JPH075734A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain an image forming device which prevents a defective image from being formed using conditions and improves the quality of the image by controlling a transfer means based on humidity data from a temperature and humidity detection means. CONSTITUTION:Signals from a temperature and humidity sensor 15, a reference clock generator 17 and a transfer drum reference position sensor 12 are inputted to a CPU 16. By the CPU 16, arithmetic operation is executed based on the signals and selection values from respective tables 18-20 for a destaticization output value with respect to relative humidity, a transfer output value with respect to absolute humidity and a timer corresponding to the absolute humidity. Then, an output signal based on it is outputted to a power source 21, a transfer corotron 10 and a post-transfer destaticization corotron 5 through the power source 21. By executing the feedback of the humidity data to the output of the corotron 5, the output of a transfer current and the off-timing value of the transfer current, the quantity of reverse-polarity electric charge generated at the trailing edge position of a paper is minimized and the excellent image quality can be maintained in all environments and under all using conditions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus used in an electrophotographic recording apparatus, and more specifically, it has a rotatable transfer means capable of adsorbing and holding a transfer body and conveying it to the transfer apparatus. The present invention also relates to an image forming apparatus using an organic photoconductor as an image carrier (photoconductor).

[0002]

2. Description of the Related Art Conventionally, a transfer member (paper) is electrostatically adsorbed by a drum-shaped or belt-shaped transfer unit that is in contact with or near an endless moving image carrier, and an image formed on the image carrier is electrostatically attracted to the transfer member. A number of electrophotographic recording devices, such as copying devices for transferring images, have been developed and put into practical use. In particular, this transfer means is often used as a multiple transfer means mainly in a full-color copying machine, and a mesh or a film has been used as a member for holding a transfer body.

In a copying machine using such a transfer means, in a high humidity environment, a change in electrostatic capacity at the edge of the paper makes it easy for discharge to occur between the paper and the image carrier, and the charge polarity of the image carrier is increased. An electric charge having a polarity opposite to that of is stored in the image carrier, and appears as black lines in the reverse development system and white lines in the normal development system, resulting in an image defect. In particular, when the image carrier has an organic photoconductive layer, the above-mentioned defects occur remarkably.

The mechanism and improving means of the above phenomenon are disclosed in Japanese Patent Application Laid-Open No. 2-73273 and the like, and in Japanese Patent Application Laid-Open No. 3-87884, the effect of removing the image carrier memory by corona discharge after transfer. Is stated.

[0005]

In the above-mentioned conventional image forming apparatus, there has not been a sufficient solution for the actual humidity condition, the water content condition of the paper, the variation of the transfer position, the variation of the transfer sheet position and the like. Further, since the image quality is improved, details can be reproduced, and even slight potential unevenness is reproduced as a defect, which causes a serious problem in image quality.

The present invention has been made in view of the above points, and it is an object of the present invention to provide an image forming apparatus capable of solving the above problems, preventing image defects under any use condition, and improving image quality. It is intended.

[0007]

In order to achieve the above object, an image forming apparatus according to the present invention comprises an image carrier which moves endlessly, a primary charging means for uniformly charging the image carrier, and an image carrier. In an image forming apparatus having a developing means for developing the latent image on the toner image into a toner image and a transfer means for transferring the toner image onto a transfer body, a post-transfer charge eliminating means for eliminating electric charge on the image carrier after the toner image is transferred. And a post-transfer static elimination power supply output varying means for variably controlling the power output applied to the post-transfer static eliminating means, and a transfer output timing varying means for changing the power output applied to the transfer means at the transfer position and its output timing. A temperature / humidity detecting means for detecting temperature / humidity in the apparatus, an output value applied to the post-transfer charge eliminating means and an output value applied to the transfer means according to temperature / humidity data from the temperature / humidity detecting means, and It consists a control means for determining the output timing. Further, the control means has means for respectively determining the relative humidity and the absolute humidity from the temperature and humidity data, and an output selected from the relative humidity for the post-transfer charge eliminating means and an absolute value for the transfer means. It has means for controlling the output and timing selected from the humidity. Further, as peripheral devices of the control means, there are provided a position detection means of the transfer means, a means for generating a reference clock for driving the apparatus, and a timer means for counting the reference clock.

[0008]

[Operation] After the humidity data from the temperature / humidity detection means is transferred, it is output to the static elimination means and the transfer current output and transfer current OFF
It is fed back to the timing value.

[0009]

EXAMPLES Examples of the present invention will be described with reference to the drawings. FIG. 1 shows an essential part of a full-color copying machine. In the figure, reference numeral 1 is a photosensitive drum. Around the photosensitive drum 1, a primary charging corotron 2, a developing device 3, a transfer drum 4, a post-transfer charge eliminating corotron 5, and a cleaning. The device 6 and the pre-priming charge eliminating corotron 7 are sequentially arranged to face each other. The developing device 3
Are K, Y, and 4 at four locations on the circumference of the holder 8 that is rotatable.
It is provided for developing M and C four colors.

