JPS63206789A - Image forming device - Google Patents

Abstract

PURPOSE:To improve separability of paper after fixing from a heating roller by adjusting the pressurizing force of a press roller by a pressure converting means. CONSTITUTION:A heater 43 is lighted to heat the heating roller to about 185 deg.C surface temp. so that this image forming device is ready for a copying operation when a power supply is turned on. A guide selector 81 of a supplying means 50 is again set to a solid line position and a guide selector 87 is set to a broken line position when, for example, a synthetic copying mode is assigned. The pressurizing force of the press roller 42 is set at 80kg which is the same as the pressure at the time of executing copying just once. Copying and developing are then executed. Paper P is supplied between this photosensitive body 2 and an electric charger 31 for transfer, by which a toner image is transferred to the paper P. The paper P is stripped from the surface of the photosensitive body 2 by an electric charger 36 for stripping and is fixed 40. A 2nd original is then set on a platen 3. The pressure converting member 60 is actuated to change over the pressurizing force to 100kg when a print key is pushed. The second fixing is thus executed. The separability of the paper P is improved when the pressurizing force is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application 1] The present invention relates to an image forming apparatus used in an electronic copying machine or the like having editing functions such as double-sided copying and composite copying.

[Prior Art] Image forming apparatuses have been used in electronic copying machines and the like, and in recent years, editing functions such as double-sided copying and composite copying have been enhanced in electronic copying machines and the like. As a prior art related to such an image forming apparatus, for example, Japanese Patent Application Laid-Open No. 142-1989
This method has been proposed in Japanese Patent Application Laid-open No. 373, Japanese Patent Application Laid-Open No. 150072-1982, and Japanese Patent Application Laid-open No. 150073-1987. The techniques disclosed in these publications are intended to prevent wrinkles or curls from occurring in paper during double-sided copying and composite copying, and are designed to reduce the fixing strength such as the pressure applied during the first or second fixing process. It is configured to be set low until the final round.

[Problems to be Solved by the Invention] In an image forming apparatus having a conventional fixing device consisting of a heating roller and a pressure roller, the separation of the paper when the paper is sent out from both rollers depends on the temperature of the paper. The higher the score, the worse it tended to be. Therefore, in double-sided copying and composite copying where one sheet of paper is copied multiple times, the paper that is fixed from the second time onwards is heated once by the heating roller, so the separation of the paper is difficult. It tended to get worse.

In such a state, the toner on the paper tends to adhere to the back portion (the surface that guides the paper backward) of the separation claw provided to separate the paper from the heating roller. If the toner adheres to the sheet as a result, there is a problem that images may be lost on the paper that is subsequently separated by the separation claw, or the adhered toner may solidify and cause a paper jam. Note that the techniques disclosed in the above-mentioned publications do not prevent toner from adhering to the separation claw.

Additionally, if the pressure roller exerts a high pressure on the heating roller during fusing, the paper will curl significantly, and paper jams may easily occur when the paper is transported to the sorter after fusing or during the second copying process. There is also the problem.

The present invention is intended to solve the above problems, and its purpose is to improve the separation of paper after fixing even in double-sided copying and composite copying, to prevent toner from adhering to the separating claw, and to prevent heat curl of paper. To provide image-forming eight mushrooms that are less likely to cause inconveniences such as paper jams.

Means for Solving Problem E] The image forming apparatus of the present invention includes an image forming means for forming a latent image on an image carrier, and a developing device for developing the latent image formed by the image forming means. , a transfer device that transfers the image on the image carrier developed by the development device onto a sheet of paper, a fixing device that fixes the image on the paper transferred by the transfer device, and an image fixed by the fixing device. In an image forming apparatus that selectively forms an image once or multiple times on one sheet of paper, the fixing device includes A heating roller that contacts the surface on which the image is transferred, a pressure roller that rotates in circumferential contact with the heating roller and presses the paper, and a pressure roller that holds the pressure roller and presses it toward the heating roller. The pressing force of the member and the pressure member is set to the same pressing force when performing the first fixing on the same paper only once, and when performing the second fixing on the already fixed paper. The present invention is characterized by comprising a pressure converting member that sets a pressure higher than the first pressure.

[Operation] In the image formation vtW1 of the present invention, image formation is selectively performed only once or multiple times on one sheet of paper.

