JPS62242979A - Offset preventive mechanism for fixing device - Google Patents

Abstract

PURPOSE:To roughly completely prevent the generation of an offset by maintaining a heat roller and a pressure roller in a suitable plus potential and a minus potential, respectively, and also, adjusting a surface potential state of the pressure roller to an optimum potential. CONSTITUTION:An unfixed form 40 is guided to a chute 38 in a state that a toner of a plus potential has been placed on it, and inserted between a heat roller 30 and a pressure roller 31. The heat roller 30 itself is held in an electrically insulated state, and by a gap l2 between a ring 36 and a ball bearing 34 which has been grounded, the surface potential of the heat roller 30 is maintained in about +0.4kV. Also, by a gap l2 between the surface of the pressure roller 31 and the tip of a destaticizing brush 37, the surface potential of the pressure roller 31 is kept in about -2kV. Accordingly, the toner the plus potential on the form 40 which has been inserted between the heat roller 30 and the pressure roller 31 receives force toward the paper surface side at all times, does not stick onto the surface of the heat roller 30 even after the fixation, and an offset can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an offset prevention mechanism for a fixing unit 5A in a P1 to roll system using toner in an image forming apparatus for a copying machine, a facsimile machine, and a printer shade. It is.

[The structure of plain paper copy lfi PPC using Kagenura toner is explained in the 4th section.
This will be briefly explained based on the diagram.

An original 3 is placed on a Braden glass 2 stretched over the L1 surface of the multi-lf machine casing 1, and the original 3 is irradiated with light by an exposure lamp 4 moving from below the platen glass 2.

The light reflected on the surface of the original through the platen glass 2 is reflected by the mirrors 5, 6, 7, 8, passes through the lens 9 on the way, reaches the surface of the photoreceptor 10, and forms an image.

Around the photoconductor 10, a charger 11,
Developing device 12. Transfer device 13. A cleaning device 14 and the like are arranged.

The surface of the photoreceptor is uniformly charged by the static charger 11, and the surface is exposed to light by the optical system to form an electrostatic latent image.

And the next step is the current f$! At step S12, toner particles 1 to 1 are attached, and the toner image thus formed is transferred to the transfer device 1.
3 onto the paper conveyed from one paper tray 15.

Toner remaining on the surface of the photoreceptor after the rotation 77 is scraped off by a cleaning device 14.

The paper that received the change/no' is fixed '4 Z I G W! The paper is fed, the toner is fixed on the paper, and the paper is ejected onto the υ1 output tray 17.

The present invention relates to the final step of fixing, which is the other side of the above-mentioned structure of paper copying.

There are various fixing methods, but the heat roll method is widely used as a fixing method that mainly uses conductive heat in combination with pressure.

A conventional example of this one-roll type fixing device is shown in FIGS. 5 and 6 and will be described.

As shown in FIG. 5, a pressure roll 21 is in contact with a heat roll 20, and a document 3 after transfer is passed between the heat roll 20 and the pressure roll 21.
It is something that passes through and is fixed.

The inside of the heat roll 20 is hollow, and a lamp 22 as a heat source is built in the center, and the secondary heat of the lamp 22 causes the inner circumferential surface of the heat roll 20 to become high in temperature, and heat is transferred to the outer circumferential surface by thermal conduction. .

The toner on the surface of the paper is melted by this conductive heat, penetrates into the fibers of the paper, and is further pressed onto the paper by the pressure of the pressure roll 21.

The heat roll 20 has a heat insulating collar 23 made of electric bamboo surrounding it near its edge, as shown in FIG. , is supported by one side plate 1-25 with a ball bearing 24 interposed on its outer periphery.

A flange 23a is formed on the outer edge of the heat insulating collar 23, and a ring 26 is fixed to the flange 23a to prevent the heat roll from shifting in the axial direction.

Since the outer shell of the ball bearing 24 is grounded, the ball bearing 24. The heat roll 20 is in contact with the ground via the heat insulating collar 23.

In addition, the removal brush 27 is applied to the surface of the pressure roll 21.
are in contact with each other, and the Brerasil roll 21 is also always in contact with the ground.

1<j"L, . . . 1Il (When the paper 3 to which the toner image has been transferred is inserted into the heat 1 call 20 and the pressure roll 21 with its surface facing upward in a fixing device such as the one described above, , the tonneau contacts the heat roll 20 and melts, thereby being fused to the paper.

