JPH0778658B2 - Heat fixing device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat fixing device.

[Prior Art] Conventionally, in an image forming apparatus such as a copying machine, a heating roller is pressed against a heating roller having a built-in heater, and a transfer paper carrying an unfixed image is passed through a nip portion between the rollers. A heat roll method for fixing is known. In this heat roll type fixing device, the heat roll must always be heated to a certain temperature or higher. Therefore, when copying is not performed, power is wasted and after the main switch of the copying machine is turned on. The warm-up time before the first copy could be performed took about 1 minute, which not only gave the user a loss time, but was annoying.

Therefore, there are pressure fixing and flash fixing methods as alternatives to the heat roll method, but they have not been often used because of high cost.

In view of these points, the present applicant has proposed a fixing method in which the warm-up time is extremely short and the heat loss is small. In this fixing method, a heat-resistant belt that moves at the conveyance speed of the transfer material while being in contact with the unfixed toner image carried on the transfer material, a heating element that heats and melts the toner image by heating in a pulsed manner, and the heat-resistant belt. A pressing mechanism that presses the heating element and a pressing roller or a pressing belt with the heating element sandwiched therebetween, and a belt feeding device that separates the heat resistant belt from the transfer material after the toner image that has been heated and melted is cooled and solidified. It is composed.

[Problems to be Solved by the Invention] However, the above-described fixing method of energizing and heating in a pulsed manner also has the following problems.

That is, the above-mentioned fixing system has a mechanism in which the pressure roller is pressed against the heat generating portion of the heat generating element, which energizes and heats in a pulsed manner, with the transfer paper carrying the unfixed toner and the heat resistant belt sandwiched in between. Therefore, it is usually necessary to set the width of the heat resistant belt to be a little wider than the width of the transfer paper.
When the transfer paper is fixed, there is a boundary between the paper passing portion and the non-paper passing portion (at the boundary between the paper passing portion and the non-paper passing portion, there is a gap microscopically). However, when the heating element is energized, the temperature rise of this boundary portion is higher than that of the paper passing portion and non-paper passing portion, and this boundary portion is poor in durability. Further, when a thick paper sheet such as a postcard is passed, the step difference at the boundary portion becomes significant, so that shearing force acts and the heat-resistant belt is likely to be damaged. Moreover, when 100 sheets or 200 sheets are continuously passed, a boundary is always generated at the same place, and therefore the life of the fixing device main body, for example, after passing 50,000 sheets, the damage is remarkable. It was Further, if a paper feed failure or the like occurs during continuous copying and the previously transferred paper is being fixed, the belt surface near the edge of the paper is likely to be scratched.

The present invention is intended to solve the above problems. That is, according to the present invention, a slight deviation is generated in the heat resistant belt so that the portion where the transfer material passes and the portion where the transfer material does not pass are not always in the same position, and the durability of the heat resistant belt can be improved. The purpose is to provide a device.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a heat-resistant belt that moves at the transport speed of the transfer material while being in contact with an unfixed toner image carried on the transfer material, and the toner image. A heating element for heating and melting the heat-resistant belt, a pressing mechanism for pressing the heat-generating element with the heat-resistant belt interposed therebetween, and a belt feeding device for separating the heat-resistant belt from the transfer material after the heat-melted toner image is cooled and solidified. In the heating and fixing device including the above, the heat-resistant belt is positively moved in a direction intersecting the conveyance direction of the belt to prevent the end portion of the transfer material and the heat-resistant belt from contacting each other at a constant position. It has a mechanism.

[Operation] According to the present invention, since the belt biasing mechanism that positively moves the heat resistant belt in the direction intersecting the transport direction of the heat resistant belt is provided, a slight deviation is generated in the heat resistant belt at a predetermined timing. Thus, it is possible to prevent the portion where the transfer material passes and the portion where the transfer material does not pass at the same position all the time. Therefore, the durability of the heat resistant belt can be improved.

[Embodiment] FIG. 1 shows a first embodiment of the present invention. That is,
1 shows a schematic structure of an image forming apparatus.

