material to be heated by nipping and transporting the heating material, wherein the pressure roller has an inverted crown shape. 6. The heating device according to claim 5, wherein the pressure roller has an inverted crown shape having a straight central portion in the roller longitudinal direction. 7. The pressure roller has an inverted crown shape having a straight central portion in the roller longitudinal direction, and the member to be heated is introduced into a heating nip portion by central reference conveyance. Any one of items 3 to 6
The heating device according to Item. 8. The heating member is an envelope carrying an unfixed image, and the straight portion at the center of the pressure roller is
The heating device according to claim 7, wherein the width of the heating device is smaller than an envelope size. 9. The heating device according to claim 3, wherein the pressure roller is driven to rotate. 10. The method according to claim 3, wherein an average value of an outer diameter of the pressure roller is set to a predetermined range.
The heating device according to Item. 11. An image forming means for carrying a developer image on a recording material, and the heating device according to claim 3, which heats the developer image on the recording material. An image forming apparatus comprising: 12. The image forming apparatus according to claim 11, wherein an average value of an outer diameter of the pressure roller is set to a predetermined range based on an image forming speed of the image forming unit. 13. The pressure roller, the heating device, or the image forming apparatus according to claim 1, wherein an inspection is performed to determine whether an average value of an outer diameter of the pressure roller is within a predetermined range. A pressure roller inspection method. 14. The image forming apparatus according to claim 11, wherein whether the average value of the outer diameter of the pressure roller is within a predetermined range obtained based on the image forming speed of the image forming unit is checked. An inspection method for a pressure roller, characterized in that: 15. The average value is obtained by measuring the outer diameter of a pressure roller at a plurality of locations, and weighing the measurement results according to the respective measurement positions.
2. The inspection method for a pressure roller according to 1.