JP3651738B2 - Double-sided recording device - Google Patents

Description

【００２１】
【発明の効果】
以上述べたように、本発明によれば、用紙搬送ロール表面への未定着トナーの付着による用紙搬送ロールの汚損を防止し、安定した印刷品質を長期間実現することが可能な両面記録装置を得ることができる。
【図面の簡単な説明】
【図１】両面記録装置の概略構成図。
【図２】本発明の実施例を示す要部拡大図。
【図３】本発明の他の実施例を示す要部拡大図。
【符号の設明】
２０,２１…トナー像形成手段、１０…定着手段、１１…用紙搬送ロール、１２…用紙搬送ロール清掃部材、２２…バイアス電源。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a double-sided recording apparatus that fixes an unfixed toner image transferred on both sides of a sheet of paper by a toner image forming unit to the same fixing unit.
[0002]
[Prior art]
The electrophotographic system is one of the most well-known image recording systems used for copying machines and printers. In particular, in a line printer where high-speed printing is desired, as the amount of information to be processed increases, higher-speed printing capability is desired, and the image quality is also desired to be high quality and high definition. In recent years, the idea of saving resources and energy has been advanced to protect the global environment, and the need for a double-sided recording (printing) function has been increasing in the fields of copying machines and printers.
[0003]
As a configuration for recording on both sides of continuous paper using the electrophotographic method, for example, as disclosed in US Pat. No. 5,179,417, electrophotographic apparatuses that handle continuous paper are arranged in front and back, A form is known in which a sheet reversing device is installed between the two electrophotographic apparatuses to perform continuous paper front and back printing. In the following description, the above form is described as a “tandem printing system” for convenience.
[0004]
The tandem printing system is suitable for high-speed printing because there is no decrease in printing speed. However, since it requires two electrophotographic apparatuses, the entire printing system becomes physically large, and the cost of the apparatus is also high. There is a disadvantage that it becomes high. In addition, since the toner image is fixed on the sheet by a fixing device provided in each electrophotographic apparatus, two fixing devices with a large power consumption burden are required, resulting in an obstacle to energy saving.
[0005]
Against this background, recording apparatuses that simultaneously print on both sides of paper have been proposed. In this configuration, unfixed toner images are formed on both sides of a sheet by two printing apparatuses, and toner images on both sides of the sheet are simultaneously fixed by one fixing apparatus. With this configuration, high-speed duplex printing can be performed with only one fixing device.
[0006]
FIG. 1 is a schematic configuration diagram showing a printer configuration of a double-side simultaneous fixing system. Here, a case where a reversal development type printing unit using a positively charged photosensitive drum such as SeTe or As ₂ Se ₃ and a positively charged toner is used as the photosensitive drum will be described. A positive charge is supplied to the photosensitive drum 1a by a corona charger 2a, and an electrostatic pattern is formed by irradiating a light pattern by an exposure unit 3a such as a laser optical system or LED, and toner development is performed by a developing unit 7a. By applying a negative charge to the back side of the sheet 5 by the corona transfer unit 4a, the toner image 6 on the photosensitive drum 1a is transferred onto the sheet 5. The above is the first printing unit 20.
[0007]
Next, the polarity of the positively charged toner 6 is reversed to a negative polarity by a toner polarity reversing device 8 comprising a combination of a negatively charged corona charger and a positively charged corona charger. Next, the positively charged toner image 9 is similarly transferred to the back surface of the paper 5 using the second printing unit 21 including the photosensitive drum 1b. As a result, the toner images 6 and 9 formed on both sides of the paper 5 on which the toner images 6 and 9 having different polarities are formed on the surface of the paper 5 are melted by the heat roll type fixing device 10 and fixed to the paper. Is done.
[0008]
[Problems to be solved by the invention]
Here, 11 is a paper transport roll provided in the paper transport path between the printing unit and the fixing device. The paper transport roll 11 is indispensable as a buffer mechanism for changing the transport direction of continuous paper or transporting paper. Since the surface of the paper transporting roll 11 is in contact with the unfixed toner image, contamination of the roll surface and the resulting disturbance of the toner image become a problem.
[0009]
The paper transport roll is adopted in the printer DPC-1 manufactured by Xeikon, and the toner and the roll surface contacting the roll surface are charged by charging the surface of the paper transport roll with the same polarity as the toner by an external charger. It causes an electrical repulsive force to electrostatically prevent toner adhesion, but the amount of charge on the roll surface charged by an external charger is not always uniform, and toner adhesion is completely prevented. Is difficult, and a cleaning device is installed on the outer periphery of the roll (see JP-A-7-7277).
[0010]
In the technique described in Japanese Patent Application No. 8-247597, a conductive material having a volume resistance of 10 ⁷ Ω · cm to 10 ¹¹ Ω · cm is used on the surface of the paper transport roll, and the core metal is in contact with the roll surface. This method uses a method of applying a bias having the same polarity as that of the unfixed toner, and does not require an external charger such as a corona charger. At this time, when unfixed toner images are attached to both sides of the sheet and the volume resistance of the roll surface is high, the repulsive force between the roll and the unfixed toner on the sheet in contact with the roll becomes weak. Also, if the roll surface resistance is less than 10 ⁶ Ω · cm, the electric field affects unfixed toner on the opposite side of the sheet that contacts the roll, and the unfixed toner on the opposite side of the sheet does not adhere to the sheet. Adhesion is weak. Therefore, a conductive material having a volume resistance of 10 ⁷ Ω · cm to 10 ¹¹ Ω · cm is used on the roll surface. However, in this case, the film thickness cannot be extremely increased in order to obtain a volume resistance of 10 ⁷ Ω · cm to 10 ¹¹ Ω · cm. Therefore, a mirror image force acts on the adhered toner, making it difficult to remove the toner. Although it is conceivable to improve the cleaning performance by increasing the rotation speed of the cleaning brush and other mechanical forces, slippage occurs between the paper transport roll and the paper due to wear on the surface of the paper transport roll and the frictional resistance of the cleaning brush. Cause image quality degradation. Therefore, there is a need for means for improving the cleaning efficiency using something other than mechanical force.
