JP2000081804A - Belt fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a belt fixing device and an image forming device capable of always accurately detecting a temperature, irrespective of the positional fluctuation of a heating tension roller caused by a belt tension fluctuation generated when the belt travels and the displacement of the roller for preventing the biasing of the belt. SOLUTION: This device 30 is provided with plural rollers including a heat roller and a fixing roller over which a belt 3 is stretched, a press-contact member which is arranged oppositely to the fixing roller through the belt 3, a heating means installed on the heat roller and for heating the belt 3, a temperature detecting means 82 for detecting the temperature of the belt 3 or the temperature of the heat roller and a supporting means 81 for supporting the temperature detecting means 82. And, the supporting means 81 and the heat roller are integrated into one body and the position of the temperature detecting means 82 with reference to the heat roller is kept constant to constitute the belt fixing device and this image forming device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt fixing device provided with a belt driving device for restricting deviation of an endless belt that is wound around a plurality of rollers and runs, and an image forming apparatus such as a copying machine, a facsimile, and a printer. .

[0002]

2. Description of the Related Art A so-called belt fixing device using an endless belt is known as a fixing device provided in an image forming apparatus such as a copying machine, a facsimile, a printer and the like. Belt fixing devices are disclosed in JP-A-6-318001 and JP-A-8-31801.
As described in JP-A-314303 and JP-A-9-138599, the apparatus has a temperature detecting unit for maintaining a temperature suitable for fixing.
It is arranged near the heating roller among the plurality of rollers around which the endless belt is stretched.

[0003]

The heating roller is often a tension roller, and its position is slightly changed when the heating roller rotates to run on the endless belt. Therefore, when the temperature detecting means is fixed to the belt fixing device main body side, the relative position between the temperature detecting means and the heating roller changes, and there is a problem that the accuracy of the temperature detection is lacking. Japanese Patent Application Laid-Open No. 9-138599 describes that the relative positional relationship between the heating roller and the temperature detecting device is kept constant, but the specific configuration is not shown, and the above-described disadvantages are taken into consideration. Does not solve this.

Further, in the belt fixing device, the endless belt is shifted in the width direction during running.
In Japanese Patent Application Laid-Open No. 4-121337, an endless belt is wound around a swingable roller, and a detection member that rides up when the end of the endless belt shifts is provided integrally with the swingable roller, and the rotational torque of the endless belt is adjusted. When the detection member is driven to rotate, the yarn having one end fixed to the detection member and the other end fixed to the immobile portion is wound around the detection member, and the swingable roller is separated from the other rollers, that is, There has been proposed a configuration in which the belt is shifted in a direction for restricting the shift to control the shift of the belt. In this case, however, the roller is positively displaced, so that the above-described problem is remarkable.

The present invention provides a belt fixing device capable of always accurately detecting temperature regardless of a position change of a heating tension roller due to a belt tension change occurring during belt running or a displacement of a roller for preventing belt deviation. And an image forming apparatus.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, an endless belt is stretched.
A plurality of rollers including at least a heating roller and a fixing roller; a pressure contact member arranged to face the fixing roller via the endless belt; and at least the endless belt, the plurality of rollers and the pressing roller A heating unit provided on a heating roller for heating the endless belt, and a belt fixing device having a temperature detection unit for detecting a temperature of the endless belt or the heating roller, wherein a supporting unit for supporting the temperature detection unit is provided. The supporting means is provided integrally with the heating roller, whereby the temperature detecting means is provided so as to maintain a constant relative position with respect to the heating roller.

According to a second aspect of the present invention, in the belt fixing device of the first aspect, the support means is provided integrally with a bearing of the heating roller.

[0008] The invention described in claim 3 is claim 1 or 2.
In the belt fixing device according to any one of the above, the heating roller is a variable roller at least one end of which can be displaced in a direction perpendicular to an axial direction thereof, and is coaxial with the variable roller at a side of the one end. A deviation detection rotator that is provided independently of the variable roller and is driven to rotate at a side edge of the endless belt, and when the endless belt is engaged with the deviation detection rotator and the deviation detection rotator rotates, And a displacement means for displacing the one end.

The invention described in claim 4 is the first to third aspects of the present invention.
In the belt fixing device according to any one of the above, the temperature detecting means is arranged apart from the endless belt and the heating roller.

[0010] The invention according to claim 5 provides the invention according to claims 1 to 4.
An image forming apparatus having the belt fixing device according to any one of the above.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a belt fixing device. In the belt fixing device, since deviation during belt running is a major problem, a belt fixing device provided with a mechanism for regulating belt deviation is employed. . The principle for restricting the belt shift will be described with reference to FIGS.

As shown in FIG. 1, a belt drive 20
Is a belt 3 as a running endless belt, which is a flat belt having a relatively wide belt width, and is stretched over the belt 3.
It has a driving roller 1 and a driven roller 2 as a plurality of rollers including a roller 2 whose both ends can be displaced. The driving roller 1 is formed integrally with a shaft 1a thereof, and the driven roller 2 is formed integrally with the shaft 2a. The driving roller 1 and the driven roller 2 are rotatably supported by the respective shafts 1a and 2a. .

