JPH0341490A - Fixing device - Google Patents

Abstract

PURPOSE:To keep a fixing film running on the central part by turnably, pivotally and reversely supporting one of two rollers, centered around the central part in the shaft direction, with the other roller as a reference among two rollers. CONSTITUTION:The driving roller and the two follower rollers form the fixing film traveling path. By using the driving roller and the one of the follower roller as a reference, the central part of the other roller 36 in the shaft direction is turnably, pivotally and reversely supported by a free bearing 45 and its end part is turnably, pivotally and reversely supported by a free bearing 38. When the fixing film is abnormally closer to one side, the tensile force of the offset film increases. Consequently, the roller tilts around the central part in the shaft direction to create the second offset force in a direction in which the offset of the film is suppressed. Accordingly, the offset of the film is automatically suppressed. Thus, a sensor detecting the position of the film edge, an actuator, etc., are eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fixing device for an image forming apparatus that heats and fixes a toner image onto a recording material.

[Conventional technology]

Conventionally, the fixing device used in this type of apparatus uses a heating roller maintained at a predetermined temperature and a pressure roller having an elastic layer that presses against the heating roller to fix unfixed toner images. A heat roller fixing method is often used in which the formed transfer material is heated while being held and conveyed.

Further, a belt fixing method as described in US Pat. No. 3,578,797 is known.

However, in the above heat roller fixing method, the first
Second, there is a so-called wait time, which is the time during which image forming operation is prohibited until the temperature is raised to a predetermined temperature.
Secondly, since the roller temperature is high in the rotating rollers, special heat-resistant bearings are required.Fourthly, the rollers are in direct contact with hands, which can be dangerous and require protective members.
Another problem is that the constant temperature and curvature of the roller causes the transfer material to wrap around, resulting in a jam. Furthermore, the belt fixing method described above also involves a wait time and requires a relatively large amount of electric power.

Therefore, the applicant has proposed the following fixing device to solve the above problems. That is, a heat-resistant film (for example, polyimide,
A release layer of about 10 μm is coated on the front surface, and the recording material is brought into close contact with a heating element having a small heat capacity via the film using a pressure member. This method heats and fixes the visible image.

[Problems to be Solved by the Invention] However, in the above-proposed fixing device, since the thin endless film is conveyed by a plurality of rollers, etc., as a means of conveying it, the endless film is rotated while applying tension. There is a problem that it moves slowly.

This type of deviation during endless film transport can be suppressed to some extent by increasing the cylindricity and surface properties of the rollers, adjusting the pitch and parallelism between the rollers, and adjusting the tension. It is possible, but there are limits when considering mass production.

Furthermore, it is impossible to control the deviation by providing an abutment member at the end of the roller or by perforation, etc., because the strength of the endless film itself is low.

Next, the deviation of the endless film will be explained.

When considering the placement position of the two-wood rollers, there are two cases: one is when the two-wood rollers are accurately assembled and are in a parallel state, and the other is when the axes on the front or back side of the rollers are different and are in a diagonal state. The height of the front or back side of the roller is different, and there are cases where the roller is in a so-called twisted state and cases where it is in a combination of a folded state and a twisted state.

Here, when the endless film is in a parallel state, it does not shift in any direction and is driven stably, and when it is in a V-shaped state, the endless film shifts toward the narrower side between the axes and is in a twisted state. In some cases, the endless film will shift toward the higher end of the roller, and if both are combined, the shifting force (shifting amount) due to the bent state and the shifting force (shifting amount) due to the twisted state will be large. Endless film moves towards you.

That is, as shown in FIG. 3(a), the drive roller 31
When the endless fixing film 48 is rotating in the direction of arrow H, the tension of the endless fixing film 48 is loosened on the upper side, and the tension is on the lower side (indicated by the broken line). The fixing film 48 sent out from the driving roller 31 comes into contact with the driven roller 36 at a point M. From contacting point M to point N, it is wrapped around the driven roller 36 for approximately 1/2 turn. At point N, the fixing film 48 is separated from the driven roller 36 and pulled toward the driving roller 31 side. At this time, since the driven roller 36 is inclined with respect to the driving roller 31, the point M and the point N are not on the same vertical plane of the driven roller 36, and are shifted by ΔS. This deviation amount ΔS is determined by the fixing film 48. Followed roller 36. The fixing film 48 reliably moves in the direction of the arrow Q, although it is difficult to determine quantitatively because it depends on the coefficient of friction with the drive roller 31, tension, etc. This shift amount (or shift force) is defined as the first shift amount.