The transfer drum 4 has a transfer film 9 made of vinyl chloride or the like wound around the circumference thereof. Inside the transfer drum 4, a transfer corotron 10 is provided at a position facing the photosensitive drum 1 and again. An adsorption corotron 11, a transfer drum reference position sensor 12, and a film static elimination corotron 13 are sequentially provided on the upstream side in the direction of rotation of the above, facing the back surface of the film 9. Further, a paper peeling corotron 14 is provided outside the transfer drum 4 on the downstream side of the transfer portion.
Reference numeral 15 is a temperature / humidity sensor for detecting the temperature and humidity in the image forming apparatus.

FIG. 2 shows a control system of the above apparatus.
6 is a control device (CPU), on which a temperature / humidity sensor 9
Then, signals from the reference clock generator 17 and the transfer drum reference position sensor 12 are input, and in the control device 16, the first table 18 for static elimination output values for these signals and relative humidity, and the transfer output value for absolute humidity Of the second table 19 and the third table 20 for the timer corresponding to the absolute humidity are calculated, and an output signal based on the calculated value is transferred through the power supplies 21 and 21 to the transfer corotron 10.
And, after the transfer, the charge is output to the corotron 5.

In the above structure, the transfer sheet is attracted to the film 9 of the transfer drum 4 by the electrostatic force of the attraction corotron 11 at the position A facing the attraction corotron 11 of the transfer drum 4, and the transfer position B is transferred in accordance with the rotation of the transfer drum 4. Be transported to. At this time, the suction position with respect to the transfer drum 4 is controlled by the paper delivery conditions so as to match the reference position on the transfer drum 4.

Next, the exposure on the photosensitive drum 1 is started with the signal of the transfer drum reference position sensor 12 in the transfer drum 4 as a reference, and the latent image formed by this is developed into a toner image by the developing device 3. The toner image on the photosensitive drum 1 is transferred onto the surface of the transfer paper at the transfer position B in synchronization with the position of the paper by the action of the transfer corotron 10.
At this time, the transfer corotron 10 is turned on by the timer value counted from the rising signal of the transfer drum reference position sensor 12. This ON timing is taken by the leading edge of the paper. The transfer corotron 10 continues to be turned on during the passage of the transfer position B in the paper, and is turned off at the set position at each humidity at the rear end of the paper. The humidity data at this time is detected by the temperature / humidity sensor 15 and converted into absolute humidity by the arithmetic circuit in the control device (CPU). The higher the absolute humidity of the humidity data is, the earlier the transfer corotron 10 is turned off with respect to the trailing edge of the sheet.

The output of the transfer corotron 10 is also determined by the absolute humidity obtained from the output of the temperature / humidity sensor 15, and is high at low humidity and low at high humidity. The absolute humidity is used for this output determination because the humidity dependency of the transfer efficiency depends more strongly on the absolute humidity than on the relative humidity, and the transfer current value is set to the optimum value at each humidity in the controller 16 (CPU).
Is selected from each of the tables 18, 19 and 20 and output.

The photoconductor potential after the transfer is the transfer corotron 10.
Also, due to the film potential of the adsorption corotron 11, an induced charge is generated on the paper interposed between the photosensitive drum 1 and the transfer film 9, and at the moment when the photosensitive drum 1 and the paper leave the transfer nip, the primary charging is performed in the form of peeling discharge. It is charged to the opposite polarity. It has been experimentally confirmed that this reverse polarity charging strongly occurs in a high humidity environment.

Generally, when an organic photoconductor is used, the negative polarity is used for the primary charge, but the positively charged charge cannot be removed by the charge removal by light, and the primary charge pre-electrification lamp 7
It is necessary to return to the negative side once before static elimination by. For this purpose, it is possible to use a negative direct current discharge corotron or a post-transfer static elimination corotron 5 in which negative direct current is superimposed on alternating current. Further, in this example, a corotron in which a negative direct current was superimposed on an alternating current was used. The alternating current at this time was a 3.8 KV-RMS output using a constant voltage power source, and the constant current power source which can vary the DC component from -60 to -300 μA was used.

With respect to the DC component, the relative humidity is detected by the temperature / humidity sensor 15, and a high current is selected when the humidity is high and a low current is selected when the humidity is low based on the humidity data. The selection of the current is calculated by a formula that determines the output with respect to humidity, and the current output value once determined is fixed until the next humidity data sampling. Therefore, the discharge current does not change during the copy cycle. On the other hand, the humidity data sampling that determines the output of the post-transfer static elimination corotron 5 is the first power-on condition in the morning, that is, when the fixing device temperature is below a certain value and the power is turned on. As described above, the relative humidity of the power ON morning is used to determine the output value of the post-transfer static elimination corotron 5, because the relationship between the amount of reverse polarity charge after transfer and the relative humidity in the device is strong, and after long-time discharge under high humidity. Is the most stressful.

