JPS62121474A - Fixing device for electrophotographic device - Google Patents

Abstract

PURPOSE:To obtain sufficient fixation effect even with special paper by moving forth and back transfer paper at a fixing part and performing fixing operation at each time. CONSTITUTION:The transfer paper passed on a guide plate 10 is heated while clamped between a couple of heat rollers 12a and 12b to fuse and fix a visible image on the transfer paper. When the special transfer paper enters a nip part N, a filler 17 is pushed to turn on a microswitch MS1 and turn off a microswitch MS2, and a motor rotates forward to rotate a lower roller 12b counterclockwise, so that the conveyed transfer paper is placed in the 1st fixing operation at the nip part N. When the transfer paper reaches the filler 18, the MS2 is turned on and the MS1 is turned off, and the motor reverses to move back the transfer paper, which is placed in the 2nd fixing operation. The operation is repeated by as many times as required according to the property of the transfer paper and then the paper is discharged to a paper discharge tray.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a fixing device used in an electrophotographic apparatus such as an electrophotographic copying machine, a printer, or the like.

Conventional technology A typical electrophotographic apparatus performs the following operations.

First, the photoreceptor is uniformly charged, a light image of the original image is exposed on the photoreceptor to form an electrostatic latent image on the photoreceptor, and the latent image is entirely developed with a developer to form a developed image. At the same time, the developed image and the transfer paper are completely superimposed, and the entire developed image is transferred onto the transfer paper by the action of a transfer charger, and after the developed image is fixed on the transfer paper by a fixing device, the transfer paper is discharged to the outside.

In the conventional apparatus, the fixing operation is performed only once while the transfer paper having a developed image passes through the fixing device.

Fixing operations include a method in which the transfer paper and developer are heated to melt and fix the developer, and a method in which the transfer paper and developer are heated and simultaneously pressurized for fixation.

When the transfer paper is so-called plain paper, a sufficient fixing effect can be obtained by performing the above-mentioned fixing operation. However, special transfer papers such as offset masters, certificate papers, postcards, etc. generally have poor fixing properties. This is because the temperature of the transfer paper does not rise sufficiently during fixing, and the toner in contact with the transfer paper is insufficiently melted, and the developer is not sufficiently fused to the surface of the transfer paper.

Purpose In view of the above points, an object of the present invention is to provide a fixing device that can obtain a sufficient fixing effect even on special transfer paper.

Structure The above object is achieved by appropriately reciprocating the transfer paper that undergoes the fixing operation by the fixing means to the front and back of the area (fixing area) where the fixing operation is performed by the fixing means.

The present invention will be fully explained below based on examples.

FIG. 1 shows a case in which one row of fixing devices is used in a photographic copying machine. In the figure, while the document table 1 carrying a document (not shown) moves to either the left or right direction in the figure, the lower surface (image surface) of the document is illuminated by a lamp 2V, and the reflected light (light image) is illuminated by the lamp 2V. ) is irradiated onto the belt-shaped photoreceptor 5 in the photoreceptor unit 4 via the convergent light transmitter array 3.

The surface of the photoreceptor 5 is uniformly charged by V by the charger 6 prior to the above-mentioned photoimage exposure, so that the photoreceptor 5 has an electrostatic charge corresponding to the image of the original on the surface of the photoreceptor 5 due to the photoimage exposure. A latent image is formed.

This electrostatic latent image is developed by the developing device 7 to become a developed image. This developed image is transferred to the transfer paper fed from the paper feed tray 8 (
(not shown) and is transferred onto transfer paper by the transfer charger 9.

The transfer paper, which now has a developed image, passes over the guide plate 1° and is conveyed to the fixing device 11. In this embodiment, the fixing device 11 is constituted by a so-called heating roller fixing device.

