JPH0695516A - Toner transfer device for electrostatic transfer type electrophotographic device - Google Patents

Abstract

(57) [Abstract] [Purpose] High transfer ability due to low applied voltage, stable transfer ability against minute deformation of the printing medium, and even for minute stains adhering to the surface of the photoconductor. In contrast,
It is an object of the present invention to provide a toner transfer device of an electrostatic transfer type electrophotographic device which does not require a large-scale cleaning member and is small in size and can respond at high speed. A photoconductor includes a conductive member 3 as a transfer electrode, a flexible member 4 for supporting the conductive member 3, and a support member 5 for rotatably supporting the flexible member 4. The printing medium 2 that is in contact with the surface of the printing medium 1 is pressed from the back side by a conductive member 3, and a charge having a polarity opposite to that of the toner is applied to the conductive member 3 to transfer the toner to the printing medium 2. And

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner transfer device for an electrostatic transfer type electrophotographic apparatus, and more specifically, a roller transfer device, in which a contact is made from a back surface of a printing medium to a printing medium so that the surface of the photoreceptor is The present invention relates to a toner transfer device that applies a charge having a polarity opposite to that of a toner to transfer the toner to a print medium.

[0002]

2. Description of the Related Art In recent years, in the field of electrostatic transfer type electrophotographic apparatuses, in order to reduce the cost of products and the amount of printing media used, instead of conventional continuous printing media, pre-cut printing is performed. Measures have been taken such as labor saving of cutting work after printing using a medium, and printing on both sides of the printing medium.

As a toner transfer device of an electrostatic transfer type electrophotographic apparatus, conventionally, a toner transfer device having a structure shown in FIGS. 3 to 5 has been used.

In FIG. 3, a tungsten thin wire 11 of about 60 to 100 μm and a box-shaped (or semi-circular) shield plate 12 with one end open are used, and an electric charge having a polarity opposite to that of the toner is added to the tungsten thin wire 11 for exposure. The toner on the surface of the body 1 is transferred to the print medium 2.

In FIG. 4, a roller 13 such as a butadiene type rubber is used, which is pressed against the back surface of the printing medium 2 and an electric charge having a polarity opposite to that of the toner is applied to the rubber roller 13 so that the toner on the surface of the photoconductor 1 is made. Is transferred to the print medium 2.

In FIG. 5, a transfer belt 15 supported by at least two rollers 17 is used, and the transfer belt 15 is pressed against the side of the photoreceptor 1 from the rear surface of the print medium 2 and the transfer belt 1 is used.
By applying a charge having a polarity opposite to that of the toner to the transfer belt 15 from the back surface of the transfer device 5 using the same transfer device as in FIG.
The toner on the surface of the photoconductor 1 is transferred to the print medium 2.

[0007]

However, each of the above-described conventional toner transfer devices has the following problems.

In the system shown in FIG. 3, the tungsten fine wire 1 is used.
In order to generate a charge (corona) having a polarity opposite to that of the toner from No. 1, it is necessary to apply a high voltage of about 4 to 10 kV to the thin wire 11 itself.

Further, the charge injection amount into the print medium 2 is
As the opening width f of the shield plate 12 and the conductivity of the shield plate 12 depend on the shield plate 12, the shield plate 12 must be made of a conductive material and always have openings.

Therefore, during the printing operation, the dust and toner floating in the atmosphere tend to stain the inner surface of the shield plate 12, the charge injection amount into the print medium 2 is likely to change, and the discharge phenomenon occurs. There is a problem that electrical noise failure is likely to occur.

Further, the print medium 2 is slightly deformed (uneven).
If so, there is a problem in that the transfer capability in the recess is lowered.

The system shown in FIG. 4 has the advantages that a stable transfer capability is given to minute deformation of the print medium 2 and that the voltage applied to the roller 13 can be lowered. In the space with the next print medium, the toner slightly attached to the surface of the photoconductor 1 directly contacts the roller 13, and the surface of the roller 13 is soiled to reduce the transfer ability thereof. It has the problem of becoming dirty.

Therefore, a cleaning member 14 for cleaning the surface of the roller 13 and a toner collecting portion (not shown) are added to keep the surface of the roller 13 in the initial state at all times. It has a drawback that the toner transfer device has a large-scale structure.

Further, in the roller system, since the pressing force of the roller 13 against the photoconductor 1 cannot be increased so much, the contact width between the photoconductor 1 and the print medium 2, that is, the contact in the running direction of the print medium 2 with respect to the photoconductor 1. The width cannot be wide and an applied voltage of about 1000 to 3000 V is required.

On the other hand, in order to keep the contact width between the photosensitive member 1 and the printing medium 2 wide, the diameter of the roller 13 cannot be reduced, and the roller diameter is generally about 40-6.
In order to reduce the size of the apparatus and further reduce the cost, in order to eliminate the cleaning member 14, the roller 13 should be separated from the photoconductor 1 in the space between the print medium 2 and the next print medium. Is also proposed, but in that case,
Since the weight of the roller 13 is large, it is difficult to swing the roller 13 at a high speed.

