JPH0695534A - Transfer separating device - Google Patents

Abstract

PURPOSE:To provide a transfer separating device in which the efficiency of transfer current can be enhanced by narrowing a discharge opening angle and in which density deterioration at high humidity can be prevented. CONSTITUTION:A transfer separating device comprises a transfer discharger 11 and a separation discharger 12, and a partition plate 14 for separating the transfer discharger 11 from the separation discharger 12 is electrically isolated from a shield 13 and a bias means 44 for applying a voltage of the same polarity as a transfer voltage to the partition plate 14 is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a printer,
The present invention relates to a transfer / separation device in an image forming apparatus using an electrostatic recording method such as a facsimile machine.

[0002]

2. Description of the Related Art Generally, in an electrostatic copying machine, as shown in FIG.
As shown in FIG. 2, the transfer / separation device 105 is arranged at a predetermined position around the photosensitive drum 101. The transfer separation device 105 that has been often used conventionally has a conductive shield 113 having a chevron cross section.
3 by the central partition plate 114 in FIG.
1 and the separate discharger 112 are partitioned. Shield 11
3 is grounded.

Transfer discharger 111 and separation discharger 112
Are equipped with tungsten wires 115 and 116 stretched in a shield 113 partitioned by a partition plate 114, respectively. On the wire 115 of the transfer discharger 111,
A voltage having a polarity opposite to that of the toner, which is a positive voltage in this example, is applied by the power supply 141. As a result, corona discharge is induced, and corona ions (+) generated thereby come into contact with the back surface of the recording paper P. As a result, an electrostatic attractive force is generated between the toner on the photosensitive drum 101 and the recording paper P, and the toner image on the photosensitive drum 101 is transferred to the recording paper P by the electrostatic attractive force.

The recording paper P is sent to a transfer position around the photosensitive drum 101 by a pair of registration rollers 125. Recording paper guides 131 and 132 for guiding the recording paper P are provided between the registration roller pair 125 and the transfer position.
133 is provided. Recording paper guides 131, 13
2, 133 are grounded.

An AC voltage is applied to the wire 116 of the separation discharger 112 by a power supply composed of a DC power supply 142 and an AC power supply 143. As a result, an AC corona discharge is induced, and the charge added to the recording paper P is neutralized. As a result, the electrostatic attraction between the photosensitive drum 101 and the recording paper P is weakened, and the recording paper P is separated from the photosensitive drum 101.

By the way, when the recording paper P is moist in a high humidity environment, the current discharged from the transfer discharger 111 is transmitted through the recording paper P and the recording paper guides 131, 13 are sent.
Since the current easily flows to the conductive member such as 2, 133 and the shield 113 that comes into contact with the recording paper P, the current used for transfer decreases, the transfer efficiency decreases, and the density decreases. .

Therefore, in order to solve such a problem, a conductive member which comes into contact with the recording paper is provided before and after the transfer discharger, and a voltage having a polarity opposite to that of the toner is applied to these conductive members. (Refer to Japanese Unexamined Patent Publication No. 3-260680 and Japanese Utility Model Laid-Open No. 62-118253), the front part of the shield of the transfer discharger is electrically separated from other parts, and a voltage opposite to the toner is applied to the front part. A device which can be applied (see JP-A-61-219071),
Techniques such as those provided with a switch for selecting whether to connect the recording paper guide and the shield of the transfer discharger to the ground portion or to isolate and separate from the ground portion (see Japanese Patent Publication No. 63-60910) have already been developed. ing.

[0008]

The above prior arts all prevent transfer current from escaping through the recording paper to a recording paper guide or the like when the recording paper having a high water content is passed, and therefore the density is Although it is useful for improving the transfer current, it does not focus on the discharge opening angle to improve the transfer current efficiency.

In other words, in the above-mentioned configuration of the prior art, since the shield, the partition plate, etc. are at zero potential or are grounded with a high resistance, when a transfer voltage is applied to the wire,
Since the transfer current flows into the shield and the partition plate,
The discharge opening angle remains wide.