In FIG. 1, reference numeral 1 denotes an original placing table made of a transparent member such as glass, which reciprocates in the direction of arrow a to scan the original. A short-focus small-diameter image-forming element array 2 is arranged immediately below the original document table 1, and the original document placed on the original document table 1 is illuminated by an illumination lamp 7, and the reflected light image is reflected by the array 2. Slit exposure is performed on the photosensitive drum 3. The photosensitive drum 3 rotates in the direction of arrow b.
Reference numeral 4 denotes a charger, which uniformly charges the photosensitive drum 3 coated with, for example, a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer. On the photosensitive drum 3 uniformly charged by the charger 4, an electrostatic image formed by image exposure by the array 2 is formed. This electrostatic image, that is, the electrostatic latent image is visualized by the developing device 5 by using a toner made of a resin or the like that is softened and melted by heating. On the other hand, the transfer paper P, which is a sheet-shaped transfer material stored in the cassette S, is rotated in pressure contact in the vertical direction at a timing synchronized with the image on the feeding roller 6 and the photosensitive drum 3. It is sent onto the photosensitive drum 3 by the carrying roller 9 of FIG. Then, the transfer discharger 8 transfers the toner image formed on the photosensitive drum 3 onto the transfer paper P.
After that, the transfer paper P separated from the photosensitive drum 3 by the known separation means is guided to the fixing device 20 described later by the conveyance guide 10, is heated and fixed, and is then discharged onto the tray 11. After the toner image is transferred, the residual toner on the photosensitive drum 3 is removed by the cleaner 12.

The fixing device 20 includes a heating element 21, a pressure roller 22, a heat resistant belt 23, a driven roller 24, a driving roller 27 and the like.

That is, the heating element 21 is heat resistant such as alumina, and
On the lower surface of the electrically insulating base material or the base material made of a composite member containing the same, a width of 160 μ and a length (length in the direction perpendicular to the paper surface) of 216 mm, for example, a linear or strip shape made of Ta ₂ N or the like. Of heat generating surface 28, and Ta ₂ O ₅ , for example, is formed on the surface as a slide protection layer. Heating element 21
Has a smooth lower surface and its front and rear end portions are rounded so that it can slide on the heat resistant belt 23. The heat-resistant belt 23 is made of polyimide as a base material and is heat-treated to have a thickness of, for example, about 30 μm. The heat-resistant belt 23 is wound around a driving roller 27 and a driven roller 24 so as to be fed in the direction of arrow c.
Further, the heat resistant belt 23 is pressed by the pressure roller 22 to generate heat.
Abut the surface of 21.

The heat generating surface 28 of the heat generating element 21 has a small heat capacity, is energized in a pulsed manner, and instantly raises its temperature to around 260 ° C. By detecting the leading edge and the trailing edge of the transfer sheet P by the transfer sheet detection lever 25 and the transfer sheet detection sensor 29, the heat generating surface 28 is energized at a necessary timing. At that time, the energization of the heating element 21 may be controlled by using the position detection of the transfer P by a sheet feeding sensor of the image forming apparatus or the like.

On the other hand, the pressure roller 22 has a core material made of metal or the like and an elastic layer made of silicon rubber or the like, and is driven by a drive source (not shown) and guided by the conveyance guide 10 to the unfixed state. The transfer paper P having the toner image T is brought into close contact with the heating element 21 via a heat resistant belt 23 that moves at the same speed as the transfer paper P. Here, the conveyance speed of the pressure roller 22 is preferably substantially the same as the conveyance speed at the time of image formation, and the movement speed of the heat resistant belt 23 is set to a value corresponding to it.

In the fixing device 20 having such a configuration, the toner image formed of the heat-melted toner on the transfer paper P is first heated by the heating element 21 via the heat resistant belt 23, and at least the surface layer portion thereof is completely softened. To melt. Then, while the toner image is separated from the heating element 21 and reaches the separation roller, the toner image naturally dissipates heat to be cooled and solidified again, and after passing through the separation roller pair having a large curvature, the heat resistant belt 23 is separated from the transfer paper P.
As described above, since the toner is once completely softened and melted and then solidified again, the cohesive force of the toner is very large and the toner behaves as a group. When the toner image is heated and softened, it is pressed by the pressure roller 22, so that the toner image permeates the surface layer of the transfer paper and is cooled and solidified as it is. Fixed on top.

2 and 3 are enlarged side views of the fixing device 20 of FIG. 1 as viewed from the back side. Of these, FIG. 2 shows a state in which the bearing 35 on the back side of the driven roller 24 is pushed up. FIG. 3 shows a state in which the bearing 35 on the inner side of the driven roller 24 is pushed up by the spring 37.