In addition, as shown in Figure 3(b), the drive roller 31
When the fixing film 48 rotates in the direction of the arrow H, the upper side of the fixing film 48 moves in the direction of the arrow, and the lower side of the fixing film 48 (indicated by a broken line) moves in the direction of the arrow E. Looking at how the end of the film wraps around the driven roller 36, the contact point D1 where the fixing film 48 contacts the driven roller 36 and the contact point E1 where the fixing film 48 leaves the driven roller 36 are separated by ill△°C. There is. The film tension is strong on the lower side and is pulled toward the contact point E1 (in the direction of reducing Δ°C).

This applies not only to the ends of the film but also to the entire width of the film, and as the drive roller 31 continues to rotate in the direction of arrow H, the fixing film 48 continues to shift in the direction of arrow G. This shift amount (or shift force) is defined as the second shift amount.

The shift of the fixing film 48 can be suppressed by balancing the first shift amount and the second shift amount and reversing the directions.

Therefore, an actuator such as a motor or a plunger is used to tilt the roller to generate a second shift amount,
In addition, there is a problem in that it is not possible to sufficiently balance the first amount of deviation and the second amount of deviation by providing a sensor for detecting the amount of deviation of the fixing film 48, and the structure becomes complicated.

The present invention aims to solve the above problems. That is, an object of the present invention is to provide a fixing device that has a simple structure and can automatically suppress shifting of the fixing film.

(Means for Solving the i%! Problem) In order to achieve the above object, the present invention provides an image forming means for forming a visible image by placing a developing material on a recording material, and a fixedly supported heating body. and a fixing means for heating and fixing the visible image by means of a pressure member that brings the recording material into close contact with the heating body through an endless fixing film by opposing pressure contact with the heater, forming a travel path for the fixing film. a driving roller and a driven roller, one of the two rollers serving as a reference roller, and the other roller being reversible about the center in the axial direction with respect to the reference roller. is rotatably supported, and
The other roller is mounted so that when the fixing film shifts in one direction, the fixing film shifts in the opposite direction.

(Function) According to the present invention, one of the driving roller and the driven roller serves as a reference roller, and the other roller is reversible about the center in the axial direction with respect to the reference roller. The other roller is rotatably supported, and the mounting of the other roller is tilted so that when the fixing film is moved to one side, the direction in which the fixing film is moved is in the opposite direction. , even without adding other actuators or sensors, when the fixing film moves to one side, the tension of the film increases on the side where the fixing film is moved, and therefore, the tension on the other side increases with the center of the axis The roller tilts and generates a second shifting force, so that shifting of the fixing film can be automatically suppressed.

〔Example〕

1 and 2 show a first embodiment of the present invention, and a fourth embodiment of the present invention is shown in FIG.
The figure shows an image forming apparatus using the fixing device of this first embodiment.

In FIG. 4, reference numeral 1 denotes a document mounting table made of a transparent member such as glass, which scans the document by reciprocating in the direction of arrow a.

A short-focus, small-diameter imaging element array 2 is arranged directly below the document platform 1, and the image of the document placed on the document platform 1 is illuminated by an illumination lamp 3, and the reflected light image is reflected by the array 2. Slit exposure is performed on the photosensitive drum 4. Note that this photosensitive tram 4 rotates in the direction of the arrow. Also 5
is a charger that uniformly charges the photosensitive drum 4 coated with, for example, a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer. The photosensitive drum 4, which is uniformly charged by the charger 5, is subjected to image exposure by the array 2, and an electrostatic image is formed thereon. This electrostatic image (electrostatic latent image)
is visualized by the developing device 6 using toner made of a resin or the like that softens and melts when heated. On the other hand, the recording material (sheet) P stored in the cassette S is rotated by being pressed against the transport roller 7 and the photosensitive drum 4 in the vertical direction while tying them in synchronization with the image on the photosensitive drum 4. The photosensitive drum 4 is fed onto the photosensitive drum 4 by a conveyance roller 8 . Then, the toner image formed on the photosensitive tram 4 is transferred onto the recording material P by the transfer discharger 9. Thereafter, the recording material P separated from the photosensitive drum 4 by a known separating means is
The paper is guided to a fixing device 11 by a conveyance guide 10, subjected to heat fixing processing, and then discharged onto a tray 12. Note that after the toner image is transferred, residual toner on the photosensitive drum 4 is removed by a cleaner 13.