When image formation is performed only once, a latent image is first formed on an image carrier by an image forming means, and after the latent image is developed by a developing device, it is transferred onto a supplied paper by a transfer means. . Then, the paper is sent to a fixing device, and the image on the paper is fixed on the paper by being heated and pressurized by a heating roller and a pressure roller. During this fixing, the pressing force of the pressure roller against the heating roller is set to an appropriate predetermined pressing force.

In addition, when image formation is performed multiple times on the same sheet of paper, the first
A second image formation is performed. During this first establishment,
The pressing force of the pressure roller against the heating roller is set to the same predetermined pressing force as when fixing is performed only once. Thereafter, the paper is again supplied to the transfer means by the supply means. Then, the second latent image formed on the image carrier by the image forming means is developed by the developing device, and the developed image is transferred onto the above-mentioned paper fed again by the transfer means, and then the fixing device 2 It is sent to and fixed. This second
During the first fixing, the pressure converting member sets the pressure of the pressure roller against the heating roller to an appropriate predetermined pressure that is higher than that during the first fixing.

[Embodiments] Specific embodiments of the image forming apparatus of the present invention will be described below with reference to the drawings.

Figure 1 shows a main body 1 of a copying machine equipped with an image forming device of this embodiment.
This is an outline of the This body forming apparatus includes an image forming means 10, a developing device I! 20, a transfer device 30, a fixing device 40, and a resupply means 50.

The image forming means 10 forms a latent image on the outer peripheral surface of the photoreceptor 2, and exposes and scans an original set on a glass original mounting table 3 fixed to the upper surface of the copying machine main body 1. It consists of an optical system consisting of an exposure lamp 11, mirrors 12, 13, 14, 15, and a copying lens 16. The optical system reciprocates along the lower surface of the document table 3, and during the forward movement (
When moving in the direction of arrow a), the mirrors 73 and 74 move at half the speed of the mirror 12 so as to keep the optical path length constant. In this optical system, during exposure scanning, the irradiation light from the exposure lamp 11 hits the original, the mirrors 12, 13, and 14 in that order, is reflected, passes through the copying lens 16, is further reflected by the mirror 15, and is exposed to light as an image carrier. The photoreceptor 11 is guided by the photoreceptor 11 and arranged so that an image of the document is formed on the outer peripheral surface of the photoreceptor 11 . Note that the photoreceptor 2 is designed to rotate in the direction of the arrow.
First, the main charger 4 charges the surface of the document, and then the image of the document is exposed to slit light to form a latent image.

The developing devices 5 and 20 develop the latent image formed on the surface of the photoreceptor 2 with toner. This developing device 20
The magnet roller 21 includes a magnet roller 21 that faces the outer circumferential surface of the photoreceptor 2 and is disposed in close proximity thereto, and a bucket portion 22 that supplies toner to the magnet roller 21 . The toner mixed with the carrier and stored in the bucket portion 22 is attracted to the outer circumferential surface of the magnet roller 21 by magnetic force, and then adheres to the outer circumferential surface of the opposing photoreceptor 2 due to the potential difference, and a latent image is developed. .

The transfer means 30 is a JJ! The latent image formed on the photoreceptor 2 is transferred onto a supplied sheet of paper. In this embodiment, the transfer is performed using a transfer band 1131 placed near the photoreceptor 2. After the paper P is fed one by one from the paper feed cassette 32 by the paper feed roller 33, it is guided through the paper guide path 34 to the registration roller 35.
5 and sent to the transfer means 30. Then, the paper is supplied between the transfer charger 31 and the rotating photoconductor 2, and the transfer charger 31 applies a predetermined voltage to remove the toner from the surface of the photoconductor 2 by electrostatic adsorption. It is transferred onto paper. Immediately after transfer, the paper is removed from the surface of the photoreceptor 2 by the peeling charger 36! ! Il#l
and is sent to the fixed W unit N40 by the conveyor belt 37.

