JPH1020692A - Fixing device and image forming device adopting same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate realizing prevention of meandering on a belt by surely evading such as twisting, waving, buckling or the like, in using an inexpensive endless belt provided with the low rigidity to a fixing device of a belt nip type. SOLUTION: This device equipped with a heating roll 1, endless belt 2 held in press contact with the heating roll 1 while rolling-traveling in company with the heating roll 1, and pressing member 3 forming a contact nip area between the endless belt 2 and the heating roll 1 by letting the endless belt 2 held in contact with the heating roll 1, and the belt strand guide 6 located at least, at one side on the extension line in the heating roll 1 shaft direction at the contact nip area between the heating roll 1 and the endless belt 2, by which the strand of end edge of the endless belt 2 is controlled while the end part with the pressing member 3 is embedded. Moreover, it is similar to a combination type of the pressure roll 7 and the endless belt 2. Furthermore, an image forming device is composed by adopting these fixing device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for fixing an unfixed toner image by heating and pressing in an image forming apparatus using an electrophotographic method such as a copying machine, a printer, and a facsimile. The present invention relates to an improvement in a belt nip type fixing device in which an endless belt is pressed against a pressure fixing roll.

[0002]

2. Description of the Related Art The present applicant has already proposed a fixing device employing a so-called belt nip system (for example, Japanese Patent Application No. 7-1995).
No. 65629). This is, for example, a rotatable heating roll having a heat source, an endless belt that presses against the heating roll and rotates following the heating roll, and is disposed inside the endless belt, and the endless belt is attached to the heating roll. A pressing member for forming a contact nip area between the endless belt and the heating roll, and heating the unfixed toner image on the recording sheet by passing the recording sheet through the contact nip area.・
The fixing is performed under pressure.

In such a belt nip type fixing device, a wide contact nip area is secured with a relatively low load as compared with, for example, a roll pair type (a type in which a heating roll and a pressure roll are pressed and arranged). can do. Due to this reduction in load, the core of the heating roll does not require the flexural strength of the related art, so that it can be made thinner than before. Therefore, the time required to raise the temperature of the heating roll from the ambient temperature to a temperature at which the fixing operation can be performed can be shortened. Further, since the pressing member is fixed in a non-rotating state, the heat absorption from the heating roll can be reduced.
Furthermore, as for the endless belt, if there is no tension roll or the like and if there is almost no contact outside the contact nip region, unnecessary heat radiation is small and heat absorption from the heating roll is small. With these measures, it is possible to shorten the time required for bringing the fixing device from the standby state to the state where the fixing operation can be performed (hereinafter, referred to as warm-up time).
By setting the warm-up time to about 15 to 30 seconds, it is possible to start the heating of the fixing device from the ambient temperature after receiving the signal for starting the image formation, and to enable the image formation with almost no waiting. That is, it can be said that the belt nip type fixing device is suitable for a so-called instant start.

[0004]

However, the above-described belt nip type fixing device has the following technical problems. The endless belt tends to move in one of the belt axial directions due to the difference in the circumferential length between both ends of the belt, the difference in load between both ends of the contact nip area, or the degree of non-parallelism with the heating roll when the belt is arranged. . As a conventional method for avoiding such a belt shift phenomenon (so-called belt walk), at least one of the stretching rolls is displaced, for example, as in a fixing device disclosed in Japanese Patent Application Laid-Open No. 5-150679. Therefore, a mechanism for controlling the deviation of the belt has been used. However, this method is expensive because it requires an endless belt shift detection mechanism, the above-described roll displacement mechanism, and the like.

[0005] In addition, from the viewpoint of reducing heat radiation from the endless belt, if the circumferential tension is not applied to the endless belt, it becomes difficult to employ the above-described deviation prevention mechanism. Therefore, for example, a method has been considered in which the end of the belt is abutted against a guide member to prevent the belt from shifting. As this type of technique, a technique is known in which a guide member regulates the end position of the endless belt except for the contact nip area (for example, Japanese Patent Application Laid-Open No. 4-440).
No. 75). When this method is adopted, the belt receives an approaching force from the contact nip area with the pressure roll and moves in the axial direction. On the other hand, when the belt abuts on the guide member, the end of the belt is deviated from the guide member and receives a regulating force. At this time, the deviation force and the deviation regulating force are parallel, but are not on the same straight line, so a moment acts on the belt, and this moment causes a technical problem that the belt is twisted, wavy, buckled, etc. .

Further, in order to prevent the belt from twisting, waving, buckling, etc. when receiving such a moment, the belt itself is required to have high rigidity. Examples of the highly rigid belt material include metals, particularly SUS and iron. However, it is difficult to produce a seamless endless belt. There are also seamless belts using welding, but the reliability of the joints is not sufficient. Although a nickel electroformed belt can be formed seamlessly, it is not preferable from the viewpoint of safety. On the other hand, resin belts made of polyimide, polytetrafluoroethylene, or the like have low strength, and thus cause twisting, waving, buckling, and the like as described above. To compensate for this, it is possible to use a belt having a large film thickness, but this is not preferable because the cost increases.