It is an object of the present invention to provide a transfer separation device capable of improving the efficiency of transfer current by narrowing the transfer discharge opening angle and preventing the concentration from decreasing at high humidity.

[0011]

A first transfer separation device according to the present invention comprises a transfer discharger and a separation discharger, and a partition plate for partitioning the transfer discharger and the separation discharger is a shield. It is electrically separated, and the partition plate is provided with bias means for applying a voltage having the same polarity as the transfer voltage.

It is preferable that a recording paper guide for guiding the recording paper from the registration roller to the transfer position is provided with means for applying a voltage having the same polarity as the transfer voltage.

A second transfer separation device according to the present invention comprises a transfer discharger and a separation discharger, and a partition plate for partitioning the transfer discharger and the separation discharger is electrically separated from the shield. Bias means for applying a voltage having the same polarity as the transfer voltage to the partition plate, and constant voltage holding means for holding the potential of the shield at a predetermined potential are provided.

It is preferable to provide means for applying a voltage having the same polarity as the transfer voltage to a recording paper guide for guiding the recording paper from the registration roller to the transfer position. As the constant voltage holding means, for example, a Zener diode connected between the shield and the ground is used.

[0015]

In the first transfer / separation device according to the present invention, the partition plate for partitioning the transfer discharger and the separation discharger is electrically separated from the shield, and a voltage having the same polarity as the transfer voltage is applied to the partition plate. Is applied. Therefore, the discharge opening angle of the transfer discharger is narrowed on the partition plate side, and the transfer current efficiency is improved.

In the second transfer separation device according to the present invention,
A partition plate for partitioning the transfer discharger and the separation discharger is electrically separated from the shield, and a voltage having the same polarity as the transfer voltage is applied to the partition plate. Further, the potential of the shield is held at a predetermined potential by the constant voltage holding means. For this reason,
The discharge opening angle of the transfer discharger is narrowed on the partition plate side, and the discharge opening angle of the transfer discharger is also narrowed on the recording paper carry-in side of the transfer discharger, further improving the transfer current efficiency.

[0017]

1 and 2 show a first embodiment of the present invention.

FIG. 1 shows the construction of a printing mechanism and a recording paper conveying mechanism of an electrostatic digital copying machine.

The printing mechanism includes a photosensitive drum 1, a main charger 2 for charging the photosensitive layer on the surface of the photosensitive drum 1, and an electrostatic latent image formed by laser exposure La on the photosensitive layer as a developer image. A developing device 3 for forming an image, a transfer separation device 5 for transferring the developer image formed on the photosensitive layer onto the recording paper P and separating the recording paper P from the photosensitive drum 1, and a developer image transferred over the recording paper. The recording sheet P is provided with a fixing device 6, a cleaning device 7 for removing the developer remaining on the photosensitive layer after the transfer, and a discharge lamp 8 for removing the charge on the photosensitive layer.

As the photosensitive drum 1, a two-layer negative charging O
A PC is used. The charging polarity of the charger 2 is negative. As the developing device 3, a dry contact two-component reversal developing system is used. The polarity of the toner is negative. The polarity of the developing bias is negative. The discharge charge polarity of the transfer discharger 11 in the transfer separation device 5 is positive. The discharge by the separation discharger 12 in the transfer separation device 5 is an AC discharge.

The recording paper feeding mechanism includes a paper feed roller 22 for feeding the recording paper P in the paper feed cassette 21, and two pairs of feed rollers 23, 2 for feeding the fed recording paper P.
4, a registration roller pair 25 for feeding the recording paper P conveyed by the feed roller pairs 23, 24 to the transfer position on the surface of the photosensitive drum 1 at a predetermined timing, and the recording paper P transferred and separated from the photosensitive drum 1. It is provided with a conveyor belt 26 that is fed to the fixing device 6, a pair of discharge rollers 27 that discharges the recording paper P that has passed through the fixing device 6, and the like.
A recording paper guide 3 for guiding the recording paper P is provided between the registration roller pair 15 and the transfer position on the surface of the photosensitive drum 1.
1, 32, 33 are provided.