The post-transfer reverse polarity charging becomes stronger as it approaches the trailing edge of the photosensitive drum 1 and reaches its maximum at the edge of the sheet. After the transfer, the reverse polarity charge of the photoconductor is neutralized by increasing the DC discharge amount of the corotron 5. However, the water content condition of the paper, the position variation of the transfer corotron 10, the nip pressure between the transfer film 9 and the photosensitive drum 1 Due to the variation, the maximum reverse charge at the trailing edge of the sheet changes, and a reverse charge exceeding the neutralizing force of the post-transfer charge eliminating corotron 5 is also generated. In order to solve this, it is necessary to further increase the minus DC, but since the applied voltage becomes high, problems such as leakage occur.

In order to solve these problems, the present invention is improved by changing the OFF timing of the transfer corotron 10 with respect to the paper depending on the humidity. The maximum amount of reverse charge at the trailing edge of the paper is proportional to the amount of transfer current applied to the transfer film 9, and has a strong correlation with the OFF position with respect to the paper. Under high humidity, the transfer charge charged on the transfer film 9 easily flows to the uncharged area. Therefore, even if the transfer current is turned off before the rear end of the sheet reaches the transfer position B, the image on the rear end compared to under low humidity. Chips are unlikely to occur.

By utilizing this characteristic, the OF of the transfer corotron
The timer value was selected at each humidity so that the trailing edge image loss did not occur under high humidity in the F timing and the amount of reverse charge after transfer was minimized.

The timing of each part in the above embodiment is shown in FIG. The OFF timing of the transfer corotron 10 in this embodiment is shown in Table 1. In Table 1, the minus sign in the column of the relationship of transfer OFF from the trailing edge of the sheet means that the sheet is turned OFF before the trailing edge of the sheet passes the transfer position B.

[0022]

[Table 1]

[0023]

As described above, according to the present invention, the humidity data is generated at the rear end position of the paper by feeding back the post-transfer static elimination corotron 5 and the transfer current output and the transfer current OFF timing value. It is possible to minimize the amount of reverse polarity charge, and it is possible to maintain good image quality under any environment and use conditions.

[Brief description of drawings]

FIG. 1 is a schematic configuration explanatory view showing a main part of a four-color full-full copy machine.

FIG. 2 is a block diagram showing an example of a control system of the present invention.

FIG. 3 is a timing chart in the embodiment of the invention.

[Explanation of symbols]

1 ... Photosensitive drum, 2 ... Primary charging corotron, 3 ... Developing device, 4 ... Transfer drum, 5 ... Transfer-erasing corotron, 6 ...
Cleaning device, 7 ... Primary charge pre-electrification lamp, 9 ... Transfer film, 10 ... Transfer corotron, 11 ... Adsorption corotron, 12 ... Transfer drum reference position sensor, 13 ... Film static corotron, 14 ... Paper peeling corotron, 15 ...
Temperature / humidity sensor, 16 ... Control device, 17 ... Reference clock generator, 18, 19, 20 ... Table, 21 ... Power supply.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G03G 21/14 2107-2H G03G 21/00 372

Claims (3)

[Claims] 1. An image carrier that moves endlessly, a primary charging unit that uniformly charges the image carrier, a developing unit that develops a latent image on the image carrier into a toner image, and a transfer unit that transfers the toner image. In an image forming apparatus having a transfer means for transferring to a post-transfer charge removing means for removing charge on the image carrier after toner image transfer, and for post-transfer charge removing for variably controlling a power output applied to the post-transfer charge removing means Power supply output varying means, power supply output applied to the transfer means at the transfer position and transfer output timing varying means for changing the output timing, temperature and humidity detecting means for detecting temperature and humidity in the apparatus, and temperature and humidity detection An image forming method comprising: an output value applied to the post-transfer charge eliminating means, an output value applied to the transfer means, and a control means for determining the output timing of these according to the temperature and humidity data from the means. apparatus. 2. The control means has means for respectively determining the relative humidity and the absolute humidity from temperature and humidity data, and an output selected from the relative humidity for the post-transfer charge eliminating means and an output for the transfer means. The image forming apparatus according to claim 1, further comprising means for controlling an output selected from absolute humidity and timing. 3. A peripheral device of the control device, which comprises a position detection device of the transfer device, a device for generating a reference clock for driving the device, and a timer device for counting a reference block. Image forming means.