JP5101330B2 - Transfer apparatus and electrostatic recording apparatus using the same - Google Patents

Description

  The present invention relates to an electrostatic recording apparatus such as an electrophotographic printer or copying machine, and in particular, records a toner image from a toner image carrier by bringing a transfer member composed of a transfer roller having a charged surface into contact with a recording medium. The present invention relates to a transfer device for transferring to a medium.

  A continuous paper printer using an electrophotographic system is used for multi-purpose printing such as direct mail, invoices, manuals, books, etc. because it can perform printing at high speed with little trouble such as jam of a recording medium. With the expansion of its use, there are increasing opportunities to use recording media with large surface irregularities such as rough paper, but when such recording media are used, toner image carriers such as photoreceptors and intermediate transfer media. When transferring a toner image from a recording medium to a recording medium, there is a problem that image defects are likely to occur due to poor adhesion.

  In addition, when duplex printing is performed by a continuous paper printer, a tandem method in which two printers are arranged side by side and a recording medium after printing by the first printer is reversed and the back side is printed by the second printer is generally used. However, in this case, even on a recording medium with few surface irregularities, the recording medium shrinks by the first fixing, resulting in irregularities, and thus image defects are likely to occur during the second transfer.

  As a transfer method capable of ensuring the adhesion between the recording medium and a toner image carrier such as a photosensitive member, the toner image is recorded by electrostatic force while pressing the recording medium against the toner image carrier with a transfer member such as a roller or a belt. A roller transfer method and a belt transfer method are generally known. As means for generating an electrostatic force, a method in which voltage or current is directly applied to a transfer member (core metal application method) and a method in which a dielectric layer on the surface of the transfer member is charged (external charging method) are known ( (See Japanese Patent Publication Nos. 57-10427, 62-3423, 51-151544, 49-18335, etc.).

  The core metal application method is a method generally used in a cut paper printer with a medium / low printing speed. Since it is necessary to apply the necessary voltage to the back side of the recording medium via a transfer member such as an elastic roller or belt, or to supply current, the resistance value range of the elastic roller or belt is limited, and the surrounding environment or As the resistance value changes with time, performance fluctuations such as transfer efficiency and image quality defects are large, and the range becomes relatively low resistance, so the current value flowing through the transfer member toner greatly changes depending on the presence or absence of the recording medium, It is necessary to adjust the voltage or current value applied to the transfer member according to the width of the recording medium. In addition, since the resistance range of the transfer member is limited, the material used is also limited, and it is difficult to maintain performance over a long period of time.

On the other hand, in the external charging method in which a dielectric layer is provided on the elastic layer of the transfer member and a predetermined charging is performed by supplying a charge to the surface of the dielectric layer using a corona charger or a roller charger, the width of the photoconductor Even in a continuous paper printer in which the area outside the recording medium is very large depending on the recording medium used, a large amount of current flows in the area outside the recording medium as in the core metal application method, There is no problem that the required electric field cannot be formed, and a material having excellent durability such as tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) can be used for the dielectric layer on the surface, so that the durability is high. This is also advantageous from the aspect.

  However, in the external charging method, the dielectric layer on the surface of the transfer member is charged by a charger, and the charge accumulated in the dielectric layer is conveyed to the contact portion (transfer nip portion) with the recording medium by the rotation of the transfer member. In this method, transfer is performed by supplying the recording medium to the recording medium, and not all of the electric charge supplied from the charger to the transfer member moves to the recording medium at the transfer nip. Will change.

  In the case of the cored bar application method, since the current value of the power source connected to the cored bar is equal to the current value flowing through the recording medium at the transfer nip portion, it is easy to adjust the voltage or current value of the power source to an appropriate range. .

However, in the case of the external charging method, the current consumption of the power source connected to the charger does not flow all the way to the recording medium as described above. In order to supply to the recording medium, the relationship between the voltage or current value applied to the charger, the amount of charge actually supplied to the transfer member, and the amount of charge supplied to the recording medium at the transfer nip is obtained. Therefore, it is necessary to adjust the voltage or current value applied to the charger. For this reason, it is difficult to appropriately adjust the amount of charge supplied to the recording medium at the transfer nip portion according to the thickness of the recording medium and changes in the environment.
Japanese Patent Publication No.57-10427 Japanese Patent Publication No.62-3423 Japanese Patent Laid-Open No. 51-151544 Japanese Patent Laid-Open No. 49-18335

  SUMMARY OF THE INVENTION An object of the present invention is to provide a highly reliable transfer device capable of eliminating such drawbacks of the prior art and capable of high-quality transfer, and an electrostatic recording device using the transfer device.

In order to achieve the above object, the first means of the present invention is a transfer apparatus for transferring a toner image carried on a toner image carrier such as a photoreceptor to a recording medium that has been conveyed,
A transfer member rotating with a dielectric layer;
A transfer member charging means arranged to face the transfer member upstream of the transfer member rotation direction of the transfer nip where the transfer member contacts the recording medium, and charges the dielectric layer from the outside of the transfer member; ,
A surface potential detecting means disposed on the downstream side of the transfer nip portion in the rotation direction of the transfer member so as to face the transfer member, and detects a surface potential of the transfer member;
When the transfer member is in contact with the toner image carrier via the recording medium and rotating, the surface potential of the transfer member in contact with the specific area of the recording medium is detected by the surface potential detecting means, and the transfer The transfer member surface potential (V ₀ ) before passing through the transfer nip portion obtained in advance from the relationship between the voltage or current setting value of the member charging means and the surface potential of the transfer member before passing through the transfer nip portion, and the surface potential detecting means The voltage value or current value applied to the transfer member charging unit is adjusted so that the difference (V ₀ -V ₁ ) from the detected transfer member surface potential (V ₁ ) after passing through the transfer nip portion becomes a constant value. And a control means.

  According to a second means of the present invention, in the first means, the specific area of the recording medium is a non-printing area.

  According to a third means of the present invention, in the first means, the potential detection area of the surface potential detection means is a position where the recording medium passes through the transfer nip portion in all the recording media used, and This is a region that is a non-printing portion in all recording media.

  According to a fourth means of the present invention, in the first to third means, the dielectric layer of the transfer member is polytetrafluoroethylene, tetrafluoroethylene / hexafluoropropylene copolymer, tetrafluoroethylene / perfluoroalkyl vinyl ether. It is composed of a fluorine resin such as a copolymer, ethylene / tetrafluoroethylene copolymer, polyvinylidene fluoride, and the like.

  The fifth means of the present invention is a photoconductor, a charging device for uniformly charging the surface of the photoconductor, and exposure for forming an electrostatic latent image by irradiating light to the surface of the charged photoconductor. A developing device for forming a toner image by attaching toner to the electrostatic latent image, a recording medium conveying device for conveying a recording medium, and a transfer device for transferring the toner image on the photosensitive member onto the recording medium And a fixing device for fixing the toner image on the transferred recording medium, wherein the transfer device is a transfer device of any one of the first to fourth means. Is.

  According to a sixth means of the present invention, in the fifth means, the recording medium is an elongated continuous paper.

  A seventh means of the present invention is characterized in that, in the fifth means, at least two electrostatic recording devices are connected, and the recording medium is a continuous continuous paper.

  The present invention is configured as described above, and can provide a reliable transfer apparatus capable of high-quality transfer and an electrostatic recording apparatus using the transfer apparatus.

  Next, each embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram for explaining a printing process of an electrostatic recording apparatus according to an embodiment of the present invention.

  In this embodiment, a negatively charged OPC (organic photosensitive member) is used for the photosensitive member 1, and a charging device 2, an exposure device 3, a developing device 4, a transfer device 6, and the like are arranged on the outer periphery thereof as shown in the figure.

  After the surface of the photosensitive member 1 is uniformly charged to a negative polarity using a scorotron charger as the charging device 2, a laser beam is applied to the surface of the photosensitive member 1 according to printing information using a laser scanning optical system as the exposure device 3. To form an electrostatic latent image, and the developing device 4 attaches toner to the electrostatic latent image to form a toner image.

  The long recording medium 16 is conveyed by the tractors 17 a and 17 b, and the toner image is transferred from the photosensitive member 1 onto the recording medium 16 by the transfer device 6. The toner image on the recording medium 16 is melted and fixed to the recording medium 16 by a fixing device (not shown). The toner remaining on the photosensitive member 1 is removed from the photosensitive member 1 by the cleaning device 5 and is prepared for the next image recording.