The fixing device 40 fixes the image on the paper 1 transferred by the transfer means 30. As shown in FIG. 2, the fixing device 40 includes a heating roller 41 that contacts the surface of the paper onto which the toner image has been transferred, a pressure roller 42 that rotates in circumferential contact with the heating roller 41 and presses the paper, and a pressure roller 42 that rotates in circumferential contact with the heating roller 41 and presses the paper. roller 42
When fixing the 1st rgJ, the pressure member 50 that holds and presses the heating roller 41 is set to the same pressure as when fixing is performed only once, and the pressure of the pressure member 50 that holds the When performing the second fixing on the fixed paper, the pressure converting member 60 is configured to set a pressure higher than the first pressure.

The heating row 541 has a diameter of 60III11 and a length of 31
ca+.

It has a cylindrical shape with a thickness of 6u+, the surface of which is coated with Teflon, and a heater 43 is disposed inside it. On the outer circumferential surface of the heating roller 41, there are provided a separating claw 45 whose tip end is biased toward the paper P sending side, a thermistor Th1 as a temperature 11fi) element, and an oil coating cleaning roller 44.

On the other hand, the pressure roller 42 has a diameter of 60 mm and a length of 31011 mm.
It has a cylindrical shape, and the surface of an aluminum core bar 428 is coated with a silicone rubber layer 42b having a thickness of 6IIIl. This pressure roller 42 is rotatably held by a side plate 51, which will be described later, via a bearing 48.

The pressure member 50 includes a pair of side plates 51 and two compression springs 52.
It becomes more. A pair of side plates 51 hold both ends of the pressure roller 42, and are held in the copying machine main body 1 so as to be swingable about a fulcrum 53. The compression spring 52 has one end locked to the side plate 51 and the other end locked to a side plate of the fixing device (not shown). It is always energized.

As shown in FIGS. 6 and 7, the pressure variable member 60 includes a solenoid 61, a spring clutch 70 that is activated by turning on and off the solenoid 61, and a pressure variable cam 62 that rotates via the spring clutch 70. It is configured.

The spring clutch 70 uses a kick spring 71, and the kick spring 71 includes a cylindrical portion 72a of a gear 72 driven via a connecting gear 79, and a cylindrical drum disposed opposite the cylindrical portion 72a. 73, one end is locked to a positioning collar 74 fixed to the drum 73, and the other end is connected to a kick spring 7.
It is locked by a ratchet 75 arranged along the outer periphery of 1. As a result, if the ratchet 75 is not prevented from rotating and the gear 72 is rotating in the direction indicated by the arrow due to the rotation of the connecting gear γ9, the kick spring 71 will cause the gear 7 to rotate.
The kick spring 71 is loosened and the gear 72 is rotated idly by tightly wrapping the drum 73 around the drum 73 and the cylindrical portion 72a of the radiator 75 to prevent the rotation of the radiator 75. It looks like this. Also drum 7
3 is fitted and fixed to a shaft 76 disposed as a shaft portion of the spring clutch 70, and a variable pressure cam 62, which will be described later, is fixed to the tip of the shaft 76. Therefore, the variable pressure cam 62 rotates as the drum 73 rotates.

The solenoid 61 has bifurcated claws 61a and 61b that swing on and off, and the claws 61a and 61b are arranged along the outer peripheral surface of the ratchet 75. When the solenoid 61 is off, the tip of one pawl 61a is in pressure contact with the outer circumferential surface of the ratchet 75, and when the solenoid 61 is on, the tip of the other pawl 61b is in pressure contact with the outer circumferential surface of the ratchet 75, so as to engage with a groove 758 formed on the outer circumferential surface of the ratchet 75. It has become. Therefore, at the moment when the solenoid 61 is turned on and the engagement between the pawl 61a and the groove 75a is disengaged, the ratchet 75 rotates and the kick spring 71 is tightened due to the force acting on the cylindrical portion 72a of the gear 72 and the drum 73, and the clutch and gear 7
2, the drum 73 and the variable pressure cam 62 are caused to rotate via the shaft 76. When the pawl 61a is released, the other pawl 61b is pressed against the outer peripheral surface of the ratchet 75, and the groove 7 of the rotating ratchet 75
When engaged with 5a, it prevents its rotation.

As a result, the tightening force of the kick spring 71 is loosened, the clutch is disengaged, the gear 72 idles, and the variable pressure cam 6
2 stops at a predetermined position.

The variable pressure cam 62 is an eccentric cam, and is fixed to both ends of the shaft 76, respectively. and the compression spring 5
One part of the outer circumferential surface thereof is placed in contact with a support portion 51a provided on the side plate 51 against the biasing force of 2. The variable pressure cam 62 is caused by the spring clutch 70 to stop at a point S on the outer circumferential surface farthest from the axis when the solenoid 61 is off, and stops at a point S closest to the axis when the solenoid 61 is on. It is set as follows. Further, the biasing force of the compression spring 52 is applied to the variable pressure cam 6
2 is set so that when it stops at S, the pressing force of the pressure roller 42 against the heating roller 41 is 80 kg/31 cm, and when it stops at T, the pressing force is 100 kg/31 cm.

Note that the pressure of the pressure roller 42 is increased by pressing the print key a second time after the first fixing is performed in both-sided copying mode and composite copying mode.
1 is turned on, and the solenoid 61 is turned off by the second fixing completion signal, thereby converting the fixing state.

The paper P carrying the toner image sent to the fixing device ff140 is sent from its leading edge between the heating roller 41 and the pressure roller 42, and is heated and pressurized to fix the toner image on the paper. After that, it is separated from the heating roller 41 by a separating claw 45 and sent out.

The supply means 80 again supplies the fixing device ff4 as shown in FIG.
0 is again supplied to the transfer means 30, and is composed of guide selectors 81, 87, a paper guide path 82, and an intermediate stacker 83. One of the guide selectors 8 is swingably provided, and at the time of the first fixing during multiple copying, it is in the position shown by the solid line in FIG. A guide path 82 leads to an intermediate stacker 83. Also, during the second fixing and the normal one-time copy fixing, the paper P sent out from both rollers 41 and 42 is placed at the position shown by the broken line in FIG.
．． 85 and onto a paper discharge tray 86.

The other guide selector 87 is also swingably provided, and in the case of double-sided copying, it is in the position shown by the solid line in FIG.
When the trailing end of the sheet P, which is conveyed and nipped by the guide roller 88, passes through the guide selector 87, the guide roller 88 rotates in the opposite direction to guide the sheet P to the intermediate stacker 83. In the case of composite copying, it is located at the position indicated by the broken line in FIG. 1, and the paper P is guided directly from the paper guide path 82 to the intermediate stacker 83.

The image forming apparatus of this embodiment configured as described above operates as follows. First, when power is turned on to the copying machine main body 1, the heater 43 is turned on to maintain the surface temperature of the heating roller 41 at approximately 185° C. and cooperate with the copying operation. Next, a selection key (not shown) on the operation panel provided on the main body 1 for copying.
When, for example, the composite copy mode is specified, the guide selector 81 of the supply means 50 is set again to the position shown by the solid line in FIG. 1, and the guide selector 87 is set to the position shown by the broken line in FIG. Further, the pressing force of the pressure roller 42 at this point is set to 80 kQ/31 cm, which is the same as when copying is performed only once on the same sheet. Then, the copying operation is started by pressing the print key on the operation panel, and the image of the first original placed on the original placing table 3 is exposed to slit light by the image forming means 10, and is projected onto the surface of the rotating photoreceptor 2. A latent image is formed. That Shungen 1st edition fi! 20 is activated, toner is attached to the rotating photoreceptor 2, and the latent image is developed as a toner image. At this time, 118 paper cassette 3
The IP is sent out from 2, guided by a pair of registration rollers 35, aligned, and on standby.

