JPH1063128A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable an excellent stable fixation even at a low fixing tamp. and to reduce the size and power consumed, with a simple constitution and at a low cost, by passing a transfer material carrying an unfixed toner image through the fixing nip part between a heating roll and a tube body. SOLUTION: The transfer material 5 on a paper feeding tray is fed to between a photoreceptor drum and a transfer roll with a prescribed timing and a toner image on the photoreceptor drum receives transfer working by the transfer roll, to be transferred onto the transfer material 5. On the other hand, the transfer material 5 after the unfixed toner image is transferred in carried to a fixing device by a paper carrying belt to receive fixation processing. In other words, the transfer material 5 after the unfixed toner image is transferred is inserted into the fixing nip part N formed by the heating roll 1 and the tube body 2 which are mutually rotated to pass through the fixing nip part N. The transfer material 5 is heated/pressurized by the passage through the fixing nip part N. Consequently, unfixed toner 5a is fixed on the transfer material 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating / pressing type fixing device used in an image forming apparatus such as a copying machine and a printer, and more specifically, to press-fit an elastically deformable tube to an outer peripheral surface of a heating roll. The present invention relates to a novel fixing device in which a fixing nip is formed.

[0002]

2. Description of the Related Art In recent years, a fixing device used in an electrophotographic copying machine or a printer has been required to be downsized in accordance with the trend of downsizing of the entire image forming apparatus. Power consumption is required. In order to meet such demands, it is indispensable to realize a fixing device that can exhibit good fixing performance even at a lower fixing temperature.

For example, in a general fixing device including a rotating heating roll and a pressing roll which rotates while being pressed against the heating roll, both rolls are increased by increasing the roll diameter of the two rolls. A countermeasure for increasing the width of the fixing nip portion (pressing portion) formed between them can be considered.

However, in the case of such a roll nip type fixing device, although the power consumption can be reduced, there is a disadvantage that the diameter of both rolls increases the size of the entire device.

Further, instead of the pressure roll in the above-described roll nip type fixing device, an endless belt that is supported and stretched on a plurality of support rolls and rotates is used as a pressure member, and this endless belt is connected to the outer periphery of the heating roll. There has been proposed a fixing device configured to be wound around a surface at a predetermined angle (Japanese Patent Application Laid-Open No. H4-50885).

However, in the case of this belt nip type fixing device, a wide fixing nip portion can be formed between the heating roll and the endless belt, so that the passage time of the transfer material passing through the fixing nip portion is reduced. As a result, the heating time can be increased and the heating time can be increased.As a result, good fixing can be performed to a certain extent even at a low fixing temperature, but the fixing performance is stable due to the unstable pressurized state in the fixing nip portion. There is a disadvantage that it does not.

Further, the belt nip type fixing device requires a large number of components and a high-precision belt driving technique for installing the endless belt, so that the device becomes complicated and expensive. Moreover, there is a problem that it is difficult to secure stable running properties of the endless belt and stable transportability of the transfer material.

On the other hand, when both of the above-mentioned fixing devices of the roll nip type and the belt nip type are used as fixing devices of a color image forming apparatus such as a full-color copying machine, a heat-resistant elastic layer is formed on the surface as a heating roll. Because a full-color image uses a large amount of toner, the separation (separation) between the surface of the heating roll and the toner at the transfer material discharge port of the fixing nip part is black and white, because a full-color image uses a large amount of toner. It tends to be more difficult than during image fixing. Therefore, when fixing a full-color image, it has been difficult to secure stable peeling performance together with good fixing performance.

Accordingly, the present applicant has disclosed in Japanese Patent Application Laid-Open No. H5-1506.
No. 79 has already proposed a belt nip type fixing device capable of simultaneously achieving good fixing performance and peeling performance even when fixing a color image. That is, this fixing device is provided with a pressure roller for pressing the endless belt against the heating roller at the outlet of the belt nip portion, and the belt is heated from the inner peripheral surface side of the belt to the heating roller at the nip portion before the pressure roller. In this case, a pressure assisting member is provided for pressing the pressing member. The placement of the pressure roll causes distortion on the surface of the heating roll, so that the transfer material can be peeled off from the heating roll by itself without the need for a peeling means. In which the pressurized state is stabilized.

In the above fixing device, although it is highly likely that good fixing performance and peeling performance can be simultaneously realized even when fixing a color image, if the pressure setting of the pressure auxiliary member is increased, A secondary obstacle occurs in that stable transferability of the transfer material in the nip portion cannot be obtained.
In addition, since the pressure roller and the pressure assisting member are provided side by side in the same belt nip, their installation positions and pressure conditions are mutually adjusted in order to simultaneously obtain peeling performance and fixing performance. It is difficult to set the optimum conditions, and there is a drawback that it cannot sufficiently cope with the case where the type of transfer material to be used is different. In addition, if the endless belt has a variation in tension or a variation in belt circumference, there is a weak point that the functions of the pressing roll and the pressing auxiliary member are easily affected.

As described above, in the conventional fixing device,
It is very difficult to improve the fixing performance at the same time as securing a stable peeling performance, especially when both types are used in a color image forming apparatus, and this tendency is observed when different types of transfer materials are used together. Was even more noticeable in the current situation.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and the first is
An object of the present invention is to provide a fixing device which can perform good and stable fixing even at a lower fixing temperature with a simple configuration and low cost, and is suitable for realizing miniaturization and low power consumption. It is in.