Next, the configuration of the transfer device 6 will be described.
The transfer device 6 includes a transfer device housing 7 in which an upper guide 8a and a lower guide 8b for guiding the conveyance of the recording medium 16 are provided in the vicinity of the opening, a transfer roller 9 disposed as a transfer member therein, and a surface of the transfer roller 9 As a transfer roller charging means for supplying a charge to the outside from the outside, a corotron charger 10 and a transfer roller potential disposed on the downstream side in the transfer roller rotation direction of the transfer nip portion where the transfer roller 9 contacts the photoreceptor 1 via the recording medium 16 A detection unit 11, a corotron static eliminator 12 disposed downstream of the potential detection unit 11 in the transfer roller rotation direction, a cleaning member 13 for cleaning the surface of the transfer roller 9, and the like are provided.

  The transfer roller 9 is pressed against the photoreceptor 1 by a spring (not shown) so that the nip width can be formed with an appropriate pressing force. Further, the transfer device 6 including the transfer roller 9 is configured to be able to make contact with and separate from the photosensitive member 1 by a cam mechanism.

  FIG. 2 is an enlarged cross-sectional view of the transfer roller 9. As shown in the figure, the transfer roller 9 has a transfer roller shaft 9c to be grounded, a conductive elastic layer 9b formed thereon, and a dielectric layer 9a formed thereon. .

Examples of the material of the elastic layer 9b include carbon black and the like for causing a general elastic material such as epichlorohydrin rubber, urethane rubber, silicon rubber, fluorine rubber, ethylene propylene rubber, and chloroprene rubber to act as a ground electrode of the dielectric layer 9a. A conductive material powder such as metal fine powder is mixed to have a volume resistivity of 10 ⁸ Ω · cm or less, preferably 10 ⁶ Ω · cm or less.

  As the dielectric layer 9a, polyester resin films such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polytetrafluoroethylene (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), tetra A dielectric film typified by a fluorine resin film such as a fluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), an ethylene / tetrafluoroethylene copolymer (ETFE), or a polyvinylidene fluoride (PVDF) can be used. Among them, a polytetrafluoroethylene (PTFE) film having excellent ozone resistance and good releasability and having a thickness of 30 to 100 μm is preferable.

  FIG. 3 is a schematic configuration diagram showing the drive roller drive system and the positional relationship between the transfer roller potential detecting means 11 and the recording medium 16 in the width direction.

  Both end portions of the transfer roller 9 are connected to a distal end portion of a support arm 19 via a bearing 18, and a base end portion of the support arm 19 is connected to a support shaft 21 via a bearing 20. Accordingly, the transfer roller 9 swings around the support shaft 21 by the support arm 19, and the transfer roller 9 contacts and separates from the photoreceptor 1 by the swinging operation.

  A first pulley 22 is connected to one end of the support arm 19, a second pulley 23 is connected to the support shaft 21, and a first timing belt 24 is installed between the first pulley 22 and the second pulley 23. ing. A third pulley 25 is connected to one end of the support shaft 21.

  On the other hand, a fourth pulley 27 and a fifth pulley 28 are connected to one end of the tractor shaft 26 of the tractor 7 a, and a second timing belt 29 is installed between the third pulley 25 and the fourth pulley 27. . A third timing belt 33 is installed between the sixth pulley 32 connected to the output shaft 31 of the recording medium transport motor 30 and the fifth pulley 28.

  Both ends of the support shaft 21 and the tractor shaft 26 of the tractor 7a are rotatably supported by side plates 34 installed on both sides.

  Accordingly, the rotational driving force of the recording medium transport motor 30 is transmitted to the tractor 7a via the output shaft 31, the sixth pulley 32, the third timing belt 33, the fifth pulley 28, and the tractor shaft 26. Further, the rotational driving force transmitted to the tractor shaft 26 passes through the fourth pulley 27, the second timing belt 29, the third pulley 25, the support shaft 21, the second pulley 23, the first timing belt 24, and the first pulley 22. Is transmitted to the transfer roller 9. By providing such a drive system, the rotation of the transfer roller 9 and the conveyance of the recording medium 16 can be performed in synchronization.