[0011]
SUMMARY OF THE INVENTION An object of the present invention is to provide a double-sided recording apparatus capable of preventing the paper conveyance roll from being soiled due to adhesion of unfixed toner to the surface of the paper conveyance roll and realizing stable printing quality for a long period of time.
[0012]
[Means for Solving the Problems]
The object is to form a toner image on both sides of the paper, a toner image forming means, a fixing means for simultaneously fixing the toner images formed on both sides of the paper by the toner image forming means, the toner image forming means and the fixing means. A paper conveyance roll having a surface layer made of a conductive material having a volume resistance of 10 ⁷ Ω · cm to 10 ¹¹ Ω · cm, and guiding the paper holding the toner image before fixing, This is achieved by having a paper transport roll cleaning member formed of a material that is charged to a polarity opposite to that of the toner particles attached to the paper transport roll by frictional charging with the paper transport roll.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the present invention will be described below. Before describing specific examples, the concept of the present invention will be described. The present invention utilizes frictional charging between the paper transporting roll cleaning member and the paper transporting roll. If the paper transporting roll cleaning member is negatively charged by frictional charging of both, positive polarity toner is transferred to the paper transporting roll cleaning member side. Can be electrostatically aspirated. The advantage of the present invention is that the sheet conveying roll cleaning member can be charged without using an external power source, and the cost can be reduced.
[0014]
Further, in order to improve the cleaning efficiency, a charging means for corona charging the attached toner is provided prior to removing the toner attached to the paper transport roll by the paper transport roll cleaning member.
[0015]
FIG. 2 is an enlarged view of a sheet transport roll portion according to the embodiment of the present invention. In recent years, demand for the high-speed printer market includes double-sided printing as well as high-definition image quality and colorization. When performing double-sided printing, a tension was applied to the printing paper 5 and a paper transport roll 11 provided with a conductive fluororesin layer was used to prevent image quality deterioration due to rubbing. However, it has become essential to remove toner particles adhering to the paper transport roll 11. Therefore, the cleaning brush 12 is provided as a paper transport roll cleaning member.
[0016]
It is preferable to use a cleaning brush 12 that is frictionally charged with a polarity opposite to that of the toner when it comes into contact with the paper transporting roll 11. In the experiment, the paper transporting roll 11 covered with a tube formed by mixing and dispersing carbon in a fluororesin so as to have a volume resistance of 10 ⁷ Ω · cm to 10 ¹¹ Ω · cm was used. The cleaning brush 12 was made of nylon, which is more likely to be charged positively (+) than the friction charging series, and rayon, which is more likely to be charged negatively (−), as main components, and the cleaning property was confirmed.
[0017]
A bias power source 22 applied a bias of +1500 V to the core of the paper transport roll 11. The unfixed toner 6 is charged to about +30 μC / g by the charger 14, so that the adhesion of the toner to the paper transport roll 11 is considerably suppressed. The polarity of the toner 15 adhering to the paper transport roll 11 is almost positive. For this reason, the cleaning brush 12 is superior in cleanability by using rayon which is easily triboelectrically charged. Even when coated with PVDF (polyvinylidene fluoride) or a material whose main component is nylon, the volume resistance of the surface of the paper transport roll 11 is adjusted to 10 ⁷ Ω · cm to 10 ¹¹ Ω · cm, It is valid. Further, polyethylene that is more easily charged negatively than rayon is also effective as a material for the cleaning brush 12.
[0018]
FIG. 3 shows a configuration in which a charger 16 is provided on the front side of the cleaning brush 12 in the configuration of FIG. In FIG. 3, the charge amount of the adhering toner 15 before the charger 16 is not uniform due to the influence of the peeling discharge that occurs when the paper 5 and the paper transporting roll 1 are separated, and all are positive. Is not limited. Therefore, the charging toner 16 was uniformly charged positively by the charger 16, and the effect was confirmed. As a result, even when a nylon cleaning brush that has caused poor cleaning when the charger 16 is not used, the toner charge amount is charged to +5 μC / g to +40 μC / g, thereby cleaning the attached toner 15. Rose. When the charge amount is +5 μC / g or less, a slight cleaning failure is recognized, and when the charge amount is +40 μC / g, the adhesion between the cleaning brush 12 and the toner increases, and there is a problem in that the toner is separated from the cleaning brush 12. Arise.
[0019]
When the peripheral speed of the cleaning brush 12 is examined in the range of 0.7 to 1.4 with respect to the paper transporting roll 1, there is no significant difference in cleanability, and the peripheral speed ratio is in the range of 0.7 to 2.0. It was confirmed that the cleaning efficiency was good. When the value was 0.7 or less, the cleaning efficiency was slightly inferior, and when the value was 2.0 or more, slippage occurred between the printing paper 5 and the paper transporting roll 11 and the image quality was disturbed. The above examination results are shown in Table 1.
[0020]
[Table 1]

