JP3326460B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile or the like.

[0002]

2. Description of the Related Art A sheet-like transfer material such as paper is brought into contact with a toner image formed on the surface of an image carrier, and a transfer bias is applied to the transfer material to transfer the toner image onto the transfer material. An image forming apparatus in which the transfer material is guided to a fixing device to fix a toner image on the surface of the transfer material by heat and pressure is well known in the related art.

FIG. 7 is a cross-sectional view showing the basic structure of a fixing device of the image forming apparatus employing a heat roller system as a specific example. The fixing devices are pressed against each other and rotate in the direction of the arrow shown in the drawing. 1 and a pressure roller 6. The fixing roller 1 is formed by forming a release layer 2 on the surface of a cylindrical core 3 containing a halogen lamp heater 4, and the pressure roller 6 is provided with a heat-resistant rubber layer 7 around a rod-shaped core 8. Further, a release layer 2 is formed on the surface of the transfer material P. The transfer material P is conveyed at the opposite nip portion, and the toner is fixed to the transfer material P by heat and pressure. Some color fixing devices use a silicone rubber layer impregnated with silicone oil instead of the release layer on the surface of the fixing roller.

FIG. 8 is a diagram showing the overall configuration of the fixing device as viewed from the paper passing direction of the transfer material P. The cylindrical core 3 of the fixing roller 1 has a frame 11 via a fixing roller bearing 9 having a small friction coefficient. The pressure roller 6 is fixed only in the front-rear direction by a longitudinal long hole 11 a provided in the frame 11, and is vertically supported by a pressure roller bearing 10.
It is configured to be pressed upward by a pressing spring 12 inserted between the fixing roller 1 and the frame 11 to generate a nip width and pressure necessary for fixing at a nip portion with the fixing roller 1.

In an image forming apparatus having a fixing device configured as described above, in recent years, it has become important to increase the printing speed, and it is necessary to increase the speed of the fixing device.

However, with the conventional configuration, the speed of the transfer material passing through the fixing device is high, so that the amount of heat per unit time necessary to sufficiently fix the toner on the transfer material is insufficient, and the fixing failure may occur. Will happen. For this reason, it is necessary to increase the amount of heat generated by the heater to compensate for the insufficient amount of heat, but this method has a limit from the viewpoint of heat resistance and power consumption of components.

Therefore, measures have been taken to increase the amount of heat applied to the transfer material per unit time by increasing the fixing nip width and increasing the area where the transfer material contacts the fixing roller and the pressure roller during fixing. More specifically, a method of enlarging the outer diameter of the fixing roller and the pressing roller, and increasing the fixing pressure is used.

However, in recent years, there has been a limit to increasing the outer diameter of each roller of the fixing device in order to satisfy market needs for downsizing and high-speed printers.
In high-speed countermeasures, the enhancement of the fixing pressure is further spurred, and as a result, a phenomenon peculiar to the envelope that wrinkles are likely to occur when the envelope is passed (hereinafter, this phenomenon is referred to as a fixing envelope wrinkle). Began to occur. The mechanism by which this phenomenon occurs will be described with reference to FIG.

That is, when the fixing pressure is increased as a measure for speeding up, the cross section of the surface of the pressure roller 6 at the nip portion falls down in an arc shape, so that each roller on the upper surface side and the lower surface side of the envelope P ' The contact area of the envelope P ′ changes in proportion to the difference between the circumferences of the upper and lower arcs, causing a difference in the upper and lower conveying forces of the envelope P ′. Cannot be caught up, and at the rear end of the envelope P ′, the upper surface side that could not be caught is excessively slackened, and finally, the envelope P ′ is discharged while the slack is wrinkled. This phenomenon is particularly likely to occur in a one-sided fixing device in which the paper passing reference position is close to the pressing portion at the roller end.

In order to solve the above problem, a method of reducing the pressing force of the upper and lower rollers of the fixing device only when the envelope is passed is adopted. Specifically, a spacer is provided between the left and right shafts of the upper and lower rollers. In addition, an electromagnetic clutch is provided between the left and right shafts, and this clutch is actuated multiple times while one envelope is being conveyed. A method such as recovery is used.