It is also known to provide a rib at the end of the endless belt and prevent the belt from shifting toward the end by the regulating member (see, for example, Japanese Patent Application Laid-Open No. 4-204680). Belt damage is inevitable due to concentration.

SUMMARY OF THE INVENTION The present invention has been made to solve the above technical problem. In a so-called belt nip type fixing device, an inexpensive endless belt having low rigidity is used. An object of the present invention is to provide a fixing device capable of easily preventing the belt from shifting while reliably avoiding buckling or the like.

[0009]

That is, the present invention provides:
As shown in FIGS. 1A and 1B, in a fixing device for fixing an unfixed toner image on a recording sheet 5 by heating and pressure,
A rotatable heating roll 1 having a heat source 4, an endless belt 2 that is pressed against the heating roll 1 and rolls with the heating roll 1, and is disposed inside the endless belt 2, and the endless belt 2 A pressing member 3 for pressing the heating roll 1 to form a contact nip area between the endless belt 2 and the heating roll 1; and a heating roll 1 axial direction in a contact nip area between the heating roll 1 and the endless belt 2. Provided on at least one of the extensions,
The endless belt 2 is provided with a belt shift guide 6 which regulates the shift of the end edge and embeds the gap between the end member 2 and the end of the pressing member 3.

In such technical means, the application of the present invention is not limited to the mode in which the belt shift guides 6 are provided at both ends of the endless belt 2, and the belt shift guide 6 is provided in one end of the endless belt 2. Also included are embodiments. At this time, in a mode in which the belt shift guide 6 is provided at one end of the endless belt 2, the outer diameter of both ends of the heating roll 1 is made different, or the outer diameter of both ends of the endless belt 2 is made different. It is necessary to always make the direction of the endless belt 2 lean toward the belt lean guide 6 by, for example, holding the heating roll 1 and the endless belt 2 in a skewed (tilted) manner.

The endless belt 2 may be made of any material such as resin and metal, and the endless belt 2 may be disposed on a tension roll or the like. Although it does not matter, from the viewpoint of minimizing the heat radiation from the endless belt 2, it is preferable to minimize the number of members that come in contact other than the contact nip region. Further, with respect to the driving method of the fixing device of the present invention, any one of the heating roller 1 and the endless belt 2 may be driven, but in a mode in which the endless belt 2 is not stretched, the heating roller 1 is driven to rotate. It is preferable that the endless belt 2 be rotated to follow.

Further, as the pressing member 3, if the endless belt 2 is pressed against the heating roll 1 and a contact nip area is formed between the endless belt 2 and the heating roll 1, a spring member or the like may be used. An elastic urging means may be used to elastically urge a rigid pressing member, or an elastic body may be used for all or a part of the pressing member, and an elastic force accompanying elastic deformation of the elastic body may be used. Alternatively, a combination of the two may be appropriately selected.

If the belt shift guide 6 is provided on an extension of the heating roll 1 in the axial direction of the contact nip area between the heating roll 1 and the endless belt 2, it may be fixedly provided on a fixing member such as a frame. May be
For example, in a situation where a bearing having a diameter substantially equal to the diameter of the roll is used as the bearing support portion of the heating roll 1, from the viewpoint of preventing interference with the heating roll 1, the heating roll 1 and the endless belt 2 are not supported. It is preferable that the belt-side guide be formed by a ring-shaped member provided outside the contact nip area.

Here, as a mode of embedding between the end of the pressing member 3 and the guide 6 near the belt, there are a mode in which the end of the pressing member 3 which is a separate member and the guide 6 near the belt, There is a mode in which a belt-side guide 6 is integrally provided at the end of the pressing member 3. In the former mode, an extension extending beyond the end of the endless belt 2 may be provided at the end of the pressing member 3 so as to abut on the belt shift guide 6, or conversely, on the belt shift guide 6 side May be provided with an extension extending toward the end of the pressing member 3 so as to be in contact with the end of the pressing member 3.
May be provided at the end and the belt-side guide 6, respectively, so that the two extensions abut. However, when the belt-side guide 6 is formed of a ring-shaped member provided on the heating roll 1 side, the belt-side guide 6 moves together with the heating roll 1, and thus the contact between the belt-side guide 6 and the endless belt 2. From the viewpoint of minimizing the area, it is preferable to provide an extension that extends beyond the end of the endless belt 2 at the end of the pressing member 3 and abut on the belt-side guide 6. In the latter mode, a belt guide 6 may be integrally formed on the end of the pressing member 3 toward the heating roll 1 or may be fixed thereto. Furthermore, in a mode in which the pressing member 3 has an elastic body and the end of the elastic body has an extension extending beyond the end of the endless belt 2, the elastic body has its end deformed in the direction of gravity. From the viewpoint of effectively preventing buckling and buckling, it is preferable to provide a support member that supports the end of the elastic body from below. At this time, the support member may be provided as a component of the pressing member 3 or may be provided independently of the pressing member 3.

