JPH04153682A - Transfer device - Google Patents

Abstract

PURPOSE:To make a device comply with a two-component type developing method and a new two-component type developing method by providing insulating rollers having a larger diameter than that of a transfer roller at both ends of the transfer roller and allowing the insulating roller to slightly contact with the photosensitive drum. CONSTITUTION:The roller main body part of the transfer roller 60 is made a conductive rubber roller part 62, and the insulating roller parts 63 and 63 having the larger roller diameter than that of the roller main body part are provided at both ends of the roller 60. A paper D which passes a resist roller is supplied between the photosensitive drum 2 and the roller 60, then moves along the surface of the drum 2 with the rotation of the drum 2, and is carried between the drum 2 and a paper guiding plate 61. The paper D tightly contacts with the surface of the drum 2 between the roller 60 and the plate 61 in virtue of the guiding action of the plate 61 and the stiffness of the paper D. Since bias voltage is impressed on the roller 60 during the above, toner is transferred and the paper D is carried in a direction shown by an arrow X, then a transfer stage is finished. Thus, the device is used without trouble even in the two- component type developing method or the new two-component type developing method.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transfer device that is installed in, for example, an electrophotographic printer and transfers a toner image on a photosensitive drum onto a sheet of paper.

In this type of printer, recorded information is exposed on a photosensitive drum to form an electrostatic latent image on the exposed area, and then toner is supplied to this to obtain a visible image (toner image). This toner image is transferred onto a sheet of paper by a transfer device placed opposite to the photosensitive drum to obtain a single copy.

Incidentally, there are various transfer methods, and among them, the roller transfer method is one of the most commonly used transfer methods along with the corona transfer method. In the roller transfer method, a voltage is directly applied to paper via a conductive roller made of conductive rubber or the like, and a toner image is transferred onto the paper using the electric field generated thereby. In this case, since the transfer is performed while directly pressing the paper and photosensitive drum with a roller, it is easy to maintain adhesion between the paper and the photosensitive drum surface, and unlike corona transfer, there is no ozone generation, so there is no possibility of image distortion. It is easy to obtain a perfectly good transferred image.

However, in adopting the above roller transfer method,
There is a restriction in that the developing method used is limited. In general, development methods include a one-component development method that uses only magnetic toner as a developer, a two-component development method that uses non-magnetic toner and a carrier, and an improved version of both of these development methods that uses a magnetic toner and carrier. New two ingredients (1
, 5-component) system development method.

In both the two-component developing method and the new two-component developing method, only the toner is consumed during development, so theoretically the carrier does not adhere to the photosensitive drum, but is magnetically attracted to the developing sleeve. However, in reality, a portion of the carrier may be transferred from the developing sleeve onto the photosensitive drum, and as a result, the carrier may be transported to the transfer device position.

Normally, a magnetic carrier such as iron powder is used as the carrier, so if such metal powder gets between the photosensitive drum and the transfer roller, a large current will locally flow only in the metal powder part during transfer. A problem occurs. As a result, not only the transfer of the toner image onto the photosensitive drum is hindered, but also the surface of the photosensitive drum is destroyed by the overcurrent. Therefore, in the roller transfer method, the developing method is limited to a one-component developing method.

The present invention has been made in view of the current situation, and it is an object of the present invention to provide an extremely easy-to-use transfer device that realizes a roller transfer method that is compatible with two-component development methods and new two-component development methods. purpose.

9. The present invention provides a transfer device for transferring a toner image on a photosensitive drum onto a sheet of paper, in which a transfer roller made of an electrically conductive material is provided at both ends with a diameter larger than that of the transfer roller. The present invention is characterized in that an insulating roller is provided and the insulating roller is brought into rolling contact with the photosensitive drum.

Operation-□-1- According to the above configuration, the roller diameter of the insulating rollers provided at both ends of the transfer roller is larger than that of the transfer roller, so that only the insulating rollers roll into contact with the photosensitive drum. Therefore, the transfer roller made of a conductive material is always in a non-contact state with the surface of the photosensitive drum, and a gap space with a constant distance is created between the transfer roller and the surface of the photosensitive drum.

When the paper is conveyed through this gap space and the transfer roller is charged to the opposite polarity to the toner on the photosensitive drum, a strong electric field is formed between the transfer roller and the photosensitive drum. In this state, the paper is electrostatically attracted to the transfer roller, and the toner on the photosensitive drum is transferred to the surface of the paper.

Practical View ■ An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a side sectional view showing an embodiment in which a transfer device according to the present invention is applied to a printer.

When a print switch (not shown) is turned on, the photosensitive drum 2 provided at the center of the printer 1 rotates in the direction shown by arrow A, and the charger 3 charges the surface of the photosensitive drum 2 accordingly. Next, an optical writing unit 4 consisting of an LED array emits light in response to an image signal given from a scanner section (not shown), thereby exposing the surface of the photosensitive drum 2. Thus, an electrostatic latent image is formed in the exposed area.

Next, a developing device 5 installed on the upper right side of the photosensitive drum 2 in the figure supplies toner to the electrostatic latent image on the photosensitive drum 2 to form a toner image (visible image).

Meanwhile, in synchronization with the image forming process, a paper feed roller 7 feeds out a paper (not shown) stored in a paper feed cassette (or tray) 8 and supplies it to a registration roller 9 . The registration rollers 9 transport the paper to the transfer device 6 in synchronization with the rotation of the photosensitive drum 2.

