JP3114767B2 - Image forming device - Google Patents

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 for use in an electrophotographic recording apparatus, and more particularly, to an image forming apparatus having rotatable transfer means capable of adsorbing and holding a transfer body and transporting the transfer body 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 Heretofore, a transfer member (paper) has been electrostatically attracted to a drum or belt-like transfer means which abuts or approaches an image carrier which moves endlessly, and an image formed on the image carrier is formed thereon. Many electrophotographic recording devices such as a copying device for transferring an image 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 apparatus using such a transfer means, in a high-humidity environment, a discharge is easily generated between the sheet and the image carrier due to a change in capacitance at the end of the sheet, and the charge polarity of the image carrier is increased. a reverse polarity charge is a memory on the image bearing member, a black stripe in reversal development systems, and in the forward developing system, it appears as white vinegar di, and image defects. In particular, when the image carrier has an organic photoconductive layer, the above-mentioned defects are significantly generated.

The mechanism of the above-mentioned phenomenon and the means for improving it are disclosed in Japanese Patent Application Laid-Open No. 2-73273, and the effect of removing the image carrier memory by corona discharge after transfer is disclosed in Japanese Patent Application Laid-Open No. 3-88884. Is stated.

[0005]

In the above-mentioned conventional image forming apparatus, there has not been sufficient means for solving the above problems due to actual humidity conditions, paper moisture content conditions, transfer position variations, transfer paper position variations, and the like. Further, the improvement in image quality makes it possible to reproduce details, and even slight potential unevenness is reproduced as a defect.

The present invention has been made in view of the above, and has as its object to provide an image forming apparatus capable of solving the above problems, preventing image defects under all use conditions, and improving image quality. It is the purpose.

[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 developing means for developing the latent image on the toner image into a toner image and transfer means for transferring the toner image to a transfer member, post-transfer charge removing means for removing charges on the image carrier after transfer of the toner image And a power supply output variable means for variably controlling a power output applied to the post-transfer charge removing means; a power supply output applied to the transfer means located at the transfer position; and a transfer output timing variable for changing the output timing. Means, temperature and humidity detecting means for detecting the temperature and humidity in the device, according to the temperature and humidity data from the temperature and humidity detecting means,
The output value to be applied to the post-transfer static elimination means and the output value to be applied to the transfer means are determined, and the OF of the output of the transfer means is determined.
And control means for determining the F timing to be one of a plurality of OFF timings . Further, the control means has means for determining the relative humidity and the absolute humidity from the temperature and humidity data, respectively, and the output after the transfer is performed by the output selected from the relative humidity, and the output from the transfer means.
On the other hand, it has a means for controlling each with an output selected from the absolute humidity . Further, as peripheral devices of the control means, there are a position detecting 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. And then move it endlessly
Image carrier and primary charging to uniformly charge the image carrier
Means for developing a latent image on an image carrier into a toner image
And a transfer means for transferring the toner image to a transfer member.
Image forming apparatus, the image carrier on which the toner image is transferred
Post-transfer static elimination means for eliminating the electric charge of the
Power supply for post-transfer neutralization that variably controls the power output applied to the stage
A variable output means, and a voltage applied to the transfer means at the transfer position.
Transfer output that can change the source output and its output timing
Timing variable means and temperature and humidity for detecting temperature and humidity in the device
Temperature and humidity data from the temperature and humidity detection means
The output value applied to the post-transfer static elimination means and the transfer
The output value to be applied to the stage is determined, and the output of the transfer means is determined.
It consists of a control means that determine the timing of the force, Katsuko
Of the relative humidity and absolute humidity from the temperature and humidity data
It has a means to determine the degree of each, the output of the charge removal means after transfer
Output with relative humidity.
For step output, select output from absolute humidity
It is configured to have control means.

[0008]

[Operation] The humidity data from the temperature / humidity detecting means is output to the charge removing means after the transfer, the transfer current output, and the transfer current OFF.
This is fed back to the timing value.