In the belt driving device 20, it is assumed that the belt 3 is shifted in one of the axial directions of the rollers 1 and 2 for some reason. In this case, belt 3
In order to provide the effect of returning to the original state, the distance between the axes of the rollers 1 and 2 which are shifted may be made larger than the distance between the other axes. Assuming that the end of the driven roller 2 is displaced, as shown in FIGS. 2 and 3, the rollers 1 and 2 are located in a direction perpendicular to the axial direction of the driven roller 2 and non-planar with each other. 4 and 5, as shown in FIGS. 4 and 5, a method in which the rollers 1 and 2 are displaced in a direction perpendicular to the axial direction of the driven roller 2 so that the rollers 1 and 2 are positioned on a plane. There is.

The former and latter methods will be considered. In the latter case shown in FIGS. 4 and 5, of the driving force F transmitted from the driving roller 1 to the belt 3, the component force f in the axial direction of the driven roller 2 is determined by the inner peripheral surface of the belt 3 and the axial direction of the driven roller 2. F = μ · N (μ: coefficient of friction between the inner peripheral surface of the belt 3 and the outer peripheral surface of the driven roller 2, N: drag force acting perpendicular to the shaft 2a of the driven roller 2) Given. In the latter case, the belt 3 moves in the direction Z1 in which the deviation has occurred.
The belt is deviated in a direction Z2 which is a direction for recovering the deviation, but the belt deviation force is reduced by the inner circumferential surface of the belt 3 and the driven roller 2.
If the frictional force changes between the initial stage and the lapse of time, the belt shift force changes, and the belt position becomes unstable. In general, the friction coefficient μ tends to increase with time, and the belt biasing force tends to increase.

In the former case shown in FIGS. 2 and 3, the belt 3 likewise shifts in the direction Z2. The shift of the belt 3 is caused by the drive roller 1
However, even if the driven roller 2 is slightly twisted, the rotation is surely generated. In the past, it has been experimentally confirmed that when the driven roller 2 is displaced by the same amount in the former and the latter, the former has a greater effect on the belt shift. From the above, it is clear that the former is more suitable for controlling and controlling the belt shift by displacing the driven roller 2, and therefore, the following is a configuration for controlling and controlling the belt shift by the former method. Is shown.

Hereinafter, an embodiment of a belt fixing device and an image forming apparatus to which the present invention is applied will be described with reference to the drawings.
In the drawings, components that are configured as a pair and do not need to be specifically distinguished and described will be replaced with the description by appropriately describing one of them.

As shown in FIG. 1, the belt driving device 20 provided in the belt fixing device includes a belt 3 which is a flat belt having a relatively wide belt width as an endless belt running clockwise in FIG. It has a plurality of drive rollers 1 and a plurality of driven rollers 2 including a driven roller 2 as a variable roller whose both ends can be displaced around a belt 3. The driving roller 1 and the driven roller 2 are formed integrally with the shaft 1a, respectively, and the driven roller 2 is formed integrally with the shaft 2a. The driving roller 1 and the driven roller 2 are clockwise in FIG. Both ends of the driven roller 2 are rotatably supported, and the driven roller 2 has two ends in the X direction and the Y direction which are directions perpendicular to the shaft 2a.
And the driving roller 1 can be displaced in the X direction, which is a direction in which the driving roller 1 and the driving roller 1 are located on a non-planar surface.

The direction in which the belt 3 is stretched is defined as the Y direction, the axial direction of each of the rollers 1 and 2 is defined as the Z direction, and the directions perpendicular to the Y and Z directions are defined as the X direction. The Y direction includes a Y1 direction from the driven roller 2 to the driving roller 1 and a Y2 direction from the driving roller 1 to the driven roller 2. The Z direction includes a Z1 direction which is a right direction in FIG. 2 and a Z2 direction which is a left direction in FIG. The X direction includes an X1 direction, which is an upper direction in FIG. 2, and an X2 direction, which is a lower direction in FIG.

FIG. 6 shows a representative example of the roller provided at the end of the driven roller 2 in the Z1 direction, which will be described below. A shift detecting rotator 5 driven to rotate by the belt 3 is provided. The deviation detecting rotator 5 has a truncated cone shape whose diameter increases as the distance from the end of the driven roller 2 increases, and rotates on the shaft 2a.

The belt shift detecting member 5 has an end portion 5a on the driven roller side and a tapered surface 5b which is an outer peripheral surface of a portion whose diameter gradually increases. The diameter of the end 5a is equal to or slightly smaller than the diameter of the driven roller 2, and the inclination angle of the tapered surface 5b is preferably 0 ° to buckling of the side end of the belt 3. It is formed at about 6 °. In each drawing, the inclination angle of the tapered surface 5a is exaggerated.
When the belt 3 runs on the tapered surface 5b in the Z1 direction, the belt shift detecting member 5 can proportionally increase the rotational torque transmitted as the amount of running increases.

The deviation detecting rotary member 5 has a larger diameter at the end in the Z1 direction than the tapered surface 5b.
b, a stopper 6 forming a step 6a is integrally formed. The deviation detecting rotator 5 has a concave portion 5c between the portion forming the tapered surface 5b and the stopper 6. One end of the recess 5c is fixed to an engagement portion 5d protruding from the recess 5c,
A string member 7 serving as a displacement means having the other end fixed to an immovable member is wound. Although the string member 7 has a thread shape in the present embodiment, a band-shaped member may be used. Below the stopper 6, that is, in the vicinity of the X2 direction, a contact detection unit 15 which is a photosensor having a well-known configuration and detects that the belt 3 has contacted the stopper 6 is provided.