Further, the belt-side guide 6 is connected to the heating roll 1.
In the aspect provided on the side, from the viewpoint of reducing the number of components, for example, it may be formed integrally with the heat insulating bush of the bearing member. Further, when the belt shift guide 6 is movable, a contact area reducing portion such as a curved surface portion is formed at one of the end of the belt shift guide 6 and the end of the pressing member 3 to reduce the contact resistance therebetween. Is preferred.

Further, the deviation of the belt has a linear relationship with the deviation of the belt, and the greater the deviation, the greater the deviation. In the state in which the deviation is regulated, slippage occurs between the heating roller 1 and the endless belt 2 to prevent the deviation, and therefore, this relationship is caused by a change in the amount of oil supplied to the heating roller 1, that is, a change in the friction coefficient. Changes. The endless belt 2 shifts due to factors such as a difference in circumference between both ends of the endless belt 2, a difference in load between both ends of the nip, and a degree of parallelism between the heating roll 1 and the endless belt 2. Therefore, it is important to reduce the deviation speed and the deviation force by increasing these precisions. In particular, from the viewpoint of reducing the biasing force acting on the belt shift guide 6 due to the variation in the end shape of the endless belt 2, the belt shift guide 6 can be swung in the axial direction of the heating roll 1, It is preferable that the elastic urging means 9 (indicated by a phantom line in FIG. 1B) elastically urge in the direction of the endless belt 2. At this time, the belt shift guide 6 is positioned in contact with the end of the pressing member 3.

Further, from the viewpoint of more reliably preventing the end of the endless belt 2 from buckling, the end of the endless belt 2 falls outside the contact nip region of the heating roll 1 toward the heating roll 1. It is preferable to provide a spacer member 8 that fills the gap, and the end of the endless belt 2 does not buckle between the embedded portion between the end of the pressing member 3 and the guide 6 near the belt and the spacer member 8. Be pinched. At this time, from the viewpoint of reducing the frictional resistance with the endless belt 2, the spacer member 8 may be moved at the same speed as the heating roll 1.
Further, from the viewpoint of further reducing the number of parts, it is preferable that the spacer member 8 is provided integrally with the belt-side guide 6 made of a ring-shaped member provided on the heating roll 1 side.

Further, from the standpoint of reducing the pressing force of the pressing member 3 during standby and during idling, and preventing wear of the endless belt 2 and the peripheral surface of the heating roll 1,
The pressing member 3 is formed by providing an elastic body on a movable body that is elastically urged, and the end of the movable body is brought into contact with a surface of the belt skew guide 6 that is orthogonal to the deviation regulating surface of the endless belt 2 to heat the member. It is preferable that the position of the movable body facing the circumferential surface of the roll 1 is regulated.

The application of the present invention is not limited to the combination of the heating roller 1 and the endless belt 2, but the pressure roller 7 and the endless belt 2 may be combined. That is, as another embodiment of the present invention, as shown in FIG. 1C, in a fixing device for fixing an unfixed toner image on a recording sheet 5 by heating and pressure,
A rotatable pressure roll 7, an endless belt 2 that is pressed against the pressure roll 7, rolls with the pressure roll 7, and is heated by a heat source 4, and is disposed inside the endless belt 2. A pressing member 3 for pressing the endless belt 2 against the pressure roll 7 to form a contact nip area between the endless belt 2 and the pressure roll 7; A belt skew guide 6 which is provided on at least one of the extension lines of the pressure roll 7 in the contact nip region in the axial direction, regulates the skew of the edge of the endless belt 2 and is buried between the end of the pressing member 3 and That are provided with As for the fixing device of this embodiment, it is needless to say that various modifications made to the fixing device shown in FIGS. 1A and 1B can be applied.

Further, the fixing device of the present invention is applied to various types of image forming apparatuses in which a toner image formed on an image carrier is transferred onto a recording sheet and is fixed by heating and pressing with a fixing device. Can be.

Next, the operation of the above technical means will be described. According to FIGS. 1 (a), (b) (or (c)),
The endless belt 2 abuts on the belt shift guide 6 on the axial extension of the contact nip area pressed by the heating roll 1 (or the pressure roll 7) and the pressing member 3, and regulates the shift position. At this time, since the deviation force of the endless belt 2 and the deviation regulating force from the belt deviation guide 6 are on the same line, the deviation force and the deviation regulating force cancel each other, and no moment acts on the belt. Therefore, the endless belt 2 is not twisted or wavy due to the moment. In addition, the endless belt 2 is positioned on an extension of the contact nip region sandwiched between the heating roll 1 (or the pressure roll 7) and the pressing member 3 so that the end thereof abuts on the belt-side guide 6 to regulate the endless belt. The rigidity of the endless belt 2 is increased by the clamping pressure, and buckling is less likely to occur. In addition, since the gap between the belt shift guide 6 and the end of the pressing member 3 is buried, even if the end of the endless belt 2 tries to buckle, the buckling phenomenon is prevented on the wall surface. You. In particular, if the spacer member 8 is provided on the side of the heating roll 1 (or the pressure roll 7), the end of the endless belt 2 is connected to the spacer member 8, the belt shift guide 6, and the pressing member 3
Buckling deformation of the end of the endless belt 2 is reliably prevented.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the accompanying drawings. Embodiment 1 FIG. 2 is an explanatory front view showing Embodiment 1 of a fixing device to which the present invention is applied, FIG. 3 is a cross-sectional view taken along line III-III in FIG.
FIG. 4 is an arrow view as viewed from the IV direction in FIG. In the figure, the fixing device includes a heating roll 20 that is driven to rotate,
An endless belt 30 which presses against the heating roll 20 and rotates following the heating roll 20;
, The endless belt 30 is pressed against the heating roll 20, and the endless belt 30
And a pressing member 50 for forming a contact nip area between the heating member 20 and the heating roll 20.

