JPS62131281A - Fixing method for both sides copying machine - Google Patents

Abstract

PURPOSE:To reduce deformation of copying paper due to thermal stress, to improve carrying property and to reduce caloric consumption of a fixing device by increasing the carrying speed of the copying paper at the fixing of the 2nd surface faster than that of the 1st surface. CONSTITUTION:A fixing roller in which a heater 6 is arranged as a heat source is rotated by a driving motor M and the rotational speed of the motor M is controlled by a control part 10. A press roller 8 is rotatably contacted with the fixing roller 7, holds the transfer paper 9 at a nip art with the fixing roller 7 and carries the transfer paper 9 to the discharge side. A toner image is fixed to the transfer paper by the pressing force to the nip part generated by pressure P to the press roller 8 and heating function. In the fixing process of the 2nd surface, the control part 10 controls the speed of the motor M by a signal indicating the fixing of the 2nd surface to increase the linear speed of the fixing roller 7.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fixing method for a copying machine having a double-sided copying function.

2. Description of the Related Art Double-sided copying machines are known that have the function of copying images on both the front and back sides of a conventional double-sided original or images of different originals on both the front and back sides of a single sheet of copy paper.

A double-sided copying machine uses a method in which images of two types of originals are sequentially formed on the same photoreceptor, transferred and fixed onto the first side of the copying machine, stored in an intermediate tray, and transferred and fixed onto the second side of copy paper. Then, two types of images of the original are formed on different photoconductors, and after the image on one photoconductor is transferred and fixed on the first side of the copy paper, another photoconductor is formed on the second side, which is the back side of the copy paper. A method of transferring and fixing an image is already known.

In conventional double-sided copying paper, fixing of the copying paper is carried out under the same conditions on both the first side and the second side in any system.

When double-sided copying is actually performed, the copy paper is heated during the fixing of the first side, the total moisture content decreases, and the temperature of the copy paper increases. Therefore, when the second side is fixed, the total water content of the copy paper is lower and the temperature is higher than that for the first side. However, since the second side is fixed under the same conditions as the first side, excessive heat is applied and hot offset occurs, and heat stress becomes large and deformations such as curling occur. This tends to cause sexual problems and wastes energy.

A further object of the present invention is to provide a fixing method that solves the above-mentioned conventional problems, does not cause deformation of copy paper, and can utilize energy effectively.

(2) Bottom In order to achieve the above-mentioned object, the present invention is characterized in that the conveyance speed of the copy paper during fixing on the second side is made faster than the conveyance speed during fixing on the first side.

The structure and operation of the present invention will be explained in detail with reference to embodiments shown in the drawings.

Since the structure of the double-sided copying machine itself is already known, the explanation thereof will be omitted.

In FIG. 1, copy paper, for example, transfer paper, is fed from a paper feed section 1 to an image forming section 2. As shown in FIG. The paper feed section 1 includes various members such as a paper feed tray, a paper feed roller, and a paper feed guide. The image forming section 2 includes, for example, a photoreceptor drum and devices arranged around the photoreceptor drum that perform various processes such as charging, exposure, development, transfer, cleaning, and neutralization. The image forming process is completed.

A developed image formed on, for example, a photoreceptor in the image forming section 1 is transferred on one side onto a copy sheet fed from a paper feeding section 1. The transferred copy paper is sent to the fixing section 3, where heat and pressure are applied to fix the toner image on the copy paper. When the fixing in the fixing section 3 is completed, the copying process for one side is completed.

In the case of single-sided copying mode, the fixed backside copy sheet is discharged to the paper discharge section 4, and copying is completed.

In the case of double-sided copying mode, after fixing one side, that is, the first side, the copy paper is sent from the fixing section 3 to the paper refeed section 5, where the copy paper is generally subjected to processes such as inversion and alignment. .

When the original image is formed and transferred on both sides of the copy paper by the same photoreceptor drum of the image forming section 2, the paper re-feeding section is provided with an intermediate tray for temporarily storing the copy paper after the first side has been copied. It will be done.