FIG. 5 shows an enlarged view of the fixing device 11 shown in FIG.

In FIG. 5, reference numeral 14 denotes a low heat capacity linear heating element fixedly supported on the device, - for example, a thickness of 1.0 mm;
A resistive material 16 is coated on an aluminum substrate 15 having a longitudinal length of 240 mm to a width of 1.0 mm, and electricity is applied from both ends in the longitudinal direction. The current was supplied with a pulse-like waveform of 100 V DC with a period of 20 m5ec, and the temperature was controlled by the thermometer 17 to reach the desired temperature. A pulse corresponding to the degree of FA and the amount of energy released is given by changing the pulse width. The habo pulse width is 0.5 to 5 m5ec.

In this way, the energy and temperature of the heating body 1 are controlled.
4, the endless fixing film 48 moves in the direction of the arrow in the figure.

An example of this fixing film is a heat-resistant film with a thickness of 20μ (for example, polyimide polyether,
PES, PFA, etc.) at least on the image contact surface, PTF
There is an endless film that is coated with 10 μm of a release layer made by adding a conductive material to a fluororesin such as E or PAF. - Numerically, the total thickness is less than 100μ, more preferably less than 40μ.

The fixing film 48 is driven by the drive roller 31 and the driven roller 36 and tension, so that the fixing film 48 moves in the direction of the arrow without wrinkles.

18 is a pressure roller having a rubber elastic layer with good releasability such as silicone rubber, and the fixing film 48 is applied with a total pressure of 4 to 7 J.
The heating body 14 is pressurized through the heating body 14 and rotates in pressure contact with the fixing film 48 .

1. The unfixed toner T on the recording material P is guided to the fixing section by the entrance guide 19, and a fixed image is obtained by the above-mentioned heating.

At the same time, means for preventing the endless fixing film 48 from shifting will be explained with reference to FIGS. 1 and 2.

FIG. 1 is a plan view of the fixing device, and main parts are shown in cross section. The drive roller 31 is for driving the fixing film 48, and the front shaft end 32 of the drive roller 31 is rotatably supported by a bearing 33, and the rear shaft end is similarly supported by a bearing (not shown). is supported by. Further, the drive roller 31 is rotated at a predetermined rotational speed by a drive device on the copying machine main body side. The bearing 33 is attached to the front side plate 34, and the bearing on the back side is similarly attached to the back side plate (not shown), and the drive roller 31 is supported in a horizontal state.

FIG. 2 is a cross-sectional side view taken along section line A-A in FIG. 1. A heating element 49 (a heating element similar to the low heat capacity linear heating element 14 of FIG. 5) is supported perpendicularly to the front side plates 34 and 2 and the back side plate.

As seen in FIG. 1, the right end of the support shaft 42 is loosely fitted into an elongated hole provided in the front plate 34, and a spring 55 is applied in the direction of the arrow. The left end of the support shaft 42 has a similar configuration, and the fixing film 48 is connected to the drive roller 31, the driven roller 36, and the heating element 4, as shown in FIG.
It is hung on 9.

Said support +i! A swivel bearing 45 having a spherical surface is fixed to the center of the shaft 42 . The free bearing 45 is fitted with a left holder 43 and a right holder 44, each of which has a spherical inner surface. A flange shaft 37 is fixed to the right end (front side) of the vibrator-shaped driven roller 36.
is rotatably supported by a swivel bearing 38. The outer peripheral surface of the universal bearing 38 is formed into a spherical shape, and the universal bearing 38 is loosely fitted into a holder 39 having a spherical recess. As shown in FIG. 2, the guide plate 40 fixed to the front side plate 34 is formed with a long hole guide groove 41 inclined at an angle θ. The halter 39 is loosely fitted into the kite groove 41. The left end of the driven roller 36 is not provided with a flange shaft, a free bearing, a holder, a guide groove, etc. unlike the right end described above. Therefore, the driven roller 36 is mounted on the swivel bearing 45.
It can be moved diagonally up and down along the guide groove 41 at the right end with .