A second object of the present invention is to secure good fixing performance and stable peeling performance at the same time without requiring complicated conditions even when fixing a color image. It is an object of the present invention to provide a fixing device that can perform the fixing.

[0014] The third object is the type (mainly thickness).
It is an object of the present invention to provide a fixing device that can simultaneously secure stable release properties of a transfer material and excellent fixing performance even when different transfer materials are used together.

[0015]

As shown in FIG. 1, a fixing device according to the present invention comprises a heating roll (1) driven to rotate.
An elastically deformable tube body (2) that forms a fixing nip (N) between the heating roll (1) and the heating roll (1) by being pressed against the outer peripheral surface of the heating roll (1). The tube body (2) is pressed against the outer peripheral surface of the heating roll (1) such that the tube body is pressed against the heating roll, and the tube body (2) is rotated so that the tube body is pressed against the heating roll. 2)
And a tube outer peripheral surface support member (3) for slidably holding the outer peripheral surface of the tube body, and a tube body (2) contacting the inner peripheral surface of the tube body (2) at a predetermined position of the fixing nip (N). A transfer member for supporting an unfixed toner image (5a) in a fixing nip portion (N) between the heating roll and the tube body, comprising a tube inner circumferential surface supporting member (4) pressed against the outer circumferential surface of the heating roll (1); The unfixed toner image is fixed by passing through the material (5). Reference numeral 13 in the figure is a heating source.

Further, the fixing device of the present invention is the fixing device having the above configuration, wherein the heating roll (1) has a roll structure having at least an elastic body surface layer (12),
Further, the heating roll (1) is brought into pressure contact with the fixing nip (N) near the transfer material discharge side to press the elastic body surface layer (1) of the heating roll (1).
It is configured such that a pressing member (6) for distorting 2) is provided.

Further, the tube (2) in the present invention is not particularly limited as long as it is made of an elastically deformable material. For example, a tube made of a heat-resistant rubber material is used. Preferably, the tube is made of silicone rubber. It should be noted that this tube body has a cylindrical or almost cylindrical shape when no external pressure is applied, and becomes elastically deformed (in a flat shape) when an external pressure is applied. It has the property of returning to its original form. The circumference of the tube body is, for example, about 0.7 to 1.4 times the circumference of the heating roll, and is shorter than the circumference of the endless belt used in the belt nip method.

The tube inner peripheral surface support member (4) in the present invention can contact the inner peripheral surface of the tube body and press the tube body toward the heating roll, so that the rotation of the tube body is not hindered. Although not particularly limited, for example, a rotatable rigid roll is used.

Still further, according to the fixing device of the present invention, in the fixing device having the above-mentioned configuration, at least one of the tube outer peripheral surface support member (3), the tube inner peripheral surface support member (4) and the pressing member (6). Are provided so that the pressing force or the installation angle with respect to the heating roll (1) can be variably adjusted, and the above-mentioned pressing force or the installation angle is individually adjusted according to the thickness of the transfer material.

As described above, since the elastically deformable tube body and its supporting member are used as the pressurizing means for forming the fixing nip portion between the heating roll and the heating roll, the conventional fixing device can be used under the same fixing pressure. Since a wider fixing nip portion can be obtained as compared with a roll nip type fixing device using a pressure roll, necessary and sufficient fixing can be performed even at a fixing temperature slightly lower than in the past. Also, compared to a belt nip type fixing device using a conventional endless belt,
There is no variation in tension or circumference, stable fixing pressure can be obtained, and there are few components for installing the tube body, and the configuration can be simplified. In addition, a sufficient fixing pressure and a stable paper transport property are secured by the restoring force against the pressure deformation of the tube body and the pressing force of the tube inner peripheral surface supporting member.

In the case where a pressing member for distorting the elastic body surface layer of the heating roll is provided, an area where the pressing member generates a distortion is formed independently of the fixing area in the fixing nip portion. After the above-described good fixing is performed in the fixing area, the transfer material is reliably separated from the heating roll by the separating action in the distortion generating area.

Further, at least one of the tube outer peripheral surface support member, the tube inner peripheral surface support member and the pressing member is provided so that the pressing force or the installation angle with respect to the heating roll can be variably adjusted, and the pressing force or the installation angle is set to the transfer material. In the case where the thickness is adjusted individually according to the thickness, for example, even if transfer materials having different thicknesses are used in combination, the fixing pressure / heating conditions and peeling conditions suitable for the thickness are set. Therefore, excellent fixing performance is ensured, and at the same time, stable release performance of the transfer material is ensured.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to examples.

Embodiment 1 FIGS. 2 to 4 show a fixing device according to an embodiment of the present invention. This fixing device is applied to an image forming apparatus such as a laser printer as shown in FIG. Used to be incorporated. In the drawing, reference numeral 1 denotes a heating roll, 2 denotes a tube body, 3 denotes a tube outer peripheral surface support member, 4 denotes a support roll as a tube inner peripheral surface support member, 5 denotes a transfer material for carrying an unfixed toner image 5a, 7 Denotes a fixing device main body.
In FIG. 5, reference numeral 100 denotes a photosensitive drum as an image carrier, 101 denotes a charging roll as a charging unit,
Reference numeral 102 denotes a laser exposure apparatus as a latent image forming unit;
3 is a developing device, 104 is a transfer roll as transfer means,
105 is a cleaning device, 106 is a paper transport belt,
Reference numeral 107 denotes a paper feed tray for accommodating the transfer paper 5, 108 denotes a paper feed roll, 109 denotes a pair of registration rolls and a registration gate, and 110 denotes a paper discharge tray.