According to the method shown in FIG. 5, the print medium 2 is
Since the flat transfer belt 15 receives a pressing force from the back side and travels while always in contact with the photoconductor 1, the photoconductor 1
The contact width between the print medium 2 and the print medium 2, that is, the contact width in the traveling direction of the print medium 2 with respect to the photoconductor 1 can be widened. However, similar to the conventional example shown in FIG. In the space of, the toner slightly attached to the surface of the photoconductor 1 directly contacts the transfer belt 15, and the surface of the transfer belt 15 is soiled to reduce the transfer capability thereof, and the back surface of the print medium 2 is soiled. I have a problem.

Therefore, also in this system, as in the embodiment shown in FIG. 4, a cleaning member 14 for cleaning the surface of the transfer belt 15 and a toner collecting section 16 are added to always make the surface of the transfer belt 15 initial. Although it has been devised to maintain the state, this has a drawback that the toner transfer device has a large-scale configuration as described above.

The object of the present invention is to have a high transfer ability with a low applied voltage, a stable transfer ability to a minute deformation of a printing medium, and to remove minute stains adhering to the surface of the photoreceptor. On the other hand, it does not require a large-scale cleaning member,
It is an object of the present invention to provide a toner transfer device of this type that is small and can respond at high speed.

[0019]

In order to exert a high transfer ability at a low voltage, the distance between the photoconductor substrate and the transfer voltage applying electrode plate should be infinitely close to each other, and the electrode width in the print medium running direction should be made small. Spreading is effective.

Further, in order to obtain a stable transfer capability with respect to a minute deformation of the print medium, the print medium is physically moved from the back surface to the photoconductor side as in the roller transfer method and the belt transfer method. Just press it.

Based on the above principle, in the present invention, a conductive member as a transfer voltage applying electrode having a predetermined width in the print medium running direction is pressed against the print medium by being supported by a flexible member which bends with a small curvature. And is configured to press the print medium against the photoconductor over a wide range.

As described above, since the conductive member directly presses the back surface of the printing medium, the distance between the photoconductor and the electrode is minimized, and thus, the high transfer ability can be exhibited at the low applied voltage. it can.

Further, the purpose of obtaining a stable transfer ability with respect to minute deformation of the print medium is achieved by physically pressing the print medium from the back surface thereof toward the photoconductor.

Further, with respect to minute stains adhering to the surface of the photoconductor, when the print medium is not in contact with the surface of the photoconductor, the flexible member is swung to displace the conductive member from the photoconductor. The conductive member is pulled apart to operate so as not to contact the photosensitive member.

The high-speed response is achieved by forming the movable member such as a conductive member and a flexible member with a simple and lightweight member.

[0026]

As described above, the conductive member functions as an electrode for transfer.

Further, the flexible member holding the conductive member acts to widen the contact width with the print medium.

Further, swinging the flexible member is
It plays the role of pressing the conductive member against the photoconductor or separating it from the photoconductor.

Further, by forming the movable member such as the conductive member and the flexible member with a simple and lightweight member, it is possible to speed up the rocking motion.

[0030]

FIG. 1 shows an embodiment of the present invention.

The transfer device is located on the back surface of the print medium 2 in contact with the surface of the photoconductor 1 and has a flexible member 4 having a conductive member 3 substantially tangential to the back surface of the print medium 2 and a flexible member. A support member 5 at one end of the flexible member 4 for rotatably supporting the flexible member 4, a power unit 6 for rotating the support member 5, and a voltage applied from one end or the entire surface of the conductive member 3. And a detection device 8 for detecting the front end position of the print medium 2.

When the print medium 2 does not pass through, the flexible member 4 having the conductive member 3 is stopped at a position apart from the surface of the photoconductor 1 as shown by the broken line in FIG.

When the printing operation is started, the photosensitive member 1 starts to rotate in the direction of arrow a in FIG. 1 with the developed toner 9 attached to the surface thereof.

On the other hand, the print medium 2 moves in the direction of arrow b in FIG. 1 and contacts the photoconductor 1.

At this time, the position of the print medium 2 has already been detected by the detection device 8 for detecting the leading edge of the print medium 2.

Next, the conductive member 3 drives the power unit 6 based on the signal from the detection device 8 so as to press the print medium 2 substantially at its leading end.

Along with this, the flexible member 4 rotates toward the photoconductor 1 in the direction of arrow c in the figure. That is, since the flexible member 4 gives a proper pressing force and contact width to the print medium 2, the flexible member 4 is flexed by the power unit 6.

On the other hand, at this time, the optimum voltage is applied to the conductive member 3 by the voltage applying device 7.

Further, the print medium 2 moves while contacting with the photoconductor 1.

When the developed toner image 9 moves on the surface of the photoconductor 1 and passes immediately below the conductive member 4, the toner image 9 is transferred to the print medium 2. At this time, of course, the electric charge opposite to the electric polarity of the toner is applied to the conductive member 3.

When the print medium 2 passes the position of the conductive member 3, the flexible member 4 rotates in a direction (direction of arrow d in the figure) away from the photosensitive member 3 to return to the position of the broken line. .