In FIG. 1, the film edge of the fixing film 48 or B
-B, the fixing film 48 is located at the center of the driven roller 36 with the swivel bearing 45 at its center, and the pressure balance between the front side and the back side is in equilibrium, and the driven roller 36
is held horizontally.

The fixing film 48 moves to the front side, and the film edge is C-
When moving to position C, the pressure acting on the driven roller 36 increases on the front side. By increasing the pressure on the front side,
The holder 39 moves downward along the guide groove 41.

Therefore, due to the movement (shifting) of the fixing film 48,
The driven roller 36 is twisted around the swivel bearing 45. By twisting the driven roller 36, the fixing film 48 is stopped from shifting, and the fixing film is moved in the opposite direction.

The driven roller 36 is rotatably supported at the center so that when the fixing film 48 shifts from its normal position to the left or right,
This is because an increase or decrease in the width of the right and left fixing films from the center creates a pressure balance that is twice the shift amount, making it easier for the driven roller 36 to tilt.

To summarize the above, the drive roller 31. Followed roller 36.
The fixing film 48 hung on the heating body 49 is driven in the direction of arrow F in FIG. Here, drive roller 3
1. If the driven roller 36 and the heating element 49 are each formed ideally, and if the cylindricity of the fixing film 48 is also ideally formed, then the fixing film 48 will not shift and will be fixed in the initial stage. Continue to hold the hung position. However, when any or each of the above elements overlap in a composite manner, the fixing film 48 moves toward the front side or toward the back side. This biasing force is referred to as the first biasing force.

When the fixing film 48 moves from the BB position to the C-C position, that is, toward the front side, as shown in FIG. decreases. Therefore, the driven roller 36 rotates around the free bearing 45, and the right end portion of the driven roller 36 moves down along the guide groove 41. Due to the inclination of the driven roller 36, the way the fixing film 48 is wound is as shown in FIG.
trying to move to. This biasing force is referred to as a second biasing force.

When the first shifting force and the second shifting force become equal, the fixing film 48 is in an equilibrium state and is stably driven.

FIG. 6 shows a second embodiment of the invention.

In the first embodiment described above, the guide groove 41 is used as a means for regulating the movement of the driven roller 36, but in this second embodiment, the lever 50 is used to regulate the movement of the end of the driven roller 36. It has become.

Also in this second embodiment, the vibrator-shaped driven roller 36
is rotatably supported at the inner center part, and the other members are also supported by the first
Components that are the same as those in the figures and FIG. 2 are designated by the same symbols.
installed in the same way.

The lever 50 is rotatably supported by a support shaft 51 implanted in a front plate (not shown).

A large diameter hole is formed at the other end of the lever 50, and a holder 39 that supports the swivel bearing 38 is fitted into this hole.

Therefore, for the reason described above, when the fixing film 48 moves toward the front side, the right end portion of the driven roller 36 tilts downward to the right due to the difference in film tension acting on the driven roller 36. Therefore, the lever 50 rotates counterclockwise as shown by the two-dot chain line. A second shifting force is generated due to the inclination of the driven roller 36, and the shifting of the fixing film 48 is balanced in an equilibrium state.

In the above description, when the fixing film 48 is shifted to either side, the guide groove 41 with the inclination angle θ or the rotation is used so that the end of the driven roller 36 to which the fixing film 48 is shifted is actively lowered. Although the case has been described in which the lever 50 is provided with its moving direction inclined, the drive roller 31. Followed roller 36. When a fixing film is applied to the heating body 49 and the at least three element portion $J, and the cross-sectional shape is triangular, the guide groove 41 may be vertically oriented, or
The inclination angle θ2 of the lever 50 may be Oo.

FIG. 7 shows a third embodiment of the invention.

In this third embodiment, the driven roller 70 is rotatably supported by a substantially U-shaped support frame 72 with both ends bent at right angles. A shaft 76 is implanted in the axial center of the support frame 72, and the shaft 76 is slidably and loosely fitted into a hole 74 provided in a stay 73 supported by a side plate (not shown). A thrust bearing 71 and a spring 75 are provided between the support frame 72 and the stay 73.

A retaining ring 77 is fixed to the other end of the shaft 76, and the stay 7
A thrust bearing 78 is provided between the retaining ring 77 and the retaining ring 77 .