  In this embodiment, the rotational driving force of the recording medium conveyance motor 30 is transmitted to the transfer roller 9 and linked to the conveyance of the recording medium 16, but an individual driving source is provided, It is good also as a structure which follows conveyance and rotates.

  As shown in FIG. 1, tractors 17a and 17b are disposed upstream and downstream of the transfer device 6 in the recording medium conveyance direction, and feed holes 16a (see FIG. 3) formed at both end portions of the recording medium 16. The tractor pin is fitted to convey the recording medium 1.

  In FIG. 3, the right tractor 17a-1 is arranged at the reference position, and when the recording medium 16 having a different width is used, the position of the left tractor 17a-2 in the figure is slid in the width direction. . FIG. 3 shows a case where the recording medium 16 having the maximum print width is used.

  Accordingly, the position on the right side of the recording medium is the same when the size of the recording medium 16 changes. As shown in the figure, the transfer roller potential detecting means 11 is an area inside the right end of the recording medium 16 and outside the right end of the print width (area indicated by a one-dot chain line). Opposing to the transfer roller 9.

  By arranging the transfer roller potential detecting means 11 at this position, the transfer roller potential after transfer when the blank paper printing section passes through the transfer nip section during the printing operation is always detected on all recording media 16 to be used. It becomes possible.

  In this embodiment, by utilizing the fact that the conveyance of the recording medium 16 is based on one side, one transfer roller potential detecting means 11 is arranged in the above-described region, so that the recording medium 16 of all sizes to be used can be handled. However, as another embodiment, a plurality of transfer roller potential detecting means 11 can be arranged in the vicinity of the transfer roller 9 in the area to be each non-printing portion corresponding to all sizes of the recording medium 16 to be used.

Based on the detection result of the potential detection means 11, the applied voltage value or current value of the corotron transfer device 10 is adjusted during printing so that the later-described transfer roller surface potential difference (V ₀ −V ₁ ) becomes constant. In addition, it is possible to suppress a change in transfer image quality during printing of a continuous paper printer that often performs continuous printing for a long time using continuous paper, and to obtain a stable image quality without deterioration in image quality over a long period of time.

  4A and 4B are diagrams for explaining the operation of the transfer device 6. FIG. 4A shows a state during printing standby, and FIG. 4B shows a state during printing.

  As shown in FIG. 5A, during printing standby, the recording medium 16 and the transfer roller 9 are not in contact with the photoreceptor 1. At the start of printing, the conveyance of the recording medium 16 is started by the tractor 17, and the transfer device housing 7 and the transfer roller 9 start the contact / separation operation with a slight delay from the start of the conveyance operation of the recording medium 16. When the leading position reaches the transfer point, the recording medium 16 comes into contact with the photosensitive member 1 by the pressure of the transfer roller 9 to form an appropriate nip width, and the transfer roller 9 is appropriately applied by a spring load (not shown). A pressing force is applied to the photosensitive member 1 [see FIG. As described above, the contact / separation operation of the transfer roller 9 is performed in a non-printing area between pages.

  When the toner image portion on the photoreceptor 1 reaches the transfer nip portion, the transfer roller 9 needs to reach the transfer nip portion with the surface charged to a predetermined potential, and rotates at the time of the separation. In this state, charging by the corotron charger 9 is started, and the surface charged to the specified potential comes into contact with the recording medium 16 at the transfer nip and starts the transfer operation.

  When printing is stopped, the procedure is the reverse of the start-up operation. That is, the transfer roller 9 and the recording medium 16 are separated from the photosensitive member 1 and continue to rotate for a while, while the transfer roller 9 is discharged by the corotron discharger 12. Thereafter, the rotation of the transfer roller 9 is stopped to prepare for the next printing operation.

  In this way, in the external charging type roller transfer, charges are supplied from the outside to the dielectric layer 9a on the roller surface, and the surface of the dielectric layer 9a that accumulates the charges contacts the back surface of the recording medium 16 at the transfer nip portion. In this way, transfer is performed by supplying charges to the recording medium 16. In this method, all the charges accumulated in the dielectric layer 9a are not supplied to the recording medium 16, and the amount of charge supplied to the recording medium 16 changes depending on the type, thickness, environment, etc. of the recording medium 16. The amount of charge remaining in the dielectric layer 9a after passing through the transfer nip also varies.