Here, the core 21 of the heating roll 20 is an aluminum cylinder having an outer diameter of 34 mm, an inner diameter of 32 mm, and a length of 350 mm. The surface of the core 21 is directly coated with an HTV silicone rubber having a hardness of 45 ° (JIS-A) with a thickness of 1 mm as a base layer, and is further dip-coated with a RTV silicone rubber with a thickness of 50 μm as a top coat layer. ing. Thus, a coating layer (not shown) is formed, and the coating layer is finished to a surface close to a mirror state. In the present embodiment, the hardness of the rubber of the underlayer is measured by a spring A type hardness tester manufactured by Teclock Co., Ltd. in accordance with JIS K6301, and a load of 1,0.
This is the result of measurement with 00gf added. In addition, core 2
As 1, a metal made of metal having high thermal conductivity can be used even if it is not aluminum, and another material can be used as the coating layer as long as it is an elastic body having high heat resistance.

Inside the core 21, an output 8 as a heating source is provided.
A 50 w halogen lamp 25 is provided. Also,
A temperature sensor (not shown) is arranged on the surface of the heating roll 20, and measures the temperature of this surface. Then, the halogen lamp 25 is feedback-controlled by a temperature controller (not shown) based on the measurement signal of the temperature sensor, so that the surface of the heating roll 20 is adjusted to, for example, 150 ° C. Note that an oil supply device (not shown) is provided near the heating roll 20, and always supplies a fixed amount of a release agent to the surface of the heating roll 20, whereby an unfixed toner is unfixed on the recording sheet 28. When the image 29 is fixed, a part of the toner is prevented from being offset to the heating roll 20.

Further, both ends of the heating roll 20 are formed as support shaft portions 23 which are slightly narrowed, and ring-shaped belt-side guides 60 are fitted to the support shaft portions 23 respectively. It is rotatably supported by a bearing (bearing member) 24 mounted on the bearing opening.

The endless belt 30 is made of, for example, a polyimide film having a thickness of 75 μm and a width of 300 mm.
It is formed with a circumference of 125 mm.
A release layer of FE (polytetrafluoroethylene) is formed. The endless belt 30 is nipped only between the pressing member 50 and the heating roll 20, and is wound without tension.

The pressing member 50 elastically urges the movable support base 41 extending in the axial direction of the heating roll 20 toward the heating roll 20 by a pair of support springs (compression coil springs) 54 and 55, and the movable support base 41. A recess 42 is formed in the recess 42, and an elastic body 45 having a predetermined thickness is fixed in the recess 42. In the present embodiment, as the elastic body 45, for example, a silicone rubber having a hardness of 23 mm (JIS-A) is used, and a low friction layer (not shown) is provided on the surface thereof (the contact surface with the endless belt 30). It is laminated.
In the present embodiment, as the low friction layer, “FGF-400-4” (trade name) manufactured by Chuko Kasei, which is a glass fiber sheet impregnated with polytetrafluoroethylene, is used.
Furthermore, dimethyl silicone oil (trade name “KF-96” manufactured by Shin-Etsu Chemical Co., Ltd.) having a viscosity of 1000 cs is applied to the surface of the low friction layer to reduce the friction coefficient between the endless belt 30 and the pressing member 50. doing. Furthermore, since the elastic body 45 of the pressing member 50 is softer than the underlayer of the heating roll 20, it is easily deformed. Here, the endless belt 30 is deformed in the direction opposite to the cylindrical shape of the belt in the contact nip region. Therefore, the second moment of area of the belt increases, and the buckling strength increases.

The movable support 41 is made of, for example, a heat-resistant resin, and the holding portion 43 of the elastic body 45 (both side walls of the concave portion 42) is formed of the endless belt 3.
The linear contact is made with a small contact area on the inner surface of the zero, and it functions as a belt running guide. In this embodiment, a part of the movable support table 41 has a belt traveling guide function, but a belt traveling guide may be provided separately.
However, the material of the belt running guide has a certain degree of rigidity, does not take too much heat from the endless belt 30, and
It is preferable that the running of the endless belt 30 is not hindered.