As shown in FIGS. 6 and 7, the end of the shaft 2a on the Z1 direction side of the deviation detecting rotary member 5 is supported by a bearing 11 having an inner ring 11a and an outer ring 12b. The bearing 11 is loosely fitted in a hole 8 provided in a side wall 10 forming a part of a housing of the belt driving device 20. The bearing 11 is supported by the side wall 10 via a bearing support plate 9 fixed to the end of the shaft 2a in the Z1 direction relative to the bearing 11. The end of the shaft 2a is stopped by a C-ring type retaining ring 16, but the retaining ring 16 may be an E-ring type.

In order to maintain a certain distance from the bearing 11, the deviation detecting rotator 5 has a shaft 2 a on an end surface of the stopper 6 in the Z1 direction.
And a ridge 5e having a certain height, which slides and rotates with respect to. The inside of the tip of the ridge 5e, that is, the portion corresponding to the inner ring 11a, is cut out, and the end face of the ridge 5e abuts only on the outer ring 11b, whereby the rotation of the inner ring 11a shifts and the detection rotating body 5 is rotated. The rotation detecting body 5 and the bearing 11 are not transmitted to the
Distance is kept constant. In addition, instead of the ridge 5e,
The same function can be obtained by a configuration in which a portion of the stopper 6 corresponding to the inner ring 11a is cut out.

As shown in FIGS. 6 and 9, the outer ring 1
A supporting means 81 for supporting a thermistor 82 (see FIGS. 11 and 16) as a temperature detecting means is fixedly fitted to the inside of the side wall 10 at 1b.

As the bearing 11, a ball bearing among the rolling bearings is used in order to minimize the rotational torque when the shaft end of the driven roller 2 is rotatably supported, so that the belt 3 rotates. When the driven roller 2 is in operation, a rotational torque with the drive roller 1 as a fulcrum acts on the driven roller 2 due to the tension caused by the rotation of the belt 3, and there is a case where a force for moving the entire driven roller 2 in the X2 direction acts, but supports the shaft 2 a. Rolling bearing 11
Is a ball bearing having an extremely small rotational torque, so that even when a rotational torque acts on the drive roller 1 as a fulcrum, the force by which the driven roller 2 is displaced in the X2 direction is extremely small. Therefore, when the belt 3 is rotating, the driven roller 2 does not move in an unstable manner against the urging force of the spring 14 due to the downward moving force of the driven roller 2.

As shown in FIG. 7, the shaft 2a has a bearing 11,
It is urged in the X1 direction and the Y2 direction by a spring 14 which is a tension spring as an elastic member stretched between the belt driving device 20 and an unillustrated immobile member via the bearing support plate 9. ing. The urging force in the X1 direction causes the bearing 11 to abut on a position above the inner peripheral edge of the hole 8,
In the X2 direction, that is, the driven roller 2 and the driving roller 1 are displaceably held such that they are positioned on a non-planar plane with each other.
The urging forces in two directions give the belt 3 a predetermined tension. As shown in FIG. 8, the string member 7 is stretched substantially parallel to the X direction in which the end of the driven roller 2 is displaced.

Although not shown, the belt 3 is composed of a base and a coat layer. The coating layer is worn out when sliding friction occurs when the end of the belt 3 is engaged with the shift detection rotating body 5, and the abrasion powder is scattered in the apparatus and adheres to various parts. The belt 3 is not provided at the end, and a non-coated region is formed. The base is made of nickel, and the coat layer is made of silicon rubber. However, the base may be made of other metals, that is, stainless steel, iron, polyimide, or the like as long as the belt 3 can be formed with low cost and high dimensional accuracy. In addition, in consideration of applying the belt driving device 20 to a belt fixing device to be described later, the coat layer is formed of a heat-resistant rubber such as silicon rubber as a material having good releasability, and a heat-resistant resin such as fluorine resin and fluorine rubber. Is also good.

The material of the deviation detecting rotary member 5 may be metal, but it is considered that the end of the belt 3 may be damaged when it comes into contact with the side end of the belt 3. Then, it is formed of polyimide resin (PI). In addition, heat-resistant engineering plastics such as polyetheretherketone (PEEK) and polyphenylene sulfide resin (PPS), and plastics that are not heat-resistant but polyacetal (PO) can be used. Aluminum or copper-based materials can be used.

In order to prevent the belt 3 from being worn, it is desirable that the deviation detecting rotating body 5 with which the belt 3 is engaged is made of a material which is softer than the belt 3 and which is appropriately worn. If the deviation detecting rotator 3 is worn, seizure does not occur due to frictional heat between the belt 3 and the deviation detecting rotator 5, and the belt 3 is worn even if the tension of the belt 3 increases due to friction. The life of the belt 3 is extended by a synergistic effect that the abrasion powder produces a function of acting as a lubricant.

In this embodiment, the hardness of the base and the longitudinal elasticity coefficient are set to appropriate values by selecting the materials of the base and the shift detecting rotary member 5 as described above, and the abrasion resistance of the base and the shift detecting rotary member 5 are determined.
, The seizure or wear of the belt 3 does not occur, and the wear powder of the deviation detecting rotary member 5 acts like a lubricant, so that the life of the belt 3 is extended. . Further, the belt is usually expensive, and the shift detecting rotating body that can be manufactured at a lower cost than the belt does not need to be replaced immediately even if a little wear occurs due to its thickness.
Since it can be used for a long period of time, it can be manufactured inexpensively, so that maintenance is also inexpensive. In general, since the contact between metals having a large bonding force increases the amount of wear, it is not preferable to use the same kind of metal as the material of the base and the deviation detecting rotating body 5. It is desirable to use different materials such as metal or metal and plastic.