In the fixing device according to this embodiment, the heating roll 1 is formed by coating a surface resin layer 12 on a metal cylindrical core 11 made of metal such as iron or aluminum. 13 is used. As the surface resin layer 12, a fluororesin layer such as a perfluoroalkylvinylether copolymer (PFA) is formed to obtain releasability from the toner.
In FIG. 3, reference numeral 14 denotes a drive transmission gear.

The heating roll 1 is connected to a heating source 13
As a result, the roll surface is kept heated to a predetermined temperature by the heat generation, and the entire roll is rotated at a constant speed in a direction indicated by an arrow in the figure by a rotation driving device (not shown). The surface temperature of the heating roll 1 is detected by a temperature sensor or the like (not shown) arranged so as to come into contact with the surface of the heating roll, and the detected information is transmitted to the heating source 13.
Is controlled so as to be maintained at a constant temperature by feedback to the temperature controller.

The tube 2 is preferably a heat-resistant rubber tube. In this embodiment, a tube made of silicone rubber having excellent heat resistance is used. As a silicone rubber tube, Liquid Silicon Rubber (LSR) is desirable from the viewpoint of low mass production cost and low hardness. In the case of a heat-resistant rubber tube, its rubber hardness (J
IS A or Asuka C) having a degree of about 15 to 40 ° is used. If the rubber hardness is less than 15 °, there are problems such as insufficient restoring force and insufficient pressurization. On the other hand, if it exceeds 40 °, elastic deformation becomes insufficient and a desired nip cannot be obtained. Or the tube is easily deformed permanently.

The heat-resistant rubber tube has a thickness:
A tube having a diameter t of about 1 to 5 mm and an outer diameter D (in the case of no load) of 15 to 30 mm is used. It is desirable that the thickness t and the outer diameter D of the tube be set to have a predetermined ratio. That is, t / D
Is too small (i.e., if the wall thickness is too thin or the outer diameter is too large, or both),
When the tube body is pressed and deformed against the heating roll to form a fixing nip portion, a desired pressing force is not obtained,
Sufficient fixing pressure cannot be applied in the fixing nip portion. Conversely, if the value of t / D is too large (ie,
If the wall thickness is too thick or the outer diameter is too small or neither of them), the fixing nip portion having a predetermined width cannot be formed, or the support roll 4 cannot be disposed in the tube, and the transfer at the nip portion is performed. It is difficult to obtain stable transportability of the material.

The value of t / D is determined as described later (see FIG. 7).
If a heat-resistant rubber tube having a tube outer diameter D of 15 to 30 mm is used, the range is preferably about 0.1 to 0.3. By appropriately selecting the thickness t and the outer diameter D of the tube body 2 within this range, a sufficient pressure contact force at the fixing nip portion and stable transfer material transportability can be obtained.
If necessary, a release agent layer may be formed on the surface of the tube body 2 in order to prevent adhesion of toner and the like.

The tube outer peripheral surface supporting member 3 is shown in FIGS.
As shown in FIG. 3, a holding unit 3 for holding (accommodating) the tube body 2 so that the tube body 2 rotates in a state of being pressed and deformed.
0, and is disposed on the opposite side of the tube body 2 from the heating roll 1 (the lower side in the figure). The holding portion 30 has a concave shape for pressing the tube body 2 against the outer peripheral surface of the heating roll 1 so that the tube body 2 is pressed against the heating roll 1 and deformed. The outer surface of the tube body 1 is slidably held so as to rotate while being pressed against the roll 1.

In particular, the recessed shape of the holding portion 30 in this embodiment is a shape in which the transfer material inflow side is sharply recessed (curved) as illustrated in FIG. 2, and the transfer material discharge side is gradually recessed. It has an irregular shape. Also, this holding part 3
Since the surface 0 is a sliding surface for slidably holding the outer peripheral surface of the tube body 2, the frictional resistance with the outer peripheral surface is configured to be extremely small. In this example,
As shown in FIG. 4, a plurality of ribs 31 orthogonal to the axial direction of the heating roll 1 are formed at equal intervals on the surface of the holding unit. Further, as illustrated in FIG. 4, at both left and right end portions of the support member 3, a position regulating surface 30 a that is raised upward so as to regulate the position of both ends 2 a of the tube body 2 is formed. The position regulating surface 30a allows the tube body 2
The meandering phenomenon (walk) when rotating is prevented.

As the support roll 4 as a tube inner peripheral surface support member, a cylindrical or cylindrical rigid roll made of metal or rigid resin is used, and is applied to the inner peripheral surface of the tube body 2 at a predetermined position of the fixing nip portion N. The tube body 2 is pressed against the outer peripheral surface of the heating roll 1 with a predetermined pressure by being in contact therewith. As shown in FIG. 4, the support roll 4 in the present embodiment is rotatably supported by bearings 40 provided on both left and right ends of the support member 3 located on the transfer material entry side of the fixing nip N. At the same time, a drive transmission gear 41 attached to one end of the drive roll meshes with the drive transmission gear 14 of the heating roll 1 and is driven to rotate at the same speed as the heating roll 1.