FIG. 2 shows the details of the transfer separation device 5.

The transfer / separation device 5 includes a transfer discharger 11 for transferring the developer image formed on the photosensitive layer of the photosensitive drum 1 onto the recording paper P, and a separation / release device for separating the recording paper P from the photosensitive drum 1. It consists of an electric appliance 12. The transfer separation device 5 has a cross section U.
The conductive discharger 11 and the separation discharger 12 are separated from each other by a conductive partition plate 14 that divides the inside of the conductive shield 13 into two parts. The shield 13 is grounded. The partition plate 14 is electrically separated from the shield 13 of the transfer separation device 5, and a voltage having the same polarity as the transfer voltage (a voltage having a polarity opposite to that of the toner) is applied by the power supply 44.

The transfer discharger 11 is provided with a tungsten wire 15 which is stretched in a space surrounded by the shield 13 and the partition plate 14 on the recording paper carry-in side. A voltage having a positive polarity having a polarity opposite to that of the toner is applied to the wire 15 by the power supply 41. As a result, corona discharge is induced, and corona ions (+) generated thereby come into contact with the back surface of the recording paper P. As a result, an electrostatic attractive force is generated between the toner on the photosensitive drum 1 and the recording paper P, and the toner image on the photosensitive drum 1 is transferred to the recording paper P by this electrostatic attractive force.

The separation discharger 12 is provided with a wire 16 made of tungsten which is stretched in a space surrounded by the shield 13 and the partition plate 14 on the recording paper discharge side. An AC voltage is applied to the wire 16 by a power supply including a DC power supply 42 and an AC power supply 43. As a result, corona discharge is induced, and the charge added to the recording paper P by the transfer discharger 11 is neutralized. As a result, the electrostatic attraction between the photosensitive drum 1 and the recording paper P is weakened, and the recording paper P is separated from the photosensitive drum 1.

Recording paper guides 31, 32 provided between the registration roller pair 25 and the transfer position of the photosensitive drum 1,
33 is grounded.

In the first embodiment, since the voltage having the same polarity as the transfer voltage is applied to the partition plate 14, the transfer discharger 11
The discharge opening angle due to is narrowed on the partition plate 14 side. Therefore, the discharge is intensively performed on the partition plate 14 side of the transfer discharger 11. Further, the transfer current is less likely to escape from the partition plate 14, and the current efficiency contributing to the discharge is improved. That is, the transfer efficiency is improved. Therefore, even if the recording paper has a high water content, the high density can be maintained. Further, the rating of the transfer voltage can be lowered, and the cost can be reduced. Further, on the partition plate 14 side of the transfer discharger 11, since the discharge by the transfer discharger 11 does not mix with the AC discharge by the separation discharger 12,
The discharge by the transfer discharger 11 is not disturbed by the AC discharge by the separation discharger 12, and the transferred image is less likely to be disturbed.

With the transfer voltage in the transfer / separation device 5 of the first embodiment set to + 4200v and the voltage applied to the partition plate 14 set to + 800v, output image density data for recording papers having various water contents were obtained by experiments. This result is shown in Figure 3.
Is shown by a triangular plot. Further, the transfer voltage in the conventional transfer / separation device 105 shown in FIG. 12 was set to +4200 v, and output image density data for recording papers having various water contents were obtained by experiments. The results are shown in the square plot in FIG. As shown in the experimental results of FIG. 3, the transfer separation device 5 of the first embodiment can obtain a higher output image density than the conventional device 105.

FIG. 4 shows a second embodiment of the present invention. 4, the same components as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted.

In the second embodiment, as in the first embodiment, the partition plate 14 is electrically separated from the shield 13 of the transfer / separation device 5, and the voltage having the same polarity as the transfer voltage is supplied to the power source. It is applied by 44.