[0011]

However, in the above-described method, since the fixing force of the envelope is reduced by reducing the pressing force, the reliability of the image quality may be impaired, and the driving of the pressure roller may be reduced. In a fixing device that is realized by being driven by contact with the fixing roller, if the pressing force is reduced until envelope wrinkles do not occur, the driving force of the fixing roller cannot be sufficiently transmitted to the pressing roller, and the pressing roller stops. As a result, the envelope may slip at the fixing nip. In addition, there is a problem that the number of parts is increased due to the provision of the means for reducing the pressing force, the assembly process is complicated, and the cost of the apparatus is increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems. An object of the present invention is to provide a fixing envelope without wrinkling without a complicated mechanism, even if the fixing speed is increased. To provide an image forming apparatus capable of performing the above.

[0013]

In order to achieve the above object, according to the present invention, there is provided a transfer means for transferring a toner image formed on an image carrier onto a transfer material, and applying heat and pressure to the transfer means. An image forming apparatus using a method in which a fixing unit for fixing the toner image on the transfer material is used, and the transfer reference position of the transfer material is set to one of left and right end portions as the fixing unit. The fixing pressure on the reference side of the fixing unit is reduced, and the heat generation distribution in the longitudinal direction of the heating element of the identification fixing unit is set so that the heat generation amount on the reference side is higher than the heat generation amount on the non-reference side. .

According to a second aspect of the present invention, there is provided a transfer means for transferring a toner image formed on an image carrier onto a transfer material, and fixing by applying heat and pressure to fix the toner image on the transfer material. An image forming apparatus using a method in which a transfer reference position of a transfer material is defined as one of the left and right end portions as a fixing means, wherein a fixing pressure on a reference side of the fixing means is reduced. The hardness distribution in the longitudinal direction of the pressure roller of the identification attaching means is set so that the hardness on the reference side is lower than the hardness on the non-reference side.

According to a third aspect of the present invention, in the first or second aspect of the present invention, means for reducing the fixing pressure of the fixing means is provided between the shafts of the reference-side fixing roller and the pressure roller. It is characterized in that it is constituted by a cam having a portion that acts to expand between the two shafts in response to the rotation of both rollers and a portion that does not act.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the cam or the opposing member is configured to be movable in the axial direction of the pressure roller or the fixing roller, and the cam or the opposing member is moved only when the envelope is passed. It is characterized in that the cam or its opposing member is moved to a position where it can be brought into contact.

According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the movement of the cam or the opposing member is automatically linked to an operation of setting an envelope size in the sheet feeding section.

[0018]

According to the first or second aspect of the present invention, since the fixing pressure on the reference side (envelope passing side) of the fixing means is reduced, generation of wrinkles in the fixing envelope due to an increase in fixing speed is prevented. be able to.

According to the first aspect of the invention, the heat generation amount of the heating element on the reference side (envelope passing side) is increased, and according to the second aspect of the invention, the pressure roller By lowering the hardness on the reference side, it is possible to compensate for a decrease in fixability due to an insufficient fixing pressure on the reference side.

According to the third, fourth or fifth aspect of the present invention, the fixing pressing force on the reference side (envelope passing side) of the fixing means in the first or second aspect of the invention is reduced by the rotational force of the roller. This can be realized by the action of a cam utilizing the structure, and a complicated configuration and extra energy are not required.

[0021]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

<First Embodiment> FIGS. 1A, 1B,
(C) is a diagram showing a first embodiment of the present invention, FIG.
2A is a cross-sectional view illustrating a configuration of a fixing device employing a heat roller system, FIG. 2B is a configuration diagram of a halogen lamp, and FIG. 2C is a diagram illustrating an axial distribution of a fixing temperature. 1
In FIG. 8A, the same elements as those shown in FIG.

In this embodiment, as shown in FIG.
A low-pressure spring 12 'is used as a reference-side pressure spring. Further, as shown in FIG. 1B, as a halogen lamp heater, the density of the reference-side heat generating coil is increased so that the light distribution can be changed to envelope passing. The axial direction of the fixing roller 1 may be increased by using a one-sided light distribution enhancing heater 4 'raised on the side, or simply increasing the heat generation area on the reference side by making the arrangement of the heating coil asymmetrical (with respect to the center of the image). As shown in FIG. 1 (C), the temperature distribution is set so that the temperature of the envelope passing area becomes high.