[0009]

[Embodiment] An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a main part of a full-color copying machine. In FIG. 1, reference numeral 1 denotes a photosensitive drum, and a primary charging corotron 2, a developing device 3, a transfer drum 4, a post-transfer neutralizing corotron 5, a cleaning drum 1 are provided around the photosensitive drum 1. The device 6 and the pre-primary charge eliminating corotron 7 are sequentially arranged in opposition. Developing device 3
Are K, Y, and K at four locations on the circumference of the rotatable holder 8.
It is provided for development of M and C 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. At the upstream side in the rotation direction, a suction corotron 11, a transfer drum reference position sensor 12, and a film discharging corotron 13 are sequentially provided to face the back surface of the film 9, respectively. A paper peeling corotron 14 is provided on the outer side of the transfer drum 4 downstream of the transfer section.
Reference numeral 15 denotes 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.
Reference numeral 6 denotes a control device (CPU), which includes a temperature and humidity sensor 1
5 , a signal from the reference clock generator 17 and signals from the transfer drum reference position sensor 12 are input. The control device 16 outputs a first table 18 for static elimination output values for these signals and relative humidity, and a transfer output value for absolute humidity. Is calculated based on the selected value from the second table 19 for the timer and the third table 20 for the timer corresponding to the absolute humidity, and an output signal based on this is transferred via the power supplies 21 and 21 to the transfer corotron 1.
0 and output to the charge removing corotron 5 after transfer.

In the above construction, the transfer paper is attracted to the film 9 of the transfer drum 4 by the electrostatic force of the suction corotron 11 at the position A opposite to the suction corotron 11 of the transfer drum 4, and the transfer position B is transferred according to the rotation of the transfer drum 4. Transported to At this time, the suction position with respect to the transfer drum 4 is controlled according to the sheet feeding condition so as to match the reference position on the transfer drum 4.

Next, exposure on the photosensitive drum 1 is started based on the signal of the transfer drum reference position sensor 12 in the transfer drum 4, and the latent image created thereby is developed into a toner image by the developing device 3. The toner image on the photosensitive drum 1 is transferred to the surface of the transfer sheet by the action of the transfer corotron 10 at the transfer position B in synchronization with the position of the sheet.
At this time, the transfer corotron 10 is turned on by a timer value counted from a rising signal of the transfer drum reference position sensor 12. This ON timing is determined by the leading edge of the sheet. The transfer corotron 10 continues to be turned on while the transfer position B is being swirled through 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 is converted into absolute humidity by an arithmetic circuit in the control device (CPU). The position where the transfer corotron 10 is turned off is earlier with respect to the trailing edge of the sheet as the absolute humidity of the humidity data is higher, that is, turned off on the front side of the trailing edge of the sheet, and closer to the edge of the sheet as it is lower.

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 the output determination because the humidity dependence of the transfer efficiency depends more on the absolute humidity than the relative humidity.
Selected from the tables 18, 19, and 20, and output.

[0015] The film potential by the transfer corotron 10 and the suction corotron 11 on the photosensitive member after the transfer, paper誘動charges interposed between the photosensitive drum 1 and the transfer film 9 is generated, the photosensitive drum 1 and the sheet transfer nip At the moment when it leaves, it is charged with the polarity opposite to the primary charge in the form of peeling discharge. It has been experimentally confirmed that the opposite polarity charging is strongly generated in a high humidity environment.

In general, when an organic photoreceptor is used, a negative polarity is used for primary charging. However, a positively charged charge cannot be removed by light removal by light.
It is necessary to return to the minus side once before static elimination by. This can be achieved by using a discharge corotron of minus direct current or a post-transfer neutralizing corotron 5 in which minus direct current is superimposed on alternating current. In this embodiment, a corotron in which a minus direct current is superimposed on an alternating current is used. At this time, a constant voltage power supply was used for the alternating current and a 3.8 KV-RMS output was used, and a constant current power supply whose DC component was variable from −60 to −300 μA was used.

The relative humidity of the DC component is detected by a temperature / humidity sensor 15, and a high current is selected at high humidity and a low current is selected at low humidity based on the humidity data. The selection of the current is calculated by an equation for determining 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 sampling of the humidity data for determining the output of the post-transfer static elimination corotron 5 is performed at the first power-on condition in the morning, that is, when the fixing device temperature is equal to or lower than a certain value and the power is turned on. As described above, the use of the relative humidity of the morning when the power is turned on to determine the output value of the post-transfer static elimination corotron 5 has a strong relationship between the amount of reverse polarity charge after the transfer and the relative humidity in the apparatus. Is the most stressful.