After the development has been completed, the simulated photoreceptor 2 continues to rotate.
A paper P is supplied between the photoreceptor 2 and the transfer charger 31. At this time, the paper P is brought into close contact with the surface of the photoreceptor 2 by electrostatic adsorption, and in this state, the transfer charger 31 is operated to transfer the toner image from the surface of the photoreceptor 2 to the paper P. Immediately thereafter, the paper P is peeled off from the surface of the photoreceptor 2 by the peeling charger 36 and sent to the fixing device 40. In the fixing device 40 , the toner image on the paper P is heated and pressed by a heating roller 41 and a pressure roller 42 to be fixed on the paper P, and the toner image is separated from the heating roller 47 by a separating claw 45 . During this first fixing, the pressing force of the pressure roller 42 is 80k.
Q/31cm, and as confirmed by the test results described later (see Figure 8), the ID of the toner image is 1.4.
Even when the value is , toner is unlikely to adhere to the separating claw. The paper P separated from the heating roller 41 after the first fixing is completed is guided by the guide selector 81 from the paper guide path 82 through the intermediate stacker 83 to the registration rollers 35, aligned, and then separated from the heating roller 41. Prepare for transfer and fixing. Then, a second original is set on the original placing table 3, and by pressing the print key, a latent image is formed on the surface of the photoreceptor 2 in the same manner as in the case of the first original, and is developed by the developing device 20. Note that the solenoid 61 is turned on by the press signal of the print key, and the pressure variable member 6 is turned on.
0 is activated. As a result, the pressing force of the pressure roller 42 against the heating roller 41 is increased from 80 kQ/31 cm to 100 k.
Switched to G/31cm and prepared for second fixing. At the same time, the guide selector 81 is switched to the position shown by the broken line in FIG.
, 42 to the paper discharge roller 85. Then, as the photoconductor 2 rotates, the paper P that was waiting on the registration rollers 35 is sent out, and the toner image on the surface of the photoconductor 2 is transferred to the paper P in the same manner as the first time, and then peeled off. It is sent to the room mounting W140 and fixed. At this time, the pressure roller 42 of the fixing device 40 is 100kQ/31
cm, and as confirmed by the test results described later (see Figure 9), the ID of the toner image was 1.4 cm.
Even when the value of is not shown, it is difficult for toner to adhere to the separating claw. Thereafter, the paper P on which the second fixing was performed is separated from the heating roller 41 by the separating claw 45, and then guided by the guide selector 81 to the paper ejection rollers 84, 85, and ejected onto the paper ejection tray 86 to be combined. Finish copying.

On the other hand, the pressing force of the pressure roller 42 is controlled by the solenoid 61 being turned off by the end signal when the second fixing is completed.
The pressure conversion member 60 switches from 100 ka/31 cra to 80 kQ/31 cm in preparation for the next copying operation. The photoreceptor 2 rotates one more time after the toner image is transferred to the paper P, and after the latent image is erased by an eraser lamp, it is cleaned by a cleaner device in preparation for the next image formation.

Note that when double-sided copying mode is specified, the paper P
This is the same as in the case of composite copying, except that the image is reversed by the guide selector 87 and the guide roller 88.

As described above, in the image forming apparatus of this embodiment, the pressing force of the pressure roller 42 against the heating roller 41 is 80 kg/31 cm during the first fixing, and 100 kg/31 cm during the second fixing. The pressure is converted by a pressure conversion member. Therefore, the separation of the paper P from the heating roller 41 after fixing was good, and it was possible to prevent toner from adhering to the separation claw 45. Therefore, inconveniences such as image defects and vapor jams due to toner adhesion to the separation claws 45 can be prevented.

In addition, compared to the case where the pressure roller 42 is always set at a constant high pressure force, there is less heat curling of the paper, which reduces inconveniences such as paper jams during the second copy or paper jams in the sorter. I was able to resolve it. Furthermore, it was possible to eliminate the occurrence of wrinkles during double-sided copying and composite copying.

In this embodiment, an example was shown in which the solenoid for converting the pressing force of the pressure roller is turned on using the mode designation key on the operation panel, but in other electrophotographic printers, signals from the host computer are used. It is also possible to do this by, etc.

(Test) When setting the pressing force of the pressure roller against the heating roller in the above example, the heating amount and image density were determined.

A test was conducted to investigate the occurrence of toner adhesion to the back of the separating claw in relation to (ID).

The results are shown in FIGS. 8 and 9. Here, the amount of heating is defined as heating temperature x heating time, tube width, and speed).

Figure 8 shows the results of one normal copying process.
The lower the ID or the greater the amount of heating, the less likely it was that toner would adhere to the separation claw. This means that if TO is low,
This is because the amount of toner (that is, adhesive) attached to the paper is small, making it easy to peel off. In addition, when heating m is large, the temperature of the toner during fixing increases and the cohesive force of the toner decreases, so the toner becomes moist and follows the behavior of the paper well, causing the paper to separate from the heating roller. This is because even if the toner image is cooled by coming into contact with a separating claw whose temperature is lower than that of the heating roller, the cohesive force of the toner does not increase enough to cause toner adhesion to the back of the separating claw.