In the second embodiment, unlike the first embodiment, the recording paper guides 31, 32, 33 provided between the registration roller pair 25 and the transfer position of the photosensitive drum 1 are also provided with the polarity of the transfer voltage. Voltages of the same polarity are applied by the power supply 44.

In the second embodiment, the transfer discharge opening angle is narrowed on the partition plate 14 side of the transfer discharger 11, and a voltage having the same polarity as the transfer voltage is applied to the recording paper guides 31, 32, 33 by the power supply. The recording paper guide 31,
It is also narrowed on the 32 and 33 sides. Therefore, the transfer discharger 1
Discharge is concentrated on the partition plate 14 side and the recording paper guides 31, 32, 33 side of No. 1. Further, the transfer current is less likely to escape from the partition plate 14, and the transfer current is changed to the recording paper P.
Also, the current does not escape from the recording paper guides 31, 32, 33, and the current efficiency contributing to the discharge is improved. That is, the transfer efficiency is improved. Therefore, a high concentration can be maintained even in a high humidity environment. On the partition plate 14 side of the transfer discharger 11, the discharge by the transfer discharger 11 does not mix with the AC discharge by the separation discharger 12, so the discharge by the transfer discharger 11 is disturbed by the discharge by the separation discharger 12. In this way, the transferred image is less likely to be disturbed.

The transfer voltage in the transfer separation device 5 of the second embodiment is + 4200v, and the applied voltage to the partition plate 14 and the recording paper guides 31, 32, 33 is + 800v.
Output image density data for recording papers with various water contents were obtained by experiments. The results are shown in a triangular plot in FIG. Further, the transfer voltage in the conventional transfer / separation device 105 shown in FIG. 12 was set to +4200 v, and output image density data for recording papers having various water contents were obtained by experiments. The results are shown in the square plot in FIG. As shown in the experimental result of FIG. 5, the output image density higher than that of the conventional apparatus 105 was obtained according to the configuration of the second embodiment. Further, comparing with the graph of FIG. 3, it can be seen that the configuration of the second embodiment can obtain a higher output image density than the configuration of the first embodiment.

FIG. 6 shows a third embodiment of the present invention. 6, the same components as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted.

In the third embodiment, as in the first embodiment, the partition plate 14 is electrically separated from the shield 13 of the transfer / separation device 5, and a voltage having the same polarity as the transfer voltage is supplied to the power source. It is applied by 44. The recording paper guides 31, 32, 33 provided between the registration roller pair 25 and the transfer position of the photosensitive drum 1 are grounded.

In the third embodiment, unlike the first embodiment, the shield 13 of the transfer separation device 5 is grounded via a voltage adjusting element 51 such as a Zener diode. Shield 1
Although a transfer current flows through 3, the potential of the shield 13 is held at the rated voltage of the voltage adjusting element 51, for example, + 740v, because the transfer current is grounded via the voltage adjusting element 51.

In the third embodiment, the transfer discharge opening angle is narrowed on the partition plate 14 side of the transfer discharger 11, and the shield 13 is held at a predetermined positive potential.
It is also narrowed down on the recording paper carry-in side. Therefore, the discharge area of the transfer discharger 11 is narrowed as a whole, so that the discharge is concentrated. Further, the transfer current is less likely to escape from the partition plate 14, and the current efficiency contributing to the discharge is improved. That is, the transfer efficiency is improved. Therefore, a high concentration can be maintained even in a high humidity environment.

As will be described below with reference to FIGS. 7 and 8, on the partition plate 14 side of the transfer discharger 11, the discharge by the transfer discharger 11 does not mix with the AC discharge by the separation discharger 12. The transfer image is not disturbed without the discharge by the transfer discharger 11 being disturbed by the discharge by the separation discharger 12. Further, since the shield 13 is held at a predetermined positive potential, the opening angle of the discharge by the separation discharger 12 is narrowed, so that the discharge efficiency of the separation discharger 12 is improved.

Consider the discharge of the separate discharger 12.
When the AC applied voltage of the separation discharger 12 has a positive component, as shown by a chain line F1 in FIG. 7, the discharge opening angle of the separation discharger 12 is larger than that of the conventional transfer separation device 105 of FIG. It is considered that it narrows on the 14 side and also slightly on the recording paper discharge side. When the AC applied voltage of the separation discharge device 12 has a negative component, as shown by a chain line F2 in FIG. 7, as compared with the conventional transfer separation device 105 of FIG.
It is considered that the discharge opening angle of the separation discharge device 12 widens on the partition plate 14 side and slightly widens on the recording paper discharge side.

However, in practice, the separate discharger 12
Since the discharge opening angle of No. 1 cannot follow the cycle of the AC applied voltage, as shown in FIG. 8, the discharge opening angle of the separation discharger 12 is an intermediate angle between F1 and F2 in FIG.
The angle is smaller than that of the conventional device 105. Therefore, the discharge of the separation discharger 12 does not disturb the discharge of the transfer discharger 11 on the partition plate 14 side, and the discharge efficiency of the separation discharger 12 is also improved.

The transfer voltage in the transfer / separation device 5 of the third embodiment is +4200 v, and the voltage applied to the partition plate 14 is +80.
The output image density data for recording papers having various moisture contents were experimentally determined with 0 v and the rated voltage of the Zener diode set to 740 v. The results are shown in a triangular plot in FIG. Further, the conventional transfer separation device 105 shown in FIG.
The transfer voltage at +4200 V was set, and output image density data for recording papers having various water contents were obtained by experiments. The results are shown in a square plot in FIG. As shown in the experimental result of FIG. 9, according to the configuration of the third embodiment,
An output image density higher than that of the conventional apparatus 105 was obtained.

FIG. 10 shows a fourth embodiment of the present invention. 10, the same parts as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted.

In the fourth embodiment, similarly to the first embodiment, the partition plate 14 is electrically separated from the shield 13 of the transfer separation device 5, and a voltage having the same polarity as the transfer voltage has a power supply 44. Is being applied by.

In the fourth embodiment, unlike the first embodiment, the shield 13 of the transfer / separation device 5 is grounded via a voltage adjusting element 51 such as a Zener diode. Although the transfer current flows through the shield 13, the voltage adjusting element 51
Since it is grounded via the
The rated voltage of the voltage adjusting element 51, for example, + 740v is held.

Further, in the fourth embodiment, unlike the first embodiment, the transfer voltage is also applied to the recording paper guides 31, 32, 33 provided between the registration roller pair 25 and the transfer position of the photosensitive drum 1. A voltage having the same polarity as the polarity is applied by the power supply 44.

In the fourth embodiment, the transfer discharge opening angle is narrowed on the partition plate 14 side of the transfer discharger 11, the shield 13 is held at a predetermined positive potential, and the recording paper guide 3 is used.
Since a voltage having the same polarity as the transfer voltage polarity is applied to 1, 32, and 33 by the power source, the transfer discharge device 11 can be narrowed on the recording paper carry-in side. Therefore, the discharge area of the transfer discharger 11 is narrowed as a whole, so that the discharge is concentrated. In addition, the transfer current is less likely to escape from the partition plate 14, and the transfer current is transmitted through the recording paper P and the recording paper guide 3
It does not escape from 1, 32, 33, and the current efficiency contributing to discharge is improved. That is, the transfer efficiency is improved. Therefore, a high concentration can be maintained even in a high humidity environment.

On the partition plate 14 side of the transfer discharger 11, the discharge by the transfer discharger 11 does not mix with the AC discharge by the separation discharger 12, so the discharge by the transfer discharger 11 becomes the discharge by the separation discharger 12. The transferred image is less likely to be disturbed without being disturbed. Further, since the shield 13 is held at a predetermined positive potential, the discharge opening angle of the separation discharge device 12 is narrowed, so that the discharge efficiency of the separation discharge device 12 is improved.

The transfer voltage in the transfer separation device of the fourth embodiment is +4200 v, the partition plate 14 and the recording paper guide 3
The output image density data for recording papers having various water contents were obtained by experiments, with the applied voltage to 1, 32, and 33 being +800 v and the rated voltage of the Zener diode being 740 v. The result is shown in FIG. 11 by a triangular plot. Also,
With the transfer voltage in the conventional transfer / separation device 105 shown in FIG. 12 set to +4200 v, output image density data for recording papers having various water contents were obtained by experiments. The results are shown in FIG. 9 as a square plot. As shown in the experimental result of FIG. 11, according to the configuration of the fourth embodiment, the conventional device 105
A higher output image density was obtained. Further, comparing with the graph of FIG. 9, it can be seen that the configuration of the fourth embodiment can obtain a higher output image density than the configuration of the third embodiment.

[0049]

According to the present invention, the transfer discharge aperture angle can be narrowed and the transfer current efficiency can be improved. Therefore, it is possible to prevent the concentration from decreasing at high humidity.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a configuration of a print mechanism and a recording paper conveyance mechanism of an electrostatic digital copying machine.

FIG. 2 is a configuration diagram showing details of a transfer separation device according to the first embodiment of the present invention.

FIG. 3 is a graph showing experimental data of image density with respect to water content of recording paper according to the first example and experimental data of image density with respect to water content of recording paper according to a conventional example.

FIG. 4 is a configuration diagram showing details of a transfer separation device according to a second embodiment of the present invention.

FIG. 5 is a graph showing experimental data of image density with respect to water content of recording paper according to the second example and experimental data of image density with respect to water content of recording paper according to a conventional example.

FIG. 6 is a configuration diagram showing details of a transfer separation device according to a third embodiment of the present invention.

FIG. 7 is an explanatory diagram for explaining a discharge opening angle of the separation discharge device.

FIG. 8 is a diagram showing a discharge opening angle of a separation discharge device.

FIG. 9 is a graph showing experimental data of image density with respect to water content of recording paper according to the third example and experimental data of image density with respect to water content of recording paper according to a conventional example.

FIG. 10 is a configuration diagram showing details of a transfer separation device according to a fourth embodiment of the present invention.

FIG. 11 is a graph showing experimental data of image density with respect to water content of recording paper according to a fourth example and experimental data of image density with respect to water content of recording paper according to a conventional example.

FIG. 12 is a configuration diagram showing details of a conventional transfer separation device.

[Explanation of symbols]

 1 Photoconductor Drum 5 Transfer Separation Device 11 Transfer Discharger 12 Separation Discharger 13 Shield 14 Partition Plate 15 Wire 16 Wire 25 Registration Roller Pair 31, 32, 33 Recording Paper Guide 41, 42, 43, 44 Power Supply 51 Zener Diode

Claims (5)

[Claims] 1. A partition plate composed of a transfer discharger and a separation discharger for partitioning the transfer discharger and the separation discharger is electrically separated from a shield, and a transfer voltage is applied to the partition plate. A transfer / separation device provided with bias means for applying voltages of the same polarity. 2. The transfer / separation device according to claim 1, further comprising means for applying a voltage having the same polarity as the transfer voltage to a recording paper guide for guiding the recording paper from the registration roller to the transfer position. 3. A partition plate, which comprises a transfer discharger and a separation discharger and partitions the transfer discharger and the separation discharger from each other, is electrically separated from the shield, and a transfer voltage is applied to the partition plate. A transfer separation device provided with bias means for applying voltages of the same polarity and constant voltage holding means for holding the potential of the shield at a predetermined potential. 4. The transfer / separation device according to claim 3, wherein a recording paper guide for guiding the recording paper from the registration roller to the transfer position is provided with a means for applying a voltage having the same polarity as the transfer voltage. 5. The constant voltage holding means is a Zener diode connected between the shield and ground.
Alternatively, the transfer separation device according to item 4.