JP4214513B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus that visualizes an image using colored particles such as a printer, an electrostatic copying machine, a facsimile machine, etc., and in particular, from an image carrier to a transfer material. The present invention relates to a transfer device that transfers a toner image to the head.
[0002]
[Prior art]
Conventionally, a recording apparatus using an electrophotographic method among the above image forming apparatuses forms a latent image on the surface of an image carrier using a laser beam on an image carrier uniformly charged by a charging device. Then, development is performed by supplying toner from a developing roll. The toner electrostatically adsorbed on the surface of the image carrier by development is applied with a voltage having a polarity opposite to the charging polarity of the toner by the transfer device to transfer the toner image to the transfer material, and the toner is fixed to the transfer material by the fixing device. It is recorded through a series of processes.
[0003]
In the operation of such an image forming apparatus, when transferring a toner image formed by development onto a transfer material, the transfer apparatus used is roughly classified into a contact transfer apparatus and a non-contact transfer apparatus. Examples of the contact transfer method include a roller transfer method and a belt transfer method, and a corona transfer method is well known as a non-contact transfer method.
[0004]
In recent years, methods other than the above-described transfer method are also known. For example, there is a method in which a transfer charger is provided at the end of a blade-like member and the end is brought into contact with the nip between the paper and the image carrier, and a method using a plate-like charging member (for example, (See Patent Document 1).
[Patent Document 1]
JP-A-9-230709 (Page 9, FIG. 5)
[0005]
[Problems to be solved by the invention]
However, the roller transfer method and the belt transfer method, which are the contact transfer methods, result in a disturbance of the toner image between the image carrier and the transfer material due to the speed difference between the image carrier and the transfer device. In order to avoid this, a transfer source device is provided in the transfer device. Since the corona transfer method is a non-contact transfer method, the voltage applied to the transfer to the transfer material is high, high voltage measures are required for the image carrier and surrounding devices, the high voltage generator is expensive, etc. As a result, the cost will be affected.
[0006]
In the patent document, a transfer width formed by an image carrier having a cylindrical cross section and a transfer member having a smooth cross section has a transfer nip formed by sandwiching both ends of a conductive member between insulators. In this case, it becomes point contact, and it becomes impossible to take a wide transfer nip. For this reason, it becomes non-contact at the end of the transfer width, and the applied voltage applied to the transfer escapes to the gap, which is not efficient.
[0007]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems and provide a simple image forming apparatus while obtaining a good image.
[0008]
[Means for Solving the Problems]
An object of the present invention is to provide an image forming apparatus including an image carrier that carries a toner image, and a transfer device that transfers the toner image from the image carrier to a transfer material. The transfer device includes a metal transfer electrode. And a transfer material width direction of the transfer electrode is inclined at a predetermined angle with respect to a longitudinal direction of the image carrier, and the transfer electrode and the image carrier And the transfer nip formed by the transfer electrode and the image carrier has a curved shape covering the surface of the image carrier, and the toner is transferred from the image carrier to the transfer material. When transferring an image, the transfer material is moved without a gap between the surface of the image carrier and the transfer electrode.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described with reference to the accompanying drawings.
[0010]
FIG. 1 is a schematic side view showing a configuration of a laser printer applied to the present invention. In FIG. 1, reference numeral 1 denotes a photosensitive drum as an image carrier, and the photosensitive drum 1 is driven to rotate clockwise. The photosensitive drum 1 is uniformly charged by a charging device 2 (here, a scorotron charger is used). In this embodiment, it is negatively charged. On the negatively charged photosensitive drum 1, an electrostatic latent image based on the image signal is formed by the exposure device 3. The photosensitive drum 1 obtains a toner image by the developing device 4. In this embodiment, a reversal development method using toner having the same polarity as the negative potential obtained by exposure is employed. The toner image is sent to the transfer device 5 while being adsorbed on the photosensitive drum 1. The transfer device 5 will be described in detail later.
