JP3396002B2 - Transfer belt device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer belt apparatus for transferring a toner image formed on an image carrier to a transfer paper by applying a voltage to a transfer belt. It is. 2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, a charger method is generally used for transferring toner from a photosensitive drum to transfer paper. However, by using a belt transfer method (contact method), the transfer property of the transfer paper after transfer and before fixing is stabilized, and not only the image quality can be improved and wrinkles at the time of fixing can be prevented, but also the photosensitive drum can be fixed. Since the transfer paper has a nip portion, it can be transferred to the entire surface up to the rear end of the paper. In addition, there are advantages such that generation of ozone can be reduced, the voltage of the power supply can be reduced, and the size and cost of the device can be reduced. A transfer belt device using this belt transfer system has a configuration shown in FIG. In FIG. 1, the transfer belt 8 is stretched by a driving roller 9 and a driven roller 3 and is in contact with the photosensitive drum 1 with a nip width equal to or greater than a predetermined value. Transfer belt 2 from high voltage power supply 21 via bias roller 5
A current (total current a) flows through the contact plate 7
Is fed back to the high-voltage power supply 21 via the transfer control plate 20 (feedback current b), and the drum current c contributes to the transfer.
Is controlled by a differential constant current method for making the constant. If this differential constant current method is adopted, the drum current c can be kept constant, so that an image of good quality can be obtained stably with respect to fluctuations in environment, belt resistance, and the like.
Further, since the contact plate 7 is provided, it is possible to suppress an increase in the potential of the transfer belt 8, and to prevent image disturbance due to discharge between the photosensitive drum 1 and transfer paper before transfer.
It is possible to easily separate the photosensitive drum 1 and the transfer paper after the transfer. However, in the above-described conventional transfer belt device, the transferability changes due to the difference in the resistance value of the transfer belt 8. That is, the appropriate applied voltage changes depending on the resistance value unevenness of the transfer belt 8, environmental fluctuation, the type of the transferred transfer paper, the area of the image portion, and the like.
There has been a problem that good image transfer cannot be performed. Particularly, in a low-temperature and low-humidity environment, when the resistance value of the transfer belt 8 decreases, the toner image on the transfer paper is easily disturbed, and an abnormal image is easily generated. Further, the easiness of the discharge between the transfer paper and the photosensitive drum 1 and the easiness of the separation discharge between the transfer paper and the transfer belt 8 also change according to the various situations. The charge on the transfer paper is discharged in a portion where the transfer belt 8 is separated from the transfer belt 8 to generate a black dot-shaped abnormal image. Is generated, the discharge pattern at the time of peeling differs depending on the location. As described above, there is a problem that the ease of occurrence of the peeling discharge varies depending on the situation, and stable transfer and conveyance cannot be performed. As a countermeasure against this, conventionally, as shown in FIG. 1, a static eliminator 16 such as a charger for applying an AC voltage is provided at a position where the transfer paper is separated from the transfer belt 8 so that the transfer paper is neutralized. A method of doing so has been proposed. However, in this case, there is no margin for applying the AC voltage (the width of the applied voltage is narrow), and the toner on the transfer paper scatters and adheres to the casing and the wire of the static elimination means 16, which causes problems such as contamination. There was a point. In view of the above, the present invention solves the above-mentioned conventional problems and provides an A-type control unit for removing the transfer paper.
It is an object of the present invention to provide a transfer belt device that can provide a wide range of C voltage application and can prevent a casing or the like of a charge removing unit from being stained with toner. SUMMARY OF THE INVENTION The gist of the present invention is to provide a transfer belt formed of a dielectric material and contacting an outer peripheral surface of an image carrier, and a transfer belt including the transfer belt. A driving unit, a bias voltage applying unit for directly applying a bias voltage to the transfer belt, a charge removing member for discharging the transfer belt, and a downstream side of the bias voltage applying unit with respect to a rotation direction of the transfer belt. And a discharging belt disposed upstream of the transfer paper separating position and applying an AC voltage for discharging the transfer paper, wherein the frequency of the AC voltage applied by the discharging device is set to 400 Hz. ５００500 Hz. Therefore, according to the first aspect, the frequency of the AC voltage applied to the charge removing means for removing charge from the transfer paper is 400H.
in the range of Z～500Hz, that most wider the AC voltage applied to good images are acquired. Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a charging device, an eraser, a developing device, a cleaning device, a pre-transfer static elimination lamp 15, a separation claw 6, and the like (not shown) are arranged close to the periphery of the photosensitive drum 1. The transfer belt 8 is disposed in contact with the transfer belt. The transfer belt unit 10 is placed in contact with the inside of the transfer belt 8 downstream of the photosensitive drum 1 and the transfer belt 8 that is stretched by the driving roller 9 and the driven roller 3 and rotates in the direction of arrow A. Drum 1
Roller 5 as a bias voltage applying means for applying a transfer bias while maintaining the nip width B and the transfer belt 8
A contact plate 7 serving as a charge removing member for flowing current from the ground to the ground, a cleaning blade 11 for cleaning the surface of the transfer belt 8, and an AC charger 16 serving as a charge removing means for removing charges on the transfer paper P on the transfer belt 8. Have been. The contact plate 7 is connected to a transfer control plate 20, and the bias roller 5 is connected to a high voltage power supply 21. In addition, the lower surface of the transfer belt unit 10 has a DC