  FIG. 5 shows a case where one-side printing is performed with 55 kg paper (simplex) using an external charging type transfer roller using PFA having a thickness of 30 μm for the dielectric layer, and 55 kg paper which has been printed once. The amount of charge supplied to the recording medium (vertical) calculated from the difference in charging potential between the transfer roller before entering the transfer nip (horizontal axis) and the potential of the transfer roller before and after passing through the transfer nip when printing on the back surface of the recording medium (duplex) It is a characteristic view showing a relationship of (axis).

  Once the recording medium has passed through the fixing device, the moisture content of the recording medium decreases and the electrical resistance increases, but when transferring to this recording medium, the charging potential of the transfer roller is charged to the same potential as during simplex printing. In this case, since the amount of charge supplied to the recording medium is reduced, the transfer efficiency is lowered.

  In the core metal application method, since the current flowing through the power source connected to the metal core is the amount of charge supplied to the transfer nip portion per unit time, the supplied charge can be easily detected and controlled. However, in the case of the external charging method, the amount of charge supplied to the transfer roller 9 is determined by using a contact type charger such as a roller charger from the discharge current value when the corotron charger 10 is used as the transfer roller charging means. However, as described above, the amount of charge supplied to the recording medium at the transfer nip portion can be directly obtained from the current value of the power supply connected to the transfer roller charging means. Therefore, it is difficult to supply appropriate charges to various recording media.

However, the transfer roller surface potential before passing through the transfer nip portion is V ₀ , the transfer roller surface potential after passing through the transfer nip portion is V ₁ , the dielectric layer thickness is t (m), and the relative dielectric constant of the dielectric layer is ε, When the dielectric constant of vacuum is ε ₀ = 8.85 × 10 ⁻¹² (F / m), the amount of charge σ supplied to the unit area of the recording medium at the transfer nip portion can be obtained by the equation (1).

σ = (V ₀ −V ₁ ) × ε ₀ × ε / t (1)
Accordingly, if the material and thickness used for the dielectric layer 9a of the transfer roller 9 are determined, the charge amount σ supplied to the recording medium 16 at the transfer nip portion can be obtained from the surface potential of the transfer roller 9 before and after the transfer nip portion. Therefore, the surface potential of the transfer roller 9 before and after the transfer nip is detected by a surface potentiometer, and the voltage value or current value applied to the corotron charger 10 is adjusted so that the supplied charge amount becomes an appropriate value. Is possible.
However, in the case of the external charging method, since the surface potential of the transfer roller 9 before passing through the transfer nip portion exceeds 1 kV as shown in FIG. 5, the detection range of the surface potential meter used for detection is as low as about 1 kV. Cannot be used, and the cost of the transfer device increases.
By the way, the external charging method is a method in which a dielectric is used for the surface layer of the transfer member. By using the above-mentioned material as the surface layer, changes in the surface potential due to environmental changes can be suppressed to a small level. In particular, fluororesins such as PFA, PTFE, FEP, ETFE, and PVDF have a low water absorption rate, so that the change in charging potential due to environmental changes can be reduced. The water absorption rate (test method ASTM D570) after 24 hours of the material is as follows.

PFA <0.03%
PTFE <0.03%
FEP <0.03%
ETFE ≒ 0.03%
PVDF = 0.04-0.6%
For this reason, even when the surface potential of the transfer roller 9 after passing through the transfer nip portion varies depending on the difference in paper thickness and the like, after passing through the transfer nip portion, after removing electricity so that the surface potential of the transfer roller 9 becomes constant By adopting a configuration in which charging is performed again, the relationship between the current supplied to the charger 10 and the surface potential of the transfer roller 9 before passing through the transfer nip can be made constant regardless of changes in the environment or the like.

  FIG. 6 shows a configuration in which the dielectric layer is composed of PFA having a thickness of 50 μm, the transfer roller 9 is charged by the corotron charger 10, and the AC corona neutralizer 12 is provided after passing through the transfer nip to neutralize the transfer roller 6 (FIG. 1). The relationship between the discharge current of the corotron charger 10 (current flowing through the discharge wire due to discharge) and the surface potential of the transfer roller 9 (vertical axis) when printing is performed at a process speed of 1700 mm / s. FIG.

  The circles in the figure are characteristic curves obtained by testing at 16 ° C. and humidity 20% RH, the triangles at 22 ° C. and humidity 40% RH, and the squares at 28 ° C. and humidity 80% RH. As is apparent from this figure, by using PFA with a small water supply rate for the dielectric layer, the relationship between the current supplied to the charger 10 and the surface potential of the transfer roller 9 can be made almost constant regardless of environmental changes. I understand. It has been confirmed in other experiments that this tendency is the same when the dielectric layer is made of other fluorine-based resins such as PTFE, FEP, ETFE, and PVDF.

  In the core metal application method, when the width dimension of the recording medium changes, the amount of current flowing outside the recording medium changes accordingly.To supply a constant amount of charge to the recording medium, the amount of current supplied to the transfer roller is set to the paper width. It is necessary to adjust accordingly. On the other hand, in the case of the external charging method, if the charge amount per unit area supplied to the recording medium at the transfer nip is constant, the same transfer performance can be obtained regardless of the paper width. If the relationship between the voltage value or current value to be applied to the charger 10 and the potential of the transfer roller 6 and the surface potential of the transfer roller 6 after passing through the transfer nip portion are known, the corotron charger 10 is obtained by the relationship of the above equation (1). It is possible to adjust the voltage or current applied to the capacitor to an appropriate value.

  FIG. 7 is a diagram showing a configuration for obtaining in advance the relationship between the discharge current or discharge voltage of the corotron charger 10 and the surface potential of the transfer roller 9 before passing through the transfer nip portion. In this example, the transfer roller 9 having a diameter of 40 mm was used and rotated at a speed of 760 mm / s, and the distance between the surface of the transfer roller 9 and the discharge wire of the corotron charger 10 was 9 mm. In order to measure the surface potential of the transfer roller 9 before passing through the transfer nip portion, a surface potential meter 35 was installed.

  FIG. 8 is a characteristic diagram showing the relationship between the discharge current of the corotron charger 10 and the surface potential of the transfer roller 9 before passing through the transfer nip in the above-described configuration, and FIG. 9 similarly shows the discharge voltage of the corotron charger 10 and the transfer. FIG. 6 is a characteristic diagram illustrating a relationship with a surface potential of the transfer roller 9 before passing through a nip portion. The relationship between the discharge current of the corotron charger 10 thus obtained in advance and the surface potential of the transfer roller 9 before passing through the transfer nip portion, or the discharge voltage of the corotron charger 10 and the transfer roller 9 before passing through the transfer nip portion. The relationship with the surface potential is stored in a table format in a storage means (not shown).

  FIG. 10 shows (1) from the surface potential (see FIG. 8) of the transfer roller 9 before passing through the transfer nip when the discharge current of the corotron charger 10 is variously changed and the detection potential of the transfer roller potential detecting means 11. FIG. 6 is a characteristic diagram showing the relationship between the amount of charge supplied to the recording medium 16 calculated using the equation (horizontal axis) and the transfer efficiency (vertical axis) of toner from the photoreceptor to the recording medium at that time.

  As described above, the amount of charge supplied from the corotron charger 10 to the transfer roller 9 is determined in advance from the relationship between the discharge current value of the corotron charger 10 and the surface potential of the transfer roller 9 before passing through the transfer nip portion. Based on the surface potential of the transfer roller 9 and the detection result of the potential detection means 11 provided after passing through the transfer nip, the discharge current value of the corotron charger 10 is adjusted so that the amount of charge supplied to the recording medium 16 becomes an appropriate value. It becomes possible to adjust.

Accordingly, an appropriate charge amount to the recording medium 16 corresponding to the thickness, type and environment of the recording medium 16 is obtained in advance, and the corotron charging is performed so that the potential difference V ₀ -V ₁ before and after transfer becomes an appropriate value. By adjusting the discharge conditions of the container 10, it becomes possible to supply an appropriate charge regardless of the type of the recording medium 16 and the environmental change, and transfer with little deterioration can be stably performed over a long period of time.