[0011]
A sheet 6 used as a transfer material is supplied from a hopper and is sent to a transfer device 5 after passing through a conveying roller 7. A transfer nip portion is formed by the transfer device 5 coming into contact with the photosensitive drum 1 at the transfer portion, and the sheet 6 conveyed so as to coincide with the rotation of the photosensitive drum 1 is transferred from the transfer bias power source 8 at the transfer nip portion. A voltage is applied, and the toner image is transferred to the paper 6. The sheet 6 with the toner image attached is output as a printed matter by the fixing device 10. On the other hand, untransferred toner remaining on the photosensitive drum 1 without being transferred during the transfer process is collected by the cleaning device 9. Through these series of steps, the photosensitive drum 1 rotates again to the charging device 2.
[0012]
FIG. 2 shows an enlarged view of the vicinity of the transfer device 5, (a) is a schematic side view including the transfer device 5, and (b) is a view of the photosensitive drum 1 and the transfer as viewed from the top when (a) is the front. FIG. 6 is a diagram showing a positional relationship of the device 5. The transfer device 5 is mainly composed of a metal transfer electrode shown in a black portion, an insulator that supports the transfer electrode and is designed to prevent a hand from coming into direct contact with the electrode, and a transfer bias power source that supplies a voltage to the transfer electrode. It consists of eight. In this embodiment, the transfer electrode has the same curvature as that of the photosensitive drum 1 and forms a transfer nip portion in surface contact with the photosensitive drum 1. The transfer upstream side of the transfer electrode is chamfered so that the sheet 6 can be easily guided to the transfer nip portion.
[0013]
A voltage is not supplied from the transfer bias power source 8 to the transfer electrode when the paper 6 is not passing through the transfer nip portion. In practice, in order to avoid fog toner or the like adhering to the photosensitive drum 1 from being transferred to the transfer electrode and smearing the transfer electrode and further the back surface of the paper 6, a voltage having the same polarity as the charged toner is applied. It is desirable to control to apply from the transfer bias power supply 8 or to apply a voltage having a polarity opposite to that of the charged toner from the transfer bias power supply 8. After the sheet 6 passes through the transport roller 7 and enters the transfer nip portion, a voltage having a polarity opposite to that of the toner charged from the transfer bias power supply 8 to the transfer electrode is applied to the sheet 6. After the sheet 6 passes through the transfer nip portion, the supply of voltage is stopped again. With this configuration, a good image can be obtained.
[0014]
FIG. 3 shows another embodiment of the present invention. In this example, the horizontal longitudinal direction of the photosensitive drum 1 and the horizontal longitudinal direction of the transfer electrode of the transfer device 5 are not the same direction as the transfer nip portion of FIG. It is a different point from the said Example that it is angle-inclined. The paper 6 is conveyed from the direction of the arrow shown on the right side of the drawing. The voltage application means at the time of transfer is the same as in the above embodiment. The sheet 6 first enters the transfer nip formed by the photosensitive drum 1 and the transfer electrode from the right side of the sheet. The sheet 6 is in close contact with the photosensitive drum 1 from the right side of the sheet surface, and a transfer voltage having a polarity opposite to that of the toner charged by the transfer electrode is applied. Thus, by first bringing the paper corners into close contact with the photosensitive drum 1, it is possible to reduce troubles such as a jam that is a paper conveyance mistake. Subsequently, the sheet 6 is separated from the transfer nip portion from the right side of the sheet. The sheet can be peeled off from the photosensitive drum 1 by utilizing the rigidity of the sheet and the dead weight of the corner. As a result, it is possible to prevent the trouble that the paper 6 is not peeled off while being wound around the photosensitive drum 1. With this configuration, a good image can be obtained.