As described above, in this fixing device,
As shown in FIG. 2, the tube body 2 is slidably held in the holding portion 30 of the support member 3 in a form in which the tube body 2 is pressed against the heating roll 1, and the tube held by the support member 3. The body 2 rotates so as to move in the same direction as the heating roll 1 in the fixing nip portion N by the rotational driving force of the support roll 4.

Next, the operation when this fixing device is applied to the laser printer shown in FIG. 5 will be described.

First, in this printer, the surface of the photosensitive drum 100 rotating in the direction of the arrow is
01, the surface of the charged drum is exposed to laser light LB corresponding to image information from the laser exposure device 102 to form an electrostatic latent image. Then, for example, in the case of performing reversal development, the exposed portion is developed by the developing device 103 to become a toner image, visualized, and sent to the transfer area. At the same time, the transfer material 5 on the paper feed tray 107 is conveyed one by one to the registration roll and the registration gate 109 by the paper feed roll 108 and then sent out between the photosensitive drum 100 and the transfer roll 104 at a predetermined timing. It is. Then, the toner image on the photosensitive drum 100 is transferred onto the transfer material 5 by receiving a transfer action of the transfer roll 104. The toner and the like remaining on the surface of the photosensitive drum 100 after the transfer are removed by the cleaning device 105.

On the other hand, the transfer material 5 to which the unfixed toner image has been transferred is transported to the fixing device (7) by the paper transport belt 106 and undergoes a fixing process. That is, in this fixing device, the transfer material 5 on which the unfixed toner image is transferred
Is drawn into the fixing nip N formed by the heating roll 1 and the tube body 2 rotating with each other, and passes through the nip. The transfer material 5 is heated and pressurized by passing through the fixing nip. As a result, the unfixed toner 5a is fixed on the transfer material. When the fixing process is completed, the transfer material 5 is discharged onto the discharge tray 110.

FIG. 6 shows the result of examining each fixing level when the surface temperature of the heating roll is changed in the fixing device according to this embodiment. Also in this figure,
For reference, the results of a similar investigation are also shown for a roll nip type fixing device using a conventional heating roll / pressure roll. Regarding the fixing level, the transfer material on which the same toner image has been transferred is passed through a fixing nip set at each surface temperature to perform fixing, and the surface of the obtained fixed image is strongly scraped off with paper to remove toner. The degree of residual was examined.
The results were classified and evaluated.

From the results shown in FIG. 6, it can be seen that a lower fixing temperature is possible to obtain the same level of fixing performance as compared with a conventional roll nip type fixing device. This is because the width of the fixing nip formed between the heating roll and the tube body is wider than that of the pressing roll under the same fixing pressure, so the heating time is longer even if the fixing temperature is lower. It is presumed that it can be removed and heated sufficiently.

FIG. 7 shows the results of an investigation on the wall thickness / outer diameter ratio (D / t) and the fixing pressure level of the tube in the fixing device according to this embodiment. That is, each of the tube bodies having an outer diameter D of 15 mm, 25 mm, and 30 mm having various thicknesses t was used.
The fixing pressure of each tube was measured by a sheet-shaped pressure distribution measuring device (commercially available), and the results were classified and evaluated.

From the results shown in FIG. 7, it can be seen that the fixing pressure varies depending on the value of t / D. Sufficient fixing pressure (when exceeding the allowable level) can be obtained only when the outer diameter of the tube is in the range of 15 to 30 mm.
When the value of D is approximately 0.1 or more, preferably 0.1 to
It can be seen that the time is between 0.3. This t / D
In other words, the wall thickness t of the tube body is 1.5 to
This corresponds to the case where the distance is in the range of 9 mm.

Embodiment 2 FIG. 8 shows a fixing device according to another embodiment of the present invention. This fixing device is, for example, a color image forming apparatus such as an electrophotographic full-color copying machine as shown in FIG. Used by being incorporated into the device. In the figure, the same parts as in the first embodiment (FIG. 2 and the like) are denoted by the same reference numerals and the description thereof is omitted, but among the other reference numerals, 6 is a pressing roll as a pressing member, and 8 is a heating roll 1 The release agent supply roll 12 rotating in contact with the surface of the elastic member 12 is an elastic body surface layer. FIG.
Reference numeral 200 denotes a photosensitive drum as an image carrier, 201 denotes a charging corotron as a charging unit, 202
Denotes a laser exposure unit as a latent image forming means;
Are black (K), yellow (Y), magenta (M),
A rotary developing device in which cyan (C) color toner developing units are integrally combined; 204, a transfer corotron as transfer means; 205, a cleaning device; 206, a transfer drum for adsorbing and carrying a transfer material; A transfer material adsorption charger, 208 is a peeling charger, 209 is a peeling pawl, 210 is a charge removing charger, 211 is a paper feed tray for storing the transfer paper 5, 212 is a paper feed roll, and 213 is a registration roll pair. , 214 a paper discharge tray, and 215 a document reading unit.