The toner used here is positively charged.
After the transfer, there is a risk that so-called offset occurs, in which the toner is not completely fixed on the paper and adheres to the surface of the heat roll.

When this offset occurs, it may be transferred to the next sheet of paper after one rotation of the heat roll 20 and form an afterimage on the surface of the paper, or it may be transferred to the pressure roll 21 and the transferred images may be transferred to the back side of the paper. This may cause problems such as the formation of remnants when the image is transferred.

In particular, if the temperature of the rolls 1 to 20 is too low, even if the toner melts, the adhesion between the toner and the paper is insufficient, so a so-called cold offset occurs, and the temperature of the heat roll 20 decreases. If the temperature is too high, the portions where 1 to 2 and 3 are in contact with the rolls will melt too much, and 1 to 2 and 3 will be separated and a so-called hot offset will occur.

Conventionally, a material such as Teflon, which has good release properties, is applied to the surface of the heat roll 20, but since both the heat roll 20 and the pressure roll 21 are in contact with the ground, it is necessary to actively keep unfixed 1-toner on the paper side. However, even if the temperature Yα of the heat roll 20 is at an appropriate temperature, there is a drawback that an off-sera!-like phenomenon occurs on the surface of the heat roll 20.

The present invention has been made in view of the above, and its purpose is to
- The present invention provides an offset prevention method for the fixing device that prevents offset by appropriately wrapping the belt.

1. -J- for nl and 1. In the present invention, in a heat roller type fixing device using a positively charged nail, the peel roll is maintained at an appropriate positive potential. This is an offset prevention mechanism for the fixing device δ, which is composed of a heat roll potential maintenance stage, a pressure roll potential maintenance means that maintains the pressure roll at a negative potential, and a surface potential adjustment means that adjusts the surface potential state of the pressure roll. .

The surface of the P1-roll is maintained at a positive potential by the P1-roll potential maintaining means, and the i-Luna, which is also positively charged, repel each other, thereby suppressing the occurrence of offset in which the P1-Luna adheres to the heat roll side. I can do it.

In addition, the pressure roll is maintained at a negative potential by the pressure roll voltage holding means, and the surface potential state of the pressure roll is adjusted to the optimum potential by the surface potential adjustment means. It is also possible to prevent offset.

Hereinafter, since the toner is attracted to the paper based on the potential state of both the heat roll and the pressure roll as shown in (g), it is possible to almost completely prevent the occurrence of offset.

EMBODIMENT OF THE INVENTION An embodiment according to the present invention illustrated in FIGS. 1 to 3 will be described.

This embodiment is applied to a paper copying machine PPC having a heat roll type fixing device using a one-component magnetic toner and a one-component non-magnetic (positively charged) toner.

FIG. 1 is a modeled view of the open surface of the fixing device used in this embodiment.

As in the prior art example, a pressure roll 31 contacts the heels 30 from the knife, and a lamp 32 is built inside the be 1-roll 30.

The heat roll 30 is made of tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer (P
I'8) It is coated and made of pressure silicone rubber.

The unfixed paper 40 is placed on its surface with a positive potential I-lunar and guided by the inlet I-shoes 1-38 on the one side.
It is inserted between the l-li-ru 30 and the pressure roll 31.

Dimension J shown in Fig. 2: The support mechanism of the sea urchin heat roll 30 is almost the same as the conventional example, but the heat insulating collar 33 is made of polyphenylene sulfide (pps) with 40% glass filler.
It has insulation properties.

And a ball bearing 3 is attached to the outer periphery of the heat insulating collar 33.
The heat rail 30 is rotatably supported by the side play i.35 with the heat rail 30 interposed therebetween.

A flange 33a is formed on the outer edge of the heat insulating collar 33, and a ring 3G abuts against the flange 33a to prevent slippage.
is fixed.

The outer edge of the ring 36 is slightly bent inward in the axial direction of the heat roll to reduce the gap j2 with the ball bearing 34 to 1#l#
(Conventionally, this gap was about 2.5M).

Therefore, the peel 30 itself is kept electrically insulated, and the surface potential of the heat roll 30 is normally ←0.4 due to the gap j2 between the ring 3G and the grounded ball bearing 34. It is maintained at about V.

Further, a static eliminating brush 37 is disposed near the surface of the pressure roll 31 and below the inflator 1-chute 38,
The gap j1 between the surface of the pressure roll 31 and the tip of the static elimination brush 37 is set to 2#I#I (conventionally, this gap was Otrn).

Then, silicon dioxide powder 39 is applied to the surface of the pressure roll 31 to adjust the potential state of the surface.

The surface of the first press roll 31 and the static elimination brush 37
The surface potential of the pressure roll 31 is maintained at around -2 KV due to the gap A1 between the pressure roll 31 and the silicon dioxide coating.

The silicon dioxide powder 39 slightly moves to the surface of the heat roll 30 upon contact with the heat roll 30, and is also effective in adjusting the surface potential of the heat roll 30.

FIG. 3 shows the temporal changes in the surface potentials of the heat roll 30 and the pressure roll 31.

The surface potential of the -I roll 30 (solid line) is 〇, 4
KV, and the surface potential of the pressure roll 31 (
(solid line) is maintained at about -2V.

Conventional Pee 1~Roll 20. Pressure [1-Rule 21]
Heat [1-
The surface potential of the roll 30 is maintained high, and the surface potential of the pressure roll 31 is maintained low.

Therefore, the heat roll 30 and the pressure roll 31
The positive potential 1-NO on the paper 40 inserted between the paper 40 and the paper 40 always receives force toward the paper surface, and the fixing 19 also does not adhere to the surface of the heat roll 30, thereby reliably preventing offset 1-. I can do it.

According to the experimental results, no off-hits occurred even after more than 20,000 copies were made.

By applying silicon dioxide to the pressure roll 31, the electric condition of the pressure roll 31 and the heat roll 30 is adjusted, and the occurrence of offset is further suppressed compared to the case where silicon dioxide is not applied.

As described above, in this embodiment, the heat roll 30 is electrically insulated, the gap j2 between the ring 36 and the ball bearing 34 is adjusted, and the pressure roll 31 and the static elimination brush 3 are
The occurrence of offset can be easily prevented by simple improvements such as adjusting the gap J+ between the printer roll 31 and coating the printer roll 31 with silicon dioxide, and the cost can be reduced.

Although this embodiment is applied to a plain paper copying machine PPC, it can also be applied to printers other than PPC, facsimiles, etc., as long as they use -component positive potential toner and have a -1-roll type fixing device. It is something that should be done.

The present invention is capable of maintaining a constant temperature by adjusting and maintaining the surface potential of the heat roll and pressure roll at appropriate values. ? J to the device
It is possible to prevent the occurrence of off-cellar 1-.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional explanatory diagram of a fixing device according to an embodiment of the present invention, and FIG. 2 is a heat roll support RJ of the same embodiment. A diagram showing the IS, Figure 3 is a diagram showing the surface potential of the Hee I roll and pressure roll, and Figure 4 is a typical plain paper copy 1.
5 is a cross-sectional view of a conventional constant RF device, and FIG. 6 is a diagram showing the same conventional heat roll support mechanism. DESCRIPTION OF SYMBOLS 1...Multi'q machine casing, 2...Brain glass, 3...Original, 4...Exposure lamp, 5,6.7.8
... Mirror, 9 ... Lens, 10 ... Photoreceptor, 1
DESCRIPTION OF SYMBOLS 1... Charger, 12... Developing device, 13... Transfer device, 14... Cleaning device, 15... Paper tray,
16... Fixing device, 17... Extraction tray, 20...
Heat roll, 21...Pressure roll, 22.
... Lamp, 23 ... Heat insulation collar, 24 ... Ball bearing, 25 ... Side plate, 26 ... Ring, 27 ... Static elimination brush, 30 ... Heat roll, 31 ... Pressure Roll, 32... Lamp, 33... Heat insulation collar, 34.
...Ball bearing, 35...4J id plate,
36...Ring, 37...Static elimination brush, 38...
Inlet shoot, 39...silica wood powder,
40...Paper.

Claims (1)

[Claims] In a heat roll type fixing device using positively charged toner, a heat roll potential maintenance means for maintaining the heat roll at an appropriate positive potential, a pressure roll potential maintenance means for maintaining the pressure roll at a negative potential, and a surface of the pressure roll. An offset prevention mechanism for a fixing device, comprising a surface potential adjustment means for adjusting a potential state, and preventing the occurrence of offset.