By using the fixing device configured as described above, the generation of wrinkles is largely prevented by reducing the pressing force on the paper passing side of the envelope with respect to the fixing wrinkles. Deterioration was also prevented by increasing the fixing temperature in the envelope passing area. In this way, by increasing the calorific value only on the reference side, measures for improving the heat resistance of peripheral members required when the overall calorific value is increased, and an increase in unnecessary power consumption can be mitigated. It is possible to suppress the occurrence of envelope wrinkles without causing abnormal temperature rise in the non-sheet passing portion, which is a problem when the sheet is continuously passed on the reference side.

In the fixing device used in this embodiment, the strength of the pressure spring 12 'on the side of the envelope passing through the envelope is 3.5 kgf, and the strength of the pressure spring 12 on the opposite side is 5.0 kgf.
And the outer diameter of the pressure roller 6 are both 25 mm, the rubber hardness of the pressure roller 6 is 46 ° in Asuka C hardness, and the fixing speed is 70.7.
mm / sec.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a perspective view of the pressure roller. In this figure, the same elements as those shown in FIG. 8 are denoted by the same reference numerals.

In this embodiment, a fixing device employing the same heat roller system as that shown in FIG. 1A is used. The fixing device is used as a pressure spring on the side of the envelope paper passing area as shown in FIG.
A partial low-hardness pressure roller 6 'is used in order to prevent a decrease in fixability when the low pressure spring 12' shown in FIG.

A plurality of horizontal holes 13 having a fixed length are formed along the circumferential direction at the reference end of the partial low hardness pressure roller 6 ′. Since the axial hardness distribution of 'becomes lower only on the side of the envelope passing, there is no need to change the axial temperature distribution of the heater as in the first embodiment.

By using the fixing device having the above-described structure, the generation of wrinkles is greatly improved by reducing the pressure on the reference side with respect to the fixing wrinkles. This could be prevented by increasing the fixing nip width due to the lower hardness of the paper passing area. As described above, by lowering the hardness of the pressure roller only on the reference side, insufficient mechanical strength and permanent deformation of the nip portion, which are problems when the hardness of the entire pressure roller is reduced, and a lateral hole in the entire pressure roller. , The envelope wrinkles and the fixing performance can be realized at the same time without causing problems such as uneven fixing at the central portion caused by insufficient transmission of the pressing force to the central portion.

The strength of the pressure spring (not shown) of the fixing device used in the present embodiment is 3.5 kgf on the paper passing side of the envelope and 5.0 kgf on the opposite side, and the fixing roller (not shown) and the pressure roller 6 ′ are used. Have an outer diameter of 25 mm and a fixing speed of 70.7 mm /
The pressure roller 6 ′ has an inner diameter of about 1 m so that its rubber hardness is 46 ° in Asuka C hardness in an area where no horizontal hole is provided and about 35 ° in an area with a horizontal hole.
A 30-hole horizontal hole having a length of about 100 mm and a length of about 100 mm was uniformly arranged at a depth of about 2 mm from the surface. In addition, as a simple manufacturing method of the pressure roller 6 ′ used in the present embodiment, when molding the pressure roller with a mold, a plurality of pins are placed on the reference side along the roller circumferential direction on the roller side. After arranging them at an appropriate distance from, a method of pouring and molding a rubber material is suitable.

Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a cross-sectional view of the fixing device as viewed from the paper passing side, and FIG. 4 is a perspective view of a pressing force reducing mechanism of the identification attachment device. In these drawings, the same as that shown in FIG. Elements have the same reference numerals.

In the fixing device used in this embodiment,
As shown in FIG. 3, unlike the conventional fixing device shown in FIG. 8, the left and right pressure springs 12 are formed of the same strength springs. As a reduction measure, a cam 14 is attached to the end of the pressure roller
As shown in FIG. 4, as the fixing roller 1 and the pressure roller 6 rotate, the cam 14
The pressing force of the pressure roller 6 is pushed down only moderately by the reaction, so that the fixing pressure when the envelope is passed is reduced. It is configured to be diffused to the first half side.

By using such a fixing device, it is not necessary to use two kinds of springs, a strong spring and a weak spring, as in the first and second embodiments. It is possible to avoid the omission of the time for selecting the spring at the time or the danger of mixing.