Since the present embodiment has the above configuration,
When the belt 3 shifts in the Z1 direction as shown in FIG. 9 from the state in which the belt 3 is rotating and running in a normal state as shown in FIGS. 1, 6, 7, and 8, the state shown in FIG. As shown in FIG. 10, the belt 3 rides on and engages with the deviation detecting rotator 5, and the frictional force between the belt 3 and the tapered surface 5 b causes the deviation detecting rotator 5 to be tied as shown by an arrow R in FIG. 10. The rotational driving force is received in the direction in which the member 7 is wound. When the deviation detecting rotating body 5 winds up the member 7 against the spring 14, the end of the driven roller 2 is displaced in the X2 direction as shown in FIG. In other words, the rollers 1 and 2 are pushed down in the direction in which they are twisted. In other words, the rotational movement of the deviation detecting rotator 5 due to the rotational torque of the belt 3 is
Is converted to linear motion.

At this time, since the rubbing area between the ridge 5c and the bearing 11 is small, the friction between the deviation detecting rotating member 5 and the bearing 11 does not hinder the rotation of the deviation rotating member 5, and the hole 8 Is large enough to allow the displacement of the bearing 11, the displacement of the bearing 11 is not hindered by the hole 8, and the displacement of the end of the driven roller 2 in the X1 direction in the Z1 direction is performed smoothly.

The larger the amount of deviation of the belt 3, the more the belt 3
Since the area of engagement between the inner peripheral surface and the deviation detecting rotating body 5 increases, the displacement of the driven roller 2 also increases, and the force for returning the belt 3 to the original state also increases. Thus, the driven roller 2 is displaced by a predetermined amount to return the deviation of the belt, and with the displacement of the driven roller 2, the belt 3 starts to return in the Z2 direction according to the above-described principle, and the belt 3
, The amount of displacement of the driven roller 2 also decreases, and the belt 3 and the driven roller 2 return to their original normal states. When returning to such a normal state, the string member 7 wound around the shift detection rotating body 5 is extended by the urging force of the spring 14.

In addition to controlling the deviation of the belt 3 by making the rollers 1 and 2 twisted relative to each other, since the materials of the belt 3 and the deviation detecting rotating body 5 are appropriately selected, the deviation of the belt 3 The abrasion caused by the rubbing with the detection rotating body 5 is small, and the damage to the side end of the belt 3 is prevented, and the action of preventing the belt shift works reliably, and the temporal deterioration of the side end of the belt 3 is greatly delayed. , Cracks and the like can be prevented, and the life of the belt can be extended.

However, deterioration of each member such as the belt 3 cannot be completely prevented, so that the deviation of the belt 3 may increase with time. In this case, Z1 of the belt 3
Since the end in the direction abuts against the stopper 6, even if the belt 3 is further displaced in the Z1 direction, the step portion 6a prevents the belt 3 from moving over the deviation detecting rotary member 5. However, the belt 3 and the like have already deteriorated, and the deterioration of the belt 3 further progresses due to the rubbing on the stopper 6. Therefore, when the contact detecting means 15 detects the contact of the belt 3 with the stopper 6, LE not shown outside the device
D is emitted to notify the operator of the life of the belt driving device.

The belt driving device provided in the belt fixing device of this embodiment has been described above. However, it is also possible to restrict and control the belt deviation by displacing the end of the driven roller 2 in the X1 direction instead of the X2 direction. it can. For this purpose, the winding state of the string member 7 and the direction in which the spring 14 is stretched may be targeted for the driven roller 2. Driven roller 2
Is displaced in a twisting direction, that is, in the X direction, which is non-planar with respect to the driving roller 1, and one end of the driven roller 2 is disposed on the same plane as the driving roller 1 as shown in FIGS. The displacement of the belt in the Y2 direction away from 1 may be restricted and controlled. To this end, the stretching direction of the string member 7 may be on a plane including the rollers 1 and 2, and the stretching direction of the spring 14 may be a direction parallel to the same plane. As shown in FIGS. 13 and 14, the springs 14 may be provided separately in the component direction of the tension.

The axis of the deviation detecting rotator may be separate from the axis of the driven roller, or the deviation detecting rotator may be configured to rotate non-coaxially with the axis of the driven roller. In this case as well, as in the above-described embodiment, it is essential that the belt rides on the deviation detecting rotating body, and thus the diameter of the end of the deviation detecting rotating body on the driven roller side is smaller than the diameter of the driven roller. The deviation of the belt is regulated and controlled by rotating the deviation detecting rotator. To rotate the deviation detecting rotator, the belt only needs to generate friction with the deviation detecting rotator. The rotator does not necessarily need to have a frusto-conical shape, and the same function can be obtained by forming the rotator into a cylindrical shape and arranging it at a position where friction occurs with the belt.

The number of rollers over which the belt is wound may be three or more. In this case, two or more rollers may be displaced. The roller for displacing the end may be a driven roller instead of a driven roller. The hole 8 is not limited to a long hole and may have another shape as long as it has a size that allows the displacement of the bearing 11 corresponding to the displacement of the driven roller to be freely and freely fitted.