That is, the transfer paper that has passed through the guide plate 1o is heated while being held between a pair of heat rollers 2a+ and 12b serving as fixing elements, thereby melting and fixing the developed image onto the transfer paper. The transfer paper that has undergone the fixing process is discharged to the paper discharge tray 13. In order to heat the heat rollers 12a and 12bi, a heater 14 is provided inside one of the rollers, for example, the upper roller 12a. Further, in order to convey the transfer paper to the paper discharge tray 13 side, the upper roller 12a rotates clockwise and the lower roller 12b rotates counterclockwise. You are free to decide which roller to drive, but in the following explanation, the lower roller 12b
'i shall be driven.

When the transfer paper is so-called plain paper, while the transfer paper on the guide plate 10, that is, the transfer paper that has reached the VC and has all the unfixed developed image, passes through the pair of heat rollers 12a++2'b once, the developed image is sufficiently developed. It is fixed on the transfer paper with a certain strength.

However, if the transfer paper is so-called special paper,
A sufficient fixing effect cannot be obtained with one fixing operation. Therefore, in this embodiment, the lower roller 12bi, which is a driving roller, is made to be able to rotate in both directions, and the rotation of the lower roller 12b in the opposite direction is repeated multiple times depending on the properties of the transfer paper.
Transfer paper is moved back and forth in the front direction (to the right in the figure) and the back direction (to the left in the figure) of the nip area between the transfer paper 2a and 2b (i.e., the fixing area of the fixing device 1), thereby transferring the transfer paper. The fixing operation on the paper is performed a plurality of times6, and the paper is discharged to the paper discharge tray 13 after the fixing operation is performed a plurality of times.

By performing the fixing operation multiple times, a sufficient fixing effect can be obtained even on special transfer paper.

Various methods can be considered for moving the transfer paper back and forth across the roller nip. An example is shown below.

FIG. 2 shows the mechanical configuration of one example.

Reference numerals 15 and 16 are separation claws provided on both sides of the nip N between the earthmoving rollers 12a and 12b, and regardless of the rotational direction of both rollers, either separation claw can be used to separate the upper roller 12a. This removes the attached transfer paper. MSI and Mg2 are microswitches provided on both sides of the nip portion N. These switch MSI
,, Mg2 turns ON when the fillers 17 and 18 rotate in the counterclockwise direction (direction A) in the figure.

When the transfer paper moves toward the paper discharge tray 13, the fillers 17 and 18 are rotated in the A direction by the leading edge of the transfer paper.

FIG. 3 is a control circuit diagram for controlling the operation of the mechanism shown in FIG. 2. Further, FIG. 4 is a timing chart showing the state of control. The operation will be explained below based on these figures.

Special transfer paper that requires multiple fixing operations is used in the nip area N.
When someone comes, the front filler 17 is first pushed in the direction A and the MSI is turned on. At this time, the back switch MS2 is OFF, so the reverse relay RA2 is OFF, and the normally open contact RA2-1 of that relay is OFF.
And the normally closed contact RA2-2 is ON. MSI and 3
When A2-2 turns ON, forward rotation relay RAI turns ON,
As a result, the normally open contact RAI-1 of that relay turns ON.
Then, the normally closed contact RAI-2 turns OFF.

When RAI-1 is turned on, motor M rotates forward.

This motor M is drivingly connected to the lower roller 12b,
As the motor M rotates forward, the lower roller 12b moves to the second position.
It rotates counterclockwise in the figure, thereby conveying the transfer paper in the paper discharge direction. The transfer paper transported in this manner undergoes the first fixing operation at the nip portion N between the rollers.

The transfer paper that has undergone the first fixing process has the back filler 18.
When it reaches, the filler 18 moves in the direction A and the switch MS2 is turned on. However, at this time, the forward rotation relay RAI
is still ON, and therefore RAI-2 is OFF, so the reverse rotation relay RA2 does not turn ON, and therefore the motor M continues to rotate in the normal direction.