The transfer device 6 is provided opposite to the photosensitive drum 2, and transfers the toner image formed on the photosensitive drum 2 onto a sheet of paper. Note that details of the transfer device 6 will be described later. The paper onto which the toner image has been transferred is then conveyed to the position of the fixing roller 10,
A fixing step is performed here. After the fixing process, the paper is conveyed in a U-turn by the paper guide 11 and the discharge roller I2, and is discharged onto the paper discharge tray 13 attached to the upper part of the main body. In addition, in the figure, the path line P of the paper is indicated by the dashed dotted line.

Next, details of the transfer device will be explained according to FIGS. 2 and 3. FIG. 2 is a perspective view showing the transfer device 6,
FIG. 3 is a side sectional view showing the transfer device 6. FIG. The transfer device 6 includes a transfer roller 60 to which a bias is applied to have a polarity opposite to that of the toner on the photosensitive drum 2 (in a positive state). The transfer roller 60 is disposed close to the photosensitive drum 2 on the registration roller 9 side from directly below the photosensitive drum 2, and furthermore, a paper guide plate 61 is provided close to the photosensitive drum 2 on the downstream side of the transfer roller 60. .

The transfer roller 60 has a conductive rubber roller section 62 as its main roller body, and insulating roller sections 63 and 63 having a diameter larger than that of the roller main body are provided at both ends thereof. The length in the longitudinal direction of the transfer roller 60, that is, the conductive rubber roller portion 62 and the insulating roller portion 63.6
The total length in the longitudinal direction of the photosensitive drum 2 is set to be equal to or slightly shorter than the length of the photosensitive drum 2 in the longitudinal direction. Further, the length of the insulating roller portion 63 in the longitudinal direction is appropriately determined to such an extent that the insulating roller portion 63 can function as a spacer.

The transfer roller 60 can be manufactured by fitting a conductive rubber tube and an insulating resin tube of a predetermined diameter onto the shaft core.

On the other hand, the roller diameter of the insulating roller section 63 is set so that the gap distance between the conductive rubber roller section 62 and the photosensitive drum 2 is equal to the sum of the thickness of one sheet of paper and the thickness of each carrier, plus the path distance. Set to .

More specifically, the gap distance is set to be 1 mm or less, preferably about 0.3 to 0.7 mm.

According to the above configuration, the paper that has passed through the registration roller 9 is supplied between the photosensitive drum 2 and the transfer roller 60 as shown in FIG. 3, and then moves along the surface of the photosensitive drum 2 as the photosensitive drum 2 rotates. The paper is then conveyed between the photosensitive drum 2 and the paper guide plate 61. And paper guide plate 61
Due to the guiding action and the rigidity of the paper stock, the paper stock is brought into close contact with the surface of the photosensitive drum 2 between the transfer roller 60 and the paper guide plate 61 (at a position close to the transfer roller 60).

During this time, since a bias is applied to the transfer roller 60, toner is transferred, the paper is conveyed in the direction of arrow X, and the transfer process is completed.

Note that a guide roller may be used instead of the paper guide plate 61, but in either case, it needs to be provided near the photosensitive drum 2, so there is a risk of electrical discharge to this part, especially when humidity is high. There is. Therefore, it is desirable to use insulating materials for these or to take measures such as grounding them through a resistance of about 100 MΩ.

According to the present invention as described above, there are no restrictions on the developer used in the roller transfer method, and it can be used without problems in two-component development methods and new two-component development methods, making it very easy to use. A transfer device with good quality can be realized.

Further, since the transfer roller is disposed opposite to the photosensitive drum at a constant distance, and the distance is extremely close, the generation of ozone is suppressed and stable toner image transfer is always performed. In other words, the image quality can be significantly improved.

Further, since the conductive roller portion of the transfer roller maintains a non-contact state with the photosensitive drum, toner does not adhere to the transfer roller and contaminate it, and there is no need to provide an extra device such as a cleaner.

4. In addition, since the transfer roller is not brought into pressure contact with the photosensitive drum as in the conventional case, and only a high voltage is applied thereto, the roller diameter can be made smaller than in the conventional case.

On the other hand, in addition to its original transfer function, the transfer roller also functions as a guide roller for the paper, and the insulating roller portions with a large roller diameter provided at both ends of the transfer roller also have the function of suppressing the meandering of the paper. have

Therefore, the device can be made more compact, and the number of parts used in manufacturing the device can be reduced, leading to cost reduction.

[Brief explanation of drawings]

FIG. 1 is a side sectional view showing an embodiment of the transfer device according to the present invention applied to a printer, FIG. 2 is a perspective view showing the transfer device, and FIG. 3 is a side sectional view showing the transfer device. DESCRIPTION OF SYMBOLS 1... Printer, 2... Photosensitive drum, 6... Transfer device, 60... Transfer roller, 62... Conductive roller part, 63... Insulating roller part, D... Paper . Figure procedure (Hosho sho (spontaneous) December 4, 1990 1990 Patent Application No. 280134 26 Name transcription device 3 of the invention, relationship with the person making the amendment case Patent applicant address Kisshoin, Minami-ku, Kyoto City Minami Ochiai-cho 3 Name Murata Machinery Co., Ltd. Representative Village 1) Jun 4, Agent 7゜In the statement of contents of the amendment, page 7, lines 17 to 19, ``The above transfer roller 60 is fixed at the specified axis. "It can be manufactured by fitting a conductive rubber tube with an insulating resin tube of the same diameter." has been deleted.

Claims (1)

[Claims] (1) In a transfer device that transfers a toner image on a photosensitive drum onto a sheet of paper, insulating rollers having a diameter larger than that of the transfer roller are provided at both ends of a transfer roller made of a conductive material, and A transfer device characterized in that a magnetic roller is brought into rolling contact with a photosensitive drum.