In the above embodiment, the Z of the driven roller 2
Although only the one-direction end has been described, the Z1-direction end is similarly configured and has a similar function. However, if the belt 3 is configured to lean in advance to one of the driven rollers 2, it is sufficient to provide the structure of the rotation detecting rotary member and the like only on the side where the belt shift occurs. In the case of the above embodiment, when the belt 3 is engaged with the shift detection rotating body 5, these rotate integrally, but when the belt is shifted in advance, the end of the belt 3 is always A configuration in which the driven roller 2 is displaced by the friction generated by sliding and abuts on the deviation detecting rotating body while sliding, thereby maintaining the deviation balance. Belt 3 and shift detection rotating body 5
The frictional force with the surface is adjusted so as to satisfy the above-described relationship with the abrasion resistance and to have the balance. In the above-described embodiment, the belt and the deviation detecting rotating body may slide within the range in which the belt returns to the original state.

As a structure for shifting the belt 3 to one of the driven rollers 2, for example, a reinforcing member having a higher tensile elastic modulus than the belt is provided at a desired outer peripheral side end of the belt. A configuration in which the belt on the side on which the reinforcing member is provided is reduced by reducing the elongation of the belt on the side on which the reinforcing member is provided,
Alternatively, as shown in FIG.
In the configuration in which the reinforcing member is provided, even if the belt constantly slides with respect to the deviation detecting rotating body, deterioration of the belt can be delayed.

FIG. 12 shows a first embodiment of a belt fixing device to which the present invention is applied.
1 shows a belt fixing device having the following. The belt fixing device described below includes plain paper generally used for copying and the like, and OH
It is possible to use any kind of P-sheet, 90K paper such as cards and postcards, thick paper having a basis weight of about 100 g / m ² or more, and so-called special sheets such as envelopes, which have a larger heat capacity than paper. It is.

The belt fixing device 30 includes the belt driving device 2
0, a heater 21 provided inside the shaft 2a as a heating unit for heating the belt 3, and a pressure roller 22 as a pressure contact member pressed against the belt 3 and the driving roller 1 as a fixing roller via the belt 3. And Heater 2
The driven roller 2 having 1 is a heating roller. The pressing roller 22 has a spring 23 engaged with a shaft 22 a of the pressing roller 22, and is pressed against the driving roller 1 from below by a spring 23. The spring 23
A pair of pressure springs are provided at both ends of the shaft 22a.
The biasing force P1 of the spring 23 is set sufficiently higher than the tension P2 of the spring 14.

Since the belt 3 functions as a fixing belt for fixing unfixed toner on the sheet-like medium, heat resistance and thermal responsiveness are required, so that polyimide, nickel, stainless steel, iron or the like is required. It is desirable to use a material having a release layer provided on a film-like substrate having a thickness in the range of about 30 to 300 μm. In this embodiment, a nickel-made one having a thickness of 150 μm is used. ing.

The thin-walled belt 3 is reduced in strength when subjected to thermal stress, and is more likely to generate wrinkles or buckling due to the belt shift as compared with when used at normal temperature, and thus the end portion is particularly susceptible to crack breakage. However, the belt drive device 20 can control and regulate the belt deviation,
Since the frictional force between the belt 3 and the surface of the deviation detecting rotary member 5 has the above-described relationship with respect to abrasion, the durability of the belt 3 is improved, and such a problem does not occur. However,
When nickel is used at a temperature of 100 ° C. or more as a thermal property, the tensile strength may be reduced and the belt 3 may be damaged. Therefore, such a reduction in the strength is prevented, the tensile strength and the compressive strength are improved, and the longitudinal elastic modulus is increased. In order to increase the size, nickel contains a few percent of a reinforcing agent such as manganese.

In consideration of the fact that the other components constituting the belt fixing device 20 also require heat resistance, for example, the deviation detecting rotary member 5 is formed of engineering plastic as described above. A second fixing portion 24b as a nip portion where the drive roller 1 and the pressure roller 22 face each other, and a certain region on the upstream side in the rotation direction 4 of the belt 3 with respect to the second fixing portion 24b. A certain first fixing unit 24a is configured such that the pressing roller 22
The fixing region 24 is pressed against the fixing region 24.

As shown in FIG. 11, the support means 81 is a U-shaped member having bases 81a, 81a to be fitted into the outer ring 11b, and a connecting part 81b connecting the two bases 81a. That is, the support means 81 is used for the bearing 1.
1 is provided integrally with the driven roller 2 which is a heating roller. A thermistor 82 is fixedly supported at the center of the connecting portion 81b. The thermistor 82 is opposed to the driven roller 2 via the belt 3 so as to be separated from the belt 3, and the width direction of the belt 3 and the driven The roller 2 is disposed so as to be located at the center in the axial direction. Therefore, the thermistor 82 supports the supporting member 8 so that the relative position with respect to the driven roller 2 is kept constant.
1 supported.

Since the belt fixing device 30 has such a configuration, the belt 3 heated by the heater 21 is driven by the driving roller 1 around the roller 1 and the driven roller 2 in the direction 4 to remove the unfixed image. The fixing is performed by transporting the sheet medium having the sheet medium and passing the sheet medium through the fixing area 24. Specifically, when the sheet-like medium passes through the first fixing unit 24a, the toner given heat from the belt 3 gradually melts and is temporarily attached to the surface of the sheet-like medium, and the first fixing unit In a second fixing unit 24b that is continuous with the first fixing unit 24a,
The toner image is completely fixed on the sheet-like medium by the pressing force between the driving roller 1 and the pressing roller 22.