After that, when the trailing edge of the transfer paper passes the front filler 17, MSI turns OFF, and therefore forward rotation relay RAI turns OFF.
FF % Contact RAI -1 is QFF, and contact RA
I-2 is turned ON. At this time, Mg2 is ON, so when RAl-2 turns ON as described above, reverse relay RA
2 turns ON, and as a result, RA2-1 turns ON, and RA2
-2 becomes OFF. When RA2-1 is turned on, the motor M starts to rotate in reverse, the lower roller 12b rotates clockwise in FIG. 2, and the transfer paper moves backward. At this time of returning, a second fixing operation is performed at the nip portion N.

When the motor M reverses and the transfer paper moves backwards, MSl becomes O.
It becomes N. However, since RA2-2 is OFF, the forward rotation relay remains OFF, so that the motor M continues to rotate in reverse.

When the leading edge of the transfer paper (towards the left in the figure), which undergoes the second fixing operation while going backwards, passes the back filler 18,
Mg2 turns OFF, turning reverse relay RA2 OFF, and as a result, RA2-1 turns OFF and RA2-2 turns ON. At this time, since MSl is 0NPC, the forward rotation relay RAI is turned on, and the motor M starts rotating forward again, so that the transfer paper is conveyed in the paper discharge direction.

The above operation is repeated a necessary number of times depending on the properties of the transfer paper, and then the paper is discharged to the paper discharge tray 13 (FIG. 1).

The number of times the transfer paper is to be reciprocated is set in advance in the reciprocating motion counter CON shown in FIG. Reciprocating motion counter CO
N counts the number of times the transfer paper moves back and forth, and when the count reaches the above set value, turns on the paper ejection relay RA3. R.A.
When 3 is QN, the contact RA3-1, which is a normally open contact of 1 and is connected in parallel with the front switch MSI, is turned ON. Therefore, the rear edge of the transfer paper (the rear edge when viewed from the paper ejection direction) passes all of the front filler 17 and switches M.
SI is OFF and Temo RAI remains ON,
As a result, the motor M continues to rotate fully in the normal direction, and the transfer paper is discharged to the outside of the machine.

When relay RA3 is set to QFF, forward rotation relay RAI becomes O.
The motor becomes FF and the motor M stops.

Although a control circuit using a relay has been shown above as an example of controlling the reciprocating motion of the transfer paper, the present invention is not limited to this, and a control circuit using a transistor or a computer control using a microcomputer can also be used.

In the example of the actual rIJ shown in FIG. 2, separation claws 15 and 16 are provided on both the front and rear sides of the upper roller 12a, so that
According to the embodiment shown in FIG. 1, the fixing device 11 is separate from the main body 19 of the copying machine, and as shown in FIG. It can be pulled out to a position away from the main body 19 at any time. The heat rollers 12a and 12b are heated to a high temperature for heat fixing. Therefore, if the heat fixing operation is performed while the fixing device 11 is kept close to the copying machine main body 19 as shown in FIG. 1, the humidity of each device inside the copying machine will increase, causing various inconveniences. For example, when the temperature of the photoreceptor 5 and surrounding equipment increases, image quality may deteriorate due to changes in characteristics.

In this case, a method has already been considered in which a blower fan is installed at a suitable location within the copying machine to prevent the heat of the fixing device 11 from being transmitted into the copying machine. However, this method has the disadvantage that the multi-gear machine becomes larger due to the provision of the blower fan and the blower path, and at the same time, the cost increases.

On the other hand, as described above, if the fixing device 11 is structured so that it can be pulled out from the main body 19 and the heat fixing work is performed in the pulled out state, the heat from the fixing device 11 is transferred between the copying machine main body 19 and the fixing device 11. It is dissipated along with the air flow F between the main body 19 and the devices inside it.

In addition, in the heat fixing work in this case, the copying machine main body 19
The transfer paper that has passed through the guide plate 10 further passes over the auxiliary guide plate 20 and is sent to the fixing device 11. Fixing device 1
1 is stored in a position close to the copying machine main body 19 as shown in FIG. 1, and the auxiliary guide plate 20 is located below the guide plate 10 as shown in FIG.