In this embodiment, the heating roll 20
The belt shift guide 60 fitted to the support shaft portion 23 of
In particular, as shown in FIG. 5, a polyamide-made ring-shaped member whose outer diameter changes in multiple stages is provided with a guide portion (large-diameter portion) 61 having an outer diameter of 50 mm and an axially outer position of the guide portion 61. 33m outside diameter to be inserted inside the bearing 24
m bush portion (medium diameter portion) 62 and the deviation guide portion 6
A collar portion (small diameter portion) 63 having an outer diameter of 35 mm is integrally formed at an inner position in the axial direction.

The deviation guide portion 61 has a deviation regulating surface 64 facing the end of the endless belt 30. Further, in the present embodiment, the end of the elastic body 45 of the pressing member 50 has the extension 45a extending beyond the end of the endless belt 30, and the end of the elastic body extension 45a is the deviation regulating surface. 64. On the other hand, the side surface of the heating roll 20 at the end of the endless belt 30 is arranged in contact with the peripheral surface of the collar portion 63. Further, in the present embodiment, the end of the movable support base 41 has an extension 41a extending from the end of the elastic body 45, and the movable support base extension 41a is provided on the peripheral surface of the shift guide 61. The contact is arranged.

Further, in the present embodiment, the deviation guide portion 61 includes the elastic body extension portion 45a and the movable support base extension portion 4.
1a has a curved surface portion 66 having a predetermined curvature in a portion facing the
The contact resistance between the elastic member 45 of the pressing member 50 and the movable support table 41 is reduced. In addition, the curved surface portion 66 includes a heating roll 20 in which the belt-side guide 60 is incorporated in advance,
Since it also functions as a guide surface when assembling the pressing member 50, it also helps to improve the assembling workability when manufacturing the fixing device.

In the present embodiment, the belt shift guide 60 is provided so as to be able to swing in the axial direction with respect to the heating roll 20, and is pressed in the direction of the endless belt 30 by the biasing spring 65. Reference numeral 67 in FIGS. 2 and 5 denotes a drive transmission gear for transmitting a rotational driving force to the heating roll 20.

Next, the operation of the fixing device according to this embodiment will be described. 2 and 3, the heating roll 20 has a peripheral speed V = 160 mm by a motor (not shown).
/ S. By this rotation, the endless belt 30 is also driven to rotate at a speed of 160 mm / s. The toner image 29 is transferred onto the recording sheet 28 by a transfer device (not shown), and the recording sheet 28 is conveyed toward the contact nip area. Then, as shown in FIGS. 3 and 6, when the recording sheet 28 enters the contact nip area of the fixing device, the toner image is formed by the pressure acting on the contact nip area and the heat given by the halogen lamp 25 through the heating roll 20. 29 is fixed on the recording sheet 28.

In the present embodiment, when the fixing device is in a standby state and idling, as shown in FIG.
Since the movable support table 41 elastically urged by the members 4 and 55 abuts on the peripheral surface of the shift guide portion 61 of the belt shift guide 60 and the position thereof is regulated, the thickness and elastic coefficient of the elastic body 45 of the pressing member 50 and the endless belt If the positional relationship between the movable member 30 and the movable support table 41 is appropriately adjusted, the contact force of the elastic member 45 of the pressing member 50 is set to be somewhat weak, and a predetermined width is provided between the heating roll 20 and the endless belt 30. Is obtained. Therefore, in the present embodiment, the pressing force by the pressing member 50 can be suppressed to some extent during standby and idle running, so that the wear of the peripheral surfaces of the endless belt 30 and the heating roll 20 can be minimized.

On the other hand, as shown in FIG.
Enters the contact nip area, the thickness t of the recording sheet 28
The endless belt 30 is moved to the elastic member 45 of the pressing member 50 in minutes.
, The contact force between the inner surface of the endless belt 30 and the elastic body 45 increases, and a good fixing operation is performed with a high contact nip pressure. At this time, since the contact nip pressure increases, meandering of the endless belt 30 itself is effectively suppressed.

Here, the belt shift guide 60 is pressed toward the endless belt 30 by the biasing spring 65, but the shift guide portion 61 of the belt shift guide 60 is attached to the end of the elastic body 45 as shown in FIG. Because of the contact, the deviation regulating surface 64 of the belt deviation guide 60 is positioned at a predetermined position. Also, the heating roll 20 shaft and the belt shift guide 6
The frictional resistance between the belt 60 and the pressing member 50
Since it is larger than the frictional resistance between the movable support 41 and the elastic body 45, the belt-side guide 60 rotates together with the heating roll 20.

In such an operation process, the endless belt 30 may be moved in one of the belt axial directions depending on a difference in circumference between both ends of the belt, a difference in load between both ends of the nip, or a degree of non-parallelism between the belt and the heating roll at the time of installation. Produces leaning on one side. Then, the end of the endless belt 30 abuts on the deviation regulating surface 64 of the belt deviation guide 60, and the deviation of the endless belt 30 is regulated. At this time, since the deviation force of the endless belt 30 and the deviation regulating force from the belt deviation guide 60 are on the same straight line, the deviation force and the deviation regulating force cancel each other out, and no moment acts on the belt. Therefore, no twisting or waving occurs in the belt. Incidentally, in the comparative embodiment in which the belt shift guide is provided corresponding to an area other than the axial extension line of the contact nip area of the endless belt 30, the shift force of the endless belt 30 and the shift regulating force from the belt shift guide are provided. Are not on the same straight line, a moment acts on the belt, which causes the belt to twist or undulate with a relatively weak biasing force on the belt made of resin, and the belt end buckles. Was confirmed.