Since the deviation of the belt 3 is regulated and controlled by the belt driving device 20, the conveyance of the sheet-like medium is favorably performed, the fixing pressure in the fixing area 24 is maintained, and the wrinkling and skew of the sheet-like medium are prevented. And good fixing is performed. At the time of regulation and control of the belt shift, any end of the driven roller 2 is displaced downward. However, since the thermistor 82 is fixed to a supporting means integral with the driven roller 2, the thermistor 82 is always in contact with the driven roller 2. Since the relative position is kept constant, the temperature of the driven roller 2 or the temperature of the belt 3 can be accurately detected. Since the thermistor 82 is separated from the belt 3, it does not rub against the belt 3, and deterioration of the belt 3 and the thermistor 82 due to rubbing is avoided.
Therefore, if the belt fixing device 30 is used in an image forming apparatus such as a copying machine, a facsimile, a printer, or the like, the image forming apparatus can form a good image.

FIG. 13 shows a second embodiment of the belt fixing device to which the present invention is applied.
9 shows a belt fixing device having a belt driving device 20 ′ having substantially the same configuration as that of FIG. The difference between the belt driving device 20 ′ and the belt driving device 20 is that, instead of the spring 14, springs 14 a and 14 b that apply tension in the X1 direction and the Y2 direction, which are component directions of the tension of the spring 14, are used. is there.

In the belt fixing device 40 of this embodiment, a pressure roller 31 as a pressure contact member is in contact with the drive roller 1 from above, and the spring 32 is in pressure contact with the shaft 1a from below, so that the drive roller 1 A pressure contact force with the belt 3 is obtained. The heater 21 is provided inside the shaft 2 a of the driven roller 2 and inside the shaft 31 a of the pressure roller 31. An oil roller 33 for applying silicone oil as a release agent and a cleaning roller 34 for removing dirt attached to the pressure roller 31 are in contact with the pressure roller 31. A blade 35 for cleaning the roller 34 is in contact. A cleaning roller 36 for removing dirt attached to the belt 3 is in contact with the belt 3 at a position facing the drive roller 1, and a blade 37 for cleaning the cleaning roller 36 is in contact with the cleaning roller 36. ing. The pressure roller 31 also functions as a fixing roller.

The opposing area between the driving roller 1 and the pressure roller 31 is a fixing area 38, and a guide 39 for guiding the sheet-like medium having an unfixed image to the fixing area 38.
Is provided above the belt driving device 20 '. The rotation direction of the belt 3 is a direction 4 ′ opposite to the rotation direction 4 of the belt driving device 20. Other configurations, materials, operations, and the like are the same as those of the belt fixing device 30, and thus description thereof is omitted.

FIG. 14 shows a third embodiment of the belt fixing device to which the present invention is applied.
1 shows a belt fixing device 50 having a belt driving device 20 ″ having substantially the same configuration as the belt driving device 20 ′ and the belt driving device 20 ′.
The difference between the belt driving device 20 ″ and the belt driving device 20 ′ is that the roller 41 is not a driving roller but a driven roller, and the belt 3 ′ of the belt driving device 20 ″ is rotated via the belt 3, 41 is to follow the running of the belt 3 '.

In the belt fixing device 50 of this embodiment, the belt driving device 20 ″ is located above the belt driving device 20 ′, and the roller 41 is in contact with the driving roller 1 from above. Functioning as
When the spring 32 is pressed against the shaft 1a from below, a pressing force between the belts 3 and 3 'can be obtained. The heater 21 is provided inside the shaft 2a of the driven roller 2 and the shaft 2 of the driven roller 2 'as a heating roller of the belt driving device 20 ".
a ′. An oil roller 42 for applying silicone oil as a release agent to the belt 3 ′
And a cleaning roller 43 for removing dirt attached to the belt 3 ′ is in contact with the roller 41 at a position facing the roller 41, and a blade 44 for cleaning the cleaning roller 43 is in contact with the cleaning roller 43.

The area where the drive roller 1 and the roller 41 face each other is a fixing area 45. The direction of rotation of the belt 3 'is the direction 4 opposite to the direction of rotation 4' of the belt drive 20 '. The sheet medium having an unfixed image is a belt 3, 3 '.
As a result, the belt is guided between these belts and reaches the fixing area 45. Other configurations, materials, functions, and the like are the same as those of the belt fixing device
Therefore, the description is omitted.

Although the first to third embodiments of the belt fixing device have been described above, the pressing member may be in the form of a plate instead of a roller if possible. In each embodiment, the heater may be provided on a shaft of another roller, may be provided in a belt, or may be used simultaneously with a pressing member, a fixing roller, a driven roller, a belt, and the like.

As shown in FIG. 16, the thermistor 82 is
Provided in the space inside the wound belt 3, the belt 3
, The temperature of the driven roller 2 can be directly detected. The supporting means 81 used in this case has the same shape as that shown in FIG. 11, and the components can be used in common regardless of the arrangement position of the thermistor 82 in either of the cases shown in FIGS. can do. The thermistor 82 is spaced apart from the driven roller 2 to avoid deterioration of the driven roller 2 and the thermistor 82 over time. Further, as the temperature detecting means, a means using a thermocouple may be used, or an infrared sensor such as a thermistor type or a thermocouple type for detecting radiant energy from a belt or a heating roller may be used.