Performing the fixing operation while the fixing device 11 is pulled out from the main body 19 has the following effect in addition to the heat dissipation effect described above. That is, if the fixing operation and the reciprocating operation of the transfer paper are performed with the fixing device 11 in the stored state shown in FIG. Otherwise, the transfer paper may be contaminated, or the transfer paper may be contaminated. On the other hand, if the transfer paper is reciprocated with the fixing device 11 separated from the main body 19 as in this embodiment, contact with the photoreceptor etc. can be avoided and stains can be prevented.

When the fixing device 11 is separated from the VC main body 19 to perform the fixing operation, it is necessary to prevent the fixing operation from being performed inadvertently in the stored state (the state shown in FIG. 1). .

In order to achieve this purpose, it is desirable to provide a switch that is turned on and off in conjunction with the draw-out and storage of the fixing device 11, and to prohibit the entire fixing operation or copying operation when the fixing device 11 is stored.

When a copying operation is not performed, that is, when the fixing device 11 is not in use, the fixing device 11 is retracted to a position close to the main body 19 (state 1 in FIG. 1). In this state, the FM camera has a compact shape as a whole.

Various configurations are conceivable that allow the fixing device 11'lzc to approach and separate from the main body 19. One line is shown below.

In FIG. 6, the fixing device 11, whose external shape is shown by a chain line, is provided with a sliding member 21 that protrudes from the lower right corner. ) A guide rail 2 having a space with a rectangular cross section fixed within
You can move along 2.

A stopper 23 is provided inside the sliding member 21. The tip (right end) bent portion 23a of the stopper 23 protrudes outward from the side window 24 of the sliding member 21, and when the protruding portion collides with the end surface of the guide rail 22, the fixing device 11 is moved toward the copying machine main body 19. Pushing is prevented. Pushing of the fixing device 11 is prevented in this way when the temperature of the heat rollers 2a and 12b is high.

The stopper 23 can rotate around a bin 25 fixed to the frame of the fixing device 11, and its rear end (left end) is in contact with a cam 26. The cam 26 is fixed to the lower end of a vertically extending shaft 27, and the upper end VC of the vertical shaft is connected to the pulley 28.
is fixed. Both ends of the wire 29 wound around the pulley 28 are tied to two bins 30a and 30b, respectively, which are fixed to the machine frame. A spring 32 is inserted into one side of the wire 29. Further, on the other side of the wire 29, there is a cylindrical moisture sensing element 33 made of a so-called shape memory alloy.
is inserted in between.

The shape memory alloy used as the temperature sensing element in this example has a shape and rigidity unique to the body when V is at high temperatures, but when Vζ is at low humidity, it has the property that as the rigidity decreases, the shape of Vζ tends to change. are doing.

With the above configuration, when the fixing device 1 is pulled out from the copying machine main body 19 and the fixing operation is completed, the heat roller 12
Since the temperature at point a is high, the temperature sensing element 33 maintains its original length and is in the state shown in the figure. In this state, the protruding cam 26a of the cam 26 is pushing the stopper 23,
A tip 23a of the stopper 23 projects outward from the window 24 of the sliding member 21.

When no fixing work is performed and the heat roller 12a is at low humidity, the temperature sensing element 33 is pulled by the spring 32 due to the properties of the shape memory alloy, and the pulley 28 rotates as shown by arrow E. As a result, the cam 26 also rotates in the same direction, and the four portions 26b abut against the rear end of the stopper. Then, the stopper 23 rotates as shown by arrow F around the bottle 25,
As a result, the bent tip 23a is drawn into the window 24. In this case, the sliding member 21 can freely slide into the guide rail 22, so that the entire fixing device 11 can be moved toward the main body of the copying machine.