Two photoreceptors are used as the image forming section, and when the first side image and the second side image are formed on separate photoreceptors, the intermediate tray is omitted and the copying machine can be operated in one without intermediate storage. It is also possible to have a structure in which it is conveyed continuously along the flow. When working on two surfaces using a common photoconductor, the fixing unit can also be configured as a common fixing device, and the common fixing device can fix the images twice. When an image is formed using the photoreceptor, a fixing device may also be provided separately so that the fixing of the first side and the second side of the copy paper are performed by separate fixing devices.

The copy paper sent to the paper refeeding section 5 in the double-sided copy mode is sent to the image forming section with an instruction to copy the second side, and the original image is transferred to the second side. The copy paper on which the second image has been formed is sent to a fixing section, where the toner image on the second side is fixed.

The copy paper on which the second side has been fixed is discharged to the paper discharge section 4 upon completion of copying.

When the copy paper on which the image has been formed on the second side is sent to the fixing section 3, the general feed speed is controlled.

When the second side is fixed, the first side of the copy paper has been subjected to the fixing process, so the total water content is lower than when the first side is fixed, and the temperature of the copy paper itself is also higher.

Therefore, even if the degree of heat application is set lower when fixing the second side than when fixing the first side, there is no fear that the fixing performance will fall below the allowable limit.

As shown in FIG. 2, the fixing device can be formed as a heat roller device including a fixing roller 7 having a heater 6 disposed therein as a heat source. In this case, a pressure roller 8 that is pressed against the fixing roller 7 is provided, and the copy paper 9 is passed between the fixing roller 7 and the pressure roller 8.

The fixing roller 7 is rotationally driven by a drive motor M, and the rotation speed of the drive motor M is controlled by a control section 10. Since the pressure roller 8 is in rolling contact with the fixing roller 7, it grips the copy paper 9 at the nip with the fixing roller 7, and conveys the toner image to the discharge side while pressing the toner image. The toner image is transferred onto the copy paper by the pressing force and heating effect at the nip portion generated by the pressure P applied to the pressure roller 8.

The amount of heat during fixing is determined by the width of the nip, the temperature of the fixing roller rough, and the linear speed of the fixing roller 7. If the width of the nip portion and the temperature of the fixing roller rough are constant, the amount of heat applied during fixing changes in accordance with changes in the linear velocity of the fixing roller 7.

The relationship between the change in linear velocity and the change in heat amount is represented by curve A shown in FIG. 3 as an example. In the figure, the horizontal axis is the linear velocity V,
The vertical axis shows the amount of heat Q.

It can be seen from FIG. 3 that as the linear velocity increases, the number of devices that provide the fixing device decreases.

If the amount of heat required for fixing the second surface is determined in advance through experiments or the like, an appropriate linear speed of the fixing roller can be selected from a linear speed-heat amount characteristic curve as shown in FIG. When fixing the second side, the temperature of the copy paper has increased due to the fixing of the first side, so the amount of heat applied may be small.

Therefore, when fixing the second side, the conveying speed of the copy paper to the fixing device is increased, for example, the linear speed of the fixing roller rough is increased, and the fixing can be carried out satisfactorily.

In other words, in FIG. 3, the linear velocity of the heat roller was V in order to give the amount of heat Q when fixing the first surface, whereas the linear velocity of the heat roller was V;
When fixing a surface, if the amount of heat Q1 required to provide Ql<Q is calculated, the linear speed of the heat roller, v<vl, can be calculated as follows.
1 is determined. Therefore, in the process of fixing the second side, the control unit 1
0 controls the speed of the drive motor M and reduces the speed so that the linear speed of the fixing roller 7 becomes Vl.

The elapsed time from the end of the copying process for the first side of the copy paper to the start of the copying process for the second side may be due to a large number of copies being made on both sides at the same time, or for other reasons. etc., and the temperature of the copy paper changes.If the copying of the second side starts immediately after the copying of the first side is completed, as described above, There is no problem simply by changing the linear speed, but if it takes time to start copying the second side, the copy paper cools while waiting in the intermediate tray, etc., so the above-mentioned high linear speed V
If fixing is performed using 1, there may be a case where the fixing is insufficient due to insufficient heat.

Taking these problems into account, as shown in FIG. ) is determined as curve B, and the temperature of the copy paper can be determined according to the elapsed time described above.