[0015]
It is more effective to provide a peeling charger in the downstream direction of the transfer device 5 via an insulating material. At this time, conventionally, the peeling charger is installed in the same horizontal longitudinal direction as that of the photosensitive drum 1, but in this embodiment, it can be seen that only a small peeling charger can be used only on the right side of the paper surface downstream of the transfer nip. .
[0016]
In both of the above-described embodiments, a metal electrode is used as the transfer device 5, but in consideration of the burden on the photosensitive drum 1, a soft material such as conductive rubber, sponge, plastic, or the like is used. Is preferred.
[0017]
Further, if the transfer device 5 is a contactable / separable device, it is possible to prevent the photosensitive drum 1 and the transfer device 5 from being worn during non-printing, and the transfer device surface is contaminated by fog toner adhering to the photosensitive drum 1. It is also possible to prevent this.
[0018]
As a material for the transfer nip portion, a material that does not reverse the charging polarity of the toner is used. As a result, the toner adhering to the nip portion does not become dirty at the time of transfer, and can be discharged from the nip portion by applying a voltage having the same polarity as the toner at the time of non-transfer. As a specific material, a material containing fluorine is used when the toner is positively charged, and a material containing silicon is used when the toner is negative.
[0019]
The present invention can be used regardless of monochrome / color, positively charged / negatively charged toner, and magnetic / nonmagnetic toner.
[0020]
【The invention's effect】
As described above, according to the present invention, it is possible to reduce the voltage required for transfer, which is excellent in terms of power saving and safety, and can cope with high-speed printing due to the wide transfer nip. Is simple and leads to cost reduction.
[0021]
In addition, since it is a contact transfer system, the frictional charging with the toner can be prevented from adhering to the toner by using a material that does not reverse the charging polarity of the toner.
[0022]
Furthermore, the transfer nip is inclined at a predetermined angle with respect to the horizontal longitudinal direction of the image carrier, so that the transfer material wound around the image carrier is peeled off by its own weight, and the transfer material peeling charger is minimized. The voltage can be increased, and at the same time, the voltage required for peeling off the transfer material can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic side view showing a configuration of a laser printer provided with an embodiment of the present invention.
2 is an enlarged view of the vicinity of the transfer in FIG. 1, (a) is a schematic side view including a transfer device, and (b) is an image carrier viewed from the top when (a) is a front view; It is a figure showing the positional relationship of a transfer apparatus.
3A and 3B show another embodiment of the present invention, in which FIG. 3A is a schematic side view including a transfer device, and FIG. 3B is an image carrier viewed from the top when FIG. It is a figure showing the positional relationship of a transfer apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum, 2 ... Charging device, 3 ... Exposure device, 4 ... Developing device, 5 ... Transfer device, 6 ... Paper, 7 ... Conveyance roller, 8 ... Bias power supply, 9 ... Cleaning device, 10... Fixing device.

Claims (4)

In an image forming apparatus comprising: an image carrier that carries a toner image; and a transfer device that transfers the toner image from the image carrier to a transfer material.
The transfer device includes a metal transfer electrode and an insulator that supports the transfer electrode, and the transfer material width direction of the transfer electrode is inclined at a predetermined angle with respect to the longitudinal direction of the image carrier. The curvature of the transfer electrode and the image carrier is the same, and the transfer nip formed by the transfer electrode and the image carrier has a curved shape covering the surface of the image carrier, An image forming apparatus, wherein when transferring a toner image from the image carrier to the transfer material, the transfer material moves between the surface of the image carrier and the transfer electrode without any gap.   The image forming apparatus according to claim 1, further comprising a charger for peeling the transfer material through the insulator in a downstream direction of the transfer nip portion.   The image forming apparatus according to claim 1, further comprising a power source that supplies a voltage to the transfer electrode, and the voltage from the power source is supplied only when the transfer material is in the transfer nip portion. 4. The image forming apparatus according to claim 1, wherein a material of the transfer device constituting the transfer nip portion is a material that does not reverse the frictional charging polarity of the toner. 5.

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