That is, the bearing 35 of the driven roller 24 is slidably supported by the side plate 46 in the vertical direction, and one end of the driven roller 24 is rotatably supported, and the other end of the driven roller 24 is provided on the side plate 47. A bearing (not shown) is rotatably supported.

The fixing member 36 attached to the side plate 46 supports one end of a spring 37 for pushing up the bearing 35, and the lower end of the bearing 35 is pressed by the other end of the spring 37. The spring clutch 38 includes an input hub (not shown), a coil spring (not shown) having a control claw (not shown), a control collar 40a provided to hold the control claw, and an output hub 41. Is
When the control collar 40a is stopped by engaging the engaging claw 40b or 40c with the lever claw 44 as shown in FIGS. 2 and 3, the power of the input hub is not transmitted to the output hub 41. When the lever claw 44 separates from the engaging claw 40b or 40c, the control collar 40a becomes rotatable,
Power is transmitted from the input hub to the output hub 41. Rotational force is constantly transmitted to the input hub in the direction of arrow B via a gear (not shown).

A cam 39 having a different radius depending on the angle is fixed to the output hub 41 so as to rotate together. As shown in FIG. 2, when the engaging claw 40b and the lever claw 44 are engaged, the lower radius of the cam 39 is the maximum, and as shown in FIG.
When the engaging claw 40c and the lever claw 44 are engaged, the lower radius of the cam 39 is the minimum, and in other positions, the gap between them is smoothly connected.

Therefore, when the engagement claw 40b is engaged with the lever claw 44, the maximum radius portion of the cam 39 pushes the bearing 35 downward, and when the engagement claw 40c is engaged with the lever claw 44, the bearing 35 springs. Pushed up by 37.

The lever 43 is rotatably supported by a support shaft 42 planted in a side plate 46, a lever claw 44 is formed at the other end, and the other end is connected to an operating rod of a solenoid 45. Solenoid 45
Is turned on for a predetermined time in response to signals from the sensors 48 and 49, as will be described later.

The sensors 48 and 49 detect that the heat-resistant belt 23 has moved a predetermined amount inward or inward from the initial state. The output signals of the sensors 48 and 49 are amplified by a well-known control circuit, and the solenoid 45 is turned on for a predetermined time to stop the cam 39 at a desired position.

Next, referring to FIG. 4, it will be described that the deviation direction of the heat resistant belt 23 is changed by the vertical movement of the driven roller 24.

FIG. 4 is an explanatory view showing a hanging state of the heat resistant belt 23 as viewed from the non-paper side, and shows only a main part.

As described above, the cam 39 shown in FIG.
When the end portion of the driven roller 24 is pushed up by 37, the belt 23 is wound while being inclined with respect to the axes of the driven roller 24 and the driving roller 27. That is, the belt 23
Is wound around the drive roller 27 with EF, and then G of the driven roller 24
It starts winding from the point, and after winding with GH, it is wound around the drive roller 27 again at point E. Where the drive roller 27
When is rotated in the direction of the arrow, the end of the heat-resistant belt 23 wound at the point E moves in the direction perpendicular to the axis of the driving roller 27, so when the driving roller 27 rotates about 180 °, it moves to the point E _1. . That is, the heat resistant belt 23 is moved in the direction of the arrow J by the distance Δd between the point F and the point E ₁ . Therefore, when the drive roller 27 continues to rotate in this state, the heat-resistant belt 23 gradually keeps approaching in the direction of arrow J.

When the heat-resistant belt 23 gets closer to a predetermined amount or more, the sensor 48 detects the belt end portion and makes the solenoid 45 conductive for a predetermined time,
Rotate the cam 39. The driven roller 24 is rotated by the rotation of the cam 39.
Is pushed down and the driven roller 24 is tilted in the opposite direction. Therefore, the direction of deviation of the heat resistant belt 23 is also reversed. By repeating this, the heat resistant belt 23 can reciprocate in a predetermined area width at a slow speed, and it is possible to prevent the end portion of the passed transfer paper P from constantly hitting the same place.

In the above description, the arrangement angle of the engaging claws 40b and 40c is about 90 °.
This is because the position of the cam 39 is the ON time of the solenoid 45 without using the cam position detection switch, etc.
This is performed by making the time longer than the time corresponding to the arrangement angle of b and 40c, and when using the cam position detection switch or the like, the arrangement angle of the engaging claws 40b and 40c may be arbitrary.