Then, when the photoconductor 1 continues to rotate and the next print medium 2 is fed, the flexible member 4 faces the photoconductor 1 again in the direction of arrow c in the figure as described above. After that, the above-described operation is repeated, and the voltage applied to the conductive member 3 is controlled so as to obtain the optimum transfer ability according to the volume resistivity of the print medium used.

In the above operation, the basic expression of the transfer current i is expressed by the following expression in the model diagram shown in FIG.

[0044]

[Equation 1]

In the above equation, I: current injected into the conductive member 3 i: current flowing into the photosensitive member 1 per unit time (required transfer current) Δt: contact time between the conductive member 3 and the photosensitive member 1, The contact width b between the conductive member 3 and the photoconductor 1 is set to the peripheral speed v of the photoconductor 1.
As is clear from the above equation, if the peripheral speed of the photoconductor 1 is high, good transfer cannot be realized unless the injection current into the conductive member 3 is increased.

On the other hand, if the contact width b between the conductive member 3 and the photosensitive member 1 can be made large even if the peripheral speed of the photosensitive member 1 is high, the contact time Δt between the conductive member 3 and the photosensitive member 1 can be reduced. Since it can be increased, the current I injected into the conductive member 3 can be decreased.

According to this embodiment, since the conductive member 3 is supported by the flexible member 4, the contact width e between the photosensitive member 1 and the conductive member 3 can be widened as shown in FIG. be able to.

During printing, the print medium 2 exists between the conductive member 3 and the photoconductor 1, and the current i flowing into the photoconductor 1 per unit time varies depending on the volume resistivity of the print medium 2. Therefore, it has already been described that the voltage applied to the conductive member 3 is controlled according to the volume resistivity of the print medium for the purpose of obtaining the optimum transfer ability.

In the illustrated embodiment, the case where the flexible member 4 and the conductive member 3 are constituted by separate members has been illustrated, but instead of this, the flexible member 4 itself has conductivity. Even if it makes it possible, the same effect as the above-mentioned embodiment can be obtained.

Further, the support member 5 for rotatably supporting the flexible member 4 has a structure having rigidity in consideration of the shape of the flexible member 4, and the support member 5 and the flexible member 4 are provided. Even if they are integrated, the same effect as that of the illustrated embodiment can be obtained.

[0051]

According to the present invention, a conductive member as a transfer voltage applying electrode having a predetermined width in the running direction of a printing medium is supported by a flexible member which bends with a small curvature and is pressed against the printing medium. , Press the printing medium against the photoconductor in a wide range.

As described above, since the conductive member directly presses the back surface of the printing medium, the distance between the photoconductor and the electrode is minimized, and thus, the high transfer ability can be exhibited at a low applied voltage. it can.

Further, by physically pressing the print medium from the back surface thereof toward the photoconductor, it is possible to obtain a stable transfer capability with respect to minute deformation of the print medium.

Further, with respect to minute stains adhering to the surface of the photoconductor, when the print medium is not in contact with the surface of the photoconductor, the flexible member is swung to remove the conductive member from the photoconductor. If the conductive member is separated so as not to contact the photosensitive member, the conductive member does not pick up minute dirt adhering to the surface of the photosensitive member, resulting in a large-scale cleaning member. The size of the device can be reduced without the need for.

Furthermore, by forming the movable member such as the conductive member, the flexible member, and the support member by a simple and lightweight member, high-speed response of these movable members becomes possible.

[Brief description of drawings]

FIG. 1 is a side view of a transfer device showing an embodiment of the present invention.

FIG. 2 is a side view of a model for explaining the principle of the present invention.

FIG. 3 is a schematic side view of a conventional transfer device using a thin tungsten wire.

FIG. 4 is a schematic side view of a conventional transfer device using a roller transfer method.

FIG. 5 is a schematic side view of a conventional transfer device using a belt transfer method.

[Explanation of Codes] 3 ... Conductive member, 4 ... Flexible member, 5 ... Support member, 7 ...
Voltage application device.

Claims (4)

[Claims] 1. An electrostatic transfer system in which a surface of a photoconductor is developed with toner, and a charge having a polarity opposite to that of the toner is electrostatically applied from the back surface of the print medium in contact with the photoconductor to transfer the toner to the print medium. A toner transfer device of an electrophotographic apparatus, comprising a conductive member as a transfer electrode, a flexible member that supports the conductive member, and a support member that rotatably supports the flexible member. An electrostatic transfer characterized in that a print medium in contact with the body surface is pressed from the backside by a conductive member, and a charge having a polarity opposite to that of the toner is applied to the conductive member to transfer the toner to the print medium. Transfer device for electrophotographic electrophotographic device. 2. The toner transfer device according to claim 1, wherein at least the side of the flexible member that comes into contact with the print medium is made of a conductive material. 3. The toner transfer device according to claim 1, wherein the flexible member holds the print medium only when the print medium passes. 4. The toner transfer device according to claim 1, wherein the applied current to the conductive member is variable according to the volume resistivity of the print medium.