In the fixing device of this embodiment, a heating roll 1 having a roll structure having an elastic surface layer 12 is used, and the heating roll 1 is brought into pressure contact with the fixing nip portion N in the vicinity of the transfer material discharge side to form a heating roll. The fixing device has the same configuration as that of the fixing device of the first embodiment except that a pressing roll 6 for distorting the first elastic body surface layer 12 is provided. In this fixing device, a release agent supply roll 8 for supplying a release agent is provided on the outer peripheral surface of the heat roll 1.

The heating roll 1 comprises a metal cylindrical core 11
Has a structure in which an elastic body surface layer 12 that can be easily elastically deformed by an external load is provided on the surface of the elastic member. The elastic body surface layer 12 has a single-layer or multi-layer structure made of, for example, silicone rubber or fluorine rubber. Further, a predetermined amount of the release agent is supplied to the elastic body surface layer 12 of the heating roll 1 by the release agent supply roll 8 in which the release agent is stored inside the roll, so that good releasability is imparted. It has become so.

The pressing roll 6 is a roll body in which a rigid roll or a roll core is coated with an elastic body having a higher hardness than the elastic body surface layer 12, and is located in the vicinity of the transfer material discharge side of the fixing nip N (with respect to the nip). (As close as possible). The outer diameter of the pressing roll 6 is smaller than the outer diameter of the heating roll 1, and is preferably about 1/2 or less of the outer diameter of the heating roll. In this example, the pressing roll 6 is installed so as to be pressed against the surface of the heating roll 1 by a biasing means such as a spring. Such a pressing roll 6
Thereby, the elastic body surface layer 12 of the heating roll 1 is pressed and maintained in a state of being distorted by a predetermined amount.

As described above, in this fixing device,
As shown in FIG. 8, similarly to the case of the first embodiment, the tube body 2 is slidably held in the holding portion 30 of the support member 3 in a form in which the tube body 2 is pressed against the heating roll 1. The tube body 2 held by the support member 3 is rotated by the rotational driving force of the support roll 4 so as to move in the same direction as the heating roll 1 in the fixing nip N. In addition, the release agent is always supplied to the outer peripheral surface of the heating roll 1, and the elastic surface layer 12 near the transfer material discharge side of the fixing nip portion N is distorted by the pressing roll 6.

Next, the operation when this fixing device is applied to the full-color copying machine shown in FIG. 9 will be described.

First, in this copying machine, the surface of the photosensitive drum 200 rotating in the direction of the arrow is charged with the charged corotron 2.
01, the surface of the charged drum is read from the laser exposure device 202 to the original reading unit 2.
The laser light LB corresponding to the color document information read by the exposure device 15 is exposed to form a first-color electrostatic latent image. Then, for example, in the case of performing reversal development, the exposed portion is developed by a developing device 203 of a predetermined color to become a toner image, and is sent to a transfer area. At the same time, the transfer material 5 on the paper feed tray 211 is conveyed one by one to the registration roll 213 by the paper feed roll 212 and then electrostatically attracted to the transfer drum 206 at a predetermined timing. The sheet is conveyed to a transfer area facing the drum 200. Then, the first color toner image on the photosensitive drum 200 is transferred onto the transfer material 5 by the transfer action of the transfer corotron 204. By repeating such steps of latent image formation, development, transfer, etc. in substantially the same manner,
The toner images of the second and subsequent colors are transferred onto the transfer material 5 so as to be sequentially superimposed. The toner and the like remaining on the surface of the photosensitive drum 200 after the transfer are removed by the cleaning device 205.

On the other hand, the transfer material 5 to which the unfixed toner image has been transferred is held and conveyed by the transfer drum 206, and is separated from the transfer drum 206 by the separating action of the separating charger 205 and the separating claw 209. Later, the fixing device (70)
And subjected to a fixing process. That is, in this fixing device, the transfer material 5 onto which the unfixed toner image has been transferred is drawn into the fixing nip portion N formed by the heating roll 1 and the tube body 2 rotating with each other, and passes through the nip portion. . The transfer material 5 is heated and pressurized by passing through the fixing nip, so that the unfixed toner 5a is fixed on the transfer material.

In the case of this fixing device, the nip portion N
The transfer material 5 that has passed through passes through the space between the pressing roll 6 while being attached to the surface of the heating roll 1, and is thereby naturally separated from the surface of the heating roll 1. This is because the elastic body surface layer 1 of the heating roll 1 provided by the pressing roll 6
When the distortion of No. 2 returns to the original shape when it is released by passing through the pressing area by the pressing roll 6, a minute slip (microslip) instantaneously occurs between the distortion and the toner image surface of the transfer material. It is assumed that the microslip functions to separate the transfer material 5 from the surface of the heating roll.

When the fixing process is completed, the transfer material 5 is discharged onto the paper discharge tray 214. Further, after the transfer drum 5 is peeled off, the transfer drum 206 is placed on standby for attracting and transferring the next transfer material after the drum surface is discharged by the discharging charger 210.

FIG. 10 shows the results of an investigation on the relationship between the width of the fixing nip N and the minimum allowable fixing temperature in the fixing device according to this embodiment. That is,
The width of the nip portion N was changed by changing the pressing force of the tube body 2 against the heating roll 1 and the minimum fixing temperature at which fixing at a level that does not cause a practical problem at that time was examined. This fixing test was carried out by using two types of transfer material 5: plain paper and thin paper, and observing the fixing results when the same full-color toner image was formed on the transfer material.