Figure 9 shows the results of the second fixing after the paper has been warmed up by the first fixing, as in double-sided copying and composite copying, and compared to the case of normal one-time copying, the separation claw The results showed that toner adhesion was likely to occur. The reason for this is that heat curls occur on the paper, making it difficult to separate as it wraps around the heating roller, or because the paper is warmed up during the second fixing process, the cohesive force distribution within the toner is distorted, causing an inflection point. It is inferred that this occurs and breaks near the inflection point when separated from the heating roller, making it easier to adhere to the separating claw. This is similar to, for example, when two plates pasted together with an adhesive are peeled off, the warmed side is more likely to separate, and if both sides are heated, it is uncertain which side will separate.

From the above, in order to prevent toner from adhering to the separating claw, the characteristics shown in FIGS. It was confirmed that it is best to set the area within the range where toner does not adhere to the area.

[Effects of the Invention] As explained above, in the image forming apparatus of the present invention, the fixing device includes a heating roller that contacts the surface of the paper onto which the image is transferred, and a heating roller that rotates in circumferential contact with the heating roller and presses the paper. A pressure roller that holds the pressure roller and presses it toward the heating roller, and a pressure member that holds the pressure roller and presses it toward the heating roller, and applies the pressure force of the pressure member to the same sheet only once during the first fixing. The pressure converting member is configured to set the same pressing force as when performing the fixing, and to set the pressing force to be higher than the first pressing force when performing the second fixing on the already fixed paper.

Therefore, even in the case of double-sided copying and composite copying, by adjusting the pressing force of the pressure roller using the focus conversion member, the separation of the sheet after fixing from the heating roller is improved, and the 1- It is possible to prevent the adhesion of Qi.

Therefore, it is possible to eliminate problems such as image defects and paper jams caused by toner adhering to the separating claw.

Also, compared to the case where the pressure roller's pressure force is always set to a high pressure force during fusing, heat curling of the paper is less likely to occur, so paper jams occur during double-sided copying, composite copying, or paper jams in the sorter. It is possible to solve this problem and further reduce the occurrence of paper wrinkles.

[Brief explanation of the drawing]

FIGS. 1 to 7 relate to Embodiment 1 of the image forming apparatus of the present invention, FIG. 1 is a schematic configuration diagram of the main body of the copying machine, and FIG. 3 is a schematic configuration diagram of the fixing device; FIG. 3 is a side view showing the relationship between the solenoid and the ratchet corresponding to FIG. 2; FIG. 4 is a side view of the fixing device when fixing paper for the second time; 5 is a side view showing the relationship between the solenoid and the ratchet corresponding to FIG. 4, FIG. 6 is an exploded perspective view of the pressure variable member, FIG. 7 is a vertical sectional view of the pressure variable member, and FIGS. 8 and 9. The figure shows the state of occurrence of toner adhesion to the back of the separating claw in relation to the amount of heating and the 'tr@ density. Figure 8 is the figure for the first fixing, and Figure 9 is the figure for the second fixing. FIG. 1... Copying machine main body 2... Photoreceptor (@carrier)
10... body forming means 20... developing device 30...
- Transfer means 40... Fixing device 41... Heating roller 42... Pressure roller 50... Pressure member
60...Pressure conversion member 61...Solenoid

Claims (1)

[Claims] (1) An image forming means for forming a latent image on an image carrier, a developing device for developing the latent image formed by the image forming means, and an image on the image carrier developed by the developing device. The image forming apparatus includes a transfer means for transferring the image onto the paper, a fixing device for fixing the image on the paper transferred by the transfer means, and a re-feeding means for again supplying the paper fixed by the fixing device to the transfer means. In an image forming apparatus that selectively forms an image once or multiple times on a sheet of paper, the fixing device includes a heating roller that contacts the surface of the sheet on which the image is transferred, and a heating roller that contacts the surface of the sheet on which the image is transferred. A pressure roller that rotates in circumferential contact with the roller and presses the paper, a pressure member that holds the pressure roller and presses it toward the heating roller, and a pressurizing force of the pressure member for the first time. When fixing, set the pressure force to be the same as when fusing the same paper only once, and when performing the second fusing onto the already fixed paper, set the pressure force higher than the first pressure force. An image forming apparatus comprising a pressure converting member.