Further, in the present embodiment, since the belt has high rigidity in the contact nip area of the endless belt 30, buckling of the belt tends to occur at the end of the endless belt 30. However, in the present embodiment, as shown in FIG. 5, the extension 45 a of the elastic body 45 abuts on the guide part 61 of the belt-side guide 60, and the gap between the end of the elastic body 45 and the belt-side guide 60. To fill the gap,
The end of the endless belt 30 does not buckle in the direction of gravity. In particular, in the present embodiment, since the end of the endless belt 30 is sandwiched between the extension 45a of the elastic body 45 and the collar 63 of the belt shift guide 60, the end of the endless belt 30 is seated. Flexural deformation is reliably prevented. For this reason, as the endless belt 30,
It becomes possible to use an inexpensive resin product.

Furthermore, the end of the endless belt 30 cannot be cut completely at right angles to the belt axis, but has a slight inclination. In addition, since the endless belt 30 may be set obliquely, the end of the endless belt 30 is not completely parallel to the deviation regulating surface 64. For this reason, the shift speed of the end of the endless belt 30 is DC
The apparent belt shift speed due to the inclination of the end of the endless belt 30 is superimposed on the component belt shift speed as an AC component. Accordingly, as shown in FIG. 7A, the biasing force also takes the DC component force F _Ave. with the AC component added _thereto , and becomes the maximum value F _Max . This F _Max , if the endless belt 30
If the end is shifted closer to being parallel to the regulating surface 64, AC
The component can be reduced and approaches F _Ave. To smooth the AC component of the biasing force, a belt biasing guide 60 is swingably attached to the heating roll 20, and is pressed toward the endless belt 30 by a biasing spring 65.
This makes it possible to reduce the biasing force in FIG. 7A to F _Max as shown in FIG. 7B. However, F _Ave. does not change because F _Ave. depends on the shift speed of the belt.
Also, by optimizing the elastic coefficient of the biasing spring 65,
The difference between F _Max and F _Ave. is made as small as possible. Further, in the present embodiment, when the biasing spring 65 elastically biases the belt shift guide 60, the belt shift guide 6
0 is always in contact with the end of the elastic body 45 of the pressing member 50 (extended portion extending from the end of the endless belt 30), so that the belt shift guide 60 always contacts the end of the endless belt 30. That is, the end wear of the endless belt 30 is suppressed to a small level.

Second Embodiment FIG. 8 is a front view of a fixing device according to a second embodiment of the present invention, and FIGS. 9 and 10 are sectional views taken along line IX-IX in FIG.
The arrow view seen from the X direction is shown. Note that components similar to those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and detailed description thereof is omitted here. The fixing device according to the present embodiment is different from the first embodiment in that a pressing roll 80 that is driven to rotate, an endless belt 30 that presses against and presses against the pressing roll 80, and an inner side of the endless belt 30 And the endless belt 3
0 is pressed against the pressure roll 80 to form a contact nip area between the endless belt 30 and the pressure roll 80, and a heater 81 for heating the endless belt 30. .

In the present embodiment, the pressure roll 80 is a hard roll having a rigid surface, and its support shaft has a ring-shaped belt shift guide 60 (a shift guide 61, a bush similar to the first embodiment). Part 62 and a collar part 63). The pressing member 50 is a member in which the elastic body 45 is accommodated in the concave portion 42 on the movable support table 41 in substantially the same manner as in the first embodiment, and the pressure roller 80 and the endless belt 30 are elastically deformed by the elastic body 45. To form a contact nip area. Furthermore, endless belt 3
A belt travel guide 40 is disposed in the endless belt 30 while maintaining the shape of the endless belt 30.
It is designed to stabilize the running. In the present embodiment, the belt travel guide 40 is formed of a heat-resistant resin, and a rib-shaped protrusion is provided on the outer peripheral surface thereof in the circumferential direction, so that the inner peripheral surface of the endless belt 30 and the belt travel guide 40 are connected to each other. The contact area is reduced. Various materials can be used as the material of the belt traveling guide 40 as long as it has a certain degree of rigidity, does not excessively remove heat from the endless belt 30, and does not hinder the traveling of the endless belt 40. Furthermore, in the present embodiment, a plate heater is used as the heater 81, and the pressing member 5
The endless belt 30 is accommodated in the bottom of the concave portion 42 of the movable support base 41 and heats the endless belt 30 via the elastic body 45.

Also in the present embodiment, the endless belt 30 is reliably restricted by the deviation guide portion 61 of the belt deviation guide 60, and the end of the endless belt 30 is connected to the extension 41 a of the movable support table 41. Since the endless belt 30 is sandwiched by the collar portion 63 of the belt shift guide 60, the end of the endless belt 30 is reliably prevented from buckling.

Embodiment 3 FIG. 11 shows an embodiment of an image forming apparatus incorporating a fixing device to which the present invention is applied. The image forming apparatus in FIG. 1 is an electrophotographic color image forming apparatus of a transfer drum type, and includes an image carrier 101 such as a photosensitive drum and a laser scanning device that writes an electrostatic latent image of each color on the image carrier 101. Image writing device 102 and image carrier 101
An image carrier that holds a multicolor developing device 103 such as a rotary developing device that visualizes the above electrostatic latent image with toner of each color, and a recording sheet (not shown) from a sheet supply cassette 104 The fixing device 106 includes a transfer drum 105 that sequentially transfers the recording sheets holding the toner images of the respective colors on the recording medium 101 and a fixing device 106 that fixes the recording sheet onto which the toner images of the respective colors are transferred. The fixing device according to the first embodiment (or the fixing device according to the second embodiment (not shown)) is used. In such an image forming apparatus, by using an inexpensive fixing device suitable for an instant start, it is possible to increase the image forming speed while reducing the apparatus cost.

[0044]

As described above, according to the present invention,
Since the deviation of the belt is regulated on the extension line of the contact nip region between the heating roll and the endless belt, the deviation force generated on the belt and the deviation regulating force acting on the belt end can be made collinear. For this reason, no moment such as twisting acts on the belt, and the belt deviation control can be easily realized without causing twisting, waving, buckling, and the like on the belt. Further, since the belt is sandwiched between the heating roll and the pressing member at the portion where the belt leaning force is exerted, the buckling strength of the belt in the contact nip region can be increased. Since the gap between the end of the endless belt and the end of the member is buried, buckling of the end of the endless belt in the direction of gravity can be reliably avoided. For this reason, it has become possible to easily use a belt made of a resin such as polyimide without causing buckling.

In the present invention, if the guide near the belt is rotated together with the heating roll, sliding with the end of the belt does not occur. For this reason, the abrasion of the belt end can be suppressed to a small level. Further, in the present invention,
If the belt shift guide is formed integrally with the heat insulating bush portion of the bearing member and other functional members, the number of parts can be reduced. Furthermore, in the present invention,
If a contact area reducing portion (curved portion or the like) between the movable belt-side guide and the end of the pressing member is formed at one of the ends, not only the frictional resistance between the both can be reduced, but also the heating can be performed. It can also be used as a guide when assembling the roll side assembly and the pressing member side assembly.

Further, if the belt shift guide is attached so as to be swingable with respect to the axial direction of the heating roll, and the belt shift guide is pressed toward the belt side by the elastic urging means, the belt shift end is pressed to the end of the pressing member. The position of the endless belt can be regulated by always contacting the position of the deviation guide, and restricting the deviation of the endless belt that is not normally in contact with the belt deviation guide. For this reason, while minimizing wear of the end of the endless belt due to the belt shift guide, the AC component of the shift force due to the non-parallelism between the belt end and the belt shift guide can be reduced. The leaning force can be reduced.

Further, in the present invention, if a spacer member is provided outside the contact nip area of the heating roll so as to fill a gap in which the end of the endless belt falls down to the heating roll side, the spacer member and the pressing member may be provided. Since the end of the endless belt can be sandwiched between the end and the buried portion between the belt detour guide, buckling of the end of the endless belt can be reliably avoided.

In the present invention, the pressing member has an elastic body and the end of the elastic body has an extension extending beyond the end of the endless belt, whereas the end of the elastic body is lower. By providing a support member that is supported from the end, it is possible to effectively prevent the deformation of the elastic body end in the direction of gravity and the buckling of the elastic body end, and the buckling of the end of the endless belt more reliably. Can be prevented.

Further, in the present invention, an elastic member is provided on a movable member whose pressing member is elastically urged, and the end of the movable member is provided on a surface orthogonal to the deviation regulating surface of the endless belt of the belt deviation guide. To reduce the pressing force of the pressing member during standby and idling of the fixing device,
Abrasion of the endless belt and the peripheral surface of the heating roll can be prevented, the contact nip pressure is increased when the recording sheet passes, the meandering of the endless belt is suppressed, and a good fixing operation by the high nip pressure is realized. Can be.

The above-described effects can be similarly obtained with a combination of a pressure roll and an endless belt. In addition, if an image forming apparatus is configured using these fixing devices, it is possible to form an image with an inexpensive fixing device suitable for an instant start, and to provide an image forming device suitable for an instant start. it can.

[Brief description of the drawings]

FIG. 1A is an explanatory view showing an outline of a fixing device according to the present invention, FIG. 1B is a partially cutaway view seen from a direction B in FIG. 1A, and FIG. FIG. 3 is an explanatory diagram illustrating an outline of a fixing device according to an aspect.

FIG. 2 is an explanatory front view showing the fixing device according to the first exemplary embodiment;

FIG. 3 is a sectional view taken along line III-III of FIG. 2;

FIG. 4 is a view as seen from an arrow IV in FIG. 2;

FIG. 5 is a detailed explanatory view of a V part in FIG. 2;

FIG. 6 is an explanatory diagram similar to FIG. 2, illustrating a state of the fixing device when passing through a recording sheet.