In the above embodiment, the driven roller 24 is twisted in order to generate the deviation in the heat resistant belt 23, but the present invention is not limited to this, and the heat resistant belt is directly changed by changing the pitch between the rollers. It is also possible to generate a deviation toward 23. Also, the means for changing the position of the roller
It is possible not only to use the spring clutch 38 and the solenoid for the trigger, but also to directly move the shaft end by the operating force of the solenoid.

FIG. 5 shows a second embodiment of the present invention. In this embodiment, the inter-axis pitch between the driven roller 24 and the drive roller 27 is made variable so that the heat resistant belt 23 is displaced. .

In FIG. 5, reference numeral 60 is a solenoid fixed to the side plate 46. Reference numeral 62 denotes a bearing, which rotatably supports the shaft end 52 of the driven roller 24. The bearing 62 is fitted in an elongated hole (not shown) provided in the side plate 46 and is mounted so as to be movable in the horizontal direction. There is. The support shaft 64 is planted in the side plate 46 and rotatably supports the lever 61. The upper end of the lever 61 is a solenoid
The lower end of the lever 61 is engaged with the bearing 62 by engaging with the operating rod of 60. When the solenoid 60 is inoperative, the bearing 62 is pulled by the tension of the heat resistant belt 23 so as to move in the direction of arrow K. The pin 63 implanted in the side plate 46 regulates the movement of the lever 61.

When the solenoid 60 is inoperative, the lever 61 abuts the pin 63, and at this time, the bearing 62 is a short distance from the driven roller 24 to the drive roller 27 as compared with the bearing (not shown) on the opposite side of the driven roller 24. It's getting closer. Then, when the solenoid 60 operates, the lever 61 rotates clockwise about the support shaft 64,
The bearing 62 is arranged so as to be farther from the drive roller 27 than the bearing on the opposite side of the driven roller 24, although it is a little away from the drive roller 27. During rotation, the heat-resistant belt 23 approaches the shorter side between the roller axes, so when the solenoid 60 is inactive, the heat-resistant belt 23
The heat-resistant belt when the solenoid 60 is activated.
23 approaches the front side.

The sensors 48, 49 turn on / off the solenoid 60 when the heat-resistant belt 23 deviates by a predetermined amount or more. In the case shown in the figure, the sensor 48 is activated when the heat resistant belt 23 is too close to the back side, and the solenoid 60 is turned from the OFF state to the ON state so that the heat resistant belt 23 is moved toward the front side. On the contrary, when the sensor 49 is activated, the solenoid 60 changes from ON to OF
Switching to the F state, the heat resistant belt 23 acts so as to approach the back side.

Therefore, the driven roller 24 can move the heat resistant belt 23 to the rear side or the front side by adjusting the axis between the driven roller 24 and the drive roller 27, and the end of the transfer paper P is always at the same position as the heat resistant belt 23. It can be prevented from abutting.

FIG. 6 shows a third embodiment of the present invention. In the third embodiment, the sensor is attached so as to be movable in the longitudinal direction, the position of the sensor is shifted in the longitudinal direction after passing a predetermined number of sheets, and the reciprocating region of the heat-resistant belt in the longitudinal direction is changed.

That is, the sensors 48 and 49 are attached to both ends of the slider 70, the sensor 48 detects the end of the heat resistant belt 23 on the back side, and the sensor 49 detects the end of the heat resistant belt 23 on the front side. The slider 70 is provided with elongated holes on the back side and the front side, and these elongated holes are supported by pins 71, 7 supported by a support plate (not shown).
The two are loosely fitted. Sensor 4 behind slider 70
A rack 73 is formed in the direction opposite to 8, and the rack 73 meshes with the pinion gear 74. The pinion gear 74 is rotated by several teeth at a time by an actuator such as a small motor or a plunger (not shown). Therefore, after passing a specified number of sheets or heat resistant belt
After a predetermined number of rotations of 23, an electric signal is given to the actuator, the pinion gear 74 rotates clockwise by several teeth, and the sensors 48 and 49 move in the direction of arrow M to the position of the chain double-dashed line. To do. After the sensors 48 and 49 move to the positions indicated by the chain double-dashed line, the heat-resistant belt 23 reciprocates between the chain double-dashed lines.

Since the conveyance position of the transfer paper P is constant, the position where the paper edge of the transfer paper P contacts the belt 23 is also displaced by the amount of the heat resistant belt 23 displaced in the longitudinal direction. Further increase.