From the results shown in FIG. 10, it is understood that the minimum allowable fixing temperature can be set lower by increasing the width of the fixing nip portion N. It can also be seen that the relationship between the nip width and the fixing temperature is the same regardless of the thickness of the paper. Therefore, from this result, it can be seen that in this fixing device, the width of the fixing nip portion N can be widened by employing the tube body 2, so that a good fixing performance can be secured even if the fixing temperature is slightly lowered.

FIG. 11 shows the result of an investigation on the relationship between the width of the fixing nip N and the rate of occurrence of paper wrinkles in the fixing nip N in the fixing device according to this embodiment. That is, when the width of the nip portion N is changed by changing the pressing force of the tube body 2 to the heating roll 1 and the transfer material 5 is passed through the nip portion to fix the paper, the paper of the transfer material 5 after passing The occurrence of wrinkles was investigated. In this fixing test, two kinds of transfer material 5 (plain paper and thin paper) are used, and the same full-color toner image is formed on the transfer material 5 to evaluate the occurrence of paper wrinkles after fixing. Was performed.

From the results shown in FIG. 11, it can be understood that paper wrinkles are more likely to occur as the width of the fixing nip N is increased. Therefore, in consideration of the results shown in FIG. 10, it can be said that when the width of the fixing nip portion N is set in an appropriate range, it is possible to achieve both a reduction in the fixing temperature and a prevention of the occurrence of paper wrinkles. . In the case of the fixing device using the tube body 2, the width of the fixing nip portion N is 5 from the viewpoint of reducing the fixing temperature and preventing the occurrence of paper wrinkles.
It is desirable to set it to about 10 to 10 mm.

FIG. 12 shows the result of an investigation on the relationship between the pressing force of the fixing nip N and the amount of distortion of the heating roll (elastic body surface layer) due to the pressing of the pressing roll 6 in the fixing device according to this embodiment. It is. For reference, a roll nip type conventional apparatus using a heating roll / a pressure roll was similarly examined. In addition, the distortion amount of the heating roll (elastic body surface layer) in the conventional apparatus is the distortion due to the pressure contact of the pressure roll. That is, this test was performed by examining the amount of distortion of the heating roll necessary for the transfer material to be able to be peeled satisfactorily when the pressing force of the fixing nip portion N was changed. FIG. 12 shows the amount of distortion of the heating roll required to always obtain stable peeling performance regardless of the pressing force of the nip portion. The amount of distortion is determined by a predetermined calculation formula.

From the results shown in FIG. 12, it is understood that the amount of distortion of the heating roll required for peeling must be increased as the pressing force of the fixing nip N is increased. In addition, when the pressing force is the same at the nip portion, it can be seen that the apparatus according to the present embodiment requires a smaller amount of strain for peeling. therefore,
It can be seen that the apparatus according to the present embodiment can reduce the stress applied to the elastic body surface layer of the heating roll.

In a so-called tube nip type fixing device in which a fixing nip is formed by a tube as exemplified above, a wide nip can be formed, so that good fixing performance can be obtained even when the fixing temperature is lowered. In addition to this, since the restoring force of the tube body against the pressure deformation is large, the pressure force at the fixing nip portion is suppressed to be low, and thus there is an advantage that paper wrinkles are hardly generated.

In the case where the pressing roll 6 is provided, a fixing section comprising a pressure contact portion between the heating roll and the tube body, and a peeling section comprising a contact portion between the pressing roll and the heating roll provided near the exit of the nip portion. Are formed independently of each other, so that the conditions for fixing and the conditions for peeling can be individually set, and good fixing performance and stable peeling performance can be obtained simultaneously. This is particularly effective when fixing a full-color image. Further, since the outer diameter of the pressing roll can be reduced, the nip width with the heating roll is narrowed and the pressing roll is not heated, so that paper wrinkles do not occur when passing through the pressing roll.

The present invention is not limited to the first and second embodiments described above, and various modifications can be made without departing from the gist of the invention.

For example, in order to prevent meandering during rotation of the tube body 2, as shown in FIG. 13, support rolls 4 serving as tube inner circumferential surface support members are provided at both ends in the axial direction as shown in FIG. A large diameter portion 42 having an outer diameter larger than the central portion (in contact with the surface), or in addition thereto, the large diameter portions 42 at both ends thereof are brought into contact with the surface of the core metal 11 of the heating roll 1. What is installed may be used.

The provision of the large-diameter portion 42 prevents the meandering of the tube body 2 because both ends 2a of the tube body 2 are regulated by the inner wall surface of the large-diameter portion 42. In this case, the dimensional difference between the width L between the large diameter portions 42 and the width W of the tube body 2 (L−
W) is preferably set to be within 2 mm. When the large-diameter portion 42 is installed in contact with the surface of the core metal 11 of the heating roll 1, the outer diameter of the large-diameter portion 42 is appropriately set, so that the heating roll of the tube body 2 by the support roll 4. 1 can be kept constant. When the large-diameter portion 42 is used solely for preventing meandering without making contact with the surface of the core metal 11 of the heating roll 1, the outer peripheral portion of the large-diameter portion 42 does not project from the upper surface of the tube body 2. It is necessary to set the outer diameter as follows. That is, at least half of the difference (R−r) between the outer diameter R of the large-diameter portion and the outer diameter r of the small-diameter portion at the center of the support roll 4 is larger than the wall thickness t of the tube body 2. It is necessary to set the value to be small [(R−r) / 2 <t)].