Furthermore, as shown in Figure 5, if the relationship between the change in copy paper temperature (horizontal axis) and the change in the amount of heat required for fixing (vertical axis) is determined as curve C, then Figure 4 shows that The required gl can be determined based on the copy paper temperature determined by

Once the amount of heat required for fixing is determined, the conveying speed during fixing can be determined from FIG.

The control device may be configured so that a timer is activated at the same time as the first side copying ends, and an appropriate linear speed is automatically obtained depending on the time when the second side copying starts. Simply operate multiple timers, set the speed of the fixing roller according to each timer, and rotate the drive motor at the speed determined according to the timer that is activated when copying starts as shown in Figure 2. Control fffl to drive? There is a way to do that.

By selecting the linear speed of the fixing roller according to the elapsed time until the start of copying of the second side, it is possible to always fix the copy paper with an appropriate amount of heat.

If a temperature detection element is installed in the intermediate tray that stores the copy paper while waiting for the second side to be copied, the waiting time for the copy paper in the intermediate tray after the first side has been copied will be longer (even if the copy paper remains in the intermediate tray). The ambient temperature of the copy paper can be detected at all times.Moreover, the temperature of the stored copy paper corresponds to the ambient temperature, so by knowing the ambient temperature, the amount of heat required for fixing the second side can be determined from Figure 5. Depending on the structure of the intermediate tray and the temperature detection position, there may be a slight deviation between the ambient temperature and the temperature of the copy paper.

However, through experiments or the like, the relationship between the ambient temperature (horizontal axis) and the copy paper temperature (vertical axis) can be determined by, for example, a curve, as shown in FIG. Therefore, by knowing the ambient temperature of the intermediate tray, an appropriate fixing in feed rate can be determined from FIGS. 6, 5, and 3. In this case, there is no need to consider the elapsed time until the start of copying on the second side.

By increasing the conveyance speed for the second fixing, fixing can be performed with an appropriate amount of heat, but if the temperature drop on the second side is large and the temperature drops to the same level as the first side, it is natural that It is necessary to feed the fixing II at the same speed as for the first side. Increasing the IM feed speed on the second side of the present invention includes, if necessary, II sending at the same speed as on the first side.

According to the present invention, unnecessary heat is not supplied during fixing, deformation of copy paper due to heat stress is reduced, and conveyance performance is improved.

Further, according to the present invention, the amount of heat consumed by the fixing device was reduced, resulting in an energy saving effect.

According to the present invention, it has become possible to obtain the above effects with a simple structure of controlling the drive υ1 motor of the conveyance means of the fixing device.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the flow of copy paper according to the present invention;
FIG. 2 is an explanatory diagram of an example of a conveyance speed control device of a fixing device;
Fig. 3 is a characteristic curve diagram showing the relationship between the amount of heat applied during fixing and the conveyance linear speed; Fig. 4 is a characteristic curve diagram showing the relationship between the elapsed time until the start of copying on the second side and copy paper temperature; FIG. 5 is a characteristic curve diagram showing the relationship between the copy paper temperature and the required amount of heat, and FIG. 6 is a curve diagram showing the relationship between the intermediate tray ambient temperature and the copy paper temperature. ■...Paper feed section 2...Image forming section 3...Fixing section 4...Paper discharge section 5...Paper refeed section 6...
・Heater 7... Fixing roller 8... Pressure roller 9
...Copy paper 10...Control unit M...Motor agent Patent attorney Hisashi Ito 1) 1, 2, high, '9 Fig. 4 0 Elapsed time - Fig. 5 Fig. 6 Figure Reimi Tomo ('C1

Claims (2)

[Claims] (1) Transfer the developed image of the photoreceptor to the first side of the copy paper and fix it, then transfer the developed image of the photoreceptor to the second side, which is the back side of the copy paper, and fix it to copy both sides of the copy paper. A fixing method for a double-sided copying machine, characterized in that the conveyance speed of copy paper during fixing of the second side is faster than the conveyance speed during fixation of the first side. (2) The conveying speed of the copy paper when fixing the second side is set according to the elapsed time from the end of copying of the first side to the start of copying of the second side. The fixing method for an internal copying machine according to item 1.