After the transfer, the reverse polarity charging becomes stronger as the photosensitive drum 1 is closer to the rear end of the sheet, and becomes maximum at the end of the sheet. By increasing the amount of DC discharge of the charge removing corotron 5 after transfer, the opposite polarity charge of the photoreceptor is neutralized, but the condition of water content 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 end of the sheet changes, and a reverse charge exceeding the neutralizing power of the charge removing corotron 5 after transfer is also generated. In order to solve this problem, it is necessary to further increase the negative direct current. However, since the applied voltage is increased, a problem such as leakage occurs.

In order to solve these problems, the present invention improves the timing by changing the OFF timing of the transfer corotron 10 with respect to the sheet according to the humidity. The maximum amount of reverse charge at the rear end of the sheet 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 sheet. Since the transfer charge charged on the transfer film 9 easily flows to the uncharged area under the high humidity, even if the transfer current is turned off before the rear end of the paper reaches the transfer position B, the image at the rear end is lower than under the low humidity. Chipping is unlikely to occur.

Utilizing this characteristic, the transfer corotron OF
The timer value was selected at each humidity such that the rear end image was not chipped when the F timing was high and the amount of reverse charge after transfer was minimized.

FIG. 3 shows the timing of each part in the above embodiment. Table 1 shows the OFF timing of the transfer corotron 10 in this embodiment. In Table 1, the minus sign in the column of “Transfer OFF from paper rear end” means that the paper is turned off before the paper rear end passes through transfer position B.

[0022]

[Table 1]

[0023]

As described above, according to the present invention, the humidity data is fed back to the output of the post-transfer static elimination corotron 5, the output of the transfer current, and the transfer current OFF timing value, thereby generating the data at the rear end position of the sheet. The amount of reverse polarity charge can be minimized, and good image quality can be maintained under any environment and use conditions.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a main part of a full-color copying machine of four colors.

FIG. 2 is a block diagram illustrating an example of a control system according to the present invention.

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum, 2 ... Primary charging corotron, 3 ... Developer, 4 ... Transfer drum, 5 ... Electrostatic discharge corotron after transfer, 6 ...
Cleaning device, 7: Static electricity removal lamp before primary charge, 9: Transfer film, 10: Transfer corotron, 11: Adsorption corotron, 12: Transfer drum reference position sensor, 13: Film static elimination 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 front page (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 15/00 303 G03G 21/00 370-500 G03G 15/14-15/16 103 G03G 21/06 G03G 21/14

Claims (4)

(57) [Claims] 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 body that transfers the toner image. And an image forming apparatus having a transfer unit for transferring the toner image onto the image carrier after transfer of the toner image, and a post-transfer charge removing unit that variably controls a power output applied to the post-transfer charge removing unit. Power output variable means, transfer output timing variable means for changing the power output applied to the transfer means at the transfer position and its output timing, temperature and humidity detecting means for detecting temperature and humidity in the apparatus, accordance temperature and humidity data from the detecting means, determine an output value to be applied to the output value and the transfer means to be applied to the post-transfer charge removing means
At the same time as turning off the output of the transfer means.
An image forming apparatus comprising: control means for determining one of the number of OFF timings . The control means has means for determining the relative humidity and the absolute humidity from the temperature and humidity data, respectively, and the output after the transfer is an output selected from the relative humidity .
2. The image forming apparatus according to claim 1, further comprising a unit that controls the output of the transfer unit with an output selected from the absolute humidity. As a peripheral device according to claim 3 the control unit, according to claim 1, characterized in that it comprises a timer means for counting the position detecting means of the transfer means, the means and reference clock to the reference clock generation for the device driver Image forming means. 4. An image carrier which moves endlessly, and the image carrier
And a latent image on the image carrier.
Developing means for developing a toner image, and a transfer member for transferring the toner image
In an image forming apparatus having a transfer unit for transferring the image to
Charge removal after transfer to remove charge on image carrier after transfer of toner image
Means and the power output applied to the post-transfer static elimination means are variable
Power supply output variable means for post-transfer charge removal to be controlled
Power output applied to a certain transfer means and its output timing
Output variable means and device for enabling change of printing
Temperature and humidity detecting means for detecting the temperature and humidity in the
According to the temperature and humidity data from the knowledge means,
Determine the output value to be applied to the stage and the output value to be applied to the transfer means.
As well as the timing of the output of the transfer means.
Control means, and the control means includes temperature and humidity data.
For determining relative humidity and absolute humidity from data
The output of the static eliminator after transfer is selected from the relative humidity.
Absolute humidity for the output and the transfer means output
Having means to control each with a more selected output
An image forming apparatus comprising: