JPH0736096B2 - Automatic duplex copier - Google Patents

Description

TECHNICAL FIELD The present invention relates to a copying machine, and more particularly to an automatic double-sided copying machine having a fixing device applicable to a copying machine having a double-sided copying function.

(Prior Art) In a fixing device of a copying machine, a transfer paper in which fixing conditions such as a fixing temperature, a pressurizing amount, and a conveying speed are used, for example, a sheet having a size of several μm to 200 μm is specified by the copying machine. It is set so that speed and fixability are satisfied. In addition, some models use a special processing method for thick 0.3 mm or more such as postcards, but for those less than this, the fixing conditions like the above general equipment are set. It is usually done.

However, if the basic transfer paper has such a large range and the above-mentioned severe fixing conditions are given to the apparatus, the temperature rise in the fixing apparatus is high when the apparatus is long in standby. Problems such as deformation of the roller below are large, and expensive parts, rollers, etc. must be replaced even in a time much shorter than the durability due to the degree of use. Ordinary transfer paper (several μm to 200 μm, comparatively thin) as in the past
In order to obtain stable fixability, the fixing conditions are high temperature and
Although the pressure is high, there is a problem in that when 80 g or less of paper is used under this condition, the paper is curled. Also,
Abnormal offset phenomenon due to severe malfunctions and inaccurate offset detection when using a transmitted light detecting means or a paper thickness detecting means for detecting thin transfer paper of several μm to 200 μm and thick transfer paper of more than 200 μm. , Curls, wrapping and other jams will occur. Further, this type of detection means cannot withstand long-term use, and malfunctions due to paper powder adhesion, toner adhesion, etc., which makes it impractical and costly. Furthermore, in a double-sided copying machine, it has been proposed to switch the fixing set temperature to a lower temperature during the second side copying than during the first side copying, but this is merely a switching between preset fixing temperatures. Therefore, it does not consider the environmental requirements that affect the fixability, and defects such as offset occur.

(Purpose) The present invention has been made to solve the above-mentioned drawbacks of the conventional apparatus.
It is an object of the present invention to provide an automatic double-sided copying machine which can improve the transportability of transfer paper and achieve energy saving by increasing the fixing transport speed at the time of surface copying to optimize the amount of heat applied.

(Structure) In order to achieve the above object, the present invention provides an automatic double-sided copying machine in which the fixing and conveying speed at the time of copying on the second side is made faster than the fixing and conveying speed at the time of copying on the first side, from the re-feed unit to before fixing. A temperature measuring element is arranged at an appropriate position, and the temperature of the transfer paper at the time of copying on the second side is measured by the temperature measuring element, and the fixing conveyance speed at the time of copying on the second side depends on the measured temperature. It is characterized by changing.

Hereinafter, a specific description will be given based on an embodiment of the present invention.

FIG. 1 is a schematic view showing a main part of an embodiment of an automatic double-sided copying machine according to the present invention, in which 1 is a re-feeding unit, 2 and 2a are feeding rollers, 3 is a photosensitive drum, and 4 is a transfer charger. Denoted at 5 is a separation charger, 6 is a transport unit, 7 and 8 are a fixing roller and a back-up roller that constitute a fixing unit, 9 is a transport roller, 10 is a transfer sheet transported by the sheet feeding roller 1, and 11 is a transfer sheet. The temperature sensor and the humidity sensor are arranged between the sheet re-feeding section 1 and the photosensitive drum 3.

The operation of the embodiment having the above configuration will be described. First, the transfer paper 10 from a paper supply unit (not shown) is sent to the vicinity of the photoconductor drum 3 by the paper supply roller 2a, and an image is formed on the transfer paper 10 by the visualization process. Next, the transfer paper 10 is sent to the fixing unit via the conveyance unit 6, and the transfer image on the transfer paper 10 is fixed, and the one-sided copy is completed. When copying to the other surface of the transfer paper 10, the transfer paper 10 is fed to the re-feeding unit 1,
The transfer paper 10 is fed through the paper feed rollers 2 and 2a, transferred and fixed through the same steps as described above, and then discharged to a paper discharge unit (not shown).

The flow of the transfer paper described above will be further described with reference to the block diagram shown in FIG. In the figure, the transfer paper fed from the paper feed unit 12 to the image formation unit 13 is subjected to the first image formation process.
The image forming unit 13 includes the photoconductor drum 3 shown in FIG. 1 and processes such as charging, exposure, development, transfer, cleaning, and charge removal arranged around the photoconductor drum 3, and each process is performed for the first time. The imaging process ends. The paper on which the toner image is transferred on one side by the image forming unit 13 is then fed to the fixing unit 14, where heat and pressure are applied to fix the toner image on the transfer paper, and the first copy is completed.

After that, in the case of the single-sided copy mode, the transfer sheet after the completion of the single-sided copy is sent to the paper output unit 15, and the single-sided mode process ends.

In the case of the double-sided copy mode, the single-sided-transferred transfer paper is sent from the fixing section 14 to the re-feeding section 1, where it is subjected to processes such as reversing and aligning to be prepared for double-sided copying. Thereafter, the transfer sheet is sent again to the image forming unit 13 together with the double-sided copy instruction, and the second image formation is performed, and a toner image is formed on the other surface of the transfer sheet. The transfer paper on which the second image formation has been completed is sent again to the fixing section 14 and subjected to the second fixing process, whereby the second copy is completed.
The transfer sheet on which copying on both sides is completed is sent to the paper output unit 15, whereby the two-sided copying is completed.

Since the transfer paper at the time when the above-described second image formation is performed has already been subjected to the fixing process once, the moisture content is decreased at least as compared with that before the fixing process, and the temperature of the transfer paper itself is also reduced. It is getting higher. Therefore, even if the heating degree in the second fixing process is made smaller than that in the first fixing process, there is no fear that the fixing property will fall below the allowable limit.

The appropriate amount of heat given differs depending on the temperature of the transfer paper and the degree of moisture content.

As can be seen from the characteristic diagram in FIG. 3, the relationship between this heat quantity and the water content of the transfer paper is that the higher the temperature of the transfer paper (T ₁ , T ₂ ) is, the more heat quantity (Q ₁ , Q) is required for fixing. ₂ , Q ₃ ) is less, and the lower the water content (A ₁ , A ₂ , A ₃ ), the less heat is required for fixing. Moisture content in the figure is A ₁ > A ₂ > A ₃ , temperature is T ₂ > T ₁ ,
And the amount of heat required for fixing is Q ₃ > Q ₂ > Q ₁ .

Next, the fixing unit 14 will be described in detail with reference to FIG. In the figure, a cylindrical fixing roller 7 is rotatably supported, and is rotated at a linear velocity V by a drive motor M in the direction of the arrow. A heater 16 as a heat source is arranged inside the fixing roller 7. A pressure roller (back-up roller) 8 is provided so as to be capable of rolling contact with the fixing roller 7 and is pressed in the direction of arrow P. The pressure roller 8 is provided at the rolling contact portion (nip portion) with the fixing roller 7 as described above.
The transfer sheet 10 on which the toner image 17 is transferred and conveyed at 13 is nipped with an appropriate pressure and is conveyed to the downstream side by its rotation. Due to the pressing force and the heating action of the fixing roller 7 at this time, the toner image 17 is fixed on the transfer paper 10. The amount of heat applied to the transfer paper 10 in this heating action is determined by the width (nip width) h of the rolling contact portion, the temperature of the fixing roller 7 and the linear velocity V of the fixing roller 7. When the linear velocity V of the fixing roller 7 changes without changing other conditions, the amount of heat given by changing the linear velocity V of the fixing roller 7 changes, as shown in FIG. That is, as can be seen from FIG. 5, the amount of heat applied decreases as the linear velocity increases. By utilizing this fact, the linear velocity of the fixing roller 7 is increased and the amount of heat applied is reduced during the second fixing.

As shown in FIG. 1, any position of the transfer paper transport path from the refeed unit 1 to the front of the fixing unit (fixing roller 7) (in FIG. 1, the refeed unit 1 and the tourist drum 3 (Between) and an element (thermocouple, thermistor, etc.) for measuring the temperature of the transfer paper 10 at the time of copying the second side, and a humidity sensor 11 for measuring the moisture content of the transfer paper 10. The temperature and moisture content of the transfer paper 10 immediately before the second fixing is measured by this measuring element. The transfer paper
By obtaining the relationship between the heat quantity, the temperature, and the water content necessary for fixing 10 in advance, the transfer paper 10 can be obtained from the characteristic diagram of FIG.
You can see how much heat is needed for fixing. The linear velocity V of the fixing roller 7 is continuously changed by the temperature of the transfer paper and the water content,
An appropriate method such as a step method can be selected.

Further, from the characteristic diagram of FIG. 5, conversely, determine the appropriate linear velocity V ₁ ,
At the time of the second fixing, as shown in FIG. 4, a signal is sent to the control unit 18 of the drive motor M so that the linear velocity of the fixing roller 7 becomes V ₁ (V
The drive motor M is controlled so that <V ₁ ).

(Effects) According to the present invention, the temperature of the transfer paper of the transfer paper at the time of copying the second side is measured by disposing the temperature measuring element in the proper place of the conveying path from the re-feeding unit to before fixing, as in the way. , The amount of heat given to the transfer paper can be properly adjusted by changing the fixing conveyance speed at the time of copying on the second side depending on the measured temperature.
Further, the thermal stress of the transfer paper is reduced, the deformation of the paper is eliminated, the transportability is improved, and the amount of heat consumed is appropriately controlled, so that it is possible to provide an automatic double-sided copying machine that has the effect of saving energy. I can.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the essential parts of an embodiment of an automatic double-sided copying machine according to the present invention, FIG. 2 is a block diagram showing the flow of transfer paper in the automatic double-sided copying machine according to the present invention, and FIG. 3 is for fixing. Characteristic diagram showing the relationship between the required amount of heat, temperature and water content, No. 4
FIG. 5 is a schematic sectional view for explaining the fixing unit, and FIG. 5 is a characteristic diagram showing the relationship between the linear velocity of the fixing roller and the amount of heat given. 1 ... Re-feeding section, 3 ... Photosensitive drum, 7 ... Fixing roller, 10 ... Transfer paper, 11 ... Temperature (humidity) measuring element, 14 ...
… Fixing section.

Claims (2)

[Claims] 1. An automatic double-sided copying machine in which a fixing and conveying speed at the time of copying on the second side is faster than a fixing and conveying speed at the time of copying on the first side, a temperature measuring element is provided at a proper position from a re-feeding unit to before fixing. Then, the temperature of the transfer paper at the time of copying on the second side is measured by the temperature measuring element, and the second temperature is measured depending on whether the temperature is high or low.
An automatic double-sided copying machine characterized by changing the fixing and conveying speed during surface copying. 2. In addition to the temperature measuring element, a moisture content measuring element is provided, the temperature and moisture content of the transfer paper at the time of copying on the second side are measured by these elements, and the measured transfer paper is measured. The automatic double-sided copying machine according to claim (1), characterized in that the fixing conveyance speed at the time of copying on the second side is changed depending on the temperature and the moisture content.