7A is a graph showing a time change of the biasing force in a mode without using the biasing spring 65, and FIG. 7B is a graph showing a time change of the biasing force in a mode using the biasing spring 65; is there.

FIG. 8 is an explanatory front view of a fixing device according to a second embodiment.

9 is a sectional view taken along line IX-IX of FIG.

FIG. 10 is a view as seen from the X direction in FIG. 8;

FIG. 11 is an explanatory diagram showing an embodiment of an image forming apparatus in which a fixing device according to the present invention is incorporated.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heating roll, 2 ... Endless belt, 3 ... Pressing member, 4 ... Heat source, 5 ... Recording sheet, 6 ... Belt guide, 7 ... Pressure roll, 8 ... Spacer member, 9 ... Elastic biasing means, 20 ... Heating roll, 25 ... Halogen lamp, 28
... recording sheet, 30 ... endless belt, 41 ... movable support, 45 ... elastic body, 50 ... pressing member, 54, 55 ... support spring, 60 ... belt guide, 61 ... guide guide, 62 ... bush, 63 … Collar part, 65… biasing spring, 80… pressure roll

Claims (14)

[Claims] 1. A fixing device for heating and pressure fixing an unfixed toner image on a recording sheet (5), comprising: a rotatable heating roll (1) having a heat source (4); An endless belt (2) that is pressed against and rolls together with the heating roll (1), and is disposed inside the endless belt (2), and presses the endless belt (2) against the heating roll (1); Pressing member (3) forming a contact nip area between the endless belt (2) and the heating roll (1)
And at least one of the contact nip area between the heating roll (1) and the endless belt (2) on the extension line in the axial direction of the heating roll (1) to restrict the shift of the end edge of the endless belt (2). And a belt-side guide (6) embedded between the end of the pressing member (3) and the fixing device. 2. The device according to claim 1, wherein the end of the pressing member has an extension extending from the end of the endless belt and abuts against the belt shift guide. A fixing device. 3. The fixing device according to claim 1, wherein the belt shift guide (6) is a ring-shaped member provided outside a contact nip area between the heating roll (1) and the endless belt (2). Characteristic fixing device. 4. The fixing device according to claim 1, wherein the belt-side guide (6) is formed integrally with the heat insulating bush of the bearing member. 5. The fixing device according to claim 3, wherein the contact area between one of the end of the belt-side guide (6) and the end of the pressing member (3) that rotates following the heating roll (1) is reduced. A fixing device, wherein a fixing portion is formed. 6. The fixing device according to claim 1, wherein the belt-side guide (6) is swingable in the axial direction of the heating roll (1), and the endless belt (2) is moved by an elastic urging means (9). A fixing device characterized by being elastically biased in the direction (1). 7. The fixing device according to claim 1, wherein the heating roller is driven to rotate, and the endless belt is driven.
Is driven by a heating roll (1) to rotate. 8. The fixing device according to claim 1, wherein a gap outside the contact nip area of the heating roll (1) is filled with a gap in which the end of the endless belt (2) falls down toward the heating roll (1). A fixing device comprising a member (8). 9. The fixing device according to claim 8, wherein the spacer member (8) moves at the same speed as the heating roll (1). 10. The fixing device according to claim 8, wherein the belt-side guide (6) is a ring-shaped member provided outside a contact nip area of the heating roll (1) with the endless belt (2), and is a spacer member. (8) A fixing device, wherein the fixing device (8) is formed integrally with the belt-side guide (6). 11. The fixing device according to claim 1, wherein the pressing member has an elastic body, and an end of the elastic body extends from an end of the endless belt. The fixing device according to claim 1, further comprising a support member that supports an end of the elastic body from below. 12. The fixing device according to claim 1, wherein the pressing member comprises an elastic member provided on a movable member which is elastically urged, and the endless belt of the belt shift guide. A fixing device characterized in that the end of the movable member is brought into contact with a surface orthogonal to the deviation regulating surface to regulate the position of the movable member facing the peripheral surface of the heating roll (1). 13. A fixing device for heating and pressure fixing an unfixed toner image on a recording sheet (5), comprising: a rotatable pressure roll (7); An endless belt (2) that rolls with a pressure roll (7) and is heated by a heat source (4); and an endless belt (2) that is disposed inside the endless belt (2) and pressurizes the endless belt (2). A pressing member (3) pressed against a roll (7) to form a contact nip area between the endless belt (2) and the pressing roll (7);
And at least one of the contact nip area between the pressure roll (7) and the endless belt (2) on the axial extension line of the pressure roll (7), to restrict the shift of the edge of the endless belt (2). And a belt-side guide (6) embedded between the end of the pressing member (3) and the pressing member (3). 14. An image forming apparatus in which a toner image formed on an image carrier is transferred onto a recording sheet (5) and is fixed by heating and pressure by a fixing device.
An image forming apparatus using the fixing device according to claim 3.