Further, in the present configuration, unlike the above-described embodiment, the reduction of the pressing force only needs to be instantaneously applied to a very small portion of the transfer material during the fixing, so that the degree of deterioration of the entire fixing property is reduced. It is easy to reduce the degree of measures as in the first or second embodiment for securing the fixability, and it is possible to omit the measures for the fixability in some cases. Such advantages can be obtained by a conventional method using an electromagnetic clutch. However, this configuration can be realized by a simple method in which the cam 14 is provided on the cored bar 8 of the pressure roller 6, and complicated parts and new components can be obtained. Without the need for a simple control circuit, etc.
It can be realized at low cost.

In the fixing device used in this embodiment, the strength of the pressing spring 12 is 5.0 kgf, the outer diameters of the fixing roller 1 and the pressing roller 6 are both 25 mm, and the fixing speed is 70.7 mm /.
The rubber hardness of the pressure roller 6 is 46 in Asuka C hardness.
°. The number of peaks that come into contact with the fixing roller core metal 3 is used as the cam 14 so that the cam 14 comes into contact with the envelope whose length in the longitudinal direction is the shortest at least once during paper passing. The height of the peak was determined so that the strength of the pressing force reduced by the action of the cam 14 was comparable to that when a 3.5 kgf spring was used.

<Fourth Embodiment> Next, a fourth embodiment of the present invention will be described with reference to FIGS. 5 and 6
Are cross-sectional views of the end portion of the fixing device. In these drawings, the same elements as those shown in FIG. 3 are denoted by the same reference numerals.

In this embodiment, as shown in FIG. 5, the present embodiment differs from the third embodiment in that a cam 14 for reducing the pressing force is used.
The cam receiving member 1 is provided on the fixing roller 1 side, and the cam receiving member 1 is movable on the pressure roller 6 side along the cored bar 8.
4 'is provided. The cam receiving member 14 'is held by a holder 16, and a spring 15 is interposed between the holder 16 and the frame 11.

On the other hand, a moving shaft 20 is provided in the paper feeding section, and an envelope passing mode setting plate 19 is movably provided on the moving shaft 20. The envelope passing mode setting plate 19 and the holder 16 are connected to each other by a wire 17 stretched via a pulley 18. still,
The envelope passing mode setting plate 19 moves along the movement axis 20 and is fixed by a temporary fixing means such as a claw (not shown).

As shown in FIG. 6, when the envelope passing mode setting plate 19 moves left on the moving shaft 20 during envelope passing, the cam receiving member 14 'moves right on the cored bar 8. In order to move the cam receiving member 14 ′ to the position facing the cam 14,
As in the case of the third embodiment, the pressing force is reduced as a measure against the envelope wrinkles. During normal paper passing, the cam receiving member 1 is used.
Since 4 ′ is retracted to the position shown in FIG. 5, it is possible to perform the fixing under the optimum fixing condition.

In the fixing device used in this embodiment, the strength of the pressure spring 12 is 5.0 kgf, the outer diameters of the fastening roller 1 and the pressure roller 6 are both 25 mm, and the fixing speed is 70.7 mm /.
sec, and the rubber hardness of the pressure roller 6 is 46 ° in Asuka C hardness. The number of peaks that come into contact with the cam receiving member 14 'is used as the cam 14 so that the length of the envelope used in the longitudinal direction of the envelope is shortest at least once during the paper passing. The height of the peak was determined so that the strength of the pressing force reduced by the action of the cam 14 was comparable to that when a 3.5 kgf spring was used. By the way, it is also possible to configure so that the envelope passing mode setting plate 19 is linked with the paper size setting plate on the normal paper feed tray only when the envelope size is selected.
Since the movement of the cam receiving member 14 'can be easily motorized by winding the wire 17 by a motor, the cam receiving member 14' is transmitted by sending a signal from a switch on the operation panel of the printer or a host computer. A configuration for automatically moving can also be easily realized.

[0041]

As is apparent from the above description, claim 1
According to the invention described in (2), since the fixing pressure on the reference side (envelope passing side) of the fixing unit is reduced, it is possible to prevent the occurrence of fixing envelope wrinkles due to an increase in fixing speed. can get.

According to the first aspect of the present invention, the heat generation amount of the heating element on the reference side (envelope passing side) is increased, and according to the second aspect of the present invention, the pressure roller By lowering the hardness on the reference side, it is possible to obtain an effect of compensating for a decrease in fixability due to insufficient fixing pressure on the reference side.

According to the third, fourth or fifth aspect of the present invention, the fixing pressing force on the reference side (envelope passing side) of the fixing means in the first or second aspect of the invention is reduced by the rotational force of the roller. Can be realized by the action of the cam utilizing the above, and an effect that a complicated configuration and extra energy are not required can be obtained.

[Brief description of the drawings]

1A is a cross-sectional view illustrating a configuration of a fixing device of an image forming apparatus according to a first embodiment of the present invention, FIG. 1B is a configuration diagram of a halogen lamp, and FIG. FIG.

FIG. 2 is a perspective view of a pressure roller of an image forming apparatus according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view of a fixing device viewed from a sheet passing side of an image forming apparatus according to a third embodiment of the present invention.

FIG. 4 is a perspective view of a pressing force reducing mechanism of an image forming apparatus according to a third embodiment of the present invention as viewed from a sheet passing side;

FIG. 5 is a sectional view of an end portion of a fixing device of an image forming apparatus according to a fourth embodiment of the present invention.

FIG. 6 is a sectional view of an end portion of a fixing device of an image forming apparatus according to a fourth embodiment of the present invention.

FIG. 7 is a cross-sectional view illustrating a basic configuration of a fixing device of a conventional image forming apparatus.

FIG. 8 is a cross-sectional view of a fixing device of a conventional image forming apparatus.

FIG. 9 is a cross-sectional view of a fixing nip portion for explaining a mechanism of generation of a fixing envelope wrinkle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing roller 3 Fixing roller core metal (shaft) 4 'One side light distribution enhancement heater (heating element) 6 Pressure roller 6' Partial low hardness pressure roller 8 Pressure roller core metal (shaft) 12 Pressure spring 12 'Low Pressure spring 13 Side hole 14 Cam 14 'Cam receiving member (opposite member) 16 Holder 17 Wire 19 Envelope paper passing mode setting plate 20 Moving axis P Transfer material P' Envelope (transfer material)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-294477 (JP, A) JP-A-3-192382 (JP, A) JP-A-61-294475 (JP, A) JP-A-63-294 272741 (JP, A) JP-A-1-307786 (JP, A) JP-A-3-231786 (JP, A) JP-A-3-2368 (JP, U) JP-A-63-4566 (JP, U) Japanese Utility Model Application Hei 2-27163 (JP, U) Japanese Utility Model Application Hei 1-153566 (JP, U) Japanese Utility Model Application Hei 2-95065 (JP, U) (58) Fields studied (Int. Cl. ⁷ , DB name) G03G 15/20

Claims (5)

(57) [Claims] A transfer means for transferring the toner image formed on the image carrier onto a transfer material; and a fixing means for applying heat and pressure to fix the toner image on the transfer material. In an image forming apparatus using a method in which a transfer reference position of a transfer material is set to one of left and right end portions as a fixing unit, a fixing pressure on a reference side of the fixing unit is reduced, and heat generation of the identification fixing unit is performed. An image forming apparatus, wherein a heat generation distribution in a longitudinal direction of a body is set such that a heat generation amount on a reference side is higher than a heat generation amount on a non-reference side. A transfer unit for transferring the toner image formed on the image carrier onto a transfer material; and a fixing unit for applying heat and pressure to fix the toner image on the transfer material. In an image forming apparatus using a method in which the transfer reference position of the transfer material is set to one of the left and right ends as a fixing unit, the fixing pressure of the reference side of the fixing unit is reduced, and the application of the identification fixing unit is performed. An image forming apparatus, wherein a hardness distribution in a longitudinal direction of a pressure roller is set so that hardness on a reference side is lower than hardness on a non-reference side. 3. The means for reducing the fixing pressure of the fixing means is provided between the shafts of the reference-side fixing roller and the pressure roller, and acts to expand the space between the two shafts in accordance with the rotation of both rollers. 3. The image forming apparatus according to claim 1, comprising a cam having a portion and a portion that does not act. 4. The cam or the opposing member thereof is configured to be movable in the axial direction of the pressure roller or the fixing roller, and the cam or the opposing member is moved to a position where the cam or the opposing member can be brought into contact only when the envelope is passed. 4. The image forming apparatus according to claim 3, wherein: 5. The image forming apparatus according to claim 4, wherein the movement of the cam or the member facing the cam automatically interlocks with an operation of setting an envelope size in a paper feeding unit.