In the case where the large diameter portions 42 are provided at both ends of the support roll 4, the rotation driving force of the heating roll 1 is transmitted to the support roll 4 by the rotation transmission gear 41 in FIG.
, But the rotation transmission gear 41
Regardless of the outer diameter of the large diameter portion 42 and the core metal 1 of the heating roll 1,
The support roll 4 may be driven to rotate by utilizing the frictional resistance with respect to one surface. In this case, the large diameter portion 42
It is preferable to provide a high friction member for increasing the coefficient of friction between the heating roll 1 and the surface of the metal core 11 on the outer peripheral surface of the heating roll 1.

In order to prevent meandering during rotation of the tube body 2, a support roll 4 serving as a tube inner peripheral surface support member is provided.
As shown in FIG. 14, tracking rollers 43 for maintaining a constant distance between the support roll 4 and the heating roll are rotatably provided at both ends in the axial direction, and the tracking rolls 43 at both ends are connected to the heating roll 1. May be used so as to be brought into contact with the surface of the metal core 11.

The provision of the tracking roll 43 prevents the meandering of the tube body 2 because the position of both ends 2 a of the tube body 2 is regulated by the inner wall surface of the tracking roll 43. In this case, the width T between the tracking rolls 43
The dimension difference (T · L−W) between L and the width W of the tube body 2 is 2
mm. Also,
Since the tracking roll 43 is brought into contact with the surface of the cored bar 11 of the heating roll 1 to keep the distance between the supporting roll 4 and the heating roll constant, the tube 2 formed by the supporting roll 4
Of the heating roll 1 can be kept constant.

The surface of the holding portion 30, which is the sliding surface of the tube outer peripheral surface supporting member 3 with the outer peripheral surface of the tube, secures the slidability with the outer peripheral surface of the tube, if necessary, as follows. May be configured. For example, it is constituted by a member having the same polarity as the outer circumferential surface of the tube electrostatically. In this case, it is possible to prevent the occurrence of electrostatic attraction due to rubbing with the outer peripheral surface of the tube. Further, the surface of the holding unit 30 may be formed of a conductive member. This can prevent generation of static electricity due to sliding friction with the outer peripheral surface of the tube. Further, the surface of the holding portion 30 may be grounded to be grounded in order to prevent generation of static electricity due to sliding friction with the outer peripheral surface of the tube.

Further, at least one of the tube outer peripheral surface support member 3, the tube inner peripheral surface support member (support roll) 4 and the pressing member (press roll) 6 can variably adjust the pressing force and the installation angle with respect to the heating roll 1. It may be provided as follows. That is, as illustrated in FIG. 15, the tube outer peripheral surface supporting member 3 is pressed against the heating roll 1 by an appropriate pressing / angle adjusting means 35 (actually, the tube body 2
And the installation angle (actually, the winding angle of the outer peripheral surface of the heating roll of the tube body 2). The tube inner peripheral surface support member (support roll) 4 adjusts the pressing force (actually, the pressing force via the tube body 2) against the heating roll 1 by an appropriate pressure adjusting unit 45. To Further, the pressing member (pressing roll) 6 is moved by an appropriate pressure adjusting means 65.
The pressing force on the heating roll 1 (elastic body surface layer) is adjusted. As the above-mentioned pressure / angle adjustment means and each pressure adjustment means, for example, those having a structure in which a link mechanism and a cam are combined can be applied.

With such a configuration, the pressing force and the installation angle with respect to the heating roll 1 can be variably adjusted individually or simultaneously under desired conditions, so that the fixing performance (particularly the pressing force) and the transfer material peeling performance can be adjusted. Can be easily changed to a more preferable characteristic level. For example, by appropriately adjusting the pressing force and the installation angle with respect to the heating roll 1 in accordance with the thickness and material of the transfer material to be used, the type of image (for example, whether the image is a black-and-white image or a full-color image), or the like, Irrespective of differences in images and the like, it is possible to always achieve better fixing and more stable peeling.

In the case where the above-described variable adjustment configuration is adopted, in addition to this, as shown in FIG. 15, the thickness of the transfer material 5 is detected before reaching the fixing nip N. The thickness detecting means 9 may be provided so that the pressing force and the installation angle with respect to the heating roll 1 can be individually adjusted according to the thickness of the transfer material 5 detected by the detecting means 9. In this case, for example, the detection information (signal) of the thickness detecting means 9 is input to the fixing-related control unit 90, and the control unit 90 pre-programs the sequence contents according to the thickness of the transfer material 5. A predetermined control signal is individually transmitted to the pressure / angle adjusting means 35, the pressure adjusting means 45, and the pressure adjusting means 65 according to the above, so that the pressing force and the installation angle with respect to the predetermined heating roll 1 can be individually set. It may be adjusted to. Thereby, the transfer material 5
It is possible to automatically and accurately set suitable fixing conditions and peeling conditions according to the thickness of the sheet. As the thickness detecting means 9, for example, a piezoelectric element formed by laminating dielectrics in multiple layers can be used.