FIG. 15 schematically shows an image forming apparatus having a belt fixing device to which the present invention is applied. The image forming apparatus is a well-known one such as a copying machine, a facsimile, a printer, or the like, and may be any type of image forming apparatus that can use a belt fixing device to which the present invention is applied.
Although the image forming apparatus of the present embodiment forms a color image, it may form a single color image.

The image forming apparatus 60 includes image forming apparatuses 61C, 61Y, 61 for forming images for each color according to the original image.
M, 61BK, and each image forming device 61C, 61Y, 61M,
61BK Belt-type transfer device 62 arranged opposite to
And a manual feed tray 6 for feeding various sheet-like media to a transfer area where the image forming apparatuses 61C, 61Y, 61M, 61BK and the transfer device 62 face each other.
3. A resist that supplies the sheet-shaped media conveyed from the paper feed cassettes 64, 64, the manual feed tray 63, and the paper feed cassettes 64, 64 at the timing of image formation by the image forming apparatuses 61C, 61Y, 61M, and 61BK. Roller 70
And a belt fixing device 30 for fixing the sheet medium after the transfer in the transfer area. The transfer device 62 drives the endless belt 73 by any of the belt driving devices described above.
Is a drive roller.

The image forming apparatus 60 is more suitable than plain paper generally used for copying and the like, 90K paper such as an OHP sheet, a card, and a postcard, thick paper having a basis weight of about 100 g / m ² or more, and envelopes. Any of so-called special sheets having a large heat capacity can be used as the sheet medium.

Each image forming device 61C, 61Y, 61M, 61
BK develops each color of cyan, yellow, magenta, and black, and uses different toner colors. However, since the configurations are almost the same, the image forming apparatus 61 is used.
The configuration of C is changed to each of the image forming apparatuses 61C, 61Y, 61M, and 61.
This will be described as a representative of BK. The image forming device 61C includes a photosensitive drum 65C as an electrostatic latent image carrier, a photosensitive drum 6
It has a well-known configuration including a charging device 67C, a developing device 66C, a cleaning device 68C, and the like, which are arranged in order in the rotation direction A of 5C, and receives exposure light 69C between the charging device 67C and the developing device 66C. The electrostatic latent image carrier may have a belt shape instead of a drum shape, and may be driven by any of the belt driving devices described above.

In the image forming apparatus of this embodiment, when the power of the image forming apparatus 60 is turned on and the operator performs a well-known operation of starting image formation, the photosensitive member 65C rotates in the direction A in the above configuration. As a result, the photosensitive drum 65C is charged by the charging device 67C, and an electrostatic latent image corresponding to the original image is formed by the exposure light 69C.
6C, the toner image formed on the photoreceptor 65C is transferred onto a sheet-like medium conveyed in the direction of arrow B over a known transfer device 62, and the toner remaining on the photoreceptor 65C after the transfer is transferred. Is scraped off by the cleaning device 68C to clean the photosensitive member 65, and is used for the next charging.

The sheet medium on which the cyan toner has been transferred is conveyed in the direction of arrow B by the transfer device 62, and performs the same image forming process as the above-described image forming process in the image forming device 61C. 61M, 61BK sequentially transfer yellow, magenta, and black toners as appropriate, transfer all the toner necessary for image formation, and then transfer the toner to the guide 71 from the transfer device 62. Is guided to the fixing area. The sheet-like medium guided to the belt fixing device 30 includes:
Fixing is performed as described above. In the image forming apparatus 60,
Instead of the belt fixing device 30, the belt fixing devices 40, 5
0 can be used.

The image forming apparatus does not directly transfer the toner image on the photosensitive drum to the sheet-like medium as in this embodiment, but first transfers the toner image to the endless belt-like transfer medium and then transfers it to the sheet-like medium. In the case of the type, the above-described belt driving device can be used as a configuration for driving the transfer medium. In addition, the above-described belt driving device can be used as a device for conveying a sheet-like medium by an endless belt. Regardless of which part of the belt driving device is used, a non-coated area is formed on the belt, so that abrasion powder generated by abrasion of the coating layer affects sheet-shaped media and other image formation. A good image can be obtained without being attached to a portion, and a highly reliable image forming apparatus can be provided. In addition, in FIGS. 1 to 15, the size, the displacement amount, and the like of each configuration are exaggerated as appropriate for convenience of description.

[0064]

According to the first aspect of the present invention, a plurality of rollers including at least a heating roller and a fixing roller, around which an endless belt is stretched, are disposed to face the fixing roller via the endless belt. A pressure contact member, a heating means provided on at least the heating roller of the endless belt, the plurality of rollers and the pressure roller for heating the endless belt, and detecting a temperature of the endless belt or the heating roller. A belt fixing device having a temperature detecting unit that has a supporting unit that supports the temperature detecting unit, and by integrally providing the supporting unit with the heating roller, the temperature detecting unit includes the heating roller and the heating roller. Is provided so that the relative position of the heating roller is kept constant by the support means. Regardless of fluctuations in the position of the heating tension roller as a heating means due to belt tension fluctuations that occur during running, and displacement of the rollers to prevent belt deviation, accurate temperature detection is always performed and stable control of the fixing temperature is achieved. By performing the fixing operation reliably, it is possible to provide a belt fixing device capable of always performing excellent fixing.