In the above description, the heat-resistant belt 23 is detected by the sensor and the heat-resistant belt 23 is moved by a predetermined amount, and then is fed back to reciprocate between the sensors, but the sensor is not used. It is also possible to operate the leaning mechanism after passing a predetermined number of sheets.

FIG. 7 shows it as a fourth embodiment of the present invention.

That is, as shown in FIG. 7, in the belt deviating mechanism, the eccentric cam 76 that rotates with the gear 77 is brought into contact with the upper end of the one-way bearing 35 of the driven roller 24, and the eccentric cam 76 is rotated by half. In addition, the bearing 35 is provided so as to move up and down. After a predetermined number of sheets have been passed or after a jam has occurred, after a predetermined number of rotations of the heat-resistant belt 23, the gear 77 is rotated by 1/2 by a well-known actuator to bias the heat-resistant belt 23, and the end portion of the transfer paper P is Do not touch the same part of the belt 23.

By operating the belt shifting mechanism after passing a predetermined number of sheets, the heat-resistant belt 23 is gradually moved to a certain direction without reciprocating, and the belt 23 is gradually moved to a certain direction.
If 23 gets closer, you may replace it with a new heat resistant belt.

[Effects of the Invention] As described above, according to the present invention, since the belt shifting mechanism that positively moves the heat-resistant belt in the direction intersecting the conveying direction is provided, A slight deviation can be generated in the heat-resistant belt so that the portion where the transfer material passes and the portion where it does not pass are not always located at the same position. Therefore, it is possible to prevent the heat-resistant belt from being damaged and improve the durability of the heat-resistant belt.

[Brief description of drawings]

FIG. 1 is an explanatory view of the entire image forming apparatus showing the first embodiment of the present invention, and FIG. 2 is a view of the fixing device of FIG.
FIG. 3 is an enlarged side view of one state, FIG. 3 is an enlarged side view of the other state, FIG. 4 is an explanatory view of the heat-resistant belt of FIG. 2 and FIG. 3, and FIG. FIG. 6 is a side view showing an embodiment, FIG. 6 is a plan view showing the same as the third embodiment,
FIG. 7 is a side view showing the same as the fourth embodiment. 1 ... Original table, 3 ... Photosensitive drum 20 ... Fixing device, 21 ... Heating element 22 ... Pressure roller, 23 ... Heat-resistant belt 24 ... Following roller, 27 ... Driving roller 28 ... Heat generation Surface 35 …… Bearing 45 …… Solenoid, 46,47 …… Side plate 60 …… Solenoid, 62 …… Bearing

Claims (9)

[Claims] 1. A heat-resistant belt which moves at a conveying speed of the transfer material while being in contact with an unfixed toner image carried on the transfer material,
A heating element for heating and melting the toner image, a pressurizing mechanism for pressing the heating element with the heat-resistant belt sandwiched therebetween, and separating the heat-resistant belt from the transfer material after the heat-melted toner image is cooled and solidified. In a heating and fixing device including a belt feeding device, the heat-resistant belt is positively moved in a direction intersecting the conveying direction of the belt so that the end portion of the transfer material and the heat-resistant belt are not in contact with each other at a constant position. A heat-fixing device having a belt biasing mechanism. 2. The heat fixing apparatus according to claim 1, wherein a heat transfer belt is defined to have a shift area, and the heat transfer belt gradually reciprocates in this area. 3. The heat fixing device according to claim 1, wherein the belt biasing mechanism is actuated for every predetermined number of transfer materials. 4. The heat fixing device according to claim 1, wherein the belt biasing mechanism is actuated every predetermined number of rotations of the heat resistant belt. 5. The heat fixing device according to claim 1, wherein the belt biasing mechanism is made to act when the power is turned on. 6. The heat fixing device according to claim 1, wherein the belt biasing mechanism is operated after the jam is removed. 7. The heat fixing device according to claim 2, wherein the heat-resistant belt is shifted in the longitudinal direction by a predetermined number of passing transfer materials in the longitudinal direction. 8. The heat fixing device according to claim 2, wherein the heat-resistant belt-side region is shifted in the longitudinal direction at every predetermined number of rotations of the belt. 9. The heat-resistant belt is set to have a width in the longitudinal direction wider than the width of the image area so as to reduce the frequency of the transfer material edge passing through the same place. The heat fixing device according to 6, 7 or 8.