[0069]

As described above, according to the fixing device of the present invention, an elastically deformable tube body and its supporting member are employed as a pressing means for forming a fixing nip portion between the heating roller and the heating roll. As a result, under the same fixing pressure, a wider fixing nip portion can be obtained as compared with a roll nip type fixing device using a conventional pressure roll,
Necessary and sufficient fixing can be performed even at a fixing temperature slightly lower than the conventional fixing temperature. Also, compared to the conventional belt nip type fixing device using an endless belt, there is no variation in tension or circumference, stable fixing pressure can be obtained, and there are fewer components for installing the tube body. Is simpler. In addition, a sufficient fixing pressure and a stable paper transport property are secured by the restoring force against the pressure deformation of the tube body and the pressing force of the tube inner peripheral surface supporting member. Therefore, according to this fixing device, with a simple configuration and low cost,
Good and stable fixing can be performed even at a lower fixing temperature, and downsizing and low power consumption can be realized.

Further, when a pressing member for distorting the elastic body surface layer of the heating roll is provided, a region where the pressing member generates a distortion is formed independently of the fixing region in the fixing nip portion. After the above-described good fixing is performed in the fixing region, the transfer material is reliably separated from the heating roll by the peeling action in the distortion generating region. Thereby, even when fixing a color (especially full-color) image, it is possible to simultaneously secure good fixing performance and stable peeling performance without complicated setting of conditions.

Further, at least one of the tube outer peripheral surface support member, the tube inner peripheral surface support member and the pressing member is provided so that the pressing force or the setting angle with respect to the heating roll can be variably adjusted, and the pressing force or the setting angle is set to the transfer material. In the case where the thickness is adjusted individually according to the thickness, for example, even if transfer materials having different thicknesses are used in combination, the fixing pressure / heating conditions and peeling conditions suitable for the thickness are set. Therefore, excellent fixing performance is ensured, and at the same time, stable release performance of the transfer material is ensured.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating a basic configuration of a fixing device of the present invention.

FIG. 2 is a main part configuration diagram showing a fixing device according to one embodiment of the present invention.

FIG. 3 is a partial cross-sectional view illustrating the fixing device of FIG. 2;

4A and 4B show an example of a tube outer peripheral surface support member, wherein FIG. 4A is a perspective view of a main part thereof, and FIG. 4B is a sectional view taken along line AA.

FIG. 5 is a main part configuration diagram showing an example of a printer to which the fixing device of the present invention is applied.

FIG. 6 is a graph showing a relationship between a surface temperature of a heating roll and a fixing level.

FIG. 7 is a graph showing the relationship between the thickness / outer diameter ratio of the tube body and the fixing pressure level.

FIG. 8 is a main part configuration diagram showing a fixing device according to another embodiment of the present invention.

FIG. 9 is a main part configuration diagram showing an example of a color copying machine to which the fixing device of the present invention is applied.

FIG. 10 is a graph showing a relationship between a width of a fixing nip portion and a minimum allowable fixing temperature.

FIG. 11 is a graph showing the relationship between the width of the fixing nip and the occurrence of paper wrinkles.

FIG. 12 is a graph showing a relationship between a pressing force of a fixing nip portion and a distortion amount of a heating roll.

FIG. 13: Tube inner peripheral surface support member (rigid roll)
FIG. 10 is a partial cross-sectional view showing another configuration example.

FIG. 14: Tube inner peripheral surface support member (rigid roll)
FIG. 10 is a partial cross-sectional view showing another configuration example.

FIG. 15 is a conceptual diagram showing a fixing device according to another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heating roll, 2 ... Tube body, 3 ... Tube outer peripheral surface support member, 4 ... Tube inner peripheral surface support member (rigid roll), 5 ... Transfer material, 5a ... Unfixed toner image, 6 ... Pressing member, 12 ... Elastic body surface layer, 35 means for applying pressure and angle,
45, 65: pressure adjusting means, N: fixing nip portion.

Claims (5)

[Claims] 1. A heating roll that is driven to rotate, an elastically deformable tube body that forms a fixing nip portion between the heating roll and a heating roll by pressing the heating roll against an outer peripheral surface of the heating roll, and the tube body. Is pressed against the outer peripheral surface of the heating roll so that the outer peripheral surface of the tube is pressed against the heating roll, and the outer peripheral surface of the tube body is slidably held so that the tube rotates while being pressed against the heating roll. A tube outer peripheral surface supporting member, and a tube inner peripheral surface supporting member that abuts against the inner peripheral surface of the tube body at a predetermined position of the fixing nip portion and presses the tube body against the outer peripheral surface of the heating roll. The unfixed toner image is fixed by passing a transfer material carrying the unfixed toner image through a fixing nip portion between the unfixed toner image and the tube body. Chakusochi. 2. The pressing device according to claim 1, wherein the heating roll has a roll structure having at least an elastic body surface layer, and is pressed against a vicinity of a transfer material discharge side of a fixing nip portion of the heating roll to deform the elastic body surface layer of the heating roll. 2. A member is provided.
The fixing device as described in the above. 3. The fixing device according to claim 1, wherein the tube body is a tube made of a heat-resistant rubber material. 4. The fixing device according to claim 1, wherein the tube inner peripheral surface support member is a rotatable rigid roll. 5. At least one of the tube outer peripheral surface support member, the tube inner peripheral surface support member, and the pressing member is provided so as to be capable of variably adjusting the pressing force or the installation angle with respect to the heating roll, and according to the thickness of the transfer material used. 3. The fixing device according to claim 1, wherein the pressing force or the installation angle is adjusted individually.