Further, the transfer roller surface potential V ₁ after passing through the transfer nip varies depending on the amount of toner adhered on the photoconductor, and the transfer roller surface potential V ₁ decreases as the amount of toner adhered increases. Accordingly, when the surface potential of the transfer roller 9 is measured by the potential detecting means 11, it is preferable that the same print pattern is always passed through the transfer nip portion, and the page interval reaches the transfer nip portion from a page start signal or the like. Stable potential by calculating the timing to perform in the non-print area between pages (inter-page non-print area) or by calculating the timing at which the blank page reaches the transfer nip from the print data Detection is possible. In the present invention, the non-printing area including the inter-page non-printing area and the blank portion is defined.

Accordingly, the value of the charge amount σ ₀ supplied to the unit area of the recording medium at an appropriate transfer nip portion corresponding to various recording media, paper thickness, and environment used in advance, and the corotron charger previously obtained in the same manner The relationship between the voltage or current value applied to 10 and the surface potential of the transfer roller 9 before passing through the transfer nip is stored in a storage means (not shown). A calculation (not shown) is performed using the surface potential V ₁ of the transfer roller 9 after passing through the transfer nip detected by the potential detection means 11 and the surface potential V ₀ of the transfer roller 9 before passing through the transfer nip read from the storage means. The current charge amount σ is calculated from the equation (1) by means, and an appropriate charge amount σ ₀ is compared by comparison operation means (not shown). If there is a difference in the comparison result, the voltage value or current value applied to the corotron charger 10 is corrected so as to be an appropriate value. By using known control means, it is stable without being affected by the paper thickness or the environment. Thus, transfer with little deterioration in image quality can be performed.

  FIG. 11 is a schematic configuration diagram of a continuous paper printer using the transfer device according to the embodiment.

  As shown in the figure, a charging device 2, an exposure device 3, a developing device 4, and a transfer device 6 are arranged at predetermined positions along the peripheral surface of the photosensitive member 1, respectively. The recording medium 16 is conveyed to the transfer nip portion by the recording medium conveying devices 36 and 37 and the tractors 17 a and 17 b, and the toner image is transferred onto the recording medium 16 by the transfer device 6. The toner image on the recording medium 16 is heated to the vicinity of the transition temperature of the toner resin when passing through the pre-heater 38, and then the toner image is melted on the recording medium 16 by a fixing device 41 including a heating roller 39 and a backup roller 40 incorporating the heater. It is fixed and then discharged out of the machine.

  FIG. 12 is a schematic configuration diagram of a tandem type continuous paper printer in which two continuous paper printers shown in FIG. 11 are connected. A first continuous paper printer P1 having a photoreceptor 1a, a developing device 4a and the like and a second continuous paper printer P2 having a photoreceptor 1b, a developing device 4b and the like are connected via a reversing device T.

  A first image 42 is formed on the surface of the recording medium 16 by the first continuous paper printer P1, and the recording medium 16 is reversed by the reversing device T, and the recording medium 16 is reversed by the second continuous paper printer P2. By forming the second image 43 on the back surface, double-sided printing can be performed on the recording medium 16.

  By using the transfer apparatus of the present invention, high-quality printing can be stably performed over a long period of time at an extremely high process speed of about 1700 mm / s.

It is a schematic block diagram for demonstrating the printing process of the electrostatic recording apparatus based on the Example of this invention. It is an expanded sectional view of the transfer roller used for the transfer device concerning the example of the present invention. FIG. 2 is a schematic configuration diagram showing a positional relationship in a width direction of a recording medium with a transfer roller driving system and a transfer roller potential detecting unit. It is a schematic block diagram for demonstrating operation | movement of a transfer apparatus. FIG. 6 is a characteristic diagram illustrating a relationship between a transfer roller charging potential and a charge amount supplied to a recording medium. FIG. 6 is a characteristic diagram showing the relationship between the discharge current of the transfer roller charger and the surface potential of the transfer roller. It is a figure which shows the structure for calculating | requiring the relationship between the discharge electric current or discharge voltage of a transfer roller charger, and the surface potential of the transfer roller before transfer nip part passage. FIG. 6 is a characteristic diagram showing the relationship between the discharge current of the transfer roller charger and the surface potential of the transfer roller before passing through the transfer nip. FIG. 6 is a characteristic diagram illustrating a relationship between a discharge voltage of a transfer roller charger and a surface potential of the transfer roller before passing through a transfer nip portion. FIG. 6 is a characteristic diagram showing the relationship between the amount of charge supplied to a recording medium and transfer efficiency. 1 is a schematic configuration diagram of a continuous paper printer according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram of a tandem type continuous paper printer in which two continuous paper printers are connected.