According to the second aspect of the present invention, since the supporting means is provided integrally with the bearing of the heating roller, the temperature detecting means makes the relative position to the heating roller constant by the supporting means integral with the bearing of the heating roller. Regardless of the fluctuation of the position of the heating tension roller as a heating means due to the fluctuation of the belt tension generated during belt running, and the displacement of the roller to prevent the belt from shifting, the temperature is always accurately detected and the fixing temperature is controlled. By performing it stably and accurately,
A belt fixing device capable of always performing good fixing can be provided.

According to a third aspect of the present invention, the heating roller is a variable roller at least one end of which is displaceable in a direction perpendicular to the axial direction thereof, and is provided coaxially with the variable roller beside the one end. When the endless belt rotates and is driven by the side edge of the endless belt independently of the variable roller, and the endless belt is engaged with the shift detection rotator and the shift detection rotator rotates, the one end is rotated. The belt fixing device that positively displaces the heating roller and regulates and controls the belt shift because it has a displacing means that displaces, always performs accurate temperature detection and stably and accurately controls the fixing temperature. By doing so, it is possible to provide a belt fixing device capable of always performing good fixing.

According to the fourth aspect of the present invention, since the temperature detecting means is arranged at a distance from the endless belt and the heating roller, the temperature is always accurately detected and the control of the fixing temperature is stably and accurately performed. In this case, good fixing can always be performed, and the relative position between the temperature detecting means and the endless belt or the heating roller is kept constant. A belt fixing device capable of reliably preventing rubbing between the pressure sensor and the temperature detecting means and avoiding deterioration due to abrasion or the like generated thereon and capable of suppressing deterioration over time.

The fifth aspect of the present invention provides the first to fifth aspects.
An image forming apparatus having a belt fixing device exhibiting the above-mentioned effects, the durability of the belt can be improved when a belt driving device is used. Prevents belt deviation and meandering and obtains belt running stability to prevent skewing and lateral displacement of the sheet-like medium, which is good without causing linearity of line drawing and lateral displacement in color image formation. The present invention can provide a reliable image forming apparatus that can form a stable image and can obtain a good image by preventing wrinkles and skew of a sheet-like medium.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a belt driving device used in a fixing device to which the present invention is applied.

FIG. 2 is a front view of the belt driving device showing a state where one end of a variable roller is displaced in an X1 direction.

FIG. 3 is a cross-sectional view of the belt driving device shown in FIG.

FIG. 4 is a front view of the belt driving device showing a state where one end of a variable roller is displaced in a Y2 direction.

FIG. 5 is a cross-sectional view of the belt driving device shown in FIG.

FIG. 6 is a fragmentary front view showing a main part of a belt driving device used in a fixing device to which the present invention is applied, showing a normal state.

FIG. 7 is a schematic side view showing a mode of supporting a displacement roller in the belt driving device shown in FIG. 6;

FIG. 8 is a schematic side view showing a mode of stretching a string member in the belt driving device shown in FIG.

FIG. 9 is a fragmentary front view showing a main part of a belt driving device used in the fixing device to which the present invention is applied, showing a state in which a belt shift has occurred.

10 is a schematic side view showing a state where one end of a variable roller in the belt driving device shown in FIG. 9 is displaced.

FIG. 11 is a perspective view showing a positioning mode of the temperature detecting means.

FIG. 12 is a schematic side view showing a belt fixing device to which the present invention is applied.

FIG. 13 is a longitudinal sectional view showing another example of the configuration of the belt fixing device to which the present invention is applied.

FIG. 14 is a longitudinal sectional view showing still another configuration example of the belt fixing device to which the present invention is applied.

FIG. 15 is a schematic side view illustrating an image forming apparatus including a belt fixing device to which the present invention is applied.

FIG. 16 is a partially crushed perspective view showing another positioning mode of the temperature detecting means.

[Explanation of symbols]

 1, 2, 2 ', 41 Plurality of rollers 1, 22, 31, 41 Press-contact member 1, 41 Fixing roller 2, 2' Variable roller 2, 2 'Heating roller 3 Endless belt 5 Deviation detecting rotating body 7 As displacement means String member 11 Bearing 21 Heating means 30, 40, 50 Belt fixing device 60 Image forming device 81 Supporting means 82 Temperature detecting means X1, X2, Y2 Direction in which variable roller is displaced

Claims (5)

[Claims] A plurality of rollers including at least a heating roller and a fixing roller over an endless belt; a pressure contact member arranged to face the fixing roller via the endless belt; A belt fixing device including a heating unit provided on at least the heating roller of the plurality of rollers and the pressure roller for heating the endless belt, and a temperature detection unit for detecting a temperature of the endless belt or the heating roller. In the above, there is a supporting means for supporting the temperature detecting means, and by providing the supporting means integrally with the heating roller, the temperature detecting means is provided so as to keep a relative position with respect to the heating roller constant. A belt fixing device. 2. The belt fixing device according to claim 1, wherein
A belt fixing device, wherein the supporting means is provided integrally with a bearing of the heating roller. 3. The belt fixing device according to claim 1, wherein the heating roller is a variable roller at least one end of which is displaceable in a direction perpendicular to an axial direction of the heating roller. And a shift detecting rotator that is provided coaxially with the variable roller and is driven independently of the variable roller by a side edge of the endless belt, and the endless belt is engaged with the shift detecting rotator. And a displacing means for displacing the one end when the shift detection rotating body rotates. 4. A belt fixing device according to claim 1, wherein said temperature detecting means is arranged apart from said endless belt and said heating roller. . 5. An image forming apparatus comprising the belt fixing device according to claim 1.