[0021]
【The invention's effect】
As described above, according to the present invention, there is provided a double-sided recording apparatus capable of preventing soiling of a paper transport roll due to adhesion of unfixed toner to the surface of the paper transport roll and realizing stable printing quality for a long time. Can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a double-sided recording apparatus.
FIG. 2 is an enlarged view of a main part showing an embodiment of the present invention.
FIG. 3 is an enlarged view of a main part showing another embodiment of the present invention.
[Designation of code]
20, 21... Toner image forming means, 10... Fixing means, 11... Paper transport roll, 12.

Claims (6)

Toner image forming means for forming toner images on both sides of the paper;
Fixing means for simultaneously fixing toner images formed on both sides of the paper by the toner image forming means;
A surface layer that is interposed between the toner image forming means and the fixing means, guides the paper holding the toner image before fixing, and is made of a conductive material having a volume resistance of 10 ⁷ Ω · cm to 10 ¹¹ Ω · cm. A paper transport roll having
A paper transport roll cleaning member for removing toner particles adhering to the paper transport roll;
Site in contact with the paper transport roll of the paper transporting roll cleaning member, the triboelectric charging with the paper transport rolls, it being formed of a material that is charged to the polarity of the toner particles opposite adhering to the sheet conveying roll A double-sided recording apparatus. When the charging polarity of the toner particles is positive, the surface layer is formed of a conductive fluorine-based resin having a volume resistance of 10 ⁷ Ω · cm to 10 ¹¹ Ω · cm in which carbon is mixed and dispersed. 2. The double-sided recording apparatus according to claim 1, wherein the member is made of a material mainly composed of rayon or polyethylene. When the charging polarity of the toner particles is negative, the surface layer is formed of a conductive fluorine resin having a volume resistance of 10 ⁷ Ω · cm to 10 ¹¹ Ω · cm in which carbon is mixed and dispersed. 2. The double-sided recording apparatus according to claim 1, wherein the member is made of a material mainly composed of nylon.   2. The double-sided recording apparatus according to claim 1, further comprising a charging unit that corona-charges the toner before the toner adhering to the paper transport roll is removed by the paper transport roll cleaning member.   5. The double-sided recording apparatus according to claim 4, wherein the absolute value of the charge amount of the toner charged by the charging means is specified to be 5 [mu] C / g to 40 [mu] C / g.   The paper transporting roll cleaning member is a cleaning brush rotatably supported, and the peripheral speed ratio between the rotational speed of the cleaning brush and the rotational speed of the paper transporting roll is defined in a range of 0.7 to 2.0. The double-sided recording apparatus according to claim 1, wherein the double-sided recording apparatus is provided.

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