Therefore, the driven roller 70 can rotate together with the support frame 72 about the shaft 76, and when the fixing film 48 is shifted to one side, the fixing film 48 is moved to the side where it is shifted, as in the previous embodiment. The driven roller 70 is lowered.

When the driven roller 70 is tilted and twisted with respect to the drive roller 31, the fixing film 48 shifts in the opposite direction, and further shift can be suppressed.

FIG. 8 shows a fourth embodiment of the invention.

In this fourth embodiment, the outer central portion of the driven roller 80 is pressed by a roller 85 in the direction in which the tension of the fixing film 48 is increased. A bearing 81 is loosely fitted into the front shaft end of the driven roller 80, and the outer diameter of the bearing 91 is loosely fitted into an oblique groove 82 provided in a side plate (not shown). The roller 985 is rotatably supported by a narrow U-shaped support member 83. The shaft 8 is located at the center of the width of the support member 83.
4 is implanted, and this shaft 84 is loosely fitted into a horizontal hole provided in a stay 87 fixed to both side plates (not shown).
4 and the support member 83 are rotatable. axis 84
A retaining ring 88 is attached to the other end, and the shaft 84 is attached to the stay 8.
This prevents a draw from 7 onwards.

Therefore, similarly to the embodiment described above, the fixing film 48 is conveyed by the drive roller 31, and as it is conveyed,
When the fixing film 48 shifts to one side, the balance of the film tension acting on the driven roller 80 is lost, and the shaft end of the driven roller 80 on which the fixing film 48 shifts falls. By tilting the driven roller 80, the fixing film 48
The shifting force of the fixing film 48 is suppressed, and the shifting of the fixing film 48 stops when a balance is achieved.

In each of the above embodiments, the drive roller 31 is used as a reference roller and the driven rollers 36, 70, 80 are tilted, but conversely, the driven roller may be used as a reference roller and the drive roller is tilted. .

〔Effect of the invention〕

As explained above, according to the present invention, one of the driving roller and the driven roller that forms the travel path of the fixing film serves as the reference roller, and the other roller is set relative to the reference roller. The other roller is mounted so as to be reversibly rotatable about the central portion in the axial direction, and in such a manner that when the fixing film is moved to one side, the direction in which the fixing film is moved is in the opposite direction. is tilted, so when the fixing film moves to one side, the film tension increases on that side.
Therefore, the other roller is tilted about the center in the axial direction, and a second shifting force is generated in a direction that suppresses shifting of the fixing film, so that shifting of the fixing film is automatically suppressed. Therefore, there is no need to install a sensor that detects the edge position of the fixing film or an actuator that operates in response to sensor signals, and there is also no need for wiring for the sensor or actuator, simplifying the structure and assembling it. Sex also improves.

[Brief explanation of drawings]

FIG. 1 is a plan view showing a first embodiment of the present invention, FIG. 2 is a cross-sectional side view taken along cutting line A-A in FIG. 1, and FIG. 3(a)
, (b) is an explanatory diagram of how an endless fixing film is hung on two wooden rollers, FIG. 4 is a cross-sectional side view showing an image forming apparatus using the fixing device of the present invention, and FIG.
The figure is an enlarged cross-sectional side view of the fixing device shown in FIG. 4, FIG. 6 is a cross-sectional side view showing the second embodiment of the present invention, and FIG. 7 is a cross-sectional view showing the third embodiment. The side view and FIG. 8 are also cross-sectional side views showing the fourth embodiment. 11... Fixing device 18... Pressure roller 31
... Drive roller 36 ... Followed roller 38 ...
・Swivel bearing 40...Guide plate 45...Swivel bearing 48...Fixing film 49...Heating body 50...Lever 70...Followed roller 80...Followed roller and 4 others

Claims (1)

[Claims] 1. An image forming means that places a developing material on a recording material to form a developed image, and a pressure member that presses against a fixedly supported heating body and brings the recording material into close contact with the heating body via an endless fixing film. an image forming apparatus having a fixing means for heating and fixing the developed image by means of a drive roller and a driven roller that form a traveling path of the fixing film, and one of the two rollers is a reference roller. The other roller is supported to be reversibly rotatable about the center in the axial direction with respect to the reference roller, and when the fixing film is shifted in one direction, the fixing film is A fixing device characterized in that the mounting state of the other roller is inclined so that the direction in which the film is shifted is in the opposite direction.