Explanation of symbols

  1: Photoconductor, 2: Charging device, 3: Exposure device, 4: Development device, 5: Cleaning device, 6: Transfer device, 7: Transfer device housing, 8a, 8b: Guide, 9: Transfer roller, 9a: Dielectric Body layer, 9b: elastic layer, 9c: transfer roller shaft, 10: transfer roller charger, 11: transfer roller potential detecting means, 12: corotron static eliminator, 13: cleaning member, 16: recording medium, 17a, 17b: tractor , 18: bearing, 19: support arm, 20: bearing, 21: support shaft, 22: first pulley, 23: second pulley, 24: first timing belt, 25: third pulley, 26: tractor shaft, 27 : Fourth pulley, 28: fifth pulley, 29: second timing belt, 30: recording medium transport motor, 31: output shaft, 32: sixth pulley, 33: third timing belt, 34: side plate, 5: surface potential meter, 36: recording medium transport device, 37: recording medium transport device, 38: preheater, 39: heating roller, 40: backup roller, 41: fixing device, 42: first image, 43: second P1: first continuous paper printer, P2: second continuous paper printer, T: reversing device.

Claims (7)

In a transfer device for transferring a toner image carried on a toner image carrier to a conveyed recording medium,
A transfer member rotating with a dielectric layer;
A transfer member charging means arranged to face the transfer member upstream of the transfer member rotation direction of the transfer nip where the transfer member contacts the recording medium, and charges the dielectric layer from the outside of the transfer member; ,
A surface potential detecting means disposed on the downstream side of the transfer nip portion in the rotation direction of the transfer member so as to face the transfer member, and detects a surface potential of the transfer member;
When the transfer member is in contact with the toner image carrier via the recording medium and rotating, the surface potential of the transfer member in contact with the specific area of the recording medium is detected by the surface potential detecting means, and the transfer The transfer member surface potential (V ₀ ) before passing through the transfer nip portion obtained in advance from the relationship between the voltage or current setting value of the member charging means and the surface potential of the transfer member before passing through the transfer nip portion, and the surface potential detecting means The voltage value or current value applied to the transfer member charging unit is adjusted so that the difference (V ₀ -V ₁ ) from the detected transfer member surface potential (V ₁ ) after passing through the transfer nip portion becomes a constant value. And a transfer unit.   The transfer device according to claim 1, wherein the specific area of the recording medium is a non-printing area.   2. The transfer apparatus according to claim 1, wherein the potential detection region of the surface potential detection means is a position where the recording medium passes through the transfer nip portion in all the recording media used, and all the recording media. A transfer device, wherein the transfer device is a non-printing area. 4. The transfer device according to claim 1, wherein the dielectric layer of the transfer member is made of polytetrafluoroethylene, tetrafluoroethylene / hexafluoropropylene copolymer, tetrafluoroethylene / perfluoroalkyl vinyl ether. A transfer apparatus comprising a fluorine resin such as a polymer, ethylene / tetrafluoroethylene copolymer, polyvinylidene fluoride, or the like. A photosensitive member, a charging device that uniformly charges the surface of the photosensitive member, an exposure device that irradiates light on the surface of the charged photosensitive member to form an electrostatic latent image, and the electrostatic latent image A developing device that forms a toner image by attaching toner, a recording medium conveying device that conveys a recording medium, a transfer device that transfers the toner image on the photosensitive member onto the recording medium, and a transferred recording medium In an electrostatic recording apparatus having a fixing device for fixing a toner image,
An electrostatic recording apparatus, wherein the transfer apparatus is the transfer apparatus according to claim 1.   6. The electrostatic recording apparatus according to claim 5, wherein the recording medium is long continuous paper.   6. The electrostatic recording apparatus according to claim 5, wherein at least two of the electrostatic recording apparatuses are connected, and the recording medium is a long continuous sheet.

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