The push-up lever 4 driven by the solenoid 17 is disposed in abutment, and the DC solenoid 17 is controlled by the control plate 18. A toner receiver 1 for receiving scraped toner and paper dust is provided below cleaning blade 11.
The toner receiver 13 is provided with a recovery coil 12 for transporting toner and paper dust to a recovery bottle (not shown). Further, a registration roller 19 and a fixing roller 14 are arranged on the transfer paper transport path upstream of the transfer belt 8 and downstream of the transfer belt 8. In the above-described configuration, the transfer paper P fed to the registration roller 19 and waiting is sent out from the registration roller 19 in synchronization with the image timing on the photosensitive drum 1. At the same time, the transfer belt 8 is also pushed up by the push-up lever 4 and comes into contact with the photosensitive drum 1 at the same time when the leading end of the transfer paper P reaches near the contact portion between the photosensitive drum 1 and the transfer belt 8. At this time, a nip width B having a width of 4 mm to 8 mm is formed at the contact portion. When the transfer paper P enters the nip width B,
A transfer bias is applied to the bias roller 5, and a charge having a polarity opposite to the polarity of the toner on the photosensitive drum 1 is applied to the transfer belt 8 to perform transfer. In this example,
The (+) toner is developed on the photosensitive drum 1 whose surface is charged to -800 V, and the surface potential of the photosensitive drum 1 is reduced by the pre-transfer neutralizing lamp 15. The toner is transferred onto the transfer paper P by applying a voltage of 0 kV. Since the transfer belt 8 has an electric resistance of 1 × 10 ⁹ to 1 × 10 ¹² Ω and an electric resistance inside the transfer belt 8 of 1 × 10 ⁷ to 1 × 10 ⁸ Ω, the transfer belt 8 is used. As the charge applied to the belt 8 and the transfer paper P moves downstream (in the traveling direction), the contact plate 7
To eliminate the charge. At this time, if the resistance value of the transfer belt 8 is low, the toner image on the transfer paper P is easily disturbed, and when the transfer paper P separates from the transfer belt 8 and enters the guide plate 12a,
Discharge occurs between the guide plate 12a and the toner image, and an abnormal image (black spot) is generated. Therefore, the charge of the transfer paper P is removed by the AC charger 16 on the upstream side of the belt separating portion, thereby preventing an abnormal image in which the toner image is disturbed. However, A applied by the AC charger 16
The degree of occurrence of the abnormal image differs depending on the frequency of the C voltage. The frequency of the AC applied voltage is 1 kHz,
AC when 500 Hz and 400 Hz are set
Table 1 shows the relationship between the applied voltage of the charger 16 and the image. In the table, the frequency was 400 Hz to 500 Hz.
It can be seen that the setting range (margin) of the voltage application of the AC charger 16 is wider when the setting is set to. However, the transfer current is 55 μA, α is the frequency, β is the AC applied voltage to the AC charger 16, ○ is a good image, × is an abnormal image, and Δ is a partially abnormal image. [Table 1] If the AC charger 16 is in the ON state, the toner on the transfer paper P is removed from the AC charger 1.
6 can be prevented from scattering and adhering. Here, as shown in FIG. 2, the distance from the rotation center of the bias roller 5 to the rear end of the transfer belt 8 (point at which the transfer paper P separates from the transfer belt 8) is x ₁ , and the linear velocity of the transfer belt 8 is v When the application time of the AC charger 16 is At and the application time of the bias roller 5 is Bt, At ≧ (Bt + x ₁ / v) That is, x ₁ / v is added to the time during which the bias is applied by the bias roller 5. If the AC charger 16 is turned on for longer than the time, it is possible to prevent the toner from adhering to the casing and the wire of the AC charger 16. Further, as in this embodiment, a mechanism for contacting and separating the transfer belt 8 from the photosensitive drum 1 (the push-up lever 4).
), The center of the nip portion between the photosensitive drum 1 and the transfer belt 8 and the rear end of the transfer belt 8 (the transfer paper P
The distance from the transfer belt 8 to the transfer belt 8) is x ₂ (FIG. 2).
), The relationship At ≧ (Bt + x ₂ / v) must be satisfied in order to prevent toner from adhering to the AC charger 16. As described above, according to the first aspect of the present invention, in a transfer belt apparatus provided with a static eliminator for applying an AC voltage for neutralizing a transfer sheet, the AC applied by the static eliminator is applied. Since the frequency of the voltage is set to 400 Hz to 500 Hz, the setting width of the AC voltage application can be widened,
A good image can always be obtained within this range. [0019]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram showing a transfer belt device according to an embodiment of the present invention. FIG. 2 is an explanatory diagram showing distances x ₁ and x ₂ in a transfer belt. FIG. 3 is a schematic configuration diagram illustrating a conventional transfer belt device. DESCRIPTION OF SYMBOLS 3, 9 Belt driving means 5 Bias voltage applying means 7 Static elimination member 8 Transfer belt 16 Static elimination means 4, 17 Contact / separation mechanism

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 15/16 G03G 15/14 101

Claims (1)

(57) Claims 1. A transfer belt formed of a dielectric material and brought into contact with the outer peripheral surface of an image carrier, means for driving the transfer belt, and a bias voltage applied to the transfer belt Bias voltage applying means for directly applying, a neutralizing member for neutralizing the transfer belt, and a downstream side of the bias voltage applying section with respect to a rotation direction of the transfer belt, and an upstream side of a transfer sheet separating position. A for discharging the transfer paper
A transfer belt device provided with a static elimination means for applying a C voltage, wherein the frequency of the AC voltage applied by the static elimination means is 400 Hz
A transfer belt device, wherein the frequency is set to 500 Hz.