In this way, when the fixing device 11 is at a high temperature, the fixing bag #
Even if an attempt is made to store all the parts 11 into the main body, this is prevented by the action of the stopper 23, so it is safe for the operator.

FIG. 7 shows another example for making the fixing device 11 detachable. This example differs from the example shown in FIG.
The temperature is detected by the thermistor 35V placed near a, and the solenoid 34iON is activated based on the detection result VC.
It is to turn it off.

A control circuit convenient for controlling the entire embodiment is shown in FIG. 8. In the figure, the thermistor 35, heater 14, and solenoid 34 are all indicated by the same reference numerals as in FIG.

Both CMPI and CMP2 are comparators.

The above description takes a so-called heat roller fixing device as an example. However, the present invention is not limited to this, and can be applied to various other fixing devices. For example, as shown in FIG. 9, the present invention can also be applied to a fixing device in which the transfer paper passes under a heat source 36 and a heat reflective material 37. In this case,
A heat source 36 and a heat reflector 37 act as fixing elements.

Incidentally, if the structure is such that the transfer paper can be moved back and forth between the front side and the back side of the fixing area of the fixing means as in the present invention, after the transfer paper is discharged unfixed, it is moved back and forth in the backward movement process V. You can also do the fixing work there. Originally, when the IS is a long one, the transfer paper sometimes straddles between the transfer section and the heat roller of the fixing means, and in this case, image blur etc. may occur due to the difference in the linear speed of the transfer paper between the two positions. This may cause inconvenience.

As described above, if the entire transfer paper is discharged as an unfixed sheet and then fixed, image blur due to linear speed deviation will be eliminated.

Effects According to the present invention, all the fixing parts of the transfer paper are moved back and forth,
Since the fixing work is performed each time, a sufficient fixing effect can be obtained even on special paper.

[Brief explanation of drawings]

1' is a side sectional view of a copying machine using a fixing device according to the present invention, FIG. 2 is an enlarged view of one row of fixing devices, FIG. 3 is a control circuit diagram, FIG. 4 is a timing chart, and FIG. 6 is a perspective view of an example of the drawer structure of the fixing device, FIG. 7 is a perspective view of another example of the drawer structure, and FIG. 8 is a perspective view of another example of the drawer structure of the fixing device. FIG. 7 is a diagram showing an example of the control circuit, and FIG. 9 is a diagram showing a main part of an embodiment of the pond of the present invention. ]2a, 12b...Fixing element, 15.16...Separation claw Figure 3 Figure 4 Knee roll

Claims (7)

[Claims] (1) An unfixed image is formed on the transfer paper, and while the transfer paper with the unfixed image is conveyed on the transfer paper conveyance path, the unfixed image is fixed onto the transfer paper by a fixing element. In the fixing device of an electrophotographic device, which then discharges the transfer paper to the outside, the transfer paper can reciprocate in the front and back directions of the area where the fixing operation is performed by the fixing element, and the properties of the transfer paper are A fixing device characterized in that the transfer paper is ejected after being reciprocated as appropriate depending on the situation. (2) The fixing device according to claim 1, wherein the fixing operation can be performed with the fixing element separated from the main body of the electrophotographic apparatus. (3) The fixing device according to claim 2, wherein the fixing element is a heat fixing element that heats the unfixed image and fixes it on the transfer paper. (4) The fixing device according to claim 1, wherein the fixing element is a roller fixing element having a pair of rollers, and the transfer paper is moved back and forth by rotating at least one of the rollers in forward and reverse directions. . (5) The fixing device according to claim 4, characterized in that separation claws for separating the transfer paper from the rollers are provided before and after the pair of rollers. (6) The fixing device according to claim 2, wherein the fixing element is pulled out from the main body of the electrophotographic apparatus so that they are separated from each other. (7) A means is provided to prevent the fixing element from returning to a position close to the electrophotographic device until the temperature of the fixing element falls below a certain temperature after heat fixing work is performed in a separated state. The fixing device according to claim 3, characterized in that: